Height growth and site index curves for western white pine in the Cascade Range of Washington and Oregon.

Treesearch

Robert O. Curtis; Nancy M. Diaz; Gary W. Clendenen

1990-01-01

Height growth and site index curves were constructed from stem analyses of mature western white pine (Pinus monticola Dougl. ex D. Don) growing in high-elevation forests of the Cascade Range in the Mount Hood and Gifford Pinchot National Forests of Oregon and Washington, respectively. Alternate systems using reference ages for site index of 50 and...

Estimates of site index and height growth for Douglas-fir in high-elevation forests of the Oregon-Washington Cascade Range: curves and tables for field application.

Treesearch

Donald J. DeMars; Francis R. Herman

1987-01-01

Estimation equations for height growth and site index were derived from stem-analysis data of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) in the highelevation forests of the Cascade Range in Oregon and Washington. Two sets of height-growth and site-index estimation curves and tables produced from...

Experimental determination of unsteady blade element aerodynamics in cascades. Volume 2: Translation mode cascade

NASA Technical Reports Server (NTRS)

Riffel, R. E.; Rothrock, M. D.

1980-01-01

A two dimensional cascade of harmonically oscillating airfoils was designed to model a near tip section from a rotor which was known to have experienced supersonic translational model flutter. This five bladed cascade had a solidity of 1.52 and a setting angle of 0.90 rad. Unique graphite epoxy airfoils were fabricated to achieve the realistic high reduced frequency level of 0.15. The cascade was tested over a range of static pressure ratios approximating the blade element operating conditions of the rotor along a constant speed line which penetrated the flutter boundary. The time steady and time unsteady flow field surrounding the center cascade airfoil were investigated.

Application of a Channel Design Method to High-Solidity Cascades and Tests of an Impulse Cascade with 90 Degrees of Turning

NASA Technical Reports Server (NTRS)

Stanitz, John D; Sheldrake, Leonard J

1953-01-01

A technique is developed for the application of a channel design method to the design of high-solidity cascades with prescribed velocity distributions as a function of arc length along the blade-element profile. The technique is applied to both incompressible and subsonic compressible, nonviscous, irrotational fluid motion. For compressible flow, the ratio of specific heats is assumed equal to -1.0. An impulse cascade with 90 degree turning was designed for incompressible flow and was tested at the design angle of attack over a range of downstream Mach number from 0.2 to coke flow. To achieve good efficiency, the cascade was designed for prescribed velocities and maximum blade loading according to limitations imposed by considerations of boundary-layer separation.

High performance, low dissipation quantum cascade lasers across the mid-IR range.

PubMed

Bismuto, Alfredo; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Muller, Antoine

2015-03-09

In this work, we present the development of low consumption quantum cascade lasers across the mid-IR range. In particular, short cavity single-mode lasers with optimised facet reflectivities have been fabricated from 4.5 to 9.2 μm. Threshold dissipated powers as low as 0.5 W were obtained in continuous wave operation at room temperature. In addition, the beneficial impact of reducing chip length on laser mounting yield is discussed. High power single-mode lasers from the same processed wafers are also presented.

Geologic field-trip guide to Mount Shasta Volcano, northern California

USGS Publications Warehouse

Christiansen, Robert L.; Calvert, Andrew T.; Grove, Timothy L.

2017-08-18

The southern part of the Cascades Arc formed in two distinct, extended periods of activity: “High Cascades” volcanoes erupted during about the past 6 million years and were built on a wider platform of Tertiary volcanoes and shallow plutons as old as about 30 Ma, generally called the “Western Cascades.” For the most part, the Shasta segment (for example, Hildreth, 2007; segment 4 of Guffanti and Weaver, 1988) of the arc forms a distinct, fairly narrow axis of short-lived small- to moderate-sized High Cascades volcanoes that erupted lavas, mainly of basaltic-andesite or low-silica-andesite compositions. Western Cascades rocks crop out only sparsely in the Shasta segment; almost all of the following descriptions are of High Cascades features except for a few unusual localities where older, Western Cascades rocks are exposed to view along the route of the field trip.The High Cascades arc axis in this segment of the arc is mainly a relatively narrow band of either monogenetic or short-lived shield volcanoes. The belt generally averages about 15 km wide and traverses the length of the Shasta segment, roughly 100 km between about the Klamath River drainage on the north, near the Oregon-California border, and the McCloud River drainage on the south (fig. 1). Superposed across this axis are two major long-lived stratovolcanoes and the large rear-arc Medicine Lake volcano. One of the stratovolcanoes, the Rainbow Mountain volcano of about 1.5–0.8 Ma, straddles the arc near the midpoint of the Shasta segment. The other, Mount Shasta itself, which ranges from about 700 ka to 0 ka, lies distinctly west of the High Cascades axis. It is notable that Mount Shasta and Medicine Lake volcanoes, although volcanologically and petrologically quite different, span about the same range of ages and bracket the High Cascades axis on the west and east, respectively.The field trip begins near the southern end of the Shasta segment, where the Lassen Volcanic Center field trip leaves off, in a field of high-alumina olivine tholeiite lavas (HAOTs, referred to elsewhere in this guide as low-potassium olivine tholeiites, LKOTs). It proceeds around the southern, western, and northern flanks of Mount Shasta and onto a part of the arc axis. The stops feature elements of the Mount Shasta area in an approximately chronological order, from oldest to youngest.

Carbamoyl anion-initiated cascade reaction for stereoselective synthesis of substituted α-hydroxy-β-amino amides.

PubMed

Lin, Chao-Yang; Ma, Peng-Ju; Sun, Zhao; Lu, Chong-Dao; Xu, Yan-Jun

2016-01-18

A carbamoyl anion-initiated cascade reaction with acylsilanes and imines has been used to rapidly construct substituted α-hydroxy-β-amino amides. The Brook rearrangement-mediated cascade allows the formation of two C-C bonds and one O-Si bond in a single pot. Using this approach, a range of α-aryl α-hydroxy-β-amino amides has been synthesized in high yields with excellent diastereoselectivities.

Progress in high-power continuous-wave quantum cascade lasers [Invited].

PubMed

Figueiredo, Pedro; Suttinger, Matthew; Go, Rowel; Tsvid, Eugene; Patel, C Kumar N; Lyakh, Arkadiy

2017-11-01

Multi-watt continuous-wave room temperature operation with efficiency exceeding 10% has been demonstrated for quantum cascade lasers essentially in the entire mid-wave and long-wave infrared spectral regions. Along with interband cascade lasers, these devices are the only room-temperature lasers that directly convert electrical power into mid- and long-infrared optical power. In this paper, we review the progress in high-power quantum cascade lasers made over the last 10 years. Specifically, an overview of the most important active region, waveguide, and thermal design techniques is presented, and various aspects of die packaging for high-power applications are discussed. Prospects of power scaling with lateral device dimensions for reaching optical power level in the range from 10 W to 20 W are also analyzed. Finally, coherent and spectral beam-combining techniques for very high-power infrared platforms are discussed.

Floristic similarity, diversity and endemism as indicators of refugia characteristics and needs in the West

USGS Publications Warehouse

Malanson, George P.; Zimmerman, Dale L.; Fagre, Daniel B.

2015-01-01

The floras of mountain ranges, and their similarity, beta diversity and endemism, are indicative of processes of community assembly; they are also the initial conditions for coming disassembly and reassembly in response to climate change. As such, these characteristics can inform thinking on refugia. The published floras or approximations for 42 mountain ranges in the three major mountain systems (Sierra-Cascades, Rocky Mountains and Great Basin ranges) across the western USA and southwestern Canada were analysed. The similarity is higher among the ranges of the Rockies while equally low among the ranges of the Sierra-Cascades and Great Basin. Mantel correlations of similarity with geographic distance are also higher for the Rocky Mountains. Endemism is relatively high, but is highest in the Sierra-Cascades (due to the Sierra Nevada as the single largest range) and lowest in the Great Basin, where assemblages are allochthonous. These differences indicate that the geologic substrates of the Cascade volcanoes, which are much younger than any others, play a role in addition to geographic isolation in community assembly. The pattern of similarity and endemism indicates that the ranges of the Cascades will not function well as stepping stones and the endemic species that they harbor may need more protection than those of the Rocky Mountains. The geometry of the ranges is complemented by geology in setting the stage for similarity and the potential for refugia across the West. Understanding the geographic template as initial conditions for the future can guide the forecast of refugia and related monitoring or protection efforts.

Correlation Scales of the Turbulent Cascade at 1 au

NASA Astrophysics Data System (ADS)

Smith, Charles W.; Vasquez, Bernard J.; Coburn, Jesse T.; Forman, Miriam A.; Stawarz, Julia E.

2018-05-01

We examine correlation functions of the mixed, third-order expressions that, when ensemble-averaged, describe the cascade of energy in the inertial range of magnetohydrodynamic turbulence. Unlike the correlation function of primitive variables such as the magnetic field, solar wind velocity, temperature, and density, the third-order expressions decorrelate at a scale that is approximately 20% of the lag. This suggests the nonlinear dynamics decorrelate in less than one wavelength. Therefore, each scale can behave differently from one wavelength to the next. In the same manner, different scales within the inertial range can behave independently at any given time or location. With such a cascade that can be strongly patchy and highly variable, it is often possible to obtain negative cascade rates for short periods of time, as reported earlier for individual samples of data.

A high-density remote reference magnetic variation profile in the Pacific northwest of North America

USGS Publications Warehouse

Hermance, J.F.; Lusi, S.; Slocum, W.; Neumann, G.A.; Green, A.W.

1989-01-01

During the summer of 1985, as part of the EMSLAB Project, Brown University conducted a detailed magnetic variation study of the Oregon Coast Range and Cascades volcanic system along an E-W profile in central Oregon. Comprised of a sequence of 75 remote reference magnetic variation (MV) stations spaced 3-4 km apart, the profile stretched for 225 km from Newport, on the Oregon coast, across the Coast Range, the Willamette Valley, and the High Cascades to a point ??? 50 km east of Santiam Pass. At all of the MV stations, data were collected for short periods (16-100 s), and at 17 of these stations data were also obtained at longer periods (100-1600 s). Data were monitored with a three-component ring core fluxgate magnetometer (Nanotesla), and were recorded with a microcomputer (DEC PDP 11/73) based data acquisition system. A 2-D generalized inversion of the magnetic transfer coefficients over the period range of 16-1600 s indicates four distinct conductors. First, we see the coast effect caused by a large sedimentary wedge offshore. Second, we see the effect of currents flowing in the conductive sediments of the Willamette Valley. Our inversion suggests that the Willamette Valley consists of two electrically distinct features, due perhaps to a horst-like structure imprinted on the valley sediments. Next we note an electric current system centered beneath the High Cascades. This latter feature may be associated with a sediment-filled graben beneath Santiam Pass as suggested by some of the gravity and MT results reported to date. Finally, we detect the presence of a deep conductor at mid-crustal depths which laterally extends westward from beneath the Basin and Range Province, and terminates beneath the western Cascades. One view of this last result is that it appears that modern Basin and Range structure is being imprinted on pre-existing Cascade structure. ?? 1989.

Experimental determination of unsteady blade element aerodynamics in cascades. Volume 1: Torsion mode cascade

NASA Technical Reports Server (NTRS)

Riffel, R. E.; Rothrock, M. D.

1980-01-01

A two dimensional cascade of harmonically oscillating airfoils was designed to model a near tip section from a rotor which was known to have experienced supersonic torsional flutter. This five bladed cascade had a solidity of 1.17 and a setting angle of 1.07 rad. Graphite epoxy airfoils were fabricated to achieve the realistically high reduced frequency level of 0.44. The cascade was tested over a range of static pressure ratios approximating the blade element operating conditions of the rotor along a constant speed line which penetrated the flutter boundary. The time-steady and time-unsteady flow field surrounding the center cascade airfoil were investigated. The effects of reduced solidity and decreased setting angle on the flow field were also evaluated.

Deuterium values from volcanic glass: A paleoelevation proxy for Oregon's Cascade Range

NASA Astrophysics Data System (ADS)

Carlson, T. B.; Bershaw, J. T.

2016-12-01

Hydrated volcanic glass has been used as a proxy to constrain Cenozoic paleoclimate across many of the world's mountain ranges. However, there are concerns that volcanic glass may not preserve the isotopic composition of syndepositional meteoric water. The Cascades are an excellent location to study the validity of hydrated volcanic glass as a paleoenvironmental proxy for several reasons. Moisture is derived from a single oceanic source and falls as orographic precipitation in the Cascades, leading to a characteristic altitude effect, or inverse relationship between elevation and the isotopic composition of meteoric water (δD). In addition, past studies have inferred uplift of the Cascades and an increase in the rain shadow effect since the Eocene through independent methods such as changing fossil assemblages, and other isotopic proxies including carbonates and fossil teeth. In this study, δD values of two hydrated tuff samples are compared: one prior to ( 29 Ma) and one following ( 5 Ma) the onset of High Cascade volcanism. The isotopic composition of these samples are interpreted in the context of modern water across the range to understand the potential of volcanic glass as a proxy for paleoelevation in the Pacific Northwest.

Active mode locking of quantum cascade lasers in an external ring cavity.

PubMed

Revin, D G; Hemingway, M; Wang, Y; Cockburn, J W; Belyanin, A

2016-05-05

Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents.

Active mode locking of quantum cascade lasers in an external ring cavity

PubMed Central

Revin, D. G.; Hemingway, M.; Wang, Y.; Cockburn, J. W.; Belyanin, A.

2016-01-01

Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents. PMID:27147409

Exact Turbulence Law in Collisionless Plasmas: Hybrid Simulations

NASA Astrophysics Data System (ADS)

Hellinger, P.; Verdini, A.; Landi, S.; Franci, L.; Matteini, L.

2017-12-01

An exact vectorial law for turbulence in homogeneous incompressible Hall-MHD is derived and tested in two-dimensional hybrid simulations of plasma turbulence. The simulations confirm the validity of the MHD exact law in the kinetic regime, the simulated turbulence exhibits a clear inertial range on large scales where the MHD cascade flux dominates. The simulation results also indicate that in the sub-ion range the cascade continues via the Hall term and that the total cascade rate tends to decrease at around the ion scales, especially in high-beta plasmas. This decrease is like owing to formation of non-thermal features, such as collisionless ion energization, that can not be retained in the Hall MHD approximation.

Cougars, Curriculum, and Community

ERIC Educational Resources Information Center

Quitadamo, Ian J.; Campanella, Ryan

2005-01-01

On the eastern edge of the Cascade Mountain range in Washington State, high school biology students have a unique opportunity to study the elusive cougar ("Felis concolor"), a large cat native to the area. Nestled in the Cascade foothills is the city of Cle Elum, a small rural community that is expected to soon experience considerable…

Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si

NASA Astrophysics Data System (ADS)

Wallace, J. B.; Aji, L. B. Bayu; Shao, L.; Kucheyev, S. O.

2018-05-01

The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ˜-30 ° C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ˜0.1 eV , independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ˜0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si.

PubMed

Wallace, J B; Aji, L B Bayu; Shao, L; Kucheyev, S O

2018-05-25

The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ∼-30 °C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ∼0.1  eV, independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ∼0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

Cascaded bidirectional recurrent neural networks for protein secondary structure prediction.

PubMed

Chen, Jinmiao; Chaudhari, Narendra

2007-01-01

Protein secondary structure (PSS) prediction is an important topic in bioinformatics. Our study on a large set of non-homologous proteins shows that long-range interactions commonly exist and negatively affect PSS prediction. Besides, we also reveal strong correlations between secondary structure (SS) elements. In order to take into account the long-range interactions and SS-SS correlations, we propose a novel prediction system based on cascaded bidirectional recurrent neural network (BRNN). We compare the cascaded BRNN against another two BRNN architectures, namely the original BRNN architecture used for speech recognition as well as Pollastri's BRNN that was proposed for PSS prediction. Our cascaded BRNN achieves an overall three state accuracy Q3 of 74.38\\%, and reaches a high Segment OVerlap (SOV) of 66.0455. It outperforms the original BRNN and Pollastri's BRNN in both Q3 and SOV. Specifically, it improves the SOV score by 4-6%.

Physical Controls on Delta Formation and Carbon Storage in Mountain Lakes

NASA Astrophysics Data System (ADS)

Scott, D.; Wohl, E.

2014-12-01

Carbon acts as a component in greenhouse gases that regulate global climate. It is imperative to understand the transport and storage of carbon in order to understand and manage climate change. We examine terrestrial carbon storage in mountain lake deltas as a way of furthering our understanding of the terrestrial carbon sink, which is a poorly understood but significant contributor to the global carbon cycle. We examined subalpine lake deltas in the Washington Cascade Range and Colorado Front Range to test the following hypotheses: 1) The size of the deltaic carbon sink is strongly correlated with incision at the outlet of the lake and the topography of the basin. 2) Areas of high exhumation rates will have smaller and fewer deltas because a high exhumation rate should lead to more confined basins and more colluvium available to dam lake outlets, preventing lake level drop and corresponding delta formation. 3) High-energy deltas will transport more carbon to lakes, avoiding the deltaic carbon sink. At 27 lakes, we surveyed mountain lake deltas and took sediment samples, surveyed lake outlets in the field, and measured lake valley confinement in GIS to test hypotheses 1 and 3. Across the Snoqualmie and Skykomish watersheds in the Washington Cascades and the Colorado Front Range, we took a census of the number of natural lakes and the proportion of those lakes with deltas to test hypothesis 2. Preliminary results indicate that the Washington Cascades (high exhumation rate) have a higher density of lakes, but fewer deltas, than the Colorado Front Range (low exhumation rate). We also suspect that deltas in the Washington Cascades will have a lower carbon content than the Colorado Front Range due to generally higher energy levels on deltas. Finally, we found a substantial difference in the geomorphology and sediment type between beaver-affected and non-beaver-affected lakes in the Colorado Front Range.

Re-solution of xenon clusters in plutonium dioxide under the collision cascade impact: A molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Seitov, D. D.; Nekrasov, K. A.; Kupryazhkin, A. Ya.; Gupta, S. K.; Akilbekov, A. T.

2017-09-01

The interaction of xenon clusters with the collision cascades in the PuO2 crystals is investigated using the molecular dynamics simulation and the approximation of the pair interaction potentials. The potentials of interaction of Xe atoms with the surrounding particles in the crystal lattice are suggested, that are valid in the range of high collision energies. The cascades created by the recoil 235U ions formed as the plutonium α-decay product are considered, and the influence of such cascades on the structure of the xenon clusters is analyzed. It is shown, that the cascade-cluster interaction leads to release of the xenon atoms from the clusters and their subsequent re-solution in the crystal bulk.

New quantum cascade laser sources for sensing applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Troccoli, Mariano

2017-05-01

In this presentation we will review our most recent results on development of Quantum Cascade Lasers (QCLs) for analytical and industrial applications. QCLs have demonstrated the capability to cover the entire range of Mid-IR, Far-IR, and THz wavelengths by skillful tuning of the material design and composition and by use of intrinsic material properties via a set of techniques collectively called "bandgap engineering". The use of MOCVD, pioneered on industrial scale by AdTech Optics, has enabled the deployment of QCL devices into a diverse range of environments and applications. QCLs can be tailored to the specific application requirements due to their unprecedented flexibility in design and thanks to the leveraging of well-known III-V fabrication technologies inherited from the NIR domain. Nevertheless, several applications and new frontiers in R and D need the constant support of new developments in device features, capabilities, and performances. We have developed a wide range of devices, from high power, high efficiency multi-mode sources, to narrow-band, single mode devices with low-power consumption, and from non-linear, multi-wavelength generating devices to broadband sources and multi-emitter arrays. All our devices are grown and processed using MOCVD technology and allow us to attain competitive performances across the whole mid-IR spectral range. This talk will present an overview of our current achievements. References 1. M. Troccoli, "High power emission and single mode operation of quantum cascade lasers for industrial applications", J. Sel. Topics in Quantum Electron., 21 (6), 1-7 (2015). Invited Review. 2. Seungyong Jung, Aiting Jiang, Yifan Jiang, Karun Vijayraghavan, Xiaojun Wang, Mariano Troccoli, and Mikhail A. Belkin, "Broadly Tunable Monolithic Terahertz Quantum Cascade Laser Sources", Nature Comm. 5, 4267 (2014).. 3. Mariano Troccoli, Arkadiy Lyakh, Jenyu Fan, Xiaojun Wang, Richard Maulini, Alexei G Tsekoun, Rowel Go, C Kumar N Patel, "Long-Wave IR Quantum Cascade Lasers for emission in the λ = 8-12μm spectral region", Opt. Mat. Expr., 3 (9), 1546-1560 (2013).

Willamette River Flow Sensitivity to Cascade Snowpack Variation: Insights from Water Stable Isotopes

EPA Science Inventory

Much of the water that people in Western Oregon rely on comes from snowpack in the Cascade Range, and this snowpack is expected to decrease in coming years. In fact, the past 7 years have shown dramatic variation in snowpack, from a high of 174% of normal in 2010-11 to a low of ...

RAINIER: A simulation tool for distributions of excited nuclear states and cascade fluctuations

NASA Astrophysics Data System (ADS)

Kirsch, L. E.; Bernstein, L. A.

2018-06-01

A new code has been developed named RAINIER that simulates the γ-ray decay of discrete and quasi-continuum nuclear levels for a user-specified range of energy, angular momentum, and parity including a realistic treatment of level spacing and transition width fluctuations. A similar program, DICEBOX, uses the Monte Carlo method to simulate level and width fluctuations but is restricted in its initial level population algorithm. On the other hand, modern reaction codes such as TALYS and EMPIRE populate a wide range of states in the residual nucleus prior to γ-ray decay, but do not go beyond the use of deterministic functions and therefore neglect cascade fluctuations. This combination of capabilities allows RAINIER to be used to determine quasi-continuum properties through comparison with experimental data. Several examples are given that demonstrate how cascade fluctuations influence experimental high-resolution γ-ray spectra from reactions that populate a wide range of initial states.

The Materosion project, a sediment cascade modeling for torrential sediment transfers: final results and perspectives

NASA Astrophysics Data System (ADS)

Rudaz, Benjamin; Loye, Alexandre; Mazotti, Benoit; Bardou, Eric; Jaboyedoff, Michel

2013-04-01

The Materosion project, conducted between the swiss canton of Valais (CREALP) and University of Lausanne (CRET) aims at forecasting sediment transfer in alpine torrents using the sediment cascade concept. The study site is the high Anniviers valley, around the village of Zinal (Valais). The torrents are divided in homogeneous reaches, to and from which sediments are transported by debris flows and bedload transport events. The model runs simulations of 100 years, with a 1-month time step, each with a given a random meteorological event ranging from no activity up to high magnitude debris flows. These events are calibrated using local rain data and observed corresponding debris flow frequencies. The model is applied to ten torrent systems with variable geological context, watershed geometries and sediment supplies. Given the high number of possible event scenarios, 10'000 simulations per torrent are performed, giving a statistical distribution of cumulated volumes and an event size distribution. A way to visualize the complex results data is proposed, and a back-analysis of the internal sediment cascade dynamic is performed. The back-analysis shows that the results' distribution stabilize after ~5'000 simulations. The model results, especially the range of debris flow volumes are crucial to maintain mitigation measures such as retention dams, and give clues for future sediment cascade modeling.

Seasonal distribution and aerial surveys of mountain goats in Mount Rainier, North Cascades, and Olympic National Parks, Washington

USGS Publications Warehouse

Jenkins, Kurt; Beirne, Katherine; Happe, Patricia; Hoffman, Roger; Rice, Cliff; Schaberl, Jim

2011-01-01

We described the seasonal distribution of Geographic Positioning System (GPS)-collared mountain goats (Oreamnos americanus) in Mount Rainier, North Cascades, and Olympic National Parks to evaluate aerial survey sampling designs and provide general information for park managers. This work complemented a companion study published elsewhere of aerial detection biases of mountain goat surveys in western Washington. Specific objectives reported here were to determine seasonal and altitudinal movements, home range distributions, and temporal dynamics of mountain goat movements in and out of aerial survey sampling frames established within each park. We captured 25 mountain goats in Mount Rainier (9), North Cascades (5), and Olympic (11) National Parks, and fitted them with GPS-collars programmed to obtain 6-8 locations daily. We obtained location data on 23 mountain goats for a range of 39-751 days from 2003 to 2008. Altitudinal distributions of GPS-collared mountain goats varied individually and seasonally, but median altitudes used by individual goats during winter ranged from 817 to 1,541 meters in Olympic and North Cascades National Parks, and 1,215 to 1,787 meters in Mount Rainier National Park. Median altitudes used by GPS-collared goats during summer ranged from 1,312 to 1,819 meters in Olympic and North Cascades National Parks, and 1,780 to 2,061 meters in Mount Rainier National Park. GPS-collared mountain goats generally moved from low-altitude winter ranges to high-altitude summer ranges between June 11 and June 19 (range April 24-July 3) and from summer to winter ranges between October 26 and November 9 (range September 11-December 23). Seasonal home ranges (95 percent of adaptive kernel utilization distribution) of males and female mountain goats were highly variable, ranging from 1.6 to 37.0 kilometers during summers and 0.7 to 9.5 kilometers during winters. Locations of GPS-collared mountain goats were almost 100 percent within the sampling frame used for mountain goat surveys in Mount Rainier National Park, whereas generally greater than 80 and greater than 60 percent of locations were within sampling units delineated in North Cascades and Olympic National Parks, respectively. Presence of GPS-collared mountain goats within the sampling frame of Olympic National Park varied by diurnal period (midday versus crepuscular), survey season (July versus September), and the interaction of diurnal period and survey season. Aerial surveys conducted in developing a sightability model for mountain goat aerial surveys indicated mean detection probabilities of 0.69, 0.76, and 0.87 in North Cascades, Olympic, and Mount Rainier National Parks, respectively. Higher detection probabilities in Mount Rainier likely reflected larger group sizes and more open habitat conditions than in North Cascades and Olympic National Parks. Use of sightability models will reduce biases of population estimates in each park, but resulting population estimates must still be considered minimum population estimates in Olympic and North Cascades National Parks because the current sampling frames do not encompass those populations completely. Because mountain goats were reliably present within the sampling frame in Mount Rainier National Park, we found no compelling need to adjust mountain goat survey boundaries in that park. Expanding survey coverage in North Cascades and Olympic National Parks to more reliably encompass the altitudinal distribution of mountain goats during summer would enhance population estimation accuracy in the future. Lowering the altitude boundary of mountain goat survey units by as little as 100 meters to 1,425 meters in Olympic National Park would increase mountain goat presence within the survey and reduce variation in counts related to movements of mountain goats outside the survey boundaries.

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal-body theory

NASA Astrophysics Data System (ADS)

Blakely, Richard J.

1994-02-01

The spatial correlation between a horizontal gradient in heat flow and a horizontal gradient in residual gravity in the Western Cascades of central Oregon has been interpreted by others as evidence of the western edge of a pervasive zone of high temperatures and partial melting at midcrustal depths (5-15 km). Both gradients are steep and relatively linear over north-south distances in excess of 150 km. The Western Cascades gravity gradient is the western margin of a broad gravity depression over most of the Oregon Cascade Range, implying that the midcrustal zone of anomalous temperatures lies throughout this region. Ideal-body theory applied to the gravity gradient, however, shows that the source of the Western Cascades gravity gradient cannot be deeper than about 2.5 km and is considerably shallower in some locations. These calculations are unique determinations, assuming that density contrasts associated with partial melting and elevated temperatures in the crust do not exceed 500 kg/cu m. Consequently, the gravity gradient and the heat flow gradient in the Western Cascades cannot be caused directly by the same source if the heat flow gradient originates at midcrustal depths. This conclusion in itself does not disprove the existence of a widespread midcrustal zone of anomalously high temperatures and partial melting in this area, but it does eliminate a major argument in support of its existence. The gravity gradient is most likely caused by lithologic varitions in the shallow crust, perhaps reflecting a relict boundary between the Cascade extensional trough to the west and Tertiary oceanic crust to the west. The boundary must have formed prior to Oligocene time, the age of the oldest rocks that now conceal it.

Multimode analysis of highly tunable, quantum cascade powered, circular graphene spaser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayasekara, Charith, E-mail: charith.jayasekara@monash.edu; Premaratne, Malin; Stockman, Mark I.

2015-11-07

We carried out a detailed analysis of a circular graphene spaser made of a circular graphene flake and a quantum cascade well structure. Owing to unique properties of graphene and quantum cascade well structure, the proposed design shows high mechanical and thermal stability and low optical losses. Additionally, operation characteristics of the model are analysed and tunability of the device is demonstrated. Some advantages of the proposed design include compact size, lower power operation, and the ability to set the operating wavelength over a wide range from Mid-IR to Near-IR. Thus, it can have wide spread applications including designing ofmore » ultracompact and ultrafast devices, nanoscopy and biomedical applications.« less

Nuclear electromagnetic cascades from nuclei with Z larger than or equal to 3

NASA Technical Reports Server (NTRS)

Jones, W. V.

1971-01-01

A Monte Carlo simulation method was developed for studying nuclear-electromagnetic cascades initiated by high energy nuclei with Z or = 3 incident on heavy absorbers. The calculations are based on a cascade model which was first adjusted until it agreed with measurements made with protons at an accelerator. Modifications of the model used for protons include the incorporation of the probabilities for fragmentation of heavy nuclei into lighter nuclei, alpha particles, and nucleons. Mean values and fluctuations of the equivalent numbers of particles in the cascades at various depths in an iron absorber are presented for protons, carbon, and iron nuclei over the 30 to 300 GeV/nucleon energy range.

[Infrared spectroscopy based on quantum cascade lasers].

PubMed

Wen, Zhong-Quan; Chen, Gang; Peng, Chen; Yuan, Wei-Qing

2013-04-01

Quantum cascade lasers (QCLs) are promising infrared coherent sources. Thanks to the quantum theory and band-gap engineering, QCL can access the wavelength in the range from 3 to 100 microm. Since the fingerprint spectrum of most gases are located in the mid-infrared range, mid-infrared quantum cascade laser based gas sensing technique has become the research focus world wide because of its high power, narrow linewidth and fast scanning. Recent progress in the QCL technology leads to a great improvement in laser output power and efficiency, which stimulates a fast development in the infrared laser spectroscopy. The present paper gives a broad review on the QCL based spectroscopy techniques according to their working principles. A discussion on their applications in gas sensing and explosive detecting is also given at the end of the paper.

Energy transfer, pressure tensor, and heating of kinetic plasma

NASA Astrophysics Data System (ADS)

Yang, Yan; Matthaeus, William H.; Parashar, Tulasi N.; Haggerty, Colby C.; Roytershteyn, Vadim; Daughton, William; Wan, Minping; Shi, Yipeng; Chen, Shiyi

2017-07-01

Kinetic plasma turbulence cascade spans multiple scales ranging from macroscopic fluid flow to sub-electron scales. Mechanisms that dissipate large scale energy, terminate the inertial range cascade, and convert kinetic energy into heat are hotly debated. Here, we revisit these puzzles using fully kinetic simulation. By performing scale-dependent spatial filtering on the Vlasov equation, we extract information at prescribed scales and introduce several energy transfer functions. This approach allows highly inhomogeneous energy cascade to be quantified as it proceeds down to kinetic scales. The pressure work, - ( P . ∇ ) . u , can trigger a channel of the energy conversion between fluid flow and random motions, which contains a collision-free generalization of the viscous dissipation in collisional fluid. Both the energy transfer and the pressure work are strongly correlated with velocity gradients.

Terahertz multiheterodyne spectroscopy using laser frequency combs

DOE PAGES

Yang, Yang; Burghoff, David; Hayton, Darren J.; ...

2014-07-01

The terahertz region is of great importance for spectroscopy since many molecules have absorption fingerprints there. Frequency combs based on terahertz quantum cascade lasers feature broadband coverage and high output powers in a compact package, making them an attractive option for broadband spectroscopy. Here, we demonstrate the first multiheterodyne spectroscopy using two terahertz quantum cascade laser combs. Over a spectral range of 250 GHz, we achieve average signal-to-noise ratios of 34 dB using cryogenic detectors and 24 dB using room-temperature detectors, all in just 100 μs. As a proof of principle, we use these combs to measure the broadband transmissionmore » spectrum of etalon samples and show that, with proper signal processing, it is possible to extend the multiheterodyne spectroscopy to quantum cascade laser combs operating in pulsed mode. Here, this greatly expands the range of quantum cascade lasers that could be suitable for these techniques and allows for the creation of completely solid-state terahertz laser spectrometers.« less

An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Cheng; Zhang, Kai; Xiong, Jian

Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-basedmore » MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.« less

An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch

DOE PAGES

Wang, Cheng; Zhang, Kai; Xiong, Jian; ...

2017-09-26

Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-basedmore » MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.« less

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

PubMed

Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

2012-01-01

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

Geologic Map of the North Cascade Range, Washington

USGS Publications Warehouse

Haugerud, Ralph A.; Tabor, Rowland W.

2009-01-01

The North Cascade Range, commonly referred to as the North Cascades, is the northern part of the Cascade Range that stretches from northern California into British Columbia, where it merges with the Coast Mountains of British Columbia at the Fraser River. The North Cascades are generally characterized by exposure of plutonic and metamorphic rocks in contrast to the volcanic terrain to the south. The rocks of the North Cascades are more resistant to erosion, display greater relief, and show evidence of more pronounced uplift and recent glaciation. Although the total length of the North Cascade Range, extending north from Snoqualmie Pass in Washington, is about 200 mi (320 km), this compilation map at 1:200,000 scale covers only that part (~150 mi) in the United States. The compilation map is derived mostly from eight 1:100,000-scale quadrangle maps that include all of the North Cascade Range in Washington and a bit of the mostly volcanic part of the Cascade Range to the south (fig. 1, sheet 2). Overall, the area represented by this compilation is about 12,740 mi2 (33,000 km2). The superb alpine scenery of the North Cascade Range and its proximity to major population centers has led to designation of much of the area for recreational use or wilderness preservation. A major part of the map area is in North Cascade National Park. Other restricted use areas are the Alpine Lakes, Boulder River, Clearwater, Glacier Peak, Henry M. Jackson, Lake Chelan-Sawtooth, Mount Baker, Noisy-Diobsud, Norse Peak, and Pasayten Wildernesses and the Mount Baker, Lake Chelan, and Ross Lake National Recreation Areas. The valleys traversed by Washington State Highway 20 east of Ross Lake are preserved as North Cascades Scenic Highway. The map area is traversed by three major highways: U.S. Interstate 90, crossing Snoqualmie Pass; Washington State Highway 2, crossing Stevens Pass; and Washington State Highway 20, crossing Washington Pass. Major secondary roads, as well as a network of U.S. Forest Service roads and a few private roads mainly used for logging, are restricted mostly to the flanks of the range. Although much of the mountainous core is inaccessible to automobiles, numerous trails serve the foot or horse traveler.

Fire history and landscape restoration in Douglas-fir ecosystems of western Oregon

Treesearch

J. E. Means; J. H. Cissel; F. J. Swanson

1996-01-01

For thousands of years fire has been a major, natural disturbance in the forest landscape from the Cascade Range westward to the coast in Oregon and Washington (Agee 1993; Brubaker 1991). Viewing the landscape of the central western Cascades in Oregon from a high point, one can see that fires of variable intensity and areal extent have created a complex mosaic of...

Research publications of the H.J. Andrews Experimental Forest, Cascade Range, Oregon: 1998 supplement.

Treesearch

Donald L. Henshaw; Sarah E. Greene; Tami Lowry

1998-01-01

This bibliography updates the list of publications, abstracts, theses, and unpublished reports included in "Research Publications of the H.J. Andrews Experimental Forest, Cascade Range, Oregon, 1948 to 1986" (General Technical Report PNW-GTR-201) and "Research Publications of the H.J. Andrews Experimental Forest, Cascade Range, Oregon: 1988 Supplement...

High power frequency comb based on mid-infrared quantum cascade laser at λ ∼ 9 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Q. Y.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu; Slivken, S.

2015-02-02

We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼ 9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm{sup −1} and a high power output of 180 mW for ∼176 comb modes.

Multi-year high-frequency hydrothermal monitoring of selected high-threat Cascade Range volcanoes

NASA Astrophysics Data System (ADS)

Crankshaw, I. M.; Archfield, S. A.; Newman, A. C.; Bergfeld, D.; Clor, L. E.; Spicer, K. R.; Kelly, P. J.; Evans, W. C.; Ingebritsen, S. E.

2018-05-01

From 2009 to 2015 the U.S. Geological Survey (USGS) systematically monitored hydrothermal behavior at selected Cascade Range volcanoes in order to define baseline hydrothermal and geochemical conditions. Gas and water data were collected regularly at 25 sites on 10 of the highest-risk volcanoes in the Cascade Range. These sites include near-summit fumarole groups and springs/streams that show clear evidence of magmatic influence (high 3He/4He ratios and/or large fluxes of magmatic CO2 or heat). Site records consist mainly of hourly temperature and hydrothermal-flux data. Having established baseline conditions during a multiyear quiescent period, the USGS reduced monitoring frequency from 2015 to present. The archived monitoring data are housed at (doi:10.5066/F72N5088). These data (1) are suitable for retrospective comparison with other continuous geophysical monitoring data and (2) will provide context during future episodes of volcanic unrest, such that unrest-related variations at these thoroughly characterized sites will be more clearly recognizable. Relatively high-frequency year-round data are essential to achieve these objectives, because many of the time series reveal significant diurnal, seasonal, and inter-annual variability that would tend to mask unrest signals in the absence of baseline data. Here we characterize normal variability for each site, suggest strategies to detect future volcanic unrest, and explore deviations from background associated with recent unrest.

RAINIER: A simulation tool for distributions of excited nuclear states and cascade fluctuations

DOE PAGES

Kirsch, L. E.; Bernstein, L. A.

2018-03-04

In this paper, a new code has been developed named RAINIER that simulates the γ-ray decay of discrete and quasi-continuum nuclear levels for a user-specified range of energy, angular momentum, and parity including a realistic treatment of level spacing and transition width fluctuations. A similar program, DICEBOX, uses the Monte Carlo method to simulate level and width fluctuations but is restricted in its initial level population algorithm. On the other hand, modern reaction codes such as TALYS and EMPIRE populate a wide range of states in the residual nucleus prior to γ-ray decay, but do not go beyond the usemore » of deterministic functions and therefore neglect cascade fluctuations. This combination of capabilities allows RAINIER to be used to determine quasi-continuum properties through comparison with experimental data. Finally, several examples are given that demonstrate how cascade fluctuations influence experimental high-resolution γ-ray spectra from reactions that populate a wide range of initial states.« less

RAINIER: A simulation tool for distributions of excited nuclear states and cascade fluctuations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirsch, L. E.; Bernstein, L. A.

In this paper, a new code has been developed named RAINIER that simulates the γ-ray decay of discrete and quasi-continuum nuclear levels for a user-specified range of energy, angular momentum, and parity including a realistic treatment of level spacing and transition width fluctuations. A similar program, DICEBOX, uses the Monte Carlo method to simulate level and width fluctuations but is restricted in its initial level population algorithm. On the other hand, modern reaction codes such as TALYS and EMPIRE populate a wide range of states in the residual nucleus prior to γ-ray decay, but do not go beyond the usemore » of deterministic functions and therefore neglect cascade fluctuations. This combination of capabilities allows RAINIER to be used to determine quasi-continuum properties through comparison with experimental data. Finally, several examples are given that demonstrate how cascade fluctuations influence experimental high-resolution γ-ray spectra from reactions that populate a wide range of initial states.« less

Monitoring Mount Baker Volcano

USGS Publications Warehouse

Malone, S.D.; Frank, D.

1976-01-01

Hisotrically active volcanoes in the conterminous United States are restricted to the Cascade Range and extend to the Cascade Range and extend from Mount Baker near the Canadian border to Lassen Peak in northern California. Since 1800 A.D, most eruptive activity has been on a relatively small scale and has not caused loss of life or significant property damage. However, future  volcanism predictably will have more serious effects because of greatly increased use of land near volcanoes during the present century. (See "Appraising Volcanic Hazards of the Cascade Range of the Northwestern United States," Earthquake Inf. Bull., Sept.-Oct. 1974.) The recognition an impending eruption is highly important in order to minimize the potential hazard to people and property. Thus, a substantial increase in hydrothermal activity at Mount Baker in March 1975 ( see "Mount Baker Heating Up," July-Aug. 1975 issue) was regarded as a possible first signal that an eruption might occur, and an intensive monitoring program was undertaken. 

Fire and water: volcanology, geomorphology, and hydrogeology of the Cascade Range, central Oregon

Treesearch

Katharine V. Cashman; Natalia I. Deligne; Marshall W. Gannett; Gordon E. Grant; Anne Jefferson

2009-01-01

This field trip guide explores the interactions among the geologic evolution, hydrology, and fluvial geomorphology of the central Oregon Cascade Range. Key topics include the geologic control of hydrologic regimes on both the wet and dry sides of the Cascade Range crest, groundwater dynamics and interaction between surface and groundwater in young volcanic arcs, and...

Database for the Geologic Map of Upper Eocene to Holocene Volcanic and Related Rocks of the Cascade Range, Oregon

USGS Publications Warehouse

Nimz, Kathryn; Ramsey, David W.; Sherrod, David R.; Smith, James G.

2008-01-01

Since 1979, Earth scientists of the Geothermal Research Program of the U.S. Geological Survey have carried out multidisciplinary research in the Cascade Range. The goal of this research is to understand the geology, tectonics, and hydrology of the Cascades in order to characterize and quantify geothermal resource potential. A major goal of the program is compilation of a comprehensive geologic map of the entire Cascade Range that incorporates modern field studies and that has a unified and internally consistent explanation. This map is one of three in a series that shows Cascade Range geology by fitting published and unpublished mapping into a province-wide scheme of rock units distinguished by composition and age; map sheets of the Cascade Range in Washington (Smith, 1993) and California will complete the series. The complete series forms a guide to exploration and evaluation of the geothermal resources of the Cascade Range and will be useful for studies of volcano hazards, volcanology, and tectonics. This digital release contains all the information used to produce the geologic map published as U.S. Geological Survey Geologic Investigations Series I-2569 (Sherrod and Smith, 2000). The main component of this digital release is a geologic map database prepared using ArcInfo GIS. This release also contains files to view or print the geologic map and accompanying descriptive pamphlet from I-2569.

Active high-resolution seismic tomography of compressional wave velocity and attenuation structure at Medicine Lake Volcano, northern California Cascade Range

USGS Publications Warehouse

Evans, J.R.; Zucca, J.J.

1988-01-01

Medicine Lake volcano is a basalt through rhyolite shield volcano of the Cascade Range, lying east of the range axis. The Pg wave from eight explosive sources which has traveled upward through the target volume to a dense array of 140 seismographs provides 1- to 2-km resolution in the upper 5 to 7 km of the crust beneath the volcano. The experiment tests the hypothesis that Cascade Range volcanoes of this type are underlain only by small silicic magma chambers. We image a low-velocity low-Q region not larger than a few tens of cubic kilometers in volume beneath the summit caldera, supporting the hypothesis. A shallower high-velocity high-density feature, previously known to be present, is imaged for the first time in full plan view; it is east-west elongate, paralleling a topographic lineament between Medicine Lake volcano and Mount Shasta. Differences between this high-velocity feature and the equivalent feature at Newberry volcano, a volcano in central regon resembling Medicine Lake volcano, may partly explain the scarcity of surface hydrothermal features at Medicine Lake volcano. A major low-velocity low-Q feature beneath the southeast flank of the volcano, in an area with no Holocene vents, is interpreted as tephra, flows, and sediments from the volcano deeply ponded on the downthrown side of the Gillem fault. A high-Q normal-velocity feature beneath the north rim of the summit caldera may be a small, possibly hot, subsolidus intrusion. A high-velocity low-Q region beneath the eastern caldera may be an area of boiling water between the magma chamber and the ponded east flank material. -from Authors

Complex delay dynamics of high power quantum cascade oscillators

NASA Astrophysics Data System (ADS)

Grillot, F.; Newell, T. C.; Gavrielides, A.; Carras, M.

2017-08-01

Quantum cascade lasers (QCL) have become the most suitable laser sources from the mid-infrared to the THz range. This work examines the effects of external feedback in different high power mid infrared QCL structures and shows that different conditions of the feedback wave can produce complex dynamics hence stabilization, destabilization into strong mode-competition or undamping nonlinear oscillations. As a dynamical system, reinjection of light back into the cavity also can also provoke apparition of chaotic oscillations, which must be avoided for a stable operation both at mid-infrared and THz wavelengths.

δ18O and δD of lake waters across the Coast Range and Cascades, central Oregon: Modern insights from hydrologically open lakes into the control of landscape on lake water composition in deep time

NASA Astrophysics Data System (ADS)

Finkelstein, D. B.; Curtin, T.

2016-12-01

Reconstructing the stable isotopic composition of paleolake water normally requires an assumption of paleotemperature. However, hydrologically open paleolakes with short water residence times may have recorded paleoprecipitation along topographic gradients that are independent of lake water temperature. To identify the environmental and geographic controls on the isotopic composition of lake water, we sampled 22 natural lakes and reservoirs along a longitudinal and elevation gradient from the Pacific Ocean up and over the Coast and Cascade Ranges of central Oregon to the High Lava Plains in 2013 and 2015. The transect spans lakes of different origins, 6 geomorphic regions and an elevation range of 2-1942 m absl. The Coast Range lakes are sand hosted whereas the remaining are bedrock (volcanic and sedimentary) hosted. The lakes are hydrologically open and dominated by meteoric recharge. The water residence time ranges from months to decades. Samples were analyzed for temperature, pH, and total dissolved solids (TDS) in the field, and alkalinity and major cations and anions and stable isotopes of D and O in the lab. The pH ranges from 7 to 9.8 and shows no systematic variation based on substrate type or elevation. The lakes are dilute (avg. TDS = 35.8 ppm) and have low alkalinties (18.9 mg/L CaCO3) except for those in the High Lava Plains (avg. TDS = 337 ppm, alk: 291.2 mg/L CaCO3). In the Coast Range, Na is the major cation on an equivalent basis, reflecting proximity to the ocean. The easternmost lakes within the Coast Range are dominated by Ca, reflecting different drainage basins and substrate type. Lakes in the Western and High Cascades are dominated by Ca. The dominant cation and stable isotopic analyses clearly differentiate waters from different geomorphic regions. The δ18O ranges from -5.7 to -9.3 ‰ (VSMOW), and δD ranges from -37.8 to -63.6 ‰ (VSMOW) in the Coast Range whereas the δ18O ranges from -9.7 to -12.1 ‰ (VSMOW) and δD ranges from -71.5 to -86.5‰ (VSMOW) in the Cascades. Stable isotopic differences between mountain ranges reflect distance from the ocean and increasing elevation. Stable isotopes of water show no correlation with air or lake water temperatures. Average annual precipitation and bedrock across this topographic gradient controls the major ions and stable isotopic composition of these lakes.

High power, electrically tunable quantum cascade lasers

NASA Astrophysics Data System (ADS)

Slivken, Steven; Razeghi, Manijeh

2016-02-01

Mid-infrared laser sources (3-14 μm wavelengths) which have wide spectral coverage and high output power are attractive for many applications. This spectral range contains unique absorption fingerprints of most molecules, including toxins, explosives, and nerve agents. Infrared spectroscopy can also be used to detect important biomarkers, which can be used for medical diagnostics by means of breath analysis. The challenge is to produce a broadband midinfrared source which is small, lightweight, robust, and inexpensive. We are currently investigating monolithic solutions using quantum cascade lasers. A wide gain bandwidth is not sufficient to make an ideal spectroscopy source. Single mode output with rapid tuning is desirable. For dynamic wavelength selection, our group is developing multi-section laser geometries with wide electrical tuning (hundreds of cm-1). These devices are roughly the same size as a traditional quantum cascade lasers, but tuning is accomplished without any external optical components. When combined with suitable amplifiers, these lasers are capable of multi-Watt single mode output powers. This manuscript will describe our current research efforts and the potential for high performance, broadband electrical tuning with the quantum cascade laser.

Broadly tunable terahertz generation in mid-infrared quantum cascade lasers.

PubMed

Vijayraghavan, Karun; Jiang, Yifan; Jang, Min; Jiang, Aiting; Choutagunta, Karthik; Vizbaras, Augustinas; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus C; Belkin, Mikhail A

2013-01-01

Room temperature, broadly tunable, electrically pumped semiconductor sources in the terahertz spectral range, similar in operation simplicity to diode lasers, are highly desired for applications. An emerging technology in this area are sources based on intracavity difference-frequency generation in dual-wavelength mid-infrared quantum cascade lasers. Here we report terahertz quantum cascade laser sources based on an optimized non-collinear Cherenkov difference-frequency generation scheme that demonstrates dramatic improvements in performance. Devices emitting at 4 THz display a mid-infrared-to-terahertz conversion efficiency in excess of 0.6 mW W(-2) and provide nearly 0.12 mW of peak power output. Devices emitting at 2 and 3 THz fabricated on the same chip display 0.09 and 0.4 mW W(-2) conversion efficiencies at room temperature, respectively. High terahertz-generation efficiency and relaxed phase-matching conditions offered by the Cherenkov scheme allowed us to demonstrate, for the first time, an external-cavity terahertz quantum cascade laser source tunable between 1.70 and 5.25 THz.

High-resolution, large dynamic range fiber-optic thermometer with cascaded Fabry-Perot cavities.

PubMed

Liu, Guigen; Sheng, Qiwen; Hou, Weilin; Han, Ming

2016-11-01

The paradox between a large dynamic range and a high resolution commonly exists in nearly all kinds of sensors. Here, we propose a fiber-optic thermometer based on dual Fabry-Perot interferometers (FPIs) made from the same material (silicon), but with different cavity lengths, which enables unambiguous recognition of the dense fringes associated with the thick FPI over the free-spectral range determined by the thin FPI. Therefore, the sensor combines the large dynamic range of the thin FPI and the high resolution of the thick FPI. To verify this new concept, a sensor with one 200 μm thick silicon FPI cascaded by another 10 μm thick silicon FPI was fabricated. A temperature range of -50°C to 130°C and a resolution of 6.8×10^-3°C were demonstrated using a simple average wavelength tracking demodulation. Compared to a sensor with only the thick silicon FPI, the dynamic range of the hybrid sensor was more than 10 times larger. Compared to a sensor with only the thin silicon FPI, the resolution of the hybrid sensor was more than 18 times higher.

Atomistic material behavior at extreme pressures

DOE PAGES

Beland, Laurent K.; Osetskiy, Yury N.; Stoller, Roger E.

2016-08-05

Computer simulations are routinely performed to model the response of materials to extreme environments, such as neutron (or ion) irradiation. The latter involves high-energy collisions from which a recoiling atom creates a so-called atomic displacement cascade. These cascades involve coordinated motion of atoms in the form of supersonic shockwaves. These shockwaves are characterized by local atomic pressures >15 GPa and interatomic distances <2 Å. Similar pressures and interatomic distances are observed in other extreme environment, including short-pulse laser ablation, high-impact ballistic collisions and diamond anvil cells. Displacement cascade simulations using four different force fields, with initial kinetic energies ranging frommore » 1 to 40 keV, show that there is a direct relationship between these high-pressure states and stable defect production. An important shortcoming in the modeling of interatomic interactions at these short distances, which in turn determines final defect production, is brought to light.« less

Applications of Quantum Cascade Laser Spectroscopy in the Analysis of Pharmaceutical Formulations.

PubMed

Galán-Freyle, Nataly J; Pacheco-Londoño, Leonardo C; Román-Ospino, Andrés D; Hernandez-Rivera, Samuel P

2016-09-01

Quantum cascade laser spectroscopy was used to quantify active pharmaceutical ingredient content in a model formulation. The analyses were conducted in non-contact mode by mid-infrared diffuse reflectance. Measurements were carried out at a distance of 15 cm, covering the spectral range 1000-1600 cm(-1) Calibrations were generated by applying multivariate analysis using partial least squares models. Among the figures of merit of the proposed methodology are the high analytical sensitivity equivalent to 0.05% active pharmaceutical ingredient in the formulation, high repeatability (2.7%), high reproducibility (5.4%), and low limit of detection (1%). The relatively high power of the quantum-cascade-laser-based spectroscopic system resulted in the design of detection and quantification methodologies for pharmaceutical applications with high accuracy and precision that are comparable to those of methodologies based on near-infrared spectroscopy, attenuated total reflection mid-infrared Fourier transform infrared spectroscopy, and Raman spectroscopy. © The Author(s) 2016.

Terahertz quantum-cascade lasers as high-power and wideband, gapless sources for spectroscopy.

PubMed

Röben, Benjamin; Lü, Xiang; Hempel, Martin; Biermann, Klaus; Schrottke, Lutz; Grahn, Holger T

2017-07-10

Terahertz (THz) quantum-cascade lasers (QCLs) are powerful radiation sources for high-resolution and high-sensitivity spectroscopy with a discrete spectrum between 2 and 5 THz as well as a continuous coverage of several GHz. However, for many applications, a radiation source with a continuous coverage of a substantially larger frequency range is required. We employed a multi-mode THz QCL operated with a fast ramped injection current, which leads to a collective tuning of equally-spaced Fabry-Pérot laser modes exceeding their separation. A continuous coverage over 72 GHz at about 4.7 THz was achieved. We demonstrate that the QCL is superior to conventional sources used in Fourier transform infrared spectroscopy in terms of the signal-to-noise ratio as well as the dynamic range by one to two orders of magnitude. Our results pave the way for versatile THz spectroscopic systems with unprecedented resolution and sensitivity across a wide frequency range.

Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States

USGS Publications Warehouse

Ingebritsen, S.E.; Randolph-Flagg, N. G.; Gelwick, K.D.; Lundstrom, E.A.; Crankshaw, I.M.; Murveit, A.M.; Schmidt, M.E.; Bergfeld, D.; Spicer, K.R.; Tucker, D.S.; Mariner, R.H.; Evans, William C.

2014-01-01

Ongoing (1996–present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the US Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade volcanic arc, from Mount Baker near the Canadian border to Lassen Peak in northern California. A concerted effort was made to develop hourly, multiyear records of temperature and/or hydrothermal solute flux, suitable for retrospective comparison with other continuous geophysical monitoring data. Targets included summit fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and/or anomalous fluxes of magmatic CO2 or heat. As of 2009–2012, summit fumarole temperatures in the Cascade Range were generally near or below the local pure water boiling point; the maximum observed superheat was 3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multidecadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in response to the 1980–present eruptive cycle, there is no clear evidence of ongoing long-term trends in hydrothermal activity at other Cascade Range volcanoes that have been active or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range hydrothermal-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more active but generally less accessible volcanoes such as those in the Aleutian arc.

Cascaded-focus laser writing of low-loss waveguides in polymers.

PubMed

Pätzold, Welm M; Reinhardt, Carsten; Demircan, Ayhan; Morgner, Uwe

2016-03-15

Waveguide writing in poly (methyl methacrylate) (PMMA) with femtosecond laser radiation is presented. An adequate refractive index change is induced in the border area below the irradiated focal volume. It supports an almost symmetric fundamental mode with propagation losses down to 0.5  dB/cm, the lowest losses observed so far in this class of materials. The writing process with a cascaded focus is demonstrated to be highly reliable over a large parameter range.

THz Local Oscillator Technology

NASA Technical Reports Server (NTRS)

Mehdi, Imran

2004-01-01

The last decade has seen a number of technological advancements that have now made it possible to implement fully solid state local oscillator chains up to 2 THz. These chains are composed of cascaded planar multiplier stages that are pumped with W-band high power sources. The high power W-band sources are achieved by power combining MMIC amplifiers and can provide in access of 150 mW with about 10% bandwidth. Planar diode technology has also enabled novel circuit topologies that can take advantage of the high input power and demonstrate significant efficiencies well into the THz range. Cascaded chains to 1.9 THz have now been demonstrated with enough output power to successfully pump hot-electron bolometer mixers in this frequency range. An overview of the current State-of-the-Art of the local oscillator technology will be presented along with highlighting future trends and challenges.

Cascades frog conservation assessment

Treesearch

Karen Pope; Catherine Brown; Marc Hayes; Gregory Green; Diane Macfarlane

2014-01-01

The Cascades frog (Rana cascadae) is a montane, lentic-breeding amphibian that has become rare in the southern Cascade Range and remains relatively widespread in the Klamath Mountains of northern California. In the southern Cascades, remaining populations occur primarily in meadow habitats where the fungal disease, chytridiomycosis, and habitat...

Climate change and hydrology in the Blue Mountains [Chapter 3

Treesearch

Caty F. Clifton; Kate T. Day; Kathie Dello; Gordon E. Grant; Jessica E. Halofsky; Daniel J. Isaak; Charles H. Luce; Mohammad Safeeq; Brian P. Staab; John Stevenson

2017-01-01

The dominant influences on climatic patterns in the Pacific Northwest are the Pacific Ocean and the Cascade Range. The diurnal temperature range is higher east of the Cascade crest, further inland from the Pacific Ocean. More precipitation falls west of the Cascade Mountains crest, and a strong rain shadow greatly reduces precipitation east of the crest. The southern...

Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hempel, Martin, E-mail: hempel@pdi-berlin.de; Röben, Benjamin; Schrottke, Lutz

2016-05-09

GaAs-based terahertz quantum-cascade lasers (QCLs) are continuously tuned in their emission frequency by illuminating the rear facet with a near-infrared, high-power diode laser. For QCLs emitting around 3.1 THz, the maximum tuning range amounts to 2.8 GHz for continuous-wave operation at a heat sink temperature of 55 K, while in pulsed mode 9.1 and 8.0 GHz are achieved at 35 and 55 K, respectively.

Facile access to 2-acyloxy-, aryloxy- and alkenyloxy-2H-azirines via an SN2'-SN2' cascade in 2-halo-2H-azirines.

PubMed

Rostovskii, Nikolai V; Smetanin, Ilia A; Agafonova, Anastasiya V; Sakharov, Pavel A; Ruvinskaya, Julia O; Khlebnikov, Alexander F; Novikov, Mikhail S

2018-05-02

Various 2-oxygen-substituted 2H-azirine-2-carboxylic acid derivatives were synthesized in high yields under mild conditions from readily available precursors, 2-halo-2H-azirines and OH-reagents having pKa values in the range of 3-10. This reaction is the first example of substitution at the azirine carbon atom for which an unusual SN2'-SN2' cascade mechanism was revealed.

A Terahertz VRT spectrometer employing quantum cascade lasers

NASA Astrophysics Data System (ADS)

Cole, William T. S.; Hlavacek, Nik C.; Lee, Alan W. M.; Kao, Tsung-Yu; Hu, Qing; Reno, John L.; Saykally, Richard J.

2015-10-01

The first application of a commercial Terahertz quantum cascade laser (QCL) system for high resolution spectroscopy of supersonic beams is presented. The QCLs exhibited continuous linear voltage tuning over a 2 GHz range about a center frequency of 3.762 THz with ∼1 ppm resolution. A sensitivity of ∼1 ppm fractional absorption was measured with a single pass optical system. Multipass operation at the quantum noise limit of the stressed photoconductor detector would produce a 100-fold improvement.

Corneal tissue ablation using 6.1 μm quantum cascade laser

NASA Astrophysics Data System (ADS)

Huang, Yong; Kang, Jin U.

2012-03-01

High absorption property of tissues in the IR range (λ> 2 μm) results in effective tissue ablation, especially near 3 μm. In the mid-infrared range, wavelengths of 6.1 μm and 6.45 μm fall into the absorption bands of the amide protein groups Amide-I and Amide-II, respectively. They also coincide with the deformation mode of water, which has an absorption peak at 6.1 μm. This coincidence makes 6.1 μm laser a better ablation tool that has promising effectiveness and minimum collateral damages than 3 μm lasers. In this work, we performed bovine corneal ablation test in-vitro using high-power 6.1μm quantum cascade laser (QCL) operated at pulse mode. Quantum cascade laser has the advantages of low cost, compact size and tunable wavelength, which makes it great alternative Mid-IR light source to conventional tunable free-electron lasers (FEL) for medical applications. Preliminary results show that effective corneal stroma craters were achieved with much less collateral damage in corneal tissue that contains less water. Future study will focus on optimizing the control parameters of QCL to attain neat and precise ablation of corneal tissue and development of high peak power QCL.

Synthesis of polycyclic spiroindolines by highly diastereoselective interrupted Ugi cascade reactions of 3-(2-isocyanoethyl)indoles.

PubMed

Saya, Jordy M; Oppelaar, Barry; Cioc, Răzvan C; van der Heijden, Gydo; Vande Velde, Christophe M L; Orru, Romano V A; Ruijter, Eelco

2016-10-13

We report a highly diastereoselective interrupted Ugi reaction to construct a broad range of structurally congested and stereochemically complex spiroindolines from tryptamine-derived isocyanides. The reaction is facilitated by using fluorinated alcohols (TFE or HFIP) as solvents and tolerates a broad range of amines, aldehydes and 2-isocyanoethylindoles to give polycyclic products in moderate to excellent yields.

Play-fairway analysis for geothermal resources and exploration risk in the Modoc Plateau region

USGS Publications Warehouse

Siler, Drew; Zhang, Yingqi; Spycher, Nicolas F.; Dobson, Patrick; McClain, James S.; Gasperikova, Erika; Zierenberg, Robert A.; Schiffman, Peter; Ferguson, Colin; Fowler, Andrew; Cantwell, Carolyn

2017-01-01

The region surrounding the Modoc Plateau, encompassing parts of northeastern California, southern Oregon, and northwestern Nevada, lies at an intersection between two tectonic provinces; the Basin and Range province and the Cascade volcanic arc. Both of these provinces have substantial geothermal resource base and resource potential. Geothermal systems with evidence of magmatic heat, associated with Cascade arc magmatism, typify the western side of the region. Systems on the eastern side of the region appear to be fault controlled with heat derived from high crustal heat flow, both of which are typical of the Basin and Range. As it has the potential to host Cascade arc-type geothermal resources, Basin and Range-type geothermal resources, and/or resources with characteristics of both provinces, and because there is relatively little current development, the Modoc Plateau region represents an intriguing potential for undiscovered geothermal resources. It remains unclear however, what specific set(s) of characteristics are diagnostic of Modoc-type geothermal systems and how or if those characteristics are distinct from Basin and Range-type or Cascade arc-type geothermal systems. In order to evaluate the potential for undiscovered geothermal resources in the Modoc area, we integrate a wide variety of existing data in order to evaluate geothermal resource potential and exploration risk utilizing ‘play-fairway’ analysis. We consider that the requisite parameters for hydrothermal circulation are: 1) heat that is sufficient to drive circulation, and 2) permeability that is sufficient to allow for fluid circulation in the subsurface. We synthesize data that indicate the extent and distribution of these parameters throughout the Modoc region. ‘Fuzzy logic’ is used to incorporate expert opinion into the utility of each dataset as an indicator of either heat or permeability, and thus geothermal favorability. The results identify several geothermal prospects, areas that are highly favorable for the occurrence of both heat and permeability. These are also areas where there is sufficient data coverage, quality, and consistency that the exploration risk is relatively low. These unknown, undeveloped, and under-developed prospects are well-suited for continued exploration efforts. The results also indicate to what degree the two ‘play-types,’ i.e. Cascade arc-type or Basin and Range-type, apply to each of the geothermal prospects, a useful guide in exploration efforts.

Diagnostic Characteristics of Submesoscale Coastal Surface Currents

NASA Astrophysics Data System (ADS)

Soh, Hyun Sup; Kim, Sung Yong

2018-03-01

Submesoscale kinetic energy (KE) spectra and fluxes at the length scales ranging from 2 to 25 km are estimated from hourly and O(1) km-scale coastal surface current maps observed from shore-based high-frequency radars off southern San Diego. The one-dimensional wave number-domain KE spectra of the surface currents have decay slopes between k-2 and k-3 at a wave number (k) of 0.5 km-1. The KE spectra exhibit anisotropy associated with anisotropic circulation, which is constrained by the shoreline and bottom bathymetry. Moreover, the KE spectra exhibit weak seasonality related to the regional submesoscale eddies and low-frequency circulation with weak seasonal variability. The estimated KE fluxes are categorized into four cases of purely forward cascades and inverse cascades at all wave numbers, inverse-then-forward cascades with a single zero-crossing within the range of wave numbers (0.04 to 0.5 km-1), and residuals, which account for approximately 33%, 39%, 19%, and 9% of the total number of realizations, respectively. An injection scale where forward enstrophy cascade and inverse energy cascade occur is estimated to be 5 to 10 km from the cases of the inverse-then-forward cascade, which is consistent with the length scales of the regional submesoscale eddies. Thus, the regional submesoscale processes are initiated by surface frontogenesis due to the weak seasonal low-frequency surface circulation and topography-related currents, then maintained by baroclinic instabilities associated with the seasonal mixed layer and O(10) km-scale submesoscale eddies with weak seasonal variability.

Change in extent of meadows and shrub fields in the central western cascade Range, Oregon

Treesearch

Sadao Takaoka; Frederick J. Swanson

2008-01-01

We examined change in areal extent of mountain meadows and fields of deciduous shrubs and conifer saplings in the central western Cascade Range of Oregon, based on analysis of aerial photographs taken in 1946 and 2000. These nonforest vegetation patches are distinctive habitats in dominantly forested landscapes, such as the Cascades, and change in extent of these...

An external-cavity quantum cascade laser operating near 5.2 µm combined with cavity ring-down spectroscopy for multi-component chemical sensing

NASA Astrophysics Data System (ADS)

Dutta Banik, Gourab; Maity, Abhijit; Som, Suman; Pal, Mithun; Pradhan, Manik

2018-04-01

We report on the performance of a widely tunable continuous wave mode-hop-free external-cavity quantum cascade laser operating at λ ~ 5.2 µm combined with cavity ring-down spectroscopy (CRDS) technique for high-resolution molecular spectroscopy. The CRDS system has been utilized for simultaneous and molecule-specific detection of several environmentally and bio-medically important trace molecular species such as nitric oxide, nitrous oxide, carbonyl sulphide and acetylene (C2H2) at ultra-low concentrations by probing numerous rotationally resolved ro-vibrational transitions in the mid-IR spectral region within a relatively small spectral range of ~0.035 cm-1. This continuous wave external-cavity quantum cascade laser-based multi-component CRDS sensor with high sensitivity and molecular specificity promises applications in environmental sensing as well as non-invasive medical diagnosis through human breath analysis.

Performance analysis of a cascaded coding scheme with interleaved outer code

NASA Technical Reports Server (NTRS)

Lin, S.

1986-01-01

A cascaded coding scheme for a random error channel with a bit-error rate is analyzed. In this scheme, the inner code C sub 1 is an (n sub 1, m sub 1l) binary linear block code which is designed for simultaneous error correction and detection. The outer code C sub 2 is a linear block code with symbols from the Galois field GF (2 sup l) which is designed for correcting both symbol errors and erasures, and is interleaved with a degree m sub 1. A procedure for computing the probability of a correct decoding is presented and an upper bound on the probability of a decoding error is derived. The bound provides much better results than the previous bound for a cascaded coding scheme with an interleaved outer code. Example schemes with inner codes ranging from high rates to very low rates are evaluated. Several schemes provide extremely high reliability even for very high bit-error rates say 10 to the -1 to 10 to the -2 power.

Sampling methods for bats.

Treesearch

D.W. Thomas; S.D. West

1989-01-01

Bats represent the second most diverse group of mammals inhabiting the western slopes of the Cascade Range in southern Washington and the Oregon Coast Range. Bat populations may well be sensitive to changes in forest age, structure, or distribution, but their nocturnal habits and high mobility render the study of the habitat requirements of bats problematical. Unlike...

Quantum cascade lasers: from tool to product.

PubMed

Razeghi, M; Lu, Q Y; Bandyopadhyay, N; Zhou, W; Heydari, D; Bai, Y; Slivken, S

2015-04-06

The quantum cascade laser (QCL) is an important laser source in the mid-infrared and terahertz frequency range. The past twenty years have witnessed its tremendous development in power, wall plug efficiency, frequency coverage and tunability, beam quality, as well as various applications based on QCL technology. Nowadays, QCLs can deliver high continuous wave power output up to 5.1 W at room temperature, and cover a wide frequency range from 3 to 300 μm by simply varying the material components. Broadband heterogeneous QCLs with a broad spectral range from 3 to 12 μm, wavelength agile QCLs based on monolithic sampled grating design, and on-chip beam QCL combiner are being developed for the next generation tunable mid-infrared source for spectroscopy and sensing. Terahertz sources based on nonlinear generation in QCLs further extend the accessible wavelength into the terahertz range. Room temperature continuous wave operation, high terahertz power up to 1.9 mW, and wide frequency tunability form 1 to 5 THz makes this type of device suitable for many applications in terahertz spectroscopy, imaging, and communication.

Gamma ray pulsars. [electron-photon cascades

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1977-01-01

Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

Generation of efficient 33 GHz optical combs using cascaded stimulated Brillouin scattering effects in optical fiber

NASA Astrophysics Data System (ADS)

Al-Mansoori, M. H.; Al-Sheriyani, A.; Al-Nassri, S.; Hasoon, F. N.

2017-06-01

In this paper, we demonstrate a multi-wavelength Brillouin-erbium fiber laser (BEFL) with ~33 GHz frequency spacing using cascaded stimulated Brillouin scattering effects in optical fiber. The proposed laser structure exhibits a stable output channel with a tuning range of 19 nm, from 1549 nm to 1568 nm. The number of stable output channels produced is six channels with a triple-Brillouin frequency spacing. The output channels exhibit high output power and high optical signal-to-noise ratios (OSNRs). The laser structure has the potential to be used as a multi-wavelength source for optical communication systems.

Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser.

PubMed

Craig, Ian M; Taubman, Matthew S; Lea, A Scott; Phillips, Mark C; Josberger, Erik E; Raschke, Markus B

2013-12-16

Utilizing a broadly-tunable external cavity quantum cascade laser for scattering-type scanning near-field optical microscopy (s-SNOM), we measure infrared spectra of particles of explosives by probing characteristic nitro-group resonances in the 7.1-7.9 µm wavelength range. Measurements are presented with spectral resolution of 0.25 cm(-1), spatial resolution of 25 nm, sensitivity better than 100 attomoles, and at a rapid acquisition time of 90 s per spectrum. We demonstrate high reproducibility of the acquired s-SNOM spectra with very high signal-to-noise ratios and relative noise of <0.02 in self-homodyne detection.

Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guoping, E-mail: guoping.lin@femto-st.fr; Diallo, Souleymane; Saleh, Khaldoun

2014-12-08

We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

Phase-locked, high power, mid-infrared quantum cascade laser arrays

NASA Astrophysics Data System (ADS)

Zhou, W.; Slivken, S.; Razeghi, M.

2018-04-01

We demonstrate phase-locked, high power quantum cascade laser arrays, which are combined using a monolithic, tree array multimode interferometer, with emission wavelengths around 4.8 μm. A maximum output power of 15 W was achieved from an eight-element laser array, which has only a slightly higher threshold current density and a similar slope efficiency compared to a Fabry-Perot laser of the same length. Calculated multimode interferometer splitting loss is on the order of 0.27 dB for the in-phase supermode. In-phase supermode operation with nearly ideal behavior is demonstrated over the working current range of the array.

Experimental studies on the influence of the degree of turbulence and of a turbulence thread on the compressible subsonic flow through flat compressor cascades

NASA Technical Reports Server (NTRS)

Barsun, K.

1978-01-01

The measurements revealed that at low Reynolds numbers the profile loss is considerably reduced both by the increased degree of turbulence and by a turbulence thread, while it is somewhat increased at high Reynolds numbers, and that a profile loss reduction is connected with an increase in deflection and in pressure shift. The turbulence generator is most effective on the one hand in the middle of the operating range of the cascades, and on the other at very high Mach numbers together with a large angle of incidence.

Southern cascades bioregion

Treesearch

Carl N. Skinner; Alan H. Taylor

2006-01-01

The Cascade Range extends from British Columbia, Canada, south to northern California where it meets the Sierra Nevada. The Southern Cascades bioregion in California is bounded on the west by the Sacramento Valley and the Klamath Mountains, and on the east by the Modoc Plateau and Great Basin. The bioregion encompasses the Southern Cascades section of Miles and Goudey...

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis.

PubMed

Zhao, C; Vassiljev, N; Konstantinidis, A C; Speller, R D; Kanicki, J

2017-03-07

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm -1 ) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

NASA Astrophysics Data System (ADS)

Zhao, C.; Vassiljev, N.; Konstantinidis, A. C.; Speller, R. D.; Kanicki, J.

2017-03-01

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm-1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Energy spectrum of cascades generated by muons in Baksan underground scintillation telescope

NASA Technical Reports Server (NTRS)

Bakatanov, V. N.; Chudakov, A. E.; Novoseltsev, Y. F.; Novoseltseva, M. V.; Achkasov, V. M.; Semenov, A. M.; Stenkin, Y. V.

1985-01-01

Spectrum of cascades generated by cosmic ray muons underground is presented. The mean zenith angle of the muon arrival is theta=35 deg the depth approx. 1000 hg/sq cm. In cascades energy range 700 GeV the measured spectrum is in agreement with the sea-level integral muon spectrum index gamma=3.0. Some decrease of this exponent has been found in the range 4000 Gev.

Frequency and volumes of ignimbrite eruptions following the Late Neogene initiation of the Central Oregon High Cascades

NASA Astrophysics Data System (ADS)

Pitcher, Bradley W.; Kent, Adam J. R.; Grunder, Anita L.; Duncan, Robert A.

2017-06-01

The late Neogene Deschutes Formation of central Oregon preserves a remarkable volcanic and sedimentary record of the initial stages of High Cascades activity following an eastward shift in the locus of volcanism at 7.5 Ma. Numerous ignimbrite and tephra-fall units are contained within the formation, and since equivalent deposits are relatively rare for the Quaternary Cascades, the eruptions of the earliest High Cascade volcanoes were likely more explosive than those of the Quaternary arc. In this study, the timing and frequency of eruptions which produced 14 laterally extensive marker ignimbrites within the Deschutes Formation are established using 40Ar/39Ar geochronology. Plagioclase 40Ar/39Ar ages for the lowermost (6.25 ± 0.07 Ma) and uppermost (5.45 ± 0.04 Ma) marker ignimbrites indicate that all major explosive eruptions within the Deschutes Formation occurred within a period of 800 ± 54 k.y. (95% confidence interval). Minimum estimates for the volumes of the 14 ignimbrites, using an ArcGIS-based method, range from 1.0 to 9.4 km3 and have a total volume of 62.5 km3. Taken over the 50 km of arc length, the explosive volcanic production rate of the central Oregon High Cascades during Deschutes Formation time was a minimum of 1.8 km3/m.y./km of arc length. By including estimates of the volumes of tephra-fall components, as well as ignimbrites that may have traveled west, we estimate a total volume range, for these 14 eruptions alone, of 188 to 363 km3 ( 121 to 227 km3 DRE), a rate of 4.7-9.1 km3/m.y./km arc length. This explosive volcanic production rate is much higher than the average Quaternary eruption rates, of all compositions, estimated for the entire Cascade arc (1.5-2.5), Alaska Peninsula segment of the Aleutian arc (0.6-1.0), and the Andean southern volcanic zone (1.1-2.0). We suggest that this atypical explosive pulse may result from the onset of regional extension and migration of the magmatic arc, which had the combined effect of increasing magmatic flux and temporarily enhancing melting of more fusible crust.

Volcanic signature of Basin and Range extension on the shrinking Cascade arc, Klamath Falls-Keno area, Oregon

NASA Astrophysics Data System (ADS)

Priest, George R.; Hladky, Frank R.; Mertzman, Stanley A.; Murray, Robert B.; Wiley, Thomas J.

2013-08-01

geologic mapping of the Klamath Falls-Keno area revealed the complex relationship between subduction, crustal extension, and magmatic composition of the southern Oregon Cascade volcanic arc. Volcanism in the study area at 7-4 Ma consisted of calc-alkaline basaltic andesite and andesite lava flowing over a relatively flat landscape. Local angular unconformities are evidence that Basin and Range extension began at by at least 4 Ma and continues today with fault blocks tilting at a long-term rate of 2°/Ma to 3°/Ma. Minimum NW-SE extension is 1.5 km over 28 km ( 5%). High-alumina olivine tholeiite (HAOT) or low-K, low-Ti transitional high-alumina olivine tholeiite (LKLT) erupted within and adjacent to the back edge of the calc-alkaline arc as the edge receded westward at a rate of 10 km/Ma at 2.7-0.45 Ma. The volcanic front migrated east much slower than the back arc migrated west: 0 km/Ma for 6-0.4 Ma calc-alkaline rocks; 0.7 km/Ma, if 6 Ma HAOT-LKLT is included; and 1 km/Ma, if highly differentiated 17-30 Ma volcanic rocks of the early Western Cascades are included. Declining convergence probably decreased asthenospheric corner flow, decreasing width of calc-alkaline and HAOT-LKLT volcanism and the associated heat flow anomaly, the margins of which focused on Basin and Range extension and leakage of HAOT-LKLT magma to the surface. This declining corner flow combined with steepening slab dip shifted the back arc west. Compensation of extension by volcanic intrusion and extrusion allowed growth of imposing range-front fault scarps only behind the trailing edge of the shrinking arc.

Achieving comb formation over the entire lasing range of quantum cascade lasers.

PubMed

Yang, Yang; Burghoff, David; Reno, John; Hu, Qing

2017-10-01

Frequency combs based on quantum cascade lasers (QCLs) are finding promising applications in high-speed broadband spectroscopy in the terahertz regime, where many molecules have their "fingerprints." To form stable combs in QCLs, an effective control of group velocity dispersion plays a critical role. The dispersion of the QCL cavity has two main parts: a static part from the material and a dynamic part from the intersubband transitions. Unlike the gain, which is clamped to a fixed value above the lasing threshold, dispersion associated with the intersubband transitions changes with bias, even above the threshold, and this reduces the dynamic range of comb formation. Here, by incorporating tunability into the dispersion compensator, we demonstrate a QCL device exhibiting comb operation from I th to I max , which greatly expands the operation range of the frequency combs.

Comparing Geant4 hadronic models for the WENDI-II rem meter response function.

PubMed

Vanaudenhove, T; Dubus, A; Pauly, N

2013-01-01

The WENDI-II rem meter is one of the most popular neutron dosemeters used to assess a useful quantity of radiation protection, namely the ambient dose equivalent. This is due to its high sensitivity and its energy response that approximately follows the conversion function between neutron fluence and ambient dose equivalent in the range of thermal to 5 GeV. The simulation of the WENDI-II response function with the Geant4 toolkit is then perfectly suited to compare low- and high-energy hadronic models provided by this Monte Carlo code. The results showed that the thermal treatment of hydrogen in polyethylene for neutron <4 eV has a great influence over the whole detector range. Above 19 MeV, both Bertini Cascade and Binary Cascade models show a good correlation with the results found in the literature, while low-energy parameterised models are not suitable for this application.

Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Atäı, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemie`re, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; Malyshev, D.

2014-02-01

Context. Very-high-energy (VHE; E > 100 GeV) γ-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these γ-rays with the extragalactic background light (EBL). Depending on the magnetic fields in the proximity of the source, the cascade initiated from pair production can result in either an isotropic halo around an initially beamed source or a magnetically broadened cascade flux. Aims: Both extended pair-halo (PH) and magnetically broadened cascade (MBC) emission from regions surrounding the blazars 1ES 1101-232, 1ES 0229+200, and PKS 2155-304 were searched for using VHE γ-ray data taken with the High Energy Stereoscopic System (H.E.S.S.) and high-energy (HE; 100 MeV < E < 100 GeV) γ-ray data with the Fermi Large Area Telescope (LAT). Methods: By comparing the angular distributions of the reconstructed γ-ray events to the angular profiles calculated from detailed theoretical models, the presence of PH and MBC was investigated. Results: Upper limits on the extended emission around 1ES 1101-232, 1ES 0229+200, and PKS 2155-304 are found to be at a level of a few per cent of the Crab nebula flux above 1 TeV, depending on the assumed photon index of the cascade emission. Assuming strong extra-Galactic magnetic field (EGMF) values, >10-12 G, this limits the production of pair haloes developing from electromagnetic cascades. For weaker magnetic fields, in which electromagnetic cascades would result in MBCs, EGMF strengths in the range (0.3-3)× 10-15 G were excluded for PKS 2155-304 at the 99% confidence level, under the assumption of a 1 Mpc coherence length.

Cascaded Raman shifting of high-peak-power nanosecond pulses in As₂S₃ and As₂Se₃ optical fibers.

PubMed

White, Richard T; Monro, Tanya M

2011-06-15

We report efficient cascaded Raman scattering of near-IR nanosecond pulses in large-core (65 μm diameter) As₂S₃ and As₂Se₃ optical fibers. Raman scattering dominates other spectral broadening mechanisms, such as four-wave mixing, modulation instability, and soliton dynamics, because the fibers have large normal group-velocity dispersion in the spectral range of interest. With ~2 ns pump pulses at a wavelength of 1.9 μm, four Stokes peaks, all with peak powers greater than 1 kW, have been measured.

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers

PubMed Central

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-01-01

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. PMID:27009375

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers.

PubMed

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-03-24

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06-4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

New Possibilities of Substance Identification Based on THz Time Domain Spectroscopy Using a Cascade Mechanism of High Energy Level Excitation

PubMed Central

Trofimov, Vyacheslav A.; Varentsova, Svetlana A.; Zakharova, Irina G.; Zagursky, Dmitry Yu.

2017-01-01

Using an experiment with thin paper layers and computer simulation, we demonstrate the principal limitations of standard Time Domain Spectroscopy (TDS) based on using a broadband THz pulse for the detection and identification of a substance placed inside a disordered structure. We demonstrate the spectrum broadening of both transmitted and reflected pulses due to the cascade mechanism of the high energy level excitation considering, for example, a three-energy level medium. The pulse spectrum in the range of high frequencies remains undisturbed in the presence of a disordered structure. To avoid false absorption frequencies detection, we apply the spectral dynamics analysis method (SDA-method) together with certain integral correlation criteria (ICC). PMID:29186849

Geomorphological Controls on Fluvial Organic Carbon Storage in Wood and Soil in the Olympic, Cascade, and Rocky Mountains

NASA Astrophysics Data System (ADS)

Scott, D.; Wohl, E.

2017-12-01

The terrestrial organic carbon (OC) pool plays a major role in impacting global climate through the storage and potential release of carbon. In particular, areas of high net primary productivity, such as mountainous regions, and high spatial complexity, such as mountain river floodplains, show potential to act as both strong OC reservoirs and potential OC emitters in a changing climate. We focus on mountain rivers as potential hot swaths of OC storage and, accordingly, as places where land management to retain OC on the landscape may be especially impactful. Mountain river OC storage magnitude and age is a function of the soil and geomorphologic conditions at a reach scale, which are in turn determined by broader characteristics, such as climate, ecology, and tectonics. We present field data on OC storage in soil and wood from three mountain ranges across the western U.S.: the Wind River Range in Wyoming and the Olympic and Central Cascade Ranges in Washington. While the Big Sandy River basin in the Wind River Range exhibits relatively low relief, a semi-arid climate, and a fire-mediated disturbance regime, the Middle Fork Snoqualmie basin in the Cascades and the Sitkum and South Fork Calawah basins in the Olympics exhibit high relief and a humid climate. In contrast to the Olympics, the study basin in the Cascades exhibits strong longitudinal disconnectivity in the form of glaciogenic lakes, whereas the study basins in the Olympics lack large depositional zones that can store sediment for long periods of time. With our expansive dataset of OC storage magnitude and age in downed wood and soil from these three disparate regions, covering a wide range of tectonic, geomorphic, climatic, and ecologic variability, we are able to evaluate both the magnitude and age of the mountain river carbon pool as well as the factors that control that magnitude and age. We present a statistical model that illuminates the dominant controls on the magnitude and age of OC storage in mountain rivers. Using this, we broadly examine mountain river carbon storage dynamics with the goal of allowing land managers to prioritize and focus management efforts to retain OC on the landscape.

Temperature-insensitive long-wavelength (λ ≈14 µm) Quantum Cascade lasers with low threshold.

PubMed

Huang, Xue; Charles, William O; Gmachl, Claire

2011-04-25

We demonstrate high-performance, long-wavelength (λ ≈14 µm) Quantum Cascade (QC) lasers based on a diagonal optical transition and a "two-phonon-continuum" depletion scheme in which the lower laser level is depopulated by resonant longitudinal optical phonon scattering followed by scattering to a lower energy level continuum. A 2.8 mm long QC laser shows a low threshold current density of 2.0 kA/cm2, a peak output power of ~336 mW, and a slope efficiency of 375 mW/A, all at 300 K, with a high characteristic temperature T0 ~310 K over a wide temperature range from 240 K to 390 K.

Effect of an increase in the density of collision cascades on the efficiency of the generation of primary displacements during the ion bombardment of Si

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karabeshkin, K. V., E-mail: yanikolaus@yandex.ru; Karaseov, P. A.; Titov, A. I.

2016-08-15

The depth distributions of structural damage induced in Si at room temperature by the implantation of P and PF{sub 4} with energies from 0.6 to 3.2 keV/amu are experimentally studied in a wide range of doses. It is found that, in all cases, the implantation of molecular PF{sub 4} ions forms practically single-mode defect distributions, with maximum at the target surface. This effect is caused by an increase in the generation of primary defects at the surface of the target. Individual cascades formed by atoms comprising molecule effectively overlap in the surface vicinity; this overlap gives rise to nonlinear processesmore » in combined cascades due to a high density of displacements in such cascades. Quantitative estimation of increase of effectiveness of point defect generation by PF{sub 4} ions in respect to P ions is done on the base of experimental data.« less

Endwall Heat Transfer Measurements in a Transonic Turbine Cascade

NASA Technical Reports Server (NTRS)

Giel, P. W.; Thurman, D. R.; VanFossen, G. J.; Hippensteele, S. A.; Boyle, R. J.

1996-01-01

Turbine blade endwall heat transfer measurements are given for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 x 106, for isentropic exit Mach numbers of 1.0 and 1.3, and for freestream turbulence intensities of 0.25% and 7.0%. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136' of turning and an axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for computational fluid dynamics (CFD) code and model verification. The flow field in the cascade is highly three-dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique.

A cascaded coding scheme for error control and its performance analysis

NASA Technical Reports Server (NTRS)

Lin, S.

1986-01-01

A coding scheme for error control in data communication systems is investigated. The scheme is obtained by cascading two error correcting codes, called the inner and the outer codes. The error performance of the scheme is analyzed for a binary symmetric channel with bit error rate epsilon < 1/2. It is shown that, if the inner and outer codes are chosen properly, extremely high reliability can be attained even for a high channel bit error rate. Various specific example schemes with inner codes ranging from high rates to very low rates and Reed-Solomon codes are considered, and their probabilities are evaluated. They all provide extremely high reliability even for very high bit error rates, say 0.1 to 0.01. Several example schemes are being considered by NASA for satellite and spacecraft down link error control.

A cascaded coding scheme for error control and its performance analysis

NASA Technical Reports Server (NTRS)

Lin, Shu; Kasami, Tadao; Fujiwara, Tohru; Takata, Toyoo

1986-01-01

A coding scheme is investigated for error control in data communication systems. The scheme is obtained by cascading two error correcting codes, called the inner and outer codes. The error performance of the scheme is analyzed for a binary symmetric channel with bit error rate epsilon <1/2. It is shown that if the inner and outer codes are chosen properly, extremely high reliability can be attained even for a high channel bit error rate. Various specific example schemes with inner codes ranging form high rates to very low rates and Reed-Solomon codes as inner codes are considered, and their error probabilities are evaluated. They all provide extremely high reliability even for very high bit error rates. Several example schemes are being considered by NASA for satellite and spacecraft down link error control.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys.

PubMed

Lu, Chenyang; Jin, Ke; Béland, Laurent K; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M; Stoller, Roger E; Wang, Lumin

2016-02-01

Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

PubMed Central

Lu, Chenyang; Jin, Ke; Béland, Laurent K.; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M.; Stoller, Roger E.; Wang, Lumin

2016-01-01

Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance. PMID:26829570

Temperature insensitive curvature sensor based on cascading photonic crystal fiber

NASA Astrophysics Data System (ADS)

Fu, Guangwei; Li, Yunpu; Fu, Xinghu; Jin, Wa; Bi, Weihong

2018-03-01

A temperature insensitive curvature sensor is proposed based on cascading photonic crystal fiber. Using the arc fusion splicing method, this sensor is fabricated by cascading together a single-mode fiber (SMF), a three layers air holes structure of photonic crystal fiber (3PCF), a five layers air holes structure of photonic crystal fiber (5PCF) and a SMF in turn. So the structure SMF-3PCF-5PCF-SMF can be obtained with a total length of 20 mm. During the process of fabrication, the splicing machine parameters and the length of each optical fiber are adjusted to obtain a high sensitivity curvature sensor. The experimental results show that the curvature sensitivity is -8.40 nm/m-1 in the curvature variation range of 0-1.09 m-1, which also show good linearity. In the range of 30-90 °C, the temperature sensitivity is only about 3.24 pm/°C, indicating that the sensor is not sensitive to temperature. The sensor not only has the advantages of easy fabricating, simple structure, high sensitivity but also can solve the problem of temperature measurement cross sensitivity, so it can be used for different areas including aerospace, large-scale bridge, architectural structure health monitoring and so on.

Screening douglas-fir for rapid early growth in common-garden tests in spain. Forest Service general technical report (Final)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez, G.T.; Alonso, G.V.; Arribas, G.P.

1993-08-01

Douglas-firs from 91 seed sources in North America were evaluated after 5 and 6 years in 15 common-garden tests in the mountainous regions of northwest and north central Spain. Analyses of tallest trees showed that most of the sources of highest potential for reforestation in Spain are found in regions where the Pacific Ocean air mass dominates climate. Fast growers came from coastal slopes of the Coast Ranges from northwest California to the Georgia Strait of southwest British Columbia and inland slopes of the Olympic Mountains and Coast and Cascade Ranges facing the Puget Trough in western Washington and Willamettemore » Valley in northwest Oregon. Slow growers came from latitudes south of 44 deg and north of 50 deg, high altitudes west of the crest of the Cascade Ranges, and regions east of the crest where the continental air mass dominated climate.« less

Hydrothermal heat discharge in the Cascade Range, northwestern United States

USGS Publications Warehouse

Ingebritsen, S.E.; Mariner, R.H.

2010-01-01

Hydrothermal heat discharge in the Cascade Range includes the heat discharged by thermal springs, by "slightly thermal" springs that are only a few degrees warmer than ambient temperature, and by fumaroles. Thermal-spring heat discharge is calculated on the basis of chloride-flux measurements and geothermometer temperatures and totals ~ 240 MW in the U.S. part of the Cascade Range, excluding the transient post-1980 discharge at Mount St. Helens (~80 MW as of 2004-5). Heat discharge from "slightly thermal" springs is based on the degree of geothermal warming (after correction for gravitational potential energy effects) and totals ~. 660. MW. Fumarolic heat discharge is calculated by a variety of indirect and direct methods and totals ~160 MW, excluding the transient mid-1970s discharge at Mount Baker (~80 MW) and transient post-1980 discharge at Mount St. Helens (>. 230. MW as of 2005). Other than the pronounced transients at Mount St. Helens and Mount Baker, hydrothermal heat discharge in the Cascade Range appears to be fairly steady over a ~25-year period of measurement. Of the total of ~. 1050. MW of "steady" hydrothermal heat discharge identified in the U.S. part of the Cascade Range, less than 50. MW occurs north of latitude 45??15' N (~0.1 MW per km arc length from 45??15' to 49??N). Much greater rates of hydrothermal heat discharge south of 45??15'N (~1.7 MW per km arc length from 40?? to 45??15'N) may reflect the influence of Basin and Range-style extensional tectonics (faulting) that impinges on the Cascades as far north as Mount Jefferson but is not evident farther north. ?? 2010.

Lakes: recent research and restoration strategies

Treesearch

Karen L. Pope; Jonathan W. Long

2014-01-01

The Sierra Nevada and southern Cascade Range support thousands of montane lakes, from small, remote tarns to iconic destinations such as Lake Tahoe. Their beauty and recreational opportunities instill high social value, in particular by serving as destinations for hiking, camping, swimming, and fishing. Lakes also have high ecological value because they support a...

Self-starting harmonic frequency comb generation in a quantum cascade laser

NASA Astrophysics Data System (ADS)

Kazakov, Dmitry; Piccardo, Marco; Wang, Yongrui; Chevalier, Paul; Mansuripur, Tobias S.; Xie, Feng; Zah, Chung-en; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2017-12-01

Optical frequency combs1,2 establish a rigid phase-coherent link between microwave and optical domains and are emerging as high-precision tools in an increasing number of applications3. Frequency combs with large intermodal spacing are employed in the field of microwave photonics for radiofrequency arbitrary waveform synthesis4,5 and for the generation of terahertz tones of high spectral purity in future wireless communication networks6,7. Here, we demonstrate self-starting harmonic frequency comb generation with a terahertz repetition rate in a quantum cascade laser. The large intermodal spacing caused by the suppression of tens of adjacent cavity modes originates from a parametric contribution to the gain due to temporal modulations of population inversion in the laser8,9. Using multiheterodyne self-detection, the mode spacing of the harmonic comb is shown to be uniform to within 5 × 10-12 parts of the central frequency. This new harmonic comb state extends the range of applications of quantum cascade laser frequency combs10-13.

Recent progress of quantum cascade laser research from 3 to 12  μm at the Center for Quantum Devices [Invited].

PubMed

Razeghi, Manijeh; Zhou, Wenjia; Slivken, Steven; Lu, Quan-Yong; Wu, Donghai; McClintock, Ryan

2017-11-01

The quantum cascade laser (QCL) is becoming the leading laser source in the mid-infrared (mid-IR) range, which contains two atmospheric transmission windows and many molecular fingerprint absorption features. Since its first demonstration in 1994, the QCL has undergone tremendous development in terms of the output power, wall plug efficiency, wavelength coverage, tunability and beam quality. At the Center for Quantum Devices, we have demonstrated high-power continuous wave operation of QCLs covering a wide wavelength range from 3 to 12 μm, with power output up to 5.1 W at room temperature. Recent research has resulted in power scaling in pulsed mode with up to 203 W output, electrically tunable QCLs based on monolithic sampled grating design, heterogeneous QCLs with a broad spectral gain, broadly tunable on-chip beam-combined QCLs, QCL-based mid-IR frequency combs, and fundamental mode surface emitting quantum cascade ring lasers. The developed QCLs will be the basis for a number of next-generation spectroscopy and sensing systems.

Research publications of the H.J. Andrews Experimental Forest, Cascade Range, Oregon: 1988 supplement.

Treesearch

T. Blinn; F.J. Swanson; A. McKee

1988-01-01

This bibliography updates the list of publications, abstracts, theses, and unpublished reports included in "Research Publications of the H.J. Andrews Experimental Forest, Cascade Range, Oregon, 1948 to 1986," General Technical Report PNW-GTR-201. Citations are referenced under appropriate keywords.

Nonconservative and reverse spectral transfer in Hasegawa-Mima turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terry, P.W.; Newman, D.E.

1993-01-01

The dual cascade is generally represented as a conservative cascade of enstrophy to short wavelengths through an enstrophy similarity range and an inverse cascade of energy to long wavelengths through an energy similarity range. This picture, based on a proof due to Kraichnan [Phys. Fluids 10, 1417 (1967)], is found to be significantly modified for a spectra of finite extent. Dimensional arguments and direct measurement of spectral flow in Hasegawa-Mima turbulence indicate that for both the energy and enstrophy cascades, transfer of the conserved quantity is accompanied by a nonconservative transfer of the other quantity. The decrease of a givenmore » invariant (energy or enstrophy) in the nonconservative transfer in one similarity range is balanced by the increase of that quantity in the other similarity range, thus maintaining net invariance. The increase or decrease of a given invariant quantity in one similarity range depends on the injection scale and is consistent with that quantity being carried in a self-similar transfer of the other invariant quantity. This leads, in an inertial range of finite size, to some energy being carried to small scales and some enstrophy being carried to large scales.« less

Nonconservative and reverse spectral transfer in Hasegawa--Mima turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terry, P.W.; Newman, D.E.

1993-07-01

The dual cascade is generally represented as a conservative cascade of enstrophy to short wavelengths through an enstrophy similarity range and an inverse cascade of energy to long wavelengths through an energy similarity range. This picture, based on a proof due to Kraichnan [Phys. Fluids [bold 10], 1417 (1967)], is found to be significantly modified for spectra of finite extent. Dimensional arguments and direct measurement of spectral flow in Hasegawa--Mima turbulence indicate that for both the energy and enstrophy cascades, transfer of the conserved quantity is accompanied by a nonconservative transfer of the other quantity. The decrease of a givenmore » invariant (energy or enstrophy) in the nonconservative transfer in one similarity range is balanced by the increase of that quantity in the other similarity range, thus maintaining net invariance. The increase or decrease of a given invariant quantity in one similarity range depends on the injection scale and is consistent with that quantity being carried in a self-similar transfer of the other invariant quantity. This leads, in an inertial range of finite size, to some energy being carried to small scales and some enstrophy being carried to large scales.« less

High power continuous operation of a widely tunable quantum cascade laser with an integrated amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slivken, S.; Sengupta, S.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu

2015-12-21

Wide electrical tuning and high continuous output power is demonstrated from a single mode quantum cascade laser emitting at a wavelength near 4.8 μm. This is achieved in a space efficient manner by integrating an asymmetric sampled grating distributed feedback tunable laser with an optical amplifier. An initial demonstration of high peak power operation in pulsed mode is demonstrated first, with >5 W output over a 270 nm (113 cm{sup −1}) spectral range. Refinement of the geometry leads to continuous operation with a single mode spectral coverage of 300 nm (120 cm{sup −1}) and a maximum continuous power of 1.25 W. The output beam is shown tomore » be nearly diffraction-limited, even at high amplifier current.« less

Biomedical terahertz imaging with a quantum cascade laser

NASA Astrophysics Data System (ADS)

Kim, Seongsin M.; Hatami, Fariba; Harris, James S.; Kurian, Allison W.; Ford, James; King, Douglas; Scalari, Giacomo; Giovannini, Marcella; Hoyler, Nicolas; Faist, Jerome; Harris, Geoff

2006-04-01

We present biomedical imaging using a single frequency terahertz imaging system based on a low threshold quantum cascade laser emitting at 3.7THz (λ=81μm). With a peak output power of 4mW, coherent terahertz radiation and detection provide a relatively large dynamic range and high spatial resolution. We study image contrast based on water/fat content ratios in different tissues. Terahertz transmission imaging demonstrates a distinct anatomy in a rat brain slice. We also demonstrate malignant tissue contrast in an image of a mouse liver with developed tumors, indicating potential use of terahertz imaging for probing cancerous tissues.

Cascade Classification with Adaptive Feature Extraction for Arrhythmia Detection.

PubMed

Park, Juyoung; Kang, Mingon; Gao, Jean; Kim, Younghoon; Kang, Kyungtae

2017-01-01

Detecting arrhythmia from ECG data is now feasible on mobile devices, but in this environment it is necessary to trade computational efficiency against accuracy. We propose an adaptive strategy for feature extraction that only considers normalized beat morphology features when running in a resource-constrained environment; but in a high-performance environment it takes account of a wider range of ECG features. This process is augmented by a cascaded random forest classifier. Experiments on data from the MIT-BIH Arrhythmia Database showed classification accuracies from 96.59% to 98.51%, which are comparable to state-of-the art methods.

Multilayer heterostructures for quantum-cascade lasers operating in the terahertz frequency range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhukov, A. E., E-mail: Zhukale@gmail.com; Cirlin, G. E.; Reznik, R. R.

2016-05-15

The results obtained in a study of the structural and optical properties of GaAs/AlGaAs heterostructures with 228 quantum cascades, grown by molecular-beam epitaxy, and in a simulation of interband optical transitions and transitions between the energy levels of a cascade are presented.

Trophic cascades: linking ungulates to shrub-dependent birds and butterflies.

PubMed

J Teichman, Kristine; Nielsen, Scott E; Roland, Jens

2013-11-01

1. Studies demonstrating trophic cascades through the loss of top-down regulatory processes in productive and biologically diverse terrestrial ecosystems are limited. 2. Elk Island National Park, Alberta and surrounding protected areas have a wide range of ungulate density due to the functional loss of top predators, management for high ungulate numbers and variable hunting pressure. This provides an ideal setting for studying the effects of hyper-abundant ungulates on vegetation and shrub-dependent bird and butterfly species. 3. To examine the cascading effects of high ungulate density, we quantified vegetation characteristics and abundances of yellow warbler Dendroica petechia and Canadian tiger swallowtail Papilio canadensis under different ungulate density in and around Elk Island National Park. 4. Using Structural Equation Models we found that ungulate density was inversely related to shrub cover, whereas shrub cover was positively related to yellow warbler abundance. In addition, chokecherry Prunus virginiana abundance was inversely related to browse impact but positively related to P. canadensis abundance. 5. These results demonstrate a cascade resulting from hyper-abundant ungulates on yellow warblers and Canadian tiger swallowtails through reductions in shrub cover and larval host plant density. The combined effect of the functional loss of top predators and management strategies that maintain high ungulate numbers can decouple top-down regulation of productive temperate ecosystems. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Cascade-based attacks on complex networks

NASA Astrophysics Data System (ADS)

Motter, Adilson E.; Lai, Ying-Cheng

2002-12-01

We live in a modern world supported by large, complex networks. Examples range from financial markets to communication and transportation systems. In many realistic situations the flow of physical quantities in the network, as characterized by the loads on nodes, is important. We show that for such networks where loads can redistribute among the nodes, intentional attacks can lead to a cascade of overload failures, which can in turn cause the entire or a substantial part of the network to collapse. This is relevant for real-world networks that possess a highly heterogeneous distribution of loads, such as the Internet and power grids. We demonstrate that the heterogeneity of these networks makes them particularly vulnerable to attacks in that a large-scale cascade may be triggered by disabling a single key node. This brings obvious concerns on the security of such systems.

Cascade Synthesis of Five-Membered Lactones using Biomass-Derived Sugars as Carbon Nucleophiles.

PubMed

Yamaguchi, Sho; Matsuo, Takeaki; Motokura, Ken; Miyaji, Akimitsu; Baba, Toshihide

2016-06-06

We report the cascade synthesis of five-membered lactones from a biomass-derived triose sugar, 1,3-dihydroxyacetone, and various aldehydes. This achievement provides a new synthetic strategy to generate a wide range of valuable compounds from a single biomass-derived sugar. Among several examined Lewis acid catalysts, homogeneous tin chloride catalysts exhibited the best performance to form carbon-carbon bonds. The scope and limitations of the synthesis of five-membered lactones using aldehyde compounds are investigated. The cascade reaction led to high product selectivity as well as diastereoselectivity, and the mechanism leading to the diastereoselectivity was discussed based on isomerization experiments and density functional theory (DFT) calculations. The present results are expected to support new approaches for the efficient utilization of biomass-derived sugars. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jet Flap Stator Blade Test in the High Reaction Turbine Blade Cascade Tunnel

NASA Image and Video Library

1970-03-21

A researcher examines the setup of a jet flap blade in the High Reaction Turbine Blade Cascade Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis researchers were seeking ways to increase turbine blade loading on aircraft engines in an effort to reduce the overall size and weight of engines. The ability of each blade to handle higher loads meant that fewer stages and fewer blades were required. This study analyzed the performance of a turbine blade using a jet flap and high loading. A jet of air was injected into the main stream from the pressure surface near the trailing edge. The jet formed an aerodynamic flap which deflected the flow and changed the circulation around the blade and thus increased the blade loading. The air jet also reduced boundary layer thickness. The jet-flap blade design was appealing because the cooling air may also be used for the jet. The performance was studied in a two-dimensional cascade including six blades. The researcher is checking the jet flat cascade with an exit survey probe. The probe measured the differential pressure that was proportional to the flow angle. The blades were tested over a range of velocity ratios and three jet flow conditions. Increased jet flow improved the turning and decreased both the weight flow and the blade loading. However, high blade loadings were obtained at all jet flow conditions.

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades in Magnetized Weakly Collisional Plasmas

NASA Astrophysics Data System (ADS)

Schekochihin, A. A.; Cowley, S. C.; Dorland, W.; Hammett, G. W.; Howes, G. G.; Quataert, E.; Tatsuno, T.

2009-05-01

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulent motions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvénic fluctuations and a passive cascade of density and magnetic-field-strength fluctuations. The former are governed by the reduced magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvénic component (in the collisional limit, these compressive fluctuations become the slow and entropy modes of the conventional MHD). In the "dissipation range" below ion gyroscale, there are again two cascades: the kinetic-Alfvén-wave (KAW) cascade governed by two fluid-like electron reduced magnetohydrodynamic (ERMHD) equations and a passive cascade of ion entropy fluctuations both in space and velocity. The latter cascade brings the energy of the inertial-range fluctuations that was Landau-damped at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAW energy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for all of these cascades. The relationship between the theoretical models proposed in this paper and astrophysical applications and observations is discussed in detail.

First search for extraterrestrial neutrino-induced cascades with IceCube

DOE Office of Scientific and Technical Information (OSTI.GOV)

IceCube Collaboration; Kiryluk, Joanna

2009-05-22

We report on the first search for extraterrestrial neutrino-induced cascades in IceCube.The analyzed data were collected in the year 2007 when 22 detector strings were installed and operated. We will discuss the analysis methods used to reconstruct cascades and to suppress backgrounds. Simulated neutrino signal events with a E-2 energy spectrum, which pass the background rejection criteria, are reconstructed with a resolution Delta(log E) ~;; 0.27 in the energy range from ~;; 20 TeV to a few PeV. We present the range of the diffuse flux of extra-terrestrial neutrinos in the cascade channel in IceCube within which we expect tomore » be able to put a limit.« less

High power and single mode quantum cascade lasers.

PubMed

Bismuto, Alfredo; Bidaux, Yves; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Rochat, Michel; Muller, Antoine; Bonzon, Christopher; Faist, Jerome

2016-05-16

We present a single mode quantum cascade laser with nearly 1 W optical power. A buried distributed feedback reflector is used on the back section for wavelength selection. The laser is 6 mm long, 3.5 μm wide, mounted episide-up and the laser facets are left uncoated. Laser emission is centered at 4.68 μm. Single-mode operation with a side mode suppression ratio of more than 30 dB is obtained in whole range of operation. Farfield measurements prove a symmetric, single transverse-mode emission in TM00-mode with typical divergences of 41° and 33° in the vertical and horizontal direction respectively. This work shows the potential for simple fabrication of high power lasers compatible with standard DFB processing.

Submillimeter sources for radiometry using high power Indium Phosphide Gunn diode oscillators

NASA Technical Reports Server (NTRS)

Deo, Naresh C.

1990-01-01

A study aimed at developing high frequency millimeter wave and submillimeter wave local oscillator sources in the 60-600 GHz range was conducted. Sources involved both fundamental and harmonic-extraction type Indium Phosphide Gunn diode oscillators as well as varactor multipliers. In particular, a high power balanced-doubler using varactor diodes was developed for 166 GHz. It is capable of handling 100 mW input power, and typically produced 25 mW output power. A high frequency tripler operating at 500 GHz output frequency was also developed and cascaded with the balanced-doubler. A dual-diode InP Gunn diode combiner was used to pump this cascaded multiplier to produce on the order of 0.5 mW at 500 GHz. In addition, considerable development and characterization work on InP Gunn diode oscillators was carried out. Design data and operating characteristics were documented for a very wide range of oscillators. The reliability of InP devices was examined, and packaging techniques to enhance the performance were analyzed. A theoretical study of a new class of high power multipliers was conducted for future applications. The sources developed here find many commercial applications for radio astronomy and remote sensing.

Real-time terahertz digital holography with a quantum cascade laser

PubMed Central

Locatelli, Massimiliano; Ravaro, Marco; Bartalini, Saverio; Consolino, Luigi; Vitiello, Miriam S.; Cicchi, Riccardo; Pavone, Francesco; De Natale, Paolo

2015-01-01

Coherent imaging in the THz range promises to exploit the peculiar capabilities of these wavelengths to penetrate common materials like plastics, ceramics, paper or clothes with potential breakthroughs in non-destructive inspection and quality control, homeland security and biomedical applications. Up to now, however, THz coherent imaging has been limited by time-consuming raster scanning, point-like detection schemes and by the lack of adequate coherent sources. Here, we demonstrate real-time digital holography (DH) at THz frequencies exploiting the high spectral purity and the mW output power of a quantum cascade laser combined with the high sensitivity and resolution of a microbolometric array. We show that, in a one-shot exposure, phase and amplitude information of whole samples, either in reflection or in transmission, can be recorded. Furthermore, a 200 times reduced sensitivity to mechanical vibrations and a significantly enlarged field of view are observed, as compared to DH in the visible range. These properties of THz DH enable unprecedented holographic recording of real world dynamic scenes. PMID:26315647

Nanoparticle Enhancement Cascade for Sensitive Multiplex Measurements of Biomarkers in Complex Fluids with Surface Plasmon Resonance Imaging.

PubMed

Hendriks, Jan; Stojanovic, Ivan; Schasfoort, Richard B M; Saris, Daniël B F; Karperien, Marcel

2018-06-05

There is a large unmet need for reliable biomarker measurement systems for clinical application. Such systems should meet challenging requirements for large scale use, including a large dynamic detection range, multiplexing capacity, and both high specificity and sensitivity. More importantly, these requirements need to apply to complex biological samples, which require extensive quality control. In this paper, we present the development of an enhancement detection cascade for surface plasmon resonance imaging (SPRi). The cascade applies an antibody sandwich assay, followed by neutravidin and a gold nanoparticle enhancement for quantitative biomarker measurements in small volumes of complex fluids. We present a feasibility study both in simple buffers and in spiked equine synovial fluid with four cytokines, IL-1β, IL-6, IFN-γ, and TNF-α. Our enhancement cascade leads to an antibody dependent improvement in sensitivity up to 40 000 times, resulting in a limit of detection as low as 50 fg/mL and a dynamic detection range of more than 7 logs. Additionally, measurements at these low concentrations are highly reliable with intra- and interassay CVs between 2% and 20%. We subsequently showed this assay is suitable for multiplex measurements with good specificity and limited cross-reactivity. Moreover, we demonstrated robust detection of IL-6 and IL-1β in spiked undiluted equine synovial fluid with small variation compared to buffer controls. In addition, the availability of real time measurements provides extensive quality control opportunities, essential for clinical applications. Therefore, we consider this method is suitable for broad application in SPRi for multiplex biomarker detection in both research and clinical settings.

Science synthesis to support socioecological resilience in the Sierra Nevada and southern Cascade Range

Treesearch

Jonathan W. Long; Lenya Quinn-Davidson; Carl N. Skinner

2014-01-01

A team of scientists integrated recent research to inform forest managers, stakeholders, and interested parties concerned with promoting socioecological resilience in the Sierra Nevada, southern Cascade Range, and Modoc Plateau. Among the focal topics were forest and fire ecology; soils; aquatic ecosystems; forest carnivores including Pacific fisher, marten, and...

Results of seismological monitoring in the Cascade Range 1962-1989: earthquakes, eruptions, avalanches and other curiosities

USGS Publications Warehouse

Weaver, C.S.; Norris, R.D.; Jonientz-Trisler, C.

1990-01-01

Modern monitoring of seismic activity at Cascade Range volcanoes began at Longmire on Mount Rainier in 1958. Since then, there has been an expansion of the regional seismic networks in Washington, northern Oregon and northern California. Now, the Cascade Range from Lassen Peak to Mount Shasta in the south and Newberry Volcano to Mount Baker in the north is being monitored for earthquakes as small as magnitude 2.0, and many of the stratovolcanoes are monitored for non-earthquake seismic activity. This monitoring has yielded three major observations. First, tectonic earthquakes are concentrated in two segments of the Cascade Range between Mount Rainier and Mount Hood and between Mount Shasta and Lassen Peak, whereas little seismicity occurs between Mount Hood and Mount Shasta. Second, the volcanic activity and associated phenomena at Mount St. Helens have produced intense and widely varied seismicity. And third, at the northern stratovolcanoes, signals generated by surficial events such as debris flows, icequakes, steam emissions, rockfalls and icefalls are seismically recorded. Such records have been used to alert authorities of dangerous events in progress. -Authors

Active standoff detection of CH4 and N2O leaks using hard-target backscattered light using an open-path quantum cascade laser sensor

NASA Astrophysics Data System (ADS)

Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

2016-05-01

Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they contribute to the global increase of greenhouse gas concentrations. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents standoff detection of CH4 and N2O leaks using a quantum cascade laser open-path system that retrieves path-averaged concentrations by collecting the backscattered light from a remote hard target. It is a true standoff system and differs from other open-path systems that are deployed as point samplers or long-path transmission systems that use retroreflectors. The measured absorption spectra are obtained using a thermal intra-pulse frequency chirped DFB quantum cascade laser at ~7.7 µm wavelength range with ~200 ns pulse width. Making fast time resolved observations, the system simultaneously realizes high spectral resolution and range to the target, resulting in path-averaged concentration retrieval. The system performs measurements at high speed ~15 Hz and sufficient range (up to 45 m, ~148 feet) achieving an uncertainty of 3.1 % and normalized sensitivity of 3.3 ppm m Hz-1/2 for N2O and 9.3 % and normalized sensitivity of 30 ppm m Hz-1/2 for CH4 with a 0.31 mW average power QCL. Given these characteristics, this system is promising for mobile or multidirectional search and remote detection of gas leaks.

Living With Volcanic Risk in the Cascades

USGS Publications Warehouse

Dzurisin, Daniel; Stauffer, Peter H.; Hendley, James W.

1997-01-01

The Cascade Range of the Pacific Northwest has more than a dozen potentially active volcanoes. Cascade volcanoes tend to erupt explosively, and on average two eruptions occur per century?the most recent were at Mount St. Helens, Washington (1980?86 and 2004?8), and Lassen Peak, California (1914?17). To help protect the Pacific Northwest?s rapidly expanding population, USGS scientists at the Cascades Volcano Observatory in Vancouver, Washington, monitor and assess the hazards posed by the region?s volcanoes.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

DOE PAGES

Lu, Chenyang; Jin, Ke; Béland, Laurent K.; ...

2016-02-01

We report that energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters farmore » exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.« less

Glimpses of Kolmogorov's spectral energy dynamics in nonlinear acoustic waves

NASA Astrophysics Data System (ADS)

Gupta, Prateek; Scalo, Carlo

2017-11-01

Gupta, Lodato, and Scalo (AIAA 2017) have demonstrated the existence of an equilibrium spectral energy cascade in shock waves formed as a result of continued modal thermoacoustic amplification consistent with Kolmogorov's theory for high-Reynolds-number hydrodynamic turbulence. In this talk we discuss the derivation of a perturbation energy density norm that guarantees energy conservation during the nonlinear wave steepening process, analogous to inertial subrange turbulent energy cascade dynamics. The energy cascade is investigated via a bi-spectral analysis limited to wave-numbers and frequencies lower than the ones associated with the shock, analogous to the viscous dissipation length scale in turbulence. The proposed norm is derived by recombining second-order nonlinear acoustic equations and is positive definite; moreover, it decays to zero in the presence of viscous dissipation and is hence classifiable as a Lyapunov function of acoustic perturbation variables. The cumulative energy spectrum wavenumber distribution demonstrates a -3/2 decay law in the inertial range. The governing equation for the thus-derived energy norm highlights terms responsible for energy cascade towards higher harmonics, analogous to vortex stretching terms in hydrodynamic turbulence.

Terahertz metasurface quantum-cascade VECSELs: theory and performance

DOE PAGES

Xu, Luyao; Curwen, Christopher; Chen, Daguan; ...

2017-04-12

A longstanding challenge for terahertz quantum-cascade (QC) lasers is achieving both a high power and high-quality beam pattern, this is due in part due to their use of sub-wavelength metallic waveguides. Recently, the vertical-external-cavity surface-emitting laser (VECSEL) concept was demonstrated for the first time in the terahertz range and for a QC-laser. This is enabled by the development of an amplifying metasurface reflector capable of coupling incident free-space THz radiation to the QC-laser material such that it is amplified and re-radiated. The THz metasurface QC-VECSEL initiates a new approach for making QC-lasers with high power and excellent beam pattern. Furthermore,more » the ability to engineer the electromagnetic phase, amplitude, and polarization response of the metasurface enables lasers with new functionality. Our article provides an overview of the fundamental theory, design considerations, and recent results for high-performance THz QC-VECSELs.« less

A cascaded silicon Raman laser

NASA Astrophysics Data System (ADS)

Rong, Haisheng; Xu, Shengbo; Cohen, Oded; Raday, Omri; Lee, Mindy; Sih, Vanessa; Paniccia, Mario

2008-03-01

One of the major advantages of Raman lasers is their ability to generate coherent light in wavelength regions that are not easily accessible with other conventional types of lasers. Recently, efficient Raman lasing in silicon in the near-infrared region has been demonstrated, showing great potential for realizing low-cost, compact, room-temperature lasers in the mid-infrared region. Such lasers are highly desirable for many applications, ranging from trace-gas sensing, environmental monitoring and biomedical analysis, to industrial process control, and free-space communications. Here we report the first experimental demonstration of cascaded Raman lasing in silicon, opening the path to extending the lasing wavelength from the near- to mid-infrared region. Using a 1,550-nm pump source, we achieve stable, continuous-wave, second-order cascaded lasing at 1,848 nm with an output power exceeding 5 mW. The laser operates in single mode, and the laser linewidth is measured to be <2.5 MHz.

Enhancement of Fast Face Detection Algorithm Based on a Cascade of Decision Trees

NASA Astrophysics Data System (ADS)

Khryashchev, V. V.; Lebedev, A. A.; Priorov, A. L.

2017-05-01

Face detection algorithm based on a cascade of ensembles of decision trees (CEDT) is presented. The new approach allows detecting faces other than the front position through the use of multiple classifiers. Each classifier is trained for a specific range of angles of the rotation head. The results showed a high rate of productivity for CEDT on images with standard size. The algorithm increases the area under the ROC-curve of 13% compared to a standard Viola-Jones face detection algorithm. Final realization of given algorithm consist of 5 different cascades for frontal/non-frontal faces. One more thing which we take from the simulation results is a low computational complexity of CEDT algorithm in comparison with standard Viola-Jones approach. This could prove important in the embedded system and mobile device industries because it can reduce the cost of hardware and make battery life longer.

Ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation.

PubMed

Guo, Changlei; Che, Kaijun; Cai, Zhiping; Liu, Shuai; Gu, Guoqiang; Chu, Chengxu; Zhang, Pan; Fu, Hongyan; Luo, Zhengqian; Xu, Huiying

2015-11-01

We experimentally demonstrate an ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation in a high-Q silica microsphere resonator. The threshold of the Brillouin microlaser is as low as 8 μW, which is close to the theoretical prediction. Moreover, the fifth-order Stokes line with a frequency shift up to 55 GHz is achieved with a coupled pump power of less than 0.6 mW. Benefiting from resonant wavelength shifts driven by thermal dynamics in the microsphere, we further realized tunable microwave signals with tuning ranges of 40 MHz at an 11 GHz band and 20 MHz at a 22 GHz band. To the best of our knowledge, it was the first attempt for tunable microwave source based on the whispering-gallery-mode Brillouin microlaser. Such a tunable microwave source from a cascaded Brillouin microlaser could find significant applications in aerospace, communication engineering, and metrology.

Cascaded lattice Boltzmann method with improved forcing scheme for large-density-ratio multiphase flow at high Reynolds and Weber numbers.

PubMed

Lycett-Brown, Daniel; Luo, Kai H

2016-11-01

A recently developed forcing scheme has allowed the pseudopotential multiphase lattice Boltzmann method to correctly reproduce coexistence curves, while expanding its range to lower surface tensions and arbitrarily high density ratios [Lycett-Brown and Luo, Phys. Rev. E 91, 023305 (2015)PLEEE81539-375510.1103/PhysRevE.91.023305]. Here, a third-order Chapman-Enskog analysis is used to extend this result from the single-relaxation-time collision operator, to a multiple-relaxation-time cascaded collision operator, whose additional relaxation rates allow a significant increase in stability. Numerical results confirm that the proposed scheme enables almost independent control of density ratio, surface tension, interface width, viscosity, and the additional relaxation rates of the cascaded collision operator. This allows simulation of large density ratio flows at simultaneously high Reynolds and Weber numbers, which is demonstrated through binary collisions of water droplets in air (with density ratio up to 1000, Reynolds number 6200 and Weber number 440). This model represents a significant improvement in multiphase flow simulation by the pseudopotential lattice Boltzmann method in which real-world parameters are finally achievable.

Illustrating harvest effects on site microclimate in a high-elevation forest stand.

Treesearch

W.B. Fowler; T.D. Anderson

1987-01-01

Three-dimensional contour surfaces were drawn for physiologically active radiation (PAR) and air and soil temperatures from measurements taken at a high-elevation site (1450 m) near the crest of the Cascade Range in central Washington. Measurements in a clearcut were compared with measurements from an adjacent uncut stand. Data for 31 days in July and August 1985...

Accurate classical short-range forces for the study of collision cascades in Fe–Ni–Cr

DOE PAGES

Béland, Laurent Karim; Tamm, Artur; Mu, Sai; ...

2017-05-10

The predictive power of a classical molecular dynamics simulation is largely determined by the physical validity of its underlying empirical potential. In the case of high-energy collision cascades, it was recently shown that correctly modeling interactions at short distances is necessary to accurately predict primary damage production. An ab initio based framework is introduced for modifying an existing embedded-atom method FeNiCr potential to handle these short-range interactions. Density functional theory is used to calculate the energetics of two atoms approaching each other, embedded in the alloy, and to calculate the equation of state of the alloy as it is compressed.more » The pairwise terms and the embedding terms of the potential are modi ed in accordance with the ab initio results. Using this reparametrized potential, collision cascades are performed in Ni 50Fe 50, Ni 80Cr 20 and Ni 33Fe 33Cr 33. The simulations reveal that alloying Ni and NiCr to Fe reduces primary damage production, in agreement with some previous calculations. Alloying Ni and NiFe to Cr does not reduce primary damage production, in contradiction with previous calculations.« less

Regeneration in mixed conifer and Douglas-fir shelterwood cuttings in the Cascade Range of Washington.

Treesearch

K.W. Seidel

1983-01-01

A survey of shelterwood cuttings in mixed conifer and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests in the Cascade Range in Washington showed that, on the average, shelterwood units were adequately-stocked with a mixture of advance, natural postharvest, and planted reproduction of a number of species. Shelterwood cuttings in the...

Breeding birds in riparian and upland dry forests of the Cascade Range

Treesearch

John F. Lehmkuhl; E. Dorsey Burger; Emily K. Drew; John P. Lindsey; Maryellen Haggard; Kent Z. Woodruff

2007-01-01

We quantified breeding bird abundance, diversity, and indicator species in riparian and upland dry forests along six third- to fourth-order streams on the east slope of the Cascade Range, Washington, USA. Upland mesic forest on southerly aspects was dominated by open ponderosa pine (Pinus ponderosa) and dry Douglas-fir (Pseudotsuga menziesii...

Snag dynamics in chronosequence of 26 wildfires on the east slope of the Cascade Range in Washington state, USA.

Treesearch

Richard L. Everett; John Lehmkuhl; Richard Schellhaas; [and others].

1999-01-01

Sang numbers and decay class were measured on a chronosequence of 26 wildfires (ages 1-81 years) on the east slope of the Cascade Range in Washington. Snag longevity and resultant snag densities varied spatially across burns in relation to micro-topographic position. Longevity of snags Picea...

Associations of the Van Dyke's salamander (Plethodon vandykei) with geomorphic conditions in headwall seeps of the Cascade Range, Washington State.

Treesearch

A.P. McIntyre; R.A. Schmitz; C.M. Crisafulli

2006-01-01

We explored the association between Van Dyke's salamander (Plethodon vandykei) and hydrologic condition, geomorphology, and vegetation structure in headwall seeps in the Cascade Range of Washington State. We modeled occurrence of P. vandykei at three site scales: between seeps, within seeps, and between microhabitat sites...

Estimating historical snag density in dry forests east of the Cascade Range

Treesearch

Richy J. Harrod; William L. Gaines; William E. Hartl; Ann. Camp

1998-01-01

Estimating snag densities in pre-European settlement landscapes (i.e., historical conditions) provides land managers with baseline information for comparing current snag densities. We propose a method for determining historical snag densities in the dry forests east of the Cascade Range. Basal area increase was calculated from tree ring measurements of old ponderosa...

Lumley's energy cascade dissipation rate model for boundary-free turbulent shear flows

NASA Technical Reports Server (NTRS)

Duncan, B. S.

1992-01-01

True dissipation occurs mainly at the highest wavenumbers where the eddy sizes are comparatively small. These high wavenumbers receive their energy through the spectral cascade of energy starting with the largest eddies spilling energy into the smaller eddies, passing through each wavenumber until it is dissipated at the microscopic scale. However, a small percentage of the energy does not spill continuously through the cascade but is instantly passed to the higher wavenumbers. Consequently, the smallest eddies receive a certain amount of energy almost immediately. As the spectral energy cascade continues, the highest wavenumber needs a certain time to receive all the energy which has been transferred from the largest eddies. As such, there is a time delay, of the order of tau, between the generation of energy by the largest eddies and the eventual dissipation of this energy. For equilibrium turbulence at high Reynolds numbers, there is a wide range where energy is neither produced by the large eddies nor dissipated by viscosity, but is conserved and passed from wavenumber to higher wavenumbers. The rate at which energy cascades from one wavenumber to another is proportional to the energy contained within that wavenumber. This rate is constant and has been used in the past as a dissipation rate of turbulent kinetic energy. However, this is true only in steady, equilibrium turbulence. Most dissipation models contend that the production of dissipation is proportional to the production of energy and that the destruction of dissipation is proportional to the destruction of energy. In essence, these models state that the change in the dissipation rate is proportional to the change in the kinetic energy. This assumption is obviously incorrect for the case where there is no production of turbulent energy, yet energy continues to cascade from large to small eddies. If the time lag between the onset on the energy cascade to the destruction of energy at the microscale can be modeled, then there will be a better representation of the dissipation process. Development of an energy cascade time scale equation is discussed.

MOVPE Growth of LWIR AlInAs/GaInAs/InP Quantum Cascade Lasers: Impact of Growth and Material Quality on Laser Performance

DTIC Science & Technology

2017-02-01

MOVPE Growth of LWIR AlInAs/GaInAs/InP Quantum Cascade Lasers: Impact of Growth and Material Quality on Laser Performance (Invited paper) Christine A...epitaxial layers in quantum cascade lasers (QCLs) has a primary impact on QCL operation, and establishing correlations between epitaxial growth and materials...QCLs emitting in this range. Index terms – Quantum cascade lasers, semiconductor growth, semiconductor epitaxial layers, infrared emitters. I

Analysis of the Exhumation Pathways Experienced in the Cascades Range

NASA Astrophysics Data System (ADS)

Giles, S. M.; Pesek, M.; Perez, N. D.

2017-12-01

The Cascades volcanic arc is the result of subduction of the Juan de Fuca plate beneath North America. The Cascades trend north to south and create a modern orographic precipitation gradient that focuses precipitation along the western flank of the range. However, the deformation style changes from shortening in the north to extension in the south. This experimental design is an ideal location to test how surface and tectonic processes contribute to rock uplift in orogens. In the Oregon Cascades, zircon U-Pb geochronology, and multiple thermochronologic techniques (apatite U-Pb, zircon U-Th/He) will be applied to an intrusive rock exposed along a west-flowing river to investigate the exhumation pathway. These intrusive rocks are capped by late Miocene basalt flows, constraining the timing of surface exposure. The results of this study will define a time-temperature pathway and be compared with existing exhumation constraints from the Washington Cascades to determine whether the exhumation pathways may correspond to the changing structural regimes or consistent climate patterns along strike.

Synthesis of Enantioenriched Indolines by a Conjugate Addition/Asymmetric Protonation/Aza-Prins Cascade Reaction

PubMed Central

Daniels, Blake E.; Ni, Jane; Reisman, Sarah E.

2016-01-01

A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3’-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl4•BINOL complex serves as a chiral Lewis acid-assisted Brønsted acid. PMID:26844668

Demystifying the PeV cascades in IceCube: Less (energy) is more (events)

NASA Astrophysics Data System (ADS)

Laha, Ranjan; Beacom, John F.; Dasgupta, Basudeb; Horiuchi, Shunsaku; Murase, Kohta

2013-08-01

The IceCube neutrino observatory has detected two cascade events with energies near 1 PeV [A. Ishihara Proceedings of Neutrino 2012 Conference, http://neu2012.kek.jp/index.html; M. Aartsen et al. (IceCube Collaboration) Phys. Rev. Lett. 111, 021103 (2013)]. Without invoking new physics, we analyze the source of these neutrinos. We show that atmospheric conventional neutrinos and cosmogenic neutrinos (those produced in the propagation of ultra-high-energy cosmic rays) are strongly disfavored. For atmospheric prompt neutrinos or a diffuse background of neutrinos produced in astrophysical objects, the situation is less clear. We show that there is tension with observed data, but that the details depend on the least-known aspects of the IceCube analysis. Very likely, prompt neutrinos are disfavored and astrophysical neutrinos are plausible. We demonstrate that the fastest way to reveal the origin of the observed PeV neutrinos is to search for neutrino cascades in the range below 1 PeV, for which dedicated analyses with high sensitivity have yet to appear, and where many more events could be found.

Accumulation of dislocation loops in the α phase of Zr Excel alloy under heavy ion irradiation

NASA Astrophysics Data System (ADS)

Yu, Hongbing; Yao, Zhongwen; Idrees, Yasir; Zhang, He K.; Kirk, Mark A.; Daymond, Mark R.

2017-08-01

In-situ heavy ion irradiations were performed on the high Sn content Zr alloy 'Excel', measuring type dislocation loop accumulation up to irradiation damage doses of 10 dpa at a range of temperatures. The high content of Sn, which diffuses slowly, and the thin foil geometry of the sample provide a unique opportunity to study an extreme case where displacement cascades dominate the loop formation and evolution. The dynamic observation of dislocation loop evolution under irradiation at 200 °C reveals that type dislocation loops can form at very low dose (0.0025 dpa). The size of the dislocation loops increases slightly with irradiation damage dose. The mechanism controlling loop growth in this study is different from that in neutron irradiation; in this study, larger dislocation loops can condense directly from the interaction of displacement cascades and the high concentration of point defects in the matrix. The size of the dislocation loop is dependent on the point defect concentration in the matrix. A negative correlation between the irradiation temperature and the dislocation loop size was observed. A comparison between cascade dominated loop evolution (this study), diffusion dominated loop evolution (electron irradiation) and neutron irradiation suggests that heavy ion irradiation alone may not be enough to accurately reproduce neutron irradiation induced loop structures. An alternative method is proposed in this paper. The effects of Sn on the displacement cascades, defect yield, and the diffusion behavior of point defects are established.

Innovative mid-infrared detector concepts

NASA Astrophysics Data System (ADS)

Höfling, Sven; Pfenning, Andreas; Weih, Robert; Ratajczak, Albert; Hartmann, Fabian; Knebl, Georg; Kamp, Martin; Worschech, Lukas

2016-09-01

Gas sensing is a key technology with applications in various industrial, medical and environmental areas. Optical detection mechanisms allow for a highly selective, contactless and fast detection. For this purpose, rotational-vibrational absorption bands within the mid infrared (MIR) spectral region are exploited and probed with appropriate light sources. During the past years, the development of novel laser concepts such as interband cascade lasers (ICLs) and quantum cascade lasers (QCLs) has driven a continuous optimization of MIR laser sources. On the other hand side, there has been relatively little progress on detectors in this wavelength range. Here, we study two novel and promising GaSb-based detector concepts: Interband cascade detectors (ICD) and resonant tunneling diode (RTD) photodetectors. ICDs are a promising approach towards highly sensitive room temperature detection of MIR radiation. They make use of the cascading scheme that is enabled by the broken gap alignment of the two binaries GaSb and InAs. The interband transition in GaSb/InAs-superlattices (SL) allows for normal incidence detection. The cut-off wavelength, which determines the low energy detection limit, can be engineered via the SL period. RTD photodetectors act as low noise and high speed amplifiers of small optically generated electrical signals. In contrast to avalanche photodiodes, where the gain originates from multiplication due to impact ionization, in RTD photodetectors a large tunneling current is modulated via Coulomb interaction by the presence of photogenerated minority charge carriers. For both detector concepts, first devices operational at room temperature have been realized.

Height growth and site index curves for managed even-aged stands of ponderosa pine in the Pacific Northwest

Treesearch

James W. Barrett

1978-01-01

This paper presents height growth and site index curves and equations for even-aged, managed stands of ponderosa pine east of the Cascade Range in Oregon and Washington where height growth has not been suppressed by high density or related factors.

Source of seed fluctuations for electromagnetic ion cyclotron waves in Earth's magnetosphere

NASA Astrophysics Data System (ADS)

Gamayunov, K. V.; Engebretson, M. J.; Zhang, M.; Rassoul, H. K.

2015-06-01

We consider a nonlinear wave energy cascade from the low frequency range into the higher frequency domain of electromagnetic ion cyclotron (EMIC) wave generation as a possible source of seed fluctuations for EMIC wave growth due to the ion cyclotron instability in Earth's magnetosphere. The presented theoretical analysis shows that energy cascade from the Pc 4-5 frequency range (2-22 mHz) into the range of Pc 1-2 pulsations (0.1-5 Hz), i.e. into the frequency range of EMIC waves, is able to supply the needed level of seed fluctuations that guarantees growth of EMIC waves up to the observable level during one pass through the near equatorial region where the ion cyclotron instability takes place. We also analyze the magnetic field data from the Polar and Van Allen Probes spacecraft to test the suggested nonlinear mechanism. In this initial study we restrict our analysis to magnetic fluctuation spectra only. We do not analyze the third-order structure function, but judge whether a nonlinear energy cascade is present or whether it is not by only analyzing the appearance of power-law distributions in the low-frequency part of the magnetic field spectra. While the power-law spectrum alone does not guarantee that a nonlinear cascade is present, the power-law distribution is a strong indication of the possible development of a nonlinear cascade. Our analysis shows that a nonlinear energy cascade is indeed observed in both the outer and inner magnetosphere data, and EMIC waves are growing from this nonthermal background. All the analyzed data are in good agreement with the theoretical model presented in this study. Overall, the results of this study support a nonlinear energy cascade in Earth's magnetosphere as a mechanism which is responsible for supplying seed fluctuating energy in the higher frequency domain where EMIC waves grow due to the ion cyclotron instability.

Volcano geodesy in the Cascade arc, USA

NASA Astrophysics Data System (ADS)

Poland, Michael P.; Lisowski, Michael; Dzurisin, Daniel; Kramer, Rebecca; McLay, Megan; Pauk, Ben

2017-08-01

Experience during historical time throughout the Cascade arc and the lack of deep-seated deformation prior to the two most recent eruptions of Mount St. Helens might lead one to infer that Cascade volcanoes are generally quiescent and, specifically, show no signs of geodetic change until they are about to erupt. Several decades of geodetic data, however, tell a different story. Ground- and space-based deformation studies have identified surface displacements at five of the 13 major Cascade arc volcanoes that lie in the USA (Mount Baker, Mount St. Helens, South Sister, Medicine Lake, and Lassen volcanic center). No deformation has been detected at five volcanoes (Mount Rainier, Mount Hood, Newberry Volcano, Crater Lake, and Mount Shasta), and there are not sufficient data at the remaining three (Glacier Peak, Mount Adams, and Mount Jefferson) for a rigorous assessment. In addition, gravity change has been measured at two of the three locations where surveys have been repeated (Mount St. Helens and Mount Baker show changes, while South Sister does not). Broad deformation patterns associated with heavily forested and ice-clad Cascade volcanoes are generally characterized by low displacement rates, in the range of millimeters to a few centimeters per year, and are overprinted by larger tectonic motions of several centimeters per year. Continuous GPS is therefore the best means of tracking temporal changes in deformation of Cascade volcanoes and also for characterizing tectonic signals so that they may be distinguished from volcanic sources. Better spatial resolution of volcano deformation can be obtained through the use of campaign GPS, semipermanent GPS, and interferometric synthetic aperture radar observations, which leverage the accumulation of displacements over time to improve signal to noise. Deformation source mechanisms in the Cascades are diverse and include magma accumulation and withdrawal, post-emplacement cooling of recent volcanic deposits, magmatic-tectonic interactions, and loss of volatiles plus densification of magma. The Cascade Range thus offers an outstanding opportunity for investigating a wide range of volcanic processes. Indeed, there may be areas of geodetic change that have yet to be discovered, and there is good potential for addressing a number of important questions about how arc volcanoes work before, during, and after eruptions by continuing geodetic research in the Cascade Range.

Volcano geodesy in the Cascade arc, USA

USGS Publications Warehouse

Poland, Michael; Lisowski, Michael; Dzurisin, Daniel; Kramer, Rebecca; McLay, Megan; Pauk, Benjamin

2017-01-01

Experience during historical time throughout the Cascade arc and the lack of deep-seated deformation prior to the two most recent eruptions of Mount St. Helens might lead one to infer that Cascade volcanoes are generally quiescent and, specifically, show no signs of geodetic change until they are about to erupt. Several decades of geodetic data, however, tell a different story. Ground- and space-based deformation studies have identified surface displacements at five of the 13 major Cascade arc volcanoes that lie in the USA (Mount Baker, Mount St. Helens, South Sister, Medicine Lake, and Lassen volcanic center). No deformation has been detected at five volcanoes (Mount Rainier, Mount Hood, Newberry Volcano, Crater Lake, and Mount Shasta), and there are not sufficient data at the remaining three (Glacier Peak, Mount Adams, and Mount Jefferson) for a rigorous assessment. In addition, gravity change has been measured at two of the three locations where surveys have been repeated (Mount St. Helens and Mount Baker show changes, while South Sister does not). Broad deformation patterns associated with heavily forested and ice-clad Cascade volcanoes are generally characterized by low displacement rates, in the range of millimeters to a few centimeters per year, and are overprinted by larger tectonic motions of several centimeters per year. Continuous GPS is therefore the best means of tracking temporal changes in deformation of Cascade volcanoes and also for characterizing tectonic signals so that they may be distinguished from volcanic sources. Better spatial resolution of volcano deformation can be obtained through the use of campaign GPS, semipermanent GPS, and interferometric synthetic aperture radar observations, which leverage the accumulation of displacements over time to improve signal to noise. Deformation source mechanisms in the Cascades are diverse and include magma accumulation and withdrawal, post-emplacement cooling of recent volcanic deposits, magmatic-tectonic interactions, and loss of volatiles plus densification of magma. The Cascade Range thus offers an outstanding opportunity for investigating a wide range of volcanic processes. Indeed, there may be areas of geodetic change that have yet to be discovered, and there is good potential for addressing a number of important questions about how arc volcanoes work before, during, and after eruptions by continuing geodetic research in the Cascade Range.

Crustal structure along the west flank of the Cascades, western Washington

USGS Publications Warehouse

Miller, K.C.; Keller, Gordon R.; Gridley, J.M.; Luetgert, J.H.; Mooney, W.D.; Thybo, H.

1997-01-01

Knowledge of the crustal structure of the Washington Cascades and adjacent Puget Lowland is important to both earthquake hazards studies and geologic studies of the evolution of this tectonically active region. We present a model for crustal velocity structure derived from analysis of seismic refraction/wide-angle reflection data collected in 1991 in western Washington. The 280-km-long north-south transect skirts the west flank of the Cascades as it crosses three tectonic provinces including the Northwest Cascades Thrust System (NWCS), the Puget Lowland, and the volcanic arc of the southern Cascades. Within the NWCS, upper crustal velocities range from 4.2 to 5.7 km s-1 and are consistent with the presence of a diverse suite of Mesozoic and Paleozoic metasediments and metavolcanics. In the upper 2-3 km of the Puget Lowland velocities drop to 1.7-3.5 km s-1 and reflect the occurrence of Oligocene to recent sediments within the basin. In the southern Washington Cascades, upper crustal velocities range from 4.0 to 5.5 km s-1 and are consistent with a large volume of Tertiary sediments and volcanics. A sharp change in velocity gradient at 5-10 km marks the division between the upper and middle crust. From approximately 10 to 35 km depth the velocity field is characterized by a velocity increase from ???6.0 to 7.2 km s-1. These high velocities do not support the presence of marine sedimentary rocks at depths of 10-20 km beneath the Cascades as previously proposed on the basis of magnetotelluric data. Crustal thickness ranges from 42 to 47 km along the profile. The lowermost crust consists of a 2 to 8-km-thick transitional layer with velocities of 7.3-7.4 km s-1. The upper mantle velocity appears to be an unusually low 7.6-7.8 km s-1. When compared to velocity models from other regions, this model most closely resembles those found in active continental arcs. Distinct seismicity patterns can be associated with individual tectonic provinces along the seismic transect. In the NWCS and Puget Lowland, most of the seismicity occurs below the base of the upper crust as defined by a seismic boundary at 5-10 km depth and continues to 20-30 km depth. The region of transition between the NWCS and the Puget Lowland appears as a gap in seismicity with notably less seismic activity north of the boundary between the two. Earthquakes within the Cascades are generally shallower (0-20 km) and are dominated by events associated with the Rainier Seismic Zone. Copyright 1997 by the American Geophysical Union.

Seed zones and breeding zones for white pine in the Cascade Range of Washington and Oregon.

Treesearch

Robert K. Campbell; Albert I. Sugano

1989-01-01

Provisional seed zones and breeding zones were developed for white pine (Pinus monticola Dougl. ex D. Don) in the Cascade Range of western Washington and Oregon. Recommendations were based on genetic variation patterns obtained by evaluating genotypes of trees from 115 locations. Genotypes controlling growth vigor and growth rhythm were assessed in...

Nest reuse by Northern Spotted Owls on the east slope of the Cascade Range, Washington

Treesearch

Stan G. Sovern; Margaret Taylor; Eric D. Forsman

2011-01-01

During a long-term demography study of Northern Spotted Owls (Strix occidentalis caurina) in the eastern Cascade Range of Washington State in 1989 to 2008, we documented 276 nests of Northern Spotted Owls at 73 different territories. Of these nests, 90.2% were on platforms, mostly in clumps of deformed limbs caused by dwarf mistletoe (primarily...

Riparian and upland small mammals on the east slope of the Cascade Range, Washington

Treesearch

John F. Lehmkuhl; Roger D. Peffer; Margaret A. O' Connell

2008-01-01

Differences in small mammal diversity and abundance between riparian and upland areas have not been consistently shown in the Pacific Northwest, and the issue is expected to be complex along the east slope of the Cascade Range with its complex biogeography and forest landscape structure. The information is important for evaluating buffer zone management and the...

Regeneration in mixed conifer shelterwood cuttings in the Cascade Range of eastern Oregon.

Treesearch

K.W. Seidel

1979-01-01

A survey of shelterwood cuttings in mixed conifer forests in the eastern Oregon Cascade Range showed that, on the average, shelterwood units were well stocked with a mixture of advance, natural subsequent, and planted reproduction of a number of species. Because of slow invasion by understory vegetation, frequent heavy seed crops, and adequate density of the overstory...

Response of ground-dwelling spider assemblages to prescribed fire following stand structure manipulation in the southern Cascade Range

Treesearch

Nancy E. Gillette; Richard S. Vetter; Sylvia R. Mori; Carline R. Rudolph; Dessa R. Welty

2008-01-01

We assessed spider (Arachnida: Araneae) responses to prescribed fire following stand s tructure treatments in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) stands in the Cascade Range of California. Stands were logged or left untreated to create three levels of structural diversity. We logged one treatment to minimize old-growth...

Historical effects of logging on forests of the Cascade and Sierra Nevada ranges of California

Treesearch

William F. Laudenslayer; Herman H. Darr

1990-01-01

Ponderosa pine, Jeffrey pine, mixed conifer, and white fir forests of the Cascade and Sierra Nevada Ranges of California have been important resources and were extensively altered by timber harvest between 1850 and 1950. Many historical logging operations were small in size and of short duration. Other operations encompassed thousands of acres and existed for...

Forest fuel reduction alters fire severity and long-term carbon storage in three Pacific Northwest ecosystems.

PubMed

Mitchell, Stephen R; Harmon, Mark E; O'Connell, Kari E B

2009-04-01

Two forest management objectives being debated in the context of federally managed landscapes in the U.S. Pacific Northwest involve a perceived trade-off between fire restoration and carbon sequestration. The former strategy would reduce fuel (and therefore C) that has accumulated through a century of fire suppression and exclusion which has led to extreme fire risk in some areas. The latter strategy would manage forests for enhanced C sequestration as a method of reducing atmospheric CO2 and associated threats from global climate change. We explored the trade-off between these two strategies by employing a forest ecosystem simulation model, STANDCARB, to examine the effects of fuel reduction on fire severity and the resulting long-term C dynamics among three Pacific Northwest ecosystems: the east Cascades ponderosa pine forests, the west Cascades western hemlock-Douglas-fir forests, and the Coast Range western hemlock-Sitka spruce forests. Our simulations indicate that fuel reduction treatments in these ecosystems consistently reduced fire severity. However, reducing the fraction by which C is lost in a wildfire requires the removal of a much greater amount of C, since most of the C stored in forest biomass (stem wood, branches, coarse woody debris) remains unconsumed even by high-severity wildfires. For this reason, all of the fuel reduction treatments simulated for the west Cascades and Coast Range ecosystems as well as most of the treatments simulated for the east Cascades resulted in a reduced mean stand C storage. One suggested method of compensating for such losses in C storage is to utilize C harvested in fuel reduction treatments as biofuels. Our analysis indicates that this will not be an effective strategy in the west Cascades and Coast Range over the next 100 years. We suggest that forest management plans aimed solely at ameliorating increases in atmospheric CO2 should forgo fuel reduction treatments in these ecosystems, with the possible exception of some east Cascades ponderosa pine stands with uncharacteristic levels of understory fuel accumulation. Balancing a demand for maximal landscape C storage with the demand for reduced wildfire severity will likely require treatments to be applied strategically throughout the landscape rather than indiscriminately treating all stands.

Efficient generation of 1.9  W yellow light by cascaded frequency doubling of a distributed Bragg reflector tapered diode.

PubMed

Hansen, A K; Christensen, M; Noordegraaf, D; Heist, P; Papastathopoulos, E; Loyo-Maldonado, V; Jensen, O B; Skovgaard, P M W

2016-11-10

Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K. At the same time, the use of a laser diode enables the modulation of the pump wavelength by controlling the drive current. This is utilized to achieve a power modulation depth above 90% for the second harmonic light, with a rise time below 40  μs.

Primary radiation damage of Zr-0.5%Nb binary alloy: atomistic simulation by molecular dynamics method

NASA Astrophysics Data System (ADS)

Tikhonchev, M.; Svetukhin, V.; Kapustin, P.

2017-09-01

Ab initio calculations predict high positive binding energy (˜1 eV) between niobium atoms and self-interstitial configurations in hcp zirconium. It allows the expectation of increased niobium fraction in self-interstitials formed under neutron irradiation in atomic displacement cascades. In this paper, we report the results of molecular dynamics simulation of atomic displacement cascades in Zr-0.5%Nb binary alloy and pure Zr at the temperature of 300 K. Two sets of n-body interatomic potentials have been used for the Zr-Nb system. We consider a cascade energy range of 2-20 keV. Calculations show close estimations of the average number of produced Frenkel pairs in the alloy and pure Zr. A high fraction of Nb is observed in the self-interstitial configurations. Nb is mainly detected in single self-interstitial configurations, where its fraction reaches tens of percent, i.e. more than its tenfold concentration in the matrix. The basic mechanism of this phenomenon is the trapping of mobile self-interstitial configurations by niobium. The diffusion of pure zirconium and mixed zirconium-niobium self-interstitial configurations in the zirconium matrix at 300 K has been simulated. We observe a strong dependence of the estimated diffusion coefficients and fractions of Nb in self-interstitials produced in displacement cascades on the potential.

Cascade Mountain Range in Oregon

USGS Publications Warehouse

Sherrod, David R.

2016-01-01

Along its Oregon segment, the Cascade Range is almost entirely volcanic in origin. The volcanoes and their eroded remnants are the visible magmatic expression of the Cascadia subduction zone, where the offshore Juan de Fuca tectonic plate is subducted beneath North America. Subduction occurs as two lithospheric plates collide, and an underthrusted oceanic plate is commonly dragged into the mantle by the pull of gravity, carrying ocean-bottom rock and sediment down to where heat and pressure expel water. As this water rises, it lowers the melting temperature in the overlying hot mantle rocks, thereby promoting melting. The molten rock supplies the volcanic arcs with heat and magma. Cascade Range volcanoes are part of the Ring of Fire, a popular term for the numerous volcanic arcs that encircle the Pacific Ocean.

Incidence loss for a core turbine rotor blade in a two-dimensional cascade

NASA Technical Reports Server (NTRS)

Stabe, R. G.; Kline, J. F.

1974-01-01

The effect of incidence angle on the aerodynamic performance of an uncooled core turbine rotor blade was investigated experimentally in a two-dimensional cascade. The cascade test covered a range of incidence angles from minus 15 deg to 15 deg in 5-degree increments and a range of pressure ratios corresponding to ideal exit critical velocity ratios of 0.6 to 0.95. The principal measurements were blade-surface static pressures and cross-channel surveys of exit total pressure, static pressure, and flow angle. The results of the investigation include blade-surface velocity distribution and overall performance in terms of weight flow and loss for the range of incidence angles and exit velocity ratios investigated. The measured losses are also compared with two common methods of predicting incidence loss.

Quantum-electrodynamic cascades in intense laser fields

NASA Astrophysics Data System (ADS)

Narozhny, N. B.; Fedotov, A. M.

2015-01-01

It is shown that in an intense laser field, along with cascades similar to extensive air showers, self-sustaining field-energized cascades can develop. For intensities of 1024~ \\text {W cm}-2 or higher, such cascades can even be initiated by a particle at rest in the focal area of a tightly focused laser pulse. The cascade appearance effect can considerably alter the progression of any process occurring in a high-intensity laser field. At very high intensities, the evolvement of such cascades can lead to the depletion of the laser field. This paper presents a design of an experiment to observe these two cascade types simultaneously already in next-generation laser facilities.

Estimated water use and general hydrologic conditions for Oregon, 1985 and 1990

USGS Publications Warehouse

Broad, T.M.; Collins, C.A.

1996-01-01

Water-use information is vital to planners, engineers, and hydrologists in water resources. This report is a compilation of water-use information for Oregon for calendar years 1985 and 1990. The report presents water-use data by geographic region for several categories of use, including public supply, domestic, commercial, industrial, mining, thermoelectric power, hydroelectric power, live-stock, irrigation, reservoir evaporation, and wastewater treatment. Hydroelectric power is the only instream use discussed; all other uses are considered offstream. The Appendix presents 1985 and 1990 data by region and by drainage basin for the previously mentioned categories of use. The Cascade Range divides Oregon into two distinct climatic zones. The area west of the Cascade Range has an average annual precipitation that ranges from 40 to 200 inches, and precipitation in the area east of the Cascade Range ranges from 10 to 20 inches. The differences in precipitation and geology have an effect on the sources, uses, and amounts of water withdrawn. Most of the large public-supply systems west of the Cascade Range rely on surface water, whereas many of the large public-supply systems east of the Cascade Range use on wells or springs. Irrigators west of the Cascade Range rely primarily on nearby surface- water sources; however, irrigators east of the Cascade Range use primarily surface water that commonly is delivered from distant sources through irrigation ditches. A variety of methods was used to estimate water-use information. Most withdrawals for public-water suppliers were metered; however, irrigation withdrawals usually were estimated by using information on crops, climate, application efficiencies, and conveyance losses. The accuracy of the estimated total withdrawal values for public supply was estimated to be within 4 percent of the values that would be obtained if all public-supply withdrawals were metered. Total withdrawals for irrigation were estimated to be within 40 percent of metered irrigation withdrawals. The estimates-of-error are presented to show the relative, rather than absolute, accuracy of the data for each water-use category. A total of 8,400 million gallons of water per day was withdrawn in Oregon during 1990, about 1,900 million gallons per day more than the 6,500 million gallons per day withdrawn in 1985. Whereas actual water use increased in 1990, the major differences between 1985 and 1990 were attributed to the inclusion of offstream fish hatcheries, the use of different crop coefficients to estimate irrigation, and the availability of more detailed information in the 1990 estimates. Surface-water withdrawals accounted for 92 percent of the total withdrawals in 1990; irrigation was the largest category of water use, accounting for 82 percent of the total withdrawals.

Olivine and chromian spinel in primitive calc-alkaline and tholeiitic lavas from the southernmost cascade range, California: A reflection of relative fertility of the source

USGS Publications Warehouse

Clynne, M.A.; Borg, L.E.

1997-01-01

Chromian spinel and coexisting olivine phenocrysts from a geochemically diverse suite of primitive tholeiitic and calc-alkaline basalts and magnesian andesites from the Lassen region, in the southernmost Cascade Range, in California, show that the sub-arc mantle is zoned. Depleted calc-alkaline basalts and magnesian andesites erupt in the forearc region, and calc-alkaline basalts contain increasing abundances of incompatible elements toward the backarc. High-alumina olivine tholeiites erupt from the arc and backarc areas. Olivine from all these lavas displays a limited compositional range, from Fo86 to Fo91, and crystallized at high temperature, generally 1225-1275??C. Chromian spinel trapped in the olivine phenocrysts displays a large range of composition: Cr# values span the range 9-76. Excess Al in the spinel relative to that in 1-atm spinel suggests that it crystallized at elevated pressure. The phenocrysts in these lavas are in equilibrium with their host liquids. The full range of Cr# of the spinel compositions cannot be explained by differentiation or variable pressure, variations in f(O2), subsolidus equilibration or variations in degree of partial melting of a single peridotitic source. Rather, the systematic compositional differences among phenocrysts in these primitive lavas result from bulk chemical variability in their mantle sources. Correlations between spinel and host-rock compositions support the assertion that the geochemical diversity of Lassen basalts reflects the relative fertility of their mantle sources.

Thermal Management of Quantum Cascade Lasers in an individually Addressable Array Architecture

DTIC Science & Technology

2016-02-08

Thermal Management of Quantum Cascade Lasers in an Individually Addressable Monolithic Array Architecture Leo Missaggia, Christine Wang, Michael...power laser systems in the mid-to-long-infrared wavelength range. By virtue of their demonstrated watt-level performance and wavelength diversity...quantum cascade laser (QCL) and amplifier devices are an excellent choice of emitter for those applications. To realize the power levels of interest

Model and Study on Cascade Control System Based on IGBT Chopping Control

NASA Astrophysics Data System (ADS)

Niu, Yuxin; Chen, Liangqiao; Wang, Shuwen

2018-01-01

Thyristor cascade control system has a wide range of applications in the industrial field, but the traditional cascade control system has some shortcomings, such as a low power factor, serious harmonic pollution. In this paper, not only analyzing its system structure and working principle, but also discussing the two main factors affecting the power factor. Chopping-control cascade control system, adopted a new power switching device IGBT, which could overcome traditional cascade control system’s two main drawbacks efficiently. The basic principle of this cascade control system is discussed in this paper and the model of speed control system is built by using MATLAB/Simulink software. Finally, the simulation results of the system shows that the system works efficiently. This system is worthy to be spread widely in engineering application.

The cascade of HIV care in British Columbia, Canada, 1996–2011: a population-based retrospective cohort study

PubMed Central

Nosyk, Bohdan; Montaner, Julio S G; Colley, Guillaume; Lima, Viviane D; Chan, Keith; Heath, Katherine; Yip, Benita; Samji, Hasina; Gilbert, Mark; Barrios, Rolando; Gustafson, Réka; Hogg, Robert S

2014-01-01

Summary Background The cascade of HIV care has become a focal point for implementation efforts to maximise the individual and public health benefits of antiretroviral therapy. We aimed to characterise longitudinal changes in engagement with the cascade of HIV care in British Columbia, Canada, from 1996 to 2011. Methods We used estimates of provincial HIV prevalence from the Public Health Agency of Canada and linked provincial population-level data to define, longitudinally, the numbers of individuals in each of the eight stages of the cascade of HIV care (HIV infected, diagnosed, linked to HIV care, retained in HIV care, highly active antiretroviral therapy (HAART) indicated, on HAART, adherent to HAART, and virologically suppressed) in British Columbia from 1996 to 2011. We used sensitivity analyses to determine the sensitivity of cascade-stage counts to variations in their definitions. Findings 13 140 people were classified as diagnosed with HIV/AIDS in British Columbia during the study period. We noted substantial improvements over time in the proportions of individuals at each stage of the cascade of care. Based on prevalence estimates, the proportion of unidentified HIV-positive individuals decreased from 49·0% (estimated range 36·2–57·5%) in 1996 to 29·0% (11·6–40·7%) in 2011, and the proportion of HIV-positive people with viral suppression reached 34·6% (29·0–43·1%) in 2011. Interpretation Careful mapping of the cascade of care is crucial to understanding what further efforts are needed to maximise the beneficial effects of available interventions and so inform efforts to contain the spread of HIV/AIDS. Funding British Columbia Ministry of Health, US National Institute on Drug Abuse (National Institutes of Health). PMID:24076277

Snow Peak, OR: Miocene and Pliocene Tholeiitic Volcanism in the Cascadia Forearc

NASA Astrophysics Data System (ADS)

Hatfield, A. K.; Kent, A. J.; Nielsen, R. L.; Rowe, M. C.; Duncan, R. A.

2007-12-01

Snow Peak is a voluminous (>150 km3), glacially dissected shield volcano located approximately 50 km southeast of Salem, OR, with a summit height of 1,310 m above sea level. Snow Peak lies approximately 60 km west of the current High Cascade arc axis. Lavas from the southeast face of Snow Peak have been previously dated using K-Ar at ~3 Ma. New Ar-Ar dating indicates that lavas from the northwest face are ~5.4 Ma, and the summit plug is ~6 Ma. Snow Peak volcanics unconformably overlie western Cascade volcanics aged from middle to late Miocene (~10- 17 Ma). The age of Snow Peak is broadly contemporaneous with the initiation of modern High Cascade volcanism. Snow Peak's location provides a rare opportunity to study magmas produced within the modern High Cascades forearc region. The goal of this investigation is to characterize the composition and timing of volcanism at Snow Peak and the role of volatiles in magma genesis. Hypotheses for the formation of Snow Peak include flux melting associated with the Cascadia subduction zone and/or decompression melting associated with extensional faulting. Preliminary geochemical data on the basalts from Snow Peak indicate that they are low-to-medium-K tholeiites (SiO2 47.9-51.7 wt.%, MgO 5.5- 8.3 wt.%, K2O, 0.36-0.55 wt.%) and that they range from primitive to moderately evolved (Mg# 0.51-0.61). Common phenocryst phases are plagioclase, olivine, and clinopyroxene. Textures are typically hypocrystalline, and fine-grained to porphyritic. Mantle-normalized multi-element plots indicate Snow Peak lavas are generally HFSE depleted and LILE enriched. These data are consistent with a preliminary interpretation of a subduction zone signature, yet the major element composition most closely resembles high alumina olivine tholeiite (HAOT), more indicative of extensional environments. The degree of LILE enrichment is significantly lower than in calc alkaline lavas from the High Cascades and western Cascades. Determining the petrogenesis of this forearc center will include a comprehensive analysis of the volcano's major and trace element geochemistry, and additional age dating to constrain eruption rates. Direct measurement of volatiles in olivine-hosted melt inclusions will complement the major and trace element geochemistry in order to measure pre-eruptive water contents.

Bushy-tailed woodrat abundance in dry forests of eastern Washington.

Treesearch

John F. Lehmkuhl; Keith D. Kistler; James S. Begley

2006-01-01

We studied bushy-tailed woodrats (Neotonza cinerea occidentalis) in the eastern Washington Cascade Range to estimate their density and survival in 3 typical dry forest cover types. We predicted woodrat density to be high, moderate, and low in mature mixed-conifer forests, young mixed-conifer forests, and open ponderosa pine forests, respectively....

Complementary Aerodynamic Performance Datasets for Variable Speed Power Turbine Blade Section from Two Independent Transonic Turbine Cascades

NASA Technical Reports Server (NTRS)

Flegel, Ashlie B.; Welch, Gerard E.; Giel, Paul W.; Ames, Forrest E.; Long, Jonathon A.

2015-01-01

Two independent experimental studies were conducted in linear cascades on a scaled, two-dimensional mid-span section of a representative Variable Speed Power Turbine (VSPT) blade. The purpose of these studies was to assess the aerodynamic performance of the VSPT blade over large Reynolds number and incidence angle ranges. The influence of inlet turbulence intensity was also investigated. The tests were carried out in the NASA Glenn Research Center Transonic Turbine Blade Cascade Facility and at the University of North Dakota (UND) High Speed Compressible Flow Wind Tunnel Facility. A large database was developed by acquiring total pressure and exit angle surveys and blade loading data for ten incidence angles ranging from +15.8deg to -51.0deg. Data were acquired over six flow conditions with exit isentropic Reynolds number ranging from 0.05×106 to 2.12×106 and at exit Mach numbers of 0.72 (design) and 0.35. Flow conditions were examined within the respective facility constraints. The survey data were integrated to determine average exit total-pressure and flow angle. UND also acquired blade surface heat transfer data at two flow conditions across the entire incidence angle range aimed at quantifying transitional flow behavior on the blade. Comparisons of the aerodynamic datasets were made for three "match point" conditions. The blade loading data at the match point conditions show good agreement between the facilities. This report shows comparisons of other data and highlights the unique contributions of the two facilities. The datasets are being used to advance understanding of the aerodynamic challenges associated with maintaining efficient power turbine operation over a wide shaft-speed range.

Using estimates of natural variation to detect ecologically important change in forest spatial patterns: a case study, Cascade Range, eastern Washington.

Treesearch

Paul F. Hessburg; Bradley G. Smith; R. Brion Salter

1999-01-01

Using hierarchical clustering techniques, we grouped subwatersheds on the eastern slope of the Cascade Range in Washington State into ecological subregions by similarity of area in potential vegetation and climate attributes. We then built spatially continuous historical and current vegetation maps for 48 randomly selected subwatersheds from interpretations of 1938-49...

Response of forest soil Acari to prescribed fire following stand structure manipulation in the southern Cascade Range.Can

Treesearch

Michael A. Camann; Nancy E. Gillette; Karen L. Lamoncha; Sylvia R. Mori

2008-01-01

We studied responses of Acari, especially oribatid mites, to prescribed low-intensity fire in an east side pine site in the southern Cascade Range in California. We compared oribatid population and assemblage responses to prescribed fire in stands that had been selectively logged to enhance old growth characteristics, in logged stands to minimize old growth...

Epiphytic lichen diversity and biomass in low-elevation forests of the eastern Washington Cascade range, USA.

Treesearch

John F. Lehmkuhl

2004-01-01

cover types in the eastern Washington Cascade range. Cover types represented a temperature/moisture and stand structural complexity gradient. Lichen litterfall biomass increased with increasing stand complexity and moisture. Lichen litterfall biomass was 3.42 kg/ha in open pine stands, 7.51 kg/ha in young mixed-species stands, 8.55 kg/ha in mature mixed-species stands...

Dynamics of wood in stream networks of the western Cascades Range, Oregon

Treesearch

Nicole M. Czarnomski; David M. Dreher; Kai U. Snyder; Julia A. Jones; Frederick J. Swanson

2008-01-01

We develop and test a conceptual model of wood dynamics in stream networks that considers legacies of forest management practices, floods, and debris flows. We combine an observational study of wood in 25 km of 2nd- through 5th-order streams in a steep, forested watershed of the western Cascade Range of Oregon with whole-network studies of forest cutting, roads, and...

Performance of a cascade in an annular vortex-generating tunnel over range of Reynolds numbers

NASA Technical Reports Server (NTRS)

Thurston, Sidney; Brunk, Ralph E

1951-01-01

Total-pressure deficiency for an annular cascade of 65-(12)10 blades was measured at three radial stations over a range of Reynolds numbers from 50,000 to 250,000 and at angles of attack of 15 degrees and 25 degrees. The variation of turning angle and shape of static pressure distribution at these stations is also shown.

Gamma ray pulsars

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1976-01-01

Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.

Conversion of alcohols to enantiopure amines through dual-enzyme hydrogen-borrowing cascades.

PubMed

Mutti, Francesco G; Knaus, Tanja; Scrutton, Nigel S; Breuer, Michael; Turner, Nicholas J

2015-09-25

α-Chiral amines are key intermediates for the synthesis of a plethora of chemical compounds at industrial scale. We present a biocatalytic hydrogen-borrowing amination of primary and secondary alcohols that allows for the efficient and environmentally benign production of enantiopure amines. The method relies on a combination of two enzymes: an alcohol dehydrogenase (from Aromatoleum sp., Lactobacillus sp., or Bacillus sp.) operating in tandem with an amine dehydrogenase (engineered from Bacillus sp.) to aminate a structurally diverse range of aromatic and aliphatic alcohols, yielding up to 96% conversion and 99% enantiomeric excess. Primary alcohols were aminated with high conversion (up to 99%). This redox self-sufficient cascade possesses high atom efficiency, sourcing nitrogen from ammonium and generating water as the sole by-product. Copyright © 2015, American Association for the Advancement of Science.

Semiconductor Terahertz Technology

DTIC Science & Technology

2009-06-15

is found in IJI-V quantum cascade lasers (QCLs). 1.I Brief overview of 5i-based QCL development Various groups have obtained electroluminescence from...sources and detectors of far-IR radiation in the range of 12-30 flm. These devices, especially quantum cascade lasers (QCLs) require efficient ...elements and their alloys that can be developed on Si substrates. The design work focused on the structure of the so-called quantum cascade laser

A 350-year reconstruction of the response of south Cascade Glacier to interannual and interdecadal climatic variability

Treesearch

Kailey W. Marcinkowski; David L. Peterson

2015-01-01

Mountain hemlock growth chronologies were used to reconstruct the mass balance of South Cascade Glacier, an alpine glacier in the North Cascade Range of Washington State. The net balance reconstruction spans 350 years, from 1659 to 2009. Summer and winter balances were reconstructed for 1346–2009 and 1615–2009, respectively. Relationships between mass balance and...

Eruptive history and tectonic setting of Medicine Lake Volcano, a large rear-arc volcano in the southern Cascades

USGS Publications Warehouse

Donnelly-Nolan, J. M.; Grove, T.L.; Lanphere, M.A.; Champion, D.E.; Ramsey, D.W.

2008-01-01

Medicine Lake Volcano (MLV), located in the southern Cascades ??? 55??km east-northeast of contemporaneous Mount Shasta, has been found by exploratory geothermal drilling to have a surprisingly silicic core mantled by mafic lavas. This unexpected result is very different from the long-held view derived from previous mapping of exposed geology that MLV is a dominantly basaltic shield volcano. Detailed mapping shows that < 6% of the ??? 2000??km2 of mapped MLV lavas on this southern Cascade Range shield-shaped edifice are rhyolitic and dacitic, but drill holes on the edifice penetrated more than 30% silicic lava. Argon dating yields ages in the range ??? 475 to 300??ka for early rhyolites. Dates on the stratigraphically lowest mafic lavas at MLV fall into this time frame as well, indicating that volcanism at MLV began about half a million years ago. Mafic compositions apparently did not dominate until ??? 300??ka. Rhyolite eruptions were scarce post-300??ka until late Holocene time. However, a dacite episode at ??? 200 to ??? 180??ka included the volcano's only ash-flow tuff, which was erupted from within the summit caldera. At ??? 100??ka, compositionally distinctive high-Na andesite and minor dacite built most of the present caldera rim. Eruption of these lavas was followed soon after by several large basalt flows, such that the combined area covered by eruptions between 100??ka and postglacial time amounts to nearly two-thirds of the volcano's area. Postglacial eruptive activity was strongly episodic and also covered a disproportionate amount of area. The volcano has erupted 9 times in the past 5200??years, one of the highest rates of late Holocene eruptive activity in the Cascades. Estimated volume of MLV is ??? 600??km3, giving an overall effusion rate of ??? 1.2??km3 per thousand years, although the rate for the past 100??kyr may be only half that. During much of the volcano's history, both dry HAOT (high-alumina olivine tholeiite) and hydrous calcalkaline basalts erupted together in close temporal and spatial proximity. Petrologic studies indicate that the HAOT magmas were derived by dry melting of spinel peridotite mantle near the crust mantle boundary. Subduction-derived H2O-rich fluids played an important role in the generation of calcalkaline magmas. Petrology, geochemistry and proximity indicate that MLV is part of the Cascades magmatic arc and not a Basin and Range volcano, although Basin and Range extension impinges on the volcano and strongly influences its eruptive style. MLV may be analogous to Mount Adams in southern Washington, but not, as sometimes proposed, to the older distributed back-arc Simcoe Mountains volcanic field.

Influence of the Kinetics of Heat and Mass Transfer in a Binary-Rectification Column on the Realizability Range of its Regimes

NASA Astrophysics Data System (ADS)

Zaeva, M. A.; Tsirlin, A. M.; Sukin, I. A.

2018-05-01

The range of realizable rates of flows in a binary-rectification column in which heat is supplied into the boiler and is removed from the dephlegmator was investigated. It is shown that this range is determined by two characteristic parameters related to the kinetics of heat and mass transfer in the column and the composition of the mixture subjected to separation. The limiting capabilities of a cascade of two binary-rectification columns for the separation of a ternary mixture in it were considered. The conditions for an optimum sequence of separation of a mixture in this cascade and for a consistent arrangement of its heat and mass exchange surfaces and the relation between the ultimate production rate of the cascade and the total heat losses in it were determined.

Influence of the Kinetics of Heat and Mass Transfer in a Binary-Rectification Column on the Realizability Range of its Regimes

NASA Astrophysics Data System (ADS)

Zaeva, M. A.; Tsirlin, A. M.; Sukin, I. A.

2018-03-01

The range of realizable rates of flows in a binary-rectification column in which heat is supplied into the boiler and is removed from the dephlegmator was investigated. It is shown that this range is determined by two characteristic parameters related to the kinetics of heat and mass transfer in the column and the composition of the mixture subjected to separation. The limiting capabilities of a cascade of two binary-rectification columns for the separation of a ternary mixture in it were considered. The conditions for an optimum sequence of separation of a mixture in this cascade and for a consistent arrangement of its heat and mass exchange surfaces and the relation between the ultimate production rate of the cascade and the total heat losses in it were determined.

Search for acoustic signals from high energy cascades

NASA Technical Reports Server (NTRS)

Bell, R.; Bowen, T.

1985-01-01

High energy cosmic ray secondaries can be detected by means of the cascades they produce when they pass through matter. When the charged particles of these cascades ionize the matter they are traveling through, the heat produced and resulting thermal expansion causes a thermoacoustic wave. These sound waves travel at about one hundred-thousandth the speed of light, and should allow an array of acoustic transducers to resolve structure in the cascade to about 1 cm without high speed electronics or segmentation of the detector.

Energy-Cascaded Upconversion in an Organic Dye-Sensitized Core/Shell Fluoride Nanocrystal.

PubMed

Chen, Guanying; Damasco, Jossana; Qiu, Hailong; Shao, Wei; Ohulchanskyy, Tymish Y; Valiev, Rashid R; Wu, Xiang; Han, Gang; Wang, Yan; Yang, Chunhui; Ågren, Hans; Prasad, Paras N

2015-11-11

Lanthanide-doped upconversion nanoparticles hold promises for bioimaging, solar cells, and volumetric displays. However, their emission brightness and excitation wavelength range are limited by the weak and narrowband absorption of lanthanide ions. Here, we introduce a concept of multistep cascade energy transfer, from broadly infrared-harvesting organic dyes to sensitizer ions in the shell of an epitaxially designed core/shell inorganic nanostructure, with a sequential nonradiative energy transfer to upconverting ion pairs in the core. We show that this concept, when implemented in a core-shell architecture with suppressed surface-related luminescence quenching, yields multiphoton (three-, four-, and five-photon) upconversion quantum efficiency as high as 19% (upconversion energy conversion efficiency of 9.3%, upconversion quantum yield of 4.8%), which is about ~100 times higher than typically reported efficiency of upconversion at 800 nm in lanthanide-based nanostructures, along with a broad spectral range (over 150 nm) of infrared excitation and a large absorption cross-section of 1.47 × 10(-14) cm(2) per single nanoparticle. These features enable unprecedented three-photon upconversion (visible by naked eye as blue light) of an incoherent infrared light excitation with a power density comparable to that of solar irradiation at the Earth surface, having implications for broad applications of these organic-inorganic core/shell nanostructures with energy-cascaded upconversion.

High sensitivity cascaded preamplifier with an optical bridge structure in Brillouin distributed fiber sensing system

NASA Astrophysics Data System (ADS)

Bi, Weihong; Lin, Hang; Fu, Xinghu; Fu, Guangwei

2013-12-01

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

Low-speed cascade investigation of loaded leading-edge compressor blades

NASA Technical Reports Server (NTRS)

Emery, James C

1956-01-01

Six percent thick NACA 63-series compressor-blade sections having a loaded leading-edge A4K6 mean line have been investigated systematically in a two-dimensional porous-wall cascade over a range of Reynolds numbers from 160,000 to 385,000. Blades cambered to have isolated-airfoil lift coefficients of 0.6, 1.2, 1.8, and 2.4 were tested over the usable angle-of-attack range at inlet-air angles of 30 degrees, 45 degrees, and 60 degrees and solidities of 1.0 and 1.5. A comparison with data of NACA RM L51G31, shows that the angle-of-attack operating range is 2 degrees to 4 degrees less than the range for the uniformly loaded section; however, the wake losses near design angle of attack are slightly lower than those for the uniformly loaded section. Except for highly cambered blades at high inlet angles, the 63-(C s oA4K6)06 compressor-blade sections are capable of more efficient operation for moderate-speed subsonic compressors at design angle of attack than are the 65-(C s oa10)10 or the 65-(c s oA2I8b)10 compressor-blade sections. In contrast to the other sections, the loaded leading-edge sections are capable of operating efficiently at the lower Reynolds numbers.

Titanium dioxide in pyroclastic layers from volcanoes in the cascade range

USGS Publications Warehouse

Czamanske, G.K.; Porter, S.C.

1965-01-01

Rapid determinations of titanium dioxide have been made by x-ray emission techniques to evaluate the potentiality of using the TiO2 content of samples for checking field correlations and assisting in identification of pyroclastic units from Cascade volcanoes. Preliminary data suggest that the two most wide-spread units have characteristic ranges of TiO2 content and that other, less extensive layers have ranges which, though characteristic, often overlap the ranges of the more widespread layers. Relative to fresh samples, weathered samples from B and C soil horizons are enriched in TiO 2.

Four centuries of soil carbon and nitrogen change after stand-replacing fire in a forest landscape in the western Cascade Range of Oregon

Treesearch

T. W. Giesen; S. S. Perakis; K. Cromack

2008-01-01

Episodic stand-replacing wildfire is a significant disturbance in mesic and moist Douglas-frr (Pseudotsuga menziesii (Mirb.) Franco) forests of the Pacific Northwest. We studied 24 forest stands with known fire histories in the western . Cascade Range in Oregon to evaluate long-tenn impacts of stand-replacing wildfire on carbon (C) and nitrogen (N)...

Land development under regulation: comparison between the east and the west sides of the Cascade Range in Oregon, Washington, and California.

Treesearch

Seong-Hoo Cho; JunJie Wu; Ralph J. Alig

2005-01-01

We compare how socioeconomic factors, physical landscape, profit uncertainty, and local land use policies have affected land development on the east and west sides of the Cascade Range in Oregon, Washington, and California. It is found that the west side has more actively planned and regulated land use than the east side. Consequently, the more intense land use...

Ponderosa promise: a history of U.S. Forest Service research in central Oregon.

Treesearch

Les Joslin

2007-01-01

Research interest in the forests of Oregon and Washington east of the Cascade Range can be traced back to 1897, when Fredrick V. Coville of the Division of Forestry, U.S. Department of Agriculture, reconnoitered the Cascade Range Forest Reserve to report on forest growth and sheep grazing there in an 1898 report. Subsequent forest survey in the late 1890s and early...

Invertebrates of The H.J. Andrews Experimental Forest, Western Cascade Range, Oregon. V: An Annotated List of Insects and Other Arthropods

Treesearch

Gary L. Parson; Gerasimos Cassis; Andrew R. Moldenke; John D. Lattin; Norman H. Anderson; Jeffrey C Miller; Paul Hammond; Timothy D. Schowalter

1991-01-01

An annotated list of species of insects and other arthropods that have been collected and studies on the H.J. Andrews Experimental forest, western Cascade Range, Oregon. The list includes 459 families, 2,096 genera, and 3,402 species. All species have been authoritatively identified by more than 100 specialists. Information is included on habitat type, functional group...

Invertebrates of The H.J. Andrews Experimental Forest, western Cascade Range, Oregon. V: An annotated list of insects and other arthropods.

Treesearch

Gary L. Parson; Gerasimos Cassis; Andrew R. Moldenke; John D. Lattin; Norman H. Anderson; Jeffrey C Miller; Paul Hammond; Timothy D. Schowalter

1991-01-01

An annotated list of species of insects and other arthropods that have been collected and studies on the H.J. Andrews Experimental forest, western Cascade Range, Oregon. The list includes 459 families, 2,096 genera, and 3,402 species. All species have been authoritatively identified by more than 100 specialists. Information is included on habitat type, functional group...

Fates of live trees retained in forest cutting units, western Cascade Range, Oregon.

Treesearch

P.E. Busby; P. Adler; T.L. Warren; F.J. Swanson

2006-01-01

To assess the fate of live trees retained in dispersed patterns across cutting units in the western Cascade Range of Oregon, we conducted repeat surveys (1993 and 2001) of sites cut as early as 1983. Our objectives in this study are to (1) survey survival and mortality of trees retained at the time of harvest, (2) describe temporal patterns of windthrow and other...

Natural tree regeneration and coarse woody debris dynamics after a forest fire in the western Cascade Range

Treesearch

Martin J. Brown; Jane Kertis; Mark H. Huff

2013-01-01

We monitored coarse woody debris dynamics and natural tree regeneration over a 14-year period after the 1991 Warner Creek Fire, a 3631-ha (8,972-ac) mixed severity fire in the western Cascade Range of Oregon. Rates for tree mortality in the fire, postfire mortality, snag fall, and snag fragmentation all showed distinct patterns by tree diameter and species, with...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukhovoj, A. M., E-mail: suchovoj@nf.jinr.ru; Mitsyna, L. V., E-mail: mitsyna@nf.jinr.ru; Jovancevic, N., E-mail: nikola.jovancevic@uns.ac.rs

The intensities of two-step cascades in 43 nuclei of mass number in the range of 28 ≤ A ≤ 200 were approximated to a high degree of precision within a modified version of the practical cascade-gammadecay model introduced earlier. In this version, the rate of the decrease in the model-dependent density of vibrational levels has the same value for any Cooper pair undergoing breakdown. The most probable values of radiative strength functions both for E1 and for M1 transitions are determined by using one or two peaks against a smooth model dependence on the gamma-transition energy. The statement that themore » thresholds for the breaking of Cooper pairs are higher for spherical than for deformed nuclei is a basic result of the respective analysis. The parameters of the cascade-decay process are now determined to a precision that makes it possible to observe the systematic distinctions between them for nuclei characterized by different parities of neutrons and protons.« less

Quantum Cascade Laser-Based Infrared Microscopy for Label-Free and Automated Cancer Classification in Tissue Sections.

PubMed

Kuepper, Claus; Kallenbach-Thieltges, Angela; Juette, Hendrik; Tannapfel, Andrea; Großerueschkamp, Frederik; Gerwert, Klaus

2018-05-16

A feasibility study using a quantum cascade laser-based infrared microscope for the rapid and label-free classification of colorectal cancer tissues is presented. Infrared imaging is a reliable, robust, automated, and operator-independent tissue classification method that has been used for differential classification of tissue thin sections identifying tumorous regions. However, long acquisition time by the so far used FT-IR-based microscopes hampered the clinical translation of this technique. Here, the used quantum cascade laser-based microscope provides now infrared images for precise tissue classification within few minutes. We analyzed 110 patients with UICC-Stage II and III colorectal cancer, showing 96% sensitivity and 100% specificity of this label-free method as compared to histopathology, the gold standard in routine clinical diagnostics. The main hurdle for the clinical translation of IR-Imaging is overcome now by the short acquisition time for high quality diagnostic images, which is in the same time range as frozen sections by pathologists.

Advances in quantum cascade lasers for security and crime-fighting

NASA Astrophysics Data System (ADS)

Normand, Erwan L.; Stokes, Robert J.; Hay, Kenneth; Foulger, Brian; Lewis, Colin

2010-10-01

Advances in the application of Quantum Cascade Lasers (QCL) to trace gas detection will be presented. The solution is real time (~1 μsec per scan), is insensitive to turbulence and vibration, and performs multiple measurements in one sweep. The QCL provides a large dynamic range, which is a linear response from ppt to % level. The concentration can be derived with excellent immunity from cross interference. Point sensing sensors developed by Cascade for home made and commercial explosives operate by monitoring key constituents in real time and matching this to a spatial event (i.e. sniffer device placed close to an object or person walking through portal (overt or covert). Programmable signature detection capability allows for detection of multiple chemical compounds along the most likely array of explosive chemical formulation. The advantages of configuration as "point sensing" or "stand off" will be discussed. In addition to explosives this method is highly applicable to the detection of mobile drugs labs through volatile chemical release.

Freedom from band-gap slavery: from diode lasers to quantum cascade lasers

NASA Astrophysics Data System (ADS)

Capasso, Federico

2010-02-01

Semiconductor heterostructure lasers, for which Alferov and Kromer received part of the Nobel Prize in Physics in 2000, are the workhorse of technologies such as optical communications, optical recording, supermarket scanners, laser printers and fax machines. They exhibit high performance in the visible and near infrared and rely for their operation on electrons and holes emitting photons across the semiconductor bandgap. This mechanism turns into a curse at longer wavelengths (mid-infrared) because as the bandgap, shrinks laser operation becomes much more sensitive to temperature, material defects and processing. Quantum Cascade Laser (QCL), invented in 1994, rely on a radically different process for light emission. QCLs are unipolar devices in which electrons undergo transitions between quantum well energy levels and are recycled through many stages emitting a cascade of photons. Thus by suitable tailoring of the layers' thickness, using the same heterostructure material, they can lase across the molecular fingerprint region from 3 to 25 microns and beyond into the far-infrared and submillimiter wave spectrum. High power cw room temperature QCLs and QCLs with large continuous single mode tuning range have found many applications (infrared countermeasures, spectroscopy, trace gas analysis and atmospheric chemistry) and are commercially available. )

Cascaded nano-porous silicon for high sensitive biosensing and functional group distinguishing by Mid-IR spectra.

PubMed

Nguyen, Minh-Hang; Tsai, Hau-Jie; Wu, Jen-Kuei; Wu, Yi-Shiuan; Lee, Ming-Chang; Tseng, Fan-Gang

2013-09-15

We present a chemical-biosensor in the Mid-IR range and based on cascaded porous silicon made on p- and n-type (100) silicon substrates of resistivities between 0.001Ωcm and 0.005Ωcm. The stacked porous layers of various porosities (20-80%) and thicknesses (5-9μm) are formed by successive electrochemical etchings with different current densities. Working with FTIR technique that possesses fast response, high sensitivity, and capability of detecting and identifying functional groups, the cascaded porous structures provided enhanced refractive index sensitivities and reduced detection limits in chemical and biodetection. The largest wavenumber shifts were 50cm(-1)/mM obtained for d-(+)-glucose and 96cm(-1)/μg/mL for Cy5-conjungated Rabbit Anti-Mouse IgG. The lowest detectable concentration of glucose was 80μM (1.4mg/mL) with PS porosity of 40% and thickness of about 9μm while it was 40ng/mL for Cy5-conjugated Rabbit Anti-Mouse IgG which is 2.5×10(5) folds better than those in literature. Copyright © 2013 Elsevier B.V. All rights reserved.

Asymmetric catalytic cascade reactions for constructing diverse scaffolds and complex molecules.

PubMed

Wang, Yao; Lu, Hong; Xu, Peng-Fei

2015-07-21

With the increasing concerns about chemical pollution and sustainability of resources, among the significant challenges facing synthetic chemists are the development and application of elegant and efficient methods that enable the concise synthesis of natural products, drugs, and related compounds in a step-, atom- and redox-economic manner. One of the most effective ways to reach this goal is to implement reaction cascades that allow multiple bond-forming events to occur in a single vessel. This Account documents our progress on the rational design and strategic application of asymmetric catalytic cascade reactions in constructing diverse scaffolds and synthesizing complex chiral molecules. Our research is aimed at developing robust cascade reactions for the systematic synthesis of a range of interesting molecules that contain structural motifs prevalent in natural products, pharmaceuticals, and biological probes. The strategies employed to achieve this goal can be classified into three categories: bifunctional base/Brønsted acid catalysis, covalent aminocatalysis/N-heterocyclic carbene catalysis, and asymmetric organocatalytic relay cascades. By the use of rationally designed substrates with properly reactive sites, chiral oxindole, chroman, tetrahydroquinoline, tetrahydrothiophene, and cyclohexane scaffolds were successfully assembled under bifunctional base/Brønsted acid catalysis from simple and readily available substances such as imines and nitroolefins. We found that some of these reactions are highly efficient since catalyst loadings as low as 1 mol % can promote the multistep sequences affording complex architectures with high stereoselectivities and yields. Furthermore, one of the bifunctional base/Brønsted acid-catalyzed cascade reactions for the synthesis of chiral cyclohexanes has been used as a key step in the construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of α-lycorane. Guided by the principles of covalent aminocatalysis and N-heterocyclic carbene catalysis, we synthesized chiral piperidine, indole, and cyclobutane derivatives. The synthesis of chiral cyclobutanes and pyrroloindolones showed unprecedented reactivity of substrates and catalysts. The development of the strategy of asymmetric organocatalytic relay cascades has provided a useful tool for the controlled synthesis of specific diastereomers in complex molecules. This Account gives a panoramic view and the logic of our research on the design, development, and applications of asymmetric catalytic cascade reactions that will potentially provide useful insights into exploring new reactions.

Do Glaciers on Cascade Volcanoes Behave Differently Than Other Glaciers in the Region?

NASA Astrophysics Data System (ADS)

Riedel, J. L.; Ryane, C.; Osborn, J.; Davis, T.; Menounos, B.; Clague, J. J.; Koch, J.; Scott, K. M.; Reasoner, M.

2006-12-01

It has been suggested that glaciers on two stratovolcanoes in the Cascade Range of Washington state, Mt. Baker and Glacier Peak, achieved their maximum extent of the past 10,000 years during the early Holocene. These findings differ from most evidence in western North America, which indicates that Little Ice Age moraines represent the most extensive glacier advances of the Holocene. Significant early Holocene advances are difficult to reconcile with the documented warm, dry conditions at this time in western North America. Our data indicate that glaciers on these volcanoes responded similarly to Holocene climatic events as glaciers in other areas in Washington and British Columbia. Heavy winter accumulation and favorable hypsometry have been proposed as the explanations for the unusual behavior of glaciers on volcanoes compared to similar-sized glaciers elsewhere in the Cascade Range. However, glacier mass balance on the volcanoes is controlled by not only these factors, but also by glacier geometry, snow erosion and ablation. Accumulation zones of glaciers on isolated Cascade stratovolcanoes are high, but are narrow at the top. For example, the accumulation zone of Deming Glacier on the southwest side of Mt. Baker extends above 3000 m asl, but due to its wedge shape lies largely below 2500 m asl. Furthermore, glaciers on Mt. Baker and other symmetrical volcanoes have high ablation rates because they are not shaded, and south-southwest aspects are subject to erosion of snow by prevailing southwesterly winds. Modern glacier observations in the North Cascades quantify the important influence of aspect and snow erosion on glacier mass balance. For example, average equilibrium line altitude (ELA) of Easton Glacier on the south flank of Mt. Baker is 2160 m, whereas the ELA of a north-facing cirque glacier 25km to the east is 2040m. Our research at Mt. Baker contradicts the claim of extensive early Holocene advances on the south flank of the volcano. Tephra set SC, which has been radiocarbon dated to about 8850 14C yr old, is found on ridges that were previously mapped as moraines younger than the tephra. This relation indicates that "early Holocene" ridges are more than 8850 14C yr old, with their maximum age unconstrained. Most of the radial ridges previously mapped as moraines cannot be conclusively shown to be moraines; they could be lahar levees or diamict-covered bedrock ridges, which are common on Cascade stratovolcanoes. Our data indicate that the record of middle and late Holocene glaciation on Mt. Baker is similar, if not identical, to that reported from the British Columbia Coast Mountains. Consequently, there is no reason to believe that the history of Holocene glaciation on Cascade volcanoes is radically different than elsewhere in western North America.

Self-assembly of magnetic nanoclusters in diamond-like carbon by diffusion processes enhanced by collision cascades

NASA Astrophysics Data System (ADS)

Gupta, P.; Williams, G. V. M.; Hübner, R.; Vajandar, S.; Osipowicz, T.; Heinig, K.-H.; Becker, H.-W.; Markwitz, A.

2017-04-01

Mono-energetic cobalt implantation into hydrogenated diamond-like carbon at room temperature results in a bimodal distribution of implanted atoms without any thermal treatment. The ˜100 nm thin films were synthesised by mass selective ion beam deposition. The films were implanted with cobalt at an energy of 30 keV and an ion current density of ˜5 μA cm-2. Simulations suggest the implantation profile to be single Gaussian with a projected range of ˜37 nm. High resolution Rutherford backscattering measurements reveal that a bimodal distribution evolves from a single near-Gaussian distribution as the fluence increases from 1.2 to 7 × 1016 cm-2. Cross-sectional transmission electron microscopy further reveals that the implanted atoms cluster into nanoparticles. At high implantation doses, the nanoparticles assemble primarily in two bands: one near the surface with nanoparticle diameters of up to 5 nm and the other beyond the projected range with ˜2 nm nanoparticles. The bimodal distribution along with the nanoparticle formation is explained with diffusion enhanced by energy deposited during collision cascades, relaxation of thermal spikes, and defects formed during ion implantation. This unique distribution of magnetic nanoparticles with the bimodal size and range is of significant interest to magnetic semiconductor and sensor applications.

Rapid Swept-Wavelength External Cavity Quantum Cascade Laser for Open Path Sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brumfield, Brian E.; Phillips, Mark C.

2015-07-01

A rapidly tunable external cavity quantum cascade laser system is used for open path sensing. The system permits acquisition of transient absorption spectra over a 125 cm-1 tuning range in less than 0.01 s.

Energy transfer in turbulence under rotation

NASA Astrophysics Data System (ADS)

Buzzicotti, Michele; Aluie, Hussein; Biferale, Luca; Linkmann, Moritz

2018-03-01

It is known that rapidly rotating turbulent flows are characterized by the emergence of simultaneous upscale and downscale energy transfer. Indeed, both numerics and experiments show the formation of large-scale anisotropic vortices together with the development of small-scale dissipative structures. However the organization of interactions leading to this complex dynamics remains unclear. Two different mechanisms are known to be able to transfer energy upscale in a turbulent flow. The first is characterized by two-dimensional interactions among triads lying on the two-dimensional, three-component (2D3C)/slow manifold, namely on the Fourier plane perpendicular to the rotation axis. The second mechanism is three-dimensional and consists of interactions between triads with the same sign of helicity (homochiral). Here, we present a detailed numerical study of rotating flows using a suite of high-Reynolds-number direct numerical simulations (DNS) within different parameter regimes to analyze both upscale and downscale cascade ranges. We find that the upscale cascade at wave numbers close to the forcing scale is generated by increasingly dominant homochiral interactions which couple the three-dimensional bulk and the 2D3C plane. This coupling produces an accumulation of energy in the 2D3C plane, which then transfers energy to smaller wave numbers thanks to the two-dimensional mechanism. In the forward cascade range, we find that the energy transfer is dominated by heterochiral triads and is dominated primarily by interaction within the fast manifold where kz≠0 . We further analyze the energy transfer in different regions in the real-space domain. In particular, we distinguish high-strain from high-vorticity regions and we uncover that while the mean transfer is produced inside regions of strain, the rare but extreme events of energy transfer occur primarily inside the large-scale column vortices.

Disturbance and net ecosystem production across three climatically distinct forest landscapes

Treesearch

John L. Campbell; O.J. Sun; B.E. Law

2004-01-01

Biometric techniques were used to measure net ecosystem production (NEP) across three climatically distinct forest chronosequences in Oregon. NEP was highly negative immediately following stand-replacing disturbance in all forests and recovered to positive values by 10, 20, and 30 years of age for the mild mesic Coast Range, mesic West Cascades, and semi-arid East...

Climate impacts on connectivity of snowmelt to flow in the Willamette River using water stable isotopes

EPA Science Inventory

Much of the water that people in Western Oregon rely on comes from snowpack in the Cascade Range, and this snowpack is expected to decrease in coming years with climate change. In fact, the past 6 years have shown dramatic variation in snowpack, from a high of 174% of normal in ...

Measurement of the nuclear electromagnetic cascade development in glass at energies above 200 GeV

NASA Technical Reports Server (NTRS)

Gillespie, C. R.; Huggett, R. W.; Humphreys, D. R.; Jones, W. V.; Levit, L. B.

1971-01-01

The longitudinal development of nuclear-electromagnetic cascades with energies greater than 200 GeV was measured in a low-Z (glass) absorber. This was done in the course of operating an ionization spectrometer at mountain altitude in an experiment to study the properties of gamma rays emitted from individual interactions at energies around 10,000 GeV. The ionization produced by a cascade is sampled by 20 sheets of plastic scintillator spaced uniformly in depth every 2.2 radiation lengths. Adjacent pairs of scintillators are viewed by photomultipliers which measure the mean ionization produced by an individual cascade in 10 layers each 1.1 interaction length (4.4 radiation lengths) thick. The longitudinal development of the cascades was measured for about 250 cascades having energies ranging from 200 GeV to 2500 GeV. The observations are compared with the predictions of calculations made for this specific spectrometer using a three-dimensional Monte Carlo model of the nuclear-electromagnetic cascade.

Multistep cascade annihilations of dark matter and the Galactic Center excess

DOE PAGES

Elor, Gilly; Rodd, Nicholas L.; Slatyer, Tracy R.

2015-05-26

If dark matter is embedded in a non-trivial dark sector, it may annihilate and decay to lighter dark-sector states which subsequently decay to the Standard Model. Such scenarios - with annihilation followed by cascading dark-sector decays - can explain the apparent excess GeV gamma-rays identified in the central Milky Way, while evading bounds from dark matter direct detection experiments. Each 'step' in the cascade will modify the observable signatures of dark matter annihilation and decay, shifting the resulting photons and other final state particles to lower energies and broadening their spectra. We explore, in a model-independent way, the effect ofmore » multi-step dark-sector cascades on the preferred regions of parameter space to explain the GeV excess. We find that the broadening effects of multi-step cascades can admit final states dominated by particles that would usually produce too sharply peaked photon spectra; in general, if the cascades are hierarchical (each particle decays to substantially lighter particles), the preferred mass range for the dark matter is in all cases 20-150 GeV. Decay chains that have nearly-degenerate steps, where the products are close to half the mass of the progenitor, can admit much higher DM masses. We map out the region of mass/cross-section parameter space where cascades (degenerate, hierarchical or a combination) can fit the signal, for a range of final states. In the current paper, we study multi-step cascades in the context of explaining the GeV excess, but many aspects of our results are general and can be extended to other applications.« less

Pair cascades in the magnetospheres of strongly magnetized neutron stars

NASA Astrophysics Data System (ADS)

Medin, Zach; Lai, Dong

2010-08-01

We present numerical simulations of electron-positron pair cascades in the magnetospheres of magnetic neutron stars for a wide range of surface fields (Bp = 1012-1015 G), rotation periods (0.1-10 s) and field geometries. This has been motivated by the discovery in recent years of a number of radio pulsars with inferred magnetic fields comparable to those of magnetars. Evolving the cascade generated by a primary electron or positron after it has been accelerated in the inner gap of the magnetosphere, we follow the spatial development of the cascade until the secondary photons and electron-positron pairs leave the magnetosphere, and we obtain the pair multiplicity and the energy spectra of the cascade pairs and photons under various conditions. Going beyond previous works, which were restricted to weaker fields (B <~ afew × 1012 G), we have incorporated in our simulations detailed treatments of physical processes that are potentially important (especially in the high-field regime) but were either neglected or crudely treated before, including photon splitting with the correct selection rules for photon polarization modes, one-photon pair production into low Landau levels for the e+/-, and resonant inverse Compton scattering from polar cap hotspots. We find that even for B >> BQ = 4 × 1013 G, photon splitting has a small effect on the multiplicity of the cascade since a majority of the photons in the cascade cannot split. One-photon decay into e+ e- pairs at low Landau levels, however, becomes the dominant pair production channel when B >~ 3 × 1012 G; this tends to suppress synchrotron radiation so that the cascade can develop only at a larger distance from the stellar surface. Nevertheless, we find that the total number of pairs and their energy spectrum produced in the cascade depend mainly on the polar cap voltage BpP-2, and are weakly dependent on Bp (and P) alone. We discuss the implications of our results for the radio pulsar death line and for the hard X-ray emission from magnetized neutron stars.

Long-range energy transfer in self-assembled quantum dot-DNA cascades

NASA Astrophysics Data System (ADS)

Goodman, Samuel M.; Siu, Albert; Singh, Vivek; Nagpal, Prashant

2015-11-01

The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient transport of energy across QD-DNA thin films.The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient transport of energy across QD-DNA thin films. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04778a

Toward a System-Based Approach to Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Gamayunov, K. V.; Engebretson, M. J.; Rassoul, H.

2015-12-01

We consider a nonlinear wave energy cascade from the low frequency range into the higher frequency domain of electromagnetic ion cyclotron (EMIC) wave generation as a possible source of seed fluctuations for EMIC wave growth due to the ion cyclotron instability in Earth's magnetosphere. The theoretical analysis shows that energy cascade from the Pc 4-5 frequency range (2-22 mHz) into the range of Pc 1-2 pulsations (0.1-5 Hz) is able to supply the level of seed fluctuations that guarantees growth of EMIC waves up to an observable level during one pass through the near equatorial region where the ion cyclotron instability takes place. We also analyze magnetic field data from the Polar and Van Allen Probes spacecraft to test this nonlinear mechanism. We restrict our analysis to magnetic spectra only. We do not analyze the third-order moment for total energy of the magnetic and velocity fluctuations, but judge whether a nonlinear energy cascade is present or whether it is not by only analyzing the appearance of power-law distributions in the low frequency part of the magnetic field spectra. While the power-law spectrum alone does not guarantee that a nonlinear cascade is present, the power-law distribution is a strong indication of the possible development of a nonlinear cascade. Our data analysis shows that a nonlinear energy cascade is indeed observed in both the outer and inner magnetosphere, and EMIC waves are growing from this nonthermal background. All the analyzed data are in good agreement with the theoretical model presented in this study. Overall, the results of this study support a nonlinear energy cascade in Earth's magnetosphere as a mechanism which is responsible for supplying seed fluctuating energy in the higher frequency domain where EMIC waves grow due to the ion cyclotron instability. Keywords: nonlinear energy cascade, ultra low frequency waves, electromagnetic ion cyclotron waves, seed fluctuationsAcknowledgments: This paper is based upon work supported by the National Science Foundation under Grant Number AGS-1203516.

Comparative effects of urea fertilizer and red alder in a site III, coast Douglas-fir plantation in the Washington Cascade Range.

Treesearch

Richard E. Miller; Harry W. Anderson; Marshall Murray; Rick. Leon

2005-01-01

Five randomly assigned treatments were used to quantify effects of adding varying numbers of red alder (Alnus rubra Bong.) or nitrogen (N) fertilization on growth of a 10-year-old conifer plantation at a medium quality site in the western Washington Cascade Range. Zero, 20, 40, and 80 alder trees per acre were retained along with about 300 conifers...

Seed rain and seed bank of third- and fifth-order streams on the western slope of the Cascade Range.

Treesearch

Janice M. Harmon; Jerry F. Franklin

1991-01-01

We compared the composition and density of the on-site vegetation, seed bank, and seed rain of three geomorphic and successional surfaces along third- and fifth-order streams on the western slope of the central Cascade Range in Oregon.The on-site vegetation generally was dominated by tree species, the seed bank by herb species, and the seed rain by tree and...

Natural range of variation for yellow pine and mixed-conifer forests in the Sierra Nevada, southern Cascades, and Modoc and Inyo National Forests, California, USA

Treesearch

Hugh D. Safford; Jens T. Stevens

2017-01-01

Yellow pine and mixed-conifer (YPMC) forests are the predominant montane forest type in the Sierra Nevada, southern Cascade Range, and neighboring forested areas on the Modoc and Inyo National Forests (the "assessment area"). YPMC forests occur above the oak woodland belt and below red fir forests, and are dominated by the yellow pines (ponderosa pine [

Weak- and strong-turbulence regimes of the Hasegawa-Mima equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ottaviani, M.; Krommes, J.A.

1992-02-01

A Kolmogorov-type analysis of the energy- and enstrophy-cascading ranges of the forced Hasegawa-Mima equation allows one to derive a criterion for the threshold of the transition between the weak turbulence and the strong turbulence regimes. It is found that, due to the inverse energy cascade, the large-scale portion of the inertial range is in the strong turbulence regime in the limit of infinite Reynolds-like numbers.

Thermal surveillance of volcanoes of the Cascade Range and Iceland utilizing ERTS DCP systems and imagery

NASA Technical Reports Server (NTRS)

Friedman, J. D. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Significant results of the thermal surveillance of volcanoes experiment during 1972 included the design, construction, emplacement, and successful operation at volcanic sites in the Cascade Range, North America and on Surtsey, Iceland, of automated thermistor arrays which transmit ground and fumarole temperatures via the ERTS-1 data communication system to Goddard Space Flight Center. Temperature, radiance, and anomalous heat flow variations are being plotted by a U.S. Geological Survey IBM 360/65 computer program to show daily fluctuations at each of the sites. Results are being compiled in conjunction with NASA and USGS aircraft infrared survey data to provide thermal energy yield estimates during the current repose period of several Cascade Range volcanic systems. ERTS-1 MSS images have provided new information on the extent of structural elements controlling thermal emission at Lassen Volcanic National Park.

Blue Mountains Ecoregion: Chapter 16 in Status and trends of land change in the Western United States--1973 to 2000

USGS Publications Warehouse

Soulard, Christopher E.

2012-01-01

The Blue Mountains Ecoregion encompasses approximately 65,461 km² (25,275 mi²) of land bordered on the north by the Columbia Plateau Ecoregion, on the east by the Northern Rockies Ecoregion, on the south by the Snake River Basin and the Northern Basin and Range Ecoregions, and on the west by the Cascades and the Eastern Cascades Slopes and Foothills Ecoregions (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). Most of the Blue Mountains Ecoregion is located within Oregon (83.5 percent); 13.8 percent is in Idaho, and 2.7 percent is in Washington. The Blue Mountains are composed of primarily Paleozoic volcanic rocks, with minor sedimentary, metamorphic, and granitic rocks. Lower mountains and numerous basin-and-range areas, as well as the lack of Quaternary-age volcanoes, distinguish the Blue Mountains from the adjacent Cascade Range (Thorson and others, 2003).

von Kármán–Howarth Equation for Hall Magnetohydrodynamics: Hybrid Simulations

NASA Astrophysics Data System (ADS)

Hellinger, Petr; Verdini, Andrea; Landi, Simone; Franci, Luca; Matteini, Lorenzo

2018-04-01

A dynamical vectorial equation for homogeneous incompressible Hall-magnetohydrodynamic (MHD) turbulence together with the exact scaling law for third-order correlation tensors, analogous to that for the incompressible MHD, is rederived and applied to the results of two-dimensional hybrid simulations of plasma turbulence. At large (MHD) scales the simulations exhibit a clear inertial range where the MHD dynamic law is valid. In the sub-ion range the cascade continues via the Hall term, but the dynamic law derived in the framework of incompressible Hall-MHD equations is obtained only in a low plasma beta simulation. For a higher beta plasma the cascade rate decreases in the sub-ion range and the change becomes more pronounced as the plasma beta increases. This break in the cascade flux can be ascribed to nonthermal (kinetic) features or to others terms in the dynamical equation that are not included in the Hall-MHD incompressible approximation.

Application of TURBO-AE to Flutter Prediction: Aeroelastic Code Development

NASA Technical Reports Server (NTRS)

Hoyniak, Daniel; Simons, Todd A.; Stefko, George (Technical Monitor)

2001-01-01

The TURBO-AE program has been evaluated by comparing the obtained results to cascade rig data and to prediction made from various in-house programs. A high-speed fan cascade, a turbine cascade, a turbine cascade and a fan geometry that shower flutter in torsion mode were analyzed. The steady predictions for the high-speed fan cascade showed the TURBO-AE predictions to match in-house codes. However, the predictions did not match the measured blade surface data. Other researchers also reported similar disagreement with these data set. Unsteady runs for the fan configuration were not successful using TURBO-AE .

Cascades Ecoregion: Chapter 11 in Status and trends of land change in the Western United States--1973 to 2000

USGS Publications Warehouse

Sorenson, Daniel G.

2012-01-01

The Cascades Ecoregion (Omernik, 1987; U.S. Environmental Protection Agency, 1997) covers approximately 46,787 km2 (18,064 mi2) in Washington, Oregon, and California (fig. 1). The main body of the ecoregion extends from Snoqualmie Pass, Washington, in the north, to Hayden Mountain, near State Highway 66 in southern Oregon. Also included in the ecoregion is a small isolated section south of Bend, Oregon, as well as a larger one around Mount Shasta, California. The ecoregion is bounded on the west by the Klamath Mountains, Willamette Valley, and Puget Lowland Ecoregions; on the north by the North Cascades Ecoregion; and on the east by the Eastern Cascades Slopes and Foothills Ecoregion. The Cascades Ecoregion is a forested, mountainous ecoregion, and it contains a large amount of Cenozoic volcanic rock and many active and inactive volcanoes, especially in the east (McNab and Avers, 1994). Elevations range from near sea level at the Columbia River to 4,390 m at Mount Rainier in Washington, with most of the ecoregion between 645 and 2,258 m. The west side of the ecoregion is characterized by long, steep ridges and wide river valleys. Subalpine meadows are present at higher elevations, and alpine glaciers have left till and outwash deposits (McNab and Avers, 1994). Precipitation in the Cascades Ecoregion ranges from 1,300 to 3,800 mm, falling mostly as rain and snow from October to June. Average annual temperatures range from –1ºC to 11ºC. The length of the growing season varies from less than 30 days to 240 days (McNab and Avers, 1994).

Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archambault, S.; Griffin, S.; Archer, A.

2017-02-01

We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron–positron pairs, which then interact with cosmic microwave background photons via inverse-Compton scattering to produce gamma-rays. Due to the deflection of the electron–positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadenedmore » emission from 1ES 1218+304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around 10{sup −14} G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission.« less

Magnetospheric Multiscale Observation of Plasma Velocity-Space Cascade: Hermite Representation and Theory.

PubMed

Servidio, S; Chasapis, A; Matthaeus, W H; Perrone, D; Valentini, F; Parashar, T N; Veltri, P; Gershman, D; Russell, C T; Giles, B; Fuselier, S A; Phan, T D; Burch, J

2017-11-17

Plasma turbulence is investigated using unprecedented high-resolution ion velocity distribution measurements by the Magnetospheric Multiscale mission (MMS) in the Earth's magnetosheath. This novel observation of a highly structured particle distribution suggests a cascadelike process in velocity space. Complex velocity space structure is investigated using a three-dimensional Hermite transform, revealing, for the first time in observational data, a power-law distribution of moments. In analogy to hydrodynamics, a Kolmogorov approach leads directly to a range of predictions for this phase-space transport. The scaling theory is found to be in agreement with observations. The combined use of state-of-the-art MMS data sets, novel implementation of a Hermite transform method, and scaling theory of the velocity cascade opens new pathways to the understanding of plasma turbulence and the crucial velocity space features that lead to dissipation in plasmas.

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie

2014-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate in conditions of low Reynolds number and a wide range in incidence resulting from rotational speed variation. A comprehensive data set obtained in a linear cascade which includes the effects of Reynolds number, free-stream turbulence and incidence is now available and this paper concerns itself with the post-diction of boundary layer transitionseparation, blade pressure loading and total pressure loss pertaining to the conditions set for measurements in that data set. The distinction between the state of the measured data presented here and the earlier publications is the addition of high free-stream turbulence intensity. We will, for the purposes of the numerical post-diction, present some of the higher free stream turbulence data in this paper but defer a comprehensive presentation and treatment of the measured data will be done elsewhere.

Spectral characteristics of quantum-cascade laser operating at 10.6 μm wavelength for a seed application in laser-produced-plasma extreme UV source.

PubMed

Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru; Endo, Akira

2012-11-15

In this Letter, we investigate, for the first time to our knowledge, the spectral properties of a quantum-cascade laser (QCL) from a point of view of a new application as a laser seeder for a nanosecond-pulse high-repetition frequency CO(2) laser operating at 10.6 μm wavelength. The motivation for this work is a renewed interest in such a pulse format and wavelength driven by a development of extreme UV (EUV) laser-produced-plasma (LPP) sources. These sources use pulsed multikilowatt CO(2) lasers to drive the EUV-emitting plasmas. Basic spectral performance characteristics of a custom-made QCL chip are measured, such as tuning range and chirp rate. The QCL is shown to have all essential qualities of a robust seed source for a high-repetition nanosecond-pulsed CO(2) laser required by EUV LPP sources.

Washington Geothermal Play Fairway Analysis Data From Potential Field Studies

DOE Data Explorer

Anderson, Megan; Ritzinger, Brent; Glen, Jonathan; Schermerhorn, William

2017-12-20

A recent study which adapts play fairway analysis (PFA) methodology to assess geothermal potential was conducted at three locations (Mount Baker, Mount St. Helens seismic zone, and Wind River valley) along the Washington Cascade Range (Forson et al. 2017). Potential field (gravity and magnetic) methods which can detect subsurface contrasts in physical properties, provides a means for mapping and modeling subsurface geology and structure. As part of the WA-Cascade PFA project, we performed potential field studies by collecting high-resolution gravity and ground-magnetic data, and rock property measurements to (1) identify and constrain fault geometries (2) constrain subsurface lithologic distribution (3) study fault interactions (4) identify areas favorable to hydrothermal flow, and ultimately (5) guide future geothermal exploration at each location.

Coherent emission from integrated Talbot-cavity quantum cascade lasers.

PubMed

Meng, Bo; Qiang, Bo; Rodriguez, Etienne; Hu, Xiao Nan; Liang, Guozhen; Wang, Qi Jie

2017-02-20

We report experimental realization of phase-locked quantum cascade laser (QCL) array using a monolithically integrated Talbot cavity. An array with six laser elements at a wavelength of ~4.8 μm shows a maximum peak power of ~4 W which is more than 5 times higher than that of a single ridge laser element and a slope efficiency of 1 W/A at room temperature. Operation of in-phase coherent supermode has been achieved over the whole dynamic range of the Talbot-cavity QCL. The structure was analysed using a straightforward theoretical model, showing quantitatively good agreement with the experimental results. The reduced thermal resistance makes the structure an attractive approach to achieve high beam quality continuous wave QCLs.

Spectroscopic study of transparency current in mid-infrared quantum cascade lasers.

PubMed

Revin, Dmitry G; Hassan, Randa S; Krysa, Andrey B; Wang, Yongrui; Belyanin, Alexey; Kennedy, Kenneth; Atkins, Chris N; Cockburn, John W

2012-08-13

We report measurements which give direct insight into the origins of the transparency current for λ ~5 µm In0.6Ga0.4As/In0.42Al0.58As quantum cascade lasers in the temperature range of 80-280 K. The transparency current values have been found from broadband transmission measurements through the laser waveguides under sub-threshold operating conditions. Two active region designs were compared. The active region of the first laser is based on double-LO-phonon relaxation approach, while the second device has only one lower level, without specially designed resonant LO-phonon assisted depopulation. It is shown that transparency current contributes more than 70% to the magnitude of threshold current at high temperatures for both designs.

Highly temperature insensitive quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Y.; Bandyopadhyay, N.; Tsao, S.

2010-12-20

An InP based quantum cascade laser (QCL) heterostructure emitting around 5 {mu}m is grown with gas-source molecular beam epitaxy. The QCL core design takes a shallow-well approach to maximize the characteristic temperatures, T{sub 0} and T{sub 1}, for operations above room temperature. A T{sub 0} value of 383 K and a T{sub 1} value of 645 K are obtained within a temperature range of 298-373 K. In room temperature continuous wave operation, this design gives a single facet output power of 3 W and a wall plug efficiency of 16% from a device with a cavity length of 5 mmmore » and a ridge width of 8 {mu}m.« less

Costly bilingualism model in a population with one zealot

NASA Astrophysics Data System (ADS)

Hong, Hyunsuk; Son, Seung-Woo

2013-08-01

We consider a costly bilingualism model in which one can take two strategies in parallel. We investigate how a single zealot triggers the cascading behavior and how the compatibility of the two strategies affects when interacting patterns change. First, the role of the interaction range in the cascading is studied by increasing the range from local to global. We find that people sometimes do not favor taking the superior strategy even though its payoff is higher than that of the inferior one. This is found to be caused by the local interactions rather than the global ones. Applying this model to social networks, we find that the location of the zealot is also important for larger cascading in heterogeneous networks.

Costly bilingualism model in a population with one zealot.

PubMed

Hong, Hyunsuk; Son, Seung-Woo

2013-08-01

We consider a costly bilingualism model in which one can take two strategies in parallel. We investigate how a single zealot triggers the cascading behavior and how the compatibility of the two strategies affects when interacting patterns change. First, the role of the interaction range in the cascading is studied by increasing the range from local to global. We find that people sometimes do not favor taking the superior strategy even though its payoff is higher than that of the inferior one. This is found to be caused by the local interactions rather than the global ones. Applying this model to social networks, we find that the location of the zealot is also important for larger cascading in heterogeneous networks.

Magnetic-Field-Assisted Terahertz Quantum Cascade Laser Operating up to 225 K

NASA Technical Reports Server (NTRS)

Wade, A.; Fedorov, G.; Smirnov, D.; Kumar, S.; Williams, B. S.; Hu, Q.; Reno, J. L.

2008-01-01

Advances in semiconductor bandgap engineering have resulted in the recent development of the terahertz quantum cascade laser1. These compact optoelectronic devices now operate in the frequency range 1.2-5 THz, although cryogenic cooling is still required2.3. Further progress towards the realization of devices operating at higher temperatures and emitting at longer wavelengths (sub-terahertz quantum cascade lasers) is difficult because it requires maintaining a population inversion between closely spaced electronic sub-bands (1 THz approx. equals 4 meV). Here, we demonstrate a magnetic-field-assisted quantum cascade laser based on the resonant-phonon design. By applying appropriate electrical bias and strong magnetic fields above 16 T, it is possible to achieve laser emission from a single device over a wide range of frequencies (0.68-3.33 THz). Owing to the suppression of inter-landau-level non-radiative scattering, the device shows magnetic field assisted laser action at 1 THz at temperatures up to 215 K, and 3 THz lasing up to 225 K.

Cascades on a class of clustered random networks

NASA Astrophysics Data System (ADS)

Hackett, Adam; Melnik, Sergey; Gleeson, James P.

2011-05-01

We present an analytical approach to determining the expected cascade size in a broad range of dynamical models on the class of random networks with arbitrary degree distribution and nonzero clustering introduced previously in [M. E. J. Newman, Phys. Rev. Lett. PRLTAO0031-900710.1103/PhysRevLett.103.058701103, 058701 (2009)]. A condition for the existence of global cascades is derived as well as a general criterion that determines whether increasing the level of clustering will increase, or decrease, the expected cascade size. Applications, examples of which are provided, include site percolation, bond percolation, and Watts’ threshold model; in all cases analytical results give excellent agreement with numerical simulations.

Cascade redox flow battery systems

DOEpatents

Horne, Craig R.; Kinoshita, Kim; Hickey, Darren B.; Sha, Jay E.; Bose, Deepak

2014-07-22

A reduction/oxidation ("redox") flow battery system includes a series of electrochemical cells arranged in a cascade, whereby liquid electrolyte reacts in a first electrochemical cell (or group of cells) before being directed into a second cell (or group of cells) where it reacts before being directed to subsequent cells. The cascade includes 2 to n stages, each stage having one or more electrochemical cells. During a charge reaction, electrolyte entering a first stage will have a lower state-of-charge than electrolyte entering the nth stage. In some embodiments, cell components and/or characteristics may be configured based on a state-of-charge of electrolytes expected at each cascade stage. Such engineered cascades provide redox flow battery systems with higher energy efficiency over a broader range of current density than prior art arrangements.

A Multiplicative Cascade Model for High-Resolution Space-Time Downscaling of Rainfall

NASA Astrophysics Data System (ADS)

Raut, Bhupendra A.; Seed, Alan W.; Reeder, Michael J.; Jakob, Christian

2018-02-01

Distributions of rainfall with the time and space resolutions of minutes and kilometers, respectively, are often needed to drive the hydrological models used in a range of engineering, environmental, and urban design applications. The work described here is the first step in constructing a model capable of downscaling rainfall to scales of minutes and kilometers from time and space resolutions of several hours and a hundred kilometers. A multiplicative random cascade model known as the Short-Term Ensemble Prediction System is run with parameters from the radar observations at Melbourne (Australia). The orographic effects are added through multiplicative correction factor after the model is run. In the first set of model calculations, 112 significant rain events over Melbourne are simulated 100 times. Because of the stochastic nature of the cascade model, the simulations represent 100 possible realizations of the same rain event. The cascade model produces realistic spatial and temporal patterns of rainfall at 6 min and 1 km resolution (the resolution of the radar data), the statistical properties of which are in close agreement with observation. In the second set of calculations, the cascade model is run continuously for all days from January 2008 to August 2015 and the rainfall accumulations are compared at 12 locations in the greater Melbourne area. The statistical properties of the observations lie with envelope of the 100 ensemble members. The model successfully reproduces the frequency distribution of the 6 min rainfall intensities, storm durations, interarrival times, and autocorrelation function.

Results of temperature gradient and heat flow in Santiam Pass Area, Oregon, Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, B.L.; Gardner, M.C.; Koenig, J.B.

The conclusions of this report are: (1) There is a weakly defined thermal anomaly within the area examined by temperature-gradient holes in the Santiam Pass area. This is a relict anomaly showing differences in permeability between the High Cascades and Western Cascades areas, more than a fundamental difference in shallow crustal temperatures. (2) The anomaly as defined by the 60 F isotherms at 400 feet follows a north-south trend immediately westward of the Cascade axis in the boundary region. It is clear that all holes spudded into High Cascades rocks result in isothermal and reversal gradients. Holes spudded in Westernmore » Cascades rocks result in positive gradients. (3) Cold groundwater flow influences and masks temperature gradients in the High Cascades to a depth of at least 700 feet, especially eastward from the major north-south trending faults. Pleistocene and Holocene rocks are very permeable aquifers. (4) Shallow gradient drilling in the lowlands westward of the faults provides more interpretable information than shallow drilling in the cold-water recharge zones. Topographic and climatological effects can be filtered out of the temperature gradient results. (5) The thermal anomaly seems to have 2 centers: one in the Belknap-Foley area, and one northward in the Sand Mountain area. The anomalies may or may not be connected along a north-south trend. (6) A geothermal effect is seen in holes downslope of the Western-High Cascade boundary. Mixing with cold waters is a powerful influence on temperature gradient data. (7) The temperature-gradient program has not yet examined and defined the geothermal resources potential of the area eastward of the Western Cascades-High Cascades boundary. Holes to 1500-2000 feet in depth are required to penetrate the high permeability-cold groundwater regime. (8) Drilling conditions are unfavorable. There are very few accessible level drill sites. Seasonal access problems and environmental restrictions together with frequent lost circulation results in very high costs per foot drilled.« less

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2014-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters-Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2015-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters- Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

External cavity tunable quantum cascade lasers and their applications to trace gas monitoring.

PubMed

Rao, Gottipaty N; Karpf, Andreas

2011-02-01

Since the first quantum cascade laser (QCL) was demonstrated approximately 16 years ago, we have witnessed an explosion of interesting developments in QCL technology and QCL-based trace gas sensors. QCLs operate in the mid-IR region (3-24 μm) and can directly access the rotational vibrational bands of most molecular species and, therefore, are ideally suited for trace gas detection with high specificity and sensitivity. These sensors have applications in a wide range of fields, including environmental monitoring, atmospheric chemistry, medical diagnostics, homeland security, detection of explosive compounds, and industrial process control, to name a few. Tunable external cavity (EC)-QCLs in particular offer narrow linewidths, wide ranges of tunability, and stable power outputs, which open up new possibilities for sensor development. These features allow for the simultaneous detection of multiple species and the study of large molecules, free radicals, ions, and reaction kinetics. In this article, we review the current status of EC-QCLs and sensor developments based on them and speculate on possible future developments.

Transfer of Metasupracrustal Rocks to Midcrustal Depths in the North Cascades Continental Magmatic Arc, Skagit Gneiss Complex, Washington

NASA Astrophysics Data System (ADS)

Sauer, K. B.; Gordon, S. M.; Miller, R. B.; Vervoort, J. D.; Fisher, C. M.

2017-12-01

The metasupracrustal units within the north central Chelan block of the North Cascades Range, Washington, are investigated to determine mechanisms and timescales of supracrustal rock incorporation into the deep crust of continental magmatic arcs. Zircon U-Pb and Hf-isotope analyses were used to characterize the protoliths of metasedimentary and metaigneous rocks from the Skagit Gneiss Complex, metasupracrustal rocks from the Cascade River Schist, and metavolcanic rocks from the Napeequa Schist. Skagit Gneiss Complex metasedimentary rocks have (1) a wide range of zircon U-Pb dates from Proterozoic to latest Cretaceous and (2) a more limited range of dates, from Late Triassic to latest Cretaceous, and a lack of Proterozoic dates. Two samples from the Cascade River Schist are characterized by Late Cretaceous protoliths. Amphibolites from the Napeequa Schist have Late Triassic protoliths. Similarities between the Skagit Gneiss metasediments and accretionary wedge and forearc sediments in northwestern Washington and Southern California indicate that the protolith for these units was likely deposited in a forearc basin and/or accretionary wedge in the Early to Late Cretaceous (circa 134-79 Ma). Sediment was likely underthrust into the active arc by circa 74-65 Ma, as soon as 7 Ma after deposition, and intruded by voluminous magmas. The incorporation of metasupracrustal units aligns with the timing of major arc magmatism in the North Cascades (circa 79-60 Ma) and may indicate a link between the burial of sediments and pluton emplacement.

Investigations of the influence of the profile thickness of the compressible plane flow through compressor cascades

NASA Technical Reports Server (NTRS)

Bahr, J.

1978-01-01

Flow-through cascade of an aircraft turbine compressor is studied experimentally over wide range of Reynolds numbers and subsonic Mach numbers; it was found that deterioration of flow properties due to decreasing Reynolds numbers is less noticeable on thin profiles than on thick ones; however, thick profiles are advantageous in compressors designed for efficient partial load behavior because thick profiles have a relatively large range of usable inlet flow angles.

Quantum cascade laser-based sensor system for nitric oxide detection

NASA Astrophysics Data System (ADS)

Tittel, Frank K.; Allred, James J.; Cao, Yingchun; Sanchez, Nancy P.; Ren, Wei; Jiang, Wenzhe; Jiang, Dongfang; Griffin, Robert J.

2015-01-01

Sensitive detection of nitric oxide (NO) at ppbv concentration levels has an important impact in diverse fields of applications including environmental monitoring, industrial process control and medical diagnostics. For example, NO can be used as a biomarker of asthma and inflammatory lung diseases such as chronic obstructive pulmonary disease. Trace gas sensor systems capable of high sensitivity require the targeting of strong rotational-vibrational bands in the mid-IR spectral range. These bands are accessible using state-of-the-art high heat load (HHL) packaged, continuous wave (CW), distributed feedback (DFB) quantum cascade lasers (QCLs). Quartz-enhanced photoacoustic spectroscopy (QEPAS) permits the design of fast, sensitive, selective, and compact sensor systems. A QEPAS sensor was developed employing a room-temperature CW DFB-QCL emitting at 5.26 μm with an optical excitation power of 60 mW. High sensitivity is achieved by targeting a NO absorption line at 1900.08 cm-1 free of interference by H2O and CO2. The minimum detection limit of the sensor is 7.5 and 1 ppbv of NO with 1and 100 second averaging time respectively . The sensitivity of the sensor system is sufficient for detecting NO in exhaled human breath, with typical concentration levels ranging from 24.0 ppbv to 54.0 ppbv.

A cascade of warming impacts brings bluefin tuna to Greenland waters.

PubMed

MacKenzie, Brian R; Payne, Mark R; Boje, Jesper; Høyer, Jacob L; Siegstad, Helle

2014-08-01

Rising ocean temperatures are causing marine fish species to shift spatial distributions and ranges, and are altering predator-prey dynamics in food webs. Most documented cases of species shifts so far involve relatively small species at lower trophic levels, and consider individual species in ecological isolation from others. Here, we show that a large highly migratory top predator fish species has entered a high latitude subpolar area beyond its usual range. Bluefin tuna, Thunnus thynnus Linnaeus 1758, were captured in waters east of Greenland (65°N) in August 2012 during exploratory fishing for Atlantic mackerel, Scomber scombrus Linnaeus 1758. The bluefin tuna were captured in a single net-haul in 9-11 °C water together with 6 tonnes of mackerel, which is a preferred prey species and itself a new immigrant to the area. Regional temperatures in August 2012 were historically high and contributed to a warming trend since 1985, when temperatures began to rise. The presence of bluefin tuna in this region is likely due to a combination of warm temperatures that are physiologically more tolerable and immigration of an important prey species to the region. We conclude that a cascade of climate change impacts is restructuring the food web in east Greenland waters. © 2014 John Wiley & Sons Ltd.

Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.

2015-07-01

Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025more » and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.« less

Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA

Treesearch

A. Jefferson; G.E. Grant; S.L. Lewis; S.T. Lancaster

2010-01-01

Young basalt terrains offer an exceptional opportunity to study landscape and hydrologic evolution through time, as the age of the landscape itself can be determined by dating lava flows. These constructional terrains are also highly permeable, allowing one to examine timescales and process of geomorphic evolution as they relate to the partitioning of hydrologic...

The cascade high productivity language

NASA Technical Reports Server (NTRS)

Callahan, David; Chamberlain, Branford L.; Zima, Hans P.

2004-01-01

This paper describes the design of Chapel, the Cascade High Productivity Language, which is being developed in the DARPA-funded HPCS project Cascade led by Cray Inc. Chapel pushes the state-of-the-art in languages for HEC system programming by focusing on productivity, in particular by combining the goal of highest possible object code performance with that of programmability offered by a high-level user interface.

Optimizing topological cascade resilience based on the structure of terrorist networks.

PubMed

Gutfraind, Alexander

2010-11-10

Complex socioeconomic networks such as information, finance and even terrorist networks need resilience to cascades--to prevent the failure of a single node from causing a far-reaching domino effect. We show that terrorist and guerrilla networks are uniquely cascade-resilient while maintaining high efficiency, but they become more vulnerable beyond a certain threshold. We also introduce an optimization method for constructing networks with high passive cascade resilience. The optimal networks are found to be based on cells, where each cell has a star topology. Counterintuitively, we find that there are conditions where networks should not be modified to stop cascades because doing so would come at a disproportionate loss of efficiency. Implementation of these findings can lead to more cascade-resilient networks in many diverse areas.

Developmental cascades: Externalizing, internalizing, and academic competence from middle childhood to early adolescence

PubMed Central

Moilanen, Kristin L.; Shaw, Daniel S.; Maxwell, Kari L.

2011-01-01

The current study was initiated to increase understanding of developmental cascades in childhood in a sample of at-risk boys (N = 291; 52% White). Mothers, teachers, and boys reported on boys’ externalizing problems, internalizing difficulties, and academic competence. Consistent with hypotheses regarding school-related transitions, high levels of externalizing problems were associated with both low levels of academic competence and high levels of internalizing problems during the early school-age period, and with elevations in internalizing problems during the transition to adolescence. Low levels of academic competence were associated with high levels of internalizing problems in middle childhood, and with high levels of externalizing problems during the transition from elementary school to middle school. Shared risk factors played a minimal role in these developmental cascades. Results suggest that there are cascading effects of externalizing problems and academic competence in childhood and early adolescence, and that some cascading effects are more likely to occur during periods of school-related transitions. Implications of developmental cascade effects for research and intervention are discussed. PMID:20576184

Quantum Cascade Lasers Modulation and Applications

NASA Astrophysics Data System (ADS)

Luzhansky, Edward

The mid-wave IR (MWIR) spectral band, extending from 3 to 5 microns, is considered to be a low loss atmospheric window. There are several spectral sub-bands with relatively low atmospheric attenuation in this region making it popular for various commercial and military applications. Relatively low thermal and solar background emissions, effective penetration through the natural and anthropogenic obscurants and eye safety add to the long list of advantages of MWIR wavelengths. Quantum Cascade Lasers are compact semiconductor devices capable of operating in MWIR spectrum. They are based on inter-subband transitions in a multiple-quantum-well (QW) hetero-structure, designed by means of band-structure engineering. The inter-subband nature of the optical transition has several key advantages. First, the emission wavelength is primarily a function of the QW thickness. This characteristic allows choosing well-understood and reliable semiconductors for the generation of light in a wavelength range of interest. Second, a cascade process in which tens of photons are generated per injected electron. This cascading process is behind the intrinsic high-power capabilities of QCLs. This dissertation is focused on modulation properties of Quantum Cascade Lasers. Both amplitude and phase/frequency modulations were studied including modulation bandwidth, modulation efficiency and chirp linearity. Research was consisted of the two major parts. In the first part we describe the theory of frequency modulation (FM) response of Distributed Feedback Quantum Cascade Lasers (DFB QCL). It includes cascading effect on the QCL's maximum modulation frequency. The "gain levering" effect for the maximum FM response of the two section QCLs was studied as well. In the second part of research we concentrated on the Pulse Position Amplitude Modulation of a single section QCL. The low complexity, low size, weight and power Mid-Wavelength Infra-Red optical communications transceiver concept is introduced. The concept was realized and tested in the laboratory environment. The resilience to atmospheric impairments are analyzed with simulated turbulence. The performance compared to typical telecom based Short Wavelength Infra-Red transceiver.

Field-trip guide to mafic volcanism of the Cascade Range in Central Oregon—A volcanic, tectonic, hydrologic, and geomorphic journey

USGS Publications Warehouse

Deligne, Natalia I.; Mckay, Daniele; Conrey, Richard M.; Grant, Gordon E.; Johnson, Emily R.; O'Connor, Jim; Sweeney, Kristin

2017-08-16

The Cascade Range in central Oregon has been shaped by tectonics, volcanism, and hydrology, as well as geomorphic forces that include glaciations. As a result of the rich interplay between these forces, mafic volcanism here can have surprising manifestations, which include relatively large tephra footprints and extensive lava flows, as well as water shortages, transportation and agricultural disruption, and forest fires. Although the focus of this multidisciplinary field trip will be on mafic volcanism, we will also look at the hydrology, geomorphology, and ecology of the area, and we will examine how these elements both influence and are influenced by mafic volcanism. We will see mafic volcanic rocks at the Sand Mountain volcanic field and in the Santiam Pass area, at McKenzie Pass, and in the southern Bend region. In addition, this field trip will occur during a total solar eclipse, the first one visible in the United States in more than 25 years (and the first seen in the conterminous United States in more than 37 years).The Cascade Range is the result of subduction of the Juan de Fuca plate underneath the North American plate. This north-south-trending volcanic mountain range is immediately downwind of the Pacific Ocean, a huge source of moisture. As moisture is blown eastward from the Pacific on prevailing winds, it encounters the Cascade Range in Oregon, and the resulting orographic lift and corresponding rain shadow is one of the strongest precipitation gradients in the conterminous United States. We will see how the products of the volcanoes in the central Oregon Cascades have had a profound influence on groundwater flow and, thus, on the distribution of Pacific moisture. We will also see the influence that mafic volcanism has had on landscape evolution, vegetation development, and general hydrology.

DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

NASA Astrophysics Data System (ADS)

Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

2013-06-01

Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

Fens as whole-ecosystem gauges of groundwater recharge under climate change

USGS Publications Warehouse

Drexler, Judith Z.; Knifong, Donna L.; JayLee Tuil,; Flint, Lorraine E.; Flint, Alan L.

2013-01-01

Currently, little is known about the impact of climate change on groundwater recharge in the Sierra Nevada and southern Cascade Range of California or other mountainous regions of the world. The purpose of this study was to determine whether small alpine peat lands called fens can be used as whole-ecosystem gauges of groundwater recharge through time. Fens are sustained by groundwater discharge and are highly sensitive to changes in groundwater flow due to hydrologic disturbance including climate change. Seven fens in the Sierra Nevada and southern Cascade Range were studied over a 50-80 year period using historic aerial photography. In each aerial photograph, fen areas were identified as open lawn and partially treed areas that exhibited (1) dark brownish-green coloring or various shades of gray and black in black and white imagery and (2) mottling of colors and clustering of vegetation, which signified a distinct moss canopy with overlying clumped sedge vegetation. In addition to the aerial photography study, a climate analysis for the study sites was carried out using both measured data (U.S. Department of Agriculture Natural Resources Conservation Service SNOwpack TELemetry system) and modeled data (a downscaled version of the Parameter-elevation Regressions on Independent Slopes Model) for the period from 1951 to 2010. Over the study period, the five fens in the Sierra Nevada were found to be decreasing between 10% and 16% in delineated area. The climate analysis revealed significant increases through time in annual mean minimum temperature (Tmin) between 1951-1980 and 1981-2010. In addition, April 1 snow water equivalent and snowpack longevity also decreased between 1951-1980 and 1981-2010. For the fens in the Cascade Range, there were no discernible changes in delineated area. At these sites, increases in Tmin occurred only within the past 20-25 years and decreases in snowpack longevity were more subtle. A conceptual model is presented, which illustrates that basic differences in hydrogeology of the Sierra Nevada vs. the Cascade Range may control the threshold at which changes in delineated fen areas are discernible. Overall, the results from this study show that fens in the Sierra Nevada have strong potential as whole ecosystem gauges for determining long-term changes in groundwater recharge under climate change. Due to either more moderate climate change and/or hydrogeological differences, fens in the southern Cascade Range currently do not appear to have the same utility. A greater sample size of fens in the Sierra Nevada is needed to confirm the general applicability of this method. In addition, future work needs to focus on integrating fen monitoring with geochemical and/or isotopic process-level studies in order to quantify changes in groundwater recharge identified using this new approach.

Electrically Tunable Terahertz Quantum-Cascade Lasers

NASA Technical Reports Server (NTRS)

Gunapala, Sarath; Soidel, Alexander; Mansour, Kamjou

2006-01-01

Improved quantum-cascade lasers (QCLs) are being developed as electrically tunable sources of radiation in the far infrared spectral region, especially in the frequency range of 2 to 5 THz. The structures of QCLs and the processes used to fabricate them have much in common with those of multiple- quantum-well infrared photodetectors.

Energy Transfer and Dual Cascade in Kinetic Magnetized Plasma Turbulence

NASA Astrophysics Data System (ADS)

Plunk, G. G.; Tatsuno, T.

2011-04-01

The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally.

Some Effects of Compressibility on the Flow Through Fans and Turbines

NASA Technical Reports Server (NTRS)

Perl, W.; Epstein, H. T.

1946-01-01

The laws of conservation of mass, momentum, and energy are applied to the compressible flow through a two-dimensional cascade of airfoils. A fundamental relation between the ultimate upstream and downstream flow angles, the inlet Mach number, and the pressure ratio across the cascade is derived. Comparison with the corresponding relation for incompressible flow shows large differences. The fundamental relation reveals two ranges of flow angles and inlet Mach numbers, for which no ideal pressure ratio exists. One of these nonideal operating ranges is analogous to a similar type in incompressible flow. The other is characteristic only of compressible flow. The effect of variable axial-flow area is treated. Some implications of the basic conservation laws in the case of nonideal flow through cascades are discussed.

Seasonal variation in diel behaviour and habitat use by age 1+ steelhead (Oncorhynchus mykiss) in Coast and Cascade Range streams in Oregon, U.S.A

Treesearch

Gordon H. Reeves; Jon B. Grunbaum; Dirk W. Lang

2009-01-01

The seasonal diel behaviour of age 1+ steelhead from Coast and Cascade Range streams in Oregon was examined in the field and in laboratory streams. During the summer, fish from both areas were active during the day in natural streams: they held position in the water column in moderate velocities and depths. At night, fish were in slower water, closer to the bottom...

Weak- and strong-turbulence regimes of the forced Hasegawa-Mima equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ottaviani, M.; Krommes, J.A.

1992-11-16

A Kolmogorov-type analysis of the energy- and enstrophy-cascading ranges of a forced Hasegawa-Mima equation allows one to derive a criterion for the threshold of the transition between the weak-turbulence and the strong-turbulence regimes. Contrary to general belief, it is found that due to the inverse energy cascade the large-scale portion of the inertial range is in the strong-turbulence regime in the limit of infinite Reynolds-like numbers for any finite amount of forcing.

Wind tunnel wall effects in a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1991-01-01

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

Novel High Power Type-I Quantum Well Cascade Diode Lasers

DTIC Science & Technology

2017-08-30

Novel High Power Type-I Quantum Well Cascade Diode Lasers The views, opinions and/or findings contained in this report are those of the author(s...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6... High Power Type-I Quantum Well Cascade Diode Lasers Report Term: 0-Other Email: leon.shterengas@stonybrook.edu Distribution Statement: 1-Approved

Protein dynamics observed by tunable mid-IR quantum cascade lasers across the time range from 10ns to 1s.

PubMed

Schultz, Bernd-Joachim; Mohrmann, Hendrik; Lorenz-Fonfria, Victor A; Heberle, Joachim

2018-01-05

We have developed a spectrometer based on tunable quantum cascade lasers (QCLs) for recording time-resolved absorption spectra of proteins in the mid-infrared range. We illustrate its performance by recording time-resolved difference spectra of bacteriorhodopsin in the carboxylic range (1800-1700cm -1 ) and on the CO rebinding reaction of myoglobin (1960-1840cm -1 ), at a spectral resolution of 1cm -1 . The spectrometric setup covers the time range from 4ns to nearly a second with a response time of 10-15ns. Absorption changes as low as 1×10 -4 are detected in single-shot experiments at t>1μs, and of 5×10 -6 in kinetics obtained after averaging 100 shots. While previous time-resolved IR experiments have mostly been conducted on hydrated films of proteins, we demonstrate here that the brilliance of tunable quantum cascade lasers is superior to perform ns time-resolved experiments even in aqueous solution (H 2 O). Copyright © 2017 Elsevier B.V. All rights reserved.

Quantum-cascade lasers in the 7-8 μm spectral range with full top metallization

NASA Astrophysics Data System (ADS)

Kurochkin, A. S.; Babichev, A. V.; Denisov, D. V.; Karachinsky, L. Ya; Novikov, I. I.; Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Bousseksou, A.; Egorov, A. Yu

2018-03-01

The paper demonstrates the generation of multistage quantum-cascade lasers (QCL) in the 7-8 μm spectral range in the pulse generation mode. The active region structure we used is based on a two-phonon resonance scheme. The QCL heterostructure based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys was grown by molecular beam epitaxy and includes 50 identical stages. A waveguide geometry with top cladding with full top metallization (surface- plasmon quantum-cascade lasers) has been used. The developed QCLs have demonstrated multimodal generation in the 7-8 μm spectral range in the pulse mode in the 78-250 K temperature range. The threshold current density for a 1.6 mm long laser and a 20 μm ridge width amounted to ˜ 2.8 kA/cm2 at a temperature of 78 К. A temperature increase to 250 K causes a long-wave shift of the wavelength from 7.6 to 7.9 μm and a jth increase to 5.0 kA/cm2.

Cascaded VLSI Chips Help Neural Network To Learn

NASA Technical Reports Server (NTRS)

Duong, Tuan A.; Daud, Taher; Thakoor, Anilkumar P.

1993-01-01

Cascading provides 12-bit resolution needed for learning. Using conventional silicon chip fabrication technology of VLSI, fully connected architecture consisting of 32 wide-range, variable gain, sigmoidal neurons along one diagonal and 7-bit resolution, electrically programmable, synaptic 32 x 31 weight matrix implemented on neuron-synapse chip. To increase weight nominally from 7 to 13 bits, synapses on chip individually cascaded with respective synapses on another 32 x 32 matrix chip with 7-bit resolution synapses only (without neurons). Cascade correlation algorithm varies number of layers effectively connected into network; adds hidden layers one at a time during learning process in such way as to optimize overall number of neurons and complexity and configuration of network.

Experimental attrition rates of bed-material sediment from geologic provinces of Western Oregon and their application to regional sediment models

NASA Astrophysics Data System (ADS)

Mangano, J.; O'Connor, J. E.; Jones, K. L.; Wallick, R.

2011-12-01

Many topographic, hydrologic, and land use variables affect the supply and transport of bed-material in rivers, but the underlying geology is a key factor controlling both the volume of introduced material and the attrition of bed-material as it moves downstream. Recent and ongoing USGS river studies in Western Oregon document strong links between geologic province and bed-material transport. Rivers originating in the Mesozoic metamorphic and intrusive igneous rocks of the Klamath terranes of southwestern Oregon have the greatest gravel transport rates (and channel and valley-bottom morphologies reflecting high bed-material fluxes), whereas the generally lesser amounts of gravel in streams that drain Oregon's Coast Range and western Cascade Range owes in large part to Tertiary sedimentary and volcanic units underlying most of these basins. Aspects of these differences are controlled by supply as well as clast attrition. Here we aim to quantify bed-material attrition rates associated with the five main geologic provinces of Western Oregon: the Klamath terranes, Western Cascades, High Cascades, Coast Range sedimentary rocks, and Coast Range volcanic rocks. Bed-material samples were collected throughout the region from streams that drain a single geologic province and tumbled with a lapidary tumbler to determine relative attrition rates. Two kilograms of each sample were sorted into an initial distribution of clast sizes (from 16 to 64mm) and tumbled, with periodic breaks to reweigh and sieve the sample. Results show marked differences in attrition rates, with the sedimentary rocks of the Coast Range having weight loss coefficients between 1.206 and 0.211/km, orders of magnitude greater than all of the other sampled provinces. For comparison, bed material from the Klamath terranes have weight loss coefficients ranging from 0.013 to 0.005/km, and a control sample of quartzite clasts (from the Klamath terranes) has a weight loss coefficient of 0.001/km. These results confirm that bed-material attrition is an important process affecting bed-material supply and transport, and will allow for more complete development of regional bed-material sediment budgets in ongoing efforts to understand patterns of gravel abundance and channel morphology in rivers of Western Oregon.

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers

NASA Astrophysics Data System (ADS)

Balaswamy, V.; Arun, S.; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V. R.

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here, a simple architecture for high power, fixed and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the Ytterbium band to the eye-safe 1.5micron region. We demonstrate pump-limited output powers of over 30W in fixed and continuously wavelength tunable configurations.

Costs along the service cascades for HIV testing and counselling and prevention of mother-to-child transmission

PubMed Central

Bautista-Arredondo, Sergio; Sosa-Rubí, Sandra G.; Opuni, Marjorie; Contreras-Loya, David; Kwan, Ada; Chaumont, Claire; Chompolola, Abson; Condo, Jeanine; Galárraga, Omar; Martinson, Neil; Masiye, Felix; Nsanzimana, Sabin; Ochoa-Moreno, Ivan; Wamai, Richard; Wang’ombe, Joseph

2016-01-01

Objective: We estimate facility-level average annual costs per client along the HIV testing and counselling (HTC) and prevention of mother-to-child transmission (PMTCT) service cascades. Design: Data collected covered the period 2011–2012 in 230 HTC and 212 PMTCT facilities in Kenya, Rwanda, South Africa, and Zambia. Methods: Input quantities and unit prices were collected, as were output data. Annual economic costs were estimated from the service providers’ perspective using micro-costing. Average annual costs per client in 2013 United States dollars (US$) were estimated along the service cascades. Results: For HTC, average cost per client tested ranged from US$5 (SD US$7) in Rwanda to US$31 (SD US$24) in South Africa, whereas average cost per client diagnosed as HIV-positive ranged from US$122 (SD US$119) in Zambia to US$1367 (SD US$2093) in Rwanda. For PMTCT, average cost per client tested ranged from US$18 (SD US$20) in Rwanda to US$89 (SD US$56) in South Africa; average cost per client diagnosed as HIV-positive ranged from US$567 (SD US$417) in Zambia to US$2021 (SD US$3210) in Rwanda; average cost per client on antiretroviral prophylaxis ranged from US$704 (SD US$610) in South Africa to US$2314 (SD US$3204) in Rwanda; and average cost per infant on nevirapine ranged from US$888 (SD US$884) in South Africa to US$2359 (SD US$3257) in Rwanda. Conclusion: We found important differences in unit costs along the HTC and PMTCT service cascades within and between countries suggesting that more efficient delivery of these services is possible. PMID:27753679

Vane Separation Control in a Linear Cascade with Area Expansion using AC DBD Plasma Actuators

NASA Astrophysics Data System (ADS)

Kleven, Christopher; Corke, Thomas

2013-11-01

Experiments are presented on the use of AC dielectric barrier discharge (DBD) plasma actuators to prevent flow separation on vanes in a linear cascade with area expansion. The inlet Mach number to the cascade ranged from 0.3 to 0.5, and the vane chord Reynolds numbers ranged from 0 . 9 ×106 to 1 . 5 ×106 . Three cascade designs with different amounts of area expansion, providing different degrees of adverse pressure gradients, were examined. Surface flow visualization revealed a 3-D separation bubble with strong recirculation that formed on the suction side of the vanes. The pattern agreed well with CFD simulations. Plasma actuators were placed on the suction sides of the vanes, just upstream of the flow separation location. Quantitative measurements were performed in the wakes of the vanes using a 5-hole Pitot probe. The measurements were used to determine the effect of the plasma actuator separation control on the pressure loss coefficient, and flow turning angle through the cascades. Overall, the plasma actuators separation control increased the velocity magnitude and dynamic pressure in the passage between the vanes, resulted in a more spanwise-uniform flow turning angle in the vane passage, and significantly lowered the loss coefficient compared to the baseline.

Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection

PubMed Central

Elia, Angela; Di Franco, Cinzia; Lugarà, Pietro Mario; Scamarcio, Gaetano

2006-01-01

Various applications, such as pollution monitoring, toxic-gas detection, non invasive medical diagnostics and industrial process control, require sensitive and selective detection of gas traces with concentrations in the parts in 109 (ppb) and sub-ppb range. The recent development of quantum-cascade lasers (QCLs) has given a new aspect to infrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLs are attractive spectroscopic sources because of their excellent properties in terms of narrow linewidth, average power and room temperature operation. In combination with these laser sources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity, compact sensor platform, fast time-response and user friendly operation. This paper reports recent developments on quantum cascade laser-based photoacoustic spectroscopy for trace gas detection. In particular, different applications of a photoacoustic trace gas sensor employing a longitudinal resonant cell with a detection limit on the order of hundred ppb of ozone and ammonia are discussed. We also report two QC laser-based photoacoustic sensors for the detection of nitric oxide, for environmental pollution monitoring and medical diagnostics, and hexamethyldisilazane, for applications in semiconductor manufacturing process.

Cascade signal amplification for electrochemical immunosensing by integrating biobarcode probes, surface-initiated enzymatic polymerization and silver nanoparticle deposition.

PubMed

Lin, Dajie; Mei, Chengyang; Liu, Aili; Jin, Huile; Wang, Shun; Wang, Jichang

2015-04-15

A cascade signal amplification strategy through combining surface-initiated enzymatic polymerization (SIEP) and the subsequent deposition of strepavidin functionalized silver nanoparticles (AgNPs) was proposed. The first step of constructing the electrochemical immunosensor involves covalently immobilizing capture antibody on a chitosan modified glass carbon electrode, which then catalyzes DNA addition of deoxynucleotides (dNTP) at the 3'-OH group by terminal deoxynucleotidyl transferase (TdT), leading to the formation of long single-stranded DNAs labeled with numerous biotins. Following the deposition of numerous strepavidin functionalized AgNPs on those long DNA chains, electrochemical stripping signal of silver was used to monitor the immunoreaction in KCl solution. Using α-fetoprotein as a model analyte, this amplification strategy could detect fetoprotein down to 0.046pg/mL with a wide linear range from 0.1pg/mL to 1.0ng/mL. The achieved high sensitivity and good reproducibility suggest that this cascade signal amplification strategy has great potential for detecting biological samples and possibly clinical application. Copyright © 2014 Elsevier B.V. All rights reserved.

Quantum cascade lasers as metrological tools for space optics

NASA Astrophysics Data System (ADS)

Bartalini, S.; Borri, S.; Galli, I.; Mazzotti, D.; Cancio Pastor, P.; Giusfredi, G.; De Natale, P.

2017-11-01

A distributed-feedback quantum-cascade laser working in the 4.3÷4.4 mm range has been frequency stabilized to the Lamb-dip center of a CO2 ro-vibrational transition by means of first-derivative locking to the saturated absorption signal, and its absolute frequency counted with a kHz-level precision and an overall uncertainty of 75 kHz. This has been made possible by an optical link between the QCL and a near-IR Optical Frequency Comb Synthesizer, thanks to a non-linear sum-frequency generation process with a fiber-amplified Nd:YAG laser. The implementation of a new spectroscopic technique, known as polarization spectroscopy, provides an improved signal for the locking loop, and will lead to a narrower laser emission and a drastic improvement in the frequency stability, that in principle is limited only by the stability of the optical frequency comb synthesizer (few parts in 1013). These results confirm quantum cascade lasers as reliable sources not only for high-sensitivity, but also for highprecision measurements, ranking them as optimal laser sources for space applications.

Refractive index and temperature sensors based on no-core fiber cascaded with long period fiber grating

NASA Astrophysics Data System (ADS)

Zhang, Jianming; Pu, Shengli; Rao, Jie; Yao, Tianjun

2018-05-01

A kind of compact fibre-optic sensor based on no-core fibre (NCF) cascaded with a strong coupling long-period fibre grating (LPFG) is proposed and experimentally demonstrated. The sensing mechanism is based on the Mach-Zehnder-like interference between the core fundamental mode and cladding mode of the fibre structure. The NCF and LPFG are used as the mode exciter and combiner, respectively. Due to the particular properties of the strong coupling LPFG, the measurements of refractive index (RI) and temperature with high sensitivity are realized by monitoring the transmission spectrum with intensity and wavelength interrogation techniques, respectively. The achieved RI sensitivity reaches -580.269 dB/RIU in the range of 1.436-1.454 and the temperature sensitivity reaches 27.2 pm/°C.

Passive mode-locking of a diode-pumped Nd:YVO(4) laser by intracavity SHG in PPKTP.

PubMed

Iliev, Hristo; Chuchumishev, Danail; Buchvarov, Ivan; Petrov, Valentin

2010-03-15

Experimental results on passive mode-locking of a Nd:YVO(4) laser using intracavity frequency doubling in periodically poled KTP (PPKTP) crystal are reported. Both, negative cascaded chi((2)) lensing and frequency doubling nonlinear mirror (FDNLM) are exploited for the laser mode-locking. The FDNLM based on intensity dependent reflection in the laser cavity ensures self-starting and self-sustaining mode-locking while the cascaded chi((2)) lens process contributes to substantial pulse shortening. This hybrid technique enables generation of stable trains of pulses at high-average output power with several picoseconds pulse width. The pulse repetition rate of the laser is 117 MHz with average output power ranging from 0.5 to 3.1 W and pulse duration from 2.9 to 5.2 ps.

Terahertz wave polarization beam splitter using a cascaded multimode interference structure.

PubMed

Li, Jiu-sheng; Liu, Han; Zhang, Le

2014-08-01

A terahertz wave polarization beam splitter, based on two cascaded multimode interference structures with different widths, is designed and numerically demonstrated. The numerical calculation results show that the designed polarization beam splitter can split transverse-electric (TE) and transverse-magnetic (TM)-polarized terahertz waves into different propagation directions with high efficiency over a frequency range from 6.40 to 6.50 THz. This polarization beam splitter shows more than a 22.06 dB extinction ratio for TE-polarization and a 31.65 dB extinction ratio for TM-polarization. Using such a polarization beam splitter, the whole length of the polarization beam splitter is reduced to about 1/12 that of a conventional design. This enables the polarization beam splitter to be used in terahertz wave integrated circuit fields.

Quantum cascade laser-based mid-IR frequency metrology system with ultra-narrow linewidth and 1  ×  10⁻¹³-level frequency instability.

PubMed

Hansen, Michael G; Magoulakis, Evangelos; Chen, Qun-Feng; Ernsting, Ingo; Schiller, Stephan

2015-05-15

We demonstrate a powerful tool for high-resolution mid-IR spectroscopy and frequency metrology with quantum cascade lasers (QCLs). We have implemented frequency stabilization of a QCL to an ultra-low expansion (ULE) reference cavity, via upconversion to the near-IR spectral range, at a level of 1×10(-13). The absolute frequency of the QCL is measured relative to a hydrogen maser, with instability <1×10(-13) and inaccuracy 5×10(-13), using a frequency comb phase stabilized to an independent ultra-stable laser. The QCL linewidth is determined to be 60 Hz, dominated by fiber noise. Active suppression of fiber noise could result in sub-10 Hz linewidth.

Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

NASA Astrophysics Data System (ADS)

Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2018-02-01

Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

Vortex scaling ranges in two-dimensional turbulence

NASA Astrophysics Data System (ADS)

Burgess, Helen; Scott, Richard; Dritschel, David

2017-11-01

We introduce a scaling theory for vortices in the forced inverse energy cascade of 2D turbulence. Far-from-equilibrium systems generically exhibit multiple scaling regimes associated with transport of conserved quantities. Motivated by this observation, we model a three-part time-evolving vortex number density distribution, n (A) tαiA-ri , i ∈ 1 , 2 , 3 , conserving the first three moments of ωv2n (A) in three distinct scaling ranges. Here ωv2 is the `vortex intensity', or mean square vorticity evaluated over vortices, and areas A are intense regions of vorticity bounded by vorticity isolines. We predict αi and ri by enforcing conservation in `comoving intervals', whose endpoints evolve at the vortex growth rate; this amounts to assuming invariance under the dilatation of flow features associated with the inverse cascade, and that vortex area growth is the appropriate measure of dilatation in all scaling ranges. High resolution numerical simulations verify the predictions, which are insensitive to the vorticity threshold used to isolate the areas. Similar concepts can be applied to model vortices in decaying 2D turbulence, pointing toward a unified description of vortices in both systems.

Dissipation of Turbulence in the Solar Wind

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.

2010-01-01

I will describe the first three-dimensional (3-D) dispersion relations and wavenumber spectra of magnetic turbulence in the solar wind at sub-proton scales. The analysis takes advantage of the short separations of the Cluster spacecraft (d/sim approx.200 km) to apply the {it k}-filtering technique to the frequency range where the transition to sub-proton scales occurs. The dispersion diagrams show unambiguously that the cascade is carried by highly oblique Kinetic Alfven Wave with \\omega\\leq 0.1\\omega_{ci} in the plasma rest frame down to k_\\perp\\rho_i \\sim 2. The wavenumber spectra in the direction perpendicular to the mean magnetic field consists of two ranges of scales separated by a breakpoint in the interval [0.4,1] k_\\perp \\rho_i. Above the breakpoint, the spectra follow the Kolmogorov scaling k_\\perp^{-1.7}, consistent with existing theoretical predictions. Below the breakpoint, the spectra steepen to \\sim k_\\perp^{-4.5}. We conjecture that the turbulence undergoes a {\\it transition-range}, where part of energy is dissipated into proton heating via Landau damping, and the remaining energy cascades down to electron scales where electron Landau damping may predominate.

Phylogeography and genetic identification of the newly-discovered populations of torrent salamanders (Rhyacotriton cascade and R. variegatus) in the central Cascades (USA)

USGS Publications Warehouse

Wagner, R.S.; Miller, Mark P.; Haig, Susan M.

2006-01-01

Newly discovered populations of Rhyacotritonidae were investigated for taxonomic identity, hybridization, and sympatry. Species in the genus Rhyacotriton have been historically difficult to identify using morphological characters. Mitochondrial (mtDNA) 16S ribosomal RNA sequences (491 bp) and allozymes (6 loci) were used to identify the distribution of populations occurring intermediate between the previously described ranges of R. variegatus and R. cascadae in the central Cascade Mountain region of Oregon. Allozyme and mitochondrial sequence data both indicated the presence of two distinct evolutionary lineages, with each lineage corresponding to the allopatric distribution of R. cascadae and R. variegatus. Results suggest the Willamette River acts as a phylogeographic barrier limiting the distribution of both species, although we cannot exclude the possibility that reproductive isolation also exists that reinforces species' distributions. This study extends the previously described geographical ranges of both R. cascadae and R. variegatus and defines an eastern range limit for R. variegatus conservation efforts.

Modeling techniques for quantum cascade lasers

NASA Astrophysics Data System (ADS)

Jirauschek, Christian; Kubis, Tillmann

2014-03-01

Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.

Modeling techniques for quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jirauschek, Christian; Kubis, Tillmann

2014-03-15

Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation ofmore » quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.« less

Perspectives on climate change, mountain hydrology, and water resources in the Oregon Cascades, USA

Treesearch

A.W. Nolin

2012-01-01

From both social and environmental perspectives, water is the main connection between highland and lowland processes in mountain watersheds: Water flows downhill while human impacts flow uphill. For example, in the Oregon Cascades mountain range, geology, vegetation, and climate influence the hydrologic connections within watersheds. Geology determines which watersheds...

Energy Cascade Rate in Compressible Fast and Slow Solar Wind Turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hadid, L. Z.; Sahraoui, F.; Galtier, S., E-mail: lina.hadid@lpp.polytechnique.fr

2017-03-20

Estimation of the energy cascade rate in the inertial range of solar wind turbulence has been done so far mostly within incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for compressible, isothermal MHD turbulence. Using in situ data from the THEMIS / ARTEMIS spacecraft in the fast and slow solar wind, we investigate in detail the role of the compressible fluctuations in modifying the energy cascade rate with respect to the prediction of the incompressible MHD model. In particular, we found that the energymore » cascade rate (1) is amplified particularly in the slow solar wind; (2) exhibits weaker fluctuations in spatial scales, which leads to a broader inertial range than the previous reported ones; (3) has a power-law scaling with the turbulent Mach number; (4) has a lower level of spatial anisotropy. Other features of solar wind turbulence are discussed along with their comparison with previous studies that used incompressible or heuristic (nonexact) compressible MHD models.« less

Increase of transient lower esophageal sphincter relaxation associated with cascade stomach

PubMed Central

Kawada, Akiyo; Kusano, Motoyasu; Hosaka, Hiroko; Kuribayashi, Shiko; Shimoyama, Yasuyuki; Kawamura, Osamu; Akiyama, Junichi; Yamada, Masanobu; Akuzawa, Masako

2017-01-01

We previously reported that cascade stomach was associated with reflux symptoms and esophagitis. Delayed gastric emptying has been believed to initiate transient lower esophageal sphincter relaxation (TLESR). We hypothesized that cascade stomach may be associated with frequent TLESR with delayed gastric emptying. Eleven subjects with cascade stomach and 11 subjects without cascade stomach were enrolled. Postprandial gastroesophageal manometry and gastric emptying using a continuous 13C breath system were measured simultaneously after a liquid test meal. TLESR events were counted in early period (0–60 min), late period (60–120 min), and total monitoring period. Three parameters of gastric emptying were calculated: the half emptying time, lag time, and gastric emptying coefficient. The median frequency of TLESR events in the cascade stomach and non-cascade stomach groups was 6.0 (median), 4.6 (interquartile range) vs 5.0, 3.0 in the early period, 5.0, 3.2 vs 3.0, 1.8 in the late period, and 10.0, 6.2 vs 8.0, 5.0 in the total monitoring period. TLESR events were significantly more frequent in the cascade stomach group during the late and total monitoring periods. In contrast, gastric emptying parameters showed no significant differences between the two groups. We concluded that TLESR events were significantly more frequent in persons with cascade stomach without delayed gastric emptying. PMID:28584403

A sensitive electrochemical aptasensor for multiplex antibiotics detection based on high-capacity magnetic hollow porous nanotracers coupling exonuclease-assisted cascade target recycling.

PubMed

Yan, Zhongdan; Gan, Ning; Li, Tianhua; Cao, Yuting; Chen, Yinji

2016-04-15

A multiplex electrochemical aptasensor was developed for simultaneous detection of two antibiotics such as chloramphenicol (CAP) and oxytetracycline (OTC), and high-capacity magnetic hollow porous nanotracers coupling exonuclease-assisted target recycling was used to improve sensitivity. The cascade amplification process consists of the exonuclease-assisted target recycling amplification and metal ions encoded magnetic hollow porous nanoparticles (MHPs) to produce voltammetry signals. Upon the specific recognition of aptamers to targets (CAP and OTC), exonuclease I (Exo I) selectively digested the aptamers which were bound with CAP and OTC, then the released CAP and OTC participated new cycling to produce more single DNA, which can act as trigger strands to hybrid with nanotracers to generate further signal amplification. MHPs were used as carriers to load more amounts of metal ions and coupling with Exo I assisted cascade target recycling can amplify the signal for about 12 folds compared with silica based nanotracers. Owing to the dual signal amplification, the linear range between signals and the concentrations of CAP and OTC were obtained in the range of 0.0005-50 ng mL(-1). The detection limits of CAP and OTC were 0.15 and 0.10 ng mL(-1) (S/N=3) which is more than 2 orders lower than commercial enzyme-linked immunosorbent immunoassay (ELISA) method, respectively. The proposed method was successfully applied to simultaneously detection of CAP and OTC in milk samples. Besides, this aptasensor can be applied to other antibiotics detection by changing the corresponding aptamer. The whole scheme is facile, selective and sensitive enough for antibiotics screening in food safety. Copyright © 2015 Elsevier B.V. All rights reserved.

Simulation of Cascaded Longitudinal-Space-Charge Amplifier at the Fermilab Accelerator Science & Technology (Fast) Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halavanau, A.; Piot, P.

2015-12-01

Cascaded Longitudinal Space Charge Amplifiers (LSCA) have been proposed as a mechanism to generate density modulation over a board spectral range. The scheme has been recently demonstrated in the optical regime and has confirmed the production of broadband optical radiation. In this paper we investigate, via numerical simulations, the performance of a cascaded LSCA beamline at the Fermilab Accelerator Science & Technology (FAST) facility to produce broadband ultraviolet radiation. Our studies are carried out using elegant with included tree-based grid-less space charge algorithm.

Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, north Cascade Range, Washington and British Columbia

USGS Publications Warehouse

Haugerud, R.A.; Van Der Heyden, P.; Tabor, R.W.; Stacey, J.S.; Zartman, R.E.

1991-01-01

The Skagit Gneiss Complex forms a more-or-less continuous terrane within the North Cascade Range. The complex comprises abundant plutons intruded at mid-crustal depths into a variety of metamorphosed supracrustal rocks of both oceanic and volcanic-arc origin. U-Pb zircon ages from gneissis plutons within and near the Skagit Gneiss Complex indicate magmatic crystallziations between 75 and 60 Ma. Deformation, recrystallization, and migmatization in part postdate intrusion of the 75-60 Ma plutons. This latest Cretaceous and earliest Tertiary plutonism and migmatization may reflect thermal relaxation following early Late Cretaceous orogeny. The complex was ductilely extended northwest-southeast shortly after intrusion of granite dikes at ~45 Ma, but before emplacement of the earliest (~34 Ma) plutons of the Cascade arc. -from Authors

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers.

PubMed

Balaswamy, V; Arun, S; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V R

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth-doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here a simple architecture for high-power, fixed, and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the ytterbium band to the eye-safe 1.5 μm region. We demonstrate pump-limited output powers of over 30 W in fixed and continuously wavelength tunable configurations.

Cascading second-order nonlinear processes in a lithium niobate-on-insulator microdisk.

PubMed

Liu, Shijie; Zheng, Yuanlin; Chen, Xianfeng

2017-09-15

Whispering-gallery-mode (WGM) microcavities are very important in both fundamental science and practical applications, among which on-chip second-order nonlinear microresonators play an important role in integrated photonic functionalities. Here we demonstrate resonant second-harmonic generation (SHG) and cascaded third-harmonic generation (THG) in a lithium niobate-on-insulator (LNOI) microdisk resonator. Efficient SHG in the visible range was obtained with only several mW input powers at telecom wavelengths. THG was also observed through a cascading process, which reveals simultaneous phase matching and strong mode coupling in the resonator. Cascading of second-order nonlinear processes gives rise to an effectively large third-order nonlinearity, which makes on-chip second-order nonlinear microresonators a promising frequency converter for integrated nonlinear photonics.

Multi-species trace gas analysis with dual-wavelength quantum cascade laser

NASA Astrophysics Data System (ADS)

Jágerská, Jana; Tuzson, Béla; Looser, Herbert; Jouy, Pierre; Hugi, Andreas; Mangold, Markus; Soltic, Patrik; Faist, Jérôme; Emmenegger, Lukas

2015-04-01

Simultaneous detection of multiple gas species using mid-IR laser spectroscopy is highly appealing for a large variety of applications ranging from air quality monitoring, medical breath analysis to industrial process control. However, state-of-the-art distributed-feedback (DFB) mid-IR lasers are usually tunable only within a narrow spectral range, which generally leads to one-laser-one-compound measurement strategy. Thus, multi-species detection involves several lasers and elaborate beam combining solutions [1]. This makes them bulky, costly, and highly sensitive to optical alignment, which limits their field deployment. In this paper, we explore an alternative measurement concept based on a dual-wavelength quantum cascade laser (DW-QCL) [2]. Such a laser can emit at two spectrally distinct wavelengths using a succession of two DFB gratings with different periodicities and a common waveguide to produce one output beam. The laser design was optimized for NOx measurements and correspondingly emits single-mode at 5.26 and 6.25 μm. Electrical separation of the respective laser sections makes it possible to address each wavelength independently. Thereby, it is possible to detect NO and NO2 species with one laser using the same optical path, without any beam combining optics, i.e. in a compact and cost-efficient single-path optical setup. Operated in a time-division multiplexed mode, the spectrometer reaches detection limits at 100 s averaging of 0.5 and 1.5 ppb for NO2 and NO, respectively. The performance of the system was validated against the well-established chemiluminescence detection while measuring the NOx emissions on an automotive test-bench, as well as monitoring the pollution at a suburban site. [1] B. Tuzson, K. Zeyer, M. Steinbacher, J. B. McManus, D. D. Nelson, M. S. Zahniser, and L. Emmenegger, 'Selective measurements of NO, NO2 and NOy in the free troposphere using quantum cascade laser spectroscopy,' Atmospheric Measurement Techniques 6, 927-936 (2013). [2] J. Jágerská, P. Jouy, A. Hugi, B. Tuzson, H. Looser, M. Mangold, M. Beck, L. Emmenegger, and J. Faist, 'Dual-wavelength quantum cascade laser for trace gas spectroscopy,' Applied Physics Letters 105, 161109-161109-4 (2014).

Influence of Additional Leading-Edge Surface Roughness on Performances in Highly Loaded Compressor Cascade

NASA Astrophysics Data System (ADS)

Chen, Shaowen; Xu, Hao; Sun, Shijun; Zhang, Longxin; Wang, Songtao

2015-05-01

Experimental research has been carried out at low speed to investigate the effect of additional leading-edge surface roughness on a highly-loaded axial compressor cascade. A 5-hole aerodynamic probe has been traversed across one pitch to obtain the distribution of total pressure loss coefficient, secondary flow vector, flow angles and other aerodynamic parameters at the exit section. Meanwhile, ink-trace flow visualization has been used to measure the flow fields on the walls of cascades and a detailed topology structure of the flow on the walls has been obtained. Aerodynamic parameters and flow characteristics are compared by arranging different levels of roughness on various parts of the leading edge. The results show that adding surface roughness at the leading edge and on the suction side obviously influences cascade performance. Aggravated 3-D flow separation significantly increases the loss in cascades, and the loss increases till 60% when the level of emery paper is 80 mm. Even there is the potential to improve cascade performance in local area of cascade passage. The influence of the length of surface roughness on cascade performance is not always adverse, and which depends on the position of surface roughness.

Pulse sequences for efficient multi-cycle terahertz generation in periodically poled lithium niobate.

PubMed

Ravi, Koustuban; Schimpf, Damian N; Kärtner, Franz X

2016-10-31

The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled (100 K) periodically poled Lithium Niobate is proposed and studied. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves (or pump depletion), show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved. The proposed methods are shown to circumvent laser induced damage limitations at Joule-level pumping by 1µm lasers to enable multi-cycle terahertz sources with pulse energies > 10 milli-joules. Various pulse sequence formats are proposed and analyzed. Numerical calculations for periodically poled structures accounting for cascaded difference frequency generation, self-phase-modulation, cascaded second harmonic generation and laser induced damage are introduced. The physics governing terahertz generation using pulse sequences in this high conversion efficiency regime, limitations and practical considerations are discussed. It is shown that varying the poling period along the crystal length and further reduction of absorption can lead to even higher energy conversion efficiencies >10%. In addition to numerical calculations, an analytic formulation valid for arbitrary pulse formats and closed-form expressions for important cases are presented. Parameters optimizing conversion efficiency in the 0.1-1 THz range, the corresponding peak electric fields, crystal lengths and terahertz pulse properties are furnished.

Wavefront measurement of single-mode quantum cascade laser beam for seed application in laser-produced plasma extreme ultraviolet system.

PubMed

Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru

2012-12-01

Quantum cascade laser (QCL) is a very attractive seed source for a multikilowatt pulsed CO2 lasers applied for driving extreme ultraviolet emitting plasmas. In this Letter, we investigate output beam properties of a QCL designed to address P18 and P20 lines of 10.6 micron band of CO2 molecule. In particular, output beam quality and stability are investigated for the first time. A well-defined linear polarization and a single-mode operation enabled a use of phase retrieval method for full description of QCL output beam. A direct, multi-image numerical phase retrieval technique was developed and successfully applied to the measured intensity patterns of a QCL beam. Very good agreement between the measured and reconstructed beam profiles was observed at distances ranging from QCL aperture to infinity, proving a good understanding of the beam propagation. The results also confirm a high spatial coherence and high stability of the beam parameters, the features expected from an excellent seed source.

An iron-catalysed C-C bond-forming spirocyclization cascade providing sustainable access to new 3D heterocyclic frameworks

NASA Astrophysics Data System (ADS)

Adams, Kirsty; Ball, Anthony K.; Birkett, James; Brown, Lee; Chappell, Ben; Gill, Duncan M.; Lo, P. K. Tony; Patmore, Nathan J.; Rice, Craig. R.; Ryan, James; Raubo, Piotr; Sweeney, Joseph B.

2017-04-01

Heterocyclic architectures offer powerful creative possibilities to a range of chemistry end-users. This is particularly true of heterocycles containing a high proportion of sp3-carbon atoms, which confer precise spatial definition upon chemical probes, drug substances, chiral monomers and the like. Nonetheless, simple catalytic routes to new heterocyclic cores are infrequently reported, and methods making use of biomass-accessible starting materials are also rare. Here, we demonstrate a new method allowing rapid entry to spirocyclic bis-heterocycles, in which inexpensive iron(III) catalysts mediate a highly stereoselective C-C bond-forming cyclization cascade reaction using (2-halo)aryl ethers and amines constructed using feedstock chemicals readily available from plant sources. Fe(acac)3 mediates the deiodinative cyclization of (2-halo)aryloxy furfuranyl ethers, followed by capture of the intermediate metal species by Grignard reagents, to deliver spirocycles containing two asymmetric centres. The reactions offer potential entry to key structural motifs present in bioactive natural products.

Research publications of the Cascade Head Experimental Forest and Scenic Research Area, Oregon Coast Range, 1934 to 1990.

Treesearch

Sarah E. Greene; Tawny Blinn

1991-01-01

A list of publications resulting from research at the Cascade Head Experimental Forest and Scenic Research Area, Siuslaw National Forest, Oregon, from 1934 to 1990 is presented. Over 200 publications are listed, including papers, theses, and reports. An index is provided that cross-references the listings under appropriate keywords.

Running dry: Where will the West get its water?

Treesearch

J. Thompson

2007-01-01

Late summer streamflow in western and central Oregon and northern California is almost exclusively due to immense groundwater storage in the Cascade Range. The volume of water stored in permeable lava flows in the Cascades is seven times that stored as snow. Nonetheless, until recently, virtually all examinations of streamflow trends under future climates in the West...

Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

2015-02-08

We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

Fire severity in intermittent stream drainages, Western Cascade Range, Oregon.

Treesearch

Jennifer E. Tollefson; Frederick J. Swanson; John H. Cissel

2004-01-01

We quantified fire severity patterns within intermittent stream drainages in a recently burned area of the central western Cascades, Oregon. Aerial photographs were used to estimate post fire live canopy cover within streamside and upland zones on the southeast and southwest-facing slopes of 33 watersheds. Live canopy cover did not differ significantly between...

Implementation effectiveness of revised (post-2010) World Health Organization guidelines on prevention of mother-to-child transmission of HIV using routinely collected data in sub-Saharan Africa

PubMed Central

Gumede-Moyo, Sehlulekile; Filteau, Suzanne; Munthali, Tendai; Todd, Jim; Musonda, Patrick

2017-01-01

Abstract Background: To synthesize and evaluate the impact of implementing post-2010 World Health Organization (WHO) prevention of mother-to-child transmission (PMTCT) guidelines on attainment of PMTCT targets. Methods: Retrospective and prospective cohort study designs that utilized routinely collected data with a focus on provision and utilization of the cascade of PMTCT services were included. The outcomes included the proportion of pregnant women who were tested during their antenatal clinic (ANC) visits; mother-to-child transmission (MTCT) rate; adherence; retention rate; and loss to follow-up (LTFU). Results: Of the 1210 references screened, 45 met the inclusion criteria. The studies originated from 14 countries in sub-Saharan Africa. The highest number of studies originated from Malawi (10) followed by Nigeria and South Africa with 7 studies each. More than half of the studies were on option A while the majority of option B+ studies were conducted in Malawi. These studies indicated a high uptake of human immunodeficiency virus (HIV) testing ranging from 75% in Nigeria to over 96% in Zimbabwe and South Africa. High proportions of CD4 count testing were reported in studies only from South Africa despite that in most of the countries CD4 testing was a prerequisite to access treatment. MTCT rate ranged from 1.1% to 15.1% and it was higher in studies where data were collected in the early days of the WHO 2010 PMTCT guidelines. During the postpartum period, adherence and retention rate decreased, and LTFU increased for both HIV-positive mothers and exposed infants. Conclusion: Irrespective of which option was followed, uptake of antenatal HIV testing was high but there was a large drop off along later points in the PMTCT cascade. More research is needed on how to improve later components of the PMTCT cascade, especially of option B+ which is now the norm throughout sub-Saharan Africa. PMID:28984760

Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, Washington

USGS Publications Warehouse

Blakely, R.J.; Sherrod, B.L.; Weaver, C.S.; Wells, R.E.; Rohay, A.C.; Barnett, E.A.; Knepprath, N.E.

2011-01-01

High-resolution aeromagnetic surveys of the Cascade Range and Yakima fold and thrust belt (YFTB), Washington, provide insights on tectonic connections between forearc and back-arc regions of the Cascadia convergent margin. Magnetic surveys were measured at a nominal altitude of 250 m above terrain and along flight lines spaced 400 m apart. Upper crustal rocks in this region have diverse magnetic properties, ranging from highly magnetic rocks of the Miocene Columbia River Basalt Group to weakly magnetic sedimentary rocks of various ages. These distinctive magnetic properties permit mapping of important faults and folds from exposures to covered areas. Magnetic lineaments correspond with mapped Quaternary faults and with scarps identified in lidar (light detection and ranging) topographic data and aerial photography. A two-dimensional model of the northwest striking Umtanum Ridge fault zone, based on magnetic and gravity data and constrained by geologic mapping and three deep wells, suggests that thrust faults extend through the Tertiary section and into underlying pre-Tertiary basement. Excavation of two trenches across a prominent scarp at the base of Umtanum Ridge uncovered evidence for bending moment faulting possibly caused by a blind thrust. Using aeromagnetic, gravity, and paleoseismic evidence, we postulate possible tectonic connections between the YFTB in eastern Washington and active faults of the Puget Lowland. We suggest that faults and folds of Umtanum Ridge extend northwestward through the Cascade Range and merge with the Southern Whidbey Island and Seattle faults near Snoqualmie Pass 35 km east of Seattle. Recent earthquakes (MW ≤ 5.3) suggest that this confluence of faults may be seismically active today.

Passive control of discrete-frequency tones generated by coupled detuned cascades

NASA Astrophysics Data System (ADS)

Sawyer, S.; Fleeter, S.

2003-07-01

Discrete-frequency tones generated by rotor-stator interactions are of particular concern in the design of fans and compressors. Classical theory considers an isolated flat-plate cascade of identical uniformly spaced airfoils. The current analysis extends this tuned isolated cascade theory to consider coupled aerodynamically detuned cascades where aerodynamic detuning is accomplished by changing the chord of alternate rotor blades and stator vanes. In a coupled cascade analysis, the configuration of the rotor influences the downstream acoustic response of the stator, and the stator configuration influences the upstream acoustic response of the rotor. This coupled detuned cascade unsteady aerodynamic model is first applied to a baseline tuned stage. This baseline stage is then aerodynamically detuned by replacing alternate rotor blades and stator vanes with decreased chord airfoils. The nominal aerodynamically detuned stage configuration is then optimized, with the stage acoustic response decreased 13 dB upstream and 1 dB downstream at the design operating condition. A reduction in the acoustic response of the optimized aerodynamically detuned stage is then demonstrated over a range of operating conditions.

An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. 1: Experimental and theoretical results. [turbine blades

NASA Technical Reports Server (NTRS)

Carta, F. O.

1982-01-01

Tests were conducted on a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blades along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and, particularly, the aerodynamic damping coefficient. Results from the unsteady Verdon/Caspar theory for cascaded blades with nonzero thickness and camber were compared with the experimental measurements. The three primary results are: (1) from the leading edge plane blade data, the cascade was judged to be periodic in unsteady flow over the range of parameters tested; (2) the interblade phase angle was found to be the single most important parameter affecting the stability of the oscillating cascade blades; and (3) the real blade theory and the experiment were in excellent agreement for the several cases chosen for comparison.

Surface fuel treatments in young, regenerating stands affect wildfire severity in a mixed conifer forest, eastside Cascade Range, Washington, USA

Treesearch

Christina Lyons-Tinsley; David L. Peterson

2012-01-01

Previous studies have debated the flammability of young regenerating stands, especially those in a matrix of mature forest, and no consensus has emerged as to whether young stands are inherently prone to high-severity wildfire. This topic has recently been addressed using spatial imagery, and weak inferences were made given the scale mismatch between the coarse...

Genetic studies of Northern Goshawks (Accipiter gentilis): genetic tagging and individual identification from feathers, and determining phylogeography, gene flow and population history for Goshawks in North America

Treesearch

Shelley Bayard de Volo

2008-01-01

The Northern Goshawk (Accipiter gentilis) is a large, highly mobile, mostly nonmigratory and widespread forest raptor. It ranges across the Boreal forests from Alaska to Newfoundland, and south into forests of the Great Lakes, and montane regions of the Appalachian, Cascade, Sierra Nevada, Rocky Mountain, and Sierra Madre Occidental.

Quantum cascade transmitters for ultrasensitive chemical agent and explosives detection

NASA Astrophysics Data System (ADS)

Schultz, John F.; Taubman, Matthew S.; Harper, Warren W.; Williams, Richard M.; Myers, Tanya L.; Cannon, Bret D.; Sheen, David M.; Anheier, Norman C., Jr.; Allen, Paul J.; Sundaram, S. K.; Johnson, Bradley R.; Aker, Pamela M.; Wu, Ming C.; Lau, Erwin K.

2003-07-01

The small size, high power, promise of access to any wavelength between 3.5 and 16 microns, substantial tuning range about a chosen center wavelength, and general robustness of quantum cascade (QC) lasers provide opportunities for new approaches to ultra-sensitive chemical detection and other applications in the mid-wave infrared. PNNL is developing novel remote and sampling chemical sensing systems based on QC lasers, using QC lasers loaned by Lucent Technologies. In recent months laboratory cavity-enhanced sensing experiments have achieved absorption sensitivities of 8.5 x 10-11 cm-1 Hz-1/2, and the PNNL team has begun monostatic and bi-static frequency modulated, differential absorption lidar (FM DIAL) experiments at ranges of up to 2.5 kilometers. In related work, PNNL and UCLA are developing miniature QC laser transmitters with the multiplexed tunable wavelengths, frequency and amplitude stability, modulation characteristics, and power levels needed for chemical sensing and other applications. Current miniaturization concepts envision coupling QC oscillators, QC amplifiers, frequency references, and detectors with miniature waveguides and waveguide-based modulators, isolators, and other devices formed from chalcogenide or other types of glass. Significant progress has been made on QC laser stabilization and amplification, and on development and characterization of high-purity chalcogenide glasses, waveguide writing techniques, and waveguide metrology.

Volcano Hazards Assessment for Medicine Lake Volcano, Northern California

USGS Publications Warehouse

Donnelly-Nolan, Julie M.; Nathenson, Manuel; Champion, Duane E.; Ramsey, David W.; Lowenstern, Jacob B.; Ewert, John W.

2007-01-01

Medicine Lake volcano (MLV) is a very large shield-shaped volcano located in northern California where it forms part of the southern Cascade Range of volcanoes. It has erupted hundreds of times during its half-million-year history, including nine times during the past 5,200 years, most recently 950 years ago. This record represents one of the highest eruptive frequencies among Cascade volcanoes and includes a wide variety of different types of lava flows and at least two explosive eruptions that produced widespread fallout. Compared to those of a typical Cascade stratovolcano, eruptive vents at MLV are widely distributed, extending 55 km north-south and 40 km east-west. The total area covered by MLV lavas is >2,000 km2, about 10 times the area of Mount St. Helens, Washington. Judging from its long eruptive history and its frequent eruptions in recent geologic time, MLV will erupt again. Although the probability of an eruption is very small in the next year (one chance in 3,600), the consequences of some types of possible eruptions could be severe. Furthermore, the documented episodic behavior of the volcano indicates that once it becomes active, the volcano could continue to erupt for decades, or even erupt intermittently for centuries, and very likely from multiple vents scattered across the edifice. Owing to its frequent eruptions, explosive nature, and proximity to regional infrastructure, MLV has been designated a 'high threat volcano' by the U.S. Geological Survey (USGS) National Volcano Early Warning System assessment. Volcanic eruptions are typically preceded by seismic activity, but with only two seismometers located high on the volcano and no other USGS monitoring equipment in place, MLV is at present among the most poorly monitored Cascade volcanoes.

Optical Sidebands Multiplier

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry V.; Yu, Nan

2010-01-01

Optical sidebands have been generated with relative frequency tens to hundreds of GHz by using optical sidebands that are generated in a cascade process in high-quality optical resonators with Kerr nonlinearity, such as whispering gallery mode (WGM) resonators. For this purpose, the WGM resonator needs to be optically pumped at two frequencies matching its resonances. These two optical components can be one or several free spectral ranges (FSRs), equal to approximately 12 GHz, in this example, apart from each other, and can be easily derived from a monochromatic pump with an ordinary EOM (electro-optic modulation) operating at half the FSR frequency. With sufficient nonlinearity, an optical cascade process will convert the two pump frequencies into a comb-like structure extending many FSRs around the carrier frequency. This has a demonstratively efficient frequency conversion of this type with only a few milliwatt optical pump power. The concept of using Kerr nonlinearity in a resonator for non-degenerate wave mixing has been discussed before, but it was a common belief that this was a weak process requiring very high peak powers to be observable. It was not thought possible for this approach to compete with electro-optical modulators in CW applications, especially those at lower optical powers. By using the high-Q WGM resonators, the effective Kerr nonlinearity can be made so high that, using even weak seeding bands available from a conventional EOM, one can effectively multiply the optical sidebands, extending them into an otherwise inaccessible frequency range.

A 2.5 kW cascaded Schwarz converter for 20 kHz power distribution

NASA Technical Reports Server (NTRS)

Shetler, Russell E.; Stuart, Thomas A.

1989-01-01

Because it avoids the high currents in a parallel loaded capacitor, the cascaded Schwarz converter should offer better component utilization than converters with sinusoidal output voltages. The circuit is relatively easy to protect, and it provides a predictable trapezoidal voltage waveform that should be satisfactory for 20-kHz distribution systems. Analysis of the system is enhanced by plotting curves of normalized variables vs. gamma(1), where gamma(1) is proportional to the variable frequency of the first stage. Light-load operation is greatly improved by the addition of a power recycling rectifier bridge that is back biased at medium to heavy loads. Operation has been verified on a 2.5-kW circuit that uses input and output voltages in the same range as those anticipated for certain future spacecraft power systems.

Contributed review: quantum cascade laser based photoacoustic detection of explosives.

PubMed

Li, J S; Yu, B; Fischer, H; Chen, W; Yalin, A P

2015-03-01

Detecting trace explosives and explosive-related compounds has recently become a topic of utmost importance for increasing public security around the world. A wide variety of detection methods and an even wider range of physical chemistry issues are involved in this very challenging area. Optical sensing methods, in particular mid-infrared spectrometry techniques, have a great potential to become a more desirable tools for the detection of explosives. The small size, simplicity, high output power, long-term reliability make external cavity quantum cascade lasers (EC-QCLs) the promising spectroscopic sources for developing analytical instrumentation. This work reviews the current technical progress in EC-QCL-based photoacoustic spectroscopy for explosives detection. The potential for both close-contact and standoff configurations using this technique is completely presented over the course of approximately the last one decade.

Contributed Review: Quantum cascade laser based photoacoustic detection of explosives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J. S., E-mail: jingsong-li@ahu.edu.cn; Yu, B.; Fischer, H.

2015-03-15

Detecting trace explosives and explosive-related compounds has recently become a topic of utmost importance for increasing public security around the world. A wide variety of detection methods and an even wider range of physical chemistry issues are involved in this very challenging area. Optical sensing methods, in particular mid-infrared spectrometry techniques, have a great potential to become a more desirable tools for the detection of explosives. The small size, simplicity, high output power, long-term reliability make external cavity quantum cascade lasers (EC-QCLs) the promising spectroscopic sources for developing analytical instrumentation. This work reviews the current technical progress in EC-QCL-based photoacousticmore » spectroscopy for explosives detection. The potential for both close-contact and standoff configurations using this technique is completely presented over the course of approximately the last one decade.« less

Contributions to the geology of Washington

USGS Publications Warehouse

Smith, G.O.; Willis, Bailey

1903-01-01

Central Washington includes a part of two great topographic provinces; the great plain of the Columbia and the Cascade Range. The former, in its position and general desert-like character, suggests at once a resemblance to the Great Basin of Utah and Nevada; and the vastness of the desert plain is emphasized by the snowy peaks of the Cascades along its western border. These provinces are not to be regarded as unconnected in their geologic history, however great the contrast in their general features. The intermediate zone between the great plain on the east and the mountain range on the west is a strategic point for the investigation of the geologic structure and history and the interpretation of the present topography of both provinces. On the extensive basalt-covered plain monotony wearies the traveler, while on the rocky peaks of the Cascades the complexity taxes the powers of the observer. 

Recent progress on gas sensor based on quantum cascade lasers and hollow fiber waveguides

NASA Astrophysics Data System (ADS)

Liu, Ningwu; Sun, Juan; Deng, Hao; Ding, Junya; Zhang, Lei; Li, Jingsong

2017-02-01

Mid-infrared laser spectroscopy provides an ideal platform for trace gas sensing applications. Despite this potential, early MIR sensing applications were limited due to the size of the involved optical components, e.g. light sources and sample cells. A potential solution to this demand is the integration of hollow fiber waveguide with novelty quantum cascade lasers.Recently QCLs had great improvements in power, efficiency and wavelength range, which made the miniaturized platforms for gas sensing maintaining or even enhancing the achievable sensitivity conceivable. So that the miniaturization of QCLs and HWGs can be evolved into a mini sensor, which may be tailored to a variety of real-time and in situ applications ranging from environmental monitoring to workplace safety surveillance. In this article, we introduce QCLs and HWGs, display the applications of HWG based on QCL gas sensing and discuss future strategies for hollow fiber coupled quantum cascade laser gas sensor technology.

Spatial correlation analysis of cascading failures: Congestions and Blackouts

PubMed Central

Daqing, Li; Yinan, Jiang; Rui, Kang; Havlin, Shlomo

2014-01-01

Cascading failures have become major threats to network robustness due to their potential catastrophic consequences, where local perturbations can induce global propagation of failures. Unlike failures spreading via direct contacts due to structural interdependencies, overload failures usually propagate through collective interactions among system components. Despite the critical need in developing protection or mitigation strategies in networks such as power grids and transportation, the propagation behavior of cascading failures is essentially unknown. Here we find by analyzing our collected data that jams in city traffic and faults in power grid are spatially long-range correlated with correlations decaying slowly with distance. Moreover, we find in the daily traffic, that the correlation length increases dramatically and reaches maximum, when morning or evening rush hour is approaching. Our study can impact all efforts towards improving actively system resilience ranging from evaluation of design schemes, development of protection strategies to implementation of mitigation programs. PMID:24946927

Potential trophic cascades triggered by the barred owl range expansion

USGS Publications Warehouse

Holm, Samantha R.; Noon, Barry R.; Wiens, David; Ripple, William J.

2016-01-01

Recently, the barred owl (Strix varia) has expanded its range into the Pacific Northwest of the United States resulting in pronounced effects on the demography and behavior of the northern spotted owl (S. occidentalis caurina). The range expansion has brought together historically allopatric species, creating the potential for significant changes in the avian predator community with possible cascading effects on food-web dynamics. The adverse effects of the barred owl on the behavior and demography of the northern spotted owl are well-documented, but little is known about the immediate and long-term effects changes in the predator community may have on native species composition and ecosystem processes. Based on northern spotted owl and barred owl selection for diet and habitat resources, there is a potential for trophic cascades within the region's predator and prey communities, differing responses by their shared and unique prey species, and possible direct and indirect effects on ecosystem processes. We explored the possible ecological consequences of the barred owl range expansion to wildlife communities of the Pacific Northwest based on the theoretical underpinnings of predator–prey relationships, interspecific competition, intraguild predation, and potential cascading trophic interactions. Negative effects on fitness of northern spotted owls because of interspecific competition with barred owls are strong selection forces that may contribute to the regional extinction of the northern spotted owl. In addition, we posit that shared prey species and those uniquely consumed by barred owls, along with other competing native predators, may experience changes in behavior, abundance, and distribution as a result of increased rates of predation by rapidly expanding populations of barred owls.

Injection-locking of terahertz quantum cascade lasers up to 35GHz using RF amplitude modulation.

PubMed

Gellie, Pierre; Barbieri, Stefano; Lampin, Jean-François; Filloux, Pascal; Manquest, Christophe; Sirtori, Carlo; Sagnes, Isabelle; Khanna, Suraj P; Linfield, Edmund H; Davies, A Giles; Beere, Harvey; Ritchie, David

2010-09-27

We demonstrate that the cavity resonance frequency - the round-trip frequency - of Terahertz quantum cascade lasers can be injection-locked by direct modulation of the bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, and show locking ranges above 200MHz. Inside this locking range the laser round-trip frequency is phase-locked, with a phase noise determined by the RF-synthesizer. We find a square-root dependence of the locking range with RF-power in agreement with classical injection-locking theory. These results are discussed in the context of mode-locking operation.

Identification of cascade water tanks using a PWARX model

NASA Astrophysics Data System (ADS)

Mattsson, Per; Zachariah, Dave; Stoica, Petre

2018-06-01

In this paper we consider the identification of a discrete-time nonlinear dynamical model for a cascade water tank process. The proposed method starts with a nominal linear dynamical model of the system, and proceeds to model its prediction errors using a model that is piecewise affine in the data. As data is observed, the nominal model is refined into a piecewise ARX model which can capture a wide range of nonlinearities, such as the saturation in the cascade tanks. The proposed method uses a likelihood-based methodology which adaptively penalizes model complexity and directly leads to a computationally efficient implementation.

Cold-air annular-cascade investigation of aerodynamic performance of cooled turbine vanes. 2: Trailing-edge ejection, film cooling, and transpiration cooling

NASA Technical Reports Server (NTRS)

Goldman, L. J.; Mclallin, K. L.

1975-01-01

The aerodynamic performance of four different cooled vane configurations was experimentally determined in a full-annular cascade at a primary- to coolant-total-temperature ratio of 1.0. The vanes were tested over a range of coolant flow rates and pressure ratios. Overall vane efficiencies were obtained and compared, where possible, with the results obtained in a four-vane, annular-sector cascade. The vane efficiency and exit flow conditions as functions of radial position were also determined and compared with solid (uncooled) vane results.

Broadband optical frequency comb generator based on driving N-cascaded modulators by Gaussian-shaped waveform

NASA Astrophysics Data System (ADS)

Hmood, Jassim K.; Harun, Sulaiman W.

2018-05-01

A new approach for realizing a wideband optical frequency comb (OFC) generator based on driving cascaded modulators by a Gaussian-shaped waveform, is proposed and numerically demonstrated. The setup includes N-cascaded MZMs, a single Gaussian-shaped waveform generator, and N-1 electrical time delayer. The first MZM is driven directly by a Gaussian-shaped waveform, while delayed replicas of the Gaussian-shaped waveform drive the other MZMs. An analytical model that describes the proposed OFC generator is provided to study the effect of number and chirp factor of cascaded MZM as well as pulse width on output spectrum. Optical frequency combs at frequency spacing of 1 GHz are generated by applying Gaussian-shaped waveform at pulse widths ranging from 200 to 400 ps. Our results reveal that, the number of comb lines is inversely proportional to the pulse width and directly proportional to both number and chirp factor of cascaded MZMs. At pulse width of 200 ps and chirp factor of 4, 67 frequency lines can be measured at output spectrum of two-cascaded MZMs setup. Whereas, increasing the number of cascaded stages to 3, 4, and 5, the optical spectra counts 89, 109 and 123 frequency lines; respectively. When the delay time is optimized, 61 comb lines can be achieved with power fluctuations of less than 1 dB for five-cascaded MZMs setup.

Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities

PubMed Central

Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John J.; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie

2016-01-01

A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m−2. Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1 ± 5.6% of soluble protein and 86.6 ± 2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost. PMID:27270788

Beyond Fourier Transform Infrared Spectroscopy: External Cavity Quantum Cascade Laser-Based Mid-infrared Transmission Spectroscopy of Proteins in the Amide I and Amide II Region.

PubMed

Schwaighofer, Andreas; Montemurro, Milagros; Freitag, Stephan; Kristament, Christian; Culzoni, María J; Lendl, Bernhard

2018-05-24

In this work, we present a setup for mid-IR measurements of the protein amide I and amide II bands in aqueous solution. Employing a latest generation external cavity-quantum cascade laser (EC-QCL) at room temperature in pulsed operation mode allowed implementing a high optical path length of 31 μm that ensures robust sample handling. By application of a data processing routine, which removes occasionally deviating EC-QCL scans, the noise level could be lowered by a factor of 4. The thereby accomplished signal-to-noise ratio is better by a factor of approximately 2 compared to research-grade Fourier transform infrared (FT-IR) spectrometers at equal acquisition times. Employing this setup, characteristic spectral features of three representative proteins with different secondary structures could be measured at concentrations as low as 1 mg mL -1 . Mathematical evaluation of the spectral overlap confirms excellent agreement of the quantum cascade laser infrared spectroscropy (QCL-IR) transmission measurements with protein spectra acquired by FT-IR spectroscopy. The presented setup combines performance surpassing FT-IR spectroscopy with large applicable optical paths and coverage of the relevant spectral range for protein analysis. This holds high potential for future EC-QCL-based protein studies, including the investigation of dynamic secondary structure changes and chemometrics-based protein quantification in complex matrices.

Thermionic/AMTEC cascade converter concept for high-efficiency space power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagan, T.H. van; Smith, J.N. Jr.; Schuller, M.

1996-12-31

This paper presents trade studies that address the use of the thermionic/AMTEC cell--a cascaded, high-efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as highmore » as 35--40%, such a cascade offers the following perceived benefits: survivability; simplicity; technology readiness; and technology growth. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems.« less

Design and analysis of linear cascade DNA hybridization chain reactions using DNA hairpins

NASA Astrophysics Data System (ADS)

Bui, Hieu; Garg, Sudhanshu; Miao, Vincent; Song, Tianqi; Mokhtar, Reem; Reif, John

2017-01-01

DNA self-assembly has been employed non-conventionally to construct nanoscale structures and dynamic nanoscale machines. The technique of hybridization chain reactions by triggered self-assembly has been shown to form various interesting nanoscale structures ranging from simple linear DNA oligomers to dendritic DNA structures. Inspired by earlier triggered self-assembly works, we present a system for controlled self-assembly of linear cascade DNA hybridization chain reactions using nine distinct DNA hairpins. NUPACK is employed to assist in designing DNA sequences and Matlab has been used to simulate DNA hairpin interactions. Gel electrophoresis and ensemble fluorescence reaction kinetics data indicate strong evidence of linear cascade DNA hybridization chain reactions. The half-time completion of the proposed linear cascade reactions indicates a linear dependency on the number of hairpins.

Preliminary report on the ground-water resources of the Klamath River basin, Oregon

USGS Publications Warehouse

Newcomb, Reuben Clair; Hart, D.H.

1958-01-01

The Klamath River basin, including the adjacent Lost River basin, includes about 5,500 square miles of plateaus, mountain-slopes and valley plains in south-central Oregon. The valley plains range in altitude from about 4,100 feet in the south to more than 4,500 feet at the northern end; the mountain and plateau lands rise to an average altitude of 6,000 feet at the drainage divide, some peaks rising above 9,000 feet. The western quarter of the basin is on the eastern slope of the Cascade Range and the remainder consists of plateaus, mountains, and valleys of the basin-and-range type. The rocks of the Klamath River basin range in age from Recent to Mesozoic. At the southwest side of the basin in Oregon, pre-Tertiary metamorphic, igneous, and sedimentary rocks, which form extensive areas farther west, are overlain by sedimentary rocks of Eocene age and volcanic rocks of Eocene and Oligocene age. These early Tertiary rocks dip east toward the central part of the Klamath River basin. The complex volcanic rocks of high Cascades include three units: the lowest unit consists of a sequence of basaltic lava flows about 800 feet thick; the medial unit is composed of volcanic-sedimentary and sedimentary rocksthe Yonna formation200 to 2,000 feet thick; the uppermost unit is a sequence of basaltic lava flows commonly about 200 feet thick. These rocks dip east from the Cascade Range and are the main bedrock formations beneath most of the basin. Extensive pumice deposits, which emanated from ancestral Mount Mazama, cover large areas in the northwestern part of the basin. The basin has an overall synclinal structure open to the south at the California boundary where it continues as the Klamath Lake basin in California. The older rocks dip into the basin in monoclinal fashion from the adjoining drainage basins. The rocks are broken along rudely rectangular nets of closely spaced normal faults, the most prominent set of which trends northwest. The network of fault displacements includes two main grabens, the Klamath and the Langell, which were downthrown approximately 50 and 1,000 feet, respectively. The average annual precipitation varies with the altitude, the higher parts of the Cascade Range getting more than 60 inches, and the semiarid valley plains receive as little as 13 inches in some places. Most precipitation occurs in the winter. The principal tributaries, Williamson and Sprague Rivers, rise near the higher parts of the eastern rim of the basin, flow through narrow valley plains to the western part, and discharge into Upper Klamath Lake. Wood River and associated creeks also empty into Upper Klamath Lake after draining southward along along the eastern foot of the Cascade Range. The Klamath River receives the outflow from Upper Klamath Lake, via Link River and Lake Ewauna, and flows southwestward through Keno Gap and hance through a youthful canyon, to its lower valley in California. The ground water occurs largely in an unconfined, or water-table, condition, though areas of local confinement are present. The regional water table is graded to a base level about equal to that of the major drainage on the valley plains. The slop of the water table, where water is confined, or the piezometric surface is downstream at about the same grade as that of the surface drainage in each of the larger valleys, and ground-water divides occur between the upper parts of adjacent major valleys. The principal water-bearing units are the lower lava rocks and upper lava rocks of the volcanic rocks of high Cascades, the pumice of Quaternary age, and the alluvium. In places layers of coarse fragmental material in the Yonna formation (Newcomb, 1958) also transmit water. The water-bearing units, especially the breccia layers of the lava rocks and the pumice, yield large amounts of water to wells and provide natural discharge outlets for the ground water. The spring outflows to the Williamson and Wood Rivers-Crooked Creek drainage, mea

Ultra-high contrast retinal display system for single photoreceptor psychophysics

PubMed Central

Domdei, Niklas; Domdei, Lennart; Reiniger, Jenny L.; Linden, Michael; Holz, Frank G.; Roorda, Austin; Harmening, Wolf M.

2017-01-01

Due to the enormous dynamic range of human photoreceptors in response to light, studying their visual function in the intact retina challenges the stimulation hardware, specifically with regard to the displayable luminance contrast. The adaptive optics scanning laser ophthalmoscope (AOSLO) is an optical platform that focuses light to extremely small retinal extents, approaching the size of single photoreceptor cells. However, the current light modulation techniques produce spurious visible backgrounds which fundamentally limit experimental options. To remove unwanted background light and to improve contrast for high dynamic range visual stimulation in an AOSLO, we cascaded two commercial fiber-coupled acousto-optic modulators (AOMs) and measured their combined optical contrast. By compensating for zero-point differences in the individual AOMs, we demonstrate a multiplicative extinction ratio in the cascade that was in accordance with the extinction ratios of both single AOMs. When latency differences in the AOM response functions were individually corrected, single switch events as short as 50 ns with radiant power contrasts up to 1:1010 were achieved. This is the highest visual contrast reported for any display system so far. We show psychophysically that this contrast ratio is sufficient to stimulate single foveal photoreceptor cells with small and bright enough visible targets that do not contain a detectable background. Background-free stimulation will enable photoreceptor testing with custom adaptation lights. Furthermore, a larger dynamic range in displayable light levels can drive photoreceptor responses in cones as well as in rods. PMID:29359094

High-Performance Three-Stage Cascade Thermoelectric Devices with 20% Efficiency

NASA Astrophysics Data System (ADS)

Cook, B. A.; Chan, T. E.; Dezsi, G.; Thomas, P.; Koch, C. C.; Poon, J.; Tritt, T.; Venkatasubramanian, R.

2015-06-01

The use of advanced materials has resulted in a significant improvement in thermoelectric device conversion efficiency. Three-stage cascade devices were assembled, consisting of nano-bulk Bi2Te3-based materials on the cold side, PbTe and enhanced TAGS-85 [(AgSbTe2)15(GeTe)85] for the mid-stage, and half-Heusler alloys for the high-temperature top stage. In addition, an area aspect ratio optimization process was applied in order to account for asymmetric thermal transport down the individual n- and p-legs. The n- and p-type chalcogenide alloy materials were prepared by high-energy mechanical ball-milling and/or cryogenic ball-milling of elementary powders, with subsequent consolidation by high-pressure uniaxial hot-pressing. The low-temperature stage materials, nano-bulk Bi2Te3- x Sb x and Bi2Te3- x Se x , exhibit a unique mixture of nanoscale features that leads to an enhanced Seebeck coefficient and reduced lattice thermal conductivity, thereby achieving an average ZT of ~1.26 and ~1.7 in the 27°C to 100°C range for the n-type and p-type materials, respectively. Also, the addition of small amounts of selected rare earth elements has been shown to improve the ZT of TAGS-85 by 25%, compared with conventional or neat TAGS-85, resulting in a ZT = 1.5 at 400°C. The incorporation of these improved materials resulted in a peak device conversion efficiency of ~20% at a temperature difference of 750°C when corrected for radiation heat losses and thermal conduction losses through the lead wires. These high-efficiency results were shown to be reproducible across multiple cascade devices.

Genetic variation and seed transfer guidelines for ponderosa pine in central Oregon.

Treesearch

Frank C. Sorensen

1994-01-01

Adaptive genetic variation in seed and seedling traits for ponderosa pine from the east slopes of the Cascade Range in Oregon was analyzed by using 307 families from 227 locations. Factor scores from three principal components based on seed and seedling traits were related by multiple regression to latitude, distance from the Cascade crest, elevation, slope, and...

Long-term effects of fire severity on oak–conifer dynamics in the southern Cascades

Treesearch

Matthew I. Cocking; J. Morgan Varner; Eric E. Knapp

2014-01-01

We studied vegetation composition and structure in a mixed conifer–oak ecosystem across a range of fire severity 10 years following wildfire. Sample plots centered on focal California black oaks (Quercus kelloggii) were established to evaluate oak and neighboring tree and shrub recovery across a gradient of fire severity in the southern Cascade...

Genetic variation and seed transfer guidelines for lodgepole pine in central Oregon.

Treesearch

Frank C. Sorensen

1992-01-01

Cones were collected from 272 trees at 189 locations uniformly distributed over the east slopes of the Oregon Cascade Range and Warner Mountains. Variation in seed and seedling traits was related to (1) seed source latitude, distance from the Cascade crest, elevation, slope, and aspect in multiple regression analyses; and (2) seed zone and elevation band in...

Photo series for quantifying natural forest residues: southern Cascades, northern Sierra Nevada

Treesearch

Kenneth S. Blonski; John L. Schramel

1981-01-01

A total of 56 photographs shows different levels of natural fuel loadings for selected size classes in seven forest types of the southern Cascade and northern Sierra-Nevada ranges. Data provided with each photo include size, weight, volumes, residue depths, and percent of ground coverage. Stand information includes sizes, weights, and volumes of the trees sampled for...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miloshevich, George; Lingam, Manasvi; Morrison, Philip J.

Recent progress regarding the noncanonical Hamiltonian formulation of extended magnetohydrodynamics (XMHD), a model with Hall drift and electron inertia, is summarized. The advantages of the Hamiltonian approach are invoked to study some general properties of XMHD turbulence, and to compare them against their ideal MHD counterparts. For instance, the helicity flux transfer rates for XMHD are computed, and Liouville's theorem for this model is also verified. The latter is used, in conjunction with the absolute equilibrium states, to arrive at the spectra for the invariants, and to determine the direction of the cascades, e.g., generalizations of the well-known ideal MHDmore » inverse cascade of magnetic helicity. After a similar analysis is conducted for XMHD by inspecting second order structure functions and absolute equilibrium states, a couple of interesting results emerge. When cross helicity is taken to be ignorable, the inverse cascade of injected magnetic helicity also occurs in the Hall MHD range-this is shown to be consistent with previous results in the literature. In contrast, in the inertial MHD range, viz at scales smaller than the electron skin depth, all spectral quantities are expected to undergo direct cascading. Finally, the consequences and relevance of our results in space and astrophysical plasmas are also briefly discussed.« less

Flow range enhancement by secondary flow effect in low solidity circular cascade diffusers

NASA Astrophysics Data System (ADS)

Sakaguchi, Daisaku; Tun, Min Thaw; Mizokoshi, Kanata; Kishikawa, Daiki

2014-08-01

High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confirm the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser (LSD) in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.

Geologic Map of the Cascade Head Area, Northwestern Oregon Coast Range (Neskiwin, Nestucca Bay, Hebo, and Dolph 7.5 minute Quadrangles)

USGS Publications Warehouse

Snavely, Parke D.; Niem, Alan; Wong, Florence L.; MacLeod, Norman S.; Calhoun, Tracy K.; Minasian, Diane L.; Niem, Wendy

1996-01-01

The geology of the Cascade Head area bridges the geology in the Tillamook Highlands to the north (Wells and others, 1994; 1995) with that of the Newport Embayment on the south (Snavely and others, 1976 a,b,c). The four 7.5-minute quadrangles (Neskowin, Nestucca Bay, Hebo, and Dolph) which comprise the Cascade Head area include significant stratigraphic, structural, and igneous data that are essential in unraveling the geology of the northern and central part of the Oregon Coast Range and of the adjacent continental shelfEarlier studies (Snavely and Vokes, 1949) were of a broad reconnaissance nature because of limited access in this rugged, densely forested part of the Siuslaw National Forest. Also, numerous thick sills of late middle Eocene diabase and middle Miocene basalt mask the Eocene stratigraphic relationships. Previous mapping was hampered by a lack of precise biostratigraphic data. However, recent advances in biostratigraphy and radiometric age dating and geochemistry have provided the necessary tools to decipher stratigraphic and structural relationships in the Eocene sedimentary and volcanic rock sequences (W.W. Rau, personal communication, 1978 to 1988; Bukry and Snavely, 1988). Many important stratigraphic and igneous relationships are displayed within the Casacde Head area: (1) turbidite sandstone of the middle Eocene Tyee Formation, which is widespread in the central and southern part of the Oregon Coast Range (Snavely and others, 1964), was not deposited in the western part of the Cascade Head, and is of limited extent north of the map area (Wells and others, 1994); (2) the late middle Eocene Yamhill Formation, which crops out along the west and east flank of the Oregon Coast Range, overlaps older strata and overlies an erosional unconformity on the lower Eocene Siletz River Volcanics (Snavely and others, 1990; 1991); (3) thick sills of late middle Eocene diabase (43 Ma) are widespread in the Cascade Head area and also form much of the eastern flank of the Tillamook Highlands (Wells and others, 1994), but are rare south of the map area; (4) Cascade Head is the northernmost eruptive center of late Eocene alkalic basalts--85 km north of the eruptive center of correlative alkalic flows of the Yachats Basalt in the Newport Embayment (Snavely and Vokes, 1949; Snavely and others, 1990; Barnes and Barnes, 1992; Davis and others, 1995); (5) early Oligocene (33 Ma) sills and dikes of nepheline syenite and camptonite present in the Newport Embayment (Snavely and Wagner, 1961) are not found in the Cascade Head area; (6) extensive middle Oligocene (30 Ma) granophyric gabbro sills that are widespread in the central part of the Oregon Coast Range (Snavely and Wagner, 1961; MacLeod, 1969) are not present in the Cascade Head area. The Cascade Head area is the last segment of the Oregon Coast to receive detailed geologic mapping. Increased logging operations in the 1970's and 1980's created numerous new roadcut exposures and access to exposures in stream beds. More importantly, microfossil biostratigraphic control, available since 1970, based upon foraminifer determinations by W.W. Rau and nannofossil determinations by David Bukry provided critical information on stratigraphic succession as well as on depositional environments of the deep water (bathyal) siltstone units present in much of the Cascade Head area. These paleontologic data also permitted correlations with other sedimentary sequences mapped in the Newport Embayment and in the Tillamook Highlands as well as in western Washington. New 7.5-minute topographic maps and aerial photographs which became available in the late 1980's provided detailed topography which can be related to the distribution of thick sills and broad landslide areas, as well as a precise geographic relationship of geologic observations in this densely forested and brush-covered terrain. New geographic information systems (GIS) technology has produced a digitized color map of the Cascade Head area that combines the four 7.5-minute quadrangles that previously were open-filed as separate black and white 7.5-minute quadrangles (Snavely and others, 1990; 1990a; 1991; 1993). The tectonic framework and stratigraphic architecture presented on the map of the Cascade Head area was obtained by classic geologic field methods. This information could have been obtained only through detailed observation and sampling along stream beds, road cuts, and outcrops. Remote sensing techniques were of minor help in unraveling the geology in this poorly exposed and complex terrain, a terrain that characterizes much of the Oregon and Washington Coast Ranges.

Cascaded Raman lasing in packaged high quality As₂S₃ microspheres.

PubMed

Vanier, Francis; Peter, Yves-Alain; Rochette, Martin

2014-11-17

We report the observation of cascaded Raman lasing in high-Q As₂S₃microspheres. Cascaded stimulated Raman scattering emission is obtained up to the 5th order for a pump wavelength of 1557 nm and up to the 3rd order for a pump wavelength of 1880 nm. High-Q As₂S₃microspheres are used in a self-frequency locking laser setup without an external laser source. Threshold curves measurements are presented and follow the expected coupled mode theory behavior with a sub-mW threshold pump power.

An agent-based model of centralized institutions, social network technology, and revolution.

PubMed

Makowsky, Michael D; Rubin, Jared

2013-01-01

This paper sheds light on the general mechanisms underlying large-scale social and institutional change. We employ an agent-based model to test the impact of authority centralization and social network technology on preference falsification and institutional change. We find that preference falsification is increasing with centralization and decreasing with social network range. This leads to greater cascades of preference revelation and thus more institutional change in highly centralized societies and this effect is exacerbated at greater social network ranges. An empirical analysis confirms the connections that we find between institutional centralization, social radius, preference falsification, and institutional change.

Nanoplasma Formation by High Intensity Hard X-rays

PubMed Central

Tachibana, T.; Jurek, Z.; Fukuzawa, H.; Motomura, K.; Nagaya, K.; Wada, S.; Johnsson, P.; Siano, M.; Mondal, S.; Ito, Y.; Kimura, M.; Sakai, T.; Matsunami, K.; Hayashita, H.; Kajikawa, J.; Liu, X.-J.; Robert, E.; Miron, C.; Feifel, R.; Marangos, J. P.; Tono, K.; Inubushi, Y.; Yabashi, M.; Son, S.-K.; Ziaja, B.; Yao, M.; Santra, R.; Ueda, K.

2015-01-01

Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at ~5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo- and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays. PMID:26077863

Cascade Mtns. Oregon

NASA Image and Video Library

2002-04-19

The ground near one of the long-dormant Three Sisters volcanoes in the Cascade Mountains of west-central Oregon has risen approximately 10centimeters in a 10-by-20-km parcel since 1996, meaning that magma or underground lava is slowly flowing into the area, according to a research team from the U.S. Geological Survey. The Three Sisters area -- which contains five volcanoes -- is only about 170 miles from Mount St. Helens, which erupted in 1980. Both are part of the Cascades Range, a line of 27volcanoes stretching from British Columbia in Canada to northern California. This perspective view was created by draping a simulated natural color ASTER image over digital topography from the U.S. Geological Survey National Elevation Dataset. This image was acquired on May 28, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03492

Real-time spectroscopic sensing using a widely tunable external cavity-QCL with MOEMS diffraction grating

NASA Astrophysics Data System (ADS)

Ostendorf, Ralf; Butschek, Lorenz; Merten, André; Grahmann, Jan; Jarvis, Jan; Hugger, Stefan; Fuchs, Frank; Wagner, Joachim

2016-02-01

We present spectroscopic measurements performed with an EC-QCL combining a broadly tunable quantum cascade laser chip with a tuning range of more than 300 cm-1 and a resonantly driven MOEMS scanner with an integrated diffraction grating for wavelength selection in Littrow configuration. The grating geometry was optimized to provide high diffraction efficiency over the wide tuning range of the QCL, thus assuring high power density and high spectral resolution in the MIR range. The MOEMS scanner has a resonance frequency of 1 kHz, hence allowing for two full wavelength scans, one up and the other downwards, within 1 ms. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets as well as on gaseous samples of carbon monoxide. For the latter one, a large portion of the characteristic CO absorption band containing several absorption lines in the range of 2070 cm-1 to 2280 cm-1 can be monitored in real-time.

Magnetohydrodynamic Turbulence in the Plasmoid-mediated Regime

NASA Astrophysics Data System (ADS)

Comisso, L.; Huang, Y.-M.; Lingam, M.; Hirvijoki, E.; Bhattacharjee, A.

2018-02-01

Magnetohydrodynamic turbulence and magnetic reconnection are ubiquitous in astrophysical environments. In most situations these processes do not occur in isolation but interact with each other. This renders a comprehensive theory of these processes highly challenging. Here we propose a theory of magnetohydrodynamic turbulence driven at a large scale that self-consistently accounts for the mutual interplay with magnetic reconnection occurring at smaller scales. Magnetic reconnection produces plasmoids (flux ropes) that grow from turbulence-generated noise and eventually disrupt the sheet-like structures in which they are born. The disruption of these structures leads to a modification of the turbulent energy cascade, which in turn exerts a feedback effect on the plasmoid formation via the turbulence-generated noise. The energy spectrum in this plasmoid-mediated range steepens relative to the standard inertial range and does not follow a simple power law. As a result of the complex interplay between turbulence and reconnection, we also find that the length scale that marks the beginning of the plasmoid-mediated range and the dissipation length scale do not obey true power laws. The transitional magnetic Reynolds number above which the plasmoid formation becomes statistically significant enough to affect the turbulent cascade is fairly modest, implying that plasmoids are expected to modify the turbulent path to dissipation in many astrophysical systems.

Magnetohydrodynamic Turbulence in the Plasmoid-mediated Regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comisso, L.; Huang, Y. -M.; Lingam, M.

Magnetohydrodynamic turbulence and magnetic reconnection are ubiquitous in astrophysical environments. In most situations these processes do not occur in isolation but interact with each other. This renders a comprehensive theory of these processes highly challenging. Here we propose a theory of magnetohydrodynamic turbulence driven at a large scale that self-consistently accounts for the mutual interplay with magnetic reconnection occurring at smaller scales. Magnetic reconnection produces plasmoids (flux ropes) that grow from turbulence-generated noise and eventually disrupt the sheet-like structures in which they are born. The disruption of these structures leads to a modification of the turbulent energy cascade, which inmore » turn exerts a feedback effect on the plasmoid formation via the turbulence-generated noise. The energy spectrum in this plasmoid-mediated range steepens relative to the standard inertial range and does not follow a simple power law. As a result of the complex interplay between turbulence and reconnection, we also find that the length scale that marks the beginning of the plasmoid-mediated range and the dissipation length scale do not obey true power laws. The transitional magnetic Reynolds number above which the plasmoid formation becomes statistically significant enough to affect the turbulent cascade is fairly modest, implying that plasmoids are expected to modify the turbulent path to dissipation in many astrophysical systems« less

Magnetohydrodynamic Turbulence in the Plasmoid-mediated Regime

DOE PAGES

Comisso, L.; Huang, Y. -M.; Lingam, M.; ...

2018-02-16

Magnetohydrodynamic turbulence and magnetic reconnection are ubiquitous in astrophysical environments. In most situations these processes do not occur in isolation but interact with each other. This renders a comprehensive theory of these processes highly challenging. Here we propose a theory of magnetohydrodynamic turbulence driven at a large scale that self-consistently accounts for the mutual interplay with magnetic reconnection occurring at smaller scales. Magnetic reconnection produces plasmoids (flux ropes) that grow from turbulence-generated noise and eventually disrupt the sheet-like structures in which they are born. The disruption of these structures leads to a modification of the turbulent energy cascade, which inmore » turn exerts a feedback effect on the plasmoid formation via the turbulence-generated noise. The energy spectrum in this plasmoid-mediated range steepens relative to the standard inertial range and does not follow a simple power law. As a result of the complex interplay between turbulence and reconnection, we also find that the length scale that marks the beginning of the plasmoid-mediated range and the dissipation length scale do not obey true power laws. The transitional magnetic Reynolds number above which the plasmoid formation becomes statistically significant enough to affect the turbulent cascade is fairly modest, implying that plasmoids are expected to modify the turbulent path to dissipation in many astrophysical systems« less

Magnesium Isotopes as a Tracer of Crustal Materials in Volcanic Arc Magmas in the Northern Cascade Arc

NASA Astrophysics Data System (ADS)

Brewer, Aaron W.; Teng, Fang-Zhen; Mullen, Emily

2018-03-01

Fifteen North Cascade Arc basalts and andesites were analyzed for Mg isotopes to investigate the extent and manner of crustal contributions to this magmatic system. The δ26Mg of these samples vary from within the range of ocean island basalts (the lightest being -0.33 ± 0.07‰) to heavier compositions (as heavy as -0.15 ± 0.06‰). The observed range in chemical and isotopic composition is similar to that of other volcanic arcs that have been assessed to date in the circum-pacific subduction zones and in the Caribbean. The heavy Mg isotope compositions are best explained by assimilation and fractional crystallization within the deep continental crust with a possible minor contribution from the addition of subducting slab-derived fluids to the primitive magma. The bulk mixing of sediment into the primitive magma or mantle source and the partial melting of garnet-rich peridotite are unlikely to have produced the observed range of Mg isotope compositions. The results show that Mg isotopes may be a useful tracer of crustal input into a magma, supplementing traditional methods such as radiogenic isotopic and trace element data, particularly in cases in which a high fraction of crustal material has been added.

Atomistic Simulation of Displacement Cascades in Zircon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devanathan, Ram; Weber, William J.; Corrales, Louis R.

2002-05-06

Low energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements were found to occur mainly in the O sublattice, and O replacements by a ring mechanism were predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects were found to occur. This Si-O-Si bridging is considerable in quenched liquid ZrSiO4.

Determining the Specificity of Cascade Binding, Interference, and Primed Adaptation In Vivo in the Escherichia coli Type I-E CRISPR-Cas System.

PubMed

Cooper, Lauren A; Stringer, Anne M; Wade, Joseph T

2018-04-17

In clustered regularly interspaced short palindromic repeat (CRISPR)-Cas (CRISPR-associated) immunity systems, short CRISPR RNAs (crRNAs) are bound by Cas proteins, and these complexes target invading nucleic acid molecules for degradation in a process known as interference. In type I CRISPR-Cas systems, the Cas protein complex that binds DNA is known as Cascade. Association of Cascade with target DNA can also lead to acquisition of new immunity elements in a process known as primed adaptation. Here, we assess the specificity determinants for Cascade-DNA interaction, interference, and primed adaptation in vivo , for the type I-E system of Escherichia coli Remarkably, as few as 5 bp of crRNA-DNA are sufficient for association of Cascade with a DNA target. Consequently, a single crRNA promotes Cascade association with numerous off-target sites, and the endogenous E. coli crRNAs direct Cascade binding to >100 chromosomal sites. In contrast to the low specificity of Cascade-DNA interactions, >18 bp are required for both interference and primed adaptation. Hence, Cascade binding to suboptimal, off-target sites is inert. Our data support a model in which the initial Cascade association with DNA targets requires only limited sequence complementarity at the crRNA 5' end whereas recruitment and/or activation of the Cas3 nuclease, a prerequisite for interference and primed adaptation, requires extensive base pairing. IMPORTANCE Many bacterial and archaeal species encode CRISPR-Cas immunity systems that protect against invasion by foreign DNA. In the Escherichia coli CRISPR-Cas system, a protein complex, Cascade, binds 61-nucleotide (nt) CRISPR RNAs (crRNAs). The Cascade complex is directed to invading DNA molecules through base pairing between the crRNA and target DNA. This leads to recruitment of the Cas3 nuclease, which destroys the invading DNA molecule and promotes acquisition of new immunity elements. We made the first in vivo measurements of Cascade binding to DNA targets. Thus, we show that Cascade binding to DNA is highly promiscuous; endogenous E. coli crRNAs can direct Cascade binding to >100 chromosomal locations. In contrast, we show that targeted degradation and acquisition of new immunity elements require highly specific association of Cascade with DNA, limiting CRISPR-Cas function to the appropriate targets. Copyright © 2018 Cooper et al.

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia

2012-01-01

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

Novel Design of Type I High Power Mid-IR Diode Lasers for Spectral Region 3 - 4.2 Microns

DTIC Science & Technology

2014-09-25

multifold improvement of the device characteristics. Cascade pumping was achieved utilizing efficient interband tunneling through "leaky" window in band...Initially cascade pumping scheme was applied to laser heterostructures utilizing gain sections based on either intersubband [1] or type-II interband ...active regions, metamorphic virtual substrate and cascade pumping scheme. Cascade pumping of type-I quantum well gain section opened the whole new

Geologic map of upper Eocene to Holocene volcanic and related rocks in the Cascade Range, Washington

USGS Publications Warehouse

Smith, James G.

1993-01-01

For geothermal reasons, the maps emphasize Quaternary volcanic rocks. Large igneous-related geothermal systems that have high temperatures are associated with Quaternary volcanic fields, and geothermal potential declines rapidly as age increases (Smith and Shaw, 1975). Most high-grade recoverable geothermal energy is likely to be associated with silicic volcanism less than 1 Ma. Lower grade (= lower temperature) geothermal resources may be associated with somewhat older rocks; however, volcanic rocks older than about 2 Ma are unlikely geothermal targets (Smith and Shaw, 1975).

A simple model of global cascades on random networks

NASA Astrophysics Data System (ADS)

Watts, Duncan J.

2002-04-01

The origin of large but rare cascades that are triggered by small initial shocks is a phenomenon that manifests itself as diversely as cultural fads, collective action, the diffusion of norms and innovations, and cascading failures in infrastructure and organizational networks. This paper presents a possible explanation of this phenomenon in terms of a sparse, random network of interacting agents whose decisions are determined by the actions of their neighbors according to a simple threshold rule. Two regimes are identified in which the network is susceptible to very large cascadesherein called global cascadesthat occur very rarely. When cascade propagation is limited by the connectivity of the network, a power law distribution of cascade sizes is observed, analogous to the cluster size distribution in standard percolation theory and avalanches in self-organized criticality. But when the network is highly connected, cascade propagation is limited instead by the local stability of the nodes themselves, and the size distribution of cascades is bimodal, implying a more extreme kind of instability that is correspondingly harder to anticipate. In the first regime, where the distribution of network neighbors is highly skewed, it is found that the most connected nodes are far more likely than average nodes to trigger cascades, but not in the second regime. Finally, it is shown that heterogeneity plays an ambiguous role in determining a system's stability: increasingly heterogeneous thresholds make the system more vulnerable to global cascades; but an increasingly heterogeneous degree distribution makes it less vulnerable.

Testing technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-10-01

This bulletin from Sandia National Laboratories presents current research highlights in testing technology. Ion microscopy offers new nondestructive testing technique that detects high resolution invisible defects. An inexpensive thin-film gauge checks detonators on centrifuge. Laser trackers ride the range and track helicopters at low-level flights that could not be detected by radar. Radiation transport software predicts electron/photon effects via cascade simulation. Acoustic research in noise abatement will lead to quieter travelling for Bay Area Rapid Transport (BART) commuters.

Variable soft X-ray excesses in active galactic nuclei from nonthermal electron-positron pair cascades

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Coppi, Paolo S.

1991-01-01

In the present study of the formation of steep soft X-ray excesses that are superposed on flatter, hard X-ray power-law spectra in nonthermal electron-positron pair cascade sources, the soft excess in pair-cascade AGN models appears as a steep power law superposed on the tail of the UV bump and the flat nonthermal (hard X-ray) power law. The model-parameter space in which an excess in soft X-rays is visible is ascertained, and the time-variability of soft excesses in pair cascade models is examined. It is established that the parameter space in which soft excesses appear encompasses the range of preferred input parameters for a recently development Compton reflection model of UV and X-ray emission from the central engine of an AGN.

Geologic map of Medicine Lake volcano, northern California

USGS Publications Warehouse

Donnelly-Nolan, Julie M.

2011-01-01

Medicine Lake volcano forms a broad, seemingly nondescript highland, as viewed from any angle on the ground. Seen from an airplane, however, treeless lava flows are scattered across the surface of this potentially active volcanic edifice. Lavas of Medicine Lake volcano, which range in composition from basalt through rhyolite, cover more than 2,000 km2 east of the main axis of the Cascade Range in northern California. Across the Cascade Range axis to the west-southwest is Mount Shasta, its towering volcanic neighbor, whose stratocone shape contrasts with the broad shield shape of Medicine Lake volcano. Hidden in the center of Medicine Lake volcano is a 7 km by 12 km summit caldera in which nestles its namesake, Medicine Lake. The flanks of Medicine Lake volcano, which are dotted with cinder cones, slope gently upward to the caldera rim, which reaches an elevation of nearly 8,000 ft (2,440 m). The maximum extent of lavas from this half-million-year-old volcano is about 80 km north-south by 45 km east-west. In postglacial time, 17 eruptions have added approximately 7.5 km3 to its total estimated volume of 600 km3, and it is considered to be the largest by volume among volcanoes of the Cascades arc. The volcano has erupted nine times in the past 5,200 years, a rate more frequent than has been documented at all other Cascades arc volcanoes except Mount St. Helens.

Willow on Yellowstone's northern range: evidence for a trophic cascade?

PubMed

Beyer, Hawthorne L; Merrill, Evelyn H; Varley, Nathan; Boyce, Mark S

2007-09-01

Reintroduction of wolves (Canis lupus) to Yellowstone National Park in 1995-1996 has been argued to promote a trophic cascade by altering elk (Cervus elaphus) density, habitat-selection patterns, and behavior that, in turn, could lead to changes within the plant communities used by elk. We sampled two species of willow (Salix boothii and S. geyeriana) on the northern winter range to determine whether (1) there was quantitative evidence of increased willow growth following wolf reintroduction, (2) browsing by elk affected willow growth, and (3) any increase in growth observed was greater than that expected by climatic and hydrological factors alone, thereby indicating a trophic cascade caused by wolves. Using stem sectioning techniques to quantify historical growth patterns we found an approximately twofold increase in stem growth-ring area following wolf reintroduction for both species of willow. This increase could not be explained by climate and hydrological factors alone; the presence of wolves on the landscape was a significant predictor of stem growth above and beyond these abiotic factors. Growth-ring area was positively correlated with the previous year's ring area and negatively correlated with the percentage of twigs browsed from the stem during the winter preceding growth, indicating that elk browse impeded stem growth. Our results are consistent with the hypothesis of a behaviorally mediated trophic cascade on Yellowstone's northern winter range following wolf reintroduction. We suggest that the community-altering effects of wolf restoration are an endorsement of ecological-process management in Yellowstone National Park.

Structure of northern spotted owl nest stands and their historical conditions on the eastern slope of the Pacific Northwest Cascades, USA.

Treesearch

Richard Everett; D. Schellhaas; D. Spurbeck; [and others].

1997-01-01

The northern spotted (Strix occidentalis caurina) uses a wide array of nesting habitat throughout its current range and successfully reproduces in a variety of stand types on the eastern slope of the Pacific Northwest Cascades. The species has the ability to utilize dynamic forest stands that continue to undergo significant changes in tree density...

High altitude airship configuration and power technology and method for operation of same

NASA Technical Reports Server (NTRS)

Choi, Sang H. (Inventor); Elliott, Jr., James R. (Inventor); King, Glen C. (Inventor); Park, Yeonjoon (Inventor); Kim, Jae-Woo (Inventor); Chu, Sang-Hyon (Inventor)

2011-01-01

A new High Altitude Airship (HAA) capable of various extended applications and mission scenarios utilizing inventive onboard energy harvesting and power distribution systems. The power technology comprises an advanced thermoelectric (ATE) thermal energy conversion system. The high efficiency of multiple stages of ATE materials in a tandem mode, each suited for best performance within a particular temperature range, permits the ATE system to generate a high quantity of harvested energy for the extended mission scenarios. When the figure of merit 5 is considered, the cascaded efficiency of the three-stage ATE system approaches an efficiency greater than 60 percent.

High power, high efficiency, continuous-wave supercontinuum generation using standard telecom fibers

NASA Astrophysics Data System (ADS)

Arun, S.; Choudhury, Vishal; Balaswamy, V.; Prakash, Roopa; Supradeepa, V. R.

2018-04-01

We demonstrate a simple module for octave spanning continuous-wave supercontinuum generation using standard telecom fiber. This module can accept any high power Ytterbium-doped fiber laser as input. The input light is transferred into the anomalous dispersion region of the telecom fiber through a cascade of Raman shifts. A recently proposed Raman laser architecture with distributed feedback efficiently performs these Raman conversions. A spectrum spanning over 1000nm(>1 octave) from 880-1900nm is demonstrated. The average power from the supercontinuum is ~34W with a high conversion efficiency of 44%. Input wavelength agility is demonstrated with similar supercontinua over a wide input wavelength range.

Phase-synchronization, energy cascade, and intermittency in solar-wind turbulence.

PubMed

Perri, S; Carbone, V; Vecchio, A; Bruno, R; Korth, H; Zurbuchen, T H; Sorriso-Valvo, L

2012-12-14

The energy cascade in solar wind magnetic turbulence is investigated using MESSENGER data in the inner heliosphere. The decomposition of magnetic field time series in intrinsic functions, each characterized by a typical time scale, reveals phase reorganization. This allows for the identification of structures of all sizes generated by the nonlinear turbulent cascade, covering both the inertial and the dispersive ranges of the turbulent magnetic power spectrum. We find that the correlation (or anticorrelation) of phases occurs between pairs of neighboring time scales, whenever localized peaks of magnetic energy are present at both scales, consistent with the local character of the energy transfer process.

Tri-channel single-mode terahertz quantum cascade laser.

PubMed

Wang, Tao; Liu, Jun-Qi; Liu, Feng-Qi; Wang, Li-Jun; Zhang, Jin-Chuan; Wang, Zhan-Guo

2014-12-01

We report on a compact THz quantum cascade laser source emitting at, individually controllable, three different wavelengths (92.6, 93.9, and 95.1 μm). This multiwavelength laser array can be used as a prototype of the emission source of THz wavelength division multiplex (WDM) wireless communication system. The source consists of three tapered single-mode distributed feedback (DFB) terahertz quantum cascade lasers fabricated monolithically on a single chip. All array elements feature longitudinal as well as lateral single-mode in the entire injection range. The peak output powers of individual lasers are 42, 73, and 37 mW at 10 K, respectively.

Regimes of external optical feedback in 5.6 μm distributed feedback mid-infrared quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; Alcatel Thales III-V Lab, Campus de Polytechnique, 1 avenue Augustin Fresnel, 91767 Palaiseau; Carras, M.

2014-09-29

External optical feedback is studied experimentally in mid-infrared quantum cascade lasers. These structures exhibit a dynamical response close to that observed in interband lasers, with threshold reduction and optical power enhancement when increasing the feedback ratio. The study of the optical spectrum proves that the laser undergoes five distinct regimes depending on the phase and amplitude of the reinjected field. These regimes are mapped in the plane of external cavity length and feedback strength, revealing unstable behavior only for a very narrow range of operation, making quantum cascade lasers much more stable than their interband counterparts.

Room temperature continuous wave operation of quantum cascade laser at λ ~ 9.4 μm

NASA Astrophysics Data System (ADS)

Hou, Chuncai; Zhao, Yue; Zhang, Jinchuan; Zhai, Shenqiang; Zhuo, Ning; Liu, Junqi; Wang, Lijun; Liu, Shuman; Liu, Fengqi; Wang, Zhanguo

2018-03-01

Continuous wave (CW) operation of long wave infrared (LWIR) quantum cascade lasers (QCLs) is achieved up to a temperature of 303 K. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 2-mm-long and 10-μm-wide laser with high-reflectivity (HR) coating on the rear facet, CW output power of 45 mW at 283 K and 9 mW at 303 K is obtained. The lasing wavelength is around 9.4 μm locating in the LWIR spectrum range. Project supported by the National Key Research And Development Program (No. 2016YFB0402303), the National Natural Science Foundation of China (Nos. 61435014, 61627822, 61574136, 61774146, 61674144, 61404131), the Key Projects of Chinese Academy of Sciences (Nos. ZDRW-XH-2016-4, QYZDJ-SSW-JSC027), and the Beijing Natural Science Foundation (No. 4162060, 4172060).

Calculation of three dimensional viscous flows in annular cascades using parabolized Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Lawerenz, M.

Numerical algorithms for describing the endwall boundary layers and secondary flows in high turning turbine cascades are described. Partially-parabolic methods which cover three-dimensional viscous flow effects are outlined. Introduction of tip-clearance models and modifications of no-slip conditions without the use of wall functions expand the range of application and improve accuracy. Simultaneous computation of the profile boundary layers by refinement of the mesh size in the circumferential direction makes it possible to describe the boundary layer interaction in the corners formed by the bladings and the endwalls. The partially-parabolic method means that the streamwise elliptic coupling is well represented by the given pressure field and that separation does not occur, but it is not possible to describe the separation of the endwall boundary layer near the leading edge and the horse-shoe vortex there properly.

Electrically tunable infrared filter based on a cascaded liquid-crystal Fabry-Perot for spectral imaging detection.

PubMed

Lin, Jiuning; Tong, Qing; Lei, Yu; Xin, Zhaowei; Wei, Dong; Zhang, Xinyu; Liao, Jing; Wang, Haiwei; Xie, Changsheng

2017-03-01

An electrically tunable infrared (IR) filter based on a key cascaded liquid-crystal Fabry-Perot (C-LC-FP) working in the wavelength range of 3-5 μm is presented. The C-LC-FP is constructed by closely stacking two FP microcavities with different depths of 12 and 15 μm and fully filled by nematic LC materials. Through continuous wavelength selection of both microcavities, radiation with a high transmittance and narrow bandwidth can pass through the filter. According to the electrically controlled birefringence characteristics of nematic LC molecules, the transmission spectrum can be shifted through applying a dual voltage signal over the C-LC-FP. Compared with common LC-FPs with a single microcavity, the C-LC-FP demonstrates better transmittance peak morphology and spectral selection performance. To be more specific, the number and the shifted scope of the IR transmission peak can be decreased and widened, respectively.

Low Power Consumption Substrate-Emitting DFB Quantum Cascade Lasers.

PubMed

Liu, Chuan-Wei; Zhang, Jin-Chuan; Jia, Zhi-Wei; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2017-09-02

In the present work, an ultra-low power consumption substrate-emitting distributed feedback (DFB) quantum cascade laser (QCL) was developed. The continuous-wave (CW) threshold power dissipation is reduced to 0.43 W at 25 °C by shortening the cavity length to 0.5 mm and depositing high-reflectivity (HR) coating on both facets. As far as we know, this is the recorded threshold power dissipation of QCLs in the same conditions. Single-mode emission was achieved by employing a buried second-order grating. Mode-hop free emission can be observed within a wide temperature range from 15 to 105 °C in CW mode. The divergence angles are 22.5 o and 1.94 o in the ridge-width direction and cavity-length direction, respectively. The maximum optical power in CW operation was 2.4 mW at 25 °C, which is sufficient to spectroscopy applications.

Multispecies absorption spectroscopy of detonation events at 100  kHz using a fiber-coupled, time-division-multiplexed quantum-cascade-laser system.

PubMed

Rein, Keith D; Roy, Sukesh; Sanders, Scott T; Caswell, Andrew W; Schauer, Frederick R; Gord, James R

2016-08-10

A mid-infrared fiber-coupled laser system constructed around three time-division-multiplexed quantum-cascade lasers capable of measuring the absorption spectra of CO, CO₂, and N₂O at 100 kHz over a wide range of operating pressures and temperatures is demonstrated. This system is first demonstrated in a laboratory burner and then used to measure temperature, pressure, and concentrations of CO, CO₂, and N₂O as a function of time in a detonated mixture of N₂O and C₃H₈. Both fuel-rich and fuel-lean detonation cases are outlined. High-temperature fluctuations during the blowdown are observed. Concentrations of CO are shown to decrease with time for fuel-lean conditions and increase for fuel-rich conditions.

The long underestimated carbonyl function of carbohydrates – an organocatalyzed shot into carbohydrate chemistry.

PubMed

Mahrwald, R

2015-09-21

The aggressive and strong development of organocatalysis provides several protocols for the convenient utilization of the carbonyl function of unprotected carbohydrates in C-C-bond formation processes. These amine-catalyzed mechanisms enable multiple cascade-protocols for the synthesis of a wide range of carbohydrate-derived compound classes. Several, only slightly different protocols, have been developed for the application of 1,3-dicarbonyl compounds in the stereoselective chain-elongation of unprotected carbohydrates and the synthesis of highly functionalized C-glycosides of defined configuration. In addition, C-glycosides can also be accessed by amine-catalyzed reactions with methyl ketones. By a one-pot cascade reaction of isocyanides with unprotected aldoses and amino acids access to defined configured glycopeptide mimetics is achieved. Depending on the reaction conditions different origins to control the installation of configuration during the bond-formation process were observed.

Active hyperspectral imaging using a quantum cascade laser (QCL) array and digital-pixel focal plane array (DFPA) camera.

PubMed

Goyal, Anish; Myers, Travis; Wang, Christine A; Kelly, Michael; Tyrrell, Brian; Gokden, B; Sanchez, Antonio; Turner, George; Capasso, Federico

2014-06-16

We demonstrate active hyperspectral imaging using a quantum-cascade laser (QCL) array as the illumination source and a digital-pixel focal-plane-array (DFPA) camera as the receiver. The multi-wavelength QCL array used in this work comprises 15 individually addressable QCLs in which the beams from all lasers are spatially overlapped using wavelength beam combining (WBC). The DFPA camera was configured to integrate the laser light reflected from the sample and to perform on-chip subtraction of the passive thermal background. A 27-frame hyperspectral image was acquired of a liquid contaminant on a diffuse gold surface at a range of 5 meters. The measured spectral reflectance closely matches the calculated reflectance. Furthermore, the high-speed capabilities of the system were demonstrated by capturing differential reflectance images of sand and KClO₃ particles that were moving at speeds of up to 10 m/s.

Low Power Consumption Substrate-Emitting DFB Quantum Cascade Lasers

NASA Astrophysics Data System (ADS)

Liu, Chuan-Wei; Zhang, Jin-Chuan; Jia, Zhi-Wei; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2017-09-01

In the present work, an ultra-low power consumption substrate-emitting distributed feedback (DFB) quantum cascade laser (QCL) was developed. The continuous-wave (CW) threshold power dissipation is reduced to 0.43 W at 25 °C by shortening the cavity length to 0.5 mm and depositing high-reflectivity (HR) coating on both facets. As far as we know, this is the recorded threshold power dissipation of QCLs in the same conditions. Single-mode emission was achieved by employing a buried second-order grating. Mode-hop free emission can be observed within a wide temperature range from 15 to 105 °C in CW mode. The divergence angles are 22.5o and 1.94o in the ridge-width direction and cavity-length direction, respectively. The maximum optical power in CW operation was 2.4 mW at 25 °C, which is sufficient to spectroscopy applications.

Reducing operating costs for struvite formation with a carbon dioxide stripper.

PubMed

Fattah, K P; Sabrina, N; Mavinic, D S; Koch, F A

2008-01-01

One of the major operational costs of phosphorus recovery as struvite is the cost of caustic chemical that is added to maintain a desired level of operative pH. A study was conducted at the Lulu Island Wastewater Treatment Plant (LIWWTP), Richmond, BC, using a struvite crystallizer and a cascade stripper designed at the University of British Columbia (UBC). The stripper was tested under different operating conditions to determine the effectiveness of CO(2) stripping in increasing the pH of the water matrix and thereby reducing caustic chemical use. This reduction is expected to reduce the operational costs of struvite production. Throughout the project, a high percentage (90%) of phosphorus removal was achieved under each condition. The cascade stripper was very effective in saving caustic usage, ranging from 35% to 86%, depending on the operating conditions. However, the stripper showed relatively poor performance regarding ammonia stripping. Copyright IWA Publishing 2008.

Compact photonic crystal circulator with flat-top transmission band created by cascading magneto-optical resonance cavities.

PubMed

Wang, Qiong; Ouyang, Zhengbiao; Lin, Mi; Liu, Qiang

2015-11-20

A new type of compact three-port circulator with flat-top transmission band (FTTB) in a two-dimensional photonic crystal has been proposed, through coupling the cascaded magneto-optical resonance cavities to waveguides. The coupled-mode theory is applied to investigate the coupled structure and analyze the condition to achieve FTTB. According to the theoretical analysis, the structure is further optimized to ensure that the condition for achieving FTTB can be satisfied for both cavity-cavity coupling and cavity-waveguide coupling. Through the finite-element method, it is demonstrated that the design can realize a high quality, nonreciprocal circulating propagation of waves with an insertion loss of 0.023 dB and an isolation of 23.3 dB, covering a wide range of operation frequency. Such a wideband circulator has potential applications in large-scale integrated photonic circuits for guiding or isolating harmful optical reflections from load elements.

Long-period grating and its cascaded counterpart in photonic crystal fiber for gas phase measurement.

PubMed

Tian, Fei; Kanka, Jiri; Du, Henry

2012-09-10

Regular and cascaded long period gratings (LPG, C-LPG) of periods ranging from 460 to 590 μm were inscribed in an endlessly single mode photonic crystal fiber (PCF) using CO(2) laser for sensing measurements of helium, argon and acetylene. High index sensitivities in excess of 1700 nm/RIU were achieved in both grating schemes with a period of 460 μm. The sharp interference fringes in the transmission spectrum of C-PCF-LPG afforded not only greatly enhanced sensing resolution, but also accuracy when the phase-shift of the fringe pattern is determined through spectral processing. Comparative numerical and experimental studies indicated LP(01) to LP(03) mode coupling as the principal coupling step for both PCF-LPG and C-PCF-LPG with emergence of multi-mode coupling at shorter grating periods or longer resonance wavelengths.

Compact, High Power, Multi-Spectral Mid-Infrared Semiconductor Laser Package

NASA Astrophysics Data System (ADS)

Guo, Bujin; Hwang, Wen-Yen; Lin, Chich-Hsiang

2001-10-01

Through a vertically integrated effort involving atomic level material engineering, advanced device processing development, state-of-the-art optomechanical packaging, and thermal management, Applied Optoelectronics, Inc. (AOI), University of Houston (U H), and Physical Science, Inc. (PSI) have made progress in both Sb-based type-II semiconductor material and in P-based type-I laser device development. We have achieved record performance on inP based quantum cascade continuous wave (CW) laser (with more than 5 mW CW power at 210 K). Grating-coupled external-cavity quantum cascade lasers were studied for temperatures from 20 to 230 K. A tuning range of 88 nm has been obtained at 80 K. The technology can be made commercially available and represents a significant milestone with regard to the Dual Use Science and Technology (DUST) intention of fostering dual use commercial technology for defense need. AOI is the first commercial company to ship products of this licensed technology.

A new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin

USGS Publications Warehouse

Parsons, T.; Trehu, A.M.; Luetgert, J.H.; Miller, K.; Kilbride, F.; Wells, R.E.; Fisher, M.A.; Flueh, E.; ten Brink, Uri S.; Christensen, N.I.

1998-01-01

In light of suggestions that the Cascadia subduction margin may pose a significant seismic hazard for the highly populated Pacific Northwest region of the United States, the U.S. Geological Survey (USGS), the Research Center for Marine Geosciences (GEOMAR), and university collaborators collected and interpreted a 530-km-long wide-angle onshore-offshore seismic transect across the subduction zone and volcanic arc to study the major structures that contribute to seismogenic deformation. We observed (1) an increase in the dip of the Juan de Fuca slab from 2°–7° to 12° where it encounters a 20-km-thick block of the Siletz terrane or other accreted oceanic crust, (2) a distinct transition from Siletz crust into Cascade arc crust that coincides with the Mount St. Helens seismic zone, supporting the idea that the mafic Siletz block focuses seismic deformation at its edges, and (3) a crustal root (35–45 km deep) beneath the Cascade Range, with thinner crust (30–35 km) east of the volcanic arc beneath the Columbia Plateau flood basalt province. From the measured crustal structure and subduction geometry, we identify two zones that may concentrate future seismic activity: (1) a broad (because of the shallow dip), possibly locked part of the interplate contact that extends from ∼25 km depth beneath the coastline to perhaps as far west as the deformation front ∼120 km offshore and (2) a crustal zone at the eastern boundary between the Siletz terrane and the Cascade Range.

Effects of snow persistence on streamflow generation in mountain regions of the western U.S.

NASA Astrophysics Data System (ADS)

Hammond, J. C.; Kampf, S. K.

2015-12-01

In mountain regions, both snowpack trend analyses and modeling studies suggest that streamflow generation is sensitive to loss of snow, yet we still lack understanding of where the most snow-sensitive regions are located. Snow persistence (SP), defined as the fraction of year that an area is snow-covered, is a useful variable for identifying snow-sensitive regions because it is easily observed globally using remote sensing. SP can affect streamflow generation by shifting the timing and magnitude of water input. All other factors being equal, we hypothesize that declining SP decreases the ratio of streamflow to precipitation (runoff ratio), and the magnitude of this effect is greater in arid climates than in humid climates. To evaluate whether streamflow generation declines with decreasing SP, we used the MODSCAG fractional snow cover product and 68 USGS reference catchments across five mountainous regions of the Western U.S. to compute annual and mean annual SP and discharge for water years 2000 to 2011. We used PRISM precipitation to compute the annual and mean annual runoff ratio for each catchment. Results show strong positive relationships between annual SP and annual runoff ratio in the Northern Rockies, Southern Rockies, and Basin and Range, where annual precipitation ranges from 0.25 m at low elevations in the Basin and Range to 2.5 m at high elevations in the Northern Rockies. Mean annual runoff ratios for these regions range from 0.32-0.53, and they also increase with mean annual SP. No relationships between annual SP and runoff ratios are evident in the wetter North Cascades and Sierra Nevada ranges, where annual precipitation ranges from 0.44 m in the low elevation Sierras to 4.8 m in the high elevation Cascades. Mean annual runoff ratios for these regions are 0.53-0.87 and show no clear dependence on SP. These results suggest that streamflow generation in arid regions may be most sensitive to loss of persistent winter snow.

Gust Response Analysis of a Turbine Cascade

NASA Technical Reports Server (NTRS)

Gorla, R. S. R.; Reddy, T. S. R.; Reddy, D. R.; Kurkov, A. P.

2001-01-01

A study was made of the gust response of an annular turbine cascade using a two-dimensional Navier Stokes code. The time-marching CFD code, NPARC, was used to calculate the unsteady forces due to the fluid flow. The computational results were compared with a previously published experimental data for the annular cascade reported in the literature. Reduced frequency, Mach number and angle of incidence were varied independently and the gust velocity was sinusoidal. For the high inlet velocity case, the cascade was nearly choked.

QED cascade saturation in extreme high fields.

PubMed

Luo, Wen; Liu, Wei-Yuan; Yuan, Tao; Chen, Min; Yu, Ji-Ye; Li, Fei-Yu; Del Sorbo, D; Ridgers, C P; Sheng, Zheng-Ming

2018-05-30

Upcoming ultrahigh power lasers at 10 PW level will make it possible to experimentally explore electron-positron (e - e + ) pair cascades and subsequent relativistic e - e + jets formation, which are supposed to occur in extreme astrophysical environments, such as black holes, pulsars, quasars and gamma-ray bursts. In the latter case it is a long-standing question as to how the relativistic jets are formed and what their temperatures and compositions are. Here we report simulation results of pair cascades in two counter-propagating QED-strong laser fields. A scaling of QED cascade growth with laser intensity is found, showing clear cascade saturation above threshold intensity of ~10 24 W/cm 2 . QED cascade saturation leads to pair plasma cooling and longitudinal compression along the laser axis, resulting in the subsequent formation of relativistic dense e - e + jets along transverse directions. Such laser-driven QED cascade saturation may open up the opportunity to study energetic astrophysical phenomena in laboratory.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoller, Roger E; Nordlund, Kai; Melerba, L

The processes that give rise to changes in the microstructure and the physical and mechanical properties of materials exposed to energetic particles are initiated by essentially elastic collisions between atoms in what has been called an atomic displacement cascade. The formation and evolution of this primary radiation damage mechanism are described to provide an overview of how stable defects are formed by displacement cascades, as well as the nature and morphology of the defects themselves. The impact of the primary variables cascade energy and irradiation temperature are discussed, along with a range of secondary factors that can influence damage formation.Radiation-inducedmore » changes in microstructure and mechanical properties in structural materials are the result of a complex set of physical processes initiated by the collision between an energetic particle (neutron or ion) and an atom in the lattice. This primary damage event is called an atomic displacement cascade. The simplest description of a displacement cascade is to view it as a series of many billiard-ball-like elastic collisions among the atoms in the material. This chapter describes the formation and evolution of this primary radiation damage mechanism to provide an overview of how stable defects are formed by displacement cascades, as well as the nature and morphology of the defects themselves. The impact of the relevant variables such as cascade energy and irradiation temperature is discussed, and defect formation in different materials is compared.« less

The ecology and management of moist mixed-conifer forests in eastern Oregon and Washington: a synthesis of the relevant biophysical science and implications for future land management

Treesearch

Peter Stine; Paul Hessburg; Thomas Spies; Marc Kramer; Christopher J. Fettig; Andrew Hansen; John Lehmkuhl; Kevin O' Hara; Karl Polivka; Peter Singleton; Susan Charnley; Andrew Merschel; Rachel White

2014-01-01

Land managers in the Pacific Northwest have reported a need for updated scientific information on the ecology and management of mixed-conifer forests east of the Cascade Range in Oregon and Washington. Of particular concern are the moist mixed-conifer forests, which have become drought-stressed and vulnerable to high-severity fire after decades of human disturbances...

Stochastic annealing simulations of defect interactions among subcascades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinisch, H.L.; Singh, B.N.

1997-04-01

The effects of the subcascade structure of high energy cascades on the temperature dependencies of annihilation, clustering and free defect production are investigated. The subcascade structure is simulated by closely spaced groups of lower energy MD cascades. The simulation results illustrate the strong influence of the defect configuration existing in the primary damage state on subsequent intracascade evolution. Other significant factors affecting the evolution of the defect distribution are the large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades. Annealing simulations are also performedmore » on high-energy, subcascade-producing cascades generated with the binary collision approximation and calibrated to MD results.« less

Measurement of Gust Response on a Turbine Cascade

NASA Technical Reports Server (NTRS)

Kurkov, A. P.; Lucci, B. L.

1995-01-01

The paper presents benchmark experimental data on a gust response of an annular turbine cascade. The experiment was particularly designed to provide data for comparison with the results of a typical linearized gust-response analysis. Reduced frequency, Mach number, and incidence were varied independently. Except for the lowest reduced frequency, the gust velocity distribution was nearly sinusoidal. For the high inlet-velocity series of tests, the cascade was near choking. The mean flow was documented by measuring blade surface pressures and the cascade exit flow. High-response pressure transducers were used to measure the unsteady pressure distribution. Inlet-velocity components and turbulence parameters were measured using hot wire. In addition to the synchronous time-average pressure spectra, typical power spectra are included for several representative conditions.

Widely tunable mid-infrared quantum cascade lasers using sampled grating reflectors.

PubMed

Mansuripur, Tobias S; Menzel, Stefan; Blanchard, Romain; Diehl, Laurent; Pflügl, Christian; Huang, Yong; Ryou, Jae-Hyun; Dupuis, Russell D; Loncar, Marko; Capasso, Federico

2012-10-08

We demonstrate a three-section, electrically pulsed quantum cascade laser which consists of a Fabry-Pérot section placed between two sampled grating distributed Bragg reflectors. The device is current-tuned between ten single modes spanning a range of 0.46 μm (63 cm(-1)), from 8.32 to 8.78 μm. The peak optical output power exceeds 280 mW for nine of the modes.

Invertebrates of the H.J. Andrews Experimental Forest, western Cascades, Oregon II. an annotated checklist of caddisflies (Trichoptera)

Treesearch

N.H. Anderson; G.M. Cooper; D.G Denning

1982-01-01

At least 99 species, representing 14 families of Trichoptera, are recorded from the H.J. Andrews Experimental Forest, near Blue River, Oregon. The collecting sites include a wide diversity of environmental conditions in a 6000-hectare watershed of the western Cascade Range (from 400 to 1 630 meters in altitude and from 1st- to 7th-order streams).

Tunable External Cavity Quantum Cascade Lasers (EC-QCL): an application field for MOEMS based scanning gratings

NASA Astrophysics Data System (ADS)

Grahmann, Jan; Merten, André; Ostendorf, Ralf; Fontenot, Michael; Bleh, Daniela; Schenk, Harald; Wagner, Hans-Joachim

2014-03-01

In situ process information in the chemical, pharmaceutical or food industry as well as emission monitoring, sensitive trace detection and biological sensing applications would increasingly rely on MIR-spectroscopic anal­ysis in the 3 μm - 12 μm wavelength range. However, cost effective, portable, low power consuming and fast spectrometers with a wide tuning range are not available so far. To provide these MIR-spectrometer properties, the combination of quantum cascade lasers with a MOEMS scanning grating as wavelength selective element in the external cavity is addressed to provide a very compact and fast tunable laser source for spectroscopic analysis.

A sight "fearfully grand": eruptions of Lassen Peak, California, 1914 to 1917

USGS Publications Warehouse

Clynne, Michael A.; Christiansen, Robert L.; Stauffer, Peter H.; Hendley, James W.; Bleick, Heather A.

2014-01-01

On May 22, 1915, a large explosive eruption at the summit of Lassen Peak, California, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as 280 miles to the east. This explosion was the most powerful in a series of eruptions during 1914–17 that were the last to occur in the Cascade Range before the 1980 eruption of Mount St. Helens, Washington. A century after the Lassen eruptions, work by U.S. Geological Survey (USGS) scientists in cooperation with the National Park Service is shedding new light on these events.

Inverse cascades and resonant triads in rotating and stratified turbulence

NASA Astrophysics Data System (ADS)

Oks, D.; Mininni, P. D.; Marino, R.; Pouquet, A.

2017-11-01

Kraichnan's seminal ideas on inverse cascades yielded new tools to study common phenomena in geophysical turbulent flows. In the atmosphere and the oceans, rotation and stratification result in a flow that can be approximated as two-dimensional at very large scales but which requires considering three-dimensional effects to fully describe turbulent transport processes and non-linear phenomena. Motions can thus be classified into two classes: fast modes consisting of inertia-gravity waves and slow quasi-geostrophic modes for which the Coriolis force and horizontal pressure gradients are close to balance. In this paper, we review previous results on the strength of the inverse cascade in rotating and stratified flows and then present new results on the effect of varying the strength of rotation and stratification (measured by the inverse Prandtl ratio N/f, of the Coriolis frequency to the Brunt-Väisäla frequency) on the amplitude of the waves and on the flow quasi-geostrophic behavior. We show that the inverse cascade is more efficient in the range of N/f for which resonant triads do not exist, 1 /2 ≤N /f ≤2 . We then use the spatio-temporal spectrum to show that in this range slow modes dominate the dynamics, while the strength of the waves (and their relevance in the flow dynamics) is weaker.

Harnessing rogue wave for supercontinuum generation in cascaded photonic crystal fiber.

PubMed

Zhao, Saili; Yang, Hua; Zhao, Chujun; Xiao, Yuzhe

2017-04-03

Based on induced modulation instability, we present a numerical study on harnessing rogue wave for supercontinuum generation in cascaded photonic crystal fibers. By selecting optimum modulation frequency, we achieve supercontinuum with a great improvement on spectrum stability when long-pulse is used as the pump. In this case, rogue wave can be obtained in the first segmented photonic crystal fiber with one zero dispersion wavelength in a controllable manner. Numerical simulations show that spectral range and flatness can be regulated in an extensive range by cascading a photonic crystal fiber with two zero dispersion wavelengths. Some novel phenomena are observed in the second segmented photonic crystal fiber. When the second zero dispersion wavelength is close to the first one, rogue wave is directly translated into dispersion waves, which is conducive to the generation of smoother supercontinuum. When the second zero dispersion wavelength is far away from the first one, rogue wave is translated into the form of fundamental soliton steadily propagating in the vicinity of the second zero dispersion wavelength. Meanwhile, the corresponding red-shifted dispersion wave is generated when the phase matching condition is met, which is beneficial to the generation of wider supercontinuum. The results presented in this work provide a better application of optical rogue wave to generate flat and broadband supercontinuum in cascaded photonic crystal fibers.

Combination of cascade chemical reactions with graphene-DNA interaction to develop new strategy for biosensor fabrication.

PubMed

Zhu, Xiaoli; Sun, Liya; Chen, Yangyang; Ye, Zonghuang; Shen, Zhongming; Li, Genxi

2013-09-15

Graphene, a single atom thick and two dimensional carbon nano-material, has been proven to possess many unique properties, one of which is the recent discovery that it can interact with single-stranded DNA through noncovalent π-π stacking. In this work, we demonstrate that a new strategy to fabricate many kinds of biosensors can be developed by combining this property with cascade chemical reactions. Taking the fabrication of glucose sensor as an example, while the detection target, glucose, may regulate the graphene-DNA interaction through three cascade chemical reactions, electrochemical techniques are employed to detect the target-regulated graphene-DNA interaction. Experimental results show that in a range from 5μM to 20mM, the glucose concentration is in a natural logarithm with the logarithm of the amperometric response, suggesting a best detection limit and detection range. The proposed biosensor also shows favorable selectivity, and it has the advantage of no need for labeling. What is more, by controlling the cascade chemical reactions, detection of a variety of other targets may be achieved, thus the strategy proposed in this work may have a wide application potential in the future. Copyright © 2013 Elsevier B.V. All rights reserved.

On the structure and statistical theory of turbulence of extended magnetohydrodynamics

DOE PAGES

Miloshevich, George; Lingam, Manasvi; Morrison, Philip J.

2017-01-16

Recent progress regarding the noncanonical Hamiltonian formulation of extended magnetohydrodynamics (XMHD), a model with Hall drift and electron inertia, is summarized. The advantages of the Hamiltonian approach are invoked to study some general properties of XMHD turbulence, and to compare them against their ideal MHD counterparts. For instance, the helicity flux transfer rates for XMHD are computed, and Liouville's theorem for this model is also verified. The latter is used, in conjunction with the absolute equilibrium states, to arrive at the spectra for the invariants, and to determine the direction of the cascades, e.g., generalizations of the well-known ideal MHDmore » inverse cascade of magnetic helicity. After a similar analysis is conducted for XMHD by inspecting second order structure functions and absolute equilibrium states, a couple of interesting results emerge. When cross helicity is taken to be ignorable, the inverse cascade of injected magnetic helicity also occurs in the Hall MHD range-this is shown to be consistent with previous results in the literature. In contrast, in the inertial MHD range, viz at scales smaller than the electron skin depth, all spectral quantities are expected to undergo direct cascading. Finally, the consequences and relevance of our results in space and astrophysical plasmas are also briefly discussed.« less

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer.

PubMed

Cnops, Kjell; Rand, Barry P; Cheyns, David; Verreet, Bregt; Empl, Max A; Heremans, Paul

2014-03-07

In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

A novel method for computing effective diffusivity: Application to helium implanted α-Fe thin films

NASA Astrophysics Data System (ADS)

Dunn, Aaron; Agudo-Merida, Laura; Martin-Bragado, Ignacio; McPhie, Mathieu; Cherkaoui, Mohammed; Capolungo, Laurent

2014-05-01

The effective diffusivity of helium in thin iron films is quantified using spatially resolved stochastic cluster dynamics and object kinetic Monte Carlo simulations. The roles of total displacement dose (in DPA), damage rate, helium to DPA ratio, layer thickness, and damage type (cascade damage vs Frenkel pair implantation) on effective He diffusivity are investigated. Helium diffusivity is found to decrease with increasing total damage and decreasing damage rate. Arrhenius plots show strongly increased helium diffusivity at high temperatures, high total implantation, and low implantation rates due to decreased vacancy and vacancy cluster concentrations. At low temperatures, effective diffusivity is weakly dependent on foil thickness while at high temperatures, narrower foils prevent defect accumulation by releasing all defects at the free surfaces. Helium to DPA ratio is not shown to strongly change helium diffusivity in the range of irradiation conditions simulated. Frenkel pair implantation is shown to cause higher effective diffusivity and more complex diffusion mechanisms than cascade implantation. The results of these simulations indicate that the differences in damage rates between implantation experiments and fission or fusion environments may result in differences in the final microstructure.

Euler flow predictions for an oscillating cascade using a high resolution wave-split scheme

NASA Technical Reports Server (NTRS)

Huff, Dennis L.; Swafford, Timothy W.; Reddy, T. S. R.

1991-01-01

A compressible flow code that can predict the nonlinear unsteady aerodynamics associated with transonic flows over oscillating cascades is developed and validated. The code solves the two dimensional, unsteady Euler equations using a time-marching, flux-difference splitting scheme. The unsteady pressures and forces can be determined for arbitrary input motions, although only harmonic pitching and plunging motions are addressed. The code solves the flow equations on a H-grid which is allowed to deform with the airfoil motion. Predictions are presented for both flat plate cascades and loaded airfoil cascades. Results are compared to flat plate theory and experimental data. Predictions are also presented for several oscillating cascades with strong normal shocks where the pitching amplitudes, cascade geometry and interblade phase angles are varied to investigate nonlinear behavior.

Enstrophy Cascade in Decaying Two-Dimensional Quantum Turbulence

NASA Astrophysics Data System (ADS)

Reeves, Matthew T.; Billam, Thomas P.; Yu, Xiaoquan; Bradley, Ashton S.

2017-11-01

We report evidence for an enstrophy cascade in large-scale point-vortex simulations of decaying two-dimensional quantum turbulence. Devising a method to generate quantum vortex configurations with kinetic energy narrowly localized near a single length scale, the dynamics are found to be well characterized by a superfluid Reynolds number Res that depends only on the number of vortices and the initial kinetic energy scale. Under free evolution the vortices exhibit features of a classical enstrophy cascade, including a k-3 power-law kinetic energy spectrum, and constant enstrophy flux associated with inertial transport to small scales. Clear signatures of the cascade emerge for N ≳500 vortices. Simulating up to very large Reynolds numbers (N =32 768 vortices), additional features of the classical theory are observed: the Kraichnan-Batchelor constant is found to converge to C'≈1.6 , and the width of the k-3 range scales as Res1 /2 .

Rescuing Ecosystems from Extinction Cascades

NASA Astrophysics Data System (ADS)

Sahasrabudhe, Sagar; Motter, Adilson

2010-03-01

Food web perturbations stemming from climate change, overexploitation, invasive species, and natural disasters often cause an initial loss of species that results in a cascade of secondary extinctions. Using a predictive modeling framework, here we will present a systematic network-based approach to reduce the number of secondary extinctions. We will show that the extinction of one species can often be compensated by the concurrent removal of a second specific species, which is a counter-intuitive effect not previously tested in complex food webs. These compensatory perturbations frequently involve long-range interactions that are not a priori evident from local predator-prey relationships. Strikingly, in numerous cases even the early removal of a species that would eventually be extinct by the cascade is found to significantly reduce the number of cascading extinctions. Other nondestructive interventions based on partial removals and growth suppression and/or mortality increase are shown to sometimes prevent all secondary extinctions.

The isentropic light piston annular cascade facil ity at RAE Pyestock

NASA Astrophysics Data System (ADS)

Brooks, A. J.; Colbourne, D. E.; Wedlake, E. T.; Jones, T. V.; Oldfield, M. L. G.; Schultz, D. L.; Loftus, P. J.

1985-09-01

An accurate assessment of heat transfer rates to turbine vanes and blades is an important aspect of efficient cooling system design and component life prediction in gas turbines. Techniques have been developed at Oxford University which permit such measurements to be obtained in test rigs which provide short duration steady flow through a turbine cascade. The temperature ratio between the gas stream and the turbine correctly models that found in an engine environment. Reynolds number and Mach numaber can be varied over a wide range to match engine conditions. The design, construction and operation of a new facility at Royal Aircraft Establishment (RAE) Pyestock, incorporating these techniques, is described. Heat transfer and aerodynamic measurements have been made on airfoil surfaces and endwalls of a fully annular cascade of nozzle guide vanes. These results are discussed and compared with those obtained from the same profile in 2-D cascade tests, and with computed 3-D flow predictions.

Tradeoffs between oscillator strength and lifetime in terahertz quantum cascade lasers

DOE PAGES

Chan, Chun Wang I.; Albo, Asaf; Hu, Qing; ...

2016-11-14

Contemporary research into diagonal active region terahertz quantum cascade lasers for high temperature operation has yielded little success. We present evidence that the failure of high diagonality alone as a design strategy is due to a fundamental trade-off between large optical oscillator strength and long upper-level lifetime. Here, we hypothesize that diagonality needs to be paired with increased doping in order to succeed, and present evidence that highly diagonal designs can benefit from much higher doping than normally found in terahertz quantum cascade lasers. In assuming the benefits of high diagonality paired with high doping, we also highlight important challengesmore » that need to be overcome, specifically the increased importance of carrier induced band-bending and impurity scattering.« less

Exact Theory of Compressible Fluid Turbulence

NASA Astrophysics Data System (ADS)

Drivas, Theodore; Eyink, Gregory

2017-11-01

We obtain exact results for compressible turbulence with any equation of state, using coarse-graining/filtering. We find two mechanisms of turbulent kinetic energy dissipation: scale-local energy cascade and ``pressure-work defect'', or pressure-work at viscous scales exceeding that in the inertial-range. Planar shocks in an ideal gas dissipate all kinetic energy by pressure-work defect, but the effect is omitted by standard LES modeling of pressure-dilatation. We also obtain a novel inverse cascade of thermodynamic entropy, injected by microscopic entropy production, cascaded upscale, and removed by large-scale cooling. This nonlinear process is missed by the Kovasznay linear mode decomposition, treating entropy as a passive scalar. For small Mach number we recover the incompressible ``negentropy cascade'' predicted by Obukhov. We derive exact Kolmogorov 4/5th-type laws for energy and entropy cascades, constraining scaling exponents of velocity, density, and internal energy to sub-Kolmogorov values. Although precise exponents and detailed physics are Mach-dependent, our exact results hold at all Mach numbers. Flow realizations at infinite Reynolds are ``dissipative weak solutions'' of compressible Euler equations, similarly as Onsager proposed for incompressible turbulence.

Landslides control the spatial and temporal variation of channel width in southern Taiwan: implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

NASA Astrophysics Data System (ADS)

Yanites, B.; Bregy, J. C.; Carlson, G.; Cataldo, K.; Holahan, M.; Johnston, G.; Mitchell, N. A.; Nelson, A.; Valenza, J.; Wanker, M.

2017-12-01

Intense precipitation or seismic events can generate clustered mass movement processes across a landscape. These rare events have significant impacts on the landscape, however, the rarity of such events leads to uncertainty in how these events impact the entire geomorphic system over a range of timescales. Taiwan is a steep, seismically active region and is highly prone to landslide and debris flows, especially when exposed to heavy rainfall events. Typhoon Morakot made landfall in Taiwan in August of 2009, delivering record-breaking rainfall and inducing more than 22,000 landslides in southern Taiwan. The topographic gradient in southern Taiwan leads to spatial variability in landslide susceptibility providing an opportunity to infer the long-term impact of landslides on channel morphology. The availability of pre and post typhoon imagery allows a quantitative reconstruction on the propagating impact of this event on channel width. The pre and post typhoon patterns of channel width to river and hillslope gradients in 20 basins in the study area reveal the importance of cascading hazards from landslides on landscape evolution. Prior to Typhoon Morakot, the river channels in the central part of the study area were about 3-10 times wider than the channels in the south. Aggradation and widening was also a maximum in these basins where hillslope gradients and channel steepness is high. The results further show that the narrowest channels are located where channel steepness is the lowest, an observation inconsistent with a detachment-limited model for river evolution. We infer this pattern is indicative of a strong role of sediment supply, and associated landslide events, on long-term channel evolution. These findings have implications across a range of spatial and temporal scales including understanding the cascade of hazards in steep landscapes and geomorphic interpretation of channel morphology.

Large MOEMS diffraction grating results providing an EC-QCL wavelength scan of 20%

NASA Astrophysics Data System (ADS)

Grahmann, Jan; Merten, André; Herrmann, Andreas; Ostendorf, Ralf; Bleh, Daniela; Drabe, Christian; Kamenz, Jörg

2015-02-01

Experimental results of a large scanning grating with a diameter of 5mm and 1 kHz scan frequency are discussed. An optical diffraction grating is fabricated on a mirror single crystal silicon plate to scan the first diffraction order in the MIR-wavelength range over a quantum cascade laser facet. Special emphasis is on the development of the grating technology module to integrate it with high accuracy and reproducibility into the IPMS AME75 process flow. The principle EC-QCL setup with the scanning grating is described and first measurement results concerning laser output power and tuning range are presented.

An Agent-Based Model of Centralized Institutions, Social Network Technology, and Revolution

PubMed Central

Makowsky, Michael D.; Rubin, Jared

2013-01-01

This paper sheds light on the general mechanisms underlying large-scale social and institutional change. We employ an agent-based model to test the impact of authority centralization and social network technology on preference falsification and institutional change. We find that preference falsification is increasing with centralization and decreasing with social network range. This leads to greater cascades of preference revelation and thus more institutional change in highly centralized societies and this effect is exacerbated at greater social network ranges. An empirical analysis confirms the connections that we find between institutional centralization, social radius, preference falsification, and institutional change. PMID:24278280

Applications of absorption spectroscopy using quantum cascade lasers.

PubMed

Zhang, Lizhu; Tian, Guang; Li, Jingsong; Yu, Benli

2014-01-01

Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

Physical Approaches to Designing a Two-Cascade Terahertz Laser Generating Difference-Frequency Radiation in a Nonlinear Optical ZnGeP2 Crystal

NASA Astrophysics Data System (ADS)

Gribenyukov, A. I.; Dyomin, V. V.; Polovtsev, I. G.; Yudin, N. N.

2018-03-01

An optical layout of a two-cascade frequency converter of the mid-IR laser radiation into the terahertz (THz) radiation is proposed. In the first stage it is assumed to convert the Tm:YLF-laser frequency in a Cr+2:ZnSe polycrystal into the radiation with the wavelength 2-3 μm. The second cascade can be presented as a parametric conversion of the frequencies of two laser sources operating in the 2-3 μm range into the THz radiation via the difference-frequency mixing in a nonlinear optical ZnGeP2 crystal. The estimates of the terahertz output signal are reported.

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade With Supersonic Leading-Edge Locus

NASA Technical Reports Server (NTRS)

Ramsey, John K.; Erwin, Dan

2004-01-01

An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.

Ultra-broad gain quantum cascade lasers tunable from 6.5 to 10.4 μm.

PubMed

Xie, Feng; Caneau, C; Leblanc, H; Ho, M-T; Zah, C

2015-09-01

We present a quantum cascade laser structure with an ultra-broad gain profile that covers the wavelength range from 6.5 to 10.4 μm. In a grating-tuned external cavity, we demonstrated continuous tuning from 1027  cm(-1) to 1492  cm(-1) with this broad gain laser chip. We also fabricated distributed feedback quantum cascade laser arrays with this active region design and varied grating periods. We demonstrated single wavelength lasing from 962 (10.4) to 1542  cm(-1) (6.5 μm). The frequency coverage (580  cm(-1)) is about 46% of center frequency.

Inverse energy cascade and emergence of large coherent vortices in turbulence driven by Faraday waves.

PubMed

Francois, N; Xia, H; Punzmann, H; Shats, M

2013-05-10

We report the generation of large coherent vortices via inverse energy cascade in Faraday wave driven turbulence. The motion of floaters in the Faraday waves is three dimensional, but its horizontal velocity fluctuations show unexpected similarity with two-dimensional turbulence. The inverse cascade is detected by measuring frequency spectra of the Lagrangian velocity, and it is confirmed by computing the third moment of the horizontal velocity fluctuations. This is observed in deep water in a broad range of wavelengths and vertical accelerations. The results broaden the scope of recent findings on Faraday waves in thin layers [A. von Kameke et al., Phys. Rev. Lett. 107, 074502 (2011)].

Directional change of fluid particles in two-dimensional turbulence and of football players

NASA Astrophysics Data System (ADS)

Kadoch, Benjamin; Bos, Wouter J. T.; Schneider, Kai

2017-06-01

Multiscale directional statistics are investigated in two-dimensional incompressible turbulence. It is shown that the short-time behavior of the mean angle of directional change of fluid particles is linearly dependent on the time lag and that no inertial range behavior is observed in the directional change associated with the enstrophy-cascade range. In simulations of the inverse-cascade range, the directional change shows a power law behavior at inertial range time scales. By comparing the directional change in space-periodic and wall-bounded flow, it is shown that the probability density function of the directional change at long times carries the signature of the confinement. The geometrical origin of this effect is validated by Monte Carlo simulations. The same effect is also observed in the directional statistics computed from the trajectories of football players (soccer players in American English).

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

NASA Astrophysics Data System (ADS)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Harmonic cascade FEL designs for LUX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penn, G.; Reinsch, M.; Wurtele, J.

LUX is a design concept for an ultrafast X-ray science facility, based on an electron beam accelerated to GeV energies in are circulating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 200-250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1more » keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.« less

Terahertz cascades from nanoparticles

NASA Astrophysics Data System (ADS)

Arnardottir, K. B.; Liew, T. C. H.

2018-05-01

In this article we propose a system capable of terahertz (THz) radiation with quantum yield above unity. The system consists of nanoparticles where the material composition varies along the radial direction of each nanoparticle in such a way that a ladder of equidistant energy levels emerges. By then exciting the highest level of this ladder we produce multiple photons of the same frequency in the THz range. We demonstrate how we can calculate a continuous material composition profile that achieves a high quantum yield and then show that a more experimentally friendly design of a multishell nanoparticle can still result in a high quantum yield.

Semiconductor light sources for near- and mid-infrared spectral ranges

NASA Astrophysics Data System (ADS)

Karachinsky, L. Ya; Babichev, A. V.; Gladyshev, A. G.; Denisov, D. V.; Filimonov, A. V.; Novikov, I. I.; Egorov, A. Yu

2017-11-01

1550 nm band wafer-fused vertical-cavity surface-emitting lasers (VCSELs) and 5-10 μm band multi-stages quantum-cascade lasers (QCL) grown by molecular beam epitaxy (MBE) were fabricated and studied. VCSELs show high output optical power up to 6 mW in single-mode regime (SMSR > 40 dB) and open-eye diagrams at 30 Gbps of standard NRZ at 20°C. QCL heterostructures show high structural quality (fluctuations of composition and thickness < 1%). 20-μm-stripe width QCLs mounted on copper heatsinks show lasing at ∼ 6, 7.5 and 9 μm.

Hemodynamic Response Alteration As a Function of Task Complexity and Expertise—An fNIRS Study in Jugglers

PubMed Central

Carius, Daniel; Andrä, Christian; Clauß, Martina; Ragert, Patrick; Bunk, Michael; Mehnert, Jan

2016-01-01

Detailed knowledge about online brain processing during the execution of complex motor tasks with a high motion range still remains elusive. The aim of the present study was to investigate the hemodynamic responses within sensorimotor networks as well as in visual motion area during the execution of a complex visuomotor task such as juggling. More specifically, we were interested in how far the hemodynamic response as measured with functional near infrared spectroscopy (fNIRS) adapts as a function of task complexity and the level of the juggling expertise. We asked expert jugglers to perform different juggling tasks with different levels of complexity such as a 2-ball juggling, 3- and 5-ball juggling cascades. We here demonstrate that expert jugglers show an altered neurovascular response with increasing task complexity, since a 5-ball juggling cascade showed enhanced hemodynamic responses for oxygenated hemoglobin as compared to less complex tasks such as a 3- or 2-ball juggling pattern. Moreover, correlations between the hemodynamic response and the level of the juggling expertise during the 5-ball juggling cascade, acquired by cinematographic video analysis, revealed only a non-significant trend in primary motor cortex, indicating that a higher level of expertise might be associated with lower hemodynamic responses. PMID:27064925

Cascading Failures as Continuous Phase-Space Transitions

DOE PAGES

Yang, Yang; Motter, Adilson E.

2017-12-14

In network systems, a local perturbation can amplify as it propagates, potentially leading to a large-scale cascading failure. We derive a continuous model to advance our understanding of cascading failures in power-grid networks. The model accounts for both the failure of transmission lines and the desynchronization of power generators and incorporates the transient dynamics between successive steps of the cascade. In this framework, we show that a cascade event is a phase-space transition from an equilibrium state with high energy to an equilibrium state with lower energy, which can be suitably described in a closed form using a global Hamiltonian-likemore » function. From this function, we show that a perturbed system cannot always reach the equilibrium state predicted by quasi-steady-state cascade models, which would correspond to a reduced number of failures, and may instead undergo a larger cascade. We also show that, in the presence of two or more perturbations, the outcome depends strongly on the order and timing of the individual perturbations. These results offer new insights into the current understanding of cascading dynamics, with potential implications for control interventions.« less

Cascading Failures as Continuous Phase-Space Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yang; Motter, Adilson E.

In network systems, a local perturbation can amplify as it propagates, potentially leading to a large-scale cascading failure. We derive a continuous model to advance our understanding of cascading failures in power-grid networks. The model accounts for both the failure of transmission lines and the desynchronization of power generators and incorporates the transient dynamics between successive steps of the cascade. In this framework, we show that a cascade event is a phase-space transition from an equilibrium state with high energy to an equilibrium state with lower energy, which can be suitably described in a closed form using a global Hamiltonian-likemore » function. From this function, we show that a perturbed system cannot always reach the equilibrium state predicted by quasi-steady-state cascade models, which would correspond to a reduced number of failures, and may instead undergo a larger cascade. We also show that, in the presence of two or more perturbations, the outcome depends strongly on the order and timing of the individual perturbations. These results offer new insights into the current understanding of cascading dynamics, with potential implications for control interventions.« less

Seismicity of Cascade Volcanoes: Characterization and Comparison

NASA Astrophysics Data System (ADS)

Thelen, W. A.

2016-12-01

Here we summarize and compare the seismicity around each of the Very High Threat Volcanoes of the Cascade Range of Washington, Oregon and California as defined by the National Volcanic Early Warning System (NVEWS) threat assessment (Ewert et al., 2005). Understanding the background seismic activity and processes controlling it is critical for assessing changes in seismicity and their implications for volcanic hazards. Comparing seismicity at different volcanic centers can help determine what critical factors or processes affect the observed seismic behavior. Of the ten Very High Threat Volcanoes in the Cascade Range, five volcanoes are consistently seismogenic when considering earthquakes within 10 km of the volcanic center or caldera edge (Mount Rainier, Mount St. Helens, Mount Hood, Newberry Caldera, Lassen Volcanic Center). Other Very High Threat volcanoes (South Sister, Mount Baker, Glacier Peak, Crater Lake and Mount Shasta) have comparatively low rates of seismicity and not enough recorded earthquakes to calculate catalog statistics. Using a swarm definition of 3 or more earthquakes occurring in a day with magnitudes above the largest of the network's magnitude of completenesses (M 0.9), we find that Lassen Volcanic Center is the "swarmiest" in terms of percent of seismicity occurring in swarms, followed by Mount Hood, Mount St. Helens and Rainier. The predominance of swarms at Mount Hood may be overstated, as much of the seismicity is occurring on surrounding crustal faults (Jones and Malone, 2005). Newberry Caldera has a relatively short record of seismicity since the permanent network was installed in 2011, however there have been no swarms detected as defined here. Future work will include developing discriminates for volcanic versus tectonic seismicity to better filter the seismic catalog and more precise binning of depths at some volcanoes so that we may better consider different processes. Ewert J. W., Guffanti, M. and Murray, T. L. (2005). An Assessment of Volcanic Threat and Monitoring Capabilities in the United States: Framework for a National Volcano Early Warning System, USGS Open File Report 2005-1164, 62 pp. Jones, J., & Malone, S. D. (2005). Mount hood earthquake activity: Volcanic or tectonic origins? Bulletin Of The Seismological Society Of America, 95(3), 818-832.

Lens Coupled Quantum Cascade Laser

NASA Technical Reports Server (NTRS)

Lee, Alan Wei Min (Inventor); Hu, Qing (Inventor)

2013-01-01

Terahertz quantum cascade (QC) devices are disclosed that can operate, e.g., in a range of about 1 THz to about 10 THz. In some embodiments, QC lasers are disclosed in which an optical element (e.g., a lens) is coupled to an output facet of the laser's active region to enhance coupling of the lasing radiation from the active region to an external environment. In other embodiments, terahertz amplifier and tunable terahertz QC lasers are disclosed.

Public acceptance of disturbance-based forest management: a study of the Blue River Landscape Strategy in the Central Cascades Adaptive Management Area.

Treesearch

Bruce Shindler; Angela L. Mallon

2009-01-01

This report examines public perspectives on disturbance-based management conducted in the central Cascade Range in Oregon as part of the Blue River Landscape Strategy. A mail survey to local residents was used to describe the public’s understanding of this form of management, identify perceived associated risks and potential barriers to implementation, and the overall...

Improvement of one-nucleon removal and total reaction cross sections in the Liège intranuclear-cascade model using Hartree-Fock-Bogoliubov calculations

NASA Astrophysics Data System (ADS)

Rodríguez-Sánchez, Jose Luis; David, Jean-Christophe; Mancusi, Davide; Boudard, Alain; Cugnon, Joseph; Leray, Sylvie

2017-11-01

The prediction of one-nucleon-removal cross sections by the Liège intranuclear-cascade model has been improved using a refined description of the matter and energy densities in the nuclear surface. Hartree-Fock-Bogoliubov calculations with the Skyrme interaction are used to obtain a more realistic description of the radial-density distributions of protons and neutrons, as well as the excitation-energy uncorrelation at the nuclear surface due to quantum effects and short-range correlations. The results are compared with experimental data covering a large range of nuclei, from carbon to uranium, and projectile kinetic energies. We find that the new approach is in good agreement with experimental data of one-nucleon-removal cross sections covering a broad range in nuclei and energies. The new ingredients also improve the description of total reaction cross sections induced by protons at low energies, the production cross sections of heaviest residues close to the projectile, and the triple-differential cross sections for one-proton removal. However, other observables such as quadruple-differential cross sections of coincident protons do not present any sizable sensitivity to the new approach. Finally, the model is also tested for light-ion-induced reactions. It is shown that the new parameters can give a reasonable description of the nucleus-nucleus total reaction cross sections at high energies.

Active Stand-off Detection of Gas Leaks Using a Short Range Hard-target Backscatter Differential Optical Absorption System Based on a Quantum Cascade Laser Transmitter

NASA Astrophysics Data System (ADS)

Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

2016-06-01

Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they can contribute to the global increase of greenhouse gas concentration. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents gas concentration measurements using a quantum cascade laser open path system (QCLOPS). The system retrieves the pathaveraged concentration of N2O and CH4 by collecting the backscattered light from a scattering target. The gas concentration measurements have a high temporal resolution (68 ms) and are achieved at sufficient range (up to 40 m, ~ 130 feet) with a detection limit of 2.6 ppm CH4 and 0.4 ppm for N2O. Given these characteristics, this system is promising for mobile/multidirectional remote detection and evaluation of gas leaks. The instrument is monostatic with a tunable QCL emitting at ~ 7.7 μm wavelength range. The backscattered radiation is collected by a Newtonian telescope and focused on an infrared light detector. Puffs of N2O and CH4 are released along the optical path to simulate a gas leak. The measured absorption spectrum is obtained using the thermal intra-pulse frequency chirped DFB QCL and is analyzed to obtain path averaged gas concentrations.

Quantum Cascade Laser (QCL) based sensor for the detection of explosive compounds

NASA Astrophysics Data System (ADS)

Normand, Erwan; Howieson, Iain; McCulloch, Michael; Black, Paul

2006-09-01

Following Cascade Technologies first success at using Quantum Cascade Lasers (QCL) for trace gas detection in the continuous emission monitoring market, the core technology platform is now being developed towards homeland security applications. This paper will highlight the potential of QCL based trace gas sensor for detecting vapours of explosives. Furthermore we will present results that let foresee the use of such technologies at addressing security gaps for protection against terrorism in infrastructures where high throughput screening of individuals or items is required. Preliminary measurements have shown that rapid identification, or fingerprinting, of explosive is achievable in 10ms at extrapolated sensitivities in the sub-part per billion range. The experiments were carried out with support form the Home Office Scientific Development Branch (HOSDB) in the UK and were focused at selecting a variety of explosive compounds and showing their detection using a novel sniffer platform system based on the use of quantum cascade lasers. Preliminary studies on the technology have indicated that direct fingerprinting (detection - identification) of explosive compounds such as NG and tagging agents such as EGDN by sniffing surrounding ambient air is achievable. Furthermore these studies have also indicated that detection of such compounds on packaging used to ship the sealed compounds is possible, making this platform a strong contender for detection through cross contamination on material that have been in contact with each other. Additionally, it was also possible to detect breakdown products associated with sample material NG providing a further capability that could be exploited to enhance the detection and identification of explosive compounds.

The ancestral cascades arc: Cenozoic evolution of the central Sierra Nevada (California) and the birth of the new plate boundary

USGS Publications Warehouse

Busby, C.J.; Hagan, J.C.; Putirka, K.; Pluhar, C.J.; Gans, P.B.; Wagner, D.L.; Rood, D.; DeOreo, S.B.; Skilling, I.

2008-01-01

We integrate new stratigraphic, structural, geochemical, geochronological, and magnetostratigraphic data on Cenozoic volcanic rocks in the central Sierra Nevada to arrive at closely inter-related new models for: (1) the paleogeography of the ancestral Cascades arc, (2) the stratigraphic record of uplift events in the Sierra Nevada, (3) the tectonic controls on volcanic styles and compositions in the arc, and (4) the birth of a new plate margin. Previous workers have assumed that the ancestral Cascades arc consisted of stratovolcanoes, similar to the modern Cascades arc, but we suggest that the arc was composed largely of numerous, very small centers, where magmas frequently leaked up strands of the Sierran frontal fault zone. These small centers erupted to produce andesite lava domes that collapsed to produce block-and-ash flows, which were reworked into paleocanyons as volcanic debris flows and streamflow deposits. Where intrusions rose up through water-saturated paleocanyon fill, they formed peperite complexes that were commonly destabilized to form debris flows. Paleocanyons that were cut into Cretaceous bedrock and filled with Oligocene to late Miocene strata not only provide a stratigraphic record of the ancestral Cascades arc volcanism, but also deep unconformities within them record tectonic events. Preliminary correlation of newly mapped unconformities and new geochronological, magnetostratigraphic, and structural data allow us to propose three episodes of Cenozoic uplift that may correspond to (1) early Miocene onset of arc magmatism (ca. 15 Ma), (2) middle Miocene onset of Basin and Range faulting (ca. 10 Ma), and (3) late Miocene arrival of the triple junction (ca. 6 Ma), perhaps coinciding with a second episode of rapid extension on the range front. Oligocene ignimbrites, which erupted from calderas in central Nevada and filled Sierran paleocanyons, were deeply eroded during the early Miocene uplift event. The middle Miocene event is recorded by growth faulting and landslides in hanging-wall basins of normal faults. Cessation of andesite volcanism closely followed the late Miocene uplift event. We show that the onset of Basin and Range faulting coincided both spatially and temporally with eruption of distinctive, very widespread, high-K lava flows and ignimbrites from the Little Walker center (Stanislaus Group). Preliminary magnetostratigraphic work on high-K lava flows (Table Mountain Latite, 10.2 Ma) combined with new 40Ar/39Ar age data allow regional-scale correlation of individual flows and estimates of minimum (28,000 yr) and maximum (230,000 yr) time spans for eruption of the lowermost latite series. This work also verifies the existence of reversed-polarity cryptochron, C5n.2n-1 at ca. 10.2 Ma, which was previously known only from seafloor magnetic anomalies. High-K volcanism continued with eruption of the three members of the Eureka Valley Tuff (9.3-9.15 Ma). In contrast with previous workers in the southern Sierra, who interpret high-K volcanism as a signal of Sierran root delamination, or input of subduction-related fluids, we propose an alternative model for K2O-rich volcanism. A regional comparison of central Sierran volcanic rocks reveals their K2O levels to be intermediate between Lassen to the north (low in K2O) and ultrapotassic volcanics in the southern Sierra. We propose that this shift reflects higher pressures of fractional crystallization to the south, controlled by a southward increase in the thickness of the granitic crust. At high pressures, basaltic magmas precipitate clinopyroxene (over olivine and plagioclase) at their liquidus; experiments and mass-balance calculations show that clinopyroxene fractionation buffers SiO 2 to low values while allowing K2O to increase. A thick crust to the south would also explain the sparse volcanic cover in the southern Sierra compared to the extensive volcanic cover to the north.

Cascaded thermoacoustic devices

DOEpatents

Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.

2003-12-09

A thermoacoustic device is formed with a resonator system defining at least one region of high specific acoustic impedance in an acoustic wave within the resonator system. A plurality of thermoacoustic units are cascaded together within the region of high specific acoustic impedance, where at least one of the thermoacoustic units is a regenerator unit.

Tracing chlorine sources of thermal and mineral springs along and across the Cascade Range using halogen and chlorine isotope compositions

USGS Publications Warehouse

Cullen, Jeffrey T.; Barnes, Jaime D.; Hurwitz, Shaul; Leeman, William P.

2015-01-01

In order to provide constraints on the sources of chlorine in spring waters associated with arc volcanism, the major/minor element concentrations and stable isotope compositions of chlorine, oxygen, and hydrogen were measured in 28 thermal and mineral springs along the Cascade Range in northwestern USA. Chloride concentrations in the springs range from 64 to 19,000 mg/L and View the MathML source values range from +0.2‰ to +1.9‰ (average=+1.0±0.4‰), with no systematic variation along or across the arc, nor correlations with their presumed underlying basement lithologies. Additionally, nine geochemically well-characterized lavas from across the Mt. St. Helens/Mt. Adams region of the Cascade Range (Leeman et al., 2004 and Leeman et al., 2005) were analyzed for their halogen concentrations and Cl isotope compositions. In the arc lavas, Cl and Br concentrations from the volcanic front are higher than in lavas from the forearc and backarc. F and I concentrations progressively decrease from forearc to backarc, similar to the trend documented for B in most arcs. View the MathML source values of the lavas range from −0.1 to +0.8‰ (average = +0.4±0.3‰). Our results suggest that the predominantly positive View the MathML source values observed in the springs are consistent with water interaction with underlying 37Cl-enriched basalt and/or altered oceanic crust, thereby making thermal spring waters a reasonable proxy for the Cl isotope compositions of associated volcanic rocks in the Cascades. However, waters with View the MathML source values >+1.0‰ also suggest additional contributions of chlorine degassed from cooling magmas due to subsurface vapor–liquid HCl fractionation in which Cl is lost to the aqueous fluid phase and 37Cl is concentrated in the ascending magmatic HCl vapor. Future work is necessary to better constrain Cl isotope behavior during volcanic degassing and fluid–rock interaction in order to improve volatile flux estimates through subduction zones.

High power, high efficiency, continuous-wave supercontinuum generation using standard telecom fibers.

PubMed

Arun, S; Choudhury, Vishal; Balaswamy, V; Prakash, Roopa; Supradeepa, V R

2018-04-02

We demonstrate a simple module for octave spanning continuous-wave supercontinuum generation using standard telecom fiber. This module can accept any high power ytterbium-doped fiber laser as input. The input light is transferred into the anomalous dispersion region of the telecom fiber through a cascade of Raman shifts. A recently proposed Raman laser architecture with distributed feedback efficiently performs these Raman conversions. A spectrum spanning over 1000nm (>1 octave) from 880 to 1900nm is demonstrated. The average power from the supercontinuum is ~34W with a high conversion efficiency of 44%. Input wavelength agility is demonstrated with similar supercontinua over a wide input wavelength range.

Impact of the operation of cascade reservoirs in upper Yangtze River on hydrological variability of the mainstream

NASA Astrophysics Data System (ADS)

Changjiang, Xu; Dongdong, Zhang

2018-06-01

As the impacts by climate changes and human activities are intensified, variability may occur in river's annual runoff as well as flood and low water characteristics. In order to understand the characteristics of variability in hydrological series, diagnosis and identification must be conducted specific to the variability of hydrological series, i.e., whether there was variability and where the variability began to occur. In this paper, the mainstream of Yangtze River was taken as the object of study. A model was established to simulate the impounding and operation of upstream cascade reservoirs so as to obtain the runoff of downstream hydrological control stations after the regulation by upstream reservoirs in different level years. The Range of Variability Approach was utilized to analyze the impact of the operation of upstream reservoirs on the variability of downstream. The results indicated that the overall hydrologic alterations of Yichang hydrological station in 2010 level year, 2015 level year and the forward level year were 68.4, 72.5 and 74.3 % respectively, belonging to high alteration in all three level years. The runoff series of mainstream hydrological stations presented variability in different degrees, where the runoff series of the four hydrological stations including Xiangjiaba, Gaochang and Wulong belonged to high alteration in the three level years; and the runoff series of Beibei hydrological station in 2010 level year belonged to medium alteration, and high alteration in 2015 level year and the forward level year. The study on the impact of the operation of cascade reservoirs in Upper Yangtze River on hydrological variability of the mainstream had important practical significance on the sustainable utilization of water resources, disaster prevention and mitigation, safe and efficient operation and management of water conservancy projects and stable development of the economic society.

Influence of volcanic history on groundwater patterns on the west slope of the Oregon High Cascades.

Treesearch

A. Jefferson; G. Grant; T. Rose

2006-01-01

Spring systems on the west slope of the Oregon High Cascades exhibit complex relationships among modern topography, lava flow geometries, and groundwater flow patterns. Seven cold springs were continuously monitored for discharge and temperature in the 2004 water year, and they were periodically sampled for ?18O, ?D, tritium, and dissolved noble gases. Anomalously high...

Very high volume hemofiltration with the Cascade system in septic shock patients.

PubMed

Quenot, Jean-Pierre; Binquet, Christine; Vinsonneau, Christophe; Barbar, Saber-David; Vinault, Sandrine; Deckert, Valerie; Lemaire, Stéphanie; Hassain, Ali Ait; Bruyère, Rémi; Souweine, Bertrand; Lagrost, Laurent; Adrie, Christophe

2015-12-01

We compared hemodynamic and biological effects of the Cascade system, which uses very high volume hemofiltration (HVHF) (120 mL kg(-1) h(-1)), with those of usual care in patients with septic shock. Multicenter, prospective, randomized, open-label trial in three intensive care units (ICU). Adults with septic shock with administration of epinephrine/norepinephrine were eligible. Patients were randomized to usual care plus HVHF (Cascade group), or usual care alone (control group). Primary end point was the number of catecholamine-free days up to 28 days after randomization. Secondary end points were number of days free of mechanical ventilation, renal replacement therapy (RRT) or ICU up to 90 days, and 7-, 28-, and 90-day mortality. We included 60 patients (29 Cascade, 31 usual care). Baseline characteristics were comparable. Median number of catecholamine-free days was 22 [IQR 11-23] vs 20 [0-25] for Cascade vs control; there was no significant difference even after adjustment. There was no significant difference in number of mechanical ventilation-free days or ICU requirement. Median number of RRT-free days was 85 [46-90] vs 74 [0-90] for Cascade vs control groups, p = 0.42. By multivariate analysis, the number of RRT-free days was significantly higher in the Cascade group (up to 25 days higher after adjustment). There was no difference in mortality at 7, 28, or 90 days. Very HVHF using the Cascade system can safely be used in patients presenting with septic shock, but it was not associated with a reduction in the need for catecholamines during the first 28 days.

Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

2016-02-13

A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

Cascade Storage and Delivery System for a Multi Mission Space Exploration Vehicle (MMSEV)

NASA Technical Reports Server (NTRS)

Yagoda, Evan; Swickrath, Michael; Stambaugh, Imelda

2012-01-01

NASA is developing a Multi Mission Space Exploration Vehicle (MMSEV) for missions beyond Low Earth Orbit (LEO). The MMSEV is a pressurized vehicle used to extend the human exploration envelope for Lunar, Near Earth Object (NEO), and Deep Space missions. The Johnson Space Center is developing the Environmental Control and Life Support System (ECLSS) for the MMSEV. The MMSEV s intended use is to support longer sortie lengths with multiple Extra Vehicular Activities (EVAs) on a higher magnitude than any previous vehicle. This paper presents an analysis of a high pressure oxygen cascade storage and delivery system that will accommodate the crew during long duration Intra Vehicular Activity (IVA) and capable of multiple high pressure oxygen fills to the Portable Life Support System (PLSS) worn by the crew during EVAs. A cascade is a high pressure gas cylinder system used for the refilling of smaller compressed gas cylinders. Each of the large cylinders are filled by a compressor, but the cascade system allows small cylinders to be filled without the need of a compressor. In addition, the cascade system is useful as a "reservoir" to accommodate low pressure needs. A regression model was developed to provide the mechanism to size the cascade systems subject to constraints such as number of crew, extravehicular activity duration and frequency, and ullage gas requirements under contingency scenarios. The sizing routine employed a numerical integration scheme to determine gas compressibility changes during depressurization and compressibility effects were captured using the Soave-Redlich-Kwong (SRK) equation of state. A multi-dimensional nonlinear optimization routine was used to find the minimum cascade tank system mass that meets the mission requirements. The sizing algorithms developed in this analysis provide a powerful framework to assess cascade filling, compressor, and hybrid systems to design long duration vehicle ECLSS architecture. 1

Facilitators and barriers for retention in HIV care between testing and treatment in Asia-A study in Bangladesh, Indonesia, Lao, Nepal, Pakistan, Philippines and Vietnam.

PubMed

Koirala, Sushil; Deuba, Keshab; Nampaisan, Oranuch; Marrone, Gaetano; Ekström, Anna Mia

2017-01-01

The need for efficient retention in HIV care is more evident than ever because of the expansion of earlier ART initiation and the shift towards 'Test and Treat'. This study assesses factors affecting participation in the HIV care cascade among people living with HIV (PLHIV) in the Asia-Pacific Region. A total of 7843 PLHIV aged 18-50 years were recruited using targeted and venue-based sampling between October 1, 2012, and May 31, 2013, across 59 sites in 7 countries (Bangladesh, Indonesia, Lao People's Democratic Republic (Lao PDR), Nepal, Pakistan, Philippines and Vietnam). Statistically significant associations between demographic and health system determinants, and various steps in the HIV care cascade were computed using a generalized structural equation model. A high proportion of PLHIV (40-51%) presented late for HIV care and delayed linkage to care in all seven countries. However, once PLHIV enrolled in care, retention in the various steps of the care cascade including adherence to antiretroviral treatment (ART) was satisfactory. The proportion still engaged in HIV care at 36 months post HIV diagnosis, varied from 78% in Nepal to >90% in Lao PDR. Similarly, the proportion of ART initiation who also were adherent to ART ranged from 91% in Bangladesh to >95% in Philippines/ Vietnam and from 70% in Lao PDR to 89% in the Philippines respectively. The following factors enhanced the likelihood of ART initiation and high adherence to HIV care and ART: good client-provider communication, high HIV treatment literacy, a referral from a health worker and TB/HIV co-infection. The following barriers were identified: young age, sex work, imprisonment, transgender identity, illiteracy, rural residence, alcohol/ injecting drug use, perceived poor health status, lack of health insurance, fear of confidentiality breach, self-referral for HIV testing, and public hospital as the place of HIV diagnosis. HIV programme planners should ensure easy access to HIV testing and earlier linkage to HIV care among PLHIV. In addition, multiple socio-economic and health systems barriers need to be addressed along the HIV care cascade to reach the UNAIDS 90-90-90 target in the Asia-Pacific region.

Resonance Effects in the NASA Transonic Flutter Cascade Facility

NASA Technical Reports Server (NTRS)

Lepicovsky, J.; Capece, V. R.; Ford, C. T.

2003-01-01

Investigations of unsteady pressure loadings on the blades of fans operating near the stall flutter boundary are carried out under simulated conditions in the NASA Transonic Flutter Cascade facility (TFC). It has been observed that for inlet Mach numbers of about 0.8, the cascade flowfield exhibits intense low-frequency pressure oscillations. The origins of these oscillations were not clear. It was speculated that this behavior was either caused by instabilities in the blade separated flow zone or that it was a tunnel resonance phenomenon. It has now been determined that the strong low-frequency oscillations, observed in the TFC facility, are not a cascade phenomenon contributing to blade flutter, but that they are solely caused by the tunnel resonance characteristics. Most likely, the self-induced oscillations originate in the system of exit duct resonators. For sure, the self-induced oscillations can be significantly suppressed for a narrow range of inlet Mach numbers by tuning one of the resonators. A considerable amount of flutter simulation data has been acquired in this facility to date, and therefore it is of interest to know how much this tunnel self-induced flow oscillation influences the experimental data at high subsonic Mach numbers since this facility is being used to simulate flutter in transonic fans. In short, can this body of experimental data still be used reliably to verify computer codes for blade flutter and blade life predictions? To answer this question a study on resonance effects in the NASA TFC facility was carried out. The results, based on spectral and ensemble averaging analysis of the cascade data, showed that the interaction between self-induced oscillations and forced blade motion oscillations is very weak and can generally be neglected. The forced motion data acquired with the mistuned tunnel, when strong self-induced oscillations were present, can be used as reliable forced pressure fluctuations provided that they are extracted from raw data sets by an ensemble averaging procedure.

The weather and climate: emergent laws and multifractal cascades

NASA Astrophysics Data System (ADS)

Lovejoy, Shaun; Schertzer, Daniel

2013-04-01

Science in general and physics and geophysics in particular are hierarchies of interlocking theories and models with low level, fundamental laws such as quantum mechanics and statistical mechanics providing the underpinnings for the emergence of the qualitatively new, higher level laws of thermodynamics and continuum mechanics that provide the current bases for modelling the weather and climate. Yest it was the belief of generations of turbulence pioneers (notably Richardson, Kolmogorov, Obhukhov, Corrsin, Bolgiano) that at sufficiently high levels of nonlinearity (quantified by the Reynold's number, of the order 10**12 in the atmosphere) that new even higher level laws would emerge describing "fully developed turbulence". However for atmospheric applications, the pioneers' eponymous laws suffered from two basic restrictions - isotropy and homogeneity - that prevented them from being valid over wide ranges of scale. Over the last thirty years both of these restrictions have been overcome - the former with the generalization from isotropic to strongly anisotropic notions of scale (to account notably for stratification), and from homogeneity to strong heterogeneity (intermittency) via multifractal cascades. In this presentation we give an overview of recent developments and analyses covering huge ranges of space-time scales (including weather, macroweather and climate time scales). We show how the combination of strong anisotropy and strong intermittency commonly leads to the "phenomenological fallacy" in which morphology is confounded with mechanism. With the help of stochastic models, we show how processes with vastly different large and small scale morphologies can arise from a unique multifractal dynamical mechanisms [Lovejoy and Schertzer, 2013]. References: Lovejoy, S., and D. Schertzer (2013), The Weather and Climate: Emergent Laws and Multifractal Cascades, 480 pp., Cambridge University Press, Cambridge.

Three-dimensional kinetic simulations of whistler turbulence in solar wind on parallel supercomputers

NASA Astrophysics Data System (ADS)

Chang, Ouliang

The objective of this dissertation is to study the physics of whistler turbulence evolution and its role in energy transport and dissipation in the solar wind plasmas through computational and theoretical investigations. This dissertation presents the first fully three-dimensional (3D) particle-in-cell (PIC) simulations of whistler turbulence forward cascade in a homogeneous, collisionless plasma with a uniform background magnetic field B o, and the first 3D PIC simulation of whistler turbulence with both forward and inverse cascades. Such computationally demanding research is made possible through the use of massively parallel, high performance electromagnetic PIC simulations on state-of-the-art supercomputers. Simulations are carried out to study characteristic properties of whistler turbulence under variable solar wind fluctuation amplitude (epsilon e) and electron beta (betae), relative contributions to energy dissipation and electron heating in whistler turbulence from the quasilinear scenario and the intermittency scenario, and whistler turbulence preferential cascading direction and wavevector anisotropy. The 3D simulations of whistler turbulence exhibit a forward cascade of fluctuations into broadband, anisotropic, turbulent spectrum at shorter wavelengths with wavevectors preferentially quasi-perpendicular to B o. The overall electron heating yields T ∥ > T⊥ for all epsilone and betae values, indicating the primary linear wave-particle interaction is Landau damping. But linear wave-particle interactions play a minor role in shaping the wavevector spectrum, whereas nonlinear wave-wave interactions are overall stronger and faster processes, and ultimately determine the wavevector anisotropy. Simulated magnetic energy spectra as function of wavenumber show a spectral break to steeper slopes, which scales as k⊥lambda e ≃ 1 independent of betae values, where lambdae is electron inertial length, qualitatively similar to solar wind observations. Specific spectral indices from simulated wavevector energy spectra do not match the frequency spectral indices from observations due to the inapplicability of Taylor's hypothesis. In contrast, the direct comparison of simulated frequency energy spectra and solar wind observations shows a closer similarity. Electron density fluctuations power spectra also exhibit a close similarity to solar wind observations and MHD predications, both qualitatively and quantitatively. Linear damping represents an intermediate fraction of the total dissipation of whistler turbulence over a wide range of betae and epsilone. The relative importance of linear damping by comparison to nonlinear dissipation increases with increasing beta e but decreases with increasing epsilone. Correlation coefficient calculations imply that the nonlinear dissipation processes in our simulation are primarily associated with dissipation in regions of intermittent current sheet structures. The simulation results suggest that whistler fluctuations could be the substantial constituent of solar wind turbulence at higher frequencies and short wavelengths, and support the magnetosonic-whistler interpretation of the quasilinear scenario. An even larger scale 3D whistler turbulence simulation exhibits both a forward cascade to shorter wavelengths with wavevectors preferentially k⊥ > k∥, and an inverse cascade to longer wavelengths with wavevectors k ≳ k⊥. The inverse cascade process is primarily driven by the nonlinear wave-wave interaction. It is shown that the energy inverse cascade rate is similar to the energy forward cascade rate at early times although the overall energy in the two cascades is very different. The presence of inverse cascade process does not affect qualitative conclusions established from the whistler turbulence forward cascade simulations.

Angle-depended photocurrent characteristics of cascade photoelectric converters on the base of homogeneous semiconductor

NASA Astrophysics Data System (ADS)

Arbuzov, Yuri D.; Evdokimov, Vladimir M.; Shepovalova, Olga V.

2018-05-01

Angle-dependent spectral photoresponse characteristics for theoretically perfect and physically implementable tunnel cascade (multi-junction) photoelectric converters (PC), for example high-voltage planar PV cells, have been studied as functions of technological parameters and number of single PCs in cascade. Angle-dependent spectral photoresponse characteristics values for real cascade silicon structures have been determined in visible and ultraviolet radiation spectra. Characteristic values of radiation incidence angle corresponding to the twofold photocurrent reduction in relation to normal incidence have been found depending on the number of single PCs in cascade, `dead' layer thickness of tunnel junction and photosensitivity of the base PC. The possibility and practicability of solar trackers use in PV systems with proposed PCs under study have been evaluated.

Conscious coupling: The challenges and opportunities of cascading enzymatic microreactors.

PubMed

Gruber, Pia; Marques, Marco P C; O'Sullivan, Brian; Baganz, Frank; Wohlgemuth, Roland; Szita, Nicolas

2017-07-01

The continuous production of high value or difficult to synthesize products is of increasing interest to the pharmaceutical industry. Cascading reaction systems have already been employed for chemical synthesis with great success, allowing a quick change in reaction conditions and addition of new reactants as well as removal of side products. A cascading system can remove the need for isolating unstable intermediates, increasing the yield of a synthetic pathway. Based on the success for chemical synthesis, the question arises how cascading systems could be beneficial to chemo-enzymatic or biocatalytic synthesis. Microreactors, with their rapid mass and heat transfer, small reaction volumes and short diffusion pathways, are promising tools for the development of such processes. In this mini-review, the authors provide an overview of recent examples of cascaded microreactors. Special attention will be paid to how microreactors are combined and the challenges as well as opportunities that arise from such combinations. Selected chemical reaction cascades will be used to illustrate this concept, before the discussion is widened to include chemo-enzymatic and multi-enzyme cascades. The authors also present the state of the art of online and at-line monitoring for enzymatic microreactor cascades. Finally, the authors review work-up and purification steps and their integration with microreactor cascades, highlighting the potential and the challenges of integrated cascades. © 2017 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

1.9 W yellow, CW, high-brightness light from a high efficiency semiconductor laser-based system

NASA Astrophysics Data System (ADS)

Hansen, A. K.; Christensen, M.; Noordegraaf, D.; Heist, P.; Papastathopoulos, E.; Loyo-Maldonado, V.; Jensen, O. B.; Stock, M. L.; Skovgaard, P. M. W.

2017-02-01

Semiconductor lasers are ideal sources for efficient electrical-to-optical power conversion and for many applications where their small size and potential for low cost are required to meet market demands. Yellow lasers find use in a variety of bio-related applications, such as photocoagulation, imaging, flow cytometry, and cancer treatment. However, direct generation of yellow light from semiconductors with sufficient beam quality and power has so far eluded researchers. Meanwhile, tapered semiconductor lasers at near-infrared wavelengths have recently become able to provide neardiffraction- limited, single frequency operation with output powers up to 8 W near 1120 nm. We present a 1.9 W single frequency laser system at 562 nm, based on single pass cascaded frequency doubling of such a tapered laser diode. The laser diode is a monolithic device consisting of two sections: a ridge waveguide with a distributed Bragg reflector, and a tapered amplifier. Using single-pass cascaded frequency doubling in two periodically poled lithium niobate crystals, 1.93 W of diffraction-limited light at 562 nm is generated from 5.8 W continuous-wave infrared light. When turned on from cold, the laser system reaches full power in just 60 seconds. An advantage of using a single pass configuration, rather than an external cavity configuration, is increased stability towards external perturbations. For example, stability to fluctuating case temperature over a 30 K temperature span has been demonstrated. The combination of high stability, compactness and watt-level power range means this technology is of great interest for a wide range of biological and biomedical applications.

RT-CW: widely tunable semiconductor THz QCL sources

NASA Astrophysics Data System (ADS)

Razeghi, M.; Lu, Q. Y.

2016-09-01

Distinctive position of Terahertz (THz) frequencies (ν 0.3 -10 THz) in the electromagnetic spectrum with their lower quantum energy compared to IR and higher frequency compared to microwave range allows for many potential applications unique to them. Especially in the security side of the THz sensing applications, the distinct absorption spectra of explosives and related compounds in the range of 0.1-5 THz makes THz technology a competitive technique for detecting hidden explosives. A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range will greatly boost the THz applications for the diagnosis and detection of explosives. Here we present a new strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based intracavity DFG. Room temperature continuous wave operation with electrical frequency tuning range of 2.06-4.35 THz is demonstrated.

Six orders of magnitude dynamic range in capillary electrophoresis with ultrasensitive laser-induced fluorescence detection

PubMed Central

Whitmore, Colin D.; Essaka, David; Dovichi, Norman J.

2009-01-01

An ultrasensitive laser-induced fluorescence detector was used with capillary electrophoresis for the study of 5-carboxy-tetramethylrhodamine. The raw signal from the detector provided roughly three orders of magnitude dynamic range. The signal saturated at high analyte concentrations due to the dead time associated with the single-photon counting avalanche photodiode employed in the detector. The signal can be corrected for the detector dead time, providing an additional order of magnitude dynamic range. To further increase dynamic range, two fiber-optic beam-splitters were cascaded to generate a primary signal and two attenuated signals, each monitored by a single-photon counting avalanche photodiode. The combined signals from the three photodiodes are reasonably linear from the concentration detection limit of 3 pM to 10 μM, the maximum concentration investigated, a range of 3,000,000. Mass detection limits were 150 yoctomoles injected onto the capillary. PMID:19836546

Hot-phonon generation in THz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Spagnolo, V.; Vitiello, M. S.; Scamarcio, G.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.

2007-12-01

Observation of non-equilibrium optical phonons population associated with electron transport in THz quantum cascade lasers is reported. The phonon occupation number was measured by using a combination of micro-probe photoluminescence and Stokes/Anti-Stokes Raman spectroscopy. Energy balance analysis allows us to estimate the phonon relaxation rate, that superlinearly increases with the electrical power in the range 1.5 W - 1.95 W, above laser threshold. This observation suggests the occurrence of stimulated emission of optical phonons.

Termination of second messenger signaling in olfaction.

PubMed Central

Boekhoff, I; Breer, H

1992-01-01

By using isolated rat olfactory cilia and a fast kinetics methodology, it has been demonstrated that odorant-induced second messenger signaling in the millisecond time range is terminated via phosphorylation reactions catalyzed by specific protein kinases. The cyclic adenosine nucleotide pathway is turned off by kinase A activity, whereas the inositol trisphosphate cascade is terminated by kinase C. The data support the concept that desensitization of odorant responses involves phosphorylation of key elements in the transduction cascade. PMID:1370581

A Low-Power All-Digital on-Chip CMOS Oscillator for a Wireless Sensor Node

PubMed Central

Sheng, Duo; Hong, Min-Rong

2016-01-01

This paper presents an all-digital low-power oscillator for reference clocks in wireless body area network (WBAN) applications. The proposed on-chip complementary metal-oxide-semiconductor (CMOS) oscillator provides low-frequency clock signals with low power consumption, high delay resolution, and low circuit complexity. The cascade-stage structure of the proposed design simultaneously achieves high resolution and a wide frequency range. The proposed hysteresis delay cell further reduces the power consumption and hardware costs by 92.4% and 70.4%, respectively, relative to conventional designs. The proposed design is implemented in a standard performance 0.18 μm CMOS process. The measured operational frequency ranged from 7 to 155 MHz, and the power consumption was improved to 79.6 μW (@7 MHz) with a 4.6 ps resolution. The proposed design can be implemented in an all-digital manner, which is highly desirable for system-level integration. PMID:27754439

A Low-Power All-Digital on-Chip CMOS Oscillator for a Wireless Sensor Node.

PubMed

Sheng, Duo; Hong, Min-Rong

2016-10-14

This paper presents an all-digital low-power oscillator for reference clocks in wireless body area network (WBAN) applications. The proposed on-chip complementary metal-oxide-semiconductor (CMOS) oscillator provides low-frequency clock signals with low power consumption, high delay resolution, and low circuit complexity. The cascade-stage structure of the proposed design simultaneously achieves high resolution and a wide frequency range. The proposed hysteresis delay cell further reduces the power consumption and hardware costs by 92.4% and 70.4%, respectively, relative to conventional designs. The proposed design is implemented in a standard performance 0.18 μm CMOS process. The measured operational frequency ranged from 7 to 155 MHz, and the power consumption was improved to 79.6 μW (@7 MHz) with a 4.6 ps resolution. The proposed design can be implemented in an all-digital manner, which is highly desirable for system-level integration.

Distributed torsion sensor based on cascaded coaxial cable Fabry-Perot interferometers

NASA Astrophysics Data System (ADS)

Cheng, Baokai; Zhu, Wenge; Hua, Liwei; Liu, Jie; Li, Yurong; Nygaard, Runar; Xiao, Hai

2016-07-01

Cascaded coaxial cable Fabry-Perot interferometers (FPI) are studied and demonstrated for distributed torsion measurement. Multiple weak reflectors are implemented on a coaxial cable so that any two consecutive reflectors can form a Fabry-Perot cavity. By fixing the cable sensor in a helical form on a shaft, the distributed torsion of the shaft can be measured by the cascaded Fabry-Perot cavities. A test on a single section shows that the sensor has a linear response with a sensitivity of 1.834 MHz (rad/m)-1 in the range of twisted rate from 0 to 8.726 rad m-1. The distributed torsion sensing capability is useful in drilling process monitoring, structure health monitoring and machine failure detection.

Soliton compression to few-cycle pulses with a high quality factor by engineering cascaded quadratic nonlinearities.

PubMed

Zeng, Xianglong; Guo, Hairun; Zhou, Binbin; Bache, Morten

2012-11-19

We propose an efficient approach to improve few-cycle soliton compression with cascaded quadratic nonlinearities by using an engineered multi-section structure of the nonlinear crystal. By exploiting engineering of the cascaded quadratic nonlinearities, in each section soliton compression with a low effective order is realized, and high-quality few-cycle pulses with large compression factors are feasible. Each subsequent section is designed so that the compressed pulse exiting the previous section experiences an overall effective self-defocusing cubic nonlinearity corresponding to a modest soliton order, which is kept larger than unity to ensure further compression. This is done by increasing the cascaded quadratic nonlinearity in the new section with an engineered reduced residual phase mismatch. The low soliton orders in each section ensure excellent pulse quality and high efficiency. Numerical results show that compressed pulses with less than three-cycle duration can be achieved even when the compression factor is very large, and in contrast to standard soliton compression, these compressed pulses have minimal pedestal and high quality factor.

The effect of alloying nickel with iron on the supersonic ballistic stage of high energy displacement cascades

DOE PAGES

Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.

2016-06-23

Previous experimental and theoretical studies suggest that the production of extended defect structures by collision cascades is inhibited in equiatomic NiFe, in comparison to pure Ni. It is also known that the production of such extend defect structures results from the formation of subcascades by high-energy recoils and their subsequent interaction. A detailed analysis of the ballistics of 40 keV cascades in Ni and NiFe is performed to identify the formation of such subcascades and to assess their spatial distribution. It is found that subcascades in Ni and NiFe are created with nearly identical energies and distributed similarly in space.more » This suggests that the differences in production of extended defect structures is not related to processes taking place in the ballistic phase of the collision cascade. Lastly, these results can be generalized to other, more chemically complex, concentrated alloys where the elements have similar atomic numbers, such as many high-entropy alloys.« less

The effect of alloying nickel with iron on the supersonic ballistic stage of high energy displacement cascades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.

Previous experimental and theoretical studies suggest that the production of extended defect structures by collision cascades is inhibited in equiatomic NiFe, in comparison to pure Ni. It is also known that the production of such extend defect structures results from the formation of subcascades by high-energy recoils and their subsequent interaction. A detailed analysis of the ballistics of 40 keV cascades in Ni and NiFe is performed to identify the formation of such subcascades and to assess their spatial distribution. It is found that subcascades in Ni and NiFe are created with nearly identical energies and distributed similarly in space.more » This suggests that the differences in production of extended defect structures is not related to processes taking place in the ballistic phase of the collision cascade. Lastly, these results can be generalized to other, more chemically complex, concentrated alloys where the elements have similar atomic numbers, such as many high-entropy alloys.« less

Design for high-power, single-lobe, grating-surface-emitting quantum cascade lasers enabled by plasmon-enhanced absorption of antisymmetric modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigler, C.; Kirch, J. D.; Mawst, L. J.

2014-03-31

Resonant coupling of the transverse-magnetic polarized (guided) optical mode of a quantum-cascade laser (QCL) to the antisymmetric surface-plasmon modes of 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antisymmetric-mode absorption. In turn, lasing in the symmetric mode, that is, surface emission in a single-lobe far-field beam pattern, is strongly favored over controllable ranges in grating duty cycle and tooth height. By using core-region characteristics of a published 4.6 μm-emitting QCL, grating-coupled surface-emitting (SE) QCLs are analyzed and optimized for highly efficient single-lobe operation. For infinite-length devices, it is found that when the antisymmetric mode is resonantly absorbed, the symmetric mode hasmore » negligible absorption loss (∼0.1 cm{sup −1}) while still being efficiently outcoupled, through the substrate, by the DFB grating. For finite-length devices, 2nd-order distributed Bragg reflector (DBR) gratings are used on both sides of the DFB grating to prevent uncontrolled reflections from cleaved facets. Equations for the threshold-current density and the differential quantum efficiency of SE DFB/DBR QCLs are derived. For 7 mm-long, 8.0 μm-wide, 4.6 μm-emitting devices, with an Ag/InP grating of ∼39% duty cycle, and ∼0.22 μm tooth height, threshold currents as low as 0.45 A are projected. Based on experimentally obtained internal efficiency values from high-performance QCLs, slope efficiencies as high as 3.4 W/A are projected; thus, offering a solution for watt-range, single-lobe CW operation from SE, mid-infrared QCLs.« less

Distribution of phytobenthos in the Yakima River basin, Washington, in relation to geology, land use, and other environmental factors

USGS Publications Warehouse

Leland, Harry V.

1995-01-01

Benthic-algal distributions in the Yakima River, Washington, basin were, examined in relation to geology, land use, water chemistry, and stream habitat using indicator-species classification (TWINSPAN) and canonical correspondence analysis (CCA). Algal assemblages identified byTWINSPAN were each associated with a narrow range of water-quality conditions. In the Cascade geologic province, where timber harvest and grazing are the dominant land uses, differences in community structure (CCA site scores) and concentrations of major ions (Ca and Mg) and nutrients (solute P, SiO2 and inorganic N) varied with dominant rock type of the basin. In agricultural areas of the Columbia Plateau province, differences in phytobenthos structure were based primarily on the degree of enrichment of dissolved solids, inorganic N, and solute P from irrigation-return flows and subsurface drainage. Habitat characteristics strongly correlated with community structure included reach altitude, turbidity, substratum embeddedness (Columbia Plateau), large woody-debris density (Cascade Range), and composition and density of the riparian vegetation. Algal biomass (AFDM) correlated with composition and density of the riparian vegetation but not with measured chemical-constituent concentrations. Nitrogen limitation in streams of the Cascade Range favored nitrogen-fixing blue-green algae and diatoms with endosymbiotic blue-greens, whereas nitrogen heterotrophs were abundant in agricultural areas of the Columbia Plateau.

Distribution of phytobenthos in the Yakima River basin, Washington, in relation to geology, land use and other environmental factors

USGS Publications Warehouse

Leland, Harry V.

1995-01-01

Benthic-algal distributions in the Yakima River, Washington, basin were, examined in relation to geology, land use, water chemistry, and stream habitat using indicator-species classification (TWINSPAN) and canonical correspondence analysis (CCA). Algal assemblages identified byTWINSPAN were each associated with a narrow range of water-quality conditions. In the Cascade geologic province, where timber harvest and grazing are the dominant land uses, differences in community structure (CCA site scores) and concentrations of major ions (Ca and Mg) and nutrients (solute P, SiO2 and inorganic N) varied with dominant rock type of the basin. In agricultural areas of the Columbia Plateau province, differences in phytobenthos structure were based primarily on the degree of enrichment of dissolved solids, inorganic N, and solute P from irrigation-return flows and subsurface drainage. Habitat characteristics strongly correlated with community structure included reach altitude, turbidity, substratum embeddedness (Columbia Plateau), large woody-debris density (Cascade Range), and composition and density of the riparian vegetation. Algal biomass (AFDM) correlated with composition and density of the riparian vegetation but not with measured chemical-constituent concentrations. Nitrogen limitation in streams of the Cascade Range favored nitrogen-fixing blue-green algae and diatoms with endosymbiotic blue-greens, whereas nitrogen heterotrophs were abundant in agricultural areas of the Columbia Plateau.

Dispersal of sticky particles

NASA Astrophysics Data System (ADS)

Reddy, Ramana; Kumar, Sanjeev

2007-12-01

In this paper, we show through simulations that when sticky particles are broken continually, particles are dispersed into fine dust only if they are present in a narrow range of volume fractions. The upper limit of this range is 0.20 in the 2D and 0.10 in the 3D space. An increase in the dimensionality of space reduces the upper limit nearly by a factor of two. This scaling holds for dispersal of particles in hyperdimensional space of dimensions up to ten, the maximum dimension studied in this work. The maximum values of volume fractions obtained are significantly lower than those required for close packing and random packing of discs in 2D and spheres in 3D space. These values are also smaller than those required for critical phenomena of cluster percolation. The results obtained are attributed to merger cascades of sticky particles, triggered by breakup events. A simple theory that incorporates this cascade is developed to quantitatively explain the observed scaling of the upper limit with the dimensionality of space. The theory also captures the dynamics of the dispersal process in the corresponding range of particle volume fractions. The theory suggests that cascades of order one and two predominantly decide the upper limit for complete dispersal of particles.

Bilayer avalanche spin-diode logic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, Joseph S., E-mail: joseph.friedman@u-psud.fr; Querlioz, Damien; Fadel, Eric R.

2015-11-15

A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

Ruthenium-Catalyzed Cascade Annulation of Indole with Propargyl Alcohols.

PubMed

Kaufmann, Julia; Jäckel, Elisabeth; Haak, Edgar

2018-05-14

Cascade transformations forming multiple bonds and one-pot procedures provide rapid access to natural-product-like scaffolds from simple precursors. These atom-economic processes are valuable tools in organic synthesis and drug discovery. Herein, we report on ruthenium-catalyzed cascade annulations of indole with readily available propargyl alcohols. These provide rapid access to diverse carbazoles, cyclohepta[b]indoles, and further fused polycycles with high selectivity. A bifunctional ruthenium complex featuring a redox-coupled cyclopentadienone ligand acts as a common catalyst for the different cascade processes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inferring network structure from cascades.

PubMed

Ghonge, Sushrut; Vural, Dervis Can

2017-07-01

Many physical, biological, and social phenomena can be described by cascades taking place on a network. Often, the activity can be empirically observed, but not the underlying network of interactions. In this paper we offer three topological methods to infer the structure of any directed network given a set of cascade arrival times. Our formulas hold for a very general class of models where the activation probability of a node is a generic function of its degree and the number of its active neighbors. We report high success rates for synthetic and real networks, for several different cascade models.

Cascaded-cladding-pumped cascaded Raman fiber amplifier.

PubMed

Jiang, Huawei; Zhang, Lei; Feng, Yan

2015-06-01

The conversion efficiency of double-clad Raman fiber laser is limited by the cladding-to-core area ratio. To get high conversion efficiency, the inner-cladding-to-core area ratio has to be less than about 8, which limits the brightness enhancement. To overcome the problem, a cascaded-cladding-pumped cascaded Raman fiber laser with multiple-clad fiber as the Raman gain medium is proposed. A theoretical model of Raman fiber amplifier with multiple-clad fiber is developed, and numerical simulation proves that the proposed scheme can improve the conversion efficiency and brightness enhancement of cladding pumped Raman fiber laser.

Inferring network structure from cascades

NASA Astrophysics Data System (ADS)

Ghonge, Sushrut; Vural, Dervis Can

2017-07-01

Many physical, biological, and social phenomena can be described by cascades taking place on a network. Often, the activity can be empirically observed, but not the underlying network of interactions. In this paper we offer three topological methods to infer the structure of any directed network given a set of cascade arrival times. Our formulas hold for a very general class of models where the activation probability of a node is a generic function of its degree and the number of its active neighbors. We report high success rates for synthetic and real networks, for several different cascade models.

Familial Hypercholesterolemia: Cascade Screening in Children and Relatives of the Affected.

PubMed

Setia, Nitika; Saxena, Renu; Sawhney, J P S; Verma, Ishwar C

2018-05-01

Familial Hypercholesterolemia (FH) is an inherited disorder of lipid metabolism characterized by very high low density lipoprotein (LDL) cholesterol since birth, resulting in premature atherosclerosis and coronary artery disease (CAD). Cascade screening of children and family members of proven FH individuals can identify more subjects who have high LDL cholesterol or the family mutation and appropriate intervention can reduce their risk of atherosclerosis and prevent its complications. Cascade screening by molecular testing, was carried out in 133 family members, comprising 24 children, of 31 probands with FH having a pathogenic mutation in LDLR/ApoB gene. Lipid profiles were obtained in 44 family members including 11 children. Of 133 family members tested, 88 (66.1%) were identified to carry the family mutation. Twelve of these were children below 18 y of age and 76 were adults. CAD was present in 15 (11.2%) family members and 63(47.4%) family members, including nine children, were already on Lipid Lowering Therapy. Cascade screening led to identification of 88 new cases, with a pathogenic mutation, who were at a very high risk of developing premature CAD. The authors identified 12 children with family specific mutation, out of which 9 were initiated on low dose statin therapy. Four homozygous children were treated with high dose statins because of substantially increased risk of CAD. Cascade screening, therefore, proved to be a successful initiative towards primary prevention of CAD in India.

Deuterium Values from Hydrated Volcanic Glass: A Paleoelevation Proxy for Oregon's Cascade Range

NASA Astrophysics Data System (ADS)

Carlson, T. B.; Bershaw, J. T.; Cassel, E. J.

2017-12-01

Deuterium ratios (δD) of hydrated volcanic glass have been used to reconstruct Cenozoic paleoenvironments. However, the reliability and proper sample preparation protocol have been debated. The Cascades are an excellent location to study the validity of hydrated volcanic glass as a paleoelevation proxy for several reasons. Moisture is largely derived from a single oceanic source and falls as orographic precipitation in the Cascades, leading to a characteristic altitude effect, or inverse relationship between elevation and the isotopic composition of meteoric water (δD). Additionally, past studies have inferred uplift of the Cascades since the Miocene based on changing fossil assemblages, tectonic models, and other isotopic proxies including soil carbonates and fossil teeth. In this study, hydrated volcanic ash samples from the lee of the Cascades were rinsed with hydrochloric acid and sonicated before glass shards were hand-selected and analyzed for δD and wt. % water. These preliminary results exhibited δD values becoming enriched with time, a trend opposite of other paleowater proxy studies in the area. A possible explanation for this trend is contamination due to inadequate removal of materials adhered to shard surfaces that can readily exchange with environmental water. Recent research asserts that hydrofluoric acid (HF) etching during sample preparation is necessary to accurately measure δD values of syndepositional water. Volcanic ash samples were reanalyzed after preparation using HF abrasion and heavy liquid separation. The data from these two subsets are interpreted in the context of modern water across the range, as well as other paleowater proxy and geologic studies to determine the implications of volcanic glass as a paleoelevation proxy in the Pacific Northwest.

Unique inhibitory cascade pattern of molars in canids contributing to their potential to evolutionary plasticity of diet

PubMed Central

Asahara, Masakazu

2013-01-01

Developmental origins that guide the evolution of dental morphology and dental formulae are fundamental subjects in mammalian evolution. In a previous study, a developmental model termed the inhibitory cascade model was established. This model could explain variations in relative molar sizes and loss of the lower third molars, which sometimes reflect diet, in murine rodents and other mammals. Here, I investigated the pattern of relative molar sizes (inhibitory cascade pattern) in canids, a taxon exhibiting a wide range of dietary habits. I found that interspecific variation in canid molars suggests a unique inhibitory cascade pattern that differs from that in murine rodents and other previously reported mammals, and that this variation reflects dietary habits. This unique variability in molars was also observed in individual variation in canid species. According to these observations, canid species have greater variability in the relative sizes of first molars (carnassials), which are functionally important for dietary adaptation in the Carnivora. In conclusion, an inhibitory cascade that differs from that in murine rodents and other mammals may have contributed to diverse dietary patterns and to their parallel evolution in canids. PMID:23467478

Petrologic, tectonic, and metallogenic evolution of the Ancestral Cascades magmatic arc, Washington, Oregon, and northern California

USGS Publications Warehouse

du Bray, Edward A.; John, David A.

2011-01-01

Present-day High Cascades arc magmatism was preceded by ~40 m.y. of nearly cospatial magmatism represented by the ancestral Cascades arc in Washington, Oregon, and northernmost California (United States). Time-space-composition relations for the ancestral Cascades arc have been synthesized from a recent compilation of more than 4000 geochemical analyses and associated age data. Neither the composition nor distribution of ancestral Cascades magmatism was uniform along the length of the ancestral arc through time. Initial (>40 to 36 Ma) ancestral Cascades magmatism (mostly basalt and basaltic andesite) was focused at the north end of the arc between the present-day locations of Mount Rainier and the Columbia River. From 35 to 18 Ma, initial basaltic andesite and andesite magmatism evolved to include dacite and rhyolite; magmatic activity became more voluminous and extended along most of the arc. Between 17 and 8 Ma, magmatism was focused along the part of the arc coincident with the northern two-thirds of Oregon and returned to more mafic compositions. Subsequent ancestral Cascades magmatism was dominated by basaltic andesite to basalt prior to the post–4 Ma onset of High Cascades magmatism. Transitional tholeiitic to calc-alkaline compositions dominated early (before 40 to ca. 25 Ma) ancestral Cascades eruptive products, whereas the majority of the younger arc rocks have a calc-alkaline affinity. Tholeiitic compositions characteristic of the oldest ancestral arc magmas suggest development associated with thin, immature crust and slab window processes, whereas the younger, calc-alkaline magmas suggest interaction with thicker, more evolved crust and more conventional subduction-related magmatic processes. Presumed changes in subducted slab dip through time also correlate with fundamental magma composition variation. The predominance of mafic compositions during latest ancestral arc magmatism and throughout the history of modern High Cascades magmatism probably reflects extensional tectonics that dominated during these periods of arc magmatism. Mineral deposits associated with ancestral Cascades arc rocks are uncommon; most are small and low grade relative to those found in other continental magmatic arcs. The small size, low grade, and dearth of deposits, especially in the southern two-thirds of the ancestral arc, probably reflect many factors, the most important of which may be the prevalence of extensional tectonics within this arc domain during this magmatic episode. Progressive clockwise rotation of the forearc block west of the evolving Oregon part of the ancestral Cascades magmatism produced an extensional regime that did not foster significant mineral deposit formation. In contrast, the Washington arc domain developed in a transpressional to mildly compressive regime that was more conducive to magmatic processes and hydrothermal fluid channeling critical to deposit formation. Small, low-grade porphyry copper deposits in the northern third of the ancestral Cascades arc segment also may be a consequence of more mature continental crust, including a Mesozoic component, beneath Washington north of Mount St. Helens.

Transition modelling implications in the CFD analysis of a turbine nozzle vane cascade tested over a range of Mach and Reynolds numbers

NASA Astrophysics Data System (ADS)

Marconcini, Michele; Pacciani, Roberto; Arnone, Andrea

2015-11-01

The aerodynamic performance of a gas turbine nozzle vane cascade was investigated over a range of Mach and Reynolds numbers. The work is part of a vast research project aimed at the analysis of fluid dynamics and heat transfer phenomena in cooled blades. In this paper computed results on the "solid vane" (without cooling devices) are presented and discussed in comparison with experimental data. Detailed measurements were provided by the University of Bergamo where the experimental campaign was carried out by means of a subsonic wind tunnel. The impact of boundary layer transition is investigated by using a novel laminar kinetic energy transport model and the widely used Langtry-Menter γ- Re θ,t model. The comparison between calculations and measurements is presented in terms of blade loading distributions, total pressure loss coefficient contours downstream of the cascade, and velocity/turbulence-intensity profiles within the boundary layer at selected blade surface locations at mid-span. It will be shown how transitional calculations compare favorably with experiments.

On the main photoelectric characteristics of three-junction InGaP/InGaAs/Ge solar cells in a broad temperature range (–197°C ≤ T ≤ +85°C)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, V. M.; Malevskiy, D. A.; Pokrovskiy, P. V.

2016-10-15

This study is aimed at investigating the main photoelectric characteristics of three-cascade InGaP/InGaAs/Ge photoelectric converters in a broad temperature range (–197°C ≤ T ≤ +85°C). On account of analysis of photosensitivity spectra and optical current–voltage characteristics, such temperature dependences as the open-circuit voltage (V{sub oc}), filling factor of the current–voltage characteristic (FF), and the photoelectric conversion efficiency of solar radiation are determined. Investigations are performed at illumination intensities corresponding to operation under concentrated radiation. Decreased temperatures facilitate the selection of samples with the minimal “parasitic” potential barriers. The influence of excitationtransfer processes from a cascade into a cascade is estimatedmore » by means of secondary luminescent radiation. The highest photoelectric conversion efficiency of 52% is measured at a concentration multiplicity of 100 “suns” and a temperature of–160°C.« less

Two-dimensional turbulent convection

NASA Astrophysics Data System (ADS)

Mazzino, Andrea

2017-11-01

We present an overview of the most relevant, and sometimes contrasting, theoretical approaches to Rayleigh-Taylor and mean-gradient-forced Rayleigh-Bénard two-dimensional turbulence together with numerical and experimental evidences for their support. The main aim of this overview is to emphasize that, despite the different character of these two systems, especially in relation to their steadiness/unsteadiness, turbulent fluctuations are well described by the same scaling relationships originated from the Bolgiano balance. The latter states that inertial terms and buoyancy terms balance at small scales giving rise to an inverse kinetic energy cascade. The main difference with respect to the inverse energy cascade in hydrodynamic turbulence [R. H. Kraichnan, "Inertial ranges in two-dimensional turbulence," Phys. Fluids 10, 1417 (1967)] is that the rate of cascade of kinetic energy here is not constant along the inertial range of scales. Thanks to the absence of physical boundaries, the two systems here investigated turned out to be a natural physical realization of the Kraichnan scaling regime hitherto associated with the elusive "ultimate state of thermal convection" [R. H. Kraichnan, "Turbulent thermal convection at arbitrary Prandtl number," Phys. Fluids 5, 1374-1389 (1962)].

Lead-isotopic data from sulfide minerals from the Cascade Range, Oregon and Washington

USGS Publications Warehouse

Church, S.E.; LeHuray, A.P.; Grant, A.R.; Delevaux, M.H.; Gray, J.E.

1986-01-01

Lead-isotopic studies of mineral deposits associated with Tertiary plutons found in the Cascade Range of Oregon and Washington demonstrate a rather uniform isotopic composition in various sulfide minerals ( 206Pb 204Pb = 18.84 to 19.05; 207Pb 204Pb = 15.57 to 15.62; 208Pb 204Pb = 38.49 to 38.74), show less variation than data from the volcanic rocks of the Cascade Range and fall within the mixing array defined by the MORB regression line and continental sediments. An evaluation of the role of crustal assimilation by hydrothermal convection during emplacement was made on five sulfide deposits associated with a single composite batholith, the Cloudy Pass pluton. The Pb-isotopic data and mass balance calculations suggest that only minor amounts of the lead were derived from the overlying Precambrian (?) Swakane Biotite Gneiss during emplacement. The bulk of the metal that occurs in sulfide deposits in the Cascade mineral belt appears to have been derived from subducted continental detritus. The variation of the Pb-isotopic signature of Sulfides from specific districts or deposits suggests that there is a correlation with age and structure of the crust. 206Pb 204Pb is greater than 18.92 in northern Washington and southern Oregon where deposits have intruded Mesozoic or older crust. However, the ore deposits between the northern Oregon border and central Oregon, south of Eugene, have intruded younger crust composed largely of mafic and andesitic volcanic rocks and 206Pb 204Pb lies between 18.84 and 18.92. This region, previously called the Columbia embayment, appears to be underlain by Tertiary volcanic rocks. Lead-isotopic data may be used to define the boundaries between discontinuous blocks of Mesozoic crust and Tertiary volcanic cover. ?? 1986.

Primary radiation damage characterization of α-iron under irradiation temperature for various PKA energies

NASA Astrophysics Data System (ADS)

Sahi, Qurat-ul-ain; Kim, Yong-Soo

2018-04-01

The understanding of radiation-induced microstructural defects in body-centered cubic (BCC) iron is of major interest to those using advanced steel under extreme conditions in nuclear reactors. In this study, molecular dynamics (MD) simulations were implemented to examine the primary radiation damage in BCC iron with displacement cascades of energy 1, 5, 10, 20, and 30 keV at temperatures ranging from 100 to 1000 K. Statistical analysis of eight MD simulations of collision cascades were carried out along each [110], [112], [111] and a high index [135] direction and the temperature dependence of the surviving number of point defects and the in-cascade clustering of vacancies and interstitials were studied. The peak time and the corresponding number of defects increase with increasing irradiation temperature and primary knock-on atom (PKA) energy. However, the final number of surviving point defects decreases with increasing lattice temperature. This is associated with the increase of thermal spike at high PKA energy and its long timespan at higher temperatures. Defect production efficiency (i.e., surviving MD defects, per Norgett-Robinson-Torrens displacements) also showed a continuous decrease with the increasing irradiation temperature and PKA energy. The number of interstitial clusters increases with both irradiation temperature and PKA energy. However, the increase in the number of vacancy clusters with PKA energy is minimal-to-constant and decreases as the irradiation temperature increases. Similarly, the probability and cluster size distribution for larger interstitials increase with temperature, whereas only smaller size vacancy clusters were observed at higher temperatures.

A High Frequency Model of Cascade Noise

NASA Technical Reports Server (NTRS)

Envia, Edmane

1998-01-01

Closed form asymptotic expressions for computing high frequency noise generated by an annular cascade in an infinite duct containing a uniform flow are presented. There are two new elements in this work. First, the annular duct mode representation does not rely on the often-used Bessel function expansion resulting in simpler expressions for both the radial eigenvalues and eigenfunctions of the duct. In particular, the new representation provides an explicit approximate formula for the radial eigenvalues obviating the need for solutions of the transcendental annular duct eigenvalue equation. Also, the radial eigenfunctions are represented in terms of exponentials eliminating the numerical problems associated with generating the Bessel functions on a computer. The second new element is the construction of an unsteady response model for an annular cascade. The new construction satisfies the boundary conditions on both the cascade and duct walls simultaneously adding a new level of realism to the noise calculations. Preliminary results which demonstrate the effectiveness of the new elements are presented. A discussion of the utility of the asymptotic formulas for calculating cascade discrete tone as well as broadband noise is also included.

A high speed and high gain CMOS receiver chip for a pulsed time-of-flight laser rangefinder

NASA Astrophysics Data System (ADS)

Yu, Jin-jin; Deng, Ruo-han; Yuan, Hong-hui; Chen, Yong-ping

2011-06-01

An integrated receiver channel for a pulsed time-of-flight (TOF) laser rangefinder has been designed. Pulsed TOF laser range finding devices using a laser diode transmitter can achieve millimeter-level distance measurement accuracy in a measurement range of several tens of meters to non-cooperative targets. The amplifier exploits the regulated cascade (RGC) configuration as the input-stage, thus achieving as large effective input trans-conductance as that of Si Bipolar or GaAs MESFET. The RGC input configuration isolates the input parasitic capacitance including photodiode capacitance from the bandwidth determination better than common-gate TIA. To enlarge the bandwidth, inductive peaking technology has been adopted. An active inductor (MOS-L) is used instead of spiral inductor in CMOS process. An R-2R resistor ladder is inserting between per-amplifier and post-amplifier as the variable attenuator for digital gain control purpose. The gain-bandwidth of a basic differential pair with resistive load is not large enough for broad band operation. A circuit solution to improve both gain and bandwidth of an amplifying stage is proposed. Traditional and modified Cherry-Hooper amplifiers are discussed and the cascading of several stages to constitute the post-amplifier is designed. The fully integrated one-chip solution is designed with Cadence IC design platform. The simulation result shows the bandwidth of the trans-impedance amplifier is 215MHz with the presence of a 2pF input capacitor and 5pF load capacitor. And the maximum trans-impedance gain is 136dB. The walk error is less than 1ns in 1:1000 dynamic range. The responsive time is less than 2.2ns.

Macroturbulence in Very High Resolution Atmospheric Models: Evidence for Two Scaling Regimes

NASA Astrophysics Data System (ADS)

Straus, D. M.

2010-12-01

The macro-turbulent properties of the atmosphere's circulation are examined in a number of very high resolution seasonal simulations using the global Nonhydrostatic ICosahedral Atmospheric Model (NICAM) at 7-km horizontal resolution (40 levels), and the forecast model of the European Centre for Medium-Range Weather Forecasts (ECMWF) at T1279 and T2047 spectral resolutions (90-levels). These simulations were carried out as part of an extraordinary collaborative project between the Center for Ocean-Land-Atmosphere Studies (COLA), the University of Tokyo, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), ECMWF, and the National Institute of Computational Sciences (NICS) The goals of the analysis are to document the rotational and divergence kinetic energy spectral characteristics, to shed light on the different scaling regimes obtained and the role of non-hydrostatic dynamics, and to asses the effects of the smallest scales on the cascades of energy. Simulations with all the models show some evidence of two scaling regimes (power law with steep slope, and a distinctly more shallow slope at smaller scales) for both rotational and divergent kinetic energy. The strength of the evidence for the two-regimes, as well as the wavenumber ranges in which they occur, do differ between models. Analysis of different time scale contributions to the spectra lend insight into the energy transfer mechanism. The implications for dynamical theories of turbulent energy exchange are discussed, as well as difference in approach to compared with multiplicative cascade theories.

Data for Design of Entrance Vanes from Two-Dimensional Tests of Airfoils in Cascade

NASA Technical Reports Server (NTRS)

Zimmey, Charles M.; Lappi, Viola M.

1945-01-01

As a part of a program of the NACA directed toward increasing the efficiency of compressors and turbines, data were obtained for application to the design of entrance vanes for axfax-flow compressors or turbines. A series of blower-blade sections with relatively high critical speeds have been developed for turning air efficiently from 0 deg to 80 deg starting with an axial direction. Tests were made of five NACA 65-series blower blades (modified NACA 65(216)-010 airfoils) and of four experimentally designed blower blades in a stationary cascade at low Mach numbers. The turning effectiveness and the pressure distributions of these blade sections at various angles of attack were evaluated over a range of solidities near 1. Entrance-vane design charts are presented that give a blade section and angle of attack for any desired turning angle. The blades thus obtained operate with peak-free pressure distributions. Approximate critical Mach numbers were calculated from the pressure distributions.

Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback

NASA Astrophysics Data System (ADS)

Ristanic, Daniela; Schwarz, Benedikt; Reininger, Peter; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried

2015-01-01

A method to improve the sensitivity and selectivity of a monolithically integrated mid-infrared sensor using a distributed feedback laser (DFB) is presented in this paper. The sensor is based on a quantum cascade laser/detector system built from the same epitaxial structure and with the same fabrication approach. The devices are connected via a dielectric-loaded surface plasmon polariton waveguide with a twofold function: it provides high light coupling efficiency and a strong interaction of the light with the environment (e.g., a surrounding fluid). The weakly coupled DFB quantum cascade laser emits narrow mode light with a FWHM of 2 cm-1 at 1586 cm-1. The room temperature laser threshold current density is 3 kA/cm2 and a pulsed output power of around 200 mW was measured. With the superior laser noise performance, due to narrow mode emission and the compensation of thermal fluctuations, the lower limit of detection was expanded by one order of magnitude to the 10 ppm range.

Photo-vibrational spectroscopy using quantum cascade laser and laser Doppler vibrometer

NASA Astrophysics Data System (ADS)

Liu, Huan; Hu, Qi; Xie, Jiecheng; Fu, Yu

2017-06-01

Photoacoustic/photothermal spectroscopy is an established technique for detection of chemicals and explosives. However, prior sample preparation is required and the analysis is conducted in a sealed space with a high-sensitivity sensor coupled with a lock-in amplifier, limiting the technique to applications in a controllable laboratory environment. Hence, this technique may not be suitable for defense and security applications where the detection of explosives or hazardous chemicals is required in an open environment at a safe standoff distance. In this study, chemicals in various forms were excited by an intensity-modulated quantum cascade laser (QCL), while a laser Doppler vibrometer (LDV) was applied to detect the vibration signal resulting from the photocoustic/photothermal effect. The photo-vibrational spectrum obtained by scanning the QCL's wavelength in MIR range, coincides well with the corresponding spectrum obtained using typical FTIR equipment. The experiment in short and long standoff distances demonstrated that the LDV is a capable sensor for chemical detection in an open environment.

Helical bottleneck effect in 3D homogeneous isotropic turbulence

NASA Astrophysics Data System (ADS)

Stepanov, Rodion; Golbraikh, Ephim; Frick, Peter; Shestakov, Alexander

2018-02-01

We present the results of modelling the development of homogeneous and isotropic turbulence with a large-scale source of energy and a source of helicity distributed over scales. We use the shell model for numerical simulation of the turbulence at high Reynolds number. The results show that the helicity injection leads to a significant change in the behavior of the energy and helicity spectra in scales larger and smaller than the energy injection scale. We suggest the phenomenology for direct turbulent cascades with the helicity effect, which reduces the efficiency of the spectral energy transfer. Therefore the energy is accumulated and redistributed so that non-linear interactions will be sufficient to provide a constant energy flux. It can be interpreted as the ‘helical bottleneck effect’ which, depending on the parameters of the injection helicity, reminds one of the well-known bottleneck effect at the end of inertial range. Simulations which included the infrared part of the spectrum show that the inverse cascade hardly develops under distributed helicity forcing.

Mid-infrared absorption spectroscopy using quantum cascade lasers

NASA Astrophysics Data System (ADS)

Haibach, Fred; Erlich, Adam; Deutsch, Erik

2011-06-01

Block Engineering has developed an absorption spectroscopy system based on widely tunable Quantum Cascade Lasers (QCL). The QCL spectrometer rapidly cycles through a user-selected range in the mid-infrared spectrum, between 6 to 12 μm (1667 to 833 cm-1), to detect and identify substances on surfaces based on their absorption characteristics from a standoff distance of up to 2 feet with an eye-safe laser. It can also analyze vapors and liquids in a single device. For military applications, the QCL spectrometer has demonstrated trace explosive, chemical warfare agent (CWA), and toxic industrial chemical (TIC) detection and analysis. The QCL's higher power density enables measurements from diffuse and highly absorbing materials and substrates. Other advantages over Fourier Transform Infrared (FTIR) spectroscopy include portability, ruggedness, rapid analysis, and the ability to function from a distance through free space or a fiber optic probe. This paper will discuss the basic technology behind the system and the empirical data on various safety and security applications.

Quantum cascade lasers for defense and security

NASA Astrophysics Data System (ADS)

Day, Timothy; Pushkarsky, Michael; Caffey, Dave; Cecchetti, Kristen; Arp, Ron; Whitmore, Alex; Henson, Michael; Takeuchi, Eric B.

2013-10-01

Quantum cascade laser (QCL) systems are mature and at the vanguard of a new generation of products that support military applications such as Infrared Countermeasures (IRCM) and targeting. The demanding product requirements for aircraft platforms that include reduced size, weight, power consumption and cost (SWaP-C) extends to portable, battery powered handheld products. QCL technology operates throughout the mid-wave (MWIR) and long-wave (LWIR) infrared to provide new capabilities that leverage existing thermal imaging cameras. In addition to their suitability for aircraft platforms, QCL products are a natural fit to meet operator demands for small, lightweight pointer and beacon capabilities. Field-testing of high power, lightweight, battery operated devices has demonstrated their utility across a range of air and ground applications. This talk will present an overview of QCL technology and the Defense and Security products and capabilities that are enabled by it. This talk will also provide an overview of the extensive environmental and performance testing associated with products based on QCL technology.

Quantum-engineered interband cascade photovoltaic devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Razeghi, Manijeh; Tournié, Eric; Brown, Gail J.

2013-12-18

Quantum-engineered multiple stage photovoltaic (PV) devices are explored based on InAs/GaSb/AlSb interband cascade (IC) structures. These ICPV devices employ multiple discrete absorbers that are connected in series by widebandgap unipolar barriers using type-II heterostructure interfaces for facilitating carrier transport between cascade stages similar to IC lasers. The discrete architecture is beneficial for improving the collection efficiency and for spectral splitting by utilizing absorbers with different bandgaps. As such, the photo-voltages from each individual cascade stage in an ICPV device add together, creating a high overall open-circuit voltage, similar to conventional multi-junction tandem solar cells. Furthermore, photo-generated carriers can be collectedmore » with nearly 100% efficiency in each stage. This is because the carriers travel over only a single cascade stage, designed to be shorter than a typical diffusion length. The approach is of significant importance for operation at high temperatures where the diffusion length is reduced. Here, we will present our recent progress in the study of ICPV devices, which includes the demonstration of ICPV devices at room temperature and above with narrow bandgaps (e.g. 0.23 eV) and high open-circuit voltages. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.« less

High-performance recombinant protein production with Escherichia coli in continuously operated cascades of stirred-tank reactors.

PubMed

Schmideder, Andreas; Weuster-Botz, Dirk

2017-07-01

The microbial expression of intracellular, recombinant proteins in continuous bioprocesses suffers from low product concentrations. Hence, a process for the intracellular production of photoactivatable mCherry with Escherichia coli in a continuously operated cascade of two stirred-tank reactors was established to separate biomass formation (first reactor) and protein expression (second reactor) spatially. Cascades of miniaturized stirred-tank reactors were implemented, which enable the 24-fold parallel characterization of cascade processes and the direct scale-up of results to the liter scale. With PAmCherry concentrations of 1.15 g L -1 cascades of stirred-tank reactors improved the process performance significantly compared to production processes in chemostats. In addition, an optimized fed-batch process was outperformed regarding space-time yield (149 mg L -1  h -1 ). This study implicates continuous cascade processes to be a promising alternative to fed-batch processes for microbial protein production and demonstrates that miniaturized stirred-tank reactors can reduce the timeline and costs for cascade process characterization.

Molecular dispersion spectroscopy based on Fabry-Perot quantum cascade lasers.

PubMed

Sterczewski, Lukasz A; Westberg, Jonas; Wysocki, Gerard

2017-01-15

Two Fabry-Perot quantum cascade lasers are used in a differential dual comb configuration to perform rapidly swept dispersion spectroscopy of low-pressure nitrous oxide with <1  ms acquisition time. Active feedback control of the laser injection current enables simultaneous wavelength modulation of both lasers at kilohertz rates. The system demonstrates similar performance in both absorption and dispersion spectroscopy modes and achieves a noise-equivalent absorption figure of merit in the low 10^-4/Hz range.

Advances in Fabry-Perot and tunable quantum cascade lasers

NASA Astrophysics Data System (ADS)

Patel, C. Kumar N.

2017-05-01

Quantum cascade lasers (QCLs) are becoming mature infrared emitting devices that convert electrical power directly into optical power and generate laser radiation in the mid wave infrared (MWIR) and long wave infrared (LWIR) regions. These lasers operate at room temperature in the 3.5 μm to >12.0 μm region. QCLs operate at longer wavelengths into the terahertz region; however, these require some level of cryogenic cooling. Nonetheless, QCLs are the only solid-state sources that convert electrical power into optical power directly in these spectral regions. Three critical advances have contributed to the broad range of applications of QCLs, since their first demonstration in 1994 [1]. The first of these was the utilization of two phonon resonance for deexcitation of electrons from the lower lasing level [2]; the second is the utilization of epi-down mounting with hard solder of QCLs for practical applications [3]; and the third is the invention of nonresonant extraction for deexciting electrons from the lower laser level and simultaneously removing constraints on QCL structure design for extending high power room temperature operation to a broad range of wavelengths [4]. Although QCLs generate CW radiation at room temperature at wavelengths ranging from 3.5 μm to <12.0 μm, two spectral regions are very important for a broad range of applications. These are the first and the second atmospheric transmission windows from 3.5 μm to 5.0 μm and from 8.0 μm to 12.0 μm, respectively. Both of these windows (except for the spectral region near 4.2 μm, which is dominated by the infrared absorption from atmospheric carbon dioxide) are relatively free from atmospheric absorption and have a range of applications that involve long distance propagation.

Acceptability and feasibility of an e-mental health intervention for parents of childhood cancer survivors: "Cascade".

PubMed

Wakefield, Claire E; Sansom-Daly, Ursula M; McGill, Brittany C; Ellis, Sarah J; Doolan, Emma L; Robertson, Eden G; Mathur, Sanaa; Cohn, Richard J

2016-06-01

The aim of this study was to evaluate the feasibility and acceptability of "Cascade": an online, group-based, cognitive behavioral therapy intervention, delivered "live" by a psychologist, to assist parents of children who have completed cancer treatment. Forty-seven parents were randomized to Cascade (n = 25) or a 6-month waitlist (n = 22). Parents completed questionnaires at baseline, 1-2 weeks and 6 months post-intervention. Thirty parents completed full evaluations of the Cascade program (n = 21 randomized to Cascade, n = 9 completed Cascade post-waitlist). Ninety-six percent of Cascade participants completed the intervention (n = 24/25). Eighty percent of parents completed every questionnaire (mean completion time 25 min (SD = 12)). Cascade was described as at least "somewhat" helpful by all parents. None rated Cascade as "very/quite" burdensome. Parents reported that the "online format was easy to use" (n = 28, 93.3 %), "I learnt new skills" (n = 28, 93.3 %), and "I enjoyed talking to others" (n = 29, 96.7 %). Peer-to-peer benefits were highlighted by good group cohesion scores. Cascade is highly acceptable and feasible. Its online delivery mechanism may address inequities in post-treatment support for parents, a particularly acute concern for rural/remote families. Future research needs to establish the efficacy of the intervention. ACTRN12613000270718, https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12613000270718.

Solar Wind Turbulence and the Role of Ion Instabilities

NASA Astrophysics Data System (ADS)

Alexandrova, O.; Chen, C. H. K.; Sorriso-Valvo, L.; Horbury, T. S.; Bale, S. D.

Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling k_{perp}^{-5/3} for the perpendicular cascade and k_⊥^{-2} for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a -3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to -2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by ˜ k_{perp}^{-α}exp(-k_{perp}elld), with α≃8/3 and the dissipation scale ℓ d close to the electron Larmor radius ℓ d ≃ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.

Optical and Electronic NOx Sensors for Applications in Mechatronics

PubMed Central

Di Franco, Cinzia; Elia, Angela; Spagnolo, Vincenzo; Scamarcio, Gaetano; Lugarà, Pietro Mario; Ieva, Eliana; Cioffi, Nicola; Torsi, Luisa; Bruno, Giovanni; Losurdo, Maria; Garcia, Michael A.; Wolter, Scott D.; Brown, April; Ricco, Mario

2009-01-01

Current production and emerging NOx sensors based on optical and nanomaterials technologies are reviewed. In view of their potential applications in mechatronics, we compared the performance of: i) Quantum cascade lasers (QCL) based photoacoustic (PA) systems; ii) gold nanoparticles as catalytically active materials in field-effect transistor (FET) sensors, and iii) functionalized III-V semiconductor based devices. QCL-based PA sensors for NOx show a detection limit in the sub part-per-million range and are characterized by high selectivity and compact set-up. Electrochemically synthesized gold-nanoparticle FET sensors are able to monitor NOx in a concentration range from 50 to 200 parts per million and are suitable for miniaturization. Porphyrin-functionalized III-V semiconductor materials can be used for the fabrication of a reliable NOx sensor platform characterized by high conductivity, corrosion resistance, and strong surface state coupling. PMID:22412315

Pair Cascades and Deathlines in Magnetic Fields with Offset Polar Caps

NASA Technical Reports Server (NTRS)

Harding, Alice K.; Muslimov, Alex G.

2012-01-01

We present results of electron-positron pair cascade simulations in a dipole magnetic field whose polar cap is offset from the dipole axis. In such a field geometry, the polar cap is displaced a small fraction of the neutron star radius from the star symmetry axis and the field line radius of curvature is modified. Using the modified parallel electric field near the offset polar cap, we simulate pair cascades to determine the pair deathlines and pair multiplicities as a function of the offset. We find that the pair multiplicity can change dr;unatically with a modest offset, with a significant increase on one side of the polar cap. Lower pair deathlines allow a larger fraction of the pulsar population, that include old and millisecond pulsars, to produce cascades with high multiplicity. The results have some important implications for pulsar particle production, high-energy emission and cosmic-ray contribution.

A separation-integrated cascade reaction to overcome thermodynamic limitations in rare-sugar synthesis.

PubMed

Wagner, Nina; Bosshart, Andreas; Failmezger, Jurek; Bechtold, Matthias; Panke, Sven

2015-03-27

Enzyme cascades combining epimerization and isomerization steps offer an attractive route for the generic production of rare sugars starting from accessible bulk sugars but suffer from the unfavorable position of the thermodynamic equilibrium, thus reducing the yield and requiring complex work-up procedures to separate pure product from the reaction mixture. Presented herein is the integration of a multienzyme cascade reaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D-psicose from sucrose in a three-step cascade reaction using invertase, D-xylose isomerase, and D-tagatose epimerase, via the intermediates D-glucose and D-fructose, is described. This set-up allowed the production of pure psicose (99.9%) with very high yields (89%) and high enzyme efficiency (300 g of D-psicose per g of enzyme). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dense 3D Face Alignment from 2D Video for Real-Time Use

PubMed Central

Jeni, László A.; Cohn, Jeffrey F.; Kanade, Takeo

2018-01-01

To enable real-time, person-independent 3D registration from 2D video, we developed a 3D cascade regression approach in which facial landmarks remain invariant across pose over a range of approximately 60 degrees. From a single 2D image of a person’s face, a dense 3D shape is registered in real time for each frame. The algorithm utilizes a fast cascade regression framework trained on high-resolution 3D face-scans of posed and spontaneous emotion expression. The algorithm first estimates the location of a dense set of landmarks and their visibility, then reconstructs face shapes by fitting a part-based 3D model. Because no assumptions are required about illumination or surface properties, the method can be applied to a wide range of imaging conditions that include 2D video and uncalibrated multi-view video. The method has been validated in a battery of experiments that evaluate its precision of 3D reconstruction, extension to multi-view reconstruction, temporal integration for videos and 3D head-pose estimation. Experimental findings strongly support the validity of real-time, 3D registration and reconstruction from 2D video. The software is available online at http://zface.org. PMID:29731533

An investigation into the utilization of HCMM thermal data for the descrimination of volcanic and Eolian geological units. [Craters of the Moon volcanic field, Idaho; San Francisco volcanic field, Arizona; High Desert, California; and the Cascade Range, California and Oregon

NASA Technical Reports Server (NTRS)

Head, J. W., III (Principal Investigator)

1982-01-01

Analysis of HCMM data shows that the resolution provided by the thermal data is inadequate to permit the identification of individual lava flows within the volcanic test sites. Thermal data of southern California reveals that dune complexes at Kelso and Algodomes are found to be too small to permit adequate investigation of their structure. As part of the study of the San Francisco volcanic field, marked variations in the thermal properties of the region between Flagstaff and the Utah State border were observed. Several well-defined units within the Grand Canyon and the Colorado Plateau were recognized and appear to be very suitable for analysis with HCMM, SEASAT and LANDSAT images. Although individual volcanic constructs within the Cascade Range are too small to permit detailed characterization with the thermal data, the regional volcano/tectonic setting offers a good opportunity for comparing the possible thermal distinction between this area and sedimentary fold belts such as those found in the eastern United States. Strong intra-regional variations in vegetation cover were also tentatively identified for the Oregon test site.

Portable open-path chemical sensor using a quantum cascade laser

NASA Astrophysics Data System (ADS)

Corrigan, Paul; Lwin, Maung; Huntley, Reuven; Chhabra, Amandeep; Moshary, Fred; Gross, Barry; Ahmed, Samir

2009-05-01

Remote sensing of enemy installations or their movements by trace gas detection is a critical but challenging military objective. Open path measurements over ranges of a few meters to many kilometers with sensitivity in the parts per million or billion regime are crucial in anticipating the presence of a threat. Previous approaches to detect ground level chemical plumes, explosive constituents, or combustion have relied on low-resolution, short range Fourier transform infrared spectrometer (FTIR), or low-sensitivity near-infrared differential optical absorption spectroscopy (DOAS). As mid-infrared quantum cascade laser (QCL) sources have improved in cost and performance, systems based on QCL's that can be tailored to monitor multiple chemical species in real time are becoming a viable alternative. We present the design of a portable, high-resolution, multi-kilometer open path trace gas sensor based on QCL technology. Using a tunable (1045-1047cm-1) QCL, a modeled atmosphere and link-budget analysis with commercial component specifications, we show that with this approach, accuracy in parts per billion ozone or ammonia can be obtained in seconds at path lengths up to 10 km. We have assembled an open-path QCL sensor based on this theoretical approach at City College of New York, and we present preliminary results demonstrating the potential of QCLs in open-path sensing applications.

Cascades and Dissipative Anomalies in Relativistic Fluid Turbulence

NASA Astrophysics Data System (ADS)

Eyink, Gregory L.; Drivas, Theodore D.

2018-02-01

We develop a first-principles theory of relativistic fluid turbulence at high Reynolds and Péclet numbers. We follow an exact approach pioneered by Onsager, which we explain as a nonperturbative application of the principle of renormalization-group invariance. We obtain results very similar to those for nonrelativistic turbulence, with hydrodynamic fields in the inertial range described as distributional or "coarse-grained" solutions of the relativistic Euler equations. These solutions do not, however, satisfy the naive conservation laws of smooth Euler solutions but are afflicted with dissipative anomalies in the balance equations of internal energy and entropy. The anomalies are shown to be possible by exactly two mechanisms, local cascade and pressure-work defect. We derive "4 /5 th-law" type expressions for the anomalies, which allow us to characterize the singularities (structure-function scaling exponents) required for their not vanishing. We also investigate the Lorentz covariance of the inertial-range fluxes, which we find to be broken by our coarse-graining regularization but which is restored in the limit where the regularization is removed, similar to relativistic lattice quantum field theory. In the formal limit as speed of light goes to infinity, we recover the results of previous nonrelativistic theory. In particular, anomalous heat input to relativistic internal energy coincides in that limit with anomalous dissipation of nonrelativistic kinetic energy.