FTIR Spectrum of the ν 4Band of DCOOD

NASA Astrophysics Data System (ADS)

Tan, T. L.; Goh, K. L.; Ong, P. P.; Teo, H. H.

1999-06-01

The FTIR spectrum of the ν4band of deuterated formic acid (DCOOD) has been measured with a resolution of 0.004 cm-1in the frequency range of 1120 to 1220 cm-1. A total of 1866 assigned transitions have been analyzed and fitted using a Watson'sA-reduced Hamiltonian in theIrrepresentation to derive rovibrational constants for the upper state (v4= 1) with a standard deviation of 0.00036 cm-1. In the course of the analysis, the constants for the ground state were improved by a simultaneous fit of microwave frequencies and combination differences from the infrared measurements. Due to the relatively unperturbed nature of the band, the constants can be used to accurately calculate the infrared line positions for the whole band. Although the band is a hybrid typeAandB, onlya-type transitions were strong enough to be observed. The band center is at 1170.79980 ± 0.00002 cm-1.

Natural Electrotransformation of Lightning-Competent Pseudomonas sp. Strain N3 in Artificial Soil Microcosms

PubMed Central

Cérémonie, Hélène; Buret, François; Simonet, Pascal; Vogel, Timothy M.

2006-01-01

The lightning-competent Pseudomonas sp. strain N3, recently isolated from soil, has been used to study the extent of natural electrotransformation (NET) or lightning transformation as a horizontal gene transfer mechanism in soil. The variation of electrical fields applied to the soil with a laboratory-scale lightning system provides an estimate of the volume of soil affected by NET. Based on the range of the electric field that induces NET of Pseudomonas strain N3, the volume of soil, where NET could occur, ranges from 2 to 950 m3 per lightning strike. The influence of DNA parameters (amount, size, and purity) and DNA soil residence time were also investigated. NET frequencies (electrotransformants/recipient cells) ranged from 10−8 for cell lysate after 1 day of residence in soil to 4 × 10−7 with a purified plasmid added immediately before the lightning. The electrical field gradient (in kilovolts per cm) also played a role as NET frequencies ranging from 1 × 10−5 at 2.3 kV/cm to 1.7 × 10−4 at 6.5 kV/cm. PMID:16597934

Effects of aromaticity in cations and their functional groups on the temperature dependence of low-frequency spectrum

DOE PAGES

Kakinuma, Shohei; Ramati, Sharon; Wishart, James F.; ...

2018-05-21

We investigate the temperature dependence of low-frequency spectra in the frequency range of 0.3–200 cm -1 for ionic liquids (ILs) whose cations possess two systematically different cyclic groups, using femtosecond Raman-induced Kerr effect spectroscopy. The target ILs are bis(trifluoromethylsulfonyl)amide [NTf 2]– salts of 1-cyclohexylmethyl-1-methylpyrrolidinium [CHxmMPyrr] +, 1-cyclohexylmethyl-3-methylimidazolium [CHxmMIm] +, N-cyclohexylmethylpyridinium [CHxmPy]+, 1-benzyl-1-methylpyrrolidinium [BzMPyrr] +, 1-benzyl-3-methylimidazolium [BzMIm] +, and N-benzylpyridinium [BzPy] + cations. The aim of this study is to better understand the effects of aromaticity in the cations’ constituent groups on the temperature-dependent low-frequency spectral features of the ILs. The low-frequency spectra of these ILs are temperature dependent, but themore » temperature-dependent spectrum of [CHxmMPyrr][NTf 2] is different from that of other ILs. While [CHxmMPyrr][NTf 2] shows spectral changes with temperature in the low-frequency region below 50 cm -1, the other ILs also show spectral changes in the high-frequency region above 80 cm -1 (above 50 cm -1 in the case of [BzMPyrr][NTf 2]). We conclude that the spectral change in the low-frequency region is due to both the cation and anion, while the change in the high-frequency region is attributed to the red shift of the aromatic ring librations. On the basis of the plots of the first moment of the spectra vs. temperature, we found that the first moment of the low-frequency spectrum of the IL whose cation does not have an aromatic ring is less temperature dependent than that of the other ILs. However, the intrinsic first moment, the first moment at 0 K, of the low-frequency spectrum is governed by the absence or presence of a charged aromatic group, while a neutral aromatic group does not have much influence on determining the intrinsic first moment.« less

Effects of aromaticity in cations and their functional groups on the temperature dependence of low-frequency spectrum

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

Kakinuma, Shohei; Ramati, Sharon; Wishart, James F.

We investigate the temperature dependence of low-frequency spectra in the frequency range of 0.3–200 cm -1 for ionic liquids (ILs) whose cations possess two systematically different cyclic groups, using femtosecond Raman-induced Kerr effect spectroscopy. The target ILs are bis(trifluoromethylsulfonyl)amide [NTf 2]– salts of 1-cyclohexylmethyl-1-methylpyrrolidinium [CHxmMPyrr] +, 1-cyclohexylmethyl-3-methylimidazolium [CHxmMIm] +, N-cyclohexylmethylpyridinium [CHxmPy]+, 1-benzyl-1-methylpyrrolidinium [BzMPyrr] +, 1-benzyl-3-methylimidazolium [BzMIm] +, and N-benzylpyridinium [BzPy] + cations. The aim of this study is to better understand the effects of aromaticity in the cations’ constituent groups on the temperature-dependent low-frequency spectral features of the ILs. The low-frequency spectra of these ILs are temperature dependent, but themore » temperature-dependent spectrum of [CHxmMPyrr][NTf 2] is different from that of other ILs. While [CHxmMPyrr][NTf 2] shows spectral changes with temperature in the low-frequency region below 50 cm -1, the other ILs also show spectral changes in the high-frequency region above 80 cm -1 (above 50 cm -1 in the case of [BzMPyrr][NTf 2]). We conclude that the spectral change in the low-frequency region is due to both the cation and anion, while the change in the high-frequency region is attributed to the red shift of the aromatic ring librations. On the basis of the plots of the first moment of the spectra vs. temperature, we found that the first moment of the low-frequency spectrum of the IL whose cation does not have an aromatic ring is less temperature dependent than that of the other ILs. However, the intrinsic first moment, the first moment at 0 K, of the low-frequency spectrum is governed by the absence or presence of a charged aromatic group, while a neutral aromatic group does not have much influence on determining the intrinsic first moment.« less

Effects of aromaticity in cations and their functional groups on the temperature dependence of low-frequency spectrum

NASA Astrophysics Data System (ADS)

Kakinuma, Shohei; Ramati, Sharon; Wishart, James F.; Shirota, Hideaki

2018-05-01

In this study, we investigate the temperature dependence of low-frequency spectra in the frequency range of 0.3-200 cm-1 for ionic liquids (ILs) whose cations possess two systematically different cyclic groups, using femtosecond Raman-induced Kerr effect spectroscopy. The target ILs are bis(trifluoromethylsulfonyl)amide [NTf2]- salts of 1-cyclohexylmethyl-1-methylpyrrolidinium [CHxmMPyrr]+, 1-cyclohexylmethyl-3-methylimidazolium [CHxmMIm]+, N-cyclohexylmethylpyridinium [CHxmPy]+, 1-benzyl-1-methylpyrrolidinium [BzMPyrr]+, 1-benzyl-3-methylimidazolium [BzMIm]+, and N-benzylpyridinium [BzPy]+ cations. The aim of this study is to better understand the effects of aromaticity in the cations' constituent groups on the temperature-dependent low-frequency spectral features of the ILs. The low-frequency spectra of these ILs are temperature dependent, but the temperature-dependent spectrum of [CHxmMPyrr][NTf2] is different from that of other ILs. While [CHxmMPyrr][NTf2] shows spectral changes with temperature in the low-frequency region below 50 cm-1, the other ILs also show spectral changes in the high-frequency region above 80 cm-1 (above 50 cm-1 in the case of [BzMPyrr][NTf2]). We conclude that the spectral change in the low-frequency region is due to both the cation and anion, while the change in the high-frequency region is attributed to the red shift of the aromatic ring librations. On the basis of the plots of the first moment of the spectra vs. temperature, we found that the first moment of the low-frequency spectrum of the IL whose cation does not have an aromatic ring is less temperature dependent than that of the other ILs. However, the intrinsic first moment, the first moment at 0 K, of the low-frequency spectrum is governed by the absence or presence of a charged aromatic group, while a neutral aromatic group does not have much influence on determining the intrinsic first moment.

Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

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

Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

2016-02-13

A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

Intraoperative microwave ablation of pulmonary malignancies with tumor permittivity feedback control: ablation and resection study in 10 consecutive patients.

PubMed

Wolf, Farrah J; Aswad, Bassam; Ng, Thomas; Dupuy, Damian E

2012-01-01

To determine histologic changes induced by microwave ablation (MWA) in patients with pulmonary malignancy by using an ablation system with tumor permittivity feedback control, enabling real-time modulation of energy power and frequency. Institutional review board approval and patient informed consent were obtained for this prospective HIPAA-complaint ablation and resection study. Between March 2009 and January 2010, 10 patients (four women, six men; mean age, 71 years; age range, 52-82 years) underwent intraoperative MWA of pulmonary malignancies. Power (10-32 W) and frequency (908-928 MHz) were continuously adjusted by the generator to maintain a temperature of 110°-120°C at the 14-gauge antenna tip for one 10-minute application. After testing for an air leak, tumors were resected surgically. Gross inspection, slicing, and hematoxylin-eosin (10 specimens) and nicotinamide adenine dinucleotide (six specimens) staining were performed. Tumors included adenocarcinomas (n = 5), squamous cell carcinomas (n = 3), and metastases from endometrial (n = 1) and colorectal (n = 1) primary carcinomas. Mean maximum tumor diameter was 2.4 cm (range, 0.9-5.0 cm), and mean maximum volume was 8.6 cm(3) (range, 0.5-52.7 cm(3)). One air leak was detected. Five of 10 specimens were grossly measurable, revealing a mean maximum ablation zone diameter of 4.8 cm (range, 3.0-6.5 cm) and a mean maximum ablation zone volume of 15.1 cm(3) (range, 7.3-25.1 cm(3)). At hematoxylin-eosin staining, coagulation necrosis was observed in all ablation zones, extended into the normal lung in nine of 10 specimens, and up to blood vessel walls without evidence of vessel (>4 mm) thrombosis. Nicotinamide adenine dinucleotide staining enabled confirmation of no viability within ablation zones extending into normal lung in five of six specimens. MWA with tumor permittivity feedback control results in cytotoxic intratumoral temperatures and extension of ablation zones into aerated peritumoral pulmonary parenchyma, possibly forming the equivalent of an oncologic resection margin. © RSNA, 2011.

Analysis of the ν 12 Band of Ethylene- 13C 2 by High-Resolution FTIR Spectroscopy

NASA Astrophysics Data System (ADS)

Tan, T. L.; Goh, K. L.; Ong, P. P.; Teo, H. H.

2001-06-01

The Fourier transform infrared (FTIR) spectrum of the ν12 fundamental band of ethylene-13C2 (13C2H4) was recorded with an unapodized resolution of 0.004 cm-1 in the frequency range from 1380 to 1500 cm-1. Rovibrational constants for the upper state (ν12=1) up to five quartic and three sextic centrifugal distortion terms were derived for the first time by assigning and fitting a total of 1177 infrared transitions using a Watson's A-reduced Hamiltonian in the Ir representation. The rms deviation of the fit was 0.00045 cm-1. The ground state rovibrational constants were also determined for the first time by a fit of 738 combination differences from the present infrared measurements, with a rms deviation of 0.00060 cm-1. The A-type ν12 band with a band center at 1436.65411±0.00005 cm-1 was found to be relatively free from local frequency perturbations. The inertial defect Δ12 was found to be 0.24300±0.00002 uÅ2.

High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak.

PubMed

Truong, D D; Austin, M E

2014-11-01

The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels' IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters' center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a "zoomed-in" analysis of a ∼2-4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, are presented.

A high-resolution atlas of the infrared spectrum of the sun and the earth atmosphere from space. A compilation of ATMOS spectra of the region from 650 to 4800 cm-1 (2.3 to 16 microns). Volume 2: Stratosphere and mesosphere, 650 to 3350 cm-1

NASA Technical Reports Server (NTRS)

Farmer, Crofton B.; Norton, Robert H.

1989-01-01

During the period April 29 to May 2, 1985, the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment was operated for the first time, as part of the Spacelab-3 payload of the shuttle Challenger. The principal purpose of this experiment was to study the distributions of the atmosphere's minor and trace molecular constituents. The instrument, a modified Michelson interferometer covering the frequency range from 600 to 5000/cm-1 at a spectral resolution of 0.01/cm-1, recorded infrared absorption spectra of the sun and of the earth's atmosphere at times close to entry into and exit from occultation by the earth's limb. Spectra were obtained that are free from absorptions due to constituents of the atmosphere (i.e., they are pure solar spectra), as well as spectra of the atmosphere itself, covering line-of-sight tangent altitudes that span the range from the lower thermosphere to the bottom of the troposphere. This atlas presents a compilation of these spectra arranged in a hardcopy format suitable for quick-look reference purposes. Volume 2 covers the stratosphere and mesosphere (i.e., tangent altitudes from 20 to 80 km) for frequencies from 650 to 3350/cm-1.

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation.

PubMed

Haemmerich, Dieter; Schutt, David J; Wright, Andrew W; Webster, John G; Mahvi, David M

2009-05-01

We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.11 versus 0.75 mS cm(-1) at 10 Hz, to 5.33 versus 2.88 mS cm(-1) at 1 MHz). We found no significant correlation between tumour size and measured electrical conductivity. While before ablation tumour tissue had considerably higher conductivity than normal tissue, the two had similar conductivity throughout the frequency range after ablation. Tumour tissue conductivity changed by +25% and -7% at 10 Hz and 1 MHz after ablation (0.23-0.29 at 10 Hz, and 0.43-0.40 at 1 MHz), while normal tissue conductivity increased by +270% and +10% at 10 Hz and 1 MHz (0.09-0.32 at 10 Hz and 0.37-0.41 at 1 MHz). These data can potentially be used to differentiate tumour from normal tissue diagnostically.

Detection of carbon-fluorine bonds in organofluorine compounds by Raman spectroscopy using a copper-vapor laser

NASA Astrophysics Data System (ADS)

Sharts, Clay M.; Gorelik, Vladimir S.; Agoltsov, A. M.; Zlobina, Ludmila I.; Sharts, Olga N.

1999-02-01

The Raman spectra of fluoro-organic compounds show specific emission bands for carbon-fluorine bonds in the range 500- 800 wave numbers (cm-1)). With very limited exceptions, biological materials do not contain carbon- fluorine bonds. Fluoro-organic compounds introduced into biological samples can be detected by a Raman emission signal. Normal mode C-F bond bands are observed: (1) at 710- 785 cm -1 for trifluoromethyl groups; (2) at 530-610 cm -1 for aromatic organofluorine bonds; (3) a range centered at 690 cm -1 for difluoromethylene groups. Specific examples of normal mode C-F bond emissions for organofluorine compounds containing trifluoromethyl groups are: 1-bromoperfluorooctane, 726 cm -1; perfluorodecanoic acid, 730 cm -1; triperfluoropropylamine, 750 cm -1; 1,3,5-tris- (trifluoromethyl)-benzene, 730 cm -1; Fluoxetine (Prozac) commercial powdered pill at 782 cm -1. Compounds containing aromatic C-F bonds are: hexafluorobenzene, 569 cm MIN1; pentafluoropyridine, 589 cm -1. Difluoromethylene groups: perfluorodecalin, 692 cm-1; perfluorocyclohexane, 691 cm -1. Raman spectra were observed with a standard single monochromator. The 510.8 nm light source was a copper-vapor laser operated at 3-10 watts with 10-12 nanosecond pulses at 10 kHz repetition rate. Detection was made with a time-gated photomultiplier tube. Resonance Raman spectra were also observed at 255.4 nm, using a frequency doubling crystal. Observed spectra were free of fluorescence with very sharp strong C-F lines.

Millimeter-wave reflectometry for electron density profile and fluctuation measurements on NSTX

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

Kubota, S.; Nguyen, X. V.; Peebles, W. A.

2001-01-01

A millimeter-wave reflectometry system for electron density profile and fluctuation measurements is being developed and installed on the National Spherical Torus Experiment. The initial frequency coverage will be in the bands 12--18, 20--32, and 33--50 GHz, provided by frequency-tunable solid-state sources. These frequencies correspond to O-mode cutoff densities ranging from 1.8x10{sup 12} to 3.1x10{sup 13}cm{sup -3}, which will span both the plasma core ({rho}=r/a<0.8) and edge ({rho}>0.8) regions. Operated as a broadband swept-frequency (frequency-modulated continuous-wave) reflectometer, the diagnostic is expected to provide routine (shot-to-shot) time- ({<=}50 {mu}s) and spatially resolved ({approx}1 cm) density profiles. The previous hardware can be easilymore » reconfigured as a fixed-frequency reflectometer for density fluctuation measurements. The combination of measurements would be valuable for studying phenomena such as possible L- to H-mode transitions and edge-localized modes.« less

Low loss and flat dispersion Kagome photonic crystal fiber in the terahertz regime

NASA Astrophysics Data System (ADS)

Rana, Sohel; Rakin, Adnan Siraj; Hasan, Md. Rabiul; Reza, Md. Salim; Leonhardt, Rainer; Abbott, Derek; Subbaraman, Harish

2018-03-01

A novel fiber design based on hexagonal shaped holes incorporated within the core of a Kagome lattice photonic crystal fiber (PCF) is presented. The modal properties of the proposed fiber are evaluated by using a finite element method (FEM) with a perfectly matched layer as boundary condition. Simulation results exhibit an ultra-low effective material loss (EML) of 0.029 cm-1 at an operating frequency of 1.3 THz with an optimized core diameter of 300 μm. A positive, low, and flat dispersion of 0.49 ± 0.06 ps/THz/cm is obtained within a broad frequency range from 1.00 to 1.76 THz. Other essential guiding features of the designed fiber such as power fraction and confinement loss are studied. The fabrication possibilities are also investigated to demonstrate feasibility for a wide range of terahertz applications.

Terahertz Frequency-Domain Spectroscopy of Low-Pressure Acetonitrile Gas by a Photomixing Terahertz Synthesizer Referenced to Dual Optical Frequency Combs

NASA Astrophysics Data System (ADS)

Hsieh, Yi-Da; Kimura, Hiroto; Hayashi, Kenta; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Yasui, Takeshi

2016-09-01

A terahertz (THz) frequency synthesizer based on photomixing of two near-infrared lasers with a sub-THz to THz frequency offset is a powerful tool for spectroscopy of polar gas molecules due to its broad spectral coverage; however, its frequency accuracy and resolution are relatively low. To tune the output frequency continuously and widely while maintaining its traceability to a frequency standard, we developed a photomixing THz synthesizer phase-locked to dual optical frequency combs (OFCs). While the phase-locking to dual OFCs ensured continuous tuning within a spectral range of 120 GHz, in addition to the traceability to the frequency standard, use of a broadband uni-traveling carrier photodiode for photomixing enabled the generation of CW-THz radiation within a frequency range from 0.2 to 1.5 THz. We demonstrated THz frequency-domain spectroscopy of gas-phase acetonitrile CH3CN and its isotope CH3 13CN in the frequency range of 0.600-0.720 THz using this THz synthesizer. Their rotational transitions were assigned with a frequency accuracy of 8.42 × 10-8 and a frequency resolution of 520 kHz. Furthermore, the concentration of the CH3CN gas at 20 Pa was determined to be (5.41 ± 0.05) × 1014 molecules/cm3 by curve fitting analysis of the measured absorbance spectrum, and the mixture ratio of the mixed CH3CN/CH3 13CN gas was determined to be 1:2.26 with a gas concentration of 1014-1015 molecules/cm3. The developed THz synthesizer is highly promising for high-precision THz-FDS of low-pressure molecular gases and will enable the qualitative and quantitative analyses of multiple gases.

Real-time spectroscopic sensing using a widely tunable external cavity-QCL with MOEMS diffraction grating

NASA Astrophysics Data System (ADS)

Ostendorf, Ralf; Butschek, Lorenz; Merten, André; Grahmann, Jan; Jarvis, Jan; Hugger, Stefan; Fuchs, Frank; Wagner, Joachim

2016-02-01

We present spectroscopic measurements performed with an EC-QCL combining a broadly tunable quantum cascade laser chip with a tuning range of more than 300 cm-1 and a resonantly driven MOEMS scanner with an integrated diffraction grating for wavelength selection in Littrow configuration. The grating geometry was optimized to provide high diffraction efficiency over the wide tuning range of the QCL, thus assuring high power density and high spectral resolution in the MIR range. The MOEMS scanner has a resonance frequency of 1 kHz, hence allowing for two full wavelength scans, one up and the other downwards, within 1 ms. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets as well as on gaseous samples of carbon monoxide. For the latter one, a large portion of the characteristic CO absorption band containing several absorption lines in the range of 2070 cm-1 to 2280 cm-1 can be monitored in real-time.

Shortwave quantum cascade laser frequency comb for multi-heterodyne spectroscopy

NASA Astrophysics Data System (ADS)

Lu, Q. Y.; Manna, S.; Wu, D. H.; Slivken, S.; Razeghi, M.

2018-04-01

Quantum cascade lasers (QCLs) are versatile light sources with tailorable emitting wavelengths covering the mid-infrared and terahertz spectral ranges. When the dispersion is minimized, frequency combs can be directly emitted from quantum cascade lasers via four-wave mixing. To date, most of the mid-infrared quantum cascade laser combs are operational in a narrow wavelength range wherein the QCL dispersion is minimal. In this work, we address the issue of very high dispersion for shortwave QCLs and demonstrate 1-W dispersion compensated shortwave QCL frequency combs at λ ˜ 5.0 μm, spanning a spectral range of 100 cm-1. The multi-heterodyne spectrum exhibits 95 equally spaced frequency comb lines, indicating that the shortwave QCL combs are ideal candidates for high-speed high-resolution spectroscopy.

[Measurements of IR absorption across section and spectrum simulation of lewisite].

PubMed

Zhang, Yuan-peng; Wang, Hai-tao; Zhang, Lin; Yang, Liu; Guo, Xiao-di; Bai, Yun; Sun, Hao

2015-02-01

The vapor infrared transmission spectra of varied concentration of lewisite-1 were measured by a long-path FT-IR spectrometer, and its characteristic frequencies are 814, 930, 1563 cm(-1); their infrared absorption cross section (a) were determined using Beer-Lambert law. The corresponding sigma values are 3.89 +/- 0.01, 1.43 +/- 0.06, 4.47 +/- 0.05 ( X 10(-20) cm2 x molecule(-1)). Two little teeny peaks, 1158, 1288 cm(-1) were found in the measured spectra. Density Functional Theory (DFT) was applied to calculated the infrared spectra of lewisite-1, -2, -3 on a b3lyp/6-311+g(d, p) level by Gauss09 package. The vibration modes were assigned by Gaussview5. 08. The calculated spectra and experimental spectra are in good agreement with each other in 600-1600 cm(-1) range, for the Person's r is 0.9991. The calculated spectra also showed three characteristic frequencies (293, 360, 374 cm(-1)) related to As atom. 0.977 was a scaling factor we determined for lewisite-1 through least-square error and its performance to scale lewisite-1, -2, -3 was acceptable. The results of this work are useful for monitoring environmental atmospheric concentrations of lewisite.

Unified Description of the Optical Phonon Modes inN-Layer MoTe2

NASA Astrophysics Data System (ADS)

Froehlicher, Guillaume; Lorchat, Etienne; Fernique, François; Joshi, Chaitanya; Molina-Sánchez, Alejandro; Wirtz, Ludger; Berciaud, Stéphane

2015-10-01

$N$-layer transition metal dichalcogenides provide a unique platform to investigate the evolution of the physical properties between the bulk (three dimensional) and monolayer (quasi two-dimensional) limits. Here, using high-resolution micro-Raman spectroscopy, we report a unified experimental description of the $\\Gamma$-point optical phonons in $N$-layer $2H$-molybdenum ditelluride (MoTe$_2$). We observe a series of $N$-dependent low-frequency interlayer shear and breathing modes (below $40~\\rm cm^{-1}$, denoted LSM and LBM) and well-defined Davydov splittings of the mid-frequency modes (in the range $100-200~\\rm cm^{-1}$, denoted iX and oX), which solely involve displacements of the chalcogen atoms. In contrast, the high-frequency modes (in the range $200-300~\\rm cm^{-1}$, denoted iMX and oMX), arising from displacements of both the metal and chalcogen atoms, exhibit considerably reduced splittings. The manifold of phonon modes associated with the in-plane and out-of-plane displacements are quantitatively described by a force constant model, including interactions up to the second nearest neighbor and surface effects as fitting parameters. The splittings for the iX and oX modes observed in $N$-layer crystals are directly correlated to the corresponding bulk Davydov splittings between the $E_{2u}/E_{1g}$ and $B_{1u}/A_{1g}$ modes, respectively, and provide a measurement of the frequencies of the bulk silent $E_{2u}$ and $B_{1u}$ optical phonon modes. Our analysis could readily be generalized to other layered crystals.

Complex permeability and permittivity spectra of percolated Fe50Co50/Cu granular composites

NASA Astrophysics Data System (ADS)

Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2017-11-01

Complex permeability and permittivity spectra of Fe50Co50/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. At low Cu particle content, the Fe50Co50/Cu hybrid sample shows a metallic percolative property with the electrical conductivity value about 0.1 S/cm. However, the low frequency plasmonic (LFP) state with negative permittivity (ENG) spectrum was not observed. An abrupt increase of electrical conductivity takes place at 14 to 16 vol% Cu content where the conductivity becomes above 1.0 S/cm; the Fe50Co50/Cu composite possesses the LFP state with negative permittivity spectrum below a characteristic frequency. The complex permittivity spectra in the LFP state can be described by the Drude model. Magnetic permeability spectrum in the LFP state showed a broad frequency dispersion above 10 MHz; a small negative permeability (MNG) dispersion was observed from 2 to 10 GHz. Consequently, the double negative (DNG) electromagnetic property with MNG and ENG was realized in the microwave range for the Cu content of 26 and 30 vol%.

Anti-inflammatory effects of low-intensity extremely high-frequency electromagnetic radiation: frequency and power dependence.

PubMed

Gapeyev, A B; Mikhailik, E N; Chemeris, N K

2008-04-01

Using a model of acute zymosan-induced footpad edema in NMRI mice, the frequency and power dependence of anti-inflammatory effect of low-intensity extremely high-frequency electromagnetic radiation (EHF EMR) was found. Single whole-body exposure of animals to EHF EMR at the intensity of 0.1 mW/cm(2) for 20 min at 1 h after zymosan injection reduced both the footpad edema and local hyperthermia on average by 20% at the frequencies of 42.2, 51.8, and 65 GHz. Some other frequencies from the frequency range of 37.5-70 GHz were less effective or not effective at all. At fixed frequency of 42.2 GHz and intensity of 0.1 mW/cm(2), the effect had bell-shaped dependence on exposure duration with a maximum at 20-40 min. Reduction of intensity to 0.01 mW/cm(2) resulted in a change of the effect dependence on exposure duration to a linear one. Combined action of cyclooxygenase inhibitor sodium diclofenac and EHF EMR exposure caused a partial additive effect of decrease in footpad edema. Combined action of antihistamine clemastine and EHF EMR exposure caused a dose-dependent abolishment of the anti-inflammatory effect of EHF EMR. The results obtained suggest that arachidonic acid metabolites and histamine are involved in realization of anti-inflammatory effects of low-intensity EHF EMR. (c) 2007 Wiley-Liss, Inc.

Speed-dependent Voigt lineshape parameter database from dual frequency comb measurements up to 1305 K. Part I: Pure H2O absorption, 6801-7188 cm-1

NASA Astrophysics Data System (ADS)

Schroeder, Paul J.; Cich, Matthew J.; Yang, Jinyu; Giorgetta, Fabrizio R.; Swann, William C.; Coddington, Ian; Newbury, Nathan R.; Drouin, Brian J.; Rieker, Gregory B.

2018-05-01

We measure speed-dependent Voigt lineshape parameters with temperature-dependence exponents for several hundred spectroscopic features of pure water spanning 6801-7188 cm-1. The parameters are extracted from broad bandwidth, high-resolution dual frequency comb absorption spectra with multispectrum fitting techniques. The data encompass 25 spectra ranging from 296 K to 1305 K and 1 to 17 Torr of pure water vapor. We present the extracted parameters, compare them to published data, and present speed-dependence, self-shift, and self-broadening temperature-dependent parameters for the first time. Lineshape data is extracted using a quadratic speed-dependent Voigt profile and a single self-broadening power law temperature-dependence exponent over the entire temperature range. The results represent an important step toward a new high-temperature database using advanced lineshape profiles.

UHF coplanar-slot antenna for aircraft-to-satellite data communications

NASA Technical Reports Server (NTRS)

Myhre, R. W.

1979-01-01

A lightweight low drag coplanar slot antenna was developed for use on commercial jet aircraft that will provide upper hemisphere coverage in the UHF band at frequencies of 402 and 468 MHz is described. The antenna is designed to transmit meteorological data from wide body jet aircraft to ground users via synchronous meteorological data relay satellites. The low profile antenna (23.5 cm wide by 38.1 cm long slot by 1.9 cm high) is a conformal antenna utilizing the coplanar approach with the advantages of broad frequency bandwidth and improved electrical integrity over wide range of temperature. The antenna is circular polarized, has anon axis gain of near +2.5 dB, and a HPBW greater than 90 deg. Areas discussed include antenna design, radiation characteristics, flight testing, and system performance.

Noise and range considerations for close-range radar sensing of life signs underwater.

PubMed

Hafner, Noah; Lubecke, Victor

2011-01-01

Close-range underwater sensing of motion-based life signs can be performed with low power Doppler radar and ultrasound techniques. Corresponding noise and range performance trade-offs are examined here, with regard to choice of frequency and technology. The frequency range examined includes part of the UHF and microwave spectrum. Underwater detection of motion by radar in freshwater and saltwater are demonstrated. Radar measurements exhibited reduced susceptibility to noise as compared to ultrasound. While higher frequency radar exhibited better signal to noise ratio, propagation was superior for lower frequencies. Radar detection of motion through saltwater was also demonstrated at restricted ranges (1-2 cm) with low power transmission (10 dBm). The results facilitate the establishment of guidelines for optimal choice in technology for the underwater measurement motion-based life signs, with respect to trade offs involving range and noise.

Electromigration analysis of solder joints under ac load: A mean time to failure model

NASA Astrophysics Data System (ADS)

Yao, Wei; Basaran, Cemal

2012-03-01

In this study, alternating current (ac) electromigration (EM) degradation simulations were carried out for Sn95.5%Ag4.0%Cu0.5 (SAC405- by weight) solder joints. Mass transport analysis was conducted with viscoplastic material properties for quantifying damage mechanism in solder joints. Square, sine, and triangle current wave forms ac were used as input signals. dc and pulsed dc (PDC) electromigration analysis were conducted for comparison purposes. The maximum current density ranged from 2.2×106A/cm2 to 5.0×106A/cm2, frequency ranged from 0.05 Hz to 5 Hz with ambient temperature varying from 350 K to 450 K. Because the room temperature is nearly two-thirds of SAC solder joint's melting point on absolute temperature scale (494.15 K), viscoplastic material model is essential. Entropy based damage evolution model was used to investigate mean time to failure (MTF) behavior of solder joints subjected to ac stressing. It was observed that MTF was inversely proportional to ambient temperature T1.1 in Celsius and also inversely proportional to current density j0.27 in A/cm2. Higher frequency will lead to a shorter lifetime with in the frequency range we studied, and a relationship is proposed as MTF∝f-0.41. Lifetime of a solder joint subjected to ac is longer compared with dc and PDC loading conditions. By introducing frequency, ambient temperature and current density dependency terms, a modified MTTF equation was proposed for solder joints subjected to ac current stressing.

Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

NASA Astrophysics Data System (ADS)

Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

2016-10-01

The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (<0.1 cm-1) components, however, are markedly influenced by sugar concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

VizieR Online Data Catalog: A variationally computed hot NH3 line list - BYTe (Yurchenko+, 2011)

NASA Astrophysics Data System (ADS)

Yurchenko, S. N.; Barber, R. J.; Tennyson, J.

2010-11-01

We present 'BYTe' a comprehensive 'hot' line list of ro-vibrational transitions of ammonia, 14NH3, in its ground electronic state. It comprises 1,138,323,351 transitions with frequencies up to 12,000cm-1^, constructed from 1,373,897 energy levels below 18,000cm-1^ having J values less than 37. The line list is sufficiently accurate and complete for high resolution spectroscopy and atmospheric modelling of astrophysical objects, including brown dwarfs and exoplanets at temperatures up to 1,500K. The data are in two parts. The first, nh3_0-41.dat contains a list of 4,167,360 rovibrational states, ordered by J (max= 41), symmetry block and energy (in cm-1^). Only one third of the states (1,373,897) are within the parameters used for generating transitions (see above), but all the states are required for computing temperature-dependent partition functions. Each state is labelled with: seven normal mode vibrational quantum numbers; three rotational quantum numbers and the total symmetry quantum number, Gamma. In addition there are six local mode vibrational numbers and a local mode vibrational symmetry quantum numbers, which we include because the basis set used in our calculations is expressed in terms of these local mode quantum numbers. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm-1^ frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1^. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, sp_byte.f90 which may be used to generate synthetic spectra (see sp_byte.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Three sample input files for use with sp_byte.f90 are supplied: "stick300.in", "gauss300.in", and "sp08900.in" (generates a spectrum for 8900-9000cm-1^). (126 data files).

A novel Zeonex based oligoporous-core photonic crystal fiber for polarization preserving terahertz applications

NASA Astrophysics Data System (ADS)

Islam, Md. Saiful; Sultana, Jakeya; Dinovitser, Alex; Ng, Brian W.-H.; Abbott, Derek

2018-04-01

A novel waveguide consisting of oligo-porous core photonic crystal fiber (PCF) with a kagome lattice cladding has been designed for highly birefringent and near zero dispersion flattened applications of terahertz waves. The wave guiding properties of the designed PCF including birefringence, dispersion, effective material loss (EML), core power fraction, confinement loss, and modal effective area are investigated using a full vector Finite Element Method (FEM) with Perfectly Matched Layer (PML) absorbing boundary condition. Simulation results demonstrate that an ultra-high birefringence of 0.079, low EML of 0.05 cm-1, higher core power fraction of 44% and negligible confinement loss of 7 . 24 × 10-7 cm-1 can be achieved at 1 THz. Furthermore, for the y-polarization mode a near zero flattened dispersion of 0 . 49 ± 0 . 05 ps/THz/cm is achieved within a broad frequency range of 0.8-1.7 THz. The fabrication of the proposed fiber is feasible using the existing fabrication technology. Due to favorable wave-guiding properties, the proposed fiber has potential for terahertz imaging, sensing and polarization maintaining applications in the terahertz frequency range.

Effects of high-frequency near-infrared diode laser irradiation on the proliferation and migration of mouse calvarial osteoblasts.

PubMed

Kunimatsu, Ryo; Gunji, Hidemi; Tsuka, Yuji; Yoshimi, Yuki; Awada, Tetsuya; Sumi, Keisuke; Nakajima, Kengo; Kimura, Aya; Hiraki, Tomoka; Abe, Takaharu; Naoto, Hirose; Yanoshita, Makoto; Tanimoto, Kotaro

2018-07-01

Laser irradiation activates a range of cellular processes and can promote tissue repair. Here, we examined the effects of high-frequency near-infrared (NIR) diode laser irradiation on the proliferation and migration of mouse calvarial osteoblastic cells (MC3T3-E1). MC3T3-E1 cells were cultured and exposed to high-frequency (30 kHz) 910-nm diode laser irradiation at a dose of 0, 1.42, 2.85, 5.7, or 17.1 J/cm 2 . Cell proliferation was evaluated with BrdU and ATP concentration assays. Cell migration was analyzed by quantitative assessment of wound healing using the Incucyt ® ZOOM system. In addition, phosphorylation of mitogen-activated protein kinase (MAPK) family members including p38 mitogen-activated protein kinase (p38), stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK), and extracellular signal-regulated protein kinase (ERK)1/2) after laser irradiation was examined with western blotting. Compared to the control, cell proliferation was significantly increased by laser irradiation at a dose of 2.85, 5.7, or 17.1 J/cm 2 . Laser irradiation at a dose of 2.85 J/cm 2 induced MC3T3-E1 cells to migrate more rapidly than non-irradiated control cells. Irradiation with the high-frequency 910-nm diode laser at a dose of 2.85 J/cm 2 induced phosphorylation of MAPK/ERK1/2 15 and 30 min later. However, phosphorylation of p38 MAPK and SAPK/JNK was not changed by NIR diode laser irradiation at a dose of 2.85 J/cm 2 . Irradiation with a high-frequency NIR diode laser increased cell division and migration of MT3T3-E1 cells, possibly via MAPK/ERK signaling. These observations may be important for enhancing proliferation and migration of osteoblasts to improve regeneration of bone tissues.

Observation of nuclear spin species conversion inside the 1593 cm -1 structure of H 2O trapped in argon matrices: Nitrogen impurities and the H 2O:N 2 complex

NASA Astrophysics Data System (ADS)

Pardanaud, Cédric; Vasserot, Anne-Marie; Michaut, Xavier; Abouaf-Marguin, L.

2008-02-01

We have investigated, at high resolution (0.03 cm -1), the 1593 cm -1 structure observed in the IR absorption spectrum of water trapped in solid argon doped with nitrogen. It exhibits a doublet at 1592.59 ± 0.05 and 1593.08 ± 0.05 cm -1 and a line centered at 1592.93 ± 0.05 cm -1. The central component, which increases irreversibly upon annealing and when the concentration is increased, is due to the proton acceptor submolecule of the H 2O dimer, as mentioned in the literature. The doublet is assigned to the H 2O:N 2 complex. After a fast cooling of the sample from 20 to 4 K, the low frequency line of the doublet decreases with time and the high frequency one increases, the total integrated absorption increasing slightly. The ratio of the integrated intensities between the low frequency component and the high frequency one reaches a constant limit of 0.5 ± 0.1 at infinite time. This time behavior, perfectly exponential with a time constant τ of about 680 min, is reproducible. As the nitrogen molecule cannot rotate in an argon substitutional site, and as the H 2O submolecule seems to preserve somewhat its identity, this is interpreted as nuclear spin species conversion between ortho and para states of the H 2O submolecule within the complex. The order of magnitude of the energy difference between the ortho and para lowest levels, about 5 cm -1, is too weak to imply any, even very hindered, rotational motion of H 2O, but it could be the energy range of a tunneling effect. When the temperature is increased, the two components coalesce at 25 K into a single symmetrical line pointing at 1593.3 cm -1 and the conversion time shortens dramatically. An Arrhenius plot leads to a weak activation energy of the conversion process (about 30 cm -1). A possible geometry of the complex in solid argon, different from the gas phase one, is proposed.

A new low voltage level-shifted FVF current mirror with enhanced bandwidth and output resistance

NASA Astrophysics Data System (ADS)

Aggarwal, Bhawna; Gupta, Maneesha; Gupta, Anil Kumar; Sangal, Ankur

2016-10-01

This paper proposes a new high-performance level-shifted flipped voltage follower (LSFVF) based low-voltage current mirror (CM). The proposed CM utilises the low-supply voltage and low-input resistance characteristics of a flipped voltage follower (FVF) CM. In the proposed CM, level-shifting configuration is used to obtain a wide operating current range and resistive compensation technique is employed to increase the operating bandwidth. The peaking in frequency response is reduced by using an additional large MOSFET. Moreover, a very high output resistance (in GΩ range) along with low-current transfer error is achieved through super-cascode configuration for a wide current range (0-440 µA). Small signal analysis is carried out to show the improvements achieved at each step. The proposed CM is simulated by Mentor Graphics Eldospice in TSMC 0.18 µm CMOS, BSIM3 and Level 53 technology. In the proposed CM, a bandwidth of 6.1799 GHz, 1% settling time of 0.719 ns, input and output resistances of 21.43 Ω and 1.14 GΩ, respectively, are obtained with a single supply voltage of 1 V. The layout of the proposed CM has been designed and post-layout simulation results have been shown. The post-layout simulation results for Monte Carlo and temperature analysis have also been included to show the reliability of the CM against the variations in process parameters and temperature changes.

The IR Absorption Spectra of Aqueous Solutions of Dimethylsulfoxide over the Frequency Range 50-300 cm-1 and the Mobility of Water Molecules

NASA Astrophysics Data System (ADS)

Klemenkova, Z. S.; Novskova, T. A.; Lyashchenko, A. K.

2008-04-01

The IR absorption spectra of aqueous solutions of dimethylsulfoxide (DMSO) with concentrations from 100% H2O to 100% DMSO were recorded over the frequency range 50-500 cm-1. The absorption spectra were described using the theoretical scheme of hindered rotators. A model was developed according to which orientation relaxation in solution was related to separate rotations of H2O and DMSO molecules through fixed small and (or) large angles in a unified network of H-bonds consisting of several subsystems ordered to various degrees. The calculated absorption spectra were in agreement with the experimental data in the far IR region. Elementary motions of molecules were found to slow down in the passage from pure dimethylsulfoxide to its aqueous solutions. The special features of the hydrophilic and hydrophobic hydration of DMSO polar and nonpolar groups were considered.

High frequency electroporation efficiency is under control of membrane capacitive charging and voltage potential relaxation.

PubMed

Novickij, Vitalij; Ruzgys, Paulius; Grainys, Audrius; Šatkauskas, Saulius

2018-02-01

The study presents the proof of concept for a possibility to achieve a better electroporation in the MHz pulse repetition frequency (PRF) region compared to the conventional low frequency protocols. The 200ns×10 pulses bursts of 10-14kV/cm have been used to permeabilize Chinese hamster ovary (CHO) cells in a wide range (1Hz-1MHz) of PRF. The permeabilization efficiency was evaluated using fluorescent dye assay (propidium iodide) and flow cytometry. It was determined that a threshold PRF exists when the relaxation of the cell transmembrane potential is longer than the delay between the consequent pulses, which results in accumulation of the charge on the membrane. For the CHO cells and 0.1S/m electroporation medium, this phenomenon is detectable in the 0.5-1MHz range. It was shown that the PRF is an important parameter that could be used for flexible control of electroporation efficiency in the high frequency range. Copyright © 2017 Elsevier B.V. All rights reserved.

VizieR Online Data Catalog: CH4 and hot methane continuum hybrid line list (Yurchenko+, 2017)

NASA Astrophysics Data System (ADS)

Yurchenko, S. N.; Amundsen, D. S.; Tennyson, J.; Waldmann, I. P.

2017-07-01

The states file ch4_e50.dat contains a list of rovibrational states. Each state is labelled with: nine normal mode vibrational quantum numbers and the vibrational symmetry; three rotational quantum numbers including the total angular momentum J and rotational symmetry; the total symmetry quantum number Gamma and the running number in the same (J,Gamma) block. In addition there are nine local mode vibrational numbers and the largest coefficient used to assign the state in question. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The total degeneracy is also given to facilitate the intensity calculations. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm-1 frequency range. These transition files t_*.dat contain the strong methane lines lines consisting of three columns: the reference number in the energy file of the upper state, that of the lower state, the Einstein A coefficient of the transition and the transition wavenumber. These entries are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the t-00500.dat file contains all the transitions in the frequency range 500-600cm-1. 19 histograms xYYYYK.dat files contain CH4_ super-lines representing the continuum computed at the temperature T=YYYYK using R=1000000 (7090081 super-lines each) covering the wavenumber range from 10 to 12000cm-1. The energy file, the transitions files and the histograms files are bzipped, and need to be extracted before use. The pressure broadening parameters used in the calculations are listed in broad.dat. A programme ExoCross to generate synthetic spectra from these line lists can be obtained at www.exomol.com. (4 data files).

Transport and charging mechanisms in Ta2O5 thin films for capacitive RF MEMS switches application

NASA Astrophysics Data System (ADS)

Persano, A.; Quaranta, F.; Martucci, M. C.; Cretı, P.; Siciliano, P.; Cola, A.

2010-06-01

The potential of sputtered Ta2O5 thin films to be used as dielectric layers in capacitive radio frequency microelectromechanical system switches is evaluated by investigating two factors of crucial importance for the performance of these devices which are the transport mechanisms and the charging effects in the dielectric layer. We find that Ta2O5 films show good electrical and dielectrical properties for the considered application in terms of a low leakage current density of 4 nA/cm2 for E =1 MV/cm, a high breakdown field of 4 MV/cm and a high dielectric constant of 32. For electric fields lower than 1 MV/cm the conduction mechanism is found to be variable-range hopping in the temperature range 300-400 K, while nearest-neighbor hopping is observed at higher temperatures. For fields in the range 1-4 MV/cm Poole-Frenkel becomes the dominant conduction mechanism. Current and capacitance transients used to investigate the charging effects show a decay which is well described by the stretched-exponential law, thus providing further insights on capture and emission processes.

Comparative structural analysis of cytidine, ethenocytidine and their protonated salts. II. IR spectral studies.

PubMed Central

Krzyzosiak, W; Jaskólski, M; Sierzputowska-Gracz, H; Wiewiórowski, M

1982-01-01

The IR spectra of crystalline cytidine (Cyd), ethenocytidine (epsilon Cyd), and their hydrochlorides (Cyd-Hcl and epsilon CyD-HCl) have been analyzed to determine the spectroscopic manifestations of the structural differences that were previously established for these nucleosides from X-ray studies. O,N-Deuteration of the samples turned out to be a successful approach to obtaining interpretable spectra. The analysis was carried out in three frequency ranges: (i) The 2600-1900 cm-1 range originating from the vO-D and VN-D vibrations. All intermolecular hydrogen bonds could be recognized here. The positions of the individual vO-D (vN-D) bands were correlated with the geometrical delta HB parameters presenting the strengths of hydrogen bonds in which these groups act as donors (ii) The 1750-1500 cm-1 region originating from the stretching vibrations of double bonds. All absorption bands in this region were interpreted in terms of electronic structures of the base fragments. (iii) The region of the C-H stretching vibrations of the base fragments (3200-3000 cm-1) and sugar moieties (3000-2800 cm-1). The Csp2-H vibrations also reflect the electronic structures of the base fragments, whereas the vCsp-H frequencies seem to be sensitive to etheno-bridging and to the presence of an intramolecular C6-H...05' hydrogen bond. PMID:7079184

High quality factor graphene varactors for wireless sensing applications

NASA Astrophysics Data System (ADS)

Koester, Steven J.

2011-10-01

A graphene wireless sensor concept is described. By utilizing thin gate dielectrics, the capacitance in a metal-insulator-graphene structure varies with charge concentration through the quantum capacitance effect. Simulations using realistic structural and transport parameters predict quality factors, Q, >60 at 1 GHz. When placed in series with an ideal inductor, a resonant frequency tuning ratio of 25% (54%) is predicted for sense charge densities ranging from 0.32 to 1.6 μC/cm2 at an equivalent oxide thickness of 2.0 nm (0.5 nm). The resonant frequency has a temperature sensitivity, df/dT, less than 0.025%/K for sense charge densities >0.32 μC/cm2.

Analysis of electronic parameters and frequency-dependent properties of Au/NiO/ n-GaN heterojunctions

NASA Astrophysics Data System (ADS)

Reddy, Varra Niteesh; Padma, R.; Gunasekhar, K. R.

2018-01-01

The electrical and frequency-dependent properties of ten Au/NiO/ n-GaN heterojunctions fabricated with similar conditions are assessed by I-V, C-V, and G-V measurement methods. In addition, C-f and G-f measurements are conducted in the frequency range of 1 kHz-1 MHz. The electronic parameters are changed from junction to junction even if they are fabricated in the similar way. The calculated barrier height and ideality factor values are fitted by the Gaussian distribution function. Statistical analysis of the data provides the mean barrier height and ideality factor values of 0.84 eV and 2.70 for the heterojunction. Besides, the mean barrier height ( V b), donor concentration ( N d), space charge layer width ( W D), and Fermi level ( E F) are determined from the C-V data and the corresponding values are 1.30 eV, 2.00 × 1017 cm-3, 8.222 × 10-6 cm, and 0.018 eV, respectively. The interface state density ( N SS) and relaxation time (τ) are assessed from C-f and G-f measurements. Moreover, the dielectric constant ( ɛ'), dielectric loss ( ɛ″), tangent loss (tan δ), and electrical conductivity ( σ ac) are determined from C-f and G-f data in the frequency range of 1 kHz-1 MHz with various biases (0.1-0.6 V). ɛ' and ɛ″ are decreased with increasing frequency.

High accuracy line positions of the ν1 fundamental band of 14N216O

NASA Astrophysics Data System (ADS)

AlSaif, Bidoor; Lamperti, Marco; Gatti, Davide; Laporta, Paolo; Fermann, Martin; Farooq, Aamir; Lyulin, Oleg; Campargue, Alain; Marangoni, Marco

2018-05-01

The ν1 fundamental band of N2O is examined by a novel spectrometer that relies on the frequency locking of an external-cavity quantum cascade laser around 7.8 μm to a near-infrared Tm:based frequency comb at 1.9 μm. Due to the large tunability, nearly 70 lines in the 1240-1310 cm-1 range of the ν1 band of N2O, from P(40) to R(31), are for the first time measured with an absolute frequency calibration and an uncertainty from 62 to 180 kHz, depending on the line. Accurate values of the spectroscopic constants of the upper state are derived from a fit of the line centers (rms ≈ 4.8 × 10-6 cm-1 or 144 kHz). The ν1 transitions presently measured in a Doppler regime validate high accuracy predictions based on sub-Doppler measurements of the ν3 and ν3-ν1 transitions.

Electronic spectroscopy of UO(2)Cl(2) isolated in solid Ar.

PubMed

Jin, Jin; Gondalia, Raj; Heaven, Michael C

2009-11-12

Laser-induced fluorescence spectra have been recorded for uranyl chloride isolated in a solid Ar matrix. Pulsed excitation was examined using a XeCl excimer laser (308 nm) and a dye laser operating in the 19500-27500 cm-1 range. Several absorption and emission band systems were observed. The emission spectra were characterized by a nearly harmonic vibrational progression with a frequency of 840 cm-1 starting at 20323 cm-1. The electronic absorption spectra were dominated by five harmonic vibrational progressions with frequencies of approximately 710 cm-1. Comparisons with theoretical calculations indicate that all of the transitions observed were associated with the UO2+2 subunit. They involved the promotion of an electron from a bonding orbital to the metal-centered 5f(delta) and 5f(phi) orbitals. Band origins and vibrational constants for five excited states were obtained. Fluorescence was observed from the lowest-energy excited state alone, regardless of the excitation wavelength. The decay curve was found to be biexponential, with characteristic decay lifetimes of 50 and 260 micros.

Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

NASA Astrophysics Data System (ADS)

Maaroufi, A.; Oabi, O.; Lucas, B.

2016-07-01

The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO-55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator - semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10-1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10-8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson-Cole model, and an account of the interpretation of results is given.

Vibrational mode frequencies of H2S and H2O adsorbed on Ge(0 0 1)-(2 × 1) surfaces

NASA Astrophysics Data System (ADS)

Hartnett, M.; Fahy, S.

2015-02-01

The equilibrium geometry and vibrational modes of H2S and H2O-terminated Ge(0 0 1)-(2 × 1) surfaces are calculated in a supercell approach using first-principles density functional theory in the local density (LDA), generalized gradient (GGA) approximations and van der Waals (vdW) interactions. Mode frequencies are found using the frozen phonon method. For the H2S-passivated surface, the calculated frequencies in LDA (GGA) are 2429 cm-1 (2490) for the Hsbnd S stretch mode, 712 cm-1 (706) for the Hsbnd S bond bending mode, 377 cm-1 (36) for the Gesbnd S stretch mode and 328 cm-1 (337) for Hsbnd S wag mode. Frequencies for the H2O passivated surface are 3590 cm-1 (3600) for the Hsbnd O stretch mode, 921 cm-1 (947) for the bending mode, 609 cm-1 (559) for the Gesbnd O stretch, 1995 cm-1 (1991) for the Gesbnd H stretch mode, 498 cm-1 (478) for the Gesbnd H bending mode and 342 cm-1 (336) for the Hsbnd O wag mode. The differences between the functionals including vdW terms and the LDA or GGA are less than the differences between LDA and GGA for the vibrational mode frequencies.

High-resolution vibrational spectroscopy of Pb-OH defects in KMgF3 fluoroperovskite single crystals

NASA Astrophysics Data System (ADS)

Baraldi, A.; Bertoli, P.; Capelletti, R.; Ruffini, A.; Scacco, A.

2001-04-01

High-resolution (0.04 cm-1) Fourier transform infrared spectroscopy in the temperature range 9-300 K is applied to detect and analyze the OH- stretching modes in air grown KMgF3 single crystals, doped with different Pb amounts. In addition to the 3733.7 cm-1 line attributed to the stretching mode of isolated OH-, two main lines peaking at 3550.9 and 3567.7 cm-1 are due to the OH- stretching modes perturbed by neighboring Pb defects. Suitable thermal treatments and isotopic substitutions provide models of the complexes in which OH and Pb are embedded. Lead is recognized as favoring the OH- inclusion into the lattice and causing an inhomogeneous broadening of the IR lines related to the stretching modes of OH- interacting with other cation impurities. Anharmonicity effects are monitored by the weak overtones of the OH-related lines and discussed in the framework of the Morse model for the anharmonic oscillator. The anharmonicity and the Morse parameters, which show a very weak temperature dependence in the 9-300 K range, are very close to those displayed by alkali fluorides. The temperature dependence of the line position and linewidth of the narrow (0.4-0.9 cm-1) Lorentzian-shaped IR lines and of the related overtones is successfully analyzed by means of the single phonon coupling model. The coupled phonon frequencies, evaluated from the fitting, for the Pb-perturbed OH- stretching modes fall in the frequency range of the highest phonon state density of the host matrix.

The effect of MLS laser radiation on cell lipid membrane.

PubMed

Pasternak, Kamila; Wróbel, Dominika; Nowacka, Olga; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

2018-03-14

Authors of numerous publications have proved the therapeutic effect of laser irradiation on biological material, but the mechanisms at cellular and subcellular level are not yet well understood. The aim of this study was to assess the effect of laser radiation emitted by the MLS M1 system (Multiwave Locked System) at two wavelengths (808 nm continuous and 905 nm pulsed) on the stability and fluidity of liposomes with a lipid composition similar to that of human erythrocyte membrane or made of phosphatidylocholine. Liposomes were exposed to low-energy laser radiation at surface densities 195 mW/cm² (frequency 1,000 Hz) and 230 mW/cm² (frequency 2,000 Hz). Different doses of radiation energy in the range 0-15 J were applied. The surface energy density was within the range 0.46 - 4.9 J/cm ². The fluidity and stability of liposomes subjected to such irradiation changed depending on the parameters of radiation used. Since MLS M1 laser radiation, depending on the parameters used, affects fluidity and stability of liposomes with the lipid content similar to erythrocyte membrane, it may also cause structural and functional changes in cell membranes.

VizieR Online Data Catalog: Cyanoacetylene (HC3N) infrared spectrum (Bizzocchi+,

NASA Astrophysics Data System (ADS)

Bizzocchi, L.; Tamassia, F.; Laas, J.; Giuliano, B. M.; Degli Esposti, C.; Dore, L.; Melosso, M.; Cane, E.; Pietropolli Charmet, A.; Muller, H. S. P.; Spahn, H.; Belloche, A.; Caselli, P.; Menten, K. M.; Garrod, R. T.

2018-01-01

A substantial amount of new spectroscopic data of HC3N was col in four laboratories located in Bologna, Italy and in Cologne and Munich, Germany. The infrared spectra in the 450-1100cm-1 range were recorded in Bologna using a Bomem DA3.002 Fourier-transform spectrometer. The resolution was generally 0.004cm-1. New mm-wave spectra in selected frequency intervals between 80 and 400GHz were observed in Bologna using a frequency-modulation (FM) mm-wave spectrometer whose details are reported elsewhere (see, e.g., Bizzocchi+ 2016, J/ApJ/820/L26). Further measurements of the sub-mm-wave spectrum of HC3N in the 200-690GHz frequency range were carried out at the Center for Astrochemical Studies (MPE Garching). The measurements performed in Cologne were carried out with leftover samples from previous studies (Yamada+ 1995ZNatA..50.1179Y ; Thorwirth+ 2000JMoSp.204..133T). Further measurements were made using the Cologne Terahertz Spectrometer. See section 2 for further explanations. (2 data files).

On Short-Time Estimation of Vocal Tract Length from Formant Frequencies

PubMed Central

Lammert, Adam C.; Narayanan, Shrikanth S.

2015-01-01

Vocal tract length is highly variable across speakers and determines many aspects of the acoustic speech signal, making it an essential parameter to consider for explaining behavioral variability. A method for accurate estimation of vocal tract length from formant frequencies would afford normalization of interspeaker variability and facilitate acoustic comparisons across speakers. A framework for considering estimation methods is developed from the basic principles of vocal tract acoustics, and an estimation method is proposed that follows naturally from this framework. The proposed method is evaluated using acoustic characteristics of simulated vocal tracts ranging from 14 to 19 cm in length, as well as real-time magnetic resonance imaging data with synchronous audio from five speakers whose vocal tracts range from 14.5 to 18.0 cm in length. Evaluations show improvements in accuracy over previously proposed methods, with 0.631 and 1.277 cm root mean square error on simulated and human speech data, respectively. Empirical results show that the effectiveness of the proposed method is based on emphasizing higher formant frequencies, which seem less affected by speech articulation. Theoretical predictions of formant sensitivity reinforce this empirical finding. Moreover, theoretical insights are explained regarding the reason for differences in formant sensitivity. PMID:26177102

Optical properties of β-BBO and potential for THz applications

NASA Astrophysics Data System (ADS)

Nikolaev, N. A.; Andreev, Yu. M.; Antsygin, V. D.; Bekker, T. B.; Ezhov, D. M.; Kokh, A. E.; Kokh, K. A.; Lanskii, G. V.; Mamrashev, A. A.; Svetlichnyi, V. A.

2018-01-01

The anisotropy of optical properties of high quality beta barium borate crystal (β-BaB2O4, β-BBO) was studied in the main transparency window by using classic spectroscopic methods and in the range of 0.2 - 2 THz by using THz time-domain spectroscopy. β-BBO crystals were grown by the top-seeded solution technique in a highly resistive furnace with a heat field of 3-fold axis symmetry. At room temperature (RT), absorption coefficient in the maximal transparency window in grown crystals did not exceed 0.05 cm-1. Strong absorption anisotropy was observed in 3 - 5 μm and the THz range. At 1 THz absorption coefficients for e and o wave were, respectively, 7 cm-1 and 21 cm-1 at RT; 2 cm-1 and 10 cm-1 at 81 K. At the most attractive for out-of-door applications range < 0.4 THz the absorption coefficient is found to be very low: below 0.2 cm-1 at RT and 1 cm-1 at 81 K. Refractive indices dispersions measured by THz-TDS were approximated in the form of Sellmeier equations. Birefringence is found quite large for phase matched difference frequency generation (DFG) or down-conversion into the THz range (THz-DFG) under near IR pump at RT and 81 K. Type II (oe-o and eo-o), and type I (ee-e) three wave interactions can be realized at RT. THz-DFG of Nd:YAG laser and KTP OPO can be realized by type II (oe-o) three-wave interaction. For selected spectral ranges of femtosecond Ti:Sapphire laser efficient phase matched and group velocity matched optical rectification can be realized by another two types of three wave interactions. Accounting other well-known attractive physical properties of β-BBO crystal, wide application in THz technique can be forecasted.

Characterization of the ultrasonic attenuation coefficient and its frequency dependence in a polymer gel dosimeter.

PubMed

Crescenti, Remo A; Bamber, Jeffrey C; Partridge, Mike; Bush, Nigel L; Webb, Steve

2007-11-21

Research on polymer-gel dosimetry has been driven by the need for three-dimensional dosimetry, and because alternative dosimeters are unsatisfactory or too slow for that task. Magnetic resonance tomography is currently the most well-developed technique for determining radiation-induced changes in polymer structure, but quick low-cost alternatives remain of significant interest. In previous work, ultrasound attenuation and speed of sound were found to change as a function of absorbed radiation dose in polymer-gel dosimeters, although the investigations were restricted to one ultrasound frequency. Here, the ultrasound attenuation coefficient mu in one polymer gel (MAGIC) was investigated as a function of radiation dose D and as a function of ultrasonic frequency f in a frequency range relevant for imaging dose distributions. The nonlinearity of the frequency dependence was characterized, fitting a power-law model mu = af(b); the fitting parameters were examined for potential use as additional dose readout parameters. In the observed relationship between the attenuation coefficient and dose, the slopes in a quasi-linear dose range from 0 to 30 Gy were found to vary with the gel batch but lie between 0.0222 and 0.0348 dB cm(-1) Gy(-1) at 2.3 MHz, between 0.0447 and 0.0608 dB cm(-1) Gy(-1) at 4.1 MHz and between 0.0663 and 0.0880 dB cm(-1) Gy(-1) at 6.0 MHz. The mean standard deviation of the slope for all samples and frequencies was 15.8%. The slope was greater at higher frequencies, but so were the intra-batch fluctuations and intra-sample standard deviations. Further investigations are required to overcome the observed variability, which was largely associated with the sample preparation technique, before it can be determined whether any frequency is superior to others in terms of accuracy and precision in dose determination. Nevertheless, lower frequencies will allow measurements through larger samples. The fit parameter a of the frequency dependence, describing the attenuation coefficient at 1 MHz, was found to be dose dependent, which is consistent with our expectations, as polymerization is known to be associated with increased absorption of ultrasound. No significant dose dependence was found for the fit parameter b, which describes the nonlinearity with frequency. This is consistent with the increased absorption being due to the introduction of new relaxation processes with characteristic frequencies similar to those of existing processes. The data presented here will help with optimizing the design of future 3D dose-imaging systems using ultrasound methods.

Relationship between P-wave attenuation and water saturation in an homogeneous unconsolidated and partially saturated porous media : An experimental study

NASA Astrophysics Data System (ADS)

Barrière, J.; Sénéchal, P.; Bordes, C.; Perroud, H.

2010-12-01

Nowadays, it is well known that hydrogeological properties of the porous media (porosity, fluid saturation and permeability) can influence seismic properties. The major theory which links hydrogeological and seismic parameters is poroelasticity proposed by Biot (1956) for saturated porous media in a wetting phase fluid. However the Biot relaxation process can't explain the level of attenuation of seismic waves generally measured on field from seismic to sonic frequency range in the case of partially saturated media. Laboratory experiments are necessary to better understand the effects of fluids on the attenuation of waves but few ones are done in the low frequency range (1Hz to 10 kHz) where the wavelength is greater than heterogeneities size. We propose an experimental study to determine the attenuation of propagative P-wave in the sonic frequency range on unconsolidated and partially saturated porous media, typical of near surface hydrogeological media. 10 accelerometers (0.0001-17kHz) and 6 capacitance probes (soil moisture sensors) are placed in a container (107 cm x 34 cm x 35cm) full of homogeneous sand (99% silica). An acoustic source (0 - 20 kHz) generate seismic waves which are recorded by the accelerometers during three cycles of imbibition-drainage (corresponding to a water saturation range from 0% to 95%). Values of attenuation (quality factor Q) versus water saturation and frequency are calculated with the well-known spectral ratio method. The spectrum of each recorded P-wave is obtained by a continuous wavelet transform, more adapted than Fourier transform for a non-stationary signal, such as seismic signal, whose frequency content varies with time. The first analyses show a strong dependence of the quality factor with frequency and water saturation, notably at high water saturation (above 60 %) where the attenuation is maximum. Knowing some important parameters of the studied media such as porosity and permeability, we interpret physically our results in accordance with some recent poroelastic models.

Far Infrared Measurements of Cirrus

NASA Technical Reports Server (NTRS)

Nolt, I. G.; Vanek, M. D.; Tappan, N. D.; Minnis, P.; Alltop, J. L.; Ade, A. R.; Lee, C.; Hamilton, P. A.; Evans, K. F.; Evans, A. H.

1999-01-01

Improved techniques for remote sensing of cirrus are needed to obtain global data for assessing the effect of cirrus in climate change models. Model calculations show that the far infrared/sub-millimeter spectral region is well suited for retrieving cirrus Ice Water Path and particle size parameters. Especially useful cirrus information is obtained at frequencies below 60 cm-1 where single particle scattering dominates over thermal emission for ice particles larger than about 50 m. Earth radiance spectra have been obtained for a range of cloud conditions using an aircraft-based Fourier transform spectrometer. The Far InfraRed Sensor for Cirrus (FIRSC) is a Martin-Puplett interferometer which incorporates a polarizer for the beamsplitter and can be operated in either intensity or linear polarization measurement mode. Two detector channels span 10 to 140 cm-1 with a spectral resolution of 0.1 cm-1; achieving a Noise Equivalent Temperature of approximately 1K at 30 cm-1 in a 4 sec scan. Examples are shown of measured and modeled Earth radiance for a range of cloud conditions from 1998 and 1999 flights.

Study of ELM Density Turbulence using the Upgraded Phase Contrast Imaging on DIII-D

NASA Astrophysics Data System (ADS)

Rost, J. C.; Davis, E. M.; Marinoni, A.; Porkolab, M.; Burrell, K. H.

2016-10-01

Recent studies of the turbulent density fluctuations accompanying ELMs in mixed ELM-type discharges have exploited the expanded wavenumber range of the upgraded Phase Contrast Imaging (PCI) diagnostic. The PCI data demonstrate the difference between the fluctuations generated by Type I ELMs, which are broadband in frequency and wavelength, and those generated by Type III ELMs, which are similar in amplitude but restricted to long wavelengths, suggesting that turbulence may play a significant role in Type I ELM transport. The high frequency response of PCI makes it ideal for studying the ELM-associated density fluctuations, which are observed at frequencies up to several MHz, evolve on time scales of 10s of μs, and persist after the magnetic component of the ELM has decayed away. The upgraded PCI, with independent systems for long and short wavelength detection (k < 5 cm-1 and 1 < k < 30 cm-1 respectively), demonstrated coverage of the full wavenumber range of interest. Work supported in part by the US Department of Energy under DE-FG02-94ER54235, DE-FC02-04ER54698, and DE-FC02-99ER54512.

Surface electrochemistry of CO on reconstructed gold single crystal surfaces studied by infrared reflection absorption spectroscopy and rotating disk electrode.

PubMed

Blizanac, Berislav B; Arenz, Matthias; Ross, Philip N; Marković, Nenad M

2004-08-18

The electrooxidation of CO has been studied on reconstructed gold single-crystal surfaces by a combination of electrochemical (EC) and infrared reflection absorption spectroscopy (IRAS) measurements. Emphasis is placed on relating the vibrational properties of the CO adlayer to the voltammetric and other macroscopic electrochemical responses, including rotating disk electrode measurements of the catalytic activity. The IRAS data show that the C-O stretching frequencies are strongly dependent on the surface orientation and can be observed in the range 1940-1990 cm(-1) for the 3-fold bridging, 2005-2070 cm(-1) for the 2-fold bridging, and 2115-2140 for the terminal position. The most complex CO spectra are found for the Au(110)-(1 x 2) surface, i.e., a band near 1965 cm(-1), with the second, weaker band shifted positively by about 45 cm(-1) and, finally, a weak band near 2115 cm(-1). While the C-O stretching frequencies for a CO adlayer adsorbed on Au(111)-(1 x 23) show nu(CO) bands at 2029-2069 cm(-1) and at 1944-1986 cm(-1), on the Au(100)-"hex" surface a single CO band is observed at 2004-2029 cm(-1). In the "argon-purged" solution, the terminal nu(CO) band on Au(110)-(1 x 2) and the 3-fold bridging band on the Au(111)-(1 x 23) disappear entirely. The IRAS/EC data show that the kinetics of CO oxidation are structure sensitive; i.e., the onset of CO oxidation increases in the order Au(110)-(1 x 2) > or = Au(100)-"hex" > Au(111)-(1 x 23). Possible explanations for the structure sensitivity are discussed.

Dispersion of Dielectric Permittivity in a Nanocrystalline Cellulose-Triglycine Sulfate Composite at Low and Ultralow Frequencies

NASA Astrophysics Data System (ADS)

Thu'o'ng, Nguyen Hoai; Sidorkin, A. S.; Milovidova, S. D.

2018-03-01

The dispersion of dielectric permittivity in nanocrystalline cellulose-triglycine sulfate composites is studied in the range of frequencies from 10-3 to 106 Hz, at temperatures varying from room temperature to the temperature of phase transition in this composite (54°C), in weak electric fields (1 V cm-1). Two behaviors for the dielectric dispersion are identified in the studied frequency range: at ultralow frequencies (10-3-10 Hz), the dispersion is due to Maxwell-Wagner polarization, while at higher frequencies (10-106 Hz), the dispersion is due to the movement of domain walls in the embedded triglycine sulfate crystallites. An additional peak in the temperature-dependent profiles of dielectric permittivity is detected at lower temperatures in freshly prepared samples of the considered composite; we associate it with the presence of residual water in these samples.

Ultrafast mid-infrared spectroscopy by chirped pulse upconversion in 1800-1000cm(-1) region.

PubMed

Zhu, Jingyi; Mathes, Tilo; Stahl, Andreas D; Kennis, John T M; Groot, Marie Louise

2012-05-07

Broadband femtosecond mid-infrared pulses can be converted into the visible spectral region by chirped pulse upconversion. We report here the upconversion of pump probe transient signals in the frequency region below 1800cm(-1), using the nonlinear optical crystal AgGaGeS4, realizing an important expansion of the application range of this method. Experiments were demonstrated with a slab of GaAs, in which the upconverted signals cover a window of 120cm(-1), with 1.5cm(-1) resolution. In experiments on the BLUF photoreceptor Slr1694, signals below 1 milliOD were well resolved after baseline correction. Possibilities for further optimization of the method are discussed. We conclude that this method is an attractive alternative for the traditional MCT arrays used in most mid-infrared pump probe experiments.

Wide Temperature Core Loss Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics

NASA Technical Reports Server (NTRS)

Niedra, Janis M.; Schwarze, Gene E.

1999-01-01

100 kHz core loss properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 C to 150 C, at selected values of B(sub peak). For B-fields not close to saturation, the core loss is not sensitive to temperature in this range and is as low as seen in the best MnZn power ferrites at their optimum temperatures. Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, but at B(sub peak) = 0.1 T and 50 C only. For example, the 100 kHz specific core loss ranged from 50 - 70 mW/cubic cm for the 3 materials, when measured at 0.1 T and 50 C. This very low high frequency core loss, together with near zero saturation magnetostriction and insensitivity to rough handling, makes these amorphous ribbons strong candidates for power magnetics applications in wide temperature aerospace environments.

Radiowaves and Tectonic Dichotomy: Two Sides of One Coin

NASA Astrophysics Data System (ADS)

Kochemasov, G.

The first theorem of the wave planetology states that "Celestial bodies are di- chotomic"[1]. This notion is best demonstrated by modulation of the high frequency orbiting in the Solar system (SS) by the low frequency orbiting the SS in Galaxy. Or- biting frequencies of all bodies in the SS -from 1/8 hours for Phobos to 1/248 years for Pluto - are high comparative to the SS orbiting in Galaxy -about 1/200 000 000 years. Modulation of a high frequency by a low frequency brings about side frequencies at both sides of a high frequency. Earlier we considered only one side of the modula- tion stressing that the lower side frequency in any celestial body can achieve only the fundamental wave and produce related to it inevitable tectonic dichotomy [2]. Now we consider the higher side frequencies and find that they are in the limits of the ra- dio frequencies. Dividing all possible orbiting frequencies of bodies in the SS by the SS orbiting frequency in Galaxy one comes to a range of side frequencies from mi- crowaves to kilometer waves. This finding is rather important as it is well known that all bodies of the SS emit often enigmatic radiowaves. Figuratively, the SS is wrapped by a cloud of crossing radiowaves of various frequencies. Some calculations below show modulation of tectonic granula sizes of some celestial bodies. A granula size is a half of a wavelength which is tied to an orbiting frequency. A scale is the Earth's orbiting period 1 year and the granula size pR/4. The tectonic granula sizes of bodies are proportional to their orbital periods (Theorem 3 [1[). The modulating frequency is 1/200 000 000 years. Jupiter (12 y : 200 000 000 y) pR= (12 : 200 000 000) 3.14°u 71400 km=13.4 m tectonic granula or 26.8 m wavelength. Varying orbital periods and bodies'radia one comes to the following wavelengths. Jupiter-26.8 m, Saturn-56.4 m, Uranus-67 m, Neptune-124 m, Pluto-10.9 m, Sun-1.46 m, Triton-11.4 m (for the cir- cumsolar frequency), 1.84 mm (circumneptunian fr.), Amalthea-4.88 cm (circumsolar fr.), 0.0028 mm (circumjovian fr.), the Moon-5.46 cm (circumsolar fr.), 0.46 cm (cir- cumterrestrial fr.) [3]. This range of frequencies (infrared-kilometer waves) is typical for the SS. Within it surely there are waves of other modulations, harmonics, reso- nances. Extra heat emissions of Amalthea, Io, Triton could be related to microwave and infrared emissions (oscillations). References. [1] Kochemasov G.G.(1999) Geophys. Res. Abstr., v.1, #3.700; [2]Kochemasov G.G. (2000) 32nd Vernadsky-Brown microsymp. on comparative planetology, Abstr.,Moscow, 88-89; [3]Kochemasov G.G. (2001) 34th Vernadsky-Brown microsymp. Topics in comparative planetology, Ab- str., Moscow,(CD-ROM).

Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current.

PubMed

Khymyn, Roman; Lisenkov, Ivan; Tiberkevich, Vasyl; Ivanov, Boris A; Slavin, Andrei

2017-03-06

The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1-2.0 THz with the driving current in the Pt layer from 10 8  A/cm 2 to 10 9  A/cm 2 . The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy.

Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current

NASA Astrophysics Data System (ADS)

Khymyn, Roman; Lisenkov, Ivan; Tiberkevich, Vasyl; Ivanov, Boris A.; Slavin, Andrei

2017-03-01

The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1-2.0 THz with the driving current in the Pt layer from 108 A/cm2 to 109 A/cm2. The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy.

Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection

NASA Technical Reports Server (NTRS)

Matsuoka, N.; Yamaguchi, S.; Nanri, K.; Fujioka, T.; Richter, D.; Tittel, F. K.

2001-01-01

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generated mid-IR at 3 microns with a powers of 2.5 microW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 microns) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm m was estimated.

Global change and relative sea level rise at Venice: what impact in term of flooding

NASA Astrophysics Data System (ADS)

Carbognin, Laura; Teatini, Pietro; Tomasin, Alberto; Tosi, Luigi

2010-11-01

Relative sea level rise (RSLR) due to climate change and geodynamics represents the main threat for the survival of Venice, emerging today only 90 cm above the Northern Adriatic mean sea level (msl). The 25 cm RSLR occurred over the 20th century, consisting of about 12 cm of land subsidence and 13 cm of sea level rise, has increased the flood frequency by more than seven times with severe damages to the urban heritage. Reasonable forecasts of the RSLR expected to the century end must be investigated to assess the suitability of the Mo.S.E. project planned for the city safeguarding, i.e., the closure of the lagoon inlets by mobile barriers. Here we consider three RSLR scenarios as resulting from the past sea level rise recorded in the Northern Adriatic Sea, the IPCC mid-range A1B scenario, and the expected land subsidence. Available sea level measurements show that more than 5 decades are required to compute a meaningful eustatic trend, due to pseudo-cyclic 7-8 year long fluctuations. The period from 1890 to 2007 is characterized by an average rate of 0.12 ± 0.01 cm/year. We demonstrate that linear regression is the most suitable model to represent the eustatic process over these 117 year. Concerning subsidence, at present Venice is sinking due to natural causes at 0.05 cm/year. The RSLR is expected to range between 17 and 53 cm by 2100, and its repercussions in terms of flooding frequency are associated here to each scenario. In particular, the frequency of tides higher than 110 cm, i.e., the value above which the gates would close the lagoon to the sea, will increase from the nowadays 4 times per year to a range between 20 and 250. These projections provide a large spread of possible conditions concerning the survival of Venice, from a moderate nuisance to an intolerable aggression. Hence, complementary solutions to Mo.S.E. may well be investigated.

High-pressure Raman study of vibrational spectra in crystalline acetanilide

NASA Astrophysics Data System (ADS)

Sakai, Masamichi; Kuroda, Noritaka; Nishina, Yuichiro

1993-01-01

We have studied the effect of pressure on the low-frequency lattice modes and the amide-I (N-CO stretching) vibrational modes in crystalline acetanilide (C6H5NHCOCH3) in the temperature range 80-300 K by means of Raman spectroscopy. The Raman intensity of the 1650-cm-1 band, which appears upon cooling, is enhanced by applying pressure. The energy difference between the amide-I phonon (Ag mode) and the 1650-cm-1 bands does not change appreciably under pressure up to at least 4 GPa. These results are analyzed in terms of the self-trapped model in which a single lattice mode couples with the amide-I excitation by taking into account the effect of pressure on the low-frequency lattice modes and on the dipole-dipole interactions associated with the amide-I vibration. A band is observed at 30 cm-1 below the amide-I phonon band at low temperatures with a pressure above ~2 GPa.

The calculated in vitro and in vivo chlorophyll a absorption bandshape.

PubMed Central

Zucchelli, Giuseppe; Jennings, Robert C; Garlaschi, Flavio M; Cinque, Gianfelice; Bassi, Roberto; Cremonesi, Oliviero

2002-01-01

The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck-Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191-200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620-1627) at low temperatures. The calculated bandshapes are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll-protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540-850 cm(-1) occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode (nu < 200 cm(-1)) must be added or else the 262-cm(-1) mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape. PMID:11751324

Experimental Investigation of Cavitation Induced Feedline Instability from an Orifice

NASA Technical Reports Server (NTRS)

Hitt, Matthew A.; Lineberry, David M.; Ahuja, Vineet; Frederick, Robert A,

2012-01-01

This paper details the results of an experimental investigation into the cavitation instabilities created by a circular orifice conducted at the University of Alabama in Huntsville Propulsion Research Center. This experiment was conducted in concert with a computational simulation to serve as a reference point for the simulation. Testing was conducted using liquid nitrogen as a cryogenic propellant simulant. A 1.06 cm diameter thin orifice with a rounded inlet was tested in an approximately 1.25 kg/s flow with inlet pressures ranging from 504.1 kPa to 829.3 kPa. Pressure fluctuations generated by the orifice were measured using a high frequency pressure sensor located 0.64 tube diameters downstream of the orifice. Fast Fourier Transforms were performed on the high frequency data to determine the instability frequency. Shedding resulted in a primary frequency with a cavitation related subharmonic frequency. For this experiment, the cavitation instability ranged from 153 Hz to 275 Hz. Additionally, the strength of the cavitation occur red as a function of cavitation number. At lower cavitation numbers, the strength of the cavitation instability ranged from 2.4 % to 7 % of the inlet pressure. However, at higher cavitation numbers, the strength of the cavitation instability ranged from 0.6 % to 1 % of the inlet pressure.

Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

PubMed

Mohseni, Pedram; Najafi, Khalil; Eliades, Steven J; Wang, Xiaoqin

2005-09-01

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.

Buried Object Detection Method Using Optimum Frequency Range in Extremely Shallow Underground

NASA Astrophysics Data System (ADS)

Sugimoto, Tsuneyoshi; Abe, Touma

2011-07-01

We propose a new detection method for buried objects using the optimum frequency response range of the corresponding vibration velocity. Flat speakers and a scanning laser Doppler vibrometer (SLDV) are used for noncontact acoustic imaging in the extremely shallow underground. The exploration depth depends on the sound pressure, but it is usually less than 10 cm. Styrofoam, wood (silver fir), and acrylic boards of the same size, different size styrofoam boards, a hollow toy duck, a hollow plastic container, a plastic container filled with sand, a hollow steel can and an unglazed pot are used as buried objects which are buried in sand to about 2 cm depth. The imaging procedure of buried objects using the optimum frequency range is given below. First, the standardized difference from the average vibration velocity is calculated for all scan points. Next, using this result, underground images are made using a constant frequency width to search for the frequency response range of the buried object. After choosing an approximate frequency response range, the difference between the average vibration velocity for all points and that for several points that showed a clear response is calculated for the final confirmation of the optimum frequency range. Using this optimum frequency range, we can obtain the clearest image of the buried object. From the experimental results, we confirmed the effectiveness of our proposed method. In particular, a clear image of the buried object was obtained when the SLDV image was unclear.

Raman spectroscopy and lattice dynamics of MgSiO3-perovskite at high pressure

NASA Astrophysics Data System (ADS)

Hemley, R. J.; Cohen, R. E.; Yeganeh-Haeri, A.; Mao, H. K.; Weidner, D. J.; Ito, E.

Vibrational Raman spectra have been obtained for 50 to 100 μm single crystals of MgSiO3 perovskite in situ at high pressure. Seven bands were tracked as a function of pressure to 26 GPa using a diamond-anvil high-pressure cell with rare-gas pressure-transmitting media. The frequency shifts with pressure are positive, and no soft modes were observed, in agreement with the present and previous lattice dynamics calculations. Zero-pressure frequency shifts (dυi/dP)0 vary between 1.7 and 4.2 cm-1/GPa, which contrasts with the uniform shift of 2.6 cm-1/GPa for modes measured in high-pressure mid-infrared spectra. The mode-Grüneisen parameters γi, determined from the present data span the range 1.6-1.9, and are generally higher than those reported in the infrared study. The Raman data are interpreted using the lattice dynamics calculated from the potential-induced breathing (PIB) model, a Gordon-Kim approach that includes the effects of charge relaxation on the dynamics. Good agreement with the experimentally determined frequencies is obtained, particularly in the lower frequency range, in comparison with previous rigid-ion results. The high thermal expansivity for MgSiO3-perovskite is shown to be due to the comparatively high values for γi associated with the lower frequency modes. Thermal weighting of the individual γi is required for an accurate calculation of the thermal Grüneisen parameter γTH and thermal expansivity.

Effect of stress on ultrasonic pulses in fiber reinforced composites

NASA Technical Reports Server (NTRS)

Hemann, J. H.; Baaklini, G. Y.

1986-01-01

An acoustical-ultrasonic technique was used to demonstrate relationships existing between changes in attenuation of stress waves and tensile stress on an eight ply 0 degree graphite-epoxy fiber reinforced composite. All tests were conducted in the linear range of the material for which no mechanical or macroscopic damage was evident. Changes in attenuation were measured as a function of tensile stress in the frequency domain and in the time domain. Stress wave propagation in these specimens was dispersive, i.e., the wave speed depends on frequency. Wave speeds varied from 267,400 cm/sec to 680,000 cm/sec as the frequency of the signal was varied from 150 kHz to 1.9 MHz which strongly suggests that flexural/lamb wave modes of propagation exist. The magnitude of the attenuation changes depended strongly on tensile stress. It was further observed that the wave speeds increased slightly for all tested frequencies as the stress was increased.

Tunable CW diode-pumped Tm,Ho:YLiF4 laser operating at or near room temperature

NASA Technical Reports Server (NTRS)

Mcguckin, Brendan T. (Inventor); Menzies, Robert T. (Inventor)

1993-01-01

A conversion efficiency of 42 percent and slope efficiency of 60 percent relative to absorbed pump power are obtained from a continuous wave diode-pumped Tm,Ho:YLiF4 laser at 2 microns with output power of 84mW at a crystal temperature of 275K. The emission spectrum is etalon tunable over a range of 7nm (16.3 cm(sup -1) centered on 2.067 microns with fine tuning capability of the transition frequency with crystal temperature at a measured rate of -0.03/(cm)K. The effective emission cross-section is measured to be 5 x 10(sup -21) cm squared. These and other aspects of the laser performance are disclosed in the context of calculated atmospheric absorption characteristics in this spectral region and potential use in remote sensing applications. Single frequency output and frequency stabilization are achieved using an intracavity etalon in conjunction with an external reference etalon.

Second-Order Vibrational Lineshapes from the Air/Water Interface.

PubMed

Ohno, Paul E; Wang, Hong-Fei; Paesani, Francesco; Skinner, James L; Geiger, Franz M

2018-05-10

We explore by means of modeling how absorptive-dispersive mixing between the second- and third-order terms modifies the imaginary χ total (2) responses from air/water interfaces under conditions of varying charge densities and ionic strength. To do so, we use published Im(χ (2) ) and χ (3) spectra of the neat air/water interface that were obtained either from computations or experiments. We find that the χ total (2) spectral lineshapes corresponding to experimentally measured spectra contain significant contributions from both interfacial χ (2) and bulk χ (3) terms at interfacial charge densities equivalent to less than 0.005% of a monolayer of water molecules, especially in the 3100 to 3300 cm -1 frequency region. Additionally, the role of short-range static dipole potentials is examined under conditions mimicking brine. Our results indicate that surface potentials, if indeed present at the air/water interface, manifest themselves spectroscopically in the tightly bonded H-bond network observable in the 3200 cm -1 frequency range.

Radio frequency ablation of small renal tumors:: intermediate results.

PubMed

Hwang, J J; Walther, M M; Pautler, S E; Coleman, J A; Hvizda, J; Peterson, James; Linehan, W M; Wood, B J

2004-05-01

With evolving radio frequency technology, the clinical application of radio frequency ablation (RFA) has been actively investigated in the treatment for small renal tumors. We present our intermediate patient outcomes after RFA. Since January 2001, 17 patients with a total of 24 hereditary renal tumors ranging from 1.2 to 2.85 cm were treated with RFA using the 200 W Cool-tip RF System (Radionics, Burlington, Massachusetts) under laparoscopic (9) or percutaneous (8) guidance and had a minimum 1-year followup. A percutaneous approach was considered unsuitable if kidney tumors were contiguous to bowel, ureter or large vessels. Treatment eligibility criteria included an average tumor diameter of less than 3.0 cm, tumor growth during 1 year and solid appearance with contrast enhancement (HU change greater than 20) on computerized tomography (CT). Postoperative followup consisted of CT with and without intravenous contrast, and renal function assessment at regular intervals. Median patient age was 38 years (range 20 to 51). At a median followup of 385 days (range 342 to 691), median tumor or thermal lesion diameter decreased from 2.26 to 1.62 cm (p = 0.0013), and only 1 lesion (4%), which was located centrally near the hilum, exhibited contrast enhancement (HU change greater than 10) on CT at 12 months. Of the 15 renal tumors ablated laparoscopically, 13 were in direct contact with the bowel and 2 were abutting the ureter, necessitating mobilization before RFA. Laparoscopic ultrasound was used to guide radio frequency electrode placement and monitor the ablation process in these cases. Operative time and intraoperative blood loss (mean +/- standard mean of error) were 243 +/- 29 minutes and 67 +/- 9 cc, respectively. In 1 patient whose ureter was adherent to the tumor a ureteropelvic junction obstruction developed after laparoscopic RFA, requiring open repair. At the minimum 1-year followup 23 of 24 ablated tumors lacked contrast uptake on CT, meeting our radiographic criteria of successful RFA treatment. RFA treatment of small renal tumors using the Radionics system appears to result in superior treatment outcomes compared to those of earlier series with lower radio frequency power generators. A high wattage generator might attain more consistent energy deposition with subsequent cell death in the targeted tissue due to less convective heat loss.

Influence of Ag, Cd or Pb Addition on Electrical and Dielectric Properties of Bulk Glassy Se-Ge

NASA Astrophysics Data System (ADS)

El-Metwally, E. G.; Shakra, A. M.

2018-05-01

Bulk glassy samples of Se0.7Ge0.3 and Se0.7Ge0.25 X 0.05 (X = Ag, Cd or Pb) chalcogenide glass have been prepared by melt-quenching method. The studied compositions were examined in powder form by x-ray diffraction analysis. The direct-current (dc) conductivity σ_{{dc}} was measured for bulk samples in the temperature range from 303 K to 433 K, revealing enhancement with temperature for all samples. The results indicate two values of activation energy ( Δ E_{{σ1 }} and Δ E_{{σ2 }} ) due to two conduction mechanisms. Measurements of the alternating-current (ac) conductivity σ_{{ac}} ( ω ) and dielectric properties for bulk samples were carried out in the temperature range from 303 K to 433 K and frequency range from 1 kHz to 1 MHz. The ac conductivity σ_{{ac}} ( ω ) was temperature dependent and proportional to ωS , where S is the frequency exponent, which reduced with rising temperature, and ω is the angular frequency. These results are discussed based on a correlated barrier hopping model. The calculated values of the maximum height of the barrier W_{{M}} for each composition are consistent with carrier hopping over a potential barrier. The density of localized states N( {E_{{F}} } ) at the Fermi level lay in the range from 1019 eV-1 cm-3 to 1020 eV-1 cm-3, and increased with temperature. The dielectric constant ɛ1 ( ω ) and loss ɛ2 ( ω ) increased with temperature but decreased with frequency. The values of σ_{{dc}} , σ_{{ac}} ( ω ) , ɛ1 ( ω ) , and ɛ2 ( ω ) increased with temperature and with addition of Ag, Cd or Pb. The observed increase was greater for Se0.7Ge0.25Pb0.05 than for Se0.7Ge0.25Cd0.05, which was greater than for Se0.7Ge0.25Ag0.05.

Synthetic, Infrared, 1Hand 13CNMR Spectral Studies on N-(p-Substituted Phenyl)-p-Substituted Benzenesulphonamides, p-X'C6H4SO2NH- (p-XC6H4), where X' or X = H, CH3, C2H5, F, Cl or Br

NASA Astrophysics Data System (ADS)

Gowda, B. Thimme; Jayalakshmi, K. L.; Shetty, Mahesha

2004-05-01

Thirty N-(p-substituted phenyl)-p-substituted benzenesulphonamides of the general formula, p-X'C6H4SO2NH(p-XC6H4), where X' or X = H, CH3, C2H5, F, Cl or Br, are synthesised and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution are measured. The N-H stretching vibrational frequencies, νN-H vary in the range 3334 - 3219 cm-1, while the asymmetric and symmetric SO2 vibrations appear in the ranges 1377 - 1311 cm-1 and 1182 - 1151 cm-1, respectively. The compounds exhibit S-N and C-N stretching vibrational absorptions in the ranges 937 - 898 cm-1 and 1310 - 1180 cm-1, respectively. There are no particular trends in the variation of these frequencies on substitution with either electron withdrawing or electron donating groups. The 1H and 13C chemical shifts of N-(p-substituted phenyl)-p-substituted benzenesulphonamides, are assigned to various protons and carbons of the two benzene rings. Further, incremental shifts of the ring protons and carbons due to -SO2NH(p-XC6H4) groups in the compounds of the formula, C6H5SO2NH(p-XC6H4), and p-X'C6H4SO2- and p-X'C6H4SO2NH- groups in the compounds of the formula, p-X'C6H4SO2NH(C6H5) are computed and used to calculate the 1H and 13C chemical shifts of the parallely substituted compounds of the general formula p-X'C6H4SO2NH(p-XC6H4). The computed values agree well with the observed chemical shifts. The above incremental shifts are found to correlate with the Hammett substituent parameters.

High-resolution FTIR spectroscopy of the Coriolis interacting nu3 and nu9 fundamentals of methylene fluoride-d2

NASA Astrophysics Data System (ADS)

Goh, K. L.; Tan, T. L.; Ong, P. P.; Chaw, K. H.; Teo, H. H.

The Fourier transform infrared spectrum of the υ3 and υ9 bands of methylene fluoride-d2 (CD2F2) has been recorded with an unapodized resolution of 0.0024cm-1 in the frequency range 970-1080cm-1. These two bands with band centres approximately 26 cm-1 apart were mutually coupled by Coriolis interactions. By fitting a total of 1639 infrared transitions of both υ3 and υ9 with a standard deviation of 0.00084cm-1 S/S using a Watson's A-reduced Hamiltonian in the Ir representation with the inclusion of a first order c-type Coriolis resonance term, two sets of rovibrational constants for υ3 = 1 and υ9 = 1 states were derived. The υ3 band is B-type while the υ9 band is A-type with band centres at 1030.1573 ± 0.0003 and 1003.7435 ± 0.0001cm-1, respectively.

The Coriolis Interaction between the ν 9 and ν 7 Fundamental Bands of Methylene Fluoride

NASA Astrophysics Data System (ADS)

Goh, K. L.; Tan, T. L.; Ong, P. P.; Teo, H. H.

2000-06-01

The infrared spectrum of the ν7 and ν9 bands of methylene fluoride-d2 (CD2F2) has been recorded with an unapodized resolution of 0.0024 cm-1 in the frequency range of 940-1030 cm-1 using the Fourier transform technique. A weak b-type Coriolis interaction term was found to couple these two vibrational states with band centers about 42 cm-1 apart. By fitting a total of 1031 infrared transitions of both ν7 and ν9 with a standard deviation of 0.0011 cm-1 using a Watson's A-reduced Hamiltonian in the Ir representation with the inclusion of a b-type Coriolis resonance term, two sets of rovibrational constants for ν7 = 1 and ν9 = 1 states up to sextic order were derived. The ν7 band is C type, while the ν9 band is A type with band centers at 961.8958 ± 0.0005 and 1003.7421 ± 0.0001 cm-1, respectively.

Room-Temperature-Synthesized High-Mobility Transparent Amorphous CdO-Ga2O3 Alloys with Widely Tunable Electronic Bands.

PubMed

Liu, Chao Ping; Ho, Chun Yuen; Dos Reis, Roberto; Foo, Yishu; Guo, Peng Fei; Zapien, Juan Antonio; Walukiewicz, Wladek; Yu, Kin Man

2018-02-28

In this work, we have synthesized Cd 1-x Ga x O 1+δ alloy thin films at room temperature over the entire composition range by radio frequency magnetron sputtering. We found that alloy films with high Ga contents of x > 0.3 are amorphous. Amorphous Cd 1-x Ga x O 1+δ alloys in the composition range of 0.3 < x < 0.5 exhibit a high electron mobility of 10-20 cm 2 V -1 s -1 with a resistivity in the range of 10 -2 to high 10 -4 Ω cm range. The resistivity of the amorphous alloys can also be controlled over 5 orders of magnitude from 7 × 10 -4 to 77 Ω cm by controlling the oxygen stoichiometry. Over the entire composition range, these crystalline and amorphous alloys have a large tunable intrinsic band gap range of 2.2-4.8 eV as well as a conduction band minimum range of 5.8-4.5 eV below the vacuum level. Our results suggest that amorphous Cd 1-x Ga x O 1+δ alloy films with 0.3 < x < 0.4 have favorable optoelectronic properties as transparent conductors on flexible and/or organic substrates, whereas the band edges and electrical conductivity of films with 0.3 < x < 0.7 can be manipulated for transparent thin-film transistors as well as electron transport layers.

Intermolecular vibrations of (CH2)2O-HF and -DF hydrogen bonded complexes investigated by Fourier transform infrared spectroscopy and ab initio calculations.

PubMed

Cirtog, M; Asselin, P; Soulard, P; Madebène, B; Alikhani, M E

2010-10-14

A series of Fourier transform infrared spectra (FTIR) of the hydrogen bonded complexes (CH(2))(2)O-HF and -DF have been recorded in the 50-750 cm(-1) range up to 0.1 cm(-1) resolution in a static cell maintained at near room temperature. The direct observation of three intermolecular transitions enabled us to perform band contour analysis of congested cell spectra and to determine reliable rovibrational parameters such as intermolecular frequencies, rovibrational and anharmonic coupling constants involving two l(1) and l(2) librations and one σ stretching intermolecular motion. Inter-inter anharmonic couplings could be identified between ν(l(1)), ν(l(2)), ν(σ) and the two lowest frequency bending modes. The positive sign of coupling constants (opposite with respect to acid stretching intra-inter ones) reveals a weakening of the hydrogen bond upon intermolecular excitation. The four rovibrational parameters ν(σ) and x(σj) (j = σ, δ(1), δ(2)) derived in the present far-infrared study and also in a previous mid-infrared one [Phys. Chem. Chem. Phys. 2005, 1, 592] make deviations appear smaller than 1% for frequencies and 12% for coupling constants which gives confidence to the reliability of the data obtained. Anharmonic frequencies obtained at the MP2 level with Aug-cc-pvTZ basis set agree well with experimental values over a large set of frequencies and coupling constants. An estimated anharmonic corrected value of the dissociation energy D for both oxirane-HF (2424 cm(-1)) and -DF (2566 cm(-1)) has been derived using a level of theory as high as CCSD(T)/Aug-cc-pvQZ, refining the harmonic value previously calculated for oxirane-HF with the MP2 method and a smaller basis set. Finally, contrary to short predissociation lifetimes evidenced for acid stretching excited states, any homogeneous broadening related to vibrational dynamics of (CH(2))(2)O-HF and -DF has been observed within the three highest frequency intermolecular states, as expected with low excitation energies largely below the dissociation limit as well as a negligible IVR contribution.

Microwave properties of solid CO2. [for Mars surface study

NASA Technical Reports Server (NTRS)

Simpson, R. A.; Howard, H. T.; Fair, B. C.

1980-01-01

Measurements over the range of 2.2 to 12.0 GHz show that CO2 snow is a slightly lossy dielectric whose constant varies with density following the Rayleigh formula to 1.27 g/cu cm. It is independent of frequency and does not vary with temperature in the 113 to 183 K range; frequency independence and agreement with the Rayleigh fit are obtained from measurements on dry block ice. The dielectric constant of solid CO2 in block form is lower than that of solid water ice or solid rock; in powder form, the constant for CO2 is also lower than that of H2O (snow) or soils. These measurements may be useful in limiting the interpretations of the Viking radio reflection experiment; a radio value of 3.0 for the dielectric constant near the North Pole would be strong evidence against the presence of cm thicknesses of CO2 in that region.

Rovibrational Constants for the ν 6 and 2ν 9 Bands of HCOOD by Fourier Transform Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Tan, T. L.; Goh, K. L.; Ong, P. P.; Teo, H. H.

1999-11-01

The Fourier transform infrared spectrum of the ν6 and 2ν9 bands of deuterated formic acid (HCOOD) was recorded with an apodized resolution of 0.004 cm-1 in the frequency range of 930-1040 cm-1. These two bands with band centers 40 cm-1 apart were mutually coupled by Coriolis and Fermi interactions. By fitting a total of 1076 infrared transitions of both ν6 and 2ν9 with a standard deviation of 0.00075 cm-1 using a Watson's A-reduced Hamiltonian in the Ir representation with the inclusion of c-type Coriolis and a Fermi-resonance term, two sets of rovibrational constants for v6 = 1, and v9 = 2 states were derived for the first time. Both ν6 and 2ν9 bands are A type with band centers at 972.8520 ± 0.0001 and 1011.6766 ± 0.0001 cm-1, respectively.

Analysis of the coriolis interaction of the ν12 band with 2 ν10 of cis-d 2-ethylene by high-resolution Fourier transform infrared spectroscopy

NASA Astrophysics Data System (ADS)

Goh, K. L.; Tan, T. L.; Ong, P. P.; Teo, H. H.

2000-08-01

The Fourier transform infrared spectrum of the ν12 band of cis-d 2-ethylene ( cis-C 2H 2D 2) has been recorded with an unapodized resolution of 0.0024 cm -1 in the frequency range of 1280-1400 cm -1. This band was found to be mutually coupled by Coriolis interaction with the unobserved 2 ν10 band situated approximately 10 cm -1 below ν12. By fitting a total of 771 infrared transitions of ν12 with a standard deviation of 0.00075 cm -1 using the Watson's Hamiltonian with the inclusion of a c-type Coriolis resonance term, a set of accurate rovibrational constants for V 12=1 state was derived. The ν12 band is A type with a band centre at 1341.1512±0.0001 cm -1. Accurate rovibrational constants for the V 10=2 state were also derived.

Spontaneous fluctuations in cerebral blood flow: insights from extended-duration recordings in humans

NASA Technical Reports Server (NTRS)

Zhang, R.; Zuckerman, J. H.; Levine, B. D.; Blomqvist, C. G. (Principal Investigator)

2000-01-01

To determine the dependence of cerebral blood flow (CBF) on arterial pressure over prolonged time periods, we measured beat-to-beat changes in mean CBF velocity in the middle cerebral artery (transcranial Doppler) and mean arterial pressure (Finapres) continuously for 2 h in six healthy subjects (5 men and 1 woman, 18-40 yr old) during supine rest. Fluctuations in velocity and pressure were quantified by the range [(peak - trough)/mean] and coefficients of variation (SD/mean) in the time domain and by spectral analysis in the frequency domain. Mean velocity and pressure over the 2-h recordings were 60 +/- 7 cm/s and 83 +/- 8 mmHg, associated with ranges of 77 +/- 8 and 89 +/- 10% and coefficients of variation of 9.3 +/- 2.2 and 7.9 +/- 2.3%, respectively. Spectral power of the velocity and pressure was predominantly distributed in the frequency range of 0.00014-0.1 Hz and increased inversely with frequency, indicating characteristics of an inverse power law (1/f(alpha)). However, linear regression on a log-log scale revealed that the slope of spectral power of pressure and velocity was steeper in the high-frequency (0.02-0.5 Hz) than in the low-frequency range (0.002-0.02 Hz), suggesting different regulatory mechanisms in these two frequency ranges. Furthermore, the spectral slope of pressure was significantly steeper than that of velocity in the low-frequency range, consistent with the low transfer function gain and low coherence estimated at these frequencies. We conclude that 1) long-term fluctuations in CBF velocity are prominent and similar to those observed in arterial pressure, 2) spectral power of CBF velocity reveals characteristics of 1/f(alpha), and 3) cerebral attenuation of oscillations in CBF velocity in response to changes in pressure may be more effective at low than that at high frequencies, emphasizing the frequency dependence of cerebral autoregulation.

Use of the characteristic Raman lines of toluene (C7 H8) as a precise frequency reference on the spectral analysis of gasoline-ethanol blends

NASA Astrophysics Data System (ADS)

Ortega Clavero, Valentin; Javahiraly, Nicolas; Weber, Andreas; Schröder, Werner; Curticapean, Dan; Meyrueis, Patrick P.

2014-09-01

In order to reduce some of the toxic emissions produced by internal combustion engines, the fossil-based fuels have been combined with less harmful materials in recent years. However, the fuels used in the automotive industry generally contain different additives, such as toluene, as anti-shock agents and as octane number enhancers. These materials can cause certain negative impact, besides the high volatility implied, on public health or environment due to its chemical composition. Toluene, among several other chemical compounds, is an additive widely used in the commercially-available gasoline-ethanol blends. Despite the negative aspects in terms of toxicity that this material might have, the Raman spectral information of toluene can be used to achieve certain level of frequency calibration without using any additional chemical marker in the sample or any other external device. Moreover, the characteristic and well-defined Raman line of this chemical compound at 1003 cm-1 (even at low v/v content) can be used to quantitatively determine certain aspects of the gasoline-ethanol blend under observation. By using an own-designed Fourier-Transform Raman spectrometer (FT-Raman), we have collected and analyzed different commercially-available and laboratory-prepared gasoline-ethanol blends. By carefully observing the main Raman peaks of toluene in these fuel blends, we have determined the frequency accuracy of the Raman spectra obtained. The spectral information has been obtained in the range of 0 cm-1 to 3500 cm-1 with a spectral resolution of 1.66 cm-1. The Raman spectra obtained presented only reduced frequency deviations in comparison to the standard Raman spectrum of toluene provided by the American Society for Testing and Materials (ASTM).

The High-Resolution Infrared Spectrum of the ν 5Band of Deuterated Formic Acid (DCOOH)

NASA Astrophysics Data System (ADS)

Goh, K. L.; Ong, P. P.; Tan, T. L.; Wang, W. F.; Teo, H. H.

1998-07-01

The Fourier transform infrared spectrum of the ν5band of deuterated formic acid (DCOOH) has been measured with a resolution of 0.004 cm-1in the frequency range of 1090-1180 cm-1. Using a Watson'sA-reduced Hamiltonian in theIrrepresentation, a total of 1731 assigned unperturbed transitions have been analyzed to provide rovibrational constants for the upper state (v5= 1) with a standard deviation of 0.000363 cm-1. The band isAtype with an unperturbed band center at 1142.31075 ± 0.00002 cm-1. The band is expected to be perturbed by a nearby ν4band through a Fermi resonance term and possibly a Coriolis term. The resonance is particularly noticeable forKa= 10, and 11, at highJvalues. About 215 perturbed lines were identified but they were not included in the final fit.

High-resolution Fourier transform infrared spectroscopy and analysis of the ν12 fundamental band of ethylene- d4

NASA Astrophysics Data System (ADS)

Tan, T. L.; Goh, K. L.; Ong, P. P.; Teo, H. H.

1999-12-01

The Fourier transform infrared (IR) spectrum of the ν12 fundamental band of ethylene- d4 (C 2D 4) has been measured with an unapodized resolution of 0.004 cm -1 in the frequency range of 1030-1130 cm -1. A total of 1340 assigned transitions have been analyzed and fitted using a Watson's A-reduced Hamiltonian in the Ir representation to derive rovibrational constants for the upper state ( v12=1) up to five quartic terms with a standard deviation of 0.00042 cm -1. They represent the most accurate constants for the band thus far. The ground state rovibrational constants were also further improved by a fit of combination-differences from the IR measurements. The relatively unperturbed band was found to be basically A-type with a band centre at 1076.98492±0.00003 cm -1.

Jet-cooled infrared absorption spectrum of the v4 fundamental band of HCOOH and HCOOD

NASA Astrophysics Data System (ADS)

Luo, Wei; Zhang, Yulan; Li, Wenguang; Duan, Chuanxi

2017-04-01

The jet-cooled absorption spectrum of the v4 fundamental band of normal formic acid (HCOOH) and deuterated formic acid (HCOOD) was recorded in the frequency range of 1370-1392 cm-1 with distributed-feedback quantum cascade lasers (DFB-QCLs) as the tunable infrared radiations. A segmented rapid-scan data acquisition scheme was developed for pulsed supersonic jet infrared laser absorption spectroscopy based on DFB-QCLs with a moderate vacuum pumping capacity. The unperturbed band-origin and rotational constants in the excited vibrational state were determined for both HCOOH and HCOOD. The unperturbed band-origin locates at 1379.05447(11) cm-1 for HCOOH, and 1366.48430(39) cm-1 for HCOOD, respectively.

Fade Measurements into Buildings from 500 to 3000 MHz

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.

1996-01-01

Slant-path fade measurements from 500 to 3000 MHz were made into six different buildings employing a vector network analyzer, a tower-mounted transmitting antenna and an automatically positioned receiving antenna. The objective of the measurements was to provide information for satellite audio broadcasting and personal communications satellite design on the correlation of fading inside buildings. Fades were measured with 5 cm spatial separation and every 0.2 percent of the frequency. Median fades ranged from 10 to 20 dB in woodframe houses with metal roofs and walls without and with an aluminum heat shield, respectively. The median decorrelation distance was from 0.5 to 1.1. m and was independent of frequency. The attenuation into the buildings increased only moderately with frequency in most of the buildings with a median slope of about 1 to 3 db/GHz, but increased fastest in the least attenuating building with a slope of 5 dB/GHz. The median decorrelation bandwidth ranged from 1.2 to 3.8 percent of frequency in five of the buildings, and was largest in the least attenuating building, with 20.2 percent of frequency.

Fade Measurements into Buildings from 500 to 3000 MHz

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.

1996-01-01

Slant-path fade measurements from 500 to 3000 MHz were made into six different buildings employing a vector network analyzer, a tower-mounted transmitting antenna and an automatically positioned receiving antenna. The objective of the measurements was to provide information for satellite audio broadcasting and personal communications satellite design on the correlation of fading inside buildings. Fades were measured with 5 cm spatial separation and every 0.2% of the frequency. Median fades ranged from 10 to 20 dB in woodframe houses with metal roofs and walls without and with an aluminum heatshield, respectively. The median decorrelation distance was from 0.5 to 1.1 m and was independent of frequency. The attenuation into the buildings increased only moderately with frequency in most of the buildings with a median slope of about 1 to 3 dB/GHz, but increased fastest in the least attenuating building with a slope of 5 dB/GHz. The median decorrelation bandwidth ranged from 1.2 to 3.8% of frequency in five of the buildings, and was largest in the least attenuating building, with 20.2% of frequency.

Effect of Atmospheric-Pressure Plasma Jet of Neon on 7-Acetoxy-6-(2,3-Dibromopropyl)-4,8-Dimethylcoumarin Molecule

NASA Astrophysics Data System (ADS)

Tanışlı, Murat; Taşal, Erol

2017-06-01

Atmospheric-pressure low-temperature plasma jets and their applications are a topic of great interest in the fields of physics, technology, and medicine. In this study, the used self-made plasma jet is based on a dielectric barrier discharge (DBD) in neon (Ne) with typical processing parameters, such as frequency in the kHz range and voltage in the kV range. The plasma is characterized by optical emission spectroscopy (OES). These types of plasma can be used in various applications such as surface modification, inactivation of microorganisms, and chemical decomposition. This study is concerned with the Fourier transform infrared spectrum (FT-IR) and ultraviolet-visible (UV-vis) absorption spectroscopy of the large 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin molecule (abbreviated as 7AC) dissolved in ethanol and methanol solvents and their modification after atmospheric-pressure plasma treatment (APPT) with the DBD. The research is motivated by the significance of this molecule in different fields of application. Also the changes in the structure are recorded. After APPT, the peak corresponding to the carbonyl bond at a wavenumber of 1715 cm-1 disappears in the IR spectrum of the ethanol solution, and when splitting at a wavenumber of 1405 cm-1 is observed, the peak at 1224 cm-1 is found to disappear after plasma is applied. It is seen new peaks at frequencies of 432 and 655 cm-1 are formed. When the same situation is analyzed for the 7AC molecule dissolved in methanol, a new peak is observed at 1634 cm-1. The intensities of the peaks at 3433 and 2075 cm-1 also increase and there is a large change in the wavenumber at 600 cm-1. In the UV spectra, a significant increase in the absorbance of the 7AC molecule dissolved in ethanol is observed after APPT, whereas a small decrease in the absorbance of the 7AC molecule dissolved in methanol is obtained. Owing to the lack of symmetry, many normal bands of vibrations are mixed.

SFG study of the ethanol in an acidic medium--Pt(110) interface: effects of the alcohol concentration.

PubMed

Gomes, Janaina F; Busson, Bertrand; Tadjeddine, Abderrahmane

2006-03-23

Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and 2325 cm(-1)) to explore primarily the effects of the alcohol concentration. Stretching bands of H-Pt (ca. 1970 or 2050 cm(-1)) and CO (ca. 1980 and 2040 cm(-1)) species, produced by the ethanol oxidation, were detected during the adsorption and oxidation of 0-1 mol L(-1) ethanol in a 0.1 mol L(-1) HClO(4) solution on the electrode surface. Hydrogen and CO coadsorb stably on Pt(110) between 0.05 and 0.15 V in ethanol-containing solutions. In this potential range, the blue shift of the hydrogen resonance (ca. 80 cm(-1)) reveals a weakening of the hydrogen bonding between adsorbed hydrogen and water molecules in the double layer. After the hydrogen desorption (0.15 V), the formation of compact CO islands, depending on the ethanol concentration, lifts the Pt(110) surface reconstruction. In ethanol-free solution, the surface remains reconstructed. The lower-frequency CO band is assigned to the CO species adsorbed on (1 x 2) reconstructed Pt(110) domains, having smaller local coverages, while the higher-frequency CO band is attributed to the close-packed CO species adsorbed on (1 x 1) patches. The reaction pathway forming CO(2) is less favored with increasing ethanol concentration.

Time averaging and stratigraphic disorder of molluscan assemblages in the Holocene sediments in the NE Adriatic (Piran)

NASA Astrophysics Data System (ADS)

Tomasovych, Adam; Gallmetzer, Ivo; Haselmair, Alexandra; Kaufman, Darrell S.; Zuschin, Martin

2016-04-01

Stratigraphic changes in temporal resolution of fossil assemblages and the degree of their stratigraphic mixing in the Holocene deposits are of high importance in paleoecology, conservation paleobiology and paleoclimatology. However, few studies quantified downcore changes in time averaging and in stratigraphic disorder on the basis of dating of multiple shells occurring in individual stratigraphic layers. Here, we investigate downcore changes in frequency distribution of postmortem ages of the infaunal bivalve Gouldia minima in two, ~150 cm-thick piston cores (separated by more than 1 km) in the northern Adriatic Sea, close to the Slovenian city Piran at a depth of 24 m. We use radiocarbon-calibrated amino acid racemization to obtain postmortem ages of 564 shells, and quantify age-frequency distributions in 4-5 cm-thick stratigraphic intervals (with 20-30 specimens sampled per interval). Inter-quartile range for individual 4-5 cm-thick layers varies between 850 and 1,700 years, and range encompassing 95% of age data varies between 2,000 and 5,000 years in both cores. The uppermost sediments (20 cm) are age-homogenized and show that median age of shells is ~700-800 years. The interval between 20 and 90 cm shows a gradual increase in median age from ~2,000 to ~5,000 years, with maximum age ranging to ~8,000 years. However, the lowermost parts of both cores show a significant disorder, with median age of 3,100-3,300 years. This temporal disorder implies that many shells were displaced vertically by ~1 m. Absolute and proportional abundance of the bivalve Gouldia minima strongly increases towards the top of the both cores. We hypothesize that such increase in abundance, when coupled with depth-declining reworking, can explain stratigraphic disorder because numerically abundant young shells from the top of the core were more likely buried to larger sediment depths than less frequent shells at intermediate sediment depths.

[The spectrum studies of structure characteristics in magma contact metamorphic coal].

PubMed

Wu, Dun; Sun, Ruo-Yu; Liu, Gui-Jian; Yuan, Zi-Jiao

2013-10-01

The structural parameters evolution of coal due to the influence of intrusions of hot magma was investigated and analyzed. X-ray diffraction and laser confocal microscope Raman spectroscopy were used to test and analyze 4 coal samples undergoing varying contact-metamorphism by igneous magmas in borehole No. 13-4 of Zhuji coal mine, Huainan coalfield. The result showed that coal XRD spectrum showed higher background intensity, with the 26 degrees and 42 degrees nearby apparent graphite diffraction peak. Two significant vibration peaks of coal Raman spectra were observed in the 1 000-2 000 cm(-1) frequency range: broad "D" peak at 1 328-1 369 cm(-1) and sharp "G" peak at 1 564-1 599 cm(-1). With the influence of magma intrusion, the relationship between coal structural parameters and coal ranks was excellent.

Calibration of the COBE FIRAS instrument

NASA Technical Reports Server (NTRS)

Fixsen, D. J.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Mather, J. C.; Massa, D. L.; Meyer, S. S.

1994-01-01

The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite was designed to accurately measure the spectrum of the cosmic microwave background radiation (CMBR) in the frequency range 1-95/cm with an angular resolution of 7 deg. We describe the calibration of this instrument, including the method of obtaining calibration data, reduction of data, the instrument model, fitting the model to the calibration data, and application of the resulting model solution to sky observations. The instrument model fits well for calibration data that resemble sky condition. The method of propagating detector noise through the calibration process to yield a covariance matrix of the calibrated sky data is described. The final uncertainties are variable both in frequency and position, but for a typical calibrated sky 2.6 deg square pixel and 0.7/cm spectral element the random detector noise limit is of order of a few times 10(exp -7) ergs/sq cm/s/sr cm for 2-20/cm, and the difference between the sky and the best-fit cosmic blackbody can be measured with a gain uncertainty of less than 3%.

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

Mandula, Gábor, E-mail: mandula.gabor@wigner.mta.hu; Kis, Zsolt; Lengyel, Krisztián

We report on a method for real-time dynamic calibration of a tunable external cavity diode laser by using a partially mode-matched plano-concave Fabry-Pérot interferometer in reflection geometry. Wide range laser frequency scanning is carried out by piezo-driven tilting of a diffractive grating playing the role of a frequency selective mirror in the laser cavity. The grating tilting system has a considerable mechanical inertness, so static laser frequency calibration leads to false results. The proposed real-time dynamic calibration based on the identification of primary- and Gouy-effect type secondary interference peaks with known frequency and temporal history can be used for amore » wide scanning range (from 0.2 GHz to more than 1 GHz). A concave spherical mirror with a radius of R = 100 cm and a plain 1% transmitting mirror was used as a Fabry-Pérot interferometer with various resonator lengths to investigate and demonstrate real-time calibration procedures for two kinds of laser frequency scanning functions.« less

Low-frequency vibrational properties of lysozyme in sugar aqueous solutions: A Raman scattering and molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Lerbret, A.; Affouard, F.; Bordat, P.; Hédoux, A.; Guinet, Y.; Descamps, M.

2009-12-01

The low-frequency (ω <400 cm-1) vibrational properties of lysozyme in aqueous solutions of three well-known protecting sugars, namely, trehalose, maltose, and sucrose, have been investigated by means of complementary Raman scattering experiments and molecular dynamics simulations. The comparison of the Raman susceptibility χ″(ω) of lysozyme/water and lysozyme/sugar/water solutions at a concentration of 40 wt % with the χ″ of dry lysozyme suggests that the protein dynamics mostly appears in the broad peak around 60-80 cm-1 that reflects the vibrations experienced by atoms within the cage formed by their neighbors, whereas the broad shoulder around 170 cm-1 mainly stems from the intermolecular O-H⋯O stretching vibrations of water. The addition of sugars essentially induces a significant high frequency shift and intensity reduction of this band that reveal a slowing down of water dynamics and a distortion of the tetrahedral hydrogen bond network of water, respectively. Furthermore, the lysozyme vibrational densities of states (VDOS) have been determined from simulations of lysozyme in 37-60 wt % disaccharide aqueous solutions. They exhibit an additional broad peak around 290 cm-1, in line with the VDOS of globular proteins obtained in neutron scattering experiments. The influence of sugars on the computed VDOS mostly appears on the first peak as a slight high-frequency shift and intensity reduction in the low-frequency range (ω <50 cm-1), which increase with the sugar concentration and with the exposition of protein residues to the solvent. These results suggest that sugars stiffen the environment experienced by lysozyme atoms, thereby counteracting the softening of protein vibrational modes upon denaturation, observed at high temperature in the Raman susceptibility of the lysozyme/water solution and in the computed VDOS of unfolded lysozyme in water. Finally, the Raman susceptibility of sugar/water solutions and the calculated VDOS of water in the different lysozyme solutions confirm that sugars induce a significant strengthening of the hydrogen bond network of water that may stabilize proteins at high temperatures.

Optical characterization of pure vegetable oils and their biodiesels using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Firdous, S.; Anwar, S.; Waheed, A.; Maraj, M.

2016-04-01

Great concern regarding energy resources and environmental polution has increased interest in the study of alternative sources of energy. Biodiesels as an alternative fuel provide a suitable diesel oil substitute for internal combustion engines. The Raman spectra of pure biodiesels of soybean oil, olive oil, coconut oil, animal fats, and petroleum diesel are optically characterized for quality and biofuel as an alternative fuel. The most significant spectral differences are observed in the frequency range around 1457 cm-1 for pure petroleum diesel, 1427 for fats biodiesel, 1670 cm-1 for pure soybean oil, 1461 cm-1 for soybean oil based biodiesel, 1670 cm-1 for pure olive oil, 1666 cm-1 for olive oil based biodiesel, 1461 cm-1 for pure coconut oil, and 1460 cm-1 for coconut oil based biodiesel, which is used for the analysis of the phase composition of oils. A diode pump solid-state laser with a 532 nm wavelength is used as an illuminating light. It is demonstrated that the peak positions and relative intensities of the vibrations of the oils can be used to identify the biodiesel quality for being used as biofuel.

Development of a two photon/laser induced fluorescence technique for the detection of atmospheric OH radicals

NASA Technical Reports Server (NTRS)

Bradshaw, John

1990-01-01

The development of a new mid-IR laser source was the primary goal. Backward propagating stimulated D2 Raman frequency down conversion of a commercially available 1.06 micron Nd:YAG laser was shown to generate an efficient source of 1.56 micron radiation with near diffraction limited beam quality. The efficient generation of a 2.9 micron laser source was also achieved using backward propagating CH4 Raman frequency down conversion of the 1.56 micron pump. Slightly higher efficiencies were obtained for frequency down conversion of the 1.06 micron Nd:YAG using the H2 Raman shift yielding a near diffraction limited source in the 200 mJ range at 1.9 micron. Similar conversion efficiencies are anticipated as a result of extending the wavelength coverage of recently available Ti:sapphire pulse laser to not only cover the 740 to 860 nm fundamental wavelength range but also the .95 to 1.15 and 1.06 to 1.33 micron range using D2 and H2, respectively. The anticipated sensitivity of a TP-LIF OH sensor using this mid-IR source would give signal limited detection of 1.4 x 10(exp 5) OH/cu cm under boundary layer conditions and 5.5 x 10(exp 4) OH/cu cm under free troposphere sampling conditions for a five minute signal integration period. This level of performance coupled with the techniques non-perturbing nature and freedom from both interferences and background would allow reliable tropospheric OH measurement to be obtained under virtually any ambient condition of current interest, including interstitial and sampling.

Hydration and ion pair formation in aqueous Y(3+)-salt solutions.

PubMed

Rudolph, Wolfram W; Irmer, Gert

2015-11-14

Raman spectra of aqueous yttrium perchlorate, triflate (trifluoromethanesulfonate), chloride and nitrate solutions were measured over a broad concentration range (0.198-3.252 mol L(-1)). The spectra range from low wavenumbers to 4200 cm(-1). A very weak mode at 384 cm(-1) with a full width at half height at 50 cm(-1) in the isotropic spectrum suggests that the Y(3+)- octa-aqua ion is thermodynamically stable in dilute perchlorate solutions (∼0.5 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The octa-hydrate, [Y(OH2)8](3+) was also detected in a 1.10 mol L(-1) aqueous Y(CF3SO3)3 solution. Furthermore, very weak and broad depolarized modes could be detected which are assigned to [Y(OH2)8](3+)(aq) at 100, 166, 234 and 320 cm(-1) confirming that a hexa-hydrate is not compatible with the hydrated species in solution. In yttrium chloride solutions contact ion pair formation was detected over the measured concentration range from 0.479-3.212 mol L(-1). The contact ion pairs in YCl3(aq) are fairly weak and disappear with dilution. At a concentration <0.2 mol L(-1) almost all complexes have disappeared. In YCl3 solutions, with additional HCl, chloro-complexes of the type [Y(OH2)8-nCln](+3-n) (n = 1,2) are formed. The Y(NO3)3(aq) spectra were compared with a spectrum of a dilute NaNO3 solution and it was concluded that in Y(NO3)3(aq) over the concentration range from 2.035-0.198 mol L(-1) nitrato-complexes [Y(OH2)8-n(NO3)ln](+3-n) (n = 1,2) are formed. The nitrato-complexes are weak and disappear with dilution <0.1 mol L(-1). DFT geometry optimizations and frequency calculations are reported for both the yttrium-water cluster in the gas phase and the cluster within a polarizable continuum model in order to implicitly describe the presence of the bulk solvent. The bond distance and angle for the square antiprismatic cluster geometry of [Y(OH2)8](3+) with the polarizable dielectric continuum is in good agreement with data from recent structural experimental measurements. The DFT frequency of the Y-O stretching mode of the [Y(OH2)8](3+) cluster, in a polarizable continuum, is at 372 cm(-1) in satisfactory agreement with the experimental value.

Photodynamic Therapy for Cancer Cells Using a Flash Wave Light Xenon Lamp

NASA Astrophysics Data System (ADS)

Kimura, Makoto; Kashikura, Kasumi; Yokoi, Satomi; Koiwa, Yumiko; Tokuoka, Yoshikazu; Kawashima, Norimichi

We determined photodynamic therapy (PDT) efficacy using a flash wave (FW) and a continuous wave (CW) light, of which the fluence rate was 70 W/cm2, for murine thymic lymphoma cells (EL-4) cultivated in vitro. The irradiation frequency and the pulse width of the FW light were in the range of 1-32 Hz and less than one millisecond, respectively. 5-Aminolevulinic acid-induced protoporphyrin IX (ALA-PpIX) was used as a photosensitizer. When EL-4 with ALA administration was irradiated by the light for 4 h (irradiation fluence: 1.0J/cm2), the survival rate of EL-4 by the FW light was lower than that by the CW light, except for the FW light with irradiation frequency of 32 Hz, and decreased gradually with decreasing irradiation frequency. Moreover, the FW light, especially at lower irradiation frequency, was superior to the CW light for the generation of singlet oxygen in an aqueous PpIX solution. Therefore, thehigher PDT efficacy for EL-4 of the FW light would be caused by the greater generation of singlet oxygen in the cells.

Turbulence scaling study in an MHD wind tunnel on the Swarthmore Spheromak Experiment

NASA Astrophysics Data System (ADS)

Schaffner, D. A.; Brown, M. R.; Wan, A.

2013-12-01

The turbulence of colliding plasmas is explored in an MHD wind tunnel on the SSX in an effort to understand solar wind physics in a laboratory setting. Fully ionized hydrogen plasma is produced by two plasma guns on opposite sides of a 1m by 15cm copper cylinder creating plasma with L/ρi ~ 75-150, β ~ 0.1-0.2 and Lundquist number ~ 1000. Modification of B-field, Ti and β are made through stuffing flux variation of the plasma guns. Presented here are turbulent f-/k-spectra and correlation times and lengths of B-field fluctuations as measured by a 16 channel B-dot radial probe array at the chamber midplane using both FFT and wavelet analysis techniques. Power-law behavior is observed spanning about two decades of frequencies [100kHz-10MHz] and about one decade of wavelength [10cm-1cm]. Power-law fits to spectra show scaling in these regions to be robust to changes in stuffing flux; fits are on the order of f-4 and k-2 for all flux variations. Low frequency fluctuations [<100kHz] can vary significantly suggesting a range of energy injection at large scales. Evidence for dissipation range modification of the spectra is also observed; divergence from power-law behavior is seen in f-spectra for frequencies around f=fci while changes in k-spectra slopes appear around 1/k ~ 5ρi. Dissipation range fits are made with an exponentially modified power-law model [Terry et al, PoP 2012]. Fluctuation measurements in axial velocity are made using a Mach probe with edge flows reaching M ~ 0.4. Both B-field and velocity fluctuations persist on the same timescale in these experiments, though Mach velocity f-spectra show power-laws slightly shallower than those for B-field. Comparison of spectra from MHD and Hall MHD simulations of SSX performed within the HiFi modeling framework are made to the experimental results.

A displaced and low-frequency vibration of phosphorescent state of trans-[Rh(ethylenediamine)2Cl2]PF6 in a range of 5-497 K

NASA Astrophysics Data System (ADS)

Islam, Ashraful; Ikeda, Noriaki; Nozaki, Koichi; Ohno, Takeshi

1998-09-01

The lowest 3(dπ-dσ*) excited states of both cis- and trans-isomers of [Rh(en)2Cl2]X (en=ethylenediamine; X=PF6-, NO3-) and the deuteriated crystal of trans-[Rh(en-d4)2Cl2]PF6 have been investigated in the solid state and in a wide temperature range of 5-497 K by means of emission spectra, lifetime and quantum yield measurements. Emission spectral simulation of trans-[Rh(en)2Cl2]PF6 shows that the emission from the lowest 3(dπ-dσ*) excited state exhibits a progression of a low-frequency metal-chloride stretching vibration (250 cm-1) with a large Huang-Rhys factor (S) of 21 and a progression of a high-frequency N-H stretching vibration (3000 cm-1). The increasing full-width at half maximum (2200 cm-1→4400 cm-1) with increasing temperature (77 K→468 K) is ascribed to hot bands from the excited levels of low-frequency vibration. The luminescence quantum yields of the crystal samples are determined to 0.0008 at 298 K and 0.003 at 80 K for trans-[Rh(en)2Cl2]PF6 and 0.18 at 298 K and 0.40 at 80 K for trans-[Rh(en-d4)2Cl2]PF6. From a combination of lifetime and emission quantum yield measurements, values for kr and knr have been obtained. The observed temperature dependence of nonradiative decay rates of trans-[Rh(en-d4)2Cl2]PF6 in a low-temperature region (<300 K) is possible to reconstitute by using the emission spectral fitting parameters and assuming nuclear tunneling mechanism. The temperature effect and deuteriation effect on the nonradiative rate definitively establishes that the dominant "accepting" modes in the nonradiative transition are a highly displaced (S=21) vibrational mode of low-frequency Cl-Rh-Cl stretching and a weakly displaced (S=0.1) vibrational mode of high-frequency N-D stretching. The nonradiative transition in a high-temperature region occurs via barrier passing along a displaced coordinate of Cl-Rh-Cl vibration with a pre-exponential factor of 1011s-1 and is relatively insensitive to the high-frequency vibrational mode. The crystal of cis-[Rh(en)2Cl2]NO3 shows a red shift of the emission peak energy and an increase in the full-width at half maximum with increasing temperature. The results of temperature-dependent decay and spectra of emission can be interpreted in terms of two 3(dπ-dσ*) emitting states model.

Cyclodextrin-complexation effects on the low-frequency vibrational dynamics of ibuprofen by combined inelastic light and neutron scattering experiments.

PubMed

Crupi, Vincenza; Fontana, Aldo; Giarola, Marco; Guella, Graziano; Majolino, Domenico; Mancini, Ines; Mariotto, Gino; Paciaroni, Alessandro; Rossi, Barbara; Venuti, Valentina

2013-04-11

The effect of the inclusion into cyclodextrins (CD) cavity on the low-frequency vibrational dynamics of the anti-inflammatory drug ibuprofen (IBP) is here investigated by using Raman and inelastic neutron scattering (INS) experiments. The differences observed in the frequency regime 0-100 cm(-1) between the vibrational modes of uncomplexed racemic and enantiomeric IBP are discussed on the basis of comparison with the quantum chemical computation results, taking into account the distinct symmetry properties of the molecules involved in the formation of the host-guest complex. Subsequently, the inspection of the same frequency range in the spectra of pure host methyl-β-CD and its IBP-inclusion complexes allows one to identify significant modifications in the vibrational dynamics of the guest molecule after their confinement into CD cavity. The experimental Raman and neutron spectra and the derived Raman coupling function C(R)(ω) show that the complexation process gives rise to a complete amorphization of the drug, as well as to a partial hindering, in the vibrational dynamics of complexes, of the modes between 50 and 150 cm(-1) attributed to CD molecule. The comparison between the Raman and neutron spectra of free and complexed IBP in the energy range of the Boson peak (BP) gives evidence that the dynamics related to this specific vibrational feature is sensitive to complexation phenomena.

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

Zhu, Cheng; Tsuge, Masashi; Khriachtchev, Leonid, E-mail: leonid.khriachtchev@helsinki.fi

Experimental and theoretical studies of HXeI and HXeH molecules in Ar, Kr, and Xe matrices are presented. HXeI exhibits the H–Xe stretching bands at 1238.0 and 1239.0 cm{sup −1} in Ar and Kr matrices, respectively, that are blue-shifted from the HXeI band observed in a Xe matrix (1193 cm{sup −1}) by 45 and 46 cm{sup −1}. These shifts are larger than those observed previously for HXeCl (27 and 16 cm{sup −1}) and HXeBr (37 and 23 cm{sup −1}); thus, the matrix effect is stronger for less stable molecules. The results for HXeI are qualitatively different from all previous results onmore » noble-gas hydrides with respect to the frequency order between Ar and Kr matrices. For previously studied HXeCl, HXeBr, and HXeCCH, the H–Xe stretching frequency is reliably (by >10 cm{sup −1}) higher in an Ar matrix than in a Kr matrix. In contrast, the H–Xe stretching frequency of HXeI in an Ar matrix is slightly lower than that in a Kr matrix. HXeH absorbs in Ar and Kr matrices at 1203.2 and 1192.1 cm{sup −1} (the stronger band for a Kr matrix), respectively. These bands are blue-shifted from the stronger band of HXeH in a Xe matrix (1166 cm{sup −1}) by 37 and 26 cm{sup −1}, and this frequency order is the same as observed for HXeCl, HXeBr, and HXeCCH but different from HXeI. The present hybrid quantum-classical simulations successfully describe the main experimental findings. For HXeI in the 〈110〉 (double substitution) site, the order of the H–Xe stretching frequencies (ν(Xe) < ν(Ar) < ν(Kr)) is in accord with the experimental observations, and also the frequency shifts in Ar and Kr matrices from a Xe matrix are well predicted (30 and 34 cm{sup −1}). Both in the theory and experiment, the order of the H–Xe stretching frequencies differs from the case of HXeCl, which suggests the adequate theoretical description of the matrix effect. For HXeH in the 〈100〉 (single substitution) site, the order of the frequencies is ν(Xe) < ν(Kr) < ν(Ar), which also agrees with the experiments. The calculated frequency shifts for HXeH in Ar and Kr matrices with respect to a Xe matrix (36 and 23 cm{sup −1}) are in a good agreement with the experiments. The present calculations predict an increase of the H–Xe stretching frequencies in the noble-gas matrices with respect to vacuum.« less

Excited-state structure and isomerization dynamics of the retinal chromophore in rhodopsin from resonance Raman intensities.

PubMed Central

Loppnow, G R; Mathies, R A

1988-01-01

Resonance Raman excitation profiles have been measured for the bovine visual pigment rhodopsin using excitation wavelengths ranging from 457.9 to 647.1 nm. A complete Franck-Condon analysis of the absorption spectrum and resonance Raman excitation profiles has been performed using an excited-state, time-dependent wavepacket propagation technique. This has enabled us to determine the change in geometry upon electronic excitation of rhodopsin's 11-cis-retinal protonated Schiff base chromophore along 25 normal coordinates. Intense low-frequency Raman lines are observed at 98, 135, 249, 336, and 461 cm-1 whose intensities provide quantitative, mode-specific information about the excited-state torsional deformations that lead to isomerization. The dominant contribution to the width of the absorption band in rhodopsin results from Franck-Condon progressions in the 1,549 cm-1 ethylenic normal mode. The lack of vibronic structure in the absorption spectrum is shown to be caused by extensive progressions in low-frequency torsional modes and a large homogeneous linewidth (170 cm-1 half-width) together with thermal population of low-frequency modes and inhomogeneous site distribution effects. The resonance Raman cross-sections of rhodopsin are unusually weak because the excited-state wavepacket moves rapidly (approximately 35 fs) and permanently away from the Franck-Condon geometry along skeletal stretching and torsional coordinates. PMID:3416032

Ultrafast time-resolved pump-probe spectroscopy of PYP by a sub-8 fs pulse laser at 400 nm.

PubMed

Liu, Jun; Yabushita, Atsushi; Taniguchi, Seiji; Chosrowjan, Haik; Imamoto, Yasushi; Sueda, Keiichi; Miyanaga, Noriaki; Kobayashi, Takayoshi

2013-05-02

Impulsive excitation of molecular vibration is known to induce wave packets in both the ground state and excited state. Here, the ultrafast dynamics of PYP was studied by pump-probe spectroscopy using a sub-8 fs pulse laser at 400 nm. The broadband spectrum of the UV pulse allowed us to detect the pump-probe signal covering 360-440 nm. The dependence of the vibrational phase of the vibrational mode around 1155 cm(-1) on the probe photon energy was observed for the first time to our knowledge. The vibrational mode coupled to the electronic transition observed in the probe spectral ranges of 2.95-3.05 and 3.15-3.35 eV was attributed to the wave packets in the ground state and the excited state, respectively. The frequencies in the ground state and excited state were determined to be 1155 ± 1 and 1149 ± 1 cm(-1), respectively. The frequency difference is due to change after photoexcitation. This means a reduction of the bond strength associated with π-π* excitation, which is related to the molecular structure change associated with the primary isomerization process in the photocycle in PYP. Real-time vibrational modes at low frequency around 138, 179, 203, 260, and 317 cm(-1) were also observed and compared with the Raman spectrum for the assignment of the vibrational wave packet.

VizieR Online Data Catalog: Spectral properties of 441 radio pulsars (Jankowski+, 2018)

NASA Astrophysics Data System (ADS)

Jankowski, F.; van Straten, W.; Keane, E. F.; Bailes, M.; Barr, E. D.; Johnston, S.; Kerr, M.

2018-03-01

We present spectral parameters for 441 radio pulsars. These were obtained from observations centred at 728, 1382 and 3100MHz using the 10-50cm and the 20cm multibeam receiver at the Parkes radio telescope. In particular, we list the pulsar names (J2000), the calibrated, band-integrated flux densities at 728, 1382 and 3100MHz, the spectral classifications, the frequency ranges the spectral classifications were performed over, the spectral indices for pulsars with simple power-law spectra and the robust modulation indices at all three centre frequencies for pulsars of which we have at least six measurement epochs. The flux density uncertainties include scintillation and a systematic contribution, in addition to the statistical uncertainty. Upper limits are reported at the 3σ level and all other uncertainties at the 1σ level. (1 data file).

The mid-IR Absorption Cross Sections of α- and β-NAT (HNO3 · 3H2O) in the range 170 to 185 K and of metastable NAD (HNO3 · 2H2O) in the range 172 to 182 K

NASA Astrophysics Data System (ADS)

Iannarelli, R.; Rossi, M. J.

2015-11-01

Growth and Fourier transform infrared (FTIR) absorption in transmission of the title nitric acid hydrates have been performed in a stirred flow reactor (SFR) under tight control of the H2O and HNO3 deposition conditions affording a closed mass balance of the binary mixture. The gas and condensed phases have been simultaneously monitored using residual gas mass spectrometry and FTIR absorption spectroscopy, respectively. Barrierless nucleation of the metastable phases of both α-NAT (nitric acid trihydrate) and NAD (nitric acid dihydrate) has been observed when HNO3 was admitted to the SFR in the presence of a macroscopic thin film of pure H2O ice of typically 1 µm thickness. The stable β-NAT phase was spontaneously formed from the precursor α-NAT phase through irreversible thermal rearrangement beginning at 185 K. This facile growth scheme of nitric acid hydrates requires the presence of H2O ice at thicknesses in excess of approximately hundred nanometers. Absolute absorption cross sections in the mid-IR spectral range (700-4000 cm-1) of all three title compounds have been obtained after spectral subtraction of excess pure ice at temperatures characteristic of the upper troposphere/lower stratosphere. Prominent IR absorption frequencies correspond to the antisymmetric nitrate stretch vibration (ν3(NO3-)) in the range 1300 to 1420 cm-1 and the bands of hydrated protons in the range 1670 to 1850 cm-1 in addition to the antisymmetric O-H stretch vibration of bound H2O in the range 3380 to 3430 cm-1 for NAT.

Synchrotron Based High Resolution Far-Ir Spectroscopy of 1,1-DICHLOROETHYLENE

NASA Astrophysics Data System (ADS)

Peebles, Rebecca A.; Elmuti, Lena F.; Peebles, Sean A.; Obenchain, Daniel A.

2013-06-01

Six vibrational bands of the ^{35}Cl_2C=CH_2 isotopologue of 1,1-dichloroethylene have been recorded in the 350 - 1150 cm^{-1} range using the 0.00096 cm^{-1} resolution far-infrared beamline of the Canadian Light Source synchrotron facility. Results from the analysis of one a-type (ν_9 = 796.01904(8) cm^{-1}, CCl asymmetric stretch) and one c-type (ν_{11} = 868.488626(26) cm^{-1}, CH_2 flap) band will be presented. Over 6000 transitions have now been fitted for these two bands, with ground state rotational and centrifugal distortion constants fixed to values determined by rotational spectroscopy, while the upper state constants have been varied. Anharmonic frequency calculations at the MP2/6-311++G(2d,2p) level were instrumental in assigning the dense spectra. Assignment of additional bands around 603 cm^{-1} (b-type, CCl symmetric stretch, ν_4) and 456 cm^{-1} (c-type, CCl_2 flap, ν_{12}), as well as attempts at assigning the mixed ^{35}Cl^{37}Cl isotopologue spectra for ν_9 and ν_{11}, are in progress. Z. Kisiel, L. Pszczółkowski, Z. Naturforsch, {{50a}, (1995), 347-351.

The scale of the problem: recovering images of reionization with Generalized Morphological Component Analysis

NASA Astrophysics Data System (ADS)

Chapman, Emma; Abdalla, Filipe B.; Bobin, J.; Starck, J.-L.; Harker, Geraint; Jelić, Vibor; Labropoulos, Panagiotis; Zaroubi, Saleem; Brentjens, Michiel A.; de Bruyn, A. G.; Koopmans, L. V. E.

2013-02-01

The accurate and precise removal of 21-cm foregrounds from Epoch of Reionization (EoR) redshifted 21-cm emission data is essential if we are to gain insight into an unexplored cosmological era. We apply a non-parametric technique, Generalized Morphological Component Analysis (gmca), to simulated Low Frequency Array (LOFAR)-EoR data and show that it has the ability to clean the foregrounds with high accuracy. We recover the 21-cm 1D, 2D and 3D power spectra with high accuracy across an impressive range of frequencies and scales. We show that gmca preserves the 21-cm phase information, especially when the smallest spatial scale data is discarded. While it has been shown that LOFAR-EoR image recovery is theoretically possible using image smoothing, we add that wavelet decomposition is an efficient way of recovering 21-cm signal maps to the same or greater order of accuracy with more flexibility. By comparing the gmca output residual maps (equal to the noise, 21-cm signal and any foreground fitting errors) with the 21-cm maps at one frequency and discarding the smaller wavelet scale information, we find a correlation coefficient of 0.689, compared to 0.588 for the equivalently smoothed image. Considering only the pixels in a central patch covering 50 per cent of the total map area, these coefficients improve to 0.905 and 0.605, respectively, and we conclude that wavelet decomposition is a significantly more powerful method to denoise reconstructed 21-cm maps than smoothing.

Modeling and experimental verification of a fan-folded vibration energy harvester for leadless pacemakers

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Karami, M. Amin

2016-03-01

This paper studies energy harvesting from heartbeat vibrations for powering leadless pacemakers. Unlike traditional pacemakers, leadless pacemakers are implanted inside the heart and the pacemaker is in direct contact with the myocardium. A leadless pacemaker is in the shape of a cylinder. Thus, in order to utilize the available 3-dimensional space for the energy harvester, we choose a fan-folded 3D energy harvester. The proposed device consists of several piezoelectric beams stacked on top of each other. The volume of the energy harvester is 1 cm3 and its dimensions are 2 cm × 0.5 cm × 1 cm. Although high natural frequency is generally a major concern with micro-scale energy harvesters, by utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, we reduced the natural frequency to the desired range. This fan-folded design makes it possible to generate more than 10 μ W of power per cubic centimeter. The proposed device is compatible with Magnetic Resonance Imaging. Although the proposed device is a linear energy harvester, it is relatively insensitive to the heart rate. The natural frequencies and the mode shapes of the device are calculated analytically. The accuracy of the analytical model is verified by experimental investigations. We use a closed loop shaker system to precisely replicate heartbeat vibrations in vitro.

Unraveling the 10 micron "silicate" feature of protostars: the detection of frozen interstellar ammonia

NASA Technical Reports Server (NTRS)

Lacy, J. H.; Faraji, H.; Sandford, S. A.; Allamandola, L. J.

1998-01-01

We present infrared spectra of four embedded protostars in the 750-1230 cm-1 (13.3-8.1 microns) range. For NGC 7538 IRS 9, a new band is reported at 1110 cm-1 (9.01 microns, and several others may be present near 785, 820, 900, 1030, and 1075 cm-1 (12.7, 12.2, 11.1, 9.71, and 9.30 microns). The band 1110 cm-1 is attributed to frozen NH3. Its position and width imply that the NH3 is frozen in a polar, H2O-rich interstellar ice component. The NH3/H2O ice ratio inferred for NGC 7538 IRS 9 is 0.1, making NH3 as important a component as CH3OH and CO2 in the polar ices along this line of sight. At these concentrations, hydrogen bonding between the NH3 and H2O can account for much of the enigmatic low-frequency wing on the 3240 cm-1 (3.09 microns) H2O interstellar ice band. The strength of the implied NH3 deformation fundamental at 1624 cm-1 (6.158 microns) can also account for the absorption at this position reported by ISO.

Analysis Of Ultra Compact Ionized Hydrogen Regions Within The Northern Half Of The Galactic Disk

NASA Astrophysics Data System (ADS)

Bruce, John

2011-01-01

From a catalog of 199 candidate ultra compact (UC) HII regions 123 sources included in the the intersection of the GLIMPSE (8 μm),Cornish (6 cm), and Bolocam ( 1.1 mm) galactic plane surveys (BGPS) were analyzed. The sources were sorted based on 6 cm morphology and coincidence with 8 μm bubbles. The 1.1 mm flux attributes were measured and calculations were performed to determine the ionized hydrogen contributions to the 1.1 mm flux. The category averages and frequencies were obtained as well. Significant differences in HII percentages were present among the morphology groups but ranged widely, without apparent distinction, between the bubble forming and triggered source categories.

GNSS global real-time augmentation positioning: Real-time precise satellite clock estimation, prototype system construction and performance analysis

NASA Astrophysics Data System (ADS)

Chen, Liang; Zhao, Qile; Hu, Zhigang; Jiang, Xinyuan; Geng, Changjiang; Ge, Maorong; Shi, Chuang

2018-01-01

Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn't appropriate for the high-frequency real-time GNSS clock estimation, like 1 Hz. Mixed differenced model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS + BeiDou + Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning (RT-PPP) and real-time Standard Point Positioning (RT-SPP). The statistical analysis of the 6 h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1-5 cm for GPS, Beidou MEO and Galileo satellites and about 10 cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1 Hz). The real-time augmentation message signal-in-space ranging error (SISRE), a comprehensive accuracy of orbit and clock and effecting the users' actual positioning performance, is introduced to evaluate and analyze the performance of GPS + BeiDou + Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4-7 cm for GPS, whlile 10 cm for Beidou IGSO/MEO, Galileo and about 30 cm for BeiDou GEO satellites. The real-time positioning results prove that the GPS + BeiDou + Galileo RT-PPP comparing to GPS-only can effectively accelerate convergence time by about 60%, improve the positioning accuracy by about 30% and obtain averaged RMS 4 cm in horizontal and 6 cm in vertical; additionally RT-SPP accuracy in the prototype system can realize positioning accuracy with about averaged RMS 1 m in horizontal and 1.5-2 m in vertical, which are improved by 60% and 70% to SPP based on broadcast ephemeris, respectively.

The effect of stress on ultrasonic pulses in fiber reinforced composites

NASA Technical Reports Server (NTRS)

Hemann, J. H.; Baaklini, G. Y.

1983-01-01

An acoustical-ultrasonic technique was used to demonstrate relationships existing between changes in attenuation of stress waves and tensile stress for an eight ply 0 degree graphite-epoxy fiber reinforced composite. All tests were conducted in the linear range of the material for which no mechanical or macroscopic damage was evident. Changes in attenuation were measured as a function of tensile stress in the frequency domain and in the time domain. Stress wave propagation in these specimens was dispersive, i.e., the wave speed depends on frequency. Wave speeds varied from 267 400 cm/sec to 680 000 cm/sec as the frequency of the signal was varied from 150 kHz to 1.9 MHz which strongly suggests that flexural/lamb wave modes of propagation exist. The magnitude of the attenuation changes depended strongly on tensile stress. It was further observed that the wave speeds increased slightly for all tested frequencies as the stress was increased.

Silicon incorporation in GaAs: From delta-doping to monolayer insertion

NASA Astrophysics Data System (ADS)

Wagner, J.; Newman, R. C.; Roberts, C.

1995-08-01

Raman spectroscopy was used to study the incorporation of Si into doping layers in GaAs, grown by molecular beam epitaxy at a temperature of 400 °C, for Si concentrations ranging from the δ-doping level to a ML coverage. The strength of the scattering by local vibrational modes of substitutional Si was almost constant for Si areal concentration [Si]A in the range 5×1012<[Si]A<5×1013 cm-2 but then decreased, dropping below the detection limit for [Si]A≳3×1014 cm-2. At these concentrations a new vibrational band emerged at a frequency close to 470 cm-1 and developed into the optic zone center phonon of a coherently strained epitaxial layer of Si embedded in GaAs when a coverage of ≊1.5 ML (9.3×1014 cm-2) was reached. These findings strongly indicate that the observed saturation and the eventual decrease of the concentration of substitutional silicon is caused by an increasing incorporation of deposited Si into two-dimensional islands of covalently bonded Si.

Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR

NASA Astrophysics Data System (ADS)

Patil, A. H.; Yatawatta, S.; Koopmans, L. V. E.; de Bruyn, A. G.; Brentjens, M. A.; Zaroubi, S.; Asad, K. M. B.; Hatef, M.; Jelić, V.; Mevius, M.; Offringa, A. R.; Pandey, V. N.; Vedantham, H.; Abdalla, F. B.; Brouw, W. N.; Chapman, E.; Ciardi, B.; Gehlot, B. K.; Ghosh, A.; Harker, G.; Iliev, I. T.; Kakiichi, K.; Majumdar, S.; Mellema, G.; Silva, M. B.; Schaye, J.; Vrbanec, D.; Wijnholds, S. J.

2017-03-01

We present the first limits on the Epoch of Reionization 21 cm H I power spectra, in the redshift range z = 7.9-10.6, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total, 13.0 hr of data were used from observations centered on the North Celestial Pole. After subtraction of the sky model and the noise bias, we detect a non-zero {{{Δ }}}{{I}}2={(56+/- 13{mK})}2 (1-σ) excess variance and a best 2-σ upper limit of {{{Δ }}}212< {(79.6{mK})}2 at k = 0.053 h cMpc-1 in the range z = 9.6-10.6. The excess variance decreases when optimizing the smoothness of the direction- and frequency-dependent gain calibration, and with increasing the completeness of the sky model. It is likely caused by (I) residual side-lobe noise on calibration baselines, (II) leverage due to nonlinear effects, (III) noise and ionosphere-induced gain errors, or a combination thereof. Further analyses of the excess variance will be discussed in forthcoming publications.

Progesterone and testosterone studies by neutron-scattering methods and quantum chemistry calculations

NASA Astrophysics Data System (ADS)

Holderna-Natkaniec, K.; Szyczewski, A.; Natkaniec, I.; Khavryutchenko, V. D.; Pawlukojc, A.

Inelastic incoherent neutron scattering (IINS) and neutron diffraction spectra of progesterone and testosterone were measured simultaneously on the NERA spectrometer at the IBR-2 pulsed reactor in Dubna. Both studied samples do not indicate any phase transition in the temperature range from 20 to 290K. The IINS spectra have been transformed to the phonon density of states (PDS) in the one-phonon scattering approximation. The PDS spectra display well-resolved peaks of low-frequency internal vibration modes up to 600cm-1. The assignment of these modes was proposed taking into account the results of calculations of the structure and dynamics of isolated molecules of the investigated substances. The quantum chemistry calculations were performed by the semi-empirical PM3 method and at the restricted Hartree-Fock level with the 6-31* basis set. The lower internal modes assigned to torsional vibration of the androstane skeleton mix with the lattice vibrations. The intense bands in the PDS spectra in the frequency range from 150 to 300cm-1 are related to librations of structurally inequivalent methyl groups.

Calculated and Experimental Vibrational Properties of P700 and the Iron Sulfur Cluster in Photosystem I

NASA Astrophysics Data System (ADS)

Lamichhane, Hari; Hastings, Gary

2009-11-01

Density functional theory (DFT) based vibrational frequency calculations of Fe4S4(SR)4^n- clusters show that the intense iron-sulfur stretching modes lie in the frequency region between 300-400 cm-1. Among them the iron-sulfur ligand (Fe-S^t) stretching modes are more intense and ˜ 30 cm-1 lower in frequency than the iron-sulfur body (Fe-S^b) stretching modes. Calculations in tetrahydrofuran (THF) show that all these iron-sulfur stretching modes of vibration downshift by ˜ 20 cm-1 upon reduction of the molecule. On the other hand, we have not observed any intense bands from chlorophyll a in the frequency region 400 to 320 cm-1 from the calculations. In an attempt to detect modes associated with iron sulfur clusters in PS I we have obtained light induced (P700^+ - P700) FTIR difference spectra for PSI particles from S. 6803 in the far infrared region. We observe difference bands at many frequencies in the 600-300 cm-1 region. Based on our calculations and literature values we claim that the negative bands at 388 cm-1 and 353 cm-1 in the (P700^+ - P700) FTIR difference spectra be assigned to Fe-S^b and Fe-S^t stretching modes of the ground state of the iron-sulfur cluster FB.

Structural, magnetic and spectral properties of Gd and Dy co-doped dielectrically modified Co-Ni (Ni0.4Co0.6Fe2O4) ferrites

NASA Astrophysics Data System (ADS)

Ditta, Allah; Khan, Muhammad Azhar; Junaid, Muhammad; Khalil, R. M. Arif; Warsi, Muhammad Farooq

2017-02-01

Gadolinium (Gd) and Dysprosium (Dy) co-doped Ni-Co (Ni0.4Co0.6Fe2O4) ferrites were prepared by micro-emulsion route. X-ray diffraction (XRD) analysis indicated the development of cubic spinel structure. The lattice parameter and X-ray density were found to increase from 8.24 to 8.31 Å and 5.57 to 5.91 (gm/cm3) respectively as the Gd-Dy contents increased in nickel-cobalt ferrites. The crystallite size calculated from the Scherrer's formula exhibited the formation of nanocrystalline ferrites (13-26 nm). Two foremost absorption bands observed in FTIR spectra within 400 cm-1 (υ2) to 600 cm-1 (υ1) which correspond to stretching vibrations of tetrahedral and octahedral complexes respectively. The dielectric constant (ε) and dielectric loss (tanδ) were decreased by the optimization of frequency and abrupt decrease in the low frequency region and higher values in the high frequency region were observed. The dielectric dispersion was due to rapid decrease of dielectric constant in the low frequency region. This variation of dielectric dispersion was explicated in the light of space charge polarization model of Maxwell-Wagner. The dielectric loss occurs in these ferrites due to electron hopping and defects in the dipoles. The electron hopping was possible at low frequency range but at higher frequency the dielectric loss was decreased with the decrease of electron hopping. Magnetic properties were observed by measuring M-H loops. Due to low dielectric loss and dielectric constant these materials were appropriate in the fabrication of switching and memory storage devices.

A calibration line list for 807-1167 cm -1 from high resolution Fourier spectroscopy of the 14NH3 nu sub 2 band

NASA Technical Reports Server (NTRS)

Hillman, J. J.; Jennings, D. E.; Brault, J. W.

1982-01-01

A calibration list of 295 lines observed over the 800 to 1170 cm to the -1 power region is presented. This list is intended for use as a calibration reference for calibrating diode laser spectra. The transition frequencies were calibrated against the well established laser frequencies of CO2. The estimated uncertainty in the corrected frequencies is + or - 1x.0001 cm to the -1 power.

ELECTRIC IMPEDANCE OF ARBACIA EGGS

PubMed Central

Cole, Kenneth S.; Cole, Robert H.

1936-01-01

The alternating current resistance and capacity of suspensions of unfertilized and fertilized eggs of Arbacia punctulata have been measured at frequencies from 103 to 1.64 x 107 cycles per second. The unfertilized egg has a static plasma membrane capacity of 0.73 µf./cm.2 which is practically independent of frequency. The fertilized egg has a static membrane capacity of 3.1 µf./cm.2 at low frequencies which decreases to a value of 0.55 µf./cm.2 at high frequencies. The decrease follows closely the relaxation dispersion of the dielectric constant if the dissipation of such a system is ignored. It is considered more probable that the effect is due to a fertilization membrane of 3.1 µf./cm.2 capacity lifted 1.5 µ. from the plasma membrane, the interspace having the conductivity of sea water. The suspensions show a frequency-dependent capacity at low frequencies which may be attributable to surface conductance. The equivalent low frequency internal specific resistance of both the unfertilized and fertilized egg is about 186 ohm cm. or about 6 times that of sea water, while the high frequency data extrapolate to a value of about 4 times sea water. There is evidence at the highest frequencies that the current is penetrating the nucleus and other materials in the cytoplasm. If this effect were entirely due to the nucleus it would lead to a very approximate value of 0.1 µf./cm.2 for the capacity of the nuclear membrane. The measurements do not indicate any change in this effect on fertilization. PMID:19872952

Absorption coefficients and frequency shifts measurement in the spectral range of 1071.88-1084.62 cm-1 vs. pressure for chlorodifluoromethane (CHClF2) using tunable CW CO2 laser

NASA Astrophysics Data System (ADS)

Al-Hawat, Sharif

2013-02-01

Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.

Characteristics and Frequency of Chipping Effects in Near-Contact Gunshot Wounds.

PubMed

Amadasi, Alberto; Mazzarelli, Debora; Merli, Daniele; Brandone, Alberto; Cattaneo, Cristina

2017-05-01

The presence of "chipping" or "flaking" around the edges of gunshot entry wounds has been described among the characteristics of gunshot wounds in bone. In this study, the real frequency of such a peculiar feature was investigated. The presence of "chipping" was assessed on 22 gunshot wounds fired at a near-contact range on bovine ribs with 9-mm bullets. As controls, five samples were shot with a 3 cm range, and five from 40 cm. In 77% of cases shot at near-contact range, a detachment of small fragments of the upper layers of bone was detected, mainly with a circumferential disposition, whereas this feature was lacking in control samples. The study demonstrated the frequency of "chipping" and that it may probably be due to a combined ballistic effect of impact of the bullet itself and expansion of gases. It may be thus considered indicative of close-range shots. © 2016 American Academy of Forensic Sciences.

Charge-carrier mobilities in Cd(0.8)Zn(0.2)Te single crystals used as nuclear radiation detectors

NASA Technical Reports Server (NTRS)

Burshtein, Z.; Jayatirtha, H. N.; Burger, A.; Butler, J. F.; Apotovsky, B.; Doty, F. P.

1993-01-01

Charge-carrier mobilities were measured for the first time in Cd(0.8)Zn(0.2)Te single crystals using time-of-flight measurements of charge carriers produced by short (10 ns) light pulses from a frequency-doubled Nd:YAG laser (532 nm). The electron mobility displayed a T exp -1.1 dependence on the absolute temperature T in the range 200-320 K, with a room-temperature mobility of 1350 sq cm/V s. The hole mobility displayed a T exp -2.0 dependence in the same temperature range, with a room-temperature mobility of 120 sq cm/V s. Cd(0.8)Zn(0.2)Te appears to be a very favorable material for a room-temperature electronic nuclear radiation detector.

Terahertz electromagnetic fields (0.106 THz) do not induce manifest genomic damage in vitro.

PubMed

Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

2012-01-01

Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment.Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm(2) to 2 mW/cm(2), representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction.

Terahertz Electromagnetic Fields (0.106 THz) Do Not Induce Manifest Genomic Damage In Vitro

PubMed Central

Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

2012-01-01

Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction. PMID:23029508

Rydberg-atom based radio-frequency electrometry using frequency modulation spectroscopy in room temperature vapor cells.

PubMed

Kumar, Santosh; Fan, Haoquan; Kübler, Harald; Jahangiri, Akbar J; Shaffer, James P

2017-04-17

Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry. Matched filtering of the signal is also implemented. Although we have reached similarly, high sensitivity with other read-out methods, frequency modulated spectroscopy is advantageous because it is well-suited for building a compact, portable sensor. In the current experiment, ∼3 µV cm^-1 Hz^-1/2 sensitivity is achieved and is found to be photon shot noise limited.

CF2 Detection in Radio-Frequency Ar/CHF3 Plasmas by Fourier Transform Infrared Spectroscopy

NASA Technical Reports Server (NTRS)

Kim, J. S.; Rao, M. V. V. S.; Cappelli, M. A.; Sharma, S. P.

1999-01-01

CFx radicals, in particular CF2, are instrumental in anisotropic etching of SiO2. In order to optimize the CFx radical population in a given process environment, it is imperative that we understand their production mechanism. Towards this goal, we have conducted a series of quantitative measurements of CF2 radicals in low pressure RF plasmas similar to those used in SiO2 etching. In this study, we present preliminary results for Ar/CHF3 plasmas operating at pressures ranging from 10-50 mTorr and powers ranging from 100-500 W in the GEC reference cell, modified for inductive (transformer) coupling. Fourier transform infrared (FTIR) spectroscop) is used to observe the absorption features of the CF2 radical in the 1114 cm-1 and 1096 cm-1 spectral regions. The FTIR spectrometer is equipped with a high-sensitivity mercury cadmium telluride (MCT) detector and has afixed resolution of 0.125 cm- 1. The CF2 concentrations are measured for a range of operating pressures and discharge power levels, and are compared to measurements of the relative CF2 concentrations made by mass spectrometry using the method of appearance potential for radical selectivity.

A Crystal-Physical Model of Electrotransfer in the Superionic Conductor Pb1 - x Sc x F2 + x ( x = 0.1)

NASA Astrophysics Data System (ADS)

Sorokin, N. I.

2018-04-01

The frequency (ν = 10-1-107 Hz) dependences of electrical conductivity σ(ν) of single crystals of superionic conductor Pb0.9Sc0.1F2.1 (10 mol % ScF3) with fluorite type structure (CaF2) in the temperature range 153-410 K have been investigated. The static bulk conductivity σ dc =1.5 × 10-4 S/cm and average hopping frequency ν h = 1.5 × 107 Hz of charge carriers (mobile ions F-) at room temperature (293 K) have been defined from the σ dc (ν) experimental curves. Enthalpies of thermoactivated processes of ionic conductivity σ dc ( T) (Δ H σ = 0.393 ± 0.005 eV) and dielectric relaxation ν h ( T) (Δ H h = 0.37 ± 0.03 eV) coincide within their errors. A crystal-physical model of fluorine-ion transport in a Pb0.9Sc0.1F2.1 crystal lattice has been proposed. The characteristic parameters of charge carriers have been calculated: concentration n mob = 2.0 × 1021 cm-3, the distance of the hopping d ≈ 0.5 nm and mobility μmob = 4.5 × 10-7 cm2/s V (293 K).

Terahertz detection of alcohol using a photonic crystal fiber sensor.

PubMed

Sultana, Jakeya; Islam, Md Saiful; Ahmed, Kawsar; Dinovitser, Alex; Ng, Brian W-H; Abbott, Derek

2018-04-01

Ethanol is widely used in chemical industrial processes as well as in the food and beverage industry. Therefore, methods of detecting alcohol must be accurate, precise, and reliable. In this content, a novel Zeonex-based photonic crystal fiber (PCF) has been modeled and analyzed for ethanol detection in terahertz frequency range. A finite-element-method-based simulation of the PCF sensor shows a high relative sensitivity of 68.87% with negligible confinement loss of 7.79×10 -12    cm -1 at 1 THz frequency and x -polarization mode. Moreover, the core power fraction, birefringence, effective material loss, dispersion, and numerical aperture are also determined in the terahertz frequency range. Owing to the simple fiber structure, existing fabrication methods are feasible. With the outstanding waveguiding properties, the proposed sensor can potentially be used in ethanol detection, as well as polarization-preserving applications of terahertz waves.

Application of spin-exchange relaxation-free magnetometry to the Cosmic Axion Spin Precession Experiment

NASA Astrophysics Data System (ADS)

Wang, Tao; Kimball, Derek F. Jackson; Sushkov, Alexander O.; Aybas, Deniz; Blanchard, John W.; Centers, Gary; Kelley, Sean R. O.'; Wickenbrock, Arne; Fang, Jiancheng; Budker, Dmitry

2018-03-01

The Cosmic Axion Spin Precession Experiment (CASPEr) seeks to measure oscillating torques on nuclear spins caused by axion or axion-like-particle (ALP) dark matter via nuclear magnetic resonance (NMR) techniques. A sample spin-polarized along a leading magnetic field experiences a resonance when the Larmor frequency matches the axion/ALP Compton frequency, generating precessing transverse nuclear magnetization. Here we demonstrate a Spin-Exchange Relaxation-Free (SERF) magnetometer with sensitivity ≈ 1 fT /√{ Hz } and an effective sensing volume of 0.1 cm3 that may be useful for NMR detection in CASPEr. A potential drawback of SERF-magnetometer-based NMR detection is the SERF's limited dynamic range. Use of a magnetic flux transformer to suppress the leading magnetic field is considered as a potential method to expand the SERF's dynamic range in order to probe higher axion/ALP Compton frequencies.

Magnetostatic wave tunable resonators

NASA Astrophysics Data System (ADS)

Castera, J.-P.; Hartemann, P.

1983-06-01

Theoretical principles and techniques for the implementation of magnetostatic surface wave and volume wave resonators in high frequency oscillators are discussed. Magnetostatic waves are magnetic waves that propagate in materials exposed to a polarized magnetic field. The propagation speed ranges from 3-300 km/sec for wavelengths between 1 micron and 10 mm, in the presence of lags from 10-1000 nsec/ cm. Tunable resonators in the 1-20 GHz frequency range have been manufactured with YIG using liquid phase epitaxy for deposition on gadolinium and gallium substrates. Distributed-mirror Fabry-Perot cavity resonators are described and performance tests results are reported, including losses of 8 dB, a quality coefficient under voltage of 450, and frequency rejection outside of resonance better than 10 dB. However, saturation occurs at low power levels at frequencies lower than 4.2 GHz, a feature overcome with forward volume magnetostatic wave generators, which have a quality factor of 500, an insertion loss of 22 dB, and rejection around 15 dB.

Fully Packaged Blue Energy Harvester by Hybridizing a Rolling Triboelectric Nanogenerator and an Electromagnetic Generator.

PubMed

Wang, Xin; Wen, Zhen; Guo, Hengyu; Wu, Changsheng; He, Xu; Lin, Long; Cao, Xia; Wang, Zhong Lin

2016-12-27

Ocean energy, in theory, is an enormous clean and renewable energy resource that can generate electric power much more than that required to power the entire globe without adding any pollution to the atmosphere. However, owing to a lack of effective technology, such blue energy is almost unexplored to meet the energy requirement of human society. In this work, a fully packaged hybrid nanogenerator consisting of a rolling triboelectric nanogenerator (R-TENG) and an electromagnetic generator (EMG) is developed to harvest water motion energy. The outstanding output performance of the R-TENG (45 cm 3 in volume and 28.3 g in weight) in the low-frequency range (<1.8 Hz) complements the ineffective output of EMG (337 cm 3 in volume and 311.8 g in weight) in the same range and thus enables the hybrid nanogenerator to deliver valuable outputs in a broad range of operation frequencies. Therefore, the hybrid nanogenerator can maximize the energy conversion efficiency and broaden the operating frequency simultaneously. In terms of charging capacitors, this hybrid nanogenerator provides not only high voltage and consistent charging from the TENG component but also fast charging speed from the EMG component. The practical application of the hybrid nanogenerator is also demonstrated to power light-emitting diodes by harvesting energy from stimulated tidal flow. The high robustness of the R-TENG is also validated based on the stable electrical output after continuous rolling motion. Therefore, the hybrid R-TENG and EMG device renders an effective and sustainable approach toward large-scale blue energy harvesting in a broad frequency range.

Infrared-Vacuum Ultraviolet Pulsed Field Ionization-Photoelectron Study of C₂H₄ + Using a High-Resolution Infrared Laser

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

Xing, Xi; Reed, Beth; Bahng, Mi-Kyung

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The infrared (IR)-vacuum ultraviolet (VUV)-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectrum for C₂H₄(X 1A g, V 11 = 1, N' Ka' Kc'=3₀₃) in the VUV range of 83 000-84 800 cm -1 obtained using a single mode infrared laser revealed 24 rotationally resolved vibrational bands for the ion C₂H₄ +(X 2B 3u) ground state. The frequencies and symmetry of the vibrational bandsmore » thus determined, together with the anharmonic frequency predictions calculated at the CCSD(T)/aug-cc-pVQZ level, have allowed the unambiguous assignment of these vibrational bands. These bands are mostly combination bands. The measured frequencies of these bands yield the fundamental frequencies for V 8 + ) 1103± ( 10 cm -1 and V 10 + ) 813 ( 10 cm -1 of C₂H₄ +(X 2B 3u), which have not been determined previously. The present IR-VUV-PFI-PE study also provides truly rovibrationally selected and resolved state-to-state cross sections for the photoionization transitions C₂H₄(X~ 1A g; V 11, N' Ka' Kc') → C₂H₄ +(X ~ 2B 3u; V i +, N + Ka + Kc +), where N' Ka' Kc' denotes the rotational level of C₂H₄(X ~ 1Ag; V 11), and V i + and N + Ka + Kc + represent the vibrational and rotational states of the cation.« less

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

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

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

2015-02-02

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

Folded Optical Phonons in Twisted Bilayer Graphene: Raman Signature of Graphene Superlattices

NASA Astrophysics Data System (ADS)

Wang, Yanan; Su, Zhihua; Wu, Wei; Xing, Sirui; Lu, Xiaoxiang; Lu, Xinghua; Pei, Shin-Shem; Robles-Hernandez, Francisco; Hadjiev, Viktor; Bao, Jiming

2013-03-01

In contrast to Bernal-stacked graphene exfoliated from HOPG, twisted bilayer graphene are widely observed in the samples prepared by silicon sublimation of SiC or chemical vapor deposition (CVD). However, many of its basic properties still remain unrevealed. In this work, hexagon-shaped bilayer graphene islands synthesized by CVD method were systematically studied using Raman spectroscopy. A series of folded phonons were observed in the range from 1375 cm-1 to 1525 cm-1. The frequency of folded phonon modes doesn't shift with laser excitation energy, but it is highly dependent on the rotational angle between two layers. In general, the frequency of folded phonon decreases with the increase of rotation angle. This rotation dependence can be qualitatively explained by the folding of phonon dispersion curve of single layer graphene into the reduced Brillouin zone of bilayer superlattice. The obseravtion of folded phonon is an important indication of superlattice band structure.

Chaos Through-Wall Imaging Radar

NASA Astrophysics Data System (ADS)

Xu, Hang; Wang, Bingjie; Zhang, Jianguo; Liu, Li; Li, Ying; Wang, Yuncai; Wang, Anbang

2017-12-01

We experimentally demonstrate a chaos through-wall imaging radar using ultra-wideband chaotic-pulse-position modulation (CPPM) microwave signal. The CPPM signal based on logistic map with 1-ns pulse width and 1-GHz bandwidth is implemented by a field programmable gate array (FPGA) and then up-converted as the radar transmitting signal. Two-dimensional image of human objects behind obstacles is obtained by correlation method and back projection algorithm. Our experiments successfully perform through-wall imaging for single and multiple human objects through 20-cm thick wall. The down-range resolution of the proposed radar is 15 cm. Furthermore, the anti-jamming properties of the proposed radar in CPPM jamming, linear frequency-modulated jamming, and Gaussian noise jamming environments are demonstrated by electromagnetic simulations using the finite-difference time-domain. The simulation results show the CPPM microwave signal possesses excellent jamming immunity to the noise and radio frequency interference, which makes it perform superbly in multiradar environments.

Comb-assisted cavity ring down spectroscopy of 17O enriched water between 7443 and 7921 cm-1

NASA Astrophysics Data System (ADS)

Mondelain, D.; Mikhailenko, S. N.; Karlovets, E. V.; Béguier, S.; Kassi, S.; Campargue, A.

2017-12-01

The room temperature absorption spectrum of water vapor highly enriched in 17O has been recorded by Cavity Ring Down Spectroscopy (CRDS) between 7443 and 7921 cm-1. Three series of recordings were performed with pressure values around 0.1, 1 and 10 Torr. The frequency calibration of the present spectra benefited of the combination of the CRDS spectrometer to a self-referenced frequency comb. The resulting CRD spectrometer combines excellent frequency accuracy over a broad spectral region with a high sensitivity (Noise Equivalent Absorption, αmin∼ 10-11-10-10 cm-1). The investigated spectral region corresponds to the high energy range of the first hexade. The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Partridge and Schwenke. Overall about 4150 lines were measured and assigned to 4670 transitions of six water isotopologues (H216O, H217O, H218O, HD16O, HD17O and HD18O). Their intensities span six orders of magnitude from 10-28 to 10-22 cm/molecule. Most of the new results concern the H217O and HD17O isotopologues for which about 1600 and 400 transitions were assigned leading to the determination of 329 and 207 new energy levels, respectively. For comparison only about 300 and four transitions of H217O and HD17O were previously known in the region, respectively. By comparison to highly accurate H216O line positions available in the literature, the average accuracy on our line centers is checked to be on the order of 3 MHz (10-4 cm-1) or better for not weak well isolated lines. This small uncertainty represents a significant improvement of the line center determination of many H216O lines included in the experimental list provided as Supplementary Material.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends.

PubMed

Wang, G; Peebles, W A; Doyle, E J; Crocker, N A; Wannberg, C; Lau, C; Hanson, G R; Doane, J L

2017-10-01

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ∼40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE 11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. It was observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ∼1.5%-3%. The polarization rotation due to the helical corrugations was in the range ∼1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ∼2.5 dB at 50 GHz and ∼6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. The primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends

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

Wang, Guiding; Peebles, W. A.; Doyle, E. J.

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ~40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. We observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ~1.5%-3%. The polarizationmore » rotation due to the helical corrugations was in the range ~1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ~2.5 dB at 50 GHz and ~6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. Finally, the primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.« less

Investigation of a van der Waals complex with C 1 symmetry: the free-jet rotational spectrum of 1,2-difluoroethane-Ar

NASA Astrophysics Data System (ADS)

Melandri, Sonia; Velino, Biagio; Favero, Paolo G.; Dell'Erba, Adele; Caminati, Walther

2000-04-01

The van der Waals complex between Ar and 1,2-difluoroethane has been investigated by free-jet absorption millimeter-wave spectroscopy in the frequency range 60-78 GHz. The analysis of the spectroscopic constants derived from the rotational spectrum allowed the determination of the dimer's structure. 1,2-Difluoroethane is in the gauche conformation and the Ar atom is in a position stabilized by the interaction with one fluorine and the two carbon atoms. The distance between Ar and the center of mass (CM) of the monomer is 3.968 Å, the angle between the Ar-CM line and the C-C bond is 65° and the dihedral angle Ar-CM-C-C is 99°. From centrifugal distortion effects the dissociation energy of the complex has been estimated to be 2.1 kJ/mol.

Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser.

PubMed

Lamperti, Marco; AlSaif, Bidoor; Gatti, Davide; Fermann, Martin; Laporta, Paolo; Farooq, Aamir; Marangoni, Marco

2018-01-22

We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm -1 , is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N 2 O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs.

Evidence for the frequency-shift of the OA A_1g mode in Hg-based superconductors

NASA Astrophysics Data System (ADS)

Yang, In-Sang; Lee, Hye-Gyong

1996-03-01

The Hg-based superconductors, HgBa_2Ca_n-1Cu_nO_2n+2+δ (n=1,2,3) have two strong Raman peaks at ~ 570 and 590 cm-1 in the high-frequency region. From the results of Raman measurements of Tl-doped Hg-1223 system, it is concluded that the peak at ~ 570 cm-1 does not arise from the vibration of the interstitial oxygen O_δ in the Hg/Tl-O plane, but from the frequency-shift of the A_1g-type vibration of the apical oxygen O_A. The peak at 570 cm-1 is from the O_As surrounded by the O_δs in the nearest neighbor, while the 590 cm-1 mode is from the O_As without the O_δs in the immediate neighbor. The intensity of the 570 cm-1 mode increases with the O_δ content, but the Raman frequencies of both modes do not change significantly. This suggests that the increase of the frequency of the OA A_1g mode under high pressure (I.-S. Yang et al., Phys. Rev. B 51, 644 (1995)) is independent from the O_δ content, in the Hg-based superconductors.

Piezoelectric energy harvesting from heartbeat vibrations for leadless pacemakers

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Karami, M. Amin

2015-12-01

This paper studies energy harvesting from heartbeat vibrations using fan-folded piezoelectric beams. The generated energy from the heartbeat can be used to power a leadless pacemaker. In order to utilize the available 3 dimensional space to the energy harvester, we chose the fan-folded design. The proposed device consists of several piezoelectric beams stacked on top of each other. The size for this energy harvester is 2 cm by 0.5 cm by 1 cm, which makes the natural frequency very high. High natural frequency is one major concern about the micro-scaled energy harvesters. By utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, this natural frequency is reduced to the desired range. This fan-folded design makes it possible to generate more than 10 μW of power. The proposed device does not incorporate magnets and is thus Magnetic resonance imaging (MRI) compatible. Although our device is a linear energy harvester, it is shown that the device is relatively insensitive to the heartrate. The natural frequencies and the mode shapes of the device are calculated. An analytical solution is presented and the method is verified by experimental investigation. We use a closed loop shaker controller and a shaker to simulate the heartbeat vibrations. The developed analytical model is verified through comparison of theoretical and experimental tip displacement and acceleration frequency response functions.

Ultrahigh-rate supercapacitors with large capacitance based on edge oriented graphene coated carbonized cellulous paper as flexible freestanding electrodes

NASA Astrophysics Data System (ADS)

Ren, Guofeng; Li, Shiqi; Fan, Zhao-Xia; Hoque, Md Nadim Ferdous; Fan, Zhaoyang

2016-09-01

Large-capacitance and ultrahigh-rate electrochemical supercapacitors (UECs) with frequency response up to kilohertz (kHz) range are reported using light, thin, and flexible freestanding electrodes. The electrode is formed by perpendicularly edge oriented multilayer graphene/thin-graphite (EOG) sheets grown radially around individual fibers in carbonized cellulous paper (CCP), with cellulous carbonization and EOG deposition implemented in one step. The resulted ∼10 μm thick EOG/CCP electrode is light and flexible. The oriented porous structure of EOG with large surface area, in conjunction with high conductivity of the electrode, ensures ultrahigh-rate performance of the fabricated cells, with large areal capacitance of 0.59 mF cm-2 and 0.53 mF cm-2 and large phase angle of -83° and -80° at 120 Hz and 1 kHz, respectively. Particularly, the hierarchical EOG/CCP sheet structure allows multiple sheets stacked together for thick electrodes with almost linearly increased areal capacitance while maintaining the volumetric capacitance nearly no degradation, a critical merit for developing practical faraday-scale UECs. 3-layers of EOG/CCP electrode achieved an areal capacitance of 1.5 mF cm-2 and 1.4 mF cm-2 at 120 Hz and 1 kHz, respectively. This demonstration moves a step closer to the goal of bridging the frequency/capacitance gap between supercapacitors and electrolytic capacitors.

Structural and electrical characteristics of Bi2YTiVO9 ceramic

NASA Astrophysics Data System (ADS)

Gupta, Prabhasini; Padhee, Rajib; Mahapatra, P. K.; Choudhary, R. N. P.

2018-04-01

Studies of structural and electrical characteristics of a member of the Aurivillius structural family (Bi2YTiVO9), prepared by a standard ceramics technology, have been carried out. The phase-pure compound is found to crystallize in the orthorhombic crystal system. The dielectric constant remains around 200 in the studied frequency range of (1 kHz to 1 MHz) and in a temperature range from room temperature to 200 °C. The loss tangent remains in the range of 0.0236 to 0.0056 at room temperature and 0.081 to 0.009 at 200 °C in the same frequency range. The room temperature hysteresis loop exhibits the ferroelectric nature of the sample with remnant polarization of 0.025 μC/cm2 at the coercive field of 4.880 kV cm‑1. The experimental data obtained from Cole-Cole plot on static as well as infinitely high-frequency permittivity, relaxation time and relaxation distribution parameters are used to simulate ε‧, ε″and tanδ which match nicely with experimental data. The conductivity can be explained on the basis of Correlated Barrier Hopping (CBH) model. With 30.92% tenability and a figure of merit of 13 at room temperature and 1 kHz frequency, combined with a stable relative permittivity around 200 with a maximum variation of 6% over a temperature range of 200 °C and low loss tangent, the compound might have some tenability applications.

High field terahertz pulse generation from plasma wakefield driven by tailored laser pulses

NASA Astrophysics Data System (ADS)

Chen, Zi-Yu

2013-06-01

A scheme to generate high field terahertz (THz) pulses by using tailored laser pulses interaction with a gas target is proposed. The laser wakefield based THz source is emitted from the asymmetric laser shape induced plasma transverse transient net currents. Particle-in-cell simulations show that THz emission with electric filed strength over 1 GV/cm can be obtained with incident laser at 1×1019 W/cm2 level, and the corresponding energy conversion efficiency is more than 10-4. The intensity scaling holds up to high field strengths. Such a source also has a broad tunability range in amplitude, frequency spectra, and temporal shape.

Transient ultrafast coherent spectroscopy of 2-propanol

NASA Astrophysics Data System (ADS)

Meiselman, Seth; Decamp, Matthew; Lorenz, Virginia

We use transient coherent spontaneous Raman spectroscopy to measure the coherence lifetimes of vibrational states in liquid propanol. By creating single-photon-level collective excitations of the vibrational states in the system we observe coherence oscillations due to simultaneous excitation of the 2885 cm-1, 2938 cm-1, and 2976 cm-1 modes. These lifetimes and oscillation frequencies agree with frequency-domain lineshape measurements.

Enhanced dielectric and electrical properties of annealed PVDF thin film

NASA Astrophysics Data System (ADS)

Arshad, A. N.; Rozana, M. D.; Wahid, M. H. M.; Mahmood, M. K. A.; Sarip, M. N.; Habibah, Z.; Rusop, M.

2018-05-01

Poly (vinylideneflouride) (PVDF) thin films were annealed at various annealing temperatures ranging from 70°C to 170°C. This study demonstrates that PVDF thin films annealed at temperature of 70°C (AN70) showed significant enhancement in their dielectric constant (14) at frequency of 1 kHz in comparison to un-annealed PVDF (UN-PVDF), dielectric constant (10) at the same measured frequency. As the annealing temperature was increased from 90°C (AN90) to 150°C (AN150), the dielectric constant value of PVDF thin films was observed to decrease gradually to 11. AN70 also revealed low tangent loss (tan δ) value at similar frequency. With respect to its resistivity properties, the values were found to increase from 1.98×104 Ω.cm to 3.24×104 Ω.cm for AN70 and UN-PVDF films respectively. The improved in dielectric constant, with low tangent loss and high resistivity value suggests that 70°C is the favorable annealing temperature for PVDF thin films. Hence, AN70 is a promising film to be utilized for application in electronic devices such as low frequency capacitor.

Use of cork as absorbent material

NASA Astrophysics Data System (ADS)

Trematerra, Amelia; Lombardi, Ilaria; D'Alesio, Andrea

2017-07-01

Cork is a green and sustainable material. At the end of its useful life, it can be disposed of into the environment without causing any damage. It can be used to improve the acoustics inside environments, as a system for the reduction of reverberation time. Sound absorption systems consist of cork panels mounted at a distance onto a rigid wall. The thickness of the cork panels considered are 1.5 mm and 2.5 mm. While the distances considered from the rigid wall are 3 cm, 5 cm, 10 cm and 15 cm. The absorption coefficient of the samples was measured in the frequency range from 100 Hz to 2,000 Hz with an impedance tube (tube of Kundt). Furthermore, the problems relating to the realization of sound-absorption systems composed of cork panels are also discussed.

Higher operation temperature quadrant photon detectors of 2-11 μm wavelength radiation with large photosensitive areas

NASA Astrophysics Data System (ADS)

Pawluczyk, J.; Sosna, A.; Wojnowski, D.; Koźniewski, A.; Romanis, M.; Gawron, W.; Piotrowski, J.

2017-10-01

We report on the quadrant photon HgCdTe detectors optimized for 2-11 μm wavelength spectral range and Peltier or no cooling, and photosensitive area of a quad-cell of 1×1 to 4×4 mm. The devices are fabricated as photoconductors or multiple photovoltaic cells connected in series (PVM). The former are characterized by a relatively uniform photosensitive area. The PVM photovoltaic cells are distributed along the wafer surface, comprising a periodical stripe structure with a period of 20 μm. Within each period, there is an insensitive gap/trench < 9 μm wide between stripe mesas. The resulting spatial quantization error prevents positioning of the beam spot of size close to the period, but becomes negligible for the optimal spot size comparable to a quadrant-cell area. The photoconductors produce 1/f noise with about 10 kHz knee frequency, due to bias necessary for their operation. The PVM photodiodes are typically operated at 0 V bias, so they generate no 1/f noise and operation from DC is enabled. At 230 K, upper corner frequency of 16 to 100 MHz is obtained for photoconductor and 60 to 80 MHz for PVM, normalized detectivity D* 6×107 cm×Hz1/2/W to >1.4×108 cm×Hz1/2/W for photoconductor and >1.7×108 cm·Hz1/2/W for PVM, allowing for position control of the radiation beam with submicron accuracy at 16 MHz, 10.6 μm wavelength of pulsed radiation spot of 0.8 mm dia at the close-to-maximal input radiation power density in a range of detector linear operation.

The coronal electron density distribution determined from dual-frequency ranging measurements during the 1991 solar conjunction of the Ulysses spacecraft

NASA Technical Reports Server (NTRS)

Bird, M. K.; Volland, H.; Paetzold, M.; Edenhofer, P.; Asmar, S. W.; Brenkle, J. P.

1994-01-01

Dual-frequency ranging and Doppler measurements were conducted in support of the Ulysses Solar Corona Experiment (SCE) at and around the spacecraft's first solar conjunction in 1991 August. The differential group delay time between range codes on the two downlink carrier signals at the wavelengths 13.1 and 3.6 cm, a direct measure of the total electron content between spacecraft and ground station, was used to derive the electron density distribution in the solar corona. Linear power-law representations of the coronal electron density were derived for the range of solar distances from 4 solar radii to 40 solar radii on both sides of the Sun. The corona was found to be very nearly symmetric; the radial falloff exponent being 2.54 +/- 0.05 for occultation ingress (east solar limb) and 2.42 +/- 0.05 for egress (west limb), respectively. The departure of these exponents from the inverse equare relation implies that significant solar wind acceleration is occurring within the radial range of the observations. The electron density level was found to be considerably lower than that observed during the 1988 December solar occultation of Voyager 2. Although the smoothed sunspot number R(sub z) (a standard indicator of solar activity) was almost the same in 1988 December and 1991 August, the mean electron density at 20 solar radii was found to be 1.7 +/- 0.1 x 10(exp 3)/cu cm during the Ulysses conjunction, a decline by almost a factor of 4 from the value obtained during the Voyager conjunction.

Rare and low-frequency coding variants alter human adult height

PubMed Central

Marouli, Eirini; Graff, Mariaelisa; Medina-Gomez, Carolina; Lo, Ken Sin; Wood, Andrew R; Kjaer, Troels R; Fine, Rebecca S; Lu, Yingchang; Schurmann, Claudia; Highland, Heather M; Rüeger, Sina; Thorleifsson, Gudmar; Justice, Anne E; Lamparter, David; Stirrups, Kathleen E; Turcot, Valérie; Young, Kristin L; Winkler, Thomas W; Esko, Tõnu; Karaderi, Tugce; Locke, Adam E; Masca, Nicholas GD; Ng, Maggie CY; Mudgal, Poorva; Rivas, Manuel A; Vedantam, Sailaja; Mahajan, Anubha; Guo, Xiuqing; Abecasis, Goncalo; Aben, Katja K; Adair, Linda S; Alam, Dewan S; Albrecht, Eva; Allin, Kristine H; Allison, Matthew; Amouyel, Philippe; Appel, Emil V; Arveiler, Dominique; Asselbergs, Folkert W; Auer, Paul L; Balkau, Beverley; Banas, Bernhard; Bang, Lia E; Benn, Marianne; Bergmann, Sven; Bielak, Lawrence F; Blüher, Matthias; Boeing, Heiner; Boerwinkle, Eric; Böger, Carsten A; Bonnycastle, Lori L; Bork-Jensen, Jette; Bots, Michiel L; Bottinger, Erwin P; Bowden, Donald W; Brandslund, Ivan; Breen, Gerome; Brilliant, Murray H; Broer, Linda; Burt, Amber A; Butterworth, Adam S; Carey, David J; Caulfield, Mark J; Chambers, John C; Chasman, Daniel I; Chen, Yii-Der Ida; Chowdhury, Rajiv; Christensen, Cramer; Chu, Audrey Y; Cocca, Massimiliano; Collins, Francis S; Cook, James P; Corley, Janie; Galbany, Jordi Corominas; Cox, Amanda J; Cuellar-Partida, Gabriel; Danesh, John; Davies, Gail; de Bakker, Paul IW; de Borst, Gert J.; de Denus, Simon; de Groot, Mark CH; de Mutsert, Renée; Deary, Ian J; Dedoussis, George; Demerath, Ellen W; den Hollander, Anneke I; Dennis, Joe G; Di Angelantonio, Emanuele; Drenos, Fotios; Du, Mengmeng; Dunning, Alison M; Easton, Douglas F; Ebeling, Tapani; Edwards, Todd L; Ellinor, Patrick T; Elliott, Paul; Evangelou, Evangelos; Farmaki, Aliki-Eleni; Faul, Jessica D; Feitosa, Mary F; Feng, Shuang; Ferrannini, Ele; Ferrario, Marco M; Ferrieres, Jean; Florez, Jose C; Ford, Ian; Fornage, Myriam; Franks, Paul W; Frikke-Schmidt, Ruth; Galesloot, Tessel E; Gan, Wei; Gandin, Ilaria; Gasparini, Paolo; Giedraitis, Vilmantas; Giri, Ayush; Girotto, Giorgia; Gordon, Scott D; Gordon-Larsen, Penny; Gorski, Mathias; Grarup, Niels; Grove, Megan L.; Gudnason, Vilmundur; Gustafsson, Stefan; Hansen, Torben; Harris, Kathleen Mullan; Harris, Tamara B; Hattersley, Andrew T; Hayward, Caroline; He, Liang; Heid, Iris M; Heikkilä, Kauko; Helgeland, Øyvind; Hernesniemi, Jussi; Hewitt, Alex W; Hocking, Lynne J; Hollensted, Mette; Holmen, Oddgeir L; Hovingh, G. Kees; Howson, Joanna MM; Hoyng, Carel B; Huang, Paul L; Hveem, Kristian; Ikram, M. Arfan; Ingelsson, Erik; Jackson, Anne U; Jansson, Jan-Håkan; Jarvik, Gail P; Jensen, Gorm B; Jhun, Min A; Jia, Yucheng; Jiang, Xuejuan; Johansson, Stefan; Jørgensen, Marit E; Jørgensen, Torben; Jousilahti, Pekka; Jukema, J Wouter; Kahali, Bratati; Kahn, René S; Kähönen, Mika; Kamstrup, Pia R; Kanoni, Stavroula; Kaprio, Jaakko; Karaleftheri, Maria; Kardia, Sharon LR; Karpe, Fredrik; Kee, Frank; Keeman, Renske; Kiemeney, Lambertus A; Kitajima, Hidetoshi; Kluivers, Kirsten B; Kocher, Thomas; Komulainen, Pirjo; Kontto, Jukka; Kooner, Jaspal S; Kooperberg, Charles; Kovacs, Peter; Kriebel, Jennifer; Kuivaniemi, Helena; Küry, Sébastien; Kuusisto, Johanna; La Bianca, Martina; Laakso, Markku; Lakka, Timo A; Lange, Ethan M; Lange, Leslie A; Langefeld, Carl D; Langenberg, Claudia; Larson, Eric B; Lee, I-Te; Lehtimäki, Terho; Lewis, Cora E; Li, Huaixing; Li, Jin; Li-Gao, Ruifang; Lin, Honghuang; Lin, Li-An; Lin, Xu; Lind, Lars; Lindström, Jaana; Linneberg, Allan; Liu, Yeheng; Liu, Yongmei; Lophatananon, Artitaya; Luan, Jian'an; Lubitz, Steven A; Lyytikäinen, Leo-Pekka; Mackey, David A; Madden, Pamela AF; Manning, Alisa K; Männistö, Satu; Marenne, Gaëlle; Marten, Jonathan; Martin, Nicholas G; Mazul, Angela L; Meidtner, Karina; Metspalu, Andres; Mitchell, Paul; Mohlke, Karen L; Mook-Kanamori, Dennis O; Morgan, Anna; Morris, Andrew D; Morris, Andrew P; Müller-Nurasyid, Martina; Munroe, Patricia B; Nalls, Mike A; Nauck, Matthias; Nelson, Christopher P; Neville, Matt; Nielsen, Sune F; Nikus, Kjell; Njølstad, Pål R; Nordestgaard, Børge G; Ntalla, Ioanna; O'Connel, Jeffrey R; Oksa, Heikki; Loohuis, Loes M Olde; Ophoff, Roel A; Owen, Katharine R; Packard, Chris J; Padmanabhan, Sandosh; Palmer, Colin NA; Pasterkamp, Gerard; Patel, Aniruddh P; Pattie, Alison; Pedersen, Oluf; Peissig, Peggy L; Peloso, Gina M; Pennell, Craig E; Perola, Markus; Perry, James A; Perry, John R.B.; Person, Thomas N; Pirie, Ailith; Polasek, Ozren; Posthuma, Danielle; Raitakari, Olli T; Rasheed, Asif; Rauramaa, Rainer; Reilly, Dermot F; Reiner, Alex P; Renström, Frida; Ridker, Paul M; Rioux, John D; Robertson, Neil; Robino, Antonietta; Rolandsson, Olov; Rudan, Igor; Ruth, Katherine S; Saleheen, Danish; Salomaa, Veikko; Samani, Nilesh J; Sandow, Kevin; Sapkota, Yadav; Sattar, Naveed; Schmidt, Marjanka K; Schreiner, Pamela J; Schulze, Matthias B; Scott, Robert A; Segura-Lepe, Marcelo P; Shah, Svati; Sim, Xueling; Sivapalaratnam, Suthesh; Small, Kerrin S; Smith, Albert Vernon; Smith, Jennifer A; Southam, Lorraine; Spector, Timothy D; Speliotes, Elizabeth K; Starr, John M; Steinthorsdottir, Valgerdur; Stringham, Heather M; Stumvoll, Michael; Surendran, Praveen; Hart, Leen M ‘t; Tansey, Katherine E; Tardif, Jean-Claude; Taylor, Kent D; Teumer, Alexander; Thompson, Deborah J; Thorsteinsdottir, Unnur; Thuesen, Betina H; Tönjes, Anke; Tromp, Gerard; Trompet, Stella; Tsafantakis, Emmanouil; Tuomilehto, Jaakko; Tybjaerg-Hansen, Anne; Tyrer, Jonathan P; Uher, Rudolf; Uitterlinden, André G; Ulivi, Sheila; van der Laan, Sander W; Van Der Leij, Andries R; van Duijn, Cornelia M; van Schoor, Natasja M; van Setten, Jessica; Varbo, Anette; Varga, Tibor V; Varma, Rohit; Edwards, Digna R Velez; Vermeulen, Sita H; Vestergaard, Henrik; Vitart, Veronique; Vogt, Thomas F; Vozzi, Diego; Walker, Mark; Wang, Feijie; Wang, Carol A; Wang, Shuai; Wang, Yiqin; Wareham, Nicholas J; Warren, Helen R; Wessel, Jennifer; Willems, Sara M; Wilson, James G; Witte, Daniel R; Woods, Michael O; Wu, Ying; Yaghootkar, Hanieh; Yao, Jie; Yao, Pang; Yerges-Armstrong, Laura M; Young, Robin; Zeggini, Eleftheria; Zhan, Xiaowei; Zhang, Weihua; Zhao, Jing Hua; Zhao, Wei; Zhao, Wei; Zheng, He; Zhou, Wei; Rotter, Jerome I; Boehnke, Michael; Kathiresan, Sekar; McCarthy, Mark I; Willer, Cristen J; Stefansson, Kari; Borecki, Ingrid B; Liu, Dajiang J; North, Kari E; Heard-Costa, Nancy L; Pers, Tune H; Lindgren, Cecilia M; Oxvig, Claus; Kutalik, Zoltán; Rivadeneira, Fernando; Loos, Ruth JF; Frayling, Timothy M; Hirschhorn, Joel N; Deloukas, Panos; Lettre, Guillaume

2016-01-01

Summary Height is a highly heritable, classic polygenic trait with ∼700 common associated variants identified so far through genome-wide association studies. Here, we report 83 height-associated coding variants with lower minor allele frequencies (range of 0.1-4.8%) and effects of up to 2 cm/allele (e.g. in IHH, STC2, AR and CRISPLD2), >10 times the average effect of common variants. In functional follow-up studies, rare height-increasing alleles of STC2 (+1-2 cm/allele) compromised proteolytic inhibition of PAPP-A and increased cleavage of IGFBP-4 in vitro, resulting in higher bioavailability of insulin-like growth factors. These 83 height-associated variants overlap genes mutated in monogenic growth disorders and highlight new biological candidates (e.g. ADAMTS3, IL11RA, NOX4) and pathways (e.g. proteoglycan/glycosaminoglycan synthesis) involved in growth. Our results demonstrate that sufficiently large sample sizes can uncover rare and low-frequency variants of moderate to large effect associated with polygenic human phenotypes, and that these variants implicate relevant genes and pathways. PMID:28146470

Full-Sky Maps of the VHF Radio Sky with the Owens Valley Radio Observatory Long Wavelength Array

NASA Astrophysics Data System (ADS)

Eastwood, Michael W.; Hallinan, Gregg

2018-05-01

21-cm cosmology is a powerful new probe of the intergalactic medium at redshifts 20 >~ z >~ 6 corresponding to the Cosmic Dawn and Epoch of Reionization. Current observations of the highly-redshifted 21-cm transition are limited by the dynamic range they can achieve against foreground sources of low-frequency (<200 MHz) of radio emission. We used the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) to generate a series of new modern high-fidelity sky maps that capture emission on angular scales ranging from tens of degrees to ~15 arcmin, and frequencies between 36 and 73 MHz. These sky maps were generated from the application of Tikhonov-regularized m-mode analysis imaging, which is a new interferometric imaging technique that is uniquely suited for low-frequency, wide-field, drift-scanning interferometers.

Quasi-cw 20-W tunable 1-sec pulse CO/sub 2/ laser for optical pumping

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

Sharp, L.E.; Barkley, H.J.

1984-05-01

A four-section CO/sub 2/ laser is described which can produce 20 W in fundamental mode during a 1-sec pulse with a frequency tuning range of +- 300 MHz. It operates at 200-Torr pressure using sonic axial flow to inhibit the discharge column from filamenting. The input power density is 598 W cm/sup -3/ corresponding to an efficiency of 2%.

Analysis of HY2A precise orbit determination using DORIS

NASA Astrophysics Data System (ADS)

Gao, Fan; Peng, Bibo; Zhang, Yu; Evariste, Ngatchou Heutchi; Liu, Jihua; Wang, Xiaohui; Zhong, Min; Lin, Mingsen; Wang, Nazi; Chen, Runjing; Xu, Houze

2015-03-01

HY2A is the first Chinese marine dynamic environment satellite. The payloads include a radar altimeter to measure the sea surface height in combination with a high precision orbit to be determined from tracking data. Onboard satellite tracking includes GPS, SLR, and the DORIS DGXX receiver which delivers phase and pseudo-range measurements. CNES releases raw phase and pseudo-range measurements with RINEX DORIS 3.0 format and pre-processed Doppler range-rate with DORIS 2.2 data format. However, the VMSI software package developed by Van Martin Systems, Inc which is used to estimate HY2A DORIS orbits can only process Doppler range-rate but not the DORIS phase data which are available with much shorter latency. We have proposed a method of constructing the phase increment data, which are similar to range-rate data, from RINEX DORIS 3.0 phase data. We compute the HY2A orbits from June, 2013 to August, 2013 using the POD strategy described in this paper based on DORIS 2.2 range-rate data and our reconstructed phase increment data. The estimated orbits are evaluated by comparing with the CNES precise orbits and SLR residuals. Our DORIS-only orbits agree with the precise GPS + SLR + DORIS CNES orbits radially at 1-cm and about 3-cm in the other two directions. SLR test with the 50° cutoff elevation shows that the CNES orbit can achieve about 1.1-cm accuracy in radial direction and our DORIS-only POD solutions are slightly worse. In addition, other HY2A DORIS POD concerns are discussed in this paper. Firstly, we discuss the frequency offset values provided with the RINEX data and find that orbit accuracy for the case when the frequency offset is applied is worse than when it is not applied. Secondly, HY2A DORIS antenna z-offsets are estimated using two kinds of measurements from June, 2013 to August, 2013. The results show that the measurement errors contribute a total of about 2-cm difference of estimated z-offset. Finally, we estimate HY2A orbits selecting 3 days with severe geomagnetic storm activity and SLR residuals suggest that estimating a drag coefficient every 6 h without any constraint is sufficient for maintaining orbit accuracy.

Raman Spectra of Crystalline Double Calcium Orthovanadates Ca10M(VO4)7 (M = Li, K, Na) and Their Interpretation Based on Deconvolution Into Voigt Profiles

NASA Astrophysics Data System (ADS)

Khodasevich, I. A.; Voitikov, S. V.; Orlovich, V. A.; Kosmyna, M. B.; Shekhovtsov, A. N.

2016-09-01

Unpolarized spontaneous Raman spectra of crystalline double calcium orthovanadates Ca10M(VO4)7 (M = Li, K, Na) in the range 150-1600 cm-1 were measured. Two vibrational bands with full-width at half-maximum (FWHM) of 37-50 cm-1 were found in the regions 150-500 and 700-1000 cm-1. The band shapes were approximated well by deconvolution into Voigt profiles. The band at 700-1000 cm-1 was stronger and deconvoluted into eight Voigt profiles. The frequencies of two strong lines were ~848 and ~862 cm-1 for Ca10Li(VO4)7; ~850 and ~866 cm-1 for Ca10Na(VO4)7; and ~844 and ~866 cm-1 for Ca10K(VO4)7. The Lorentzian width parameters of these lines in the Voigt profiles were ~5 times greater than those of the Gaussian width parameters. The FWHM of the Voigt profiles were ~18-42 cm-1. The two strongest lines had widths of 21-25 cm-1. The vibrational band at 300-500 cm-1 was ~5-6 times weaker than that at 700-1000 cm-1 and was deconvoluted into four lines with widths of 25-40 cm-1. The large FWHM of the Raman lines indicated that the crystal structures were disordered. These crystals could be of interest for Raman conversion of pico- and femtosecond laser pulses because of the intense vibrations with large FWHM in the Raman spectra.

Chronic migraine prevalence, disability, and sociodemographic factors: results from the American Migraine Prevalence and Prevention Study.

PubMed

Buse, Dawn C; Manack, Aubrey N; Fanning, Kristina M; Serrano, Daniel; Reed, Michael L; Turkel, Catherine C; Lipton, Richard B

2012-01-01

To estimate the prevalence and distribution of chronic migraine (CM) in the US population and compare the age- and sex-specific profiles of headache-related disability in persons with CM and episodic migraine. Global estimates of CM prevalence using various definitions typically range from 1.4% to 2.2%, but the influence of sociodemographic factors has not been completely characterized. The American Migraine Prevalence and Prevention Study mailed surveys to a sample of 120,000 US households selected to represent the US population. Data on headache frequency, symptoms, sociodemographics, and headache-related disability (using the Migraine Disability Assessment Scale) were obtained. Modified Silberstein-Lipton criteria were used to classify CM (meeting International Classification of Headache Disorders, second edition, criteria for migraine with a headache frequency of ≥15 days over the preceding 3 months). Surveys were returned by 162,756 individuals aged ≥12 years; 19,189 individuals (11.79%) met International Classification of Headache Disorders, second edition, criteria for migraine (17.27% of females; 5.72% of males), and 0.91% met criteria for CM (1.29% of females; 0.48% of males). Relative to 12 to 17 year olds, the age- and sex-specific prevalence for CM peaked in the 40s at 1.89% (prevalence ratio 4.57; 95% confidence interval 3.13-6.67) for females and 0.79% (prevalence ratio 3.35; 95% confidence interval 1.99-5.63) for males. In univariate and adjusted models, CM prevalence was inversely related to annual household income. Lower income groups had higher rates of CM. Individuals with CM had greater headache-related disability than those with episodic migraine and were more likely to be in the highest Migraine Disability Assessment Scale grade (37.96% vs. 9.50%, respectively). Headache-related disability was highest among females with CM compared with males. CM represented 7.68% of migraine cases overall, and the proportion generally increased with age. In the US population, the prevalence of CM was nearly 1%. In adjusted models, CM prevalence was highest among females, in mid-life, and in households with the lowest annual income. Severe headache-related disability was more common among persons with CM and most common among females with CM. © 2012 American Headache Society.

A segmented multi-loop antenna for selective excitation of azimuthal mode number in a helicon plasma source.

PubMed

Shinohara, S; Tanikawa, T; Motomura, T

2014-09-01

A flat type, segmented multi-loop antenna was developed in the Tokai Helicon Device, built for producing high-density helicon plasma, with a diameter of 20 cm and an axial length of 100 cm. This antenna, composed of azimuthally splitting segments located on four different radial positions, i.e., r = 2.8, 4.8, 6.8, and 8.8 cm, can excite the azimuthal mode number m of 0, ±1, and ±2 by a proper choice of antenna feeder parts just on the rear side of the antenna. Power dependencies of the electron density ne were investigated with a radio frequency (rf) power less than 3 kW (excitation frequency ranged from 8 to 20 MHz) by the use of various types of antenna segments, and n(e) up to ~5 × 10(12) cm(-3) was obtained after the density jump from inductively coupled plasma to helicon discharges. Radial density profiles of m = 0 and ±1 modes with low and high rf powers were measured. For the cases of these modes after the density jump, the excited mode structures derived from the magnetic probe measurements were consistent with those expected from theory on helicon waves excited in the plasma.

Perception of fore-and-aft whole-body vibration intensity measured by two methods.

PubMed

Forta, Nazım Gizem; Schust, Marianne

2015-01-01

This experimental study investigated the perception of fore-and-aft whole-body vibration intensity using cross-modality matching (CM) and magnitude estimation (ME) methods. Thirteen subjects were seated on a rigid seat without a backrest and exposed to sinusoidal stimuli from 0.8 to 12.5 Hz and 0.4 to 1.6 ms(-2) r.m.s. The Stevens exponents did not significantly depend on vibration frequency or the measurement method. The ME frequency weightings depended significantly on vibration frequency, but the CM weightings did not. Using the CM and ME weightings would result in higher weighted exposures than those calculated using the ISO (2631-1, 1997) Wd. Compared with ISO Wk, the CM and ME-weighted exposures would be greater at 1.6 Hz and lesser above that frequency. The CM and ME frequency weightings based on the median ratings for the reference vibration condition did not differ significantly. The lack of a method effect for weightings and for Stevens exponents suggests that the findings from the two methods are comparable. Frequency weighting curves for seated subjects for x-axis whole-body vibration were derived from an experiment using two different measurement methods and were compared with the Wd and Wk weighting curves in ISO 2631-1 (1997).

Anomalous frequency-dependent ionic conductivity of lesion-laden human-brain tissue

NASA Astrophysics Data System (ADS)

Emin, David; Akhtari, Massoud; Fallah, Aria; Vinters, Harry V.; Mathern, Gary W.

2017-10-01

We study the effect of lesions on our four-electrode measurements of the ionic conductivity of (˜1 cm3) samples of human brain excised from patients undergoing pediatric epilepsy surgery. For most (˜94%) samples, the low-frequency ionic conductivity rises upon increasing the applied frequency. We attributed this behavior to the long-range (˜0.4 mm) diffusion of solvated sodium cations before encountering intrinsic impenetrable blockages such as cell membranes, blood vessels, and cell walls. By contrast, the low-frequency ionic conductivity of some (˜6%) brain-tissue samples falls with increasing applied frequency. We attribute this unusual frequency-dependence to the electric-field induced liberation of sodium cations from traps introduced by the unusually severe pathology observed in samples from these patients. Thus, the anomalous frequency-dependence of the ionic conductivity indicates trap-producing brain lesions.

Features of anti-inflammatory effects of modulated extremely high-frequency electromagnetic radiation.

PubMed

Gapeyev, Andrew B; Mikhailik, Elena N; Chemeris, Nikolay K

2009-09-01

Using a model of acute zymosan-induced paw edema in NMRI mice, we test the hypothesis that anti-inflammatory effects of extremely high-frequency electromagnetic radiation (EHF EMR) can be essentially modified by application of pulse modulation with certain frequencies. It has been revealed that a single exposure of animals to continuous EHF EMR for 20 min reduced the exudative edema of inflamed paw on average by 19% at intensities of 0.1-0.7 mW/cm(2) and frequencies from the range of 42.2-42.6 GHz. At fixed effective carrier frequency of 42.2 GHz, the anti-inflammatory effect of EHF EMR did not depend on modulation frequencies, that is, application of different modulation frequencies from the range of 0.03-100 Hz did not lead to considerable changes in the effect level. On the contrary, at "ineffective" carrier frequencies of 43.0 and 61.22 GHz, the use of modulation frequencies of 0.07-0.1 and 20-30 Hz has allowed us to restore the effect up to a maximal level. The results obtained show the critical dependence of anti-inflammatory action of low-intensity EHF EMR on carrier and modulation frequencies. Within the framework of this study, the possibility of changing the level of expected biological effect of modulated EMR by a special selection of combination of carrier and modulation frequencies is confirmed.

Contact flexible microstrip applicators (CFMA) in a range from microwaves up to short waves.

PubMed

Gelvich, Edward A; Mazokhin, Vladimir N

2002-09-01

Contact flexible microstrip applicator (CFMA) is a new light-weight microstrip applicator type for superficial and deep local hyperthermia. Typical specimens are developed for operation at frequencies of 434, 70, 40, and 27 MHz. The main common features of CFMA, namely, their flexibility and light weight, as well as their aperture dimensions slightly depend on the operating frequency. Two antenna types are used in CFMAs: inductive antennas with a radiating plane electrical dipole at microwaves, and coplanar capacitive antennas, providing depression of the normal component of the electrical field in the very high-frequency (VHF) and high-frequency (HF) range. The flexibility of the applicators enables one to conform them with curved surfaces. In a bent state of the applicators there arises a focusing effect of energy deposition in deeper located tissues due to linear polarization of the irradiated electromagnetic (EM) field, inherent in CFMA. All CFMA are integrated with silicon water boluses which serve as a matching element, so as a skin cooling agent. Due to this and to the predominance of the tangential electrical component in the radiated EM field, no fat overheating effects are noticed, as a rule. The aperture of the developed applicators overlap the range 160-630 cm2 providing effective heating field sizes (EFSs) 64-400 cm2, respectively. The most bulky CFMAs with an aperture of (21 x 29) cm2 operating at the frequency of 434 MHz weigh 0.8 kg and 2.5 kg at 27 MHz. Phenomenological analysis of the radiating systems, as well as experimental evaluation of the applicators are presented. CFMAs operating at frequencies of 434 and 40 MHz are used in clinical practice. CFMA at 70 and 27 MHz are subjected to laboratory clinical investigations.

A Raman scattering study of the structural ordering in Bi1- x La x FeO3 ceramic ferroelectromagnetics

NASA Astrophysics Data System (ADS)

Teplyakova, N. A.; Titov, S. V.; Verbenko, I. A.; Sidorov, N. V.; Reznichenko, L. A.

2015-09-01

Based on Raman spectra, we have studied structural ordering processes in ceramics of ferroelectromagnetics Bi1- x La x FeO3 ( x = 0.075-0.20). It has been found that the structure of Bi1- x La x FeO3 is close to the structure of the crystal BiFeO3. However, lines in Raman spectra of Bi1- x La x FeO3 are considerably broadened compared to lines in the Raman spectrum of the BiFeO3 single crystal, which indicates that the structure of solid solutions is much more disordered. In Raman spectra of Bi1- x La x FeO3, in the range of librational vibrations of octahedra as a whole (50-90 cm-1), several groups of lines are observed in frequency ranges 59-69, 72-77, and 86-92 cm-1 (depending on the composition of solid solution). This confirms X-ray data that examined solid solutions are not single-phase. At a La content x = 0.120, Raman lines in the low-frequency spectral range narrow, which indicates that the ordering of structural units in cationic sublattices somewhat increases. Upon an increase in the content of La in the Bi1- x La x FeO3 structure, no unambiguous dependence of parameters of spectral lines is observed. It is likely that this is explained by the fact that, as the value of x increases, the character of the incorporation of La into the structure of the solid solution changes.

Electrochemical Investigations of the Interface at Li/Li+ Ion Conducting Channel

DTIC Science & Technology

2006-10-04

calculated using the Nernst -Einstein equation . The values of σi vary in the range of 2.65 x 10-5 - 8.40 x 10-5 S cm-1 at 27 0C, the variation being...Rct). The double-layer capacitance (Cdl) can be calculated from the frequency (f*) corresponding to the maximum of the semicircle using the equation

Tunability of the dielectric function of heavily doped germanium thin films for mid-infrared plasmonics

NASA Astrophysics Data System (ADS)

Frigerio, Jacopo; Ballabio, Andrea; Isella, Giovanni; Sakat, Emilie; Pellegrini, Giovanni; Biagioni, Paolo; Bollani, Monica; Napolitani, Enrico; Manganelli, Costanza; Virgilio, Michele; Grupp, Alexander; Fischer, Marco P.; Brida, Daniele; Gallacher, Kevin; Paul, Douglas J.; Baldassarre, Leonetta; Calvani, Paolo; Giliberti, Valeria; Nucara, Alessandro; Ortolani, Michele

2016-08-01

Heavily doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μ m wavelength range at least. In this work, we investigate the electrodynamics of heavily n -type-doped germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and germanium substrates, are in situ doped with phosphorous in the 1017 to 1019 cm-3 range, then screened plasma frequencies in the 100 to 1200 cm-1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n -type-doped germanium at room temperature.

Fabrication and characterization of the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors

NASA Astrophysics Data System (ADS)

Qing-Wen, Song; Xiao-Yan, Tang; Yan-Jing, He; Guan-Nan, Tang; Yue-Hu, Wang; Yi-Meng, Zhang; Hui, Guo; Ren-Xu, Jia; Hong-Liang, Lv; Yi-Men, Zhang; Yu-Ming, Zhang

2016-03-01

In this paper, the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFFETs) have been fabricated and characterized. A sandwich- (nitridation-oxidation-nitridation) type process was used to grow the gate dielectric film to obtain high channel mobility. The interface properties of 4H-SiC/SiO2 were examined by the measurement of HF I-V, G-V, and C-V over a range of frequencies. The ideal C-V curve with little hysteresis and the frequency dispersion were observed. As a result, the interface state density near the conduction band edge of 4H-SiC was reduced to 2 × 1011 eV-1·cm-2, the breakdown field of the grown oxides was about 9.8 MV/cm, the median peak field-effect mobility is about 32.5 cm2·V-1·s-1, and the maximum peak field-effect mobility of 38 cm2·V-1·s-1 was achieved in fabricated lateral 4H-SiC MOSFFETs. Projcet supported by the National Natural Science Foundation of China (Grant Nos. 61404098, 61176070, and 61274079), the Doctoral Fund of Ministry of Education of China (Grant Nos. 20110203110010 and 20130203120017), the National Key Basic Research Program of China (Grant No. 2015CB759600), and the Key Specific Projects of Ministry of Education of China (Grant No. 625010101).

An observational program to search for radio signals from extraterrestrial intelligence through the use of existing facilities

NASA Technical Reports Server (NTRS)

Edelson, R. E.

1976-01-01

It is argued that a substantial portion of the capability for detecting microwave signals from extraterrestrial civilizations lies not in the application of ever larger antenna collecting areas but rather in the application of millions or billions of simultaneous frequency-channel observations combined with rapid and powerful data processing techniques. The application of these methods to existing facilities is discussed in terms of a program of modest expense and duration which will seek to discover certain classes of extraterrestrial signals of intelligent origin while defining boundaries to the search problem throughout the range of interest. This program will investigate radio-astronomical phenomena of interest and simultaneously define the background of environmental radiation in order to determine physical limitations on both the search strategies and the potential for deep-space communications. Signal parameters that must be determined are examined along with the potential of existing radio-astronomical facilities for detecting narrow-band signals. A seven-year program is described which will carry out a search for extraterrestrial intelligence over 80% of the sky and over the entire frequency range from 1 to 25 GHz with a sensitivity limit varying from 10 to the -21st power W/sq cm at the lowest frequencies to 10 to the -19th power W/sq cm at the higher frequencies.

Correlation of vapor phase infrared spectra and regioisomeric structure in synthetic cannabinoids

NASA Astrophysics Data System (ADS)

Smith, Lewis W.; Thaxton-Weissenfluh, Amber; Abiedalla, Younis; DeRuiter, Jack; Smith, Forrest; Clark, C. Randall

2018-05-01

The twelve 1-n-pentyl-2-, 3-, 4-, 5-, 6- and 7-(1- and 2-naphthoyl)-indoles each have the same substituents attached to the indole ring, identical elemental composition (C24H23NO) yielding identical nominal and accurate masses. These twelve isomers cover all possible positions of carbonyl bridge substitution for both indole (positons 2-7) and naphthalene rings (positions 1 and 2). Regioisomeric compounds can represent significant challenges for mass based analytical methods however, infrared spectroscopy is a powerful tool for the identification of positional isomers in organic compounds. The vapor phase infrared spectra of these twelve uniquely similar compounds were evaluated in GC-IR experiments. These spectra show the bridge position on the indole ring is a dominating influence over the carbonyl absorption frequency observed for these compounds. Substitution on the pyrrole moiety of the indole ring yields the lowest Cdbnd O frequency values for position 2 and 3 giving a narrow range from 1656 to 1654 cm-1. Carbonyl absorption frequencies are higher when the naphthoyl group is attached to the benzene portion of the indole ring yielding absorption values from 1674 to 1671 cm-1. The aliphatic stretching bands in the 2900 cm-1 region yield a consistent triplet pattern because the N-alkyl substituent tail group remains unchanged for all twelve regioisomers. The asymmetric CH2 stretch is the most intense of these three bands. Changes in positional bonding for both the indole and naphthalene ring systems results in unique patterns within the 700 wavenumber out-of-plane region and these absorption bands are different for all 12 regioisomers.

Dynamic Pressure Calibration Standard

NASA Technical Reports Server (NTRS)

Schutte, P. C.; Cate, K. H.; Young, S. D.

1986-01-01

Vibrating columns of fluid used to calibrate transducers. Dynamic pressure calibration standard developed for calibrating flush diaphragm-mounted pressure transducers. Pressures up to 20 kPa (3 psi) accurately generated over frequency range of 50 to 1,800 Hz. System includes two conically shaped aluminum columns one 5 cm (2 in.) high for low pressures and another 11 cm (4.3 in.) high for higher pressures, each filled with viscous fluid. Each column mounted on armature of vibration exciter, which imparts sinusoidally varying acceleration to fluid column. Signal noise low, and waveform highly dependent on quality of drive signal in vibration exciter.

Electromagnetic Radiation Efficiency of Body-Implanted Devices

NASA Astrophysics Data System (ADS)

Nikolayev, Denys; Zhadobov, Maxim; Karban, Pavel; Sauleau, Ronan

2018-02-01

Autonomous wireless body-implanted devices for biotelemetry, telemedicine, and neural interfacing constitute an emerging technology providing powerful capabilities for medicine and clinical research. We study the through-tissue electromagnetic propagation mechanisms, derive the optimal frequency range, and obtain the maximum achievable efficiency for radiative energy transfer from inside a body to free space. We analyze how polarization affects the efficiency by exciting TM and TE modes using a magnetic dipole and a magnetic current source, respectively. Four problem formulations are considered with increasing complexity and realism of anatomy. The results indicate that the optimal operating frequency f for deep implantation (with a depth d ≳3 cm ) lies in the (108- 109 )-Hz range and can be approximated as f =2.2 ×107/d . For a subcutaneous case (d ≲3 cm ), the surface-wave-induced interference is significant: within the range of peak radiation efficiency (about 2 ×108 to 3 ×109 Hz ), the max-to-min ratio can reach a value of 6.5. For the studied frequency range, 80%-99% of radiation efficiency is lost due to the tissue-air wave-impedance mismatch. Parallel polarization reduces the losses by a few percent; this effect is inversely proportional to the frequency and depth. Considering the implantation depth, the operating frequency, the polarization, and the directivity, we show that about an order-of-magnitude efficiency improvement is achievable compared to existing devices.

The Unusual Wolf-Rayet Star EZ CMa

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.

2002-01-01

The XMM-Newton observations were obtained on 29 - 30 October 2001 during the AO-1 Guest Observer program. Our X-ray analysis focused on data from the European Photon Imaging Camera (EPIC). The VLA observations were obtained during a 3.5 hour interval on 1999 Oct. 19 with the array in hybrid BnA configuration. Radio continuum data were acquired at five different frequencies 1.42 GHz (21 cm), 4.86 GHz (6 cm), 8.44 GHz (3.6 cm), 14.94 GHz (2 cm), and 22.46 GHz (1.3 cm). These radio data are unique since they provide an excellent snapshot picture of the dependence of the radio flux on frequency obtained over a short time interval and are thus immune to the variability effects which can distort results obtained from non-contemporaneous observations at different frequencies.

Experimental Structural Dynamic Response of Plate Specimens Due to Sonic Loads in a Progressive Wave Tube

NASA Technical Reports Server (NTRS)

Betts, Juan F.

2001-01-01

The objective of the current study was to assess the repeatability of experiments at NASA Langley's Thermal Acoustic Fatigue Apparatus (TAFA) facility and to use these experiments to validate numerical models. Experiments show that power spectral density (PSD) curves were repeatable except at the resonant frequencies, which tended to vary between 5 Hz to 15 Hz. Results show that the thinner specimen had more variability in the resonant frequency location than the thicker sample, especially for modes higher than the first mode in the frequency range. Root Mean Square (RMS) tended to be more repeatable. The RMS behaved linearly through the SPL range of 135 to 153 dB. Standard Deviations (STDs) of the results tended to be relatively low constant up to about 147 dB. The RMS results were more repeatable than the PDS results. The STD results were less than 10% of the RMS results for both the 0.125 in (0.318 cm) and 0.062 in (0.1588 cm) thick plate. The STD of the PSD results were around 20% to 100% of the mean PSD results for non-resonant and resonant frequencies, respectively, for the 0.125 in (0.318 cm) thicker plate and between 25% to 125% of the mean PSD results, for nonresonant and resonant frequencies, respectively, for the thinner plate.

High-Resolution FTIR Spectrum of the ν 9 Band of Ethylene- D4 (C 2D 4)

NASA Astrophysics Data System (ADS)

Tan, T. L.; Goh, K. L.; Ong, P. P.; Teo, H. H.

2000-08-01

The spectrum of the ν9 fundamental band of ethylene-d4 (C2D4) has been measured with an unapodized resolution of 0.004 cm-1 in the frequency range of 2300-2400 cm-1 using a Fourier transform infrared spectrometer. A total of 549 transitions have been assigned and fitted using a Watson's A-reduced Hamiltonian in the Ir representation to derive rovibrational constants for the upper state (v9 = 1) up to five quartic terms with a standard deviation of 0.00087 cm-1. They represent the most accurate rovibrational constants for the ν9 band so far. About 30 transitions of Ka‧ = 0, one transition of ν9 which were identified to be perturbed possibly by the nearby ν11 and ν2 + ν12 transitions, were not included in the final fit. The ν9 band of C2D4 was found to be basically B-type with an unperturbed band center at 2341.836 94 ± 0.000 13 cm-1.

Ventilation by high-frequency chest wall compression in dogs with normal lungs.

PubMed

Zidulka, A; Gross, D; Minami, H; Vartian, V; Chang, H K

1983-06-01

In 6 anesthetized and paralyzed supine dogs, ventilation by high-frequency chest wall compression (HFCWC) was accomplished by a piston pump rapidly oscillating the pressure in a modified double blood pressure cuff wrapped around the lower thorax. Testing applied frequencies at 3, 5, 8, and 11 Hz, applied peak cuff pressures ranged from 30 to 230 cmH2O. This produced swings of esophageal pressure as high as 18 cmH2O and peak oscillatory air flow ranging from 0.7 to 1.6 L/s. Oscillatory tidal volume declined with increasing frequency and ranged from a mean of 61 to 45 ml. After 30 min of applied HFCWC, arterial blood gas determinations revealed a mean PaCO2 of 29.3 mmHg at 5 Hz, 35 mmHg at 3 Hz, 36 mmHg at 8 Hz, and 51 mmHg at 11 Hz. Mean PaO2 improved from ventilator control values at 3 Hz, remained unchanged at 5 and 8 Hz, and declined at 11 Hz. In 2 dogs breathing spontaneously, HFCWC applied at 5 and 11 Hz resulted in a reduction in spontaneous minute ventilation, mainly by a reduction in spontaneous tidal volume, whereas arterial blood gas values changed slightly. One dog ceased to breath spontaneously within 5 min of application of HFCWC as the PaCO2 fell below control values. We conclude that in dogs with normal lungs, HFCWC may assist spontaneous ventilation. In paralyzed dogs, HFCWC may be of sufficient magnitude to cause hyperventilation.

Effect of mid-scan breathing changes on quality of 4DCT using a commercial phase-based sorting algorithm.

PubMed

Noel, Camille E; Parikh, Parag J

2011-05-01

Though it is known that irregular breathing can introduce artifacts in commercial 4DCT, this has not been systematically explored. The purpose of this study is to investigate the effect of variations in basic parameters of the breathing wave on 4DCT imaging quality. A four-dimensional motion platform holding an acrylic sphere was scanned while moving in a trajectory modeled from a lung cancer patient. A bellows device was used as a respiratory surrogate, and the images were sorted by a commercial phase-based sorting algorithm. Motion during the first half of the scan was produced at a baseline trajectory with a consistent frequency and amplitude of 15 breaths per minute and 1 cm, peak to peak. The two parameters were then varied mid-scan to new frequency and amplitude values, with frequencies ranging from 7.5 to 22 bpm and amplitudes ranging from 0.5 to 1.5 cm. Image sets representing four respiratory phases were contoured. Each set was analyzed to compare centroid displacement, density homogeneity, and volumetric and geometric distortions of the imaged sphere. Undercoverage of the target ITV and overcoverage of healthy tissue was also evaluated. Changes in amplitude of 25% or more, with or without changes in frequency, consistently caused measurable distortions in shape, position, and density of the imaged sphere. Frequency changes over 50% showed a similar trend. This study suggests that basic breathing statistics can be used to quickly assess the quality of a 4DCT scan prior to image reconstruction. Such information can help give indication of the proper course of action when irregular breathing patterns are observed during CT scanning.

Effective electron mass and phonon modes in n-type hexagonal InN

NASA Astrophysics Data System (ADS)

Kasic, A.; Schubert, M.; Saito, Y.; Nanishi, Y.; Wagner, G.

2002-03-01

Infrared spectroscopic ellipsometry and micro-Raman scattering are used to study vibrational and electronic properties of high-quality hexagonal InN. The 0.22-μm-thick highly n-conductive InN film was grown on c-plane sapphire by radio-frequency molecular-beam epitaxy. Combining our results from the ellipsometry data analysis with Hall-effect measurements, the isotropically averaged effective electron mass in InN is determined as 0.14m0. The resonantly excited zone center E1 (TO) phonon mode is observed at 477 cm-1 in the ellipsometry spectra. Despite the high electron concentration in the film, a strong Raman mode occurs in the spectral range of the unscreened A1(LO) phonon. Because an extended carrier-depleted region at the sample surface can be excluded from the ellipsometry-model analysis, we assign this mode to the lower branch of the large-wave-vector LO-phonon-plasmon coupled modes arising from nonconserving wave-vector scattering processes. The spectral position of this mode at 590 cm-1 constitutes a lower limit for the unscreened A1(LO) phonon frequency.

Study of the adsorption of sodium dodecyl sulfate (SDS) at the air/water interface: targeting the sulfate headgroup using vibrational sum frequency spectroscopy.

PubMed

Johnson, C Magnus; Tyrode, Eric

2005-07-07

The surface sensitive technique vibrational sum frequency spectroscopy (VSFS), has been used to study the adsorption behaviour of SDS to the liquid/vapour interface of aqueous solutions, specifically targeting the sulfate headgroup stretches. In the spectral region extending from 980 to 1850 cm(-1), only the vibrations due to the SO(3) group were detectable. The fitted amplitudes for the symmetric SO(3) stretch observed at 1070 cm(-1) for the polarization combinations ssp and ppp, were seen to follow the adsorption isotherm calculated from surface tension measurements. The orientation of the sulfate headgroup in the concentration range spanning from 1.0 mM to above the critical micellar concentration (c.m.c.) was observed to remain constant within experimental error, with the pseudo-C(3) axis close to the surface normal. Furthermore, the effect of increasing amounts of sodium chloride at SDS concentrations above c.m.c. was also studied, showing an increase of approximately 12% in the fitted amplitude for the symmetric SO(3) stretch when increasing the ionic strength from 0 to 300 mM NaCl. Interestingly, the orientation of the SDS headgroup was also observed to remain constant within this concentration range and identical to the case without NaCl.

Spend today, clean tomorrow: Predicting methamphetamine abstinence in a randomized controlled trial

PubMed Central

Murtaugh, Kimberly Ling; Krishnamurti, Tamar; Davis, Alexander L.; Reback, Cathy J.; Shoptaw, Steven

2013-01-01

Objective This secondary analysis of data from a randomized controlled trial tested two behavioral economics mechanisms (substitutability and delay discounting) to explain outcomes using contingency management (CM) for methamphetamine dependence. Frequency and purchase type (hedonic/utilitarian and consumable/durable) of CM payments were also examined. Methods 82 methamphetamine-dependent gay/bisexual men randomly assigned to conditions delivering CM received monetary vouchers in exchange for stimulant-negative urine samples in a 16-week trial requiring thrice weekly visits (Shoptaw et al., 2005). At any visit participants could redeem vouchers for goods. A time-lagged counting process Cox Proportional Hazards model for recurrent event survival analysis examined aspects of the frequency and type of these CM purchases. Results After controlling for severity of baseline methamphetamine use and accumulated CM wealth, as measured by cumulative successful earning days, participants who redeemed CM earnings at any visit (“spenders”) were significantly more likely to produce stimulant-negative urine samples in the subsequent visit, compared to those who did not redeem (“savers”) 1.011* [1.005, 1.017], Z=3.43, p<0.001. Conclusions Findings support the economic concept of substitutability of CM purchases and explain trial outcomes as a function of frequency of CM purchases rather than frequency or accumulated total CM earnings. Promotion of frequent purchases in incentive-based programs should facilitate substitution for the perceived value of methamphetamine and improve abstinence outcomes. PMID:24001246

Sound propagation in water containing large tethered spherical encapsulated gas bubbles with resonance frequencies in the 50 Hz to 100 Hz range.

PubMed

Lee, Kevin M; Hinojosa, Kevin T; Wochner, Mark S; Argo, Theodore F; Wilson, Preston S; Mercier, Richard S

2011-11-01

The efficacy of large tethered encapsulated gas bubbles for the mitigation of low frequency underwater noise was investigated with an acoustic resonator technique. Tethered latex balloons were used as the bubbles, which had radii of approximately 5 cm. Phase speeds were inferred from the resonances of a water and balloon-filled waveguide approximately 1.8 m in length. The Commander and Prosperetti effective-medium model [J. Acoust. Soc. Am. 85, 732-746 (1989)] quantitatively described the observed dispersion from well below to just below the individual bubble resonance frequency, and it qualitatively predicted the frequency range of high attenuation for void fractions between 2% and 5% for collections of stationary balloons within the waveguide. A finite-element model was used to investigate the sensitivity of the waveguide resonance frequencies, and hence the inferred phase speeds, to changes in individual bubble size and position. The results indicate that large tethered encapsulated bubbles could be used mitigate low frequency underwater noise and that the Commander and Prosperetti model would be useful in the design of such a system.

MEMS based Doppler velocity measurement system

NASA Astrophysics Data System (ADS)

Shin, Minchul

The design, fabrication, modeling and characterization of a capacitive micromachined ultrasonic transducer (cMUT) based in-air Doppler velocity measurement system using a 1 cm2 planar array are described. Continuous wave operation in a narrowband was chosen in order to maximize range, as it allows for better rejection of broadband noise. The sensor array has a 160-185 kHz resonant frequency to achieve a 10 degree beamwidth. A model for the cMUT and the acoustic system which includes electrical, mechanical, and acoustic components is provided. Furthermore, characterization of the cMUT sensor with a variety of testing procedures is provided. Laser Doppler vibrometry (LDV), beampattern, reflection, and velocity testing characterize the performance of the sensors. The sensor is capable of measuring the velocity of a moving specular reflector with a resolution of 5 cm/s, an update rate of 0.016 second, and a range of 1.5 m.

In Situ Polymerization and Characterization of Highly Conducting Polypyrrole Fish Scales for High-Frequency Applications

NASA Astrophysics Data System (ADS)

Velhal, Ninad B.; Patil, Narayan D.; Puri, Vijaya R.

2015-12-01

Polypyrrole (Ppy) thin films on alumina were synthesized by an in situ chemical oxidative polymerization method at 300 K with equal monomer-to-oxidant ratio. Fourier transform infrared spectroscopy (FTIR) and FT-Raman spectroscopy confirmed the formation of Ppy. A thickness-dependent change from cauliflower to fish-scale morphology was observed. Microwave properties such as transmission, reflection, shielding effectiveness, permittivity, and microwave conductivity are reported in the frequency range from 8 GHz to 12 GHz. The direct-current (DC) conductivity varied from 9.45 × 10-3 S/cm to 17.29 × 10-3 S/cm, whereas the microwave conductivity varied from 63.07 S/cm to 349.08 S/cm. The shielding effectiveness varied between 6.18 dB and 10.39 dB.

Comprehensive electrical analysis of metal/Al2O3/O-terminated diamond capacitance

NASA Astrophysics Data System (ADS)

Pham, T. T.; Maréchal, A.; Muret, P.; Eon, D.; Gheeraert, E.; Rouger, N.; Pernot, J.

2018-04-01

Metal oxide semiconductor capacitors were fabricated using p - type oxygen-terminated (001) diamond and Al2O3 deposited by atomic layer deposition at two different temperatures 250 °C and 380 °C. Current voltage I(V), capacitance voltage C(V), and capacitance frequency C(f) measurements were performed and analyzed for frequencies ranging from 1 Hz to 1 MHz and temperatures from 160 K to 360 K. A complete model for the Metal-Oxide-Semiconductor Capacitors electrostatics, leakage current mechanisms through the oxide into the semiconductor and small a.c. signal equivalent circuit of the device is proposed and discussed. Interface states densities are then evaluated in the range of 1012eV-1cm-2 . The strong Fermi level pinning is demonstrated to be induced by the combined effects of the leakage current through the oxide and the presence of diamond/oxide interface states.

Quantitative infrared and near-infrared gas-phase spectra for pyridine: Absolute intensities and vibrational assignments

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

Johnson, T. J.; Aker, P. M.; Scharko, N. K.

Using vetted methods for generating quantitative absorption reference data, broadband infrared and near-infrared spectra (total range 11,000 – 600 cm-1) of pyridine vapor were recorded at 0.1 cm-1 spectral resolution, with the analyte thermostatted at 298 K and pressure-broadened to 1 atmosphere using N2 ballast gas. The quantitative spectrum is reported for the first time, and we have re-assigned some of the 27 fundamental modes. Fundamental assignments were confirmed by IR vapor phase band shapes, FT-Raman measurements and comparison with previous analyses. For the 760-Torr vapor-phase IR data several bands show resolved peaks (Q-branches). We have also assigned for themore » first time hundreds of combination and overtone bands in the mid- and near-IR. All assignments were made via comparison to theoretically calculated frequencies and intensities: The frequencies were computed with Gaussian03 with the anharmonic option, using MP2 and the ccpvtz basis set. The intensities were taken from a VSCF calculation in GAMESS using Hartree-Fock (for overtones and combination bands) or from the harmonic MP2 for fundamentals. Overtone and combination band harmonic and anharmonic frequencies, as well as intensities were also calculated using the CFOUR program. It is seen in the NIR spectrum near 6000 cm-1 that the very strong bands arise from the C-H first overtones, whereas only much weaker bands are observed for combination bands of C-H stretching modes. Certain features are discussed for their potential utility for atmospheric monitoring.« less

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1985-01-01

Dynamic dielectric analysis (DDA) is used to study curing polymer systems and thermoplastics. Measurements are made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity epsilon sup *, specific conductivity sigma (ohm/cm) and the relaxation time tau, parameters which are characteristic of the cure state of the material and independent of the size of the sample.

Early results from the Far Infrared Absolute Spectrophotometer (FIRAS)

NASA Technical Reports Server (NTRS)

Mather, J. C.; Cheng, E. S.; Shafer, R. A.; Eplee, R. E.; Isaacman, R. B.; Fixsen, D. J.; Read, S. M.; Meyer, S. S.; Weiss, R.; Wright, E. L.

1991-01-01

The Far Infrared Absolute Spectrophotometer (FIRAS) on the Cosmic Background Explorer (COBE) mapped 98 percent of the sky, 60 percent of it twice, before the liquid helium coolant was exhausted. The FIRAS covers the frequency region from 1 to 100/cm with a 7 deg angular resolution. The spectral resolution is 0.2/cm for frequencies less than 20/cm and 0.8/cm for higher frequencies. Preliminary results include: a limit on the deviations from a Planck curve of 1 percent of the peak brightness from 1 to 20/cm, a temperature of 2.735 +/- 0.06 K, a limit on the Comptonization parameter y of 0.001, on the chemical potential parameter mu of 0.01, a strong limit on the existence of a hot smooth intergalactic medium, and a confirmation that the dipole anisotropy spectrum is that of a Doppler shifted blackbody.

Longitudinal endolymph movements and endocochlear potential changes induced by stimulation at infrasonic frequencies.

PubMed

Salt, A N; DeMott, J E

1999-08-01

The inner ear is continually exposed to pressure fluctuations in the infrasonic frequency range (< 20 Hz) from external and internal body sources. The cochlea is generally regarded to be insensitive to such stimulation. The effects of stimulation at infrasonic frequencies (0.1 to 10 Hz) on endocochlear potential (EP) and endolymph movements in the guinea pig cochlea were studied. Stimuli were applied directly to the perilymph of scala tympani or scala vestibuli of the cochlea via a fluid-filled pipette. Stimuli, especially those near 1 Hz, elicited large EP changes which under some conditions exceeded 20 mV in amplitude and were equivalent to a cochlear microphonic (CM) response. Accompanying the electrical responses was a cyclical, longitudinal displacement of the endolymph. The amplitude and phase of the CM varied according to which perilymphatic scala the stimuli were applied to and whether a perforation was made in the opposing perilymphatic scala. Spontaneously occurring middle ear muscle contractions were also found to induce EP deflections and longitudinal endolymph movements comparable to those generated by perilymphatic injections. These findings suggest that cochlear fluid movements induced by pressure fluctuations at infrasonic frequencies could play a role in fluid homeostasis in the normal state and in fluid disturbances in pathological states.

Fabrication of PbFe12O19 nanoparticles and study of their structural, magnetic and dielectric properties

NASA Astrophysics Data System (ADS)

Mousavi Ghahfarokhi, S. E.; Rostami, Z. A.; Kazeminezhad, I.

2016-02-01

In this study, M-type Lead hexaferrite (PbFe12O19) nanoparticles were prepared by a sol-gel method and the prepared powders were annealed at 700-1000 °C for 1, 1.5, 2, 2.5 and 3 h. The Lead hexaferrite powders were characterized using thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, LCR meter, vibrating sample magnetometer, and Fourier transforms infrared spectroscopy. The size of the nanoparticles was increased with the annealing temparature. The results reveal that the best annealing temperature and annealing time for preparing PbFe12O19 nanoparticles at 800 °C and 3 h are obtained. The infrared spectra measured in range of 4000-400 cm-1 exhibit stretching modes of metal ions in tetrahedral site at 580-550 cm-1 and octahedral site at 470-430 cm-1. The variation in ac conductivity (σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.

Feasibility of RACT for 3D dose measurement and range verification in a water phantom.

PubMed

Alsanea, Fahed; Moskvin, Vadim; Stantz, Keith M

2015-02-01

The objective of this study is to establish the feasibility of using radiation-induced acoustics to measure the range and Bragg peak dose from a pulsed proton beam. Simulation studies implementing a prototype scanner design based on computed tomographic methods were performed to investigate the sensitivity to proton range and integral dose. Derived from thermodynamic wave equation, the pressure signals generated from the dose deposited from a pulsed proton beam with a 1 cm lateral beam width and a range of 16, 20, and 27 cm in water using Monte Carlo methods were simulated. The resulting dosimetric images were reconstructed implementing a 3D filtered backprojection algorithm and the pressure signals acquired from a 71-transducer array with a cylindrical geometry (30 × 40 cm) rotated over 2π about its central axis. Dependencies on the detector bandwidth and proton beam pulse width were performed, after which, different noise levels were added to the detector signals (using 1 μs pulse width and a 0.5 MHz cutoff frequency/hydrophone) to investigate the statistical and systematic errors in the proton range (at 20 cm) and Bragg peak dose (of 1 cGy). The reconstructed radioacoustic computed tomographic image intensity was shown to be linearly correlated to the dose within the Bragg peak. And, based on noise dependent studies, a detector sensitivity of 38 mPa was necessary to determine the proton range to within 1.0 mm (full-width at half-maximum) (systematic error < 150 μm) for a 1 cGy Bragg peak dose, where the integral dose within the Bragg peak was measured to within 2%. For existing hydrophone detector sensitivities, a Bragg peak dose of 1.6 cGy is possible. This study demonstrates that computed tomographic scanner based on ionizing radiation-induced acoustics can be used to verify dose distribution and proton range with centi-Gray sensitivity. Realizing this technology into the clinic has the potential to significantly impact beam commissioning, treatment verification during particle beam therapy and image guided techniques.

Ultrasound attenuation estimation using backscattered echoes from multiple sources.

PubMed

Bigelow, Timothy A

2008-08-01

The objective of this study was to devise an algorithm that can accurately estimate the attenuation along the propagation path (i.e., the total attenuation) from backscattered echoes. It was shown that the downshift in the center frequency of the backscattered ultrasound echoes compared to echoes obtained in a water bath was calculated to have the form Deltaf=mf(o)+b after normalizing with respect to the source bandwidth where m depends on the correlation length, b depends on the total attenuation, and f(o) is the center frequency of the source as measured from a reference echo. Therefore, the total attenuation can be determined independent of the scatterer correlation length by measuring the downshift in center frequency from multiple sources (i.e., different f(o)) and fitting a line to the measured shifts versus f(o). The intercept of the line gives the total attenuation along the propagation path. The calculations were verified using computer simulations of five spherically focused sources with 50% bandwidths and center frequencies of 6, 8, 10, 12, and 14 MHz. The simulated tissue had Gaussian scattering structures with effective radii of 25 mum placed at a density of 250 mm(3). The attenuation of the tissue was varied from 0.1 to 0.9 dB / cm-MHz. The error in the attenuation along the propagation path ranged from -3.5+/-14.7% for a tissue attenuation of 0.1 dB / cm-MHz to -7.0+/-3.1% for a tissue attenuation of 0.9 dB / cm-MHz demonstrating that the attenuation along the propagation path could be accurately determined using backscattered echoes from multiple sources using the derived algorithm.

Space-qualified submillimeter radiometer

NASA Technical Reports Server (NTRS)

Huguenin, G. R.

1987-01-01

The purpose of this research was to develop a reliable submillimeter wave spectrometer for space-borne high frequency spectral line work. The emphasis was on improving the efficiency of frequency multipliers to limit the system components to rugged, low power consumption solid-state devices. This research has allowed Millitech to develop increased efficiency and performance in Millitech's existing line of submillimeter components and systems. Millitech has fabricated and tested a complete solid-state spectrometer front end for use at 560 GHz (the 1(sub 10) to 1(sub 01) transition of water vapor). The spectrometer was designed with the rigors of flight conditions in mind. The spectrometer uses a phase-locked, solid-state Gunn diode oscillator as the local oscillator, employing a tripler to produce about 3 mW of power at 285 GHz, and a low noise second harmonic waveguide mixer which requires less than 2 mW of LO power. The LO (and the signal) is injected into the mixer by means of a quasioptical diplexer. The measured system noise temperature is 2800 K (DSB) over 400 MHz. The whole spectrometer front end is compact (21 cm by 21 cm by 24 cm), light (7.4 kg), and has a power consumption of less than 8 W. Other topics explored in this work include compact frequency agile phase lock loops, optical filters, and InP Gunn oscillators for low noise applications. As a result of this research, the improvement in the design of multipliers and harmonic mixers will allow their use as the LO power for a variety of satellite-borne receivers operating in the 200 to 600 GHz frequency range.

Size-Frequency Distributions of Dust - Size Debris from the Impact Disruption of Chondritic Meteorites

NASA Astrophysics Data System (ADS)

Durda, Daniel D.; Flynn, George J.; Sandel, L. Erica; Strait, Melissa M.

2007-01-01

We present mass-frequency data for fragments from the impact disruption of four chondritic meteorites, extending to masses several orders of magnitude smaller the mass-frequency data that are usually measured in similar impact experiments. Masses of mm- to cm-scale fragments were determined by directly weighing debris collected from the floor of the Ames Vertical Gun Range impact chamber. Masses of sub-mm to dust-size fragments were determined from analysis of foil penetration data. The mass-frequency distributions display a range of morphologies ranging from nearly linear power-law distributions to `broken' power laws with progressively shallower slopes at smaller fragment masses, apparently dependent on the magnitude of the impact specific energy.

Elliptical Acoustic Particle Motion in Underwater Waveguides

DTIC Science & Technology

2013-03-27

Folkert, ”Tracking sperm whales with a towed acoustic vector sensor,” J. Acoust. Soc. Am. Volume 128, Issue 5, pp. 2681-2694 (2010). 2 Santos, P...modal amplitudes Bm and Cm are weak functions of frequency and range independent. This holds for any normal mode description of the acoustic field in a...wavelengths. Error in measurement aside, the frequency range relation- ship described by the waveguide invariant holds for any directional component of I

Magnetic and High-Frequency Dielectric Parameters of Divalent Ion-Substituted W-Type Hexagonal Ferrites

NASA Astrophysics Data System (ADS)

Ali, Akbar; Grössinger, R.; Imran, Muhammad; Khan, M. Ajmal; Elahi, Asmat; Akhtar, Majid Niaz; Mustafa, Ghulam; Khan, Muhammad Azhar; Ullah, Hafeez; Murtaza, Ghulam; Ahmad, Mukhtar

2017-02-01

Polycrystalline W-type hexagonal ferrites with chemical formulae Ba0.5Sr0.5 Co2- x Me x Fe16O27 ( x = 0, 0.5, Me = Mn, Mg, Zn, Ni) have been prepared using sol-gel autocombustion. It has been reported in our earlier published work that all the samples exhibit a single-phase W-type hexagonal structure which was confirmed by x-ray diffraction (XRD) analysis. The values of bulk density lie in the range of 4.64-4.78 g/cm3 for all the samples which are quite high as compared to those for other types of hexaferrites. It was also observed that Zn-substituted ferrite reflects the highest (14.7 × 107 Ω-cm) whereas Mn-substituted ferrite has the lowest (11.3 × 107 Ω-cm) values of direct current (DC) electrical resistivity. The observed values of saturation magnetization ( M s) are found to be in the range of 62.01-68.7 emu/g depending upon the type of cation substitution into the hexagonal lattice. All the samples exhibit a typical soft magnetic character with low values of coercivity ( H c) that are in the range of 26-85 Oe. These ferrites may be promising materials for microwave absorbers due to their higher saturation magnetization and low coercivities. Both the dielectric constant and tangent loss decrease with increasing frequency in the lower frequency region and become constant in the higher frequency region. The much lower dielectric constant obtained in this study makes the investigated ferrites very useful for high-frequency applications, i.e. dielectric resonators and for camouflaging military targets such as ships, tanks and aircrafts, etc.

Spectral monitoring of toluene and ethanol in gasoline blends using Fourier-Transform Raman spectroscopy

NASA Astrophysics Data System (ADS)

Ortega Clavero, Valentin; Weber, Andreas; Schröder, Werner; Curticapean, Dan; Meyrueis, Patrick; Javahiraly, Nicolas

2013-04-01

The combination of fossil-derived fuels with ethanol and methanol has acquired relevance and attention in several countries in recent years. This trend is strongly affected by market prices, constant geopolitical events, new sustainability policies, new laws and regulations, etc. Besides bio-fuels these materials also include different additives as anti-shock agents and as octane enhancer. Some of the chemical compounds in these additives may have harmful properties for both environment and public health (besides the inherent properties, like volatility). We present detailed Raman spectral information from toluene (C7H8) and ethanol (C2H6O) contained in samples of ElO gasoline-ethanol blends. The spectral information has been extracted by using a robust, high resolution Fourier-Transform Raman spectrometer (FT-Raman) prototype. This spectral information has been also compared with Raman spectra from pure additives and with standard Raman lines in order to validate its accuracy in frequency. The spectral information is presented in the range of 0 cm-1 to 3500 cm-1 with a resolution of 1.66cm-1. This allows resolving tight adjacent Raman lines like the ones observed around 1003cm-1 and 1030cm-1 (characteristic lines of toluene). The Raman spectra obtained show a reduced frequency deviation when compared to standard Raman spectra from different calibration materials. The FT-Raman spectrometer prototype used for the analysis consist basically of a Michelson interferometer and a self-designed photon counter cooled down on a Peltier element arrangement. The light coupling is achieved with conventional62.5/125μm multi-mode fibers. This FT-Raman setup is able to extract high resolution and frequency precise Raman spectra from the additives in the fuels analyzed. The proposed prototype has no additional complex hardware components or costly software modules. The mechanical and thermal disturbances affecting the FT-Raman system are mathematically compensated by accurately extracting the optical path information of the Michelson interferometer. This is accomplished by generating an additional interference pattern with a λ = 632.8 nm Helium-Neon laser (HeNe laser). It enables the FT-Raman system to perform reliable and clean spectral measurements from the materials under observation.

Frequency-tuning radiofrequency plasma source operated in inductively-coupled mode under a low magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Nakano, Yudai; Ando, Akira

2017-07-01

A radiofrequency (rf) inductively-coupled plasma source is operated with a frequency-tuning impedance matching system, where the rf frequency is variable in the range of 20-50 MHz and the maximum power is 100 W. The source consists of a 45 mm-diameter pyrex glass tube wound by an rf antenna and a solenoid providing a magnetic field strength in the range of 0-200 Gauss. A reflected rf power for no plasma case is minimized at the frequency of ˜25 MHz, whereas the frequency giving the minimum reflection with the high density plasma is about 28 MHz, where the density jump is observed when minimizing the reflection. A high density argon plasma above 1× {{10}12} cm-3 is successfully obtained in the source for the rf power of 50-100 W, where it is observed that an external magnetic field of a few tens of Gauss yields the highest plasma density in the present configuration. The frequency-tuning plasma source is applied to a compact and high-speed silicon etcher in an Ar-SF6 plasma; then the etching rate of 8~μ m min-1 is obtained for no bias voltage to the silicon wafer, i.e. for the case that a physical ion etching process is eliminated.

A segmented multi-loop antenna for selective excitation of azimuthal mode number in a helicon plasma source

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

Shinohara, S., E-mail: sshinoha@cc.tuat.ac.jp; Tanikawa, T.; Motomura, T.

2014-09-15

A flat type, segmented multi-loop antenna was developed in the Tokai Helicon Device, built for producing high-density helicon plasma, with a diameter of 20 cm and an axial length of 100 cm. This antenna, composed of azimuthally splitting segments located on four different radial positions, i.e., r = 2.8, 4.8, 6.8, and 8.8 cm, can excite the azimuthal mode number m of 0, ±1, and ±2 by a proper choice of antenna feeder parts just on the rear side of the antenna. Power dependencies of the electron density n{sub e} were investigated with a radio frequency (rf) power less thanmore » 3 kW (excitation frequency ranged from 8 to 20 MHz) by the use of various types of antenna segments, and n{sub e} up to ∼5 × 10{sup 12} cm{sup −3} was obtained after the density jump from inductively coupled plasma to helicon discharges. Radial density profiles of m = 0 and ±1 modes with low and high rf powers were measured. For the cases of these modes after the density jump, the excited mode structures derived from the magnetic probe measurements were consistent with those expected from theory on helicon waves excited in the plasma.« less

Study of vibrational modes in CuxAg1-xIn5S8 mixed crystals by infrared reflection measurements

NASA Astrophysics Data System (ADS)

Gasanly, N. M.

2018-04-01

Infrared reflection spectra of CuxAg1-xIn5S8 mixed crystals, grown by Bridgman method, were studied in the wide frequency range of 50-2000 cm-1. All four infrared-active modes were detected, which are in full agreement with the prediction of group-theoretical analysis. Real and imaginary parts of the dielectric function, refractive index and the energy losses function were evaluated from reflectivity measurements. The frequencies of TO and LO modes and oscillator strengths were also determined. The bands detected in IR spectra of studied crystals were assigned to various vibration types (valence and valence-deformation) on the basis of the symmetrized displacements of atoms obtained employing the Melvin projection operators. The linear dependencies of optical mode frequencies on the composition of CuxAg1-xIn5S8 mixed crystals were obtained. These dependencies display one-mode behavior.

Tunable CW diode-pumped Tm,Ho:YLiF4 laser operating at or near room temperature

NASA Technical Reports Server (NTRS)

Mcguckin, Brendan T. (Inventor); Menzies, Robert T. (Inventor)

1995-01-01

A conversion efficiency of 42% and slope efficiency of 60% relative to absorbed pump power are obtained from a continuous wave diode-pumped Tm,Ho:YLiF4 laser at 2 microns with output power of 84 mW at a crystal temperature of 275 K. The emission spectrum is etalon tunable over a range of7 nm (16.3/cm) centered on 2.067 microns with fine tuning capability of the transition frequency with crystal temperature at a measured rate of -0.03/(cm)K. The effective emission cross-section is measured to be 5 x 10(exp -21) cm squared. These and other aspects of the laser performance are disclosed in the context of calculated atmospheric absorption characteristics in this spectral region and potential use in remote sensing applications. Single frequency output and frequency stabilization are achieved using an intracavity etalon in conjunction with an external reference etalon.

Mid-Infrared Vibrational Spectra of Discrete Acetone-Ligated Cerium Hydroxide Cations

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

Groenewold, G. S.; Gianotto, Anita K.; Cossel, Kevin C.

2007-02-15

Cerium (III) hydroxy reactive sites are responsible for several important heterogeneous catalysis processes, and understanding the reaction chemistry of substrate molecules like CO, H2O, and CH3OH as they occur in heterogeneous media is a challenging task. We report here the first infrared spectra of model gas-phase cerium complexes and use the results as a benchmark to assist evaluation of the accuracy of ab initio calculations. Complexes containing [CeOH]2+ ligated by three- and four-acetone molecules were generated by electrospray ionization and characterized using wavelength-selective infrared multiple photon dissociation (IRMPD). The C=O stretching frequency for the [CeOH(acetone)4]2+ species appeared at 1650 cm-1more » and was red-shifted by 90 cm-1 compared to unligated acetone. The magnitude of this shift for the carbonyl frequency was even greater for the [CeOH(acetone)3]2+ complex: the IRMPD peak consisted of two dissociation channels, an initial elimination of acetone at 1635 cm-1, and elimination of acetone accompanied by a serial charge separation producing [CeO(acetone)]+ at 1599 cm-1, with the overall frequency centered at 1616 cm-1. The increasing red shift observed as the number of acetone ligands decreases from four to three is consistent with transfer of more electron density per ligand in the less coordinated complexes. The lower frequency measured for the elimination/charge separation process is likely due to anharmonicity resulting from population of higher vibrational states. The C-C stretching frequency in the complexes is also influenced by coordination to the metal: it is blue-shifted compared to bare acetone, indicating a slight strengthening of the C-C bond in the complex, with the intensity of the absorption decreasing with decreasing ligation. Density functional theory (DFT) calculations using three different functionals (LDA, B3LYP, and PBE0) are used to predict the infrared spectra of the complexes. Calculated frequencies for the carbonyl stretch are within 40 cm-1 of the IRMPD of the three-acetone complex measured using the single acetone loss, and within 60 cm-1 of the measurement for the four-acetone complexes. The B3LYP and LDA functionals provided the best agreement with the measured spectra. The C-C stretching frequencies calculated using B3LYP are higher in energy than the measured values by ~ 30 cm-1, and reproduce the observed trend which shows that the C-C stretching frequency decreases with increasing ligation. Agreement between C-C frequency and calculation was not as good using the LDA functional, but still within 70 cm-1. The results provide an evaluation of changes in the acceptor properties of the metal center as ligands are added, and of the utility of DFT for modeling f-block coordination complexes.« less

Frequency, outcome, and risk factors of contrast media extravasation in 142,651 intravenous contrast-enhanced CT scans.

PubMed

Hwang, Eui Jin; Shin, Cheong-Il; Choi, Young Hun; Park, Chang Min

2018-06-06

To evaluate the frequency, outcome, and risk factors of intravenous contrast media (CM) extravasation during contrast-enhanced CT scans in a large population. After institutional review board approval, 142,651 patients (72,976 males and 69,675 females; mean age, 59.9 ± 13.0 years) who underwent contrast-enhanced CT scans with intravenous CM between January 2015 and April 2017 were retrospectively included. The frequency of CM extravasations and their clinical outcomes were investigated. Risk factors of CM extravasation were evaluated using logistic regression with generalized estimating equation analyses. In addition, the frequency and risk factors of large-volume (≥100 ml) CM extravasation were also investigated. CM extravasation occurred in 0.23% (321/142,651) of patients, all of which were of mild degree and resolved without any sequelae through conservative management. Multivariate analysis revealed that female gender [odds ratio (OR) = 1.61; p < 0.001], 60 < age ≤ 70 years (OR = 1.71; p = 0.004) or age > 70 years (OR = 2.49; p < 0.001), patients in general wards (OR = 2.71; p < 0.001) or ICUs (OR = 4.76; p < 0.001), 9.4 < CM viscosity ≤ 10.0 (OR = 1.65; p = 0.015), 10.0 < CM viscosity ≤ 10.6 (OR = 1.60; p = 0.002), and CM viscosity > 16.0 (OR = 2.55, p < 0.001) were independent risk factors for CM extravasation. CM extravasation during contrast-enhanced CT scans was uncommon with no substantial clinical consequences. Several risk factors that may have the potential to reduce the occurrence of CM extravasation were identified. • The observed frequency of contrast media extravasation during contrast-enhanced CT scans was 0.23% (321/142,651). • Significant risk factors for contrast media extravasation were female gender, age older than 60 years, patients in general wards or ICUs, and the viscosity of contrast media greater than 9.4 mPa∙s. • The main preventive action for contrast media extravasation would be to lower the viscosity of contrast media.

Low-frequency dielectric properties of intrinsic and Al-doped rutile TiO{sub 2} thin films grown by the atomic layer deposition technique

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

Kassmi, M.; LMOP, El Manar University, Tunis 2092; Pointet, J.

2016-06-28

Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO{sub 2} rutile films which are deposited on RuO{sub 2} by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz–100 kHz range, for ac electric fields up to 1 MV{sub rms}/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreasesmore » the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MV{sub rms}/cm range, strong voltage non-linearities are evidenced in undoped films. The conductance increases exponentially with the ac field and the capacitance displays negative values (inductive behavior). Hopping barrier lowering is proposed to explain high-field effects. Finally, it is shown that Al doping strongly improves the high-field dielectric behavior.« less

Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects

NASA Technical Reports Server (NTRS)

Noever, David A.; Koczor, Ronald J.

1998-01-01

We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. It have been indicated three essential components to achieve anomalous gravity effects, namely large, two-layer high-temperature YBCO superconductors, magnetic levitation and AC input in the form of radio-frequency (RF) electromagnetic fields. We report experiments on RF-illuminated (1-15 MHz) superconducting disks with corresponding gravity readings indicating an apparent increase in observed gravity of approximately 3-5 x l0(exp -5)cm/sq s, above and to the side of the superconductor. In this preliminary study, RF- illumination is achieved using a series of large radius (15 cm) spiral antenna with RF power inputs equal to or greater than 90 W. The observed gravitational modification range is significantly lower than the 2.1% gravity modification. The error analyses of thermal and electromagnetic interference in a magnetically shielded gravimeter with vacuum enclosures, Faraday cages and shielded instrument leads, are outlined both experimentally and theoretically. The nearly exact correspondence between the peak gravity effects reported and the well-known peak in AC resistance in superconductors (2-7 MHz, owing to reverse Josephson quantum effects) suggests that electrical resistance will arise in this frequency range and subsequently any trapped magnetic fields in the superconductor may disperse partially into the measuring instrument's local environment. Implications for propulsion initiatives and RF-heating in superconductors will be discussed.

Hawkmoth flight stability in turbulent vortex streets.

PubMed

Ortega-Jimenez, Victor Manuel; Greeter, Jeremy S M; Mittal, Rajat; Hedrick, Tyson L

2013-12-15

Shedding of vortices is a common phenomenon in the atmosphere over a wide range of spatial and temporal scales. However, it is unclear how these vortices of varying scales affect the flight performance of flying animals. In order to examine these interactions, we trained seven hawkmoths (Manduca sexta) (wingspan ~9 cm) to fly and feed in a wind tunnel under steady flow (controls) and in the von Kármán vortex street of vertically oriented cylinders (two different cylinders with diameters of 10 and 5 cm) at speeds of 0.5, 1 and 2 m s(-1). Cylinders were placed at distances of 5, 25 and 100 cm upstream of the moths. Moths exhibited large amplitude yaw oscillations coupled with modest oscillations in roll and pitch, and slight increases in wingbeat frequency when flying in both the near (recirculating) and middle (vortex dominated) wake regions. Wingbeat amplitude did not vary among treatments, except at 1 m s(-1) for the large cylinder. Yaw and roll oscillations were synchronized with the vortex shedding frequencies in moths flying in the wake of the large cylinder at all speeds. In contrast, yaw and pitch were synchronized with the shedding frequency of small vortices at speeds ≤1 m s(-1). Oscillations in body orientation were also substantially smaller in the small cylinder treatment when compared with the large cylinder, regardless of temporal or non-dimensional spatial scale. Moths flying in steady conditions reached a higher air speed than those flying into cylinder wakes. In general, flight effects produced by the cylinder wakes were qualitatively similar among the recirculating and vortex-dominated wake regions; the magnitude of those effects, however, declined gradually with downstream distance.

Endurance testing of a 30-cm Kaufman thruster

NASA Technical Reports Server (NTRS)

Collett, C. R.

1973-01-01

Results of a program to demonstrate lifetime capability of a 30-cm Kaufman ion thruster with a 6000 hour endurance test are described. Included in the program are (1) thruster fabrication, (2) design and construction of a test console containing a transistorized high frequency power processor, and control circuits which provide unattended automatic operation of the thruster, and (3) modification of a vacuum facility to incorporate a frozen mercury collector and permit unattended operation. Four tests ranging in duration from 100 to 1100 hours have been completed. These tests and the resulting thruster modifications are described. The status of the endurance test is also presented.

SLAC pulsed X-ray facility

NASA Astrophysics Data System (ADS)

Ipe, N. E.; McCall, R. C.; Baker, E. D.

1986-05-01

The Stanford Linear Accelerator Center (SLAC) operates a high energy (up to 33 GeV) linear accelerator delivering pulses up to a few microseconds wide. The pulsed nature of the electron beam creates problems in the detection and measurement of radiation both from the accelerator beam and the klystrons that provide the RF power for the accelerator. Hence, a pulsed X-ray facility has been built at SLAC mainly for the purpose of testing the response of different radiation detection instruments to pulsed radiation fields. The X-ray tube consists of an electron gun with a control grid. This provides a stream of pulsed electrons that can be accelerated towards a confined target-window. The window is made up of aluminum 0.051 cm (20 mils) thick, plated on the vacuum side with a layer of gold 0.0006 cm (1/4 mil) thick. The frequency of electron pulses can be varied by an internal pulser from 60 to 360 pulses per second with pulse widths of 360 ns to 5 ms. The pulse amplitude can be varied over a wide range of currents. An external pulser can be used to obtain other frequencies or special pulse shapes. The voltage across the gun can be varied from 0 to 100 kV. The major part of the X-ray tube is enclosed in a large walk-in-cabinet made of 1.9 cm (3/4 in) plywood and lined with 0.32 cm (1/8 in) lead to make a very versatile facility.

Study of the amplified spontaneous emission spectral width and gain coefficient for a KrF laser in unsaturated and saturated conditions

NASA Astrophysics Data System (ADS)

Hariri, A.; Sarikhani, S.

2014-01-01

On the basis of a model of a geometrically dependent gain coefficient, the amplified spontaneous emission (ASE) spectral width was calculated analytically for the nearly resonant transition of ν ˜ ν0, and also numerically for a wide range of transition frequencies. For this purpose, the intensity rate equation was used under unsaturated and saturated conditions. For verifying the proposed model, reported measurements of the ASE energy versus the excitation length for a KrF laser were used. For the excitation length of l = 84 cm corresponding to single-path propagation, the ASE spectral width for the homogeneously broadened transition was calculated to be 6.28 Å, to be compared with the measured 4.1 Å spectral width reported for a KrF oscillator utilizing a two-mirror resonator. With the gain parameters obtained from the ASE energy measurements, the unsaturated and saturated gain coefficients for l = 84 cm were calculated to be 0.042 cm-1 and 0.014 cm-1, respectively. These values of the gain coefficient are comparable to but slightly lower than the measured gain coefficient for laser systems of 80-100 cm excitation lengths reported from different laboratories.

Novel Waveguide Structures in the Terahertz Frequency Range

NASA Astrophysics Data System (ADS)

Mbonye, Marx

Over the last decade, considerable research interest has peaked in realizing an efficient Terahertz (THz) waveguide for potential applications in imaging, sensing, and communications applications. Two of the promising candidates are the two-wire waveguide and the parallel-plate waveguide (PPWG). I present theoretical and experimental evidence that show that the two-wire waveguide supports low loss terahertz pulse propagation, and illustrate that the mode pattern at the end of the waveguide resembles that of a dipole. In comparison to the weakly guided Sommerfeld wave of a single wire waveguide, this two-wire structure exhibits much lower bending losses. I also observe that a commercial 300-Ohm two-wire TVantenna cable can be used for guiding frequency components of up to 0.2 THz, although these cables are generally designed to operate only up to about 800 MHz. The parallel-plate waveguide is another promising candidate that would make an efficient THz waveguide, since it has relatively low Ohmic losses. The transverse electromagnetic mode (TEM) of this waveguide has been generally preferred since it has no cutoff frequency, and therefore no group velocity dispersion. Utilizing this TEM mode, I study the reflection of THz radiation at the end of a PPWG, due to the impedance mismatch between the propagating transverse-electromagnetic mode and the free-space background. I find that for a PPWG with uniformly spaced plates, the reflection coefficient at the output face increases as the plate separation decreases, consistent with predictions by early low frequency ray optical theory. I observe this same trend in tapered PPWGs, when the input separation is fixed, and the output separation is varied. In another study, I investigate how to minimize diffraction losses in PPWGs by using plates with slightly concave surfaces. Using a simple "bouncing plane wave" analysis, I demonstrate how to determine an ideal radius of curvature for a waveguide operating at a given THz frequency. I perform a detailed experimental and simulation study that illustrates, for a waveguide with a plate separation of 1 cm, one can inhibit the diffraction around a frequency of 0.1 THz, when the surface has a curvature of 6.7 cm. Using much longer PPWGs (about 170cm), I reliably measure the overall losses in a PPWG with a radius of curvature of R=6.7 cm, and find it to be less than 1db/m around the design frequency (of 0.1 THz). This is very close to the lowest achieved loss to date with any terahertz waveguide.

Effect of Al2O3 nanoparticles in plasticized PMMA-LiClO4 based solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Pal, P.; Ghosh, A.

2017-05-01

We have studied the broadband complex conductivity spectra covering a 0.01 Hz-3 GHz frequency range for plasticized PMMA-LiClO4 based solid polymer electrolyte embedded with Al2O3 nanoparticle. We have analyzed the conductivity spectra using the random free-energy barrier model (RBM) coupled with electrode polarization contribution in the low frequency region and at high temperatures. The temperature dependence of the ionic conductivity obtained from the analysis has been analyzed using Vogel-Tammann-Fulcher equation. The maximum ionic conductivity ˜ 1.93×10-4 S/cm has been obtained for 1 wt% Al2O3 nanoparticle.

Soviet Free-Electron Laser Research

DTIC Science & Technology

1985-05-01

can generate a narrow band electromagnetic radiation over a wide frequency range that can potentially extend from microwaves through the visible and...refer to experiments listed in Table 2. Table 2 COMPARISON OF SOVIET-U.S. HIGH-CURRENT FEL EXPERIMENT S SOVIET u.s. Pulse line accelerators...Power ... Pulse length Efficiency . 3cm 10MW 0.7 p.sec 1.5% 2. Columbia, 2 February 1977 [9] Hollow electron beam Energy

Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection

NASA Astrophysics Data System (ADS)

Khodabakhsh, Amir; Johansson, Alexandra C.; Foltynowicz, Aleksandra

2015-04-01

Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS) and validate the model by comparing it to experimental CO2 spectra around 1,575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long-term stability of the system, allowing averaging times on the order of minutes. Using a cavity with a finesse of ~9,000, we obtain absorption sensitivity of 6.4 × 10-11 cm-1 Hz-1/2 per spectral element and concentration detection limit for CO2 of 450 ppb Hz-1/2, determined by multiline fitting.

Investigations of different doping concentration of phosphorus and boron into silicon substrate on the variable temperature Raman characteristics

NASA Astrophysics Data System (ADS)

Li, Xiaoli; Ding, Kai; Liu, Jian; Gao, Junxuan; Zhang, Weifeng

2018-01-01

Different doped silicon substrates have different device applications and have been used to fabricate solar panels and large scale integrated circuits. The thermal transport in silicon substrates are dominated by lattice vibrations, doping type, and doping concentration. In this paper, a variable-temperature Raman spectroscopic system is applied to record the frequency and linewidth changes of the silicon peak at 520 cm-1 in five chips of silicon substrate with different doping concentration of phosphorus and boron at the 83K to 1473K temperature range. The doping has better heat sensitive to temperature on the frequency shift over the low temperature range from 83K to 300K but on FWHM in high temperature range from 300K to 1473K. The results will be helpful for fundamental study and practical applications of silicon substrates.

Avoiding neuromuscular stimulation in liver irreversible electroporation using radiofrequency electric fields

NASA Astrophysics Data System (ADS)

Castellví, Quim; Mercadal, Borja; Moll, Xavier; Fondevila, Dolors; Andaluz, Anna; Ivorra, Antoni

2018-02-01

Electroporation-based treatments typically consist of the application of high-voltage dc pulses. As an undesired side effect, these dc pulses cause electrical stimulation of excitable tissues such as motor nerves. The present in vivo study explores the use of bursts of sinusoidal voltage in a frequency range from 50 kHz to 2 MHz, to induce irreversible electroporation (IRE) whilst avoiding neuromuscular stimulation. A series of 100 dc pulses or sinusoidal bursts, both with an individual duration of 100 µs, were delivered to rabbit liver through thin needles in a monopolar electrode configuration, and thoracic movements were recorded with an accelerometer. Tissue samples were harvested three hours after treatment and later post-processed to determine the dimensions of the IRE lesions. Thermal damage due to Joule heating was ruled out via computer simulations. Sinusoidal bursts with a frequency equal to or above 100 kHz did not cause thoracic movements and induced lesions equivalent to those obtained with conventional dc pulses when the applied voltage amplitude was sufficiently high. IRE efficacy dropped with increasing frequency. For 100 kHz bursts, it was estimated that the electric field threshold for IRE is about 1.4 kV cm-1 whereas that of dc pulses is about 0.5 kV cm-1.

Surface phonons on Bi2Sr2CaCu2O8+δ

NASA Astrophysics Data System (ADS)

Phelps, R. B.; Akavoor, P.; Kesmodel, L. L.; Demuth, J. E.; Mitzi, D. B.

1993-11-01

We report measurements of surface optical phonons on Bi2Sr2CaCu2O8+δ with high-resolution electron-energy-loss spectroscopy (HREELS). In addition to peaks near 50 and 80 meV (403 and 645 cm-1), which have been previously observed, our loss spectra exhibit a peak at 26 meV (210 cm-1). Loss spectra were measured at temperatures from 45 to 146 K, and the temperature dependence of the peaks was found to be weak. The 50 and 80 meV peaks shift to lower frequency by ~1.5 meV over this temperature range. All three peaks are attributed to surface optical phonons. The identification of particular bulk modes corresponding to the surface modes observed with HREELS is discussed.

Fast low frequency (down to 10 cm(-1)) multichannel Raman spectroscopy using an iodine vapor filter.

PubMed

Okajima, Hajime; Hamaguchi, Hiro-o

2009-08-01

We have constructed a multi-channel Raman spectrometer that is capable of recording the low frequency region down to 5 cm(-1) with a measurement time of a few tenths of a second. An iodine vapor filter, which uses a narrow (approximately 0.03 cm(-1)) absorption line of iodine for Rayleigh scattering elimination, is combined with a multi-channel Raman spectrometer composed of a single polychromator and a charge-coupled device (CCD) camera. Thanks to the high Rayleigh scattering elimination efficiency of the filter, which is over 10(6), Raman spectra of microcrystalline L-cystine from -300 cm(-1) to 1000 cm(-1) are simultaneously measurable with a small gap of 10 cm(-1) (-5 cm(-1) to 5 cm(-1)). Although raw spectra contain many sharp spikes due to the fine structures of iodine absorption, they can be correctly compensated with the use of a transmittance spectrum measured under the same experimental conditions. Many Raman bands including the 9.8 cm(-1) band are measured with a high signal-to-noise ratio in both the Stokes and anti-Stokes sides with a measurement time as short as 0.2 s.

Electronic and vibrational spectroscopy and vibrationally mediated photodissociation of V+(OCO).

PubMed

Citir, Murat; Altinay, Gokhan; Metz, Ricardo B

2006-04-20

Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm(-1) and in the visible from 15,500 to 16,560 cm(-1), using photofragment spectroscopy. The near-IR band is complex, with a 107 cm(-1) progression in the metal-ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal-ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal-ligand stretch frequency in the ground electronic state nu3'' = 210 cm(-1). The OCO antisymmetric stretch frequency in the ground electronic state (nu1'') is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to nu1'' = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the nu1' = 1 <-- nu1'' = 1 transition. Rotational structure in the resulting vibrational action spectrum confirms that V+(OCO) is linear and gives nu1'' = 2392.0 cm(-1). The OCO antisymmetric stretch frequency in the excited electronic state is nu1' = 2368 cm(-1). Both show a blue shift from the value in free CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO)n clusters.

Influence of Sm doping on structural and dielectric properties of Y{sub 1-x}Sm{sub x}MnO{sub 3} (x = 0, 0.10, 0.20) manganites

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

Dar, Mashkoor Ahmad, E-mail: darmashkoor.phst@gmail.com; Dar, Hilal Ahmad; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com

2016-05-06

Structural and dielectric properties of polycrystalline YMnO{sub 3} (x = 0.0, 0.10 and 0.20) which was prepared by solid-state reaction route, have been investigated. The X-ray diffraction pattern reveals that all the samples are in single phase and show hexagonal structure with P63cm space group. The particle size decreases with increase in Sm doping while to that X-ray density increases with increasing x. The dielectric constant (ε’) of Y{sub 1-x}Sm{sub x}MnO{sub 3} measured in the frequency range 10 Hz to 1MHz is much higher at lower frequencies (≤ 1KHz) and its value decreases with enhanced frequency. At very high frequencies, ε’more » becomes frequency independent and is attributed to Maxwell Wagner type of interfacial polarization model. A very high value of dielectric constant ∼18642 is observed for x = 10%. The dielectric loss (tan δ) decreases wit increase in Sm doping.« less

Waves on Thin Plates: A New (Energy Based) Method on Localization

NASA Astrophysics Data System (ADS)

Turkaya, Semih; Toussaint, Renaud; Kvalheim Eriksen, Fredrik; Lengliné, Olivier; Daniel, Guillaume; Grude Flekkøy, Eirik; Jørgen Måløy, Knut

2016-04-01

Noisy acoustic signal localization is a difficult problem having a wide range of application. We propose a new localization method applicable for thin plates which is based on energy amplitude attenuation and inversed source amplitude comparison. This inversion is tested on synthetic data using a direct model of Lamb wave propagation and on experimental dataset (recorded with 4 Brüel & Kjær Type 4374 miniature piezoelectric shock accelerometers, 1 - 26 kHz frequency range). We compare the performance of this technique with classical source localization algorithms, arrival time localization, time reversal localization, localization based on energy amplitude. The experimental setup consist of a glass / plexiglass plate having dimensions of 80 cm x 40 cm x 1 cm equipped with four accelerometers and an acquisition card. Signals are generated using a steel, glass or polyamide ball (having different sizes) quasi perpendicular hit (from a height of 2-3 cm) on the plate. Signals are captured by sensors placed on the plate on different locations. We measure and compare the accuracy of these techniques as function of sampling rate, dynamic range, array geometry, signal to noise ratio and computational time. We show that this new technique, which is very versatile, works better than conventional techniques over a range of sampling rates 8 kHz - 1 MHz. It is possible to have a decent resolution (3cm mean error) using a very cheap equipment set. The numerical simulations allow us to track the contributions of different error sources in different methods. The effect of the reflections is also included in our simulation by using the imaginary sources outside the plate boundaries. This proposed method can easily be extended for applications in three dimensional environments, to monitor industrial activities (e.g boreholes drilling/production activities) or natural brittle systems (e.g earthquakes, volcanoes, avalanches).

Investigation of geometric design in piezoelectric microelectromechanical systems diaphragms for ultrasonic energy harvesting

NASA Astrophysics Data System (ADS)

Shi, Qiongfeng; Wang, Tao; Kobayashi, Takeshi; Lee, Chengkuo

2016-05-01

Acoustic energy transfer (AET) has been widely used for contactless energy delivery to implantable devices. However, most of the energy harvesters (ultrasonic receivers) for AET are macro-scale transducers with large volume and limited operation bandwidth. Here, we propose and investigate two microelectromechanical systems diaphragm based piezoelectric ultrasonic energy harvesters (PUEHs) as an alternative for AET. The proposed PUEHs consist of micro-scale diaphragm array with different geometric parameter design. Diaphragms in PUEH-1 have large length to width ratio to achieve broadband property, while its energy harvesting performance is compromised. Diaphragms in PUEH-2 have smaller length to width ratio and thinner thickness to achieve both broadband property and good energy harvesting performance. Both PUEHs have miniaturized size and wide operation bandwidth that are ideally suitable to be integrated as power source for implantable biomedical devices. PUEH-1 has a merged -6 dB bandwidth of 74.5% with a central frequency of 350 kHz. PUEH-2 has two separate -6 dB bandwidth of 73.7%/30.8% with central frequencies of 285 kHz/650 kHz. They can adapt to various ultrasonic sources with different working frequency spectrum. Maximum output power is 34.3 nW and 84.3 nW for PUEH-1 and PUEH-2 at 1 mW/cm2 ultrasound intensity input, respectively. The associated power density is 0.734 μW/cm2 and 4.1 μW/cm2, respectively. Better energy harvesting performance is achieved for PUEH-2 because of the optimized length to width ratio and thickness design. Both PUEHs offer more alignment flexibility with more than 40% power when they are in the range of the ultrasound transmitter.

THz wave sensing for petroleum industrial applications

NASA Astrophysics Data System (ADS)

Al-Douseri, Fatemah M.; Chen, Yunqing; Zhang, X.-C.

2006-04-01

We present the results of terahertz (THz) sensing of gasoline products. The frequency-dependent absorption coefficients, refractive indices, and complex dielectric constants of gasoline and xylene isomers were extracted in the spectral range from 0.5 3.0 THz. The THz spectra of gasoline (#87, #89, #93) and related BTEX (benzene, toluene, ethylbenzene, and xylene) compounds were studied by using Fourier transform infrared spectroscopy (FTIR) in the 1.5 20 THz (50 660 cm-1). The xylene isomers, which are used as antiknock agent in gasoline were determined quantitatively in gasoline in the THz range. Our investigations show the potential of THz technology for the petroleum industrial applications.

Miniature piezoresistive solid state integrated pressure sensors

NASA Technical Reports Server (NTRS)

Kahng, S. K.

1980-01-01

The characteristics of silicon pressure sensors with an ultra-small diaphragm are described. The pressure sensors utilize rectangular diaphragm as small as 0.0127 x 0.0254 cm and a p-type Wheatstone bridge consisting of diffused piezoresistive elements, 0.000254 cm by 0.00254 cm. These sensors exhibit as high as 0.5 MHz natural frequency and 1 mV/V/psi pressure sensitivity. Fabrication techniques and high frequency results from shock tube testing and low frequency comparison with microphones are presented.

Laser Induced Damage in Optical Materials: 1979.

DTIC Science & Technology

1980-07-01

as pre- T -1-1viously reported by Hellwarth. Values n2 ranged from 10 13 esu for acetic acid to 10 esu for carbon disulphide. For these nine liquids a...vibrational frequencies of various surface carbonate complexes [13]. It is interesting to note that our data reveal in general a peak in absorption...this valley. The absorption between 5.5 to 8 pm seems to be due to surface carbonates . However, the absence of absorption at 1070 cmŕ signals that the

Photonics-based real-time ultra-high-range-resolution radar with broadband signal generation and processing.

PubMed

Zhang, Fangzheng; Guo, Qingshui; Pan, Shilong

2017-10-23

Real-time and high-resolution target detection is highly desirable in modern radar applications. Electronic techniques have encountered grave difficulties in the development of such radars, which strictly rely on a large instantaneous bandwidth. In this article, a photonics-based real-time high-range-resolution radar is proposed with optical generation and processing of broadband linear frequency modulation (LFM) signals. A broadband LFM signal is generated in the transmitter by photonic frequency quadrupling, and the received echo is de-chirped to a low frequency signal by photonic frequency mixing. The system can operate at a high frequency and a large bandwidth while enabling real-time processing by low-speed analog-to-digital conversion and digital signal processing. A conceptual radar is established. Real-time processing of an 8-GHz LFM signal is achieved with a sampling rate of 500 MSa/s. Accurate distance measurement is implemented with a maximum error of 4 mm within a range of ~3.5 meters. Detection of two targets is demonstrated with a range-resolution as high as 1.875 cm. We believe the proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging.

Wavelength-resolved emission spectroscopy of the alkoxy and alkylthio radicals in a supersonic jet

NASA Technical Reports Server (NTRS)

Misra, Prabhakar; Zhu, Xinming; Hsueh, Ching-Yu; Kamal, Mohammed M.

1993-01-01

Wavelength-resolved emission spectra of methoxy (CH3O) and methylthio (CH3S) radicals have been obtained in a supersonic jet environment with a resolution of 0.3 nm by dispersing the total laser-induced fluorescence with a 0.6 m monochromator. A detailed analysis of the single vibronic level dispersed fluorescence spectra yields the following vibrational frequencies for CH3O in the X(2)E state; nu(sub 1 double prime) = 2953/cm, nu(sub 2 double prime) = 1375/cm, nu(sub 3 double prime) = 1062/cm, nu(sub 4 double prime) = 2869/cm, nu(sub 5 double prime) = 1528/cm and nu(sub 6 double prime) = 688/cm. A similar analysis of the wavelength-resolved emission spectra of CH3S provides the following ground state vibrational frequencies: nu(sub 2 double prime) = 1329/cm, nu(sub 3 double prime) = 739/cm and nu(sub 6 double prime) = 601/cm. An experimental uncertainty of 20/cm is estimated for the assigned frequencies.

Vibrational assignment of aluminum(III) Tris-acetylacetone

NASA Astrophysics Data System (ADS)

Tayyari, Sayyed Faramarz; Raissi, Haydar; Ahmadabadi, Zahra

2002-10-01

The geometry, frequency and intensity of the vibrational bands of aluminum(III) Tris-acetylacetone Al(AA) 3 and its 1, 3, 5- 13C derivative were obtained by the Hartree-Fock (HF) and Density Functional Theory (DFT) with the B3LYP, B1LYP, and G96LYP functionals and using the 6-31G* basis set. The calculated frequencies are compared with the solid IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated bond lengths and bond angles are in good agreement with the experimental results. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands in the 500-390 cm -1 frequency range are assigned to the vibrations of metalligand bonds.

Infrared and Raman spectroscopic study of BDA-TTP [2,5-bis(1,3-dithian-2-ylidene) 1,3,4,6-tetrathiapentalene] and its charge-transfer salts

NASA Astrophysics Data System (ADS)

Uruichi, Mikio; Nakano, Chikako; Tanaka, Masayuki; Yakushi, Kyuya; Kaihatsu, Takayuki; Yamada, Jun-ichi

2008-09-01

Infrared and Raman spectra in the frequency range of 1200-1600 cm -1 were observed using BDA-TTP and (BDA-TTP)CuCl 2 crystals. The C =C stretching and CH 2 bending modes in this frequency region were assigned based on quantum chemical calculation of the normal modes by the density functional theory (DFT) method. The three C =C stretching modes of BDA-TTP showed a significant low-frequency shift upon oxidation. One of the Raman-active C =C stretching modes is strongly coupled with the charge-transfer excited state. Vibrational analysis was applied to β-(BDA-TTP) 2I 3. The infrared-active C =C stretching mode strongly suggests that the insulating state of β-(BDA-TTP) 2I 3 is characterized as a dimer-Mott state below 150 K.

Evidence of an Intermediate Phase in bulk alloy oxide glass sysem

NASA Astrophysics Data System (ADS)

Chakraborty, S.; Boolchand, P.

2011-03-01

Reversibility windows have been observed in modified oxides (alkali-silicates and -germanates) and identified with Intermediate Phases(IPs). Here we find preliminary evidence of an IP in a ternary oxide glass, (B2 O3)5 (Te O2)95-x (V2O5)x , which is composed of network formers. Bulk glasses are synthesized across the 18% x 35 % composition range, and examined in Raman scattering, modulated DSC and molar volume experiments. Glass transition temperatures Tg (x) steadily decrease with V2O5 content x, and reveal the enthalpy of relaxation at Tg to show a global minimum in the 24% x < 27 range, the reversibility window (IP). Molar volumes reveal a minimum in this window. Raman scattering reveals a Boson mode, and at least six other vibrational bands in the 100cm-1 < ν < 1700cm-1 range. Compositional trends in vibrational mode strengths and frequency are established. These results will be presented in relation to glass structure evolution with vanadia content and the underlying elastic phases. Supported by NSF grant DMR 08-53957.

Onset of hydrogen bonded collective network of water in 1,4-dioxane.

PubMed

Luong, Trung Quan; Verma, Pramod Kumar; Mitra, Rajib Kumar; Havenith, Martina

2011-12-22

We have studied the evolution of water hydrogen bonded collective network dynamics in mixtures of 1,4-dioxane (Dx) as the mole fraction of water (X(w)) increases from 0.005 to 0.54. The inter- and intramolecular vibrations of water have been observed using terahertz time domain spectroscopy (THz-TDS) in the frequency range 0.4-1.4 THz (13-47 cm(-1)) and Fourier transform infrared (FTIR) spectroscopy in the far-infrared (30-650 cm(-1)) and mid-infrared (3000-3700 cm(-1)) regions. These results have been correlated with the reactivity of water in these mixtures as determined by kinetic studies of the solvolysis reaction of benzoyl chloride (BzCl). Our studies show an onset of intermolecular hydrogen bonded water network dynamics beyond X(w) ≥ 0.1. At the same concentration, we observe a rapid increase of the rate constant of solvolysis of BzCl in water-Dx mixtures. Our results establish a correlation between the onset of collective hydrogen bonded network with the solvation dynamics and the activity of clustered water.

Far-Infrared and Raman Spectra and The Ring-Twisting Potential Energy Function of 1,3-Cyclohexadiene

NASA Astrophysics Data System (ADS)

Autrey, Daniel; Choo, Jaebum; Laane, Jaan

2001-10-01

The nu19 (A2) ring-twisting vibration of 1,3-cyclohexadiene has been analyzed from the vapor-phase Raman and infrared spectra. The Raman spectrum shows nine ring-twisting transitions in the 116 - 199 cm-1 region. The far-infrared spectrum confirms five of these transitions, despite the fact that the vibration is infrared forbidden in the C2v (planar) approximation. Other Raman and infrared combination bands verify the assignments and provide information on the vibrational coupling. A coordinate dependent kinetic energy expansion for the ring-twisting motion was calculated, and this was used to determine the ring-twisting potential function, which has a barrier to planarity of 1132 cm-1 and energy minima corresponding to twisting angles of 9.1º and 30.1º. Ab initio calculations were also carried out using Moller-Plesset perturbation theory (MP2) with a large number of different basis sets. The various ab initio calculations gave barriers to planarity in the 1197 - 1593 cm-1 range and calculated vibrational frequencies in excellent agreement with the experimental values.

Stress-induced crystal transition of poly(butylene succinate) studied by terahertz and low-frequency Raman spectroscopy and quantum chemical calculation

NASA Astrophysics Data System (ADS)

Tatsuoka, Seika; Sato, Harumi

2018-05-01

We measured terahertz (THz) and low-frequency Raman spectra of Poly (butylene succinate) (PBS) which shows the crystal transition from α to β by stretching. For the assignment of the absorption peaks in the low-frequency region, we performed quantum chemical calculations with Cartesian-coordinate tensor transfer (CCT) method. Four major peaks appeared in the THz spectra of PBS at around 58, 76, 90, and 100 cm-1, and in the low-frequency Raman spectra a peak was observed at 88 cm-1. The THz peak at 100 cm-1 and the Raman peak at 88 cm-1 show a shift to a lower wavenumber region with increasing temperature. The quantum chemical calculation of β crystal form reveals the new peak appears above 100 cm-1. It was found that two kinds of peaks overlapped at around 100 cm-1 in the THz spectra of PBS. One of them can be assigned to a weak hydrogen bond between the C=O and CH2 groups in the intermolecular chains, which is perpendicular to the molecular chain of the α crystal form. Another one showed a parallel polarization which can be assigned to the intramolecular interaction between O (ether) and H-C groups in the β crystal form. The position of the peak at around 100 cm-1 in the perpendicular polarization changed to a lower wavenumber region with stretching, because of the weakening of the intermolecular hydrogen bonding by increasing the interatomic distances. On the other hand, that of the parallel polarization shifts to a higher wavenumber region because of the shortening of the interatomic distance from α to β crystal form (the strength of the intramolecular hydrogen bonding became stronger) by stretching.

Effect of solvent polarity on the vibrational dephasing dynamics of the nitrosyl stretch in an Fe(II) complex revealed by 2D IR spectroscopy.

PubMed

Brookes, Jennifer F; Slenkamp, Karla M; Lynch, Michael S; Khalil, Munira

2013-07-25

The vibrational dephasing dynamics of the nitrosyl stretching vibration (ν(NO)) in sodium nitroprusside (SNP, Na2[Fe(CN)5NO]·2H2O) are investigated using two-dimensional infrared (2D IR) spectroscopy. The ν(NO) in SNP acts as a model system for the nitrosyl ligand found in metalloproteins which play an important role in the transportation and detection of nitric oxide (NO) in biological systems. We perform a 2D IR line shape study of the ν(NO) in the following solvents: water, deuterium oxide, methanol, ethanol, ethylene glycol, formamide, and dimethyl sulfoxide. The frequency of the ν(NO) exhibits a large vibrational solvatochromic shift of 52 cm(-1), ranging from 1884 cm(-1) in dimethyl sulfoxide to 1936 cm(-1) in water. The vibrational anharmonicity of the ν(NO) varies from 21 to 28 cm(-1) in the solvents used in this study. The frequency-frequency correlation functions (FFCFs) of the ν(NO) in SNP in each of the seven solvents are obtained by fitting the experimentally obtained 2D IR spectra using nonlinear response theory. The fits to the 2D IR line shape reveal that the spectral diffusion time scale of the ν(NO) in SNP varies from 0.8 to 4 ps and is negatively correlated with the empirical solvent polarity scales. We compare our results with the experimentally determined FFCFs of other charged vibrational probes in polar solvents and in the active sites of heme proteins. Our results suggest that the vibrational dephasing dynamics of the ν(NO) in SNP reflect the fluctuations of the nonhomogeneous electric field created by the polar solvents around the nitrosyl and cyanide ligands. The solute solvent interactions occurring at the trans-CN ligand are sensed through the π-back-bonding network along the Fe-NO bond in SNP.

TRANSVERSE ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON

PubMed Central

Curtis, Howard J.; Cole, Kenneth S.

1938-01-01

The impedance of the excised giant axon from hindmost stellar nerve of Loligo pealii has been measured over the frequency range from 1 to 2500 kilocycles per second. The measurements have been made with the current flow perpendicular to the axis of the axon to permit a relatively simple analysis of the data. It has been found that the axon membrane has a polarization impedance with an average phase angle of 76° and an average capacity of 1.1µf./cm2 at 1 kilocycle. The direct current resistance of the membrane could not be measured, but was greater than 3 ohm cm.2 and the average internal specific resistance was four times that of sea water. There was no detectable change in the membrane impedance when the axon lost excitability, but some time later it decreased to zero. PMID:19873081

Dielectrophoretic spectra of single cells determined by feedback-controlled levitation.

PubMed Central

Kaler, K V; Jones, T B

1990-01-01

In this paper we have utilized the principle of dielectrophoresis (DEP) to develop an apparatus to stably levitate single biological cells using a digital feedback control scheme. Using this apparatus, the positive DEP spectra of both Canola plant protoplast and ligament fibroblast cells have been measured over a wide range of frequencies (1 kHz to 50 MHz) and suspending medium conductivities (11-800 muS/cm). The experimental data thus obtained have been interpreted in terms of a simple spherical cell model. Furthermore, utilizing such a model, we have shown that various cellular parameters of interest can be readily obtained from the measured DEP levitation spectrum. Specifically, the effective membrane capacitance of single cells has been determined. Values of 0.47 +/- 0.03 muF/cm2 for Canola protoplasts and 1.52 +/- 0.26 muF/cm2 for ligament fibroblasts thus obtained are consistent with those determined by other existing electrical methods. Images FIGURE A1 PMID:2317544

UV Raman detection of 2,4-DNT in contact with sand particles

NASA Astrophysics Data System (ADS)

Blanco, Alejandro; Pacheco-Londoño, Leonardo C.; Peña-Quevedo, Alvaro J.; Hernández-Rivera, Samuel P.

2006-05-01

Deep Ultra Violet Raman Spectroscopy (DUV-RS) is an emerging tool for vibrational spectroscopy analysis and can be used in Point Detection mode to detect explosive components of landmines and Improvised Explosive Devices (IED). Interactions of explosives with different substrates can be measured by using quantitative vibrational signal shift information of scattered Raman light associated with these interactions. In this research, grounds were laid for detection of explosives using UV-Raman Spectroscopy equipped with 244 nm laser excitation line from a 488 nm frequency doubled Coherent FreD laser. In other experiments, samples of 2,4-DNT were allowed to interact with Ottawa Sand and were studied using DUV-RS. Characteristic vibrational signals of energetic compounds were analyzed in the ranges: 400-1200 cm -1, 1200-1800 cm -1, and 2800-3500 cm -1. In addition these Raman spectra were compared with dispersive spectra that were acquired using Raman Microscopy equipped with 514.5 nm (VIS) 785 nm (NIR) and 1064 nm (NIR) excitation lasers.

Evidence for a continuous spectrum of equatorial waves in the Indian Ocean

NASA Astrophysics Data System (ADS)

Eriksen, Charles C.

1980-06-01

Seven-month records of current and temperature measurements from a moored array centered at 53°E on the equator in the Indian Ocean are consistent with a continuous spectrum of equatorially trapped internal inertial-gravity, mixed Rossby-gravity, and Kelvin waves. A model spectrum of free linear waves analogous to those for mid-latitude internal gravity waves is used to compute spectra of observed quantities at depths greater than about 2000 m. Model parameters are adjusted to fit general patterns in the observed spectra over periods from roughly 2 days to 1 month. Measurements at shallower depths presumably include forced motions which we have not attempted to model. This `straw-person' spectrum is consistent with the limited data available. The model spectru Ē (n, m, ω) = K · B(m) · C(n, ω), where Ē is an average local energy density in the equatorial wave guide which has amplitude K, wave number shape B(m) ∝ (1 + m/m*)-3, where m is vertical mode number and the bandwidth parameter m* is between 4 and 8, and frequency shape C(n, ω) ∝ [(2n + 1 + s2)½ · σ3]-1 where n is meridional mode number, and s and σ are dimensionless zonal wave number and frequency related by the usual dispersion relation. The scales are (β/cm)½ and (β · cm)½ for horizontal wave number and frequency, where cm is the Kelvin wave speed of the vertical mode m. At each frequency and vertical wave number, energy is partitioned equally among the available inertial gravity modes so that the field tends toward horizontal isotropy at high frequency. The transition between Kelvin and mixed Rossby-gravity motion at low frequency and inertial-gravity motion at high frequency occurs at a period of roughly 1 week. At periods in the range 1-3 weeks, the model spectrum which fits the observations suggests that mixed Rossby-gravity motion dominates; at shorter periods gravity motion dominates. The model results are consistent with the low vertical coherence lengths observed (roughly 80 m). Horizontal coherence over 2 km is consistent with isotropic energy flux. Evidence for net zontal energy flux is not found in this data, and the presence of a red wave number shape suggests that net flux will be difficult to observe from modest moored arrays. The equatorial wave spectrum does not match across the diurnal and semidiurnal tides to the high-frequency internal wave spectrum (the latter is roughly 1 decade higher).

Purely hopping conduction in c-axis oriented LiNbO3 thin films

NASA Astrophysics Data System (ADS)

Shandilya, Swati; Tomar, Monika; Sreenivas, K.; Gupta, Vinay

2009-05-01

Dielectric constant and ac conductivity of highly c-axis oriented LiNbO3 thin film grown by pulsed laser deposition were studied in a metal-insulator-metal configuration over a wide temperature (200 to 450 K) and frequency (100 Hz to 1 MHz) range. The preferred oriented Al (1%) doped ZnO film with electrical conductivity 1.1×103 Ω-1 cm-1 was deposited for dual purpose: (1) to serve as nucleating center for LiNbO3 crystallites along preferred c-axis growth direction, and (2) to act as a suitable bottom electrode for electrical studies. The room temperature dc conductivity (σdc) of LiNbO3 film was about 5.34×10-10 Ω-1 cm-1 with activation energy ˜0.3 eV, indicating extrinsic conduction. The ac conductivity σac was found to be much higher in comparison to σdc in the low temperature region (<300 K) and exhibits a power law behavior due to the hopping of charge carriers. In higher temperature region (>300 K), σac shows a weak frequency dependence, whereas dielectric constant exhibits a strong frequency dispersion. The dielectric dispersion data has been discussed in the light of theoretical models based on Debye type mixed conduction and purely hopping conduction. The dominant conduction in c-axis oriented LiNbO3 thin film is attributed to the purely hopping where both σdc and σac arise due to same mechanism.

The visible spectrum of zirconium dioxide, ZrO2

NASA Astrophysics Data System (ADS)

Le, Anh; Steimle, Timothy C.; Gupta, Varun; Rice, Corey A.; Maier, John P.; Lin, Sheng H.; Lin, Chih-Kai

2011-09-01

The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO2, has been investigated using laser induced fluorescence (LIF) in the region from 17 000 cm-1 to 18 800 cm-1 and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17 000 cm-1-21 000 cm-1. The LIF and REMPI spectra are assigned to progressions in the tilde A{^1}B_2(ν1, ν2, ν3) ← tilde X{^1}A_1(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the tilde X{^1}A_1 state of ω1 = 898(1) cm-1, ω2 = 287(2) cm-1, and ω3 = 808(3) cm-1. The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the tilde A{^1}B_2 state of Te = 16 307(8) cm-1, ω1 = 819(3) cm-1, ω2 = 149(3) cm-1, and ω3 = 518(4) cm-1. The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the tilde A{^1}B_2 and tilde X{^1}A_1 states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO2 is made.

The raman spectrum of biosynthetic human growth hormone. Its deconvolution, bandfitting, and interpretation

NASA Astrophysics Data System (ADS)

Tensmeyer, Lowell G.

1988-05-01

The Raman spectrum of amorphous biosynthetic human growth hormone, somatotropin, has been measured at high signal-to-noise ratios, using a CW argon ion laser and single channel detection. The rms signal-to-noise ratio varies from 1800:1 in the Amide I region near 1650 cm -1 region, to 500:1 in the disulfide stretch region near 500 cm -1. Component Raman bands have been extracted from the entire spectral envelope from 1800-400 cm -1, by an interactive process involving both partial deconvolution and band-fitting. Interconsistency of all bands has been achieved by multiple overlapping of adjacent regions that had been isolated for the band-fitting programs. The resulting areas of the Raman component bands have been interpreted to show the ratios of peptide conformations in the hormone: 64% α-helix, 24% β-sheet, 8% β-turns and 4% γ-turns. Analysis of the tyrosine region, usually described as a Fermi resonance doublet near ˜830-850 cm -1, shows four bands, at 825, 833, 853, and 859 cm -1 in this macromolecule. Integrated intensities of these bands (2:2:2:2) are interpreted to show that only half of the eight tyrosine residues function as hydrogen-bond bridges via the acceptance of protons. Both disulfide bridges fall within the frequency ranges for normal, unstressed SS bonds: The 511 and 529 cm -1 bands are indicative of the gauche-gauche-gauche and trans-gauche-gauche conformations, respectively.

CH3Cl, CH2Cl2, CHCl3, and CCl4: Infrared spectra, radiative efficiencies, and global warming potentials

NASA Astrophysics Data System (ADS)

Wallington, Timothy J.; Pivesso, Bruno Pasquini; Lira, Alane Moura; Anderson, James E.; Nielsen, Claus Jørgen; Andersen, Niels Højmark; Hodnebrog, Øivind

2016-05-01

Infrared spectra for the title compounds were measured experimentally in 700 Torr of air at 295 K and systematically modeled in B3LYP, M06-2X and MP2 calculations employing various basis sets. Calibrated infrared spectra over the wavenumber range 600-3500 cm-1 are reported and combined with literature data to provide spectra for use in experimental studies and radiative transfer calculations. Integrated absorption cross sections are (units of cm-1 molecule-1): CH3Cl, 660-780 cm-1, (3.89±0.19)×10-18; CH2Cl2, 650-800 cm-1, (2.16±0.11)×10-17; CHCl3, 720-810 cm-1, (4.08±0.20)×10-17; and CCl4, 730-825 cm-1, (6.30±0.31)×10-17. CH3Cl, CH2Cl2, CHCl3, and CCl4 have radiative efficiencies of 0.004, 0.028, 0.070, and 0.174 W m-2 ppb-1 and global warming potentials (100 year horizon) of 5, 8, 15, and 1775, respectively. Quantum chemistry calculations generally predict larger band intensities than the experimental values. The best agreement with experiments is obtained in MP2(Full) calculations employing basis sets of at least triple-zeta quality augmented by diffuse functions. The B3LYP functional is found ill-suited for calculating vibrational frequencies and infrared intensities of halocarbons.

Photodissociation resonances of jet-cooled NO2 at the dissociation threshold by CW-CRDS

NASA Astrophysics Data System (ADS)

Dupré, Patrick

2015-05-01

Around 398 nm, the jet-cooled-spectrum of NO2 exhibits a well identified dissociation threshold (D0). Combining the continuous-wave absorption-based cavity ringdown spectroscopy technique and laser induced fluorescence detection, an energy range of ˜25 cm-1 is analyzed at high resolution around D0. In addition to the usual molecular transitions to long-lived energy levels, ˜115 wider resonances are observed. The position, amplitude, and width of these resonances are determined. The resonance width spreads from ˜0.006 cm-1 (i.e., ˜450 ps) to ˜0.7 cm-1 (˜4 ps) with large fluctuations. The identification of at least two ranges of resonance width versus the excess energy can be associated with the opening of the dissociation channels NO 2 → NO (X 2 Π 1 / 2 , v = 0 , J = 1 / 2) + O (3 P 2) and NO 2 → NO (X 2 Π 1 / 2 , v = 0 , J = 3 / 2) + O (3 P 2). This analysis corroborates the existence of loose transition states close to the dissociation threshold as reported previously and in agreement with the phase space theory predictions as shown by Tsuchiya's group [Miyawaki et al., J. Chem. Phys. 99, 254-264 (1993)]. The data are analyzed in the light of previously reported frequency- and time-resolved data to provide a robust determination of averaged unimolecular dissociation rate coefficients. The density of reactant levels deduced (ρreac ˜ 11 levels/cm-1) is discussed versus the density of transitions, the density of resonances, and the density of vibronic levels.

Ultra-Wideband Chaos Life-Detection Radar with Sinusoidal Wave Modulation

NASA Astrophysics Data System (ADS)

Xu, Hang; Li, Ying; Zhang, Jianguo; Han, Hong; Zhang, Bing; Wang, Longsheng; Wang, Yuncai; Wang, Anbang

2017-12-01

We propose and experimentally demonstrate an ultra-wideband (UWB) chaos life-detection radar. The proposed radar transmits a wideband chaotic-pulse-position modulation (CPPM) signal modulated by a single-tone sinusoidal wave. A narrow-band split ring sensor is used to collect the reflected sinusoidal wave, and a lock-in amplifier is utilized to identify frequencies of respiration and heartbeat by detecting the phase change of the sinusoidal echo signal. Meanwhile, human location is realized by correlating the CPPM echo signal with its delayed duplicate and combining the synthetic aperture technology. Experimental results demonstrate that the human target can be located accurately and his vital signs can be detected in a large dynamic range through a 20-cm-thick wall using our radar system. The down-range resolution is 15cm, benefiting from the 1-GHz bandwidth of the CPPM signal. The dynamic range for human location is 50dB, and the dynamic ranges for heartbeat and respiration detection respectively are 20dB and 60dB in our radar system. In addition, the bandwidth of the CPPM signal can be adjusted from 620MHz to 1.56GHz to adapt to different requirements.

Terahertz and infrared spectroscopic evidence of phonon-paramagnon coupling in hexagonal piezomagnetic YMnO3

NASA Astrophysics Data System (ADS)

Kadlec, C.; Goian, V.; Rushchanskii, K. Z.; Kužel, P.; Ležaić, M.; Kohn, K.; Pisarev, R. V.; Kamba, S.

2011-11-01

Terahertz and far-infrared electric and magnetic responses of hexagonal piezomagnetic YMnO3 single crystals are investigated. Antiferromagnetic resonance is observed in the spectra of magnetic permeability μa [H(ω) oriented within the hexagonal plane] below the Néel temperature TN. This excitation softens from 41 to 32 cm-1 upon heating and finally disappears above TN. An additional weak and heavily-damped excitation is seen in the spectra of complex dielectric permittivity ɛc within the same frequency range. This excitation contributes to the dielectric spectra in both antiferromagnetic and paramagnetic phases. Its oscillator strength significantly increases upon heating toward room temperature, thus providing evidence of piezomagnetic or higher-order couplings to polar phonons. Other heavily-damped dielectric excitations are detected near 100 cm-1 in the paramagnetic phase in both ɛc and ɛa spectra, and they exhibit similar temperature behavior. These excitations appearing in the frequency range of magnon branches well below polar phonons could remind electromagnons, however their temperature dependence is quite different. We have used density functional theory for calculating phonon dispersion branches in the whole Brillouin zone. A detailed analysis of these results and of previously published magnon dispersion branches brought us to the conclusion that the observed absorption bands stem from phonon-phonon and phonon-paramagnon differential absorption processes. The latter is enabled by strong short-range in-plane spin correlations in the paramagnetic phase.

Association of Exposure to Radio-Frequency Electromagnetic Field Radiation (RF-EMFR) Generated by Mobile Phone Base Stations with Glycated Hemoglobin (HbA1c) and Risk of Type 2 Diabetes Mellitus.

PubMed

Meo, Sultan Ayoub; Alsubaie, Yazeed; Almubarak, Zaid; Almutawa, Hisham; AlQasem, Yazeed; Hasanato, Rana Muhammed

2015-11-13

Installation of mobile phone base stations in residential areas has initiated public debate about possible adverse effects on human health. This study aimed to determine the association of exposure to radio frequency electromagnetic field radiation (RF-EMFR) generated by mobile phone base stations with glycated hemoglobin (HbA1c) and occurrence of type 2 diabetes mellitus. For this study, two different elementary schools (school-1 and school-2) were selected. We recruited 159 students in total; 96 male students from school-1, with age range 12-16 years, and 63 male students with age range 12-17 years from school-2. Mobile phone base stations with towers existed about 200 m away from the school buildings. RF-EMFR was measured inside both schools. In school-1, RF-EMFR was 9.601 nW/cm² at frequency of 925 MHz, and students had been exposed to RF-EMFR for a duration of 6 h daily, five days in a week. In school-2, RF-EMFR was 1.909 nW/cm² at frequency of 925 MHz and students had been exposed for 6 h daily, five days in a week. 5-6 mL blood was collected from all the students and HbA1c was measured by using a Dimension Xpand Plus Integrated Chemistry System, Siemens. The mean HbA1c for the students who were exposed to high RF-EMFR was significantly higher (5.44 ± 0.22) than the mean HbA1c for the students who were exposed to low RF-EMFR (5.32 ± 0.34) (p = 0.007). Moreover, students who were exposed to high RF-EMFR generated by MPBS had a significantly higher risk of type 2 diabetes mellitus (p = 0.016) relative to their counterparts who were exposed to low RF-EMFR. It is concluded that exposure to high RF-EMFR generated by MPBS is associated with elevated levels of HbA1c and risk of type 2 diabetes mellitus.

Time-resolved detection of the CF3 photofragment using chirped QCL radiation.

PubMed

Hancock, G; Horrocks, S J; Ritchie, G A D; Helden, J H van; Walker, R J

2008-10-09

This paper demonstrates how a quantum cascade laser (QCL) in its intrapulse mode can provide a simple method for probing the products of a photolysis event. The system studied is the 266 nm photodissociation of CF3I with the CF3 fragments subsequently detected using radiation at approximately 1253 cm(-1) generated by a pulsed QCL. The tuning range provided by the frequency down-chirp of the QCL operated in its intrapulse mode allows a approximately 1 cm(-1) segment of the CF3 nu3 band to be measured following each photolysis laser pulse. Identification of features within this spectral region allows the CF3 ( v = 0) number density to be calculated as a function of pump-probe delay, and consequently the processes which populate and deplete this quantum state may be examined. Rate constants for the population cascade from higher vibrational levels into the v = 0 state, k 1, and for the recombination of the CF3 radicals to form C2F6, k2, are measured. The returned values of k1 = (2.3 +/- 0.34) x 10(-12) cm(3) molecule(-1) s(-1) and k2 = (3.9 +/- 0.34) x 10(-12) cm(3) molecule(-1) s(-1) are found to be in good agreement with reported literature values.

Structural and vibrational study of 2-MethoxyEthylAmmonium Nitrate (2-OMeEAN): Interpretation of experimental results with ab initio molecular dynamics

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

Campetella, M.; Caminiti, R.; Bencivenni, L.

2016-07-14

In this work we report an analysis of the bulk phase of 2-methoxyethylammonium nitrate based on ab initio molecular dynamics. The structural and dynamical features of the ionic liquid have been characterized and the computational findings have been compared with the experimental X-ray diffraction patterns, with infrared spectroscopy data, and with the results obtained from molecular dynamics simulations. The experimental infrared spectrum was interpreted with the support of calculated vibrational density of states as well as harmonic frequency calculations of selected gas phase clusters. Particular attention was addressed to the high frequency region of the cation (ω > 2000 cm{supmore » −1}), where the vibrational motions involve the NH{sub 3}+ group responsible for hydrogen bond formation, and to the frequency range 1200-1400 cm{sup −1} where the antisymmetric stretching mode (ν{sub 3}) of nitrate is found. Its multiple absorption lines in the liquid arise from the removal of the degeneracy present in the D{sub 3h} symmetry of the isolated ion. Our ab initio molecular dynamics leads to a rationalization of the frequency shifts and splittings, which are inextricably related to the structural modifications induced by a hydrogen bonding environment. The DFT calculations lead to an inhomogeneous environment.« less

SEMI-DIURNAL SEICHING IN A SHALLOW, MICRO-TIDAL LAGOONAL ESTUARY. (R826938,R828677C001)

EPA Science Inventory

Abstract

Analysis of current meter data in the Neuse River Estuary (NRE) associates over half of the along channel velocity variance with roughly the semi-diurnal frequency band. Velocity in this frequency range is episodic, has a typical magnitude of 10 cm s...

Computation of Power Spectral Densities and Correlations Using Digital FFT Techniques

DTIC Science & Technology

1975-12-01

NUMBER increases and DELTAT decreases the region over which the transform is accurate increases. For NUMBER equal to 2048 , the results are very close...to the actual function G for the entire range plotted. At higher frequencies, even the case for NUMBER equal to 2048 will deviate from the actual...J o o o CM — o o O 30 io-’ io-2 G(w) >-3 IO𔃾 1 1 1 I I I I I O N= 2048 , AT = O.OI NO REFLECTION o N= 2048 , AT =0.0 I

Electrical conductivity and dielectric properties of TlInS2 single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Youssef, S. B.; Ali, H. A. M.; Hassan, A.

2011-07-01

TlInS2 single crystals were grown by using Bridgman-Stockbauer technique. Measurements of DC conductivity were carried out in parallel (σ//) and perpendicular (σ⊥) directions to the c-axis over a temperature range from 303 to 463 K. The anisotropic behaviour of the electrical conductivity was also detected. AC conductivity and dielectric measurements were studied as a function of both frequency (102-106 Hz) and temperature (297-375 K). The frequency dependence of the AC conductivity revealed that σac(ω) obeys the universal law: σac(ω) = Aωs. The mechanism of the ac charge transport across the layers of TlInS2 single crystals was referred to the hopping over localized states near the Fermi level in the frequency range >3.5 × 103 Hz. The temperature dependence of σac(ω) for TlInS2 showed that σac is thermally activated process. Both of ɛ1 and ɛ2 decrease by increasing frequency and increase by increasing temperature. Some parameters were calculated as: the density of localized states near the Fermi level NF = 1.5 × 1020 eV-1 cm-3, the average time of charge carrier hoping between localized states τ = 3.79 μs and the average hopping distance R = 6.07 nm.

Analysis of sound pressure levels emitted by children's toys.

PubMed

Sleifer, Pricila; Gonçalves, Maiara Santos; Tomasi, Marinês; Gomes, Erissandra

2013-06-01

To verify the levels of sound pressure emitted by non-certified children's toys. Cross-sectional study of sound toys available at popular retail stores of the so-called informal sector. Electronic, mechanical, and musical toys were analyzed. The measurement of each product was carried out by an acoustic engineer in an acoustically isolated booth, by a decibel meter. To obtain the sound parameters of intensity and frequency, the toys were set to produce sounds at a distance of 10 and 50cm from the researcher's ear. The intensity of sound pressure [dB(A)] and the frequency in hertz (Hz) were measured. 48 toys were evaluated. The mean sound pressure 10cm from the ear was 102±10 dB(A), and at 50cm, 94±8 dB(A), with p<0.05. The level of sound pressure emitted by the majority of toys was above 85dB(A). The frequency ranged from 413 to 6,635Hz, with 56.3% of toys emitting frequency higher than 2,000Hz. The majority of toys assessed in this research emitted a high level of sound pressure.

Probing Pharmaceutical Mixtures during Milling: The Potency of Low-Frequency Raman Spectroscopy in Identifying Disorder.

PubMed

Walker, Greg; Römann, Philipp; Poller, Bettina; Löbmann, Korbinian; Grohganz, Holger; Rooney, Jeremy S; Huff, Gregory S; Smith, Geoffrey P S; Rades, Thomas; Gordon, Keith C; Strachan, Clare J; Fraser-Miller, Sara J

2017-12-04

This study uses a multimodal analytical approach to evaluate the rates of (co)amorphization of milled drug and excipient and the effectiveness of different analytical methods in detecting these changes. Indomethacin and tryptophan were the model substances, and the analytical methods included low-frequency Raman spectroscopy (785 nm excitation and capable of measuring both low- (10 to 250 cm -1 ) and midfrequency (450 to 1800 cm -1 ) regimes, and a 830 nm system (5 to 250 cm -1 )), conventional (200-3000 cm -1 ) Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The kinetics of amorphization were found to be faster for the mixture, and indeed, for indomethacin, only partial amorphization occurred (after 360 min of milling). Each technique was capable of identifying the transformations, but some, such as low-frequency Raman spectroscopy and XRPD, provided less ambiguous signatures than the midvibrational frequency techniques (conventional Raman and FTIR). The low-frequency Raman spectra showed intense phonon mode bands for the crystalline and cocrystalline samples that could be used as a sensitive probe of order. Multivariate analysis has been used to further interpret the spectral changes. Overall, this study demonstrates the potential of low-frequency Raman spectroscopy, which has several practical advantages over XRPD, for probing (dis-)order during pharmaceutical processing, showcasing its potential for future development, and implementation as an in-line process monitoring method.

Effect of a low-frequency magnetic field on the structure of globular blood proteins

NASA Astrophysics Data System (ADS)

Zalesskaya, G. A.; Ulashchik, V. S.; Mit'kovskaya, N. P.; Laskina, O. V.; Kuchinskii, A. V.

2007-09-01

We used IR Fourier absorption spectra of blood to study changes in the structure of globular blood proteins with extracorporeal autohemomagnetotherapy, used to treat ischemic heart disease. We compare the spectra of blood before and after magnetotherapy in the regions: amide I (1655 cm-1), amide II (1545 cm-1), amide III (1230-1350 cm-1), amide IV and amide V (400-700 cm-1). We have shown that pronounced changes in the spectra in the indicated regions on direct exposure of blood in vivo to a low-frequency pulsed magnetic field are connected with conformational changes in the secondary structure of globular blood proteins, which are apparent in the increase in the contribution of the α-helix conformation. We discuss the magnetotherapy-initiated appearance of new IR absorption bands at 1018 and 1038 cm-1 and an increase in the intensity of a number of other bands located in the 1000-1200 cm-1 region, which suggests a change in the concentration of some blood components.

Optical coatings for high average power XeF lasers

NASA Astrophysics Data System (ADS)

Milam, D.; Thomas, I.; Wilder, J.; George, D.

1988-03-01

Porous silica, calcium and magnesium fluorides were investigated for potential use as antireflective coatings for XeF lasers. Excellent optical properties were obtained for all types, and laser damage thresholds were in the range 18 to 25 J/sq cm at 350 nm for 25 ns pulses at 25 Hz pulse repetition frequency. Studies of the effects of the XeF laser environment on these coatings were incomplete. Three oxides, ZrO2, HfO2, and Ta2O5 were investigated as the high index components to be paired with low index porous SiO2 for highly reflective dielectric coatings. Single oxide layers had indices in the 1.7 to 1.8 range and HfO2 coatings had the highest damage threshold at about 5 J/sq cm. An unexpected problem arose on attempts to prepare multilayer coatings. Stress in the coating after 6 to 8 layers had been put down, gave rise to crazing and peeling. This could not be avoided even on extending the curing process between coats.

Deviation of tracheal pressure from airway opening pressure during high-frequency oscillatory ventilation in a porcine lung model.

PubMed

Johannes, Amélie; Zollhoefer, Bernd; Eujen, Ulrike; Kredel, Markus; Rauch, Stefan; Roewer, Norbert; Muellenbach, Ralf M

2013-04-01

Oxygenation during high-frequency oscillatory ventilation is secured by a high level of mean airway pressure. Our objective was to identify a pressure difference between the airway opening of the respiratory circuit and the trachea during application of different oscillatory frequencies. Six female Pietrain pigs (57.1 ± 3.6 kg) were first ventilated in a conventional mechanical ventilation mode. Subsequently, the animals were switched to high-frequency oscillatory ventilation by setting mean airway opening pressure 5 cmH(2)O above the one measured during controlled mechanical ventilation. Measurements at the airway opening and at tracheal levels were performed in healthy lungs and after induction of acute lung injury by surfactant depletion. During high-frequency oscillatory ventilation, the airway opening pressure was set at a constant level. The pressure amplitude was fixed at 90 cmH(2)O. Starting from an oscillatory frequency of 3 Hz, the frequency was increased in steps of 3 Hz to 15 Hz and then decreased accordingly. At each frequency, measurements were performed in the trachea through a side-lumen of the endotracheal tube and the airway opening pressure was recorded. The pressure difference was calculated. At every oscillatory frequency, a pressure loss towards the trachea could be shown. This pressure difference increased with higher oscillatory frequencies (3 Hz 2.2 ± 2.1 cmH(2)O vs. 15 Hz 7.5 ± 1.8 cmH(2)O). The results for healthy and injured lungs were similar. Tracheal pressures decreased with higher oscillatory frequencies. This may lead to pulmonary derecruitment. This has to be taken into consideration when increasing oscillatory frequencies and differentiated pressure settings are mandatory.

Interstellar PAH emission in the 11-14 micron region: new insights from laboratory data and a tracer of ionized PAHs

NASA Technical Reports Server (NTRS)

Hudgins, D. M.; Allamandola, L. J.

1999-01-01

The Ames infrared spectral database of isolated, neutral and ionized polycyclic aromatic hydrocarbons (PAHS) shows that aromatic CH out-of-plane bending frequencies are significantly shifted upon ionization. For solo- and duet-CH groups, the shift is pronounced and consistently toward higher frequencies. The solo-CH modes are blueshifted by an average of 27 cm-1 and the duet-CH modes by an average of 17 cm-1. For trio- and quartet-CH groups, the ionization shifts of the out-of-plane modes are more erratic and typically more modest. As a result of these ionization shifts, the solo-CH out-of-plane modes move out of the region classically associated with these vibrations in neutral PAHS, falling instead at frequencies well above those normally attributed to out-of-plane bending, vibrations of any type. In addition, for the compact PAHs studied, the duet-CH out-of-plane modes are shifted into the frequency range traditionally associated with the solo-CH modes. These results refine our understanding of the origin of the dominant interstellar infrared emission feature near 11.2 microns, whose envelope has traditionally been attributed only to the out-of-plane bending of solo-CH groups on PAHS, and provide a natural explanation for the puzzling emission feature near 11.0 microns within the framework of the PAH model. Specifically, the prevalent but variable long-wavelength wing or shoulder that is often observed near 11.4 microns likely reflects the contributions of duet-CH units in PAH cations. Also, these results indicate that the emission between 926 and 904 cm-1 (10.8 and 11.1 microns) observed in many sources can be unambiguously attributed to the out-of-plane wagging, of solo-CH units in moderately sized (fewer than 50 carbon atom) PAH cations, making this emission an unequivocal tracer of ionized interstellar PAHS.

Reconsidering gender relative to risk of rupture in the contemporary management of abdominal aortic aneurysms.

PubMed

Skibba, Afshin A; Evans, James R; Hopkins, Steven P; Yoon, H Richard; Katras, Tony; Kalbfleisch, John H; Rush, Daniel S

2015-12-01

Abdominal aortic aneurysms (AAAs) may rupture at smaller diameters in women than in men, and women may be at higher risk and have poorer outcomes in elective and emergent interventions because of age and comorbidities. Practice guidelines recommending elective AAA repair at >5.5 cm are gender neutral and may not adequately reflect increased risks in women or the potential advantages of elective lower risk endovascular procedures. Patients with a diagnosis of AAA discharged from a single referral hospital during a 14-year period were identified for retrospective analysis. A total of 2121 patients with AAAs were studied, 499 women (23.5%) and 1622 men (76.5%). Women were older and had a greater incidence of hypertension, smoking, chronic obstructive pulmonary disease, dyslipidemia, and renal insufficiency. Intact AAAs in 467 women had a mean diameter of 4.4 ± 1.3 cm compared with 1538 men at 5.0 ± 1.4 cm (P < .01). The ruptured AAAs in 32 women (6.4%) had a mean diameter of 6.1 ± 1.5 cm compared with 84 men (5.2%) at 7.7 ± 1.9 cm (P < .01). Women had a twofold increased frequency of AAA rupture than men at all size intervals (P < .01). The frequency of ruptured AAAs <5.5 cm among 10 of 32 women with ruptured AAAs was 31.3%; among 7 of 84 men with ruptured AAAs, it was 8.3% (P < .01). The frequency of ruptured AAAs <5.5 cm in all 383 women with AAAs <5.5 cm was 2.6%; in 1042 men, it was 0.6% (P < .01). Of the 1211 AAA repairs, 574 (47.4%) were open aneurysm repair (OAR) and 637 (52.6%) were endovascular aneurysm repair (EVAR). Mortality after elective OAR in 475 patients of both sexes was 5.1%; for EVAR in 676 patients, mortality was 1.6% (P < .01). No differences in mortality with respect to OAR or EVAR were found between the female and male cohorts in either intact or ruptured AAAs. Women with AAAs are older and have a higher frequency of cardiovascular risk factors than men. Women rupture AAAs with a greater frequency than men at all size intervals and have a fourfold increased frequency of rupture at <5.5 cm. No differences in surgical mortality between women and men were found. Current practice guidelines for elective AAA operative intervention should be reconsidered and stratified by gender. Published by Elsevier Inc.

Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene

NASA Astrophysics Data System (ADS)

Araujo, Paulo; Mafra, Daniela; Sato, Kentaro; Saito, Richiiro; Kong, Jing; Dresselhaus, Mildred

2012-02-01

Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the G* and the G'-band features originating from a double-resonant Raman process with q 0. The observed phonon renormalization effects are different from what is observed for the zone-center q = 0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with non-zero wave-vectors (q 0) in 1LG in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q = 0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G* Raman feature at 2450 cm-1 to include the iTO+LA combination modes with q 0 and the 2iTO overtone modes with q = 0, showing both to be associated with wave-vectors near the high symmetry point K in the Brillouin zone.

Changes of Dust Opacity with Density in the Orion A Molecular Cloud

NASA Astrophysics Data System (ADS)

Roy, Arabindo; Martin, Peter G.; Polychroni, Danae; Bontemps, Sylvain; Abergel, Alain; André, Philippe; Arzoumanian, Doris; Di Francesco, James; Hill, Tracey; Konyves, Vera; Nguyen-Luong, Quang; Pezzuto, Stefano; Schneider, Nicola; Testi, Leonardo; White, Glenn

2013-01-01

We have studied the opacity of dust grains at submillimeter wavelengths by estimating the optical depth from imaging at 160, 250, 350, and 500 μm from the Herschel Gould Belt Survey and comparing this to a column density obtained from the Two Micron All Sky Survey derived color excess E(J - K s). Our main goal was to investigate the spatial variations of the opacity due to "big" grains over a variety of environmental conditions and thereby quantify how emission properties of the dust change with column (and volume) density. The central and southern areas of the Orion A molecular cloud examined here, with N H ranging from 1.5 × 1021 cm-2 to 50 × 1021 cm-2, are well suited to this approach. We fit the multi-frequency Herschel spectral energy distributions (SEDs) of each pixel with a modified blackbody to obtain the temperature, T, and optical depth, τ1200, at a fiducial frequency of 1200 GHz (250 μm). Using a calibration of N H/E(J - Ks ) for the interstellar medium (ISM) we obtained the opacity (dust emission cross-section per H nucleon), σe(1200), for every pixel. From a value ~1 × 10-25 cm2 H-1 at the lowest column densities that is typical of the high-latitude diffuse ISM, σe(1200) increases as N 0.28 H over the range studied. This is suggestive of grain evolution. Integrating the SEDs over frequency, we also calculated the specific power P (emission power per H) for the big grains. In low column density regions where dust clouds are optically thin to the interstellar radiation field (ISRF), P is typically 3.7 × 10-31 W H-1, again close to that in the high-latitude diffuse ISM. However, we find evidence for a decrease of P in high column density regions, which would be a natural outcome of attenuation of the ISRF that heats the grains, and for localized increases for dust illuminated by nearby stars or embedded protostars.

Optical conductivity of Nd_0.7Sr_0.3MnO_3-δ in the infrared-UV range

NASA Astrophysics Data System (ADS)

Quijada, M. A.; Drew, H. D.; Kwon, C.; Ramesh, R.; Venkatesan, T.

1997-03-01

We have measured the infrared-UV (2000-40,000 cm-1) transmittance and reflectance of thin films of Nd_0.7Sr_0.3MnO_3-δ at temperatures in the range of 15-300 K.(S.G. Kaplan et al., Phys. Rev. Lett. 77), 2081 (1996). The optical properties are derived by inverting the full Fresnel equations for a thin film on a thick substrate. The real part of the optical conductivity shows a broad peak feature near 10,000 cm-1 which shifts to lower frequency as the temperature is lowered or the magnetic field is increased. In addition, there is a redistribution of spectral weight from high to low energies as the temperature is lowered through the paramagnetic/ferromagnetic phase transition. The optical data are found to be consistent with models that include both the double-exchange interaction and the dynamic Jahn-Teller (J-T) effect on the Mn^3+ d(e_g) levels. Within these models, the conductivity peak represents the optical charge transfer transition from the lower J-T split Mn^3+ level to a neighboring Mn^4+ ion. We will also report on the sum rule analysis of the optical conductivity up to 40,000 cm-1.

Raman Spectroscopy with High Power Diode Lasers

NASA Astrophysics Data System (ADS)

Claps, Ricardo

1998-10-01

Our group has demonstrated in the past that it is possible to record, with a high power Diode Laser, Raman spectra of low pressure gases. An external cavity was used to lock the laser into single mode operation. Also, the use of atomic filters permitted the observation of rotational Raman lines only 1 cm-1 apart from the excitation frequency ( J.Sabbaghzadeh, M.Fink, et-all; Applied Physics ) B 60 (1995), p.261-265.. We present now an improved version of the experiment, with beamshaping optics that help to correct the highly astigmatic output of the Diode Laser; this allowed us to put 300 mW of cw power through a multi-pass cell in the sample chamber, `increasing the signal by a factor of ~ 15. We present examples of rotational and vibrational spectra from CO_2, N_2, and air. The results show that we are able to obtain spectra with a S/N ratio of 0.011 per Torr, per √s, which means that we can detect 1 Torr of these gases in a few hours of exposure, at a maximum resolution of 0.85 cm-1 over a range of 200 cm-1. The laser stability in power, frequency and bandwidth, ensures the feasibility of long exposure experiments. We plan to apply the Raman technique to study flow properties of gases under different dynamic conditions; as a result, we expect to use our instrument for the study of the vibrational Raman spectra of alkali-halide dimers in vapour phase at low pressures.

Comparison of low and high frequency transducers in the detection of liver metastases.

PubMed

Schacherer, D; Wrede, C; Obermeier, F; Schölmerich, J; Schlottmann, K; Klebl, F

2006-09-01

To evaluate the benefit of the additional use of a high frequency ultrasound probe (7.5 MHz) in finding suspicious liver lesions compared to the examination using a 3.5-MHz transducer only. One hundred and fifty-seven patients with underlying malignant disease were examined with both transducers using one of three ultrasound machines (Siemens Sonoline Elegra, GE Healthcare Logic 9, or Hitachi EUB-8500). Findings on hepatic lesions were collected on a standardised documentation sheet and evaluated by descriptive statistics. Ninety-three patients (59.2% of all patients) showed no evident liver lesion on conventional ultrasound with the 3.5 MHz probe. In 29 patients (18.5%) new suspicious liver lesions were found by using the high frequency transducer. Thirteen of these 29 patients (44.8%) were suspected to suffer from diffuse infiltration of the liver with malignant lesions or at least 10 additional visible lesions. In 14 patients, no liver lesion had been known before high frequency ultrasound examination. The size of newly described liver lesions ranged from 2 mm to 1.5 cm. Time needed for the additional examination with the high frequency transducer ranged between 1 and 15 min with an average of 4.0 min. The additional use of a high frequency transducer in patients with underlying malignant disease slightly extends the examination time, but reveals new, potentially malignant hepatic lesions in almost every fifth patient.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Microwave generation in an optical breakdown plasma created by modulated laser radiation

NASA Astrophysics Data System (ADS)

Antipov, A. A.; Grasyuk, Arkadii Z.; Losev, Leonid L.; Soskov, V. I.

1990-06-01

It was established that when laser radiation, intensity modulated at a frequency of 2.2 GHz, interacted with an optical breakdown plasma which it had created, a microwave component appeared in the thermal emf of the plasma. The amplitude of the microwave thermal emf reached 0.7 V for a laser radiation intensity of 6 GW/cm2. Laser radiation with λL = 1.06 μm was converted to the microwave range with λmω = 13 cm in the optical breakdown plasma. A microwave signal power of ~ 0.5 W was obtained from a laser power of ~ 5 MW.

Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2-/3-Substituted Phenyl)-4-Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br, and X = CH3 or Cl

NASA Astrophysics Data System (ADS)

Gowda, B. Thimme; Shetty, Mahesha; Jayalakshmi, K. L.

2005-02-01

Twenty three N-(2-/3-substituted phenyl)-4-substituted benzenesulphonamides of the general formula, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br and X = CH3 or Cl have been prepared and characterized, and their infrared spectra in the solid state, 1H and 13C NMR spectra in solution were studied. The N-H stretching vibrations, νN-H, absorb in the range 3285 - 3199 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1376 - 1309 cm-1 and 1177 - 1148 cm-1, respectively. The S-N and C-N stretching vibrations absorb in the ranges 945 - 893 cm-1 and 1304 - 1168 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbons of the two benzene rings. Incremental shifts of the ring protons and carbons due to -SO2NH(2-/3-XC6H4) groups in C6H5SO2NH(2-/3-XC6H4), and 4- X'C6H4SO2- and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H5) are computed and employed to calculate the chemical shifts of the ring protons and carbons in the substituted compounds, 4-X'C6H4SO2NH(2-/3-XC6H4). The computed values agree well with the observed chemical shifts.

Microwave monolithic filter and phase shifter using magnetic nanostructures

NASA Astrophysics Data System (ADS)

Aslam, Shehreen; Khanna, Manoj; Veenugopal, Veerakumar; Kuanr, Bijoy K.

2018-05-01

Monolithic Microwave Integrated Circuit (MMIC) have major impact on the development of microwave communication technology. Transition metal based ferromagnetic nano-wired (FMNWs) substrate are of special interest in order to fabricate these MMIC devices. Their saturation magnetization is comparatively higher than ferrites which makes them suitable for high frequency (>10 ˜ 40 GHz) operation at zero or a small applied magnetic field. The CoFeB nanowires in anodic alumina templates were synthesized using three-electrode electro-deposition system. After electro-deposition, 1μm thick Cu layer was sputtered on the top surface of FMNW substrate and lithography was done to design microstrip lines. These microstrip transmission lines were tested for band-stop filters and phase shifters based on ferromagnetic resonance (FMR) over a wide applied magnetic field (H) range. It was observed that attenuation and frequency increase with the increase of magnetic field (upto 5.3 kOe). For phase shifter, the influence of magnetic material was studied for two frequency regions: (i) below FMR and (ii) above FMR. These two frequency regions were suitable for many practical device applications as the insertion loss was very less in these regions in comparison to resonance frequency regions. In the high frequency region (at 35 GHz), the optimal differential phase shift increased significantly to ˜ 250 deg/cm and around low frequency region (at 24 GHz), the optimal differential phase shift is ˜175 deg/cm at the highest field (H) value.

VizieR Online Data Catalog: ExoMol line lists for phosphine (PH3) (Sousa-Silva+,

NASA Astrophysics Data System (ADS)

Sousa-Silva, C.; Al-Refaie, A. F.; Tennyson, J.; Yurchenko, S. N.

2014-11-01

The data are in two parts. The first, ph3_0-46.dat contains a list of 9,787,832 rovibrational states. Each state is labelled with: 6 normal mode vibrational quantum numbers, 1 multiplexed L quantum number and the vibrational symmetry; three rotational quantum numbers including the total angular momentum J, the projection of J in the z-axis K,rotational symmetry and the total symmetry quantum number Gamma In addition there are nine local mode vibrational numbers and the largest coefficient used to assign the state in question. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The total degeneracy is also given to facilitate the intensity calculations. Because of their size, the transitions are listed in 100 separate files, each containing all the transitions in a 100cm-1 frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, s_SAlTY.f90 which may be used to generate synthetic spectra (see s_SAlTY.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else cross-sections convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Sample input files s*.inp for use with sSAlTY.f90 are supplied. (10 data files).

Mid-Infrared Frequency-Agile Dual-Comb Spectroscopy

NASA Astrophysics Data System (ADS)

Luo, Pei-Ling; Yan, Ming; Iwakuni, Kana; Millot, Guy; Hänsch, Theodor W.; Picqué, Nathalie

2016-06-01

We demonstrate a new approach to mid-infrared dual-comb spectroscopy. It opens up new opportunities for accurate real-time spectroscopic diagnostics and it significantly simplifies the technique of dual-comb spectroscopy. Two mid-infrared frequency combs of slightly different repetition frequencies and moderate, but rapidly tunable, spectral span are generated in the 2800-3200 cm-1 region. The generators rely on electro-optic modulators, nonlinear fibers for spectral broadening and difference frequency generation and do not involve mode-locked lasers. Flat-top frequency combs span up to 10 cm-1 with a comb line spacing of 100 MHz (3×10-3 cm-1). The performance of the spectrometer without any phase-lock electronics or correction scheme is illustrated with spectra showing resolved comb lines and Doppler-limited spectra of methane. High precision on the spectroscopic parameter (line positions and intensities) determination is demonstrated for spectra measured on a millisecond time scale and it is validated with comparison with literature data. G. Millot, S. Pitois, M. Yan, T. Hovannysyan, A. Bendahmane, T.W. Hänsch, N. Picqué, Frequency-agile dual-comb spectroscopy, Nature Photonics 10, 27-30 (2016).

Temporal variation in biodeposit organic content and sinking velocity in long-line shellfish culture

NASA Astrophysics Data System (ADS)

Ren, Lihua; Zhang, Jihong

2016-09-01

We measured the organic content and sinking velocities of biodeposits from two scallop species ( Chlamys farreri, Patinopecten yessoensis) and abalone ( Haliotis discus hannai) that were cultured on suspended long-lines. Measurements were conducted every two months from April 2010 to February 2011. The shellfish were divided into three size groups (small, middle, and big sizes). At each sample point, we assessed biodeposit organic content, average sinking velocity, the frequency distribution of sinking velocities, and the correlation between organic content and sinking velocity. The organic content of biodeposits varied significantly among months ( P<0.05) and the pattern of change varied among species. Sinking velocities varied significantly, ranging from <0.5 cm/s to >1.9 cm/s. The sinking velocities of biodeposits from C. farreri and P. yessoensis were 0.5-1.5 cm/s and from H. discus hannai were <0.7 cm/s. The organic content was significantly negatively correlated to the sinking velocity of biodeposits in C. farreri ( P<0.001) and P. yessoensis ( P<0.05).

Benchmarks of simple, generic, shaped plates for validation of low-frequency electromagnetic computational codes

NASA Technical Reports Server (NTRS)

Deshpande, M. D.; Cockrell, C. R.; Beck, F. B.; Nguyen, T. X.

1993-01-01

The validation of low-frequency measurements and electromagnetic (EM) scattering computations for several simple, generic shapes, such as an equilateral-triangular plate, an equilateral-triangular plate with a concentric equilateral-triangular hole, and diamond- and hexagonal-shaped plates, is discussed. The plates were constructed from a thin aluminum sheet with a thickness of 0.08 cm. EM scattering by the planar plates was measured in the experimental test range (ETR) facility of NASA Langley Research Center. The dimensions of the plates were selected such that, over the frequency range of interest, the dimensions were in the range of lambda0 to 3(lambda0). In addition, the triangular plate with a triangular hole was selected to study internal-hole resonances.

Effective line intensity measurements of trans-nitrous acid (HONO) of the ν1 band near 3600 cm-1 using laser difference-frequency spectrometer

NASA Astrophysics Data System (ADS)

Maamary, Rabih; Fertein, Eric; Fourmentin, Marc; Dewaele, Dorothée; Cazier, Fabrice; Chen, Changshui; Chen, Weidong

2017-07-01

We report on the measurements of the effective line intensities of the ν1 fundamental band of trans-nitrous acid (trans-HONO) in the infrared near 3600 cm-1 (2.78 μm). A home-made widely tunable laser spectrometer based on difference-frequency generation (DFG) was used for this study. The strengths of 28 well-resolved absorption lines of the ν1 band were determined by scaling their absorption intensities to the well referenced absorption line intensity of the ν3 band of trans-HONO around 1250 cm-1 recorded simultaneously with the help of a DFB quantum cascade laser (QCL) spectrometer. The maximum measurement uncertainty of 12% in the line intensities is mainly determined by the uncertainty announced in the referenced line intensities, while the measurement precision in frequency positions of the absorption lines is better than 6×10-4 cm-1. The cross-measurement carried out in the present work allows one to perform intensity calibration using well referenced line parameters.

A demonstration of centimeter-level monitoring of polar motion with the Global Positioning System

NASA Technical Reports Server (NTRS)

Lindqwister, U. J.; Freedman, A. P.; Blewitt, G.

1992-01-01

Daily estimates of the Earth's pole position were obtained with the Global Positioning System (GPS) by using measurements obtained during the GPS IERS (International Earth Rotation Service) and Geodynamics (GIG'91) experiment from 22 Jan. to 13 Feb. 1991. Data from a globally distributed network consisting of 21 Rogue GPS receivers were chosen for the analysis. A comparison of the GPS polar motion series with nine 24-hour very long baseline interferometry (VLBI) estimates yielded agreement in the day-to-day pole position of about 1.5 cm for both X and Y polar motion. A similar comparison of GPS and satellite laser ranging (SLR) data showed agreement to about 1.0 cm. These preliminary results indicate that polar motion can be determined by GPS independent of, and at a level comparable to, that which is obtained from either VLBI or SLR. Furthermore, GPS can provide these data with a daily frequency that neither alternative technique can readily achieve. Thus, GPS promises to be a powerful tool for determining high-frequency platform parameter variation, essential for the ultraprecise spacecraft-tracking requirements of the coming years.

Fourier transform infrared study on microemulsion system of potassium salt of bis(2-ethylhexyl) phosphinic acid (HA)

NASA Astrophysics Data System (ADS)

Zhou, Weijin; Shi, Nai; Wang, Yi; Chang, Zhiyuan; Wu, JinGuang

1994-01-01

To study microemulsion formation in a solvent extraction system is to probe into some basic principles of extraction chemistry in the light of combining extraction chemistry with surface chemistry. In our previous investigations, the microemulsions of the salts of HDEHP and PC88A have been studied systematically by FT-IR. In the experiment, we observed the change of peak positions and intensities of P equals O, P-O-C and P-O-H groups during saponification and hydration, and discovered that the peak of P-O-C splits apart into 1045 and 1075 cm-1. The vibration frequency of the P-O-C group in HDEHP and PC88A is quite close to the symmetric stretching frequency of the POO- group, and thus causes difficulties in the study of their peak position and absorbance variation. For this reason we synthesized bis(2-ethylhexyl) phosphinic acid without the P-O-C group. Infrared spectra in the range of 800 - 4000 cm-1 of this microemulsion system was studied.

Experimental results for a prototype 3-D acoustic imaging system using an ultra-sparse planar array

NASA Astrophysics Data System (ADS)

Impagliazzo, John M.; Chiang, Alice M.; Broadstone, Steven R.

2002-11-01

A handheld high resolution sonar has been under development to provide Navy Divers with a 3-D acoustic imaging system for mine reconnaissance. An ultra-sparse planar array, consisting of 121 1 mm x1 mm, 2 MHz elements, was fabricated to provide 3-D acoustic images. The array was 10 cm x10 cm. A full array at this frequency with elements at half-wavelength spacing would consist of 16384 elements. The first phase of testing of the planar array was completed in September 2001 with the characterization of the array in the NUWC Acoustic Test Facility (ATF). The center frequency was 2 MHz with a 667 kHz bandwidth. A system-level technology demonstration will be conducted in July 2002 with a real-time beamformer and near real-time 3-D imaging software. The demonstration phase consists of imaging simple targets at a range of 3 m in the ATF. Experimental results obtained will be reported on. [Work supported by the Defense Applied Research Project Agency, Advance Technology Office, Dr. Theo Kooij, Program Manager.

A qualitative and quantitative analysis of radiation dose and image quality of computed tomography images using adaptive statistical iterative reconstruction.

PubMed

Hussain, Fahad Ahmed; Mail, Noor; Shamy, Abdulrahman M; Suliman, Alghamdi; Saoudi, Abdelhamid

2016-05-08

Image quality is a key issue in radiology, particularly in a clinical setting where it is important to achieve accurate diagnoses while minimizing radiation dose. Some computed tomography (CT) manufacturers have introduced algorithms that claim significant dose reduction. In this study, we assessed CT image quality produced by two reconstruction algorithms provided with GE Healthcare's Discovery 690 Elite positron emission tomography (PET) CT scanner. Image quality was measured for images obtained at various doses with both conventional filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR) algorithms. A stan-dard CT dose index (CTDI) phantom and a pencil ionization chamber were used to measure the CT dose at 120 kVp and an exposure of 260 mAs. Image quality was assessed using two phantoms. CT images of both phantoms were acquired at tube voltage (kV) of 120 with exposures ranging from 25 mAs to 400 mAs. Images were reconstructed using FBP and ASIR ranging from 10% to 100%, then analyzed for noise, low-contrast detectability, contrast-to-noise ratio (CNR), and modulation transfer function (MTF). Noise was 4.6 HU in water phantom images acquired at 260 mAs/FBP 120 kV and 130 mAs/50% ASIR 120 kV. The large objects (fre-quency < 7 lp/cm) retained fairly acceptable image quality at 130 mAs/50% ASIR, compared to 260 mAs/FBP. The application of ASIR for small objects (frequency >7 lp/cm) showed poor visibility compared to FBP at 260 mAs and even worse for images acquired at less than 130 mAs. ASIR blending more than 50% at low dose tends to reduce contrast of small objects (frequency >7 lp/cm). We concluded that dose reduction and ASIR should be applied with close attention if the objects to be detected or diagnosed are small (frequency > 7 lp/cm). Further investigations are required to correlate the small objects (frequency > 7 lp/cm) to patient anatomy and clinical diagnosis.

Dual-comb coherent Raman spectroscopy with lasers of 1-GHz pulse repetition frequency.

PubMed

Mohler, Kathrin J; Bohn, Bernhard J; Yan, Ming; Mélen, Gwénaëlle; Hänsch, Theodor W; Picqué, Nathalie

2017-01-15

We extend the technique of multiplex coherent Raman spectroscopy with two femtosecond mode-locked lasers to oscillators of a pulse repetition frequency of 1 GHz. We demonstrate a spectra of liquids, which span 1100  cm^-1 of Raman shifts. At a resolution of 6  cm^-1, their measurement time may be as short as 5 μs for a refresh rate of 2 kHz. The waiting period between acquisitions is improved 10-fold compared to previous experiments with two lasers of 100-MHz repetition frequencies.

Olprinone/dopamine combination for improving diaphragmatic fatigue in pentobarbital-anesthetized dogs.

PubMed

Fujii, Yoshitaka

2006-05-01

Diaphragmatic fatigue might contribute to the development of respiratory failure. In particular, the spontaneous, natural rate of phrenic nerve discharge occurs mainly in low-frequency ranges making low-frequency fatigue clinically important in both humans and animals. Olprinone, a phosphodiesterase 3 inhibitor, improves contractility in fatigued diaphragm, but is also associated with hypotension. Dopamine might be used concomitantly for treating related hypotension. The purpose of the study was to assess the effect of olprinoneplus dopamine on diaphragmatic fatigue in pentobarbital-anesthetized dogs. This nonblinded study was conducted at the Department ofAnesthesiology, Institute of Clinical Medicine, Tsukuba, Japan. Diaphragmatic fatigue (assessed by a decrease in diaphragmatic contractility) was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 minutes. Immediately after the fatigue-producing period, groups 2, 3, and 4 received an initial 10 μg/kg dose of olprinone. Group 2 then received maintenance olprinone of 0.3 μg/kg · min; group 3 received maintenance olprinone 0.3 μg/kg · min plus dopamine 2 μg/kg · min; and group 4 received maintenance olprinone 0.3 μg/kg · min plus dopamine 5 μg/kg · min. Group 1 received no study drug. Olprinone and dopamine were administered IV for 30 minutes. Diaphragmatic contractility was assessed by measuring the maximal transdiaphragmatic pressure (Pdi) generated by test stimuli after airway occlusion at functional residual capacity. Hypotension induced by the study drugs was defined as a >10 mm Hg decrease in mean arterial pressure (MAP), calculated by diastolic pressure plus ⅓ pulse pressure, from baseline. Twenty-eight mongrel dogs (18 males and 10 females, weighing 10-15 kg)were used in the study; 7 dogs were randomly assigned to each treatment group. When fatigue was established in each group, mean (SD) Pdi at low-frequency (20 Hz) stimulation decreased significantly from baseline in all groups (group 1: 15.6 [2.2] vs 11.7 [2.4] cm H2O, P = 0.008; group 2: 15.4 [1.5] vs 11.6 [1.3] cm H2O, P= 0.005; group 3:15.5 [2.0] vs 11.6 [1.8] cm H2O, P= 0.006; group 4: 15.7 [1.4] vs 12.0 [1.4] cm H2O, P= 0.008), while no significant change existed in Pdi at high-frequency (100 Hz) stimulation (P = NS). After study drug administration, Pdi in groups 2, 3, and 4 increased significantly from fatigued values at both 20 Hz stimulation (group 2: 11.6 [1.3] vs 21.8 [2.0] cm H2O, P = 0.001; group 3: 11.6 [1.8] vs 22.2 [1.8] cm H2O, P = 0.001; group 4: 12.0 [1.4] vs 25.9 [1.9 ] cm H2O, P = 0.001) and 100 Hz stimulation (group 2: 22.0 [2.2] vs 29.0 [1.9] cm H2O, P = 0.002; group 3: 22.1 [2.0] vs 29.3 [2.2] cm H2O, P = 0.002; group 4: 21.8 [2.2] vs 31.7 [2.4] cm H2O, P= 0.001). The increase in Pdi was significantly larger in group 4 compared with the other 3 groups (all, P < 0.05). Hypotension was not observed in group 4. MAP did not change significantly in group 1 or group 4 compared with baseline or fatigued MAP values (P = NS). Groups 2 and 3 had significant decreases in MAP with treatment compared with values in group 1 and with baseline and fatigued MAP values (all, P < 0.05). The MAP of group 4 was significantly greater than the MAP of groups 2 and 3 with treatment (both, P < 0.05). Olprinone 0.3 μg/kg sd min plus dopamine 5 μg/kg · min improved contractility in fatigued diaphragms and was not associated with hypotension in these pentobarbital-anesthetized dogs. Olprinone monotherapy and olprinone 0.3 μg/kg · min plus dopamine 2 μg/kg · min might improve contractility significantly. However, it was also associated with significant decreases in MAP.

Absolute response and noise equivalent power of cyclotron resonance-assisted InSb detectors at submillimeter wavelengths

NASA Technical Reports Server (NTRS)

Brown, E. R.; Wengler, M. J.; Phillips, T. G.

1985-01-01

Spectra are presented of the responsivity and noise equivalent power (NEP) of liquid-helium-cooled InSb detectors as a function of magnetic field in the range 20-110 per cm. The measurements are all made using a Fourier transform spectrometer with thermal sources. The results show a discernable peak in the detector response at the conduction electron cyclotron resonance (CCR) frequency for magnetic fields as low as 3 kG. The magnitude of responsivity at the resonance peaks is roughly constant with magnetic field and is comparable to the low-frequency hot-electron bolometer response. The NEP at the peaks is found to be comparable to the best long wavelength results previously reported. For example, NEP = 4.5 x 10 to the 13th W/(square root of Hz) at 4.2 K, 6 kG, and 40 per cm was measured. The InSb CCR will provide a much improved detector for laboratory spectroscopy, as compared with hot electron bolometers, in the 20-100 per cm range.

A qualitative and quantitative analysis of radiation dose and image quality of computed tomography images using adaptive statistical iterative reconstruction

PubMed Central

Mail, Noor; Shamy, Abdulrahman M.; Alghamdi, Suliman; Saoudi, Abdelhamid

2016-01-01

Image quality is a key issue in radiology, particularly in a clinical setting where it is important to achieve accurate diagnoses while minimizing radiation dose. Some computed tomography (CT) manufacturers have introduced algorithms that claim significant dose reduction. In this study, we assessed CT image quality produced by two reconstruction algorithms provided with GE Healthcare's Discovery 690 Elite positron emission tomography (PET) CT scanner. Image quality was measured for images obtained at various doses with both conventional filtered back‐projection (FBP) and adaptive statistical iterative reconstruction (ASIR) algorithms. A standard CT dose index (CTDI) phantom and a pencil ionization chamber were used to measure the CT dose at 120 kVp and an exposure of 260 mAs. Image quality was assessed using two phantoms. CT images of both phantoms were acquired at tube voltage (kV) of 120 with exposures ranging from 25 mAs to 400 mAs. Images were reconstructed using FBP and ASIR ranging from 10% to 100%, then analyzed for noise, low‐contrast detectability, contrast‐to‐noise ratio (CNR), and modulation transfer function (MTF). Noise was 4.6 HU in water phantom images acquired at 260 mAs/FBP 120 kV and 130 mAs/50% ASIR 120 kV. The large objects (frequency<7 lp/cm) retained fairly acceptable image quality at 130 mAs/50% ASIR, compared to 260 mAs/FBP. The application of ASIR for small objects (frequency>7 lp/cm) showed poor visibility compared to FBP at 260 mAs and even worse for images acquired at less than 130 mAs. ASIR blending more than 50% at low dose tends to reduce contrast of small objects (frequency>7 lp/cm). We concluded that dose reduction and ASIR should be applied with close attention if the objects to be detected or diagnosed are small (frequency>7 lp/cm). Further investigations are required to correlate the small objects (frequency>7 lp/cm) to patient anatomy and clinical diagnosis. PACS number(s): 87.57.‐s, 87.57.C, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.N, 87.57.nf, 87.57.np, 87.57.nt, 87.57.Q, 87.59.‐e, 87.59.B PMID:27167261

Frequency content of sea surface height variability from internal gravity waves to mesoscale eddies

NASA Astrophysics Data System (ADS)

Savage, Anna C.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Alford, Matthew H.; Buijsman, Maarten C.; Thomas Farrar, J.; Sharma, Hari; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis

2017-03-01

High horizontal-resolution (1/12.5° and 1/25°) 41-layer global simulations of the HYbrid Coordinate Ocean Model (HYCOM), forced by both atmospheric fields and the astronomical tidal potential, are used to construct global maps of sea surface height (SSH) variability. The HYCOM output is separated into steric and nonsteric and into subtidal, diurnal, semidiurnal, and supertidal frequency bands. The model SSH output is compared to two data sets that offer some geographical coverage and that also cover a wide range of frequencies—a set of 351 tide gauges that measure full SSH and a set of 14 in situ vertical profilers from which steric SSH can be calculated. Three of the global maps are of interest in planning for the upcoming Surface Water and Ocean Topography (SWOT) two-dimensional swath altimeter mission: (1) maps of the total and (2) nonstationary internal tidal signal (the latter calculated after removing the stationary internal tidal signal via harmonic analysis), with an average variance of 1.05 and 0.43 cm2, respectively, for the semidiurnal band, and (3) a map of the steric supertidal contributions, which are dominated by the internal gravity wave continuum, with an average variance of 0.15 cm2. Stationary internal tides (which are predictable), nonstationary internal tides (which will be harder to predict), and nontidal internal gravity waves (which will be very difficult to predict) may all be important sources of high-frequency "noise" that could mask lower frequency phenomena in SSH measurements made by the SWOT mission.

New stable tunable solid-state dye laser in the red

NASA Astrophysics Data System (ADS)

Gvishi, Raz; Reisfeld, Renata; Burshtein, Zeev; Miron, Eli

1993-08-01

A red perylene derivative was impregnated into a composite silica-gel glass, and characterized as a dye laser material. The absorption spectrum in the range 480 - 600 nm belongs to the S0 - S1 electronic transition, with a structure reflecting the perylene skeletal vibrations, of typical energy 1100 - 1200 cm-1. An additional peak between 400 and 460 nm belongs to the S0 - S2 transition. The fluorescence exhibits a mirror image relative to the S0 - S1 absorption, with a Stokes shift of about 40 nm for the 0 - 0 transition. Laser tunability was obtained in the range 605 - 630 nm using a frequency-doubled Nd:YAG laser for pumping ((lambda) equals 532 nm). This wavelength range is important for medical applications, such as photodynamic therapy of some cancer tumors. Maximum laser efficiency of approximately 2.5% was obtained at 617 nm. Maximum output was approximately 0.36 mJ/pulse at a repetition rate of 10 Hz. Minimum laser threshold obtained was 0.45 mJ/pulse. The medium losses are attributed to an excited-state singlet-singlet absorption, with an upper limit cross-section of approximately 2.5 X 10-16 cm2. The laser output was stable over more than approximately 500,000 pulses, under excitation with the green line of a copper vapor laser (510 nm), of energy density approximately 40 mJ/cm2 per pulse. Good prospects exist for a considerable enhancement in laser output efficiency.

Influence of tree size, taxonomy, and edaphic conditions on heart rot in mixed-dipterocarp Bornean rainforests: implications for aboveground biomass estimates

NASA Astrophysics Data System (ADS)

Heineman, K. D.; Russo, S. E.; Baillie, I. C.; Mamit, J. D.; Chai, P. P.-K.; Chai, L.; Hindley, E. W.; Lau, B.-T.; Tan, S.; Ashton, P. S.

2015-05-01

Fungal decay of heartwood creates hollows and areas of reduced wood density within the stems of living trees known as heart rot. Although heart rot is acknowledged as a source of error in forest aboveground biomass estimates, there are few datasets available to evaluate the environmental controls over heart rot infection and severity in tropical forests. Using legacy and recent data from drilled, felled, and cored stems in mixed dipterocarp forests in Sarawak, Malaysian Borneo, we quantified the frequency and severity of heart rot, and used generalized linear mixed effect models to characterize the association of heart rot with tree size, wood density, taxonomy, and edaphic conditions. Heart rot was detected in 55% of felled stems > 30 cm DBH, while the detection frequency was lower for stems of the same size evaluated by non-destructive drilling (45%) and coring (23%) methods. Heart rot severity, defined as the percent stem volume lost in infected stems, ranged widely from 0.1-82.8%. Tree taxonomy explained the greatest proportion of variance in heart rot frequency and severity among the fixed and random effects evaluated in our models. Heart rot frequency, but not severity, increased sharply with tree diameter, ranging from 56% infection across all datasets in stems > 50 cm DBH to 11% in trees 10-30 cm DBH. The frequency and severity of heart rot increased significantly in soils with low pH and cation concentrations in topsoil, and heart rot was more common in tree species associated with dystrophic sandy soils than with nutrient-rich clays. When scaled to forest stands, the percent of stem biomass lost to heart rot varied significantly with soil properties, and we estimate that 7% of the forest biomass is in some stage of heart rot decay. This study demonstrates not only that heart rot is a significant source of error in forest carbon estimates, but also that it strongly covaries with soil resources, underscoring the need to account for edaphic variation in estimating carbon storage in tropical forests.

The mechanism and realization of a band-agile coaxial relativistic backward-wave oscillator

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

Ge, Xingjun; Zhang, Jun; Zhong, Huihuang

2014-11-03

The mechanism and realization of a band-agile coaxial relativistic backward-wave oscillator (RBWO) are presented. The operation frequency tuning can be easily achieved by merely altering the inner-conductor length. The key effects of the inner-conductor length contributing to the mechanical frequency tunability are investigated theoretically and experimentally. There is a specific inner-conductor length where the operation frequency can jump from one mode to another mode, which belongs to a different operation band. In addition, the operation frequency is tunable within each operation band. During simulation, the L-band microwave with a frequency of 1.61 GHz is radiated when the inner-conductor length ismore » 39 cm. Meanwhile, the S-band microwave with a frequency of 2.32 GHz is radiated when the inner-conductor length is 5 cm. The frequency adjustment bandwidths of L-band and S-band are about 8.5% and 2%, respectively. Moreover, the online mechanical tunability process is described in detail. In the initial experiment, the generated microwave frequencies remain approximately 1.59 GHz and 2.35 GHz when the inner-conductor lengths are 39 cm and 5 cm. In brief, this technical route of the band-agile coaxial RBWO is feasible and provides a guide to design other types of band-agile high power microwaves sources.« less

Near millimeter wave bandpass filters

NASA Technical Reports Server (NTRS)

Timusk, T.; Richards, P. L.

1981-01-01

The properties of bandpass filters for broadband photometry are reported in the 3-12/cm frequency range. The filters are based on a combination of capacitive grids deposited on thick Mylar substrates and are designed to have very high out-of-band rejection. Low frequencies are blocked by a thick grill that consists of a hexagonal grid of circular holes in a thick metal plate.

Altered oscillatory cerebral blood flow velocity and autoregulation in postural tachycardia syndrome.

PubMed

Medow, Marvin S; Del Pozzi, Andrew T; Messer, Zachary R; Terilli, Courtney; Stewart, Julian M

2014-01-01

Decreased upright cerebral blood flow (CBF) with hyperpnea and hypocapnia is seen in a minority of patients with postural tachycardia syndrome (POTS). More often, CBF is not decreased despite upright neurocognitive dysfunction. This may result from time-dependent changes in CBF. We hypothesized that increased oscillations in CBF occurs in POTS (N = 12) compared to healthy controls (N = 9), and tested by measuring CBF velocity (CBFv) by transcranial Doppler ultrasound of the middle cerebral artery, mean arterial pressure (MAP) and related parameters, supine and during 70° upright tilt. Autospectra for mean CBFv and MAP, and transfer function analysis were obtained over the frequency range of 0.0078-0.4 Hz. Upright HR was increased in POTS (125 ± 8 vs. 86 ± 2 bpm), as was diastolic BP (74 ± 3 vs. 65 ± 3 mmHg) compared to control, while peripheral resistance, cardiac output, and mean CBFv increased similarly with tilt. Upright BP variability (BPV), low frequency (LF) power (0.04-0.13 Hz), and peak frequency of BPV were increased in POTS (24.3 ± 4.1, and 18.4 ± 4.1 mmHg(2)/Hz at 0.091 Hz vs. 11.8 ± 3.3, and 8.8 ± 2 mmHg(2)/Hz c at 0.071 Hz), as was upright overall CBFv variability, low frequency power and peak frequency of CBFv variability (29.3 ± 4.7, and 22.1 ± 2.7 [cm/s](2)/Hz at.092 Hz vs. 14.7 ± 2.6, and 6.7 ± 1.2 [cm/s](2)/Hz at 0.077Hz). Autospectra were sharply peaked in POTS. LF phase was decreased in POTS (-14 ± 4 vs. -25 ± 10 degrees) while upright. LF gain was increased (1.51 ± 0.09 vs. 0.86 ± 0.12 [cm/s]/ mmHg) while coherence was increased (0.96 ± 0.01 vs. 0.80 ± 0.04). Increased oscillatory BP in upright POTS patients is closely coupled to oscillatory CBFv over a narrow bandwidth corresponding to the Mayer wave frequency. Therefore combined increased oscillatory BP and increased LF gain markedly increases CBFv oscillations in a narrow bandwidth. This close coupling of CBF to MAP indicates impaired cerebral autoregulation that may underlie upright neurocognitive dysfunction in POTS.

Local vibrational modes of the formic acid dimer - the strength of the double hydrogen bond

NASA Astrophysics Data System (ADS)

Kalescky, R.; Kraka, E.; Cremer, D.

2013-07-01

The 24 normal and 24 local vibrational modes of the formic acid dimer formed by two trans formic acid monomers to a ring (TT1) are analysed utilising preferentially experimental frequencies, but also CCSD(T)/CBS and ωB97X-D harmonic vibrational frequencies. The local hydrogen bond (HB) stretching frequencies are at 676 cm-1 and by this 482 and 412 cm-1 higher compared to the measured symmetric and asymmetric HB stretching frequencies at 264 and 194 cm-1. The adiabatic connection scheme between local and normal vibrational modes reveals that the lowering is due to the topology of dimer TT1, mass coupling, and avoided crossings involving the HṡṡṡOC bending modes. The HB local mode stretching force constant is related to the strength of the HB whereas the normal mode stretching force constant and frequency lead to an erroneous underestimation of the HB strength. The HB in TT1 is stabilised by electron delocalisation in the O=C-O units fostered by forming a ring via double HBs. This implies that the CO apart from the OH local stretching frequencies reflect the strength of the HB via their red or blue shifts relative to their corresponding values in trans formic acid.

A self-powered glucose biosensing system.

PubMed

Slaughter, Gymama; Kulkarni, Tanmay

2016-04-15

A self-powered glucose biosensor (SPGS) system is fabricated and in vitro characterization of the power generation and charging frequency characteristics in glucose analyte are described. The bioelectrodes consist of compressed network of three-dimensional multi-walled carbon nanotubes with redox enzymes, pyroquinoline quinone glucose dehydrogenase (PQQ-GDH) and laccase functioning as the anodic and cathodic catalyst, respectively. When operated in 45 mM glucose, the biofuel cell exhibited an open circuit voltage and power density of 681.8 mV and 67.86 µW/cm(2) at 335 mV, respectively, with a current density of 202.2 µA/cm(2). Moreover, at physiological glucose concentration (5mM), the biofuel cell exhibits open circuit voltage and power density of 302.1 mV and 15.98 µW/cm(2) at 166.3 mV, respectively, with a current density of 100 µA/cm(2). The biofuel cell assembly produced a linear dynamic range of 0.5-45 mM glucose. These findings show that glucose biofuel cells can be further investigated in the development of a self-powered glucose biosensor by using a capacitor as the transducer element. By monitoring the capacitor charging frequencies, which are influenced by the concentration of the glucose analyte, a linear dynamic range of 0.5-35 mM glucose is observed. The operational stability of SPGS is monitored over a period of 63 days and is found to be stable with 15.38% and 11.76% drop in power density under continuous discharge in 10mM and 20mM glucose, respectively. These results demonstrate that SPGSs can simultaneously generate bioelectricity to power ultra-low powered devices and sense glucose. Copyright © 2015 Elsevier B.V. All rights reserved.

Radiation Performance of Commercial SiGe HBT BiCMOS-High Speed Operational Amplifiers

NASA Technical Reports Server (NTRS)

Chen, Dakai; Pellish, Jonathan; Phan, Anthony; Kim, Hak; Burns, Sam; Albarian, Rafi; Holcombe, Bruce; Little, Bradley; Salzman, James; LaBel, Kenneth

2010-01-01

We present results on heavy-ion and proton irradiations for commercial SiGe BiCMOS operational amplifiers: LTC6400-20 from Linear Technology and THS4304 from Texas Instruments. We found that the devices are susceptible to heavy-ion-induced SETs. The SET cross-sections increase with increasing operating frequency. The LTC6400 exhibits a LET(sub th) < 7.4 MeV·sq cm/mg for frequencies ranging from 10 to 1000 MHz. The THS4304 exhibits a LET(sub th) < 4.4 MeV·sq cm/mg at 200 MHz; the LET(sub th) decreases with increasing frequency. The significance of the SETs also increases with frequency. The SETs at 1000 MHz can erase several signal cycles. We al.so found that the LTC6400 is relatively robust against 198 and 54 MeV protons. We did not observe angular sensitivity from the proton irradiations.

Admittance–voltage profiling of Al{sub x}Ga{sub 1−x}N/GaN heterostructures: Frequency dependence of capacitance and conductance

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

Köhler, K.; Pletschen, W.; Godejohann, B.

2015-11-28

Admittance–voltage profiling of Al{sub x}Ga{sub 1−x}N/GaN heterostructures was used to determine the frequency dependent capacitance and conductance of FET devices in the frequency range from 50 Hz to 1 MHz. The nominally undoped low pressure metal-organic vapor-phase epitaxy structures were grown with an Al-content of 30%. An additional 1 nm thick AlN interlayer was placed in one structure before the Al{sub 0.3}Ga{sub 0.7}N layer growth. For frequencies below 10{sup 8} Hz it is convenient to use equivalent circuits to represent electric or dielectric properties of a material, a method widely used, for example, in impedance spectroscopy. We want to emphasize the relation betweenmore » frequency dependent admittance–voltage profiling and the corresponding equivalent circuits to the complex dielectric function. Debye and Drude models are used for the description of the frequency dependent admittance profiles in a range of depletion onset of the two-dimensional electron gas. Capacitance- and conductance-frequency profiles are fitted in the entire measured range by combining both models. Based on our results, we see contributions to the two-dimensional electron gas for our samples from surface states (80%) as well as from background doping in the Al{sub 0.3}Ga{sub 0.7}N barriers (20%). The specific resistance of the layers below the gate is above 10{sup 5} Ω cm for both samples and increases with increasing negative bias, i.e., the layers below the gate are essentially depleted. We propose that the resistance due to free charge carriers, determined by the Drude model, is located between gate and drain and, because of the AlN interlayer, the resistance is lowered by a factor of about 30 if compared to the sample without an AlN layer.« less

Ambient formaldehyde detection with a laser spectrometer based on difference-frequency generation in PPLN.

PubMed

Rehle, D; Leleux, D; Erdelyi, M; Tittel, F; Fraser, M; Friedfeld, S

2001-01-01

A laser spectrometer based on difference-frequency generation in periodically poled LiNbO3 (PPLN) has been used to quantify atmospheric formaldehyde with a detection limit of 0.32 parts per billion in a given volume (ppbV) using specifically developed data-processing techniques. With state-of-the-art fiber-coupled diode-laser pump sources at 1083 nm and 1561 nm, difference-frequency radiation has been generated in the 3.53-micrometers (2832-cm-1) spectral region. Formaldehyde in ambient air in the 1- to 10-ppb V range has been detected continuously for nine and five days at two separate field sites in the Greater Houston area operated by the Texas Natural Resource Conservation Commission (TNRCC) and the Houston Regional Monitoring Corporation (HRM). The acquired spectroscopic data are compared with results obtained by a well-established wet-chemical o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) technique.

Ambient formaldehyde detection with a laser spectrometer based on difference-frequency generation in PPLN

NASA Technical Reports Server (NTRS)

Rehle, D.; Leleux, D.; Erdelyi, M.; Tittel, F.; Fraser, M.; Friedfeld, S.

2001-01-01

A laser spectrometer based on difference-frequency generation in periodically poled LiNbO3 (PPLN) has been used to quantify atmospheric formaldehyde with a detection limit of 0.32 parts per billion in a given volume (ppbV) using specifically developed data-processing techniques. With state-of-the-art fiber-coupled diode-laser pump sources at 1083 nm and 1561 nm, difference-frequency radiation has been generated in the 3.53-micrometers (2832-cm-1) spectral region. Formaldehyde in ambient air in the 1- to 10-ppb V range has been detected continuously for nine and five days at two separate field sites in the Greater Houston area operated by the Texas Natural Resource Conservation Commission (TNRCC) and the Houston Regional Monitoring Corporation (HRM). The acquired spectroscopic data are compared with results obtained by a well-established wet-chemical o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) technique.

Wake loss and energy spread factor of the LEReC Booster cavity caused by short range wake field

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

Xiao, Binping; Blaskiewicz, Michael; Fedotov, Alexei

LEReC project uses a DC photoemission gun with multi-alkali (CsK 2Sb or NaK 2Sb) cathode [1]. To get 24 mm “flat-top” distribution, 32 Gaussian laser bunches with 0.6 mm rms length are stacked together with 0.75 mm distance [2]. In this case one cannot simply use a 1 cm rms length Gaussian/step/delta bunch for short range wake field simulation since a 0.6 mm bunch contains frequency much higher than the 1 cm bunch. A short range wake field simulation was done using CST Particle Studio™ with 0.6 mm rms Gaussian bunch at the speed of light, and this result wasmore » compared with the result for 1 cm rms Gaussian bunch in Figure 1, from where one notice that the wake potential for the 0.6 mm bunch is ~10 times higher than that of the 1 cm bunch. The wake potential of the 0.6 mm bunch, as well as the charge distribution, was then “shift and stack” every 0.75 mm, the normalized results are shown in Figure 2. The wake loss factor (WLF) is the integration of the product of wake potential and normalized bunch charge, and the energy spread factor (ESF) is the rms deviation from the average energy loss. It is calculated by summing the weighted squares of the differences and taking the square root of the sum. These two factors were then divided by β 2 for 1.6 MV beam energy. The wake loss factor is at 0.86 V/pC and energy spread factor is at 0.54 V/pC rms. With 100 pC electron bunch, the energy spread inter-bunch is 54 V rms.« less

SU-E-CAMPUS-T-02: Exploring Radiation Acoustics CT Dosimeter Design Aspects for Proton Therapy

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

Alsanea, F; Moskvin, V; Stantz, K

2014-06-15

Purpose: Investigate the design aspects and imaging dose capabilities of the Radiation Acoustics Computed Tomography (RA CT) dosimeter for Proton induced acoustics, with the objective to characterize a pulsed pencil proton beam. The focus includes scanner geometry, transducer array, and transducer bandwidth on image quality. Methods: The geometry of the dosimeter is a cylindrical water phantom (length 40cm, radius 15cm) with 71 ultrasound transducers placed along the length and end of the cylinder to achieve a weighted set of projections with spherical sampling. A 3D filtered backprojection algorithm was used to reconstruct the dosimetric images and compared to MC dosemore » distribution. First, 3D Monte Carlo (MC) Dose distributions for proton beam energies (range of 12cm, 16cm, 20cm, and 27cm) were used to simulate the acoustic pressure signal within this scanner for a pulsed proton beam of 1.8x107 protons, with a pulse width of 1 microsecond and a rise time of 0.1 microseconds. Dose comparison within the Bragg peak and distal edge were compared to MC analysis, where the integrated Gaussian was used to locate the 50% dose of the distal edge. To evaluate spatial fidelity, a set of point sources within the scanner field of view (15×15×15cm3) were simulated implementing a low-pass bandwidth response function (0 to 1MHz) equivalent to a multiple frequency transducer array, and the FWHM of the point-spread-function determined. Results: From the reconstructed images, RACT and MC range values are within 0.5mm, and the average variation of the dose within the Bragg peak are within 2%. The spatial resolution tracked with transducer bandwidth and projection angle sampling, and can be kept at 1.5mm. Conclusion: This design is ready for fabrication to start acquiring measurements. The 15 cm FOV is an optimum size for imaging dosimetry. Currently, simulations comparing transducer sensitivity, bandwidth, and proton beam parameters are being evaluated to assess signal-to-noise.« less

The terrestrial gravitational wave environment from known sources

NASA Technical Reports Server (NTRS)

Webbink, Ronald F.

1993-01-01

The objective of this project was to produce a gravitational wave spectral line list of all known binary stars producing expected strain amplitudes at Earth in excess of h = 10 (exp -21), or gravitational wave fluxes in excess of F = 10 (exp -12) erg cm(exp -2) s(exp -1). These strain and flux limits lie above the anticipated detection thresholds for space-borne laser interferometers capable of detecting gravitational radiation in the 10 micron Hz to 1 Hz frequency range. The source list was intended to provide frequency (including each harmonic), amplitude and phase (for each polarization and harmonic), and celestial coordinates for each system, lacking only the orientation of the principal polarization axis with respect to the pole of the coordinate system, and the sign of the source phase and frequency (or, equivalently, of the sense of rotation of the strain tensor with time) from providing a complete source description. Such a spectral line list would lay essential groundwork for high-sensitivity, low-frequency searches for gravitational radiation.

Terahertz birefringence of potassium niobate crystals

NASA Astrophysics Data System (ADS)

Antsygin, V. D.; Mamrashev, A. A.; Nikolaev, N. A.

2018-03-01

We present terahertz optical properties (refractive indices and absorption coefficients) of potassium niobate crystals measured by time-domain spectroscopy in the range of 0.2-2.0 THz. We observe average refractive indices nx = 5.25, ny = 4.8, nz = 5.9 for corresponding optical axes X, Y, Z with the large birefringence of Δn = nz - ny = 1.1. We report rising absorption coefficient at higher frequencies (α ∼ 50 cm-1 at 1 THz for all three axes) while the dichroism is not pronounced. Somewhat higher absorption compared to the previous results could be attributed to some polydomain structure remaining in the crystal.

Self-broadening of the sodium resonance lines and excitation transfer between the 3P32 and 3P12 levels

NASA Astrophysics Data System (ADS)

Huennekens, J.; Gallagher, A.

1983-04-01

Sodium vapor, in the density range 1013 to 5 × 1014 cm-3, was excited by a cw dye laser, tuned 20-150 GHz from either the D1 or D2 resonance line. We observed a three-peak scattered spectrum, consisting of the Rayleigh component at the laser frequency, and the two fluorescence components (direct and sensitized) at the atomic resonance-line frequencies. Corrections to the Rayleigh signals for anisotropy and polarization effects, and to the fluorescence signals for radiation trapping, were made in order to obtain the ratio of the sum of the total intensities of the two fluorescence components to that of the Rayleigh component. This ratio combined with a measurement of the line-wing absorption coefficient yields the sodium density and the D-line self-broadening rate coefficients [kbr=4.67×10-7 cm3s-1 (+/-15%) for the D2 line and kbr=3.07×10-7 cm3s-1 (+/-15%) for the D1 line]. Asymmetry in the self-broadened line wings due to fine-structure recoupling was observed. The measured intensity ratio of the D lines, combined with pulsed measurements of the effective radiative decay rates in the presence of radiation trapping, yields the fine-structure collisional-mixing cross section [σ(3P32-->3P12)=172Å2(+/-18%)] at T≅300° C. Our results are compared to other experiments and to theory.

The potential applications of high-intensity focused ultrasound (HIFU) in vascular neurosurgery.

PubMed

Serrone, Joseph; Kocaeli, Hasan; Douglas Mast, T; Burgess, Mark T; Zuccarello, Mario

2012-02-01

This review assesses the feasibilty of high-intensity focused ultrasound (HIFU) in neurosurgical applications, specifically occlusion of intact blood vessels. Fourteen articles were examined. In summary, MRI was effective for HIFU guidance whereas MR angiography assessed vessel occlusion. Several studies noted immediate occlusion of blood vessels with HIFU. Long-term data, though scarce, indicated a trend of vessel recanalization and return to pre-treatment diameters. Effective parameters for extracranial vascular occlusion included intensity ranges of 1,690-8,800 W/cm(2), duration <15 seconds, and 0.68-3.3 MHz frequency. A threshold frequency-intensity product of 8,250 MHzW/cm(2) was needed for vascular occlusion with a sensitivity of 70% and a specificity of 86%. Complications include skin burns, hemorrhage, and damage to surrounding structures. With evidence that HIFU can successfully occlude extracranial blood vessels, refinement in applications and demonstrable intracranial occlusion are needed. Copyright © 2011 Elsevier Ltd. All rights reserved.

Chaotic Brillouin optical correlation-domain analysis

NASA Astrophysics Data System (ADS)

Zhang, Jianzhong; Zhang, Mingtao; Zhang, Mingjiang; Liu, Yi; Feng, Changkun; Wang, Yahui; Wang, Yuncai

2018-04-01

We propose and experimentally demonstrate a chaotic Brillouin optical correlation-domain analysis (BOCDA) system for distributed fiber sensing. The utilization of the chaotic laser with low coherent state ensures high spatial resolution. The experimental results demonstrate a 3.92-cm spatial resolution over a 906-m measurement range. The uncertainty in the measurement of the local Brillouin frequency shift is 1.2MHz. The measurement signal-to-noise ratio is given, which is agreement with the theoretical value.

Development of the acoustically evoked behavioral response in larval plainfin midshipman fish, Porichthys notatus.

PubMed

Alderks, Peter W; Sisneros, Joseph A

2013-01-01

The ontogeny of hearing in fishes has become a major interest among bioacoustics researchers studying fish behavior and sensory ecology. Most fish begin to detect acoustic stimuli during the larval stage which can be important for navigation, predator avoidance and settlement, however relatively little is known about the hearing capabilities of larval fishes. We characterized the acoustically evoked behavioral response (AEBR) in the plainfin midshipman fish, Porichthys notatus, and used this innate startle-like response to characterize this species' auditory capability during larval development. Age and size of larval midshipman were highly correlated (r(2) = 0.92). The AEBR was first observed in larvae at 1.4 cm TL. At a size ≥ 1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re1 µPa or -15.2 dB re 1 g (z-axis). Lowest AEBR thresholds were 140-150 dB re 1 µPa or -33 to -23 dB re 1 g for frequencies below 225 Hz. Larval fish with size ranges of 1.9-2.4 cm TL had significantly lower best evoked frequencies than the other tested size groups. We also investigated the development of the lateral line organ and its function in mediating the AEBR. The lateral line organ is likely involved in mediating the AEBR but not necessary to evoke the startle-like response. The midshipman auditory and lateral line systems are functional during early development when the larvae are in the nest and the auditory system appears to have similar tuning characteristics throughout all life history stages.

A blind green bank telescope millimeter-wave survey for redshifted molecular absorption

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

Kanekar, N.; Gupta, A.; Carilli, C. L.

2014-02-10

We present the methodology for 'blind' millimeter-wave surveys for redshifted molecular absorption in the CO/HCO{sup +} rotational lines. The frequency range 30-50 GHz appears optimal for such surveys, providing sensitivity to absorbers at z ≳ 0.85. It is critical that the survey is 'blind', i.e., based on a radio-selected sample, including sources without known redshifts. We also report results from the first large survey of this kind, using the Q-band receiver on the Green Bank Telescope (GBT) to search for molecular absorption toward 36 sources, 3 without known redshifts, over the frequency range 39.6-49.5 GHz. The GBT survey has amore » total redshift path of Δz ≈ 24, mostly at 0.81 < z < 1.91, and a sensitivity sufficient to detect equivalent H{sub 2} column densities ≳ 3 × 10{sup 21} cm{sup –2} in absorption at 5σ significance (using CO-to-H{sub 2} and HCO{sup +}-to-H{sub 2} conversion factors of the Milky Way). The survey yielded no confirmed detections of molecular absorption, yielding the 2σ upper limit n(z = 1.2) < 0.15 on the redshift number density of molecular gas at column densities N(H{sub 2}) ≳ 3 × 10{sup 21} cm{sup –2}.« less

MEMS-based Optic Fiber Fabry-Perot Sensor for Underwater Acoustic Measurement with A Wavelength-switched System

NASA Astrophysics Data System (ADS)

Xia, J.; Y Wang, F.; Luo, H.; Hu, Y. M.; Xiong, S. D.

2017-12-01

In this paper, a MEMS-based extrinsic Farby-Perot Interferometric (EFPI) acoustic pressure acoustic sensor is presented. The diaphragm structure is used as the second reflected surface, and the sensitive surface to acoustic pressure. A wavelength-switched phase demodulation system for EFPI sensors is used for acoustic signal recovery. The modified phase demodulation system has been demonstrated to recover the signal to a stable intensity fluctuation level of ±0.5 dB at the test frequency of 2000 Hz. In the test depth of 50cm, the sensor has a resonant frequency of 3.7 kHz, a flat frequency range of 10-800Hz, and a corresponding acoustic pressure sensitivity of -159 dB re. 1/μPa.

Hybrid porous core low loss dispersion flattened fiber for THz propagation

NASA Astrophysics Data System (ADS)

Ali, Sharafat; Ahmed, Nasim; Aljunid, Syed; Ahmad, Badlishah

2016-11-01

This manuscript represents a novel porous core fiber design for Terahertz (THz) propagation with low loss and near zero flat dispersion properties. In this proposed fiber a hexagonal arrangement is used as cladding structure and a hybrid core containing circular and triangular designs is used as the central porous region. The Effective Material Loss (EML), confinement loss and bending loss are investigated for the proposed fiber along with dispersion characteristics. Simulation results show a very low EML of 0.01944 cm-1 at 1 THz operating frequency with negligible confinement and bending loss. The proposed novel porous design shows 0.55 THz range near zero flat dispersion of ±0.05 ps/THz/cm at 0.95 ps/THz/cm. The reported design consists of only circular shaped air holes with proper core diameter and porosity to simplify the fabrication process. The newly proposed hybrid design in the porous core region can be considered as an improved edition in the research of THz porous core fibers.

High-pressure cell for terahertz time-domain spectroscopy.

PubMed

Zhang, Wei; Nickel, Daniel; Mittleman, Daniel

2017-02-06

We introduce a sample cell that can be used for pressure-dependent terahertz time-domain spectroscopy. Compared with traditional far-IR spectroscopy with a diamond anvil cell, the larger aperture permits measurements down to much lower frequencies as low as 3.3 cm^-1 (0.1 THz), giving access to new spectroscopic results. The pressure tuning range reaches up to 34.4 MPa, while the temperature range is from 100 to 473 K. With this large range of tuning parameters, we are able to map out phase diagrams of materials based on their THz spectrum, as well as to track the changing of the THz spectrum within a single phase as a function of temperature and pressure. Pressure-dependent THz-TDS results for nitrogen and R-camphor are shown as an example.

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

NASA Astrophysics Data System (ADS)

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi; Nam, Chang-Yong; Stacchiola, Dario; Sadowski, Jerzy; Boscoboinik, J. Anibal

2017-10-01

This paper describes the design and construction of a compact, "user-friendly" polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, from the surface bound species. A spectral frequency range between 1000 cm-1 and 4000 cm-1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ˜2 min at 4 cm-1 resolution, we have also acquired higher resolution spectra at 0.25 cm-1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a "vacuum suitcase" that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.

Raman spectra from very concentrated aqueous NaOH and from wet and dry, solid, and anhydrous molten, LiOH, NaOH, and KOH.

PubMed

Walrafen, George E; Douglas, Rudolph T W

2006-03-21

High-temperature, high-pressure Raman spectra were obtained from aqueous NaOH solutions up to 2NaOHH2O, with X(NaOH)=0.667 at 480 K. The spectra corresponding to the highest compositions, X(NaOH)> or =0.5, are dominated by H3O2-. An IR xi-function dispersion curve for aqueous NaOH, at 473 K and 1 kbar, calculated from the data of Franck and Charuel indicates that the OH- ion forms H3O2- by preferential H bonding with nonhydrogen-bonded OH groups. Raman spectra from wet to anhydrous, solid LiOH, NaOH, and KOH yield sharp, symmetric OH- stretching peaks at 3664, 3633, and 3596 cm(-1), respectively, plus water-related, i.e., H3O2-, peaks near LiOH, 3562 cm(-1), NaOH, 3596 cm(-1), and, KOH, 3500 cm(-1). Absence of H3O2- peaks from the solid assures that the corresponding melt is anhydrous. Raman spectra from the anhydrous melts yield OH- stretching peak frequencies: LiOH, 3614+/-4 cm(-1), 873 K; NaOH, 3610+/-2 cm(-1), 975 K; and, KOH, 3607+/-2 cm(-1), 773 K, but low-frequency asymmetry due to ion-pair interactions is present which is centered near 3550 cm(-1). The ion-pair-related asymmetry corresponds to the sole IR maximum near 3550 cm(-1) from anhydrous molten NaOH, at 623 K. Bose-Einstein correction of published low-frequency Raman data from molten LiOH revealed an acoustic phonon, near 205 cm(-1), related to restricted translation of OH- versus Li+, and an optical phonon, at 625 cm(-1) and tau approximately 0.05 ps, due to protonic precession and/or pendular motion. Strong H bonding between water and the O atom of OH- forms H3O2-, but the proton of OH- does not bond with H significantly. Large Raman bandwidths (aqueous solutions) are explained in terms of inhomogeneous broadening due to proton transfer in a double well. Vibrational assignments are presented for H3O2-.

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

León, Iker; ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels; Ruipérez, Fernando

We report a joint photoelectron spectroscopy and theoretical study on AuC{sub 4}{sup −}, AuC{sub 6}{sup −}, and AuC{sub n}H{sup −} (n = 2, 4, and 6) using high-resolution photoelectron imaging and ab initio calculations. The ground state of AuC{sub 2}H{sup −}, AuC{sub 4}H{sup −}, and AuC{sub 6}H{sup −} is found to be linear, while that of AuC{sub 4}{sup −} and AuC{sub 6}{sup −} is bent. All the species are found to be linear in their neutral ground states. The electron affinities (EAs) are measured to be 3.366(1) and 3.593(1) eV for AuC{sub 4} and AuC{sub 6}, respectively. Both bending andmore » stretching frequencies are resolved in the spectra of AuC{sub 4}{sup −} and AuC{sub 6}{sup −}. High-resolution data of AuC{sub n}H{sup −} reveal major vibrational progressions in the Au—C stretching and bending modes. AuC{sub 2}H{sup −} has a ground state stretching frequency of 445(10) cm{sup −1} and a bending frequency of 260(10) cm{sup −1}; AuC{sub 4}H{sup −} has a ground state stretching frequency of 340(10) cm{sup −1}; AuC{sub 6}H{sup −} has a ground state stretching frequency of 260(10) cm{sup −1} and a bending frequency of 55(10) cm{sup −1}. The EAs are measured to be 1.475(1), 1.778(1), and 1.962(1) eV for AuC{sub 2}H, AuC{sub 4}H, and AuC{sub 6}H, respectively. The strength of the Au—C bond decreases as the number of carbon atoms increases. The current study provides a wealth of electronic structure information about AuC{sub 4}{sup −}, AuC{sub 6}{sup −}, and AuC{sub n}H{sup −} (n = 2, 4, and 6) and their corresponding neutrals.« less

Effects of Middle Ear Pressure on Otoacoustic Emission Measures.

NASA Astrophysics Data System (ADS)

Zhang, Ming

1995-01-01

Otoacoustic emissions (OAEs) are used extensively in hearing evaluations. Changes in middle ear pressure may have an effect on both forward and backward transmission of signals through the middle ear. The effect that such changes have on OAEs may depend on extent of pressure change, stimulus frequency, and stimulus level. This study quantitatively evaluates the effects of these variables on distortion product OAEs (DPOAEs) and cochlear microphonic distortion products (CMDPs) for a wide range of stimuli. Pigmented adult guinea pigs were experimental subjects. An animal surgical model was established to manipulate pressure in the middle ear and CMDP and DPOAE were simultaneously measured. The effects on forward transmission were determined from the CMDP data. It was assumed that the DPOAE measures were affected by changes in both forward and backward transmission. The effects on backward transmission were determined from the DPOAE data after the effect on forward transmission were subtracted out. For all conditions the frequency ratio rm f_2/f_1 was held at 1.2 and the level ratio rm L_1/L_2 was 10 dB. The effects on forward transmission were similar to those for backward transmission in all experimental conditions. Negative pressure had a greater effect than positive pressure. Positive pressures of +10 and +20 cmH_2O affected transmission for low frequency stimuli (f_2 = 1620 and 2680 Hz) but had little effect for high frequency stimuli (f_2 = 6980 and 10250 Hz). Negative pressures of -2.5 to -10 cmH_2O affected transmission across all frequencies tested. The effect at low frequencies is hypothesized to be related to tympanic membrane stiffness. The effect of negative pressure at high frequencies may be related to change in the incudostapedial joint. The slope of growth function decreased with the pressure change for DPOAEs but changed little for CMDPs. The decrease in slope for DPOAEs suggests that the level chosen for analysis can influence the result of the evaluation. In this study, such influence was minimized by averaging over a range of stimulus level. Finally it was noted that pressure could have a greater effect on OAE threshold (affected by both forward and backward transmission) than on behavioral threshold (affected only by forward transmission).

Emulation of Forward-looking Radar Technology for Threat Detection in Rough Terrain Environments: A Scattering and Imaging Study

DTIC Science & Technology

2012-12-01

a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm, lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm...horizontal-horizontal (hh)-polarized images for 20 m×10 m scene: (a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm...lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm, lc=14.93 cm. Ground electrical properties: εr=6, σd=10 mS/m. Frequency span: 0.3

A comparison of the far-infrared and low-frequency Raman spectra of glass-forming liquids

NASA Astrophysics Data System (ADS)

Perova, T. S.; Vij, J. K.; Christensen, D. H.; Nielsen, O. F.

1999-04-01

Far-infrared and low-frequency Raman spectra in the wavenumber range from 15 to 500 cm -1 were recorded for glycerol, triacetin (glycerol triacetate) and o-terphenyl at temperatures from 253 to 355 K. The far-infrared spectra of glycerol appear complex compared with the spectra of triacetin owing to the presence of hydrogen bonding in glycerol. The experimental results obtained for o-terphenyl are in good agreement with normal mode analyses carried out for crystalline o-terphenyl (A. Criado, F.J. Bermejo, A. de Andres, Mol. Phys. 82 (1994) 787). The far-infrared results are compared with the low-frequency Raman spectra of these three glass-forming liquids. The difference in temperature dependences found from these spectra is explained on the basis of different temperature contributions of the relaxational and vibrational processes to the low-frequency vibrational spectra.

Energy harvesting device based on a metallic glass/PVDF magnetoelectric laminated composite

NASA Astrophysics Data System (ADS)

Lasheras, A.; Gutiérrez, J.; Reis, S.; Sousa, D.; Silva, M.; Martins, P.; Lanceros-Mendez, S.; Barandiarán, J. M.; Shishkin, D. A.; Potapov, A. P.

2015-06-01

A flexible, low-cost energy-harvesting device based on the magnetoelectric (ME) effect was designed using Fe64Co17Si7B12 as amorphous magnetostrictive ribbons and polyvinylidene fluoride (PVDF) as the piezoelectric element. A 3 cm-long sandwich-type laminated composite was fabricated by gluing the ribbons to the PVDF with an epoxy resin. A voltage multiplier circuit was designed to produce enough voltage to charge a battery. The power output and power density obtained were 6.4 μW and 1.5 mW cm-3, respectively, at optimum load resistance and measured at the magnetomechanical resonance of the laminate. The effect of the length of the ME laminate on power output was also studied: the power output exhibited decays proportionally with the length of the ME laminate. Nevertheless, good performance was obtained for a 0.5 cm-long device working at 337 KHz within the low radio frequency (LRF) range.

Measurement of the cosmic microwave background spectrum by the COBE FIRAS instrument

NASA Technical Reports Server (NTRS)

Mather, J. C.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Fixsen, D. J.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Meyer, S. S.; Noerdlinger, P. D.

1994-01-01

The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).

Optimization of low frequency sound absorption by cell size control and multiscale poroacoustics modeling

NASA Astrophysics Data System (ADS)

Park, Ju Hyuk; Yang, Sei Hyun; Lee, Hyeong Rae; Yu, Cheng Bin; Pak, Seong Yeol; Oh, Chi Sung; Kang, Yeon June; Youn, Jae Ryoun

2017-06-01

Sound absorption of a polyurethane (PU) foam was predicted for various geometries to fabricate the optimum microstructure of a sound absorbing foam. Multiscale numerical analysis for sound absorption was carried out by solving flow problems in representative unit cell (RUC) and the pressure acoustics equation using Johnson-Champoux-Allard (JCA) model. From the numerical analysis, theoretical optimum cell diameter for low frequency sound absorption was evaluated in the vicinity of 400 μm under the condition of 2 cm-80 K (thickness of 2 cm and density of 80 kg/m3) foam. An ultrasonic foaming method was employed to modulate microcellular structure of PU foam. Mechanical activation was only employed to manipulate the internal structure of PU foam without any other treatment. A mean cell diameter of PU foam was gradually decreased with increase in the amplitude of ultrasonic waves. It was empirically found that the reduction of mean cell diameter induced by the ultrasonic wave enhances acoustic damping efficiency in low frequency ranges. Moreover, further analyses were performed with several acoustic evaluation factors; root mean square (RMS) values, noise reduction coefficients (NRC), and 1/3 octave band spectrograms.

Induction magnetometer using a high-Tc superconductor coil

NASA Astrophysics Data System (ADS)

Sasada, Ichiro

2010-05-01

An induction magnetometer consisting of a search coil and an inverting operational amplifier is simple in structure and in signal transferring mechanism from the magnetic field input to the voltage output. Because this magnetometer is based on Faraday's law of induction, it has a lower cutoff frequency r/(2πL), where r is the resistance of the coil and L is its inductance. An attempt has been made to lower the cutoff frequency of the induction magnetometer by using a high-Tc superconductor coil. With a pancake coil (inner diameter ≈18 cm and outer diameter ≈23 cm, 92 turns, 3.23 mH) made of a Bismuth strontium calcium copper oxide (BSCCO) superconductor tape of 5 mm in width and 0.23 mm in thickness, the cutoff frequency achieved was 1.7 Hz which is much lower than that obtained with a bulky copper search coil which is typically in the range of 10-20 Hz. In the experiment, an inverting amplifier was made with a complementary metal-oxide semiconductor operational amplifier and was immersed in liquid nitrogen together with a BSCCO high-Tc superconducting coil. Discussion is made on the resolution of the induction magnetometer using a high-Tc superconductor search coil.

Organic permeable-base transistors - superb power efficiency at highest frequencies (Conference Presentation)

NASA Astrophysics Data System (ADS)

Klinger, Markus P.; Fischer, Axel; Kaschura, Felix; Scholz, Reinhard; Lüssem, Björn; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Kasemann, Daniel; Leo, Karl

2016-11-01

Organic field-effect transistors (OFET) are important elements in thin-film electronics, being considered for flat-panel or flexible displays, radio frequency identification systems, and sensor arrays. To optimize the devices for high-frequency operation, the channel length, defined as the horizontal distance between the source and the drain contact, can be scaled down. Here, an architecture with a vertical current flow, in particular the Organic Permeable-Base Transistors (OPBT), opens up new opportunities, because the effective transit length in vertical direction is precisely tunable in the nanometer range by the thickness of the semiconductor layer. We present an advanced OPBT, competing with best OFETs while a low-cost, OLED-like fabrication with low-resolution shadow masks is used (Klinger et al., Adv. Mater. 27, 2015). Its design consists of a stack of three parallel electrodes separated by two semiconductor layers of C60 . The vertical current flow is controlled by the middle base electrode with nano-sized openings passivated by an native oxide. Using insulated layers to structure the active area, devices show an on/off ratio of 10⁶ , drive 11 A/cm² at an operation voltage of 1 V, and have a low subthreshold slope of 102 mV/decade. These OPBTs show a unity current-gain transit frequency of 2.2 MHz and off-state break-down fields above 1 MV/cm. Thus, our optimized setup does not only set a benchmark for vertical organic transistors, but also outperforms best lateral OFETs using similar low-cost structuring techniques in terms of power efficiency at high frequencies.

Structural and electrical properties of Li4Ti5O12 anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Vikram Babu, B.; Vijaya Babu, K.; Tewodros Aregai, G.; Seeta Devi, L.; Madhavi Latha, B.; Sushma Reddi, M.; Samatha, K.; Veeraiah, V.

2018-06-01

In this work we investigate Li4Ti5O12 (LTO) anode material synthesized by conventional solid state reaction method calcined at 850 °C for 16 h. Thermal analysis reveals the temperature dependence of the material properties. The phase composition, micro-morphology and elemental analysis of the compound are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectra (EDS) respectively. The results of XRD pattern possessed cubic spinel structure with space group Fd-3m. The morphological features of the powder sample are in the range of 1.1 μm. The EDS spectra confirm the constituent elemental composition of the sample. Electrical conductivity measurement at different frequencies and temperatures had been carried out; and at room temperature it is found to be 5.96 × 10-7 S/cm. Besides, for the different frequencies applied, the activation energies were calculated and obtained to be in the range of 0.2-0.4 eV.

The VLA-COSMOS Survey - V. 324 MHz continuum observations

NASA Astrophysics Data System (ADS)

Smolčić, Vernesa; Ciliegi, Paolo; Jelić, Vibor; Bondi, Marco; Schinnerer, Eva; Carilli, Chris L.; Riechers, Dominik A.; Salvato, Mara; Brković, Alen; Capak, Peter; Ilbert, Olivier; Karim, Alexander; McCracken, Henry; Scoville, Nick Z.

2014-09-01

We present 90 cm Very Large Array imaging of the COSMOS field, comprising a circular area of 3.14 square degrees at 8.0arcsec × 6.0arcsec angular resolution with an average rms of 0.5 mJy beam-1. The extracted catalogue contains 182 sources (down to 5.5σ), 30 of which are multicomponent sources. Using Monte Carlo artificial source simulations, we derive the completeness of the catalogue, and we show that our 90 cm source counts agree very well with those from previous studies. Using X-ray, NUV-NIR and radio COSMOS data to investigate the population mix of our 90 cm radio sample, we find that our sample is dominated by active galactic nuclei. The average 90-20 cm spectral index (Sν ∝ να, where Sν is the flux density at frequency ν and α the spectral index) of our 90 cm selected sources is -0.70, with an interquartile range from -0.90 to -0.53. Only a few ultra-steep-spectrum sources are present in our sample, consistent with results in the literature for similar fields. Our data do not show clear steepening of the spectral index with redshift. Nevertheless, our sample suggests that sources with spectral indices steeper than -1 all lie at z ≳ 1, in agreement with the idea that ultra-steep-spectrum radio sources may trace intermediate-redshift galaxies (z ≳ 1).

Wide temperature range (T = 295 K and 770-1305 K) study of the kinetics of the reactions HCO + NO and HCO + NO2 using frequency modulation spectroscopy.

PubMed

Dammeier, J; Colberg, M; Friedrichs, G

2007-08-21

The rate constants for , HCO + NO --> HNO + CO, and , HCO + NO(2)--> products, have been measured at temperatures between 770 K < T < 1305 K behind reflected shock waves and, for the purpose of a consistency check, in a slow flow reactor at room temperature. HCO radicals were generated by 193 nm excimer laser photolysis of diluted gas mixtures containing glyoxal, (CHO)(2), and NO or NO(2) in argon and were monitored using frequency modulation (FM) absorption spectroscopy. Kinetic simulations based on a comprehensive reaction mechanism showed that the rate constants for the title reactions could be sensitively extracted from the measured HCO profiles. The determined high temperature rate constants are k(1)(769-1307 K) = (7.1 +/- 2.7) x 10(12) cm(3) mol(-1) s(-1) and k(2)(804-1186 K) = (3.3 +/- 1.8) x 10(13) cm(3) mol(-1) s(-1). The room temperature values were found to be in very good agreement with existing literature data and show that both reactions are essentially temperature independent. The weak temperature dependence of can be explained by the interplay of a dominating direct abstraction pathway and a complex-forming mechanism. Both pathways yield the products HNO + CO. In contrast to , no evidence for a significant contribution of a direct high temperature abstraction channel was found for . Here, the observed temperature independent overall rate constant can be described by a complex-forming mechanism with several product channels. Detailed information on the strongly temperature dependent channel branching ratios is provided. Moreover, the high temperature rate constant of , OH + (CHO)(2), has been determined to be k(7) approximately 1.1 x 10(13) cm(3) mol(-1) s(-1).

Particle-In-Cell Simulations of Asymmetric Dual Frequency Capacitive Discharge Physics

NASA Astrophysics Data System (ADS)

Wu, Alan; Lichtenberg, A. J.; Lieberman, M. A.; Verboncoeur, J. P.

2003-10-01

Dual frequency capacitive discharges are finding increasing use for etching in the microelectronics industry. In the ideal case, the high frequency power (typically 27.1-160 MHz) controls the plasma density and the low frequency power (typically 2-13.56 MHz) controls the ion energy. The electron power deposition and the dynamics of dual frequency rf sheaths are not well understood. We report on particle-in-cell computer simulations of an asymmetric dual frequency argon discharge. The simulations are performed in 1D (radial) geometry using the bounded electrostatic code XPDP1. Operating parameters are 27.1/2 MHz high/low frequencies, 10/13 cm inner/outer radii, 3-200 mTorr pressures, and 10^9-10^11 cm-3 densities. We determine the power deposition and sheath dynamics for the high frequency power alone, and with various added low frequency powers. We compare the simulation results to simple global models of dual frequency discharges. Support provided by Lam Research, NSF Grant ECS-0139956, California industries, and UC-SMART Contract SM99-10051.

The analysis of soil characteristics near the animal feed and fertiliser mill using the Bartington

NASA Astrophysics Data System (ADS)

Azhari, Adinda Syifa; Agustine, Eleonora; Fitriani, Dini

2017-07-01

Industrial activities have the potential to make pollution in agricultural land, the waste contains poisonous material and it is dangerous for the environment. In general, waste from factory is dumped directly into the river, but in the current study an object that is going to be conscientious is soil on around mill. There are three sampling sites are around fertilizer plants, feed mills and original uncontaminated soil. This research has been conducted to assess the impact of pollution resulting from the two mills for the environment. Physical parameter that used is magnetic susceptibility. Sampling was conducted using the method of magnetic susceptibility of rock to see the value of low frequency (lf) and shows Frequency Dependent (fd%) using the MS2B Bartington. The results from this study is at a location close to the fertilizer plant at a depth of 0-5 cm has a value susceptibility low frequency ( lf)=187.1 - 494.8, fd (%)=1.37 - 2:46, at a depth of 6-10 cm susceptibility value of low frequency (lf)=211 - 832.7,fd (%)=1.04 - 5.37. Results in the area of animal feed mill at a depth of 0-5 cm value susceptibility low frequency (lf)=111.9 - 325.7, fd (%)=0.8 - 3.57, at a depth of 6-10 cm value susceptibility low frequency (lf)=189.2 to 386.8,fd (%)=0.33 - 3.7. Results in the original soil at a depth of 0-5 cm susceptibility value of low frequency (lf)=1188.7 - 2237.8,fd (%)=2.75 - 4.65, at a depth of 6-10 cm value susceptibility low frequency (lf)=977.7 - 2134.7,fd (%)=3.06 - 6.21. The highest value was in the arealf original, shows the area has a high mineral content andlf lows were in the area near the factory fodder it is caused by high pollution, resulting in lower mineral content in the soil.

Extreme sea level implications of 1.5 °C, 2.0 °C, and 2.5 °C temperature stabilization targets in the 21st and 22nd centuries

NASA Astrophysics Data System (ADS)

Rasmussen, D. J.; Bittermann, Klaus; Buchanan, Maya K.; Kulp, Scott; Strauss, Benjamin H.; Kopp, Robert E.; Oppenheimer, Michael

2018-03-01

Sea-level rise (SLR) is magnifying the frequency and severity of extreme sea levels (ESLs) that can cause coastal flooding. The rate and amount of global mean sea-level (GMSL) rise is a function of the trajectory of global mean surface temperature (GMST). Therefore, temperature stabilization targets (e.g. 1.5 °C and 2.0 °C of warming above pre-industrial levels, as from the Paris Agreement) have important implications for coastal flood risk. Here, we assess, in a global network of tide gauges, the differences in the expected frequencies of ESLs between scenarios that stabilize GMST warming at 1.5 °C, 2.0 °C, and 2.5 °C above pre-industrial levels. We employ probabilistic, localized SLR projections and long-term hourly tide gauge records to estimate the expected frequencies of historical and future ESLs for the 21st and 22nd centuries. By 2100, under 1.5 °C, 2.0 °C, and 2.5 °C GMST stabilization, the median GMSL is projected to rise 48 cm (90% probability of 28-82 cm), 56 cm (28-96 cm), and 58 cm (37-93 cm), respectively. As an independent comparison, a semi-empirical sea level model calibrated to temperature and GMSL over the past two millennia estimates median GMSL rise within 7-8 cm of these projections. By 2150, relative to the 2.0 °C scenario and based on median sea level projections, GMST stabilization of 1.5 °C spares the inundation of lands currently home to about 5 million people, including 60 000 individuals currently residing in Small Island Developing States. We quantify projected changes to the expected frequency of historical 10-, 100-, and 500-year ESL events using frequency amplification factors that incorporate uncertainty in both local SLR and historical return periods of ESLs. By 2150, relative to a 2.0 °C scenario, the reduction in the frequency amplification of the historical 100 year ESL event arising from a 1.5 °C GMST stabilization is greatest in the eastern United States, with ESL event frequency amplification being reduced by about half at most tide gauges. In general, smaller reductions are projected for Small Island Developing States.

Frequency metrology of the acetylene lines near 789 nm from lamb-dip measurements

NASA Astrophysics Data System (ADS)

Tao, Lei-Gang; Hua, Tian-Peng; Sun, Yu R.; Wang, Jin; Liu, An-Wen; Hu, Shui-Ming

2018-05-01

Lamb-dips of the ro-vibrational lines of 12C2H2 near 789 nm were recorded using cavity ring-down saturation spectroscopy. Calibrated by an optical frequency comb, frequencies of 45 acetylene lines were determined with an accuracy of 1.1 ×10-7 cm-1 (δν / ν = 8 ×10-12), which is over two orders of magnitude more accurate than previous Doppler-limited studies. An averaged shift of about 0.01 cm-1 were found by comparing the upper energies obtained in this work to those recently presented by Chubb et al. from a MARVEL analysis.

Coherent Doppler lidar for automated space vehicle rendezvous, stationkeeping and capture

NASA Technical Reports Server (NTRS)

Bilbro, James A.

1991-01-01

The inherent spatial resolution of laser radar makes ladar or lidar an attractive candidate for Automated Rendezvous and Capture application. Previous applications were based on incoherent lidar techniques, requiring retro-reflectors on the target vehicle. Technology improvements (reduced size, no cryogenic cooling requirement) have greatly enhanced the construction of coherent lidar systems. Coherent lidar permits the acquisition of non-cooperative targets at ranges that are limited by the detection capability rather than by the signal-to-noise ratio (SNR) requirements. The sensor can provide translational state information (range, velocity, and angle) by direct measurement and, when used with any array detector, also can provide attitude information by Doppler imaging techniques. Identification of the target is accomplished by scanning with a high pulse repetition frequency (dependent on the SNR). The system performance is independent of range and should not be constrained by sun angle. An initial effort to characterize a multi-element detection system has resulted in a system that is expected to work to a minimum range of 1 meter. The system size, weight and power requirements are dependent on the operating range; 10 km range requires a diameter of 3 centimeters with overall size at 3 x 3 x 15 to 30 cm, while 100 km range requires a 30 cm diameter.

The Importance of High Frequency Observations for the SKA

NASA Astrophysics Data System (ADS)

Welch, William J.

2007-12-01

The plan for the Square Kilometer Array (SKA) is one or more very large arrays operating in two or more contiguous frequency bands: roughly 15 - 90 MHz, 120 - 500 MHz, and 500 MHz - 25 GHz. The last band may be further divided into roughly 500 MHz - 1.5 GHz and 1.5 - 25 GHz. Construction costs may delay or forgo one or more of these bands. We argue that the entire high frequency band is of special importance for astronomy both in the local universe and at great distances and early times. One of the Key Science Projects, the Cradle of Life, requires high sensitivity and resolution at frequencies up to 20 GHz for the study of forming disks around new stars with disk opacities too great for millimeter wave observations. The larger issue of star formation, a poorly understood area, will also benefit from high sensitivity observations at short cm wavelengths. Magnetic field measurements through the Zeeman effect in the densest star forming gas are best done using tracers such as CCS at frequencies of 11 and 22 GHz. The wide frequency range of the SKA permits the observation of multiple rotational transitions of long chain molecules, providing accurate measures of both gas densities and temperatures. The wide field of view will permit large scale surveys of entire star forming clouds revealing, at high resolution, the formation of clusters of pre-protostellar stars and class 0-2 protostars in line radiation. The continuum cm wave radiation will reveal the growth of grains in disks. On the larger scale, observations of CO at high redshifts will trace the evolution of star formation and the formation of metals back to the Epic of Reionization.

Treatment of burning mouth syndrome with a low-level energy diode laser.

PubMed

Yang, Hui-Wen; Huang, Yu-Feng

2011-02-01

To test the therapeutic efficacy of low-level energy diode laser on burning mouth syndrome. Burning mouth syndrome is characterized by burning and painful sensations in the mouth, especially the tongue, in the absence of significant mucosal abnormalities. Although burning mouth syndrome is relatively common, little is known regarding its etiology and pathophysiology. As a result, no treatment is effective in all patients. Low-level energy diode laser therapy has been used in a variety of chronic and acute pain conditions, including neck, back and myofascial pain, degenerative osteoarthritis, and headache. A total of 17 patients who had been diagnosed with burning mouth syndrome were treated with an 800-nm wavelength diode laser. A straight handpiece was used with an end of 1-cm diameter with the fiber end standing 4 cm away from the end of handpiece. When the laser was applied, the handpiece directly contacted or was immediately above the symptomatic lingual surface. The output used was 3 W, 50 msec intermittent pulsing, and a frequency of 10 Hz, which was equivalent to an average power of 1.5 W/cm(2) (3 W × 0.05 msec × 10 Hz = 1.5 W/cm(2)). Depending on the involved area, laser was applied to a 1-cm(2) area for 70 sec until all involved area was covered. Overall pain and discomfort were analyzed with a 10-cm visual analogue scale. All patients received diode laser therapy between one and seven times. The average pain score before the treatment was 6.7 (ranging from 2.9 to 9.8). The results showed an average reduction in pain of 47.6% (ranging from 9.3% to 91.8%). The burning sensation remained unchanged for up to 12 months. Low-level energy diode laser may be an effective treatment for burning mouth syndrome.

Infrared spectroscopy of the NO3 radical from 2000 to 3000 cm-1

NASA Astrophysics Data System (ADS)

Kawaguchi, Kentarou; Fujimori, Ryuji; Tang, Jian; Ishiwata, Takashi

2018-02-01

The present paper reports high-resolution spectroscopic study of the 14NO3 radical in the 2000-3000 cm-1 region, where eight E‧-A2‧ bands from the ground state are observed. Three bands at 2206, 2246, and 2377 cm-1 are analyzed for the first time, and assigned to the ν1 + 3ν4, 2ν2 + 2ν4, and ν3 + 3ν4 bands, respectively. Bands at 2024, 2155, 2518, and 2585 cm-1 are reassigned to the ν1 + ν3, 2ν3, ν1 + ν3 + ν4, and 2ν3 + ν4 bands, respectively, by adopting the new ν3 vibrational frequency of 1055 cm-1 lower than the previous ν3 = 1492 cm-1. The band at 2902 cm-1 is observed for the first time and assigned to the ν1 + ν3 + 2ν4 band which is the ν1 combined band with the 1927 cm-1 band. Band intensities observed in the 2000-3000 cm-1 region are attributed to the intensity borrowing from the B˜2E‧ -X˜2 A2‧ electronic transition through the vibronic interaction. Although the ν3 fundamental band has not been observed due to the cancelation of vibrational intensity and borrowed intensity, the 2ν3 band becomes stronger than ν3 by a factor of more than 50. Perturbation effects are recognized for the bands observed except for the 2206 cm-1 and 2377 cm-1 bands, and are analyzed by taking into account the Coriolis interaction in the most cases. However, the 2024 cm-1 band is free from the Coriolis interaction, and the v1-v3 interaction is incorporated in the analysis, leading to the 2ν1 frequency of 2008.8 cm-1, which is close to the energy value of 2010 cm-1 observed by a laser induced fluorescence study.

Radiofrequency penetration and absorption in the human body: limitations to high-field whole-body nuclear magnetic resonance imaging.

PubMed

Röschmann, P

1987-01-01

This study presents experimental results about the effective depth of penetration and about the radiofrequency (rf) power absorption in humans as a function of frequency. The frequency range investigated covers 10 up to 220 MHz. For the main part, the results were derived from bench measurements of the quality factor Q, and of the resonance frequency shift due to the loading of the coil. Different types of head-, body-, and surface coils were investigated loaded with volunteers or metallic phantoms. For spin-echo imaging at 2 T (85 MHz), the local specific absorption rate (SAR) was found to be approximately equal to 0.05 W/kg using a pi pulse of 1-ms duration and pulse repetition time TR = 1 s. Measurements of the quality factor Q as a function of frequency show that the SAR depends upon the frequency f according to approximately f2.15. The effective depth of rf penetration as derived drops from 17 cm at 85 MHz to 7 cm at 220 MHz. Head imaging with B1 penetrating from practically all sides into the object should be possible up to 220 MHz (5 T) with SAR values staying within the local limit of 2 W/kg as set by the FDA. Whole-body imaging of large subjects as well as surface coil imaging is depth limited above 100-MHz frequency. Perturbation methods are applied in order to separate the total rf power deposition in the patient into dielectric and magnetic contributions. The observed effects due to interactions of rf magnetic fields with biological tissue contradict predictions based on homogeneous tissue models. A refined tissue model with regions of high electrical conductivity, subdivided by quasi-insulating adipose layers, provides a rationale for a better understanding of the underlying processes. At frequencies below 100 MHz, the rf power deposition in patients is apparently more evenly distributed over the exposed body volume than currently assumed.

Development of a compact, rf-driven, pulsed ion source for neutron generation

NASA Astrophysics Data System (ADS)

Perkins, L. T.; Celata, C.; Lee, Y.; Leung, K. N.; Picard, D. S.; Vilaithong, R.; Williams, M. D.; Wutte, D.

1997-02-01

Lawrence Berkeley National Laboratory is currently developing a compact, sealed-accelerator-tube neutron generator capable of producing a neutron flux in the range of 109 to 1010 D-T neutrons per second. The ion source, a miniaturized variation of earlier radio-frequency (rf)-driven multicusp ion sources, is designed to fit within a ˜5 cm diameter borehole. Typical operating parameters include repetition rates up to 100 pps, with pulse widths between 10 and 80 μs (limited only by the available rf power supply) and source pressures as low as ˜5 mTorr. In this configuration, peak extractable hydrogen current densities exceeding 1180 mA/cm2 with H1+ yields over 94% having been achieved.

Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

NASA Technical Reports Server (NTRS)

Steffes, P. G.

1986-01-01

After long arduous work with the simulator, measurements of the refractivity and absorptivity of nitrogen under conditions similar to those for Titan were completed. The most significant measurements, however, were those of the microwave absorption from gaseous ammonia under simulated conditions for the Jovian atmospheres over wavelengths from 1.3 to 22 cm. The results of these measurements are critical in that they confirm the theoretical calculation of the ammonia opacity using the Ben-Reuven lineshape. The application of both these results, and results obtained previously, to planetary observations at microwave frequencies were especially rewarding. Applications of the results for ammonia to radio astronomical observations of Jupiter in the 1.3 to 20 cm wavelength range and the application of results for gaseous H2SO4 under simulated Venus conditions are discussed.

Alkylation effects on the energy transfer of highly vibrationally excited naphthalene.

PubMed

Hsu, Hsu Chen; Tsai, Ming-Tsang; Dyakov, Yuri A; Ni, Chi-Kung

2011-11-04

The energy transfer of highly vibrationally excited isomers of dimethylnaphthalene and 2-ethylnaphthalene in collisions with krypton were investigated using crossed molecular beam/time-of-flight mass spectrometer/time-sliced velocity map ion imaging techniques at a collision energy of approximately 300 cm(-1). Angular-resolved energy-transfer distribution functions were obtained directly from the images of inelastic scattering. The results show that alkyl-substituted naphthalenes transfer more vibrational energy to translational energy than unsubstituted naphthalene. Alkylation enhances the V→T energy transfer in the range -ΔE(d)=-100~-1500 cm(-1) by approximately a factor of 2. However, the maximum values of V→T energy transfer for alkyl-substituted naphthalenes are about 1500~2000 cm(-1), which is similar to that of naphthalene. The lack of rotation-like wide-angle motion of the aromatic ring and no enhancement in very large V→T energy transfer, like supercollisions, indicates that very large V→T energy transfer requires special vibrational motions. This transfer cannot be achieved by the low-frequency vibrational motions of alkyl groups. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection and quantification of anionic detergent (lissapol) in milk using attenuated total reflectance-Fourier Transform Infrared spectroscopy.

PubMed

Jaiswal, Pranita; Jha, Shyam Narayan; Kaur, Jaspreet; Borah, Anjan

2017-04-15

Adulteration of milk to gain economic benefit is rampant. Addition of detergent in milk can cause food poisoning and other complications. Fourier Transform Infrared spectroscopy was evaluated as rapid method for detection and quantification of anionic detergent (lissapol) in milk. Spectra of pure and artificially adulterated milk (0.2-2.0% detergent) samples revealed clear differences in wavenumber range of 4000-500cm -1 . The apparent variations observed in region of 1600-995 and 3040-2851cm -1 corresponds to absorption frequencies of common constituents of detergent (linear alkyl benzene sulphonate). Principal component analysis showed discrete clustering of samples based on level of detergent (p⩽0.05) in milk. The classification efficiency for test samples were recorded to be >93% using Soft Independent Modelling of Class Analogy approach. Maximum coefficient of determination for prediction of detergent was 0.94 for calibration and 0.93 for validation, using partial least square regression in wavenumber combination of 1086-1056, 1343-1333, 1507-1456, 3040-2851cm -1 . Copyright © 2016 Elsevier Ltd. All rights reserved.

Resonance Raman detection of the heme Fe(II)-NO/2-nitrovinyl species in myoglobin

NASA Astrophysics Data System (ADS)

Ioannou, Androulla; Pinakoulaki, Eftychia

2018-01-01

The six-coordinate heme Fe(II)-NO/2-nitrovinyl species in myoglobin has been detected and characterized by resonance Raman spectroscopy. The Fe(II)-14NO and 15N-O stretching frequencies of the ferrous heme nitrosyl/2-nitrovinyl species are detected at 560 and 1587 cm-1, frequencies that are similar to those observed in the Mb heme Fe(II)-NO species. For the 2-nitrovinyl (Ca=CbNO2) moiety, which is formed upon H-abstraction from the -CbH2 group, the νs(NO2) is observed at 1322 cm-1, the νas(NO2) at 1516 cm-1 and the ν(Ca=Cb14NO2)/ ν(Ca=Cb15NO2) at 1623/1615 cm-1. The frequencies of the 2-nitrovinyl are largely unaffected by NO2-/NO binding to the heme Fe(II)/(III). The properties of the six-coordinate heme Fe(II)-NO/2-nitrovinyl species are compared to those of six-coordinate heme Fe(II)-NO and the five-coordinate heme Fe(II)-NO species isolated from meat products.

Handheld spatial frequency domain spectrographic imager for depth-sensitive, quantitative spectroscopy of skin tissue

NASA Astrophysics Data System (ADS)

Saager, Rolf B.; Dang, An N.; Huang, Samantha S.; Kelly, Kristen M.; Durkin, Anthony J.

2017-02-01

Here we present a handheld, implementation of Spatial Frequency Domain Spectroscopy (SFDS) that employs line imaging. The new instrument can measure 1088 spatial locations that span a 3 cm line as opposed to our benchtop system that only collects a single 1 mm diameter spot. This imager, however, retains the spectral resolution ( 1 nm) and range (450 to 1000 nm) of our benchtop system. The device also has tremendously improved mobility and portability, allowing for greater ease of use in clinical setting. A smaller size also enables access to different tissue locations, which increases the flexibility of the device. The design of this portable system not only enables SFDS to be used in clinical settings, but also enables visualization of properties of layered tissues such as skin.

Anatomy of the septomarginal trabecula in goat hearts.

PubMed

Leão, Camila Ribeiro; Pacha, Diego Lago; Cyriaco, Thiago; da Silva, Cavalcante; Wafae, Nader; Pereira, Heloisa Maria Lemes; Ruiz, Cristiane Regina

2010-01-01

Our aim in this study was to examine the right septomarginal trabecula of goats regarding the frequency, origin course of the septal and free component, attachment to the papillaris magnus muscle and size . The material used consisted in 32 hearts from non-pedigree goats of both sexes, preserved in 10% formalin. The right septomarginal trabecula was present in all hearts. It could also present a prominence in the form of a cord in the septum before detaching and going towards the wall or the papillary muscle. We called this a septal component and found it in 69% of all hearts studied. In the remaining specimens, the exit of the septomarginal trabecula was abrupt, without presenting a septal component. It could be attached solely to the papillaris magnus muscle or to the papillary muscle and the ventricle wall, originated in the cranial third of the septum, and was attached to the middle third of the papillary muscle or its caudal third. Its free part, from the septum to the papillaris magnus muscle, ranged in length from 1.3 cm to 2.6 cm. The mean value was 1.7 cm, and the most frequent values were 1.9 and 1.5 cm. In conclusion, in goats, the septomarginal trabecula is a constant and invariable structure.

Io: Intensive Heating and Degassing, Rising and Falling Stripes In Crossing Wavy Patterns Do Not Require Molten Interior

NASA Astrophysics Data System (ADS)

Kochemasov, G.

"Orbits make structures". This fundamental concept unfolded in four theorems of the wave planetary tectonics [1] simply means that Keplerian non-circular orbits imply inertia forces which make planetary bodies oscillate and produce structures. Many examples of regular wave woven structures on surfaces of planets (and asteroids and comets - Borrelli !) and satellites prove it. Theorem 3 ("Celestial bodies are granular "[1]) connects a size of tectonic granulation with an orbital frequency. But what to do with satellites having more orbits than planets ? Here acts the wave modulation pro- cess. A low frequency modulates a high frequency producing lower and higher side frequencies. Actually we explained ubiquitous tectonic dichotomy (Theorem 1, [1]) by modulation of all frequencies in the Solar System (SS) by the very low galactic frequency of the SS. In this case we considered the lower side frequency. But at the opposite side there are the higher side frequencies which fall into a range of radio- and microwave frequencies so typical for bodies of the SS [2]. These higher side frequen- cies depend on a body's radius and its orbital frequency. For example, the Io orbital frequency is modulated by the Jupiter orbital frequency and by the galactic orbital frequency of the SS (1/12 years and ~1/200 000 000 years). The Io circumsolar fre- quency (together with Jupiter) is also modulated by the galactic frequency. So, there are three higher side frequencies for Io to which correspond three wavelengths: 4.62 km (Io orbits Jupiter),68 cm (Io's circumsolar orbit in the galactic orbit), 0.276 mm (Io's circumjovian orbit in the galactic orbit). For smaller and faster Amalthea these wave oscillations are: 93.2 m - 4.88 cm - 0.0056 mm. So "microwave stove" heating might be an appreciable source of heating for Io as well as for Amalthea (also anoma- lously heated body) [3]. Very variable Io's surface and very short wave (upto 10 m) crossing patterns are already observed. Io's 5 micron outbursts are reported [4]. They could be produced by the heated Io's body. Surprisingly, 5 micron (0.0056 mm) oscil- 1 lations we calculate for Amalthea. The 2002 y. meeting "Galileo" with Amalthea will bring additional information. References: [1] Kochemasov G.G.(1999) Theorems of wave planetary tectonics // Geophys. Res. Abstr., v.1, #3, 700; [2] Kochemasov G.G. (2001) Vernadsky-Brown 34th microsymp. Topics in comparative planetology. Abstr., Moscow, (CD-ROM); [3] Kochemasov G.G. (1997) Ibid. 26th, 58-59; [4]Sinton W.M. (1980) Astrophys.J., v. 235, #1, 149-151. 2

Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Molten Bis(trifluoromethylsulfonyl)amide Salts: Effects of Cation Species.

PubMed

Kakinuma, Shohei; Shirota, Hideaki

2018-05-25

In this study, we have investigated the effects of cation structures on the temperature dependence of the intermolecular vibrational dynamics of ionic liquids using femtosecond Raman-induced Kerr effect spectroscopy. The ionic liquids used in this study are bis(trifluoromethylsulfonyl)amide [NTf 2 ] - salts of the cations 1-butyl-3-methylimidazolium [C 4 MIm] + , 1-butyl-1-methylpyrrolidinium [Pyrr 14 ] + , 1-butylpyridinium [C 4 Py] + , butyldiethylmethylammonium [N 1224 ] + , triethyloctylammonium [N 2228 ] + , and triethyloctylphosphonium [P 2228 ] + . All of the ionic liquids show temperature-dependent low-frequency spectra. A difference in the temperature dependence between the spectra of the aromatic and nonaromatic cation based ionic liquids is especially significant. In the case of the aromatic cation based ionic liquids [C 4 MIm][NTf 2 ] and [C 4 Py][NTf 2 ], the spectral intensities in the low-frequency region below ca. 50 cm -1 increase and the high-frequency components at ca. 80 cm -1 shift to lower frequencies with rising temperature. In contrast, the ionic liquids based on nonaromatic cations only exhibit an increase in the low-frequency region below ca. 50 cm -1 with increasing temperature, while the high-frequency region of the spectra above ca. 50 cm -1 shows little change with variation of the temperature. These results suggest that the presence or absence of aromatic rings is the main factor in determining the temperature-dependent spectral features, particularly in the high-frequency region. We also found that the alkyl chain length and central atoms of the nonaromatic quaternary cations do not have much influence on the temperature-dependent spectral features. The first moments of the aromatic cation based ionic liquids are a little more sensitive to temperature than those of the nonaromatic cation based ionic liquids. The temperature-dependent viscosities and fragilities of the ionic liquids have also been examined.

Stratospheric ozone measurement with an infrared heterodyne spectrometer

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Kostiuk, T.; Mumma, M. J.; Buhl, D.; Kunde, V. G.; Brown, L. W.

1978-01-01

A stratospheric ozone absorption line in the 10 microns band was measured and resolved completely, using an infrared heterodyne spectrometer with spectral resolution of 5 MHz (0.000167 cm to -1 power). The vertical concentration profile of stratospheric ozone was obtained through an analytical inversion of the measured spectral line profile. The absolute total column density was 0.34 cm atm with a peak mixing ratio occurring at approximately 24 km. The (7,1,6) to (7,1,7) O3 line center frequency was found to be 1043.1775 + or - 0.00033 cm to toe -1 power, or 430 + or - 10 MHz higher than the P(24) CO2 laser line frequency.

Solar array synthesis computer program

NASA Technical Reports Server (NTRS)

Faith, T. J.

1973-01-01

Photovoltaic characteristics have been measured on solar cells irradiated by 1 MeV electrons to fluences ranging from 1 x 10 to the 13th power e/sq cm to 1 x 10 to the 16th power e/sq cm, for cell temperatures ranging from 123 K to 473 K and for illumination intensities ranging from 5m W/sq cm to 1830m W/sq cm. Empirical equations have been derived from these measurements to describe the behavior of light generated current, open circuit voltage and I-V curve shape over various portions of these temperature/illumination ranges. Both 10 ohms/cm and 17 ohms/cm n-p silicon solar cells were tested, and similar analytical expressions were formulated for easy comparison between the two resistivities.

Far Infrared and Dielectric Relaxation Spectra in Supercooled Water and Water + Propylene Glycol Solutions.

DTIC Science & Technology

1987-08-01

cm - 1 were obtained using a Digilahs [TIR spectrophotometer with a 6.25 pm Mylar beam splitter . The instrument was alignced so ihai the maximum...of polar molecular liquids, has been extensively studied over the frequency range 10- 2-10 7 Hz using a.c. bridge or polarisation current techniques...reference beam during all experiments. Baselines for determination of absorp- tion coefficients, were made using an empty cell with two DPE windows in the

High energy, widely tunable Si-prism-array coupled terahertz-wave parametric oscillator with a deformed pump and optimal crystal location for angle tuning.

PubMed

Zhang, Ruiliang; Qu, Yanchen; Zhao, Weijiang; Chen, Zhenlei

2017-03-20

A high energy, widely tunable Si-prism-array coupled terahertz-wave parametric oscillator (TPO) has been demonstrated by using a deformed pump. The deformed pump is cut from a beam spot of 2 mm in diameter by a 1-mm-wide slit. In comparison with a small pump spot (1-mm diameter), the THz-wave coupling area for the deformed pump is increased without limitation to the low-frequency end of the tuning range. Besides, the crystal location is specially designed to eliminate the alteration of the output position of the pump during angle tuning, so the initially adjusted nearest pumped region to the THz-wave exit surface is maintained throughout the tuning range. The tuning range is 0.58-2.5 THz for the deformed pump, while its low frequency end is limited at approximately 1.2 THz for the undeformed pump with 2 mm diameter. The highest THz-wave output of 2 μJ, which is 2.25 times as large as that from the pump of 1 mm in diameter, is obtained at 1.15 THz under 38 mJ (300  MW/cm²) pumping. The energy conversion efficiency is 5.3×10^-5.

Homogeneous and inhomogeneous broadenings and the Voigt line shapes in the phase-resolved and intensity sum-frequency generation vibrational spectroscopy.

PubMed

Chen, Shun-Li; Fu, Li; Gan, Wei; Wang, Hong-Fei

2016-01-21

In this report, we show that the ability to measure the sub-1 cm(-1) resolution phase-resolved and intensity high-resolution broadband sum frequency generation vibrational spectra of the -CN stretch vibration of the Langmuir-Blodgett (LB) monolayer of the 4-n-octyl-4'-cyanobiphenyl (8CB) on the z-cut α-quartz surface allows the direct comparison and understanding of the homogeneous and inhomogeneous broadenings in the imaginary and intensity SFG vibrational spectral line shapes in detail. The difference of the full width at half maximum (FWHM) of the imaginary and intensity sum-frequency generation vibrational spectroscopy spectra of the same vibrational mode is the signature of the Voigt line shape and it measures the relative contribution to the overall line shape from the homogeneous and inhomogeneous broadenings in SFG vibrational spectra. From the phase-resolved and intensity spectra, we found that the FWHM of the 2238.00 ± 0.02 cm(-1) peak in the phase-resolved imaginary and intensity spectra is 19.2 ± 0.2 cm(-1) and 21.6 ± 0.4 cm(-1), respectively, for the -CN group of the 8CB LB monolayer on the z-cut α-quartz crystal surface. The FWHM width difference of 2.4 cm(-1) agrees quantitatively with a Voigt line shape with a homogeneous broadening half width of Γ = 5.29 ± 0.08 cm(-1) and an inhomogeneous standard derivation width Δω = 5.42 ± 0.07 cm(-1). These results shed new lights on the understanding and interpretation of the line shapes of both the phase-resolved and the intensity SFG vibrational spectra, as well as other incoherent and coherent spectroscopic techniques in general.

Impedance spectroscopy of water soluble resin modified by zirconium sulphate

NASA Astrophysics Data System (ADS)

Joseph, Anandraj; Joshi, Girish M.

2018-04-01

We successfully modified water soluble resin polyvinyl alcohol (PVA) by loading zirconium sulphate (ZrSO4). We demonstrated the measurement of electrical properties by using impedance analyser across frequency range (10 Hz-1 MHz) and the temperature range of (30°C to 150°C). The impedance spectroscopy demonstrates decrease in bulk resistance as a function of temperature loading of zirconia 2.5 wt. %. Increase in AC (10-5 S/cm and DC conductivity (10- 2 S/m) observed due to ionic contribution of zirconia. However, the electrical properties of PVA/ZrSO4 composite useful to develop battery electrolyte applications.

Time-resolved diode laser infrared absorption spectroscopy of the nascent HCl in the infrared laser chemistry of 1,2-dichloro-1,1-difluoroethane

NASA Astrophysics Data System (ADS)

Dietrich, Peter; Quack, Martin; Seyfang, George

1990-04-01

The IR multiphoton excitation and the frequency, fluence and intensity dependence of the IR-laser chemical yields of CF 2ClCH 2Cl have been studied in the fluence range of 1 to 10 J cm -2 yielding a steady-state constant k(st)/ I=0.74×10 6 s -1 MW -1 cm 2 which is approximately independent of intensity. Time-resolved IR absorption spectroscopy with diode laser sources has been used to observe the nascent HCl during the first few 100 ns indicating a population inversion between the levels ν=1, J=4 and ν=2, J=5. At low reactant pressures ( p⩽10 Pa) the time-resolved measurement gives a steady-state rate constant consistent with the theoretical result adjusted to the static yield measurements. The capability of state-selective and time-resolved IR spectroscopy is thus demonstrated, giving real-time determinations of rate constants.

3D conformal MRI-guided transurethral ultrasound therapy: results of gel phantom experiments

NASA Astrophysics Data System (ADS)

N'Djin, W. A.; Burtnyk, M.; McCormick, S.; Bronskill, M.; Chopra, R.

2011-09-01

MRI-guided transurethral ultrasound therapy shows promise for minimally invasive treatment of localized prostate cancer. Previous in-vivo studies demonstrated the feasibility of performing conservative treatments using real-time temperature feedback to control accurately the establishment of coagulative lesions within circumscribed prostate regions. This in-vitro study tested device configuration and control options for achieving full prostate treatments. A multi-channel MRI compatible ultrasound therapy system was evaluated in gel phantoms using 3 canine prostate models. Prostate profiles were 5 mm-step-segmented from T2-weighted MR images performed during previous in-vivo experiments. During ultrasound exposures, each ultrasound element was controlled independently by the 3D controller. Decisions on acoustic power, frequency, and device rotation rate were made in real time based on MR thermometry feedback and prostate radii. Low and high power treatment approaches using maximum acoustic powers of 10 or 20 W.cm-2 were tested as well as single and dual-frequency strategies (4.05/13.10 MHz). The dual-frequency strategy used either the fundamental frequency or the 3rd harmonic component, depending on the prostate radius. The 20 W.cm-2 dual frequency approach was the most efficient configuration in achieving full prostate treatments. Treatment times were about half the duration of those performed with 10 W.cm-2 configurations. Full prostate coagulations were performed in 16.3±6.1 min at a rate of 1.8±0.2 cm3.min-1, and resulted in very little undertreated tissue (<3%). Surrounding organs positioned beyond a safety distance of 1.4±1.0 mm from prostate boundaries were not damaged, particularly rectal wall tissues. In this study, a 3D, MR-thermometry-guided transurethral ultrasound therapy was validated in vitro in a tissue-mimicking phantom for performing full prostate treatment. A dual-frequency configuration with 20 W.cm-2 ultrasound intensity exposure showed good results with direct application to full human prostate treatments.

The LWA1 Low Frequency Sky Survey

NASA Astrophysics Data System (ADS)

Dowell, Jayce; Taylor, Gregory B.; LWA Collaboration

2015-01-01

The LWA1 Low Frequency Sky Survey is a survey of the sky visible from the first station of the Long Wavelength Array (LWA1) across the frequency range of 35 to 80 MHz. The primary motivation behind this effort is to improve our understanding of the sky at these frequencies. In particular, an understanding of the low frequency foreground emission is necessary for work on detecting the epoch of reionization and the cosmic dark ages where the foreground signal dwarfs the expected redshifted HI signal by many orders of magnitude (Pritchard & Loeb 2012, Rep. Prog. Phys., 75, 086901). The leading model for the sky in the frequency range of 20 to 200 MHz is the Global Sky Model (GSM) by de Oliveria-Costas et al. (2008, MNRAS, 288, 247). This model is based upon a principle component analysis of 11 sky maps ranging in frequency from 10 MHz to 94 GHz. Of these 11 maps, only four are below 1 GHz; 10 MHz from Caswell (1976, MNRAS, 177, 601), 22 MHz from Roger et al. (1999, A&AS, 137, 7), 45 MHz from Alvarez et al. (1997, A&AS, 124, 315) and Maeda et al. (1999, A&AS, 140, 145), and 408 MHz from Haslam et al. (1982, A&AS, 47, 1). Thus, within this model, the region of interest to both cosmic dawn and the epoch of reionization is largely unconstrained based on the available survey data, and are also limited in terms of the spatial coverage and calibration. A self-consistent collection of maps is necessary for both our understanding of the sky and the removal of the foregrounds that mask the redshifted 21-cm signal.We present the current state of the survey and discuss the imaging and calibration challenges faced by dipole arrays that are capable of imaging nearly 2π steradians of sky simultaneously over a large fractional bandwidth.Construction of the LWA has been supported by the Office of Naval Research under Contract N00014-07-C-0147. Support for operations and continuing development of the LWA1 is provided by the National Science Foundation under grants AST-1139963 and AST-1139974 of the University Radio Observatory program.

2-D inner-shelf current observations from a single VHF WEllen RAdar (WERA) station

USGS Publications Warehouse

Voulgaris, G.; Kumar, N.; Gurgel, K.-W.; Warner, J.C.; List, J.H.

2011-01-01

The majority of High Frequency (HF) radars used worldwide operate at medium to high frequencies (8 to 30 MHz) providing spatial resolutions ranging from 3 to 1.5 km and ranges from 150 to 50 km. This paper presents results from the deployment of a single Very High Frequency (VHF, 48 MHz) WEllen RAdar (WERA) radar with spatial resolution of 150 m and range 10-15 km, used in the nearshore off Cape Hatteras, NC, USA. It consisted of a linear array of 12 antennas operating in beam forming mode. Radial velocities were estimated from radar backscatter for a variety of wind and nearshore wave conditions. A methodology similar to that used for converting acoustically derived beam velocities to an orthogonal system is presented for obtaining 2-D current fields from a single station. The accuracy of the VHF radar-derived radial velocities is examined using a new statistical technique that evaluates the system over the range of measured velocities. The VHF radar velocities showed a bias of 3 to 7 cm/s over the experimental period explainable by the differences in radar penetration and in-situ measurement height. The 2-D current field shows good agreement with the in-situ measurements. Deviations and inaccuracies are well explained by the geometric dilution analysis. ?? 2011 IEEE.

High frequency measures of OHC nonlinear capacitance (NLC) and their significance: Why measures stray away from predictions

NASA Astrophysics Data System (ADS)

Santos-Sacchi, Joseph

2018-05-01

Measures of membrane capacitance (Cm) can be used to assess important characteristics of voltage-dependent membrane proteins (e.g., channels and transporters). In particular, a protein's time-dependent voltage-sensor charge movement is equivalently represented as a frequency-dependent component of Cm, telling much about the kinetics of the protein's conformational behavior. Recently, we have explored the frequency dependence of OHC voltage-dependent capacitance (aka nonlinear capacitance, NLC) to query rates of conformational switching within prestin (SLC26a5), the cell's lateral membrane molecular motor 1. Following removal of confounding stray capacitance effects, high frequency Cm measures using wide-band stimuli accurately reveal unexpected low pass behavior in prestin's molecular motions.

VizieR Online Data Catalog: ExoMol line lists for CH4 (Yurchenko+, 2014)

NASA Astrophysics Data System (ADS)

Yurchenko, S. N.; Tennyson, J.

2014-02-01

The data are in two parts. The first, ch4_0-39.dat contains a list of 7,819,352 rovibrational states. Each state is labelled with: nine normal mode vibrational quantum numbers and the vibrational symmety; three rotational quantum numbers including the total angular momentum J and rotational symmetry; the total symmetry quantum number Gamma and the running number in the same (J,Gamma,Polyad) combination, where Polyad is a polyad number (see paper). In addition there are nine local mode vibrational numbers and the largest coefficient used to assign the state in question. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The total degeneracy is also given to facilitate the intensity calculations. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm-1 frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, s_10to10.f90 which may be used to generate synthetic spectra (see s_10to10.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else cross-sections convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Sample input files s*.inp for use with s10to10.f90 are supplied. (9 data files).

VizieR Online Data Catalog: ExoMol line lists for formaldehyde H2CO (Al-Refaie+,

NASA Astrophysics Data System (ADS)

Al-Refaie, A. F.; Yachmenev, A.; Tennyson, J.; Yurchenko, S. N.

2015-01-01

The data are in two parts. The first, h2co_0-70.dat contains a list of 10,296,998 rovibrational states. Each state is labelled with: 6 normal mode vibrational quantum numbers, and the vibrational symmetry; three rotational quantum numbers including the total angular momentum J, the projection of J in the z-axis K,rotational symmetry and the total symmetry quantum number Gamma In addition there are six local mode vibrational numbers and the largest coeffecient used to assign the state in question. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The total degeneracy is also given to facilitate the intensity calculations. Because of their size, the transitions are listed in 100 separate files, each containing all the transitions in a 100cm-1 frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, s_AYTY.f90 which may be used to generate synthetic spectra (see s_AYTY.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else cross-sections convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Sample input files s*.inp for use with sSAlTY.f90 are supplied. (9 data files).

VizieR Online Data Catalog: ExoMol line lists for H216O2 (Al-Refaie+, 2016)

NASA Astrophysics Data System (ADS)

Al-Refaie, A. F.; Polyansky, O. L.; Tennyson, J.; Yurchenko, S. N.

2016-06-01

The data are in two parts. The first, h2o20-85.dat contains a list of 7,560,352 rovibrational states. Each state is labelled with: six normal mode vibrational quantum numbers the torsional symmetry number (tau) and the vibrational symmetry; three rotational quantum numbers including the total angular momentum J and rotational symmetry; the total symmetry quantum number Gamma and the running number in the same J,Gamma block. In addition there are six local mode vibrational numbers and the largest coefficient used to assign the state in question. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The total degeneracy is also given to facilitate the intensity calculations. Because of their size, the transitions are listed in 60 separate files, each containing all the transitions in a 100cm-1 frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-0500.dat file contains all the transitions in the frequency range 500-600cm-1. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, s_APTY.f90 which may be used to generate synthetic spectra (see s_APTY.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else cross-sections convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Sample input files s*.inp for use with sAPTY.f90 are supplied. (10 data files).

RELEC Mission: Relativistic Electron Precipitation and TLE study on-board small spacecraft

NASA Astrophysics Data System (ADS)

Svertilov, Sergey

The main goal of RELEC mission is studying of magnetosphere relativistic electron precipitation and its acting on the upper Atmosphere as well as transient luminous events (TLE) observation in wide range of electromagnetic spectrum. The RELEC set of instruments includes two identical detectors of X- and gamma-rays of high temporal resolution and sensitivity (DRGE-1 & DRGE-2), three axe directed detectors of energetic electrons and protons DRGE-3, UV TLE imager MTEL, UV detector DUV, low-frequency analyser LFA, radio-frequency analyser RFA, module of electronics intended for commands and data collection BE. During the RELEC mission following experiments will be provided: - simultaneous observations of energetic electron & proton flux (energy range ~0.1-10.0 MeV and low-frequency (~0.1-10 kHz) electromagnetic wave field intensity variations with high temporal resolution (~1 ms); - fine time structure (~1 mcs) measurements of transient atmospheric events in UV, X- and gamma rays with a possibility of optical imaging with resolution of ~km in wide FOV; - measurements of electron flux pitch-angle distribution in dynamical range from ~0.1 up to 105 part/cm2s; - monitoring of charge and neutral background particles in different areas of near-Earth space. Now the all RELEC instruments are installed on-board small spacecraft manufactured by Lavochkin space corporation. The launch is scheduled on May, 2014 as by-pass mission with Meteor spacecraft. The RELEC mission orbit is planned to be quasi-circular solar-synchronous with about 700 km height. The total volume of transmitted data is about 1.2 Gbyte per day.

Self-assembly of silver nanoparticles as high active surface-enhanced Raman scattering substrate for rapid and trace analysis of uranyl(VI) ions

NASA Astrophysics Data System (ADS)

Wang, Shaofei; Jiang, Jiaolai; Wu, Haoxi; Jia, Jianping; Shao, Lang; Tang, Hao; Ren, Yiming; Chu, Mingfu; Wang, Xiaolin

2017-06-01

A facile surface-enhanced Raman scattering (SERS) substrate based on the self-assembly of silver nanoparticles on the modified silicon wafer was obtained, and for the first time, an advanced SERS analysis method basing on this as-prepared substrate was established for high sensitive and rapid detection of uranyl ions. Due to the weakened bond strength of Odbnd Udbnd O resulting from two kinds of adsorption of uranyl species (;strong; and ;weak; adsorption) on the substrate, the ν1 symmetric stretch vibration frequency of Odbnd Udbnd O shifted from 871 cm- 1 (normal Raman) to 720 cm- 1 and 826 cm- 1 (SERS) along with significant Raman enhancement. Effects of the hydrolysis of uranyl ions on SERS were also investigated, and the SERS band at 826 cm- 1 was first used to approximately define the constitution of uranyl species at trace quantity level. Besides, the SERS intensity was proportional to the variable concentrations of uranyl nitrate ranging from 10- 7 to 10- 3 mol L- 1 with an excellent linear relation (R2 = 0.998), and the detection limit was 10- 7 mol L- 1. Furthermore, the related SERS approach involves low-cost substrate fabrication, rapid and trace analysis simultaneously, and shows great potential applications for the field assays of uranyl ions in the nuclear fuel cycle and environmental monitoring.

Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

NASA Astrophysics Data System (ADS)

Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

2017-11-01

A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

Potentials of acousto-optical spectrum analysis on a basis of a novel algorithm of the collinear wave heterodyning in a large-aperture KRS-5 crystalline cell

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Maximov, Jewgenij; Bliznetsov, Alexej M.; Sanchez Perez, Karla J.

2011-03-01

The technique under proposal for a precise spectrum analysis within an algorithm of the collinear wave heterodyning implies a two-stage integrated processing, namely, the wave heterodyning of a signal in a square-law nonlinear medium and then the optical processing in the same solid state cell. The technical advantage of this approach lies in providing a direct multichannel parallel processing of ultra-high-frequency radio-wave signals with essentially improved frequency resolution. This technique imposes specific requirements on the cell's material. We focus our attention on the solid solutions of thallium chalcogenides and take the TlBr-TlI (thallium bromine-thallium iodine) solution, which forms KRS-5 cubic-symmetry crystals with the mass-ratio 58% of TlBr to 42% of TlI. Analysis shows that the acousto-optical cell made of a KRS-5 crystal oriented along the [111]-axis and the corresponding longitudinal elastic mode for producing the dynamic diffractive grating can be exploited. With the acoustic velocity of about 1.92 × 105 cm/s and attenuation of ~10 dB/(cm GHz2), a similar cell is capable of providing an optical aperture of ~5.0 cm and one of the highest figures of acousto-optical merit in solid states in the visible range. Such a cell is rather desirable for the application to direct 5000-channel parallel spectrum analysis with an improved up to 10-5 relative frequency resolution.

Investigation of Trap States in AlInN/AlN/GaN Heterostructures by Frequency-Dependent Admittance Analysis

NASA Astrophysics Data System (ADS)

Arslan, Engin; Bütün, Serkan; Şafak, Yasemin; Ozbay, Ekmel

2010-12-01

We present a systematic study on the admittance characterization of surface trap states in unpassivated and SiN x -passivated Al0.83In0.17N/AlN/GaN heterostructures. C- V and G/ ω- V measurements were carried out in the frequency range of 1 kHz to 1 MHz, and an equivalent circuit model was used to analyze the experimental data. A detailed analysis of the frequency-dependent capacitance and conductance data was performed, assuming models in which traps are located at the metal-AlInN surface. The density ( D t) and time constant ( τ t) of the surface trap states have been determined as a function of energy separation from the conduction-band edge ( E c - E t). The D st and τ st values of the surface trap states for the unpassivated samples were found to be D_{{st}} \\cong (4 - 13) × 10^{12} {eV}^{ - 1} {cm}^{ - 2} and τ st ≈ 3 μs to 7 μs, respectively. For the passivated sample, D st decreased to 1.5 × 10^{12} {eV}^{ - 1} {cm}^{ - 2} and τ st to 1.8 μs to 2 μs. The density of surface trap states in Al0.83In0.17N/AlN/GaN heterostructures decreased by approximately one order of magnitude with SiN x passivation, indicating that the SiN x insulator layer between the metal contact and the surface of the Al0.83In0.17N layer can passivate surface states.

Smart nanocoated structure for energy harvesting at low frequency vibration

NASA Astrophysics Data System (ADS)

Sharma, Sudhanshu

Increasing demands of energy which is cleaner and has an unlimited supply has led development in the field of energy harvesting. Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources. In this research, a piezoelectric power generator composite prototype was developed to maximize the power output of the system. A lead zirconate titanate (PZT) composite structure was formed and mounted on a cantilever bar and was studied to convert vibration energy of the low range vibrations at 30 Hz--1000 Hz. To improve the performance of the PZT, different coatings were made using different percentage of Ferrofluid (FNP) and Zinc Oxide nanoparticles (ZnO) and binder resin. The optimal coating mixture constituent percentage was based on the performance of the composite structure formed by applying the coating on the PZT. The fabricated PZT power generator composite with an effective volume of 0.062 cm3 produced a maximum of 44.5 μW, or 0.717mW/cm3 at its resonant frequency of 90 Hz. The optimal coating mixture had the composition of 59.9%FNP + 40% ZnO + 1% Resin Binder. The coating utilizes the opto-magneto-electrical properties of ZnO and Magnetic properties of FNP. To further enhance the output, the magneto-electric (ME) effect was increased by subjecting the composite to magnetic field where coating acts as a magnetostrictive material. For the effective volume of 0.0062 cm 3, the composite produced a maximum of 68.5 μW, or 1.11mW/cm 3 at its resonant frequency of 90 Hz at 160 gauss. The optimal coating mixture had the composition of 59.9% FNP + 40% ZnO + 1% Resin Binder. This research also focused on improving the efficiency of solar cells by utilizing the magnetic effect along with gas plasma etching to improve the internal reflection. Preliminary results showed an improvement in solar cell efficiency from 14.6% to 17.1%.

Characterization of a subtropical hawksbill sea turtle (Eretmocheyles imbricata) assemblage utilizing shallow water natural and artificial habitats in the Florida Keys.

PubMed

Gorham, Jonathan C; Clark, David R; Bresette, Michael J; Bagley, Dean A; Keske, Carrie L; Traxler, Steve L; Witherington, Blair E; Shamblin, Brian M; Nairn, Campbell J

2014-01-01

In order to provide information to better inform management decisions and direct further research, vessel-based visual transects, snorkel transects, and in-water capture techniques were used to characterize hawksbill sea turtles in the shallow marine habitats of a Marine Protected Area (MPA), the Key West National Wildlife Refuge in the Florida Keys. Hawksbills were found in hardbottom and seagrass dominated habitats throughout the Refuge, and on man-made rubble structures in the Northwest Channel near Cottrell Key. Hawksbills captured (N = 82) were exclusively juveniles and subadults with a straight standard carapace length (SSCL) ranging from 21.4 to 69.0cm with a mean of 44.1 cm (SD = 10.8). Somatic growth rates were calculated from 15 recaptured turtles with periods at large ranging from 51 to 1188 days. Mean SSCL growth rate was 7.7 cm/year (SD = 4.6). Juvenile hawksbills (<50 cm SSCL) showed a significantly higher growth rate (9.2 cm/year, SD = 4.5, N = 11) than subadult hawksbills (50-70 cm SSCL, 3.6 cm/year, SD = 0.9, N = 4). Analysis of 740 base pair mitochondrial control region sequences from 50 sampled turtles yielded 12 haplotypes. Haplotype frequencies were significantly different compared to four other Caribbean juvenile foraging aggregations, including one off the Atlantic coast of Florida. Many-to-one mixed stock analysis indicated Mexico as the primary source of juveniles in the region and also suggested that the Refuge may serve as important developmental habitat for the Cuban nesting aggregation. Serum testosterone radioimmunoassay results from 33 individuals indicated a female biased sex ratio of 3.3 females: 1 male for hawksbills in the Refuge. This assemblage of hawksbills is near the northern limit of the species range, and is one of only two such assemblages described in the waters of the continental United States. Since this assemblage resides in an MPA with intensive human use, basic information on the assemblage is vital to resource managers charged with conservation and species protection in the MPA.

Characterization of a Subtropical Hawksbill Sea Turtle (Eretmocheyles imbricata) Assemblage Utilizing Shallow Water Natural and Artificial Habitats in the Florida Keys

PubMed Central

Gorham, Jonathan C.; Clark, David R.; Bresette, Michael J.; Bagley, Dean A.; Keske, Carrie L.; Traxler, Steve L.; Witherington, Blair E.; Shamblin, Brian M.; Nairn, Campbell J.

2014-01-01

In order to provide information to better inform management decisions and direct further research, vessel-based visual transects, snorkel transects, and in-water capture techniques were used to characterize hawksbill sea turtles in the shallow marine habitats of a Marine Protected Area (MPA), the Key West National Wildlife Refuge in the Florida Keys. Hawksbills were found in hardbottom and seagrass dominated habitats throughout the Refuge, and on man-made rubble structures in the Northwest Channel near Cottrell Key. Hawksbills captured (N = 82) were exclusively juveniles and subadults with a straight standard carapace length (SSCL) ranging from 21.4 to 69.0cm with a mean of 44.1 cm (SD = 10.8). Somatic growth rates were calculated from 15 recaptured turtles with periods at large ranging from 51 to 1188 days. Mean SSCL growth rate was 7.7 cm/year (SD = 4.6). Juvenile hawksbills (<50 cm SSCL) showed a significantly higher growth rate (9.2 cm/year, SD = 4.5, N = 11) than subadult hawksbills (50–70 cm SSCL, 3.6 cm/year, SD = 0.9, N = 4). Analysis of 740 base pair mitochondrial control region sequences from 50 sampled turtles yielded 12 haplotypes. Haplotype frequencies were significantly different compared to four other Caribbean juvenile foraging aggregations, including one off the Atlantic coast of Florida. Many-to-one mixed stock analysis indicated Mexico as the primary source of juveniles in the region and also suggested that the Refuge may serve as important developmental habitat for the Cuban nesting aggregation. Serum testosterone radioimmunoassay results from 33 individuals indicated a female biased sex ratio of 3.3 females: 1 male for hawksbills in the Refuge. This assemblage of hawksbills is near the northern limit of the species range, and is one of only two such assemblages described in the waters of the continental United States. Since this assemblage resides in an MPA with intensive human use, basic information on the assemblage is vital to resource managers charged with conservation and species protection in the MPA. PMID:25517946

Development of a compact optical absolute frequency reference for space with 10^-15 instability.

PubMed

Schuldt, Thilo; Döringshoff, Klaus; Kovalchuk, Evgeny V; Keetman, Anja; Pahl, Julia; Peters, Achim; Braxmaier, Claus

2017-02-01

We report on a compact and ruggedized setup for laser frequency stabilization employing Doppler-free spectroscopy of molecular iodine near 532 nm. Using a 30 cm long iodine cell in a triple-pass configuration in combination with noise-canceling detection and residual amplitude modulation control, a frequency instability of 6×10^-15 at 1 s integration time and a Flicker noise floor below 3×10^-15 for integration times between 100 and 1000 s was found. A specific assembly-integration technology was applied for the realization of the spectroscopy setup, ensuring high beam pointing stability and high thermal and mechanical rigidity. The setup was developed with respect to future applications in space, including high-sensitivity interspacecraft interferometry, tests of fundamental physics, and navigation and ranging.

Target-strength Measurements of Sandfish Arctoscopus japonicus

NASA Astrophysics Data System (ADS)

Yoon, Eun-A.; Lee, Kyounghoon; Oh, Wooseok; Choi, Junghwa; Hwang, Kangseok; Kang, Myounghee

2018-03-01

The goal of this study was to estimate the target strength (TS) of the sandfish Arctoscopus japonicus using in-situ and ex-situ methods with an echosounder. For the in-situ TS measurement, the survey was conducted by taking hydroacoustic measurements at 38 and 120 kHz and using a coastal gill net, in Goseong, in the northeastern sea of Korea in early December 2009. Ex-situ measurement of TS used live specimens and the tethering method, and was conducted at 120 kHz. The distribution of fork length (FL) was bimodal: 14.6-19.8 cm (n = 241 individuals, mean = 17.0 cm) for males and 16.3-24.5 cm (n = 105 individuals, mean = 19.6 cm) for females. The in-situ TS ranged from -79.8 to -59.1 dB (mean = -74.3 dB for males and -64.1 dB for females) at 38 kHz and -79.9 to -56.2 dB (mean = -74.3 dB for males and -64.1 dB for females) at 120 kHz. The mean TS of females was approximately 10 dB higher than that of males at each dominant frequency. The female ex-situ TS values ranged from 68.5 to -54.6 dB, and those of males was from -67.7 to -59.3 dB. The mean TS value for females was 2.9 dB higher than that of males. These results may be used in echo-integration surveys of sandfish to estimate their abundance and seasonal distribution.

Molecular characterization of a long range haplotype affecting protein yield and mastitis susceptibility in Norwegian Red cattle.

PubMed

Sodeland, Marte; Grove, Harald; Kent, Matthew; Taylor, Simon; Svendsen, Morten; Hayes, Ben J; Lien, Sigbjørn

2011-08-11

Previous fine mapping studies in Norwegian Red cattle (NRC) in the region 86-90.4 Mb on Bos taurus chromosome 6 (BTA6) has revealed a quantitative trait locus (QTL) for protein yield (PY) around 88 Mb and a QTL for clinical mastitis (CM) around 90 Mb. The close proximity of these QTLs may partly explain the unfavorable genetic correlation between these two traits in NRC. A long range haplotype covering this region was introduced into the NRC population through the importation of a Holstein-Friesian bull (1606 Frasse) from Sweden in the 1970s. It has been suggested that this haplotype has a favorable effect on milk protein content but an unfavorable effect on mastitis susceptibility. Selective breeding for milk production traits is likely to have increased the frequency of this haplotype in the NRC population. Association mapping for PY and CM in NRC was performed using genotypes from 556 SNPs throughout the region 86-97 Mb on BTA6 and daughter-yield-deviations (DYDs) from 2601 bulls made available from the Norwegian dairy herd recording system. Highest test scores for PY were found for single-nucleotide polymorphisms (SNPs) within and surrounding the genes CSN2 and CSN1S2, coding for the β-casein and α(S2)-casein proteins. High coverage re-sequencing by high throughput sequencing technology enabled molecular characterization of a long range haplotype from 1606 Frasse encompassing these two genes. Haplotype analysis of a large number of descendants from this bull indicated that the haplotype was not markedly disrupted by recombination in this region. The haplotype was associated with both increased milk protein content and increased susceptibility to mastitis, which might explain parts of the observed genetic correlation between PY and CM in NRC. Plausible causal polymorphisms affecting PY were detected in the promoter region and in the 5'-flanking UTR of CSN1S2. These polymorphisms could affect transcription or translation of CSN1S2 and thereby affect the amount of α(S2)-casein in milk. Highest test scores for CM were found in the region 89-91 Mb on BTA6, very close to a cluster of genes coding for CXC chemokines. Expression levels of some of these CXC chemokines have previously been shown to increase in bovine mammary gland cell lines after exposure to bacterial cell wall components. Molecular characterization of the long range haplotype from the Holstein-Friesian bull 1606 Frasse, imported into NRC in the 1970s, revealed polymorphisms that could affect transcription or translation of the casein gene CSN1S2. Sires with this haplotype had daughters with significantly elevated milk protein content and selection for milk production traits is likely to have increased the frequency of this haplotype in the NRC population. The haplotype was also associated with increased mastitis susceptibility, which might explain parts of the genetic correlation between PY and CM in NRC.

Transparent nanotubular capacitors based on transplanted anodic aluminum oxide templates.

PubMed

Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Wu, Wenhui; Yue, Jin; Liu, Chang

2015-03-11

Transparent AlZnO/Al2O3/AlZnO nanocapacitor arrays have been fabricated by atomic layer deposition in anodic aluminum oxide templates transplanted on the AlZnO/glass substrates. A high capacitance density of 37 fF/μm(2) is obtained, which is nearly 5.8 times bigger than that of planar capacitors. The capacitance density almost remains the same in a broad frequency range from 1 kHz to 200 kHz. Moreover, a low leakage current density of 1.7 × 10(-7) A/cm(2) at 1 V has been achieved. The nanocapacitors exhibit an average optical transmittance of more than 80% in the visible range, and thus open the door to practical applications in transparent integrated circuits.

Fast calculation of tissue optical properties using MC and the experimental evaluation for diagnosis of cervical cancer

NASA Astrophysics Data System (ADS)

Zhang, Shuying; Zhou, Xiaoqing; Qin, Zhuanping; Zhao, Huijuan

2011-02-01

This article aims at the development of the fast inverse Monte Carlo (MC) simulation for the reconstruction of optical properties (absorption coefficient μs and scattering coefficient μs) of cylindrical tissue, such as a cervix, from the measurement of near infrared diffuse light on frequency domain. Frequency domain information (amplitude and phase) is extracted from the time domain MC with a modified method. To shorten the computation time in reconstruction of optical properties, efficient and fast forward MC has to be achieved. To do this, firstly, databases of the frequency-domain information under a range of μa and μs were pre-built by combining MC simulation with Lambert-Beer's law. Then, a double polynomial model was adopted to quickly obtain the frequency-domain information in any optical properties. Based on the fast forward MC, the optical properties can be quickly obtained in a nonlinear optimization scheme. Reconstruction resulting from simulated data showed that the developed inverse MC method has the advantages in both the reconstruction accuracy and computation time. The relative errors in reconstruction of the μs and μs are less than +/-6% and +/-12% respectively, while another coefficient (μs or μs) is in a fixed value. When both μs and μs are unknown, the relative errors in reconstruction of the reduced scattering coefficient and absorption coefficient are mainly less than +/-10% in range of 45< μs <80 cm-1 and 0.25< a μ <0.55 cm-1. With the rapid reconstruction strategy developed in this article the computation time for reconstructing one set of the optical properties is less than 0.5 second. Endoscopic measurement on two tubular solid phantoms were also carried out to evaluate the system and the inversion scheme. The results demonstrated that less than 20% relative error can be achieved.

Computer Simulation of Digital Signal Modulation Techniques in Satellite Communications.

DTIC Science & Technology

1985-09-01

frequency bands ate shown in Figures 2. 4 and 2. 5 ( Ref . 6] Radio frequency (9F) I Infrared (IR) 0Ptc. Microwave %100cm 10cm 1 m lomm 100um l jjm 101...1c :N-4 V- O b-I E = - -. N .. - on : aA ft - : W- W 0 39 .. q w & C3 Q1 V 4 ++ 0 a WW2 *E4 ’-.0 E-- XC-e𔃾if - 1 T.V% .H .W -1 12’z = E - =.45.4

Rapid spectral and flux time variations in a solar burst observed at various dm-mm wavelengths and at hard X-rays

NASA Technical Reports Server (NTRS)

Zodivaz, A. M.; Kaufmann, P.; Correia, E.; Costa, J. E. R.; Takakura, T.; Cliver, E. W.; Tapping, K. F.

1986-01-01

A solar burst was observed with high sensitivity and time resolution at cm-mm wavelengths by two different radio observatories (Itapetinga and Algonquin), with high spectral time resolution at dm-mm wavelengths by patrol instruments (Sagamore Hill), and at hard X-rays (HXM Hinotori). At the onset of the major burst time structure there was a rapid rise in the spectral turnover frequency (from 5 to 15 GHz), in about 10s, coincident to a reduction of the spectral index in the optically thin part of the spectrum. The burst maxima were not time coincident at the optically thin radio frequencies and at the different hard X-ray energy ranges. The profiles at higher radio frequencies exhibited better time coincidence to the high energy X-rays. The hardest X-ray spectrum (-3) coincided with peak radio emission at the higher frequency (44 GHz). The event appeared to be built up by a first major injection of softer particles followed by other injections of harder particles. Ultrafast time structures were identified as superimposed on the burst emission at the cm-mm high sensitivity data at X-rays, with predominant repetition rates ranging from 2.0 to 3.5 Hz.

Resonance ionization spectroscopy of sodium Rydberg levels using difference frequency generation of high-repetition-rate pulsed Ti:sapphire lasers

NASA Astrophysics Data System (ADS)

Naubereit, P.; Marín-Sáez, J.; Schneider, F.; Hakimi, A.; Franzmann, M.; Kron, T.; Richter, S.; Wendt, K.

2016-05-01

The generation of tunable laser light in the green to orange spectral range has generally been a deficiency of solid-state lasers. Hence, the formalisms of difference frequency generation (DFG) and optical parametric processes are well known, but the DFG of pulsed solid-state lasers was rarely efficient enough for its use in resonance ionization spectroscopy. Difference frequency generation of high-repetition-rate Ti:sapphire lasers was demonstrated for resonance ionization of sodium by efficiently exciting the well-known D1 and D2 lines in the orange spectral range (both ≈589 nm). In order to prove the applicability of the laser system for its use at resonance ionization laser ion sources of radioactive ion beam facilities, the first ionization potential of Na was remeasured by three-step resonance ionization into Rydberg levels and investigating Rydberg convergences. A result of EIP=41449.455 (6) stat(7) syscm-1 was obtained, which is in perfect agreement with the literature value of EIPlit =41449.451(2)cm-1 . A total of 41 level positions for the odd-parity Rydberg series n f 2F5/2,7/2o for principal quantum numbers of 10 ≤n ≤60 were determined experimentally.

Resonances and wave propagation velocity in the subglottal airways.

PubMed

Lulich, Steven M; Alwan, Abeer; Arsikere, Harish; Morton, John R; Sommers, Mitchell S

2011-10-01

Previous studies of subglottal resonances have reported findings based on relatively few subjects, and the relations between these resonances, subglottal anatomy, and models of subglottal acoustics are not well understood. In this study, accelerometer signals of subglottal acoustics recorded during sustained [a:] vowels of 50 adult native speakers (25 males, 25 females) of American English were analyzed. The study confirms that a simple uniform tube model of subglottal airways, closed at the glottis and open at the inferior end, is appropriate for describing subglottal resonances. The main findings of the study are (1) whereas the walls may be considered rigid in the frequency range of Sg2 and Sg3, they are yielding and resonant in the frequency range of Sg1, with a resulting ~4/3 increase in wave propagation velocity and, consequently, in the frequency of Sg1; (2) the "acoustic length" of the equivalent uniform tube varies between 18 and 23.5 cm, and is approximately equal to the height of the speaker divided by an empirically determined scaling factor; (3) trachea length can also be predicted by dividing height by another empirically determined scaling factor; and (4) differences between the subglottal resonances of males and females can be accounted for by height-related differences. © 2011 Acoustical Society of America

Application of the independent molecule model to elucidate the dynamics of structure I methane hydrate: a third report.

PubMed

Yoshioki, Shuzo

2009-01-01

Two new model systems of methane hydrate, larger than the previous systems, are constructed. One consists of 63 small and large cages with a small cage at the centre. The other has 65 small and large cages with a large cage at the centre. Three different H-bonding network patterns between water are formed, and three random orientations of methane in each cage are chosen. Using the surface water fixed method, we obtained the energy minimum conformations, fitted to the X-ray crystallographic structure. With normal mode analysis, we calculated frequencies of 2915.1 cm(-1) for a small cage, and 2911.0 cm(-1) for a large cage. These frequencies are a little nearer to the Raman spectra than were previous model systems. Treating three force constants of anharmonic potential energy and the strength of H-bonding between methane and water as four parameters, we obtained frequencies of 2913.6 cm(-1) for a small cage, a little lower than the Raman, and 2906.6 cm(-1) for a large cage, a little higher than the Raman. The calculations thus almost reach the Raman spectra.

Improving sensitivity and source attribution of homemade explosives with low-frequency/THz-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Carriere, James T. A.; Havermeyer, Frank; Heyler, Randy A.

2014-05-01

Rapid identification and source attribution of homemade explosives (HMEs) is vital to national defense and homeland security efforts. Since HMEs can be prepared in a variety of methods with different component ingredients, telltale traces can be left behind in the final structural form of the material. These differences manifest as polymorphs, isomers, conformers or even contaminants that can all impact the low energy vibrational modes of the molecule. Conventional Raman spectroscopy systems confine their measurements to the "chemical fingerprint" region and are unable to detect low frequency Raman signals (<200cm-1) where these low energy modes are found. This gap in sensitivity limits the conclusions that can be drawn from a single Raman measurement and creates the need for multiple measurement techniques to confirm any results. We present results from a new rugged, portable approach that is capable of extending the range of Raman to include these low frequency signals down to ~5cm-1, plus complementary anti-Stokes spectra, with measurement times on the order of seconds. We demonstrate the diversity of signals that lie in this region that directly correlate to the molecular structure of the material, resulting in a new Raman "structural fingerprint" region. By correlating the measured results with known samples from a spectral library, rapid identification of the specific method of manufacture can be made.

Ab initio study of structural, elastic, and vibrational properties of transition-metal disilicides NbSi2 and TaSi2 in hexagonal C40 structure

NASA Astrophysics Data System (ADS)

Ertürk, Esra; Gürel, Tanju

2018-05-01

We present an ab initio study of structural, elastic and vibrational properties of transition-metal disilicides NbSi2 and TaSi2. The calculations have been carried out within the density-functional theory and linear-response formalism using norm-conserving pseudopotentials and a plane-wave basis. The calculated lattice parameters, bulk moduli, and elastic constants agree well with previous theoretical and experimental results. The calculated phonon frequencies at the Brillouin zone center are in good agreement with the reported Raman spectra and provide reference values for the future infrared and neutron phonon measurements. Phonon dispersion relations, mode Grüneisen parameters, and total and partial phonon density of states are also discussed. Mode Grüneisen parameters of NbSi2 and TaSi2 at Brillouin zone center show similar trends and all values are found to be positive. From phonon dispersion relations and phonon density of states, we have found a gap around 200 cm-1 for TaSi2, where the frequencies below this gap mainly belong to Ta vibrations and frequencies above the gap is mainly related with Si vibrations. In the case of NbSi2, there is no such gap and both Nb and Si atoms contribute to the phonon density of states in an energy range of 150-270 cm-1.

Three-dimensional analysis of the respiratory interplay effect in helical tomotherapy: Baseline variations cause the greater part of dose inhomogeneities seen.

PubMed

Tudor, G Samuel J; Harden, Susan V; Thomas, Simon J

2014-03-01

Dose differences from those planned can occur due to the respiratory interplay effect on helical tomotherapy. The authors present a technique to calculate single-fraction doses in three-dimensions resulting from craniocaudal motion applied to a patient CT set. The technique is applied to phantom and patient plans using patient respiratory traces. An additional purpose of the work is to determine the contribution toward the interplay effect of different components of the respiratory trace. MATLAB code used to calculate doses to a CT dataset from a helical tomotherapy plan has been modified to permit craniocaudal motion and improved temporal resolution. Real patient traces from seven patients were applied to ten phantom plans of differing field width, modulation factor, pitch and fraction dose, and simulations made with peak-to-peak amplitudes ranging from 0 to 2.5 cm. PTV voxels near the superior or inferior limits of the PTV are excluded from the analysis. The maximum dose discrepancy compared with the static case recorded along with the proportion of voxels receiving more than 10% and 20% different from prescription dose. The analysis was repeated with the baseline variation of the respiratory trace removed, leaving the cyclic component of motion only. Radiochromic film was used on one plan-trace combination and compared with the software simulation. For one case, filtered traces were generated and used in simulations which consisted only of frequencies near to particular characteristic frequencies of the treatment delivery. Intraslice standard deviation of dose differences was used to identify potential MLC interplay, which was confirmed using nonmodulated simulations. Software calculations were also conducted for four realistic patient plans and modeling movement of a patient CT set with amplitudes informed by the observed motion of the GTV on 4DCT. The maximum magnitude of dose difference to a PTV voxel due to the interplay effect within a particular plan-trace combination for peak-to-peak amplitudes of up to 2.5 cm ranged from 4.5% to 51.6% (mean: 23.8%) of the dose delivered in the absence of respiratory motion. For cyclic motion only, the maximum dose differences in each combination ranged from 2.1% to 26.2% (mean: 9.2%). There is reasonable correspondence between an example of the phantom plan simulations and radiochromic film measurement. The filtered trace simulations revealed that frequencies close to the characteristic frequency of the jaw motion across the target were found to generate greater interplay effect than frequencies close to the gantry frequency or MLC motion. There was evidence of interplay between respiratory motion and MLC modulation, but this is small compared with the interplay between respiratory motion and jaw motion. For patient-plan simulations, dose discrepancies are seen of up to 9.0% for a patient with 0.3 cm peak-to-peak respiratory amplitude and up to 17.7% for a patient with 0.9 cm peak-to-peak amplitude. These values reduced to 1.3% and 6.5%, respectively, when only cyclic motion was considered. Software has been developed to simulate craniocaudal respiratory motion in phantom and patient plans using real patient respiratory traces. Decomposition of the traces into baseline andcyclic components reveals that the large majority of the interplay effect seen with the full trace is due to baseline variation during treatment.

ELECTRIC IMPEDANCE OF THE FROG EGG

PubMed Central

Cole, Kenneth S.; Guttman, Rita M.

1942-01-01

Electrical impedance measurements were made upon unfertilized and fertilized eggs of the leopard frog, Rana pipiens, over a frequency range of 0.05 to 10 kc. Average values of 170 ohm cm.2 were obtained for the plasma membrane resistance of the egg, 2.0 µf/cm.2 for the plasma membrane capacity, 86° for the phase angle of the membrane, and 570 ohm cm. for the specific resistance of the interior. These values did not change upon fertilization. No spontaneous rhythmical impedance changes such as have been found by Hubbard and Rothschild in the trout egg were found in frog eggs. PMID:19873312

Development of the Acoustically Evoked Behavioral Response in Larval Plainfin Midshipman Fish, Porichthys notatus

PubMed Central

Alderks, Peter W.; Sisneros, Joseph A.

2013-01-01

The ontogeny of hearing in fishes has become a major interest among bioacoustics researchers studying fish behavior and sensory ecology. Most fish begin to detect acoustic stimuli during the larval stage which can be important for navigation, predator avoidance and settlement, however relatively little is known about the hearing capabilities of larval fishes. We characterized the acoustically evoked behavioral response (AEBR) in the plainfin midshipman fish, Porichthys notatus, and used this innate startle-like response to characterize this species' auditory capability during larval development. Age and size of larval midshipman were highly correlated (r2 = 0.92). The AEBR was first observed in larvae at 1.4 cm TL. At a size ≥1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re1 µPa or −15.2 dB re 1 g (z-axis). Lowest AEBR thresholds were 140–150 dB re 1 µPa or −33 to −23 dB re 1 g for frequencies below 225 Hz. Larval fish with size ranges of 1.9–2.4 cm TL had significantly lower best evoked frequencies than the other tested size groups. We also investigated the development of the lateral line organ and its function in mediating the AEBR. The lateral line organ is likely involved in mediating the AEBR but not necessary to evoke the startle-like response. The midshipman auditory and lateral line systems are functional during early development when the larvae are in the nest and the auditory system appears to have similar tuning characteristics throughout all life history stages. PMID:24340003

Statistical 21-cm Signal Separation via Gaussian Process Regression Analysis

NASA Astrophysics Data System (ADS)

Mertens, F. G.; Ghosh, A.; Koopmans, L. V. E.

2018-05-01

Detecting and characterizing the Epoch of Reionization and Cosmic Dawn via the redshifted 21-cm hyperfine line of neutral hydrogen will revolutionize the study of the formation of the first stars, galaxies, black holes and intergalactic gas in the infant Universe. The wealth of information encoded in this signal is, however, buried under foregrounds that are many orders of magnitude brighter. These must be removed accurately and precisely in order to reveal the feeble 21-cm signal. This requires not only the modeling of the Galactic and extra-galactic emission, but also of the often stochastic residuals due to imperfect calibration of the data caused by ionospheric and instrumental distortions. To stochastically model these effects, we introduce a new method based on `Gaussian Process Regression' (GPR) which is able to statistically separate the 21-cm signal from most of the foregrounds and other contaminants. Using simulated LOFAR-EoR data that include strong instrumental mode-mixing, we show that this method is capable of recovering the 21-cm signal power spectrum across the entire range k = 0.07 - 0.3 {h cMpc^{-1}}. The GPR method is most optimal, having minimal and controllable impact on the 21-cm signal, when the foregrounds are correlated on frequency scales ≳ 3 MHz and the rms of the signal has σ21cm ≳ 0.1 σnoise. This signal separation improves the 21-cm power-spectrum sensitivity by a factor ≳ 3 compared to foreground avoidance strategies and enables the sensitivity of current and future 21-cm instruments such as the Square Kilometre Array to be fully exploited.

Inelastic neutron scattering spectrum of cyclotrimethylenetrinitramine: a comparison with solid-state electronic structure calculations.

PubMed

Ciezak, Jennifer A; Trevino, S F

2006-04-20

Solid-state geometry optimizations and corresponding normal-mode analysis of the widely used energetic material cyclotrimethylenetrinitramine (RDX) were performed using density functional theory with both the generalized gradient approximation (BLYP and BP functionals) and the local density approximation (PWC and VWN functionals). The structural results were found to be in good agreement with experimental neutron diffraction data and previously reported calculations based on the isolated-molecule approximation. The vibrational inelastic neutron scattering (INS) spectrum of polycrystalline RDX was measured and compared with simulated INS constructed from the solid-state calculations. The vibrational frequencies calculated from the solid-state methods had average deviations of 10 cm(-1) or less, whereas previously published frequencies based on an isolated-molecule approximation had deviations of 65 cm(-1) or less, illustrating the importance of including crystalline forces. On the basis of the calculations and analysis, it was possible to assign the normal modes and symmetries, which agree well with previous assignments. Four possible "doorway modes" were found in the energy range defined by the lattice modes, which were all found to contain fundamental contributions from rotation of the nitro groups.

Presentation of a complex permittivity-meter with applications for sensing the moisture and salinity of a porous media.

PubMed

Chavanne, Xavier; Frangi, Jean-Pierre

2014-08-26

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm distance to scan a significant volume of the medium (~1 L). It measures their admittances owing to a self-balanced impedance bridge operating at a frequency in the range of 1-20 MHz, possibly 30 MHz. Thanks to accurate design and electronic circuit theory-based modeling, the determination of the admittances takes into account all distortions due to lead and bridge electromagnetic effects inside the sensor when working at high frequencies. Calibration procedures and uncertainties are presented. The article also describes developments to make the present sensor autonomous on digital acquisition, basic data treatment and energy, as well as able to transfer stored data by a radio link. These steps in progress are prerequisites for a wireless network of sensors.

Presentation of a Complex Permittivity-Meter with Applications for Sensing the Moisture and Salinity of a Porous Media

PubMed Central

Chavanne, Xavier; Frangi, Jean-Pierre

2014-01-01

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm distance to scan a significant volume of the medium (∼1 L). It measures their admittances owing to a self-balanced impedance bridge operating at a frequency in the range of 1–20 MHz, possibly 30 MHz. Thanks to accurate design and electronic circuit theory-based modeling, the determination of the admittances takes into account all distortions due to lead and bridge electromagnetic effects inside the sensor when working at high frequencies. Calibration procedures and uncertainties are presented. The article also describes developments to make the present sensor autonomous on digital acquisition, basic data treatment and energy, as well as able to transfer stored data by a radio link. These steps in progress are prerequisites for a wireless network of sensors. PMID:25162233

Structural confirmation and spectroscopic study of a biomolecule: Norepinephrine.

PubMed

Yadav, T; Mukherjee, V

2018-05-21

The present work deals with the conformational and vibrational spectroscopic study of an important bio-molecule named norepinephrine in gas phase. The FTIR and FTRaman spectrum of norepinephrine in amorphous form were recorded in wavenumber range 4000-400 cm -1 and 4000-50 cm -1 respectively. We have investigated twenty-seven stable conformational structures of norepinephrine molecule. All the calculations have been done using Density Functional Theory with exchange functional B3LYP incorporated with the 6-31++G(d, p) basis set. The effect of hydrochloride on different bond lengths, bond angles and dihedral angles in the most stable conformer has also been studied. The total potential energy distribution for both the most stable conformer and the most stable conformer in hydrochloride was performed with the help Normal coordinate analysis method. Most of the calculated vibrational frequencies are in good agreement with the experimental frequencies. The natural bond orbital analysis was also performed to ensure the stability of electronic structures of norepinephrine. To know chemical reactivity of norepinephrine molecule we have calculated the energy gap between HOMO and LUMO orbitals and it has found above 5 eV in all the conformers. Copyright © 2018 Elsevier B.V. All rights reserved.

Raman effect in multiferroic Bi5Fe1+xTi3-xO15 solid solutions: A temperature study

NASA Astrophysics Data System (ADS)

Rodríguez Aranda, Ma. Del Carmen; Rodríguez-Vázquez, Ángel G.; Salazar-Kuri, Ulises; Mendoza, María Eugenia; Navarro-Contreras, Hugo R.

2018-02-01

In this work, a Raman study of powder samples of multiferroic Bi5Fe1+xTi3-xO15 solid solutions and Bi6Fe2Ti3O18 as a function of temperature from 27 °C (room temperature) to 850 °C is presented. The values of x (i.e., the Fe composition) for the solid solutions were 1.0, 1.1, 1.3, and 1.4. The temperature coefficients of eight phonon frequencies were determined for all the samples. The large observed phonon broadenings with increasing temperature precluded the observation of several of the phonon bands above defined temperatures in the range of 200-700 °C depending on the sample. These phonon broadenings were explained on the basis of the Klemens model, which considers that the broadenings are due to the thermal expansion of the lattice with a major contribution in terms of magnitude from anharmonic phonon-phonon interactions. However, some evidence for the presence of several of the phonons persisted up to 800-850 °C. These solid solutions are expected to exhibit a ferroelectric-paraelectric phase transition at 742 to 750 °C and a ferromagnetic-antiferromagnetic transition at 426 °C. We also observed changes in the slopes of the temperature dependence of the phonon frequencies for the lines at 228 cm-1 for Bi5FeTi3O15 and 330 cm-1 for Bi6Fe2Ti3O18 at temperatures of 247 °C and 347 °C, respectively. No similar temperature-frequency slope changes indicative of possible phase transitions were observed for any of the phonon lines of the other three Bi5Fe1+xTi3-xO15 solid solutions examined.

A study on the measurement of radar cross section of flighting model based on the range-Doppler imaging

NASA Astrophysics Data System (ADS)

Hashimoto, Osamu; Mizokami, Osamu

The method for measuring radar cross section (RCS) based on Range-Doppler Imaging is discussed. In this method, the measured targets are rotated and the Doppler frequencies caused by each scattering element along the targets are analyzed by FFT. Using this method, each scattered power peak along the flying model is measured. It is found that each part of the RCS of a flying model can be measured and its RCS of a main wing (about 46 dB/sq cm) is greater than of its body (about 20-30 dB/sq cm).

Lysis of Chlamydomonas reinhardtii by high-intensity focused ultrasound as a function of exposure time.

PubMed

Bigelow, Timothy A; Xu, Jin; Stessman, Dan J; Yao, Linxing; Spalding, Martin H; Wang, Tong

2014-05-01

Efficient lysis of microalgae for lipid extraction is an important concern when processing biofuels. Historically, ultrasound frequencies in the range of 10-40 kHz have been utilized for this task. However, greater efficiencies might be achievable if higher frequencies could be used. In our study, we evaluated the potential of using 1.1 MHz ultrasound to lyse microalgae for biofuel production while using Chlamydomonas reinhardtii as a model organism. The ultrasound was generated using a spherically focused transducer with a focal length of 6.34 cm and an active diameter of 6.36 cm driven by 20 cycle sine-wave tone bursts at a pulse repetition frequency of 2 kHz (3.6% duty cycle). The time-average acoustic power output was 26.2 W while the spatial-peak-pulse-average intensity (ISPPA) for each tone burst was 41 kW/cm(2). The peak compressional and rarefactional pressures at the focus were 102 and 17 MPa, respectively. The exposure time was varied for the different cases in the experiments from 5s to 9 min and cell lysis was assessed by quantifying the percentage of protein and chlorophyll release into the supernate as well as the lipid extractability. Free radical generation and lipid oxidation for the different ultrasound exposures were also determined. We found that there was a statistically significant increase in lipid extractability for all of the exposures compared to the control. The longer exposures also completely fragmented the cells releasing almost all of the protein and chlorophyll into the supernate. The cavitation activity did not significantly increase lipid oxidation while there was a minor trend of increased free radical production with increased ultrasound exposure. Copyright © 2013 Elsevier B.V. All rights reserved.

Regional propagation characteristics and source parameters of earthquakes in northeastern North America

USGS Publications Warehouse

Boatwright, John

1994-01-01

The vertical components of the S wave trains recorded on the Eastern Canadian Telemetered Network (ECTN) from 1980 through 1990 have been spectrally analyzed for source, site, and propagation characteristics. The data set comprises some 1033 recordings of 97 earthquakes whose magnitudes range from M ≈ 3 to 6. The epicentral distances range from 15 to 1000 km, with most of the data set recorded at distances from 200 to 800 km. The recorded S wave trains contain the phases S, SmS, Sn, and Lg and are sampled using windows that increase with distance; the acceleration spectra were analyzed from 1.0 to 10 Hz. To separate the source, site, and propagation characteristics, an inversion for the earthquake corner frequencies, low-frequency levels, and average attenuation parameters is alternated with a regression of residuals onto the set of stations and a grid of 14 distances ranging from 25 to 1000 km. The iteration between these two parts of the inversion converges in about 60 steps. The average attenuation parameters obtained from the inversion were Q = 1997 ± 10 and γ = 0.998 ± 0.003. The most pronounced variation from this average attenuation is a marked deamplification of more than a factor of 2 at 63 km and 2 Hz, which shallows with increasing frequency and increasing distance out to 200 km. The site-response spectra obtained for the ECTN stations are generally flat. The source spectral shape assumed in this inversion provides an adequate spectral model for the smaller events (Mo < 3 × 1021 dyne-cm) in the data set, whose Brune stress drops range from 5 to 150 bars. For the five events in the data set with Mo ≧ 1023 dyne-cm, however, the source spectra obtained by regressing the residuals suggest that an ω2 spectrum is an inadequate model for the spectral shape. In particular, the corner frequencies for most of these large events appear to be split, so that the spectra exhibit an intermediate behavior (where |ü(ω)| is roughly proportional to ω).

Mechanical design, fabrication, and test of biomimetic fish robot using LIPCA as artificial muscle

NASA Astrophysics Data System (ADS)

Wiguna, T.; Syaifuddin, M.; Park, Hoon C.; Heo, S.

2006-03-01

This paper presents a mechanical design, fabrication and test of biomimetic fish robot using the Lightweight Piezocomposite Curved Actuator (LIPCA). We have designed a mechanism for converting actuation of the LIPCA into caudal fin movement. This linkage mechanism consists of rack-pinion system and four-bar linkage. We also have tested four types of caudal fin in order to examine effect of different shape of caudal fin on thrust generation by tail beat. Subsequently, based on the caudal fin test, four caudal fins which resemble fish caudal fin shapes of ostraciiform, subcarangiform, carangiform and thunniform, respectively, are attached to the posterior part of the robotic fish. The swimming test using 300 V pp input with 1 Hz to 1.5 Hz frequency was conducted to investigate effect of changing tail beat frequency and shape of caudal fin on the swimming speed of the robotic fish. The maximum swimming speed was reached when the device was operated at its natural swimming frequency. At the natural swimming frequency 1 Hz, maximum swimming speeds of 1.632 cm/s, 1.776 cm/s, 1.612 cm/s and 1.51 cm/s were reached for ostraciiform-, subcarangiform-, carangiform- and thunniform-like caudal fins, respectively. Strouhal numbers, which are a measure of thrust efficiency, were calculated in order to examine thrust performance of the present biomimetic fish robot. We also approximated the net forward force of the robotic fish using momentum conservation principle.

Harmonic generation by yeast cells in response to low-frequency electric fields

NASA Astrophysics Data System (ADS)

Nawarathna, D.; Claycomb, J. R.; Cardenas, G.; Gardner, J.; Warmflash, D.; Miller, J. H., Jr.; Widger, W. R.

2006-05-01

We report on harmonic generation by budding yeast cells (Saccharomyces cerevisiae, 108cells/ml ) in response to sinusoidal electric fields with amplitudes ranging from zero to 5V/cm in the frequency range 10-300Hz . The cell-generated harmonics are found to exhibit strong amplitude and frequency dependence. Sodium metavanadate, an inhibitor of the proton pump known as H+ -ATPase, and glucose, a substrate of H+ -ATPase, are found to increase harmonic production at low amplitudes while reducing it at large amplitudes. This P-type proton pump can be driven by an oscillatory transmembrane potential, and its nonlinear response is believed to be largely responsible for harmonic production at low frequencies in yeast cells. We find that the observed harmonics show dramatic changes with time and in their field and frequency dependence after perturbing the system by adding an inhibitor, substrate, or membrane depolarizer to the cell suspension.

THz-IR spectroscopy of single H2O molecules confined in nanocage of beryl crystal lattice

NASA Astrophysics Data System (ADS)

Gorshunov, Boris P.; Zhukova, Elena S.; Torgashev, Victor I.; Motovilova, Elizaveta A.; Lebedev, Vladimir V.; Prokhorov, Anatoly S.; Shakurov, Gil'man S.; Kremer, Reinhard K.; Uskov, Vladimir V.; Pestrjakov, Efim V.; Thomas, Victor G.; Fursenko, Dimitri A.; Kadlec, Christelle; Kadlec, Filip; Dressel, Martin

2014-11-01

We have measured the terahertz-infrared (3-7000 cm-1) spectra of the optical conductivity of iron-doped single crystals of beryl, (Mn,Fe):Be3Al2Si6O18, that contain lone water molecules isolated within nanometer-sized cages formed by the ions of beryl crystal lattice. By comparing the spectra with those of dehydrated crystals, we exclude phonon resonances and reconstruct the spectra determined exclusively by vibrations of the water molecules. At liquid-helium temperatures, well-known intramolecular H2O modes are observed above 1000 cm-1 and accompanied with satellite resonances that are combinations of intramolecular and external vibrations of H2O molecules. At terahertz frequencies, a broad bump centred around 20 cm-1 (at 5 K) is observed with three rather narrow resonances at its high-frequency shoulder (38, 42 and 46 cm-1). The origin of these low-energy excitations is discussed.

Characterization of a low frequency magnetic noise from a two-stage pulse tube cryocooler

NASA Astrophysics Data System (ADS)

Eshraghi, M. J.; Sasada, I.; Kim, J. M.; Lee, Y. H.

2009-07-01

Magnetic noise of a two-stage pulse tube cryocooler (PT) was measured by a fundamental mode orthogonal fluxgate magnetometer and by a LTS Double Relaxation Oscillation SQUID (DROS) first-order planar gradiometer. The magnetometer was installed in a dewar made of aluminum at 12 cm distance from a section containing magnetic regenerative materials of the second pulse tube. The magnetic noise spectrum showed a clear peak at 1.8 Hz, which is the fundamental frequency of the He gas pumping rate. The 1.8 Hz magnetic noise registered a peak, during the cooling down process, when the second cold-stage temperature was around 12 K, which is well correlated with the 1.8 Hz variation of the temperature of the second cold stage. Hence, we attributed the main source of this magnetic noise to the temperature variation of the magnetic moments resulting from magnetic regenerative materials, Er 3Ni and HoCu 2, in the presence of background static magnetic fields. We have also pointed out that the superconducting magnetic shield of lead sheets reduced the low frequency magnetic noise generated from the magnetic regenerative materials. With this arrangement, the magnetic noise amplitude measured with the LTS DROS gradiometer, mounted at 7 cm horizontal distance from the magnetic regenerative materials, in the optimum condition, was lower than 500 pT peak-to-peak, whereas the noise level without lead shielding was higher than the dynamic range of DROS instrumentations which was around ±10nT.

Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy.

PubMed

Slenkamp, Karla M; Lynch, Michael S; Van Kuiken, Benjamin E; Brookes, Jennifer F; Bannan, Caitlin C; Daifuku, Stephanie L; Khalil, Munira

2014-02-28

Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (νCN) vibrations found in [(NH3)5Ru(III)NCFe(II)(CN)5](-) (FeRu) dissolved in D2O and formamide and [(NC)5Fe(II)CNPt(IV)(NH3)4NCFe(II)(CN)5](4-) (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the νCN modes in the electronic ground state. The FTIR spectra of the νCN modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic νCN modes. The vibrational mode anharmonicities of the individual νCN modes range from 14 to 28 cm(-1). The mixed-mode anharmonicities range from 2 to 14 cm(-1). In general, the bridging νCN mode is most weakly coupled to the radial νCN mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four νCN modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D2O. The νCN modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm(-1). This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the νCN modes in cyanide-bridged transition metal mixed valence complexes.

Development of a large-area planar surface-wave plasma source with a cavity launcher driven by a 915 MHz UHF wave

NASA Astrophysics Data System (ADS)

Chang, Xijiang; Kunii, Kazuki; Liang, Rongqing; Nagatsu, Masaaki

2013-04-01

A large-area planar surface-wave plasma (SWP) source driven by a 915 MHz ultrahigh frequency (UHF) wave was developed. To avoid using large, thick dielectric plates as vacuum windows, we propose a cavity launcher consisting of a cylindrical cavity with several small quartz discs at the bottom. Three types of launchers with quartz discs located at different positions were tested to compare their plasma production efficiencies and spatial distributions of electron density. With the optimum launcher, large-area plasma discharges with a radial uniformity within ±10% were obtained in a radius of about 25-30 cm in Ar gas at 8 Pa for incident power in the range 0.5-2.5 kW. The maximum electron density and temperature were approximately (0.95-1.1) × 1011 cm-3 and 1.9-2.0 eV, respectively, as measured by a Langmuir probe located 24 cm below the bottom of the cavity launcher. Using an Ar/NH3 SWP with the optimum launcher, we demonstrated large-area amino-group surface modification of polyurethane sheets. Experimental results indicated that a uniform amino-group modification was achieved over a radius of approximately 40 cm, which is slightly larger than the radial uniformity of the electron density distribution.

Piezoelectric-nanowire-enabled power source for driving wireless microelectronics.

PubMed

Xu, Sheng; Hansen, Benjamin J; Wang, Zhong Lin

2010-10-19

Harvesting energy from irregular/random mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric nanowires are robust and can be stimulated by tiny physical motions/disturbances over a range of frequencies. Here, we demonstrate the first chemical epitaxial growth of PbZr(x)Ti(1-x)O(3) (PZT) nanowire arrays at 230 °C and their application as high-output energy converters. The nanogenerators fabricated using a single array of PZT nanowires produce a peak output voltage of ~0.7 V, current density of 4 μA cm(-2) and an average power density of 2.8 mW cm(-3). The alternating current output of the nanogenerator is rectified, and the harvested energy is stored and later used to light up a commercial laser diode. This work demonstrates the feasibility of using nanogenerators for powering mobile and even personal microelectronics.

A system for measuring complex dielectric properties of thin films at submillimeter wavelengths using an open hemispherical cavity and a vector network analyzer.

PubMed

Rahman, Rezwanur; Taylor, P C; Scales, John A

2013-08-01

Quasi-optical (QO) methods of dielectric spectroscopy are well established in the millimeter and submillimeter frequency bands. These methods exploit standing wave structure in the sample produced by a transmitted Gaussian beam to achieve accurate, low-noise measurement of the complex permittivity of the sample [e.g., J. A. Scales and M. Batzle, Appl. Phys. Lett. 88, 062906 (2006); R. N. Clarke and C. B. Rosenberg, J. Phys. E 15, 9 (1982); T. M. Hirovnen, P. Vainikainen, A. Lozowski, and A. V. Raisanen, IEEE Trans. Instrum. Meas. 45, 780 (1996)]. In effect the sample itself becomes a low-Q cavity. On the other hand, for optically thin samples (films of thickness much less than a wavelength) or extremely low loss samples (loss tangents below 10(-5)) the QO approach tends to break down due to loss of signal. In such a case it is useful to put the sample in a high-Q cavity and measure the perturbation of the cavity modes. Provided that the average mode frequency divided by the shift in mode frequency is less than the Q (quality factor) of the mode, then the perturbation should be resolvable. Cavity perturbation techniques are not new, but there are technological difficulties in working in the millimeter/submillimeter wave region. In this paper we will show applications of cavity perturbation to the dielectric characterization of semi-conductor thin films of the type used in the manufacture of photovoltaics in the 100 and 350 GHz range. We measured the complex optical constants of hot-wire chemical deposition grown 1-μm thick amorphous silicon (a-Si:H) film on borosilicate glass substrate. The real part of the refractive index and dielectric constant of the glass-substrate varies from frequency-independent to linearly frequency-dependent. We also see power-law behavior of the frequency-dependent optical conductivity from 316 GHz (9.48 cm(-1)) down to 104 GHz (3.12 cm(-1)).

Measurement technology for seismomagnetic signals

NASA Astrophysics Data System (ADS)

Korepanov, Valery; Dudkin, Fedir; Marusenkov, Andriy

2010-05-01

Ultra low frequency (ULF) band (0.001-3 Hz) is usually used for study of natural magnetic field variations of ionospheric and magnetospheric origin. At present this frequency range gains in importance at monitoring of lithospheric magnetic activity in seismo-hazardous areas for application to short-time earthquake (EQ) forecasting. A big number of publications confirm that ULF magnetic precursors were recorded from few weeks up to few hours before EQ. The measurement technology of these signals has several peculiarities. First, the lithospheric ULF EQ magnetic precursors as a rule are very weak and their frequency range is overlapping with signals of magnetospheric or ionospheric origin. Second, for resolution of magnetic precursors at the background of more powerful sources it is necessary to have magnetic field sensors with wide dynamics and minimum possible spectral noise density (SND) level. Additionally, monitoring of lithospheric activity should be provided in close proximity to probable EQ area and almost in real-time regime. For the study of ULF magnetic precursors the magnetometers with search-coil (SC) and fluxgate (FG) sensors are used. SC sensors for ULF band usually have length 0.8-1.2 m, diameter 10-15 cm and weight few kilograms with SND 0.1-200 pT/Hz0.5 (here and further maximum SND value relates to a lower part of frequency range). FG sensors are very compact (pencil-shaped with length ~ 4 cm) but have greater SND in this band (about 10-500 pT/Hz0.5). Next requirement, if to use SC, is that at 3-component magnetic field measurement it is necessary to provide spacing between sensors about 1-2 of their length for avoiding mutual influence between them. This requirement creates problems caused by non-rigidity of such construction and their spatial instability relatively ground surface (or horizontal plane). In addition, for such a long sensor a ratio of core length/diameter is big enough, what leads to increased SC sensor sensitivity to variety of mechanical deformations of sensor body. These factors increase the real SC SND because of induction effect in the Earth's magnetic field. Simple estimations show that sensitivity to changing of sensor axis direction can achieve a level about 250 pT for one second of arc. To overcome majority of these problems, a specialized FG with length 10 cm has been developed. This newly developed device has SND in ULF band about 1-30 pT/Hz0.5 and moderate consumed power. Additional merit of this sensor is extremely low noise density in the most prospective EQ magnetic precursors frequency range (0.001-0.03 Hz) - about 3-30 pT/Hz0.5- which is less than SND for the best recent SCs. A ULF magnetometer with such a compact solid sensor unit at partial compensation of the Earth's magnetic field in the sensor volume allows drastic decreasing the mechanical artefacts influence and facilitates the constructing of measuring sites for field works. As an example of SND necessity decrease the experimental data from seismo-hazardous region of China are discussed. It is shown that high SND of magnetometers leads to appearance of false background lithospheric signals and complicates the procedure of EQ related signals selection. The comparison of parameter set for FG and SC has been made and a specific design of FG dedicated for seismogenic ULF signals measurements has been discussed. This work is supported by STCU grant 4818.

GPS-Based Precision Orbit Determination for a New Era of Altimeter Satellites: Jason-1 and ICESat

NASA Technical Reports Server (NTRS)

Luthcke, Scott B.; Rowlands, David D.; Lemoine, Frank G.; Zelensky, Nikita P.; Williams, Teresa A.

2003-01-01

Accurate positioning of the satellite center of mass is necessary in meeting an altimeter mission's science goals. The fundamental science observation is an altimetric derived topographic height. Errors in positioning the satellite's center of mass directly impact this fundamental observation. Therefore, orbit error is a critical Component in the error budget of altimeter satellites. With the launch of the Jason-1 radar altimeter (Dec. 2001) and the ICESat laser altimeter (Jan. 2003) a new era of satellite altimetry has begun. Both missions pose several challenges for precision orbit determination (POD). The Jason-1 radial orbit accuracy goal is 1 cm, while ICESat (600 km) at a much lower altitude than Jason-1 (1300 km), has a radial orbit accuracy requirement of less than 5 cm. Fortunately, Jason-1 and ICESat POD can rely on near continuous tracking data from the dual frequency codeless BlackJack GPS receiver and Satellite Laser Ranging. Analysis of current GPS-based solution performance indicates the l-cm radial orbit accuracy goal is being met for Jason-1, while radial orbit accuracy for ICESat is well below the 54x1 mission requirement. A brief overview of the GPS precision orbit determination methodology and results for both Jason-1 and ICESat are presented.

Performance-Enhanced Bolometric Terahertz Detectors Based on V2O5 for 15 to 30 THz

NASA Astrophysics Data System (ADS)

Sumesh, M. A.; Karanth, S. P.; Thomas, Beno; Rao, G. M.; Viswanathan, M.; Chakraborty, P.; Rao, G. N.

2017-02-01

Terahertz (THz) radiation perception using uncooled detectors are gaining importance due to the increasing demands in the areas of military, space, and industrial, medical, and surveillance applications. In spite of the efforts of researchers to fill the THz gap, there exists a need for detectors in the range between 15 THz and 30 THz. In this paper, we discuss the development of bolometric detectors whose performance is enhanced by an optical immersion technique and their characterization in the aforesaid range of frequencies. These detectors are characterized by high specific detectivity ( D*) of 1.28 × 109 cmHz1/2 W-1 and high radiometric resolution (noise-equivalent temperature difference = 26 mK) and are fast enough for bolometric detectors (time constant = 1.7 ms), which make them suitable for spectroscopic and imaging applications.

LCGTO-Xα model cluster study for the chemisorption of CO on twofold sites of Ni surfaces

NASA Astrophysics Data System (ADS)

Jörg, H.; Rösch, N.

The cluster Ni 2CO is studied as a simplified model for the chemisorption of CO on twofold bridging sites of transition metal surfaces. Using the LCGTO-Xα method we have calculated the potential energy surface for the totally symmetric stretching motion keeping the Ni-Ni distance fixed at the bulk value. The minimum energy is found at a Ni-C distance of 1.72 Å and a C-O bond length of 1.19 Å. The vibrational frequency for the CO bond (1850 cm -1) shows reasonable agreement with EELS data (1810, 1870 cm -1), whereas the (Ni 2)-C frequency of 495 cm -1 is remarkably higher than the experimental values (380, 400 cm -1) indicating an overestimation of the chemisorption bond strength in this simple cluster model. The bonding between CO and Ni is analyzed using orbital correlations, ionization energies and Mulliken population analysis. Important bonding contributions from π backdonation are identified while the a 1 orbital manifold exhibits strong antibonding effects.

LCGTO-Xα model cluster study for the chemisorption of CO on twofold sites of Ni surfaces

NASA Astrophysics Data System (ADS)

Jörg, H.; Rösch, N.

1985-11-01

The cluster Ni 2CO is studied as a simplified model for the chemisorption of CO on twofold bridging sites of transition metal surfaces. Using the LCGTO-Xα method we have calculated the potential energy surface for the totally symmetric stretching motion keeping the NiNi distance fixed at the bulk value. The minimum energy is found at a NiC distance of 1.72 Å and a CO bond length of 1.19 Å. The vibrational frequency for the CO bond (1850 cm -1) shows reasonable agreement with EELS data (1810, 1870 cm -1), whereas the (Ni 2)C frequency of 495 cm -1 is remarkably higher than the experimental values (380, 400 cm -1) indicating an overestimation of the chemisorption bond strength in this simple cluster model. The bonding between CO and Ni is analyzed using orbital correlations, ionization energies and Mulliken population analysis. Important bonding contributions from π backdonation are identified while the a 1orbital manifold exhibits strong antibonding effects.

On-chip dual-comb based on quantum cascade laser frequency combs

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

Villares, G., E-mail: gustavo.villares@phys.ethz.ch; Wolf, J.; Kazakov, D.

2015-12-21

Dual-comb spectroscopy is emerging as an appealing application of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs. Here, we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs. Control of the combs repetition and offset frequencies is obtained by integrating micro-heaters next to each laser. We show that a full control of the dual-comb system is possible, by measuring a multi-heterodyne beating corresponding to an optical bandwidth of 32 cm{sup −1} centered at 1330 cm{sup −1} (7.52 μm), demonstrating that this device represents a critical step towards compact dual-combmore » systems.« less

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

Ghosh, Tushar; Basak, Durga

A rapid dark thermal annealing process at 800 deg. C of radio frequency sputtered P doped ZnO thin films have resulted in improved electrical transport properties with hole concentration of 1 x 1018 cm-3, mobility 4.37 cm2/Vs and resistivity 1.4 {Omega}-cm. X-ray photoelectron spectroscopy shows the presence of inactivated P in as-grown ZnO films.

30 pJ/b, 67 Mbps, Centimeter-to-Meter Range Data Telemetry With an IR-UWB Wireless Link.

PubMed

Ebrazeh, Ali; Mohseni, Pedram

2015-06-01

This paper reports an energy-efficient, impulse radio ultra wideband (IR-UWB) wireless link operating in 3-5 GHz for data telemetry over centimeter-to-meter range distances at rates extended to tens of Mbps. The link comprises an all-digital, integrated transmitter (TX) fabricated in 90 nm 1P/9M CMOS that incorporates a waveform-synthesis pulse generator and a timing generator for on-off-keying (OOK) pulse modulation and phase scrambling. The link also incorporates an energy-detection receiver (RX) realized with commercial off-the-shelf (COTS) components that performs radio-frequency (RF) filtering, amplification, logarithmic power detection for data demodulation and automatic level control for robust operation in the presence of distance variations. Employing a miniaturized, UWB, chip antenna for the TX and RX, wireless transmission of pseudo-random binary sequence (PRBS) data at rates up to 50 Mbps over 10 cm-1 m is shown. Further, employing a high-gain horn antenna for the RX, wireless transmission of PRBS data at rates up to 67 Mbps over 50 cm-4 m is shown with a TX energy consumption of 30 pJ/b (i.e., power consumption of 2 mW) from 1.2 V. The measured bit error rate (BER) in both cases is < 10(-7) . Results from wireless recording of the background current of a carbon-fiber microelectrode (CFM) in one fast-scan cyclic voltammetry (FSCV) scan using the IR-UWB link are also included, exhibiting excellent match with those obtained from a conventional frequency-shift-keyed (FSK) link at ~433 MHz.

Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer.

PubMed

N'djin, William Apoutou; Burtnyk, Mathieu; Bronskill, Michael; Chopra, Rajiv

2012-01-01

Transurethral ultrasound therapy uses real-time magnetic resonance (MR) temperature feedback to enable the 3D control of thermal therapy accurately in a region within the prostate. Previous canine studies showed the feasibility of this method in vivo. The aim of this study was to reduce the procedure time, while maintaining targeting accuracy, by investigating new combinations of treatment parameters. Simulations and validation experiments in gel phantoms were used, with a collection of nine 3D realistic target prostate boundaries obtained from previous preclinical studies, where multi-slice MR images were acquired with the transurethral device in place. Acoustic power and rotation rate were varied based on temperature feedback at the prostate boundary. Maximum acoustic power and rotation rate were optimised interdependently, as a function of prostate radius and transducer operating frequency. The concept of dual frequency transducers was studied, using the fundamental frequency or the third harmonic component depending on the prostate radius. Numerical modelling enabled assessment of the effects of several acoustic parameters on treatment outcomes. The range of treatable prostate radii extended with increasing power, and tended to narrow with decreasing frequency. Reducing the frequency from 8 MHz to 4 MHz or increasing the surface acoustic power from 10 to 20 W/cm(2) led to treatment times shorter by up to 50% under appropriate conditions. A dual frequency configuration of 4/12 MHz with 20 W/cm(2) ultrasound intensity exposure can treat entire prostates up to 40 cm(3) in volume within 30 min. The interdependence between power and frequency may, however, require integrating multi-parametric functions in the controller for future optimisations.

Design of an FT-NIR spectrometer for online quality analysis of traditional Chinese medicine manufacturing process

NASA Astrophysics Data System (ADS)

Zhu, Ren; Wu, Lan; Wang, Shiming; Ye, Linhua; Ding, Zhihua

2008-03-01

As a fast, non-destructive analysis method, Fourier transform (FT) near-infrared (NIR) spectroscopy is very suitable and effective for online quality analysis of traditional Chinese medicine (TCM) manufacturing process. In this thesis, the theoretics of FT-NIRS was analyzed and an FT-NIR spectrometer with 4 cm -1 resolution in the 12500-5000 cm -1 frequency range was designed. The spectrometer was based on a Michelson interferometer with Bromine tungsten lamp as the NIR light source and InGaAs detector to collect the interference signal. Each element was designed and chosen to provide maximum sensitivity in the NIR spectral region. A fiber-optic flow cell system was used to realize online analysis of traditional Chinese medicine. The performance of the spectrometer was evaluated and the feasibility of using FT-NIR spectrometer to get absorption spectra of traditional Chinese medicine was demonstrated.

Foreign molecules and ions in beryl obtained by infrared and visible spectroscopy

NASA Astrophysics Data System (ADS)

Jelić, Ivana; Logar, Mihovil; Milošević, Maja

2017-04-01

Beryl minerals of Serbia were slightly studied in the last century and despite that there is some obtainable data about main characteristics there is a limited amount of information about foreign molecules in the mineral structure. Two beryl samples from different locations in Serbia were examined in detail but infrared spectroscopy (IR) and spectrophotometry (VIS) was used for determination of foreign molecules and ions in the structure and the obtained data is shown in this paper. The infrared (IR) and visible spectra (VIS) of two natural beryl samples indicate the presence of two types of water molecule, Fe2+, Fe3+ ions and CO3. The spectra of two types of water molecules can be recognized with molecular fundamental vibrations at 3687 cm-1 (asymmetric stretching) for type I, at 3574 cm-1 and 3585 cm-1 both symmetric stretching, and with deformation vibrations at 1627 cm-1 and 1632 cm-1 for type II. In range of symmetric stretching there is broad vibrational band which can be explained by presence of water molecules type II near alkali ions. Overtones and combinations of these fundamental vibrations have been identified. The type I molecules have their C2 symmetry axes perpendicular to the crystal C6 axis, while the type II molecules are rotated by 90 degrees and have their C2 symmetry axes parallel to the crystal C6 axis. Vibrational absorption frequency of 1425 cm-1 indicate the presence of CO3. Pale blue beryl is colored according to the relative intensities of two spectral features attributable to iron ions: a) a broad band in the extraordinary ray (Er) at 16000 cm-1 due to Fe2+ in a channel site and b) a broad band in range of 22500-31400 cm-1 in both ordinary ray (Or) and Er due to octahedral Fe3+ in the Al3+ site. Two other features, also attributable to iron, do not produce any visible coloration: a) an absorption edge at 12350 cm-1 in Or is due to Fe2+ in the octahedral site and b) a broad band in Er and Or, centered around 12350 cm-1, is due to Fe2+ in channel site. These spectral features are interpreted on the basis of the crystal field theory. Infrared and visible spectroscopy data of two natural beryl minerals from Serbia has shown that water molecules, carbonates and iron ions represent the main impurities in the crystal structure. Nature of the fluid inclusions and quantitative content of Fe2+ and Fe3+ ions remain to be examined in the future.

Zonal Acoustic Velocimetry in 30-cm, 60-cm, and 3-m Laboratory Models of the Outer Core

NASA Astrophysics Data System (ADS)

Rojas, R.; Doan, M. N.; Adams, M. M.; Mautino, A. R.; Stone, D.; Lekic, V.; Lathrop, D. P.

2016-12-01

A knowledge of zonal flows and shear is key in understanding magnetic field dynamics in the Earth and laboratory experiments with Earth-like geometries. Traditional techniques for measuring fluid flow using visualization and particle tracking are not well-suited to liquid metal flows. This has led us to develop a flow measurement technique based on acoustic mode velocimetry adapted from helioseismology. As a first step prior to measurements in the liquid sodium experiments, we implement this technique in our 60-cm diameter spherical Couette experiment in air. To account for a more realistic experimental geometry, including deviations from spherical symmetry, we compute predicted frequencies of acoustic normal modes using the finite element method. The higher accuracy of the predicted frequencies allows the identification of over a dozen acoustic modes, and mode identification is further aided by the use of multiple microphones and by analyzing spectra together with those obtained at a variety of nearby Rossby numbers. Differences between the predicted and observed mode frequencies are caused by differences in flow patterns present in the experiment. We compare acoustic mode frequency splittings with theoretical predictions for stationary fluid and solid body flow condition with excellent agreement. We also use this technique to estimate the zonal shear in those experiments across a range of Rossby numbers. Finally, we report on initial attempts to use this in liquid sodium in the 3-meter diameter experiment and parallel experiments performed in water in the 30-cm diameter experiment.

Forecasting space weather: Can new econometric methods improve accuracy?

NASA Astrophysics Data System (ADS)

Reikard, Gordon

2011-06-01

Space weather forecasts are currently used in areas ranging from navigation and communication to electric power system operations. The relevant forecast horizons can range from as little as 24 h to several days. This paper analyzes the predictability of two major space weather measures using new time series methods, many of them derived from econometrics. The data sets are the A p geomagnetic index and the solar radio flux at 10.7 cm. The methods tested include nonlinear regressions, neural networks, frequency domain algorithms, GARCH models (which utilize the residual variance), state transition models, and models that combine elements of several techniques. While combined models are complex, they can be programmed using modern statistical software. The data frequency is daily, and forecasting experiments are run over horizons ranging from 1 to 7 days. Two major conclusions stand out. First, the frequency domain method forecasts the A p index more accurately than any time domain model, including both regressions and neural networks. This finding is very robust, and holds for all forecast horizons. Combining the frequency domain method with other techniques yields a further small improvement in accuracy. Second, the neural network forecasts the solar flux more accurately than any other method, although at short horizons (2 days or less) the regression and net yield similar results. The neural net does best when it includes measures of the long-term component in the data.

Low- and high-frequency Raman investigations on caffeine: polymorphism, disorder and phase transformation.

PubMed

Hédoux, Alain; Decroix, Anne-Amandine; Guinet, Yannick; Paccou, Laurent; Derollez, Patrick; Descamps, Marc

2011-05-19

Raman investigations are carried out both in crystalline forms of caffeine and during the isothermal transformation of the orientationally disordered form I into the stable form II at 363 K. The time dependence of the Raman spectrum exhibits no significant change in the intramolecular regime (above 100 cm(-1)), resembling the spectrum of the liquid state. By contrast, significant changes are observed below 100 cm(-1), and the low-frequency spectra of forms I and II are observed to be different from that of the liquid. The temperature dependence of the 5-600 cm(-1) spectrum gives information on the static disorder through the analysis of collective motions, while information on dynamic disorder are obtained from the study of the 555 cm(-1) band corresponding to internal vibrations in the pyrimidine ring. This analysis indubitably reveals that form II is also orientationally disordered with a local molecular arrangement that mimics that in form I and the liquid state. The comparison of the low-frequency spectra recorded in theophylline and form II of caffeine allows one to describe the stable form of caffeine from the packing arrangement of anhydrous theophylline with the consideration of reorientational molecular disorder. © 2011 American Chemical Society

Simultaneous measurements of L- and S-band tree shadowing for space-Earth communications

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.; Lin, Hsin P.

1995-01-01

We present results from simultaneous L- and S-Band slant-path fade measurements through trees. One circularly-polarized antenna was used at each end of the dual-frequency link to provide information on the correlation of tree shadowing at 1620 and 2500 MHz. Fades were measured laterally in the shadow region with 5 cm spacing. Fade differences between L- and S-Band had a normal distribution with low means and standard deviations from 5.2 to 7.5 dB. Spatial variations occurred with periods larger than 1-2 wavelengths. Swept measurements over 160 MHz spans showed that the stdv. of power as function of frequency increased from approximately 1-6 dB at locations with mean fades of 4 and 20 dB, respectively. At a 5 dB fade, the central 90% of fade slopes were within a range of 0.7 (1.9) dB/MHz at L-(S-) Band.

Optical frequency comb profilometry using a single-pixel camera composed of digital micromirror devices.

PubMed

Pham, Quang Duc; Hayasaki, Yoshio

2015-01-01

We demonstrate an optical frequency comb profilometer with a single-pixel camera to measure the position and profile of an object's surface that exceeds far beyond light wavelength without 2π phase ambiguity. The present configuration of the single-pixel camera can perform the profilometry with an axial resolution of 3.4 μm at 1 GHz operation corresponding to a wavelength of 30 cm. Therefore, the axial dynamic range was increased to 0.87×10⁵. It was found from the experiments and computer simulations that the improvement was derived from higher modulation contrast of digital micromirror devices. The frame rate was also increased to 20 Hz.

Hyperfine-resolved 3.4-{mu}m spectroscopy of CH{sub 3}I with a widely tunable difference frequency generation source and a cavity-enhanced cell: A case study of a local Coriolis interaction between the v{sub 1}=1 and (v{sub 2},v{sub 6}{sup l})=(1,2{sup 2}) states

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

Okubo, Sho; Nakayama, Hirotaka; Sasada, Hiroyuki

Saturated absorption spectra of the {nu}{sub 1} fundamental band of CH{sub 3}I are recorded with a cavity-enhanced cell and a tunable difference frequency generation source having an 86-cm{sup -1} range. The recorded spectral lines are 250 kHz wide, and most of them are resolved into the individual hyperfine components. The Coriolis interaction between the v{sub 1}=1 and (v{sub 2},v{sub 6}{sup l})=(1,2{sup 2}) states locally perturbing the hyperfine structures is analyzed to yield the Coriolis and hyperfine coupling constants with uncertainties similar to those in typical microwave spectroscopy. The spectrometer has demonstrated the potential for precisely determining the energy structure inmore » the vibrational excited states.« less

Synthetic and Spectroscopic Studies on N-(i,j-Disubstituted Phenyl)-4- Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i, j = 2, 3; 2, 4; 2, 5; 2, 6 or 3, 4; and X = CH3 or Cl

NASA Astrophysics Data System (ADS)

Shetty, Mahesha; Gowda, B. Thimme

2005-02-01

Fifty four N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides of the general formula 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i,j = 2,3; 2,4; 2,5; 2,6 or 3, 4; and X = CH3 or Cl, are prepared and characterized and their infrared, 1H and 13C NMR spectra in solution are studied. The N-H stretching vibrations νN-H absorb in the range 3305 - 3205 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1377 - 1307 cm-1 and 1184 - 1128 cm-1, respectively. The N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides show C-S, S-N and C-N stretching vibrations in the ranges 844 - 800 cm-1, 945 - 891 cm-1 and 1309 - 1170 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbon atoms of the two benzene rings. Incremental shifts of the ring protons and carbon atoms due to -SO2NH(i,j-X2C6H3) groups in C6H5SO2NH(i,j-X2C6H3) and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H*) are computed and employed to calculate the chemical shifts of the ring protons and carbon atoms in the substituted compounds 4-X'C6H4SO2NH(i,j-X2C6H3). The different methods of calculation lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating the validity of the principle of additivity of the substituent effects with chemical shifts in these compounds.

First Demonstration of ECHO: an External Calibrator for Hydrogen Observatories

NASA Astrophysics Data System (ADS)

Jacobs, Daniel C.; Burba, Jacob; Bowman, Judd D.; Neben, Abraham R.; Stinnett, Benjamin; Turner, Lauren; Johnson, Kali; Busch, Michael; Allison, Jay; Leatham, Marc; Serrano Rodriguez, Victoria; Denney, Mason; Nelson, David

2017-03-01

Multiple instruments are pursuing constraints on dark energy, observing reionization and opening a window on the dark ages through the detection and characterization of the 21 cm hydrogen line for redshifts ranging from ˜1 to 25. These instruments, including CHIME in the sub-meter and HERA in the meter bands, are wide-field arrays with multiple-degree beams, typically operating in transit mode. Accurate knowledge of their primary beams is critical for separation of bright foregrounds from the desired cosmological signals, but difficult to achieve through astronomical observations alone. Previous beam calibration work at low frequencies has focused on model verification and does not address the need of 21 cm experiments for routine beam mapping, to the horizon, of the as-built array. We describe the design and methodology of a drone-mounted calibrator, the External Calibrator for Hydrogen Observatories (ECHO), that aims to address this need. We report on a first set of trials to calibrate low-frequency dipoles at 137 MHz and compare ECHO measurements to an established beam-mapping system based on transmissions from the Orbcomm satellite constellation. We create beam maps of two dipoles at a 9° resolution and find sample noise ranging from 1% at the zenith to 100% in the far sidelobes. Assuming this sample noise represents the error in the measurement, the higher end of this range is not yet consistent with the desired requirement but is an improvement on Orbcomm. The overall performance of ECHO suggests that the desired precision and angular coverage is achievable in practice with modest improvements. We identify the main sources of systematic error and uncertainty in our measurements and describe the steps needed to overcome them.

Large 21-cm signals from AGN-dominated reionization

NASA Astrophysics Data System (ADS)

Kulkarni, Girish; Choudhury, Tirthankar Roy; Puchwein, Ewald; Haehnelt, Martin G.

2017-08-01

We present predictions for the spatial distribution of 21-cm brightness temperature fluctuations from high-dynamic-range simulations for active galactic nucleus (AGN)-dominated reionization histories that have been tested against available Lyα and cosmic microwave background (CMB) data. We model AGNs by extrapolating the observed Mbh - σ relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. We assess the observability of the predicted spatial 21-cm fluctuations in the late stages of reionization in the limit in which the hydrogen 21-cm spin temperature is significantly larger than the CMB temperature. Our AGN-dominated reionization histories increase the variance of the 21-cm emission by a factor of up to 10 compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK2 at scales accessible to experiments (k ≲ 1 cMpc-1 h). This is lower than the sensitivity reached by ongoing experiments only by a factor of about 2 or less. When reionization is dominated by AGNs, the 21-cm power spectrum is enhanced on all scales due to the enhanced bias of the clustering of the more massive haloes and the peak in the large scale 21-cm power is strongly enhanced and moved to larger scales due to bigger characteristic bubble sizes. AGN-dominated reionization should be easily detectable by Low Frequency Array (and later Hydrogen Epoch of Reionization Array and Phase 1 of the Square Kilometre Array) at their design sensitivity, assuming successful foreground subtraction and instrument calibration. Conversely, these could become the first non-trivial reionization scenarios to be ruled out by 21-cm experiments, thereby constraining the contribution of AGNs to reionization.

Magnetic properties of FeCuNbSiB nanocrystalline alloy powder cores using ball-milled powder

NASA Astrophysics Data System (ADS)

Kim, G. H.; Noh, T. H.; Choi, G. B.; Kim, K. Y.

2003-05-01

Cold-pressed nanocrystalline powder cores were fabricated using powders of nanocrystalline ribbons which were ball milled for short time. Their magnetic properties at high frequency were measured. The powder size ranges from 20 to 850 μm and the contents of the glass binder are between 1 and 8 wt %. For cores composed of large particles of 300-850 μm with 5 wt % glass binder, we obtained a stable permeability of 100 up to 800 kHz, a maximum level 31 of quality factor at frequency of 50 kHz, and 320 mW/cm3 core loss at f=50 kHz and Bm=0.1 T. This is mainly due to the good soft magnetic properties of the powders and the higher insulation of powder cores which cause low eddy current losses.

Assessing dry density and gravimetric water content of soils in geotechnics with complex conductivity measurements : preliminary investigations

NASA Astrophysics Data System (ADS)

Kaouane, C.; Beck, Y.; Fauchard, C.; Chouteau, M.

2012-12-01

Quality controls of geotechnical works need gravimetric water content (w) and dry density (γd) measurements. Afterwards, results are compared to Proctor tests and referred to soil classification. Depending on the class of soils, different objectives must be achieved. Those measurements are usually carried out with neutron and gamma probes. Combined use of theses probes directly access (w, γd). Theses probes show great disadvantages as: nuclear hazard, heavy on-site, transporation and storage restrictions and low sampling volumes. Last decades showed a strong development of electrical and electromagnetic methods for mapping water content in soils. Still, their use in Geotechnics is limited due to interfacial effects neglected in common models but strong in compacted soils. We first showed that (w, γd) is equivalent to (φ, Sr) assuming density of particles γs=2.7 (g.cm-3). This assumption is true for common soils used in civil engineering. That first relationship allows us to work with meaningful parameters for geophysicists. Revil&Florsh recently adapted Vinegar&Waxman model for Spectal Induced Polarization (SIP) measurements at low frequencies (<50 kHz). This model relates quantitatively the electrical double layer polarization at the surface of grains. It takes into account saturation, porosity and granulometry. Standard granulometry and mineralogy are generally available in geotechnical campaigns. In-phase conductivity would be mostly related to saturation as quadrature conductivity would be related to porosity and surface conductivity. Although this model was developed for oil-bearing sands, we investigated its potential for compacted soils. Former DC-resistivity (ρ) measurements were carried out on a silty fined-grained soil (A1 in GTR classification or ML-CL in USCS) in a cylindrical cell (radius ~4 cm, heigth 7 cm). Median diameter of grain was 50 μm. For each measurement, samples were compacted at Proctor energy. We assessed (w, γd) by weighting and drying samples. We obtained γd = 1.6-1.9 (g.cm-3) and w=7-14% which lead to φ=0.3-0.4 and Sr=0.3-0.8. Tap water (ρw= 30 Ω.m) was used for the experiment. We first evaluated the saturation factor n=1.35 by fitting a power law ρ/ρw =a*Sr^n+b. a=0.223 agreed with φ^(-n)=F, F being the formation factor. This leads to a mean tortuosity α=1.47. b=0.5 might be related to surface conductivity. An empirical Rhoades-Corwin model also fit great to data. Revil&Florsh model allows us to predict a phase peak in case of complex conductivity measurements. We predicted a frequency peak at 2.4 Hz. This peak is well located in the frequency range of SIP (from 1 mHz to ~10 Hz). At the frequency peak, this model allows the direct evaluation of saturation and porosity. Hence, complex conductivity measurements might be a fine alternative to nuclear probes. Still, driving in electrodes in compacted soils remains difficult. Ongoing studies are looking further to extend this model to higher frequency range (5-200 kHz) where capacitively coupled resistivity arrays might be used allowing continuous measurements.

Wet oxidation of GeSi strained layers by rapid thermal processing

NASA Astrophysics Data System (ADS)

Nayak, D. K.; Kamjoo, K.; Park, J. S.; Woo, J. C. S.; Wang, K. L.

1990-07-01

A cold-wall rapid thermal processor is used for the wet oxidation of the commensurately grown GexSi1-x layers on Si substrates. The rate of oxidation of the GexSi1-x layer is found to be significantly higher than that of pure Si, and the oxidation rate increases with the increase in the Ge content in GexSi1-x layer. The oxidation rate of GexSi1-x appears to decrease with increasing oxidation time for the time-temperature cycles considered here. Employing high-frequency and quasi-static capacitance-voltage measurements, it is found that a fixed negative oxide charge density in the range of 1011- 1012/cm2 and the interface trap level density (in the mid-gap region) of about 1012/cm2 eV are present. Further, the density of this fixed interface charge at the SiO2/GeSi interface is found to increase with the Ge concentration in the commensurately grown GeSi layers.

Si-H bond dynamics in hydrogenated amorphous silicon

NASA Astrophysics Data System (ADS)

Scharff, R. Jason; McGrane, Shawn D.

2007-08-01

The ultrafast structural dynamics of the Si-H bond in the rigid solvent environment of an amorphous silicon thin film is investigated using two-dimensional infrared four-wave mixing techniques. The two-dimensional infrared (2DIR) vibrational correlation spectrum resolves the homogeneous line shapes ( <2.5cm-1 linewidth) of the 0→1 and 1→2 vibrational transitions within the extensively inhomogeneously broadened ( 78cm-1 linewidth) Si-H vibrational band. There is no spectral diffusion evident in correlation spectra obtained at 0.2, 1, and 4ps waiting times. The Si-H stretching mode anharmonic shift is determined to be 84cm-1 and decreases slightly with vibrational frequency. The 1→2 linewidth increases with vibrational frequency. Frequency dependent vibrational population times measured by transient grating spectroscopy are also reported. The narrow homogeneous line shape, large inhomogeneous broadening, and lack of spectral diffusion reported here present the ideal backdrop for using a 2DIR probe following electronic pumping to measure the transient structural dynamics implicated in the Staebler-Wronski degradation [Appl. Phys. Lett. 31, 292 (1977)] in a-Si:H based solar cells.

Evaluation of stem rot in 339 Bornean tree species: implications of size, taxonomy, and soil-related variation for aboveground biomass estimates

NASA Astrophysics Data System (ADS)

Heineman, K. D.; Russo, S. E.; Baillie, I. C.; Mamit, J. D.; Chai, P. P.-K.; Chai, L.; Hindley, E. W.; Lau, B.-T.; Tan, S.; Ashton, P. S.

2015-10-01

Fungal decay of heart wood creates hollows and areas of reduced wood density within the stems of living trees known as stem rot. Although stem rot is acknowledged as a source of error in forest aboveground biomass (AGB) estimates, there are few data sets available to evaluate the controls over stem rot infection and severity in tropical forests. Using legacy and recent data from 3180 drilled, felled, and cored stems in mixed dipterocarp forests in Sarawak, Malaysian Borneo, we quantified the frequency and severity of stem rot in a total of 339 tree species, and related variation in stem rot with tree size, wood density, taxonomy, and species' soil association, as well as edaphic conditions. Predicted stem rot frequency for a 50 cm tree was 53 % of felled, 39 % of drilled, and 28 % of cored stems, demonstrating differences among methods in rot detection ability. The percent stem volume infected by rot, or stem rot severity, ranged widely among trees with stem rot infection (0.1-82.8 %) and averaged 9 % across all trees felled. Tree taxonomy explained the greatest proportion of variance in both stem rot frequency and severity among the predictors evaluated in our models. Stem rot frequency, but not severity, increased sharply with tree diameter, ranging from 13 % in trees 10-30 cm DBH to 54 % in stems ≥ 50 cm DBH across all data sets. The frequency of stem rot increased significantly in soils with low pH and cation concentrations in topsoil, and stem rot was more common in tree species associated with dystrophic sandy soils than with nutrient-rich clays. When scaled to forest stands, the maximum percent of stem biomass lost to stem rot varied significantly with soil properties, and we estimate that stem rot reduces total forest AGB estimates by up to 7 % relative to what would be predicted assuming all stems are composed strictly of intact wood. This study demonstrates not only that stem rot is likely to be a significant source of error in forest AGB estimation, but also that it strongly covaries with tree size, taxonomy, habitat association, and soil resources, underscoring the need to account for tree community composition and edaphic variation in estimating carbon storage in tropical forests.

Hematite from Natural Iron Stones as Microwave Absorbing Material on X-Band Frequency Ranges

NASA Astrophysics Data System (ADS)

Zainuri, Mochamad

2017-05-01

This study has been investigated the effect of hematite as microwave absorbing materials (RAM) on X-Band frequency ranges. Hematite was succesfully processed by coprecipitation method and calcined at 500 °C for 5 hour. It was synthesized from natural iron stones from Tanah Laut, South Kalimantan, Indonesia. The products were characterized by X-ray diffraxtion (XRD), conductivity measurement, Vibrating Sample Magnetometer (VSM), and Vector Network Analyzer (VNA). The result was shown that hematite has conductivity value on (2.5-3).10-7 S/cm and be included as dielectric materials. The hysterisis curve was shown that hematite was a super paramagnetic materials. The product was mixed on paint with procentage 10% of total weight and coated on steel grade AH36 with spray methods. Then, the maximum of reflection loss on x - band’s frequency range (8,2-12,4) GHz was -7 dB on frequency of 10.5 GHz. It mean that almost 50% electromagnetic energy was absorbed by hematite.

Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit.

PubMed

Dehairs, M; Bosmans, H; Desmet, W; Marshall, N W

2017-07-31

Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust their acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC techniques. Phantom thickness covered a water equivalent thickness (WET) range of 2.5 cm to 37.5 cm. Acquisition parameter settings (tube potential, tube current, pulse length, copper filtration and focus size) and phantom entrance air kerma rate (EAKR) were recorded as the thickness changed. Signal difference to noise ratio (SDNR) was measured using a 0.3 mm iron insert centred in the PMMA stack, positioned at the system isocentre. SDNR was then multiplied by modulation transfer function (MTF) based correction factors for focal spot penumbral blurring and motion blurring, to give a spatial frequency dependent parameter, SDNR(u). These MTF correction factors were evaluated for an object motion of 25 mm s -1 and at a spatial frequency of 1.4 mm -1 in the object plane, typical for cardiac imaging. The figure of merit (FOM) was calculated as SDNR(u)²/EAKR for the two ADRC regimes. Using 5P versus 3P technique showed clear improvements over all thicknesses. Averaged over clinically relevant adult WET values (20 cm-37.5 cm), EAKR was reduced by 13% and 27% for fluoroscopy and acquisition modes, respectively, while the SDNR(u) based FOM increased by 16% and 34% for fluoroscopy and acquisition. In conclusion, the generalized FOM, taking into account the influence of focus size and object motion, showed benefit in terms of image quality and patient dose for the 5-parameter control over 3-parameter method for the ADRC programming of dynamic x-ray imaging systems.

Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit

NASA Astrophysics Data System (ADS)

Dehairs, M.; Bosmans, H.; Desmet, W.; Marshall, N. W.

2017-08-01

Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust their acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC techniques. Phantom thickness covered a water equivalent thickness (WET) range of 2.5 cm to 37.5 cm. Acquisition parameter settings (tube potential, tube current, pulse length, copper filtration and focus size) and phantom entrance air kerma rate (EAKR) were recorded as the thickness changed. Signal difference to noise ratio (SDNR) was measured using a 0.3 mm iron insert centred in the PMMA stack, positioned at the system isocentre. SDNR was then multiplied by modulation transfer function (MTF) based correction factors for focal spot penumbral blurring and motion blurring, to give a spatial frequency dependent parameter, SDNR(u). These MTF correction factors were evaluated for an object motion of 25 mm s-1 and at a spatial frequency of 1.4 mm-1 in the object plane, typical for cardiac imaging. The figure of merit (FOM) was calculated as SDNR(u)²/EAKR for the two ADRC regimes. Using 5P versus 3P technique showed clear improvements over all thicknesses. Averaged over clinically relevant adult WET values (20 cm-37.5 cm), EAKR was reduced by 13% and 27% for fluoroscopy and acquisition modes, respectively, while the SDNR(u) based FOM increased by 16% and 34% for fluoroscopy and acquisition. In conclusion, the generalized FOM, taking into account the influence of focus size and object motion, showed benefit in terms of image quality and patient dose for the 5-parameter control over 3-parameter method for the ADRC programming of dynamic x-ray imaging systems.

Acceleration spectra for subduction zone earthquakes

USGS Publications Warehouse

Boatwright, J.; Choy, G.L.

1989-01-01

We estimate the source spectra of shallow earthquakes from digital recordings of teleseismic P wave groups, that is, P+pP+sP, by making frequency dependent corrections for the attenuation and for the interference of the free surface. The correction for the interference of the free surface assumes that the earthquake radiates energy from a range of depths. We apply this spectral analysis to a set of 12 subduction zone earthquakes which range in size from Ms = 6.2 to 8.1, obtaining corrected P wave acceleration spectra on the frequency band from 0.01 to 2.0 Hz. Seismic moment estimates from surface waves and normal modes are used to extend these P wave spectra to the frequency band from 0.001 to 0.01 Hz. The acceleration spectra of large subduction zone earthquakes, that is, earthquakes whose seismic moments are greater than 1027 dyn cm, exhibit intermediate slopes where u(w)???w5/4 for frequencies from 0.005 to 0.05 Hz. For these earthquakes, spectral shape appears to be a discontinuous function of seismic moment. Using reasonable assumptions for the phase characteristics, we transform the spectral shape observed for large earthquakes into the time domain to fit Ekstrom's (1987) moment rate functions for the Ms=8.1 Michoacan earthquake of September 19, 1985, and the Ms=7.6 Michoacan aftershock of September 21, 1985. -from Authors

Echocardiographic and Blood Pressure Characteristics of First-Year Collegiate American-Style Football Players.

PubMed

Crouse, Stephen F; White, Stephanie; Erwin, John P; Meade, Thomas H; Martin, Steven E; Oliver, Jonathan M; Joubert, Dustin P; Lambert, Bradley S; Bramhall, Joe P; Gill, Kory; Weir, David

2016-01-01

Echocardiographic (echo) and blood pressure (BP) reference values may help identify athletes at cardiovascular risk, yet benchmarks are inadequate for collegiate American-style football (ASF) players. Our purpose was to describe echo characteristics and BP values in collegiate ASF athletes compared with normal. First-year players (n = 80, age = 18 ± 1 years, height = 186 ± 7 cm, weight = 100.1 ± 22.0 kg, body mass index = 28.7 ± 5.0), body surface area [BSA] = 2.24 ± 0.25; percentage fat = 16.5 ± 9.7%) were measured for systolic and diastolic BP, and underwent echo procedures by a certified sonographer. Data analyses included simple statistics, Pearson r, frequencies in normal ranges, and t test; α = 0.05. Selected echo measurements (and indexed by BSA) were: left ventricular (LV) internal diameter diastole = 5.3 ± 0.5 cm (2.4 ± 0.3); left atrial diameter = 3.9 ± 0.5 cm (1.8 ± 0.2): LV end-diastolic volume = 138 ± 30 ml (62 ± 11); septal wall thickness = 1.0 ± 0.2 cm (0.5 ± 0.1); LV posterior wall thickness = 1.0 ± 0.1 cm (0.5 ± 0.1), LV mass = 212 ± 46 g (95 ± 18); and relative wall thickness = 0.39 ± 0.07. Correlations between BSA and echo variables were significant (r = 0.26 to 0.50). Indexing by BSA reduced percentages above reference ranges from 36% to 7%. Septal wall thickness index was significantly greater in black (0.5 ± 0.1) than nonblack (0.4 ± 0.1) athletes. Fifty-nine athletes were hypertensive or prehypertensive, and diastolic BP was significantly greater in black (76 ± 10 mm Hg) compared with nonblack athletes (71 ± 8 mm Hg). ASF athletes demonstrated LV wall thicknesses and cavity sizes consistent with sport-training hypertrophy but which were unremarkable when indexed by BSA. Ethnicity generally did not influence echo variables. No ASF players were identified with cardiac dysfunction or disease. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of a 3D Graphene Electrode Dielectrophoretic Device

PubMed Central

Xie, Hongyu; Tewari, Radheshyam; Fukushima, Hiroyuki; Narendra, Jeffri; Heldt, Caryn; King, Julia; Minerick, Adrienne R.

2014-01-01

The design and fabrication of a novel 3D electrode microdevice using 50 µm thick graphene paper and 100 µm double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 µm x 0.7 cm x 2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 μm diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 μm polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete. PMID:24998694

Development of a 3D graphene electrode dielectrophoretic device.

PubMed

Xie, Hongyu; Tewari, Radheshyam; Fukushima, Hiroyuki; Narendra, Jeffri; Heldt, Caryn; King, Julia; Minerick, Adrienne R

2014-06-22

The design and fabrication of a novel 3D electrode microdevice using 50 µm thick graphene paper and 100 µm double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 µm x 0.7 cm x 2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 μm diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 μm polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

Influence of stress on the structural and dielectric properties of rf magnetron sputtered zinc oxide thin film

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Sreenivas, K.; Gupta, Vinay

2008-05-01

Highly c axis oriented zinc oxide (ZnO) thin films have been prepared on 1737 Corning glass substrate by planar rf magnetron sputtering under varying pressure (10-50mTorr) and different oxygen percentage (40%-100%) in reactive gas mixtures. The as-grown ZnO thin films were found to have stress over a wide range from -6×1010to-9×107dynes/cm2. The presence of stress depends strongly on processing conditions, and films become almost stress free under a unique combination of sputtering pressure and reactive gas composition. The studies show a correlation of stress with structural and electrical properties of the ZnO thin film. The stressed films possess high electrical conductivity and exhibits strong dielectric dispersion over a wide frequency (1kHz-1MHz). The dielectric constant ɛ'(ω) of stress free ZnO film was almost frequency independent and was close to the bulk value. The measured value of dc conductivity, σdc(ω) and ac conductivity σac(ω) of stress free ZnO film was 1.3×10-9 and 6.8×10-5Ω-1cm-1, respectively. The observed variation in the structural and electrical properties of ZnO thin film with stress has been analyzed in the light of growth kinetics.

Growth temperature modulated phase evolution and functional characteristics of high quality Pb1-x Lax (Zr0.9Ti0.1)O3 thin films

NASA Astrophysics Data System (ADS)

Kumar, Anuj; Pawar, Shuvam; Singh, Kirandeep; Kaur, Davinder

2018-05-01

In this study, we have reported the influence of growth temperature on perovskite phase evolution in sputtered deposited high quality Pb1-x Lax (Zr0.9 Ti0.1)O3 (PLZT) thin films on Pt/Ti/SiO2/Si substrate. PLZT thin films were fabricated at substrate temperature ranging from 400 to 700 °C. We have investigated the structural, dielectric, ferroelectric and leakage current characteristics of these thin films. XRD patterns reveal that 600 °C is the optimized temperature to deposit highly (110) oriented perovskite phase PLZT thin film. The further increase in temperature (700 °) causes reappearance of additional peaks corresponding to lead deficient pyrochlore phase. All PLZT thin films show decrease in dielectric constant with frequency. However, PLZT thin film fabricated at 600 °C displays dielectric constant ˜532 at 1 MHz frequency which is relatively higher than other deposited thin films. The P-E loops of these PLZT thin films exhibit strong dependence on deposition temperature. The pure perovskite PZLT thin film shows saturation polarization of ˜51.2µC/cm2 and coercive field (2Ec) ˜67.85 kV/cm. These high quality PLZT thin films finds their applications in non-volatile memory and nano-electro-mechanical systems (NEMS).

Nondestructive Evaluation of Young's Moduli of Full-Size wood Laminated Composite Poles

Treesearch

Cheng Piao; Todd F. Shube; Chung Y. Hse; R.C. Tang

2004-01-01

An exploratory study was conducted to evaluate the Young's moduli of wood laminated composite poles (LCP) by using a free transverse vibration method. Full-size LCP, 6.1 m long and 10.2 cm in diameter, were lab-fabricated with 9 and/or 12 southern yellow pine [SYP] strips of thickness, 1.9 cm, 2.9 cm and 3.8 cm. The frequency of free transverse vibration in a LCP...

Probability of cell hits in selected organs and tissues by high-LET particles at the ISS orbit

NASA Technical Reports Server (NTRS)

Yasuda, H.; Komiyama, T.; Fujitaka, K.; Badhwar, G. D. (Principal Investigator)

2002-01-01

The fluence of high-LET particles (HLP) with LET infinity H2O greater than 15 keV micrometers-1 in selected organs and tissues were measured with plastic nuclear track detectors using a life-size human phantom on the 9th Shuttle-Mir Mission (STS-91). The planar-track fluence of HLP during the 9.8-day mission ranged from 1.9 x 10(3) n cm-2 (bladder) to 5.1 x 10(3) n cm-2 (brain) by a factor of 2.7. Based on these data, a probability of HLP hits to a matured cell of each organ or tissue was roughly estimated for a 90-day ISS mission. In the calculation, all cells were assumed to be spheres with a geometric cross-sectional area of 500 micrometers2 and the cell-hit frequency from isotropic space radiation can be described by the Poisson-distribution function. As results, the probability of one or more than 1 hit to a single cell by HLP for 90 days ranged from 17% to 38%; that of two or more than 2 hits was estimated to be 1.3-8.2%. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

High-rate in-plane micro-supercapacitors scribed onto photo paper using in situ femtolaser-reduced graphene oxide/Au nanoparticle microelectrodes

DOE PAGES

Li, Ruozhou; Peng, Rui; Tumuluri, Uma; ...

2016-02-11

Direct laser-reduction of graphene oxide (GO), as a lithography-free approach, has been proven effective in manufacturing in-plane micro-supercapacitors (MSCs) with fast ion diffusion. However, the power density and the charge/discharge rate are still limited by the relatively low conductivity of electrodes. Here, we report a facile approach by exploiting femtolaser in situ reduction of the hydrated GO and chloroauric acid (HAuCl 4) nanocomposite simultaneously, which incorporates both the patterning of rGO electrodes and the fabrication of Au current collectors in a single step. These flexible MSCs boast achievements of one-hundred fold increase in electrode conductivities of up to 1.1 ×more » 10 6 S m –1, which provide superior rate capability (50% for the charging rate increase from 0.1 V s –1 to 100 V s –1), sufficiently high frequency responses (362 Hz, 2.76 ms time constant), and large specific capacitances of 0.77 mF cm –2 (17.2 F cm –3 for volumetric capacitance) at 1 V s –1, and 0.46 mF cm –2 (10.2 F cm –3) at 100 V s –1. The use of photo paper substrates enables the flexibility of this fabrication protocol. Moreover, proof-of-concept 3D MSCs are demonstrated with enhanced areal capacitance (up to 3.84 mF cm –2 at 1 V s –1) while keeping high rate capabilities. As a result, this prototype of all solid-state MSCs demonstrates the broad range of potentials of thin-film based energy storage device applications for flexible, portable, and wearable electronic devices that require a fast charge/discharge rate and high power density.« less

High-rate in-plane micro-supercapacitors scribed onto photo paper using in situ femtolaser-reduced graphene oxide/Au nanoparticle microelectrodes

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

Li, Ruozhou; Peng, Rui; Tumuluri, Uma

Direct laser-reduction of graphene oxide (GO), as a lithography-free approach, has been proven effective in manufacturing in-plane micro-supercapacitors (MSCs) with fast ion diffusion. However, the power density and the charge/discharge rate are still limited by the relatively low conductivity of electrodes. Here, we report a facile approach by exploiting femtolaser in situ reduction of the hydrated GO and chloroauric acid (HAuCl 4) nanocomposite simultaneously, which incorporates both the patterning of rGO electrodes and the fabrication of Au current collectors in a single step. These flexible MSCs boast achievements of one-hundred fold increase in electrode conductivities of up to 1.1 ×more » 10 6 S m –1, which provide superior rate capability (50% for the charging rate increase from 0.1 V s –1 to 100 V s –1), sufficiently high frequency responses (362 Hz, 2.76 ms time constant), and large specific capacitances of 0.77 mF cm –2 (17.2 F cm –3 for volumetric capacitance) at 1 V s –1, and 0.46 mF cm –2 (10.2 F cm –3) at 100 V s –1. The use of photo paper substrates enables the flexibility of this fabrication protocol. Moreover, proof-of-concept 3D MSCs are demonstrated with enhanced areal capacitance (up to 3.84 mF cm –2 at 1 V s –1) while keeping high rate capabilities. As a result, this prototype of all solid-state MSCs demonstrates the broad range of potentials of thin-film based energy storage device applications for flexible, portable, and wearable electronic devices that require a fast charge/discharge rate and high power density.« less

Excited stilbene: intramolecular vibrational redistribution and solvation studied by femtosecond stimulated Raman spectroscopy.

PubMed

Weigel, A; Ernsting, N P

2010-06-17

Excited-state relaxation of cis- and trans-stilbene is traced with femtosecond stimulated Raman spectroscopy, exploiting S(n) <-- S(1) resonance conditions. For both isomers, decay in Raman intensity, shift of spectral positions, and broadening of the bands indicate intramolecular vibrational redistribution (IVR). In n-hexane this process effectively takes 0.5-0.7 ps. Analysis of the intensity decay allows us to further distinguish two phases for trans-stilbene: fast IVR within a subset of modes (approximately 0.3 ps) followed by slower equilibration over the full vibrational manifold (approximately 0.9 ps). In acetonitrile IVR completes with 0.15 ps; this acceleration may originate from symmetry breakage induced by the polar solvent. Another process, dynamic solvation by acetonitrile, is seen as spectral narrowing and characteristic band shifts of the C=C stretch and phenyl bending modes with 0.69 ps. Wavepacket motion is observed in both isomers as oscillation of low-frequency bands with their pertinent mode frequency (90 or 195 cm(-1) in trans-stilbene; 250 cm(-1) in cis-stilbene). Anharmonic coupling shows up as a modulation of high-frequency peak positions by phenyl/ethylene torsion modes of 57 and 90 cm(-1). Decay and shift of the 90 cm(-1) inverse Raman band within the first 0.3 ps suggests a gradual involvement of phenyl/ethylene torsion in relaxation. In cis- and trans-stilbene, low-frequency spectral changes are found within 0.15 ps, indicating an additional ultrafast process.

Global Model for Asymmetric, Diode-Type Dual Frequency Capacitive Discharge

NASA Astrophysics Data System (ADS)

Kim, Jisoo; Lieberman, M. A.; Lichtenberg, A. J.

2003-10-01

Dual frequency capacitive reactors can have desirable properties for dielectric etch: low cost, robust uniformity over large areas, and control of dissociation. In the ideal case, the high frequency power controls the plasma density (ion flux) and the low frequency voltage controls the ion bombarding energy. Typical operating conditions are: discharge radius 15-30 cm, length 1-3 cm, pressure 30-200 mTorr, high frequency 27.1-160 MHz, low frequency 2-13.6 MHz, and powers of 500-3000 W for both high and low frequencies. The decoupling of the high and low frequencies is an important feature of dual frequency capacitive discharges. In this work, we describe a global (volume-averaged) model having different top and bottom plate areas that incorporates particle balance, and ohmic and stochastic heating for high and low frequencies. The model is used to obtain the decoupling of high and low frequencies and to investigate limitations to ideal decoupling. Support provided by Lam Research, NSF Grant ECS-0139956, California industries, and UC-SMART Contract SM99-10051.

Intrafraction Bladder Motion in Radiation Therapy Estimated From Pretreatment and Posttreatment Volumetric Imaging

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

Foroudi, Farshad, E-mail: farshad.foroudi@petermac.org; Pham, Daniel; Bressel, Mathias

2013-05-01

Purpose: The use of image guidance protocols using soft tissue anatomy identification before treatment can reduce interfractional variation. This makes intrafraction clinical target volume (CTV) to planning target volume (PTV) changes more important, including those resulting from intrafraction bladder filling and motion. The purpose of this study was to investigate the required intrafraction margins for soft tissue image guidance from pretreatment and posttreatment volumetric imaging. Methods and Materials: Fifty patients with muscle-invasive bladder cancer (T2-T4) underwent an adaptive radiation therapy protocol using daily pretreatment cone beam computed tomography (CBCT) with weekly posttreatment CBCT. A total of 235 pairs of pretreatmentmore » and posttreatment CBCT images were retrospectively contoured by a single radiation oncologist (CBCT-CTV). The maximum bladder displacement was measured according to the patient's bony pelvis movement during treatment, intrafraction bladder filling, and bladder centroid motion. Results: The mean time between pretreatment and posttreatment CBCT was 13 minutes, 52 seconds (range, 7 min 52 sec to 30 min 56 sec). Taking into account patient motion, bladder centroid motion, and bladder filling, the required margins to cover intrafraction changes from pretreatment to posttreatment in the superior, inferior, right, left, anterior, and posterior were 1.25 cm (range, 1.19-1.50 cm), 0.67 cm (range, 0.58-1.12 cm), 0.74 cm (range, 0.59-0.94 cm), 0.73 cm (range, 0.51-1.00 cm), 1.20 cm (range, 0.85-1.32 cm), and 0.86 cm (range, 0.73-0.99), respectively. Small bladders on pretreatment imaging had relatively the largest increase in pretreatment to posttreatment volume. Conclusion: Intrafraction motion of the bladder based on pretreatment and posttreatment bladder imaging can be significant particularly in the anterior and superior directions. Patient motion, bladder centroid motion, and bladder filling all contribute to changes between pretreatment and posttreatment imaging. Asymmetric expansion of CTV to PTV should be considered. Care is required in using image-guided radiation therapy protocols that reduce CTV to PTV margins based only on daily pretreatment soft tissue position.« less

The nighttime ionosphere of Mars from Mars-4 and Mars-5 radio occultation dual-frequency measurements

NASA Technical Reports Server (NTRS)

Savich, N. A.; Samovol, V. A.; Vasilyev, M. B.; Vyshlov, A. S.; Samoznaev, L. N.; Sidorenko, A. I.; Shtern, D. Y.

1976-01-01

Dual frequency radio sounding of the Martian nighttime ionosphere was carried out during the exits from behind the planet of the Mars-4 spacecraft on February 2, 1974 and the Mars-5 spacecraft on February 18, 1974. In these experiments, the spacecraft transmitter emitted two coherent monochromatic signals in decimeter and centimeter wavelength ranges. At the Earth receiving station, the reduced phase difference (or frequencies) of these signals was measured. The nighttime ionosphere of Mars measured in both cases had a peak electron density of approximately 5 X 1,000/cu cm at an altitude of 110 to 130 km. At the times of spacecraft exit, the solar zenith angles at the point of occultation were 127 deg and 106 deg, respectively. The height profiles of electron concentration were obtained assuming spherical symmetry of the Martian ionosphere.

Stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor

NASA Astrophysics Data System (ADS)

Ferdous, T.; Salahuddin, M.; Amin, M. R.; Salimullah, M.

1995-09-01

In the present paper we have studied the stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor. The nonlinearity in the low-frequency ion-acoustic wave arises through the ponderomotive force on both electrons and holes. The high-frequency nonlinearity arises through the nonlinear current density. For typical plasma parameters in compensated Ge, ɛL=16, T0=77 K, n00=1017 cm-3, Bs=60 kG, θ=30°, laser power density corresponding to a CO2 laser ~=0.1 MW cm-2, the growth rate of the low-frequency ion-acoustic wave turns out to be ~=107 rad sec-1.

Local vibrational modes of the water dimer - Comparison of theory and experiment

NASA Astrophysics Data System (ADS)

Kalescky, R.; Zou, W.; Kraka, E.; Cremer, D.

2012-12-01

Local and normal vibrational modes of the water dimer are calculated at the CCSD(T)/CBS level of theory. The local H-bond stretching frequency is 528 cm-1 compared to a normal mode stretching frequency of just 143 cm-1. The adiabatic connection scheme between local and normal vibrational modes reveals that the lowering is due to mass coupling, a change in the anharmonicity, and coupling with the local HOH bending modes. The local mode stretching force constant is related to the strength of the H-bond whereas the normal mode stretching force constant and frequency lead to an erroneous underestimation of the H-bond strength.

A Bayesian analysis of redshifted 21-cm H I signal and foregrounds: simulations for LOFAR

NASA Astrophysics Data System (ADS)

Ghosh, Abhik; Koopmans, Léon V. E.; Chapman, E.; Jelić, V.

2015-09-01

Observations of the epoch of reionization (EoR) using the 21-cm hyperfine emission of neutral hydrogen (H I) promise to open an entirely new window on the formation of the first stars, galaxies and accreting black holes. In order to characterize the weak 21-cm signal, we need to develop imaging techniques that can reconstruct the extended emission very precisely. Here, we present an inversion technique for LOw Frequency ARray (LOFAR) baselines at the North Celestial Pole (NCP), based on a Bayesian formalism with optimal spatial regularization, which is used to reconstruct the diffuse foreground map directly from the simulated visibility data. We notice that the spatial regularization de-noises the images to a large extent, allowing one to recover the 21-cm power spectrum over a considerable k⊥-k∥ space in the range 0.03 Mpc-1 < k⊥ < 0.19 Mpc-1 and 0.14 Mpc-1 < k∥ < 0.35 Mpc-1 without subtracting the noise power spectrum. We find that, in combination with using generalized morphological component analysis (GMCA), a non-parametric foreground removal technique, we can mostly recover the spherical average power spectrum within 2σ statistical fluctuations for an input Gaussian random root-mean-square noise level of 60 mK in the maps after 600 h of integration over a 10-MHz bandwidth.

A system for measuring complex dielectric properties of thin films at submillimeter wavelengths using an open hemispherical cavity and a vector network analyzer

NASA Astrophysics Data System (ADS)

Rahman, Rezwanur; Taylor, P. C.; Scales, John A.

2013-08-01

Quasi-optical (QO) methods of dielectric spectroscopy are well established in the millimeter and submillimeter frequency bands. These methods exploit standing wave structure in the sample produced by a transmitted Gaussian beam to achieve accurate, low-noise measurement of the complex permittivity of the sample [e.g., J. A. Scales and M. Batzle, Appl. Phys. Lett. 88, 062906 (2006);, 10.1063/1.2172403 R. N. Clarke and C. B. Rosenberg, J. Phys. E 15, 9 (1982);, 10.1088/0022-3735/15/1/002 T. M. Hirovnen, P. Vainikainen, A. Lozowski, and A. V. Raisanen, IEEE Trans. Instrum. Meas. 45, 780 (1996)], 10.1109/19.516996. In effect the sample itself becomes a low-Q cavity. On the other hand, for optically thin samples (films of thickness much less than a wavelength) or extremely low loss samples (loss tangents below 10-5) the QO approach tends to break down due to loss of signal. In such a case it is useful to put the sample in a high-Q cavity and measure the perturbation of the cavity modes. Provided that the average mode frequency divided by the shift in mode frequency is less than the Q (quality factor) of the mode, then the perturbation should be resolvable. Cavity perturbation techniques are not new, but there are technological difficulties in working in the millimeter/submillimeter wave region. In this paper we will show applications of cavity perturbation to the dielectric characterization of semi-conductor thin films of the type used in the manufacture of photovoltaics in the 100 and 350 GHz range. We measured the complex optical constants of hot-wire chemical deposition grown 1-μm thick amorphous silicon (a-Si:H) film on borosilicate glass substrate. The real part of the refractive index and dielectric constant of the glass-substrate varies from frequency-independent to linearly frequency-dependent. We also see power-law behavior of the frequency-dependent optical conductivity from 316 GHz (9.48 cm-1) down to 104 GHz (3.12 cm-1).

Dielectric method of high-resolution gas hydrate estimation

NASA Astrophysics Data System (ADS)

Sun, Y. F.; Goldberg, D.

2005-02-01

In-situ dielectric properties of natural gas hydrate are measured for the first time in the Mallik 5L-38 Well in the Mackenzie Delta, Canada. The average dielectric constant of the hydrate zones is 9, ranging from 5 to 20. The average resistivity is >5 ohm.m in the hydrate zones, ranging from 2 to 10 ohm.m at a 1.1 GHz dielectric tool frequency. The dielectric logs show similar trends with sonic and induction resistivity logs, but exhibits inherently higher vertical resolution (<5 cm). The average in-situ hydrate saturation in the well is about 70%, ranging from 20% to 95%. The dielectric estimates are overall in agreement with induction estimates but the induction log tends to overestimate hydrate content up to 15%. Dielectric estimates could be used as a better proxy of in-situ hydrate saturation in modeling hydrate dynamics. The fine-scale structure in hydrate zones could help reveal hydrate formation history.

A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

PubMed

Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

2008-04-03

Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.

Calculation of far wing of allowed spectra: The water continuum

NASA Technical Reports Server (NTRS)

Tipping, R. H.; Ma, Q.

1995-01-01

A far-wing line shape theory based on the binary collision and quasistatic approximations that is applicable for both the low- and high-frequency wings of allowed vibrational-rotational lines has been developed. This theory has been applied in order to calculate the frequency and temperature dependence of the continuous absorption coefficient for frequencies up to 10,000 cm(exp -1) for pure H2O and for H2O-N2 mixtures. The calculations are made assuming an interaction potential consisting of an isotropic Lennard-Jones part and the leading long-range anisotropic part, and utilizing the measured line strengths and transition frequencies. The results compare well with existing data, both in magnitude and in temperature dependence. This leads us to the conclusion that although dimer and collision-induced absorptions are present, the primary mechanism responsible for the observed water continuum is the far-wing absorption of allowed lines. Recent progress on near-wing corrections to the theory and validations with recent laboratory measurements are discussed briefly.

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

DOE PAGES

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi; ...

2017-10-01

This article describes the design and construction of a compact, “user-friendly” polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, frommore » the surface bound species. A spectral frequency range between 1000 cm -1 and 4000 cm -1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ~2 min at 4 cm -1 resolution, we have also acquired higher resolution spectra at 0.25 cm -1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a “vacuum suitcase” that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.« less

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

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

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi

This article describes the design and construction of a compact, “user-friendly” polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, frommore » the surface bound species. A spectral frequency range between 1000 cm -1 and 4000 cm -1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ~2 min at 4 cm -1 resolution, we have also acquired higher resolution spectra at 0.25 cm -1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a “vacuum suitcase” that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.« less

Study of terahertz-radiation-induced DNA damage in human blood leukocytes

NASA Astrophysics Data System (ADS)

Angeluts, A. A.; Gapeyev, A. B.; Esaulkov, M. N.; Kosareva, O. G.; Matyunin, S. N.; Nazarov, M. M.; Pashovkin, T. N.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

2014-03-01

We have carried out the studies aimed at assessing the effect of terahertz radiation on DNA molecules in human blood leukocytes. Genotoxic testing of terahertz radiation was performed in three different oscillation regimes, the blood leukocytes from healthy donors being irradiated for 20 minutes with the mean intensity of 8 - 200 μW cm-2 within the frequency range of 0.1 - 6.5 THz. Using the comet assay it is shown that in the selected regimes such radiation does not induce a direct DNA damage in viable human blood leukocytes.

Steady-state unbalance response of a three-disk flexible rotor on flexible, damped supports

NASA Technical Reports Server (NTRS)

Cunningham, R. E.

1977-01-01

Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31 000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalance applied varied from 0.62 to 15.1 gm-cm.

Boson mode, Medium Range Structure and Intermediate Phase (IP) in (Na2O)x(B2O3)1-x glasses

NASA Astrophysics Data System (ADS)

Vignarooban, K.; Boolchand, P.; Micoulaut, M.; Malki, M.

2012-02-01

Raman scattering of titled glasses are examined using a T64000 Dispersive system. Scattering strengths of the Boson mode (40 cm-1, 70 cm-1) and the Boroxyl ring (BR) mode (808 cm-1) are found to decrease with increasing x at the same rate in the 0 < x < 20% soda range. Apparently, the 2D character of BRs embedded in a 3D network gives rise to the Boson mode.ootnotetextM. Flores-Ruiz and G. Naumis, PRB, 2011. 83: p. 184204 The triad of modes (705, 740, 770 cm-1) near the 808 cm-1 mode are found to display a maximum in scattering strength near x = 37% (705 cm-1), 33% (740 cm-1) and 25% (770 cm-1), suggesting that these are also ring modes of Na-tripentaborate (STPB), Na-diborate (SDB) and Na-triborate (STB) super-structures. Variations in Raman scattering strengths also suggest that STB percolate near x = 20%, the stress transition, while the STPB and SDTB percolate near x = 40%, the rigidity transition. These transitions were inferred from m-DSC experiments that show an intermediate phase in the 20% < x < 40% range in dry and homogeneous glasses.

Stable room-temperature LiF:F2+* tunable color-center laser for the 830-1060-nm spectral range pumped by second-harmonic radiation from a neodymium laser

NASA Astrophysics Data System (ADS)

Ter-Mikirtychev, V. V.

1995-09-01

Simultaneous photostability and thermostability of a room-temperature LiF:F2+ * tunable color-center laser, with an operating range over 830-1060 nm, pumped by second-harmonic radiation of a YAG:Nd3+ laser with a 532-nm wavelength has been achieved. The main lasing characteristics of the obtained LiF:F2+* laser have been measured. Twenty-five percent real efficiency in a nonselective resonator cavity and 15% real efficiency in a selective resonator cavity have been obtained. The stable LiF:F2 +* laser operates at a 1-100-Hz pulse-repetition rate with a 15-ns pulse duration, a 1-1.5-cm-1 narrow-band oscillation bandwidth, and divergency of better than 6 \\times 10-4. Doubling the fundamental frequencies of F2+ * oscillation made it possible to obtain stable blue-green tunable radiation over the 415-530-nm range.

Effect of zinc substitution on the structural, electrical and magnetic properties of nano-structured Ni0.5Co0.5Fe2O4 ferrites

NASA Astrophysics Data System (ADS)

Babu, K. Vijaya; Sailaja, B.; Jalaiah, K.; Shibeshi, Paulos Taddesse; Ravi, M.

2018-04-01

A series of Ni0.5Co0.5-xZnxFe2O4 (x = 0, 0.02, 0.04 and 0.06) nanoferrites were synthesized by sol-gel method using citric acid as chelating reagent. The synthesized ferrite systems are characterized by XRD, SEM, FTIR, ESR and dielectric techniques. The formation of cubic spinel phase belonging to space group Fd3m is identified from the X-ray diffraction patterns. SEM showed the particles are in spherical shape with an average grain size 5-10 nm. FTIR spectra portrait the fundamental absorption bands in the range 400-600 cm-1 relating to octahedral and tetrahedral sites. Dielectric properties are investigated over the frequency range of 20 Hz to 1 MHz at room temperature. A difference in dielectric constant (εr) and dissipation factor (tanδ) of the ferrites has been observed. The dielectric constant and dielectric loss tangent decreases exponentially with increase in frequency. The obtained results are good agreeing with the reported values.

The Group Delay and Suppression Pattern of the Cochlear Microphonic Potential Recorded at the Round Window

PubMed Central

He, Wenxuan; Porsov, Edward; Kemp, David; Nuttall, Alfred L.; Ren, Tianying

2012-01-01

Background It is commonly assumed that the cochlear microphonic potential (CM) recorded from the round window (RW) is generated at the cochlear base. Based on this assumption, the low-frequency RW CM has been measured for evaluating the integrity of mechanoelectrical transduction of outer hair cells at the cochlear base and for studying sound propagation inside the cochlea. However, the group delay and the origin of the low-frequency RW CM have not been demonstrated experimentally. Methodology/Principal Findings This study quantified the intra-cochlear group delay of the RW CM by measuring RW CM and vibrations at the stapes and basilar membrane in gerbils. At low sound levels, the RW CM showed a significant group delay and a nonlinear growth at frequencies below 2 kHz. However, at high sound levels or at frequencies above 2 kHz, the RW CM magnitude increased proportionally with sound pressure, and the CM phase in respect to the stapes showed no significant group delay. After the local application of tetrodotoxin the RW CM below 2 kHz became linear and showed a negligible group delay. In contrast to RW CM phase, the BM vibration measured at location ∼2.5 mm from the base showed high sensitivity, sharp tuning, and nonlinearity with a frequency-dependent group delay. At low or intermediate sound levels, low-frequency RW CMs were suppressed by an additional tone near the probe-tone frequency while, at high sound levels, they were partially suppressed only at high frequencies. Conclusions/Significance We conclude that the group delay of the RW CM provides no temporal information on the wave propagation inside the cochlea, and that significant group delay of low-frequency CMs results from the auditory nerve neurophonic potential. Suppression data demonstrate that the generation site of the low-frequency RW CM shifts from apex to base as the probe-tone level increases. PMID:22470560

Application of Fourier transform infrared (FTIR) spectroscopy for the identification of wheat varieties.

PubMed

Amir, Rai Muhammad; Anjum, Faqir Muhammad; Khan, Muhammad Issa; Khan, Moazzam Rafiq; Pasha, Imran; Nadeem, Muhammad

2013-10-01

Quality characteristics of wheat are determined by different physiochemical and rheological analysis by using different AACC methods. AACC methods are expensive, time consuming and cause destruction of samples. Fourier transforms infrared (FTIR) spectroscopy is one of the most important and emerging tool used for analyzing wheat for different quality parameters. This technique is rapid and sensitive with a great variety of sampling techniques. In the present study different wheat varieties were analyzed for quality assessment and were also characterized by using AACC methods and FTIR technique. The straight grade flour was analyzed for physical, chemical and rheological properties by standard methods and results were obtained. FTIR works on the basis of functional groups and provide information in the form of peaks. On basis of peaks the value of moisture, protein, fat, ash, carbohydrates and hardness of grain were determined. Peaks for water were observed in the range 1,640 cm(-1) and 3,300 cm(-1) on the basis of functional group H and OH. Protein was observed in the range from 1,600 cm(-1) to 1,700 cm(-1) and 1,550 cm(-1) to 1,570 cm(-1) on the basis of bond amide I and amide II respectively. Fat was also observed within these ranges but on the basis of C-H bond and also starch was observed in the range from 2,800 and 3,000 cm(-1) (C-H stretch region) and in the range 3,000 and 3,600 cm(-1) (O-H stretch region). As FTIR is a fast tool it can be easily emplyed for wheat varieties identification according to a set criterion.

Terahertz acoustic phonon detection from a compact surface layer of spherical nanoparticles powder mixture of aluminum, alumina and multi-walled carbon nanotube

NASA Astrophysics Data System (ADS)

Abouelsayed, A.; Ebrahim, M. R.; El hotaby, W.; Hassan, S. A.; Al-Ashkar, Emad

2017-10-01

We present terahertz spectroscopy study on spherical nanoparticles powder mixture of aluminum, alumina, and MWCNTs induced by surface mechanical attrition treatment (SMAT) of aluminum substrates. Surface alloying of AL, Al2O3 0.95% and MWCNTs 0.05% powder mixture was produced during SMAT process, where a compact surface layer of about 200 μm due to ball bombardment was produced from the mixture. Al2O3 alumina powder played a significant role in MWCNTs distribution on surface, those were held in deformation surface cites of micro-cavities due to SMAT process of Al. The benefits are the effects on resulted optical properties of the surface studied at the terahertz frequency range due to electrical isolation confinement effects and electronic resonance disturbances exerted on Al electronic resonance at the same range of frequencies. THz acoustic phonon around 0.53-0.6 THz (17-20 cm-1) were observed at ambient conditions for the spherical nanoparticles powder mixture of Al, Al2O3 and MWCNTs. These results suggested that the presence of Al2O3 and MWCNTs during SMAT process leads to the optically detection of such acoustic phonon in the THz frequency range.

Line Intensity Measurements in 14N 216O and Their Treatment Using the Effective Dipole Moment Approach . I. The 4300- to 5200-cm -1 Region

NASA Astrophysics Data System (ADS)

Daumont, L.; Auwera, J. Vander; Teffo, J.-L.; Perevalov, V. I.; Tashkun, S. A.

2001-08-01

This work continues a series of publications devoted to the application of the effective operator approach to the vibrational-rotational treatment of linear triatomic molecules, aiming at the analysis and prediction of their infrared spectra. In that frame work, we have started a large-scale work aiming at the global description of line intensities of cold and hot bands of 14N216O in its ground electronic state in the spectral range above 3600 cm-1. In 14N216O, vibrational interacting levels group in polyads as a result of the relation 2ω1≈4ω2≈ω3 existing between the harmonic frequencies. The polyads are identified by the so-called polyad number P=2V1+V2+4V3. The work described in the present paper concerns bands associated with transitions corresponding to ΔP=7, 8, and 9. The absorption spectra of N2O at room temperature have been recorded at a resolution of 0.007 cm-1 in the range from 4300 to 5200 cm-1 using a Bruker IFS120HR Fourier transform spectrometer. Sample pressure/absorption path length products ranging from 7 to 1753 mbar × m have been used. More than 3000 absolute line intensities have been measured in 66 different bands belonging to the ΔP=7, 8, and 9 series. Dicke narrowing has been observed in the high-pressure spectra. Using wavefunctions previously determined from a global fit of an effective Hamiltonian to about 18,000 line positions (S. A. Tashkun, V. I. Perevalov, and J.-L. Teffo to be published), the experimental intensities measured in this work and by R. A. Toth (J. Mol. Spectrosc.197, 158-187 (1999)) were fitted to 47 parameters of a corresponding effective dipole moment, with residuals very close to the experimental uncertainty. Exa mples are given showing that the modeling reproduces intensities of perturbed lines well.

Lack of maintenance of shortwave diathermy equipment has a negative impact on power output.

PubMed

Guirro, Rinaldo Roberto de Jesus; Guirro, Elaine Caldeira de Oliveira; Alves de Sousa, Natanael Teixeira

2014-04-01

Although shortwave diathermy has been widely used by physiotherapists, there are a few studies assessing the performance of the equipment in use. The aim of the present study was to evaluate the procedures adopted by physiotherapists as users of shortwave diathermy continuous (CSWD), as well as to measure the power output and frequency of CSWD equipment. [Subjects and Methods] Twenty-three physical therapists were interviewed and 23 CSWD equipment were evaluated. Admeasurement was carried out by using a standard phantom to simulate the electrode-skin distance, which ranged from 0.5 to 3.0 cm. Data analysis was performed by using descriptive statistics, ANOVA, and a post-hoc Tukey's test or Pearson's correlation coefficient. [Results] The questionnaires showed that 48% of the interviewees use the correct electrode-skin distance, 70% use a single electrical outlet, and 35% use a grounded electrical outlet, and that 48% of the physiotherapy tables and 61% of the plinths were made of wood. However, only 13% of the interviewees perform yearly preventive maintenance. The highest power (95.56 W) was achieved at electrode-skin distances ranging from 1.0 to 1.5 cm, with distances of 2.5 cm and 3.0 cm being null in four and eight equipment, respectively. There was a negative correlation between power output and electrode-skin distance as well as between power output and purchase date. [Conclusion] The physiotherapists involved in this study had inadequate knowledge about the correct use of CSWD equipment, which may adversely affect its performance and patient safety.

ELECTRIC IMPEDANCE OF ASTERIAS EGGS

PubMed Central

Cole, Kenneth S.; Cole, Robert H.

1936-01-01

The alternating current resistance and capacity of suspensions of unfertilized eggs of Asterias forbesi have been measured at frequencies from one thousand to sixteen million cycles per second. The plasma membrane of the egg has a static capacity of 1.10µf/cm.2 which is practically independent of frequency. The suspensions show a capacity dependent on frequency at low frequencies which may be attributable to surface conductance. The specific resistance of the cytoplasm is between 136 and 225 ohm cm. (4 to 7 times sea water), indicating a relatively high concentration of non-electrolytes. At frequencies above one million cycles there is definite evidence of another element of which the nucleus is presumably a part. PMID:19872951

Absorption spectrum and absorption cross sections of the 2ν1 band of HO2 between 20 and 760 Torr air in the range 6636 and 6639 cm-1

NASA Astrophysics Data System (ADS)

Assaf, Emmanuel; Liu, Lu; Schoemaecker, Coralie; Fittschen, Christa

2018-05-01

The absorption spectrum of HO2 radicals has been measured in the range 6636-6639 cm-1 at several pressures between 20 and 760 Torr of air. Absolute absorption cross sections of the strongest line at around 6638.2 cm-1 have been determined from kinetic measurements, taking advantage of the well known rate constant of the self-reaction. Peak absorption cross sections of 22.6, 19.5, 14.4, 7.88, 5.12 and 3.23 × 10-20 cm2 were obtained at 20, 50, 100, 200, 400 and 760 Torr, respectively. By fitting these data, an empirical expression has been obtained for the absorption cross section of HO2 in the range 20-760 Torr air: σ6638.2cm-1 = 1.18 × 10-20 + (2.64 × 10-19 × (1-exp (-63.1/p (Torr))) cm2.

Solubility, Partitioning, and Speciation of Carbon in Shallow Magma Oceans of Terrestrial Planets Constrained by High P-T Experiments

NASA Astrophysics Data System (ADS)

Chi, H.; Dasgupta, R.; Shimizu, N.

2011-12-01

Deep planetary volatile cycles have a critical influence on planetary geodynamics, atmospheres, climate, and habitability. However, the initial conditions that prevailed in the early, largely molten Earth and other terrestrial planets, in terms of distribution of volatiles between various reservoirs - metals, silicates, and atmosphere - remains poorly constrained. Here we investigate the solubility, partitioning, and speciation of carbon-rich volatile species in a shallow magma ocean environment, i.e., in equilibrium with metallic and silicate melts. A series of high pressure-temperature experiments using a piston cylinder apparatus were performed at 1-3 GPa, 1500-1800 °C on synthetic basaltic mixtures + Fe-Ni metal powders contained in graphite capsules. All the experiments produced glassy silicate melt pool in equilibrium with quenched metal melt composed of dendrites of cohenite and kamacite. Major element compositions of the resulting phases and the carbon content of metallic melts were analyzed by EPMA at NASA-JSC. Carbon and hydrogen concentrations of basaltic glasses were determined using Cameca IMS 1280 SIMS at WHOI and speciation of dissolved volatiles was constrained using FTIR and Raman spectroscopy at Rice University. Based on the equilibria - FeO (silicate melt) = Fe (metal alloy melt) + 1/2O2, we estimate the oxygen fugacity of our experiments in the range of ΔIW of -1 to -2. FTIR analysis on doubly polished basaltic glass chips suggests that the concentrations of dissolved CO32- or molecular CO2 are negligible in graphite and metal saturated reduced conditions, whereas the presence of dissolved OH- is evident from the asymmetric peak at 3500 cm-1. Collected Raman spectra of basaltic glasses in the frequency range of 200-4200 cm-1 suggest that hydrogen is present both as dissolved OH- species (band at 3600 cm-1) and as molecular H2 (band near 4150 cm-1) for all of our experiments. Faint peaks near 2915 cm-1 and consistent peaks near 740 cm-1 suggest that possible carbon species in our reduced glasses are likely minor CH4 and Si-C, respectively and are consistent with the recent solubility studies at reduced conditions [1,2]. Carbon solubility (calibrated using 12C/30Si) at graphite saturation in our reduced basaltic glasses is only in the range 20-100 ppm C, with H2O contents in the range of 0.2-0.7 wt.%. In contrast to the low dissolved carbon concentration in the basaltic silicate melts, carbon solubility in quenched metallic melts vary in the range of 5-7 wt.%. Our preliminary work indicates that the solubility of carbon in reduced basaltic melts relevant for early magma conditions may be several orders of magnitude lower compared to the solubility of carbon in modern terrestrial basalts. This coupled with significant solubility of carbon in Fe-Ni metallic melt suggests that most of magma ocean carbon was likely partitioned into deep metallic melts. Further metal-silicate experiments with more depolymerized basaltic melts of variable compositions are underway and will be presented. [1] Kadik et al. JPetrol 45, 1297-1310, 2004; [2] Kadik et al. Geochem Int 44, 33-47, 2006.

Characterization of the SAR-distribution of the Sigma-60 applicator for regional hyperthermia using a Schottky diode sheet.

PubMed

Van Rhoon, G C; Van Der Heuvel, D J; Ameziane, A; Rietveld, P J M; Volenec, K; Van Der Zee, J

2003-01-01

Characterization of the performance of an hyperthermia applicator by phantom experiments is an essential aspect of quality assurance in hyperthermia. The objective of this study was to quantitatively characterize the energy distribution of the Sigma-60 applicator of the BSD2000 phased array system operated within the normal frequency range of 70-120 MHz. Additionally, the accuracy of the flexible Schottky diode sheet to measure E-field distributions was assessed. The flexible Schottky diode sheet (SDS) consists of 64 diodes mounted on a flexible 125 microm thick polyester foil. The diodes are connected through high resistive wires to the electronic readout system. With the SDS E-field distributions were measured with a resolution of 2.5 x 2.5 cm in a cylindrical phantom, diameter of 26 cm and filled with saline water (2 g/l). The phantom was positioned symmetrically in the Sigma-60 applicator. RF-power was applied to the 4-channel applicator with increasing steps from 25W to a total output of 400 W. The complete system to measure the E-field distribution worked fine and reliably within the Sigma-60 applicator. The E-field distributions measured showed that the longitudinal length of the E-field distribution is more or less constant, e.g. 21-19 cm, over the frequency range of 70-120 MHz, respectively. As expected, the radial E-field distributions show a better focusing towards the centre of the phantom for higher frequencies, e.g. from 15.3-8.7 cm diameter for 70-120 MHz, respectively. The focusing target could be moved accurately from the left to the right side of the phantom. Further it was found that the sensitivity variation of nine diodes located at the centre of the phantom was very small, e.g. < 3% over the whole frequency range. The SAR distributions of the Sigma-60 applicator are in good agreement with theoretically expected values. The flexible Schottky diode sheet proves to be an excellent tool to make accurate, quantitative measurements of E-field distributions at low (25 W) and medium (400 W) power levels. An important feature of the SDS is that it enables one to significantly improve quantitative quality assurance procedures and to start quantitative comparisons of the performance of the different deep hyperthermia systems used by the various hyperthermia groups.

Quantum cascade transmitters for ultrasensitive chemical agent and explosives detection

NASA Astrophysics Data System (ADS)

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

2003-07-01

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

The detection of interstellar methylcyanoacetylene

NASA Technical Reports Server (NTRS)

Broten, N. W.; Macleod, J. M.; Avery, L. W.; Friberg, P.; Hjalmarson, A.; Hoglund, B.; Irvine, W. M.

1984-01-01

A new interstellar molecule, methylcyanoacetylene (CH3C3N), has been detected in the molecular cloud TMC-1. The J = 8 to 7, J = 7 to 6, J = 6 to 5, and J = 5 to 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 to 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity V(LSR) = 5.8 km/s for TMC-1, typical of other molecules in the cloud. All observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al. (1982), so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 to 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined from these observations is quite low, with T(rot) in the range from 2.7 to 4 K. The total column density is approximately 5 x 10 to the 12th per sq cm.

Conformational stability, barriers to internal rotation, normal coordinate analyses, and vibrational assignments of bromoacetyl halides

NASA Astrophysics Data System (ADS)

Durig, J. R.; Phan, H. V.; Little, T. S.

1989-09-01

The Raman (3200-10 cm -1) and IR (3200-30 cm -1) spectra of bromoacetyl fluoride, bromoacetyl chloride and bromoacetyl bromide in the gaseous and annealed solid phases have been recorded. Additionally, the Raman spectra and the qualitative depolarization measurements for each molecule in the liquid phase have been obtained. All of these data indicate that these bromoacetyl halides exist in mixtures of two conformers, with the trans rotamer (halogen atoms oriented trans to one another) being the thermodynamically preferred, and the gauche conformation being the high energy form. From the studies of Raman spectra at different temperatures, the enthalpy differences have been determined for the gaseous and liquid phases, respectively, to be 185 ± 23 cm -1 (0.53 ± 0.06 kcal mol -1) and 249 ± 27 cm -1 (0.71 ± 0.08 kcal mol -1) for bromoacetyl fluoride, 391 ± 130 cm -1 (1.12 ± 0.37 kcal mol -1) and 317 ± 27 cm -1 (0.91 ± 0.08 kcal mol -1) for bromoacetyl chloride, and 341 ± 48 cm -1 (0.98 ± 0.14 kcal mol -1) and 286 ± 26 cm -1 (0.82 ± 0.07 kcal mol -1) for bromoacetyl bromide. Potential functions have been calculated for the fluoride and chloride from the observed asymmetric torsional frequencies and values of 580 ± 11 cm -1 (1.66 ± 0.03 kcal mol -1), 359 ± 8 cm -1 (1.03 ± 0.02 kcal mol -1), and 387 ± 16 cm -1 (1.11 ± 0.04 kcal mol -1) for the trans to gauche, gauche to gauche to gauche and gauche to trans barrier, respectively, were determined for bromoacetyl fluoride. The corresponding quantities were 967 ± 30 cm -1 (2.76 ± 0.08 kcal mol -1), 696 ± 67 cm -1 (1.99 ± 0.19 kcal mol -1), and 663 ± 30 cm -1 (1.61 ± 0.08 kcal mol -1) for bromoacetyl chloride. These potential functions are consistent with the dihedral angle of the gauche conformation being 120° and 117° for the fluoride and chloride, respectively. Complete vibrational assignments have been carried out based on the observed IR band contours, the depolarization ratios, and group frequencies. The results are compared to those for other haloacetyl halides.

Interface properties of an O2 annealed Au/Ni/n-Al0.18Ga0.82N Schottky contact

NASA Astrophysics Data System (ADS)

Legodi, M. J.; Meyer, W. E.; Auret, F. D.

2012-05-01

We oxidized a Ni/Au metal bi-layer contact fabricated on HVPE Al0.18Ga0.82N from 373 K to 573 K in 100 K steps. In the range 1 kHz to 2 MHz, the Capacitance-Voltage-Frequency (C-V-f) measurements reveal a frequency dispersion of the capacitance and the presence of an anomalous peak at 0.4 V owing to the presence of interface states in the as deposited contact system. The dispersion was progressively removed by O2 anneals from temperatures as low as 373 K. These changes are accompanied by an improvement in the overall quality of the Schottky system: the ideality factor, n, improves from 2.09 to 1.26; the Schottky barrier height (SBH), determined by the Norde [1] method, increases from 0.72 eV to 1.54 eV. From the Nicollian and Goetzberger model [2], we calculated the energy distribution of the density of interface states, NSS. Around 1 eV above the Al0.18Ga0.82N valence band, NSS, decreases from 2.3×1012 eV-1 cm-2 for the un-annealed diodes to 1.3×1012 eV-1 cm-2 after the 573 K anneal. Our results suggest the formation of an insulating NiO leading to a MIS structure for the oxidized Au/Ni/Al0.18Ga0.82N contact.

Electromagnetic malfunction of semiconductor-type electronic personal dosimeters caused by access control systems for radiation facilities.

PubMed

Deji, Shizuhiko; Ito, Shigeki; Ariga, Eiji; Mori, Kazuyuki; Hirota, Masahiro; Saze, Takuya; Nishizawa, Kunihide

2006-08-01

High frequency electromagnetic fields in the 120 kHz band emitted from card readers for access control systems in radiation control areas cause abnormally high and erroneous indicated dose readings on semiconductor-type electronic personal dosimeters (SEPDs). All SEPDs malfunctioned but recovered their normal performance by resetting after the exposure ceased. The minimum distances required to prevent electromagnetic interference varied from 5.0 to 38.0 cm. The electric and magnetic immunity levels ranged from 35.1 to 267.6 V m(-1) and from 1.0 to 16.6 A m(-1), respectively. Electromagnetic immunity levels of SEPDs should be strengthened from the standpoint of radiation protection.

Infrared spectra of N2O-(ortho-D2)N and N2O-(HD)N clusters trapped in bulk solid parahydrogen.

PubMed

Lorenz, Britney D; Anderson, David T

2007-05-14

High-resolution infrared spectra of the clusters N2O-(ortho-D2)N and N2O-(HD)N, N=1-4, isolated in bulk solid parahydrogen at liquid helium temperatures are studied in the 2225 cm-1 region of the nu3 antisymmetric stretch of N2O. The clusters form during vapor deposition of separate gas streams of a precooled hydrogen mixture (ortho-D2para-H2 or HDpara-H2) and N2O onto a BaF2 optical substrate held at approximately 2.5 K in a sample-in-vacuum liquid helium cryostat. The cluster spectra reveal the N2O nu3 vibrational frequency shifts to higher energy as a function of N, and the shifts are larger for ortho-D2 compared to HD. These vibrational shifts result from the reduced translational zero-point energy for N2O solvated by the heavier hydrogen isotopomers. These spectra allow the N=0 peak at 2221.634 cm-1, corresponding to the nu3 vibrational frequency of N2O isolated in pure solid parahydrogen, to be assigned. The intensity of the N=0 absorption feature displays a strong temperature dependence, suggesting that significant structural changes occur in the parahydrogen solvation environment of N2O in the 1.8-4.9 K temperature range studied.

Poster 1: Global frequency and intensity analysis of the ν10/ν7/ν4/ν12 band system of 12C2H4 at 10 µm using the D2h Top Data System

NASA Astrophysics Data System (ADS)

Alkadrou, Abdulsamee; Bourgeois, Marie-Therese; Rotger, Maud; Boudon, Vincent; Vander Auwera, Jean

2016-06-01

A global frequency and intensity analysis of the infrared tetrad of 12C2H4 located in the 600-1500 cm-1 region was carried out using the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. It relies on spectroscopic information available in the literature and retrieved from high-resolution Fourier transform infrared spectra recorded in Brussels in the frame of either the present or previous work. In particular, 645 and 131 lines intensities have been respectively measured for the weak ν10 and ν4 bands. Including the Coriolis interactions affecting the upper vibrational levels 101, 71, 41 and 121 , a total of 10,737 line positions and 1,867 line intensities have been assigned and fitted with global root mean square deviations of 2.6 10-4 cm-1 and 2.4 %, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65,420 lines in the ν10, ν7, ν4 and ν12 bands of 12C2H4 was generated. To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum.

SOME COMMENTS ON TYPE IV BURSTS

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

Tanaka, H.; Kakinuma, T.

1962-01-01

It has become clear that a large continuum burst is composed of 4 distinctive types, CM/sub 1/, CM/sub 2/, DM, and IV, which originate from different altitudes over the photosphere. The observational characters of each type are given. CM/sub 1/ is the main phase of a centimeter-wave burst originating from about 0.02-0.05 R/sub S/ in height. DM burst is polarized in the ordinary sense, which is the cause of reversal of polarization with frequency. Its center frequency lies between about 1000 and 200 Mc/s, and is often misunderstood as the original Type IV burst. The movement of magnetic field duringmore » a burst is suggested. CM/sub 2/ may be considered as an enhancement of the upper part of the source of S-component caused by this movement of the field. (auth)« less

Restoration of continence following rectopexy for rectal prolapse and recovery of the internal anal sphincter electromyogram.

PubMed

Farouk, R; Duthie, G S; Bartolo, D C; MacGregor, A B

1992-05-01

Twenty-two patients with full-thickness rectal prolapse underwent ambulatory fine wire electromyography of the internal and sphincter (IAS), external and sphincter and puborectalis, together with anorectal manometry, using a computerized system. Examinations were performed both before and 3 to 4 months after rectopexy. The median (interquartile range (i.q.r.)) preoperative IAS electromyogram (EMG) frequency was 0.18 (0.05-0.31) Hz and the median (i.q.r.) preoperative resting anal pressure was 28 (15-64) cmH2O. An improvement in the IAS EMG frequency, median (i.q.r.) 0.29 (0.19-0.38) Hz (P less than 0.03), and resting anal pressure, median (i.q.r.) 41 (20-72) cmH2O (P less than 0.05), was recorded after operation, but these variables remained significantly lower than those found in normal controls: median (i.q.r.) IAS EMG frequency 0.44 (0.36-0.48) Hz and median (i.q.r.) resting anal pressure 92 (74-98) cmH2O. We suggest that repair of the prolapse allows the IAS to recover by removing the cause of persistent rectoanal inhibition.

Ionospheres of outer planet satellites: The legacy of Galileo and the promise of Cassini

NASA Astrophysics Data System (ADS)

Kliore, A. J.; Nagy, A. F.

The Galileo spacecraft was placed into orbit about Jupiter in 1995 and until the end of 2003 it has provided multiple opportunities for the study of the plasma environments of the icy Galilean satellites Europa, Ganymede, and Callisto by means of radio occultation of its S-band (13.5 cm. wavelength) signal. There have been four occultations each by Europa, Ganymede, and Callisto that have provided useful data, in addition to five occultations by the volcanic satellite Io.. Analysis of these data revealed small excursions in the received frequency (of the order of 0.01 Hz, or about 4 parts in 1012), which indicated the presence of tenuous plasma above the surfaces of these bodies. When observed, the maximum electron densities range from about 5 to about 20 x 103 cm-3. The vertical structure of these plasma layers range from classical ionospheric profiles observed at Callisto on two occasions, to multi-peaked structures observed at Europa. On several occasions no discernible plasma was observed. These observations could be explained by a process in which a tenuous neutral atmosphere (about 1010 cm-3), consisting dissociation products of H2O, is created on the trailing hemisphere of the satellite by sputtering from the icy surface by energetic particles of the Jovian magnetosphere. If the trailing hemisphere is at that time also illuminated by the Sun, plasma is produced by photoionization, and is observed by radio occultation. The configuration of this plasma is, however, determined by its interaction with the corotating Jovian magnetospheric plasma, which under certain geometries would lead to the observation of multipeaked structures. The Cassini orbiter, which will be placed into orbit about Saturn in 2004 , will provide at least four occultations of Titan. In contrast to Galileo, Cassini has three downlink frequencies - in addition to s-band, it also has x-band (˜ 5.5 cm), and Ka-band (˜ 1 cm) downlinks, which will provide excellent data on Titan's ionosphere and plasma environment during the standard tour of the Saturnian system, and possibly of some of the icy satellites during the extended mission..

SU-F-I-33: Estimating Radiation Dose in Abdominal Fat Quantitative CT

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

Li, X; Yang, K; Liu, B

Purpose: To compare size-specific dose estimate (SSDE) in abdominal fat quantitative CT with another dose estimate D{sub size,L} that also takes into account scan length. Methods: This study complied with the requirements of the Health Insurance Portability and Accountability Act. At our institution, abdominal fat CT is performed with scan length = 1 cm and CTDI{sub vol} = 4.66 mGy (referenced to body CTDI phantom). A previously developed CT simulation program was used to simulate single rotation axial scans of 6–55 cm diameter water cylinders, and dose integral of the longitudinal dose profile over the central 1 cm length wasmore » used to predict the dose at the center of one-cm scan range. SSDE and D{sub size,L} were assessed for 182 consecutive abdominal fat CT examinations with mean water-equivalent diameter (WED) of 27.8 cm ± 6.0 (range, 17.9 - 42.2 cm). Patient age ranged from 18 to 75 years, and weight ranged from 39 to 163 kg. Results: Mean SSDE was 6.37 mGy ± 1.33 (range, 3.67–8.95 mGy); mean D{sub size,L} was 2.99 mGy ± 0.85 (range, 1.48 - 4.88 mGy); and mean D{sub size,L}/SSDE ratio was 0.46 ± 0.04 (range, 0.40 - 0.55). Conclusion: The conversion factors for size-specific dose estimate in AAPM Report No. 204 were generated using 15 - 30 cm scan lengths. One needs to be cautious in applying SSDE to small length CT scans. For abdominal fat CT, SSDE was 80–150% higher than the dose of 1 cm scan length.« less

Diamond-Based Supercapacitors: Realization and Properties.

PubMed

Gao, Fang; Nebel, Christoph E

2016-10-26

In this Spotlight on Applications, we describe our recent progress on the fabrication of surface-enlarged boron-doped polycrystalline diamond electrodes, and evaluate their performance in supercapacitor applications. We begin with a discussion of the fabrication methods of porous diamond materials. The diamond surface enlargement starts with a top-down plasma etching method. Although the extra surface area provided by surface roughening or nanostructuring provides good outcome for sensing applications, a capacitance value <1 mF cm -2 or a surface-enlargement factor <100 fail to meet the requirement of a practical supercapacitor. Driven by the need for large surface areas, we recently focused on the tempated-growth method. We worked on both supported and free-standing porous diamond materials to enhance the areal capacitance to the "mF cm -2 " range. With our newly developed free-standing diamond paper, areal capacitance can be multiplied by stacking multilayers of the electrode material. Finally, considering the fact that there is no real diamond-based supercapacitor device up to now, we fabricated the first prototype pouch-cell device based on the free-standing diamond paper to evaluate its performance. The results reveal that the diamond paper is suitable for operation in high potential windows (up to 2.5 V) in aqueous electrolyte with a capacitance of 0.688 mF cm -2 per layer of paper (or 0.645 F g -1 ). Impedance spectroscopy revealed that the operation frequency of the device exceeds 30 Hz. Because of the large potential window and the ability to work at high frequency, the specific power of the device reached 1 × 10 5 W kg -1 . In the end, we made estimations on the future target performance of diamond supercapacitors based on the existing information.

Plasma turbulence imaging using high-power laser Thomson scattering

NASA Astrophysics Data System (ADS)

Zweben, S. J.; Caird, J.; Davis, W.; Johnson, D. W.; Le Blanc, B. P.

2001-01-01

The two-dimensional (2D) structure of plasma density turbulence in a magnetically confined plasma can potentially be measured using a Thomson scattering system made from components of the Nova laser of Lawrence Livermore National Laboratory. For a plasma such as the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory, the laser would form an ≈10-cm-wide plane sheet beam passing vertically through the chamber across the magnetic field. The scattered light would be imaged by a charge coupled device camera viewing along the direction of the magnetic field. The laser energy required to make 2D images of density turbulence is in the range 1-3 kJ, which can potentially be obtained from a set of frequency-doubled Nd:glass amplifiers with diameters in the range of 208-315 mm. A laser pulse width of ⩽100 ns would be short enough to capture the highest frequency components of the expected density fluctuations.

An experimental study of turbulence by phase-contrast imaging in the DIII-D tokamak

NASA Astrophysics Data System (ADS)

Coda, Stefano

1997-10-01

A CO2-laser imaging system employing the Zernike phase-contrast technique was designed, built, installed, and operated on the DIII-D tokamak. This system measures the line integrals of plasma density fluctuations along 16 vertical chords at the outer edge of the tokamak (0.85

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

NASA Astrophysics Data System (ADS)

de Lange, Arno; Dickenson, Gareth D.; Salumbides, Edcel J.; Ubachs, Wim; de Oliveira, Nelson; Joyeux, Denis; Nahon, Laurent

2012-06-01

An extensive survey of the D2 absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90 000-119 000 cm-1 covers the full depth of the potential wells of the B sideset{^1}{+u}{Σ}, B^' } sideset{^1}{+u}{Σ}, and C 1Πu electronic states up to the D(1s) + D(2ℓ) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ≈0.35 cm-1. Extended calibration methods are employed to extract line positions of D2 lines at absolute accuracies of 0.03 cm-1. The D 1Πu and B^' ' } sideset{^1}{+u}{Σ} electronic states correlate with the D(1s) + D(3ℓ) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D2. The observations are compared with previous studies, both experimental and theoretical.

Spin dynamics and frequency dependence of magnetic damping study in soft ferromagnetic FeTaC film with a stripe domain structure

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

Samantaray, B., E-mail: iitg.biswanath@gmail.com; Ranganathan, R.; Mandal, P.

Perpendicular magnetic anisotropy (PMA) and low magnetic damping are the key factors for the free layer magnetization switching by spin transfer torque technique in magnetic tunnel junction devices. The magnetization precessional dynamics in soft ferromagnetic FeTaC thin film with a stripe domain structure was explored in broad band frequency range by employing micro-strip ferromagnetic resonance technique. The polar angle variation of resonance field and linewidth at different frequencies have been analyzed numerically using Landau-Lifshitz-Gilbert equation by taking into account the total free energy density of the film. The numerically estimated parameters Landé g-factor, PMA constant, and effective magnetization are foundmore » to be 2.1, 2 × 10{sup 5} erg/cm{sup 3} and 7145 Oe, respectively. The frequency dependence of Gilbert damping parameter (α) is evaluated by considering both intrinsic and extrinsic effects into the total linewidth analysis. The value of α is found to be 0.006 at 10 GHz and it increases monotonically with decreasing precessional frequency.« less

Dosimetric Factors and Toxicity in Highly Conformal Thoracic Reirradiation

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

Binkley, Michael S.; Hiniker, Susan M.; Chaudhuri, Aadel

Purpose: We determined cumulative dose to critical structures, rates of toxicity, and outcomes following thoracic reirradiation. Methods and Materials: We retrospectively reviewed our institutional database for patients treated between 2008 and 2014, who received thoracic reirradiation with overlap of 25% prescribed isodose lines. Patients received courses of hyperfractionated (n=5), hypofractionated (n=5), conventionally fractionated (n=21), or stereotactic ablative radiation therapy (n=51). Doses to critical structures were converted to biologically effective dose, expressed as 2 Gy per fraction equivalent dose (EQD2; α/β = 2 for spinal cord; α/β = 3 for other critical structures). Results: We identified 82 courses (44 for retreatment) in 38 patients reirradiated atmore » a median 16 months (range: 1-71 months) following initial RT. Median follow-up was 17 months (range: 3-57 months). Twelve- and 24-month overall survival rates were 79.6% and 57.3%, respectively. Eighteen patients received reirradiation for locoregionally recurrent non-small cell lung cancer with 12-month rates of local failure and regional recurrence and distant metastases rates of 13.5%, 8.1%, and 15.6%, respectively. Critical structures receiving ≥75 Gy EQD2 included spinal cord (1 cm{sup 3}; n=1), esophagus (1 cm{sup 3}; n=10), trachea (1 cm{sup 3}; n=11), heart (1 cm{sup 3}; n=9), aorta (1 cm{sup 3}; n=16), superior vena cava (1 cm{sup 3}; n=12), brachial plexus (0.2 cm{sup 3}; n=2), vagus nerve (0.2 cm{sup 3}; n=7), sympathetic trunk (0.2 cm{sup 3}; n=4), chest wall (30 cm{sup 3}; n=12), and proximal bronchial tree (1 cm{sup 3}; n=17). Cumulative dose-volume (D cm{sup 3}) toxicity following reirradiation data included esophagitis grade ≥2 (n=3, D1 cm{sup 3} range: 41.0-100.6 Gy), chest wall grade ≥2 (n=4; D30 cm{sup 3} range: 35.0-117.2 Gy), lung grade 2 (n=7; V20{sub combined-lung} range: 4.7%-21.7%), vocal cord paralysis (n=2; vagus nerve D0.2 cm{sup 3} range: 207.5-302.2 Gy), brachial plexopathy (n=1; D0.2 cm{sup 3} = 242.5 Gy), and Horner's syndrome (n=1; sympathetic trunk D0.2 cm{sup 3} = 130.8 Gy). No grade ≥4 toxicity was observed. Conclusions: Overlapping courses of reirradiation can be safely delivered with acceptable toxicity. Some toxicities occurred acutely at doses considered safe for a single course of therapy (esophagus). We observed rib fracture, brachial plexopathy, and Horner's syndrome for patients receiving high cumulative doses to corresponding critical structures.« less

An analysis of source structure effects in radio interferometry measurements

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1980-01-01

To begin a study of structure effects, this report presents a theoretical framework, proposes an effective position approach to structure corrections based on brightness distribution measurements, and analyzes examples of analytical and measured brightness distributions. Other topics include the effect of the frequency dependence of a brightness distribution on bandwidth synthesis (BWS) delay, the determination of the absolute location of a measured brightness distribution, and structure effects in dual frequency calibration of charged particle delays. For the 10 measured distributions analyzed, it was found that the structure effect in BWS delay at X-band (3.6 cm) can reach 30 cm, but typically falls in the range of 0 to 5 cm. A trial limit equation that is dependent on visibility was successfully tested against the 10 measured brightness distributions (seven sources). If the validity of this particular equation for an upper limit can be established for nearly all sources, the structure effect in BWS delay could be greatly reduced without supplementary measurements of brightness distributions.

Life-history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island.

PubMed

Nolan, E T; Downes, K J; Richardson, A; Arkhipkin, A; Brickle, P; Brown, J; Mrowicki, R J; Shcherbich, Z; Weber, N; Weber, S B

2017-12-01

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life-history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L ∞  = 55·14, K = 0·19, t 0  = -0·88. Monthly gonad staging and analysis of gonad-somatic index (I G ) provide evidence for spawning from July to November with an I G peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L T ; 95% C.I. 27·1-30·7 cm) and no females were found >12 years and 48·0 cm L T , whereas all confirmed males sampled were mature, >35·1 cm L T with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4-43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life-history parameters are needed to inform long-term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls. © 2017 The Fisheries Society of the British Isles.

Invasion of xylem of mature tree stems by Phytophthora ramorum and P. kernoviae

Treesearch

Anna Brown; Clive Brasier

2008-01-01

The aetiology and frequency of Phytophthoras in discoloured xylem tissue beneath phloem lesions was investigated in a range of broadleaved trees infected with P. ramorum, P. kernoviae and several other Phytophthoras. Isolation was attempted from the inner surface of 81, 6 x 4 cm sterilised...

Photochemical hole-burned spectra of protonated and deuterated reaction centers of Rhodobacter sphaeroides

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

Lyle, P.A.; Kolaczkowski, S.V.; Small, G.J.

1993-07-01

Photochemical hole-burned spectra with improved signal-to-noise ratio ([times]20) are reported for the protonated and deuterated reaction center of the purple bacterium Rhodobacter sphaeroides. Spectra obtained as a function of burn frequency ([omega][sub B]) establish that the lifetime of P870*, the primary electron-donor state, is invariant to location of [omega][sub B] within the inhomogeneous distribution of P870 zero-phonon line transition frequencies. For both the protonated and deuterated RC, which exhibit P870 absorption widths at 4.2 K of only 440 and 420 cm[sup [minus]1], the zero-phonon holes yield a lifetime of 0.93 [+-] 0.10 ps. This lifetime is independent of temperature betweenmore » 1.6 and 8.0 K (range over which the zero-phonon hole could be studied). The invariance of the P870* lifetime to [omega][sub B] and other data indicates that the nonexponential decay of P870* (Vos et al. Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 8885) is due neither to a distribution of values from the electronic coupling matrix element associated with electron transfer, which one might expect from the normal glasslike structural heterogeneity of the RC, nor to gross heterogeneity. The higher quality of the hole spectra has allowed for more stringent testing of the theoretical model previously used to simulate the P870 hole profiles and absorption spectrum. Although the essential findings reported earlier (see, e.g., Reddy et al. Photosyn. Res. 1992, 31, 167) are not altered, it is concluded that the modeling of the distribution of low-frequency phonons (mean frequency approximately 30 cm[sup [minus]1]), which couples to P870*, in terms of a Debye distribution is inadequate. The anomalous low-frequency modes of glasses and polymers are suggested to be important also for proteins. 60 refs., 8 figs., 2 tabs.« less

Broadband sensitive pump-probe setup for ultrafast optical switching of photonic nanostructures and semiconductors.

PubMed

Euser, Tijmen G; Harding, Philip J; Vos, Willem L

2009-07-01

We describe an ultrafast time resolved pump-probe spectroscopy setup aimed at studying the switching of nanophotonic structures. Both femtosecond pump and probe pulses can be independently tuned over broad frequency range between 3850 and 21,050 cm(-1). A broad pump scan range allows a large optical penetration depth, while a broad probe scan range is crucial to study strongly photonic crystals. A new data acquisition method allows for sensitive pump-probe measurements, and corrects for fluctuations in probe intensity and pump stray light. We observe a tenfold improvement of the precision of the setup compared to laser fluctuations, allowing a measurement accuracy of better than DeltaR=0.07% in a 1 s measurement time. Demonstrations of the improved technique are presented for a bulk Si wafer, a three-dimensional Si inverse opal photonic bandgap crystal, and z-scan measurements of the two-photon absorption coefficient of Si, GaAs, and the three-photon absorption coefficient of GaP in the infrared wavelength range.

Mapping Soil Carbon in the Yukon Kuskokwim River Delta Alaska

NASA Astrophysics Data System (ADS)

Natali, S.; Fiske, G.; Schade, J. D.; Mann, P. J.; Holmes, R. M.; Ludwig, S.; Melton, S.; Sae-lim, N.; Jardine, L. E.; Navarro-Perez, E.

2017-12-01

Arctic river deltas are hotspots for carbon storage, occupying <1% of the pan-Arctic watershed but containing >10% of carbon stored in arctic permafrost. The Yukon Kuskokwim (YK) Delta, Alaska is located in the lower latitudinal range of the northern permafrost region in an area of relatively warm permafrost that is particularly vulnerable to warming climate. Active layer depths range from 50 cm on peat plateaus to >100 cm in wetland and aquatic ecosystems. The size of the soil organic carbon pool and vulnerability of the carbon in the YK Delta is a major unknown and is critically important as climate warming and increasing fire frequency may make this carbon vulnerable to transport to aquatic and marine systems and the atmosphere. To characterize the size and distribution of soil carbon pools in the YK Delta, we mapped the land cover of a 1910 km2 watershed located in a region of the YK Delta that was impacted by fire in 2015. The map product was the result of an unsupervised classification using the Weka K Means clustering algorithm implemented in Google's Earth Engine. Inputs to the classification were Worldview2 resolution optical imagery (1m), Arctic DEM (5m), and Sentinel 2 level 1C multispectral imagery, including NDVI, (10 m). We collected 100 soil cores (0-30 cm) from sites of different land cover and landscape position, including moist and dry peat plateaus, high and low intensity burned plateaus, fens, and drained lakes; 13 lake sediment cores (0-50 cm); and 20 surface permafrost cores (to 100 cm) from burned and unburned peat plateaus. Active layer and permafrost soils were analyzed for organic matter content, soil moisture content, and carbon and nitrogen pools (30 and 100 cm). Soil carbon content varied across the landscape; average carbon content values for lake sediments were 12% (5- 17% range), fens 26% (9-44%), unburned peat plateaus 41% (34-44%), burned peat plateaus 19% (7-34%). These values will be used to estimate soil carbon pools, which will be applied to the spatial extent of each landcover class in our map, yielding a watershed-wide and spatially explicit map of soil carbon in the YK Delta. This map will provide the basis for understanding where carbon is stored in the watershed and the vulnerability of that carbon to climate change and fire.

Frequency and Severity of Trauma in Fishes Subjected to Multiple-pass Depletion Electrofishing

USGS Publications Warehouse

Panek, Frank; Densmore, Christine L.

2013-01-01

The incidence and severity of trauma associated with multiple-pass electrofishing and the effects on short-term (30-d) survival and growth of Rainbow Trout Oncorhynchus mykiss, Brook Trout Salvelinus fontinalis, and five representative co-inhabiting nontarget or bycatch species were examined. Fish were held in four rectangular fiberglass tanks (190 × 66 cm) equipped with electrodes, a gravel–cobble stream substrate, and continuous water flow. Fish were exposed to one, two, or three electroshocks (100-V, 60-Hz pulsed DC) spaced 1 h apart or were held as a control. The heterogeneous field produced a mean (±SD) voltage gradient of 0.23 ± 0.024 V/cm (range = 0.20–0.30 V/cm) with a duty cycle of 30% and a 5-s exposure. Radiographs of 355 fish were examined for evidence of spinal injuries, and necropsies were performed on 303 fish to assess hemorrhagic trauma in soft tissue. Using linear regression, we demonstrated significant relationships between the number of electrical shocks and the frequency and severity of hemorrhagic and spinal trauma in each of the nontarget species (Potomac Sculpin Cottus girardi, Channel Catfish Ictalurus punctatus, Fathead Minnow Pimephales promelas, Green Sunfish Lepomis cyanellus, and Largemouth Bass Micropterus salmoides). Most of the injuries in these species were either minor or moderate. Rainbow Trout and Brook Trout generally sustained the highest incidence and severity of injuries, but those injuries were generally independent of the number of treatments. The 30-d postshock survival for the trout species was greater than 94%; survival for the bycatch species ranged from 80% (Fathead Minnow) to 100% (Green Sunfish and Channel Catfish). There were no significant differences in 30-d postshock condition factors despite observations of altered feeding behavior lasting several days to 1 week posttreatment in several of the study species.

Theoretical investigation of the ultra-intense laser interaction with plasma mirrors in radiation pressure dominant regime

NASA Astrophysics Data System (ADS)

Sonia, Krishna Kumar; Maheshwari, K. P.; Jaiman, N. K.

2017-05-01

At laser intensity in the range ~ 1022 -1023W/cm2, the radiation pressure starts to play a key role in the interaction of an intense electromagnetic wave with a dense plasma foil. Depending upon the incident laser intensity, polarization of the incident beam and also on the density of the thin plasma layer the mirror motion may be assumed to be uniform, accelerated, or oscillatory. A solid dense plasma slab, accelerated in the radiation pressure dominant (RPD) regime, can efficiently reflect a counter-propagating relativistically strong source pulse consisting of up-shifted frequency and high harmonics. In this RPD regime we present our numerical results for the frequency and brightness of the reflected radiation from a uniformly moving plasma mirror. Our numerical results show that for the appropriate laser and plasma parameters in the case 2γ < {({n}e{λ }s3)}1/6 there are approximately 8.03 × 1042 photons / (mm2 - mrad2 - sec.-0.1% bandwidth) in the energy range ~ 10keV. In the case when 2γ > {({n}e{λ }s3)}1/6 for the same parameters and ad = 300, λd = 0.8 μm, the brightness is found to be 3.27 × 1034 photons / (mm2 - mrad2 - sec. - 0.1% bandwidth) in the energy range ~100 keV.

Symmetry breaking and spectral considerations of the surprisingly floppy c-C3H radical and the related dipole-bound excited state of c-C3H-

NASA Astrophysics Data System (ADS)

Bassett, Matthew K.; Fortenberry, Ryan C.

2017-06-01

The C3H radical is believed to be prevalent throughout the interstellar medium and may be involved in the formation of polycyclic aromatic hydrocarbons. C3H exists as both a linear and a cyclic isomer. The C2 v cyclopropenylidenyl radical isomer was detected in the dark molecular cloud TMC-1, and the linear propenylidenyl radical isomer has been observed in various dark molecular clouds. Even though the c-C3H radical has been classified rotationally, the vibrational frequencies of this seemingly important interstellar molecule have never been directly observed. Established, highly accurate quartic force field methodologies are employed here to compute useful geometrical data, spectroscopic constants, and vibrational frequencies. The computed rotational constants are consistent with the experimental results. Consequently, the three a1 (ν1, ν2, and ν3) and one b1 (ν6) anharmonic vibrational frequencies at 3117.7 cm-1, 1564.3 cm-1, 1198.5 cm-1, and 826.7 cm-1, respectively, are reliable predictions for these, as of yet unseen, observables. Unfortunately, the two b2 fundamentals (ν4 and ν5) cannot be treated adequately in the current approach due to a flat and possible double-well potential described in detail herein. The dipole-bound excited state of the anion suffers from the same issues and may not even be bound. However, the trusted fundamental vibrational frequencies described for the neutral radical should not be affected by this deformity and are the first robustly produced for c-C3H. The insights gained here will also be applicable to other structures containing three-membered bare and exposed carbon rings that are surprisingly floppy in nature.

Turbulence intensity in a region of interest 2cm distal to the carotid bifurcation in a family of seven anthropomorphic flow phantoms

NASA Astrophysics Data System (ADS)

Powell, Janet L.; Poepping, Tamie L.

2011-03-01

An in vitro flow system has been used to assess the flow disturbances downstream of the stenosis in a family of seven carotid bifurcation phantoms modelling varying plaque build-up both axially symmetrically (concentrically) and asymmetrically (eccentrically). Radio frequency data were collected for 10 s at each of over 1000 sites within each model, and a sliding 1024-point FFT is applied to the data to extract the Doppler spectrum every 12 ms. From this, the ensemble average over 10 cardiac cycles of the spectral mean velocity, and the root mean square over these same 10 cardiac cycles - the turbulence intensity (TI), can be obtained as a function of an ensemble averaged cardiac cycle at each spatial point in all phantoms. TI was investigated by looking at the average over a 25 mm2 square region of interest in the ICA centered 2 cm distal to the apex of the bifurcation. TI in the region of interest increased with stenosis severity; at 23ms following peak systole, the time point when TI was maximal for the majority of models, this ranged from 2.4+/-0.1 cm/s in the non-diseased model to 6.6+/-0.3, 16.0+/-1.4 and 26.1+/-1.3 cm/s in the 30, 50 and 70% concentrically stenosed (by NASCET criteria) models, respectively. Similarly, TI was 8.3+/-0.7, 19.9+/-1.1, and 26.2+/-1.2 cm/s in the 30, 50 and 70% eccentrically stenosed models, respectively. Differences in TI between models, both in increasing stenosis severity and between eccentricities, were statistically different except between the 70% concentric and eccentric models.

New Crystalline Materials for Nonlinear Frequency Conversion, Electro-Optic Modulation, and Mid-Infrared Gain Media

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

Adams, J

New crystalline materials were investigated for applications in frequency conversion of near-infrared wavelengths and as gain media for tunable mid-infrared solid-state lasers. GaCa{sub 4}O(BO{sub 3}){sub 3} (GdCOB), YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), LaCa{sub 4}O(BO{sub 3}){sub 3} (LaCOB), and Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} were characterized for frequency conversion of 1 {micro}m lasers. For type I doubling at 1064 nm, LaCOB, GdCOB, and YCOB were found to have effective coupling coefficients (d{sub eff}) of 0.52 {+-} 0.05, 0.78 {+-} 0.06, and 1.12 {+-} 0.07 pm/V, respectively. LaCOB was measured to have angular and thermal sensitivities of 1224 {+-} 184 (cm-rad){supmore » -1} and < 0.10 (cm-{sup o}C){sup -1}, respectively. The effective coupling coefficient for type II noncritically phasematched (NCPM) doubling at 1064 nm in Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} was measured to be 0.37 {+-} 0.04 pm/V. We predict LaCOB to have a type I NCPM fundamental wavelength of 1042 {+-} 1.5 nm. Due to its low angular and thermal sensitivities for doubling near 1047 nm, LaCOB has potential for frequency doubling of high-average power Nd:LiYF{sub 4} and Yb:Sr{sub 5}(P0{sub 4}){sub 3}F lasers. LaCOB, GdCOB, and YCOB were also investigated for optical parametric oscillator applications and we determined that they may have potential in a Ti:sapphire pumped oscillator. The effective linear electro-optic coefficients (r{sub eff}) were measured along dielectric directions in YCOB and a maximum r{sub eff} of 10.8 pm/V was found. For a crystal with a 5:1 aspect ratio, the corresponding half-wave voltage at 1064 nm would be 19.6 kV. Therefore a Pockels cell composed of two YCOB crystals with 5:1 aspect ratios would have a required half-wave voltage <10 kV. Moderate coupling coefficients (3 x KH{sub 2}PO{sub 4}), low thermal sensitivities, ease of growth to large sizes, non-hygroscopicity, and favorable polishing and coating characteristics make LaCOB, GdCOB, and YCOB attractive for frequency conversion of high-average power near-infrared lasers. Absorption and emission cross-sections of {approx}10{sup -18} cm{sup 2} were measured for Fe{sup 2+}:ZnSe in the 4 {micro}m region at temperatures below 220 K. Luminescence lifetimes were found that ranged from 5-110 {micro}s below 220 K. Tunable lasing action was demonstrated for the first time in Fe{sup 2+}:ZnSe with a tuning range from 3.98 {micro}m (20 K) to 4.54 {micro}m (180 K). The Fe{sup 2+}:ZnSe laser had thresholds {le}50 {micro}J and slope efficiencies {le}10% with 0.6% output coupling.« less

Modeling of postural stability borders during heel-toe rocking.

PubMed

Murnaghan, Chantelle D; Elston, Beth; Mackey, Dawn C; Robinovitch, Stephen N

2009-08-01

To maintain balance during movements such as bending and reaching, the CNS must generate muscle forces to counteract destabilizing torques produced by gravitational (position-dependent) and inertial (acceleration-dependent) forces. This may create a trade-off between the attainable frequency and amplitude of movements. We used experiments and mathematical modeling to examine this relationship during the task of heel-toe rocking. During the experiments, participants (n=15) rocked about the ankles in the sagittal plane with maximum attainable amplitude at a frequency of 0.33 Hz or 0.66 Hz. As the frequency doubled, the maximum anterior position of the whole-body centre-of-gravity (COG) with respect to the ankle decreased by 11% of foot length (from 11.9 cm (S.D. 1.6) to 9.2 cm (S.D. 1.2); p<0.001), the minimum anterior position of the COG increased by 8% of foot length (from 1.6 cm to 3.5 cm in front on the ankle; p<0.0005), and the ankle stiffness increased from 787 Nm/rad (S.D. 156) to 1625 Nm/rad (S.D. 339). However, there was no difference between conditions in the maximum anterior position of the COP (p=0.51), the minimum anterior position of the COP (p=0.23), or the peak ankle torque (p=0.39). An inverted pendulum model driven by a rotational spring predicted the measured ankle stiffness to within 0.9% (S.D. 6.8), and the maximum anterior COG position to within 1.2% (S.D. 4.0). These results indicate that COG amplitude decreases with increasing rocking frequency, due to (a) invariability in peak ankle torque and (b) the need to allocate torque between gravitational and inertial components, the latter of which scales with the square of frequency.

Spatial Identification of Passive Radio Frequency Identification Tags Using Software Defined Radios

DTIC Science & Technology

2012-03-01

75 3.4 Experiment Configurations . . . . . . . . . . . . . . . . . . . . 77 4.1 Simulation Enviromental Elements . . . . . . . . . . . . . . . . 79...tabletop zReader 20cm Tag vertical offset from reader z 10 cm 3dB angle of sensor antenna theat3db 0.698 radians Table 4.1: Simulation Enviromental

Study of 42 and 85 GHz coupled cavity traveling-wave tubes for space use

NASA Technical Reports Server (NTRS)

Kennedy, J. B.; Tammaru, I.; Wolcott, P. S.

1977-01-01

Designs were formulated for four CW, millimeter wavelength traveling-wave tubes having high efficiency and long life. Three of these tubes, in the 42 to 44 GHz frequency region, develop power outputs of 100 to 300 watts with overall efficiencies of typically 45 percent. Another tube, which covers the frequency range of 84 to 86 GHz, provides a power output of 200 watts at 25 percent efficiency. The cathode current density in each design was 1A/sq cm. Each tube includes: metal-ceramic construction, periodic permanent magnet focusing, a two step velocity taper, an electron beam refocusing section, and a radiation cooled three-stage depressed collector. The electrical and mechanical design for each tube type is discussed in detail. The results of thermal and mechanical analyses are presented.