HF-enhanced 4278-Å airglow: evidence of accelerated ionosphere electrons?

NASA Astrophysics Data System (ADS)

Fallen, C. T.; Watkins, B. J.

2013-12-01

We report calculations from a one-dimensional physics-based self-consistent ionosphere model (SCIM) demonstrating that HF-heating of F-region electrons can produce 4278-Å airglow enhancements comparable in magnitude to those reported during ionosphere HF modification experiments at the High-frequency Active Auroral Research Program (HAARP) observatory in Alaska. These artificial 'blue-line' emissions, also observed at the EISCAT ionosphere heating facility in Norway, have been attributed to arise solely from additional production of N2+ ions through impact ionization of N2 molecules by HF-accelerated electrons. Each N2+ ion produced by impact ionization or photoionization has a probability of being created in the N2+(1N) excited state, resulting in a blue-line emission from the allowed transition to its ground state. The ionization potential of N2 exceeds 18 eV, so enhanced impact ionization of N2 implies that significant electron acceleration processes occur in the HF-modified ionosphere. Further, because of the fast N2+ emission time, measurements of 4278-Å intensity during ionosphere HF modification experiments at HAARP have also been used to estimate artificial ionization rates. To the best of our knowledge, all observations of HF-enhanced blue-line emissions have been made during twilight conditions when resonant scattering of sunlight by N2+ ions is a significant source of 4278-Å airglow. Our model calculations show that F-region electron heating by powerful O-mode HF waves transmitted from HAARP is sufficient to increase N2+ ion densities above the shadow height through temperature-enhanced ambipolar diffusion and temperature-suppressed ion recombination. Resonant scattering from the modified sunlit region can cause a 10-20 R increase in 4278-Å airglow intensity, comparable in magnitude to artificial emissions measured during ionosphere HF-modification experiments. This thermally-induced artificial 4278-Å aurora occurs independently of any artificial aurora maintained by HF-accelerated (non-thermal) electrons. The numerical results presented here do not necessarily rule out the presence of HF-accelerated electrons with energies exceeding 18 eV. However, vertical or field-aligned airglow intensity measurements made during twilight conditions do not provide definitive evidence of energetic HF-accelerated electrons. Consequently, artificial blue-line airglow measurements should not be used to estimate N2+ ionization rates without also accounting for temperature-dependent chemistry and diffusion. Future experiments that make simultaneous measurements of N2+ ion airglow emissions from both the first negative bands and the Meinel bands can potentially resolve the relative contributions of accelerated electron and resonant scattering mechanisms. Airglow emission rates from these bands are expected to be in strict proportion when the emissions result from electron impact ionization of N2 molecules. Side-view altitude-resolved 4278-Å airglow measurements may also indicate the presence of energetic HF-accelerated electrons if the blue-line emissions are determined to occur below the shadow height.

ELF/VLF Wave Generation and Scattering from Modulated Heating of the Ionosphere at Arecibo Observatory

NASA Astrophysics Data System (ADS)

Maxworth, A. S.; Golkowski, M.; McCormick, J.; Cohen, M.; Hosseini, P.; Bittle, J.

2017-12-01

The recently completed ionospheric heater at Arecibo Observatory is used for modulated HF (5 or 8 MHz) heating of the ionosphere, to generate ELF/VLF (3 Hz - 30 kHz) waves. Observation of ramp and tone signals at frequencies from hundreds of Hz to several kHz at multiple receivers confirms the ability of the heater to modulate D region currents and create an ELF/VLF antenna in the ionosphere. Observed ELF/VLF signal amplitudes are lower than for similar experiments performed at high latitudes at the HAARP and Tromso facilities, for a variety of reasons including the reduced natural currents at mid latitudes, and the lower HF power of the Arecibo heater. The heating of the overhead ionosphere is also observed to change the Earth-ionosphere waveguide propagation characteristics as is evident from simultaneous observations of lightning induced sferics and VLF transmitter signals that propagate under the heated region. The active heating of the ionosphere modifies the reflection of incident VLF (3-30 kHz) waves. We present initial observations of HF heating of the D-region and resulting ELF/VLF wave generation.

Studies of the Ionospheric Turbulence Excited by the Fourth Gyroharmonic at HAARP

NASA Astrophysics Data System (ADS)

Milikh, G. M.; Najmi, A. C.; Mahmoudian, A.; Bernhardt, P. A.; Briczinski, S.; Siefring, C. L.; Yampolski, Y.; Alexander, K.; Sopin, A.; Zalizovski, A.; Chiang, K.; Psiaki, M. L.; Morton, Y.; Taylor, S.; Papadopoulos, K.

2014-12-01

We report the results of a set of experiments conducted during the HAARP June 2014 campaign, whose objective was to study the development of artificial ionospheric turbulence. During the experiments, the heating frequency was stepped up and down near the 4th gyroharmonic, and the power of the heating HF radiation was varied. Our diagnostics included: measurements of phase-derived Slant Total Electron Content using the L1/L2 signals from PRN 25 GPS satellite received at HAARP; measurements of Stimulated Electromagnetic Emission (SEE) conducted 15 km away from the HAARP site; detection of the HAARP HF radiation at Vernadsky station located in Antarctica ~15.6 Mm from HAARP; ionograms from HAARP's digisonde and reflectance data from Kodiak radar. Our observations showed: a distinct correlation between the broad upshifted maximum detected by the SEE and strong suppression of the HF signals detected at Vernadsky station; drift velocity of the ionospheric irregularities causing HF scattering detected at Vernadsky station corresponds to that measured by the Kodiak radar; the intensity of the scattered radar signals by Kodiak correlates with the amplitude of downshifted maximum observed by the SEE.

Radiotomographic imaging and GNSS remote sensing of the midlatitude ionosphere modified by powerful HF radiowaves.

NASA Astrophysics Data System (ADS)

Kunitsyn, V.; Andreeva, E. S.; Padokhin, A. M.; Vorontsov, A.; Frolov, V. L.; Komrakov, G.; Bernhardt, P. A.; Siefring, C. L.

2014-12-01

We present the results of the radiotomographic imaging and GNSS remote sensing of the artificial ionospheric disturbances obtained in the recent experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out at the Sura heating facility. The experiments were conducted using both O- and X- mode radiowaves, in daytime and nighttime conditions with various schemes of the radiation of the heating wave. Radio transmissions from the low- (Parus, e-POP on CASSIOPE) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. We study the variations in TEC caused by HF heating showing that the GNSS TEC spectra often contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. In this work we also present the radiotomographic reconstructions (including first time e-POP-SURA reconstructions) of the spatial structure of the disturbed area of the ionosphere corresponding to the directivity pattern of the heater as well as the spatial structure of the wave- like disturbances, which are possibly heating-induced AGWs, diverging from the heated area of the ionosphere. The spatial period of observed disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region, which is in good agreement with the modeling results.

Investigation of ELF/VLF waves created by a "beat-wave" HF ionospheric heating at high latitudes

NASA Astrophysics Data System (ADS)

Shumilov, Oleg; Tereshchenko, Evgeniy; Kasatkina, Elena; Gomonov, Alexandr

2015-04-01

The generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) electromagnetic waves by modulated ionospheric high frequency (HF, 2-30 MHz) heating is one of the main directions of ionospheric modification experiments. In this work, we present observations of ELF waves generated during a "beat-wave" heating experiments at the EISCAT heating facility. ELF waves were registered with the ELF receiver located at Lovozero (68 N, 35 E), 660 km east from the EISCAT Tromso heating facility (69.6 N, 19.2 E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

Prompt Ion Outflows and Artificial Ducts during High-Power HF Heating at HAARP: Effect of Suprathermal Electrons?

NASA Astrophysics Data System (ADS)

Mishin, E. V.; Milikh, G. M.

2014-12-01

In situ observations from the DMSP and Demeter satellites established that high-power HF heating of the ionosphere F-region results in significant ion outflows associated with 10-30% density enhancements in the topside ionosphere magnetically-conjugate to the heated region. As follows from the SAMI2 two-fluid model calculations, their formation time should exceed 5-7 minutes. However, specially designed DMSP-HAARP experiments have shown that artificial ducts and ion outflows appear on the topside within 2 minutes. We describe the results of these observations and present a semi-quantitative explanation of the fast timescale due to suprathermal electrons accelerated by HF-induced plasma turbulence. There are two possible effects of suprathermal electrons: (1) the increase of the ambipolar electric field over the usual thermal ambipolar diffusion and (2) excitation of heat flux-driven plasma instability resulting in an anomalous electron-ion momentum exchange. Both effects result in faster upward ion flows.

Thermal response of the F region ionosphere in artificial modification experiments by HF radio waves

NASA Technical Reports Server (NTRS)

Mantas, G. P.; Lahoz, C. H.; Carlson, H. C., Jr.

1981-01-01

The thermal response of the nighttime F region ionosphere to local heating by HF radio waves has been observed with the incoherent scatter radar at Arecibo, Puerto Rico. The observations consist of high-resolution space and time variation of the electron temperature as a high-power HF transmitter is switched on and off with a period 240 s. As soon as the HF transmitter is turned on, the electron temperature begins to rise rapidly in a narrow altitude region near 300 km, below the F2 layer peak. The electron temperature perturbation subsequently spreads over a broader altitude region. The observations are compared with the anticipated thermal response of the ionosphere based on numerical solutions of the coupled time-dependent heat conduction equations for the electron and composite ion gases and are found to be in good agreement over the entire altitude region covered by the observations.

Nonlinear Interactions within the D-Region Ionosphere

NASA Astrophysics Data System (ADS)

Moore, Robert

2016-07-01

This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we saw a tremendous improvement in ELF/VLF wave generation efficiency. We identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.

High-speed measurement of an air transect's temperature shift heated by laser beam

NASA Astrophysics Data System (ADS)

Li, WenYu; Jiang, ZongFu; Xi, Fengjie; Li, Qiang; Xie, Wenke

2005-02-01

Laser beam heat the air on the optic path, Beam-deflection optical tomography is a non-intrusive method to measure the 2-dimension temperature distribution in the transect. By means of linear Hartmann Sensor at the rate of 27kHz, the optic path was heated by a 2.7μm HF laser, continuous and high time resolution gradients of optic phase were obtained. the result of analysing and calculation showed the temperament shift in the heated beam path was not higher than 50K when the HF laser power was 9W. The experiment showed that it is a practical non-intrusive temperature shift measurement method for a small area aero-optical medium.

Hardness and Second Phase Percentage of Ni-Ti-Hf Compounds After Heat Treatment at 700C

NASA Technical Reports Server (NTRS)

Stanford, Malcolm K.

2017-01-01

The Vickers hardness and second phase precipitation of three ternary intermetallic Ni-Ti-Hf compounds containing either 1, 3 or 5 at.% Hf were compared to 60-Nitinol (55 at.% Ni - 45 at.% Ti). Heat treatment either at 700 C or with a subsequent aging step, hardened the 3 and 5 at.% Hf-containing ternaries to approximately 620 HV (56 HRC). Heat treatment increased the hardness of the 1 at.% Hf compound by more than 25 percent. Average hardness of the 3 and 5 at.% Hf ternaries, though higher than that of the binary Ni-Ti or the Ni-Ti-Hf compound containing 1 at.% Hf, appeared to be fairly insensitive to the different heat treatments. There was a drastic reduction of fatigue-enhancing second phase precipitates for the 5 at.% Hf ternaries compared to the other compounds. These results should guide materials selection for development of aerospace componentry.

Dumping of auroral kilometric radiation caused by HF heating facility

NASA Astrophysics Data System (ADS)

Mogilevsky, M.; Romantsova, T.; Moiseenko, I.; Bosenger, T.; Rietveld, M.; Hanasz, J.

2012-04-01

We have use measurements of electromagnetic waves and plasma onboard of INTERBALL-2 satellite during joint experiment with Tromso HF heating facility. During the selected event the satellite crossed magnetic flux tube with a footprint at the ionosphere above heater. It was found significant dumping of AKR few minutes after the pumping was switched on. The most prominent dumping was detected at high frequency AKR (500-600 kHz) which were emitted at the height of 2-3 thousands km. Two possible mechanisms of this phenomenon are discussed: (i) reflection AKR from the region with increased electron density and (ii) suppression emission by decrease efficiency of the source caused up going plasma from the heated ionosphere.

Effects of modification of the polar ionosphere with high-power short-wave extraordinary-mode HF waves produced by the spear heating facility

NASA Astrophysics Data System (ADS)

Borisova, T. D.; Blagoveshchenskaya, N. F.; S. Kalishin, A.; Oksavik, K.; Baddelley, L.; K. Yeoman, T.

2012-06-01

We present the results of modifying the F2 layer of the polar ionosphere experimentally with highpower HF extraordinary-mode waves. The experiments were performed in October 2010 using the short-wave SPEAR heating facility (Longyearbyen, Spitsbergen). To diagnose the effects of high-power HF waves by the aspect-scattering method in a network of diagnostic paths, we used the short-wave Doppler radar CUTLASS (Hankasalmi, Finland) and the incoherent scatter radar ESR (Longyearbyen, Spitsbergen). Excitation of small-scale artificial ionospheric irregularities was revealed, which were responsible for the aspect and backward scattering of the diagnostic signals. The measurements performed by the ESR incoherent scatter radar simultaneously with the heating demonstrated changes in the parameters of the ionospheric plasma, specifically, an increase in the electron density by 10-25 % and an increase in the electron temperature by 10-30 % at the altitudes of the F2 layer, as well as formation of sporadic ionization at altitudes of 140-180 km (below the F2 layer maximum). To explain the effects of ionosphere heating with HF extraordinary-mode waves, we propose a hypothesis of transformation of extraordinary electromagnetic waves to ordinary in the anisotropic, smoothly nonuniform ionosphere.

High Power Radio Wave Interactions within the D-Region Ionosphere

NASA Astrophysics Data System (ADS)

Moore, R. C.

2014-12-01

This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we have seen a tremendous improvement in ELF/VLF wave generation efficiency. We have identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.

Artificial excitation of ELF waves with frequency of Schumann resonance

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Guido, T.; Tulegenov, B.; Labenski, J.; Chang, C.-L.

2014-11-01

We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8-8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20-4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere.

Altered thermoregulatory responses in heart failure patients exercising in the heat.

PubMed

Balmain, Bryce N; Jay, Ollie; Sabapathy, Surendran; Royston, Danielle; Stewart, Glenn M; Jayasinghe, Rohan; Morris, Norman R

2016-11-01

Heart failure (HF) patients appear to exhibit impaired thermoregulatory capacity during passive heating, as evidenced by diminished vascular conductance. Although some preliminary studies have described the thermoregulatory response to passive heating in HF, responses during exercise in the heat remain to be described. Therefore, the aim of this study was to compare thermoregulatory responses in HF and controls (CON) during exercise in the heat. Ten HF (NYHA classes I-II) and eight CON were included. Core temperature (T c ), skin temperature (T sk ), and cutaneous vascular conductance (CVC) were assessed at rest and during 1 h of exercise at 60% of maximal oxygen uptake. Metabolic heat production (H prod ) and the evaporative requirements for heat balance (E req ) were also calculated. Whole-body sweat rate was determined from pre-post nude body mass corrected for fluid intake. While H prod (HF: 3.9 ± 0.9; CON: 6.4 ± 1.5 W/kg) and E req (HF: 3.3 ± 0.9; CON: 5.6 ± 1.4 W/kg) were lower (P < 0.01) for HF compared to CON, both groups demonstrated a similar rise in T c (HF: 0.9 ± 0.4; CON: 1.0 ± 0.3°C). Despite this similar rise in T c , T sk (HF: 1.6 ± 0.7; CON: 2.7 ± 1.2°C), and the elevation in CVC (HF: 1.4 ± 1.0; CON: 3.0 ± 1.2 au/mmHg) was lower (P < 0.05) in HF compared to CON Additionally, whole-body sweat rate (HF: 0.36 ± 0.15; CON: 0.81 ± 0.39 L/h) was lower (P = 0.02) in HF compared to CON Patients with HF appear to be limited in their ability to manage a thermal load and distribute heat content to the body surface (i.e., skin), secondary to impaired circulation to the periphery. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

SPEAR-induced field-aligned irregularities observed from bi-static HF radio scattering in the polar ionosphere

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Kalishin, A. S.; Robinson, T. R.; Yeoman, T. K.; Wright, D. M.; Baddeley, L. J.

2009-01-01

Experimental results from SPEAR HF heating experiments in the polar ionosphere are examined. Bi-static scatter measurements of HF diagnostic signals were carried out on the Pori (Finland)-SPEAR-St. Petersburg path at operational frequencies of 11,755 and 15,400 kHz and the London-SPEAR-St. Petersburg path at frequencies of 12,095 and 17,700 kHz, using a Doppler spectral method. The SPEAR HF heating facility generates heater-induced artificial field-aligned small-scale irregularities (AFAIs), which can be detected by HF diagnostic bi-static radio scatter techniques at St. Petersburg at a distance of about 2000 km. In accordance with the Bragg condition, HF bi-static backscatters were sensitive to small-scale irregularities having spatial sizes of the order of 9-13 m across the geomagnetic field line. The properties and behaviour of AFAIs have been considered in the winter and summer seasons under quiet magnetic conditions and under various status of the polar ionosphere (the presence of "thick" and "thin" sporadic Es layers, different structures of the F2 layer). The experimental results obtained have shown that AFAIs can be excited in the F as well as in the E regions of the polar ionosphere. The excitation of a very intense wide-band spectral component with an abrupt increase in the spectral width up to 16-20 Hz has been found in the signals scattered from striations. Along with a wide-band component, a narrow-band spectral component can be also seen in the Doppler sonograms and in the average spectra of the signals scattered from the SPEAR-induced striations. AFAIs were excited even when the HF heater frequency was up to 0.5 MHz larger than the critical frequency. A simulation of the ray geometry for the diagnostic HF radio waves scattered from AFAIs in the polar ionosphere has been made for the geophysical conditions prevailing during experiments carried out in both the winter and summer seasons.

The CERTO Beacon on CASSIOPE/e-POP and Experiments Using High-Power HF Ionospheric Heaters

NASA Astrophysics Data System (ADS)

Siefring, Carl L.; Bernhardt, Paul A.; James, H. Gordon; Parris, Richard Todd

2015-06-01

A new Coherent Electromagnetic Radio Tomography (CERTO) beacon is on the CASSIOPE satellite and part of the enhanced-Polar Outflow Probe (e-POP) suite of scientific instruments. CERTO signals can be used to measure ionospheric Total Electron Content (TEC) and radio scintillations along propagation paths between CERTO and receivers. The combination of CERTO and the array of e-POP in-situ diagnostics form a powerful tool for studying ionospheric plasma processes that have not been previously possible. Of note, the combination CERTO and the Radio Receiver Instrument (RRI), a modern digital receiver, which measures between 10 Hz to 18 MHz in selectable bands allows for innovative High Frequency (HF) radio propagation experiments. The use of high-power HF ionospheric heating facilities for such experiments further allows for repeatable studies of a number of important plasma processes. The new CERTO beacon transmits un-modulated, phase-coherent waves at 150, 400, and 1067 MHz with either right-hand-circular or linear polarization and TEC is measured using either differential phase and/or Faraday rotation. With a linear array of CERTO receivers, TEC data can be used for tomographic imaging of the ionosphere yielding two-dimensional maps of the plasma below the satellite orbit. In addition, the three CERTO frequencies cover a wide range for determination of radio scintillation effects caused by diffraction from propagation through ionospheric irregularities. We will describe the CERTO beacon and several potential innovative experiments using HF heating facilities in conjunction with CERTO, the RRI and other e-POP instruments.

Optimizing an ELF/VLF Phased Array at HAARP

NASA Astrophysics Data System (ADS)

Fujimaru, S.; Moore, R. C.

2013-12-01

The goal of this study is to maximize the amplitude of 1-5 kHz ELF/VLF waves generated by ionospheric HF heating and measured at a ground-based ELF/VLF receiver. The optimization makes use of experimental observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) Observatory in Gakona, Alaska. During these experiments, the amplitude, phase, and propagation delay of the ELF/VLF waves were carefully measured. The HF beam was aimed at 15 degrees zenith angle in 8 different azimuthal directions, equally spaced in a circle, while broadcasting a 3.25 MHz (X-mode) signal that was amplitude modulated (square wave) with a linear frequency-time chirp between 1 and 5 kHz. The experimental observations are used to provide reference amplitudes, phases, and propagation delays for ELF/VLF waves generated at these specific locations. The presented optimization accounts for the trade-off between duty cycle, heated area, and the distributed nature of the source region in order to construct a "most efficient" phased array. The amplitudes and phases generated by modulated heating at each location are combined in post-processing to find an optimal combination of duty cycle, heating location, and heating order.

Upper Hybrid Effects in Artificial Ionization

NASA Astrophysics Data System (ADS)

Papadopoulos, K.; Eliasson, B. E.

2014-12-01

A most fascinating result of recent ionospheric experiments has been the discovery of artificial ionization by Pedersen et al. (GRL, 37, L02106, 2010). The Artificial Ionospheric Layers (AIL) were the result of F-region O-mode HF irradiation using the HAARP ionospheric heater operating at 3.6 MW power. As demonstrated by Eliasson et al. (JGR, 117, A10321, 2012) the physics controlling the observed phenomenon and its threshold can be summarized as: " Collisional ionization due to high energy (~ 20 eV) electron tails generated by the interaction of strong Langmuir turbulence with plasma heated at the upper hybrid resonance and transported at the reflection height". The objective of the current presentation is to explore the role of the upper hybrid heating in the formation of AIL and its implications to future experiments involving HF heaters operating in middle and equatorial latitudes.

Topside enhancements of the ionline in response to high-power HF-radio wave pumping at high latitudes

NASA Astrophysics Data System (ADS)

Rexer, Theresa; Gustavsson, Björn; Grydeland, Tom; Rietveld, Mike; Leyser, Thomas; Brändström, Urban; Sergienko, Tima

2017-04-01

A high power, high frequency heating experiment of the polar ionosphere was conducted in Tromsø, Norway in March 2016. The wave-plasma interactions were observed with the European Incoherent SCATer UHF radar co-located with the heating facility. HF pulses in a 3 minute ON 3 minute OFF cycles were transmitted, sweeping frequencies in 10 and 20 kHz steps from just below to just above the 3rd and 4th multiples of the F-region gyro-frequency. Several interesting features have been found in the radar measurements of the backscatter from the heated plasma. In agreement with current theory we observed an enhanced ionline near the HF reflection height on the bottom-side of the F layer. Simultaneously, a less intense, but clearly visible, ionline enhancement was observed approximately 100 km above this bottom-side enhancement for several 3 minute sweep pulses. We present the observations and discuss the top-side enhanced ion-line in relation to Z and L-mode propagation through the F-region peak.

Artificial Aurora and Ionospheric Heating by HAARP

NASA Astrophysics Data System (ADS)

Hadavandkhani, S.; Nikouravan, Bijan; Ghazimaghrebi, F.

2016-08-01

A recent experiment was achieved at HAARP to study the scaling of the ionospherically generated ELF signal with power transmitted from the high frequency (HF) array. The results were in excellent agreement with computer simulations. The outcomes approving that the ELF power increases with the square of the incident HF power. This paper present a review on the situation of the ionized particles in Ionospheric layer when stimulated by artificial an ELF and VLF external high energy radio waves.

Initial Results from CASSIOPE/ePOP Satellite Overpasses above HAARP in 2014

NASA Astrophysics Data System (ADS)

Siefring, C. L.; Bernhardt, P. A.; Briczinski, S. J., Jr.; James, H. G.; Yau, A. W.; Knudsen, D. J.

2015-12-01

The High Frequency Active Auroral Research Program (HAARP) facility was operated in conjunction with overpasses of the enhanced Polar Outflow Probe (ePOP) instruments on the Canadian CASSIOPE satellite. During these overpasses HAARP was operated in several different heating modes and regimes as diagnosed by the characteristics of Stimulated Electromagnetic Emissions (SEE) using ground-based receivers while simultaneously ePOP monitored in-situ HF and VLF signals, looked for ion and electron heating, and provided VHF and UHF signals for propagation effects studies. The e-POP suite of instruments and particularly the ePOP Radio Receiver Instrument (RRI) offer a unique combination diagnostics appropriate for studying the non-linear plasma effects generated high-power HF waves in the ionosphere. In this presentation, the initial results from ePOP observations from two separate 2014 measurement campaigns at HAARP (April 16 to April 29 and May 25 to June 9) will be discussed. Several innovative experiments were performed during the campaign. Experiments explored a wide range of ionospheric effects. These include: 1) Penetration of HF pump waves into the ionosphere via large and small scale irregularities, 2) effects of gyro-harmonic heating and artificial ionization layers, 3) effects of HAARP beam shape with O- and X-mode transmissions, 4) coupling of Lower Hybrid modes into Whistler waves, 5) D/E-region VLF generation in the ionosphere using VLF modulation of the HF pump 6) scattering of VHF and UHF signals and 7) scattering and non-linear modulation of a 9.5 MHz probe wave propagating through the region of the ionosphere modified by HAARP. This work supported by the Naval Research Laboratory Base Program.

ELF Waves Generated by Modulated HF Heating of the Auroral Electrojet and Observed at a Ground Distance of Approximately 4400 km

DTIC Science & Technology

2007-05-22

HAARP ) HF transmitter in Gakona, Alaska, and detected after propagating more than 4400 km in the Earth-ionosphere waveguide to Midway Atoll. The...conductivity variation (created by modulated HF heating) and radiating 4–32 W. The HF-ELF conversion efficiency at HAARP is thus estimated to be...Program ( HAARP ) research station in Gakona, Alaska. The HAARP HF transmitter (or heater), which JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, A05309, doi

Generation of whistler waves by continuous HF heating of the upper ionosphere

NASA Astrophysics Data System (ADS)

Vartanyan, A.; Milikh, G. M.; Eliasson, B. E.; Sharma, A.; Chang, C.; Parrot, M.; Papadopoulos, K.

2013-12-01

We report observations of VLF waves by the DEMETER satellite overflying the HAARP facility during ionospheric heating experiments. The detected VLF waves were in the range 8-17 kHz and coincided with times of continuous heating. The experiments indicate whistler generation due to conversion of artificial lower hybrid waves to whistlers on small scale field-aligned plasma density striations. The observations are compared with theoretical models, taking into account both linear and nonlinear processes. Implications of the mode conversion technique on VLF generation with subsequent injection into the radiation belts to trigger particle precipitation are discussed.

Do mitochondria limit hot fish hearts? Understanding the role of mitochondrial function with heat stress in Notolabrus celidotus.

PubMed

Iftikar, Fathima I; Hickey, Anthony J R

2013-01-01

Hearts are the first organs to fail in animals exposed to heat stress. Predictions of climate change mediated increases in ocean temperatures suggest that the ectothermic heart may place tight constraints on the diversity and distribution of marine species with cardiovascular systems. For many such species, their upper temperature limits (Tmax) and respective heart failure (HF) temperature (T(HF)) are only a few degrees from current environmental temperatures. While the ectothermic cardiovascular system acts as an "ecological thermometer," the exact mechanism that mediates HF remains unresolved. We propose that heat-stressed cardiac mitochondria drive HF. Using a common New Zealand fish, Notolabrus celidotus, we determined the THF (27.5°C). Haemoglobin oxygen saturation appeared to be unaltered in the blood surrounding and within heat stressed hearts. Using high resolution respirometry coupled to fluorimeters, we explored temperature-mediated changes in respiration, ROS and ATP production, and overlaid these changes with T(HF). Even at saturating oxygen levels several mitochondrial components were compromised before T(HF). Importantly, the capacity to efficiently produce ATP in the heart is limited at 25°C, and this is prior to the acute T(HF) for N. celidotus. Membrane leakiness increased significantly at 25°C, as did cytochrome c release and permeability to NADH. Maximal flux rates and the capacity for the electron transport system to uncouple were also altered at 25°C. These data indicate that mitochondrial membrane integrity is lost, depressing ATP synthesis capacity and promoting cytochrome c release, prior to T(HF). Mitochondria can mediate HF in heat stressed hearts in fish and play a significant role in thermal stress tolerance, and perhaps limit species distributions by contributing to HF.

Spatial Structure of Large-Scale Plasma Density Perturbations HF-Induced in the Ionospheric F 2 Region

NASA Astrophysics Data System (ADS)

Frolov, V. L.; Komrakov, G. P.; Glukhov, Ya. V.; Andreeva, E. S.; Kunitsyn, V. E.; Kurbatov, G. A.

2016-07-01

We consider the experimental results obtained by studying the large-scale structure of the HF-disturbed ionospheric region. The experiments were performed using the SURA heating facility. The disturbed ionospheric region was sounded by signals radiated by GPS navigation satellite beacons as well as by signals of low-orbit satellites (radio tomography). The results of the experiments show that large-scale plasma density perturbations induced at altitudes higher than the F2 layer maximum can contribute significantly to the measured variations of the total electron density and can, with a certain arrangement of the reception points, be measured by the GPS sounding method.

Effect of HF Heating Array Directivity Pattern on the Frequency Response of Generated ELF/VLF.

DTIC Science & Technology

1983-01-01

radiators ....... ............ 4 1-2 HF heating array ........ ................... 9 1-3 HF heating array element ...... ................ 9 1-4 View of top...elements looking down at pyramid ....... 9 1-5 Non-planar log-periodic antenna semi-structure dimensions ............ . ....... 10 l-6a Power gain vs...22 1-8 Orientation of 4- and 8-element arrays .. ......... .. 24 1- 9 Comparison of experimental and theoretical patterns. . . 27 1-10 Directive

Consequences of adding gum Arabic as a cryoprotectant on motility and viability of frozen stallion semen.

PubMed

Ali, Mohamed; Musa, Musa M; Alfadul, Sulaiman; Al-Sobayel, K

2017-12-01

A trial was conducted to check effect of adding gum Arabic (GA) instead of egg yolk (EY) as a cryoprotectant for stallion sperm. Two experiments were designed; experiment I tested adding 3 levels of nonheated GA (i.e., 3, 6 and 9 g/100 mL diluents) in HF-20 extender. However, in experiment II the same levels were tested except that GA was heated at 80 °C for 60 min. HF-20 containing 10% of EY was used as control. In experiment I, sperm frozen in HF-20 containing nonheated GA exhibited lower percentages of motile sperm, progressively motile sperm and sperm with intact plasma membranes, vitality rate, and acrosome integrity after cooling or after deep freezing. Frozen semen in HF-20 containing 3-6% of preheated GA in experiment II maintained sperm motility at 46-50% and elevated progressive motility at 27%. The semen diluted in preheated GA (6%) and frozen exhibited a fertility rate of 40% (2/5). A similar fertility rate (40%) was found in the control semen (i.e. 10%) compared to those that were inseminated with frozen semen in preheated 3% GA (20%, 1/5). These results suggest that preheated GA could be used as an alternative cryoprotectant for cryopreserving stallion sperm. Copyright © 2017 Elsevier Inc. All rights reserved.

Response of mesospheric ozone to the heating of the lower ionosphere by high-power HF radio emission

NASA Astrophysics Data System (ADS)

Kulilov, Yu. Yu.; Frolov, V. L.; Grigor'ev, G. I.; Demkin, V. M.; Komrakov, G. P.; Krasilnokov, A. A.; Ryskin, V. G.

2013-01-01

We detected a decrease in the intensity of microwave radiation at the atmospheric ozone line at a frequency of 110836.04 MHz during ionospheric modification by high-power HF radiowaves radiated by the Sura Ionospheric Heating Facility. The obtained experimental data allowed us to hypothesize that this effect was caused by the fact that mesospheric ozone was affected by internal gravity waves generated in the E region of the ionosphere during its high-power HF radiowave heating.

High Frequency Resolution TOA Analysis for ELF/VLFWave Generation Experiments at HAARP

NASA Astrophysics Data System (ADS)

Ruddle, J. D.; Moore, R. C.

2014-12-01

Modulated HF heating of the ionosphere in the presence of natural ionospheric current sources has been used as a method to generate electromagnetic ELF/VLF waves since the 1970's. In the ~1-5 kHz band, the amplitude and phase of the received ELF/VLF signal depends on the amplitude and phase of the conductivity modulation generated throughout the HF-heated ionospheric body, as well as on the signal propagation parameters (i.e., the attenuation and phase constants) between each of the current sources and the receiver. Recent signal processing advances have produced an accurate ELF/VLF time-of-arrival (TOA) analysis technique that differentiates line-of-sight and ionospherically-reflected signal components, determining the amplitude and phase of each component observed at the receiver. This TOA method requires a wide bandwidth (> 2.5 kHz) and therefore is relatively insensitive to the frequency-dependent nature of ELF/VLF wave propagation. In this paper, we present an improved ELF/VLF TOA method that is capable of providing high frequency resolution. The new analysis technique is applied to experimental observations of ELF/VLF signals generated by modulated heating at HAARP. We present measurements of the amplitude and phase of the received ELF/VLF signal as a function of frequency and compare the results with the predictions of an HF heating model.

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence

NASA Astrophysics Data System (ADS)

Rietveld, M. T.; Kosch, M. J.; Blagoveshchenskaya, N. F.; Kornienko, V. A.; Leyser, T. B.; Yeoman, T. K.

2003-04-01

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees and magnetic field-aligned measurements show ion outflows increasing with height up to 300 m s-1 at 582 km. The electron density decreases by up to 20%. When the radar antenna was scanned between three elevations from near field-aligned to vertical, the strongest heating effects were always obtained in the field-aligned position. When the HF-pump beam was scanned between the same three positions, the heating was still almost always strongest in the field-aligned direction. Simultaneous images of the 630 nm O(1D) line in the radio-induced aurora showed that the enhancement caused by the HF radio waves also remained localized near the field-aligned position. Coherent HF radar backscatter also appeared strongest when the pump beam was pointed field-aligned. These results are similar to some Langmuir turbulence phenomena which also show a strong preference for excitation by HF rays launched in the field-aligned direction. The correlation of the position of largest temperature enhancement with the position of the radio-induced aurora suggests that a common mechanism, upper-hybrid wave turbulence, is responsible for both effects. Why the strongest heating effects occur for HF rays directed along the magnetic field is still unclear, but self-focusing on field-aligned striations is a candidate mechanism, and possibly ionospheric tilts may be important.

Protective effect of anti-oxidants on endothelial function in young Korean-Asians compared to Caucasians.

PubMed

Yim, Jongeun; Petrofsky, Jerrold; Berk, Lee; Daher, Noha; Lohman, Everett; Moss, Abigail; Cavalcanti, Paula

2012-08-01

Previous studies show that Asians have an impaired blood flow response (BFR) to occlusion after a single high fat (HF) meal. The mechanism is believed to be the presence and susceptibility to high free radicals in their blood. The free radical concentration after a HF meal has not been examined in Asians. Further the BFR to heat after a single HF meal in Koreans has not been measured. This study evaluated postprandial endothelial function by measuring the BFR to vascular occlusion and local heat before and after a HF meal and the interventional effects of anti-oxidant vitamins on improving endothelial function in young Korean-Asians (K) compared to Caucasians (C) with these assessments. Ten C and ten K participated in the study (mean age 25.3±3.6 years old). BFR to vascular occlusion and local heat and oxidative stress were assessed after a single low fat (LF) and HF meal at 2 hours compared to baseline. After administration of vitamins (1000 mg of vitamin C, 800 IU of vitamin E, and 300 mg of Coenzyme Q-10) for 14 days, the same measurements were made. This study showed that the skin BFR to vascular occlusion and local heat following a HF meal significantly decreased and free radicals significantly increased at 2 hours compared to baseline in K (p<.001), but not in C. When vitamins were given, the BFR to vascular occlusion and local heat before and after HF meal were not significantly different in K and C. These findings suggest that even a single HF meal can reduce endothelial response to stress through an oxidative stress mechanism but can be blocked by antioxidants, probably through scavenging free radicals in K. Since endothelial function improved even before a HF meal in K, endothelial damage from an Americanized diet may be reduced in K by antioxidants.

Protective effect of anti-oxidants on endothelial function in young Korean-Asians compared to Caucasians

PubMed Central

Yim, Jongeun; Petrofsky, Jerrold; Berk, Lee; Daher, Noha; Lohman, Everett; Moss, Abigail; Cavalcanti, Paula

2012-01-01

Summary Background Previous studies show that Asians have an impaired blood flow response (BFR) to occlusion after a single high fat (HF) meal. The mechanism is believed to be the presence and susceptibility to high free radicals in their blood. The free radical concentration after a HF meal has not been examined in Asians. Further the BFR to heat after a single HF meal in Koreans has not been measured. Material/Methods This study evaluated postprandial endothelial function by measuring the BFR to vascular occlusion and local heat before and after a HF meal and the interventional effects of anti-oxidant vitamins on improving endothelial function in young Korean-Asians (K) compared to Caucasians (C) with these assessments. Ten C and ten K participated in the study (mean age 25.3±3.6 years old). BFR to vascular occlusion and local heat and oxidative stress were assessed after a single low fat (LF) and HF meal at 2 hours compared to baseline. After administration of vitamins (1000 mg of vitamin C, 800 IU of vitamin E, and 300 mg of Coenzyme Q-10) for 14 days, the same measurements were made. Results This study showed that the skin BFR to vascular occlusion and local heat following a HF meal significantly decreased and free radicals significantly increased at 2 hours compared to baseline in K (p<.001), but not in C. When vitamins were given, the BFR to vascular occlusion and local heat before and after HF meal were not significantly different in K and C. Conclusions These findings suggest that even a single HF meal can reduce endothelial response to stress through an oxidative stress mechanism but can be blocked by antioxidants, probably through scavenging free radicals in K. Since endothelial function improved even before a HF meal in K, endothelial damage from an Americanized diet may be reduced in K by antioxidants. PMID:22847195

Heat treatment study 2

NASA Technical Reports Server (NTRS)

Workman, Gary L.

1990-01-01

The microstructural variations in nickel based superalloys that result from modifications in processing were examined. These superalloys include MAR-M246(HF) and PWA1480. Alternate heat treatments for equiaxed as-cast specimens were studied and a sample matrix of 42 variations in the heat treatments were processed, as well as different directional solidification parameters. Variation in temperature and times for both solution and aging were performed. Photomicrographs were made of the microstructure and volume fraction analysis of primary gamma-prime and aged gamma-prime precipitates were performed. The results of the heat treatment, cooling rate, and directional solidification experiments are discussed.

Geometric Aspects of Artificial Ionospheric Layers Driven by High-Power HF-Heating

NASA Astrophysics Data System (ADS)

Milikh, G. M.; Eliasson, B.; Shao, X.; Djordjevic, B.; Mishin, E. V.; Zawdie, K.; Papadopoulos, K.

2013-12-01

We have generalized earlier developed multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere [Eliasson et al, 2012] by including two dimensional effects in the horizontal direction. Such layers were observed during high-power high frequency HF heating experiments at HAARP [Pedersen et al., 2010]. We have numerically investigated the importance of different angles of incidence of ordinary mode waves on the Langmuir turbulence and the resulting electron acceleration that leads to the formation of artificial ionospheric layers. It was shown that the most efficient electron acceleration and subsequent ionization is obtained at angles between magnetic zenith and the vertical, where strong Langmuir turbulence dominates over weak turbulence. A role played by the heating wave propagation near caustics was also investigated. Eliasson, B. et al. (2012), J. Geophys. Res. 117, A10321, doi:10.1029/2012JA018105. Pedersen, T., et al. (2010), Geophys. Res. Lett., 37, L02106, doi:10.1029/2009GL041895.

Analysis of the backscatter spectrum in an ionospheric modification experiment

NASA Technical Reports Server (NTRS)

Kim, H.

1973-01-01

Predictions of the backscatter spectrum are compared, including effects of ionospheric inhomogeneity with experimental observations of incoherent backscatter from an artificially heated region. Calculations show that the strongest backscatter echo received is not, in fact, from the reflection level, but from a region some distance below (about 0.5 km for an experiment carried out at Arecibo), where the pump wave from a HF transmitter approximately 100 kW) is below the threshold for parametric amplification. By taking the standing wave pattern of the pump into account, asymmetry is explained of the up-shifted and down-shifted plasma lines in the backscatter spectrum, and the several peaks typically observed in the region of the spectrum near the HF transmitter frequency.

Optimizing ELF/VLF generation via HF heating utilizing beam motion

NASA Astrophysics Data System (ADS)

Cohen, M. B.; Inan, U. S.; Lehtinen, N. G.; Golkowski, M. A.

2008-12-01

ELF/VLF (300 Hz - 30 kHz) waves are difficult to generate with conventional antennae due to their extraordinary long wavelengths, and the good conductance of the Earth at these frequencies. Recently, ELF and VLF waves have been generated using HF (3-10 MHz) heating of the lower ionosphere, in the presence of natural currents such as the auroral electrojet, which modulates the ionospheric conductivity and therefore turns the lower ionosphere into a large radiating element. The recently upgraded HAARP facility, near Gakona Alaska, utilizes 3.6 MW of HF power, along with an unprecedented ability to steer the HF heating beam over a large area extremely rapidly. Since the completion of the upgrade in 2007, the first successful implementation of techniques such as geometric modulation [Cohen et al. 2008, Borisov et al. 1998], and beam painting [Papadopoulos et al. 1989] have occurred. These results have shown as much as 7-11 dB improvement in the signal strengths, as well as the first ability to direct ELF/VLF signals via an unprecedented ELF/VLF phased array. Here, we use a combination of experimental and theoretical investigations to discuss the optimization of ELF/VLF generation via HF heating, including the effect of HF and ELF frequency on the amplitude and the directional pattern for various generation techniques. The experimental observations occur over an array of receivers across Alaska. The theoretical formulation utilizes a 3D model of the HF heating and subsequent electron cooling processes, leading to spatial structure of modulated ionospheric conductivities, the results of which are input into a model of ELF/VLF propagation in the Earth-ionosphere waveguide.

Differences of skin morphology in Bos indicus, Bos taurus, and their crossbreds

NASA Astrophysics Data System (ADS)

Jian, Wang; Duangjinda, M.; Vajrabukka, C.; Katawatin, Suporn

2014-08-01

Cutaneous evaporation is the main avenue by which cattle dissipate heat via the involvement of sweat glands and other skin components. The difference in skin morphology between B. indicus and B. taurus has been recognized, as well as differences in their ability to tolerate heat. The objective of this study was to compare skin morphology between B. indicus, B. taurus, and their crossbreds. Skin samples of Sahiwal ( B. indicus) ( n = 10, reddish brown skin) and Holstein Friesian (HF) ( B. taurus) ( n = 10, black and white skin) and crossbred of HF75% ( n = 10, black and white skin) and HF87.5 % ( n = 10, black and white skin) were biopsied for histological study, followed by measurement of skin components. The results indicated that breed significantly affected sweat gland morphology. The shape of the sweat gland, as indicated by the ratio of length/diameter, in Sahiwal was baggier in shape compared to HF (5.99 and 9.52) while values for crossbreds were intermediate (7.82, 8.45). The density and volume of sweat glands in Sahiwal (1,058 glands/cm2; 1.60 μ3 × 10-6) were higher than in HF (920 glands/cm2; 0.51 μ3x10-6) and crossbreds, both HF 75 % (709 glands/cm2; 0.68 μ3 × 10-6) and HF 87.5 % (691 glands/cm2; 0.61 μ3 × 10-6) respectively. However, capillary surface area was greater for HF (2.07 cm2) compared to Sahiwal (1.79 cm2); accordingly, the lower genetic fraction of HF in crossbred cattle showed less capillary surface area (1.83 and 1.9 cm2 for HF75% and HF87.5 %) ( P < 0.01). Nerve density was not significantly different between Sahiwal and HF but was higher in the crossbred ( P < 0.01) cattle. Moreover, the effect of skin color (black and white) was evaluated and it was found that there was an interaction ( P < 0.01) between breed and skin color on the skin components. This study reveals that there are differences in skin morphology among B. indicus, B. taurus and their crossbreds, with these differences being more or less related to the genetic fraction of HF. This may imply that capability for cutaneous evaporative heat loss and tolerance to heat in crossbred cattle could be related to skin morphology.

Influence of heating experiments on parameters of Schumann resonances

NASA Astrophysics Data System (ADS)

Agranat, Irina; Sivokon, Vladimir

2017-10-01

Recently the significant increase in intensity of researches in the field of the fissile impact on geophysical processes in various environments is noted. Special attention is paid to a research of impact on an ionosphere of a potent short-wave radio emission of heating stands. Today experiments on change of an ionosphere are made generally at stands HAARP, EISCAT in Tromse (Norway). Within the Russian campaign (Tomsk) EISCAT/heating (AARI_HFOX) made from October 19 to October 30, 2016 experiments on impact on an ionosphere F-layer by the radiation potent HF. For assessment of impact of these experiments on geophysical processes mathematical methods carried out the analysis of change of the parameters of the Schumann resonances received on the basis of data from the station of constant observation of the Schumann resonances in the city of Tomsk, the Tomsk State University (Russia).

First demonstration of HF-driven ionospheric currents

NASA Astrophysics Data System (ADS)

Papadopoulos, K.; Chang, C.-L.; Labenski, J.; Wallace, T.

2011-10-01

The first experimental demonstration of HF driven currents in the ionosphere at low ELF/ULF frequencies without relying in the presence of electrojets is presented. The effect was predicted by theoretical/computational means in a recent letter and given the name Ionospheric Current Drive (ICD). The effect relies on modulated F-region HF heating to generate Magneto-Sonic (MS) waves that drive Hall currents when they reach the E-region. The Hall currents inject ELF waves into the Earth-Ionosphere waveguide and helicon and Shear Alfven (SA) waves in the magnetosphere. The proof-of-concept experiments were conducted using the HAARP heater in Alaska under the BRIOCHE program. Waves between 0.1-70 Hz were measured at both near and far sites. The letter discusses the differences between ICD generated waves and those relying on modulation of electrojets.

Effects of substrate heating and post-deposition annealing on characteristics of thin MOCVD HfO2 films

NASA Astrophysics Data System (ADS)

Gopalan, Sundararaman; Ramesh, Sivaramakrishnan; Dutta, Shibesh; Virajit Garbhapu, Venkata

2018-02-01

It is well known that Hf-based dielectrics have replaced the traditional SiO2 and SiON as gate dielectric materials for conventional CMOS devices. By using thicker high-k materials such as HfO2 rather than ultra-thin SiO2, we can bring down leakage current densities in MOS devices to acceptable levels. HfO2 is also one of the potential candidates as a blocking dielectric for Flash memory applications for the same reason. In this study, effects of substrate heating and oxygen flow rate while depositing HfO2 thin films using CVD and effects of post deposition annealing on the physical and electrical characteristics of HfO2 thin films are presented. It was observed that substrate heating during deposition helps improve the density and electrical characteristics of the films. At higher substrate temperature, Vfb moved closer to zero and also resulted in significant reduction in hysteresis. Higher O2 flow rates may improve capacitance, but also results in slightly higher leakage. The effect of PDA depended on film thickness and O2 PDA improved characteristics only for thick films. For thinner films forming gas anneal resulted in better electrical characteristics.

Investigation of the spatial structure and developmental dynamics of near-Earth plasma perturbations under the action of powerful HF radio waves

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

Belov, A. S., E-mail: alexis-belov@yandex.ru

2015-10-15

Results of numerical simulations of the near-Earth plasma perturbations induced by powerful HF radio waves from the SURA heating facility are presented. The simulations were performed using a modified version of the SAMI2 ionospheric model for the input parameters corresponding to the series of in-situ SURA–DEMETER experiments. The spatial structure and developmental dynamics of large-scale plasma temperature and density perturbations have been investigated. The characteristic formation and relaxation times of the induced large-scale plasma perturbations at the altitudes of the Earth’s outer ionosphere have been determined.

Large-Scale Ionospheric Effects Related to Electron-Gyro Harmonics: What We Have Learned from HAARP.

NASA Astrophysics Data System (ADS)

Watkins, B. J.; Fallen, C. T.; Secan, J. A.

2014-12-01

The HAARP ionospheric modification facility has unique capabilities that enable a wide range of HF frequencies with transmit powers ranging from very low to very high values. We will review a range of experiment results that illustrate large-scale ionospheric effects when the HF frequencies used are close to electron gyro-harmoncs and we focus mainly on the 3rd and 4th harmonics. The data are primarily from the UHF diagnosticc radar and total electron content (TEC) observations through the heated topside ionosphere. Radar data for HF frequencies just above and just below gyro harmoncs show significant differences in radar scatter cross-section that suggest differing plasma processes, and this effect is HF power dependent with some effects only observable with full HF power. For the production of artificial ionization in the E-region when the HF frequency is near gyro-harmoncs the results differ significantly for relatively small (50 kHz) variations in the HF frequency. We show how slow FM scans in conjunction with gyro-harmonic effects are effective in producing artificial ionization in the lower ionosphere.In the topside ionosphere enhanced density and upward fluxes have been observed and these may act as effective ducts for the propagation of VLF waves upward into the magneosphere. Experimental techniques have been developed that may be used to continuously maintain these effects in the topside ionossphere.

THERMODYNAMIC PROPERTIES OF Zr AND Hf HALIDES (in Rumanian)

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

Lungu, S.N.

1962-01-01

The following standard heats of formation were found: ZrCl/sub 3/, 178.6 plus or minus 3.2; ZrCl/sub 2/, 124.3 plus or minus 3; ZrBr/sub 3/, 151 plus or minus 7; Zr Br/sbu 2/, 100 plus or minus 6; ZrI/sub 3/, 103 plus or minus 6; ZrI/sub 2/, 68 plus or minus 4; and HfCl/sub 4/, 239.4 plus or minus 5.5; HfCl/sub 3/, 186.6; HfCl/sub 2/, 130; HfBr/sub 4/, 200; HfBr/sub 3/, 157; HfBr / sub 2/, 108; HfI/sub 4/, 140; HfI/sub 3/, 113; and HfI/sub 2/, 72 kcal/mole. (R.V.J.)

Investigation of Third Gyro-harmonic Heating at HAARP Using Stimulated Radio Emissions, the MUIR and SuperDARN Radars

NASA Astrophysics Data System (ADS)

Mahmoudian, Alireza; Bernhardt, Paul; Ruohoniemi, J. Michael; Isham, Brett; Watkins, Brenton; Scales, Wayne

2016-07-01

Use of high frequency (HF) heating experiments has been extended in recent years as a useful methodology for plasma physicists wishing to remotely study the properties and behavior of the ionosphere as well as nonlinear plasma processes. Our recent work using high latitude heating experiments has lead to several important discoveries that have enabled assessment of active geomagnetic conditions, determination of minor ion species and their densities, ion mass spectrometry, electron temperature measurements in the heating ionosphere, as well a deeper understanding of physical processes associated with electron acceleration and formation of field aligned irregularities. The data recorded during two campaigns at HAARP in 2011 and 2012 will be presented. Several diagnostic instruments have been used to detect HAARP heater-generated ionospheric irregularities and plasma waves. These diagnostics include an ionosonde, MUIR (Modular UHF Ionospheric Radar at 446 MHz), SuperDARN HF backscatter radar and ground-based SEE receivers. Variation of the wideband/ narrowband SEE features, SuperDARN echoes, and enhanced ion lines were studied with pump power variation, pump frequency stepping near 3fce as well as changing beam angle relative to the magnetic zenith. In particular, formation of field-aligned irregularities (FAIs) and upper hybrid (UH) waves through oscillating two-stream instability (OSTI) and resonance instability is studied. During heating, Narrowband SEE (NSEE) showed enhancements that correlated with the enhanced MUIR radar ion lines. IA MSBS (Magnetized Stimulated Brillouin Scatter) lines are much narrower than Wideband SEE (WSEE) lines and as a result electron temperature calculated using NSEE line offset has potential to be more accurate. This technique may therefore complement the electron temperature calculation using ISR spectra. Strength of IA MSBS lines correlate with EHIL in the MUIR spectrum during HF pump frequency variation near 3fce. Therefore, NSEE could be used for similar diagnostic information, particularly temperature assessment during heating. More detailed physics-based modeling of such SEE is expected to provide further diagnostic information/capabilities. This work has demonstrated the tremendous future potential of Narrowband SEE (NSEE) as a powerful untapped ionospheric diagnostic which could provide complementary measurements for locations that ISR facilities are not available or as a complementary measurement for the waves and irregularities that cannot be observed by ISR.

Multiple frequency backscatter observations of heater-induced field-aligned striations in the auroral E region

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

Noble, S.T.

1985-01-01

In September 1983 a series of HF ionospheric modification experiments were conducted in Scandinavia using the heat facility near Tromosoe Norway. The purpose of these experiments was to examine the mechanisms by which high-power HF radio waves produce geomagnetic field-aligned striations (FAS) in the auroral E region. The vast majority of the backscatter observations were made with radars operating at 47 and 144 MHz (STARE Finland). Additionally, limited observations were conducted at 140 (STARE Norway) and 21 MHz (SAFARI). These radars are sensitive to irregularities having scale lengths between 1 and 7 m across the geomagnetic field lines. During periodsmore » of full power O-mode heating, striations having peak cross sections of 40 to 50 dBsm are observed. Striations are not detected during times of X-mode heating. When the heater output is varied, a corresponding change in the cross section is measured. The magnitude of the change is most pronounced for heater level changes in the range 12.5 to 50% of full power. These cross sections are significantly larger than those measured at midlatitudes using the Arecibo heater (approx.10/sup 1/ m/sup 2/). This is consistent with theoretical studies which indicate that it is easier to excite short-scale FAS at places where the geomagnetic dip angle is large. The growth and decay times of the striations are frequency dependent.« less

Peripheral blood mononuclear cells: a potential cellular system to understand differential heat shock response across native cattle (Bos indicus), exotic cattle (Bos taurus), and riverine buffaloes (Bubalus bubalis) of India.

PubMed

Kishore, Amit; Sodhi, Monika; Kumari, Parvesh; Mohanty, A K; Sadana, D K; Kapila, Neha; Khate, K; Shandilya, Umesh; Kataria, R S; Mukesh, M

2014-09-01

Circulating leukocytes can be used as an effective model to understand the heat stress response of different cattle types and buffaloes. This investigation aimed to determine the temporal profile of HSPs (HSP40, HSP60, HSP70, and HSP90) expression in circulating peripheral blood mononuclear cells (PBMCs) of Murrah buffaloes, Holstein-Friesian (HF), and Sahiwal cows in response to sublethal heat shock at 42 °C. The viability data indicated HF PBMCs to be the most affected to the heat shock, whereas Sahiwal PBMCs were least affected, indicating its better survivability during the heat stress condition. The qRT-PCR expression data showed significant increase in mRNA expression of the analyzed HSPs genes after heat stimuli to the PBMCs under in vitro condition. In each case, the HSPs were most upregulated at 2 h after the heat stress. Among the HSPs, HSP70 was relatively more expressed followed by HSP60 indicating the action of molecular chaperones to stabilize the native conformation of proteins. However, PBMCs from different cattle types and buffaloes showed difference in the extent of transcriptional response. The level of expression of HSPs throughout the time period of heat stress was highest in buffaloes, followed by HF and Sahiwal cows. The higher abundance of HSP70 mRNA at each time point after heat stress showed prolonged effect of heat stress in HF PBMCs. The data presented here provided initial evidence of transcriptional differences in PBMCs of different cattle types and buffaloes and warrant further research.

Measurement and Simulation of Thermal Conductivity of Hafnium-Aluminum Thermal Neutron Absorber Material

DOE PAGES

Guillen, Donna Post; Harris, William H.

2016-05-11

A metal matrix composite (MMC) material comprised of hafnium aluminide (Al3Hf) intermetallic particles in an aluminum matrix has been identified as a promising material for fast-flux irradiation testing applications. This material can filter thermal neutrons while simultaneously providing high rates of conductive cooling for experiment capsules. Our purpose is to investigate effects of Hf-Al material composition and neutron irradiation on thermophysical properties, which were measured before and after irradiation. When performing differential scanning calorimetry (DSC) on the irradiated specimens, a large exotherm corresponding to material annealment was observed. Thus, a test procedure was developed to perform DSC and laser flashmore » analysis (LFA) to obtain the specific heat and thermal diffusivity of pre- and post-annealment specimens. This paper presents the thermal properties for three states of the MMC material: (1) unirradiated, (2) as-irradiated, and (3) irradiated and annealed. Microstructure-property relationships were obtained for the thermal conductivity. These relationships are useful for designing components from this material to operate in irradiation environments. Furthermore, the ability of this material to effectively conduct heat as a function of temperature, volume fraction Al 3Hf, radiation damage and annealing is assessed using the MOOSE suite of computational tools.« less

Observations of HF backscatter decay rates from HAARP generated FAI

NASA Astrophysics Data System (ADS)

Bristow, William; Hysell, David

2016-07-01

Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

Observations of HF backscatter decay rates from HAARP generated FAI

NASA Astrophysics Data System (ADS)

Bristow, W. A.; Hysell, D. L.

2016-12-01

Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

Creep Properties of NiAl-1Hf Single Crystals Re-Investigated

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Locci, Ivan E.; Darolia, Ram; Bowman, Randy R.

2000-01-01

NiAl-1Hf single crystals have been shown to be quite strong at 1027 C, with strength levels approaching those of advanced Ni-based superalloys. Initial testing, however, indicated that the properties might not be reproducible. Study of the 1027 C creep behavior of four different NiAl-1Hf single-crystal ingots subjected to several different heat treatments indicated that strength lies in a narrow band. Thus, we concluded that the mechanical properties are reproducible. Recent investigations of the intermetallic NiAl have confirmed that minor alloying additions combined with single-crystal growth technology can produce elevated temperature strength levels approaching those of Ni-based superalloys. For example, General Electric alloy AFN 12 {Ni-48.5(at.%) Al-0.5Hf-1Ti-0.05Ga} has a creep rupture strength equivalent to Rene 80 combined with a approximately 30-percent lower density, a fourfold improvement in thermal conductivity, and the ability to form a self-protective alumina scale in aggressive environments. Although the compositions of strong NiAl single crystals are relatively simple, the microstructures are complex and vary with the heat treatment and with small ingot-toingot variations in the alloy chemistry. In addition, initial testing suggested a strong dependence between microstructure and creep strength. If these observations were true, the ability to utilize NiAl single-crystal rotating components in turbine machinery could be severely limited. To investigate the possible limitations in the creep response of high-strength NiAl single crystals, the NASA Glenn Research Center at Lewis Field initiated an in depth investigation of the effect of heat treatment on the microstructure and subsequent 1027 C creep behavior of [001]-oriented NiAl-1Hf with a nominal chemistry of Ni-47.5Al-1Hf-0.5Si. This alloy was selected since four ingots, grown over a number of years and possessing slightly different compositions, were available for study. Specimens taken from the ingots were subjected to several heat treatment schedules, examined by transmission electron microscopy, and tested in both compression and tension. An example of the microstructure found in a [001]-oriented NiAl-1Hf specimen after a solution treatment at 1317 C for 50 hr followed by air cooling is illustrated in the image on the left, where the NiAl matrix contains a uniform distribution of nanometer-scale Gphase (Ni16Hf6Si7) precipitates. Other heat treating schedules produced microstructures with nanometer-sized G-phase cubes and plates or, in an extreme case, produced a microstructure with all the G-phase converted to Heusler (Ni2AlHf) particles. The results of 1027 C creep strength and strain rate testing are illustrated which summarizes data from tensile and compressive testing of samples cut from all four NiAl-1Hf ingots and subjected to a variety of heat treatment schedules. With one exception, all the strength values lie in a narrow band that spans six orders of magnitude in strain rate. The only factor that produced results outside of this band was the heat treatment schedule that dissolved all the G-phase and replaced it with Heusler precipitates. The results portrayed in this figure lead to the important practical conclusion that the elevated-temperature creep properties of NiAl-1Hf single crystals are reproducible and are not affected by small variations in alloy chemistry from ingot to ingot or by different initial distributions of G-phase in the heat-treated alloy. The only variable in this study that produced a significant and delerious effect on mechanical strength was a post-solution heat treatment that lead to the complete disappearance of the G-phase in favor of Heusler precipitates.

Pre-launch simulation experiment of microwave-ionosphere nonlinear interaction rocket experiment in the space plasma chamber

NASA Astrophysics Data System (ADS)

Kaya, N.; Tsutsui, M.; Matsumoto, H.; Kimura, I.

1980-09-01

A pre-flight test experiment of a microwave-ionosphere nonlinear interaction rocket experiment (MINIX) has been carried out in a space plasma simulation chamber. Though the first rocket experiment ended up in failure because of a high voltage trouble, interesting results are observed in the pre-flight experiment. A significant microwave heating of plasma up to 300% temperature increase is observed. Strong excitations of plasma waves by the transmitted microwaves in the VLF and HF range are observed as well. These microwave effects may have to be taken into account in solar power satellite projects in the future.

The polar-ionosphere phenomena induced by high-power radio waves from the spear heating facility

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Janzhura, A. S.; Kalishin, A. S.; Robinson, T. R.; Yeoman, T. K.; Wright, D. M.; Baddeley, L. J.

2008-11-01

We present the results of experimental studies of specific features in the behavior of small-scale artificial field-aligned irregularities (AFAIs) and the DM component in the spectra of stimulated electromagnetic emission (SEE). Analysis of experimental data shows that AFAIs in the polar ionosphere are generated under different background geophysical conditions (season, local time, the presence of sporadic layers in the E region, etc.). It is shown that AFAIs can be excited not only in the F region, but also in “thick” sporadic E s layers of the polar ionosphere. The AFAIs were observed in some cycles of heating when the HF heater frequency exceeded the critical frequency by 0.3-0.5 MHz. Propagation paths of diagnostic HF radio waves scattered by AFAIs were modelled for geophysical conditions prevailing during the SPEAR heating experiments. Two components, namely, a narrow-banded one with a Doppler-spectrum width of up to 2 Hz and a broadband one observed in a band of up to 20 Hz, were found in the sporadic E s layer during the AFAI excitation. Analysis of the SEE spectra shows that the behavior of the DM component in time is irregular, which is possibly due to strong variations in the critical frequency of the F 2 layer from 3.5 to 4.6 MHz. An interesting feature observed in the SPEAR heating experiments is that the generation of the DM component was similar to the excitation of AFAIs when the heater frequency was up to 0.5 MHz higher than the critical frequency.

Investigating the highest melting temperature materials: A laser melting study of the TaC-HfC system.

PubMed

Cedillos-Barraza, Omar; Manara, Dario; Boboridis, K; Watkins, Tyson; Grasso, Salvatore; Jayaseelan, Daniel D; Konings, Rudy J M; Reece, Michael J; Lee, William E

2016-12-01

TaC, HfC and their solid solutions are promising candidate materials for thermal protection structures in hypersonic vehicles because of their very high melting temperatures (>4000 K) among other properties. The melting temperatures of slightly hypostoichiometric TaC, HfC and three solid solution compositions (Ta 1-x Hf x C, with x = 0.8, 0.5 and 0.2) have long been identified as the highest known. In the current research, they were reassessed, for the first time in the last fifty years, using a laser heating technique. They were found to melt in the range of 4041-4232 K, with HfC having the highest and TaC the lowest. Spectral radiance of the hot samples was measured in situ, showing that the optical emissivity of these compounds plays a fundamental role in their heat balance. Independently, the results show that the melting point for HfC 0.98 , (4232 ± 84) K, is the highest recorded for any compound studied until now.

Energy efficient microwave synthesis of mesoporous Ce 0.5M 0.5O 2 (Ti, Zr, Hf) nanoparticles for low temperature CO oxidation in an ionic liquid – a comparative study

DOE PAGES

Alammar, Tarek; Chow, Ying -Kit; Mudring, Anja -Verena

2014-11-19

Ce 0.5M 0.5O 2 (M = Ti, Zr, Hf) nanoparticles have been successfully synthesized by microwave irradiation in the ionic liquid [C 4mim][Tf 2N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide). The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N 2–adsorption measurements. XRD and Raman spectroscopy analyses confirmed the formation of solid solutions with cubic fluorite structure. The catalytic activities of the Ce 0.5M 0.5O 2 (M = Ti, Zr, Hf) nanoparticles were investigated in the low-temperature oxidation of CO. Ce 0.5Zr 0.5O 2 nanospheresmore » exhibit the best performance (100% conversion at 350 °C), followed by Ce 0.5Hf 0.5O 2 (55% conversion at 360 °C) and Ce 0.5Ti 0.5O 2 (11% conversion at 350 °C). Heating the as-prepared Ce 0.5Zr 0.5O 2 to 600 °C for extended time leads to a decrease in surface area and, as expected decreased catalytic activity. Depending on the ionic liquid the obtained Ce 0.5Zr 0.5O 2 exhibits different morphologies, varying from nano-spheres in [C 4mim][Tf 2N] and [P 66614][Tf 2N] (P 66614 = trishexyltetradecylphosphonium) to sheet-like assemblies in [C 3mimOH][Tf 2N] (C 3mimOH = 1-(3-hydroxypropyl)-3-methylimidazolium). As a result, the microwave synthesis superiority to other heating methods like sonochemical synthesis and conventional heating was proven by comparative experiments where the catalytic activity of Ce 0.5Zr 0.5O 2 obtained by alternate methods such as conventional heating was found to be poorer than that of the microwave-synthesised material.« less

Recent Science Campaigns at HAARP

NASA Astrophysics Data System (ADS)

McCoy, R. P.; Bristow, W. A.; Fallen, C. T.

2017-12-01

Experiments in HF ionospheric heating using the High­frequency Active Auroral Research Program (HAARP) facilities have tremendous potential for informing our investigation of the Earth's upper atmosphere, ionosphere, and magnetosphere. They provide a unique opportunity for quantifying and modeling the multi­scale coupled processes that characterize the interactions between the plasma in near­Earth space, the Earth's magnetic field, and the neutral gasses of the atmosphere. Physical parameters of the region are often difficult to measure with ground­based instruments, and the measurements that are possible are often poorly resolved in range or time or unavailable outside narrow altitude regimes. HF ionospheric modification experiments allow us to measure ionospheric and thermospheric state parameters more systematically and over a broader range of conditions than would otherwise be possible. HAARP is the world's most powerful and most flexible HF transmitting facility, capable of generating 3.6 MW of RF power over a frequency range from about 2 MHz to about 10 MHz. The electronic phased array antenna provides the ability to direct the RF energy to a large region of the sky above Alaska. HAARP was constructed through a research program managed by the Air Force Research Laboratory (AFRL), and the Office of Naval Research (ONR). It was jointly funded by AFRL, ONR, and the Defense Advanced Projects Research Agency (DARPA). These agencies ended of their program of HAARP research in 2014, and donated the site equipment to the University of Alaska, Fairbanks (UAF), in the summer of 2015, who now operate the facility as an international observatory for radio plasma heating and subauroral physics. Since taking control of HAARP, UAF has carried out research campaigns in February 2017, and September 2017. The topics investigated in the campaigns included the physics of ionospheric irregularities (FAI), the stimulated electromagnetic emissions (SEE), generation of optical emissions from the heated region, and technological impacts of irregularities. This paper will give an overview of the status of the facility and will present preliminary results from the experiments carried out in the campaigns.

The role of Upper Hybrid Turbulence on HF Artificial Ionization

NASA Astrophysics Data System (ADS)

Papadopoulos, Konstantinos Dennis; Najmi, Amir; Eliasson, Bengt; Milikh, Gennady

2016-07-01

One of the most fascinating and scientifically interesting phenomena of active space experiments is the discovery of artificial ionization by Todd Pedersen when the HAARP ERP reached the GW level. The phenomenon has been well documented experimentally. A theoretical model based on ionization by energetic electrons accelerated by 50-100 V/m localized electric fields due to Strong Langmuir Turbulence (SLT) near the reflection surface of the HF pump wave, reproduced the observed dynamics of the descending plasma layer quite accurately. A major defect of the model was that the electron temperature in the SLT region was a free parameter. When taken as the 2000 K representing the ambient electron temperature the SLT driven electron flux was insufficient to produce ionization. An equivalent electron temperature of 5000 K or higher was necessary to reproduce the observations. The needed electron heating was attributed to the interaction of the HF at the Upper Hybrid (UH) resonant layer, approximately 5 Km below the reflection region where the HF electric field is perpendicular to the ambient magnetic field. The heated electrons expanded upwards along the magnetic field line and interacted with SLT fields near the resonance region. A consequence of this defect was that the theory could not explain the puzzling double resonance effect. Namely the observation that the ionization level was much stronger when the HF frequency and the UH resonance were a multiple of the electron cyclotron frequency. To remedy this we used a series of Vlasov simulations to explore the HF-plasma interaction in the vicinity of the UH resonance. The simulations followed the evolution of the spectral density of the electric field over a 7.5 MHz frequency band and cm scale lengths and of the electron distribution function over one millisecond for both double resonant and non-resonant cases. Many new features were revealed by the analysis of the simulations such as: 1. Broadening of the wave-number spectral region at the at the UH frequency 2. Excitation of all Bernstein modes associated with cyclotron frequency harmonics both below and above the UH frequency for both the resonant and non0resonant cases. 3. Moderate electron heating, in the form of bulk heating caused by first Bernstein mode, although its wave intensity is more than 20 dB lower than the intensity of the UH branch for all non-resonant cases. 4. Strong generation of non-thermal tails for the resonant cases, by the UH waves downshifted by the lower hybrid frequency when the downshifted frequency was equal to an harmonic of the electron gyro-frequency. The new UH turbulence resolves several f the mysteries associated with artificial ionization and suggests several new observations. Acknowledgment:Work supported by AFOSR MURI grant FA95501410019.

Effect of structural evolution of ZnO/HfO2 nanocrystals on Eu2+/Eu3+ emission in glass-ceramic waveguides for photonic applications

NASA Astrophysics Data System (ADS)

Ghosh, Subhabrata; N, Shivakiran Bhaktha B.

2018-06-01

Eu-doped 70SiO2–23HfO2–7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦C, both, Eu2+ as well as Eu3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu3+ to Eu2+ takes place in such ZnO/HfO2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 65d \\to 4f 7 energy level transition of Eu2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm‑1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO2–23HfO2–7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.

Relationship between core temperature, skin temperature, and heat flux during exercise in heat.

PubMed

Xu, Xiaojiang; Karis, Anthony J; Buller, Mark J; Santee, William R

2013-09-01

This paper investigates the relationship between core temperature (T c), skin temperature (T s) and heat flux (HF) during exercise in hot conditions. Nine test volunteers, wearing an Army Combat Uniform and body armor, participated in three sessions at 25 °C/50 % relative humidity (RH); 35 °C/70 % RH; and 42 °C/20 % RH. Each session consisted of two 1-h treadmill walks at ~350 W and ~540 W intensity. T s and HF from six sites on the forehead, sternum, pectoralis, left rib cage, left scapula, and left thigh, and T c (i.e., core temperature pill used as a suppository) were measured. Multiple linear regressions were conducted to derive algorithms that estimate T c from T s and HF at each site. A simple model was developed to simulate influences of thermal conductivity and thickness of the local body tissues on the relationship between T c, T s, and HF. Coefficient of determination (R (2)) ranged from 0.30 to 0.88, varying with locations and conditions. Good sites for T c measurement at surface were the sternum, and a combination of the sternum, scapula, and rib sites. The combination of T s and HF measured at the sternum explained ~75 % or more of variance in observed T c in hot environments. The forehead was found unsuitable for exercise in heat due to sweating and evaporative heat loss. The derived algorithms are likely applicable only for the same ensemble or ensembles with similar thermal and vapor resistances. Algorithms for T c measurement are location-specific and their accuracy is dependent, to a large degree, on sensor placement.

Do Mitochondria Limit Hot Fish Hearts? Understanding the Role of Mitochondrial Function with Heat Stress in Notolabrus celidotus

PubMed Central

Iftikar, Fathima I.; Hickey, Anthony J. R.

2013-01-01

Hearts are the first organs to fail in animals exposed to heat stress. Predictions of climate change mediated increases in ocean temperatures suggest that the ectothermic heart may place tight constraints on the diversity and distribution of marine species with cardiovascular systems. For many such species, their upper temperature limits (Tmax) and respective heart failure (HF) temperature (THF) are only a few degrees from current environmental temperatures. While the ectothermic cardiovascular system acts as an “ecological thermometer,” the exact mechanism that mediates HF remains unresolved. We propose that heat-stressed cardiac mitochondria drive HF. Using a common New Zealand fish, Notolabrus celidotus, we determined the THF (27.5°C). Haemoglobin oxygen saturation appeared to be unaltered in the blood surrounding and within heat stressed hearts. Using high resolution respirometry coupled to fluorimeters, we explored temperature-mediated changes in respiration, ROS and ATP production, and overlaid these changes with THF. Even at saturating oxygen levels several mitochondrial components were compromised before THF. Importantly, the capacity to efficiently produce ATP in the heart is limited at 25°C, and this is prior to the acute THF for N. celidotus. Membrane leakiness increased significantly at 25°C, as did cytochrome c release and permeability to NADH. Maximal flux rates and the capacity for the electron transport system to uncouple were also altered at 25°C. These data indicate that mitochondrial membrane integrity is lost, depressing ATP synthesis capacity and promoting cytochrome c release, prior to THF. Mitochondria can mediate HF in heat stressed hearts in fish and play a significant role in thermal stress tolerance, and perhaps limit species distributions by contributing to HF. PMID:23724026

Effect of structural evolution of ZnO/HfO2 nanocrystals on Eu2+/Eu3+ emission in glass-ceramic waveguides for photonic applications.

PubMed

Ghosh, Subhabrata; Bhaktha B N, Shivakiran

2018-06-01

Eu-doped 70SiO 2 -23HfO 2 -7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO 2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦ C, both, Eu 2+ as well as Eu 3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦ C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu 3+ to Eu 2+ takes place in such ZnO/HfO 2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 6 5d [Formula: see text] 4f 7 energy level transition of Eu 2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm -1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO 2 -23HfO 2 -7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.

Unusual superconducting behavior in HfV2Ga4

NASA Astrophysics Data System (ADS)

Santos, F. B.; Correa, L. E.; de Lima, B. S.; Cigarroa, O. V.; da Luz, M. S.; Grant, T.; Fisk, Z.; Machado, A. J. S.

2018-04-01

Bulk superconductivity in HfV2Ga4 with critical temperature close to 4.1 K was determined via magnetic susceptibility, electrical resistivity and specific heat measurements. Both the upper and lower critical field dependence with reduced temperature (T /Tc) exhibit non-conventional behavior. The electronic component of specific heat shows a double-jump, the first close to Tc and the other close to 0.75Tc. We speculate about the nature of the douple jump observed in specific heat considering two plausable scenarios: bulk inhomogeneities and the existence of a second gap.

Artificial Excitation of Schumann Resonance with HAARP

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Chang, C. L.

2014-12-01

We report results from the experiment aimed at the artificial excitation of extremely-low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance (typically, 7.5 - 8.0 Hz frequency range). Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated by the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range of the Schumann resonance, when the ionosphere has a strong F-layer and an electric field greater than 5 mV/m is present in the E-region.

Creating space plasma from the ground

NASA Astrophysics Data System (ADS)

Carlson, H. C.; Djuth, F. T.; Zhang, L. D.

2017-01-01

We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground-based high-power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above 20 eV. Incoherent scatter radar (ISR) plasma-line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self-damping. We present data from an HF heating experiment on November 2015 at Arecibo, which even more directly confirm the only prior midlatitude estimate, of order 10% efficiency for conversion of HF energy to ionospheric ionization. We note the theoretical maximum possible is 1/3, while 1% or less reduces the question to near practical irrelevance. Our measurements explicitly confirm the prediction that radio-frequency production of artificial ionospheres can be practicable, even at midlatitudes. Furthermore, that this midlatitude efficiency is comparable to efficiencies measured at high latitudes (which include enhancements unique to high latitudes including magnetic zenith effect, gyrofrequency multiples, and double resonances) requires reexamination of current theoretical thinking about soft-electron acceleration processes in weakly magnetized plasmas. The implications are that electron acceleration by any of a variety of processes may be a fundamental underpinning to energy redistribution in space plasmas.

Characteristics of VLF wave propagation in the Earth's magnetosphere in the presence of an artificial density duct

NASA Astrophysics Data System (ADS)

Pasmanik, Dmitry; Demekhov, Andrei

We study the propagation of VLF waves in the Earth's ionosphere and magnetosphere in the presence of large-scale artificial plasma inhomogeneities which can be created by HF heating facilities like HAARP and ``Sura''. A region with enhanced cold plasma density can be formed due to the action of HF heating. This region is extended along geomagnetic field (up to altitudes of several thousand km) and has rather small size across magnetic field (about 1 degree). The geometric-optical approximation is used to study wave propagation. The plasma density and ion composition are calculated with the use of SAMI2 model, which was modified to take the effect of HF heating into account. We calculate ray trajectories of waves with different initial frequency and wave-normal angles and originating at altitudes of about 100 km in the region near the heating area. The source of such waves could be the lightning discharges, modulated HF heating of the ionosphere, or VLF transmitters. Variation of the wave amplitude along the ray trajectories due to refraction is considered and spatial distribution of wave intensity in the magnetosphere is analyzed. We show that the presence of such a density disturbances can lead to significant changes of wave propagation trajectories, in particular, to efficient guiding of VLF waves in this region. This can result in a drastic increase of the VLF-wave intensity in the density duct. The dependence of wave propagation properties on parameters of heating facility operation regime is considered. We study the variation of the spatial distribution of VLF wave intensity related to the slow evolution of the artificial inhomogeneity during the heating.

Effectiveness of Haemodiafiltration with Heat Sterilized High-Flux Polyphenylene HF Dialyzer in Reducing Free Light Chains in Patients with Myeloma Cast Nephropathy

PubMed Central

2015-01-01

Introduction In cases of myeloma cast nephropathy in need of haemodialysis (HD), reduction of free light chains using HD with High-Cut-Off filters (HCO-HD), in combination with chemotherapy, may be associated with better renal recovery. The aim of the present study is to evaluate the effectiveness of haemodiafiltration (HDF) in reducing free light chain levels using a less expensive heat sterilized high-flux polyphenylene HF dialyzer (HF-HDF). Methods In a single-centre prospective cohort study, 327 dialysis sessions were performed using a 2.2 m2 heat sterilized high-flux polyphenylene HF dialyzer (Phylther HF22SD), a small (1.1m2) or large (2.1 m2) high-cut-off (HCO) dialyzer (HCOS and HCOL) in a cohort of 16 patients presenting with dialysis-dependent acute cast nephropathy and elevated free light chains (10 kappa, 6 lambda). The outcomes of the study were the mean reduction ratio (RR) of kappa and lambda, the proportion of treatments with an RR of at least 0.65, albumin loss and the description of patient outcomes. Statistical analysis was performed using linear and logistic regression through generalized estimating equation analysis so as to take into account repeated observation within subjects and adjust for session duration. Results There were no significant differences in the estimated marginal mean of kappa RR, which were respectively 0.67, 0.69 and 0.70 with HCOL-HD, HCOS-HDF and HF-HDF (P = 0.950). The estimated marginal mean of the proportions of treatments with a kappa RR ≥0.65 were 68%, 63% and 71% with HCOL-HD, HCOS-HDF and HF-HDF, respectively (P = 0.913). The estimated marginal mean of lambda RR were higher with HCOL-HDF (0.78), compared to HCOL-HD and HF-HDF (0.62, and 0.61 respectively). The estimated marginal mean proportion of treatments with a lambda RR ≥0.65 were higher with HCOL-HDF (81%), compared to 57% in HF-HDF (P = 0.042). The median albumin loss were 7, 21 and 63 g/session with HF-HDF, HCOL-HD and HCOL-HDF respectively (P = 0.044). Among survivors, 9 out of 10 episodes of acute kidney injuries became dialysis-independent following a median time of renal replacement therapy of 40 days (range 7–181). Conclusion Therefore, in patients with acute dialysis-dependent myeloma cast nephropathy, in addition to chemotherapy, HDF with a heat sterilized high-flux polyphenylene HF dialyzer could offer an alternative to HCO dialysis for extracorporeal kappa reduction with lower albumin loss. PMID:26466100

Microstructure and Phase Stability of Single Crystal NiAl Alloyed with Hf and Zr

NASA Technical Reports Server (NTRS)

Locci, I. E.; Dickerson, R. M.; Garg, A.; Noebe, R. D.; Whittenberger, J. D.; Nathal, M. V.; Darolia, R.

1996-01-01

Six near stoichiometric, NiAl single-crystal alloys, with 0.05-1.5 at.% of Hf and Zr additions plus Si impurities, were microstructurally analyzed in the as-cast, homogenized, and aged conditions. Hafnium-rich interdendritic regions, containing the Heusler phase (Ni2AlHf), were found in all the as-cast alloys containing Hf. Homogenization heat treatments partially reduced these interdendritic segregated regions. Transmission electron microscopy (TEM) observations of the as-cast and homogenized microstructures revealed the presence of a high density of fine Hf (or Zr) and Si-rich precipitates. These were identified as G-phase, Nil6X6Si7, or as an orthorhombic NiXSi phase, where X is Hf or Zr. Under these conditions the expected Heusler phase (beta') was almost completely absent. The Si responsible for the formation of the G and NiHfSi phases is the result of molten metal reacting with the Si-containing crucible used during the casting process. Varying the cooling rates after homogenization resulted in the refinement or complete suppression of the G and NiHfSi phases. In some of the alloys studied, long-term aging heat treatments resulted in the formation of Heusler precipitates, which were more stable at the aging temperature and coarsened at the expense of the G-phase. In other alloys, long-term aging resulted in the formation of the NiXSi phase. The stability of the Heusler or NiXSi phases can be traced to the reactive element (Hf or Zr) to silicon ratio. If the ratio is high, then the Heusler phase appears stable after long time aging. If the ratio is low, then the NiHfSi phase appears to be the stable phase.

Magnetic ground state of the two isostructual polymeric quantum magnets [ Cu ( HF 2 ) ( pyrazine ) 2 ] SbF 6 and [ Co ( HF 2 ) ( pyrazine ) 2 ] SbF 6 investigated with neutron powder diffraction

DOE PAGES

Brambleby, J.; Goddard, P. A.; Johnson, R. D.; ...

2015-10-07

The magnetic ground state of two isostructural coordination polymers, (i) the quasi-two-dimensional S=1/2 square-lattice antiferromagnet [Cu(HF 2)(pyrazine) 2]SbF 6 and (ii) a related compound [Co(HF 2)(pyrazine)2]SbF6, was examined with neutron powder diffraction measurements. We find that the ordered moments of the Heisenberg S=1/2 Cu(II) ions in [Cu(HF 2)(pyrazine) 2]SbF 6 are 0.6(1)μ b, while the ordered moments for the Co(II) ions in [Co(HF 2)(pyrazine) 2]SbF 6 are 3.02(6)μ b. For Cu(II), this reduced moment indicates the presence of quantum fluctuations below the ordering temperature. We also show from heat capacity and electron spin resonance measurements that due to the crystalmore » electric field splitting of the S=3/2 Co(II) ions in [Co(HF 2)(pyrazine) 2]SbF 6, this isostructual polymer also behaves as an effective spin-half magnet at low temperatures. Furthermore, the Co moments in [Co(HF 2)(pyrazine) 2]SbF 6 show strong easy-axis anisotropy, neutron diffraction data, which do not support the presence of quantum fluctuations in the ground state, and heat capacity data, which are consistent with 2D or close to 3D spatial exchange anisotropy.« less

Effects of Transcutaneous Electrical Nerve Stimulation on Pain, Pain Sensitivity, and Function in People With Knee Osteoarthritis: A Randomized Controlled Trial

PubMed Central

Vance, Carol Grace T.; Rakel, Barbara A.; Blodgett, Nicole P.; DeSantana, Josimari Melo; Amendola, Annunziato; Zimmerman, Miriam Bridget; Walsh, Deirdre M.

2012-01-01

Background Transcutaneous electrical nerve stimulation (TENS) is commonly used for the management of pain; however, its effects on several pain and function measures are unclear. Objective The purpose of this study was to determine the effects of high-frequency TENS (HF-TENS) and low-frequency TENS (LF-TENS) on several outcome measures (pain at rest, movement-evoked pain, and pain sensitivity) in people with knee osteoarthritis. Design The study was a double-blind, randomized clinical trial. Setting The setting was a tertiary care center. Participants Seventy-five participants with knee osteoarthritis (29 men and 46 women; 31–94 years of age) were assessed. Intervention Participants were randomly assigned to receive HF-TENS (100 Hz) (n=25), LF-TENS (4 Hz) (n=25), or placebo TENS (n=25) (pulse duration=100 microseconds; intensity=10% below motor threshold). Measurements The following measures were assessed before and after a single TENS treatment: cutaneous mechanical pain threshold, pressure pain threshold (PPT), heat pain threshold, heat temporal summation, Timed “Up & Go” Test (TUG), and pain intensity at rest and during the TUG. A linear mixed-model analysis of variance was used to compare differences before and after TENS and among groups (HF-TENS, LF-TENS, and placebo TENS). Results Compared with placebo TENS, HF-TENS and LF-TENS increased PPT at the knee; HF-TENS also increased PPT over the tibialis anterior muscle. There was no effect on the cutaneous mechanical pain threshold, heat pain threshold, or heat temporal summation. Pain at rest and during the TUG was significantly reduced by HF-TENS, LF-TENS, and placebo TENS. Limitations This study tested only a single TENS treatment. Conclusions Both HF-TENS and LF-TENS increased PPT in people with knee osteoarthritis; placebo TENS had no significant effect on PPT. Cutaneous pain measures were unaffected by TENS. Subjective pain ratings at rest and during movement were similarly reduced by active TENS and placebo TENS, suggesting a strong placebo component of the effect of TENS. PMID:22466027

Investigating the highest melting temperature materials: A laser melting study of the TaC-HfC system

NASA Astrophysics Data System (ADS)

Cedillos-Barraza, Omar; Manara, Dario; Boboridis, K.; Watkins, Tyson; Grasso, Salvatore; Jayaseelan, Daniel D.; Konings, Rudy J. M.; Reece, Michael J.; Lee, William E.

2016-12-01

TaC, HfC and their solid solutions are promising candidate materials for thermal protection structures in hypersonic vehicles because of their very high melting temperatures (>4000 K) among other properties. The melting temperatures of slightly hypostoichiometric TaC, HfC and three solid solution compositions (Ta1-xHfxC, with x = 0.8, 0.5 and 0.2) have long been identified as the highest known. In the current research, they were reassessed, for the first time in the last fifty years, using a laser heating technique. They were found to melt in the range of 4041-4232 K, with HfC having the highest and TaC the lowest. Spectral radiance of the hot samples was measured in situ, showing that the optical emissivity of these compounds plays a fundamental role in their heat balance. Independently, the results show that the melting point for HfC0.98, (4232 ± 84) K, is the highest recorded for any compound studied until now.

Separation and quantification of monoclonal-antibody aggregates by hollow-fiber-flow field-flow fractionation.

PubMed

Fukuda, Jun; Iwura, Takafumi; Yanagihara, Shigehiro; Kano, Kenji

2014-10-01

Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation-sedimentation velocity and asymmetric-flow field-flow fractionation.

Investigating the highest melting temperature materials: A laser melting study of the TaC-HfC system

PubMed Central

Cedillos-Barraza, Omar; Manara, Dario; Boboridis, K.; Watkins, Tyson; Grasso, Salvatore; Jayaseelan, Daniel D.; Konings, Rudy J. M.; Reece, Michael J.; Lee, William E.

2016-01-01

TaC, HfC and their solid solutions are promising candidate materials for thermal protection structures in hypersonic vehicles because of their very high melting temperatures (>4000 K) among other properties. The melting temperatures of slightly hypostoichiometric TaC, HfC and three solid solution compositions (Ta1−xHfxC, with x = 0.8, 0.5 and 0.2) have long been identified as the highest known. In the current research, they were reassessed, for the first time in the last fifty years, using a laser heating technique. They were found to melt in the range of 4041–4232 K, with HfC having the highest and TaC the lowest. Spectral radiance of the hot samples was measured in situ, showing that the optical emissivity of these compounds plays a fundamental role in their heat balance. Independently, the results show that the melting point for HfC0.98, (4232 ± 84) K, is the highest recorded for any compound studied until now. PMID:27905481

Shear Alfven Wave Injection in the Magnetosphere by Ionospheric Modifications in the Absence of Electrojet Currents

NASA Astrophysics Data System (ADS)

Papadopoulos, K.; Eliasson, B.; Shao, X.; Labenski, J.; Chang, C.

2011-12-01

A new concept of generating ionospheric currents in the ULF/ELF range with modulated HF heating using ground-based transmitters even in the absence of electrojet currents is presented. The new concept relies on using HF heating of the F-region to modulate the electron temperature and has been given the name Ionospheric Current Drive (ICD). In ICD, the pressure gradient associated with anomalous or collisional F-region electron heating drives a local diamagnetic current that acts as an antenna to inject mainly Magneto-Sonic (MS) waves in the ionospheric plasma. The electric field associated with the MS wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that inject waves in the Earth-Ionosphere Waveguide (EIW) below and shear Alfven waves or EMIC waves upwards towards the conjugate regions. The paper presents: (i) Theoretical results using a cold Hall MHD model to study ICD and the generation of ULF/ELF waves by the modulation of the electron pressure at the F2-region with an intense HF electromagnetic wave. The model solves equations governing the dynamics of the shear Alfven and magnetosonic modes, of the damped modes in the diffusive Pedersen layer, and of the weakly damped helicon wave mode in the Hall-dominated E-region. The model incorporates realistic profile of the ionospheric conductivities and magnetic field configuration. We use the model to simulate propagation and dynamics of the low-frequency waves and their injection into the magnetosphere from the HAARP and Arecibo ionospheric heaters. (ii) Proof of principle experiments using the HAARP ionospheric heater in conjunction with measurements by the DEMETER satellite This work is supported by ONR MURI grant and DARPA BRIOCHE Program

Synthesis of Hf 8O 7, a new binary hafnium oxide, at high pressures and high temperatures

DOE PAGES

Bayarjargal, L.; Morgenroth, W.; Schrodt, N.; ...

2017-01-23

In this paper, two binary phases in the system Hf-O have been synthesized at pressures between 12 and 34 GPa and at temperatures up to 3000 K by reacting Hf with HfO 2 using a laser-heated diamond anvil cell. In situ X-ray diffraction in conjunction with density functional theory calculations has been employed to characterize a previously unreported tetragonal Hf 8O 7 phase. This phase has a structure which is based on an fcc Hf packing with oxygen atoms occupying octahedral interstitial positions. Its predicted bulk modulus is 223(1) GPa. The second phase has a composition close to Hf 6O,more » where oxygen atoms occupy octahedral interstitial sites in an hcp Hf packing. Its experimentally determined bulk modulus is 128(30) GPa. Finally, the phase diagram of Hf metal was further constrained at high pressures and temperatures, where we show that α-Hf transforms to β-Hf around 2160(150) K and 18.2 GPa and β-Hf remains stable up to at least 2800 K at this pressure.« less

Basis of Ionospheric Modification by High-Frequency Waves

DTIC Science & Technology

2007-06-01

for conducting ionospheric heating experiments in Gakona, Alaska, as part of the High Frequency Active Auroral Research Program ( HAARP ) [5], is being...upgraded. The upgraded HAARP HF transmitting system will be a phased-array antenna of 180 elements. Each element is a cross dipole, which radiates a...supported by the High Frequency Active Auroral Research Program ( HAARP ), the Air Force Research Laboratory at Hanscom Air Force Base, MA, and by the Office

Spatial Characteristics of the 630-nm Artificial Ionospheric Airglow Generation Region During the Sura Facility Pumping

NASA Astrophysics Data System (ADS)

Shindin, A. V.; Klimenko, V. V.; Kogogin, D. A.; Beletsky, A. B.; Grach, S. M.; Nasyrov, I. A.; Sergeev, E. N.

2018-05-01

We describe the method and the results of modeling and retrieval of the spatial distribution of excited oxygen atoms in the HF-pumped ionospheric region based on two-station records of artificial airglow in the red line (λ = 630 nm). The HF ionospheric pumping was provided by the Sura facility. The red-line records of the night-sky portraits were obtained at two reception points—directly at the heating facility and 170 km east of it. The results were compared with the vertical ionospheric sounding data. It was found that in the course of the experiments the airglow region was about 250 km high and did not depend on the altitude of the pump-wave resonance. The characteristic size of the region was 35 km, and the shape of the distribution isosurfaces was well described by oblique spheroids or a drop-shaped form. The average value of the maximum concentration of excited atoms during the experiment was about 1000 cm-3.

Ionospheric Modification from Under-Dense Heating by High-Power HF Transmitter

DTIC Science & Technology

2011-03-03

Auroral Research Program ( HAARP ) is a HF transmitter, which delivers 0.36 to 3.6 GW effective isotropic radiated powers (F.IRP) for the radiation...dense heating, the EIRP of the HAARP heater can be increased significantly by increasing the heater frequency. With higher heater frequency, the loss...1304 local time) and on 13 April from 0812 to 0844 UTC (0012 to 0044 local time), using the HAARP transmitter facility at Gakona, AK, at full power

Effect of Hf-Rich Particles on the Creep Life of a High-strength Nial Single Crystal Alloy

NASA Technical Reports Server (NTRS)

Garg, A.; Raj, S. V.; Darolia, R.

1995-01-01

Additions of small amounts of Hf and Si to NiAl single crystals significantly improve their high-temperature strength and creep properties. However, if large Hf-rich dendritic particles formed during casting of the alloyed single crystals are not dissolved completely during homogenization heat treatment, a large variation in creep rupture life can occur. This behavior, observed in five samples of a Hf containing NiAl single crystal alloy tested at 1144 K under an initial stress of 241.4 MPa, is described in detail highlighting the role of interdendritic Hf-rich particles in limiting creep rupture life.

Excitation of small-scale waves in the F region of the ionosphere by powerful HF radio waves

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Chernyshev, M. Y.; Kornienko, V. A.

1998-01-01

Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev-N. Novgorod-St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have been made by a Doppler spectrum device with high temporal resolution. Analysis of the experimental data shows a relation between the heater power level and the parameters of ionospheric small-scale oscillations falling within the range of Pc 3-4 magnetic pulsations. It is found that the periods of wave processes in the F region of the ionosphere, induced by the heating facility, decrease with increasing heating power. The level of heating power also has an impact on the horizontal east-west component of the electric field E, the vertical component of the Doppler velocity Vd and the amplitude of the vertical displacements M of the heated region. Typical magnitudes of these parameters are the following: E = 1.25 mVm, Vd = 6 ms, M = 600-1500 m for ERP = 20 MW and E = 2.5-4.5 mVm, Vd = 11-25 ms, M = 1000-5000 m for ERP = 100 MW. The results obtained confirm the hypothesis of excitation of the Alfvén resonator by powerful HF radio waves which leads to the generation of magnetic field oscillations in the heated region giving rise to artificial Pc 3-4 magnetic pulsations and ionospheric small-scale wave processes. In this situation an increase of the heater power would lead to a growth of the electric field of hydromagnetic waves propagating in the ionosphere as well as the amplitude of the vertical displacements of the heated region.

SEE Observations of Ionospheric Heating from HAARP Using Orbital Angular Momentum

NASA Astrophysics Data System (ADS)

Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.

2013-12-01

High power HF radio waves exciting the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, providing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emission (SEE) is of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. These production modes have been extensively studied at HAARP using traditional beam heating patterns and SEE detection. New results are present from HAARP experiments using an excitation mode that attempts to impart orbital angular momentum (OAM) into the heating region. This OAM mode is also referred to as a 'twisted beam.' Previous analysis of twisted beam heating shows that the SEE results obtained are nearly identical to the modes without OAM. Recent twisted beam heating experiments have produced SEE modes not previously characterized. These new modes are presented and discussed. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional 'solid spot' region. The ring heating pattern may be more conducive to the creation of artificial ionization clouds. The results of these runs include artificial ionization creation and evolution as pertaining to the twisted beam pattern.

Interharmonic modulation products as a means to quantify nonlinear D-region interactions

NASA Astrophysics Data System (ADS)

Moore, Robert

Experimental observations performed during dual beam ionospheric HF heating experiments at the High frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska are used to quantify the relative importance of specific nonlinear interactions that occur within the D region ionosphere. During these experiments, HAARP broadcast two amplitude modulated HF beams whose center frequencies were separated by less than 20 kHz. One beam was sinusoidally modulated at 500 Hz while the second beam was sinusoidally modulated using a 1-7 kHz linear frequency-time chirp. ELF/VLF observations performed at two different locations (3 and 98 km from HAARP) provide clear evidence of strong interactions between all field components of the two HF beams in the form of low and high order interharmonic modulation products. From a theoretical standpoint, the observed interharmonic modulation products could be produced by several different nonlinearities. The two primary nonlinearities take the form of wave-medium interactions (i.e., cross modulation), wherein the ionospheric conductivity modulation produced by one signal crosses onto the other signal via collision frequency modification, and wave-wave interactions, wherein the conduction current associated with one wave mixes with the electric field of the other wave to produce electron temperature oscillations. We are able to separate and quantify these two different nonlinearities, and we conclude that the wave-wave interactions dominate the wave-medium interactions by a factor of two. These results are of great importance for the modeling of transioinospheric radio wave propagation, in that both the wave-wave and the wave-medium interactions could be responsible for a significant amount of anomalous absorption.

Effect of heat treatment on properties of HfO2 film deposited by ion-beam sputtering

NASA Astrophysics Data System (ADS)

Liu, Huasong; Jiang, Yugang; Wang, Lishuan; Li, Shida; Yang, Xiao; Jiang, Chenghui; Liu, Dandan; Ji, Yiqin; Zhang, Feng; Chen, Deying

2017-11-01

The effects of atmosphere heat treatment on optical, stress, and microstructure properties of an HfO2 film deposited by ion-beam sputtering were systematically researched. The relationships among annealing temperature and refractive index, extinction coefficient, physical thickness, forbidden-band width, tape trailer width, Urbach energy, crystal phase structure, and stress were assessed. The results showed that 400 °C is the transformation point, and the microstructure of the HfO2 film changed from an amorphous into mixed-phase structure. Multistage phonons appeared on the HfO2 film, and the trends of the refractive index, extinction coefficient, forbidden-band width change, and Urbach energy shifted from decrease to increase. With the elevation of the annealing temperature, the film thickness increased monotonously, the compressive stress gradually turned to tensile stress, and the transformation temperature point for the stress was between 200 °C and 300 °C. Therefore, the change in the stress is the primary cause for the shifts in thin-film thickness.

First results from the energetic particle instrument on the OEDIPUS-C sounding rocket

NASA Astrophysics Data System (ADS)

Gough, M. P.; Hardy, D. A.; James, H. G.

The Canadian / US OEDIPUS-C rocket was flown from the Poker Flat Rocket Range November 6th 1995 as a mother-son sounding rocket. It was designed to study auroral ionospheric plasma physics using active wave sounding and prove tether technology. The payload separated into two sections reaching a separation of 1200m along the Earth's magnetic field. One section included a frequency stepped HF transmitter and the other included a synchronised HF receiver. Both sections included Energetic Particle Instruments, EPI, stepped in energy synchronously with the transmitter steps. On-board EPI particle processing in both payloads provided direct measurements of electron heating, wave-particle interactions via particle correlators, and a high resolution measurement of wave induced particle heating via transmitter synchronised fast sampling. Strong electron heating was observed at times when the HF transmitter frequency was equal to a harmonic of the electron gyrofrequency, f_ce, or equal to the upper hybrid frequency, f_uh.

Remote sensing of ELF/VLF radiation induced in experiments on artificial modification of the ionosphere

NASA Astrophysics Data System (ADS)

Gavrilov, B. G.; Zetser, Yu. I.; Ryakhovskii, I. A.; Poklad, Yu. V.; Ermak, V. M.

2015-07-01

In 2012, remote measurements of electromagnetic signals in the ELF/VLF band were taken at different points in Russia during experiments on artificial ionospheric modification with the powerful HF wave at the EISCAT heating facility (Tromsø, Norway). The use of the new, highly sensitive magnetometric equipment allowed signals with an amplitude of a few femtoteslas to be recorded at a distance of up to 2000 km from the source. Analysis of the measurement results discovered substantial differences in the amplitude-phase characteristics of the signals, which were caused by a change in helio-geophysical conditions in the region of heating and along the signal passage route, and features of signal propagation, which are related to their mode of guided propagation, the directivity of the source, and angles of reception.

Handling Nonlinearities in ELF/VLF Generation Using Modulated Heating at HAARP

NASA Astrophysics Data System (ADS)

Jin, G.; Spasojevic, M.; Cohen, M.; Inan, U. S.

2011-12-01

George Jin Maria Spasojevic Morris Cohen Umran Inan Stanford University Modulated HF heating of the D-region ionosphere near the auroral electrojet can generate extremely low frequency (ELF) waves in the kilohertz range. This process is nonlinear and generates harmonics at integer multiples of the ELF modulation frequency. The nonlinear distortion has implications for any communications applications since the harmonics contain a substantial fraction of the signal power and use up bandwidth. We examine two techniques for handling the nonlinearity. First we modulate the HF heating with a non-sinusoidal envelope designed to create a sinusoidal change in the Hall conductivity at a particular altitude in the ionosphere to minimize any generated harmonics. The modulation waveform is generated by inverting a numerical HF heating model, starting from the desired conductivity time series, and obtaining the HF power envelope that will result in that conductivity. The second technique attempts to use the energy in the harmonics to improve bit error rates when digital modulation is applied to the ELF carrier. In conventional quadrature phase-shift keying (QPSK), where a ELF carrier is phase-shifted by 0°, 90°, 180°, and 270° in order to transmit a pair of bits, the even harmonics cannot distinguish between the four possible shifts. By using different phase values, all the energy in the harmonics can contribute to determining the phase of the carrier and thus improve the bit error rate.

Heat treatment of pre-hydrolyzed silane increases adhesion of phosphate monomer-based resin cement to glass ceramic.

PubMed

de Carvalho, Rodrigo Furtado; Cotes, Caroline; Kimpara, Estevão Tomomitsu; Leite, Fabíola Pessoa Pereira; Özcan, Mutlu

2015-01-01

This study evaluated the influence of different forms of heat treatment on a pre-hydrolyzed silane to improve the adhesion of phosphate monomer-based (MDP) resin cement to glass ceramic. Resin and feldspathic ceramic blocks (n=48, n=6 for bond test, n=2 for microscopy) were randomly divided into 6 groups and subject to surface treatments: G1: Hydrofluoric acid (HF) 9.6% for 20 s + Silane + MDP resin cement (Panavia F); G2: HF 9.6% for 20 s + Silane + Heat Treatment (oven) + Panavia F; G3: Silane + Heat Treatment (oven) + Panavia F; G4: HF 9.6% for 20 s + Silane + Heat Treatment (hot air) + Panavia F; G5: Silane + Heat Treatment (hot air) + Panavia F; G6: Silane + Panavia F. Microtensile bond strength (MTBS) test was performed using a universal testing machine (1 mm/min). After debonding, the substrate and adherent surfaces were analyzed using stereomicroscope and scanning electron microscope (SEM) to categorize the failure types. Data were analyzed statistically using two-way test ANOVA and Tukey's test (=0.05). Heat treatment of the silane containing MDP, with prior etching with HF (G2: 13.15 ± 0.89a; G4: 12.58 ± 1.03a) presented significantly higher bond strength values than the control group (G1: 9.16 ± 0.64b). The groups without prior etching (G3: 10.47 ± 0.70b; G5: 9.47 ± 0.32b) showed statistically similar bond strength values between them and the control group (G1). The silane application without prior etching and heat treatment resulted in the lowest mean bond strength (G6: 8.05 ± 0.37c). SEM analysis showed predominantly adhesive failures and EDS analysis showed common elements of spectra (Si, Na, Al, K, O, C) characterizing the microstructure of the glass-ceramic studied. Heat treatment of the pre-hydrolyzed silane containing MDP in an oven at 100 °C for 2 min or with hot air application at 50 ± 5 ºC for 1 min, was effective in increasing the bond strength values between the ceramic and resin cement containing MDP.

Field-induced phase transition in Ce3M4Sn13 with M = Co, Rh, and Ru

NASA Astrophysics Data System (ADS)

Ślebarski, Andrzej; Goraus, Jerzy

2018-05-01

Large electronic specific heat coefficient, C (T) / T , suggests that the family of Ce3M4Sn13 heavy-fermions (HF) is near a magnetic quantum critical point (QCP). We analyze the 4 f contribution to the specific heat in terms of the single-ion Kondo resonance model. An unexpected change in the Kondo temperature TK versus magnetic field B signals a field-induced phase transition between the magnetically correlated HF phase and a single-ion Kondo impurity state.

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

NASA Astrophysics Data System (ADS)

Fu, H. Y.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Ruohoniemi, J. M.

2015-08-01

Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Wheel running decreases palatable diet preference in Sprague-Dawley rats.

PubMed

Moody, Laura; Liang, Joy; Choi, Pique P; Moran, Timothy H; Liang, Nu-Chu

2015-10-15

Physical activity has beneficial effects on not only improving some disease conditions but also by preventing the development of multiple disorders. Experiments in this study examined the effects of wheel running on intakes of chow and palatable diet e.g. high fat (HF) or high sucrose (HS) diet in male and female Sprague-Dawley rats. Experiment 1 demonstrated that acute wheel running results in robust HF or HS diet avoidance in male rats. Although female rats with running wheel access initially showed complete avoidance of the two palatable diets, the avoidance of the HS diet was transient. Experiment 2 demonstrated that male rats developed decreased HF diet preferences regardless of the order of diet and wheel running access presentation. Running associated changes in HF diet preference in females, on the other hand, depended on the testing schedule. In female rats, simultaneous presentation of the HF diet and running access resulted in transient complete HF diet avoidance whereas running experience prior to HF diet access did not affect the high preference for the HF diet. Ovariectomy in females resulted in HF diet preference patterns that were similar to those in male rats during simultaneous exposure of HF and wheel running access but similar to intact females when running occurred before HF exposure. Overall, the results demonstrated wheel running associated changes in palatable diet preferences that were in part sex dependent. Furthermore, ovarian hormones play a role in some of the sex differences. These data reveal complexity in the mechanisms underlying exercise associated changes in palatable diet preference. Published by Elsevier Inc.

Wheel running decreases palatable diet preference in Sprague-Dawley rats

PubMed Central

Moody, Laura; Liang, Joy; Choi, Pique P.; Moran, Timothy H.; Liang, Nu-Chu

2015-01-01

Physical activity has beneficial effects on not only improving some disease conditions but also by preventing the development of multiple disorders. Experiments in this study examined the effects of wheel running on intakes of chow and palatable diet e.g. high fat (HF) or high sucrose (HS) diet in male and female Sprague Dawley rats. Experiment 1 demonstrated that acute wheel running results in robust HF or HS diet avoidance in male rats. Although female rats with running wheel access initially showed complete avoidance of the two palatable diets, the avoidance of the HS diet was transient. Experiment 2 demonstrated that male rats developed decreased HF diet preferences regardless of the order of diet and wheel running access presentation. Running associated changes in HF diet preference in females, on the other hand, depended on the testing schedule. In female rats, simultaneous presentation of the HF diet and running access resulted in transient complete HF diet avoidance whereas running experience prior to HF diet access did not affect the high preference for the HF diet. Ovariectomy in females resulted in HF diet preference patterns that were similar to those in male rats during simultaneous exposure of HF and wheel running access but similar to intact females when running occurred before HF exposure. Overall, the results demonstrated wheel running associated changes in palatable diet preferences that were in part sex dependent. Furthermore, ovarian hormones play a role in some of the sex differences. These data reveal complexity in the mechanisms underlying exercise associated changes in palatable diet preference. PMID:25791204

"Twisted Beam" SEE Observations of Ionospheric Heating from HAARP

NASA Astrophysics Data System (ADS)

Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.; Han, S.-M.; Pedersen, T. R.; Scales, W. A.

2015-10-01

Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world's largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP experiments using a "twisted beam" excitation mode. Analysis of twisted beam heating shows that the SEE results obtained are identical to more traditional patterns. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional "solid spot" region from a pencil beam. The ring heating pattern may be more conducive to the creation of stable artificial airglow layers because of the horizontal structure of the ring. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.

Dynamics of cavitons in strong Langmuir turbulence

NASA Astrophysics Data System (ADS)

Dubois, D. F.; Rose, Harvey A.; Russell, David

Recent studies of Langmuir turbulence as described by Zakharov's model will be reviewed. For parameters of interest in laser-plasma experiments and for ionospheric hf heating experiments a significant fraction of the turbulent energy is in nonlinear caviton excitations which are localized in space and time. A local caviton model will be presented which accounts for the nucleation-collapse-burnout cycles of individual cavitons as well as their space-time correlations. This model is in detailed agreement with many features of the electron density fluctuation spectra in the ionosphere modified by powerful hf waves as measured by incoherent scatter radar. Recently such observations have verified a prediction of the theory that free Langmuir waves are emitted in the caviton collapse process. Observations and theoretical considerations also imply that when the pump frequency is slightly lower than the ambient electron plasma frequency cavitons may evolve to states in which they are ordered in space and time. The sensitivity of the high frequency Langmuir field dynamics to the low frequency ion density fluctuations and the related caviton nucleation process will be discussed.

A phenomenological study of day-to-day experiences of living with heart failure: do cultural differences matter?

PubMed

Chiaranai, Chantira

2014-07-01

Although there is a significant body of literature addressing heart failure (HF) epidemiology, physiology, and treatment, little is known about the experiences of Thai patients living with this chronic condition. The primary goal of this study was to gain a better understanding of how Thai patients with HF live with chronic and debilitating illness. A phenomenological approach was chosen to investigate the experience of living with HF. Fifteen Thai men and women with HF in New York Heart Association classes I to III, aged between 47 and 75 years, were interviewed with open-ended questions. Data were analyzed using qualitative inductive content analysis. Three themes emerged from the data analysis: identifying losses or changes in their lives, accepting the losses, and regaining some control. Unlike their western counterparts, the Thai patients with HF incorporated their karma, a Buddhist belief system, as a tool to rationalize the occurrence of their HF experience. The participants of this study used kreng jai as a cultural desire not to disrupt the happiness of others, even at the expense of efficiency, or to burden others, which might affect their own quality of life. The Thai patients with HF faced many limitations. The Thai patients with HF use religion and traditional culture to overcome their life situations. To support Thai patients with HF, healthcare providers must have an understanding of cultural differences.

Comment on "Parametric Instability Induced by X-Mode Wave Heating at EISCAT" by Wang et al. (2016)

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.

2017-12-01

In their recent article Wang et al. (2016) analyzed observations from EISCAT (European Incoherent Scatter) Scientific Association Russian X-mode heating experiments and claimed to explain the potential mechanisms for the parametric decay instability (PDI) and oscillating two-stream instability (OTSI). Wang et al. (2016) claim that they cannot separate the HF-enhanced plasma and ion lines excited by O or X mode in the EISCAT UHF radar spectra. Because of this they distinguished the parametric instability excited by O-/X-mode heating waves according to their different excitation heights. Their reflection heights were determined from ionosonde records, which provide a rough measure of excitation altitudes and cannot be used for the separation of the O- and X-mode effects. The serious limitation in their analysis is the use of a 30 s integration time of the UHF radar data. There are also serious disagreements between their analysis and the real observational facts. The fact is that it is the radical difference in the behavior of the X- and O-mode plasma and ion line spectra derived with a 5 s resolution, which provides the correct separation of the X- and O-mode effects. It is not discussed and explained how the parallel component of the electric field under X-mode heating is generated. Apart from the leakage to the O mode, results by Wang et al. (2016) do not explain the potential mechanisms for PDI and OTSI and add nothing to understanding the physical factors accounting for the parametric instability generated by an X-mode HF pump wave.

Comparison of maintenance energy requirement and energetic efficiency between lactating Holstein-Friesian and other groups of dairy cows.

PubMed

Dong, L F; Yan, T; Ferris, C P; McDowell, D A

2015-02-01

The objectives of the present study were to investigate the effects of cow group on energy expenditure and utilization efficiency. Data used were collated from 32 calorimetric chamber experiments undertaken from 1992 to 2010, with 823 observations from lactating Holstein-Friesian (HF) cows and 112 observations from other groups of lactating cows including Norwegian (n=50), Jersey × HF (n=46), and Norwegian × HF (n=16) cows. The metabolizable energy (ME) requirement for maintenance (MEm) for individual cows was calculated from heat production (HP) minus energy losses from inefficiencies of ME use for lactation, energy retention, and pregnancy. The efficiency of ME use for lactation (kl) was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. The effects of cow groups were first evaluated using Norwegian cows against HF crossbred cows (F1 hybrid, Jersey × HF and Norwegian × HF). The results indicated no significant difference between the 2 groups in terms of energy digestibility, ratio of ME intake over gross energy intake, MEm (MJ per kg of metabolic body weight, MJ/kg(0.75)), or kl. Consequently, their data were combined (categorized as non-HF cows) and used to compare with those of HF cows. Again, we detected no significant difference in energy digestibility, ratio of ME intake over gross energy intake, MEm (MJ/kg(0.75)), or kl between non-HF and HF cows. The effects were further evaluated using linear regression to examine whether any significant differences existed between HF and non-HF cows in terms of relationships between ME intake and energetic parameters. With a common constant, no significant difference was observed between the 2 groups of cows in coefficients in each set of relationships between ME intake (MJ/kg(0.75)) and MEm (MJ/kg(0.75)), El(0) (MJ/kg(0.75)), HP (MJ/kg(0.75)), MEm:ME intake, El(0):ME intake, or HP:ME intake. However, MEm values (MJ/kg(0.75)) were positively related to ME intake (MJ/kg(0.75)), irrespective of cow group. We concluded, therefore, that cow groups evaluated in the present study had no significant effects on energy expenditure or energetic efficiency. However, the maintenance energy requirement (MJ/kg(0.75)) was not constant (as adopted in the majority of energy rationing systems across the world) but increased with increasing feed intake. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Neogene volcanism associated with back-arc basin tectonics at the northern Fossa Magna, NE Japan

NASA Astrophysics Data System (ADS)

Okamura, S.; Inaba, M.; Shinjo, R.; Adachi, Y.

2016-12-01

New isotopic and trace element data presented here imply a temporal change in magma sources and thermal conditions beneath the northern Fossa Magna of NE Japan from the Miocene to the Pliocene. Rocks from more sediment melt-rich Early Miocene volcanoes have less radiogenic 176Hf/177Hf and 143Nd/144Nd, high Zr/Hf, and little or no Hf anomaly (Hf/Hf*; ˜1.0). The mantle wedge in the Early Miocene consisted of enriched mantle source. We propose that during the onset of subduction, influx of hot asthenospheric mantle provided sufficient heat to partially melt newly subducting sediment. Geochemical modeling results suggest breakdown of zircon in the slab surface sediments for the Early Miocene lavas in the northern Fossa Magna region. In the Middle Miocene, the injection of hot and depleted asthenospheric material replaced the mantle beneath the northern Fossa Magna region of NE Japan. This caused the isotopic signature of the rocks to change from enriched to depleted. The Middle Miocene lavas characterized by most radiogenic Hf and Nd isotope ratios, have high Zr/Hf, low Lu/Hf, and little or no Hf anomaly. An appropriate working petrogenetic model is that the Middle Miocene lavas were derived from asthenospheric depleted mantle, slightly ( < 1%) contaminated by slab melt accompanied by full dissolution of zircon. All the Late Miocene and Pliocene samples are characterized by distinctly more radiogenic 176Hf/177Hf and 143Nd/144Nd, and more negative Hf anomalies (greater Hf/Hf* variability; ˜0.3). The Pliocene samples are displaced toward lower Hf/Hf* and Zr/Hf, and higher Lu/Hf relative to the Middle Miocene samples, which requires mixing between depleted mantle and a partial melt of subducted metasediment saturated with trace quantity of zircon.

Improved Mo-Re VPS Alloys for High-Temperature Uses

NASA Technical Reports Server (NTRS)

Hickman, Robert; Martin, James; McKechnie, Timothy; O'Dell, John Scott

2011-01-01

Dispersion-strengthened molybdenum- rhenium alloys for vacuum plasma spraying (VPS) fabrication of high-temperature-resistant components are undergoing development. In comparison with otherwise equivalent non-dispersion-strengthened Mo-Re alloys, these alloys have improved high-temperature properties. Examples of VPS-fabricated high-temperature-resistant components for which these alloys are expected to be suitable include parts of aircraft and spacecraft engines, furnaces, and nuclear power plants; wear coatings; sputtering targets; x-ray targets; heat pipes in which liquid metals are used as working fluids; and heat exchangers in general. These alloys could also be useful as coating materials in some biomedical applications. The alloys consist of 60 weight percent Mo with 40 weight percent Re made from (1) blends of elemental Mo and Re powders or (2) Re-coated Mo particles that have been subjected to a proprietary powder-alloying-and-spheroidization process. For most of the dispersion- strengthening experiments performed thus far in this development effort, 0.4 volume percent of transition-metal ceramic dispersoids were mixed into the feedstock powders. For one experiment, the proportion of dispersoid was 1 volume percent. In each case, the dispersoid consisted of either ZrN particles having sizes <45 m, ZrO2 particles having sizes of about 1 m, HfO2 particles having sizes <45 m, or HfN particles having sizes <1 m. These materials were chosen for evaluation on the basis of previously published thermodynamic stability data. For comparison, Mo-Re feedstock powders without dispersoids were also prepared.

Methods for Melting Temperature Calculation

NASA Astrophysics Data System (ADS)

Hong, Qi-Jun

Melting temperature calculation has important applications in the theoretical study of phase diagrams and computational materials screenings. In this thesis, we present two new methods, i.e., the improved Widom's particle insertion method and the small-cell coexistence method, which we developed in order to capture melting temperatures both accurately and quickly. We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments. We propose the small-cell coexistence method based on the statistical analysis of small-size coexistence MD simulations. It eliminates the risk of a metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated melting points. The method converges to the exact result in the limit of a large system size. An accuracy within 100 K in melting temperature is usually achieved when the simulation contains more than 100 atoms. DFT examples of Tantalum, high-pressure Sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which the melting temperature is a design criterion. We present in detail two examples of refractory materials. First, we demonstrate how key material properties that provide guidance in the design of refractory materials can be accurately determined via ab initio thermodynamic calculations in conjunction with experimental techniques based on synchrotron X-ray diffraction and thermal analysis under laser-heated aerodynamic levitation. The properties considered include melting point, heat of fusion, heat capacity, thermal expansion coefficients, thermal stability, and sublattice disordering, as illustrated in a motivating example of lanthanum zirconate (La2Zr2O7). The close agreement with experiment in the known but structurally complex compound La2Zr 2O7 provides good indication that the computation methods described can be used within a computational screening framework to identify novel refractory materials. Second, we report an extensive investigation into the melting temperatures of the Hf-C and Hf-Ta-C systems using ab initio calculations. With melting points above 4000 K, hafnium carbide (HfC) and tantalum carbide (TaC) are among the most refractory binary compounds known to date. Their mixture, with a general formula TaxHf 1-xCy, is known to have a melting point of 4215 K at the composition Ta4HfC 5, which has long been considered as the highest melting temperature for any solid. Very few measurements of melting point in tantalum and hafnium carbides have been documented, because of the obvious experimental difficulties at extreme temperatures. The investigation lets us identify three major chemical factors that contribute to the high melting temperatures. Based on these three factors, we propose and explore a new class of materials, which, according to our ab initio calculations, may possess even higher melting temperatures than Ta-Hf-C. This example also demonstrates the feasibility of materials screening and discovery via ab initio calculations for the optimization of "higher-level" properties whose determination requires extensive sampling of atomic configuration space.

Exaggerated response to mild stress in rats fed high-fat diet.

PubMed

Legendre, Ariadne; Harris, Ruth B S

2006-11-01

It has been suggested that high-fat (HF) diet exaggerates the stress-induced release of glucocorticoids due to activation of the hypothalamic-pituitary-adrenal (HPA) axis. In an initial experiment, in which rats were fed HF diet for 4 days, we found that HF-fed controls stopped gaining weight, indicating that they were hyperresponsive to the mild stress of tail bleeding but responded the same as low-fat (LF)-fed rats to the more severe stress of restraint. A second experiment confirmed these results when rats fed a HF diet for 4 days showed an exaggerated corticosterone release in response to an intraperitoneal injection of saline and movement to a novel cage, compared with LF-fed rats. Experiment 3 tested the same parameters as experiment 2 but interchanged the diets. This allowed us to differentiate between the effects of the dietary fat and the novelty of the diet. Additionally, this experiment determined whether hyperresponsiveness to mild stress in HF-fed rats was sustained during a prolonged exposure to diet. The results confirmed that a HF diet, not novelty, exaggerated the endocrine stress response after 9 days on the diet but that the effect was no longer present after 23 days on the diet. The hyperresponsiveness of the HPA axis in HF-fed rats is similar to that observed in animals that have been exposed to a significant chronic or acute stress, suggesting that the HF diet may initially be perceived as a stressor.

Interdiffusion behavior between NiAlHf coating and Ni-based single crystal superalloy with different crystal orientations

NASA Astrophysics Data System (ADS)

Wang, Ruili; Gong, Xueyuan; Peng, Hui; Ma, Yue; Guo, Hongbo

2015-01-01

NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like μ phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like μ phases were formed in the SC alloy after heat-treatment 10 h at 1100 °C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (0 1 1) crystal orientation is about 14 μm after 50 h heat-treatment at 1100 °C, which is relatively thicker than that in the SC alloy with (0 0 1) crystal orientation, whereas the IDZ revealed similar thickness.

1300 K Creep Behavior of [001] Oriented Ni-49Al-1Hf (at.%) Single Crystals

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Locci, I. E.; Darolia, Ram; Bowman, R.

1999-01-01

A study of the 1300 K compressive and tensile creep properties of [001]-oriented NiAl-1Hf (D209) single crystals has been undertaken. Neither post homogenization cooling treatment, minor chemical variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mechanical behavior; however a heat treatment which dissolved the initial G-phase precipitates and promoted formation of Heusler particles led to a strength reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18 deg from the [001] did not reduce the creep strength. The effects of heat treatments on properties and a comparison of the flow stress-strain rate data to those predicted by the Jaswon-Cottrell solid solution hardening model indicate that the 1300 K strength in NiAl-1Hf single crystals is mainly due to precipitation hardening mechanisms.

Could thermal sensitivity of mitochondria determine species distribution in a changing climate?

PubMed

Iftikar, Fathima I; MacDonald, Julia R; Baker, Daniel W; Renshaw, Gillian M C; Hickey, Anthony J R

2014-07-01

For many aquatic species, the upper thermal limit (Tmax) and the heart failure temperature (THF) are only a few degrees away from the species' current environmental temperatures. While the mechanisms mediating temperature-induced heart failure (HF) remain unresolved, energy flow and/or oxygen supply disruptions to cardiac mitochondria may be impacted by heat stress. Recent work using a New Zealand wrasse (Notolabrus celidotus) found that ATP synthesis capacity of cardiac mitochondria collapses prior to T(HF). However, whether this effect is limited to one species from one thermal habitat remains unknown. The present study confirmed that cardiac mitochondrial dysfunction contributes to heat stress-induced HF in two additional wrasses that occupy cold temperate (Notolabrus fucicola) and tropical (Thalassoma lunare) habitats. With exposure to heat stress, T. lunare had the least scope to maintain heart function with increasing temperature. Heat-exposed fish of all species showed elevated plasma succinate, and the heart mitochondria from the cold temperate N. fucicola showed decreased phosphorylation efficiencies (depressed respiratory control ratio, RCR), cytochrome c oxidase (CCO) flux and electron transport system (ETS) flux. In situ assays conducted across a range of temperatures using naive tissues showed depressed complex II (CII) and CCO capacity, limited ETS reserve capacities and lowered efficiencies of pyruvate uptake in T. lunare and N. celidotus. Notably, alterations of mitochondrial function were detectable at saturating oxygen levels, indicating that cardiac mitochondrial insufficiency can occur prior to HF without oxygen limitation. Our data support the view that species distribution may be related to the thermal limits of mitochondrial stability and function, which will be important as oceans continue to warm. © 2014. Published by The Company of Biologists Ltd.

Multi Station Frequency Response and Polarization of ELF/VLF Signals Generated via Ionospheric Modification

NASA Astrophysics Data System (ADS)

Maxworth, Ashanthi; Golkowski, Mark; University of Colorado Denver Team

2013-10-01

ELF/VLF wave generation via HF modulated ionospheric heating has been practiced for many years as a unique way to generate waves in the ELF/VLF band (3 Hz - 30 kHz). This paper presents experimental results and associated theoretical modeling from work performed at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. An experiment was designed to investigate the modulation frequency dependence of the generated ELF/VLF signal amplitudes and polarization at multiple sites at distances of 37 km, 50 km and 99 km from the facility. While no difference is observed for X mode versus O mode modulation of the heating wave, it is found that ELF/VLF amplitude and polarization as a function of modulated ELF/VLF frequency is different for each site. An ionospheric heating code is used to determine the primary current sources leading to the observations.

Plasma line overshoot Observations during the July 2017 HF campaign at the Arecibo Observatory

NASA Astrophysics Data System (ADS)

Coster, A. J.; Nossa, E.; Kendall, E. A.; Bhatt, A.

2017-12-01

In the 1970's and 80's, enhanced plasma waves were frequently detected by the 430 MHz radar at the Arecibo Observatory within 2 to 8 msec after the HF heater had been turned on (Showen, 1975). This phenomenon is best described as an increase in the return power level of the plasma line by one or two orders of magnitude, followed by a slow decay back to its steady-state value. The formation of short scale striations has frequently been cited as a plausible explanation of the plasma line overshoot. The idea is that as the striations form, they absorb or scatter energy from the HF heater wave. This diminishes the amount of power available to excite the plasma waves detected. Short scale striations are thought to form at the altitude where the frequency of the HF wave matches the upper hybrid resonance - below the altitude of HF reflection. In 1981, the decay of the plasma line overshoot was correlated with the rise of the short scale striations utilizing an HF pulse rate of 4 seconds on/off, with the HF transmitter tuned to 5.1 MHz, and an estimated E.R.P. of 38 MW (Coster et al., 1984). In July 2017, a new series of experiments were performed using the new Arecibo HF facility to reexamine the enhanced plasma line issue, and utilizing the superior diagnostic capabilities available in 2017. These experiments were designed to study possible mechanisms responsible for the formation and decay of the plasma line overshoot. In the experiment, the HF heater was cycled on and off at various sequences including: 8 min on/off, 4 min on/off, and 2 min on/off. The enhanced plasma line was detected throughout the experiment. We will summarize the observations of this experiment, report on the significant findings, and provide suggestions for future experiments.

Work production using the two-way shape memory effect in NiTi and a Ni-rich NiTiHf high-temperature shape memory alloy

NASA Astrophysics Data System (ADS)

Atli, K. C.; Karaman, I.; Noebe, R. D.; Bigelow, G.; Gaydosh, D.

2015-12-01

The work output capacity of the two-way shape memory effect (TWSME) in a Ni50.3Ti29.7Hf20 (at%) high-temperature shape memory alloy (HTSMA) was investigated and compared to that of binary Ni49.9Ti50.1 (at%). TWSME was induced through a training procedure of 100 thermomechanical cycles under different tensile stresses. It was observed that TWSME in as-extruded and trained Ni50.3Ti29.7Hf20 could produce 0.7% strain against a compressive stress of 100 MPa, corresponding to a maximum work output of 0.08 J g-1, compared to a maximum value of 0.06 J g-1 for binary NiTi. A peak aging heat treatment of 3 h at 550 °C, which previously has been shown to result in near-perfect functional stability in Ni50.3Ti29.7Hf20 during isobaric thermal cycling, did not improve the TWSME and actually resulted in a decrease in the magnitude and stability of the TWSME and its work output capacity. Nevertheless, the magnitude of TWSM behavior of Ni50.3Ti29.7Hf20, in the absence of an aging heat treatment, renders it an attractive candidate for high-temperature TWSM actuation.

Separating Test Artifacts from Material Behavior in the Oxidation Studies of HfB2 SiC at 2000 deg C and Above (POSTPRINT)

DTIC Science & Technology

2012-02-01

h. Typical weight loss of the SiC grinding media after milling was 0.2 mg (0.2 wt% of the total batch). The powders were sieved through an 80-mesh...crucible (Advalue, Tuscon, AZ; 10 mL Ca -stabilized ZrO2 crucible; 95% ZrO2 and 4 ± 1% Ca ). Direct electrical resistance heat- ing was controlled by the...in furnace heating has been described previously by the authors, which was shown to contain Al and Ca as major impu- rities.15 In addition, HfSiO4

Separating Test Artifacts from Material Behavior in the Oxidation Studies of HfB2-SiC at 2000 degs C and Above (Preprint)

DTIC Science & Technology

2011-11-01

milled for 12 h. Typical weight loss of the SiC grinding media after milling was 0.2 mg (0.2 wt% of the total batch). The powders were sieved...10-mL Ca -stabilized ZrO2 crucible; 95% ZrO2 and 4±1% Ca ). Direct electrical resistance heating was controlled by the power output of an AC power...furnace heating has been described previously by the authors, which was shown to contain Al and Ca as major impurities [14]. Additionally, HfSiO4 (with

Electronic and thermodynamic properties of layered Hf2Sfrom first-principles calculations

NASA Astrophysics Data System (ADS)

Nandadasa, Chandani; Yoon, Mina; Kim, Seong-Gon; Erwin, Steve; Kim, Sungho; Kim, Sung Wng; Lee, Kimoon

Theoretically we explored two stable phases of inorganic fullerene-like structure of the layered dihafnium sulfide (Hf2 S) . We investigated structural and electronic properties of the two phases of Hf2 S by using first-principles calculations. Our calculation identifies experimentally observed anti-NbS2 structure of Hf2 S . Our electronic calculation results indicate that the density of states of anti- NbS2 structure of Hf2 S at fermi level is less than that of the other phase of Hf2 S . To study the relative stability of different phases at finite temperature Helmholtz free energies of two phases are obtained using density functional theory and density functional perturbation theory. The free energy of the anti-NbS2 structure of Hf2 S always lies below the free energy of the other phase by confirming the most stable structure of Hf2 S . The phonon dispersion, phonon density of states including partial density of states and total density of states are obtained within density functional perturbation theory. Our calculated zero-pressure phonon dispersion curves confirm that the thermodynamic stability of Hf2 S structures. For further investigation of thermodynamic properties, the temperature dependency of thermal expansion, heat capacities at constant pressure and volume are evaluated within the quasiharmonic approximations (QHA).

Features of Crystallization of Rapidly Quenched Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 Alloys from Melt with High-Temperature Shape Memory Effect

NASA Astrophysics Data System (ADS)

Pushin, A. V.; Pushin, V. G.; Kuntsevich, T. E.; Kuranova, N. N.; Makarov, V. V.; Uksusnikov, A. N.; Kourov, N. I.

2017-12-01

A comparative study of the structure and the chemical and phase composition of Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 amorphous alloys obtained by fast-quenching of melt stream by spinning has been carried out by transmission and scanning electron microscopy and X-ray diffraction. The critical temperatures of their devitrification were determined by the data of temperatures measurements of electrical resistance. The features of the formation of ultrafine structure and the phase transformation at the vitrification depending on the regimes of heat treatment and chemical composition of alloy have been established.

Phase Stability and Thermal Conductivity of Composite Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Benkel, Samantha; Zhu, Dongming

2011-01-01

Advanced environmental barrier coatings are being developed to protect SiC/SiC ceramic matrix composites in harsh combustion environments. The current coating development emphasis has been placed on the significantly improved cyclic durability and combustion environment stability in high-heat-flux and high velocity gas turbine engine environments. Environmental barrier coating systems based on hafnia (HfO2) and ytterbium silicate, HfO2-Si nano-composite bond coat systems have been processed and their stability and thermal conductivity behavior have been evaluated in simulated turbine environments. The incorporation of Silicon Carbide Nanotubes (SiCNT) into high stability (HfO2) and/or HfO2-silicon composite bond coats, along with ZrO2, HfO2 and rare earth silicate composite top coat systems, showed promise as excellent environmental barriers to protect the SiC/SiC ceramic matrix composites.

Energy-dense diets increase FGF23, lead to phosphorus retention and promote vascular calcifications in rats

PubMed Central

Raya, Ana I.; Rios, Rafael; Pineda, Carmen; Rodriguez-Ortiz, Maria E.; Diez, Elisa; Almaden, Yolanda; Muñoz-Castañeda, Juan R.; Rodriguez, Mariano; Aguilera-Tejero, Escolastico; Lopez, Ignacio

2016-01-01

Rats with normal renal function (Experiment 1, n = 12) and uninephrectomized (1/2Nx) rats (Experiment 2, n = 12) were fed diets with normal P (NP) and either normal (NF) or high fat (HF). Rats with intact renal function (Experiment 3, n = 12) were also fed NF or HF diets with high P (HP). Additionally, uremic (5/6Nx) rats (n = 16) were fed HP diets with NF or HF. Feeding the HF diets resulted in significant elevation of plasma FGF23 vs rats fed NF diets: Experiment 1, 593 ± 126 vs 157 ± 28 pg/ml (p < 0.01); Experiment 2, 538 ± 105 vs 250 ± 18 pg/ml (p < 0.05); Experiment 3, 971 ± 118 vs 534 ± 40 pg/ml (p < 0.01). Rats fed HF diets showed P retention and decreased renal klotho (ratio klotho/actin) vs rats fed NF diets: Experiment 1, 0.75 ± 0.06 vs 0.97 ± 0.02 (p < 0.01); Experiment 2, 0.69 ± 0.07 vs 1.12 ± 0.08 (p < 0.01); Experiment 3, 0.57 ± 0.19 vs 1.16 ± 0.15 (p < 0.05). Uremic rats fed HF diet showed more severe vascular calcification (VC) than rats fed NF diet (aortic Ca = 6.3 ± 1.4 vs 1.4 ± 0.1 mg/g tissue, p < 0.001). In conclusion, energy-rich diets increased plasma levels of FGF23, a known risk factor of cardiovascular morbidity and mortality. Even though FGF23 has major phosphaturic actions, feeding HF diets resulted in P retention, likely secondary to decreased renal klotho, and aggravated uremic VC. PMID:27841294

Energy-dense diets increase FGF23, lead to phosphorus retention and promote vascular calcifications in rats.

PubMed

Raya, Ana I; Rios, Rafael; Pineda, Carmen; Rodriguez-Ortiz, Maria E; Diez, Elisa; Almaden, Yolanda; Muñoz-Castañeda, Juan R; Rodriguez, Mariano; Aguilera-Tejero, Escolastico; Lopez, Ignacio

2016-11-14

Rats with normal renal function (Experiment 1, n = 12) and uninephrectomized (1/2Nx) rats (Experiment 2, n = 12) were fed diets with normal P (NP) and either normal (NF) or high fat (HF). Rats with intact renal function (Experiment 3, n = 12) were also fed NF or HF diets with high P (HP). Additionally, uremic (5/6Nx) rats (n = 16) were fed HP diets with NF or HF. Feeding the HF diets resulted in significant elevation of plasma FGF23 vs rats fed NF diets: Experiment 1, 593 ± 126 vs 157 ± 28 pg/ml (p < 0.01); Experiment 2, 538 ± 105 vs 250 ± 18 pg/ml (p < 0.05); Experiment 3, 971 ± 118 vs 534 ± 40 pg/ml (p < 0.01). Rats fed HF diets showed P retention and decreased renal klotho (ratio klotho/actin) vs rats fed NF diets: Experiment 1, 0.75 ± 0.06 vs 0.97 ± 0.02 (p < 0.01); Experiment 2, 0.69 ± 0.07 vs 1.12 ± 0.08 (p < 0.01); Experiment 3, 0.57 ± 0.19 vs 1.16 ± 0.15 (p < 0.05). Uremic rats fed HF diet showed more severe vascular calcification (VC) than rats fed NF diet (aortic Ca = 6.3 ± 1.4 vs 1.4 ± 0.1 mg/g tissue, p < 0.001). In conclusion, energy-rich diets increased plasma levels of FGF23, a known risk factor of cardiovascular morbidity and mortality. Even though FGF23 has major phosphaturic actions, feeding HF diets resulted in P retention, likely secondary to decreased renal klotho, and aggravated uremic VC.

Plasma Pancakes and Deep Cavities Generated by High Power Radio Waves from the Arecibo Observatory

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Briczinski, S. J., Jr.; Zawdie, K.; Huba, J.; Siefring, C. L.; Sulzer, M. P.; Nossa, E.; Aponte, N.; Perillat, P.; Jackson-Booth, N.

2017-12-01

Breakdown of the neutral atmosphere at ionospheric altitudes can be achieved with high power HF waves that reflect on the bottomside of the ionosphere. For overdense heating (i.e., wave frequency < maximum plasma frequency in the F-layer), the largest electric fields in the plasma are found just below the reflection altitude. There, electromagnetic waves are converted into electron plasma (Langmir) waves and ion acoustic waves. These waves are measured by scattering of the 430 MHz radar at Arecibo to from an enhanced plasma line. The photo-electron excitation of Langmuir waves yields a weaker plasma-line profile that shows the complete electron profile with the radar. Once HF enhanced Langmuir waves are formed, they can accelerate the photo-electron population to sufficient energies for neutral breakdown and enhanced ionization inside the HF Radio Beam. Plasma pancakes are produced because the breakdown process continues to build up plasma on bottom of the breakdown clouds and recombination occurs on the older breakdown plasma at the top of these clouds. Thus, the plasma pancake falls with altitude from the initial HF wave reflection altitude near 250 km to about 160 km where ion-electron recombination prevents the plasma cloud from being sustained by the high power HF. Experiments in March 2017 have produced plasma pancakes with about 100 Mega-Watts effective radiated power 5.1 MHz with the Arecibo HF Facility. Observations using the 430 MHz radar show falling plasma pancakes that disappear at low altitudes and reform at the F-layer critical reflection altitude. Sometimes the periodic and regular falling motion of the plasma pancakes is influenced by Acoustic Gravity Waves (AGW) propagating through the modified HF region. A rising AGW can cause the plasma pancake to reside at nearly constant altitude for 10 to 20 minutes. Dense cavities are also produced by high power radio waves interacting with the F-Layer. These structures are observed with the Arecibo 430 MHz radar as intense bight-outs in the plasma profile. Multiple cavities are seen simultaneously.

Taguchi Analysis on the Effect of Process Parameters on Densification During Spark Plasma Sintering of HfB2-20SiC (Preprint)

DTIC Science & Technology

2011-11-01

30 kN pressure and heating rate of 100 K/min. Introduction Boride , carbides and nitrides of the group IVB and VB transition metals are considered...10. Sciti D., Silvestroni L., Nygren M. Spark plasma sintering of Zr- and Hf- borides with decreasing amounts of MoSi2 as sintering aid Journal of

Arecibo - HF experiments in the E_region

NASA Astrophysics Data System (ADS)

Nossa, E.; Jain, K.; Sulzer, M. P.; Perillat, P.

2017-12-01

The new Arecibo Observatory - HF facility started operations in 2015. The HF facility is fully operational, acquiring consecutive days of data without unwanted interruptions. It has a maximum transmitted power of 600kW, with center frequencies at 5.125 MHz and 8.175 MHz. The 8.175 (5.125) MHz band frequency has a gain of 25.5 (22) dB and HPBW of 8.5 (13) degrees. The effects of the HF experiments in the ionosphere are being observed with the Arecibo incoherent scatter radar (ISR). The ISR has two beams that simultaneously could sense the modified region and the region outside of the affected volume. The ISR has height resolution of 300 m. and allows to observe from altitudes 95 km to the topside ionosphere. Observation of the E-region - HF experiments are sparse but possible at Arecibo. High ionization at a height 100 km are needed to modify the region artificially. This paper presents examples of E-region enhanced plasma lines (See Figure). Diagnostic of the layers is made using the ISR to estimate electron density, temperatures, ion drifts, among others. The data shows exceptional modifications of the ionosphere that range from creating artificial cavities and layers, induced irregularities, substantial variations in temperature profiles to enhanced ion and plasma densities.Previously, the HF experiments were performed to study specific effects in a narrow region. However, the extent of the data collected with the ISR during 2017 is revealing new features and different kind of forces that artificially modify extended regions of the ionosphere. This paper exhibits examples where the interaction between the E and F-region when HF experiments are evident. A theory of a correlation between the two layers due to different conductivities is explored to illustrate how the enhancement of irregularities is produced and maintained over time. Examples of strong artificially induced irregularities formed at F-region heights when Sporadic E-layer is present are shown to support the theory.The Figure shows an enhanced plasma line for the diurnal E-region. For this HF experiment, the plasma density increased from 3.6 MHz to 5.1MHz (which corresponds to the HF frequency). The vertical lines observed in the Figure are artifacts from the data, as well as the fake enhanced plasma lines at frequencies different than the HF frequency.

Study on molecular sieve absorption of ground state HF molecules in a non-chain pulsed HF Laser

NASA Astrophysics Data System (ADS)

Ma, Lianying; Zhou, Songqing; Chao, Huang; Huang, Ke; Zhu, Feng; Luan, Kunpeng; Chen, Hongwei

2017-05-01

This paper describes the principle of non-chain pulsed HF laser, and analyzes the reason why the laser energy dropped severely with the accumulation of shots when the HF laser was in repetitive operation. In order to solve this problem, a molecular sieve absorption device was designed and mounted in the recirculation loop of the HF laser. Measurements of flow velocity indicated that the absorption device would just introduce a small decrease of flow velocity which would not influence the laser operation. Several types of molecular sieve (3A,4A,5A,13X) were used in absorbing experiments and the experiment results inferred that 3A molecular sieve was the most effective sorbent. All the experiments showed that the average drop of the output energy was not more than 5% after 1000 shots at 50Hz/20s. Compared to the energy drop of about 40% without the device, the absorption device could significantly improve the stability of the HF laser output energy and prolong the lifespan of laser medium gases.

Vlasov Simulations of Ionospheric Heating Near Upper Hybrid Resonance

NASA Astrophysics Data System (ADS)

Najmi, A. C.; Eliasson, B. E.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

2014-12-01

It is well-known that high-frequency (HF) heating of the ionosphere can excite field- aligned density striations (FAS) in the ionospheric plasma. Furthermore, in the neighborhood of various resonances, the pump wave can undergo parametric instabilities to produce a variety of electrostatic and electromagnetic waves. We have used a Vlasov simulation with 1-spatial dimension, 2-velocity dimensions, and 2-components of fields, to study the effects of ionospheric heating when the pump frequency is in the vicinity of the upper hybrid resonance, employing parameters currently available at ionospheric heaters such as HAARP. We have found that by seeding theplasma with a FAS of width ~20% of the simulation domain, ~10% depletion, and by applying a spatially uniform HF dipole pump electric field, the pump wave gives rise to a broad spectrum of density fluctuations as well as to upper hybrid and lower hybrid oscillating electric fields. We also observe collisionless bulk-heating of the electrons that varies non-linearly with the amplitude of the pump field.

Discrete stages of core formation survive the Moon-forming impact

NASA Astrophysics Data System (ADS)

Jackson, C.; Bennett, N.; Du, Z.; Fei, Y.

2016-12-01

There is mounting evidence that Earth contains isotopic variations produced by short-lived systems, namely Hf-W and I-Xe. The lifetimes of these systems are 50 Ma and 80 Ma, respectively, requiring that chemical heterogeneities that were formed extremely early in solar system history and have survived within Earth's mantle to the modern day. The isotopic heterogeneity observed within Earth's mantle contrasts the isotopic similarity of bulk silicate Earth and bulk silicate Moon. This suggests the process(es) responsible for the isotopic variations within Earth predate the Moon-forming impact. Here, we focus on the potential role of core-formation in generating coupled isotopic variations associated with the Hf-W and I-Xe systems. We present metal-silicate partitioning data for W and I from experiments employing laser-heated diamond anvil cells. Experiments were conducted up to the pressure and temperature conditions directly relevant to core formation at GSECARS, APS. Samples were prepared using focused ion beam milling and analyzed by field emission electron microbeam techniques (EDS & WDS). These analyses demonstrate that W and I preferentially partition into the core under a wide range of conditions. In combination with literature data, this suggests that core formation left the residual mantle with an increased Hf/W ratio and a decreased I/Xe ratio. These parent-daughter fractionations lead to radiogenic W and unradiogenic Xe isotopic signatures compared to mantle that experienced the extraction of core material at a later date, on average. Relatively radiogenic W and unradiogenic Xe isotopic signatures are associated with plume rocks, potentially linking the plume source to mantle reservoirs that experienced early core extraction relative to the bulk mantle. Compositional variables, pressure, and temperature also affect the magnitude of Hf/W and I/Xe fractionation associated with core formation. The interplay of these variables will be evaluated alongside the timing of core formation in the context of generating short-lived isotopic variations associated with plume mantle.

Diet choice patterns in rodents depend on novelty of the diet, exercise, species, and sex.

PubMed

Yang, Tiffany; Xu, Wei-Jie; York, Haley; Liang, Nu-Chu

2017-07-01

Prolonged consumption of a palatable, high fat (HF) diet paired with a lack of physical activity can exacerbate the development of obesity. Exercise can facilitate the maintenance of a healthy body weight, possibly though mediating changes in diet preference. Using a two-diet choice and wheel running (WR) paradigm, our laboratory previously demonstrated that WR induces HF diet avoidance with different persistency in male and female rats when HF diet and WR are introduced simultaneously. The aims of this study were to examine whether this behavior is species dependent and to what extent the novelty of the diet affects WR induced HF diet avoidance. Experiment 1 utilized male C57BL6 mice in a two-diet choice and WR paradigm. Results show that all mice preferred HF to chow diet regardless of exercise and the order in which exercise and HF diet were presented. Experiment 2A (diet novelty) utilized Sprague-Dawley rats that were first habituated to a 45% HF diet prior to the simultaneous introduction of WR and a novel high-carbohydrate, low-fat (DK) diet. All rats avoided the novel high-carbohydrate diet and neither male nor female wheel running rats exhibited reduction in HF diet intake or HF diet avoidance. After all rats were returned to a sedentary condition, female rats consumed significantly more of the DK diet than the male rats. In Experiment 2B (diet familiarity), rats remained sedentary and were re-habituated to the DK diet until intake stabilized. Subsequently, a 60% HF diet was introduced for all rats and for running rats, access to the running wheels were provided simultaneously. Consistent with our previous findings, HF diet intake and preference was significantly reduced in all wheel running rats. These data suggest that exercise induced HF diet avoidance is affected by species and the novelty of the diet. Copyright © 2017 Elsevier Inc. All rights reserved.

Development and validation of a house finch interleukin-1β (HfIL-1β) ELISA system.

PubMed

Kim, Sungwon; Park, Myeongseon; Leon, Ariel E; Adelman, James S; Hawley, Dana M; Dalloul, Rami A

2017-08-30

A unique clade of the bacterium Mycoplasma gallisepticum (MG), which causes chronic respiratory disease in poultry, has resulted in annual epidemics of conjunctivitis in North American house finches since the 1990s. Currently, few immunological tools have been validated for this songbird species. Interleukin-1β (IL-1β) is a prototypic multifunctional cytokine and can affect almost every cell type during Mycoplasma infection. The overall goal of this study was to develop and validate a direct ELISA assay for house finch IL-1β (HfIL-1β) using a cross-reactive chicken antibody. A direct ELISA approach was used to develop this system using two different coating methods, carbonate and dehydration. In both methods, antigens (recombinant HfIL-1b or house finch plasma) were serially diluted in carbonate-bicarbonate coating buffer and either incubated at 4 °C overnight or at 60 °C on a heating block for 2 hr. To generate the standard curve, rHfIL-1b protein was serially diluted at 0, 3, 6, 9, 12, 15, 18, 21, and 24 ng/mL. Following blocking and washing, anti-chicken IL-1b polyclonal antibody was added, plates were later incubated with detecting antibodies, and reactions developed with tetramethylbenzidine solution. A commercially available anti-chicken IL-1β (ChIL-1β) polyclonal antibody (pAb) cross-reacted with house finch plasma IL-1β as well as bacterially expressed recombinant house finch IL-1β (rHfIL-1β) in immunoblotting assays. In a direct ELISA system, rHfIL-1β could not be detected by an anti-ChIL-1β pAb when the antigen was coated with carbonate-bicarbonate buffer at 4°C overnight. However, rHfIL-1β was detected by the anti-ChIL-1β pAb when the antigen was coated using a dehydration method by heat (60°C). Using the developed direct ELISA for HfIL-1β with commercial anti-ChIL-1β pAb, we were able to measure plasma IL-1β levels from house finches. Based on high amino acid sequence homology, we hypothesized and demonstrated cross-reactivity of anti-ChIL-1β pAb and HfIL-1β. Then, we developed and validated a direct ELISA system for HfIL-1β using a commercial anti-ChIL-1β pAb by measuring plasma HfIL-1β in house finches.

Transmissivity Changes and Microseismicity Induced by Small-Scale Hydraulic Fracturing Tests in Crystalline Rock

NASA Astrophysics Data System (ADS)

Jalali, Mohammadreza; Gischig, Valentin; Doetsch, Joseph; Näf, Rico; Krietsch, Hannes; Klepikova, Maria; Amann, Florian; Giardini, Domenico

2018-03-01

Multiple meter-scale hydraulic fracturing (HF) experiments were executed in the crystalline rock at the Grimsel Test Site, Switzerland. The effect of the HF on the rock transmissivity has been quantified with hydraulic tests before and after each HF experiment. We observe transmissivity enhancement of 2 to 3 orders of magnitude and a change in the dominant flow regime after most of the HF tests. From microseismicity induced by the HF, we do not observe a systematic correlation between transmissivity enhancement and event numbers, frequency-magnitude distribution, or maximum magnitude. However, the radii of hydraulic fractures inferred independently from seismicity clouds and hydraulic responses coincide, implying that slip along fractures is the common underlying mechanism for transmissivity increase and seismicity.

Post-transition state dynamics and product energy partitioning following thermal excitation of the F⋯HCH2CN transition state: Disagreement with experiment

NASA Astrophysics Data System (ADS)

Pratihar, Subha; Ma, Xinyou; Xie, Jing; Scott, Rebecca; Gao, Eric; Ruscic, Branko; Aquino, Adelia J. A.; Setser, Donald W.; Hase, William L.

2017-10-01

Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH3CN → HF + CH2CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. The experiments were performed at 300 K, and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F⋯HCH2CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation. The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH2CN and then trapping in the CH2CN⋯HF post-reaction potential energy well of ˜10 kcal/mol with respect to the HF + CH2CN products. In contrast to this IRC, five different trajectory types were observed: the majority proceeded by direct H-atom transfer and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH2CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. Simulations with an anharmonic zero-point energy constraint gave product distributions for relative translation, HF rotation, HF vibration, CH2CN rotation, and CH2CN vibration as 5%, 11%, 60%, 7%, and 16%, respectively. In contrast, the experimental energy partitioning percentages to HF rotation and vibration are 6% and 41%. Comparisons are made between the current simulation and those for other F + H-atom abstraction reactions. The simulation product energy partitioning and HF vibrational population for F + CH3CN → HF + CH2CN resemble those for other reactions. A detailed discussion is given of possible origins of the difference between the simulation and experimental energy partitioning dynamics for F + CH3CN → HF + CH2CN. The F + CH3CN reaction also forms the CH3C(F)N intermediate, in which the F-atom adds to the C≡N bond. However, this intermediate and F⋯CH3CN and CH3CN⋯F van der Waals complexes are not expected to affect the F + CH3CN → HF + CH2CN product energy partitioning.

Post-transition state dynamics and product energy partitioning following thermal excitation of the F∙∙∙HCH 2 CN transition state: Disagreement with experiment

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

Pratihar, Subha; Ma, Xinyou; Xie, Jing

Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH 3CN → HF + CH 2CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. In accord with experiment and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F-HCH 2CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST for the simulation. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation.more » The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH 2CN and then trapping in the CH 2CN-HF post-reaction potential energy well of ~10 kcal/mol with respect to the HF + CH 2CN products. In contrast to this IRC, five different trajectory types were observed, with the majority involving direct dissociation and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH 2CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. From the simulations and with an anharmonic zero-point energy constraint, the percentage partitioning of the product energy to relative translation, HF rotation, HF vibration, CH 2CN rotation and CH 2CN vibration is 5, 11, 60, 7, and 16%, respectively. In contrast the experimental energy partitioning percentages to HF rotation and vibration are 6 and 41%. Comparisons are made between the current simulation and those for other F + H-atom abstraction reactions. The simulation product energy partitioning and HF vibrational population for F + CH 3CN → HF + CH 2CN are similar to those for these other reactions. A detailed discussion is given of possible origins of the difference between the simulation and experimental energy partitioning dynamics for the F + CH 3CN → HF + CH 2CN reaction. The F + CH 3CN reaction also forms the CH 3C(F)N intermediate, in which the F-atom adds to the C≡N bond. However, this intermediate and the F---CH 3CN and CH 3CN-F van der Waals complexes are not expected to affect the F + CH 3CN → HF + CH 2CN product energy partitioning.« less

Post-transition state dynamics and product energy partitioning following thermal excitation of the F⋯HCH2CN transition state: Disagreement with experiment.

PubMed

Pratihar, Subha; Ma, Xinyou; Xie, Jing; Scott, Rebecca; Gao, Eric; Ruscic, Branko; Aquino, Adelia J A; Setser, Donald W; Hase, William L

2017-10-14

Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH 3 CN → HF + CH 2 CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. The experiments were performed at 300 K, and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F⋯HCH 2 CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation. The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH 2 CN and then trapping in the CH 2 CN⋯HF post-reaction potential energy well of ∼10 kcal/mol with respect to the HF + CH 2 CN products. In contrast to this IRC, five different trajectory types were observed: the majority proceeded by direct H-atom transfer and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH 2 CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. Simulations with an anharmonic zero-point energy constraint gave product distributions for relative translation, HF rotation, HF vibration, CH 2 CN rotation, and CH 2 CN vibration as 5%, 11%, 60%, 7%, and 16%, respectively. In contrast, the experimental energy partitioning percentages to HF rotation and vibration are 6% and 41%. Comparisons are made between the current simulation and those for other F + H-atom abstraction reactions. The simulation product energy partitioning and HF vibrational population for F + CH 3 CN → HF + CH 2 CN resemble those for other reactions. A detailed discussion is given of possible origins of the difference between the simulation and experimental energy partitioning dynamics for F + CH 3 CN → HF + CH 2 CN. The F + CH 3 CN reaction also forms the CH 3 C(F)N intermediate, in which the F-atom adds to the C≡N bond. However, this intermediate and F⋯CH 3 CN and CH 3 CN⋯F van der Waals complexes are not expected to affect the F + CH 3 CN → HF + CH 2 CN product energy partitioning.

Remote sensing of mesospheric dust layers using active modulation of PMWE by high-power radio-waves

NASA Astrophysics Data System (ADS)

Cohen, M.; Zhang, X.; Cohen, M.; Mahmoudian, A.; Scales, W.; Kosch, M. J.; M Farahani, M.; Mohebalhojeh, A.

2016-12-01

So-called polar mesospheric winter echoes (PMWE) are radar echoes observed during winter at altitudes around 50-80 km and are much weaker than their PMSE (Polar Mesospheric Summer Echoes) counterpart. Unlike PMSE, PMWE are less studied and understood. Breaking of gravity waves and the associated turbulence are proposed as the major source for PMWE echoes. The action of neutral turbulence alone does not appear to give a good explanation for PMWE. PMWE is also attributed to Bragg scatter from electron irregularities which result from charging of free electrons onto sub-visible particles. The temporal behavior of PMWE response to HF pump heating can be employed to diagnose the charged dust layer. Specifically, the rise and fall time of radar echo strength as well as relaxation and recovery time after heater turn-on and off are distinct parameters that are a function of radar frequency. This work presents the first study of the modulation of PMWE by artificial radiowave heating using computational modeling and experimental observation in different radar frequency bands. Variation of dust plasma parameters associated with PMWE such as dust radius, dust density, recombination rate, electron- and dust-neutral collision frequencies, photo-detachment current and electron temperature enhancement ratio are included. Computational results derived from different sets of parameters are considered and compared with recent observations at EISCAT using 224 MHz and 56 MHz radars. The agreement between the model results and the observations show the high potential of remote sensing of dust and plasma parameters associated with PMWE. Measurement of Te/Ti using ISR and simultaneous observations in two frequency bands may lead to a more accurate estimation of dust density and radius. The enhancement of backscattered signal in the HF band during PMWE heating is predicted for the first time. The required background dust-plasma parameters as well as heater power (Te/Ti) for the observation of turn-on overshoot are investigated. It has been shown that the similarity of the temporal evolution of radar echoes in HF band and average charge on the dust particles can be used to study the fundamental physics associated with the dust charging in the PMWE source region. The possibilities of perusing PMWE heating experiments at HAARP will be discussed.

Radar investigation of barium releases over Arecibo Observatory, Puerto Rico

NASA Technical Reports Server (NTRS)

Djuth, Frank T.

1995-01-01

The NASA Combined Release and Radiation Effects Satellite (CRRES) El Coqui rocket campaign was successfully carried out in Puerto Rico during the period 18 May through 12 July 1992. This report describes five chemical release experiments in the upper ionosphere supported by Geospace Research, Inc. during the El Coqui campaign. Additional spin-off science is also discussed. The El Coqui releases are designated AA-1 (rocket 36-082), AA-2 (rocket 36-081), AA-3b (rocket 36-064), AA-4 (rocket 36-065), and AA-7 (rocket 36-083). Particular attention is paid to releases AA-2 and AA-4. These two experiments involved the illumination of ionospheric release regions with powerful high-frequency (HF) radio waves transmitted from the Arecibo HF facility. In the AA-2 experiment, microinstabilities excited by the HF wave in a Ba(+) plasma were examined. This release yielded a smooth plasma cloud that helped clarify several fundamental issues regarding the physics of wave plasma instabilities. During AA-2 extremely strong HF-induced Langmuir turbulence was detected with the Arecibo 430 MHz radar. CF3Br was released in the AA-4 study to create an ionospheric hole that focused the HF beam. This experiment successfully explored wave-plasma coupling in an O(+) ionosphere under conditions of very high HF electric field strengths.

Simultaneous Multi-angle Observations of Strong Langmuir Turbulence at HAARP

NASA Astrophysics Data System (ADS)

Watanabe, Naomi; Golkowski, Mark; Sheerin, James P.; Watkins, Brenton J.

2015-10-01

We report results from a recent series of experiments employing the HF transmitter of the High Frequency Active Auroral Research Program (HAARP) to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. The Modular UHF Ionospheric Radar (MUIR) located at the HAARP facility is used as the primary diagnostic. Short pulse, low duty cycle experiments are used to avoid generation of artificial field-aligned irregularities and isolate ponderomotive plasma turbulence effects. The HF pump frequency is close to the 3rd gyro-harmonic frequency and the HF pointing angle and MUIR look angle are between the HF Spitze angle and Magnetic Zenith angle. Plasma line spectra measured simultaneously in different spots of the interaction region display differences dependent on the aspect angle of the HF pump beam in the boresight direction and the pointing angle of the MUIR diagnostic radar. Outshifted Plasma Lines, cascade, collapse, coexistence, spectra are observed in agreement with existing theory and simulation results of Strong Langmuir Turbulence in ionospheric interaction experiments. It is found that SLT at HAARP is most readily observed at a HF pointing angle of 11° and UHF observation angle of 15°, which is consistent with the magnetic zenith effect as documented in previous works and optimal orientation of the refracted HF electric field vector.

An experimental assessment of the quartz-in-epidote barometer

NASA Astrophysics Data System (ADS)

Cisneros, M.; Ashley, K.

2017-12-01

We focus on quantifying the suitability of a quartz-in-epidote (qtz-in-ep) solid mineral barometer because theoretical calculations applying an isotropic elastic model suggest that qtz-in-ep inclusion pressures (Pincl) exhibit minimal temperature dependence, with the potential to elucidate the growth conditions of epidote in geologic environments with poor PT constraints (e.g., skarn deposits, retrograde metamorphic rocks). We carried-out heating experiments and compare Raman spectroscopic shifts in the 464 cm-1 band of quartz (and therefore Pincl) with modeled Pincl for three epidotes derived from samples with well constrained PT conditions: 1) FT-1E from Frosnitztal Tal (Pincl = 6.8 kbar), 2) LdC-31C from Lago-di-Cignana (Pincl = 2.6 kbar), and 3) HF-14C from the Upper Schieferhuelle in Western Tauern (Pincl = 0.74 kbar). At elevated temperatures, we encountered difficulties in separating the quartz 464 cm-1 Raman peak and shoulder epidote peaks due to the convergence resulting from the T-sensitivity of the quartz band. Our low pressure HF14C quartz peaks were particularly difficult to fit at elevated temperatures and displayed lower entrapment pressures (Pent) than modelled Pent for most entrapment temperatures (Tent); however, experimental Pent for samples FT-1E and LdC-31C match modelled Pent extremely well. Ambient quartz inclusion pressures are consistent with previously constrained PT conditions: 1) FT-1E: Pent = 21.5 (Tent = 625 ºC), 2) LdC-31C: Pent= 11.7 kbar (Tent = 550 ºC), 3) HF-14C: Pent = 7.4 kbar (Tent= 500 ºC). Reference PT conditions for these samples are as follows: 1) FT-1E: P = 20 - 24 kbar, T = 625 ºC, 2) LdC-31C: P = 32 - 34 kbar, T = 550 ºC, 3) HF-14C: P = 7 - 8 kbar, T = 500 ºC. Qtz-in-ep pressures from sample LdC-31C are consistent with early, low-P vein epidote precipitation that pre-dates high-P metamorphism or low-P retrogression in the Lago-di-Cignana region. Our work successfully demonstrates that a qtz-in-ep barometer can be used for accurate, robust entrapment pressure estimates of rocks from moderate to high pressure metamorphic terranes. Furthermore, our work suggests that other anisotropic mineral pairs may be suitable for Raman thermobarometry without the need to carry-out heating experiments to apply temperature-dependent Pent corrections.

Isotopic constraints on the cooling of the continental lithosphere

NASA Astrophysics Data System (ADS)

Bedini, R.-M.; Blichert-Toft, J.; Boyet, M.; Albarède, F.

2004-06-01

A new model of continuous diffusion of radiogenic isotopes was applied to mineral 147Sm- 143Nd and 176Lu- 176Hf data on low-temperature garnet-peridotite xenoliths from Cretaceous South African kimberlites. The radiometric ages are younger than the Archean whole-rock Re-Os and U-Pb ages and reflect that both the Sm-Nd and Lu-Hf chronometric systems remained open under the thermal conditions of the lithospheric mantle. The radiogenic character of Hf in garnets, however, indicates that even if essentially no pyroxene remained immune to the effects of metasomatic events, the core of many garnets may preserve memory of the long history of this mineral in the subcontinental lithosphere. The cooling rates deduced from the garnet Sm-Nd ages in the South African lithosphere are fairly low (40-105 °C Gy -1), but compare well with values obtained on similar samples from different regions. These unexpectedly low values imply that the heat flow at the base of the subcontinental lithospheric mantle has changed only very slowly through time. They further support the recent suggestion that, as a result of viscous dissipation by plate bending, convection vigor and heat flow are to some extent decoupled, which argues against a thermal feedback on geodynamics. Modern convection may still be mining fossil heat stored in the lower mantle.

A closer look: Alternative pain management practices by heart failure patients with chronic pain.

PubMed

McDonald, Deborah Dillon; Soutar, Christina; Chan, Maria Agudelo; Afriyie, Angela

2015-01-01

To describe alternative non-pharmaceutical non-nutraceutical pain self-management strategies used by people with heart failure (HF) in order to reduce chronic non-cardiac pain. Little is known about alternative pain self-treatments used by HF patients with chronic pain. A cross-sectional descriptive design was used with 25 hospitalized HF patients who had chronic pain and used at least one alternative pain treatment. Pain intensity, pain interference with function, and current pain treatments were measured with the Brief Pain Inventory. Alternative treatments included walking, stretching, use of heat and cold. Five patients used evidence-based pain treatments for their chronic pain conditions. Patients reported moderate pain intensity and pain interference with activity. Patients with HF and chronic pain use few alternative pain treatments. Screening for chronic pain and referral to Integrative Medicine and/or Palliative care for a pain management consult might reduce the added burden of pain in people with HF. Copyright © 2015 Elsevier Inc. All rights reserved.

Role of excess ligand and effect of thermal treatment in hybrid inorganic-organic EUV resists

NASA Astrophysics Data System (ADS)

Mattson, Eric C.; Rupich, Sara M.; Cabrera, Yasiel; Chabal, Yves J.

2018-03-01

The chemical structure and thermal reactivity of recently discovered inorganic-organic hybrid resist materials are characterized using a combination of in situ and ex situ infrared (IR) spectroscopy and x-ray photoemission spectroscopy (XPS). The materials are comprised of a small HfOx core capped with methacrylic acid ligands that form a combined hybrid cluster, HfMAA. The observed IR modes are consistent with the calculated modes predicted from the previously determined x-ray crystal structure of the HfMAA-12 cluster, but also contain extrinsic hydroxyl groups. We find that the water content of the films is dependent on the concentration of excess ligand added to the solution. The effect of environment used during post-application baking (PAB) is studied and correlated to changes in solubility of the films. In doing so, we find that hydroxylation of the clusters results in formation of additional Hf-O-Hf linkages upon heating, which in turn impacts the solubility of the films.

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

Rodenbücher, C.; Hildebrandt, E.; Sharath, S. U.

On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO{sub 2−x}) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC{sub x}) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC{sub x} surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO{sub 2} thin films prepared and measured under identical conditions, the formation of HfC{sub x} was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films providesmore » a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.« less

Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

NASA Technical Reports Server (NTRS)

Lawson, JOhn W.; Daw, Murray S.; Bauschlicher, Charles W.

2011-01-01

Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 are candidate materials for applications in extreme environments because of their high melting point, good mechanical properties and reasonable oxidation resistance. Unlike many ceramics, these materials have high thermal conductivity which can be advantageous, for example, to reduce thermal shock. Recently, we developed Tersoff style interatomic potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current. Results at room temperature and at elevated temperatures will be reported.

Investigation of Ionospheric Turbulence and Whistler Wave Interactions with Space Plasmas

DTIC Science & Technology

2012-11-21

an oscillating LOS velocity with the same periodicity as the heating modulation pattern. A set of Fourier periodogram from the MUIR LOS velocity...scale ionospheric turbulence are discussed separately, viz., (a) anomalous heat source-induced acoustic gravity waves (AGW), and (b) HF radio wave...ionospheric ducts, acoustic gravity waves (AGWs), anomalous heat sources, inner and outer radiation belts, L parameter, whistler wave interactions

Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden

NASA Astrophysics Data System (ADS)

Lucazeau, Francis; Leroy, Sylvie; Rolandone, Frédérique; d'Acremont, Elia; Watremez, Louise; Bonneville, Alain; Goutorbe, Bruno; Düsünur, Doga

2010-07-01

In order to investigate the importance of fluid circulation associated with the formation of ocean-continent transitions (OCT), we examine 162 new heat-flow (HF) measurements in the eastern Gulf of Aden, obtained at close locations along eight seismic profiles and with multi-beam bathymetry. The average HF values in the OCT and in the oceanic domain (~ 18 m.y.) are very close to the predictions of cooling models, showing that the overall importance of fluids remains small at the present time compared to oceanic ridge flanks of the same age. However, local HF anomalies are observed, although not systematically, in the vicinity of the unsedimented basement and are interpreted by the thermal effect of meteoric fluids flowing laterally. We propose a possible interpretation of hydrothermal paths based on the shape of HF anomalies and on the surface morphology: fluids can circulate either along-dip or along-strike, but are apparently focussed in narrow "pipes". In several locations in the OCT, there is no detectable HF anomaly while the seismic velocity structure suggests serpentinization and therefore past circulation. We relate the existence of the present day fluid circulation in the eastern Gulf of Aden to the presence of unsedimented basement and to the local extensional stress in the vicinity of the Socotra-Hadbeen fault zone. At the scale of rifted-margins, fluid circulation is probably not as important as in the oceanic domain because it can be inhibited rapidly with high sedimentation rates, serpentinization and stress release after the break-up.

Radar investigation of barium releases over Arecibo Observatory, Puerto Rico. Final report, 12 August 1991-30 June 1994

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

Djuth, F.T.

1995-07-01

The NASA Combined Release and Radiation Effects Satellite (CRRES) El Coqui rocket campaign was successfully carried out in Puerto Rico during the period 18 May through 12 July 1992. This report describes five chemical release experiments in the upper ionosphere supported by Geospace Research, Inc. during the El Coqui campaign. Additional spin-off science is also discussed. The El Coqui releases are designated AA-1 (rocket 36-082), AA-2 (rocket 36-081), AA-3b (rocket 36-064), AA-4 (rocket 36-065), and AA-7 (rocket 36-083). Particular attention is paid to releases AA-2 and AA-4. These two experiments involved the illumination of ionospheric release regions with powerful high-frequencymore » (HF) radio waves transmitted from the Arecibo HF facility. In the AA-2 experiment, microinstabilities excited by the HF wave in a Ba(+) plasma were examined. This release yielded a smooth plasma cloud that helped clarify several fundamental issues regarding the physics of wave plasma instabilities. During AA-2 extremely strong HF-induced Langmuir turbulence was detected with the Arecibo 430 MHz radar. CF3Br was released in the AA-4 study to create an ionospheric hole that focused the HF beam. This experiment successfully explored wave-plasma coupling in an O(+) ionosphere under conditions of very high HF electric field strengths.« less

Enhancement of thermoelectric figure-of-merit at low temperatures by titanium substitution for hafnium in n-type half-Heuslers Hf0.75-xTixZr0.25NiSn0.99Sb0.01

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

Joshi, Giri; Dahal, Tulashi; Chen, Shuo

The effect of titanium (Ti) substitution for hafnium (Hf) on thermoelectric properties of (Hf, Zr)-based n-type half-Heuslers: Hf0.75-xTixZr0.25NiSn0.99Sb0.01, has been studied. The samples are made by arc melting followed by ball milling and hot pressing via the nanostructuring approach. A peak thermoelectric figure-of-merit (ZT) of ~1.0 is achieved at 500 °C in samples with a composition of Hf0.5Zr0.25Ti0.25NiSn0.99Sb0.01 due to a slight increase in carrier concentration and also a lower thermal conductivity caused by Ti. The ZT values below 500 °C of hot pressed Hf0.5Zr0.25Ti0.25NiSn0.99Sb0.01 samples are significantly higher than those of the same way prepared Hf0.75Zr0.25NiSn0.99Sb0.01 samples at eachmore » temperature, which are very much desired for mid-range temperature applications such as waste heat recovery in automobiles.« less

Enhancement of thermoelectric figure-of-merit at low temperatures by titanium substitution for hafnium in n-type half-Heuslers Hf0.75-xTixZr0.25NiSn0.99Sb0.01

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

Joshi, Giri; Dahal, Tulashi; Chen, Shuo

The effect of titanium (Ti) substitution for hafnium (Hf) on thermoelectric properties of (Hf, Zr)-based n-type half-Heuslers: Hf 0.75-xTi xZr 0.25NiSn 0.99Sb 0.01, has been studied. The samples are made by arc melting followed by ball milling and hot pressing via the nanostructuring approach. A peak thermoelectric figure-of-merit (ZT) of ~1.0 is achieved at 500 °C in samples with a composition of Hf 0.5Zr 0.25Ti 0.25NiSn 0.99Sb 0.01 due to a slight increase in carrier concentration and also a lower thermal conductivity caused by Ti. TheZT values below 500 °C of hot pressed Hf 0.5Zr 0.25Ti 0.25NiSn 0.99Sb 0.01 samplesmore » are significantly higher than those of the same way prepared Hf 0.75Zr 0.25NiSn 0.99Sb 0.01samples at each temperature, which are very much desired for mid-range temperature applications such as waste heat recovery in automobiles.« less

Analysis of energy expenditure in diet-induced obese rats

PubMed Central

Assaad, Houssein; Yao, Kang; Tekwe, Carmen D.; Feng, Shuo; Bazer, Fuller W.; Zhou, Lan; Carroll, Raymond J.; Meininger, Cynthia J.; Wu, Guoyao

2014-01-01

Development of obesity in animals is affected by energy intake, dietary composition, and metabolism. Useful models for studying this metabolic problem are Sprague-Dawley rats fed low-fat (LF) or high-fat (HF) diets beginning at 28 days of age. Through experimental design, their dietary intakes of energy, protein, vitamins, and minerals per kg body weight (BW) do not differ in order to eliminate confounding factors in data interpretation. The 24-h energy expenditure of rats is measured using indirect calorimetry. A regression model is constructed to accurately predict BW gain based on diet, initial BW gain, and the principal component scores of respiratory quotient and heat production. Time-course data on metabolism (including energy expenditure) are analyzed using a mixed effect model that fits both fixed and random effects. Cluster analysis is employed to classify rats as normal-weight or obese. HF-fed rats are heavier than LF-fed rats, but rates of their heat production per kg non-fat mass do not differ. We conclude that metabolic conversion of dietary lipids into body fat primarily contributes to obesity in HF-fed rats. PMID:24896330

Experiments and theory on parametric instabilities excited in HF heating experiments at HAARP

NASA Astrophysics Data System (ADS)

Kuo, Spencer; Snyder, Arnold; Lee, M. C.

2014-06-01

Parametric instabilities excited by O-mode HF heater and the induced ionospheric modification were explored via HAARP digisonde operated in a fast mode. The impact of excited Langmuir waves and upper hybrid waves on the ionosphere are manifested by bumps in the virtual spread, which expand the ionogram echoes upward as much as 140 km and the downward range spread of the sounding echoes, which exceeds 50 km over a significant frequency range. The theory of parametric instabilities is presented. The theory identifies the ionogram bump located between the 3.2 MHz heater frequency and the upper hybrid resonance frequency and the bump below the upper hybrid resonance frequency to be associated with the Langmuir and upper hybrid instabilities, respectively. The Langmuir bump is located close to the upper hybrid resonance frequency, rather than to the heater frequency, consistent with the theory. Each bump in the virtual height spread of the ionogram is similar to the cusp occurring in daytime ionograms at the E-F2 layer transition, indicating that there is a small ledge in the density profile similar to E-F2 layer transitions. The experimental results also show that the strong impact of the upper hybrid instability on the ionosphere can suppress the Langmuir instability.

Experiments and theory on parametric instabilities excited in HF heating experiments at HAARP

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

Kuo, Spencer; Snyder, Arnold; Lee, M. C.

2014-06-15

Parametric instabilities excited by O-mode HF heater and the induced ionospheric modification were explored via HAARP digisonde operated in a fast mode. The impact of excited Langmuir waves and upper hybrid waves on the ionosphere are manifested by bumps in the virtual spread, which expand the ionogram echoes upward as much as 140 km and the downward range spread of the sounding echoes, which exceeds 50 km over a significant frequency range. The theory of parametric instabilities is presented. The theory identifies the ionogram bump located between the 3.2 MHz heater frequency and the upper hybrid resonance frequency and the bump below themore » upper hybrid resonance frequency to be associated with the Langmuir and upper hybrid instabilities, respectively. The Langmuir bump is located close to the upper hybrid resonance frequency, rather than to the heater frequency, consistent with the theory. Each bump in the virtual height spread of the ionogram is similar to the cusp occurring in daytime ionograms at the E-F2 layer transition, indicating that there is a small ledge in the density profile similar to E-F2 layer transitions. The experimental results also show that the strong impact of the upper hybrid instability on the ionosphere can suppress the Langmuir instability.« less

Implication of fermentable carbohydrates targeting the gut microbiota on conjugated linoleic acid production in high-fat-fed mice.

PubMed

Druart, Céline; Neyrinck, Audrey M; Dewulf, Evelyne M; De Backer, Fabienne C; Possemiers, Sam; Van de Wiele, Tom; Moens, Frédéric; De Vuyst, Luc; Cani, Patrice D; Larondelle, Yvan; Delzenne, Nathalie M

2013-09-28

In vitro experiments have shown that isolated human gut bacteria are able to metabolise PUFA into conjugated PUFA like conjugated linoleic acids (CLA). The hypothesis of the present paper was that high-fat (HF) diet feeding and supplementation with fermentable carbohydrates that have prebiotic properties modulate the in vivo production of CLA by the mouse gut microbiota. Mice were treated for 4 weeks as follows: control (CT) groups were fed a standard diet; HF groups were fed a HF diet rich in linoleic acid (18 : 2n-6); the third groups were fed with the HF diet supplemented with either inulin-type fructans (HF-ITF) or arabinoxylans (HF-Ax). HF diet feeding increased rumenic acid (cis-9,trans-11-18 : 2 CLA) content both in the caecal and liver tissues compared with the CT groups. ITF supplementation had no major effect compared with the HF diet whereas Ax supplementation increased further rumenic acid (cis-9,trans-11-18 : 2 CLA) in the caecal tissue. These differences between both prebiotics may be linked to the high fat-binding capacity of Ax that provides more substrates for bacterial metabolism and to differential modulation of the gut microbiota (specific increase in Roseburia spp. in HF-Ax v. HF). In conclusion, these experiments supply the proof of concept that the mouse gut microbiota produces CLA in vivo, with consequences on the level of CLA in the caecal and liver tissues. We postulate that the CLA-producing bacteria could be a mediator to consider in the metabolic effects of both HF diet feeding and prebiotic supplementation.

Corticosterone administration in drinking water decreases high-fat diet intake but not preference in male rats

PubMed Central

Boersma, Gretha J.; Tamashiro, Kellie L.; Moran, Timothy H.

2016-01-01

One of the mechanisms through which regular exercise contributes to weight maintenance could be by reducing intake and preference for high-fat (HF) diets. Indeed, we previously demonstrated that wheel-running rats robustly reduced HF diet intake and preference. The reduced HF diet preference by wheel running can be so profound that the rats consumed only the chow diet and completely avoided the HF diet. Because previous research indicates that exercise activates the hypothalamic-pituitary-adrenal axis and increases circulating levels of corticosterone, this study tested the hypothesis that elevation of circulating corticosterone is involved in wheel running-induced reduction in HF diet preference in rats. Experiment 1 measured plasma corticosterone levels under sedentary and wheel-running conditions in the two-diet-choice (high-carbohydrate chow vs. HF) feeding regimen. The results revealed that plasma corticosterone is significantly increased and positively correlated with the levels of running in wheel-running rats with two-diet choice. Experiments 2 and 3 determined whether elevated corticosterone without wheel running is sufficient to reduce HF diet intake and preference. Corticosterone was elevated by adding it to the drinking water. Compared with controls, corticosterone-drinking rats had reduced HF diet intake and body weight, but the HF diet preference between groups did not differ. The results of this study support a role for elevated corticosterone on the reduced HF diet intake during wheel running. The elevation of corticosterone alone, however, is not sufficient to produce a robust reduction in HF diet preference. PMID:26818055

Corticosterone administration in drinking water decreases high-fat diet intake but not preference in male rats.

PubMed

Boersma, Gretha J; Tamashiro, Kellie L; Moran, Timothy H; Liang, Nu-Chu

2016-04-15

One of the mechanisms through which regular exercise contributes to weight maintenance could be by reducing intake and preference for high-fat (HF) diets. Indeed, we previously demonstrated that wheel-running rats robustly reduced HF diet intake and preference. The reduced HF diet preference by wheel running can be so profound that the rats consumed only the chow diet and completely avoided the HF diet. Because previous research indicates that exercise activates the hypothalamic-pituitary-adrenal axis and increases circulating levels of corticosterone, this study tested the hypothesis that elevation of circulating corticosterone is involved in wheel running-induced reduction in HF diet preference in rats.Experiment 1 measured plasma corticosterone levels under sedentary and wheel-running conditions in the two-diet-choice (high-carbohydrate chow vs. HF) feeding regimen. The results revealed that plasma corticosterone is significantly increased and positively correlated with the levels of running in wheel-running rats with two-diet choice.Experiments 2 and 3 determined whether elevated corticosterone without wheel running is sufficient to reduce HF diet intake and preference. Corticosterone was elevated by adding it to the drinking water. Compared with controls, corticosterone-drinking rats had reduced HF diet intake and body weight, but the HF diet preference between groups did not differ. The results of this study support a role for elevated corticosterone on the reduced HF diet intake during wheel running. The elevation of corticosterone alone, however, is not sufficient to produce a robust reduction in HF diet preference. Copyright © 2016 the American Physiological Society.

Soluble Fermentable Dietary Fibre (Pectin) Decreases Caloric Intake, Adiposity and Lipidaemia in High-Fat Diet-Induced Obese Rats

PubMed Central

Adam, Clare L.; Thomson, Lynn M.; Williams, Patricia A.; Ross, Alexander W.

2015-01-01

Consumption of a high fat diet promotes obesity and poor metabolic health, both of which may be improved by decreasing caloric intake. Satiety-inducing ingredients such as dietary fibre may be beneficial and this study investigates in diet-induced obese (DIO) rats the effects of high or low fat diet with or without soluble fermentable fibre (pectin). In two independently replicated experiments, young adult male DIO rats that had been reared on high fat diet (HF; 45% energy from fat) were given HF, low fat diet (LF; 10% energy from fat), HF with 10% w/w pectin (HF+P), or LF with 10% w/w pectin (LF+P) ad libitum for 4 weeks (n = 8/group/experiment). Food intake, body weight, body composition (by magnetic resonance imaging), plasma hormones, and plasma and liver lipid concentrations were measured. Caloric intake and body weight gain were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Body fat mass increased in HF, was maintained in LF, but decreased significantly in LF+P and HF+P groups. Final plasma leptin, insulin, total cholesterol and triglycerides were lower, and plasma satiety hormone PYY concentrations were higher, in LF+P and HF+P than in LF and HF groups, respectively. Total fat and triglyceride concentrations in liver were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Therefore, the inclusion of soluble fibre in a high fat (or low fat) diet promoted increased satiety and decreased caloric intake, weight gain, adiposity, lipidaemia, leptinaemia and insulinaemia. These data support the potential of fermentable dietary fibre for weight loss and improving metabolic health in obesity. PMID:26447990

Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

NASA Technical Reports Server (NTRS)

Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

2011-01-01

Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

Relationships Between Base-Catalyzed Hydrolysis Rates or Glutathione Reactivity for Acrylates and Methacrylates and Their NMR Spectra or Heat of Formation

PubMed Central

Fujisawa, Seiichiro; Kadoma, Yoshinori

2012-01-01

The NMR chemical shift, i.e., the π-electron density of the double bond, of acrylates and methacrylates is related to the reactivity of their monomers. We investigated quantitative structure-property relationships (QSPRs) between the base-catalyzed hydrolysis rate constants (k1) or the rate constant with glutathione (GSH) (log kGSH) for acrylates and methacrylates and the 13C NMR chemical shifts of their α,β-unsaturated carbonyl groups (δCα and δCβ) or heat of formation (Hf) calculated by the semi-empirical MO method. Reported data for the independent variables were employed. A significant linear relationship between k1 and δCβ, but not δCα, was obtained for methacrylates (r2 = 0.93), but not for acrylates. Also, a significant relationship between k1 and Hf was obtained for both acrylates and methacrylates (r2 = 0.89). By contrast, log kGSH for acrylates and methacrylates was linearly related to their δCβ (r2 = 0.99), but not to Hf. These findings indicate that the 13C NMR chemical shifts and calculated Hf values for acrylates and methacrylates could be valuable for estimating the hydrolysis rate constants and GSH reactivity of these compounds. Also, these data for monomers may be an important tool for examining mechanisms of reactivity. PMID:22754331

Shape memory behavior of single crystal and polycrystalline Ni-rich NiTiHf high temperature shape memory alloys

NASA Astrophysics Data System (ADS)

Saghaian, Sayed M.

NiTiHf shape memory alloys have been receiving considerable attention for high temperature and high strength applications since they could have transformation temperatures above 100 °C, shape memory effect under high stress (above 500 MPa) and superelasticity at high temperatures. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf alloys have some drawbacks such as low ductility and high work hardening in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti 29.3Hf20, Ni51.2Ti28.8Hf20, and Ni52Ti28Hf20 (at. %)) were systematically characterized in the furnace cooled condition. H-phase precipitates were formed during furnace cooling in compositions with greater than 50.3Ni and the driving force for nucleation increased with Ni content. Alloy strength increased while recoverable strain decreased with increasing Ni content due to changes in precipitate characteristics. The effects of the heat treatments on the transformation characteristics and microstructure of the Ni-rich NiTiHf shape memory alloys have been investigated. Transformation temperatures are found to be highly annealing temperature dependent. Generation of nanosize precipitates (˜20 nm in size) after three hours aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability under high stress levels (> 1500 MPa) with a work output of 20-30 J cm- 3. Superelastic behavior with 4% recoverable strain was demonstrated at low and high temperatures where stress could reach to a maximum value of more than 2 GPa after three hours aging at 450 and 550 °C for alloys with Ni great than 50.3 at. %. Shape memory properties of polycrystalline Ni50.3Ti29.7 Hf20 alloys were studied via thermal cycling under stress and isothermal stress cycling experiments in tension. Recoverable strain of ˜5% was observed for the as-extruded samples while it was decreased to ˜4% after aging due to the formation of precipitates. The aged alloys demonstrated near perfect shape memory effect under high tensile stress level of 700 MPa and perfect superelasticity at high temperatures up to 230 °C. Finally, the tension-compression asymmetry observed in NiTiHf where recoverable tensile strain was higher than compressive strain. The shape memory properties of solutionized and aged Ni-rich Ni50.3Ti29.7Hf20 single crystals were investigated along the [001], [011], and [111] orientations in compression. [001]-oriented single crystals showed high dimensional stability under stress levels as high as 1500 MPa in both the solutionized and aged conditions, but with transformation strains of less than 2%. Perfect superelasticity with recoverable strain of more than 4% was observed for solutionized and 550 °C-3h aged single crystals along the [011] and [111] orientations, and general superelastic behavior was observed over a wide temperature range. The calculated transformation strains were higher than the experimentally observed strains since the calculated strains could not capture the formation of martensite plates with (001) compound twins. KEYWORDS: NiTiHf, High Temperature Shape memory alloys, Mechanical Characterization, High Strength Shape Memory Alloy, Orientation Dependence of NiTiHf Sayed.

Authentication of meat products: determination of animal feeding by parallel GC-MS analysis of three adipose tissues.

PubMed

Sivadier, Guilhem; Ratel, Jérémy; Bouvier, Frédéric; Engel, Erwan

2008-11-12

Authentication of farm animal rearing conditions, especially the type of feeding, is a key issue in certification of meat quality and meat products. The purpose of this article was to analyze in parallel the volatile fraction of three adipose tissues excised from 16 lambs in order to authenticate two animal diets: pasture (n = 8) and concentrate (n = 8). On the basis of growth rate and anatomical location, three different lamb adipose tissues were analyzed: perirenal fat (PRF), caudal subcutaneous fat (CSCF), and heart fat (HF). An initial experiment was used to optimize the extraction of volatile compounds from the adipose tissues. Using a lipid liquid phase extraction, heating the ground tissue to 70 degrees C, was shown to be the best sample preparation mode before dynamic headspace-gas chromatography-mass spectrometry (DH-GC-MS) analysis to achieve a good representation of the starting material, while getting a good extraction and reproducibility. Next, the application of an instrumental drifts correction procedure to DH-GC-MS data enabled the identification of 130 volatile compounds that discriminate the two diets in one or several of the three tissues: 104 were found in PRF, 75 in CSCF, and 70 in HF. Forty-eight of these diet tracers, including 2,3-octanedione, toluene, terpenes, alkanes, alkenes, and ketones, had previously been identified as ruminant pasture-diet tracers and can be considered generic of this type of animal feeding. Moreover, 49 of the 130 compounds could identify diets in only one tissue, suggesting that complementary analysis of several tissues is superior for diet identification. Finally, multivariate discriminant analyses confirmed that the discrimination was improved when PRF, CSCF, and HF were considered simultaneously, even if HF contributed minimal information.

Hippocampal lesions do not disrupt navigational map retention in homing pigeons under conditions when map acquisition is hippocampal dependent.

PubMed

Gagliardo, Anna; Ioalè, Paolo; Odetti, Francesca; Kahn, Meghan C; Bingman, Verner P

2004-08-12

In contrast to map-like navigation by familiar landmarks, understanding the relationship between the avian hippocampal formation (HF) and the homing pigeon navigational map has remained a challenge. With the goal of filling an empirical gap, we performed an experiment in which young homing pigeons learned a navigational map while being held in an outdoor aviary, and then half the birds were subjected to HF ablation. The question was whether HF lesion would impair retention of a navigational map learned under conditions known to require participation of HF. The pigeons, which had never flown from the aviary before, together with an additional control group that learned a navigational map with free-flight experience, were then released from two distant release sites. Contrary to expectation, the HF-lesioned birds oriented in a homeward direction in manner indistinguishable from the intact control pigeons raised in the same outdoor aviary. HF lesion did not result in a navigational map retention deficit. Together with previous results, it is now clear that regardless of the learning environment present during acquisition, HF plays no necessary role in the subsequent retention or operation of the homing pigeon navigational map.

LVAD patients' and surrogates' perspectives on SPIRIT-HF: An advance care planning discussion.

PubMed

Metzger, Maureen; Song, Mi-Kyung; Devane-Johnson, Stephanie

2016-01-01

To describe LVAD patients' and surrogates' experiences with, and perspectives on SPIRIT-HF, an advance care planning (ACP) intervention. ACP is important for patients with LVAD, yet little is known about their experiences or those of their surrogates who have participated in ACP discussions. We used qualitative content analysis techniques to conduct a secondary analysis of 28 interviews with patients with LVAD (n = 14) and their surrogates (n = 14) who had participated in an RCT pilot study of SPIRIT-HF. Main themes from the data include: 1) sharing their HF stories was very beneficial; 2) participating in SPIRIT-HF led to greater peace of mind for patients and surrogates; 3) "one size does not fit all" when it comes to timing of ACP discussions. An understanding patient and surrogate perspectives may inform clinicians' approach to ACP discussions. Copyright © 2016 Elsevier Inc. All rights reserved.

Wheel running reduces high-fat diet intake, preference and mu-opioid agonist stimulated intake

PubMed Central

Liang, Nu-Chu; Bello, Nicholas T.; Moran, Timothy H.

2015-01-01

The ranges of mechanisms by which exercise affects energy balance remain unclear. One potential mechanism may be that exercise reduces intake and preference for highly palatable, energy dense fatty foods. The current study used a rodent wheel running model to determine whether and how physical activity affects HF diet intake/preference and reward signaling. Experiment 1 examined whether wheel running affected the ability of intracerebroventricular (ICV) µ opioid receptor agonist D-Ala2, NMe-Phe4, Glyol5-enkephalin (DAMGO) to increase HF diet intake. Experiment 2 examined the effects of wheel running on the intake of and preference for a previously preferred HF diet. We also assessed the effects of wheel running and diet choice on mesolimbic dopaminergic and opioidergic gene expression. Experiment 1 revealed that wheel running decreased the ability of ICV DAMGO administration to stimulate HF diet intake. Experiment 2 showed that wheel running suppressed weight gain and reduced intake and preference for a previously preferred HF diet. Furthermore, the mesolimbic gene expression profile of wheel running rats was different from that of their sedentary paired-fed controls but similar to that of sedentary rats with large HF diet consumption. These data suggest that alterations in preference for palatable, energy dense foods play a role in the effects of exercise on energy homeostasis. The gene expression results also suggest that the hedonic effects of exercise may substitute for food reward to limit food intake and suppress weight gain. PMID:25668514

Post-peak metamorphic evolution of the Sumdo eclogite from the Lhasa terrane of southeast Tibet

NASA Astrophysics Data System (ADS)

Cao, Dadi; Cheng, Hao; Zhang, Lingmin; Wang, Ke

2017-08-01

A reconstruction of the pressure-temperature-time (P-T-t) path of high-pressure eclogite-facies rocks in subduction zones may reveal important information about the tectono-metamorphic processes that occur at great depths along the plate interface. The majority of studies have focused on prograde to peak metamorphism of these rocks, whereas after-peak metamorphism has received less attention. Herein, we present a detailed petrological, pseudosection modeling and radiometric dating study of a retrograded eclogite sample from the Sumdo ultrahigh pressure belt of the Lhasa terrane, Tibet. Mineral chemical variations, textural discontinuities and thermodynamic modeling suggest that the eclogite underwent an exhumation-heating period. Petrographic observations and phase equilibria modeling suggest that the garnet cores formed at the pressure peak (∼2.5 GPa and ∼520 °C) within the lawsonite eclogite-facies and garnet rims (∼1.5 GPa and <650 °C) grew during post-peak amphibole eclogite-facies metamorphism. The metamorphic evolution of the Sumdo eclogite is characterized by a clockwise P-T path with a heating stage during early exhumation, a finding that conflicts with previously reported heating-compression P-T paths for the Sumdo eclogite. A garnet-whole rock Lu-Hf age of 266.6 ± 0.7 Ma, which is consistent with the loosely constrained zircon U-Pb age of 261 ± 15 Ma within uncertainty, was obtained for the sample. The peak metamorphic temperature of the sample is lower than the Lu-Hf closure temperature of garnet, which combined with the general core-to-rim decrease in the Mn and Lu concentrations and the occurrence of a second maximum Lu peak in the inner rim, is consistent with the Lu-Hf system skewing to the age of the garnet inner rim. Thus the Lu-Hf age likely reflects late eclogite-facies metamorphism. The new U-Pb and Lu-Hf ages, together with previously published radiometric dating results, suggest that the overall growth of garnet spans an interval of ∼7 million years, which is a minimum estimate of the duration of the eclogite-facies metamorphism of the Sumdo eclogite.

Attenuation of Scintillation of Discrete Cosmic Sources during Nonresonant HF Heating of the Upper Ionosphere

NASA Astrophysics Data System (ADS)

Bezrodny, V. G.; Watkins, B.; Charkina, O. V.; Yampolski, Y. M.

2014-03-01

The aim of the work is to experimentally investigate the response of scintillation spectra and indices of discrete cosmic sources (DCS) to modification of the ionospheric F-region by powerful electromagnetic fields with frequencies exceeding the Langmuir and upper hybrid ones. The results of a special experiment on the scintillations of radiation from DCS Cygnus A observed with using the 64-beam imaging riometer located near the Gakona village (Alaska, USA) are here presented. The ionosphere was artificially disturbed by powerful HAARP heater. Under the studied conditions of nonresonant heating of the ionospheric plasma, an earlier unknown effect of reducing the level of DCS scintillation was discovered. The theoretical interpretation has been given for the discovered effect, which using allowed the proposed technique of solving the inverse problem (recovery deviations of average electron density and temperature in the modified region from their unperturbed values).

Effects of acetylate hyperforin on the processing of amyloid precursor protein.

PubMed

Chen, Xiang; Feng, Wenshang; Chen, Qing; Yang, Xiangling; Yang, Depo; Wang, Dongmei; Zhong, Ling

2009-02-20

Hyperforin (HF) is a phloroglucinol compound obtained from St. John's Wort (Hypericum perforatum). Recent studies have shown that Hyperforin can be used to improve psychopathologic symptoms of Alzheimer's disease but the mechanism is not clear. This may be partly due to the difficult in studying Hyperforin, since this chemical is unstable and is sensitive to light, oxygen, and heat. In this study, we explored the effects of acetylate hyperforin (ace-HF), a stable derivative of hyperforin, on the processing of amyloid precursor protein (APP). HEK293 cells transfected with pcDNA3.1APP695sw and SH-SY5Y cells were treated with ace-HF, followed by measuring the levels of APP and sAPPα. Twelve hours of treatment led to an increase in extracellular sAPPα, but APP mRNA and protein levels were unchanged. Further studies with α-secretase and a pan PKC inhibitor, Calphostin C, indicated that ace-HF's effect on extracellular sAPPα was closely related to PKC activities and α-secretase activities. Our findings suggest that ace-HF can modulate α-secretase-mediated APP processing via a PKC signaling pathway.

Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

2004-01-01

HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

Lunar Radar Cross Section at Low Frequency

NASA Technical Reports Server (NTRS)

Rodriguez, P.; Kennedy, E. J.; Kossey, P.; McCarrick, M.; Kaiser, M. L.; Bougeret, J.-L.; Tokarev, Y. V.

2002-01-01

Recent bistatic measurements of the lunar radar cross-section have extended the spectrum to long radio wavelength. We have utilized the HF Active Auroral Research Program (HAARP) radar facility near Gakona, Alaska to transmit high power pulses at 8.075 MHz to the Moon; the echo pulses were received onboard the NASA/WIND spacecraft by the WAVES HF receiver. This lunar radar experiment follows our previous use of earth-based HF radar with satellites to conduct space experiments. The spacecraft was approaching the Moon for a scheduled orbit perturbation when our experiment of 13 September 2001 was conducted. During the two-hour experiment, the radial distance of the satellite from the Moon varied from 28 to 24 Rm, where Rm is in lunar radii.

Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation.

PubMed

Herynek, Vít; Turnovcová, Karolína; Veverka, Pavel; Dědourková, Tereza; Žvátora, Pavel; Jendelová, Pavla; Gálisová, Andrea; Kosinová, Lucie; Jiráková, Klára; Syková, Eva

2016-01-01

Magnetic nanoparticles (NPs) represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency (HF) magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (T c) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Perovskite NPs (T c =66°C-74°C) were characterized and tested both in vitro and in vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated. In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase substantially in comparison with animals without particles during HF exposure. We proved that the deposited power from the NPs is too small and that thermoregulation of the animal is sufficient to conduct the heat away. Histology did not detect substantially higher apoptosis in NP-treated animals after ablation. Magnetic particles with low T c can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only. However, their effect in the case of extracellular deposition in vivo is questionable due to low deposited power and active thermoregulation of the tissue.

A STUDY OF THE STABILITY OF ZIRCONIUM AND HAFNIUM TETRAHALIDES ON HITTING A HOT SURFACE IN VACUUM (in Russian)

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

Tsirel'nikov, V.I.; Komissarova, L.N.; Spitsyn, V.I.

1962-09-01

The decomposition coefficients of the chlorides, bromides, and iodides of Zr and Hf were determined as a function of the temperature of a hot surface. The tetrahalides were carefully purified in an inert atmosphere of argon. The halide compound in a quartz ampoule was heated by a removable heater. The vapors passed through a capillary opening and struck a tungsten foil 0.5 mm thick and 12 to 15 mm wide. The Mo foil was heated electrically to control the surface temperature which was measured by an optical pyrometer. The tetrahalide decomposed according to the following reaction: Me(Hal)/sub 4/ yields Memore » + 2(Hal)/sub 2/. The lower halides dissociated completely to metal and free halides, since the temperature was >600 deg C. The Mo backing was dissolved in nitric acid, and the unsupported metal deposit of Zr or Hf was weighed, The decomposition coefficient was calcuweight of metal evaporated. Zrl/sub 4/ decomposed completely (100%) at 1500 deg C, while only 96% of the HfI/sub 4/ was decomposed at this temperature. The ZrBr/sub 4/ and HfBr/sub 4/ were decomposed by 68 and 61% respectively. The ZrCl/sub 4/ and HfCl/sub 4/ were stable at l500 deg C (5% of the ZrCl/sub 4/ was decomposed at l500 deg C). In all cases, the hafnium halide was more stable than the zirconium halide, especially in the case of the iodides. The decomposition was directly proportional to the temperature of the molybdenum target. (TTT)« less

High Fragmentation Steel Production Process

DTIC Science & Technology

1981-08-01

Hsv j , —U -I* : -’ 1 . ’ ; - * - 1 "^Sv i ! :.:.; 1 HEBUCTIOK AHU.,, .../y?.;-’" • jttoireAnoi..|..r!.5^«. ::^;;;i:^l^~!’in...on rmrerae aide 11 neceaaary and Identity by block number) HF- 1 Steel Metallurgical Evaluation MMT-Process improvement 20. ABSTRACT ("ContfBu...ao reraram attba tt n*c*aaMey and. IderUlty by block numbat) Two heats of B0F HF- 1 steel were purchased, one from Republic Steel and one from

Collision-Induced Dissociation Study of Strong Hydrogen-Bonded Cluster Ions Y-(HF) n (Y=F, O2) Using Atmospheric Pressure Corona Discharge Ionization Mass Spectrometry Combined with a HF Generator.

PubMed

Sakamoto, Kenya; Sekimoto, Kanako; Takayama, Mitsuo

2017-01-01

Hydrogen fluoride (HF) was produced by a homemade HF generator in order to investigate the properties of strong hydrogen-bonded clusters such as (HF) n . The HF molecules were ionized in the form of complex ions associated with the negative core ions Y - produced by atmospheric pressure corona discharge ionization (APCDI). The use of APCDI in combination with the homemade HF generator led to the formation of negative-ion HF clusters Y - (HF) n (Y=F, O 2 ), where larger clusters with n ≥4 were not detected. The mechanisms for the formation of the HF, F - (HF) n , and O 2 - (HF) n species were discussed from the standpoints of the HF generator and APCDI MS. By performing energy-resolved collision-induced dissociation (CID) experiments on the cluster ions F - (HF) n ( n =1-3), the energies for the loss of HF from F - (HF) 3 , F - (HF) 2 , and F - (HF) were evaluated to be 1 eV or lower, 1 eV or higher, and 2 eV, respectively, on the basis of their center-of-mass energy ( E CM ). These E CM values were consistent with the values of 0.995, 1.308, and 2.048 eV, respectively, obtained by ab initio calculations. The stability of [O 2 (HF) n ] - ( n =1-4) was discussed on the basis of the bond lengths of O 2 H-F - (HF) n and O 2 - H-F(HF) n obtained by ab initio calculations. The calculations indicated that [O 2 (HF) 4 ] - separated into O 2 H and F - (HF) 3 .

Should heart failure be regarded as a terminal illness requiring palliative care? A study of heart failure patients', carers' and clinicians' understanding of heart failure prognosis and its management.

PubMed

Stocker, Rachel; Close, Helen; Hancock, Helen; Hungin, A Pali S

2017-12-01

Communication and planning for heart failure (HF) care near the end of life is known to be complex. Little is known about how the patient experience of palliative assessment and communication needs change over time, and how this might inform management. Our aim was to explore experiences of giving or receiving a prognosis and advanced palliative care planning (ACP) for those with HF. We carried out a longitudinal grounded theory study, employing in-depth interviews with 14 clinicians (primary and secondary care) and observations of clinic and home appointments, followed by a series of interviews with 13 patients with HF and 9 carers. Overall, the majority of participants rejected notions of HF as a terminal illness in favour of a focus on day-to-day management and maintenance, despite obvious deterioration in disease stage and needs over time. Clinicians revealed frustration about the uncertain nature of HF prognosis, leading to difficulties in planning. Others highlighted the need to deliver problem-based, individualised care but felt constrained sometimes by the lack of multidisciplinary ACP. Patients reported an absence of prognostic discussions with clinicians. This is the first study exploring the experiences of prognostic communication at all stages of HF. Findings raise questions regarding the pragmatic utility of the concept of HF as a terminal illness and have implications for future HF care pathway development. Findings support the incorporation of a problem-based approach to management, which recognises the importance of everyday functioning for patients and carers as well as the opportunity for ACP. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

NASA Astrophysics Data System (ADS)

Yushi, Zou; Xinfang, Ma; Tong, Zhou; Ning, Li; Ming, Chen; Sihai, Li; Yinuo, Zhang; Han, Li

2017-09-01

Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

Proposed truncated Cu-Hf tight-binding potential to study the crystal-to-amorphous phase transition

NASA Astrophysics Data System (ADS)

Cui, Yuanyuan; Li, Jiahao; Dai, Ye; Liu, Baixin

2010-09-01

Proposed truncated Cu-Hf tight-binding potential was constructed by fitting the physical properties of Cu, Hf, and their stable compounds, i.e., Cu5Hf, Cu8Hf3, Cu10Hf7, and CuHf2. Based on the constructed potentials, molecular dynamics simulations were carried out to compare the relative stability of the crystalline solid solution and the disordered state. Simulation results not only reveal that the physical origin of crystal-to-amorphous transition is the crystalline lattice collapsing when the solute atoms exceeding the critical concentration, but also predict that the glass forming range (GFR) of the Cu-Hf system is 21-77 at. % Cu, which covers the GFRs determined by various metallic glass-producing techniques. Ion beam mixing experiments of the Cu-Hf system were conducted using 200 keV xenon ions and the results show that a uniform amorphous phase can be obtained in the Cu23Hf77 sample, matching well with the GFR determined by the interatomic potential, which, in turn, provides additional evidence to the relevance of the constructed Cu-Hf potential.

Collision-Induced Dissociation Study of Strong Hydrogen-Bonded Cluster Ions Y−(HF)n (Y=F, O2) Using Atmospheric Pressure Corona Discharge Ionization Mass Spectrometry Combined with a HF Generator

PubMed Central

Sakamoto, Kenya; Sekimoto, Kanako; Takayama, Mitsuo

2017-01-01

Hydrogen fluoride (HF) was produced by a homemade HF generator in order to investigate the properties of strong hydrogen-bonded clusters such as (HF)n. The HF molecules were ionized in the form of complex ions associated with the negative core ions Y− produced by atmospheric pressure corona discharge ionization (APCDI). The use of APCDI in combination with the homemade HF generator led to the formation of negative-ion HF clusters Y−(HF)n (Y=F, O2), where larger clusters with n≥4 were not detected. The mechanisms for the formation of the HF, F−(HF)n, and O2−(HF)n species were discussed from the standpoints of the HF generator and APCDI MS. By performing energy-resolved collision-induced dissociation (CID) experiments on the cluster ions F−(HF)n (n=1–3), the energies for the loss of HF from F−(HF)3, F−(HF)2, and F−(HF) were evaluated to be 1 eV or lower, 1 eV or higher, and 2 eV, respectively, on the basis of their center-of-mass energy (ECM). These ECM values were consistent with the values of 0.995, 1.308, and 2.048 eV, respectively, obtained by ab initio calculations. The stability of [O2(HF)n]− (n=1–4) was discussed on the basis of the bond lengths of O2H–F−(HF)n and O2−H–F(HF)n obtained by ab initio calculations. The calculations indicated that [O2(HF)4]− separated into O2H and F−(HF)3. PMID:28966900

Appropriate evaluation and treatment of heart failure patients after implantable cardioverter-defibrillator discharge: time to go beyond the initial shock.

PubMed

Mishkin, Joseph D; Saxonhouse, Sherry J; Woo, Gregory W; Burkart, Thomas A; Miles, William M; Conti, Jamie B; Schofield, Richard S; Sears, Samuel F; Aranda, Juan M

2009-11-24

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.

Magnetic zenith effect in the ionospheric modification by an X-mode HF heater wave

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Haggstrom, I.; Rietveld, M. T.; Yeoman, T. K.

2013-12-01

We report experimental results aimed at an investigation of the magnetic zenith effect in the high latitude ionosphere F region from ionospheric modification by powerful HF heater wave with X-polarization. The ionospheric modification was produced by the HF heating facility at Tromsø (Norway) using the phased array with a narrow beam with of 6 degrees. Effective radiated power was varied between 450 and 1000 MW. The HF pump wave radiated in different directions relative to the magnetic field from 90 degrees (vertical) to 78 degrees (magnetic zenith) at frequencies near or above the ordinary-mode critical frequency. The response of the ionosphere plasma to the HF pump wave impact was checked by the UHF incoherent scatter radar located in the immediate vicinity of the HF heater. UHF radar was probing the plasma parameters, such as electron density and temperature (Ne and Te), HF-induced plasma and ion lines in the altitude range from 90 to 600 km. It was running in a scanning mode when UHF radar look angles were changed from 74 to 90 degrees by 1 or 2 degree step. It was clearly demonstrated that the strongest heater-induced effects took place in the magnetic field-aligned direction when HF pointing was also to the magnetic zenith. It was found that strong Ne enhancement of up to 80 % along magnetic field (artificial density ducts) were excited only under HF pumping towards magnetic zenith. The width of the artificial ducts comes to only 2 degrees. The Ne increases were accompanied by the Te enhancements of up to about 50 %. Less pronounced Te increases were also observed in the directions of 84 and 90 degrees. Strong Ne enhancements can be accompanied by excitation of strong HF-induced plasma and ion lines. Thus experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization.

The lived experience of caregivers of persons with heart failure: A phenomenological study.

PubMed

Petruzzo, Antonio; Paturzo, Marco; Naletto, Monica; Cohen, Marlene Z; Alvaro, Rosaria; Vellone, Ercole

2017-10-01

Heart failure (HF) patients need to follow a strict pharmacological and nonpharmacological regimen in order to counteract the burden of the disease, and informal caregivers are an important resource for HF patients in managing and coping with their disease. Few studies have examined the lived experience of these caregivers with a rigorous phenomenological approach, and none have been conducted in Italy. To describe the lived experience of the caregivers of HF patients. A hermeneutic phenomenological method was used. Caregivers were enrolled in a HF clinic in central Italy. Interviews were analysed using a phenomenological approach. Credibility, dependability, confirmability and transferability were adopted in order to strengthen trustworthiness. Thirty HF caregivers (mean age: 53 years) were enrolled. Of these, 63% of the caregivers were female and 80% were patients' spouses or children. Six themes emerged: (1) fear and worry related to the illness; (2) life changes and restrictions; (3) burden due to caregiving; (4) uncertainty about illness management; (5) helping patients to cope with the illness; and (6) love and affection towards the patient. The findings of our study may help providers to guide interventions for HF caregivers. Providers should be supportive of caregivers and provide them with education in order to reduce their fears and worries about the illness and to handle the course of HF and its symptoms. An empathetic and practical approach with caregivers that considers the patient-caregiver relationship may help caregivers to cope with the changes and restrictions that caregiving brings to their lives and to reduce their burden.

The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures

PubMed Central

Eraslan, Oguz

2016-01-01

PURPOSE To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics. MATERIALS AND METHODS 288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm2). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin–ceramic interface. RESULTS SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (P<.001). FIN ceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF. CONCLUSION The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments. PMID:27141250

The Vibrational Deactivation of HF(v = 3) and HF(v = 2) by H Atoms

DTIC Science & Technology

1977-08-18

experiments. A silicon flat in front of the photomultiplier restricted the monitored fluores- cence to wavelengths > I 4tm. An RCA C-31034 (GaAs... stent with the present results f’ir HF(v =1) and HI-F(v = 2’ remioval rates but can not explain the fast HF(v = 3) rate. Wilk-ins performed trajectory...Sciences Laboratory: Development of new materials; metal matrix composites and new forms of carbon; test and evaluation of graphite and ceramics in

Exploring patient experiences and perspectives of a heart failure telerehabilitation program: A mixed methods approach.

PubMed

Hwang, Rita; Mandrusiak, Allison; Morris, Norman R; Peters, Robyn; Korczyk, Dariusz; Bruning, Jared; Russell, Trevor

To describe patient experiences and perspectives of a group-based heart failure (HF) telerehabilitation program delivered to the homes via online video-conferencing. Limited information currently exists on patient experiences of telerehabilitation for HF. Patient feedback and end-user perspectives provide important information regarding the acceptability of this new delivery model which may have a substantial impact on future uptake. We used mixed-methods design with purposive sampling of patients with HF. We used self-report surveys and semi-structured interviews to measure patient experiences and perspectives following a 12-week telerehabilitation program. The telerehabilitation program encompassed group-based exercise and education, and were delivered in real-time via videoconferencing. Interviews were transcribed and coded, with thematic analysis undertaken. Seventeen participants with HF (mean age [SD] of 69 [12] years and 88% males) were recruited. Participants reported high visual clarity and ease of use for the monitoring equipment. Major themes included motivating and inhibiting influences related to telerehabilitation and improvement suggestions. Participants liked the health benefits, access to care and social support. Participants highlighted a need for improved audio clarity and connectivity as well computer training for those with limited computer experience. The majority of participants preferred a combined face-to-face and online delivery model. Participants in this study reported high visual clarity and ease-of-use, but provided suggestions for further improvements in group-based video telerehabilitation for HF. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.

The Effects of Aerodynamic Heating and Heat Transfer on the Surface Temperature of a Body of Revolution in Steady Supersonic Flight

DTIC Science & Technology

1947-07-01

HF..-I.T THA.:\\SFER 0.:\\ THE SnlfACE TDJPER.Hl’RE Of ... BODY OF RE’·OLt·TIO.:\\ 471 o~~---~~~--~~~~~--~~~~--~ 1.2 1.6 2.0 2,4 2.8 3.2 Moch number

ELF/VLF wave disturbances detected by the DEMETER satellite over the HAARP transmitter

NASA Astrophysics Data System (ADS)

Titova, Elena; Demekhov, Andrei; Parrot, Michel; Mogilevsky, Mikhail; Mochalov, Alexey; Pashin, Anatoly

We report observations of electromagnetic the ELF/VLF wave disturbances by the DEMETER satellite (670 km altitude) overflying the HAARP heating facility (62.39(°) N, 145.15(°) W, L = 4.9). The HAARP HF transmitter operated at the maximum available power of 3.6 MW, O-mode polarization, and the beam directed towards the magnetic zenith. ELF/VLF waves caused by the HAARP heating are detected by the DEMETER satellite when the HF radio wave frequency was close to the critical frequency (foF2) of the ionospheric F2 layer but below it. ELF/VLF wave disturbances observed above the HAARP transmitter were detected by electrical antennas in an area with characteristic size 10 (2) km. We analyze amplitude and polarization spectra of the ELF disturbances and compare them with the characteristics of natural ELF hiss above HAARP. The VLF wave disturbances in the topside ionosphere above the HAARP transmitter were detected in the frequency ranges 8-17 kHz and 15-18 kHz which are close to the lower hybrid resonance frequency f _LHR in the heating region and its second harmonic (2f _LHR), respectively. In the case where the HAARP HF power was modulated, the detected VLF waves were also modulated with the same frequency whereas in the ELF frequency range the modulation period of the HAARP power was not observed. Possible mechanisms of generation of the ELF/VLF disturbances produced by the HAARP transmitter in the topside ionosphere are discussed.

Experimental study on the mechanism of hydraulic fracture growth in a glutenite reservoir

NASA Astrophysics Data System (ADS)

Ma, Xinfang; Zou, Yushi; Li, Ning; Chen, Ming; Zhang, Yinuo; Liu, Zizhong

2017-04-01

Glutenite reservoirs are frequently significantly heterogeneous because of their unique depositional environment. The presence of gravel in this type of formation complicates the growth path of hydraulic fracture (HF). In this study, laboratory fracturing experiments were conducted on six large natural glutenite specimens (300 mm × 300 mm × 300 mm) using a true triaxial hydraulic fracturing system to investigate the growth law of HF in glutenite reservoirs. Before the experiments were performed, the rock properties of the gravel particles and matrix in the glutenite specimens were determined using various apparatuses. The effects of gravel size, horizontal differential stress, fracturing fluid type (or viscosity), and flow rate on the HF growth pattern, fracture width, and injection pressure were examined in detail. Similar to previous studies, four types of HF intersections with gravel particles, namely, termination, penetration, deflection, and attraction, were observed. The HF growth path in the glutenite specimens with large gravel (40 mm-100 mm) is likely branched and tortuous even under high horizontal differential stress. The HF growth path in the glutenite specimens with small gravel (less than 20 mm) is simple, but a process zone with multiple thin fractures may be created. Breakdown pressure may increase significantly when HF initiates from high-strength gravel particles, which are mainly composed of quartz. HF propagation is likely limited within high-strength gravel particles, thereby resulting in narrow fractures and even termination. The use of low-viscosity fluids, such as slickwater, and the low injection rate can further limit HF growth, particularly its width. As a response, high extension pressure builds up during fracturing.

HF propagation results from the Metal Oxide Space Cloud (MOSC) experiment

NASA Astrophysics Data System (ADS)

Joshi, Dev; Groves, Keith M.; McNeil, William; Carrano, Charles; Caton, Ronald G.; Parris, Richard T.; Pederson, Todd R.; Cannon, Paul S.; Angling, Matthew; Jackson-Booth, Natasha

2017-06-01

With support from the NASA sounding rocket program, the Air Force Research Laboratory launched two sounding rockets in the Kwajalein Atoll, Marshall Islands in May 2013 known as the Metal Oxide Space Cloud experiment. The rockets released samarium metal vapor at preselected altitudes in the lower F region that ionized forming a plasma cloud. Data from Advanced Research Project Agency Long-range Tracking and Identification Radar incoherent scatter radar and high-frequency (HF) radio links have been analyzed to understand the impacts of the artificial ionization on radio wave propagation. The HF radio wave ray-tracing toolbox PHaRLAP along with ionospheric models constrained by electron density profiles measured with the ALTAIR radar have been used to successfully model the effects of the cloud on HF propagation. Up to three new propagation paths were created by the artificial plasma injections. Observations and modeling confirm that the small amounts of ionized material injected in the lower F region resulted in significant changes to the natural HF propagation environment.

Palliative Care in Heart Failure: Rationale, Evidence, and Future Priorities.

PubMed

Kavalieratos, Dio; Gelfman, Laura P; Tycon, Laura E; Riegel, Barbara; Bekelman, David B; Ikejiani, Dara Z; Goldstein, Nathan; Kimmel, Stephen E; Bakitas, Marie A; Arnold, Robert M

2017-10-10

Patients with heart failure (HF) and their families experience stress and suffering from a variety of sources over the course of the HF experience. Palliative care is an interdisciplinary service and an overall approach to care that improves quality of life and alleviates suffering for those living with serious illness, regardless of prognosis. In this review, we synthesize the evidence from randomized clinical trials of palliative care interventions in HF. While the evidence base for palliative care in HF is promising, it is still in its infancy and requires additional high-quality, methodologically sound studies to clearly elucidate the role of palliative care for patients and families living with the burdens of HF. Yet, an increase in attention to primary palliative care (e.g., basic physical and emotional symptom management, advance care planning), provided by primary care and cardiology clinicians, may be a vehicle to address unmet palliative needs earlier and throughout the illness course. Published by Elsevier Inc.

Estimation of core body temperature from skin temperature, heat flux, and heart rate using a Kalman filter.

PubMed

Welles, Alexander P; Xu, Xiaojiang; Santee, William R; Looney, David P; Buller, Mark J; Potter, Adam W; Hoyt, Reed W

2018-05-18

Core body temperature (T C ) is a key physiological metric of thermal heat-strain yet it remains difficult to measure non-invasively in the field. This work used combinations of observations of skin temperature (T S ), heat flux (HF), and heart rate (HR) to accurately estimate T C using a Kalman Filter (KF). Data were collected from eight volunteers (age 22 ± 4 yr, height 1.75 ± 0.10 m, body mass 76.4 ± 10.7 kg, and body fat 23.4 ± 5.8%, mean ± standard deviation) while walking at two different metabolic rates (∼350 and ∼550 W) under three conditions (warm: 25 °C, 50% relative humidity (RH); hot-humid: 35 °C, 70% RH; and hot-dry: 40 °C, 20% RH). Skin temperature and HF data were collected from six locations: pectoralis, inner thigh, scapula, sternum, rib cage, and forehead. Kalman filter variables were learned via linear regression and covariance calculations between T C and T S , HF, and HR. Root mean square error (RMSE) and bias were calculated to identify the best performing models. The pectoralis (RMSE 0.18 ± 0.04 °C; bias -0.01 ± 0.09 °C), rib (RMSE 0.18 ± 0.09 °C; bias -0.03 ± 0.09 °C), and sternum (RMSE 0.20 ± 0.10 °C; bias -0.04 ± 0.13 °C) were found to have the lowest error values when using T S , HF, and HR but, using only two of these measures provided similar accuracy. Copyright © 2018. Published by Elsevier Ltd.

Zircon U-Pb geochronology, Sr-Nd-Hf isotopic composition and geological significance of the Late Triassic Baijiazhuang and Lvjing granitic plutons in West Qinling Orogen

NASA Astrophysics Data System (ADS)

Duan, Meng; Niu, Yaoling; Kong, Juanjuan; Sun, Pu; Hu, Yan; Zhang, Yu; Chen, Shuo; Li, Jiyong

2016-09-01

The Qinling Orogen was a consequence of continental collision of the South China Craton with the North China Craton in the Triassic and caused widespread granitoid magmatism. However, the petrogenesis of these granitoids remains controversial. In this paper, we choose the Baijiazhuang (BJZ) and Lvjing (LJ) plutons in the West Qinling Orogen for a combined study of the zircon U-Pb geochronology, whole-rock major and trace element compositions and Sr-Nd-Hf isotopic characteristics. We obtained zircon crystallization ages of 216 Ma and 212 Ma for the BJZ and the LJ plutons, respectively. The granitoid samples from both plutons have high K2O metaluminous to peraluminous compositions. They are enriched in large ion lithophile elements (LILEs), light rare earth elements (LREEs) and depleted in high field-strength elements (HFSEs) with significant negative Eu anomalies. The BJZ samples have initial Sr isotopic ratios of 0.7032 to 0.7078, εNd(t) of - 10.99 to - 8.54 and εHf (t) of - 10.22 to - 6.41. The LJ granitoids have initial Sr isotopic ratios of 0.7070 to 0.7080, εNd(t) of - 5.37 to - 4.58 and εHf(t) of - 3.64 to - 1.78. The enriched isotopic characteristics of the two plutons are consistent with their source being dominated by ancient continental crust. However, two BJZ samples show depleted Sr isotope compositions, which may infer possible involvement of mantle materials. Mantle-derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. That is, the two granitic plutons are magmatic responses to the closure of the Mianlue ocean basin and the continental collision between the Yangtze and South Qinling crustal terranes. (143Nd/144Nd)i = (143Nd/144Nd) - (147Sm/144Nd) × (eλt - 1), εNd(t) = [(143Nd/144Nd) / (143Nd/144Nd)CHUR(t) - 1] × 104, (143Nd/144Nd)CHUR(t) = 0.512638-0.1967 × (eλt - 1), TDM = 1/λ × ln{1 + [((143Nd/144Nd) - 0.51315) / ((147Sm/144Nd) - 0.21317)]}, λ Sm-Nd = 6.54 × 10- 12a- 1. (176Hf/177Hf)i = [(176Hf/177Hf) - (176Lu/177Hf) × (eλt - 1), εHf(t) = [(176Hf/177Hf) / (176Hf/177Hf)CHUR(t) - 1] × 104, TDM1 = 1/λ × ln[1 + ((176Hf/177Hf)Sample - (176Hf/177Hf)DM)/((176Lu/177Hf)Sample - (176Lu/177Hf)DM)], TDM2 = TDM1 - (TDM1 - t)((fCC - fSample) / (fCC - fDM)), fLu-Hf = (176Lu/177Hf)Sample / (176Lu/177Hf)CHUR-1, (176Lu/177Hf)CHUR = 0.0332, (176Hf/177Hf)CHUR, 0 = 0.282785, (176Lu/177Hf)DM = 0.0384, (176Hf/177Hf)DM = 0.28325, fCC, fSample, fDM are their own fLu-Hf, λ = 1.867 × 10- 11a- 1.

Multi-angle Spectra Evolution of Ionospheric Turbulence Excited by RF Interactions at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Rayyan, N.; Watkins, B. J.; Watanabe, N.; Golkowski, M.; Bristow, W. A.; Bernhardt, P. A.; Briczinski, S. J., Jr.

2014-12-01

The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. For a narrow range of HF pointing between Spitze and magnetic zenith, a reduced threshold for AFAI is observed. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts

Practical considerations on the introduction of sacubitril/valsartan in clinical practice: Current evidence and early experience.

PubMed

Farmakis, Dimitrios; Bistola, Vassiliki; Karavidas, Apostolos; Parissis, John

2016-11-15

The combination of neprilysin inhibitor sacubitril with the angiotensin II receptor 1 blocker valsartan is the first agent from the angiotensin receptor neprilysin inhibitors (ARNI) class authorized for clinical use in heart failure (HF) patients with reduced ejection fraction (HFrEF). Sacubitril/valsartan resulted in 20% reduction in the incidence rate of death or HF hospitalization compared to enalapril in symptomatic HFrEF patients in the seminal PARADIGM-HF trial. As a result, the recently updated European and American HF guidelines granted this agent a class IB indication for the treatment of ambulatory/chronic symptomatic HFrEF patients. However, translating the positive results of trials into true clinical benefit is often challenging. This is particularly true in the case of sacubitril/valsartan, as HF is a heterogeneous syndrome including many severely ill patients who are prone to decompensation, while this new agent comes to replace a cornerstone of current evidence-based HF therapy. In the present paper, we address a number of practical issues regarding the introduction of sacubitril/valsartan and propose an algorithm based on available evidence and early clinical experience. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Fundamental Thermal and Mechanical Properties of Boride Ceramics

DTIC Science & Technology

2014-02-28

Zr ,Y)B2 ( Zr ,Hf)B2 ( Zr ,Ti)B2 ZrB2 El ec tri ca l R es is tiv ity (µ Ω -c m ) Temperature (°C) Figure 17. Electrical resistivity as a function...family as Zr , namely Ti and Hf, had minimal effect on thermal conductivity, while others such as Nb , Ta, and W had an increasing impact based on their...diffusivity (α), heat capacity (Cp) from the NIST-JANAF tables, and bulk density (ρ) using Equation 6. (5) (6) Electrical resistivity

Effects of acetylate hyperforin on the processing of amyloid precursor protein

PubMed Central

Chen, Xiang; Feng, Wenshang; Chen, Qing; Yang, Xiangling; Yang, Depo; Wang, Dongmei; Zhong, Ling

2009-01-01

Hyperforin (HF) is a phloroglucinol compound obtained from St. John's Wort (Hypericum perforatum). Recent studies have shown that Hyperforin can be used to improve psychopathologic symptoms of Alzheimer's disease but the mechanism is not clear. This may be partly due to the difficult in studying Hyperforin, since this chemical is unstable and is sensitive to light, oxygen, and heat. In this study, we explored the effects of acetylate hyperforin (ace-HF), a stable derivative of hyperforin, on the processing of amyloid precursor protein (APP). HEK293 cells transfected with pcDNA3.1APP695sw and SH-SY5Y cells were treated with ace-HF, followed by measuring the levels of APP and sAPPα. Twelve hours of treatment led to an increase in extracellular sAPPα, but APP mRNA and protein levels were unchanged. Further studies with α-secretase and a pan PKC inhibitor, Calphostin C, indicated that ace-HF's effect on extracellular sAPPα was closely related to PKC activities and α-secretase activities. Our findings suggest that ace-HF can modulate α-secretase-mediated APP processing via a PKC signaling pathway. PMID:21383880

Human Factors Checklist: Think Human Factors - Focus on the People

NASA Technical Reports Server (NTRS)

Miller, Darcy; Stelges, Katrine; Barth, Timothy; Stambolian, Damon; Henderson, Gena; Dischinger, Charles; Kanki, Barbara; Kramer, Ian

2016-01-01

A quick-look Human Factors (HF) Checklist condenses industry and NASA Agency standards consisting of thousands of requirements into 14 main categories. With support from contractor HF and Safety Practitioners, NASA developed a means to share key HF messages with Design, Engineering, Safety, Project Management, and others. It is often difficult to complete timely assessments due to the large volume of HF information. The HF Checklist evolved over time into a simple way to consider the most important concepts. A wide audience can apply the checklist early in design or through planning phases, even before hardware or processes are finalized or implemented. The checklist is a good place to start to supplement formal HF evaluation. The HF Checklist was based on many Space Shuttle processing experiences and lessons learned. It is now being applied to ground processing of new space vehicles and adjusted for new facilities and systems.

Energy partitioning in polyatomic chemical reactions: Quantum state resolved studies of highly exothermic atom abstraction reactions from molecules in the gas phase and at the gas-liquid interface

NASA Astrophysics Data System (ADS)

Zolot, Alexander M.

This thesis recounts a series of experiments that interrogate the dynamics of elementary chemical reactions using quantum state resolved measurements of gas-phase products. The gas-phase reactions F + HCl → HF + Cl and F + H2O → HF + OH are studied using crossed supersonic jets under single collision conditions. Infrared (IR) laser absorption probes HF product with near shot-noise limited sensitivity and high resolution, capable of resolving rovibrational states and Doppler lineshapes. Both reactions yield inverted vibrational populations. For the HCl reaction, strongly bimodal rotational distributions are observed, suggesting microscopic branching of the reaction mechanism. Alternatively, such structure may result from a quantum-resonance mediated reaction similar to those found in the well-characterized F + HD system. For the H2O reaction, a small, but significant, branching into v = 2 is particularly remarkable because this manifold is accessible only via the additional center of mass collision energy in the crossed jets. Rotationally hyperthermal HF is also observed. Ab initio calculations of the transition state geometry suggest mechanisms for both rotational and vibrational excitation. Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic jet of F atoms with liquid squalane (C30H62), a low vapor pressure hydrocarbon compatible with the high vacuum environment. IR spectroscopy provides absolute HF( v,J) product densities and Doppler resolved velocity component distributions perpendicular to the surface normal. Compared to analogous gas-phase F + hydrocarbon reactions, the liquid surface is a more effective "heat sink," yet vibrationally excited populations reveal incomplete thermal accommodation with the surface. Non-Boltzmann J-state populations and hot Doppler lineshapes that broaden with HF excitation indicate two competing scattering mechanisms: (i) a direct reactive scattering channel, whereby newly formed molecules leave the surface without equilibrating, and (ii) a partially accommodated fraction that shares vibrational, rotational, and translational energy with the liquid surface before returning to the gas phase. Finally, a velocity map ion imaging apparatus has been implemented to investigate reaction dynamics in crossed molecular beams. Resonantly enhanced multiphoton ionization (REMPI) results in rotational, vibrational, and electronic state selectivity. Velocity map imaging measurements provide differential cross sections and information about the internal energy distribution of the undetected collision partner.

Polar azimuth diversity HF propagation experiment

NASA Astrophysics Data System (ADS)

Baker, Kurt A.; Haines, D. M.; Weijers, Bertus

1986-03-01

Presented are the results of an HF Azimuth Diversity Propagation Experiment conducted by RADC over several paths, transauroral and polar, separated in azimuth by 30, 70, and 100 degrees, as part of the RADC Adaptive HF Propagation Program. The data presented give the occurrence of several ionospheric characteristics important to the operation of HF networks in a disturbed environment. The analysis was performed on data collected during the four seasonal periods to obtain statistical samples representative of each season under slightly disturbed as well as quiet conditions. The system used to collect the data was a network of three chirpsounder transmitters and one receiver, each sweeping over a frequency range of 2 to 30 MHz, once every five minutes. The transmitters were located at Ava, N.Y., Grand Forks, N. Dak., and Barter Island, Alaska. The receiving system was located at Thule Air Base, Greenland.

Plasma Density and Electro-Magnetic Field Perturbations Hf-Induced in the Outer Ionosphere: Review of Experimental Results

NASA Astrophysics Data System (ADS)

Frolov, Vladimir; Rauch, Jean-Louis; Parrot, Michel; Rapoport, Victor; Shorokhova, Elena

In the report we consider features of plasma density and electro-magnetic field perturbations induced in the Earth’s outer ionosphere by modification of F _{2} region by O-mode powerful HF radio waves radiated by the SURA heating facility. Experiments presented were carried out in 2005 - 2010. Plasma density perturbations were detected at altitudes of about of 700 km by instruments onboard the French DEMETER satellite when it intersected the disturbed magnetic flux tube. The formation of artificial HF-induced plasma density ducts in the outer ionosphere is a central discovery, which was made during the SURA-DEMETER experiments [1,2]. Analysis of experimental data available makes it possible to formulate ducts features and point out the conditions under which the formation of such ducts takes place. 1. Under night conditions ducts are characterized by the increased plasma density in the range from 20% to 80% relatively to its background value. As this takes place, the excess in the plasma ion component is due to O (+) ions dominating at altitudes of about 700 km, whereas the densities of lower mass H (+) and He ({+) } ions typically decrease by a percentage amount that is much more the relative increase in the density of O (+) ions. The duct formation was never observed under daytime conditions. According to [3] the HF-induced ducts were observed by ionosphere pumping in morning and evening hours but in these cases their intensity was no more than a few percentages. 2. The size of the ducts along the satellite orbits is of about 80 - 100 km. It is a reason why such ducts can be observed only if the minimal distance between the satellite and the center of the heated flux tube is less than 50 km. 3. The formation of ducts is observed only if the effective radiated power is more than 40 MW. For the SURA facility, to heat the ionosphere at higher efficiency due to the “magnetic-zenith effect”, the HF beam is often inclined by 12 - 16(°) southward. 4. The pump wave frequency should be no less than 0.5 - 0.7 MHz below the F _{2} layer critical frequency f _{0F2}. In the opposed case the penetration of the radiated power behind the F _{2} ionospheric layer can take place [4]. 5. Strong variations of the electron temperature are observed inside the ducts, at the same time the ion temperature is unchanged. 6. A feature of the ducts is the presence of strong electro-magnetic field fluctuations in a frequency range from a few Hz to tens of kHz [1,5]. 7. It was revealed that the formation of the ducts in the outer ionosphere can stimulate the precipitation of energetic electrons with E ≥ 100 keV from the Earth’s radiation belts [6]. The work was supported by RFBR grants (## 12-05-00312, 13-02-12074, 13-02-12241) and by the scientific program “Geophysics”. References: 1. Rapoport V.O., V.L. Frolov, G.P. Komrakov, et al. // Radiophysics and Quantum Electronics, 2007. Vol. 50(8), p. 645. 2. Frolov V.L., V.O. Rapoport, G.P. Komrakov, et. al. // JETP Letters, 2008. Vol. 88, No. 12, p. 790. 3. Frolov V.L., I.A. Bolotin, V.O. Rapoport, et. al. // XXIV All-Russian conference “Radio Wave Propagation”. Irkutsk, 2014 (submitted for publication). 4. Frolov V.L., N.A. Mityakov, E.A. Shorokhova, M. Parrot. // Radiophysics and Quantum Electronics, 2013. Vol. 56(6), p. 325. 5. Rapoport V.O., V.L. Frolov, S.V. Polyakov, et al. // J. Geophys. Res., 2010. Vol. 115, A10322, doi:10.1029/2010JA015484. 6. Markov G.A., A.S. Belov, V.L. Frolov, et al. // JETPh, 2010. Vol. 138, No. 6(12), p. 1037.

Impacts of distinct observations during the 2009 Prince William Sound field experiment: A data assimilation study

NASA Astrophysics Data System (ADS)

Li, Zhijin; Chao, Yi; Farrara, John D.; McWilliams, James C.

2013-07-01

A set of data assimilation experiments, known as Observing System Experiments (OSEs) are performed to assess the relative impacts of different types of observations acquired during the 2009 Prince William Sound Field Experiment. The observations assimilated consist primarily of two types: High Frequency (HF) radar surface velocities and vertical profiles of temperature/salinity (T/S) measured by ships, moorings, an Autonomous Underwater Vehicle and a glider. The impact of all the observations, HF radar surface velocities, and T/S profiles is assessed. Without data assimilation, a frequently occurring cyclonic eddy in the central Sound is overly persistent and intense. The assimilation of the HF radar velocities effectively reduces these biases and improves the representation of the velocities as well as the T/S fields in the Sound. The assimilation of the T/S profiles improves the large scale representation of the temperature/salinity and also the velocity field in the central Sound. The combination of the HF radar surface velocities and sparse T/S profiles results in an observing system capable of representing the circulation in the Sound reliably and thus producing analyses and forecasts with useful skill.

Revisiting the Cause of the 1989-2009 Arctic Surface Warming Using the Surface Energy Budget: Downward Infrared Radiation Dominates the Surface Fluxes

NASA Astrophysics Data System (ADS)

Lee, Sukyoung; Gong, Tingting; Feldstein, Steven B.; Screen, James A.; Simmonds, Ian

2017-10-01

The Arctic has been warming faster than elsewhere, especially during the cold season. According to the leading theory, ice-albedo feedback warms the Arctic Ocean during the summer, and the heat gained by the ocean is released during the winter, causing the cold-season warming. Screen and Simmonds (2010; SS10) concluded that the theory is correct by comparing trend patterns in surface air temperature (SAT), surface turbulence heat flux (HF), and net surface infrared radiation (IR). However, in this comparison, downward IR is more appropriate to use. By analyzing the same data used in SS10 using the surface energy budget, it is shown here that over most of the Arctic the skin temperature trend, which closely resembles the SAT trend, is largely accounted for by the downward IR, not the HF, trend.

METHOD OF PRODUCING HAFNIUM-FREE "CRYSTAL-BAR" ZIRCONIUM FROM A CRUDE SOURCE OF ZIRCONIUM

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

Newnham, I.E.

1959-05-01

Production of Hf-free crystal-bar Zr is described. The crude source of Zr is carbided with carbon in a graphite resistance furnace, then treated with iodide to form ZrI/sub 4/. The ZrI/sub 4/ plus iodide impurities is heated with Zr powder in an evacuated vessel to 500 C. This causes ZrI/sub 3/ to form and be separated from the more volatile HfI/sub 4/ and AlI/sub 3/ which deposit on the condenserlid. The ZrI/sub 3/ is further separated from iodides of Fe, and V by heating to 350 C to re-form ZrI/sub 4/. The morevolatile ZrI/sub 4/ then is collected in puremore » form on another condenser-lid from which it can be removed and reduced to Zr. (T.R.H.)« less

The effect of tantalum on the structure/properties of two polycrystalline nickel-base superalloys: B-1900 + Hf MAR-M247. M.S. Thesis, Final Report

NASA Technical Reports Server (NTRS)

Janowski, G. M.

1985-01-01

The microstructure, phase compositions, and phase fractions were studied in conventionally cast B-1900 + Hf and both conventionally cast and directionally solidified MAR-M247 as a function of tantalum concentration. The hot tensile and creep rupture properties of the solutionized and aged MAR-M247-type alloys were also determined as a function of tantalum level. The effects of tantalum on the microstructure and phase compositions of B-1900 + Hf and MAR-M247 (conventionally cast and directionally solidified) were found to be very similar. The addition of tantalum to the as cast and heat treated alloys was shown to cause the partial replacement of the Hf in the MC carbides by Ta, although the degree of replacement was decreased by the solutionizing and aging heat treatment. The gamma prime and minor phase fractions (primarily MC type carbides) both increased approximately linearly with tantalum concentration. The gamma prime phase compositions were relatively insensitive to tantalum variations with the exception of the tantalum and/or hafnium levels. Bulk tantalum additions increased the tantalum, chromium, and cobalt levels of the gamma phase in both alloy series. The increase in the concentrations of the latter two elements in the gamma phase was a result of the decrease in the gamma phase fraction with increasing bulk tantalum concentration and constant gamma/gamma prime partitioning ratio. Tantalum additions increased the yield stress and ultimate tensile strength of the directionally solidified MAR-M247 type alloys and had no significant effect on ductility.

Systematic effects in the HfF+-ion experiment to search for the electron electric dipole moment

NASA Astrophysics Data System (ADS)

Petrov, A. N.

2018-05-01

The energy splittings for J =1 , F =3 /2 , | mF|=3 /2 hyperfine levels of the 3Δ1 electronic state of 180Hf+19F ion are calculated as functions of the external variable electric and magnetic fields within two approaches. In the first one, the transition to the rotating frame is performed, whereas in the second approach, the quantization of rotating electromagnetic field is performed. Calculations are required for understanding possible systematic errors in the experiment to search for the electron electric dipole moment (e EDM ) with the 180Hf+19F ion.

Hafnium oxide films for application as gate dielectrics

NASA Astrophysics Data System (ADS)

Hsu, Shuo-Lin

The deposition and characterization of HfO2 films for potential application as a high-kappa gate dielectric in MOS devices has been investigated. DC magnetron reactive sputtering was utilized to prepare the HfO2 films. Structural, chemical, and electrical analyses were performed to characterize the various physical, chemical and electrical properties of the sputtered HfO2 films. The sputtered HfO2 films were annealed to simulate the dopant activation process used in semiconductor processing, and to study the thermal stability of the high-kappa, films. The changes in the film properties due to the annealing are also discussed in this work. Glancing angle XRD was used to analyse the atomic scale structure of the films. The as deposited films exhibit an amorphous, regardless of the film thickness. During post-deposition annealing, the thicker films crystallized at lower temperature (< 600°C), and ultra-thin (5.8 nm) film crystallized at higher temperature (600--720°C). The crystalline phase which formed depended on the thickness of the films. The low temperature phase (monoclinic) formed in the 10--20 nm annealed films, and high temperature phase (tetragonal) formed in the ultra-thin annealed HfO2 film. TEM cross-section studies of as deposited samples show that an interfacial layer (< 1nm) exists between HfO2/Si for all film thicknesses. The interfacial layer grows thicker during heat treatment, and grows more rapidly when grain boundaries are present. XPS surface analysis shows the as deposited films are fully oxidized with an excess of oxygen. Interfacial chemistry analysis indicated that the interfacial layer is a silicon-rich silicate layer, which tends to transform to silica-like layer during heat treatment. I-V measurements show the leakage current density of the Al/as deposited-HfO 2/Si MOS diode is of the order of 10-3 A/cm 2, two orders of magnitude lower than that of a ZrO2 film with similar physical thickness. Carrier transport is dominated by Schottky emission at lower electric fields, and by Frenkel-Poole emission in the higher electric field region. After annealing, the leakage current density decreases significantly as the structure remains amorphous structure. It is suggested that this decrease is assorted with the densification and defect healing which accures when the porous as-deposited amorphous structure is annealed. The leakage current density increases of the HfO2 layer crystallizes on annealing, which is attributed to the presence of grain boundaries. C-V measurements of the as deposited film shows typical C-V characteristics, with negligible hystersis, a small flat band voltage shift, but great frequency dispersion. The relative permittivity of HfO2/interfacial layer stack obtained from the capacitance at accumulation is 15, which corresponds to an EOT (equivalent oxide thickness) = 1.66 nm. After annealing, the frequency dispersion is greatly enhanced, and the C-V curve is shifted toward the negative voltage. Reliability tests show that the HfO2 films which remain amorphous after annealing possess superior resistance to constant voltage stress and ambient aging. This study concluded that the sputtered HfO 2 films exhibit an amorphous as deposited. Postdeposition annealing alters the crystallinity, interfacial properties, and electrical characteristics. The HfO2 films which remain amorphous structure after annealing possess the best electrical properties.

Characterization, shaping, and joining of SiC/superalloy sheet for exhaust system components

NASA Technical Reports Server (NTRS)

Cornie, J. A.

1977-01-01

Hafnium carbide was shown to be virtually inert when in contact with silicon carbide and Waspaloy for at least 200 hr at 1093 C (2000 F). Extensive interaction was noted with other superalloys such as HA-188. A continuous CVD HfC deposition process was developed for deposition of up to 8 microns on .14 mm (.0056 in.) SiC tungsten core filament at rates as high as .6 m/min. The rate can be increased by increasing the length of the reactor and the output of the power supply used in resistive heating of the filament substrate. The strength of HfC coated filament varies with thickness in a Griffith-like manner. This strength reduction was greater for HfC coatings than for tungsten coatings, presumably because of the greater ductility of tungsten.

Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation

PubMed Central

Herynek, Vít; Turnovcová, Karolína; Veverka, Pavel; Dědourková, Tereza; Žvátora, Pavel; Jendelová, Pavla; Gálisová, Andrea; Kosinová, Lucie; Jiráková, Klára; Syková, Eva

2016-01-01

Introduction Magnetic nanoparticles (NPs) represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency (HF) magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (Tc) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Methods Perovskite NPs (Tc =66°C–74°C) were characterized and tested both in vitro and in vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated. Results and discussion In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase substantially in comparison with animals without particles during HF exposure. We proved that the deposited power from the NPs is too small and that thermoregulation of the animal is sufficient to conduct the heat away. Histology did not detect substantially higher apoptosis in NP-treated animals after ablation. Conclusion Magnetic particles with low Tc can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only. However, their effect in the case of extracellular deposition in vivo is questionable due to low deposited power and active thermoregulation of the tissue. PMID:27540292

Generation of whistler waves by continuous HF heating of the upper ionosphere

NASA Astrophysics Data System (ADS)

Vartanyan, A.; Milikh, G. M.; Eliasson, B.; Najmi, A. C.; Parrot, M.; Papadopoulos, K.

2016-07-01

Broadband VLF waves in the frequency range 7-10 kkHz and 15-19 kHz, generated by F region CW HF ionospheric heating in the absence of electrojet currents, were detected by the DEMETER satellite overflying the High Frequency Active Auroral Research Program (HAARP) transmitter during HAARP/BRIOCHE campaigns. The VLF waves are in a frequency range corresponding to the F region lower lybrid (LH) frequency and its harmonic. This paper aims to show that the VLF observations are whistler waves generated by mode conversion of LH waves that were parametrically excited by HF-pump-plasma interaction at the upper hybrid layer. The paper discusses the basic physics and presents a model that conjectures (1) the VLF waves observed at the LH frequency are due to the interaction of the LH waves with meter-scale field-aligned striations—generating whistler waves near the LH frequency; and (2) the VLF waves at twice the LH frequency are due to the interaction of two counterpropagating LH waves—generating whistler waves near the LH frequency harmonic. The model is supported by numerical simulations that show good agreement with the observations. The (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions results and model discussions are complemented by the Kodiak radar, ionograms, and stimulated electromagnetic emission observations.

H.F. emission related to the Li+ ion beam injected into ionosphere - ``PLAZMA'' rocket experiment

NASA Astrophysics Data System (ADS)

Klos, Z.; Zbyszynski, Z.; Agafonov, U. F.; Managadze, G. G.; Mayorov, A. D.

1993-10-01

The H.F. emission generated by artificial ion beam injected into ionosphere was observed either with a wave detector and ion gun attached to the rocket through out the flight, or when the gun was deployed on subpayload. Generally the observations show unstructured shape of the H.F. spectrum. In the PLAZMA active rocket experiment - when ionospheric plasma was perturbed by the operation of impulse ion gun, which injected 300 A, 8.3 eV Li+ions - the waves in the 0.1 - 10 MHz frequency range were observed. The results have shown, that when the wave detector and the ion gun are attached to the rocket the emission enhances in the lower as well as in the upper parts of the spectrum. On the other hand only the lower increase is maintained when ion gun is removing away on the subpayload. The observed sequence of H.F. spectra is presented.

Numerical Model of Hydraulic Fracturing Fluid Transport in the Subsurface with Pressure Transient, Density Effects, and Imbibition

NASA Astrophysics Data System (ADS)

Birdsell, D.; Rajaram, H.; Dempsey, D.; Viswanathan, H.

2014-12-01

Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated from an environmental and public health perspective and to understand formation damage from an oil and gas production perspective. Upward pressure gradients, permeable pathways such as faults or improperly abandoned wellbores, and the density contrast of the HF fluid to the surrounding brine encourages upward HF fluid migration. In contrast, the very low shale permeability and the imbibition of water into partially-saturated shale may sequester much of the HF fluid. Using the Finite Element Heat and Mass Transfer Code (FEHM), single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore as flowback and produced water and how much reaches overlying aquifers; imbibition is calculated with a semi-analytical one-dimensional solution and treated as a sink term. The travel time for HF fluid to reach the shallow aquifers is highly dependent on the amount of water imbibed and the suction applied to the well. If imbibition rates and suction are small, the pressure transient due to injection and the density contrast allows rapid upward plume migration at early times. The density contrast diminishes considerably within tens to hundreds of years as mixing occurs. We present estimates of HF fluid migration to shallow aquifers during the first 1,000 years after hydraulic fracturing begins for ranges of subsurface properties.

Early postweaning exercise improves central leptin sensitivity in offspring of rat dams fed high-fat diet during pregnancy and lactation.

PubMed

Sun, Bo; Liang, Nu-Chu; Ewald, Erin R; Purcell, Ryan H; Boersma, Gretha J; Yan, Jianqun; Moran, Timothy H; Tamashiro, Kellie L K

2013-11-01

Maternal high-fat (HF) diet has long-term consequences on the metabolic phenotype of the offspring. Here, we determined the effects of postweaning exercise in offspring of rat dams fed HF diet during gestation and lactation. Pregnant Sprague-Dawley rats were maintained on chow or HF diet throughout gestation and lactation. All pups were weaned onto chow diet on postnatal day (PND) 21. At 4 wk of age, male pups were given free access to running wheels (RW) or remained sedentary (SED) for 3 wk, after which all rats remained sedentary, resulting in four groups: CHOW-SED, CHOW-RW, HF-SED, and HF-RW. Male HF offspring gained more body weight by PND7 compared with CHOW pups and maintained this weight difference through the entire experiment. Three weeks of postweaning exercise did not affect body weight gain in either CHOW or HF offspring, but reduced adiposity in HF offspring. Plasma leptin was decreased at the end of the 3-wk running period in HF-RW rats but was not different from HF-SED 9 wk after the exercise period ended. At 14 wk of age, intracerebroventricular injection of leptin suppressed food intake in CHOW-SED, CHOW-RW, and HF-RW, while it did not affect food intake in HF-SED group. At death, HF-RW rats also had higher leptin-induced phospho-STAT3 level in the arcuate nucleus than HF-SED rats. Both maternal HF diet and postweaning exercise had effects on hypothalamic neuropeptide and receptor mRNA expression in adult offspring. Our data suggest that postweaning exercise improves central leptin sensitivity and signaling in this model.

Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

NASA Technical Reports Server (NTRS)

Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

2012-01-01

Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

Lattice Thermal Conductivity from Atomistic Simulations: ZrB2 and HfB2

NASA Technical Reports Server (NTRS)

Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

2012-01-01

Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

First-principles modeling of hafnia-based nanotubes.

PubMed

Evarestov, Robert A; Bandura, Andrei V; Porsev, Vitaly V; Kovalenko, Alexey V

2017-09-15

Hybrid density functional theory calculations were performed for the first time on structure, stability, phonon frequencies, and thermodynamic functions of hafnia-based single-wall nanotubes. The nanotubes were rolled up from the thin free layers of cubic and tetragonal phases of HfO 2 . It was shown that the most stable HfO 2 single-wall nanotubes can be obtained from hexagonal (111) layer of the cubic phase. Phonon frequencies have been calculated for different HfO 2 nanolayers and nanotubes to prove the local stability and to find the thermal contributions to their thermodynamic functions. The role of phonons in stability of nanotubes seems to be negligible for the internal energy and noticeable for the Helmholtz free energy. Zone folding approach has been applied to estimate the connection between phonon modes of the layer and nanotubes and to approximate the nanotube thermodynamic properties. It is found that the zone-folding approximation is sufficiently accurate for heat capacity, but less accurate for entropy. The comparison has been done between the properties of TiO 2 , ZrO 2 , and HfO 2 . © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The mechanical, optoelectronic and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys

NASA Astrophysics Data System (ADS)

Hamioud, Farida; Mubarak, A. A.

2017-09-01

First-principle calculations are performed using DFT as implemented in Wien2k code to compute the mechanical, electronic, optical and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys. The computed lattice constants, bulk modulus and cohesive energy of these alloys at 0 K and 0 GPa are performed. NiZrSn and NiHfSn are found to be anisotropic and elastically stable. Furthermore, both alloys are confirmed to be thermodynamically stable by the calculated values of the standard enthalpy of formation. The Young’s and shear moduli values show that NiZrSn seems to be stiffer than NiHfSn. The optical properties are performed using the dielectric function. Some beneficial optoelectronic applications are found as exposed in the optical spectra. Moreover, the alloys are classified as good insulators for solar heating. The thermoelectric properties as a function of temperature are computed utilizing BoltzTrap code. The major charge carriers are found to be electrons and the alloys are classified as p-type doping alloys.

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

Hong, A.; Mariwala, R.K.; Kane, M.S.

Experimental evidence is provided for adsorptive shape selectivity in the separation of the azeotrope between HF and 1,1,1,2-tetrafluoroethane (134a) over pyrolyzed poly(furfuryl alcohol)-derived carbogenic molecular sieve (PPFA-CMS). The separation can be accomplished over coconut charcoal or Carbosieve G on the basis of the differences in the extent of equilibrium adsorption of HF and 134a. On these adsorbents 134a is more strongly bound than HF, thus it elutes much more slowly from the bed. The heat of adsorption for 134a in the vicinity of 200 C on Carbosieve G is {approximately}8.8 kcal/mol. In contrast, when the same azeotropic mixture is separatedmore » over PPFA-CMS prepared at 500 C, 134a is not adsorbed. As a result 134a elutes from the bed first, followed by HF. The reversal is brought about by the narrower pore size and pore size distribution of the PPFA-CMS versus that for Carbosieve G. Thus the separation over PPFA-CMS is an example of adsorbate shape selectivity and represents a limiting case of kinetic separation.« less

Modeling of NiTiHf using finite difference method

NASA Astrophysics Data System (ADS)

Farjam, Nazanin; Mehrabi, Reza; Karaca, Haluk; Mirzaeifar, Reza; Elahinia, Mohammad

2018-03-01

NiTiHf is a high temperature and high strength shape memory alloy with transformation temperatures above 100oC. A constitutive model based on Gibbs free energy is developed to predict the behavior of this material. Two different irrecoverable strains including transformation induced plastic strain (TRIP) and viscoplastic strain (VP) are considered when using high temperature shape memory alloys (HTSMAs). The first one happens during transformation at high levels of stress and the second one is related to the creep which is rate-dependent. The developed model is implemented for NiTiHf under uniaxial loading. Finite difference method is utilized to solve the proposed equations. The material parameters in the equations are calibrated from experimental data. Simulation results are captured to investigate the superelastic behavior of NiTiHf. The extracted results are compared with experimental tests of isobaric heating and cooling at different levels of stress and also superelastic tests at different levels of temperature. More results are generated to investigate the capability of the proposed model in the prediction of the irrecoverable strain after full transformation in HTSMAs.

Do Hf isotopes in magmatic zircons represent those of their host rocks?

NASA Astrophysics Data System (ADS)

Wang, Di; Wang, Xiao-Lei; Cai, Yue; Goldstein, Steven L.; Yang, Tao

2018-04-01

Lu-Hf isotopic system in zircon is a powerful and widely used geochemical tracer in studying petrogenesis of magmatic rocks and crustal evolution, assuming that zircon Hf isotopes can represent initial Hf isotopes of their parental whole rock. However, this assumption may not always be valid. Disequilibrium partial melting of continental crust would preferentially melt out non-zircon minerals with high time-integrated Lu/Hf ratios and generate partial melts with Hf isotope compositions that are more radiogenic than those of its magma source. Dissolution experiments (with hotplate, bomb and sintering procedures) of zircon-bearing samples demonstrate this disequilibrium effect where partial dissolution yielded variable and more radiogenic Hf isotope compositions than fully dissolved samples. A case study from the Neoproterozoic Jiuling batholith in southern China shows that about half of the investigated samples show decoupled Hf isotopes between zircons and the bulk rocks. This decoupling could reflect complex and prolonged magmatic processes, such as crustal assimilation, magma mixing, and disequilibrium melting, which are consistent with the wide temperature spectrum from ∼630 °C to ∼900 °C by Ti-in-zircon thermometer. We suggest that magmatic zircons may only record the Hf isotopic composition of their surrounding melt during crystallization and it is uncertain whether their Hf isotopic compositions can represent the primary Hf isotopic compositions of the bulk magmas. In this regard, using zircon Hf isotopic compositions to trace crustal evolution may be biased since most of these could be originally from disequilibrium partial melts.

Engineering of the chemical reactivity of the Ti/HfO₂ interface for RRAM: experiment and theory.

PubMed

Calka, Pauline; Sowinska, Malgorzata; Bertaud, Thomas; Walczyk, Damian; Dabrowski, Jarek; Zaumseil, Peter; Walczyk, Christian; Gloskovskii, Andrei; Cartoixà, Xavier; Suñé, Jordi; Schroeder, Thomas

2014-04-09

The Ti/HfO2 interface plays a major role for resistance switching performances. However, clear interface engineering strategies to achieve reliable and reproducible switching have been poorly investigated. For this purpose, we present a comprehensive study of the Ti/HfO2 interface by a combined experimental-theoretical approach. Based on the use of oxygen-isotope marked Hf*O2, the oxygen scavenging capability of the Ti layer is clearly proven. More importantly, in line with ab initio theory, the combined HAXPES-Tof-SIMS study of the thin films deposited by MBE clearly establishes a strong impact of the HfO2 thin film morphology on the Ti/HfO2 interface reactivity. Low-temperature deposition is thus seen as a RRAM processing compatible way to establish the critical amount of oxygen vacancies to achieve reproducible and reliable resistance switching performances.

Kisilidjan hf - A unique diatomite plant

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

Sigurdsson, F.

This paper gives a short description of Kisilidjan hf. (The Icelandic Diatomite Plant, Ltd.), a description of the production, the use of geothermal steam in the plant, steam supply, steam use, steam price, experience associated with the use of steam, and some conclusions.

Altitude and intensity characteristics of parametric instability excited by an HF pump wave near the fifth electron harmonic

NASA Astrophysics Data System (ADS)

Jun, WU; Jian, WU; M, T. RIETVELD; I, HAGGSTROM; Haisheng, ZHAO; Zhengwen, XU

2017-12-01

An ionospheric heating experiment involving an O mode pump wave was carried out at European Incoherent Scatter Scientific Association site in Tromsø. The observation of the ultra high frequency radar illustrates the systematic variations of the enhanced ion line and plasma line in altitude and intensity as a function of the pump frequency. The analysis shows that those altitude variations are due to the thermal effect, and the intensity variations of the enhanced ion line are dependent on whether or not the enhanced ion acoustic wave satisfy the Bragg condition of radar. Moreover, a prediction that if the enhancement in electron temperature is suppressed, those systematic variations will be absent, is given.

Quantum-state resolved reactive scattering at the gas-liquid interface: F+squalane (C30H62) dynamics via high-resolution infrared absorption of nascent HF(v,J).

PubMed

Zolot, Alexander M; Dagdigian, Paul J; Nesbitt, David J

2008-11-21

Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic beam of F atoms [E(com)=0.7(3) kcalmol] with a continuously refreshed liquid hydrocarbon (squalane) surface under high vacuum conditions. Absolute HF(v,J) product densities are determined by infrared laser absorption spectroscopy, with velocity distributions along the probe axis derived from high resolution Dopplerimetry. Nascent HF(v

Quantum-state resolved reactive scattering at the gas-liquid interface: F +squalane (C30H62) dynamics via high-resolution infrared absorption of nascent HF(v,J)

NASA Astrophysics Data System (ADS)

Zolot, Alexander M.; Dagdigian, Paul J.; Nesbitt, David J.

2008-11-01

Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic beam of F atoms [Ecom=0.7(3)kcal/mol] with a continuously refreshed liquid hydrocarbon (squalane) surface under high vacuum conditions. Absolute HF(v,J) product densities are determined by infrared laser absorption spectroscopy, with velocity distributions along the probe axis derived from high resolution Dopplerimetry. Nascent HF(v ⩽3) products are formed in a highly nonequilibrium (inverted) vibrational distribution [⟨Evib⟩=13.2(2)kcal/mol], reflecting insufficient time for complete thermal accommodation with the surface prior to desorption. Colder, but still non-Boltzmann, rotational state populations [⟨Erot⟩=1.0(1)kcal/mol] indicate that some fraction of molecules directly scatter into the gas phase without rotationally equilibrating with the surface. Nascent HF also recoils from the liquid surface with excess translational energy, resulting in Doppler broadened linewidths that increase systematically with internal HF excitation. The data are consistent with microscopic branching in HF-surface dynamics following the reactive event, with (i) a direct reactive scattering fraction of newly formed product molecules leaving the surface promptly and (ii) a trapping desorption fraction that accommodates rotationally (though still not vibrationally) with the bulk liquid. Comparison with analogous gas phase F +hydrocarbon processes reveals that the liquid acts as a partial "heat sink" for vibrational energy flow on the time scale of the chemical reaction event.

Active experiments in geospace plasmas with gigawatts of RF power at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, James

2016-07-01

The ionosphere provides a relatively quiescent plasma target, stable on timescales of minutes, for a whole host of active plasma experiments. The largest HF transmitter built to date is the HAARP phased-array HF transmitter near Gakona, Alaska which can deliver up to 3.6 Gigawatts (ERP) of CW RF power in the range of 2.8 - 10 MHz to the ionosphere with millisecond pointing, power modulation, and frequency agility. With an ionospheric background thermal energy in the range of only 0.1 eV, this amount of power gives access to the highest regimes of the nonlinearity (RF intensity to thermal pressure) ratio. HAARP's unique features have enabled the conduct of a number of nonlinear plasma experiments in the inter¬action region of overdense ionospheric plasma including generation of artificial aurorae, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, parametric instabilities, stimulated electromagnetic emissions (SEE), strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and optics for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the HF-enhanced plasma line, and production of suprathermal electrons. Applications are made to the controlled study of fundamental nonlinear plasma processes of relevance to laboratory plasmas, ionospheric irregularities affecting spacecraft communication and navigation systems, artificial ionization mirrors, wave-particle interactions in the magnetosphere, active global magnetospheric experiments, and many more.

Experience-Related Changes in Place Cell Responses to New Sensory Configuration That Does Not Occur in the Natural Environment in the Rat Hippocampus

PubMed Central

Zou, Dan; Nishimaru, Hiroshi; Matsumoto, Jumpei; Takamura, Yusaku; Ono, Taketoshi; Nishijo, Hisao

2017-01-01

The hippocampal formation (HF) is implicated in a comparator that detects sensory conflict (mismatch) among convergent inputs. This suggests that new place cells encoding the new configuration with sensory mismatch develop after the HF learns to accept the new configuration as a match. To investigate this issue, HF CA1 place cell activity in rats was analyzed after the adaptation of the rats to the same sensory mismatch condition. The rats were placed on a treadmill on a stage that was translocated in a figure 8-shaped pathway. We recorded HF neuronal activities under three conditions; (1) an initial control session, in which both the stage and the treadmill moved forward, (2) a backward (mismatch) session, in which the stage was translocated backward while the rats locomoted forward on the treadmill, and (3) the second control session. Of the 161 HF neurons, 56 place-differential activities were recorded from the HF CA1 subfield. These place-differential activities were categorized into four types; forward-related, backward-related, both-translocation-related, and session-dependent. Forward-related activities showed predominant spatial firings in the forward sessions, while backward-related activities showed predominant spatial firings in the backward sessions. Both-translocation-related activities showed consistent spatial firings in both the forward and backward conditions. On the other hand, session-dependent activities showed different spatial firings across the sessions. Detailed analyses of the place fields indicated that mean place field sizes were larger in the forward-related, backward-related, and both-translocation-related activities than in the session-dependent activities. Furthermore, firing rate distributions in the place fields were negatively skewed and asymmetric, which is similar to place field changes that occur after repeated experience. These results demonstrate that the HF encodes a naturally impossible new configuration of sensory inputs after adaptation, suggesting that the HF is capable of updating its stored memory to accept a new configuration as a match by repeated experience. PMID:28878682

Application of diffusion barriers to high modulus fibers

NASA Technical Reports Server (NTRS)

Veltri, R. D.; Douglas, F. C.; Paradis, E. L.; Galasso, F. S.

1977-01-01

Barrier layers were coated onto high-modulus fibers, and nickel and titanium layers were overcoated as simulated matrix materials. The objective was to coat the high-strength fibers with unreactive selected materials without degrading the fibers. The fibers were tungsten, niobium, and single-crystal sapphire, while the materials used as barrier coating layers were Al2O3, Y2O3, TiC, ZrC, WC with 14% Co, and HfO2. An ion-plating technique was used to coat the fibers. The fibers were subjected to high-temperature heat treatments to evaluate the effectiveness of the barrier layer in preventing fiber-metal interactions. Results indicate that Al2O3, Y2O3, and HfO2 can be used as barrier layers to minimize the nickel-tungsten interaction. Further investigation, including thermal cycling tests at 1090 C, revealed that HfO2 is probably the best of the three.

First-principles study of transition-metal nitrides as diffusion barriers against Al

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

Mei, Zhi-Gang; Yacout, Abdellatif M.; Kim, Yeon Soo

2016-04-01

Using density-functional theory based first-principles calculations we provided a comparative study of the diffusion barrier properties of TiN, ZrN, and HfN against Al for U-Mo dispersion fuel applications. We firstly examined the thermodynamic stability of these transition-metal nitrides with Al. The calculated heats of reaction show that both TiN and ZrN are thermodynamically unstable diffusion barrier materials, which might be decomposed by Al at relatively high temperatures. As a comparison, HfN is a stable diffusion barrier material for Al. To evaluate the kinetic stability of these nitride systems against Al diffusion, we investigated the diffusion mechanisms of Al in TiN,more » ZrN and HfN using atomic scale simulations. The effect of non-stoichiometry on the defect formation and Al migration was systematically studied. (C) 2015 ELSEVIER B.V. All rights reserved« less

[Analysis of methods for measurement and assessment of occupational exposure to electromagnetic fields in dielectric heating].

PubMed

Aniołczyk, Halina; Mamrot, Paweł; Mariańska, Magda

2012-01-01

High-frequency (HF) welders are the most common devices that make use of dielectric heating. They are a source of high-intensity electromagnetic fields (EMFs). Manual operation of those welders makes that the limbs are exposed to EMFs of extremely high intensity, far in excess of the currently admissible values. The aim of this study was to update knowledge of actual exposure of HF welder operators to EMF and to optimize the procedure of exposure assessment. Measurements of the EMF intensity in the vicinity of 10 dielectric welders at work posts of 12 operators were performed. EMF measurements were made using the reference method, extended by auxiliary measurement points to measure induced currents I(L) in the limbs. Induced current measurements were performed in 20 operators tending the same HF welder. the highest values of the electric (E) and magnetic (H) fields measured at work posts were for whole body: E, up to 350 V/m, and H, up to 1.00 A/m; and for limbs: E, up to 600 V/m and H, up to 3.30 A/m. The W exposure indicator in the primary vertical measurement points was almost as high as 60. I(L) values measured at the wrist exceeded 64 mA and were individual-operator-dependent. EMF exposure of 25% of HF welder operators exceeded the national admissible values and after taking into account the operators' hands, this figure rose to 50%. The measured value of I(L), representing a measure of internal exposure to EMF, should serve as the main criterion in deciding whether working conditions are admissible.

Spectroscopic requirements for HALOE: An analysis of the HCl and HF channels

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Smith, M. A. H.; Park, J. H.; Harvey, G. A.; Russell, J. M., III; Richardson, D. J.

1982-01-01

Spectral line parameters that have absorption features within the HCl and HF channels of the Halogen Occultation Experiment (HALOE) were evaluated. Line positions and identification of stratospheric and solar absorption features in both channels are presented based on an analysis of high-resolution, balloon-borne solar occultation spectra. For the relevant HCl and HF lines and for transitions of the interfering species, the accuracy of the following spectral parameters was assessed: line positions, line strengths, lower state energies, air-broadened collisional half-widths, and temperature dependence of the air-broadened half-widths. In addition, since the HALOE instrument and calibration cells are filled with mixtures of HCl in N2 and HF in N2, the self-broadened and N2-broadened HF and HCl half-widths were also considered.

Planning for coordinated space and ground-based ionospheric modification experiments

NASA Technical Reports Server (NTRS)

Lee, M. C.; Burke, William J.; Carlson, Herbert C.; Heckscher, John L.; Kossey, Paul A.; Weber, E. J.; Kuo, S. P.

1990-01-01

The planning and conduction of coordinated space and ground-based ionospheric modification experiments are discussed. The purpose of these experiments is to discuss: (1) the nonlinear VLF wave interaction with the ionospheric plasmas; and (2) the nonlinear propagation of VLF waves in the HF-modified ionosphere. It is expected that the HF-induced ionospheric density striations can render the nonlinear mode conversion of VLF waved into lower hybrid waves. Lower hybrid waves can also be excited parametrically by the VLF waves in the absence of the density striations if the VLF waves are intense enough. Laboratory experiments are planned for crosschecking the results obtained from the field experiments.

Studies of High Power RF-induced Turbulence in the Ionosphere over HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.

2016-12-01

The HAARP phased-array HF transmitter at Gakona, AK delivers up to 3.6 GW (ERP) of HF power in the range of 2.8 - 10 MHz to the ionosphere with millisecond pointing, power modulation, and frequency agility. HAARP's unique features have enabled the conduct of a number of nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including stimulated electromagnetic emissions (SEE), artificial aurora, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the plasma line, and production of suprathermal electrons. For a narrow range of HF pointing between Spitze and magnetic zenith, a reduced threshold for AFAI is observed. Recent results of simulations of these experiments enable interpretation of many observed features. Applications are made to the study of irregularities relevant to spacecraft communication and navigation systems.

Superconductivity and valence state in layered single-crystal HfAs1.67Te0.12

NASA Astrophysics Data System (ADS)

Peng, Jian; Yu, Jia; Zhang, Shuai; Chen, Genfu

2018-01-01

We report a detailed study on single crystals of HfAs1.67Te0.12 within a PbFCl-type layered structure. The single crystals of the title compound were successfully grown using a chemical transport reaction. The temperature dependence of electrical resistivity ρ (T), AC magnetic susceptibility {χ }{AC}(T) and specific heat C(T) show a bulk superconductivity with transition temperature T c = 1.67 K. The jump of C/T at T c is comparable to the traditional BCS weak-coupling model. A full H-T phase diagram is established using the results of ρ (T,H) and C(T) under fields, suggesting a rather weak anisotropy [({H}c2\\parallel {ab}(0)/{H}c2\\parallel c(0)] of 1.8 in orbital limit dominated three-dimension-like superconducting system. The mixed-valence states of Hf and As observed in the binding energy from x-ray photoelectron spectroscopy are consistent with the single-crystal x-ray diffraction analysis, indicating that the As-Te disorder prefers to occur in the [HfAs] layer and a large amount of vacancies are present in tetragonal As layer. As compared to HfAs1.7Se0.2 (T c = 0.52 K), a positive-like vacancy effect on T c has been confirmed in HfAs1.67Te0.12. The analysis of the Hall coefficient implies that the hole-type carriers dominate the transport properties, which is in good agreement with the hole pockets at Fermi surface obtained in a band structure calculation. The detailed study of single-crystal HfAs1.67Te0.12 provides a possible candidate to discuss the non-magnetic Kondo effect.

The effect of Crataegus oxycantha Special Extract WS 1442 on clinical progression in patients with mild to moderate symptoms of heart failure.

PubMed

Zick, Suzanna M; Gillespie, Brenda; Aaronson, Keith D

2008-06-01

To examine whether hawthorn (Crataegus Special Extract WS 1442 {CSE}) inhibits progression in heart failure (HF) patients. We performed a retrospective analysis of data from the HERB CHF study in which patients with mild to moderate HF were randomised to either CSE 900 mg or placebo for 6 months. The primary outcome was time to progression of HF (HF death, hospitalisation, or sustained increase in diuretics) as assessed by log-rank tests and by Cox modelling. Progression of HF occurred in 46.6% of the CSE and 43.3% of the placebo groups (OR 1.14, 95% CI=0.56, 2.35: p=0.86). Patients receiving CSE were 3.9 times (95% CI=1.1-13.7: p=0.035) more likely to experience HF progression at baseline. In adjusted analysis, the risk of having early HF progression in the CSE group increased to 6.4 (95% CI=1.5, 26.5: p=0.011). In patients with LVEF< or =35%, those taking CSE were at significantly greater risk (3.2, 95% CI=1.3, 8.3: p=0.02) than the placebo group. CSE does not reduce heart failure progression in patients who have HF. CSE appears to increase the early risk of HF progression.

Translating and testing the ENABLE: CHF-PC concurrent palliative care model for older adults with heart failure and their family caregivers.

PubMed

Dionne-Odom, J Nicholas; Kono, Alan; Frost, Jennifer; Jackson, Lisa; Ellis, Daphne; Ahmed, Ali; Azuero, Andres; Bakitas, Marie

2014-09-01

Heart failure (HF) and palliative care (PC) organizations recommend early PC to improve the quality of life of patients living with HF. We conducted a two-phase formative evaluation study to translate a cancer-focused concurrent PC intervention into one that would be appropriate for rural-dwelling adults with New York Heart Association Class III-IV HF and their primary caregivers. Phase I: We tailored the intervention for an HF population via literature review, expert consultation, and clinician (N=15) small group interviews. Phase II: We enrolled 11 patient/caregiver dyads to assess intervention feasibility and satisfaction. We assessed participants' experiences and satisfaction after session/week three and session/week six via digitally recorded interviews. Clinician and participant interviews were transcribed and content analyzed. Outcome measures were evaluated for completion rates and effect sizes. Phase I: Clinicians described barriers to initiating PC in HF, triggers for initiating PC, and suggestions for intervention improvement. Phase II: Participants were able to complete the majority of study sessions, measures, and interviews. Satisfaction interviews revealed the content to be relevant and comprehensive in addressing HF patient and caregiver primary concerns; however, participants unanimously suggested making the intervention available earlier in the illness trajectory. Efficacy measures demonstrated small to medium effect sizes. We tailored and demonstrated feasibility of providing an early, concurrent palliative care intervention to patients with advanced HF and their caregivers. Based on this experience we are now conducting an efficacy trial in a racially diverse sample.

Nonlinear Plasma Experiments in Geospace with Gigawatts of RF Power at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Rayyan, N.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.

2014-10-01

The HAARP phased-array HF transmitter at Gakona, AK delivers up to 3.6 GW (ERP) of HF power in the range of 2.8 - 10 MHz to the ionosphere with millisecond pointing, power modulation, and frequency agility. HAARP's unique features have enabled the conduct of a number of nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including stimulated electromagnetic emissions (SEE), artificial aurora, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the plasma line, and suprathermal electrons. Applications are made to the study and control of irregularities affecting spacecraft communication and navigation systems.

Transition between strong and weak topological insulator in ZrTe5 and HfTe5

NASA Astrophysics Data System (ADS)

Fan, Zongjian; Liang, Qi-Feng; Chen, Y. B.; Yao, Shu-Hua; Zhou, Jian

2017-04-01

ZrTe5 and HfTe5 have attracted increasingly attention recently since the theoretical prediction of being topological insulators (TIs). However, subsequent works show many contradictions about their topolog-ical nature. Three possible phases, i.e. strong TI, weak TI, and Dirac semi-metal, have been observed in different experiments until now. Essentially whether ZrTe5 or HfTe5 has a band gap or not is still a question. Here, we present detailed first-principles calculations on the electronic and topological prop-erties of ZrTe5 and HfTe5 on variant volumes and clearly demonstrate the topological phase transition from a strong TI, going through an intermediate Dirac semi-metal state, then to a weak TI when the crystal expands. Our work might give a unified explain about the divergent experimental results and propose the crucial clue to further experiments to elucidate the topological nature of these materials.

Calving traits, milk production, body condition, fertility, and survival of Holstein-Friesian and Norwegian Red dairy cattle on commercial dairy farms over 5 lactations.

PubMed

Ferris, C P; Patterson, D C; Gordon, F J; Watson, S; Kilpatrick, D J

2014-01-01

The objective of this study was to compare calving traits, BCS, milk production, fertility, and survival of Holstein-Friesian (HF) and Norwegian Red (NR) dairy cattle in moderate-concentrate input systems. The experiment was conducted on 19 commercial Northern Ireland dairy farms, and involved 221 HF cows and 221 NR cows. Cows completed 5 lactations during the experiment, unless they died or were culled or sold. Norwegian Red cows had a lower calving difficulty score than HF cows when calving for the first and second time, but not for the third and fourth time. At first calving, the incidence of stillbirths for NR cows was 4%, compared with 13% for HF cows, whereas no difference existed between breeds in the proportion of calves born alive when calving for the second time. When calving for the first time, NR cows had a poorer milking temperament than HF cows, whereas milking temperament was unaffected by breed following the second calving. Holstein-Friesian cows had a higher full-lactation milk yield than NR cows, whereas NR cows produced milk with a higher milk fat and protein content. Full-lactation fat + protein yield was unaffected by genotype. Norwegian Red cows had a lower somatic cell score than HF cows during all lactations. Although NR cattle had a higher BCS than the HF cows during lactations 1 and 2, no evidence existed that the 2 genotypes either lost or gained body condition at different rates. Conception rates to first artificial insemination were higher with the NR cows during lactations 1 to 4 (57.8 vs. 40.9%, respectively), with 28.5% of HF cows and 11.8% of NR cows culled as infertile before lactation 6. A greater percentage of NR cows calved for a sixth time compared with HF cows (27.2 vs. 16.3%, respectively). In general, NR cows outperformed HF cows in traits that have been historically included in the NR breeding program. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Single-source-precursor synthesis of hafnium-containing ultrahigh-temperature ceramic nanocomposites (UHTC-NCs).

PubMed

Yuan, Jia; Hapis, Stefania; Breitzke, Hergen; Xu, Yeping; Fasel, Claudia; Kleebe, Hans-Joachim; Buntkowsky, Gerd; Riedel, Ralf; Ionescu, Emanuel

2014-10-06

Amorphous SiHfBCN ceramics were prepared from a commercial polysilazane (HTT 1800, AZ-EM), which was modified upon reactions with Hf(NEt2)4 and BH3·SMe2, and subsequently cross-linked and pyrolyzed. The prepared materials were investigated with respect to their chemical and phase composition, by means of spectroscopy techniques (Fourier transform infrared (FTIR), Raman, magic-angle spinning nuclear magnetic resonance (MAS NMR)), as well as X-ray diffraction (XRD) and transmission electron microscopy (TEM). Annealing experiments of the SiHfBCN samples in an inert gas atmosphere (Ar, N2) at temperatures in the range of 1300-1700 °C showed the conversion of the amorphous materials into nanostructured UHTC-NCs. Depending on the annealing atmosphere, HfC/HfB2/SiC (annealing in argon) and HfN/Si3N4/SiBCN (annealing in nitrogen) nanocomposites were obtained. The results emphasize that the conversion of the single-phase SiHfBCN into UHTC-NCs is thermodynamically controlled, thus allowing for a knowledge-based preparative path toward nanostructured ultrahigh-temperature stable materials with adjusted compositions.

Dual-frequency glow discharges in atmospheric helium

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

Huang, Xiaojiang; Guo, Ying; Magnetic Confinement Fusion Research Center, Ministry of Education of the People's Republic of China, Shanghai 201620

2015-10-15

In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

Oxidation Behavior of HfB2-SiC Materials in Dissociated Environments

NASA Technical Reports Server (NTRS)

Ellerby, Don; Irby, Edward; Johnson, Sylvia M.; Beckman, Sarah; Gusman, Michael; Gasch, Matthew

2002-01-01

Hafnium diboride based materials have shown promise for use in extremely high temperature applications, such as sharp leading edges on future reentry vehicles. During reentry, the oxygen and nitrogen in the atmosphere are dissociated by the shock layer ahead of the sharp leading edge such that surface reactions are determined by reactions of monatomic oxygen and nitrogen rather than O2, and N2. Simulation of the reentry environment on the ground requires the use of arc jet (plasma jet) facilities that provide monatomic species and are the closest approximation to actual flight conditions. Simple static or flowing oxidation studies under ambient pressures and atmospheres are not adequate to develop an understanding of a materials behavior in flight. Arc jet testing is required to provide the appropriate stagnation pressures, heat fluxes, enthalpies, heat loads and atmospheres encountered during flight. This work looks at the response of HfB2/SiC materials exposed to various simulated reentry environments.

Degradation of hydraulic fracturing additive 2-butoxyethanol using heat activated persulfate in the presence of shale rock.

PubMed

Manz, Katherine E; Carter, Kimberly E

2018-09-01

Changes in fluid composition during hydraulic fracturing (HF) for natural gas production can impact well productivity and the water quality of the fluids returning to the surface during productivity. Shale formation conditions can influence the extent of fluid transformation. Oxidizers, such as sodium persulfate, likely play a strong role in fluid transformation. This study investigates the oxidation of 2-butoxyethanol (2-BE), a surfactant used in HF, by sodium persulfate in the presence of heat, pH changes, Fe(II), and shale rock. Increasing temperature and Fe(II) concentrations sped up 2-BE oxidation, while pH played little to no role in 2-BE degradation. The presence of shale rock impeded 2-BE oxidation with increasing shale concentrations causing decreasing pseudo-first-order reaction rate constant to be observed. Over the course of reactions containing shales, dissolved solids were tracked to better understand how reactions with minerals in the shale impact water quality. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Harder, Bryan James

2014-01-01

Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.

On Spatial Structuring of the F2 Layer Studied by the Satellite Radio Sounding of the Ionosphere Disturbed by High-Power HF Radio Waves

NASA Astrophysics Data System (ADS)

Tereshchenko, E. D.; Turyansky, V. A.; Khudukon, B. Z.; Yurik, R. Yu.; Frolov, V. L.

2018-01-01

We present the results of studying the characteristics of the artificial plasma structures excited in the ionospheric F2 region modified by high-power HF radio waves. The experiments were carried out at the Sura heating facility using satellite radio sounding of the ionosphere. The plasma density profile was reconstructed with the highest possible spatial resolution for today, about 4 km. In a direction close to the magnetic zenith of the pump wave, the following phenomena were observed: the formation of a cavity with a 15% lower plasma density at the altitudes of the F2 layer and below; the formation of an area with plasma density increased by 12% at altitudes greater than 400 km. With a long-term quasiperiodic impact of the pump wave on the ionosphere, wavy large-scale electron-density perturbations (the meridional scale λx ≈ 130 km and the vertical scale λz ≈ 440 km) are also formed above the Sura facility. These perturbations can be due to the plasma density modulation by an artificial acoustic-gravity wave with a period of 10.6 m, which was formed by the heat source inside a large-scale cavity with low plasma density; there is generation of the electron density irregularities for the electrons with ΔNe/Ne ≈ 3% in the form of layers having the sizes 10-12 km along and about 24 km across the geomagnetic field, which are found both below and above the F2-layer maximum. The mechanisms of the formation of these plasma structures are discussed.

Decision-Making of Patients With Implantable Cardioverter-Defibrillators at End of Life: Family Members' Experiences.

PubMed

Lee, Mei Ching; Sulmasy, Daniel P; Gallo, Joseph; Kub, Joan; Hughes, Mark T; Russell, Stuart; Kellogg, Anela; Owens, Sharon G; Terry, Peter; Nolan, Marie T

2017-07-01

Many patients with advanced heart failure (HF) experience the life-extending benefits of implantable cardioverter-defibrillators (ICD), but at the end stage of HF, patients may experience shocks with increasing frequency and change the plan for end-of-life (EOL) care including the deactivation of the ICD. This report describes family members' experiences of patients with ICD making decisions at EOL. Understanding the decision-making of patients with ICD at EOL can promote informed decision-making and improve the quality of EOL care. This pilot study used a mixed methods approach to test the effects of a nurse-guided discussion in decision-making about ICD deactivation (turning off the defibrillation function) at the EOL. Interviews were conducted, audiotaped, and transcribed in 2012 to 2013 with 6 family members of patients with advanced HF and ICDs. Three researchers coded the data and identified themes in 2014. Three main themes described family members' experiences related to patients having HF with ICDs making health-care decision at EOL: decision-making preferences, patients' perception on ICD deactivation, and communication methods. Health-care providers need to have knowledge of patients' decision-making preferences. Preferences for decision-making include the allowing of appropriate people to involve and encourages direct conversation with family members even when advance directives is completed. Information of ICD function and the option of deactivation need to be clearly delivered to patients and family members. Education and guidelines will facilitate the communication of the preferences of EOL care.

Cryogen-free superconducting magnet system for multifrequency electron paramagnetic resonance up to 12.1 T

NASA Astrophysics Data System (ADS)

Smirnov, Alex I.; Smirnova, Tatyana I.; MacArthur, Ryan L.; Good, Jeremy A.; Hall, Renny

2006-03-01

Multifrequency and high field/high frequency (HF) electron paramagnetic resonance (EPR) is a powerful spectroscopy for studying paramagnetic spin systems ranging from organic-free radicals to catalytic paramagnetic metal ion centers in metalloproteins. Typically, HF EPR experiments are carried out at resonant frequencies ν =95-300GHz and this requires magnetic fields of 3.4-10.7T for electronic spins with g ≈2.0. Such fields could be easily achieved with superconducting magnets, but, unlike NMR, these magnets cannot operate in a persistent mode in order to satisfy a wide range of resonant fields required by the experiment. Operating and maintaining conventional passively cooled superconducting magnets in EPR laboratories require frequent transfer of cryogens by trained personnel. Here we describe and characterize a versatile cryogen-free magnet system for HF EPR at magnetic fields up to 12.1T that is suitable for ramping the magnetic field over the entire range, precision scans around the target field, and/or holding the field at the target value. We also demonstrate that in a nonpersistent mode of operation the magnetic field can be stabilized to better than 0.3ppm/h over 15h period by employing a transducer-controlled power supply. Such stability is sufficient for many HF EPR experiments. An important feature of the system is that it is virtually maintenance-free because it is based on a cryogen-free technology and therefore does not require any liquid cryogens (liquid helium or nitrogen) for operation. We believe that actively cooled superconducting magnets are ideally suited for a wide range of HF EPR experiments including studies of spin-labeled nucleic acids and proteins, single-molecule magnets, and metalloproteins.

Symptom burden in heart failure: assessment, impact on outcomes, and management.

PubMed

Alpert, Craig M; Smith, Michael A; Hummel, Scott L; Hummel, Ellen K

2017-01-01

Evidence-based management has improved long-term survival in patients with heart failure (HF). However, an unintended consequence of increased longevity is that patients with HF are exposed to a greater symptom burden over time. In addition to classic symptoms such as dyspnea and edema, patients with HF frequently suffer additional symptoms such as pain, depression, gastrointestinal distress, and fatigue. In addition to obvious effects on quality of life, untreated symptoms increase clinical events including emergency department visits, hospitalizations, and long-term mortality in a dose-dependent fashion. Symptom management in patients with HF consists of two key components: comprehensive symptom assessment and sufficient knowledge of available approaches to alleviate the symptoms. Successful treatment addresses not just the physical but also the emotional, social, and spiritual aspects of suffering. Despite a lack of formal experience during cardiovascular training, symptom management in HF can be learned and implemented effectively by cardiology providers. Co-management with palliative medicine specialists can add significant value across the spectrum and throughout the course of HF.

Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

NASA Astrophysics Data System (ADS)

Kirichok, A. V.; Kuklin, V. M.; Pryimak, A. V.; Zagorodny, A. G.

2015-09-01

The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

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

Kirichok, A. V., E-mail: sandyrcs@gmail.com; Kuklin, V. M.; Pryimak, A. V.

The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lowermore » than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.« less

Thermal Conductivity and Stability of HfO2-Y2O3 and La2Zr2O7 Evaluated for 1650 Deg C Thermal/Environmental Barrier Coating Applications

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Bansal, Narottam P.; Miller, Robert A.

2003-01-01

HfO2-Y2O3 and La2Zr2O7 are candidate thermal and environmental barrier coating (T/EBC) materials for gas turbine ceramic matrix composite (CMC) combustor applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature stability of hot-pressed and plasma sprayed specimens with representative partially-stabilized and fully-cubic HfO2-Y2O3 compositions and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasmasprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC hexoloy or SiC/SiC CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications are also discussed.

Long-term feeding of red algae (Gelidium amansii) ameliorates glucose and lipid metabolism in a high fructose diet-impaired glucose tolerance rat model.

PubMed

Liu, Hshuan-Chen; Chang, Chun-Ju; Yang, Tsung-Han; Chiang, Meng-Tsan

2017-07-01

This study was designed to investigate the effect of Gelidium amansii (GA) on carbohydrate and lipid metabolism in rats with high fructose (HF) diet (57.1% w/w). Five-week-old male Sprague-Dawley rats were fed a HF diet to induce glucose intolerance and hyperlipidemia. The experiment was divided into three groups: (1) control diet group (Con); (2) HF diet group (HF); and (3) HF with GA diet group (HF + 5% GA). The rats were fed the experimental diets and drinking water ad libitum for 23 weeks. The results showed that GA significantly decreased retroperitoneal fat mass weight of HF diet-fed rats. Supplementation of GA caused a decrease in plasma glucose, insulin, tumor necrosis factor-α, and leptin. HF diet increased hepatic lipid content. However, intake of GA reduced the accumulation of hepatic lipids including total cholesterol (TC) and triglyceride contents. GA elevated the excretion of fecal lipids and bile acid in HF diet-fed rats. Furthermore, GA significantly decreased plasma TC, triglyceride, low density lipoprotein plus very low density lipoprotein cholesterol, and TC/high density lipoprotein cholesterol ratio in HF diet-fed rats. HF diet induced an in plasma glucose and an impaired glucose tolerance, but GA supplementation decreased homeostasis model assessment equation-insulin resistance and improved impairment of glucose tolerance. Taken together, these results indicate that supplementation of GA can improve the impairment of glucose and lipid metabolism in an HF diet-fed rat model. Copyright © 2016. Published by Elsevier B.V.

Development of a practice tool for community-based nurses: the Heart Failure Palliative Approach to Care (HeFPAC).

PubMed

Strachan, Patricia H; Joy, Cathy; Costigan, Jeannine; Carter, Nancy

2014-04-01

Patients living with advanced heart failure (HF) require a palliative approach to reduce suffering. Nurses have described significant knowledge gaps about the disease-specific palliative care (PC) needs of these patients. An intervention is required to facilitate appropriate end-of-life care for HF patients. The purpose of this study was to develop a user-friendly, evidence-informed HF-specific practice tool for community-based nurses to facilitate care and communication regarding a palliative approach to HF care. Guided by the Knowledge to Action framework, we identified key HF-specific issues related to advanced HF care provision within the context of a palliative approach to care. Informed by current evidence and subsequent iterative consultation with community-based and specialist PC and HF nurses, a pocket guide tool for community-based nurses was created. We developed the Heart Failure Palliative Approach to Care (HeFPAC) pocket guide to promote communication and a palliative approach to care for HF patients. The HeFPAC has potential to improve the quality of care and experiences for patients with advanced HF. It will be piloted in community-based practice and in a continuing education program for nurses. The HeFPAC pocket guide offers PC nurses a concise, evidence-informed and practical point-of care tool to communicate with other clinicians and patients about key HF issues that are associated with improving disease-specific HF palliative care and the quality of life of patients and their families. Pilot testing will offer insight as to its utility and potential for modification for national and international use.

Crystallography of the NiHfSi Phase in a NiAl (0.5 Hf) Single-Crystal Alloy

NASA Technical Reports Server (NTRS)

Garg, A.; Noebe, R. D.; Darolia, R.

1996-01-01

Small additions of Hf to conventionally processed NiAl single crystals result in the precipitation of a high density of cuboidal G-phase along with a newly identified silicide phase. Both of these phases form in the presence of Si which is not an intentional alloying addition but is a contaminant resulting from contact with the ceramic shell molds during directional solidification of the single-crystal ingots. The morphology, crystal structure and Orientation Relationship (OR) of the silicide phase in a NiAl (0.5 at.%Hf) single-crystal alloy have been determined using transmission electron microscopy, electron microdiffraction and energy dispersive X-ray spectroscopy. Qualitative elemental analysis and indexing of the electron microdiffraction patterns from the new phase indicate that it is an orthorhombic NiHfSi phase with unit cell parameters, a = 0.639 nm, b = 0.389 nm and c = 0.72 nm, and space group Pnma. The NiHfSi phase forms as thin rectangular plates on NiAl/111/ planes with an OR that is given by NiHfSi(100))(parallel) NiAl(111) and NiHfSi zone axes(010) (parallel) NiAl zone axes (101). Twelve variants of the NiHfSi phase were observed in the alloy and the number of variants and rectangular morphology of NiHfSi plates are consistent with symmetry requirements. Quenching experiments indicate that nucleation of the NiHfSi phase in NiAI(Hf) alloys is aided by the formation of NiAl group of zone axes (111) vacancy loops that form on the NiAl /111/ planes.

Association of ambient particulate matter with heart failure incidence and all-cause readmissions in Tasmania: an observational study.

PubMed

Huynh, Quan L; Blizzard, Christopher Leigh; Marwick, Thomas H; Negishi, Kazuaki

2018-05-10

We sought to investigate the relationship between air quality and heart failure (HF) incidence and rehospitalisation to elucidate whether there is a threshold in this relationship and whether this relationship differs for HF incidence and rehospitalisation. This retrospective observational study was performed in an Australian state-wide setting, where air pollution is mainly associated with wood-burning for winter heating. Data included all 1246 patients with a first-ever HF hospitalisation and their 3011 subsequent all-cause readmissions during 2009-2012. Daily particulate matter <2.5 µm (PM 2.5 ), temperature, relative humidity and influenza infection were recorded. Poisson regression was used, with adjustment for time trend, public and school holiday and day of week. Tasmania has excellent air quality (median PM 2.5 =2.9 µg/m 3 (IQR: 1.8-6.0)). Greater HF incidences and readmissions occurred in winter than in other seasons (p<0.001). PM 2.5 was detrimentally associated with HF incidence (risk ratio (RR)=1.29 (1.15-1.42)) and weakly so with readmission (RR=1.07 (1.02-1.17)), with 1 day time lag. In multivariable analyses, PM 2.5 significantly predicted HF incidence (RR=1.12 (1.01-1.24)) but not readmission (RR=0.96 (0.89-1.04)). HF incidence was similarly low when PM <4 µg/m 3 and only started to rise when PM 2.5 ≥4 µg/m 3 . Stratified analyses showed that PM 2.5 was associated with readmissions among patients not taking beta-blockers but not among those taking beta-blockers (p interaction =0.011). PM 2.5 predicted HF incidence, independent of other environmental factors. A possible threshold of PM 2.5 =4 µg/m 3 is far below the daily Australian national standard of 25 µg/m 3 . Our data suggest that beta-blockers might play a role in preventing adverse association between air pollution and patients with HF. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

The Effect of Crataegus oxycantha Special Extract WSS 1442 on Clinical Progression in Patients with Mild to Moderate Symptoms of Heart Failure

PubMed Central

Zick, Suzanna M.; Gillespie, Brenda; Aaronson, Keith D.

2008-01-01

Aim To examine whether hawthorn (Crataegus Special Extract WS 1442 {CSE}) inhibits progression in heart failure (HF) patients. Methods We performed a retrospective analysis of data from the HERB CHF study in which patients with mild to moderate HF were randomised to either CSE 900 mg or placebo for 6 months. The primary outcome was time to progression of HF (HF death, hospitalisation, or sustained increase in diuretics) as assessed by log-rank tests and by Cox modelling. Results Progression of HF occurred in 46.6% of the CSE and 43.3% of the placebo groups (OR 1.14, 95% CI = 0.56, 2.35: p = 0.86). Patients receiving CSE were 3.9 times (95% CI = 1.1 – 13.7: p = 0.035) more likely to experience HF progression at baseline. In adjusted analysis, the risk of having early HF progression in the CSE group increased to 6.4 (95% CI = 1.5, 26.5: p = 0.011). In patients with LVEF 35%, those taking CSE were at significantly greater risk (3.2, 95% CI = 1.3, 8.3: p = 0.02) than the placebo group. Conclusions CSE does not reduce heart failure progression in patients who have HF. CSE appears to increase the early risk of HF progression. PMID:18490196

The anti-obesity effect of starch in a whole grain-like structural form.

PubMed

Luo, Kaiyun; Wang, Xufeng; Zhang, Genyi

2018-06-13

Obesity is a risk factor for many chronic diseases, and the anti-obesity effect of starch in a whole grain-like structural form (WGLSF) prepared through co-gelation with oat β-glucan and alginate was studied using high-fat (HF) induced obese male C57BL/6J mice. In vitro human fecal fermentation of WGLSF-starch showed a slower rate of fermentation and a higher production of butyric acid (132.0 μmol per 50 mg sample) when compared to the physical mixture counterpart of starch, β-glucan, and alginate (PM) (110.5 μmol per 50 mg) or β-glucan itself (96.2 μmol per 50 mg). The body weight gain of obese mice fed with a HF-WGLSF diet was significantly reduced (42.0% lower than the HF group, 30.2% lower than the physical mixture) with decreased cell size in white adipose tissue and similar levels of serum lipid profiles to the control of the low-fat (LF) group. Western blotting experiments showed the down-regulated lipogenic transcription factor of SREBP-1c and fatty acid synthase (FAS), but the lipid-oxidation related transcription factors of peroxisome proliferator-activated receptor-α (PPAR-α) and phosphorylated AMP-activated protein kinase (p-AMPK) were up-regulated. Energy metabolism analysis revealed increased lipid-sourced energy expenditure with higher heat production and respiratory exchange ratios. Consistently, the expression of hypothalamic pro-opiomelanocortin (POMC), favoring energy expenditure, was increased significantly while the neuropeptide Y (NPY) was reduced. Thus, the increased energy expenditure stimulated by starch in a whole-grain-like structural form is responsible for the reduced body weight gain of obese mice fed with a high fat-based diet.

Multi-angle Spectra Evolution of Langmuir Turbulence Excited by RF Ionospheric Interactions at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Rayyan, N.; Watkins, B. J.; Bristow, W. A.; Spaleta, J.; Watanabe, N.; Golkowski, M.; Bernhardt, P. A.

2013-12-01

The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. Among the effects observed and studied are: SLT spectra including cascade, collapse, and co-existence spectra and an outshifted plasma line under certain ionospheric conditions. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Bursty turbulence is observed in the collapse and cascade lines. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

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

Soares Azevedo e Silva, Paulo Ricardo, E-mail: paulori@alunos.eel.usp.br; Baldan, Renato, E-mail: renato@ppgem.eel.usp.br; Nunes, Carlos Angelo, E-mail: cnunes@demar.eel.usp.br

MAR-M247 superalloy has excellent mechanical properties and good oxidation resistance at elevated temperatures. Niobium is an element known as {gamma} Prime phase hardener in nickel-based superalloys, besides promoting homogeneous distribution of MC carbides. This work is inserted in a project that aims to evaluate the total replacement of tantalum by niobium atoms in MAR-M247 superalloy (10.2 Co, 10.2 W, 8.5Cr, 5.6 Al, 1.6 Nb, 1.4 Hf, 1.1 Ti, 0.7 Mo, 0.15 C, 0.06 Zr, 0.015 B, Ni balance-wt.%). Based on microstructural characterizations (SEM and FEG-SEM, both with EDS) of the as-cast material and heat-treated materials as well as utilizing Thermocalcmore » simulations and experiments of differential thermal analysis (DTA), heat-treatment at 1260 Degree-Sign C for 8 h was chosen as an ideal condition for the solution of Nb-modified MAR-M247 superalloy. The hardness of as-cast and ideally solution treated materials was 390 {+-} 14 HV and 415 {+-} 6 HV, respectively. - Highlights: Black-Right-Pointing-Pointer DTA and microstructure of MAR-M247(Nb) showed a good agreement with Thermocalc. Black-Right-Pointing-Pointer An ideal condition for solution heat-treatment of MAR-M247(Nb) is 1260 Degree-Sign C for 8 h. Black-Right-Pointing-Pointer It was an observed evidence of incipient melting in samples heat-treated at 1280 Degree-Sign C.« less

HF Accelerated Electron Fluxes, Spectra, and Ionization

NASA Astrophysics Data System (ADS)

Carlson, Herbert C.; Jensen, Joseph B.

2015-10-01

Wave particle interactions, an essential aspect of laboratory, terrestrial, and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth's weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich in Usp Fizicheskikh Nauk 177(11):1145-1177, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al. in J Atmos Terr Phys 44:1089-1100, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~eV, but instead to -100 times thermal energy (10 s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich et al (J Atmos Terr Phys 47:1057-1070, 1985) quantified the theory of this transport effect. Merging experiment with theory in plasma physics and aeronomy, enabled prediction (Carlson in Adv Space Res 13:1015-1024, 1993) of creating artificial ionospheres once ~GW HF effective radiated power could be achieved. Eventual confirmation of this prediction (Pedersen et al. in Geophys Res Lett 36:L18107, 2009; Pedersen et al. in Geophys Res Lett 37:L02106, 2010; Blagoveshchenskaya et al. in Ann Geophys 27:131-145, 2009) sparked renewed interest in optical inversion to estimate electron spectra in terrestrial (Hysell et al. in J Geophys Res Space Phys 119:2038-2045, 2014) and planetary (Simon et al. in Ann Geophys 29:187-195, 2011) atmospheres. Here we present our unpublished optical data, which combined with our modeling, lead to conclusions that should meaningfully improve future estimates of the spectrum of HF accelerated electron fluxes. Photometric imaging data can significantly improve detection of emissions near ionization threshold, and confirm depth of penetration of accelerated electrons many km below the excitation altitude. Comparing observed to modeled emission altitude shows future experiments need electron density profiles to derive more accurate HF electron flux spectra.

Airglow during ionospheric modifications by the sura facility radiation. experimental results obtained in 2010

NASA Astrophysics Data System (ADS)

Grach, S. M.; Klimenko, V. V.; Shindin, A. V.; Nasyrov, I. A.; Sergeev, E. N.; A. Yashnov, V.; A. Pogorelko, N.

2012-06-01

We present the results of studying the structure and dynamics of the HF-heated volume above the Sura facility obtained in 2010 by measurements of ionospheric airglow in the red (λ = 630 nm) and green (λ = 557.7 nm) lines of atomic oxygen. Vertical sounding of the ionosphere (followed by modeling of the pump-wave propagation) and measurements of stimulated electromagnetic emission were used for additional diagnostics of ionospheric parameters and the processes occurring in the heated volume.

Research on Molecular Lasers

DTIC Science & Technology

1974-11-01

double resonance experiments to study vibration to rotation energy transfer; chemical laser initiation and pumping by electrical discharges in...8217) + HF(v=0,J2’). (7) Ihe experiment consists of the use of one HF laser to pump the IIFfv^jp molecules in less than 500 nanoseconds and the...each stage of diöüUaUcm, Ihc mid- dle 90’c of the .-.ample was rolained." The distilled sam- ple was condensed and pumped on at TV K in r

Examining mortality among formerly homeless adults enrolled in Housing First: An observational study.

PubMed

Henwood, Benjamin F; Byrne, Thomas; Scriber, Brynn

2015-12-04

Adults who experience prolonged homelessness have mortality rates 3 to 4 times that of the general population. Housing First (HF) is an evidence-based practice that effectively ends chronic homelessness, yet there has been virtually no research on premature mortality among HF enrollees. In the United States, this gap in the literature exists despite research that has suggested chronically homeless adults constitute an aging cohort, with nearly half aged 50 years old or older. This observational study examined mortality among formerly homeless adults in an HF program. We examined death rates and causes of death among HF participants and assessed the timing and predictors of death among HF participants following entry into housing. We also compared mortality rates between HF participants and (a) members of the general population and (b) individuals experiencing homelessness. We supplemented these analyses with a comparison of the causes of death and characteristics of decedents in the HF program with a sample of adults identified as homeless in the same city at the time of death through a formal review process. The majority of decedents in both groups were between the ages of 45 and 64 at their time of death; the average age at death for HF participants was 57, compared to 53 for individuals in the homeless sample. Among those in the HF group, 72% died from natural causes, compared to 49% from the homeless group. This included 21% of HF participants and 7% from the homeless group who died from cancer. Among homeless adults, 40% died from an accident, which was significantly more than the 14% of HF participants who died from an accident. HIV or other infectious diseases contributed to 13% of homeless deaths compared to only 2% of HF participants. Hypothermia contributed to 6% of homeless deaths, which was not a cause of death for HF participants. Results suggest HF participants face excess mortality in comparison to members of the general population and that mortality rates among HF participants are higher than among those reported among members of the general homeless population in prior studies. However, findings also suggest that causes of death may differ between HF participants and their homeless counterparts. Specifically, chronic diseases appear to be more prominent causes of death among HF participants, indicating the potential need for integrating medical support and end-of-life care in HF.

High temperature calorimetric studies of heat of solution of NiO, CuO, La2O3, TiO2, HfO2 in sodium silicate liquids

NASA Astrophysics Data System (ADS)

Linard, Yannick; Wilding, Martin C.; Navrotsky, Alexandra

2008-01-01

The enthalpies of solution of La2O3, TiO2, HfO2, NiO and CuO were measured in sodium silicate melts at high temperature. When the heat of fusion was available, we derived the corresponding liquid-liquid enthalpies of mixing. These data, combined with previously published work, provide insight into the speciation reactions in sodium silicate melts. The heat of solution of La2O3 in these silicate solvents is strongly exothermic and varies little with La2O3 concentration. The variation of heat of solution with composition of the liquid reflects the ability of La(III) to perturb the transient silicate framework and compete with other cations for oxygen. The enthalpy of solution of TiO2 is temperature-dependent and indicates that the formation of Na-O-Si species is favored over Na-O-Ti at low temperature. The speciation reactions can be interpreted in terms of recent spectroscopic studies of titanium-bearing melts which identify a dual role of Ti4+ as both a network-former end network-modifier. The heats of solution of oxides of transition elements (Ni and Cu) are endothermic, concentration-dependent and reach a maximum with concentration. These indicate a charge balanced substitution which diminishes the network modifying role of Na+ by addition of Ni2+ or Cu2+. The transition metal is believed to be in tetrahedral coordination, charge balanced by the sodium cation in the melts.

Beating HF waves to generate VLF waves in the ionosphere

NASA Astrophysics Data System (ADS)

Kuo, Spencer; Snyder, Arnold; Kossey, Paul; Chang, Chia-Lie; Labenski, John

2012-03-01

Beat-wave generation of very low frequency (VLF) waves by two HF heaters in the ionosphere is formulated theoretically and demonstrated experimentally. The heater-induced differential thermal pressure force and ponderomotive force, which dominate separately in the D and F regions of the ionosphere, drive an electron current for the VLF emission. A comparison, applying appropriate ionospheric parameters shows that the ponderomotive force dominates in beat-wave generation of VLF waves. Three experiments, one in the nighttime in the absence of D and E layers and two in the daytime in the presence of D and E layers, were performed. X mode HF heaters of slightly different frequencies were transmitted at CW full power. VLF waves at 10 frequencies ranging from 3.5 to 21.5 kHz were generated. The frequency dependencies of the daytime and nighttime radiation intensities are quite similar, but the nighttime radiation is much stronger than the daytime one at the same radiation frequency. The intensity ratio is as large as 9 dB at 11.5 kHz. An experiment directly comparing VLF waves generated by the beat-wave approach and by the amplitude modulation (AM) approach was also conducted. The results rule out the likely contribution of the AM mechanism acting on the electrojet and indicate that beat-wave in the VLF range prefers to be generated in the F region of the ionosphere through the ponderomotive nonlinearity, consistent with the theory. In the nighttime experiment, the ionosphere was underdense to the HF heaters, suggesting a likely setting for effective beat-wave generation of VLF waves by the HF heaters.

Nonlinear plasma experiments in geospace with gigawatts of RF power at HAARP

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

Sheerin, J. P., E-mail: jsheerin@emich.edu; Cohen, Morris B., E-mail: mcohen@gatech.edu

2015-12-10

The ionosphere is the ionized uppermost layer of our atmosphere (from 70 – 500 km altitude) where free electron densities yield peak critical frequencies in the HF (3 – 30 MHz) range. The ionosphere thus provides a quiescent plasma target, stable on timescales of minutes, for a whole host of active plasma experiments. High power RF experiments on ionospheric plasma conducted in the U.S. have been reported since 1970. The largest HF transmitter built to date is the HAARP phased-array HF transmitter near Gakona, Alaska which can deliver up to 3.6 Gigawatts (ERP) of CW RF power in the range of 2.8more » – 10 MHz to the ionosphere with microsecond pointing, power modulation, and frequency agility. With an ionospheric background thermal energy in the range of only 0.1 eV, this amount of power gives access to the highest regimes of the nonlinearity (RF intensity to thermal pressure) ratio. HAARP’s unique features have enabled the conduct of a number of unique nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including generation of artificial aurorae, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, parametric instabilities, stimulated electromagnetic emissions (SEE), strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the HF-enhanced plasma line, and production of suprathermal electrons. One of the primary missions of HAARP, has been the generation of ELF (300 – 3000 Hz) and VLF (3 – 30 kHz) radio waves which are guided to global distances in the Earth-ionosphere waveguide. We review recent efforts to improve the efficiency of the generation ELF/VLF and develop alternative mechanisms that do not require a natural ionospheric current. Applications include the controlled study of ionospheric irregularities affecting spacecraft communication and navigation systems.« less

Nonlinear plasma experiments in geospace with gigawatts of RF power at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Cohen, Morris B.

2015-12-01

The ionosphere is the ionized uppermost layer of our atmosphere (from 70 - 500 km altitude) where free electron densities yield peak critical frequencies in the HF (3 - 30 MHz) range. The ionosphere thus provides a quiescent plasma target, stable on timescales of minutes, for a whole host of active plasma experiments. High power RF experiments on ionospheric plasma conducted in the U.S. have been reported since 1970. The largest HF transmitter built to date is the HAARP phased-array HF transmitter near Gakona, Alaska which can deliver up to 3.6 Gigawatts (ERP) of CW RF power in the range of 2.8 - 10 MHz to the ionosphere with microsecond pointing, power modulation, and frequency agility. With an ionospheric background thermal energy in the range of only 0.1 eV, this amount of power gives access to the highest regimes of the nonlinearity (RF intensity to thermal pressure) ratio. HAARP's unique features have enabled the conduct of a number of unique nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including generation of artificial aurorae, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, parametric instabilities, stimulated electromagnetic emissions (SEE), strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the HF-enhanced plasma line, and production of suprathermal electrons. One of the primary missions of HAARP, has been the generation of ELF (300 - 3000 Hz) and VLF (3 - 30 kHz) radio waves which are guided to global distances in the Earth-ionosphere waveguide. We review recent efforts to improve the efficiency of the generation ELF/VLF and develop alternative mechanisms that do not require a natural ionospheric current. Applications include the controlled study of ionospheric irregularities affecting spacecraft communication and navigation systems.

Bistatic radar sea state monitoring

NASA Technical Reports Server (NTRS)

Ruck, G. T.; Barrick, D. E.; Kaliszewski, T.

1972-01-01

Bistatic radar techniques were examined for remote measurement of the two-dimensional surface wave height spectrum of the ocean. One technique operates at high frequencies (HF), 3-30 MHz, and the other at ultrahigh frequencies (UHF), approximately 1 GHz. Only a preliminary theoretical examination of the UHF technique was performed; however the principle underlying the HF technique was demonstrated experimentally with results indicating that an HF bistatic system using a surface transmitter and an orbital receiver would be capable of measuring the two-dimensional wave height spectrum in the vicinity of the transmitter. An HF bistatic system could also be used with an airborne receiver for ground truth ocean wave spectrum measurements. Preliminary system requirements and hardware configurations are discussed for both an orbital system and an aircraft verification experiment.

Differences in response to corticotropin-releasing factor after short- and long-term consumption of a high-fat diet.

PubMed

Legendre, Ariadne; Papakonstantinou, Emilia; Roy, Marie-Claude; Richard, Denis; Harris, Ruth B S

2007-09-01

We previously reported an exaggerated endocrine and weight loss response to stress in rats fed a high-fat (HF) diet for 5 days. Others report blunted stress-induced anxiety in rats made obese on a HF diet. Experiments described here tested whether sensitivity to stress-related peptides was changed in obese and nonobese HF-fed rats. Third ventricle infusion of corticotropin-releasing factor (CRF) in rats made obese on HF diet (40% kcal fat) produced an exaggerated hypophagia, which is thought to be mediated by CRF(2) receptors. Obese rats responded to a lower dose of CRF for a longer time than rats fed a low-fat (LF) diet (12% kcal fat). CRF-induced release of corticosterone, which is thought to be mediated by CRF(1) receptors, was not exaggerated in obese HF-fed rats. In contrast, rats fed HF diet for 5 days showed the same food intake and corticosterone response to CRF as LF-fed rats. CRF mRNA expression in the paraventricular nucleus of the hypothalamus was stimulated by mild stress (ip saline injection and placement in a novel cage) in LF-fed rats but not in rats fed HF diet for 5 days because of a nonsignificant increase in expression in nonstressed HF-fed rats. In addition, nonstressed levels of urocortin (UCN) I mRNA expression in the Edinger-Westphal nucleus were significantly inhibited in HF-fed rats. These data suggest that rats that have become obese on a HF diet show a change in responsiveness to stress peptides, whereas the increased stress response in nonobese HF-fed rats may be associated with changes in basal CRF and UCN I mRNA expression.

Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations

NASA Astrophysics Data System (ADS)

Harrison, Jeremy J.; Chipperfield, Martyn P.; Boone, Christopher D.; Dhomse, Sandip S.; Bernath, Peter F.; Froidevaux, Lucien; Anderson, John; Russell, James, III

2016-08-01

The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Many of these fluorine-containing species deplete stratospheric ozone and are regulated by the Montreal Protocol. Once in the atmosphere they slowly degrade, ultimately leading to the formation of hydrogen fluoride (HF), the dominant reservoir of stratospheric fluorine due to its extreme stability. Monitoring the growth of stratospheric HF is therefore an important marker for the success of the Montreal Protocol. We report the comparison of global distributions and trends of HF measured in the Earth's atmosphere by the satellite remote-sensing instruments ACE-FTS (Atmospheric Chemistry Experiment Fourier transform spectrometer), which has been recording atmospheric spectra since 2004, and HALOE (HALogen Occultation Experiment), which recorded atmospheric spectra between 1991 and 2005, with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the agreement between observation and model is good, although the ACE-FTS measurements are biased high by ˜ 10 % relative to HALOE. The observed global HF trends reveal a substantial slowing down in the rate of increase of HF since the 1990s: 4.97 ± 0.12 % year-1 (1991-1997; HALOE), 1.12 ± 0.08 % year-1 (1998-2005; HALOE), and 0.52 ± 0.03 % year-1 (2004-2012; ACE-FTS). In comparison, SLIMCAT calculates trends of 4.01, 1.10, and 0.48 % year-1, respectively, for the same periods; the agreement is very good for all but the earlier of the two HALOE periods. Furthermore, the observations reveal variations in the HF trends with latitude and altitude; for example, between 2004 and 2012 HF actually decreased in the Southern Hemisphere below ˜ 35 km. An additional SLIMCAT simulation with repeating meteorology for the year 2000 produces much cleaner trends in HF with minimal variations with latitude and altitude. Therefore, the variations with latitude and altitude in the observed HF trends are due to variability in stratospheric dynamics on the timescale of a few years. Overall, the agreement between observation and model points towards the ongoing success of the Montreal Protocol and the usefulness of HF as a metric for stratospheric fluorine.

Stability of Ceramics in Hydrogen between 4000 and 4500 F

NASA Technical Reports Server (NTRS)

May, Charles E.; Koneval, Donald; Fryburg, George C.

1959-01-01

The various reactions that are possible between hydrogen and certain ceramic materials are discussed as well as the means of measuring the extent of such reactions. Powdered carbides, nitrides, borides, and oxides were tested. These materials were heated inductively in a tungsten cup between 4000 and 4500 F for two 1-hour periods under a static hydrogen atmosphere. Weight, pressure, and diffraction pattern changes were observed, and these served to indicate the extent of reaction. Most of the ceramics, HfC, ZrC, TiC, TaC, NbC, WC, MO2C, HfN, ZrN, NbN, ZrB2, NbB2, and WB, showed less reaction than the minimum detectable value. However, the ceramics, TiN, TaN, HfB2, TiB2, ZrO2, and Cr2O3, apparently reacted to a measurable extent with hydrogen. Reactions of SiC, VC, and TaB2 with hydrogen were not determinable because of their incompatibility with the tungsten container.

Transequatorial Propagation and Depletion Precursors

NASA Astrophysics Data System (ADS)

Miller, E. S.; Bust, G. S.; Kaeppler, S. R.; Frissell, N. A.; Paxton, L. J.

2014-12-01

The bottomside equatorial ionosphere in the afternoon and evening sector frequently evolves rapidly from smoothly stratified to violently unstable with large wedges of depleted plasma growing through to the topside on timescales of a few tens of minutes. These depletions have numerous practical impacts on radio propagation, including amplitude scintillation, field-aligned irregularity scatter, HF blackouts, and long-distance transequatorial propagation at frequencies above the MUF. Practical impacts notwithstanding, the pathways and conditions under which depletions form remain a topic of vigorous inquiry some 80 years after their first report. Structuring of the pre-sunset ionosphere---morphology of the equatorial anomalies and long-wavelength undulations of the isodensity contours on the bottomside---are likely to hold some clues to conditions that are conducive to depletion formation. The Conjugate Depletion Experiment is an upcoming transequatorial forward-scatter HF/VHF experiment to investigate pre-sunset undulations and their connection with depletion formation. We will present initial results from the Conjugate Depletion Experiment, as well as a companion analysis of a massive HF propagation data set.

Transforming the culture of surgical education: promoting teacher identity through human factors training.

PubMed

Cahan, Mitchell A; Starr, Susan; Larkin, Anne C; Litwin, Demetrius E M; Sullivan, Kate M; Quirk, Mark E

2011-07-01

Promoting a culture of teaching may encourage students to choose a surgical career. Teaching in a human factors (HF) curriculum, the nontechnical skills of surgery, is associated with surgeons' stronger identity as teachers and with clinical students' improved perception of surgery and satisfaction with the clerkship experience. To describe the effects of an HF curriculum on teaching culture in surgery. Surgeons and educators developed an HF curriculum including communication, teamwork, and work-life balance. Teacher identity, student interest in a surgical career, student perception of the HF curriculum, and teaching awards. Ninety-two of 123 faculty and residents in a single program (75% of total) completed a survey on teacher identity. Fifteen of the participants were teachers of HF. Teachers of HF scored higher than control participants on the total score for teacher identity (P < .001) and for subcategories of global teacher identity (P = .001), intrinsic satisfaction (P = .001), skills and knowledge (P = .006), belonging to a group of teachers (P < .001), feeling a responsibility to teach (P = .008), receiving rewards (P =.01), and HF (P = .02). Third-year clerks indicated that they were more likely to select surgery as their career after the clerkship and rated the curriculum higher when it was taught by surgeons than when taught by educators. Of the teaching awards presented to surgeons during HF years, 100% of those awarded to attending physicians and 80% of those awarded to residents went to teachers of HF. Curricular focus on HF can strengthen teacher identity, improve teacher evaluations, and promote surgery as a career choice.

Home care nurses' knowledge of evidence-based education topics for management of heart failure.

PubMed

Delaney, Colleen; Apostolidis, Beka; Lachapelle, Leeanne; Fortinsky, Richard

2011-01-01

We primarily sought to evaluate home care nurses' knowledge of evidence-based education topics in managing heart failure (HF). Moreover, we wanted to determine if differences were evident in nurses' knowledge based on education and work experience, and to identify home care nurses' specific educational needs. A cross-sectional survey design was used. Home care nurses (n = 94) were recruited from 4 home care agencies. A previously published 20-item HF knowledge questionnaire was administered to participants, and an open-ended question determined participants' need for further HF-related education. Home care nurses' scores demonstrated a 78.9% knowledge level in overall HF education principles. The mean HF knowledge score was 15.78 (SD, ±1.69) out of a possible 20 points. Nurses scored lowest on knowledge related to asymptomatic hypotension (24.5% answered correctly), daily weight monitoring (26.6% answered correctly), and transient dizziness (30.9% answered correctly). Nurses requested further information on all HF topics addressed in the survey as well as on psychosocial issues, research evidence, and more information from other healthcare providers. Our findings suggest that home care nurses may not be sufficiently knowledgeable in evidence-based education topics for managing HF. The results help confirm the need to develop educational programs for home care nurses in managing HF, which may lead to improved quality of patient education. Further research is needed to address specific deficits in the knowledge of home care nurses, and to determine if HF educational programs for nurses would enhance and sustain nurses' knowledge of HF management education. Copyright © 2011 Elsevier Inc. All rights reserved.

Electron Acceleration and Ionization Production in High-Power Heating Experiments at HAARP

NASA Astrophysics Data System (ADS)

Mishin, E. V.; Pedersen, T.

2012-12-01

Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60-80 km. Artificial ionization production is indicated by significant 427.8 nm emissions from the 1st negative band of N2+ and the appearance of transmitter-induced bottomside traces in ionosonde data during the periods of most intense optical emissions. However, the exact mechanisms producing the artificial plasmas remain to be determined. Yet the only existing theoretical models explain the development of artificial plasma as an ionizing wavefront moving downward due to ionization by electrons accelerated by HF-excited strong Langmuir turbulence (SLT) generated near the plasma resonance, where the pump frequency matches the plasma frequency. However, the observations suggest also the significance of interactions with upper hybrid and electron Bernstein waves near multiples of the electron gyrofrequency. We describe recent observations and discuss suitable acceleration mechanisms.

Artificial plasma jet in the ionosphere

NASA Astrophysics Data System (ADS)

Haerendel, G.; Sagdeev, R. Z.

The dynamics of an artificially injected plasma beam in the near-earth space are analyzed in terms of the beam structure, its propagation across the magnetic field, and the resulting wave phenomena (Porcupine Project, flight 4, March 31, 1979). Out of the four ejectable canisters attached to the main payload, two were instrumented by the U.S., one by the USSR (the Xenon plasma beam experiment), and one by West Germany (carrying a barium ion jet experiment). The propagation of the plasma seems to occur in three stages, with high-frequency broad-band oscillations mainly localized in the 'core' of the jet, while low-frequency oscillations were spatially separated from it. The generation region of LF oscillations was found to be much wider than the jet core. As a result of the interaction between the plasma beam and the ambient medium a heating of electrons, up to energies of about 20 eV, associated with LF noise was observed. The behavior of high-energy ions and the observed HF wave phenomena need further analysis.

[INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

NASA Astrophysics Data System (ADS)

Gamaly, Eugene G.; Rode, Andrei V.

2016-08-01

Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval's axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

Impacts of distinct observations during the 2009 Prince William Sound field experiment: A data assimilation study

NASA Astrophysics Data System (ADS)

Li, Z.; Chao, Y.; Farrara, J.; McWilliams, J. C.

2012-12-01

A set of data assimilation experiments, known as Observing System Experiments (OSEs), are performed to assess the relative impacts of different types of observations acquired during the 2009 Prince William Sound Field Experiment. The observations assimilated consist primarily of three types: High Frequency (HF) radar surface velocities, vertical profiles of temperature/salinity (T/S) measured by ships, moorings, Autonomous Underwater Vehicles and gliders, and satellite sea surface temperatures (SSTs). The impact of all the observations, HF radar surface velocities, and T/S profiles is assessed. Without data assimilation, a frequently occurring cyclonic eddy in the central Sound is overly persistent and intense. The assimilation of the HF radar velocities effectively reduces these biases and improves the representation of the velocities as well as the T/S fields in the Sound. The assimilation of the T/S profiles improves the large scale representation of the temperature/salinity and also the velocity field in the central Sound. The combination of the HF radar surface velocities and sparse T/S profiles results in an observing system capable of representing the circulation in the Sound reliably and thus producing analyses and forecasts with useful skill. It is suggested that a potentially promising observing network could be based on satellite SSHs and SSTs along with sparse T/S profiles, and future satellite SSHs with wide swath coverage and higher resolution may offer excellent data that will be of great use for predicting the circulation in the Sound.

The Structure of Liquid and Amorphous Hafnia.

PubMed

Gallington, Leighanne C; Ghadar, Yasaman; Skinner, Lawrie B; Weber, J K Richard; Ushakov, Sergey V; Navrotsky, Alexandra; Vazquez-Mayagoitia, Alvaro; Neuefeind, Joerg C; Stan, Marius; Low, John J; Benmore, Chris J

2017-11-10

Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf-O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that show density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf-Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf-Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO 6,7 polyhedra resembling that observed in the monoclinic phase.

High- and low-frequency transcutaneous electrical nerve stimulation does not reduce experimental pain in elderly individuals

PubMed Central

Bergeron-Vézina, Kayla; Corriveau, Hélène; Martel, Marylie; Harvey, Marie-Philippe; Léonard, Guillaume

2015-01-01

Abstract Despite its widespread clinical use, the efficacy of transcutaneous electrical nerve stimulation (TENS) remains poorly documented in elderly individuals. In this randomized, double-blind crossover study, we compared the efficacy of high-frequency (HF), low-frequency (LF), and placebo (P) TENS in a group of 15 elderly adults (mean age: 67 ± 5 years). The effect of HF-, LF-, and P-TENS was also evaluated in a group of 15 young individuals (26 ± 5 years; same study design) to validate the effectiveness of the TENS protocols that were used in the elderly group. Each participant came to the laboratory on 3 separate occasions to receive, in random order, HF-, LF-, and P-TENS. Pain intensity and pain perception thresholds were assessed before, during, and after TENS, using an experimental heat pain paradigm. For the young group, there was a significant decrease in pain intensity during and after HF- and LF-TENS when compared with baseline, with both HF- and LF-TENS being superior to P-TENS. In the older group, HF- and LF-TENS did not reduce pain when compared with baseline and no difference was observed between the 2 active TENS sessions and P-TENS. High-frequency, LF-, and P-TENS all increased pain thresholds in young individuals, whereas in older individuals, only LF-TENS increased pain thresholds. Taken together, these results suggest that TENS is effective in young, but not in older, individuals. Future studies should be conducted to confirm these results in pain populations and to identify strategies that could enhance the effect of TENS in the elderly. PMID:26101836

An on-line push/pull perfusion-based hollow-fiber liquid-phase microextraction system for high-performance liquid chromatographic determination of alkylphenols in water samples.

PubMed

Chao, Yu-Ying; Jian, Zhi-Xuan; Tu, Yi-Ming; Wang, Hsaio-Wen; Huang, Yeou-Lih

2013-06-07

In this study, we employed a novel on-line method, push/pull perfusion hollow-fiber liquid-phase microextraction (PPP-HF-LPME), to extract 4-tert-butylphenol, 2,4-di-tert-butylphenol, 4-n-nonylphenol, and 4-n-octylphenol from river and tap water samples; we then separated and quantified the extracted analytes through high-performance liquid chromatography (HPLC). Using this approach, we overcame the problem of fluid loss across the porous HF membrane to the donor phase, permitting on-line coupling of HF-LPME to HPLC. In our PPP-HF-LPME system, we used a push/pull syringe pump as the driving source to perfuse the acceptor phase, while employing a heating mantle and an ultrasonic probe to accelerate mass transfer. We optimized the experimental conditions such as the nature of the HF supported intermediary phase and the acceptor phase, the composition of the donor and acceptor phases, the sample temperature, and the sonication conditions. Our proposed method provided relative standard deviations of 3.1-6.2%, coefficients of determination (r(2)) of 0.9989-0.9998, and limits of detection of 0.03-0.2 ng mL(-1) for the analytes under the optimized conditions. When we applied this method to analyses of river and tap water samples, our results confirmed that this microextraction technique allows reliable monitoring of alkylphenols in water samples.

Numerical simulation of the plasma thermal disturbances during ionospheric modification experiments at the SURA heating facility

NASA Astrophysics Data System (ADS)

Belov, Alexey; Huba, J. D.

indent=1cm We present the results of numerical simulation of the near-Earth plasma disturbances produced by resonant heating of the ionospheric F-region by high-power HF radio emission from the SURA facility. The computational model is based on the modified version of the SAMI2 code (release 1.00). The model input parameters are appropriated to the conditions of the SURA-DEMETER experiment. In this work, we study the spatial structure and temporal characteristics of stimulated large-scale disturbances of the electron number density and temperature. It is shown that the stimulated disturbances are observed throughout the ionosphere. Disturbances are recorded both in the region below the pump wave reflection level and in the outer ionosphere (up to 3000 km). At the DEMETER altitude, an increase in the ion number density is stipulated by the oxygen ions O (+) , whereas the number density of lighter H (+) ions decreases. A typical time of the formation of large-scale plasma density disturbances in the outer ionosphere is 2-3 min. After the heater is turned off, the disturbances relaxation time is approximately 30 min. The simulation results are important for planning future promising experiments on the formation of ionospheric artificial density ducts. This work was supported by the Russian Foundation for Basic Research (project No. 12-02-00747-a), and the Government of the Russian Federation (contract No. 14.B25.31.0008).

Understanding palliative care on the heart failure care team: an innovative research methodology.

PubMed

Lingard, Lorelei A; McDougall, Allan; Schulz, Valerie; Shadd, Joshua; Marshall, Denise; Strachan, Patricia H; Tait, Glendon R; Arnold, J Malcolm; Kimel, Gil

2013-05-01

There is a growing call to integrate palliative care for patients with advanced heart failure (HF). However, the knowledge to inform integration efforts comes largely from interview and survey research with individual patients and providers. This work has been critically important in raising awareness of the need for integration, but it is insufficient to inform solutions that must be enacted not by isolated individuals but by complex care teams. Research methods are urgently required to support systematic exploration of the experiences of patients with HF, family caregivers, and health care providers as they interact as a care team. To design a research methodology that can support systematic exploration of the experiences of patients with HF, caregivers, and health care providers as they interact as a care team. This article describes in detail a methodology that we have piloted and are currently using in a multisite study of HF care teams. We describe three aspects of the methodology: the theoretical framework, an innovative sampling strategy, and an iterative system of data collection and analysis that incorporates four data sources and four analytical steps. We anticipate that this innovative methodology will support groundbreaking research in both HF care and other team settings in which palliative integration efforts are emerging for patients with advanced nonmalignant disease. Copyright © 2013 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved.

Thermophysical properties of 22 pure metals in the solid and liquid state - The pulse-heating data collection

NASA Astrophysics Data System (ADS)

Hüpf, T.; Cagran, C.; Pottlacher, G.

2011-05-01

The workgroup of subsecond thermophysics in Graz has a long tradition in performing fast pulseheating experiments on metals and alloys. Thereby, wire-shaped specimens are rapidly heated (108 K/s) by a large current-pulse (104 A). This method provides thermophysical properties like volume-expansion, enthalpy and electrical resistivity up to the end of the liquid phase. Today, no more experiments on pure metals are to be expected, because almost all elements, which are suitable for pulse-heating so far, have been investigated. The requirements for pulse-heating are: a melting point which is high enough to enable pyrometric temperature measurements and the availability of wire-shaped specimens. These elements are: Co, Cu, Au, Hf, In, Ir, Fe, Pb, Mo, Ni, Nb, Pd, Pt, Re, Rh, Ag, Ta, Ti, W, V, Zn, and Zr. Hence, it is the correct time to present the results in a collected form. We provide data for the above mentioned quantities together with basic information on each material. The uniqueness of this compilation is the high temperature range covered and the homogeneity of the measurement conditions (the same method, the same laboratory, etc.). The latter makes it a good starting point for comparative analyses (e.g. a comparison of all 22 enthalpy traces is in first approximation conform with the rule of Dulong-Petit which states heat capacity - the slope of enthalpy traces - as a function of the number of atoms). The data is useful for input parameters in numerical simulations and it is a major purpose of our ongoing research to provide data for simulations of casting processes for the metal working industry. This work demonstrates some examples of how a data compilation like this can be utilized. Additionally, the latest completive measurement results on Ag, Ni, Ti, and Zr are described.

Structural and functional alterations in the atrioventricular node and atrioventricular ring tissue in ischaemia-induced heart failure.

PubMed

Yanni, Joseph; Maczewski, Michal; Mackiewicz, Urszula; Siew, Samuel; Fedorenko, Olga; Atkinson, Andrew; Price, Marcus; Beresewicz, Andrzej; Anderson, Robert H; Boyett, Mark R; Dobrzynski, Halina

2014-07-01

Heart failure (HF) causes dysfunction of the atrioventricular node (AVN) - first or second-degree heart block is a risk factor for sudden cardiac death in HF patients. The aim of the study was to determine if HF causes remodelling of the AVN and right atrioventricular ring (RAVR). HF was induced in rats (n=4) by ligation of the proximal left coronary artery, which resulted in a large infarct of the left ventricle. Sham-operated rats (n=4) were used as controls. Eight weeks after surgery, functional experiments were performed and the hearts were frozen. The body weight of HF rats was similar to control rats, but the mean heart weight of HF rats was significantly enlarged. In HF rats compared to controls, the left ventricle was dilated, left ventricular end-diastolic pressure elevated (21.0 ± 0.6 and 5.4 ± 0.2 mm Hg), left ventricular ejection fraction reduced (0.2 ± 0.02 and 0.5 ± 0.02) and left ventricular end-systolic pressure reduced (102 ± 4.2 and 127 ± 3.1 mm Hg). In HF rats, the in vivo and in vitro PR intervals were increased (41% and 20%), as was the Wenckebach cycle length, indicative of AVN dysfunction. The collagen content was significantly increased in the AVN and RAVR indicating fibrosis. Immunolabelling of caveolin3 (cell membrane marker) showed that there was hypertrophy in HF (cell diameter was increased by 63%, 39% in AVN, RAVR). The TUNEL assay showed that the myocytes of the AVN and RAVR in HF undergo apoptotic cell death. Immunolabelling showed that expression of HCN4 was significantly decreased in the AVN and RAVR (43% and 47%) in HF. We conclude that in HF there is remodelling of the AVN and RAVR and this remodelling may explain the AVN dysfunction.

Collisional stripping of planetary crusts

NASA Astrophysics Data System (ADS)

Carter, Philip J.; Leinhardt, Zoë M.; Elliott, Tim; Stewart, Sarah T.; Walter, Michael J.

2018-02-01

Geochemical studies of planetary accretion and evolution have invoked various degrees of collisional erosion to explain differences in bulk composition between planets and chondrites. Here we undertake a full, dynamical evaluation of 'crustal stripping' during accretion and its key geochemical consequences. Crusts are expected to contain a significant fraction of planetary budgets of incompatible elements, which include the major heat producing nuclides. We present smoothed particle hydrodynamics simulations of collisions between differentiated rocky planetesimals and planetary embryos. We find that the crust is preferentially lost relative to the mantle during impacts, and we have developed a scaling law based on these simulations that approximates the mass of crust that remains in the largest remnant. Using this scaling law and a recent set of N-body simulations of terrestrial planet formation, we have estimated the maximum effect of crustal stripping on incompatible element abundances during the accretion of planetary embryos. We find that on average approximately one third of the initial crust is stripped from embryos as they accrete, which leads to a reduction of ∼20% in the budgets of the heat producing elements if the stripped crust does not reaccrete. Erosion of crusts can lead to non-chondritic ratios of incompatible elements, but the magnitude of this effect depends sensitively on the details of the crust-forming melting process on the planetesimals. The Lu/Hf system is fractionated for a wide range of crustal formation scenarios. Using eucrites (the products of planetesimal silicate melting, thought to represent the crust of Vesta) as a guide to the Lu/Hf of planetesimal crust partially lost during accretion, we predict the Earth could evolve to a superchondritic 176Hf/177Hf (3-5 parts per ten thousand) at present day. Such values are in keeping with compositional estimates of the bulk Earth. Stripping of planetary crusts during accretion can lead to detectable changes in bulk composition of lithophile elements, but the fractionation is relatively subtle, and sensitive to the efficiency of reaccretion.

Drastic shift of lava geochemistry between pre- and post- Japan Sea opening in NE Japan subduction zone: constraints on source composition and slab surface melting processes

NASA Astrophysics Data System (ADS)

Okamura, S.; Inaba, M.; Igarashi, S.; Aizawa, M.; Shinjo, R.

2017-12-01

Isotopic and trace element data imply a temporal change in magma sources and thermal conditions beneath the northern Fossa Magna, NE Japan arc from the Oligocene to the Pleistocene. Less radiogenic 176Hf/177Hf and 143Nd/144Nd, and high Zr/Hf characterize the Oligocene - Early Miocene volcanism in the northern Fossa Magna region. The mantle wedge in the Oligocene - Early Miocene consisted of enriched mantle source. We propose that during the onset of subduction, influx of hot asthenospheric mantle provided sufficient heat to partially melt newly subducting sediment. Geochemical modeling results suggest breakdown of zircon in the slab surface sediments for the Oligocene - Early Miocene lavas in the northern Fossa Magna region. In the Middle Miocene, the injection of hot and depleted asthenospheric material replaced the mantle beneath the northern Fossa Magna region of NE Japan. The Middle Miocene lavas characterized by most radiogenic Hf and Nd isotope ratios, have high Zr/Hf. An appropriate working petrogenetic model is that the Middle Miocene lavas were derived from asthenospheric depleted mantle, slightly (<1%) contaminated by slab melt accompanied by full dissolution of zircon. All the Late Miocene - Pleistocene samples are characterized by distinctly more radiogenic 176Hf/177Hf and 143Nd/144Nd, and are displaced toward lower Zr/Hf, which requires mixing between depleted mantle and a partial melt of subducted metasediment saturated with trace quantity of zircon. The Oligocene - Early Miocene volcanism in the northern Fossa Magna region may represent the early stage of continental margin magmatism associated with a back-arc rift. Here volcanism is dominated by sediment melts. Perhaps asthenospheric injection, triggering Japan Sea opening, allowed higher temperatures and more melting at the slab-mantle interface. The mantle wedge was gradually cooled during the Middle Miocene to the Pleistocene with back-arc opening ending in the Late Miocene. Slab surface temperatures were still high enough for sediments to melt but not too high (< 780 °C) to lose zircon as a residual phase.

Studies of Plasma Instability Processes Excited by Ground Based High Power HF (Heating) Facilities

DTIC Science & Technology

2001-04-01

and Megill, 1974; Carlson, 1974; Bernhardt et al., 1989). During the last years new interesting results have been obtained at HAARP facility (Peterson...Haslett and Megill, 1974; Carlson, 1974; Bernhardt et al., 1989). During the last years new interesting results have been obtained at HAARP facility

Effects of diet forage proportion on maintenance energy requirement and the efficiency of metabolizable energy use for lactation by lactating dairy cows.

PubMed

Dong, L F; Ferris, C P; McDowell, D A; Yan, T

2015-12-01

The objective of the present study was to examine the effect of dietary forage proportion (FP) on metabolizable energy (ME) requirement for maintenance (MEm) and the efficiency of ME use for lactation (kl) in lactating dairy cows. Data used were derived from 32 calorimetric chamber experiments undertaken at our institute between 1992 and 2010, including data from 818 Holstein-Friesian cows (HF), 50 Norwegian Red cows, and 62 crossbred cows (Jersey × HF or Norwegian Red × HF). Animals were offered forage-only rations (n=66) or forage and concentrate rations (n=864) with FP ranging from 18 to 100% (dry matter basis). The effect of FP was evaluated by dividing the whole data set into 4 groups according to the FP ranges, categorized as FP <30%, FP=30 to 59%, FP=60 to 99%, and FP=100%. The MEm for individual cows was calculated from heat production minus energy losses from inefficiencies of ME use for lactation, energy retention and pregnancy, and kl was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. Increasing FP significantly reduced ME intake and milk energy output, although the differences between the 2 low FP groups were not significant. However, increasing FP significantly increased the ratio of heat production over ME intake and MEm (MJ/kg(0.75)), with the exception that the increases did not reach significance in heat production/ME intake between FP <30% and FP=30 to 59%, or in MEm between FP=60 to 99% and FP=100%. However, the FP had no significant effect on the kl values, which were similar among the 4 groups of cows. The effect of FP was also evaluated using the linear mixed regression technique relating El(0) to ME intake. The results demonstrated that with a common regression coefficient (slope), the regression constants (intercepts) taken as net energy requirement for maintenance significantly increased with increasing FP. However, the increase between the 2 high FP groups did not research significance. It is concluded that increasing diet FP had no effects on kl but significantly increased maintenance energy requirement (MJ/kg(0.75)). These results indicate that using the current energy feeding systems to ration dairy cows managed under low input systems may underestimate their nutrient requirements, because the majority of feeding systems adopted globally do not differentiate the maintenance energy requirements between low and high forage input systems. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Local heat stress and skin blood flowmotion in subjects with familial predisposition or newly diagnosed hypertension.

PubMed

Gryglewska, Barbara; Nęcki, Mirosław; Cwynar, Marcin; Baron, Tomasz; Grodzicki, Tomasz

2010-12-01

The aim of the study was to investigate the skin microcirculation blood flow and flowmotion response to heat stress in normotensive subjects with familial predisposition to hypertension and in hypertensive patients. Normotensives without [NT(-)] or with [NT(+)] familial predisposition and subjects with newly diagnosed hypertension (HT) were studied. Clinic blood pressure (BP) measurements and ambulatory BP monitoring as well as laboratory assessments were performed. Resting (RF), heat (HF) and maximal heat (MHF) blood flows were measured using PeriFlux laser Doppler flowmetry (LDF) and expressed as absolute units (AU) and as index of cutaneous vascular conductance (CVC). Spectral analysis of the skin LDF signal was performed by means of the Perisoft dedicated software. Kruskall-Wallis analysis of variance, χ(2) statistic and multivariate reverse regression analysis were used for calculation. The studied population consisted of 70 persons (mean age 36.1 ± 10.3 years, 44.3% women): 17 NT(-), 22 NT(+) and 31 HT, age and gender matched. Higher values of body mass index (BMI), and insulin, glucose and triglyceride levels were observed in HT than in NT groups. RF, HF and MHF were similar in all study groups, but CVC of maximal heat flow differed (p=0.02); in particular, lower values were observed in the HT than in NT(-) group (p=0.01). The study groups differed with regard to total power (p=0.01) and myogenic (p=0.03) origin flowmotion with the lowest values in the NT(+) group. BMI and night BP characteristics were strong predictors of reduction of CVC, MHF and myogenic origin flowmotion. Skin microcirculation response to local heat stress is altered in hypertensive patients with decrease in maximal heat CVC values. Moreover, normotensive subjects with familial predisposition to hypertension are characterized by diminished myogenic origin of skin blood flowmotion.

Low frequency electric field variations during HF transmissions on a mother-daughter rocket

NASA Technical Reports Server (NTRS)

Rosenberg, T. J.; Maynard, M. C.; Holtet, J. A.; Karlsen, N. O.; Egeland, A.; Moe, T. E.; Troim, J.

1977-01-01

HF wave propagation experiments were conducted on Mother-Daughter rockets in the polar ionosphere. Swept frequency transmissions from the Mother, nominally covering the range from 0.5 to 5 MHz in both CW and pulse modes, are received by the Daughter. In the most recent rocket of the series, the Mother also contained an AC electric field spectrometer covering the frequency range from 10 Hz to 100 kHz in four decade bands. The low frequency response of the ionosphere with respect to waves emitted from the onboard HF transmitter is examined.

Optimization of antioxidant activity by response surface methodology in hydrolysates of jellyfish (Rhopilema esculentum) umbrella collagen.

PubMed

Zhuang, Yong-liang; Zhao, Xue; Li, Ba-fang

2009-08-01

To optimize the hydrolysis conditions to prepare hydrolysates of jellyfish umbrella collagen with the highest hydroxyl radical scavenging activity, collagen extracted from jellyfish umbrella was hydrolyzed with trypsin, and response surface methodology (RSM) was applied. The optimum conditions obtained from experiments were pH 7.75, temperature (T) 48.77 degrees C, and enzyme-to-substrate ratio ([E]/[S]) 3.50%. The analysis of variance in RSM showed that pH and [E]/[S] were important factors that significantly affected the process (P<0.05 and P<0.01, respectively). The hydrolysates of jellyfish umbrella collagen were fractionated by high performance liquid chromatography (HPLC), and three fractions (HF-1>3000 Da, 1000 Da

Optimization of antioxidant activity by response surface methodology in hydrolysates of jellyfish (Rhopilema esculentum) umbrella collagen*

PubMed Central

Zhuang, Yong-liang; Zhao, Xue; Li, Ba-fang

2009-01-01

To optimize the hydrolysis conditions to prepare hydrolysates of jellyfish umbrella collagen with the highest hydroxyl radical scavenging activity, collagen extracted from jellyfish umbrella was hydrolyzed with trypsin, and response surface methodology (RSM) was applied. The optimum conditions obtained from experiments were pH 7.75, temperature (T) 48.77 °C, and enzyme-to-substrate ratio ([E]/[S]) 3.50%. The analysis of variance in RSM showed that pH and [E]/[S] were important factors that significantly affected the process (P<0.05 and P<0.01, respectively). The hydrolysates of jellyfish umbrella collagen were fractionated by high performance liquid chromatography (HPLC), and three fractions (HF-1>3000 Da, 1000 Da

The temporal evolution of 3-m striations in the modified ionosphere

NASA Technical Reports Server (NTRS)

Coster, A. J.; Djuth, F. T.; Jost, R. J.; Gordon, W. E.

1985-01-01

Experiments were performed at Arecibo, Puerto Rico, to investigate the evolution times of 3-m field-aligned striations produced in the ionosphere by powerful high-frequency (HF) radio waves. The results of this investigation are now summarized. First, the striations' rise times are dependent on the HF electric field. The E region data suggest that this dependence is nonlinear. Second, the threshold value of the HF electric field required to produce detectable striations was experimentally determined. At threshold the component of the HF electric field perpendicular to the geomagnetic field is calculated to be 0.09 V/m in the F region and 0.37 V/m in the E region. Third, both the E and the F region data verify theoretical predictions that the striations' decay times are directly proportional to the electron diffusion across B. Finally, a one-to-one correspondence between the growth of the 3-m striations and the decline of the HF-enhanced plasma line during overshoot is sometimes observed.

HF coherent backscatter in the ionosphere: In situ measurements of SuperDARN backscatter with e-POP RRI

NASA Astrophysics Data System (ADS)

Perry, G. W.; James, H. G.; Hussey, G. C.; Howarth, A. D.; Yau, A. W.

2017-12-01

We report in situ polarimetry measurements of HF scattering obtained by the Enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument (RRI) during a coherent backscatter scattering event detected by the Saskatoon Super Dual Auroral Radar Network (SuperDARN). On April 1, 2015, e-POP conducted a 4 minute coordinated experiment with SuperDARN Saskatoon, starting at 3:38:44 UT (21:38:44 LT). Throughout the experiment, SuperDARN was transmitting at 17.5 MHz and e-POP's ground track moved in a northeastward direction, along SuperDARN's field-of-view, increasing in altitude from 331 to 352 km. RRI was tuned to 17.505 MHz, and recorded nearly 12,000 SuperDARN radar pulses during the experiment. In the first half of the experiment, radar pulses recorded by RRI were "well behaved": they retained their transmitted amplitude envelope, and their pulse-to-pulse polarization characteristics were coherent - Faraday rotation was easily measured. During the second half of the experiment the pulses showed clear signs of scattering: their amplitude envelopes became degraded and dispersed, and their pulse-to-pulse polarization characteristics became incoherent - Faraday rotation was difficult to quantify. While these pulses were being received by RRI, SuperDARN Saskatoon detected a latitudinal band of coherent backscatter at e-POP's location, indicating that the scattered pulses measured by RRI may be a signature of HF backscatter. In this presentation, we will outline the polarimetric details of the scattered pulses, and provide an analytic interpretation of RRI's measurements to give new insight into the nature of HF coherent backscatter mechanism taking place in the terrestrial ionosphere.

Intensity modulation of HF heater-induced plasma lines

NASA Technical Reports Server (NTRS)

Kuo, S. P.; Lee, M. C.

1990-01-01

The Arecibo HF heater is normally composed of two separate sets of antenna array, transmitting waves vertically at the same frequency and polarization. However, when these two sets of antenna array radiate at slightly different frequencies, the intensities of HF heater-induced plasma lines (HFPLs) can be drastically modulated. In recent Duncan et al.'s (1989) experiments the 100 percent intensity modulation of HFPLs was seen to persist even when the secondary set of antenna array radiated at a few percent of the power transmitted by the primary set of antenna array. An explanation is offered, and it is shown that there exists a minimum power, Pmin, and if the secondary set of antenna array radiates at a power lower than Pmin, the 100-percent intensity modulation of HFPLs will not be observed. The functional dependence of Pmin on the difference frequency of the two sets of antenna array is also predicted for future experiments to corroborate.

Validation of HF Radar ocean surface currents in the Ibiza Channel using lagrangian drifters, moored current meter and underwater gliders

NASA Astrophysics Data System (ADS)

Lana, Arancha; Fernández, Vicente; Orfila, Alejandro; Troupin, Charles; Tintoré, Joaquín

2015-04-01

SOCIB High Frequency (HF) radar is one component of a multi-platform system located in the Balearic Islands and made up of Lagrangian platforms (profilers and drifting buoys), fixed stations (sea-level, weather, mooring and coastal), beach monitoring (camera), gliders, a research vessel as well as an ocean forecast system (waves and hydrodynamics). The HF radar system overlooks the Ibiza Channel, known as a 'choke point" where Atlantic and Mediterranean water masses interact and where meridional exchanges of water mass properties between the Balearic and the Algerian sub-basins take place. In order to determine the reliability of surface velocity measurements in this area, a quality assessment of the HF Radar is essential. We present the results of several validation experiments performed in the Ibiza Channel in 2013 and 2014. Of particular interest is an experiment started in September 2014 when a set of 13 surface drifters with different shapes and drogue lengths were released in the area covered by the HF radar. The drifter trajectories can be examined following the SOCIB Deployment Application (DAPP): http://apps.socib.es/dapp. Additionally, a 1-year long time series of surface currents obtained from a moored surface current-meter located in the Ibiza Channel, inside the area covered by the HF radar, was also used as a useful complementary validation exercise. Direct comparison between both radial surface currents from each radar station and total derived velocities against drifters and moored current meter velocities provides an assessment of the HF radar data quality at different temporal periods and geographical areas. Statistics from these comparisons give good correlation and low root-mean-square deviation. The results will be discussed for different months, geographical areas and types of surface drifters and wind exposure. Moreover, autonomous underwater glider constitutes an additional source of information for the validation of the observed velocity structures and some statistics will be presented.

Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations

NASA Astrophysics Data System (ADS)

Harrison, J. J.; Chipperfield, M. P.; Boone, C. D.; Dhomse, S. S.; Bernath, P. F.; Froidevaux, L.; Anderson, J.; Russell, J., III

2015-12-01

The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Many of these fluorine-containing species deplete stratospheric ozone, and are regulated by the Montreal Protocol. Once in the atmosphere they slowly degrade, ultimately leading to the formation of HF, the dominant reservoir of stratospheric fluorine due to its extreme stability. Monitoring the growth of stratospheric HF is therefore an important marker for the success of the Montreal Protocol. We report the comparison of global distributions and trends of HF measured in the Earth's atmosphere by the satellite remote-sensing instruments ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer), which has been recording atmospheric spectra since 2004, and HALOE (HALogen Occultation Experiment), which recorded atmospheric spectra between 1991 and 2005, with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the agreement between observation and model is good, although the ACE-FTS measurements are biased high by ∼ 10 % relative to HALOE. The observed global HF trends reveal a substantial slowing down in the rate of increase of HF since the 1990s: 4.97 ± 0.12 % year-1 (1991-1997; HALOE), 1.12 ± 0.08 % year-1 (1998-2005; HALOE), and 0.52 ± 0.03 % year-1 (2004-2012; ACE-FTS). In comparison, SLIMCAT calculates trends of 4.01, 1.10, and 0.48 % year-1, respectively, for the same periods; the agreement is very good for all but the earlier of the two HALOE periods. Furthermore, the observations reveal variations in the HF trends with latitude and altitude, for example between 2004 and 2012 HF actually decreased in the Southern Hemisphere below ∼ 35 km. SLIMCAT calculations broadly agree with these observations, most notably between 2004 and 2012. Such variations are attributed to variability in stratospheric dynamics over the observation period.

Coulomb excitation of the K π= 8⁻ isomeric band in 178Hf

DOE PAGES

Napiorkovsk, P. J.; Srebrny, J.; Czosnyka, T.; ...

2001-12-01

The Coulomb excitation experiment on the 178Hf was performed using 650 MeV beam of 136Xe. The first observation of discrete transitions in the K π = 8 - isomeric band. Coulomb excited from K π = 0+ ground state, is reported. The possible mechanisms of El coupling of the ground state band and the isomeric band is discussed.

Excitation of earth-ionosphere waveguide in the ELF and lower VLF bands by modulated ionospheric current. Technical report

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

Field, E.C.; Bloom, R.M.

1993-05-21

In this report the authors use the principal of reciprocity in conjunction with a full-wave propagation code to calculate ground-level fields excited by ionospheric currents modulated at frequencies between 50 and 100 Hz with HF heaters. Their results show the dependence on source orientation, altitude, and dimension and therefore pertain to experiments using the HIPAS or HAARP ionospheric heaters. In the end-fire mode, the waveguide excitation efficiency of an ELF HED in the ionosphere is up to 20 dB greater than for a ground-based antenna, provided its altitude does not exceed 80-to-90 km. The highest efficiency occurs for a sourcemore » altitude of around 70 km; if that altitude is raised to 100 km, the efficiency drops by about 20 dB in the day and 10 dB at night. That efficiency does not account for the greater conductivity modulation that might be achieved at altitudes greater than 70 km, however. The trade-off between the altitude dependencies of the excitation efficiency and maximum achievable modulation depends on the ERP of the HF heater, the optimum altitude increasing with increasing ERP. For HIPAS the best modulation altitude is around 70 km, whereas for HAARP there might be marginal value in modulating at attitudes as high as 100 Km. Ionospheric modification, Ionospheric currents, Ionospheric heating.« less

A Diagnostic System for Studying Energy Partitioning and Assessing the Response of the Ionosphere during HAARP Modification Experiments

NASA Technical Reports Server (NTRS)

Djuth, Frank T.; Elder, John H.; Williams, Kenneth L.

1996-01-01

This research program focused on the construction of several key radio wave diagnostics in support of the HF Active Auroral Ionospheric Research Program (HAARP). Project activities led to the design, development, and fabrication of a variety of hardware units and to the development of several menu-driven software packages for data acquisition and analysis. The principal instrumentation includes an HF (28 MHz) radar system, a VHF (50 MHz) radar system, and a high-speed radar processor consisting of three separable processing units. The processor system supports the HF and VHF radars and is capable of acquiring very detailed data with large incoherent scatter radars. In addition, a tunable HF receiver system having high dynamic range was developed primarily for measurements of stimulated electromagnetic emissions (SEE). A separate processor unit was constructed for the SEE receiver. Finally, a large amount of support instrumentation was developed to accommodate complex field experiments. Overall, the HAARP diagnostics are powerful tools for studying diverse ionospheric modification phenomena. They are also flexible enough to support a host of other missions beyond the scope of HAARP. Many new research programs have been initiated by applying the HAARP diagnostics to studies of natural atmospheric processes.

Eu-doped ZnO-HfO2 hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

NASA Astrophysics Data System (ADS)

Ghosh, Subhabrata; N, Shivakiran Bhaktha B.

2016-03-01

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 -(30-x) HfO2-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO2-HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu2+ and Eu3+ in the SiO2-HfO2-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu{}2+,3+-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm-1 at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO2 nanocrystal-embedded SiO2-HfO2-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.

Excitation of the ionospheric Alfvén resonator from the ground: Theory and experiments

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Chang, C.-L.; Labenski, J.; Milikh, G.; Vartanyan, A.; Snyder, A. L.

2011-10-01

We report results from numerical and experimental studies of the excitation of ULF shear Alfvén waves inside the ionospheric Alfvén resonator (IAR) by heating the ionosphere with powerful HF waves launched from the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Numerical simulations of the two-fluid MHD model describing IAR in a dipole magnetic field geometry with plasma parameters taken from the observations at HAARP during the October-November 2010 experimental campaign reveal that the IAR quality is higher during nighttime conditions, when the ionospheric conductivity is very low. Simulations also reveal that the resonance wave cannot be identified from the magnetic measurements on the ground or at an altitude above 600 km because the magnetic field in this wave has nodes on both ends of the resonator, and the best way to detect IAR modes is by measuring the electric field on low Earth orbit satellites. These theoretical predictions are in good, quantitative agreement with results from observations: In particular, (1) observations from the ground-based magnetometer at the HAARP site demonstrate no significant difference in the amplitudes of the magnetic field generated by HAARP in the frequency range from 0 to 5 Hz, and (2) the DEMETER satellite detected the electric field of the IAR first harmonic at an altitude of 670 km above HAARP during the heating experiment.

Patients with heart failure and their partners with chronic illness: interdependence in multiple dimensions of time.

PubMed

Nimmon, Laura; Bates, Joanna; Kimel, Gil; Lingard, Lorelei

2018-01-01

Informal caregivers play a vital role in supporting patients with heart failure (HF). However, when both the HF patient and their long-term partner suffer from chronic illness, they may equally suffer from diminished quality of life and poor health outcomes. With the focus on this specific couple group as a dimension of the HF health care team, we explored this neglected component of supportive care. From a large-scale Canadian multisite study, we analyzed the interview data of 13 HF patient-partner couples (26 participants). The sample consisted of patients with advanced HF and their long-term, live-in partners who also suffer from chronic illness. The analysis highlighted the profound enmeshment of the couples. The couples' interdependence was exemplified in the ways they synchronized their experience in shared dimensions of time and adapted their day-to-day routines to accommodate each other's changing health status. Particularly significant was when both individuals were too ill to perform caregiving tasks, which resulted in the couples being in a highly fragile state. We conclude that the salience of this couple group's oscillating health needs and their severe vulnerabilities need to be appreciated when designing and delivering HF team-based care.

Clinical Utility of Exercise Training in Heart Failure with Reduced and Preserved Ejection Fraction

PubMed Central

Asrar Ul Haq, Muhammad; Goh, Cheng Yee; Levinger, Itamar; Wong, Chiew; Hare, David L

2015-01-01

Reduced exercise tolerance is an independent predictor of hospital readmission and mortality in patients with heart failure (HF). Exercise training for HF patients is well established as an adjunct therapy, and there is sufficient evidence to support the favorable role of exercise training programs for HF patients over and above the optimal medical therapy. Some of the documented benefits include improved functional capacity, quality of life (QoL), fatigue, and dyspnea. Major trials to assess exercise training in HF have, however, focused on heart failure with reduced ejection fraction (HFREF). At least half of the patients presenting with HF have heart failure with preserved ejection fraction (HFPEF) and experience similar symptoms of exercise intolerance, dyspnea, and early fatigue, and similar mortality risk and rehospitalization rates. The role of exercise training in the management of HFPEF remains less clear. This article provides a brief overview of pathophysiology of reduced exercise tolerance in HFREF and heart failure with preserved ejection fraction (HFPEF), and summarizes the evidence and mechanisms by which exercise training can improve symptoms and HF. Clinical and practical aspects of exercise training prescription are also discussed. PMID:25698883

Method of making porous ceramic fluoride

DOEpatents

Reiner, Robert H.; Holcombe, Cressie E.

1990-01-01

A process for making a porous ceramic composite where fumed silica particles are coated with a nitrate, preferably aluminum nitrate. Next the nitrate is converted to an oxide and formed into a desired configuration. This configuration is heated to convert the oxide to an oxide silicate which is then react with HF, resulting in the fluoride ceramic, preferably aluminum fluoride.

High speed metal removal

NASA Astrophysics Data System (ADS)

Pugh, R. F.; Pohl, R. F.

1982-10-01

Four types of steel (AISI 1340, 4140, 4340, and HF-1) which are commonly used in large caliber projectile manufacture were machined at different hardness ranges representing the as-forged and the heat treated condition with various ceramic tools using ceramic coated tungsten carbide as a reference. Results show that machining speeds can be increased significantly using present available tooling.

Ultra-high surface speed for metal removal, artillery shell

NASA Astrophysics Data System (ADS)

Pugh, R. F.; Walsh, M. R.; Pohl, R. F.

1981-07-01

Four types of steel (AISI 1340, 4140, 4340, and HF-1) which are commonly used in large caliber projectile manufacture were machined with five types of tools at different hardness ranges representing the as-forged and the heat-treated condition. Results show that machining speeds can be increased significantly over current practice using the present available tooling.

Hydrogen doping in HfO{sub 2} resistance change random access memory

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

Duncan, D.; Magyari-Köpe, B.; Nishi, Y.

2016-01-25

The structures and energies of hydrogen-doped monoclinic hafnium dioxide were calculated using density-functional theory. The electronic interactions are described within the LDA + U formalism, where on-site Coulomb corrections are applied to the 5d orbital electrons of Hf atoms and 2p orbital electrons of the O atoms. The effects of charge state, defect-defect interactions, and hydrogenation are investigated and compared with experiment. It is found that hydrogenation of HfO{sub 2} resistance-change random access memory devices energetically stabilizes the formation of oxygen vacancies and conductive vacancy filaments through multiple mechanisms, leading to improved switching characteristic and device yield.

Terrestrial bitumen analogue of orgueil organic material demonstrates high sensitivity to usual HF-HCl treatment

NASA Technical Reports Server (NTRS)

Korochantsev, A. V.; Nikolaeva, O. V.

1993-01-01

The relationship between the chemical composition and the interlayer spacing (d002) of organic materials (OM's) is known for various terrestrial OM's. We improved this general trend by correlation with corresponding trend of natural solid bitumens (asphaltite-kerite-anthraxolite) up to graphite. Using the improved trend we identified bitumen analogs of carbonaceous chondrite OM's residued after HF-HCl treatment. Our laboratory experiment revealed that these analogs and, hence, structure and chemical composition of carbonaceous chondrite OM's are very sensitive to the HF-HCl treatment. So, usual extraction of OM from carbonaceous chondrites may change significantly structural and chemical composition of extracted OM.

Slow DNA Transport through Nanopores in Hafnium Oxide Membranes

PubMed Central

Bell, David C.; Cohen-Karni, Tzahi; Rosenstein, Jacob K.; Wanunu, Meni

2016-01-01

We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2–7 nm thick) free-standing hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

Ab Initio Calculations of Anharmonic Vibrational Spectroscopy for Hydrogen Fluoride (HF)n (n=3,4) and Mixed Hydrogen Fluoride/Water (HF)n(H20)n (n=1,2,4) Clusters

NASA Technical Reports Server (NTRS)

Chaban, Galina M.; Gerber, R. Benny; Kwak, Dochan (Technical Monitor)

2001-01-01

Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n with n=3,4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n=1,2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field (CC-VSCF) method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the MP2 potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.

Ab initio calculations of anharmonic vibrational spectroscopy for hydrogen fluoride (HF)n (n = 3, 4) and mixed hydrogen fluoride/water (HF)n(H2O)n (n = 1, 2, 4) clusters

NASA Technical Reports Server (NTRS)

Chaban, Galina M.; Gerber, R. Benny

2002-01-01

Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the Moller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.

Heater-induced altitude descent of the EISCAT UHF ion line enhancements: Observations and modelling

NASA Astrophysics Data System (ADS)

Ashrafi, M.; Kosch, M. J.; Honary, F.

2006-01-01

On 12 November 2001, artificial optical annuli were produced using the EISCAT high-frequency (HF) ionospheric heating facility. This unusual phenomenon was induced using O-mode transmissions at 5.423 MHz with 550 MW effective isotropic radiated power and the pump beam dipped 9° south of the zenith. The pump frequency corresponds to the fourth electron gyroharmonic frequency at 215 km altitude. The EISCAT UHF radar observed a persistent pump-induced enhancement in the ion line backscatter power near the HF reflection altitude. The optical and radar signatures of HF pumping started at ˜230 km and descended to ˜220 km within ˜60 s. This effect has been modelled using the solution to differential equations describing pump-induced electron temperature and density perturbations. The decrease in altitude of the ion line by ˜10 km and changes in electron density have been modelled. The results show that a maximum electron temperature enhancement of up to ˜5700 K can be achieved on average, which is not sufficient to explain the observed optical emissions.

Spectroscopic (FT-IR/FT-Raman) and computational (HF/DFT) investigation and HOMO/LUMO/MEP analysis on 1,1-difluoro-2-vinyl-cyclopropane

NASA Astrophysics Data System (ADS)

Senthil Raj, P.; Shoba, D.; Ramalingam, S.; Periandy, S.

2015-08-01

All the computational calculations were made in the ground state using the HF and DFT (B3LYP) methods with 6-31++G (d,p) and 6-311++G (d,p) basis sets. Making use of the recorded data, the complete vibrational assignments were made and analysis of the observed fundamental bands of molecule was carried out. The shifting of the frequencies in the vibrational pattern of the title molecule due to the substitutions; sbnd CHdbnd CH2 and F were deeply investigated by the vibrational analysis. Moreover, 13C NMR and 1H NMR chemical shifts were calculated by using the gauge independent atomic orbital (GIAO) method with HF/B3LYP methods with 6-311++G (d,p). A study on the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Mulliken charges of the 1DF2VCP were also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase.

Indomethacin treatment prevents diet-induced obesity and insulin resistance, but not glucose intolerance in C57BL/6J mice

USDA-ARS?s Scientific Manuscript database

OBJECTIVE: We performed experiments to examine the metabolic consequences of inhibition of cyclooxygenase (COX) activity in obesity-prone C57BL/6J mice fed a high fat/high sucrose (HF/HS) diet. RESEARCH DESIGN AND METHODS: C57BL/6J mice were fed a HF/HS diet for 7 weeks under thermoneutral conditio...

Neurohormones and heart failure.

PubMed

Mendzef, Scott D; Slovinski, Jennifer R

2004-12-01

The management of several neurohormonal pathways is crucial to treating the progression of HF, in addition to improving the quality of life for patients diagnosed with HF. Stimulation of the sympathetic and retin-angiogensin-aldosterone systems begins the initial and primary neurohormonal stimulation associated with the progression of this disease. However, it is becoming increasingly evident that other systems, including the cellular immune, endothelin-NO pathway, kallikrein-kinin system, the arachidonic acid cascade, and the natriuretic peptides need to be considered by clinicians when treating HF. Once treated solely with nitrates, diuretics, and morphine, the management of HF is becoming a more complex and intricate balancing act among several interdependent neurohormonal systems. Understanding the complex nature and proper management of these systems are crucial if patients with HF are to enjoy a better quality of life and experience an improvement in their symptoms. Current recommendations for the treatment and management of HF use several medications, which affect multiple neurohormonal pathways. The Heart Failure Society of America and the American Heart Association both recommend in their recent guidelines for management of HF the use of beta-adrenergic receptor blockers (beta-blockers), loop diuretics, digitalis glycosides(digoxin), ACE-I, aldactone antagonists (spironolactone), and in selected instances, ARBs and the combination of hydralazine and isosorbide dinitrate. No discussion of HF is complete without mention of the larger challenges associated with the management of HF. It is a complex syndrome that requires a multidisciplinary approach with expertise in nutrition, exercise, pharmacology, education, and the basic pathophysiology of complex neurohormonal systems. Patients with uncompensated HF are frightened, vulnerable, and require frequent medication adjustments as well as substantial time dedicated to counseling, physical assessment, and innovative educational programs for them and their families. In fact, a majority of hospital readmissions for HF occur because of patients' dietary indiscretions, medication noncompliance, or ignorance about when to call their health providers. The management of HF represents a careful balancing act between powerful neurohormonal pathways and medications but also between the basics of diet, exercise, educating both family and patient, and most importantly, caring.

Kinetics of Glass Transition and Crystallization of a Zr40Hf10Ti4Y1Al10Cu25Ni7Co2Fe1 Bulk Metallic Glass with High Mixing Entropy

NASA Astrophysics Data System (ADS)

Gong, Pan; Wang, Sibo; Li, Fangwei; Wang, Xinyun

2018-04-01

The kinetics of glass transition and crystallization of a novel Zr40Hf10Ti4Y1Al10Cu25Ni7Co2Fe1 bulk metallic glass (BMG) with high mixing entropy have been studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The continuous DSC curves show five stages of crystallization at lower heating rates (≤ 20 K/min). The activation energies of glass transition were determined by Moynihan and Kissinger methods, while the activation energies of crystallization were calculated utilizing Kissinger, Ozawa, and Boswell models. The crystalline phases corresponding to each crystallization step have been found out. The kinetic fragility of Zr40Hf10Ti4Y1Al10Cu25Ni7Co2Fe1 BMG has also been evaluated. Based on the isothermal DSC curves, the Avrami exponent, evaluated from the Johnson-Mehl-Avrami equation, has been analyzed in detail. The current study reveals that the crystallization behavior of Zr40Hf10Ti4Y1Al10Cu25Ni7Co2Fe1 BMG exhibits characteristics of both the high entropy BMGs and traditional BMGs with a single principal element, leading to its high glass-forming ability.

Increase in Operator's Sympathetic Nerve Activity during Complicated Hepatobiliary Surgery: Evidence for Surgeons' Mental Stress.

PubMed

Yamanouchi, Kosho; Hayashida, Naomi; Kuba, Sayaka; Sakimura, Chika; Kuroki, Tamotsu; Togo, Michita; Katayama, Noritada; Takamura, Noboru; Eguchi, Susumu

2015-11-01

Surgeons often experience stress during operations. The heart rate variability (HRV) is the variability in the beat-to-beat interval, which has been used as parameters of stress. The purpose of this study was to evaluate mental stress of surgeons before, during and after operations, especially during pancreaticoduodenectomy (PD) and living donor liver transplantation (LDLT). Additionally, the parameters were compared in various procedures during the operations. By frequency domain method using electrocardiograph, we measured the high frequency (HF) component, representing the parasympathetic activity, and the low frequency (LF)/HF ratio, representing the sympathetic activity. In all 5 cases of PD, the surgeon showed significantly lower HF component and higher LF/HF during operation, indicating predominance of sympathetic nervous system and increased stress, than those before the operation (p < 0.01) and these did not return to the baseline level one hour after the operation. Out of the 4 LDLT cases, the value of HF was decreased in two and the LF/HF increased in three cases (p < 0.01) during the operation compared to those before the operation. In all cases, the value of HF was decreased and/or the LF/HF increased significantly during the reconstruction of the vessels or bile ducts than during the removal of the liver. Thus, sympathetic nerve activity increased during hepatobiliary surgery compared with the level before the operation, and various procedures during the operations induced diverse changes in the autonomic nervous activities. The HRV analysis could assess the chronological changes of mental stress by measuring the autonomic nervous balances.

What Happens After the Demonstration Phase? The Sustainability of Canada's At Home/Chez Soi Housing First Programs for Homeless Persons with Mental Illness.

PubMed

Nelson, Geoffrey; Caplan, Rachel; MacLeod, Timothy; Macnaughton, Eric; Cherner, Rebecca; Aubry, Tim; Méthot, Christian; Latimer, Eric; Piat, Myra; Plenert, Erin; McCullough, Scott; Zell, Sarah; Patterson, Michelle; Stergiopoulos, Vicky; Goering, Paula

2017-03-01

This research examined the sustainability of Canada's At Home/Chez Soi Housing First (HF) programs for homeless persons with mental illness 2 years after the end of the demonstration phase of a large (more than 2000 participants enrolled), five-site, randomized controlled trial. Qualitative interviews were conducted with 142 participants (key informants, HF staff, and persons with lived experience) to understand sustainability outcomes and factors that influenced those outcomes. Also, a self-report HF fidelity measure was completed for nine HF programs that continued after the demonstration project. A cross-site analysis was performed, using the five sites as case studies. The findings revealed that nine of the 12 HF programs (75%) were sustained, and that seven of the nine programs reported a high level of fidelity (achieving an overall score of 3.5 or higher on a 4-point scale). The sites varied in terms of the level of systems integration and expansion of HF that were achieved. Factors that promoted or impeded sustainability were observed at multiple ecological levels: broad contextual (i.e., dissemination of research evidence, the policy context), community (i.e., partnerships, the presence of HF champions), organizational (i.e., leadership, ongoing training, and technical assistance), and individual (i.e., staff turnover, changes, and capacity). The findings are discussed in terms of the implementation science literature and their implications for how evidence-based programs like HF can be sustained. © Society for Community Research and Action 2017.

A lateralized avian hippocampus: preferential role of the left hippocampal formation in homing pigeon sun compass-based spatial learning.

PubMed

Gagliardo, Anna; Vallortigara, Giorgio; Nardi, Daniele; Bingman, Verner P

2005-11-01

The hippocampal formation (HF) plays a crucial role in amniote spatial cognition. There are also indications of functional lateralization in the contribution of the left and right HF in processes that enable birds to navigate space. The experiments described in this study were designed to examine left and right HF differences in a task of sun compass-based spatial learning in homing pigeons (Columba livia). Control, left (HFL) and right (HFR) HF lesioned pigeons were trained in an outdoor arena to locate a food reward using their sun compass in the presence or absence of alternative feature cues. Subsequent to training, the pigeons were subjected to test sessions to determine if they learned to represent the goal location with their sun compass and the relative importance of the sun compass vs. feature cues. Under all test conditions, the control pigeons demonstrated preferential use of the sun compass in locating the goal. By contrast, the HFL pigeons demonstrated no ability to locate the goal by the sun compass but an ability to use the feature cues. The behaviour of the HFR pigeons demonstrated that an intact left HF is sufficient to support sun compass-based learning, but in conflict situations and in contrast to controls, they often relied on feature cues. In conclusion, only the left HF is capable of supporting sun compass-based learning. However, preferential use of the sun compass for learning requires an intact right HF. The data support the hypothesis that the left and right HF make different but complementary contributions toward avian spatial cognition.

Experimental study on the human thermal comfort based on the heart rate variability (HRV) analysis under different environments.

PubMed

Zhu, Hui; Wang, Hanqing; Liu, Zhiqiang; Li, Duanru; Kou, Guangxiao; Li, Can

2018-03-01

In order to study the human thermal comfort under different environments, the electrocardiogram (ECG) data of 6 subjects were recorded continuously under 60 environments composed by different air temperature, relative humidity and air speed that were created by an environmental chamber. Based on the ECG data, the frequency-domain method was adopted to obtain the heart rate variability (HRV) results. Among the HRV indices, the ratio of the low frequency power and high frequency power of the HRV analysis results (LF/HF), which reflects the balance of the autonomic nervous system, was selected as an indicator of the thermal comfort in the study. And the effects of air temperature, relative humidity and air speed on LF/HF were scrutinized. Meanwhile, a questionnaire survey was conducted during the experiment to evaluate the thermal comfort of the subjects. And the relationships between mean LF/HF and thermal sensation, mean thermal comfort were established based on the survey. The results showed that different LF/HF was observed under different environments, and that the air temperature had the most significant effects on LF/HF. The changes in the air temperature could easily lead to the excitation of the sympathetic nerve that could promote the activities of the thermoregulatory effectors thus thermal discomfort. Additionally, the fitting curves illustrating the relationships between LF/HF and thermal sensation and thermal comfort showed that the higher LF/HF yielded thermal discomfort, while the low LF/HF indicated a thermally acceptable state. Copyright © 2017 Elsevier B.V. All rights reserved.

Canadian Palliative Community Milrinone Infusions: A Case Series.

PubMed

Reimche, Ruthanne; Salcedo, Daniel

2016-01-01

Abstract Symptom managementfor end-of-life heartfailure (HF) patients is a significant concern. Currently, Canadian practice does not support community milrinone therapy in end-of-life HF patients. Two patients had severe HF that was unresponsive to optimal medications. Further optimization and furosemide infusions were ineffective for symptom management. Both patients' symptoms were better controlled with optimal medication, furosemide, and milrinone infusions. A tailored discharge plan was developed to assist with community milrinone infusions. We discuss the challenges and successes of transitioning two patients to the community. By providing symptom management and meaningful patient and family experience, both patients were able to die in a setting of their choosing. Milrinone infusions as a bridge to end of life may improve symptoms and quality of life. Select patients may benefit from milrinone infusions with resources put in place; these end-of-life HF patients can be supported in the community.

Ionospheric Turbulence and the Evolution of Artificial Irregularities Excited by RF Interactions at HAARP

NASA Astrophysics Data System (ADS)

Sheerin, J. P.; Rayyan, N.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.

2015-12-01

The HAARP phased-array HF transmitter at Gakona, AK delivers up to 3.6 GW (ERP) of HF power in the range of 2.8 - 10 MHz to the ionosphere with millisecond pointing, power modulation, and frequency agility. HAARP's unique features have enabled the conduct of a number of nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including stimulated electromagnetic emissions (SEE), artificial aurora, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the plasma line, and suprathermal electrons. For a narrow range of HF pointing between Spitze and magnetic zenith, a reduced threshold for AFAI is observed. Applications are made to the study of irregularities relevant to spacecraft communication and navigation systems.

Cooling hyperthermic firefighters by immersing forearms and hands in 10 degrees C and 20 degrees C water.

PubMed

Giesbrecht, Gordon G; Jamieson, Christopher; Cahill, Farrell

2007-06-01

Firefighters experience significant heat stress while working with heavy gear in a hot, humid environment. This study compared the cooling effectiveness of immersing the forearms and hands in 10 and 20 degrees C water. Six men (33 +/- 10 yr; 180 +/- 4 cm; 78 +/- 9 kg; 19 +/- 5% body fat) wore firefighter 'turn-out gear' (heavy clothing and breathing apparatus weighing 27 kg) in a protocol including three 20-min exercise bouts (step test, 78 W, 40 degrees C air, 40% RH) each followed by a 20-min rest/cooling (21 degrees C air); i.e., 60 min of exercise, 60 min of cooling. Turn-out gear was removed during rest/cooling periods and subjects either rested (Control), immersed their hands in 10 or 20 degrees C water (H-10, H-20), or immersed their hands and forearms in 10 or 20 degrees C water (HF-10, HF-20). In 20 degrees C water, hand immersion did not reduce core temperature compared with Control; however, including forearm immersion decreased core temperature below Control values after both the second and final exercise periods (p < 0.001). In 10 degrees C water, adding forearm with hand immersion produced a lower core temperature (0.8 degrees C above baseline) than all other conditions (1.1 to 1.4 degrees C above baseline) after the final exercise period (p < 0.001). Sweat loss during Control (1458 g) was greater than all active cooling protocols (1146 g) (p < 0.001), which were not different from each other. Hand and forearm immersion in cool water is simple, reduces heat strain, and may increase work performance in a hot, humid environment. With 20 degrees C water, forearms should be immersed with the hands to be effective. At lower water temperatures, forearm and/or hand immersion will be effective, although forearm immersion will decrease core temperature further.

Efficacy of Sacubitril/Valsartan Relative to a Prior Decompensation: The PARADIGM-HF Trial.

PubMed

Solomon, Scott D; Claggett, Brian; Packer, Milton; Desai, Akshay; Zile, Michael R; Swedberg, Karl; Rouleau, Jean; Shi, Victor; Lefkowitz, Martin; McMurray, John J V

2016-10-01

This study assessed whether the benefit of sacubtril/valsartan therapy varied with clinical stability. Despite the benefit of sacubitril/valsartan therapy shown in the PARADIGM-HF (Prospective Comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) trial, it has been suggested that switching from an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker should be delayed until occurrence of clinical decompensation. Outcomes were compared among patients who had prior hospitalization within 3 months of screening (n = 1,611 [19%]), between 3 and 6 months (n = 1,009 [12%]), between 6 and 12 months (n = 886 [11%]), >12 months (n = 1,746 [21%]), or who had never been hospitalized (n = 3,125 [37%]). Twenty percent of patients without prior HF hospitalization experienced a primary endpoint of cardiovascular death or heart failure (HF) hospitalization during the course of the trial. Despite the increased risk associated with more recent hospitalization, the efficacy of sacubitril/valsartan therapy did not differ from that of enalapril according to the occurrence of or time from hospitalization for HF before screening, with respect to the primary endpoint or with respect to cardiovascular or all-cause mortality. Patients with recent HF decompensation requiring hospitalization were more likely to experience cardiovascular death or HF hospitalization than those who had never been hospitalized. Patients who were clinically stable, as shown by a remote HF hospitalization (>3 months prior to screening) or by lack of any prior HF hospitalization, were as likely to benefit from sacubitril/valsartan therapy as more recently hospitalized patients. (Prospective Comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure [PARADIGM-HF]; NCT01035255). Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Changes in autonomic activity preceding onset of nonsustained ventricular tachycardia

NASA Technical Reports Server (NTRS)

Osaka, M.; Saitoh, H.; Sasabe, N.; Atarashi, H.; Katoh, T.; Hayakawa, H.; Cohen, R. J.

1996-01-01

Background: The triggering role of the autonomic nervous system in the initiation of ventricular tachycardia has not been established. To investigate the relationship between changes in autonomic activity and the occurrence of nonsustained ventricular tachycardia (NSVT) we examined heart rate variability (HRV) during the 2-hour period preceding spontaneous episodes of NSVT. Twenty-four subjects were identified retrospectively as having had one episode of NSVT during 24-hour Holter ECC recording. Methods: We measured the mean interval between normal heats (meanRR), the standard deviation of the intervals between beats (SD), the percentage of counts of sequential intervals between normal beats with a change of >50 ms (%RR50), the logarithms of low- and high-frequency spectral components (lnLF, lnHF) of HRV for sequential 10-minute segments preceding NSVT. The correlation dimension (CDim) of HRV was calculated similarly for sequential 20-minute segments. We assessed the significance of the time-course change of each marker over the 120-minute period prior to NSVT onset. Results: MeanRR (P < 0.05), lnLF (P < 0.0001), lnHF (P < 0.0001), the natural logarithm of the ratio of LF to HF (ln[LF/HF]; P < 0.05), and CDim (P < 0.05) showed significant time-course changes during that period, while SD and %RR50 did not. MeanRR, lnLF, lnHF, and CDim all decreased prior to the onset of NSVT, whereas ln(LF/HF) increased. We divided the subjects into two groups: one consisting of 12 patients with coronary artery disease; and the second group of 12 patients without known coronary artery disease. Both groups showed significant changes (P < 0.05) of CDim, lnLF, and lnHF preceding the episodes of NSVT. Conclusions: Changes in the pattern of HRV prior to the onset of episodes of NSVT suggest that changes in autonomic activity may commonly play a role in the triggering of spontaneous episodes of NSVT in susceptible patients. The measured changes suggest a reduction in parasympathetic activity, perhaps in conjunction with an increase in sympathetic activity, may trigger NSVT.

Digital HF communications for the polar regions - a low-cost alternative to satellite?

NASA Astrophysics Data System (ADS)

Prior-Jones, Michael; Warrington, Mike

2010-05-01

Digital HF communications for the polar regions - a low-cost alternative to satellite? Prior-Jones, M.R. and Warrington, E. M Communications within the polar regions pose unique technical challenges, due to the physical isolation, lack of infrastructure and extreme weather conditions. Geostationary satellite links are widely used, but they cannot function poleward of 80 degrees due to the curvature of the Earth. Low-earth-orbit systems like Iridium and ARGOS will function all the way to the poles. However, they are expensive, particularly for experiments requiring long time-series. Transferring data by Iridium satellite phone costs of the order of 60USD per megabyte. HF (i.e. 3-30 MHz) radio signals propagate via the ionosphere, allowing long distance transmission beyond the horizon. Ranges of thousands of kilometres can be easily achieved with relatively low transmission powers when propagation is favourable. The polar ionosphere is, however, a challenging environment for radio signals - the signals often reflect from multiple regions of the ionosphere and by multiple hops with intermediate ground reflections producing multipath effects. As the ionosphere is moving, these signals are also subject to very significant Doppler shifts that add to the complexity of the environment. These effects may make data communications at polar latitudes difficult or impossible at times and often only at low data rates. In this paper we discuss our experiments to use modern signal-processing and modulation techniques for digital transmission on HF, offering a similar speed to satellite but without paying the high cost of satellite airtime. Using an HF channel simulator developed by Warrington et al based on measurements of propagation at high latitudes, we have tested the performance of an OFDM-based modem derived from the Digital Radio Mondiale standard used for digital HF broadcasting and found that it outperforms current military modems developed by NATO (STANAG 4285 and 4539). The NATO modems were developed for operation in mid-latitude regions and thus it is unsurprising that they do not perform particularly well in the more demanding polar channels. We have also conducted on-air experiments over a 1600km test link between Halley and Rothera stations in Antarctica, and present the results showing the availability and capacity of this data link. We will also show how HF systems can provide inexpensive data communications for autonomous instruments, field parties, aircraft and ships operating in and around the Arctic and Antarctic. References: Warrington, E. M., A. J. Stocker, and D. R. Siddle (2006), Measurement and modeling of HF channel directional spread characteristics for northerly paths, Radio Sci., 41, RS2006, doi: 10.1029/2005RS003294.

Real-time Specification and Forecasting for HF Links During Disturbed Conditions

NASA Astrophysics Data System (ADS)

Rice, D.; Hunsuker, R. D.; Eccles, J.; Sojka, J. J.

2004-05-01

The HF communications community has long been dependent on climatological ionosphere descriptions to support HF propagation programs. Additionally, these programs include solar zenith angle and frequency-squared variation of HF absorption but do not include space weather effects due to solar x-ray events and sporadic E layers. The usefulness of real-time specification and forecasting of HF links is desired in programs such as Operational Space Environment Network Display (OpSend). The creation of HF illumination maps requires proper specifications of D, E and F regions of the ionosphere. We present results and validation efforts of the Data-Driven D region (DDDR) model of HF absorption for mid-latitude HF paths. The DDDR programs assimilate real-time data such as the NOAA/GOES 12 x-ray measurements to produce space weather related absorption predictions. The data-driven model is being validated with observations from the HF Investigation of D-Region Ionospheric Variation Experiment (HIDIVE). Monitoring of standard time-frequency HF stations has been employed for the past three decades. The passive monitoring technique used in HIDIVE was mainly applied for studies of the high-latitude and equatorial ionosphere, thus long-term, quantitative data on the mid-latitude ionosphere are difficult to find in archival literature. HIDIVE is a careful examination of long-term observations HF absorption to study seasonal variation and space weather events. Simultaneous continuous measurements of NOAA/GOES 12 solar x-ray flux and calibrated HF signal strength were initiated in December 2002 to provide validation data for the DDDR model. Continuous recording of transmissions of standard time-frequency stations (WWV and WWVH) over the range of 2.5 to 20.0 MHz and 5-minute averages of 1.0 to 8.0 nm solar x-ray flux have been studied for 35 solar flares ranging from Class C to Class X from March through August 2003 during the descending phase of solar cycle 23. The monitoring stations are located at Providence, Utah and at Klamath Falls, Oregon and continuous recordings are planned through August 2005. In particular, we will examine the extreme solar events of October-November 2003 as an example of the Societal Impact of Space Weather. This is timely because of renewed interest in the use of HF circuits by the Military and by commercial airlines.

Features of CO2 fracturing deduced from acoustic emission and microscopy in laboratory experiments

NASA Astrophysics Data System (ADS)

Ishida, Tsuyoshi; Chen, Youqing; Bennour, Ziad; Yamashita, Hiroto; Inui, Shuhei; Nagaya, Yuya; Naoi, Makoto; Chen, Qu; Nakayama, Yoshiki; Nagano, Yu

2016-11-01

We conducted hydraulic fracturing (HF) experiments on 170 mm cubic granite specimens with a 20 mm diameter central hole to investigate how fluid viscosity affects HF process and crack properties. In experiments using supercritical carbon dioxide (SC-CO2), liquid carbon dioxide (L-CO2), water, and viscous oil with viscosity of 0.051-336.6 mPa · s, we compared the results for breakdown pressure, the distribution and fracturing mechanism of acoustic emission, and the microstructure of induced cracks revealed by using an acrylic resin containing a fluorescent compound. Fracturing with low-viscosity fluid induced three-dimensionally sinuous cracks with many secondary branches, which seem to be desirable pathways for enhanced geothermal system, shale gas recovery, and other processes.

Development of Ion-Plasma Coatings for Protecting Intermetallic Refractory Alloys VKNA-1V and VKNA-25 in the Temperature Range of 1200 - 1250°C

NASA Astrophysics Data System (ADS)

Budinovskii, S. A.; Matveev, P. V.; Smirnov, A. A.

2017-05-01

Multilayer heat-resistant ion-plasma coatings for protecting the parts of the hot duct of gas-turbine engines produced from refractory nickel alloys based on VKNA intermetallics from high-temperature oxidation are considered. Coatings of the Ni - Cr - Al (Ta, Re, Hf, Y) + Al - Ni - Y systems are tested for high-temperature strength at 1200 and 1250°C. Metallographic and microscopic x-ray spectrum analyses of the structure and composition of the coatings in the initial condition and after the testing are performed. The effect of protective coatings of the Ni - Cr - Al - Hf + Al - Ni - Y systems on the long-term strength of alloys VKNA-1V and VKNA-25 at 1200°C is studied.

NASA research on refractory compounds.

NASA Technical Reports Server (NTRS)

Gangler, J. J.

1971-01-01

The behavior and properties of the refractory carbides, nitrides, and borides are being investigated by NASA as part of its research aimed at developing superior heat resistant materials for aerospace applications. Studies of the zirconium-carbon-oxygen system show that zirconium oxycarbides of different compositions and lattice parameters can be formed between 1500 C and 1900 C and are stable below 1500 C. More applied studies show that hot working generally improves the microstructure and therefore the strength of TiC and NbC. Sintering studies on UN indicate that very high densities can be achieved. Hot pressing of cermets of HfN and HfC produces good mechanical properties for high temperature bearing applications. Attempts to improve the impact resistance of boride composites by the addition of a nickel or carbon yarn were not overly successful.

PROCESS OF FORMING PLUOTONIUM SALTS FROM PLUTONIUM EXALATES

DOEpatents

Garner, C.S.

1959-02-24

A process is presented for converting plutonium oxalate to other plutonium compounds by a dry conversion method. According to the process, lower valence plutonium oxalate is heated in the presence of a vapor of a volatile non- oxygenated monobasic acid, such as HCl or HF. For example, in order to produce plutonium chloride, the pure plutonium oxalate is heated to about 700 deg C in a slow stream of hydrogen plus HCl. By the proper selection of an oxidizing or reducing atmosphere, the plutonium halide product can be obtained in either the plus 3 or plus 4 valence state.

Has the Time Come to Be More Aggressive With Bariatric Surgery in Obese Patients With Chronic Systolic Heart Failure?

PubMed

Vest, Amanda R

2018-06-01

Obesity is a strong risk factor for the development of heart failure (HF). Diet, exercise, and weight-loss pharmacotherapies have limited potential to achieve significant and sustainable weight loss, especially in patients with symptomatic systolic HF. This review seeks to determine the role of bariatric surgery for patients with systolic HF and obesity. Bariatric surgeries such as the laparoscopic sleeve gastrectomy (LSG) and Roux-en-Y gastric bypass (RYGB) represent the most successful long-term strategy for achieving weight loss and diabetes and hypertension remission in the general obese population. These benefits translate to reductions in cardiovascular events and mortality, as well as improvements in myocardial structure and function. There is also now data supporting the safety of LSG or RYGB in patients with systolic dysfunction and a reduction in HF admissions post-operatively. Current literature and clinical experience suggest that the most appropriate bariatric surgery candidates with HF are patients aged < 50-60 years, with severely depressed systolic function and NYHA II-III symptoms, who have failed non-surgical strategies and have a high likelihood of future cardiac transplantation candidacy after weight loss. This review seeks to determine the role of bariatric surgery for patients with systolic HF and obesity.

Undertreatment of hyperlipidemia in patients with coronary artery disease and heart failure.

PubMed

Sueta, Carla A; Massing, Mark W; Chowdhury, Mridul; Biggs, David P; Simpson, Ross J

2003-02-01

Coronary artery disease patients with heart failure (CAD+HF) are at high risk for cardiovascular events. We examined the frequency of lipid assessment and prescription of lipid-lowering agents in outpatients with combined CAD+HF compared with patients with CAD alone. We analyzed an administrative data set from the Quality Assurance Program II, a Merck & Co., Inc., sponsored national retrospective chart audit of 41,487 CAD patients seen at 296 ambulatory medical practices. About 34% of these patients had CAD+HF. Documentation of low-density lipoprotein (LDL) cholesterol was significantly lower in patients with CAD+HF (53%) compared with those with CAD alone (69%). Lipid-lowering drugs were prescribed in only 36% of patients with CAD+HF, compared with 52% of patients with CAD alone. Lipid levels alone did not justify this disparity. Patients with documented LDL cholesterol values were 4 times more likely to receive a prescription for a lipid-lowering medication than those without recorded values. Other predictors of lipid-lowering prescription included: younger age, history of myocardial infarction, revascularization, care by a cardiologist, and geographic region. Patients with CAD, HF, and advanced age simultaneously experience among the highest risk and the lowest lipid-lowering treatment rates. Strategies to increase LDL testing and aggressively treat patients with heart failure and CAD are warranted.

Patients with heart failure and their partners with chronic illness: interdependence in multiple dimensions of time

PubMed Central

Nimmon, Laura; Bates, Joanna; Kimel, Gil; Lingard, Lorelei

2018-01-01

Background Informal caregivers play a vital role in supporting patients with heart failure (HF). However, when both the HF patient and their long-term partner suffer from chronic illness, they may equally suffer from diminished quality of life and poor health outcomes. With the focus on this specific couple group as a dimension of the HF health care team, we explored this neglected component of supportive care. Materials and methods From a large-scale Canadian multisite study, we analyzed the interview data of 13 HF patient–partner couples (26 participants). The sample consisted of patients with advanced HF and their long-term, live-in partners who also suffer from chronic illness. Results The analysis highlighted the profound enmeshment of the couples. The couples’ interdependence was exemplified in the ways they synchronized their experience in shared dimensions of time and adapted their day-to-day routines to accommodate each other’s changing health status. Particularly significant was when both individuals were too ill to perform caregiving tasks, which resulted in the couples being in a highly fragile state. Conclusion We conclude that the salience of this couple group’s oscillating health needs and their severe vulnerabilities need to be appreciated when designing and delivering HF team-based care. PMID:29588596

Origin of high thermoelectric performance of FeNb1−xZr/HfxSb1−ySny alloys: A first-principles study

PubMed Central

Zhang, Xiwen; Wang, Yuanxu; Yan, Yuli; Wang, Chao; Zhang, Guangbiao; Cheng, Zhenxiang; Ren, Fengzhu; Deng, Hao; Zhang, Jihua

2016-01-01

The previous experimental work showed that Hf- or Zr-doping has remarkably improved the thermoelectric performance of FeNbSb. Here, the first-principles method was used to explore the possible reason for such phenomenon. The substitution of X (Zr/Hf) atoms at Nb sites increases effective hole-pockets, total density of states near the Fermi level (EF), and hole mobility to largely enhance electrical conductivity. It is mainly due to the shifting the EF to lower energy and the nearest Fe atoms around X atoms supplying more d-states to hybrid with X d-states at the vicinity of the EF. Moreover, we find that the X atoms indirectly affect the charge distribution around Nb atoms via their nearest Fe atoms, resulting in the reduced energy difference in the valence band edge, contributing to enhanced Seebeck coefficients. In addition, the further Bader charge analysis shows that the reason of more holes by Hf-doping than Zr in the experiment is most likely derived from Hf atoms losing less electrons and the stronger hybridization between Hf atoms and their nearest Fe atoms. Furthermore, we predict that Hf/Sn co-doping may be an effective strategy to further optimize the thermoelectric performance of half-Heusler (HH) compounds. PMID:27604826

Role of point defects and HfO2/TiN interface stoichiometry on effective work function modulation in ultra-scaled complementary metal-oxide-semiconductor devices

NASA Astrophysics Data System (ADS)

Pandey, R. K.; Sathiyanarayanan, Rajesh; Kwon, Unoh; Narayanan, Vijay; Murali, K. V. R. M.

2013-07-01

We investigate the physical properties of a portion of the gate stack of an ultra-scaled complementary metal-oxide-semiconductor (CMOS) device. The effects of point defects, such as oxygen vacancy, oxygen, and aluminum interstitials at the HfO2/TiN interface, on the effective work function of TiN are explored using density functional theory. We compute the diffusion barriers of such point defects in the bulk TiN and across the HfO2/TiN interface. Diffusion of these point defects across the HfO2/TiN interface occurs during the device integration process. This results in variation of the effective work function and hence in the threshold voltage variation in the devices. Further, we simulate the effects of varying the HfO2/TiN interface stoichiometry on the effective work function modulation in these extremely-scaled CMOS devices. Our results show that the interface rich in nitrogen gives higher effective work function, whereas the interface rich in titanium gives lower effective work function, compared to a stoichiometric HfO2/TiN interface. This theoretical prediction is confirmed by the experiment, demonstrating over 700 meV modulation in the effective work function.

Rare-gas-rich separates from carbonaceous chondrites

NASA Technical Reports Server (NTRS)

Reynolds, J. H.; Frick, U.; Neil, J. M.; Phinney, D. L.

1978-01-01

This paper describes an analysis of carbon-rich separates prepared by demineralization of colloidal fractions after disaggregation of bulk samples of the type C2 meteorites Murray, Murchison, and Cold Bokkeveld, as well as a methanol colloid extracted from acid-resistant residues of the Allende meteorite (type C3V) obtained by dissolution of most of the minerals in HCl and HF acids. The carbonaceous separates, or lAlates (a coined word designating colloids prepared sometimes before and sometimes after acid treatment), are characterized incompletely and with difficulty. A stepwise heating experiment on a Murray lAlate is discussed which revealed bimodal release of all noble gases, with similar patterns for Ar, Kr, and Xe. Chemical reactions are suggested as the likely mechanism for gas release. The results are shown to support the concept of a carbonaceous gas carrier uniformly present in meteorites of various types.

Mantle eclogites and garnet pyroxenites - the meaning of two-point isochrons, Sm-Nd and Lu-Hf closure temperatures and the cooling of the subcratonic mantle

NASA Astrophysics Data System (ADS)

Shu, Qiao; Brey, Gerhard P.; Gerdes, Axel; Hoefer, Heidi E.

2014-03-01

The Earth's mantle is a huge metamorphic complex which undergoes permanent changes ruled by plate tectonics. It also has enclaves underneath Archean crust which are exempt from the convecting mantle since at least 2.5 Ga. Since then, this mantle may cool slowly as a result of diminishing heat input from the asthenosphere, of declining heat production from radioactive decay and of denudation of the crust. Under such circumstances, two point garnet-clinopyroxene isochrons from mantle xenoliths (here garnet pyroxenites and eclogites) reflect either cooling ages or eruption ages depending on whether the mantle portion under consideration was below or above the closure temperature of a radiogenic system. Available literature data from the Slave and Kaapvaal craton for the Sm-Nd and Lu-Hf isotope systems and our own new data from Bellsbank (Kaapvaal) provide a whole range of two-point isochron ages from younger than the kimberlite eruption age to early Proterozoic. The meaning of ages other than the kimberlite eruption age is unclear. We use here a compilation of Sm-Nd and Lu-Hf two-point isochron age data from this study and the literature, to assess the meaning of such isochrons. This is achieved by plotting the temperature of last equilibration as derived from the Fe-Mg exchange between garnet and clinopyroxene versus the two-point isochron age. There is a low temperature alignment for both systems of increasing age with decreasing temperature and an alignment around the kimberlite eruption ages at high temperatures. We interpret the intersect between the low temperature limb and the kimberlite eruption age as closure temperature which gives about 920 °C for the Lu-Hf system and about 850 °C for the Sm-Nd system. The differences of the cooling ages between the two isotope systems for individual samples combined with the closure temperatures from this study are used to deduce the cooling of the Slave and Kaapvaal subcratonic mantle from the early Proterozoic until today. We deduce that the subcratonic mantle cooled since 2 Ga from a geothermal gradient of 46 mW/m to 38 mW/m at 120 Ma ago with a rate of around 0.1 °C/Ma. This value is in agreement with previous estimates which were based on various geophysical and geological constraints, heat production by radioactive elements and diffusivity of radiogenic elements.

Upper atmospheric effects of the hf active auroral research program ionospheric research instrument (HAARP IRI)

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

Eccles, V.; Armstrong, R.

1993-05-01

The earth's ozone layer occurs in the stratosphere, primarily between 10 and 30 miles altitude. The amount of ozone, O3, present is the result of a balance between production and destruction processes. Experiments have shown that natural processes such as auroras create molecules that destroy O. One family of such molecules is called odd nitrogen of which nitric oxide (NO) is an example. Because the HAARP (HF Active Auroral Research Program) facility is designed to mimic and investigate certain natural processes, a study of possible effects of HAARP on the ozone layer was conducted. The study used a detailed modelmore » of the thermal and chemical effects of the high power HF beam, which interacts with free electrons in the upper atmosphere above 50 miles altitude. It was found only a small fraction of the beam energy goes into the production of odd nitrogen molecules, whereas odd nitrogen is efficiently produced by auroras. Since the total energy emitted by HAARP in the year is some 200,000 times less than the energy deposited in the upper atmosphere by auroras, the study demonstrates that HAARP HF beam experiments will cause no measurable depletion of the earth's ozone layer.... Ozone, Ozone depletion, Ozone layer, Odd nitrogen, Nitric oxide, HAARP Emitter characteristics.« less

Biochemical responses of isolated lung CSCs after application of low intensity laser irradiation

NASA Astrophysics Data System (ADS)

Abrahamse, Heidi; Crous, Anine

2016-03-01

Studies have shown that using high fluences of Low Intensity Laser Irradiation (HF-LILI) produce apoptotic effects on normal and neoplastic cells. This study aimed to determine whether HF-LILI induce cell death in lung CSCs. Lung CSCs were isolated using the stem cell marker CD 133, characterized using flow cytometry, and applied in experiments which included treatment with LILI at wavelengths of 636, 825 and 1060 nm with fluences ranging from 5 J/cm2 to 40 J/cm2. Viability and proliferation studies, using Alamar blue assay and adenosine triphosphate luminescence (ATP), indicated an increase when treating lung CSCs with low fluences of 5 - 20 J/cm2 and a decrease in viability and proliferation as well as an increase in apoptosis when applying a fluence of 40 J/cm2 indicated by flow cytometry using Annexin V and propidium iodide (PI) dyes. Results indicate that LILI, when treating lung CSCs, can induce either a bio-stimulatory or bio-inhibitory effect depending on the wavelength and fluence used. This study indicated successful apoptotic induction of lung CSCs. Future experiments should be able to conclude the exact mechanism behind HF-LILI, which can be used in the targeted treatments of CSC elimination, implementing HF-LILI in the same manner as PDT in the absence of a photosensitizer.

VLF wave generation by beating of two HF waves in the ionosphere

NASA Astrophysics Data System (ADS)

Kuo, Spencer; Snyder, Arnold; Kossey, Paul; Chang, Chia-Lie; Labenski, John

2011-05-01

Theory of a beat-wave mechanism for very low frequency (VLF) wave generation in the ionosphere is presented. The VLF current is produced by beating two high power HF waves of slightly different frequencies through the nonlinearity and inhomogeneity of the ionospheric plasma. Theory also shows that the density irregularities can enhance the beat-wave generation. An experiment was conducted by transmitting two high power HF waves of 3.2 MHz and 3.2 MHz + f, where f = 5, 8, 13, and 2.02 kHz, from the HAARP transmitter. In the experiment, the ionosphere was underdense to the O-mode heater, i.e., the heater frequency f0 > foF2, and overdense or slightly underdense to the X-mode heater, i.e., f0 < fxF2 or f0 ≥ fxF2. The radiation intensity increased with the VLF wave frequency, was much stronger with the X-mode heaters, and was not sensitive to the electrojet. The strongest VLF radiation of 13 kHz was generated when the reflection layer of the X-mode heater was just slightly below the foF2 layer and the spread of the O-mode sounding echoes had the largest enhancement, suggesting an optimal setting for beat-wave generation of VLF waves by the HF heaters.

Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes

NASA Astrophysics Data System (ADS)

Xu, Xiang; Zhou, Chen; Shi, Run; Ni, Binbin; Zhao, Zhengyu; Zhang, Yuannong

2016-09-01

Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) model and the neutral atmosphere model (NRLMSISE-00), including the High Frequency Active Auroral Research Program (HAARP; 62.39° N, 145.15° W), Wuhan (30.52° N, 114.32° E) and Jicamarca (11.95° S, 76.87° W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.

Thermal degradation of TiO2 nanotubes on titanium

NASA Astrophysics Data System (ADS)

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2014-10-01

The objective of this research was to study thermal degradation behavior of TiO2 nanotubes on titanium (Ti). TiO2 nanotubes were grown via anodization method on commercially pure Ti (Cp-Ti) discs using two different electrolytes, 1 vol. % HF in deionized (DI) water and 1 vol. % HF + 0.5 wt. % NH4F + 10 vol. % DI water in ethylene glycol, to obtain nanotubes with two different lengths, 300 nm and 950 nm keeping the nanotube diameter constant at 100 ± 20 nm. As grown TiO2 nanotubes were subjected to heat treatment to understand thermal degradation as a function of both temperature and hold time. The signs of degradation were observed mainly when amorphous nanotubes started to crystallize, however the crystallization temperature varied based on TiO2 nanotubes length and anodizing condition. Overall, 300 nm nanotubes were thermally stable at least up to 400 °C for 12 h, while the 950 nm long nanotubes show signs of degradation from 400 °C for 6 h only. Clearly, length of nanotubes, heat treatment temperature as well as hold times show influence toward degradation kinetics of TiO2 nanotubes on titanium.

Lu-Hf isotope constraints on plume-lithosphere interaction during emplacement of the Bushveld Large Igneous Province at 2.06 Ga: Implications for the structure and evolution of the Kaapvaal Craton's lithospheric mantle

NASA Astrophysics Data System (ADS)

Zirakparvar, N. A.; Mathez, E. A.; Rajesh, H.; Vervoort, J. D.; Choe, S.

2016-12-01

The Bushveld Large Igneous Province (B-LIP) comprises a diverse array of >30 magma bodies that intruded the Kaapvaal Craton at 2.06 Ga. In this talk we use zircon and bulk-rock Lu-Hf isotope data to show that the B-LIP formed in response to the arrival of a plume(s) from the deep mantle. New zircon Hf isotope compositions for four B-LIP bodies yield intrusion-specific average ɛHf (2.06 Ga) values that range from -20.7 ± 2.8 to -2.7 ± 2.8, largely consistent with literature zircon data for other B-LIP intrusions. Bulk-rock solution ɛHf (2.06 Ga) values for a variety of B-LIP intrusions range from -2.1 ± 0.2 to -10.6 ± 0.2. Because the most radiogenic Hf isotope compositions across the entire B-LIP are nearly primordial with an ɛHf (2.06 Ga) close to 0, it is likely that the heat source of the B-LIP was a plume(s) from deep mantle. The Hf isotope data further suggests that individual intrusions in the B-LIP can be grouped into four categories based on their ultimate sources: 1) melts generated in subduction and plume modified continental lithospheric mantle; 2) melts generated by melting of a mafic-ultramafic reservoir composed of older ( 2.7 Ga) plume-related material trapped in the Kaapvaal lithosphere; 3) melts generated in the mid- to upper crust; and 4) melts generated from the 2.06 Ga mantle plume itself. The presence of 2.7 Ga mafic-ultramafic material in the Kaapvaal lithosphere may have acted to strengthen the lithosphere so that it was able to resist being dispered by the arrival of the B-LIP plume at 2.06 Ga. Because the B-LIP extends into a 2.7 Ga aged suture zone between the Kaapvaal and Zimbabwe cratons, it is also possible to understand the role of the lithospheric mantle in producing the Lu-Hf signatures observed in the various B-LIP intrusions as a function of two different types of the continental lithosphere: The very old lithosphere comprising the Kaapvaal Craton and the somewhat younger lithosphere comprising the suture zone. A basic observation is that the Hf isotope signature of the plume source is only directly expressed in B-LIP bodies that intruded the suture zone, providing further evidence that the craton was already underlain by thick lithospheric mantle at the time of B-LIP magmatism.

Ar(n)HF van der Waals clusters revisited: II. Energetics and HF vibrational frequency shifts from diffusion Monte Carlo calculations on additive and nonadditive potential-energy surfaces for n=1-12.

PubMed

Jiang, Hao; Xu, Minzhong; Hutson, Jeremy M; Bacić, Zlatko

2005-08-01

The ground-state energies and HF vibrational frequency shifts of Ar(n)HF clusters have been calculated on the nonadditive potential-energy surfaces (PESs) for n=2-7 and on the pairwise-additive PESs for the clusters with n=1-12, using the diffusion Monte Carlo (DMC) method. For n>3, the calculations have been performed for the lowest-energy isomer and several higher-lying isomers which are the closest in energy. They provide information about the isomer dependence of the HF redshift, and enable direct comparison with the experimental data recently obtained in helium nanodroplets. The agreement between theory and experiment is excellent, in particular, for the nonadditive DMC redshifts. The relative, incremental redshifts are reproduced accurately even at the lower level of theory, i.e., the DMC and quantum five-dimensional (rigid Ar(n)) calculations on the pairwise-additive PESs. The nonadditive interactions make a significant contribution to the frequency shift, on the order of 10%-12%, and have to be included in the PESs in order for the theory to yield accurate magnitude of the HF redshift. The energy gaps between the DMC ground states of the cluster isomers are very different from the energy separation of their respective minima on the PES, due to the considerable variations in the intermolecular zero-point energy of different Ar(n)HF isomers.

Being on sick leave due to heart failure: Encounters with social insurance officers and associations with sociodemographic factors and self-estimated ability to return to work.

PubMed

Nordgren, Lena; Söderlund, Anne

2016-04-01

Little is known about sick leave and the ability to return to work (RTW) for people with heart failure (HF). Previous research findings raise questions about the significance of encounters with social insurance officers (SIOs) and sociodemographics in people sick-listed due to HF. To investigate how people on sick leave due to HF experience encounters with SIOs and associations between sociodemographic factors, experiences of positive/negative encounters with SIOs, and self-estimated ability to RTW. This was a population-based study with a cross-sectional design. The sample consisted of 590 sick-listed people with HF in Sweden. A register-based investigation supplemented with a postal survey questionnaire was conducted. Bivariate correlations and logistic regression analysis was used to test associations between sociodemographic factors, positive and negative encounters, and self-estimated ability to RTW. People with low income were more likely to receive sickness compensation. A majority of the responders experienced encounters with SIOs as positive. Being married was significantly associated with positive encounters. Having a low income was related to negative encounters. More than a third of the responders agreed that positive encounters with SIOs facilitated self-estimated ability to RTW. High income was strongly associated with the impact of positive encounters on self-estimated ability to RTW. Encounters between SIOs and people on sick leave due to HF need to be characterized by a person-centred approach including confidence and trust. People with low income need special attention. © The European Society of Cardiology 2015.

Biological applications and effects of optical masers

NASA Astrophysics Data System (ADS)

Ham, William T., Jr.; Mueller, Harold A.; Williams, Ray C.; Geeraets, Walter J.; Ruffolo, John J., Jr.

1988-02-01

Research experiments and projects pertaining to the ocular hazards of lasers and other optical sources are reviewed and discussed in some detail. Early studies to determine threshold retinal damage in the rabbit from ruby and neodymium lasers are described and followed by more elaborate experiments with monkeys using the He;Ne laser. A comparison between threshold retinal lesions in human volunteers, monkeys and rabbits is given. Retinal damage in the rhesus monkey is evaluated in terms of visual acuity. Quantitative data on solar retinitis as determined in the rhesus monkey are provided and the effects of wavelength on light toxicity are evaluated for eight monochromatic laser lines. Experiments performed at Los Alamos to evaluate the ocular effects and hazards of picosecond and nanosecond pulses of radiation from CO2 and HF lasers are described. A list of published papers describing the above research is included. The HF laser effects on the rabbit cornea were very similar to those caused by exposure to the CO2 laser. The energy from the CO2 and HF lasers is completely absorbed in the superficial layers of the cornea, creating a sharp sonic or shock wave which can disrupt the epithelial cells but does not penetrate to the stroma.

The success and complementarity of Sm-Nd and Lu-Hf garnet geochronology

NASA Astrophysics Data System (ADS)

Baxter, E. F.; Scherer, E. E.

2013-12-01

Garnet's potential as a direct chronometer of tectonometamorphic processes and conditions was first realized over 30 years ago. Since then, the Sm-Nd and Lu-Hf systems have emerged as the most effective, with both permitting age precision < ×1 Myr. Both have proven successful not merely in dating garnet growth itself, but rather in constraining the ages, durations, and rates of particular earth processes or conditions that can be directly linked to garnet growth via chemical, thermodynamic, or petrographic, means. Appreciating important differences between Sm-Nd and Lu-Hf in terms of contaminant phases, partitioning, daughter element diffusivity, and isotopic analysis makes these two systems powerfully complementary when used and interpreted in concert. Well established, robust analytical methods mitigate the effects of ubiquitous mineral inclusions (monazite is most significant for Sm-Nd; zircon is most significant for Lu-Hf), improving the precision and accuracy of garnet dates from both systems. Parent-daughter ratios tend to be higher for Lu-Hf leading to the potential for better age precision in general. The Lu-176 decay rate is faster than Sm-147, meaning that Lu-Hf provides better age precision potential for young (Cenozoic) samples. However, Sm-Nd provides better precision potential for older (Precambrian) samples primarily because of the higher precisions on the parent-daughter ratios (i.e., 147Sm/144Nd) that can be achieved by ID-TIMS analysis. For dating microsampled zones or growth rings in single garnet crystals, Sm-Nd has proven most successful owing to more uniform distribution of Sm, and established methods to measure <10 ng quantities of Nd at high precision via TIMS. However, new MC-ICP-MS sample introduction technologies are closing this gap for small samples. For analyses of bulk garnet that grew over a protracted interval, Lu-Hf dates are expected to be older than Sm-Nd dates owing to differences in Lu and Sm zonation (i.e. Lu tends to be strongly sequestered by garnet cores, whereas Sm is more evenly distributed). Thus, Lu-Hf is often useful for targeting nucleation times (and earliest growth zones), whereas Sm-Nd is preferable when targeting the mid- to later stages (and outermost growth zones) of garnet. Depending on grain size and heating duration, most garnets can retain their primary growth chronology up to about 700 C, and thus they are one of the few metamorphic minerals that faithfully record prograde metamorphic processes and conditions. For granulite facies rocks (e.g., > about 700 C), higher retentivity (i.e., slower diffusivity) for Hf than for Nd can lead to older Lu-Hf (growth) ages compared to Sm-Nd (partially reset) dates for the same sample. Finally, as with all geochronometers, decay constant uncertainties and sources of systematic error in methods (e.g., spike calibrations) should be considered when comparing absolute Lu-Hf and Sm-Nd dates to each other or to other chronometers.

Fire Tests on E-vehicle Battery Cells and Packs.

PubMed

Sturk, David; Hoffmann, Lars; Ahlberg Tidblad, Annika

2015-01-01

The purpose of this study was to investigate the effects of abuse conditions, including realistic crash scenarios, on Li ion battery systems in E-vehicles in order to develop safe practices and priorities when responding to accidents involving E-vehicles. External fire tests using a single burning item equipment were performed on commercial Li ion battery cells and battery packs for electric vehicle (E-vehicle) application. The 2 most common battery cell technologies were tested: Lithium iron phosphate (LFP) and mixed transition metal oxide (lithium nickel manganese cobalt oxide, NMC) cathodes against graphite anodes, respectively. The cell types investigated were "pouch" cells, with similar physical dimensions, but the NMC cells have double the electric capacity of the LFP cells due to the higher energy density of the NMC chemistry, 7 and 14 Ah, respectively. Heat release rate (HRR) data and concentrations of toxic gases were acquired by oxygen consumption calorimetry and Fourier transform infrared spectroscopy (FTIR), respectively. The test results indicate that the state of charge (SOC) affects the HRR as well as the amount of toxic hydrogen fluoride (HF) gas formed during combustion. A larger number of cells increases the amount of HF formed per cell. There are significant differences in response to the fire exposure between the NMC and LFP cells in this study. The LFP cells generate a lot more HF per cell, but the overall reactivity of the NMC cells is higher. However, the total energy released by both batteries during combustion was independent of SOC, which indicates that the electric energy content of the test object contributes to the activation energy of the thermal and heat release process, whereas the chemical energy stored in the materials is the main source of thermal energy in the batteries. The results imply that it is difficult to draw conclusions about higher order system behavior with respect to HF emissions based on data from tests on single cells or small assemblies of cells. This applies to energy release rates as well. The present data show that mass and shielding effects between cells in multicell assemblies affect the propagation of a thermal event.

Oxidation Characterization of Hafnium-Based Ceramics Fabricated by Hot Pressing and Electric Field-Assisted Sintering

NASA Technical Reports Server (NTRS)

Gasch, Matt; Johnson, Sylvia; Marschall, Jochen

2010-01-01

Ceramic borides, such as hafnium diboride (HfB2) and zirconium diboride (ZrB2), are members of a family of materials with extremely high melting temperatures referred to as Ultra High Temperature Ceramics (UHTCs). UHTCs constitute a class of promising materials for use in high temperature applications, such as sharp leading edges on future-generation hypersonic flight vehicles, because of their high melting points. The controlled development of microstructure has become important to the processing of UHTCs, with the prospect of improving their mechanical and thermal properties. The improved oxidation resistance of HfB2 has also become important if this material is to be successfully used at temperatures above 2000 C. Furthermore, the use of UHTCs on the leading edges of vehicles traveling at hypersonic speeds will mean exposure to a mixed oxidation environment comprised of both molecular and atomic oxygen. The current study has investigated the high-temperature oxidation behavior of HfB2-based materials in a pure O2 environment, as well as in environments containing different levels of dissociated oxygen (O/O2). Materials were processed by two techniques: conventional hot pressing (HP) and electric field-assisted sintering (FAS). Their oxidation behavior was evaluated in both a tube furnace at 1250 C for 3 hours and in a simulated re-entry environment in the Advanced Heating Facility (AHF) arcjet at NASA Ames Research Center, during a 10-minute exposure to a cold wall heat flux of 250W/sq cm and stagnation pressure of 0.1-0.2 atm. The microstructure of the different materials was characterized before and after oxidation using scanning electron microscopy (SEM).

The effects of non-invasive respiratory support on oropharyngeal temperature and humidity: a neonatal manikin study.

PubMed

Roberts, Calum T; Kortekaas, Rebecca; Dawson, Jennifer A; Manley, Brett J; Owen, Louise S; Davis, Peter G

2016-05-01

Heating and humidification of inspired gases is routine during neonatal non-invasive respiratory support. However, little is known about the temperature and humidity delivered to the upper airway. The International Standards Organization (ISO) specifies that for all patients with an artificial airway humidifiers should deliver ≥33 g/m(3) absolute humidity (AH). We assessed the oropharyngeal temperature and humidity during different non-invasive support modes in a neonatal manikin study. Six different modes of non-invasive respiratory support were applied at clinically relevant settings to a neonatal manikin, placed in a warmed and humidified neonatal incubator. Oropharyngeal temperature and relative humidity (RH) were assessed using a thermohygrometer. AH was subsequently calculated. Measured temperature and RH varied between devices. Bubble and ventilator continuous positive airway pressure (CPAP) produced temperatures >34°C and AH >38 g/m(3). Variable flow CPAP resulted in lower levels of AH than bubble or ventilator CPAP, and AH decreased with higher gas flow. High-flow (HF) therapy delivered by Optiflow Junior produced higher AH with higher gas flow, whereas with Vapotherm HF the converse was true. Different non-invasive devices deliver inspiratory gases of variable temperature and humidity. Most AH levels were above the ISO recommendation; however, with some HF and variable flow CPAP devices at higher gas flow this was not achieved. Clinicians should be aware of differences in the efficacy of heating and humidification when choosing modes of non-invasive respiratory support. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Perinatal undernutrition alters intestinal alkaline phosphatase and its main transcription factors KLF4 and Cdx1 in adult offspring fed a high-fat diet.

PubMed

Lallès, Jean-Paul; Orozco-Solís, Ricardo; Bolaños-Jiménez, Francisco; de Coppet, Pierre; Le Dréan, Gwénola; Segain, Jean-Pierre

2012-11-01

Nutrient restriction during gestation and/or suckling is associated with an increased risk of developing inflammation, obesity and metabolic diseases in adulthood. However, the underlying mechanisms, including the role of the small intestine, are unclear. We hypothesized that intestinal adaptation to the diet in adulthood is modulated by perinatal nutrition. This hypothesis was tested using a split-plot design experiment with 20 controls and 20 intrauterine growth-retarded (IUGR) rats aged 240 days and randomly assigned to be fed a standard chow or a high-fat (HF) diet for 10 days. Jejunal tissue was collected at necropsy and analyzed for anatomy, digestive enzymes, goblet cells and mRNA levels. Cecal contents and blood serum were analyzed for alkaline phosphatase (AP). IUGR rats failed to adapt to HF by increasing AP activity in jejunal tissue and cecal content as observed in controls. mRNA levels of transcription factors KLF4 and Cdx1 were blunted in jejunal epithelial cell of IUGR rats fed HF. mRNA levels of TNF-α were lower in IUGR rats. They also displayed exacerbated aminopeptidase N response and reduced jejunal goblet cell density. Villus and crypt architecture and epithelial cell proliferation increased with HF in both control and IUGR rats. Serum AP tended to be lower, and serum levamisole inhibition-resistant AP fraction was lower, in IUGR than controls with HF. Serum fatty acids and triglycerides were higher in IUGR rats and higher with HF. In conclusion, the adult intestine adapts to an HF diet differentially depending on early nutrition, jejunal AP and transcription factors being blunted in IUGR individuals fed HF. Copyright © 2012 Elsevier Inc. All rights reserved.

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

Fang, Zongtang; Both, Johan; Li, Shenggang

The heats of formation and the normalized clustering energies (NCEs) for the group 4 and group 6 transition metal oxide (TMO) trimers and tetramers have been calculated by the Feller-Peterson-Dixon (FPD) method. The heats of formation predicted by the FPD method do not differ much from those previously derived from the NCEs at the CCSD(T)/aT level except for the CrO3 nanoclusters. New and improved heats of formation for Cr3O9 and Cr4O12 were obtained using PW91 orbitals instead of Hartree-Fock (HF) orbitals. Diffuse functions are necessary to predict accurate heats of formation. The fluoride affinities (FAs) are calculated with the CCSD(T)more » method. The relative energies (REs) of different isomers, NCEs, electron affinities (EAs), and FAs of (MO2)n ( M = Ti, Zr, Hf, n = 1 – 4 ) and (MO3)n ( M = Cr, Mo, W, n = 1 – 3) clusters have been benchmarked with 55 exchange-correlation DFT functionals including both pure and hybrid types. The absolute errors of the DFT results are mostly less than ±10 kcal/mol for the NCEs and the EAs, and less than ±15 kcal/mol for the FAs. Hybrid functionals usually perform better than the pure functionals for the REs and NCEs. The performance of the two types of functionals in predicting EAs and FAs is comparable. The B1B95 and PBE1PBE functionals provide reliable energetic properties for most isomers. Long range corrected pure functionals usually give poor FAs. The standard deviation of the absolute error is always close to the mean errors and the probability distributions of the DFT errors are often not Gaussian (normal). The breadth of the distribution of errors and the maximum probability are dependent on the energy property and the isomer.« less

Maternal high fat diet and its consequence on the gut microbiome: A rat model.

PubMed

Mann, Phyllis E; Huynh, Kevin; Widmer, Giovanni

2017-11-14

The biological changes that occur during pregnancy in the female mammal include shifts in hormonal regulation in preparation for parturition and lactation, and changes in energy metabolism. In women, studies have also shown that during pregnancy there is a reduction in bacterial species richness in the gut. In the current experiment rats were used to model the interaction of diet, reproductive status, and intestinal bacterial microbiota during pregnancy and lactation. In Experiment 1 rats were exposed to either standard chow or high-fat chow (60%) and were divided into two groups: unmated (NULL) or mated (RE). In Experiment 2, both NULL and RE rats were exposed to high-fat chow for a 30-day period. High-throughput sequencing of the 16S rRNA gene revealed that pregnancy impacted the gut microbiota in a similar manner to humans. The impact of reproductive status on microbiota composition, however, was stronger in rats fed a high-fat (HF) diet. Diet-induced changes replicated some of the changes observed in humans, such as increasing the Firmicutes/Bacteroidetes ratio. However, in contrast to humans, pregnancy in rats did not increase β-diversity between microbiota from different animals. These results indicate that during pregnancy in rats, the gut microbiota is altered in a similar manner to that which occurs in women, and that these changes are further exaggerated by exposure to a HF diet. Thus, the rat may allow modelling the effects of consumption of HF food during pregnancy and enable future studies to determine the risks of HF diets during pregnancy and its consequences on the offspring.

Glass-water interactions: Effect of high-valence cations on glass structure and chemical durability

DOE PAGES

Pierce, Eric M.; Kerisit, Sebastien N.; Charpentier, Thibault; ...

2016-02-27

Spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na 2O Al 2O 3 B 2O 3 HfO 2 SiO 2 system (e.g., Na/(Al+B) = 1.0 and HfO 2/SiO 2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N 4 and increasesmore » the amount of Si–O–Hf moieties in the glass. Results from flow through experiments conducted under dilute and near saturated conditions show a decrease of approximately 100 or more in the dissolution rate over the series from 0 to 20 mol% HfO 2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveal a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the formation of a low coordination Si sites when Si from the saturated solution adsorbs to Hf on the glass surface. The residence time of the newly formed low coordination Si sites is longer at the glass surface and increases the density of anchor sites from which altered layers with higher Si densities can form than in the absence of Hf. These results illustrate the importance of understanding solid water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.« less

Thermodynamics of Anharmonic Systems: Uncoupled Mode Approximations for Molecules

DOE PAGES

Li, Yi-Pei; Bell, Alexis T.; Head-Gordon, Martin

2016-05-26

The partition functions, heat capacities, entropies, and enthalpies of selected molecules were calculated using uncoupled mode (UM) approximations, where the full-dimensional potential energy surface for internal motions was modeled as a sum of independent one-dimensional potentials for each mode. The computational cost of such approaches scales the same with molecular size as standard harmonic oscillator vibrational analysis using harmonic frequencies (HO hf). To compute thermodynamic properties, a computational protocol for obtaining the energy levels of each mode was established. The accuracy of the UM approximation depends strongly on how the one-dimensional potentials of each modes are defined. If the potentialsmore » are determined by the energy as a function of displacement along each normal mode (UM-N), the accuracies of the calculated thermodynamic properties are not significantly improved versus the HO hf model. Significant improvements can be achieved by constructing potentials for internal rotations and vibrations using the energy surfaces along the torsional coordinates and the remaining vibrational normal modes, respectively (UM-VT). For hydrogen peroxide and its isotopologs at 300 K, UM-VT captures more than 70% of the partition functions on average. By con trast, the HO hf model and UM-N can capture no more than 50%. For a selected test set of C2 to C8 linear and branched alkanes and species with different moieties, the enthalpies calculated using the HO hf model, UM-N, and UM-VT are all quite accurate comparing with reference values though the RMS errors of the HO model and UM-N are slightly higher than UM-VT. However, the accuracies in entropy calculations differ significantly between these three models. For the same test set, the RMS error of the standard entropies calculated by UM-VT is 2.18 cal mol -1 K -1 at 1000 K. By contrast, the RMS error obtained using the HO model and UM-N are 6.42 and 5.73 cal mol -1 K -1, respectively. For a test set composed of nine alkanes ranging from C5 to C8, the heat capacities calculated with the UM-VT model agree with the experimental values to within a RMS error of 0.78 cal mol -1 K -1 , which is less than one-third of the RMS error of the HO hf (2.69 cal mol -1 K -1) and UM-N (2.41 cal mol -1 K -1) models.« less

Clean Metal Finishing Alternatives

DTIC Science & Technology

2006-05-01

Cr, must heat treat for hardness 4 4 Trivalent chrome Trivalent plating chemistry Varying success, some must be brush plate 3 3 Alloy plating...metals. Hard coating deposition unproven. 3 N/A Weld coating Electrospark Deposition/ Alloying (ESD/ ESA) Microarc welding Localized repair of non...Alternatives to chromate conversion coatings Al TriChrome Pretreatment (TCP)* – AnoChem TCP, Aluminescent, TCP-HF Trivalent Cr3+ conversion with Zr

Gender and racial differences in surgical outcomes among adult patients with acute heart failure.

PubMed

Arslanian-Engoren, Cynthia; Sferra, Joseph J; Engoren, Milo

Approximately three million U.S. adult women have heart failure (HF), increasing their risk of adverse perioperative outcomes. While gender and racial differences are reported in surgical outcomes, less is known about 30-day perioperative outcomes in HF patients. To characterize and compare gender and racial differences in 30-day perioperative outcomes in adults with new or acute/worsening HF. The 2012-2013 American College of Surgeons National Surgical Quality Improvement Program database of surgical patients (n = 9458) with HF was analyzed. Logistic regression was used to adjust for gender and racial differences in baseline covariates. No gender difference in mortality (odds ratio = 0.922, 95% confidence interval = 0.0792-1.073, p = 0.294) was noted. Whites were more likely than Blacks to die 30 days after surgery (14% vs 9%, p < 0.001); after adjustment, Blacks were more likely to experience complications and be readmitted compared to Whites. There was no gender difference in mortality. White patients with HF were more likely to die after surgery than Black patients. Copyright © 2017 Elsevier Inc. All rights reserved.

NASA research on refractory compounds.

NASA Technical Reports Server (NTRS)

Gangler, J. J.

1971-01-01

The behavior and properties of the refractory carbides, nitrides, and borides are being investigated by NASA as part of its research aimed at developing superior heat resistant materials for aerospace applications. Fundamental studies on the electronic and defect structures of the carbides indicate that there is promise for improving the strength and ductility of these materials. Studies of the zirconium-carbon-oxygen system show that zirconium oxycarbides of different compositions and lattice parameters can be formed between 1500 and 1900 C and are stable below 1500 C. More applied studies show that hot working generally improves the microstructure and therefore the strength of TiC and NbC. Sintering studies on UN indicate that very high densities can be achieved. Hot pressing of cermets of HfN and HfC produces good mechanical properties for high temperature bearing applications.

Evidence for a dynamical ground state in the frustrated pyrohafnate Tb2Hf2O7

NASA Astrophysics Data System (ADS)

Anand, V. K.; Opherden, L.; Xu, J.; Adroja, D. T.; Hillier, A. D.; Biswas, P. K.; Herrmannsdörfer, T.; Uhlarz, M.; Hornung, J.; Wosnitza, J.; Canévet, E.; Lake, B.

2018-03-01

We report the physical properties of Tb2Hf2O7 based on ac magnetic susceptibility χac(T ) , dc magnetic susceptibility χ (T ) , isothermal magnetization M (H ) , and heat capacity Cp(T ) measurements combined with muon spin relaxation (μ SR ) and neutron powder diffraction measurements. No evidence for long-range magnetic order is found down to 0.1 K. However, χac(T ) data present a frequency-dependent broad peak (near 0.9 K at 16 Hz) indicating slow spin dynamics. The slow spin dynamics is further evidenced from the μ SR data (characterized by a stretched exponential behavior) which show persistent spin fluctuations down to 0.3 K. The neutron powder diffraction data collected at 0.1 K show a broad peak of magnetic origin (diffuse scattering) but no magnetic Bragg peaks. The analysis of the diffuse scattering data reveals a dominant antiferromagnetic interaction in agreement with the negative Weiss temperature. The absence of long-range magnetic order and the presence of slow spin dynamics and persistent spin fluctuations together reflect a dynamical ground state in Tb2Hf2O7 .

Thermoelectric and Structural Properties of Zr-/Hf-Based Half-Heusler Compounds Produced at a Large Scale

NASA Astrophysics Data System (ADS)

Zillmann, D.; Waag, A.; Peiner, E.; Feyand, M.-H.; Wolyniec, A.

2018-02-01

The half-Heusler (HH) systems are promising candidates for thermoelectric (TE) applications since they have shown high figures of merit ( zT) of ˜ 1, which are directly related to the energy conversion efficiency. To use HH compounds for TE devices, the materials must be phase-stable at operating temperatures up to 600°C. Currently, only a few HH compositions are available in large quantities. Hence, we focus on the TE and structural properties of three commercially available Zr-/Hf-based HH compounds in this publication. In particular, we evaluate the thermal conductivities and the figures of merit and critically discuss uncertainties and propagation error in the measurements. We find thermal conductivities of less than 6.0 W K^{-1}m^{-1} for all investigated materials and notably high figures of merit of 0.93 and 0.60 for n- and p-type compounds, respectively, at 600°C. Additionally, our investigations reveal that the grain structures of all materials also contain secondary phases like HfO2, Sn-Ni and Ti-Zr-Sn rich phases while an additional SnO_2 phase was found following several hours of harsh heat treatment at 800°C.

Processing, Structure and High Temperature Oxidation Properties of Polymer-Derived and Hafnium Oxide Based Ceramic Systems

NASA Astrophysics Data System (ADS)

Terauds, Kalvis

Demands for hypersonic aircraft are driving the development of ultra-high temperature structural materials. These aircraft, envisioned to sustain Mach 5+, are expected to experience continuous temperatures of 1200--1800°C on the aircraft surface and temperatures as high as 2800°C in combustion zones. Breakthroughs in the development of fiber based ceramic matrix composites (CMCs) are opening the door to a new class of high-tech UHT structures for aerospace applications. One limitation with current carbon fiber or silicon carbide fiber based CMC technology is the inherent problem of material oxidation, requiring new approaches for protective environmental barrier coatings (EBC) in extreme environments. This thesis focuses on the development and characterization of SiCN-HfO2 based ceramic composite EBC systems to be used as a protective layer for silicon carbide fiber based CMCs. The presented work covers three main architectures for protection (i) multilayer films, (ii) polymer-derived HfSiCNO, and (iii) composite SiCN-HfO 2 infiltration. The scope of this thesis covers processing development, material characterization, and high temperature oxidation behavior of these three SiCN-HfO2 based systems. This work shows that the SiCN-HfO 2 composite materials react upon oxidation to form HfSiO4, offering a stable EBC in streaming air and water vapor at 1600°C.

Psychometric properties of the Symptom Status Questionnaire-Heart Failure.

PubMed

Heo, Seongkum; Moser, Debra K; Pressler, Susan J; Dunbar, Sandra B; Mudd-Martin, Gia; Lennie, Terry A

2015-01-01

Many patients with heart failure (HF) experience physical symptoms, poor health-related quality of life (HRQOL), and high rates of hospitalization. Physical symptoms are associated with HRQOL and are major antecedents of hospitalization. However, reliable and valid physical symptom instruments have not been established. Therefore, this study examined the psychometric properties of the Symptom Status Questionnaire-Heart Failure (SSQ-HF) in patients with HF. Data on symptoms using the SSQ-HF were collected from 249 patients (aged 61 years, 67% male, 45% in New York Heart Association functional class III/IV). Internal consistency reliability was assessed using Cronbach's α. Item homogeneity was assessed using item-total and interitem correlations. Construct validity was assessed using factor analysis and testing hypotheses on known relationships. Data on depressive symptoms (Beck Depression Inventory II), HRQOL (Minnesota Living With Heart Failure Questionnaire), and event-free survival were collected to test known relationships. Internal consistency reliability was supported: Cronbach's α was .80. Item-total correlation coefficients and interitem correlation coefficients were acceptable. Factor analysis supported the construct validity of the instrument. More severe symptoms were associated with more depressive symptoms, poorer HRQOL, and more risk for hospitalization, emergency department visit, or death, controlling for covariates. The findings of this study support the reliability and validity of the SSQ-HF. Clinicians and researchers can use this instrument to assess physical symptoms in patients with HF.

First observations of stimulated electromagnetic emission in the ionosphere modified by the spear heating facility on Spitsbergen

NASA Astrophysics Data System (ADS)

Tereshchenko, E. D.; Yurik, R. Yu.; Yeoman, T. K.; Robinson, T. R.

2008-11-01

We present the first results of observations of the stimulated electromagnetic emission (SEE) in the ionosphere modified by the Space Plasma Exploration by Active Radar (SPEAR) heating facility. Observation of the SEE is the key method of ground-based diagnostics of the ionospheric plasma disturbances due to high-power HF radiation. The presented results were obtained during the heating campaign performed at the SPEAR facility in February-March 2007. Prominent SEE special features were observed in periods in which the critical frequency of the F 2 layer was higher than the pump-wave frequency (4.45 MHz). As an example, such special features as the downshifted maximum and the broad continuum in the region of negative detunings from the pump-wave frequency are presented. Observations clearly demonstrate that the ionosphere was efficiently excited by the SPEAR heating facility despite the comparatively low pump-wave power.

Study of structure and antireflective properties of LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 trilayers for UV applications

NASA Astrophysics Data System (ADS)

Marszalek, K.; Jaglarz, J.; Sahraoui, B.; Winkowski, P.; Kanak, J.

2015-01-01

The aim of this paper is to study antireflective properties of the tree-layer systems LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 deposited on heated optical glass substrates. The films were evaporated by the use two deposition techniques. In first method oxide films were prepared by means of e-gun evaporation in vacuum of 5 × 10-5 mbar in the presence of oxygen. The second was used for the deposition of fluoride films. They were obtained by means of thermal source evaporation. Simulation of reflectance was performed for 1M2H1L (Quarter Wavelength Optical Thickness) film stack on an optical quartz glass with the refractive index n = 1.46. The layer thickness was optimized to achieve the lowest light scattering from glass surface covered with dioxide and fluoride films. The values of the interface roughness were determined through atomic force microscopy measurements. The essence of performed calculation was to find minimum reflectance of light in wide ultraviolet region. The spectral dispersion of the refractive index needed for calculations was determined from ellipsometric measurements using the spectroscopic ellipsometer M2000. Additionally, the total reflectance measurements in integrating sphere coupled with Perkin Elmer 900 spectrophotometer were performed. These investigations allowed to determine the influence of such film features like surface and interface roughness on light scattering.

Flotation of Metallurgical Grade Silicon and Silicon Metal from Slag by Selective Hydrogen Fluoride-Assisted Flotation

NASA Astrophysics Data System (ADS)

Larsen, E.; Kleiv, R. A.

2017-12-01

Flotation experiments performed on metallurgical grade silicon have demonstrated that silicon (Si) can be floated in diluted solutions of hydrogen fluoride (HF) and a frother. The recovery was found to depend on HF conditioning time, frother type, and the concentration of both HF and frother. Although Brij 58 produced the highest recoveries of the frothers that was tested, good recoveries were also obtained for Flotanol C07. Chemical analyses showed that the flotation products were purer than the corresponding feed materials, and that most impurity elements were concentrated in the tailings. A case study on cleaning of slag containing 36 pct metallurgical silicon showed promising results concerning the recovery of silicon by flotation.

Potential energy and dipole moment surfaces for HF@C60: Prediction of spectral and electric response properties

NASA Astrophysics Data System (ADS)

Kalugina, Yulia N.; Roy, Pierre-Nicholas

2017-12-01

We present a five-dimensional potential energy surface (PES) for the HF@C60 system computed at the DF-LMP2/cc-pVTZ level of theory. We also calculated a five-dimensional dipole moment surface (DMS) based on DFT(PBE0)/cc-pVTZ calculations. The HF and C60 molecules are considered rigid with bond length rHF = 0.9255 Å (gas phase ground rovibrational state geometry). The C60 geometry is of Ih symmetry. The ab initio points were fitted to obtain a PES in terms of bipolar spherical harmonics. The minimum of the PES corresponds to a geometry where the center of mass of HF is located 0.11 Å away from the center of the cage with an interaction energy of -6.929 kcal/mol. The DMS was also represented in terms of bipolar spherical harmonics. The PES was used to calculate the rotation-translation bound states of HF@C60, and good agreement was found relative to the available experimental data [A. Krachmalnicoff et al., Nat. Chem. 8, 953 (2016)] except for the splitting of the first rotational excitation levels. We propose an empirical adjustment to the PES in order to account for the experimentally observed symmetry breaking. The form of that effective PES is additive. We also propose an effective Hamiltonian with an adjusted rotational constant in order to quantitatively reproduce the experimental results including the splitting of the first rotational state. We use our models to compute the molecular volume polarizability of HF confined by C60 and obtain good agreement with experiment.

Potential energy and dipole moment surfaces for HF@C60: Prediction of spectral and electric response properties.

PubMed

Kalugina, Yulia N; Roy, Pierre-Nicholas

2017-12-28

We present a five-dimensional potential energy surface (PES) for the HF@C 60 system computed at the DF-LMP2/cc-pVTZ level of theory. We also calculated a five-dimensional dipole moment surface (DMS) based on DFT(PBE0)/cc-pVTZ calculations. The HF and C 60 molecules are considered rigid with bond length r HF = 0.9255 Å (gas phase ground rovibrational state geometry). The C 60 geometry is of I h symmetry. The ab initio points were fitted to obtain a PES in terms of bipolar spherical harmonics. The minimum of the PES corresponds to a geometry where the center of mass of HF is located 0.11 Å away from the center of the cage with an interaction energy of -6.929 kcal/mol. The DMS was also represented in terms of bipolar spherical harmonics. The PES was used to calculate the rotation-translation bound states of HF@C 60 , and good agreement was found relative to the available experimental data [A. Krachmalnicoff et al., Nat. Chem. 8, 953 (2016)] except for the splitting of the first rotational excitation levels. We propose an empirical adjustment to the PES in order to account for the experimentally observed symmetry breaking. The form of that effective PES is additive. We also propose an effective Hamiltonian with an adjusted rotational constant in order to quantitatively reproduce the experimental results including the splitting of the first rotational state. We use our models to compute the molecular volume polarizability of HF confined by C 60 and obtain good agreement with experiment.

Heart transplantation in adult congenital heart disease.

PubMed

Burchill, Luke J

2016-12-01

Heart failure (HF) in adult congenital heart disease (ACHD) is vastly different to that observed in acquired heart disease. Unlike acquired HF in which pharmacological strategies are the cornerstone for protecting and improving ventricular function, ACHD-related HF relies heavily upon structural and other interventions to achieve these aims. patients with ACHD constitute a small percentage of the total adult heart transplant population (∼3%), although the number of ACHD heart transplant recipients is growing rapidly with a 40% increase over the last two decades. The worldwide experience to date has confirmed heart transplantation as an effective life-extending treatment option in carefully selected patients with ACHD with end-stage cardiac disease. Opportunities for improving outcomes in patients with ACHD-related HF include (i) earlier recognition and referral to centres with combined expertise in ACHD and HF, (ii) increased awareness of arrhythmia and sudden cardiac death risk in this population, (iii) greater collaboration between HF and ACHD specialists at the time of heart transplant assessment, (iv) expert surgical planning to reduce ischaemic time and bleeding risk at the time of transplant, (v) tailored immunosuppression in the post-transplant period and (vi) development and validation of ACHD-specific risk scores to predict mortality and guide patient selection. The purpose of this article is to review current approaches to diagnosing and treating advanced HF in patients with ACHD including indications, contraindications and clinical outcomes after heart transplantation. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Effect of Microstructure on the Radioluminescence and Transparency of Ce-Doped Strontium Hafnate Ceramics

PubMed Central

van Loef, Edgar V.; Wang, Yimin; Miller, Stuart R.; Brecher, Charles; Rhodes, William H.; Baldoni, Gary; Topping, Stephen; Lingertat, Helmut; Sarin, Vinod K.; Shah, Kanai S.

2011-01-01

In this paper we report on the fabrication and characterization of SrHfO3:Ce ceramics. Powders were prepared by solid-state synthesis using metal oxides and carbonates. X-ray diffraction measurements showed that phase-pure SrHfO3 is formed at 1200°C. Inductively coupled plasma spectroscopy confirmed the purity and composition of each batch. SrHfO3 exhibits several phase changes in the solid, but this does not appear to be detrimental to the ceramics. Microprobe experiments showed uniform elemental grain composition, whereas aluminum added as charge compensation for trivalent cerium congregated at grain boundaries and triple points. Radioluminescence spectra revealed that the light yield decreases when the concentration of excess Sr increases. The decrease in the light yield may be related to the change of Ce3+ into Ce4+ ions. For stoichiometric SrHfO3:Ce, the light yield is about four times that of bismuth germanate (BGO), the conventional benchmark, indicating great potential for many scintillator applications. PMID:21339835

HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations

NASA Technical Reports Server (NTRS)

Frey, A.; Gordon, W. E.

1982-01-01

Three observations of radio star intensity fluctuations at UHF are reported for HF ionospheric modification experiments carried out at the Arecibo Observatory. Two observations at 430 MHz and one at 1400 MHz suggest that the the thin phase screen theory is a good approximation to the observed power spectra. It is noted, however, that the theory has to be extended to include antenna filtering. This type of filtering is important for UHF radio star scintillations since the antenna usually has a narrow beamwidth. HF power densities of less than 37 microwatts/sq m incident on the ionosphere give rise to electron density irregularities larger than 13% of the ambient density (at 260 km) having scale sizes of approximately 510 m perpendicular to the geomagnetic field. The irregularities are found to form within 20-25 s after the HF power is turned on. The drift velocities of the irregularities can be estimated from the observed power spectra.

High psychosis liability is associated with altered autonomic balance during exposure to Virtual Reality social stressors.

PubMed

Counotte, Jacqueline; Pot-Kolder, Roos; van Roon, Arie M; Hoskam, Olivier; van der Gaag, Mark; Veling, Wim

2017-06-01

Social stressors are associated with an increased risk of psychosis. Stress sensitisation is thought to be an underlying mechanism and may be reflected in an altered autonomic stress response. Using an experimental Virtual Reality design, the autonomic stress response to social stressors was examined in participants with different liability to psychosis. Fifty-five patients with recent onset psychotic disorder, 20 patients at ultra-high risk for psychosis, 42 siblings of patients with psychosis and 53 controls were exposed to social stressors (crowdedness, ethnic minority status and hostility) in a Virtual Reality environment. Heart rate variability parameters and skin conductance levels were measured at baseline and during Virtual Reality experiments. High psychosis liability groups had significantly increased heart rate and decreased heart rate variability compared to low liability groups both at baseline and during Virtual Reality experiments. Both low frequency (LF) and high frequency (HF) power were reduced, while the LF/HF ratio was similar between groups. The number of virtual social stressors significantly affected heart rate, HF, LF/HF and skin conductance level. There was no interaction between psychosis liability and amount of virtual social stress. High liability to psychosis is associated with decreased parasympathetic activity in virtual social environments, which reflects generally high levels of arousal, rather than increased autonomic reactivity to social stressors. Copyright © 2016 Elsevier B.V. All rights reserved.

High Frequency Propagation modeling in a disturbed background ionosphere: Results from the Metal Oxide Space Cloud (MOSC) experiment

NASA Astrophysics Data System (ADS)

Joshi, D. R.; Groves, K. M.

2015-12-01

The Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud. A host of diagnostic instruments were used to probe and characterize the cloud including the ALTAIR incoherent scatter radar, multiple GPS and optical instruments, satellite radio beacons, and a dedicated network of high frequency (HF) radio links. Data from ALTAIR incoherent scatter radar and HF radio links have been analyzed to understand the impacts of the artificial ionization on radio wave propagation. During the first release the ionosphere was disturbed, rising rapidly and spread F formed within minutes after the release. To address the disturbed conditions present during the first release, we have developed a new method of assimilating oblique ionosonde data to generate the background ionosphere that can have numerous applications for HF systems. The link budget analysis of the received signals from the HF transmitters explains the missing low frequencies in the received signals along the great circle path. Observations and modeling confirm that the small amounts of ionized material injected in the lower-F region resulted in significant changes to the natural propagation environment.

Polysaccharide characterization by hollow-fiber flow field-flow fractionation with on-line multi-angle static light scattering and differential refractometry.

PubMed

Pitkänen, Leena; Striegel, André M

2015-02-06

Accurate characterization of the molar mass and size of polysaccharides is an ongoing challenge, oftentimes due to architectural diversity but also to the broad molar mass (M) range over which a single polysaccharide can exist and to the ultra-high M of many polysaccharides. Because of the latter, many of these biomacromolecules experience on-column, flow-induced degradation during analysis by size-exclusion and, even, hydrodynamic chromatography (SEC and HDC, respectively). The necessity for gentler fractionation methods has, to date, been addressed employing asymmetric flow field-flow fractionation (AF4). Here, we introduce the coupling of hollow-fiber flow field-flow fractionation (HF5) to multi-angle static light scattering (MALS) and differential refractometry (DRI) detection for the analysis of polysaccharides. In HF5, less stresses are placed on the macromolecules during separation than in SEC or HDC, and HF5 can offer a higher sensitivity, with less propensity for system overloading and analyte aggregation, than generally found in AF4. The coupling to MALS and DRI affords the determination of absolute, calibration-curve-independent molar mass averages and dispersities. Results from the present HF5/MALS/DRI experiments with dextrans, pullulans, and larch arabinogalactan were augmented with hydrodynamic radius (RH) measurements from off-line quasi-elastic light scattering (QELS) and by RH distribution calculations and fractogram simulations obtained via a finite element analysis implementation of field-flow fractionation theory by commercially available software. As part of this study, we have investigated analyte recovery in HF5 and also possible reasons for discrepancies between calculated and simulated results vis-à-vis experimentally determined data. Published by Elsevier B.V.

Lack of promotion of colon carcinogenesis by high-oleic safflower oil.

PubMed

Takeshita, M; Ueda, H; Shirabe, K; Higuchi, Y; Yoshida, S

1997-04-15

The nonpromoting effect of olive oil on colon carcinogenesis has been attributed to its high oleic acid content, whereas a positive association of monounsaturated fat in beef tallow with colon tumors has been reported. The effect of constituents other than fatty acids could not be neglected in these experiments. In order to minimize the effects of minor constituents in the oils, the authors compared conventional safflower oil with oil from a mutant strain of safflower that is rich in oleic acid. ICR mice were treated with 1,2-dimethylhydrazine (DMH, 20 mg/kg body weight every week for 12 weeks) and then were fed either a high-fat diet (23.5% by weight), containing safflower oil (HF-LA) or high-oleic safflower oil (HF-OA), or a low-fat diet (5% by weight), containing safflower oil (LF-LA) or high-oleic safflower oil (LF-OA). The test diets were continued until termination of the experiment at 30 weeks after the first administration of DMH. Fatty acid composition of colon phospholipids was determined by gas-liquid chromatography-mass spectrometry. Tumor multiplicity in animals fed the HF-OA diet was indistinguishable from that in animals fed LF-LA or LF-OA. In contrast, animals fed the HF-LA diet had a significantly higher incidence of colon tumors (mostly adenocarcinomas) than the other groups. Fatty acid profiles of colon phospholipids reflected those of the diet. Animals fed a HF-LA diet showed a marked decrease of nervonic acid (C24:1, n-9) in the colon sphingomyelin. These data indicate that oleic acid does not enhance DMH-induced colon carcinogenesis in mice, even when they are fed a high-fat diet.

The high-frequency component of heart rate variability during extended wakefulness is closely associated with the depth of the ensuing sleep in C57BL6 mice.

PubMed

Kuo, T B J; Lai, C T; Chen, C Y; Yang, Y C; Yang, C C H

2016-08-25

This study aimed to test the hypothesis that, during extended wakefulness, parasympathetic activity is associated with the depth of the subsequent recovery sleep in mice. Fourteen male C57BL/6 mice were implanted with electrodes for sleep recording. Continuous spectral analysis was performed on the electroencephalogram (EEG) to obtain theta power (6-9Hz) and delta power (0-4Hz), as well as the R-R interval signals in order to quantify the high-frequency power (HF) and normalized low-frequency power (LF%) that are used to assess parasympathetic and sympathetic activity, respectively. All animals underwent a sleep deprivation experiment and a control experiment (6-h intervention and 1-h recovery period) on two separate days. During sleep deprivation, HF and theta power during wakefulness were significantly higher than during the control wakefulness after the second hour and first hour, respectively. During recovery non-rapid eye movement sleep, there was a rebound in sleep time and delta power as well as an elevation in HF relative to control post-intervention sleep. Both the rise in HF and theta power during extended wakefulness were found to be positively correlated with the delta power rebound. Furthermore, the HF change during extended wakefulness was also correlated with the amount of sleep loss and the enhancement of waking theta power. Our finding suggests that waking parasympathetic activity intimately reflects the cumulative sleep pressure, suggesting a potential role to be an autonomic marker for sleep propensity. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

The WIND-HAARP Experiment: Initial Results of High Power Radiowave Interactions with Space Plasmas

DTIC Science & Technology

1997-11-10

Results from the first science experiment with the new HF Active Auroral Research Program ( HAARP ) facility in Alaska are reported. The initial...experiments involved transmission of high frequency waves from HAARP to the NASA/WIND satellite. The objective was to investigate the effects of space

High temperature oxidation behavior of gamma-nickel+gamma'-nickel aluminum alloys and coatings modified with platinum and reactive elements

NASA Astrophysics Data System (ADS)

Mu, Nan

Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000°C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455°C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain beta-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used beta-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase gamma-Ni and gamma'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al 2O3 formation by suppressing the NiO growth on both gamma-Ni and gamma'-Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures (˜970°C) in the very early stage of oxidation. It was also inferred that Pt enhances the diffusive flux of aluminum from the substrate to the scale/alloy interface. Relatively low levels of hafnium addition to Pt-free gamma'-Ni 3Al increased the extent of external NiO formation due to non-protective HfO2 formation. Accordingly, this effect intensified with increasing Hf content from 0.2 to 0.5at.%. The synergistic effect of Pt and Hf co-addition was realized by examining Pt+Hf-modified gamma'-Ni3Al alloys. It was inferred that Pt decreases the chemical activity of Hf so that HfO2 formation could be suppressed with increasing Pt content. Thus, the early-stage Al2O3 formation facilitated by Pt additions and NiO development assisted by Hf additions are the competing scale growth processes that are influenced by the relative contents of Pt and Hf. Large interfacial voids were observed on the gamma'-Ni 3Al alloy after 4-days isothermal oxidation at 1150°C, which could be attributed to the Kirkendall effect. Platinum addition was also found to improve Al2O3-scale adhesion. Pt and Hf effects on two-phase gamma-Ni+gamma'-Ni3Al alloys of compositions Ni-20Al-20Pt-xHf (x ranges from 0 to 0.91) were examined by both thermal gravimetric analyses and cyclic oxidation tests. Scale microstructures were characterized by confocal photo-stimulated microspectroscopy (CPSM), in-lens SEM, and FIB-TEM. Hafnium additions up to about 0.48at.% markedly decreased the weight change of isothermally oxidized Pt-modified gamma+gamma' alloys by forming thinner oxide scales than that on the Hf-free Ni-20Al-20Pt base alloy. This could be attributed to an Al2O3 grain boundary blocking effect imparted by the segregated Hf. However, an over-doped alloy with 0.91at.% Hf exhibited detrimental effect by forming internal HfO 2. It was observed that Hf additions altered the Al2O3 scale microstructure. The most remarkable difference was that the columnar width of the Al2O3 scale grains formed on Ni-20Al-20Pt was much larger than it was on Ni-20Al-20Pt-0.48Hf. Even so, the Hf-doped alloys exhibited much slower scaling kinetics with a correspondingly thinner scale. This behavior could be ascribed to the Hf blocking diffusing paths as it segregated into Al2O3 grain boundaries. Therefore, the Hf-doped scale grew at a lower rate even though it contained more grain boundaries. Accompanied with this scale microstructure modification, Hf additions led to the following two additional effects: (1) Hf delayed the theta→alpha structural transformation of Al2O3; and (2) compressive residual stress in the scale formed on Hf-doped alloys was lower than that on the Hf-free Ni-20Al-20Pt alloy. Guided by the results from the bulk-alloy studies, a feasible method to deposit Pt+Hf-modified gamma+gamma' coatings having overall compositions closely approaching Ni-Al15-20-Pt15-20-Hf was subsequently developed. A key improvement of the application of Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al coatings is the relief of TCP phases generated from coating/substrate interdiffusion. This could be simply attributed to the inherited phase compatibility between gamma+gamma' coatings with Ni-based superalloys. Another important advantage of gamma+gamma' coatings is the exclusion of phase transformations during thermal cycling. The Pt+Hf-modified gamma-Ni+gamma'-Ni3Al coating compositions had a strong dependence on the temperature and time in both pack cementation and post-heat-treatment processes. Meanwhile, coating performance was apparently more sensitive to the Hf content than what was observed with the alloys. Coating performance was also considerable affected by the surface finish and the composition of the superalloy substrate.

Dynamical resonances in the fluorine atom reaction with the hydrogen molecule.

PubMed

Yang, Xueming; Zhang, Dong H

2008-08-01

[Reaction: see text]. The concept of transition state has played a crucial role in the field of chemical kinetics and reaction dynamics. Resonances in the transition state region are important in many chemical reactions at reaction energies near the thresholds. Detecting and characterizing isolated reaction resonances, however, have been a major challenge in both experiment and theory. In this Account, we review the most recent developments in the study of reaction resonances in the benchmark F + H 2 --> HF + H reaction. Crossed molecular beam scattering experiments on the F + H 2 reaction have been carried out recently using the high-resolution, highly sensitive H-atom Rydberg tagging technique with HF rovibrational states almost fully resolved. Pronounced forward scattering for the HF (nu' = 2) product has been observed at the collision energy of 0.52 kcal/mol in the F + H 2 (j = 0) reaction. Quantum dynamical calculations based on two new potential energy surfaces, the Xu-Xie-Zhang (XXZ) surface and the Fu-Xu-Zhang (FXZ) surface, show that the observed forward scattering of HF (nu' = 2) in the F + H 2 reaction is caused by two Feshbach resonances (the ground resonance and first excited resonance). More interestingly, the pronounced forward scattering of HF (nu' = 2) at 0.52 kcal/mol is enhanced considerably by the constructive interference between the two resonances. In order to probe the resonance potential more accurately, the isotope substituted F + HD --> HF + D reaction has been studied using the D-atom Rydberg tagging technique. A remarkable and fast changing dynamical picture has been mapped out in the collision energy range of 0.3-1.2 kcal/mol for this reaction. Quantum dynamical calculations based on the XXZ surface suggest that the ground resonance on this potential is too high in comparison with the experimental results of the F + HD reaction. However, quantum scattering calculations on the FXZ surface can reproduce nearly quantitatively the resonance picture of the F + HD reaction observed in the experiment. It is clear that the dynamics of the F + HD reaction below the threshold was dominated by the ground resonance state. Furthermore, the forward scattering HF (nu' = 3) channel from the F + H 2 ( j = 0) reaction was investigated and was attributed mainly to a slow-down mechanism over the centrifugal exit barrier, with small contributions from a shape resonance mechanism in a narrow collision energy range. A striking effect of the reagent rotational excitation on resonance was also observed in F + H 2 ( j = 1), in comparison with F + H 2 ( j = 0). From these concerted experimental and theoretical studies, a clear physical picture of the reaction resonances in this benchmark reaction has emerged, providing a textbook example of dynamical resonances in elementary chemical reactions.

Acta Aeronautica et Astronautica Sinica.

DTIC Science & Technology

1987-04-07

quantity of cocrystallized 7’-phase will be formed between the crystal boundaries and crystalline 97 branches; therefore the status of grain boundaries... cocrystallized Y’-phase under the high temperature stress [4]. In order to balance the medium and high temperature properties, the concentration of Hf in...will become large. 3. The influence of heat treatment. In the microscopic structures of DZ-22 alloy, there are 13 vol.% cocrystal ?’- and many large

Origin of traps and charge transport mechanism in hafnia

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

Islamov, D. R., E-mail: damir@isp.nsc.ru; Gritsenko, V. A., E-mail: grits@isp.nsc.ru; Novosibirsk State University, Novosibirsk 630090

2014-12-01

In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the charge transport in HfO{sub 2}. Basing on the model of phonon-assisted tunneling between traps, and assuming that the electron traps are oxygen vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics was achieved. The thermal trap energy of 1.25 eV in HfO{sub 2} was determined based on the charge transport experiments.

Accuracy in inference of nursing diagnoses in heart failure patients.

PubMed

Pereira, Juliana de Melo Vellozo; Cavalcanti, Ana Carla Dantas; Lopes, Marcos Venícios de Oliveira; da Silva, Valéria Gonçalves; de Souza, Rosana Oliveira; Gonçalves, Ludmila Cuzatis

2015-01-01

Heart failure (HF) is a common cause of hospitalization and requires accuracy in clinical judgment and appropriate nursing diagnoses. to determine the accuracy of nursing diagnoses of fatigue, intolerance to activity and decreased cardiac output in hospitalized HF patients. descriptive study applied to nurses with experience in NANDA-I and/or HF nursing diagnoses. Evaluation and accuracy were determined by calculating efficacy (E), false negative (FN), false positive (FP) and trend (T) measures. Nurses who showed acceptable inspection for two diagnoses were selected. the nursing diagnosis of fatigue was the most commonly mistaken diagnosis identified by the nursing evaluators. the search for improving diagnostic accuracy reaffirms the need for continuous and specific training to improve the diagnosis capability of nurses. the training allowed the exercise of clinical judgment and better accuracy of nurses.

Characterizing Radio Emission From Extensive Air Showers with the SLAC-T510 Experiment, with Applications to ANITA

NASA Astrophysics Data System (ADS)

McGuire, Felicia Ann

Essential to metal-oxide-semiconductor field-effect transistor (MOSFET) scaling is the reduction of the supply voltage to mitigate the power consumption and corresponding heat dissipation. Conventional dielectric materials are subject to the thermal limit imposed by the Boltzmann factor in the subthreshold swing, which places an absolute minimum on the supply voltage required to modulate the current. Furthermore, as technology approaches the 5 nm node, electrostatic control of a silicon channel becomes exceedingly difficult, regardless of the gating technique. This notion of "the end of silicon scaling" has rapidly increased research into more scalable channel materials as well as new methods of transistor operation. Among the many promising options are two-dimensional (2D) FETs and negative capacitance (NC) FETs. 2D-FETs make use of atomically thin semiconducting channels that have enabled demonstrated scalability beyond what silicon can offer. NC-FETs demonstrate an effective negative capacitance arising from the integration of a ferroelectric into the transistor gate stack, allowing sub-60 mV/dec switching. While both of these devices provide significant advantages, neither can accomplish the ultimate goal of a FET that is both low-voltage and scalable. However, an appropriate fusion of the 2D-FET and NC-FET into a 2D NC-FET has the potential of enabling a steep-switching device that is dimensionally scalable beyond the 5 nm technology node. In this work, the motivation for and operation of 2D NC-FETs is presented. Experimental realization of 2D NC-FETs using 2D transition metal dichalcogenide molybdenum disulfide (MoS2) as the channel is shown with two different ferroelectric materials: 1) a solution-processed, polymeric poly(vinylidene difluoride trifluoroethylene) ferroelectric and 2) an atomic layer deposition (ALD) grown hafnium zirconium oxide (HfZrO2) ferroelectric. Each ferroelectric was integrated into the gate stack of a 2D-FET having either a top-gate (polymeric ferroelectric) or bottom-gate (HfZrO2 ferroelectric) configuration. HfZrO 2 devices with metallic interfacial layers (between ferroelectric and dielectric) and thinner ferroelectric layers were found to reduce both the hysteresis and the threshold voltage. Detailed characterization of the devices was performed and, most significantly, the 2D NC-FETs with HfZrO2 reproducibly yielded subthreshold swings well below the thermal limit with over more than four orders of magnitude in drain current modulation. HfZrO 2 devices without metallic interfacial layers were utilized to explore the impact of ferroelectric thickness, dielectric thickness, and dielectric composition on device performance. The impact of an interfacial metallic layer on the device operation was investigated in devices with HfZrO2 and shown to be crucial at enabling sub-60 mV/dec switching and large internal voltage gains. The significance of dielectric material choice on device performance was explored and found to be a critical factor in 2D NC-FET transistor operation. These successful results pave the way for future integration of this new device structure into existing technology markets.

Discharge Processes and 30-Day Readmission Rates of Patients Hospitalized for Heart Failure on General Medicine and Cardiology Services.

PubMed

Salata, Brian M; Sterling, Madeline R; Beecy, Ashley N; Ullal, Ajayram V; Jones, Erica C; Horn, Evelyn M; Goyal, Parag

2018-05-01

Given high rates of heart failure (HF) hospitalizations and widespread adoption of the hospitalist model, patients with HF are often cared for on General Medicine (GM) services. Differences in discharge processes and 30-day readmission rates between patients on GM and those on Cardiology during the contemporary hospitalist era are unknown. The present study compared discharge processes and 30-day readmission rates of patients with HF admitted on GM services and those on Cardiology services. We retrospectively studied 926 patients discharged home after HF hospitalization. The primary outcome was 30-day all-cause readmission after discharge from index hospitalization. Although 60% of patients with HF were admitted to Cardiology services, 40% were admitted to GM services. Prevalence of cardiovascular and noncardiovascular co-morbidities were similar between patients admitted to GM services and Cardiology services. Discharge summaries for patients on GM services were less likely to have reassessments of ejection fraction, new study results, weights, discharge vital signs, discharge physical examinations, and scheduled follow-up cardiologist appointments. In a multivariable regression analysis, patients on GM services were more likely to experience 30-day readmissions compared with those on Cardiology services (odds ratio 1.43 95% confidence interval [1.05 to 1.96], p = 0.02). In conclusion, outcomes are better among those admitted to Cardiology services, signaling the need for studies and interventions focusing on noncardiology hospital providers that care for patients with HF. Copyright © 2018 Elsevier Inc. All rights reserved.

Development and psychometric evaluation of the Thirst Distress Scale for patients with heart failure.

PubMed

Waldréus, Nana; Jaarsma, Tiny; van der Wal, Martje Hl; Kato, Naoko P

2018-03-01

Patients with heart failure can experience thirst distress. However, there is no instrument to measure this in patients with heart failure. The aim of the present study was to develop the Thirst Distress Scale for patients with Heart Failure (TDS-HF) and to evaluate psychometric properties of the scale. The TDS-HF was developed to measure thirst distress in patients with heart failure. Face and content validity was confirmed using expert panels including patients and healthcare professionals. Data on the TDS-HF was collected from patients with heart failure at outpatient heart failure clinics and hospitals in Sweden, the Netherlands and Japan. Psychometric properties were evaluated using data from 256 heart failure patients (age 72±11 years). Concurrent validity of the scale was assessed using a thirst intensity visual analogue scale. Patients did not have any difficulties answering the questions, and time taken to answer the questions was about five minutes. Factor analysis of the scale showed one factor. After psychometric testing, one item was deleted. For the eight item TDS-HF, a single factor explained 61% of the variance and Cronbach's alpha was 0.90. The eight item TDS-HF was significantly associated with the thirst intensity score ( r=0.55, p<0.001). Regarding test-retest reliability, the intraclass correlation coefficient was 0.88, and the weighted kappa values ranged from 0.29-0.60. The eight-item TDS-HF is valid and reliable for measuring thirst distress in patients with heart failure.

Self-efficacy strategies to improve exercise in patients with heart failure: A systematic review

PubMed Central

Rajati, Fatemeh; Sadeghi, Masoumeh; Feizi, Awat; Sharifirad, Gholamreza; Hasandokht, Tolu; Mostafavi, Firoozeh

2014-01-01

BACKGROUND Despite exercise is recommended as an adjunct to medication therapy in patients with heart failure (HF), non-adherence to exercise is a major problem. While improving self-efficacy is an effective way to increase physical activity, the evidence concerning the relationship between strategies to enhance self-efficacy and exercise among HF has not been systematically reviewed. The objective of this systematic review is to assess the effect of interventions to change the self-efficacy on exercise in patients with HF. METHODS A systematic database search was conducted for articles reporting exercise self-efficacy interventions. Databases such as PubMed, ProQuest, CINAHL, Scopus, and PsycINFO, and the Cochrane Library were searched with restrictions to the years 2000-June 2014. A search of relevant databases identified 10 studies. Published randomized controlled intervention studies focusing strategies to change self-efficacy to exercise adherence in HF were eligible for inclusion. In addition, studies that have applied self-efficacy-based interventions to improve exercise are discussed. RESULTS Limited published data exist evaluating the self-efficacy strategies to improve exercise in HF. Dominant strategies to improve patients’ self-efficacy were performance accomplishments, vicarious experience, verbal persuasion, emotional arousal. CONCLUSION Evidence from some trials supports the view that incorporating the theory of self-efficacy into the design of an exercise intervention is beneficial. Moreover, exercise interventions aimed at integrating the four strategies of exercise self-efficacy can have positive effects on confidence and the ability to initiate exercise and recover HF symptoms. Findings of this study suggest that a positive relationship exists between self-efficacy and initiating and maintaining exercise in HF, especially in the short-term period. PMID:25815022

Combining training in knowledge translation with quality improvement reduced 30-day heart failure readmissions in a community hospital: a case study.

PubMed

Wyer, Peter; Stojanovic, Zorica; Shaffer, Jonathan A; Placencia, Mitzy; Klink, Kathleen; Fosina, Michael J; Lin, Susan X; Barron, Beth; Graham, Ian D

2016-04-01

Training programmes in evidence-based practice (EBP) frequently fail to translate their content into practice change and care improvement. We linked multidisciplinary training in EBP to an initiative to decrease 30-day readmissions among patients admitted to a community teaching hospital for heart failure (HF). Hospital staff reflecting all services and disciplines relevant to care of patients with HF attended a 3-day innovative capacity building conference in evidence-based health care over a 3-year period beginning in 2009. The team, facilitated by a conference faculty member, applied a knowledge-to-action model taught at the conference. We reviewed published research, profiled our population and practice experience, developed a three-phase protocol and implemented it in late 2010. We tracked readmission rates, adverse clinical outcomes and programme cost. The protocol emphasized patient education, medication reconciliation and transition to community-based care. Senior administration approved a full-time nurse HF coordinator. Thirty-day HF readmissions decreased from 23.1% to 16.4% (adjusted OR = 0.64, 95% CI = 0.42-0.97) during the year following implementation. Corresponding rates in another hospital serving the same population but not part of the programme were 22.3% and 20.2% (adjusted OR = 0.87, 95% CI = 0.71-1.08). Adherence to mandated HF quality measures improved. Following a start-up cost of $15 000 US, programme expenses balanced potential savings from decreased HF readmissions. Training of a multidisciplinary hospital team in use of a knowledge translation model, combined with ongoing facilitation, led to implementation of a budget neutral programme that decreased HF readmissions. © 2015 John Wiley & Sons, Ltd.

Changes in environmental temperature influence leptin responsiveness in low- and high-fat-fed mice.

PubMed

Harris, Ruth B S; Mitchell, Tiffany D; Kelso, Emily W; Flatt, W P

2007-07-01

Loss of body fat in leptin-treated animals has been attributed to reduced energy intake, increased thermogenesis, and preferential fatty acid oxidation. Leptin does not decrease food intake or body fat in leptin-resistant high-fat (HF)-fed mice, possibly due to a failure of leptin to activate hypothalamic receptors. We measured energy expenditure of male C57BL/6 mice adapted to low-fat (LF) or HF diet and infused them for 13 days with PBS or 10 mug leptin/day from an intraperitoneal mini-osmotic pump to test whether leptin resistance prevented leptin-induced increases in energy expenditure and fatty acid oxidation. There was no effect of low-dose leptin infusions on either of these measures in LF-fed or HF-fed mice, even though LF-fed mice lost body fat. Experiment 2 tested leptin responsiveness in LF-fed and HF-fed mice housed at different temperatures (18 degrees C, 23 degrees C, 27 degrees C), assuming that the cold would increase and the hot environment would inhibit food intake and thermogenesis, which could potentially interfere with leptin action. LF-fed mice housed at 23 degrees C were the only mice that lost body fat during leptin infusion, suggesting that an ability to modify energy expenditure is essential to the maintenance of leptin responsiveness. HF-fed mice in cold or warm environments did not respond to leptin. HF-fed mice in the hot environment were fatter than other HF-fed mice, and, surprisingly, leptin caused a further increase in body fat, demonstrating that the mice were not totally leptin resistant and that partial leptin resistance in a hot environment favors positive energy balance and fat deposition.

“It’s Somebody else’s responsibility” - perceptions of general practitioners, heart failure nurses, care home staff, and residents towards heart failure diagnosis and management for older people in long-term care: a qualitative interview study

PubMed Central

2013-01-01

Background Older people in care-facilities may be less likely to access gold standard diagnosis and treatment for heart failure (HF) than non residents; little is understood about the factors that influence this variability. This study aimed to examine the experiences and expectations of clinicians, care-facility staff and residents in interpreting suspected symptoms of HF and deciding whether and how to intervene. Methods This was a nested qualitative study using in-depth interviews with older residents with a diagnosis of heart failure (n=17), care-facility staff (n=8), HF nurses (n=3) and general practitioners (n=5). Results Participants identified a lack of clear lines of responsibility in providing HF care in care-facilities. Many clinical staff expressed negative assumptions about the acceptability and utility of interventions, and inappropriately moderated residents’ access to HF diagnosis and treatment. Care-facility staff and residents welcomed intervention but experienced a lack of opportunity for dialogue about the balance of risks and benefits. Most residents wanted to be involved in healthcare decisions but physical, social and organisational barriers precluded this. An onsite HF service offered a potential solution and proved to be acceptable to residents and care-facility staff. Conclusions HF diagnosis and management is of variable quality in long-term care. Conflicting expectations and a lack of co-ordinated responsibility for care, contribute to a culture of benign neglect that excludes the wishes and needs of residents. A greater focus on rights, responsibilities and co-ordination may improve healthcare quality for older people in care. Trial registration ISRCTN: ISRCTN19781227 PMID:23829674

"It's Somebody else's responsibility" - perceptions of general practitioners, heart failure nurses, care home staff, and residents towards heart failure diagnosis and management for older people in long-term care: a qualitative interview study.

PubMed

Close, Helen; Hancock, Helen; Mason, James M; Murphy, Jerry J; Fuat, Ahmet; de Belder, Mark; Hungin, A Pali S

2013-07-05

Older people in care-facilities may be less likely to access gold standard diagnosis and treatment for heart failure (HF) than non residents; little is understood about the factors that influence this variability. This study aimed to examine the experiences and expectations of clinicians, care-facility staff and residents in interpreting suspected symptoms of HF and deciding whether and how to intervene. This was a nested qualitative study using in-depth interviews with older residents with a diagnosis of heart failure (n=17), care-facility staff (n=8), HF nurses (n=3) and general practitioners (n=5). Participants identified a lack of clear lines of responsibility in providing HF care in care-facilities. Many clinical staff expressed negative assumptions about the acceptability and utility of interventions, and inappropriately moderated residents' access to HF diagnosis and treatment. Care-facility staff and residents welcomed intervention but experienced a lack of opportunity for dialogue about the balance of risks and benefits. Most residents wanted to be involved in healthcare decisions but physical, social and organisational barriers precluded this. An onsite HF service offered a potential solution and proved to be acceptable to residents and care-facility staff. HF diagnosis and management is of variable quality in long-term care. Conflicting expectations and a lack of co-ordinated responsibility for care, contribute to a culture of benign neglect that excludes the wishes and needs of residents. A greater focus on rights, responsibilities and co-ordination may improve healthcare quality for older people in care. ISRCTN19781227.

Theory of HF induced turbulence in the ionosphere: Status and challenges

NASA Astrophysics Data System (ADS)

Dubois, D. F.

In the past five years the combination of new theoretical concepts and computer simulations along with dramatically improved observational diagnostics appear to have led to a detailed, quantitative, understanding of the properties of the Langmuir turbulence induced in the unpreconditioned ionosphere at Arecibo during the first tens of milliseconds following the turn-on of the HF heater. This is the only observational regime in which the initial ionospheric conditions are known to a high level of confidence. The so called strong Langmuir turbulence (SLT) theory predicts observed features in this early time heating which are completely at odds with the prediction of the traditional weak turbulence approximation. The understanding of the observed signatures for times greater than say 30-50 ms following the onset of heating at Arecibo is still incomplete. The same is apparently true for the observations at Tromso where the unique predictions of SLT theory are not so clearly observed. Density irregularities, induced by heating at Arecibo and perhaps present in the ambient ionosphere at Tromso, appear to control the properties of the turbulence. The proper description of the coexistence of Langmuir turbulence with various density irregularities and accounting for the turbulent modification of the electron velocity distribution are challenges for the theory. In this paper the author reviews, starting from the Vlasov-Poisson equations, the fundamental basis of the reduced models used to describe SLT and suggest improvements to the standard model including a new local quasi linear theory for the treatment of hot electron acceleration and transit time damping or burnout of collapsing Langmuir cavitons.

Feasibility Study for Casting of High Temperature Refractory Superalloy Composites

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

1998-01-01

Abstract This study investigated the feasibility of using conventional casting technique to fabricate refractory wires reinforced superalloy composites. These composites were being developed for advanced rocket engine turbine blades and other high temperature applications operating up to 2000 F. Several types of refractory metal wires such as W- Th, W-Re, Mo-Hf-C and W-HF-C reinforced waspaloy were experimentally cast and heat treated at 2000 F up to 48 hrs. Scanning electron microscope analysis was conducted in regions adjacent to the wire-matrix interface to determine the reaction zone and chemical compatibility resulting from material interdiffusion. It was concluded that fabrication using conventional casting may be feasible because the wire-matrix reaction zone thickness was comparable to similar composites produced by arc-sprayed monotape with hot isostatic pressing technique, Moreover, it was also found that the chemical compatibility could be improved significantly through a slight modification of the superalloy matrix compositions.

Energetics of lithium ion battery failure.

PubMed

Lyon, Richard E; Walters, Richard N

2016-11-15

The energy released by failure of rechargeable 18-mm diameter by 65-mm long cylindrical (18650) lithium ion cells/batteries was measured in a bomb calorimeter for 4 different commercial cathode chemistries over the full range of charge using a method developed for this purpose. Thermal runaway was induced by electrical resistance (Joule) heating of the cell in the nitrogen-filled pressure vessel (bomb) to preclude combustion. The total energy released by cell failure, ΔHf, was assumed to be comprised of the stored electrical energy E (cell potential×charge) and the chemical energy of mixing, reaction and thermal decomposition of the cell components, ΔUrxn. The contribution of E and ΔUrxn to ΔHf was determined and the mass of volatile, combustible thermal decomposition products was measured in an effort to characterize the fire safety hazard of rechargeable lithium ion cells. Published by Elsevier B.V.

Outpatient Palliative Cardiology Service Embedded Within a Heart Failure Clinic: Experiences With an Emerging Model of Care.

PubMed

Gandesbery, Benjamin; Dobbie, Krista; Gorodeski, Eiran Z

2018-04-01

The role of palliative care consultation in the outpatient treatment of patients with symptomatic heart failure (HF) is poorly studied. In August 2015, we created an outpatient palliative care service embedded within the HF clinic at Cleveland Clinic main campus. To characterize patients cared for by our novel outpatient palliative cardiology service, including their degree of HF, symptoms, comorbidities, topics addressed in clinic, palliative treatments prescribed, advanced directives status, and mortality. We conducted a retrospective chart review of all patients evaluated by this outpatient service. Eighty patients were seen in 229 outpatient encounters. The most commonly reported symptoms were tiredness (74%), pain (64%), dyspnea (57%), drowsiness (45%), anxiety (45%), and depression (43%). The most frequently addressed issues were pain management (55%) and advanced care planning (54%). The most common palliative medications prescribed in palliative care clinic were opiates (48%), laxatives (22%), antineuropathics (22%), and antidepressants (16%). The 1-year survival rate was 70% (CI 65-75%). Embedding palliative medicine services in an HF outpatient clinic is feasible. Patients seen in this setting had an array of quality-of-life limiting symptoms and were medically managed with several interventions familiar to palliative medicine specialists. Outpatients with chronic HF have a significant symptom burden and may benefit from outpatient specialist palliative care.

A levitation instrument for containerless study of molten materials.

PubMed

Nordine, Paul C; Merkley, Dennis; Sickel, Jeffrey; Finkelman, Steve; Telle, Rainer; Kaiser, Arno; Prieler, Robert

2012-12-01

A new aero-acoustic levitation instrument (AAL) has been installed at the Institute for Mineral Engineering at RWTH University in Aachen, Germany. The AAL employs acoustically stabilized gas jet levitation with laser-beam heating and melting to create a contact-free containerless environment for high temperature materials research. Contamination-free study of liquids is possible at temperatures in excess of 3000 °C and of undercooled liquids at temperatures far below the melting point. Digital control technology advances the art of containerless experiments to obtain long-term levitation stability, allowing new experiments in extreme temperature materials research and to study operation of the levitation instrument itself. Experiments with liquid Al(2)O(3) at temperatures more than 3200 °C, 1200 °C above the melting point, and with liquid Y(3)Al(5)O(12) far below the melting point are reported. Fast pyrometry and video recording instruments yield crystallization rates in undercooled liquid Al(2)O(3) as a function of temperature. Levitation of dense liquid HfO(2) at temperatures above 2900 °C is demonstrated. Capabilities are described for resonant frequency matching in the three-axis acoustic positioning system, acoustic control of sample spin, and position control of standing wave nodes to stabilize levitation under changing experimental conditions. Further development and application of the levitation technology is discussed based on the results of experiments and modeling of instrument operations.

A levitation instrument for containerless study of molten materials

NASA Astrophysics Data System (ADS)

Nordine, Paul C.; Merkley, Dennis; Sickel, Jeffrey; Finkelman, Steve; Telle, Rainer; Kaiser, Arno; Prieler, Robert

2012-12-01

A new aero-acoustic levitation instrument (AAL) has been installed at the Institute for Mineral Engineering at RWTH University in Aachen, Germany. The AAL employs acoustically stabilized gas jet levitation with laser-beam heating and melting to create a contact-free containerless environment for high temperature materials research. Contamination-free study of liquids is possible at temperatures in excess of 3000 °C and of undercooled liquids at temperatures far below the melting point. Digital control technology advances the art of containerless experiments to obtain long-term levitation stability, allowing new experiments in extreme temperature materials research and to study operation of the levitation instrument itself. Experiments with liquid Al2O3 at temperatures more than 3200 °C, 1200 °C above the melting point, and with liquid Y3Al5O12 far below the melting point are reported. Fast pyrometry and video recording instruments yield crystallization rates in undercooled liquid Al2O3 as a function of temperature. Levitation of dense liquid HfO2 at temperatures above 2900 °C is demonstrated. Capabilities are described for resonant frequency matching in the three-axis acoustic positioning system, acoustic control of sample spin, and position control of standing wave nodes to stabilize levitation under changing experimental conditions. Further development and application of the levitation technology is discussed based on the results of experiments and modeling of instrument operations.

Ground and Satellite Observations of ULF Waves Artificially Produced by HAARP

NASA Astrophysics Data System (ADS)

Chang, C.; Labenski, J.; Shroff, H.; Doxas, I.; Papadopoulos, D.; Milikh, G.; Parrot, M.

2008-12-01

Modulated ionospheric heating at ULF frequencies using the HAARP heater was performed from April 28 to May 3, 2008 (http://www.haarp.alaska.edu). Simultaneous ground-based ULF measurements were made locally at Gakona, AK and at Lake Ozette, WA that is 2000 km away. The ground-based results showed that ULF amplitudes measured at Gakona are mostly proportional to the electrojet strength above HAARP, indicating electrojet modulation to be the source of the local ULF waves. However, the timing of ULF events recorded at Lake Ozette did not correlated with the electrojet strength at Gakona, indicating that modulation of F region pressure is the more likely source for distant ULF waves. These observations are consistent with the theoretical understanding that ULF waves generated by current modulation are shear Alfven waves propagating along the magnetic field line, thus at high latitude their observations are limited to the vicinity of the heated spot. On the other hand, propagation of ULF waves at significant lateral distances requires generation of magnetosonic waves since they are the only mode that propagates isotropically and can thus couple efficiently in the Alfvenic duct. In addition to ground-based observations, the DEMETER satellite also provided space measurements of the heating effects during its passes over HAARP. The DEMETER results showed direct detection of HAARP ULF waves at 0.1 Hz. Moreover, density dips were observed every time HAARP was operated at CW mode, which provides clear evidence of duct formation by direct HF heating at F peak. Details of these results will be presented at the meeting. We would like to acknowledge the support provided by the HAARP facility during our ULF experiments.

[[Estimation of bilio-oigestive and interintestinal anastomoses, formed in accordance to method of a high-frequency electric welding of tissues, in experiment].

PubMed

Hutsuliak, A I

2016-08-01

In the experiment on 50 rabbits cholecysto-entero and entero-entero anastomoses were formed on intestinal Roux loop. In 35 animals (the main group) a single layer evert- ing anastomoses by using high frequence (HF) electric welding method were formed, in 15 (the comparison group) single row suture anastomoses has been done. The anas- tomosis sufficiency were performed by using hydropressure, pneumopressure meth- ods and breakload test. It was established that all anastomoses formed by HF-electric welding method were passable and hermetic, also had strong sufficiency. Strength of weld joint in the postoperative period increased in a linear progression and after 3 weeks almost reached strength intact intestine (240-250 mm Hg).

Influence of immunostimulant polysaccharides, nucleic acids, and Bacillus strains on the innate immune and acute stress response in turbots (Scophthalmus maximus) fed soy bean- and wheat-based diets.

PubMed

Fuchs, V I; Schmidt, J; Slater, M J; Buck, B H; Steinhagen, D

2017-12-01

Immunostimulants are widely applied in aquaculture practice and may have beneficial effects on the immune system and physical functions allowing higher tolerance to stress. In the current study, the impact of four (i-iv) dietary active ingredients on the immune and stress response of turbot was examined in two experiments (I and II). A basal low fish meal (FM; 32%) diet was formulated and supplemented with (i) yeast β-glucan and mannan oligosaccharide (GM), (ii) alginic acid (AC), (iii) yeast nucleotides and RNA (NR), or (iv) Bacillus strains (BS). The basal diet (C-LF) and a high FM (59%) control (C-HF) were maintained. All six diets were fed to juvenile turbots for 84 days in experiment I and for additional 28 days prior to experiment II. Immunological and hematological parameters were determined in experiment I. In experiment II, physical stress response to a typical short-term (<1 day) aquaculture handling procedure (combination of capture, netting/transfer, and crowding) was investigated. For this, turbot blood was sampled before and at 0.5, 1, 4, and 24 h post stress. Plasma lysozyme activity, neutrophil reactive oxygen species (ROS) production, and total plasma protein levels did not significantly differ between treatment groups; however, plasma cholesterol increased significantly in fish fed GM, AC, NR, and C-HF compared to C-LF (I). A significant increase in plasma glucose and triglyceride was observed in GM and NR treatments, while glucose levels were significantly higher in C-HF compared to C-LF. Moreover, the immunostimulant-supplemented diets exhibited significantly lower cortisol levels compared to controls C-LF (at 0.5 h) and C-HF (at 1 h) post stress, respectively (II). According to our findings, FM substitution did not modulate the innate immune response but was associated with reduced levels of cholesterol. Dietary immunostimulants were not effective enough to boost the immune response, but we believe they might be helpful to trigger metabolic advantages during stressful handling events on fish farms.

PubMed

Rachbauer, R; Blutmager, A; Holec, D; Mayrhofer, P H

2012-01-25

Protective coatings for high temperature applications, as present e.g. during cutting and milling operations, require excellent mechanical and thermal properties during work load. The Ti(1 - x)Al(x)N system is industrially well acknowledged as it covers some of these requirements, and even exhibits increasing hardness with increasing temperature in its cubic modification, known as age hardening. The thermally activated diffusion at high temperatures however enables for the formation of wurtzite AlN, which causes a rapid reduction of mechanical properties in Ti(1 - x)Al(x)N coatings. The present work investigates the possibility to increase the formation temperature of w-AlN due to Hf alloying up to 10 at.% at the metal sublattice of Ti(1 - x)Al(x)N films. Ab initio predictions on the phase stability and decomposition products of quaternary Ti(1 - x - y)Al(x)Hf(y)N alloys, as well as the ternary Ti(1 - x)Al(x)N, Hf(1 - x)Al(x)N and Ti(1 - z)Hf(z)N systems, facilitate the interpretation of the experimental findings. Vacuum annealing treatments from 600 to 1100 °C indicate that the isostructural decomposition, which is responsible for age hardening, of the Ti(1 - x - y)Al(x)Hf(y)N films starts at lower temperatures than the ternary Ti(1 - x)Al(x)N coating. However, the formation of a dual phase structure of c-Ti(1 - z)Hf(z)N (with z = y/(1 - x)) and w-AlN is shifted to ~ 200 °C higher temperatures, thus retaining a film hardness of ~ 40 GPa up to ~ 1100 °C, while the Hf free films reach the respective hardness maximum of ~ 38 GPa already at ~ 900 °C. Additional annealing experiments at 850 and 950 °C for 20 h indicate a substantial improvement of the oxidation resistance with increasing amount of Hf in Ti(1 - x - y)Al(x)Hf(y)N.

Do surgeon interviewers have human factor-related issues during the long day UK National Trauma and Orthopaedic specialty recruitment process?

PubMed

Scrimgeour, D S G; Higgins, J; Bucknall, V; Arnett, R; Featherstone, C R; Cleland, J; Lee, A J; Brennan, P A

2018-03-05

The role that human factors (HF) play in contributing to medical error is increasingly being recognised by healthcare professionals. Surprisingly, much less is known about the possible effects of HF including boredom, fatigue and organisational influences, on performance outside of the clinical environment such as examining or assessing candidates in other high stakes situations. The authors used a validated 38 response questionnaire based around the HF analysis and classification system (HFACS) to assess factors including stress and pressure, care and support and working within the rules for surgeon interviewers at the UK national trainee selection process in Trauma and Orthopaedic surgery. 121 completed questionnaires were analysed (86% response rate). No statistically significant differences were found between interviewer experience, grade or role at the interview and the mean scores obtained for all four factor items. Overall interviewers had a positive experience during national selection with mean factor scores ranging from 3.80 to 3.98 (out of a maximum satisfaction score of 5). Careful planning by organisations and recognising the importance of the human element are essential to ensure assessors are looked after properly during high stakes assessment processes. Our data suggests that a positive experience for examiners is likely to benefit candidate performance and contribute to a fair and reliable recruitment process. The relationship between examiner experience and candidate performance merits further investigation. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

‘Engage me in taking care of my heart’: a grounded theory study on patient–cardiologist relationship in the hospital management of heart failure

PubMed Central

Barello, Serena; Graffigna, Guendalina; Vegni, Elena; Savarese, Mariarosaria; Lombardi, Federico; Bosio, A Claudio

2015-01-01

Objective In approaching the study and practice of heart failure (HF) management, authors recognise that the patient–doctor relationship has a central role in engaging patients in their care. This study aims at identifying the features and the levers of HF patient engagement and suggestions for orienting clinical encounters. Design Using a grounded theory approach, we conducted 22 in-depth interviews (13 patients with HF, 5 physicians and 4 caregivers). Data were collected and analysed using open, axial and selective coding procedures according to the grounded theory principles. Settings All interviews were conducted in an office in a university hospital located in a metropolitan area of Milan, Italy. Participants The data comprised a total of 22 patient, hospital cardiologist and caregiver interviews. Patients aged ≥18 years with New York Heart Association (NYHA) Functional Class of II or III were eligible to take part. Patients were recruited primarily through their referral cardiologist. Results The HF patient engagement process develops in four main phases that are characterised by different patients’ emotional, cognitive and behavioural dynamics that contribute to shape the process of a patient's meaning making towards health and illness regarding their care. The emerging model illustrates that HF patient engagement entails a meaning-making process enacted by the patient after the critical event. This implies patients’ ability to give sense to their care experience and to their disease, symptomatology and treatments, and their changes along their illness course. Doctors are recognised as crucial in fostering patients’ engagement along all the phases of the process as they contribute to providing patients with self-continuity and give new meaning to their illness experience. Conclusions This study identifies the core experiential domains and the main levers involved in driving patients with HF to effectively engage in their disease management. The model emerging from this study may help clinicians think in a fresh way about encounters with patients and their role in fostering their patients’ health engagement. PMID:25776041

Glass-water interaction: Effect of high-valence cations on glass structure and chemical durability

NASA Astrophysics Data System (ADS)

Hopf, J.; Kerisit, S. N.; Angeli, F.; Charpentier, T.; Icenhower, J. P.; McGrail, B. P.; Windisch, C. F.; Burton, S. D.; Pierce, E. M.

2016-05-01

Borosilicate glass is a durable solid, but it dissolves when in contact with aqueous fluids. The dissolution mechanism, which involves a variety of sequential reactions that occur at the solid-fluid interface, has important implications for the corrosion resistance of industrial and nuclear waste glasses. In this study, spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high-valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na2O-Al2O3-B2O3-HfO2-SiO2 system (e.g., Na/[Al + B] = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 (tetrahedral boron/total boron) and increases the amount of Si-O-Hf moieties in the glass. Results from flow-through experiments conducted under dilute and near-saturated conditions show a decrease of approximately 100× or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveals a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the stronger binding of Si sites that deposit on the surface from the influent when Hf is present in the glass. As a result, the residence time at the glass surface of these newly-formed Si sites is longer in the presence of Hf, which increases the density of anchor sites from which altered layers with higher Si densities can form. These results illustrate the importance of understanding solid-water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.

'Engage me in taking care of my heart': a grounded theory study on patient-cardiologist relationship in the hospital management of heart failure.

PubMed

Barello, Serena; Graffigna, Guendalina; Vegni, Elena; Savarese, Mariarosaria; Lombardi, Federico; Bosio, A Claudio

2015-03-16

In approaching the study and practice of heart failure (HF) management, authors recognise that the patient-doctor relationship has a central role in engaging patients in their care. This study aims at identifying the features and the levers of HF patient engagement and suggestions for orienting clinical encounters. Using a grounded theory approach, we conducted 22 in-depth interviews (13 patients with HF, 5 physicians and 4 caregivers). Data were collected and analysed using open, axial and selective coding procedures according to the grounded theory principles. All interviews were conducted in an office in a university hospital located in a metropolitan area of Milan, Italy. The data comprised a total of 22 patient, hospital cardiologist and caregiver interviews. Patients aged ≥18 years with New York Heart Association (NYHA) Functional Class of II or III were eligible to take part. Patients were recruited primarily through their referral cardiologist. The HF patient engagement process develops in four main phases that are characterised by different patients' emotional, cognitive and behavioural dynamics that contribute to shape the process of a patient's meaning making towards health and illness regarding their care. The emerging model illustrates that HF patient engagement entails a meaning-making process enacted by the patient after the critical event. This implies patients' ability to give sense to their care experience and to their disease, symptomatology and treatments, and their changes along their illness course. Doctors are recognised as crucial in fostering patients' engagement along all the phases of the process as they contribute to providing patients with self-continuity and give new meaning to their illness experience. This study identifies the core experiential domains and the main levers involved in driving patients with HF to effectively engage in their disease management. The model emerging from this study may help clinicians think in a fresh way about encounters with patients and their role in fostering their patients' health engagement. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

NASA Astrophysics Data System (ADS)

Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

2014-12-01

In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

Generation of Artificial Ionospheric Irregularities by the Modification of the Earth's Middle-Latitude Ionosphere by X-Mode Powerful HF Radio Waves

NASA Astrophysics Data System (ADS)

Frolov, Vladimir; Padokhin, Artem; Kunitsyn, Viacheslav; Akchurin, Adel; Bolotin, Ilya; Zykov, Evgeniy; Vertogradov, Gennadiy

Basing on experimental data obtained at the SURA heating facility by modification of the Earth’s middle-latitude ionosphere, we consider in the report some peculiarities of the generation of artificial plasma density irregularities when X-mode powerful waves (PW) are used for ionosphere pumping [1]. Experiments were carried out during 2008 - 2012 under quite ionospheric conditions (Sigma K_p = 10 - 30). Analysis of obtained experimental data has shown that: 1) In our measurements the generation of small-scale irregularities with l{_⊥} {≃} 10 - 20 m is not observed in contrast to analogous measurements conducted at the EISCAT-heater [2,3]. 2) The generation of irregularities with l{_⊥} {≃} 50 m - 3 km is mainly observed in evening and night hours. In these conditions their intensity is by 3 to 4 times below in comparison with the O-mode pumping. During day hours these irregularities are not detected due to both strong PW energy absorption in the lower ionosphere and forming a defocusing lens at altitudes of 130 - 150 km [4]. 3) The generation of irregularities with l{_⊥} {≥} 5 - 10 km is only observed in evening and night hours. In these conditions their intensity is by 10 times below in comparison with the O-mode pumping. 4) The generation of the irregularities with l{_⊥} {≥} 50 m is observed only when the PW reflects in the ionospheric F _{2} region. 5) Under day-time conditions the defocusing lens is forming at altitudes of about of 130 - 150 km when the ionosphere is pumping both X- and O- mode powerful waves [4]. Its horizontal size is determined by the HF beam. In our experiments [1] it was revealed that the stronger generation of irregularities with scale-lengths l{_⊥} {≃} 5 - 10 km is observed at the HF beam edge where the effective radiated power is of about 0.1 P _{max}. Such a “beam-edge” effect is also observed when the ionosphere is modified by O-mode PW. The enhancement of irregularity generation at the HF beam edge was considered in [5]. The work was supported by RFBR grants (## 12-05-00312, 13-02-12074, 13-02-12241, 14-05-31445, 14-05-00855, 14-05-10069), grant MK-2670.2014.5, and by the scientific program “Geophysics”. References: 1. Frolov et al. // Radiophys. Quant. Electron., Engl. Transl., 2013 (submitted for publication). 2. Blagovethshenskaya N.F., et al. // Geophys. Res. Lett., 2011. Vol. 38, L08802, doi:10.1029/2011GL046724. 3. Blagoveshchensraya N.F. et al. // J. Atmos. Sol.-Terr. Phys., 2013. Vol. 105-106, p. 231. 4. Boiko G.N. et al. // Radiophys. Quant. Electron., Engl. Transl., 1985. Vol. 28, No. 8, p. 960. 5. Kuo S., et al. // Geophys. Res. Lett., 2010. Vol. 37, L01101, doi:10.1029/2009GL041471.

Low-cost directionally-solidified turbine blades, volume 2. [TFE731-3 turbofan engine

NASA Technical Reports Server (NTRS)

Dennis, R. E.; Hoppin, G. S., III; Hurst, L. G.

1979-01-01

An endothermically heated technology was used to manufacture low cost, directionally solidified, uncooled nickel-alloy blades for the TFE731-3 turbofan engine. The MAR-M 247 and MER-M 100+Hf blades were finish processed through heat treatment, machining, and coating operations prior to 150 hour engine tests consisting of the following sequences: (1) 50 hours of simulated cruise cycling (high fatigue evaluation); (2) 50 hours at the maximum continuous power rating (stress rupture endurance (low cycle fatigue). None of the blades visually showed any detrimental effects from the test. This was verified by post test metallurgical evaluation. The specific fuel consumption was reduced by 2.4% with the uncooled blades.

Psychophysiological Correlates of Generalized Anxiety Disorder with or without Comorbid Depression

PubMed Central

Hofmann, Stefan G.; Schulz, Stefan M.; Heering, Sanna; Muench, Frederick; Bufka, Lynn F.

2010-01-01

It remains uncertain whether generalized anxiety disorder (GAD) and major depressive disorder (MDD) represent two separate diagnostic entities. The goal of this study was to examine whether comorbid MDD distinguishes individuals with GAD on a psychophysiological level during an experimentally-induced worrying procedure. Participants included 39 individuals with GAD, 14 of whom met criteria for MDD. During the experimental procedure, participants were asked to worry or relax after an initial baseline phase while measuring their heart rate, high frequency heart rate variability (HF-HRV), skin conductance level, and subjective level of anxiety. The two groups did not differ in their subjective anxiety, heart rate response, and skin conductance levels. However, participants with comorbid MDD had greater HF-HRV values throughout the experiment than did those without MDD. At baseline, HF-HRV was significantly correlated with a self-report measure of depression. These results suggest that individuals with comorbid GAD and MDD can be distinguished based on HF-HRV from individuals with GAD but without MDD. These results support the distinction between GAD and MDD. PMID:20093149

The Role of Hydromagnetic Waves in the Magnetosphere and the Ionosphere

DTIC Science & Technology

1988-05-01

ionospheric heating ex- ( MINIX ) was carried out recently by the Kyoto Uni- periments [Stubbe and Kopka, 198! Stubbe et al., versity group in Japan to...ionospheric irregularities and other predicted netosphere with growth times of a few minutes. Our phenomena could not be produced in MINIX be- work...ionosphere: Project- HF produced electron density irregularities in the polar iono- MINIX for future solar power satellite, paper presented at 21st

High-frequency ECG

NASA Technical Reports Server (NTRS)

Tragardh, Elin; Schlegel, Todd T.

2006-01-01

The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire ventricular surface and were signal-averaged and filtered in the 30-250 Hz frequency range. The results showed that the decrease noted in the HF-QRS correlated linearly with the local conduction delay. The results suggest that HF-QRS is a potent indicator of disturbed local conduction. An alternative theory is that HF-QRS reflect the shape of the original electrocardiographic signal. Bennhagen et al showed that root mean square (RMS) voltage values of the depolarization signal correlate poorly with the signal amplitude but highly with the first and second derivatives, i.e. the velocity and the acceleration of the signal. It has also been suggested that the autonomic nervous system affects HF-QRS. For example, sitting up causes significant changes in HF-QRS in some leads compared to the supine position [Douglas et al., 2006]. Unpublished results indicate that familial dysautonomic patients (both vagal and sympathetic degeneration) have very little Reduced Amplitude Zones (RAZ) formation . Athletic individuals, especially elite athletes, who have vagally-mediated changes on the conventional ECG (i.e. early repolarization, bradycardia) have increased RAZ formation. Further electrophysiological studies are needed, however, to better understand the underlying mechanisms of HF-QRS. Several investigators have studied HF-QRS in different cardiac conditions, including acute myocardial ischemia and myocardial infarction (MI). However, in order for clinicians to confidently use HF-QRS as an adjunct to standard ECG, more knowledge about the characteristics of HF-QRS is needed.

LOW-TEMPERATURE HEAT CAPACITIES AND THERMODYNAMIC FUNCTIONS OF SOME PLATINUM AND PALLADIUM GROUP CHALCOGENIDES. I. MONO-CHALCOGENIDES. Pts, PtTe, AND PdTe

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

Groenvold, F.; Thurmann-Moe, T.; Westrum, E.F. Jr.

1961-11-01

Heat capacities of platinum monosulfide, platinum monotelluride, and palladium monotelluride were measured in the range 5--350 deg K. They show the normal sigmoidal temperature dependence with no evidence of transivions or other anomalies. The derived heat-capacity equations were integrated. Values of heat capacitles, entropy, and enthalpy increments, and of the free-energy function are tabulated for selected temperatures. Av 298,15 deg K, the third-law entroples are 13,16 cal gfw/sup -1/ deg K/sup -1/ for PtS 19.41 cal gfw/sup -1/ deg K/sup - 1/ for PtTe, and 2l.42 cal gfw/sup -1/ deg K/sup -1/ for PdTe. The new dava on PvS weremore » correlaved wlvh exlstlng decomposlvlonpressure data vo evaluate DELTA Hf, DELTA Ff, and DELTA Sf 298.15 deg K. Entropies for other platlnum-metal monochalcogenides were estimated. (auth)« less

Scanning electron microscopy of heat treated TiO2 nanotubes arrays obtained by anodic oxidation

NASA Astrophysics Data System (ADS)

Naranjo, D. I.; García-Vergara, S. J.; Blanco, S.

2017-12-01

Scanning electron microscopy was used to investigate the anatase-rutile transformation of self-organized TiO2 nanotubes obtained on titanium foil by anodizing and subsequent heat treatment. The anodizing was carried out at 20V in an 1% v/v HF acid and ethylene glycol:water (50:50) electrolyte at room temperature. The anodized samples were initially pre-heat treated at 450°C for 4 hours to modify the amorphous structure of TiO2 nanotubes into anatase structure. Then, the samples were heated between 600 to 800°C for different times, in order to promote the transformation to rutile structure. The formation of TiO2 nanotubes is evident by SEM images. Notably, when the samples are treated at high temperature, the formation of rutile crystals starts to become evident at the nanotubes located on the originally grain boundaries of the titanium. Thus, the anatase - rutile transformation has a close relationship with the microstructure of the titanium, more exactly with grain boundaries.

Heat capacity from 12 to 305°K and entropy of talc and tremolite

USGS Publications Warehouse

Robie, R.A.; Stout, J.W.

1963-01-01

The heat capacities of talc, Mg3Si4O10(OH)2, and tremolite, Ca2Mg6Si8O22(OH)2, have been measured between 12 and 305??K. Smoothed values of heat capacity, entropy, enthalpy, and free energy are tabulated. At 298.15?? K. the values of the thermodynamic functions are: talc, Cp?? = 76.89 ?? 0.23 cal. deg.-1 mole-1, S?? = 62.33 ?? 0.19 cal. deg.-1 mole-1, H?? - H6?? = 11,206 ?? 34 cal. mole-1; tremolite, Cp?? = 156.7 ?? 0.6 cal. deg.-1 mole-1, S?? = 131.2 ?? 0.5 cal. deg.-1 mole-1, H?? - H6?? = 23,335 ?? 90 cal. mole-1. From the equilibrium data of Bowen and Tuttle and the entropy of talc, the heat of formation of talc from MgO, SiO2, and H2O (liq.) is calculated to be ??H??f298 = -43.6 ?? 1 kcal.

Active mode-locked operation of a diode pumped colour-centre laser

NASA Astrophysics Data System (ADS)

Mazighi, K.; Doualan, J. L.; Hamel, J.; Margerie, J.; Mounier, D.; Ostrovsky, A.

1991-09-01

The cw laser diode pumping of an (F +2) ∗ colour centre laser has been recently demonstrated in our laboratory. The intensity of the pumping diode can easily be hf modulated. We present here the first experiments in which the colour centre laser is synchronously pumped at the mode spacing frequency, resulting in the emission of clean, regularly spaced pulses. The opto-electronic feedback is a very promising method of obtaining such a pulsed operation of a diode pumped colour centre laser without the use of an external hf oscillator.

Consumption of a High-Fat Diet Induces Central Insulin Resistance Independent of Adiposity

PubMed Central

Clegg, Deborah J.; Gotoh, Koro; Kemp, Christopher; Wortman, Matthew D.; Benoit, Stephen C.; Brown, Lynda M.; D’Alessio, David; Tso, Patrick; Seeley, Randy J.; Woods, Stephen C.

2011-01-01

Plasma insulin enters the CNS where it interacts with insulin receptors in areas that are related to energy homeostasis and elicits a decrease of food intake and body weight. Here, we demonstrate that consumption of a high-fat (HF) diet impairs the central actions of insulin. Male Long-Evans rats were given chronic (70-day) or acute (3-day) ad libitum access to HF, low-fat (LF), or chow diets. Insulin administered into the 3rd-cerebral ventricle (i3vt) decreased food intake and body weight of LF and chow rats but had no effect on HF rats in either the chronic or the acute experiment. Rats chronically pair-fed the HF diet to match the caloric intake of LF rats, and with body weights and adiposity levels comparable to those of LF rats, were also unresponsive to i3vt insulin when returned to ad lib food whereas rats pair-fed the LF diet had reduced food intake and body weight when administered i3vt insulin. Insulin’s inability to reduce food intake in the presence of the high-fat diet was associated with a reduced ability of insulin to activate its signaling cascade, as measured by pAKT. Finally, i3vt administration of insulin increased hypothalamic expression of POMC mRNA in the LF-but not the HF-fed rats. We conclude that consumption of a HF diet leads to central insulin resistance following short exposure to the diet, and as demonstrated by reductions in insulin signaling and insulin-induced hypothalamic expression of POMC mRNA. PMID:21241723

Conditional recall and the frequency effect in the serial recall task: an examination of item-to-item associativity.

PubMed

Miller, Leonie M; Roodenrys, Steven

2012-11-01

The frequency effect in short-term serial recall is influenced by the composition of lists. In pure lists, a robust advantage in the recall of high-frequency (HF) words is observed, yet in alternating mixed lists, HF and low-frequency (LF) words are recalled equally well. It has been argued that the preexisting associations between all list items determine a single, global level of supportive activation that assists item recall. Preexisting associations between items are assumed to be a function of language co-occurrence; HF-HF associations are high, LF-LF associations are low, and mixed associations are intermediate in activation strength. This account, however, is based on results when alternating lists with equal numbers of HF and LF words were used. It is possible that directional association between adjacent list items is responsible for the recall patterns reported. In the present experiment, the recall of three forms of mixed lists-those with equal numbers of HF and LF items and pure lists-was examined to test the extent to which item-to-item associations are present in serial recall. Furthermore, conditional probabilities were used to examine more closely the evidence for a contribution, since correct-in-position scoring may mask recall that is dependent on the recall of prior items. The results suggest that an item-to-item effect is clearly present for early but not late list items, and they implicate an additional factor, perhaps the availability of resources at output, in the recall of late list items.

Judiciary views on criminal behaviour and intention of offenders with high-functioning autism

PubMed Central

Berryessa, Colleen M.

2015-01-01

Purpose The purpose of this paper is to explore how judges perceive High Functioning Autistic Spectrum Disorders (hfASDs) and the disorders’ effects on an offender’s ability to formulate criminal intent and control behaviour. Design/methodology/approach Semi-structured interviews on topics related to offenders with hfASDs were conducted with 21 California Superior Court Judges. A coding scheme was developed and an iterative qualitative coding process was used for analysis. Findings Analysis yielded three major themes on how an hfASD diagnosis affects an offender’s ability to regulate actions and criminal behaviour. Interviewed judges reported beliefs that hfASD offenders view the world in a different way and that much of their behaviour is not under their direct control. Judges reported these perceptions likely affect how they criminally process and make legal decisions regarding offenders with hfASDs. Research limitations/implications The sample size was small and therefore no statistical significance can be drawn from results; findings cannot be applied to perceptions or experiences of the entire California Superior Court Judge population. Originality/value Past academic research reports that individuals with hfASDs that offend often do so because of specific symptoms associated with the disorder. This presents a complex dilemma for the criminal justice system regarding how best to understand the disorder and process these offenders. This study and its findings aim to shed light on issues judges encounter in determining these offenders’ responsibility and sentencing, in what ways this information might be integrated into judicial decision making, and areas where future research is needed. PMID:25866642

[Development and evaluation of a dance-based exercise therapy for patients with haemophilia].

PubMed

Czepa, D; van Ravenstein, S; Stäuber, F; Hilberg, T

2013-01-01

So far, the use of methods derived from creative arts has not been considered in the haemophilia treatment. The AIM was to investigate the expectations for a dance-based exercise therapy for patients with haemophilia and the extent of its acceptance. The one-hour dance-based exercise therapy was offered to 30 haemophilia patients (HI30) (49 ± 11, 30-67 years). For the evaluation of expectations, questionnaires were created and filled out by participants before and after the intervention. Additionally, 19 haemophilia patients (HF) and 20 controls without haemophilia (KF) who did not participate in the intervention were also questioned. The RESULTS show that haemophilia patients have more experience in dance than controls (HI30:62%, HF:74%, KF:45%). In contrast, the proportion of those who are currently dancing is higher in controls without haemophilia (HI30: 17%, HF: 10%, KF:26%). The termination of dance activity in patients with haemophilia who were part of the intervention was mainly due to pain (HI30: 40%, HF: 29%, KF: 0%), whereby controls without intervention terminated the dance activity mainly due to lack of time (HI30: 30%, HF: 57%, KF: 56%). Ultimately, 24 out of 30 patients with haemophilia (HI24) completed the intervention. All HI24 met their expectations. 38% felt limited by haemophilia while carrying out the exercises. The majority of the participants were able to follow the exercises well (96%) and were did not overstrain physically (92%) nor mentally (87%), also 79% did not have pain. 23 of HI24 (96%) can envision a continuation of the dance-based exercise therapy. The experience with the dance-based exercise therapy was predominantly positive. It represents an alternative sports therapy programme for patients with haemophilia. Further studies are needed in order to make statements concerning the long-term use of such training.

Effects of Fortunella margarita fruit extract on metabolic disorders in high-fat diet-induced obese C57BL/6 mice.

PubMed

Tan, Si; Li, Mingxia; Ding, Xiaobo; Fan, Shengjie; Guo, Lu; Gu, Ming; Zhang, Yu; Feng, Li; Jiang, Dong; Li, Yiming; Xi, Wanpeng; Huang, Cheng; Zhou, Zhiqin

2014-01-01

Obesity is a nutritional disorder associated with many health problems such as dyslipidemia, type 2 diabetes and cardiovascular diseases. In the present study, we investigated the anti-metabolic disorder effects of kumquat (Fortunella margarita Swingle) fruit extract (FME) on high-fat diet-induced C57BL/6 obese mice. The kumquat fruit was extracted with ethanol and the main flavonoids of this extract were analyzed by HPLC. For the preventive experiment, female C57BL/6 mice were fed with a normal diet (Chow), high-fat diet (HF), and high-fat diet with 1% (w/w) extract of kumquat (HF+FME) for 8 weeks. For the therapeutic experiment, female C57BL/6 mice were fed with high-fat diet for 3 months to induce obesity. Then the obese mice were divided into two groups randomly, and fed with HF or HF+FME for another 2 weeks. Body weight and daily food intake amounts were recorded. Fasting blood glucose, glucose tolerance test, insulin tolerance test, serum and liver lipid levels were assayed and the white adipose tissues were imaged. The gene expression in mice liver and brown adipose tissues were analyzed with a quantitative PCR assay. In the preventive treatment, FME controlled the body weight gain and the size of white adipocytes, lowered the fasting blood glucose, serum total cholesterol (TC), serum low density lipoprotein cholesterol (LDL-c) levels as well as liver lipid contents in high-fat diet-fed C57BL/6 mice. In the therapeutic treatment, FME decreased the serum triglyceride (TG), serum TC, serum LDL-c, fasting blood glucose levels and liver lipid contents, improved glucose tolerance and insulin tolerance. Compared with the HF group, FME significantly increased the mRNA expression of PPARα and its target genes. Our study suggests that FME may be a potential dietary supplement for preventing and ameliorating the obesity and obesity-related metabolic disturbances.

Hydrogen bond spectroscopy in the near infrared: Out-of-plane torsion and antigeared bend combination bands in (HF)2

NASA Astrophysics Data System (ADS)

Anderson, David T.; Davis, Scott; Nesbitt, David J.

1996-09-01

High-resolution near infrared spectra of the two ``high'' frequency intermolecular modes of (HF)2 have been characterized in HF-stretch excited states using a slit jet spectrometer. In the spectral region between 4280 and 4480 cm-1, four vibration-rotation-tunneling (VRT) bands are observed and assigned to tunneling pairs of the out-of-plane torsion (ν6) and antigeared bend (ν3) intermolecular modes, in combination with the hydrogen bond donor (ν2) and acceptor (ν1) high-frequency intramolecular HF stretches, respectively. Analysis of the jet-cooled, rotationally resolved spectra provide intermolecular frequencies, rotational constants, tunneling splittings, and predissociation rates for the ν3/ν6 intermolecular excited states. The relatively small changes in the hydrogen bond interconversion tunneling splitting with either ν3 or ν6 excitation indicate that neither intermolecular mode is strongly coupled to the tunneling coordinate. The high-resolution VRT linewidths reveal mode specific predissociation broadening sensitive predominantly to intramolecular excitation, but with significant additional effects due to low-frequency intermolecular excitation as well. The intermolecular vibrational frequencies in the combination states display a systematic dependence on intramolecular redshift that allows all four intermolecular fundamental frequencies to be extrapolated from the near-ir data. Agreement between full 6-D quantum calculations and experiment for the out-of-plane torsion (ν6) vibration is remarkably good (0.5%). However, significant discrepancies (≳10%) between theory and experiment are obtained for the antigeared bend (ν3), indicating the need for further refinement of the HF dimer potential surface. Finally, the observation of all four intermolecular modes allows zero-point contributions to the binding energy to be reliably estimated. The revised value for the binding energy, De=1580(35) cm-1, is slightly higher than semiempirical estimates but now in excellent agreement with recent high level ab initio calculations.

Weak quadrupole moments

NASA Astrophysics Data System (ADS)

Lackenby, B. G. C.; Flambaum, V. V.

2018-07-01

We introduce the weak quadrupole moment (WQM) of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The WQM produces a tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, Q n , the WQMs, {Q}W(2), and the Lorentz invariance violating energy shifts in 9Be, 21Ne, 27Al, 131Xe, 133Cs, 151Eu, 153Eu, 163Dy, 167Er, 173Yb, 177Hf, 179Hf, 181Ta, 201Hg and 229Th.

Toxic fluoride gas emissions from lithium-ion battery fires.

PubMed

Larsson, Fredrik; Andersson, Petra; Blomqvist, Per; Mellander, Bengt-Erik

2017-08-30

Lithium-ion battery fires generate intense heat and considerable amounts of gas and smoke. Although the emission of toxic gases can be a larger threat than the heat, the knowledge of such emissions is limited. This paper presents quantitative measurements of heat release and fluoride gas emissions during battery fires for seven different types of commercial lithium-ion batteries. The results have been validated using two independent measurement techniques and show that large amounts of hydrogen fluoride (HF) may be generated, ranging between 20 and 200 mg/Wh of nominal battery energy capacity. In addition, 15-22 mg/Wh of another potentially toxic gas, phosphoryl fluoride (POF 3 ), was measured in some of the fire tests. Gas emissions when using water mist as extinguishing agent were also investigated. Fluoride gas emission can pose a serious toxic threat and the results are crucial findings for risk assessment and management, especially for large Li-ion battery packs.

Heat and PAHs Emissions in Indoor Kitchen Air and Its Impact on Kidney Dysfunctions among Kitchen Workers in Lucknow, North India.

PubMed

Singh, Amarnath; Kamal, Ritul; Mudiam, Mohana Krishna Reddy; Gupta, Manoj Kumar; Satyanarayana, Gubbala Naga Venkata; Bihari, Vipin; Shukla, Nishi; Khan, Altaf Hussain; Kesavachandran, Chandrasekharan Nair

2016-01-01

Indoor air quality and heat exposure have become an important occupational health and safety concern in several workplaces including kitchens of hotels. This study investigated the heat, particulate matter (PM), total volatile organic compounds (TVOCs) and polycyclic aromatic hydrocarbons (PAHs) emissions in indoor air of commercial kitchen and its association with kidney dysfunctions among kitchen workers. A cross sectional study was conducted on 94 kitchen workers employed at commercial kitchen in Lucknow city, North India. A questionnaire-based survey was conducted to collect the personal and occupational history of the kitchen workers. The urine analysis for specific gravity and microalbuminuria was conducted among the study subjects. Indoor air temperature, humidity, wet/ dry bulb temperature and humidex heat stress was monitored during cooking activities at the kitchen. Particulate matter (PM) for 1 and 2.5 microns were monitored in kitchen during working hours using Hazdust. PAHS in indoor air was analysed using UHPLC. Urinary hydroxy-PAHs in kitchen workers were measured using GC/MS-MS. Higher indoor air temperature, relative humidity, PM1 and PM2.5 (p<0.001) was observed in the kitchen due to cooking process. Indoor air PAHs identified are Napthalene, fluorine, acenaphthene, phenanthrene, pyrene, chrysene and indeno [1,2,3-cd) pyrene. Concentrations of all PAHs identified in kitchen were above the permissible OSHA norms for indoor air. Specific gravity of urine was significantly higher among the kitchen workers (p<0.001) as compared to the control group. Also, the prevalence of microalbuminuria was higher (p<0.001) among kitchen workers. Urinary PAH metabolites detected among kitchen workers were 1-NAP, 9-HF, 3-HF, 9-PHN and 1-OHP. Continuous heat exposure in kitchens due to cooking can alter kidney functions viz., high specific gravity of urine in kitchen workers. Exposure to PM, VOCs and PAHs in indoor air and presence of urinary PAHs metabolites may lead to inflammation, which can cause microalbuminuria in kitchen workers, as observed in the present study.

Heat and PAHs Emissions in Indoor Kitchen Air and Its Impact on Kidney Dysfunctions among Kitchen Workers in Lucknow, North India

PubMed Central

Singh, Amarnath; Kamal, Ritul; Mudiam, Mohana Krishna Reddy; Gupta, Manoj Kumar; Satyanarayana, Gubbala Naga Venkata; Bihari, Vipin; Shukla, Nishi; Khan, Altaf Hussain; Kesavachandran, Chandrasekharan Nair

2016-01-01

Indoor air quality and heat exposure have become an important occupational health and safety concern in several workplaces including kitchens of hotels. This study investigated the heat, particulate matter (PM), total volatile organic compounds (TVOCs) and polycyclic aromatic hydrocarbons (PAHs) emissions in indoor air of commercial kitchen and its association with kidney dysfunctions among kitchen workers. A cross sectional study was conducted on 94 kitchen workers employed at commercial kitchen in Lucknow city, North India. A questionnaire-based survey was conducted to collect the personal and occupational history of the kitchen workers. The urine analysis for specific gravity and microalbuminuria was conducted among the study subjects. Indoor air temperature, humidity, wet/ dry bulb temperature and humidex heat stress was monitored during cooking activities at the kitchen. Particulate matter (PM) for 1 and 2.5 microns were monitored in kitchen during working hours using Hazdust. PAHS in indoor air was analysed using UHPLC. Urinary hydroxy-PAHs in kitchen workers were measured using GC/MS-MS. Higher indoor air temperature, relative humidity, PM1 and PM2.5 (p<0.001) was observed in the kitchen due to cooking process. Indoor air PAHs identified are Napthalene, fluorine, acenaphthene, phenanthrene, pyrene, chrysene and indeno [1,2,3-cd) pyrene. Concentrations of all PAHs identified in kitchen were above the permissible OSHA norms for indoor air. Specific gravity of urine was significantly higher among the kitchen workers (p<0.001) as compared to the control group. Also, the prevalence of microalbuminuria was higher (p<0.001) among kitchen workers. Urinary PAH metabolites detected among kitchen workers were 1-NAP, 9-HF, 3-HF, 9-PHN and 1-OHP. Continuous heat exposure in kitchens due to cooking can alter kidney functions viz., high specific gravity of urine in kitchen workers. Exposure to PM, VOCs and PAHs in indoor air and presence of urinary PAHs metabolites may lead to inflammation, which can cause microalbuminuria in kitchen workers, as observed in the present study. PMID:26871707

First observations of SPEAR-induced topside and bottomside sporadic E layer heating observed using the EISCAT Svalbard and SuperDARN radars

NASA Astrophysics Data System (ADS)

Baddeley, L. J.; Haggstrøm, I.; Yeoman, T. K.; Rietveld, M.

2012-01-01

We present the first observations of heater-induced simultaneous topside and bottomside sporadic E layer enhancements at very high latitudes (78.15°N) using the Space Plasma Exploration by Active Radar (SPEAR) heating facility and the European Incoherent Scatter (EISCAT) Svalbard Radar. During the experiment the SPEAR heating facility was transmitting with O-mode polarization in a field-aligned direction with a constant effective radiated power of ˜16 MW. Results show distinct heater-induced enhancements in both the ion and plasma line spectra. The plasma line enhancements are observed at the SPEAR heater frequency of 4.45 MHz. The plasma line observations represent the highest spatial resolution data (100 m) obtained of such heater-induced enhancements and indicate simultaneous enhancements at both the topside and bottomside of the layer, respectively (located at ˜107.5 and 109 km altitude, respectively). It is postulated that the results represent evidence of O- to Z-mode conversion of the heater wave occurring at the bottom of the E layer, allowing propagation through the layer resulting in simultaneous topside enhancements. The Z-mode enhancements are observed outside the Spitze angle, which is thought to be a result of field-aligned irregularities causing an increase in angular extent of the observations. Additional data from the Super Dual Auroral Radar Network (SuperDARN) HF Finland radar are also shown, which indicate that upon a thinning of the sporadic E layer, the heater beam propagated into the F region, where it induced artificial field-aligned irregularities.

Nanoscale Imaging with a Single Quantum Dot

DTIC Science & Technology

2011-12-19

mL round-bottom flask equipped with a condenser , a thermometer and a magnetic stirring bar. After the EG was heated to 160 °C in an oil bath, 0.5 mL...radiatively transferred to the wire’s SPP mode through an electric dipole interaction19. The efficiency of this process scales as the spontaneous emission...Liu, J., Gao, D., Li, H.-F. & Lin, J.-M. Controlled photopolymerization of hydrogel microstructures inside microchannels for bioassays. Lab. Chip 9

High temperature coefficient of resistance achieved by ion beam assisted sputtering with no heat treatment in V{sub y}M{sub 1−y}O{sub x} (M = Nb, Hf)

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

Vardi, Naor; Sharoni, Amos, E-mail: amos.sharoni@biu.ac.il

2015-11-15

Thermal imaging based on room temperature bolometer sensors is a growing market, constantly searching for improved sensitivity. One important factor is the temperature coefficient of resistance (TCR), i.e., the sensitivity of the active material. Herein, the authors report the improved TCR properties attainable by the “ion beam assisted deposition” method for room temperature deposition. V{sub y}M{sub 1−y}O{sub x} (M = Nb, Hf) thin-film alloys were fabricated on 1 μm thermal SiO{sub 2} atop Si (100) substrates by reactive magnetron cosputtering at room temperature using a low energy ion source, aimed at the film, to insert dissociated oxygen species and increase film density. Themore » authors studied the influence of deposition parameters such as oxygen partial pressure, V to M ratio, and power of the plasma source, on resistance and TCR. The authors show high TCR (up to −3.7% K{sup −1}) at 300 K, and excellent uniformity, but also an increase in resistance. The authors emphasize that samples were prepared at room temperature with no heat treatment, much simpler than common processes that require annealing at high temperatures. So, this is a promising fabrication route for uncooled microbolometers.« less

Preparation and characterizations of SnO2 nanopowder and spectroscopic (FT-IR, FT-Raman, UV-Visible and NMR) analysis using HF and DFT calculations.

PubMed

Ayeshamariam, A; Ramalingam, S; Bououdina, M; Jayachandran, M

2014-01-24

In this work, pure and singe phase SnO2 Nano powder is successfully prepared by simple sol-gel combustion route. The photo luminescence and XRD measurements are made and compared the geometrical parameters with calculated values. The FT-IR and FT-Raman spectra are recorded and the fundamental frequencies are assigned. The optimized parameters and the frequencies are calculated using HF and DFT (LSDA, B3LYP and B3PW91) theory in bulk phase of SnO2 and are compared with its Nano phase. The vibrational frequency pattern in nano phase gets realigned and the frequencies are shifted up to higher region of spectra when compared with bulk phase. The NMR and UV-Visible spectra are simulated and analyzed. Transmittance studies showed that the HOMO-LUMO band gap (Kubo gap) is reduced from 3.47 eV to 3.04 eV while it is heated up to 800°C. The Photoluminescence spectra of SnO2 powder showed a peak shift towards lower energy side with the change of Kubo gap from 3.73 eV to 3.229 eV for as-prepared and heated up to 800°C. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Synthesis and characterization of F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles with improved near infrared shielding ability

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

Liu, Jingxiao; Luo, Jiayu; Shi, Fei, E-mail: shifei@dlpu.edu.cn

2015-01-15

F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source, and a new kind of heat insulating films were prepared from dispersion of Cs{sub 0.33}WO{sub 3−x}F{sub x} nanoparticles in polyvinyl alcohol (PVA) aqueous solution. The effects of F doping on the crystal structure and morphology of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles as well as the near-infrared (NIR) shielding ability and heat insulation properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} films were investigated. The results indicated that HF acid addition could promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles during hydrothermalmore » synthesis and increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders. Moreover, the as-prepared films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs{sub 0.33}WO{sub 3} film. Particularly, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} sample with F/W (molar ratio)=0.45 showed best NIR shielding ability and transparent heat insulating performance. The formation mechanism of nanorod-like particles and the effects of F doping on the properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} products were discussed. - Graphical abstract: F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source. HF acid addition in the precursor solution could increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders and promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles. Moreover, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs{sub x}WO{sub 3} film. Particularly, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} sample with F/W (molar ratio)=0.45 showed best NIR shielding ability and transparent heat insulating performance. - Highlights: • F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} powders were successfully synthesized by the hydrothermal method. • HF acid addition could promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles. • The near infrared shielding ability of Cs{sub 0.33}WO{sub 3} was further improved by F doping. • The Cs{sub 0.33}WO{sub 3−x}F{sub x} films exhibited higher transparent heat insulation than Cs{sub 0.33}WO{sub 3}.« less

Shock tube study of dissociation and relaxation in 1,1-difluoroethane and vinyl fluoride.

PubMed

Xu, Hui; Kiefer, John H; Sivaramakrishnan, Raghu; Giri, Binod R; Tranter, Robert S

2007-08-21

This paper reports measurements of the thermal dissociation of 1,1-difluoroethane in the shock tube. The experiments employ laser-schlieren measurements of rate for the dominant HF elimination using 10% 1,1-difluoroethane in Kr over 1500-2000 K and 43 < P < 424 torr. The vinyl fluoride product of this process then dissociates affecting the late observations. We thus include a laser schlieren study (1717-2332 K, 75 < P < 482 torr in 10 and 4% vinyl fluoride in Kr) of this dissociation. This latter work also includes a set of experiments using shock-tube time-of-flight mass spectrometry (4% vinyl fluoride in neon, 1500-1980 K, 500 < P < 1300 torr). These time-of-flight experiments confirm the theoretical expectation that the only reaction in vinyl fluoride is HF elimination. The dissociation experiments are augmented by laser schlieren measurements of vibrational relaxation (1-20% C(2)H(3)F in Kr, 415-1975 K, 5 < P < 50 torr, and 2 and 5% C(2)H(4)F(2) in Kr, 700-1350 K, 6 < P < 22 torr). These experiments exhibit very rapid relaxation, and incubation delays should be negligible in dissociation. An RRKM model of dissociation in 1,1-difluoroethane based on a G3B3 calculation of barrier and other properties fits the experiments but requires a very large DeltaE(down) of 1600 cm(-1), similar to that found in a previous examination of 1,1,1-trifluoroethane. Dissociation of vinyl fluoride is complicated by the presence of two parallel HF eliminations, both three-center and four-center. Structure calculations find nearly equal barriers for these, and TST calculations show almost identical k(infinity). An RRKM fit to the observed falloff again requires an unusually large DeltaE(down) and the experiments actually support a slightly reduced barrier. These large energy-transfer parameters now seem routine in these large fluorinated species. It is perhaps a surprising result for which there is as yet no explanation.

Impact of heat treatments on the fatigue resistance of different rotary nickel-titanium instruments.

PubMed

Braga, Lígia Carolina Moreira; Faria Silva, Ana Cristina; Buono, Vicente Tadeu Lopes; de Azevedo Bahia, Maria Guiomar

2014-09-01

The aim of this study was to assess the influence of M-Wire (Dentsply Tulsa Dental Specialties, Tulsa, OK) and controlled memory technologies on the fatigue resistance of rotary nickel-titanium (NiTi) files by comparing files made using these 2 technologies with conventional NiTi files. Files with a similar cross-sectional design and diameter were chosen for the study: new 30/.06 files of the EndoWave (EW; J. Morita Corp, Osaka, Japan), HyFlex (HF; Coltene/Whaledent, Inc, Cuyahoga Falls, OH), ProFile Vortex (PV; Dentsply Tulsa Dental Specialties, Tulsa, OK), and Typhoon (TYP; Clinician's Choice Dental Products, New Milford, CT) systems together with ProTaper Universal F2 instruments (PTU F2; Dentsply Maillefer, Ballaigues, Switzerland). The compositions and transformation temperatures of the instruments were analyzed using x-ray energy-dispersive spectroscopy and differential scanning calorimetry, whereas the mean file diameter values at 3 mm from the tip (D3) were measured using image analysis software. The average number of cycles to failure was determined using a fatigue test device. X-ray energy-dispersive spectroscopy analysis showed that, on average, all the instruments exhibited the same chemical composition, namely, 51% Ni-49% Ti. The PV, TYP, and HF files exhibited increased transformation temperatures. The PTU F2, PV, and TYP files had similar D3 values, which were less than those of the EW and HF files. The average number of cycles to failure values were 150% higher for the TYP files compared with the PV files and 390% higher for the HF files compared with the EW files. M-Wire and controlled memory technologies increase the fatigue resistance of rotary NiTi files. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

NASA Astrophysics Data System (ADS)

Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

2014-01-01

Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

Investigating the Structural, Thermal, and Electronic Properties of the Zircon-Type ZrSiO4, ZrGeO4 and HfSiO4 Compounds

NASA Astrophysics Data System (ADS)

Chiker, Fafa; Boukabrine, Fatiha; Khachai, H.; Khenata, R.; Mathieu, C.; Bin Omran, S.; Syrotyuk, S. V.; Ahmed, W. K.; Murtaza, G.

2016-11-01

In the present study, the structural, thermal, and electronic properties of some important orthosilicate dielectrics, such as the ZrSiO4, ZrGeO4, and HfSiO4 compounds, have been investigated theoretically with the use of first-principle calculations. We attribute the application of the modified Becke-Johnson exchange potential, which is basically an improvement over the local density approximation and the Perdew-Burke-Ernzerhof exchange-correlation functional, for a better description of the band gaps of the compounds. This resulted in a good agreement with our estimated values in comparison with the reported experimental data, specifically for the ZrSiO4, and HfSiO4 compounds. Conversely, for the ZrGeO4 compound, the calculated electronic band structure shows a direct band gap at the Γ point with the value of 5.79 eV. Furthermore, our evaluated thermal properties that are calculated by using the quasi-harmonic Debye model indicated that the volume variation with temperature is higher in the ZrGeO4 compound as compared to both the ZrSiO4 and HfSiO4 compounds, which is ascribed to the difference between the electron shells of the Si and Ge atoms. Therefore, these results also indicate that while the entropy ( S) and enthalpy ( U) parameters increase monotonically, the free energy ( G), in contrast, decreases monotonically with increasing temperature, respectively. Moreover, the pressure and temperature dependencies of the Debye temperature Θ, thermal expansion coefficient, and heat capacities C V were also predicted in our study.

Single-site properties of U impurities doped in La2Zn17 (abstract)

NASA Astrophysics Data System (ADS)

Suzuki, H.; Anzai, K.; Takagi, S.

1997-04-01

Thermodynamic and transport properties of heavy Fermion (HF) U compounds show similar behavior to HF Ce compounds. Although most of the magnetic properties of HF Ce compounds can be qualitatively understood on the basis of the impurity Kondo model, no such consensus for HF U compounds has been reached. In addition to this, the single-site properties of U impurities are not understood so well, in contrast to the case of Ce impurities. Recent works for dilute U systems reported new features as are not seen in dilute Ce systems. We have investigated a dilute-U2Zn17 system of (La1-zUz)2Zn17 in order to reveal the single U ion site properties of this system by preparing single crystals. The impurity contributions to various physical quantities such as ρimp(T), χimp(T), and Cimp(T) can be scaled by the U concentration between z=0.025 and 0.05, and the system is considered as in the dilute limit still for z=0.05. The electrical resistivity shows the typical impurity-Kondo upturn at low temperatures. The electronic specific-heat coefficient is strongly enhanced (γimp≈1.5 J/K2 mole U) and about 4 times as large as that for dense U2Zn17. Suppressions of the Kondo effect by the magnetic field are seen in γimp(H) and magnetoresistance. The relatively large anisotropy in χimp(T) indicates an existence of the crystal field. These features of this system will be explained in terms of the Kondo effect in the presence of the crystal field.

Electronic structure and relative stability of the coherent and semi-coherent HfO2/III-V interfaces

NASA Astrophysics Data System (ADS)

Lahti, A.; Levämäki, H.; Mäkelä, J.; Tuominen, M.; Yasir, M.; Dahl, J.; Kuzmin, M.; Laukkanen, P.; Kokko, K.; Punkkinen, M. P. J.

2018-01-01

III-V semiconductors are prominent alternatives to silicon in metal oxide semiconductor devices. Hafnium dioxide (HfO2) is a promising oxide with a high dielectric constant to replace silicon dioxide (SiO2). The potentiality of the oxide/III-V semiconductor interfaces is diminished due to high density of defects leading to the Fermi level pinning. The character of the harmful defects has been intensively debated. It is very important to understand thermodynamics and atomic structures of the interfaces to interpret experiments and design methods to reduce the defect density. Various realistic gap defect state free models for the HfO2/III-V(100) interfaces are presented. Relative energies of several coherent and semi-coherent oxide/III-V semiconductor interfaces are determined for the first time. The coherent and semi-coherent interfaces represent the main interface types, based on the Ga-O bridges and As (P) dimers, respectively.

Reuse of nuclear byproducts, NaF and HF in metal glass industries

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

Park, J.W.; Lee, H.W.; Yoo, S.H.

1997-02-01

A study has been performed to evaluate the radiological safety and feasibility associated with reuse of NaF(Sodium Fluoride) and HF(Hydrofluoric Acid) which are generated as byproducts from the nuclear fuel fabrication process. The investigation of oversea`s experience reveals that the byproduct materials are most often used in the metal and glass industries. For the radiological safety evaluation, the uranium radioactivities in the byproduct materials were examined and shown to be less than radioactivities in natural materials. The radiation doses to plant personnel and the general public were assessed to be very small and could be ignored. The Korea nuclear regulatorymore » body permits the reuse of NaF in the metal industry on the basis of associated radioactivity being {open_quote}below regulatory concern{close_quote}. HF is now under review for reuse acceptability in the steel and glass industries.« less

Thermomechanical and bithermal fatigue behavior of cast B1900 + Hf and wrought Haynes 188

NASA Technical Reports Server (NTRS)

Halford, G. R.; Verrilli, M. J.; Kalluri, S.; Ritzert, F. J.; Duckert, R. E.; Holland, F. A.

1992-01-01

A thermomechanical fatigue (TMF) high-temperature life prediction method has been evaluated using the experimental data. Bithermal fatigue (BTF), bithermal creep-fatigue (BTC-F), and TMF experiments were performed using two aerospace structural alloys, cast B1900 + Hf and wrought Haynes 188. The method which is based on the total strain version of strain range partitioning and unified cyclic constitutive modeling requires, as an input, information on the flow and failure behavior of the material of interest. Bithermal temperatures of 483 and 871 C were used for the cast B1900 + Hf nickel-base alloy and 316 and 760 C for the wrought Haynes 188 cobalt-base alloy. Maximum and minimum temperatures were also used in both TMF and BTF tests. Comparisons were made between the results of these tests and isothermal tensile and fatigue test data obtained previously. Qualitative correlations were observed between tensile and isothermal fatigue tests.

Rationale and design of the comParIson Of sacubitril/valsartaN versus Enalapril on Effect on nt-pRo-bnp in patients stabilized from an acute Heart Failure episode (PIONEER-HF) trial.

PubMed

Velazquez, Eric J; Morrow, David A; DeVore, Adam D; Ambrosy, Andrew P; Duffy, Carol I; McCague, Kevin; Hernandez, Adrian F; Rocha, Ricardo A; Braunwald, Eugene

2018-04-01

The objective is to assess the safety, tolerability, and efficacy of sacubitril/valsartan compared with enalapril in patients with heart failure (HF) with a reduced ejection fraction (EF) stabilized during hospitalization for acute decompensated HF. Sacubitril/valsartan, a first-in-class angiotensin receptor-neprilysin inhibitor, improves survival among ambulatory HF patients with a reduced EF. However, there is very limited experience with the in-hospital initiation of sacubitril/valsartan in patients who have been stabilized following hospitalization for acute decompensated HF. PIONEER-HF is a 12-week, prospective, multicenter, double-blind, randomized controlled trial enrolling a planned 882 patients at more than 100 participating sites in the United States. Medically stable patients >18 years of age with an EF <40% and an amino terminal-pro b-type natriuretic peptide >1600 pg/mL or b-type natriuretic peptide >400 pg/mL are eligible for participation no earlier than 24 hours and up to 10 days from initial presentation while still hospitalized. Patients are randomly assigned 1:1 to in-hospital initiation of sacubitril/valsartan titrated to 97/103 mg by mouth twice daily versus enalapril titrated to 10 mg by mouth twice daily for 8 weeks. All patients receive open-label treatment with sacubitril/valsartan for the remaining 4 weeks of the study. The primary efficacy end point is the time-averaged proportional change in amino terminal-pro b-type natriuretic peptide from baseline through weeks 4 and 8. Secondary and exploratory end points include serum and urinary biomarkers as well as clinical outcomes. Safety end points include the incidence of angioedema, hypotension, renal insufficiency, and hyperkalemia. The PIONEER-HF trial will inform clinical practice by providing evidence on the safety, tolerability, and efficacy of in-hospital initiation of sacubitril/valsartan among patients who have been stabilized following an admission for acute decompensated HF with a reduced EF. Copyright © 2018 Elsevier Inc. All rights reserved.

Chemical evolution of Himalayan leucogranites based on an O, U-Pb and Hf study of zircon

NASA Astrophysics Data System (ADS)

Hopkinson, Thomas N.; Warren, Clare J.; Harris, Nigel B. W.; Hammond, Samantha J.; Parrish, Randall R.

2015-04-01

Crustal melting is a characteristic process at convergent plate margins, where crustal rocks are heated and deformed. Miocene leucogranite sheets and plutons are found intruded into the high-grade metasedimentary core (the Greater Himalayan Sequence, GHS) across the Himalayan orogen. Previously-published Himalayan whole-rock data suggest that these leucogranites formed from a purely meta-sedimentary source, isotopically similar to those into which they now intrude. Bulk rock analyses carry inherent uncertainties, however: they may hide contributions from different contributing sources, and post-crystallization processes such as fluid interaction may significantly alter the original chemistry. In contrast, zircon is more able to retain precise information of the contributing sources of the melt from which it crystallises whilst its resistant nature is impervious to post-magmatic processes. This multi-isotope study of Oligocene-Miocene leucogranite zircons from the Bhutan Himalaya, seeks to differentiate between various geochemical processes that contribute to granite formation. Hf and O isotopes are used to detect discrete changes in melt source while U-Pb isotopes provide the timing of zircon crystallisation. Our data show that zircon rims of Himalayan age yield Hf-O signatures that lie within the previously reported whole-rock GHS field, confirming the absence of a discernible mantle contribution to the leucogranite source. Importantly, we document a decrease in the minimum ɛHf values during Himalayan orogenesis through time, correlating to a change in Hf model age from 1.4 Ga to 2.4 Ga. Nd model ages for the older Lesser Himalayan metasediments (LHS) that underthrust the GHS are significantly older than those for the GHS (2.4-2.9 Ga compared with 1.4-2.2 Ga), and as such even minor contributions of LHS material incorporated into a melt would significantly increase the resulting Hf model age. Hence our leucogranite data suggest either a change of source within the GHS over time, or an increasing contribution from older Lesser Himalayan (LHS) material in the melt. This is the first time that an evolutionary trend in the chemistry of Himalayan crustal melts has been recognized. Thus these new data show that, at least in the Himalaya, accessory phase geochemistry can provide more detailed insight into tectonic processes than bulk rock geochemistry.

Experimental investigations of electron density and ion energy distributions in dual-frequency capacitively coupled plasmas for Ar/CF{sub 4} and Ar/O{sub 2}/CF{sub 4} discharges

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

Liu, Jia; Liu, Yong-Xin; Gao, Fei

2014-01-07

The electron density and ion energy distribution (IED) are investigated in low-pressure dual-frequency capacitively coupled Ar/CF{sub 4} (90%/10%) and Ar/O{sub 2}/CF{sub 4} (80%/10%/10%) plasmas. The relations between controllable parameters, such as high-frequency (HF) power, low-frequency (LF) power and gas pressure, and plasma parameters, such as electron density and IEDs, are studied in detail by utilizing a floating hairpin probe and an energy resolved quadrupole mass spectrometer, respectively. In our experiment, the electron density is mainly determined by the HF power and slightly influenced by the LF power. With increasing gas pressure, the electron density first goes up rapidly to amore » maximum value and then decreases at various HF and LF powers. The HF power also plays a considerable role in affecting the IEDs under certain conditions and the ion energy independently controlled by the LF source is discussed here. For clarity, some numerical results obtained from a two-dimensional fluid model are presented.« less

A guide to studying human hair follicle cycling in vivo

PubMed Central

Oh, Ji Won; Kloepper, Jennifer; Langan, Ewan A.; Kim, Yongsoo; Yeo, Joongyeub; Kim, Min Ji; Hsi, Tsai-Ching; Rose, Christian; Yoon, Ghil Suk; Lee, Seok-Jong; Seykora, John; Kim, Jung Chul; Sung, Young Kwan

2015-01-01

Hair follicles (HFs) undergo life-long cyclical transformations, progressing through stages of rapid growth (anagen), regression (catagen), and relative “quiescence” (telogen). Since HF cycling abnormalities underlie many human hair growth disorders, the accurate classification of individual cycle stages within skin biopsies is clinically important and essential for hair research. For preclinical human hair research purposes, human scalp skin can be xenografted onto immunocompromised mice to study human HF cycling and manipulate long-lasting anagen in vivo. While available for mice, a comprehensive guide on how to recognize different human hair cycle stages in vivo is lacking. Here, we present such a guide, which uses objective, well-defined, and reproducible criteria and integrates simple morphological indicators with advanced, (immuno)-histochemical markers. This guide also characterizes human HF cycling in xenografts and highlights the utility of this model for in vivo hair research. Detailed schematic drawings and representative micrographs provide examples of how best to identify human HF stages, even in sub-optimally sectioned tissue, and practical recommendations are given for designing human-on-mouse hair cycle experiments. Thus, this guide seeks to offer a benchmark for human hair cycle stage classification, for both hair research experts and newcomers to the field. PMID:26763421

Behavioral in-effectiveness of high frequency electromagnetic field in mice.

PubMed

Salunke, Balwant P; Umathe, Sudhir N; Chavan, Jagatpalsingh G

2015-03-01

The present investigation was carried out with an objective to study the influence of high frequency electromagnetic field (HF-EMF) on anxiety, obsessive compulsive disorder (OCD) and depression-like behavior. For exposure to HF-EMF, non-magnetic material was used to fabricate the housing. Mice were exposed to HF-EMF (2.45GHz), 60min/day for 7 or 30 or 60 or 90 or 120days. The exposure was carried out by switching-on inbuilt class-I BLUETOOTH device that operates on 2.45GHz frequency in file transfer mode at a peak density of 100mW. Mice were subjected to the assessment of anxiety, OCD and depression-like behavior for 7 or 30 or 60 or 90 or 120days of exposure. The anxiety-like behavior was assessed by elevated plus maze, open field test and social interaction test. OCD-like behavior was assessed by marble burying behavior, whereas depression-like behavior was assessed by forced swim test and tail suspension test. The present experiment demonstrates that up to 120days of exposure to HF-EMF does not produce anxiety, OCD and depression-like behavior in mice. Copyright © 2014 Elsevier Inc. All rights reserved.

A full-dimensional ab initio potential energy surface and rovibrational energies of the Ar–HF complex

NASA Astrophysics Data System (ADS)

Huang, Jing; Zhou, Yanzi; Xie, Daiqian

2018-04-01

We report a new full-dimensional ab initio potential energy surface for the Ar-HF van der Waals complex at the level of coupled-cluster singles and doubles with noniterative inclusion of connected triples levels [CCSD(T)] using augmented correlation-consistent quintuple-zeta basis set (aV5Z) plus bond functions. Full counterpoise correction was employed to correct the basis-set superposition error. The hypersurface was fitted using artificial neural network method with a root mean square error of 0.1085 cm-1 for more than 8000 ab initio points. The complex was found to prefer a linear Ar-H-F equilibrium structure. The three-dimensional discrete variable representation method and the Lanczos propagation algorithm were then employed to calculate the rovibrational states without separating inter- and intra- molecular nuclear motions. The calculated vibrational energies of Ar-HF differ from the experiment values within about 1 cm-1 on the first four HF vibrational states, and the predicted pure rotational energies on (0000) and (1000) vibrational states are deviated from the observed value by about 1%, which shows the accuracy of our new PES.

Water quality impacts of hydraulic-fracturing chemicals observed in a permeable, quartz-sand aquifer

NASA Astrophysics Data System (ADS)

Kent, D. B.; LeBlanc, D. R.; Smith, R. L.

2012-12-01

A pilot scale experiment was conducted on western Cape Cod, Massachusetts to test the use of hydraulic fracturing (HF) for emplacing permeable reactive barriers (PRB) where the water table is too far below land surface to use standard excavation methods. Two PRB were emplaced 24 to 36 meters below land surface in a plume with low concentrations of perchloroethylene in oxic, mildly acidic groundwater with low concentrations of dissolved salts. The granular aquifer sediments consist of permeable sands and gravels. Quartz comprises greater than 90% by weight of the aquifer sediments but chemical reactivity of the sediments is controlled by micrometer-scale chlorite and illite and nanometer-scale aluminum-substituted goethite. HF fluids contained guar gum (gelling agent), cellulose enzyme and acetic acid (breakers), sodium borate (cross-linker), potassium (K) carbonate (pH adjustor), and sodium (Na) chloride (tracer). Water-quality impacts within about 20 meters of the PRB were monitored over a 1.7-year period following HF. Arrival of HF-chemicals was marked by an increase in boron (B) from ambient concentrations of 6 uM to >800 uM. B concentrations rose for approximately 50 days, much longer than the 22-day period over which HF was conducted. B concentrations subsequently decreased but remained 2-3 times above background concentrations for almost one year. Elevated Na and K concentrations in the HF fluids drove sorption (including ion exchange) reactions resulting in transient increases in naturally occurring major, minor, and trace cations up to 20 to 50 times background concentrations. Increases in dissolved organic carbon (DOC) and decreases in dissolved oxygen (DO) concentrations were observed as B concentrations increased. DOC concentration subsequently decreased but remained significantly above background. DO concentrations remained below detection. Dissolved iron (Fe) and manganese (Mn) concentrations increased as DO concentrations decreased below detection and remained elevated 1.7 years after HF. Reactions with Fe in the PRB may have contributed to the observed Fe concentrations but Mn was likely released from the aquifer sediments. Fe and Mn concentrations remained elevated throughout the sampling period. Dissolved arsenic concentrations increased after anaerobic conditions were established from below detection to 0.3-0.5 uM. HF fluids contained only a subset of the chemicals used in typical HF stimulations and aquifer sediments were likely less reactive than aquifer solids at other sites. Despite these differences, several findings have applicability to other sites. B is a potentially useful tracer of intrusion of HF fluids into aquifers, but elevated concentrations may be short-lived. Sorption reactions driven by differences in dissolved salt concentrations between HF fluids and ambient groundwater result in changes in cation concentrations, including barium and strontium. Organic compounds in HF fluids may drive aerobic aquifers anaerobic. Anaerobic conditions may lead to mobilization of naturally occurring contaminants like arsenic, whose reduced forms are more mobile than oxidized forms.

Myocardial Adeno-Associated Virus Serotype 6–βARKct Gene Therapy Improves Cardiac Function and Normalizes the Neurohormonal Axis in Chronic Heart Failure

PubMed Central

Rengo, Giuseppe; Lymperopoulos, Anastasios; Zincarelli, Carmela; Donniacuo, Maria; Soltys, Stephen; Rabinowitz, Joseph E.; Koch, Walter J.

2009-01-01

Background The upregulation of G protein–coupled receptor kinase 2 in failing myocardium appears to contribute to dysfunctional β-adrenergic receptor (βAR) signaling and cardiac function. The peptide βARKct, which can inhibit the activation of G protein–coupled receptor kinase 2 and improve βAR signaling, has been shown in transgenic models and short-term gene transfer experiments to rescue heart failure (HF). This study was designed to evaluate long-term βARKct expression in HF with the use of stable myocardial gene delivery with adeno-associated virus serotype 6 (AAV6). Methods and Results In HF rats, we delivered βARKct or green fluorescent protein as a control via AAV6-mediated direct intramyocardial injection. We also treated groups with concurrent administration of the β-blocker metoprolol. We found robust and long-term transgene expression in the left ventricle at least 12 weeks after delivery. βARKct significantly improved cardiac contractility and reversed left ventricular remodeling, which was accompanied by a normalization of the neurohormonal (catecholamines and aldosterone) status of the chronic HF animals, including normalization of cardiac βAR signaling. Addition of metoprolol neither enhanced nor decreased βARKct-mediated beneficial effects, although metoprolol alone, despite not improving contractility, prevented further deterioration of the left ventricle. Conclusions Long-term cardiac AAV6-βARKct gene therapy in HF results in sustained improvement of global cardiac function and reversal of remodeling at least in part as a result of a normalization of the neurohormonal signaling axis. In addition, βARKct alone improves outcomes more than a β-blocker alone, whereas both treatments are compatible. These findings show that βARKct gene therapy can be of long-term therapeutic value in HF. PMID:19103992

Cost-Effectiveness of Ventricular Assist Device Destination Therapy for Advanced Heart Failure in Duchenne Muscular Dystrophy.

PubMed

Magnetta, Defne A; Kang, JaHyun; Wearden, Peter D; Smith, Kenneth J; Feingold, Brian

2018-05-17

Destination ventricular assist device therapy (DT-VAD) is well accepted in select adults with medically refractory heart failure (HF) who are not transplant candidates; however, its use in younger patients with progressive diseases is unclear. We sought to evaluate the cost-effectiveness of DT-VAD in Duchenne muscular dystrophy (DMD) patients with advanced HF. We created a Markov-state transition model (5-year horizon) to compare survival, costs, and quality of life (QOL) between medical management and DT-VAD in DMD with advanced HF. Model input parameters were derived from the literature. We used sensitivity analyses to explore uncertainty around model assumptions. DT-VAD had higher costs ($435,602 vs. $125,696), survival (3.13 vs. 0.60 years), and quality-adjusted survival (1.99 vs. 0.26 years) than medical management. The incremental cost-effectiveness ratio (ICER) for DT-VAD was $179,086 per quality-adjusted life year (QALY). In sensitivity analyses that were widely varied to account for uncertainty in model assumptions, the DT-VAD strategy generally remained more costly and effective than medical management. Only when VAD implantation costs were <$113,142 did the DT-VAD strategy fall below the $100,000/QALY willingness-to-pay threshold commonly considered to be "cost-effective." In this exploratory analysis, DT-VAD for patients with DMD and advanced HF exceeded societal expectations for cost-effectiveness but had an ICER similar to the accepted practice of DT-VAD in adult HF patients. While more experience and research in this population is needed, our analysis suggests that DT-VAD for advanced HF in DMD should not be dismissed solely based on cost.

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

Ding, Kun; Wang, Dan; Yang, Ping

Graphical abstract: Anatase TiO{sub 2} nanocaps prepared by HF-assisted chemical etching method exhibit enhanced photocatalytic activity compared with commercial P25 because of HF served as an etching agent to remove doped impurities. - Highlights: • Anatase TiO{sub 2} nanocaps were synthesized by HF etching process. • The optimal conditions of experiment are 700 °C calcination and 0.2 mL HF solution. • The photocatalytic properties was studied upon UV and Visible irradiation. • The unique TiO{sub 2} nanocaps structure shows excellent photocatalytic activity. - Abstract: Anatase titanium dioxide (TiO{sub 2}) nanocaps were created via a four-step process including the preparation ofmore » SiO{sub 2} spheres, the deposition of a TiO{sub 2} layer to fabricate SiO{sub 2}@TiO{sub 2} composite spheres, the calcination for obtaining the crystal structure of anatase phase, and hydrofluoric acid (HF) etching to dissolve SiO{sub 2} cores. The SiO{sub 2}@TiO{sub 2} spheres calcined at 700 °C revealed fine photocatalytic activity. Interestingly, most of samples transformed into TiO{sub 2} nanocaps via HF etching, and TiO{sub 2} nanocaps prepared using optimal conditions exhibited quick degradation (k is 0.052 min{sup −1}) compared with commercial P25 (k is 0.030 min{sup −1}) and the TiO{sub 2} nanostructures etched by a NaOH solution. The excellent photocatalytic performance is attributed to its unique hollow hemispherical nanocaps structure, which is in favor of making full use of incident light. The photocatalysis phenomenon in visible light was also observed after depositing Au nanoparticles on anantase TiO{sub 2} nanocaps.« less

Excitation of Ionospheric Alfvén Resonator with HAARP

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Chang, C.; Labenski, J.; Milikh, G. M.; Vartanyan, A.; Snyder, A. L.

2011-12-01

We report results from numerical and experimental studies of the excitation of ULF waves inside the ionospheric Alfvén resonator (IAR) by heating the ionosphere with powerful HF waves launched from the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Numerical simulations of the two-fluid MHD model describing IAR in a dipole magnetic field geometry with plasma parameters taken from the observations at HAARP during October-November 2010 experimental campaign reveal that the IAR quality is higher during night-time conditions, when the ionospheric conductivity is very low. Simulations also reveal that the resonance wave cannot be identified from the magnetic measurements on the ground or at an altitude above 600 km because the magnetic field in this wave has nodes on both ends of the resonator, and the best way to detect IAR modes is by measuring the electric field on low-Earth-orbit satellites. These theoretical predictions are in good, quantitative agreement with results from observations: In particular, 1) observations from the ground-based magnetometer at the HAARP site demonstrate no any significant difference in the amplitudes of the magnetic field generated by HAARP in the frequency range from 0 to 5 Hz, and 2) the DEMETER satellite detected the electric field of the IAR first harmonic at an altitude of 670 km above HAARP during the heating experiment.

Glass–water interaction: Effect of high-valence cations on glass structure and chemical durability

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

Hopf, J.; Kerisit, Sebastien N.; Angeli, F.

2016-05-15

Borosilicate glass is a durable solid, but it dissolves when in contact with aqueous fluids. The dissolution mechanism, which involves a variety of sequential reactions that occur at the solid-fluid interface, has important implications for the corrosion resistance of industrial and nuclear waste glasses. In this study, spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high–valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), withmore » the addition of the HVC element hafnium in the Na2O–Al2O3–B2O3–HfO2–SiO2 system (e.g., Na/[Al+B] = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 (tetrahedral boron/total boron) and increases the amount of Si—O—Hf moieties in the glass. Results from flow–through experiments conducted under dilute and near–saturated conditions show a decrease of approximately 100× or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveals a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the stronger binding of Si sites that deposit on the surface from the influent when Hf is present in the glass. As a result, the residence time at the glass surface of these newly-formed Si sites is longer in the presence of Hf, which increases the density of anchor sites from which altered layers with higher Si densities can form. These results illustrate the importance of understanding solid–water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.« less

A Heart Failure Management Program Using Shared Medical Appointments.

PubMed

Carroll, Allison J; Howrey, Hillary L; Payvar, Susan; Deshida-Such, Kristen; Kansal, Mayank; Brar, Charanjit K

2017-04-01

Disease management programs for heart failure (HF) effectively reduce HF-related hospitalization rates and mortality. Shared medical appointments (SMAs) offer a cost-effective delivery method for HF disease management programs. However, few studies have evaluated this cost-effective delivery method of HF disease management among Veterans with acute HF. We hypothesized that Veterans who attended a multidisciplinary HF-SMA clinic promoting HF self-management, compared those who only received individual treatment through the HF specialty clinic, would have better 12-month hospitalization outcomes. We completed a retrospective review of the VA electronic health record for HF-SMA clinic appointments (1/1/2012 to 12/31/2013). The multidisciplinary HF-SMA program comprised 4 weekly sessions covering topics including HF disease, HF medications, diet adherence, physical activity, psychological well-being, and stress management. Patients who attended the HF-SMA clinic ( n =54) were compared to patients who were scheduled for an HF-SMA appointment but never attended and were followed only in the HF clinic ( n =37). Outcomes were 12-month HF-related and all-cause hospitalization rates, days in the hospital, and time to first hospitalization. Of 141 patients scheduled for an HF-SMA clinic appointment, 54 met criteria for the HF-SMA clinic group and 37 were included in the HF clinic group. The groups did not significantly differ on any sociodemographic variables. Furthermore, no significant differences were observed between the HF-SMA group and the HF clinic group on demographics or hospitalization outcomes, p >.05 for all comparisons. Our results did not support our hypothesis that offering multidisciplinary, HF-SMAs promoting HF self-management skills, above and beyond the individual disease management care provided in an HF specialty clinic, would improve hospitalization outcomes among Veterans with acute HF. Limitations of the present study and recommendations for HF self-management programs for Veterans are discussed.

Hyperfine Fields of 181Ta in UFe4Al8

NASA Astrophysics Data System (ADS)

Marques, J. G.; Barradas, N. P.; Alves, E.; Ramos, A. R.; Gonçalves, A. P.; da Silva, M. F.; Soares, J. C.

2001-11-01

The γ γ Perturbed Angular Correlation technique was used to study the hyperfine interaction of 181Ta at the Hf site(s) in UFe4Al8 at room temperature and 12 K. The data at room temperature are well described by two electric field gradients, while at low temperature two combined hyperfine interactions have to be considered, one with the magnetic hyperfine field collinear with the c-axis and another with the magnetic hyperfine field in the basal plane. The results are compared with previous Mössbauer and neutron diffraction experiments and the lattice site of Hf is discussed.

Deep inelastic neutron scattering on 207Pb and NaHF 2 as a test of a detectors array on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Senesi, R.

2008-01-01

A prototype array of resonance detectors for deep inelastic neutron scattering experiments has been installed on the VESUVIO spectrometer, at the ISIS spallation neutron source. Deep inelastic neutron scattering measurements on a reference lead sample and on NaHF 2 molecular system are presented. Despite on an explorative level, the results obtained for the values of mean kinetic energy are found in good agreement with the theoretical predictions, thus assessing the potential capability of the device for a routine use on the instrument.

Experimental studies of a continuous-wave HF(DF) confocal unstable resonator. Interim report

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

Chodzko, R.A.; Cross, E.F.; Durran, D.A.

1976-05-03

A series of experiments were performed on a continuous-wave HF(DF) multiline edge-coupled confocal unstable resonator at The Aerospace Corporation MESA facility. Experimental techniques were developed to measure remotely (from a blockhouse) the output power, the near-field intensity distribution, the spatially resolved spectral content of the near field, and the far-field power distribution. A new technique in which a variable aperture calorimeter absorbing scraper (VACAS) was used for measuring the continuous-wave output power from an unstable resonator with variable-mode geometry and without the use of an output coupling mirror was developed. (GRA)

Angular distributions for the F+H2-->HF+H reaction: The role of the F spin-orbit excited state and comparison with molecular beam experiments

NASA Astrophysics Data System (ADS)

Tzeng, Yi-Ren; Alexander, Millard H.

2004-09-01

We report quantum mechanical calculations of center-of-mass differential cross sections (DCS) for the F+H2→HF+H reaction performed on the multistate [Alexander-Stark-Werner (ASW)] potential energy surfaces (PES) that describe the open-shell character of this reaction. For comparison, we repeat single-state calculations with the Stark-Werner (SW) and Hartke-Stark-Werner (HSW) PESs. The ASW DCSs differ from those predicted for the SW and HSW PES in the backward direction. These differences arise from nonadiabatic coupling between several electronic states. The DCSs are then used in forward simulations of the laboratory-frame angular distributions (ADs) measured by Lee, Neumark, and co-workers [J. Chem. Phys. 82, 3045 (1985)]. The simulations are scaled to match experiment over the range 12°<Θlab<80°. As a natural consequence of the reduced backward scattering, the ASW ADs are more forward and sideways scattered than predicted by the HSW PES. At the two higher collision energies (2.74 and 3.42 kcal/mol) the enhanced sideways scattering of HF v'=2 products bring the ASW ADs in very good agreement with the experiment. At the lowest collision energy (1.84 kcal/mol), the simulations, for all three sets of PESs consistently underestimate the sideways scattering. The residual disagreements, particularly at the lowest collision energy, may be due to the known deficiencies in the PESs.

Ultra high temperature ceramics for hypersonic vehicle applications.

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

Tandon, Rajan; Dumm, Hans Peter; Corral, Erica L.

2006-01-01

HfB{sub 2} and ZrB{sub 2} are of interest for thermal protection materials because of favorable thermal stability, mechanical properties, and oxidation resistance. We have made dense diboride ceramics with 2 to 20 % SiC by hot pressing at 2000 C and 5000 psi. High-resolution transmission electron microscopy (TEM) shows very thin grain boundary phases that suggest liquid phase sintering. Fracture toughness measurements give RT values of 4 to 6 MPam{sup 1/2}. Four-pt flexure strengths measured in air up to 1450 C were as high as 450-500 MPa. Thermal diffusivities were measured to 2000 C for ZrB{sub 2} and HfB{sub 2}more » ceramics with SiC contents from 2 to 20%. Thermal conductivities were calculated from thermal diffusivities and measured heat capacities. Thermal diffusivities were modeled using different two-phase composite models. These materials exhibit excellent high temperature properties and are attractive for further development for thermal protection systems.« less

Real-time atomistic observation of structural phase transformations in individual hafnia nanorods

DOE PAGES

Hudak, Bethany M.; Depner, Sean W.; Waetzig, Gregory R.; ...

2017-05-12

High-temperature phases of hafnium dioxide have exceptionally high dielectric constants and large bandgaps, but quenching them to room temperature remains a challenge. Scaling the bulk form to nanocrystals, while successful in stabilizing the tetragonal phase of isomorphous ZrO 2, has produced nanorods with a twinned version of the room temperature monoclinic phase in HfO 2. Here we use in situ heating in a scanning transmission electron microscope to observe the transformation of an HfO 2 nanorod from monoclinic to tetragonal, with a transformation temperature suppressed by over 1000°C from bulk. When the nanorod is annealed, we observe with atomic-scale resolutionmore » the transformation from twinned-monoclinic to tetragonal, starting at a twin boundary and propagating via coherent transformation dislocation; the nanorod is reduced to hafnium on cooling. Unlike the bulk displacive transition, nanoscale size-confinement enables us to manipulate the transformation mechanism, and we observe discrete nucleation events and sigmoidal nucleation and growth kinetics.« less

Damping of High-temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Duffy, Kirsten P.; Padula, Santo A., II; Scheiman, Daniel A.

2008-01-01

Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf

Ab initio Computations of the Electronic, Mechanical, and Thermal Properties of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2

NASA Technical Reports Server (NTRS)

Lawson, John W.; Bauschlicher, Charles W.; Daw, Murray

2011-01-01

Refractory materials such as metallic borides, often considered as ultra high temperature ceramics (UHTC), are characterized by high melting point, high hardness, and good chemical inertness. These materials have many applications which require high temperature materials that can operate with no or limited oxidation. Ab initio, first principles methods are the most accurate modeling approaches available and represent a parameter free description of the material based on the quantum mechanical equations. Using these methods, many of the intrinsic properties of these material can be obtained. We performed ab initio calculations based on density functional theory for the UHTC materials ZrB2 and HfB2. Computational results are presented for structural information (lattice constants, bond lengths, etc), electronic structure (bonding motifs, densities of states, band structure, etc), thermal quantities (phonon spectra, phonon densities of states, specific heat), as well as information about point defects such as vacancy and antisite formation energies.

Effect of Dielectric Interface on the Performance of MoS2 Transistors.

PubMed

Li, Xuefei; Xiong, Xiong; Li, Tiaoyang; Li, Sichao; Zhang, Zhenfeng; Wu, Yanqing

2017-12-27

Because of their wide bandgap and ultrathin body properties, two-dimensional materials are currently being pursued for next-generation electronic and optoelectronic applications. Although there have been increasing numbers of studies on improving the performance of MoS 2 field-effect transistors (FETs) using various methods, the dielectric interface, which plays a decisive role in determining the mobility, interface traps, and thermal transport of MoS 2 FETs, has not been well explored and understood. In this article, we present a comprehensive experimental study on the effect of high-k dielectrics on the performance of few-layer MoS 2 FETs from 300 to 4.3 K. Results show that Al 2 O 3 /HfO 2 could boost the mobility and drain current. Meanwhile, MoS 2 transistors with Al 2 O 3 /HfO 2 demonstrate a 2× reduction in oxide trap density compared to that of the devices with the conventional SiO 2 substrate. Also, we observe a negative differential resistance effect on the device with 1 μm-channel length when using conventional SiO 2 as the gate dielectric due to self-heating, and this is effectively eliminated by using the Al 2 O 3 /HfO 2 gate dielectric. This dielectric engineering provides a highly viable route to realizing high-performance transition metal dichalcogenide-based FETs.

First-principles anharmonic quantum calculations for peptide spectroscopy: VSCF calculations and comparison with experiments.

PubMed

Roy, Tapta Kanchan; Sharma, Rahul; Gerber, R Benny

2016-01-21

First-principles quantum calculations for anharmonic vibrational spectroscopy of three protected dipeptides are carried out and compared with experimental data. Using hybrid HF/MP2 potentials, the Vibrational Self-Consistent Field with Second-Order Perturbation Correction (VSCF-PT2) algorithm is used to compute the spectra without any ad hoc scaling or fitting. All of the vibrational modes (135 for the largest system) are treated quantum mechanically and anharmonically using full pair-wise coupling potentials to represent the interaction between different modes. In the hybrid potential scheme the MP2 method is used for the harmonic part of the potential and a modified HF method is used for the anharmonic part. The overall agreement between computed spectra and experiment is very good and reveals different signatures for different conformers. This study shows that first-principles spectroscopic calculations of good accuracy are possible for dipeptides hence it opens possibilities for determination of dipeptide conformer structures by comparison of spectroscopic calculations with experiment.

The Production and Modification of Ionospheric Irregularities by Powerful HF Radio Transmissions

DTIC Science & Technology

1990-09-11

BASE, MASSACHUSETS 01731,-5000 ’_hi techn-ical report has been reviewed and is approved for publication" S A WIT B ASI X._____ ~ f Contract Manager ...energy ’lec- 0. 12 trons decelerated. The maximum power in the 5.25- to 5.35-MHz Doppler range is reached without a measurable dehly according to o...vacuum. In principle the nonlinear effects of heating and of the pondcromotive force (the nonlinearity results from the depen- dence of both effects

Impacts of Aerosol-Monsoon Interaction on Rainfall and Circulation over Northern India and the Himalaya Foothills

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Kim, Kyu-Myong; Shi, Jainn-Jong; Matsui, T.; Chin, M.; Tan, Qian; Peters-Lidard, C.; Tao, W. K.

2016-01-01

The boreal summer of 2008 was unusual for the Indian monsoon, featuring exceptional heavy loading of dust aerosols over the Arabian Sea and northern-central India, near normal all- India rainfall, but excessive heavy rain, causing disastrous flooding in the Northern Indian Himalaya Foothills (NIHF) regions, accompanied by persistent drought conditions in central and southern India. Using NASA Unified-physics Weather Research Forecast (NUWRF) model with fully interactive aerosol physics and dynamics, we carried out three sets of 7-day ensemble model forecast experiments: 1) control with no aerosol, 2) aerosol radiative effect only and 3) aerosol radiative and aerosol-cloud-microphysics effects, to study the impacts of aerosol monsoon interactions on monsoon variability over the NIHF during the summer of 2008. Results show that aerosol-radiation interaction (ARI), i.e., dust aerosol transport, and dynamical feedback processes induced by aerosol-radiative heating, plays a key role in altering the large scale monsoon circulation system, reflected by an increased north-south tropospheric temperature gradient, a northward shift of heavy monsoon rainfall, advancing the monsoon onset by 1-5 days over the HF, consistent with the EHP hypothesis (Lau et al. 2006). Additionally, we found that dust aerosols, via the semi-direct effect, increase atmospheric stability, and cause the dissipation of a developing monsoon onset cyclone over northeastern India northern Bay of Bengal. Eventually, in a matter of several days, ARI transforms the developing monsoon cyclone into mesoscale convective cells along the HF slopes. Aerosol-Cloud-microphysics Interaction (ACI) further enhances the ARI effect in invigorating the deep convection cells and speeding up the transformation processes. Results indicate that even in short-term (up to weekly) numerical forecasting of monsoon circulation and rainfall, effects of aerosol-monsoon interaction can be substantial and cannot be ignored.

First-principles study of lattice thermal conductivity in ZrTe5 and HfTe5

NASA Astrophysics Data System (ADS)

Wang, Cong; Wang, Haifeng; Chen, Y. B.; Yao, Shu-Hua; Zhou, Jian

2018-05-01

Recently, the layered transition-metal pentatellurides ZrTe5 and HfTe5 have attracted increasing attention because of their interesting topological electronic properties. Nevertheless, some of their other good physical properties seem to be ignored now. Actually, both ZrTe5 and HfTe5 have high electric conductivities (>105 Ω-1 m-1) and Seebeck coefficients (> 100 μV/K) at room temperature, thus making them promising thermoelectric materials. However, the disadvantage is that the thermal conductivities of the two materials are relatively high according to the few available experiments; meanwhile, the detailed mechanism of the intrinsic thermal conductivity has not been studied yet. Based on the density functional theory and the Boltzmann transport theory, we present here the theoretical study of the intrinsic lattice thermal conductivities of ZrTe5 and HfTe5, which are found to be in the range of 5-8 W/mṡK at room temperature and well consistent with the experimental results. We also find that the thermal conductivities of the two materials are anisotropic, which are mainly caused by their anisotropic crystal structures. Based on the detailed analysis, we proposed that the thermal conductivities of the two materials could possibly be reduced by different kinds of structural engineering at the atomic and mesoscopic scales, such as alloying, doping, nano-structuring, and polycrystalline structuring, which could make ZrTe5 and HfTe5 good thermoelectric materials for room temperature thermoelectric applications.

Experimental Analysis of Hydraulic Fracture Growth and Acoustic Emission Response in a Layered Formation

NASA Astrophysics Data System (ADS)

Ning, Li; Shicheng, Zhang; Yushi, Zou; Xinfang, Ma; Shan, Wu; Yinuo, Zhang

2018-04-01

Microseismic/acoustic emission (AE) monitoring is an essential technology for understanding hydraulic fracture (HF) geometry and stimulated reservoir volume (SRV) during hydraulic fracturing in unconventional reservoirs. To investigate HF growth mechanisms and features of induced microseismic/AE events in a layered formation, laboratory fracturing experiments were performed on shale specimens (30 cm × 30 cm × 30 cm) with multiple bedding planes (BPs) under triaxial stresses. AE monitoring was used to reveal the spatial distribution and hypocenter mechanisms of AE events induced by rock failure. Computerized tomography scanning was used to observe the internal fracture geometry. Experimental results showed that the various HF geometries could be obviously distinguished based on injection pressure curves and AE responses. Fracture complexity was notably increased when vertically growing HFs connected with and opened more BPs. The formation of a complex fracture network was generally indicated by frequent fluctuations in injection pressure curves, intense AE activity, and three-dimensionally distributed AE events. Investigations of the hypocenter mechanisms revealed that shear failure/event dominated in shale specimens. Shear and tensile events were induced in hydraulically connected regions, and shear events also occurred around BPs that were not hydraulically connected. This led to an overestimation of HF height and SRV in layered formations based on the AE location results. The results also showed that variable injection rate and using plugging agent were conducive in promoting HF to penetrate through the weak and high-permeability BPs, thereby increasing the fracture height.

Relationship between hot flashes and ambulatory blood pressure: the Hilo women's health study.

PubMed

Brown, Daniel E; Sievert, Lynnette L; Morrison, Lynn A; Rahberg, Nichole; Reza, Angela

2011-01-01

To examine ambulatory blood pressure (BP) differences between women who report hot flashes (HFs) and those who do not, and to observe whether an objectively measured HF is associated with transient changes in BP. HFs have been associated with elevated BP, but studies have not examined the relationship between objectively measured HFs and blood pressure during normal daily activities. A sample of 202 women in Hilo, Hawaii, aged 45 to 55 years, were asked to fill out a questionnaire that included demographic information and an inventory of symptoms. The women underwent simultaneous 24-hour monitoring of ambulatory BP and HFs, at the same time keeping a diary that included mood and HF reports. No significant difference was present in mean BP between women who reported having an HF during the last 2 weeks and those who did not. When measurements controlled for negative mood reports and posture, there was a highly significant elevation in Z scores of systolic BP when a measured, objective HF occurred within 10 minutes before a BP reading, and a significant elevation of Z scores of diastolic BP when a subjectively reported HF occurred within 10 minutes after a BP reading. These results suggest that objectively measured HFs precede transient elevations of systolic BP, but it is unclear if there is a causal relationship. These results also suggest that women experience subjective HFs within 10 minutes after a transient increase in diastolic BP. Again, the causal relationship is not understood.

Histopathology Image Analysis in Two Long-Term Animal Experiments with Helical Flow Total Artificial Heart.

PubMed

Wotke, Jiri; Homolka, Pavel; Vasku, Jaromír; Dobsak, Petr; Palanova, Petra; Mrkvicova, Veronika; Konecny, Petr; Soska, Vladimir; Pohanka, Michal; Novakova, Marie; Yurimoto, Terumi; Saito, Itsuro; Inoue, Yusuke; Isoyama, Takashi; Abe, Yusuke

2016-12-01

Histopathological analysis can provide important information in long-term experiments with total artificial heart (TAH). Recently, a new type of blood pump, the helical flow total artificial heart (HF-TAH) was developed. This study aimed to investigate the changes in selected vital organs in animal experiments with implanted HF-TAH. Samples from lung, liver, and kidneys from two female goats (No. 1301 and No. 1304) with implanted HF-TAH were analyzed. Tissue samples were fixed in 10% formaldehyde and 4 µm thick transverse sections were stained with hematoxylin-eosin (HE). Additional staining was done for detection of connective tissue (Masson-Goldner stain) and for detection of iron (hemosiderin) deposits (Perls stain). Sections were scanned at 100× and 500× magnification with a light microscope. Experiment no. 1301 survived 100 days (cause of termination was heavy damage of the right pump); experimental goat no.1304 survived 68 days and was sacrificed due to severe right hydrodynamic bearing malfunction. Histopathological analysis of liver samples proved signs of chronic venostasis with limited focal necrotic zones. Dilated tubules, proteinaceous material in tubular lumen, and hemosiderin deposits were detected in kidney samples. Contamination of the organs by embolized micro-particles was suspected at the autopsy after discovery of visible damage (scratches) of the pump impeller surface (made from titanium alloy) in both experiments. Sporadic deposits of foreign micro-particles (presumably titanium) were observed in most of the analyzed parenchymal organs. However, the described deposits were not in direct connection with inflammatory reactions in the analyzed tissues. Histopathological analysis showed the presence of minimal contamination of the lung, kidney, and liver tissue samples by foreign material (titanium very likely). The analysis showed only limited pathological changes, especially in liver and kidneys, which might be attributed to the influence of artificial perfusion often observed in chronic TAH experiments. © 2016 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.

Clinical presentation at first heart failure hospitalization does not predict recurrent heart failure admission.

PubMed

Kosztin, Annamaria; Costa, Jason; Moss, Arthur J; Biton, Yitschak; Nagy, Vivien Klaudia; Solomon, Scott D; Geller, Laszlo; McNitt, Scott; Polonsky, Bronislava; Merkely, Bela; Kutyifa, Valentina

2017-11-01

There are limited data on whether clinical presentation at first heart failure (HF) hospitalization predicts recurrent HF events. We aimed to assess predictors of recurrent HF hospitalizations in mild HF patients with an implantable cardioverter defibrillator or cardiac resynchronization therapy with defibrillator. Data on HF hospitalizations were prospectively collected for patients enrolled in MADIT-CRT. Predictors of recurrent HF hospitalization (HF2) after the first HF hospitalization were assessed using Cox proportional hazards regression models including baseline covariates and clinical presentation or management at first HF hospitalization. There were 193 patients with first HF hospitalization, and 156 patients with recurrent HF events. Recurrent HF rate after the first HF hospitalization was 43% at 1 year, 52% at 2 years, and 55% at 2.5 years. Clinical signs and symptoms, medical treatment, or clinical management of HF at first HF admission was not predictive for HF2. Baseline covariates predicting recurrent HF hospitalization included prior HF hospitalization (HR = 1.59, 95% CI: 1.15-2.20, P = 0.005), digitalis therapy (HR = 1.58, 95% CI: 1.13-2.20, P = 0.008), and left ventricular end-diastolic volume >240 mL (HR = 1.62, 95% CI: 1.17-2.25, P = 0.004). Recurrent HF events are frequent following the first HF hospitalization in patients with implanted implantable cardioverter defibrillator or cardiac resynchronization therapy with defibrillator. Neither clinical presentation nor clinical management during first HF admission was predictive of recurrent HF. Prior HF hospitalization, digitalis therapy, and left ventricular end-diastolic volume at enrolment predicted recurrent HF hospitalization, and these covariates could be used as surrogate markers for identifying a high-risk cohort. © 2017 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.

Multiple-Station Observation of Frequency Dependence and Polarization Characteristics of ELF/VLF waves generated via Ionospheric Modification

NASA Astrophysics Data System (ADS)

Maxworth, A. S.; Golkowski, M.; Cohen, M.; Moore, R. C.

2014-12-01

Generation of Extremely Low Frequency (ELF) and Very Low Frequency (VLF) signals through ionospheric modification has been practiced for many years. Heating the lower ionosphere with high power HF waves allows for modulation of natural current systems. Our experiments were carried out at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. In this experiment, the ionosphere was heated with a vertical amplitude modulating signal and the modulation frequency was changed sequentially within an array of 40 frequencies followed by a frequency ramp. The observed magnetic field amplitude and polarization of the generated ELF/VLF signals were analyzed for multiple sites and as a function of modulation frequency. Our three observation sites: Chistochina, Paxson and Paradise are located within 36km (azimuth 47.7°), 50.2km (azimuth -20°) and 99km (azimuth 80.3°) respectively. We show that the peak amplitudes observed as a function of frequency result from vertical resonance in the Earth-ionosphere waveguide and can be used to diagnose the D-region profile. Polarization analysis showed that out of the three sites Paxson shows the highest circularity in the magnetic field polarization, compared to Chistochina and Paradise which show highly linear polarizations. The experimental results were compared with a theoretical simulation model results and it was clear that in both cases, the modulated Hall current dominates the observed signals at Chistochina and Paradise sites and at Paxson there is an equal contribution from Hall and Pedersen currents. The Chistochina site shows the highest magnetic field amplitudes in both experimental and simulation environments. Depending upon the experimental and simulation observations at the three sites, a radiation pattern for the HAARP ionospheric heater can be mapped

Post-collisional magmatism in the Late Miocene Rodna-Bârgău district (East Carpathians, Romania): Geochemical constraints and petrogenetic models

NASA Astrophysics Data System (ADS)

Fedele, Lorenzo; Seghedi, Ioan; Chung, Sun-Lin; Laiena, Fabio; Lin, Te-Hsien; Morra, Vincenzo; Lustrino, Michele

2016-12-01

Post-collisional magmatism in the Late Miocene Rodna-Bârgău subvolcanic district (East Carpathians) gave rise to a wide variety of rock compositions, allowing recognition of four groups of calcalkaline rocks with distinctive petrography, mineral chemistry, whole-rock geochemistry and Sr-Nd-Hf isotope features. New U-Pb zircon datings, together with literature data, indicate that the emplacement of the four rock groups was basically contemporaneous in the 11.5-8 Ma time span. The low potassium group (LKG) includes the most abundant lithotypes of the area, ranging from basaltic andesite to dacite, characterized by K-poor tschermakitic amphibole, weak enrichment in LILE and LREE, relatively low 87Sr/86Sr, coupled with relatively high 143Nd/144Nd and 176Hf/177Hf. The high potassium group (HKG) includes amphibole-bearing microgabbro, amphibole andesite and amphibole- and biotite dacite, with K-richer magnesio-hastingsite to hastingsite amphibole, more marked enrichments in incompatible elements, higher 87Sr/86Sr and lower 143Nd/144Nd and 176Hf/177Hf. These two main rock groups seem to have originated from similar juxtaposed mantle sources, with the HKG possibly related to slightly more enriched domains (with higher H2O reflected by the higher modal amphibole) with respect to LKG (with higher plagioclase/amphibole ratios). The evolution of the two rock series involved also open-system processes, taking place mainly in the upper crust for the HKG, in the lower crust for LKG magmas. In addition, limited occurrences of generally younger strongly evolved peraluminous rhyolites and microgranites (Acid group) and sialic-dominated "leucocratic" andesites and dacites (LAD group) were also recognized to the opposite outermost areas of the district. These two latter rock groups were generated by the melting of a basic metamorphic crustal source (respectively in hydrous and anhydrous conditions), favored by the heat released by mantle melts from the adjoining central area. The peculiar distribution of the products of the four rock groups in well defined sectors argues for a strong control of the local crustal tectonic regime on magmatism, influenced by the change from a transpressional to trastensional stage.

Pre- and postnatal transplantation of fetal mesenchymal stem cells in osteogenesis imperfecta: a two-center experience.

PubMed

Götherström, Cecilia; Westgren, Magnus; Shaw, S W Steven; Aström, Eva; Biswas, Arijit; Byers, Peter H; Mattar, Citra N Z; Graham, Gail E; Taslimi, Jahan; Ewald, Uwe; Fisk, Nicholas M; Yeoh, Allen E J; Lin, Ju-Li; Cheng, Po-Jen; Choolani, Mahesh; Le Blanc, Katarina; Chan, Jerry K Y

2014-02-01

Osteogenesis imperfecta (OI) can be recognized prenatally with ultrasound. Transplantation of mesenchymal stem cells (MSCs) has the potential to ameliorate skeletal damage. We report the clinical course of two patients with OI who received prenatal human fetal MSC (hfMSC) transplantation and postnatal boosting with same-donor MSCs. We have previously reported on prenatal transplantation for OI type III. This patient was retransplanted with 2.8 × 10(6) same-donor MSCs per kilogram at 8 years of age, resulting in low-level engraftment in bone and improved linear growth, mobility, and fracture incidence. An infant with an identical mutation who did not receive MSC therapy succumbed at 5 months despite postnatal bisphosphonate therapy. A second fetus with OI type IV was also transplanted with 30 × 10(6) hfMSCs per kilogram at 31 weeks of gestation and did not suffer any new fractures for the remainder of the pregnancy or during infancy. The patient followed her normal growth velocity until 13 months of age, at which time longitudinal length plateaued. A postnatal infusion of 10 × 10(6) MSCs per kilogram from the same donor was performed at 19 months of age, resulting in resumption of her growth trajectory. Neither patient demonstrated alloreactivity toward the donor hfMSCs or manifested any evidence of toxicities after transplantation. Our findings suggest that prenatal transplantation of allogeneic hfMSCs in OI appears safe and is of likely clinical benefit and that retransplantation with same-donor cells is feasible. However, the limited experience to date means that it is not possible to be conclusive and that further studies are required.

Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

USGS Publications Warehouse

Patchett, P.J.

1983-01-01

The 176Lu-176Hf isotope method and its applications in earth sciences are discussed. Greater fractionation of Lu/Hf than Sm/Nd in planetary magmatic processes makes 176Hf 177Hf a powerful geochemical tracer. In general, proportional variations of 176Hf 177Hf exceed those of 143Nd l44Nd by factors of 1.5-3 in terrestrial and lunar materials. Lu-Hf studies therefore have a major contribution to make in understanding of terrestrial and other planetary evolution through time, and this is the principal importance of Lu-Hf. New data on basalts from oceanic islands show unequivocally that whereas considerable divergences occur in 176Hf 177Hf- 87Sr 86Sr and 143Nd l44Nd- 87Sr 86Sr diagrams, 176Hf 177Hf and 143Nd 144Nd display a single, linear isotopic variation in the suboceanic mantle. These discordant 87Sr 86Sr relationships may allow, with the acquisition of further Hf-Nd-Sr isotopic data, a distinction between processes such as mantle metasomatism, influence of seawater-altered material in the magma source, or recycling of sediments into the mantle. In order to evaluate the Hf-Nd isotopic correlation in terms of mantle fractionation history, there is a need for measurements of Hf distribution coefficients between silicate minerals and liquids, and specifically for a knowledge of Hf behavior in relation to rareearth elements. For studying ancient terrestrial Hf isotopic variations, the best quality Hf isotope data are obtained from granitoid rocks or zircons. New data show that very U-Pb discordant zircons may have upwardly-biased 176Hf 177Hf, but that at least concordant to slightly discordant zircons appear to be reliable carriers of initial 176Hf 177Hf. Until the controls on addition of radiogenic Hf to zircon are understood, combined zircon-whole rock studies are recommended. Lu-Hf has been demonstrated as a viable tool for dating of ancient terrestrial and extraterrestrial samples, but because it offers little advantage over existing methods, is unlikely to find wide application in pure chronological studies. ?? 1983.

Informing the Design of "Lifestyle Monitoring" Technology for the Detection of Health Deterioration in Long-Term Conditions: A Qualitative Study of People Living With Heart Failure.

PubMed

Hargreaves, Sarah; Hawley, Mark S; Haywood, Annette; Enderby, Pamela M

2017-06-28

Health technologies are being developed to help people living at home manage long-term conditions. One such technology is "lifestyle monitoring" (LM), a telecare technology based on the idea that home activities may be monitored unobtrusively via sensors to give an indication of changes in health-state. However, questions remain about LM technology: how home activities change when participants experience differing health-states; and how sensors might capture clinically important changes to inform timely interventions. The objective of this paper was to report the findings of a study aimed at identifying changes in activity indicative of important changes in health in people with long-term conditions, particularly changes indicative of exacerbation, by exploring the relationship between home activities and health among people with heart failure (HF). We aimed to add to the knowledge base informing the development of home monitoring technologies designed to detect health deterioration in order to facilitate early intervention and avoid hospital admissions. This qualitative study utilized semistructured interviews to explore everyday activities undertaken during the three health-states of HF: normal days, bad days, and exacerbations. Potential recruits were identified by specialist nurses and attendees at an HF support group. The sample was purposively selected to include a range of experience of living with HF. The sample comprised a total of 20 people with HF aged 50 years and above, and 11 spouses or partners of the individuals with HF. All resided in Northern England. Participant accounts revealed that home activities are in part shaped by the degree of intrusion from HF symptoms. During an exacerbation, participants undertook activities specifically to ease symptoms, and detailed activity changes were identified. Everyday activity was also influenced by a range of factors other than health. The study highlights the importance of careful development of LM technology to identify changes in activities that occur during clinically important changes in health. These detailed activity changes need to be considered by developers of LM sensors, platforms, and algorithms intended to detect early signs of deterioration. Results suggest that for LM to move forward, sensor set-up should be personalized to individual circumstances and targeted at individual health conditions. LM needs to take account of the uncertainties that arise from placing technology within the home, in order to inform sensor set-up and data interpretation. This targeted approach is likely to yield more clinically meaningful data and address some of the ethical issues of remote monitoring. ©Sarah Hargreaves, Mark S Hawley, Annette Haywood, Pamela M Enderby. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 28.06.2017.

The effect of randomised exposure to different types of natural outdoor environments compared to exposure to an urban environment on people with indications of psychological distress in Catalonia

PubMed Central

Gidlow, Christopher J.; Martínez, David; de Bont, Jeroen; Carrasco-Turigas, Glòria; Martínez-Íñiguez, Tania; Hurst, Gemma; Masterson, Daniel; Donaire-Gonzalez, David; Seto, Edmund; Jones, Marc V.; Nieuwenhuijsen, Mark J.

2017-01-01

Introduction Experimental studies have reported associations between short-term exposure to natural outdoor environments (NOE) and health benefits. However, they lack insight into mechanisms, often have low external and ecological validity, and have rarely focused on people with some psycho-physiological affection. The aim of this study was to use a randomized, case-crossover design to investigate: (i) the effects of unconstrained exposure to real natural and urban environments on psycho-physiological indicators of people with indications of psychological distress, (ii) the possible differential effects of 30 and 30+180 minutes exposures, and (iii) the possible mechanisms explaining these effects. Material and methods People (n = 26) with indications of psychological distress were exposed to green (Collserola Natural Park), blue (Castelldefels beach) and urban (Eixample neighbourhood) environments in Catalonia. They were exposed to all environments in groups for a period of 30+180 minutes between October 2013 and January 2014. During the exposure period, participants were instructed to do what they would usually do in that environment. Before, during (at 30 and 30+180 minutes) and after each exposure, several psycho-physiological measures were taken: mood (measured as Total Mood Disturbance, TMD), attention capacity (measured as backwards digit-span task), stress levels (measures as salivary cortisol), systolic and diastolic blood pressure, heart rate, autonomous nervous system (assessed as heart rate variability and the indicators: low frequency power (LF), high frequency power (HF), ratio between LF and HF (LF:HF), and coefficients of component variance of LF, HF, and LF:HF). We also measured several potential mediators: air pollution, noise, physical activity, social interactions, and self-perceived restoration experience. Results When compared with responses to urban environment, we found statistically significantly lower TMD [-4.78 (-7.77, -1.79) points difference], and salivary cortisol [-0.21 (-0.34, -0.08) log nmol/L] in the green exposure environment, and statistically significantly lower TMD [-4.53 (-7.57, -1.49) points difference], and statistically significant favourable changes in heart rate variability indicators (specifically LF:HF and CCV-LF:HF with around -0.20 points of difference of the indicators) in the blue exposure environment. Physical activity and self-perceived restoration experience partially mediated the associations between NOE and TMD. Physical activity and air pollution partially mediated the associations between NOE and heart rate variability. Discussion and conclusions This study extends the existing evidence on the benefits of NOE for people's health. It also suggests NOE potential as a preventive medicine, specifically focusing on people with indications of psychological distress. Trial registration Clinicaltrials.gov NCT02624921 PMID:28248974

The effect of randomised exposure to different types of natural outdoor environments compared to exposure to an urban environment on people with indications of psychological distress in Catalonia.

PubMed

Triguero-Mas, Margarita; Gidlow, Christopher J; Martínez, David; de Bont, Jeroen; Carrasco-Turigas, Glòria; Martínez-Íñiguez, Tania; Hurst, Gemma; Masterson, Daniel; Donaire-Gonzalez, David; Seto, Edmund; Jones, Marc V; Nieuwenhuijsen, Mark J

2017-01-01

Experimental studies have reported associations between short-term exposure to natural outdoor environments (NOE) and health benefits. However, they lack insight into mechanisms, often have low external and ecological validity, and have rarely focused on people with some psycho-physiological affection. The aim of this study was to use a randomized, case-crossover design to investigate: (i) the effects of unconstrained exposure to real natural and urban environments on psycho-physiological indicators of people with indications of psychological distress, (ii) the possible differential effects of 30 and 30+180 minutes exposures, and (iii) the possible mechanisms explaining these effects. People (n = 26) with indications of psychological distress were exposed to green (Collserola Natural Park), blue (Castelldefels beach) and urban (Eixample neighbourhood) environments in Catalonia. They were exposed to all environments in groups for a period of 30+180 minutes between October 2013 and January 2014. During the exposure period, participants were instructed to do what they would usually do in that environment. Before, during (at 30 and 30+180 minutes) and after each exposure, several psycho-physiological measures were taken: mood (measured as Total Mood Disturbance, TMD), attention capacity (measured as backwards digit-span task), stress levels (measures as salivary cortisol), systolic and diastolic blood pressure, heart rate, autonomous nervous system (assessed as heart rate variability and the indicators: low frequency power (LF), high frequency power (HF), ratio between LF and HF (LF:HF), and coefficients of component variance of LF, HF, and LF:HF). We also measured several potential mediators: air pollution, noise, physical activity, social interactions, and self-perceived restoration experience. When compared with responses to urban environment, we found statistically significantly lower TMD [-4.78 (-7.77, -1.79) points difference], and salivary cortisol [-0.21 (-0.34, -0.08) log nmol/L] in the green exposure environment, and statistically significantly lower TMD [-4.53 (-7.57, -1.49) points difference], and statistically significant favourable changes in heart rate variability indicators (specifically LF:HF and CCV-LF:HF with around -0.20 points of difference of the indicators) in the blue exposure environment. Physical activity and self-perceived restoration experience partially mediated the associations between NOE and TMD. Physical activity and air pollution partially mediated the associations between NOE and heart rate variability. This study extends the existing evidence on the benefits of NOE for people's health. It also suggests NOE potential as a preventive medicine, specifically focusing on people with indications of psychological distress. Clinicaltrials.gov NCT02624921.

Multi-year evaluation of stocking rate and animal genotype on milk production per hectare within intensive pasture-based production systems.

PubMed

Coffey, E L; Delaby, L; Fleming, C; Pierce, K M; Horan, B

2018-03-01

The objective of this experiment was to evaluate the effect of stocking rate (SR) and animal genotype (BR) on milk production, body weight (BW), and body condition score (BCS) within intensive pasture-based systems. A total of 533 lactation records, from 246 elite genetic merit dairy cows were available for analysis; 68 Holstein-Friesian (HF) and 71 Jersey × Holstein-Friesian (JxHF) crossbred cows in each of 4 consecutive years (2013-2016, inclusive). Cows from each BR were randomly allocated to 1 of 3 whole-farm comparative SR treatments, low (LSR; 1,200 kg of BW/ha), medium (MSR; 1,400 kg of BW/ha), and high (HSR; 1,600 kg of BW/ha), and remained in the same SR treatments for the duration of the experiment. The effects of SR, BR, and their interaction on milk production/cow and per hectare, BW, BCS, and grazing characteristics were analyzed. Total pasture utilization per hectare consumed in the form of grazed pasture increased linearly as SR increased: least in LSR (10,237 kg of dry matter/ha), intermediate in MSR (11,016 kg of dry matter/ha), and greatest in HSR (11,809 kg of dry matter/ha). Milk and milk solids (MS) yield per hectare was greatest for HSR (15,942 and 1,354 kg, respectively), intermediate for MSR (14,191 and 1,220 kg, respectively), and least for LSR (13,186 and 1,139 kg, respectively) with similar trends evident for fat, protein, and lactose yield/ha. At higher SR (MSR and HSR), MS yield per kg of BW per ha was reduced (0.85 and 0.82 kg of MS/kg of BW, respectively) compared with LSR (0.93 kg of MS/kg of BW/ha). Holstein-Friesian cows achieved fewer grazing days per hectare (-37 d), and produced more milk (+561 kg/ha) but less fat plus protein (-57 kg/ha) compared with JxHF cows; the JxHF cows were lighter. At similar BW per hectare, JxHF cows produced more fat plus protein/ha during the grazing season at low (1,164 vs. 1,113 kg), medium (1,254 vs. 1,185 kg), and high (1,327 vs. 1,380 kg) SR. In addition, JxHF cows produced more fat plus protein per kg of BW/ha (0.90 kg) compared with HF cows (0.84 kg). The results highlight the superior productive efficiency of high genetic potential crossbred dairy cows within intensive pasture-based production systems. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

A Mid-Latitude Skywave Propagation Experiment: Overview and Results

NASA Astrophysics Data System (ADS)

Munton, D. C.; Calfas, R. S.; Gaussiran, T., II; Rainwater, D.; Flesichmann, A. M.; Schofield, J. R.

2016-12-01

We will describe a mid-latitude HF skywave propagation experiment conducted during 19-27 January, 2014. There were two primary goals to the experiment. First, we wanted to build an understanding of the impact that medium scale traveling ionospheric disturbances have on the angles of arrival of the HF signals. The second goal was to provide a diverse data set that could serve as a baseline for propagation model development and evaluation. We structured individual tests during the experiment to increase the knowledge of temporal and spatial length scales of various ionospheric features. The experiment was conducted during both day and night periods and spanned a wide range of ionospheric states. We conducted the experiment at White Sands Missile Range, New Mexico and in the surrounding area. As part of the experiment, we deployed a number of active HF transmitters, and an array of dipole antennas to provide angle of arrival measurements. We also deployed a smaller array of more novel compact electro-magnetic vector sensors (EMVSs). Other instrumentation specific to the remote sensing of the ionosphere included digisondes, GNSS receivers, beacon satellite receivers, and optical instruments. We will provide a complete description of the experiment configuration and the data products.Finally, we will provide a discussion of experimental results, focusing on ionospheric conditions during the angle-of-arrival determinations, and the impact ionospheric disturbances can have on these measurements. We use the angle-of-arrival determinations to estimate TID properties, including velocity and direction.This research is based upon work supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via US Navy Contract N00024-07-D-6200. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, US Navy, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon.

Reduced SIRT1 expression correlates with enhanced oxidative stress in compensated and decompensated heart failure

PubMed Central

Akkafa, Feridun; Halil Altiparmak, Ibrahim; Erkus, Musluhittin Emre; Aksoy, Nurten; Kaya, Caner; Ozer, Ahmet; Sezen, Hatice; Oztuzcu, Serdar; Koyuncu, Ismail; Umurhan, Berrin

2015-01-01

Sirtuin-1 (SIRT1) is a longevity factor in mammals initiating the cell survival mechanisms, and preventing ischemic injury in heart. In the etiopathogenesis of heart failure (HF), impairment in cardiomyocyte survival is a notable factor. Oxidative stress comprises a critical impact on cardiomyocyte lifespan in HF. The aim of the present study was to investigate SIRT1 expression in patients with compensated (cHF) and decompensated HF (dHF), and its correlation with oxidative stress. SIRT1 expression in peripheral leukocytes was examined using quantitative RT-PCR in 163 HF patients and 84 controls. Serum total oxidant status (TOS) and total antioxidant status (TAS) were measured via colorimetric assays, and oxidative stress index (OSI) was calculated. Lipid parameters were also determined by routine laboratory methods. SIRT1 mRNA expression was significantly downregulated in HF with more robust decrease in dHF (p=0.002, control vs cHF; p<0.001, control vs dHF). Markedly increased oxidative stress defined as elevated TOS, OSI and low TAS levels were detected in HF patients comparing with the controls (TAS; p=0.010, control vs cHF, p=0.045 control vs dHF, TOS; p=0.004 control vs cHF; p<0.001 control vs dHF, OSI; p<0.001 for both comparisons, respectively). With SIRT1 expression levels, TAS, TOS, OSI, and high density lipoprotein levels in cHF and dHF were determined correlated. SIRT1 expression were significantly reduced in both HF subtypes, particularly in dHF. SIRT1 expression was correlated with the oxidant levels and antioxidant capacity. Data suggest that SIRT1 may have a significant contribution in regulation of oxidant/antioxidant balance in HF etiology and compensation status. PMID:26233702

Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth.

PubMed

Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

2015-04-28

Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago.

Meteorite zircon constraints on the bulk Lu−Hf isotope composition and early differentiation of the Earth

PubMed Central

Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

2015-01-01

Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The 176Lu−176Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day 176Hf/177Hf and 176Lu/177Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess 176Hf due to the accelerated decay of 176Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu−Hf system. Herein we report the first, to our knowledge, high-precision Lu−Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial 176Hf/177Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess 176Hf and accurately represent the Lu−Hf system of the bulk Earth (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago. PMID:25870298

Reconciliation of the excess 176Hf conundrum in meteorites: Recent disturbances of the Lu-Hf and Sm-Nd isotope systematics

NASA Astrophysics Data System (ADS)

Bast, Rebecca; Scherer, Erik E.; Sprung, Peter; Mezger, Klaus; Fischer-Gödde, Mario; Taetz, Stephan; Böhnke, Mischa; Schmid-Beurmann, Hinrich; Münker, Carsten; Kleine, Thorsten; Srinivasan, Gopalan

2017-09-01

The long-lived 176Lu-176Hf and 147Sm-143Nd radioisotope systems are commonly used chronometers, but when applied to meteorites, they can reveal disturbances. Specifically, Lu-Hf isochrons commonly yield dates up to ∼300 Myr older than the solar system and varying initial 176Hf/177Hf values. We investigated this problem by attempting to construct mineral and whole rock isochrons for eucrites and angrites. Meteorites from different parent bodies exhibit similar disturbance features suggesting that a common process is responsible. Minerals scatter away from isochron regressions for both meteorite classes, with low-Hf phases such as plagioclase and olivine typically being most displaced above (or left of) reference isochrons. Relatively Hf-rich pyroxene is less disturbed but still to the point of steepening Lu-Hf errorchrons. Using our Lu-Hf and Sm-Nd data, we tested various Hf and Lu redistribution scenarios and found that decoupling of Lu/Hf from 176Hf/177Hf must postdate the accumulation of significant radiogenic 176Hf. Therefore early irradiation or diffusion cannot explain the excess 176Hf. Instead, disturbed meteorite isochrons are more likely caused by terrestrial weathering, contamination, or common laboratory procedures. The partial dissolution of phosphate minerals may predominantly remove rare earth elements including Lu, leaving relatively immobile and radiogenic Hf behind. Robust Lu-Hf (and improved Sm-Nd) meteorite geochronology will require the development of chemical or physical methods for removing unsupported radiogenic Hf and silicate-hosted terrestrial contaminants without disturbing parent-daughter ratios.

Cinnamon improves insulin sensitivity and alters the body composition in an animal model of the metabolic syndrome.

PubMed

Couturier, K; Batandier, C; Awada, M; Hininger-Favier, I; Canini, F; Anderson, R A; Leverve, X; Roussel, A M

2010-09-01

Polyphenols from cinnamon (CN) have been described recently as insulin sensitizers and antioxidants but their effects on the glucose/insulin system in vivo have not been totally investigated. The aim of this study was to determine the effects of CN on insulin resistance and body composition, using an animal model of the metabolic syndrome, the high fat/high fructose (HF/HF) fed rat. Four groups of 22 male Wistar rats were fed for 12 weeks with: (i) (HF/HF) diet to induce insulin resistance, (ii) HF/HF diet containing 20 g cinnamon/kg of diet (HF/HF + CN), (iii) Control diet (C) and (iv) Control diet containing 20 g cinnamon/kg of diet (C + CN). Data from hyperinsulinemic euglycemic clamps showed a significant decrease of the glucose infusion rates in rats fed the HF/HF diet. Addition of cinnamon to the HF/HF diet increased the glucose infusion rates to those of the control rats. The HF/HF diet induced a reduction in pancreas weight which was prevented in HF/HF+CN group (p<0.01). Mesenteric white fat accumulation was observed in HF/HF rats vs. control rats (p<0.01). This deleterious effect was alleviated when cinnamon was added to the diet. In summary, these results suggest that in animals fed a high fat/high fructose diet to induce insulin resistance, CN alters body composition in association with improved insulin sensitivity. 2010 Elsevier Inc. All rights reserved.

Obesity-induced oocyte mitochondrial defects are partially prevented and rescued by supplementation with co-enzyme Q10 in a mouse model

PubMed Central

Boots, C.E.; Boudoures, A.; Zhang, W.; Drury, A.; Moley, K.H.

2016-01-01

STUDY QUESTION Does supplementation with co-enzyme Q10 (CoQ10) improve the oocyte mitochondrial abnormalities associated with obesity in mice? SUMMARY ANSWER In an obese mouse model, CoQ10 improves the mitochondrial function of oocytes. WHAT IS KNOWN ALREADY Obesity impairs oocyte quality. Oocytes from mice fed a high-fat/high-sugar (HF/HS) diet have abnormalities in mitochondrial distribution and function and in meiotic progression. STUDY DESIGN, SIZE, DURATION Mice were randomly assigned to a normal, chow diet or an isocaloric HF/HS diet for 12 weeks. After 6 weeks on the diet, half of the mice receiving a normal diet and half of the mice receiving a HF/HS diet were randomly assigned to receive CoQ10 supplementation injections for the remaining 6 weeks. PARTICIPANTS/MATERIALS, SETTING, METHODS Dietary intervention was initiated on C57Bl6 female mice at 4 weeks of age, CoQ10 versus vehicle injections were assigned at 10 weeks, and assays were conducted at 16 weeks of age. Mice were super-ovulated, and oocytes were collected and stained to assess mitochondrial distribution, quantify reactive oxygen species (ROS), assess meiotic spindle formation, and measure metabolites. In vitro fertilization was performed, and blastocyst embryos were transferred into control mice. Oocyte number, fertilization rate, blastulation rate and implantation rate were compared between the four cohorts. Bivariate statistics were performed appropriately. MAIN RESULTS AND THE ROLE OF CHANCE HF/HS mice weighed significantly more than normal diet mice (29 versus 22 g, P< 0.001). CoQ10 supplementation did not influence weight. Levels of ATP, citrate, and phosphocreatine were lower and ROS levels were higher in HF/HS mice than in controls (P< 0.001). CoQ10 supplementation significantly increased the levels of metabolites and decreased ROS levels in oocytes from normal diet mice but not in oocytes from HF/HS mice. However, CoQ10 completely prevented the mitochondrial distribution abnormalities observed in the HF/HS mice. Overall, CoQ10 supplementation significantly increased the percentage of normal spindle and chromosome alignment (92.3 versus 80.2%, P= 0.039). In the sub-analysis by diet, the difference did not reach statistical significance. When undergoing IVF, there were no statistically significant differences in the number of mature oocytes, the fertilization rate, blastocyst formation rates, implantation rates, resorption rates or litter size between HF/HS mice receiving CoQ10 or vehicle injections. LIMITATIONS, REASONS FOR CAUTION Experiments were limited to one species and strain of mice. The majority of experiments were performed after ovulation induction, which may not represent natural cycle fertility. WIDER IMPLICATIONS OF THE FINDINGS Improvement in oocyte mitochondrial distribution and function of normal, chow-fed mice and HF/HS-fed mice demonstrates the importance of CoQ10 and the efficiency of the mitochondrial respiratory chain in oocyte competence. Clinical studies are now needed to evaluate the therapeutic potential of CoQ10 in women's reproductive health. STUDY FUNDING/COMPETING INTEREST(S) C.E.B. received support from the National Research Training Program in Reproductive Medicine sponsored by the National Institute of Health (T32 HD040135-13) and the Scientific Advisory Board of Vivere Health. K.H.M received support from the American Diabetes Association and the National Institute of Health (R01 HD083895). There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER This study is not a clinical trial. PMID:27432748

New Generation of ELF/VLF Wave Injection Experiments for HAARP

NASA Astrophysics Data System (ADS)

Sonwalkar, V. S.; Reddy, A.; Watkins, B. J.

2016-12-01

We present a ray tracing study to investigate the feasibility of a new generation of wave injection experiments from HAARP transmitter (L 4.9). Highly successful whistler mode wave injection experiments from SIPLE station, Antarctica, have established the importance of such experiments to study magnetospheric wave-particle interactions, and for cold and hot plasma diagnostics [Helliwell and Katsufrakis, 1974; Carpenter and Miller, 1976; Sonwalkar et al., 1997]. Modulated heating experiments from HAARP have shown that it is possible to launch ELF/VLF waves into the magnetosphere that can be observed on the ground after one-, two-, and multi-hop ducted propagation [Inan et al., 2004]. Recent research has also shown that ionospheric heating experiments using HAARP can lead to the formation of magnetospheric ducts [e.g. Milikh et al., 2010; Fallen et al., 2011]. Collectively, these results indicate that the HAARP (or similar) transmitter can be used first to form ducts on nearby L shells, and then to inject and trap transmitter generated ELF/VLF waves in those ducts. Ray tracing studies using a model magnetosphere shows that ELF/VLF waves in a few kilohertz range can be trapped in ducts with L shells near the HAARP transmitter. For example, 1.5 kHz waves injected from L shell = 4.9 and altitude = 200 km can be trapped in ducts located within 0.3 L of the transmitter L-shell. The duct parameters needed for ray-trapping are typically duct width dL 0.1-0.3 and duct enhancement factor dNe/Ne 10-20% or more. The location of plasmapause with respect to transmitter plays a role in the nature of trapping. The duct locations and parameters required for trapping ELF/VLF waves inside the ducts are consistent with past observations of ducts generated by the HAARP transmitter. Ray tracing calculations provide trapped wave normal angles, time delays, resonant energetic electron energy, estimates of wave intensity inside the duct, on the ground, and on satellites such DEMETER, Van Allen probe, and planned DSX. We discuss the potential of a new generation of wave injection experiments from HAARP transmitter to investigate: duct and ELF/VLF generation by high power HF transmitters, whistler mode wave propagation and wave particle interactions, and cold and hot plasma diagnostics.

e-POP RRI provides new opportunities for space-based, high-frequency radio science experiments

NASA Astrophysics Data System (ADS)

Burrell, Angeline G.

2017-04-01

Perry et al. (2016, https://doi.org/10.1002/2017JG003855) present the first results of the Radio Receiver Instrument (RRI), a part of the enhanced Polar Outflow Probe (e-POP) that flies on board the CAScade, Smallsat and IOnospheric Polar Explorer satellite. Using a matched filter technique, e-POP RRI was able to observe individual radio pulses transmitted by a ground-based radar. These results were used to examine the temporal variations in the dispersion, polarization, and power of the pulses, demonstrating the capacity for e-POP RRI to contribute to studies of radio propagation at high-frequency (HF) ranges. Understanding radio propagation in the presence and absence of ionospheric irregularities is crucial for ionospheric physics, as well as commercial and military radio applications. Conjunctions between e-POP RRI and ground- or space-based HF transmitters offer a new opportunity for coherent scatter experiments.

Modeling Hf-W Evolution for Earth, Moon and Mars in Grand Tack Accretion Simulations: The Isotopic Consequences of Rapid Accretion

NASA Astrophysics Data System (ADS)

Zube, N.; Nimmo, F.; Jacobson, S. A.; Fischer, R. A.

2017-12-01

Short-lived isotopes, such as the decay of lithophile 182Hf into siderophile 182W with a half-life of 9 My, can provide constraints on the timescales of planetary core formation and accretion. Classical accretion scenarios have produced Hf-W isotopic outcomes like those measured presently on the Earth [2,3]. We examine Grand Tack accretion simulations [4,5] and determine the mantle equilibration conditions necessary to produce the observed tungsten isotopic anomaly. Additionally, we follow Hf-W evolution for pairs of bodies that experience a last giant impact fitting the conditions of Earth's Moon-forming collision. In this way, we determine the likelihood of producing the observed almost indistinguishable W isotope anomalies of the Earth and Moon mantles [6]. We model Hf-W evolution for growing planets in 141 N-body simulations during late accretion in the Grand Tack scenario. For each case, we vary the equilibration factor during collisions—the fraction of impactor core that experiences re-equilibration with the entire target mantle—in steps ranging from none (cores merging) to complete equilibration. For Earth-like and Mars-like surviving planets, we find that cases with a high equilibration factor (k > 0.8) and an intermediate (2:1 - 4:1) ratio of initial embryo mass to planetesimal mass were most frequently able to approximate the observed W measurements for Earth and Mars. The equilibration factor required is more restrictive than the one found for classical accretion scenarios [2,3] and may not be consistent with fluid-dynamical predictions [7]. Moons made of impactor material from Earth's last giant impact are only able to result in an Earth-Moon pair having sufficiently similar W anomalies with a likelihood of 8% or less across all simulations. This indicates that a scenario where the Moon isotopically equilibrated with the Earth's mantle after the impact [8] may be required to explain the measured values. [1] Kleine et al. 2009 [2] Nimmo et al. 2010 [3] Rudge et al. 2010 [4] Walsh et al. 2009 [5] Jacobson et al. 2014 [6] Touboul et al., 2007 [7] Deguen et al. 2014 [8] Pahlevan and Stevenson 2007

Influence of dietary nonstructural carbohydrate concentration on growth performance and carcass characteristics of Holstein steers.

PubMed

Ramos-Aviña, Daniel; Plascencia, Alejandro; Zinn, Richard

2018-06-01

Since very little information exists about the topic; in this experiment we compare, in a long-term finishing program, the growth-performance responses and carcass characteristics of Holstein steers where non-structural carbohydrate concentration of the diet is reduced from 64% to 51% (dry matter basis). Sixty Holstein steer calves (129±2.2 kg) were blocked by initial weight into five groups and randomly assigned within weight groupings to 10 pens. Calves were fed with a steam-flaked corn-based finishing diets containing 51% higher fiber (HF) or 64% lower fiber (LF) nonstructural carbohydrates. Non-structural carbohydrates concentrations were manipulated substituting dried distiller grain with solubles and alfalfa hay for flaked corn. Cattle were weighed every 112 days and at the end of the experiment (day 308) when the cattle were harvested and carcass characteristics were evaluated. Steers fed the HF diet showed improvement (8.8%) in average daily gain (ADG) during the initial 112-d period. This effect was followed by a numerical trend for greater ADG throughout the remainder of the study so that overall ADG tended to be greater (4.9%, p = 0.06) for the HF than for LF. There were no treatment effects on dry matter intake. Gain efficiency and estimated dietary net energy (NE) were greater 8.3% and 5.2%, respectively for HF during the initial 112-d period. Overall (308-d) gain efficiency and estimated dietary NE were similar for both dietary treatments. However, due to differences in tabular dietary NE, the ratio of observed:expected dietary NE tended to be greater (4.1%, p = 0.06) for the HF vs LF diet. There were no treatment effects on carcass characteristics except for a tendency toward a slightly greater (0.5%, p = 0.09) estimated carcass yield. Reducing the non-structural carbohydrate concentration of a conventional steam-flaked corn-based growing finishing diet for Holstein steers can effectively enhance growth performance, particularly during the early growing and late finishing phases.

Living with and dying from advanced heart failure: understanding the needs of older patients at the end of life.

PubMed

Klindtworth, Katharina; Oster, Peter; Hager, Klaus; Krause, Olaf; Bleidorn, Jutta; Schneider, Nils

2015-10-15

Heart failure (HF) is a life-limiting illness and patients with advanced heart failure often suffer from severe physical and psychosocial symptoms. Particularly in older patients, HF often occurs in conjunction with other chronic diseases, resulting in complex co-morbidity. This study aims to understand how old and very old patients with advanced HF perceive their disease and to identify their medical, psychosocial and information needs, focusing on the last phase of life. Qualitative longitudinal interview study with old and very old patients (≥70 years) with severe HF (NYHA III-IV). Interviews were conducted at three-month intervals over a period of up to 18 months and were analysed using qualitative methods in relation to Grounded Theory. A total of 95 qualitative interviews with 25 patients were conducted and analysed. The following key categories were developed: (1a) dealing with advanced heart failure and ageing, (1b) dealing with end of life; (2a) perceptions regarding care, and (2b) interpersonal relations. Overall, our data show that older patients do not experience HF as a life-limiting disease. Functional restrictions and changed conditions leading to problems in daily life activities were often their prime concerns. The needs and priorities of older HF patients vary depending on their disease status and individual preferences. Pain resulting in reduced quality of life is an example of a major symptom requiring treatment. Many older HF patients lack sufficient knowledge about their condition and its prognosis, particularly concerning emergency situations and end of life issues, and many expressed a wish for open discussions. From the patients' perspective, there is a need for improvement in interaction with health care professionals, and limits in treatment and medical care are not openly discussed. Old and very old patients with advanced HF often do not acknowledge the seriousness and severity of the disease. Their communication with physicians predominantly focuses on curative treatment. Therefore, aspects such as self-management of the disease, dealing with emergency situations and end-of-life issues should be addressed more prominently. An advanced care planning (ACP) programme for heart disease in older people could be an option to improve patient-centred care.

A search for a heavy Majorana neutrino and a radiation damage simulation for the HF detector

NASA Astrophysics Data System (ADS)

Wetzel, James William

A search for heavy Majorana neutrinos is performed using an event signature defined by two same-sign muons accompanied by two jets. This search is an extension of previous searches, (L3, DELPHI, CMS, ATLAS), using 19.7 fb -1 of data from the 2012 Large Hadron Collider experimental run collected by the Compact Muon Solenoid experiment. A mass window of 40-500 GeV/ c2 is explored. No excess events above Standard Model backgrounds is observed, and limits are set on the mixing element squared, |VmuN|2, as a function of Majorana neutFnrino mass. The Hadronic Forward (HF) Detector's performance will degrade as a function of the number of particles delivered to the detector over time, a quantity referred to as integrated luminosity and measured in inverse femtobarns (fb-1). In order to better plan detector upgrades, the CMS Forward Calorimetry Task Force (FCAL) group and the CMS Hadronic Calorimeter (HCAL) group have requested that radiation damage be simulated and the subsequent performance of the HF subdetector be studied. The simulation was implemented into both the CMS FastSim and CMS FullSim simulation packages. Standard calorimetry performance metrics were computed and are reported. The HF detector can expect to perform well through the planned delivery of 3000 fb-1.

Distribution of electron traps in SiO2/HfO2 nMOSFET

NASA Astrophysics Data System (ADS)

Xiao-Hui, Hou; Xue-Feng, Zheng; Ao-Chen, Wang; Ying-Zhe, Wang; Hao-Yu, Wen; Zhi-Jing, Liu; Xiao-Wei, Li; Yin-He, Wu

2016-05-01

In this paper, the principle of discharge-based pulsed I-V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO2 layer have been extracted. Two peaks are observed, which are located at ΔE ˜ -1.0 eV and -1.43 eV, respectively. It is found that the former one is close to the SiO2/HfO2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment, and reliability improvement for advanced semiconductor devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the New Experiment Development Funds for Xidian University, China (Grant No. SY1434), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China (Grant No. JY0600132501).

A Guide to Studying Human Hair Follicle Cycling In Vivo.

PubMed

Oh, Ji Won; Kloepper, Jennifer; Langan, Ewan A; Kim, Yongsoo; Yeo, Joongyeub; Kim, Min Ji; Hsi, Tsai-Ching; Rose, Christian; Yoon, Ghil Suk; Lee, Seok-Jong; Seykora, John; Kim, Jung Chul; Sung, Young Kwan; Kim, Moonkyu; Paus, Ralf; Plikus, Maksim V

2016-01-01

Hair follicles (HFs) undergo lifelong cyclical transformations, progressing through stages of rapid growth (anagen), regression (catagen), and relative "quiescence" (telogen). Given that HF cycling abnormalities underlie many human hair growth disorders, the accurate classification of individual cycle stages within skin biopsies is clinically important and essential for hair research. For preclinical human hair research purposes, human scalp skin can be xenografted onto immunocompromised mice to study human HF cycling and manipulate long-lasting anagen in vivo. Although available for mice, a comprehensive guide on how to recognize different human hair cycle stages in vivo is lacking. In this article, we present such a guide, which uses objective, well-defined, and reproducible criteria, and integrates simple morphological indicators with advanced, (immuno)-histochemical markers. This guide also characterizes human HF cycling in xenografts and highlights the utility of this model for in vivo hair research. Detailed schematic drawings and representative micrographs provide examples of how best to identify human HF stages, even in suboptimally sectioned tissue, and practical recommendations are given for designing human-on-mouse hair cycle experiments. Thus, this guide seeks to offer a benchmark for human hair cycle stage classification, for both hair research experts and newcomers to the field. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

ELF/VLF Waves Generated by an Artificially-Modulated Auroral Electrojet Above the HAARP HF Transmitter

NASA Astrophysics Data System (ADS)

Moore, R. C.; Inan, U. S.; Bell, T. F.

2004-12-01

Naturally-forming, global-scale currents, such as the polar electrojet current and the mid-latitude dynamo, have been used as current sources to generate electromagnetic waves in the Extremely Low Frequency (ELF) and Very Low Frequency (VLF) bands since the 1970's. While many short-duration experiments have been performed, no continuous multi-week campaign data sets have been published providing reliable statistics for ELF/VLF wave generation. In this paper, we summarize the experimental data resulting from multiple ELF/VLF wave generation campaigns conducted at the High-frequency Active Auroral Research Project (HAARP) HF transmitter in Gakona, Alaska. For one 14-day period in March, 2002, and one 24-day period in November, 2002, the HAARP HF transmitter broadcast ELF/VLF wave generation sequences for 10 hours per day, between 0400 and 1400 UT. Five different modulation frequencies broadcast separately using two HF carrier frequencies are examined at receivers located 36, 44, 147, and 155 km from the HAARP facility. Additionally, a continuous 24-hour transmission period is analyzed to compare day-time wave generation to night-time wave generation. Lastly, a power-ramping scheme was employed to investigate possible thresholding effects at the wave-generating altitude. Wave generation statistics are presented along with source-region property calculations performed using a simple model.

A Polyphenol-Rich Fraction Obtained from Table Grapes Decreases Adiposity, Insulin Resistance, and Markers of Inflammation and Impacts Gut Microbiota in High-Fat Fed Mice

PubMed Central

Collins, Brian; Hoffman, Jessie; Martinez, Kristina; Grace, Mary; Lila, Mary Ann; Cockrell, Chase; Nadimpalli, Anuradha; Chang, Eugene; Chuang, Chia-Chi; Zhong, Wei; Mackert, Jessica; Shen, Wan; Cooney, Paula; Hopkins, Robin; McIntosh, Michael

2016-01-01

The objective of this study was to determine if consuming an extractable or non-extractable fraction of table grapes reduced the metabolic consequences of consuming a high-fat, American-type diet. Male C57BL/6J mice were fed a low fat (LF) diet, a high fat (HF) diet, or a HF diet containing whole table grape powder (5% w/w), an extractable, polyphenol-rich (HF-EP) fraction, a non-extractable, polyphenol-poor (HF-NEP) fraction, or equal combinations of both fractions (HF-EP+NEP) from grape powder for 16 weeks. Mice fed the HF-EP and HF-EP+NEP diets had lower percentages of body fat and amounts of white adipose tissue (WAT) and improved glucose tolerance compared to the HF-fed controls. Mice fed the HF-EP+NEP diet had lower liver weights and triglyceride (TG) levels compared to the HF-fed controls. Mice fed the HF-EP+NEP diets had higher hepatic mRNA levels of hormone sensitive lipase and adipose TG lipase, and decreased expression of c-reactive protein compared to the HF-fed controls. In epididymal (visceral) WAT, the expression levels of several inflammatory genes were lower in mice fed the HF-EP and HF-EP+NEP diets compared to the HF-fed controls. Mice fed the HF diets had increased myeloperoxidase activity and impaired localization of the tight junction protein zonula occludens-1 in ileal mucosa compared to the HF-EP and HF-NEP diets. Several of these treatment effects were associated with alterations in gut bacterial community structure. Collectively, these data demonstrate that the polyphenol-rich, EP fraction from table grapes attenuated many of the adverse health consequences associated with consuming a HF diet. PMID:27133434

Development of Low Cost Gas Atomization of Precursor Powders for Simplified ODS Alloy Production

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

Anderson, Iver

2014-08-05

A novel gas atomization reaction synthesis (GARS) method was developed in this project to enable production (at our partner’s facility) a precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE) containing intermetallic compound (IMC) phase. Consolidation and heat-treatment experiments were performed at Ames Lab to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nano-metric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiments at Ames Lab and found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloy, i.e., the Hf-containing system exhibitedmore » five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was less complex to characterize, and make observations on the effects of processing parameters, the Ti-containing system was selected by Ames Lab for experimental atomization trials at our partner. An internal oxidation model was developed at Ames Lab and used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed at Ames Lab with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing at Ames Lab to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed at our partner to investigate the effects of: gas atomization pressure and reactive gas concentration on the particle size distribution (PSD) and the oxygen content of the resulting powder. Also, the effect on the rapidly solidified microstructure (as a function of powder size) was investigated at Ames Lab as a function of reactive gas composition and bulk alloy composition. The results indicated that the pulsatile gas atomization mechanism and a significantly enhanced yield of fine powders reported in the literature for this type of process were not observed. Also it was determined that reactive gas may marginally improve the fine powder yield but further experiments are required. The oxygen content in the gas also did not have any detrimental effect on the microstructure (i.e. did not significantly reduce undercooling). On the contrary, the oxygen addition to the atomization gas may have mitigated some potent catalytic nucleation sites, but not enough to significantly alter the microstructure vs. particle size relationship. Overall the downstream injection of oxygen was not found to significantly affect either the particle size distribution or undercooling (as inferred from microstructure and XRD observations) but injection further upstream, including in the gas atomization nozzle, remains to be investigated in later work.« less