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Sample records for mp3-de miksimiseks ka

  1. Ka-band study: 1988

    NASA Technical Reports Server (NTRS)

    Layland, J. W.; Horttor, R. L.; Clauss, R. C.; Wilcher, J. H.; Wallace, R. J.; Mudgway, D. J.

    1989-01-01

    The Ka-band study team was chartered in late 1987 to bring together all the planning elements for establishing 32 GHz (Ka-band) as the primary downlink frequency for deep-space operation, and to provide a stable baseline from which to pursue that development. This article summarizes the results of that study at its conclusion in mid-1988, and corresponds to material presented to NASA's Office of Space Operations on July 14, 1988. For a variety of reasons, Ka-band is the right next major step in deep-space communications. It offers improved radio metric accuracy through reduced plasma sensitivity and increased bandwidth. Because of these improvements, it offers the opportunity to reduce costs in the flight radio system or in the DSN by allocating part of the overall benefits of Ka-band to this cost reduction. A mission scenario is being planned that can drive at least two and possibly all three of the DSN subnets to provide a Ka-band downlink capability by the turn of the century. The implementation scenario devised by the study team is believed to be feasible within reasonable resource expectations, and capable of providing the needed upgrade as a natural follow-on to the technology development which is already underway.

  2. Benchmarking pKa prediction

    PubMed Central

    Davies, Matthew N; Toseland, Christopher P; Moss, David S; Flower, Darren R

    2006-01-01

    Background pKa values are a measure of the protonation of ionizable groups in proteins. Ionizable groups are involved in intra-protein, protein-solvent and protein-ligand interactions as well as solubility, protein folding and catalytic activity. The pKa shift of a group from its intrinsic value is determined by the perturbation of the residue by the environment and can be calculated from three-dimensional structural data. Results Here we use a large dataset of experimentally-determined pKas to analyse the performance of different prediction techniques. Our work provides a benchmark of available software implementations: MCCE, MEAD, PROPKA and UHBD. Combinatorial and regression analysis is also used in an attempt to find a consensus approach towards pKa prediction. The tendency of individual programs to over- or underpredict the pKa value is related to the underlying methodology of the individual programs. Conclusion Overall, PROPKA is more accurate than the other three programs. Key to developing accurate predictive software will be a complete sampling of conformations accessible to protein structures. PMID:16749919

  3. Ka-band MMIC subarray technology program (Ka-Mist)

    NASA Technical Reports Server (NTRS)

    Pottenger, Warren

    1995-01-01

    The broad objective of this program was to demonstrate a proof of concept insertion of Monolithic Microwave Integrated Circuit (MMIC) device technology into an innovative (tile architecture) active phased array antenna application supporting advanced EHF communication systems. Ka-band MMIC arrays have long been considered as having high potential for increasing the capability of space, aircraft, and land mobile communication systems in terms of scan performance, data rate, link margin, and flexibility while offering a significant reduction in size, weight, and power consumption. Insertion of MMIC technology into antenna systems, particularly at millimeter wave frequencies using low power and low noise amplifiers in close proximity to the radiating elements, offers a significant improvement in the array transmit efficiency, receive system noise figure, and overall array reliability. Application of active array technology also leads to the use of advanced beamforming techniques that can improve beam agility, diversity, and adaptivity to complex signal environments.

  4. Ka-band MMIC subarray technology program (Ka-Mist)

    NASA Astrophysics Data System (ADS)

    Pottenger, Warren

    1995-06-01

    The broad objective of this program was to demonstrate a proof of concept insertion of Monolithic Microwave Integrated Circuit (MMIC) device technology into an innovative (tile architecture) active phased array antenna application supporting advanced EHF communication systems. Ka-band MMIC arrays have long been considered as having high potential for increasing the capability of space, aircraft, and land mobile communication systems in terms of scan performance, data rate, link margin, and flexibility while offering a significant reduction in size, weight, and power consumption. Insertion of MMIC technology into antenna systems, particularly at millimeter wave frequencies using low power and low noise amplifiers in close proximity to the radiating elements, offers a significant improvement in the array transmit efficiency, receive system noise figure, and overall array reliability. Application of active array technology also leads to the use of advanced beamforming techniques that can improve beam agility, diversity, and adaptivity to complex signal environments.

  5. KaVA ESTEMA project

    NASA Astrophysics Data System (ADS)

    Oyadomari, Miyako; Imai, Hiroshi; Cho, Se-Hyung; Asaki, Yoshiharu; Choi, Yoon-Kyong; Kim, Jaeheon; Yun, Youngjoo; Matsumoto, Naoko; Min, Cheul-Hong; Oyama, Tomoaki; Yoon, Sung-Chul; Yoon, Dong-Hwan; Kim, Dong-Jin; Dodson, Richard; Rioja, Maria; Burns, Ross; Orosz, Gabor; Nakagawa, Akiharu; Chibueze O, James; Nakashima, Jun-ichi; Sobolev, Andrey

    2016-07-01

    The ESTEMA (Expanded Study on Stellar Masers) project is one of three Large Programs of the KaVA (the combined array of the Korean VLBI Network and Japanese VLBI Exploration of Radio Astrometry), and conducted in 2015-2016. It aims to publish a database of the largest sample of VLBI images of circumstellar water (H2O) and silicon-monoxide (SiO) maser sources towards circumstellar envelopes (CSEs) of 80 evolved stars in late AGB to early post-AGB phase. Here we present the specifications of the ESTEMA observations and the planned scientific goals in order to share the basic information of the ESTEMA with astronomical community and encourage future collaborations with the ESTEMA and future follow-up observations for the targeted stars.

  6. SARAL/AltiKa Project Overview

    NASA Astrophysics Data System (ADS)

    Picot, Nicolas; Sengenes, Pierre; Lambin, Juliette; Noubel, Jocelyne; Mazeau, Sophie; Verron, Jacques

    2015-04-01

    The SARAL-AltiKa satellite mission is an India-France ISRO-CNES joint project. The satellite has been put into orbit by a PSLV vehicle supplied by ISRO, and launched from Sriharikota, the main ISRO launch base, on Feb. 25, 2013. The SARAL (Satellite for ARgos and ALtika) payload consists of an ARGOS instrument, and an altimetry payload including the AltiKa radiometer-altimeter. SARAL/AltiKa is intended to be a gap filler mission between the RA-2 on-board ENVISAT and Sentinel-3. As such, SARAL/AltiKa is flying on the same orbit as ENVISAT. The special feature of SARAL/AltiKa is mainly related to a wideband Ka-band altimeter (35.75 GHz, 500 MHz), which is the very first satellite altimeter dedicated to oceanography to operate at such a high frequency. The AltiKa instrument consists in a Ka-band altimeter based on already developed subsystems inherited from Siral (CRYOSAT) and Poseidon-3 (JASON-2) in particular, and an embedded dual frequency radiometer. The altimeter and the radiometer share the same antenna. Due to the single frequency Ka-band altimeter, the enhanced bandwidth leads to a better vertical resolution. The spatial resolution is also improved, thanks to the Ka-band smaller footprint and the increased PRF. This talk will present the main characteristics of the mission and the main outcome regarding the data availability and overall quality after 2 years of mission. In particular, we will focus on the main advantages and/or drawbacks of the Ka band frequency compared to the classical Ku band used on other missions like Jason-2. A specific point will be performed on the rain attenuation and corresponding impacts on the altimeter data quality.

  7. Ka-Band MMIC Subarray Technology Program (Ka-Mist)

    NASA Technical Reports Server (NTRS)

    Pottinger, W.

    1995-01-01

    Ka-band monolithic microwave integrated circuit (MMIC) arrays have been considered as having high potential for increasing the capability of space, aircraft, and land mobile communication systems in terms of scan performance, data rate, link margin, and flexibility while offering a significant reduction in size, weight, and power consumption. Insertion of MMIC technology into antenna systems, particularly at millimeter wave frequencies using low power and low noise amplifiers in closed proximity to the radiating elements, offers a significant improvement in the array transmit efficiency, receive system noise figure, and overall array reliability. Application of active array technology also leads to the use of advanced beamforming techniques that can improve beam agility, diversity, and adaptivity to complex signal environments. The objective of this program was to demonstrate the technical feasibility of the 'tile' array packaging architecture at EHF via the insertion of 1990 MMIC technology into a functional tile array or subarray module. The means test of this objective was to demonstrate and deliver to NASA a minimum of two 4 x 4 (16 radiating element) subarray modules operating in a transmit mode at 29.6 GHz. Available (1990) MMIC technology was chosen to focus the program effort on the novel interconnect schemes and packaging requirements rather than focusing on MMIC development. Major technical achievements of this program include the successful integration of two 4 x 4 subarray modules into a single antenna array. This 32 element array demonstrates a transmit EIRP of over 300 watts yielding an effective directive power gain in excess of 55 dB at 29.63 GHz. The array has been actively used as the transmit link in airborne/terrestrial mobile communication experiments accomplished via the ACTS satellite launched in August 1993.

  8. Ka-band MMIC subarray technology program (Ka-Mist)

    NASA Astrophysics Data System (ADS)

    Pottinger, W.

    1995-09-01

    Ka-band monolithic microwave integrated circuit (MMIC) arrays have been considered as having high potential for increasing the capability of space, aircraft, and land mobile communication systems in terms of scan performance, data rate, link margin, and flexibility while offering a significant reduction in size, weight, and power consumption. Insertion of MMIC technology into antenna systems, particularly at millimeter wave frequencies using low power and low noise amplifiers in closed proximity to the radiating elements, offers a significant improvement in the array transmit efficiency, receive system noise figure, and overall array reliability. Application of active array technology also leads to the use of advanced beamforming techniques that can improve beam agility, diversity, and adaptivity to complex signal environments. The objective of this program was to demonstrate the technical feasibility of the 'tile' array packaging architecture at EHF via the insertion of 1990 MMIC technology into a functional tile array or subarray module. The means test of this objective was to demonstrate and deliver to NASA a minimum of two 4 x 4 (16 radiating element) subarray modules operating in a transmit mode at 29.6 GHz. Available (1990) MMIC technology was chosen to focus the program effort on the novel interconnect schemes and packaging requirements rather than focusing on MMIC development. Major technical achievements of this program include the successful integration of two 4 x 4 subarray modules into a single antenna array. This 32 element array demonstrates a transmit EIRP of over 300 watts yielding an effective directive power gain in excess of 55 dB at 29.63 GHz. The array has been actively used as the transmit link in airborne/terrestrial mobile communication experiments accomplished via the ACTS satellite launched in August 1993.

  9. The Asteroid 2015 KA122

    NASA Astrophysics Data System (ADS)

    Vodniza, Alberto Quijano; Pereira, Mario Rojas

    2015-11-01

    The Asteroid “2015 KA122” was discovered on May 25/2015 by the Catalina Sky Survey. This object is not well known. Its absolute magnitude, of 23.2, indicates a diameter of about 70 meters. The asteroid was at aproximately 3.3 lunar distances from the Earth, on June 6/2015. It has an orbital period of 2.11 years. From our Observatory, located in Pasto-Colombia, we captured several pictures, videos and astrometry data during three days. Our data was published by the Minor Planet Center (MPC) and also appears at the web page of NEODyS. Our observatory’s code at the MPC is “H78”. Pictures of the asteroid were captured with the following equipment: 14” LX200 GPS MEADE (f/10 Schmidt-Cassegrain Telescope) and STL-1001 SBIG camera. Astrometry was carried out, and we calculated the orbital elements. We obtained the following orbital parameters: eccentricity = 0.4089630 +/- 0.00189, semi-major axis = 1.64254884 +/- 0.00505 A.U, orbital inclination = 12.68490 +/- 0.039 deg, longitude of the ascending node = 73.14715 +/- 0.0013 deg, argument of perihelion = 214.82393 +/- 0.007 deg, orbital period = 2.11 years (768.90 days), mean motion = 0.46819485 +/- 0.00216 deg/d, perihelion distance = 0.97080706 +/- 0.000119 A.U, aphelion distance = 2.31429061 +/- 0.0103 A.U. The parameters were calculated based on 81 observations (2015 June 3-5) with mean residual = 0.343 arcseconds. Our videos appear in the following links:http://spaceweathergallery.com/indiv_upload.php?upload_id=113197http://spaceweathergallery.com/indiv_upload.php?upload_id=113238&PHPSESSID=f2lkigjogsfgcmi1rscc9jil36http://spaceweathergallery.com/indiv_upload.php?upload_id=113257

  10. AltiKa in-flight performances

    NASA Astrophysics Data System (ADS)

    Boy, Francois; Desjonquères, Jean-Damien; Steunou, Nathalie

    2015-04-01

    The SARAL/AltiKa satellite has been launched the 25th of February 2013 from the launch pad of Sriharikota (India). Since this date, AltiKa provides measurements and affords the first altimetry results in Ka band. This paper recalls the instrument design and assesses the in-flight performance. The SARAL/AltiKa mission has been developed in the frame of a cooperation between CNES (French Space Agency) and ISRO (Indian Space Research Organization). AltiKa is a single frequency Ka-band altimeter with a bi-frequency radiometer embedded. Both altimeter and radiometer share the same antenna. Altimeter expertise and routine calibrations performed during assessment phase demonstrate the stability of the instrument. Moreover the performance assessed over ocean are noteworthy such as 0.9 cm on epoch 1 Hz noise for 2 m of SWH, which is fully consistent with simulations and ground pre-flight tests results. The data availability is also very good and very few altimeter measurements are lost due to rain attenuation. Radiometer data analysis shows that the instrument is very stable and its performances are consistent with pre-flight tests results.

  11. A Prototype Ka-/Ka-Band Dichroic Plate With Stepped Rectangular Apertures

    NASA Technical Reports Server (NTRS)

    Chen, J. C.; Stanton, P. H.; Reilly, H. F., Jr.

    1996-01-01

    A prototype five-layer Ka-/Ka-band dichroic plate was fabricated and measured. This dichroic plate was designed to pass Ka-band uplink (34.2-34.7 GHz) and to reflect Ka-band downlink (31.8-32.3 GHz) for dual-frequency operation in the Deep Space Network to support the future Cassini mission. The theoretical calculation and the experimental measurement of the reflected resonant frequencies were within 0.24 percent for circular polarization. The computer program, which was used to design the dichroic plate with stepped apertures, was then verified.

  12. A prototype Ka-/Ka-band dichroic plate with stepped rectangular apertures

    NASA Technical Reports Server (NTRS)

    Chen, J. C.; Stanton, P. H.; Reilly, H. F., Jr.

    1996-01-01

    A prototype five-layer Ka-/Ka-band dichroic plate was fabricated and measured. This dichroic plate was designed to pass Ka-band uplink (34.2-34.7 GHz) and to reflect Ka-band downlink (31.8-32.3 GHz) for dual-frequency operation in the Deep Space Network to support the future Cassini mission. The theoretical calculation and the experimental measurement of the reflected resonant frequencies were within 0.24 percent for circular polarization. The computer program, which was used to design the dichroic plate with stepped apertures, was then verified.

  13. Arginine: Its pKa value revisited

    PubMed Central

    Fitch, Carolyn A; Platzer, Gerald; Okon, Mark; Garcia-Moreno E, Bertrand; McIntosh, Lawrence P

    2015-01-01

    Using complementary approaches of potentiometry and NMR spectroscopy, we have determined that the equilibrium acid dissociation constant (pKa value) of the arginine guanidinium group is 13.8 ± 0.1. This is substantially higher than that of ∼12 often used in structure-based electrostatics calculations and cited in biochemistry textbooks. The revised intrinsic pKa value helps explains why arginine side chains in proteins are always predominantly charged, even at pH values as great as 10. The high pKa value also reinforces the observation that arginine side chains are invariably protonated under physiological conditions of near neutral pH. This occurs even when the guanidinium moiety is buried in a hydrophobic micro-environment, such as that inside a protein or a lipid membrane, thought to be incompatible with the presence of a charged group. PMID:25808204

  14. Arginine: Its pKa value revisited.

    PubMed

    Fitch, Carolyn A; Platzer, Gerald; Okon, Mark; Garcia-Moreno, Bertrand E; McIntosh, Lawrence P

    2015-05-01

    Using complementary approaches of potentiometry and NMR spectroscopy, we have determined that the equilibrium acid dissociation constant (pKa value) of the arginine guanidinium group is 13.8 ± 0.1. This is substantially higher than that of ∼ 12 often used in structure-based electrostatics calculations and cited in biochemistry textbooks. The revised intrinsic pKa value helps explains why arginine side chains in proteins are always predominantly charged, even at pH values as great as 10. The high pKa value also reinforces the observation that arginine side chains are invariably protonated under physiological conditions of near neutral pH. This occurs even when the guanidinium moiety is buried in a hydrophobic micro-environment, such as that inside a protein or a lipid membrane, thought to be incompatible with the presence of a charged group.

  15. K/Ka-Band Aeronautical Experiments

    NASA Technical Reports Server (NTRS)

    Agan, Martin J.; Connally, Michael J.; Jedrey, Thomas C.

    1997-01-01

    This paper discusses a series of aeronautical experiments that utilize the Advanced Communication Technology Satellite (ACTS) Broadband Aeronautical Terminal (BAT). These experiments were designed to explore the uses of K and Ka-band for aeronautical applications. Planned experiments are also discussed.

  16. An Ka Bamanankan Kalan: Intermediate Bambara.

    ERIC Educational Resources Information Center

    Bird, Charles; Kante, Mamadou

    This textbook follows the third edition of "Introductory Bambara: An Ka Bamanankan Kalan", and is designed so that Bambara can be used almost exclusively in the classroom. Each of the twenty lessons has a culturally oriented topic and consists of a reading selection, drills on grammar and vocabulary list. The grammar notes are not…

  17. The Mars Global Surveyor Ka-Band Link Experiment (MGS/KaBLE-II)

    NASA Astrophysics Data System (ADS)

    Morabito, D.; Butman, S.; Shambayati, S.

    1999-01-01

    The Mars Global Surveyor (MGS) spacecraft, launched on November 7, 1996, carries an experimental space-to-ground telecommunications link at Ka-band (32 GHz) along with the primary X-band (8.4-GHz) downlink. The signals are simultaneously transmitted from a 1.5-m-diameter parabolic antenna on MGS and received by a beam-waveguide (BWG) research and development (R&D) 34-meter a ntenna located in NASA's Goldstone Deep Space Network (DSN) complex near Barstow, California. This Ka-band link experiment (KaBLE-II) allows the performances of the Ka-band and X-band signals to be compared under nearly identical conditions. The two signals have been regularly tracked during the past 2 years. This article presents carrier-signal-level data (P_c/N_o) for both X-band and Ka-band acquired over a wide range of station elevation angles, weather conditions, and solar elongation angles. The cruise phase of the mission covered the period from launch (November 7, 1996) to Mars orbit capture (September 12, 1997). Since September 12, 1997, MGS has been in orbit around Mars. The measurements confirm that Ka-band could increase data capacity by at least a factor of three (5 dB) as compared with X-band. During May 1998, the solar corona experiment, in which the effects of solar plasma on the X-band and Ka-band links were studied, was conducted. In addition, frequency and difference frequency (f_x - f_(Ka)/3.8), ranging, and telemetry data results are presented. MGS/KaBLE-II measured signal strengths (for 54 percent of the experiments conducted) that were in reasonable agreement with predicted values based on preflight knowledge, and frequency residuals that agreed between bands and whose statistics were consistent with expected noise sources. For passes in which measured signal strengths disagreed with predicted values, the problems were traced to known deficiencies, for example, equipment operating under certain conditions, such as a cold Ka-band solid-state power amplifier (SSPA

  18. Modulation transfer functions at Ka band

    NASA Astrophysics Data System (ADS)

    Hesany, Vahid; Sistani, Bita; Salam, Asif; Haimov, Samuel; Gogineni, Prasad; Moore, Richard K.

    The modulation transfer function (MTF) is often used to describe the modulation of the radar signal by the long waves. MTFs were measured at 35 GHz (Ka band) with a switched-beam vector slope gauge/scatterometer on the research platform NORDSEE as part of the SAXON-FPN experiment. Three independent measurements of the scattering were available for each height measurement. This provided the opportunity to average the time series to reduce the effects of fading noise and sea spikes, or, alternatively, to append the time series to achieve more degrees of freedom in the spectral estimates. For upwind measurements, the phase of the VV-polarized Ka-band MTF was always positive, which implies that the maximum of the radar return originates from the forward face of the long-scale waves. This phase increases with increasing wind speed. The magnitude of the MTF decreases with increasing wind speed.

  19. Mars Global Surveyor Ka-Band Link Experiment Results

    NASA Technical Reports Server (NTRS)

    Morabito, David

    1999-01-01

    This paper presents The Mars Global Surveyor Ka-Band Link Experimental Results in viewgraph form. Topics include: 1) Deep Space Ka-band Link Advantage; 2) Deep Space Ka-band Telecommunications; 3) Mars Global Surveyor (MGS) Signal Levels and Ka-band Top for Clear Weather Pass; 4) MGS Signal Levels and Ka-band Top for Rainy Weather Pass; 5) MGS Ka-band to X-band Link Advantage; and 6) Conclusion. A 6 to 8 dB link advantage can be realized by using Ka band (32 GHz) as a telecommunications link frequency in place of X-band (8.4 GHz). This link advantage was demonstrated using two years worth of Mars Global Surveyor simultaneous Ka/X data after correcting for known equipment deficiencies.

  20. Validation of GPM Ka-Radar Algorithm Using a Ground-based Ka-Radar System

    NASA Astrophysics Data System (ADS)

    Nakamura, Kenji; Kaneko, Yuki; Nakagawa, Katsuhiro; Furukawa, Kinji; Suzuki, Kenji

    2016-04-01

    GPM led by the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration of US (NASA) aims to observe global precipitation. The core satellite is equipped with a microwave radiometer (GMI) and a dual-frequency radar (DPR) which is the first spaceborne Ku/Ka-band dual-wavelength radar dedicated for precipitation measurement. In the DPR algorithm, measured radar reflectivity is converted to effective radar reflectivity by estimating the rain attenuation. Here, the scattering/attenuation characteristics of Ka-band radiowaves are crucial, particularly for wet snow. A melting layer observation using a dual Ka-band radar system developed by JAXA was conducted along the slope of Mt. Zao in Yamagata Prefecture, Japan. The dual Ka-band radar system consists of two nearly identical Ka-band FM-CW radars, and the precipitation systems between two radars were observed in opposite directions. From this experiment, equivalent radar reflectivity (Ze) and specific attenuation (k) were obtained. The experiments were conducted for two winter seasons. During the data analyses, it was found that k estimate easily fluctuates because the estimate is based on double difference calculation. With much temporal and spatial averaging, k-Ze relationship was obtained for melting layers. One of the results is that the height of the peak of k seems slightly higher than that of Ze. The results are compared with in-situ precipitation particle measurements.

  1. High-power Ka-band amplifier

    NASA Technical Reports Server (NTRS)

    Cormier, R.

    1993-01-01

    Development of a high-power tube suitable to power a Ka-band (34.5-GHz) antenna transmitter located at the Goldstone, California, tracking station is continuing. The University of Maryland Laboratory for Plasma Research and JPL are conducting a joint effort to test the feasibility of phase locking a second-harmonic gyrotron both by direct injection at the output cavity and by using a priming cavity to bunch the electrons in the beam. This article describes several design options and the results of computer simulation testing.

  2. Last Major Ice Collapse (17ka - 16ka) of the Anchorage Lowland, Alaska

    NASA Astrophysics Data System (ADS)

    Kopczynski, S. B.; Lowell, T.; Evenson, E. B.

    2009-12-01

    This research presents evidence describing the final ice collapse of the Anchorage Lowland of the Upper Cook Inlet, Alaska. A field research effort conducted with Richard Reger and the author analyzed over 14,000 drift pebble provenance samples to distinguish flow paths of this ice lobe composed of a twinned terrestrial glacier and tidewater glacier. Terrain geomorphological interpretations, 14 new basal lake radiocarbon ages, and a suite of previously collected radiocarbon ages are brought to bear to bracket ice retreat chronology. We interpret our evidence to argue that the Matanuska-Knik Lobe retreated between 16ka and 17ka by a coupled calving margin and ice stagnation collapse. The oldest age in the lowland is a basal age of 16.4ka collected on the Knik portion of the Elmendorf Moraine. Basal ages 140km away near the modern Matanuska Terminus indicate ice retreated to this position by 14.5ka. Two large esker swarms along the Matanuska route suggest evidence for a two phased terrestrial retreat. The Anchorage lowland retreat started well before the Bolling warming, though radiocarbon data and esker-swarm patterns suggest evidence for a two stepped retreat, with the second faster phase occurring during the Bolling. We find it curious that the onset of Anchorage Lowland ice retreat falls within the mystery interval and is concordant with retreat patterns at the Puget Lowland and the Des Moines Lobe.

  3. p Ka calculation of poliprotic acid: histamine

    NASA Astrophysics Data System (ADS)

    De Abreu, Heitor A.; De Almeida, Wagner B.; Duarte, Hélio A.

    2004-01-01

    Various theoretical studies have been reported addressing the performance of solvation models available to estimate p Ka values. However, no attention has been paid so far to the role played by the electronic, thermal and solvation energy individual contributions to the Gibbs free energy of the deprotonation process. In this work, we decompose the total Gibbs free energy into three distinct terms and then evaluate the dependence of each contribution on the level of theory employed for its determination using different levels of theory. The three possible p Kas of histamine have been estimated and compared with available experimental data. We found that the electronic energy term is sensitive to the level of theory and basis set, and, therefore, could be also a source of error in the theoretical calculation of p Kas.

  4. Aeronautical applications of steerable K/Ka-band antennas

    NASA Technical Reports Server (NTRS)

    Helmken, Henry; Prather, Horton

    1995-01-01

    The expected growth of wideband data and video transmission via satellite will press existing satellite Ku-band services and push development of the Ka-band region. Isolated ground based K/Ka-band terminals can experience severe fading due to rain and weather phenomena. However, since aircraft generally fly above the severe weather, they are attractive platforms for developing commercial K/Ka-band communication links.

  5. Study of sea ice regions using AltiKa measurements

    NASA Astrophysics Data System (ADS)

    Poisson, Jean-Christophe; Thibaut, Pierre; Hoang, Duc; Boy, François; Guillot, Amandine; Picot, Nicolas

    2015-04-01

    Since the launch of the SARAL/AltiKa mission on February 25th, 2013, altimeter measurements of excellent quality are acquired all over the globe for the first time in Ka-band. One of the main benefits of the Ka-band is to have a very low penetration length in the ice (unlike the Ku-band historically used by previous altimetry missions), which allows to significantly reduce measurements uncertainties of the sea ice topography. Flying on the Envisat orbit and providing measurements at 40 Hz, the exploitation of AltiKa waveforms on sea ice is of great interest. Sea ice covered regions are characterized by a large number of different surfaces with a multitude of backscattering properties rapidly evolving with time. Thanks to the high resolution and precision of the AltiKa measurements, backscattering properties from each of these surfaces (first year ice, multiyear ice, fast ice, leads, polynyas, etc. …) can be observed through rapid changes of the returned echo shape. In the framework of the PEACHI project (Prototype for Expertise on AltiKa, for Coastal, Hydrology and Ice funded by CNES) which aims at analyzing and improving AltiKa measurements, a waveform processing based on an altimeter echo classification is developed and performed on all available AltiKa data in the Arctic ocean. Through this processing a study is conducted on the the evolution of the sea ice cover observed in Ka-band.

  6. Elucidating the Conformational Dependence of Calculated pKa Values.

    PubMed

    Livesay, Dennis R; Jacobs, Donald J; Kanjanapangka, Julie; Chea, Eric; Cortez, Hector; Garcia, Jorge; Kidd, Patrick; Marquez, Mario Pulido; Pande, Swati; Yang, David

    2006-07-01

    The variability within calculated protein residue pKa values calculated using Poisson-Boltzmann continuum theory with respect to small conformational fluctuations is investigated. As a general rule, sites buried in the protein core have the largest pKa fluctuations but the least amount of conformational variability; conversely, sites on the protein surface generally have large conformational fluctuations but very small pKa fluctuations. These results occur because of the heterogeneous or uniform nature of the electrostatic microenvironments at the protein core or surface, respectively. Atypical surface sites with large pKa fluctuations occur at the interfaces between significant anionic and cationic potentials.

  7. DARHT 2 kA Cathode Development

    SciTech Connect

    Henestroza, E.; Houck, T.; Kwan, J.W.; Leitner, M.; Miram, G.; Prichard, B.; Roy, P.K.; Waldron, W.; Westenskow, G.; Yu, S.; Bieniosek, F.M.

    2009-03-09

    In the campaign to achieve 2 kA of electron beam current, we have made several changes to the DARHT-II injector during 2006-2007. These changes resulted in a significant increase in the beam current, achieving the 2 kA milestone. Until recently (before 2007), the maximum beam current that was produced from the 6.5-inch diameter (612M) cathode was about 1300 A when the cathode was operating at a maximum temperature of 1140 C. At this temperature level, the heat loss was dominated by radiation which is proportional to temperature to the fourth power. The maximum operating temperature was limited by the damage threshold of the potted filament and the capacity of the filament heater power supply, as well as the shortening of the cathode life time. There were also signs of overheating at other components in the cathode assembly. Thus it was clear that our approach to increase beam current could not be simply trying to run at a higher temperature and the preferred way was to operate with a cathode that has a lower work function. The dispenser cathode initially used was the type 612M made by SpectraMat. According to the manufacturer's bulletin, this cathode should be able to produce more than 10 A/cm{sup 2} of current density (corresponding to 2 kA of total beam current) at our operating conditions. Instead the measured emission (space charge limited) was 6 A/cm{sup 2}. The result was similar even after we had revised the activation and handling procedures to adhere more closely to the recommend steps (taking longer time and nonstop to do the out-gassing). Vacuum was a major concern in considering the cathode's performance. Although the vacuum gauges at the injector vessel indicated 10{sup -8} Torr, the actual vacuum condition near the cathode in the central region of the vessel, where there might be significant out-gassing from the heater region, was never determined. Poor vacuum at the surface of the cathode degraded the emission (by raising the work function value). We

  8. Assigning the pKa's of Polyprotic Acids.

    ERIC Educational Resources Information Center

    Bodner, George M.

    1986-01-01

    Discusses (1) polyproptic acids for which the difference between K-a's is large; (2) the Henderson-Hasselbach equation; (3) polyprotic acids for which the difference between K-a's is small; (4) analysis of microscopic dissociation constants for cysteine; and (5) analysis of pK-a data. (JN)

  9. Assigning the pKa's of Polyprotic Acids.

    ERIC Educational Resources Information Center

    Bodner, George M.

    1986-01-01

    Discusses (1) polyproptic acids for which the difference between K-a's is large; (2) the Henderson-Hasselbach equation; (3) polyprotic acids for which the difference between K-a's is small; (4) analysis of microscopic dissociation constants for cysteine; and (5) analysis of pK-a data. (JN)

  10. Ka-Band Autonomous Formation Flying Sensor

    NASA Technical Reports Server (NTRS)

    Tien, Jeffrey; Purcell, George, Jr.; Srinivasan, Jeffrey; Ciminera, Michael; Srinivasan, Meera; Meehan, Thomas; Young, Lawrence; Aung, MiMi; Amaro, Luis; Chong, Yong; Quirk, Kevin

    2004-01-01

    Ka-band integrated range and bearing-angle formation sensor called the Autonomous Formation Flying (AFF) Sensor has been developed to enable deep-space formation flying of multiple spacecraft. The AFF Sensor concept is similar to that of the Global Positioning System (GPS), but the AFF Sensor would not use the GPS. The AFF Sensor would reside in radio transceivers and signal-processing subsystems aboard the formation-flying spacecraft. A version of the AFF Sensor has been developed for initial application to the two-spacecraft StarLight optical-interferometry mission, and several design investigations have been performed. From the prototype development, it has been concluded that the AFF Sensor can be expected to measure distances and directions with standard deviations of 2 cm and 1 arc minute, respectively, for spacecraft separations ranging up to about 1 km. It has also been concluded that it is necessary to optimize performance of the overall mission through design trade-offs among the performance of the AFF Sensor, the field of view of the AFF Sensor, the designs of the spacecraft and the scientific instruments that they will carry, the spacecraft maneuvers required for formation flying, and the design of a formation-control system.

  11. Dating loess up to 800 ka by thermoluminescence

    SciTech Connect

    Berger, G.W. ); Pillans, B.J. ); Palmer, A.S. )

    1992-05-01

    Thermoluminescence (TL) ages agreeing with expected ages have been obtained for 13 loess samples spanning the age range from 20 to 800 ka. The authors samples are from Alaska and North Island, New Zealand, and are unusual in TL dating studies of loess older than 80-100 ka by having independent age assignments that are generally well constrained, from ages of associated tephra beds. With the polymineral fine-silt-sized (4-11 {mu}m) grains the partial-bleach TL technique yielded expected ages up to about 350 ka, whereas the total-bleach method gave accurate ages in the range 100 to 800 ka. Thus, the much disputed upper age limit of 100-150 ka for the TL dating of loess now appears to be sample and worker dependent, rather than a global property of the TL signals in the TL-dominant feldspars.

  12. On the development of protein pKa calculation algorithms

    SciTech Connect

    Carstensen, Tommy; Farrell, Damien; Huang, Yong; Baker, Nathan A.; Nielsen, Jens E.

    2011-12-01

    Protein pKa calculation algorithms are typically developed to reproduce experimental pKa values and provide us with a better understanding of the fundamental importance of electrostatics for protein structure and function. However, the approximations and adjustable parameters employed in almost all pKa calculation methods means that there is the risk that pKa calculation algorithms are 'over-fitted' to the available datasets, and that these methods therefore do not model protein physics realistically. We employ simulations of the protein pKa calculation algorithm development process to show that careful optimization procedures and non-biased experimental datasets must be applied to ensure a realistic description of the underlying physical terms. We furthermore investigate the effect of experimental noise and find a significant effect on the pKa calculation algorithm optimization landscape. Finally, we comment on strategies for ensuring the physical realism of protein pKa calculation algorithms and we assess the overall state of the field with a view to predicting future directions of development.

  13. NASA SCaN Overview and Ka-Band Actvities

    NASA Technical Reports Server (NTRS)

    Stegeman, James D.; Midon, Marco Mario; Davarian, Faramaz; Geldzahler, Barry

    2014-01-01

    The Ka- and Broadband Communications Conference is an international forum attended by worldwide experts in the area of Ka-Band Propagation and satellite communications. Since its inception, NASA has taken the initiative of organizing and leading technical sections on RF Propagation and satellite communications, solidifying its worldwide leadership in the aforementioned areas. Consequently, participation in this conference through the contributions described below will maintain NASA leadership in Ka- and above RF Propagation as it relates to enhancing current and future satellite communication systems supporting space exploration.

  14. Onboard Interferometric SAR Processor for the Ka-Band Radar Interferometer (KaRIn)

    NASA Technical Reports Server (NTRS)

    Esteban-Fernandez, Daniel; Rodriquez, Ernesto; Peral, Eva; Clark, Duane I.; Wu, Xiaoqing

    2011-01-01

    An interferometric synthetic aperture radar (SAR) onboard processor concept and algorithm has been developed for the Ka-band radar interferometer (KaRIn) instrument on the Surface and Ocean Topography (SWOT) mission. This is a mission- critical subsystem that will perform interferometric SAR processing and multi-look averaging over the oceans to decrease the data rate by three orders of magnitude, and therefore enable the downlink of the radar data to the ground. The onboard processor performs demodulation, range compression, coregistration, and re-sampling, and forms nine azimuth squinted beams. For each of them, an interferogram is generated, including common-band spectral filtering to improve correlation, followed by averaging to the final 1 1-km ground resolution pixel. The onboard processor has been prototyped on a custom FPGA-based cPCI board, which will be part of the radar s digital subsystem. The level of complexity of this technology, dictated by the implementation of interferometric SAR processing at high resolution, the extremely tight level of accuracy required, and its implementation on FPGAs are unprecedented at the time of this reporting for an onboard processor for flight applications.

  15. Accumulation rates from 38 ka and 160 ka radio-echo sounding horizons in East Antarctica

    NASA Astrophysics Data System (ADS)

    Winter, Anna; Steinhage, Daniel; Creyts, Timothy; Eisen, Olaf

    2017-04-01

    The internal layering architecture of ice sheets, as detected with radio-echo sounding (RES), contains clues to past ice-flow dynamics and mass balance and supplies flow models with starting and boundary conditions. In comparison to the Greenland Ice Sheet, the coverage of the East Antarctic Ice Sheet with information on internal ice structure is still sparse. This hampers the constraining or initialization of ice-flow models with geometry and surface mass balance data in adequate resolution. We traced two RES horizons, 38 ka and 160 ka, over great parts and in the most remote areas of the East Antarctic Ice Sheet. We dated the horizons at the EPICA Dome C Ice Core and followed them along RES lines of the Alfred Wegener Institute to Vostok and Dome A. There, they could be connected to the RES grid, covering the Gamburtsev mountains, that was collected as part of the AGAP (Antarctica's Gamburtsev Province) project, and continued to South Pole. From this widespread age-depth distribution we reconstruct mean accumulation rates and analyze spatial variations in surface mass balance, as well as differences between the two time periods.

  16. Mars Telecommunications Orbiter Ka-band system design and operations

    NASA Technical Reports Server (NTRS)

    Noreen, Gary; Komarek, Tomas; Diehl, Roger; Shambayati, Shervin; Breidenthal, Julian; Lopez, Saturnino; Jordan, Frank

    2003-01-01

    NASA's Mars Telecommunications Orbiter (MTO) will relay broadband communications from landers, rovers and spacecraft in the vicinity of Mars to Earth. This paper describes the MTO communications system and how the MTO Ka-band system will be operated.

  17. Deep space propagation experiments at Ka-band

    NASA Technical Reports Server (NTRS)

    Butman, Stanley A.

    1990-01-01

    Propagation experiments as essential components of the general plan to develop an operational deep space telecommunications and navigation capability at Ka-band (32 to 35 GHz) by the end of the 20th century are discussed. Significant benefits of Ka-band over the current deep space standard X-band (8.4 GHz) are an improvement of 4 to 10 dB in telemetry capacity and a similar increase in radio navigation accuracy. Propagation experiments are planned on the Mars Observer Mission in 1992 in preparation for the Cassini Mission to Saturn in 1996, which will use Ka-band in the search for gravity waves as well as to enhance telemetry and navigation at Saturn in 2002. Subsequent uses of Ka-band are planned for the Solar Probe Mission and the Mars Program.

  18. The Mars Observer Ka-band link experiment

    NASA Technical Reports Server (NTRS)

    Rebold, T. A.; Kwok, A.; Wood, G. E.; Butman, S.

    1994-01-01

    The Ka-Band Link Experiment was the first demonstration of a deep-space communications link in the 32- to 35-GHz band (Ka-band). It was carried out using the Mars Observer spacecraft while the spacecraft was in the cruise phase of its mission and using a 34-meter beam-waveguide research and development antenna at the Goldstone complex of the DSN. The DSN has been investigating the performance benefits of a shift from X-band (8.4 GHz) to Ka-band (32 GHz) for deep-space communications. The fourfold increase in frequency is expected to offer a factor of 3 to 10 improvement (5 to 10 dB) in signal strength for a given spacecraft transmitter power and antenna size. Until recently, the expected benefits were based on performance studies, with an eye to implementing such a link, but theory was transformed to reality when a 33.7-GHz Ka-band signal was received from the spacecraft by DSS 13. This article describes the design and implementation of the Ka-Band Link Experiment from the spacecraft to the DSS-13 system, as well as results from the Ka-band telemetry demonstration, ranging demonstration, and long-term tracking experiment. Finally, a preliminary analysis of comparative X- and Ka-band tracking results is included. These results show a 4- to 7-dB advantage for Ka-band using the system at DSS 13, assuming such obstacles as antenna pointing loss and power conversion loss are overcome.

  19. An 85-ka Paleoclimate Record From Lowland Central America

    NASA Astrophysics Data System (ADS)

    Escobar, J.; Hodell, D. A.; Anselmetti, F. S.; Ariztegui, D.; Brenner, M.; Curtis, J. H.; Gilli, A.; Grzesik, D. A.; Guilderson, T. J.; Müller, A. D.; Bush, M. B.; Correa-Metrio, A.; Kutterolf, S.

    2008-05-01

    Lake sediment cores recovered at seven sites in Lake Peten Itza, northern Guatemala, contain a record of climate change from lowland Central America extending back to ~200 ka. Drill cores at site PI-6 contain a high- resolution record (1 m/ka) for the last ~85 ka. Peten climate generally varied between wetter conditions during interstadials and a drier state during stadials of Marine Isotope Stage (MIS) 3. The most arid periods coincided with Heinrich Events in the North Atlantic and reductions in the strength of meridional overturning circulation. The pattern of clay-gypsum (wet-dry) oscillations during MIS 3 closely resembles the temperature record from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. Previous studies suggested that cool, dry conditions prevailed in the region during the last glacial maximum (LGM) chronozone, ~23 to 18 ka BP. Sedimentologic and palynologic data support a moist climate in the Peten lowlands during this period whenvegetation consisted of a temperate pine-oak forest. This finding contradicts the previous inferences. At the end of the LGM, Peten climate switched abruptly from moist to arid conditions during the so-called "Mystery Period" from 18 to 14.9 ka. Moister conditions prevailed during the warmer Bolling-Allerod (14.7 to 12.8 ka), with the exception of a drier climate, with greater δ18O values between ca. 14.5 and 13.5 ka BP. This drier period in Central America coincided with Meltwater Pulse 1A (14.1- 13.5 ka) (Fairbanks et al., 2005) when a substantial volume of glacial meltwater was introduced to the Gulf of Mexico (e.g. Flower et al., 2004). The greatest δ18O values in Peten Itza occurred at 13.7 ka coinciding with the greatest rate of sea level rise (4.3 cm yr-1) at 13.9 ka. In contrast, sea surface temperature (SST) reconstructions (Lea et al., 2003), color reflectance, and elemental (Fe, Ti) data (Peterson et al., 2000) from Cariaco Basin cores, north of

  20. Sea surface temperatures in the North Atlantic Ocean from 30ka to 10ka

    NASA Astrophysics Data System (ADS)

    Barrack, Kerr; Greenop, Rosanna; Burke, Andrea; Barker, Stephen; Chalk, Thomas; Crocker, Anya

    2016-04-01

    Some of the most striking features of the Late Pleistocene interval are the rapid changes in climate between warmer interstadial and cold stadial periods which, when coupled, are termed Dansgaard-Oeschger (D-O) events. This shift between warm and cold climates has been interpreted to result from changes in the thermohaline circulation (Broecker et al., 1985) triggered by, for instance, freshwater input from the collapse of the Laurentide ice sheet (Zahn et al., 1997). However, a recent study suggests that major ice rafting events cannot be the 'trigger' for the centennial to millennial scale cooling events identified over the past 500kyr (Barker at al., 2015). Polar planktic foraminiferal and lithogenic/terrigenous grain counts reveal that the southward migration of the polar front occurs before the deposition of ice rafted debris and therefore the rafting of ice during stadial periods. Based upon this evidence, Barker et al. suggest that the transition to a stadial state is a non-linear response to gradual cooling in the region. In order to test this hypothesis, our study reconstructs sea surface temperature across D-O events and the deglaciation in the North Atlantic between 30ka and 10ka using Mg/ Ca paleothermometry in Globigerina bulloides at ODP Sites 980 and 983 (the same sites as used in Barker et al., 2015) with an average sampling resolution of 300 years. With our new record we evaluate the timing of surface ocean temperature change, frontal shift movement, and ice rafting to investigate variations in the temperature gradient across the polar front over D-O events. References: Barker, S., Chen, J., Gong, X., Jonkers, L., Knorr, G., Thornalley, D., 2015. Icebergs not the trigger for North Atlantic cold events. Nature, 520(7547), pp.333-336. Broecker, W.S., Peteer, D.M., Rind, D., 1985. Does the ocean-atmosphere system have more than one stable mode of operation? Nature, 315 (6014), pp.21-26. Zahn, R., Schönfeld, J., Kudrass, H.-R., Park, M

  1. On the development of protein pKa calculation algorithms

    PubMed Central

    Carstensen, Tommy; Farrell, Damien; Huang, Yong; Baker, Nathan A.; Nielsen, Jens Erik

    2011-01-01

    Protein pKa calculation methods are developed partly to provide fast non-experimental estimates of the ionization constants of protein side chains. However, the most significant reason for developing such methods is that a good pKa calculation method is presumed to provide an accurate physical model of protein electrostatics, which can be applied in methods for drug design, protein design and other structure-based energy calculation methods. We explore the validity of this presumption by simulating the development of a pKa calculation method using artificial experimental data derived from a human-defined physical reality. We examine the ability of an RMSD-guided development protocol to retrieve the correct (artificial) physical reality and find that a rugged optimization landscape and a huge parameter space prevent the identification of the correct physical reality. We examine the importance of the training set in developing pKa calculation methods and investigate the effect of experimental noise on our ability to identify the correct physical reality, and find that both effects have a significant and detrimental impact on the physical reality of the optimal model identified. Our findings are of relevance to all structure-based methods for protein energy calculations and simulation, and have large implications for all types of current pKa calculation methods. Our analysis furthermore suggests that careful and extensive validation on many types of experimental data can go some way in making current models more realistic. PMID:21744393

  2. Xen clusters in the alpha cages of zeolite KA

    NASA Astrophysics Data System (ADS)

    Jameson, Cynthia J.; Jameson, A. Keith; Gerald, Rex E., II; Lim, Hyung-Mi

    1995-11-01

    We have observed the individual signals of the Xen clusters (n=1-5) trapped in the alpha cages of zeolite KA. The 129Xe NMR chemical shift of each cluster in zeolite KA is larger than that of the corresponding Xen cluster in zeolite NaA. The temperature dependence of the chemical shifts of the clusters vary systematically with cluster size as they do in NaA, but the change of the temperature coefficients with n is somewhat more pronounced for Xen in the cages of KA than in NaA. The Xen chemical shifts and their variation with temperature are reproduced by the grand canonical Monte Carlo (GCMC) simulations. GCMC simulations of the distribution of the Xe atoms among the alpha cages in KA provide the fractions of cages containing n Xe atoms which agree reasonably well with the observed equilibrium distributions. The characteristics of Xe distribution and chemical shifts in KA are compared with that in NaA.

  3. Ku/Ka band observations over polar ice sheets

    NASA Astrophysics Data System (ADS)

    Thibaut, Pierre; Lasne, Yannick; Guillot, Amandine; Picot, Nicolas; Rémy, Frédérique

    2015-04-01

    For the first time, comparisons between Ku and Ka altimeter measurements are possible thanks to the new AltiKa instrument embarked onboard the Saral mission launched on February 25, 2013. This comparison is of particular interest when dealing with ice sheet observations because both frequencies have different penetration characteristics. We propose in this paper to revisit the estimation of the ice sheet topography (and other related parameters) with altimeter systems and to present illustrations of the differences observed in Ku and Ka bands using AltiKa, Envisat/RA-2 but also Cryosat-2 measurements. Working on AltiKa waveforms in the frame of the PEACHI project has allowed us to better understand the impact of the penetration depth on the echo shape, to improve the estimation algorithm and to compare its output with historical results obtained on Envisat and ERS missions. In particular, analyses at cross-overs of the Cryosat-2 and Saral data will be presented. Sentinel-3 mission should be launch during 2015. Operating in Ku band and in delay/doppler mode, it will be crucial to account for penetration effects in order to accurately derive the ice sheet heights and trends. The results of the work presented here, will benefit to the Sentinel-3 mission.

  4. Ka-band MMIC microstrip array for high rate communications

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.; Raquet, C. A.; Tolleson, J. B.; Sanzgiri, S. M.

    1991-01-01

    In a recent technology assessment of alternative communication systems for the space exploration initiative (SEI), Ka-band (18 to 40 GHz) communication technology was identified to meet the mission requirements of telecommunication, navigation, and information management. Compared to the lower frequency bands, Ka-band antennas offer higher gain and broader bandwidths; thus, they are more suitable for high data rate communications. Over the years, NASA has played an important role in monolithic microwave integrated circuit (MMIC) phased array technology development, and currently, has an ongoing contract with Texas Instrument (TI) to develop a modular Ka-band MMIC microstrip subarray (NAS3-25718). The TI contract emphasizes MMIC integration technology development and stipulates using existing MMIC devices to minimize the array development cost. The objective of this paper is to present array component technologies and integration techniques used to construct the subarray modules.

  5. Predicting pKa for proteins using COSMO-RS

    PubMed Central

    Jensen, Jan Halborg; Stipp, Susan Louise Svane

    2013-01-01

    We have used the COSMO-RS implicit solvation method to calculate the equilibrium constants, pKa, for deprotonation of the acidic residues of the ovomucoid inhibitor protein, OMTKY3. The root mean square error for comparison with experimental data is only 0.5 pH units and the maximum error 0.8 pH units. The results show that the accuracy of pKa prediction using COSMO-RS is as good for large biomolecules as it is for smaller inorganic and organic acids and that the method compares very well to previous pKa predictions of the OMTKY3 protein using Quantum Mechanics/Molecular Mechanics. Our approach works well for systems of about 1000 atoms or less, which makes it useful for small proteins as well as for investigating portions of larger proteins such as active sites in enzymes. PMID:24244915

  6. X-/Ka-band dichroic plate noise temperature reduction

    NASA Technical Reports Server (NTRS)

    Veruttipong, W.; Lee, P.

    1994-01-01

    The X-/Ka-band (8.4 GHz/32.0 GHz) dichroic plate installed as DSS 13 contributes an estimated 3 K to the system noise temperature at 32.0 GHz. Approximately 1 percent of the Ka-band incident field is reflected by the plate into the 300-K environment of the DSS-13 pedestal room. A low-cost, easily implemented method of reducing the noise temperature is presented. Using a curved reflector, the reflected field can be re-focused into an 80-K cold load, reducing the noise temperature contribution of the dichroic plate by about 2 K.

  7. Screening and Isolation of Penicillinase Inhibitor, KA-107

    PubMed Central

    Iwai, Y.; Ohno, H.; Takeshima, H.; Yamaguchi, N.; Ōmura, S.; Hata, T.

    1973-01-01

    It is known that penicillin resistance of bacteria is mainly caused by the inactivation of penicillin by penicillinase derived from such strains. We have developed a screening procedure for penicillinase inhibitors. Several microorganisms were found to produce such inhibitors, and from the culture filtrate of Streptomyces gedanensis ATCC 4880 a penicillinase inhibitor, named KA-107, was isolated. The characteristics of this inhibitor were revealed by an in vitro test by using penicillinase derived from penicillin resistant Staphylococcus aureus, FS-1277. When KA-107 was used in combination with penicillin-G, ampicillin, d- or l-phenethicillin, the growth inhibitory activity of these penicillins was maintained. PMID:4202340

  8. X-/Ka-Band Dichroic Plate Noise Temperature Reduction

    NASA Astrophysics Data System (ADS)

    Veruttipong, W.; Lee, P.

    1994-07-01

    The X-/Ka-band (8.4-GHz/32.0-GHz) dichroic plate installed at DSS 13 contributes an estimated 3 K to the system noise temperature at 32.0 GHz. Approximately 1 percent of the Ka-band incident field is reflected by the plate into the 300-K environment of the DSS-13 pedestal room. A low-cost, easily implemented method of reducing the noise temperature is presented. Using a curved reflector, the reflected field can be refocused into an 80-K cold load, reducing the noise temperature contribution of the dichroic plate by about 2 K.

  9. X-/Ka-band dichroic plate noise temperature reduction

    NASA Astrophysics Data System (ADS)

    Veruttipong, W.; Lee, P.

    1994-11-01

    The X-/Ka-band (8.4 GHz/32.0 GHz) dichroic plate installed as DSS 13 contributes an estimated 3 K to the system noise temperature at 32.0 GHz. Approximately 1 percent of the Ka-band incident field is reflected by the plate into the 300-K environment of the DSS-13 pedestal room. A low-cost, easily implemented method of reducing the noise temperature is presented. Using a curved reflector, the reflected field can be re-focused into an 80-K cold load, reducing the noise temperature contribution of the dichroic plate by about 2 K.

  10. Pollen-climate relationships in time (9 ka, 6 ka, 0 ka) and space (upland vs. lowland) in eastern continental Asia

    NASA Astrophysics Data System (ADS)

    Tian, Fang; Cao, Xianyong; Dallmeyer, Anne; Zhao, Yan; Ni, Jian; Herzschuh, Ulrike

    2017-01-01

    Temporal and spatial stability of the vegetation-climate relationship is a basic ecological assumption for pollen-based quantitative inferences of past climate change and for predicting future vegetation. We explore this assumption for the Holocene in eastern continental Asia (China, Mongolia). Boosted regression trees (BRT) between fossil pollen taxa percentages (Abies, Artemisia, Betula, Chenopodiaceae, Cyperaceae, Ephedra, Picea, Pinus, Poaceae and Quercus) and climate model outputs of mean annual precipitation (Pann) and mean temperature of the warmest month (Mtwa) for 9 and 6 ka (ka = thousand years before present) were set up and results compared to those obtained from relating modern pollen to modern climate. Overall, our results reveal only slight temporal differences in the pollen-climate relationships. Our analyses suggest that the importance of Pann compared with Mtwa for taxa distribution is higher today than it was at 6 ka and 9 ka. In particular, the relevance of Pann for Picea and Pinus increases and has become the main determinant. This change in the climate-tree pollen relationship parallels a widespread tree pollen decrease in north-central China and the eastern Tibetan Plateau. We assume that this is at least partly related to vegetation-climate disequilibrium originating from human impact. Increased atmospheric CO2 concentration may have permitted the expansion of moisture-loving herb taxa (Cyperaceae and Poaceae) during the late Holocene into arid/semi-arid areas. We furthermore find that the pollen-climate relationship between north-central China and the eastern Tibetan Plateau is generally similar, but that regional differences are larger than temporal differences. In summary, vegetation-climate relationships in China are generally stable in space and time, and pollen-based climate reconstructions can be applied to the Holocene. Regional differences imply the calibration-set should be restricted spatially.

  11. The Determination of "Apparent" pKa's. Part II: An Experiment Using Very Weak Acids (pKa's > 11.4).

    ERIC Educational Resources Information Center

    Cawley, John J.

    1995-01-01

    Presents an experiment designed to show students that the Henderson-Hasselbalch equation will fail when they use this particular one-half titration technique for acids with large pKa's. Involves determining the apparent pKa for such acids and using that to calculate the true pKa. (JRH)

  12. Multi-Step Ka/Ka Dichroic Plate with Rounded Corners for NASA's 34m Beam Waveguide Antenna

    NASA Technical Reports Server (NTRS)

    Veruttipong, Watt; Khayatian, Behrouz; Hoppe, Daniel; Long, Ezra

    2013-01-01

    A multi-step Ka/Ka dichroic plate Frequency Selective Surface (FSS structure) is designed, manufactured and tested for use in NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antennas. The proposed design allows ease of manufacturing and ability to handle the increased transmit power (reflected off the FSS) of the DSN BWG antennas from 20kW to 100 kW. The dichroic is designed using HFSS and results agree well with measured data considering the manufacturing tolerances that could be achieved on the dichroic.

  13. Multi-Step Ka/Ka Dichroic Plate with Rounded Corners for NASA's 34m Beam Waveguide Antenna

    NASA Technical Reports Server (NTRS)

    Veruttipong, Watt; Khayatian, Behrouz; Hoppe, Daniel; Long, Ezra

    2013-01-01

    A multi-step Ka/Ka dichroic plate Frequency Selective Surface (FSS structure) is designed, manufactured and tested for use in NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antennas. The proposed design allows ease of manufacturing and ability to handle the increased transmit power (reflected off the FSS) of the DSN BWG antennas from 20kW to 100 kW. The dichroic is designed using HFSS and results agree well with measured data considering the manufacturing tolerances that could be achieved on the dichroic.

  14. Cassini Downlink Ka-Band Carrier Signal Analysis

    NASA Astrophysics Data System (ADS)

    Morabito, D. D.; Kahan, D.; Oudrhiri, K.; Lee, C.-A.

    2017-02-01

    Lower frequency telemetry bands are becoming more limited in bandwidth with more competition between flight projects and other entities. Higher frequency bands offer significantly more bandwidth and hence the prospect of much higher data rates. Future or prospective flight projects considering Ka-band (32-GHz) telemetry data links are interested in past flight experience with received Ka-band data. Over 10 years of Cassini closed-loop received Ka-band carrier data involving over 2 million individual measurements were acquired at all three Deep Space Network (DSN) sites. We analyzed these data to characterize link performance over a wide range of weather conditions and as a function of elevation angle. Based on this analysis, we have derived a recommendation for telecommunications link margin for preflight planning purposes. These results suggest that a 4-dB margin will ensure a 94 percent data return at a minimum 20-deg elevation angle under 90 percent weather conditions at 32 GHz (Ka-band).

  15. Marine04 Marine radiocarbon age calibration, 26 ? 0 ka BP

    SciTech Connect

    Hughen, K; Baille, M; Bard, E; Beck, J; Bertrand, C; Blackwell, P; Buck, C; Burr, G; Cutler, K; Damon, P; Edwards, R; Fairbanks, R; Friedrich, M; Guilderson, T; Kromer, B; McCormac, F; Manning, S; Bronk-Ramsey, C; Reimer, P; Reimer, R; Remmele, S; Southon, J; Stuiver, M; Talamo, S; Taylor, F; der Plicht, J v; Weyhenmeyer, C

    2004-11-01

    New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration datasets extend an additional 2000 years, from 0-26 ka cal BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically dated tree-ring samples, converted with a box-diffusion model to marine mixed-layer ages, cover the period from 0-10.5 ka cal BP. Beyond 10.5 ka cal BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific {sup 14}C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 ka cal BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the radiocarbon age to calculate the underlying calibration curve. The marine datasets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring datasets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al.

  16. Anatomically modern human in Southeast Asia (Laos) by 46 ka

    PubMed Central

    Demeter, Fabrice; Shackelford, Laura L.; Bacon, Anne-Marie; Duringer, Philippe; Westaway, Kira; Sayavongkhamdy, Thongsa; Braga, José; Sichanthongtip, Phonephanh; Khamdalavong, Phimmasaeng; Ponche, Jean-Luc; Wang, Hong; Lundstrom, Craig; Patole-Edoumba, Elise; Karpoff, Anne-Marie

    2012-01-01

    Uncertainties surround the timing of modern human emergence and occupation in East and Southeast Asia. Although genetic and archeological data indicate a rapid migration out of Africa and into Southeast Asia by at least 60 ka, mainland Southeast Asia is notable for its absence of fossil evidence for early modern human occupation. Here we report on a modern human cranium from Tam Pa Ling, Laos, which was recovered from a secure stratigraphic context. Radiocarbon and luminescence dating of the surrounding sediments provide a minimum age of 51–46 ka, and direct U-dating of the bone indicates a maximum age of ∼63 ka. The cranium has a derived modern human morphology in features of the frontal, occipital, maxillae, and dentition. It is also differentiated from western Eurasian archaic humans in aspects of its temporal, occipital, and dental morphology. In the context of an increasingly documented archaic–modern morphological mosaic among the earliest modern humans in western Eurasia, Tam Pa Ling establishes a definitively modern population in Southeast Asia at ∼50 ka cal BP. As such, it provides the earliest skeletal evidence for fully modern humans in mainland Southeast Asia. PMID:22908291

  17. Mars Global Surveyor Ka-Band Frequency Data Analysis

    NASA Technical Reports Server (NTRS)

    Morabito, D.; Butman, S.; Shambayati, S.

    2000-01-01

    The Mars Global Surveyor (MGS) spacecraft, launched on November 7, 1996, carries an experimental space-to-ground telecommunications link at Ka-band (32 GHz) along with the primary X-band (8.4 GHz) downlink. The signals are simultaneously transmitted from a 1.5-in diameter parabolic high gain antenna (HGA) on MGS and received by a beam-waveguide (BWG) R&D 34-meter antenna located in NASA's Goldstone Deep Space Network (DSN) complex near Barstow, California. The projected 5-dB link advantage of Ka-band relative to X-band was confirmed in previous reports using measurements of MGS signal strength data acquired during the first two years of the link experiment from December 1996 to December 1998. Analysis of X-band and Ka-band frequency data and difference frequency (f(sub x)-f(sub ka)/3.8) data will be presented here. On board the spacecraft, a low-power sample of the X-band downlink from the transponder is upconverted to 32 GHz, the Ka-band frequency, amplified to I-W using a Solid State Power Amplifier, and radiated from the dual X/Ka HGA. The X-band signal is amplified by one of two 25 W TWTAs. An upconverter first downconverts the 8.42 GHz X-band signal to 8 GHz and then multiplies using a X4 multiplier producing the 32 GHz Ka-band frequency. The frequency source selection is performed by an RF switch which can be commanded to select a VCO (Voltage Controlled Oscillator) or USO (Ultra-Stable Oscillator) reference. The Ka-band frequency can be either coherent with the X-band downlink reference or a hybrid combination of the USO and VCO derived frequencies. The data in this study were chosen such that the Ka-band signal is purely coherent with the X-band signal, that is the downconverter is driven by the same frequency source as the X-band downlink). The ground station used to acquire the data is DSS-13, a 34-meter BWG antenna which incorporates a series of mirrors inside beam waveguide tubes which guide the energy to a subterranean pedestal room, providing a stable

  18. Experimental radio frequency link for Ka-band communications applications

    NASA Technical Reports Server (NTRS)

    Fujikawa, Gene; Conray, Martin J.; Saunders, Alan L.; Pope, Dale E.

    1988-01-01

    An experimental radio frequency link has been demonstrated to provide two-way communication between a remote user ground terminal and a ground-based Ka-band transponder. Bit-error-rate performance and radio frequency characteristics of the communication link were investigated.

  19. Anatomically modern human in Southeast Asia (Laos) by 46 ka.

    PubMed

    Demeter, Fabrice; Shackelford, Laura L; Bacon, Anne-Marie; Duringer, Philippe; Westaway, Kira; Sayavongkhamdy, Thongsa; Braga, José; Sichanthongtip, Phonephanh; Khamdalavong, Phimmasaeng; Ponche, Jean-Luc; Wang, Hong; Lundstrom, Craig; Patole-Edoumba, Elise; Karpoff, Anne-Marie

    2012-09-04

    Uncertainties surround the timing of modern human emergence and occupation in East and Southeast Asia. Although genetic and archeological data indicate a rapid migration out of Africa and into Southeast Asia by at least 60 ka, mainland Southeast Asia is notable for its absence of fossil evidence for early modern human occupation. Here we report on a modern human cranium from Tam Pa Ling, Laos, which was recovered from a secure stratigraphic context. Radiocarbon and luminescence dating of the surrounding sediments provide a minimum age of 51-46 ka, and direct U-dating of the bone indicates a maximum age of ~63 ka. The cranium has a derived modern human morphology in features of the frontal, occipital, maxillae, and dentition. It is also differentiated from western Eurasian archaic humans in aspects of its temporal, occipital, and dental morphology. In the context of an increasingly documented archaic-modern morphological mosaic among the earliest modern humans in western Eurasia, Tam Pa Ling establishes a definitively modern population in Southeast Asia at ~50 ka cal BP. As such, it provides the earliest skeletal evidence for fully modern humans in mainland Southeast Asia.

  20. K/Ka-band Antenna for Broadband Aeronautical Mobile Application

    NASA Technical Reports Server (NTRS)

    Densmore, A.

    1994-01-01

    The Jet Propulsion Laboratory (JPL) has recently begun the development of a Broadband Aeronauical Terminal (BAT) for duplex video satellite communications on commercial or business class aircraft. The BAT is designed for use with NASA's K/Ka-band Advanced Communications Technology Satellite (ACTS).

  1. Mars Global Surveyor Ka-Band Frequency Data Analysis

    NASA Astrophysics Data System (ADS)

    Morabito, D.; Butman, S.; Shambayati, S.

    2000-01-01

    The Mars Global Surveyor (MGS) spacecraft, launched on November 7, 1996, carries an experimental space-to-ground telecommunications link at Ka-band (32 GHz) along with the primary X-band (8.4 GHz) downlink. The signals are simultaneously transmitted from a 1.5-in diameter parabolic high gain antenna (HGA) on MGS and received by a beam-waveguide (BWG) R&D 34-meter antenna located in NASA's Goldstone Deep Space Network (DSN) complex near Barstow, California. The projected 5-dB link advantage of Ka-band relative to X-band was confirmed in previous reports using measurements of MGS signal strength data acquired during the first two years of the link experiment from December 1996 to December 1998. Analysis of X-band and Ka-band frequency data and difference frequency (fx-fka)/3.8 data will be presented here. On board the spacecraft, a low-power sample of the X-band downlink from the transponder is upconverted to 32 GHz, the Ka-band frequency, amplified to I-W using a Solid State Power Amplifier, and radiated from the dual X/Ka HGA. The X-band signal is amplified by one of two 25 W TWTAs. An upconverter first downconverts the 8.42 GHz X-band signal to 8 GHz and then multiplies using a X4 multiplier producing the 32 GHz Ka-band frequency. The frequency source selection is performed by an RF switch which can be commanded to select a VCO (Voltage Controlled Oscillator) or USO (Ultra-Stable Oscillator) reference. The Ka-band frequency can be either coherent with the X-band downlink reference or a hybrid combination of the USO and VCO derived frequencies. The data in this study were chosen such that the Ka-band signal is purely coherent with the X-band signal, that is the downconverter is driven by the same frequency source as the X-band downlink). The ground station used to acquire the data is DSS-13, a 34-meter BWG antenna which incorporates a series of mirrors inside beam waveguide tubes which guide the energy to a subterranean pedestal room, providing a stable environment

  2. Calibration of the radiocarbon time scale at 37ka BP

    SciTech Connect

    Southon, J.R.; Deino, A.L.; Orsi, G.

    1995-12-01

    Results from radiocarbon and U-Th measurements on corals have provided a radiocarbon calibration beyond the range covered by tree ring series, but the uncertainties in the measurements beyond 20ka BP are very large. We have obtained new calibration data from radiocarbon dates on material associated with the catastrophic Campanian Ignimbrite eruption from the Phlegrean Fields near Naples. The eruption has been well dated by {sup 40}Ar/{sup 39}Ar to 37ka BP. Radiocarbon measurements were carried out on charcoal from a carbonized branch exposed within the ignimbrite tuff on the wall of an active quarry. The sample was split and analyzed at both the Naples and Lawrence Livermore AMS facilities. The offset between the Ar-Ar data and the radiocarbon results (recalculated using the true 5730-year half life for {sup 14}C) is consistent with predictions from paleomagnetic data and carbon cycle modeling.

  3. Ka-band MMIC arrays for ACTS Aero Terminal Experiment

    NASA Technical Reports Server (NTRS)

    Raquet, C.; Zakrajsek, R.; Lee, R.; Turtle, J.

    1992-01-01

    An antenna system consisting of three experimental Ka-band active arrays using GaAs MMIC devices at each radiating element for electronic beam steering and distributed power amplification is presented. The MMIC arrays are to be demonstrated in the ACTS Aeronautical Terminal Experiment, planned for early 1994. The experiment is outlined, with emphasis on a description of the antenna system. Attention is given to the way in which proof-of-concept MMIC arrays featuring three different state-of-the-art approaches to Ka-band MMIC insertion are being incorporated into an experimental aircraft terminal for the demonstration of an aircraft-to-satellite link, providing a basis for follow-on MMIC array development.

  4. EUReKA! A Conceptual Model of Emotion Understanding.

    PubMed

    Castro, Vanessa L; Cheng, Yanhua; Halberstadt, Amy G; Grühn, Daniel

    2016-07-01

    The field of emotion understanding is replete with measures, yet lacks an integrated conceptual organizing structure. To identify and organize skills associated with the recognition and knowledge of emotions, and to highlight the focus of emotion understanding as localized in the self, in specific others, and in generalized others, we introduce the conceptual framework of Emotion Understanding in Recognition and Knowledge Abilities (EUReKA). We then categorize fifty-six existing methods of emotion understanding within this framework to highlight current gaps and future opportunities in assessing emotion understanding across the lifespan. We hope the EUReKA model provides a systematic and integrated framework for conceptualizing and measuring emotion understanding for future research.

  5. MMIC's for Ka-band multibeam satellite transponder

    NASA Astrophysics Data System (ADS)

    Kato, Haruhiko; Araki, Katsuhiko

    The key monolithic microwave integrated circuits (MMICs), such as a 30-GHz amplifier, frequency converter, multiplier, voltage-controlled oscillator, 15-GHz analog frequency divider and 1-GHz IF switch, that comprise a Ka-band full MMIC transponder are described. Some elements unsuitable for MMIC implementation, such as filters, dielectric resonators, and IF hybrid couplers, have been completely eliminated by novel designs. A Ka-band receiver and a 1-GHz 16 x 16 IF switch matrix using these MMICs have been assembled, and their performance was evaluated. The test data indicate the feasibility of a full MMIC transponder that weighs approximately 1/3 as much as conventional hybrid-IC transponders.

  6. Interim Findings of ACTS Ka-Band Propagation Campaign

    NASA Technical Reports Server (NTRS)

    Golshan, N.

    1997-01-01

    The ACTS propagation campaign is focusing on two broad areas: 1) Rain/signal attenuation data collection at seven sites in North America, 2) Theoretical and empirical consideratons for a global model to predict first & second order temporal and spatial statistics on attenuation, scintillation, conherence bandwidth, and depolarization due to weather (precipitation and atmospheric including interaction of weather with the antenna) for satellite systems at Ka-band.

  7. Interim Findings of ACTS Ka-Band Propagation Campaign

    NASA Technical Reports Server (NTRS)

    Golshan, N.

    1997-01-01

    The ACTS propagation campaign is focusing on two broad areas: 1) Rain/signal attenuation data collection at seven sites in North America, 2) Theoretical and empirical consideratons for a global model to predict first & second order temporal and spatial statistics on attenuation, scintillation, conherence bandwidth, and depolarization due to weather (precipitation and atmospheric including interaction of weather with the antenna) for satellite systems at Ka-band.

  8. X/Ka Celestial Frame Improvements: Vision to Reality

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Bagri, D. S.; Britcliffe, M. J.; Clark, J. E.; Franco, M. M.; Garcia-Miro, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Moll, V. E.; hide

    2010-01-01

    In order to extend the International Celestial Reference Frame from its S/X-band (2.3/8.4 GHz) basis to a complementary frame at X/Ka-band (8.4/32 GHz), we began in mid-2005 an ongoing series of X/Ka observations using NASA s Deep Space Network (DSN) radio telescopes. Over the course of 47 sessions, we have detected 351 extra-galactic radio sources covering the full 24 hours of right ascension and declinations down to -45 degrees. Angular source position accuracy is at the part-per-billion level. We developed an error budget which shows that the main errors arise from limited sensitivity, mismodeling of the troposphere, uncalibrated instrumental effects, and the lack of a southern baseline. Recent work has improved sensitivity by improving pointing calibrations and by increasing the data rate four-fold. Troposphere calibration has been demonstrated at the mm-level. Construction of instrumental phase calibrators and new digital baseband filtering electronics began in recent months. We will discuss the expected effect of these improvements on the X/Ka frame.

  9. Rain Fade Compensation Alternatives for Ka Band Communication Satellites

    NASA Technical Reports Server (NTRS)

    Acosta, Roberto J.

    1997-01-01

    Future satellite communications systems operating in Ka-band frequency band are subject to degradation produced by the troposphere which is much more severe than those found at lower frequency bands. These impairments include signal absorption by rain, clouds and gases, and amplitude scintillation's arising from refractive index irregularities. For example, rain attenuation at 20 GHz is almost three times that at 11 GHz. Although some of these impairments can be overcome by oversizing the ground station antennas and high power amplifiers, the current trend is using small (less than 20 inches apertures), low-cost ground stations (less than $1000) that can be easily deployed at user premises. As a consequence, most Ka-band systems are expected to employ different forms of fade mitigation that can be implemented relatively easily and at modest cost. The rain fade mitigation approaches are defined by three types of Ka-band communications systems - a low service rate (less than 1.5 Mb/s), a moderate service rate (1.5 to 6 Mb/s) system and a high service rate (greater than 43 Mb/s) system. The ACTS VSAT network, which includes an adaptive rain fade technique, is an example of a moderate service rate.

  10. X/Ka Celestial Reference Frame Improvements: Vision to Reality

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Bagri, D. S.; Brticliffe, M. J.; Clark, J. E.; Franco, M. M.; García-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Moll, V. E.; Navarro, R.; Rogstad, S. P.; Proctor, R. C.; Skjerve, L. J.; Soriano, M. A.; Sovers, O. J.; Tucker, B. C.; Wang, D.; White, L. A.

    2010-12-01

    In order to extend the International Celestial Reference Frame from its S/X-band (2.3/8.4 GHz) basis to a complementary frame at X/Ka-band (8.4/32 GHz), we began in mid-2005 an ongoing series of X/Ka observations using NASA's Deep Space Network (DSN) radio telescopes. Over the course of 47 sessions, we have detected 351 extra-galactic radio sources covering the full 24 hours of right ascension and declinations down to -45 degrees. Angular source position accuracy is at the part-per-billion level. We developed an error budget which shows that the main errors arise from limited sensitivity, mismodeling of the troposphere, uncalibrated instrumental effects, and the lack of a southern baseline. Recent work has improved sensitivity by improving pointing calibrations and by increasing the data rate four-fold. Troposphere calibration has been demonstrated at the mm-level. Construction of instrumental phase calibrators and new digital baseband filtering electronics began in recent months. We will discuss the expected effect of these improvements on the X/Ka frame.

  11. AltiKa: a Ka-band Altimetry Payload and System for Operational Altimetry during the GMES Period

    PubMed Central

    Vincent, Patrick; Steunou, Nathalie; Caubet, Eric; Phalippou, Laurent; Rey, Laurent; Thouvenot, Eric; Verron, Jacques

    2006-01-01

    This paper describes the Ka-band altimetry payload and system that has been studied for several years by CNES, ALCATEL SPACE and some science laboratories. Altimetry is one of the major elements of the ocean observing system to be made sustainable through the GEOSS (Global Earth Observation System of Systems) and GMES (Global Monitoring of the Environment and Security) programs. A short review of some mission objectives to be fulfilled in terms of mesoscale oceanography in the frame of the GEOSS and GMES programs is performed. To answer the corresponding requirements, the approach consisting in a constellation of nadir altimeter is discussed. A coupled Ka-band altimeter-radiometer payload is then described; technical items are detailed to explain how this payload shall meet the science and operational requirements, and expected performances are displayed. The current status of the payload development and flight perspectives are given.

  12. HCO (N,Ka,Kc,J) distributions from near-threshold photolysis of H2CO (J,Ka,Kc)

    NASA Astrophysics Data System (ADS)

    Terentis, Andrew C.; Waugh, Siobhan E.; Metha, Gregory F.; Kable, Scott H.

    1998-02-01

    The dynamics of the reaction H2CO+hν(λ≈330 nm)→H+HCO have been studied following excitation of formaldehyde into the Ã(1A2) state, just above the dissociation threshold of the X˜(1A1) state. Formaldehyde was excited via specific J, Ka, Kc rotational states and the ensuing rotational distribution of HCO measured by fully resolving N, Ka, Kc, and J=N±S of the fragment. When only the N and Ka quantum numbers of both formaldehyde and the formyl radical are considered, the distributions are generally modeled well by phase space theory (PST). Within ≈10 cm-1 of the threshold, however, the PST predictions consistently exceed the experimental populations. This was accounted for by the inclusion of a centrifugal barrier in the PST model. The attractive part of the effective centrifugal potential was modeled by a dipole-induced dipole plus dispersion interaction. The barrier is weak and long range (>5 Å). Resolution of Kc in the reaction, in both parent and product, gave large deviations from the PST model. The HCO population distributions separate according to whether Kc was the upper- or lower-energy state. Additionally, the upper/lower preference was sensitive to the choice of Kc in the parent. Insufficient data are currently available to quantify this observation. The product state distribution was also found to be independent of the spin-rotation state of HCO.

  13. Determination of pKa values of organic bases in aqueous acetonitrile solutions using capillary electrophoresis.

    PubMed

    Buckenmaier, Stephan M C; McCalley, David V; Euerby, Melvin R

    2003-07-04

    Capillary electrophoresis (CE) was used for the determination of ionisation constants (pKa) of a variety of organic bases in aqueous acetonitrile solutions over the range 0-60% (v/v) acetonitrile. These bases are used as test compounds in HPLC column evaluation, thus knowledge of their pKa in hydro-organic solutions is useful. The base pKa decreased with acetonitrile concentration and significant shifts from the aqueous pKa (up to -0.8) were found using 60% acetonitrile. The CE application was confirmed to be very suitable for fast and accurate pKa measurement in aqueous organic solutions.

  14. Determination of pKa of felodipine using UV-Visible spectroscopy

    NASA Astrophysics Data System (ADS)

    Pandey, M. M.; Jaipal, A.; Kumar, A.; Malik, R.; Charde, S. Y.

    2013-11-01

    In the present study, for the first time, experimental pKa value of felodipine is reported. Dissociation constant, pKa, is one of the very important physicochemical properties of drugs. It is of paramount significance from the perspective of pharmaceutical analysis and dosage form design. The method used for the pKa determination of felodipine was essentially a UV-Visible spectrophotometric method. The spectrophotometric method for the pKa determination was opted by acknowledging the established fact that spectrophotometric determination of pKa produces most precise values. The pKa of felodipine was found to be 5.07. Furthermore, the ruggedness of the determined value is also validated in this study in order to produce exact pKa of the felodipine.

  15. Four-Way Ka-Band Power Combiner

    NASA Technical Reports Server (NTRS)

    Perez, Raul; Li, Samuel

    2007-01-01

    A waveguide structure for combining the outputs of four amplifiers operating at 35 GHz (Ka band) is based on a similar prior structure used in the X band. The structure is designed to function with low combining loss and low total reflected power at a center frequency of 35 GHz with a 160 MHz bandwidth. The structure (see figure) comprises mainly a junction of five rectangular waveguides in a radial waveguide. The outputs of the four amplifiers can be coupled in through any four of the five waveguide ports. Provided that these four signals are properly phased, they combine and come out through the fifth waveguide port.

  16. Ka-band mobile and personal systems development at JPL

    NASA Technical Reports Server (NTRS)

    Dessouky, K.; Estabrook, P.; Jedrey, T.; Sue, M. K.

    1991-01-01

    Expanding the commercial applications of space is one of the primary goals of NASA. Throughout the eighties NASA has pursued this objective by sponsoring and undertaking the development of system concepts, enabling high risk technologies, and actual proof of concept demonstration hardware. In the mobile and personal arena, or the so-called low data rate applications area, JPL is NASA's lead center. JPL's focus of activities has been the Mobile Satellite-Experiment (MSAT-X) project, which developed mobile communication technologies at L-band, and its present successors, which aim to expand the mobile arena by exploiting Ka-band.

  17. Ka- and W-band PM-HFET DRO's

    NASA Astrophysics Data System (ADS)

    Wenger, J.; Guettich, U.

    1993-06-01

    Dielectric resonator stabilized oscillators have been designed, fabricated, and investigated. The oscillators consist of microstrip matching and biasing circuits on alumina substrate, a dielectric resonator puck, and a low-noise quarter-micron InGaAs-GaAs pseudomorphic (PM) HFET as the active device. At 37 GHz and 81 GHz, output powers of 10 dBm and 0 dBm have been measured. The phase noise of the Ka-band and W-band oscillators has been determined to be -97 dBc/Hz at 100 kHz and -90 dBc/Hz at 1 MHz off carrier, respectively.

  18. Ka-Band ARM Zenith Radar (KAZR) Instrument Handbook

    SciTech Connect

    Widener, K; Bharadwaj, N; Johnson, K

    2012-03-06

    The Ka-band ARM zenith radar (KAZR) is a zenith-pointing Doppler cloud radar operating at approximately 35 GHz. The KAZR is an evolutionary follow-on radar to ARM's widely successful millimeter-wavelength cloud radar (MMCR). The main purpose of the KAZR is to provide vertical profiles of clouds by measuring the first three Doppler moments: reflectivity, radial Doppler velocity, and spectra width. At the sites where the dual-polarization measurements are made, the Doppler moments for the cross-polarization channel are also available. In addition to the moments, velocity spectra are also continuously recorded for each range gate.

  19. Design of High Power Density Amplifiers: Application to Ka Band

    NASA Astrophysics Data System (ADS)

    Passi, Davide; Leggieri, Alberto; Di Paolo, Franco; Bartocci, Marco; Tafuto, Antonio

    2017-10-01

    Recent developments in the design of high-power-high-frequency amplifiers are assessed in this paper by the analysis and measurements of a high power density amplifier operating in the Ka Band. Design procedure is presented and a technical investigation is reported. The proposed device has shown over 23% of useful frequency bandwidth. It is an ensemble of 16 monolithic solid state power amplifiers that employees mixed technologies as spatial and planar combiners. Test performed have given maximum delivered power of 47.2 dBm.

  20. Stability measurements on the 50 kA SMES conductor

    NASA Astrophysics Data System (ADS)

    Pfotenhauer, M. J.

    Stability measurements have been made on a large aluminium stabilized conductor designed for use in a superconducting magnetic energy storage (SMES) coil. The conductor has been built to carry 50 kA at 1.8 K and in 4.6 T field. It consists of a 25.4 mm diameter, high purity aluminium stabilizer with eight superconducting strands of 2.8 mm diameter each, composed of 60% Cu, 40% NbTi. The strands are set in eight helical grooves, evenly spaced around the outer diameter of the aluminium. The conductor is designed for use in full scale SMES units and has been tested in the 1 m diameter, three-turn test coil of the University of Wisconsin proof of principle experiment (POPE). The POPE facility includes the test coil, a 4 T background magnet, a dewar for a 1.8 K, 1 atm environment and a 100 kA d.c. power supply. Test results demonstrate good agreement with a new dynamic stability model. The balance of time-dependent heat generation during current diffusion and time-dependent cooling to the helium produces three new features of stability: 1, a threshold current for propagation; 2, large propagation velocities; and 3, a finite length travelling normal zone. POPE measurements verify all three features of the dynamic stability model.

  1. ITIL and Grid services at GridKa

    NASA Astrophysics Data System (ADS)

    Marten, H.; Koenig, T.

    2010-04-01

    The Steinbuch Centre for Computing (SCC) is a new organizational unit of the Karlsruhe Institute of Technology (KIT). Founded in February 2008 as a merger of the previous Institute for Scientific Computing of Forschungszentrum Karlsruhe and the Computing Centre of the Technical University Karlsruhe, SCC provides a broad spectrum of IT services for 8.000 employees and 18.000 students and carries out research and development in key areas of information technology under the same roof. SCC is also known to host the German WLCG [1] Tier-1 centre GridKa. In order to accompany the merging of the two existing computing centres located at a distance of about 10 km and to provide common first class services for science, SCC has selected the IT service management according to the industrial quasi-standard "IT Infrastructure Library (ITIL)" [3] as a strategic element. The paper discusses the implementation of a few ITIL key components from the perspective of a Scientific Computing Centre using examples of Grid services at GridKa.

  2. K/Ka-band channel characterization for mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Pinck, Deborah S.; Rice, Michael D.

    1995-01-01

    Mobile satellite systems allow truly ubiquitous wireless communications to users anywhere and anytime. NASA's Advanced Communications Technology Satellite (ACTS) provides an ideal space-based platform for the measurement of K/Ka band propagation characteristics in a land mobile satellite application. Field tests conducted in Southern California during the first seven months of 1994 using JPL's ACTS Mobile Terminal (AMT) provided channel characterization data for the K/Ka-band link. A pilot tone was transmitted from a fixed station in Cleveland, Ohio through the satellite and downlinked at 20 GHz in the Southern California spot beam. The AMT was equipped with a narrow beam, high gain antenna which tracked the satellite in azimuth for a fixed elevation angle (46 degrees for this case). The field tests were conducted in three basic environments: clear line-of-sight (LOS) highways, lightly shadowed suburban, and heavily shadowed suburban. Preliminary results of these field tests indicate very little multipath for rural environments and for clear LOS links (as expected with a narrow beam antenna). Deep fades were experienced in shadowed areas, especially those where tree canopies covered the road.

  3. Ka-Band, Multi-Gigabit-Per-Second Transceiver

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.; Smith, Francis J.; Harris, Johnny M.; Landon, David G.; Haddadin, Osama S.; McIntire, William K.; Sun, June Y.

    2011-01-01

    A document discusses a multi-Gigabit-per-second, Ka-band transceiver with a software-defined modem (SDM) capable of digitally encoding/decoding data and compensating for linear and nonlinear distortions in the end-to-end system, including the traveling-wave tube amplifier (TWTA). This innovation can increase data rates of space-to-ground communication links, and has potential application to NASA s future spacebased Earth observation system. The SDM incorporates an extended version of the industry-standard DVB-S2, and LDPC rate 9/10 FEC codec. The SDM supports a suite of waveforms, including QPSK, 8-PSK, 16-APSK, 32- APSK, 64-APSK, and 128-QAM. The Ka-band and TWTA deliver an output power on the order of 200 W with efficiency greater than 60%, and a passband of at least 3 GHz. The modem and the TWTA together enable a data rate of 20 Gbps with a low bit error rate (BER). The payload data rates for spacecraft in NASA s integrated space communications network can be increased by an order of magnitude (>10 ) over current state-of-practice. This innovation enhances the data rate by using bandwidth-efficient modulation techniques, which transmit a higher number of bits per Hertz of bandwidth than the currently used quadrature phase shift keying (QPSK) waveforms.

  4. Rationalization of the pKa values of alcohols and thiols using atomic charge descriptors and its application to the prediction of amino acid pKa's.

    PubMed

    Ugur, Ilke; Marion, Antoine; Parant, Stéphane; Jensen, Jan H; Monard, Gerald

    2014-08-25

    In a first step toward the development of an efficient and accurate protocol to estimate amino acids' pKa's in proteins, we present in this work how to reproduce the pKa's of alcohol and thiol based residues (namely tyrosine, serine, and cysteine) in aqueous solution from the knowledge of the experimental pKa's of phenols, alcohols, and thiols. Our protocol is based on the linear relationship between computed atomic charges of the anionic form of the molecules (being either phenolates, alkoxides, or thiolates) and their respective experimental pKa values. It is tested with different environment approaches (gas phase or continuum solvent-based approaches), with five distinct atomic charge models (Mulliken, Löwdin, NPA, Merz-Kollman, and CHelpG), and with nine different DFT functionals combined with 16 different basis sets. Moreover, the capability of semiempirical methods (AM1, RM1, PM3, and PM6) to also predict pKa's of thiols, phenols, and alcohols is analyzed. From our benchmarks, the best combination to reproduce experimental pKa's is to compute NPA atomic charge using the CPCM model at the B3LYP/3-21G and M062X/6-311G levels for alcohols (R(2) = 0.995) and thiols (R(2) = 0.986), respectively. The applicability of the suggested protocol is tested with tyrosine and cysteine amino acids, and precise pKa predictions are obtained. The stability of the amino acid pKa's with respect to geometrical changes is also tested by MM-MD and DFT-MD calculations. Considering its strong accuracy and its high computational efficiency, these pKa prediction calculations using atomic charges indicate a promising method for predicting amino acids' pKa in a protein environment.

  5. Review: Bilirubin pKa studies: new models and theories indicate high pKa values in water, dimethylformamide and DMSO.

    PubMed

    Mukerjee, Pasupati; Ostrow, J Donald

    2010-01-01

    Correct aqueous pKa values of unconjugated bilirubin (UCB), a poorly-soluble, unstable substance, are essential for understanding its functions. Our prior solvent partition studies, of unlabeled and [14C] UCB, indicated pKa values above 8.0. These high values were attributed to effects of internal H-bonding in UCB. Many earlier and subsequent studies have reported lower pKa values, some even below 5.0, which are often used to describe the behavior of UCB. We here review 18 published studies that assessed aqueous pKa values of UCB, critically evaluating their methodologies in relation to essential preconditions for valid pKa measurements (short-duration experiments with purified UCB below saturation and accounting for self-association of UCB). These re-assessments identified major deficiencies that invalidate the results of all but our partition studies. New theoretical modeling of UCB titrations shows remarkable, unexpected effects of self-association, yielding falsely low pKa estimates, and provides some rationalization of the titration anomalies. The titration behavior reported for a soluble thioether conjugate of UCB at high aqueous concentrations is shown to be highly anomalous. Theoretical re-interpretations of data in DMSO and dimethylformamide show that those indirectly-derived aqueous pKa values are unacceptable, and indicate new, high average pKa values for UCB in non-aqueous media (>11 in DMSO and, probably, >10 in dimethylformamide). No reliable aqueous pKa values of UCB are available for comparison with our partition-derived results. A companion paper shows that only the high pKa values can explain the pH-dependence of UCB binding to phospholipids, cyclodextrins, and alkyl-glycoside and bile salt micelles.

  6. Highly Perturbed pKa Values in the Unfolded State of Hen Egg White Lysozyme

    PubMed Central

    Bradley, John; O'Meara, Fergal; Farrell, Damien; Nielsen, Jens Erik

    2012-01-01

    The majority of pKa values in protein unfolded states are close to the amino acid model pKa values, thus reflecting the weak intramolecular interactions present in the unfolded ensemble of most proteins. We have carried out thermal denaturation measurements on the WT and eight mutants of HEWL from pH 1.5 to pH 11.0 to examine the unfolded state pKa values and the pH dependence of protein stability for this enzyme. The availability of accurate pKa values for the folded state of HEWL and separate measurements of mutant-induced effects on the folded state pKa values, allows us to estimate the pKa values of seven acidic residues in the unfolded state of HEWL. Asp-48 and Asp-66 display pKa values of 2.9 and 3.1 in our analysis, thus representing the most depressed unfolded state pKa values observed to date. We observe a strong correlation between the folded state pKa values and the unfolded state pKa values of HEWL, thus suggesting that the unfolded state of HEWL possesses a large degree of native state characteristics. PMID:22500764

  7. Ka-Band Multibeam Aperture Phased Array Being Developed

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Kacpura, Thomas J.

    2004-01-01

    Phased-array antenna systems offer many advantages to low-Earth-orbiting satellite systems. Their large scan angles and multibeam capabilities allow for vibration-free, rapid beam scanning and graceful degradation operation for high rate downlink of data to users on the ground. Technology advancements continue to reduce the power, weight, and cost of these systems to make phased arrays a competitive alternative in comparison to the gimbled reflector system commonly used in science missions. One effort to reduce the cost of phased arrays is the development of a Ka-band multibeam aperture (MBA) phased array by Boeing Corporation under a contract jointly by the NASA Glenn Research Center and the Office of Naval Research. The objective is to develop and demonstrate a space-qualifiable dual-beam Ka-band (26.5-GHz) phased-array antenna. The goals are to advance the state of the art in Ka-band active phased-array antennas and to develop and demonstrate multibeam transmission technology compatible with spacecraft in low Earth orbit to reduce the cost of future missions by retiring certain development risks. The frequency chosen is suitable for space-to-space and space-to-ground communication links. The phased-array antenna has a radiation pattern designed by combining a set of individual radiating elements, optimized with the type of radiating elements used, their positions in space, and the amplitude and phase of the currents feeding the elements. This arrangement produces a directional radiation pattern that is proportional to the number of individual radiating elements. The arrays of interest here can scan the main beam electronically with a computerized algorithm. The antenna is constructed using electronic components with no mechanical parts, and the steering is performed electronically, without any resulting vibration. The speed of the scanning is limited primarily by the control electronics. The radiation performance degrades gracefully if a portion of the elements

  8. Malama I Ka `Aina: Fostering the Culture-Science connection

    NASA Astrophysics Data System (ADS)

    Bruno, B.; Chinn, P.

    2005-12-01

    The Malama I Ka `Aina Project (Caring for the land, or sustainability) aims to improve and expand the education of Hawai`i's children by developing and disseminating standards-based, culturally relevant science curricular materials based on an understanding and appreciation of the ways in which traditional Hawaiians interacted with their environment for sustainability. Key concepts include the role of water and the ahupua`a (traditional Hawaiian system of land management), and a culture-based sense of place that includes knowledge of and connection to the land. Elementary, middle, high school and University of Hawai`i teachers work together to develop and implement curricula that are especially relevant to a particular school's science program and issues, e.g., invasive species, students, community and/or geographical location. Participants (typically a mix of teachers, education majors and science majors) enroll in Malama I Ka `Aina, a three-credit course offered through the University of Hawai`i`s Dept. of Curriculum Studies and applicable toward a Bachelor's or Master's degree. This course (team taught by scientists, cultural experts and educational professionals) enables participants to: (1) Study Hawai`i`s unique geology, geography and environmental issues in the context of Hawaiian culture and post Western contact; (2) Use course knowledge to develop, teach and assess Hawaii-oriented, project-based, inquiry activities that address the Hawaii Science Content Standards; (3) Gain an appreciation for the scientific method, and the curiosity that drives science (4) Use educational technology such as PowerPoint, graphing packages and web authoring software to develop electronic resources for educational activities. A sample of the lessons developed by course participants can be found on http://malama.hawaii.edu/schools/index2.html. This project is based at the University of Hawai`i College of Education and funded by an award to P. Chinn by the US Department of

  9. The 8.2 ka event in the northern Alps

    NASA Astrophysics Data System (ADS)

    Luetscher, M.; Hoffmann, D. L.; Müller, W.; Spötl, C.

    2012-04-01

    The 8.2 ka event has been identified as a widespread climate excursion affecting most of the Northern Hemisphere. High-resolution records from ice cores and speleothems constrain the chronology of this event to between 8.21±0.02 and 8.08±0.03 ka BP (Vinther et al. 2006, Cheng et al. 2009). A distinctive asymmetrical pattern in d18O is consistent with modelling results suggesting rapid input of freshwater into the northern Atlantic due to catastrophic drainage of ice-marginal lakes (LeGrande et al., 2008). Despite an increasing amount of data, the regional expression of this event is still poorly understood. Here, we present a new speleothem record from Gasselhöhle in the Northern Calcareous Alps, Austria. The 205 mm-long GAS19 stalagmite was analysed at high resolution for stable isotopes (100 µm) and trace elements (~10-15 µm; continuous LA-ICPMS profiles). Twelve individual MC-ICP-MS U/Th ages underline an annual growth rate of ca. 60 µm during the Early Holocene. The d18O averages -8.9‰, only slightly more depleted than modern carbonate precipitates from the same cave chamber. The 8.2 ka event is marked in GAS19 by a ca. 1‰ excursion with a minimum value of -9.9‰. Largely invariant trace element concentrations (e.g. Mg, U, Sr, Ba) indicate essentially no changes in the local hydrological regime and therefore support the hypothesis of a temperature-dominated signal. The proximity to the lacustrine isotope record from Mondsee (eg. Lauterbach et al. 2011) opens new perspectives for the interpretation of the oxygen isotope signal using two archives at different elevations. Moreover, several coeval speleothem records are available across the Eastern Alps fostering a spatial comparison of the proxy signals associated with this event. Cheng, H. et al. (2009), Geology, 37, 1007-1010 Lauterbach, S. et al. (2011), JQS, 26, 253-267 LeGrande, A.N., Schmidt, G.A. (2008), Paleoceanography, 23, doi: 10.1029/2008PA001610 Vinther, B. et al. (2006), JGR, 111, D13103

  10. Biorelevant pKa (37°C) predicted from the 2D structure of the molecule and its pKa at 25°C

    PubMed Central

    Sun, Na; Avdeef, Alex

    2011-01-01

    Values of the ionization constants at 37°C, which are scarcely reported, are more meaningful for interpreting mechanisms of cellular transport by ionizable molecules and in mechanistic dissolution studies, which are often performed at the biorelevant temperature. An equation was developed where the pKa values of drug-like molecules determined at 25°C can be simply converted to values at 37°C, without additional measurement. The differences between the values, ΔpKa = pKa37 − pKa25, were linearly fitted to a function of pKa25 and the standard entropy of ionization, ΔSo, where the latter term was approximated by the five Abraham linear free energy solvation descriptors using multiple linear regression. The Abraham descriptors (H-bond donor and acceptor strengths, dipolar solute-solvent interactions potential, the pi- and n-electrons dispersion force, and molar volume) were determined from the 2-dimensional structure of the molecules. A total of 143 mostly drug-like molecules (207 pKa values at 25°C and at 37°C) were chosen for the study. The pKa values of many were determined here for the first time. Included were 34 weak acids, 85 weak bases, and 24 amphoteric compounds (6 ordinary ampholytes, 18 zwitterions). PMID:21652160

  11. pKa predictions for proteins, RNAs, and DNAs with the Gaussian dielectric function using DelPhi pKa.

    PubMed

    Wang, Lin; Li, Lin; Alexov, Emil

    2015-12-01

    We developed a Poisson-Boltzmann based approach to calculate the pKa values of protein ionizable residues (Glu, Asp, His, Lys and Arg), nucleotides of RNA and single stranded DNA. Two novel features were utilized: the dielectric properties of the macromolecules and water phase were modeled via the smooth Gaussian-based dielectric function in DelPhi and the corresponding electrostatic energies were calculated without defining the molecular surface. We tested the algorithm by calculating pKa values for more than 300 residues from 32 proteins from the PPD dataset and achieved an overall RMSD of 0.77. Particularly, the RMSD of 0.55 was achieved for surface residues, while the RMSD of 1.1 for buried residues. The approach was also found capable of capturing the large pKa shifts of various single point mutations in staphylococcal nuclease (SNase) from pKa-cooperative dataset, resulting in an overall RMSD of 1.6 for this set of pKa's. Investigations showed that predictions for most of buried mutant residues of SNase could be improved by using higher dielectric constant values. Furthermore, an option to generate different hydrogen positions also improves pKa predictions for buried carboxyl residues. Finally, the pKa calculations on two RNAs demonstrated the capability of this approach for other types of biomolecules. © 2015 Wiley Periodicals, Inc.

  12. A personal communications network using a Ka-band satellite

    NASA Technical Reports Server (NTRS)

    Palmer, Larry C.; Laborde, Enrique; Stern, Alan; Sohn, Philip Y.

    1992-01-01

    The feasibility of a personal communications network using portable terminals that can provide 4.8-kb/s voice communications to a hub station via a Ka-band geosynchronous satellite has been investigated. Tradeoffs are examined so that the combined system of hub and gateway earth stations, the satellite, and the personal terminals can provide a competitive service in terms of cost, availability, and quality. A baseline system that uses a spacecraft with approximately 140 spot beams to cover the contiguous US (CONUS) and 5-W power amplifiers in each beam is described. Satellite access in both the forward and return directions uses frequency-division multiple-access/code-division multiple-access (FDMA/CDMA) with a chip rate of 2.5 Mchip/s.

  13. A personal communications network using a Ka-band satellite

    NASA Technical Reports Server (NTRS)

    Palmer, L. C.; Stern, A.; Sohn, P. Y.

    1991-01-01

    The feasibility of portable communications terminals that can provide 4.8-kbps voice communications to a hub station via a Ka-band geosynchronous satellite was investigated. Tradeoffs are examined so that the combined system of the hub and gateway earth stations, the satellite, and the personal terminals can provide a competitive service in terms of cost, availability, and quality. A baseline system is described using a spacecraft with approximately 140 spot beams that cover CONUS with 5-watt power amplifiers in each beam. Satellite access in both the forward and return directions uses Frequency Division Multiple Access/Code Division Multiple Access (FDMA/CDMA) with a chip rate of 2.5 Mchip/sec. An experiment is recommended using the Advanced Communications Technology Satellite (ACTS) to demonstrate some of the features of the portable terminal concept.

  14. Advanced Ka-Band Transceiver With Monopulse Tracking

    NASA Technical Reports Server (NTRS)

    Khan, Abdur; Hoppe, Dan; Epp, Larry; Perez, Raul

    2006-01-01

    A proposed Ka-band transmitting/ receiving system would embody a unique combination of established and semi-proven design features. The proposed system (see figure) would include a monopulse receiving feedback loop and a mirror that could be moved by piezoelectric actuators in the feedback loop to adjust the aim of the transmitted and received radio beams. Unlike in a phased-array tracking system, phase shifters (which can be complex and expensive) would not be needed in this monopulse tracking system. Moreover, the monopulse-tracking loop could be combined with other subsystems used in established subreflector and antenna designs. The final transmitter power amplifier in the proposed system would be a quasi-optical power amplifier (QOPA) -- a combination of a planar array of 25 amplifiers and corresponding planar arrays of antenna elements, such that free-space power combining would take place at the output.

  15. A personal communications network using a Ka-band satellite

    NASA Technical Reports Server (NTRS)

    Palmer, L. C.; Stern, A.; Sohn, P. Y.

    1991-01-01

    The feasibility of portable communications terminals that can provide 4.8-kbps voice communications to a hub station via a Ka-band geosynchronous satellite was investigated. Tradeoffs are examined so that the combined system of the hub and gateway earth stations, the satellite, and the personal terminals can provide a competitive service in terms of cost, availability, and quality. A baseline system is described using a spacecraft with approximately 140 spot beams that cover CONUS with 5-watt power amplifiers in each beam. Satellite access in both the forward and return directions uses Frequency Division Multiple Access/Code Division Multiple Access (FDMA/CDMA) with a chip rate of 2.5 Mchip/sec. An experiment is recommended using the Advanced Communications Technology Satellite (ACTS) to demonstrate some of the features of the portable terminal concept.

  16. A Ka-band GaAs monolithic phase shifter

    NASA Technical Reports Server (NTRS)

    Sokolov, V.; Geddes, J. J.; Contolatis, A.; Bauhahn, P. E.; Chao, C.

    1983-01-01

    The design and performance of a GaAs monolithic 180-degree one-bit switched line phase shifter test circuit for Ka-band operation is presented. A self-aligned gate (SAG) fabrication technique is also described that reduces resistive parasitics in the switching FET's. Over the 27.5-30 GHz band, typical measured differential insertion phase is within 10-20 deg of the ideal time delay characteristic. Over the same band, the insertion loss for the SAG phase shifter is about 2.5-3 dB per bit. The SAG fabrication technique holds promise in reducing phase shifter insertion loss to about 1.5 dB/bit for 30-GHz operation.

  17. Explicit solvent models in protein pKa calculations.

    PubMed

    Gibas, C J; Subramaniam, S

    1996-07-01

    Continuum methods for calculation of protein electrostatics treat buried and ordered water molecules by one of two approximations; either the dielectric constant of regions containing ordered water molecules is equal to the bulk solvent dielectric constant, or it is equal to the protein dielectric constant though no fixed atoms are used to represent water molecules. A method for calculating the titration behavior of individual residues in proteins has been tested on models of hen egg white lysozyme containing various numbers of explicit water molecules. Water molecules were included based on hydrogen bonding, solvent accessibility, and/or proximity to titrating groups in the protein. Inclusion of water molecules significantly alters the calculated titration behavior of individual titrating sites, shifting calculated pKa values by up to 0.5 pH unit. Our results suggest that approximately one water molecule within hydrogen-bonding distance of each charged group should be included in protein electrostatics calculations.

  18. A personal communications network using a Ka-band satellite

    NASA Technical Reports Server (NTRS)

    Palmer, Larry C.; Laborde, Enrique; Stern, Alan; Sohn, Philip Y.

    1992-01-01

    The feasibility of a personal communications network using portable terminals that can provide 4.8-kb/s voice communications to a hub station via a Ka-band geosynchronous satellite has been investigated. Tradeoffs are examined so that the combined system of hub and gateway earth stations, the satellite, and the personal terminals can provide a competitive service in terms of cost, availability, and quality. A baseline system that uses a spacecraft with approximately 140 spot beams to cover the contiguous US (CONUS) and 5-W power amplifiers in each beam is described. Satellite access in both the forward and return directions uses frequency-division multiple-access/code-division multiple-access (FDMA/CDMA) with a chip rate of 2.5 Mchip/s.

  19. Miniaturized Ka-Band Dual-Channel Radar

    NASA Technical Reports Server (NTRS)

    Hoffman, James P.; Moussessian, Alina; Jenabi, Masud; Custodero, Brian

    2011-01-01

    Smaller (volume, mass, power) electronics for a Ka-band (36 GHz) radar interferometer were required. To reduce size and achieve better control over RFphase versus temperature, fully hybrid electronics were developed for the RF portion of the radar s two-channel receiver and single-channel transmitter. In this context, fully hybrid means that every active RF device was an open die, and all passives were directly attached to the subcarrier. Attachments were made using wire and ribbon bonding. In this way, every component, even small passives, was selected for the fabrication of the two radar receivers, and the devices were mounted relative to each other in order to make complementary components isothermal and to isolate other components from potential temperature gradients. This is critical for developing receivers that can track each other s phase over temperature, which is a key mission driver for obtaining ocean surface height. Fully hybrid, Ka-band (36 GHz) radar transmitter and dual-channel receiver were developed for spaceborne radar interferometry. The fully hybrid fabrication enables control over every aspect of the component selection, placement, and connection. Since the two receiver channels must track each other to better than 100 millidegrees of RF phase over several minutes, the hardware in the two receivers must be "identical," routed the same (same line lengths), and as isothermal as possible. This level of design freedom is not possible with packaged components, which include many internal passive, unknown internal connection lengths/types, and often a single orientation of inputs and outputs.

  20. ACTIVE GALACTIC NUCLEI AND THE TRUNCATION OF STAR FORMATION IN K+A GALAXIES

    SciTech Connect

    Brown, Michael J. I.; Palamara, David; Moustakas, John; Caldwell, Nelson; Cool, Richard J.; Zaritsky, Dennis; Dey, Arjun; Jannuzi, Buell T.; Hickox, Ryan C.; Murray, Stephen S.

    2009-09-20

    We have searched for active galactic nuclei (AGNs) in K+A galaxies, using multiwavelength imaging and spectroscopy in the Booetes field of the NOAO Deep Wide-Field Survey. The K+A galaxies, which have had their star formation rapidly truncated, are selected via their strong Balmer absorption lines and weak Halpha emission. Our sample consists of 24 K+A galaxies selected from 6594 0.10 < z < 0.35 galaxies brighter than I = 20 with optical spectroscopy from the AGN and Galaxy Evolution Survey. Two thirds of the K+A galaxies are likely ongoing galaxy mergers, with nearby companion galaxies or tidal tails. Galaxy mergers may be responsible for the truncation of star formation, or we are observing the aftermath of merger triggered starbursts. As expected, the optical colors of K+A galaxies largely fall between blue galaxies with ongoing star formation and red passive galaxies. However, only 1% of the galaxies with colors between the red and blue populations are K+A galaxies, and we conclude that the truncation of star formation in K+A galaxies must have been unusually abrupt ({approx}<100 Myr). We examined the AGN content of K+A galaxies with both optical emission-line ratios (BPT diagrams) and Chandra X-ray imaging. At least half of all K+A galaxies display the optical emission-line ratios of AGNs, and a third of M{sub R} < -22 K+A galaxies host AGNs with X-ray luminosities of {approx}10{sup 42} erg s{sup -1}. The faintest K+A galaxies do not show clear evidence for hosting AGNs, having emission-line ratios consistent with photoionization by massive stars and few X-ray detections. We speculate that two mechanisms may be responsible for the truncation of star formation in K+A galaxies, with AGN feedback only playing a role in M{sub R} {approx}< -20.5 galaxies.

  1. Heat loss analysis of a 10 kA warm dielectric HTS DC cable

    NASA Astrophysics Data System (ADS)

    Dai, Shaotao; Xiao, Liye; Teng, Yuping; Song, Naihao; Gao, Zhiyuan; Zhu, Zhiqing; Liang, Xueming; Cao, Zhicheng; Zhang, Dong; Ma, Tao; Zhang, Hongen; Lin, Liangzhen

    2014-09-01

    A 10 kA/360 m warm-dielectric high-temperature superconducting direct current (DC) power cable system (10 kA cable), supported jointly the Chinese government and industrial enterprise, was developed and has been operating as a branch circuit to transmit power for a 320 kA aluminum electrolyzing production line for more than 10 months at an industrial plant in central China. Both the 10 kA cable and its supporting system of the cable system are introduced. The cryogenic system for the 10 kA cable adopts closed loop and the sub-cooled liquid nitrogen is forced to flow inside by a pump. The design of corrugated cryogenic envelope pipe is modularized and every independent module has two standardized joints, which makes it easy to integrate with the other pipes and the terminations. The heat loss sources and the structure including both the termination and the cryogenic envelope pipe of the 10 kA cable are discussed. The total heat loss of the 10 kA cable excluding the loss of cryogenic pipe for liquid nitrogen backward flowing is designed to be less than 1698 W at 10 kA, and the heat loss was compared and discussed with that of the aluminum bar. The field test and commissioning of the cable show that the 10 kA cable performs steadily and its heat loss is less than the expected value.

  2. Dating North European mammoths (Mammuthus primigenius Blum.): a nearly continuous record from 53 ka to 11 ka

    NASA Astrophysics Data System (ADS)

    Ukkonen, P.; Aaris-Sørensen, K.; Arppe, L.; Clark, P. U.; Daugnora, L.; Lister, A.; Lõugas, L.; Seppä, H. A.; Stuart, A. J.; Wojtal, P.; Zupins, I.

    2010-05-01

    nearly continuously from 53 ka to 11 ka, completely disappearing from the area only during the Last Glacial Maximum (LGM). From the northern parts of the study area, mammoths disappeared ca. 27 ka ago. In the south they survived until the LGM, and occupied the area again during deglaciation. Mammoths survived in the eastern part of the study area until the end of Younger Dryas. References Weninger, B., Jöris, O., 2008. A 14C age calibration curve for the last 60 ka: the Greenland-Hulu U/Th timescale and its impact on understanding the Middle to Upper Paleolithic transition in Western Eurasia. Journal of Human Evolution 55,772-781. Weninger, B., Jöris, O., Danzeglocke, U., 2008. CalPal-2007. Cologne Radiocarbon Calibration & Palaeoclimate Research Package. http://www.calpal.de/ [2008-09-18].

  3. New insights on water level variability for Lake Turkana for the past 15 ka and at 150 ka from relict beaches

    NASA Astrophysics Data System (ADS)

    Forman, S. L.; Wright, D.

    2015-12-01

    Relict beaches adjacent to Lake Turkana provide a record of water level variability for the Late Quaternary. This study focused on deciphering the geomorphology, sedimentology, stratigraphy and 14C chronology of strand plain sequences in the Kalokol and Lothagam areas. Nine >30 m oscillations in water level were documented between ca. 15 and 4 ka. The earliest oscillation between ca. 14.5 and 13 ka is not well constrained with water level to at least 70 m above the present surface and subsequently fell to at least 50 m. Lake level increased to ~ 90 m between ca. 11.2 and 10.4 ka, post Younger Dryas cooling. Water level fell by >30 m by 10.2 ka, with another potential rise at ca. 8.5 ka to >70 m above current level. Lake level regressed by > 40 m at 8.2 ka coincident with cooling in the equatorial Eastern Atlantic Ocean. Two major >70 m lake level oscillations centered at 6.6 and 5.2 ka may reflect enhanced convection with warmer sea surface temperatures in the Western Indian Ocean. The end of the African Humid Period occurred from ca. 8.0 to 4.5 ka and was characterized by variable lake level (± > 40 m), rather than one monotonic fall in water level. This lake level variability reflects a complex response to variations in the extent and intensity of the East and West African Monsoons near geographic and topographic limits within the catchment of Lake Turkana. Also, for this closed lake basin excess and deficits in water input are amplified with a cascading lake effect in the East Rift Valley and through the Chew Bahir Basin. The final regression from a high stand of > 90 m began at. 5.2 ka and water level was below 20 m by 4.5 ka; and for the remainder of the Holocene. This sustained low stand is associated with weakening of the West African Monsoon, a shift of the mean position of Congo Air Boundary west of the Lake Turkana catchment and with meter-scale variability in lake level linked to Walker circulation across the Indian Ocean. A surprising observation is

  4. Post-200-ka Pyroclastic Eruptions of the Yellowstone Plateau

    NASA Astrophysics Data System (ADS)

    Morgan, L. A.; Shanks, W. C.

    2010-12-01

    Pyroclastic deposits intercalated in post-Yellowstone-caldera rhyolitic lava flows form a minor component of the total volume of high-silica rhyolites erupted between 200 and 70 ka. Such events produced significant volumes of ash, fast-moving pyroclastic flows, and volcanic gases during young eruptions on the Plateau. Thus, while these were less common events, it is important to know the details of these deposits, including the number and frequency of eruptions, their sources, and possible associations or relations to other volcanic or tectonic events. The tuff of Bluff Point is the largest of these <640-ka pyroclastic flows and is mapped within the Central Plateau Member above the Yellowstone Caldera. Eruption of the tuff of Bluff Point, around 170-200 ka, is estimated from current maps to be ~50 km3 and resulted in collapse of the 10-km-wide West Thumb caldera, centered in the western-most basin of Yellowstone Lake. Large amounts of water derived from an ancestral Yellowstone Lake may have been involved in the eruption, suggested by large blocks of glass and abundant smaller fragments of obsidian incorporated into the ignimbrite. The oval-shaped West Thumb caldera occurs within the much larger and older Yellowstone Caldera and has dimensions comparable to Crater Lake (Oregon). New mapping, variable 40Ar/39Ar ages, and differences in mineralogy, grain size, and component data between key exposures all suggest that the tuff of Bluff Point, as mapped, represents as many as three pyroclastic eruptions. These eruptions may have occurred over a 20- to 40-k.y. interval, which may explain enigmatic age discrepancies. Stratigraphic, mineralogical, geochemical, radiometric, granulometric, and component analyses are being employed to unravel the details and origins of these pyroclastic deposits, which are rich in glass, pumice, ash, crystal, and lithic fragments. Several pumice morphologies are present in each deposit. Pyroclastic fallout, sinter, and volcaniclastic

  5. Highly Efficient Amplifier for Ka-Band Communications

    NASA Technical Reports Server (NTRS)

    1996-01-01

    An amplifier developed under a Small Business Innovation Research (SBIR) contract will have applications for both satellite and terrestrial communications. This power amplifier uses an innovative series bias arrangement of active devices to achieve over 40-percent efficiency at Ka-band frequencies with an output power of 0.66 W. The amplifier is fabricated on a 2.0- by 3.8-square millimeter chip through the use of Monolithic Microwave Integrated Circuit (MMIC) technology, and it uses state-of-the-art, Pseudomorphic High-Electron-Mobility Transistor (PHEMT) devices. Although the performance of the MMIC chip depends on these high-performance devices, the real innovations here are a unique series bias scheme, which results in a high-voltage chip supply, and careful design of the on-chip planar output stage combiner. This design concept has ramifications beyond the chip itself because it opens up the possibility of operation directly from a satellite power bus (usually 28 V) without a dc-dc converter. This will dramatically increase the overall system efficiency. Conventional microwave power amplifier designs utilize many devices all connected in parallel from the bias supply. This results in a low-bias voltage, typically 5 V, and a high bias current. With this configuration, substantial I(sup 2) R losses (current squared times resistance) may arise in the system bias-distribution network. By placing the devices in a series bias configuration, the total current is reduced, leading to reduced distribution losses. Careful design of the on-chip planar output stage power combiner is also important in minimizing losses. Using these concepts, a two-stage amplifier was designed for operation at 33 GHz and fabricated in a standard MMIC foundry process with 0.20-m PHEMT devices. Using a 20-V bias supply, the amplifier achieved efficiencies of over 40 percent with an output power of 0.66 W and a 16-dB gain over a 2-GHz bandwidth centered at 33 GHz. With a 28-V bias, a power

  6. Ka Hana `Imi Na`auao: A Science Curriculum Project

    NASA Astrophysics Data System (ADS)

    Napeahi, K.; Roberts, K. D.; Galloway, L. M.; Stodden, R. A.; Akuna, J.; Bruno, B.

    2005-12-01

    In antiquity, the first people to step foot on what are now known as the Hawaiian islands skillfully traversed the Pacific Ocean using celestial navigation and learned observations of scientific phenomena. Long before the Western world ventured beyond the horizon, Hawaiians had invented the chronometer, built aqueduct systems (awai) that continue to amaze modern engineers, and had preventive health systems as well as a comprehensive knowledge of medicinal plants (including antivirals) which only now are working their way through trials for use in modern pharmacopia. Yet, today, Native Hawaiians are severely underrepresented in science-related fields, reflecting (in part) a failure of the Western educational system to nurture the potential of these resourceful students, particularly the many "at-risk" students who are presently over-represented in special education. A curriculum which draws from and incorporates traditional Hawaiian values and knowledge is needed to reinforce links to the inquiry process which nurtured creative thinking during the renaissance of Polynesian history. The primary goal of the Ka Hana `Imi Na`auao Project (translation: `science` or `work in which you seek enlightenment, knowledge or wisdom`) is to increase the number of Native Hawaiian adults in science-related postsecondary education and employment fields. Working closely with Native Hawaiian cultural experts and our high school partners, we will develop and implement a culturally responsive 11th and 12th grade high school science curriculum, infused with math, literacy and technology readiness skills. Software and assistive technology will be used to adapt instruction to individual learners` reading levels, specific disabilities and learning styles. To ease the transition from secondary to post-secondary education, selected grade 12 students will participate in planned project activities that link high school experiences with college science-related programs of study. Ka Hana `Imi Na

  7. Did the 8.2 ka event affect southern Africa?

    NASA Astrophysics Data System (ADS)

    Shaw, Paul

    2014-05-01

    Palaeoenvironmental reconstruction of southern Africa over the past 4 decades has focused largely on the last glacial cycle, and, more recently, events during to Holocene, interpreted largely at the millennial scale. Little attention has been given to sub-millenial drivers and impacts, other than the Little Ice Age (HolmgreN et al 2001). The 8.2ka event has been recognized in Europe for over half a century from peat cores and dendrochronology. A Bond Event caused by disruption of the Gulf Stream by melting Laurentian ice, it lasted around 100 years and resulted in a fall in temperature in northern Europe of up to 6o C. Recently published high-resolution speleothem records have indicated significant short-term change over a much wider area than previously thought, including the Caribbean, eastern Brazil, Spain, Oman and China. A recent paper on Trinidad (Boyd et al, in press) emphasizes a period of prolonged drought in the southern Caribbean due to a southerly emplacement of the ITCZ. The question then arises whether this shift affected the southern hemisphere, and if so, what would be the likely impacts and evidence. A study of late Quaternary lake levels in Lake Chilwa, Malawi (Thomas et al 2009) noted a correspondence between high lake stands and Heinrich events, whilst modeling of Atlantic freshwater influx using the HadCM3 GCM indicates negative precipitation anomalies in the Caribbean and west Africa, with a significant positive anomaly in the interior of southern Africa, possibly linked to enhanced monsoonal activity in the Indian Ocean. These patterns in southern and western Africa have been suggested around 8.2 ka in a review of early Holocene data (Burrough & Thomas 2013), but the chronological resolution is not sufficient to conclude the observation. The only speleothem record for this period, T8 in Cold Air Cave, Makapansgat Valley (Holmgren et al 2003) shows an anomaly, but with temporal resolution at a 50 yr sampling interval, this again is speculative

  8. A View from the Cocoon--Space Categorization in the Korean Verb [na-ka-ta].

    ERIC Educational Resources Information Center

    Kim, Alan Hyun-Oak

    1996-01-01

    Analysis of the Korean verb "na-ka-ta" ("to get out, exit") focuses on why an expression such as "kyengkicang-ey na-ka-ta" ("someone goes out/in to the sports arena") is acceptable only in the context that the person's entering the arena is for the purpose of a contest, while it becomes semantically…

  9. Radiocarbon dating from 40 to 60 ka BP at Border Cave, South Africa

    NASA Astrophysics Data System (ADS)

    Bird, M. I.; Fifield, L. K.; Santos, G. M.; Beaumont, P. B.; Zhou, Y.; di Tada, M. L.; Hausladen, P. A.

    2003-04-01

    We present 21 radiocarbon dates on 19 charcoal samples from the sedimentary sequence preserved in Border Cave, South Africa. The background radiocarbon activity for charcoal from the cave was determined to be 0.050±0.018 percent modern carbon, from the analysis of a radiocarbon-dead sample from unit 5WA. Radiocarbon ages for individual samples ranged from 25.2 to >58.2 ka BP. The error-weighted mean ages for successively older strata are 38.5+0.85/-0.95 ka BP for unit 1WA, 50.2+1.1/-1.0 ka BP for units 2BS.LR.A and 2BS.LR.B, 56.5+2.7/-2.0 ka BP for unit 2BS.LR.C and 59.2+3.4/-2.4 ka BP for unit 2WA. This radiocarbon chronology is consistent with independent chronologies derived from electron spin resonance and amino acid racemization dating. The results therefore provide further evidence that radiocarbon dating of charcoal by the ABOX-SC technique can yield reliable radiocarbon ages beyond 40 ka BP. They also imply that Border Cave 5, a modern human mandible, predates >58.2 ka BP and that the Middle Stone Age (Mode 3)—Later Stone Age (Mode 5) transition of Border Cave was largely effected between ˜56.5 and ˜41.6 ka ago.

  10. X/X/Ka-band prime focus feed antenna for the Mars Observer beacon spacecraft

    NASA Technical Reports Server (NTRS)

    Stanton, P.; Reilly, H.; Esquivel, M.

    1988-01-01

    The results of an X/X/Ka-band feed design concept demonstration are presented. The purpose is to show the feasibility of adding a Ka-band beacon to the Mars Observer spacecraft. Scale model radiation patterns were made and analyzed.

  11. Electrostatic forces in two lysozymes: calculations and measurements of histidine pKa values.

    PubMed

    Takahashi, T; Nakamura, H; Wada, A

    1992-08-01

    In order to examine the electrostatic forces in globular proteins, pKa values and their ionic strength dependence of His residues of hen egg white lysozyme (HEWL) and human lysozyme (HUML) were measured, and they were compared with those calculated numerically. pKa values of His residues in HEWL, HUML, and short oligopeptides were determined from chemical shift changes of His side chains by 1H-nmr measurements. The associated changes in pKa values in HEWL and HUML were calculated by solving the Poisson-Boltzmann equations numerically for macroscopic dielectric models. The calculated pKa changes and their ionic strength dependence agreed fairly well with the observed ones. The contribution from each residue of each alpha-helix dipole to the pKa values and their ionic strength dependence was analyzed using Green's reciprocity theorem. The results indicate that (1) the pKa of His residues are largely affected by surrounding ionized and polar groups; (2) the ionic strength dependence of the pKa values is determined by the overall charge distributions and their accessibilities to solvent; and (3) alpha-helix dipoles make a significant contribution to the pKa, when the His residue is close to the helix terminus and not fully exposed to the solvent.

  12. Toba Eruption Simulations with 74 ka B.P. Forcing

    NASA Astrophysics Data System (ADS)

    Robock, A.

    2011-12-01

    Previous simulations of the effects of the 74 ka B.P Toba volcanic eruption have used present-day orbital, greenhouse gas, tropospheric aerosol, sea level, ice sheet, and land albedo boundary conditions, and have found that a very large volcanic eruption would not produce ice sheet initiation. Even though winter conditions would prevail for several years with snow not melting in the summer over Northern Hemisphere continents, once the stratospheric aerosols settled out of the atmosphere, the climate tended back toward present conditions. However, the Toba eruption occurred with different orbital forcing, lower greenhouse gas and tropospheric aerosol concentrations, lower sea level, more extensive ice sheets, and different vegetation producing, for the most part, a higher land albedo. Therefore, to investigate whether a supervolcano eruption at the time of the Toba eruption could have been partly responsible for the observed widespread glaciation that followed it, I conducted general circulation model simulations with the NCAR Community Earth System Model 1.0, forced by large stratospheric aerosol loading and 74k BP boundary conditions. The simulations were done with three different assumptions about aerosol lifetime, the same as for the 1991 Pinatubo eruption, shorter lifetimes accounting for aerosol growth, and longer lifetimes accounting for slower sulfur dioxide conversion to sulfates. The results show strong dependence on both boundary conditions and aerosol forcing.

  13. Absolute paleointensity from Hawaiian lavas younger than 35 ka

    USGS Publications Warehouse

    Valet, J.-P.; Tric, E.; Herrero-Bervera, E.; Meynadier, L.; Lockwood, J.P.

    1998-01-01

    Paleointensity studies have been conducted in air and in argon atmosphere on nine lava flows with radiocarbon ages distributed between 3.3 and 28.2 ka from the Mauna Loa volcano in the big island of Hawaii. Determinations of paleointensity obtained at eight sites depict the same overall pattern as the previous results for the same period in Hawaii, although the overall average field intensity appears to be lower. Since the present results were determined at higher temperatures than in the previous studies, this discrepancy raises questions regarding the selection of low versus high-temperature segments that are usually made for absolute paleointensity. The virtual dipole moments are similar to those displayed by the worldwide data set obtained from dated lava flows. When averaged within finite time intervals, the worldwide values match nicely the variations of the Sint-200 synthetic record of relative paleointensity and confirm the overall decrease of the dipole field intensity during most of this period. The convergence between the existing records at Hawaii and the rest of the world does not favour the presence of persistent strong non-dipole components beneath Hawaii for this period.

  14. Proxy benchmarks for intercomparison of 8.2 ka simulations

    NASA Astrophysics Data System (ADS)

    Morrill, C.; Anderson, D. M.; Bauer, B. A.; Buckner, R.; Gille, E. P.; Gross, W. S.; Hartman, M.; Shah, A.

    2013-02-01

    The Paleoclimate Modelling Intercomparison Project (PMIP3) now includes the 8.2 ka event as a test of model sensitivity to North Atlantic freshwater forcing. To provide benchmarks for intercomparison, we compiled and analyzed high-resolution records spanning this event. Two previously-described anomaly patterns that emerge are cooling around the North Atlantic and drier conditions in the Northern Hemisphere tropics. Newer to this compilation are more robustly-defined wetter conditions in the Southern Hemisphere tropics and regionally-limited warming in the Southern Hemisphere. Most anomalies around the globe lasted on the order of 100 to 150 yr. More quantitative reconstructions are now available and indicate cooling of ~ 1 °C and a ~ 20% decrease in precipitation in parts of Europe as well as spatial gradients in δ18O from the high to low latitudes. Unresolved questions remain about the seasonality of the climate response to freshwater forcing and the extent to which the bipolar seesaw operated in the early Holocene.

  15. Proxy benchmarks for intercomparison of 8.2 ka simulations

    NASA Astrophysics Data System (ADS)

    Morrill, C.; Anderson, D. M.; Bauer, B. A.; Buckner, R.; Gille, E. P.; Gross, W. S.; Hartman, M.; Shah, A.

    2012-08-01

    The Paleoclimate Modelling Intercomparison Project (PMIP3) now includes the 8.2 ka event as a test of model sensitivity to North Atlantic freshwater forcing. To provide benchmarks for intercomparison, we compiled and analyzed high-resolution records spanning this event. Two previously-described anomaly patterns that emerge are cooling around the North Atlantic and drier conditions in the Northern Hemisphere tropics. Newer to this compilation are more robustly-defined wetter conditions in the Southern Hemisphere tropics and regionally-limited warming in the Southern Hemisphere. Most anomalies around the globe lasted on the order of 100 to 150 yr. More quantitative reconstructions are now available and indicate cooling of 1.0 to 1.2 °C and a ~20% decrease in precipitation in parts of Europe, as well as spatial gradients in δ18O from the high to low latitudes. Unresolved questions remain about the seasonality of the climate response to freshwater forcing and the extent to which the bipolar seesaw operated in the early Holocene.

  16. Ka-Band Transponder for Deep-Space Radio Science

    NASA Technical Reports Server (NTRS)

    Dennis, Matthew S.; Mysoor, Narayan R.; Folkner, William M.; Mendoza, Ricardo; Venkatesan, Jaikrishna

    2008-01-01

    A one-page document describes a Ka-band transponder being developed for use in deep-space radio science. The transponder receives in the Deep Space Network (DSN) uplink frequency band of 34.2 to 34.7 GHz, transmits in the 31.8- to 32.3 GHz DSN downlink band, and performs regenerative ranging on a DSN standard 4-MHz ranging tone subcarrier phase-modulated onto the uplink carrier signal. A primary consideration in this development is reduction in size, relative to other such transponders. The transponder design is all-analog, chosen to minimize not only the size but also the number of parts and the design time and, thus, the cost. The receiver features two stages of frequency down-conversion. The receiver locks onto the uplink carrier signal. The exciter signal for the transmitter is derived from the same source as that used to generate the first-stage local-oscillator signal. The ranging-tone subcarrier is down-converted along with the carrier to the second intermediate frequency, where the 4-MHz tone is demodulated from the composite signal and fed into a ranging-tone-tracking loop, which regenerates the tone. The regenerated tone is linearly phase-modulated onto the downlink carrier.

  17. Detecting small seamounts in AltiKa repeat cycle data

    NASA Astrophysics Data System (ADS)

    Marks, K. M.; Smith, W. H. F.

    2016-12-01

    We present a technique of stacking repeat cycles of satellite altimeter sea surface height profiles that lowers the noise and improves the resolution of small seamounts. Our approach differs from other studies because it uses the median (not the mean) of the stacks, which suppresses outliers. Seamounts as small as 720 m tall are easily detected in stacked 40 Hz AltiKa data profiles, and a 500 m tall seamount is perceptible. Noise variance decreases with an increase in the number of cycles stacked, and RMS noise dips below 2 cm when 11 or more cycles are stacked. Coherence analyses between geoid height and bathymetry show that full wavelengths down to about 10 km can be resolved. Comparisons of study areas with and without seamounts find that signal from small seamounts lies in the 10-28 km waveband. A simple Gaussian band-pass filter based on the seamount waveband passes signals that can be used in seamount detection studies. Such studies may find seamounts <2 km tall that are predicted to be abundant on the ocean floor.

  18. Thomson Scattering on exploding wires at 800 kA

    NASA Astrophysics Data System (ADS)

    Greenly, John; Seyler, Charles; Banasek, Jacob; Potter, William

    2016-10-01

    Laser Thomson scattering measurements have been carried out on a single 0.25 mm diameter Al wire load driven with an 800 kA, 100 ns risetime pulse on the COBRA pulsed power facility. The 527 nm, 10 J, 5 ns laser is brought to a line focus on a chord across the unstable, roughly cylindrical plasma column of the wire, which reaches 8mm outer diameter at 100 ns. The laser path is either on axis or 2mm or 4mm off axis. Scattered signals are collected on a fiber array yielding data across the laser path through the plasma. The scattered light is easily visible over the wire plasma self-emission. The scattered spectra have highly complex structures comprised of as many as four distinct spectral peaks spread over 1 nm in wavelength, both red-and blue-shifted. On axis, the laser does not reach the far side of the plasma, being totally absorbed and/or refracted out of its path. 2 mm off-axis the beam is severely refracted, probably from near the critical surface in the plasma, appearing in images taken with cameras 45 degrees off its entering path. The scattering should be in the collective regime, and analysis is underway to extract information on flow velocities and temperatures within the volume, of 0.5mm radius, imaged by each fiber. Work supported by US DOE NNSA Grant DE-NA0001855.

  19. Ka-band (32 GHz) benefits to planned missions

    NASA Technical Reports Server (NTRS)

    Hansen, D. M.; Kliore, A. J.

    1987-01-01

    The benefits of using 32 GHz downlinks for a set of deep space missions, as well as the implications to radio science and the Deep Space Network (DSN) are documented. The basic comparison is between the use of the current X-band (8.4 GHz) and a 32 GHZ (Ka-band) downlink. There was shown to be approximately an 8 dB (about 600%) link advantage for 32 GHz. This 8 dB advantage would be able to either reduce mission cost or improve mission science return. Included here are studies on how the 8 dB advantage would be used for the Cassini and Mars Sample Return missions. While the work is preliminary, it shows that the 8 dB advantage can be exploited to provide large benefits to future deep space missions. There can be significant mass and/or power savings to the spacecraft, which can translate into cost savings. Alternatively, the increased downlink telecommunications performance can provide a greater science return.

  20. A transportable 50 kA dual mode lightning simulator

    NASA Technical Reports Server (NTRS)

    Salisbury, K.; Lloyd, S.; Chen, Y. G.

    1991-01-01

    A transportable lightning simulator was designed, built and tested, which is capable of delivering more than 50 kA to an 8 micro-H test object. The simulator was designed to be a versatile device in the lightning laboratory while meeting the requirements of MIL-STD-1757A for component E current waveforms. The system is capable of operating in either a ringing mode with a Q greater than 5 and a nominal frequency of 160 kHz, or a unipolar mode with no hardware configuration changes. The ringing mode is obtained by the LCR series circuit formed by the pulse generator and test object. The unipolar mode is obtained by closing an electrically triggered crowbar switch at peak current. The simulator exceeds the peak current requirement and rate of rise requirements for MIL-STD-1757A in both the ringing and unipolar modes. The pulse half width in the unipolar mode is in excess of 50 microsec and the action is in excess of 10(exp 5) A(exp 2)s. The design, component values, and test results are presented.

  1. Rain Fade Compensation for Ka-Band Communications Satellites

    NASA Technical Reports Server (NTRS)

    Mitchell, W. Carl; Nguyen, Lan; Dissanayake, Asoka; Markey, Brian; Le, Anh

    1997-01-01

    This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.

  2. Ka-Band Parabolic Deployable Antenna (KaPDA) Enabling High Speed Data Communication for CubeSats

    NASA Technical Reports Server (NTRS)

    Sauder, Jonathan F.; Chahat, Nacer; Hodges, Richard; Thomson, Mark W.; Rahmat-Samii, Yahya

    2015-01-01

    CubeSats are at a very exciting point as their mission capabilities and launch opportunities are increasing. But as instruments become more advanced and operational distances between CubeSats and earth increase communication data rate becomes a mission-limiting factor. Improving data rate has become critical enough for NASA to sponsor the Cube Quest Centennial Challenge when: one of the key metrics is transmitting as much data as possible from the moon and beyond Currently, many CubeSats communicate on UHF bands and those that have high data rate abilities use S-band or X-band patch antennas. The CubeSat Aneas, which was launched in September 2012, pushed the envelope with a half-meter S-band dish which could achieve 100x the data rate of patch antennas. A half-meter parabolic antenna operating at Ka-band would increase data rates by over 100x that of the AMOS antenM and 10,000 that of X-band patch antennas.

  3. The rise and fall of Lake Bonneville between 45 and 10.5 ka

    USGS Publications Warehouse

    Benson, L.V.; Lund, S.P.; Smoot, J.P.; Rhode, D.E.; Spencer, R.J.; Verosub, K.L.; Louderback, L.A.; Johnson, C.A.; Rye, R.O.; Negrini, R.M.

    2011-01-01

    A sediment core taken from the western edge of the Bonneville Basin has provided high-resolution proxy records of relative lake-size change for the period 45.1-10.5 calendar ka (hereafter ka). Age control was provided by a paleomagnetic secular variation (PSV)-based age model for Blue Lake core BL04-4. Continuous records of ??18O and total inorganic carbon (TIC) generally match an earlier lake-level envelope based on outcrops and geomorphic features, but with differences in the timing of some hydrologic events/states. The Stansbury Oscillation was found to consist of two oscillations centered on 25 and 24 ka. Lake Bonneville appears to have reached its geomorphic highstand and began spilling at 18.5 ka. The fall from the highstand to the Provo level occurred at 17.0 ka and the lake intermittently overflowed at the Provo level until 15.2 ka, at which time the lake fell again, bottoming out at ~14.7 ka. The lake also fell briefly below the Provo level at ~15.9 ka. Carbonate and ??18O data indicate that between 14.7 and 13.1 ka the lake slowly rose to the Gilbert shoreline and remained at about that elevation until 11.6 ka, when it fell again. Chemical and sedimentological data indicate that a marsh formed in the Blue Lake area at 10.5 ka.Relatively dry periods in the BL04-4 records are associated with Heinrich events H1-H4, suggesting that either the warming that closely followed a Heinrich event increased the evaporation rate in the Bonneville Basin and (or) that the core of the polar jet stream (PJS) shifted north of the Bonneville Basin in response to massive losses of ice from the Laurentide Ice Sheet (LIS) during the Heinrich event. The second Stansbury Oscillation occurred during Heinrich event H2, and the Gilbert wet event occurred during the Younger Dryas cold interval. Several relatively wet events in BL04-4 occur during Dansgaard-Oeschger (DO) warm events.The growth of the Bear River glacier between 32 and 17 ka paralleled changes in the values of proxy

  4. Mars Reconnaissance Orbiter Ka-band (32 GHz) Demonstration: Cruise Phase Operations

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin; Morabito, David; Border, James S.; Davarian, Faramaz; Lee, Dennis; Mendoza, Ricardo; Britcliffe, Michael; Weinreb, Sander

    2006-01-01

    The X-band (8.41 GHz) frequency currently used for deep space telecommunications is too narrow (50 MHz) to support future high rate missions. Because of this NASA has decided to transition to Ka-band (32 GHz) frequencies. As weather effects cause much larger fluctuations on Ka-band than on X-band, the traditional method of using a few dBs of margin to cover these fluctuations is wasteful of power for Ka-band; therefore, a different operations concept is needed for Ka-band links. As part of the development of the operations concept for Ka-band, NASA has implemented a fully functioning Ka-band communications suite on its Mars Reconnaissance Orbiter (MRO). This suite will be used during the primary science phase to develop and refine the Ka-band operations concept for deep space missions. In order to test the functional readiness of the spacecraft and the Deep Space Network's (DSN) readiness to support the demonstration activities a series of passes over DSN 34-m Beam Waveguide (BWG) antennas were scheduled during the cruise phase of the mission. MRO was launched on August 12, 2005 from Kennedy Space Center, Cape Canaveral, Florida, USA and went into Mars Orbit on March 10, 2006. A total of ten telemetry demonstration and one high gain antenna (HGA) calibration passes were allocated to the Ka-band demonstration. Furthermore, a number of "shadow" passes were also scheduled where, during a regular MRO track over a Ka-band capable antenna, Ka-band was identically configured as the X-band and tracked by the station. In addition, nine Ka-band delta differential one way ranging ((delta)DOR) passes were scheduled. During these passes, the spacecraft and the ground system were put through their respective paces. Among the highlights of these was setting a single day record for data return from a deep space spacecraft (133 Gbits) achieved during one 10-hour pass; achieving the highest data rate ever from a planetary mission (6 Mbps) and successfully demonstrating Ka-band DDOR

  5. Mars Reconnaissance Orbiter Ka-band (32 GHz) Demonstration: Cruise Phase Operations

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin; Morabito, David; Border, James S.; Davarian, Faramaz; Lee, Dennis; Mendoza, Ricardo; Britcliffe, Michael; Weinreb, Sander

    2006-01-01

    The X-band (8.41 GHz) frequency currently used for deep space telecommunications is too narrow (50 MHz) to support future high rate missions. Because of this NASA has decided to transition to Ka-band (32 GHz) frequencies. As weather effects cause much larger fluctuations on Ka-band than on X-band, the traditional method of using a few dBs of margin to cover these fluctuations is wasteful of power for Ka-band; therefore, a different operations concept is needed for Ka-band links. As part of the development of the operations concept for Ka-band, NASA has implemented a fully functioning Ka-band communications suite on its Mars Reconnaissance Orbiter (MRO). This suite will be used during the primary science phase to develop and refine the Ka-band operations concept for deep space missions. In order to test the functional readiness of the spacecraft and the Deep Space Network's (DSN) readiness to support the demonstration activities a series of passes over DSN 34-m Beam Waveguide (BWG) antennas were scheduled during the cruise phase of the mission. MRO was launched on August 12, 2005 from Kennedy Space Center, Cape Canaveral, Florida, USA and went into Mars Orbit on March 10, 2006. A total of ten telemetry demonstration and one high gain antenna (HGA) calibration passes were allocated to the Ka-band demonstration. Furthermore, a number of "shadow" passes were also scheduled where, during a regular MRO track over a Ka-band capable antenna, Ka-band was identically configured as the X-band and tracked by the station. In addition, nine Ka-band delta differential one way ranging ((delta)DOR) passes were scheduled. During these passes, the spacecraft and the ground system were put through their respective paces. Among the highlights of these was setting a single day record for data return from a deep space spacecraft (133 Gbits) achieved during one 10-hour pass; achieving the highest data rate ever from a planetary mission (6 Mbps) and successfully demonstrating Ka-band DDOR

  6. Cyclone Xaver seen by SARAL/AltiKa

    NASA Astrophysics Data System (ADS)

    Scharroo, Remko; Fenoglio, Luciana; Annunziato, Alessandro

    2014-05-01

    During the first week of December 2013, Cyclone Xaver pounded the coasts and the North Sea. On 6 December, all along the Wadden Sea, the barrier islands along the north of the Netherlands and the northwest of Germany experienced record storm surges. We show a comparison of the storm surge measured by the radar altimeter AltiKa on-board the SARAL satellite and various types of in-situ data and models. Two tide gauges along the German North Sea coast, one in the southern harbour of the island of Helgoland and one on an offshore lighthouse Alte Weser, confirmed that the storm drove sea level to about three meters above the normal tide level. Loading effects during the storm are also detected by the GPS measurements at several tide gauge stations. The altimeter in the mean time shows that the storm surge was noticeable as far as 400 km from the coast. The altimeter measured wind speeds of 20 m/s nearly monotonically throughout the North Sea. An offshore anemometer near the island of Borkum corroborated this value. A buoy near the FINO1 offshore platform measured wave heights of 8 m, matching quite well the measurements from the altimeter, ranging from 6 m near the German coast to 12 m further out into the North Sea. Furthermore we compare the altimeter-derived and in-situ sea level, wave height and wind speed products with outputs from the Operation Circulation and Forecast model of the Bundesamt für Seeschifffahrt und Hydrographie (BSH) and with a global storm surge forecast and inundation model of the Joint Research Centre (JRC) of the European Commission. The Operational circulation model of BSH (BSHcmod) and its component, the surge model (BSHsmod), perform daily predictions for the next 72 hours based on the meteorological model of the Deutsche Wetterdienst (DWD). The JRC Storm Surge Calculation System is a new development that has been established at the JRC in the framework of the Global Disasters Alerts and Coordination System (GDACS). The system uses

  7. A 75 ka Stalagmite Paleoclimate Record from Northern Venezuela

    NASA Astrophysics Data System (ADS)

    Retrum, J. B.; Gonzalez, L. A.; Edwards, R.; Tincher, S. M.; Cheng, H.; Urbani, F.

    2011-12-01

    A stalagmite collected from Cueva Zarraga in the northern Venezuelan Andes was analyzed to determine local paleoclimatic history and help examine climate change in the Caribbean. Ages were determined by U/Th disequilibrium and the stalagmite shows a nearly complete record for ~ 75 ka. Two significant periods of non-deposition have been identified. The first period ranges between the Last Glacial Maximum at 19,820 ± 149 cal yr BP and a brief resumption of stalagmite growth at 15,409 ± 747 cal yr BP, likely representing the Bølling-Allerød interstadial. After the brief period of deposition, growth does not resume unil the Holocene at 10,408 ± 78 cal yr BP. Carbon and oxygen isotopes show a major depletion shift from the last glacial period to the Holocene, suggesting warmer and wetter conditions during the Holocene. The oxygen isotope depletion shift is also seen in the Cariaco Basin foraminifera record off the northern coast of Venezuela. While tempting to attribute δ13C depletion to decrease of the C4 plant contribution, there is no evidence that the area experience major vegetation changes. We attribute the δ13C depletion to enhanced recycling of soil CO2 resulting from canopy effects. Today, Cueva Zarraga is at the northern extent of the Inter-Tropical Convergence Zone (ITCZ). The cooler and drier conditions of the last glacial period suggest a southern displacement of the ITCZ. The close proximity of Cueva Zarraga to Cariaco Basin may allow for a high resolution tropical terrestrial and oceanic climatic response comparison.

  8. KA-SB: from data integration to large scale reasoning

    PubMed Central

    Roldán-García, María del Mar; Navas-Delgado, Ismael; Kerzazi, Amine; Chniber, Othmane; Molina-Castro, Joaquín; Aldana-Montes, José F

    2009-01-01

    Background The analysis of information in the biological domain is usually focused on the analysis of data from single on-line data sources. Unfortunately, studying a biological process requires having access to disperse, heterogeneous, autonomous data sources. In this context, an analysis of the information is not possible without the integration of such data. Methods KA-SB is a querying and analysis system for final users based on combining a data integration solution with a reasoner. Thus, the tool has been created with a process divided into two steps: 1) KOMF, the Khaos Ontology-based Mediator Framework, is used to retrieve information from heterogeneous and distributed databases; 2) the integrated information is crystallized in a (persistent and high performance) reasoner (DBOWL). This information could be further analyzed later (by means of querying and reasoning). Results In this paper we present a novel system that combines the use of a mediation system with the reasoning capabilities of a large scale reasoner to provide a way of finding new knowledge and of analyzing the integrated information from different databases, which is retrieved as a set of ontology instances. This tool uses a graphical query interface to build user queries easily, which shows a graphical representation of the ontology and allows users o build queries by clicking on the ontology concepts. Conclusion These kinds of systems (based on KOMF) will provide users with very large amounts of information (interpreted as ontology instances once retrieved), which cannot be managed using traditional main memory-based reasoners. We propose a process for creating persistent and scalable knowledgebases from sets of OWL instances obtained by integrating heterogeneous data sources with KOMF. This process has been applied to develop a demo tool , which uses the BioPax Level 3 ontology as the integration schema, and integrates UNIPROT, KEGG, CHEBI, BRENDA and SABIORK databases. PMID:19796402

  9. Resilient FTS3 service at GridKa

    NASA Astrophysics Data System (ADS)

    Hartmann, T.; Bubeliene, J.; Hoeft, B.; Obholz, L.; Petzold, A.; Wisniewski, K.

    2015-12-01

    The FTS (File Transfer Service) service provides a transfer job scheduler to distribute and replicate vast amounts of data over the heterogeneous WLCG infrastructures. Compared to the channel model of the previous versions, the most recent version of FTS simplifies and improves the flexibility of the service while reducing the load to the service components. The improvements allow to handle a higher number of transfers with a single FTS3 setup. Covering now continent-wide transfers compared to the previous version, whose installations handled only transfers within specific clouds, a resilient system becomes even more necessary with the increased number of depending users. Having set up a FTS3 services at the German T1 site GridKa at KIT in Karlsruhe, we present our experiences on the preparations for a high-availability FTS3 service. Trying to avoid single points of failure, we rely on a database cluster as fault tolerant data back-end and the FTS3 service deployed on an own cluster setup to provide a resilient infrastructure for the users. With the database cluster providing a basic resilience for the data back-end, we ensure on the FTS3 service level a consistent and reliable database access through a proxy solution. On each FTS3 node a HAproxy instance is monitoring the integrity of each database node and distributes database queries over the whole cluster for load balancing during normal operations; in case of a broken database node, the proxy excludes it transparently to the local FTS3 service. The FTS3 service itself consists of a main and a backup instance, which takes over the identity of the main instance, i.e., IP, in case of an error using a CTDB (Cluster Trivial Database) infrastructure offering clients a consistent service.

  10. The Potential for a Ka-band (32 GHz) Worldwide VLBI Network

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Bach, U.; Colomer, F.; Garcia-Miro, C.; Gomez-Gonzalez, J.; Gulyaev, S.; Horiuchi, S.; Ichikawa, R.; Kraus, A.; Kronschnabl, G.; Lopez-Fernandez, J. A.; Lovell, J.; Majid, W.; Natusch, T.; Neidhardt, A.; Phillips, C.; Porcas, R.; Romero-Wolf, A.; Saldana, L.; Schreiber, U.; Sotuela, I.; Takeuchi, H.; Trinh, J.; Tzioumis, A.; deVincente, P.

    2012-01-01

    Ka-band (32 GHz, 9mm) Very Long Baseline Interferometric (VLBI) networking has now begun and has tremendous potential for expansion over the next few years. Ka-band VLBI astrometry from NASA's Deep Space Network has already developed a catalog of 470 observable sources with highly accurate positions. Now, several antennas worldwide are planning or are considering adding Ka-band VLBI capability. Thus, there is now an opportunity to create a worldwide Ka-band network with potential for high resolution imaging and astrometry. With baselines approaching a Giga-lambda, a Ka-band network would be able to probe source structure at the nano-radian (200 as) level ( 100X better than Hubble) and thus gain insight into the astrophysics of the most compact regions of emission in active galactic nuclei. We discuss the advantages of Ka-band, show the known sources and candidates, simulate projected baseline (uv) coverage, and discuss potential radio frequency feeds. The combination of these elements demonstrates the feasibility of a worldwide Ka network within the next few years!

  11. The Potential for a Ka-band (32 GHz) Worldwide VLBI Network

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Bach, U.; Colomer, F.; Garcia-Miro, C.; Gomez-Gonzalez, J.; Gulyaev, S.; Horiuchi, S.; Ichikawa, R.; Kraus, A.; Kronschnabl, G.; hide

    2012-01-01

    Ka-band (32 GHz, 9mm) Very Long Baseline Interferometric (VLBI) networking has now begun and has tremendous potential for expansion over the next few years. Ka-band VLBI astrometry from NASA's Deep Space Network has already developed a catalog of 470 observable sources with highly accurate positions. Now, several antennas worldwide are planning or are considering adding Ka-band VLBI capability. Thus, there is now an opportunity to create a worldwide Ka-band network with potential for high resolution imaging and astrometry. With baselines approaching a Giga-lambda, a Ka-band network would be able to probe source structure at the nano-radian (200 as) level ( 100X better than Hubble) and thus gain insight into the astrophysics of the most compact regions of emission in active galactic nuclei. We discuss the advantages of Ka-band, show the known sources and candidates, simulate projected baseline (uv) coverage, and discuss potential radio frequency feeds. The combination of these elements demonstrates the feasibility of a worldwide Ka network within the next few years!

  12. Studying NASA's Transition to Ka-Band Communications for Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Chelmins, David T.; Reinhart, Richard C.; Mortensen, Dale; Welch, Bryan; Downey, Joseph; Evans, Michael

    2014-01-01

    As the S-band spectrum becomes crowded, future space missions will need to consider moving command and telemetry services to Ka-band. NASA's Space Communications and Navigation (SCaN) Testbed provides a software-defined radio (SDR) platform that is capable of supporting investigation of this service transition. The testbed contains two S-band SDRs and one Ka-band SDR. Over the past year, SCaN Testbed has demonstrated Ka-band communications capabilities with NASAs Tracking and Data Relay Satellite System (TDRSS) using both open- and closed-loop antenna tracking profiles. A number of technical areas need to be addressed for successful transition to Ka-band. The smaller antenna beamwidth at Ka-band increases the criticality of antenna pointing, necessitating closed loop tracking algorithms and new techniques for received power estimation. Additionally, the antenna pointing routines require enhanced knowledge of spacecraft position and attitude for initial acquisition, versus an S-band antenna. Ka-band provides a number of technical advantages for bulk data transfer. Unlike at S-band, a larger bandwidth may be available for space missions, allowing increased data rates. The potential for high rate data transfer can also be extended for direct-to-ground links through use of variable or adaptive coding and modulation. Specific examples of Ka-band research from SCaN Testbeds first year of operation will be cited, such as communications link performance with TDRSS, and the effects of truss flexure on antenna pointing.

  13. Standard Observing Bands: Is Now the Time to Replace S/X with X/Ka?

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Lanyi, G. E.; Naudet, C. J.

    2004-06-01

    In this paper we will argue that the VLBI community should be developing a road map to transition from S/X to simultaneous X and Ka-band (32 GHz) observations. There are both negative and positive reasons for planning such a transition. On the negative side, we will outline concerns that S-band observations may be headed toward obsolescence. On the positive side, we will refer to evidence that X/Ka has potential for providing a more stable reference frame than S/X. We will propose timetables for a transition to X/Ka observing starting from the current status of X/Ka and plans that are now taking shape. First X/Ka fringes were obtained in 2001 with the Deep Space Network. Future plans will be discussed including a proposed X/Ka-band upgrade to the VLBA. Lastly, we will consider the need for a period of overlap between S/X and X/Ka so that the long and rich history of astrometric and geodetic VLBI is not compromised.

  14. Tephrochronology of a 70 ka-long marine record in the Marsili Basin (southern Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Tamburrino, S.; Insinga, D. D.; Pelosi, N.; Kissel, C.; Laj, C.; Capotondi, L.; Sprovieri, M.

    2016-11-01

    A sequence of tephra layers is studied in a 13.9 m-long deep-sea core (MD01-2474G) from the southern Tyrrhenian Sea. The chronology of the succession is provided by a high-resolution age-depth model based on isotope stratigraphy and AMS radiocarbon dating, which place the succession of events in a time interval spanning the last 70 ka. Based on a precise chronological framework and proximal-distal correlations, the Y-1, Y-6 and Y-7 main marker tephras were identified. Compositional data on fresh micro-pumice or glass shards of selected tephras were correlated with the coeval volcanic activity of Aeolian Arc (Vulcano and Salina), Mt. Etna, Phlegrean Fields Pantelleria and Ischia. The tephra sequence contains a number of deposits documenting recurrent activity on Vulcano Island at ca. 6.9 ka BP (MD3), ca. 16.7 ka BP (MD11), ca. 23.2 ka BP (MD14), ca. 29.6 ka BP (MD15), ca. 36.9 ka BP (MD22) and ca. 42.5 ka BP (MD27). The results presented in this study improve the southern Tyrrhenian Sea tephrostratigraphic framework and provide new insights into chemistry and dispersal area of Aeolian Arc pyroclastic deposits in this sector of the Central Mediterranean.

  15. Studying NASA's Transition to Ka-Band Communications for Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Chelmins, David; Reinhart, Richard; Mortensen, Dale; Welch, Bryan; Downey, Joseph; Evans, Mike

    2014-01-01

    As the S-band spectrum becomes crowded, future space missions will need to consider moving command and telemetry services to Ka-band. NASAs Space Communications and Navigation (SCaN) Testbed provides a software-defined radio (SDR) platform that is capable of supporting investigation of this service transition. The testbed contains two S-band SDRs and one Ka-band SDR. Over the past year, SCaN Testbed has demonstrated Ka-band communications capabilities with NASAs Tracking and Data Relay Satellite System (TDRSS) using both open- and closed-loop antenna tracking profiles. A number of technical areas need to be addressed for successful transition to Ka-band. The smaller antenna beamwidth at Ka-band increases the criticality of antenna pointing, necessitating closed loop tracking algorithms and new techniques for received power estimation. Additionally, the antenna pointing routines require enhanced knowledge of spacecraft position and attitude for initial acquisition, versus an S-band antenna. Ka-band provides a number of technical advantages for bulk data transfer. Unlike at S-band, a larger bandwidth may be available for space missions, allowing increased data rates. The potential for high rate data transfer can also be extended for direct-to-ground links through use of variable or adaptive coding and modulation. Specific examples of Ka-band research from SCaN Testbeds first year of operation will be cited, such as communications link performance with TDRSS, and the effects of truss flexure on antenna pointing.

  16. Standard Observing Bands: Is Now the Time to Replace S/X with X/Ka?

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Lanyi, G. E.; Naudet, C. J.

    2004-01-01

    In this paper we will argue that the VLBI community should be developing a road map to transition from S/X to simultaneous X and Ka-band (32 GHz) observations. There are both negative and positive reasons for planning such a transition. On the negative side, we will outline concerns that S-band observations may be headed toward obsolescence. On the positive side, we will refer to evidence that X/Ka has potential for providing a more stable reference frame than S/X. We will propose timetables for a transition to X/Ka observing starting from the current status of X/Ka and plans that are now taking shape. First X/Ka fringes were obtained in 2001 with the Deep Space Network. Future plans will be discussed including a proposed X/Ka-band upgrade to the VLBA. Lastly, we will consider the need for a period of overlap between S/X and X/Ka so that the long and rich history of astrometric and geodetic VLBI is not compromised.

  17. Performance of a Ka-Band Transponder Breadboard for Deep-Space Applications

    NASA Astrophysics Data System (ADS)

    Mysoor, N. R.; Lane, J. P.; Kayalar, S.; Kermode, A. W.

    1995-04-01

    This article summarizes the design concepts applied in the development of an advanced Ka-band (34.4 GHz/32 GHz) transponder breadboard for the next generation of space communications systems applications. The selected architecture upgrades the X-band (7.2 GHz/8.4 GHz) deep-space transponder (DST) to provide Ka-band up/Ka- and X-band down capability. In addition, it can also be configured to provide X-band up/Ka- and X-band down capability. The Ka-band transponder breadboard incorporates several state-of-the-art components, including sampling mixers, a Ka-band dielectric resonator oscillator, and microwave monolithic integrated circuits (MMICs). The MMICs that were tested in the breadboard include upconverters, downconverters, automatic gain control circuits, mixers, phase modulators, and amplifiers. The measured receiver dynamic range, tracking range, acquisition rate, static phase error, and phase jitter characteristics of the Ka-band breadboard interfaced to the advanced engineering model X-band DST are in good agreement with the expected performance. The results show a receiver tracking threshold of -149 dBm with a dynamic range of 80 dB and a downlink phase jitter of 7-deg rms. The analytical results of phase noise and Allan standard deviation are in good agreement with the experimental results.

  18. Coeval ages of Australasian, Central American and Western Canadian tektites reveal multiple impacts 790 ka ago

    NASA Astrophysics Data System (ADS)

    Schwarz, Winfried H.; Trieloff, Mario; Bollinger, Klemens; Gantert, Niklas; Fernandes, Vera A.; Meyer, Hans-Peter; Povenmire, Hal; Jessberger, Elmar K.; Guglielmino, Massimo; Koeberl, Christian

    2016-04-01

    High resolution 40Ar-39Ar step heating dating of australites and indochinites, representing a large area of the Australasian strewn field, and more recently discovered tektite-like glasses from Central America (Belize) and Western Canada, were carried out. Precise plateau ages were obtained in all cases, yielding indistinguishable ages of 789 ± 9 ka for four australites, 783 ± 5 ka for four indochinites, 783 ± 17 ka for one Western Canadian and 769 ± 16 ka for one Belize impact glass. Concerning major elements and REEs, australites and the Western Canadian impact glass are indistinguishable. If the Western Canadian sample was transported by impact ejection and belongs to the Australasian strewn field, this implies extremely far ballistic transport of 9000 km distance, assuming a source crater in southern Asia. The distinct major element and REE composition of the Belize impact glass suggests formation in another separate impact event. We conclude that the Australasian/Western Canadian impact glasses formed 785 ± 7 ka ago in a single event and Belize impact glass in a separate event 769 ± 16 ka ago. The two impact events forming these two strewn fields occurred remarkably closely related in time, i.e., separated by <30 ka.

  19. Prediction of Absolute Hydroxyl pKa Values for 3-Hydroxypyridin-4-ones.

    PubMed

    Chen, Yu-Lin; Doltsinis, Nikos L; Hider, Robert C; Barlow, Dave J

    2012-10-18

    pKa values have been calculated for a series of 3-hydroxypyridin-4-one (HPO) chelators in aqueous solution using coordination constrained ab initio molecular dynamics (AIMD) in combination with thermodynamic integration. This dynamics-based methodology in which the solvent is treated explicitly at the ab initio level has been compared with more commonly used simple, static, approaches. Comparison with experimental numbers has confirmed that the AIMD-based approach predicts the correct trend in the pKa values and produces the lowest average error (∼0.3 pKa units). The corresponding pKa predictions made via static quantum mechanical calculations overestimate the pKa values by 0.3-7 pKa units, with the extent of error dependent on the choice of thermodynamic cycle employed. The use of simple quantitative structure property relationship methods gives prediction errors of 0.3-1 pKa units, with some values overestimated and some underestimated. Beyond merely calculating pKa values, the AIMD simulations provide valuable additional insight into the atomistic details of the proton transfer mechanism and the solvation structure and dynamics at all stages of the reaction. For all HPOs studied, it is seen that proton transfer takes place along a chain of three H2O molecules, although direct hydrogen bonds are seen to form transiently. Analysis of the solvation structure before and after the proton transfer event using radial pair distribution functions and integrated number densities suggests that the trends in the pKa values correlate with the strength of the hydrogen bond and the average number of solvent molecules in the vicinity of the donor oxygen.

  20. Experimental Approaches for Measuring pKa's in RNA and DNA

    PubMed Central

    Thaplyal, Pallavi; Bevilacqua, Philip C.

    2017-01-01

    RNA and DNA carry out diverse functions in biology including catalysis, splicing, gene regulation, and storage of genetic information. Interest has grown in understanding how nucleic acids perform such sophisticated functions given their limited molecular repertoire. RNA can fold into diverse shapes that often perturb pKa values and allow it to ionize appreciably under biological conditions, thereby extending its molecular diversity. The goal of this article is to enable experimental measurement of pKa's in RNA and DNA. A number of experimental methods for measuring pKa values in RNA and DNA have been developed over the last ten years, including RNA cleavage kinetics; UV-, fluorescence-, and NMR-detected pH titrations; and Raman crystallography. We begin with general considerations for choosing a pKa assay and then describe experimental conditions, advantages and disadvantages for these methods. Potential pitfalls in measuring a pKa are provided including the presence of apparent pKa's due to a kinetic pKa or coupled acid- and alkali-promoted RNA unfolding, as well as RNA degradation, precipitation of metal hydroxides and poor baselines. Use of multiple data fitting procedures and the study of appropriate mutants are described as ways to avoid some of these pitfalls. Application of these experimental methods to RNA and DNA will increase the number of nucleic acid pKa values in the literature, which should deepen insight into biology and provide benchmarks for calculations. Future directions for measuring pKa's in nucleic acids are discussed. PMID:25432750

  1. A Novel Ku-Band/Ka-Band and Ka-Band/E-Band Multimode Waveguide Couplers for Power Measurement of Traveling-Wave Tube Amplifier Harmonic Frequencies

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.; Simons, Rainee N.

    2015-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler, fabricated from two dissimilar frequency band waveguides, is capable of isolating power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT) amplifier. Test results from proof-of-concept demonstrations are presented for a Ku-band/Ka-band MDC and a Ka-band/E-band MDC. In addition to power measurements at harmonic frequencies, a potential application of the MDC is in the design of a satellite borne beacon source for atmospheric propagation studies at millimeter-wave (mm-wave) frequencies (Ka-band and E-band).

  2. Effect of methylation on the side-chain pKa value of arginine.

    PubMed

    Evich, Marina; Stroeva, Ekaterina; Zheng, Yujun George; Germann, Markus W

    2016-02-01

    Arginine methylation is important in biological systems. Recent studies link the deregulation of protein arginine methyltransferases with certain cancers. To assess the impact of methylation on interaction with other biomolecules, the pKa values of methylated arginine variants were determined using NMR data. The pKa values of monomethylated, symmetrically dimethylated, and asymmetrically dimethylated arginine are similar to the unmodified arginine (14.2 ± 0.4). Although the pKa value has not been significantly affected by methylation, consequences of methylation include changes in charge distribution and steric effects, suggesting alternative mechanisms for recognition. © 2015 The Protein Society.

  3. Abrupt hydroclimate disruption across the Australian arid zone 50 ka coincident with human colonization

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Fogel, M. L.; Magee, J. W.; Gagan, M. K.

    2016-12-01

    Although many studies focus on how climate change impacted ancient societies, in Australia a growing body of evidence indicates that activities of the earliest human colonizers in turn altered the Australian climate. We utilize the stable isotopes of carbon and oxygen preserved in near-continuous 100 ka time series of avian eggshell from five regions across the Australian arid zone to reconstruct ecosystem status (d13C) and effective moisture (d18O). Training sets of sub-modern samples provide the basis for the reconstructions. Together, d13C and d18O provide independent estimates of ecosystem status and climate over the past 100 ka from the same dated sample, reducing correlation uncertainties between proxies. Changes in eggshell d13C document a dramatic reduction of palatable summer-wet C4 grasses in all regions between 50 and 45 ka, that has persisted through to modern times. Continuous 100 ka records of effective moisture derived from eggshell d18O show moist conditions from 100 to 60 ka, with variable drying after 60 ka, but the strong shift toward greatest aridity is coincident with the onset of the last glacial maximum 30 ka ago, 15 ka after the observed ecosystem restructuring. Combining the d13C and d18O time-series shows that an abrupt and permanent restructuring of the moisture/ecosystem balance occurred between 50 and 45 ka. Additional studies show that most large monsoon-fed inland arid-zone lakes carried permanent water at least intermittently between 120 and 50 ka, but never experienced permanent deep-water status after 45 ka, despite a wide range of global climate states, including the early Holocene when most other monsoon systems were reinvigorated. The lack of exceptional climate shifts either locally or globally between 60 and 40 ka eliminates climate as the cause of the ecosystem restructuring and persistent lake desiccation. Collectively these data suggest the wave of human colonization across Australia in altered land surface characteristics

  4. A Ka-band (32 GHz) beacon link experiment (KABLE) with Mars Observer

    NASA Technical Reports Server (NTRS)

    Riley, A. L.; Hansen, D. M.; Mileant, A.; Hartop, R. W.

    1987-01-01

    A proposal for a Ka-Band (32 GHz) Link Experiment (KABLE) with the Mars Observer mission was submitted to NASA. The experiment will rely on the fourth harmonic of the spacecraft X-band transmitter to generate a 33.6 GHz signal. The experiment will rely also on the Deep Space Network (DSN) receiving station equipped to simultaneously receive X- and Ka-band signals. The experiment will accurately measure the spacecraft-to-Earth telecommunication link performance at Ka-band and X-band (8.4 GHz).

  5. A ˜50 ka record of monsoonal variability in the Darjeeling foothill region, eastern Himalayas

    NASA Astrophysics Data System (ADS)

    Ghosh, Ruby; Bera, Subir; Sarkar, Anindya; Paruya, Dipak Kumar; Yao, Yi-Feng; Li, Cheng-Sen

    2015-04-01

    Pollen, phytoliths and δ 13C signatures of soil organic matter from two fluvial sedimentary sequences of the Darjeeling foothill region, eastern Himalayas are used to portray palaeoclimatic oscillations and their impact on regional plant communities over the last ˜50 ka. Quantitative palaeoclimate estimation using coexistence approach on pollen data and other proxies indicate significant oscillations in precipitation during the late part of MIS 3 (46.4-25.9 ka), early and middle part of MIS 2 (25.9-15.6 ka), and 5.4 to 3.5 ka. Middle to late MIS 3 (ca 46.4-31 ka.) was characterized by a comparatively low monsoonal activity and slightly higher temperature than that during ca 31 ka onwards. Simultaneous expansion of deciduous trees and chloridoid grasses also imply a drier and warmer phase. Between 31 and 22.3 ka (late MIS 3 to mid-MIS 2), higher precipitation and a slightly cooler temperature led to an increase in evergreen elements over deciduous taxa and wet-loving panicoid grasses over dry-loving chloridoid grasses than earlier. After ca 22.3 ka, shrinking of forest cover, expansion of C4 chloridoid grasses, Asteraceae and Cheno-ams in the vegetation with lowering of temperature and precipitation characterized the onset of the LGM which continued till 18.3 ka. End of the LGM is manifested by a restoration in the forest cover and in the temperature and precipitation regime. Later, during 5.4 to 4.3 ka, a strong monsoonal activity supported a dense moist evergreen forest cover that subsequently declined during 4.3 to 3.5 ka. A further increase in deciduous elements and non-arboreals might be a consequence of reduced precipitation and higher temperature during this phase. A comparison between monsoonal rainfall, MAT and palaeoatmospheric CO2 with floral dynamics since last ˜50 ka indicates that these fluctuations in plant succession were mainly driven by monsoonal variations.

  6. Validation Studies for CHRISTINE-CC Using a Ka-Band Coupled-Cavity TWT

    DTIC Science & Technology

    2006-04-01

    Cavity TWT for 29-31 GHz Figure 3: Output power vs. input power at f=30.0 Communications Systems," I Ith Ka and Broadband GHz for the VTA-6430A1 Ka...Coupled-Cavity TWT DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: 2006 IEEE...Studies for CHRISTINE-CC Using a Ka-Band Coupled-Cavity TWT * D. Chernin, D. Dialetis, T. M. Antonsen, Jr.t, Science Applications International Corp McLean

  7. Advances in Ka-Band Communication System for CubeSats and SmallSats

    NASA Technical Reports Server (NTRS)

    Kegege, Obadiah; Wong, Yen F.; Altunc, Serhat

    2016-01-01

    A study was performed that evaluated the feasibility of Ka-band communication system to provide CubeSat/SmallSat high rate science data downlink with ground antennas ranging from the small portable 1.2m/2.4m to apertures 5.4M, 7.3M, 11M, and 18M, for Low Earth Orbit (LEO) to Lunar CubeSat missions. This study included link analysis to determine the data rate requirement, based on the current TRL of Ka-band flight hardware and ground support infrastructure. Recent advances in Ka-band transceivers and antennas, options of portable ground stations, and various coverage distances were included in the analysis. The link/coverage analysis results show that Cubesat/Smallsat missions communication requirements including frequencies and data rates can be met by utilizing Near Earth Network (NEN) Ka-band support with 2 W and high gain (>6 dBi) antennas.

  8. Design and Validation of High Date Rate Ka-Band Software Defined Radio for Small Satellite

    NASA Technical Reports Server (NTRS)

    Xia, Tian

    2016-01-01

    The Design and Validation of High Date Rate Ka- Band Software Defined Radio for Small Satellite project will develop a novel Ka-band software defined radio (SDR) that is capable of establishing high data rate inter-satellite links with a throughput of 500 megabits per second (Mb/s) and providing millimeter ranging precision. The system will be designed to operate with high performance and reliability that is robust against various interference effects and network anomalies. The Ka-band radio resulting from this work will improve upon state of the art Ka-band radios in terms of dimensional size, mass and power dissipation, which limit their use in small satellites.

  9. Multiscale Reactive Molecular Dynamics for Absolute pKa Predictions and Amino Acid Deprotonation

    PubMed Central

    2015-01-01

    Accurately calculating a weak acid’s pKa from simulations remains a challenging task. We report a multiscale theoretical approach to calculate the free energy profile for acid ionization, resulting in accurate absolute pKa values in addition to insights into the underlying mechanism. Importantly, our approach minimizes empiricism by mapping electronic structure data (QM/MM forces) into a reactive molecular dynamics model capable of extensive sampling. Consequently, the bulk property of interest (the absolute pKa) is the natural consequence of the model, not a parameter used to fit it. This approach is applied to create reactive models of aspartic and glutamic acids. We show that these models predict the correct pKa values and provide ample statistics to probe the molecular mechanism of dissociation. This analysis shows changes in the solvation structure and Zundel-dominated transitions between the protonated acid, contact ion pair, and bulk solvated excess proton. PMID:25061442

  10. Test results of 12/18 kA ReBCO coated conductor current leads

    NASA Astrophysics Data System (ADS)

    Kovalev, I. A.; Surin, M. I.; Naumov, A. V.; Novikov, M. S.; Novikov, S. I.; Ilin, A. A.; Polyakov, A. V.; Scherbakov, V. I.; Shutova, D. I.

    2017-07-01

    A pair of hybrid current leads (brass + stacked & soldered ReBCO tapes) rated for 12 kA in steady state and for up to 18 kA at pulsed over current conditions was designed, developed and tested at NRC ;Kurchatov Institute; (NRC ;KI;). During the experiment at LN2 temperature, the current leads (CLs) were successfully charged with 18 kA at 100 A/s ramp rate. To date, as far as we know, this is the highest current capacity achieved for 2G HTS current leads. The feasibility of ;stack-and-soldering technique; for 10 kA+ class coated conductor CLs for accelerators and fusion was demonstrated. This paper gives an overview of the leads design and presents the preliminary test results. Detailed studies of magnetic properties and current sharing process for the stacked and staggered HTS joints are also reported.

  11. Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification

    NASA Astrophysics Data System (ADS)

    Vega-Hissi, Esteban G.; Estrada, Mario R.; Lavecchia, Martín J.; Pis Diez, Reinaldo

    2013-01-01

    The pKa, the negative logarithm of the acid dissociation equilibrium constant, of the carboxylic acid groups of unconjugated bilirubin in water is a discussed issue because there are quite different experimental values reported. Using quantum mechanical calculations we have studied the conformational behavior of unconjugated bilirubin species (in gas phase and in solution modeled implicitly and explicitly) to provide evidence that may clarify pKa values because of its pathophysiological relevance. Our results show that rotation of carboxylate group, which is not restricted, settles it in a suitable place to establish stronger interactions that stabilizes the monoanion and the dianion to be properly solvated, demonstrating that the rationalization used to justify the high pKa values of unconjugated bilirubin is inappropriate. Furthermore, low unconjugated bilirubin (UCB) pKa values were estimated from a linear regression analysis.

  12. Effect of tualang honey against KA-induced oxidative stress and neurodegeneration in the cortex of rats.

    PubMed

    Mohd Sairazi, Nur Shafika; K N S, Sirajudeen; Asari, Mohd Asnizam; Mummedy, Swamy; Muzaimi, Mustapha; Sulaiman, Siti Amrah

    2017-01-09

    Administration of KA on rodents has resulted in seizures, behavioral changes, oxidative stress, and neuronal degeneration on selective population of neurons in the brain. The present study was undertaken to investigate the extent of neuroprotective effect conferred by Malaysian Tualang Honey (TH), an antioxidant agent, in the cerebral cortex of rats against KA-induced oxidative stress and neurodegeneration in an animal model of KA-induced excitotoxicity. Male Sprague-Dawley rats were randomly divided into five groups: Control, KA-treated group, TH + KA-treated group, aspirin (ASP; anti-inflammatory agent) + KA-treated group and topiramate (TPM; antiepileptic agent) + KA-treated group. The animals were pretreated orally with drinking water, TH (1.0g/kg BW), ASP (7.5mg/kg BW) or TPM (40mg/kg BW), respectively, five times at 12 h intervals. KA (15mg/kg BW) was injected subcutaneously 30 min after last treatment to all groups except the control group (normal saline). Behavioral change was observed using an open field test (OFT) to assess the locomotor activity of the animals. Animals were sacrificed after 2 h, 24 h and 48 h of KA administration. KA significantly inflicted more neuronal degeneration in the piriform cortex and heightened the predilection to seizures as compared with the control animals. Pretreatment with TH reduced the KA-induced neuronal degeneration in the piriform cortex but failed to prevent the occurrence of KA-induced seizures. In the OFT, KA-induced animals showed an increased in locomotor activity and hyperactivity and these were attenuated by TH pretreatment. Furthermore, TH pretreatment significantly attenuated an increase of thiobarbituric acid reactive substances level and a decrease of total antioxidant status level enhanced by KA in the cerebral cortex. These results suggest that pretreatment with TH has a therapeutic potential against KA-induced oxidative stress and neurodegeneration through its antioxidant effect.

  13. NASA's Evolution to Ka-Band Space Communications for Near-Earth Spacecraft

    NASA Technical Reports Server (NTRS)

    McCarthy, Kevin; Stocklin, Frank; Geldzahler, Barry; Friedman, Daniel; Celeste, Peter

    2010-01-01

    This slide presentation reviews the exploration of NASA using a Ka-band system for spacecraft communications in Near-Earth orbits. The reasons for changing to Ka-band are the higher data rates, and the current (X-band spectrum) is becoming crowded. This will require some modification to the current ground station antennas systems. The results of a Request for Information (RFI) are discussed, and the recommended solution is reviewed.

  14. An abrupt and prominent climatic reversal at 9.2 ka in the northeastern North America

    NASA Astrophysics Data System (ADS)

    Hou, J.; Huang, Y.; Shuman, B. N.; Oswald, W.; Foster, D. R.

    2008-12-01

    Continental climate during the early Holocene (from 10 to 7 ka) is characterized by multiple abrupt climatic reversals such as the well-known 8.2 ka event that has been observed worldwide and attributed to the terminal collapse of the Laurentide Ice Sheet (LIS) in the North American continent. However, many episodes of meltwater releases occurred prior to the final collapse of LIS, their impact on the continental climate is much less understood. We present in this paper decadal-scale hydrogen isotopic records of aquatic and terrestrial plant biomarkers from Blood Pond, Massachusetts during the early Holocene. Our isotopic records infer a cooling of 3~4 degree between 9.3 and 9.1 ka against the millennial scale climate background, mainly induced by changes in precipitation seasonality. In comparison, the 8.2 ka event displays smaller amplitude of temperature cooling of 1~2 degree at our southern New England site. We interpret our observed climatic reversal at ~ 9.2 ka as representing increased proportion of winter precipitation in conjunction with a drier and cooler summer, triggered by slowdown in thermohaline circulation as a result of freshwater release from the proglacial lakes. We attribute the difference in climate response at 8.2 ka and 9.2 ka events to the configuration of LIS, with 9.2 ka LIS having a much stronger blocking effect on the moisture from the Gulf of Mexico during the summer. Our data suggest that the seasonality of the precipitation at the southern New England was highly sensitive to meltwater releases, especially prior to the final collapse of the LIS.

  15. Global calibration/validation of 2 years of SARAL/AltiKa data

    NASA Astrophysics Data System (ADS)

    Scharroo, Remko; Lillibridge, John; Leuliette, Eric; Bonekamp, Hans

    2015-04-01

    The AltiKa altimeter flying onboard the French/Indian SARAL satellite provides the first opportunity to examine Ka-band measurements of sea surface height, significant wave height and ocean surface wind speed. In this presentation we provide the results from our global calibration/validation analysis of the AltiKa measurements, with an emphasis on near real-time applications of interest to both EUMETSAT and NOAA. Traditional along-track SSHA, and single as well as dual-satellite crossover assessments of the AltiKa performance are be provided. Unique aspects of the AltiKa mission such as improved along-track resolution, reduced ionospheric path delay corrections, mission-specific wind speed and sea state bias corrections, and sensitivity to liquid moisture and rain are also explored. In February 2014, a major update to the ground processing was introduced. "Patch-2" improved the way wind speed was derived from altimeter backscatter, as suggested by Lillibridge et al. (1). The backscatter attenuation is now derived from the radiometer measurements via neural network algorithms, which also determine the wet tropospheric correction. We emphasize these improvements in our analysis. After 2 years in flight, SARAL/AltiKa is already providing a significant contribution to the constellation of operational radar altimetry missions, demonstrating the large benefits of high-rate Ka-band altimetry. (1) Lillibridge, John, Remko Scharroo, Saleh Abdalla, Doug Vandemark, 2014: One- and Two-Dimensional Wind Speed Models for Ka-Band Altimetry. J. Atmos. Oceanic Technol., 31, 630-638. doi: http://dx.doi.org/10.1175/JTECH-D-13-00167.1

  16. Experiments for Ka-band mobile applications: The ACTS mobile terminal

    NASA Technical Reports Server (NTRS)

    Estabrook, Polly; Dessouky, Khaled; Jedrey, Thomas

    1990-01-01

    To explore the potential of Ka-band to support mobile satellite services, the Jet Propulsion Laboratory (JPL) has initiated the design and development of a Ka-band land-mobile terminal to be used with the Advanced Communications Technology Satellite (ACTS). The planned experimental setup with ACTS is described. Brief functional descriptions of the mobile and fixed terminals are provided. The inputs required from the propagation community to support the design activities and the planned experiments are also discussed.

  17. Complete Genome Sequence of the Thermophilic, Piezophilic, Heterotrophic Bacterium Marinitoga piezophila KA3

    SciTech Connect

    Lucas, Susan; Han, James; Lapidus, Alla L.; Cheng, Jan-Fang; Goodwin, Lynne A.; Pitluck, Sam; Peters, Lin; Mikhailova, Natalia; Teshima, Hazuki; Detter, J. Chris; Han, Cliff; Tapia, Roxanne; Land, Miriam L; Hauser, Loren John; Kyrpides, Nikos C; Ivanova, N; Pagani, Ioanna; Vannier, Pauline; Oger, Phil; Bartlett, Douglas; Noll, Kenneth M; Woyke, Tanja; Jebbar, Mohamed

    2012-01-01

    Marinitoga piezophila KA3 is a thermophilic, anaerobic, chemoorganotrophic, sulfur-reducing bacterium isolated from the Grandbonum deep-sea hydrothermal vent site at the East Pacific Rise (13 degrees N, 2,630-m depth). The genome of M. piezophila KA3 comprises a 2,231,407-bp circular chromosome and a 13,386-bp circular plasmid. This genome was sequenced within Department of Energy Joint Genome Institute CSP 2010.

  18. A Ka-Band Celestial Reference Frame with Applications to Deep Space Navigation

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.; Clark, J. Eric; Garcia-Miro, Cristina; Horiuchi, Shinji; Sotuela, Ioana

    2011-01-01

    The Ka-band radio spectrum is now being used for a wide variety of applications. This paper highlights the use of Ka-band as a frequency for precise deep space navigation based on a set of reference beacons provided by extragalactic quasars which emit broadband noise at Ka-band. This quasar-based celestial reference frame is constructed using X/Ka-band (8.4/32 GHz) from fifty-five 24-hour sessions with the Deep Space Network antennas in California, Australia, and Spain. We report on observations which have detected 464 sources covering the full 24 hours of Right Ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the international standard S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of approximately 200 micro-arcsec in alpha cos(delta) and approximately 300 micro-arcsec in delta. There is evidence for systematic errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of instrumental phase calibration, tropospheric refraction mis-modeling, and limited southern geometry. The motivation for extending the celestial reference frame to frequencies above 8 GHz is to access more compact source morphology for improved frame stability and to support spacecraft navigation for Ka-band based NASA missions.

  19. Improving Cry8Ka toxin activity towards the cotton boll weevil (Anthonomus grandis)

    PubMed Central

    2011-01-01

    Background The cotton boll weevil (Anthonomus grandis) is a serious insect-pest in the Americas, particularly in Brazil. The use of chemical or biological insect control is not effective against the cotton boll weevil because of its endophytic life style. Therefore, the use of biotechnological tools to produce insect-resistant transgenic plants represents an important strategy to reduce the damage to cotton plants caused by the boll weevil. The present study focuses on the identification of novel molecules that show improved toxicity against the cotton boll weevil. In vitro directed molecular evolution through DNA shuffling and phage display screening was applied to enhance the insecticidal activity of variants of the Cry8Ka1 protein of Bacillus thuringiensis. Results Bioassays carried out with A. grandis larvae revealed that the LC50 of the screened mutant Cry8Ka5 toxin was 3.15-fold higher than the wild-type Cry8Ka1 toxin. Homology modelling of Cry8Ka1 and the Cry8Ka5 mutant suggested that both proteins retained the typical three-domain Cry family structure. The mutated residues were located mostly in loops and appeared unlikely to interfere with molecular stability. Conclusions The improved toxicity of the Cry8Ka5 mutant obtained in this study will allow the generation of a transgenic cotton event with improved potential to control A. grandis. PMID:21906288

  20. Pre-Flight Testing and Performance of a Ka-Band Software Defined Radio

    NASA Technical Reports Server (NTRS)

    Downey, Joseph A.; Reinhart, Richard C.; Kacpura, Thomas

    2012-01-01

    National Aeronautics and Space Administration (NASA) has developed a space-qualified, reprogrammable, Ka-band Software Defined Radio (SDR) to be utilized as part of an on-orbit, reconfigurable testbed. The testbed will operate on the truss of the International Space Station beginning in late 2012. Three unique SDRs comprise the testbed, and each radio is compliant to the Space Telecommunications Radio System (STRS) Architecture Standard. The testbed provides NASA, industry, other Government agencies, and academic partners the opportunity to develop communications, navigation, and networking applications in the laboratory and space environment, while at the same time advancing SDR technology, reducing risk, and enabling future mission capability. Designed and built by Harris Corporation, the Ka-band SDR is NASA's first space-qualified Ka-band SDR transceiver. The Harris SDR will also mark the first NASA user of the Ka-band capabilities of the Tracking Data and Relay Satellite System (TDRSS) for on-orbit operations. This paper describes the testbed's Ka-band System, including the SDR, travelling wave tube amplifier (TWTA), and antenna system. The reconfigurable aspects of the system enabled by SDR technology are discussed and the Ka-band system performance is presented as measured during extensive pre-flight testing.

  1. A Ka-band Celestial Reference Frame with Applications to Deep Space Navigation

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Clark, J. E.; García-Miró, C.; Horiuchi, S.; Sotuela, I.

    2011-10-01

    The Ka-band radio spectrum is now being used for a wide variety of applications. This paper highlights the use of Ka-band as a frequency for precise deep space navigation based on a set of reference beacons provided by extragalactic quasars which emit broadband noise at Ka-band. This quasar-based celestial reference frame is constructed using X/Ka-band (8.4/32 GHz) from fifty-five 24-hour sessions with the Deep Space Network antennas in California, Australia, and Spain. We report on observations which have detected 464 sources covering the full 24 hours of Right Ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the international standard S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of ~200 micro-arcsec (μas) in α cos δ and ~300 μas in δ. There is evidence for systematic errors at the 100 μas level. Known errors include limited SNR, lack of instrumental phase calibration, tropospheric refraction mis-modeling, and limited southern geometry. The motivation for extending the celestial reference frame to frequencies above 8 GHz is to access more compact source morphology for improved frame stability and to support spacecraft navigation for Ka-band based NASA missions.

  2. Design research on the conductor of 10 kA class HTS DC power cable

    NASA Astrophysics Data System (ADS)

    Zhang, Dong; Dai, Shaotao; Zhang, Fengyuan; Huang, Tianbin; Wang, Yinshun; Lin, Yubao; Teng, Yuping; Zhang, Guomin; Xiao, Liye; Lin, Liangzhen

    2012-12-01

    High temperature superconducting (HTS) DC power cable shows a wide application prospect in the field of power transmission for its nearly lossless and rather high capacity. A 360 m/10 kA HTS DC power cable system, which connects the rectifier output of a substation with the bus bar of an electrolytic aluminium cell, will be put into operation at Henan Zhongfu Industrial Co., Ltd. As one of the items in this project, a 5 m/10 kA HTS DC power cable was developed, which is used to investigate the conductor design, fabrication, current-carrying capacity and stability of the 360 m/10 kA HTS power cable. The HTS DC power cable core consists of five conductor layers wound with spliced Bi-2223 wires with the length of 600 m. The cable core has five layers and 23 conductors in each layer with the outer diameter of 45.42 mm. The superconducting power cable is fabricated and tested. The critical current is about 14.3 kA at 77 K. The superconducting power cable is charged to 10 kA with rate of 10 A/s and operates at steady-state for 30 min. In this paper, the 10 kA HTS DC power cable design, fabrication and test are presented. The experimental research of the performance of spliced superconducting wire and charging, steady-state operating performance of the cable was carried out.

  3. Stratigraphic constraints for explosive activity in the past 100 ka at Etna Volcano, Italy

    NASA Astrophysics Data System (ADS)

    Coltelli, Mauro; Del Carlo, Paola; Vezzoli, Luigina

    2000-08-01

    The pyroclastic deposits of Etna have been correlated over the whole volcanic edifice for the first time, allowing the construction of a continuous record of tephra-producing events, which extends from approximately 100 ka to the Present. In this interval, five main periods of explosive activity have been identified: (a) 100-ka strombolian to subplinian activity; (b) 80- to 100-ka plinian benmoreitic activity; (c) 16- to 80-ka strombolian to subplinian from basaltic to mugearitic activity; (d) 15.5- to 15-ka plinian benmoreitic activity accompanying the caldera-forming eruptions of the Ellittico Volcano; and (e) the most recent 13-ka basaltic explosive activity of strombolian and subplinian type of the present edifice that also includes the 122-B.C. plinian eruption. This study results in a semi-quantitative and in some cases quantitative definition of the intensity and chronology of the explosive activity at Etna. Moreover, this work gives a new significance to the volcanic hazards of Etna, a volcano generally considered to be the site of gentle effusive eruptions.

  4. The GridKa Tier-1 Computing Center within the ALICE Grid Framework

    NASA Astrophysics Data System (ADS)

    Park, WooJin J.; Christopher, Jung; Heiss, Andreas; Petzold, Andreas; Schwarz, Kilian

    2014-06-01

    The GridKa computing center, hosted by Steinbuch Centre for Computing at the Karlsruhe Institute for Technology (KIT) in Germany, is serving as the largest Tier-1 center used by the ALICE collaboration at the LHC. In 2013, GridKa provides 30k HEPSPEC06, 2.7 PB of disk space, and 5.25 PB of tape storage to ALICE. The 10Gbit/s network connections from GridKa to CERN, several Tier-1 centers and the general purpose network are used by ALICE intensively. In 2012 a total amount of ~1 PB was transferred to and from GridKa. As Grid framework, AliEn (ALICE Environment) is being used to access the resources, and various monitoring tools including the MonALISA (MONitoring Agent using a Large Integrated Services Architecture) are always running to alert in case of any problem. GridKa on-call engineers provide 24/7 support to guarantee minimal loss of availability of computing and storage resources in case of hardware or software problems. We introduce the GridKa Tier-1 center from the viewpoint of ALICE services.

  5. Progress in the prediction of pKa values in proteins

    SciTech Connect

    Alexov, Emil; Mehler, Ernest L.; Baker, Nathan A.; Baptista, Antonio; Huang, Yong; Milletti, Francesca; Nielsen, Jens E.; Farrell, Damien; Carstensen, Tommy; Olsson, Mats H.; Shen, Jana K.; Warwicker, Jim; Williams, Sarah; Word, J Michael

    2011-12-15

    The pKa-cooperative aims to provide a forum for experimental and theoretical researchers interested in protein pKa values and protein electrostatics in general. The first round of the pKa -cooperative, which challenged computational labs to carry out blind predictions against pKas experimentally determined in the laboratory of Bertrand Garcia-Moreno, was completed and results discussed at the Telluride meeting (July 6-10, 2009). This paper serves as an introduction to the reports submitted by the blind prediction participants that will be published in a special issue of PROTEINS: Structure, Function and Bioinformatics. Here we briefly outline existing approaches for pKa calculations, emphasizing methods that were used by the participants in calculating the blind pKa values in the first round of the cooperative. We then point out some of the difficulties encountered by the participating groups in making their blind predictions, and finally try to provide some insights for future developments aimed at improving the accuracy of pKa calculations.

  6. Silicic magma accumulation beneath Mount Mazama, Oregon, 71 ka to 24 ka constrained by SHRIMP measurements of dissolved volatile concentrations in melt inclusions

    NASA Astrophysics Data System (ADS)

    Wright, H. M.; Bacon, C. R.; Vazquez, J. A.; Sisson, T. W.

    2010-12-01

    Dissolved volatile contents of melt inclusions trapped in pyroxene and plagioclase crystals from 7 silicic eruptions preceding the climactic ~7.7 ka Mazama eruption were measured by SIMS with the Stanford-USGS SHRIMP-RG. Melt inclusions in crystals were intersected, polished, and crystals were mounted in indium in Al mounts. A 1.2-3.0 nA (depending on the session), O2- primary beam was accelerated and focused to a 15-25 μm spot on the sample surface, which generated positive secondary ions of analyzed Li, Be, B, C, OH, F, Mg, Si, SiH, S, Cl, Ca, AlO, KO, Rb, and Sr. Measurements were made at high mass resolution (6000-7000). Trace element and volatile concentrations were calculated using a best-fit regression to count rate ratios (normalized to 30Si) vs. variable known concentrations in experimental and natural rhyolite glass standards. Pumiceous samples were chosen from dacitic to rhyodacitic eruptive deposits, consisting of the 71ka dacite of Pumice Castle, 70ka dacite below Llao Rock, 50ka dacite of the Watchman, 35ka dacite of Munson Valley, 35ka Williams Crater tephra, 27ka Redcloud Cliff rhyodacite, and 24ka andesite S of Bear Bluff. Melt inclusions are abundant in spongy, mineral-inclusion-rich interiors of pyroxene crystals in early (71-35ka) eruptive deposits and are less abundant throughout pyroxenes from later eruptions (35-24ka) and in plagioclase crystals. Over the entire time interval, most trace element and volatile concentrations remain approximately constant between melt inclusion populations. However, there are some variations in water and carbon dioxide concentration. A large proportion of inclusions in the smaller eruptive deposits (0.003-0.4 km3) of the dacite of the Watchman, dacite of Munson Valley, and Williams Crater tephra have low water contents, ~1 wt% H2O, corresponding to a saturation pressure of 25MPa, or ~1km depth (at 870°, approximate average temperature for these deposits, e.g., Druitt and Bacon, Contrib Mineral Petrol 1989

  7. Molecular Paleoclimate Reconstructions over the Last 9 ka from a Peat Sequence in South China.

    PubMed

    Wang, Xinxin; Huang, Xianyu; Sachse, Dirk; Ding, Weihua; Xue, Jiantao

    2016-01-01

    To achieve a better understanding of Holocene climate change in the monsoon regions of China, we investigated the molecular distributions and carbon and hydrogen isotope compositions (δ13C and δD values) of long-chain n-alkanes in a peat core from the Shiwangutian (SWGT) peatland, south China over the last 9 ka. By comparisons with other climate records, we found that the δ13C values of the long-chain n-alkanes can be a proxy for humidity, while the δD values of the long-chain n-alkanes primarily recorded the moisture source δD signal during 9-1.8 ka BP and responded to the dry climate during 1.8-0.3 ka BP. Together with the average chain length (ACL) and the carbon preference index (CPI) data, the climate evolution over last 9 ka in the SWGT peatland can be divided into three stages. During the first stage (9-5 ka BP), the δ13C values were depleted and CPI and Paq values were low, while ACL values were high. They reveal a period of warm and wet climate, which is regarded as the Holocene optimum. The second stage (5-1.8 ka BP) witnessed a shift to relatively cool and dry climate, as indicated by the more positive δ13C values and lower ACL values. During the third stage (1.8-0.3 ka BP), the δ13C, δD, CPI and Paq values showed marked increase and ACL values varied greatly, implying an abrupt change to cold and dry conditions. This climate pattern corresponds to the broad decline in Asian monsoon intensity through the latter part of the Holocene. Our results do not support a later Holocene optimum in south China as suggested by previous studies.

  8. Molecular Paleoclimate Reconstructions over the Last 9 ka from a Peat Sequence in South China

    PubMed Central

    Wang, Xinxin; Huang, Xianyu; Sachse, Dirk; Ding, Weihua; Xue, Jiantao

    2016-01-01

    To achieve a better understanding of Holocene climate change in the monsoon regions of China, we investigated the molecular distributions and carbon and hydrogen isotope compositions (δ13C and δD values) of long-chain n-alkanes in a peat core from the Shiwangutian (SWGT) peatland, south China over the last 9 ka. By comparisons with other climate records, we found that the δ13C values of the long-chain n-alkanes can be a proxy for humidity, while the δD values of the long-chain n-alkanes primarily recorded the moisture source δD signal during 9–1.8 ka BP and responded to the dry climate during 1.8–0.3 ka BP. Together with the average chain length (ACL) and the carbon preference index (CPI) data, the climate evolution over last 9 ka in the SWGT peatland can be divided into three stages. During the first stage (9–5 ka BP), the δ13C values were depleted and CPI and Paq values were low, while ACL values were high. They reveal a period of warm and wet climate, which is regarded as the Holocene optimum. The second stage (5–1.8 ka BP) witnessed a shift to relatively cool and dry climate, as indicated by the more positive δ13C values and lower ACL values. During the third stage (1.8–0.3 ka BP), the δ13C, δD, CPI and Paq values showed marked increase and ACL values varied greatly, implying an abrupt change to cold and dry conditions. This climate pattern corresponds to the broad decline in Asian monsoon intensity through the latter part of the Holocene. Our results do not support a later Holocene optimum in south China as suggested by previous studies. PMID:27505008

  9. Low solubility of unconjugated bilirubin in dimethylsulfoxide – water systems: implications for pKa determinations

    PubMed Central

    2002-01-01

    Background Aqueous pKa values of unconjugated bilirubin are important determinants of its solubility and transport. Published pKa data on an analog, mesobilirubin-XIIIα, studied by 13C-NMR in buffered solutions containing 27 and 64 vol% (C2H3)2SO because of low aqueous solubility of mesobilirubin, were extrapolated to obtain pKa values in water of 4.2 and 4.9. Previous chloroform-water partition data on bilirubin diacid led to higher estimates of its pKa, 8.12 and 8.44, and its aqueous solubility. A thermodynamic analysis, using this solubility and a published solubility in DMSO, suggested that the systems used to measure 13C-NMR shifts were highly supersaturated. This expectation was assessed by measuring the residual concentrations of bilirubin in the supernatants of comparable DMSO-buffer systems, after mild centrifugation to remove microprecipitates. Results Extensive sedimentation was observed from numerous systems, many of which appeared optically clear. The very low supernatant concentrations at the lowest pH values (4.1-5.9) were compatible with the above thermodynamic analysis. Extensive sedimentation and low supernatant concentrations occurred also at pH as high as 7.2. Conclusions The present study strongly supports the validity of the aqueous solubility of bilirubin diacid derived from partition data, and, therefore, the corresponding high pKa values. Many of the mesobilirubin systems in the 13C-NMR studies were probably supersaturated, contained microsuspensions, and were not true solutions. This, and previously documented errors in pH determinations that caused serious errors in pKa values of the many soluble reference acids and mesobilirubin, raise doubts regarding the low pKa estimates for mesobilirubin from the 13C-NMR studies. PMID:12079498

  10. Records of the paleoclimate during the fast transgression period (13 ka BP-8 ka BP) from the mud area on the inner shelf of the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, S.

    2015-12-01

    A 35.30m-long core (MZ02) recovered from a water depth of 32.4m from the inner shelf mud deposit of the East China Sea was analyzed for sedimentary characteristics, color reflectance, clay mineral, and element geochemistry components as well as by AMS 14C dating to research the sedimentation rate, sediment provenance and paleocwan mountainous river and clay fralimate evolution during the fast transgression period in the study area. Rare earth element and clay mineral proxies indicated that the mixed provenance sediment accumulated in the foreshore-nearshore region at the beginning of the fast transgression period, with a higher sedimentation rate of 5.58m/ka. While from 9800-9500 a B.P., the sedimentation rate keep lower about 1.73m/ka, and the sediment provenance changed obviously, silt fraction were apt to Taiction prone to be transported from the Yangtze River. Multiple proxy system including sediment redness (a*), chemical index of alteration (CIA), clay mineral proxy (smectite/kaolinite), major and trace element proxy (CaO/MgO, Ba/Sr) also showed a good paleoclimate record during the fast transgression period, which could be divided into three units. All the proxies changed little during Unit I (13-11.3ka B.P.) and revealed the climate kept in a relative stable level. Obvious fluctuation happened in Unit II (11.3-10.1ka B.P.) and the temperature kept decreasing more than 1ka till the Younger Dryas event, showed a well regional response to global climate changes. While continuous warming trend resumed again in Unit III (10.1-8 ka B.P.), which may be the signal for Holocene warm period. In addition, we also found significant 80yr, 89yr and 100yr cycles in our CIA, CaO/MgO and Ba/Sr records that imply a possible solar influence on the regional climate changes during the fast transgression period. Keywords: East China Sea, provenance, transgression, mud deposit, late Pleistocene, paleoclimate

  11. Neuroprotective Effect of Electric Conduction Treatment on Hippocampus Cell Apoptosis in KA Induced Acute Temporal Lobe Epileptic Rats.

    PubMed

    Liang, Shuli; Zhang, Limin; Yu, Xiaoman; Zhang, Shaohui; Zhang, Guojun; Ding, Ping

    Electronic conduction, a new treatment approach for epilepsy, has been confirmed to reduce epileptiform discharge on EEG and convulsive behaviors, particularly epileptic discharge propagation and serious behavioral seizures, in rats with kainic acid (KA)-induced acute temporal lobe epilepsy (TLE). Hippocampal cell apoptosis was examined to confirm the neuroprotective effect of electronic conduction therapy in rats with KA-induced acute TLE. Rats were divided into four groups: control group (right CA3 injection of saline), KA group (right CA3 injection of KA), sham conduction group (KA rats with sham conduction), and conduction group (KA rats with electric conduction). Apoptotic cells were evaluated by flow cytometry, TUNEL staining, and mRNA expression levels of caspase-3, tumor necrosis factor-alpha, and glial fibrillary acidic protein measured by real-time quantitative PCR (qRT-PCR). The frequency of convulsive behaviors in the conduction group decreased significantly compared with the KA group and the sham conduction group. Significantly fewer apoptotic cells were detected in rats with conduction based on flow cytometry and TUNEL staining results. The qRT-PCR results indicated that KA-induced up-regulation of hippocampal caspase-3 mRNA expression was reduced 24 hours after KA injection in rats that received conduction treatment. Electronic conduction treatment can reduce seizure frequency and hippocampal cell apoptosis in rats with KA-induced acute TLE. Copyright © 2016. Published by Elsevier Inc.

  12. A 600-ka Arctic sea-ice record from Mendeleev Ridge based on ostracodes

    USGS Publications Warehouse

    Cronin, Thomas M.; Polyak, L.V.; Reed, D.; Kandiano, E. S.; Marzen, R. E.; Council, E. A.

    2013-01-01

    Arctic paleoceanography and sea-ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) covers several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, ∼500 ka) with an average sedimentation rate of ∼0.5 cm/ka for most of the stratigraphy (MIS 5–13). Results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (∼400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea ice occurred after MIS 11 based on the distribution of an ice-dwelling ostracode Acetabulastoma arcticum. Spectral analyses of the ostracode assemblages indicate sea ice and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (∼22 ka) and obliquity (∼40 ka) frequencies.

  13. Geological record of meltwater events at Qinghai Lake, China from the past 40 ka

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Liu, Taibei; Wang, Hao; An, Zhisheng; Cheng, Peng; Zhu, Yizhi; Burr, G. S.

    2016-10-01

    We report here on a previously unpublished sediment core from Qinghai Lake, China, that preserves a continuous record of sedimentation for the past 40 ka. A striking feature of the record is a set of distinct meltwater events recorded at 35, 19 and 14 ka respectively. These events are manifest as distinct pulses of relatively old organic radiocarbon in the sediments. We interpret these as a signal of glacial melting in the Qinghai Lake watershed. The meltwater signals are closely correlated to temperature and precipitation records associated with deglaciation. The events at 19 ka and 14 ka correspond to well-established high latitude Melt Water Pulse (MWP) events during Marine Isotope Stage (MIS) 2, and the 35 ka event corresponds to a period of pervasive high lake levels in western China during late MIS 3. We interpret these anomalous dates as the result of relatively old carbon that was destabilized by the glaciers, and released into the lake as the glaciers melted. The data indicate that this process takes thousands of years. We expect that the approach employed here to identify these events is generally applicable to any lake system with a significant glacial meltwater component.

  14. Performance of a Ka-band transponder breadboard for deep-space applications

    NASA Technical Reports Server (NTRS)

    Mysoor, N. R.; Lane, J. P.; Kayalar, S.; Kermode, A. W.

    1995-01-01

    This article summarizes the design concepts applied in the development of and advanced Ka-band (34.4 GHz/32 GHz) transponder breadboard for the next generation of space communications systems applications. The selected architecture upgrades the X-band (7.2 GHz/8.4 GHz) deep-space transponder (DST) to provide Da-band up/Ka- and X-band down capability. The Ka-band transponder breadboard incorporates several state-of-the-art components, including sampling mixers, a Ka-band dielectric resonator oscillator, and microwave monolithic integrated circuits (MMICs). The MMICs that were tested in the breadboard include upconverters, downconverters, automatic gain control circuits, mixers, phase modulators, and amplifiers. The measured receiver dynamic range, tracking range, acquisition rate, static phase error, and phase jitter characteristics of the Ka-band breadboard interfaced to the advanced engineering model X-band DST are in good agreement with the expected performance. The results show a receiver tracking threshold of -149 dBm with a dynamic range of 80 dB and a downlink phase jitter of 7 deg rms. The analytical results of phase noise and Allan standard deviation are in good agreement with the experimental results.

  15. Ka-band Technologies for Small Spacecraft Communications via Relays and Direct Data Downlink

    NASA Technical Reports Server (NTRS)

    Budinger, James M.; Niederhaus, Charles; Reinhart, Richard; Downey, Joe; Roberts, Anthony

    2016-01-01

    As the scientific capabilities and number of small spacecraft missions in the near Earth region increase, standard yet configurable user spacecraft terminals operating in Ka-band are needed to lower mission cost and risk and enable significantly higher data return than current UHF or S-band terminals. These compact Ka-band terminals are intended to operate with both the current and next generation of Ka-band relay satellites and via direct data communications with near Earth tracking terminals. This presentation provides an overview of emerging NASA-sponsored and commercially provided technologies in software defined radios (SDRs), transceivers, and electronically steered antennas that will enable data rates from hundreds of kbps to over 1 Gbps and operate in multiple frequency bands (such as S- and X-bands) and expand the use of NASA's common Ka-bands frequencies: 22.55-23.15 GHz for forward data or uplink; and 25.5-27.0 GHz for return data or downlink. Reductions in mass, power and volume come from integration of multiple radio functions, operations in Ka-band, high efficiency amplifiers and receivers, and compact, flat and vibration free electronically steered narrow beam antennas for up to + 60 degrees field of regard. The software defined near Earth space transceiver (SD-NEST) described in the presentation is intended to be compliant with NASA's space telecommunications radio system (STRS) standard for communications waveforms and hardware interoperability.

  16. A 600-ka Arctic sea-ice record from Mendeleev Ridge based on ostracodes

    NASA Astrophysics Data System (ADS)

    Cronin, T. M.; Polyak, L.; Reed, D.; Kandiano, E. S.; Marzen, R. E.; Council, E. A.

    2013-11-01

    Arctic paleoceanography and sea-ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) covers several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, ˜500 ka) with an average sedimentation rate of ˜0.5 cm/ka for most of the stratigraphy (MIS 5-13). Results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (˜400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea ice occurred after MIS 11 based on the distribution of an ice-dwelling ostracode Acetabulastoma arcticum. Spectral analyses of the ostracode assemblages indicate sea ice and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (˜22 ka) and obliquity (˜40 ka) frequencies.

  17. Overview of Ka-band communications technology requirements for the space exploration initiative

    NASA Astrophysics Data System (ADS)

    Miller, Edward F.

    1991-12-01

    In the Space Exploration Initiative, Ka-band frequencies are likely to carry the bulk of the communications traffic both in the vicinity of and on the return links from the moon and Mars. The four exploration architectures identified by the Synthesis Group are examined and Ka-band technology requirements to meet the data traffic needs and schedule are identified. Specific Ka-band technology requirements identified are: transmitters - 0.5 to 200 W with high efficiency; antennas - 5m and 9m diameter, with multiple beams and/or scanning beams; and spacecraft receivers - noise figure of 2 dB. For each component, the current state of technology is assessed and needed technology development programs are identified. It is concluded that to meet the schedules of lunar and Mars precursor missions beginning in approximately the year 2000, aggressive technology development and advanced development programs are required immediately for Ka-band communications systems components. Additionally, the greater data transmission rates for the cargo and piloted phases of the exploration program require further Ka-band communications technology developments targeted for operations beginning in about 2010.

  18. Performance of a Ka-band transponder breadboard for deep-space applications

    NASA Astrophysics Data System (ADS)

    Mysoor, N. R.; Lane, J. P.; Kayalar, S.; Kermode, A. W.

    1995-08-01

    This article summarizes the design concepts applied in the development of and advanced Ka-band (34.4 GHz/32 GHz) transponder breadboard for the next generation of space communications systems applications. The selected architecture upgrades the X-band (7.2 GHz/8.4 GHz) deep-space transponder (DST) to provide Da-band up/Ka- and X-band down capability. The Ka-band transponder breadboard incorporates several state-of-the-art components, including sampling mixers, a Ka-band dielectric resonator oscillator, and microwave monolithic integrated circuits (MMICs). The MMICs that were tested in the breadboard include upconverters, downconverters, automatic gain control circuits, mixers, phase modulators, and amplifiers. The measured receiver dynamic range, tracking range, acquisition rate, static phase error, and phase jitter characteristics of the Ka-band breadboard interfaced to the advanced engineering model X-band DST are in good agreement with the expected performance. The results show a receiver tracking threshold of -149 dBm with a dynamic range of 80 dB and a downlink phase jitter of 7 deg rms. The analytical results of phase noise and Allan standard deviation are in good agreement with the experimental results.

  19. Overview of Ka-band communications technology requirements for the space exploration initiative

    NASA Technical Reports Server (NTRS)

    Miller, Edward F.

    1991-01-01

    In the Space Exploration Initiative, Ka-band frequencies are likely to carry the bulk of the communications traffic both in the vicinity of and on the return links from the moon and Mars. The four exploration architectures identified by the Synthesis Group are examined and Ka-band technology requirements to meet the data traffic needs and schedule are identified. Specific Ka-band technology requirements identified are: transmitters - 0.5 to 200 W with high efficiency; antennas - 5m and 9m diameter, with multiple beams and/or scanning beams; and spacecraft receivers - noise figure of 2 dB. For each component, the current state of technology is assessed and needed technology development programs are identified. It is concluded that to meet the schedules of lunar and Mars precursor missions beginning in approximately the year 2000, aggressive technology development and advanced development programs are required immediately for Ka-band communications systems components. Additionally, the greater data transmission rates for the cargo and piloted phases of the exploration program require further Ka-band communications technology developments targeted for operations beginning in about 2010.

  20. Ka-band monopulse antenna-pointing systems analysis and simulation

    NASA Technical Reports Server (NTRS)

    Lo, V. Y.

    1996-01-01

    NASA 's Deep Space Network (DSN) has been using both 70-m and 34-m reflector antennas to communicate with spacecraft at S-band (2.3 GHz) and X-band (8.45 GHz). To improve the quality of telecommunication and to meet future mission requirements, JPL has been developing 34-m Ka-band (32-GHz) beam waveguide antennas. Presently, antenna pointing operates in either the open-loop mode with blind pointing using navigation predicts or the closed-loop mode with conical scan (conscan). Pointing accuracy under normal conscan operating conditions is in the neighborhood of 5 mdeg. This is acceptable at S- and X-bands, but not enough at Ka-band. Due to the narrow beamwidth at Ka-band, it is important to improve pointing accuracy significantly (approximately 2 mdeg). Monopulse antenna tracking is one scheme being developed to meet the stringent pointing-accuracy requirement at Ka-band. Other advantages of monopulse tracking include low sensitivity to signal amplitude fluctuations as well as single-pulse processing for acquisition and tracking. This article presents system modeling, signal processing, simulation, and implementation of Ka-band monopulse tracking feed for antennas in NASA/DSN ground stations.

  1. Equatorial Precession in the Control Software of the Ka-Band Object Observation and Monitoring Experiment

    NASA Technical Reports Server (NTRS)

    Jakeman, Hali L.

    2013-01-01

    The Ka-Band Object Observation and Monitoring, or KaBOOM, project is designed mainly to track and characterize near Earth objects. However, a smaller goal of the project would be to monitor pulsars and study their radio frequency signals for use as a clock in interstellar travel. The use of pulsars and their timing accuracy has been studied for decades, but never in the Ka-band of the radio frequency spectrum. In order to begin the use of KaBOOM for this research, the control systems need to be analyzed to ensure its capability. Flaws in the control documentation leave it unclear as to whether the control software processes coordinates from the J200 epoch. This experiment will examine the control software of the Intertronic 12m antennas used for the KaBOOM project and detail its capabilities in its "equatorial mode." The antennas will be pointed at 4 chosen points in the sky on several days while probing the virtual azimuth and elevation (horizon coordinate) registers. The input right ascension and declination coordinates will then be converted separately from the control software to horizontal coordinates and compared, thus determining the ability of the control software to process equatorial coordinates.

  2. The question of the AltiKa/Ice-1 bias over rivers

    NASA Astrophysics Data System (ADS)

    Santos da Silva, Joecila; Calmant, stéphane; Medeiros Moreira, Daniel; Conchy, Taina; Frappart, Frederic; Becker, Mélanie

    2015-04-01

    The SARAL satellite embarks AltiKa, a Ka band altimeter. SARAL is flying the same orbit as ERS-2 and ENVISAT did previously. The altimetric pulses of AltiKa are also routinely processed in the GDR with the ICE-1 algorithm, the one performing best over rivers for ENVISAT. Thus, it can be expected that the ERS-2 and ENVISAT time series of the river levels can be continued with the SARAL series, same as between the ERS-2 and ENVISAT series. However, the gap between the decommissioning of ENVISAT and the launch of SARAL prevents the estimate of the bias between the series on a case by case basis by simple comparison of the water levels at similar dates. Therefore, a mean value of the AltiKa bias has to be estimated and be applied globally. In the present study, we present and discuss the different estimates of such a bias (ICE-1 algorithm) that we obtained by comparing AltiKa series of river levels to GPS-levelled gauges and/or to Jason-2 series used to bridge the ENVISAT and SARAL series at cross-overs between the two ground tracks. The series used in this study were computed in the Congo and Amazon basins.

  3. Sea-level records at ~80 ka from tectonically stable platforms: Florida and Bermuda

    USGS Publications Warehouse

    Ludwig, K. R.; Muhs, D.R.; Simmons, K.R.; Halley, R.B.; Shinn, E.A.

    1996-01-01

    Studies from technically active coasts on New Guinea and Barbados have suggested that sea level at ???80 ka was significantly lower than present, whereas data from the Atlantic and Pacific coasts of North America indicate an ???80 ka sea level close to that of the present. We determined ages of corals from a shallow submerged reef off the Florida Keys and an emergent marine deposit on Bermuda. Both localities are on tectonically stable platforms distant from plate boundaries. Uranium-series ages show that corals at both localities grew during the ???80 ka sea-level highstand, and geologic data show that sea level at that time was no lower than 7-9 m below present (Florida) and may have been 1-2 m above present (Bermuda). The ice-volume discrepancy of the 80 ka sea-level estimates is greater than the volume of the Greenland or West Antarctic ice sheets. Comparison of our ages with high-latitude insolation values indicates that the sea-level stand near the present at ???80 ka could have been orbitally forced.

  4. Evaluating North America Paleoclimate Simulations for 6 ka and 21 ka Using a Combination of Observed Paleovegetation Data and Process-Based Vegetation Model Simulations

    NASA Astrophysics Data System (ADS)

    Shafer, S. L.; Bartlein, P. J.

    2015-12-01

    Paleoclimate model simulations are often evaluated using observed paleovegetation data (e.g., pollen and plant macrofossils) that record vegetation responses to past climate changes. These observed vegetation data can be combined with mechanistic vegetation model simulations to develop process-based evaluations of paleoclimate model simulations. The use of mechanistic vegetation model simulations allows us to identify the particular spatial and temporal features of individual paleoclimate simulations that may be producing agreement or disagreement between the observed and simulated vegetation data. We used this approach to evaluate a set of eight PMIP3 (Paleoclimate Modelling Intercomparison Project phase 3) paleoclimate simulations for 6 ka and 21 ka from the CMIP5 (Coupled Model Intercomparison Project phase 5) database. Climate data were regridded onto a 10-km grid of North America using the PMIP3 vegetation simulation protocol. The regridded climate data were used as input to BIOME4, an equilibrium vegetation model, to simulate 6 ka and 21 ka biomes across the study area. The simulated biome data were compared with observed paleovegetation data from the BIOME 6000 (version 4.2) dataset. In general, agreement between simulated and observed biomes was greater for forest biomes than for non-forest biomes. We evaluated specific instances of disagreement between the simulated and observed biomes to determine whether the biome disagreement was produced by the climate model simulation (e.g., temperature bias), the vegetation model simulation (e.g., inability to simulate important disturbance regimes), the observed paleovegetation data (e.g., limits in the biomization method), or a combination of these factors. The results are summarized and we describe some of the strengths and limitations of this data-model comparison approach for evaluating paleoclimate simulations.

  5. Decoding Proton-Coupled Electron Transfer with Potential-pKa Diagrams.

    PubMed

    McCarthy, Brian D; Dempsey, Jillian L

    2017-02-06

    Aqueous potential-pH diagrams, commonly called Pourbaix diagrams, were originally developed to study metal corrosion in the 1930s and 1940s. Pourbaix diagrams have since been widely adopted for use across chemistry disciplines, particularly for the study of aqueous proton-coupled electron transfer reactions. Despite this enormous versatility, a clear extension of analogous diagrams to nonaqueous solvents is lacking. The problem hinges on the difficulty of defining the nonaqueous solution pH. Here, we address this issue by reporting the development of diagrams based on nonaqueous pKa scales. We experimentally construct diagrams for two transition-metal complexes that undergo proton-coupled electron transfer reactivity by recording their reduction potentials in the presence of acids with varying pKa values. These experimental diagrams validate the potential-pKa theory and provide valuable thermochemical information for proton-coupled electron transfer reactions, including for fleetingly stable species.

  6. Experiments on Tree Reflectivity at C, X, K and Ka-bands

    NASA Astrophysics Data System (ADS)

    Eskelinen, Pekka; Ylinen, Juhana

    2014-07-01

    Dedicated field portable radars have been used to measure the reflectivity of identified deciduous and coniferous trees at C to Ka frequency bands with perpendicular illumination. Actual test radars, their electrical parameters including antennas and calibration devices are described. First results show summer time reflectivities from -30 to -10 dB (m2/m2) for deciduous trees and from -30 to 0 dB (2/m2) for coniferous samples, depending on frequency band. Late autumn and spring measurements show particularly well in Ka-band the absence of leaves. Variations in histogram detail, from one frequency to another, exceed 10 dB despite the cumulative probabilities for all bands are quite similar. The measured power spectral density of deciduous trees in the spring was typically 20 dB/Hz at X-band and 30 dB/Hz in Ka-band. Midsummer tests gave values close to 15 and 25 dB/Hz.

  7. NASA's K/Ka-Band Broadband Aeronautical Terminal for Duplex Satellite Video Communications

    NASA Technical Reports Server (NTRS)

    Densmore, A.; Agan, M.

    1994-01-01

    JPL has recently begun the development of a Broadband Aeronautical Terminal (BAT) for duplex video satellite communications on commercial or business class aircraft. The BAT is designed for use with NASA's K/Ka-band Advanced Communications Technology Satellite (ACTS). The BAT system will provide the systems and technology groundwork for an eventual commercial K/Ka-band aeronautical satellite communication system. With industry/government partnerships, three main goals will be addressed by the BAT task: 1) develop, characterize and demonstrate the performance of an ACTS based high data rate aeronautical communications system; 2) assess the performance of current video compression algorithms in an aeronautical satellite communication link; and 3) characterize the propagation effects of the K/Ka-band channel for aeronautical communications.

  8. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2011-01-01

    A celestial reference frame at X/Ka-band (8.4/32 GHz) has been constructed using fifty-one 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec in a cos delta and 290 micro-arcsec in delta. There is evidence for zonal errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  9. Validation of SARAL/AltiKa data in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Santos da Silva, Joecila; Calmant, Stephane; Medeiros Moreira, Daniel; Oliveira, Robson; Conchy, Taina; Gennero, Marie-Claude; Seyler, Frederique

    2015-04-01

    SARAL/AltiKa is a link between past missions (since it flies on the ERS-ENVISAT orbit with Ku band nadir altimeters in LRM) and future missions such as SWOT's Ka band interferometry swaths. In the present study, we compare the capability of its altimeter AltiKa to that of previous missions working in the Ku band such as ENVISAT and Jason-2 in retrieving water levels over the Amazon basin. Same as for the aforementioned preceding missions, the best results were obtained with the ICE-1 retracking algorithm. We qualitatively analyze the impact of rainfalls in the loss of measurements. Since making long -multi mission- time series is of major importance either for hydro-climatic studies or for basin management, we also present an estimate of the altimeter bias in order that the SARAL series of water level can be appended to those of these previous missions.

  10. Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

    NASA Astrophysics Data System (ADS)

    Frappart, F.; Fatras, C.; Mougin, E.; Marieu, V.; Diepkilé, A. T.; Blarel, F.; Borderies, P.

    This study presents a comprehensive comparison of radar altimetry signatures at Ka-, Ku-, C-, and S-bands using SARAL, ENVISAT and Jason-2 data over the major bioclimatic zones, soil and vegetation types encountered in West-Africa, with an emphasis on the new information at Ka-band provided by the recently launched SARAL-Altika mission. Spatio-temporal variations of the radar altimetry responses were related to changes in surface roughness, land cover and soil wetness. Analysis of time series of backscattering coefficients along the West African bioclimatic gradient shows that radar echoes at nadir incidence are well correlated to soil moisture in semi-arid savannah environments. Radar altimeters are able to detect the presence of water even under a dense canopy cover at all frequencies. But only measurements at Ka-band are able to penetrate underneath the canopy of non-inundated tropical evergreen forests.

  11. Development of Methods for the Determination of pKa Values

    PubMed Central

    Reijenga, Jetse; van Hoof, Arno; van Loon, Antonie; Teunissen, Bram

    2013-01-01

    The acid dissociation constant (pKa) is among the most frequently used physicochemical parameters, and its determination is of interest to a wide range of research fields. We present a brief introduction on the conceptual development of pKa as a physical parameter and its relationship to the concept of the pH of a solution. This is followed by a general summary of the historical development and current state of the techniques of pKa determination and an attempt to develop insight into future developments. Fourteen methods of determining the acid dissociation constant are placed in context and are critically evaluated to make a fair comparison and to determine their applications in modern chemistry. Additionally, we have studied these techniques in light of present trends in science and technology and attempt to determine how these trends might affect future developments in the field. PMID:23997574

  12. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2011-01-01

    A celestial reference frame at X/Ka-band (8.4/32 GHz) has been constructed using fifty-one 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec in a cos delta and 290 micro-arcsec in delta. There is evidence for zonal errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  13. The Ka-band microwave generation using the Smith-Purcell effect

    NASA Astrophysics Data System (ADS)

    Ekdahl, C. A.; Davis, H. A.

    The CERETRON microwave generator concept relies on the conversion of intense relativistic electron beam (REB) energy into highpower microwave emission through the Smith-Purcell effect. Initial results from experiments with the production of Ka-band Smith-Purcell radiation generated by a 50-kA, 2.8-MeV propagated through a cylindrical transmission grating with lambda 0 = 1 cm were reported. These experiments were performed without a quasi-optical resonator, and the output was limited by breakdown of the grating and by limited access through the 90-kG magnet coil. Nevertheless, the measured power output from these initial experiments was about 7 kW in the Ka band.

  14. Ka-band microwave generation using the Smith-Purcell effect

    SciTech Connect

    Ekdahl, C.A.; Davis, H.A.

    1983-01-01

    The CERETRON microwave generator concept relies on the conversion of intense relativistic electron beam (REB) energy into highpower microwave emission through the Smith-Purcell effect. We report initial results from experiments with the production of Ka-band Smith-Purcell radiation generated by a 50-kA, 2.8-MeV beam propagated through a cylindrical transmission grating with lambda/sub 0/ = 1 cm. These experiments were performed without a quasi-optical resonator, and the output was limited by breakdown of the grating and by limited access through the 90-kG magnet coil. Nevertheless, the measured power output from these initial experiments was about 7 kW in the Ka band.

  15. The pKa of the protonated Schiff bases of gecko cone and octopus visual pigments.

    PubMed Central

    Liang, J; Steinberg, G; Livnah, N; Sheves, M; Ebrey, T G; Tsuda, M

    1994-01-01

    A visual pigment is composed of retinal bound to its apoprotein by a protonated Schiff base linkage. Light isomerizes the chromophore and eventually causes the deprotonation of this Schiff base linkage at the meta II stage of the bleaching cycle. The meta II intermediate of the visual pigment is the active form of the pigment that binds to and activates the G protein transducin, starting the visual cascade. The deprotonation of the Schiff base is mandatory for the formation of meta II intermediate. We studied the proton binding affinity, pKa, of the Schiff base of both octopus rhodopsin and the gecko cone pigment P521 by spectral titration. Several fluorinated retinal analogs have strong electron withdrawing character around the Schiff base region and lower the Schiff base pKa in model compounds. We regenerated octopus and gecko visual pigments with these fluorinated and other retinal analogs. Experiments on these artificial pigments showed that the spectral changes seen upon raising the pH indeed reflected the pKa of the Schiff base and not the denaturation of the pigment or the deprotonation of some other group in the pigment. The Schiff base pKa is 10.4 for octopus rhodopsin and 9.9 for the gecko cone pigment. We also showed that although the removal of Cl- ions causes considerable blue-shift in the gecko cone pigment P521, it affects the Schiff base pKa very little, indicating that the lambda max of visual pigment and its Schiff base pKa are not tightly coupled. PMID:7948697

  16. The pKa of the protonated Schiff bases of gecko cone and octopus visual pigments.

    PubMed

    Liang, J; Steinberg, G; Livnah, N; Sheves, M; Ebrey, T G; Tsuda, M

    1994-08-01

    A visual pigment is composed of retinal bound to its apoprotein by a protonated Schiff base linkage. Light isomerizes the chromophore and eventually causes the deprotonation of this Schiff base linkage at the meta II stage of the bleaching cycle. The meta II intermediate of the visual pigment is the active form of the pigment that binds to and activates the G protein transducin, starting the visual cascade. The deprotonation of the Schiff base is mandatory for the formation of meta II intermediate. We studied the proton binding affinity, pKa, of the Schiff base of both octopus rhodopsin and the gecko cone pigment P521 by spectral titration. Several fluorinated retinal analogs have strong electron withdrawing character around the Schiff base region and lower the Schiff base pKa in model compounds. We regenerated octopus and gecko visual pigments with these fluorinated and other retinal analogs. Experiments on these artificial pigments showed that the spectral changes seen upon raising the pH indeed reflected the pKa of the Schiff base and not the denaturation of the pigment or the deprotonation of some other group in the pigment. The Schiff base pKa is 10.4 for octopus rhodopsin and 9.9 for the gecko cone pigment. We also showed that although the removal of Cl- ions causes considerable blue-shift in the gecko cone pigment P521, it affects the Schiff base pKa very little, indicating that the lambda max of visual pigment and its Schiff base pKa are not tightly coupled.

  17. Simulated Changes in Extreme Temperature and Precipitation Events at 6 ka

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.; Bell, J. L.; Sloan, L. C.

    2003-12-01

    Paleoenviromental archives record a range of information about past environments. Three key influences shaping paleoclimate records at a given time plane are the mean state of the climate system, interannual variability, and the frequency and seasonality of extreme climate events. We have employed a high resolution regional climate model (RCM) to test the sensitivity of extreme climate events to 6 ka orbital forcing, using western North America as a case study. Extreme precipitation and temperature events were defined by the distribution of daily precipitation and temperature values in the control simulation. Simulated anomalies (6 ka - control) in the number of extreme precipitation events per year were positive throughout the RCM domain, as were anomalies in the percent of annual precipitation delivered by extreme precipitation events. These annual-scale positive anomalies in extreme precipitation were driven by changes in the seasonality of extreme precipitation events at 6 ka, with January, October and November showing the greatest positive anomalies in percent of monthly precipitation delivered by extreme precipitation events. The frequency and length of extreme temperature events in the western United States was also sensitive to 6 ka orbital forcing. Positive anomalies in the frequency of extreme maximum daily temperature values occurred inland in the RCM domain, with peak anomalies of 24 days/year centered over the Great Basin. Likewise, the number of days/year in which the maximum daily temperature exceeded 32° C increased over land by 24%, with the average heat-wave up to 12 days longer in the 6 ka simulation than in the control simulation. Finally, mean first and last freeze dates were later inland in the 6 ka simulation than in the control simulation.

  18. Systematic Behavior of the Non-dipole Magnetic Field during the 32 ka Mono Lake Excursion

    NASA Astrophysics Data System (ADS)

    Negrini, R. M.; McCuan, D.; Cassata, W. S.; Channell, J. E.; Verosub, K. L.; Liddicoat, J. C.; Knott, J. R.; Coe, R. S.; Benson, L. V.; Sarna-Wojcicki, A.; Lund, S.; Horton, R.; Lopez, J.

    2012-12-01

    Paleomagnetic excursions are enigmatic phenomena that reveal geodynamo behavior in its transitional state and provide important refinements in age control for the late Pleistocene, a critical time period for the study of paleoclimate and human evolution. We report here on two widely separated, unusually detailed records of the Mono Lake excursion (MLE) from sedimentary sequences dated at 32 ka. One of the records is from Summer Lake, Oregon. The vector components of this new record faithfully reproduce the principle features of the MLE as recorded at the type localities around Mono Lake, CA, though with greater detail and higher amplitude. Radiocarbon dates on bulk organics in the Summer Lake record confirm the 32 ka age of the MLE. The other record is from the marine Irminger Basin off of eastern Greenland and is based on the measurement of discrete samples rather than u-channels. The associated VGP paths of the two records strongly suggest systematic field behavior that includes three loci of nondipole flux whose relative dominance oscillates through time. The staggered sequence followed by the two paths through each flux locus further suggests that both the demise and return of the main field floods zonally during the excursion. The composite path is also compatible with the VGPs of a 32 ka set of lavas from New Zealand and, notably, it does not include VGPs associated with the 40 ka Laschamp excursion. This confirms that these two excursions are distinct events and, more specifically, shows that it is the 32 ka Mono Lake excursion that is recorded in the sediments surrounding Mono Lake rather than the ~40 ka Laschamp excursion.

  19. pKa values in proteins determined by electrostatics applied to molecular dynamics trajectories.

    PubMed

    Meyer, Tim; Knapp, Ernst-Walter

    2015-06-09

    For a benchmark set of 194 measured pKa values in 13 proteins, electrostatic energy computations are performed in which pKa values are computed by solving the Poisson-Boltzmann equation. In contrast to the previous approach of Karlsberg(+) (KB(+)) that essentially used protein crystal structures with variations in their side chain conformations, the present approach (KB2(+)MD) uses protein conformations from four molecular dynamics (MD) simulations of 10 ns each. These MD simulations are performed with different specific but fixed protonation patterns, selected to sample the conformational space for the different protonation patterns faithfully. The root-mean-square deviation between computed and measured pKa values (pKa RMSD) is shown to be reduced from 1.17 pH units using KB(+) to 0.96 pH units using KB2(+)MD. The pKa RMSD can be further reduced to 0.79 pH units, if each conformation is energy-minimized with a dielectric constant of εmin = 4 prior to calculating the electrostatic energy. The electrostatic energy expressions upon which the computations are based have been reformulated such that they do not involve terms that mix protein and solvent environment contributions and no thermodynamic cycle is needed. As a consequence, conformations of the titratable residues can be treated independently in the protein and solvent environments. In addition, the energy terms used here avoid the so-called intrinsic pKa and can therefore be interpreted without reference to arbitrary protonation states and conformations.

  20. Accurate calculation of the p Ka of trifluoroacetic acid using high-level ab initio calculations

    NASA Astrophysics Data System (ADS)

    Namazian, Mansoor; Zakery, Maryam; Noorbala, Mohammad R.; Coote, Michelle L.

    2008-01-01

    The p Ka value of trifluoroacetic acid has been successfully calculated using high-level ab initio methods such as G3 and CBS-QB3. Solvation energies have been calculated using CPCM continuum model of solvation at the HF and B3-LYP levels of theory with various basis sets. Excellent agreement with experiment (to within 0.4 p Ka units) was obtained using CPCM solvation energies at the B3-LYP/6-31+G(d) level (or larger) in conjunction with CBS-QB3 or G3 gas-phase energies of trifluoroacetic acid and its anion.

  1. A portfolio of fine resolution Ka-band SAR images : part l.

    SciTech Connect

    Thompson, Martin; Gutierrez, Vivian Dee; Dubbert, Dale Francis; Doerry, Armin Walter

    2005-03-01

    Sandia National Laboratories designs and builds Synthetic Aperture Radar (SAR) systems capable of forming high-quality exceptionally fine resolution images. During the spring of 2004 a series of test flights were completed with a Ka-band testbed SAR on Sandia's DeHavilland DHC-6 Twin Otter aircraft. A large data set was collected including real-time fine-resolution images of a variety of target scenes. This paper offers a sampling of high quality images representative of the output of Sandia's Ka-band testbed radar with resolutions as fine as 4 inches. Images will be annotated with descriptions of collection geometries and other relevant image parameters.

  2. First Results from an Airborne Ka-Band SAR Using SweepSAR and Digital Beamforming

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory A.; Ghaemi, Hirad; Hensley, Scott C.

    2012-01-01

    SweepSAR is a wide-swath synthetic aperture radar technique that is being studied for application on the future Earth science radar missions. This paper describes the design of an airborne radar demonstration that simulates an 11-m L-band (1.2-1.3 GHz) reflector geometry at Ka-band (35.6 GHz) using a 40-cm reflector. The Ka-band SweepSAR Demonstration system was flown on the NASA DC-8 airborne laboratory and used to study engineering performance trades and array calibration for SweepSAR configurations. We present an instrument and experiment overview, instrument calibration and first results.

  3. Mars Reconnaissance Orbiter: Ka Band Radio Science Experiments and the Effect of the Troposphere

    NASA Technical Reports Server (NTRS)

    Asmar, Sami W.; Morabito, David

    2006-01-01

    This viewgraph presentation reviews the possibilities of utilizing the telecommunication links between spacecraft and Earth to examine changes in the phase/frequency, amplitude, and polarization of radio signals to investigate, specifically for the Mars Reconnaissance Orbiter (MRO)mission utilizes X-band coherent (uplink and downlink) carrier Doppler and range for its gravity investigation Gravity team will also take advantage of Ka-band downlink signal Tropospheric calibration data from Advanced Water Vapor Radiometer (AWVR) will be used. The calibration of the received Ka band signal for the effect of the troposphere is discussed.

  4. Mars Reconnaissance Orbiter: Ka Band Radio Science Experiments and the Effect of the Troposphere

    NASA Technical Reports Server (NTRS)

    Asmar, Sami W.; Morabito, David

    2006-01-01

    This viewgraph presentation reviews the possibilities of utilizing the telecommunication links between spacecraft and Earth to examine changes in the phase/frequency, amplitude, and polarization of radio signals to investigate, specifically for the Mars Reconnaissance Orbiter (MRO)mission utilizes X-band coherent (uplink and downlink) carrier Doppler and range for its gravity investigation Gravity team will also take advantage of Ka-band downlink signal Tropospheric calibration data from Advanced Water Vapor Radiometer (AWVR) will be used. The calibration of the received Ka band signal for the effect of the troposphere is discussed.

  5. Microvibrations in a 20 M Long Ka-Band SAR Interferometer

    NASA Astrophysics Data System (ADS)

    Rodriques, G.; Ludwig, M.; Santiago-Prowald, J.

    2014-06-01

    Interferometric SAR operating at Ka-band has the potential for offering high-resolution 3D images of the surface of the Earth taken from a single-platform.The stability of the mechanical baseline of such an instrument has been considered as a key critical area for the feasibility of the concept.This paper is devoted to the analysis of the micro- vibrations in a 20-m long Ka-band SAR interferometer arising during typical attitude changing manoeuvers and the mechanical noise transmitted from reaction wheels. It is preliminarily concluded that the expected microvibration levels are within the requirements of the instrument.

  6. First Results from an Airborne Ka-Band SAR Using SweepSAR and Digital Beamforming

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory A.; Ghaemi, Hirad; Hensley, Scott C.

    2012-01-01

    SweepSAR is a wide-swath synthetic aperture radar technique that is being studied for application on the future Earth science radar missions. This paper describes the design of an airborne radar demonstration that simulates an 11-m L-band (1.2-1.3 GHz) reflector geometry at Ka-band (35.6 GHz) using a 40-cm reflector. The Ka-band SweepSAR Demonstration system was flown on the NASA DC-8 airborne laboratory and used to study engineering performance trades and array calibration for SweepSAR configurations. We present an instrument and experiment overview, instrument calibration and first results.

  7. Design of a Ka-Band Propagation Terminal for Atmospheric Measurements in Polar Regions

    NASA Technical Reports Server (NTRS)

    Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

    2016-01-01

    This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer [2] located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation [3] receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

  8. Design of a Ka-band Propagation Terminal for Atmospheric Measurements in Polar Regions

    NASA Technical Reports Server (NTRS)

    Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

    2016-01-01

    This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

  9. LPJ-GUESS Simulated North America Vegetation for 21-0 ka Using the TraCE-21ka Climate Simulation

    NASA Astrophysics Data System (ADS)

    Shafer, S. L.; Bartlein, P. J.

    2016-12-01

    Transient climate simulations that span multiple millennia (e.g., TraCE-21ka) have become more common as computing power has increased, allowing climate models to complete long simulations in relatively short periods of time (i.e., months). These climate simulations provide information on the potential rate, variability, and spatial expression of past climate changes. They also can be used as input data for other environmental models to simulate transient changes for different components of paleoenvironmental systems, such as vegetation. Long, transient paleovegetation simulations can provide information on a range of ecological processes, describe the spatial and temporal patterns of changes in species distributions, and identify the potential locations of past species refugia. Paleovegetation simulations also can be used to fill in spatial and temporal gaps in observed paleovegetation data (e.g., pollen records from lake sediments) and to test hypotheses of past vegetation change. We used the TraCE-21ka transient climate simulation for 21-0 ka from CCSM3, a coupled atmosphere-ocean general circulation model. The TraCE-21ka simulated temperature, precipitation, and cloud data were regridded onto a 10-minute grid of North America. These regridded climate data, along with soil data and atmospheric carbon dioxide concentrations, were used as input to LPJ-GUESS, a general ecosystem model, to simulate North America vegetation from 21-0 ka. LPJ-GUESS simulates many of the processes controlling the distribution of vegetation (e.g., competition), although some important processes (e.g., dispersal) are not simulated. We evaluate the LPJ-GUESS-simulated vegetation (in the form of plant functional types and biomes) for key time periods and compare the simulated vegetation with observed paleovegetation data, such as data archived in the Neotoma Paleoecology Database. In general, vegetation simulated by LPJ-GUESS reproduces the major North America vegetation patterns (e

  10. Validation of SARAL/AltiKa significant wave height and wind speed observations over the North Indian Ocean

    NASA Astrophysics Data System (ADS)

    Kumar, U. Mahesh; Swain, D.; Sasamal, S. K.; Reddy, N. Narendra; Ramanjappa, T.

    2015-12-01

    SARAL/AltiKa, a joint Ka-band altimetry mission of the Centre National d'Etudes Spatiales (CNES) and Indian Space Research Organisation (ISRO) was successfully launched on February 25, 2013. The main purpose of this mission is to explore the ocean surface topography. As it is a Ka-band altimeter mission unlike other altimeters which were primarily in Ku-band, it is essential to calibrate and validate AltiKa data products before using the data for oceanographic applications. With this objective, two important geophysical parameters, Significant Wave Height (SWH) and Wind Speed (WS) from SARAL/AltiKa are inter-compared with those from 18 moored buoy stations in the North Indian Ocean (NIO) for a two year period from March 2013 to March 2015. SARAL/AltiKa GDR-T patch-2 version products are collocated with moored buoy observations with a collocation criteria of spatio-temporal window of 50 km radius about the buoy location and 30 min time for all the altimeter measurements. Following this, linear regression relations are developed and statistical analyses carried out to assess the performance of SARAL/AltiKa. The correlation between SARAL/AltiKa derived SWHs and those from moored buoys is 0.98 m with a bias of -0.02 m and Root Mean Square Error (RMSE) of 0.15 m at 95% confidence level. The WSs derived from SARAL/AltiKa Ka-band correlates reasonably well with buoy observations with a correlation coefficient of 0.91, bias of -0.28 m/s and RMSE of 1.13 m/s. The inter-comparison results are found to be interesting with a good agreement between SARAL/AltiKa and moored buoys observations of SWH and WS in the NIO where SWHs are less than ∼4 m and WS are less than ∼13 m/s during the entire analysis period.

  11. A new method for SARAL/AltiKa waveform classification: contextual analysis over the Maithon Reservoir, Jharkhand, India

    NASA Astrophysics Data System (ADS)

    Ghosh, Surajit; Thakur, Praveen Kumar; Dutta, Suvajit; Sharma, Rashmi; Nandy, Subrata; Garg, Vaibhav; Aggarwal, Shivprasad; Bhattacharyya, Soumya

    2016-05-01

    The Indian Space Research Organisation (ISRO) and the Centre National d'etudes Spatiales (CNES) jointly launched SARAL/AltiKa (Satellite with ARgos and ALtiKa) in February 2013. AltiKa is the first mono frequency (Ka-band) radar altimeter with dual frequency radiometer. SARAL/AltiKa promises reliable results on retrieving water level of inland water and coastal bodies, though recognition pattern as well as interpreting and modeling of AltiKa waveforms at land water boundary is still a challenge. Different Retracking methods are widely used for determining the water level more correctly. An altimetry waveform also gives vital information about the reflecting surface. So, waveform classification is many times needed for retrieving surface information or before applying retracking method. In this paper, SARAL/AltiKa 40 Hz waveform dataset (Pass #152) over the Maithon Reservoir, Jharkhand, India were classified using evolutionary minimize indexing function (EMIF) with k-means. A fitness function was used in EMIF to map sampled AltiKa waveforms into single valued scalar. Four waveform groups were identified according to reflection from water, land and land-water boundary. Land-water boundary again divided into two classes viz., land-to-water and water-to-land based on direction of the AltiKa pass over the reservoir. Normalized Differenced Water Index (NDWI) derived from Landsat 8 OLI and Google Earth imagery of nearest date of AltiKa pass was used for accuracy assessment of the proposed method. It was found that the waveforms were classified with 85.7 kappa accuracy. The results of the proposed EMIF will be helpful for identify the SARAL/AltiKa waveforms classes over the inland water bodies.

  12. The Status of Ka-Band Communications for Future Deep Space Missions

    NASA Technical Reports Server (NTRS)

    Edwards, C.; Deutsch, L.; Gatti, M.; Layland, J.; Perret, J.; Stelzried, C.

    1997-01-01

    Over the past decade, the Jet Propulsion Laboratory's Telecommunications and Mission Operations Directorate has invested in a variety of technologies, targeted at both the flight and ground sides of the communications link, with the goal of developing a Ka-band (32 GHz) communications capability for future deep space missions.

  13. The Ka Values of Water and the Hydronium Ion for Comparison with Other Acids.

    ERIC Educational Resources Information Center

    Campbell, Mark L.; Waite, Boyd A.

    1990-01-01

    Provided is a rebuttal to an argument concerning the use of Ka values for water and the hydronium ion. The derivation of new values as a result of the treatment of the water as the solvent and using a Raoult's Law standard state is discussed. (CW)

  14. A dual-cavity ruby maser for the Ka-band link experiment

    NASA Technical Reports Server (NTRS)

    Shell, J.; Quinn, R. B.

    1994-01-01

    A 33.68-GHz dual-cavity ruby maser was built to support the Ka-Band Link Experiment (KABLE) conducted with the Mars Observer spacecraft. It has 25 dB of net gain and a 3-dB bandwidth of 85 MHz. Its noise temperature in reference to the cooled feedhorn aperture is 5 K.

  15. Social Metaphorical Mapping of the Concept of Force "CHI-KA-RA" in Japanese

    ERIC Educational Resources Information Center

    Suzuki, Mariko

    2005-01-01

    This research focused on the concept of "force" ("CHI-KA-RA" in Japanese) in Newtonian mechanics. The primary objective was to develop a tool, based on metaphor, to interpret student thinking in learning scientific topics. The study provides an example of using the tool to trace the process of mutual changes in thinking during a dialog among…

  16. Performance evolution of 60 kA HTS cable prototypes in the EDIPO test facility

    NASA Astrophysics Data System (ADS)

    Bykovsky, N.; Uglietti, D.; Sedlak, K.; Stepanov, B.; Wesche, R.; Bruzzone, P.

    2016-08-01

    During the first test campaign of the 60 kA HTS cable prototypes in the EDIPO test facility, the feasibility of a novel HTS fusion cable concept proposed at the EPFL Swiss Plasma Center (SPC) was successfully demonstrated. While the measured DC performance of the prototypes at magnetic fields from 8 T to 12 T and for currents from 30 kA to 70 kA was close to the expected one, an initial electromagnetic cycling test (1000 cycles) revealed progressive degradation of the performance in both the SuperPower and SuperOx conductors. Aiming to understand the reasons for the degradation, additional cycling (1000 cycles) and warm up-cool down tests were performed during the second test campaign. I c performance degradation of the SuperOx conductor reached ∼20% after about 2000 cycles, which was reason to continue with a visual inspection of the conductor and further tests at 77 K. AC tests were carried out at 0 and 2 T background fields without transport current and at 10 T/50 kA operating conditions. Results obtained in DC and AC tests of the second test campaign are presented and compared with appropriate data published recently. Concluding the first iteration of the HTS cable development program at SPC, a summary and recommendations for the next activity within the HTS fusion cable project are also reported.

  17. High Power High Efficiency Ka-Band Power Combiners for Solid-State Devices

    NASA Technical Reports Server (NTRS)

    Freeman, Jon C.; Wintucky, Edwin G.; Chevalier, Christine T.

    2006-01-01

    Wide-band power combining units for Ka-band are simulated for use as MMIC amplifier applications. Short-slot couplers as well as magic-tees are the basic elements for the combiners. Wide bandwidth (5 GHz) and low insertion (approx.0.2 dB) and high combining efficiencies (approx.90 percent) are obtained.

  18. Configuration management and monitoring of the middleware at GridKa

    NASA Astrophysics Data System (ADS)

    Nilsen, Dimitri; Weber, Pavel

    2012-12-01

    GridKa is a computing centre located in Karlsruhe. It serves as Tier-1 centre for the four LHC experiments and also provides its computing and storage resources for other non-LHC HEP and astroparticle physics experiments as well as for several communities of the German Grid Initiative D-Grid. The middleware layer at GridKa comprises three main flavours: Globus, gLite and UNICORE. This layer provides the access to the several clusters, according to the requirements of the corresponding communities. The heterogeneous structure of middleware resources and services requires their effective administration for stable and sustainable operation of the whole computing centre. In the presentation the overview of the middleware system at GridKa is given with focus on the configuration management and monitoring. These are the crucial components of the administration task for the system with high-availability setup. The various configuration tools used at GridKa, their benefits and limitations as well as developed automation procedures of the configuration management will be discussed. The overview of the monitoring system which evaluates the information delivered by central and local grid information services and provides status and detailed diagnostics for the middleware services is presented.

  19. Ka-Band High-Rate Telemetry System Upgrade for the NASA Deep Space Network

    NASA Technical Reports Server (NTRS)

    LaBelle, Remi; Bernardo, Abner; Bowen, James; Britcliffe, Michael; Bucknam, Neil; Link, Christopher; Long, Ezra; Manalo, Leslie; O'Dea, James A.; Rochblatt, David; Sosnowski, John; Veruttipong, Watt

    2009-01-01

    The NASA Deep Space Network (DSN) has a new requirement to support high-data-rate Category A (Cat A) missions (within 2 million kilometers of Earth) with simultaneous S-band uplink, S-band downlink and Ka-band downlink. The S-band links are required for traditional TT&C (Telemetry, Tracking, and Command) support to the spacecraft, while the Ka-band link is intended for high-data-rate science returns. The new Ka-band system combines the use of proven DSN cryogenic designs, for low system temperature, and high data rate capability using commercial telemetry receivers. The initial Cat A support is required for the James Webb Space Telescope (JWST) in 2013 and possibly other missions. The upgrade has been implemented into 3 different 34-meter Beam Waveguide (BWG) antennas in the DSN, one at each of the complexes in Canberra (Australia), Goldstone (California) and Madrid (Spain). System test data is presented to show that the requirements were met and the DSN is ready for Cat A Ka-band operational support.

  20. A Satellite-Tracking K and Ka Band Mobile Vehicle Antenna System

    NASA Technical Reports Server (NTRS)

    Densmore, A.; Jamnejad, V.

    1993-01-01

    This paper describes the development of the K/Ka-band, satellite-tracking mobile-vehicular antenna system for NASA's ACTS Mobile Terminal (AMT) project. ACTS is NASA's Advanced Communications Technology Satellite, which will be launched into its geostationary orbit in 1993.

  1. Results from Two Years of Ka-Band Propagation Characterization at Svalbard, Norway

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Morse, Jacquelynne Rose; Zemba, Michael

    2014-01-01

    Over the several years, NASA plans to launch several earth science missions which are expected to achieve data throughputs of 5-40 terabits per day transmitted from low earth orbiting spacecraft to ground stations. The current S-band and X-band frequency allocations in use by NASA, however, are incapable of supporting the data rates required to meet this demand. As such, NASA is in the planning stages to upgrade its existing Near Earth Network (NEN) Polar ground stations to support Ka-band (25.5-27 GHz) operations. Consequently, it becomes imperative that characterization of propagation effects at these NEN sites is conducted to determine expected system performance, particularly at low elevation angles ((is) less than 10 deg) where spacecraft signal acquisition typically occurs. Since May 2011, NASA Glenn Research Center has installed and operated a Ka-band radiometer at the NEN site located in Svalbard, Norway. The Ka-band radiometer monitors the water vapor line, as well as 6 frequencies around 26.5 GHz at multiple elevation angles: 45 deg, 20 deg, and 10 deg. Two year data collection results indicate comparable performance to previously characterized northern latitude sites in the United States, i.e., Fairbanks, Alaska. It is observed that cloud cover at the Svalbard site remains the dominant loss mechanism for Ka-band links, resulting in a margin requirement of 4.1 dB to maintain link availability of 99% at 10 deg elevation.

  2. Determination of pKa values by capillary zone electrophoresis with a dynamic coating procedure.

    PubMed

    Geiser, Laurent; Henchoz, Yveline; Galland, Alexandra; Carrupt, Pierre-Alain; Veuthey, Jean-Luc

    2005-11-01

    CZE allows to measure the acidic dissociation constant (pKa) of many drug substances. However, determining the EOF intensity may be time-consuming, especially at a low pH. In order to overcome this drawback, a dynamic coating procedure of the capillary was carried out to increase microEOF, and thus to reduce the analysis time. In addition, this coating procedure enhanced migration time stability. The effective mobilities of 15 compounds were measured at different pH, producing pK'a values dependent on BGE ionic strength. The latter values were corrected with the activity coefficient to obtain a "true" pKa value. The 15 investigated compounds were (i) five acids: namely, salicylic acid, benzoic acid, ketoprofen, phenobarbital, and phenol, (ii) four bases: lidocaine, propafenone, propranolol, and quinine, (iii), five ampholytes: sulfanilamide, sulfabenzamide, sulfadimethoxine, sulfadoxine, and sulfisoxazole, and (iv) one zwitterion: cetirizine. The range of determined pKa values was between 1.2 and 11.2, and close to the pKa values available from the literature.

  3. Lake-Level Responses to Abrupt Climate Changes in North-Central Pennsylvania since >16 ka

    NASA Astrophysics Data System (ADS)

    Halstead, T. M.; Shuman, B. N.

    2016-12-01

    Water levels in small lakes and ponds have widely responded to late-Quaternary climate changes, and we use a combination of geophysical surveys and sediment cores to reconstruct the hydrologic history of Sunfish Pond near Leroy, Pennsylvania (41°38'N 76°41'W). The small lake sits atop Barclay Mountain, a narrow ridge of the Appalachian Mountains near the southern limit of the Wisconsin glaciation. Ground-penetrating radar (GPR) profiles and a transect of three sediment cores indicate that the shoreline position of the lake has shifted over time with sandy littoral sediments extending outward into the lake stratigraphy, which is primarily composed of organic-rich muds. Calibrated radiocarbon ages from a sediment core collected in 2.25 m of water indicate that the lake formed by ca. 16.1 ka. Deposition of organic-rich muds in the near-shore core indicates moderately high water levels during the period of Heinrich Event 1, the Younger Dryas, and portions of the early Holocene. Sand layers and exceptionally low sediment accumulation rates indicate low water, however, from <16-12.5 ka and again from 5.5-2.8 ka. The water level has been near its modern high level since 2.8 ka based on extensive deposition of rapidly accumulating, organic-rich muds across the basin. The changes coincide with major changes in regional pollen records, and confirm the hydrologic significance of late-Pleistocene abrupt events in the Mid-Atlantic region.

  4. Design of a Ka-band gyro-TWT amplifier for broadband operation

    SciTech Connect

    Alaria, Mukesh Kumar; Sinha, A. K.; Choyal, Y.

    2013-07-15

    In this paper, the design of a Ka-band periodically ceramic loaded gyro-TWT amplifier has been carried out. The design predict that the interaction structure can produce more than 80 kW output power, 50 dB saturated gain, and 3 dB bandwidth for 65 kV and 5 A electron beam with velocity ratio (α) of 1.2. This paper describes the design and simulation of a high performance 35 GHz TE{sub 01} mode gyro-TWT that applies the same technique of employing a periodic dielectric loaded interaction structure to achieve stability and wide bandwidth. The design of input coupler with loaded interaction structure for Ka-band Gyro-TWT has been carried out using Ansoft hfss. The return loss (S{sub 11}) and transmission loss (S{sub 21}) of the Ka-band gyro-TWT input coupler have been found to be −27.3 dB and −0.05 dB, respectively. The design of output window for Ka-band Gyro-TWT has been carried out using cst microwave studio.

  5. An integrated Ka/Ku-band payload for personal, mobile and private business communications

    NASA Technical Reports Server (NTRS)

    Hayes, Edward J.; Keelty, J. Malcolm

    1991-01-01

    The Canadian Department of Communications has been studying options for a government-sponsored demonstration payload to be launched before the end of the century. A summary of the proposed system concepts and network architectures for providing an advanced private business network service at Ku-band and personal and mobile communications at Ka-band is presented. The system aspects addressed include coverage patterns, traffic capacity, and grade of service, multiple access options as well as special problems, such as Doppler in mobile applications. Earth terminal types and the advanced payload concept proposed in a feasibility study for the demonstration mission are described. This concept is a combined Ka-band/Ku-band payload which incorporates a number of advanced satellite technologies including a group demodulator to convert single-channel-per-carrier frequency division multiple access uplink signals to a time division multiplex downlink, on-board signal regeneration, and baseband switching to support packet switched data operation. The on-board processing capability of the payload provides a hubless VSAT architecture which permits single-hop full mesh interconnectivity. The Ka-band and Ku-band portions of the payload are fully integrated through an on-board switch, thereby providing the capability for fully integrated services, such as using the Ku-band VSAT terminals as gateway stations for the Ka-band personal and mobile communications services.

  6. Ultra-Compact Ka-Band Parabolic Deployable Antenna for RADAR and Interplanetary CubeSats

    NASA Technical Reports Server (NTRS)

    Sauder, Jonathan; Chahat, Nacer; Thomson, Mark; Hodges, Richard; Peral, Eva; Rahmat-Samii, Yahya

    2015-01-01

    Over the past several years, technology and launch opportunities for CubeSats have exploded, enabling a wide variety of missions. However, as instruments become more complex and CubeSats travel deeper into space, data communication rates become an issue. To solve this challenge, JPL has initiated a research and technology development effort to design a 0.5 meter Ka-band parabolic deployable antenna (KaPDA) which would stow in 1.5U (10 x 10 x 15 cu cm) and provide 42dB of gain (50% efficiency). A folding rib architecture and dual reflector Cassegrainian design was selected as it best balances RF gain and stowed size. The design implements an innovative telescoping waveguide and gas powered deployment. RF simulations show that after losses, the antenna would have over 42 dB gain, supported by preliminary test results. KaPDA would create opportunities for a host of new CubeSat missions by allowing high data rate communication which would enable using high fidelity instruments or venturing further into deep space, including potential interplanetary missions. Additionally KaPDA would provide a solution for other small antenna needs and the opportunity to obtain Earth science data. This paper discusses the design challenges encountered, the architecture of the solution, and the antennas expected performance capabilities.

  7. A Satellite-Tracking K and Ka Band Mobile Vehicle Antenna System

    NASA Technical Reports Server (NTRS)

    Densmore, A.; Jamnejad, V.

    1993-01-01

    This paper describes the development of the K/Ka-band, satellite-tracking mobile-vehicular antenna system for NASA's ACTS Mobile Terminal (AMT) project. ACTS is NASA's Advanced Communications Technology Satellite, which will be launched into its geostationary orbit in 1993.

  8. Ka-Band, RF MEMS Switches on CMOS Grade Silicon with a Polyimide Interface Layer

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Varaljay, Nicholas C.; Papapolymerou, John

    2003-01-01

    For the first time, RF MEMS switcbes on CMOS grade Si witb a polyimide interface layer are fabricated and characterized. At Ka-Band (36.6 GHz), an insertion loss of 0.52 dB and an isolation of 20 dB is obtained.

  9. An integrated Ka/Ku-band payload for personal, mobile and private business communications

    NASA Technical Reports Server (NTRS)

    Hayes, Edward J.; Keelty, J. Malcolm

    1991-01-01

    The Canadian Department of Communications has been studying options for a government-sponsored demonstration payload to be launched before the end of the century. A summary of the proposed system concepts and network architectures for providing an advanced private business network service at Ku-band and personal and mobile communications at Ka-band is presented. The system aspects addressed include coverage patterns, traffic capacity, and grade of service, multiple access options as well as special problems, such as Doppler in mobile applications. Earth terminal types and the advanced payload concept proposed in a feasibility study for the demonstration mission are described. This concept is a combined Ka-band/Ku-band payload which incorporates a number of advanced satellite technologies including a group demodulator to convert single-channel-per-carrier frequency division multiple access uplink signals to a time division multiplex downlink, on-board signal regeneration, and baseband switching to support packet switched data operation. The on-board processing capability of the payload provides a hubless VSAT architecture which permits single-hop full mesh interconnectivity. The Ka-band and Ku-band portions of the payload are fully integrated through an on-board switch, thereby providing the capability for fully integrated services, such as using the Ku-band VSAT terminals as gateway stations for the Ka-band personal and mobile communications services.

  10. The Matuyama-Brunhes boundary interval (500-900 ka) in North Atlantic drift sediments

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.; Curtis, J. H.; Flower, B. P.

    2004-08-01

    Ocean Drilling Program (ODP) sites 984 and 983, located on North Atlantic sediment drifts, provide high-resolution records across the Matuyama-Brunhes boundary. At ODP site 984 (Bjorn Drift, Iceland Basin), the mean sedimentation rate in the 500-900 ka interval is ~12 cm kyr-1 based on an age model derived by matching the planktonic and benthic oxygen isotope records to an Ice Volume Model. The Matuyama-Brunhes polarity transition at site 984, as defined by virtual geomagnetic polar (VGP) latitudes <50°, has an apparent duration of ~7 kyr with a mid-point at 773.5 ka, compared with 772.5 ka at neighbouring site 983. Outside the polarity transition at both sites 984 and 983, excursions in VGP latitudes, to values <20°, at 540, 590 and 670 ka correspond to troughs in the palaeointensity record. New u-channel palaeomagnetic data across the Matuyama-Brunhes boundary, for working and archive halves of core sections from three holes at both sites 984 and 983, augment data published by Channell & Lehman (1997) and are compared with back-to-back 1 cm3 discrete samples. Clusters of VGPs in the South Atlantic and northeast Asia in both u-channel and discrete sample records imply that polarity transition fields have characteristics similar to the modern non-axial-dipole (NAD) field.

  11. Ka-Band High-Rate Telemetry System Upgrade for the NASA Deep Space Network

    NASA Technical Reports Server (NTRS)

    LaBelle, Remi; Bernardo, Abner; Bowen, James; Britcliffe, Michael; Bucknam, Neil; Link, Christopher; Long, Ezra; Manalo, Leslie; O'Dea, James A.; Rochblatt, David; hide

    2009-01-01

    The NASA Deep Space Network (DSN) has a new requirement to support high-data-rate Category A (Cat A) missions (within 2 million kilometers of Earth) with simultaneous S-band uplink, S-band downlink and Ka-band downlink. The S-band links are required for traditional TT&C (Telemetry, Tracking, and Command) support to the spacecraft, while the Ka-band link is intended for high-data-rate science returns. The new Ka-band system combines the use of proven DSN cryogenic designs, for low system temperature, and high data rate capability using commercial telemetry receivers. The initial Cat A support is required for the James Webb Space Telescope (JWST) in 2013 and possibly other missions. The upgrade has been implemented into 3 different 34-meter Beam Waveguide (BWG) antennas in the DSN, one at each of the complexes in Canberra (Australia), Goldstone (California) and Madrid (Spain). System test data is presented to show that the requirements were met and the DSN is ready for Cat A Ka-band operational support.

  12. A circularly polarized Ka-band stacked patch antenna with increased gain

    NASA Technical Reports Server (NTRS)

    Zawadzki, M.

    2002-01-01

    Stacking layers of microstrip patches is a technique often used to improve the bandwidth of a patch antenna, but rarely used to increase its gain. The work presented here scales the three-layer S-band work done in to Ka-band.

  13. Computer Aided Design of Ka-Band Waveguide Power Combining Architectures for Interplanetary Spacecraft

    NASA Technical Reports Server (NTRS)

    Vaden, Karl R.

    2006-01-01

    Communication systems for future NASA interplanetary spacecraft require transmitter power ranging from several hundred watts to kilowatts. Several hybrid junctions are considered as elements within a corporate combining architecture for high power Ka-band space traveling-wave tube amplifiers (TWTAs). This report presents the simulated transmission characteristics of several hybrid junctions designed for a low loss, high power waveguide based power combiner.

  14. Steerable K/Ka-Band Antenna For Land-Mobile Satellite Applications

    NASA Technical Reports Server (NTRS)

    Densmore, Arthur; Jamnejad, Vahraz; Woo, Kenneth

    1994-01-01

    Prototype steerable microwave antenna tracks and communicates with geostationary satellite. Designed to mount on roof of vehicle and only 10 cm tall. K/Ka-band antenna rugged and compact to suit rooftop mobile operating environment. More-delicate signal-processing and control equipment located inside vehicle.

  15. Ka-Band, RF MEMS Switches on CMOS Grade Silicon with a Polyimide Interface Layer

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Varaljay, Nicholas C.; Papapolymerou, John

    2003-01-01

    For the first time, RF MEMS switcbes on CMOS grade Si witb a polyimide interface layer are fabricated and characterized. At Ka-Band (36.6 GHz), an insertion loss of 0.52 dB and an isolation of 20 dB is obtained.

  16. The All Sky Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Astrophysics Data System (ADS)

    Horiuchi, S.; Clark, J. E.; García-Miró, C.; Goodhart, C. E.; Jacobs, Christopher S.; Maddè, R.; Mercolino, M.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2014-08-01

    We have constructed an X/Ka-band (8.4/32 GHz) celestial reference frame using over seventy ~24-hour sessions with the Deep Space Network. We detected 646 sources covering the full 24 hours of right ascension and the full range of declinations. Comparison of 520 X/Ka sources in common with the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 167 micro-arcsec μas in RA cos(dec) and 219 μas in Dec. There is evidence for systematic errors at the 100 μas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling. We recently began a collaboration with ESA using their Malargüe, Argentina antenna. This site greatly improves our geometry in the south. Compared to X-band, Ka-band allows access to more compact source morphology and reduced core shift. Existing X/Ka data and simulated Gaia data predict a frame tie precision of 7 μas (1-sigma, per 3-D rotation component) with anticipated improvements reducing that to ~5 μas per component.

  17. ACTS Ka-band Propagation Research in a Spatially Diversified Network with Two USAT Ground Stations

    NASA Technical Reports Server (NTRS)

    Kalu, Alex; Acousta, R.; Durand, S.; Emrich, Carol; Ventre, G.; Wilson, W.

    1999-01-01

    Congestion in the radio spectrum below 18 GHz is stimulating greater interest in the Ka (20/30 GHz) frequency band. Transmission at these shorter wavelengths is greatly influenced by rain resulting in signal attenuation and decreased link availability. The size and projected cost of Ultra Small Aperture Terminals (USATS) make site diversity methodology attractive for rain fade compensation. Separation distances between terminals must be small to be of interest commercially. This study measures diversity gain at a separation distance <5 km and investigates utilization of S-band weather radar reflectivity in predicting diversity gain. Two USAT ground stations, separated by 2.43 km for spatial diversity, received a continuous Ka-band tone sent from NASA Glenn Research Center via the Advanced Communications Technology Satellite (ACTS) steerable antenna beam. Received signal power and rainfall were measured, and Weather Surveillance Radar-1998 Doppler (WSR-88D) data were obtained as a measure of precipitation along the USAT-to-ACTS slant path. Signal attenuation was compared for the two sites, and diversity gain was calculated for fades measured on eleven days. Correlation of WSR-88D S-band reflectivity with measured Ka-band attenuation consisted of locating radar volume elements along each slant path, converting reflectivity to Ka-band attenuation with rain rate calculation as an intermediate step. Specific attenuation for each associated path segment was summed, resulting in total attenuation along the slant path. Derived Ka-band attenuation did not correlate closely with empirical data (r = 0.239), but a measured signal fade could be matched with an increase in radar reflectivity in all fade events. Applying a low pass filter to radar reflectivity prior to deriving Ka-band attenuation improved the correlation between measured and derived signal attenuation (r = 0.733). Results indicate that site diversity at small separation distances is a viable means of rain fade

  18. Results from Three Years of Ka-Band Propagation Characterization at Svalbard, Norway

    NASA Technical Reports Server (NTRS)

    Nessel, James; Zemba, Michael; Morse, Jacquelynne

    2015-01-01

    Over the next several years, NASA plans to launch several earth science missions which are expected to achieve data throughputs of 5-40 terabits per day transmitted from low earth orbiting spacecraft to ground stations. The current S-band and X-band frequency allocations in use by NASA, however, are incapable of supporting the data rates required to meet this demand. As such, NASA is in the planning stages to upgrade its existing Near Earth Network (NEN) polar ground stations to support Ka-band (25.5-27 GHz) operations. Consequently, it installed and operated a Ka-band radiometer at the Svalbard site. Svalbard was chosen as the appropriate site for two primary reasons: (1) Svalbard will be the first site to be upgraded to Ka-band operations within the NEN Polar Network enhancement plan, and (2) there exists a complete lack of Ka-band propagation data at this site (as opposed to the Fairbanks, AK NEN site, which has 5 years of characterization collected during the Advanced Communications Technology becomes imperative that characterization of propagation effects at these NEN sites is conducted to determine expected system Satellite (ACTS) campaign). processing and provide the Herein, we discuss the data three-year measurement results performance, particularly at low elevation angles ((is) less than 10 deg) from the ongoing Ka-band propagation characterization where spacecraft signal acquisition typically occurs. Since May 2011, NASA Glenn Research Center has installed and operated a Ka-band radiometer at the NEN site located in Svalbard, Norway. The Ka-band radiometer monitors the water vapor line, as well as 4 frequencies around 26.5 GHz at a fixed 10 deg elevation angle. Three-year data collection results indicate good campaign at Svalbard, Norway. Comparison of these results with the ITU models and existing ERA profile data indicates very good agreement when the 2010 rain maps and cloud statistics are used. Finally, the Svalbard data is used to derive the expected

  19. SARAL/AltiKa observations for the studies of ice cover on lakes and oceans

    NASA Astrophysics Data System (ADS)

    Kouraev, Alexei; Zakharova, Elena; Remy, Frederique; Fleury, Sara; Guerreiro, Kevin; Willmes, Sascha; Suknev, Andrei

    2015-04-01

    With the launch of SARAL/AltiKa satellite mission scientific community has now a new source of information to study ice cover on water bodies and oceans. AltiKa observations provide a continuity with the previous satellite radar altimetry observations from ERS-1, -2 and ENVISAT mission that have the same orbit. Moreover, with the new Ka-band altimeter it gives new insights into the ice cover structure and properties. We present studies of ice cover on lakes (Lake Baikal) and Arctic ocean (for leads and polynyas detection). For Lake Baikal we use the synergy of simultaneous active (radar altimeter) and passive (radiometer) observations from radar altimetric satellites - SARAL/Altika and also TOPEX/Poseidon, Jason-1, ENVISAT and Geosat Follow-On. We present ice discrimination methodology from different satellite missions and discuss specificity of AltiKa observations. We analyse temporal variability of altimetric waveform parameters over ice-covered and ice-free surface for AltiKa and complement this analysis by satellite imagery (MODIS, Landsat), as well as our dedicated field observations of ice cover properties along the AltiKa tracks in spring 2013 and 2014. For the Arctic ocean we investigate the performance of SARAL/AltiKa to detect the leads and the coastal polynyas as well as its ability to represent spatial and temporal dynamic of water openings. The method consists first in analysis of along-track radar waveforms with collocated high-resolution Landsat images in order to localise ice/water transitions. We discuss the potential of several techniques that could be used for leads and polynya studies and for freeboard estimation. This research has been done in the framework of the Russian-French cooperation GDRI "CAR-WET-SIB", CNES TOSCA AO, ANR "CLASSIQUE", IDEX Transversalité InHERA, CNRS-Russia "Franco-Siberian Center for Research and Education" and PICS BaLaLaICA, ESA Proposal C1P.13132, Russian FZP 1.5 and EU FP7 "MONARCH-A" projects.

  20. Tephra record from the Sea of Marmara for the last 70 ka and its paleoceanographic implications

    NASA Astrophysics Data System (ADS)

    Cagatay, M.; Wulf, S.; Guichard, F.; Ozmaral, A.; Sancar; Akçer-Ön, S.; Henry, P.; Gasperini, L.

    2013-12-01

    Sea of Marmara (SoM) is a gateway between the Mediterraean and Black seas, and a tectonically active basin located on a transform plate boundary. Tephra record in the SoM is therefore very important for dating palaeoceanographic, paleoclimatic and tectonic events. We report three tephra units in cores from the SoM extending back to ca 70 ka BP and including an upper marine and a lower lacustrine units separated by a 12 ka (uncalib.) boundary. The uppermost tephra unit is up to 8 mm thick layer in the marine unit. It is heterogenous phonolitic with high total alkali content of 12.4-15.7 wt % and K2O/Na2O of 0.9 to 1.2. The middle and lower tephra layers occur in the lacustrine unit in ca 29 m-long Core MD-01-2430. The middle tephra (MT-1) is a 70 mm-thick homogeneously rhyolitic layer. The lower tephra (MT-2) is 140 mm thick and has a phonolitic-trachytic composition with CaO content of 1.7-1.9 wt % and bimodal K2O/Na2O of 1.0-1.4. Using their geochemical composition and stratigraphic analysis, we assign the tephra units, from top to bottom, to Vesuvius AP2 Pumice, Santorini Cape Riva and Campanian Ignimbrite, which have been previously dated at 3.5 ka BP, 21.95 ka BP, and 39.3 ka BP (all calender ka). The continuous sedimentary record in the Core MD-01-2430 covering the last ca 70 ka indicates that the SoM was lacustrine, disconnected from the Mediterraean Sea during MIS4, MIS3 and most of MIS2. This implies that the sill depth of the Çanakkale Strait (Dardanelles) was shallower than the present-day -65 m sill depth during MIS3 and MIS4. Figure 1: Morphotectonic map of the Sea of Marmara showing location of the studied cores (red stars). Figure 2: Geochemical biplots of tephra glass composition. a) Total alkali silica diagram b) FeO versus total alkalies for allocating cryptotephras from core MNTKS34 and ML01 to the AP2 tephra from Vesuvius. c) FeO versus CaO for correlating tephra MT1 with the Y-2 tephra from Santorini. d) SiO2 versus CaO for discriminating the

  1. Results from Three Years of Ka-band Propagation Characterization at Svalbard, Norway

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Zemba, Michael; Morse, Jacquelynne

    2015-01-01

    Over the next several years, NASA plans to launch several earth science missions which are expected to achieve data throughputs of 5-40 terabits per day transmitted from low earth orbiting spacecraft to ground stations. The current S-band and X-band frequency allocations in use by NASA, however, are incapable of supporting the data rates required to meet this demand. As such, NASA is in the planning stages to upgrade its existing Near Earth Network (NEN) polar ground stations to support Ka-band (25.5-27 GHz) operations. Consequently, it installed and operated a Ka-band radiometer at the Svalbard site. Svalbard was chosen as the appropriate site for two primary reasons: (1) Svalbard will be the first site to be upgraded to Ka-band operations within the NEN Polar Network enhancement plan, and (2) there exists a complete lack of Ka-band propagation data at this site (as opposed to the Fairbanks, AK NEN site, which has 5 years of characterization collected during the Advanced Communications Technology becomes imperative that characterization of propagation effects at these NEN sites is conducted to determine expected system Satellite (ACTS) campaign). processing and provide the Herein, we discuss the data three-year measurement results performance, particularly at low elevation angles ((is) less than 10 deg) from the ongoing Ka-band propagation characterization where spacecraft signal acquisition typically occurs. Since May 2011, NASA Glenn Research Center has installed and operated a Ka-band radiometer at the NEN site located in Svalbard, Norway. The Ka-band radiometer monitors the water vapor line, as well as 4 frequencies around 26.5 GHz at a fixed 10 deg elevation angle. Three-year data collection results indicate good campaign at Svalbard, Norway. Comparison of these results with the ITU models and existing ERA profile data indicates very good agreement when the 2010 rain maps and cloud statistics are used. Finally, the Svalbard data is used to derive the expected

  2. Tephrostratigraphy of the last 170 ka in sedimentary successions from the Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Calanchi, Natale; Dinelli, Enrico

    2008-10-01

    In this study are discussed new SEM-EDS analyses performed on glass shards from five cores collected in the Central Adriatic Sea and two cores recovered from the South Adriatic Sea. A total of 26 tephra layers have been characterized and compared with the geochemical features of terrestrial deposits and other tephra archives in the area (South Adriatic Sea and Lago Grande di Monticchio, Vulture volcano). The compositions are compatible with either a Campanian or a Roman provenance. The cores, located on the Central Adriatic inner and outer shelf, recorded tephra referred to explosive events described in the literature: AP3 (sub-Plinian activity of the Somma-Vesuvius, 2710 ± 60 14C years BP); Avellino eruption (Somma-Vesuvius, 3548 ± 129 14C years BP); Agnano Monte Spina (Phlegrean Fields, 4100 ± 400 years BP); Mercato eruption (Somma-Vesuvius, 8010 ± 35 14C years BP; Agnano Pomici Principali eruption (Phlegrean Fields, 10,320 ± 50 14C years BP); Neapolitan Yellow Tuff (Phlegrean Fields, 12,100 ± 170 14C years BP). Some of these layers were also observed in the South Adriatic core IN68-9 in addition to younger ( AP2, sub-Plinian eruption, Somma-Vesuvius, 3225 ± 140 14C years BP), and older layers ( Pomici di Base eruption, Somma-Vesuvius, 18,300 ± 150 14C years BP). Significant is the tephra record of core RF95-7 that, for the first time in the Adriatic Sea, reports the occurrence of tephra layers older than 60 ka: the well known Mediterranean tephra layers X2 (ca. 70 ka), W1 (ca. 140 ka) and V2 (Roman origin, ca. 170 ka) as well as other tephra layers attributed, on the basis of geochemistry and biostratigraphy, to explosive eruptions occurred at Vico (138 ± 2 and 151 ± 3 ka BP) and Ischia (147-140 ka BP). Previous tephra correlations performed on other cores in the Central Adriatic Sea were also critically revised according to new available data, and integrated with the results of this study for a correlation at a regional scale. The most important key

  3. ACTS Ka-band Propagation Research in a Spatially Diversified Network with Two USAT Ground Stations

    NASA Technical Reports Server (NTRS)

    Kalu, Alex; Acousta, R.; Durand, S.; Emrich, Carol; Ventre, G.; Wilson, W.

    1999-01-01

    Congestion in the radio spectrum below 18 GHz is stimulating greater interest in the Ka (20/30 GHz) frequency band. Transmission at these shorter wavelengths is greatly influenced by rain resulting in signal attenuation and decreased link availability. The size and projected cost of Ultra Small Aperture Terminals (USATS) make site diversity methodology attractive for rain fade compensation. Separation distances between terminals must be small to be of interest commercially. This study measures diversity gain at a separation distance <5 km and investigates utilization of S-band weather radar reflectivity in predicting diversity gain. Two USAT ground stations, separated by 2.43 km for spatial diversity, received a continuous Ka-band tone sent from NASA Glenn Research Center via the Advanced Communications Technology Satellite (ACTS) steerable antenna beam. Received signal power and rainfall were measured, and Weather Surveillance Radar-1998 Doppler (WSR-88D) data were obtained as a measure of precipitation along the USAT-to-ACTS slant path. Signal attenuation was compared for the two sites, and diversity gain was calculated for fades measured on eleven days. Correlation of WSR-88D S-band reflectivity with measured Ka-band attenuation consisted of locating radar volume elements along each slant path, converting reflectivity to Ka-band attenuation with rain rate calculation as an intermediate step. Specific attenuation for each associated path segment was summed, resulting in total attenuation along the slant path. Derived Ka-band attenuation did not correlate closely with empirical data (r = 0.239), but a measured signal fade could be matched with an increase in radar reflectivity in all fade events. Applying a low pass filter to radar reflectivity prior to deriving Ka-band attenuation improved the correlation between measured and derived signal attenuation (r = 0.733). Results indicate that site diversity at small separation distances is a viable means of rain fade

  4. Prediction of the pKa's of aqueous metal ion +2 complexes.

    PubMed

    Jackson, Virgil E; Felmy, Andrew R; Dixon, David A

    2015-03-26

    Aqueous metal ions play an important role in many areas of chemistry. The acidities of [Be(H2O)4](2+), [M(H2O)6](2+), M = Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+), and [M(H2O)n](2+), M = Ca(2+) and Sr(2+), n = 7 and 8, complexes have been predicted using density functional theory, second-order Møller-Plesset perturbation theory (MP2), and coupled cluster CCSD(T) theory in the gas phase. pKa's in aqueous solution were predicted by using self-consistent reaction field (SCRF) calculations with different solvation models. The most common binding motif of the majority of the metal +2 complexes is coordination number (CN) 6, with each hexaaquo cluster having reasonably high symmetry for the best arrangement of the water molecules in the first solvation shell. Be(2+) is tetracoordinated, but a second solvation shell of 8 waters is needed to predict the pKa. The Ca(2+) and Sr(2+) aquo clusters have a coordination number of 7 or 8 as found in terms of the energy of the reaction M(H2O)7(2+) + H2O → M(H2O)8(2+) and the pKa values. The calculated geometries are in reasonable agreement with experiment. The SCRF calculations with the conductor-like screening model (COSMO), and the conductor polarized continuum model (CPCM) using COSMO-RS radii, consistently agree best with experiment at the MP2/aug-cc-pVDZ and CCSD(T)/aug-cc-pVDZ levels of theory. The CCSD(T) level provides the most accurate pKa's, and the MP2 level also provides reliable predictions. Our predictions were used to elucidate the properties of metal +2 ion complexes. The pKa predictions provide confirmation of the size of the first solvation shell sizes. The calculations show that it is still difficult to predict pKa's using this cluster/implicit solvent approach to better than 1 pKa unit.

  5. Propagation experiment of COMETS Ka/Q-band communication link for future satellite cellular system

    NASA Technical Reports Server (NTRS)

    Hase, Yoshihiro

    1995-01-01

    Mobile/Personal Satellite Communication Systems in L/S-bands are going into the operational phase. In the future, they will be operated in much higher frequency bands, for example in Ka-band, because the available bandwidth in L-band is limited. Systems with large on-board antennas in higher frequencies allow the same configuration as terrestrial cellular radio systems, since the on-board antennas will have many small spot beams. This may be true especially in a low earth orbit system such as Teledesic, which will use Ka-band. The most important parameter of Satellite Cellular may be cell size, that is, a diameter of the spot beam. A system designer needs the local correlation data in a cell and the size of the correlative area. On the other hand, the most significant difficulty of Ka and higher band systems is the countermeasure to rain attenuation. Many-cell systems can manage the limited power of on-board transponders by controlling output power of each beam depending on the rain attenuation of each cell. If the cell size is equal to the correlative area, the system can probably achieve the maximum performance. Propagation data of Ka and higher band obtained in the past shows a long term cumulative feature and link availability, but do not indicate the correlative area. The Japanese COMETS satellite, which will be launched in February 1997, has transponders in Ka and Q-band. The CRL is planning to measure the correlative area using 21 GHz and 44 GHz CW transmissions from the COMETS.

  6. Molecular determinants of KA1 domain-mediated autoinhibition and phospholipid activation of MARK1 kinase

    PubMed Central

    Emptage, Ryan P.; Lemmon, Mark A.; Ferguson, Kathryn M.

    2017-01-01

    Protein kinases are frequently regulated by intramolecular autoinhibitory interactions between protein modules that are reversed when these modules bind other ‘activating’ protein or membrane-bound targets. One group of kinases, the MAP/microtubule affinity-regulating kinases (MARKs) contain a poorly understood regulatory module, the KA1 (kinase associated-1) domain, at their C-terminus. KA1 domains from MARK1 and several related kinases from yeast to humans have been shown to bind membranes containing anionic phospholipids, and peptide ligands have also been reported. Deleting or mutating the C-terminal KA1 domain has been reported to activate the kinase in which it is found — also suggesting an intramolecular autoinhibitory role. Here, we show that the KA1 domain of human MARK1 interacts with, and inhibits, the MARK1 kinase domain. Using site-directed mutagenesis, we identify residues in the KA1 domain required for this auto-inhibitory activity, and find that residues involved in autoinhibition and in anionic phospholipid binding are the same. We also demonstrate that a ‘mini’ MARK1 becomes activated upon association with vesicles containing anionic phospholipids, but only if the protein is targeted to these vesicles by a second signal. These studies provide a mechanistic basis for understanding how MARK1 and its relatives may require more than one signal at the membrane surface to control their activation at the correct location and time. MARK family kinases have been implicated in a plethora of disease states including Alzheimer’s, cancer, and autism, so advancing our understanding of their regulatory mechanisms may ultimately have therapeutic value. PMID:27879374

  7. Dichroic Filter for Separating W-Band and Ka-Band

    NASA Technical Reports Server (NTRS)

    Epp, Larry W.; Durden, Stephen L.; Jamnejad, Vahraz; Long, Ezra M.; Sosnowski, John B.; Higuera, Raymond J.; Chen, Jacqueline C.

    2012-01-01

    The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel. A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength. First, a mechanical prototype was built using an approximately 102-micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higher-frequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly. This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.

  8. Reproducing basic pKa values for turkey ovomucoid third domain using a polarizable force field

    PubMed Central

    Click, Timothy H.; Kaminski, George A.

    2009-01-01

    We have extended our previous studies of calculating acidity constants for the acidic residues found in the turkey ovomucoid third domain protein (OMTKY3) by determining the relative pKa values for the basic residues (Lys13, Arg21, Lys29, Lys34, His52, and Lys55). A polarizable force field (PFF) was employed. The values of the pKa were found by direct comparison of energies of solvated protonated and deprotonated forms of the protein. Poisson Boltzmann (PBF) and Generalized Born (SGB) continuum solvation models represent the hydration, and a non-polarizable fixed-charges OPLS-AA force field was used for comparison. Our results indicate that (i) the pKa values of the basic residues can be found in close agreement with the experimental values when a PFF is used in conjunction with the PBF solvation model, (ii) it is sufficient to take into the account only the residues which are in close proximity (hydrogen bonded) to the residue in question, and (iii) The PBF solvation model is superior to the SGB solvation model for these pKa calculations. The average error with the PBF/PFF model is only 0.7 pH units, compared with 2.2 and 6.1 units for the PBF/OPLS and SGB/OPLS, respectively. The maximum deviation of the PBF/PFF results from the experimental values is 1.7 pH units compared with 6.0 pH units for the PBF/OPLS. Moreover, the best results were obtained while using an advanced non-polar energy calculation scheme. The overall conclusion is that this methodology and force field are suitable for accurate assessment of pKa shifts for both acidic basic protein residues. PMID:19432439

  9. KaBOB: ontology-based semantic integration of biomedical databases.

    PubMed

    Livingston, Kevin M; Bada, Michael; Baumgartner, William A; Hunter, Lawrence E

    2015-04-23

    The ability to query many independent biological databases using a common ontology-based semantic model would facilitate deeper integration and more effective utilization of these diverse and rapidly growing resources. Despite ongoing work moving toward shared data formats and linked identifiers, significant problems persist in semantic data integration in order to establish shared identity and shared meaning across heterogeneous biomedical data sources. We present five processes for semantic data integration that, when applied collectively, solve seven key problems. These processes include making explicit the differences between biomedical concepts and database records, aggregating sets of identifiers denoting the same biomedical concepts across data sources, and using declaratively represented forward-chaining rules to take information that is variably represented in source databases and integrating it into a consistent biomedical representation. We demonstrate these processes and solutions by presenting KaBOB (the Knowledge Base Of Biomedicine), a knowledge base of semantically integrated data from 18 prominent biomedical databases using common representations grounded in Open Biomedical Ontologies. An instance of KaBOB with data about humans and seven major model organisms can be built using on the order of 500 million RDF triples. All source code for building KaBOB is available under an open-source license. KaBOB is an integrated knowledge base of biomedical data representationally based in prominent, actively maintained Open Biomedical Ontologies, thus enabling queries of the underlying data in terms of biomedical concepts (e.g., genes and gene products, interactions and processes) rather than features of source-specific data schemas or file formats. KaBOB resolves many of the issues that routinely plague biomedical researchers intending to work with data from multiple data sources and provides a platform for ongoing data integration and development and for

  10. Climatic Forcings of the Last Major Glacial Inception: A GCM Simulation of 115.5 Ka

    NASA Astrophysics Data System (ADS)

    Essig, M.; Oglesby, R.; Otieno, F.; Bromwich, D.

    2007-12-01

    The onset of Northern Hemisphere glaciation at around 115.5 Ka is thought to have been caused by a number of factors. Two of the most important of these are a reduction in atmospheric CO2 from approximately 380 ppm to 180 ppm, and changes in the earth's eccentricity, precession, and obliquity due to Milankovitch orbital cycles. We used the NCAR CCSM3 GCM in fully coupled mode to simulate the climate at 115.5 ka B.P. The fully-coupled mode includes dynamical atmospheric and oceanic components, as well as sophisticated land surface and sea ice schemes. Sea level and the distribution of the continents were held at present-day values, since they changed little between 0 Ka and 115.5 Ka. Thus, our model simulation can also be thought of as examining the roles of lowered CO2 and orbital configuration in driving glacial inception. In particular, we hypothesize that these climatic forcings will lead to a succession of cool summers and warm wet winters in key regions of the high latitude Northern Hemisphere. In turn, we expect this will be conducive to building the perennial snow pack that is an essential precursor to the Laurentide and Fenno-Scandinavian ice sheets. Though the simulation is still underway at this writing, preliminary results from the first 100 years of the run suggest that this does indeed take place. Key results from the completed run will be presented at the meeting, along with an assessment of how they differ from a present-day CCSM3 control run. Furthermore, in glacial inception regions the performance of both the control run and an existing CCSM3 preindustrial simulation are being compared to ERA40 reanalyses as an additional test of model fidelity. The model simulation is also being verified using all available data from geologic record for the time around 115.5 Ka.

  11. Microwave Spectrum of the H_2S Dimer: Observation of K_{a}=1 Lines

    NASA Astrophysics Data System (ADS)

    Das, Arijit; Mandal, Pankaj; Lovas, Frank J.; Medcraft, Chris; Arunan, Elangannan

    2017-06-01

    Large amplitude tunneling motions in (H_2S)_{2} complicate the analysis of its microwave spectrum. The previous rotational spectrum of (H_2S)_{2} was observed using the Balle-Flygare pulsed nozzle FT microwave spectrometers at NIST and IISc. For most isotopomers of (H_2S)_{2} a two state pattern of a-type K_{a}=0 transitions had been observed and were interpreted to arise from E_{1}^{+/-} and E_{2}^{+/-} states of the six tunneling states expected for (H_2S)_{2}. K_{a}=0 lines gave us only the distance between the acceptor and donor S atoms. The (B+C)/2 for E_{1} and E_{2} states were found to be 1749.3091(8) MHz and 1748.1090(8) MHz respectively. In this work, we have observed the K_{a}=1 microwave transitions which enable us to determine finer structural details of the dimer. The observation of the K_{a}=1 lines indicate that (H_2S)_{2} is not spherical in nature, their interactions do have some anisotropy. Preliminary assignment of K_{a}=1 lines for the E_{1} state results in B=1752.859 MHz and C=1745.780 MHz. We also report a new progression of lines which probably belongs to the parent isotopomers. F. J. Lovas, P. K. Mandal and E. Arunan, unpublished work P. K. Mandal Ph.D. Dissertation, Indian Institute of Science, (2005) F. J. Lovas, R. D. Suenram, and L. H. Coudert. 43rd Int.Symp. on Molecular Spectroscopy. (1988)

  12. Conservation of angular momentum in polyatomic photochemical reactions: H2CO(v,J,Ka,Kc)yields+HCO(N,Ka,Kc,J)

    NASA Astrophysics Data System (ADS)

    Waugh, Siobhan E.; Terentis, Andrew C.; Metha, Gregory F.; Kable, Scott H.

    1998-05-01

    The photodissociation dynamics of the reaction H2CO + hv yields H + HCO have been investigated just above the reaction threshold. Formaldehyde was excited into specific J, Ka, Kc rotational states of three vibrational levels in the A(1A2) state. Molecules in these states undergo internal conversion back to the X (1A1) ground state on which the radical fragments are formed. The ensuring distribution of rotational energy in the HCO fragment was measured as a function of the N, Ka, Kc and J equals N +/- S quantum numbers of the fragment, and also the initial v, J, Ka, Kc quantum numbers of the parent. In a previous publication we investigated the dynamics of this reaction at low available energy and concluded that when only the N and Ka quantum numbers of both formaldehyde and the formyl radical are considered, the distributions are modeled well by phase space theory (PST). This is consistent with statistical dynamics on a bound, barrier less surface. Within approximately equals 10 cm-1 of the energetic threshold, a centrifugal barrier affected the populations by inhibiting product states that require large orbital angular momentum. Resolution of Kc in the parent and product gave large deviations from the PST model, however little data were available to quantify this observation. In this work we have extended then umber of initially excited H2CO levels to explore this 'Kc effect' further. We find that in the HCO Kc state or the lower energy state. This preference is consistent over all N for any particular initial H2CO state but may very for different initial states. Over the seven initial states probed here, four favored Kc and the other three Kc. A correlation between this Kc preference and the initial state was observed: odd Kc formaldehyde states produce Kc preference in HCO and vice versa for initially even Kc states. A comparison with one previous observation of this effect is presented, however no concrete explanation can be offered at this stage.

  13. Eolian depositional phases during the past 50 ka and inferred climate variability for the Pampean Sand Sea, western Pampas, Argentina

    NASA Astrophysics Data System (ADS)

    Tripaldi, Alfonsina; Forman, Steven L.

    2016-05-01

    The Pampean Sand Sea, which occurs from the Argentinian Pampas to the eastern Andean piedmont, hosts presently stabilized dune fields spanning the late Quaternary. This study integrates previous results and presents new geomorphic, stratigraphic, sedimentological, and chronologic data for nineteen >2 m-thick eolian successions for the San Luis paleo-dune field, western Pampas, to better constrain the depositional history. Six eolian depositional phases are identified spanning the past 50 ka, interposed with paleosols and/or bounded by erosive surfaces. Age control was from 61 OSL ages of small aliquots of quartz grains from eolian stratigraphic units. The inferred timing of eolian phases are at ca. 70 ± 10 yr, 190 ± 20 yr, 12 to 1 ka, 22 to 17 ka, 29 to 24 ka, and 40 to 32 ka. A maximum span for periods of pedogenesis at ca. 12 to 17 ka, 22 to 24 ka, and 29 to 32 ka was provided by bounding OSL ages, which broadly overlap with high stands of pluvial lakes and glacier advances in the central Andes. We infer that the added precipitation may reflect expansion of the Southern Hemisphere monsoon, associated with Northern Hemisphere Heinrich events, leading to episodes of significantly wetter conditions (>350 mm MAP) to at least 35° S. Most of the Holocene (12 ka to 0.8 ka) was characterized by sand sheet deposit under drier than present conditions (100-450 mm MAP), associated with Monte-type vegetation (shrub steppe). The latest two eolian depositional phases, occurred at ca. 190 and 70 yr ago, during the historic period with European settlement and are related to anthropogenic landscape disturbance, though the youngest phase was concomitant with 1930s drought. Wet conditions dominated since ca. AD 1970 with new lakes and rivers forming across this eolian terrain; an incongruous environmental response in reference to drier conditions for most of the Holocene.

  14. Synaptic Pattern of KA1 and KA2 upon the Direction-Selective Ganglion Cells in Developing and Adult Mouse Retina

    PubMed Central

    Lee, Jee-Geon; Lee, Kyoung-Pil; Jeon, Chang-Jin

    2012-01-01

    The detection of image motion is important to vision. Direction-selective retinal ganglion cells (DS-RGCs) respond strongly to stimuli moving in one direction of motion and are strongly inhibited by stimuli moving in the opposite direction. In this article, we investigated the distributions of kainate glutamate receptor subtypes KA1 and KA2 on the dendritic arbors of DS-RGCs in developing (5, 10) days postnatal (PN) and adult mouse retina to search for anisotropies. The distribution of kainate receptor subtypes on the DS-RGCs was determined using antibody immunocytochemistry. To identify their characteristic morphology, DS-RGCs were injected with Lucifer yellow. The triple-labeled images of dendrites, kinesin II, and receptors were visualized by confocal microscopy and were reconstructed from high-resolution confocal images. We found no evidence of asymmetry in any of the kainate receptor subunits examined on the dendritic arbors of both the On and Off layers of DS-RGCs in all periods of developing and adult stage that would predict direction selectivity. PMID:22489103

  15. Mineralogy and geochemistry of the older (> 40 ka) ignimbrites on the Campanian Plain, southern Italy

    NASA Astrophysics Data System (ADS)

    Belkin, H. E.; Rolandi, G.; Jackson, J. C.; Cannatelli, C.; Doherty, A. L.; Petrosino, P.; De Vivo, B.

    2016-09-01

    The Campanian Plain in southern Italy has been volcanically active for at least the last 300 ka. The Campanian Ignimbrite (CI) erupted at 39.3 ka, has a volume of ≥ 310 km3 and a great areal extent. However, significant, but scattered deposits of older ignimbrites underlie the CI and document a long history of volcanism. We examined the mineralogy and geochemistry of 11 older ignimbrite strata by optical petrography, electron microprobe, scanning electron microscope, X-ray diffraction, and various whole-rock geochemical techniques. We have analyzed strata at Durazzano (116.1 ka), Moschiano (184.7 ka), Seiano Valley (245.9 and 289.6 ka), and Taurano - Acqua Feconia (157.4, 183.8, 205.6, and 210.4 ka) that have been previously dated on unaltered sanidine. The older ignimbrites are highly altered with loss on ignition (LOI) that ranges from 17 to 8 wt%. Whole-rock compositions reflect variable element mobility during weathering; e.g., CaO is enriched and Na2O depleted relative to hydration. X-ray diffraction identified major chabazite, kaolinite, and illite alteration products in some samples. Rhabdophane-(Nd), usually intergrown with chabazite and Mn-carbonate, indicates that some LREE were also mobilized during weathering. The phenocryst mineralogy is typical for Campanian Plain (CP) magmas and consists of plagioclase (An88 Ab11 Or1 to An32 Ab63 Or5), potassium feldspar (Or40 Ab57 An3 to Or79 Ab18 An3), biotite (TiO2 = ~ 4-7 wt%, BaO = up to 2 wt%, F = up to 2 wt%), diopside (Ca47Mg47Fe6 to Ca48Mg29Fe23), and titaniferous magnetite. Relatively immobile trace elements Zr, Hf, Th, Ta, V, and Nb were used to investigate element abundance and ratio compared to the Campanian Ignimbrite and other CP magmas. Zr/Hf of the older ignimbrites is similar to that of the CI, but Ta is depleted relative to Th and V is enriched compared to CI. Th/Ta and Nb/V distributions for most of the older ignimbrites are similar to those in the Neapolitan Yellow Tuff with the exception of

  16. Delay-Throughput Performance the Deep-Space Ka-Band Link

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2008-01-01

    In this paper, performance of a first-in, first-out (FIFO), selective retransmission scheme for the deep-space Ka-band link is presented and compared to the performance of a comparable X-band link. In this analysis, 16 months of water vapor radiometer (WVR) and advanced water vapor radiometer (AWVR) data from the three Deep Space Network (DSN) Communication Complexes (DSCC) were used to emulate weather effects on X-band and Ka-band links from Mars. Mars Reconnaissance Orbiter (MRO) X-band and Ka-band telecommunications parameters were used for spacecraft telecommunications capabilities. One pass per week per complex was selected from MRO's Deep Space Network (DSN) schedule from April 1, 2006 to August 31, 2007 for a total of 207 passes (69 passes per complex) for this analysis. For each pass both X-band and Ka-band links were designed using at most two data rates so that the expected pass capacity would be maximized subject to a minimum availability requirement (MAR). In conjunction with the WVR/AWVR data, elevation profiles of the selected passes and models for the performance of the antennas in the DSN were used to emulate the performance of both links. It was assumed that the retransmission of the data takes place not on the same pass as the original transmission but during subsequent passes. The data collected before a pass was assumed to be a fraction of the expected capacity of the pass as calculated through the link design process. Infinite spacecraft storage was assumed to obtain an upper bound on the spacecraft storage requirement. The independent parameters of this analysis were MAR and the ratio of data collected before a pass to the expected pass capacity. Since the selected passes did not occur at regular intervals, the delay in this analysis was measured in terms of number of passes. The throughput was measured in terms of number of bits received successfully on the ground. The results indicate that reasonable delay performance could be achieved with

  17. Delay-Throughput Performance of the Deep-Space Ka-band Link

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2008-01-01

    In this paper, performance of a first-in, first-out (FIFO), selective retransmission scheme for the deep-space Ka-band link is presented and compared to the performance of a comparable X-band link. In this analysis, 16 months of water vapor radiometer (WVR) and advanced water vapor radiometer (AWVR) data from the three Deep Space Network (DSN) Communication Complexes (DSCC) were used to emulate weather effects on X-band and Ka-band links from Mars. Mars Reconnaissance Orbiter (MRO) X-band and Ka-band telecommunications parameters were used for spacecraft telecommunications capabilities. One pass per week per complex was selected from MRO's Deep Space Network (DSN) schedule from April 1, 2006 to August 31, 2007 for a total of 207 passes (69 passes per complex) for this analysis. For each pass both X-band and Ka-band links were designed using at most two data rates so that the expected pass capacity would be maximized subject to a minimum availability requirement (MAR). In conjunction with the WVR/AWVR data, elevation profiles of the selected passes and models for the performance of the antennas in the DSN were used to emulate the performance of both links. It was assumed that the retransmission of the data takes place not on the same pass as the original transmission but during subsequent passes. The data collected before a pass was assumed to be a fraction of the expected capacity of the pass as calculated through the link design process. Infinite spacecraft storage was assumed to obtain an upper bound on the spacecraft storage requirement. The independent parameters of this analysis were MAR and the ratio of data collected before a pass to the expected pass capacity. Since the selected passes did not occur at regular intervals, the delay in this analysis was measured in terms of number of passes. The throughput was measured in terms of number of bits received successfully on the ground. The results indicate that reasonable delay performance could be achieved with

  18. Delay-Throughput Performance the Deep-Space Ka-Band Link

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2008-01-01

    In this paper, performance of a first-in, first-out (FIFO), selective retransmission scheme for the deep-space Ka-band link is presented and compared to the performance of a comparable X-band link. In this analysis, 16 months of water vapor radiometer (WVR) and advanced water vapor radiometer (AWVR) data from the three Deep Space Network (DSN) Communication Complexes (DSCC) were used to emulate weather effects on X-band and Ka-band links from Mars. Mars Reconnaissance Orbiter (MRO) X-band and Ka-band telecommunications parameters were used for spacecraft telecommunications capabilities. One pass per week per complex was selected from MRO's Deep Space Network (DSN) schedule from April 1, 2006 to August 31, 2007 for a total of 207 passes (69 passes per complex) for this analysis. For each pass both X-band and Ka-band links were designed using at most two data rates so that the expected pass capacity would be maximized subject to a minimum availability requirement (MAR). In conjunction with the WVR/AWVR data, elevation profiles of the selected passes and models for the performance of the antennas in the DSN were used to emulate the performance of both links. It was assumed that the retransmission of the data takes place not on the same pass as the original transmission but during subsequent passes. The data collected before a pass was assumed to be a fraction of the expected capacity of the pass as calculated through the link design process. Infinite spacecraft storage was assumed to obtain an upper bound on the spacecraft storage requirement. The independent parameters of this analysis were MAR and the ratio of data collected before a pass to the expected pass capacity. Since the selected passes did not occur at regular intervals, the delay in this analysis was measured in terms of number of passes. The throughput was measured in terms of number of bits received successfully on the ground. The results indicate that reasonable delay performance could be achieved with

  19. Delay-Throughput Performance of the Deep-Space Ka-band Link

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2008-01-01

    In this paper, performance of a first-in, first-out (FIFO), selective retransmission scheme for the deep-space Ka-band link is presented and compared to the performance of a comparable X-band link. In this analysis, 16 months of water vapor radiometer (WVR) and advanced water vapor radiometer (AWVR) data from the three Deep Space Network (DSN) Communication Complexes (DSCC) were used to emulate weather effects on X-band and Ka-band links from Mars. Mars Reconnaissance Orbiter (MRO) X-band and Ka-band telecommunications parameters were used for spacecraft telecommunications capabilities. One pass per week per complex was selected from MRO's Deep Space Network (DSN) schedule from April 1, 2006 to August 31, 2007 for a total of 207 passes (69 passes per complex) for this analysis. For each pass both X-band and Ka-band links were designed using at most two data rates so that the expected pass capacity would be maximized subject to a minimum availability requirement (MAR). In conjunction with the WVR/AWVR data, elevation profiles of the selected passes and models for the performance of the antennas in the DSN were used to emulate the performance of both links. It was assumed that the retransmission of the data takes place not on the same pass as the original transmission but during subsequent passes. The data collected before a pass was assumed to be a fraction of the expected capacity of the pass as calculated through the link design process. Infinite spacecraft storage was assumed to obtain an upper bound on the spacecraft storage requirement. The independent parameters of this analysis were MAR and the ratio of data collected before a pass to the expected pass capacity. Since the selected passes did not occur at regular intervals, the delay in this analysis was measured in terms of number of passes. The throughput was measured in terms of number of bits received successfully on the ground. The results indicate that reasonable delay performance could be achieved with

  20. Weak acid-concentration Atot and dissociation constant Ka of plasma proteins in racehorses.

    PubMed

    Stampfli, H R; Misiaszek, S; Lumsden, J H; Carlson, G P; Heigenhauser, G J

    1999-07-01

    The plasma proteins are a significant contributor to the total weak acid concentration as a net anionic charge. Due to potential species difference, species-specific values must be confirmed for the weak acid anionic concentrations of proteins (Atot) and the effective dissociation constant for plasma weak acids (Ka). We studied the net anion load Atot of equine plasma protein in 10 clinically healthy mature Standardbred horses. A multi-step titration procedure, using a tonometer covering a titration range of PCO2 from 25 to 145 mmHg at 37 degrees C, was applied on the plasma of these 10 horses. Blood gases (pH, PCO2) and electrolytes required to calculate the strong ion difference ([SID] = [(Na(+) + K(+) + Ca(2+) + Mg(2+))-(Cl(-) + Lac(-) + PO4(2-))]) were simultaneously measured over a physiological pH range from 6.90-7.55. A nonlinear regression iteration to determine Atot and Ka was performed using polygonal regression curve fitting applied to the electrical neutrality equation of the physico-chemical system. The average anion-load Atot for plasma protein of 10 Standardbred horses was 14.89 +/- 0.8 mEq/l plasma and Ka was 2.11 +/- 0.50 x 10(-7) Eq/l (pKa = 6.67). The derived conversion factor (iterated Atot concentration/average plasma protein concentration) for calculation of Atot in plasma is 0.21 mEq/g protein (protein-unit: g/l). This value compares closely with the 0.24 mEq/g protein determined by titration of Van Slyke et al. (1928) and 0.22 mEq/g protein recently published by Constable (1997) for horse plasma. The Ka value compares closely with the value experimentally determined by Constable in 1997 (2.22 x 10(7) Eq/l). Linear regression of a set of experimental data from 5 Thoroughbred horses on a treadmill exercise test, showed excellent correlation with the regression lines not different from identity for the calculated and measured variables pH, HCO3 and SID. Knowledge of Atot and Ka for the horse is useful especially in exercise studies and in

  1. ACTS Ka-Band Earth Stations: Technology, Performance, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Struharik, Steven J.; Diamond, John J.; Stewart, David

    2000-01-01

    The Advanced Communications Technology Satellite (ACTS) Project invested heavily in prototype Ka-band satellite ground terminals to conduct an experiments program with the ACTS satellite. The ACTS experiment's program proposed to validate Ka-band satellite and ground station technology. demonstrate future telecommunication services. demonstrate commercial viability and market acceptability of these new services, evaluate system networking and processing technology, and characterize Ka-band propagation effects, including development of techniques to mitigate signal fading. This paper will present a summary of the fixed ground terminals developed by the NASA Glenn Research Center and its industry partners, emphasizing the technology and performance of the terminals (Part 1) and the lessons learned throughout their six year operation including the inclined orbit phase of operations (Full Report). An overview of the Ka-band technology and components developed for the ACTS ground stations is presented. Next. the performance of the ground station technology and its evolution during the ACTS campaign are discussed to illustrate the technical tradeoffs made during the program and highlight technical advances by industry to support the ACTS experiments program and terminal operations. Finally. lessons learned during development and operation of the user terminals are discussed for consideration of commercial adoption into future Ka-band systems. The fixed ground stations used for experiments by government, academic, and commercial entities used reflector based offset-fed antenna systems ranging in size from 0.35m to 3.4m antenna diameter. Gateway earth stations included two systems, referred to as the NASA Ground Station (NGS) and the Link Evaluation Terminal (LET). The NGS provides tracking, telemetry, and control (TT&C) and Time Division Multiple Access (TDMA) network control functions. The LET supports technology verification and high data rate experiments. The ground

  2. Paleoceanographic and Paleoclimatologic Records of the Sea of Marmara during the Last 70 KA

    NASA Astrophysics Data System (ADS)

    Cagatay, M. N.

    2015-12-01

    The Sea of Marmara is located between the Mediterranean and the Black Sea to which it is connected with the İstanbul (Bosporus) and Çanakkale (Dardanelles) straits having sill depths of 35 and 65 m below the present sea level, respectively. It is presently characterized by a two-way flow system consisting of the upper Black Sea and lower Mediterranean waters separated with a permanent halocline at -25 m. A 28.88 m long RV Marion Dufresne core MD01-2430 from the western high provides a continuous stratigraphic record for the last ca 70 ka. This record shows only one lacustrine-marine transition at ~ 12.6 cal ka BP over this period, indicating that the Sea of Marmara was under lacustrine conditions disconnected from the Mediterranean Sea from the beginning of Marine Isotope Stage 4 (MIS-4) to the early MIS-1. Soon after the reconnection, the Marmara sapropel started depositing under dysoxic-suboxic conditions during 12.33-5.7 cal ka BP. The periods of high inorganic (carbonate) and organic carbon production and burial in the Sea of Marmara correlate very closely with the Greenland Intertadials (GI) recorded in the NGRIP oxygen isotope and Black Sea Ca data sets. The two partly overlapping Ca peaks in the Sea of Marmara record corresponding to ~12.6 cal ka BP and 14.5 cal ka BP represent the authigenic carbonate deposition that resulted from the mixing of lacustrine Marmara and saline Mediterranean waters during the latest marine reconnection and the Greenland Interstadial-1 (GI-1) high productivity period, respectively. Low δ18O (down to -9‰) and high δ13C (+2.4‰) values of bulk carbonate during the GIs strongly suggest high input of fresh waters from the Black Sea and high organic productivity in the lacustrine Marmara under warm and humid conditions. Low "carbonate-free" K concentrations during the GIs suggest low detrital input in the Marmara "Lake", which in turn indicates low erosion rates in the catchment with a high vegetation density. In contrast, the

  3. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2010-01-01

    A celestial reference frame at X/Kaband (8.4/32 GHz) has been constructed using fiftyone 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec ( mu as) in alpha cos delta and 290 mu as in delta. There is evidence for zonal errors at the 100 mu as level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  4. Ka-band Digitally Beamformed Airborne Radar Using SweepSAR Technique

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory A.; Chuang, Chung-Lun; Ghaemi, Hirad; Heavey, Brandon A.; Lin, Lung-Sheng S.; Quaddus, Momin

    2012-01-01

    A paper describes a frequency-scaled SweepSAR demonstration that operates at Ka-Band (35.6 GHz), and closely approximates the DESDynl mission antenna geometry, scaled by 28. The concept relies on the SweepSAR measurement technique. An array of digital receivers captures waveforms from a multiplicity of elements. These are combined using digital beamforming in elevation and SAR processing to produce imagery. Ka-band (35.6 GHz) airborne SweepSAR using array-fed reflector and digital beamforming features eight simultaneous receive beams generated by a 40-cm offset-fed reflector and eight-element active array feed, and eight digital receiver channels with all raw data recorded and later used for beamforming. Illumination of the swath is accomplished using a slotted-waveguide antenna radiating 250 W peak power. This experiment has been used to demonstrate digital beamforming SweepSAR systems.

  5. Test results for a subscale (100 kA) SMES splice

    NASA Astrophysics Data System (ADS)

    Peck, Scott D.; Zeigler, John C.

    1994-07-01

    The design for the 20 MW-hr SMES-ETM for the Bechtel concept calls for two splices per turn of conductor, and over 100 turns. The design value of resistance for the splices is on the order of 10(exp -11) ohms (0.4 W/splice at 200 kA), which is an order of magnitude less than the state of the art for high current devices. The splice design utilizes a superconducting braid wrapped around lapped subcables for an extremely low resistance joint. A history of the manufacturing development for the splice is presented. The performance of a sub-scale version of the splice joint has been measured at Texas Accelerator Center. Values of splice resistance at 1.8 K and background fields up to 5 T are reported. Performance of a 100 kA conductor is also reported.

  6. Linking the 8.2 ka Event and its Freshwater Forcing in the Labrador Sea

    NASA Technical Reports Server (NTRS)

    Hoffman, Jeremy S.; Carlson, Anders E.; Winsor, Kelsey; Klinkhammer, Gary P.; LeGrande, Allegra N.; Andrews, John T.; Strasser, C.

    2012-01-01

    The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in (delta)18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that approx. 3 C of near-surface ocean cooling masked an 1.0 % decrease in western Labrador Sea (delta)18O of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic (delta)18O of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event.

  7. The 100 kA VLHC transmission line magnet superconducting cable test facility

    SciTech Connect

    Foster, G. W.; Kashikhin, V. S.; Malamud, E.; Mazur, P.; Oleck, A.; Piekarz, Piekarz,H.; Fuerst, J.; Rabahl, R.; Schlabach, P.; Volk, J.

    2000-03-01

    A superconducting transmission line magnet test facility was built and commissioned at Fermilab. The test facility is capable of generating a 100 kA current in a 17-meter length short-circuited superconducting loop, as well as driving 15 m long test magnets. The current is excited by a room temperature primary winding and iron yoke operated as a current transformer. This approach avoids the expense and difficulty of 100 kA current leads, and allows the facility to be Dewar-based. The loop has a replaceable superconductor section 4 m long for testing various types of VLHC transmission line cables. The system design, 3D magnetic field analysis, magnetic force distribution and test results are discussed.

  8. 250 kA compact linear transformer driver for wire array z-pinch loads

    NASA Astrophysics Data System (ADS)

    Bott, S. C.; Haas, D. M.; Madden, R. E.; Ueda, U.; Eshaq, Y.; Collins, G., IV; Gunasekera, K.; Mariscal, D.; Peebles, J.; Beg, F. N.; Mazarakis, M.; Struve, K.; Sharpe, R.

    2011-05-01

    We present the application of a short rise (˜150ns) 250 kA linear transformer driver (LTD) to wire array z-pinch loads for the first time. The generator is a modification of a previous driver in which a new conical power feed provides a low inductance coupling to wire loads. Performance of the new design using both short circuit and plasma loads is presented and discussed. The final design delivers ˜200kA to a wire array load which is in good agreement with SCREAMER calculations using a simplified representative circuit. Example results demonstrate successful experiments using cylindrical, conical, and inverse wire arrays as well as previously published work on x-pinch loads.

  9. Controlling the pKa of the bacteriorhodopsin Schiff base by use of artificial retinal analogues

    SciTech Connect

    Sheves, M.; Albeck, A.; Friedman, N.; Ottolenghi, M.

    1986-05-01

    Artificial bacteriorhodopsin pigments based on synthetic retinal analogues carrying an electron-withdrawing CF3 substituent group were prepared. The effects of CF3 on the spectra, photocycles, and Schiff base pKa values of the pigments were analyzed. A reduction of 5 units in the pKa of the Schiff base is observed when the CF3 substituent is located at the C-13 polyene position, in the vicinity of the protonated Schiff base nitrogen. The results lead to the unambiguous characterization of the (direct) titration of the Schiff base in bacteriorhodopsin and to the conclusion that the deprotonation rate of the Schiff base during the photocycle (i.e., the generation of the M412 intermediate) is determined by a structural change in the protein.

  10. Link Design and Planning for Mars Reconnaissance Orbiter (MRO) Ka-band (32 GHz) Telecom Demonstration

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin; Davarian, Faramaz; Morabito, David

    2004-01-01

    NASA is planning an engineering telemetry demonstration with Mars Reconnaissance Orbiter (MRO). Capabilities of Ka-band (32 GHz) for use with deep space mission are demonstrated using the link optimization algorithms and weather forecasting. Furthermore, based on the performance of previous deep space missions with Ka-band downlink capabilities, experiment plans are developed for telemetry operations during superior solar conjunction. A general overview of the demonstration is given followed by a description of the mission planning during cruise, the primary science mission and superior conjunction. As part of the primary science mission planning the expected data return for various data optimization methods is calculated. These results indicate that, given MRO's data rates, a link optimized to use of at most two data rates, subject to a minimum availability of 90%, performs almost as well as a link with no limits on the number of data rates subject to the same minimum availability.

  11. pH indicator titration: a novel fast pKa determination method.

    PubMed

    Kong, Xiaole; Zhou, Tao; Liu, Zudong; Hider, Robert C

    2007-10-01

    This study describes a fast spectrophotometic titration method for apparent ionization constant (pKa) determination. In this method, a Universal pH indicator is utilized instead of the conventional pH electrode. An autoburette is set to add HCl at a constant rate to a vigorously stirred 1 cm UV cuvette which contains sample and indicator solution. A spectrophotometer continuously records the spectra. Acquired spectral data are processed by calculating the pH from the indicator spectra in the visible region and extracting sample spectra from the UV region. Five compounds possessing pKa values in the range 2-10 were investigated. These results differed from measurements by conventional spectrophotometric titration by +/-0.05 to +/-0.10 log unit. (c) 2007 Wiley-Liss, Inc.

  12. Silicon-Germanium Films Grown on Sapphire for Ka-Band Communications Applications

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Mueller, Carl H.; Croke, Edward T.

    2004-01-01

    NASA's vision in the space communications area is to develop a broadband data network in which there is a high degree of interconnectivity among the various satellite systems, ground stations, and wired systems. To accomplish this goal, we will need complex electronic circuits integrating analog and digital data handling at the Ka-band (26 to 40 GHz). The purpose of this project is to show the feasibility of a new technology for Ka-band communications applications, namely silicon germanium (SiGe) on sapphire. This new technology will have several advantages in comparison to the existing silicon-substrate- based circuits. The main advantages are extremely low parasitic reactances that enable much higher quality active and passive components, better device isolation, higher radiation tolerance, and the integration of digital and analog circuitry on a single chip.

  13. A Gigabit-per-Second Ka-Band Demonstration Using a Reconfigurable FPGA Modulator

    NASA Technical Reports Server (NTRS)

    Lee, Dennis; Gray, Andrew A.; Kang, Edward C.; Tsou, Haiping; Lay, Norman E.; Fong, Wai; Fisher, Dave; Hoy, Scott

    2005-01-01

    Gigabit-per-second communications have been a desired target for future NASA Earth science missions, and for potential manned lunar missions. Frequency bandwidth at S-band and X-band is typically insufficient to support missions at these high data rates. In this paper, we present the results of a 1 Gbps 32-QAM end-to-end experiment at Ka-band using a reconfigurable Field Programmable Gate Array (FPGA) baseband modulator board. Bit error rate measurements of the received signal using a software receiver demonstrate the feasibility of using ultra-high data rates at Ka-band, although results indicate that error correcting coding and/or modulator predistortion must be implemented in addition. Also, results of the demonstration validate the low-cost, MOS-based reconfigurable modulator approach taken to development of a high rate modulator, as opposed to more expensive ASIC or pure analog approaches.

  14. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2010-01-01

    A celestial reference frame at X/Kaband (8.4/32 GHz) has been constructed using fiftyone 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec ( mu as) in alpha cos delta and 290 mu as in delta. There is evidence for zonal errors at the 100 mu as level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  15. A Ka-band radial relativistic backward wave oscillator with GW-class output power

    SciTech Connect

    Zhu, Jiaxin; Zhang, Xiaoping Dang, Fangchao

    2016-07-15

    A novel radial relativistic backward wave oscillator with a reflector is proposed and designed to generate GW-level high power microwaves at Ka-band. The segmented radial slow wave structure and the reflector are matched to enhance interaction efficiency. We choose the volume wave TM{sub 01} mode as the working mode due to the volume wave characteristic. The main structural parameters of the novel device are optimized by particle-in-cell simulation. High power microwaves with power of 2 GW and a frequency of 29.4 GHz are generated with 30% efficiency when the electron beam voltage is 383 kV, the beam current is 17 kA, and the guiding magnetic field is only 0.6 T. Simultaneously, the highest electric field in the novel Ka-band device is just about 960 kV/cm in second slow wave structure.

  16. Link Design and Planning for Mars Reconnaissance Orbiter (MRO) Ka-band (32 GHz) Telecom Demonstration

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin; Davarian, Faramaz; Morabito, David

    2004-01-01

    NASA is planning an engineering telemetry demonstration with Mars Reconnaissance Orbiter (MRO). Capabilities of Ka-band (32 GHz) for use with deep space mission are demonstrated using the link optimization algorithms and weather forecasting. Furthermore, based on the performance of previous deep space missions with Ka-band downlink capabilities, experiment plans are developed for telemetry operations during superior solar conjunction. A general overview of the demonstration is given followed by a description of the mission planning during cruise, the primary science mission and superior conjunction. As part of the primary science mission planning the expected data return for various data optimization methods is calculated. These results indicate that, given MRO's data rates, a link optimized to use of at most two data rates, subject to a minimum availability of 90%, performs almost as well as a link with no limits on the number of data rates subject to the same minimum availability.

  17. Royal sun medicinal mushroom, Agaricus brasiliensis Ka21 (higher Basidiomycetes), as a functional food in humans.

    PubMed

    Yamanaka, Daisuke; Liu, Ying; Motoi, Masuro; Ohno, Naohito

    2013-01-01

    The Royal Sun medicinal mushroom, Agaricus brasiliensis, is used as a natural health product. In Japan, however, the quality control of some of these mushroom products has been viewed as a safety problem. Focusing on the quality control of A. brasiliensis KA21, we have performed several safety studies. To date, we have established evidence that this mushroom can be used safely as an immunostimulant and to mediate biochemical parameters associated with obesity or diabetes. Furthermore, to improve the manufacturing process of this mushroom, we have studied the relationship between its pharmaceutical actions and the conditions of its cultivation and thermal management. The purpose of this review is to report the findings of basic and clinical studies of the fruit body of A. brasiliensis KA21.

  18. Reconfigurable phased antenna array for extending cubesat operations to Ka-band: Design and feasibility

    NASA Astrophysics Data System (ADS)

    Buttazzoni, G.; Comisso, M.; Cuttin, A.; Fragiacomo, M.; Vescovo, R.; Vincenti Gatti, R.

    2017-08-01

    Started as educational tools, CubeSats have immediately encountered the favor of the scientific community, subsequently becoming viable platforms for research and commercial applications. To ensure competitive data rates, some pioneers have started to explore the usage of the Ka-band beside the conventional amateur radio frequencies. In this context, this study proposes a phased antenna array design for Ka-band downlink operations consisting of 8×8 circularly polarized subarrays of microstrip patches filling one face of a single CubeSat unit. The conceived structure is developed to support 1.5 GHz bandwidth and dual-task missions, whose feasibility is verified by proper link budgets. The dual-task operations are enabled by a low-complexity phase-only control algorithm that provides pattern reconfigurability in order to satisfy both orbiting and intersatellite missions, while remaining adherent to the cost-effective CubeSat paradigm.

  19. Design Versatility Of The Prism Panoramic Camera: The KS-116 And KA-95 Cameras

    NASA Astrophysics Data System (ADS)

    Ruck, Richard

    1981-12-01

    The increased need for smaller and more versatile aerial reconnaissance equipment has led to the use of the KS-116 camera in the RF-4B aircraft, and the KA-95 in the RIF-5E. Both cameras use a 12-inch fl, f/4.0 lens and a 5-inch film transport. The main difference between these two cameras is their configuration. This paper describes the features of the two cameras, including: selectable scan angle, forward motion compensation (FMC), roll stabilization, exposure control, unique packaging differences and focus correction. The inherent packaging flexibility of the prism pan camera and the availability of key modules have led to multiple configurations of which the KS-116 and KA-95 are two examples.

  20. Low-cost Ka band SAR/ISAR for UAV applications

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Hwoon; Pergande, Albert N.; Hughen, James H.

    2004-08-01

    Growing interest in low cost unattended observations has lead Lockheed Martin Missiles and Fire Control to examine and demonstrate feasibility of a small inexpensive SAR/ISAR system at Ka band. By trading off state of the art performance for cost and volume, system performance for UAV applications is still adequate to provide important tactical information to battle field commanders in real time while reducing the exposure of war fighters to hostile fire. As RF and millimeterwave component become cheaper and more robust, system costs are expected to fall further. To demonstrate this concept, we have built a portable system with 500 Mhz instantaneous bandwidth, and have used to it gather SAR and ISAR data along with conventional HRR and LFM target data at Ka Band. Here we present sample data collected with our system along with supporting system performance supporting the use of such inexpensive systems in near term applications.

  1. A high power Ka band millimeter wave generator with low guiding magnetic field

    SciTech Connect

    Zhu Jun; Shu Ting; Zhang Jun; Li Guolin; Zhang Zehai

    2010-08-15

    A slow wave type gigawatt millimeter wave generator is proposed in this paper. In order to increase power capacity, overmoded slow wave structures (SWSs) with larger diameter have been used. Taking advantage of the ''surface wave'' property of overmoded SWSs, the TM{sub 01} mode can be selected to be the operating mode. Calculations have also been carried out to choose a proper low operating magnetic field strength, and it agrees with particle in cell (PIC) simulations. Main structure parameters of the device are optimized by PIC simulations. A typical simulation result is that, at the beam parameters of 600 keV and 5.05 kA, and guiding magnetic field of 0.85 T, a Ka band millimeter wave with an output power of 1.05 GW is generated, yielding a conversion efficiency of about 35%.

  2. Multiple access capacity trade-offs for a Ka-band personal access satellite system

    NASA Technical Reports Server (NTRS)

    Dessouky, Khaled; Motamedi, Masoud

    1990-01-01

    System capability is critical to the economic viability of a personal satellite communication system. Ka band has significant potential to support a high capacity multiple access system because of the availability of bandwidth. System design tradeoffs are performed and multiple access schemes are compared with the design goal of achieving the highest capacity and efficiency. Conclusions regarding the efficiency of the different schemes and the achievable capacities are given.

  3. Climate of Australia over the past 100 ka inferred from stable isotopes in avian eggshells (Invited)

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Fogel, M.; Magee, J. W.; Gagan, M. K.; Newsome, S. D.

    2010-12-01

    Climate reconstructions for the past glacial cycle across interior Australia are hampered by the lack of suitable proxies in the harsh chemical environment of most long archives. We have developed training sets for the stable isotopes of carbon and oxygen derived from the calcite matrix and enclosed organic residues of the eggshell. Organic and inorganic δ13C track the birds’ diets, whereas inorganic δ18O tracks the birds’ drinking water and is a proxy for aridity. Nearly continuous records of both isotopes over the past 80 to 140 ka are available from 5 regions, Lake Eyre (~1000 records), Lake Frome (~220), Port Augusta (~440), lower Darling lakes (~220), and Ningaloo region of Western Australia (~500). The central Australia sites indicate peak wetness during MIS 5e with slightly lower values in later MIS 5. Conditions remain relatively wet until 60 ka in the arid interior and 40 ka in the Darling lakes. Peak aridity occurs during the LGM and is followed by a clear indication of early Holocene wetness, reflecting the reactivation of the Australian summer monsoon, although conditions are not as moist as in MIS 5-3. The paleodietary records suggest that vegetation does not closely track effective moisture, which we interpret to reflect a human overprint on a primary climate control. The relative weakness of the early Holocene monsoon, when the regional drivers of monsoon circulation are strong, relative to conditions 60 ka, when monsoon forcing is weaker, suggests that a changed vegetation regime may have weakened the penetration of monsoon moisture into the continental interior. All records show a trend toward greater aridity in the late Holocene. The clear pattern of early Holocene monsoon activity and late Holocene aridity suggests that the Australian monsoon is more closely responding to Northern Hemisphere insolation, than directly to insolation forcing over the Australian continent.

  4. The Dual Wavelength Ratio knee: a signature of multiple scattering in airborne Ku-Ka observations

    NASA Astrophysics Data System (ADS)

    Battaglia, Alessandro; Tanelli, Simone; Heymsfield, Gerald; Tian, Lin

    2014-05-01

    Deep convective systems observed by the HIWRAP radar during the 2011 MC3E field campaign in Oklahoma provide the first evidence of multiple scattering effects simultaneously at Ku and Ka band. One feature is novel and noteworthy: often, in correspondence to shafts with strong convection and when moving from the top of the cloud downward, the dual wavelength ratio (DWR) first increases as usual in Ku-/Ka-band observations, but then it reaches a maximum and after that point it steadily decreases all the way to the surface, forming what will be hereinafter referred to as a knee. This DWR knee cannot be reproduced by single-scattering theory under almost any plausible cloud microphysical profile, on the other hand it is explained straightforwardly with the help of multiple scattering theory when simulations involving hail-bearing convective cores with large horizontal extents are performed. The DWR reduction in the lower troposphere (i.e., DWR increasing with altitude) is interpreted as the result of multiple scattering pulse stretching caused by the highly-diffusive hail layer positioned high up in the atmosphere, with Ka multiple scattering typically exceeding that occurring in the Ku channel. Since the effects of multiple scattering increase with increasing footprint size, if multiple scattering effects are present in the aircraft measurements, they are likely to be more pronounced in the space-borne dual-frequency Ku - Ka radar observations, envisaged for the NASA-JAXA Global Precipitation (GPM) Measurement Mission, whose launch is expected in February 2014. Our notional study supports the idea that DWR knees will be observed by the GPM radar when overflying high-density ice shafts embedded in large convective systems and suggests that their explanation must not be sought in differential attenuation or differential Mie but via multiple scattering effects.

  5. A High Performance Frequency Standard and Distribution System for Cassini Ka-Band Experiment

    DTIC Science & Technology

    2005-08-01

    spacecraft in a series of occultation measurements performed over a 78 day period from March to June 2005. I. INTRODUCTION The Cassini - Huygens project...successful Huygens landing on the moon Titan, the Cassini Spacecraft has begun a 3 year mission of continued moon flybys and observations. During this time...A High Performance Frequency Standard and Distribution System for Cassini Ka-Band Experiment R. T. WANG, M. D. CALHOUN, A. KIRK, W. A. DIENER

  6. Radial Color Gradients in K+A Galaxies in Distant Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Bartholomew, Lindsay J.; Rose, James A.; Gaba, Alejandro E.; Caldwell, Nelson

    2001-12-01

    Galaxies in rich clusters with z>~0.3 are observed to have a higher fraction of photometrically blue galaxies than their nearby counterparts. This raises the important question of what environmental effects can cause the termination of star formation between z~0.3 and the present. The star formation may be truncated because of ram pressure stripping, or the gas in the disk may be depleted by an episode of star formation caused by some external perturbation. To help resolve this issue, surface photometry was carried out for a total of 70 early-type galaxies in the cluster Cl 1358+62, at z~0.33, using two-color images from the Hubble archive. The galaxies were divided into two categories based on spectroscopic criteria: 24 are type K+A (e.g., strong Balmer lines, with no visible emission lines), while the remaining 46 are in the control sample, with normal spectra. Radial color profiles were produced to see whether the K+A galaxies show bluer nuclei in relation to their surrounding disks. Specifically, a linear gradient was fitted to the radial color profile of each galaxy. We find that the K+A galaxies on average tend to have slightly bluer gradients toward the center than the normal galaxies. A Kolmogorov-Smirnov two-sample test has been applied to the two sets of color gradients. The result of the test indicates that there is only a ~2% probability that the K+A and normal samples are drawn from the same parent distribution. There is a possible complication from a trend in the apparent magnitude-versus-color gradient relation, but overall our results favor the centralized star formation scenario as an important process in the evolution of galaxies in dense clusters.

  7. A satellite system for multimedia personal communications at Ka-band and beyond

    NASA Technical Reports Server (NTRS)

    Vatalaro, F.; Losquadro, G.

    1995-01-01

    The main characteristics of the satellite extremely high frequency (EHF) communication of multimedia mobile services (SECOMS) system are given and the results of the preliminary analysis are included. The SECOMS provides a first generation Ka band system with coverage over Western Europe, in order to satisfy business user needs of very large bandwidths and terminal mobility. The satellite system also provides a second generation EHF enhanced system with increased capacity and enlarged coverage, to serve all of Europe and the nearby countries.

  8. Prediction of pKa values using the PM6 semiempirical method

    PubMed Central

    Kromann, Jimmy C.; Larsen, Frej; Moustafa, Hadeel

    2016-01-01

    The PM6 semiempirical method and the dispersion and hydrogen bond-corrected PM6-D3H+ method are used together with the SMD and COSMO continuum solvation models to predict pKa values of pyridines, alcohols, phenols, benzoic acids, carboxylic acids, and phenols using isodesmic reactions and compared to published ab initio results. The pKa values of pyridines, alcohols, phenols, and benzoic acids considered in this study can generally be predicted with PM6 and ab initio methods to within the same overall accuracy, with average mean absolute differences (MADs) of 0.6–0.7 pH units. For carboxylic acids, the accuracy (0.7–1.0 pH units) is also comparable to ab initio results if a single outlier is removed. For primary, secondary, and tertiary amines the accuracy is, respectively, similar (0.5–0.6), slightly worse (0.5–1.0), and worse (1.0–2.5), provided that di- and tri-ethylamine are used as reference molecules for secondary and tertiary amines. When applied to a drug-like molecule where an empirical pKa predictor exhibits a large (4.9 pH unit) error, we find that the errors for PM6-based predictions are roughly the same in magnitude but opposite in sign. As a result, most of the PM6-based methods predict the correct protonation state at physiological pH, while the empirical predictor does not. The computational cost is around 2–5 min per conformer per core processor, making PM6-based pKa prediction computationally efficient enough to be used for high-throughput screening using on the order of 100 core processors. PMID:27602298

  9. A satellite system for multimedia personal communications at Ka-band and beyond

    NASA Technical Reports Server (NTRS)

    Vatalaro, F.; Losquadro, G.

    1995-01-01

    The main characteristics of the satellite extremely high frequency (EHF) communication of multimedia mobile services (SECOMS) system are given and the results of the preliminary analysis are included. The SECOMS provides a first generation Ka band system with coverage over Western Europe, in order to satisfy business user needs of very large bandwidths and terminal mobility. The satellite system also provides a second generation EHF enhanced system with increased capacity and enlarged coverage, to serve all of Europe and the nearby countries.

  10. First Experiments at the Yale University Ka-band Test Facility

    NASA Astrophysics Data System (ADS)

    LaPointe, M. A.; Jiang, Y.; Shchelkunov, S. V.; Yakovlev, V. P.; Kazakov, S. Yu.; Vikharev, A. L.; Vikharev, A. A.; Ivanov, O. A.; Gorbachev, A.; Lobaev, M.; Hirshfield, J. L.

    2009-01-01

    User experiments aimed toward discovering pathways towards development of high gradient accelerator structures have begun in the Ka-Band Test Facility at Yale University. This facility is based on use of the Yale/Omega-P 34.3 GHz magnicon. The first two experiments, a quasi-optical active pulse compressor and an RF breakdown cavity test cell, have been installed and are undergoing initial testing. The status of these experiments and others awaiting installation will be reviewed.

  11. A distal 145 ka sediment record of Nile discharge and East African monsoon variability

    NASA Astrophysics Data System (ADS)

    Ehrmann, W.; Schmiedl, G.; Seidel, M.; Krüger, S.; Schulz, H.

    2015-09-01

    Clay mineral assemblages in a sediment core from the distal Nile discharge plume off Israel have been used to reconstruct the late Quaternary Nile sediment discharge into the Eastern Mediterranean Sea (EMS). The record spans the last ca. 145 ka. Smectite abundances indicate the influence of the Blue Nile and Atbara that have their headwaters in the volcanic rocks of the Ethiopian highlands. Kaolinite abundances indicate the influence of wadis, which contribute periodically to the suspension load of the Nile. Due to the geographical position, the climate and the sedimentary framework of the EMS is controlled by two climate systems. The long-term climate regime was governed by the African monsoon that caused major humid periods with enhanced sediment discharge at 132 to < 122 ka (AHP 5), 113 to 104 ka (AHP 4), and 86 to 74 ka (AHP 3). They lasted much longer than the formation of the related sapropel layers S5, S4 and S3. During the last glacial period (MIS 4-2) the long-term changes of the monsoonal system were superimposed by millennial-scale changes of an intensified mid-latitude glacial system. This climate regime caused short but pronounced drought periods in the Nile catchment, which are linked to Heinrich Events and alternate with more humid interstadials. The clay mineral record further implies that feedback mechanisms between vegetation cover and sediment discharge of the Nile are detectable but of minor importance for the sedimentary record in the southeastern Mediterranean Sea during the investigated African Humid Periods.

  12. Central European vegetation response to abrupt climate change at 8.2 ka

    NASA Astrophysics Data System (ADS)

    Tinner, Willy; Lotter, André F.

    2001-06-01

    Oxygen isotope records show a major climatic reversal at 8.2 ka in Greenland and Europe. Annually laminated sediments from two lakes in Switzerland and Germany were sampled contiguously to assess the response of European vegetation to climate change ca. 8.2 ka with time resolution and precision comparable to those of the Greenland ice cores. The pollen assemblages show pronounced and immediate responses (0 20 yr) of terrestrial vegetation to the climatic change at 8.2 ka. A sudden collapse of Corylus avellana (hazel) was accompanied by the rapid expansion of Pinus (pine), Betula (birch), and Tilia (linden), and by the invasion of Fagus silvatica (beech) and Abies alba (fir). Vegetational changes suggest that climatic cooling reduced drought stress, allowing more drought-sensitive and taller growing species to out-compete Corylus avellana by forming denser forest canopies. Climate cooling at 8.2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies. On the basis of our data we conclude that the early Holocene high abundance of C. avellana in Europe was climatically caused, and we question the conventional opinion that postglacial expansions of F. silvatica and A. alba were controlled by low migration rates rather than by climate. The close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses, expansions, and invasions of tree species.

  13. 15 kA energy-evacuation switch for test bench of superconducting magnets

    NASA Astrophysics Data System (ADS)

    Kudashkin, A. V.; Sidorin, A. O.; Karpinskiy, V. N.; Savelev, A. A.; Osipenkov, A. L.; Makarov, A. A.

    2016-12-01

    A new 15-kA energy-evacuation switch based on the operational experience of the protection system of Nuclotron superconducting magnets has been developed. It is used at the test bench of superconducting magnets being produced for NICA (Nuclotron-based Ion Collider fAcility, which is implemented at the Joint Institute for Nuclear Research (JINR)) [1] and FAIR (Facility for Antiproton and Ion Research, Darmstadt, Germany) accelerator facilities.

  14. Food safety assessment of Cry8Ka5 mutant protein using Cry1Ac as a control Bt protein.

    PubMed

    Farias, Davi Felipe; Viana, Martônio Ponte; Oliveira, Gustavo Ramos; Santos, Vanessa Olinto; Pinto, Clidia Eduarda Moreira; Viana, Daniel Araújo; Vasconcelos, Ilka Maria; Grossi-de-Sa, Maria Fátima; Carvalho, Ana Fontenele Urano

    2015-07-01

    Cry8Ka5 is a mutant protein from Bacillus thuringiensis (Bt) that has been proposed for developing transgenic plants due to promising activity against coleopterans, like Anthonomus grandis (the major pest of Brazilian cotton culture). Thus, an early food safety assessment of Cry8Ka5 protein could provide valuable information to support its use as a harmless biotechnological tool. This study aimed to evaluate the food safety of Cry8Ka5 protein following the two-tiered approach, based on weights of evidence, proposed by ILSI. Cry1Ac protein was used as a control Bt protein. The history of safe use revealed no convincing hazard reports for Bt pesticides and three-domain Cry proteins. The bioinformatics analysis with the primary amino acids sequence of Cry8Ka5 showed no similarity to any known toxic, antinutritional or allergenic proteins. The mode of action of Cry proteins is well understood and their fine specificity is restricted to insects. Cry8Ka5 and Cry1Ac proteins were rapidly degraded in simulated gastric fluid, but were resistant to simulated intestinal fluid and heat treatment. The LD50 for Cry8Ka5 and Cry1Ac was >5000 mg/kg body weight when administered by gavage in mice. Thus, no expected relevant risks are associated with the consumption of Cry8Ka5 protein.

  15. Climatic implications of the Quaternary fluvial tufa record in the NE Iberian Peninsula over the last 500 ka

    NASA Astrophysics Data System (ADS)

    Sancho, Carlos; Arenas, Concha; Vázquez-Urbez, Marta; Pardo, Gonzalo; Lozano, María Victoria; Peña-Monné, José Luis; Hellstrom, John; Ortiz, José Eugenio; Osácar, María Cinta; Auqué, Luis; Torres, Trinidad

    2015-11-01

    The drainage area of the Iberian Ranges (NE Spain) houses one of the most extensive Quaternary fluvial tufaceous records in Europe. In this study, tufa deposits in the Añamaza, Mesa, Piedra and Ebrón river valleys were mapped, stratigraphically described and chronologically referenced from U/Th disequilibrium series, amino acid racemization and radiocarbon methods. Tufa deposits accumulated in cascades, barrage-cascades and related damming areas developed in stepped fluvial systems. The maximum frequency of tufa deposition was identified at 120 ka (Marine Oxygen Isotope Stage [MIS] 5e), 102 ka (MIS 5c), 85 ka ( MIS 5a) and 7 ka (MIS 1), probably under warmer and wetter conditions than today. Additional phases of tufa deposition appear at 353 ka ( end of MIS 11), 258-180 ka (MIS 7) and 171-154 ka (MIS 6). Although most tufa deposition episodes are clearly correlated with interstadial periods, the occurrence of tufa deposits during the penultimate glaciation (MIS 6) is remarkable, indicating that the onset of this stage was climatically favourable in the Iberian Peninsula. Biostatic conditions and the dynamics of karstic systems regulating tufa deposition seem to be sensitive to the precipitation regime, controlled by shifts in the position of North Atlantic atmospheric belts, and summer insolation, regulated by orbital forcing.

  16. First-principles calculation of pKa for cocaine, nicotine, neurotransmitters, and anilines in aqueous solution.

    PubMed

    Lu, Haiting; Chen, Xi; Zhan, Chang-Guo

    2007-09-06

    The absolute pKa values of 24 representative amine compounds, including cocaine, nicotine, 10 neurotransmitters, and 12 anilines, in aqueous solution were calculated by performing first-principles electronic structure calculations that account for the solvent effects using four different solvation models, i.e., the surface and volume polarization for electrostatic interaction (SVPE) model, the standard polarizable continuum model (PCM), the integral equation formalism for the polarizable continuum model (IEFPCM), and the conductor-like screening solvation model (COSMO). Within the examined computational methods, the calculations using the SVPE model lead to the absolute pKa values with the smallest root-mean-square-deviation (rmsd) value (1.18). When the SVPE model was replaced by the PCM, IEFPCM, and COSMO, the rmsd value of the calculated absolute pKa values became 3.21, 2.72, and 3.08, respectively. All types of calculated pKa values linearly correlate with the experimental pKa values very well. With the empirical corrections using the linear correlation relationships, the theoretical pKa values are much closer to the corresponding experimental data and the rmsd values become 0.51-0.83. The smallest rmsd value (0.51) is also associated with the SVPE model. All of the results suggest that the first-principles electronic structure calculations using the SVPE model are a reliable approach to the pKa prediction for the amine compounds.

  17. A Record of Changes in the Indian Monsoon From ~29 ka to 11 ka Based on a Stalagmite from Socotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    Shakun, J. D.; Burns, S. J.; Fleitmann, D.; Kramers, J.; Matter, A.; Al-Subary, A.

    2005-12-01

    Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from 28.5-11.1 ka based on 681 stable isotope and 28 234U/ 230Th measurements. Variations in M1-5 oxygen isotope ratios are interpreted to be primarily driven by an amount effect and to principally reflect changes in the mean position and/or intensity of convection of the intertropical convergence zone. Migration of the ITCZ over the region is the island's source of precipitation. The M1-5 d18O time series is strongly correlated to the Greenland ice cores, similar to an earlier Socotra speleothem record from 53-40 ka (Burns et al., 2003), indicating a North Atlantic-Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. D/O events 1, 2, 3, Heinrich events 0 and 1, and the Holocene onset are well expressed in M1-5, and the Last Glacial Maximum occurs at ~23 ka, consistent with northern hemisphere ice volume and temperature forcing. M1-5 correlates well with Arabian Sea monsoon-driven productivity and denitrification records as well as the Hulu and Dongge Cave speleothem records from China over decadal to millennial timescales, indicating the entire East African-Asian monsoon system behaved as a cohesive unit during the last deglaciation. M1-5 is also highly coherent with records from the Cariaco Basin during the Bolling/Allerod period, and generally coherent over longer timescales as well, suggesting the intertropical convergence zone fluctuated in unison in the Indian and Atlantic Ocean basins. Significant antiphasing is seen between M1-5 and the Byrd ice core from Antarctica throughout the entire length of the speleothem record, implying the operation of the bipolar seesaw during this interval. In fact, M1-5 is more strongly anticorrelated with Antarctica than is Greenland, suggesting a potential bipolar seesaw mechanism (or feedback) other than the Atlantic thermohaline circulation, perhaps

  18. Membrane environment modulates the pKa values of transmembrane helices.

    PubMed

    Panahi, Afra; Brooks, Charles L

    2015-04-02

    In this work, we apply the recently developed constant pH molecular dynamics technique to study protonation equilibria of titratable side chains in the context of simple transmembrane (TM) helices and explore the effect of pH on their configurations in membrane bilayers. We observe that, despite a significant shift toward neutral states, considerable population of different side chains stay in the charged state that give rise to pKa values around 9.6 for Asp and Glu and 4.5 to 6 for His and Lys side chains, respectively. These charged states are highly stabilized by favorable interactions between head groups, water molecules, and the charged side chains that are facilitated by substantial changes in the configuration of the peptides. The pH dependent configurations and the measured pKa values are in good agreement with relatively recent solid state NMR measurements. Our results presented here demonstrate that all-atom constant pH molecular dynamics can be applied to membrane proteins and peptides to obtain reliable pKa values and pH dependent behavior for these systems.

  19. The Greenland Ice Core Chronology 2005, 15 42 ka. Part 2: comparison to other records

    NASA Astrophysics Data System (ADS)

    Svensson, Anders; Andersen, Katrine K.; Bigler, Matthias; Clausen, Henrik B.; Dahl-Jensen, Dorthe; Davies, Siwan M.; Johnsen, Sigfus J.; Muscheler, Raimund; Rasmussen, Sune O.; Röthlisberger, Regine; Peder Steffensen, Jørgen; Vinther, Bo. M.

    2006-12-01

    A new Greenland Ice Core Chronology (GICC05) based on multi-parameter counting of annual layers has been obtained for the last 42 ka. Here we compare the glacial part of the new time scale, which is based entirely on records from the NorthGRIP ice core, to existing time scales and reference horizons covering the same period. These include the GRIP and NorthGRIP modelled time scales, the Meese-Sowers GISP2 counted time scale, the Shackleton-Fairbanks GRIP time scale (SFCP04) based on 14C calibration of a marine core, the Hulu Cave record, three volcanic reference horizons, and the Laschamp geomagnetic excursion event occurring around Greenland Interstadial 10. GICC05 is generally in good long-term agreement with the existing Greenland ice core chronologies and with the Hulu Cave record, but on shorter time scales there are significant discrepancies. Around the Last Glacial Maximum there is a more than 1 ka age difference between GICC05 and SFCP04 and a more than 0.5 ka discrepancy in the same direction between GICC05 and the age of a recently identified tephra layer in the NorthGRIP ice core. Both SFCP04 and the tephra age are based on 14C-dated marine cores and fixed marine reservoir ages. For the Laschamp event, GICC05 agrees with a recent independent dating within the uncertainties.

  20. Identification of a pKa-regulating motif stabilizing imidazole-modified double-stranded DNA

    PubMed Central

    Buyst, Dieter; Gheerardijn, Vicky; Fehér, Krisztina; Van Gasse, Bjorn; Van Den Begin, Jos; Martins, José C.; Madder, Annemieke

    2015-01-01

    The predictable 3D structure of double-stranded DNA renders it ideally suited as a template for the bottom-up design of functionalized nucleic acid-based active sites. We here explore the use of a 14mer DNA duplex as a scaffold for the precise and predictable positioning of catalytic functionalities. Given the ubiquitous participation of the histidine-based imidazole group in protein recognition and catalysis events, single histidine-like modified duplexes were investigated. Tethering histamine to the C5 of the thymine base via an amide bond, allows the flexible positioning of the imidazole function in the major groove. The mutual interactions between the imidazole and the duplex and its influence on the imidazolium pKaH are investigated by placing a single modified thymine at four different positions in the center of the 14mer double helix. Using NMR and unrestrained molecular dynamics, a structural motif involving the formation of a hydrogen bond between the imidazole and the Hoogsteen side of the guanine bases of two neighboring GC base pairs is established. The motif contributes to a stabilization against thermal melting of 6°C and is key in modulating the pKaH of the imidazolium group. The general features, prerequisites and generic character of the new pKaH-regulating motif are described. PMID:25520197

  1. Humans permanently occupied the Andean highlands by at least 7 ka.

    PubMed

    Haas, Randall; Stefanescu, Ioana C; Garcia-Putnam, Alexander; Aldenderfer, Mark S; Clementz, Mark T; Murphy, Melissa S; Llave, Carlos Viviano; Watson, James T

    2017-06-01

    High-elevation environments above 2500 metres above sea level (m.a.s.l.) were among the planet's last frontiers of human colonization. Research on the speed and tempo of this colonization process is active and holds implications for understanding rates of genetic, physiological and cultural adaptation in our species. Permanent occupation of high-elevation environments in the Andes Mountains of South America tentatively began with hunter-gatherers around 9 ka according to current archaeological estimates, though the timing is currently debated. Recent observations on the archaeological site of Soro Mik'aya Patjxa (8.0-6.5 ka), located at 3800 m.a.s.l. in the Andean Altiplano, offer an opportunity to independently test hypotheses for early permanent use of the region. This study observes low oxygen (δ(18)O) and high carbon (δ(13)C) isotope values in human bone, long travel distances to low-elevation zones, variable age and sex structure in the human population and an absence of non-local lithic materials. These independent lines of evidence converge to support a model of permanent occupation of high elevations and refute logistical and seasonal use models. The results constitute the strongest empirical support to date for permanent human occupation of the Andean highlands by hunter-gatherers before 7 ka.

  2. Test of 60 kA coated conductor cable prototypes for fusion magnets

    NASA Astrophysics Data System (ADS)

    Uglietti, D.; Bykovsky, N.; Sedlak, K.; Stepanov, B.; Wesche, R.; Bruzzone, P.

    2015-12-01

    Coated conductors could be promising materials for the fabrication of the large magnet systems of future fusion devices. Two prototype conductors (flat cables in steel conduits), each about 2 m long, were manufactured using coated conductor tapes (4 mm wide) from Super Power and SuperOx, with a total tape length of 1.6 km. Each flat cable is assembled from 20 strands, each strand consisting of a stack of 16 tapes surrounded by two half circular copper profiles, twisted and soldered. The tapes were measured at 12 T and 4.2 K and the results of the measurements were used for the assessment of the conductor electromagnetic properties at low temperature and high field. The two conductors were assembled together in a sample that was tested in the European Dipole (EDIPO) facility. The current sharing temperatures of the two conductors were measured at background fields from 8 T up to 12 T and for currents from 30 kA up to 70 kA: the measured values are within a few percent of the values expected from the measurements on tapes (short samples). After electromagnetic cycling, T cs at 12 T and 50 kA decreased from about 12 K to 11 K (about 10%), corresponding to less than 3% of I c.

  3. Design and Manufacture of 20 kA HTS Current Leads for a Hybrid Magnet System

    NASA Astrophysics Data System (ADS)

    Wesche, R.; Bruzzone, P.; March, S.; Vogel, M.; Ehmler, H.; Smeibidl, P.

    A new series connected 25 T hybrid magnet system is being developed by the Helmholtz Zentrum Berlin (HZB) for neutron scattering experiments. In collaboration with CRPP, high temperature superconducting (HTS) current leads have been developed for the powering of the outer superconducting coil. These HTS current leads, with a nominal current rating of 20 kA, have been designed and are being manufactured by CRPP, based on the design of the 18 kA EDIPO leads. Each of the two current leads consists of an HTS module cooled only by heat conduction from the cold end and a copper part actively cooled by helium gas of 44 K inlet temperature. To reach a temperature of 53.7 K at the warm end of the HTS a helium mass flow rate of 1.37 g/s per lead is required at a current of 20 kA. The estimated heat leak at the 4.5 K level caused only by heat conduction is as low as 1.4 W. The evolution of the temperatures in the case of a loss of flow has been calculated. In addition to the design, the main fabrication steps are described.

  4. Optimization of crude oil degradation by Dietzia cinnamea KA1, capable of biosurfactant production.

    PubMed

    Kavynifard, Amirarsalan; Ebrahimipour, Gholamhossein; Ghasempour, Alireza

    2016-05-01

    The aim of this study was isolation and characterization of a crude oil degrader and biosurfactant-producing bacterium, along with optimization of conditions for crude oil degradation. Among 11 isolates, 5 were able to emulsify crude oil in Minimal Salt Medium (MSM) among which one isolate, named KA1, showed the highest potency for growth rate and biodegradation. The isolate was identified as Dietzia cinnamea KA1 using morphological and biochemical characteristics and 16S rRNA gene sequencing. The optimal conditions were 510 mM NaCl, pH 9.0, 35 °C, and minimal requirement of 46.5 mM NH4 Cl and 2.10 mM NaH2 PO4 . Gravimetric test and Gas chromatography-Mass spectroscopy technique (GC-MS) showed that Dietzia cinnamea KA1 was able to utilize and degrade 95.7% of the crude oil after 5 days, under the optimal conditions. The isolate was able to grow and produce biosurfactant when cultured in MSM supplemented with crude oil, glycerol or whey as the sole carbon sources, but bacterial growth was occurred using molasses with no biosurfactant production. This is the first report of biosurfactant production by D. cinnamea using crude oil, glycerol and whey and the first study to report a species of Dietzia degrading a wide range of hydrocarbons in a short time.

  5. Brief communication: preliminary radiocarbon dates from Florida crania in Hrdlička's gulf states catalog.

    PubMed

    Stojanowski, Christopher M; Johnson, Kent M

    2011-05-01

    Aleš Hrdlička produced a tremendous amount of data in his career, much of which was published in a series of catalogs by the US National Museum. The Gulf States catalog, for example, contains raw craniometric data for over 700 individuals from the state of Florida alone. However, many of these skeletons are poorly sourced by Hrdlička, thus limiting their utility in modern bioarchaeological analyses where context is critical. In particular, the age of the skeletal material is often based solely on associated material culture and information on the sites themselves is not presented by Hrdlička. To address this impasse we attempted radiocarbon dates for 10 of the largest Florida sites published in the Gulf States catalog. In addition, archival data in the form of unpublished field notes and personal correspondence were accessed to better contextualize the radiocarbon dates and to provide some guidance on the degree of temporal variability at the sites. Eight AMS radiocarbon dates were successful. Archival data was of variable quality per site. In some cases very little is known about the provenience of the specimens. In other cases, however, individual burials could be allocated to specific strata within specific mounds. The relevance of using published raw data is discussed with respect to the Howells and Boas Immigrant datasets and the impact the dissemination of these resources has had on the discipline.

  6. Results of the test of a pair of 20 kA HTS currents leads

    NASA Astrophysics Data System (ADS)

    Wesche, R.; Bruzzone, P.; Fiamozzi Zignani, C.; Affinito, L.; Chiarelli, S.; Freda, R.; Formichetti, A.; Marchetti, M.; Ehmler, H.; Heinrich, J.; Smeibidl, P.

    2014-05-01

    A new series connected 25 T hybrid magnet system is being set up by the Helmholtz Zentrum Berlin (HZB) for neutron scattering experiments. CRPP has designed and manufactured a pair of 20 kA current leads for the powering of the outer superconducting coils of the hybrid magnet system. In connection with the test of joints for JT60SA, the current leads were tested at ENEA at low voltage up to a current of 18 kA. The mass flow rates required to cool the current leads at different currents measured in the test are in line with the design calculations. For the sum of the resistances of the warm and cold end copper contacts of the HTS module values of 13 (Lead A) and 11 nΩ (Lead B) were measured. In addition, the helium flow through the heat exchanger part was stopped at 10 and 12 kA to study the behaviour of the current leads in case of a loss of flow. The time elapsed between stopping of the helium mass flow and the initiation of a quench was found to be 117 s (Lead A) and 125 s (Lead B) compared to a calculated value of 86 s. The lower value obtained by the calculation can be attributed to the lower initial temperatures in the experiment.

  7. Membrane Environment Modulates the pKa Values of Transmembrane Helices

    PubMed Central

    2015-01-01

    In this work, we apply the recently developed constant pH molecular dynamics technique to study protonation equilibria of titratable side chains in the context of simple transmembrane (TM) helices and explore the effect of pH on their configurations in membrane bilayers. We observe that, despite a significant shift toward neutral states, considerable population of different side chains stay in the charged state that give rise to pKa values around 9.6 for Asp and Glu and 4.5 to 6 for His and Lys side chains, respectively. These charged states are highly stabilized by favorable interactions between head groups, water molecules, and the charged side chains that are facilitated by substantial changes in the configuration of the peptides. The pH dependent configurations and the measured pKa values are in good agreement with relatively recent solid state NMR measurements. Our results presented here demonstrate that all-atom constant pH molecular dynamics can be applied to membrane proteins and peptides to obtain reliable pKa values and pH dependent behavior for these systems. PMID:25734901

  8. Contribution of X/Ka VLBI to Multi-Wavelength Celestial Frame Studies

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Garcia-Miro, C.; Horiuchi, S.; Sotuela, I.

    2011-01-01

    This paper is an update of Sotuela et al. (2011) which improves their simulated Gaia frame tie precision by approximately 10% by adding three additional VLBI observing sessions. Astrometry at X/Ka-band (8.4/32 GHz) using NASAs Deep Space Network has detected 466 quasars with accuracies of 200-300 micro-arc seconds. A program is underway to reduce errors by a factor of 2-3. From our sample, 245 sources have optical magnitudes V less than 20 and should also be detectable by Gaia. A covariance study using existing X/Ka data and simulated Gaia uncertainties for the 345 objects yields a frame tie precision of 10-15 micro-arc seconds (1 - sigma). The characterization of wavelength dependent systematic from extended source morphology and core shift should benefit greatly from adding X/Ka-band measurements to S/X-band (2.3/8.4 GHz) measurements thus helping to constrain astrophysical models of the wavelength dependence of positions.

  9. An ostracode based paleolimnologic and paleohydrologic history of Death Valley: 200 to 0 ka

    USGS Publications Warehouse

    Forester, R.M.; Lowenstein, T.K.; Spencer, R.J.

    2005-01-01

    Death Valley, a complex tectonic and hydrologic basin, was cored from its lowest surface elevation to a depth of 186 m. The sediments range from bedded primary halite to black muds. Continental ostracodes found in the black muds indicate that those sediments were deposited in a variety of hydrologic settings ranging from deep, relatively fresh water to shallow saline lakes to spring discharge supported wetlands. The alkaline-enriched, calcium-depleted paleolake waters indicate extrabasinal streamflow and basin-margin spring discharge. The alkaline-depleted, calcium-enriched paleowetland waters indicate intrabasinal spring discharge. During Marine Isotope Stage 6 (MIS 6, ca. 180-140 ka) the hydrologic settings were highly variable, implying that complex relations existed between climate and basin hydrology. Termination II (MIS 6 to MIS 5E) was a complex multicyclic sequence of paleoenvironments, implying that climates oscillated between high and low effective moisture. MIS 4 (ca. 73-61 ka) was a spring discharge supported wetland complex. During MIS 2 (ca. 20-12 ka) the hydrologic settings were variable, although they are not fully understood because some black muds deposited during that time were lost during coring. ?? 2005 Geological Society of America.

  10. Bayesian model aggregation for ensemble-based estimates of protein pKa values

    SciTech Connect

    Gosink, Luke J.; Hogan, Emilie A.; Pulsipher, Trenton C.; Baker, Nathan A.

    2014-03-01

    This paper investigates an ensemble-based technique called Bayesian Model Averaging (BMA) to improve the performance of protein amino acid p$K_a$ predictions. Structure-based p$K_a$ calculations play an important role in the mechanistic interpretation of protein structure and are also used to determine a wide range of protein properties. A diverse set of methods currently exist for p$K_a$ prediction, ranging from empirical statistical models to {\\it ab initio} quantum mechanical approaches. However, each of these methods are based on a set of assumptions that have inherent bias and sensitivities that can effect a model's accuracy and generalizability for p$K_a$ prediction in complicated biomolecular systems. We use BMA to combine eleven diverse prediction methods that each estimate pKa values of amino acids in staphylococcal nuclease. These methods are based on work conducted for the pKa Cooperative and the pKa measurements are based on experimental work conducted by the Garc{\\'i}a-Moreno lab. Our study demonstrates that the aggregated estimate obtained from BMA outperforms all individual prediction methods in our cross-validation study with improvements from 40-70\\% over other method classes. This work illustrates a new possible mechanism for improving the accuracy of p$K_a$ prediction and lays the foundation for future work on aggregate models that balance computational cost with prediction accuracy.

  11. Retrieval of Snow Properties for Ku- and Ka-Band Dual-Frequency Radar

    NASA Technical Reports Server (NTRS)

    Liao, Liang; Meneghini, Robert; Tokay, Ali; Bliven, Larry F.

    2016-01-01

    The focus of this study is on the estimation of snow microphysical properties and the associated bulk parameters such as snow water content and water equivalent snowfall rate for Ku- and Ka-band dual-frequency radar. This is done by exploring a suitable scattering model and the proper particle size distribution (PSD) assumption that accurately represent, in the electromagnetic domain, the micro-macrophysical properties of snow. The scattering databases computed from simulated aggregates for small-to-moderate particle sizes are combined with a simple scattering model for large particle sizes to characterize snow-scattering properties over the full range of particle sizes. With use of the single-scattering results, the snow retrieval lookup tables can be formed in a way that directly links the Ku- and Ka-band radar reflectivities to snow water content and equivalent snowfall rate without use of the derived PSD parameters. A sensitivity study of the retrieval results to the PSD and scattering models is performed to better understand the dual-wavelength retrieval uncertainties. To aid in the development of the Ku- and Ka-band dual-wavelength radar technique and to further evaluate its performance, self-consistency tests are conducted using measurements of the snow PSD and fall velocity acquired from the Snow Video Imager Particle Image Probe (SVIPIP) during the winter of 2014 at the NASA Wallops Flight Facility site in Wallops Island, Virginia.

  12. Retrieval of Snow Properties for Ku- and Ka-band Dual-Frequency Radar

    NASA Technical Reports Server (NTRS)

    Liao, Liang; Meneghini, Robert; Tokay, Ali; Bliven, Larry F.

    2016-01-01

    The focus of this study is on the estimation of snow microphysical properties and the associated bulk parameters such as snow water content and water equivalent snowfall rate for Ku- and Ka-band dual-frequency radar. This is done by exploring a suitable scattering model and the proper particle size distribution (PSD) assumption that accurately represent, in the electromagnetic domain, the micro/macro-physical properties of snow. The scattering databases computed from simulated aggregates for small-to-moderate particle sizes are combined with a simple scattering model for large particle sizes to characterize snow scattering properties over the full range of particle sizes. With use of the single-scattering results, the snow retrieval lookup tables can be formed in a way that directly links the Ku- and Ka-band radar reflectivities to snow water content and equivalent snowfall rate without use of the derived PSD parameters. A sensitivity study of the retrieval results to the PSD and scattering models is performed to better understand the dual-wavelength retrieval uncertainties. To aid in the development of the Ku- and Ka-band dual-wavelength radar technique and to further evaluate its performance, self-consistency tests are conducted using measurements of the snow PSD and fall velocity acquired from the Snow Video Imager Particle Image Probe (SVIPIP) duringthe winter of 2014 at the NASA Wallops Flight Facility site in Wallops Island, Virginia.

  13. Computing pKa Values with a Mixing Hamiltonian Quantum Mechanical/Molecular Mechanical Approach.

    PubMed

    Liu, Yang; Fan, Xiaoli; Jin, Yingdi; Hu, Xiangqian; Hu, Hao

    2013-09-10

    Accurate computation of the pKa value of a compound in solution is important but challenging. Here, a new mixing quantum mechanical/molecular mechanical (QM/MM) Hamiltonian method is developed to simulate the free-energy change associated with the protonation/deprotonation processes in solution. The mixing Hamiltonian method is designed for efficient quantum mechanical free-energy simulations by alchemically varying the nuclear potential, i.e., the nuclear charge of the transforming nucleus. In pKa calculation, the charge on the proton is varied in fraction between 0 and 1, corresponding to the fully deprotonated and protonated states, respectively. Inspired by the mixing potential QM/MM free energy simulation method developed previously [H. Hu and W. T. Yang, J. Chem. Phys. 2005, 123, 041102], this method succeeds many advantages of a large class of λ-coupled free-energy simulation methods and the linear combination of atomic potential approach. Theory and technique details of this method, along with the calculation results of the pKa of methanol and methanethiol molecules in aqueous solution, are reported. The results show satisfactory agreement with the experimental data.

  14. A novel Ka-band coaxial transit-time oscillator with a four-gap buncher

    NASA Astrophysics Data System (ADS)

    Song, Lili; He, Juntao; Ling, Junpu

    2015-05-01

    A novel Ka-band coaxial transit-time oscillator (TTO) with a four-gap buncher is proposed and investigated. Simulation results show that an output power of 1.27 GW and a frequency of 26.18 GHz can be achieved with a diode voltage of 447 kV and a beam current of 7.4 kA. The corresponding power efficiency is 38.5%, and the guiding magnetic field is 0.6 T. Studies and analysis indicate that a buncher with four gaps can modulate the electron beam better than the three-gap buncher in such a Ka-band TTO. Moreover, power efficiency increases with the coupling coefficient between the buncher and the extractor. Further simulation demonstrates that power efficiency can reach higher than 30% with a guiding magnetic field of above 0.5 T. Besides, the power efficiency exceeds 30% in a relatively large range of diode voltage from 375 kV to 495 kV.

  15. Beam tests on the 4-kA, 1. 5-MeV injector for FXR

    SciTech Connect

    Kulke, B.; Kihara, R.; Ravenscroft, D.; Scarpetti, R.; Vogtlin, G.

    1981-01-01

    The new flash x-ray machine (FXR) at Lawrence Livermore National Laboratory is scheduled for completion in late 1981. This is a 54 module, linear induction accelertor, designed to deliver 500 Roentgen at 1 m as bremsstrahlung from a 20 MeV, 4 kA, 60 ns pulsed electron beam. The 9 cm diameter, cold-cathode electron source generates a 15 kA emitted beam at 1.5 MeV, and collimation is being used to reduce the transmitted current to 3.5 kA, with an emittance of 70 mr-cm. The collimated beam diameter is 4 cm. Six ferrite-loaded cavities are used in tandem to energize the injector. The high voltage performance of the injector cavities and other pulsed-power conditioning elements was tested earlier in a series of 10/sup 5/ shots at 400 kV per cavity. An overview of the injector design and of the beam test results is given.

  16. Packaging Considerations for Integrated RF Microphotonic Receiver at Ka-Band

    NASA Technical Reports Server (NTRS)

    Nguyen, Hung; Pouch, John; Lee, Richard; Miranda, Felix; Hossein-Zadeh, Mani; Harriague, Ferando; Levi, Anthony

    2003-01-01

    The NASA Computing, Information and Communications Technology (CICT) Program is supporting the development of an RF microphotonic Ka-band receiver. The receiver consists of a lithium niobate micro-disk that enables the incoming RF signal (up to Ka-band) to be coupled to the optical signal (approx. 200 THz). The modulated optical signal is detected by the high-speed photonic signal processing electronics. When compared with an all-electronic approach, the microphotonic receiver technology offers 1 Ox smaller volume, smaller weight, and smaller power consumption, greater sensitivity, and optical isolation for applications in extreme environments. It could potentially be implemented to support planetary surface-to-surface and surface-to-relay communications, as well as high-data-rate inter-satellite links. We are currently studying a number of fabrication and integration issues that could result as this technology is advanced for potential insertion into a NASA mission. The results of our preliminary effort to integrate the RF microphotonic receiver components (e.g., the lithium niobate micro-disk, the optical elements, and the Ka-band patch antenna) on an etched silicon wafer will be presented, In addition, the concomitant integration and packaging issues, and the potential NASA applications will be discussed.

  17. DelPhiPKa web server: predicting pKa of proteins, RNAs and DNAs.

    PubMed

    Wang, Lin; Zhang, Min; Alexov, Emil

    2016-02-15

    A new pKa prediction web server is released, which implements DelPhi Gaussian dielectric function to calculate electrostatic potentials generated by charges of biomolecules. Topology parameters are extended to include atomic information of nucleotides of RNA and DNA, which extends the capability of pKa calculations beyond proteins. The web server allows the end-user to protonate the biomolecule at particular pH based on calculated pKa values and provides the downloadable file in PQR format. Several tests are performed to benchmark the accuracy and speed of the protocol. The web server follows a client-server architecture built on PHP and HTML and utilizes DelPhiPKa program. The computation is performed on the Palmetto supercomputer cluster and results/download links are given back to the end-user via http protocol. The web server takes advantage of MPI parallel implementation in DelPhiPKa and can run a single job on up to 24 CPUs. The DelPhiPKa web server is available at http://compbio.clemson.edu/pka_webserver. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  18. Humans permanently occupied the Andean highlands by at least 7 ka

    PubMed Central

    Stefanescu, Ioana C.; Garcia-Putnam, Alexander; Aldenderfer, Mark S.; Clementz, Mark T.; Murphy, Melissa S.; Llave, Carlos Viviano; Watson, James T.

    2017-01-01

    High-elevation environments above 2500 metres above sea level (m.a.s.l.) were among the planet's last frontiers of human colonization. Research on the speed and tempo of this colonization process is active and holds implications for understanding rates of genetic, physiological and cultural adaptation in our species. Permanent occupation of high-elevation environments in the Andes Mountains of South America tentatively began with hunter–gatherers around 9 ka according to current archaeological estimates, though the timing is currently debated. Recent observations on the archaeological site of Soro Mik'aya Patjxa (8.0–6.5 ka), located at 3800 m.a.s.l. in the Andean Altiplano, offer an opportunity to independently test hypotheses for early permanent use of the region. This study observes low oxygen (δ18O) and high carbon (δ13C) isotope values in human bone, long travel distances to low-elevation zones, variable age and sex structure in the human population and an absence of non-local lithic materials. These independent lines of evidence converge to support a model of permanent occupation of high elevations and refute logistical and seasonal use models. The results constitute the strongest empirical support to date for permanent human occupation of the Andean highlands by hunter–gatherers before 7 ka. PMID:28680685

  19. The pKa of butaclamol and the mode of butaclamol binding to central dopamine receptors.

    PubMed

    Chrzanowski, F A; McGrogan, B A; Maryanoff, B E

    1985-03-01

    The pKa values for butaclamol (1), 1,2,3,5,6,10b beta-hexahydro-6 alpha-phenylpyrrolo[2,1-alpha]isoquinoline (2, McN-4612-Y), and 2-tert-butyl-1,3,4,6,7,11b beta-hexahydro-7 beta-phenyl-2H-benzo[alpha]quinolizin-2 alpha-ol (3, McN-4171) were determined to be 7.2, 9.1, and 7.0, respectively. The values for 1 and 3 are anomalous; however, the value for 1 (7.2) is not as low as the one reported in the literature (pKa = 5.9). We also determined pKa values for apomorphine, chlorpromazine, and lidocaine, for reference purposes (7.6, 9.2, and 7.9, respectively). The results indicate that 1 would not be predominantly unprotonated under the physiological conditions of receptor binding, rather it would be about 50% protonated. This fact may contravene a suggested binding model used to map the central dopamine receptor (viz., ref 3).

  20. ACTS Ka-Band Earth Stations: Technology, Performance, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Struharik, Steven J.; Diamond, John J.; Stewart, David

    2000-01-01

    The Advanced Communications Technology Satellite (ACTS) Project invested heavily in prototype Ka-band satellite ground terminals to conduct an experiments program with ACTS. The ACTS experiments program proposed to validate Ka-band satellite and ground-station technology, demonstrate future telecommunication services, demonstrate commercial viability and market acceptability of these new services, evaluate system networking and processing technology, and characterize Ka-band propagation effects, including development of techniques to mitigate signal fading. This paper will present a summary of the fixed ground terminals developed by the NASA Glenn Research Center and its industry partners, emphasizing the technology and performance of the terminals and the lessons learned throughout their 6-year operation, including the inclined orbit phase-of-operations. The fixed ground stations used for experiments by government, academic, and commercial entities used reflector-based offset-fed antenna systems with antennas ranging in size from 0.35 to 3.4 in. in diameter. Gateway earth stations included two systems referred to as the NASA Ground Station (NGS) and the Link Evaluation Terminal (LET).

  1. Predicting the pKa and stability of organic acids and bases at an oil-water interface.

    PubMed

    Andersson, M P; Olsson, M H M; Stipp, S L S

    2014-06-10

    We have used density functional theory and the implicit solvent model, COSMO-RS, to investigate how the acidity constant, pKa, of organic acids and bases adsorbed at the organic compound-aqueous solution interface changes, compared to its value in the aqueous phase. The pKa determine the surface charge density of the molecules that accumulate at the fluid-fluid interface. We have estimated the pKa by comparing the stability of the protonated and unprotonated forms of a series of molecules in the bulk aqueous solution and at an interface where parts of each molecule reside in the hydrophobic phase and the rest remains in the hydrophilic phase. We found that the pKa for acids is shifted by ∼1 pH unit to higher values compared to the bulk water pKa, whereas they are shifted to lower values by a similar amount for bases. Because this pKa shift is similar in magnitude for each of the molecules studied, we propose that the pKa for molecules at a water-organic compound interface can easily be predicted by adding a small shift to the aqueous pKa. This shift is general and correlates with the functional group. We also found that the relative composition of molecules at the fluid-fluid interface is not the same as in the bulk. For example, species such as carboxylic acids are enriched at the interface, where they can dominate surface properties, even when they are a modest component in the bulk fluid. For high surface concentrations of carboxylic acid groups at an interface, such as a self-assembled monolayer, we have demonstrated that the pKa depends on the degree of deprotonation through direct hydrogen bonding between protonated and deprotonated acidic headgroups.

  2. A ~25 ka Indian Ocean monsoon variability record from the Andaman Sea

    USGS Publications Warehouse

    Rashid, H.; Flower, B.P.; Poore, R.Z.; Quinn, T.M.

    2007-01-01

    Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ18O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ18O of seawater (δ18Osw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ∼3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ18Osw exhibited higher than present values during the Lateglacial interval ca 19–15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ18Osw values during the BØlling/AllerØd ca 14.5–12.6 ka BP and during the early Holocene ca 10.8–5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation–precipitation (E–P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.

  3. Sea surface Ka-band radar cross-section from field observations in the Black Sea

    NASA Astrophysics Data System (ADS)

    Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand

    2016-04-01

    An interest in Ka-band radar backscattering from the ocean surface is growing due to better spatial resolution and more accurate Doppler anomaly estimate. But, available empirical models of Ka-band cross-section are quite scarce and sometime controversial. Here we present multi-year (2009-2015) field measurements of Ka-band co-polarized (VV and HH) sea surface normalized radar cross-section (NRCS) from research platform in the Black sea collected in a wide range of observation and sea state conditions. The data are fitted by polynomial function of incidence angle, azimuth and wind speed with accounting for measured radar antenna pattern. This empirical NRCS is compared with published Ka- and Ku-band data. Our Ka-band NRCS is close to Ku-band, but is 5-7 dB higher than 'pioneer' measurements by Masuko et al. (1986). Following the two-scale Bragg paradigm, the NRCS is split into polarized (Bragg) and non-polarized components and analyzed in terms of polarization ratio (VV/HH) and polarization difference (VV-HH) to estimate wave spectra at the Bragg wave number. Non-polarized component dominates at low incidence angles <30° due to specular reflection from regular surface. At larger incidence angles, the relative non-polarized contribution decreases, but grows again at HH-polarization approaching 0.7-0.8 at 65° for 10 m/s wind speed, suggesting that backscattering from breaking waves dominates HH NRCS at low grazing angles. At high incidence angles (>60°) NRCS azimuth dependency is unimodal (upwind peak) for HH and bimodal (with up- and downwind peaks) for VV polarization. This again can be attributed to different backscattering mechanisms for VV and HH polarizations. With decreasing of incidence angle, up- to downwind ratio tends to 1, and under light wind conditions (4-6 m/s) can be less than 1. The same situation is observed for polarization difference, which reflects Bragg backscattering properties only. This effect can be explained by enhanced roughness on

  4. Eruptive history of Sundoro volcano, Central Java, Indonesia since 34 ka

    NASA Astrophysics Data System (ADS)

    Prambada, Oktory; Arakawa, Yoji; Ikehata, Kei; Furukawa, Ryuta; Takada, Akira; Wibowo, Haryo Edi; Nakagawa, Mitsuhiro; Kartadinata, M. Nugraha

    2016-11-01

    Reconstruction of the eruptive history of Sundoro volcano is needed to forecast the probability of future eruptions and eruptive volumes. Sundoro volcano is located in Central Java (Indonesia), 65 km northwest of Yogyakarta, and in one of the most densely populated areas of Indonesia. On the basis of stratigraphy, radiocarbon dating, petrography, and whole-rock geochemistry, we recognize the following 12 eruptive groups: (1) Ngadirejo, (2) Bansari, (3) Arum, (4) Kembang, (5) Kekep, (6) Garung, (7) Kertek, (8) Watu, (9) Liyangan, (10) Kledung, (11) Summit, and (12) Sibajak. The Ngadirejo (34 ka BP) to Kledung (1 ka) eruptive groups are inferred to have been the stratovolcano building phase. Based on compositions of deposits, one or more magma reservoirs of intermediate chemical composition are inferred to have existed below the volcano during the periods of time represented by the eruptive groups. SiO2 of juvenile eruptive products ranges from 50 to 63 wt%, and K2O contents range from high K to medium K. The chemical composition and phenocryst content of eruptive products change with time. The lower SiO2 products contain mainly plagioclase, clinopyroxene, and olivine, whereas the more evolved rocks contain plagioclase, clinopyroxene, orthopyroxene, and rare hornblende and olivine. Our work has defined Sundoro's eruptive history for the period 1-34 ka, and this history helps us to forecast future activity. We estimated that the total amount of magma discharged since 34 ka is approximately 4.4 km3. The average eruption rate over this group ranges from 0.14 to 0.17 km3/kyr. The eruption rate and the frequency of individual eruptions indicate that the volcano has been very active since 34 ka, and this activity in combination with our petrological data suggest the presence of one or more magma reservoirs that have been repeatedly filled and then discharged as eruptions have taken place. Our data further suggest that the volume of the crustal reservoir system has

  5. Excitatory Mechanisms in the Suprachiasmatic Nucleus: The Role of AMPA/KA Glutamate Receptors

    PubMed Central

    Michel, Stephan; Itri, Jason; Colwell, Christopher S.

    2008-01-01

    A variety of evidence suggests that the effects of light on the mammalian circadian system are mediated by direct retinal ganglion cell projection to the suprachiasmatic nucleus (SCN). This synaptic connection is glutamatergic and the release of glutamate is detected by both N-methyl-d-asparate (NMDA) and amino-methyl proprionic acid/kainate (AMPA/KA) iontotropic glutamate receptors (GluRs). It is well established that NMDA GluRs play a critical role in mediating the effects of light on the circadian system; however, the role of AMPA/KA GluRs has received less attention. In the present study, we sought to better understand the contribution of AMPA/KA-mediated currents in the circadian system based in the SCN. First, whole cell patch-clamp electrophysiological techniques were utilized to measure spontaneous excitatory postsynaptic currents (sEPSCs) from SCN neurons. These currents were widespread in the SCN and not just restricted to the retino-recipient region. The sEPSC frequency and amplitude did not vary with the daily cycle. Similarly, currents evoked by the exogenous application of AMPA onto SCN neurons were widespread within the SCN and did not exhibit a diurnal rhythm in their magnitude. Fluorometric techniques were utilized to estimate AMPA-induced calcium (Ca2+) concentration changes in SCN neurons. The resulting data indicate that AMPA-evoked Ca2+ transients were widespread in the SCN and that there was a daily rhythm in the magnitude of AMPA-induced Ca2+ transients that peaked during the night. By itself, blocking AMPA/KA GluRs with a receptor blocker decreased the spontaneous firing of some SCN neurons as well as reduced resting Ca2+ levels, suggesting tonic glutamatergic excitation. Finally, immunohistochemical techniques were used to describe expression of the AMPA-preferring GluR subunits GluR1 and GluR2/3s within the SCN. Overall, our data suggest that glutamatergic synaptic transmission mediated by AMPA/KA GluRs play an important role throughout

  6. The widespread ~10ka Saksunarvatn tephra is not a product single eruption

    NASA Astrophysics Data System (ADS)

    Thordarson, T.

    2014-12-01

    Since its identification as a 45 cm-thick basaltic ash horizon in a sediment core from Lake Saksunarvatn on Streymoy in the Faeroe archipelago the ~10 ka Saksunarvatn ash has been taken to represent one discrete stratigraphic marker horizon in early Holocene sedimentary sequences across the North Atlantic; from Greenland to Western Europe, carrying the inference that it was produced by one continuous eruption. If taken at face value, the volume of this basaltic tephra would be >450 km3, which not only makes it - by far - the largest tephra fall deposit produced by an explosive eruption at an Icelandic volcano but also puts it in the category of 'super-eruptions'. It also implies that the inferred 'Saksunarvatn eruption' would have been about 40 times bigger than the ~3 ka H3 and ~4.2 ka H4 events, two of largest post-glacial silicic explosive eruptions in Iceland. Also, the largest known post-glacial basaltic explosive eruption in Iceland produced tephra volumes of 5-8 km3, or factor of 60 smaller than the anticipated 'Saksunarvatn' event. Although the geological record in Iceland contains ample examples of volcanic events with magnitudes in the range of VEI5-7, it does not reveal evidence of events on the super-eruption scale. These question the validity of the inference that the tephra referred to as the Saksunarvatn ash is a product of a single eruption. New studies on lake sediment cores and soil profiles in Iceland have identified several tephra layers in the time interval 10.4 - 9.9 ka that exhibit major element composition identical to that of the Saksunarvatn ash. Thus, over a period of ~500-years the Grímsvötn volcano produced a series of events erupting tephra of composition identical to that of the Saksunarvatn ash and we will present stratigraphic and geochemical evidence to demonstrate that the 10.4 - 9.9 ka interval of the early Holocene sediment archives contains at least six widespread tephra layers of Saksunarvatn composition and that an early

  7. The Geology of the Ka'u Desert, Hawaii as a Mars Analog

    NASA Astrophysics Data System (ADS)

    Craddock, R. A.; Irwin, R. P.; Williams, R.; Swanson, D.; Howard, A. D.; Quantin, C.; Kuzmin, R.; Zimbelman, J. R.

    2005-12-01

    The Ka'u Desert is located on the western flank of Kilauea volcano on the Big Island of Hawaii. It is a desert because it receives little annual rainfall (about 150 mm/yr) but also because it is subjected to constant outgassing from Kilauea, which creates a harsh, acidic environment. Near the summit of Kilauea the Ka'u Desert is characterized by the Keanakako'i tephra deposit, which is several meters deep thinning out to a discontinuous deposit 1.5 km (1 mile) towards the center of the desert. The deposit itself has been incised by a number of gullies that are flat-floored and terminate in a series of amphitheater-shaped plunge pools. Most of the interior desert contains undulating weathered lava flows, extensive deposits of sand, and several more recent lava flows and volcanic edifices. The southern portion of the desert is bounded by the Hilina Pali fault scarp, which is 500 m (1,500 ft) above the nearby Pacific Ocean and contains a complex series of outwash plains, alluvial fans, and debris flows. We will present a summary of the geology of the Ka'u Desert. Contrary to published interpretations, we will present evidence that the Keanakako'i was not emplaced by two separate catastrophic eruption events but rather by two distinct eruption episodes that included multiple eruption events often interrupted by long hiatuses. Despite the morphology of the gullies contained on the Keanakako'i we will present evidence that the gullies were formed exclusively by surface runoff and not groundwater sapping, including quantitative estimates about the large amounts of discharge that occur during extreme storms. We will also present analyses of the sand deposits and determine the likely provenance of these materials. For the first time, we will also describe alluvial fans and mass wasting features on Hilina Pali and show evidence that they are part of poorly integrated channel system that originates in the Keanakako'i tephra. The Ka'u Desert represents a good Mars analog

  8. Cataclysmic Rock Avalanche from El Capitan, Yosemite Valley, circa 3.6 ka

    NASA Astrophysics Data System (ADS)

    Stock, G. M.

    2008-12-01

    El Capitan in Yosemite Valley is one of the largest and most iconic granite faces in the world. Despite glacially steepened walls exceeding 90 degrees, a historic database shows relatively few rock falls from El Capitan in the past 150 years. However, a massive bouldery deposit beneath the southeast face suggests an earlier rock avalanche of unusually large size. Spatial analysis of airborne LiDAR data indicate that the rock avalanche deposit has a volume of ~2.70 x 106 m3, a maximum thickness of 18 m, and a runout distance of 660 m, roughly twice the horizontal extent of the adjacent talus. The deposit is very coarse on its distal edge, with individual boulder volumes up to 2500 m3. Cosmogenic 10Be exposure dates from boulders distributed across the deposit confirm this interpretation. Four 10Be samples are tightly clustered between 3.5 and 3.8 ka, with a mean age of 3.6 +/- 0.6 ka. A fifth sample gives a much older age of 22.0 ka, but a glacier occupied Yosemite Valley at this time, prohibiting deposition; thus, the older age likely results from exposure on the cliff face prior to failure. The similarity of ages and overall morphology suggest that the entire deposit formed during a single event. The mean exposure age coincides with inferred Holocene rupture of the northern Owens Valley and/or White Mountain fault(s) between 3.3 and 3.8 ka (Lee et al., 2001; Bacon and Pezzopane, 2007). This time coincidence, combined with the fact that historic rupture of the Owens Valley fault in A.D. 1872 generated numerous large rock falls in Yosemite Valley, strongly suggests that the El Capitan rock avalanche was triggered by a seismic event along the eastern margin of the Sierra Nevada circa 3.6 ka. As there is not an obvious "scar" on the expansive southeast face, the exact source area of the rock avalanche is not yet known. Detrital apatite U-Th/(He) thermochronometry can determine the elevation(s) from which rock fall boulders originate, but significant inter-sample age

  9. A New Sediment Core From Lake Elsinore, CA Reveals Evidence for Large Amplitude Hydrologic Change Between 9ka and 30ka

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Feakins, S. J.; Fantozzi, J. M.; Lund, S.; Zimmerman, S. R.; Hiner, C.

    2011-12-01

    Lake Elsinore is the largest natural lake in coastal southwestern North America (CSWNA). Building on cores taken in 2003, a new 20-meter core (LEDC10-1) spanning 9ka to 30ka was acquired in 2010. Twenty-one AMS 14C dates, mostly on discrete organic material (e.g. seeds, charcoal), provide an initial age model. On average 1 cm equals 13 years of sedimentation making this new core the highest resolution, most complete glacial-age terrestrial archive yet obtained from CSWNA. We present initial multi-proxy results including magnetic susceptibility, organic and carbonate content, grain size, CN ratios, and δD plant leaf waxes to infer past climate state and change. The deglacial sequence is characterized by large amplitude hydrologic change: from a very wet full glacial to a dry Holocene. A δD shift of 100 per mil indicates a dramatic shift in either P:E ratio or changes in storm tracks/moisture sources. Sand % increases from the Holocene into the glacial, which is interpreted to indicate a wetter-than-present glacial climate in CSWNA. High amplitude sand variability at centennial-to-millennial scales also suggests a highly dynamic climate in CSWNA during the last glacial. Comparisons of the Elsinore record of abrupt hydrologic events to high latitude records show coherence with various climate intervals including Heinrich events 2 and 3. We also observe connections to local marine conditions in the Santa Barbara Basin. Future plans include additional dates, grain size, elemental data, compound specific isotope analyses, microfossil identification/counts, and palynology.

  10. Post-2 ka Carbon Accumulation in the James Bay and Hudson Bay Lowlands

    NASA Astrophysics Data System (ADS)

    Holmquist, J. R.; MacDonald, G. M.

    2012-12-01

    The James Bay, and Hudson Bay Lowlands of Canada (JBL/HBL) are the second largest peatland complex in the world and contain major stores of soil Carbon (C) (Keddy 2002). The goal of this study was to quantify the size, and rate of accumulation of these peatland C stocks since 2,000 years before present (2 ka), as well as investigate the effect of climate on vertical peat accumulation. We analyzed the relationship between 2 ka depth and mean annual air temperature (MAAT), growing degree days over 5°C (GDD5), and photosynthetically active radiation over the growing season ( PAR0). This study utilized a transect of eight peat cores from ombrotrophic bogs ranging from 55°25'N to 50°27'N. Carbon content was estimated using Loss-On-Ignition at 550°C and Bulk Density measurements. The ages of the deposits were estimated using 14C dates and BACON age-depth modeling. These new data were supplemented by 17 millennially resolved chronologies from a literature review. In the southwest JBL ombrotrophic peatlands accumulated between 63.03-16.85 kg C m-2 since 2 ka at a rate of 31.41-8.79 gC m-2 yr -1. 2 ka depth displays a significant latitudinal gradient (r2=0.45, p=2.45*10-4) with shallower deposits in northern permafrost peatlands. 2 ka ybp depth correlates significantly and positively with MAAT (r2=0.47, p=8.56*10-5), GDD5 (r2=0.58, p=9.36*10-5), and PAR0 (figure 1). These results support past research that shows 2 ka depth correlates significantly with MAAT in West Siberia (Beilman et al. 2009), as well as data that shows that PAR0 is a major driver of Sphagnum productivity (Loisel et al. 2012). These results support the idea that peatland vertical growth may increase in the HBL/JBL under projected climate change scenarios. Beilman, D.W., G.M. MacDonald, L.C. Smith, P.J. Reimer (2009). Carbon Accumulation in Peatlands of West Siberia over the Last 2000 Years. Biogeochemical Cycles. GB1012. Keddy, P.A. (2000) Wetland Ecology: Principles and Conservation. Cambridge

  11. Glacier extent during the Younger Dryas and 8.2-ka event on Baffin Island, Arctic Canada.

    PubMed

    Young, Nicolás E; Briner, Jason P; Rood, Dylan H; Finkel, Robert C

    2012-09-14

    Greenland ice cores reveal that mean annual temperatures during the Younger Dryas (YD) cold interval--about 12.9 to 11.7 thousand years ago (ka)--and the ~150-year-long cold reversal that occurred 8.2 thousand years ago were ~15° and 3° to 4°C colder than today, respectively. Reconstructing ice-sheet response to these climate perturbations can help evaluate ice-sheet sensitivity to climate change. Here, we report the widespread advance of Laurentide Ice Sheet outlet glaciers and independent mountain glaciers on Baffin Island, Arctic Canada, in response to the 8.2-ka event and show that mountain glaciers during the 8.2-ka event were larger than their YD predecessors. In contrast to the wintertime bias of YD cooling, we suggest that cooling during the 8.2-ka event was more evenly distributed across the seasons.

  12. Aqueous-only, pH-induced nanoassembly of dual pKa-driven contraphilic block copolymers

    PubMed Central

    Lee, Nam S.; Li, Yali; Ruda, C. Marcus

    2009-01-01

    pH-Responsive block copolymers, having two segments with functionalities of differing pKa, were prepared by NMP, providing a “green” route to the assembly of core/shell functionalizable nanostructures. PMID:18985203

  13. The 13 ka Pelée-Type Dome Collapse at Nevado de Toluca Volcano, México.

    NASA Astrophysics Data System (ADS)

    D'Antonio, M.; Capra, L.; Sarocchi, D.; Bellotti, F.

    2007-05-01

    The Nevado de Toluca is an active volcano located in the central sector of the Trans-Mexican Volcanic Belt, 80 km southwest of Mexico City. Activity at this andesitic to dacitic stratovolcano began ca. 2.6 Ma ago. During the last 42 ka, the volcano has been characterized by different eruptive styles, including five dome collapses dated at 37, 32, 28, 26, and 13 ka and five Plinian eruptions at 42 ka, 36 ka, 21.7 ka, 12.1 ka and 10.5 ka. The 13 ka dome collapse is the youngest event of this type, and originated a 0.11 km3 block-and-ash flow deposit on the north-eastern sector of the volcano. The deposit consists of two facies: channel-like, 10 m thick, monolitologic, that is composed of up to five units, with decimetric dacitic clasts set in a sandy matrix; and a lateral facies that consists of a gray, sandy horizon, up to 4 m thick, with a 30 cm-thick surge layer at the base. The main component is a dacitic lava, with different degree of vesciculation, with mineral association of Pl-Hbl-Opx. Plagioclases show two different textures: in equilibrium, with normal zoning (core = An37-64.3, rim = An30.7-45.8) or with spongy cellular texture with inverse zoning (core = An38-43.5, rim = An45-51.2). Hornblende is normally light green, barren of oxidation. The rock matrix contains up to 53 perc. of glass with abundant microlites, indicating over-pressure on the crystallizing magma and a rapid expulsion. All these stratigraphic and petrographic features indicate that the dome was quickly extruded on the summit of the volcano, probably triggered by a magma mixing process, and its collapse was accompanied by an explosive component, being classified as a Pelée-type event.

  14. Estimated pKa values for the environmentally relevant C1 through C8 perfluorinated sulfonic acid isomers.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2016-10-14

    In order to estimate isomer-specific acidity constants (pKa) for the perfluorinated sulfonic acid (PFSA) environmental contaminants, the parameterization method 6 (PM6) pKa prediction method was extensively validated against a wide range of carbon oxyacids and related sulfonic/sulfinic acids. Excellent pKa prediction performance was observed for the carbon oxyacids using the PM6 method, but this approach was found to have a severe positive bias for sulfonic/sulfinic acids. To overcome this obstacle, a correlation was developed between non-adjusted PM6 pKa values and the corresponding experimentally obtained/estimated acidity constants for a range of representative alkyl, aryl and halogen-substituted sulfonic acids. Application of this correction to the PM6 values allows for extension of this computational method to a new acid functional group. When used to estimate isomer-specific pKa values for the C1 through C8 PFSAs, the modified PM6 approach suggests an adjusted pKa range from -5.3 to -9.0, indicating that all members of this class of well-known environmental contaminants will be effectively completely dissociated in aquatic systems.

  15. pKa of fentanyl varies with temperature: implications for acid-base management during extremes of body temperature.

    PubMed

    Thurlkill, Richard L; Cross, David A; Scholtz, J Martin; Pace, C Nick

    2005-12-01

    The pKa of fentanyl has not been measured previously at varying extremes of body temperature. The goal of this laboratory investigation was to test the hypothesis that the pKa of fentanyl changes with temperature. The investigation involved measuring the pKa values of aqueous fentanyl at varying temperatures. The investigation was conducted in a controlled laboratory environment. No human or animal subjects were involved. Because no live subjects were involved in the investigation, no interventions were necessary. This paper reports the effect of temperature on the pKa of fentanyl. The pKa of aqueous fentanyl was measured at 15 degrees C, 25 degrees C, 37 degrees C, 42 degrees C, and 47.5 degrees C by potentiometric titration in 0.01 mmol/L of potassium chloride after extensive degassing. Data were analyzed using the least squares method with an appropriately fitting equation. The pKa of fentanyl was found to change in a similar manner to the neutral point of water at varying temperatures. This finding has implications for the bioavailability of fentanyl at extremes of body temperature in association with the clinical acid-base management of the patient. Clinical implications for differing methods of intraoperative acid-base management at varying temperatures are discussed.

  16. Evidence for an Elevated Aspartate pKa in the Active Site of Human Aromatase*

    PubMed Central

    Di Nardo, Giovanna; Breitner, Maximilian; Bandino, Andrea; Ghosh, Debashis; Jennings, Gareth K.; Hackett, John C.; Gilardi, Gianfranco

    2015-01-01

    Aromatase (CYP19A1), the enzyme that converts androgens to estrogens, is of significant mechanistic and therapeutic interest. Crystal structures and computational studies of this enzyme shed light on the critical role of Asp309 in substrate binding and catalysis. These studies predicted an elevated pKa for Asp309 and proposed that protonation of this residue was required for function. In this study, UV-visible absorption, circular dichroism, resonance Raman spectroscopy, and enzyme kinetics were used to study the impact of pH on aromatase structure and androstenedione binding. Spectroscopic studies demonstrate that androstenedione binding is pH-dependent, whereas, in contrast, the D309N mutant retains its ability to bind to androstenedione across the entire pH range studied. Neither pH nor mutation perturbed the secondary structure or heme environment. The origin of the observed pH dependence was further narrowed to the protonation equilibria of Asp309 with a parallel set of spectroscopic studies using exemestane and anastrozole. Because exemestane interacts with Asp309 based on its co-crystal structure with the enzyme, its binding is pH-dependent. Aromatase binding to anastrozole is pH-independent, consistent with the hypothesis that this ligand exploits a distinct set of interactions in the active site. In summary, we assign the apparent pKa of 8.2 observed for androstenedione binding to the side chain of Asp309. To our knowledge, this work represents the first experimental assignment of a pKa value to a residue in a cytochrome P450. This value is in agreement with theoretical calculations (7.7–8.1) despite the reliance of the computational methods on the conformational snapshots provided by crystal structures. PMID:25425647

  17. Relative sea level changes in southeastern Sweden the last 6ka mapped by paleo-shorelines.

    NASA Astrophysics Data System (ADS)

    Svensson, N. O.

    2015-12-01

    Emerged Holocene paleo-shorelines, formed during sea level high-stand periods are mostly morphological prominent and thus relatively easily identified in the field. In the study area of southeastern Sweden sediment stratigraphic investigations were used to identify and define the vertical extent of two Baltic Sea transgressive events. In-between these geographically spread study areas, the paleo-shorelines of these transgressive stages were mapped at places they were distinct, well developed and believed to be closely related to paleo sea level. The main factors determining formation of distinct shore-lines is exposure to the open sea and ample supply of erodible coarse grained minerogenic material. The paleo-shorelines were traced and their absolute elevation established with the help of detailed LIDAR based shaded digital terrain models. These models were derived from the detailed LIDAR point cloud recently made available by the National Land Survey of Sweden. Additionally the paleo-shorelines were confirmed during field visits and details such as sedimentary composition were noted. One of the more difficult variable to determine, the paleo-sea level stand in relation to the shoreline were accessed also in field and related ground surfaces without tree canopies were GPS mapped. The absolute paleo sea level was later derived from the LIDAR ground surface model for these spots. The c. 6ka shoreline, which is not fully synchronous throughout the whole study area, shows a rather smooth rise from c. 7 m a.s.l. in the south to more than 30 m a.s.l. in the north. Comparison between the 6 ka and the 10.5 ka paleo-shoreline, formed in the Ancylus Lake, further emphasize the glacioisostatic imprint of the Scandinavian ice sheet, but also reveals uplift irregularities, probably of neo tectonic origin.

  18. Determination of acid dissociation constants (pKa) of cephalosporin antibiotics: Computational and experimental approaches.

    PubMed

    Ribeiro, Alyson R; Schmidt, Torsten C

    2017-02-01

    Cefapirin (CEPA) and ceftiofur (CEF) are two examples of widely used veterinarian cephalosporins presenting multiple ionization centers. However, the acid dissociation constants (pKa) of CEF are missing and experimental data about CEPA are rare. The same is true for many cephalosporins, where available data are either incomplete or even wrong. Environmentally relevant biotic and abiotic processes depend primordially on the antibiotic pH-dependent speciation. Consequently, this physicochemical parameter should be reliable, including the correct ionization center identification. In this direction, two experimental techniques, potentiometry and spectrophotometry, along with two well-known pKa predictors, Marvin and ACD/Percepta, were used to study the macro dissociation constants of CEPA and CEF. Additionally, the experimental dissociation constants of 14 cephalosporins available in the literature were revised, compiled and compared with data obtained in silico. Only one value was determined experimentally for CEF (2.68 ± 0.05), which was associated to the carboxylic acid group deprotonation. For CEPA two values were obtained experimentally: 2.74 ± 0.01 for the carboxylic acid deprotonation and 5.13 ± 0.01 for the pyridinium ring deprotonation. In general, experimentally obtained values agree with the in silico predicted data (ACD/Percepta RMSE: 0.552 and Marvin RMSE: 0.706, n = 88). However, for cephalosporins having imine and aminothiazole groups structurally close, Marvin presented problems in pKa predictions. For the biological and environmental fate and effect discussion, it is important to recognize that CEPA and CEF, as well as many other cephalosporins, are present as anionic species in the biologic and environmentally relevant pH values of 6-7.5.

  19. Ka-Band Site Characterization of the NASA Near Earth Network in Svalbard, Norway

    NASA Technical Reports Server (NTRS)

    Acosta, R.; Morse, J.; Nessel, J.; Zemba, M.; Tuttle, K.; Caroglanian, A.; Younes, B.; Pedersen, Sten-Chirstian

    2011-01-01

    Critical to NASA s rapid migration toward Ka-Band is the comprehensive characterization of the communication channels at NASA's ground sites to determine the effects of the atmosphere on signal propagation and the network's ability to support various classes of users in different orbits. Accordingly, NASA has initiated a number of studies involving the ground sites of its Near Earth and Deep Space Networks. Recently, NASA concluded a memorandum of agreement (MOA) with the Norwegian Space Centre of the Kingdom of Norway and began a joint site characterization study to determine the atmospheric effects on Ka-Band links at the Svalbard Satellite Station in Norway, which remains a critical component of NASA s Near Earth Communication Network (NEN). System planning and design for Ka-band links at the Svalbard site cannot be optimally achieved unless measured attenuation statistics (e.g. cumulative distribution functions (CDF)) are obtained. In general, the CDF will determine the necessary system margin and overall system availability due to the atmospheric effects. To statistically characterize the attenuation statistics at the Svalbard site, NASA has constructed a ground-based monitoring station consisting of a multi-channel total power radiometer (25.5 - 26.5 GHz) and a weather monitoring station to continuously measure (at 1 second intervals) attenuation and excess noise (brightness temperature). These instruments have been tested in a laboratory environment as well as in an analogous outdoor climate (i.e. winter in Northeast Ohio), and the station was deployed in Svalbard, Norway in May 2011. The measurement campaign is planned to last a minimum of 3 years but not exceeding a maximum of 5 years.

  20. A 100 ka record of fluvial activity in the Fitzroy River Basin, tropical northeastern Australia

    NASA Astrophysics Data System (ADS)

    Croke, Jacky; Jansen, John D.; Amos, Kathryn; Pietsch, Timothy J.

    2011-06-01

    This study reports the nature and timing of Quaternary fluvial activity in the Fitzroy River basin, which drains a diverse 143,000 km 2 area in northeastern Queensland, before discharging into the Great Barrier Reef Marine Park. The catchment consists of an extensive array of channel and floodplain types that we show have undergone large-scale fluvial adjustment in-channel planform, geometry and sinuosity. Optically stimulated luminescence (OSL) dating of quartz sediments from fifteen (3-18 m) floodplain cores throughout the basin indicates several discrete phases of active bedload activity: at ˜105-85 ka in Marine Isotope Stage (MIS) 5, at ˜50-40 ka (MIS 3), and at ˜30-10 ka (MIS 3/2). The overall timing of late Quaternary fluvial activity correlates well with previous accounts from across Australia with rivers being primarily active during interstadials. Fluvial activity, however, does not appear to have been synchronous throughout the basin's major sub-catchments. Fluvial activity throughout MIS 2 (i.e. across the Last Glacial Maximum) in the meandering channels of the Fitzroy correlates well with regional data in tropical northeastern Queensland, and casts new light on the river response to reduced rainfall and vegetation cover suggested by regional palaeoclimate indicators. Moreover, the absence of a strong Holocene signal is at odds with previous accounts from elsewhere throughout Australia. The latitudinal position of the Fitzroy across the Tropic of Capricorn places this catchment at a key location for elucidating the main hydrological drivers of Quaternary fluvial activity in northeastern Australia, and especially for determining tropical moisture sources feeding into the headwaters of Cooper Creek, a major river system of the continental interior.

  1. Transmission characteristic of graphene/TiO2 paper measured at Ka-band

    NASA Astrophysics Data System (ADS)

    Agusu, La; Mitsudo, Seitaro; Ahmad, La Ode; Herdianto, Fujii, Yutaka; Ishikawa, Yuya; Furuya, Takahashi; Ramadhan, La Ode Ahmad Nur

    2017-01-01

    The commercial telecommunication system in future would explore the electromagnetic spectrum with higher frequency than used now, because it requires higher speed of transmission data. Using the millimeter waves (mmW) with frequency ranging from 30 to 300 GHz, such requirement could be fulfilled. The upcoming 5G cellular technology is expected to use frequency 30 GHz or higher. Then materials with a specific characteristic at the mmW range are interesting to be explored and investigated. Here, we report the synthesis process of graphene/TiO2 deposited on paper and their transmission characteristics to the electromagnetic energy at frequency 27-40 GHz (Ka-Band). The reduced graphene oxide (rGO) was synthesized by a modified Hummers method with introduction of microwave irradiation in the process. rGO and TiO2 were mixed in ethanol solution and deposited on the paper by a spraying technique. Transmission coefficient of electromagnetic wave energy at Ka-Band was measured by using the millimeter vector network analyzer. Conductivity of rGO is 1.89 Scm-1 and for the graphene/TiO2 with TiO2 content is up to 50%, conductivity is down to Scm-1 Graphene/TiO2 layer with thickness of 60).lm and TiO2 loading up to 25% can has the transmission coefficient of -4 dB at the middle frequency of 31 GHz and bandwidth of 2.2 GHz. This can be useful as the electromagnetic interference shielding material at Ka-band.

  2. Aspartate embedding depth affects pHLIP's insertion pKa.

    PubMed

    Fendos, Justin; Barrera, Francisco N; Engelman, Donald M

    2013-07-09

    We have used the pHlow insertion peptide (pHLIP) family to study the role of aspartate embedding depth in pH-dependent transmembrane peptide insertion. pHLIP binds to the surface of a lipid bilayer as a largely unstructured monomer at neutral pH. When the pH is lowered, pHLIP inserts spontaneously across the membrane as a spanning α-helix. pHLIP insertion is reversible when the pH is adjusted back to a neutral value. One of the critical events facilitating pHLIP insertion is the protonation of aspartates in the spanning domain of the peptide: the negative side chains of these residues convert to uncharged, polar forms, facilitating insertion by altering the hydrophobicity of the spanning domain. To examine this protonation mechanism further, we created pHLIP sequence variants in which the two spanning aspartates (D14 and D25) were moved up or down in the sequence. We hypothesized that the aspartate depth in the inserted state would directly affect the proton affinity of the acidic side chains, altering the pKa of pH-dependent insertion. To this end, we also mutated the arginine at position 11 to determine whether arginine snorkeling modulates the insertion pKa by affecting the aspartate depth. Our results indicate that both types of mutations change the insertion pKa, supporting the idea that the aspartate depth is a participating parameter in determining the pH dependence. We also show that pHLIP's resistance to aggregation can be altered with our mutations, identifying a new criterion for improving the performance of pHLIP in vivo when targeting acidic disease tissues such as cancer and inflammation.

  3. Toward the accurate calculation of pKa values in water and acetonitrile.

    PubMed

    Muckerman, James T; Skone, Jonathan H; Ning, Ming; Wasada-Tsutsui, Yuko

    2013-01-01

    We present a simple approach for the calculation of accurate pKa values in water and acetonitrile based on the straightforward calculation of the gas-phase absolute free energies of the acid and conjugate base with use of only a continuum solvation model to obtain the corresponding solution-phase free energies. Most of the error in such an approach arises from inaccurate differential solvation free energies of the acid and conjugate base which is removed in our approach using a correction based on the realization that the gas-phase acidities have only a small systematic error relative to the dominant systematic error in the differential solvation. The methodology is outlined in the context of the calculation of a set of neutral acids with water as the solvent for a reasonably accurate electronic structure level of theory (DFT), basis set, and implicit solvation model. It is then applied to the comparison of results for three different hybrid density functionals to illustrate the insensitivity to the functional. Finally, the approach is applied to the comparison of results for sets of neutral acids and protonated amine cationic acids in both aqueous (water) and nonaqueous (acetonitrile) solvents. The methodology is shown to generally predict the pKa values for all the cases investigated to within 1 pH unit so long as the differential solvation error is larger than the systematic error in the gas-phase acidity calculations. Such an approach is rather general and does not have additional complications that would arise in a cluster-continuum method, thus giving it strength as a simple high-throughput means to calculate absolute pKa values. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Paleomagnetic secular variation at the Azores during the last 3 ka

    NASA Astrophysics Data System (ADS)

    Di Chiara, A.; Speranza, F.; Porreca, M.

    2012-12-01

    We report on 33 new paleomagnetic directions obtained from 16 lava flows emplaced in the last 3 ka on São Miguel, the largest island of the Azores. The data provide 27 directions from historical or 14C dated flows which, together with 6 directions previously gathered from the same flows by Johyson et al., (1998), yield the first paleomagnetic record of the last 3 ka from the Atlantic Ocean. Within-flow directions are consistent, suggesting that inclination swings from 60° to 25° and declination changes between -10° to 20° reflect variations in the geomagnetic field over the last 3 ka. To a first approximation, the declination record is consistent with predictions from CALS3k.4 and gufm1 global field models. Conversely, inclination values are lower than model predictions at two different ages: 1) four different sites from the 1652 AD flow yield I=48° instead of I=63° predicted by gufm1; 2) data from several flows nicely mimic the inclination minimum of 800-1400 AD, but inclination values are lower by ca. 10° than CALS3k.4 model predictions. By interpolating a cubic spline fit on declination / inclination versus age data, we tentatively infer the directional evolution of the geomagnetic field at the Azores from 1000 BC to 1600 AD.The obtained curve shows three tracks in virtual overlap during the 1000-800 BC, 800-500 BC, and 400-700 AD time spans; Cubic spline interpolation of flow mean declinations (a) and inclinations (b) versus respective calendar ages; c) directions derived every 100 years from cubic spline interpolation, superimposed on paleomagnetic directions (and relative confidence cones) from three loosely-dated flows (Fig. 1). For ages older than 750 AD the fit line is dashed, as it is constrained by a limited number of data. Vertical error bars for declination and inclination data are α95 /cos(I) and α95 values, respectively

  5. Oxygen Isotopes and Meltwater: Younger Dryas and 8.2 ka Event

    NASA Astrophysics Data System (ADS)

    Keigwin, L. D.

    2015-12-01

    Delta 18-O is one of our most powerful and widely used proxies, with, arguably, the fewest likely unknown unknowns. Here I will consider the d18-O evidence for the two best-known floods of mostly liquid water to the ocean, the Younger Dryas (YD) and the 8.2 ka event. The first d18-O signal of a meltwater flood in the ocean was reported 40 years ago by Kennett and Shackleton (1975) and that paper led directly to the meltwater diversion hypothesis for the origin of the YD cooling. It was later suggested by Rooth (1982) that such a flood could interrupt Nordic seas convection and trigger the YD cold episode. It was reported at this meeting last year that a candidate flood has been found in the Mackenzie River region of the western Arctic based on low d18-O and multiple other lines of evidence. The 8.2 ka event was about one-tenth the duration of the YD but with possibly higher transport, and is more difficult to detect in open marine sediments. As with the YD, it has been modeled by hosing and low salinities have been derived by temperature correcting the d18-O. The resulting low salinity was shown not to follow the prediction of the highest resolution modeling, and theory, that the fresh water would be transported mostly equatorward along the continental shelf. However, I report here that the low d18-O signal of the 8.2 ka flooding is present in new cores from near Logan Canyon on the Scotian shelf break, and in Jordan Basin, Gulf of Maine. These results substantially validate the modeling of Condron and Winsor that fresh water transport must have been along the continental shelf.

  6. A portable Ka-band front-end test package for beam-waveguide antenna performance evaluation. Part 2: Tests on the antenna

    NASA Technical Reports Server (NTRS)

    Otoshi, T. Y.; Stewart, S. R.; Franco, M. M.

    1991-01-01

    In part one of this article, a description was given of a Ka-band test package developed to enable testing of the Deep Space Station (DDS) 13 34-m beam-waveguide (BWG) antenna at 32 GHz. Test results were given for the Ka-band test package in an on-the-ground test configuration. This article is a companion article concerned with Ka-band test results for the test package in an on-the-antenna test configuration. Included are Ka-band zenith noise-temperature values, tipping-curve data, and subreflector test results obtained at the Cassegrain focal point, as well as at the final BWG focal point (located in a subterranean pedestal room). Test results show that, through the use of the Ka-band test package, the BWG antenna performance was successfully evaluated at Ka-band. The Ka-band test package operated well in all of the different antenna test configurations.

  7. A low-power, high-efficiency Ka-band TWTA

    NASA Technical Reports Server (NTRS)

    Curren, Arthur N.; Dayton, James A., Jr.; Palmer, Raymond W.; Force, Dale A.; Tamashiro, Rodney N.; Wilson, John F.; Dombro, Louis; Harvey, Wayne L.

    1992-01-01

    NASA has developed a new class of Ka-band TWT amplifiers (TWTAs) which achieve their high efficiency/low power performance goals by means of an advanced dynamic velocity taper (DVT). The DVT is characterized by a continuous, nonlinear reduction in helix pitch from its initial synchronous value in the output section of the TWT to near the end of the helix. Another efficiency-maximizing feature is the inclusion of a multistage depressed collector employing oxygen-free, high-conductivity Cu electrodes treated for secondary electron emission suppression by means of ion bombardment. An efficiency of 43 percent is expected to be reached.

  8. Use of elliptical orbits for a Ka-band personal access satellite system

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud; Estabrook, Polly

    1990-01-01

    The use of satellites in elliptical orbits for a Ka-band personal communications system application designed to provide voice and data service within the continental U.S. is examined. The impact of these orbits on system parameters such as signal carrier-to-noise ratio, roundtrip delay, Doppler shift, and satellite antenna size is quantized for satellites in two elliptical orbits, the Molniya and the ACE orbits. The number of satellites necessary for continuous CONUS coverage has been determined for the satellites in these orbits. The increased system complexity brought about by the use of satellites at such altitudes is discussed.

  9. Economic comparison of FDMA and TDMA options for communications by Ka-band multiple beam satellites

    NASA Technical Reports Server (NTRS)

    Stevens, G. H.

    1984-01-01

    An assessment is made of the feasibility of providing low data rate service to small earth stations by satellite at Ka-band. Technological as well as economic factors are considered. The results of NASA-sponsored contractual studies are compared and results of internal NASA studies are presented. Several FDMA and TDMA scenarios are critically examined with the objective of establishing the relative utility of such systems to end users. It is shown that FDMA has no advantage over TDMA in a multibeam scenario for 56 Kbs of data by voice, video, or the equivalent. For the same assumptions, significant weight and power advantages are realized in the space segment using TDMA.

  10. The Development and Demonstration of a 360m/10 kA HTS DC Power Cable

    NASA Astrophysics Data System (ADS)

    Xiao, Liye

    With the quick development of renewable energy, it is expected that the electric power from renewable energy would be the dominant one for the future power grid. Due to the specialty of the renewable energy, the HVDC power transmission would be very useful for the transmission of electric power from renewable energy. DC power cable made of High Tc Superconductor (HTS) would be a possible alternative for the construction of HVDC power transmission system. In this chapter, we report the development and demonstration of a 360 m/10 kA HTS DC power cable and the test results.

  11. Ka-band Dielectric Waveguide Antenna Array for Millimeter Wave Active Imaging System

    NASA Astrophysics Data System (ADS)

    Fang, Weihai; Fei, Peng; Nian, Feng; Yang, Yujie; Feng, Keming

    2014-11-01

    Ka-band compact dielectric waveguide antenna array for active imaging system is given. Antenna array with WR28 metal waveguide direct feeding is specially designed with small size, high gain, good radiation pattern, easy realization, low insertion loss and low mutual coupling. One practical antenna array for 3-D active imaging system is shown with theoretic analysis and experimental results. The mutual coupling of transmitting and receiving units is less than -30dB, the gain from 26.5GHz to 40GHz is (12-16) dB. The results in this paper provide guidelines for the designing of millimeter wave dielectric waveguide antenna array.

  12. ASASSN-17ka: Discovery of A Probable Supernova in ESO 244-G 019

    NASA Astrophysics Data System (ADS)

    Monard, L. A. G.; Brimacombe, J.; Brown, J. S.; Stanek, K. Z.; Holoien, T. W.-S.; Kochanek, C. S.; Shields, J.; Thompson, T. A.; Shappee, B. J.; Prieto, J. L.; Bersier, D.; Dong, Subo; Bose, S.; Chen, Ping; Bock, G.; Fernandez, J. M.; Kiyota, S.; Masi, G.; Post, R. S.

    2017-07-01

    During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy ESO 244-G 019. ASASSN-17ka (AT 2017frr) was discovered in images obtained on UT 2017-07-27.23 at V 16.5 mag. We also detect the object in images obtained on UT 2017-07-24.24 (V 16.6), UT 2017-07-29.23 (V 16.0), and UT 2017-07-30.23 (V 16.5).

  13. Weather related continuity and completeness on Deep Space Ka-band links: statistics and forecasting

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2006-01-01

    In this paper the concept of link 'stability' as means of measuring the continuity of the link is introduced and through it, along with the distributions of 'good' periods and 'bad' periods, the performance of the proposed Ka-band link design method using both forecasting and long-term statistics has been analyzed. The results indicate that the proposed link design method has relatively good continuity and completeness characteristics even when only long-term statistics are used and that the continuity performance further improves when forecasting is employed. .

  14. A 74 or 75 ka Age for the Toba Super-eruption? Resolving the Debate.

    NASA Astrophysics Data System (ADS)

    Storey, M.; Roberts, R. G.; Haslam, M.

    2015-12-01

    The Toba super-eruption in Sumatra, ~74,000 years ago, was the largest terrestrial volcanic event of the Quaternary. Some have proposed that the eruption produced widespread perturbations of climate and ecosystems. Evaluation of the environmental impact of the eruption and linkage to rapid climate oscillations recorded in ice core, sediment and speleothem records requires an accurate and precise age for the event, with uncertainties at the centurial level. Two recent studies, however, have proposed quite different 40Ar/39Ar ages for this volcanic event of 73.88 ± 0.32 ka (Storey et al., 2012) and 75.0 ± 0.9 ka (Mark et al, 2014), with both uncertainties expressed at 1σ, leading to radically different interpretations of its global impact. 40Ar/39Ar is a relative dating method, in which the unknown is run against a mineral standard of known age. Storey et al (2012) obtained their age estimate using a new-generation, multi-collector noble gas mass spectrometer (NU Instruments Noblesse) equipped with ion-counters, while Mark et al. (2014) used an earlier generation of lower resolution, single-collector mass spectrometer (MAP 215-50). Both studies used the same mineral standard (Alder Creek sanidine, ACs), except that Mark et al. (2014) used an older value, which accounts for the discrepancy in ages between the two studies. The value used by Mark et al. for ACs is geologically implausible, because it results in older 40Ar/39Ar dates than the youngest co-existing zircon U/Pb CATIMS ages (e.g., Rivera et al., 2013, 2014). Use of the same value for ACs as used by Storey et al. (2012) results in an identical, but less precise, astronomically calibrated age of 73.9 ± 0.9 ka for the Mark et al. data. Here, we review combined U/Pb and 40Ar/39Ar age data (both published and unpublished) for a number of Quaternary and older volcanic ash deposits, and U/Th ages for late Quaternary speleothems. These data strongly support the age assigned to ACs by Storey et al. (2012) and

  15. Ka-Band Waveguide Hybrid Combiner for MMIC Amplifiers With Unequal and Arbitrary Power Output Ratio

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Chevalier, Christine T.; Wintucky, Edwin G.; Freeman, Jon C.

    2009-01-01

    The design, simulation and characterization of a novel Ka-band (32.05 +/- 0.25 GHz) rectangular waveguide branch-line hybrid unequal power combiner is presented. The manufactured combiner was designed to combine input signals, which are in phase and with an amplitude ratio of two. The measured return loss and isolation of the branch-line hybrid are better than 22 and 27 dB, respectively. The application of the branch-line hybrid for combining two MMIC power amplifiers with output power ratio of two is demonstrated. The measured combining efficiency is approximately 93 percent over the above frequency band.

  16. Ka-Band Waveguide Hybrid Combiner for MMIC Amplifiers with Unequal and Arbitrary Power Output Ratio

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Chevalier, Christine T.; Wintucky, Edwin G.; Freeman, Jon C.

    2009-01-01

    The design, simulation and characterization of a novel Ka-band (32.05 +/- 0.25 GHz) rectangular waveguide branchline hybrid unequal power combiner is presented. The manufactured combiner was designed to combine input signals, which are nearly in phase and with an amplitude ratio of two. The measured return loss and isolation of the branch-line hybrid are better than 22 and 27 dB, respectively. The application of the branch-line hybrid for combining two monolithic microwave integrated circuit (MMIC) power amplifiers with output power ratio of two is demonstrated. The measured combining efficiency is 92.9% at the center frequency of 32.05 GHz.

  17. SARAL/ALtiKa : From the satellite telemetry to end-users products

    NASA Astrophysics Data System (ADS)

    Guinle, Thierry; Mazeau, Sophie; Dieterle, Susanne

    2015-04-01

    This paper describes all the SARAL/AltiKa ground facilities and resources used for a routine delivery of oceanography products to users. After a brief summary of the Indian-French organization in place, a focus is made on the different steps needed for the generation of valuable users products. It covers the command/control of the altimetric payload (Altimeter, radiometer, DORIS) as well as orbit and radar data processing including future upgrades and reprocessings planned in the next years. Finally it gives the portfolio of all the available products from level2 up to level4.

  18. Post-Mazama (7 KA) faulting beneath Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Colman, Steven M.; Rosenbaum, J.G.; Reynolds, R.L.; Sarna-Wojcicki, A. M.

    2000-01-01

    High-resolution seismic-reflection profiles (3.5 kHz) show that a distinctive, widespread reflection occurs in the sediments beneath Upper Klamath Lake, Oregon. Coring reveals that this reflection is formed by Mazama tephra (MT), about 7 ka in age. The MT horizon is faulted in many places and locally displaced by as much as 3.1 m. Differential displacement of multiple horizons indicates recurrent fault movement, perhaps three episodes since deposition of the Mazama. The pattern of faulting indicates northeast-southwest extension beneath the lake basin.

  19. Advanced mobile satellite communications using COMETS satellite in MM-wave and Ka-band

    NASA Technical Reports Server (NTRS)

    Ohmori, Shingo; Isobe, Shunkichi; Takeuchi, Makoto; Naito, Hideyuki

    1993-01-01

    Early in the 21st century, the demand for personal communications using mobile, hand-held, and VSAT terminals will rapidly increase. In a future system, many different types of services should be provided with one-hop connection. The Communications Research Laboratory (CRL) has studied a future advanced mobile satellite communications system using millimeter wave and Ka band. In 1990, CRL started the Communications and Broadcasting Engineering Test Satellite (COMETS) project. The satellite has been developed in conjunction with NASDA and will be launched in 1997. This paper describes the COMETS payload configuration and the experimental system for the advanced mobile communications mission.

  20. Role of pKa of Nucleobases in the Origins of Chemical Evolution

    PubMed Central

    2012-01-01

    The formation of canonical base pairs through Watson–Crick hydrogen bonding sits at the heart of the genetic apparatus. The specificity of the base pairing of adenine with thymine/uracil and guanine with cytosine preserves accurate information for the biochemical blueprint and replicates the instructions necessary for carrying out biological function. The chemical evolution question of how these five canonical nucleobases were selected over various other possibilities remains intriguing. Since these and alternative nucleobases would have been available for chemical evolution, the reasons for the emergence of this system appear to be primarily functional. While investigating the base-pairing properties of structural nucleic acid analogs, we encountered a relationship between the pKa of a series of nonstandard (and canonical) nucleobases and the pH of the aqueous medium. This relationship appeared to correspond with the propensity of these molecules to self-assemble via Watson–Crick-type base-pairing interactions. A simple correlation of the “magnitude of the difference between the pKa and pH” (pKa–pH correlation) enables a general prediction of which types of heterocyclic recognition elements form hydrogen-bonded base pairs in aqueous media. Using the pKa–pH relationship, we can rationalize why nature chose the canonical nucleobases in terms of hydrophobic and hydrophilic interactions, and further extrapolate its significance within the context of chemical evolution. The connection between the physicochemical properties of bioorganic compounds and the interactions with their aqueous environment directly affects structure and function, at both a molecular and a supramolecular level. A general structure–function pattern emerges in biomolecules and biopolymers in aqueous media near neutral pH. A pKa – pH < 2 generally prompts catalytic functions, central to metabolism, but a difference in pKa – pH > 2 seems to result in the emergence of structure

  1. Megawatt-power Ka-band gyroklystron oscillator with external feedback

    NASA Astrophysics Data System (ADS)

    Guznov, Y. M.; Danilov, Y. Y.; Kuzikov, S. V.; Novozhilova, Y. V.; Shevchenko, A. S.; Zaitsev, N. I.; Ryskin, N. M.

    2013-10-01

    We report design and experimental demonstration of a high-power regenerative oscillator based on the gyroklystron amplifier with external delayed feedback. The oscillator operates on axially non-symmetric TE7.1.1 and TE7.3.1 modes in the input and output cavity, respectively. Peak output power of 1.5-2.0 MW with nearly 1 μs pulse duration in Ka-band is observed experimentally. Application of the selective delayed feedback not only overcomes the mode competition problem but also provides controlled mode switching within 1-2 GHz frequency band.

  2. Proposal for a Joint NASA/KSAT Ka-band RF Propagation Terminal at Svalbard, Norway

    NASA Technical Reports Server (NTRS)

    Volosin, Jeffrey; Acosta, Roberto; Nessel, James; McCarthy, Kevin; Caroglanian, Armen

    2010-01-01

    This slide presentation discusses the placement of a Ka-band RF Propagation Terminal at Svalbard, Norway. The Near Earth Network (NEN) station would be managed by Kongsberg Satellite Services (KSAT) and would benefit NASA and KSAT. There are details of the proposed NASA/KSAT campaign, and the responsibilities each would agree to. There are several reasons for the placement, a primary reason is comparison with the Alaska site, Based on climatological similarities/differences with Alaska, Svalbard site expected to have good radiometer/beacon agreement approximately 99% of time.

  3. Ka-band dual frequency array feed for a low cost ACTS ground terminal

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.; Simons, Rainee N.; Sil, Ajit K.

    1992-01-01

    Because of low cost and ease of fabrication, microstrip arrays are attractive as feeds for reflector antenna systems. The development of a 4 x 4 microstrip array which will be used as a feed for a low cost Advanced Communications Technology Satellite (ACTS) ground terminal is described. The array feed consisting of four 2 x 2 subarrays is fed with coplanar waveguide power dividing networks. The patch radiator is designed to excite two orthogonal, linearly polarized waves at Ka-band frequencies (around 20 and 30 GHz). Test results for the developed array are presented.

  4. Ka-Band Dual Frequency Array Feed for a Low Cost ACTS Ground Terminal

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.; Simons, Rainee N.; Sil, Ajit K.

    1992-01-01

    Because of low cost and ease of fabrication, microstrip arrays are attractive as feeds for reflector antenna systems. This paper describes the development of a 4x4 microstrip array which will be used as a feed for a low cost ACTS ground terminal. The array feed consisting of four 2x2 subarrays is fed with coplanar waveguide power dividing networks. The patch radiator is designed to excite two orthogonal, linearly polarized waves at Ka-band frequencies (around 20 and 30 GHz). Test results for the developed array are presented.

  5. Toward more realistic freshwater forcing experiments of the 8.2 ka event

    NASA Astrophysics Data System (ADS)

    Morrill, C.; Wagner, A. J.; Ward, E. M.; Otto-Bliesner, B. L.; Rosenbloom, N. A.

    2015-12-01

    The 8.2 ka event is a key test case for simulating the coupled climate response to changes in the Atlantic Meridional Overturning Circulation (AMOC). Most previous model experiments of this event were forced by the drainage of proglacial Lake Agassiz-Ojibway into the Hudson Bay and entering the Atlantic Ocean through the Hudson Strait. This drainage contained enough water to raise global sea level about 0.2 meters or more, but it likely had a short duration on the order of one year. Recent advances in quantifying the meltwater forcing associated with the 8.2 ka event point towards a forcing larger than the drainage of Lake Agassiz-Ojibway, probably involving the collapse of the Hudson Bay ice dome and raising global sea level on the order of 1.5 to 3.0 meters. Using the Community Climate System Model version 3 (CCSM3), we show that this larger forcing yields a better match to paleoclimate proxy records. Despite these improvements in forcing magnitude in model simulations, the forcing itself is still generally applied in an unrealistic geographic manner, across most of the Labrador Sea rather than only along the Labrador coast. We present additional experiments using the CCSM3, with an ocean model resolution only slightly coarser than that used in previous eddy-resolving simulations, to test the sensitivity to freshwater forcing location. When revised freshwater forcing is applied across the Labrador Sea, the AMOC is reduced by about 40% and climate anomalies compare well with proxy records of the 8.2 ka event in terms of magnitude and duration. When the forcing is added only along the Labrador coast, however, most meltwater joins the subtropical gyre and travels to the subtropics with minor impact to the AMOC (about 10% decrease). It is likely that model biases in the placement of the North Atlantic Current remain an important limitation for correctly simulating the 8.2 ka event, though the effects of icebergs or alternative freshwater sources cannot be completely

  6. Comment on 'Thermodynamic cycles and the calculation of p Ka' [Chem. Phys. Lett. 367 (2003) 145

    NASA Astrophysics Data System (ADS)

    da Silva, Clarissa O.; da Silva, Edilson C.; Nascimento, Marco A. C.

    2003-11-01

    In a recent Letter, Pliego [Chem. Phys. Lett. 367 (2003) 145] has raised some questions about the methodology that we have employed for calculating p Ka values in aqueous solutions. In this comment we show that the problem with Pliego's analysis is the fact that he used Ben-Naim's definition of Δ Gsol for both the solute and the solvent, which implies that the concentration, for both components, should be equal to 1 M. For the solute, this is a reference state fully compatible with the quantum description, but for the solvent this choice is unphysical, as discussed in the Letter.

  7. Abrupt Climate Change & Paleoindian Environments in western Colorado from 17-9 ka yr BP

    NASA Astrophysics Data System (ADS)

    Whitlock, C. L.; Briles, C.; Meltzer, D. J.

    2010-12-01

    The late-glacial period was characterized by rapid climate changes that resulted in significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in North American today, mountain environments during the late-glacial period are poorly known. Yet, archeological evidence indicates that Folsom-age Paleoindians were present in the region, perhaps even occasionally over-wintering in the Gunnison Basin during the Younger Dryas Chronozone (YDC; 12.9 to 11.5ka yr BP). To determine the climate, vegetation, and fire history during the late-glacial/early-Holocene transition, a 17-kyr-old sediment core from Lily Pond (38°56’06” N, 106°38’37”W, 3208m elevation) was analyzed for pollen and charcoal and compared with other high-resolution records from the region. The data suggest that, following deglaciation, the region supported an alpine parkland dominated by Artemisia and scattered Picea. Conditions warmed and became wetter than before during the Bølling-Allerød period (B/A; 14.7 to 12.9ka yr BP), when the region was covered by open Picea, Pinus, and Abies forest. Cooling during the YDC is inferred from abundant Picea, slightly more Artemisia and decreased Pinus, which indicate the presence of subalpine parkland. With the onset of the Holocene at ~11.5 ka yr BP, Pinus, Quercus, Artemisia, and Chenopodiaceae increased, suggesting an upslope expansion of xerophytic taxa in response to warmer and effectively drier summers than before or at present. Fire activity was absent prior to 14.7 ka yr BP, increased substantially during the B/A, decreased during the YDC, increased at the beginning of the Holocene, and declined in the early Holocene. The vegetation changes that occurred at Lily Pond are generally consistent with other high-resolution records in the Colorado Rockies in showing cooler-than-present YDC followed by rapid warming. The Lily Lake data provide new information that indicates substantial warming and establishment of

  8. Simulation and measurement of a Ka-band HTS MMIC Josephson junction mixer

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Pegrum, Colin; Du, Jia; Guo, Yingjie Jay

    2017-01-01

    We report modeling and simulation results for a Ka band high-temperature superconducting (HTS) monolithic microwave integrated circuit (MMIC) Josephson junction mixer. A Verilog-A model of a Josephson junction is established and imported into the system simulator to realize a full HTS MMIC circuit simulation containing the HTS passive circuit models. Impedance matching optimization between the junction and passive devices is investigated. Junction DC I-V characteristics, current and local oscillator bias conditions and mixing performance are simulated and compared with the experimental results. Good agreement is obtained between the simulation and measurement results.

  9. The Celestial Reference Frame at X/Ka-band: Status & Prospects for Improving the South

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Alonso, J.; Clark, J. E.; Gamborino, L.; García-Miró, C.; Horiuchi, S.; Lobo, J.; Maddè, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2012-10-01

    Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN).We discuss the construction of such a frame based on radio observations of AGN at X/Ka-band (8.4/32 GHz). Compared to S/Xband frames such as the international standard ICRF2, X/Ka-band allows access to more compact source morphology and reduced core shift. Both these effects allow for a more well-defined and stable reference frame at X/Ka. Using sixty-seven 24-hour sessions with NASA's Deep Space Network, we detected over 482 sources covering the full 24 hours of right ascension and declinations down to -45deg. There is evidence for systematic errors at the 100 µas level. Known errors include limited SNR, lack of phase calibration, troposphere mis-modelling, and limited southern geometry. We discuss our plans to address these errors with an emphasis on plans to use ESA's new 35-meter antenna in Malargüe, Argentina to greatly improve our southern hemisphere geometric coverage. We report successful fringe tests between ESA's 35-m antenna in Cebreros, Spain and the NASA 34-m in Robledo, Spain thereby validating the NASA-ESA interfaces and the portable VLBI recorder intended for use at Malargüe when that station is ready in the Fall of 2012. Allan variance tests on time scales of 1-1000 sec on the Cebreros-Robledo baseline were limited by tropospheric stability thus confirming that instrumental stability is not expected to be a limiting factor on these time scales once we go to Malargüe. In the next decade, we expect that ESA's optically based Gaia mission will produce a competitive frame. In anticipation of this development, we simulated a frame tie between our X/Ka frame and the Gaia frame. The simulation predicts a frame tie precision of 10-15 µas (1-sigma, per 3-D rotation component) with anticipated improvements in the radio reducing that to 5-10 µas per component by the time of Gaia's end of mission ca

  10. A low-power, high-efficiency Ka-band TWTA

    NASA Astrophysics Data System (ADS)

    Curren, Arthur N.; Dayton, James A., Jr.; Palmer, Raymond W.; Force, Dale A.; Tamashiro, Rodney N.; Wilson, John F.; Dombro, Louis; Harvey, Wayne L.

    1992-03-01

    NASA has developed a new class of Ka-band TWT amplifiers (TWTAs) which achieve their high efficiency/low power performance goals by means of an advanced dynamic velocity taper (DVT). The DVT is characterized by a continuous, nonlinear reduction in helix pitch from its initial synchronous value in the output section of the TWT to near the end of the helix. Another efficiency-maximizing feature is the inclusion of a multistage depressed collector employing oxygen-free, high-conductivity Cu electrodes treated for secondary electron emission suppression by means of ion bombardment. An efficiency of 43 percent is expected to be reached.

  11. Weather related continuity and completeness on Deep Space Ka-band links: statistics and forecasting

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2006-01-01

    In this paper the concept of link 'stability' as means of measuring the continuity of the link is introduced and through it, along with the distributions of 'good' periods and 'bad' periods, the performance of the proposed Ka-band link design method using both forecasting and long-term statistics has been analyzed. The results indicate that the proposed link design method has relatively good continuity and completeness characteristics even when only long-term statistics are used and that the continuity performance further improves when forecasting is employed. .

  12. Immunomodulating Activity of Agaricus brasiliensis KA21 in Mice and in Human Volunteers

    PubMed Central

    Fukuwatari, Yasushi; Okumura, Ko; Takeda, Kazuyoshi; Ishibashi, Ken-ichi; Furukawa, Mai; Ohno, Naohito; Mori, Kazu; Gao, Ming; Motoi, Masuro

    2008-01-01

    We performed studies on murine models and human volunteers to examine the immunoenhancing effects of the naturally outdoor-cultivated fruit body of Agaricus brasiliensis KA21 (i.e. Agaricus blazei). Antitumor, leukocyte-enhancing, hepatopathy-alleviating and endotoxin shock-alleviating effects were found in mice. In the human study, percentage body fat, percentage visceral fat, blood cholesterol level and blood glucose level were decreased, and natural killer cell activity was increased. Taken together, the results strongly suggest that the A. brasiliensis fruit body is useful as a health-promoting food. PMID:18604247

  13. Deep-Space Ka-Band Link Priority Data Protection: Pre-Emptive Retransmission vs. Margin

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2009-01-01

    In this paper the performance of two preemptive retransmission schemes for protection of priority data over deep-space Ka-band links is evaluated. The first scheme merges the correctly received bit from each transmission to create the most complete set of priority data for each pass (bit merge). The second scheme (symbol combining) combines the soft symbols received from each transmission of the priority data to increase the priority data's signal to noise ratio (SNR), thus increasing the liklihood of the correct reception.

  14. Evaluation of Deep Space Ka-Band Data Transfer using Radiometeorological Forecasts and Radiometer Measurements

    NASA Astrophysics Data System (ADS)

    Montopoli, Mario; Marzano, Frank S.; Biscarini, Marianna; Milani, Luca; Cimini, Domenico; De Sanctis, Klaide; Di Fabio, Saverio

    2016-04-01

    Deep space exploration is aimed at acquiring information about the solar system. In this scenario, telecommunications links between Earth ground receiving stations and extra-terrestrial satellite platforms have to be designed in order to ensure the optimal transfer of the acquired scientific data back to the Earth. A significant communication capacity has to be planned when very large distances, as those characterising deep space links, are involved thus fostering more ambitious scientific mission requirements. At the current state of the art, two microwave channel frequencies are used to perform the deep space data transfer: X band (~ 8.4 GHz) and Ka band (~ 32 GHz) channel. Ka-band transmission can offer an advantage over X-band in terms of antenna performance with the same antenna effective area and an available data transfer bandwidth (50 times higher at Ka band than X band). However, Earth troposphere-related impairments can affects the space-to-Earth carrier signals at frequencies higher than 10 GHz by degrading its integrity and thus reducing the deep space channel temporal availability. Such atmospheric impairments, especially in terms of path attenuation, their statistic and the possibility to forecast them in the next 24H at the Earth's receiving station would allow a more accurate design of the deep space link, promoting the mitigation of the detrimental effects on the link availability. To pursue this aim, meteorological forecast models and in situ measurements need to be considered in order to characterise the troposphere in terms of signal path attenuation at current and future time. In this work, we want to show how the synergistic use of meteorological forecasts, radiative transfer simulations and in situ measurements such as microwave radiometry observations, rain gauges and radiosoundings, can aid the optimisation of a deep space link at Ka band and improve its performance with respect to usual practices. The outcomes of the study are in the

  15. Severe stunting in blackgram caused by the Mungbean yellow mosaic virus (MYMV) KA27 DNA B component is ameliorated by co-infection or post-infection with the KA22 DNA B: MYMV nuclear shuttle protein is the symptom determinant.

    PubMed

    Mahajan, Nagrani; Parameswari, Chidambaram; Veluthambi, Karuppannan

    2011-04-01

    Mungbean yellow mosaic virus-[India:Vigna] (MYMV-[IN:Vig]), a blackgram isolate of MYMV, has five variable and infective DNA B components of which KA22 and KA27 DNA Bs share only 72% nucleotide sequence identity between them. Agroinoculation of blackgram with partial dimers of DNA A and KA27 DNA B caused severe stunting and an inordinate delay in flowering. Interestingly, co-agroinoculation of KA27+KA22 DNA B components along with DNA A ameliorated severe stunting, rescued from the delay in flowering and caused the appearance of yellow mosaic symptom characteristic of KA22 DNA B. Post-agroinoculation of KA27 DNA B-infected blackgram plants with KA22 DNA B also resulted in the amelioration from severe stunting and in the alleviation from the delay in flowering. Alleviation from KA27 DNA B-type of symptom by co-infection or post-infection with KA22 DNA B did not result in a corresponding reduction in KA27 DNA B levels. Swapping of KA27 DNA B with the nuclear shuttle protein gene (NSP) of KA22 DNA B abolished severe stunting and caused the appearance of mild yellow symptom, suggesting that the NSP is the major symptom determinant in MYMV DNA B.

  16. Electrostatic Energetics of Bacillus subtilis Ribonuclease P Protein Determined by Nuclear Magnetic Resonance-Based Histidine pKa Measurements.

    PubMed

    Mosley, Pamela L; Daniels, Kyle G; Oas, Terrence G

    2015-09-08

    The pKa values of ionizable groups in proteins report the free energy of site-specific proton binding and provide a direct means of studying pH-dependent stability. We measured histidine pKa values (H3, H22, and H105) in the unfolded (U), intermediate (I), and sulfate-bound folded (F) states of RNase P protein, using an efficient and accurate nuclear magnetic resonance-monitored titration approach that utilizes internal reference compounds and a parametric fitting method. The three histidines in the sulfate-bound folded protein have pKa values depressed by 0.21 ± 0.01, 0.49 ± 0.01, and 1.00 ± 0.01 units, respectively, relative to that of the model compound N-acetyl-l-histidine methylamide. In the unliganded and unfolded protein, the pKa values are depressed relative to that of the model compound by 0.73 ± 0.02, 0.45 ± 0.02, and 0.68 ± 0.02 units, respectively. Above pH 5.5, H22 displays a separate resonance, which we have assigned to I, whose apparent pKa value is depressed by 1.03 ± 0.25 units, which is ∼0.5 units more than in either U or F. The depressed pKa values we observe are consistent with repulsive interactions between protonated histidine side chains and the net positive charge of the protein. However, the pKa differences between F and U are small for all three histidines, and they have little ionic strength dependence in F. Taken together, these observations suggest that unfavorable electrostatics alone do not account for the fact that RNase P protein is intrinsically unfolded in the absence of ligand. Multiple factors encoded in the P protein sequence account for its IUP property, which may play an important role in its function.

  17. Experimental determination of net protein charge and A(tot) and K(a) of nonvolatile buffers in human plasma.

    PubMed

    Staempfli, Henry R; Constable, Peter D

    2003-08-01

    The mechanism for an acid-base disturbance can be determined by using the strong ion approach, which requires species-specific values for the total concentration of plasma nonvolatile buffers (Atot) and the effective dissociation constant for plasma weak acids (Ka). The aim of this study was to experimentally determine Atot and Ka values for human plasma by using in vitro CO2 tonometry. Plasma Pco2 was systematically varied from 25 to 145 Torr at 37 degrees C, thereby altering plasma pH over the physiological range of 6.90-7.55, and plasma pH, Pco2, and concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl-, lactate) and buffer ions (total protein, albumin, phosphate) were measured. Strong ion difference was estimated, and nonlinear regression was used to calculate Atot and Ka from the measured pH and Pco2 and estimated strong ion difference; the Atot and Ka values were then validated by using a published data set (Figge J, Rossing TH, and Fencl V, J Lab Clin Med 117: 453-467, 1991). The values (mean +/- SD) were as follows: Atot = 17.2 +/- 3.5 mmol/l (equivalent to 0.224 mmol/g of protein or 0.378 mmol/g of albumin); Ka = 0.80 +/- 0.60 x 10-7; negative log of Ka = 7.10. Mean estimates were obtained for strong ion difference (37 meq/l) and net protein charge (13+.0 meq/l). The experimentally determined values for Atot, Ka, and net protein charge should facilitate the diagnosis and treatment of acid-base disturbances in critically ill humans.

  18. Tree-Ring Proxies of Hydroclimate Variability in the Great Lakes Region during Cold Excursions Back to 15ka

    NASA Astrophysics Data System (ADS)

    Panyushkina, I. P.; Leavitt, S. W.

    2014-12-01

    A decade-long investigation of subfossil wood buried in glacio-fluvial, fluvial and lacustrine deposits from the U.S. Great Lakes region has resulted in a Great Lakes tree-ring network (GLTRN) comprising 47 sites dated from ca. 15 ka to 3ka. The GLTRN provides high-resolution proxies for exploration of local and regional responses to hydroclimate change at inter-annual scales during the transition from the Late Pleistocene to the Holocene. Classification of radiometric ages of GLTRN wood with relative cumulative-probability function delineates intervals and importance of hydrological changes in time and space. The overwhelming majority of wood burial events correlate with generally cold climate excursions. Forest-stand deterioration and tree mortality events at the studied sites are demonstrated to result from flooding, via river aggradation (identifying occurrence of extreme hydrologic events), rise of water table, or lake inundation. To better evaluate the special patterns of hydrological change back to 15ka, we developed four floating d13C chronologies from spruce tree rings. The length of these tree-ring proxy series that capture high-frequency moisture variability of the Great Lakes area ranges from 120 to 250 years. Our data indicate progressive wet intervals during the cold excursions precisely dated with 14C tree-ring wiggles at 13.7ka, 12.1ka, and 11.3ka that fall in the Bølling-Allerød and Pre-Boreal Interstadials, and Younger Dryas Stadial. The inter-annual and decadal variability of tree-ring moisture proxies are similar across the studied locations and time intervals. Such coherence of respective proxies may result from both local ecological stability of spruce communities or regional response to a common source of moisture at the studied time intervals and locations. This study demonstrates a potential of GLTRN proxies for modeling hydroclimatic changes at the North American continent back 15 ka.

  19. Towards a bipolar layer-counted ice-core chronology for the 41-75 ka time interval

    NASA Astrophysics Data System (ADS)

    Svensson, Anders; Bigler, Matthias; Blunier, Thomas; Dahl-Jensen, Dorthe; Fischer, Hubertus; Kipfstuhl, Sepp; Rasmussen, Sune; Schwander, Jakob; Seierstad, Inger; Steffensen, Jørgen Peder; Vallelonga, Paul; Vinther, Bo; Wegner, Anna; Wilhelms, Frank; Winstrup, Mai

    2015-04-01

    Precise chronologies have been developed for Greenland and Antarctic ice cores based on counting of annual layers in high-resolution water isotope and impurity profiles. Antarctic ice cores are layer-counted back to 31 ka (WAIS Divide ice core) whereas Greenland ice cores are dated back to 60 ka (NGRIP ice core, GICC05 time scale). Beyond 60 ka, in Marine Isotope Stage 4 (MIS4), annual layers in Greenland are thin (less than 1 cm in NGRIP in the coldest periods) and annual layer counting is more uncertain. In the Antarctic EDML ice core annual layers are somewhat thicker over most of MIS4 although they are still marginal for counting. Greenland and Antarctic ice cores are tightly linked at the Laschamp geomagnetic excursion (41 ka) and at the Toba YTT eruption (74 ka) providing end constrains for the investigated time interval. In this work, annual layer counting has been performed in parallel in the NGRIP and EDML ice cores for the time interval 41-75 ka using high-resolution records of visual stratigraphy, dust concentrations, and continuous chemistry. For NGRIP the GICC05 time scale is adapted for the period 41-60 ka. The NGRIP and EDML ice cores are then synchronized by identifying series of bipolar volcanic eruptions in acidity records of electrolytic conductivity, sulfur concentrations, and electric measurements of the solid ice (ECM and DEP). The synchronization is constrained by the layer counting that provides interval durations between volcanic markers. In some periods, a pattern of several bipolar volcanic events provides robust synchronization, but there are longer intervals for which there are no synchronization due to the lack of unambiguous bipolar markers. Over periods of robust synchronization the North-South phasing of climate (water isotopes) and dust concentrations can be investigated at decadal precision. During MIS4 the resulting time scale shows a North-South phasing somewhat different from that of the modelled AICC2012 time scale.

  20. Synthetic Lethality Screen Identifies RPS6KA2 as Modifier of Epidermal Growth Factor Receptor Activity in Pancreatic Cancer12

    PubMed Central

    Milosevic, Nada; Kühnemuth, Benjamin; Mühlberg, Leonie; Ripka, Stefanie; Griesmann, Heidi; Lölkes, Carolin; Buchholz, Malte; Aust, Daniela; Pilarsky, Christian; Krug, Sebastian; Gress, Thomas; Michl, Patrick

    2013-01-01

    Pancreatic cancer is characterized by a high degree of resistance to chemotherapy. Epidermal growth factor receptor (EGFR) inhibition using the small-molecule inhibitor erlotinib was shown to provide a small survival benefit in a subgroup of patients. To identify kinases whose inhibition acts synergistically with erlotinib, we employed a kinome-wide small-interfering RNA (siRNA)-based loss-of-function screen in the presence of erlotinib. Of 779 tested kinases, we identified several targets whose inhibition acted synergistically lethal with EGFR inhibition by erlotinib, among them the S6 kinase ribosomal protein S6 kinase 2 (RPS6KA2)/ribosomal S6 kinase 3. Activated RPS6KA2 was expressed in approximately 40% of 123 human pancreatic cancer tissues. RPS6KA2 was shown to act downstream of EGFR/RAS/mitogen-activated protein kinase kinase (MEK)/extracellular-signal regulated kinase (ERK) signaling and was activated by EGF independently of the presence of KRAS mutations. Knockdown of RPS6KA2 by siRNA led to increased apoptosis only in the presence of erlotinib, whereas RPS6KA2 activation or overexpression rescued from erlotinib- and gemcitabine-induced apoptosis. This effect was at least in part mediated by downstream activation of ribosomal protein S6. Genetic as well as pharmacological inhibition of RPS6KA2 by the inhibitor BI-D1870 acted synergistically with erlotinib. By applying this synergistic lethality screen using a kinome-wide RNA interference-library approach, we identified RPS6KA2 as potential drug target whose inhibition synergistically enhanced the effect of erlotinib on tumor cell survival. This kinase therefore represents a promising drug candidate suitable for the development of novel inhibitors for pancreatic cancer therapy. PMID:24403857

  1. Amplitude Scintillation due to Atmospheric Turbulence for the Deep Space Network Ka-Band Downlink

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wheelon, A.

    2004-01-01

    Fast amplitude variations due to atmospheric scintillation are the main concerns for the Deep Space Network (DSN) Ka-band downlink under clear weather conditions. A theoretical study of the amplitude scintillation variances for a finite aperture antenna is presented. Amplitude variances for weak scattering scenarios are examined using turbulence theory to describe atmospheric irregularities. We first apply the Kolmogorov turbulent spectrum to a point receiver for three different turbulent profile models, especially for an exponential model varying with altitude. These analytic solutions then are extended to a receiver with a finite aperture antenna for the three profile models. Smoothing effects of antenna aperture are expressed by gain factors. A group of scaling factor relations is derived to show the dependences of amplitude variances on signal wavelength, antenna size, and elevation angle. Finally, we use these analytic solutions to estimate the scintillation intensity for a DSN Goldstone 34-m receiving station. We find that the (rms) amplitude fluctuation is 0.13 dB at 20-deg elevation angle for an exponential model, while the fluctuation is 0.05 dB at 90 deg. These results will aid us in telecommunication system design and signal-fading prediction. They also provide a theoretical basis for further comparison with other measurements at Ka-band.

  2. Ferroelectric switch for a high-power Ka-band active pulse compressor

    SciTech Connect

    Hirshfield, Jay L.

    2013-12-18

    Results are presented for design of a high-power microwave switch for operation at 34.3 GHz, intended for use in an active RF pulse compressor. The active element in the switch is a ring of ferroelectric material, whose dielectric constant can be rapidly changed by application of a high-voltage pulse. As envisioned, two of these switches would be built into a pair of delay lines, as in SLED-II at SLAC, so as to allow 30-MW μs-length Ka-band pulses to be compressed in time by a factor-of-9 and multiplied in amplitude to generate 200 MW peak power pulses. Such high-power pulses could be used for testing and evaluation of high-gradient mm-wave accelerator structures, for example. Evaluation of the switch design was carried out with an X-band (11.43 GHz) prototype, built to incorporate all the features required for the Ka-band version.

  3. A high performance frequency standard and distribution system for Cassini Ka-band experiment

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Calhoun, M. D.; Kirk, A.; Diener, W. A.; Dick, G. J.; Tjoelker, R. L.

    2005-01-01

    This paper provides an overview and update of a specialized frequency reference system for the NASA Deep Space Network (DSN) to support Ka-band radio science experiments with the Cassini spacecraft, currently orbiting Saturn. Three major components, a Hydrogen Maser, Stabilized Fiber-optic Distribution Assembly (SFODA), and 10 Kelvin Cryocooled Sapphire Oscillator (10K CSO) and frequency-lock-loop, are integrated to achieve the very high performance, ground based frequency reference at a remote antenna site located 16 km from the hydrogen maser. Typical measured Allan Deviation is 1.6 -14 1 0a't 1 second and 1.7 x 10 -15 at 1000 seconds averaging intervals. Recently two 10K CSOs have been compared in situ while operating at the remote DSN site DSS-25. The CSO references were used operationally to downconvert the Ka band downlink received from the Cassini spacecraft in a series of occultation measurements performed over a 78 day period from March to June 2005.

  4. The 100 kA current leads for a superconducting transmission line magnet

    SciTech Connect

    Huang, Yuenian; Foster, William; Kim, Seog-Whan; Mazur, Peter; Oleck, Andrew; Piekarz, Henryk; Rabehl, Roger; Wake, Masayoshi; /Fermilab /KEK, Tsukuba

    2005-09-01

    A pair of current leads to power a transmission line magnet cooled at liquid helium temperature has been designed and developed at Fermilab. The leads designed to carry 100 kA dc current. Each lead consists of a warm end, heat exchange section and a cold end. The warm end is a half moon plate and cylinder brazed together. The heat exchange section is made of 202 copper rods arranged in a staggered pattern. Each rod is 6.35 mm in diameter and 1650 mm in length. The rods were soft-soldered into 12.7 mm deep holes at both warm and cold ends. The helium gas flow, guided by anodized aluminum baffles along the lead length, allows for a relatively high heat transfer coefficient between the current carrying rods and cooling helium gas. As a result the current leads were successfully tested with a ramping current of up to 104 kA. The current lead design, assembly work and the test results are presented.

  5. Unraveling the sequence and structure of the protein osteocalcin from a 42 ka fossil horse

    NASA Astrophysics Data System (ADS)

    Ostrom, Peggy H.; Gandhi, Hasand; Strahler, John R.; Walker, Angela K.; Andrews, Philip C.; Leykam, Joseph; Stafford, Thomas W.; Kelly, Robert L.; Walker, Danny N.; Buckley, Mike; Humpula, James

    2006-04-01

    We report the first complete amino acid sequence and evidence of secondary structure for osteocalcin from a temperate fossil. The osteocalcin derives from a 42 ka equid bone excavated from Juniper Cave, Wyoming. Results were determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-MS) and Edman sequencing with independent confirmation of the sequence in two laboratories. The ancient sequence was compared to that of three modern taxa: horse ( Equus caballus), zebra ( Equus grevyi), and donkey ( Equus asinus). Although there was no difference in sequence among modern taxa, MALDI-MS and Edman sequencing show that residues 48 and 49 of our modern horse are Thr, Ala rather than Pro, Val as previously reported (Carstanjen B., Wattiez, R., Armory, H., Lepage, O.M., Remy, B., 2002. Isolation and characterization of equine osteocalcin. Ann. Med. Vet.146(1), 31-38). MALDI-MS and Edman sequencing data indicate that the osteocalcin sequence of the 42 ka fossil is similar to that of modern horse. Previously inaccessible structural attributes for ancient osteocalcin were observed. Glu 39 rather than Gln 39 is consistent with deamidation, a process known to occur during fossilization and aging. Two post-translational modifications were documented: Hyp 9 and a disulfide bridge. The latter suggests at least partial retention of secondary structure. As has been done for ancient DNA research, we recommend standards for preparation and criteria for authenticating results of ancient protein sequencing.

  6. Changes in North African dust deposition: 35 ka through the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Kinsley, C. W.; McGee, D.; Winckler, G.; deMenocal, P. B.; Stuut, J. W.; Bradtmiller, L. I.

    2013-12-01

    Past changes in atmospheric circulation and aridity in the North African region can be explored by examining continuous records of reconstructed eolian dust accumulation in West African margin sediments. Recent high-resolution reconstructions of dust deposition by McGee et al. (2013) from a meridional transect of cores stretching from 27°N to 19°N along the northwest African margin indicate dramatic changes in North African dust emissions over the last 20 ka. Times of high dust emissions were documented during Heinrich Stadial 1 and the Younger Dryas, and lower dust emissions during the African Humid Period. Here we present a continuation of these records, combining grain size endmember modeling with 230Th-normalized fluxes in these cores to document spatial and temporal changes in dust loads and grain size distributions within the North African dust plume from 20 to ~35 ka. Our results provide quantitative estimates of the magnitude of dust flux changes associated with previous Heinrich Stadials, and lend insight to the nature of the North African dust plume through the entirety of the Last Glacial Maximum. References: McGee, D., deMenocal, P.B., Winckler, G., Stuut, J.B.W., Bradtmiller, L.I., 2013. The magnitude, timing and abruptness of changes in North African dust deposition over the last 20,000 yr. Earth And Planetary Science Letters 371-372, 163-176.

  7. Did Lake Bonneville Experience A Major Water-Budget Shift At 17.4 cal ka?

    NASA Astrophysics Data System (ADS)

    Oviatt, C.

    2009-12-01

    Lake Bonneville, in western Utah, had transgressed to its highest level by 18.3 cal ka, overflowed into the Snake River drainage basin until 17.4 cal ka, then catastrophically dropped 100 m as its overflow threshold was washed out. This event, which is referred to as the “Bonneville flood,” is well documented geomorphically, stratigraphically, and geochronologically. At the same time the Bonneville flood was occurring, the level of Lake Estancia in central New Mexico dropped over 30 m then returned to its previous high level in an event caused by climate change in that basin. The question is: “did Lake Bonneville experience a correlative climate-induced shift in its water budget (a decrease in the ratio of input to output), even while it continuously overflowed before, during, and after the Bonneville flood?” The answer to this question has a bearing on the global effects of the climate change that is well documented in the Estancia basin. Data from sediment cores from the Bonneville basin are providing a means to address the question. Data include: ostracode faunal changes, total inorganic carbon, stable isotopes, detrital sand, and mineralogy. The challenge is to identify the measurable characteristics of the sediment core that can be used to clearly separate the effects of water-budget change from those caused by the catastrophic (essentially instantaneous) 100-m lowering of Lake Bonneville.

  8. Pollen-based continental climate reconstructions at 6 and 21 ka: A global synthesis

    USGS Publications Warehouse

    Bartlein, P.J.; Harrison, S.P.; Brewer, S.; Connor, S.; Davis, B.A.S.; Gajewski, K.; Guiot, J.; Harrison-Prentice, T. I.; Henderson, A.; Peyron, O.; Prentice, I.C.; Scholze, M.; Seppa, H.; Shuman, B.; Sugita, S.; Thompson, R.S.; Viau, A.E.; Williams, J.; Wu, H.

    2011-01-01

    Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance. ?? 2010 The Author(s).

  9. Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis

    USGS Publications Warehouse

    Bartlein, P.J.; Harrison, S.P.; Brewer, S.; Connor, S.; Davis, B.A.S.; Gajewski, K.; Guiot, J.; Harrison-Prentice, T. I.; Henderson, A.; Peyron, O.; Prentice, I.C.; Scholze, M.; Seppa, H.; Shuman, B.; Sugita, S.; Thompson, R.S.; Viau, A.E.; Williams, J.; Wu, H.

    2010-01-01

    Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance.

  10. Channel characterisation for future Ka-band Mobile Satellite Systems and preliminary results

    NASA Technical Reports Server (NTRS)

    Sforza, Mario; Buonomo, Sergio; Arbesser-Rastburg, Bertram

    1994-01-01

    Mobile satellite systems (MSS) are presently designed or planned to operate, with the exception of OMNITRACKS, in the lower part of the frequency spectrum (UHF to S-bands). The decisions taken at the last World Administrative Radio Conference in 1992 to increase the allocated L- and S-bands for MSS services will only partly alleviate the problem of system capacity. In addition the use of L-and S-band frequencies generally requires large antenna apertures on board the satellite terminal side. The idea of exploiting the large spectrum resources available at higher frequencies (20-30 GHz) and the perspective of reducing user terminal size (and possibly price too) have spurred the interest of systems designers and planners. On the other hand, Ka-band frequencies suffer from increased slant path losses due to atmospheric attenuation phenomena. The European Space Agency (ESA) has recently embarked on a number of activities aimed at studying the effect of the typical mobile propagation impairments at Ka-band. This paper briefly summarizes ESA efforts in this field of research and presents preliminary experimental results.

  11. Ka-Band Atmospheric Phase Stability Measurements in Goldstone, CA; White Sands, NM; and Guam

    NASA Technical Reports Server (NTRS)

    Zemba, Michael J.; Morse, Jacquelynne Rose; Nessel, James A.

    2014-01-01

    As spacecraft communication links are driven to higher frequencies (e.g. Ka-band) both by spectrum congestion and the appeal of higher data rates, the propagation phenomena at these frequencies must be well characterized for effective system design. In particular, the phase stability of a site at a given frequency will govern whether or not the site is a practical location for an antenna array, particularly if uplink capabilities are desired. Propagation studies to characterize such phenomena must be done on a site-by-site basis due to the wide variety of climates and weather conditions at each ground terminal. Accordingly, in order to statistically characterize the atmospheric effects on Ka-Band links, site test interferometers (STIs) have been deployed at three of NASA's operational sites to directly measure each site's tropospheric phase stability. Using three years of results from these experiments, this paper will statistically characterize the simultaneous atmospheric phase noise measurements recorded by the STIs deployed at the following ground station sites: the Goldstone Deep Space Communications Complex near Barstow, CA; the White Sands Ground Terminal near Las Cruces, NM; and the Guam Remote Ground Terminal on the island of Guam.

  12. Operational experience in the use of 18 kA HTS current leads for Edipo

    NASA Astrophysics Data System (ADS)

    March, S.; Wesche, R.; Bruzzone, P.

    2014-05-01

    In spring 2013, the Edipo facility of CRPP was commissioned. The dipole is powered via two 18 kA HTS current leads, designed and manufactured at CRPP. As part of the Edipo commissioning framework, the operational parameters of the leads were implemented in the control system. The in-situ tests were found to be in good agreement with the tests performed without a background field in 2011. The leads consist of a conduction cooled HTS module, made of AgMgAu/Bi-2223 stacks, and a wire bundle heat exchanger. The heat exchanger is cooled by forced flow helium gas, the inlet temperature of which was measured to vary between 65 K and 85 K. During operation with field, the mass flow rate is a function of current (2.05 g/s per lead at full field, 12.35 T, 17.2 kA). Reduced cooling investigations showed that 0.31 g/s per lead is suitable for overnight standby and 0.2 g/s per lead for longer periods. For detection of and protection against quench in the HTS module, a threshold of 10 mV was found to be appropriate. The heat exchanger has a voltage protection threshold of 120 mV. The temperatures of the heat exchanger, the HTS, and the helium inlet temperature were monitored in order to provide a further layer of protection.

  13. Generation of Data-Rate Profiles of Ka-Band Deep-Space Links

    NASA Technical Reports Server (NTRS)

    Shambayati, Shervin

    2006-01-01

    A short report discusses a methodology for designing Ka-band Deep-Space-to- Earth radio-communication links. This methodology is oriented toward minimizing the effects of weather on the Ka-band telecommunication link by maximizing the expected data return subject to minimum link availability and a limited number of data rates. This methodology differs from the current standard practices in which a link is designed according to a margin policy for a given link availability at 10 elevation. In this methodology, one chooses a data-rate profile that will maximize the average data return over a pass while satisfying a minimum-availability requirement for the pass, subject to mission operational limitations expressed in terms of the number of data rates used during the pass. The methodology is implemented in an intelligent search algorithm that first finds the allowable data-rate profiles from the mission constraints, spacecraft-to-Earth distance, spacecraft EIRP (effective isotropic radiated power), and the applicable zenith atmospheric noise temperature distribution, and then selects the best data rate in terms of maximum average data return from the set of allowable data-rate profiles.

  14. A novel Ka-band coaxial transit-time oscillator with a four-gap buncher

    SciTech Connect

    Song, Lili; He, Juntao; Ling, Junpu

    2015-05-15

    A novel Ka-band coaxial transit-time oscillator (TTO) with a four-gap buncher is proposed and investigated. Simulation results show that an output power of 1.27 GW and a frequency of 26.18 GHz can be achieved with a diode voltage of 447 kV and a beam current of 7.4 kA. The corresponding power efficiency is 38.5%, and the guiding magnetic field is 0.6 T. Studies and analysis indicate that a buncher with four gaps can modulate the electron beam better than the three-gap buncher in such a Ka-band TTO. Moreover, power efficiency increases with the coupling coefficient between the buncher and the extractor. Further simulation demonstrates that power efficiency can reach higher than 30% with a guiding magnetic field of above 0.5 T. Besides, the power efficiency exceeds 30% in a relatively large range of diode voltage from 375 kV to 495 kV.

  15. Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

    NASA Astrophysics Data System (ADS)

    Pourmand, Ali; Marcantonio, Franco; Schulz, Hartmut

    2004-04-01

    High-resolution (one to two samples/ka) radionuclide proxy records from core 93KL in the northeastern Arabian Sea provide evidence for millennial climate variability over the past 110 ka. We interpret 230Th-normalized 232Th fluxes as a proxy for eolian input, and authigenic uranium concentrations as a proxy for past productivity. We attribute orbital and suborbital variations in both proxies to changes in the intensity of the southwest Indian Ocean monsoon. The highest 230Th-normalized 232Th fluxes occur at times that are consistent with the timing of the Younger Dryas, Heinrich events 1-7 and cold Dansgaard-Oeschger stadial events recorded in the GISP2 ice core. Such high dust fluxes may be due to a weakened southwest monsoon in conjunction with strengthened northwesterlies from the Arabian Peninsula and Mesopotamia. Authigenic uranium concentrations, on the other hand, are highest during warm Dansgaard-Oeschger interstadials when the southwest monsoon is intensified relative to the northwesterly winds. Our results also indicate that on orbital timescales maximum average eolian fluxes coincide with the timing of marine isotopic stage (MIS) 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5. Although the forcing mechanism(s) controlling suborbital variabilities in monsoonal intensity is still debated, our findings suggest an atmospheric teleconnection between the low-latitude southwest monsoon and North Atlantic climate.

  16. Paleoproductivity evolution in the West Philippine Sea during the last 700 ka

    NASA Astrophysics Data System (ADS)

    Tang, Zheng; Li, Tiegang; Chang, Fengming; Nan, Qingyun; Li, Qing

    2013-03-01

    In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka, the vertical gradient of Δδ13C in dissolved inorganic carbon (Δδ13C between those of foraminifera Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi) and planktonic foraminiferal assemblages were analysed in piston Core MD06-3047 retrieved from the Benham Rise (east of the Luzon Island). Paleoproductivity evolution in the West Philippine Sea during the last 700 ka is closely related to glacial-interglacial cycles and precession-controlled insolation. Controlling factors of paleoproductivity could have been both thermocline fluctuations related with ENSO-like processes and eolian input associated with East Asian winter monsoon, and the former could have been the primary factor. A higher productivity and a shallower thermocline coeval with the occurrence of low CO2 concentrations in the EPICA Dome C ice core might indicate that biological export production in the low-latitude could act as a significant sink in the global carbon cycle, and modify atmospheric CO2 concentrations. Spectral analysis further reveals that the paleoproductivity is mainly controlled by thermocline fluctuations subjected to ENSO processes responding to processional variability of insolation. High coherences in eccentricity, obliquity and precession periods further revealing the close link between thermocline fluctuations, paleoproductivity and atmospheric CO2 levels.

  17. Diagnostics for a 1.2 kA, 1 MeV, electron induction injector

    NASA Astrophysics Data System (ADS)

    Houck, T. L.; Anderson, D. E.; Eylon, S.; Henestroza, E.; Lidia, S. M.; Vanecek, D. L.; Westenskow, G. A.; Yu, S. S.

    1998-12-01

    We are constructing a 1.2 kA, 1 MeV, electron induction injector as part of the RTA program, a collaborative effort between LLNL and LBNL to develop relativistic klystrons for Two-Beam Accelerator applications. The RTA injector will also be used in the development of a high-gradient, low-emittance, electron source and beam diagnostics for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility. The electron source will be a 3.5″-diameter, thermionic, flat-surface, m-type cathode with a maximum shroud field stress of approximately 165 kV/cm. Additional design parameters for the injector include a pulse length of over 150 ns flat top (1% energy variation), and a normalized edge emittance of less than 200 π-mm-mr. Precise measurement of the beam parameters is required so that performance of the RTA injector can be confidently scaled to the 4 kA, 3 MeV, and 2-microsecond pulse parameters of the DARHT injector. Planned diagnostics include an isolated cathode with resistive divider for direct measurement of current emission, resistive wall and magnetic probe current monitors for measuring beam current and centroid position, capacitive probes for measuring A-K gap voltage, an energy spectrometer, and a pepperpot emittance diagnostic. Details of the injector, beam line, and diagnostics are presented.

  18. Experience of 12 kA / 16 V SMPS during the HTS Current Leads Test

    NASA Astrophysics Data System (ADS)

    Panchal, P.; Christian, D.; Panchal, R.; Sonara, D.; Purwar, G.; Garg, A.; Nimavat, H.; Singh, G.; Patel, J.; Tanna, V.; Pradhan, S.

    2017-04-01

    As a part of up gradation plans in SST-1 Tokamak, one pair of 3.3 kA rated prototype hybrid current leads were developed using Di-BSCCO as High Temperature Superconductors (HTS) and the copper heat exchanger. In order to validate the manufacturing procedure prior to go for series production of such current leads, it was recommended to test these current leads using dedicated and very reliable DC switch mode power supply (SMPS). As part of test facility, 12 kA, 16 VDC programmable SMPS was successfully installed, commissioned and tested. This power supply has special features such as modularity, N+1 redundancy, very low ripple voltage, precise current measurements with Direct Current Current Transformer, CC/CV modes with auto-crossover and auto-sequence programming. As a part of acceptance of this converter, A 5.8 mΩ water-cooled resistive dummy load and PLC based SCADA system is designed, developed for commissioning of power supply. The same power supply was used for the testing of the prototype HTS current leads. The paper describes the salient features and experience of state-of-art of power supply and results obtained from this converter during the HTS current leads test.

  19. Spaceflight Ka-Band High-Rate Radiation-Hard Modulator

    NASA Technical Reports Server (NTRS)

    Jaso, Jeffery M.

    2011-01-01

    A document discusses the creation of a Ka-band modulator developed specifically for the NASA/GSFC Solar Dynamics Observatory (SDO). This flight design consists of a high-bandwidth, Quadriphase Shift Keying (QPSK) vector modulator with radiation-hardened, high-rate driver circuitry that receives I and Q channel data. The radiationhard design enables SDO fs Ka-band communications downlink system to transmit 130 Mbps (300 Msps after data encoding) of science instrument data to the ground system continuously throughout the mission fs minimum life of five years. The low error vector magnitude (EVM) of the modulator lowers the implementation loss of the transmitter in which it is used, thereby increasing the overall communication system link margin. The modulator comprises a component within the SDO transmitter, and meets the following specifications over a 0 to 40 C operational temperature range: QPSK/OQPSK modulator, 300-Msps symbol rate, 26.5-GHz center frequency, error vector magnitude less than or equal to 10 percent rms, and compliance with the NTIA (National Telecommunications and Information Administration) spectral mask.

  20. Germline recessive mutations in PI4KA are associated with perisylvian polymicrogyria, cerebellar hypoplasia and arthrogryposis.

    PubMed

    Pagnamenta, Alistair T; Howard, Malcolm F; Wisniewski, Eva; Popitsch, Niko; Knight, Samantha J L; Keays, David A; Quaghebeur, Gerardine; Cox, Helen; Cox, Phillip; Balla, Tamas; Taylor, Jenny C; Kini, Usha

    2015-07-01

    Polymicrogyria (PMG) is a structural brain abnormality involving the cerebral cortex that results from impaired neuronal migration and although several genes have been implicated, many cases remain unsolved. In this study, exome sequencing in a family where three fetuses had all been diagnosed with PMG and cerebellar hypoplasia allowed us to identify regions of the genome for which both chromosomes were shared identical-by-descent, reducing the search space for causative variants to 8.6% of the genome. In these regions, the only plausibly pathogenic mutations were compound heterozygous variants in PI4KA, which Sanger sequencing confirmed segregated consistent with autosomal recessive inheritance. The paternally transmitted variant predicted a premature stop mutation (c.2386C>T; p.R796X), whereas the maternally transmitted variant predicted a missense substitution (c.5560G>A; p.D1854N) at a conserved residue within the catalytic domain. Functional studies using expressed wild-type or mutant PI4KA enzyme confirmed the importance of p.D1854 for kinase activity. Our results emphasize the importance of phosphoinositide signalling in early brain development. © The Author 2015. Published by Oxford University Press.

  1. Optical Spectroscopy Experiments on the 500 kA XP Pulsed-Power Generator

    SciTech Connect

    Bell, K. S.; Shelkovenko, T. A.; Pikuz, S. A.; McBride, R. D.; Blesener, I. C.; Knapp, P. F.; Hammer, D. A.; Greenly, J. B.; Maron, Y.

    2009-01-21

    Recent experiments on the 500 kA XP pulsed-power generator at Cornell University have explored the properties of optical spectra in single wires and wire arrays. In the single wire experiments, {approx}1% of the current from XP has been directed through the single wire. Spectra have been recorded using a half-meter spectrometer and a CCD camera located adjacent to the XP pulser. We are studying the visible spectra emitted by the wires and the background light from the machine hardware in order to identify the levels of current per wire for which visible spectroscopy might provide a means to measure magnetic field strength. We have also investigated the dependence of single wire visible spectra on the current, which was measured using a calibrated non-integrating Rogowski coil. UV and XUV diodes were employed to gather information about the temporal structure of the background and wire radiation. The line radiation in the spectra was recorded with wire currents at the few kA level. This is comparable to the first 10 ns of a 32-wire array experiment on 1 Ma generator and a 600-wire array at 20 MA.

  2. Channel characterisation for future Ka-band Mobile Satellite Systems and preliminary results

    NASA Astrophysics Data System (ADS)

    Sforza, Mario; Buonomo, Sergio; Arbesser-Rastburg, Bertram

    1994-08-01

    Mobile satellite systems (MSS) are presently designed or planned to operate, with the exception of OMNITRACKS, in the lower part of the frequency spectrum (UHF to S-bands). The decisions taken at the last World Administrative Radio Conference in 1992 to increase the allocated L- and S-bands for MSS services will only partly alleviate the problem of system capacity. In addition the use of L-and S-band frequencies generally requires large antenna apertures on board the satellite terminal side. The idea of exploiting the large spectrum resources available at higher frequencies (20-30 GHz) and the perspective of reducing user terminal size (and possibly price too) have spurred the interest of systems designers and planners. On the other hand, Ka-band frequencies suffer from increased slant path losses due to atmospheric attenuation phenomena. The European Space Agency (ESA) has recently embarked on a number of activities aimed at studying the effect of the typical mobile propagation impairments at Ka-band. This paper briefly summarizes ESA efforts in this field of research and presents preliminary experimental results.

  3. pH dependencies of the Tetrahymena ribozyme reveal an unconventional origin of an apparent pKa.

    PubMed

    Knitt, D S; Herschlag, D

    1996-02-06

    The L-21 ScaI ribozyme derived from the Tetrahymena thermophila pre-rRNA group I intron catalyzes a site-specific endonucleolytic cleavage of RNA, DNA, and chimeric RNA/DNA oligonucleotides: CCCUCUA5 + G-->CCCUCU + GA5. The pH-rate dependence was determined for the reaction of the E.G complex with the oligonucleotide substrate d(CCCUC)r(U)d(A5) [(kcat/Km)S conditions]. Although it was shown that the pH dependence is not affected by specific buffers, there is inhibition by specific monovalent cations. The intrinsic pH-rate dependence is log-linear with slope 1 below pH 7, displays an apparent pKa of 7.6, remains nearly level until pH 8.5, and then begins to fall. Two models to explain the apparent pKa were ruled out: (1) the pKa represents loss of a proton from the nucleophilic 3' OH of G, and (2) the pKa arises from a change in rate-limiting step from a pH-dependent to a pH-independent step. In addition, these models, or others involving a single titration, cannot account for the decrease in activity at high pH. A third, unconventional, model is consistent with all of the data. It involves inactivation of the ribozyme by any of several independent titrations of groups with pKa values considerably higher than the apparent pKa of 7.6. The data are consistent with loss of catalytic function upon release of a proton from any one of 19 independent sites with pKa = 9.4 (the unperturbed pKa of N1 of G and N3 of U in solution). Independent experiments investigating the effect of pH on different reaction steps supported this model and suggested the identity of some of the required protons. This mechanism of inactivation is expected to generally affect the behavior of RNAs at pH values removed from the pKa of the titrating bases.

  4. Indian Summer Monsoon: A Reconstruction Based on Terrestrial Archive During the Last 30 ka from Indian Subcontinent

    NASA Astrophysics Data System (ADS)

    Basavaiah, N.; Juyal, N.

    2012-04-01

    Reconstruction of Late Quaternary monsoon variability from the Indian subcontinent using terrestrial archives requires understanding long-term (104years) and short-term (102-103 years) climatic events. Here, we synthesize results gained from environmental magnetism technique to reconstruct Indian Summer Monsoon (ISM) using sediment samples from lakes, playas, loess and mudflats. Most importantly, efforts have been made to understand global, regional and local factors responsible for modulating the ISM at millennial and centennial time-scales. Our study delineates relict proglacial lakes, thus providing one of the most complete records of ISM variability from 25 ka till the beginning of Holocene. Mineral magnetic parameters and its derivatives in association with geochemistry suggest majority of proglacial lakes in the Central Himalaya emerged following the recession of the local Glacial Maximum (>20 ka). The global Last Glacial Maximum (LGM) is represented by appreciable decrease in magnetic susceptibility and magnetic remanence parameter S-ratio around 20 ka, indicating significant reduction in periglacial processes at the expense of aeolian activity in the Central Himalaya, which is manifested in the deposition of loess. The low frequency high magnitude millennial time-scale ISM variability from relict lake records of the Trans Himalaya compares well with δ18O record of GRIP ice core and the Northern Atlantic marine record. For example, the cooling event identified between 25 ka and 22 ka in the lake record corresponds with the cooling event in the GRIP ice core data and the Heinrich event-2 (H2). Similarly, the 16.5 ka - 14.5 ka cooling event corresponds with the Heinrich event-1 (H1) and compares well with the GRIP record. However, high frequency low magnitude centennial scale fluctuations in ISM is attributed to the unstable climatic conditions particularly between 17 ka and 13 ka. These fluctuations probably represent local perturbations influenced by

  5. VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability

    NASA Astrophysics Data System (ADS)

    Niinuma, Kotaro; Lee, Sang-Sung; Kino, Motoki; Sohn, Bong Won; Akiyama, Kazunori; Zhao, Guang-Yao; Sawada-Satoh, Satoko; Trippe, Sascha; Hada, Kazuhiro; Jung, Taehyun; Hagiwara, Yoshiaki; Dodson, Richard; Koyama, Shoko; Honma, Mareki; Nagai, Hiroshi; Chung, Aeree; Doi, Akihiro; Fujisawa, Kenta; Han, Myoung-Hee; Kim, Joeng-Sook; Lee, Jeewon; Lee, Jeong Ae; Miyazaki, Atsushi; Oyama, Tomoaki; Sorai, Kazuo; Wajima, Kiyoaki; Bae, Jaehan; Byun, Do-Young; Cho, Se-Hyung; Choi, Yoon Kyung; Chung, Hyunsoo; Chung, Moon-Hee; Han, Seog-Tae; Hirota, Tomoya; Hwang, Jung-Wook; Je, Do-Heung; Jike, Takaaki; Jung, Dong-Kyu; Jung, Jin-Seung; Kang, Ji-Hyun; Kang, Jiman; Kang, Yong-Woo; Kan-ya, Yukitoshi; Kanaguchi, Masahiro; Kawaguchi, Noriyuki; Kim, Bong Gyu; Kim, Hyo Ryoung; Kim, Hyun-Goo; Kim, Jaeheon; Kim, Jongsoo; Kim, Kee-Tae; Kim, Mikyoung; Kobayashi, Hideyuki; Kono, Yusuke; Kurayama, Tomoharu; Lee, Changhoon; Lee, Jung-Won; Lee, Sang Hyun; Minh, Young Chol; Matsumoto, Naoko; Nakagawa, Akiharu; Oh, Chung Sik; Oh, Se-Jin; Park, Sun-Youp; Roh, Duk-Gyoo; Sasao, Tetsuo; Shibata, Katsunori M.; Song, Min-Gyu; Tamura, Yoshiaki; Wi, Seog-Oh; Yeom, Jae-Hwan; Yun, Young Joo

    2014-12-01

    The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23-43 GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M 87. This is one of the initial results of KaVA's early operation. Our KaVA images reveal extended outflows with complex substructures such as knots and limb brightening, in agreement with previous Very Long Baseline Array (VLBA) observations. Angular resolutions are better than 1.4 and 0.8 mas at 23 and 43 GHz, respectively. KaVA achieves a high dynamic range of ˜ 1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN outflows, at least comparable to the best existing radio interferometric arrays.

  6. Accurate pKa calculation of the conjugate acids of alkanolamines, alkaloids and nucleotide bases by quantum chemical methods.

    PubMed

    Gangarapu, Satesh; Marcelis, Antonius T M; Zuilhof, Han

    2013-04-02

    The pKa of the conjugate acids of alkanolamines, neurotransmitters, alkaloid drugs and nucleotide bases are calculated with density functional methods (B3LYP, M08-HX and M11-L) and ab initio methods (SCS-MP2, G3). Implicit solvent effects are included with a conductor-like polarizable continuum model (CPCM) and universal solvation models (SMD, SM8). G3, SCS-MP2 and M11-L methods coupled with SMD and SM8 solvation models perform well for alkanolamines with mean unsigned errors below 0.20 pKa units, in all cases. Extending this method to the pKa calculation of 35 nitrogen-containing compounds spanning 12 pKa units showed an excellent correlation between experimental and computational pKa values of these 35 amines with the computationally low-cost SM8/M11-L density functional approach. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. The IUPAC aqueous and non-aqueous experimental pKa data repositories of organic acids and bases.

    PubMed

    Slater, Anthony Michael

    2014-10-01

    Accurate and well-curated experimental pKa data of organic acids and bases in both aqueous and non-aqueous media are invaluable in many areas of chemical research, including pharmaceutical, agrochemical, specialty chemical and property prediction research. In pharmaceutical research, pKa data are relevant in ligand design, protein binding, absorption, distribution, metabolism, elimination as well as solubility and dissolution rate. The pKa data compilations of the International Union of Pure and Applied Chemistry, originally in book form, have been carefully converted into computer-readable form, with value being added in the process, in the form of ionisation assignments and tautomer enumeration. These compilations offer a broad range of chemistry in both aqueous and non-aqueous media and the experimental conditions and original reference for all pKa determinations are supplied. The statistics for these compilations are presented and the utility of the computer-readable form of these compilations is examined in comparison to other pKa compilations. Finally, information is provided about how to access these databases.

  8. On the Performance of Adaptive Data Rate over Deep Space Ka-Bank Link: Case Study Using Kepler Data

    NASA Technical Reports Server (NTRS)

    Gao, Jay L.

    2016-01-01

    Future missions envisioned for both human and robotic exploration demand increasing communication capacity through the use of Ka-band communications. The Ka-band channel, being more sensitive to weather impairments, presents a unique trade-offs between data storage, latency, data volume and reliability. While there are many possible techniques for optimizing Ka-band operations such as adaptive modulation and coding and site-diversity, this study focus exclusively on the use of adaptive data rate (ADR) to achieve significant improvement in the data volume-availability tradeoff over a wide range of link distances for near Earth and Mars exploration. Four years of Kepler Ka-band downlink symbol signal-to-noise (SNR) data reported by the Deep Space Network were utilized to characterize the Ka-band channel statistics at each site and conduct various what-if performance analysis for different link distances. We model a notional closed-loop adaptive data rate system in which an algorithm predicts the channel condition two-way light time (TWLT) into the future using symbol SNR reported in near-real time by the ground receiver and determines the best data rate to use. Fixed and adaptive margins were used to mitigate errors in channel prediction. The performance of this closed-loop adaptive data rate approach is quantified in terms of data volume and availability and compared to the actual mission configuration and a hypothetical, optimized single rate configuration assuming full a priori channel knowledge.

  9. Abrupt climate change around 4 ka BP: Role of the Thermohaline circulation as indicated by a GCM experiment

    NASA Astrophysics Data System (ADS)

    Wang, Shaowu; Zhou, Tianjun; Cai, Jingning; Zhu, Jinhong; Xie, Zhihui; Gong, Daoyi

    2004-04-01

    A great deal of palaeoenvironmental and palaeoclimatic evidence suggests that a predominant temperature drop and an aridification occurred at ca. 4.0 ka BP. Palaeoclimate studies in China support this dedution. The collapse of ancient civilizations at ca. 4.0 ka BP in the Nile Valley and Mesopotamia has been attributed to climate-induced aridification. A widespread alternation of the ancient cultures was also found in China at ca. 4.0 ka BP in concert with the collapse of the civilizations in the Old World. Palaeoclimatic studies indicate that the abrupt climate change at 4.0 ka BP is one of the realizations of the cold phase in millennial scale climate oscillations, which may be related to the modulation of the Thermohaline Circulation (THC) over the Atlantic Ocean. Therefore, this study conducts a numerical experiment of a GCM with SST forcing to simulate the impact of the weakening of the THC. Results show a drop in temperature from North Europe, the northern middle East Asia, and northern East Asia and a significant reduction of precipitation in East Africa, the Middle East, the Indian Peninsula, and the Yellow River Valley. This seems to support the idea that coldness and aridification at ca. 4.0 ka BP was caused by the weakening of the THC.

  10. The IUPAC aqueous and non-aqueous experimental pKa data repositories of organic acids and bases

    NASA Astrophysics Data System (ADS)

    Slater, Anthony Michael

    2014-10-01

    Accurate and well-curated experimental pKa data of organic acids and bases in both aqueous and non-aqueous media are invaluable in many areas of chemical research, including pharmaceutical, agrochemical, specialty chemical and property prediction research. In pharmaceutical research, pKa data are relevant in ligand design, protein binding, absorption, distribution, metabolism, elimination as well as solubility and dissolution rate. The pKa data compilations of the International Union of Pure and Applied Chemistry, originally in book form, have been carefully converted into computer-readable form, with value being added in the process, in the form of ionisation assignments and tautomer enumeration. These compilations offer a broad range of chemistry in both aqueous and non-aqueous media and the experimental conditions and original reference for all pKa determinations are supplied. The statistics for these compilations are presented and the utility of the computer-readable form of these compilations is examined in comparison to other pKa compilations. Finally, information is provided about how to access these databases.

  11. Deep Space Ka-band Link Management and the MRO Demonstration: Long-term Weather Statistics Versus Forecasting

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz; Shambayati, Shervin; Slobin, Stephen

    2004-01-01

    During the last 40 years, deep space radio communication systems have experienced a move toward shorter wavelengths. In the 1960s a transition from L- to S-band occurred which was followed by a transition from S- to X-band in the 1970s. Both these transitions provided deep space links with wider bandwidths and improved radio metrics capability. Now, in the 2000s, a new change is taking place, namely a move to the Ka-band region of the radio frequency spectrum. Ka-band will soon replace X-band as the frequency of choice for deep space communications providing ample spectrum for the high data rate requirements of future missions. The low-noise receivers of deep space networks have a great need for link management techniques that can mitigate weather effects. In this paper, three approaches for managing Ka-band Earth-space links are investigated. The first approach uses aggregate annual statistics, the second one uses monthly statistics, and the third is based on the short-term forecasting of the local weather. An example of weather forecasting for Ka-band link performance prediction is presented. Furthermore, spacecraft commanding schemes suitable for Ka-band link management are investigated. Theses schemes will be demonstrated using NASA's Mars Reconnaissance Orbiter (MRO) spacecraft in the 2007 to 2008 time period, and the demonstration findings will be reported in a future publication.

  12. Internal standard capillary electrophoresis as a high-throughput method for pKa determination in drug discovery and development.

    PubMed

    Cabot, Joan M; Fuguet, Elisabet; Rosés, Martí

    2014-10-13

    A novel high-throughput method for determining acidity constants (pKa) by capillary electrophoresis (CE) is developed. The method, based on the use of an internal standard (IS-CE), is implemented as a routine method for accurate experimental pKa determination of drugs undergoing physicochemical measurements in drug discovery laboratories. Just two electropherograms at 2 different pH values are needed to calculate an acidity constant. Several ISs can be used in the same buffer and run to enhance precision. With 3 ISs, for example, the pKa of the test compound (TC) can be obtained in triplicate in less than 3 min of electrophoresis. It has been demonstrated that the IS-CE method eliminates some systematic errors, maintaining, or even increasing the precision of the results compared with other methods. Furthermore, pH buffer instability during electrophoretic runs is not a problem in the IS-CE method. It is also proved that after 16 h of electroseparation using the same buffer vial, pH may change by around one unit; but the pKa calculated by the IS-CE method remains constant. Thus, IS-CE is a powerful high-throughput method for pKa determination in drug discovery and development.

  13. Deep Space Ka-band Link Management and the MRO Demonstration: Long-term Weather Statistics Versus Forecasting

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz; Shambayati, Shervin; Slobin, Stephen

    2004-01-01

    During the last 40 years, deep space radio communication systems have experienced a move toward shorter wavelengths. In the 1960s a transition from L- to S-band occurred which was followed by a transition from S- to X-band in the 1970s. Both these transitions provided deep space links with wider bandwidths and improved radio metrics capability. Now, in the 2000s, a new change is taking place, namely a move to the Ka-band region of the radio frequency spectrum. Ka-band will soon replace X-band as the frequency of choice for deep space communications providing ample spectrum for the high data rate requirements of future missions. The low-noise receivers of deep space networks have a great need for link management techniques that can mitigate weather effects. In this paper, three approaches for managing Ka-band Earth-space links are investigated. The first approach uses aggregate annual statistics, the second one uses monthly statistics, and the third is based on the short-term forecasting of the local weather. An example of weather forecasting for Ka-band link performance prediction is presented. Furthermore, spacecraft commanding schemes suitable for Ka-band link management are investigated. Theses schemes will be demonstrated using NASA's Mars Reconnaissance Orbiter (MRO) spacecraft in the 2007 to 2008 time period, and the demonstration findings will be reported in a future publication.

  14. High-Resolution Speleothem Records of the Indian Ocean Monsoon Variability of the Last 6 ka and 0,5 ka From Soqotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    de Geest, P.; Verheyden, S.; Cheng, H.; Edwards, L. R.; Keppens, E.

    2004-12-01

    Soqotra is an arid tropical island in the Indian Ocean, situated between the Horn of Africa and the Arabian Peninsula. The inter-tropical convergence zone (ITCZ) passes there twice each year, resulting in a bi-annual rainy season. High-resolution \\delta18O and \\delta13C ratios of speleothems from two different caves are used to reconstruct changes in the Monsoon intensity and/or variability. Based on 10 TIMS 234U/230Th dating, two active speleothems from Hoq (S-STM1) and Kazekas Caves (S-STM5) have formed over a period of 6 ka BP and 0,5 ka BP, respectively. To obtain a detailed climate reconstruction more than 1000 \\delta13C and \\delta18O measurements were carried out, providing a time resolution between 2,5 and 10 years. In S-STM1 \\delta18O -values range between -4,5\\permil and -1,5\\permil and \\delta13C -values between -10,5\\permil and -5,5\\permil; while for S-STM5 these values range respectively between -4\\permil and -2\\permil and -7\\permil and -3\\permil (vs VPDB). Based on the comparison between \\delta18O excursions and historical meteorological data, the amount of precipitation is reflected in the \\delta18O signal. Different mechanisms for the \\delta13C are considered, such as a diminution of the C4-type vegetation during droughts, resulting in more positive \\delta13C -value or kinetic effects during the calcification process itself. Throughout the time series, co-variation occur between \\delta13C and \\delta18O -values (R2= 0,69) exhibiting long term (millennial) and short term (decadal) variations. In both stalagmites, layers of white porous calcite (WPC) (0,1-0,5mm) and dark dense calcite (DDC) (0,01-0,1mm) alternate, most probably due to seasonal variations. The WPC has more positive \\delta13C and \\delta18O -values, while the DDC shows more negative values, clearly demonstrated by high-resolution micro sampling up to a monthly to bi-weekly resolution. A positive correlation between the greyscale variations in the calcite fabric, the

  15. Calibration of the KA Band Tracking of the Bepi-Colombo Spacecraft (more Experiment)

    NASA Astrophysics Data System (ADS)

    Barriot, J.; Serafini, J.; Sichoix, L.

    2013-12-01

    The radiosciences Bepi-Colombo MORE experiment will use X/X, X/Ka and Ka/Ka band radio links to make accurate measurements of the spacecraft range and range rate. Tropospheric zenith wet delays range from 1.5 cm to 10 cm, with high variability (less than 1000 s) and will impair these accurate measurements. Conditions vary from summer (worse) to winter (better), from day (worse) to night (better). These wet delays cannot be estimated from ground weather measurements and alternative calibration methods should be used in order to cope with the MORE requirements (no more than 3 mm at 1000 s). Due to the Mercury orbit, MORE measurements will be performed by daylight and more frequently in summer than in winter (from Northern hemisphere). Two systems have been considered to calibrate this wet delay: Water Vapor Radiometers (WVRs) and GPS receivers. The Jet Propulsion Laboratory has developed a new class of WVRs reaching a 5 percent accuracy for the wet delay calibration (0.75 mm to 5 mm), but these WVRs are expensive to build and operate. GPS receivers are also routinely used for the calibration of data from NASA Deep Space probes, but several studies have shown that GPS receivers can give good calibration (through wet delay mapping functions) for long time variations, but are not accurate enough for short time variations (100 to 1000 s), and that WVRs must be used to efficiently calibrate the wet troposphere delays over such time spans. We think that such a calibration could be done by assimilating data from all the GNSS constellations (GPS, GLONASS, Galileo, Beidou and IRNSS) that will be available at the time of the Bepi-Colombo arrival at Mercury (2021), provided that the underlying physics of the turbulent atmosphere and evapotranspiration processes are properly taken into account at such time scales. This implies to do a tomographic image of the troposphere overlying each Deep Space tracking station at time scales of less than 1000 s. For this purpose, we have

  16. NALPS: a precisely dated European climate record 120-60 ka

    NASA Astrophysics Data System (ADS)

    Boch, R.; Cheng, H.; Spötl, C.; Edwards, R. L.; Wang, X.; Häuselmann, Ph.

    2011-11-01

    Accurate and precise chronologies are essential in understanding the rapid and recurrent climate variations of the Last Glacial - known as Dansgaard-Oeschger (D-O) events - found in the Greenland ice cores and other climate archives. The existing chronological uncertainties during the Last Glacial, however, are still large. Radiometric age data and stable isotopic signals from speleothems are promising to improve the absolute chronology. We present a record of several precisely dated stalagmites from caves located at the northern rim of the Alps (NALPS), a region that favours comparison with the climate in Greenland. The record covers most of the interval from 120 to 60 ka at an average temporal resolution of 2 to 22 yr and 2σ-age uncertainties of ca. 200 to 500 yr. The rapid and large oxygen isotope shifts of 1 to 4.5‰ occurred within decades to centuries and strongly mimic the Greenland D-O pattern. Compared to the updated Greenland ice-core timescale (GICC05modelext) the NALPS record confirms the timing of rapid warming and cooling transitions between 118 and 106 ka, but suggests younger ages for D-O events between 106 and 60 ka. As an exception, the timing of the rapid transitions into and out of the stadial following GI 22 is earlier in NALPS than in the Greenland ice-core timescale. In addition, there is a discrepancy in the duration of this stadial between the ice-core and the stalagmite chronology (ca. 2900 vs. 3650 yr). The short-lived D-O events 18 and 18.1 are not recorded in NALPS, provoking questions with regard to the nature and the regional expression of these events. NALPS resolves recurrent short-lived climate changes within the cold Greenland stadial and warm interstadial successions, i.e. abrupt warming events preceding GI 21 and 23 (precursor-type events) and at the end of GI 21 and 25 (rebound-type events), as well as intermittent cooling events during GI 22 and 24. Such superimposed events have not yet been documented outside Greenland.

  17. Chemostratigraphy of Products of The Astroni Activity (4.1-3.8 Ka, Campi Flegrei, Italy)

    NASA Astrophysics Data System (ADS)

    D'Antonio, M.; Isaia, R.; Bolognesi, L.; Civetta, L.; di Vito, M. A.; Orsi, G.; Tonarini, S.

    The Astroni volcano is a well-preserved tuff-ring in the NE sector of the Neapolitan Yellow Tuff (NYT, 12 ka BP) caldera, the youngest of the two major collapses which generated the nested Campi Flegrei caldera (CFc). The volcano has been characterised by a long-lasting activity in the age range 4.1-3.8 ka BP, generating 7 pyroclastic and 2 lava units. Thus the whole rock sequence is subdivided in Units named 1 through 9 upsection. Detailed petrographical, geochemical and isotopic investigations have been carried out on these rocks (pumice and scoria fragments, lavas) which have tex- tures variable from sub-aphyric to highly porphyritic to glomeroporphyritic. The phe- nocrysts are plagioclase, alkali-feldspar, Mg- to Fe-rich zoned clinopyroxene, biotite, opaques and apatite, in order of decreasing abundance. Their abundance is variable along the sequence: lower in Units 1 to 4, higher in Units 5 to 9. The groundmass ranges from hypocrystalline to hyalopilitic in pumice and scoria fragments, to felty in the lavas. The analysed rocks are nepheline normative trachyte to alkali-trachyte. Whole-rock major and trace element contents vary regularly with D.I. (71.5 and 81.0), suggesting fractional crystallization of mineral phases in a magma evolving from tra- chyte to alkali-trachyte. However, whole-rock 87Sr/86Sr values range from 0.70725 to 0.70755. It is noteworthy that the extreme detected values match those of the prod- ucts of the largest caldera-forming eruptions: the Campanian Ignimbrite (37 ka) and NYT, respectively. The 87Sr/86Sr ratio is variable with the chemical composition of the products, suggesting open-system evolution process acting in the magma reser- voir feeding the Astroni volcano. Furthermore, the chemostratigraphy of the Astroni sequence shows that activity started with extrusion of more evolved, alkali-trachytic magma (DI about 80-81; 87Sr/86Sr = 0.70755), becoming progressively less differ- entiated and less radiogenic up to emplacement of the

  18. 625 kb microduplication at Xp22.12 including RPS6KA3 in a child with mild intellectual disability.

    PubMed

    Bertini, Veronica; Cambi, Francesca; Bruno, Rossella; Toschi, Benedetta; Forli, Francesca; Berrettini, Stefano; Simi, Paolo; Valetto, Angelo

    2015-12-01

    Here, we report on a patient with a 625 kb duplication in Xp22.12, detected by array comparative genomic hybridization (CGH). The duplicated region contains only one gene, RPS6KA3, that results in partial duplication. The same duplication was present in his mother and his maternal uncle. This partial duplication inhibits the RPS6KA3 expression, mimicking the effect of loss-of-function mutations associated with Coffin-Lowry syndrome (CLS). The phenotype of the patient here presented is not fully evocative of this syndrome because he does not present some of the facial, digital and skeletal abnormalities that are considered the main diagnostic features of CLS. This case is one of the few examples where RPS6KA3 mutations are associated with a non-specific X-linked mental retardation.

  19. Bandwidth Efficient Modulation and Coding Techniques for NASA's Existing Ku/Ka-Band 225 MHz Wide Service

    NASA Technical Reports Server (NTRS)

    Gioannini, Bryan; Wong, Yen; Wesdock, John

    2005-01-01

    The National Aeronautics and Space Administration (NASA) has recently established the Tracking and Data Relay Satellite System (TDRSS) K-band Upgrade Project (TKUP), a project intended to enhance the TDRSS Ku-band and Ka-band Single Access Return 225 MHz (Ku/KaSAR-225) data service by adding the capability to process bandwidth efficient signal design and to replace the White Sand Complex (WSC) KSAR high data rate ground equipment and high rate switches which are nearing obsolescence. As a precursor to this project, a modulation and coding study was performed to identify signal structures which maximized the data rate through the Ku/KaSAR-225 channel, minimized the required customer EIRP and ensured acceptable hardware complexity on the customer platform. This paper presents the results and conclusions of the TKUP modulation and coding study.

  20. Morphotectonic control of the Białka drainage basin (Central Carpathians): Insights from DEM and morphometric analysis.

    NASA Astrophysics Data System (ADS)

    Wołosiewicz, Bartosz

    2016-06-01

    The Białka river valley is directly related to a deep NNW-SSE oriented fault zone. According to the results of previous morphometric analyses, the Białka drainage basin is one of the most tectonically active zones in the Central Carpathians. It is also located within an area of high seismic activity. In this study Digital Elevation Model (DEM) based, morphometric analyses were used to investigate the morphotectonic conditions of the watershed. The results reveal the relationships between the main tectonic feature and the landforms within the research area. The lineaments, as obtained from the classified aspect map, seem to coincide with the orientation of the main structures as well as the trends revealed by the theoretical Riedel-Skempton shear model. Base-level and isolong maps support the conclusion that the Białka and Biały Dunajec fault zones exert a strong influence on the morphology of the adjacent area.

  1. Theoretical pKa prediction of the α-phosphate moiety of uridine 5‧-diphosphate-GlcNAc

    NASA Astrophysics Data System (ADS)

    Vipperla, Bhavaniprasad; Griffiths, Thomas M.; Wang, Xingyong; Yu, Haibo

    2017-01-01

    The pKa value of the α-phosphate moiety of uridine 5‧-diphosphate-GlcNAc (UDP-GlcNAc) has been successfully calculated using density functional theory methods in conjunction with the Polarizable Continuum Models. Theoretical methods were benchmarked over a dataset comprising of alkyl phosphates. B3LYP/6-31+G(d,p) calculations using SMD solvation model provide excellent agreement with the experimental data. The predicted pKa for UDP-GlcNAc is consistent with most recent NMR studies but much higher than what it has long been thought to be. The importance of this study is evident that the predicted pKa for UDP-GlcNAc supports its potential role as a catalytic base in the substrate-assisted biocatalysis.

  2. Acidity Constant (pKa ) Calculation of Large Solvated Dye Molecules: Evaluation of Two Advanced Molecular Dynamics Methods.

    PubMed

    De Meyer, Thierry; Ensing, Bernd; Rogge, Sven M J; De Clerck, Karen; Meijer, Evert Jan; Van Speybroeck, Veronique

    2016-11-04

    pH-Sensitive dyes are increasingly applied on polymer substrates for the creation of novel sensor materials. Recently, these dye molecules were modified to form a covalent bond with the polymer host. This had a large influence on the pH-sensitive properties, in particular on the acidity constant (pKa ). Obtaining molecular control over the factors that influence the pKa value is mandatory for the future intelligent design of sensor materials. Herein, we show that advanced molecular dynamics (MD) methods have reached the level at which the pKa values of large solvated dye molecules can be predicted with high accuracy. Two MD methods were used in this work: steered or restrained MD and the insertion/deletion scheme. Both were first calibrated on a set of phenol derivatives and afterwards applied to the dye molecule bromothymol blue. Excellent agreement with experimental values was obtained, which opens perspectives for using these methods for designing dye molecules.

  3. Deprotonation yields, pKa, and aci-nitro decay rates in some substituted o-nitrobenzaldehydes.

    PubMed

    Abbruzzetti, Stefania; Carcelli, Mauro; Rogolino, Dominga; Viappiani, Cristiano

    2003-07-01

    In this paper we report the deprotonation yields, the pKa, and decay kinetics of the aci-nitro intermediates of some substituted 2-nitrobenzaldehydes that can be used as photoactivatable caged proton compounds. The decay of the aci-nitro absorbance for 2-nitrobenzaldehyde occurs within a few nanoseconds from photoexcitation. Addition of electron donating methoxy substituents at positions 4 and 5 leads to lower deprotonation yields, higher pKa, and slower decays of the aci-nitro intermediates. On the contrary, the decay rate is accelerated by the introduction of an electron-withdrawing Cl atom at position 4 in the phenyl ring, with little influence on the deprotonation yield and pKa of the aci-nitro intermediate.

  4. Bandwidth Efficient Modulation and Coding Techniques for NASA's Existing Ku/Ka-Band 225 MHz Wide Service

    NASA Technical Reports Server (NTRS)

    Gioannini, Bryan; Wong, Yen; Wesdock, John

    2005-01-01

    The National Aeronautics and Space Administration (NASA) has recently established the Tracking and Data Relay Satellite System (TDRSS) K-band Upgrade Project (TKUP), a project intended to enhance the TDRSS Ku-band and Ka-band Single Access Return 225 MHz (Ku/KaSAR-225) data service by adding the capability to process bandwidth efficient signal design and to replace the White Sand Complex (WSC) KSAR high data rate ground equipment and high rate switches which are nearing obsolescence. As a precursor to this project, a modulation and coding study was performed to identify signal structures which maximized the data rate through the Ku/KaSAR-225 channel, minimized the required customer EIRP and ensured acceptable hardware complexity on the customer platform. This paper presents the results and conclusions of the TKUP modulation and coding study.

  5. p Ka calculation for monoprotonated bipiperidine, bimorpholine and their derivatives in H 2O and MeCN

    NASA Astrophysics Data System (ADS)

    Uudsemaa, Merle; Kanger, Tõnis; Lopp, Margus; Tamm, Toomas

    2010-01-01

    Density-functional theory has been used to estimate the proton affinity (PA) and the acidity constants p Ka of monoprotonated bipiperidine, bimorpholine and their derivatives in water and in acetonitrile (MeCN). Five different conformations of derivatives of bimorpholine and bipiperidine were explored. Monoprotonated bimorpholine has lower p Ka values (9.1 in H 2O and 17.4 in MeCN) than monoprotonated bipiperidine (12.8 in H 2O and 21.0 in MeCN). For N-iPr derivatives of bimorpholine, the p Ka values are 8.8 in H 2O and 17.0 in MeCN and for N-iPr derivatives of bipiperidine the values are 12.5 in H 2O and 20.8 in MeCN.

  6. Operating experience with the 50 MeV 10kA ATA power conditioning system

    SciTech Connect

    Rogers, D.; Lee, F.D.; Newton, M.; Reginato, L.L.; Smith, M.E.

    1984-06-01

    The Advanced Test Accelerator (ATA) has been operational for over one year and has achieved full parameters in the power conditioning system. The pulsed power system has been previously described, however, during the past year of operation a considerable amount of statistical data has been accumulated on the 211 gas blown spark gaps that perform the main switching function in the ATA. These spark gaps were designed for 250kV, 40 kA and 70ns pulse. The parameter that made this spark gap somewhat unique was the requirement that it be able to provide a burst of ten pulses at one kilohertz with an average repetition rate of 5Hz. 2 references, 7 figures.

  7. Thermal Deformation and RF Performance Analyses for the SWOT Large Deployable Ka-Band Reflectarray

    NASA Technical Reports Server (NTRS)

    Fang, H.; Sunada, E.; Chaubell, J.; Esteban-Fernandez, D.; Thomson, M.; Nicaise, F.

    2010-01-01

    A large deployable antenna technology for the NASA Surface Water and Ocean Topography (SWOT) Mission is currently being developed by JPL in response to NRC Earth Science Tier 2 Decadal Survey recommendations. This technology is required to enable the SWOT mission due to the fact that no currently available antenna is capable of meeting SWOT's demanding Ka-Band remote sensing requirements. One of the key aspects of this antenna development is to minimize the effect of the on-orbit thermal distortion to the antenna RF performance. An analysis process which includes: 1) the on-orbit thermal analysis to obtain the temperature distribution; 2) structural deformation analysis to get the geometry of the antenna surface; and 3) the RF performance with the given deformed antenna surface has been developed to accommodate the development of this antenna technology. The detailed analysis process and some analysis results will be presented and discussed by this paper.

  8. S/Ka Dichroic Plate with Rounded Corners for NASA's 34-m Beam-Waveguide Antenna

    NASA Astrophysics Data System (ADS)

    Veruttipong, W.; Khayatian, B.; Imbriale, W.

    2016-02-01

    An S-/Ka-band frequency selective surface (FSS) or a dichroic plate is designed, manufactured, and tested for use in NASA's Deep Space Network (DSN) 34-m beam-waveguide (BWG) antennas. Due to its large size, the proposed dichroic incorporates a new design feature: waveguides with rounded corners to cut cost and allow ease of manufacturing the plate. The dichroic is designed using an analysis that combines the finite-element method (FEM) for arbitrarily shaped guides with the method of moments and Floquet mode theory for periodic structures. The software was verified by comparison with previously measured and computed dichroic plates. The large plate was manufactured with end-mill machining. The RF performance was measured and is in excellent agreement with the analytical results. The dichroic has been successfully installed and is operational at DSS-24, DSS-34, and DSS-54.

  9. Estimation of currents using SARAL/AltiKa in the coastal regions of India

    NASA Astrophysics Data System (ADS)

    Chaudhary, A.; Agarwal, N.; Sharma, R.

    2014-12-01

    The present study explores the possibility of deriving the across track currents along the Indian coastal region from SARAL/AltiKa mission. The across track surface geostrophic currents obtained from along track SARAL altimeter data are directly compared (qualitatively) with high frequency (HF) radar observations of surface currents in the Bay of Bengal. The velocity component from HF radar which is perpendicular to the altimeter tracks is considered. Since the ageostrophic velocity contribution is ignored for the moment, the surface geostrophic currents SARAL compare well only under low wind conditions. Due to high along track resolution of SARAL there are large variations in velocity which are not captured by the HF radar observations. In general, the magnitude and variations in surface currents derived from SARAL altimeter are comparable with HF radar observations.

  10. An active K/Ka-band antenna array for the NASA ACTS mobile terminal

    NASA Technical Reports Server (NTRS)

    Tulintseff, A.; Crist, R.; Densmore, Art; Sukamto, L.

    1993-01-01

    An active K/Ka-band antenna array is currently under development for NASA's ACTS Mobile Terminal (AMT). The AMT task will demonstrate voice, data, and video communications to and from the AMT vehicle in Los Angeles, California, and a base station in Cleveland, Ohio, via the ACTS satellite at 30 and 20 GHz. Satellite tracking for the land-mobile vehicular antenna system involves 'mechanical dithering' of the antenna, where the antenna radiates a fixed beam 46 deg. above the horizon. The antenna is to transmit horizontal polarization and receive vertical polarization at 29.634 plus or minus 0.15 GHz and 19.914 plus or minus 0.15 GHz, respectively. The active array will provide a minimum of 22 dBW EIRP transmit power density and a -8 dB/K deg. receive sensitivity.

  11. Thermal Deformation and RF Performance Analyses for the SWOT Large Deployable Ka-Band Reflectarray

    NASA Technical Reports Server (NTRS)

    Fang, H.; Sunada, E.; Chaubell, J.; Esteban-Fernandez, D.; Thomson, M.; Nicaise, F.

    2010-01-01

    A large deployable antenna technology for the NASA Surface Water and Ocean Topography (SWOT) Mission is currently being developed by JPL in response to NRC Earth Science Tier 2 Decadal Survey recommendations. This technology is required to enable the SWOT mission due to the fact that no currently available antenna is capable of meeting SWOT's demanding Ka-Band remote sensing requirements. One of the key aspects of this antenna development is to minimize the effect of the on-orbit thermal distortion to the antenna RF performance. An analysis process which includes: 1) the on-orbit thermal analysis to obtain the temperature distribution; 2) structural deformation analysis to get the geometry of the antenna surface; and 3) the RF performance with the given deformed antenna surface has been developed to accommodate the development of this antenna technology. The detailed analysis process and some analysis results will be presented and discussed by this paper.

  12. Cryo-Cooled Sapphire Oscillator for the Cassini Ka-Band Experiment

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Dick, G. John

    1997-01-01

    We present features for an ultra-stable sapphire cryogenic oscillator which has been designed to support the Cassini Ka-band Radio Science experiment. The design of this standard is new in several respects. It is cooled by a commercial cryocooler instead of liquid cryogens to increase operating time, and it uses a technology to adjust the temperature turn-over point to extend the upper operating temperature limit and to enable construction of multiple units with uniform operating characteristics. Objectives are 3 x 10(exp -15) stability for measuring times 1 second less than or equal to (tau) less than or equal to 100 seconds, phase noise of -85 dBc/Hz from offset frequencies of 1 Hz to 1000 Hz at 10 GHz carrier frequency, and a one year continuous operating period.

  13. Reconstruction of past climate variability in SE Spain between 14 and 8 ka

    NASA Astrophysics Data System (ADS)

    Budsky, Alexander; Scholz, Denis; Mertz-Kraus, Regina; Christoph, Spötl; Gibert, Luis; Jochum, Klaus Peter; Andreae, Meinrat O.

    2016-04-01

    In comparison to the large climatic oscillations during the Pleistocene, Holocene climate only underwent minor changes. Nevertheless, cyclic climate changes also occurred during the Holocene. The Bond events, represented by the presence of cold, ice-bearing waters from the north of Iceland as far south as the latitude of Britain, occurred at a cyclicity of about 1500 a and were particularly pronounced during the Early Holocene. However, their climatic impact on the terrestrial realm was not consistent over Europe, in particular with respect to changes in precipitation. Here we present a precisely dated high-resolution flowstone record from Cueva Victoria, SE Spain, a site well suited to study the competing influence of the Atlantic and Mediterranean Sea on the southern Iberian Peninsula. We sampled several flowstones with a thickness of up to 60 cm. 230Th/U-dating has shown that these deposits mainly formed during relatively warm climate intervals of the Middle and Late Pleistocene, i.e. interglacials and interstadials (Budsky et al., 2015; Gibert et al., 2016). Here we focus on a short (11 cm) flowstone sequence from the Holocene with a high temporal resolution (centennial for stable isotopes and annual for trace elements). The flowstone grew between 14 and ca. 8 ka b2k. The decreasing trend of the δ18O and δ13C values as well as of several trace elements between 12 and 11 ka b2k reflects an increase in temperature and precipitation at the beginning of the Holocene. In particular, Sr and Mg show a trend towards low and stable values. Subsequently, from 10.5 to 8 ka b2k, the δ13C values show a high variability (-11 to -4), whereas the δ18O values are rather stable (between -6 and -7). Maxima in δ13C are interpreted as drier conditions in response to Bond events. These events possibly led to a change of the atmospheric circulation, affecting the vegetation in SE Spain, which evolved towards an open C3 vegetation at ca. 8 ka b2k concomitant with drier conditions

  14. High Efficiency Ka-Band Solid State Power Amplifier Waveguide Power Combiner

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.; Simons, Rainee N.; Chevalier, Christine T.; Freeman, Jon C.

    2010-01-01

    A novel Ka-band high efficiency asymmetric waveguide four-port combiner for coherent combining of two Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifiers (SSPAs) having unequal outputs has been successfully designed, fabricated and characterized over the NASA deep space frequency band from 31.8 to 32.3 GHz. The measured combiner efficiency is greater than 90 percent, the return loss greater than 18 dB and input port isolation greater than 22 dB. The manufactured combiner was designed for an input power ratio of 2:1 but can be custom designed for any arbitrary power ratio. Applications considered are NASA s space communications systems needing 6 to 10 W of radio frequency (RF) power. This Technical Memorandum (TM) is an expanded version of the article recently published in Institute of Engineering and Technology (IET) Electronics Letters.

  15. Enhancing End-to-End Performance of Information Services Over Ka-Band Global Satellite Networks

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B.; Glover, Daniel R.; Ivancic, William D.; vonDeak, Thomas C.

    1997-01-01

    The Internet has been growing at a rapid rate as the key medium to provide information services such as e-mail, WWW and multimedia etc., however its global reach is limited. Ka-band communication satellite networks are being developed to increase the accessibility of information services via the Internet at global scale. There is need to assess satellite networks in their ability to provide these services and interconnect seamlessly with existing and proposed terrestrial telecommunication networks. In this paper the significant issues and requirements in providing end-to-end high performance for the delivery of information services over satellite networks based on various layers in the OSI reference model are identified. Key experiments have been performed to evaluate the performance of digital video and Internet over satellite-like testbeds. The results of the early developments in ATM and TCP protocols over satellite networks are summarized.

  16. SAD phasing with in-house cu Ka radiation using barium as anomalous scatterer.

    PubMed

    Dhanasekaran, V; Velmurugan, D

    2011-12-01

    Phasing of lysozyme crystals using co-crystallized barium ions was performed using single-wavelength anomalous diffraction (SAD) method using Cu Ka radiation with in-house source of data collection. As the ion binding sites vary with respect to the pH of the buffer during crystallization, the highly isomorphic forms of lysozyme crystals grown at acidic and alkaline pH were used for the study. Intrinsic sulphur anomalous signal was also utilized with anomalous signal from lower occupancy ions for phasing. The study showed that to solve the structure by SAD technique, 2.8-fold data redundancy was sufficient when barium was used as an anomalous marker in the in-house copper X-ray radiation source for data collection. Therefore, co-crystallization of proteins with barium containing salt can be a powerful tool for structure determination using lab source.

  17. Radar Altimetry Backscattering Signatures at Ka, Ku, C and S Bands over Land

    NASA Astrophysics Data System (ADS)

    Blarel, F.; Frappart, F.; Legresy, B.; Blumstein, D.; Fatras, C.; Mougin, E.; Papa, F.; Prigent, C.; Remy, F.; Nino, F.; Borderies, P.; Biancamaria, S.; Calmant, S.

    2016-08-01

    Satellite radar altimetry, initially designed for studying ocean surface topography, demonstrated a strong potential for the continuous monitoring of ice sheets and land surfaces over the last 25 years. If radar altimetry is mostly used for its capacity to determine surface height, the backscattering coefficients provide information on the surface properties.Spatio-temporal variations of radar altimetry backscattering over land were related to the nature of the surface and its changes against time. This study presents the results of an along-track analysis of radar altimetry echoes over land at S, C, Ku and Ka bands using data from Jason-2, ERS-2, ENVISAT and SARAL on their nominal orbit. Temporal average and deviations are presented at global scale.

  18. Dielectric Resonator for Ka-Band Pulsed EPR Measurements at Cryogenic Temperatures: Probehead Construction and Applications

    PubMed Central

    Astashkin, A.; Enemark, J. H.; Blank, A.; Twig, Y.; Song, Y.; Meade, T. J.

    2013-01-01

    The construction and performance of a Ka-band pulsed electron paramagnetic resonance (EPR) cryogenic probehead that incorporates dielectric resonator (DR) is presented. We demonstrate that the use of DR allows one to optimize pulsed double electron–electron resonance (DEER) measurements utilizing large resonator bandwidth and large amplitude of the microwave field B1. In DEER measurements of Gd-based spin labels, use of this probe finally allows one to implement the potentials of Gd-based labels in distance measurements. Evidently, this DR is well suited to any applications requiring large B1-fields and resonator bandwidths, such as electron spin echo envelope modulation spectroscopy of nuclei having low magnetic moments and strong hyperfine interactions and double quantum coherence dipolar spectroscopy as was recently demonstrated in the application of a similar probe based on an loop-gap resonator and reported by Forrer et al. (J Magn Reson 190:280, 2008). PMID:23626406

  19. Did accelerated North American ice sheet melt contribute to the 8.2 ka cooling event ?

    NASA Astrophysics Data System (ADS)

    Matero, Ilkka S. O.; Gregoire, Lauren J.; Ivanović, Ruža F.; Tindall, Julia C.; Haywood, Alan M.

    2016-04-01

    The 8.2 ka event was an abrupt cooling of the Northern Hemisphere 8,200 years ago. It is an almost ideal case study to benchmark the sensitivity of climate models to freshening of the North Atlantic by ice sheet melt (Schmidt and LeGrande, 2005). The event is attributed to the outburst of North American proglacial lakes into the Labrador Sea, causing a slow-down in Atlantic overturning circulation and cooling of 1-2.5 °C around the N. Atlantic (Alley and Ágústsdóttir,2005). Climate models fail to simulate the ~150 year duration of the event when forced with a sudden (0.5 to 5 years) drainage of the lakes (Morrill et al., 2013a). This could be because of missing forcings. For example, the separation of ice sheet domes around the Hudson Bay is thought to have produced a pronounced acceleration in ice sheet melt through a saddle collapse mechanism around the time of the event (Gregoire et al., 2012). Here we investigate whether this century scale acceleration of melt contributed to the observed climatic perturbation, using the coupled Ocean-Atmosphere climate model HadCM3. We designed and ran a set of simulations with temporally variable ice melt scenarios based on a model of the North American ice sheet. The simulated magnitude and duration of the cold period is controlled by the duration and amount of freshwater introduced to the ocean. With a 100-200 year-long acceleration of ice melt up to a maximum of 0.61 Sv, we simulate 1-3 °C cooling in the North Atlantic and ~0.5-1 °C cooling in Continental Europe; which are similar in magnitude to the ~1-2 °C cooling estimated from records for these areas (Morrill et al., 2013b). Some of the observed features are however not reproduced in our experiments, such as the most pronounced cooling of ~6 °C observed in central Greenland (Alley and Ágústsdóttir, 2005). The results suggest that the ~150 year North Atlantic and European cooling could be caused by ~200 years of accelerated North American ice sheet melt. This

  20. Design of a Cryocooled Sapphire Oscillator for the Cassini Ka-Band Experiment

    NASA Astrophysics Data System (ADS)

    Dick, G. J.; Wang, R. T.

    1998-04-01

    We present design aspects of a cryogenic sapphire oscillator that is being developed for ultra-high short-term stability and low phase noise in support of the Cassini Ka-band (32-GHz) radio science experiment. With cooling provided by a commercial cryocooler instead of liquid helium, this standard is designed to operate continuously for periods of a year or more. Performance targets are a stability of 3 x 10^(-15) (1 second ≤ τ ≤ 100 seconds) and a phase noise of -73 dBc/Hz at 1 Hz measured at 34 GHz. Test results are reported for several subsystems, including the cryocooler, vibration isolation system, and ruby compensating element.

  1. Low phase noise GaAs HBT VCO in Ka-band

    NASA Astrophysics Data System (ADS)

    Ting, Yan; Yuming, Zhang; Hongliang, Lü; Yimen, Zhang; Yue, Wu; Yifeng, Liu

    2015-02-01

    Design and fabrication of a Ka-band voltage-controlled oscillator (VCO) using commercially available 1-μm GaAs heterojunction bipolar transistor technology is presented. A fully differential common-emitter configuration with a symmetric capacitance with a symmetric inductance tank structure is employed to reduce the phase noise of the VCO, and a novel π-feedback network is applied to compensate for the 180° phase shift. The on-wafer test shows that the VCO exhibits a phase noise of -96.47 dBc/Hz at a 1 MHz offset and presents a tuning range from 28.312 to 28.695 GHz. The overall dc current consumption of the VCO is 18 mA with a supply voltage of -6 V The chip area of the VCO is 0.7 × 0.7 mm2.

  2. High-Efficiency Ka-Band Waveguide Two-Way Asymmetric Power Combiner

    NASA Technical Reports Server (NTRS)

    Wintucky, E. G.; Simons, R. N.; Freeman, J. C.; Chevalier, C. T.

    2011-01-01

    NASA is planning a number of Space Exploration, Earth Observation and Space Science missions where Ka-band solid-state power amplifiers (SSPAs) could have a role. Monolithic microwave integrated circuit (MMIC) based SSPAs with output powers on the order of 10 W at Ka-band frequencies would be adequate to satisfy the data transmission rate requirements at the distances involved. MMICs are a type of integrated circuit fabricated on a GaAs wafer, which operates at micro wave frequencies and performs the function of signal amplification. The highest power Ka-band (31.8 to 32.3 GHz) SSPA to have flown in space had an output power of 2.6 W with an overall efficiency of 14.3 percent. This SSPA was built around discrete GaAs pHEMT (high electron mobility transistor) devices and flew aboard the Deep Space One spacecraft. State-of-the-art GaAs pHEMT-based MMIC power amplifiers (PAs) can deliver RF power at Ka-band frequencies anywhere from 3 W with a power added efficiency (PAE) of 32 percent to 6 W with a PAE of 26 percent. However, to achieve power levels higher than 6 W, the output of several MMIC PAs would need to be combined using a high-efficiency power combiner. Conventional binary waveguide power combiners, based on short-slot and magic-T circuits, require MMIC PAs with identical amplitude and phase characteristics for high combining efficiency. However, due to manufacturing process variations, the output powers of the MMIC PAs tend to be unequal, and hence the need to develop unequal power combiners. A two-way asymmetric magic-T based power combiner for MMIC power amplifiers, which can take in unequal inputs, has been successfully designed, fabricated, and characterized over NASA s Deep Space Network (DSN) frequency range of 31.8 to 32.3 GHz. The figure is a transparent view of the a sym - metric combiner that shows the 4-port configuration and the internal structure. The rod, post, and iris are positioned by design to achieve the desired asymmetric power ratio

  3. Critical evaluation of buffering solutions for pKa determination by capillary electrophoresis.

    PubMed

    Fuguet, Elisabet; Reta, Mario; Gibert, Carme; Rosés, Martí; Bosch, Elisabeth; Ràfols, Clara

    2008-07-01

    The performance of the most common and also some other less common CE buffers has been tested for the pKa determination of several types of compounds (pyridine, amines, and phenols). The selected buffers cover a pH ranging from 3.7 to 11.8. Whereas some buffers, like acetic acid/acetate, BisTrisH+/BisTris, TrisH+/Tris, CHES/CHES-, and CAPS/CAPS- can be used with all type of analytes, others like ammonium/ammonia, butylammonium/butylammonia, ethylammonium/ethylammonia, diethylammonium/diethylammonia, and hydrogenphosphate/phosphate are not recommended because they interact with a wide range of compounds. The rest of the tested buffers (dihydrogenphosphate/hydrogenphosphate, MES/MES-, HEPES/HEPES-, and boric acid/borate) can show specific interactions depending on the nature of the analytes, and their use in some applications should be restricted.

  4. Ka-band IQ vector modulator employing GaAs HBTs

    NASA Astrophysics Data System (ADS)

    Yuxiong, Cao; Danyu, Wu; Gaopeng, Chen; Zhi, Jin; Xinyu, Liu

    2011-06-01

    The importance of high-performance, low-cost and millimeter-wave transmitters for digital communications and radar applications is increasing. The design and performance of a Ka-band balanced in-phase and quadrature-phase (I-Q) type vector modulator, using GaAs heterojunction bipolar transistors (HBTs) as switching elements, are presented. The balanced technique is used to remove the parasitics of the HBTs to result in near perfect constellations. Measurements of the monolithic microwave integrated circuit (MMIC) chip with a size of 1.89 × 2.26 mm2 demonstrate an amplitude error below 1.5 dB and the phase error within 3° between 26 and 40 GHz except for a singular point at 35.6 GHz. The results show that the technique is suitable for millimeter-wave digital communications.

  5. Low-loss microstrip MEMS technology for passive components design in the Ka-band

    NASA Astrophysics Data System (ADS)

    Martoglio, L.; Richalot, E.; Picon, O.

    2002-04-01

    The development of Wireless Local Loop applications require low-cost technologies in the Ka-band. As transmission lines and passive circuit components on standard low-resistivity silicon substrates have high loss in this frequency range, a new microstrip MEMS technology is proposed for high- frequency applications. It has many advantages as the low cost of the substrates (glass and standard silicon), the simple technological process, the good electrical performances, and the low sensitivity to electromagnetic radiation. This technology consists in inverted microstrip lines, either on low loss silicon or on glass, which can be combined to obtain compact circuits associating active and passive components. Moreover, this technology seems suitable for current microwave and radiofrequency applications because it could be easily adapted to silicon fabrication technologies dedicated to planar circuits.

  6. First Results from an Airborne Ka-band SAR Using SweepSAR and Digital Beamforming

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory; Ghaemi, Hirad; Hensley, Scott

    2012-01-01

    NASA/JPL has developed SweepSAR technique that breaks typical Synthetic Aperture Radar (SAR) trade space using time-dependent multi-beam DBF on receive. Developing SweepSAR implementation using array-fed reflector for proposed DESDynI Earth Radar Mission concept. Performed first-of-a-kind airborne demonstration of the SweepSAR concept at Ka-band (35.6 GHz). Validated calibration and antenna pattern data sufficient for beam forming in elevation. (1) Provides validation evidence that the proposed Deformation Ecosystem Structure Dynamics of Ice (DESDynI) SAR architecture is sound. (2) Functions well even with large variations in receiver gain / phase. Future plans include using prototype DESDynI SAR digital flight hardware to do the beam forming in real-time onboard the aircraft.

  7. Ka-Band SiGe Receiver Front-End MMIC for Transponder Applications

    NASA Technical Reports Server (NTRS)

    Venkatesan, Jaikrishna; Mysoor, Narayan R.; Hashemi, Hassein; Aflatouni, Firooz

    2010-01-01

    A fully integrated, front-end Ka-band monolithic microwave integrated circuit (MMIC) was developed that houses an LNA (low noise amplifier) stage, a down-conversion stage, and output buffer amplifiers. The MMIC design employs a two-step quadrature down-conversion architecture, illustrated in the figure, which results in improved quality of the down-converted IF quadrature signals. This is due to the improved sensitivity of this architecture to amplitude and phase mismatches in the quadrature down-conversion process. Current sharing results in reduced power consumption, while 3D-coupled inductors reduce the chip area. Improved noise figure is expected over previous SiGe-based, frontend designs

  8. Study on Ka-Band Sheet Beam Traveling Wave Tube Focused by Closed PCM

    NASA Astrophysics Data System (ADS)

    Wang, Zhan-Liang; Shi, Xianbao; Gong, Yu-Bin; Wei, Yan-Yu; Duan, Zhao-Yun; Su, Xiaogang; Gong, Huarong; Feng, Jinjun; Huang, Hua

    2016-06-01

    This paper reports a Ka-band sheet beam traveling wave tube (TWT) focused by a 0.2 T closed periodic cusped magnet (PCM) system. The TWT with one section of staggered double-vane slow-wave structure (SWS) is driven by a 0.8-A sheet beam with rectangular cross-sectional area of 3.2 mm × 0.6 mm. This sheet beam TWT can produce 100 W output power, and the 3 dB band is 33-38.5 GHz. In order to improve the output power, an optimized sheet beam TWT with two sections of SWSs focused by a novel closed PCM system is proposed. The new closed PCM system is with annular magnetic blocks and can be fabricated and adjusted easily. The simulation shows that the optimized sheet beam TWT can produce 2000 W output power and the 3 dB band ranging from 33 to 40 GHz.

  9. ALICE Grid Computing at the GridKa Tier-1 Center

    NASA Astrophysics Data System (ADS)

    Jung, C.; Petzold, A.; Pfeiler, C.-E.; Schwarz, K.

    2012-12-01

    The GridKa center at the Karlsruhe Institute of Technology is the largest ALICE Tier-1 center. It hosts 40,000 HEPSEPC'06, approximately 2.75 PB of disk space, and 5.25 PB of tape space for the ‘A Large Ion Collider Experiment’ (ALICE), at the CERN Large Hadron Collider (LHC). These resources are accessed via the AliEn (ALICE Environment) middleware. The storage is divided into two instances, both using the storage middleware xrootd. We will focus on the set-up of these resources and on the topic of monitoring. The latter serves a vast number of purposes, ranging from efficiency statistics for process and procedure optimization to alerts for on-call duty engineers.

  10. First Results from an Airborne Ka-band SAR Using SweepSAR and Digital Beamforming

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory; Ghaemi, Hirad; Hensley, Scott

    2012-01-01

    NASA/JPL has developed SweepSAR technique that breaks typical Synthetic Aperture Radar (SAR) trade space using time-dependent multi-beam DBF on receive. Developing SweepSAR implementation using array-fed reflector for proposed DESDynI Earth Radar Mission concept. Performed first-of-a-kind airborne demonstration of the SweepSAR concept at Ka-band (35.6 GHz). Validated calibration and antenna pattern data sufficient for beam forming in elevation. (1) Provides validation evidence that the proposed Deformation Ecosystem Structure Dynamics of Ice (DESDynI) SAR architecture is sound. (2) Functions well even with large variations in receiver gain / phase. Future plans include using prototype DESDynI SAR digital flight hardware to do the beam forming in real-time onboard the aircraft.

  11. An active K/Ka-band antenna array for the NASA ACTS mobile terminal

    NASA Astrophysics Data System (ADS)

    Tulintseff, A.; Crist, R.; Densmore, Art; Sukamto, L.

    An active K/Ka-band antenna array is currently under development for NASA's ACTS Mobile Terminal (AMT). The AMT task will demonstrate voice, data, and video communications to and from the AMT vehicle in Los Angeles, California, and a base station in Cleveland, Ohio, via the ACTS satellite at 30 and 20 GHz. Satellite tracking for the land-mobile vehicular antenna system involves 'mechanical dithering' of the antenna, where the antenna radiates a fixed beam 46 deg. above the horizon. The antenna is to transmit horizontal polarization and receive vertical polarization at 29.634 plus or minus 0.15 GHz and 19.914 plus or minus 0.15 GHz, respectively. The active array will provide a minimum of 22 dBW EIRP transmit power density and a -8 dB/K deg. receive sensitivity.

  12. Multichannel Ka-Band Microwave Oscillator Based on Frequency-Shifted Relativistic Backward-Wave Oscillators

    NASA Astrophysics Data System (ADS)

    Yalandin, M. I.; Sharypov, K. A.; Pedos, M. S.; Romanchenko, I. V.; Rostov, V. V.; Rukin, S. N.; Ul'maskulov, M. R.; Shpak, V. G.; Shunailov, S. A.

    2017-01-01

    Experiments on summation of linearly polarized Gaussian wave beams in free space from two and four synchronous nanosecond Ka-band relativistic backward wave oscillators (BWOs), each having an output power of about 200 MW with controllably shifted oscillator frequencies have been carried out. An about 0.5% frequency shift in one of the channels was equivalent to a one-period phase delay of the carrier frequency. In a two-channel version of the device, a full beat cycle was obtained for a pulse with quadratic (with respect to the number of sources) enhancement of the power flux density at the interference maximum of the integral directional pattern (DP). In the case of a four-channel device, a diagonal displacement of the DP lobes has been demonstrated.

  13. A Ka-band reflection-type analog electrically controlled phase shifter

    NASA Astrophysics Data System (ADS)

    Li, Wenchao; Chen, Yanhui; Shen, Hui; Zhang, Bin

    2017-03-01

    In order to modulate the phase of RF signal continuously, a new miniaturized Ka-band analog electrically controlled phase shifter is presented. The phase shifter based on 90°directional coupler and parallel variable capacitance diodes(VCD) achieves matching circuit and shift phase, the circuit can gain wide range phase shift by changing the bias voltage of variable capacitance diodes (VCD), and the insertion loss fluctuations of the phase shifter has a significant improvement by parallel compensation resistance. Simulation and experimental results show that the phase shifter in 29˜31 GHz range obtains 180° phase shift, the insertion loss is better than 6.5 dB, and the insertion loss fluctuations are within 1 dB.

  14. Climatic records over the past 30 ka from temperate Australia - a synthesis from the Oz-INTIMATE workgroup

    NASA Astrophysics Data System (ADS)

    Petherick, L.; Bostock, H.; Cohen, T. J.; Fitzsimmons, K.; Tibby, J.; Fletcher, M.-S.; Moss, P.; Reeves, J.; Mooney, S.; Barrows, T.; Kemp, J.; Jansen, J.; Nanson, G.; Dosseto, A.

    2013-08-01

    Temperate Australia sits between the heat engine of the tropics and the cold Southern Ocean, encompassing a range of rainfall regimes and falling under the influence of different climatic drivers. Despite this heterogeneity, broad-scale trends in climatic and environmental change are evident over the past 30 ka. During the early glacial period (˜30-22 ka) and the Last Glacial Maximum (˜22-18 ka), climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important Murray-Darling Basin. The temperate region at this time appears to be dominated by expanded sea ice in the Southern Ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast (including Tasmania) and southwest Australian coasts. The deglacial period (˜18-12 ka) was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records, while there is some evidence for climatic reversals (e.g. the Antarctic Cold Reversal) in high resolution marine sediment cores through this period. The high spatial density of Holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after ˜12 ka, presumably in response to increasing temperature, while hydrological records reveal spatially heterogeneous hydro-climatic trends. Patterns after ˜6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the El Niño/Southern Oscillation.

  15. Quantification of southwest China rainfall during the 8.2 ka BP event with response to North Atlantic cooling

    NASA Astrophysics Data System (ADS)

    Liu, Yuhui; Hu, Chaoyong

    2016-07-01

    The 8.2 ka BP event could provide important information for predicting abrupt climate change in the future. Although published records show that the East Asian monsoon area responded to the 8.2 ka BP event, there is no high-resolution quantitative reconstructed climate record in this area. In this study, a reconstructed 10-year moving average annual rainfall record in southwest China during the 8.2 ka BP event is presented by comparing two high-resolution stalagmite δ18O records from Dongge cave and Heshang cave. This decade-scale rainfall reconstruction is based on a central-scale model and is confirmed by inter-annual monitoring records, which show a significant positive correlation between the regional mean annual rainfall and the drip water annual average δ18O difference from two caves along the same monsoon moisture transport pathway from May 2011 to April 2014. Similar trends between the reconstructed rainfall and the stalagmite Mg / Ca record, another proxy of rainfall, during the 8.2 ka BP period further increase the confidence of the quantification of the rainfall record. The reconstructed record shows that the mean annual rainfall in southwest China during the central 8.2 ka BP event is less than that of present (1950-1990) by ˜ 200 mm and decreased by ˜ 350 mm in ˜ 70 years experiencing an extreme drying period lasting for ˜ 50 years. Comparison of the reconstructed rainfall record in southwest China with Greenland ice core δ18O and δ15N records suggests that the reduced rainfall in southwest China during the 8.2 ka BP period was coupled with Greenland cooling with a possible response rate of 110 ± 30 mm °C-1.

  16. Biotic response of benthic foraminifera to 4 ka cooling event in the Nakdong River delta of the southeast Korea

    NASA Astrophysics Data System (ADS)

    Takata, Hiroyuki; Khim, Boo-Keun; Cheong, Daekyo; Shin, Seungwon

    2017-04-01

    It has been reported that the cooling event at 4 ka caused climatic deterioration in the world, which is closely associated with the decline/development of the civilizations (e.g., Kawahata et al., 2009). In particular, various climate events at about 4 ka have been reported in the East Asian margin such as the decline pattern of total sulfur content in Lake Tougou-ike (southwest Japan) (Kato et al., 2003), and the enhanced precipitation and freshwater event in northeast China (Hong et al., 2005) and South Korea (Lim et al., 2015). We investigated fossil benthic foraminiferal faunas at two borehole cores (ND-01: landward site and ND-02: seaward site) drilled at the Nakdong River delta in the southeastern coast of Korea, in order to reveal whether the paleoclimate changes across 4 ka occurred in the southeast Korea. The planktonic/total foraminiferal ratio (P/T ratio) and MDS axis 1, representing the faunal composition, show temporal decline at 4 ka at core ND-01, despite no marked change at core ND-02. In contrast, MDS axis 2, which is negatively related to the dominance of Haynesina sp. A (an opportunistic species in organic-rich condition of neritic environments), at core ND-01 shows positive shift across 4 ka. These biotic changes are interpreted as the increase of river water discharge with rainfalls by East Asian summer monsoon and the weakening of northwestly winds possibly with East Asian winter monsoon. Thus, despite insufficient, benthic foraminifera in the Nakdong River delta likely experienced the paleoclimate change across 4 ka.

  17. Reconstructing Hydrothermal Activity on the Juan de Fuca Ridge over the Last 25ka

    NASA Astrophysics Data System (ADS)

    Mehmel, N.; Costa, K.; McManus, J. F.

    2016-12-01

    Hydrothermal activity on mid-ocean ridges plays a unique role in biogeochemical cycles in the ocean. Hydrothermal vents are a significant source of dissolved Fe, a critical micronutrient in the ocean that supports primary productivity and can modulate the carbon cycle. Little is known about hydrothermal activity in the Last Glacial Maximum (LGM), but new evidence suggests lower sea levels may generate enhanced hydrothermal activity. If hydrothermal activity was higher during the LGM, an Fe fertilized biological pump could have contributed to lower atmospheric CO2 levels. In this study we investigate sediment cores from the Juan de Fuca Ridge (JdFR) to reconstruct hydrothermal activity over the past 25 ka. Five multicores were examined from a spatial array, covering a depth transect along the ridge flank and crest, with a temporal resolution of between 500 and 1000 years. Fe and Cu concentrations were measured by flux fusion, corrected for lithogenic inputs, and normalized to 230Th to calculate hydrothermal fluxes. Hydrothermal flux of Fe and Cu was observed at all times from all sites, suggesting persistent hydrothermal activity on the JdFR. Furthermore, Fe flux into the sediment increases with proximity to the ridge, consistent with a hydrothermal source. The sediment record indicates a stable flux of Fe during the Holocene, compared to flux variations that change by up to 100% between 15 and 20ka. Averaged over 5-7kyr time slices, Cu flux is greater in all 5 records during the LGM than during the Holocene, but in contrast, Fe flux overall appears slightly lower during the LGM than the Holocene. These are the first records from the JdFR to cover the last deglaciation at millennial timescales, and they suggest a more complicated hydrothermal response to glacial sea level changes than observed at other mid-ocean ridges.

  18. Cryogenic Cooling System for 5 kA, 200 μH Class HTS DC Reactor

    NASA Astrophysics Data System (ADS)

    Park, Heecheol; Kim, Seokho; Kim, Kwangmin; Park, Minwon; Park, Taejun; Kim, A.-rong; Lee, Sangjin

    DC reactors, made by aluminum busbar, are used to stabilize the arc of an electric furnace. In the conventional arc furnace, the transport current is several tens of kilo-amperes and enormous resistive loss is generated. To reduce the resistive loss at the DC reactor, a HTS DC reactor can be considered. It can dramatically improve the electric efficiency as well as reduce the installation space. Similar with other superconducting devices, the HTS DC reactor requires current leads from a power source in room temperature to the HTS coil in cryogenic environment. The heat loss at the metal current leads can be minimized through optimization process considering the geometry and the transport current. However, the transport current of the HTS DC reactor for the arc furnace is much larger than most of HTS magnets and the enormous heat penetration through the current lead should be effectively removed to keep the temperature around 70∼77 K. Current leads are cooled down by circulation of liquid nitrogen from the cooling system with a stirling cryocooler. The operating temperature of HTS coil is 30∼40 K and circulation of gaseous helium is used to remove the heat generation at the HTS coil. Gaseous helium is transported through the cryogenic helium blower and a single stage GM cryocooler. This paper describes design and experimental results on the cooling system for current leads and the HTS coil of 5 kA, 200 μH class DC reactor as a prototype. The results are used to verify the design values of the cooling systems and it will be applied to the design of scale-up cooling system for 50 kA, 200 μH class DC reactor.

  19. Reverberation mapping of the Kepler field AGN KA1858+4850

    SciTech Connect

    Pei, Liuyi; Barth, Aaron J.; Carson, Daniel J.; Aldering, Greg S.; Cucchiara, Antonino; Briley, Michael M.; Carroll, Carla J.; Cenko, S. Bradley; Edelson, Rick; Clubb, Kelsey I.; Cohen, Daniel P.; Filippenko, Alexei V.; Fox, Ori D.; Desjardins, Tyler D.; Fang, Jerome J.; Fedrow, Joseph M.; Furniss, Amy; Gates, Elinor L.; Gregg, Michael; Gustafson, Scott; and others

    2014-11-01

    KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3 m telescope from 2012 February to November, and obtained complementary V-band images from five other ground-based telescopes. We measured the Hβ light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method and found rest-frame lags of τ{sub CCF}=13.53{sub −2.32}{sup +2.03} days and τ {sub JAVELIN} =13.15{sub −1.00}{sup +1.08} days. The Hβ rms line profile has a width of σ{sub line} = 770 ± 49 km s{sup –1}. Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M{sub BH}=8.06{sub −1.72}{sup +1.59}×10{sup 6}M{sub ⊙} for the mass of the central black hole and an Eddington ratio of L/L {sub Edd} ≈ 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.

  20. Ka-Band Waveguide Three-Way Serial Combiner for MMIC Amplifiers

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.; Freeman, Jon C.; Chevalier, Christine T.

    2012-01-01

    In this innovation, the three-way combiner consists internally of two branch-line hybrids that are connected in series by a short length of waveguide. Each branch-line hybrid is designed to combine input signals that are in phase with an amplitude ratio of two. The combiner is constructed in an E-plane split-block arrangement and is precision machined from blocks of aluminum with standard WR-28 waveguide ports. The port impedances of the combiner are matched to that of a standard WR-28 waveguide. The component parts include the power combiner and the MMIC (monolithic microwave integrated circuit) power amplifiers (PAs). The three-way series power combiner is a six-port device. For basic operation, power that enters ports 3, 5, and 6 is combined in phase and appears at port 1. Ports 2 and 4 are isolated ports. The application of the three-way combiner for combining three PAs with unequal output powers was demonstrated. NASA requires narrow-band solid-state power amplifiers (SSPAs) at Ka-band frequencies with output power in the range of 3 to 5 W for radio or gravity science experiments. In addition, NASA also requires wideband, high-efficiency SSPAs at Ka-band frequencies with output power in the range of 5 to 15 W for high-data-rate communications from deep space to Earth. The three-way power combiner is designed to operate over the frequency band of 31.8 to 32.3 GHz, which is NASA s deep-space frequency band.

  1. Reverberation Mapping of the KEPLER Field AGN KA1858+4850

    NASA Astrophysics Data System (ADS)

    Pei, Liuyi; Barth, Aaron J.; Aldering, Greg S.; Briley, Michael M.; Carroll, Carla J.; Carson, Daniel J.; Cenko, S. Bradley; Clubb, Kelsey I.; Cohen, Daniel P.; Cucchiara, Antonino; Desjardins, Tyler D.; Edelson, Rick; Fang, Jerome J.; Fedrow, Joseph M.; Filippenko, Alexei V.; Fox, Ori D.; Furniss, Amy; Gates, Elinor L.; Gregg, Michael; Gustafson, Scott; Horst, J. Chuck; Joner, Michael D.; Kelly, Patrick L.; Lacy, Mark; Laney, C. David; Leonard, Douglas C.; Li, Weidong; Malkan, Matthew A.; Margon, Bruce; Neeleman, Marcel; Nguyen, My L.; Prochaska, J. Xavier; Ross, Nathaniel R.; Sand, David J.; Searcy, Kinchen J.; Shivvers, Isaac S.; Silverman, Jeffrey M.; Smith, Graeme H.; Suzuki, Nao; Smith, Krista Lynne; Tytler, David; Werk, Jessica K.; Worseck, Gábor

    2014-11-01

    KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3 m telescope from 2012 February to November, and obtained complementary V-band images from five other ground-based telescopes. We measured the Hβ light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method and found rest-frame lags of τ CCF = 13.53+2.03-2.32 days and τ JAVELIN = 13.15+1.08-1.00 days. The Hβ rms line profile has a width of σline = 770 ± 49 km s-1. Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M{BH} = 8.06+1.59-1.72 × 106 {M}⊙ for the mass of the central black hole and an Eddington ratio of L/L Edd ≈ 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.

  2. Simultaneous Ka-Band Site Characterization: Goldstone, CA, White Sands, NM, and Guam, USA

    NASA Technical Reports Server (NTRS)

    Acosta, Roberto; Morse, Jacquelynne; Zemba, Michael; Nessel, James; Morabito, David; Caroglanian, Armen

    2011-01-01

    To statistically characterize atmospheric effects on Ka-band links at NASA operational sites, NASA has constructed site test interferometers (STI s) which directly measure the tropospheric phase stability and rain attenuation. These instruments observe an unmodulated beacon signal broadcast from a geostationary satellite (e.g., Anik F2) and measure the phase difference between the signals received by the two antennas and its signal attenuation. Three STI s have been deployed so far: the first one at the NASA Deep Space Network Tracking Complex in Goldstone, California (May 2007); the second at the NASA White Sands Complex, in Las Cruses, New Mexico (February 2009); and the third at the NASA Tracking and Data Relay Satellite (TDRS) Remote Ground Terminal (GRGT) complex in Guam (May 2010). Two station-years of simultaneous atmospheric phase fluctuation data have been collected at Goldstone and White Sands, while one year of data has been collected in Guam. With identical instruments operating simultaneously, we can directly compare the phase stability and rain attenuation at the three sites. Phase stability is analyzed statistically in terms of the root-mean-square (rms) of the tropospheric induced time delay fluctuations over 10 minute blocks. For two years, the time delay fluctuations at the DSN site in Goldstone, CA, have been better than 2.5 picoseconds (ps) for 90% of the time (with reference to zenith), meanwhile at the White Sands, New Mexico site, the time delay fluctuations have been better than 2.2 ps with reference to zenith) for 90% of time. For Guam, the time delay fluctuations have been better than 12 ps (reference to zenith) at 90% of the time, the higher fluctuations are as expected from a high humidity tropical rain zone. This type of data analysis, as well as many other site quality characteristics (e.g., rain attenuation, infrastructure, etc.) will be used to determine the suitability of all the sites for NASA s future communication services at Ka-band.

  3. NALPS: a precisely dated European climate record 120-60 ka

    NASA Astrophysics Data System (ADS)

    Boch, R.; Cheng, H.; Spötl, C.; Edwards, R. L.; Wang, X.; Häuselmann, Ph.

    2011-03-01

    Accurate and precise chronologies are essential in understanding the rapid and recurrent climate variations of the Last Glacial - known as Dansgaard-Oeschger (D-O) events - found in the Greenland ice cores and other climate archives. The existing chronological uncertainties during the Last Glacial, however, are still large. Radiometric age data and stable isotopic signals from speleothems are promising to improve the absolute chronology. We present a record of several precisely dated stalagmites from caves located at the northern rim of the Alps (NALPS), a region that favours comparison with the climate in Greenland. The record covers most of the interval from 120 to 60 ka at an average temporal resolution of 2 to 22 a and 2 σ-age uncertainties of ca. 200 to 500 a. The rapid and large oxygen isotope shifts of 1 to 4.5‰ occurred within decades to centuries and strongly mimic the Greenland D-O pattern. Compared to the current Greenland ice-core timescale the NALPS record suggests overall younger ages of rapid warming and cooling transitions between 120 to 60 ka. In particular, there is a discrepancy in the duration of stadial 22 between the ice-core and the stalagmite chronology (ca. 3000 vs. 3650 a). The short-lived D-O events 18 and 18.1 are not recorded in NALPS, provoking questions with regard to the nature and the regional expression of these events. NALPS resolves recurrent short-lived climate changes within the cold Greenland stadial (GS) and warm interstadial (GI) successions, i.e. abrupt warming events preceding GI 21 and 23 (precursor-type events) and at the end of GI 21 and 25 (rebound-type events), as well as intermittent cooling events during GI 22 and 24. Such superimposed Last Glacial events have not been documented in Europe before.

  4. Climate, herbivory, and fire controls on tropical African forest for the last 60ka

    NASA Astrophysics Data System (ADS)

    Ivory, S.; Russell, J. M.

    2016-12-01

    Vegetation history in Africa is generally assumed to be strongly related to climate. However, disturbance by fire, herbivory, and human land use is also important to maintaining vegetation structure and may interact with climate to create tipping points for ecosystems. During the last 60ka, the transition from glacial aridity to increased moisture in much of northern and equatorial Africa led to widespread forest expansion; however, forests in southeastern Africa do not appear to have changed dramatically during arid periods associated with high-latitude cooling, suggesting a more complex biogeographic history. Here we present analyses of fossil pollen, charcoal, and Sporormiella (dung fungus) along with multiproxy climate reconstructions from a 60kyr record from central Lake Tanganyika, southeast Africa, which illustrate the interplay of climate and disturbance regimes in shaping vegetation composition and structure. We observe that forests dominated the region during the last glacial period despite decreased rainfall. At the end of the glacial, forest opening at 17.5 ka followed warming temperatures but preceded wetting, suggesting that water stress and disturbance from fire and herbivory affected initial landscape transformation. Our Sporormiella record indicates that mega-herbivore populations increased in the early Holocene. This higher animal density increased plant species richness and encouraged landscape heterogeneity until the mid-Holocene. At this time, regional drying followed by the onset of the Iron Age in the late Holocene resulted in expansion of thicket, more open woodland, and disturbance taxa that still characterize the landscape today. This work has important implications for the understanding the how climate change will alter the distribution of lowland and highland forests, in particular how disturbance processes influence the rate of vegetation change.

  5. High Stability CFRP Support Structure for Ka Band Multi-Spot Cluster

    NASA Astrophysics Data System (ADS)

    Yarza, A.; Cano, J.; Ozores, E.

    2012-07-01

    In the recent days, Ka band mission are being implemented for telecommunication satellites as emergent technology. EADS CASA Espacio (ASTRIUM) has been doing developments able to face up the demanding requirements associated to this frequency band where aspects such as in orbit stability o manufacturing accuracy are essential. Once it has been demonstrated the capability to offer excellent antenna reflectors with low mass, very low ohmic losses, excellent RF performances and very stable in orbit thermoelastic behaviour, improvements at feeder-chain level have been developed with the aim to cover the global antenna mission with excellent performances. This paper presents the product developed to accommodate a KA band multi-spot cluster to cover a telecommunication mission. It includes a description of the tasks carried out until the current development status, with the definition of the mechanical specification used as applicable and the solutions applied to meet the requirements. A CFRP structure is proposed with the aim to achieve a light mass concept, structurally speaking optimized and capable to assemble multiple feeder chain and make independent the thermomechanical behaviour of each one. Moreover, the design with CFRP leads to very stable thermoelastic behaviour of the assembly and the feeder-chain with the scope to guaranty the stability of the RF-beam for the correct electrical performances. The compatibility between the carbon fibre structure and the Aluminium feeder chain is solved by means of isostatic devices that are capable to absorb the thermal stresses coming from the different thermal expansion coefficients of the materials used. The proposed design is to be confirmed over a Qualification Model, already manufactured, with the scope to be implemented as flight hardware in a commercial spacecraft. The product is to be tested in a full qualification environmental test campaign where the capability to withstand the dynamic loads and the thermal

  6. First Airswot Ka-Band Radar Backscatter Returns over a Complex California Wetland

    NASA Astrophysics Data System (ADS)

    Baney, O. N.; Smith, L. C.; Pitcher, L. H.; Gleason, C. J.; Chu, V. W.; Bennett, M. M.; Pavelsky, T.; Sadowy, G. A.

    2014-12-01

    In anticipation of the launch of the NASA Surface Water Ocean Topography (SWOT) mission, this project was conducted around the Piute Ponds of Edwards Air Force Base within the Mojave Desert, California to characterize ground conditions simultaneously with two AirSWOT flights collected May 14th, 2014. Both SWOT and AirSWOT employ a Ka-band interferometer to map water surface elevations and extent, but the ability of Ka-band radar to discriminate shorelines and flooded vegetation is not well known. Presumed bright returns from moist soils surrounding surface water bodies have also been speculated to confound interpretation of SWOT/AirSWOT data. The Piute Ponds are a dynamic area of constantly changing water conditions, providing a convenient test site for field studies to assess open water, dry shorelines, vegetation edges, islands, flooded vegetation and soil moisture in conjunction with AirSWOT backscatter and visible/near-infrared camera imagery. Islands were characterized into dry islands and flooded vegetation stands including species such as bulrush (Scripus acutus) and tamarisk (Tammarix ramosissima). Results demonstrate that full water extent can be determined by near-range backscatter returns which are strong for both open water and flooded vegetation. Far-range backscatter returns over open water were unreliable for flooded extent. Comparing near-range and far-range backscatter results to the soil moisture transect shows correlation, however as soil moisture increases, discriminating between wet sediment and water becomes difficult. In sum, first results suggest near-return backscatter results prove most useful in distinguishing open water from non-water, with a strong correlation between soil moisture and backscatter returns.

  7. Modeling atmospheric precipitation impact on synthetic aperture radar imagery at X and Ka bands

    NASA Astrophysics Data System (ADS)

    Mori, Saverio; Polverari, Federica; Pulvirenti, Luca; Montopoli, Mario; Pierdicca, Nazzareno; Marzano, Frank S.

    2014-10-01

    Spaceborne synthetic aperture radars (SARs) operating at X-band and above allow observations of Earth surface at very high spatial resolution. Moreover, recent polarimetric SARs enable the complete characterization of target scattering and extinction properties. Nowadays several spaceborne X-band SAR systems are operative, and plans exist for systems operating at higher frequency bands (i.e. Ku, Ka and W). Although higher frequencies may have interesting and distinctive applications, atmospheric effects, especially in precipitating conditions, may affect the surface SAR response in both the signal amplitude and its phase, as assessed by numerous works in the last years. A valid tool to analyze and characterize the SAR response in these conditions is represented by forward modeling, where a known synthetic scenario, which is described by user-selected surface and atmospheric conditions, is considered. Thus, the SAR echoes corresponding to the synthetic scenarios are simulated using electromagnetic models. In this work a 3-D realistic polarimetric SAR response numerical simulator is presented. The proposed model framework accounts for the SAR slant observing geometry and it is able to characterize the polarimetric response both in amplitude and phase. In this work we have considered both X and Ka bands, thus exploring the atmospheric effects for the present and future polarimetric systems. The atmospheric conditions are simulated using the System for Atmospheric Modeling (SAM) which is an high-resolution mesoscale model. SAM is used to define the three-dimensional distribution of hydrometeors which are among the inputs used in the Hydrometeor Ensemble Scattering Simulator (HESS) T-Matrix which allow simulating the SAR signal due to the atmospheric component. The SAR surface component is, instead, simulated by a Semi Empirical Model (SEM) for bare-soils conditions and SEAWIND2 two-scale model for ocean surfaces. The proposed methodology has been applied in this work

  8. Ka-Band GaAs FET Monolithic Power Amplifier Development

    NASA Technical Reports Server (NTRS)

    Saunier, Paul; Tserng, Hua Quen

    1997-01-01

    Over the course of this program, very extensive progress was made in Ka-band GaAs technology. At the beginning of the program, odd-shaped VPE MESFET wafers were used. A breakthrough in power and efficiency was achieved with highly doped (8 x 10(exp 17) cm(exp -3) MBE grown MESFET material. We obtained power of 112 mW with 16 dB gain and 21.6% efficiency at 34 GHz with a monolithic 50-100-250 micron amplifier. The next breakthrough came with the use of heterostructures grown by MBE (AlGaAs/InGaAs where the InGaAs is highly doped). This allowed us to achieve high power density with high efficiency. A benchmark 40% efficiency was achieved with a single-stage 100 micron MMIC at 32.5 GHz. The corresponding three-stage 50-100-250 micron amplifier achieved 180 mW with 23 dB gain and 30.3% efficiency. The next breakthrough came with 3-inch MBE grown PHEMT wafers incorporating an etch-stop layer for the gate recess (using RIE). Again, state-of-the-art performances were achieved: 40% efficiency with 235 mW output power and 20.7 dB gain. The single-stage 2 x 600 micron chip demonstrated 794 mW output power with 5 dB gain and 38.2% power-added efficiency (PAE). The Ka-band technology developed under this program has promise for extensive use: JPL demonstrated 32 GHz phased arrays with a three-stage amplifier developed under this contract. A variation of the three-stage amplifier was used successfully in a 4 x 4 phased array transmitter developed under another NASA contract.

  9. Silica in a Mars analog environment: Ka u Desert, Kilauea Volcano, Hawaii

    USGS Publications Warehouse

    Seelos, K.D.; Arvidson, R. E.; Jolliff, B.L.; Chemtob, S.M.; Morris, R.V.; Ming, D. W.; Swayze, G.A.

    2010-01-01

    Airborne Visible/Near-Infrared Imaging Spectrometer (AVIRIS) data acquired over the Ka u Desert are atmospherically corrected to ground reflectance and used to identify the mineralogic components of relatively young basaltic materials, including 250-700 and 200-400 year old lava flows, 1971 and 1974 flows, ash deposits, and solfatara incrustations. To provide context, a geologic surface units map is constructed, verified with field observations, and supported by laboratory analyses. AVIRIS spectral endmembers are identified in the visible (0.4 to 1.2 ??m) and short wave infrared (2.0 to 2.5 ??m) wavelength ranges. Nearly all the spectral variability is controlled by the presence of ferrous and ferric iron in such minerals as pyroxene, olivine, hematite, goethite, and poorly crystalline iron oxides or glass. A broad, nearly ubiquitous absorption feature centered at 2.25 ??m is attributed to opaline (amorphous, hydrated) silica and is found to correlate spatially with mapped geologic surface units. Laboratory analyses show the silica to be consistently present as a deposited phase, including incrustations downwind from solfatara vents, cementing agent for ash duricrusts, and thin coatings on the youngest lava flow surfaces. A second, Ti-rich upper coating on young flows also influences spectral behavior. This study demonstrates that secondary silica is mobile in the Ka u Desert on a variety of time scales and spatial domains. The investigation from remote, field, and laboratory perspectives also mimics exploration of Mars using orbital and landed missions, with important implications for spectral characterization of coated basalts and formation of opaline silica in arid, acidic alteration environments. Copyright 2010 by the American Geophysical Union.

  10. Hunter-Gatherer Responses to the 8.2 Ka Cold Event in the Fennoscandian Arctic

    NASA Astrophysics Data System (ADS)

    Manninen, M. A.

    2014-12-01

    Because of a marked influence of warm Atlantic water to primary productivity in the Barents Sea, the marine ecosystem in northernmost Fennoscandia is sensitive to disturbances in the North Atlantic oceanographic system. The 8.2 ka climate event, according to current knowledge, was triggered by a disturbance in the North Atlantic Thermohaline circulation. This suggests concurrent and strong climatic and marine cooling in the area covering the northernmost parts of Finland, Norway, and Sweden during the climate event. In this area ecosystem response to the 8.2 ka event can therefore be expected to have been prominent, which in turn should be reflected in the contemporary human socio-economic systems. A study that employs lithic technological, statistical, and spatial analyses of Late Mesolithic (ca. 8450-6850 cal BP) lithic technology and settlement configuration in the area indicates that lithic technology and settlement patterns were reorganised following the climatic and marine cooling. The studied groups changed their lithic technology as a result of developments that led to increased use of terrestrial resources and an accompanying long-distance coast/inland residential mobility pattern. Besides lithic technological changes and long-distance mobility on land, decreased marine productivity probably also explains the disappearance of semi-subterranean houses from the coast at ca. 8200 cal BP, while their reappearance after ca. 7500 cal BP can be linked to a increased influx of warm salty water into the Barents Sea. The results suggest that in the past a long period of decreased influx of Atlantic water into the Barents Sea has had disastrous consequences for the marine ecosystem. At present the Barents Sea fisheries have notable economic importance and produce, for example, over 90% of the Norwegian Atlantic cod (Gadus morhua) catch.

  11. Reverberation Mapping of the Kepler-Field AGN KA1858+4850

    NASA Technical Reports Server (NTRS)

    Pei, Liuyi; Barth, Aaron J.; Aldering, Greg S.; Briley, Michael M.; Carroll, Carla J.; Carson, Daniel J.; Cenko, S., Bradley; Clubb, Kelsey I.; Cohen, Daniel P.; Cucchiara, Antonino; Desjardins, Tyler D.

    2014-01-01

    KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m telescope from February to November of 2012, and obtained complementary V-band images from five other ground-based telescopes. We measured the Hbeta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method, and found rest-frame lags of tCCF = 13.53+2.03 -2.32 days and tJAVELIN = 13.15+1.08 -1.00 days. The Hbeta root-mean-square line profile has a width of sigma line = 770 +/- 49 km s(exp -1). Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M(sub BH) = 8.06+1.59 -1.72 ×10(exp 6) solar mass for the mass of the central black hole and an Eddington ratio of L/L(sub Edd) (is) approx. 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.

  12. VizieR Online Data Catalog: Photometry/spectroscopic measurements for KA1858+4850 (Pei+, 2014)

    NASA Astrophysics Data System (ADS)

    Pei, L.; Barth, A. J.; Aldering, G. S.; Briley, M. M.; Carroll, C. J.; Carson, D. J.; Cenko, S. B.; Clubb, K. I.; Cohen, D. P.; Cucchiara, A.; Desjardins, T. D.; Edelson, R.; Fang, J. J.; Fedrow, J. M.; Filippenko, A. V.; Fox, O. D.; Furniss, A.; Gates, E. L.; Gregg, M.; Gustafson, S.; Horst, J. C.; Joner, M. D.; Kelly, P. L.; Lacy, M.; Laney, C. D.; Leonard, D. C.; Li, W.; Malkan, M. A.; Margon, B.; Neeleman, M.; Nguyen, M. L.; Prochaska, J. X.; Ross, N. R.; Sand, D. J.; Searcy, K. J.; Shivvers, I. S.; Silverman, J. M.; Smith, G. H.; Suzuki, N.; Smith, K. L.; Tytler, D.; Werk, J. K.; Worseck, G.

    2017-05-01

    We employed the Lick Observatory 3 m Shane telescope with the Kast Spectrograph and five other ground-based telescopes to spectroscopically and photometrically monitor KA1858+4850 from 2012 February to November. Reverberation mapping requires a continuum light curve with high sampling cadence and S/N. To achieve this, we obtained V-band images from ground-based telescopes and used aperture photometry to construct a light curve for KA1858+4850 that has nearly nightly sampling for a span of 290 days. For several reasons, we chose to use the V-band light curve rather than the Kepler light curve for reverberation measurements. (2 data files).

  13. Petrology and geochronology of lavas from Ka'ula Volcano: Implications for rejuvenated volcanism of the Hawaiian mantle plume

    NASA Astrophysics Data System (ADS)

    Garcia, Michael O.; Weis, Dominique; Jicha, Brian R.; Ito, Garrett; Hanano, Diane

    2016-07-01

    Marine surveying and submersible sampling of Ka'ula Volcano, located 100 km off the axis of the Hawaiian chain, revealed widespread areas of young volcanism. New 40Ar/39Ar and geochemical analyses of the olivine-phyric submarine and subaerial volcanic rocks show that Ka'ula is shrouded with 1.9-0.5 Ma alkalic basalts. The ages and chemistry of these rocks overlap with rejuvenated lavas on nearby, northern Hawaiian Island shields (Ni'ihau, Kaua'i and South Kaua'i Swell). Collectively, these rejuvenated lavas cover a vast area (∼7000 km2), much more extensive than any other area of rejuvenated volcanism worldwide. Ka'ula rejuvenated lavas range widely in alkalinity and incompatible element abundances (e.g., up to 10× P2O5 at a given MgO value) and ratios indicating variable degrees of melting of a heterogeneous source. Heavy REE elements in Ka'ula lavas are pinned at a mantle normalized Yb value of 10 ± 1, reflecting the presence of garnet in the source. Trace element ratios indicate the source also contained phlogopite and an Fe-Ti oxide. The new Ka'ula ages show that rejuvenated volcanism was nearly coeval from ∼0.3 to 0.6 Ma along a 450 km segment of the Hawaiian Islands (from West Maui to north of Ka'ula). The ages and volumes for rejuvenated volcanism are inconsistent with all but one geodynamic melting model proposed to date. This model advocates a significant contribution of pyroxenite to rejuvenated magmas. Analyses of olivine phenocryst compositions suggest a major (33-69%) pyroxenite component in Ka'ula rejuvenated lavas, which correlates positively with radiogenic Pb isotope ratios for Ka'ula. This correlation is also observed in lavas from nearby South Kaua'i lavas, as was reported for Atlantic oceanic islands. The presence of pyroxenite in the source may have extended the duration and volume of Hawaiian rejuvenated volcanism.

  14. The characterization of lactic acid bacteria isolated during the traditional production of Užička sausage

    NASA Astrophysics Data System (ADS)

    Borović, B.; Velebit, B.; Vesković, S.; Lakićević, B.; Baltić, T.

    2017-09-01

    Užička sausage is a traditionally fermented dry sausage that is produced in western Serbia. It is made of beef and pork with the addition of solid fat and natural spices. The whole manufacturing process lasted for 21 days. The goal of this study was to create a collection of lactic acid bacteria isolated during the ripening and identify them using molecular methods. A total of 50 isolates from different stages of ripening (fermentation and drying) were identified by molecular methods. Leuconococcus mesenteroides, Lactobacillus brevis, and Lactobacillus sakei were the predominant microorganisms in Užička sausage.

  15. Two high levels of continental waters in the southern Tunisian chotts at about 90 and 150 ka

    SciTech Connect

    Causse, C. ); Coque, R. ); Fontes, J.Ch.; Gasse, F.; Gibert, E.; Zouari, K. ); Ouezdou, H.B. )

    1989-10-01

    Uranium and thorium content and activity ratios were measured on 20 samples (19 molluscs and 1 calcareous concretion) from the Great Chotts in southern Tunisia. Results were studied by the isochron method and by age frequency histograms. They suggest that two major flood episodes took place about 150 and 90 ka. Uranium activity ratios indicate a ground-water supply of continental origin, in agreement with biological indicators, which show large variations in salinity from fresh to marine-like conditions. The existence of a lacustrine phase, radiocarbon dated to 17-40 ka, as previously suggested for the northern Sahara, is highly questionable.

  16. Magnetic Mineral diagenesis in changing water environments in the Black Sea since ˜41.6 ka

    NASA Astrophysics Data System (ADS)

    Liu, Jiabo; Nowaczyk, Norbert; Frank, Ute; Arz, Helge

    2017-04-01

    Magnetic mineral diagenesis plays a key role in the global iron cycle. To understand the authigenic magnetic mineral formation by diagenesis is also fundamentally important for the interpretation of environmental magnetic as well as paleomagnetic signals. Core MSM33-55-1, recovered from the SW Black Sea, was subjected to rock-magnetic and SEM studies. The results demonstrate that four different magnetic mineral assemblages associated to specific water conditions can be observed. Between ˜41.6 ka and ˜19 ka, magnetite and greigite are alternatively in dominance in the sediment. Due to low organic matter input during the late MIS 3 and the last glacial maximum (LGM), oxygenated bottom water in the Black Sea was favourable for preserving detrital magnetite. Greigite in this interval have irregular shapes and assemble in spots, which were formed in a micro environment with limited sulfate availability. Between ˜19 ka and ˜16.5 ka, black layers were deposited as a result of organic matter accumulation induced by productivity blooming and riverine discharge soaring after the LGM. Hence less oxygenated bottom water conditions developed, and more fine grained greigite was formed. After melt-water pulse (MWP) events (˜16.5 ka), both primary productivity and the sea level were continuously rising until ˜8.3 ka, leading to the depletion of oxygen in bottom water. In addition to greigite, pyrite was also formed and gradually in dominance as approaching the Holocene. The influx of salt water masses from the Mediterranean Sea after ˜8.3 ka contributed to the establishment of the anoxic Black Sea, which resulted in the formation of ubiquitous frambiods of pyrite. Additionally, bacterial magnetic minerals are likely present in the sediment younger than ˜8.3 ka as indicated by rock magnetic results. In this paper, four different magnetic mineral assemblages, reflecting gradual changes from an oxic to an anoix Black Sea, were identified, yielding insights into the relation

  17. Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (SE Europe) during the past 500 ka

    NASA Astrophysics Data System (ADS)

    Sadori, L.; Koutsodendris, A.; Masi, A.; Bertini, A.; Combourieu-Nebout, N.; Francke, A.; Kouli, K.; Joannin, S.; Mercuri, A. M.; Panagiotopoulos, K.; Peyron, O.; Torri, P.; Wagner, B.; Zanchetta, G.; Donders, T. H.

    2015-09-01

    Lake Ohrid is located at the border between FYROM and Albania and formed during the latest phases of Alpine orogenesis. It is the deepest, the largest and the oldest tectonic lake in Europe. To better understand the paleoclimatic and paleoenvironmental evolution of Lake Ohrid a deep drilling was carried out in 2013 within the framework of the Scientific Collaboration on Past Speciation Conditions (SCOPSCO) project that was funded by the International Continental Drilling Program (ICDP). Preliminary results indicate that lacustrine sedimentation of Lake Ohrid started between 1.2 and 1.9 Ma ago. Here we present new pollen data (selected percentage and concentration taxa/groups) of the uppermost ~200 m of the 569 m-long DEEP core drilled in the depocenter of Lake Ohrid. The study is the fruit of a cooperative work carried out in several European palynological laboratories. The age model is based on nine tephra layers and on tuning of biogeochemical proxy data to orbital parameters and to the global benthic isotope stack LR04. According to the age model the studied sequence covers the last ~500 000 years at a millennial-scale resolution (~1.6 ka) and record the major vegetation and climate changes that occurred during the last 12 (13 only pro parte) marine isotope stages (MIS). Our results indicate that there is a general good correspondence between forested/non-forested periods and glacial/interglacial cycles of marine isotope stratigraphy. Our record shows a progressive change from cooler and wetter to warmer and dryer interglacial conditions. This shift is visible also in glacial vegetation. The interglacial phase corresponding to MIS11 (pollen assemblage zone, PAZ OD-12, 488-455 ka BP and OD-19, 367-328 ka BP) is dominated by montane trees such as conifers. The two younger interglacial periods, MIS5 (PAZ OD-3, 126-70 ka BP) and MIS1 (PAZ OD-1, 12 ka BP to present) are marked by dominance of mesophilous elements such as deciduous and semi-deciduous oaks. Moreover

  18. A 20-ka reconstruction of a Sahelo-Sudanian paleoenvironment using multi-method dating on pedogenic carbonate

    NASA Astrophysics Data System (ADS)

    Diaz, Nathalie; Dietrich, Fabienne; King, Georgina E.; Valla, Pierre G.; Sebag, David; Herman, Frédéric; Verrecchia, Eric P.

    2016-04-01

    Soils can be precious environmental archives as they are open systems resulting from external persistent disturbance, or forcing (Jenny, 1941). Pedogenic carbonate nodules associated with clay-rich soils have been investigated in the Far North region of Cameroon in non-carbonate watersheds (Chad Basin). Nodule bearing soils have mima-like mound morphologies, within stream networks. Such settings raise questions on the processes leading to carbonate precipitation as well as landscape genesis. The mima-like mounds have been identified as degraded Vertisols, resulting from differential erosion induced by a former gilgai micro-relief (Diaz et al., 2016). Non-degraded Vertisols occur in waterlogged areas, located downstream from mima-like mound locations (Braband and Gavaud, 1985). Therefore during a former wetter period Vertisols may have been extended to the mima-like mound areas, followed by a shift toward drier conditions and erosion (Diaz et al., 2016). Consequently, mima-like mounds and associated carbonate nodules are inherited from climatic changes during the Late Pleistocene-Holocene period. The aim of this study is to validate the scenario above using the carbonate nodules collected in a mima-like mound as time archives. Optically stimulated luminescence (OSL) dating of K-feldspars trapped within the nodules is used to assess the deposition time of the soil parent material, composing the mima-like mounds. The carbonate and organic nodule parts have been radiocarbon dated with the aim of assessing the carbonate precipitation age and the age range of soil formation, respectively. Results show that the soil parent material was deposited between 18 ka and 12 ka BP and that the nodules precipitated between 7 ka and 5 ka BP. These results suggest that the deposition occurred during the arid climatic period of the Bossoumian (20 ka to 15 ka BP; Hervieu, 1970) and during the first drier part of the African Humid Period (14.8 ka to 11.5 ka BP; deMenocal et al., 2000

  19. Formation of a 100-kA tokamak discharge in the Princeton large torus by lower hybrid waves

    SciTech Connect

    Jobes, F.; Stevens, J.; Bell, R.; Bernabei, S.; Cavallo, A.; Chu, T.K.; Cohen, S.; Denne, B.; Efthimion, P.; Hinnov, E.

    1984-03-01

    The development of non-inductive current drive is of great importance in establishing the tokamak as a long-pulse or steady-state fusion reactor. Lower hybrid waves, carrying 200 kW of power at 800 MHz, have been launched into the PLT tokamak to initiate and drive the discharge current to a level in excess of 100 kA.

  20. Using membrane composition to fine-tune the pKa of an optical liposome pH sensor.

    PubMed

    Clear, Kasey J; Virga, Katelyn; Gray, Lawrence; Smith, Bradley D

    2016-04-14

    Liposomes containing membrane-anchored pH-sensitive optical probes are valuable sensors for monitoring pH in various biomedical samples. The dynamic range of the sensor is maximized when the probe pKa is close to the expected sample pH. While some biomedical samples are close to neutral pH there are several circumstances where the pH is 1 or 2 units lower. Thus, there is a need to fine-tune the probe pKa in a predictable way. This investigation examined two lipid-conjugated optical probes, each with appended deep-red cyanine dyes containing indoline nitrogen atoms that are protonated in acid. The presence of anionic phospholipids in the liposomes stabilized the protonated probes and increased the probe pKa values by < 1 unit. The results show that rational modification of the membrane composition is a general non-covalent way to fine-tune the pKa of an optical liposome sensor for optimal pH sensing performance.

  1. UV/vis, 1H, and 13C NMR spectroscopic studies to determine mangiferin pKa values.

    PubMed

    Gómez-Zaleta, Berenice; Ramírez-Silva, María Teresa; Gutiérrez, Atilano; González-Vergara, Enrique; Güizado-Rodríguez, Marisol; Rojas-Hernández, Alberto

    2006-07-01

    The acid constants of mangiferin (a natural xanthonoid) in aqueous solution were determined through an UV/vis spectroscopic study employing the SQUAD program as a computational tool. A NMR study complements the pK(a) values assignment and evidences a H-bridge presence on 1-C. The chemical model used was consistent with the experimental data obtained. The pK(a) values determined with this procedure were as follows: H(4)(MGF)=H(3)(MGF)(-)+H(+), pKa1 (6-H)=6.52+/-0.06; H(3)(MGF)(-)=H(2)(MGF)(2-)+H(+), pKa2 (3-H)=7.97+/-0.06; H(2)(MGF)(2-)=H(MGF)(3-)+H(+), pKa3 (7-H)=9.44+/-0.04; H(MGF)(3-)=(MGF)(4-)+H(+), pKa4 (1-H)=12.10+/-0.01; where it has been considered mangiferin C(19)H(18)O(11) as H(4)(MGF). Mangiferin UV/vis spectral behavior, stability study in aqueous solution as well as NMR spectroscopy studies: one-dimensional (1)H,(13)C, 2D correlated (1)H/(13)C performed by (g)-HSQC and (g)-HMBC methods; are also presented. pK(a) values determination of H(4)(MGF) in aqueous solution is a necessary contribution to subsequent pharmacokinetic study, and a step towards the understanding of its biological effects.

  2. Arctic sea ice freeboard from AltiKa and comparison with CryoSat-2 and Operation IceBridge

    NASA Astrophysics Data System (ADS)

    Armitage, Thomas W. K.; Ridout, Andy L.

    2015-08-01

    Satellite radar altimeters have improved our knowledge of Arctic sea ice thickness over the past decade. The main sources of uncertainty in sea ice thickness retrievals are associated with inadequate knowledge of the snow layer depth and the radar interaction with the snow pack. Here we adapt a method of deriving sea ice freeboard from CryoSat-2 to data from the AltiKa Ka band radar altimeter over the 2013-14 Arctic sea ice growth season. AltiKa measures basin-averaged freeboards between 4.4 cm and 6.9 cm larger than CryoSat-2 in October and March, respectively. Using airborne laser and radar measurements from spring 2013 and 2014, we estimate the effective scattering horizon for each sensor. While CryoSat-2 echoes penetrate to the ice surface over first-year ice and penetrate the majority (82 ± 3%) of the snow layer over multiyear ice, AltiKa echoes are scattered from roughly the midpoint (46 ± 5%) of the snow layer over both ice types.

  3. Polysaccharide Nanoparticles for Efficient siRNA Targeting in Cancer Cells by Supramolecular pKa Shift

    PubMed Central

    Zhang, Ying-Ming; Yang, Yang; Zhang, Yu-Hui; Liu, Yu

    2016-01-01

    Biomacromolecular pKa shifting is considered as one of the most ubiquitous processes in biochemical events, e.g., the enzyme-catalyzed reaction and protein conformational stabilization. In this paper, we report on the construction of biocompatible polysaccharide nanoparticle with targeting ability and lower toxicity by supramolecular pKa shift strategy. This was realized through a ternary assembly constructed by the dual host‒guest interactions of an adamantane-bis(diamine) conjugate (ADA) with cucurbit[6]uril (CB[6]) and a polysaccharide. The potential application of such biocompatible nanostructure was further implemented by the selective transportation of small interfering RNA (siRNA) in a controlled manner. It is demonstrated that the strong encapsulation of the ADA’s diammonium tail by CB[6] not only reduced the cytotoxicity of the nano-scaled vehicle but also dramatically enhanced cation density through an obvious positive macrocycle-induced pKa shift, which eventually facilitated the subsequent siRNA binding. With a targeted polysaccharide shell containing a cyclodextrin‒hyaluronic acid conjugate, macrocycle-incorporated siRNA polyplexes were specifically delivered into malignant human prostate PC-3 cells. The supramolecular polysaccharide nanoparticles, the formation of which was enabled and promoted by the complexation-assisted pKa shift, may be used as a versatile tool for controlled capture and release of biofunctional substrates. PMID:27363811

  4. Evaluation of thiol Raman activities and pKa values using internally referenced Ramanbased pH titration

    NASA Astrophysics Data System (ADS)

    Suwandaratne, Nuwanthi

    Thiols are one of the most important classes of chemicals used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. This study is an internally-referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and di-thiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S-H stretching feature relative to an internal reference peak as a function of solution pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curve-fitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation. Using this Raman titration method, first and second thiol pKa values for 1,2-benzenedithol in water were determined for the first time. This method is convenient to implement and its underlying theory is easy to follow.

  5. Human predation contributed to the extinction of the Australian megafaunal bird Genyornis newtoni ∼47 ka.

    PubMed

    Miller, Gifford; Magee, John; Smith, Mike; Spooner, Nigel; Baynes, Alexander; Lehman, Scott; Fogel, Marilyn; Johnston, Harvey; Williams, Doug; Clark, Peter; Florian, Christopher; Holst, Richard; DeVogel, Stephen

    2016-01-29

    Although the temporal overlap between human dispersal across Australia and the disappearance of its largest animals is well established, the lack of unambiguous evidence for human-megafauna interactions has led some to question a human role in megafaunal extinction. Here we show that diagnostic burn patterns on eggshell fragments of the megafaunal bird Genyornis newtoni, found at >200 sites across Australia, were created by humans discarding eggshell in and around transient fires, presumably made to cook the eggs. Dating by three methods restricts their occurrence to between 53.9 and 43.4 ka, and likely before 47 ka. Dromaius (emu) eggshell occur frequently in deposits from >100 ka to present; burnt Dromaius eggshell first appear in deposits the same age as those with burnt Genyornis eggshell, and then continually to modern time. Harvesting of their eggs by humans would have decreased Genyornis reproductive success, contributing to the bird's extinction by ∼47 ka.

  6. An IR Study of Benzoyl Chloride Adsorbed on KA, NaA, and CaA Zeolites

    NASA Astrophysics Data System (ADS)

    Bardakçı, B.; Bahçeli, Semiha

    2005-09-01

    Infrared spectroscopy has been used to investigate the adsorption of liquid benzoyl chloride on A-type zeolites. The data show that at room temperature the Fermi resonance phenomenon occurs in the adsorption on KA, NaA and CaA zeolites which are little acidic aluminosilicates.

  7. The WAIS Divide deep ice core WD2014 chronology - Part 2: Annual-layer counting (0-31 ka BP)

    NASA Astrophysics Data System (ADS)

    Sigl, M.; Fudge, T. J.; Winstrup, M.; Cole-Dai, J.; Ferris, D.; McConnell, J. R.; Taylor, K. C.; Welten, K. C.; Woodruff, T. E.; Adolphi, F.; Bisiaux, M.; Brook, E. J.; Buizert, C.; Caffee, M. W.; Dunbar, N. W.; Edwards, R.; Geng, L.; Iverson, N.; Koffman, B.; Layman, L.; Maselli, O. J.; McGwire, K.; Muscheler, R.; Nishiizumi, K.; Pasteris, D. R.; Rhodes, R. H.; Sowers, T. A.

    2015-07-01

    We present the WD2014 chronology for the upper part (0-2850 m, 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes in the source, transport, and deposition of aerosols. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing to two high-accuracy, absolutely dated chronologies. For the Holocene, the cosmogenic isotope records of 10Be from WAIS Divide and 14C for Intcal13 demonstrated WD2014 was consistently accurate to better than 0.5 % of the age. For the glacial period, comparisons to the Hulu Cave chronology demonstrated WD2014 had an accuracy of better than 1 % of the age at three abrupt climate change events between 27 and 31 ka. WD2014 has consistently younger ages than Greenland ice-core chronologies during most of the Holocene. For the Younger Dryas-Preboreal transition (11 546 ka BP, 24 years younger) and the Bølling-Allerød Warming (14 576 ka, 7 years younger) WD2014 ages are within the combined uncertainties of the timescales. Given its high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere, with synchronization to other chronologies feasible using high quality proxies of volcanism, solar activity, atmospheric mineral dust, and atmospheric methane concentrations.

  8. The WAIS Divide deep ice core WD2014 chronology - Part 2: Annual-layer counting (0-31 ka BP)

    NASA Astrophysics Data System (ADS)

    Sigl, Michael; Fudge, Tyler J.; Winstrup, Mai; Cole-Dai, Jihong; Ferris, David; McConnell, Joseph R.; Taylor, Ken C.; Welten, Kees C.; Woodruff, Thomas E.; Adolphi, Florian; Bisiaux, Marion; Brook, Edward J.; Buizert, Christo; Caffee, Marc W.; Dunbar, Nelia W.; Edwards, Ross; Geng, Lei; Iverson, Nels; Koffman, Bess; Layman, Lawrence; Maselli, Olivia J.; McGwire, Kenneth; Muscheler, Raimund; Nishiizumi, Kunihiko; Pasteris, Daniel R.; Rhodes, Rachael H.; Sowers, Todd A.

    2016-03-01

    We present the WD2014 chronology for the upper part (0-2850 m; 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes in the source, transport, and deposition of aerosols. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing to two high-accuracy, absolutely dated chronologies. For the Holocene, the cosmogenic isotope records of 10Be from WAIS Divide and 14C for IntCal13 demonstrated that WD2014 was consistently accurate to better than 0.5 % of the age. For the glacial period, comparisons to the Hulu Cave chronology demonstrated that WD2014 had an accuracy of better than 1 % of the age at three abrupt climate change events between 27 and 31 ka. WD2014 has consistently younger ages than Greenland ice core chronologies during most of the Holocene. For the Younger Dryas-Preboreal transition (11.595 ka; 24 years younger) and the Bølling-Allerød Warming (14.621 ka; 7 years younger), WD2014 ages are within the combined uncertainties of the timescales. Given its high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere, with synchronization to other chronologies feasible using high-quality proxies of volcanism, solar activity, atmospheric mineral dust, and atmospheric methane concentrations.

  9. 20 kA PFN capacitor bank with solid-state switching. [pulse forming network for plasma studies

    NASA Technical Reports Server (NTRS)

    Posta, S. J.; Michels, C. J.

    1973-01-01

    A compact high-current pulse-forming network capacitor bank using paralleled silicon controlled rectifiers as switches is described. The maximum charging voltage of the bank is 1kV and maximum load current is 20 kA. The necessary switch equalization criteria and performance with dummy load and an arc plasma generator are described.

  10. Progress in GaAs Metamorphic HEMT Technology for Microwave Applications. High Efficiency Ka-Band MHEMT Power MMICs

    NASA Technical Reports Server (NTRS)

    Smith, P. M.; Dugas, D.; Chu, K.; Nichols, K.; Duh, K. H.; Fisher, J.; MtPleasant, L.; Xu, D.; Gunter, L.; Vera, A.

    2003-01-01

    This paper reviews recent progress in the development of GaAs metamorphic HEMT (MHEMT) technology for microwave applications. Commercialization has begun, while efforts to further improve performance, manufacturability and reliability continue. We also report the first multi-watt MHEMT MMIC power amplifiers, demonstrating up to 3.2W output power and record power-added efficiency (PAE) at Ka-band.

  11. Was there a '4.2 ka event' in Great Britain and Ireland? Evidence from the peatland record

    NASA Astrophysics Data System (ADS)

    Roland, T. P.; Caseldine, C. J.; Charman, D. J.; Turney, C. S. M.; Amesbury, M. J.

    2014-01-01

    Palaeoenvironmental and archaeological data from several regions around the world show evidence of a multi-centennial climatic event occurring approximately 4200 cal yr BP (4.2 ka). Whilst the climatic change and/or impact of the 4.2 ka event is clear in certain regions, such as western Asia, evidence for the event has yet to be fully evaluated in northwest Europe. This study presents high-resolution, multi-proxy palaeoclimate records from sites in Northern Ireland, ideally located for an objective examination of the nature of the event in Great Britain and Ireland within the broader context of mid-Holocene climate change c. 6.5-2.5 ka. The peatlands of northwest Europe possess considerable potential for the examination of climatic change in the North Atlantic region, demonstrated by the range of palaeohydrological proxy data generated during this study (peat humification, plant macrofossil and testate amoebae analyses) supported by a high-resolution chronology (including comprehensive AMS 14C and tephrochronology). The inter-site testate amoebae reconstructions appear coherent and were combined to produce a regional climatic record, in marked contrast to the plant macrofossil and peat humification records that appear climatically complacent. The testate amoebae reconstruction, however, provides no compelling evidence for a 4.2 ka event signal and is consistent with previously reported studies from across northwest Europe, suggesting the origin and impact of this event is spatially complex.

  12. Determination of the pKa of the N-terminal amino group of ubiquitin by NMR

    PubMed Central

    Oregioni, Alain; Stieglitz, Benjamin; Kelly, Geoffrey; Rittinger, Katrin; Frenkiel, Tom

    2017-01-01

    Ubiquitination regulates nearly every aspect of cellular life. It is catalysed by a cascade of three enzymes and results in the attachment of the C-terminal carboxylate of ubiquitin to a lysine side chain in the protein substrate. Chain extension occurs via addition of subsequent ubiquitin molecules to either one of the seven lysine residues of ubiquitin, or via its N-terminal α-amino group to build linear ubiquitin chains. The pKa of lysine side chains is around 10.5 and hence E3 ligases require a mechanism to deprotonate the amino group at physiological pH to produce an effective nucleophile. In contrast, the pKa of N-terminal α-amino groups of proteins can vary significantly, with reported values between 6.8 and 9.1, raising the possibility that linear chain synthesis may not require a general base. In this study we use NMR spectroscopy to determine the pKa for the N-terminal α-amino group of methionine1 of ubiquitin for the first time. We show that it is 9.14, one of the highest pKa values ever reported for this amino group, providing a rational for the observed need for a general base in the E3 ligase HOIP, which synthesizes linear ubiquitin chains. PMID:28252051

  13. β-(1-Azulenyl)-L-alanine--a functional probe for determination of pKa of histidine residues.

    PubMed

    Gosavi, Pallavi M; Moroz, Yurii S; Korendovych, Ivan V

    2015-03-28

    β-(1-Azulenyl)-L-alanine (AzAla) can be incorporated into the influenza A virus M2 proton channel. AzAla's sensitivity to the protonation state of the nearby histidines and the lack of environmental fluorescence dependence allow for direct and straightforward determination of histidine pKa values in ion channels.

  14. Human predation contributed to the extinction of the Australian megafaunal bird Genyornis newtoni ∼47 ka

    PubMed Central

    Miller, Gifford; Magee, John; Smith, Mike; Spooner, Nigel; Baynes, Alexander; Lehman, Scott; Fogel, Marilyn; Johnston, Harvey; Williams, Doug; Clark, Peter; Florian, Christopher; Holst, Richard; DeVogel, Stephen

    2016-01-01

    Although the temporal overlap between human dispersal across Australia and the disappearance of its largest animals is well established, the lack of unambiguous evidence for human–megafauna interactions has led some to question a human role in megafaunal extinction. Here we show that diagnostic burn patterns on eggshell fragments of the megafaunal bird Genyornis newtoni, found at >200 sites across Australia, were created by humans discarding eggshell in and around transient fires, presumably made to cook the eggs. Dating by three methods restricts their occurrence to between 53.9 and 43.4 ka, and likely before 47 ka. Dromaius (emu) eggshell occur frequently in deposits from >100 ka to present; burnt Dromaius eggshell first appear in deposits the same age as those with burnt Genyornis eggshell, and then continually to modern time. Harvesting of their eggs by humans would have decreased Genyornis reproductive success, contributing to the bird's extinction by ∼47 ka. PMID:26823193

  15. Radar Cross-Section (RCS) Measurements of a Dismount With Rocket-Propelled Grenade (RPG) Launcher at Ka-Band

    DTIC Science & Technology

    2006-07-01

    corner reflector of known cross section was placed on the... Radar Cross - Section (RCS) Measurements of a Dismount with Rocket-Propelled Grenade (RPG) Launcher at Ka-Band by Suzanne R. Stratton and...Laboratory Aberdeen Proving Ground, MD 21005 ARL-TR-3855 July 2006 Radar Cross - Section (RCS) Measurements of a Dismount with

  16. A New Blind Pointing Model Improves Large Reflector Antennas Precision Pointing at Ka-Band (32 GHz)

    NASA Technical Reports Server (NTRS)

    Rochblatt, David J.

    2009-01-01

    The National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)-Deep Space Network (DSN) subnet of 34-m Beam Waveguide (BWG) Antennas was recently upgraded with Ka-Band (32-GHz) frequency feeds for space research and communication. For normal telemetry tracking a Ka-Band monopulse system is used, which typically yields 1.6-mdeg mean radial error (MRE) pointing accuracy on the 34-m diameter antennas. However, for the monopulse to be able to acquire and lock, for special radio science applications where monopulse cannot be used, or as a back-up for the monopulse, high-precision open-loop blind pointing is required. This paper describes a new 4th order pointing model and calibration technique, which was developed and applied to the DSN 34-m BWG antennas yielding 1.8 to 3.0-mdeg MRE pointing accuracy and amplitude stability of 0.2 dB, at Ka-Band, and successfully used for the CASSINI spacecraft occultation experiment at Saturn and Titan. In addition, the new 4th order pointing model was used during a telemetry experiment at Ka-Band (32 GHz) utilizing the Mars Reconnaissance Orbiter (MRO) spacecraft while at a distance of 0.225 astronomical units (AU) from Earth and communicating with a DSN 34-m BWG antenna at a record high rate of 6-megabits per second (Mb/s).

  17. Phase and frequency structure of superradiance pulses generated by relativistic Ka-band backward-wave oscillator

    SciTech Connect

    Rostov, V. V.; Romanchenko, I. V.; Elchaninov, A. A.; Sharypov, K. A.; Shunailov, S. A.; Ul'masculov, M. R.; Yalandin, M. I.

    2016-08-15

    Phase and frequency stability of electromagnetic oscillations in sub-gigawatt superradiance (SR) pulses generated by an extensive slow-wave structure of a relativistic Ka-band backward-wave oscillator were experimentally investigated. Data on the frequency tuning and radiation phase stability of SR pulses with a variation of the energy and current of electron beam were obtained.

  18. New magnetic command system for a 200-kA circuit breaker with 10-mus current transfer time.

    PubMed

    Baget, R; Rioux-Damidau, F

    1979-04-01

    We present improvements of the previously described command system of a 200-kA circuit breaker with 10-mus current transfer time. It uses the magnetic pressure produced by a high-current pulse sent through two flat conductors instead of a coaxial circuit. The necessary command current is cut in half and the standoff voltage is higher.

  19. Beam dynamics in the ETA and ATA 10 kA linear induction accelerators: observations and issues

    SciTech Connect

    Briggs, R.J.; Birx, D.L.; Caporaso, G.J.; Fessenden, T.J.; Hester, R.E.; Melendez, R.; Neil, V.K.; Paul, A.C.; Struve, K.W.

    1981-03-06

    The 10 kA ETA and ATA linear induction accelerators are described. Beam instability is the major concern in these high current machines, and the current status of theoretical understanding, and experimental investigations with the 8 cavity ETA, are reviewed. Modifications to the induction cavities are described that have essentially eliminated the transverse resonant modes seen in the ETA.

  20. Determination of the pKa of the N-terminal amino group of ubiquitin by NMR.

    PubMed

    Oregioni, Alain; Stieglitz, Benjamin; Kelly, Geoffrey; Rittinger, Katrin; Frenkiel, Tom

    2017-03-02

    Ubiquitination regulates nearly every aspect of cellular life. It is catalysed by a cascade of three enzymes and results in the attachment of the C-terminal carboxylate of ubiquitin to a lysine side chain in the protein substrate. Chain extension occurs via addition of subsequent ubiquitin molecules to either one of the seven lysine residues of ubiquitin, or via its N-terminal α-amino group to build linear ubiquitin chains. The pKa of lysine side chains is around 10.5 and hence E3 ligases require a mechanism to deprotonate the amino group at physiological pH to produce an effective nucleophile. In contrast, the pKa of N-terminal α-amino groups of proteins can vary significantly, with reported values between 6.8 and 9.1, raising the possibility that linear chain synthesis may not require a general base. In this study we use NMR spectroscopy to determine the pKa for the N-terminal α-amino group of methionine1 of ubiquitin for the first time. We show that it is 9.14, one of the highest pKa values ever reported for this amino group, providing a rational for the observed need for a general base in the E3 ligase HOIP, which synthesizes linear ubiquitin chains.