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Sample records for 1h resonance frequency

  1. Spinning-frequency-dependent linewidths in 1H-decoupled 13C magic-angle spinning NMR spectra

    NASA Astrophysics Data System (ADS)

    Nakai, Toshihito; McDowell, Charles A.

    1994-09-01

    The broadenings observed in 13C MAS NMR spectra, which depend on the sample-spinning speed, were studied, using polycrystalline adamantane. Not only was a monotonic increase of the linewidths with the increase of the spinning frequency observed, but also a novel resonant feature was found. The phenomena were interpreted as originating from rotary-resonance 13C 1H recoupling.

  2. {sup 1}H nuclear magnetic resonance study of hydrated water dynamics in perfluorosulfonic acid ionomer Nafion

    SciTech Connect

    Han, Jun Hee; Lee, Kyu Won; Jeon, G. W.; Lee, Cheol Eui; Park, W. K.; Choi, E. H.

    2015-01-12

    We have studied the dynamics of hydrated water molecules in the proton exchange membrane of Nafion by means of high-resolution {sup 1}H nuclear magnetic resonance (NMR) measurements. “Bound” and “free” states of hydrated water clusters as well as the exchange protons were identified from the NMR chemical shift measurements, and their activation energies were obtained from the temperature-dependent laboratory- and rotating-frame spin-lattice relaxation measurements. Besides, a peculiar motional transition in the ultralow frequency region was observed at 373 K for the “free” hydrated water from the rotating-frame NMR spin-lattice relaxation time measurements.

  3. High resolution 1H nuclear magnetic resonance of a transmembrane peptide.

    PubMed Central

    Davis, J. H.; Auger, M.; Hodges, R. S.

    1995-01-01

    Although the strong 1H-1H dipolar interaction is known to result in severe homogeneous broadening of the 1H nuclear magnetic resonance (NMR) spectra of ordered systems, in the fluid phase of biological and model membranes the rapid, axially symmetric reorientation of the molecules about the local bilayer normal projects the dipolar interaction onto the motional symmetry axis. Because the linewidth then scales as (3 cos2 theta-1)/2, where theta is the angle between the local bilayer normal and the magnetic field, the dipolar broadening has been reduced to an "inhomogeneous" broadening by the rapid axial reorientation. It is then possible to obtain high resolution 1H-NMR spectra of membrane components by using magic angle spinning (MAS). Although the rapid axial reorientation effectively eliminates the homogeneous dipolar broadening, including that due to n = 0 rotational resonances, the linewidths observed in both lipids and peptides are dominated by low frequency motions. For small peptides the most likely slow motions are either a "wobble" or reorientation of the molecular diffusion axis relative to the local bilayer normal, or the reorientation of the local bilayer normal itself through surface undulations or lateral diffusion over the curved surface. These motions render the peptide 1H-NMR lines too broad to be observed at low spinning speeds. However, the linewidths due to these slow motions are very sensitive to spinning rate, so that at higher speeds the lines become readily visible. The synthetic amphiphilic peptide K2GL20K2A-amide (peptide-20) has been incorporated into bilayers of 1,2-di-d 27-myristoyl-sn-glycero-3-phosphocholine (DMPC-d54) and studied by high speed 1H-MAS-NMR. The linewidths observed for this transbilayer peptide, although too broad to be observable at spinning rates below -5 kHz, are reduced to 68 Hz at a spinning speed of 14 kHz (at 500C). Further improvements in spinning speed and modifications in sample composition designed to reduce

  4. Rotary resonance recoupling of 13C- 1H dipolar interactions in magic angle spinning 13C NMR of dynamic solids

    NASA Astrophysics Data System (ADS)

    Kitchin, Simon J.; Harris, Kenneth D. M.; Aliev, Abil E.; Apperley, David C.

    2000-06-01

    Rotary resonance recoupling of heteronuclear 13C- 1H dipolar interactions in magic angle spinning solid state 13C NMR spectra (recorded under conditions of 1H decoupling at frequency ν1 and magic angle spinning at frequency νr) has been studied for three examples of molecular solids (adamantane, ferrocene and hexamethylbenzene) in which substantial molecular motion is known to occur. It is shown that when rotary resonance conditions are satisfied (i.e. ν1/νr= n, for n=1 or 2), the recoupling can lead to motionally averaged Pake-like powder patterns from which information on 13C- 1H internuclear distances and/or molecular motion can be derived.

  5. Resonance frequency analysis.

    PubMed

    Gupta, Rajiv K; Padmanabhan, Thallam V

    2011-01-01

    Initial stability at the placement and development of osseointegration are two major issues for implant survival. Implant stability is a mechanical phenomenon which is related to the local bone quality and quantity, type of implant, and placement technique used. The application of a simple, clinically applicable, non-invasive test to assess implant stability and osseointegration is considered highly desirable. Resonance frequency analysis (RFA) is one of such techniques which is most frequently used now days. The aim of this paper was to review and analyze critically the current available literature in the field of RFA, and to also discuss based on scientific evidence, the prognostic value of RFA to detect implants at risk of failure. A search was made using the PubMed database to find all the literature published on "Resonance frequency analysis for implant stability" till date. Articles discussed in vivo or in vitro studies comparing RFA with other methods of implant stability measurement and articles discussing its reliability were thoroughly reviewed and discussed. A limited number of clinical reports were found. Various studies have demonstrated the feasibility and predictability of the technique. However, most of these articles are based on retrospective data or uncontrolled cases. Randomized, prospective, parallel-armed longitudinal human trials are based on short-term results and long-term follow up are still scarce in this field. Nonetheless, from available literature, it may be concluded that RFA technique evaluates implant stability as a function of stiffness of the implant bone interface and is influenced by factors such as bone type, exposed implant height above the alveolar crest. Resonance frequency analysis could serve as a non-invasive diagnostic tool for detecting the implant stability of dental implants during the healing stages and in subsequent routine follow up care after treatment. Future studies, preferably randomized, prospective

  6. [(1)H] magnetic resonance spectroscopy of urine: diagnosis of a guanidinoacetate methyl transferase deficiency case.

    PubMed

    Tassini, Maria; Zannolli, Raffaella; Buoni, Sabrina; Engelke, Udo; Vivi, Antonio; Valensin, Gianni; Salomons, Gajja S; De Nicola, Anna; Strambi, Mirella; Monti, Lucia; Morava, Eva; Wevers, Ron A; Hayek, Joseph

    2010-01-01

    For the first time, the use of urine [(1)H] magnetic resonance spectroscopy has allowed the detection of 1 case of guanidinoacetate methyl transferase in a database sample of 1500 pediatric patients with a diagnosis of central nervous system impairment of unknown origin. The urine [(1)H] magnetic resonance spectroscopy of a 9-year-old child, having severe epilepsy and nonprogressive mental and motor retardation with no apparent cause, revealed a possible guanidinoacetic acid increase. The definitive assignment of guanidinoacetic acid was checked by addition of pure substance to the urine sample and by measuring [(1)H]-[(1)H] correlation spectroscopy. Diagnosis of guanidinoacetate methyl transferase deficiency was further confirmed by liquid chromatography-mass spectrometry, brain [(1)H] magnetic resonance spectroscopy, and mutational analysis of the guanidinoacetate methyl transferase gene. The replacement therapy was promptly started and, after 1 year, the child was seizure free. We conclude that for this case, urine [(1)H] magnetic resonance spectroscopy screening was able to diagnose guanidinoacetate methyl transferase deficiency. PMID:19461121

  7. Selective excitation enables assignment of proton resonances and (1)H-(1)H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of (1)H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as (13)C or (15)N. In this method, after the initial preparation of proton magnetization and cross-polarization to (13)C nuclei, transverse magnetization of desired (13)C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific (13)C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of (1)H-(1)H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids. PMID:26203019

  8. Selective excitation enables assignment of proton resonances and 1H-1H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-01

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of 1H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as 13C or 15N. In this method, after the initial preparation of proton magnetization and cross-polarization to 13C nuclei, transverse magnetization of desired 13C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific 13C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of 1H-1H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  9. Selective excitation enables assignment of proton resonances and {sup 1}H-{sup 1}H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of {sup 1}H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as {sup 13}C or {sup 15}N. In this method, after the initial preparation of proton magnetization and cross-polarization to {sup 13}C nuclei, transverse magnetization of desired {sup 13}C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific {sup 13}C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of {sup 1}H-{sup 1}H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  10. Non-invasive detection of cocaine dissolved in wine bottles by (1) H magnetic resonance spectroscopy.

    PubMed

    Gambarota, Giulio; Perazzolo, Chiara; Leimgruber, Antoine; Meuli, Reto; Mangin, Patrice; Augsburger, Marc; Grabherr, Silke

    2011-09-01

    Recently, a number of cases of smuggling dissolved cocaine in wine bottles have been reported. The aim of the present study was to determine whether cocaine dissolved in wine can be detected by proton magnetic resonance spectroscopy ((1) H MRS) on a standard clinical MR scanner, in intact (i.e. unopened) wine bottles. (1) H MRS experiments were performed with a 3 Tesla clinical scanner on wine phantoms with or without cocaine contamination. The aromatic protons of cocaine displayed resonance peaks in the 7-8 ppm region of the spectrum, where no overlapping resonances of wine were present. Additional cocaine resonances were detected in the 2-3 ppm region of the spectrum, between the resonances of ethanol and other wine constituents. Detection of cocaine in wine (at 5 mM, i.e. ∼1.5 g/L) was feasible in a scan time of 1 min. We conclude that dissolved cocaine can be detected in intact wine bottles, on a standard clinical MR scanner. Thus, (1) H MRS is the technique of choice to examine this type of suspicious cargo, since it allows for a non-destructive and rapid content characterization. PMID:20886462

  11. Multislice 1H magnetic resonance spectroscopic imaging: assessment of epilepsy, Alzheimer's disease, and amyotrophic lateral sclerosis

    NASA Astrophysics Data System (ADS)

    Weiner, Michael W.; Maudsley, Andrew A.; Schuff, Norbert; Soher, Brian J.; Vermathen, Peter P.; Fein, George; Laxer, Kenneth D.

    1998-07-01

    Proton magnetic resonance spectroscopic imaging (1H MRSI) with volume pre-selection (i.e. by PRESS) or multislice 1H MRSI was used to investigate changes in brain metabolites in Alzheimer's disease, epilepsy, and amyotrophic lateral sclerosis. Examples of results from several ongoing clinical studies are provided. Multislice 1H MRSI of the human brain, without volume pre-selection offers considerable advantages over previously available techniques. Furthermore, MRI tissue segmentation and completely automated spectra curve fitting greatly facilitate quantitative data analysis. Future efforts will be devoted to obtaining full brain coverage and data acquisition at short spin echo times (TE less than 30 ms) for the detection of metabolites with short T2 relaxation times.

  12. Discussion of human resonant frequency

    NASA Astrophysics Data System (ADS)

    Brownjohn, James M. W.; Zheng, Xiahua

    2001-06-01

    Human bodies are often exposed to vertical vibrations when they are in the workplace or on vehicles. Prolonged exposure may cause undue stress and discomfort in the human body especially at its resonant frequency. By testing the response of the human body on a vibrating platform, many researchers found the human whole-body fundamental resonant frequency to be around 5 Hz. However, in recent years, an indirect method has been prosed which appears to increase the resonant frequency to approximately 10 Hz. To explain this discrepancy, experimental work was carried out in NTU. The study shows that the discrepancy lies in the vibration magnitude used in the tests. A definition of human natural frequency in terms of vibration magnitude is proposed.

  13. Visualizing brain inflammation with a shingled-leg radio-frequency head probe for 19F/1H MRI.

    PubMed

    Waiczies, Helmar; Lepore, Stefano; Drechsler, Susanne; Qadri, Fatimunnisa; Purfürst, Bettina; Sydow, Karl; Dathe, Margitta; Kühne, André; Lindel, Tomasz; Hoffmann, Werner; Pohlmann, Andreas; Niendorf, Thoralf; Waiczies, Sonia

    2013-01-01

    Magnetic resonance imaging (MRI) provides the opportunity of tracking cells in vivo. Major challenges in dissecting cells from the recipient tissue and signal sensitivity constraints albeit exist. In this study, we aimed to tackle these limitations in order to study inflammation in autoimmune encephalomyelitis. We constructed a very small dual-tunable radio frequency (RF) birdcage probe tailored for (19)F (fluorine) and (1)H (proton) MR mouse neuroimaging. The novel design eliminated the need for extra electrical components on the probe structure and afforded a uniform -field as well as good SNR. We employed fluorescently-tagged (19)F nanoparticles and could study the dynamics of inflammatory cells between CNS and lymphatic system during development of encephalomyelitis, even within regions of the brain that are otherwise not easily visualized by conventional probes. (19)F/(1)H MR Neuroimaging will allow us to study the nature of immune cell infiltration during brain inflammation over an extensive period of time. PMID:23412352

  14. 14N quadrupole resonance and 1H T1 dispersion in the explosive RDX.

    PubMed

    Smith, John A S; Blanz, Martin; Rayner, Timothy J; Rowe, Michael D; Bedford, Simon; Althoefer, Kaspar

    2011-12-01

    The explosive hexahydro-1,3,5-trinitro-s-triazine (CH2-N-NO2)3, commonly known as RDX, has been studied by 14N NQR and 1H NMR. NQR frequencies and relaxation times for the three ν+ and ν- lines of the ring 14N nuclei have been measured over the temperature range 230-330 K. The 1H NMR T1 dispersion has been measured for magnetic fields corresponding to the 1H NMR frequency range of 0-5.4 M Hz. The results have been interpreted as due to hindered rotation of the NO2 group about the N-NO2 bond with an activation energy close to 92 kJ mol(-1). Three dips in the 1H NMR dispersion near 120, 390 and 510 kHz are assigned to the ν0, ν- and ν+ transitions of the 14NO2 group. The temperature dependence of the inverse line-width parameters T2∗ of the three ν+ and ν- ring nitrogen transitions between 230 and 320 K can be explained by a distribution in the torsional oscillational amplitudes of the NO2 group about the N-NO2 bond at crystal defects whose values are consistent with the latter being mainly edge dislocations or impurities in the samples studied. Above 310 K, the 14N line widths are dominated by the rapid decrease in the spin-spin relaxation time T2 due to hindered rotation of the NO2 group. A consequence of this is that above this temperature, the 1H T1 values at the quadrupole dips are dominated by the spin mixing time between the 1H Zeeman levels and the combined 1H and 14N spin-spin levels. PMID:21978662

  15. Dynamic nuclear polarization-enhanced 1H-13C double resonance NMR in static samples below 20 K

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H-13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H-13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H-13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C-13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils.

  16. An efficient 1H/31P double-resonance solid-state NMR probe that utilizes a scroll coil

    PubMed Central

    Grant, Christopher V.; Sit, Siu-Ling; De Angelis, Anna A.; Khuong, Kelli S.; Wu, Chin H.; Plesniak, Leigh A.; Opella, Stanley J.

    2007-01-01

    The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of 1H and 31P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples. PMID:17719813

  17. An efficient (1)H/(31)P double-resonance solid-state NMR probe that utilizes a scroll coil.

    PubMed

    Grant, Christopher V; Sit, Siu-Ling; De Angelis, Anna A; Khuong, Kelli S; Wu, Chin H; Plesniak, Leigh A; Opella, Stanley J

    2007-10-01

    The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of (1)H and (31)P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples. PMID:17719813

  18. Classification of iron-sulfur cores in ferredoxins by 1H nuclear magnetic resonance spectroscopy.

    PubMed

    Nagayama, K; Ozaki, Y; Kyogoku, Y; Hase, T; Matsubara, H

    1983-09-01

    A 1H nuclear magnetic resonance (NMR) study was carried out on various ferredoxins which possess one of three types of iron-sulfur clusters, (2Fe-2S), (3Fe-3S), or (4Fe-4S). In the isolated form, (2Fe-2S) ferredoxins from spinach (Spinacea oleracia), pokeweed (Phytolacca americana), a blue-green alga (Spirulina platensis), and a halobacterium (Halobacterium halobium) exhibited two broad resonances common in chemical shift at the region downfield of 10 ppm. In their reduced forms, seven contact-shifted resonances appeared spread over 30 ppm. Although the positions of the contact-shifted resonances in the reduced state differed among the four, a common trend in the temperature dependence of their resonance positions was recognized. Two (4Fe-4S) ferredoxins from Bacillus stearothermophilus and Bacillus thermoproteolyticus exhibited almost indistinguishable spectral patterns in both the oxidized and reduced forms. The ferricyanide-treated ferredoxins of B. stearothermophilus and B. thermoproteolyticus showed characteristic contact-shifted resonances distinct from the spectra of the original (4Fe-4S) ferredoxins. This corresponds to the recent finding of the interconversion of (4Fe-4S) and (3Fe-3S) clusters with ferricyanide in the ferredoxin. Based on our data together with reported NMR data on other ferredoxins, contact-shift resonances of three types of clusters were tabulated. The reliability of NMR classification increases when we compare the NMR spectra of a ferredoxin with the classification standards at the two redox states. Moreover, not only the absolute values of the chemical shifts of contact-shifted resonances but also their temperature dependence give distinctive information applicable to iron core identification. PMID:6417123

  19. Acoustic resonance frequency locked photoacoustic spectrometer

    DOEpatents

    Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

    2003-09-09

    A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.

  20. 1H nuclear magnetic resonance study of distinct interstitial hydrogen dynamics in ZnO

    NASA Astrophysics Data System (ADS)

    Kue Park, Jun; Won Lee, Kyu; Eui Lee, Cheol

    2013-07-01

    A comprehensive 1H nuclear magnetic resonance (NMR) study has been carried out for hydrogen dynamics in a sol-gel-prepared ZnO system. The temperature-dependent linewidth and chemical shift measurements sensitively reflected the proton motions and changes in the local environment. Besides, two types of interstitial proton (Hi+) motions were distinguished from the spin-spin relaxation time measurements, one of them with an activation energy of 0.16 eV and the other with that of 0.33 eV depending on the temperature ranges.

  1. Key metabolites in tissue extracts of Elliptio complanata identified using 1H nuclear magnetic resonance spectroscopy

    PubMed Central

    Hurley-Sanders, Jennifer L.; Levine, Jay F.; Nelson, Stacy A. C.; Law, J. M.; Showers, William J.; Stoskopf, Michael K.

    2015-01-01

    We used 1H nuclear magnetic resonance spectroscopy to describe key metabolites of the polar metabolome of the freshwater mussel, Elliptio complanata. Principal components analysis documented variability across tissue types and river of origin in mussels collected from two rivers in North Carolina (USA). Muscle, digestive gland, mantle and gill tissues yielded identifiable but overlapping metabolic profiles. Variation in digestive gland metabolic profiles between the two mussel collection sites was characterized by differences in mono- and disaccharides. Variation in mantle tissue metabolomes appeared to be associated with sex. Nuclear magnetic resonance spectroscopy is a sensitive means to detect metabolites in the tissues of E. complanata and holds promise as a tool for the investigation of freshwater mussel health and physiology. PMID:27293708

  2. 1H, 13C and 15N resonance assignments of URNdesign, a computationally redesigned RRM protein

    SciTech Connect

    Dobson, Neil; Dantas, Gautam; Varani, Gabriele

    2005-10-01

    Protein design represents one of the great challenges of computational structural biology. The ability to successfully design new proteins would allow us to generate new reagents and enzymes, while at the same time providing us with an understanding of the principles of protein stability. Here we report 1H, 15N and 13C resonance assignments of a redesigned U1A protein, URNdesign. U1A has been studied extensively by our group and hence was chosen as a design target. For the assignments we sued 2D and 3D heteronuclearNMR experiments with uniformly 13C, 15N-labeled URNdesign. The assignments for the backbone NH, CO,Ca and Cb nuclei are 94%complete. Sidechain 1Hand13C, aromatic andQ/NNH2 resonances are essentially complete with guanidinium and K NH3 residues unassigned. BMRB deposit with accession number 6493

  3. Serum metabolic signature of minimal hepatic encephalopathy by (1)H-nuclear magnetic resonance.

    PubMed

    Jiménez, Beatriz; Montoliu, Carmina; MacIntyre, David A; Serra, Miguel A; Wassel, Abdallah; Jover, María; Romero-Gomez, Manuel; Rodrigo, Jose M; Pineda-Lucena, Antonio; Felipo, Vicente

    2010-10-01

    Minimal hepatic encephalopathy (MHE) reduces quality of life of cirrhotic patients, predicts overt hepatic encephalopathy, and is associated with poor prognosis. We hypothesized that MHE arises once metabolic alterations derived from the liver reach a particular threshold. Our aim was to assess whether metabolic profiling of serum samples by high-field (1)H-nuclear magnetic resonance spectroscopy ((1)H NMR) and subsequent multivariate analyses would be useful to characterize metabolic perturbations associated with MHE and to identify potential metabolic biomarkers. Metabolic serum profiles from controls (n = 69) and cirrhotic patients without MHE (n = 62) and with MHE (n = 39) were acquired using high field NMR. Supervised modeling of the data provided perfect discrimination between healthy controls and cirrhotic patients and allowed the generation of a predictive model displaying strong discrimination between patients with and without MHE (R(2)Y = 0.68, Q(2)Y = 0.63). MHE patients displayed increased serum concentrations of glucose, lactate, methionine, TMAO, and glycerol, as well as decreased levels of choline, branch amino acids, alanine, glycine, acetoacetate, NAC, and lipid moieties. Serum metabonomics by (1)H NMR offers a useful approach for characterizing underlying metabolic differences between patients with and without MHE. This procedure shows great potential as a diagnostic tool of MHE as it objectively reflects measurable biochemical differences between the patient groups and may facilitate monitoring of both disease progression and effects of therapeutic treatments. PMID:20690770

  4. Binding of thiocyanate to lactoperoxidase: 1H and 15N nuclear magnetic resonance studies

    SciTech Connect

    Modi, S.; Behere, D.V.; Mitra, S. )

    1989-05-30

    The binding of thiocyanate to lactoperoxidase (LPO) has been investigated by 1H and 15N NMR spectroscopy. 1H NMR of LPO shows that the major broad heme methyl proton resonance at about 61 ppm is shifted upfield by addition of the thiocyanate, indicating binding of the thiocyanate to the enzyme. The pH dependence of line width of 15N resonance of SC15N- in the presence of the enzyme has revealed that the binding of the thiocyanate to the enzyme is facilitated by protonation of an ionizable group (with pKa of 6.4), which is presumably distal histidine. Dissociation constants (KD) of SC15N-/LPO, SC15N-/LPO/I-, and SC15N-/LPO/CN- equilibria have been determined by 15N T1 measurements and found to be 90 +/- 5, 173 +/- 20, and 83 +/- 6 mM, respectively. On the basis of these values of KD, it is suggested that the iodide ion inhibits the binding of the thiocyanate but cyanide ion does not. The thiocyanate is shown to bind at the same site of LPO as iodide does, but the binding is considerably weaker and is away from the ferric ion. The distance of 15N of the bound thiocyanate ion from the iron is determined to be 7.2 +/- 0.2 A from the 15N T1 measurements.

  5. Assignment of 1H and 13C hyperfine-shifted resonances for tuna ferricytochrome c.

    PubMed Central

    Sukits, S F; Satterlee, J D

    1996-01-01

    Tuna ferricytochrome c has been used to demonstrate the potential for completely assigning 1H and 13C strongly hyperfine-shifted resonances in metalloprotein paramagnetic centers. This was done by implementation of standard two-dimensional NMR experiments adapted to take advantage of the enhanced relaxation rates of strongly hyperfine-shifted nuclei. The results show that complete proton assignments of the heme and axial ligands can be achieved, and that assignments of several strongly shifted protons from amino acids located close to the heme can also be made. Virtually all proton-bearing heme 13C resonances have been located, and additional 13C resonances from heme vicinity amino acids are also identified. These results represent an improvement over previous proton resonance assignment efforts that were predicated on the knowledge of specific assignments in the diamagnetic protein and relied on magnetization transfer experiments in heterogeneous solutions composed of mixtures of diamagnetic ferrocytochrome c and paramagnetic ferricytochrome c. Even with that more complicated procedure, complete heme proton assignments for ferricytochrome c have never been demonstrated by a single laboratory. The results presented here were achieved using a more generally applicable strategy with a solution of the uniformly oxidized protein, thereby eliminating the requirement of fast electron self-exchange, which is a condition that is frequently not met. PMID:8913622

  6. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples. PMID:23913630

  7. Novel 1H low field nuclear magnetic resonance applications for the field of biodiesel

    PubMed Central

    2013-01-01

    Background Biodiesel production has increased dramatically over the last decade, raising the need for new rapid and non-destructive analytical tools and technologies. 1H Low Field Nuclear Magnetic Resonance (LF-NMR) applications, which offer great potential to the field of biodiesel, have been developed by the Phyto Lipid Biotechnology Lab research team in the last few years. Results Supervised and un-supervised chemometric tools are suggested for screening new alternative biodiesel feedstocks according to oil content and viscosity. The tools allowed assignment into viscosity groups of biodiesel-petrodiesel samples whose viscosity is unknown, and uncovered biodiesel samples that have residues of unreacted acylglycerol and/or methanol, and poorly separated and cleaned glycerol and water. In the case of composite materials, relaxation time distribution, and cross-correlation methods were successfully applied to differentiate components. Continuous distributed methods were also applied to calculate the yield of the transesterification reaction, and thus monitor the progress of the common and in-situ transesterification reactions, offering a tool for optimization of reaction parameters. Conclusions Comprehensive applied tools are detailed for the characterization of new alternative biodiesel resources in their whole conformation, monitoring of the biodiesel transesterification reaction, and quality evaluation of the final product, using a non-invasive and non-destructive technology that is new to the biodiesel research area. A new integrated computational-experimental approach for analysis of 1H LF-NMR relaxometry data is also presented, suggesting improved solution stability and peak resolution. PMID:23590829

  8. Effect of Exercise on the Creatine Resonances in 1H MR Spectra of Human Skeletal Muscle

    NASA Astrophysics Data System (ADS)

    Kreis, R.; Jung, B.; Slotboom, J.; Felblinger, J.; Boesch, C.

    1999-04-01

    1H MR spectra of human muscles were recorded before, during, and after fatiguing exercise. In contrast to expectations, it was found that the spectral contributions of creatine/phosphocreatine (Cr/PCr) were subject to change as a function of exercise. In particular, the dipolar-coupled methylene protons of Cr/PCr were found to be reduced in intensity in proportion to the co-registered PCr levels. Recovery after exercise and behavior under ischemic conditions provide further evidence to suggest that the contributions of the CH2protons of Cr/PCr to1H MR spectra of human musclein vivoreflect PCr rather than Cr levels. Variation of experimental parameters showed that this effect is not due to a trivial change in relaxation times. At present it can only be speculated about why the Cr resonances have reduced NMR visibility. If temporary binding to macromolecules should be involved, the free Cr concentration-important for equilibrium calculations of the creatine kinase reaction-might be different from what was previously assumed.

  9. Coupled Resonance Laser Frequency Stabilization

    NASA Astrophysics Data System (ADS)

    Burd, Shaun; Uys, Hermann; MAQClab Team

    2013-05-01

    We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to the same photodiode signal derived from the UV laser only. For trapping and cooling Yb+ ions, a frequency stabilized laser is required at 369.9 nm to drive the S1/2-P1/2 cooling cycle. Since that cycle is not closed, a repump beam is needed at 935.18 nm to drive the D3/2-D[ 3 / 2 ] transition, which rapidly decays back to the S1/2 state. Our 369 nm laser is locked using Doppler free polarization spectroscopy of Yb+ ions, generated in a hollow cathode discharge lamp. Without pumping, the metastable D3/2 level is only sparsely populated, making direct absorption of 935 nm light difficult to detect. A resonant 369 nm pump laser can populate the D3/2 state, and fast repumping to the S1/2 ground state by on resonant 935 nm light, can be detected via the change in absorption of the 369 nm laser. This is accomplished using lock-in detection on the same photodiode signal to which the 369 nm laser is locked. In this way, simultaneous locking of two frequencies in very different spectral regimes is accomplished, while exploiting only the photodiode signal from one of the lasers. A rate equation model gives good qualitative agreement with experimental observation. This work was partially funded by the South African National Research Foundation.

  10. 1H and 13C resonance designation of antimycin A1 by two-dimensional NMR spectroscopy

    USGS Publications Warehouse

    Abidi, S.L.; Adams, B.R.

    1987-01-01

    Complete 1H and 13C resonance assignments of antimycin A1 were accomplished by two-dimensional NMR techniques, viz. 1H homonuclear COSY correlation, heteronuclear 13C-1H chemical shift correlation and long-range heteronuclear 13C-1H COLOC correlation. Antimycin A1 was found to consist of two isomeric components in a 2:1 ratio based on NMR spectroscopic evidence. The structure of the major component was newly assigned as the 8-isopentanoic acid ester. The spectra of the minor component were consistent with the known structure of antimycin A1.

  11. MUSIC in Triple-Resonance Experiments: Amino Acid Type-Selective 1H- 15N Correlations

    NASA Astrophysics Data System (ADS)

    Schubert, Mario; Smalla, Maika; Schmieder, Peter; Oschkinat, Hartmut

    1999-11-01

    Amino acid type-selective triple-resonance experiments can be of great help for the assignment of protein spectra, since they help to remove ambiguities in either manual or automated assignment procedures. Here, modified triple-resonance experiments that yield amino acid type-selective 1H-15N correlations are presented. They are based on novel coherence transfer schemes, the MUSIC pulse sequence elements, that replace the initial INEPT transfer and are selective for XH2 or XH3 (X can be 15N or 13C). The desired amino acid type is thereby selected based on the topology of the side chain. Experiments for Gly (G-HSQC); Ala (A-HSQC); Thr, Val, Ile, and Ala (TAVI-HSQC); Thr and Ala (TA-HSQC), as well as Asn and Gln (N-HSQC and QN-HSQC), are described. The new experiments are recorded as two-dimensional experiments and therefore need only small amounts of spectrometer time. The performance of the experiments is demonstrated with the application to two protein domains.

  12. MUSIC in triple-resonance experiments: amino acid type-selective (1)H-(15)N correlations

    PubMed

    Schubert; Smalla; Schmieder; Oschkinat

    1999-11-01

    Amino acid type-selective triple-resonance experiments can be of great help for the assignment of protein spectra, since they help to remove ambiguities in either manual or automated assignment procedures. Here, modified triple-resonance experiments that yield amino acid type-selective (1)H-(15)N correlations are presented. They are based on novel coherence transfer schemes, the MUSIC pulse sequence elements, that replace the initial INEPT transfer and are selective for XH(2) or XH(3) (X can be (15)N or (13)C). The desired amino acid type is thereby selected based on the topology of the side chain. Experiments for Gly (G-HSQC); Ala (A-HSQC); Thr, Val, Ile, and Ala (TAVI-HSQC); Thr and Ala (TA-HSQC), as well as Asn and Gln (N-HSQC and QN-HSQC), are described. The new experiments are recorded as two-dimensional experiments and therefore need only small amounts of spectrometer time. The performance of the experiments is demonstrated with the application to two protein domains. Copyright 1999 Academic Press. PMID:10527741

  13. Automated classification of human brain tumours by neural network analysis using in vivo 1H magnetic resonance spectroscopic metabolite phenotypes.

    PubMed

    Usenius, J P; Tuohimetsä, S; Vainio, P; Ala-Korpela, M; Hiltunen, Y; Kauppinen, R A

    1996-07-01

    We present a novel method to integrate in vivo nuclear magnetic resonance spectroscopy (MRS) information into the clinical diagnosis of brain tumours. Water-suppressed 1H MRS data were collected from 33 patients with brain tumours and 28 healthy controls in vivo. The data were treated in the time domain for removal of residual water and a region from the frequency domain (from 3.4 to 0.3 p.p.m.) together with the unsuppressed water signal were used as inputs for artificial neural network (ANN) analysis. The ANN distinguished tumour and normal tissue in each case and was able to classify benign and malignant gliomas as well as other brain tumours to match histology in a clinically useful manner with an accuracy of 82%. Thus the present data indicate existence of tumour tissue-specific metabolite phenotypes that can be detected by in vivo 1H MRS. We believe that a user-independent ANN analysis may provide an alternative method for tumour classification in clinical practice. PMID:8904763

  14. Microwave Frequency Discriminator With Sapphire Resonator

    NASA Technical Reports Server (NTRS)

    Santiago, David G.; Dick, G. John

    1994-01-01

    Cooled sapphire resonator provides ultralow phase noise. Apparatus comprises microwave oscillator operating at nominal frequency of about 8.1 GHz, plus frequency-discriminator circuit measuring phase fluctuations of oscillator output. One outstanding feature of frequency discriminator is sapphire resonator serving as phase reference. Sapphire resonator is dielectric ring resonator operating in "whispering-gallery" mode. Functions at room temperature, but for better performance, typically cooled to operating temperature of about 80 K. Similar resonator described in "Sapphire Ring Resonator for Microwave Oscillator" (NPO-18082).

  15. Selective inversion of 1H resonances in solid-state nuclear magnetic resonance: Use of double-DANTE pulse sequence

    NASA Astrophysics Data System (ADS)

    Mithu, Venus Singh; Tan, Kong Ooi; Madhu, P. K.

    2013-12-01

    We here present a method based on DANTE pulses and homonuclear dipolar decoupling scheme to invert selectively any desired resonance in a proton spin system under magic-angle spinning. Experimental results are reported on a sample of L-histidine·HCl·H2O at magic-angle spinning frequencies of 15 and 60 kHz. The results are also substantiated numerically.

  16. Biochemical classification of kidney carcinoma biopsy samples using magic-angle-spinning 1H nuclear magnetic resonance spectroscopy.

    PubMed

    Moka, D; Vorreuther, R; Schicha, H; Spraul, M; Humpfer, E; Lipinski, M; Foxall, P J; Nicholson, J K; Lindon, J C

    1998-05-01

    High resolution 1H nuclear magnetic resonance (NMR) spectra using spinning at the magic angle (1H MAS NMR) have been obtained on intact normal and pathological kidney tissue samples from patients undergoing surgery for renal cell carcinoma (RCC). The spectra were measured on ca. 80 mg samples and provided high resolution 1H NMR spectra in which effects of dipolar couplings, chemical shift anisotropy and magnetic susceptibility differences are minimised thus yielding high spectral resolution. Conventional one-dimensional and spin-echo spectra and two-dimensional J-resolved, TOCSY and 1H-13C HMQC spectra were also measured on selected samples and these allowed the assignment of resonances of endogenous substances comprising both cytosolic and membrane components. The tumour tissues were characterised principally by an increased lipid content. These are the first reported results on human tumour tissues using this technique and the approach offers potential for the rapid classification of different types of tumour tissue. PMID:9608434

  17. Magnetic Earth Ionosphere Resonant Frequencies

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1994-01-01

    The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

  18. (1)H nuclear magnetic resonance-based metabolomics study of earthworm Perionyx excavatus in vermifiltration process.

    PubMed

    Wang, Lei; Huang, Xulei; Laserna, Anna Karen Carrasco; Li, Sam Fong Yau

    2016-10-01

    In this study, (1)H nuclear magnetic resonance (NMR)-based metabolomics approach was used to characterize the metabolic response of the earthworm Perionyx excavatus in continuous vermifiltration for two months under hydraulic loading rates of 1m(3)m(-2)d(-1) (VF1) and 1.5m(3)m(-2)d(-1) (VF1.5). Both VF1 and VF1.5 showed higher removal of chemical oxygen demand and total nitrogen than the biofilter without earthworms. Principal component analysis of the NMR spectra of earthworm metabolites showed significant separations between those not subjected to wastewater filtration (control) and VF1 or VF1.5. Temporal variations of earthworm biomass, and the identified metabolites that are significantly different between control, VF1 and VF1.5 revealed that worms underwent increasing metabolic activity within 20days in VF1 and 14days in VF1.5, then decreasing metabolic activity. The use of NMR-based metabolomics in monitoring earthworm metabolism was demonstrated to be a novel approach in studying engineered vermifiltration systems. PMID:27469092

  19. Purity Assessment of Aryltetralin Lactone Lignans by Quantitative 1H Nuclear Magnetic Resonance.

    PubMed

    Sun, Yan-Jun; Zhang, Yan-Li; Wang, Yu; Wang, Jun-Min; Zhao, Xuan; Gong, Jian-Hong; Gao, Wei; Guan, Yan-Bin

    2015-01-01

    In the present work, a quantitative 1H Nuclear Magnetic Resonance (qHNMR) was established for purity assessment of six aryltetralin lactone lignans. The validation of the method was carried out, including specificity, selectivity, linearity, accuracy, precision, and robustness. Several experimental parameters were optimized, including relaxation delay (D1), scan numbers (NS), and pulse angle. 1,4-Dinitrobenzene was used as internal standard (IS), and deuterated dimethyl sulfoxide (DMSO-d6) as the NMR solvent. The purities were calculated by the area ratios of H-2,6 from target analytes vs. aromatic protons from IS. Six aryltetralin lactone lignans (deoxypodophyllotoxin, podophyllotoxin, 4-demethylpodophyllotoxin, podophyllotoxin-7'-O-β-d-glucopyranoside, 4-demethylpodophyllotoxin-7'-O-β-d-glucopyranoside, and 6''-acetyl-podophyllotoxin-7'-O-β -d-glucopyranoside) were analyzed. The analytic results of qHNMR were further validated by high performance liquid chromatography (HPLC). Therefore, the qHNMR method was a rapid, accurate, reliable tool for monitoring the purity of aryltetralin lactone lignans. PMID:26016553

  20. Kinetics of the in vivo31P 1H nuclear overhauser effect of the human-calf-muscle phosphocreatine resonance

    NASA Astrophysics Data System (ADS)

    Bachert, Peter; Bellemann, Matthias E.

    In 31P 1H double-resonance experiments in a 1.5 T whole-body MR system, we observed in vivo the truncated driven, transient, and steady-state 31P- 1H nuclear Overhauser effect of the phosphocreatine resonance in 31P MR spectra of human gastrocnemius muscle. Maximum signal enhancements of 0.52 ± 0.01, 0.20 ± 0.01, and 0.79 ± 0.02 were measured, respectively. Fitting the data with theoretical functions which solve the multispin Solomon equations for N protons (S spins) dipolar coupled to a 31P nucleus (I spin) yields cross-relaxation times {2}/{[Σ i=1-N σIS(i) ] } in the order of 20 s. In vivo experiments are feasible for studying relaxation mechanisms in coupled 31P 1H spin systems in intact tissue.

  1. Improved 1H amide resonance line narrowing in oriented sample solid-state NMR of membrane proteins in phospholipid bilayers

    NASA Astrophysics Data System (ADS)

    Lu, George J.; Park, Sang Ho; Opella, Stanley J.

    2012-07-01

    We demonstrate 1H amide resonance line widths <300 Hz in 1H/15N heteronuclear correlation (HETCOR) spectra of membrane proteins in aligned phospholipid bilayers. This represents a substantial improvement over typically observed line widths of ˜1 kHz. Furthermore, in a proton detected local field (PDLF) version of the experiment that measures heteronuclear dipolar couplings, line widths <130 Hz are observed. This dramatic line narrowing of 1H amide resonances enables many more individual signals to be resolved and assigned from uniformly 15N labeled membrane proteins in phospholipid bilayers under physiological conditions of temperature and pH. Finding that the decrease in line widths occurs only for membrane proteins that undergo fast rotational diffusion around the bilayer normal, but not immobile molecules, such as peptide single crystals, identifies a potential new direction for pulse sequence development that includes overall molecular dynamics in their design.

  2. Pressure dependent resonant frequency of micromechanical drumhead resonators

    SciTech Connect

    Southworth, D. R.; Craighead, H. G.; Parpia, J. M.

    2009-05-25

    We examine the relationship between squeeze film effects and resonance frequency in drum-type resonators. We find that the resonance frequency increases linearly with pressure as a result of the additional restoring force contribution from compression of gas within the drum cavity. We demonstrate trapping of the gas by squeeze film effects and geometry. The pressure sensitivity is shown to scale inversely with cavity height and sound radiation is found to be the predominant loss mechanism near and above atmospheric pressure. Drum resonators exhibit linearity and sensitivity suitable to barometry from below 10 Torr up to several atmospheres.

  3. Direct and simultaneous quantification of ATP, ADP and AMP by (1)H and (31)P Nuclear Magnetic Resonance spectroscopy.

    PubMed

    Lian, Yakun; Jiang, Hua; Feng, Jinzhou; Wang, Xiaoyan; Hou, Xiandeng; Deng, Pengchi

    2016-04-01

    ATP, ADP and AMP are energy substances with vital biological significance. Based on the structural differences, a simple, rapid and comprehensive method has been established by (1)H and (31)P Nuclear Magnetic Resonance ((1)H-NMR and (31)P-NMR) spectroscopies. Sodium 3-(trimethylsilyl) propionate-2,2,3,3-d4 (TMSP) and anhydrous disodium hydrogen phosphate (Na2HPO4) were selected as internal standards for (1)H-NMR and (31)P-NMR, respectively. Those three compounds and corresponding internal standards can be easily distinguished both by (1)H-NMR and (31)P-NMR. In addition, they all have perfect linearity in a certain range: 0.1-100mM for (1)H-NMR and 1-75mM for (31)P-NMR. To validate the precision of this method, mixed samples of different concentrations were measured. Recovery experiments were conducted in serum (91-113% by (1)H-NMR and 89-113% by (31)P-NMR). PMID:26838434

  4. Detection of hydrogen dissolved in acrylonitrile butadiene rubber by 1H nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Nishimura, Shin; Fujiwara, Hirotada

    2012-01-01

    Rubber materials, which are used for hydrogen gas seal, can dissolve hydrogen during exposure in high-pressure hydrogen gas. Dissolved hydrogen molecules were detected by solid state 1H NMR of the unfilled vulcanized acrylonitrile butadiene rubber. Two signals were observed at 4.5 ppm and 4.8 ppm, which were assignable to dissolved hydrogen, in the 1H NMR spectrum of NBR after being exposed 100 MPa hydrogen gas for 24 h at room temperature. These signals were shifted from that of gaseous hydrogen molecules. Assignment of the signals was confirmed by quantitative estimation of dissolved hydrogen and peak area of the signals.

  5. A double-tuned 1H/23Na dual resonator system for tissue sodium concentration measurements in the rat brain via Na-MRI

    NASA Astrophysics Data System (ADS)

    Wetterling, Friedrich; Tabbert, Martin; Junge, Sven; Gallagher, Lindsay; Mhairi Macrae, I.; Fagan, Andrew J.

    2010-12-01

    A method for quantifying the tissue sodium concentration (TSC) in the rat brain from 23Na-MR images was developed. TSC is known to change in a variety of common human diseases and holds considerable potential to contribute to their study; however, its accurate measurement in small laboratory animals has been hindered by the extremely low signal to noise ratio (SNR) in 23Na images. To address this, the design, construction and characterization of a double-tuned 1H/23Na dual resonator system for 1H-guided quantitative 23Na-MRI are described. This system comprises an SNR-optimized surface detector coil for 23Na image acquisition, and a volume resonator producing a highly homogeneous B1 field (<5% inhomogeneity) for the Na channel across the rat head. The resonators incorporated channel-independent balanced matching and tuning capabilities with active decoupling circuitry at the 23Na resonance frequency. A quantification accuracy of TSC of <10 mM was achieved in Na-images with 1.2 µl voxel resolution acquired in 10 min. The potential of the quantification technique was demonstrated in an in vivo experiment of a rat model of cerebral stroke, where the evolution of the TSC was successfully monitored for 8 h after the stroke was induced.

  6. NMR resonance splitting of urea in stretched hydrogels: proton exchange and (1)H/(2)H isotopologues.

    PubMed

    Kuchel, Philip W; Naumann, Christoph; Chapman, Bogdan E; Shishmarev, Dmitry; Håkansson, Pär; Bacskay, George; Hush, Noel S

    2014-10-01

    Urea at ∼12 M in concentrated gelatin gel, that was stretched, gave (1)H and (2)H NMR spectral splitting patterns that varied in a predictable way with changes in the relative proportions of (1)H2O and (2)H2O in the medium. This required consideration of the combinatorics of the two amide groups in urea that have a total of four protonation/deuteration sites giving rise to 16 different isotopologues, if all the atoms were separately identifiable. The rate constant that characterized the exchange of the protons with water was estimated by back-transformation analysis of 2D-EXSY spectra. There was no (1)H NMR spectral evidence that the chiral gelatin medium had caused in-equivalence in the protons bonded to each amide nitrogen atom. The spectral splitting patterns in (1)H and (2)H NMR spectra were accounted for by intra-molecular scalar and dipolar interactions, and quadrupolar interactions with the electric field gradients of the gelatin matrix, respectively. PMID:25241007

  7. Cavities for electron spin resonance: predicting the resonant frequency

    NASA Astrophysics Data System (ADS)

    Colton, John; Miller, Kyle; Meehan, Michael; Spencer, Ross

    Microwave cavities are used in electron spin resonance to enhance magnetic fields. Dielectric resonators (DRs), pieces of high dielectric material, can be used to tailor the resonant frequency of a cavity. However, designing cavities with DRs to obtain desired frequencies is challenging and in general can only be done numerically with expensive software packages. We present a new method for calculating the resonant frequencies and corresponding field modes for cylindrically symmetric cavities and apply it to a cavity with vertically stacked DRs. The modes of an arbitrary cavity are expressed as an expansion of empty cavity modes. The wave equation for D gives rise to an eigenvalue equation whose eigenvalues are the resonant frequencies and whose eigenvectors yield the electric and magnetic fields of the mode. A test against theory for an infinitely long dielectric cylinder inside an infinite cavity yields an accuracy better than 0.4% for nearly all modes. Calculated resonant frequencies are also compared against experiment for quasi-TE011 modes in resonant cavities with ten different configurations of DRs; experimental results agree with predicted values with an accuracy better than 1.0%. MATLAB code is provided at http://www.physics.byu.edu/research/coltonlab/cavityresonance.

  8. Secondary structure and (1)H, (13)C, (15)N resonance assignments of the endosomal sorting protein sorting nexin 3.

    PubMed

    Overduin, Michael; Rajesh, Sandya; Gruenberg, Jean; Lenoir, Marc

    2015-10-01

    Sorting nexin 3 (SNX3) belongs to a sub-family of sorting nexins that primarily contain a single Phox homology domain capable of binding phosphoinositides and membranes. We report the complete (1)H, (13)C and (15)N resonance assignments of the full-length human SNX3 protein and identification of its secondary structure elements, revealing a canonical fold and unstructured termini. PMID:25893673

  9. 1H nuclear magnetic resonance studies of sarcoplasmic oxygenation in the red cell-perfused rat heart.

    PubMed

    Jelicks, L A; Wittenberg, B A

    1995-05-01

    The proximal histidine N delta H proton of deoxymyoglobin experiences a large hyperfine shift resulting in its 1H nuclear magnetic resonance (NMR) signal appearing at approximately 76 ppm (at 35 degrees C), downfield of the diamagnetic spectral region. 1H NMR of this proton is used to monitor sarcoplasmic oxygen pressure in isolated perfused rat heart. This method monitors intracellular oxygenation in the whole heart and does not reflect oxygenation in a limited region. The deoxymyoglobin resonance intensity is reduced upon conversion of myoglobin to the ferric form by sodium nitrite. 1H resonances of the N delta H protons of the alpha and beta subunits of bovine deoxyhemoglobin do not interfere with the measurement of myoglobin deoxygenation in blood-perfused rat heart. We find that steady-state myoglobin deoxygenation is increased progressively (and reversibly) as oxygenation of the perfusing medium is decreased in both saline and red blood cell-perfused hearts at constant work output. An eightfold increase in the heart rate of the blood-perfused heart resulted in no change in the deoxymyoglobin signal intensity. Intracellular PO2 of myoglobin-containing cells is maintained remarkably constant in changing work states. PMID:7612857

  10. Sequence-specific sup 1 H and sup 15 N resonance assignments for human dihydrofolate reductase in solution

    SciTech Connect

    Stockman, B.J.; Nirmala, N.R.; Wagner, G. ); Delcamp, T.J.; DeYarman, M.T.; Freisheim, J.H. )

    1992-01-14

    Dihydrofolate reductase is an intracellular target enzyme for folate antagonists, including the anticancer drug methotrexate. In order to design novel drugs with altered binding properties, a detailed description of protein-drug interactions in solution is desirable to understand the specificity of drug binding. As a first step in this process, heteronuclear three-dimensional NMR spectroscopy has been used to make sequential resonance assignments for more than 90% of the residues in human dihydrofolate reductase complexed with methotrexate. Uniform enrichment of the 21.5-kDa protein with {sup 15}N was required to obtain the resonance assignments via heteronuclear 3D NMR spectroscopy since homonuclear 2D spectra did not provide sufficient {sup 1}H resonance dispersion. Medium- and long-range NOE's have been used to characterize the secondary structure of the binary ligand-enzyme complex in solution.

  11. Identification of Gastric Cancer Biomarkers Using 1H Nuclear Magnetic Resonance Spectrometry.

    PubMed

    Ramachandran, Gokula Krishnan; Yong, Wei Peng; Yeow, Chen Hua

    2016-01-01

    Existing gastric cancer diagnosing methods were invasive, hence, a reliable non-invasive gastric cancer diagnosing method is needed. As a starting point, we used 1H NMR for identifying gastric cancer biomarkers using a panel of gastric cancer spheroids and normal gastric spheroids. We were able to identify 8 chemical shift biomarkers for gastric cancer spheroids. Our data suggests that the cancerous and non-cancerous spheroids significantly differ in the lipid composition and energy metabolism. These results encourage the translation of these biomarkers into in-vivo gastric cancer detection methodology using MRI-MS. PMID:27611679

  12. Application of cryoprobe 1H nuclear magnetic resonance spectroscopy and multivariate analysis for the verification of corsican honey.

    PubMed

    Donarski, James A; Jones, Stephen A; Charlton, Adrian J

    2008-07-23

    Proton nuclear magnetic resonance spectroscopy ((1)H NMR) and multivariate analysis techniques have been used to classify honey into two groups by geographical origin. Honey from Corsica (Miel de Corse) was used as an example of a protected designation of origin product. Mathematical models were constructed to determine the feasibility of distinguishing between honey from Corsica and that from other geographical locations in Europe, using (1)H NMR spectroscopy. Honey from 10 different regions within five countries was analyzed. (1)H NMR spectra were used as input variables for projection to latent structures (PLS) followed by linear discriminant analysis (LDA) and genetic programming (GP). Models were generated using three methods, PLS-LDA, two-stage GP, and a combination of PLS and GP (PLS-GP). The PLS-GP model used variables selected by PLS for subsequent GP calculations. All models were generated using Venetian blind cross-validation. Overall classification rates for the discrimination of Corsican and non-Corsican honey of 75.8, 94.5, and 96.2% were determined using PLS-LDA, two-stage GP, and PLS-GP, respectively. The variables utilized by PLS-GP were related to their (1)H NMR chemical shifts, and this led to the identification of trigonelline in honey for the first time. PMID:18564849

  13. On Frequency Combs in Monolithic Resonators

    NASA Astrophysics Data System (ADS)

    Savchenkov, A. A.; Matsko, A. B.; Maleki, L.

    2016-06-01

    Optical frequency combs have become indispensable in astronomical measurements, biological fingerprinting, optical metrology, and radio frequency photonic signal generation. Recently demonstrated microring resonator-based Kerr frequency combs point the way towards chip scale optical frequency comb generator retaining major properties of the lab scale devices. This technique is promising for integrated miniature radiofrequency and microwave sources, atomic clocks, optical references and femtosecond pulse generators. Here we present Kerr frequency comb development in a historical perspective emphasizing its similarities and differences with other physical phenomena. We elucidate fundamental principles and describe practical implementations of Kerr comb oscillators, highlighting associated solved and unsolved problems.

  14. Rod Driven Frequency Entrainment and Resonance Phenomena.

    PubMed

    Salchow, Christina; Strohmeier, Daniel; Klee, Sascha; Jannek, Dunja; Schiecke, Karin; Witte, Herbert; Nehorai, Arye; Haueisen, Jens

    2016-01-01

    A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30(∗)α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90-1.10(∗)α) and half of the alpha frequency (0.40-0.55(∗)α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00(∗)α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30-2.30(∗)α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex. PMID:27588002

  15. Rod Driven Frequency Entrainment and Resonance Phenomena

    PubMed Central

    Salchow, Christina; Strohmeier, Daniel; Klee, Sascha; Jannek, Dunja; Schiecke, Karin; Witte, Herbert; Nehorai, Arye; Haueisen, Jens

    2016-01-01

    A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30∗α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90–1.10∗α) and half of the alpha frequency (0.40–0.55∗α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00∗α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30–2.30∗α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex. PMID:27588002

  16. Metal mesh resonant filters for terahertz frequencies.

    PubMed

    Melo, Arline M; Kornberg, Mariano A; Kaufmann, Pierre; Piazzetta, Maria H; Bortolucci, Emílio C; Zakia, Maria B; Bauer, Otto H; Poglitsch, Albrecht; da Silva, Alexandre M P Alves

    2008-11-10

    The interest in terahertz photometric and imaging measurements has motivated the development of bandpass resonant filters to be coupled to multiple-pixel devices such as bolometer arrays. Resonant grids are relatively simple to fabricate, exhibiting high transmission at the central frequency, a narrow bandpass, and good rejection of the side frequencies of the spectrum. We have fabricated filters centered at different frequencies between 0.4 and 10 THz, using photolithography and electroforming techniques. Transmission measurements have shown center frequencies and bandwidths close to the design predictions. The performance of the filters was found not to be critically dependent on small physical deformations in the mesh, becoming more noticeable at higher frequencies (i.e., for smaller physical sizes). Wider bandwidths, needed to attain higher sensitivities in the continuum, were obtained by changing the design parameters for filters at 2 and 3 THz. PMID:19002231

  17. Interaction of thiocyanate with horseradish peroxidase. 1H and 15N nuclear magnetic resonance studies.

    PubMed

    Modi, S; Behere, D V; Mitra, S

    1989-11-25

    Interaction of thiocyanate with horseradish peroxidase (HRP) was investigated by relaxation rate measurements (at 50.68 MHz) of the 15N resonance of thiocyanate nitrogen and by following the hyperfine shifted ring methyl proton resonances (at 500 MHz) of the heme group of SCN-.HRP solutions. At pH 4.0, the apparent dissociation constant (KD) for thiocyanate binding to HRP was deduced to be 158 mM from the relaxation rate measurements. Chemical shift changes of 1- and 8-ring methyl proton resonances in the presence of various amounts of thiocyanate at pH 4.0 yielded KD values of 166 and 136 mM, respectively. From the pH dependence of KD and the 15N resonance line width, it was observed that thiocyanate binds to HRP only under acidic conditions (pH less than 6). The binding was found to be facilitated by protonation of an acid group on the enzyme with pKa 4.0. The pH dependence of the 15N line width as well as the apparent dissociation constant were quantitatively analyzed on the basis of a reaction scheme in which thiocyanate in deprotonated ionic form binds to the enzyme in protonated acidic form. The KD for thiocyanate binding to HRP was also evaluated in the presence of an excess of exogenous substrates such as resorcinol, cyanide, and iodide ions. It was found that the presence of cyanide (which binds to heme iron at the sixth coordination position) and resorcinol did not have any effect on the binding of thiocyanate, indicating that the binding site of the thiocyanate ion is located away from the ferric center as well as from the aromatic donor binding site. The KD in the presence of iodide, however, showed that iodide competes with thiocyanate for binding at the same site. The distance of the bound thiocyanate ion from the ferric center was deduced from the 15N relaxation time measurements and was found to be a 6.8 A. From the distance as well as the change in the chemical shifts and line width of 1- and 8-methyl proton resonances, it is suggested that the

  18. Hydration effect on solid DNA-didecyldimethylammonium chloride complexes measured using 1H-nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Nizioł, J.; Harańczyk, H.; Kobierski, J.; Hebda, E.; Pielichowski, J.; Ostachowicz, B.

    2013-10-01

    Complexes like the studied DNA and didecyldimethylammonium chloride are promising materials for organic electronics and photonics. Water content in this material as the solid state is a key factor for its electronics properties and microstructure. DNA complex was subjected to controlled hydration from gaseous phase and next studied by 1H-nuclear magnetic resonance spectroscopy. Variations of spin-spin and spin-lattice relaxation times as a function of hydration level are reported. Formation of tightly and loosely bound water fractions at rehydration process is discussed.

  19. 1H Nuclear Magnetic Resonance (NMR) Metabolomic Study of Chronic Organophosphate Exposure in Rats

    PubMed Central

    Alam, Todd M.; Neerathilingam, Muniasamy; Alam, M. Kathleen; Volk, David E.; Ansari, G. A. Shakeel; Sarkar, Swapna; Luxon, Bruce A.

    2012-01-01

    1H NMR spectroscopy and chemometric analysis were used to characterize rat urine obtained after chronic exposure to either tributyl phosphate (TBP) or triphenyl phosphate (TPP). In this study, the daily dose exposure was 1.5 mg/kg body weight for TBP, or 2.0 mg/kg body weight for TPP, administered over a 15-week period. Orthogonal signal correction (OSC) -filtered partial least square discriminant analysis (OSC-PLSDA) was used to predict and classify exposure to these organophosphates. During the development of the model, the classification error was evaluated as a function of the number of latent variables. NMR spectral regions and corresponding metabolites important for determination of exposure type were identified using variable importance in projection (VIP) coefficients obtained from the OSC-PLSDA analysis. As expected, the model for classification of chronic (1.5–2.0 mg/kg body weight daily) TBP or TPP exposure was not as strong as the previously reported model developed for identifying acute (15–20 mg/kg body weight) exposure. The set of majorly impacted metabolites identified for chronic TBP or TPP exposure was slightly different than those metabolites previously identified for acute exposure. These metabolites were then mapped to different metabolite pathways and ranked, allowing the metabolic response to chronic organophosphate exposure to be addressed. PMID:24957643

  20. (1)H and (13)C magic-angle spinning nuclear magnetic resonance studies of the chicken eggshell.

    PubMed

    Pisklak, Dariusz Maciej; Szeleszczuk, Lukasz; Wawer, Iwona

    2012-12-19

    The chicken eggshell, a product of biomineralization, contains inorganic and organic substances whose content changes during the incubation process. Bloch-decay (BD) (1)H, (13)C, and cross-polarization (CP) (13)C nuclear magnetic resonance (NMR) spectra of chicken eggshells were acquired under magic-angle spinning (MAS). Variable contact time (13)C CP MAS NMR experiments revealed the signals of carbonyl groups from organic and inorganic compounds. In the (13)C BD NMR spectra, a single peak at 168.1 ppm was detected, whereas in the (1)H BD spectra, the signals from water and the bicarbonate ion were assigned. A simultaneous decrease of the water signal in the (1)H MAS NMR spectra and an increase of the carbonate ion signal in the (13)C CP MAS NMR spectra of eggshells collected during the incubation period indicate the substitution of calcium ions by hydrogen ions in the calcium carbonate crystalline phase during the incubation of an egg. PMID:23157303

  1. In vivo 1H magnetic resonance spectroscopy in young-adult daily marijuana users☆

    PubMed Central

    Muetzel, Ryan L.; Marjańska, Małgorzata; Collins, Paul F.; Becker, Mary P.; Valabrègue, Romain; Auerbach, Edward J.; Lim, Kelvin O.; Luciana, Monica

    2013-01-01

    To date, there has been little work describing the neurochemical profile of young, heavy marijuana users. In this study, we examined 27 young-adult marijuana users and 26 healthy controls using single-voxel magnetic resonance spectroscopy on a 3 T scanner. The voxel was placed in the dorsal striatum, and estimated concentrations of glutamate + glutamine, myo-inositol, taurine + glucose, total choline and total N-acetylaspartate were examined between groups. There were no overall group effects, but two metabolites showed group by sex interactions. Lower levels of glutamate + glutamine (scaled to total creatine) were observed in female, but not male, marijuana users compared to controls. Higher levels of myo-inositol were observed in female users compared to female non-users and to males in both groups. Findings are discussed in relation to patterns of corticostriatal connectivity and function, in the context of marijuana abuse. PMID:23956957

  2. Absolute hydrogen depth profiling using the resonant 1H(15N, αγ)12C nuclear reaction

    NASA Astrophysics Data System (ADS)

    Reinhardt, Tobias P.; Akhmadaliev, Shavkat; Bemmerer, Daniel; Stöckel, Klaus; Wagner, Louis

    2016-08-01

    Resonant nuclear reactions are a powerful tool for the determination of the amount and profile of hydrogen in thin layers of material. Usually, this tool requires the use of a standard of well-known composition. The present work, by contrast, deals with standard-less hydrogen depth profiling. This approach requires precise nuclear data, e.g. on the widely used 1 H(15 N, αγ)12 C reaction, resonant at 6.4 MeV 15 N beam energy. Here, the strongly anisotropic angular distribution of the emitted γ -rays from this resonance has been re-measured, resolving a previous discrepancy. Coefficients of (0.38 ± 0.04) and (0.80 ± 0.04) have been deduced for the second and fourth order Legendre polynomials, respectively. In addition, the resonance strength has been re-evaluated to (25.0 ± 1.5) eV, 10% higher than previously reported. A simple working formula for the hydrogen concentration is given for cases with known γ -ray detection efficiency. Finally, the absolute approach is illustrated using two examples.

  3. Quantification of ethanol methyl 1H magnetic resonance signal intensity following intravenous ethanol administration in primate brain

    PubMed Central

    Flory, Graham S.; O’Malley, Jean; Grant, Kathleen A.; Park, Byung; Kroenke, Christopher D.

    2009-01-01

    In vivo 1H magnetic resonance spectroscopy (MRS) can be used to directly monitor brain ethanol. Previously, studies of human subjects have lead to the suggestion that the ethanol methyl 1H MRS signal intensity relates to tolerance to ethanol’s intoxicating effects. More recently, the ethanol 1H MRS signal intensity has been recognized to vary between brain gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) due to differences in T2 within these environments. The methods presented here extend ethanol MRS techniques to nonhuman primate subjects. Twelve monkeys were administered ethanol while sedated and positioned within a 3T MRI system. Chemical shift imaging (CSI) measurements were performed following intravenous infusion of 1g/kg ethanol. Magnetic resonance imaging (MRI) data were also recorded for each monkey to provide volume fractions of GM, WM, and CSF for each CSI spectrum. To estimate co-variance of ethanol MRS intensity with GM, WM, and CSF volume fractions, the relative contribution of each tissue subtype was determined following corrections for radiofrequency pulse profile non-uniformity, chemical shift artifacts, and differences between the point spread function in the CSI data and the imaging data. The ethanol MRS intensity per unit blood ethanol concentration was found to differ between GM, WM, and CSF. Individual differences in MRS intensity were larger in GM than WM. This methodology demonstrates the feasibility of ethanol MRS experiments and analysis in nonhuman primate subjects, and suggests GM may be a site of significant variation in ethanol MRS intensity between individuals. PMID:20018244

  4. Frequency Comb Generation in Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Pappas, David; Erickson, Robert; Vissers, Michael; Ku, Hsiang-Sheng

    2015-03-01

    We have generated frequency combs spanning 0.5 to 20 GHz in superconducting λ = 2 resonators at T =3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 108 The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves. Generation of combs in this frequency range allows for unprecedented analysis of this non-linear phenomena in the time domain. We acknowledge DARPA and the NIST Quantum Information program.

  5. Frequency division using a micromechanical resonance cascade

    SciTech Connect

    Qalandar, K. R. Gibson, B.; Sharma, M.; Ma, A.; Turner, K. L.; Strachan, B. S.; Shaw, S. W.

    2014-12-15

    A coupled micromechanical resonator array demonstrates a mechanical realization of multi-stage frequency division. The mechanical structure consists of a set of N sequentially perpendicular microbeams that are connected by relatively weak elastic elements such that the system vibration modes are localized to individual microbeams and have natural frequencies with ratios close to 1:2:⋯:2{sup N}. Conservative (passive) nonlinear inter-modal coupling provides the required energy transfer between modes and is achieved by finite deformation kinematics. When the highest frequency beam is excited, this arrangement promotes a cascade of subharmonic resonances that achieve frequency division of 2{sup j} at microbeam j for j = 1, …, N. Results are shown for a capacitively driven three-stage divider in which an input signal of 824 kHz is passively divided through three modal stages, producing signals at 412 kHz, 206 kHz, and 103 kHz. The system modes are characterized and used to delineate the range of AC input voltages and frequencies over which the cascade occurs. This narrow band frequency divider has simple design rules that are scalable to higher frequencies and can be extended to a larger number of modal stages.

  6. Alterations in brain metabolism and function following administration of low-dose codeine phosphate: 1H-magnetic resonance spectroscopy and resting-state functional magnetic resonance imaging studies

    PubMed Central

    Cao, Zhen; Lin, Pei-Yin; Shen, Zhi-Wei; Wu, Ren-Hua; Xiao, Ye-Yu

    2016-01-01

    The aim of the present study was to identify alterations in brain function following administration of a single, low-dose of codeine phosphate in healthy volunteers using resting-state functional magnetic resonance imaging (fMRI). In addition, the metabolic changes in the two sides of the frontal lobe were identified using 1H-magnetic resonance spectroscopy (1H-MRS). A total of 20 right-handed healthy participants (10 males, 10 females) were evaluated, and a Signa HDx 1.5T MRI scanner was used for data acquisition. An echo planar imaging sequence was used for resting-state fMRI, whereas a point resolved spectroscopy sequence was used for 1H-MRS. Regional Saturation Technique, Data Processing Assistant for Resting-State fMRI, and Statistical Parameter Mapping 8 were used to analyze the fMRI data. The 1H-MRS data were analyzed using LCModel software. At 1 h after oral administration of codeine phosphate (1.0 mg/kg), the amplitude of low-frequency fluctuation (ALFF) and regional homogeneity were altered in different brain areas. The choline content was significantly increased in the right and left frontal lobes following codeine phosphate administration (P=0.02 and P=0.03, respectively), whereas the inositol content was significantly decreased in the left frontal lobe (P=0.02). There was no change in the glutamic acid content in the frontal lobes. In conclusion, the functions of different brain regions can be affected by a single, low-dose administration of codeine phosphate. The alterations in metabolite content in the two frontal lobes may be associated with changes in brain function, whereas the ALFF in the globus pallidus may have an effect on codeine phosphate addiction. Finally, glutamic acid may be useful in the estimation of codeine dependence. PMID:27446252

  7. 1H-Nuclear Magnetic Resonance-Based Plasma Metabolic Profiling of Dairy Cows with Fatty Liver

    PubMed Central

    Xu, Chuang; Sun, Ling-wei; Xia, Cheng; Zhang, Hong-you; Zheng, Jia-san; Wang, Jun-song

    2016-01-01

    Fatty liver is a common metabolic disorder of dairy cows during the transition period. Historically, the diagnosis of fatty liver has involved liver biopsy, biochemical or histological examination of liver specimens, and ultrasonographic imaging of the liver. However, more convenient and noninvasive methods would be beneficial for the diagnosis of fatty liver in dairy cows. The plasma metabolic profiles of dairy cows with fatty liver and normal (control) cows were investigated to identify new biomarkers using 1H nuclear magnetic resonance. Compared with the control group, the primary differences in the fatty liver group included increases in β-hydroxybutyric acid, acetone, glycine, valine, trimethylamine-N-oxide, citrulline, and isobutyrate, and decreases in alanine, asparagine, glucose, γ-aminobutyric acid glycerol, and creatinine. This analysis revealed a global profile of endogenous metabolites, which may present potential biomarkers for the diagnosis of fatty liver in dairy cows. PMID:26732447

  8. (1)H-Nuclear Magnetic Resonance-Based Plasma Metabolic Profiling of Dairy Cows with Fatty Liver.

    PubMed

    Xu, Chuang; Sun, Ling-Wei; Xia, Cheng; Zhang, Hong-You; Zheng, Jia-San; Wang, Jun-Song

    2016-02-01

    Fatty liver is a common metabolic disorder of dairy cows during the transition period. Historically, the diagnosis of fatty liver has involved liver biopsy, biochemical or histological examination of liver specimens, and ultrasonographic imaging of the liver. However, more convenient and noninvasive methods would be beneficial for the diagnosis of fatty liver in dairy cows. The plasma metabolic profiles of dairy cows with fatty liver and normal (control) cows were investigated to identify new biomarkers using (1)H nuclear magnetic resonance. Compared with the control group, the primary differences in the fatty liver group included increases in β-hydroxybutyric acid, acetone, glycine, valine, trimethylamine-N-oxide, citrulline, and isobutyrate, and decreases in alanine, asparagine, glucose, γ-aminobutyric acid glycerol, and creatinine. This analysis revealed a global profile of endogenous metabolites, which may present potential biomarkers for the diagnosis of fatty liver in dairy cows. PMID:26732447

  9. Mild hydration of didecyldimethylammonium chloride modified DNA by 1H-nuclear magnetic resonance and by sorption isotherm

    NASA Astrophysics Data System (ADS)

    Harańczyk, H.; Kobierski, J.; Nizioł, J.; Hebda, E.; Pielichowski, J.; Zalitacz, D.; Marzec, M.; El-Ghayoury, A.

    2013-01-01

    The gaseous phase hydration of deoxyribonucleic acid and didecyldimethylammonium chloride (C19H42ClN) complexes (DNA-DDCA) was observed using hydration kinetics, sorption isotherm, and high power nuclear magnetic resonance. Three bound water fractions were distinguished: (i) a very tightly bound water not removed by incubation over silica gel, (ii) a tightly bound water saturating with the hydration time t1h = (0.59 ± 0.04) h, and a loosely bound water fraction, (iii) with the hydration time t2h = (20.9 ± 1.3) h. Proton free induction decay was decomposed into the signal associated with the solid matrix of DNA-DDCA complex (T2S∗≈ 30 μs) and two liquid signal components coming from tightly bound (T2L1∗≈ 100 μs) and from loosely bound water fraction (T2L2∗≈ 1000 μs).

  10. 1H nuclear magnetic resonance-based extracellular metabolomic analysis of multidrug resistant Tca8113 oral squamous carcinoma cells

    PubMed Central

    WANG, HUI; CHEN, JIAO; FENG, YUN; ZHOU, WENJIE; ZHANG, JIHUA; YU, YU; WANG, XIAOQIAN; ZHANG, PING

    2015-01-01

    A major obstacle of successful chemotherapy is the development of multidrug resistance (MDR) in the cancer cells, which is difficult to reverse. Metabolomic analysis, an emerging approach that has been increasingly applied in various fields, is able to reflect the unique chemical fingerprints of specific cellular processes in an organism. The assessment of such metabolite changes can be used to identify novel therapeutic biomarkers. In the present study, 1H nuclear magnetic resonance (NMR) spectroscopy was used to analyze the extracellular metabolomic spectrum of the Tca8113 oral squamous carcinoma cell line, in which MDR was induced using the carboplatin (CBP) and pingyangmycin (PYM) chemotherapy drugs in vitro. The data were analyzed using the principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) methods. The results demonstrated that the extracellular metabolomic spectrum of metabolites such as glutamate, glycerophosphoethanol amine, α-Glucose and β-Glucose for the drug-induced Tca8113 cells was significantly different from the parental Tca8113 cell line. A number of biochemicals were also significantly different between the groups based on their NMR spectra, with drug-resistant cells presenting relatively higher levels of acetate and lower levels of lactate. In addition, a significantly higher peak was observed at δ 3.35 ppm in the spectrum of the PYM-induced Tca8113 cells. Therefore, 1H NMR-based metabolomic analysis has a high potential for monitoring the formation of MDR during clinical tumor chemotherapy in the future. PMID:26137105

  11. Morpholine Degradation Pathway of Mycobacterium aurum MO1: Direct Evidence of Intermediates by In Situ 1H Nuclear Magnetic Resonance

    PubMed Central

    Combourieu, B.; Besse, P.; Sancelme, M.; Veschambre, H.; Delort, A. M.; Poupin, P.; Truffaut, N.

    1998-01-01

    Resting Mycobacterium aurum MO1 cells were incubated with morpholine, a waste from the chemical industry. The kinetics of biodegradation was monitored by using in situ nuclear magnetic resonance (NMR). The incubation medium was directly analyzed by 1H NMR. This technique allowed the unambiguous identification of two intermediates of the metabolic pathway involved in the biodegradation process, glycolate and 2-(2-aminoethoxy)acetate. The latter compound, which was not commercially available, was synthesized, in three steps, from 2-(2-aminoethoxy)ethanol. Quantitative analysis of the kinetics of degradation of morpholine was performed by integrating the signals of the different metabolites in 1H-NMR spectra. Morpholine was degraded within 10 h. The intermediates increased during the first 10 h and finally disappeared after 20 h incubation. Assays of degradation were also carried out with glycolate and ethanolamine, hypothetical intermediates of the morpholine degradation pathway. They were degraded within 4 and 8 h, respectively. Until now, no tool for direct detection of intermediates or even morpholine has been available, consequently, only hypothetical pathways have been proposed. The approach described here gives both qualitative and quantitative information about the metabolic routes used in morpholine degradation by M. aurum MO1. It could be used to investigate many biodegradative processes. PMID:9435073

  12. Magnetic plasmonic Fano resonance at optical frequency.

    PubMed

    Bao, Yanjun; Hu, Zhijian; Li, Ziwei; Zhu, Xing; Fang, Zheyu

    2015-05-13

    Plasmonic Fano resonances are typically understood and investigated assuming electrical mode hybridization. Here we demonstrate that a purely magnetic plasmon Fano resonance can be realized at optical frequency with Au split ring hexamer nanostructure excited by an azimuthally polarized incident light. Collective magnetic plasmon modes induced by the circular electric field within the hexamer and each of the split ring can be controlled and effectively hybridized by designing the size and orientation of each ring unit. With simulated results reproducing the experiment, our suggested configuration with narrow line-shape magnetic Fano resonance has significant potential applications in low-loss sensing and may serves as suitable elementary building blocks for optical metamaterials. PMID:25594885

  13. Integration of 3D 1H-magnetic resonance spectroscopy data into neuronavigation systems for tumor biopsies

    NASA Astrophysics Data System (ADS)

    Kanberoglu, Berkay; Moore, Nina Z.; Frakes, David; Karam, Lina J.; Debbins, Josef P.; Preul, Mark C.

    2013-03-01

    Many important applications in clinical medicine can benefit from the fusion of spectroscopy data with anatomical images. For example, the correlation of metabolite profiles with specific regions of interest in anatomical tumor images can be useful in characterizing and treating heterogeneous tumors that appear structurally homogeneous. Such applications can build on the correlation of data from in-vivo Proton Magnetic Resonance Spectroscopy Imaging (1HMRSI) with data from genetic and ex-vivo Nuclear Magnetic Resonance spectroscopy. To establish that correlation, tissue samples must be neurosurgically extracted from specifically identified locations with high accuracy. Toward that end, this paper presents new neuronavigation technology that enhances current clinical capabilities in the context of neurosurgical planning and execution. The proposed methods improve upon the current state-of-the-art in neuronavigation through the use of detailed three dimensional (3D) 1H-MRSI data. MRSI spectra are processed and analyzed, and specific voxels are selected based on their chemical contents. 3D neuronavigation overlays are then generated and applied to anatomical image data in the operating room. Without such technology, neurosurgeons must rely on memory and other qualitative resources alone for guidance in accessing specific MRSI-identified voxels. In contrast, MRSI-based overlays provide quantitative visual cues and location information during neurosurgery. The proposed methods enable a progressive new form of online MRSI-guided neuronavigation that we demonstrate in this study through phantom validation and clinical application.

  14. Magnetic resonance imaging of 1H long lived states derived from parahydrogen induced polarization in a clinical system

    NASA Astrophysics Data System (ADS)

    Graafen, Dirk; Franzoni, María Belén; Schreiber, Laura M.; Spiess, Hans W.; Münnemann, Kerstin

    2016-01-01

    Hyperpolarization is a powerful tool to overcome the low sensitivity of nuclear magnetic resonance (NMR). However, applications are limited due to the short lifetime of this non equilibrium spin state caused by relaxation processes. This issue can be addressed by storing hyperpolarization in slowly decaying singlet spin states which was so far mostly demonstrated for non-proton spin pairs, e.g. 13C-13C. Protons hyperpolarized by parahydrogen induced polarization (PHIP) in symmetrical molecules, are very well suited for this strategy because they naturally exhibit a long-lived singlet state. The conversion of the NMR silent singlet spin state to observable magnetization can be achieved by making use of singlet-triplet level anticrossings. In this study, a low-power radiofrequency pulse sequence is used for this purpose, which allows multiple successive singlet-triplet conversions. The generated magnetization is used to record proton images in a clinical magnetic resonance imaging (MRI) system, after 3 min waiting time. Our results may open unprecedented opportunities to use the standard MRI nucleus 1H for e.g. metabolic imaging in the future.

  15. Multi-frequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

    NASA Astrophysics Data System (ADS)

    Andersen, Christian Kraglund; Mølmer, Klaus

    2015-03-01

    A SQUID inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency side bands. We calculate the multi-frequency eigenmodes and these can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application, we determine their coupling to transmon qubits with different frequencies and we present a bi-chromatic scheme for entanglement and gate operations. In this calculation, we obtain a maximally entangled state with a fidelity F = 95 % . Our proposal is competitive with the achievements of other entanglement-gates with superconducting devices and it may offer some advantages: (i) There is no need for additional control lines and dephasing associated with the conventional frequency tuning of qubits. (ii) When our qubits are idle, they are far detuned with respect to each other and to the resonator, and hence they are immune to cross talk and Purcell-enhanced decay.

  16. High-frequency resonant-tunneling oscillators

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Calawa, A. R.; Manfra, M. J.; Chen, C. L.

    1991-01-01

    Advances in high-frequency resonant-tunneling-diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped-element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak-to-valley current ratio.

  17. A phytochemical comparison of saw palmetto products using gas chromatography and 1H nuclear magnetic resonance spectroscopy metabolomic profiling

    PubMed Central

    Booker, Anthony; Suter, Andy; Krnjic, Ana; Strassel, Brigitte; Zloh, Mire; Said, Mazlina; Heinrich, Michael

    2014-01-01

    Objectives Preparations containing saw palmetto berries are used in the treatment of benign prostatic hyperplasia (BPH). There are many products on the market, and relatively little is known about their chemical variability and specifically the composition and quality of different saw palmetto products notwithstanding that in 2000, an international consultation paper from the major urological associations from the five continents on treatments for BPH demanded further research on this topic. Here, we compare two analytical approaches and characterise 57 different saw palmetto products. Methods An established method – gas chromatography – was used for the quantification of nine fatty acids, while a novel approach of metabolomic profiling using 1H nuclear magnetic resonance (NMR) spectroscopy was used as a fingerprinting tool to assess the overall composition of the extracts. Key findings The phytochemical analysis determining the fatty acids showed a high level of heterogeneity of the different products in the total amount and of nine single fatty acids. A robust and reproducible 1H NMR spectroscopy method was established, and the results showed that it was possible to statistically differentiate between saw palmetto products that had been extracted under different conditions but not between products that used a similar extraction method. Principal component analysis was able to determine those products that had significantly different metabolites. Conclusions The metabolomic approach developed offers novel opportunities for quality control along the value chain of saw palmetto and needs to be followed further, as with this method, the complexity of a herbal extract can be better assessed than with the analysis of a single group of constituents. PMID:24417505

  18. Quantitative, In Situ Visualization of Metal-Ion Dissolution and Transport Using (1) H Magnetic Resonance Imaging.

    PubMed

    Bray, Joshua M; Davenport, Alison J; Ryder, Karl S; Britton, Melanie M

    2016-08-01

    Quantitative mapping of metal ions freely diffusing in solution is important across a diverse range of disciplines and is particularly significant for dissolution processes in batteries, metal corrosion, and electroplating/polishing of manufactured components. However, most current techniques are invasive, requiring sample extraction, insertion of an electrode, application of an electric potential or the inclusion of a molecular sensor. Thus, there is a need for techniques to visualize the distribution of metal ions non-invasively, in situ, quantitatively, in three dimensions (3D) and in real time. Here we have used (1) H magnetic resonance imaging (MRI) to make quantitative 3D maps showing evolution of the distribution of Cu(2+) ions, not directly visible by MRI, during the electrodissolution of copper, with high sensitivity and spatial resolution. The images are sensitive to the speciation of copper, the depletion of dissolved O2 in the electrolyte and show the dissolution of Cu(2+) ions is not uniform across the anode. PMID:27329307

  19. Metabolic profile of the hippocampus of Zucker Diabetic Fatty rats assessed by in vivo 1H magnetic resonance spectroscopy.

    PubMed

    van der Graaf, Marinette; Janssen, Susan W J; van Asten, Jack J A; Hermus, Ad R M M; Sweep, C G J; Pikkemaat, Jeroen A; Martens, Gerard J M; Heerschap, Arend

    2004-10-01

    Localized in vivo 1H magnetic resonance spectroscopy (MRS) was used to investigate metabolite levels in the brain of adult Zucker Diabetic Fatty (ZDF) rats, an animal model for type 2 diabetes mellitus. This study focussed on the hippocampus, assumed to be one of the main brain areas affected by this disease. Together with an almost 5-fold increase in blood glucose concentration measured by glucose oxidation, significant increases were found in the hippocampal concentrations of glucose (4.93 vs 1.66 mM p < 0.001), myo-inositol (6.52 vs 4.30 mM; p < 0.05), and total creatine (12.71 vs 10.50 mM; p < 0.05) in ZDF rats (n = 5) compared with littermates (n = 5). Although no obvious alterations were detected in the hippocampal levels of other metabolites, including NAA + NAAG and choline-containing compounds in the ZDF rats, the increase in Glc and Ins levels is in line with elevated brain tissue contents of these metabolites in patients with diabetes mellitus. PMID:15386626

  20. Calcium silicate hydrates investigated by solid-state high resolution {sup 1}H and {sup 29}Si nuclear magnetic resonance

    SciTech Connect

    Meducin, Fabienne . E-mail: meducin@cnrs-orleans.fr; Bresson, Bruno; Lequeux, Nicolas; Noirfontaine, Marie-Noelle de; Zanni, Helene

    2007-05-15

    This work focuses on phases formed during cement hydration under high pressure and temperature: portlandite Ca(OH){sub 2} (CH); hillebrandite Ca{sub 2}(SiO{sub 3})(OH){sub 2} ({beta}-dicalcium silicate hydrate); calcium silicate hydrate (C-S-H); jaffeite Ca{sub 6}(Si{sub 2}O{sub 7})(OH){sub 6} (tricalcium silicate hydrate); {alpha}-C{sub 2}SH Ca{sub 2}(SiO{sub 3})(OH){sub 2} ({alpha}-dicalcium silicate hydrate); xonotlite Ca{sub 6}(Si{sub 6}O{sub 17})(OH){sub 2} and kilchoanite Ca{sub 6}(SiO{sub 4})(Si{sub 3}O{sub 10}). Portlandite and hillebrandite were synthesized and characterised by high resolution solid-state {sup 1}H and {sup 29}Si Nuclear Magnetic Resonance. In addition, information from the literature concerning the last five phases was gathered. In certain cases, a schematic 3D-structure could be determined. These data allow identification of the other phases present in a mixture. Their morphology was also observed by Scanning Electron Microscopy.

  1. Resonator power to frequency conversion in a cryogenic sapphire oscillator

    NASA Astrophysics Data System (ADS)

    Nand, Nitin R.; Parker, Stephen R.; Ivanov, Eugene N.; le Floch, Jean-Michel; Hartnett, John G.; Tobar, Michael E.

    2013-07-01

    We report on the measurement and characterization of power to frequency conversion in the resonant mode of a cryogenic sapphire loaded cavity resonator, which is used as the frequency discriminating element of a loop oscillator circuit. Fluctuations of power incident on the resonator lead to changes in radiation pressure and temperature in the sapphire dielectric, both of which contribute to a shift in the resonance frequency. We measure a modulation and temperature independent radiation pressure induced power to frequency sensitivity of -0.15 Hz/mW and find that this is the primary factor limiting the stability of the resonator frequency.

  2. Frequency splitting of a multi-layered electric ring resonator

    NASA Astrophysics Data System (ADS)

    Kim, S. G.; Kim, K. H.; Jung, H. S.; Cho, H.; Choi, E. M.

    2011-07-01

    We present experimental results on the multilayering effects of an electric ring resonator. The electromagnetic response of the electric ring resonator is measured via a scattering matrix using a vector network analyzer at the X-band frequency. Structures of the electric ring resonator with up to four layers were tested and analyzed using commercial software. We demonstrate that, in an electric ring resonator, the electric and magnetic dipole polarization effect gives rise to resonance frequency splitting when the cell is multilayered.

  3. Cardiac effects of MDMA on the metabolic profile determined with 1H-magnetic resonance spectroscopy in the rat.

    PubMed

    Perrine, Shane A; Michaels, Mark S; Ghoddoussi, Farhad; Hyde, Elisabeth M; Tancer, Manuel E; Galloway, Matthew P

    2009-05-01

    Despite the potential for deleterious (even fatal) effects on cardiac physiology, 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) abuse abounds driven mainly by its euphoric effects. Acute exposure to MDMA has profound cardiovascular effects on blood pressure and heart rate in humans and animals. To determine the effects of MDMA on cardiac metabolites in rats, MDMA (0, 5, or 10 mg/kg) was injected every 2 h for a total of four injections; animals were sacrificed 2 h after the last injection (8 h drug exposure), and their hearts removed and tissue samples from left ventricular wall dissected. High resolution magic angle spinning proton magnetic resonance spectroscopy ((1)H-MRS) at 11.7 T, a specialized version of MRS aptly suited for analysis of semi-solid materials such as intact tissue samples, was used to measure the cardiac metabolomic profile, including alanine, lactate, succinate, creatine, and carnitine, in heart tissue from rats treated with MDMA. MDMA effects on MR-visible choline, glutamate, glutamine, and taurine were also determined. Body temperature was measured following each MDMA administration and serotonin and norepinephrine (NE) levels were measured by high pressure liquid chromatography (HPLC) in heart tissue from treated animals. MDMA significantly and dose-dependently increased body temperature, a hallmark of amphetamines. Serotonin, but not NE, levels were significantly and dose-dependently decreased by MDMA in the heart wall. MDMA significantly altered the MR-visible profile with an increase in carnitine and no change in other key compounds involved in cardiomyocyte energy metabolomics. Finally, choline levels were significantly decreased by MDMA in heart. The results are consistent with the notion that MDMA has significant effects on cardiovascular serotonergic tone and disrupts the metabolic homeostasis of energy regulation in cardiac tissue, potentially increasing utilization of fatty acid metabolism. The contributions of serotonergic

  4. Longitudinal, Noninvasive Monitoring of Compensatory Lung Growth in Mice after Pneumonectomy via 3He and 1H Magnetic Resonance Imaging

    PubMed Central

    Wang, Wei; Nguyen, Nguyet M.; Guo, Jinbang

    2013-01-01

    In rodents and some other mammals, partial pneumonectomy (PNX) of adult lungs results in rapid compensatory lung growth. In the past, quantification of compensatory lung growth and realveolarization could only be accomplished after killing the animal, removal of lungs, and histologic analysis of lungs at single time points. Hyperpolarized 3He diffusion magnetic resonance imaging (MRI) allows in vivo morphometry of human lungs; our group has adapted this technique for application to mouse lungs. Through imaging, we can obtain maps of lung microstructural parameters that allow quantification of morphometric and physiologic measurements. In this study, we employed our 3He MRI technique to image in vivo morphometry at baseline and to serially assess compensatory growth after left PNX of mice. 1H and hyperpolarized 3He diffusion MRI were performed at baseline (pre-PNX), 3-days, and 30-days after PNX. Compared with the individual mouse’s own baseline, MRI was able to detect and serially quantify changes in lung volume, alveolar surface area, alveolar number, and regional changes in alveolar size that occurred during the course of post-PNX lung growth. These results are consistent with morphometry measurements reported in the literature for mouse post-PNX compensatory lung growth. In addition, we were also able to serially assess and quantify changes in the physiologic parameter of lung compliance during the course of compensatory lung growth; this was consistent with flexiVent data. With these techniques, we now have a noninvasive, in vivo method to serially assess the effectiveness of therapeutic interventions on post-PNX lung growth in the same mouse. PMID:23763461

  5. Metabolic profiles using (1)H-nuclear magnetic resonance spectroscopy in postpartum dairy cows with ovarian inactivity.

    PubMed

    Xu, Chuchu; Xia, Cheng; Sun, Yuhang; Xiao, Xinhuan; Wang, Gang; Fan, Ziling; Shu, Shi; Zhang, Hongyou; Xu, Chuang; Yang, Wei

    2016-10-01

    To understand the differences in metabolic changes between cows with ovarian inactivity and estrus cows, we selected cows at 60-90 days postpartum from an intensive dairy farm. According to clinical manifestations, B-ultrasound scan, rectal examination, 10 cows were assigned to the estrus group (A) and 10 to the ovarian inactivity group (B). All plasma samples were analyzed by (1)H-nuclear magnetic resonance spectroscopy to compare plasma metabolomic profiles between the groups. We used multivariate pattern recognition to screen for different metabolites in plasma of anestrus cows. Compared with normal estrous cows, there were abnormalities in 12 kinds of metabolites in postpartum cows with ovarian inactivity (|r|> 0.602), including an increase in acetic acid (r = -0.817), citric acid (r = -0.767), and tyrosine (r = -0.714), and a decrease in low-density lipoprotein (r = 0.820), very low-density lipoprotein (r = 0.828), lipids (r = 0.769), alanine (r = 0.816), pyruvate (r = 0.721), creatine (r = 0.801), choline (r = 0.639), phosphorylcholine (r = 0.741), and glycerophosphorylcholine (r = 0.881). These metabolites were closely related to abnormality of glucose, amino acid, lipoprotein and choline metabolism, which may disturb the normal estrus. The decrease in plasma creatine and the increase in tyrosine were new changes for ovarian inactivity of postpartum cows. The decrease in plasma creatine and choline and the increase in tyrosine and p-hydroxyphenylalanine in cows with ovarian inactivity provide new directions for research on the mechanism of ovarian inactivity in cows. PMID:27291083

  6. Cardiac effects of MDMA on the metabolic profile determined with 1H-magnetic resonance spectroscopy in the rat†

    PubMed Central

    Perrine, Shane A.; Michaels, Mark S.; Ghoddoussi, Farhad; Hyde, Elisabeth M.; Tancer, Manuel E.; Galloway, Matthew P.

    2010-01-01

    Despite the potential for deleterious (even fatal) effects on cardiac physiology, 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) abuse abounds driven mainly by its euphoric effects. Acute exposure to MDMA has profound cardiovascular effects on blood pressure and heart rate in humans and animals. To determine the effects of MDMA on cardiac metabolites in rats, MDMA (0, 5, or 10 mg/kg) was injected every 2 h for a total of four injections; animals were sacrificed 2 h after the last injection (8 h drug exposure), and their hearts removed and tissue samples from left ventricular wall dissected. High resolution magic angle spinning proton magnetic resonance spectroscopy (1H-MRS) at 11.7 T, a specialized version of MRS aptly suited for analysis of semi-solid materials such as intact tissue samples, was used to measure the cardiac metabolomic profile, including alanine, lactate, succinate, creatine, and carnitine, in heart tissue from rats treated with MDMA. MDMA effects on MR-visible choline, glutamate, glutamine, and taurine were also determined. Body temperature was measured following each MDMA administration and serotonin and norepinephrine (NE) levels were measured by high pressure liquid chromatography (HPLC) in heart tissue from treated animals. MDMA significantly and dose-dependently increased body temperature, a hallmark of amphetamines. Serotonin, but not NE, levels were significantly and dose-dependently decreased by MDMA in the heart wall. MDMA significantly altered the MR-visible profile with an increase in carnitine and no change in other key compounds involved in cardiomyocyte energy metabolomics. Finally, choline levels were significantly decreased by MDMA in heart. The results are consistent with the notion that MDMA has significant effects on cardiovascular serotonergic tone and disrupts the metabolic homeostasis of energy regulation in cardiac tissue, potentially increasing utilization of fatty acid metabolism. The contributions of serotonergic

  7. Measurement of the 14N nuclear quadrupole resonance frequencies by the solid effect

    NASA Astrophysics Data System (ADS)

    Seliger, J.; Žagar, V.

    2008-07-01

    1H- 14N nuclear quadrupole double resonance using magnetic field cycling between high and low magnetic field and solid effect in the low magnetic field is analyzed in details. The transition probabilities per unit time for the solid-effect transitions are calculated. The double resonance spectra are calculated in the limiting cases of fast and slow nitrogen spin-lattice relaxation. The double resonance spectra are measured in histamine and quinolinic acid. The experimental spectra are analyzed and the 14N NQR frequencies are determined.

  8. Resonant frequency method for bearing ball inspection

    DOEpatents

    Khuri-Yakub, B.T.; Chungkao Hsieh.

    1993-11-02

    The present invention provides for an inspection system and method for detecting defects in test objects which includes means for generating expansion inducing energy focused upon the test object at a first location, such expansion being allowed to contract, thereby causing pressure wave within and on the surface of the test object. Such expansion inducing energy may be provided by, for example, a laser beam or ultrasonic energy. At a second location, the amplitudes and phases of the acoustic waves are detected and the resonant frequencies' quality factors are calculated and compared to predetermined quality factor data, such comparison providing information of whether the test object contains a defect. The inspection system and method also includes means for mounting the bearing ball for inspection. 5 figures.

  9. Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1993-01-01

    The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of the research activity at the Sir Isaac Newton Conference in St. Petersburg, Russia, and the second Day of Discovery Conference, focusing on economic recovery in West Virginia. An active antenna concept utilizing a signal feedback principle similar to regenerative receivers used in early radio was studied. The device has potential for ELF research and other commercial applications for improved signal reception. Finally, work continues to progress on the development of a prototype monitoring station. Signal monitoring, data display, and data storage are major areas of activity. In addition, we plan to continue our dissemination of research activity through presentations at seminars and other universities.

  10. Resonant frequency method for bearing ball inspection

    DOEpatents

    Khuri-Yakub, B. T.; Hsieh, Chung-Kao

    1993-01-01

    The present invention provides for an inspection system and method for detecting defects in test objects which includes means for generating expansion inducing energy focused upon the test object at a first location, such expansion being allowed to contract, thereby causing pressure wave within and on the surface of the test object. Such expansion inducing energy may be provided by, for example, a laser beam or ultrasonic energy. At a second location, the amplitudes and phases of the acoustic waves are detected and the resonant frequencies' quality factors are calculated and compared to predetermined quality factor data, such comparison providing information of whether the test object contains a defect. The inspection system and method also includes means for mounting the bearing ball for inspection.

  11. Measuring frequency response of surface-micromachined resonators

    NASA Astrophysics Data System (ADS)

    Cowan, William D.; Bright, Victor M.; Dalton, George C.

    1997-09-01

    Resonator structures offer a unique mechanism for characterizing MEMS materials, but measuring the resonant frequency of microstructures is challenging. In this effort a network analyzer system was used to electrically characterize surface-micromachined resonator structures in a carefully controlled pressure and temperature environment.A microscope laser interferometer was used to confirm actual device deflections.Cantilever, comb, and piston resonators fabricated in the DARPA-sponsored MUMPs process were extensively tested. Measured resonator frequency results show reasonable agreement with analytic predictions computed using manufacturer measured film thickness and residual material stress. Alternatively the measured resonant frequency data can be used to extract materials data. Tuning of resonant frequency with DC bias was also investigated. Because the tested devices vary widely in complexity, form a simple cantilever beam to a comb resonator, the data collected is especially well suited for validation testing of MEMS modeling codes.

  12. Reliable and integrated technique for determining resonant frequency in radio frequency resonators. Application to a high-precision resonant cavity-based displacement sensor

    NASA Astrophysics Data System (ADS)

    Jauregui, Rigoberto; Asua, Estibaliz; Portilla, Joaquin; Etxebarria, Victor

    2015-03-01

    This paper presents a reliable and integrated technique for determining the resonant frequency of radio frequency resonators, which can be of interest for different purposes. The approach uses a heterodyne scheme as phase detector coupled to a voltage-controlled oscillator. The system seeks the oscillator frequency that produces a phase null in the resonator, which corresponds to the resonant frequency. A complete explanation of the technique to determine the resonant frequency is presented and experimentally tested. The method has been applied to a high-precision displacement sensor based on resonant cavity, obtaining a theoretical nanometric precision.

  13. 1H, 13C and 15N nuclear magnetic resonance coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with phenylpyridines.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2009-08-01

    1H, 13C and 15N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4-phenylpyridine, 4ppy; 3-phenylpyridine, 3ppy; and 2-phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl3], trans-/cis-[Pd(PPY)2Cl2] and trans-/cis-[Pt(PPY)2Cl2] were performed and the respective chemical shifts (delta1H, delta13C and delta15N) reported. 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(coord)(1H) = delta(complex)(1H)-delta(ligand)(1H), Delta(coord)(13C) = delta(complex)(13C)-delta(ligand)(13C), Delta(coord)(15N) = delta(complex)(15N)-delta(ligand)(15N)) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans-/cis-) and the position of a phenyl group in the pyridine ring system. PMID:19472306

  14. A vibration energy harvesting device with bidirectional resonance frequency tunability

    NASA Astrophysics Data System (ADS)

    Challa, Vinod R.; Prasad, M. G.; Shi, Yong; Fisher, Frank T.

    2008-02-01

    Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22-32 Hz to enable a continuous power output 240-280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined.

  15. Phase transition in triglycine sulfate crystals by 1H and 13C nuclear magnetic resonance in the rotating frame

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Jeong, Se-Young

    2013-09-01

    The ferroelectric phase transition in triglycine sulfate ((NH2CH2COOH)3·H2SO4, TGS)) crystals, occurring at TC of 322 K, was studied using 1H and 13C CP/MAS NMR. From the spin-lattice relaxation time in the rotating frame, T1ρ, of 1H and 13C, we found that the slopes of the T1ρ versus temperature curve changed near TC. In addition, the change of intensities for the protons and carbons NMR signals in the ferroelectric and the paraelectric phases led to the noticeable changes in the environments of proton and carbon in the carboxyl groups. The carboxyl ordering was the dominant factor driving the phase transition. Our study of the 1H and 13C spectra showed that the ferroelectric phase transition of TGS is of the order-disorder type due to ordering of the carboxyl groups.

  16. Selective Detection of 1H NMR Resonances of 13CH n Groups Using Two-Dimensional Maximum-Quantum Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, M.; Farrant, R. D.; Nicholson, J. K.; Lindon, J. C.

    Methods for editing spectra based upon maximum-quantum filtering in two-dimensional 1H NMR are presented (MAXY NMR). Separation of 1H resonances from 13CH, 13CH 2, and 13CH 3 groups is demonstrated, using the coherence of the attached natural-abundance 13C spin. Two-dimensional correlation pulse sequences based on J connectivity (MAXY-COSY), total J connectivity (MAXY-TOCSY), and NOE and exchange processes (MAXY-NOESY) are given and exemplified using dexamethasone as a model compound. In addition, an improved form of a 13CH 2 only COSY spectrum (gem-COSY) is shown, and the application of z magnetic-field gradients is demonstrated as an alternative to phase cycling. The approach should have utility in the assignment of complex 1H NMR spectra which arise from peptides or complex mixtures such as biofluids.

  17. Selective Detection of 1H NMR Resonances of CH n Groups Using a Heteronuclear Maximum-Quantum Filter and Pulsed Field Gradients

    NASA Astrophysics Data System (ADS)

    Liu, M.; Farrant, R. D.; Nicholson, J. K.; Lindon, J. C.

    A number of approaches are described for the provision of separate one-dimensional 1H NMR spectra of CH, CH 2, and CH 3 groups utilizing the natural-abundance 13C spins and based upon the selection of the maximum multiple-quantum coherences of the various groups, This sequence is termed edited maximum-quantum proton spectroscop y (MAXY) spectroscopy, The replacement of phase cycling with the application of z magnetic field gradient pulses is also demonstrated, The editing approach is demonstrated using the 1H NMR spectrum of dexamethasone in DMSO- d6 solution, Extension to a complex mixture biofluid is exemplified by the CH 3-only 1H NMR spectrum of human seminal plasma. This aid to the assignment of endogenous metabolite resonances is demonstrated to result in dramatic spectral simplification.

  18. Detection of poly(ethylene glycol) residues from nonionic surfactants in surface water by1h and13c nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Brown, P.A.; Noyes, T.I.

    1991-01-01

    ??? Poly(ethylene glycol) (PEG) residues were detected in organic solute isolates from surface water by 1H nuclear magnetic resonance spectrometry (NMR), 13C NMR spectrometry, and colorimetric assay. PEG residues were separated from natural organic solutes in Clear Creek, CO, by a combination of methylation and chromatographic procedures. The isolated PEG residues, characterized by NMR spectrometry, were found to consist of neutral and acidic residues that also contained poly(propylene glycol) moieties. The 1H NMR and the colorimetric assays for poly(ethylene glycol) residues were done on samples collected in the lower Mississippi River and tributaries between St. Louis, MO, and New Orleans, LA, in July-August and November-December 1987. Aqueous concentrations for poly(ethylene glycol) residues based on colorimetric assay ranged from undetectable to ???28 ??g/L. Concentrations based on 1H NMR spectrometry ranged from undetectable to 145 ??g/L.

  19. Detection of poly(ethylene glycol) residues from nonionic surfactants in surface water by sup 1 H and sup 13 C nuclear magnetic resonance spectrometry

    SciTech Connect

    Leenheer, J.A.; Wershaw, R.L.; Brown, P.A.; Noyes, T.I. )

    1991-01-01

    Poly(ethylene glycol) (PEG) residues were detected in organic solute isolates from surface water by {sup 1}H nuclear magnetic resonance spectrometry (NMR), {sup 13}C NMR spectrometry, and colorimetric assay. PEG residues were separated from natural organic solutes in Clear Creek, CO, by a combination of methylation and chromatographic procedures. The isolated PEG residues, characterized by NMR spectrometry, were found to consist of neutral and acidic residues that also contained poly(propylene glycol) moieties. The {sup 1}H NMR and the colorimetric assays for poly(ethylene glycol) residues were done on samples collected in the lower Mississippi River and tributaries between S. Louis, MO, and New Orleans, LA, in July-August and November-December 1987. Aqueous concentrations for poly(ethylene glycol) residues based on colorimetric assay ranged from undetectable to {approximately}28 {mu}g/L. Concentrations based on {sup 1}H NMR spectrometry ranged from undetectable to 145 {mu}g/L.

  20. Size Dependence of Ferromagnetic Resonance Frequency in Submicron Patterned Magnet

    NASA Astrophysics Data System (ADS)

    Manago, Takashi; Yamanoi, Kazuto; Yakata, Satoshi; Kimura, Takashi

    2013-05-01

    We investigated the size effect on ferromagnetic resonance (FMR) in a submicron-wide single permalloy bar. The resonant frequency markedly increased with decreasing bar width to less than 1 µm, since the demagnetizing field is effectively modified by changing the bar width even in thin films. The resonant frequency difference between 100- and 1000-nm-wide bars was over 4 GHz in the absence of a magnetic field. This characteristic is promising for practical microwave devices because the desired resonant frequency can be obtained simply by varying the width of narrow ferromagnetic bars so that it is not necessary to change the material or magnetic field.

  1. Improved atomic resonance gas cell for use in frequency standards

    NASA Technical Reports Server (NTRS)

    Huggett, G. R.

    1968-01-01

    Atomic resonance gas cell maintains a stable operating frequency in the presence of pressure fluctuations in the ambient atmosphere. The new cell includes an envelope which is transparent to radiation in the optical region and to microwave energy at the atomic resonance frequency of the alkali-metal vapor within the envelope.

  2. Characterization of the structure and redox behaviour of cytochrome c3 from Desulfovibrio baculatus by 1H-nuclear-magnetic-resonance spectroscopy.

    PubMed Central

    Coutinho, I B; Turner, D L; LeGall, J; Xavier, A V

    1993-01-01

    Complete assignment of the aromatic and haem proton resonances in the cytochromes c3 isolated from Desulfovibrio baculatus strains (Norway 4, DSM 1741) and (DSM 1743) was achieved using one- and two-dimensional 1H n.m.r. Nuclear Overhauser enhancements observed between haem and aromatic resonances and between resonances due to different haems, together with the ring-current contributions to the chemical shifts of haem resonances, support the argument that the haem core architecture is conserved in the various cytochromes c3, and that the X-ray structure of the D. baculatus cytochrome c3 is erroneous. The relative orientation of the haems for both cytochromes was determined directly from n.m.r. data. The n.m.r. structures have a resolution of approximately 0.25 nm and are found to be in close agreement with the X-ray structure from D. vulgaris cytochrome c3. The proton assignments were used to relate the highest potential to a specific haem in the three-dimensional structure by monitoring the chemical-shift variation of several haem resonances throughout redox titrations followed by 1H n.m.r. The haem with highest redox potential is not the same as that in other cytochromes c3. PMID:8397513

  3. Sequence-specific 1H, 15N and 13C resonance assignments of the 23.7-kDa homodimeric toxin CcdB from Vibrio fischeri.

    PubMed

    Respondek, Michal; Buts, Lieven; De Jonge, Natalie; Haesaerts, Sarah; Loris, Remy; Van Melderen, Laurence; Wyns, Lode; Zangger, Klaus

    2009-06-01

    CcdB is the toxic component of a bacterial toxin-antitoxin system. It inhibits DNA gyrase (a type II topoisomerase), and its toxicity can be neutralized by binding of its antitoxin CcdA. Here we report the sequential backbone and sidechain (1)H, (15)N and (13)C resonance assignments of CcdB(Vfi) from the marine bacterium Vibrio fischeri. The BMRB accession number is 16135. PMID:19636967

  4. Variable frequency iteration MPPT for resonant power converters

    SciTech Connect

    Zhang, Qian; Bataresh, Issa; Chen, Lin

    2015-06-30

    A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.

  5. Radio frequency quadrupole resonator for linear accelerator

    DOEpatents

    Moretti, Alfred

    1985-01-01

    An RFQ resonator for a linear accelerator having a reduced level of interfering modes and producing a quadrupole mode for focusing, bunching and accelerating beams of heavy charged particles, with the construction being characterized by four elongated resonating rods within a cylinder with the rods being alternately shorted and open electrically to the shell at common ends of the rods to provide an LC parallel resonant circuit when activated by a magnetic field transverse to the longitudinal axis.

  6. 2D NMR studies of aminoglycoside antibiotics. Use of relayed coherence transfer for /sub 1/H resonance assignment and in situ structure elucidation of amikacin derivatives in reaction mixtures

    SciTech Connect

    Andersen, N.H.; Eaton, H.L.; Nguyen, K.T.; Hartzell, C.; Nelson, R.J.; Priest, J.H.

    1988-04-19

    Phase-sensitive 2D /sup 1/H//sup 1/H COSY spectra can be used to identify the structures of individual pure specimens of the aminoglycoside antibiotic amikacin and its N-hemisuccinyl derivatives. However, even at 500 MHz the 2D chemical shift dispersion does not allow for unambiguous assignment of all cross-peaks. By use of 2D relayed coherence transfer experiments (RELAY) optimized to detect two-step /sup 1/H//sup 1/H scalar interactions in which one of the J-values is small, sufficient additional correlations can be obtained from the frequency-isolated resonances to allow facile tracing of all scalar connectivities. Complete assignments of the /sup 1/H NMR spectra of amikacin, its 6'-N-hemisuccinamide, and a novel bis(acylate) (..gamma..-N-(p-vinylbenzoyl)amikacin 6'-N-hemisuccinamide) were obtained for aqueous media. The NMR spectrum of amikacin free base was also assigned in dimethyl sulfoxide solution. The RELAY experiment can be extended to the analysis of reaction mixtures, which allows for the identification and resonance assignment of regioisomeric amikacin haptens in the mixture state. All of the N-monohemisuccinyl isomers of amikacin have been identified in reaction mixtures through the RELAY experiment. The relative reactivities of the amino functions of amikacin toward acylating agents were found to be 6'-N > 3-N greater than or equal to 3''-N greater than or equal to ..gamma..-N. However, this reactivity order is altered after the initial acylation event.

  7. Resonant difference-frequency atomic force ultrasonic microscope

    NASA Technical Reports Server (NTRS)

    Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

    2010-01-01

    A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

  8. 1H nuclear magnetic resonance spectroscopy-based metabonomic study in patients with cirrhosis and hepatic encephalopathy

    PubMed Central

    Dabos, Konstantinos John; Parkinson, John Andrew; Sadler, Ian Howard; Plevris, John Nicholas; Hayes, Peter Clive

    2015-01-01

    AIM: To identify plasma metabolites used as biomarkers in order to distinguish cirrhotics from controls and encephalopathics. METHODS: A clinical study involving stable cirrhotic patients with and without overt hepatic encephalopathy was designed. A control group of healthy volunteers was used. Plasma from those patients was analysed using 1H - nuclear magnetic resonance spectroscopy. We used the Carr Purcell Meiboom Gill sequence to process the sample spectra at ambient probe temperature. We used a gated secondary irradiation field for water signal suppression. Samples were calibrated and referenced using the sodium trimethyl silyl propionate peak at 0.00 ppm. For each sample 128 transients (FID’s) were acquired into 32 K complex data points over a spectral width of 6 KHz. 30 degree pulses were applied with an acquisition time of 4.0 s in order to achieve better resolution, followed by a recovery delay of 12 s, to allow for complete relaxation and recovery of the magnetisation. A metabolic profile was created for stable cirrhotic patients without signs of overt hepatic encephalopathy and encephalopathic patients as well as healthy controls. Stepwise discriminant analysis was then used and discriminant factors were created to differentiate between the three groups. RESULTS: Eighteen stabled cirrhotic patients, eighteen patients with overt hepatic encephalopathy and seventeen healthy volunteers were recruited. Patients with cirrhosis had significantly impaired ketone body metabolism, urea synthesis and gluconeogenesis. This was demonstrated by higher concentrations of acetoacetate (0.23 ± 0.02 vs 0.05 ± 0.00, P < 0.01), and b-hydroxybutarate (0.58 ± 0.14 vs 0.08 ± 0.00, P < 0.01), lower concentrations of glutamine (0.44 ± 0.08 vs 0.63 ± 0.03, P < 0.05), histidine (0.16 ± 0.01 vs 0.36 ± 0.04, P < 0.01) and arginine (0.08 ± 0.01 vs 0.14 ± 0.02, P < 0.03) and higher concentrations of glutamate (1.36 ± 0.25 vs 0.58 ± 0.04, P < 0.01), lactate (1.53 ± 0

  9. Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Li, Ping; Wen, Yu-Mei; Zhu, Yong

    2013-07-01

    As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation, the ME effect is significantly enhanced in the vicinity of resonance frequency. The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied, and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the ΔE effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses. The experimental results show that with Hdc increasing from 0 Oe (1 Oe=79.5775 A/m) to 700 Oe, the bending resonance frequency can be shifted in a range of 32.68 kHz <= fr <= 33.96 kHz. In addition, with the thickness of the FeCuNbSiB layer increasing from 0 μm to 90 μm, the bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz. This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite, which plays a guiding role in the ME composite design for real applications.

  10. Ultrasonic plastic welding using fundamental and higher resonance frequencies.

    PubMed

    Tsujino, Jiromaru; Hongoh, Misugi; Tanaka, Ryoko; Onoguchi, Rie; Ueoka, Tetsugi

    2002-05-01

    Ultrasonic plastic welding using fundamental and higher resonance frequency vibrations simultaneously was studied. Using higher frequency, welding characteristics is improved due to the larger vibration loss of plastic materials. The 26 kHz welding tip vibrates in maximum velocity of over 4.5 m/s (peak-to-zero value) under a fundamental resonance frequency and there are several higher resonance frequencies up to 95 kHz whose vibration velocities are over one-third that of the fundamental frequency. Welding characteristics of 1.0-mm-thick polypropylene sheets are measured in the cases the vibration system are driven under combined driving voltages of fundamental and higher resonance frequencies. Welded area increases as number of driven higher frequencies increases. The welded area by three frequencies is about three to four times that of the case where only the fundamental frequency is driven. The welding characteristics of ultrasonic plastic welding are improved significantly by driving higher resonance frequencies simultaneously. PMID:12159969

  11. Frequency shifts of ionospheric nfH resonances.

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1972-01-01

    New observational data are analyzed to interpret mechanisms responsible for large positive frequency shifts of Alouette II plasma resonances (corresponding to the first and second electron cyclotron harmonics) relative to frequency values expected from model magnetic field calculations. It is shown that the frequency shifts can be consistently explained by plasma wave dispersion effects combined with sounder transmitter frequency deviation (positive offset of several kilohertz) and a negative offset (several tens of gammas) in the geomagnetic field relative to the model field. Plasma wave dispersion effects are observed on the electron cyclotron second harmonic resonance when it is in the vicinity of the resonance observed near the upper hybrid frequency. The observations suggest that an oblique echo model may be required for interpretation of the electron cyclotron second harmonic resonance.

  12. Toxicometabolomics approach to urinary biomarkers for mercuric chloride (HgCl{sub 2})-induced nephrotoxicity using proton nuclear magnetic resonance ({sup 1}H NMR) in rats

    SciTech Connect

    Kim, Kyu-Bong; Um, So Young; Chung, Myeon Woo; Jung, Seung Chul; Oh, Ji Seon; Kim, Seon Hwa; Na, Han Sung; Lee, Byung Mu; Choi, Ki Hwan

    2010-12-01

    The primary objective of this study was to determine and characterize surrogate biomarkers that can predict nephrotoxicity induced by mercuric chloride (HgCl{sub 2}) using urinary proton nuclear magnetic resonance ({sup 1}H NMR) spectral data. A procedure for {sup 1}H NMR urinalysis using pattern recognition was proposed to evaluate nephrotoxicity induced by HgCl{sub 2} in Sprague-Dawley rats. HgCl{sub 2} at 0.1 or 0.75 mg/kg was administered intraperitoneally (i.p.), and urine was collected every 24 h for 6 days. Animals (n = 6 per group) were sacrificed 3 or 6 days post-dosing in order to perform clinical blood chemistry tests and histopathologic examinations. Urinary {sup 1}H NMR spectroscopy revealed apparent differential clustering between the control and HgCl{sub 2} treatment groups as evidenced by principal component analysis (PCA) and partial least square (PLS)-discriminant analysis (DA). Time- and dose-dependent separation of HgCl{sub 2}-treated animals from controls was observed by PCA of {sup 1}H NMR spectral data. In HgCl{sub 2}-treated rats, the concentrations of endogenous urinary metabolites of glucose, acetate, alanine, lactate, succinate, and ethanol were significantly increased, whereas the concentrations of 2-oxoglutarate, allantoin, citrate, formate, taurine, and hippurate were significantly decreased. These endogenous metabolites were selected as putative biomarkers for HgCl{sub 2}-induced nephrotoxicity. A dose response was observed in concentrations of lactate, acetate, succinate, and ethanol, where severe disruption of the concentrations of 2-oxoglutarate, citrate, formate, glucose, and taurine was observed at the higher dose (0.75 mg/kg) of HgCl{sub 2}. Correlation of urinary {sup 1}H NMR PLS-DA data with renal histopathologic changes suggests that {sup 1}H NMR urinalysis can be used to predict or screen for HgCl{sub 2}-induced nephrotoxicity{sub .}

  13. Assignment of 1H NMR resonances of histidine and other aromatic residues in met-, cyano-, oxy-, and (carbon monoxy)myoglobins.

    PubMed

    Carver, J A; Bradbury, J H

    1984-10-01

    The resolved 1H NMR resonances of the aromatic region in the 270-MHz NMR spectrum of sperm whale, horse, and pig metmyoglobin (metMb) have been assigned, including the observable H-2 and H-4 histidine resonances, the tryptophan H-2 resonances, and upfield-shifted resonances from one tyrosine residue. The use of different Mb species, carboxymethylation, and matching of pK values allows the assignment of the H-4 resonances, which agree in only three cases out of seven with scalar-correlated two-dimensional NMR spectroscopy assignments by others. The conversion to hydroxymyoglobin at high pH involves rearrangements throughout the molecule and is observed by many assigned residues. In sperm whale ferric cyanomyoglobin, nine H-2 and eight H-4 histidine resonances have been assigned, including the His-97 H-2 resonance and tyrosine resonances from residues 103 and 146. The hyperfine-shifted resonances from heme and near-heme protons observe a shift with a pK = 5.3 +/- 0.3 (probably due to deprotonation of His-97, pK = 5.6) and another shift at pK = 10.8 +/- 0.3. The spectrum of high-spin ferrous sperm whale deoxymyoglobin is very similar to that of metMb, which allows the assignment of seven surface histidine H-2 and H-4 resonances and also resonances from the two tryptophan residues and one tyrosine. In diamagnetic sperm whale (carbon monoxy)myoglobin (COMb), 10 His H-2 and 11 His H-4 resonances are observed, and 8 H-2 and 9 H-4 resonances are assigned, including His-64 H-4, the distal histidine. This important resonance is not observed in sperm whale oxymyoglobin, which in general shows very similar titration curves to COMb. Histidine-36 shows unusual titration behavior in the paramagnetic derivatives but normal behavior in the diamagnetic derivatives, which is discussed in the accompanying paper [Bradbury, J. H., & Carver, J. A. (1984) Biochemistry (following paper in this issue)]. PMID:6498166

  14. Identification of endogenous metabolites in human sperm cells using proton nuclear magnetic resonance ((1) H-NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS).

    PubMed

    Paiva, C; Amaral, A; Rodriguez, M; Canyellas, N; Correig, X; Ballescà, J L; Ramalho-Santos, J; Oliva, R

    2015-05-01

    The objective of this study was to contribute to the first comprehensive metabolomic characterization of the human sperm cell through the application of two untargeted platforms based on proton nuclear magnetic resonance ((1) H-NMR) spectroscopy and gas chromatography coupled to mass spectrometry (GC-MS). Using these two complementary strategies, we were able to identify a total of 69 metabolites, of which 42 were identified using NMR, 27 using GC-MS and 4 by both techniques. The identity of some of these metabolites was further confirmed by two-dimensional (1) H-(1) H homonuclear correlation spectroscopy (COSY) and (1) H-(13) C heteronuclear single-quantum correlation (HSQC) spectroscopy. Most of the metabolites identified are reported here for the first time in mature human spermatozoa. The relationship between the metabolites identified and the previously reported sperm proteome was also explored. Interestingly, overrepresented pathways included not only the metabolism of carbohydrates, but also of lipids and lipoproteins. Of note, a large number of the metabolites identified belonged to the amino acids, peptides and analogues super class. The identification of this initial set of metabolites represents an important first step to further study their function in male gamete physiology and to explore potential reasons for dysfunction in future studies. We also demonstrate that the application of NMR and MS provides complementary results, thus constituting a promising strategy towards the completion of the human sperm cell metabolome. PMID:25854681

  15. 1H-nuclear magnetic resonance studies on the conformational changes related to the foaming properties of beta-lactoglobulin.

    PubMed

    Belloque, J; Smith, G M

    1998-10-01

    beta-Lactoglobulin (beta-LG) is a whey protein with foaming ability that can be used as a food ingredient. The structural changes that occur during foaming cannot be easily assessed. In combination with deuterium exchange, 1H-NMR allows new insight into the structural features of beta-LG during foaming. beta-Lactoglobulin was dissolved in D2O and forced to foam. During foaming, the amide protons of exposed residues were exchanged for deuterium atoms, which do not appear in the 1H-NMR spectrum. Protein in solutions that had produced unstable foams showed no exchange beyond that found in unfoamed controls, indicating that the structure had remained intact. Protein in solutions that had produced stable foams showed extensive exchange. Protons of both Trp19 and Met107 exchanged with deuterium, indicating that most of the interior had been exposed to solvent. Most of the beta-LG structure was recovered after collapse of the foam. In the early steps of foaming, apparently only random coil or other exposed regions are involved in foam stabilization. More vigorous shear stress forces induce further unfolding of the beta-strands. This unfolding is suggested to be a dynamic, reversible equilibrium between an open and closed conformation of beta-strands that allows not only for interaction of the protein with the air phase but also for some secondary structure to be retained and the original structure to be recovered. Freeze-dry foaming is also discussed. PMID:9812263

  16. Eddy-current crack detection at frequencies approaching electrical resonance

    NASA Astrophysics Data System (ADS)

    Hughes, Robert R.; Dixon, Steve

    2014-02-01

    The effect of operating an absolute eddy-current (EC) probe at frequencies around its electrical resonance was investigated. A defect signal enhancement phenomenon was observed and characterised. Experimental tests were performed on notch defects in typical aerospace superalloys. An absolute mode EC probe was operated by sweeping through a range of frequencies, in the MHz range, encompassing the electrical resonance of the system. Resonance decoupling above defects results in a signal-to-noise ratio (SNR) peak, within a band of frequencies approaching resonance, of up to 3.7 times that measured at 1MHz. This near electrical resonance signal enhancement (NERSE) phenomenon poses the possibility for a simple operational approach method for improving the sensitivity of conventional eddy-current testing.

  17. Phase-Shift Control of Resonant Frequencies of Magnetostatic Wave Resonators

    NASA Astrophysics Data System (ADS)

    Koike, Takuro; Nakazawa, Hiroaki

    1994-05-01

    We discuss a possible technique to control the resonant frequencies of a straight-edge magnetostatic wave (MSW) resonator without changing the external applied magnetic field and the circuit parameters of a feedback load circuit. The method is to use two additional microstrip electrodes at the edges of the resonator and two varactor diodes connected in series. Upon varying the bias voltages to the varactor diodes, the input admittance at the center electrode can be changed. Theoretical investigation reveals that very large resonant frequency shifts can be obtained by changing only the bias voltage change to the varactor diodes, which may be useful in mobile telephone applications in the gigaherz frequency range.

  18. Method and apparatus for resonant frequency waveform modulation

    DOEpatents

    Taubman, Matthew S [Richland, WA

    2011-06-07

    A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

  19. Hysteresis of the resonance frequency of magnetostrictive bending cantilevers

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard

    2015-05-01

    Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.

  20. Cortical Resonance Frequencies Emerge from Network Size and Connectivity

    PubMed Central

    Lea-Carnall, Caroline A.; Montemurro, Marcelo A.; Trujillo-Barreto, Nelson J.; Parkes, Laura M.; El-Deredy, Wael

    2016-01-01

    Neural oscillations occur within a wide frequency range with different brain regions exhibiting resonance-like characteristics at specific points in the spectrum. At the microscopic scale, single neurons possess intrinsic oscillatory properties, such that is not yet known whether cortical resonance is consequential to neural oscillations or an emergent property of the networks that interconnect them. Using a network model of loosely-coupled Wilson-Cowan oscillators to simulate a patch of cortical sheet, we demonstrate that the size of the activated network is inversely related to its resonance frequency. Further analysis of the parameter space indicated that the number of excitatory and inhibitory connections, as well as the average transmission delay between units, determined the resonance frequency. The model predicted that if an activated network within the visual cortex increased in size, the resonance frequency of the network would decrease. We tested this prediction experimentally using the steady-state visual evoked potential where we stimulated the visual cortex with different size stimuli at a range of driving frequencies. We demonstrate that the frequency corresponding to peak steady-state response inversely correlated with the size of the network. We conclude that although individual neurons possess resonance properties, oscillatory activity at the macroscopic level is strongly influenced by network interactions, and that the steady-state response can be used to investigate functional networks. PMID:26914905

  1. Decrease in Middle Ear Resonance Frequency During Pregnancy.

    PubMed

    Dag, Emine Kutlu; Gulumser, Cagri; Erbek, Seyra

    2016-04-20

    Many physiological changes occur during pregnancy. The aim of the study was to reveal whether there is a change in middle ear resonance frequency during pregnancy. A prospective case-control study was designed at a tertiary referral center. The study included 46 pregnant women at the third trimester (27-40 weeks) and 43 nonpregnant voluntary women. All the study subjects underwent pure-tone audiometry and multifrequency tympanometry. Pure-tone hearing levels at frequencies of 250 to 8000 Hz and resonance frequency values were compared between pregnant and nonpregnant women. Impact of age, side of the tested ear, and weight gained in pregnancy on resonance frequency were evaluated. Air conduction threshold values at frequencies of 250 Hz and 500 Hz were significantly higher in pregnant women than in the control group (P<0.001). Middle ear resonance frequency values of both ears in pregnant women were found to be significantly lower than those in control group (P<0.001). There was no statistically significant relation of middle ear resonance frequency values to age or side of the tested ear in both groups (P>0.05). A negative correlation between weight gained in pregnancy and middle ear resonance frequency values was determined for the left ear (correlation coefficient for left ears: -0.348, P=0.018). The results of this study suggest that resonance frequency may be decreased during the pregnancy. More comprehensive studies in which many pregnant women followed regularly before and after pregnancy are needed to have more certain links. PMID:27588163

  2. Decrease in Middle Ear Resonance Frequency During Pregnancy

    PubMed Central

    Dag, Emine Kutlu; Gulumser, Cagri; Erbek, Seyra

    2016-01-01

    Many physiological changes occur during pregnancy. The aim of the study was to reveal whether there is a change in middle ear resonance frequency during pregnancy. A prospective case-control study was designed at a tertiary referral center. The study included 46 pregnant women at the third trimester (27-40 weeks) and 43 nonpregnant voluntary women. All the study subjects underwent pure-tone audiometry and multifrequency tympanometry. Pure-tone hearing levels at frequencies of 250 to 8000 Hz and resonance frequency values were compared between pregnant and nonpregnant women. Impact of age, side of the tested ear, and weight gained in pregnancy on resonance frequency were evaluated. Air conduction threshold values at frequencies of 250 Hz and 500 Hz were significantly higher in pregnant women than in the control group (P<0.001). Middle ear resonance frequency values of both ears in pregnant women were found to be significantly lower than those in control group (P<0.001). There was no statistically significant relation of middle ear resonance frequency values to age or side of the tested ear in both groups (P>0.05). A negative correlation between weight gained in pregnancy and middle ear resonance frequency values was determined for the left ear (correlation coefficient for left ears: –0.348, P=0.018). The results of this study suggest that resonance frequency may be decreased during the pregnancy. More comprehensive studies in which many pregnant women followed regularly before and after pregnancy are needed to have more certain links. PMID:27588163

  3. (1)H-Nuclear magnetic resonance-based metabolic profiling of nonsteroidal anti-inflammatory drug-induced adverse effects in rats.

    PubMed

    Um, So Young; Park, Jung Hyun; Chung, Myeon Woo; Choi, Ki Hwan; Lee, Hwa Jeong

    2016-09-10

    Nonsteroidal anti-inflammatory drugs (NSAIDs), which are globally prescribed, exhibit mainly anti-inflammatory and analgesic effects but also can cause adverse effects including gastrointestinal erosions, ulceration, bleeding, and perforation. The purpose of this study was to investigate surrogate biomarkers associated with the gastrointestinal (GI) damage caused by NSAID treatment using pattern recognition analysis of (1)H-nuclear magnetic resonance ((1)H NMR) spectra of rat urine. Urine was collected for 5h after oral administration of the following NSAIDs at low or high doses: acetylsalicylic acid (10 or 200mgkg(-1)), diclofenac (0.5 or 15mgkg(-1)), piroxicam (1 or 10mgkg(-1)), indomethacin (1 or 25mgkg(-1)), or ibuprofen (10, or 150mgkg(-1)) as nonselective COX inhibitors and celecoxib (10 or 100mgkg(-1)) as a COX-2 selective inhibitor. The urine was analyzed using 500MHz (1)H NMR for spectral binning and targeted profiling and the level of gastric damage was examined. The nonselective COX inhibitors caused severe gastric damage while no lesions were observed in the celecoxib-treated rats. The (1)H NMR urine spectra were divided into spectral bins (0.04ppm) for global profiling, and a total of 44 endogenous metabolites were assigned for targeted profiling. Multivariate data analyses were performed to recognize the spectral pattern of endogenous metabolites related to NSAIDs using partial least square-discrimination analysis (PLS-DA). The (1)H NMR spectra clustered differently according to gastric damage score in global profiling. In targeted profiling, the endogenous metabolites of citrate, allantoin, 2-oxoglutarate, acetate, benzoate, glycine, and trimethylamine N-oxide were selected as putative biomarkers for gastric damage caused by NSAIDs. These putative biomarkers might be useful for predicting the risk of adverse effects caused by NSAIDs in the early stage of drug development process. PMID:27497650

  4. Sequence-specific (1)H, (13)C and (15)N backbone resonance assignments of the plakin repeat domain of human envoplakin.

    PubMed

    Jeeves, Mark; Fogl, Claudia; Al-Jassar, Caezar; Chidgey, Martyn; Overduin, Michael

    2016-04-01

    The plakin repeat domain is a distinctive hallmark of the plakin superfamily of proteins, which are found within all epithelial tissues. Plakin repeat domains mediate the interactions of these proteins with the cell cytoskeleton and are critical for the maintenance of tissue integrity. Despite their biological importance, no solution state resonance assignments are available for any homologue. Here we report the essentially complete (1)H, (13)C and (15)N backbone chemical shift assignments of the singular 22 kDa plakin repeat domain of human envoplakin, providing the means to investigate its interactions with ligands including intermediate filaments. PMID:26590577

  5. High glycolytic activity in rat glioma demonstrated in vivo by correlation peak 1H magnetic resonance imaging.

    PubMed

    Ziegler, A; von Kienlin, M; Décorps, M; Rémy, C

    2001-07-15

    High-grade brain tumors are known to have a high rate of glucose (Glc) consumption. Postmortem measurements have suggested that Glc content in experimental brain tumors is relatively low. We used magnetic resonance spectroscopy to investigate this, in vivo, in the brains of seven rats bearing intracerebral C6 gliomas. We combined the high spectral resolution allowed by two-dimensional proton nuclear magnetic resonance with spatial encoding by magnetic field gradient pulses to obtain in vivo maps of Glc, alanine, hypotaurine, aspartate, phosphoethanolamine, Glu/Gln, N-acetylaspartate (NAA), phosphocreatine/creatine (PCr/Cr), choline-containing compounds, and lactate (Lac) (some of which are involved in energy metabolism). Compared with normal brain tissue, the main differences found in the gliomas were that Glc, NAA, PCr/Cr, and aspartate concentrations were much lower, whereas concentrations of alanine, hypotaurine, phosphoethanolamine, and Lac were higher, whatever the extent of necrosis. A striking observation is the similarity of the NAA and Glc images: the concentrations of both metabolites are lower in the tumor than they are in the contralateral brain. If Glc was completely absent from the tumor tissue, and if the residual Glc level was due only to a partial volume effect like that for NAA, a neuronal marker, the ratio [Glc]tumor/[Glc]contralateral tissue, should be similar to that found for NAA. The ratio for Glc was 0.48 +/- 0.22 (+/- SD; n = 6), a ratio similar to that found for PCr/Cr (0.50 +/- 0.19) but significantly higher than that obtained for NAA (0.29 +/- 0.07). This observation indicates that a measurable Glc concentration is still present in the tumor tissue. Intense glycolysis in tumor cells may explain the increased production of Lac and alanine and decreased amount of Glc. These nuclear magnetic resonance measurements of metabolite concentrations are complementary to positron emission tomography, which measures Glc consumption. PMID:11454713

  6. Frequency comb transferred by surface plasmon resonance.

    PubMed

    Geng, Xiao Tao; Chun, Byung Jae; Seo, Ji Hoon; Seo, Kwanyong; Yoon, Hana; Kim, Dong-Eon; Kim, Young-Jin; Kim, Seungchul

    2016-01-01

    Frequency combs, millions of narrow-linewidth optical modes referenced to an atomic clock, have shown remarkable potential in time/frequency metrology, atomic/molecular spectroscopy and precision LIDARs. Applications have extended to coherent nonlinear Raman spectroscopy of molecules and quantum metrology for entangled atomic qubits. Frequency combs will create novel possibilities in nano-photonics and plasmonics; however, its interrelation with surface plasmons is unexplored despite the important role that plasmonics plays in nonlinear spectroscopy and quantum optics through the manipulation of light on a subwavelength scale. Here, we demonstrate that a frequency comb can be transformed to a plasmonic comb in plasmonic nanostructures and reverted to the original frequency comb without noticeable degradation of <6.51 × 10(-19) in absolute position, 2.92 × 10(-19) in stability and 1 Hz in linewidth. The results indicate that the superior performance of a well-defined frequency comb can be applied to nanoplasmonic spectroscopy, quantum metrology and subwavelength photonic circuits. PMID:26898307

  7. Frequency comb transferred by surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Geng, Xiao Tao; Chun, Byung Jae; Seo, Ji Hoon; Seo, Kwanyong; Yoon, Hana; Kim, Dong-Eon; Kim, Young-Jin; Kim, Seungchul

    2016-02-01

    Frequency combs, millions of narrow-linewidth optical modes referenced to an atomic clock, have shown remarkable potential in time/frequency metrology, atomic/molecular spectroscopy and precision LIDARs. Applications have extended to coherent nonlinear Raman spectroscopy of molecules and quantum metrology for entangled atomic qubits. Frequency combs will create novel possibilities in nano-photonics and plasmonics; however, its interrelation with surface plasmons is unexplored despite the important role that plasmonics plays in nonlinear spectroscopy and quantum optics through the manipulation of light on a subwavelength scale. Here, we demonstrate that a frequency comb can be transformed to a plasmonic comb in plasmonic nanostructures and reverted to the original frequency comb without noticeable degradation of <6.51 × 10-19 in absolute position, 2.92 × 10-19 in stability and 1 Hz in linewidth. The results indicate that the superior performance of a well-defined frequency comb can be applied to nanoplasmonic spectroscopy, quantum metrology and subwavelength photonic circuits.

  8. Frequency comb transferred by surface plasmon resonance

    PubMed Central

    Geng, Xiao Tao; Chun, Byung Jae; Seo, Ji Hoon; Seo, Kwanyong; Yoon, Hana; Kim, Dong-Eon; Kim, Young-Jin; Kim, Seungchul

    2016-01-01

    Frequency combs, millions of narrow-linewidth optical modes referenced to an atomic clock, have shown remarkable potential in time/frequency metrology, atomic/molecular spectroscopy and precision LIDARs. Applications have extended to coherent nonlinear Raman spectroscopy of molecules and quantum metrology for entangled atomic qubits. Frequency combs will create novel possibilities in nano-photonics and plasmonics; however, its interrelation with surface plasmons is unexplored despite the important role that plasmonics plays in nonlinear spectroscopy and quantum optics through the manipulation of light on a subwavelength scale. Here, we demonstrate that a frequency comb can be transformed to a plasmonic comb in plasmonic nanostructures and reverted to the original frequency comb without noticeable degradation of <6.51 × 10−19 in absolute position, 2.92 × 10−19 in stability and 1 Hz in linewidth. The results indicate that the superior performance of a well-defined frequency comb can be applied to nanoplasmonic spectroscopy, quantum metrology and subwavelength photonic circuits. PMID:26898307

  9. 1H, 13C, and 15N resonance assignments for the protein coded by gene locus BB0938 of Bordetella bronchiseptica

    SciTech Connect

    Rossi, Paolo; Ramelot, Theresa A.; Xiao, Rong; Ho, Chi K.; Ma, LiChung; Acton, Thomas; Kennedy, Michael A.; Montelione, Gaetano

    2005-11-01

    The product of gene locus BB0938 from Bordetella bronchiseptica (Swiss-Prot ID: Q7WNU7-BORBR; NESG target ID: BoR11; Wunderlich et al., 2004; Pfam ID: PF03476) is a 128-residue protein of unknown function. This broadly conserved protein family is found in eubacteria and eukaryotes. Using triple resonance NMR techniques, we have determined 98% of backbone and 94% of side chain 1H, 13C, and 15N resonance assignments. The chemical shift and 3J(HN?Ha) scalar coupling data reveal a b topology with a seven-residue helical insert, ??????????. BMRB deposit with accession number 6693. Reference: Wunderlich et al. (2004) Proteins, 56, 181?187.

  10. 1H, 13C, and 15N resonance assignments for Escherichia coli ytfP, a member of the broadly conserved UPF0131 protein domain family

    SciTech Connect

    Aramini, James M.; Swapna, G.V.T.; Huang, Yuanpeng; Rajan, Paranji K.; Xiao, Rong; Shastry, Ritu; Acton, Thomas; Cort, John R.; Kennedy, Michael A.; Montelione, Gaetano

    2005-11-01

    Protein ytfP from Escherichia coli (Swiss-Prot ID: YTFP-ECOLI; NESG target ID: ER111; Wunderlich et al., 2004) is a 113-residue member of the UPF0131 protein family (Pfam ID: PF03674) of unknown function. This domain family is found in organisms from all three kingdoms, archaea, eubacteria and eukaryotes. Using triple resonance NMR techniques, we have determined 97% of backbone and 91% of side chain 1H, 13C, and 15N resonance assignments. The chemical shift and 3J(HN?Ha) scalar coupling data reveal a mixed a/b topology,????????. BMRB deposit with Accession No. 6448. Reference: Wunderlich et al. (2004) Proteins, 56, 181?187.

  11. Experimental attempt to simulate receptor site environment. A 500-MHz 1H nuclear magnetic resonance study of enkephalin amides.

    PubMed

    Temussi, P A; Tancredi, T; Pastore, A; Castiglione-Morelli, M A

    1987-12-01

    The amides of Leu5-enkephalin, Met5-enkephalin, and three analogues, D-Ala2,Leu5-enkephalin, (AcO)Tyr1,Met5-enkephalin, and (AcO)Tyr1,D-Ala2,Met5-enkephalin, have been studied by means of 1H NMR spectroscopy in two different solvent systems: Me2SO-d6 and CDCl3. In the latter solvent the peptides were dissolved as complexes with 18-crown-6-ether, a coronand that binds strongly to the NH3+ groups. The crown ether complexation and the apolar solvent were used to simulate the anionic subsite of the receptor and the hydrophobic environment of the receptor cavity, respectively. The very unusual amide proton chemical shifts and their temperature coefficients suggest the presence of folded conformations in CDCl3 for all peptides, consistent with several models of opioid receptors and with the crystal structure of Leu5-enkephalin. The differences among the proposed cyclic conformations of the five peptides may be correlated, in part, with their different biological activity. All peptides in Me2SO-d6 are characterized by complex mixtures of extended fully solvated conformations. PMID:2827761

  12. Reexamination of the Energy Levels of 15F by 14O + 1H ElasticResonance Scattering with BEARS

    SciTech Connect

    Guo, F.Q.; Powell, J.; Lee, D.W.; Leitner, D.; McMahan, M.A.; Moltz, D.M.; O'Neil, J.P.; Perajarvi, K.; Phair, L.; Ramsey, C.A.; Xu,X.J.; Cerny, Joseph

    2005-05-30

    The energy levels of 15F have been measured by the p(14O,p)14O reaction. The 120 MeV 14O radioactive ion beam was produced by the BEARS coupled cyclotron system at an intensity averaging 1x104 particles/second on target. Energy calibration was obtained using resonances from the p(14N,p)14N reaction. The two lowest resonances in 15F were fitted with an R-matrix calculation. The fit to the ground state had Jp = 1/2+ at 1.23+-0.05 MeV (width 0.5-0.84 MeV), and the first excited state was Jp=5/2+ at 2.81+-0.02 MeV (width 0.30+-0.06 MeV), both relative to the mass-energy of the proton and 14O. The 15F ground state energy supports the disappearance of the Z=8 proton magic number for odd Z, Tz=-3/2 nuclei.

  13. YBCO superconducting ring resonators at millimeter-wave frequencies

    NASA Technical Reports Server (NTRS)

    Chorey, Christopher M.; Kong, Keon-Shik; Bhasin, Kul B.; Warner, J. D.; Itoh, Tatsuo

    1991-01-01

    Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performances compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

  14. Fractionation of technical octabromodiphenyl ether by countercurrent chromatography combined with gas chromatography/mass spectrometry and offline and online (1)H nuclear magnetic resonance spectroscopy.

    PubMed

    Hammann, Simon; Conrad, Jürgen; Vetter, Walter

    2015-06-12

    Countercurrent chromatography (CCC) is a technique, which uses two immiscible liquid phases for a separation process in a long and hollow tube. The technique allows the separation of high amounts of sample (50mg to several grams) with a low consumption of solvents. In this study, we fractionated 50mg technical octabromodiphenyl ether (DE-79) and analyzed the fractions by gas chromatography with mass spectrometry (GC/MS) and proton nuclear magnetic resonance ((1)H NMR) spectroscopy. CCC separations were performed with n-hexane/acetonitrile as solvent system in tail-to-head (i.e. the upper phase is mobile) mode. Twelve CCC fractions were studied for the PBDE composition. CCC elution of PBDE congeners was dependent both on the degree of bromination and substitution pattern. Higher brominated congeners eluted faster than lower brominated congeners and isomers with vicinal hydrogen atoms eluted last. In addition to several known PBDE congeners in DE-79, we were able to unequivocally identify BDE 195 in DE-79 and we could verify the presence of BDE 184. Finally, we also established the online hyphenation of CCC with (1)H NMR. The use of deuterated solvents could be avoided by using n-hexane/acetonitrile as two-phase system. By online CCC-(1)H NMR in stop-flow mode we were able to detect eight PBDE congeners in the mixture. PMID:25913330

  15. Excitation of dark multipolar plasmonic resonances at terahertz frequencies

    PubMed Central

    Chen, Lin; Wei, YuMing; Zang, XiaoFei; Zhu, YiMing; Zhuang, SongLin

    2016-01-01

    We experimentally observe the excitation of dark multipolar spoof localized surface plasmon resonances in a hybrid structure consisting of a corrugated metallic disk coupled with a C-shaped dipole resonator. The uncoupled corrugated metallic disk only supports a dipolar resonance in the transmission spectrum due to perfect symmetry of the structure. However, the dark multipolar spoof localized surface plasmon resonances emerge when coupled with a bright C-shaped resonator which is placed in the vicinity of the corrugated metallic disk. These excited multipolar resonances show minimum influence on the coupling distance between the C-shaped resonator and corrugated metallic disk. The resonance frequencies of the radiative modes are controlled by varying the angle of the C-shaped resonator and the inner disk radius, both of which play dominant roles in the excitation of the spoof localized surface plasmons. Observation of such a transition from the dark to radiative nature of multipolar spoof localized plasmon resonances would find potential applications in terahertz based resonant plasmonic and metamaterial devices. PMID:26903382

  16. (1)H, (15)N and (13)C resonance assignments of translationally-controlled tumor protein from photosynthetic microalga Nannochloropsis oceanica.

    PubMed

    Yao, Xingzhe; Xiao, Yan; Cui, Qiu; Feng, Yingang

    2015-10-01

    Translationally-controlled tumor protein (TCTP) is a eukaryote-conserved protein with crucial roles in cellular growth. It has also been proposed that plant TCTP has functions specific to plant, while no structure of TCTP from photosynthetic organism has been reported. Nannochloropsis is a photosynthetic microalga with high yield of lipid and high-value polyunsaturated fatty acid, which is promising for biodiesel production. Study of growth-related proteins may provide new clue for improving the yield of lipid. TCTP from Nannochloropsis oceanica shares low sequence identity with structure-known TCTPs. Here we reported the NMR resonance assignments of TCTP from N. oceanica for further structural and functional studies. PMID:25680850

  17. 1H Magnetic Resonance Spectroscopy Predicts Hepatocellular Carcinoma in a Subset of Patients With Liver Cirrhosis: A Randomized Trial.

    PubMed

    Wang, Dan; Li, Yuehua

    2015-07-01

    The goal of this study was to investigate the utility of H magnetic resonance spectroscopy (H-MRS) to quantify the differences in liver metabolites. Magnetic resonance spectroscopy was used as a means of predicting the probability of developing hepatocellular carcinoma (HCC) in patients with liver cirrhosis secondary to chronic hepatitis B.This study included 20 healthy volunteers, 20 patients with liver cirrhosis secondary to chronic hepatitis B (cirrhosis group), and 20 patients with small HCC secondary to cirrhosis liver parenchyma (HCC group). All patients underwent routine MRI and H-MRS scanning. LCModel software was used to quantify Cho (Choline), Lip (lipid), and Cho/Lip in the 3 groups, and a one-way ANOVA was used to compare the differences in these metabolites between groups.Choline levels were significantly different between the control and HCC group and between the cirrhosis group and the HCC group (all P < 0.001). There was also a significant difference in Lip levels between the control and cirrhosis group and the control and HCC groups (all P < 0.001). There were also differences in Cho/Lip between the control and cirrhosis groups, the control and HCC groups, and the cirrhosis and HCC groups (all P < 0.001).H-MRS followed by the analysis with LCModel can be used to measure changes in hepatic metabolite levels in patients with liver cirrhosis secondary to chronic hepatitis B and HCC. Thus, H-MRS may be helpful in monitoring HCC and liver cirrhosis development. PMID:26166077

  18. Whole-brain patterns of (1)H-magnetic resonance spectroscopy imaging in Alzheimer's disease and dementia with Lewy bodies.

    PubMed

    Su, L; Blamire, A M; Watson, R; He, J; Hayes, L; O'Brien, J T

    2016-01-01

    Magnetic resonance spectroscopy has demonstrated metabolite changes in neurodegenerative disorders such as Alzheimer's disease (AD) and dementia with Lewy bodies (DLB); however, their pattern and relationship to clinical symptoms is unclear. To determine whether the spatial patterns of brain-metabolite changes in AD and DLB are regional or diffused, and to examine whether the key metabolite levels are associated with cognitive and non-cognitive symptoms, we acquired whole-brain spatially resolved 3T magnetic resonance spectroscopic imaging (MRSI) data from subjects with AD (N=36), DLB (N=35) and similarly aged controls (N=35). Voxel-wise measurement of N-acetylaspartate to creatine (NAA/Cr), choline to Cr (Cho/Cr), myo-inositol to Cr (mI/Cr) as well as glutamate and glutamine to Cr (Glx/Cr) ratios were determined using MRSI. Compared with controls, AD and DLB groups showed a significant decrease in most brain metabolites, with NAA/Cr, Cho/Cr and mI/Cr levels being reduced in posterior cingulate, thalamus, frontotemporal areas and basal ganglia. The Glx/Cr level was more widely decreased in DLB (posterior cingulate, hippocampus, temporal regions and caudate) than in AD (only in posterior cingulate). DLB was also associated with increased levels of Cho/Cr, NAA/Cr and mI/Cr in occipital regions. Changes in metabolism in the brain were correlated with cognitive and non-cognitive symptoms in the DLB but not in the AD group. The different patterns between AD and DLB may have implications for improving diagnosis, better understanding disease-specific neurobiology and targeting therapeutics. In addition, the study raised important questions about the role of occipital neuroinflammation and glial activation as well as the glutamatergic treatment in DLB. PMID:27576166

  19. Theoretical investigation of resonant frequencies of unstrapped magnetron with arbitrary side resonators

    SciTech Connect

    Yue, Song; Zhang, Zhao-chuan; Gao, Dong-ping

    2015-04-15

    In this paper, a sector steps approximation method is proposed to investigate the resonant frequencies of magnetrons with arbitrary side resonators. The arbitrary side resonator is substituted with a series of sector steps, in which the spatial harmonics of electromagnetic field are also considered. By using the method of admittance matching between adjacent steps, as well as field continuity conditions between side resonators and interaction regions, the dispersion equation of magnetron with arbitrary side resonators is derived. Resonant frequencies of magnetrons with five common kinds of side resonators are calculated with sector steps approximation method and computer simulation softwares, in which the results have a good agreement. The relative error is less than 2%, which verifies the validity of sector steps approximation method.

  20. Squeezing Alters Frequency Tuning of WGM Optical Resonator

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Maleki, Lute

    2010-01-01

    Mechanical squeezing has been found to alter the frequency tuning of a whispering-gallery-mode (WGM) optical resonator that has an elliptical shape and is made of lithium niobate. It may be possible to exploit this effect to design reconfigurable optical filters for optical communications and for scientific experiments involving quantum electrodynamics. Some background information is prerequisite to a meaningful description of the squeezing-induced alteration of frequency tuning: The spectrum of a WGM resonator is represented by a comblike plot of intensity versus frequency. Each peak of the comblike plot corresponds to an electromagnetic mode represented by an integer mode number, and the modes are grouped into sets represented by integer mode indices. Because lithium niobate is an electro-optically active material, the WGM resonator can be tuned (that is, the resonance frequencies can be shifted) by applying a suitable bias potential. The frequency shift of each mode is quantified by a tuning rate defined as the ratio between the frequency shift and the applied potential. In the absence of squeezing, all modes exhibit the same tuning rate. This concludes the background information. It has been demonstrated experimentally that when the resonator is squeezed along part of either of its two principal axes, tuning rates differ among the groups of modes represented by different indices (see figure). The differences in tuning rates could be utilized to configure the resonance spectrum to obtain a desired effect; for example, through a combination of squeezing and electrical biasing, two resonances represented by different mode indices could be set at a specified frequency difference something that could not be done through electrical biasing alone.

  1. Protonation of carbon single-walled nanotubes studied using 13C and 1H-13C cross polarization nuclear magnetic resonance and Raman spectroscopies.

    PubMed

    Engtrakul, Chaiwat; Davis, Mark F; Gennett, Thomas; Dillon, Anne C; Jones, Kim M; Heben, Michael J

    2005-12-14

    The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nafion was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nafion films was probed with the 1H-13C CP-MAS technique. PMID:16332107

  2. Resonant frequency tuning of an industrial vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Toh, T. T.; Wright, S. W.; Mitcheson, P. D.

    2014-11-01

    This paper presents preliminary results of tuning the resonant frequency of two industrial vibration energy harvesters. The VEH-450 from Ferro Solutions and the PMG17-50 from Perpetuum were tested using discrete reactive electrical loads. The former could be tuned to +0.5 Hz and -2 Hz from its natural resonant frequency of 50.5 Hz at 0.1g. The latter, however, has a broadband output power spectrum that spans ±10 Hz and its output voltage saturates at 7 Vrms, thereby rendering it un-tunable using the method presented here. A comparison of output power between a tuned VEH-450 and an un-tuned PMG17-50, normalised by harvester weight, shows that the former outperforms the latter only at a tuned frequency of 49.8 Hz. A discussion of a resonant frequency tuning circuit that can be fitted to an existing harvester without making modifications to the harvester is presented.

  3. Phase steps and resonator detuning measurements in microresonator frequency combs.

    PubMed

    Del'Haye, Pascal; Coillet, Aurélien; Loh, William; Beha, Katja; Papp, Scott B; Diddams, Scott A

    2015-01-01

    Experiments and theoretical modelling yielded significant progress toward understanding of Kerr-effect induced optical frequency comb generation in microresonators. However, the simultaneous Kerr-mediated interaction of hundreds or thousands of optical comb frequencies with the same number of resonator modes leads to complicated nonlinear dynamics that are far from fully understood. An important prerequisite for modelling the comb formation process is the knowledge of phase and amplitude of the comb modes as well as the detuning from their respective microresonator modes. Here, we present comprehensive measurements that fully characterize optical microcomb states. We introduce a way of measuring resonator dispersion and detuning of comb modes in a hot resonator while generating an optical frequency comb. The presented phase measurements show unpredicted comb states with discrete π and π/2 steps in the comb phases that are not observed in conventional optical frequency combs. PMID:25565467

  4. Analysis of Continuous Microseismic Recordings: Resonance Frequencies and Unconventional Events

    NASA Astrophysics Data System (ADS)

    Tary, J.; van der Baan, M.

    2012-12-01

    Hydrofracture experiments, where fluids and proppant are injected into reservoirs to create fractures and enhance oil recovery, are often monitored using microseismic recordings. The total stimulated volume is then estimated by the size of the cloud of induced micro-earthquakes. This implies that only brittle failure should occur inside reservoirs during the fracturing. Yet, this assumption may not be correct, as the total energy injected into the system is orders of magnitude larger than the total energy associated with brittle failure. Instead of using only triggered events, it has been shown recently that the frequency content of continuous recordings may also provide information on the deformations occurring inside reservoirs. Here, we use different kinds of time-frequency transforms to track the presence of resonance frequencies. We analyze different data sets using regular, long-period and broadband geophones. The resonance frequencies observed are mainly included in the frequency band of 5-60 Hz. We systematically examine first the possible causes of resonance frequencies, dividing them into source, path and receiver effects. We then conclude that some of the observed frequency bands likely result from source effects. The resonance frequencies could be produced by either interconnected fluid-filled fractures in the order of tens of meters, or by small repetitive events occurring at a characteristic periodicity. Still, other mechanisms may occur or be predominant during reservoir fracturing, depending on the lithology as well as the pressure and temperature conditions at depth. During one experiment, both regular micro-earthquakes, long-period long-duration events (LPLD) and resonance frequencies are observed. The lower part of the frequency band of these resonance frequencies (5-30 Hz) overlaps with the anticipated frequencies of observed LPLDs in other experiments (<50 Hz). The exact origin of both resonance frequencies and LPLDs is still under debate

  5. High-resolution magic angle spinning and 1H magnetic resonance spectroscopy reveal significantly altered neuronal metabolite profiles in CLN1 but not in CLN3.

    PubMed

    Sitter, Beathe; Autti, Taina; Tyynelä, Jaana; Sonnewald, Ursula; Bathen, Tone F; Puranen, Johanna; Santavuori, Pirkko; Haltia, Matti J; Paetau, Anders; Polvikoski, Tuomo; Gribbestad, Ingrid S; Häkkinen, Anna-Maija

    2004-09-01

    The neuronal ceroid lipofuscinoses (NCLs) are among the most severe inherited progressive neurodegenerative disorders of children. The purpose of this study was to compare the in vivo 1.5-T 1H magnetic resonance (MR) and ex vivo 14.3-T high-resolution (HR) magic angle spinning (MAS) 1H MR brain spectra of patients with infantile (CLN1) and juvenile (CLN3) types of NCL, to obtain detailed information about the alterations in the neuronal metabolite profiles in these diseases and to test the suitability of the ex vivo HR MAS (1)H MRS technique in analysis of autopsy brain tissue. Ex vivo spectra from CLN1 autopsy brain tissue (n = 9) significantly differed from those of the control (n = 9) and CLN3 (n = 5) groups, although no differences were found between the CLN3 and the control groups. Principal component analysis of ex vivo data showed that decreased levels of N-acetylaspartate (NAA), gamma-aminobutyric acid (GABA), glutamine, and glutamate as well as increased levels of inositols characterized the CLN1 spectra. Also, the intensity ratio of lipid methylene/methyl protons was decreased in spectra of CLN1 brain tissue compared with CLN3 and control brain tissue. In concordance with the ex vivo data, the in vivo spectra of late-stage patients with CLN1 (n = 3) revealed a dramatic decrease of NAA and a proportional increase of myo-inositol and lipids compared with control subjects. Again, the spectra of patients with CLN3 (n = 13) did not differ from those of controls (n = 15). In conclusion, the ex vivo and in vivo spectroscopic findings were in good agreement within all analyzed groups and revealed significant alterations in metabolite profiles in CLN1 brain tissue but not in CLN3 compared with controls. Furthermore, HR MAS 1H MR spectra facilitated refined detection of neuronal metabolites, including GABA, and composition of lipids in the autopsy brain tissue of NCL patients. PMID:15352223

  6. 1H, 13C, and 15N backbone and side chain resonance assignments of thermophilic Geobacillus kaustophilus cyclophilin-A

    SciTech Connect

    Holliday, Michael; Zhang, Fengli; Isern, Nancy G.; Armstrong, Geoffrey S.; Eisenmesser, Elan Z.

    2014-04-01

    Cyclophilins catalyze the reversible peptidyl-prolyl isomerization of their substrates and are present across all kingdoms of life from humans to bacteria. Although numerous biological roles have now been discovered for cyclophilins, their function was initially ascribed to their chaperone-like activity in protein folding where they catalyze the often rate-limiting step of proline isomerization. This chaperone-like activity may be especially important under extreme conditions where cyclophilins are often over expressed, such as in tumors for human cyclophilins {Lee, 2010 #1167}, but also in organisms that thrive under extreme conditions, such as theromophilic bacteria. Moreover, the reversible nature of the peptidyl-prolyl isomerization reaction catalyzed by cyclophilins has allowed these enzymes to serve as model systems for probing the role of conformational changes during catalytic turnover {Eisenmesser, 2002 #20;Eisenmesser, 2005 #203}. Thus, we present here the resonance assignments of a thermophilic cyclophilin from Geobacillus kaustophilus derived from deep-sea sediment {Takami, 2004 #1384}. This thermophilic cyclophilin may now be studied at a variety of temperatures to provide insight into the comparative structure, dynamics, and catalytic mechanism of cyclophilins.

  7. (1)H, (13)C and (15)N resonance assignment of the cytosolic dithiol glutaredoxin 1 from the pathogen Trypanosoma brucei.

    PubMed

    Stefani, Monica; Sturlese, Mattia; Manta, Bruno; Löhr, Frank; Mammi, Stefano; Comini, Marcelo; Bellanda, Massimo

    2016-04-01

    Trypanosomatids are parasites responsible for several tropical and subtropical diseases, such as Chaga's disease, sleeping sickness and Leishmaniasis. In contrast to the mammalian host, the thiol-redox metabolism of these pathogens depends on trypanothione [bis-glutathionylspermidine, T(SH)2] instead of glutathione (GSH) providing a set of lineage-specific proteins as drug target candidates. Glutaredoxins (Grx) are ubiquitous small thiol-disulfide oxidoreductases that belong to the thioredoxin-fold family. They play a central role in redox homeostasis and iron sulfur-cluster biogenesis. Each species, including trypanosomes, possesses its own set of isoforms distributed in different subcellular compartments. The genome of trypanosomatids encodes for two class I (dithiolic) Grxs named 2-C-Grx1 and 2-C-Grx2. Both proteins were shown to efficiently reduce different disulfides at the expenses of T(SH)2 using a mechanism that involves the two cysteines in the active site. Moreover, the cytosolic Trypanosoma brucei 2-C-Grx1 but not the mitochondrial 2-C-Grx2 was able to coordinate an iron-sulfur cluster with T(SH)2 or GSH as ligand. As a first step to unravel the structural basis for the specificity observed in the trypanosomal glutaredoxins, we present here the NMR resonance assignment of 2-C-Grx1 from the parasite T. brucei brucei. PMID:26386962

  8. Resonant Cavities for Frequency Tunable Gyrotrons

    NASA Astrophysics Data System (ADS)

    Sabchevski, S.; Idehara, T.

    2008-01-01

    In this paper we present, discuss and compare several concepts based on both well-known and novel ideas for tunable gyrotron cavities. Although theoretical and design considerations are presented and discussed together the main focus is on the underlying principles and feasibility of different approaches rather than on their specific implementations. Illustrative examples are provided for configurations and frequency range appropriate for gyrotrons used as radiation sources for NMR spectroscopy with signal enhancement through DNP.

  9. Modeling sickle cell vasoocculsion in the rat leg: Quantification of trapped sickle cells and correlation with sup 31 P metabolic and sup 1 H magnetic resonance imaging changes

    SciTech Connect

    Fabry, M.E.; Rajanayagam, V.; Fine, E.; Holland, S.; Gore, J.C.; Nagel, R.L.; Kaul, D.K. )

    1989-05-01

    The authors have developed an animal model to elucidate the acute effects of perfusion abnormalities on muscle metabolism induced by different density-defined classes of erythrocytes isolated from sickle cell anemia patients. Technetium-99m ({sup 99m}Tc)-labeled, saline-washed normal (AA), homozygous sickle (SS), or high-density SS (SS4) erythrocytes were injected into the femoral artery of the rat and quantitative {sup 99m}Tc imaging, {sup 31}P magnetic resonance spectroscopy by surface coil at 2 teslas, and {sup 1}H magnetic resonance imaging at 0.15 tesla were performed. Between 5 and 25 {mu}l of SS4 cells was trapped in the microcirculation of the thigh. In contrast, fewer SS discocytes (SS2) or AA cells were trapped. After injection of SS4 cells an initial increase in inorganic phosphate was observed in the region of the thigh served by the femoral artery, intracellular pH decreased, and subsequently the proton relaxation time T{sub 1} reached a broad maximum at 18-28 hr. When T{sub 1} obtained at this time was plotted against the volume of cells trapped, an increase of T{sub 1} over the control value of 411 {plus minus} 48 msec was found that was proportional to the number of cells trapped. They conclude that the densest SS cells are most effective at producing vasoocclusion. The extent of the change detected by {sup 1}H magnetic resonance imaging is dependent on the amount of cells trapped in the microcirculation and the magnitude of the initial increase of inorganic phosphate.

  10. Characterisation and evaluation of paramagnetic fluorine labelled glycol chitosan conjugates for (19)F and (1)H magnetic resonance imaging.

    PubMed

    De Luca, Elena; Harvey, Peter; Chalmers, Kirsten H; Mishra, Anurag; Senanayake, P Kanthi; Wilson, J Ian; Botta, Mauro; Fekete, Marianna; Blamire, Andrew M; Parker, David

    2014-02-01

    Medium molecular weight glycol chitosan conjugates have been prepared, linked by an amide bond to paramagnetic Gd(III), Ho(III) and Dy(III) macrocyclic complexes in which a trifluoromethyl reporter group is located 6.5 Å from the paramagnetic centre. The faster relaxation of the observed nucleus allows modified pulse sequences to be used with shorter acquisition times. The polydisperse materials have been characterised by gel permeation chromatography, revealing an average molecular weight on the order of 13,800 (Gd), 14,600 (Dy) and 16,200 (Ho), consistent with the presence of 8.5, 9.5 and 13 complexes, respectively. The gadolinium conjugate was prepared for both a q = 1 monoamide tricarboxylate conjugate (r1p 11.2 mM(-1) s(-1), 310 K, 1.4 T) and a q = 0 triphosphinate system, and conventional contrast-enhanced proton MRI studies at 7 T were undertaken in mice bearing an HT-29 or an HCT-116 colorectal tumour xenograft (17 μmol/kg). Enhanced contrast was observed following injection in the tail vein in tumour tissue, with uptake also evident in the liver and kidney with a tumour-to-liver ratio of 2:1 at 13 min, and large amounts in the kidney and bladder consistent with predominant renal clearance. Parallel experiments observing the (19)F resonance in the holmium conjugate complex using a surface coil did not succeed owing to its high R2 value (750 Hz, 7 T). However, the fluorine signal in the dysprosium triphosphinate chitosan conjugate [R1/R2 = 0.6 and R1 = 145 Hz (7 T)] was sharper and could be observed in vivo at -65.7 ppm, following intravenous tail vein injection of a dose of 34 μmol/kg. PMID:23955558

  11. Chronic Cocaine Use and Its Association with Myocardial Steatosis Evaluated by 1H Magnetic Resonance Spectroscopy in African Americans

    PubMed Central

    Lai, Shenghan; Gerstenblith, Gary; Li, Ji; Zhu, Hong; Bluemke, David A.; Liu, Chia-Ying; Zimmerman, Stefan L.; Chen, Shaoguang; Lai, Hong; Treisman, Glenn

    2014-01-01

    Objectives Cardiac steatosis is a manifestation of ectopic fat deposition and is associated with obesity. The impact of chronic cocaine use on obesity measures and on the relationship between obesity measures and cardiac steatosis is not well-characterized. The objectives of this study were to compare obesity measures in chronic cocaine users and non-users, and to explore which factors, in addition to obesity measures, are associated with myocardial triglyceride in African Americans (AAs), using noninvasive magnetic resonance spectroscopy (MRS). Methods Between June 2004 and January 2014, 180 healthy AA adults without HIV infection, hypertension and diabetes were enrolled in an observational proton MRS and imaging study investigating factors associated with cardiac steatosis. Results Among these 180 participants, 80 were chronic cocaine users, and 100 were non-users. The median age (with IQR) was 42 (34-47) years. Obesity measures trended higher in cocaine users than non-users. The median myocardial triglyceride was 0.6% (IQR:0.4-1.1%). Among the factors investigated, years of cocaine use, leptin and visceral fat were independently associated with myocardial triglyceride. BMI and visceral fat, which were significantly associated with myocardial triglyceride in non-cocaine users, were not associated with myocardial triglycerides content in cocaine users. Conclusions This study shows (1) cocaine users may have more fat than nonusers and (2) myocardial triglyceride is independently associated with duration of cocaine use, leptin, and visceral fat in all subjects, while leptin and HDL-cholesterol, but not visceral fat or BMI, in cocaine users, suggesting that chronic cocaine use may modify the relationships between obesity measures and myocardial triglyceride. PMID:25325298

  12. A high frequency resonance gravity gradiometer

    SciTech Connect

    Bagaev, S. N.; Kvashnin, N. L.; Skvortsov, M. N.; Bezrukov, L. B.; Krysanov, V. A.; Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Samoilenko, A. A.; Yudin, I. S.; Rudenko, V. N.

    2014-06-15

    A new setup OGRAN—the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events—gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.

  13. A high frequency resonance gravity gradiometer.

    PubMed

    Bagaev, S N; Bezrukov, L B; Kvashnin, N L; Krysanov, V A; Oreshkin, S I; Motylev, A M; Popov, S M; Rudenko, V N; Samoilenko, A A; Skvortsov, M N; Yudin, I S

    2014-06-01

    A new setup OGRAN--the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events--gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS. PMID:24985859

  14. Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies.

    PubMed

    Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G J; Chen, X H; Shan, Jie; Feng, Philip X-L

    2015-01-21

    We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ∼100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ∼200 nm down to ∼20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus. PMID:25385657

  15. Multiplexed infrared photodetection using resonant radio-frequency circuits

    NASA Astrophysics Data System (ADS)

    Liu, R.; Lu, R.; Roberts, C.; Gong, S.; Allen, J. W.; Allen, M. S.; Wenner, B. R.; Wasserman, D.

    2016-02-01

    We demonstrate a room-temperature semiconductor-based photodetector where readout is achieved using a resonant radio-frequency (RF) circuit consisting of a microstrip split-ring resonator coupled to a microstrip busline, fabricated on a semiconductor substrate. The RF resonant circuits are characterized at RF frequencies as function of resonator geometry, as well as for their response to incident IR radiation. The detectors are modeled analytically and using commercial simulation software, with good agreement to our experimental results. Though the detector sensitivity is weak, the detector architecture offers the potential for multiplexing arrays of detectors on a single read-out line, in addition to high speed response for either direct coupling of optical signals to RF circuitry, or alternatively, carrier dynamics characterization of semiconductor, or other, material systems.

  16. 2D-1H proton magnetic resonance spectroscopic imaging study on brain metabolite alterations in patients with diabetic hypertension.

    PubMed

    Cao, Zhen; Ye, Bi-Di; Shen, Zhi-Wei; Cheng, Xiao-Fang; Yang, Zhong-Xian; Liu, Yan-Yan; Wu, Ren-Hua; Geng, Kuan; Xiao, Ye-Yu

    2015-06-01

    The aim of the present study was to investigate the possible metabolic alterations in the frontal cortex and parietal white matter in patients with diabetic hypertension (DHT) using proton magnetic resonance (MR) spectroscopic imaging. A total of 33 DHT patients and 30 healthy control subjects aged between 45 and 75 were included in the present study. All subjects were right‑handed. The spectroscopy data were collected using a GE Healthcare 1.5T MR scanner. The multi‑voxels were located in the semioval center (repetition time/echo time=1,500 ms/35 ms). The area of interest was 8x10x2 cm in volume and contained the two sides of the frontal cortex and the parietal white matter. The spectra data were processed using SAGE software. The ratios of brain metabolite concentrations, particularly for N‑acetylaspartate (NAA)/creatine (Cr) and Choline (Cho)/Cr were calculated and analyzed. Statistical analyses were performed using SPSS 17.0. The NAA/Cr ratio of the bilateral prefrontal cortex of the DHT group was significantly lower than that of the control group (left t=‑7.854, P=0.000 and right t=‑5.787, P=0.000), The Cho/Cr ratio was also much lower than the control group (left t=2.422, P=0.024 and right t=2.920, P=0.007). NAA/Cr ratio of the left parietal white matter of the DHT group was extremely lower than that of the control group (t=‑4.199, P=0.000). Therefore, DHT may result in metabolic disorders in the frontal cortex and parietal white matter but the metabolic alterations are different in various regions of the brain. The alteration in cerebral metabolism is associated with diabetes and hypertension. The ratios of NAA/Cr and Cho/Cr are potential metabolic markers for the brain damage induced by DHT. PMID:25652580

  17. Relationship between wingbeat frequency and resonant frequency of the wing in insects.

    PubMed

    Ha, Ngoc San; Truong, Quang Tri; Goo, Nam Seo; Park, Hoon Cheol

    2013-12-01

    In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ~ m(1/2)/Af, while the natural frequency was significantly correlated with area density (f0 ~ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports--that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy. PMID:24166827

  18. Resonance at the Rabi frequency in a superconducting flux qubit

    SciTech Connect

    Greenberg, Ya. S.; Il'ichev, E.; Oelsner, G.; Shevchenko, S. N.

    2014-10-15

    We analyze a system composed of a superconducting flux qubit coupled to a transmission-line resonator driven by two signals with frequencies close to the resonator's harmonics. The first strong signal is used for exciting the system to a high energetic state while a second weak signal is applied for probing effective eigenstates of the system. In the framework of doubly dressed states we showed the possibility of amplification and attenuation of the probe signal by direct transitions at the Rabi frequency. We present a brief review of theoretical and experimental works where a direct resonance at Rabi frequency have been investigated in superconducting flux qubits. The interaction of the qubit with photons of two harmonics has prospects to be used as a quantum amplifier (microwave laser) or an attenuator.

  19. Design of tunable GHz-frequency optomechanical crystal resonators.

    PubMed

    Pfeifer, Hannes; Paraïso, Taofiq; Zang, Leyun; Painter, Oskar

    2016-05-30

    We present a silicon optomechanical nanobeam design with a dynamically tunable acoustic mode at 10.2 GHz. The resonance frequency can be shifted by 90 kHz/V2 with an on-chip capacitor that was optimized to exert forces up to 1 µN at 10 V operation voltage. Optical resonance frequencies around 190 THz with Q-factors up to 2.2 × 106 place the structure in the well-resolved sideband regime with vacuum optomechanical coupling rates up to g0/2π = 353 kHz. Tuning can be used, for instance, to overcome variation in the device-to-device acoustic resonance frequency due to fabrication errors, paving the way for optomechanical circuits consisting of arrays of optomechanical cavities. PMID:27410069

  20. Resonant oscillations of intermediate frequency in a stratified atmosphere.

    NASA Technical Reports Server (NTRS)

    Thompson, O. E.

    1973-01-01

    A class of solutions to a model of forced oscillations in a rotating stratified atmospheric layer is derived and analyzed. The basic model is found to reduce to a boundary value problem with a second-order linear partial differential equation of the hyperbolic type for this range of forcing frequencies. The forced solutions are shown to exhibit resonances with the normal modes of oscillation of the layer. The characteristics of the resonant modes are analyzed in terms of mean tropospheric values of temperature, temperature lapse, wind speed, horizontal and vertical wind shears, latitude, and the frequency and horizontal wavelength of the forcing mechanism. These solutions are compared with solutions to the model for a different (subinertial) range of forcing frequencies. This comparison leads to an elliptic boundary value problem. The solutions in that case do not exhibit the same type of resonance and generally decay away from the region of forcing.

  1. Frequency-scanning marginal oscillator for ion cyclotron resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kemper, Paul R.; Bowers, Michael T.

    1982-07-01

    A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency-scanned detection system. Since the traditional marginal oscillator detector has always been a fixed-frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency-scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.

  2. Experimental study on resonant frequency of the thermoacoustic cooling system

    NASA Astrophysics Data System (ADS)

    Sakamoto, Shin-ichi; Hirano, Hiroyuki; Fujita, Takashi; Watanabe, Yoshiaki

    2006-05-01

    The purpose of our study is to construct a new cooling system applying the thermoacoustic effect. Stainless loop-tube is employed as our thermoacoustic cooling system and temperature decrease of 40 degrees C from the room temperature has been confirmed. In this paper, it is investigated that the relation between the viscosity boundary layer and the resonant frequency of the generated sound is investigated. Also, the sound pressure and temperature variation are observed with various total lengths of the loop-tube, with the view toward improvement in the cooling effect of the thermoacoustic cooling system. It was generally considered that the sound generated in the thermoacoustic cooling system is resonated with the tube length by 1 wavelength. However, when the total length of the loop-tube is over 2600 mm and inner pressure is 0.1 MPa, the resonant wavelength is 2. This is resulted from the influence of the viscosity boundary layer. It is found that the loop-tube decides the resonant frequency so that the thickness of the viscosity boundary layer is smaller than the stack channel radius. As a result, the resonant wavelength is 2 in a certain condition. The frequency is an important parameter for the thermoacoustic cooling system. From obtained results, one of the factors to select the frequency is found.

  3. WGM Resonators for Terahertz-to-Optical Frequency Conversion

    NASA Technical Reports Server (NTRS)

    Strekalov,Dmitry; Savchenkov, Anatoliy; Matsko, Andrey; Nu, Nan

    2008-01-01

    Progress has been made toward solving some practical problems in the implementation of terahertz-to-optical frequency converters utilizing whispering-gallery-mode (WGM) resonators. Such frequency converters are expected to be essential parts of non-cryogenic terahertz- radiation receivers that are, variously, under development or contemplated for a variety of applications in airborne and spaceborne instrumentation for astronomical and military uses. In most respects, the basic principles of terahertz-to-optical frequency conversion in WGM resonators are the same as those of microwave (sub-terahertz)-to-optical frequency conversion in WGM resonators, various aspects of which were discussed in the three preceeding articles. To recapitulate: In a receiver following this approach, a preamplified incoming microwave signal (in the present case, a terahertz signal) is up-converted to an optical signal by a technique that exploits the nonlinearity of the electromagnetic response of a whispering-gallery-mode (WGM) resonator made of LiNbO3 or another suitable electro-optical material. Upconversion takes place by three-wave mixing in the resonator. To ensure the required interaction among the optical and terahertz signals, the WGM resonator must be designed and fabricated to function as an electro-optical modulator while simultaneously exhibiting (1) resonance at the required microwave and optical operating frequencies and (2) phase matching among the microwave and optical signals circulating in the resonator. Downstream of the WGM resonator, the up-converted signal is processed photonically by use of a tunable optical filter or local oscillator and is then detected. The practical problems addressed in the present development effort are the following: Satisfaction of the optical and terahertz resonance-frequency requirement is a straightforward matter, inasmuch as the optical and terahertz spectra can be measured. However, satisfaction of the phase-matching requirement is

  4. Artificial excitation of ELF waves with frequency of Schumann resonance

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  5. Time domain characterization of oscillating sensors: Application of frequency counting to resonance frequency determination

    NASA Astrophysics Data System (ADS)

    Zeng, Kefeng; Ong, Keat G.; Mungle, Casey; Grimes, Craig A.

    2002-12-01

    A frequency counting technique is described for determining the resonance frequency of a transiently excited sensor; the technique is applicable to any sensor platform where the characteristic resonance frequency is the parameter of interest. The sensor is interrogated by a pulse-like excitation signal, and the resonance frequency of the sensor subsequently determined by counting the number of oscillations per time during sensor ring-down. A repetitive time domain interrogation technique is implemented to overcome the effects of sensor damping, such as that associated with mass loading, which reduces the duration of the sensor ring-down and hence the measurement resolution. The microcontroller based, transient frequency counting technique is detailed with application to the monitoring of magnetoelastic sensors [C. A. Grimes, D. Kouzoudis, and C. Mungle, Rev. Sci. Instrum. 71, 3822 (2000)], with a measurement resolution of 0.001% achieved in approximately 40 ms.

  6. Analysis of brain metabolism by proton magnetic resonance spectroscopy (1H-MRS) in attention-deficit/hyperactivity disorder suggests a generalized differential ontogenic pattern from controls.

    PubMed

    Arcos-Burgos, Mauricio; Londoño, Ana C; Pineda, David A; Lopera, Francisco; Palacio, Juan David; Arbelaez, Andres; Acosta, Maria T; Vélez, Jorge I; Castellanos, Francisco Xavier; Muenke, Maximilian

    2012-12-01

    Attention-deficit/hyperactivity disorder (ADHD) is the most common behavioral disorder of childhood. Preliminary studies with proton magnetic resonance spectroscopy ((1)H-MRS) of the brain have reported differences in brain metabolite concentration-to-Cr ratios between individuals with ADHD and unaffected controls in several frontal brain regions including anterior cingulate cortex. Using multivoxel (1)H-MRS, we compared 14 individuals affected with ADHD to 20 individuals without ADHD from the same genetic isolate. After controlling by sex, age, and multiple testing, we found significant differences at the right posterior cingulate of the Glx/Cr ratio density distribution function between ADHD cases and controls (P < 0.05). Furthermore, we found several interactions of metabolite concentration-to-Cr ratio, age, and ADHD status: Ins/Cr and Glx/Cr ratios at the left posterior cingulate, and NAA/Cr at the splenius, right posterior cingulate, and at the left posterior cingulate. We also found a differential metabolite ratio interaction between ADHD cases and controls for Ins/Cr and NAA/Cr at the right striatum. These results show that: (1) NAA/Cr, Glx/Cr, and Ins/Cr ratios, as reported in other studies, exhibit significant differences between ADHD cases and controls; (2) differences of these metabolite ratios between ADHD cases and controls evolve in specific and recognizable patterns throughout age, a finding that replicates previous results obtained by structural MRI, where is demonstrated that brain ontogeny follows a different program in ADHD cases and controls; (3) Ins/Cr and NAA/Cr ratios, at the right striatum, interact in a differential way between ADHD cases and controls. As a whole, these results replicate previous 1H-MRS findings and add new intriguing differential metabolic and ontogeny patterns between ADHD cases and controls that warrant further pursue. PMID:23012086

  7. Cerebral metabolic changes in a depression-like rat model of chronic forced swimming studied by ex vivo high resolution 1H magnetic resonance spectroscopy.

    PubMed

    Li, Chun-Xia; Wang, Yaqiang; Gao, Hongchang; Pan, Wen-Ju; Xiang, Yun; Huang, Mingming; Lei, Hao

    2008-11-01

    Many previous in vivo (1)H magnetic resonance spectroscopy (MRS) studies have shown that patients with major depressive disorder (MDD) are associated with perturbations of cerebral metabolism of neurotransmitters glutamate (Glu) and gamma-aminobutyric acid (GABA). In this study, we investigated the changes of cerebral metabolism in a depression-like rat model of chronic forced swimming stress (CFSS). The aims are to further understand the pathophysiological mechanisms underlying CFSS treatment, and to further establish the face and predictive validity of the CFSS model. The results showed that, relative to control, the CFSS rats had significantly reduced Glu, taurine and glutamate + glutamine (Glx) levels in the PFC, and significantly reduced N-acetyl aspartate (NAA) level, Glu level and Glu/GABA ratio in the hippocampus. Taking together, these results suggest that CFSS treatment can induce region-specific changes in the metabolism of Glu. The CFSS model might be used to study antidepressants specifically targeting the central glutamatergic system. PMID:18473166

  8. 1H and 129Xe nuclear magnetic resonance studies of hydrogen chemisorption on supported platinum. Application to the metal dispersion and spillover.

    PubMed

    Rouabah, D; Fraissard, J

    1994-06-01

    Chemisorption of hydrogen, electron microscopy and 1H nuclear magnetic resonance (NMR) have confirmed that the chemical shift of hydrogen chemisorbed on platinum is directly related to the size of the metal particles. The influence of the hydrogen adsorbate concentration and the chemisorption temperature on the chemical shift delta H and the distribution of the hydrogen chemisorbed on these particles have been determined. This study also shows how the dispersion can be deduced from the variation of delta H with the H2 concentration and clarifies the effect of temperature on the concentration of spillover H2. 129Xe NMR of adsorbed xenon used as a probe confirmed most of the previous results. PMID:7827982

  9. Two-photon absorption resonance in 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP)

    NASA Astrophysics Data System (ADS)

    Miniewicz, Andrzej; Delysse, Stéphane; Nunzi, Jean-Michel; Kajzar, François

    1998-04-01

    A two-photon absorption spectrum of 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) in tetrahydrofuran solution has been studied by the Kerr ellipsometry technique. The spectral shape and amplitude of the imaginary part of the dominant molecular hyperpolarizability term Im( γXXXX) is compared with the relevant linear absorption spectrum within a simple two-level model. Agreement between the measured γXXXX=2.0×10 -48 m 5 V -2 and calculated γXXXX=(1.2-1.5)×10 -48 m 5 V -2 two-photon absorption molecular hyperpolarizabilties in the vicinity of the two-photon resonance transition is satisfactory.

  10. Frequency-swept detector for ion cyclotron resonance mass spectrometers

    NASA Astrophysics Data System (ADS)

    Wronka, J.; Ridge, D. P.

    1982-04-01

    Design, construction, performance, and use of a frequency-swept bridge detector for ion cyclotron resonance mass spectrometry are described. Special features include characterization and simple automatic correction of phase shift to allow broadband detection. The result is a detection system that may be used either at constant field or constant frequency. Drift-mode operation is simplified in that it may be satisfactorily used without the various signal modulation schemes used in previous detectors. In the trapped mode the detector may be pulsed to control the timing of ion detection. This detector makes it possible to do frequency-swept double resonance experiments which provide spectra of all the product ions of a given reactant ion. Circuit schematics and typical frequency- and field-swept spectra are shown.

  11. Frequency-tunable superconducting resonators via nonlinear kinetic inductance

    SciTech Connect

    Vissers, M. R.; Hubmayr, J.; Sandberg, M.; Gao, J.; Chaudhuri, S.; Bockstiegel, C.

    2015-08-10

    We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Q{sub i} > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.

  12. Near-complete 1H, 13C, 15N resonance assignments of dimethylsulfoxide-denatured TGFBIp FAS1-4 A546T.

    PubMed

    Kulminskaya, Natalia V; Yoshimura, Yuichi; Runager, Kasper; Sørensen, Charlotte S; Bjerring, Morten; Andreasen, Maria; Otzen, Daniel E; Enghild, Jan J; Nielsen, Niels Chr; Mulder, Frans A A

    2016-04-01

    The transforming growth factor beta induced protein (TGFBIp) is a major protein component of the human cornea. Mutations occurring in TGFBIp may cause corneal dystrophies, which ultimately lead to loss of vision. The majority of the disease-causing mutations are located in the C-terminal domain of TGFBIp, referred as the fourth fascilin-1 (FAS1-4) domain. In the present study the FAS1-4 Ala546Thr, a mutation that causes lattice corneal dystrophy, was investigated in dimethylsulfoxide using liquid-state NMR spectroscopy, to enable H/D exchange strategies for identification of the core formed in mature fibrils. Isotope-labeled fibrillated FAS1-4 A546T was dissolved in a ternary mixture 95/4/1 v/v/v% dimethylsulfoxide/water/trifluoroacetic acid, to obtain and assign a reference 2D (1)H-(15)N HSQC spectrum for the H/D exchange analysis. Here, we report the near-complete assignments of backbone and aliphatic side chain (1)H, (13)C and (15)N resonances for unfolded FAS1-4 A546T at 25 °C. PMID:26275916

  13. Effects of time and temperature of firing on Fe-rich ceramics studied by Moessbauer spectroscopy and two-dimensional {sup 1}H-nuclear magnetic resonance relaxometry

    SciTech Connect

    Casieri, Cinzia; De Luca, Francesco; Nodari, Luca; Russo, Umberto; Terenzi, Camilla; Tudisca, Valentina

    2012-10-15

    The combined effects of firing temperature and soaking time on the microstructure of iron-rich porous ceramics have been studied by {sup 57}Fe-Moessbauer spectroscopy and 2D {sup 1}H nuclear magnetic resonance (NMR) relaxometry using a single-sided probe. Examining water-saturated ceramics using the relaxation correlation method, where longitudinal (T{sub 1}) and transverse (T{sub 2}) relaxation times are measured concurrently, provides information about firing-induced changes in both porosity (related to T{sub 1}) and magnetic properties (related to T{sub 2}). Comparing the information obtained from {sup 1}H-NMR analyses with that obtained from Moessbauer spectroscopy (which characterizes changes in iron-bearing species) shows that the T{sub 1}-T{sub 2} NMR correlation technique is very sensitive to even subtle modifications in the magnetic behavior of Fe-bearing species. Moreover, the single-sided NMR approach allows us to perform millimeter-scale depth-resolved measurements, which can be used to non-invasively study the microstructural heterogeneities associated with non-uniform firing effects inside ceramics. This is in contrast to Moessbauer spectroscopy, which requires that the ceramic samples be ground.

  14. An Evaluation of 1-Deoxynojirimycin Oral Administration in Eri Silkworm through Fat Body Metabolomics Based on 1H Nuclear Magnetic Resonance

    PubMed Central

    Wen, Chao-wei; Lin, Xiao-dong; Dong, Min-jian; Deng, Ming-jie

    2016-01-01

    1-Deoxynojirimycin (DNJ), the main hypoglycemic constituent in mulberry (Morus alba) latex, has been extensively researched. Although there is considerable interest in the biological effects of DNJ, the roles of 1-deoxynojirimycin (DNJ) in glycometabolism and energy metabolism in insects have received little attention. In this paper, 1H nuclear magnetic resonance (1H NMR) based metabonomic was performed to study the effects of the oral supplementation of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) on the fat body glycometabolism and energy metabolism of the fourth-instar larvae of Eri silkworms, Samia cynthia ricini. Metabolic pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) of fat body extracts indicated that the groups of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) were significantly different from the control group. Further, compared to the control group, the metabolites levels of lactate, trehalose, succinate, malate, and fumarate were remarkably changed in experimental groups, which were involved in glycolysis, hydrolysis of trehalose, and tricarboxylic acid (TCA) cycle. Our results indicate that DNJ has a positive impact on the reverse energy metabolism of Eri silkworms and metabonomic analysis based on NMR can be used as a tool to identify potential biomarkers. PMID:27294120

  15. An Evaluation of 1-Deoxynojirimycin Oral Administration in Eri Silkworm through Fat Body Metabolomics Based on (1) H Nuclear Magnetic Resonance.

    PubMed

    Wen, Chao-Wei; Lin, Xiao-Dong; Dong, Min-Jian; Deng, Ming-Jie

    2016-01-01

    1-Deoxynojirimycin (DNJ), the main hypoglycemic constituent in mulberry (Morus alba) latex, has been extensively researched. Although there is considerable interest in the biological effects of DNJ, the roles of 1-deoxynojirimycin (DNJ) in glycometabolism and energy metabolism in insects have received little attention. In this paper, (1)H nuclear magnetic resonance ((1)H NMR) based metabonomic was performed to study the effects of the oral supplementation of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) on the fat body glycometabolism and energy metabolism of the fourth-instar larvae of Eri silkworms, Samia cynthia ricini. Metabolic pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) of fat body extracts indicated that the groups of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) were significantly different from the control group. Further, compared to the control group, the metabolites levels of lactate, trehalose, succinate, malate, and fumarate were remarkably changed in experimental groups, which were involved in glycolysis, hydrolysis of trehalose, and tricarboxylic acid (TCA) cycle. Our results indicate that DNJ has a positive impact on the reverse energy metabolism of Eri silkworms and metabonomic analysis based on NMR can be used as a tool to identify potential biomarkers. PMID:27294120

  16. A Spectrometer for Dynamic Nuclear Polarization and Electron Paramagnetic Resonance at High Frequencies

    NASA Astrophysics Data System (ADS)

    Becerra, L. R.; Gerfen, G. J.; Bellew, B. F.; Bryant, J. A.; Hall, D. A.; Inati, S. J.; Weber, R. T.; Un, S.; Prisner, T. F.; McDermott, A. E.; Fishbein, K. W.; Kreischer, K. E.; Temkin, R. J.; Singel, D. J.; Griffin, R. G.

    A high-frequency dynamic nuclear polarization (DNP)/electron paramagnetic resonance spectrometer operating at 211 MHz for 1H and 140 GHz for g= 2 paramagnetic centers (5 T static field) is described. The salient feature of the instrument is a cyclotron-resonance maser (gyrotron) which generates high-frequency, high-power microwave radiation. This gyrotron, which under conventional operation produces millisecond pulses at kilowatt powers, has been adapted to operate at ˜100 W for 1 to 20 s pulses and in the continuous wave mode at the 10 W power level. Experiments combining DNP with magic-angle spinning (MAS) nuclear magnetic resonance were performed on samples consisting of 2% by weight of the free radical BDPA doped into polystyrene. Room-temperature DNP enhancement factors of 10 for 1H and 40 for 13C were obtained in the NMR-MAS spectra. Static DNP NMR has also been performed on samples containing nitroxides dissolved in water:glycerol solvent mixtures. Enhancements of approximately 200 have been obtained for low-temperature (14 K) 1H NMR. A pulsed/CW EPR spectrometer operating at 140 GHz has been developed in conjunction with the DNP spectrometer. Microwave sources include Gunn-diode oscillators which provide low-power (20 mW) radiation, and the gyrotron, which has been used to deliver higher power levels in pulsed experiments. Results using this spectrometer are presented for continuous-wave and echo-detected EPR, electron spin-echo-envelope modulation (ESEEM), and Fourier-transform EPR.

  17. Two- and three-dimensional sup 1 H NMR studies of a wheat phospholipid transfer protein: Sequential resonance assignments and secondary structure

    SciTech Connect

    Simorre, J.P.; Caille, A. ); Marion, D. ); Marion, D. ); Ptak, M. Univ. d'Orleans )

    1991-12-10

    Two- and three-dimensional {sup 1}H NMR experiments have been used to sequentially assign nearly all proton resonances of the 90 residues of wheat phospholipid transfer protein. Only a few side-chain protons were not identified because of degeneracy or overlapping. The identification of spin systems and the sequential assignment were made at the same time by combining the data of the two- and three-dimensional experiments. The classical two-dimensional COSY, HOHAHA, and NOESY experiments benefit from both good resolution and high sensitivity, allowing the detection of long-range dipolar connectivities. The three-dimensional HOHAHA-NOESY experiment offers the advantage of a faster and unambiguous assignment. As a matter of fact, homonuclear three-dimensional NMR spectroscopy prove to be a very efficient method for resonance assignments of protein {sup 1}H NMR spectra which cannot be unraveled by 2D methods. An assignment strategy which overcomes most of the ambiguities has been proposed, in which each individual assignment toward the C-terminal end is supported by another in the opposite direction originating from a completely different part of the spectrum. Location of secondary structures of the phospholipid transfer protein was determined by using the method of analysis introduced here and was confirmed by {sup 3}J{sub {alpha}NH} coupling and NH exchange rates. Except for the C-terminal part, the polypeptide chain appears to be organized mainly as helical fragments connected by disulfide bridges. Further modeling will display the overall folding of the protein and should provide a better understanding of its interactions with lipids.

  18. Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

    NASA Astrophysics Data System (ADS)

    Tary, J. B.; Baan, M.; Eaton, D. W.

    2014-02-01

    Hydraulic fracturing treatments are often monitored by strings of geophones deployed in boreholes. Instead of picking discrete events only, we here use time-frequency representations of continuous recordings to identify resonances in two case studies. This paper outlines an interpretational procedure to identify their cause using a subdivision into source, path, and receiver-side effects. For the first case study, two main resonances are observed both at depth by the downhole geophones and on the surface by two broadband arrays. The two acquisition networks have different receiver and path effects, yet recorded the same resonances; these resonances are therefore likely generated by source effects. The amplitude pattern at the surface arrays indicates that these resonances are probably due to pumping operations. In the second case study, selective resonances are detected by the downhole geophones. Resonances coming from receiver effects are either lower or higher frequency, and wave propagation modeling shows that path effects are not significant. We identify two possible causes within the source area, namely, eigenvibrations of fractures or non-Darcian flow within the hydraulic fractures. In the first situation, 15-30 m long fluid-filled cracks could generate the observed resonances. An interconnected fracture network would then be required, corresponding to mesoscale deformation of the reservoir. Alternatively, systematic patterns in non-Darcian fluid flow within the hydraulic fracture could also be their leading cause. Resonances can be used to gain a better understanding of reservoir deformations or dynamic fluid flow perturbations during fluid injection into hydrocarbon and geothermal reservoirs, CO2 sequestration, or volcanic eruptions.

  19. Ionospheric nf sub H resonances: Frequency shifts versus plasma conditions

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1971-01-01

    The Alouette 2 resonances observed near the harmonics of the electron cyclotron frequency f sub H reveal frequency shifts (relative to the n(f sub H) values derived from model field calculations) which can be interpreted in terms of plasma wave dispersion effects. These effects are observed on the 2(f sub H) resonance when it is near the resonance observed close to the upper hybrid frequency f sub T. The observations suggest that an oblique echo model may be required to give a proper interpretation of the 2(f sub H) resonance. Cyclotron damping can be ignored only when the angle between the propagation vector and the direction perpendicular to the earth's magnetic field B is less than a few degrees for the 2(f sub H) wave, and less than a few tenths of a degree for the n(f sub H) waves with n 2. The negative offset of the absolute value of B inferred from the plasma resonance observations is consistent with expectations based on recent OGO 3 and OGO 5 rubidium magnetometer observations at higher altitudes in the equatorial regions.

  20. Photonic measurement of microwave frequency using a silicon microdisk resonator

    NASA Astrophysics Data System (ADS)

    Liu, Li; Jiang, Fan; Yan, Siqi; Min, Shucun; He, Mengying; Gao, Dingshan; Dong, Jianji

    2015-01-01

    A simple photonic approach to the measurement of microwave signal frequency with adjustable measurement range and resolution is proposed and demonstrated. In this approach, the unknown microwave signal is converted to an optical signal with single sideband modulation. Subsequently, a notch microwave photonic filter (MPF) is implemented by employing a high-Q silicon microdisk resonator (MDR). The MPF is tunable by changing the frequency interval between the optical carrier and the MDR notch so as to obtain different amplitude responses. A fixed frequency-to-power mapping is established by obtaining an amplitude comparison function (ACF) of the microwave power ratio and the microwave frequency. A proof-of-concept experiment demonstrates a frequency measurement range of 10 GHz, with measurement error of ±0.1 GHz. Different frequency measurement ranges and resolutions are also discussed.

  1. Mapping extracellular pH in rat brain gliomas in vivo by 1H magnetic resonance spectroscopic imaging: comparison with maps of metabolites.

    PubMed

    García-Martín, M L; Hérigault, G; Rémy, C; Farion, R; Ballesteros, P; Coles, J A; Cerdán, S; Ziegler, A

    2001-09-01

    The value of extracellular pH (pH(e)) in tumors is an important factor in prognosisand choice of therapy. We demonstrate here that pH(e) can be mappedin vivo in a rat brain glioma by (1)H magnetic resonance spectroscopic imaging (SI) of the pH buffer (+/-)2-imidazole-1-yl-3-ethoxycarbonylpropionic acid (IEPA). (1)H SI also allowed us to map metabolites, and, to better understand the determinants of pH(e), we compared maps of pH(e), metabolites, and the distribution of the contrast agent gadolinium1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraaceticacid (Gd-DOTA). C6 cells injected in caudate nuclei of four Wistar rats gave rise to gliomas of approximately 10 mm in diameter. Three mmols of IEPA were injected in the right jugular vein from t = 0 to t = 60 min. From t = 50 min to t = 90 min, spin-echo (1)H SI was performed with an echo time of 40 ms in a 2.5-mm slice including the glioma (nominal voxel size, 2.2 microl). IEPA resonances were detected only within the glioma and were intense enough for pH(e) to be calculated from the chemical shift of the H2 resonance in almost all voxels of the glioma. (1)H spectroscopic images with an echo time of 136 ms were then acquired to map metabolites: lactate, choline-containing compounds (tCho), phosphocreatine/creatine, and N-acetylaspartate. Finally, T(1)-weighted imaging after injection of a bolus of Gd-DOTA gave a map indicative of extravasation. On average, the gradient of pH(e) (measured where sufficient IEPA was present) from the center to the periphery was not statistically significant. Mean pH(e) was calculated for each of the four gliomas, and the average was 7.084 +/- 0.017 (+/- SE; n = 4 rats), which is acid with respect to pH(e) of normal tissue. After normalization of spectra to their water peak, voxel-by-voxel comparisons of peak areas showed that N-acetylaspartate, a marker of neurons, correlated negatively with IEPA (P < 0.0001) and lactate (P < 0.05), as expected of a glioma surrounded by normal tissue. t

  2. Backbone 1H, 13C and 15N resonance assignments of the 39 kDa staphylococcal hemoglobin receptor IsdH.

    PubMed

    Spirig, Thomas; Clubb, Robert T

    2012-10-01

    During infections Stahpylococcus aureus preferentially uses heme as an iron source, which it captures from human hemoglobin using the Iron regulated surface determinant (Isd) system. On the cell surface two related staphylococcal surface receptors called IsdH and IsdB bind to hemoglobin and extract its heme. Both receptors contain multiple NEAr iron Transporter (NEAT) domains that either bind to hemoglobin, or to heme. All previous structural studies have investigated individual NEAT domains and have not explored how the domains might interact with one another to synergistically extract heme from hemoglobin. Here, we report the near complete (1)H, (13)C and (15)N backbone resonance assignments of a bi-domain unit from IsdH that contains the N2 and N3 NEAT domains, which bind to hemoglobin and heme, respectively (IsdH(N2N3), residues 326-660, 39 kDa). The assigned backbone resonances lay the foundation for future NMR studies that will explore the molecular basis of IsdH function. PMID:22101872

  3. Schumann resonance frequency increase during solar X-ray bursts

    NASA Astrophysics Data System (ADS)

    Roldugin, V. C.; Maltsev, Y. P.; Vasiljev, A. N.; Schokotov, A. Y.; Belyajev, G. G.

    2004-01-01

    Variations of the first mode Schumann resonance frequency in the Kola Peninsula and of the first and second mode frequencies in Kamchatka during seven days of March-April 2001, when the intensive solar X-ray bursts occurred, are studied with 5 min averaging. All X-ray bursts were accompanied by ˜0.2 Hz increase in the first mode frequency, at least in one of the magnetic components. Duration of the increases coincided with that of the bursts. For the second mode the increase (in average by ˜0.3 Hz) was registered in most events, when the ELF noise level was not very high.

  4. 1H nuclear-magnetic-resonance investigation of oxidized Fe4S4 ferredoxin from Thermotoga maritima. Hyperfine-shifted resonances, sequence-specific assignments and secondary structure.

    PubMed

    Wildegger, G; Bentrop, D; Ejchart, A; Alber, M; Hage, A; Sterner, R; Rösch, P

    1995-05-01

    The oxidized Fe4S4 ferredoxin from the hyperthermophilic bacterium Thermotoga maritima has been investigated by one- and two-dimensional NMR in order to characterize its hyperfine-shifted resonances originating from the cysteinyl cluster ligands and to assign its resonances in the diamagnetic shift range. The chemical shift and relaxation time pattern of the hyperfine-shifted signals is very similar to other oxidized Fe4S4 ferredoxins. A tentative sequence-specific assignment of these resonances according to a general pattern of chemical shift of cysteine protons versus sequence position of cluster ligand is presented. Furthermore, sequence-specific assignments for 85% of the amino acid residues that were obtained without any guidance by known X-ray structures of ferredoxins are given. They reveal the formation of at least two elements of secondary structure by the polypeptide chain of T. maritima ferredoxin: an alpha-helix comprising residues C43-D49 and a double-stranded antiparallel beta-sheet consisting of the N- and C-terminal parts of the protein. This folding pattern is very similar to that of the crystallographically characterized ferredoxin from the mesophile Desulfovibrio gigas [Kissinger, C.R., Sieker, L.C., Adman E.T. & Jensen, L.H. (1991) J. Mol. Biol. 219, 693-715] and therefore suggesting different mechanisms of stabilization for T. maritima ferredoxin and the ferredoxin from the hyperthermophilic archaeon Pyrococcus furiosus that was recently investigated by NMR [Teng, Q., Zhou, Z.H., Smith, E.T., Busse, S. C., Howard, J.B., Adams M.W.W. & La Mar, G.N. (1994) Biochemistry 33, 6316-6326]. PMID:7758460

  5. Detection of electron paramagnetic resonance absorption using frequency modulation.

    PubMed

    Hirata, Hiroshi; Kuyama, Toshifumi; Ono, Mitsuhiro; Shimoyama, Yuhei

    2003-10-01

    A frequency modulation (FM) method was developed to measure electron paramagnetic resonance (EPR) absorption. The first-derivative spectrum of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder was measured with this FM method. Frequency modulation of up to 1.6 MHz (peak-to-peak) was achieved at a microwave carrier frequency of 1.1 GHz. This corresponds to a magnetic field modulation of 57microT (peak-to-peak) at 40.3 mT. By using a tunable microwave resonator and automatic control systems, we achieved a practical continuous-wave (CW) EPR spectrometer that incorporates the FM method. In the present experiments, the EPR signal intensity was proportional to the magnitude of frequency modulation. The background signal at the modulation frequency (1 kHz) for EPR detection was also proportional to the magnitude of frequency modulation. An automatic matching control (AMC) system reduced the amplitude of noise in microwave detection and improved the baseline stability. Distortion of the spectral lineshape was seen when the spectrometer settings were not appropriate, e.g., with a lack of the open-loop gain in automatic tuning control (ATC). FM is an alternative to field modulation when the side-effect of field modulation is detrimental for EPR detection. The present spectroscopic technique based on the FM scheme is useful for measuring the first derivative with respect to the microwave frequency in investigations of electron-spin-related phenomena. PMID:14511592

  6. Detection of electron paramagnetic resonance absorption using frequency modulation

    NASA Astrophysics Data System (ADS)

    Hirata, Hiroshi; Kuyama, Toshifumi; Ono, Mitsuhiro; Shimoyama, Yuhei

    2003-10-01

    A frequency modulation (FM) method was developed to measure electron paramagnetic resonance (EPR) absorption. The first-derivative spectrum of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder was measured with this FM method. Frequency modulation of up to 1.6 MHz (peak-to-peak) was achieved at a microwave carrier frequency of 1.1 GHz. This corresponds to a magnetic field modulation of 57 μT (peak-to-peak) at 40.3 mT. By using a tunable microwave resonator and automatic control systems, we achieved a practical continuous-wave (CW) EPR spectrometer that incorporates the FM method. In the present experiments, the EPR signal intensity was proportional to the magnitude of frequency modulation. The background signal at the modulation frequency (1 kHz) for EPR detection was also proportional to the magnitude of frequency modulation. An automatic matching control (AMC) system reduced the amplitude of noise in microwave detection and improved the baseline stability. Distortion of the spectral lineshape was seen when the spectrometer settings were not appropriate, e.g., with a lack of the open-loop gain in automatic tuning control (ATC). FM is an alternative to field modulation when the side-effect of field modulation is detrimental for EPR detection. The present spectroscopic technique based on the FM scheme is useful for measuring the first derivative with respect to the microwave frequency in investigations of electron-spin-related phenomena.

  7. Radio-frequency association of molecules: an assisted Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Beaufils, Q.; Crubellier, A.; Zanon, T.; Laburthe-Tolra, B.; Maréchal, É.; Vernac, L.; Gorceix, O.

    2010-01-01

    We develop a theoretical model to describe the radio-frequency (rf) induced coupling of a pair of colliding atoms to a Feshbach molecule when a magnetic field arbitrarily far from the Feshbach resonance is modulated in time. We use the dressed atom picture, and show that the coupling strength in presence of rf is equal to the Feshbach coupling strength multiplied by the square of a Bessel function. The argument of this function is equal to the ratio of the atomic rf Rabi frequency to the rf frequency. We experimentally demonstrate this law by measuring the rate of rf-association of molecules using a Feshbach resonance in d wave collisions between ultra-cold chromium atoms.

  8. Analytical investigation into the resonance frequencies of a curling probe

    NASA Astrophysics Data System (ADS)

    Arshadi, Ali; Brinkmann, Ralf Peter

    2016-08-01

    The term ‘active plasma resonance spectroscopy’ (APRS) denotes a class of closely related plasma diagnostic methods which utilize the natural ability of plasmas to resonate on or near the electron plasma frequency {ω\\text{pe}} ; an electrical radio frequency signal (in the GHz range) is coupled into the plasma via an antenna or a probe, the spectral response is recorded and a mathematical model is employed to determine plasma parameters such as the plasma density and the electron temperature. The curling probe, recently invented by Liang et al (2011 Appl. Phys. Express 4 066101), is a novel realization of the APRS concept which has many practical advantages. In particular, it can be miniaturized and flatly embedded into the chamber wall, thus allowing the monitoring of plasma processes without contamination nor disturbance. Physically, the curling probe can be understood as a ‘coiled’ form of the hairpin probe (Stenzel 1976 Rev. Sci. Instrum. 47 603). Assuming that the spiralization of the probe has little electrical effect, this paper investigates the characteristcs of a ‘straightened’ curling probe by modeling it as an infinite slot-type resonator that is in direct contact with the plasma. The diffraction of an incident plane wave at the slot is calculated by solving the cold plasma model and Maxwell’s equations simultaneously. The resonance frequencies of the probe are derived and are found to be in good agreement with the numerical results of the probe inventors.

  9. 1H NMR, electronic-absorption and resonance-Raman spectra of isomeric okenone as compared with those of isomeric β-carotene, canthaxanthin, β-apo-8'-carotenal and spheroidene

    NASA Astrophysics Data System (ADS)

    Fujii, Ritsuko; Chen, Chun-Hai; Mizoguchi, Tadashi; Koyama, Yasushi

    1998-05-01

    Eleven cis- trans isomers of okenone were isolated by means of HPLC using a silica-gel column from an isomeric mixture which was obtained by iodine-sensitized photo-isomerization of the all- trans isomer. The configurations of eight isomers among them were determined by NMR spectroscopy using the isomerization shifts of the olefinic 1Hs and the 1H- 1H NOE correlations to be all- trans, 7- cis, 7- cis,8-s- cis, 9- cis, 9'- cis, 13- cis, 13'- cis and 9,9'-di- cis, and their electronic-absorption and resonance-Raman spectra were recorded. Based on the results: (1) the chemical shifts of the olefinic 1Hs in NMR; (2) the wavelength of the A g-→B u+ transition; and (3) the relative intensity of the A g-→A g+ versus the A g-→B u+ transition in electronic absorption; (4) the CC stretching frequency; and (5) the relative intensity of the C10-C11 (C10'-C11') versus the C14-C15 (C14'-C15') stretching vibration in resonance Raman were compared among the all- trans, 7- cis, 9- cis (9'- cis) and 13- cis (13'- cis) isomers of β-carotene, canthaxanthin, β-apo-8'-carotenal, neurosporene, spheroidene and okenone. Relevance of the systematic changes in the above five different parameters originally found in β-carotene was examined in the rest of the carotenoids, and the effects of the peripheral groups on them were explained in terms of the length and asymmetry of the conjugated system consisting of the CC and CO bonds.

  10. Dynamics of ferroelectric bis(imidazolium) pentachloroantimonate(III) by means of nuclear magnetic resonance 1H relaxometry and dielectric spectroscopy.

    PubMed

    Piecha-Bisiorek, A; Jakubas, R; Medycki, W; Florek-Wojciechowska, M; Wojciechowski, M; Kruk, D

    2014-05-22

    Some of haloantimonates(III) and halobismuthates(III) are ferroelectric. Bis(imidazolium) pentachloroantimonate(III), (C3N2H5)2SbCl5 (abbreviation: ICA) is the first example of such compounds with a one-dimensional anionic chain which exhibits ferroelectric properties. The relation between the ionic dynamics and network structure and the ferroelectric features is not clear. Here Nuclear Magnetic Resonance (NMR) (1)H spin-lattice relaxation experiments at 25 MHz are reported for ICA in the temperature range of 80 K-360 K, covering ferroelectric-paraelectric and structural phase transitions of the compound occurring at 180 and 342 K, respectively. The relaxation process is biexponential in the whole temperature range indicating two dynamically nonequivalent types of imidazolium cations. Temperature dependences of both relaxation contributions allow for identifying three motional processes. Two of them are cation-specific - i.e. they are attributed to the two types of imidazolium cations, respectively. The third process involves both types of cations, and it is characterized by much lower activation energy. Moreover, the relaxation data (combined with (1)H second moment measurements) show that the ferroelectric-paraelectric phase transition mechanism is governed, to a large extent, by the anionic network arrangement. The NMR studies are complemented by dielectric spectroscopy experiments performed in the vicinity of the Curie temperature, TC = 180 K, to get insight into the mechanism of the ferroelectric-paraelectric phase transition. The dielectric dispersion data show critical slowing down of the macroscopic relaxation time, τ, in ICA when approaching TC from the paraelectric side, indicating an order-disorder type of ferroelectrics. PMID:24804840

  11. Quantitative 1H Nuclear Magnetic Resonance Metabolite Profiling as a Functional Genomics Platform to Investigate Alkaloid Biosynthesis in Opium Poppy1[W

    PubMed Central

    Hagel, Jillian M.; Weljie, Aalim M.; Vogel, Hans J.; Facchini, Peter J.

    2008-01-01

    Opium poppy (Papaver somniferum) produces a diverse array of bioactive benzylisoquinoline alkaloids and has emerged as a versatile model system to study plant alkaloid metabolism. The plant is widely cultivated as the only commercial source of the narcotic analgesics morphine and codeine. Variations in plant secondary metabolism as a result of genetic diversity are often associated with perturbations in other metabolic pathways. As part of a functional genomics platform, we used 1H nuclear magnetic resonance (NMR) metabolite profiling for the analysis of primary and secondary metabolism in opium poppy. Aqueous and chloroform extracts of six different opium poppy cultivars were subjected to chemometric analysis. Principle component analysis of the 1H NMR spectra for latex extracts clearly distinguished two varieties, including a low-alkaloid variety and a high-thebaine, low-morphine cultivar. Distinction was also made between pharmaceutical-grade opium poppy cultivars and a condiment variety. Such phenotypic differences were not observed in root extracts. Loading plots confirmed that morphinan alkaloids contributed predominantly to the variance in latex extracts. Quantification of 34 root and 21 latex metabolites, performed using Chenomx NMR Suite version 4.6, showed major differences in the accumulation of specific alkaloids in the latex of the low-alkaloid and high-thebaine, low-morphine varieties. Relatively few differences were found in the levels of other metabolites, indicating that the variation was specific for alkaloid metabolism. Exceptions in the low-alkaloid cultivar included an increased accumulation of the alkaloid precursor tyramine and reduced levels of sucrose, some amino acids, and malate. Real-time polymerase chain reaction analysis of 42 genes involved in primary and secondary metabolism showed differential gene expression mainly associated with alkaloid biosynthesis. Reduced alkaloid levels in the condiment variety were associated with the

  12. Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies

    NASA Astrophysics Data System (ADS)

    Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G. J.; Chen, X. H.; Shan, Jie; Feng, Philip X.-L.

    2014-12-01

    We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus.We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory

  13. Magnetic resonance imaging at frequencies below 1 kHz.

    PubMed

    Hilschenz, Ingo; Körber, Rainer; Scheer, Hans-Jürgen; Fedele, Tommaso; Albrecht, Hans-Helge; Mario Cassará, Antonino; Hartwig, Stefan; Trahms, Lutz; Haase, Jürgen; Burghoff, Martin

    2013-02-01

    Within the magnetic resonance imaging (MRI) community the trend is going to higher and higher magnetic fields, ranging from 1.5 T to 7 T, corresponding to Larmor frequencies of 63.8-298 MHz. Since for high-field MRI the magnetization increases with the applied magnetic field, the signal-to-noise-ratio increases as well, thus enabling higher image resolutions. On the other hand, MRI is possible also at ultra-low magnetic fields, as was shown by different groups. The goal of our development was to reach a Larmor frequency range of the low-field MRI system corresponding to the frequency range of human brain activities ranging from near zero-frequency (near-DC) to over 1 kHz. Here, first 2D MRI images of phantoms taken at Larmor frequencies of 100 Hz and 731 Hz will be shown and discussed. These frequencies are examples of brain activity triggered by electrostimulation of the median nerve. The method will allow the magnetic fields of the brain currents to influence the magnetic resonance image, and thus lead to a direct functional imaging modality of neuronal currents. PMID:22898690

  14. Resonant-frequency discharge in a multi-cell radio frequency cavity

    SciTech Connect

    Popović, S.; Upadhyay, J.; Nikolić, M.; Vušković, L.; Mammosser, J.

    2014-11-07

    We are reporting experimental results on a microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency cryo-module. This discharge offers a mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the issues related to resonant detuning due to sustained multi-cell cavity plasma. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.

  15. Increasing ferromagnetic resonance frequency using lamination and shape

    NASA Astrophysics Data System (ADS)

    El-Ghazaly, A.; White, R. M.; Wang, S. X.

    2015-05-01

    The magnetic permeability frequency spectrum is one of the most critical properties for the operation of high frequency magnetic devices in the gigahertz regime. Permeability is fairly constant up to the ferromagnetic resonance (FMR) frequency, at which point the relative permeability drops to unity. Extending FMR to higher frequencies is thus imperative for developing GHz-range magnetic devices. The simulation and experimental investigations presented in this paper demonstrate how stacking layers to form a laminated film increases the FMR frequency by allowing flux closure between layers along the induced easy-axis direction. This flux closure reduces the demagnetization factor along the easy-axis direction by two orders of magnitude. This effect, however, is only observable in patterned films where the shape anisotropy is enough to result in variation of the FMR frequency. Experiments using patterned magnetic cores were performed to illustrate this effect. Through detailed investigation of the permeability spectra of both single layer and laminated CoTaZr magnetic films patterned into 500 μm × L films (where L ranged from 200 μm to 1000 μm), the FMR frequency was extracted and proven to increase as a result of lamination. The degree to which the frequency is boosted by lamination increases exponentially as the length of the film is decreased. Through a combination of lamination and shape demagnetization, the effective anisotropy, which directly relates to FMR frequency, was shown to increase by about 100%.

  16. In Vivo{sup 1}H Magnetic Resonance Spectroscopy of Lactate in Patients With Stage IV Head and Neck Squamous Cell Carcinoma

    SciTech Connect

    Le, Quynh-Thu Koong, Albert; Lieskovsky, Yee Yie; Narasimhan, Balasubramanian; Graves, Edward; Pinto, Harlan; Brown, J. Martin; Spielman, Daniel

    2008-07-15

    Purpose: To investigate in vivo{sup 1}H magnetic resonance spectroscopy imaging of lactate for assessing tumor hypoxia in head and neck cancers and to determine its utility in predicting the response and outcomes. Methods and Materials: Volume-localized lactate-edited {sup 1}H magnetic resonance spectroscopy at 1.5 T was performed in vivo on involved neck nodes and control subcutaneous tissues in 36 patients with Stage IV head and neck cancer. The signal intensities (SIs) of lactate, choline, and creatine and the choline/creatine ratio were measured. The tumor partial pressure of oxygen (pO{sub 2}) was obtained in the same lymph node before MRS. Patients were treated with either two cycles of induction chemotherapy (tirapazamine, cisplatin, 5-fluorouracil) followed by simultaneous chemoradiotherapy or the same regimen without tirapazamine. The lactate SI and the choline/creatine ratio correlated with the tumor pO{sub 2}, nodal response, and locoregional control. Results: The lactate SI was greater for the involved nodes (median, 0.25) than for the subcutaneous tissue (median, 0.04; p = 0.07). No significant correlation was found between the lactate SI and tumor pO{sub 2} (mean, 0.46 {+-} 0.10 for hypoxic nodes [pO{sub 2} {<=}10 mm Hg, n = 15] vs. 0.36 {+-} 0.07 for nonhypoxic nodes [pO{sub 2} >10 mm Hg, n = 21], p = 0.44). A significant correlation was found between the choline/creatine ratios and tumor pO{sub 2} (mean, 2.74 {+-} 0.34 for hypoxic nodes vs. 1.78 {+-} 0.31 for nonhypoxic nodes, p = 0.02). No correlation was found between the lactate SI and the complete nodal response (p = 0.52) or locoregional control rates. Conclusions: The lactate SI did not correlate with tumor pO{sub 2}, treatment response, or locoregional control. Additional research is needed to refine this technique.

  17. Tuning the resonant frequency of resonators using molecular surface self-assembly approach.

    PubMed

    Liu, Wenpeng; Wang, Jingwei; Yu, Yifei; Chang, Ye; Tang, Ning; Qu, Hemi; Wang, Yanyan; Pang, Wei; Zhang, Hao; Zhang, Daihua; Xu, Huaping; Duan, Xuexin

    2015-01-14

    In this work, a new method to tune the resonant frequency of microfabricated resonator using molecular layer-by-layer (LbL) self-assembly approach is demonstrated. By simply controlling the polymer concentration and the number of layers deposited, precisely tuning the frequency of microfabricated resonators is realized. Due to its selective deposition through specific molecular recognitions, such technique avoids the high-cost and complex steps of conventional semiconductor fabrications and is able to tune individual diced device. Briefly, film bulk acoustic resonator (FBAR) is used to demonstrate the tuning process and two types of LbL deposition methods are compared. The film thickness and morphology have been characterized by UV-vis reflection spectra, ellipsometer and AFM. As a result, the maximum resonant frequency shift of FBAR reaches more than 20 MHz, meaning 1.4% tunability at least. The minimum frequency shift is nearly 10 kHZ per bilayer, indicating 7 ppm tuning resolution. Pressure cooker test (PCT) is performed to evaluate the reliability of LbL coated FBAR. Furthermore, applications for wireless broadband communication and chemical sensors of LbL coated FBAR have been demonstrated. PMID:25487349

  18. Global Doppler frequency shift detection with near-resonant interferometry

    NASA Astrophysics Data System (ADS)

    Landolt, Andrin; Roesgen, Thomas

    2009-10-01

    The recent development in measuring 2D Doppler shift distributions for flow velocimetry using the dispersive properties of atomic line filters is presented. On the basis of velocity field measurements on a subsonic jet flow and a tip vortex flow in a medium-sized wind tunnel, the technique was assessed. Atomic line filters near a resonant transition combine imaging capabilities with a sharp frequency cutoff and an associated region of strong anomalous dispersion. While conventional Doppler global velocimetry relies on the absorption of the filter to convert frequency shifts to intensity variations, near-resonant interferometry uses its dispersion to detect frequency shifts as phase changes in an interference pattern. In the present setup, an iodine vapor cell in an imaging Michelson interferometer is used. With the illuminating laser frequency tuned near a resonant transition, the cell’s dispersion converts the frequency content of the field of view into a distortion of the carrier-fringe pattern recorded at the image plane of the interferometer. The phase distribution in the fringe images is reconstructed by filtering the individual images with a 2D Gabor filter pair tuned to the spatial frequencies of the basic carrier-fringe pattern. The post-processing is concluded with subsequent phase-unwrapping and subtraction of the carrier reference fringe phase. The method and the setup were demonstrated and calibrated experimentally on a rotating disc. The capability of the technique to operate in a real experimental environment was validated in a free subsonic jet and a tip vortex flow behind a wing section in a medium-sized wind tunnel facility. The measurements were found to be in generally good agreement with the theoretically predicted system characteristics and the reference measurements. As with other Doppler global techniques, the stability of the pulsed laser system and the secondary scattering in the test volume were identified as the main error sources.

  19. Study of asymmetric U-shaped resonator at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Yang, Zhou; Zhou, Qingli; Long, Wen; Li, Chenyu; Shi, Yulei; Wu, Ani; Liu, Jianfeng; Zhang, Cunlin

    2016-06-01

    We demonstrate the asymmetric U-shaped array exhibits different spectral patterns in response to incident terahertz wave with horizontal and vertical polarizations. In the horizontal incident polarization, where terahertz electric-field Ein is in parallel with the bottom bar of U-shaped structure, the two-absorption-dip transmission spectrum is similar to that of a typical split-ring resonator. When Ein is perpendicular to bottom bar, an interesting phenomenon comes up with three dips. This differs from the split-ring resonator which only has one dip in the transmission spectrum. The bottom-bar length also has significant impacts on frequency-shift and absorptive depth related to this resonant phenomenon.

  20. Effect of geometry in frequency response modeling of nanomechanical resonators

    NASA Astrophysics Data System (ADS)

    Esfahani, M. Nasr; Yilmaz, M.; Sonne, M. R.; Hattel, J. H.; Alaca, B. Erdem

    2016-06-01

    The trend towards nanomechanical resonator sensors with increasing sensitivity raises the need to address challenges encountered in the modeling of their mechanical behavior. Selecting the best approach in mechanical response modeling amongst the various potential computational solid mechanics methods is subject to controversy. A guideline for the selection of the appropriate approach for a specific set of geometry and mechanical properties is needed. In this study, geometrical limitations in frequency response modeling of flexural nanomechanical resonators are investigated. Deviation of Euler and Timoshenko beam theories from numerical techniques including finite element modeling and Surface Cauchy-Born technique are studied. The results provide a limit beyond which surface energy contribution dominates the mechanical behavior. Using the Surface Cauchy-Born technique as the reference, a maximum error on the order of 50 % is reported for high-aspect ratio resonators.

  1. Bevacizumab impairs oxidative energy metabolism and shows antitumoral effects in recurrent glioblastomas: a 31P/1H MRSI and quantitative magnetic resonance imaging study.

    PubMed

    Hattingen, Elke; Jurcoane, Alina; Bähr, Oliver; Rieger, Johannes; Magerkurth, Jörg; Anti, Sandra; Steinbach, Joachim P; Pilatus, Ulrich

    2011-12-01

    Bevacizumab shows unprecedented rates of response in recurrent glioblastomas (GBM), but the detailed mechanisms are still unclear. We employed in vivo magnetic resonance spectroscopic imaging (MRSI) and quantitative magnetic resonance imaging to investigate whether bevacizumab alters oxygen and energy metabolism and whether this effect has antitumoral activity in recurrent GBM. (31)P and (1)H MRSI, apparent diffusion coefficient (ADC), and high-resolution T2 and T2' mapping (indirect marker of oxygen extraction) were investigated in 16 patients with recurrent GBM at 3 Tesla before and 1.5-2 months after initiation of therapy with bevacizumab. Changes of metabolite concentrations and of the quantitative values in the tumor and normal appearing brain tissue were calculated. The Wilcoxon signed-ranks test was used to evaluate differences for tumor/edema versus control as well as changes before versus after commencement of therapy. Survival analyses were performed for significant parameters. Tumor T2', pH, ADC, and T2 decreased significantly in patients responding to bevacizumab therapy (n = 10). Patients with at least 25% T2' decrease during treatment showed longer progression-free and overall survival durations. Levels of high-energy metabolites were lower at baseline; these persisted under therapy. Glycerophosphoethanolamine as catabolic phospholipid metabolite increased in responders. The MRSI data support the hypothesis that bevacizumab induces relative tumor hypoxia (T2' decrease) and affects energy homeostasis in recurrent GBM, suggesting that bevacizumab impairs vascular function. The antiangiogenic effect of bevacizumab is predictive of better outcome and seems to induce antitumoral activity in the responding GBMs. PMID:21890539

  2. Resonant interactions between cometary ions and low frequency electromagnetic waves

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Tsurutani, Bruce T.

    1987-01-01

    The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

  3. Control of resonant frequencies in adaptive structures by prestressing

    NASA Technical Reports Server (NTRS)

    Baycan, Can M.; Utku, Senol; Wada, Ben K.

    1992-01-01

    The natural vibration frequencies of a structure can be affected by inducing stress in the structure. The success of this kind of control of the resonant frequencies of a truss structure depends on the geometry of the structure. It is shown that in adaptive truss structures the method is effective for vibrations in less stiff directions, such as the normal direction of the plane containing all of the bars of a node, suggesting its applicability for cable, membrane, and thin plate and shell structures.

  4. Optimizations of ozone generator at low resonance frequency

    NASA Astrophysics Data System (ADS)

    Garamoon, A. A.; Elakshar, F. F.; Elsawah, M.

    2009-11-01

    The effect of the frequency on the different parameters of ozone generation in the dielectric barrier discharge (DBD) has been investigated. It is found that at low frequency, (f0 = 325 Hz), an electric resonance can be obtained in the electric circuit. The onset voltage, at which the ozone starts to build up, was reduced from 3.25 kV at 50 Hz to 1.57 kV at 325 Hz. The efficiency has been increased from nearly zero at 50 Hz to 232.94 g/kW h at 200 Hz under applied voltage of 2.025 kV. in here

  5. Observations of High Frequency Harmonics of the Ionospheric Alfven Resonator

    NASA Astrophysics Data System (ADS)

    Mann, Ian; Usanova, Maria; Bortnik, Jacob; Milling, David; Kale, Andy; Shao, Leo; Miles, David; Rae, I. Jonathan

    We present observations of high frequency harmonics of the ionospheric Alfven Resonator (IAR). These are seen in the form of spectral resonance structures (SRS) recorded by a ground-based search coil magnetometer sampling at 100 samples/s at the Ministik Lake station at L=4.2 within the expanded CARISMA magnetometer array. Previous observational studies have indicated that such SRS are typically confined to frequencies <~5 Hz with only several SRS harmonics being observed. We report the first observations of clear and discrete SRS, which we believe are harmonics of the IAR, and which extend to around 20 Hz in at least 10-12 clear SRS harmonics. We additionally demonstrate the utility of the Bortnik et al. (2007) auto-detection algorithm, designed for Pc1 wavepackets, for characterising the properties of the IAR. Our results also indicate that the cavity supporting SRS in the IAR at this time must be structured to support and trap much higher frequency IAR harmonics than previously assumed. This impacts the potential importance of the IAR for magnetosphere-ionosphere coupling, especially in relation to the impacts of incident Alfven waves on the ionosphere including Alfvenic aurora. Our observations also highlight the potential value of IAR observations for diagnosing the structure of the topside ionosphere, not least using the observed structure of the SRS. These are the first mid-latitude observations demonstrating that the IAR can extend to frequencies beyond those of the lowest few harmonics of the Schumann resonances - significantly suggesting the possibility that the Schumann resonance modes and the IAR may be coupled. The in-situ structure of the IAR is also examined by combining satellite data with conjugate measurements from the ground, and the impacts of the IAR for magnetosphere-ionosphere-thermosphere coupling examined.

  6. Sequence-specific (1)H, (15)N, and (13)C resonance assignments of the autophagy-related protein LC3C.

    PubMed

    Krichel, Carsten; Weiergräber, Oliver H; Pavlidou, Marina; Mohrlüder, Jeannine; Schwarten, Melanie; Willbold, Dieter; Neudecker, Philipp

    2016-04-01

    Autophagy is a versatile catabolic pathway for lysosomal degradation of cytoplasmic material. While the phenomenological and molecular characteristics of autophagic non-selective (bulk) decomposition have been investigated for decades, the focus of interest is increasingly shifting towards the selective mechanisms of autophagy. Both, selective as well as bulk autophagy critically depend on ubiquitin-like modifiers belonging to the Atg8 (autophagy-related 8) protein family. During evolution, Atg8 has diversified into eight different human genes. While all human homologues participate in the formation of autophagosomal membrane compartments, microtubule-associated protein light chain 3C (LC3C) additionally plays a unique role in selective autophagic clearance of intracellular pathogens (xenophagy), which relies on specific protein-protein recognition events mediated by conserved motifs. The sequence-specific (1)H, (15)N, and (13)C resonance assignments presented here form the stepping stone to investigate the high-resolution structure and dynamics of LC3C and to delineate LC3C's complex network of molecular interactions with the autophagic machinery by NMR spectroscopy. PMID:26280529

  7. Quantitative 1H nuclear magnetic resonance diffusion spectroscopy of BT4C rat glioma during thymidine kinase-mediated gene therapy in vivo: identification of apoptotic response.

    PubMed

    Hakumäki, J M; Poptani, H; Puumalainen, A M; Loimas, S; Paljärvi, L A; Ylä-Herttuala, S; Kauppinen, R A

    1998-09-01

    We have investigated the effects of thymidine kinase-mediated gene therapy in a malignant rat BT4C glioma by using 1H nuclear magnetic resonance spectroscopy in vivo. Ganciclovir has been successfully used in thymidine kinase gene therapy as treatment for various experimental malignancies. The cell damaging effect seems to be mediated by apoptosis, optimally leading to eradication of tumor tissue. In this study, we show that ganciclovir treatment of tumors transfected with the herpes simplex thymidine kinase gene causes profound changes in water, metabolites, and macromolecules observable by diffusion spectroscopy. During treatment, a 50% reduction from 0.14 +/- 0.01 x 10(-9) m2/s in the apparent diffusion coefficient of choline-containing compounds can be observed, concomitant with a 219% increase in the apparent diffusion coefficient of the rapidly diffusing water component. These changes are associated with an increase in the relative fraction of this water component from 87 to 94%. The apparent diffusion coefficients of the slowly diffusing water component and macromolecules remain unaltered. The results imply a reduction in cell size and number, a significant increase in intracellular viscosity, and a possible reduction in the hydrodynamic radii of macromolecular components, which are ascribed as biophysical signatures for apoptotic cell death. PMID:9731486

  8. Slow Magic Angle Sample Spinning: A Non- or Minimally Invasive Method for High- Resolution 1H Nuclear Magnetic Resonance (NMR) Metabolic Profiling

    SciTech Connect

    Hu, Jian Z.

    2011-05-01

    High resolution 1H magic angle spinning nuclear magnetic resonance (NMR), using a sample spinning rate of several kHz or more (i.e., high resolution-magic angle spinning (hr-MAS)), is a well established method for metabolic profiling in intact tissues without the need for sample extraction. The only shortcoming with hr-MAS is that it is invasive and is thus unusable for non-destructive detections. Recently, a method called slow-MAS, using the concept of two dimensional NMR spectroscopy, has emerged as an alternative method for non- or minimal invasive metabolomics in intact tissues, including live animals, due to the slow or ultra-slow-sample spinning used. Although slow-MAS is a powerful method, its applications are hindered by experimental challenges. Correctly designing the experiment and choosing the appropriate slow-MAS method both require a fundamental understanding of the operation principles, in particular the details of line narrowing due to the presence of molecular diffusion. However, these fundamental principles have not yet been fully disclosed in previous publications. The goal of this chapter is to provide an in depth evaluation of the principles associated with slow-MAS techniques by emphasizing the challenges associated with a phantom sample consisting of glass beads and H2O, where an unusually large magnetic susceptibility field gradient is obtained.

  9. 1H resonance assignments and secondary structure of the carbon monoxide complex of soybean leghemoglobin determined by homonuclear two-dimensional and three-dimensional NMR spectroscopy.

    PubMed

    Morikis, D; Lepre, C A; Wright, P E

    1994-01-15

    Homonuclear two-dimensional and three-dimensional 1H-NMR spectroscopy has been utilized to study the 15.9-kDa protein soybean leghemoglobin. NMR experiments were performed on the diamagnetic carbon monoxide complex at two temperatures and two pH values. Sequence-specific assignments have been made for 94% of the backbone and approximately 70% of the expected side-chain resonances. The secondary structure of leghemoglobin in solution has been determined on the basis of NOE connectivity patterns, hydrogen exchange and chemical-shift analyses. Leghemoglobin consists of seven helices and, unlike mammalian myoglobins, is missing the D helix. Instead an extended loop, the CE loop, is observed which might have importance for ligand entry into and exit from the protein interior. The hydrogen exchange behavior for the F helix and at the beginning of the A helix suggests different dynamic stability compared to other helical regions in leghemoglobin. Population of a second protein conformation, in which there is perturbation at the A-G-H helix interface, is observed at low pH. PMID:8307026

  10. Contribution of proteolysis and de novo synthesis to alanine production in diabetic rat skeletal muscle: a 15N/1H nuclear magnetic resonance study.

    PubMed

    Meynial-Denis, D; Chavaroux, A; Foucat, L; Mignon, M; Prugnaud, J; Bayle, G; Renou, J P; Arnal, M

    1997-10-01

    To assess the role of leucine as a precursor of alanine alpha-amino nitrogen in skeletal muscle during diabetes, extensor digitorum longus muscles from control (n = 7 experiments) and streptozotocin-diabetic rats (n = 8 experiments) were isolated and superfused with [15N]leucine (3 mmol/l) in the presence of glucose (10 mmol/l) for 2 h. Muscle perchloric acid extraction was performed at the end of superfusion in order to quantify newly synthesized alanine by 15N/1H nuclear magnetic resonance. Release of [15N]alanine in the superfusion medium was also measured. The pool of newly synthesized [15N]alanine was significantly increased (approximately 40%) in extensor digitorum longus muscles from streptozotocin-diabetic rats. Whereas a significant enhancement of total alanine release from muscle was induced by diabetes (20%), only a slight increase in [15N]alanine release was detectable under our experimental conditions. Consequently, we conclude that streptozotocin-diabetes in growing rats induces in skeletal muscle: 1) an increase in nitrogen exchange between leucine and alanine leading to newly synthesized [15N]alanine; and 2) an increase of total alanine release from muscle originating from both proteolysis and de novo synthesis. PMID:9349596

  11. Prefrontal grey and white matter neurometabolite changes after atomoxetine and methylphenidate in children with attention deficit/hyperactivity disorder: a (1)H magnetic resonance spectroscopy study.

    PubMed

    Husarova, Veronika; Bittsansky, Michal; Ondrejka, Igor; Dobrota, Dusan

    2014-04-30

    Attention deficit/hyperactivity disorder (ADHD) is the most common neurobehavioral childhood disorder. Dysfunction of prefrontal neural circuits which are responsible for executive and attentional functions has been previously shown in ADHD. We investigated the neurometablite changes in areas included in dorsolateral prefrontal neural circuits after 2 months of long-acting methylphenidate or atomoxetine medication in children with ADHD who were responders to treatment. Twenty-one ADHD children were examined by single voxel (1)H-magnetic resonance spectroscopy (MRS) before and after 2 months of medication with OROS methylphenidate (n=10) or atomoxetine (n=11). The spectra were taken from the dorsolateral prefrontal cortex (DLPFC, 8ml) and white matter behind the DLPFC (anterior semioval center, 7.5ml), bilaterally. NAA and NAA/Cr (N-acetylaspartate/creatine) decreased in the left DLPFC and Cho/Cr (choline/creatine) increased in the right DLPFC after atomoxetine medication. Glu+Gln and Glu+Gln/Cr (glutamate/glutamine) increased in the left white matter after methylphenidate medication. We hypothesize that atomoxetine could decrease hyperactivation of DLPFC neurons and methylphenidate could lead to increased activation of cortical glutamatergic projections with the consequences of increased tonic dopamine release in the mesocortical system. PMID:24679996

  12. (1) H-nuclear magnetic resonance-based metabonomic analysis of brain in rhesus monkeys with morphine treatment and withdrawal intervention.

    PubMed

    Deng, Yi; Bu, Qian; Hu, Zhengtao; Deng, Pengchi; Yan, Guangyan; Duan, Jiachuan; Hu, Chunyan; Zhou, Jiaqing; Shao, Xue; Zhao, Jinxuan; Li, Yan; Zhu, Ruiming; Zhao, Yinglan; Cen, Xiaobo

    2012-11-01

    Comprehensive cerebral metabolites involved in morphine dependence have not been well explored. To gain a better understanding of morphine dependence and withdrawal therapy in a model highly related to humans, metabolic changes in brain hippocampus and prefrontal cortex (PFC) of rhesus monkeys were measured by (1) H-nuclear magnetic resonance spectroscopy, coupled with partial least squares and orthogonal signal correction analysis. The results showed that concentrations of myoinositol (M-Ins) and taurine were significantly reduced, whereas lactic acid was increased in hippocampus and PFC of morphine-dependent monkeys. Phosphocholine and creatine increased in PFC but decreased in hippocampus after chronic treatment of morphine. Moreover, N-acetyl aspartate (NAA), γ-aminobutyric acid, glutamate, glutathione, methionine, and homocysteic acid also changed in these brain regions. These results suggest that chronic morphine exposure causes profound disturbances of neurotransmitters, membrane, and energy metabolism in the brain. Notably, morphine-induced dysregulations in NAA, creatine, lactic acid, taurine, M-Ins, and phosphocholine were clearly reversed after intervention with methadone or clonidine. Our study highlights the potential of metabolic profiling to enhance our understanding of metabolite alteration and neurobiological actions associated with morphine addiction and withdrawal therapy in primates. PMID:22847893

  13. Effect of off-frequency sampling in magnetic resonance elastography.

    PubMed

    Johnson, Curtis L; Chen, Danchin D; Olivero, William C; Sutton, Bradley P; Georgiadis, John G

    2012-02-01

    In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results were compared with numerical simulations to quantify these effects. It is known that off-frequency encoding alone results in a scaling of wave amplitude, and it is shown here that off-frequency sampling can result in two main effects: (1) errors in the overall shear stiffness estimate of the material on the global scale and (2) local variations appearing as stiffer and softer structures in the material. For small differences in frequency, it was found that measured global stiffness of the brain could theoretically vary by up to 12.5% relative to actual stiffness with local variations of up to 3.7% of the mean stiffness. It was demonstrated that performing MRE experiments at a frequency other than that of tissue vibration can lead to artifacts in the MRE stiffness images, and this mismatch could explain some of the large-scale scatter of stiffness data or lack of repeatability reported in the brain MRE literature. PMID:22055750

  14. Low-frequency nuclear quadrupole resonance with a dc SQUID

    SciTech Connect

    Chang, J.W.

    1991-07-01

    Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.

  15. High frequency MoS2 nanomechanical resonators.

    PubMed

    Lee, Jaesung; Wang, Zenghui; He, Keliang; Shan, Jie; Feng, Philip X-L

    2013-07-23

    Molybdenum disulfide (MoS2), a layered semiconducting material in transition metal dichalcogenides (TMDCs), as thin as a monolayer (consisting of a hexagonal plane of Mo atoms covalently bonded and sandwiched between two planes of S atoms, in a trigonal prismatic structure), has demonstrated unique properties and strong promises for emerging two-dimensional (2D) nanodevices. Here we report on the demonstration of movable and vibrating MoS2 nanodevices, where MoS2 diaphragms as thin as 6 nm (a stack of 9 monolayers) exhibit fundamental-mode nanomechanical resonances up to f0 ~ 60 MHz in the very high frequency (VHF) band, and frequency-quality (Q) factor products up to f0 × Q ~ 2 × 10(10)Hz, all at room temperature. The experimental results from many devices with a wide range of thicknesses and lateral sizes, in combination with theoretical analysis, quantitatively elucidate the elastic transition regimes in these ultrathin MoS2 nanomechanical resonators. We further delineate a roadmap for scaling MoS2 2D resonators and transducers toward microwave frequencies. This study also opens up possibilities for new classes of vibratory devices to exploit strain- and dynamics-engineered ultrathin semiconducting 2D crystals. PMID:23738924

  16. Water permeability of capillaries in the subfornical organ of rats determined by Gd-DTPA2- enhanced 1H magnetic resonance imaging

    PubMed Central

    Seo, Yoshiteru; Takamata, Akira; Ogino, Takashi; Morita, Hironobu; Nakamura, Shun; Murakami, Masataka

    2002-01-01

    The water permeability of capillaries in the subfornical organ (SFO) of rat was measured by a 1H nuclear magnetic resonance method in combination with a venous injection of a relaxation reagent, gadolinium-diethylene triamine-N,N,N′,N″,N″-pentaacetic acid (Gd-DTPA2-), which could not pass through the blood-brain barrier (BBB). Judging from results of Gd-DTPA2- dose dependency in the intact brain and the BBB-permeabilized brain, Gd-DTPA2- could not have leaked out from the capillaries in the cortex, thalamus or SFO, but it could have been extravasated in the posterior lobe of the pituitary gland. The longitudinal (T1) relaxation time of water in the SFO region was measured by inversion-recovery magnetic resonance imaging at 4.7 T. The T1 relaxation rates (1/T1) before and after Gd-DTPA2- infusion were 0.70 ± 0.02 s−1 (mean ± s.e.m., n = 9) and 1.53 ± 0.11 s−1 (n = 9), respectively. The rate constant for water influx to the capillaries was estimated to be 0.84 ± 0.11 s−1 (n = 9) which corresponds with a diffusive membrane permeability (Pd) of 3.7 × 10−3 cm s−1. Compared with values found in the literature available on this subject, this Pd value for the capillaries in the SFO was the same order of magnitude as that for transmembrane permeability of water for the vasa recta, and it may be 10–100 times larger than that of the blood-brain barrier in the cortex. Areas of the cortex and thalamus showed minimal changes in the T1 relaxation rate (ca 0.09 s−1), but these values were not statistically significant and they corresponded to Pd values much smaller than those found in the SFO. From these results, we conclude that the capillaries in the SFO have one of the highest water permeability values among all of the capillaries in the brain. It is also suggested that this magnetic resonance imaging, based on T1 relaxation rate, is a useful method to detect local water permeability in situ. PMID:12433962

  17. Study of Proton Resonances in 2626Si and 27P by the Elastic Scattering of 1H(25Al, p) 25Al, 1H(26Si, p)26Si

    NASA Astrophysics Data System (ADS)

    Moon, J. Y.; Lee, C. S.; Lee, J. H.; Yun, C. C.; Kim, J. C.; Youn, M.; Kubono, S.; Teranishi, T.; He, J. J.; Notani, M.; Nishimura, S.; Nishimura, M.; Guimarães, V.; Lihitenthaler, R. F.; Kato, S.

    2005-12-01

    The observational space map of 1.809-MeV gamma rays - coming from the decay of 26Al - taken by COMPTEL requires the sources and their nucleosynthetic activity to be unveiled. One suggestion for the observation is the explosive hydrogen burning process which occurs in novae or X-ray bursts. Two capture reactions such as 25 Al(p,γ)26Si and 26Si(p,γ)27P are of great importance in the production of 1.809-MeV gamma rays. Resonance states within the Gamow window should be precisely known to determine their reaction rates. As for the latter reaction, only a few levels in 27P have been known above the proton threshold in comparison with many levels known in its mirror nucleus 27Mg. We studied proton resonances in 26Si and 27P by the elastic scattering at low energies, respectively using low-energy 25Al and 26Si radioactive ion beams available from the CRIB facility at CNS, University of Tokyo. We carried out an experiment to investigate proton resonances in 26Si up to EC.M. = 3.016 MeV, especially to determine the resonance parameters of the states at Ex = 7.019 and 8.120 MeV. We also measured the elastic scattering of p + 26Si up to EC.M. = 3.290 MeV.

  18. Frequency-selective analysis of multichannel magnetic resonance spectroscopy data.

    PubMed

    Sandgren, Niclas; Stoica, Petre

    2005-01-01

    In several practical magnetic resonance spectroscopy (MRS) applications the user is interested only in the spectral content of a specific frequency band of the spectrum. A frequency-selective (or sub-band) method estimates only the parameters of those spectroscopic components that lie in a pre-selected frequency band of the spectrum in a computationally efficient manner. Multichannel MRS is a technique that employs phased-array receive coils to increase the signal-to-noise ratio (SNR) in the spectra by combining several simultaneous measurements of the magnetic resonance (MR) relaxation of an excited sample. In this paper we suggest a frequency-selective multichannel parameter estimation approach that combines the appealing features (high speed and improved SNR) of the two techniques above. The presented method shows parameter estimation accuracies comparable to those of existing fullband multichannel techniques in the high SNR case, but at a considerably lower computational complexity, and significantly better parameter estimation accuracies in low SNR scenarios. PMID:17282712

  19. Resonant microwave pulse compressor operating in two frequencies

    NASA Astrophysics Data System (ADS)

    Beilin, L.; Shlapakovski, A.; Krasik, Ya. E.

    2013-07-01

    A resonant microwave pulse compressor with a hybrid (Magic) waveguide tee as an interference switch was studied in numerical simulations and experimentally. In this compressor, the necessary condition for energy storage in the compressor cavity is frequency-independent, so that its operation in different cavity eigenmodes without mechanical tuning is possible. An S-band compressor operating in two different frequencies (neighboring modes) was investigated. Two characteristic geometries corresponding to different regimes of the microwave energy accumulation and release were tested using input pulses of 200-400 kW power, 2.4 μs duration, and variable frequency, 2.8 to 2.9 GHz. The geometries are characterized by an RF electric field in the interference switch that is higher or lower than the field in the cavity. The plasma discharge that switches the phases of compressor operation from energy storage to release was initiated by small metallic cones placed in the appropriate location. For both geometries, the nanosecond output pulses in two resonant frequencies were obtained; the maximal peak output power measured was ˜1.8 MW. The efficiency of the microwave extraction was limited by either an insufficient coupling to the tee output arm (in the case of a high field in the tee) or non-uniformity of the plasma discharge (in the case of low field in the tee).

  20. A Resonator for Low-Threshold Frequency Conversion

    NASA Technical Reports Server (NTRS)

    Iltchenko, Vladimir; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

    2004-01-01

    A proposed toroidal or disklike dielectric optical resonator (dielectric optical cavity) would be made of an optically nonlinear material and would be optimized for use in parametric frequency conversion by imposition of a spatially periodic permanent electric polarization. The poling (see figure) would suppress dispersions caused by both the material and the geometry of the optical cavity, thereby effecting quasi-matching of the phases of high-resonance-quality (high-Q) whispering-gallery electromagnetic modes. The quasi-phase-matching of the modes would serve to maximize the interactions among them. Such a resonator might be a prototype of a family of compact, efficient nonlinear devices for operation over a broad range of optical wavelengths. A little background information is prerequisite to a meaningful description of this proposal: (1) Described in several prior NASA Tech Briefs articles, the whispering-gallery modes in a component of spheroidal, disklike, or toroidal shape are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. (2) For the sake of completeness, it must be stated that even though optical resonators of the type considered here are solid dielectric objects and light is confined within them by total internal reflection at dielectric interfaces without need for mirrors, such components are sometimes traditionally called cavities because their effects upon the light propagating within them are similar to those of true cavities bounded by mirrors. (3) For a given set of electromagnetic modes interacting with each other in an optically nonlinear material (e.g., modes associated with the frequencies involved in a frequency-conversion scheme), the threshold power for oscillation depends on the mode volumes and the mode-overlap integral. (4) Whispering-gallery modes are attractive in nonlinear optics because they maximize the effects of

  1. Application of the double relaxation oscillation superconducting quantum interference device sensor to micro-tesla 1H nuclear magnetic resonance experiments

    NASA Astrophysics Data System (ADS)

    Kang, Chan Seok; Kim, Kiwoong; Lee, Seong-Joo; Hwang, Seong-min; Kim, Jin-Mok; Yu, Kwon Kyu; Kwon, Hyukchan; Lee, Sang Kil; Lee, Yong-Ho

    2011-09-01

    We developed an ultra-low field (ULF)-nuclear magnetic resonance (NMR) measurement system capable of working with a measurement field (Bm) of several micro-tesla and performed basic NMR studies with a double relaxation oscillation superconducting quantum interference device (DROS) instead of conventional dc-SQUIDs. DROS is a SQUID sensor utilizing a relaxation oscillation between a dc-SQUID and a relaxation circuit; the new unit consists of an inductor and a resistor, and is connected in parallel with the SQUID. DROS has a 10 times larger flux-to-voltage transfer coefficient (˜mV/ϕ0) than that of the dc-SQUID, and this large transfer coefficient enables the acquisition of the SQUID signal with a simple flux-locked-loop (FLL) circuit using room temperature pre-amplifiers. The DROS second-order gradiometer showed average field noise of 9.2 μϕ0/√Hz in a magnetically shielded room (MSR). In addition, a current limiter formed of a Josephson junction array was put in a flux-transformer of DROS to prevent excessive currents that can be generated from the high pre-polarization field (Bp). Using this system, we measured an 1H NMR signal in water under 2.8 μT Bm field and reconstructed a one-dimensional MR image from the 1H NMR signal under a gradient field BG of 4.09 nT/mm. In addition, we confirmed that the ULF-NMR system can measure the NMR signal in the presence of metal without any distortion by measuring the NMR signal of a sample wrapped with metal. Lastly, we have measured the scalar J-coupling of trimethylphosphate and were able to confirm a clear doublet NMR signal with the coupling strength J3[P,H] = 10.4 ± 0.8 Hz. Finally, because the existing ULF-NMR/MRI studies were almost all performed with dc-SQUID based systems, we constructed a dc-SQUID-based ULF-NMR system in addition to the DROS based system and compared the characteristics of the two different systems by operating the two systems under identical experimental conditions.

  2. Deterministic coherence resonance in coupled chaotic oscillators with frequency mismatch

    NASA Astrophysics Data System (ADS)

    Pisarchik, A. N.; Jaimes-Reátegui, R.

    2015-11-01

    A small mismatch between natural frequencies of unidirectionally coupled chaotic oscillators can induce coherence resonance in the slave oscillator for a certain coupling strength. This surprising phenomenon resembles "stabilization of chaos by chaos," i.e., the chaotic driving applied to the chaotic system makes its dynamics more regular when the natural frequency of the slave oscillator is a little different than the natural frequency of the master oscillator. The coherence is characterized with the dominant component in the power spectrum of the slave oscillator, normalized standard deviations of both the peak amplitude and the interpeak interval, and Lyapunov exponents. The enhanced coherence is associated with increasing negative both the third and the fourth Lyapunov exponents, while the first and second exponents are always positive and zero, respectively.

  3. Deterministic coherence resonance in coupled chaotic oscillators with frequency mismatch.

    PubMed

    Pisarchik, A N; Jaimes-Reátegui, R

    2015-11-01

    A small mismatch between natural frequencies of unidirectionally coupled chaotic oscillators can induce coherence resonance in the slave oscillator for a certain coupling strength. This surprising phenomenon resembles "stabilization of chaos by chaos," i.e., the chaotic driving applied to the chaotic system makes its dynamics more regular when the natural frequency of the slave oscillator is a little different than the natural frequency of the master oscillator. The coherence is characterized with the dominant component in the power spectrum of the slave oscillator, normalized standard deviations of both the peak amplitude and the interpeak interval, and Lyapunov exponents. The enhanced coherence is associated with increasing negative both the third and the fourth Lyapunov exponents, while the first and second exponents are always positive and zero, respectively. PMID:26651632

  4. Fundamental resonance frequency dependence of the proximity effect of quartz crystal resonators

    NASA Astrophysics Data System (ADS)

    Yao, Yao

    2015-11-01

    The fundamental frequency dependence of the proximity effect of a quartz crystal resonator (QCR) has been experimentally observed. By an impedance analysis method, the response mechanism underlying this effect has been examined. It is found that the disturbance of the fringing electric field of QCR due to adjacent metal is the main reason. Moreover, this experiment demonstrates that the proximity effect of QCR is strongly associated with the fundamental resonance frequency. Also, the effect of the size of the adjacent copper disk on the proximity effect of QCR has also been studied. The accurate understanding and prediction of this effect, on one hand, can help us distinguish abnormal frequency fluctuation especially in the presence of the adjacent metal. On the other hand, this effect can also be used for sensing applications.

  5. Whispering gallery mode resonators for frequency metrology applications

    NASA Astrophysics Data System (ADS)

    Baumgartel, Lukas

    This dissertation describes an investigation into the use of whispering gallery mode (WGM) resonators for applications towards frequency reference and metrology. Laser stabilization and the measurement of optical frequencies have enabled myriad technologies of both academic and commercial interest. A technology which seems to span both motivations is optical atomic clocks. These devices are virtually unimaginable without the ultra stable lasers plus frequency measurement and down-conversion afforded by Fabry Perot (FP) cavities and model-locked laser combs, respectively. However, WGM resonators can potentially perform both of these tasks while having the distinct advantages of compactness and simplicity. This work represents progress towards understanding and mitigating the performance limitations of WGM cavities for such applications. A system for laser frequency stabilization to a the cavity via the Pound-Drever-Hall (PDH) method is described. While the laser lock itself is found to perform at the level of several parts in 1015, a variety of fundamental and technical mechanisms destabilize the WGM frequency itself. Owing to the relatively large thermal expansion coefficients in optical crystals, environmental temperature drifts set the stability limit at time scales greater than the thermal relaxation time of the crystal. Uncompensated, these drifts pull WGM frequencies about 3 orders of magnitude more than they would in an FP cavity. Thus, two temperature compensation schemes are developed. An active scheme measures and stabilizes the mode volume temperature to the level of several nK, reducing the effective temperature coefficient of the resonator to 1.7x10-7 K-1; simulations suggest that the value could eventually be as low as 3.5x10-8 K-1, on par with the aforementioned FP cavities. A second, passive scheme is also described, which employs a heterogeneous resonator structure that capitalizes on the thermo-mechanical properties of one material and the optical

  6. Changes in water content and distribution in Quercus ilex leaves during progressive drought assessed by in vivo 1H magnetic resonance imaging

    PubMed Central

    2010-01-01

    Background Drought is a common stressor in many regions of the world and current climatic global circulation models predict further increases in warming and drought in the coming decades in several of these regions, such as the Mediterranean basin. The changes in leaf water content, distribution and dynamics in plant tissues under different soil water availabilities are not well known. In order to fill this gap, in the present report we describe our study withholding the irrigation of the seedlings of Quercus ilex, the dominant tree species in the evergreen forests of many areas of the Mediterranean Basin. We have monitored the gradual changes in water content in the different leaf areas, in vivo and non-invasively, by 1H magnetic resonance imaging (MRI) using proton density weighted (ρw) images and spin-spin relaxation time (T2) maps. Results ρw images showed that the distal leaf area lost water faster than the basal area and that after four weeks of similar losses, the water reduction was greater in leaf veins than in leaf parenchyma areas and also in distal than in basal leaf area. There was a similar tendency in all different areas and tissues, of increasing T2 values during the drought period. This indicates an increase in the dynamics of free water, suggesting a decrease of cell membranes permeability. Conclusions The results indicate a non homogeneous leaf response to stress with a differentiated capacity to mobilize water between its different parts and tissues. This study shows that the MRI technique can be a useful tool to follow non-intrusively the in vivo water content changes in the different parts of the leaves during drought stress. It opens up new possibilities to better characterize the associated physiological changes and provides important information about the different responses of the different leaf areas what should be taken into account when conducting physiological and metabolic drought stress studies in different parts of the leaves

  7. Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes

    NASA Astrophysics Data System (ADS)

    Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

    2006-05-01

    Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

  8. Resonance Frequency of Optical Microbubble Resonators: Direct Measurements and Mitigation of Fluctuations.

    PubMed

    Cosci, Alessandro; Berneschi, Simone; Giannetti, Ambra; Farnesi, Daniele; Cosi, Franco; Baldini, Francesco; Nunzi Conti, Gualtiero; Soria, Silvia; Barucci, Andrea; Righini, Giancarlo; Pelli, Stefano

    2016-01-01

    This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system. PMID:27589761

  9. Superconducting radio-frequency resonator in magnetic fields up to 6 T

    NASA Astrophysics Data System (ADS)

    Ebrahimi, M. S.; Stallkamp, N.; Quint, W.; Wiesel, M.; Vogel, M.; Martin, A.; Birkl, G.

    2016-07-01

    We have measured the characteristics of a superconducting radio-frequency resonator in an external magnetic field. The magnetic field strength has been varied with 10 mT resolution between zero and 6 T. The resonance frequency and the quality factor of the resonator have been found to change significantly as a function of the magnetic field strength. Both parameters show a hysteresis effect which is more pronounced for the resonance frequency. Quantitative knowledge of such behaviour is particularly important when experiments require specific values of resonance frequency and quality factor or when the magnetic field is changed while the resonator is in the superconducting state.

  10. {sup 13}C, {sup 1}H, {sup 6}Li magic-angle spinning nuclear magnetic resonance, electron paramagnetic resonance, and Fourier transform infrared study of intercalation electrodes based in ultrasoft carbons obtained below 3100 K

    SciTech Connect

    Alcantara, R.; Madrigal, F.J.F.; Lavela, P.; Tirado, J.L.; Mateos, J.M.J.; Stoyanova, R.; Zhecheva, E.

    1999-01-01

    The past decade has seen an important development of materials for high-performance energy storage systems. Particularly, the field of electrode materials for advanced lithium batteries has attracted the interest of numerous researchers. Petroleum coke samples of different origins and heat treated at different temperatures below 3100 K have been studied by spectroscopic and electrochemical procedures. According to {sup 13}C and {sup 1}H magic-angle spinning (MAS) nuclear magnetic resonance (NMR), infrared (IR), and electron paramagnetic resonance (EPR) data, aromatic compounds and surface OH groups are present in green coke samples. The preparation of CMB (combustible) sample from 1673 K leads to a low-temperature graphitization process, as shown by the occurrence of multiphase products containing both turbostatic and graphitized solid. This process is accompanied by the loss of aromatic compounds and surface hydroxyls. The optimization of the lithium intercalation electrodes based in the green coke materials was carried out by thermal treatment at 1023 K under dynamic vacuum conditions. Such pretreatment of the electrode material leads to marked enhancement of reversible capacities without the higher temperatures usually required for other soft carbon materials. Finally, the results of {sup 6}Li MAS NMR and EPR have been correlated with the experimental determination of lithium diffusion coefficients and surface properties. On the basis of these results, spin resonance spectroscopies are found to be a powerful tool to discern between the different petroleum coke samples to select the active electrode material with best performance.

  11. A time domain based method for the accurate measurement of Q-factor and resonance frequency of microwave resonators

    SciTech Connect

    Gyüre, B.; Márkus, B. G.; Bernáth, B.; Simon, F.; Murányi, F.

    2015-09-15

    We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation.

  12. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  13. Frequency selectivity without resonance in a fluid waveguide.

    PubMed

    van der Heijden, Marcel

    2014-10-01

    This study analyzes a waveguide consisting of two parallel fluid-filled chambers connected by a narrow slit that is spanned by two coupled elastic beams. A stiffness gradient exists in the longitudinal direction. This simple linear system, which contains no lumped mass, is shown to act as a spectral analyzer. Fluid waves traveling in the waveguide exhibit a distinct amplitude peak at a longitudinal location that varies systematically with frequency. The peaking is not based on resonance, but entirely on wave dispersion. When entering its peak region, the wave undergoes a sharp deceleration associated with a transition in which two propagation modes exchange roles. It is proposed that this mode shape swapping underlies the frequency analysis of the mammalian cochlea. PMID:25237137

  14. Ion cyclotron resonance bridge detector for frequency sweep

    NASA Astrophysics Data System (ADS)

    Pitsakis, Michael N.; Wobschall, Darold C.

    1983-11-01

    An electronic ion cyclotron resonance detection system was designed and constructed. The ions are excited by sweeping the frequency of the electric field (3-300 kHz) using a sweep frequency generator with a nonlinear sweep voltage in order to maintain an approximately constant mass resolution. Ion detection is accomplished by a bridge with a phase-sensitive detector as a demodulator. The required reference signal for the phase-sensitive detector is generated by a circuit with a transfer function which approximates that of the ICR signal in order to obtain an accurate phase match between the signal source and the detector. The device is capable of detecting a minimum concentration of 50 ions/cm3 over a mass range of 15 to 1500 amu.

  15. High-frequency instability of the sheath-plasma resonance

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1989-01-01

    Coherent high frequency oscillations near the electron plasma frequency (omega approx. less than omega sub p) are generated by electrodes with positive dc bias immersed in a uniform Maxwellian afterglow plasma. The instability occurs at the sheath-plasma resonance and is driven by a negative RF sheath resistance associated with the electron inertia in the diode-like electron-rich sheath. With increasing dc bias, i.e., electron transit time, the instability exhibits a hard threshold, downward frequency pulling, line broadening and copious harmonics. The fundamental instability is a bounded oscillation due to wave evanescence, but the harmonics are radiated as electromagnetic waves from the electrodes acting like antennas. Wavelength and polarization measurements confirm the emission process. Electromagnetic waves are excited by electrodes of various geometries (planes, cylinders, spheres) which excludes other radiation mechanisms such as orbitrons or beam-plasma instabilities. The line broadening mechanism was identified as a frequency modulation via the electron transit time by dynamic ions. Ion oscillations at the sheath edge give rise to burst-like RF emissions. These laboratory observations of a new instability are important for antennas in space plasmas, generation of coherent beams with diodes, and plasma diagnostics.

  16. Resonant-frequency discharge in a multi-cell radio frequency cavity

    SciTech Connect

    Popovic, S; Upadhyay, J; Mammosser, J; Nikolic, M; Vuskovic, L

    2014-11-07

    We are reporting experimental results on microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency (SRF) cryomodule (in situ operation). This discharge offers an efficient mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the problems related to generation and sustaining the multi-cell cavity plasma, which are breakdown and resonant detuning. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.

  17. Resonant Frequency Dependence on Outer Diameter of High Tc rf-SQUID

    NASA Astrophysics Data System (ADS)

    Ashizuka, Takuya; Sakai, Akira; Miyato, Yuji; Itozaki, Hideo

    Superconducting quantum interference devices (SQUIDs) have been applied to various magnetic sensing. An rf-SQUID can measure magnetic signals by applying external rf-magnetic field whose frequency is tuned to its resonance. Our rf-SQUID having the outer diameter of 3.5 mm needed a substrate resonator to operate it within the operation frequency range of our using FLL electronics. The designs of the rf-SQUID and the resonator were critical to the resonant frequency and the effective area. In this paper, the outer diameter dependence of the resonant frequency and the effective area were investigated by both the electromagnetic simulations and the experiments. The results showed that the rf-SQUID having the larger outer diameter has the smaller resonant frequency and the larger effective area. The rf-SQUIDs having the larger outer diameter were fabricated according to the simulation results. They could be operated within the operation frequency range even though a resonator was omitted.

  18. Assignment of the 1H nuclear magnetic resonance spectrum of the trypsin inhibitor homologue K from Dendroaspis polylepis polylepis. Two-dimensional nuclear magnetic resonance at 360 and 500 MHz.

    PubMed

    Keller, R M; Baumann, R; Hunziker-Kwik, E H; Joubert, F J; Wüthrich, K

    1983-02-01

    The assignment of the 1H nuclear magnetic resonance (n.m.r.) spectrum of the trypsin inhibitor homologue K from the venom of Dendroaspis polylepis polylepis is described and documented. The assignments are based entirely on the amino acid sequence and on 2-dimensional n.m.r. experiments at 360 and 500 M Hz. Individual assignments were obtained for the backbone and C beta protons of all 57 residues of the inhibitor homologue K, with the exceptions of the N-terminal amino group, the amide protons of Arg16, Gly37 and Gly40 and the C beta protons of Arg16 and Pro19. The assignments for the non-labile protons of the amino acid side-chains are complete, with the exception of Gln29, Glu49 and all the proline, lysine and arginine residues. For Asn and Trp the labile side-chain protons have also been assigned. The chemical shifts for the assigned resonances are listed for an aqueous solution at 50 degrees C and pH 3.4. PMID:6842589

  19. Clinical evaluation of osseointegration using resonance frequency analysis

    PubMed Central

    Satwalekar, Parth; Nalla, Sandeep; Reddy, Ramaswamy; Chowdary, Sheeba Glory

    2015-01-01

    The stability of the implant at the time of placement and during the development of the osseointegration process are the two major issues governing the implant survival. Implant stability is a mechanical phenomenon related to local factors such as bone quality, quantity, type of placement technique and type of implant used. The application of a user-friendly, clinically reliable, non-invasive method to assess implant stability and the osseointegration process is considered highly desirable. Resonance frequency analysis (RFA) is one such method which shows almost perfect reproducibility and repeatability after statistical analysis. The aim of this paper is to review the various methods used to assess implant stability and on the currently used RFA method which is being highly accepted in the recent times. PMID:26929512

  20. Clinical evaluation of osseointegration using resonance frequency analysis.

    PubMed

    Satwalekar, Parth; Nalla, Sandeep; Reddy, Ramaswamy; Chowdary, Sheeba Glory

    2015-01-01

    The stability of the implant at the time of placement and during the development of the osseointegration process are the two major issues governing the implant survival. Implant stability is a mechanical phenomenon related to local factors such as bone quality, quantity, type of placement technique and type of implant used. The application of a user-friendly, clinically reliable, non-invasive method to assess implant stability and the osseointegration process is considered highly desirable. Resonance frequency analysis (RFA) is one such method which shows almost perfect reproducibility and repeatability after statistical analysis. The aim of this paper is to review the various methods used to assess implant stability and on the currently used RFA method which is being highly accepted in the recent times. PMID:26929512

  1. Low radio frequency biased electron cyclotron resonance plasma etching

    NASA Astrophysics Data System (ADS)

    Samukawa, Seiji; Toyosato, Tomohiko; Wani, Etsuo

    1991-03-01

    A radio frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology has been developed to realize an efficient ion acceleration in high density and uniform ECR plasma for accurate Al-Si-Cu alloy film etching. In this technology, the substrate is located at the ECR position (875 G position) and the etching is carried out with a 400 kHz rf bias power. This Al-Si-Cu etching technology achieves a high etching rate (more than 5000 A/min), excellent etching uniformity (within ±5%), highly anisotropic etching, and Cu residue-free etching in only Cl2 gas plasma. These etching characteristics are accomplished by the combination of the dense and uniform ECR plasma generation at the ECR position with the efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.

  2. Piezoelectric-Crystal-Resonator High-Frequency Gravitational Wave Generation and Synchro-Resonance Detection

    NASA Astrophysics Data System (ADS)

    Baker, Robert M. L.; Woods, R. Clive; Li, Fangyu

    2006-01-01

    Here we show the generation of high-frequency-gravitational-waves (HFGWs) utilizing piezoelectric elements such as the ubiquitous Film-Bulk-Acoustic-Resonators (FBARs), found in cell phones, as energized by inexpensive magnetrons, found in microwave ovens, generating GWs having a frequency of about 4.9GHz and their detection by means of new synchro-resonance techniques developed in China. In the 1960s Weber suggested piezoelectric crystals for gravitational-wave (GW) generation. Since then researchers have proposed specific designs. The major obstacle has been the cost of procuring, installing, and energizing a sufficient number of such resonators to generate sufficiently powerful GWs to allow for detection. Recent mass-production techniques, spurred on by the production of cell phones, have driven the cost of resonators down. The new Chinese detector for detecting the 4.9×109Hz HFGW is a coupling-system of fractal membranes-beam-splitters and a narrow, 6.1 cm-radius, pulsed-Gaussian-laser or continuous-Gaussian detection beam passing through a static 15T-magnetic field. The detector is sensitive to GW amplitudes of ~10-30 to be generated with signal-to-noise ratios greater than one. It is concluded that a cost-effective HFGW generation and detection apparatus can now be fabricated and operated in the laboratory. If the two groups or clusters of magnetrons and FBARs were space borne and at lunar distance (e.g., at the Moon and at the lunar L3 libration point) and the quadrupole formalism approximately holds for GW radiators (the FBAR clusters) many GW wavelengths apart, then the HFGW power would be about 420 W and the flux about 2×105 Wm-2 (or more than one hundred times greater than the solar radiation flux at the Earth) focused at the focal spot, or remote-HFGW-emitter, anywhere in the Earth's environs - on or below the Earth's surface.

  3. Monitoring tumor response of prostate cancer to radiation therapy by multi-parametric 1H and hyperpolarized 13C magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Vickie Yi

    Radiation therapy is one of the most common curative therapies for patients with localized prostate cancer, but despite excellent success rates, a significant number of patients suffer post- treatment cancer recurrence. The accurate characterization of early tumor response remains a major challenge for the clinical management of these patients. Multi-parametric MRI/1H MR spectroscopy imaging (MRSI) has been shown to increase the diagnostic performance in evaluating the effectiveness of radiation therapy. 1H MRSI can detect altered metabolic profiles in cancerous tissue. In this project, the concentrations of prostate metabolites from snap-frozen biopsies of recurrent cancer after failed radiation therapy were correlated with histopathological findings to identify quantitative biomarkers that predict for residual aggressive versus indolent cancer. The total choline to creatine ratio was significantly higher in recurrent aggressive versus indolent cancer, suggesting that use of a higher threshold tCho/Cr ratio in future in vivo 1H MRSI studies could improve the selection and therapeutic planning for patients after failed radiation therapy. Varying radiation doses may cause a diverse effect on prostate cancer micro-environment and metabolism, which could hold the key to improving treatment protocols for individual patients. The recent development and clinical translation of hyperpolarized 13C MRI have provided the ability to monitor both changes in the tumor micro-environment and its metabolism using a multi-probe approach, [1-13C]pyruvate and 13C urea, combined with 1H Multi-parametric MRI. In this thesis, hyperpolarized 13C MRI, 1H dynamic contrast enhancement, and diffusion weighted imaging were used to identify early radiation dose response in a transgenic prostate cancer model. Hyperpolarized pyruvate to lactate metabolism significantly decreased in a dose dependent fashion by 1 day after radiation therapy, prior to any changes observed using 1H DCE and diffusion

  4. Measurement of Resonant Frequencies and Modes of Freestanding Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Kanjanaboos, Pongsakorn; Lin, Xiao-Min; Jaeger, Heinrich; Guest, Jeffrey

    2012-02-01

    We recently showed that freestanding membranes of ligated nanoparticles can be assembled in a one-step drying-mediated process [1]. These 10nm thin membranes can stretch over holes up to 100 microns in diameter and are supported by a substrate only along their outer edge, thereby freely suspending of the order of 100 million close-packed particles [2]. Previous work has focused on quasi-static mechanical properties [1-3]. Here we present the first investigation of the full dynamic response of freely suspended nanoparticle membranes, utilizing a high frequency laser interferometer with picometer sensitivity. This instrument allows us to rapidly measure the dynamical properties of freestanding nanoparticle monolayers for the first time including resonant frequencies, quality factors, and images of different modes.[4pt] [1] Klara E. Mueggenburg et al., ``Elastic membranes of close-packed nanoparticle arrays,'' Nature Materials 6, 656-660 (2007). [0pt] [2] Jinbo He et al., ``Fabrication and Mechanical properties of large-scale freestanding nanoparticle membranes,'' Small 6, 1449-1456 (2010).[0pt] [3] Pongsakorn Kanjanaboos et al., ``Strain Patterning and Direct Measurement of Poisson's Ratio in Nanoparticle Monolayer Sheets,'' Nano Letters 11, 2567-2571 (2011).

  5. A resonance phenomenon observed in a swept frequency experiment on a mother-daughter ionospheric rocket

    NASA Technical Reports Server (NTRS)

    Folkestad, K.; Troim, J.

    1974-01-01

    The report presents observations obtained in a swept frequency experiment conducted in a mother-daughter rocket flight at auroral latitudes. The discussion is essentially restricted to the possible interpretation of the experimental signal structures noted at and in the vicinity of a resonance frequency where signal components apparently are generated by nonlinear mechanisms. Various resonance frequencies have been considered in attempts to identify this multichannel response frequency. It is concluded that of all the possibilities invoked, the best consistency is provided by identifying the frequency concerned with the cone resonance frequency demonstrated experimentally in the case of a laboratory plasma by Fisher and Gould (1971).

  6. Collisionless dissociation of SF6 using two resonant frequency CO2 laser fields

    NASA Technical Reports Server (NTRS)

    Gower, M. C.; Gustafson, T. K.

    1977-01-01

    The collisionless dissociation of SF6 has been studied using simultaneous irradiation by two frequencies from a CO2 laser which are both nearly resonant with the SF6nu3 absorption band. It was found that the dissociation was enhanced, and occurred over a wider frequency range, than for single frequency dissociation. No threshold effect was observed for a weak resonant and a much higher energy field pumping slightly off-resonance. For such two frequency irradiation, the peak in the dissociation curve was found to be shifted to lower frequencies with respect to that for single frequency dissociation.

  7. Lower "N"-Acetyl-Aspartate Levels in Prefrontal Cortices in Pediatric Bipolar Disorder: A (Superscript 1]H Magnetic Resonance Spectroscopy Study

    ERIC Educational Resources Information Center

    Caetano, Sheila C.; Olvera, Rene L.; Hatch, John P.; Sanches, Marsal; Chen, Hua Hsuan; Nicoletti, Mark; Stanley, Jeffrey A.; Fonseca, Manoela; Hunter, Kristina; Lafer, Beny; Pliszka, Steven R.; Soares, Jair C.

    2011-01-01

    Objective: The few studies applying single-voxel [superscript 1]H spectroscopy in children and adolescents with bipolar disorder (BD) have reported low "N"-acetyl-aspartate (NAA) levels in the dorsolateral prefrontal cortex (DLPFC), and high myo-inositol/phosphocreatine plus creatine (PCr+Cr) ratios in the anterior cingulate. The aim of this study…

  8. (1)H, (13)C and (15)N backbone and side-chain resonance assignment of the LAM-RRM1 N-terminal module of La protein from Dictyostelium discoideum.

    PubMed

    Chasapis, Christos T; Argyriou, Aikaterini I; Apostolidi, Maria; Konstantinidou, Parthena; Bentrop, Detlef; Stathopoulos, Constantinos; Spyroulias, Georgios A

    2015-10-01

    The N-terminal half of La protein consists of two concatenated motifs: La motif (LAM) and the N-terminal RNA recognition motif (RRM1) both of which are responsible for poly(U) RNA binding. Here, we present the backbone and side-chain assignments of the (1)H, (13)C and (15)N resonances of the 191-residue LAM-RRM1 region of the La protein from the lower eukaryote Dictyostelium discoideum and its secondary structure prediction. PMID:25687647

  9. Detection and characterization of fatigue cracks in thin metal plates by low frequency resonant model analysis

    NASA Technical Reports Server (NTRS)

    Wincheski, B.; Namkung, M.; Birt, E. A.

    1992-01-01

    Low-frequency resonant model analysis, a technique for the detection and characterization of fatigue cracks in thin metal plates, which could be adapted to rapid scan or large area testing, is considered. Experimental data displaying a direct correlation between fatigue crack geometry and resonance frequency for the second vibrational plate mode are presented. FEM is used to calculate the mechanical behavior of the plates, and provides a comparison basis for the experimentally determined resonance frequency values. The waveform of the acoustic emission generated at the resonant frequency is examined; it provides the basis for a model of the interaction of fatigue crack faces during plate vibration.

  10. Detection and characterization of fatigue cracks in thin metal plates by low frequency resonant model analysis

    NASA Astrophysics Data System (ADS)

    Wincheski, B.; Namkung, M.; Birt, E. A.

    Low-frequency resonant model analysis, a technique for the detection and characterization of fatigue cracks in thin metal plates, which could be adapted to rapid scan or large area testing, is considered. Experimental data displaying a direct correlation between fatigue crack geometry and resonance frequency for the second vibrational plate mode are presented. FEM is used to calculate the mechanical behavior of the plates, and provides a comparison basis for the experimentally determined resonance frequency values. The waveform of the acoustic emission generated at the resonant frequency is examined; it provides the basis for a model of the interaction of fatigue crack faces during plate vibration.

  11. sup 17 O, sup 1 H, and sup 2 H electron nuclear double resonance characterization of solvent, substrate, and inhibitor binding to the (4Fe-4S) sup + cluster of aconitase

    SciTech Connect

    Werst, M.M.; Hoffman, B.M. ); Kennedy, M.C.; Beinert, H. )

    1990-11-01

    {sup 17}O electron nuclear double resonance (ENDOR) studies at X-band (9-GHz) and Q-band (35-GHz) microwave frequencies reveal that the (4Fe-4S){sup {plus}} cluster of substrate-free aconitase (citrate (isocitrate) hydro-lyase, EC 4.2.1.3) binds solvent, H{sub x}O (x = 1,2). Previous {sup 17}O ENDOR studies had disclosed that H{sub x}{sup 17}O binds to the enzyme-substrate complex and also to complexes of enzyme with the substrate analogues trans-aconitate and nitroisocitrate (1-hydroxy-2-nitro-1,3-propanedicarboxylate). The authors have used {sup 1}H and {sup 2}H ENDOR to characterize these solvent species. The authors propose that the fourth ligand of Fe{sub a} in substrate-free enzyme is a hydroxyl ion from the solvent; upon binding of substrate or substrate analogues at this Fe{sub a} site, the solvent species becomes protonated to form a water molecule. Previous {sup 17}O and {sup 13}C ENDOR studies showed that only a single carboxyl, at C-2 of the propane backbone of cis-aconitate or at C-1 of the inhibitor nitroisocitrate, coordinates to the cluster. Together, these results imply that enzyme-catalyzed interconversion of citrate and isocitrate does not involve displacement of an endogenous fourth ligand, but rather addition of the anionic carboxylate ligand and a change in protonation state of a solvent species bound to Fe{sub a}. The authors further report the {sup 17}O hyperfine tensor parameters of the C-2 carboxyl oxygen of substrate bound to the cluster as determined by the field dependence of the {sup 17}O ENDOR signals. {sup 17}O ENDOR studies also show that the carboxyl group of the inhibitor trans-aconitate binds similarly to that off substrate.

  12. Quantum dot admittance probed at microwave frequencies with an on-chip resonator

    NASA Astrophysics Data System (ADS)

    Frey, T.; Leek, P. J.; Beck, M.; Faist, J.; Wallraff, A.; Ensslin, K.; Ihn, T.; Büttiker, M.

    2012-09-01

    We present microwave frequency measurements of the dynamic admittance of a quantum dot tunnel-coupled to a two-dimensional electron gas. The measurements are made via a high-quality 6.75 GHz on-chip resonator capacitively coupled to the dot. The resonator frequency is found to shift both down and up close to conductance resonance of the dot corresponding to a change of sign of the reactance of the system from capacitive to inductive. The observations are consistent with a scattering matrix model. The sign of the reactance depends on the detuning of the dot from conductance resonance and on the magnitude of the tunnel rate to the lead with respect to the resonator frequency. Inductive response is observed on a conductance resonance when tunnel coupling and temperature are sufficiently small compared to the resonator frequency.

  13. Temperature compensation method for the resonant frequency of a differential vibrating accelerometer using electrostatic stiffness control

    NASA Astrophysics Data System (ADS)

    Lee, Jungshin; Rhim, Jaewook

    2012-09-01

    Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment.

  14. Method of shifting and fixing optical frequency of an optical resonator, and optical resonator made by same

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A. (Inventor); Strekalov, Dmitry V. (Inventor); Maleki, Lute (Inventor); Matsko, Andrey B. (Inventor); Iltchenko, Vladimir S. (Inventor); Martin, Jan M. (Inventor)

    2010-01-01

    A method of shifting and fixing an optical frequency of an optical resonator to a desired optical frequency, and an optical resonator made by such a method are provided. The method includes providing an optical resonator having a surface and a refractive index, and obtaining a coating composition having a predetermined concentration of a substance and having a refractive index that is substantially similar to the refractive index of the optical resonator. The coating composition inherently possesses a thickness when it is applied as a coating. The method further includes determining a coating ratio for the surface of the optical resonator and applying the coating composition onto a portion of the surface of the optical resonator based upon the determined coating ratio.

  15. Nanoscale Subsurface Imaging via Resonant Difference-Frequency Atomic Force Ultrasonic Microscopy

    NASA Technical Reports Server (NTRS)

    Cantrell, Sean A.; Cantrell, John H.; Lilehei, Peter T.

    2007-01-01

    A novel scanning probe microscope methodology has been developed that employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by the fundamental resonance frequency of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever fundamental resonance. The resonance-enhanced difference-frequency signals are used to create images of embedded nanoscale features.

  16. Note: A frequency modulated wireless interrogation system exploiting narrowband acoustic resonator for remote physical quantity measurement

    NASA Astrophysics Data System (ADS)

    Droit, C.; Martin, G.; Ballandras, S.; Friedt, J.-M.

    2010-05-01

    We demonstrate the wireless conversion of frequency modulation to amplitude modulation by radio frequency resonators as means of accurately determining the resonance frequency of passive acoustoelectronic sensors. The emitted frequency modulated radio frequency pulses are generated by a pulsed radar for probing a surface acoustic wave based sensor. The sharp sign transition of the amplitude modulated received signal provides a signal on which a feedback loop is locked to monitor the resonance signal. The strategy is demonstrated using a full software implementation on a generic hardware, resulting in 2 Hz resolution at 1 s integration time limited by the proportional feedback loop.

  17. Radio-frequency energy quantification in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Alon, Leeor

    Mapping of radio frequency (RF) energy deposition has been challenging for 50+ years, especially, when scanning patients in the magnetic resonance imaging (MRI) environment. As result, electromagnetic simulation software is often used for estimating the specific absorption rate (SAR), the rate of RF energy deposition in tissue. The thesis work presents challenges associated with aligning information provided by electromagnetic simulation and MRI experiments. As result of the limitations of simulations, experimental methods for the quantification of SAR were established. A system for quantification of the total RF energy deposition was developed for parallel transmit MRI (a system that uses multiple antennas to excite and image the body). The system is capable of monitoring and predicting channel-by-channel RF energy deposition, whole body SAR and capable of tracking potential hardware failures that occur in the transmit chain and may cause the deposition of excessive energy into patients. Similarly, we demonstrated that local RF power deposition can be mapped and predicted for parallel transmit systems based on a series of MRI temperature mapping acquisitions. Resulting from the work, we developed tools for optimal reconstruction temperature maps from MRI acquisitions. The tools developed for temperature mapping paved the way for utilizing MRI as a diagnostic tool for evaluation of RF/microwave emitting device safety. Quantification of the RF energy was demonstrated for both MRI compatible and non-MRI-compatible devices (such as cell phones), while having the advantage of being noninvasive, of providing millimeter resolution and high accuracy.

  18. High-frequency nano-optomechanical disk resonators in liquids

    NASA Astrophysics Data System (ADS)

    Gil-Santos, E.; Baker, C.; Nguyen, D. T.; Hease, W.; Gomez, C.; Lemaître, A.; Ducci, S.; Leo, G.; Favero, I.

    2015-09-01

    Nano- and micromechanical resonators are the subject of research that aims to develop ultrasensitive mass sensors for spectrometry, chemical analysis and biomedical diagnosis. Unfortunately, their merits generally diminish in liquids because of an increased dissipation. The development of faster and lighter miniaturized devices would enable improved performances, provided the dissipation was controlled and novel techniques were available to drive and readout their minute displacement. Here we report a nano-optomechanical approach to this problem using miniature semiconductor disks. These devices combine a mechanical motion at high frequencies (gigahertz and above) with an ultralow mass (picograms) and a moderate dissipation in liquids. We show that high-sensitivity optical measurements allow their Brownian vibrations to be resolved directly, even in the most-dissipative liquids. We investigate their interaction with liquids of arbitrary properties, and analyse measurements in light of new models. Nano-optomechanical disks emerge as probes of rheological information of unprecedented sensitivity and speed, which opens up applications in sensing and fundamental science.

  19. Spiral resonators for on-chip laser frequency stabilization

    NASA Astrophysics Data System (ADS)

    Lee, Hansuek; Suh, Myoung-Gyun; Chen, Tong; Li, Jiang; Diddams, Scott A.; Vahala, Kerry J.

    2013-09-01

    Frequency references are indispensable to radio, microwave and time keeping systems, with far reaching applications in navigation, communication, remote sensing and basic science. Over the past decade, there has been an optical revolution in time keeping and microwave generation that promises to ultimately impact all of these areas. Indeed, the most precise clocks and lowest noise microwave signals are now based on a laser with short-term stability derived from a reference cavity. In spite of the tremendous progress, these systems remain essentially laboratory devices and there is interest in their miniaturization, even towards on-chip systems. Here we describe a chip-based optical reference cavity that uses spatial averaging of thermorefractive noise to enhance resonator stability. Stabilized fibre lasers exhibit relative Allan deviation of 3.9 × 10-13 at 400 μs averaging time and an effective linewidth <100 Hz by achieving over 26 dB of phase-noise reduction.

  20. Spiral resonators for on-chip laser frequency stabilization

    PubMed Central

    Lee, Hansuek; Suh, Myoung-Gyun; Chen, Tong; Li, Jiang; Diddams, Scott A.; Vahala, Kerry J.

    2013-01-01

    Frequency references are indispensable to radio, microwave and time keeping systems, with far reaching applications in navigation, communication, remote sensing and basic science. Over the past decade, there has been an optical revolution in time keeping and microwave generation that promises to ultimately impact all of these areas. Indeed, the most precise clocks and lowest noise microwave signals are now based on a laser with short-term stability derived from a reference cavity. In spite of the tremendous progress, these systems remain essentially laboratory devices and there is interest in their miniaturization, even towards on-chip systems. Here we describe a chip-based optical reference cavity that uses spatial averaging of thermorefractive noise to enhance resonator stability. Stabilized fibre lasers exhibit relative Allan deviation of 3.9 × 10−13 at 400 μs averaging time and an effective linewidth <100 Hz by achieving over 26 dB of phase-noise reduction. PMID:24043134

  1. Exploring the Frequency Stability Limits of Whispering Gallery Mode Resonators for Metrological Applications

    NASA Technical Reports Server (NTRS)

    Chembo, Yanne K.; Baumgartel, Lukas; Grudinin, Ivan; Strekalov, Dmitry; Thompson, Robert; Yu, Nan

    2012-01-01

    Whispering gallery mode resonators are attracting increasing interest as promising frequency reference cavities. Unlike commonly used Fabry-Perot cavities, however, they are filled with a bulk medium whose properties have a significant impact on the stability of its resonance frequencies. In this context that has to be reduced to a minimum. On the other hand, a small monolithic resonator provides opportunity for better stability against vibration and acceleration. this feature is essential when the cavity operates in a non-laboratory environment. In this paper, we report a case study for a crystalline resonator, and discuss the a pathway towards the inhibition of vibration-and acceleration-induced frequency fluctuations.

  2. Zero field anti ferromagnetic resonance at optical frequencies in dilute magnetic system

    NASA Astrophysics Data System (ADS)

    Paul, Somnath; Sarkar, A.

    2015-06-01

    An experimental study of Antiferromagnetic resonance on Cobalt and Nickel oxide at room temperature has been undertaken. The zero field resonance frequency is detected in near infrared frequency regime. The measurement makes use of UV-VIS spectrophotometer. The overall results are found to be good and encouraging.

  3. Waveguide-type optical passive ring resonator gyro using frequency modulation spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Liang, Ning; Lijun, Guo; Mei, Kong; Tuoyuan, Chen

    2014-12-01

    This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator is composed of a 4 cm diameter silica waveguide. By testing at λ = 1550 nm, the FSR, FWHM and the depth of resonance are 3122 MHz, 103.07 MHz and 0.8 respectively. By using a polarization controller, the resonance curve under the TM mode can be inhibited. The depth of resonance increased from 0.8 to 0.8913, namely the finesse increase from 30.33 to 33.05. In the experiments, there is an acoustic-optical frequency shifter (AOFS) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for the counterclockwise lightwave; the frequency difference between the driving frequencies of the two AOFS is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed. The slope of the linear fit is about 0.330 mV/(°/s) based on the -900 to 900 kHz equivalent frequency and the gyro dynamic range is ±2.0 × 103 rad/s.

  4. Higher-order vibrational mode frequency tuning utilizing fishbone-shaped microelectromechanical systems resonator

    NASA Astrophysics Data System (ADS)

    Suzuki, Naoya; Tanigawa, Hiroshi; Suzuki, Kenichiro

    2013-04-01

    Resonators based on microelectromechanical systems (MEMS) have received considerable attention for their applications for wireless equipment. The requirements for this application include small size, high frequency, wide bandwidth and high portability. However, few MEMS resonators with wide-frequency tuning have been reported. A fishbone-shaped resonator has a resonant frequency with a maximum response that can be changed according to the location and number of several exciting electrodes. Therefore, it can be expected to provide wide-frequency tuning. The resonator has three types of electrostatic forces that can be generated to deform a main beam. We evaluate the vibrational modes caused by each exciting electrodes by comparing simulated results with measured ones. We then successfully demonstrate the frequency tuning of the first to fifth resonant modes by using the algorithm we propose here. The resulting frequency tuning covers 178 to 1746 kHz. In addition, we investigate the suppression of the anchor loss to enhance the Q-factor. An experiment shows that tapered-shaped anchors provide a higher Q-factor than rectangular-shaped anchors. The Q-factor of the resonators supported by suspension beams is also discussed. Because the suspension beams cause complicated vibrational modes for higher frequencies, the enhancement of the Q-factor for high vibrational modes cannot be obtained here. At present, the tapered-anchor resonators are thought to be most suitable for frequency tuning applications.

  5. Dual resonant structure for energy harvesting from random vibration sources at low frequency

    NASA Astrophysics Data System (ADS)

    Li, Shanshan; Peng, Zhuoteng; Zhang, Ai; Wang, Fei

    2016-01-01

    We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.

  6. Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies.

    PubMed

    Gutruf, Philipp; Zou, Chengjun; Withayachumnankul, Withawat; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe

    2016-01-26

    Devices that manipulate light represent the future of information processing. Flat optics and structures with subwavelength periodic features (metasurfaces) provide compact and efficient solutions. The key bottleneck is efficiency, and replacing metallic resonators with dielectric resonators has been shown to significantly enhance performance. To extend the functionalities of dielectric metasurfaces to real-world optical applications, the ability to tune their properties becomes important. In this article, we present a mechanically tunable all-dielectric metasurface. This is composed of an array of dielectric resonators embedded in an elastomeric matrix. The optical response of the structure under a uniaxial strain is analyzed by mechanical-electromagnetic co-simulations. It is experimentally demonstrated that the metasurface exhibits remarkable resonance shifts. Analysis using a Lagrangian model reveals that strain modulates the near-field mutual interaction between resonant dielectric elements. The ability to control and alter inter-resonator coupling will position dielectric metasurfaces as functional elements of reconfigurable optical devices. PMID:26617198

  7. Radio-frequency quadrupole resonator for linear accelerator

    DOEpatents

    Moretti, A.

    1982-10-19

    An RFQ resonator for a linear accelerator having a reduced level of interfering modes and producing a quadrupole mode for focusing, bunching and accelerating beams of heavy charged particles, with the construction being characterized by four elongated resonating rods within a cylinder with the rods being alternately shorted and open electrically to the shell at common ends of the rods to provide an LC parallel resonant circuit when activated by a magnetic field transverse to the longitudinal axis.

  8. Variable Coupling Scheme for High Frequency Electron Spin Resonance Resonators Using Asymmetric Meshes

    PubMed Central

    Tipikin, D. S.; Earle, K. A.; Freed, J. H.

    2010-01-01

    The sensitivity of a high frequency electron spin resonance (ESR) spectrometer depends strongly on the structure used to couple the incident millimeter wave to the sample that generates the ESR signal. Subsequent coupling of the ESR signal to the detection arm of the spectrometer is also a crucial consideration for achieving high spectrometer sensitivity. In previous work, we found that a means for continuously varying the coupling was necessary for attaining high sensitivity reliably and reproducibly. We report here on a novel asymmetric mesh structure that achieves continuously variable coupling by rotating the mesh in its own plane about the millimeter wave transmission line optical axis. We quantify the performance of this device with nitroxide spin-label spectra in both a lossy aqueous solution and a low loss solid state system. These two systems have very different coupling requirements and are representative of the range of coupling achievable with this technique. Lossy systems in particular are a demanding test of the achievable sensitivity and allow us to assess the suitability of this approach for applying high frequency ESR to the study of biological systems at physiological conditions, for example. The variable coupling technique reported on here allows us to readily achieve a factor of ca. 7 improvement in signal to noise at 170 GHz and a factor of ca. 5 at 95 GHz over what has previously been reported for lossy samples. PMID:20458356

  9. 1H nuclear magnetic resonance of modified bases of valine transfer ribonucleic acid (Escherichia coli). A direct monitor of sequential thermal unfolding.

    PubMed

    Kastrup, R V; Schmidt, P G

    1975-08-12

    Proton magnetic resonances at 220 MHz from three nucleotide residues of valine I tRNA (Escherichia coli) serve as intrinsic probes of local molecular structure. Resonances from the methyl group of ribothymidine, the methyl group of N6-methyladenosine, and the C-5 methylene of dihydrouridine monitor separate conformational transitions in the TpsiC, anticodon, and dihydrouridine loops, respectively. As the temperature is raised in a solution containing 0.23 M Na+ and no Mg2+, the dihydrouridine region melts with a Tm of 55 degrees, the anticodon region at 58 degrees, and the TpsiC region at 67 degrees. The dihydrouridine nuclear magnetic resonance (NMR) transition correlates with the major change in absorbance monitored in the uv at 330 nm which is ascribed to structural pertubations near the 4-thiouracil moiety. On the NMR time scale slow exchange is seen throughout the temperature range for dihydrouridine and below the apparent Tm for the ribothymidine methyl group. Chemical shift and line width differences between folded and unfolded forms of the polynucleotide indicate that, in the native structure, ribothymidine is in a highly structured region and N6-methyladenosine is in a somewhat less restricted environment. Narrow line widths for the C-5 methylene triplet are found over the whole temperature range indicating that this base is undergoing rapid internal reorientation relative to the overall macromolecule. PMID:1100098

  10. Investigation of the neuroprotective effects of bee-venom acupuncture in a mouse model of Parkinson's disease by using immunohistochemistry and In-vivo 1H magnetic resonance spectroscopy at 9.4 T

    NASA Astrophysics Data System (ADS)

    Yoon, Moon-Hyun; Lee, Do-Wan; Kim, Hyun-Jin; Chung, Jin-Yeung; Doo, Ah-Reum; Park, Hi-Joon; Kim, Seung-Nam; Choe, Bo-Young

    2013-01-01

    Neuroprotective therapeutics slows down the degeneration process in animal models of Parkinson's disease (PD). The neuronal survival in PD animal models is often measured by using immunohistochemistry. However, dynamic changes in the pathology of the brain cannot be explored with this technique. Application of in-vivo 1H magnetic resonance spectroscopy (1H MRS) can cover this shortcoming, as these techniques are non-invasive and can be repeated over time in the same animal. Thus, the sensitivity of both techniques to measure changes in the PD pathology was explored in an experiment studying the neuroprotective effects of the vigilance enhancer bee-venom (BV) in a mouse model of PD. The mice were pre-treated with 0.02-ml BV administered to the acupuncture point GB34 (Yangneungcheon) once every 3 days for 2 weeks. Three groups were classified as control, MPTP-intoxicated PD model and BV-treated mice. Outer volume suppression combined with the ultra-short echo-time STEAM (TE = 2.2 ms, TM = 20 ms, TR = 5000 ms) was used for localized in-vivo 1H MRS. Based on the 1H MRS spectral analysis, substantial changes of the neurochemical profiles were evaluated in the three investigated groups. In particular, the glutamate complex (Glx)/creatine (Cr) ratio (7.72 ± 1.25) in the PD group was significantly increased compared to that in the control group (3.93 ± 2.21, P = 0.001). Compared to the baseline values, the Glx/Cr ratio of the BV-treated group was significantly decreased 2 weeks after MPTP intoxication (one-way ANOVA, p < 0.05). In conclusion, the present study demonstrated that neurochemical alterations occurred in the three groups and that the neuroprotective effects of the BV acupuncture in a mouse model of PD could be quantified by using immunohistochemistry and 1H MRS.

  11. New Method for Determining the Quality Factor and Resonance Frequency of Superconducting Micro-Resonators from Sonnet Simulations

    NASA Astrophysics Data System (ADS)

    Wisbey, D. S.; Martin, A.; Reinisch, A.; Gao, J.

    2014-08-01

    Lithographed superconducting microwave resonators (micro-resonators) are useful in a number of important applications, including microwave kinetic inductance detectors (Day et al., Nature 425:817, 2003), as memory elements in quantum information circuits, and as readouts of qubits and nanomechanical resonators. One of the major tasks in designing these devices is to find the resonance frequency (f) and quality factor (Q) for these microwave circuits using EM simulation software such as Sonnet. The traditional method iteratively runs simulations over successively smaller frequency ranges. In this way the simulated transmission S data is zoomed in on to yield a well-sampled resonance curve of a circuit. Designing microwave resonators in this manner is often time consuming since it requires many simulation runs. In this work, we show a new—and much faster—method for determining f and Q by adding an internal (virtual) port in the Sonnet model and examining the input impedance through the added port. Accurate f and Q values can be retrieved from a single simulation with a wide frequency sweep. This method works on many types of resonance circuits and dramatically reduces the simulation time.

  12. sup 1 H and sup 31 P nuclear magnetic resonance and kinetic studies of the active site structure of chloroplast CF sub 1 ATP synthase

    SciTech Connect

    Devlin, C.C.; Grisham, C.M. )

    1990-07-03

    The interaction of nucleotides and nucleotide analogues and their complexes with Mn{sup 2+} bound to both the latent and dithiothreitol-activated CF{sub 1} ATP synthase has been examined by means of steady-state kinetics, water proton relaxation rate (PRR) measurements, and {sup 1}H and {sup 31}P nuclear relaxation measurements. Titration of both the latent and activated Mn{sup 2+}-CF{sub 1} complexes with ATP, ADP, P{sub i}, Co(NH{sub 3}){sub 4}ATP, Co(NH{sub 3}){sub 4}ADP, and Co(NH{sub 3}){sub 4}AMPPCP leads to increases in the water relaxation enhancement, consistent with enhanced metal binding and a high ternary complex enhancement. Steady-state kinetic studies are consistent with competitive inhibition of CF{sub 1} by Co(NH{sub 3}){sub 4}AMPPCP with respect to CaATP. {sup 1}H and {sup 31}P nuclear relaxation measurements in solutions of CF{sub 1} and Co(NH{sub 3}){sub 4}AMPPCP were used to determine the conformation of the bound substrate analogue and the arrangement with respect to this structure of high- and low-affinity sites for Mn{sup 2+}. The bound nucleotide analogue adopts a bent conformation, with the low-affinity sites for Mn{sup 2+}. The bound nucleotide analogue adopts a bent conformation, with the low-affinity Mn{sup 2+} site situated between the adenine and triphosphate moieties and the high-affinity metal site located on the far side of the triphosphate chain. The low-affinity metal forms a distorted inner-sphere complex with the {beta}-P and {gamma}-P of the substrate. The distances from Mn{sup 2+} to the triphosphate chain are too large for first coordination sphere complexes but are appropriate for second-sphere complexes involving, for example, intervening hydrogen-bonded water molecules or residues from the protein.

  13. Comparison of resonance frequencies of major atomic lines in 398-423 nm

    NASA Astrophysics Data System (ADS)

    Enomoto, Katsunari; Hizawa, Nagisa; Suzuki, Takahiro; Kobayashi, Kaori; Moriwaki, Yoshiki

    2016-05-01

    We have demonstrated spectroscopy of Ca, Rb, In, K, Ga, and Yb atomic lines in 398-423 nm. Using an etalon of an ultralow-expansion coefficient, we have determined ratios of the resonance frequencies of these atoms. The etalon has small group-delay-dispersion mirrors to be an accurate frequency reference over a wavelength span of a few tens of nanometer. The etalon resonance frequencies are calibrated with accurately known transition frequencies of Ca at 423 nm and Rb at 422 nm. Based on this calibration, the absolute frequencies are also determined for some atomic lines with smaller uncertainties than earlier reports.

  14. 1H, 13C and 15N resonance assignments and secondary structure analysis of CmPI-II, a serine protease inhibitor isolated from marine snail Cenchritis muricatus.

    PubMed

    Cabrera-Muñoz, Aymara; Rojas, Laritza; Alonso-del-Rivero Antigua, Maday; Pires, José Ricardo

    2016-04-01

    A protease inhibitor (CmPI-II) (UNIPROT: IPK2_CENMR) from the marine mollusc Cenchritis muricatus, has been isolated and characterized. It is the first member of a new group (group 3) of non-classical Kazal-type inhibitors. CmPI-II is a tight-binding inhibitor of serine proteases: trypsin, human neutrophil elastase (HNE), subtilisin A and pancreatic elastase. This specificity is exceptional in the members of Kazal-type inhibitor family. Several models of three-dimensional structure of CmPI-II have been constructed by homology with other inhibitors of the family but its structure has not yet been solved experimentally. Here we report the (1)H, (15)N and (13)C chemical shift assignments of CmPI-II as basis for NMR structure determination and interaction studies. Secondary structure analyses deduced from the NMR chemical shift data have identified three β-strands β1: residues 14-19, β2: 23-35 and β3: 43-45 and one helix α1: 28-37 arranged in the sequential order β1-β2-α1-β3. These secondary structure elements suggest that CmPI-II adopts the typical scaffold of a Kazal-type inhibitor. PMID:26547437

  15. 1H, 15N and 13C resonance assignments of light organ-associated fatty acid-binding protein of Taiwanese fireflies.

    PubMed

    Tseng, Kai-Li; Lee, Yi-Zong; Chen, Yun-Ru; Lyu, Ping-Chiang

    2016-04-01

    Fatty acid-binding proteins (FABPs) are a family of proteins that modulate the transfer of various fatty acids in the cytosol and constitute a significant portion in many energy-consuming cells. The ligand binding properties and specific functions of a particular type of FABP seem to be diverse and depend on the respective binding cavity as well as the cell type from which this protein is derived. Previously, a novel FABP (lcFABP; lc: Luciola cerata) was identified in the light organ of Taiwanese fireflies. The lcFABP was proved to possess fatty acids binding capabilities, especially for fatty acids of length C14-C18. However, the structural details are unknown, and the structure-function relationship has remained to be further investigated. In this study, we finished the (1)H, (15)N and (13)C chemical shift assignments of (15)N/(13)C-enriched lcFABP by solution NMR spectroscopy. In addition, the secondary structure distribution was revealed based on the backbone N, H, Cα, Hα, C and side chain Cβ assignments. These results can provide the basis for further structural exploration of lcFABP. PMID:26373428

  16. Investigation of Proton Dynamics in a (CH3)4 NCdCl3 Single Crystal by using 1H Nuclear Magnetic Resonance Measurements

    NASA Astrophysics Data System (ADS)

    Lee, Moohee; Sim, Jung Seok; Kang, Kihyeok; Hyoun Kim, Ho; Kim, Ae Ran

    2013-03-01

    (CH3)4 NCdCl3(TMCC) is reported to exhibit two first-order structural phase transitions. The crystal has a hexagonal structure in phase I at room temperature and then changes to a monoclinic one in phase II below 118 K. Finally a ferro-elastic monoclinic phase III appears below 104 K. The a- and c-axes of TMMC were found by using X-ray diffraction at room temperature. 1H NMR measurements of spectrum, spin-lattice relaxation time T1 and rotating-frame relaxation time T1ρ were performed at 4.8 T parallel or perpendicular to the c-axis from 300 K down to 65 K. The spectrum shows no significant changes at both transition temperatures. T1 and T1ρ monotonically decrease at low temperature and then show an abrupt decrease around 110 K. As the temperature decreases further, T1 shows a minimum at 100 K and becomes longer whereas T1ρ continuously decreases. From these data, the proton dynamical behavior is analyzed and identified.

  17. Theoretical approach for plasma series resonance effect in geometrically symmetric dual radio frequency plasma

    SciTech Connect

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.

    2012-02-27

    Plasma series resonance (PSR) effect is well known in geometrically asymmetric capacitively couple radio frequency plasma. However, plasma series resonance effect in geometrically symmetric plasma has not been properly investigated. In this work, a theoretical approach is made to investigate the plasma series resonance effect and its influence on Ohmic and stochastic heating in geometrically symmetric discharge. Electrical asymmetry effect by means of dual frequency voltage waveform is applied to excite the plasma series resonance. The results show considerable variation in heating with phase difference between the voltage waveforms, which may be applicable in controlling the plasma parameters in such plasma.

  18. An Improved Performance Frequency Estimation Algorithm for Passive Wireless SAW Resonant Sensors

    PubMed Central

    Liu, Boquan; Zhang, Chenrui; Ji, Xiaojun; Chen, Jing; Han, Tao

    2014-01-01

    Passive wireless surface acoustic wave (SAW) resonant sensors are suitable for applications in harsh environments. The traditional SAW resonant sensor system requires, however, Fourier transformation (FT) which has a resolution restriction and decreases the accuracy. In order to improve the accuracy and resolution of the measurement, the singular value decomposition (SVD)-based frequency estimation algorithm is applied for wireless SAW resonant sensor responses, which is a combination of a single tone undamped and damped sinusoid signal with the same frequency. Compared with the FT algorithm, the accuracy and the resolution of the method used in the self-developed wireless SAW resonant sensor system are validated. PMID:25429410

  19. Running, hopping and trotting: tuning step frequency to the resonant frequency of the bouncing system favors larger animals.

    PubMed

    Cavagna, Giovanni A; Legramandi, Mario A

    2015-10-01

    A long-lasting challenge in comparative physiology is to understand why the efficiency of the mechanical work done to maintain locomotion increases with body mass. It has been suggested that this is due to a more elastic step in larger animals. Here, we show in running, hopping and trotting animals, and in human running during growth, that the resonant frequency of the bouncing system decreases with increasing body mass and is, surprisingly, independent of species or gait. Step frequency roughly equals the resonant frequency in trotting and running, whereas it is about half the resonant frequency in hopping. The energy loss by elastic hysteresis during loading and unloading the bouncing system from its equilibrium position decreases with increasing body mass. Similarity to a symmetrical bounce increases with increasing body mass and, for a given body mass, seems to be maximal in hopping, intermediate in trotting and minimal in running. We conclude that: (1) tuning step frequency to the resonant frequency of the bouncing system coincides with a lower hysteresis loss in larger, more-compliant animals; (2) the mechanism of gait per se affects similarity with a symmetrical bounce, independent of hysteresis; and (3) the greater efficiency in larger animals may be due, at least in part, to a lower hysteresis loss. PMID:26347555

  20. Sequence-specific {sup 1}H, {sup 13}C, and {sup 15}N resonance assignments for intestinal fatty-acid-binding protein complexed with palmitate (15.4 kDA)

    SciTech Connect

    Hodsdon, M.E.; Toner, J.J.; Cistola, D.P.

    1994-12-01

    Intestinal fatty-acid-binding protein (I-FABP) belongs to a family of soluble, cytoplasmic proteins that are thought to function in the intracellular transport and trafficking of polar lipids. Individual members of this protein family have distinct specificities and affinities for fatty acids, cholesterol, bile salts, and retinoids. We are comparing several retinol- and fatty-acid-binding proteins from intestine in order to define the factors that control molecular recognition in this family of proteins. We have established sequential resonance assignments for uniformly {sup 13}C/{sup 15}N-enriched I-FABP complexed with perdeuterated palmitate at pH7.2 and 37{degrees}C. The assignment strategy was similar to that introduced for calmodulin. We employed seven three-dimensional NMR experiments to establish scalar couplings between backbone and sidechain atoms. Backbone atoms were correlated using triple-resonance HNCO, HNCA, TOCSY-HMQC, HCACO, and HCA(CO)N experiments. Sidechain atoms were correlated using CC-TOCSY, HCCH-TOCSY, and TOCSY-HMQC. The correlations of peaks between three-dimensional spectra were established in a computer-assisted manner using NMR COMPASS (Molecular Simulations, Inc.) Using this approach, {sup 1}H, {sup 13}C, and {sup 15}N resonance assignments have been established for 120 of the 131 residues of I-FABP. For 18 residues, amide {sup 1}H and {sup 15}N resonances were unobservable, apparently because of the rapid exchange of amide protons with bulk water at pH 7.2. The missing amide protons correspond to distinct amino acid patterns in the protein sequence, which will be discussed. During the assignment process, several sources of ambiguity in spin correlations were observed. To overcome this ambiguity, the additional inter-residue correlations often observed in the HNCA experiment were used as cross-checks for the sequential backbone assignments.

  1. A resonant frequency switching scheme of a cantilever based on polyvinylidene fluoride for vibration energy harvesting

    NASA Astrophysics Data System (ADS)

    Jo, Sung-Eun; Kim, Myoung-Soo; Kim, Yong-Jun

    2012-01-01

    A mismatch between the ambient frequency and the resonant frequency of the vibrational energy harvester causes decrease of the energy transduction efficiency. Therefore, there is a great demand for the resonant frequency tuning of the vibrational energy harvester. In this paper, a flexible PVDF (polyvinylidene fluoride) cantilever, which can switch its resonant frequency automatically and maintain the switched resonant frequency without energy consumption, is proposed. The proposed energy harvester is composed of cantilever couples which are similar with a seesaw structure. When the proposed energy harvester is excited by an external vibration and the excited frequency fluctuates, the cantilever couples can be horizontally moved by using the large deflection of a flexible cantilever. So the beam length of each cantilever which corresponds to each arm of the seesaw structure can be changed and the resonant frequency of the proposed energy harvester can be switched in real time. The proposed energy harvester was realized by application of a piezoelectric polymer, PVDF. Also, it was confirmed that the proposed energy harvester can switch its resonant frequency in several seconds without an additional energy source.

  2. (1)H-(13)C-(29)Si triple resonance and REDOR solid-state NMR-A tool to study interactions between biosilica and organic molecules in diatom cell walls.

    PubMed

    Wisser, Dorothea; Brückner, Stephan I; Wisser, Florian M; Althoff-Ospelt, Gerhard; Getzschmann, Jürgen; Kaskel, Stefan; Brunner, Eike

    2015-01-01

    Triple resonance solid-state NMR experiments using the spin combination (1)H-(13)C-(29)Si are still rarely found in the literature. This is due to the low natural abundance of the two heteronuclei. Such experiments are, however, increasingly important to study hybrid materials such as biosilica and others. A suitable model substance, ideally labeled with both (13)C and (29)Si, is thus very useful to optimize the experiments before applying them to studies of more complex samples such as biosilica. Tetraphenoxysilane could be synthesized in an easy, two-step synthesis including double isotope labelling. Using tetraphenoxysilane, we established a (1)H-(13)C-(29)Si double CP-based HETCOR experiment and applied it to diatom biosilica from the diatom species Thalassiosira pseudonana. Furthermore, we carried out (1)H-(13)C{(29)Si} CP-REDOR experiments in order to estimate the distance between the organic matrix and the biosilica. Our experiments on diatom biosilica strongly indicate a close contact between polyamine-containing parts of the organic matrix and the silica. This corroborates the assumption that the organic matrix is essential for the control of the cell wall formation. PMID:25638422

  3. Secondary structure and side-chain sup 1 H and sup 13 C resonance assignments of calmodulin in solution by heteronuclear multidimensional NMR spectroscopy

    SciTech Connect

    Ikura, Mitsuhiko; Spera, S.; Barbato, G.; Kay, L.E.; Bax, A. ); Krinks, M. )

    1991-09-24

    Heteronuclear 2D and 3D NMR experiments were carried out on recombinant Drosophila calmodulin (CaM), a protein of 148 residues and with molecular mass of 16.7 kDa, that is uniformly labeled with {sup 15}N and {sup 13}C to a level of > 95%. Nearly complete {sup 1}H and {sup 13}C side-chain assignments for all amino acid residues are obtained by using the 3D HCCH-COSY and HCCH-TOCSY experiments that rely on large heteronuclear one-bond scalar couplings to transfer magnetization and establish through-bond connectivities. The secondary structure of this protein in solution has been elucidated by a qualitative interpretation of nuclear Overhauser effects, hydrogen exchange data, and {sup 3}J{sub HNH{alpha}} coupling constants. A clear correlation between the {sup 13}C{alpha} chemical shift and secondary structure is found. The secondary structure in the two globular domains of Drosophila CaM in solution is essentially identical with that of the X-ray crystal structure of mammalian CaM which consists of two pairs of a helix-loop-helix motif in each globular domain. The existence of a short antiparallel {beta}-sheet between the two loops in each domain has been confirmed. The eight {alpha}-helix segments identified from the NMR data are located at Glu-6 to Phe-19, thr-29 to Ser-38, Glu-45 to Glu-54, Phe-65 to Lys-77, Glu-82 to Asp-93, Ala-102 to Asn-111, Asp-118 to Glu-127, and Tyr-138 to Thr-146. Although the crystal structure has a long central helix from Phe-65 to Phe-92 that connects the two globular domains, NMR data indicate that residues Asp-78 to Ser-81 of this central helix adopt a nonhelical conformation with considerable flexibility.

  4. 1H, 13C and 15N resonance assignments of a highly-soluble murine interleukin-3 analogue with wild-type bioactivity.

    PubMed

    Yao, Shenggen; Murphy, James M; Low, Andrew; Norton, Raymond S

    2010-04-01

    Interleukin-3 (IL-3) is a cytokine that acts as a critical mediator of inflammation and immune responses to infections. IL-3, like interleukin-5 (IL-5) and granulocyte-macrophage colony stimulating factor (GM-CSF), exerts its effects on target cells via receptors composed of cytokine-specific alpha-subunits and a common beta-subunit (betac-subunit, shared with IL-5 and GM-CSF). In contrast to humans, mice also possess an additional beta-receptor, beta(IL-3), that can specifically bind IL-3. Except for a study carried out on an analogue of human IL-3 that contains 14 mutations, structure-related studies of IL-3 have been very limited, largely because of its poor solution behaviour. Here we report (1)H, (13)C, and (15)N chemical shift assignments of murine IL-3 comprising residues 33-156 (SWISS-PROT accession number: P01586), in which the only mutation is an alanine substitution of Cys105. The mIL-3 construct used in the present study was engineered by eliminating residues 27-32 of the N-terminus (the first 26 residues of the primary sequence of mIL-3 are cleaved in vivo during secretion), the C-terminal 10 residues (157-166), and a disulfide bond between Cys105 and Cys166 that is poorly conserved in orthologue sequences. The new construct vastly improves the solubility of murine IL-3 while maintaining its wild-type biological activity. PMID:20174897

  5. Frequency dependence in seismoacoustic imaging of shallow free gas due to gas bubble resonance

    NASA Astrophysics Data System (ADS)

    Tóth, Zsuzsanna; Spiess, Volkhard; Keil, Hanno

    2015-12-01

    Shallow free gas is investigated in seismoacoustic data in 10 frequency bands covering a frequency range between 0.2 and 43 kHz. At the edge of a gassy patch in the Bornholm Basin (Baltic Sea), compressional wave attenuation caused by free gas is estimated from reflection amplitudes beneath the gassy sediment layer. Imaging of shallow free gas is considerably influenced by gas bubble resonance, because in the resonance frequency range attenuation is significantly increased. At the resonance frequency of the largest bubbles between 3 and 5 kHz, high scattering causes complete acoustic blanking beneath the top of the gassy sediment layer. In the wider resonance frequency range between 3 and 15 kHz, the effect of smaller bubbles becomes dominant and the attenuation slightly decreases. This allows acoustic waves to be transmitted and reflections can be observed beneath the gassy sediment layer for higher frequencies. Above resonance beginning at ˜19 kHz, attenuation is low and the presence of free gas can be inferred from the decreased reflection amplitudes beneath the gassy layer. Below the resonance frequency range (<1 kHz), attenuation is generally very low and not dependent on frequency. Using the geoacoustic model of Anderson and Hampton, the observed frequency boundaries suggest gas bubble sizes between 1 and 4-6 mm, and gas volume fractions up to 0.02% in a ˜2 m thick sediment layer, whose upper boundary is the gas front. With the multifrequency acoustic approach and the Anderson and Hampton model, quantification of free gas in shallow marine environments is possible if the measurement frequency range allows the identification of the resonance frequency peak. The method presented is limited to places with only moderate attenuation, where the amplitudes of a reflection can be analyzed beneath the gassy sediment layer.

  6. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  7. Resonant frequencies of irregularly shaped microstrip antennas using method of moments

    NASA Technical Reports Server (NTRS)

    Deshpande, Manohar D.; Shively, David G.; Cockrell, C. R.

    1993-01-01

    This paper describes an application of the method of moments to determine resonant frequencies of irregularly shaped microstrip patches embedded in a grounded dielectric slab. For analysis, the microstrip patch is assumed to be excited by a linearly polarized plane wave that is normal to the patch. The surface-current density that is induced on the patch because of the incident field is expressed in terms of subdomain functions by dividing the patch into identical rectangular subdomains. The amplitudes of the subdomain functions, as a function of frequency, are determined using the electric-field integral equation (EFIE) approach in conjunction with the method of moments. The resonant frequencies of the patch are then obtained by selecting the frequency at which the amplitude of the surface-current density is real. The resonant frequencies of the equilateral triangular and other nonrectangular patches are computed using the present technique, and these frequencies are compared with measurements and other independent calculations.

  8. The Role of High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy for Predicting the Invasive Component in Patients with Ductal Carcinoma In Situ Diagnosed on Preoperative Biopsy.

    PubMed

    Chae, Eun Young; Shin, Hee Jung; Kim, Suhkmann; Baek, Hyeon-Man; Yoon, Dahye; Kim, Siwon; Shim, Ye Eun; Kim, Hak Hee; Cha, Joo Hee; Choi, Woo Jung; Lee, Jeong Hyun; Shin, Ji Hoon; Lee, Hee Jin; Gong, Gyungyub

    2016-01-01

    The purpose of this study was to evaluate the role of high-resolution magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy in patients with ductal carcinoma in situ (DCIS) diagnosed on preoperative biopsy. We investigated whether the metabolic profiling of tissue samples using HR-MAS 1H NMR spectroscopy could be used to distinguish between DCIS lesions with or without an invasive component. Our institutional review board approved this combined retrospective and prospective study. Tissue samples were collected from 30 patients with pure DCIS and from 30 with DCIS accompanying invasive carcinoma. All patients were diagnosed with DCIS by preoperative core-needle biopsy and underwent surgical resection. The metabolic profiling of tissue samples was performed by HR-MAS 1H NMR spectroscopy. All observable metabolite signals were identified and quantified in all tissue samples. Metabolite intensity normalized by total spectral intensities was compared according to the tumor type using the Mann-Whitney test. Multivariate analysis was performed with orthogonal projections to latent structure-discriminant analysis (OPLS-DA). By univariate analysis, the metabolite concentrations of choline-containing compounds obtained with HR-MAS 1H NMR spectroscopy did not differ significantly between the pure DCIS and DCIS accompanying invasive carcinoma groups. However, the GPC/PC ratio was higher in the pure DCIS group than in the DCIS accompanying invasive carcinoma group (p = 0.004, Bonferroni-corrected p = 0.064), as well as the concentration of myo-inositol and succinate. By multivariate analysis, the OPLS-DA models built with HR-MAS MR metabolic profiles could clearly discriminate between pure DCIS and DCIS accompanying invasive carcinoma. Our preliminary results suggest that HR-MAS MR metabolomics on breast tissue may be able to distinguish between DCIS lesions with or without an invasive component. PMID:27560937

  9. The Role of High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy for Predicting the Invasive Component in Patients with Ductal Carcinoma In Situ Diagnosed on Preoperative Biopsy

    PubMed Central

    Chae, Eun Young; Kim, Suhkmann; Baek, Hyeon-Man; Yoon, Dahye; Kim, Siwon; Shim, Ye Eun; Kim, Hak Hee; Cha, Joo Hee; Choi, Woo Jung; Lee, Jeong Hyun; Shin, Ji Hoon; Lee, Hee Jin; Gong, Gyungyub

    2016-01-01

    The purpose of this study was to evaluate the role of high-resolution magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy in patients with ductal carcinoma in situ (DCIS) diagnosed on preoperative biopsy. We investigated whether the metabolic profiling of tissue samples using HR-MAS 1H NMR spectroscopy could be used to distinguish between DCIS lesions with or without an invasive component. Our institutional review board approved this combined retrospective and prospective study. Tissue samples were collected from 30 patients with pure DCIS and from 30 with DCIS accompanying invasive carcinoma. All patients were diagnosed with DCIS by preoperative core-needle biopsy and underwent surgical resection. The metabolic profiling of tissue samples was performed by HR-MAS 1H NMR spectroscopy. All observable metabolite signals were identified and quantified in all tissue samples. Metabolite intensity normalized by total spectral intensities was compared according to the tumor type using the Mann-Whitney test. Multivariate analysis was performed with orthogonal projections to latent structure-discriminant analysis (OPLS-DA). By univariate analysis, the metabolite concentrations of choline-containing compounds obtained with HR-MAS 1H NMR spectroscopy did not differ significantly between the pure DCIS and DCIS accompanying invasive carcinoma groups. However, the GPC/PC ratio was higher in the pure DCIS group than in the DCIS accompanying invasive carcinoma group (p = 0.004, Bonferroni-corrected p = 0.064), as well as the concentration of myo-inositol and succinate. By multivariate analysis, the OPLS-DA models built with HR-MAS MR metabolic profiles could clearly discriminate between pure DCIS and DCIS accompanying invasive carcinoma. Our preliminary results suggest that HR-MAS MR metabolomics on breast tissue may be able to distinguish between DCIS lesions with or without an invasive component. PMID:27560937

  10. Three-frequency parametric amplification in magneto-inductive ring resonators

    NASA Astrophysics Data System (ADS)

    Syms, R. R. A.; Solymar, L.; Young, I. R.

    2008-09-01

    Parametric amplification of magneto-inductive (MI) waves propagating in magnetically coupled chains of nonlinear L- C resonators is studied. Analysis is first presented for a three-frequency travelling wave scheme in which the signal, idler and pump all propagate as MI waves. The effect of de-coupling the idlers is then considered and it is shown that this configuration relaxes the standard phase matching condition. Confirmation of the theory is provided using low-frequency PCB unit cells containing varactor diodes. The cells are characterised individually and then arranged as a 16-element ring resonator. Frequency matching and selective amplification of the primary resonance is demonstrated. The primary resonance can be excited using the field of a rotating magnetic dipole, and an application in magnetic resonance imaging is described.

  11. Flexible optical manipulation of ring resonator by frequency detuning and double-port excitation.

    PubMed

    Geng, Yong; Zhu, Tongtong; Lv, Haiyi; Cao, Yongyin; Sun, Fangkui; Ding, Weiqiang

    2016-07-11

    Optical force exerted on a ring resonator, which can move freely in plane, is investigated using the finite-difference in time-domain method. In order to manipulate the ring resonator more flexibly, two assistant waveguides are introduced to form a microring resonator based add-drop device. Results show that a blue tuned source is more suitable for the manipulation of the ring, rather than the central resonant frequency as expected. A red-tuned frequency, however, is difficult to trap the ring stably. When the frequency detuning is combined with selected double-port excitation, the ring can be trapped stably at some discrete positions, some determined regions, or be transported continuously along the waveguide. This optically reconfigurable opto-mechanical resonant system may find potential applications in tunable photonic devices and precise sensing. PMID:27410856

  12. Sub-Wavelength Resonant Structures at Microwave and Optical Frequencies

    NASA Astrophysics Data System (ADS)

    Simic, Aleksandar

    Sub-wavelength scale resonant structures have been at the forefront of physics and engineering in the past decade. They offer a path for creation of new materials and great advancements in the field of photonics. This dissertation deals with design, fabrication and characterization of sub-wavelength resonant structures. In the first part, we investigate the application of passive sub-wavelength resonators in meta-materials---materials that have electromagnetic properties otherwise unattainable in nature. We develop a technique for characterization of negative index meta-materials by free-space measurement of the phase change in the meta-material. We also discuss the application of sub-wavelength resonators to highly efficient antenna design. In the second part of the dissertation we focus on active sub-wavelength resonant structures, specifically nanolasers. We present a first truly sub-wavelength nanolaser operating at the room temperature and later investigate cryogenic operation of this laser design. We also offer a new, highly compatible, fabrication approach that could enable the integration of nanolasers in various silicon photonic devices. Lastly, we show a coaxial nanolaser that offers some new and truly unique features. For one it is the first sub-wavelength laser that operates at continuous wave at room temperature. More importantly, it exhibits single mode, thresholdless lasing at cryogenic temperatures. We discuss the significance and the implications of these results.

  13. Locally resonant periodic structures with low-frequency band gaps

    NASA Astrophysics Data System (ADS)

    Cheng, Zhibao; Shi, Zhifei; Mo, Y. L.; Xiang, Hongjun

    2013-07-01

    Presented in this paper are study results of dispersion relationships of periodic structures composited of concrete and rubber, from which the frequency band gap can be found. Two models with fixed or free boundary conditions are proposed to approximate the bound frequencies of the first band gap. Studies are conducted to investigate the low-frequency and directional frequency band gaps for their application to engineering. The study finds that civil engineering structures can be designed to block harmful waves, such as earthquake disturbance.

  14. Single-frequency and tunable operation of a continuous intracavity-frequency-doubled singly resonant optical parametric oscillator.

    PubMed

    My, Thu-Hien; Drag, Cyril; Bretenaker, Fabien

    2008-07-01

    A widely tunable continuous intracavity-frequency-doubled singly resonant optical parametric oscillator based on MgO-doped periodically poled stoichiometric lithium tantalate crystal is described. The idler radiation resonating in the cavity is frequency doubled by an intracavity BBO crystal. Pumped in the green, this system can provide up to 485 mW of single-frequency orange radiation. The system is continuously temperature tunable between 1170 and 1355 nm for the idler, 876 and 975 nm for the signal, and between 585 and 678 nm for the doubled idler. The free-running power and frequency stability of the system have been observed to be better than those for a single-mode dye laser. PMID:18594663

  15. Surface plasmon optical antennae in the infrared region with high resonant efficiency and frequency selectivity.

    PubMed

    Ueno, Kosei; Sun, Quan; Mino, Masahiro; Itoh, Takumi; Oshikiri, Tomoya; Misawa, Hiroaki

    2016-08-01

    Infrared light has received attention for sensor applications, including fingerprint spectroscopy, in the bioengineering and security fields. Surface plasmon physics enables the operation of a light harvesting optical antenna. Gold nanochains exhibit localized surface plasmon resonance (LSPR) in the infrared region with high frequency selectivity. However, a feasible design for optical antennae with a higher resonant efficiency and frequency selectivity as a function of structural design and periodicity is still unknown. In the present study, we investigated the relationship between the resonant efficiency and frequency selectivity as a function of the structural design of gold nanochains and explored structural periodicity for obtaining highly frequency-selective optical antennae. An optical antenna design with higher resonant efficiency is proposed on the basis of its efficient interaction with non-polarized light. PMID:27505741

  16. An acoustic dual filter in the audio frequencies with two local resonant systems

    NASA Astrophysics Data System (ADS)

    Liu, Zhao-qun; Zhang, Hui; Zhang, Shu-yi; Fan, Li

    2014-08-01

    We report an acoustic dual filter to realize the sound regulation in the audio frequency range, in which resonant vibrations of two membrane-air and metal-elastomer systems generate two sound transmission peaks and a sound blocking below 3000 Hz. The local vibrational profiles manifest that the transmission peak at lower frequency is mainly dependent on the resonant vibration of the membrane-air system, and the coupling vibrations of two systems generate the blocking frequency and transmission peak at higher frequency. Importantly, two transmission peaks can be controlled independently. It is feasible to realize the acoustic device in sound shield and dual filters.

  17. Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

    SciTech Connect

    Donko, Z.; Schulze, J.; Czarnetzki, U.; Luggenhoelscher, D.

    2009-03-30

    At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies.

  18. Electrostatically tunable resonance frequency beam utilizing a stress-sensitive film

    DOEpatents

    Thundat, Thomas G.; Wachter, Eric A.; Davis, J. Kenneth

    2001-01-01

    Methods and apparatus for detecting particular frequencies of acoustic vibration utilize an electrostatically-tunable beam element having a stress-sensitive coating and means for providing electrostatic force to controllably deflect the beam element thereby changing its stiffness and its resonance frequency. It is then determined from the response of the electrostatically-tunable beam element to the acoustical vibration to which the beam is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.

  19. Magnetically tunable resonance frequency beam utilizing a stress-sensitive film

    DOEpatents

    Davis, J. Kenneth; Thundat, Thomas G.; Wachter, Eric A.

    2001-01-01

    Methods and apparatus for detecting particular frequencies of vibration utilize a magnetically-tunable beam element having a stress-sensitive coating and means for providing magnetic force to controllably deflect the beam element thereby changing its stiffness and its resonance frequency. It is then determined from the response of the magnetically-tunable beam element to the vibration to which the beam is exposed whether or not a particular frequency or frequencies of vibration are detected.

  20. Resonance frequencies of a cavity containing a compressible viscous fluid

    NASA Astrophysics Data System (ADS)

    Conca, C.; Planchard, J.; Vanninathan, M.

    1993-03-01

    The aim of this paper is to study the resonance spectrum of a cavity containing a compressible viscous fluid. This system admits a discrete infinite sequence of eigenvalues whose real parts are negative, which is interpreted as the damping effect introduced by viscosity. Only a finite number of them have non-zero imaginary parts and this number depends on viscosity; a simple criterion is given for their position in the complex plane. The case of a cavity containing an elastic mechanical system immersed in the fluid is also examined; from a qualitative point of view, the nature of the resonance spectrum remains unchanged.

  1. Effects of size, shape, and frequency on the antiferromagnetic resonance linewidth of MnF

    NASA Technical Reports Server (NTRS)

    Obrien, K. C.

    1973-01-01

    The research concerning the properties and application of solid state materials at submillimeter frequencies is summarized. Work reported includes: far infrared Fourier spectroscopy; studies of the antiferromagnetic resonance line in MnF2 at millimeter wavelengths; numerical solution of the equations of motion of a general two-sublattice antiferromagnet; study of antiferromagnetic resonance line in NiO powder; and resonance investigations of several indium thisospinels at millimeter wavelengths.

  2. Dark resonances in the field of frequency-shifted feedback laser radiation

    NASA Astrophysics Data System (ADS)

    Romanenko, V. I.; Romanenko, A. V.; Yatsenko, L. P.; Kazakov, G. A.; Litvinov, A. N.; Matisov, B. G.; Rozhdestvensky, Yu V.

    2010-11-01

    We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.

  3. Evaluation of the applicability of Helmholtz resonators for low frequency acoustic liners

    NASA Astrophysics Data System (ADS)

    Vanderwal, J. M. M.

    1988-09-01

    A literature study was performed on the acoustic behavior of those Helmholtz resonator type liners which are most promising for low frequency sound absorption in aero-engine applications. The equations for the acoustic impedance of various types of Helmholtz resonators were analyzed as well as the conditions for the validity of these equations. An experimental program is defined for a further analysis of various types of resonators.

  4. THz-range generation frequency growth in semiconductor superlattice coupled to external high-quality resonator

    NASA Astrophysics Data System (ADS)

    Makarov, Vladimir V.; Maksimenko, Vladimir A.; Khramova, Marina V.; Pavlov, Alexey N.; Hramov, Alexander E.

    2016-03-01

    We investigate effects of a linear resonator on spatial electron dynamics in semiconductor superlattice. We have shown that coupling the external resonant system to superlattice leads to occurrence of the additional area of negative differential conductance on the current-voltage characteristic, which does not occur in autonomous system. Furthermore, this region shows great increase of generation frequency, that contains practical interest.

  5. Primary and secondary biomass burning aerosols determined by proton nuclear magnetic resonance (1H-NMR) spectroscopy during the 2008 EUCAARI campaign in the Po Valley (Italy)

    NASA Astrophysics Data System (ADS)

    Paglione, M.; Saarikoski, S.; Carbone, S.; Hillamo, R.; Facchini, M. C.; Finessi, E.; Giulianelli, L.; Carbone, C.; Fuzzi, S.; Moretti, F.; Tagliavini, E.; Swietlicki, E.; Eriksson Stenström, K.; Prévôt, A. S. H.; Massoli, P.; Canaragatna, M.; Worsnop, D.; Decesari, S.

    2014-05-01

    Atmospheric organic aerosols are generally classified as primary and secondary (POA and SOA) according to their formation processes. An actual separation, however, is challenging when the timescales of emission and gas-to-particle formation overlap. The presence of SOA formation in biomass burning plumes leads to scientific questions about whether the oxidized fraction of biomass burning aerosol is rather of secondary or primary origin, as some studies would suggest, and about the chemical compositions of oxidized biomass burning POA and SOA. In this study, we apply nuclear magnetic resonance (NMR) spectroscopy to investigate the functional group composition of fresh and aged biomass burning aerosols during an intensive field campaign in the Po Valley, Italy. The campaign was part of the EUCAARI project and was held at the rural station of San Pietro Capofiume in spring 2008. Factor analysis applied to the set of NMR spectra was used to apportion the wood burning contribution and other organic carbon (OC) source contributions, including aliphatic amines. Our NMR results, referred to the polar, water-soluble fraction of OC, show that fresh wood burning particles are composed of polyols and aromatic compounds, with a sharp resemblance to wood burning POA produced in wood stoves, while aged samples are clearly depleted of alcohols and are enriched in aliphatic acids with a smaller contribution of aromatic compounds. The comparison with biomass burning organic aerosols (BBOA) determined by high-resolution aerosol mass spectrometry (HR-TOF-AMS) at the site shows only a partial overlap between NMR BB-POA and AMS BBOA, which can be explained by either the inability of BBOA to capture all BB-POA composition, especially the alcohol fraction, or the fact that BBOA account for insoluble organic compounds unmeasured by the NMR. Therefore, an unambiguous composition for biomass burning POA could not be derived from this study, with NMR analysis indicating a higher O / C ratio

  6. Tumor Metabolism and Perfusion in Head and Neck Squamous Cell Carcinoma: Pretreatment Multimodality Imaging With {sup 1}H Magnetic Resonance Spectroscopy, Dynamic Contrast-Enhanced MRI, and [{sup 18}F]FDG-PET

    SciTech Connect

    Jansen, Jacobus F.A.; Schoeder, Heiko; Lee, Nancy Y.; Stambuk, Hilda E.; Wang Ya; Fury, Matthew G.; Patel, Senehal G.; Pfister, David G.; Shah, Jatin P.; Koutcher, Jason A.; Shukla-Dave, Amita

    2012-01-01

    Purpose: To correlate proton magnetic resonance spectroscopy ({sup 1}H-MRS), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and {sup 18}F-labeled fluorodeoxyglucose positron emission tomography ([{sup 18}F]FDG PET) of nodal metastases in patients with head and neck squamous cell carcinoma (HNSCC) for assessment of tumor biology. Additionally, pretreatment multimodality imaging was evaluated for its efficacy in predicting short-term response to treatment. Methods and Materials: Metastatic neck nodes were imaged with {sup 1}H-MRS, DCE-MRI, and [{sup 18}F]FDG PET in 16 patients with newly diagnosed HNSCC, before treatment. Short-term patient radiological response was evaluated at 3 to 4 months. Correlations among {sup 1}H-MRS (choline concentration relative to water [Cho/W]), DCE-MRI (volume transfer constant [K{sup trans}]; volume fraction of the extravascular extracellular space [v{sub e}]; and redistribution rate constant [k{sub ep}]), and [{sup 18}F]FDG PET (standard uptake value [SUV] and total lesion glycolysis [TLG]) were calculated using nonparametric Spearman rank correlation. To predict short-term responses, logistic regression analysis was performed. Results: A significant positive correlation was found between Cho/W and TLG ({rho} = 0.599; p = 0.031). Cho/W correlated negatively with heterogeneity measures of standard deviation std(v{sub e}) ({rho} = -0.691; p = 0.004) and std(k{sub ep}) ({rho} = -0.704; p = 0.003). Maximum SUV (SUVmax) values correlated strongly with MRI tumor volume ({rho} = 0.643; p = 0.007). Logistic regression indicated that std(K{sup trans}) and SUVmean were significant predictors of short-term response (p < 0.07). Conclusion: Pretreatment multimodality imaging using {sup 1}H-MRS, DCE-MRI, and [{sup 18}F]FDG PET is feasible in HNSCC patients with nodal metastases. Additionally, combined DCE-MRI and [{sup 18}F]FDG PET parameters were predictive of short-term response to treatment.

  7. Self-powered resonant frequency tuning for Piezoelectric Vibration Energy Harvesters

    NASA Astrophysics Data System (ADS)

    Ahmed-Seddik, B.; Despesse, G.; Boisseau, S.; Defay, E.

    2013-12-01

    This paper reports on the design, fabrication and testing of an innovative 33-mode piezoelectric vibration energy harvester (VEH). This system is able to change its resonant frequency in real time to follow the main frequency of a vibration source. The system proposed in this paper enables to adapt VEH characteristics (resonant frequency, electrical damping) to vibration parameters variations (frequency and amplitude) in order to optimize the extraction of energy and then the output power at any time. This solution allows up to 40% of resonant frequency tuning ratio; moreover, the adaptation is made in real time and the consumption of the regulation electronic is less than 10% of the VEH output power (480μW@0.1g-276Hz).

  8. Exceeding natural resonance frequency limit of monodisperse Fe3O4 nanoparticles via superparamagnetic relaxation

    PubMed Central

    Song, Ning-Ning; Yang, Hai-Tao; Liu, Hao-Liang; Ren, Xiao; Ding, Hao-Feng; Zhang, Xiang-Qun; Cheng, Zhao-Hua

    2013-01-01

    Magnetic nanoparticles have attracted much research interest in the past decades due to their potential applications in microwave devices. Here, we adopted a novel technique to tune cut-off frequency exceeding the natural resonance frequency limit of monodisperse Fe3O4 nanoparticles via superparamagnetic relaxation. We observed that the cut-off frequency can be enhanced from 5.3 GHz for Fe3O4 to 6.9 GHz forFe3O4@SiO2 core-shell structure superparamagnetic nanoparticles, which are much higher than the natural resonance frequency of 1.3 GHz for Fe3O4 bulk material. This finding not only provides us a new approach to enhance the resonance frequency beyond the Snoek's limit, but also extend the application for superparamagnetic nanoparticles to microwave devices. PMID:24196377

  9. The origin of SH-wave resonance frequencies in sedimentary layers

    NASA Astrophysics Data System (ADS)

    van der Baan, Mirko

    2009-09-01

    Resonance frequencies are often analysed in geo-engineering studies to evaluate seismic risk and microzonation in urban areas. The Nakamura technique constitutes a popular approach that computes the spectral ratio of horizontal-to-vertical ground motion in ambient noise recordings to reveal the existence of any site resonance frequencies. Its theoretical basis remains however unclear with some authors arguing that the method de-emphasizes any Rayleigh-wave contributions and that the resonance frequencies are solely caused by vertically incident SH waves. Other authors explain the same resonance frequencies by the ellipticity of the fundamental Rayleigh wave. Recent numerical simulations reveal that the magnitude of the peak frequency is proportional to the relative portion of Love waves present. This study demonstrates that Love waves alone can be responsible for any observed resonance frequencies in sedimentary layers. Yet sharp SH-wave resonance frequencies are only excited by a source in the bedrock. These resonance frequencies are caused by inhomogeneous waves excited by the bedrock source that tunnel through the high-velocity bedrock to emerge in the low-velocity sediments with a very reduced range of slownesses. The resulting SH waves are then free to interfere constructively thereby creating the observed resonance frequencies. This general trigger mechanism leads to resonances that are almost offset independent. The resulting resonance frequencies map onto points of maximum curvature in the Love-wave phase-velocity dispersion curves at or just beyond the critical horizontal slowness. They can be analysed with the quarter-wavelength law if a large velocity contrast exists between the unconsolidated sediments and the bedrock. A minor modification of the quarter-wavelength law provides more accurate predictions, also for smaller velocity contrasts. Multisource simulations show that site amplification factors as determined by horizontal-over-vertical (H

  10. A comparative study of feature extraction and blind source separation of independent component analysis (ICA) on childhood brain tumour 1H magnetic resonance spectra.

    PubMed

    Hao, Jie; Zou, Xin; Wilson, Martin P; Davies, Nigel P; Sun, Yu; Peet, Andrew C; Arvanitis, Theodoros N

    2009-10-01

    Independent component analysis (ICA) has the potential of determining automatically the metabolite signals which make up MR spectra. However, the reliability with which this is accomplished and the optimal approach for investigating in vivo MRS have not been determined. Furthermore, the properties of ICA in brain tumour MRS with respect to dataset size and data quality have not been systematically explored. The two common techniques for applying ICA, blind source separation (BSS) and feature extraction (FE) were examined in this study using simulated data and the findings confirmed on patient data. Short echo time (TE 30 ms), low and high field (1.5 and 3 T) in vivo brain tumour MR spectra of childhood astrocytoma, ependymoma and medulloblastoma were generated by using a quantum mechanical simulator with ten metabolite and lipid components. Patient data (TE 30 ms, 1.5 T) were acquired from children with brain tumours. ICA of simulated data shows that individual metabolite components can be extracted from a set of MRS data. The BSS method generates independent components with a closer correlation to the original metabolite and lipid components than the FE method when the number of spectra in the dataset is small. The experiments also show that stable results are achieved with 300 MRS at an SNR equal to 10. The FE method is relatively insensitive to different ranges of full width at half maximum (FWHM) (from 0 to 3 Hz), whereas the BSS method degrades on increasing the range of FWHM. The peak frequency variations do not affect the results within the range of +/-0.08 ppm for the FE method, and +/-0.05 ppm for the BSS method. When the methods were applied to the patient dataset, results consistent with the synthesized experiments were obtained. PMID:19431141

  11. Point-Wise Phase Matching for Nonlinear Frequency Generation in Dielectric Resonators

    NASA Technical Reports Server (NTRS)

    Yu, Nan (Inventor); Strekalov, Dmitry V. (Inventor); Lin, Guoping (Inventor)

    2016-01-01

    An optical resonator fabricated from a uniaxial birefringent crystal, such as beta barium borate. The crystal is cut with the optical axis not perpendicular to a face of the cut crystal. In some cases the optical axis lies in the plane of the cut crystal face. An incident (input) electromagnetic signal (which can range from the infrared through the visible to the ultraviolet) is applied to the resonator. An output signal is recovered which has a frequency that is an integer multiple of the frequency of the input signal. In some cases a prism is used to evanescently couple the input and the output signals to the resonator.

  12. Characterization technique of optical whispering gallery mode resonators in the microwave frequency domain for optoelectronic oscillators.

    PubMed

    Merrer, Pierre-Henri; Saleh, Khaldoun; Llopis, Olivier; Berneschi, Simone; Cosi, Franco; Conti, Gualtiero Nunzi

    2012-07-10

    Optical Q factor measurements are performed on a whispering gallery mode (WGM) disk resonator using a microwave frequency domain approach instead of using an optical domain approach. An absence of hysteretic behavior and a better linearity are obtained when performing linewidth measurements by using a microwave modulation for scanning the resonances instead of the piezoelectric-based frequency tuning capability of the laser. The WGM resonator is then used to stabilize a microwave optoelectronic oscillator. The microwave output of this system generates a 12.48 GHz signal with -94 dBc/Hz phase noise at 10 kHz offset. PMID:22781250

  13. Creating Feshbach resonances for ultracold molecule formation with radio-frequency fields

    NASA Astrophysics Data System (ADS)

    Owens, Daniel J.; Xie, Ting; Hutson, Jeremy M.

    2016-08-01

    We show that radio-frequency (rf) radiation may be used to create Feshbach resonances in ultracold gases of alkali-metal atoms at desired magnetic fields that are convenient for atomic cooling and degeneracy. For the case of 39K+133Cs , where there are no rf-free resonances in regions where Cs may be cooled to degeneracy, we show that a resonance may be created near 21 G with 69.2 MHz rf radiation. This resonance is almost lossless with circularly polarized rf, and the molecules created are long-lived even with plane-polarized rf.

  14. Performance and modeling of superconducting ring resonators at millimeter-wave frequencies

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Chorey, C. M.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Kong, K. S.; Lee, H. Y.; Itoh, T.

    1990-01-01

    Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO thin films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performance compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

  15. Fluorescence resonance energy transfer from a bio-active imidazole derivative 2-(1-phenyl-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol to a bioactive indoloquinolizine system

    NASA Astrophysics Data System (ADS)

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Venkatesh Perumal, Marimuthu; Srinivasan, Natesan

    2011-06-01

    Novel donor imidazole derivative, 2-(1-phenyl-1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)-phenol (PIPP) was screened as highly sensitive chemisensor for transition metal ions and it can be used as a "multi-way" optically switchable material. Solvatochromic effects on the fluorescence behaviour of PIPP were studied in different solvents. The fluorescence of PIPP was highly sensitive to both the polarity as well as protic nature of the solvent. Fluorescence (Forster) resonance energy transfer (FRET) process from PIPP to a potent bioactive indoloquinolizine molecule was studied and it is argued that long-range dipole-dipole interaction is operating for the energy transfer mechanism. The energy transfer efficiency ( E) and the distance between the acceptor and the donor ( r0) have been determined.

  16. Backbone 1H, 15N, and 13C resonance assignments and secondary structure of a novel protein OGL-20P(T)-358 from hyperthermophile Thermococcus thioreducens sp. nov.

    PubMed

    Wilson, Randall; Hughes, Ronny; Curto, Ernest; Ng, Joseph; Twigg, Pamela

    2007-12-31

    OGL-20P(T)-358 is a novel 66 amino acid residue protein from the hyperthermophile Thermococcus thioreducens sp. nov., strain OGL-20PT, which was collected from the wall of the hydrothermal black smoker in the Rainbow Vent along the mid-Atlantic ridge. This protein, which has no detectable sequence homology with proteins or domains of known function, has a calculated pI of 4.76 and a molecular mass of 8.2 kDa. We report here the backbone 1H, 15N, and 13C resonance assignments of OGL-20PT-358. Assignments are 97.5% (316/324) complete. Chemical shift index was used to determine the secondary structure of the protein, which appears to consist of primarily alpha-helical regions. This work is the foundation for future studies to determine the three-dimensional solution structure of the protein. PMID:18182861

  17. Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

    SciTech Connect

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

    2011-10-15

    Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

  18. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    NASA Astrophysics Data System (ADS)

    Gaskell, J.; Eaves, L.; Novoselov, K. S.; Mishchenko, A.; Geim, A. K.; Fromhold, T. M.; Greenaway, M. T.

    2015-09-01

    We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.

  19. Frequency-selective propagation of localized spoof surface plasmons in a graded plasmonic resonator chain.

    PubMed

    Gao, Zhen; Gao, Fei; Shastri, Kunal Krishnaraj; Zhang, Baile

    2016-01-01

    Localized spoof surface plasmon polaritons (spoof-SPPs) in a graded spoof-plasmonic resonator chain with linearly increasing spacing are experimentally investigated at microwave frequencies. Transmission measurements and direct near-field mappings on this graded chain show that the propagation of localized spoof-SPPs can be cutoff at different positions along the graded chain under different frequencies due to the graded coupling between adjacent resonators. This mechanism can be used to guide localized spoof-SPPs in the graded chain to specific positions depending on the frequency and thereby implement a device that can work as a selective switch in integrated plasmonic circuits. PMID:27149656

  20. Frequency-selective propagation of localized spoof surface plasmons in a graded plasmonic resonator chain

    PubMed Central

    Gao, Zhen; Gao, Fei; Shastri, Kunal Krishnaraj; Zhang, Baile

    2016-01-01

    Localized spoof surface plasmon polaritons (spoof-SPPs) in a graded spoof-plasmonic resonator chain with linearly increasing spacing are experimentally investigated at microwave frequencies. Transmission measurements and direct near-field mappings on this graded chain show that the propagation of localized spoof-SPPs can be cutoff at different positions along the graded chain under different frequencies due to the graded coupling between adjacent resonators. This mechanism can be used to guide localized spoof-SPPs in the graded chain to specific positions depending on the frequency and thereby implement a device that can work as a selective switch in integrated plasmonic circuits. PMID:27149656

  1. Frequency-selective propagation of localized spoof surface plasmons in a graded plasmonic resonator chain

    NASA Astrophysics Data System (ADS)

    Gao, Zhen; Gao, Fei; Shastri, Kunal Krishnaraj; Zhang, Baile

    2016-05-01

    Localized spoof surface plasmon polaritons (spoof-SPPs) in a graded spoof-plasmonic resonator chain with linearly increasing spacing are experimentally investigated at microwave frequencies. Transmission measurements and direct near-field mappings on this graded chain show that the propagation of localized spoof-SPPs can be cutoff at different positions along the graded chain under different frequencies due to the graded coupling between adjacent resonators. This mechanism can be used to guide localized spoof-SPPs in the graded chain to specific positions depending on the frequency and thereby implement a device that can work as a selective switch in integrated plasmonic circuits.

  2. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    SciTech Connect

    Gaskell, J.; Fromhold, T. M.; Greenaway, M. T.; Eaves, L.; Novoselov, K. S.; Mishchenko, A.; Geim, A. K.

    2015-09-07

    We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.

  3. Advanced simulation methods to detect resonant frequency stack up in focal plane design

    NASA Astrophysics Data System (ADS)

    Adams, Craig; Malone, Neil R.; Torres, Raymond; Fajardo, Armando; Vampola, John; Drechsler, William; Parlato, Russell; Cobb, Christopher; Randolph, Max; Chiourn, Surath; Swinehart, Robert

    2014-09-01

    Wire used to connect focal plane electrical connections to external electrical circuitry can be modeled using the length, diameter and loop height to determine the resonant frequency. The design of the adjacent electric board and mounting platform can also be analyzed. The combined resonant frequency analysis can then be used to decouple the different component resonant frequencies to eliminate the potential for metal fatigue in the wires. It is important to note that the nominal maximum stress values that cause metal fatigue can be much less than the ultimate tensile stress limit or the yield stress limit and are degraded further at resonant frequencies. It is critical that tests be done to qualify designs that are not easily simulated due to material property variation and complex structures. Sine wave vibration testing is a critical component of qualification vibration and provides the highest accuracy in determining the resonant frequencies which can be reduced or uncorrelated improving the structural performance of the focal plane assembly by small changes in design damping or modern space material selection. Vibration flow down from higher levels of assembly needs consideration for intermediary hardware, which may amplify or attenuate the full up system vibration profile. A simple pass through of vibration requirements may result in over test or missing amplified resonant frequencies that can cause system failure. Examples are shown of metal wire fatigue such as discoloration and microscopic cracks which are visible at the submicron level by the use of a scanning electron microscope. While it is important to model and test resonant frequencies the Focal plane must also be constrained such that Coefficient of Thermal expansion mismatches are allowed to move and not overstress the FPA.

  4. Off-resonance frequency operation for power transfer in a loosely coupled air core transformer

    DOEpatents

    Scudiere, Matthew B

    2012-11-13

    A power transmission system includes a loosely coupled air core transformer having a resonance frequency determined by a product of inductance and capacitance of a primary circuit including a primary coil. A secondary circuit is configured to have a substantially same product of inductance and capacitance. A back EMF generating device (e.g., a battery), which generates a back EMF with power transfer, is attached to the secondary circuit. Once the load power of the back EMF generating device exceeds a certain threshold level, which depends on the system parameters, the power transfer can be achieved at higher transfer efficiency if performed at an operating frequency less than the resonance frequency, which can be from 50% to 95% of the resonance frequency.

  5. Precise rainbow trapping for low-frequency acoustic waves with micro Mie resonance-based structures

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Yuan, Baoguo; Cheng, Ying; Liu, Xiaojun

    2016-02-01

    We have realized the acoustic rainbow trapping in the low frequency region (200-500 Hz) through micro Mie resonance-based structures. The structure has eight channels with a high refractive index obtained by coiling space, that can excite strong interactions with incident waves and support various orders of multipoles due to the Mie resonances of the microstructure. By utilizing the structure, the precise spatial modulation of the acoustic wave is demonstrated both theoretically and experimentally. The effect of trapping broadband acoustic waves and spatially separating different frequency components are ascribed to the monopolar Mie resonances of the structures. The trapping frequency is derived and the trapping positions can be tuned arbitrarily. With enhanced wave-structure interactions and tailored frequency responses, such micro structures show precise spectral-spatial control of acoustic waves and open a diverse venue for high performance acoustic wave detection, sensing, filtering, and a nondestructive test.

  6. Diode-laser frequency stabilization based on the resonant Faraday effect

    NASA Technical Reports Server (NTRS)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    The authors present the results of a method for frequency stabilizing laser diodes based on the resonant Faraday effects. A Faraday cell in conjunction with a polarizer crossed with respect to the polarization of the laser diode comprises the intracavity frequency selective element. In this arrangement, a laser pull-in range of 9 A was measured, and the laser operated at a single frequency with a linewidth less than 6 MHz.

  7. Ultra-Narrow Bandwidth Optical Resonators for Integrated Low Frequency Noise Lasers

    NASA Astrophysics Data System (ADS)

    Spencer, Daryl T.

    The development of narrowband resonators has far reaching applications in integrated optics. As a precise reference of wavelength, filters can be used in sensors, metrology, nonlinear optics, microwave photonics, and laser stabilization. In this work, we develop record high quality factor (Q) Si 3N4 waveguide resonators, and utilize them to stabilize a heterogeneously integrated Si/III V laser. To increase the Q factor of waveguide resonators, particular attention is given to loss mechanisms. Propagation loss of <0.1 dB/m is demonstrated on the ultra low loss waveguide platform, a low index contrast, high aspect ratio Si3N4 waveguide geometry fabricated with high quality materials and high temperature anneals. Ideality in the directional couplers used for coupling to the resonators is studied and losses are reduced such that 81 million intrinsic Q factor is achieved. Additional results include 1x16 resonant splitters, low ? narrowband gratings, and a dual layer waveguide technology for low loss and low bend radius in separate regions of the same device layer. We then combine an ultra high Q resonator and a heterogeneous Si/III V laser in a Pound Drever Hall (PDH) frequency stabilization system to yield narrow linewidth characteristics for a stable on chip laser reference. The high frequency noise filtering is performed with Si resonant mirrors in the laser cavity. A 30 million Q factor Si3N4 resonator is used with electrical feedback to reduce close in noise and frequency walk off. The laser shows high frequency noise levels of 60x103 Hz2/Hz corresponding to 160 kHz linewidth, and the low frequency noise is suppressed 33 dB to 103 Hz2/Hz with the PDH system.

  8. (1)H, (13)C, and (15)N backbone resonance assignments of the full-length 40 kDa S. acidocaldarius Y-family DNA polymerase, dinB homolog.

    PubMed

    Moro, Sean L; Cocco, Melanie J

    2015-10-01

    The dinB homolog (Dbh) is a member of the Y-family of translesion DNA polymerases, which are specialized to accurately replicate DNA across from a wide variety of lesions in living cells. Lesioned bases block the progression of high-fidelity polymerases and cause detrimental replication fork stalling; Y-family polymerases can bypass these lesions. The active site of the translesion synthesis polymerase is more open than that of a replicative polymerase; consequently Dbh polymerizes with low fidelity. Bypass polymerases also have low processivity. Short extension past the lesion allows the high-fidelity polymerase to switch back onto the site of replication. Dbh and the other Y-family polymerases have been used as structural models to investigate the mechanisms of DNA polymerization and lesion bypass. Many high-resolution crystal structures of Y-family polymerases have been reported. NMR dynamics studies can complement these structures by providing a measure of protein motions. Here we report the (15)N, (1)H, and (13)C backbone resonance assignments at two temperatures (35 and 50 °C) for Sulfolobus acidocaldarius Dbh polymerase. Backbone resonance assignments have been obtained for 86 % of the residues. The polymerase active site is assigned as well as the majority of residues in each of the four domains. PMID:26154586

  9. Resonant oscillation modes of sympathetically cooled ions in a radio-frequency trap

    SciTech Connect

    Hasegawa, Taro; Shimizu, Tadao

    2002-12-01

    Sympathetic cooling of Ca{sup +}, Zn{sup +}, Sr{sup +}, Ba{sup +}, and Yb{sup +} as guest ions with laser-cooled {sup 24}Mg{sup +} as host ions in a rf ion trap is carried out, and resonant frequencies of their motion in the trap potential are measured. Various oscillation modes of the sympathetically cooled ions are observed. The resonant frequency of the oscillation mode is different from the frequency of either the collective oscillation frequency of the trapped ions or the oscillation frequency of each ion without host ions. This difference is well explained by a theoretical model in which coupled equations of motion of the host ion cloud with a single guest ion are considered.

  10. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    NASA Astrophysics Data System (ADS)

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-01

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.

  11. Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge

    SciTech Connect

    Hu, M.; Bai, Y. Z. Zhou, Z. B. Li, Z. X.; Luo, J.

    2014-05-15

    The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided.

  12. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    SciTech Connect

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-15

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

  13. Nanoscale Subsurface Imaging of Nanocomposites via Resonant Difference-Frequency Atomic Force Ultrasonic Microscopy

    NASA Technical Reports Server (NTRS)

    Cantrell, Sean A.; Cantrell, John H.; Lillehei, Peter T.

    2007-01-01

    A scanning probe microscope methodology, called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), has been developed. The method employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope engages the sample top surface. The cantilever is driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave at the sample surface generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create amplitude and phase-generated images of nanoscale near-surface and subsurface features. RDF-AFUM phase images of LaRC-CP2 polyimide polymer containing embedded nanostructures are presented. A RDF-AFUM micrograph of a 12.7 micrometer thick film of LaRC-CP2 containing a monolayer of gold nanoparticles embedded 7 micrometers below the specimen surface reveals the occurrence of contiguous amorphous and crystalline phases within the bulk of the polymer and a preferential growth of the crystalline phase in the vicinity of the gold nanoparticles. A RDF-AFUM micrograph of LaRC-CP2 film containing randomly dispersed carbon nanotubes reveals the growth of an interphase region at certain nanotube-polymer interfaces.

  14. Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge

    NASA Astrophysics Data System (ADS)

    Hu, M.; Bai, Y. Z.; Zhou, Z. B.; Li, Z. X.; Luo, J.

    2014-05-01

    The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided.

  15. Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge.

    PubMed

    Hu, M; Bai, Y Z; Zhou, Z B; Li, Z X; Luo, J

    2014-05-01

    The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided. PMID:24880402

  16. Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies

    PubMed Central

    Wang, Ren; Wang, Bing-Zhong; Gong, Zhi-Shuang; Ding, Xiao

    2015-01-01

    A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green’s function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments. PMID:26053074

  17. A model for precalculus students to determine the resonance frequency of a trumpet mouthpiece

    NASA Astrophysics Data System (ADS)

    Chapman, Robert C.

    2001-05-01

    The trumpet mouthpiece as a Helmholtz resonator is used to show precalculus students a mathematical model for determining the approximate resonance frequency of the mouthpiece. The mathematics is limited to algebra and trigonometry. Using a system of mouthpieces that have interchangeable cups and backbores, students are introduced to the acoustics of this resonator. By gathering data on 51 different configurations of mouthpieces, the author modifies the existing Helmholtz resonator equation to account for both cup volumes and backbore configurations. Students then use this model for frequency predictions. Included are how to measure the different physical attributes of a trumpet mouthpiece at minimal cost. This includes methods for measuring cup volume, backbore volume, backbore length, throat area, etc. A portion of this phase is de-signed for students to become acquainted with some of the vocabulary of acoustics and the physics of sound.

  18. Enhancing the low frequency THz resonances (< 1 THz) of organic molecules via electronegative atom substitution

    NASA Astrophysics Data System (ADS)

    Dash, Jyotirmayee; Ray, Shaumik; Pesala, Bala

    2015-03-01

    Terahertz (THz) technology is an active area of research with various applications in non-intrusive imaging and spectroscopy. Very few organic molecules have significant resonances below 1 THz. Understanding the origin of low frequency THz modes in these molecules and their absence in other molecules could be extremely important in design and engineering molecules with low frequency THz resonances. These engineered molecules can be used as THz tags for anti-counterfeiting applications. Studies show that low frequency THz resonances are commonly observed in molecules having higher molecular mass and weak intermolecular hydrogen bonds. In this paper, we have explored the possibility of enhancing the strength of THz resonances below 1 THz through electronegative atom substitution. Adding an electronegative atom helps in achieving higher hydrogen bond strength to enhance the resonances below 1 THz. Here acetanilide has been used as a model system. THz-Time Domain Spectroscopy (THz-TDS) results show that acetanilide has a small peak observed below 1 THz. Acetanilide can be converted to 2-fluoroacetanilide by adding an electronegative atom, fluorine, which doesn't have any prominent peak below 1 THz. However, by optimally choosing the position of the electronegative atom as in 4-fluoroacetanilide, a significant THz resonance at 0.86 THz is observed. The origin of low frequency resonances can be understood by carrying out Density Functional Theory (DFT) simulations of full crystal structure. These studies show that adding an electronegative atom to the organic molecules at an optimized position can result in significantly enhanced resonances below 1 THz.

  19. Selective engineering of cavity resonance for frequency matching in optical parametric processes

    SciTech Connect

    Lu, Xiyuan; Rogers, Steven; Jiang, Wei C.; Lin, Qiang

    2014-10-13

    We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.

  20. High-power 467-nm passively locked signal-resonant sum-frequency laser

    SciTech Connect

    Wigley, P.G.; Zhang, Q.; Miesak, E.; Dixon, G.J.

    1995-12-01

    We have generated more than 120 mW of TEM{sub 00} radiation at 467 nm by summing the resonantly enhanced output of an 845-nm GaAlAs tapered semiconductor amplifier with the intracavity field of a 1047-nm diode-pumped Nd:YLF laser, using a KTP crystal. Optical feedback was used to lock the frequency of the tapered amplifier to a cavity resonance. {copyright} {ital 1995 Optical Society of America.}

  1. Selective engineering of cavity resonance for frequency matching in optical parametric processes

    NASA Astrophysics Data System (ADS)

    Lu, Xiyuan; Rogers, Steven; Jiang, Wei C.; Lin, Qiang

    2014-10-01

    We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.

  2. Decrease of the first Schumann resonance frequency during solar proton events

    NASA Astrophysics Data System (ADS)

    Roldugin, V. C.; Maltsev, Y. P.; Petrova, G. A.; Vasiljev, A. N.

    2001-09-01

    The variations of the first-order Schumann resonance frequency in Kola peninsula are studied for four solar proton events on November 4 and 6, 1997 and on May 2 and May 6, 1998. It is found that the frequency decrease by about 0.15 Hz during the peaks of the proton penetrations. Such a decrease is in agreement with modeling calculations. A very intensive solar X ray burst preceding the proton flare on November 6 caused an increase of the resonance frequency. The decrease of amplitude about of 0.2 pT and the decrease of the resonance bandwidth about of 0.2 Hz are observed in the November events.

  3. Cellular-foam polypropylene ferroelectrets with increased film thickness and reduced resonance frequency

    NASA Astrophysics Data System (ADS)

    Sborikas, Martynas; Wegener, Michael

    2013-12-01

    Ferroelectrets are piezoelectric materials suitable for acoustic applications such as airborne ultrasonic transducers. Typical ferroelectrets exhibit resonance frequencies in the high kHz to low MHz range. In order to decrease the transducer resonance frequencies to the low kHz range, processes such as gas-diffusion expansion and electric charging were adjusted to cellular films which are initially twice as thick as in earlier studies. The demonstrated film expansion and electric charging lead to mechanically soft cellular structures which show high piezoelectric activities with coefficients up to 130 pC/N. Due to the simultaneously increased film thicknesses, the resonance frequencies are lowered down to about 233 kHz.

  4. Evaluation of acetabular cup initial fixation by using resonance frequency principle.

    PubMed

    Henys, Petr; Capek, Lukas; Fencl, Jaroslav; Prochazka, Egon

    2015-01-01

    The clinical practice shows that the loosening of acetabular cups is more frequent than stem loosening. With standard cups, the incidence of dislocation failure is highest in the first year after arthroplasty implantation. The aim of the study was to quantitatively evaluate the implant-bone stability of a cementless acetabular cup prosthesis by using a device based on resonance frequency analysis. The evaluation of this device was done by finite element analysis and in vitro experiments. It was shown that not all the resonance frequencies can be measured by our device. The resonance frequencies vary within the range of 500-3000 Hz. The proposed power spectrum measurement gives the information about the absolute stiffness of the press-fit implant. PMID:25655952

  5. Estimation of Resonant Frequency of a Circular Microstrip Antenna Using Artificial Neural Network

    NASA Astrophysics Data System (ADS)

    Singh, Jagtar; Singh, A. P.; Kamal, T. S.

    2012-03-01

    In recent years the art of using artificial neural networks for wireless communication engineers has been gaining momentum. In this paper a general procedure is suggested for estimating the resonant frequency of circular microstrip patch antenna using artificial neural networks. The method of moments (MOM) based IE3D software was used to generate data dictionary for training and validation set of ANN. The proposed technique uses multilayer feed-forward back-propagation artificial neural network with one hidden layers for estimating the resonant frequency of a circular microstrip antenna. A relative performance of the different training algorithms is carried out for estimating the resonant frequency with particular attention paid to the speed of computation and accuracy achieved. This type of performance comparison has not been attempted so far.

  6. Non-contact excitation of fundamental resonance frequencies of an asphalt concrete specimen

    NASA Astrophysics Data System (ADS)

    Gudmarsson, Anders; Ryden, Nils; Birgisson, Björn

    2015-03-01

    Impact hammer and non-contact speaker excitation were applied to an asphalt concrete, a PVC-U and a concrete specimen to measure the fundamental longitudinal resonance frequency at different strain levels. The impact and the noncontact excitation methods resulted in similar resonance frequencies for the undamaged asphalt concrete and for the PVC-U specimen. However, the two excitation approaches gave different results for the concrete specimen, which was shown to have a nonlinear response to increasing strain levels. A reduction and a following recovery of the resonance frequency of the asphalt concrete were shown after the specimen was exposed to a small amount of damage. However, no fast nonlinear dynamics were observed for the asphalt concrete through the speaker measurements.

  7. Theory and experiment on resonant frequencies of liquid-air interfaces trapped in microfluidic devices

    NASA Astrophysics Data System (ADS)

    Chindam, Chandraprakash; Nama, Nitesh; Ian Lapsley, Michael; Costanzo, Francesco; Jun Huang, Tony

    2013-11-01

    Bubble-based microfluidic devices have been proven to be useful for many biological and chemical studies. These bubble-based microdevices are particularly useful when operated at the trapped bubbles' resonance frequencies. In this work, we present an analytical expression that can be used to predict the resonant frequency of a bubble trapped over an arbitrary shape. Also, the effect of viscosity on the dispersion characteristics of trapped bubbles is determined. A good agreement between experimental data and theoretical results is observed for resonant frequency of bubbles trapped over different-sized rectangular-shaped structures, indicating that our expression can be valuable in determining optimized operational parameters for many bubble-based microfluidic devices. Furthermore, we provide a close estimate for the harmonics and a method to determine the dispersion characteristics of a bubble trapped over circular shapes. Finally, we present a new method to predict fluid properties in microfluidic devices and complement the explanation of acoustic microstreaming.

  8. Frequency stabilization of spin-torque-driven oscillations by coupling with a magnetic nonlinear resonator

    SciTech Connect

    Kudo, Kiwamu Suto, Hirofumi; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie

    2014-10-28

    The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.

  9. Magnetic Earth Ionosphere Resonant Frequencies (NASA-MEIRF Project)

    NASA Technical Reports Server (NTRS)

    1994-01-01

    During this current reporting period, the project has focused on completing Phase 1 of the field monitoring work and documenting research results. Highlights of these efforts include presentations of papers at the annual joint meeting of the American Physical Society/American Association of Physics Teachers, April 18-22, 1994, in Crystal City, Virginia, and at the International Space, Time, and Gravitation Conference and Etoiles de L'Ecole Polytechnique Symposium, May 23-28, 1994, in St. Petersburg, Russia. Field measurements of the background ultra low frequency (ULF) electromagnetic spectrum in the New Mexico and Texas regions show interesting differences. Included are papers entitled 'Triplet Solution of the Twin Paradox' and 'Classical Electron Mass and Fields, Part 3.'

  10. 1/f frequency noise of 2-GHZ high-Q thin-film sapphire resonators.

    PubMed

    Ferre-Pikal, E S; Delgado Arámburo, M C; Walls, F L; Lakin, K M

    2001-03-01

    We present experimental results on intrinsic 1/f frequency modulation (FM) noise in high-overtone thin-film sapphire resonators that operate at 2 GHz. The resonators exhibit several high-Q resonant modes approximately 100 kHz apart, which repeat every 13 MHz. A loaded Q of approximately 20,000 was estimated from the phase response. The results show that the FM noise of the resonators varied between Sy (10 Hz) = -202 dB relative (rel) to 1/Hz and -210 dB rel to 1/Hz. The equivalent phase modulation (PM) noise of an oscillator using these resonators (assuming a noiseless amplifier) would range from [symbol: see text](10 Hz) = -39 to -47 dBc/Hz. PMID:11370364

  11. The determination of Schumann resonance mode frequencies using iterative procedure of complex demodulation

    NASA Astrophysics Data System (ADS)

    Ondrášková, Adriena; Ševčík, Sebastian

    2013-12-01

    The more precise determination of instantaneous peak frequency of Schumann resonance (SR) modes, especially based on relatively short signal sequences, seems to be important for detailed analysis of SR modal frequencies variations. Contrary to commonly used method of obtaining modal frequencies by Lorentzian fitting of DFT spectra, the attempt was made to employ the complex demodulation method in iterated form. The results for SR signals contaminated with low-frequency noise and hum in various degree as well as the comparison with standard method are presented. Real signals of vertical electric field component picked up at the Astronomical and Geophysical Observatory of Comenius University at Modra, Slovakia, were the primary sources.

  12. Piezoelectrically tunable resonance frequency beam utilizing a stress-sensitive film

    DOEpatents

    Thundat, Thomas G.; Wachter, Eric A.

    2002-01-01

    Methods and apparatus for detecting particular frequencies of acoustic vibration utilize a piezoelectrically-tunable beam element having a piezoelectric layer and a stress sensitive layer and means for providing an electrical potential across the piezoelectric layer to controllably change the beam's stiffness and thereby change its resonance frequency. It is then determined from the response of the piezoelectrically-tunable beam element to the acoustical vibration to which the beam element is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.

  13. Radio frequency spectral characterization and model parameters extraction of high Q optical resonators.

    PubMed

    Abdallah, Zeina; Boucher, Yann G; Fernandez, Arnaud; Balac, Stéphane; Llopis, Olivier

    2016-01-01

    A microwave domain characterization approach is proposed to determine the properties of high quality factor optical resonators. This approach features a very high precision in frequency and aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing an optical resonator using a microwave vector network analyzer. It is able to discriminate between the different coupling regimes, from the under-coupling to the selective amplification, and it is used together with a model from which the main resonator parameters are extracted, i.e. coupling factor, intrinsic losses, phase slope, intrinsic and external quality factor. PMID:27251460

  14. Radio frequency spectral characterization and model parameters extraction of high Q optical resonators

    PubMed Central

    Abdallah, Zeina; Boucher, Yann G.; Fernandez, Arnaud; Balac, Stéphane; Llopis, Olivier

    2016-01-01

    A microwave domain characterization approach is proposed to determine the properties of high quality factor optical resonators. This approach features a very high precision in frequency and aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing an optical resonator using a microwave vector network analyzer. It is able to discriminate between the different coupling regimes, from the under-coupling to the selective amplification, and it is used together with a model from which the main resonator parameters are extracted, i.e. coupling factor, intrinsic losses, phase slope, intrinsic and external quality factor. PMID:27251460

  15. Radio frequency spectral characterization and model parameters extraction of high Q optical resonators

    NASA Astrophysics Data System (ADS)

    Abdallah, Zeina; Boucher, Yann G.; Fernandez, Arnaud; Balac, Stéphane; Llopis, Olivier

    2016-06-01

    A microwave domain characterization approach is proposed to determine the properties of high quality factor optical resonators. This approach features a very high precision in frequency and aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing an optical resonator using a microwave vector network analyzer. It is able to discriminate between the different coupling regimes, from the under-coupling to the selective amplification, and it is used together with a model from which the main resonator parameters are extracted, i.e. coupling factor, intrinsic losses, phase slope, intrinsic and external quality factor.

  16. Registration of Alfven resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

    SciTech Connect

    Ruchko, L. F.; Elfimov, A. G.; Teixeira, C. M.; Elizondo, J. I.; Sanada, E.; Galvao, R. M. O.; Manso, M. E.; Silva, A.

    2011-02-15

    A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfven wave (LAW) excitation in the Tokamak Chauffage Alfven Bresilien (TCABR) at the frequency f{sub A}= 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the ''beat'' frequency f{sub B}, is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f=f{sub A}{+-}f{sub B}. This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.

  17. Resonance of Gaussian Electromagnetic Field to the High Frequency Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Li, Jin; Zhang, Lu; Lin, Kai; Wen, Hao

    2016-08-01

    We consider a Gaussian Beam (GB) resonant system for high frequency gravitational waves (HFGWs) detection. At present, we find the optimal signal strength in theory through setting the magnetic component of GB in a standard gaussian form. Under the synchro-resonance condition, we study the signal strength (i.e., transverse perturbative photon fluxes) from the relic HFGWs (predicted by ordinary inflationary model) and the braneworld HFGWs (from braneworld scenarios). Both of them would generate potentially detectable transverse perturbative photon fluxes (PPFs). Furthermore we find optimal system parameters and the relationship between frequency and effective width of energy fluxes accumulation.

  18. Experimental determination of resonant frequencies by transient scattering from conducting spheres and cylinders

    NASA Astrophysics Data System (ADS)

    Tseng, F.-I.; Sarkar, T. K.

    1984-09-01

    A new experimental technique to measure resonant frequencies of a target is presented. A Tektronix WP 1310 waveform processing system has been employed, which features signal processing software with extensive control over instruments, waveform manipulations, and graphic display. Numerous transient waveforms scattered from spheres and cylinders of various sizes have been recorded. A recently developed data-processing technique has been described and applied to these transient waveforms to extract their resonant frequencies. With the use of a new window designed to have a low near-sidelobe level, the modified fast Fourier transform (FFT) is shown to be able to improve the measurement capability of the system.

  19. A silicon photonics circuit based on micro-ring resonators in the instantaneous frequency measurement system

    NASA Astrophysics Data System (ADS)

    Wang, Wanjun; Zhou, Jie; Wang, Jun; Feng, Junbo; Guo, Jin

    2015-10-01

    In this paper, a compact silicon photonics circuit is proposed. It consists of add-drop filter, input/output grating coupler. The resonance peak of add-drop filter can be tuned with the assist of p-i-n diode. The unknown frequency of microwave is loaded at the optical wave and coupled into the chip. The optical power ratio of through port and drop port is monotonous, which is corresponding to the unknown frequency. Meanwhile, the resonance peak of the ring can shift with the assist of p-i-n diode.

  20. Five-mode frequency spectra of x3-dependent modes in AT-cut quartz resonators.

    PubMed

    Chen, Guijia; Wu, Rongxing; Wang, Ji; Du, Jianke; Yang, Jiashi

    2012-04-01

    We study straight-crested waves and vibration modes with variations along the x(3) direction only in an AT-cut quartz plate resonator near the operating frequency of the fundamental thickness-shear mode. Mindlin's two-dimensional equations for anisotropic crystal plates are used. Dispersion relations and frequency spectra of the five relevant waves are obtained. It is found that, to avoid unwanted couplings between the resonator operating mode and other undesirable modes, in addition to certain known values of the plate length/thickness ratio that need to be avoided, an additional series of discrete values of the plate length/thickness ratio also must be excluded. PMID:22547292

  1. Resonance of Gaussian Electromagnetic Field to the High Frequency Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Li, Jin; Zhang, Lu; Lin, Kai; Wen, Hao

    2016-04-01

    We consider a Gaussian Beam (GB) resonant system for high frequency gravitational waves (HFGWs) detection. At present, we find the optimal signal strength in theory through setting the magnetic component of GB in a standard gaussian form. Under the synchro-resonance condition, we study the signal strength (i.e., transverse perturbative photon fluxes) from the relic HFGWs (predicted by ordinary inflationary model) and the braneworld HFGWs (from braneworld scenarios). Both of them would generate potentially detectable transverse perturbative photon fluxes (PPFs). Furthermore we find optimal system parameters and the relationship between frequency and effective width of energy fluxes accumulation.

  2. Tissue specific resonance frequencies of water and metabolites within the human brain

    NASA Astrophysics Data System (ADS)

    Chadzynski, Grzegorz L.; Bender, Benjamin; Groeger, Adriane; Erb, Michael; Klose, Uwe

    2011-09-01

    Chemical shift imaging (CSI) without water suppression was used to examine tissue-specific resonance frequencies of water and metabolites within the human brain. The aim was to verify if there are any regional differences in those frequencies and to determine the influence of chemical shift displacement in slice-selection direction. Unsuppressed spectra were acquired at 3 T from nine subjects. Resonance frequencies of water and after water signal removal of total choline, total creatine and NAA were estimated. Furthermore, frequency distances between the water and those resonances were calculated. Results were corrected for chemical shift displacement. Frequency distances between water and metabolites were consistent and greater for GM than for WM. The highest value of WM to GM difference (14 ppb) was observed for water to NAA frequency distance. This study demonstrates that there are tissue-specific differences between frequency distances of water and metabolites. Moreover, the influence of chemical shift displacement in slice-selection direction is showed to be negligible.

  3. Temperature Drift Compensation for Hemispherical Resonator Gyro Based on Natural Frequency

    PubMed Central

    Wang, Xu; Wu, Wenqi; Fang, Zhen; Luo, Bing; Li, Yun; Jiang, Qingan

    2012-01-01

    Temperature changes have a strong effect on Hemispherical Resonator Gyro (HRG) output; therefore, it is of vital importance to observe their influence and then make necessary compensations. In this paper, a temperature compensation model for HRG based on the natural frequency of the resonator is established and then temperature drift compensations are accomplished. To begin with, a math model of the relationship between the temperature and the natural frequency of HRG is set up. Then, the math model is written into a Taylor expansion expression and the expansion coefficients are calibrated through temperature experiments. The experimental results show that the frequency changes correspond to temperature changes and each temperature only corresponds to one natural frequency, so the output of HRG can be compensated through the natural frequency of the resonator instead of the temperature itself. As a result, compensations are made for the output drift of HRG based on natural frequency through a stepwise linear regression method. The compensation results show that temperature-frequency method is valid and suitable for the gyroscope drift compensation, which would ensure HRG's application in a larger temperature range in the future. PMID:22778651

  4. Heme Orientation of Cavity Mutant Hemoglobins (His F8 → Gly) in Either α or β Subunits: Circular Dichroism, (1) H NMR, and Resonance Raman Studies.

    PubMed

    Nagai, Masako; Nagai, Yukifumi; Aki, Yayoi; Sakurai, Hiroshi; Mizusawa, Naoki; Ogura, Takashi; Kitagawa, Teizo; Yamamoto, Yasuhiko; Nagatomo, Shigenori

    2016-08-01

    Native human adult hemoglobin (Hb A) has mostly normal orientation of heme, whereas recombinant Hb A (rHb A) expressed in E. coli contains both normal and reversed orientations of heme. Hb A with the normal heme exhibits positive circular dichroism (CD) bands at both the Soret and 260-nm regions, while rHb A with the reversed heme shows a negative Soret and decreased 260-nm CD bands. In order to examine involvement of the proximal histidine (His F8) of either α or β subunits in determining the heme orientation, we prepared two cavity mutant Hbs, rHb(αH87G) and rHb(βH92G), with substitution of glycine for His F8 in the presence of imidazole. CD spectra of both cavity mutant Hbs did not show a negative Soret band, but instead exhibited positive bands with strong intensity at the both Soret and 260-nm regions, suggesting that the reversed heme scarcely exists in the cavity mutant Hbs. We confirmed by (1) H NMR and resonance Raman (RR) spectroscopies that the cavity mutant Hbs have mainly the normal heme orientation in both the mutated and native subunits. These results indicate that the heme Fe-His F8 linkage in both α and β subunits influences the heme orientation, and that the heme orientation of one type of subunit is related to the heme orientation of the complementary subunits to be the same. The present study showed that CD and RR spectroscopies also provided powerful tools for the examination of the heme rotational disorder of Hb A, in addition to the usual (1) H NMR technique. Chirality 28:585-592, 2016. © 2016 Wiley Periodicals, Inc. PMID:27427792

  5. U1h Superstructure

    SciTech Connect

    Glen Sykes

    2000-11-01

    The U1H Shaft Project is a design build subcontract to supply the U. S. Department of Energy (DOE) a 1,045 ft. deep, 20 ft. diameter, concrete lined shaft for unspecified purposes. The subcontract awarded to Atkinson Construction by Bechtel Nevada to design and construct the shaft for the DOE has been split into phases with portions of the work being released as dictated by available funding. The first portion released included the design for the shaft, permanent hoist, headframe, and collar arrangement. The second release consisted of constructing the shaft collar to a depth of 110 ft., the service entry, utility trenches, and installation of the temporary sinking plant. The temporary sinking plant included the installation of the sinking headframe, the sinking hoist, two deck winches, the shaft form, the sinking work deck, and temporary utilities required to sink the shaft. Both the design and collar construction were completed on schedule. The third release consisted of excavating and lining the shaft to the station depth of approximately 950 feet. Work is currently proceeding on this production sinking phase. At a depth of approximately 600 feet, Atkinson has surpassed production expectation and is more than 3 months ahead of schedule. Atkinson has employed the use of a Bobcat 331 excavator as the primary means of excavation. the shaft is being excavated entirely in an alluvial deposit with varying degrees of calcium carbonate cementation. Several more work packages are expected to be released in the near future. The remaining work packages include, construction of the shaft station a depth of 975 ft. and construction of the shaft sump to a depth of 1,045 ft., installation of the loading pocket and station steel and equipment, installation of the shaft steel and guides, installation of the shaft utilities, and installation of the permanent headframe, hoist, collar utilities, and facilities.

  6. Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region

    NASA Astrophysics Data System (ADS)

    Tripathi, Saroj R.; Miyata, Eisuke; Ishai, Paul Ben; Kawase, Kodo

    2015-03-01

    It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 +/- 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings.

  7. Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region

    PubMed Central

    Tripathi, Saroj R.; Miyata, Eisuke; Ishai, Paul Ben; Kawase, Kodo

    2015-01-01

    It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 ± 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings. PMID:25766116

  8. High-frequency voltage-controlled-oscillator for use with inverted- mesa quartz resonators

    SciTech Connect

    Wessendorf, K.O.

    1996-08-01

    An oscillator circuit has been developed that uses inverted mesa resonators, in a high precision VCO application, at frequencies historically dominated by SAW designs. This design incorporates a frequency tripler that provides a 600 MHz output capability using a 200 MHz 3{sup rd} overtone resonator. This design has advantages over equivalent SAW alternatives: lower power consumption, superior aging characteristics, linear frequency pulling and low frequency versus temperature sensitivity. The VCO presented demonstrates {gt} +/- 60 ppm pullability (0 to 7V control), tuning linearity better than +/- 5% with phase noise at 1 kHz {lt} -110 DBc/Hz. this oscillator- tripler exploits the nonlinear characteristics of an emitter-coupled pair differential amplifier to obtain a high performance oscillator design.

  9. Stabilization of a laser on a large-detuned atomic-reference frequency by resonant interferometry

    NASA Astrophysics Data System (ADS)

    Barboza, Priscila M. T.; Nascimento, Guilherme G.; Araújo, Michelle O.; da Silva, Cícero M.; Cavalcante, Hugo L. D. de S.; Oriá, Marcos; Chevrollier, Martine; Passerat de Silans, Thierry

    2016-04-01

    We report a simple technique for stabilization of a laser frequency at the wings of an atomic resonance. The reference signal used for stabilization issues from interference effects obtained in a low-quality cavity filled with a resonant atomic vapour. For a frequency detuned 2.6 GHz from the 133Cs D2 6S{}1/2 F = 4 to 6P{}3/2 F’ = 5 transition, the fractional frequency Allan deviation is 10-8 for averaging times of 300 s, corresponding to a frequency deviation of 4 MHz. Adequate choice of the atomic density and of the cell thickness allows locking the laser at detunings larger than 10 GHz. Such a simple technique does not require magnetic fields or signal modulation.

  10. Resonance Assisted Synchronization of Coupled Oscillators: Frequency Locking without Phase Locking

    NASA Astrophysics Data System (ADS)

    Thévenin, J.; Romanelli, M.; Vallet, M.; Brunel, M.; Erneux, T.

    2011-09-01

    Frequency locking without phase locking of two coupled nonlinear oscillators is experimentally demonstrated. This synchronization regime is found for two coupled laser modes, beyond the phase-locking range fixed by Adler’s equation, because of a resonance mechanism. Specifically, we show that the amplitudes of the two modes exhibit strong fluctuations that produce average frequency synchronization, even if the instantaneous phases are unlocked. The experimental results are in good agreement with a theoretical model.

  11. Analysis of glass-reinforced epoxy material for radio frequency resonator.

    PubMed

    Zaman, M R; Islam, M T; Misran, N; Yatim, Baharudin

    2014-01-01

    A radio frequency (RF) resonator using glass-reinforced epoxy material for C and X band is proposed in this paper. Microstrip line technology for RF over glass-reinforced epoxy material is analyzed. Coupling mechanism over RF material and parasitic coupling performance is explained utilizing even and odd mode impedance with relevant equivalent circuit. Babinet's principle is deployed to explicate the circular slot ground plane of the proposed resonator. The resonator is designed over four materials from different backgrounds which are glass-reinforced epoxy, polyester, gallium arsenide (GaAs), and rogers RO 4350B. Parametric studies and optimization algorithm are applied over the geometry of the microstrip resonator to achieve dual band response for C and X band. Resonator behaviors for different materials are concluded and compared for the same structure. The final design is fabricated over glass-reinforced epoxy material. The fabricated resonator shows a maximum directivity of 5.65 dBi and 6.62 dBi at 5.84 GHz and 8.16 GHz, respectively. The lowest resonance response is less than -20 dB for C band and -34 dB for X band. The resonator is prototyped using LPKF (S63) drilling machine to study the material behavior. PMID:24977230

  12. Analysis of Glass-Reinforced Epoxy Material for Radio Frequency Resonator

    PubMed Central

    Islam, M. T.; Misran, N.; Yatim, Baharudin

    2014-01-01

    A radio frequency (RF) resonator using glass-reinforced epoxy material for C and X band is proposed in this paper. Microstrip line technology for RF over glass-reinforced epoxy material is analyzed. Coupling mechanism over RF material and parasitic coupling performance is explained utilizing even and odd mode impedance with relevant equivalent circuit. Babinet's principle is deployed to explicate the circular slot ground plane of the proposed resonator. The resonator is designed over four materials from different backgrounds which are glass-reinforced epoxy, polyester, gallium arsenide (GaAs), and rogers RO 4350B. Parametric studies and optimization algorithm are applied over the geometry of the microstrip resonator to achieve dual band response for C and X band. Resonator behaviors for different materials are concluded and compared for the same structure. The final design is fabricated over glass-reinforced epoxy material. The fabricated resonator shows a maximum directivity of 5.65 dBi and 6.62 dBi at 5.84 GHz and 8.16 GHz, respectively. The lowest resonance response is less than −20 dB for C band and −34 dB for X band. The resonator is prototyped using LPKF (S63) drilling machine to study the material behavior. PMID:24977230

  13. Resonance frequency and mass identification of zeptogram-scale nanosensor based on the nonlocal beam theory.

    PubMed

    Li, Xian-Fang; Tang, Guo-Jin; Shen, Zhi-Bin; Lee, Kang Yong

    2015-01-01

    Free vibration and mass detection of carbon nanotube-based sensors are studied in this paper. Since the mechanical properties of carbon nanotubes possess a size effect, the nonlocal beam model is used to characterize flexural vibration of nanosensors carrying a concentrated nanoparticle, where the size effect is reflected by a nonlocal parameter. For nanocantilever or bridged sensor, frequency equations are derived when a nanoparticle is carried at the free end or the middle, respectively. Exact resonance frequencies are numerically determined for clamped-free, simply-supported, and clamped-clamped resonators. Alternative approximations of fundamental frequency are given in closed form within the relative error less than 0.4%, 0.6%, and 1.4% for cantilever, simply-supported, and bridged sensors, respectively. Mass identification formulae are derived in terms of the frequency shift. Identified masses via the present approach coincide with those using the molecular mechanics approach and reach as low as 10(-24)kg. The obtained results indicate that the nonlocal effect decreases the resonance frequency except for the fundamental frequency of nanocantilever sensor. These results are helpful to the design of micro/nanomechanical zeptogram-scale biosensor. PMID:25149195

  14. General model with experimental validation of electrical resonant frequency tuning of electromagnetic vibration energy harvesters

    NASA Astrophysics Data System (ADS)

    Zhu, Dibin; Roberts, Stephen; Mouille, Thomas; Tudor, Michael J.; Beeby, Stephen P.

    2012-10-01

    This paper presents a general model and its experimental validation for electrically tunable electromagnetic energy harvesters. Electrical tuning relies on the adjustment of the electrical load so that the maximum output power of the energy harvester occurs at a frequency which is different from the mechanical resonant frequency of the energy harvester. Theoretical analysis shows that for this approach to be feasible the electromagnetic vibration energy harvester’s coupling factor must be maximized so that its resonant frequency can be tuned with the minimum decrease of output power. Two different-sized electromagnetic energy harvesters were built and tested to validate the model. Experimentally, the micro-scale energy harvester has a coupling factor of 0.0035 and an untuned resonant frequency of 70.05 Hz. When excited at 30 mg, it was tuned by 0.23 Hz by changing its capacitive load from 0 to 4000 nF its effective tuning range is 0.15 Hz for a capacitive load variation from 0 to 1500 nF. The macro-scale energy harvester has a coupling factor of 552.25 and an untuned resonant frequency of 95.1 Hz and 95.5 Hz when excited at 10 mg and 25 mg, respectively. When excited at 10 mg, it was tuned by 3.8 Hz by changing its capacitive load from 0 to 1400 nF it has an effective tuning range of 3.5 Hz for a capacitive load variation from 0 to 1200 nF. When excited at 25 mg, its resonant frequency was tuned by 4.2 Hz by changing its capacitive load from 0 to 1400 nF it has an effective tuning range of about 5 Hz. Experimental results were found to agree with the theoretical analysis to within 10%.

  15. Adsorption induced differential surface stress versus adsorption induced resonance frequency change: a comparison

    NASA Astrophysics Data System (ADS)

    Amirola, J.; Rodriguez, A.; Castaner, L.; Lozano, J.; Gutierrez, F. J.; Horrillo, M. C.

    2005-07-01

    In order to compare their gas sensing properties two kinds of sensors based on silicon cantilevers of similar characteristics have been fabricated: On one side we fabricated gravimetric gas sensors based on silicon cantilevers acting as resonators. The active layers consisted of polymer films deposited on top of the cantilevers. Sensors were maintained oscillating at their natural resonance frequency with electronic circuitry also developed in this work. Basically they consist of mass-spring mechanical resonators in which the mass increment due to gas sorption in the polymer provokes a shift on the resonance frequency. The output signal is a sinusoidal voltage extracted directly from the oscillator, and the amount of gas absorbed is related to the frequency of this output signal. The second type of sensors consisted of capacitors in which one electrode is a silicon cantilever and the other is a fixed metallic electrode fabricated parallel to the silicon cantilever. The silicon cantilever of these devices is covered with the same polymer films as for the resonators. The sensing principle in this case relies on the bending produced by the internal mechanical stress induced by the absorption of the gas in the polymeric layer. In these devices the signal is obtained by measuring the capacitance between the two plates of the capacitor, in this case the out coming signal was the current of the capacitor: an amplitude modulated signal. The gas response of both types of sensors have been characterized and a comparison is presented in this paper.

  16. Resonance frequencies and Young's modulus determination of magnetorheological elastomers using the photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Daniel Macias, J.; Ordonez-Miranda, J.; Alvarado-Gil, J. J.

    2012-12-01

    A simple and reliable methodology for determining the Young's modulus of magnetorheological elastomers is proposed based on the resonance frequencies of the amplitude of the photoacoustic signal. An explicit expression for the pressure changes within a photoacoustic cell, due to the thermal expansion of the air and the elastic bending of a clamped circular elastic membrane, is derived and analyzed. It is found that the resonance behavior of the amplitude of the photoacoustic signal is due to the contribution of the axial bending of its thickness. It is also shown that the Young's modulus of the membrane is proportional to its density, the square of its resonance frequencies and the fourth power of its radius, and inversely proportional to the square of its thickness. The application of the proposed approach to membranes made up of spherical microparticles of carbonyl iron powder embedded in a matrix of silicone rubber with weight concentrations of 0%, 5.2%, and 13.7% yields accurate and reproducible results, which are in good agreement with reported data in the literature. The highest accuracy on the measurement of the resonance frequencies and therefore on the Young's modulus is found for the first resonance peak. When a magnetic field is applied to the samples to modify their stiffness, it is observed that the Young's modulus increases with the magnetic field. This novel application of the photoacoustic technique opens the possibility of performing mechanical characterization of a broad diversity of magnetorheological membranes.

  17. Resonant modal group theory of membrane-type acoustical metamaterials for low-frequency sound attenuation

    NASA Astrophysics Data System (ADS)

    Ma, Fuyin; Wu, Jiu Hui; Huang, Meng

    2015-09-01

    In order to overcome the influence of the structural resonance on the continuous structures and obtain a lightweight thin-layer structure which can effectively isolate the low-frequency noises, an elastic membrane structure was proposed. In the low-frequency range below 500 Hz, the sound transmission loss (STL) of this membrane type structure is greatly higher than that of the current sound insulation material EVA (ethylene-vinyl acetate copo) of vehicle, so it is possible to replace the EVA by the membrane-type metamaterial structure in practice engineering. Based on the band structure, modal shapes, as well as the sound transmission simulation, the sound insulation mechanism of the designed membrane-type acoustic metamaterials was analyzed from a new perspective, which had been validated experimentally. It is suggested that in the frequency range above 200 Hz for this membrane-mass type structure, the sound insulation effect was principally not due to the low-level locally resonant mode of the mass block, but the continuous vertical resonant modes of the localized membrane. So based on such a physical property, a resonant modal group theory is initially proposed in this paper. In addition, the sound insulation mechanism of the membrane-type structure and thin plate structure were combined by the membrane/plate resonant theory.

  18. Identification of two cracks in a rod by minimal resonant and antiresonant frequency data

    NASA Astrophysics Data System (ADS)

    Rubio, Lourdes; Fernández-Sáez, José; Morassi, Antonino

    2015-08-01

    In this paper we consider the identification of two cracks of equal severity in a uniform free-free rod under longitudinal vibration. Each crack is simulated by a translational spring connecting the two adjacent segments of the rod and the cracks are considered to be small. We show that the inverse problem can be formulated and solved in terms of three frequency data only, corresponding to a suitable set of low resonant and antiresonant frequencies. Closed-form expressions of the damage parameters in terms of the measured frequency shifts are obtained. The paper improves existing results available in the literature, since the use of antiresonant frequencies allows us to exclude all the symmetrical crack locations occurring when only natural frequency are used as data. The analysis also explains why the use of high frequency data introduces spurious damage locations in the inverse problem solution. Numerical simulations show that if accurate input data are available then damage identification leads to satisfactory results.

  19. Resonant tectorial membrane motion in the inner ear: its crucial role in frequency tuning.

    PubMed Central

    Gummer, A W; Hemmert, W; Zenner, H P

    1996-01-01

    The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a parallel resonance between the mass of the tectorial membrane and the compliance of the stereocilia of the outer hair cells. Moreover, in combination with the contractile force of outer hair cells, it is proposed that inertial motion of the tectorial membrane provides the necessary conditions to allow positive feedback of mechanical energy into the cochlear partition, thereby amplifying and tuning the cochlear response. PMID:8710939

  20. EM localization for resonance frequency of pre-Cantor bar of higher stages

    NASA Astrophysics Data System (ADS)

    Kaino, K.; Obata, T.; Sonoda, J.; Kojo, J.

    2013-02-01

    Using the transmission-line theory, we investigate properties of wave propagation and resonance in a pre-Cantor multilayer called pre-Cantor bars whose interval is [0,L]. When the stage number n increases, the pre-Cantor bar will not transmit almost anywhere for ɛr2 > 1 where ɛr2 is the ratio of dielectric constants of two kinds of layers. For resonance frequencies of the n-th pre-Cantor bar, the largest amplitude of voltage at the midpoint of the bar, V(L/2), increases double-exponentially because of the inequality |V(L/2)|≤ɛr22n-2. For such a resonance frequency, the amplitude of the voltage at the midpoint of an interval [L/3k+1,2L/3k+1] is given by |V(L/2ṡ3k)|≤ɛr22n-k-2 where k = 1,2, ..., n - 1. Because the voltage |V(x)| is localized around x = L/2, the electro-magnetic wave (EM) localization occurs for the resonance frequencies of the pre-Cantor bar of the higher stages. Using a microstripline of the 3rd stage Cantor structure we will show that the measured transmission spectrum is consistent with the ideal one if the dissipation factor of the substrate is tan δ = 0.023 that is a typical value for the substrate of glassy epoxy resin in microwave frequencies.

  1. Frequency, Prognosis and Surgical Treatment of Structural Abnormalities Seen with Magnetic Resonance Imaging in Childhood Epilepsy

    ERIC Educational Resources Information Center

    Berg, Anne T.; Mathern, Gary W.; Bronen, Richard A.; Fulbright, Robert K.; DiMario, Francis; Testa, Francine M.; Levy, Susan R.

    2009-01-01

    The epidemiology of lesions identified by magnetic resonance imaging (MRI), along with the use of pre-surgical evaluations and surgery in childhood-onset epilepsy patients has not previously been described. In a prospectively identified community-based cohort of children enrolled from 1993 to 1997, we examined (i) the frequency of lesions…

  2. Negative effective mass density of acoustic metamaterial plate decorated with low frequency resonant pillars

    NASA Astrophysics Data System (ADS)

    Oudich, Mourad; Djafari-Rouhani, Bahram; Pennec, Yan; Assouar, M. Badreddine; Bonello, Bernard

    2014-11-01

    We investigate the elastic wave dispersion by a phononic metamaterial plate containing low frequency resonator stubs arranged periodically over the plate. We show that this system not only provides stop bands for wavelengths much larger than the periodicity but also displays negative behavior of its effective mass density under the homogenization assumption. A numerical method is used to calculate the plate's effective dynamic mass density as function of the frequency where the metamaterial is considered as homogeneous plate for these large wavelengths. Strong anisotropy of the effective mass density matrix is observed around the resonance frequencies where the gaps are opened. In these regions, we demonstrate that the effective matrix density components take negative values. For each of these components, the negative behavior is studied by taking into account the polarization of the involved resonant modes as well as their associated partial band gaps opened for each specific Lamb symmetry modes. We found that coupling between Lamb waves and resonant modes strongly affects the effective density of the whole plate especially in the coupling frequency regions of the gaps.

  3. A study of the high frequency limitations of series resonant converters

    NASA Technical Reports Server (NTRS)

    Stuart, T. A.; King, R. J.

    1982-01-01

    A transformer induced oscillation in series resonant (SR) converters is studied. It may occur in the discontinuous current mode. The source of the oscillation is an unexpected resonant circuit formed by normal resonance components in series with the magnetizing inductance of the output transformers. The methods for achieving cyclic stability are: to use a half bridge SR converter where q0.5. Q should be as close to 1.0 as possible. If 0.5q1.0, the instability will be avoided if psi2/3q-1/3. The second objective was to investigate a power field effect transistor (FET) version of the SR converter capable of operating at frequencies above 100 KHz, to study component stress and losses at various frequencies.

  4. High Frequency Resonant Ultrasound Spectroscopy to 50 MHz: Experimental Developments and Analytical Refinement

    NASA Astrophysics Data System (ADS)

    Yoneda, Akira; Aizawa, Yoshitaka; Rahman, Md. Mahbubar; Sakai, Shunsuke

    2007-12-01

    High-frequency transducers up to 50 MHz were developed for resonant ultrasound spectroscopy (RUS). The transducers were carefully designed as composites of high-Q (>100) and low-Q (<100) materials in order to be able to distinguish the resonant peaks of samples from the instrumental background. Combining the transducers with a high performance lock-in amplifier enabled us to conduct RUS of a specimen as small as ˜0.2 mm. One of the features of a lock-in amplifier is its ability to measure the phase of a resonance signal against the reference signal. We utilized this to subtract background noise and to decompose peaks that overlapped at a small frequency interval. The present experimental and analytical developments are useful for obtaining the elastic constants of high-pressure phases of minerals from sub millimeter single-crystal grains synthesized in a high-pressure apparatus.

  5. Nanoliter liquid characterization by open whispering-gallery mode dielectric resonators at millimeter wave frequencies

    NASA Astrophysics Data System (ADS)

    Shaforost, E. N.; Klein, N.; Vitusevich, S. A.; Offenhäusser, A.; Barannik, A. A.

    2008-10-01

    We present an approach for identification and concentration determination of liquids of pico to nanoliter volumes at a frequency of 35 GHz based on a whispering-gallery mode (WGM) dielectric resonator technique. A quasioptical coupling scheme based on dielectric image waveguides was employed to excite high-Q running wave WGMs with uniform azimuthal field distribution in cylindrical sapphire disks with quality factors up to 4×105 at room temperature. Measurement of the liquid induced changes in the resonator quality factor and resonance frequency has been performed for droplets down to 90 pl volume spotted at different positions on the surface of the sapphire disk. We have employed our method for concentration determination of ethanol, glucose, and albumin dissolved in water. Solutions with concentration values well below 10% could be clearly separated from pure water. Our method is promising for the characterization of biological liquids.

  6. Ab initio analysis of frequency selective surfaces based on conventional and complementary split ring resonators

    NASA Astrophysics Data System (ADS)

    Marqués, R.; Baena, J. D.; Beruete, M.; Falcone, F.; Lopetegi, T.; Sorolla, M.; Martín, F.; Garcia, J.

    2005-02-01

    Frequency selective surfaces (FSSs) made up of periodic arrays of split ring resonators (SRRs) are analysed. This analysis includes complementary screens, or complementary SRR-FSSs (CSRR-FSSs). It is shown that these FSSs show a dual behaviour, with a stop/pass band behaviour at the frequency of resonance of the SRRs/CSRRs. Cross-polarization effects in the SRR and the CSRR are considered, and it is shown that they permit resonance to occur for normally incident plane wave excitation. This latter property of SRRs and CSRRs also implies that the FSSs considered may act as polarizers and polarization converters as well. An analytical theory, valid for perfectly conducting and infinitely thin screens, is proposed for the SRR-FSSs and CSRR-FSSs. These approximations are valid in the microwave and millimetre-wave range, and up to the terahertz range.

  7. Development of qualitative and quantitative analysis methods in pharmaceutical application with new selective signal excitation methods for 13 C solid-state nuclear magnetic resonance using 1 H T1rho relaxation time.

    PubMed

    Nasu, Mamiko; Nemoto, Takayuki; Mimura, Hisashi; Sako, Kazuhiro

    2013-01-01

    Most pharmaceutical drug substances and excipients in formulations exist in a crystalline or amorphous form, and an understanding of their state during manufacture and storage is critically important, particularly in formulated products. Carbon 13 solid-state nuclear magnetic resonance (NMR) spectroscopy is useful for studying the chemical and physical state of pharmaceutical solids in a formulated product. We developed two new selective signal excitation methods in (13) C solid-state NMR to extract the spectrum of a target component from such a mixture. These methods were based on equalization of the proton relaxation time in a single domain via rapid intraproton spin diffusion and the difference in proton spin-lattice relaxation time in the rotating frame ((1) H T1rho) of individual components in the mixture. Introduction of simple pulse sequences to one-dimensional experiments reduced data acquisition time and increased flexibility. We then demonstrated these methods in a commercially available drug and in a mixture of two saccharides, in which the (13) C signals of the target components were selectively excited, and showed them to be applicable to the quantitative analysis of individual components in solid mixtures, such as formulated products, polymorphic mixtures, or mixtures of crystalline and amorphous phases. PMID:23147444

  8. Influence of the colloidal structure of dairy gels on milk fat fusion behavior: quantification of the liquid fat content by in situ quantitative proton nuclear magnetic resonance spectroscopy (isq (1) H NMR).

    PubMed

    Bouteille, Romain; Perez, Jeanne; Khifer, Farid; Jouan-Rimbaud-Bouveresse, Delphine; Lecanu, Bruno; This, Hervé

    2013-04-01

    Dairy gels (DG), such as yoghurts, contain both solid and liquid fats at the time of consumption, as their temperature rises to anything between 10 and 24 °C after being introduced into the mouth at 4 °C. The mass ratio between solid and liquid fats, which depends on the temperature, impacts the organoleptic properties of DG. As the ordinary methods for determining this ratio can only be applied to samples consisting mainly in fat materials, a fat extraction step needs to be added into the analytical process when applied to DG, which prevents the study of the potential impact of their colloidal structure on milk fat fusion behavior. In situ quantitative proton nuclear magnetic resonance spectroscopy (isq (1) H NMR) was investigated as a method for direct measurements in DG: at temperatures between 20.0 and 70.0 °C, the liquid fat content and the composition of triacylglycerols of the liquid phase (in terms of alkyl chains length) were determined. Spectra of isolated milk fat also enable the quantification of the double bonds of triacylglycerols. Statistical tests showed no significant difference between isolated milk fat and milk fat inside a DG in terms of melting behavior: the fat globule membrane does not seem to have a significant influence on the fat melting behavior. PMID:23464867

  9. 13C and 31P chemical shielding tensors of a single crystal of dipotassium α- D-glucose-1-phosphate dihydrate. An application of a 13C-{ 1H, 31P} triple-resonance technique

    NASA Astrophysics Data System (ADS)

    McDowell, C. A.; Naito, A.; Sastry, D. L.; Takegoshi, K.

    The 13C NMR spectra of a single crystal of dipotassium α- D-glucose-l-phosphate dehydrate for different orientations in the external magnetic field, were recorded by using 1H and 31P double nuclear decoupling. To overcome difficulties encountered because of the high 13C RF power required to achieve the Hartmann-Hahn condition, a new cross-polarization method (K. Takegoshi and C. A. McDowell, J. Magn. Reson.67, 356 (1986)) was used. The directions of the most shielded principal value of the 13C chemical shielding tensors for the C2-C6 carbon nuclei in the glucose group were along the CO bond, and that for the CI carbon nucleus made an angle of 42† with the C1-O5 bond direction in the O1-C1-O5 plane. The 31P chemical shielding tensors are axially symmetric and the direction of the least shielded principal value is almost parallel to the P-O1(R) bond, which is the longest among the four PO bonds in the phosphate moiety.

  10. Numerical and experimental investigation of a low-frequency measurement technique: differential acoustic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Yin, Hanjun; Zhao, Jianguo; Tang, Genyang; Ma, Xiaoyi; Wang, Shangxu

    2016-06-01

    Differential acoustic resonance spectroscopy (DARS) has been developed to determine the elastic properties of saturated rocks within the kHz frequency range. This laboratory technique is based on considerations from perturbation theory, wherein the resonance frequencies of the resonant cavity with and without a perturbation sample are used to estimate the acoustic properties of the test sample. In order to better understand the operating mechanism of DARS and therefore optimize the procedure, it is important to develop an accurate and efficient numerical model. Accordingly, this study presents a new multiphysics model by coupling together considerations from acoustics, solid mechanics, and electrostatics. The numerical results reveal that the newly developed model can successfully simulate the acoustic pressure field at different resonance modes, and that it can accurately reflect the measurement process. Based on the understanding of the DARS system afforded by the numerical simulation, we refine the system configuration by utilizing cavities of different lengths and appropriate radii to broaden the frequency bandwidth and ensure testing accuracy. Four synthetic samples are measured to test the performance of the optimized DARS system, in conjunction with ultrasonic and static measurements. For nonporous samples, the estimated bulk moduli are shown to be independent of the different measurement methods (i.e. DARS or ultrasonic techniques). In contrast, for sealed porous samples, the differences in bulk moduli between the low- and high-frequency techniques can be clearly observed; this discrepancy is attributed to frequency dispersion. In summary, the optimized DARS system with an extended frequency range of 500–2000 Hz demonstrates considerable utility in investigating the frequency dependence of the acoustic properties of reservoir rocks.

  11. Frequency Shifts of Resonant Modes of the Sun due to Near-Surface Convective Scattering

    NASA Astrophysics Data System (ADS)

    Bhattacharya, J.; Hanasoge, S.; Antia, H. M.

    2015-06-01

    Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the “surface term.” The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun. We show that the full oscillation equations, in the presence of temporally stationary three-dimensional (3D) flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt-Väisäla frequency, and Lamb frequency. We derive the modified equation and relations for the appropriate averaging of 3D flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from 3D numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.

  12. Solitons and frequency combs in silica microring resonators: Interplay of the Raman and higher-order dispersion effects

    NASA Astrophysics Data System (ADS)

    Milián, C.; Gorbach, A. V.; Taki, M.; Yulin, A. V.; Skryabin, D. V.

    2015-09-01

    The influence of Raman scattering and higher order dispersions on solitons and frequency comb generation in silica microring resonators is investigated. The Raman effect introduces a threshold value in the resonator quality factor above which the frequency-locked solitons cannot exist, and instead, a rich dynamics characterized by generation of self-frequency-shifting solitons and dispersive waves is observed. A mechanism for broadening the Cherenkov radiation through Hopf instability of the frequency-locked solitons is also reported.

  13. Resonant frequency and bandwidth of metamaterial emitters and absorbers predicted by an RLC circuit model

    NASA Astrophysics Data System (ADS)

    Sakurai, Atsushi; Zhao, Bo; Zhang, Zhuomin M.

    2014-12-01

    Metamaterial thermal emitters and absorbers have been widely studied for different geometric patterns by exciting a variety of electromagnetic resonances. A resistor-inductor-capacitor (RLC) circuit model is developed to describe the magnetic resonances (i.e. magnetic polaritons) inside the structures. The RLC circuit model allows the prediction of not only the resonance frequency, but also the full width at half maximum and quality factor for various geometric patterns. The parameters predicted by the RLC model are compared with the finite-difference time-domain simulation. The magnetic field distribution and the power dissipation density profile are also used to justify the RLC circuit model. The geometric effects on the resonance characteristics are elucidated in the wire (or strip), cross, and square patterned metamaterial in the infrared region. This study will facilitate the design of metamaterial absorbers and emitters based on magnetic polaritons.

  14. Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies

    SciTech Connect

    Zou, Longfang; López-García, Martin; Oulton, Ruth; Klemm, Maciej; Withayachumnankul, Withawat; Fumeaux, Christophe; Shah, Charan M.; Mitchell, Arnan; Bhaskaran, Madhu; Sriram, Sharath

    2014-11-10

    The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that coupling between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.

  15. Circuit for continuous motional series resonant frequency and motional resistance monitoring of quartz crystal resonators by parallel capacitance compensation

    NASA Astrophysics Data System (ADS)

    Arnau, A.; Sogorb, T.; Jimenez, Y.

    2002-07-01

    A deep analysis of the problem associated with oscillators as interface circuits for quartz-crystal-microbalance sensors, reveals that the so-called static capacitance of the sensor is one of the elements that makes the use of oscillators more critical for sensors applications. A phase-locked-loop based circuit specifically designed for compensating the parallel capacitance effects in quartz crystal resonator sensors is presented. This circuit permits the calibration of the external circuitry to the sensor and an accurate determination of the effective capacitive compensation. The system provides a continuous measurement of the motional series resonant frequency and motional resistance. An extension and automation of the proposed system for multiple sensor characterization is introduced. The theoretical analysis of the circuit along with the experimental results presented prove that the proposed system is a good alternative for quartz sensors characterization.

  16. Single-frequency, fully integrated, miniature DPSS laser based on monolithic resonator

    NASA Astrophysics Data System (ADS)

    Dudzik, G.; Sotor, J.; Krzempek, K.; Soboń, G.; Abramski, K. M.

    2014-02-01

    We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm3, are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003ºC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3ṡ10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.

  17. CFAVC scheme for high frequency series resonant inverter-fed domestic induction heating system

    NASA Astrophysics Data System (ADS)

    Nagarajan, Booma; Reddy Sathi, Rama

    2016-01-01

    This article presents the investigations on the constant frequency asymmetric voltage cancellation control in the AC-AC resonant converter-fed domestic induction heating system. Conventional fixed frequency control techniques used in the high frequency converters lead to non-zero voltage switching operation and reduced output power. The proposed control technique produces higher output power than the conventional fixed-frequency control strategies. In this control technique, zero-voltage-switching operation is maintained during different duty cycle operation for reduction in the switching losses. Complete analysis of the induction heating power supply system with asymmetric voltage cancellation control is discussed in this article. Simulation and experimental study on constant frequency asymmetric voltage cancellation (CFAVC)-controlled full bridge series resonant inverter is performed. Time domain simulation results for the open and closed loop of the system are obtained using MATLAB simulation tool. The simulation results prove the control of voltage and power in a wide range. PID controller-based closed loop control system achieves the voltage regulation of the proposed system for the step change in load. Hardware implementation of the system under CFAVC control is done using the embedded controller. The simulation and experimental results validate the performance of the CFAVC control technique for series resonant-based induction cooking system.

  18. High-frequency current oscillations in graphene-boron nitride resonant tunnel diodes

    NASA Astrophysics Data System (ADS)

    Greenaway, Mark; Gaskell, Jenn; Eaves, Laurence; Novoselov, Kostya; Mishchenko, Artem; Geim, Andre; Fromhold, Mark

    The successful realisation of multilayer graphene-hBN-graphene resonant tunnelling diodes (graphene- RTDs) with negative differential conductance (NDC) and MHz current oscillations offers the exciting possibility of exploiting them as high-frequency oscillators and mixers. In this paper, we examine their potential for generating higher frequencies by simulating the oscillations in the tunnel current and charge that arise when the device is biased in the NDC region and placed in a resonant circuit. Using the Bardeen transfer Hamiltonian method, we examine the effect on the device characteristics of the twist angle, θ, between the two graphene electrodes, the hBN barrier thickness and of the carrier density in the graphene electrodes, which can be adjusted by chemical doping or by an applied bias voltage. The simulations accurately reproduce our recently-reported measurements on these RTDs (Fig. 4,). The results of simulations show that frequencies of tens of GHz are achievable by optimising the device parameters. Leverhulme Trust, UK.

  19. Localized surface plasmon resonances in graphene ribbon arrays for sensing of dielectric environment at infrared frequencies

    NASA Astrophysics Data System (ADS)

    Vasić, Borislav; Isić, Goran; Gajić, Radoš

    2013-01-01

    High confinement of surface plasmon polaritons in graphene at infrared frequencies enhances the light-matter interaction and can be used for the sensing of the environment. The considered sensing platform consists of parallel graphene ribbons which enables efficient coupling of an electromagnetic field into localized surface plasmons. Changes in the environment are then detected by measuring the resulting frequency shifts of the plasmonic resonances. It is shown that the graphene ribbons have the sensitivity comparable to the sensitivity of noble metal nanoparticles at visible frequencies, which enable sensing of only several nanometers thick films at wavelengths around ten microns. At the same time, the tunability of graphene plasmons enables a design of broadband substrates for surface enhanced infrared absorption of thin films. By changing the Fermi level in graphene, the plasmonic resonance of graphene ribbons can be adjusted to desired vibrational mode which facilitates detection of multiple absorption bands.

  20. Predicting substrate resonance mode frequency shifts using conductive, through-substrate vias

    NASA Astrophysics Data System (ADS)

    Murray, Conal E.; Abraham, D. W.

    2016-02-01

    Through-substrate-vias (TSVs) provide conduction paths to allow for three-dimensional integration of microelectronic structures. It is also known that metallic TSVs can be used to suppress resonance modes within dielectric substrates by altering the propagation of electromagnetic waves. Numerical analyses of transmission through substrates containing metallic TSVs revealed that although resonance modes of the composite structure are shifted to higher frequencies, these frequencies are not solely dictated by the TSV periodicity. Simulations show that hybrid modes are formed through a convolution of the original substrate modes and a long-wavelength mode analogous to that found in a two-dimensional photonic crystal. An analytical formula is proposed that provides a simple relation between the intrinsic substrate mode frequencies and the long-wavelength mode that scales with the ratio of TSV radius to its periodicity.

  1. Resonant light scattering of a laser frequency comb by a quantum dot

    NASA Astrophysics Data System (ADS)

    Konthasinghe, K.; Peiris, M.; Muller, A.

    2014-08-01

    We investigate the spectral and temporal properties of light scattered near resonantly by a single quantum dot when the incident laser field is a frequency comb consisting of a superposition of monochromatic waves equidistant in frequency. Such fields encompass those generated by, e.g., a periodically pulsed laser. A general theoretical treatment for the calculation of first- and second-order correlation functions is given which takes account of spectral diffusion through a slowly varying detuning from resonance, permitting accurate comparison with experiments. We explore the two distinct regimes in which the frequency-comb separation is either larger or smaller than the radiative decay rate. We verify the validity of our calculations by a comparison with experimental data for the case of a bichromatic field and discuss the manifestation of phase coherence between the incoming field and the scattered single-photon wave packet.

  2. Four-channel magnetic resonance imaging receiver using frequency domain multiplexing

    NASA Astrophysics Data System (ADS)

    He, Wang; Qin, Xu; Jiejing, Ren; Gengying, Li

    2007-01-01

    An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60dB, the phase fluctuations were about 1°, and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.

  3. Resonances observed on mother-daughter rocket flights in the ionosphere. [signal frequency enhancement in auroral zones

    NASA Technical Reports Server (NTRS)

    Folkestad, K.; Troeim, J.

    1973-01-01

    Resonance phenomena have been observed in swept frequency experiments carried out on two mother-daughter Nike-Tomahawk rocket flights at auroral latitudes. The experimental method is briefly described and characteristic samples of the results are presented. A possible interpretation of some main resonances is offered, involving cold plasma cone resonances.

  4. Frequency-Temperature Compensation Techniques for High-Q Microwave Resonators

    NASA Astrophysics Data System (ADS)

    Hartnett, John G.; Tobar, Michael E.

    Low-noise high-stability resonator oscillators based on high-Q monolithic sapphire ``Whispering Gallery'' (WG)-mode resonators have become important devices for telecommunication, radar and metrological applications. The extremely high quality factor of sapphire, of 2 x10^5 at room temperature, 5 x10^7 at liquid nitrogen temperature and 5 x10^9 at liquid helium temperature has enabled the lowest phase noise and highly frequency-stable oscillators in the microwave regime to be constructed. To create an oscillator with exceptional frequency stability, the resonator must have its frequency-temperature dependence annulled at some temperature, as well as a high quality factor. The Temperature Coefficient of Permittivity (TCP) for sapphire is quite large, at 10-100parts per million/K above 77K. This mechanism allows temperature fluctuations to transform to resonator frequency fluctuations.A number of research groups worldwide have investigated various methods of compensating the TCP of a sapphire dielectric resonator at different temperatures. The usual electromagnetic technique of annulment involves the use of paramagnetic impurities contributing an opposite temperature coefficient of the magnetic susceptibility to the TCP. This technique has only been realized successfully in liquid helium environments. Near 4K the thermal expansion and permittivity effects are small and only small quantities of the paramagnetic ions are necessary to compensate the mode frequency. Compensation is due to impurity ions that were incidentally left over from the manufacturing process.Recently, there has been an effort to dispense with the need for liquid helium and make a compact flywheel oscillator for the new generation of primary frequency standards such as the cesium fountain at the Laboratoire Primaire du Temps et des Fréquences (LPTF), France. To achieve the stability limit imposed

  5. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    SciTech Connect

    Hanham, S. M. Watts, C.; Klein, N.; Otter, W. J.; Lucyszyn, S.

    2015-07-20

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  6. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Hanham, S. M.; Watts, C.; Otter, W. J.; Lucyszyn, S.; Klein, N.

    2015-07-01

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ˜4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ˜5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  7. Frequency-comb formation in doubly resonant second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Leo, F.; Hansson, T.; Ricciardi, I.; De Rosa, M.; Coen, S.; Wabnitz, S.; Erkintalo, M.

    2016-04-01

    We theoretically study the generation of optical frequency combs and corresponding pulse trains in doubly resonant intracavity second-harmonic generation (SHG). We find that, despite the large temporal walk-off characteristic of realistic cavity systems, the nonlinear dynamics can be accurately and efficiently modeled using a pair of coupled mean-field equations. Through rigorous stability analysis of the system's steady-state continuous-wave solutions, we demonstrate that walk-off can give rise to an unexplored regime of temporal modulation instability. Numerical simulations performed in this regime reveal rich dynamical behaviors, including the emergence of temporal patterns that correspond to coherent optical frequency combs. We also demonstrate that the two coupled equations that govern the doubly resonant cavity behavior can, under typical conditions, be reduced to a single mean-field equation akin to that describing the dynamics of singly-resonant-cavity SHG [F. Leo et al., Phys. Rev. Lett. 116, 033901 (2016), 10.1103/PhysRevLett.116.033901]. This reduced approach allows us to derive a simple expression for the modulation instability gain, thus permitting us to acquire significant insight into the underlying physics. We anticipate that our work will have a wide impact on the study of frequency combs in emerging doubly resonant cavity SHG platforms, including quadratically nonlinear microresonators.

  8. Frequencies and resonances around L4 in the elliptic restricted three-body problem

    NASA Astrophysics Data System (ADS)

    Rajnai, R.; Nagy, I.; Érdi, B.

    2014-09-01

    More and more Trojan asteroids are discovered in our Solar system, suggesting that they are probably a common spinoff of planet formation and evolution. Till date we know thousands of Trojan followers of Jupiter, and Trojan asteroids and moons of other major planets have also been discovered. The large number of such celestial bodies can mean that Trojan companions to extrasolar planets may also be common. Trojan celestial bodies are examples for the Lagrangian triangular solutions of the three-body problem. In this paper, the stability of the Lagrangian point L4 is investigated in the elliptic restricted three-body problem by using Floquet's theory. Stable and unstable domains are determined in the parameter plane of the mass parameter and the eccentricity by computing the characteristic exponents. Frequencies of motion around L4 have been determined both in the stable and unstable domains, and fitting functions for the frequencies are derived depending on the mass parameter and the eccentricity. Resonances between the frequencies are studied in the whole parameter plane. It is shown that the 1:1 resonances are not restricted only to single curves but extend to the whole unstable domain. In the unstable domains, longer escape times of the test particle from the neighbourhood of L4 are related to certain resonances, but changing the parameters the same resonances may lead to faster escape.

  9. Raman and infrared spectra of barium and strontium halide monohydrates, MX2 · 1H2O (M = Ba, Sr; X = Cl, Br, I). A new interpretation of the frequency shiftings of OH stretching modes in solid hydrates

    NASA Astrophysics Data System (ADS)

    Lutz, H. D.; Christian, H.

    The infrared and Raman spectra of the isotypic alkaline earth halide monohydrates, MX2 · 1H2O, with M = Sr, Ba and X = Cl, Br, I, and of deuterated and isotopically dilute samples have been recorded in the H2O stretching and bending mode region. From the temperature dependence of the stretching modes it is shown that bifurcated hydrogen bridges are present in these hydrates. The water molecules are symmetrically bonded in the case of the iodides, possibly caused by dipole-like interactions with adjacent iodide ions, and assymmetrically bonded in the case of the chlorides and bromides due to normal hydrogen bonds, as shown from the absence or presence of splitting of the stretching modes in isotopically dilute samples. The relative Raman intensities of the two H2O stretching modes, {Ivsym}/{Ivasym}, which reveal the amount of intramolecular coupling of the stretching vibrations, give an additional view of the bond structure of the water molecules. The frequency shiftings of the stretching modes of water molecules in solid hydrates are discussed in terms of hydrogen bonds, metal-oxygen interaction and the repulsion potential of the lattice, as shown, for example, by the correlation with the unit cell volumes.

  10. A novel radio frequency coil for veterinary magnetic resonance imaging system

    NASA Astrophysics Data System (ADS)

    Meng, Bin; Huang, Kai-Wen; Wang, Wei-Min

    2010-07-01

    In this article, a novel designed radio frequency (RF) coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging (MRI) system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method (FEM). Good magnetic resonance (MR) images are achieved on a shepherd dog.

  11. Finite size effect on spread of resonance frequencies in arrays of coupled vortices

    SciTech Connect

    Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido

    2011-01-25

    Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.

  12. Quasipatterns in a Model for Chemical Oscillations Forced at Multiple Resonance Frequencies

    SciTech Connect

    Conway, Jessica M.; Riecke, Hermann

    2007-11-23

    Multifrequency forcing of systems undergoing a Hopf bifurcation to spatially homogeneous oscillations is investigated. For weak forcing composed of frequencies near the 1 ratio 1, 1 ratio 2, and 1 ratio 3 resonances, such systems can be described systematically by a suitably extended complex Ginzburg-Landau equation. Weakly nonlinear analysis shows that, generically, the forcing function can be tuned such that resonant triad interactions with weakly damped modes stabilize subharmonic 4- and 5-mode quasipatterns. In simulations starting from random initial conditions, domains of these quasipatterns compete and yield complex, slowly ordering patterns.

  13. Reentrant radio-frequency resonator for automated phase-equilibria and dielectric measurements in fluids

    SciTech Connect

    Goodwin, A.R.; Mehl, J.B.; Moldover, M.R.

    1996-12-01

    A reentrant rf cavity resonator has been developed for automated detection of phase separation of fluid mixtures contained within the cavity. Successful operation was demonstrated by redetermining the phase boundaries of a CO{sub 2}+C{sub 2}H{sub 6} mixture in the vicinity of its critical point. We developed an accurate electrical model for the resonator and used helium to determine the deformation of the resonator under pressure. With the model and pressure compensation, the resonator was capable of very accurate dielectric measurements. We confirmed this by remeasuring the molar dielectric polarizability {ital A}{sub {epsilon}} of argon and obtained the result {ital A}{sub {epsilon}}=(4.140{plus_minus}0.006) cm{sup 3}/mol (standard uncertainty) in excellent agreement with published values. We exploited the capability for accurate dielectric measurements to determine the densities of the CO{sub 2}+C{sub 2}H{sub 6} mixture at the phase boundaries and to determine the dipole moment of 1,1,1,2,3,3-hexafluoropropane, a candidate replacement refrigerant. Near the operating frequency of 375 MHz the capacitor in the resonator has an impedance near 14 {Omega}. This low impedance is more tolerant of electrical conductivity within the test fluid and in parallel paths in the support structures than comparable capacitors operating at audio frequencies. This will be an advantage for operation at high temperatures where some conductivity must be expected in all fluids. Of further value for high-temperature applications, the present rf resonator has only two metal{endash}insulator joints. These joints seal coaxial cables; neither joint is subjected to large mechanical stresses and neither joint is required to maintain precise dimensional tolerances. The resonator is rugged and may be operated with inexpensive electronics.

  14. Method and apparatus for sensing a target characteristic by measuring both impedance and resonant frequency of a tank circuit

    NASA Technical Reports Server (NTRS)

    Laskowski, Edward L. (Inventor)

    1995-01-01

    An apparatus for sensing a target characteristic, such as relative distance between the apparatus and target, target thickness, target material, or lateral position between the apparatus and the target, includes a coil for directing an electro-magnetic field at the target. A voltage controlled oscillator energizes the coil at a resonant frequency which is functionally related to the target characteristic. The coil has an effective impedance value at resonance functionally related to the target characteristic. A frequency monitor measures the resonant frequency. An impedance monitor determines the impedance value when the drive frequency is at the resonant value. A PROM or controller determines the target characteristic in response to the measured resonant frequency and the determined impedance value. The PROM or controller provides a signal responsive to the determined target characteristic.

  15. Two Novel Measurements for the Drive-Mode Resonant Frequency of a Micromachined Vibratory Gyroscope

    PubMed Central

    Wang, Ancheng; Hu, Xiaoping; Luo, Bing; Jiang, Mingming; He, Xiaofeng; Tang, Kanghua

    2013-01-01

    To investigate the drive-mode resonance frequency of a micromachined vibratory gyroscope (MVG), one needs to measure it accurately and efficiently. The conventional approach to measure the resonant frequency is by performing a sweep frequency test and spectrum analysis. The method is time-consuming and inconvenient because of the requirements of many test points, a lot of data storage and off-line analyses. In this paper, we propose two novel measurement methods, the search method and track method, respectively. The former is based on the magnitude-frequency characteristics of the drive mode, utilizing a one-dimensional search technique. The latter is based on the phase-frequency characteristics, applying a feedback control loop. Their performances in precision, noise resistivity and efficiency are analyzed through detailed simulations. A test system is implemented based on a field programmable gate array (FPGA) and experiments are carried out. By comparing with the common approach, feasibility and superiorities of the proposed methods are validated. In particular, significant efficiency improvements are achieved whereby the conventional frequency method consumes nearly 5,000 s to finish a measurement, while only 5 s is needed for the track method and 1 s for the search method. PMID:24256977

  16. Multilayer-split-tube resonators with low-frequency band gaps in phononic crystals

    NASA Astrophysics Data System (ADS)

    Jing, Li; Wu, Jiu Hui; Guan, Dong; Gao, Nansha

    2014-09-01

    In this paper, low-frequency band gaps in two-dimensional Helmholtz resonant phononic crystals (PCs) composed of multilayer-split-tube resonators are investigated. The band structures, transmission spectra, and pressure field of the acoustic modes of these PCs are calculated by using a finite element method (FEM). The numerical results show that the first band gap of the structure is from 88 to 140 Hz. The transmission spectra are in accordance with those of the dispersion relation calculations. The acoustic modes of the bands are analyzed to reveal the nature of this phenomenon. It is found that the interaction between the local resonance and the traveling wave modes in proposed structure is responsible for the formation of the first band gap. The influences of the structural parameters on the band gaps are investigated by using FEM and the electrical circuit analogy. Numerical results show that the band gaps can be modulated in an even wider frequency range by changing the structural parameters, such as the rotation angle, the number of tubes, and the radius of the outer tube. The structural design results provide an effective way for phononic crystals to obtain the low-frequency band gaps, which have potential application in the low-frequency noise reduction.

  17. HIGHER MODE FREQUENCY EFFECTS ON RESONANCE IN MACHINERY, STRUCTURES, AND PIPE SYSTEMS

    SciTech Connect

    Leishear, R.

    2010-05-02

    The complexities of resonance in multi-degree of freedom systems (multi-DOF) may be clarified using graphic presentations. Multi-DOF systems represent actual systems, such as beams or springs, where multiple, higher order, natural frequencies occur. Resonance occurs when a cyclic load is applied to a structure, and the frequency of the applied load equals one of the natural frequencies. Both equations and graphic presentations are available in the literature for single degree of freedom (SDOF) systems, which describe the response of spring-mass-damper systems to harmonically applied, or cyclic, loads. Loads may be forces, moments, or forced displacements applied to one end of a structure. Multi-DOF systems are typically described only by equations in the literature, and while equations certainly permit a case by case analysis for specific conditions, graphs provide an overall comprehension not gleaned from single equations. In fact, this collection of graphed equations provides novel results, which describe the interactions between multiple natural frequencies, as well as a comprehensive description of increased vibrations near resonance.

  18. Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers.

    PubMed

    Tian, Zheng; Ren, Dahai; You, Zheng

    2016-01-01

    This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰-only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability. PMID:27213401

  19. Coupling of Helmholtz resonators to improve acoustic liners for turbofan engines at low frequency

    NASA Technical Reports Server (NTRS)

    Dean, L. W.

    1975-01-01

    An analytical and test program was conducted to evaluate means for increasing the effectiveness of low frequency sound absorbing liners for aircraft turbine engines. Three schemes for coupling low frequency absorber elements were considered. These schemes were analytically modeled and their impedance was predicted over a frequency range of 50 to 1,000 Hz. An optimum and two off-optimum designs of the most promising, a parallel coupled scheme, were fabricated and tested in a flow duct facility. Impedance measurements were in good agreement with predicted values and validated the procedure used to transform modeled parameters to hardware designs. Measurements of attenuation for panels of coupled resonators were consistent with predictions based on measured impedance. All coupled resonator panels tested showed an increase in peak attenuation of about 50% and an increase in attenuation bandwidth of one one-third octave band over that measured for an uncoupled panel. These attenuation characteristics equate to about 35% greater reduction in source perceived noise level (PNL), relative to the uncoupled panel, or a reduction in treatment length of about 24% for constant PNL reduction. The increased effectiveness of the coupled resonator concept for attenuation of low frequency broad spectrum noise is demonstrated.

  20. Resonance properties of Ag-ZnO nanostructures at terahertz frequencies.

    PubMed

    Sanchez, John E; Díaz de León, Ramón; Mendoza-Santoyo, Fernando; González, Gabriel; José-Yacaman, Miguel; Ponce, Arturo; González, Francisco Javier

    2015-09-21

    Nanoantennas have been fabricated by scaling down traditional antenna designs using nanolithographic techniques and testing them at different optical wavelengths, these particular nanoantennas have shown responses in a broad range of frequencies going from visible wavelengths to the range of the terahertz. Some self-assembled nanostructures exist that exhibit similar shapes and properties to those of traditional antenna structures. In this work the emission and absorption properties of self-assembled nanostructures made of zinc oxide nanorods on silver nanowires, which resemble traditional dipole antennas, were measured and simulated in order to test their antenna performance. These structures show resonant properties in the 10-120 THz range, with the main resonance at 60 THz. The radiation pattern of these nanostructures was also obtained by numerical simulations, and it is shown that it can be tailored to increase or decrease its directivity as a function of the location of the energy source of excitation. Experimental measurements were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) in order to show existing vibrational frequencies at the resonant frequencies of the nanostructures, measurements were made from ~9 to 103 THz and the results were in agreement with the simulations. These characteristics make these metal-semiconductor Ag/ZnO nanostructures useful as self-assembled nanoantennas in applications such as terahertz spectroscopy and sensing at terahertz frequencies. PMID:26406710

  1. Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers

    PubMed Central

    Tian, Zheng; Ren, Dahai; You, Zheng

    2016-01-01

    This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰—only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability. PMID:27213401

  2. Two-dimensional sup 1 H nuclear magnetic resonance study of AaH IT, an anti-insect toxin from the scorpion Androctonus australis Hector. Sequential resonance assignments and folding of the polypeptide chain

    SciTech Connect

    Darbon, H. ); Weber, C.; Braun, W. )

    1991-02-19

    Sequence-specific nuclear magnetic resonance assignments for the polypeptide backbone and for most of the amino acid side-chain protons, as well as the general folding of AaH IT, are described. AaH IT is a neurotoxin purified from the venom of the scorpion Androctonus australis Hector and is specifically active on the insect nervous system. The secondary structure and the hydrogen-bonding patterns in the regular secondary structure elements are deduced from nuclear Overhauser effects and the sequence locations of the slowly exchanging amide protons. The backbone folding is determined by distance geometry calculations with the DISMAN program. The regular secondary structure includes two and a half turns of {alpha}-helix running from residues 21 to 30 and a three-stranded antiparallel {beta}-sheet including peptides 3-5, 34-38, and 41-46. Two tight turns are present, one connecting the end of the {alpha}-helix to an external strand of the {beta}-sheet, i.e., turn 31-34, and another connecting this same strand to the central one, i.e., turn 38-41. The differences in the specificity of these related proteins, which are able to discriminate between mammalian and insect voltage-dependent sodium channels of excitable tissues, are most probably brought about by the position of the C-terminal peptide with regard to a hydrophobic surface common to all scorpion toxins examined thus far. Thus, the interaction of a given scorpion toxin with its receptor might well be governed by the presence of this solvent-exposed hydrophobic surface, whereas adjacent areas modulate the specificity of the interaction.

  3. 1H, 13C, 15N backbone and side chain NMR resonance assignments for the N-terminal RNA recognition motif of the HvGR-RBP1 protein involved in the regulation of barley (Hordeum vulgare L.) senescence

    PubMed Central

    Mason, Katelyn E.; Tripet, Brian P.; Parrott, David; Fischer, Andreas M.; Copié, Valérie

    2013-01-01

    Leaf senescence is an important process in the developmental life of all plant species. Senescence efficiency influences important agricultural traits such as grain protein content and plant growth, which are often limited by nitrogen use. Little is known about the molecular mechanisms regulating this highly orchestrated process. To enhance our understanding of leaf senescence and its regulation, we have undertaken the structural and functional characterization of previously unknown proteins that are involved in the control of senescence in barley (Hordeum vulgare L.). Previous microarray analysis highlighted several barley genes whose transcripts are differentially expressed during senescence, including a specific gene which is greater than 40 fold up-regulated in the flag leaves of early- as compared to late-senescing near-isogenic barley lines at 14 and 21 days past flowering (anthesis). From inspection of its amino acid sequence, this gene is predicted to encode a glycine-rich RNA-binding protein herein referred to as HvGR-RBP1. HvGR-RBP1 has been expressed as a recombinant protein in E. coli, and preliminary NMR data analysis has revealed that its glycine-rich C-terminal region [residues: 93–162] is structurally disordered whereas its N-terminal region [residues: 1–92] forms a well-folded domain. Herein, we report the complete 1H, 13C, and 15N resonance assignments of backbone and sidechain atoms, and the secondary structural topology of the N-terminal RNA Recognition Motif (RRM) domain of HvGR-RBP1, as a first step to unraveling its structural and functional role in the regulation of barley leaf senescence. PMID:23417794

  4. Gamma-aminobutyric acid and glutamic acid levels in the auditory pathway of rats with chronic tinnitus: a direct determination using high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS)

    PubMed Central

    Brozoski, Thomas; Odintsov, Boris; Bauer, Carol

    2012-01-01

    Damage to the auditory system following high-level sound exposure reduces afferent input. Homeostatic mechanisms appear to compensate for the loss. Overcompensation may produce the sensation of sound without an objective physical correlate, i.e., tinnitus. Several potential compensatory neural processes have been identified, such as increased spontaneous activity. The cellular mechanisms enabling such compensatory processes may involve down-regulation of inhibitory neurotransmission mediated by γ-amino butyric acid (GABA), and/or up-regulation of excitatory neurotransmission, mediated by glutamic acid (Glu). Because central processing systems are integrated and well-regulated, compensatory changes in one system may produce reactive changes in others. Some or all may be relevant to tinnitus. To examine the roles of GABA and Glu in tinnitus, high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS) was used to quantify their levels in the dorsal cochlear nucleus (DCN), inferior colliculus (IC), medial geniculate body (MGB), and primary auditory cortex (A1) of rats. Chronic tinnitus was produced by a single high-level unilateral exposure to noise, and was measured using a psychophysical procedure sensitive to tinnitus. Decreased GABA levels were evident only in the MGB, with the greatest decrease, relative to unexposed controls, obtained in the contralateral MGB. Small GABA increases may have been present bilaterally in A1 and in the contralateral DCN. Although Glu levels showed considerable variation, Glu was moderately and bilaterally elevated both in the DCN and in A1. In the MGB Glu was increased ipsilaterally but decreased contralaterally. These bidirectional and region-specific alterations in GABA and Glu may reflect large-scale changes in inhibitory and excitatory equilibrium accompanying chronic tinnitus. The present results also suggest that targeting both neurotransmitter systems may be optimal in developing more effective therapeutics

  5. Broadening the Frequency Bandwidth of Piezoelectric Energy Harvesters Using Coupled Linear Resonators

    NASA Astrophysics Data System (ADS)

    Sadeqi, Soheil

    The desire to reduce power consumption of current integrated circuits has led design engineers to focus on harvesting energy from free ambient sources such as vibrations. The energy harvested this way can eliminate the need for battery replacement, particularly, in low-energy remote sensing and wireless devices. Currently, most vibration-based energy harvesters are designed as linear resonators, therefore, they have a narrow resonance frequency. The optimal performance of such harvesters is achieved only when their resonance frequency is matched with the ambient excitation. In practice, however, a slight shift of the excitation frequency will cause a dramatic reduction in their performance. In the majority of cases, the ambient vibrations are totally random with their energy distributed over a wide frequency spectrum. Thus, developing techniques to extend the bandwidth of vibration-based energy harvesters has become an important field of research in energy harvesting systems. This thesis first reviews the broadband vibration-based energy harvesting techniques currently known in some detail with regard to their merits and applicability under different circumstances. After that, the design, fabrication, modeling and characterization of three new piezoelectric-based energy harvesting mechanism, built typically for rotary motion applications, is discussed. A step-by-step procedure is followed in order to broaden the bandwidth of such energy harvesters by introducing a coupled spring-mass system attached to a PZT beam undergoing rotary motion. It is shown that the new strategies can indeed give rise to a wide-band frequency response making it possible to fine-tune their dynamical response. The numerical results are shown to be in good agreement with the experimental data as far as the frequency response is concerned.

  6. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory

    NASA Astrophysics Data System (ADS)

    Elnaggar, Sameh Y.; Tervo, Richard; Mattar, Saba M.

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance.

  7. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory.

    PubMed

    Elnaggar, Sameh Y; Tervo, Richard; Mattar, Saba M

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance. PMID:24246950

  8. Low-distortion detection system for frequency-swept ion cyclotron resonance spectrometry

    NASA Astrophysics Data System (ADS)

    Wise, M. B.; Freiser, B. S.

    1986-07-01

    A high-performance frequency-swept capacitance bridge detector for ion cyclotron resonance (ICR) spectrometry has been constructed in our laboratory. Although the basic design of the system is similar to that of previously reported bridge circuits, careful design, layout, construction, and component selection have resulted in excellent frequency-swept performance over a bandwidth of 15 kHz to 1 MHz. At a magnetic field strength of 1.0 T, this corresponds to a mass range of 15-1000 Daltons. Problems with base-line drift and frequency-dependent signal distortion common to many other designs have been significantly reduced. Circuit diagrams are included for all parts of the detector and frequency response curves have been included where appropriate. In addition, several simple circuit diagrams for support devices have also been included.

  9. Excitation of low frequency waves by streaming ions via anomalous cyclotron resonance

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Dillenburg, D.; Gaffey, J. D., Jr.; Ziebell, L. F.; Goedert, J.; Freund, H. P.

    1978-01-01

    The effect of a small population of streaming ions on low-frequency waves with frequencies below the ion cyclotron frequency is analyzed for three modes of interest: Alfven waves, magnetosonic waves, and ion-cyclotron waves. The instability mechanism is the anomalous cyclotron resonance of the waves with the streaming ions. Conditions for excitation of the three types of waves are derived and expressions for the growth rates are obtained. Excitation of Alfven waves is possible even if the ratio of the densities of the streaming ions to the thermal ions is very small. For magnetosonic waves, excitation can easily occur if waves are propagating parallel or nearly parallel to the ambient magnetic field. As for ion-cyclotron waves, it is found that for the ion-whistler branch the excitation is suppressed over a broader range of wave frequencies than for the fast magnetosonic branch.

  10. Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: Nitroxide radicals in solution

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Korpała, A.; Kubica, A.; Meier, R.; Rössler, E. A.; Moscicki, J.

    2013-01-01

    For nitroxide radicals in solution one can identify three frequency regimes in which 1H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the 1H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854 with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for 14N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to 15N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)], 10.1021/jp980397h). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of 1H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data—1H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of 14N and 15N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in 1H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.

  11. Inverse Bloch-oscillator: Strong Thz-photocurrent resonances at the Bloch frequency

    SciTech Connect

    Unterrainer, K.; Keay, B.J.; Wanke, M.C.

    1995-12-31

    We have observed resonant changes in the current-voltage characteristics of miniband semiconductor superlattices when the Bloch frequency is resonant with a terahertz field and its harmonics: the inverse Bloch oscillator effect. The resonant feature consists of a peak in the current which grows with increasing laser intensity accompanied by a decrease of the current at the low bias side. The peak position moves linearly with the laser frequency. When the intensity is increased further the first peak starts to decrease and a second peak at about twice the voltage of the first peak is observed due to a two photon resonance. At the highest intensities we observe up to a four photon resonance. A superlattice is expected to show negative differential conductance due to the strong nonparabolicity of the miniband. In this situation the carriers should undergo Bloch oscillations with a frequency {omega}{sub B} = eEd/h. Transient Bloch oscillations of photo excited carriers have been observed in time resolved Thz emission measurements. However, the possibility of Thz generation form a DC voltage biased superlattice is still under discussion. We have approached this problem by exploring the inverse Bloch oscillator effect in a superlattice excited by the Thz radiation form the UCSB FEL. The superlattice consists of 40 periods of 80{angstrom} GaAs wells and 20{angstrom} Al{sub 0.3}Ga{sub 0.7}As barriers. To couple the electric field of the Terahertz radiation parallel to the growth direction a coplanar bowtie antenna has been employed. Our results show clearly that the external radiation couples to Bloch oscillations in contrary to theoretical suggestions that Thz radiation would not couple to a uniform Wannier Stark ladder. We conclude that this result is intimately related to dissipation and line broadening of the otherwise identical states in the ladder: absorption appears above the Wannier Stark splitting ({omega}{sub B}<{omega}) and gain below ({omega}{sub B}>{omega}).

  12. Computing resonant frequency of C-shaped compact microstrip antennas by using ANFIS

    NASA Astrophysics Data System (ADS)

    Akdagli, Ali; Kayabasi, Ahmet; Develi, Ibrahim

    2015-03-01

    In this work, the resonant frequency of C-shaped compact microstrip antennas (CCMAs) operating at UHF band is computed by using the adaptive neuro-fuzzy inference system (ANFIS). For this purpose, 144 CCMAs with various relative dielectric constants and different physical dimensions were simulated by the XFDTD software package based on the finite-difference time domain (FDTD) method. One hundred and twenty-nine CCMAs were employed for training, while the remaining 15 CCMAs were used for testing of the ANFIS model. Average percentage error (APE) values were obtained as 0.8413% and 1.259% for training and testing, respectively. In order to demonstrate its validity and accuracy, the proposed ANFIS model was also tested over the simulation data given in the literature, and APE was obtained as 0.916%. These results show that ANFIS can be successfully used to compute the resonant frequency of CCMAs.

  13. Polymer Microring Resonators for High-Frequency Ultrasound Detection and Imaging

    PubMed Central

    Maxwell, Adam; Huang, Sheng-Wen; Ling, Tao; Kim, Jin-Sung; Ashkenazi, Shai; Guo, L. Jay

    2009-01-01

    Polymer microring resonators fabricated by nanoimprinting are presented as a means of ultrasound detection. Acoustic waves impinging on a ring-shaped optical resonator cause strain in the ring dimensions, modulating optical output. Basic acoustic and optical characteristics of the microring sensor are presented. Measurements at several frequencies show a high sensitivity and low noise-equivalent pressure. The angular response is determined by sensing the optoacoustic excitation of a 49 μm polyester microsphere and shows wide-angle sensitivity. A 1-D array consisting of 4 microrings is demonstrated using wavelength multiplexing for addressing each element. The high sensitivity, bandwidth, and angular response make it a potentially useful sensor platform for many applications including high-frequency ultrasonic and photoacoustic imaging. PMID:20700482

  14. Overtone frequency spectra for x3-dependent modes in AT-cut quartz resonators.

    PubMed

    Zhu, Jun; Chen, Weiqiu; Yang, Jiashi

    2013-04-01

    We study straight-crested waves and vibration modes with spatial variations along the x3 direction only in an AT-cut quartz plate resonator. The equations of anisotropic elasticity are used. Dispersion relations for face-shear and thickness-twist waves in unbounded plates are plotted. Frequency spectra are obtained for face-shear and thickness-twist vibrations of finite plates in which these modes are coupled by boundary conditions. Most importantly, our analysis produces the frequency spectra for overtone modes which do not seem to have been obtained before for x3-dependent modes. Numerical results for third- and fifth-overtone AT-cut quartz resonators are presented, showing that higher-order overtone modes are associated with more mode couplings. PMID:23549548

  15. Generation of XUV light by resonant frequency tripling in a two-wiggler FEL amplifier

    SciTech Connect

    Bonifacio, R.; de Salvo Souza, L.; Pierini, P. . Dipt. di Fisica Istituto Nazionale di Fisica Nucleare, Milan ); Scharlemann, E.T. )

    1989-01-01

    FEL operation at short wavelength is limited by electron beam quality, by the availability of mirrors for oscillators, and by the availability of input sources for FEL amplifiers. It is possible to use and FEL amplifier as a resonant frequency tripling device, generating light and strong bunching at the 3rd harmonic of a conventional input source in an initial section of wiggler, then using a second section of wiggler resonant at the tripled frequency to amplify the short wavelength light. Neither mirrors nor a short-wavelength input source are required, and some relaxation of electron beam quality appears to be possible. We illustrate the scheme with a one-dimensional model and then with NUTMEG simulations of an 80 nm FEL amplifier initiated by a 240 nm input signal, in which an efficiency of conversion of electron beam power to 80 nm light of nearly 10{sup -4} was obtained. 3 refs., 6 figs., 1 tab.

  16. Generation of XUV light by resonant frequency tripling in a two-wiggler FEL amplifier

    NASA Astrophysics Data System (ADS)

    Bonifacio, R.; Desalvosouza, L.; Pierini, P.; Scharlemann, E. T.

    FEL operation at short wavelength is limited by electron beam quality, by the availability of mirrors for oscillators, and by the availability of input sources for FEL amplifiers. It is possible to use and FEL amplifier as a resonant frequency tripling device, generating light and strong bunching at the 3rd harmonic of a conventional input source in an initial section of wiggler, then using a second section of wiggler resonant at the tripled frequency to amplify the short wavelength light. Neither mirrors nor a short-wavelength input source are required, and some relaxation of electron beam quality appears to be possible. We illustrate the scheme with a one-dimensional model and then with NUTMEG simulations of an 80 nm FEL amplifier initiated by a 240 nm input signal, in which an efficiency of conversion of electron beam power to 80 nm light of nearly 10(exp -4) was obtained.

  17. Generation of XUV light by resonant frequency tripling in a two-wiggler FEL amplifier

    NASA Astrophysics Data System (ADS)

    Bonifacio, R.; De Salvo Souza, L.; Pierini, P.; Scharlemann, E. T.

    1990-10-01

    FEL operation at short wavelengths is limited by electron-beam quality, by the availability of mirrors for oscillators and by the availability of input sources for FEL amplifiers. It is possible to use an FEL amplifier as a resonant-frequency tripling device, generating light and strong bunching at the third harmonic of a conventional input source in an initial wiggler section, then using a second wiggler section resonant at the tripled frequency to amplify the short-wavelength light. Neither mirrors nor a short-wavelength input source are required, and some relaxation of the electron-beam quality appears to be possible. We illustrate the scheme with a one-dimensional model and then with NUTMEG simulations of an 80 nm FEL amplifier initiated by a 240 nm input signal, in which an efficiency of the electron-beam power conversion to 80 nm light of nearly 10-4 was obtained.

  18. Frequency stabilization and transverse mode discrimination in injection-seeded unstable resonator TEA CO2 lasers

    NASA Technical Reports Server (NTRS)

    Ancellet, G. M.; Menzies, R. T.; Brothers, A. M.

    1987-01-01

    Longitudinal mode selection by injection has been demonstrated as a viable technique for TEA-CO2 lasers with pulse energies of a Joule or greater. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, the characteristics and the causes of intrapulse frequency variation can be studied. These include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with large spatial dimensions to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are discussed in this paper, and relevant experimental results are included.

  19. Frequency Locking and Stabilization Regimes in High-Power Gyrotrons with Low-Q Resonators

    NASA Astrophysics Data System (ADS)

    Zotova, I. V.; Ginzburg, N. S.; Denisov, G. G.; Rozental', R. M.; Sergeev, A. S.

    2016-02-01

    Using a nonstationary self-consistent model, we analyze the frequency locking and stabilization regimes arising in gyrotrons with low-Q resonators under the action of an external signal or when reflections from a remote nonresonant load are introduced. In the simulations, we used the parameters of high-power gyrotrons designed for controlled thermonuclear fusion with optimized resonator profile. This approach makes it possible to determine output characteristics of the gyrotrons operated in considered regimes taking into account the effect of the incident wave (external or reflected) on the longitudinal field structure with greater precision compared with the earlier results based on the fixed RF-field structure approximation, while qualitative results of the two approaches coincide. Analysis of the effect of reflections from a remote load has demonstrated a substantial dependence of the efficiency of the gyrotron frequency stabilization on the ratio between the characteristic time scale of the synchronism detuning fluctuations and the signal delay time.

  20. Fractal frequency spectrum in laser resonators and three-dimensional geometric topology of optical coherent waves

    NASA Astrophysics Data System (ADS)

    Tung, J. C.; Tuan, P. H.; Liang, H. C.; Huang, K. F.; Chen, Y. F.

    2016-08-01

    We theoretically verify that the symmetry breaking in spherical resonators can result in a fractal frequency spectrum that is full of numerous new accidental degeneracies to cluster around the unperturbed degenerate cavity. We further experimentally discover that the fractal frequency spectrum excellently reflects the intimate connection between the emission power and the degenerate mode numbers. It is observed that the wave distributions of lasing modes at the accidental degeneracies are strongly concentrated on three-dimensional (3D) geometric topology. Considering the overlapping effect, the wave representation of the coherent states is analytically derived to manifest the observed 3D geometric surfaces.

  1. Suppression of cyclotron instability in Electron Cyclotron Resonance ion sources by two-frequency heating

    SciTech Connect

    Skalyga, V.; Izotov, I.; Mansfeld, D.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Tarvainen, O.

    2015-08-15

    Multiple frequency heating is one of the most effective techniques to improve the performance of Electron Cyclotron Resonance (ECR) ion sources. The method increases the beam current and average charge state of the extracted ions and enhances the temporal stability of the ion beams. It is demonstrated in this paper that the stabilizing effect of two-frequency heating is connected with the suppression of electron cyclotron instability. Experimental data show that the interaction between the secondary microwave radiation and the hot electron component of ECR ion source plasmas plays a crucial role in mitigation of the instabilities.

  2. Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging.

    PubMed

    Hardman, K S; Wigley, P B; Everitt, P J; Manju, P; Kuhn, C C N; Robins, N P

    2016-06-01

    Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 μm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer. PMID:27244400

  3. Resonant instability near the two-ion crossover frequency in the Io plasma torus

    NASA Astrophysics Data System (ADS)

    Thorne, R. M.; Moses, J. J.

    1985-07-01

    Thorne and Scarf (1984) have presented evidence for the existence of intense low-frequency fluctuating electric fields in the Io plasma torus. Two distinct mechanisms have been proposed for this phenomenon, namely, ion cyclotron instability which occurs at intermediate latitude, and whistler instability near the equator. The present investigation is concerned with a quantitative appraisal of each of these mechanisms, taking into account an evaluation of the net convective growth rate of waves along ray paths which traverse the Io torus. Aspects of wave propagation near the crossover frequency are considered along with questions regarding the resonant interaction with energetic particles.

  4. Microwave and RF applications for micro-resonator based frequency combs

    NASA Astrophysics Data System (ADS)

    Nguyen, Thach G.; Shoeiby, Mehrdad; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T.; Little, Brent E.; Morandotti, Roberto; Mitchell, Arnan; Moss, David J.

    2016-02-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contrast, doped-silica glass platform. The high quality and large frequency spacing of the comb enables filters with up to 20 taps, allowing us to demonstrate a quadrature filter with more than a 5-octave (3 dB) bandwidth and an almost uniform phase response.

  5. Frequency-stepped acquisition in nuclear magnetic resonance spectroscopy under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Pell, Andrew J.; Clément, Raphaële J.; Grey, Clare P.; Emsley, Lyndon; Pintacuda, Guido

    2013-03-01

    The nuclear magnetic resonance of paramagnetic solids is usually characterized by the presence of large chemical shifts and shift anisotropies due to hyperfine interactions. Frequently the resulting spectra cover a frequency range of several megahertz, which is greater than the bandwidth of commercially available radio-frequency (RF) probes, making it impossible to acquire the whole spectrum in a single experiment. In these cases it common to record a series of spectra, in which the probe is tuned to a different frequency for each, and then sum the results to give the "true" spectrum. While this method is very widely used on static samples, the application of frequency stepping under magic-angle spinning (MAS) is less common, owing to the increased complexity of the spin dynamics when describing the interplay of the RF irradiation with the mechanical rotation of the shift tensor. In this paper, we present a theoretical description, based on the jolting frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983), 10.1016/0022-2364(83)90279-2], for describing the spin dynamics of a powder sample under MAS when subjected to a selective pulse of low RF-field amplitude. The formalism is used to describe the frequency stepping method under MAS, and under what circumstances the true spectrum is reproduced. We also present an experimental validation of the methodology under ultra-fast MAS with the paramagnetic materials LiMnPO4 and TbCsDPA.

  6. Differential frequency-dependent antidromic resonance of the Schaffer collaterals and mossy fibers.

    PubMed

    Franco, Luis M; Beltrán, Jesús Q; Tapia, Jesús A; Ortiz, Franco; Manjarrez, Elías; Gutiérrez, Rafael

    2016-05-01

    To better understand information transfer along the hippocampal pathways and its plasticity, here we studied the antidromic responses of the dentate gyrus (DG) and CA3 to activation of the mossy fibers and Schaffer collaterals, respectively, in hippocampal slices from naïve and epileptic rats. We applied trains of 600 electrical stimuli at functionally meaningful frequencies (θ, β/γ and γ). The responses of the DG to θ frequency trains underwent rapid potentiation that lasted about 400 stimuli, after which they progressively returned to control value. At β/γ and γ frequencies, however, the initial potentiation was followed by a strong frequency-dependent depression within the first 50 stimuli. In kindled animals, the initial potentiation was stronger than in control preparations and the resonant phase at θ frequency lasted longer. In contrast, CA3 responses were exponentially depressed at all frequencies, but depression was significantly less intense at θ frequency in epileptic preparations. Failure of fibers to fire action potentials could account for some of the aforementioned characteristics, but waveforms of the intracellular action potentials also changed as the field responses did, i.e., half-duration and time-to-peak increased in both structures along the stimulation trains. Noteworthy, block of glutamate and GABA ionotropic receptors prevented resonance and reduced the depression of antidromic responses to β/γ and γ stimulation recorded in the DG, but not in CA3. We show that the different behavior in the information transfer along these pathways depends on the frequency at which action potentials are generated, excitability history and anatomical features, including myelination and tortuosity. In addition, the mossy fibers are endowed with ionotropic receptors and terminal active properties conferring them their sui generis non-passive antidromic responses. PMID:25665800

  7. Far off-resonance laser frequency stabilization using multipass cells in Faraday rotation spectroscopy.

    PubMed

    Quan, Wei; Li, Yang; Li, Rujie; Shang, Huining; Fang, Zishan; Qin, Jie; Wan, Shuangai

    2016-04-01

    We propose a far off-resonance laser frequency stabilization method by using multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if multipass cells with several meters optical path length are used in the conventional Faraday spectroscopy, the detuning of the lock point can be extended much further from the alkali metal resonance. A plate beam splitter was used to generate two different Faraday signals at the same time. The transmitted optical path length was L=50  mm and the reflected optical path length was 2L=100  mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110°C and 130°C. We achieved an rms fluctuation of 0.9 MHz/23 h at a detuning of 0.5 GHz. A frequency drift of 16 MHz/h at a detuning of -5.6  GHz and 4 MHz/h at a detuning of -5.2  GHz were also obtained for the transmitted and reflected light Faraday signal. PMID:27139650

  8. Vibration Mode Observation of Piezoelectric Disk-type Resonator by High Frequency Laser Doppler Vibrometer

    NASA Astrophysics Data System (ADS)

    Matsumura, Takeshi; Esashi, Masayoshi; Harada, Hiroshi; Tanaka, Shuji

    For future mobile phones based on cognitive radio technology, a compact multi-band RF front-end architecture is strongly required and an integrated multi-band RF filter bank is a key component in it. Contour-mode resonators are receiving increased attention for a multi-band filter solution, because its resonant frequency is mainly determined by its size and shape, which are defined by lithography. However, spurious responses including flexural vibration are also excited due to its thin structure. To improve resonator performance and suppress spurious modes, visual observation with a laser probe system is very effective. In this paper, we have prototyped a mechanically-coupled disk-array filter, which consists of a Si disk and 2 disk-type resonators of higher-order wine-glass mode, and observed its vibration modes using a high-frequency laser-Doppler vibrometer (UHF-120, Polytec, Inc.). As a result, it was confirmed that higher order wine-glass mode vibration included a compound displacement, and that its out-of-plane vibration amplitude was much smaller than other flexural spurious modes. The observed vibration modes were compared with FEM (Finite Element Method) simulation results. In addition, it was also confirmed that the fabrication error, e.g. miss-alignment, induced asymmetric vibration.

  9. Electron cyclotron harmonic resonances in high-frequency heating of the ionosphere

    SciTech Connect

    Kuo, Spencer P.

    2013-09-15

    Electron acceleration by upper hybrid waves under cyclotron harmonic resonance interaction is studied. Theory is formulated; the analytical solutions in the second and fourth harmonic cyclotron resonance cases are obtained, and in the third harmonic case, a first order differential equation governing the evolution of the electron energy is derived. The theory is applied for explaining the generation of artificial ionization layers observed in high-frequency (HF) ionospheric heating experiments. The upper hybrid waves are assumed to be excited parametrically by the O-mode HF heating wave. As the decay mode is the lower hybrid wave, the excited upper hybrid waves have wavelengths ranging from 0.25 to 0.5 m, which are short enough to effectively incorporate the finite Larmour radius effect for the harmonic cyclotron resonance interactions as well as have a frequency bandwidth of about 20 kHz, which provides an altitude region of about 10 km for continuous harmonic cyclotron resonance interaction between electrons and descending waves in the slightly inhomogeneous geomagnetic field. The numerical results on electron acceleration show that electron fluxes with energies larger than 14 eV are generated in the three harmonic cases. These energetic electrons cause impact ionizations, which are descending to form artificial ionization layers at the bottom of the ionospheric F region.

  10. Power conversion distribution system using a resonant high-frequency AC link

    NASA Technical Reports Server (NTRS)

    Sood, P. K.; Lipo, T. A.

    1986-01-01

    Static power conversion systems based on a resonant high frequency (HF) link offers a significant reduction in the size and weight of the equipment over that achieved with conventional approaches, especially when multiple sources and loads are to be integrated. A faster system response and absence of audible noise are the other principal characteristics of such systems. A conversion configuration based on a HF link which is suitable for applications requiring distributed power is proposed.

  11. Validation of the load-resilient ion cyclotron resonance frequency antenna concept on Tore Supra plasmas

    NASA Astrophysics Data System (ADS)

    Vulliez, K.; Argouarch, A.; Bosia, G.; Berger-By, G.; Bremond, S.; Colas, L.; Lombard, G.; Mendes, A.; Millon, L.; Mollard, P.; Volpe, D.; Beaumont, B.; Bécoulet, A.; Clairet, F.; Ekedahl, A.; Elkhaldi, M.; Gunn, J.; Hoang, G. T.; Tore Supra Team

    2008-06-01

    In the framework of the ion cyclotron resonance frequency heating development at CEA Cadarache, a prototype antenna based on the load-resilient electrical layout foreseen for ITER has been built. This prototype was recently tested in Tore Supra. The ITER-like electrical scheme has been validated during fast perturbations at the edge plasma. Clear load resilience properties are reported. The main conclusions and consequences learned from the development of the ITER antenna are discussed.

  12. Effective side length formula for resonant frequency of equilateral triangular microstrip antenna

    NASA Astrophysics Data System (ADS)

    Guney, Kerim; Kurt, Erhan

    2016-02-01

    A novel and accurate expression is obtained by employing the differential evolution algorithm for the effective side length (ESL) of the equilateral triangular microstrip antenna (ETMA). This useful formula allows the antenna engineers to accurately calculate the ESL of the ETMA. The computed resonant frequencies (RFs) show very good agreement with the experimental RFs when this accurate ESL formula is utilised for the computation of the RFs for the first five modes.

  13. Analytical Modeling for the Bending Resonant Frequency of Multilayered Microresonators with Variable Cross-Section

    PubMed Central

    Herrera-May, Agustín L.; Aguilera-Cortés, Luz A.; Plascencia-Mora, Hector; Rodríguez-Morales, Ángel L.; Lu, Jian

    2011-01-01

    Multilayered microresonators commonly use sensitive coating or piezoelectric layers for detection of mass and gas. Most of these microresonators have a variable cross-section that complicates the prediction of their fundamental resonant frequency (generally of the bending mode) through conventional analytical models. In this paper, we present an analytical model to estimate the first resonant frequency and deflection curve of single-clamped multilayered microresonators with variable cross-section. The analytical model is obtained using the Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. Our model is applied to two multilayered microresonators with piezoelectric excitation reported in the literature. Both microresonators are composed by layers of seven different materials. The results of our analytical model agree very well with those obtained from finite element models (FEMs) and experimental data. Our analytical model can be used to determine the suitable dimensions of the microresonator’s layers in order to obtain a microresonator that operates at a resonant frequency necessary for a particular application. PMID:22164071

  14. Vocal tract motor patterns and resonance during constant frequency song: the white-throated sparrow.

    PubMed

    Riede, Tobias; Suthers, Roderick A

    2009-02-01

    Bird song is a complex behavior that requires the coordination of several motor systems. Sound is produced in the syrinx and then modified by the upper vocal tract. Movements of the hyoid skeleton have been shown in the northern cardinal (Cardinalis cardinalis) to be extensively involved in forming an oropharyngeal-esophageal cavity (OEC), which contributes a major resonance to the vocal tract transfer function. Here we report that a similar relationship exists between the volume of the OEC and the fundamental frequency in the white-throated sparrow (Zonotrichia albicollis) whose song, unlike that of the cardinal, consists of a series of almost constant frequency notes. Cineradiography of singing sparrows shows that the oropharyngeal cavity and cranial end of the esophagus expand abruptly at the start of each note and maintain a relatively constant volume until the end of the note. Computation of the vocal tract transfer function suggests a major resonance of the OEC follows the fundamental frequency, making sound transmission more efficient. The presence of similar prominent song-related vocal tract motor patterns in two Oscine families suggests that the active control of the vocal tract resonance by varying the volume of the OEC may be widespread in songbirds. PMID:19082607

  15. Dynamics of suspended microchannel resonators conveying opposite internal fluid flow: Stability, frequency shift and energy dissipation

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Ming; Yan, Han; Jiang, Hui-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

    2016-04-01

    In this paper, the dynamics of suspended microchannel resonators which convey internal flows with opposite directions are investigated. The fluid-structure interactions between the laminar fluid flow and oscillating cantilever are analyzed by comprehensively considering the effects of velocity profile, flow viscosity and added flowing particle. A new model is developed to characterize the dynamic behavior of suspended microchannel resonators with the fluid-structure interactions. The stability, frequency shift and energy dissipation of suspended microchannel resonators are analyzed and discussed. The results demonstrate that the frequency shifts induced by the added flowing particle which are obtained from the new model have a good agreement with the experimental data. The steady mean flow can cause the frequency shift and influence the stability of the dynamic system. As the flow velocity reaches the critical value, the coupled-mode flutter occurs via a Hamiltonian Hopf bifurcation. The perturbation flow resulted from the vibration of the microcantilever leads to energy dissipation, while the steady flow does not directly cause the damping which increases with the increasing of the flow velocity predicted by the classical model. It can also be found that the steady flow firstly changes the mode shape of the cantilever and consequently affects the energy dissipation.

  16. Kinetic interpretation of resonance phenomena in low pressure capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Eremin, Denis; Brinkmann, Ralf Peter; Schulze, Julian; Schuengel, Edmund; Derzsi, Aranka; Korolov, Ihor; Hartmann, Peter; Donkó, Zoltán; Mussenbrock, Thomas

    2016-06-01

    Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important questions open: How is current continuity ensured in the presence of energetic electron beams generated by the expanding sheaths that lead to a local enhancement of the conduction current propagating through the bulk? How do the beam electrons interact with cold bulk electrons? What is the kinetic origin of resonance phenomena? Based on kinetic simulations, we find that the energetic beam electrons interact with cold bulk electrons (modulated on a timescale of the inverse local electron plasma frequency) via a time dependent electric field outside the sheaths. This electric field is caused by the electron beam itself, which leaves behind a positive space charge, that attracts cold bulk electrons towards the expanding sheath. The resulting displacement current ensures current continuity by locally compensating the enhancement of the conduction current. The backflow of cold electrons and their interaction with the nonlinear plasma sheath cause the generation of multiple electron beams during one phase of sheath expansion and contribute to a strongly non-sinusoidal RF current. These kinetic mechanisms are the basis for a fundamental understanding of the electron power absorption dynamics and resonance phenomena in such plasmas, which are found to occur in discharges of different symmetries including perfectly symmetric plasmas.

  17. A micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications

    NASA Astrophysics Data System (ADS)

    Wingqvist, G.; Arapan, L.; Yantchev, V.; Katardjiev, I.

    2009-03-01

    Micromachined thin film plate acoustic wave resonators (FPARs) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2 µm thick aluminium nitride (AlN) membranes have been successfully demonstrated (Yantchev and Katardjiev 2007 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54 87-95). The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900 MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is the non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm K-1 to -25 ppm K-1. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.

  18. An Application of Artificial Neural Network to Compute the Resonant Frequency of E-Shaped Compact Microstrip Antennas

    NASA Astrophysics Data System (ADS)

    Akdagli, Ali; Toktas, Abdurrahim; Kayabasi, Ahmet; Develi, Ibrahim

    2013-09-01

    An application of artificial neural network (ANN) based on multilayer perceptrons (MLP) to compute the resonant frequency of E-shaped compact microstrip antennas (ECMAs) is presented in this paper. The resonant frequencies of 144 ECMAs with different dimensions and electrical parameters were firstly determined by using IE3D(tm) software based on the method of moments (MoM), then the ANN model for computing the resonant frequency was built by considering the simulation data. The parameters and respective resonant frequency values of 130 simulated ECMAs were employed for training and the remaining 14 ECMAs were used for testing the model. The computed resonant frequencies for training and testing by ANN were obtained with the average percentage errors (APE) of 0.257% and 0.523%, respectively. The validity and accuracy of the present approach was verified on the measurement results of an ECMA fabricated in this study. Furthermore, the effects of the slots loading method over the resonant frequency were investigated to explain the relationship between the slots and resonant frequency.

  19. Suppression of frequency locking noise in resonator fiber optic gyro by differential detection method

    NASA Astrophysics Data System (ADS)

    Feng, Lishuang; Zhi, Yinzhou; Lei, Ming; Wang, Junjie

    2014-10-01

    The performance of the resonator fiber optic gyro (RFOG) is influenced by frequency locking noise. This paper proposes a differential detection method (DDM) to suppress the frequency locking noise. First, the frequency locking noise induced by the frequency locking error is described theoretically; the description indicates that it acts as the common-mode noise in the RFOG. In the traditional signal-path detection method (SDM), there is a trade-off between suppressing the frequency locking noise and improving the gyro sensitivity. Thus, a model of the DDM is set up and analyzed. The frequency locking noise can be suppressed using the DDM by adjusting the gains of two lock-in amplifiers. Finally, the experimental setup is established, and the SDM and DDM are compared. When the tested equivalent frequency locking noise is 10.6°/h, the bias stability of the RFOG is improved from 12.9°/h to 1.1°/h by the DDM.

  20. A solid-mounted resonator-oscillator-based 4.596 GHz frequency synthesis.

    PubMed

    Boudot, R; Li, M D; Giordano, V; Rolland, N; Rolland, P A; Vincent, P

    2011-03-01

    This paper describes a 4.596 GHz frequency synthesis based on a 2.1 GHz solid mounted resonator (SMR) voltage-controlled oscillator (VCO). The SMR oscillator presents a chip size lower than 2 mm(2), a power consumption of 18.2 mW, and exhibits a phase noise of -89 dBc/Hz and -131 dBc/Hz at 2 kHz and 100 kHz offset frequencies, respectively. The VCO temperature-frequency dependence is measured to be -14 ppm∕°C over a range of -20°C to 60°C. From this source, a low noise frequency synthesizer is developed to generate a 4.596 GHz signal (half of the Cs atom hyperfine transition frequency) with a phase noise of -81 dBc/Hz and -120 dBc/Hz at 2 kHz and 100 kHz from the carrier. The frequency synthesis output is used as a local oscillator in a Cs vapor microcell-based compact atomic clock. Preliminary results are reported and discussed. To the authors knowledge, this is the first development of a SMR-oscillator-based frequency synthesizer for miniature atomic clocks applications. PMID:21456775

  1. Tire-road friction coefficient estimation based on the resonance frequency of in-wheel motor drive system

    NASA Astrophysics Data System (ADS)

    Chen, Long; Bian, Mingyuan; Luo, Yugong; Qin, Zhaobo; Li, Keqiang

    2016-01-01

    In this paper, a resonance frequency-based tire-road friction coefficient (TRFC) estimation method is proposed by considering the dynamics performance of the in-wheel motor drive system under small slip ratio conditions. A frequency response function (FRF) is deduced for the drive system that is composed of a dynamic tire model and a simplified motor model. A linear relationship between the squared system resonance frequency and the TFRC is described with the FRF. Furthermore, the resonance frequency is identified by the Auto-Regressive eXogenous model using the information of the motor torque and the wheel speed, and the TRFC is estimated thereafter by a recursive least squares filter with the identified resonance frequency. Finally, the effectiveness of the proposed approach is demonstrated through simulations and experimental tests on different road surfaces.

  2. Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR

    PubMed Central

    Wu, C.H.; De Angelis, Anna A.; Opella, Stanley J.

    2014-01-01

    The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped 13C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly 13C, 15N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700 MHz and 900 MHz 1H resonance frequencies, respectively. For the single 13Cα of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three 13Cα signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment. PMID:25051542

  3. Carbon Nanofiber-Based, High-Frequency, High-Q, Miniaturized Mechanical Resonators

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Epp, Larry W.; Bagge, Leif

    2011-01-01

    High Q resonators are a critical component of stable, low-noise communication systems, radar, and precise timing applications such as atomic clocks. In electronic resonators based on Si integrated circuits, resistive losses increase as a result of the continued reduction in device dimensions, which decreases their Q values. On the other hand, due to the mechanical construct of bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators, such loss mechanisms are absent, enabling higher Q-values for both BAW and SAW resonators compared to their electronic counterparts. The other advantages of mechanical resonators are their inherently higher radiation tolerance, a factor that makes them attractive for NASA s extreme environment planetary missions, for example to the Jovian environments where the radiation doses are at hostile levels. Despite these advantages, both BAW and SAW resonators suffer from low resonant frequencies and they are also physically large, which precludes their integration into miniaturized electronic systems. Because there is a need to move the resonant frequency of oscillators to the order of gigahertz, new technologies and materials are being investigated that will make performance at those frequencies attainable. By moving to nanoscale structures, in this case vertically oriented, cantilevered carbon nanotubes (CNTs), that have larger aspect ratios (length/thickness) and extremely high elastic moduli, it is possible to overcome the two disadvantages of both bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators. Nano-electro-mechanical systems (NEMS) that utilize high aspect ratio nanomaterials exhibiting high elastic moduli (e.g., carbon-based nanomaterials) benefit from high Qs, operate at high frequency, and have small force constants that translate to high responsivity that results in improved sensitivity, lower power consumption, and im - proved tunablity. NEMS resonators have recently been demonstrated using topdown

  4. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  5. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  6. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  7. Dynamic field-frequency lock for tracking magnetic field fluctuations in electron spin resonance experiments

    NASA Astrophysics Data System (ADS)

    Asfaw, Abraham; Tyryshkin, Alexei; Lyon, Stephen

    Global magnetic field fluctuations present significant challenges to pulsed electron spin resonance experiments on systems with long spin coherence times. We will discuss results from experiments in which we follow instantaneous changes in magnetic field by locking to the free induction decay of a proton NMR signal using a phase-locked loop. We extend conventional field-frequency locking techniques used in NMR to follow slow magnetic field drifts by using a modified Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence in which the phase of the pi-pulses follows the phase of the proton spins at all times. Hence, we retain the ability of the CPMG pulse sequence to refocus local magnetic field inhomogeneities without refocusing global magnetic field fluctuations. In contrast with conventional field-frequency locking techniques, our experiments demonstrate the potential of this method to dynamically track global magnetic field fluctuations on timescales of about 2 seconds and with rates faster than a kHz. This frequency range covers the dominant noise frequencies in our electron spin resonance experiments as previously reported.

  8. Frequency stability of an RF oscillator with an MEMS-based encapsulated resonator

    NASA Astrophysics Data System (ADS)

    Bohua, Peng; Wei, Luo; Jicong, Zhao; Quan, Yuan; Jinling, Yang; Fuhua, Yang

    2015-07-01

    This paper presents a high-Q RF MEMS oscillator consisting of a micro-disk resonator and low noise feedback circuits. The oscillator has high frequency stability and low phase noise. The two-port resonator was hermetically encapsulated using low-cost Sn-rich Au-Sn solder bonding, which significantly improves the frequency stability. A low noise oscillator circuit was designed with a two-stage amplifying architecture which effectively improves both the frequency stability and phase noise performance. The measured phase noise is -96 dBc/Hz at 1 kHz offset and -128 dBc/Hz at far-from-carrier offsets. Moreover, the medium-term frequency stability and Allan deviation of the oscillator are ±4 ppm and 10 ppb, respectively. The oscillator is a promising component in future wireless communication application. Project supported by the National Natural Science Foundation of China (Nos. 61234007, 61404136) and the State Key Development Program for Basic Research of China (Nos. 2011CB933102, 2013YQ16055103).

  9. Recent developments in phyroshock simulation using fixtures with tunable resonant frequencies

    SciTech Connect

    Davie, N.T.; Bateman, V.I.

    1994-02-01

    Pyroshock is a potentially severe environment produced by the detonation of explosively actuated components and stage separation hardware. Electronic components exposed to pyroshock events during flight or deployment can be damaged by this high frequency, high G shock. Flight qualification of these components may be accomplished using one of many existing techniques to simulate the pyroshock environment in the laboratory. Two new techniques developed at Sandia National Laboratories allow larger components to be tested to a wide variety of pyroshock environments. The frequency content and amplitude of the simulated pyroshock can be easily controlled in a predictable manner. The pyroshock environment is produced by the resonant response of a test fixture that has been excited by a mechanical impact. The resonant fixture has a dominant frequency that can be continuously adjusted over a frequency range that is typically found in most pyroshock environments. The test apparatus and techniques utilized by each method will be described in this paper. Experimental results will be presented which illustrate the capabilities of each method.

  10. A new resonance-frequency based electrical impedance spectroscopy and its application in biomedical engineering

    NASA Astrophysics Data System (ADS)

    Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Zheng, Bin

    2014-03-01

    Electrical Impedance Spectroscopy (EIS) has shown promising results for differentiating between malignant and benign tumors, which exhibit different dielectric properties. However, the performance of current EIS systems has been inadequate and unacceptable in clinical practice. In the last several years, we have been developing and testing a new EIS approach using resonance frequencies for detection and classification of suspicious tumors. From this experience, we identified several limitations of current technologies and designed a new EIS system with a number of new characteristics that include (1) an increased A/D (analog-to-digital) sampling frequency, 24 bits, and a frequency resolution of 100 Hz, to increase detection sensitivity (2) automated calibration to monitor and correct variations in electronic components within the system, (3) temperature sensing and compensation algorithms to minimize impact of environmental change during testing, and (4) multiple inductor-switching to select optimum resonance frequencies. We performed a theoretical simulation to analyze the impact of adding these new functions for improving performance of the system. This system was also tested using phantoms filled with variety of liquids. The theoretical and experimental test results are consistent with each other. The experimental results demonstrated that this new EIS device possesses the improved sensitivity and/or signal detection resolution for detecting small impedance or capacitance variations. This provides the potential of applying this new EIS technology to different cancer detection and diagnosis tasks in the future.

  11. Electron density and collision frequency of microwave resonant cavity produced discharges. [Progress report

    SciTech Connect

    McColl, W.; Brooks, C.; Brake, M.L.

    1992-12-31

    This progress report consists of an article, the abstract of which follows, and apparently the references and vita from a proposal. A review of perturbation diagnostics applied to microwave resonant cavity discharges is presented. The classical microwave perturbation technique examines the shift in the resonant frequency and cavity quality factor of the resonant cavity caused by low electron density discharges. However, modifications presented here allow the analysis to be applied to discharges with electron densities beyond the limit predicted by perturbation theory. An {open_quote}exact{close_quote} perturbation analysis is presented which models the discharge as a separate dielectric, thereby removing the restrictions on electron density imposed by the classical technique. The {open_quote}exact{close_quote} method also uses measurements of the shifts in the resonant conditions of the cavity. Thirdly, an electromagnetic analysis is presented which uses a characteristic equation, based upon Maxwell`s laws, and predicts the discharge conductivity based upon measurements of a complex axial wave number. By allowing the axial wave number of the electromagnetic fields to be complex, the fields are experimentally and theoretically shown to be spatially attenuated. The diagnostics are applied to continuous-wave microwave (2.45 GHz) discharges produced in an Asmussen resonant cavity. Double Langmuir probes, placed directly in the discharge at the point where the radial electric field is zero, act as a comparison with the analytic diagnostics. Microwave powers ranging from 30 to 100 watts produce helium and nitrogen discharges with pressures ranging from 0.5 to 6 torr. Analysis of the data predicts electron temperatures from 5 to 20 eV, electron densities from 10{sup 11} to 3 {times} 10{sup 12} cm{sup {minus}3}, and collision frequencies from 10{sup 9} to 10{sup 11} sec{sup {minus}1}.

  12. The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

    NASA Astrophysics Data System (ADS)

    Rossini, Aaron J.; Hamaed, Hiyam; Schurko, Robert W.

    2010-09-01

    The acquisition of nuclear quadrupole resonance (NQR) spectra with wideband uniform rate and smooth truncation (WURST) pulses is investigated. 75As and 35Cl NQR spectra acquired with the WURST echo sequence are compared to those acquired with standard Hahn-echo sequences and echo sequences which employ composite refocusing pulses. The utility of WURST pulses for locating NQR resonances of unknown frequency is investigated by monitoring the integrated intensity and signal to noise of 35Cl and 75As NQR spectra acquired with transmitter offsets of several hundreds kilohertz from the resonance frequencies. The WURST echo sequence is demonstrated to possess superior excitation bandwidths in comparison to the pulse sequences which employ conventional monochromatic rectangular pulses. The superior excitation bandwidths of the WURST pulses allows for differences in the characteristic impedance of the receiving and excitation circuits of the spectrometer to be detected. Impedance mismatches have previously been reported by Marion and Desvaux [D.J.Y. Marion, H. Desvaux, J. Magn. Reson. (2008) 193(1) 153-157] and Muller et al. [M. Nausner, J. Schlagnitweit, V. Smrecki, X. Yang, A. Jerschow, N. Muller, J. Magn. Reson. (2009) 198(1) 73-79]. In this regard, WURST pulse sequences may afford an efficient new method for experimentally detecting impedance mismatches between receiving and excitation circuits, allowing for the optimization of solids and solution NMR and NQR spectrometer systems. The use of the Carr-Purcell Meiboom-Gill (CPMG) pulse sequence for signal enhancement of NQR spectra acquired with WURST pulses and conventional pulses is also investigated. Finally, the utility of WURST pulses for the acquisition of wideline NQR spectra is demonstrated by acquiring part of the 63/65Cu NQR spectrum of CuCN.

  13. The measurement of the resonant frequency of quartz crystal units: An ongoing saga

    NASA Astrophysics Data System (ADS)

    Kentley, Eric

    1992-06-01

    The history of practical methods of industrial measurement leading to the present situation is traced. Resonant frequency measurement of a quartz crystal unit has always presented problems due to the fact that a quartz crystal unit is not an absolute frequency determining device. The frequency of oscillation of a quartz crystal unit in an oscillator circuit is a function of the crystal unit and the maintaining oscillator circuit. Since the introduction of zero phase type measurements in a passive network by the I.E.C. in the early 1970's many of these measurement problems have been eliminated or much reduced, but there are still some problem areas. Using the computer aided test methods now available, automatic crystal measurements can be made. These can cause what might be termed computer aided correlation errors due to slightly different measuring procedures and methods of computation.

  14. High-frequency resonant tunnelling diode oscillator with high-output power

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Alharbi, Khalid; Ofiare, Afesomeh; Khalid, Ata; Cumming, David; Wasige, Edward

    2015-10-01

    In this paper, a prototype G-band (140 GHz-220 GHz) monolithic microwave integrated circuit (MMIC) resonant tunneling diode (RTD) oscillator is reported. The oscillator employs two In0.53Ga0.47As/AlAs RTD devices in the circuit to increase the output power. The measured output power was about 0.34 mW (-4.7 dBm) at 165.7 GHz, which is the highest power reported for RTD oscillator in G-band frequency range. This result demonstrates the validity of the high frequency/high power RTD oscillator design. It indicates that RTD devices, as one of the terahertz (THz) source candidates, have promising future for room-temperature THz applications in such as imaging, wireless communication and spectroscopy analysis, etc. By optimizing RTD oscillator design, it is expected that considerably higher power (>1 mW) at THz frequencies (>300 GHz) will be obtained.

  15. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process.

    PubMed

    Zheng, Jian; Katsuragawa, Masayuki

    2015-01-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm. PMID:25748023

  16. The mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets.

    PubMed

    Girard, Adrien; Saviot, Lucien; Pedetti, Silvia; Tessier, Mickaël D; Margueritat, Jérémie; Gehan, Hélène; Mahler, Benoit; Dubertret, Benoit; Mermet, Alain

    2016-07-01

    Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. The calculated eigen frequencies of vibrating platelets weighed down by the mass of the organic ligands are in very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances. PMID:27334524

  17. Resonance-based low-frequency synthetic jet actuator modeling, design, and testing

    NASA Astrophysics Data System (ADS)

    Gravatt, Lynn; Flatau, Alison

    2006-03-01

    Synthetic Jet Actuators have been the topic of extensive study in the aerospace industry because of their ability to actively control flow over aerodynamic surfaces without discrete control surfaces such as a flap. One challenge has been to develop a low frequency, lightweight actuator that can provide large displacements. This study will discuss the modeling, design, manufacture, and testing of a bimorph piezo-composite actuator that will provide such displacements at low frequencies. The design employs two opposing benders that provide a piston-type motion. The initial goals of this study were to achieve 30 m/s out of the slot while maintaining the mechanical resonant frequency of the system at about 100 Hz.

  18. Field and frequency modulated sub-THz electron spin resonance spectrometer

    NASA Astrophysics Data System (ADS)

    Caspers, Christian; da Silva, Pedro Freire; Soundararajan, Murari; Haider, M. Ali; Ansermet, Jean-Philippe

    2016-05-01

    260-GHz radiation is used for a quasi-optical electron spin resonance (ESR) spectrometer which features both field and frequency modulation. Free space propagation is used to implement Martin-Puplett interferometry with quasi-optical isolation, mirror beam focusing, and electronic polarization control. Computer-aided design and polarization pathway simulation lead to the design of a compact interferometer, featuring lateral dimensions less than a foot and high mechanical stability, with all components rated for power levels of several Watts suitable for gyrotron radiation. Benchmark results were obtained with ESR standards (BDPA, DPPH) using field modulation. Original high-field ESR of 4f electrons in Sm3+-doped Ceria was detected using frequency modulation. Distinct combinations of field and modulation frequency reach a signal-to-noise ratio of 35 dB in spectra of BDPA, corresponding to a detection limit of about 1014 spins.

  19. Frequency Split Elimination Method for a Solid-State Vibratory Angular Rate Gyro with an Imperfect Axisymmetric-Shell Resonator

    PubMed Central

    Lin, Zhen; Fu, Mengyin; Deng, Zhihong; Liu, Ning; Liu, Hong

    2015-01-01

    The resonator of a solid-state vibratory gyro is responsible for sensing angular motion. Frequency splitting of an axisymmetric-shell resonator is a common problem caused by manufacturing defects. The defect causes a frequency difference between two working modes which consist of two nodes and two antinodes. The difference leads to the loss of gyroscopic effect, and thus the resonator cannot sense angular motion. In this paper, the resonator based on an axisymmetric multi-curved surface shell structure is investigated and an approach to eliminate frequency splits is proposed. Since axisymmetric multi-curved surface shell resonators are too complex to be modeled, this paper proposes a simplified model by focusing on a common property of the axisymmetric shell. The resonator with stochastic imperfections is made equivalent to a perfect shell with an imperfect mass point. Rayleigh's energy method is used in the theoretical analysis. Finite element modeling is used to demonstrate the effectiveness of the elimination approach. In real cases, a resonator's frequency split is eliminated by the proposed approach. In this paper, errors in the theoretical analysis are discussed and steps to be taken when the deviation between assumptions and the real situation is large are figured out. The resonator has good performance after processing. The elimination approach can be applied to any kind of solid-state vibratory gyro resonators with an axisymmetric shell structure. PMID:25648707

  20. Observation of 1H-13C and 1H-1H proximities in a paramagnetic solid by NMR at high magnetic field under ultra-fast MAS.

    PubMed

    Li, Shenhui; Trébosc, Julien; Lafon, Olivier; Zhou, Lei; Shen, Ming; Pourpoint, Frédérique; Amoureux, Jean-Paul; Deng, Feng

    2015-02-01

    The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum↔single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. PMID:25557861

  1. The mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets

    NASA Astrophysics Data System (ADS)

    Girard, Adrien; Saviot, Lucien; Pedetti, Silvia; Tessier, Mickaël D.; Margueritat, Jérémie; Gehan, Hélène; Mahler, Benoit; Dubertret, Benoit; Mermet, Alain

    2016-07-01

    Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. The calculated eigen frequencies of vibrating platelets weighed down by the mass of the organic ligands are in very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances.Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. The calculated eigen frequencies of vibrating platelets weighed down by the mass of the organic ligands are in very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR07383A

  2. Experimental study on the characteristic of the NS-GT cut quartz crystal resonator oscillating in the sub-resonant frequency.

    PubMed

    Yamagata, S; Kawashima, H

    1999-01-01

    We previously reported that the dynamic photo-elastic method was a very effective measuring technique for the stress distribution of vibrating quartz crystal resonators. The existence of a twisted asymmetrical vibration mode has been verified experimentally when the NS-GT cut quartz crystal resonator was vibrating in the main resonant frequency (MRF). A MRF and a sub-resonant frequency (SRF) of the NS-GT cut quartz resonator were defined as follows. If a mechanical standing wave was in the x' or y' direction of the resonator, the former was MRF vibration and the latter was SRF vibration, respectively. In this paper, stress distributions of two samples of the NS-GT cut quartz crystal resonator, one of which had a thickness of 80 mum and the other 150 mum, were measured by the dynamic photo-elastic method when the resonators were vibrating in each SRF. Thereafter, vibration modes of those resonators were estimated by the experimental data of stress distributions. We find that the vibration mode of the 80-mum resonator had a simple mechanical standing wave on the y' direction and the vibration mode of the 150-mum resonator was combined with a shearing mode in the SRF vibration. From the experiment, we decided that vibration modes of the NS-GT cut quartz crystal resonator were composed of the longitudinal stress T(3)' belonging to the z' direction of the plate and of the shearing stress T(5)' when the plate thickness was thickened and the resonator was oscillating in the SRF. PMID:18244311

  3. Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

    NASA Astrophysics Data System (ADS)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

    Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

  4. High-frequency electron resonances and surface waves in unmagnetized bounded plasmas

    NASA Astrophysics Data System (ADS)

    Bowers, Kevin James

    2001-10-01

    As all laboratory and industrial plasma devices have boundaries, understanding the plasma-wall interaction is critical. This thesis explores high frequency (beyond the ion plasma frequency) resonances and surface waves in unmagnetized bounded plasmas. Special emphasis is placed on low-temperature plasmas in planar systems as such are useful for materials processing. Chapter 1, Chapter 2 and Chapter 3 conduct simulation studies of electron series resonance sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics (resistive V-I phase, frequency tunable density, low-temperature, low- pressure). Surface wave plasmas are the natural extension to resonant plasmas and are promising for use in large-area plasma sources. Appropriate for large-area device modeling, an electromagnetic theory of surface wave propagation in a warm non-uniform plasma is developed and compared to previous theoretical work (Chapter 4 and Chapter 5). In Chapter 6, several PIC simulations are conducted to validate the electromagnetic theory. In Chapter 7, numerical techniques suitable for computing the wave dispersion and impedance in a large-area low- temperature plasma are developed. Utilizing much of the research conducted here, Chapter 8 demonstrates a novel application of surface waves. Through a resonant wave-particle interaction (``Landau resonant heating''), the electron velocity distribution function is controllably modified by a standing surface wave excited with a distributed periodic electrode. Simulation results indicate this Landau resonant heating can be used to dramatically enhance important reactions in low-temperature low- pressure plasmas including electron-impact excitation and electron-impact ionization. In conducting this research, an algorithm to effectively eliminate cache thrashing in a particle-in-cell simulation was developed, resulting in a 40 to 70 percent performance gain on typical workstations. The algorithm is

  5. Harvesting under transient conditions: harvested energy as a proxy for optimal resonance frequency detuning

    NASA Astrophysics Data System (ADS)

    Hynds, Taylor D.; Kauffman, Jeffrey L.

    2015-04-01

    Piezoelectric-based vibration energy harvesting is of interest in a wide range of applications, and a number of harvesting schemes have been proposed and studied { primarily when operating under steady state conditions. However, energy harvesting behavior is rarely studied in systems with transient excitations. This paper will work to develop an understanding of this behavior within the context of a particular vibration reduction technique, resonance frequency detuning. Resonance frequency detuning provides a method of reducing mechanical response at structural resonances as the excitation frequency sweeps through a given range. This technique relies on switching the stiffness state of a structure at optimal times to detune its resonance frequency from that of the excitation. This paper examines how this optimal switch may be triggered in terms of the energy harvested, developing a normalized optimal switch energy that is independent of the open- and short-circuit resistances. Here the open- and short-circuit shunt resistances refer to imposed conditions that approximate the open- and short-circuit conditions, via high and low resistance shunts. These conditions are practically necessary to harvest the small amounts of power needed to switch stiffness states, as open-circuit and closed-circuit refer to infinite resistance and zero resistance, respectively, and therefore no energy passes through the harvesting circuit. The limiting stiffness states are then defined by these open- and short-circuit resistances. The optimal switch energy is studied over a range of sweep rates, damping ratios, and coupling coefficients; it is found to increase with the coupling coefficient and decrease as the sweep rate and damping ratio increase, behavior which is intuitive. Higher coupling means more energy is converted by the piezoelectric material, and therefore more energy is harvested in a given time; an increased sweep rate means resonance is reached sooner, and there will less

  6. Utilizing a high fundamental frequency quartz crystal resonator as a biosensor in a digital microfluidic platform.

    PubMed

    Lederer, Thomas; Stehrer, Brigitte P; Bauer, Siegfried; Jakoby, Bernhard; Hilber, Wolfgang

    2011-12-01

    We demonstrate the operation of a digital microfluidic lab-on-a-chip system utilizing Electro Wetting on Dielectrics (EWOD) as the actuation principle and a High Fundamental Frequency (HFF; 50 MHz) quartz crystal microbalance (QCM) resonator as a mass-sensitive sensor. In a first experiment we have tested the reversible formation of a phosphor-lipid monolayer of phospholipid vesicles out of an aqueous buffer suspension onto a bio-functionalized integrated QCM sensor. A binding of bio-molecules results in an altered mass load of the resonant sensor and a shift of the resonance frequency can be measured. In the second part of the experiment, the formation of a protein multilayer composed of the biomolecule streptavidin and biotinylated immunoglobulin G was monitored. Additionally, the macroscopic contact angle was optically measured in order to verify the bio-specific binding and to test the implications onto the balance of the surface tensions. Using these sample applications, we were able to demonstrate and to verify the feasibility of integrating a mass-sensitive QCM sensor into a digital microfluidic chip. PMID:22241942

  7. Low frequency acoustic energy harvesting using PZT piezoelectric plates in a straight tube resonator

    NASA Astrophysics Data System (ADS)

    Li, Bin; You, Jeong Ho; Kim, Yong-Joe

    2013-05-01

    A novel and practical acoustic energy harvesting mechanism to harvest traveling sound at low audible frequency is introduced and studied both experimentally and numerically. The acoustic energy harvester in this study contains a quarter-wavelength straight tube resonator with lead zirconate titanate (PZT) piezoelectric cantilever plates placed inside the tube. When the tube resonator is excited by an incident sound at its acoustic resonance frequency, the amplified acoustic pressure inside the tube drives the vibration motions of piezoelectric plates, resulting in the generation of electricity. To increase the total voltage and power, multiple PZT plates were placed inside the tube. The number of PZT plates to maximize the voltage and power is limited due to the interruption of air particle motion by the plates. It has been found to be more beneficial to place the piezoelectric plates in the first half of the tube rather than along the entire tube. With an incident sound pressure level of 100 dB, an output voltage of 5.089 V was measured. The output voltage increases linearly with the incident sound pressure. With an incident sound pressure of 110 dB, an output voltage of 15.689 V and a power of 12.697 mW were obtained. The corresponding areal and volume power densities are 0.635 mW cm-2 and 15.115 μW cm-3, respectively.

  8. Non-destructive testing of ceramic balls using high frequency ultrasonic resonance spectroscopy.

    PubMed

    Petit, S; Duquennoy, M; Ouaftouh, M; Deneuville, F; Ourak, M; Desvaux, S

    2005-12-01

    Although ceramic balls are used more and more for bearings in the aerospace and space industries, defects in this type of ceramic material could be dangerous, particularly if such defects are located close to the surface. In this paper, we propose a non-destructive testing method for silicon nitride balls, based on ultrasonic resonance spectroscopy. Through the theoretical study of their elastic vibrations, it is possible to characterize the balls using a vibration mode that is similar to surface wave propagation. The proposed methodology can both excite spheroidal vibrations in the ceramic balls and detect such vibrations over a large frequency range. Studying their resonance spectrums allows the balls' elastic parameters be characterized. Ours is an original method that can quickly estimate the velocity of surface waves using high frequency resonances, which permits surface and sub-surface areas to be tested specifically. Two applications are described in this paper. Both use velocity measurements to achieve their different goals, the first to differentiate between flawless balls from different manufacturing processes, and the second to detect small defects, such as cracks. Our method is rapid and permits the entire ceramic ball to be tested in an industrial context. PMID:16083931

  9. All-dielectric frequency selective surface design based on dielectric resonator

    NASA Astrophysics Data System (ADS)

    Zheng-Bin, Wang; Chao, Gao; Bo, Li; Zhi-Hang, Wu; Hua-Mei, Zhang; Ye-Rong, Zhang

    2016-06-01

    In this work, we propose an all-dielectric frequency selective surface (FSS) composed of periodically placed high-permittivity dielectric resonators and a three-dimensional (3D) printed supporter. Mie resonances in the dielectric resonators offer strong electric and magnetic dipoles, quadrupoles, and higher order terms. The re-radiated electric and magnetic fields by these multipoles interact with the incident fields, which leads to total reflection or total transmission in some special frequency bands. The measured results of the fabricated FSS demonstrate a stopband fractional bandwidth (FBW) of 22.2%, which is consistent with the simulated result. Project supported by the National Natural Science Foundation of China (Grant Nos. 61201030, 61372045, 61472045, and 61401229), the Science and Technology Project of Jiangsu Province, China (Grant No. BE2015002), the Open Research Program of the State Key Laboratory of Millimeter Waves, China (Grant Nos. K201616 and K201622), and the Nanjing University of Posts and Telecommunications Scientific Foundation, China (Grant No. NY214148).

  10. The super-low frequency resonances at magnetospheric boundaries versus geostationary and ionospheric data

    NASA Astrophysics Data System (ADS)

    Savin, Sergey; Surjalal Sharma, A.; Pilipenko, Viacheslav; Marcucci, Maria Federica; Nemecek, Zdenek; Safrankova, Jana; Consolini, Giuseppe; Belakhovsky, Vladimir; Kozak, Ludmila; Blecki, Jan; Kronberg, Elena

    2016-07-01

    We do a multi-point study of the influence of the lowest frequency resonances (0.02-10 mHz) at the outer magnetospheric boundaries on the fluctuations inside the magnetosphere and ionosphere presented. The correlations of the dynamic pressure data from CLUSTER, DOUBLE STAR, GEOTAIL, ACE/ WIND, particle data from LANL, GOES with the magnetic data from polar ionospheric stations on March 27, 2005, show that: i) the waves generated by boundary resonances and their harmonics penetrate inside the magnetosphere and reach the ionosphere; ii) correlations between the dynamic pressure fluctuations at the magnetospheric boundaries and magnetospheric/ ionospheric disturbances, including indices such as AE and SYM-H, can exceed 80%; iii) the new resonance frequencies are lower by an order of magnitude compared with our previous studies, which are as low as 0.02 mHz. Furthermore, such resonances are characteristic also for the night-side geostationary/ionospheric data and for the middle tail, i.e., they are global magnetospheric features. Analysis of different types of correlations yields the unexpected result that in ~48% of the cases with pronounced maximum in the correlation function the geostationary/ ionospheric response is seen before the magnetosheath (MSH) response. We propose that some global magnetospheric resonances (e.g. membrane bow shock surface (0.2-0.5 mHz) and/or magnetopause (0.5-0.9 mHz) modes along with the cavity MHS/ cusp (3-10 mHz) and magnetospheric global modes (0.02-0.09mHz)) can account for the data presented. The multiple jets at the sampled MSH locations can be a consequence of the resonances, while an initial disturbance (e.g. through the interplanetary shocks, Hot Flow Anomalies, foreshock irregularities etc., were not observed by particular spacecraft in MSH because they were localized in the plane perpendicular to the Sun-Earth line. So, in the explorations of the solar wind - magnetosphere interactions one should take into account these

  11. Quanty for core level spectroscopy - excitons, resonances and band excitations in time and frequency domain

    NASA Astrophysics Data System (ADS)

    Haverkort, Maurits W.

    2016-05-01

    Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty, a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org.

  12. Rectangular split-ring resonators with single-split and two-splits under different excitations at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Zahertar, S.; Yalcinkaya, A. D.; Torun, H.

    2015-11-01

    In this work, transmission characteristics of rectangular split-ring resonators with single-split and two-splits are analyzed at microwave frequencies. The resonators are coupled with monopole antennas for excitation. The scattering parameters of the devices are investigated under different polarizations of E and H fields. The magnetic resonances induced by E and H fields are identified and the differences in the behavior of the resonators due to orientations of the fields are explained based on simulation and experimental results. The addition of the second split of the device is investigated considering different configurations of the excitation vectors. It is demonstrated that the single-split and the two-splits resonators exhibit identical transmission characteristics for a certain excitation configuration as verified with simulations and experiments. The presented resonators can effectively function as frequency selective media for varying excitation conditions.

  13. A Novel Piezoresistive Accelerometer with SPBs to Improve the Tradeoff between the Sensitivity and the Resonant Frequency

    PubMed Central

    Xu, Yu; Zhao, Libo; Jiang, Zhuangde; Ding, Jianjun; Peng, Niancai; Zhao, Yulong

    2016-01-01

    For improving the tradeoff between the sensitivity and the resonant frequency of piezoresistive accelerometers, the dependency between the stress of the piezoresistor and the displacement of the structure is taken into consideration in this paper. In order to weaken the dependency, a novel structure with suspended piezoresistive beams (SPBs) is designed, and a theoretical model is established for calculating the location of SPBs, the stress of SPBs and the resonant frequency of the whole structure. Finite element method (FEM) simulations, comparative simulations and experiments are carried out to verify the good agreement with the theoretical model. It is demonstrated that increasing the sensitivity greatly without sacrificing the resonant frequency is possible in the piezoresistive accelerometer design. Therefore, the proposed structure with SPBs is potentially a novel option for improving the tradeoff between the sensitivity and the resonant frequency of piezoresistive accelerometers. PMID:26861343

  14. Global lightning dynamics deduced from Schumann resonance frequency variations at two sites ~ 550 km apart

    NASA Astrophysics Data System (ADS)

    Satori, G.; Mushtak, V.; Neska, M.; Nagy, T.; Barta, V.

    2012-04-01

    Schumann resonance (SR) peak frequencies depend on the lightning source-observer angular distance. The modal phase shift interaction at nodal distances manifests itself as sharp frequency variations: increases or decreases depend on the direction of the source motion with respect to the observer and the mode number. Nagycenk Observatory (47.6° N, 16.7° E), Hungary and Belsk (51.8 ° N, 20.8 ° E), Poland, are relatively close to each other ( ~550 km apart) compared with SR wavelengths. Both stations can approach the nodal position with respect to the African source region for the third Ez mode and to the Asian/American "chimney" regions for the first Ez mode as lightning activity migrates as the seasons change. These two observation sites can be on the different sides of the nodal line region for some weeks twice during a year, indicating the fine seasonal motion of the source regions which causes relatively large frequency variations (some tenth Hz) and different frequency values at the two stations, especially for the third Ez mode. Source-observer distance dependent frequency variations are presented throughout a year by using simultaneous SR observations at Nagycenk (NCK) and Belsk (BLK). The observed frequency changes are supported by the simulation of the distance-dependent frequency variation based on the computed spectra of the vertical electric field components using the Two-Dimensional Telegraph Equation (TDTE) technique (Kirillov, 2002). For the tropical "chimney" regions the diurnal phase of greatest activity has well established spatial-temporal dynamics. Modal peak frequencies are obtained, along with modal intensities and quality factors, by means of the least-squares fitting of "experimental" spectra by the "classic" Lorentzian function (Williams et al., 2006).

  15. Resonance frequency of fluid-filled and prestressed spherical shell-A model of the human eyeball.

    PubMed

    Shih, Po-Jen; Guo, Yi-Ren

    2016-04-01

    An acoustic tonometer that measures shifts in resonance frequencies associated with intraocular pressure (IOP) could provide an opportunity for a type of tonometer that can be operated at home or worn by patients. However, there is insufficient theoretical background, especially with respect to the uncertainty in operating frequency ranges and the unknown relationships between IOPs and resonance frequencies. The purpose of this paper is to develop a frequency function for application in an acoustic tonometer. A linear wave theory is used to derive an explicit frequency function, consisting of an IOP and seven other physiological parameters. In addition, impulse response experiments are performed to measure the natural frequencies of porcine eyes to validate the provided function. From a real-time detection perspective, explicitly providing a frequency function can be the best way to set up an acoustic tonometer. The theory shows that the resonance oscillation of the eyeball is mainly dominated by liquid inside the eyeball. The experimental validation demonstrates the good prediction of IOPs and resonance frequencies. The proposed explicit frequency function supports further modal analysis not only of the dynamics of eyeballs, but also of the natural frequencies, for further development of the acoustic tonometer. PMID:27106326

  16. Self-excitation of the plasma series resonance in radio-frequency discharges: An analytical description

    SciTech Connect

    Czarnetzki, U.; Mussenbrock, T.; Brinkmann, R. P.

    2006-12-15

    Self-excited plasma series resonances (PSR) are observed in capacitve discharges as high-frequency oscillations superimposed on the normal rf current. This high-frequency contribution to the current is generated by a series resonance between the capacitive sheath and the inductive and ohmic bulk of the plasma. The nonlinearity of the sheath leads to a complex dynamic. The effect is applied, e.g., as a diagnostic technique in commercial etch reactors where analysis is performed by a numerical model. Here a simple analytical investigation is introduced. In order to solve the nonlinear equations analytically, a series of approximation is necessary. Nevertheless, the basic physics is conserved and excellent agreement with numerical solutions is found. The model provides explicit and simple formula for the current waveform and the spectral range of the oscillations. In particular, the dependence on the discharge parameters is shown. Further, the model gives insight into an additional dissipation channel opened by the high-frequency oscillations. With decreasing pressure, the ohmic resistance of the bulk decreases as well, while the amplitude of the PSR oscillations grows. This results in substantially higher power dissipation that exceeds the contribution of classical stochastic heating.

  17. Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting

    NASA Astrophysics Data System (ADS)

    Dong, Lin; Prasad, M. G.; Fisher, Frank T.

    2016-06-01

    Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.

  18. Single-resonator dual-frequency AIN-on-Si MEMS oscillators.

    PubMed

    Lavasani, Hossein Miri; Abdolvand, Reza; Ayazi, Farrokh

    2015-05-01

    This paper reports on the design, implementation, and phase-noise optimization of low-power interface IC for dual-frequency oscillators that utilize two high quality factor (Q) width-extensional bulk acoustic modes of the same AlN-on-silicon resonator. Two 0.5-μm CMOS transimpedance amplifiers (TIA) have been designed, characterized, and interfaced with two dual-mode resonators operating at 35.5/105.7 MHz (first/third order modes) and 35.5/174.9 MHz (first/ fifth order modes). One TIA uses open-loop regulated cascode (RGC) topology in the first stage to enable low power operation, whereas the second one uses an inverter with shunt-shunt feedback to deliver higher gain with lower phase noise. An on-chip switching network is incorporated into each TIA to change the oscillation frequency based on the different phase shift. The effect of TIA on the phase-noise performance of oscillators is studied and compared for both topologies. The measured phase noise of low- and high-frequency modes at 1 kHz offset from carrier are -114 and -108 dBc/Hz for the 35/105 MHz oscillator, and -108 and -105 dBc/Hz for the 35/175 MHz oscillator, respectively, whereas the far-from-carrier reaches below -140 dBc/Hz in all cases. PMID:25965675

  19. Chip Scale Atomic Resonator Frequency Stabilization System With Ultra-Low Power Consumption for Optoelectronic Oscillators.

    PubMed

    Zhao, Jianye; Zhang, Yaolin; Lu, Haoyuan; Hou, Dong; Zhang, Shuangyou; Wang, Zhong

    2016-07-01

    We present a long-term chip scale stabilization scheme for optoelectronic oscillators (OEOs) based on a rubidium coherent population trapping (CPT) atomic resonator. By locking a single mode of an OEO to the (85)Rb 3.035-GHz CPT resonance utilizing an improved phase-locked loop (PLL) with a PID regulator, we achieved a chip scale frequency stabilization system for the OEO. The fractional frequency stability of the stabilized OEO by overlapping Allan deviation reaches 6.2 ×10(-11) (1 s) and  ∼ 1.45 ×10 (-11) (1000 s). This scheme avoids a decrease in the extra phase noise performance induced by the electronic connection between the OEO and the microwave reference in common injection locking schemes. The total physical package of the stabilization system is [Formula: see text] and the total power consumption is 400 mW, which provides a chip scale and portable frequency stabilization approach with ultra-low power consumption for OEOs. PMID:26529751

  20. Frequency control of a 1163 nm singly resonant OPO based on MgO:PPLN.

    PubMed

    Gross, P; Lindsay, I D; Lee, C J; Nittmann, M; Bauer, T; Bartschke, J; Warring, U; Fischer, A; Kellerbauer, A; Boller, K-J

    2010-03-15

    We report the realization of a singly resonant optical parametric oscillator (SRO) that is designed to provide narrow-bandwidth, continuously tunable radiation at a wavelength of 1163 nm for optical cooling of osmium ions. The SRO is based on periodically poled, magnesium-oxide-doped lithium niobate and pumped at 532 nm. The output coupling of the resonant idler wave is adjusted to yield up to 400 mW of 1163 nm radiation, with a bandwidth of a few megahertz. For continuous frequency tuning of the idler wave, the SRO is equipped with an intracavity etalon, and the cavity length is controlled with a piezo-actuated mirror synchronized to the etalon angle. PMID:20237610