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1

Explosives detection by nuclear quadrupole resonance (NQR)  

NASA Astrophysics Data System (ADS)

Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a laboratory prototype NQR explosives detector which interrogates a volume of 300 liters (10 ft3). This paper presents abbreviated results from a demonstration of the laboratory prototype NQR explosives detector conducted at the Federal Aviation Administration Technical Center in May 1994 on RDX-based explosives.

Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.; Krauss, Ronald A.

1994-10-01

2

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

NASA Astrophysics Data System (ADS)

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.

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

2006-05-01

3

Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer  

SciTech Connect

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe {sup 11}B and {sup 27}Al NQR resonances. The scope of this study was increased to include {sup 23}Na, {sup 51}V, and {sup 55}Mn NQR transitions. Also, a technique was presented to observe {sup 14}N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two {sup 14}N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

Black, B.E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

1993-07-01

4

Measurement of in-situ stress in salt and rock using NQR techniques  

SciTech Connect

A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising system involves pulsed nuclear double resonance detection; and alterative is to observe the quadrupolar splitting of the NMR signal. Choices to be made in the measurement and mapping techniques are discussed. The well-known perturbation of the homogenous stress field in the neighborhood of a borehole is shown to be advantageous from the point of view of obtaining directional information on the stress. Construction and operation of a borehole stress sensor are considered. The NQR technique seems feasible for measuring the magnitude and direction of underground stress with a resolution of about 25 psi, or 2.5% at 1000 psi. Downhole instrumentation suitable for in-situ determinations of stress appears within the state of the art. Additional tasks required on the project are identified.

Schempp, E.; Hirschfeld, T.; Klainer, S.

1980-12-01

5

Some features of double-resonance detection of 17O NQR in ice  

NASA Astrophysics Data System (ADS)

Proton oxygen-17 double resonance was used to detect the NQR signals of 17O in natural abundance and isotope-enriched ice. When a nonmodulated rf irradiation was applied to a search for the NQR signals, absorptions due to the "solid state effect" which were shifted toward higher frequencies from resonance were detected only in enriched samples. In such circumtances, a saturation phenomenon was observed; at a given frequency (in the vicinity of a resonance) and 17O concentration, the scaling-down factor of the proton signal reaches a characteristic minimum value. The dependence of this value on the 17O concentration indicates that the two spin systems evolve toward a common final spin temperature in the rotating frame, limiting the signal detection to enriched ice. When the NQR irradiation was modulated at a frequency comparable to the dipole-dipole interaction energy between the two nuclear spin systems and applied at resonance, the proton spin temperature evolved to infinity, thus allowing signal detection even at very low concentrations such as the natural abundance of 17O. Distinct signals were detected at 1615 ± 5, 1710 ± 5, and 3320 ± 10 kHz, which yield the quadrupolar parameters e2qQ = 6.42 MHz and ? = 0.924, consistent with a recent report by Brosnon and Edmonds.

Margalit, Yair; Shporer, Mordechai

6

NQR Spin--Echo Double Resonance (SEDOR) Study of Interplane Coupling in Y_2Ba_4Cu_7O_15  

NASA Astrophysics Data System (ADS)

We report a detailed spin--echo double resonance study(R. Stern, M. Mali, J. Roos, and D. Brinkmann, Phys. Rev. B 52), (in press). of the planar Cu sites in Y_2Ba_4Cu_7O_15 above Tc employing nuclear quadrupole resonance (NQR). Due to the alternation of YBa_2Cu_3O7 and YBa_2Cu_4O8 blocks in its structure the individual planes of a CuO2 double plane in Y_2Ba_4Cu_7O_15 are inequivalent and hence can separately be monitored by NMR/NQR methods.(R. Stern et al.), Phys. Rev. B 50, 426 (1994), ibid. 51, 15478 (1995). The experiments directly reveal the coupling between the inequivalent single planes of a double CuO2 plane. The ratio of particular NQR relaxation rates is a measure for the strength of this interplane coupling with respect to the intraplane coupling. This ratio increases with decreasing temperature. Using recent calculations by Millis and Monien,(A. J. Millis and H. Monien, cond-mat # 9506088.) an interplane coupling constant of about 5 meV is deduced.

Stern, Raivo

1996-03-01

7

NQR Spin--Echo Double Resonance (SEDOR) Study of Interplane Coupling in Y_2Ba_4Cu_7O_15  

Microsoft Academic Search

We report a detailed spin--echo double resonance study(R. Stern, M. Mali, J. Roos, and D. Brinkmann, Phys. Rev. B 52), (in press). of the planar Cu sites in Y_2Ba_4Cu_7O_15 above Tc employing nuclear quadrupole resonance (NQR). Due to the alternation of YBa_2Cu_3O7 and YBa_2Cu_4O8 blocks in its structure the individual planes of a CuO2 double plane in Y_2Ba_4Cu_7O_15 are inequivalent

Raivo Stern

1996-01-01

8

Interplane coupling in the superconductor Y2Ba4Cu7O15 as revealed by NQR spin-echo double resonance  

NASA Astrophysics Data System (ADS)

We report a detailed spin-echo double-resonance study of the planar Cu sites in Y2Ba4Cu7O15 above Tc employing nuclear quadrupole resonance (NQR). The experiments directly reveal the coupling between the inequivalent single planes of a double CuO2 plane. The ratio of particular NQR relaxation rates is a measure for the strength of this interplane coupling with respect to the intraplane coupling. This ratio increases with decreasing temperature. Using recent calculations by Millis and Monien, an interplane coupling constant of about 5 meV is deduced.

Stern, R.; Mali, M.; Roos, J.; Brinkmann, D.

1995-12-01

9

NQR investigation and characterization of cocrystals and crystal polymorphs  

NASA Astrophysics Data System (ADS)

The application of 14N NQR to the study of cocrystals and crystal polymorphs is reviewed. In ferroelectric and antiferroelectric organic cocrystals 14N NQR is used to determine proton position in an N-H...O hydrogen bond and proton displacement below TC. In cocrystal isonicitinamide - oxalic acid (2:1) 14N NQR is used to distinguish between two polymorphs and to determine the type of the hydrogen bond (N-...H-O). The difference in the 14N NQR spectra of cocrystal formers and cocrystal is investigated in case of carbamazepine, saccharin and carbamazepine - saccharin (1:1). The experimental resolution allows an unambiguous distinction between the 14N NQR spectrum of the cocrystal and the 14N NQR spectra of the cocrystal formers. The possibility of application of NQR and double resonance for the determination of the inhomogeneity of the sample and for the study of the life time of an unstable polymorph is discussed.

Seliger, Janez; Žagar, Veselko; Asaji, Tetsuo

2013-05-01

10

14N NQR and relaxation in ammonium nitrate  

NASA Astrophysics Data System (ADS)

The complete 14N nuclear quadrupole resonance (NQR) spectrum of ammonium nitrate is presented recorded using two double resonance techniques - double contact cross relaxation and zero field NQR. The spectra gave the quadrupole coupling constant (Qcc) and asymmetry parameter (?) values for the nitro of 611 kHz, 0.229 and that for the ammonium nitrogen of 242 kHz, 0.835. The three relaxation transition probabilities have been determined for both the nitro and ammonium nitrogen atoms. The bi-exponential relaxation times (T 1) were measured at 295 K. The values for nitro are 16.9 s and 10.5 s and that of the ammonium are 23.0 s and 16.4 s.

Stephenson, David

2014-11-01

11

NQR and Raman spectroscopy study of ?-dichlorobiphenyl  

Microsoft Academic Search

Pulsed 0953-8984\\/8\\/21\\/016\\/img9 nuclear quadrupole resonance (NQR) and Raman spectroscopy studies were performed to get information about the structural and dynamic thermal behaviour of the 0953-8984\\/8\\/21\\/016\\/img10 dichlorobiphenyl. NQR measurements of the line-shape and the spin - lattice relaxation time 0953-8984\\/8\\/21\\/016\\/img11 were obtained in the temperature range 80 K - 320 K. Raman spectra from powder samples were recorded for temperatures between

J. Schneider; A. Wolfenson; A. Brunetti; L. A. de O. Nunes

1996-01-01

12

Detection of {sup 14}N and {sup 35}Cl in cocaine base and hydrochloride using NQR, NMR, and SQUID techniques  

SciTech Connect

Results from {sup 14}N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e{sup 2}Qq/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter {eta} of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) {sup 14}N transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 ({+-}0.0014) MHz and the asymmetry parameter is 0.2632 ({+-}0.0034). Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum. The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies. 31 refs., 8 figs., 1 tab.

Yesinowski, J.P.; Buess, M.L.; Garroway, A.N. [Naval Research Lab., Washington, DC (United States); Ziegeweid, M.; Pines, A. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

1995-07-01

13

75As, 63Cu NMR and NQR characterization of selected arsenic minerals.  

PubMed

The direct measurement and identification of solid state arsenic phases using (75)As NMR is made difficult by the simultaneous conditions of large quadrupole moment and low coordination symmetry in many compounds. However, specific arsenic minerals can efficiently be detected and discriminated via nuclear quadrupolar resonance (NQR). We report on the first NMR and NQR measurements in the natural minerals enargite (Cu3AsS4), niccolite (NiAs), arsenopyrite (FeAsS) and loellingite (FeAs2). The NQR frequencies have been determined from both high-field NMR powder patterns and via zero-field frequency sweeps. Density functional theory (DFT) based ab initio calculations support the experimental results. The compounds studied here are common in terms of the known set of As-containing minerals. They are sometimes encountered in the context of base metal or gold mining. The study represents a significant addition to the list of arsenic minerals that can now be detected with NQR techniques. PMID:23706610

Lehmann-Horn, J A; Miljak, D G; Bastow, T J

2013-01-01

14

Intensity of NQR lines for integer spins  

NASA Astrophysics Data System (ADS)

Because of the publication of contradictory information demonstrating an incorrect approach to the modeling of NQR-NMR frequency-intensity spectra of integral-spin isotopes (for example, boron-10), we study the NQR-NMR double resonance with level crossing (DRLC) in10B-1H,11B-1H,59K-1H and23Na-1H in crystal hydrates of sodium tetraborate (Na2B4O7·10H2O) and potassium tetraborate (K2B4O7·4H2O) and the results of the measurements are compared with theoretical calculations. The fact that for a system including three elements-quadrupole (NQR), Zeeman (NMR), and dipole-dipole, which establishes the interaction of the first two- the intensities of the lines in double resonance spectra are determined both by the equations of balance of the populations of the levels of the quadrupole and Zeeman reservoirs and by the probabilities of transitions within each reservoir is taken into account in the calculations. The distortion of the energy levels of the NQR subsystem by the magnetic field in the process of level crossing with the NMR subsystem is taken into account.

Anferov, V. P.; Beloglazov, G. S.; Grechishkin, V. S.

1986-12-01

15

Partial disorder and molecular motion of 4-chlorobiphenyl studied by 35Cl NQR and Raman spectroscopy  

Microsoft Academic Search

Pulsed 35Cl nuclear quadrupole resonance (NQR) and Raman spectroscopy studies were performed to get information about the structural and dynamic thermal behavior of the 4-chlorobiphenyl. NQR measurements of the line shape and the spin-lattice relaxation time (T1) were obtained in the temperature range 80-320 K. An inhomogeneously broadened NQR line shape was observed, suggesting a disordered structure in all the

J. Schneider; A. Wolfenson; C. Schürrer; A. Brunetti; L. A. de O. Nunes

1996-01-01

16

Low-frequency NMR and NQR with a dc SQUID amplifier  

SciTech Connect

A sensitive Fourier-transform spectrometer based on a dc SQUID (Superconducting QUantum Interference Device) has been developed for the direct detection of nuclear magnetic resonance (NMR) in zero applied magnetic field and pure nuclear quadrupole resonance (NQR) at low frequencies. The motivation to detect zero field NMR and NQR is to provide a new high resolution spectroscopy technique at frequencies below 200 kHz to study ultra-weak interactions in chemicals and materials. By comparing the sensitivity of a SQUID amplifier with that of a conventional semiconductor amplifier, it is shown that a SQUID amplifier is essential for the direct detection of low frequency resonant signals. The spectrometer has a frequency response extending from about 10 to 200 kHz, and a recovery time (after the magnetic pulse is removed) of about 50 {mu}s. The spectrometer is used to detect NMR spectra from Pt and Cu metal powders in a magnetic field of 6 mtesla, and NQR spectra from {sup 2}D in a tunneling methyl group and {sup 14}N in NH{sub 4}ClO{sub 4}. Finally, the zero field NMR spectrum from a quantum tunneling methyl group is calculated. 25 refs., 34 figs., 2 tabs.

Fan, Nong-Qiang.

1990-11-01

17

NQR Characteristics of an RDX Plastic Explosives Simulant.  

PubMed

For reliable detection of explosives, a combination of methods integrated within a single measurement platform may increase detection performance. However, the efficient field testing of such measurement platforms requires the use of inexplosive simulants that are detectable by a wide range of methods. Physical parameters such as simulant density, elemental composition and crystalline structure must closely match those of the target explosive. The highly discriminating bulk detection characteristics of nuclear quadrupole resonance (NQR) especially constrain simulant design. This paper describes the development of an inexplosive RDX simulant suited to a wide range of measurement methods, including NQR. Measurements are presented that confirm an RDX NQR response from the simulant. The potential use of the simulant for field testing a prototype handheld NQR-based RDX detector is analyzed. Only modest changes in prototype operation during field testing would be required to account for the use of simulant rather than real explosive. PMID:23204647

Turecek, J; Schwitter, B; Miljak, D; Stancl, M

2012-12-01

18

Detection of ¹⁴N and ³⁵Cl in cocaine base and hydrochloride using NQR, NMR, and SQUID techniques  

Microsoft Academic Search

Results from ¹⁴N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e²Qq\\/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter η of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum

James P. Yesinowski; Michael L. Buess; Allen N. Garroway; Marcia. Ziegeweid; Alexander. Pines

1995-01-01

19

NMR and NQR studies of quadrupolar effects in glasses and polycrystals with half-integer spins  

NASA Astrophysics Data System (ADS)

NMR and NQR techniques have been used in the present study to investigate glasses and polycrystalline compounds containing nuclei with half-integer spins such as: sp{11}B, sp{23}Na, sp{45}Sc, and sp{93}Nb. The low field ({˜}1.2{-}1.5 Tesla) continuous wave (CW) NMR experiments were performed using the Non-Adiabatic Superfast Passage (NASP) or the slow passage methods. A BRUKER MSL 300 pulsed NMR spectrometer was used for the high field (7.1 Tesla) studies. The CW NQR experiments at room and liquid nitrogen temperature were carried out on a home built Robinson-type spectrometer. Using pulsed NMR the sp{45}Sc response from the glass system CaO-Bsb2Osb3-Scsb2Osb3, yielded a first-order quadrupolar interaction with eta=0 and Qsb{cc}?617 kHz. A new Sc site with Qsb{cc}=23.44 MHz and eta=0 was found in polycrystalline Scsb2Osb3 and it was confirmed by NQR. Employing the NASP method it was found that the fraction of four-coordinated (Nsb4) boron atoms in the alkali thioborate (Nasb2S-Bsb2Ssb3) glass system follows a 3x/(1 - x) relationship for x?0.15, where x is the molar fraction of Nasb2S in the glass. For the NQR spectra the 10% Nasb2S content glass exhibited a broader NQR resonance than the NQR resonance for pure v-Bsb2Ssb3. The additional width was attributed to responses of BSsb3 units whose Qsb{cc} values differ somewhat from the BSsb3 units in the pure vitreous Bsb2Ssb3. The CW NASP method was used to study the sp{23}Na response in the Nasb2O*2SiOsb2 glass, heat treated in three ways: annealed, slow cooled and splat quenched. Subjecting the glass to rapid cooling will produce an increased range of values for the components of the electric field gradient (EFG), and, hence an increased range of values for Qsb{cc} and eta. This was observed for the slow cooled sample when compared with the annealed glass. The effect should be seen also from the slow cooled to the splat quenched sample, but this was not observed. Crystalline sodium disilicate was examined by both NMR and NQR and yielded Qsb{cc} = 1.89 MHz for sp{23}Na and eta=0.9. Furthermore the response from sp{23}Na in the polycrystalline forms of sodium molybdate, sodium tungstate, sodium stanate and albite was examined by means of NASP, pulsed NMR, and NQR. The sp{23}Na spectra for these compounds yielded values of Qsb{cc}, in the range 2.56 MHz to 2.80 MHz. A computer simulation program was used to simulate the spectra of sp{93}Nb-containing compounds. The survey of the niobium response in various polycrystalline compounds using the pulse-echo technique revealed first-order and second-order quadrupolar effects. The sp{93}Nb responses from five glasses in the Nbsb2Osb5-Nasb2O-SiOsb2 ternary glass system produced a second-order quadrupole pattern, but the response might contain more than one Nb site.

Orengo-Aviles, Moises

20

Rapid detection of arsenic minerals using portable broadband NQR  

NASA Astrophysics Data System (ADS)

remote real-time detection of specific arsenic species would significantly benefit in minerals processing to mitigate the release of arsenic into aquatic environments and aid in selective mining. At present, there are no technologies available to detect arsenic minerals in bulk volumes outside of laboratories. Here we report on the first room-temperature broadband 75As nuclear quadrupole resonance (NQR) detection of common and abundant arsenic ores in the Earth crust using a large sample (0.78 L) volume prototype sensor. Broadband excitation aids in detection of natural minerals with low crystallinity. We briefly discuss how the proposed NQR detector could be employed in mining operations.

Lehmann-Horn, J. A.; Miljak, D. G.; O'Dell, L. A.; Yong, R.; Bastow, T. J.

2014-10-01

21

Two-dimensional NQR using ultra-broadband electronics.  

PubMed

We have recently developed an ultra-broadband instrument that can effectively excite and detect NMR and NQR signals over a wide frequency range. Our current system operates between 100 kHz and 3.2 MHz using an un-tuned sample coil. The major benefits of this instrument compared to conventional NQR/NMR systems include increased robustness, ease of use (in particular for multi-frequency experiments), and elimination of the need for tuning adjustments in the hardware. Here we describe its use for performing two-dimensional (2D) scans, which allow improved interpretation of complex NQR spectra by detecting the connected resonances. Our method relies on population transfers between the three energy levels of spin-1 nuclei (such as (14)N) by using multi-frequency excitation and a single RF coil. Experimental results on pure samples and mixtures are also presented. PMID:24495675

Mandal, S; Song, Y-Q

2014-03-01

22

Ultra-Low Temperature Thermometry Using Zeeman Perturbed NQR  

Microsoft Academic Search

We report the results of measurements of the magnetic field perturbed nuclear quadrupole resonance (NQR) lines of powdered Sb immersed in liquid3He at low temperatures. The magnetic field was used to separate the frequencies of the allowed transitions between the \\u000a

E. B. Genio; G. G. Ihas; N. S. Sullivan

1998-01-01

23

An analytical method for estimating the {sup 14}N nuclear quadrupole resonance parameters of organic compounds with complex free induction decays for radiation effects studies  

SciTech Connect

The use of {sup 14}N nuclear quadrupole resonance (NQR) as a radiation dosimetry tool has only recently been explored. An analytical method for analyzing {sup 14}N NQR complex free induction decays is presented with the background necessary to conduct pulsed NQR experiments. The {sup 14}N NQR energy levels and possible transitions are derived in step-by-step detail. The components of a pulsed NQR spectrometer are discussed along with the experimental techniques for conducting radiation effects experiments using the spectrometer. Three data analysis techniques -- the power spectral density Fourier transform, state space singular value decomposition (HSVD), and nonlinear curve fitting (using the downhill simplex method of global optimization and the Levenberg-Marquart method) -- are explained. These three techniques are integrated into an analytical method which uses these numerical techniques in this order to determine the physical NQR parameters. Sample data sets of urea and guanidine sulfate data are used to demonstrate how these methods can be employed to analyze both simple and complex free induction decays. By determining baseline values for biologically significant organics, radiation effects on the NQR parameters can be studied to provide a link between current radiation dosimetry techniques and the biological effects of radiation.

Iselin, L.H.

1992-12-31

24

The incommensurate phase of 4,4'-dichlorobiphenyl sulphone reinvestigated by 35Cl NQR  

Microsoft Academic Search

In order to acquire new information about the normal-incommensurate (IC) phase transition and to check the existence of a lock-in transition in 4,4'-dichlorobiphenyl sulphone (4,4'-DCBS), a comprehensive 35Cl nuclear quadrupole resonance (NQR) study is reported. Detailed NQR measurements of frequency, line width and spin relaxation time (Tl) were obtained in the temperature range 80-270 K. The results show that the

J. Schneider; A. Wolfenson; A. Brunetti

1994-01-01

25

Correlation between proton transfer and (35)Cl NQR frequency as well as molecular geometry of chloranilic acid in co-crystals with some organic bases.  

PubMed

Proton transfer in hydrogen-bonded organic co-crystals of chloranilic acid with some organic bases was investigated by nuclear quadrupole resonance (NQR) spectroscopy. The (35)Cl NQR frequencies of chloranilic acid molecule as well as (14)N NQR frequencies of the organic base molecule were measured with the conventional pulse methods as well as double-resonance methods, respectively. The extent of proton transfer in the O...H...N hydrogen bond was estimated from Townes-Dailey analysis of the (14)N NQR parameters. The (35)Cl NQR frequency and molecular geometry of chloranilic acid are correlated to the extent of proton transfer in the protonation process of the organic base molecule. It is shown that the hydrogen bond affects the pi-electron system of chloranilic acid. Geometry dependence of the O...H...N hydrogen bond, i.e. the H-N valence bond order versus the hydrogen-bond geometry correlation is also discussed. PMID:20535777

Asaji, Tetsuo; Seliger, Janez; Zagar, Veselko; Ishida, Hiroyuki

2010-07-01

26

SQUID detected NMR and NQR  

Microsoft Academic Search

The dc Superconducting QUantum Interference Device (SQUID) is a sensitive detector of magnetic flux, with a typical flux noise of the order 1 ??0 Hz?1\\/2 at liquid helium temperatures. Here ?0=?\\/2e is the flux quantum. In our NMR or NQR spectrometer, a niobium wire coil wrapped around the sample is coupled to a thin film superconducting coil deposited on the

Matthew P. Augustine; Dinh M. TonThat; John Clarke

1998-01-01

27

Copper valence, structural separation and lattice dynamics in tennantite (fahlore): NMR, NQR and SQUID studies  

NASA Astrophysics Data System (ADS)

Electronic and magnetic properties of tennantite subfamily of tetrahedrite-group minerals have been studied by copper nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and SQUID magnetometry methods. The temperature dependences of copper NQR frequencies and line-width, nuclear spin-lattice relaxation rate T {1/-1} and nuclear spin-echo decay rate T {2/-1} in tennantite samples in the temperature range 4.2-210 K is evidence of the presence of field fluctuations caused by electronic spins hopping between copper CuS3 positions via S2 bridging atom. The analysis of copper NQR data at low temperatures points to the magnetic phase transition near 65 K. The magnetic susceptibility in the range 2-300 K shows a Curie-Weiss behavior, which is mainly determined by Fe2+ paramagnetic substituting ions.

Gainov, R. R.; Dooglav, A. V.; Pen'kov, I. N.; Mukhamedshin, I. R.; Savinkov, A. V.; Mozgova, N. N.

2008-01-01

28

35Cl NQR of an organic ferroelectric phenazine chloranilic acid co-crystal  

NASA Astrophysics Data System (ADS)

A ferroelectric transition of phenazine (Phz) chloranilic acid (H 2ca) co-crystal was studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 36.689 MHz at 295 K, split into a doublet below the ferroelectric transition temperature Tc=253 K in accord with the inversion-symmetry breaking at the H 2ca molecular center in the crystal. The continuous variation of the splitting-width through Tc suggests a second-order nature of this phase transition. The NQR frequency is consistent with the crystal structure in which the two acid hydrogen atoms of H 2ca remain as attached to the quinone molecules. The spin-lattice relaxation time T1 showed a decrease with decreasing temperature in the ferroelectric phase. This suggests the existence of a fast motion of nearby atomic group, which is a cause of electric field gradient fluctuation.

Asaji, Tetsuo; Gotoh, Kazuma; Watanabe, Jun

2006-06-01

29

IMPLEMENTATION OF A -NQR SYSTEM AT THE NSCL FOR GROUND STATE QUADRUPOLE MOMENT  

E-print Network

The nuclear electric quadrupole moment, Q, is a direct measure of the nuclear charge distribution, and provides an important test of nuclear structure models. The detected nuclear quadrupole resonance (-NQR, my family, all my teachers and friends iii #12;ACKNOWLEDGMENTS I am very grateful to my advisor

Mantica, Paul F.

30

Gapless superconductivity in overdoped Hg System; Cu-NQR study  

Microsoft Academic Search

The nuclear quadrupole resonance (NQR) investigation of Cu in the overdoped compounds HgBa2CuOy (Hg1201) with y=4. 06 (Tc=92K) and 4.11 (64K) and HgBa2CaCu2Oy (Hg1212) with y=6.13 (Tc=125K) and 6.21 (117K) was carried out in zero field. From the temperature (T) dependence of the nuclear spin-lattice relaxation time, T1, of63Cu, we discuss a cause of the Tc suppression with decreasing the

Shigeki Ohsugi; Tetsuo Tsuchiya; Tadashi Koyama; Kazuo Fueki

1996-01-01

31

Copper NQR and NMR in the superconductor YBa2Cu4O8+x  

Microsoft Academic Search

The frequencies nuQ, the linewidth and the spin-lattice and spin-spin relaxation times T1 and T2, respectively, of the 63Cu nuclear quadrupole resonance (NQR) signals for chain and planar copper sites in YBa2Cu4O8 were measured between 6 and 750 K; in addition nuclear magnetic resonance (NMR) spectra were taken at 150 and 300 K. The results are compared with data known

H. Zimmermann; M. Mali; D. Brinkmann; J. Karpinski; E. Kaldis; S. Rusiecki

1989-01-01

32

A miniaturized NQR spectrometer for a multi-channel NQR-based detection device.  

PubMed

A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting (14)N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring (14)N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel (14)N NQR based detection device. PMID:25233110

Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

2014-10-01

33

Nuclear quadrupole resonance: a technique to control hydration processes in the pharmaceutical industry.  

PubMed

Pharmaceuticals can exist in many solid forms, which can have different physical and chemical properties. These solid forms include polymorphs, solvates, amorphous, and hydrates. Particularly, hydration process can be quite common since pharmaceutical solids can be in contact with water during manufacturing process and can also be exposed to water during storage. In the present work, it is proved that NQR technique is capable of detecting different hydrated forms not only in the pure raw material but also in the final product (tablets), being in this way a useful technique for quality control. This technique was also used to study the dehydration process from pentahydrate to trihydrate. PMID:21314133

Limandri, Silvina; Visñovezky, Claudia; Pérez, Silvina C; Schurrer, Clemar A; Wolfenson, Alberto E; Ferro, Maribel; Cuffini, Silvia L; de Souza, Joel Gonçalves; Aguiar, F Armani; de Gaitani, C Masetto

2011-03-01

34

Review: Magnetic resonance imaging techniques in ophthalmology  

PubMed Central

Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye’s propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology. PMID:23112569

Fagan, Andrew J.

2012-01-01

35

127 I and 79 Br NQR spectra of halo-substituted phenols and phenylmercury phenoxides  

Microsoft Academic Search

The full127I NQR spectra of a series of iodo-substituted phenols and phenylmercury phenoxides have been studied. The quadrupole coupling constants and asymmetry parameters have been determined. The character of the OH...Hal hydrogen bond has been found to depend on the nature of substituents in the ring. Correlation dependences of the asymmetry parameters on the sum of the substituents resonance constants

G. K. Semin; S. I. Gushchin; S. B. Karpov; E. V. Bryukhova; L. S. Golovchenko; D. N. Kramov

1996-01-01

36

Electron density distribution in cladribine (2-chloro-2?-deoxyadenosine) - A drug against leukemia and multiple sclerosis - Studied by multinuclear NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

2-Chloro-2'-deoxyadenosine (Cladribine) chemotherapeutic drug has been studied experimentally in solid state by 35Cl NQR and NMR-NQR double resonance and theoretically by the Density Functional Theory. Fifteen resonance frequencies on 14N have been detected and assigned to particular nitrogen sites in the 2-CdA molecule. The effects of tautomerism, regioisomerism, conformations and molecular aggregations, related to intermolecular hydrogen bond formation, on the NQR parameters have been analysed within the DFT and AIM ( Atoms in Molecules) formalism. The properties of the whole molecule, the so-called global reactivity descriptors, have been calculated for a comparison of both syn and anti conformations of 2-CdA molecule to check the effect of crystal packing on molecular conformation.

Latosi?ska, J. N.; Latosi?ska, M.; Seliger, J.; Žagar, V.; Kazimierczuk, Z.

2009-07-01

37

Ultrasonic signal enhancement by resonator techniques  

NASA Technical Reports Server (NTRS)

Ultrasonic resonators increase experimental sensitivity to acoustic dispersion and changes in attenuation. Experimental sensitivity enhancement line shapes are presented which were obtained by modulating the acoustic properties of a CdS resonator with a light beam. Small changes in light level are made to produce almost pure absorptive or dispersive changes in the resonator signal. This effect is due to the coupling of the ultrasonic wave to the CdS conductivity which is proportional to incident light intensity. The resonator conductivity is adjusted in this manner to obtain both dispersive and absorptive sensitivity enhancement line shapes. The data presented verify previous thoretical calculations based on a propagating wave model.

Heyman, J. S.

1973-01-01

38

Crystallization and preliminary analysis of the NqrA and NqrC subunits of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae.  

PubMed

The Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) from Vibrio cholerae is a membrane protein complex consisting of six different subunits NqrA-NqrF. The major domains of the NqrA and NqrC subunits were heterologously expressed in Escherichia coli and crystallized. The structure of NqrA1-377 was solved in space groups C222? and P2? by SAD phasing and molecular replacement at 1.9 and 2.1?Å resolution, respectively. NqrC devoid of the transmembrane helix was co-expressed with ApbE to insert the flavin mononucleotide group covalently attached to Thr225. The structure was determined by molecular replacement using apo-NqrC of Parabacteroides distasonis as search model at 1.8?Å resolution. PMID:25005105

Vohl, Georg; Nedielkov, Ruslan; Claussen, Björn; Casutt, Marco S; Vorburger, Thomas; Diederichs, Kay; Möller, Heiko M; Steuber, Julia; Fritz, Günter

2014-07-01

39

Analysis and calibration techniques for superconducting resonators.  

PubMed

A method is proposed and experimentally explored for in-situ calibration of complex transmission data for superconducting microwave resonators. This cryogenic calibration method accounts for the instrumental transmission response between the vector network analyzer reference plane and the device calibration plane. Once calibrated, the observed resonator response is analyzed in detail by two approaches. The first, a phenomenological model based on physically realizable rational functions, enables the extraction of multiple resonance frequencies and widths for coupled resonators without explicit specification of the circuit network. In the second, an ABCD-matrix representation for the distributed transmission line circuit is used to model the observed response from the characteristic impedance and propagation constant. When used in conjunction with electromagnetic simulations, the kinetic inductance fraction can be determined with this method with an accuracy of 2%. Datasets for superconducting microstrip and coplanar-waveguide resonator devices were investigated and a recovery within 1% of the observed complex transmission amplitude was achieved with both analysis approaches. The experimental configuration used in microwave characterization of the devices and self-consistent constraints for the electromagnetic constitutive relations for parameter extraction are also presented. PMID:25638068

Cataldo, Giuseppe; Wollack, Edward J; Barrentine, Emily M; Brown, Ari D; Moseley, S Harvey; U-Yen, Kongpop

2015-01-01

40

Analysis and calibration techniques for superconducting resonators  

NASA Astrophysics Data System (ADS)

A method is proposed and experimentally explored for in-situ calibration of complex transmission data for superconducting microwave resonators. This cryogenic calibration method accounts for the instrumental transmission response between the vector network analyzer reference plane and the device calibration plane. Once calibrated, the observed resonator response is analyzed in detail by two approaches. The first, a phenomenological model based on physically realizable rational functions, enables the extraction of multiple resonance frequencies and widths for coupled resonators without explicit specification of the circuit network. In the second, an ABCD-matrix representation for the distributed transmission line circuit is used to model the observed response from the characteristic impedance and propagation constant. When used in conjunction with electromagnetic simulations, the kinetic inductance fraction can be determined with this method with an accuracy of 2%. Datasets for superconducting microstrip and coplanar-waveguide resonator devices were investigated and a recovery within 1% of the observed complex transmission amplitude was achieved with both analysis approaches. The experimental configuration used in microwave characterization of the devices and self-consistent constraints for the electromagnetic constitutive relations for parameter extraction are also presented.

Cataldo, Giuseppe; Wollack, Edward J.; Barrentine, Emily M.; Brown, Ari D.; Moseley, S. Harvey; U-Yen, Kongpop

2015-01-01

41

Site-directed mutagenesis of conserved cysteine residues in NqrD and NqrE subunits of Na+-translocating NADH:quinone oxidoreductase.  

PubMed

Each of two hydrophobic subunits of Na+-translocating NADH:quinone oxidoreductase (NQR), NqrD and NqrE, contain a pair of strictly conserved cysteine residues within their transmembrane alpha-helices. Site-directed mutagenesis showed that substitutions of these residues in NQR of Vibrio harveyi blocked the Na+-dependent and 2-n-heptyl-4-hydroxyquinoline N-oxide-sensitive quinone reductase activity of the enzyme. However, these mutations did not affect the interaction of NQR with NADH and menadione. It was demonstrated that these conserved cysteine residues are necessary for the correct folding and/or the stability of the NQR complex. Mass and EPR spectroscopy showed that NQR from V. harveyi bears only a 2Fe-2S cluster as a metal-containing prosthetic group. PMID:18298367

Fadeeva, M S; Bertsova, Y V; Verkhovsky, M I; Bogachev, A V

2008-02-01

42

115In-NQR study of CeRh1-xIrxIn5 under pressure  

NASA Astrophysics Data System (ADS)

We report on pressure-induced evolutions of antiferromagnetic spin fluctuations (AFM-SFs) and unconventional superconductivity on the x=0.6 sample in a series of compounds CeRh1-xIrxIn5 via the 115In nuclear-quadrupole-resonance (NQR) experiment. The In-NQR 1/T1 measurements have revealed that the slight application of pressure makes Tc=0.9 K at P=0 increase up to Tc=1.06 K at P=0.47 GPa. Concomitantly, the character of AFM-SF evolves from an isotropic regime to an anisotropic one as P increases. These results suggest that AFM-SFs play vital role in mediating the strong-coupling superconductivity in CeRh1-xIrxIn5.

Mugino, Y.; Kawasaki, S.; Yashima, M.; Mukuda, H.; Kitaoka, Y.; Shishido, H.; ?nuki, Y.

2007-03-01

43

A study of hydrogen bond of imidazole and its 4-nitro derivative by ab initio and DFT calculated NQR parameters  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) parameters of 14N, 2H of N 2H groups are calculated for imidazole and 4-nitroimidazole using HF and B3LYP methods. These computations are performed on the basis of X-ray and neutron diffraction structural data which are collected at 100, 103, 123 and 293 K temperatures. In order to take into account intermolecular hydrogen bonds and the van der Waals effects, two different sizes of clusters have been considered. Results of calculation have been compared with that of a single molecule in each case. Calculations illustrate that for imidazole and 4-nitroimidazole octameric and trimeric clusters, respectively, suffice to generate results which are compatible with experimental data. Our calculated NQR parameters and X-ray data show no significant structural change for 4-nitroimidazole at 293 and 100 K.

Amini, S. K.; Hadipour, N. L.; Elmi, F.

2004-06-01

44

Nuclear quadrupole resonance of 35Cl nuclei in glassy solution of chlorobenzene in pyridine  

Microsoft Academic Search

Pulsed nuclear quadrupole resonance (NQR) measurements of 35Cl nuclei were performed on 43.5 mol % chlorobenzene solution in pyridine (a) in glassy state (Tg=131 K) after quenching in liquid nitrogen and (b) in crystalline precipitate under slow cooling starting from liquid phase. In both cases the NQR line shape, obtained by the fast Fourier transform (FFT) method, consisted of a

A. E. Wolfenson; A. H. Brunetti; D. J. Pusiol; W. M. Pontuschka

1990-01-01

45

Possibility of valence-fluctuatsion-mediated superconductivity in Cd-doped CeIrIn(5) probed by In NQR.  

PubMed

We report on a pressure-induced evolution of exotic superconductivity and spin correlations in CeIr(In(1-x)Cd(x))(5) by means of in-nuclear-quadrupole-resonance (NQR) studies. Measurements of an NQR spectrum and nuclear-spin-lattice-relaxation rate 1/T(1) have revealed that antiferromagnetism induced by Cd doping emerges locally around Cd dopants, but superconductivity is suddenly induced at T(c)=0.7 and 0.9 K at 2.34 and 2.75 GPa, respectively. The unique superconducting characteristics with a large fraction of the residual density of state at the Fermi level which increases with T(c) differ from those for anisotropic superconductivity mediated by antiferromagnetic correlations. By incorporating the pressure dependence of the NQR frequency pointing to the valence change of Ce, we suggest that unconventional superconductivity in the CeIr(In(1-x)Cd(x))(5) system may be mediated by valence fluctuations. PMID:23005666

Yashima, M; Tagami, N; Taniguchi, S; Unemori, T; Uematsu, K; Mukuda, H; Kitaoka, Y; Ota, Y; Honda, F; Settai, R; Onuki, Y

2012-09-14

46

Nuclear quadrupole resonance study of hydrogen bonded solid materials.  

PubMed

Nuclear quadrupole resonance is presented as a method for the study of solid hydrogen bonded materials. NQR study of hydrogen bonds in ferroelectric and paraelectric KH2PO4, antiferroelectric and paraelectric squaric acid, ferroelectric croconic acid and antiferroelectric and paraelectric cocrystal 5'-dimethyl-2, 2'-bipyridine - chloranilic acid (1:1) are discussed in more details. A 14N NQR study of the strong short O-HKN hydrogen bond in two polymorphic forms of cocrystal isonicotinamide-oxalic acid (2:1) is presented as well. Various correlations between the NQR parameters and between the NQR and structural parameters have been observed. These correlations may be used to determine the proton position in a hydrogen bond and some other structural parameters from the NQR data. PMID:24062106

Seliger, Janez

2011-09-01

47

101Ru NQR study in CeRu 2  

NASA Astrophysics Data System (ADS)

We present measurements of the NQR spectrum and the nuclear spin lattice relaxation rate, 1/ T1, of 101Ru in superconducting CeRu 2 from 1.9 K to 10 K. From the NQR spectrum, the electric quadrupole interaction parameters were determined to be ?Q = 13.2 MHz and ? = 0.1/ T1 varies in proportion to temperature in the normal state, has the Hebel-Slichter coherence peak just below the superconducting transition temperature, TC, of 6.2 K, and decreases exponentially at low temperatures with the energy gap of 2 ? = 4.0 kBTC. 101Ru NQR study indicates that CeRu 2 is an s-wave and strong-coupling superconductor.

Matsuda, K.; Kohori, Y.; Kohara, T.

1996-02-01

48

Narcotics and explosives detection by 14N pure nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.

Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.

1994-03-01

49

Improved technique for Young's modulus determination by flexural resonance  

SciTech Connect

Elastic properties in structural ceramics are widely studied with different experimental techniques in order to obtain engineering and diagnostic data about the processed materials. A new set-up for measuring flexural resonance is presented. The apparatus is based on electrostatic excitation where sample vibrations are detected by a laser modulation technique. Due to the high sensitivity and accuracy of this experimental set-up, it was possible to measure Young's modulus of samples with relatively high thickness/length ratios, thus allowing elastic properties determination directly on bending-strength test bars. The measurements were performed according to ASTM procedure. The high frequency resolution allowed the evaluation of internal friction variation due to processing, by nonlinear least square analysis of resonance curves. 10 refs.

Scafe, E.; Fabbri, L.; Grillo, G.; Di Rese, L.

1992-10-01

50

Total body water measurements using resonant cavity perturbation techniques  

NASA Astrophysics Data System (ADS)

A recent paper proposed a novel technique for determining the total body water (TBW) of patients suffering with abnormal hydration levels, using a resonant cavity perturbation method. Current techniques to measure TBW are limited by resolution and technical constraints. However, this new method involves measuring the dielectric properties of the body, by placing a subject in a large cavity resonator and measuring the subsequent change in its resonant frequency, fres and its Q-factor. Utilizing the relationship that water content correlates to these dielectric properties, it has been shown that the measured response of these parameters enables determination of TBW. Results are presented for a preliminary study using data estimated from anthropometric measurements, where volunteers were asked to lie and stand in an electromagnetic screened room, before and after drinking between 1 and 2 l of water, and in some cases, after voiding the bladder. Notable changes in the parameters were observed; fres showed a negative shift and Q was reduced. Preliminary calibration curves using estimated values of water content have been developed from these results, showing that for each subject the measured resonant frequency is a linear function of TBW. Because the gradients of these calibration curves correlate to the mass-to-height-ratio of the volunteers, it has proved that a system in which TBW can be unequivocally obtained is possible. Measured values of TBW have been determined using this new pilot-technique, and the values obtained correlate well with theoretical values of body water (r = 0.87) and resolution is very good (750 ml). The results obtained are measurable, repeatable and statistically significant. This leads to confidence in the integrity of the proposed technique.

Stone, Darren A.; Robinson, Martin P.

2004-05-01

51

Studies of the electronic structure and biological activity of chosen 1,4-benzodiazepines by 35Cl NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

Selected derivatives of 1,4-benzodiazepine: lorazepam, lormetazepam, oxazepam and temazepam, used as active substances in anxiolytic drugs, have been studied by 35Cl NQR method in order to find the correlation between electronic structure and biological activity. The 35Cl NQR resonance frequencies ( ?Q) measured at 77 K have been correlated with the following parameters characterising their biological activity: biological half-life period ( t0.5), affinity to benzodiazepine receptor (IC 50) and mean dose equivalent. The results of experimental study of some benzodiazepine derivatives by nuclear quadrupole resonance of 35Cl nuclei are compared with theoretical results based on DFT calculations which were carried out by means of Gaussian'98 W software.

Bronisz, K.; Ostafin, M.; Poleshchuk, O. Kh.; Mielcarek, J.; Nogaj, B.

2006-11-01

52

Surface plasmon resonance based biosensor technique: a review.  

PubMed

Optical Surface plasmon resonance (SPR) biosensors represent the most advanced and developed optical label-free biosensor technology. Optical SPR biosensors are a powerful detection and analysis tool that has vast applications in environmental protection, biotechnology, medical diagnostics, drug screening, food safety and security. This article reviews the recent development of SPR biosensor techniques, including bulk SPR and localized SPR (LSPR) biosensors, for detecting interactions between an analyte of interest in solution and a biomolecular recognition. The concepts of bulk and localized SPs and the working principles of both sensing techniques are introduced. Major sensing advances on biorecognition elements, measurement formats, and sensing platforms are presented. Finally, the discussions on both biosensor techniques as well as comparison of both SPR sensing techniques are made. PMID:22467335

Guo, Xiaowei

2012-07-01

53

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.  

PubMed

Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined ?iso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and ?33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (?11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. PMID:24581866

Peri?, Berislav; Gautier, Régis; Pickard, Chris J; Bosio?i?, Marko; Grbi?, Mihael S; Požek, Miroslav

2014-01-01

54

Weak Magnetic Order in Bilayered-Hydrate NaxCoO2\\\\cdotyH2O Structure Probed by Co Nuclear Quadrupole Resonance Proposed Phase Diagram in Superconducting NaxCoO2\\\\cdotyH2O---  

Microsoft Academic Search

A weak magnetic order was found in a nonsuperconducting bilayered-hydrate NaxCoO2\\\\cdotyH2O sample by Co nuclear quadrupole resonance (NQR) measurement. The nuclear spin-lattice relaxation rate divided by temperature 1\\/T_1T shows a prominent peak at 5.5 K, below which a Co NQR peak splits due to an internal field at the Co site. From the analyses of the Co NQR spectrum at

Yoshihiko Ihara; Kenji Ishida; Chishiro Michioka; Masaki Kato; Kazuyoshi Yoshimura; Kazunori Takada; Takayoshi Sasaki; Hiroya Sakurai; Eiji Takayama-Muromachi

2005-01-01

55

1H NMR and 14N NQR study of the ferroelectric phase transition in (CH3)2NH2H2PO4  

Microsoft Academic Search

The ferroelectric phase transition in (CH3)2NH2H2PO4 has been studied by 14N nuclear-quadrupole resonance (NQR) and 1H spin-lattice relaxation. Both above and below TC, the 14N quadrupole coupling constant is approximately 1.2 MHz and the asymmetry parameter eta is close to 1. Two nonequivalent nitrogen positions in the unit cell are observed below TC whereas, above TC, all nitrogen crystallographic positions

J. Seliger; V. Zagar

1998-01-01

56

[Magnetic resonance enterography: technique and indications. Findings in Crohn's disease].  

PubMed

Radiology with oral contrast, or enteroclysis, have traditionally been the techniques of choice in the examination of the small intestine, due to the excellent visualisation of the mucosal pattern. However, the absence of extra-luminal information and the use of ionising radiation have replaced these examinations with sectional techniques which enable the abdominal cavity to be viewed with good resolution. Magnetic resonance enterography is a simple technique, with no ionising radiation, provided quality images, distends the intestinal lumen well by the administration of non-reabsorbable oral substances, minimises peristalsis, and establishes a protocol which includes sequences with intravenous contrast. These properties can be used in patients with Crohn's disease, achieving good diagnostic precision in the assessment of activity and monitoring of treatment, in intestinal obstruction, in the suspicion of small intestine tumours, and in paediatric patients due to it being harmless. PMID:22265162

Torregrosa, A; Pallardó, Y; Hinojosa, J; Insa, S; Molina, R

2013-09-01

57

NUCLEAR SPIN RESONANCE  

Microsoft Academic Search

I. Introduction 566 II. NSR energy levels and frequencies 568 1. Energy levels for resonating nuclei with spins 1 or 3\\/2 568 2. NSR energy levels for spin 5\\/2 571 III. Relative intensities of NSR lines 571 1. Relative intensities of Zeeman components in NQR 571 2. Generalized NSR equations 572 3. Relative intensities of NSR lines for spin 1

Vadim S Grechishkin; N. E. Ajnbinder

1964-01-01

58

Low-power stimulated emission nuclear quadrupole resonance detection system utilizing Rabi transitions  

NASA Astrophysics Data System (ADS)

The application of CW radar techniques to Nuclear Quadrupole Resonance (NQR) detection of nitrogen based explosives and chlorine based narcotics enables the use of low power levels, in the range of 10's of watts, to yield high signal strengths. By utilizing Rabi transitions the nucleus oscillates between states one and two under the time dependent incident electromagnetic field and alternately absorbs energy from the incident field while emitting coherent energy via stimulated emission. Through the application of a cancellation algorithm the incident field is eliminated from the NQR response, allowing the receive signal to be measured while transmitting. The response signal is processed using matched filters of the NQR response which enables the direct detection of explosives. This technology has applicability to the direct detection of explosives and narcotics for security screening, all at safe low power levels, opposed to the current XRay and Millimeter wave screening systems that detect objects that may contain explosives and utilize high power. The quantum mechanics theoretical basis for the approach and an application for a system for security screening are described with empirical results presented to show the effects observed.

Apostolos, John; Mouyos, William; Feng, Judy; Chase, Walter

2013-06-01

59

Thermal hysteresis in 4,4' dichlorobenzophenone studied by 35Cl NQR  

Microsoft Academic Search

A pulsed NQR study of 4,4' dichlorobenzophenone has been performed to get information about dynamic features in its three crystalline phases. The authors found in phases I (T>190 K) and III (T<180 K) a normal thermal behaviour of the NQR frequency and spin-lattice relaxation time. In the intermediate phase II (180 KNQR parameters could

J. F. Schneider; A. E. Wolfenson; A. H. Brunetti

1992-01-01

60

Resonant marker design and fabrication techniques for device visualization during interventional magnetic resonance imaging.  

PubMed

Abstract Magnetic resonance imaging (MRI) has great potential as an imaging modality for guiding minimally invasive interventions because of its superior soft tissue contrast and the possibility of arbitrary slice positioning while avoiding ionizing radiation and nephrotoxic iodine contrast agents. The major constraints are: limited patient access, the insufficient assortment of compatible instruments and the difficult device visualization compared to X-ray based techniques. For the latter, resonant MRI markers, fabricated by using the wire-winding technique, have been developed. This fabrication technique serves as a functional model but has no clinical use. Thus, the aim of this study is to illustrate a four-phase design process of resonant markers involving microsystems technologies. The planning phase comprises the definition of requirements and the simulation of electromagnetic performance of the MRI markers. The following technologies were considered for the realization phase: aerosol-deposition process, hot embossing technology and thin film technology. The subsequent evaluation phase involves several test methods regarding electrical and mechanical characterization as well as MRI visibility aspects. The degree of fulfillment of the predefined requirements is determined within the analysis phase. Furthermore, an exemplary evaluation of four realized MRI markers was conducted, focusing on the performance within the MRI environment. PMID:25460277

Kaiser, Mandy; Detert, Markus; Rube, Martin A; El-Tahir, Abubakr; Elle, Ole Jakob; Melzer, Andreas; Schmidt, Bertram; Rose, Georg H

2014-12-01

61

Nuclear quadrupole resonance studies of the SORC sequence and nuclear magnetic resonance studies of polymers  

SciTech Connect

The behavior of induction signals during steady-state pulse irradiation in {sup 14}N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method. Also as part of the NQR work, cocaine base has been detected using conventional NQR techniques. The experimental results show that SORC detection can be of sufficient sensitivity to form the basis of narcotics screening devices for both mail and airline baggage. A new NMR technique, to obtain the correlation time of the random thermal motion of a polymer at temperatures near the glass transition has been introduced. The temperature dependence is a result of thermal motion. For slow-motion of a polymer chain near the glass transition, the CSA parameter begins to decrease. This motional narrowing can be interpreted to yield the correlation time of the thermal motion. In this work nitrocellulose isotopically highly enriched with {sup 15}N was studied at four different temperatures between 27{degrees} and 120{degrees} Celsius and the correlation times for polymer backbone motions were obtained. Naflon films containing water (D{sub 2}O and H{sub 2} {sup 17}O) and methanol (CH{sub 3}OD, CH{sub 3} {sup 17}OH), have been studied using deuteron and oxygen-17 NMR spectroscopy. Glassy behavior of the water domains at low temperature is evidenced by the specific nature of the {sup 2}H NMR lineshapes. Activation energies extracted from {sup 2}H spin-lattice relaxation data on the high temperature side of the T{sub 1} minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra of both unstretched and stretched samples reflect considerable anisotrophy of the host polymer.

Jayakody, J.R.P.

1993-12-31

62

Novel technique in the segmentation of magnetic resonance image  

NASA Astrophysics Data System (ADS)

In this investigation, automatic image segmentation is carried out on magnetic resonance image (MRI). A novel technique based on the maximum minimum measure is devised. The measure is improved by combining the smoothing and counting processes, and then normalizing the number of maximum and minimum positions over the region of interest (ROI). Two parameters (MM_H and MM_V) are generated and used for the segmentation. The technique is tested on some brain MRIs of a human male from the Visible Human Project of the National Library of Medicine, National Institutes of Health, USA. Preliminary results indicate that the maximum minimum measure can provide effective parameters for human tissue characterization and image segmentation with an added advantage of faster computation.

Chan, Kwok-Leung

1996-04-01

63

Superconductivity and Magnetic Fluctuations in Cd2Re2O7 via Cd Nuclear Magnetic Resonance and Re Nuclear Quadrupole Resonance  

Microsoft Academic Search

We report Cd nuclear magnetic resonance (NMR) and Re nuclear quadrupole resonance (NQR) studies on Cd 2Re2O7, the first superconductor among pyrochlore oxides (Tc~=1 K). The Re NQR spectrum at zero magnetic field below 100 K rules out any magnetic or charge order. The spin-lattice relaxation rate below Tc exhibits a pronounced coherence peak and follows the weak-coupling BCS theory

O. Vyaselev; K. Arai; K. Kobayashi; J. Yamazaki; K. Kodama; M. Takigawa; M. Hanawa; Z. Hiroi

2002-01-01

64

Nuclear quadrupole resonance and nuclear magnetic resonance of copper in the high-Tc superconductor YBa2Cu3O7-delta  

Microsoft Academic Search

The 65Cu and 63Cu zero-field nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) at 4.7 and 8.5 T and the spin-lattice relaxation time T1 at 8.5 T are measured in the superconducting oxide YBa2Cu3O7-delta between 80 and 300 K. No sign of magnetic order or localized moments are found. The NQR linewidth is strongly dependent on the oxygen content. We

I. Furo; A. Jánossy; L. Mihály; P. Bánki; I. Pócsik; I. Bakonyi; I. Heinmaa; E. Joon; E. Lippmaa

1987-01-01

65

Magnetic resonance imaging of the elbow. Part I: Normal anatomy, imaging technique, and osseous abnormalities  

Microsoft Academic Search

Part I of this comprehensive review on magnetic resonance imaging of the elbow discusses normal elbow anatomy and the technical factors involved in obtaining high-quality magnetic resonance images of the elbow. Part I also discusses the role of magnetic resonance imaging in evaluating patients with osseous abnormalities of the elbow. With proper patient positioning and imaging technique, magnetic resonance imaging

Richard Kijowski; Michael Tuite; Matthew Sanford

2004-01-01

66

NMR and NQR investigations of local symmetry in the hidden order phase of URu2Si2  

NASA Astrophysics Data System (ADS)

In order to study local symmetries at the 4e(Si)- and 4d(Ru)-sites above and below hidden order transition temperature TO = 17.5 K in URu2Si2, we have investigated the nuclear quadrupole interaction by 73Ge-nuclear magnetic resonance (NMR) measurement on a 10% 73Ge-substituted sample URu2(Si0.9Ge0.1)2, and by 101Ru-nuclear quadrupole resonance (NQR) measurement on a pure single crystal sample. The present 73Ge-NMR measurements do not give any evidence for change in the local symmetry at 4e-site within experimental accuracy. On the other hand, the precise measurement of 101Ru-NQR frequency has detected an anomaly just below TO as sensitively as the thermal expansion measurement dose. Its temperature dependence shows a linear relation with that of the in-plane lattice parameter, which may be a clue to clarify a modification in microscopic charge distribution at TO.

Mito, T.; Hattori, M.; Motoyama, G.; Sakai, Y.; Koyama, T.; Ueda, K.; Kohara, T.; Yokoyama, M.; Amitsuka, H.

2012-12-01

67

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1 A Resonant Switch for LNA Protection  

E-print Network

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1 A Resonant Switch for LNA Protection in Watt Moussessian Abstract--An integrated resonant switch designed to protect low-noise amplifier (LNA) circuits

Kuhn, William B.

68

Utilization of pure nuclear quadrupole resonance spectroscopy for the study of pharmaceutical crystal forms.  

PubMed

Solid-state physical characterization of a pharmaceutical substance is necessary for successful development and approval of the final product. Different physical analytical techniques are available to do so: X-ray diffraction (XRD), IR, Raman, DSC, TG and NMR. Moreover, all of them detect the presence of excipients perturbing the analysis of the pure substance in low doses. In order to study polymorphism and pseudo polymorphism of drug, this paper introduces possible applications of pure nuclear quadrupole resonance, as a non-destructive technique in qualitative and quantitative approaches. Chlorpropamide and diclofenac sodium were used as examples. Unlike the mentioned techniques, the nuclear quadrupole resonance (NQR) signal of pharmaceutical compounds is not perturbed by the presence of solid excipient or other substances unless they possess resonance frequencies in the same frequency range of the compound studied. PMID:15913931

Pérez, S C; Cerioni, L; Wolfenson, A E; Faudone, S; Cuffini, S L

2005-07-14

69

79 Br and 127 I nqr spectra in series of acetylene derivatives  

Microsoft Academic Search

The complete79Br and127I NQR spectra of a number of bromo and iodo derivatives of acetylene were studied for the first time, and the field constants of the NQR frequencies were determined. It was found that the asymmetry parameters in them are low. Changes in the field constants are determined by the competing conjugation of the iodine atom and the corresponding

G. K. Semin; S. A. Petukhov; S. I. Gushchin; I. R. Gol'ding; E. V. Bryukhova; A. M. Sladkov

1983-01-01

70

35 Cl, 79 Br, and 127 I NQR spectra of some halogen-containing organoselenium compounds  

Microsoft Academic Search

1.The35Cl,79Br, and127I NQR spectra of a number of halogen-containing organoselenium compounds were obtained.2.The35Cl NQR frequencies of compounds of type R1R2R3SeCl (Ri=Me, Ph, Cl) are linearly related to the induction constants of the substituentssi.

V. V. Saatsazov; T. L. Khotsyanova; N. N. Magdesieva; S. I. Kuznetsov; I. M. Alymov; R. A. Kyandzhetsian; E. V. Bryukhova

1974-01-01

71

I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics  

SciTech Connect

NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C{sub 5}H{sub 5}) and Sn({eta}{sup 1}-C{sub 5}H{sub 5}){sub 4}. This work was undertaken in the hope of gaining insight into the intramolecuhrr dynamics, specifically which fluxional processes exist in the solid state, by what mechanism rearrangements are occurring, and the activation energies by which these processes are governed.

Ziegeweid, M.A.

1995-11-29

72

Novel nuclear magnetic resonance techniques for studying biological molecules  

SciTech Connect

Over the fifty-five year history of Nuclear Magnetic Resonance (NMR), considerable progress has been made in the development of techniques for studying the structure, function, and dynamics of biological molecules. The majority of this research has involved the development of multi-dimensional NMR experiments for studying molecules in solution, although in recent years a number of groups have begun to explore NMR methods for studying biological systems in the solid-state. Despite this new effort, a need still exists for the development of techniques that improve sensitivity, maximize information, and take advantage of all the NMR interactions available in biological molecules. In this dissertation, a variety of novel NMR techniques for studying biomolecules are discussed. A method for determining backbone ({phi}/{psi}) dihedral angles by comparing experimentally determined {sup 13}C{sub a}, chemical-shift anisotropies with theoretical calculations is presented, along with a brief description of the theory behind chemical-shift computation in proteins and peptides. The utility of the Spin-Polarization Induced Nuclear Overhauser Effect (SPINOE) to selectively enhance NMR signals in solution is examined in a variety of systems, as are methods for extracting structural information from cross-relaxation rates that can be measured in SPINOE experiments. Techniques for the production of supercritical and liquid laser-polarized xenon are discussed, as well as the prospects for using optically pumped xenon as a polarizing solvent. In addition, a detailed study of the structure of PrP 89-143 is presented. PrP 89-143 is a 54 residue fragment of the prion proteins which, upon mutation and aggregation, can induce prion diseases in transgenic mice. Whereas the structure of the wild-type PrP 89-143 is a generally unstructured mixture of {alpha}-helical and {beta}-sheet conformers in the solid state, the aggregates formed from the PrP 89-143 mutants appear to be mostly {beta}-sheet.

Laws, David D.

2000-06-01

73

Detecting body cavity bombs with nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a technology with great potential for detecting hidden explosives. Past NQR research has studied the detection of land mines and bombs concealed within luggage and packages. This thesis focuses on an NQR application that has received less attention and little or no publicly available research: detecting body cavity bombs (BCBs). BCBs include explosives that have been ingested, inserted into orifices, or surgically implanted. BCBs present a threat to aviation and secure facilities. They are extremely difficult to detect with the technology currently employed at security checkpoints. To evaluate whether or not NQR can be used to detect BCBs, a computational model is developed to assess how the dielectric properties of biological tissue affect the radio frequency magnetic field employed in NQR (0.5-5MHz). The relative permittivity of some biological tissue is very high (over 1,000 at 1MHz), making it conceivable that there is a significant effect on the electromagnetic field. To study this effect, the low-frequency approximation known as the Darwin model is employed. First, the electromagnetic field of a coil is calculated in free space. Second, a dielectric object or set of objects is introduced, and the free-space electric field is modified to accommodate the dielectric object ensuring that the relevant boundary conditions are obeyed. Finally, the magnetic field associated with the corrected electric field is calculated. This corrected magnetic field is evaluated with an NQR simulation to estimate the impact of dielectric tissue on NQR measurements. The effect of dielectric tissue is shown to be small, thus obviating a potential barrier to BCB detection. The NQR model presented may assist those designing excitation and detection coils for NQR. Some general coil design considerations and strategies are discussed.

Collins, Michael London

74

Contact Resonance Force Microscopy Techniques for Nanomechanical Measurements  

NASA Astrophysics Data System (ADS)

Contact resonance force microscopy (CR-FM) methods such as atomic force acoustic microscopy show great promise as tools for nanoscale materials research. However, accurate and reliable CR-FM measurements require the simultaneous optimization of a large number of experimental conditions. Among these variables are cantilever spring constant, applied static load, reference material, and resonant mode (mode type and order). In addition, results depend on the models used for data analysis and interpretation (e.g., choice of contact-mechanics model). All of these parameters are linked in numerous ways that are not straighforward to classify. In this chapter, we present a "user's guide" to quantitative measurements of nanomechanical properties with CR-FM methods. The discussion emphasizes the experimental methods and their practical implementation, providing a snapshot of the current state of the art. We discuss the basic physical principles involved and show how they can be used to make informed choices about experimental parameters and operating conditions. Experimental data and the results of theoretical models are provided as specific examples of the abstract concepts. Ideas for future work are also discussed, including ways to simplify the measurement process or improve measurement accuracy. The objective is not only to enable readers to perform their own CR-FM measurements, but also to optimize experimental conditions for a given material system. By gaining a better understanding of the underlying measurement principles, more researchers will be encouraged to further extend the technique and use it for an ever-wider range of applications for the nanoscale characterization of materials.

Hurley, Donna C.

75

35Cl NQR study of lattice dynamic and magnetic property of a crystalline coordination polymer {CuCA(phz)(H 2O) 2} n  

NASA Astrophysics Data System (ADS)

Copper(II) compounds {CuCA(phz)(H 2O) 2} n (H 2CA = chloranilic acid, phz = phenazine) having a layer structure of -CuCA(H 2O) 2- polymer chains and phenazine were studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 35.635 MHz at 261.5 K increased to 35.918 MHz at 4.2 K. The degree of reduction of electric field gradient due to lattice vibrations was similar to that of chloranilic acid crystal. Temperature dependence of spin-lattice relaxation time, T1, of the 35Cl NQR signal below 20 K, between 20 and 210 K, and above 210 K, was explained by (1) a decrease of effective electron-spin density caused by antiferromagnetic interaction, (2) a magnetic interaction between Cl nuclear-spin and electron-spins on paramagnetic Cu(II) ions, and (3) an increasing contribution from reorientation of ligand molecules, respectively. The electron spin-exchange parameter ? J? between the neighboring Cu(II) electrons was estimated to be 0.33 cm -1 from the T1 value of the range 20-210 K. Comparing this value with that of J = -1.84 cm -1 estimated from the magnetic susceptibility, it is suggested that the magnetic dipolar coupling with the electron spins on Cu(II) ions must be the principal mechanism for the 35Cl NQR spin-lattice relaxation of {CuCA(phz)(H 2O) 2} n but a delocalization of electron spin over the chloranilate ligand has to be taken into account.

Gotoh, Kazuma; Terao, Takeshi; Asaji, Tetsuo

2007-01-01

76

ADVANCES IN OPTICALLY PUMPED He4 MAGNETOMETERS : RESONANCE AND NONRESONANCE TECHNIQUES  

E-print Network

109. ADVANCES IN OPTICALLY PUMPED He4 MAGNETOMETERS : RESONANCE AND NONRESONANCE TECHNIQUES By R. E pumped 23S1 helium atoms are currently studied in our laboratory for use in advanced magnetometer pumping process is used to construct a non- resonance magnetometer (no magnetic resonance) suitable

Boyer, Edmond

77

Studies of Diamonds Using Electron Paramagnetic Resonance and Other Techniques  

NASA Astrophysics Data System (ADS)

Studies of impurities/defects in diamonds grown with the high-temperature high-pressure technique (HTHP) and B- and P-doped diamond films using fast ion implantation and chemical evaporation have been carried out. The main technique employed in the study is electron paramagnetic resonance (EPR). Raman, laser and X-ray fluorescence are also used to characterize the samples. While other commonly used techniques such as infrared (IR) spectroscopy detect no nitrogen in an isotopically enriched ^ {12}C diamond, the clear EPR spectrum consistently measures a nitrogen concentration of about 0.05ppm by calibration against a few standards. The ^{12}C diamond is evaluated to be ideal for optical window application and studies of diamond properties. Neither the EPR lineshape nor the second moment supports a random nitrogen distribution in the ^{12}C diamond. Instead, the average nitrogen distance is found to be larger than the of the random nitrogen distribution. The g-tensor for substitutional nitrogen is found to be axially symmetric along the (111) direction with g_| - g_| = 0.00002(5). In the study of a HTHP IIb blue semiconducting diamond, neutral N is measured with a concentration of 0.02ppm. The result is not well understood since neutral nitrogen is expected to lose its extra electron to boron due to electron-hole recombination. Further studies are suggested to better understand this result. EPR studies of two sets of P-doped diamond films grown using fast ion implantation and chemical incorporation reveal that defect levels caused by diamond doping are still too high for semiconductor applications. As expected, P doping causes a defect level two orders of magnitude higher than B doping, which can be explained by the relatively larger size of P than B. The theoretical analysis based on EPR hyperfine interaction suggest that P forms a shallow donor in diamond and that the electron density at the P site is |psi(0)|^2 = 0.27 times 10^{24} cm^ {-3}. This is consistent with the temperature dependent EPR experimental results. The EPR spectra for all diamond samples I have studied are compared, revealing that the HTHP diamonds show no defect related spectrum, which are commonly observed in natural IIa and IIb diamonds. This result indicates that HTHP diamond has superior quality compared to other diamonds.

Zhang, Shigang

78

Colorimetric resonant reflection as a direct biochemical assay technique  

Microsoft Academic Search

A novel approach for the detection of molecular interactions is presented in which a colorimetric resonant diffractive grating surface is used as a surface binding platform. A guided mode resonant phenomenon is used to produce an optical structure that, when illuminated with white light, is designed to reflect only a single wavelength. When molecules are attached to the surface, the

Brian Cunningham; Peter Li; Bo Lin; Jane Pepper

2002-01-01

79

Temperature and baric dependence of nuclear quadruple resonance spectra in indium and gallium monoselenides  

NASA Astrophysics Data System (ADS)

Pulsed radiospectroscopy method has been used to study nuclear quadruple resonance (NQR) spectra of 69Ga and 115In isotopes in the layered semiconductors GaSe and InSe. It has been found that in GaSe and InSe there is a considerable temperature dependence of NQR frequency which in the temperature range of 250 to 390 K is practically linear with conversion slope 1.54 kHz/degree for 69Ga and 2.35 kHz/degree for 115In. In the same crystals the effect of uniaxial pressure on NQR spectra applied along the optical axis ? up to the values of 500 kg/?m2 has been studied. A strong attenuation of NQR spectra intensity with increase in pressure on layered crystal package has been established. The unvaried multiplicity of resonance spectra indicates the absence of structural transformations in these layered crystals over the investigated range of temperatures and pressures.

Khandozhko, Victor; Raranskii, Nikolai; Balazjuk, Vitaly; Samila, Andriy; Kovalyuk, Zahar

2013-12-01

80

35Cl nuclear quadrupole resonance study in 4,4'-dichlorobiphenyl sulphone: A possible incommensurate system  

Microsoft Academic Search

Pulsed nuclear quadrupole resonance (NQR) has been used to get information about the nature of the molecular dynamics in two crystalline phases of 4,4'-dichlorobiphenyl sulphone. This work includes detailed experimental measurements of the NQR frequency, spin-lattice relaxation time, and line intensity temperature behavior in the range of temperature where a possible normal-to-incommensurate phase transition occurs. The experimental results show the

D. J. Pusiol; A. E. Wolfenson; A. H. Brunetti

1989-01-01

81

Development of adaptive resonator techniques for high-power lasers  

SciTech Connect

The design of an adaptive wavefront control system for a high-power Nd:Glass laser will be presented. Features of this system include: an unstable resonator in confocal configuration, a multi-module slab amplifier, and real-time intracavity adaptive phase control using deformable mirrors and high-speed wavefront sensors. Experimental results demonstrate the adaptive correction of an aberrated passive resonator (no gain).

An, J; Brase, J; Carrano, C; Dane, C B; Flath, L; Fochs, S; Hurd, R; Kartz, M; Sawvel, R

1999-07-12

82

Field constants of 79 Br and 127 I NQR of halogen derivatives of carbon  

Microsoft Academic Search

A study has been made of the NQR frequency field constants for the chlorine, bromine, and iodine atoms. It has been shown that the degree to which the field constants are characteristic decreases in the series Cl-Br-I.

S. A. Petukhov; E. V. Bryukhova; G. K. Semin; A. A. Boguslavskii

1984-01-01

83

High Pressure NQR Measurement in CeCu2Si2 up to Sudden Disappearance of Superconductivity  

NASA Astrophysics Data System (ADS)

We report the results of 63Cu nuclear quadrupole resonance (NQR) measurements on CeCu2Si2 under high pressures up to 4.8 GPa. Enhanced spin fluctuations due to quantum criticality at ambient pressure are drastically suppressed with increasing pressure, whereas Tc increases from 0.7 K at ambient pressure to 1.64 K at 4.2 GPa. We have found that bulk superconductivity suddenly disappears at 4.8 GPa accompanied with a rapid decrease in the density of states at the Fermi level. The nuclear spin-lattice relaxation rate 1/T1 at 4.2 GPa reveals that anisotropic superconductivity in the strong-coupling regime is realized even under high pressure far from the antiferromagnetic critical point. Superconductivity under high pressure is unconventional in origin, but the spin fluctuation scenario is not likely to be applicable.

Fujiwara, Kenji; Hata, Yoshiki; Kobayashi, Keigo; Miyoshi, Kiyotaka; Takeuchi, Jun; Shimaoka, Yoshiyuki; Kotegawa, Hisashi; Kobayashi, Tatsuo C.; Geibel, Christoph; Steglich, Frank

2008-12-01

84

Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat  

NASA Technical Reports Server (NTRS)

La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for x ranging from 0 up to 0.3, with particular emphasis on the effect of doping on the Cu(2+) magnetic correlations and dynamics, are reviewed. In the low doping limit, x less than or equal to 0.05, the results can be interpreted consistently in terms of a simple phenomenological 'two-fluids' model whereby the effect of thermally-activated mobile O(2p) holes is the one of disrupting locally the Cu(2+) spin correlations. For x greater than or equal to 0.1, the results indicate the onset, as T approaches T(sub c)(+), of a strong coupling between Cu(2+) spins and the Fermi liquid of O(2p) holes leading to the apparent disappearance of localized Cu(2+) moment in connection with the opening of a superconducting gap.

Borsa, F.; Rigamonti, A.

1991-01-01

85

35 Cl, 79 Br, and 127 I NQR spectra of several polyhalophenols and their phenylmercury derivatives  

Microsoft Academic Search

1.The intramolecular contribution to the splitting of the NQR frequencies in the 2,6-dihalo-4-X-derivatives of phenol has been separated out. The strength of the intramolecular hydrogen bond is substantially dependent on the nature of the substituants in position 4. The splittings in the NQR spectra are reduced upon passing from electron-accepting substituents to electron-donating substituents.2.The intramolecular coordination interactions of mercury atoms

G. Ko Semin; E. V. Bryukhova; D. N. Kravtsov; L. S. Golovchenko

1982-01-01

86

Studies of Ga NMR and NQR in SrGa4  

NASA Astrophysics Data System (ADS)

In order to microscopically investigate the properties in SrGa4, the Ga NMR measurements of a powder sample were carried out. The Ga NMR spectra corresponding to Ga(I) and Ga(II) sites are obtained. The NMR spectra of 69&71Ga (a nuclear spin I = 3/2) in the powder sample of SrGa4 do not take a typical powder pattern caused by the NQR interaction, but take the spectra consisting of three well resolved resonance-lines, which indicates that the nonuniform distribution of crystal orientation in the powder sample occurs because of the magnetic anisotropy. From the analysis of the Ga NMR spectrum, it is found that the ab-plane of the crystal is parallel to the external magnetic field, which would be attributed to the anisotropy of the magnetic susceptibility with the easy axis parallel to the ab-plane. This result is also confirmed by the 69Ga NQR in SrGa4. The Knight shifts of the 69Ga(I) and 69Ga(II) shift slightly to the negative side with decreasing temperature due to the core polarization of the d-electrons. The values of the Knight shift of the 69Ga(I) and 69Ga(II) are 0.01 and -0.11 % at 4.2 K, and 0.09 and -0.08 % at 300 K, respectively. The values of the 1/ T 1 T of the NMR of both 69Ga(I) and 69Ga(II) are almost constant between 4.2 and 100 K, whose values are 1.5 s -1 K -1 at 69Ga(I) and 0.12 s -1 K -1 at 69Ga(II), while the 1/ T 1 T slightly increase above 100K with increasing temperature. The value of T 1 of 69Ga(I) is one order of magnitude less than that of 69Ga(II).

Niki, H.; Higa, N.; Nakamura, S.; Kuroshima, H.; Toji, T.; Yogi, M.; Nakamura, A.; Hedo, M.; Nakama, T.; ?nuki, Y.; Harima, H.

2014-11-01

87

Surface Plasmon Resonance: An Introduction to a Surface Spectroscopy Technique  

ERIC Educational Resources Information Center

Surface plasmon resonance (SPR) has become an important optical biosensing technology in the areas of biochemistry, biology, and medical sciences because of its real-time, label-free, and noninvasive nature. The high cost of commercial devices and consumables has prevented SPR from being introduced in the undergraduate laboratory. Here, we present…

Tang, Yijun; Zeng, Xiangqun; Liang, Jennifer

2010-01-01

88

Stationary cantilever vibrations in the oscillating cantilever-driven adiabatic reversals -- magnetic resonance force microscopy technique  

E-print Network

We consider theoretically the novel technique in magnetic resonance force microscopy which is called ``oscillating cantilever-driven adiabatic reversals''. We present analytical and numerical analysis for the stationary cantilever vibrations in this technique. For reasonable values of parameters we estimate the resonant frequency shift as 6Hz per the Bohr magneton. We analyze also the regime of small oscillations of the paramagnetic moment near the transversal plane and the frequency shift of the damped cantilever vibrations.

G. P. Berman; D. I. Kamenev; V. I. Tsifrinovich

2002-03-04

89

Reviews of Topical Problems: Nuclear Spin Resonance  

Microsoft Academic Search

I. Introduction 566 II. NSR energy levels and frequencies 568 1. Energy levels for resonating nuclei with spins 1 or 3\\/2 568 2. NSR energy levels for spin 5\\/2 571 III. Relative intensities of NSR lines 571 1. Relative intensities of Zeeman components in NQR 571 2. Generalized NSR equations 572 3. Relative intensities of NSR lines for spin 1

Vadim S. Grechishkin; N. E. Ainbinder

1964-01-01

90

Low frequency magnetic resonance with a dc SQUID (Superconducting QUantum Interference Device)  

SciTech Connect

Conventional NMR and NQR spectrometers use transistor-based detectors, which are responsive only to voltage. This forces the experimenter to convert the sample magnetization to a voltage, a process that is less efficient at low frequencies when the Faraday induction effect is used. However, the SQUID directly measures the magnetization, so there is no frequency dependent sensitivity to the sample magnetization. Of course, many other devices also measure magnetic field directly, but none has the low frequency sensitivity of the SQUID. Chapter 2 presents the theory required to extend conventional magnetic resonance to z-axis magnetic resonance, a form most efficient for the SQUID. The operating principles of the SQUID, as well as the techniques used to convert the SQUID response into a useful output voltage, are outlined in Chapter 3. The SQUID spectrometer constructed for these experiments is described in Chapter 4. Also in this chapter are a discussion of the design considerations for a SQUID spectrometer, and indications of the overall performance of our instrument. Experimental results on NQR and low frequency NMR are found in Chapters 5 and 6, respectively. 96 refs., 38 figs., 5 tabs.

Connor, C.

1989-10-01

91

Coal thickness gauge using RRAS techniques, part 1. [radiofrequency resonance absorption  

NASA Technical Reports Server (NTRS)

A noncontacting sensor having a measurement range of 0 to 6 in or more, and with an accuracy of 0.5 in or better is needed to control the machinery used in modern coal mining so that the thickness of the coal layer remaining over the rock is maintained within selected bounds. The feasibility of using the radiofrequency resonance absorption (RRAS) techniques of electron magnetic resonance (EMR) and nuclear magnetic resonance (NMR) as the basis of a coal thickness gauge is discussed. The EMR technique was found, by analysis and experiments, to be well suited for this application.

Rollwitz, W. L.; King, J. D.

1978-01-01

92

Charge-carrier density and interplane coupling in Y2Ba4Cu7O15: A Cu NMR-NQR study  

NASA Astrophysics Data System (ADS)

We report an observation of the 63,65Cu nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) in Y2Ba4Cu7O15. We have measured the temperature dependence of the Cu NQR frequency and spin-lattice relaxation at all four chemically inequivalent Cu sites, and of the Cu magnetic shift at two inequivalent plane Cu sites (for the magnetic field parallel and perpendicular to the c axis). The Y2Ba4Cu7O15 compound turns out to be a structure containing two inequivalent CuO2 planes of differing doping levels, a multilattice in which YBa2Cu4O8 blocks and YBa2Cu3O7 blocks alternate. In the normal conducting state both the static and the dynamic electron spin susceptibilities of the individual planes of a double plane are governed by the same temperature dependence, which shows a behavior typical for an underdoped high-Tc compound. The same temperature dependence means strong coupling between these planes, with the lower limit of the coupling constant not much less than 30 meV. Although the planes are strongly coupled, their spin susceptibilities retain a distinct q dependence. The temperature variation of relaxation rate and Knight shift is described in terms of spin-gap formation or, alternatively, of frustrated phase separation. Below Tc, the common temperature dependence is lost, which could arise from the opening of two superconducting gaps that differ in the individual planes.

Stern, R.; Mali, M.; Mangelschots, I.; Roos, J.; Brinkmann, D.; Genoud, J.-Y.; Graf, T.; Muller, J.

1994-07-01

93

Sensitivity of Optically Enhanced Magnetic Resonance While magnetic resonance is one of the less sensitive spectroscopic techniques, there are a number  

E-print Network

Sensitivity of Optically Enhanced Magnetic Resonance While magnetic resonance is one of the less sensitive spectroscopic techniques, there are a number of possible means to correct this deficiency. Optical electronic or nuclear spins. Compared to conventional magnetic resonance, the sensitivity can be increased

Suter, Dieter

94

Surface Plasmon Resonance: An Introduction to a Surface Spectroscopy Technique  

PubMed Central

Surface plasmon resonance (SPR) has become an important optical biosensing technology in the areas of biochemistry, biology, and medical sciences because of its real-time, label-free, and noninvasive nature. The high cost of commercial devices and consumables has prevented SPR from being introduced in the undergraduate laboratory. Here we present an affordable homemade SPR device with all of its components accessible to visualization. This design allows ease of integration with electrochemistry and makes the device suitable for education. We describe a laboratory experiment in which students examine the relationship between the SPR angle and the solution refractive index at the interface and perform a coupled SPR–electrochemistry experiment. Students also study the antibody–antigen binding activity. Most of the experimental work was done as a project by a grade 12 high-school student under proper supervision. We believe that the SPR device and the SPR laboratory will enhance undergraduate chemical education by introducing students to this important modern instrumentation and will help students to learn and understand the molecular interactions occurring at interfaces. PMID:21359107

Tang, Yijun; Zeng, Xiangqun; Liang, Jennifer

2010-01-01

95

Nuclear Quadrupole Resonance Studies of the Sorc Sequence and Nuclear Magnetic Resonance Studies of Polymers.  

NASA Astrophysics Data System (ADS)

The behavior of induction signals during steady -state pulse irradiation in ^{14} N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method. Also as part of the NQR work, Cocaine base has been detected using conventional NQR techniques. The experimental results show that SORC detection can be of sufficient sensitivity to form the basis of narcotics screening devices for both mail and airline baggage. A new NMR technique, to obtain the correlation time of the random thermal motion of a polymer at temperatures near the glass transition has been introduced. The temperature dependence is a result of thermal motion. For slow-motion of a polymer chain near the glass transition, the CSA parameter begins to decrease. This motional narrowing can be interpreted to yield the correlation time of the thermal motion. In this work Nitrocellulose isotopically highly enriched with ^{15}N was studied at four different temperatures between 27^ circ and 120^circ Celsius and the correlation times for polymer backbone motions were obtained. Nafion films containing, water (D_2 O and H_2^{17}O) and methanol (CH_3OD, CH _3^{17}OH), have been studied using Deuteron and Oxygen-17 NMR spectroscopy. Glassy behavior of the water domains at low temperature is evidenced by the specific nature of the ^2H NMR lineshapes. Activation energies extracted from ^2H spin-lattice relaxation data on the high temperature side of the T_1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra of both unstretched and stretched samples reflect considerable anisotropy of the host polymer. Activation volumes corresponding to a specific dynamical process were obtained from measurements of spin-lattice relaxation vs. pressure. From the NMR measurements of Nafion films containing methanol, it was found that the molecular motion is much more rapid than the molecular motion of water in Nafion membranes.

Jayakody, Jayakody R. Pemadasa

1993-01-01

96

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

NASA Astrophysics Data System (ADS)

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 ? = 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.

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

2014-12-01

97

Foil cycling technique for the VESUVIO spectrometer operating in the resonance detector configuration  

SciTech Connect

This article reports a novel experimental technique, namely, the foil cycling technique, developed on the VESUVIO spectrometer (ISIS spallation source) operating in the resonance detector configuration. It is shown that with a proper use of two foils of the same neutron absorbing material it is possible, in a double energy analysis process, to narrow the width of the instrumental resolution of a spectrometer operating in the resonance detector configuration and to achieve an effective subtraction of the neutron and gamma backgrounds. Preliminary experimental results, obtained from deep inelastic neutron scattering measurements on lead, zirconium hydride, and deuterium chloride samples, are presented.

Schooneveld, E. M.; Mayers, J.; Rhodes, N. J.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Gorini, G.; Perelli-Cippo, E.; Tardocchi, M. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Consiglio Nazionale delle Ricerche-Istituto Nazionale per la Fisica della Materia, Universita degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, 00133 Rome (Italy); Dipartimento di Fisica 'G. Occhialini', Universita degli Studi di Milano Bicocca, Piazza della Scienza 2, I-20126 Milan (Italy) and CNR-INFM, Universita degli Studi di Milano Bicocca, Piazza della Scienza 2, I-20126 Milan (Italy)

2006-09-15

98

NMR and NQR Studies on Non-centrosymmetric Superconductors Re7B3, LaBiPt, and BiPd  

NASA Astrophysics Data System (ADS)

We report the nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements for non-centrosymmetric superconductors Re7B3, LaBiPt, and BiPd containing heavy elements. For all three compounds, the spin--lattice relaxation rate 1/T1 shows a coherence peak just below Tc and decreases exponentially at low temperatures, which indicates that an isotropic superconducting gap is dominant in these compounds. In BiPd, the height of the coherence peak just below Tc is much suppressed, which suggests that there exists a substantial component of gap with nodes in this compound. Our results indicate that heavy element is not the only factor, but the extent of inversion symmetry breaking is also important to induce a large spin--orbit coupling and an unconventional superconducting state.

Matano, Kazuaki; Maeda, Satoki; Sawaoka, Hiroki; Muro, Yuji; Takabatake, Toshiro; Joshi, Bhanu; Ramakrishnan, Srinivasan; Kawashima, Kenji; Akimitsu, Jun; Zheng, Guo-qing

2013-08-01

99

1H NMR and 14N NQR study of the ferroelectric phase transition in (CH3)2NH2H2PO4  

NASA Astrophysics Data System (ADS)

The ferroelectric phase transition in (CH3)2NH2H2PO4 has been studied by 14N nuclear-quadrupole resonance (NQR) and 1H spin-lattice relaxation. Both above and below TC, the 14N quadrupole coupling constant is approximately 1.2 MHz and the asymmetry parameter ? is close to 1. Two nonequivalent nitrogen positions in the unit cell are observed below TC whereas, above TC, all nitrogen crystallographic positions are equivalent. Proton spin-lattice relaxation times T1 and T1D show the presence of two molecular motions. Both below and above TC, proton T1 as measured at ?L=32 MHz is dominated by a motion that slows down on the NMR frequency scale below -100 °C. This motion is most probably the 180° reorientation of a dimethylammonium ion around its twofold axis. In the paraelectric phase we observed a slow motion dominating T1D and T1 at low Larmor frequencies. This motion seems to be an up-down reorientation of a dimethylammonium ion along its twofold axis. The NMR and NQR data are interpreted in a model assuming close similarities between the crystal structures of KH2PO4 and (CH3)2NH2H2PO4.

Seliger, J.; Žagar, V.

1998-04-01

100

NMR/NQR and disorder effects in URu2Si2  

NASA Astrophysics Data System (ADS)

NMR experiments at ambient pressure in URu2Si2 demonstrate a linewidth enhancement effect at the hidden order transition temperature (T0). We find that larger amounts of sample disorder appear to induce larger linewidth enhancement at T0. We will present recent NMR and NQR experiments in oriented powder and single crystal samples of URu2Si2 and discuss the measurements with emphasis on a possible connection between linewidth/disorder effects and hidden order. Both NQR and NMR spectra as functions of temperature and NMR for different magnetic field strengths and orientations will be reported.

Bernal, O. O.; Ishida, K.; Reyes, A. P.; Maclaughlin, D. E.; Lukefarh, H. G.; Mydosh, J. A.; Gortenmulder, T. J.; Amitsuka, H.

2005-03-01

101

Effect of substituents on the /sup 35/Cl NQR frequencies of atoms in conditions of hyperconjugation  

SciTech Connect

The authors studied the mechanisms of the change in the NOR spectra in a series of alpha-chloro-substituted dialkyl ethers, organonitrogen compounds, and benzyl and benzylidene chlorides. The NQR spectra were made on a pulsed IS-3 spectrometer at a temperature of 77 degrees K. There are n-o and ..pi..-o interactions which decrease the Cl 35 and Br 79 NQR frequencies in the series of alpha-chloro ethers, alpha-chloroalkylamides, and benzyl halides. The introduction of a geminal halogen atom (dichloromethyl ethers, benzylidene halides) decreases the effect of hyperconjugation.

Arbuzov, B.A.; Andreeva, A.I.; Bredikhin, A.A.; Safin, I.A.; Vereshchagin, A.N.

1985-12-10

102

Nuclear Quadrupole Resonance in Superconducting Gallium  

Microsoft Academic Search

The nuclear quadrupole resonance (NQR) of Ga69 is investigated between 0.8 and 4.2°K. (The super-conducting critical temperature is 1.084°K.) Progressive saturation of the resonance is produced at increasing rf power levels of a frequency-modulated marginal oscillator. The nuclear spin-lattice relaxation rate 1T1 (sec-1) is approximately 12T (°K) in the normal state. The contact part of the hyperfine interaction appears to

R. H. Hammond; W. D. Knight

1960-01-01

103

Experimental study on a resonance mesh coating fabricated using a UV-lithography technique.  

PubMed

In order to achieve high optical transparency and Ka-band bandpass filtering simultaneously, a resonance mesh coating sample is fabricated using a UV-lithography technique. Optical transmission is measured using an Ocean Optics QE65000 spectrometer. And Ka-band bandpass filtering is measured using an Agilent E8363B PNA series network analyzer. Experimental results indicate that the optical transmission of the resonance mesh coating is 63.4% higher than that of non-meshed Frequency Selective Surfaces (FSS) with equivalent aperture parameters, and the transmittance loss of the coating is lower than 0.21 dB while the coating has a Ka-band resonance frequency of 32 GHz. It can therefore be concluded that the resonance mesh coating can be used as a dual-mode spatial filter to achieve high optical transparency and Ka-band bandpass filtering. PMID:23481956

Liu, Yongmeng; Tan, Jiubin

2013-02-25

104

Investigating real-time activation of adenosine receptors by bioluminescence resonance energy transfer technique  

NASA Astrophysics Data System (ADS)

Adenosine receptors play important roles in many physiological and pathological processes, for example regulating myocardial oxygen consumption and the release of neurotransmitters. The activations of adenosine receptors have been studied by some kinds of techniques, such as western blot, immunohistochemistry, etc. However, these techniques cannot reveal the dynamical response of adenosine receptors under stimulation. In this paper, bioluminescence resonance energy transfer technique was introduced to study the real-time activation of adenosine receptors by monitoring the dynamics of cyclic adenosine monophosphate (cAMP) level. The results showed that there were significant differences between adenosine receptors on real-time responses under stimulation. Moreover, the dynamics of cAMP level demonstrated that competition between adenosine receptors existed. Taken together, our study indicates that monitoring the dynamics of cAMP level using bioluminescence resonance energy transfer technique could be one potential approach to investigate the mechanism of competitions between adenosine receptors.

Huang, Yimei; Yang, Hongqin; Zheng, Liqin; Chen, Jiangxu; Wang, Yuhua; Li, Hui; Xie, Shusen

2013-02-01

105

Superconductivity and Magnetic Fluctuations in Cd2Re2O7 via Cd Nuclear Magnetic Resonance and Re Nuclear Quadrupole Resonance  

NASA Astrophysics Data System (ADS)

We report Cd nuclear magnetic resonance (NMR) and Re nuclear quadrupole resonance (NQR) studies on Cd 2Re2O7, the first superconductor among pyrochlore oxides (Tc~=1 K). The Re NQR spectrum at zero magnetic field below 100 K rules out any magnetic or charge order. The spin-lattice relaxation rate below Tc exhibits a pronounced coherence peak and follows the weak-coupling BCS theory with nearly isotropic energy gap. The results of Cd NMR point to a moderate ferromagnetic enhancement at high temperatures followed by a rapid decrease of the density of states below the structural transition temperature of 200 K.

Vyaselev, O.; Arai, K.; Kobayashi, K.; Yamazaki, J.; Kodama, K.; Takigawa, M.; Hanawa, M.; Hiroi, Z.

2002-06-01

106

Application of Advanced Magnetic Resonance Imaging Techniques in Evaluation of the Lower Extremity  

PubMed Central

Synopsis This article reviews current magnetic resonance imaging techniques for imaging the lower extremity, focusing on imaging of the knee, ankle, and hip joints. Recent advancements in MRI include imaging at 7 Tesla, using multiple receiver channels, T2* imaging, and metal suppression techniques, allowing more detailed visualization of complex anatomy, evaluation of morphological changes within articular cartilage, and imaging around orthopedic hardware. PMID:23622097

Braun, Hillary J.; Dragoo, Jason L.; Hargreaves, Brian A.; Levenston, Marc E.; Gold, Garry E.

2012-01-01

107

The role of magnetic resonance techniques in understanding and managing multiple sclerosis  

Microsoft Academic Search

Summary Magnetic resonance (MR) techniques have had a major impact in the last 10-15 years in understanding and managing multiple sclerosis. This review summarizes the current uses of MR in multiple sclerosis, based on the proceedings of a recent international workshop, under four headings: (i) technical issues; (ii) role in diagnosis; (iii) natural history studies in understanding the disease; (iv)

D. H. Miller; R. I. Grossman; S. C. Reingold; H. F. McFarland

1998-01-01

108

Noninvasive muscle tension measurement using the novel technique of magnetic resonance elastography (MRE)  

Microsoft Academic Search

A novel method for direct measurement of the state of skeletal muscle contraction is introduced called magnetic resonance elastography (MRE). Such a technique is useful for avoiding the indeterminacy inherent in most inverse dynamic models of the musculoskeletal system. Within a standard MRI scanner, mechanical vibration is applied to muscle via the skin, creating shear waves that penetrate the tissue

Thomas R. Jenkyn; Richard L. Ehman; Kai-Nan An

2003-01-01

109

RESONANCE-BASED ACOUSTIC TECHNIQUE APPLIED TO THE DETERMINATION OF YOUNG'S MODULUS IN GRANITES  

Microsoft Academic Search

The natural stone industry plays an important role in construction sector activity, and due to this fact the accurate knowledge of the physico-mechanical properties of this kind of materials is indispensable for the configuration of their quality standards. In this work we have optimized an acoustic technique, based on the measurement of the fundamental mode resonance frequency of the longitudinal

Beatriz Calleja; San Emeterio; José Luis; Antonio Ramos

110

An Interventional Magnetic Resonance Imaging Technique for the Molecular Characterization of Intraprostatic  

E-print Network

an important role in cancer care and clinical research if the molecular processes that underlie the image data, molecular imaging, interventional MRI, prostate cancer, micro- array analysis. Introduction Dynamic contrastAn Interventional Magnetic Resonance Imaging Technique for the Molecular Characterization

Whitcomb, Louis L.

111

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. The authors will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in their laboratory. In particular, they will deal with Knight shift and relaxation studies of copper and oxygen. They will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-04-01

112

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. We will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in our laboratory. In particular, we will deal with Knight shift and relaxation studies of copper and oxygen. We will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-04-01

113

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

NASA Technical Reports Server (NTRS)

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. We will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in our laboratory. In particular, we will deal with Knight shift and relaxation studies of copper and oxygen. We will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-01-01

114

Investigation of Wavelet-Based Enhancements to Nuclear Quadrupole Resonance Explosives Detectors  

SciTech Connect

Nuclear Quadrupole Resonance (NQR) is effective for the detection and identification of certain types of explosives such as RDX, PETN and TNT. In explosive detection, the NQR response of certain 14N nuclei present in the crystalline material is probed. The 14N nuclei possess a nuclear quadrupole moment which in the presence of an electric field gradient produces an energy level splitting which may be excited by radio-frequency magnetic fields. Pulsing on the sample with a radio signal of the appropriate frequency produces a transient NQR response which may then be detected. Since the resonant frequency is dependent upon both the quadrupole moment of the 14N nucleus and the nature of the local electric field gradients, it is very compound specific. Under DARPA sponsorship, the authors are using multiresolution methods to investigate the enhancement of operation of NQR explosives detectors used for land mine detection. For this application, NQR processing time must be reduced to less than one second. False alarm responses due to acoustic and piezoelectric ringing must be suppressed. Also, as TNT is the most prevalent explosive found in land mines, NQR detection of TNT must be made practical despite unfavorable relaxation tunes. All three issues require improvement in signal-to-noise ratio, and all would benefit from improved feature extraction. This paper reports some of the insights provided by multiresolution methods that can be used to obtain these improvements. It includes results of multiresolution analysis of experimentally observed NQR signatures for RDX responses and various false alarm signatures in the absence of explosive compounds.

Kercel, Stephen W.; Dress, William B.; Hibbs, Andrew D.; Barrall, Geoffrey A.

1998-06-01

115

35 Cl, 79 Br, 81 Br, and 127 I NQR spectra of organomercury halides  

Microsoft Academic Search

A study of the NQR spectra of some halides disclosed that in the crystals of organomercury halides the behavior of the quadrupole constants is determined to a greater degree by the effect of the nature of the substituants on the intermolecular coordination reactions of Hg... Hal than by the usual transfer of the influence of the electronic effects along the

E. V. Bryukhova; A. K. Prokof'ev; T. Ya. Mel'nikova; O. Yu. Okhlobystia; G. K. Semin

1974-01-01

116

An efficient technique for the reduction of wavelength noise in resonance-based integrated photonic sensors.  

PubMed

A systematic study of the limit of detection (LOD) in resonance-based silicon photonic lab-on-chip sensors is presented. The effects of the noise, temperature fluctuations, and the fundamental thermodynamic limit of the resonator are studied. Wavelength noise is identified as the dominant source of noise, and an efficient technique for suppressing this noise is presented. A large ensemble of statistical data from the transmission measurements in a laser-scanning configuration on five silicon nitride (SiN) microrings is collected to discuss and identify the sources of noise. The experimental results show that the LOD is limited by a 3? wavelength noise of ?1.8 pm. We present a sub-periodic interferometric technique, relying on an inverse algorithm, to suppress this noise. Our technique reduces the wavelength noise by more than one order of magnitude to an ensemble average of 3? = 120 fm, for a resonator quality factor (Q) of about 5 × 10(4) without any temperature stabilization or cooling. This technique is readily amenable to on-chip integration to realize highly accurate and low-cost lab-on-chip sensors. PMID:25243248

Ghasemi, Farshid; Chamanzar, Maysamreza; Eftekhar, Ali A; Adibi, Ali

2014-11-21

117

Peptide backbone orientation and dynamics in spider dragline silk and two-photon excitation in nuclear magnetic and quadrupole resonance  

NASA Astrophysics Data System (ADS)

In the first part of the dissertation, spider dragline silk is studied by solid state NMR techniques. The dependence of NMR frequency on molecular orientation is exploited using the DECODER experiment to determine the orientation of the protein backbone within the silk fibre. Practical experimental considerations require that the silk fibres be wound about a cylindrical axis perpendicular to the external magnetic field, complicating the reconstruction of the underlying orientation distribution and necess-itating the development of numerical techniques for this purpose. A two-component model of silk incorporating static b-sheets and polyglycine II helices adequately fits the NMR data and suggests that the b-sheets are well aligned along the silk axis (20 FWHM) while the helices are poorly aligned (68 FWHM). The effects of fibre strain, draw rate and hydration on orientation are measured. Measurements of the time-scale for peptide backbone motion indicate that when wet, a strain-dependent frac-tion of the poorly aligned component becomes mobile. This suggests a mechanism for the supercontraction of silk involving latent entropic springs that undergo a local strain-dependent phase transition, driving supercontraction. In the second part of this dissertation a novel method is developed for exciting NMR and nuclear quadrupole resonance (NQR) by rf irradiation at multiple frequencies that sum to (or differ by) the resonance frequency. This is fundamentally different than traditional NMR experiments where irradiation is applied on-resonance. With excitation outside the detection bandwidth, two-photon excitation allows for detection of free induction signals during excitation, completely eliminating receiver dead-time. A theoretical approach to describing two-photon excitation is developed based on average Hamiltonian theory. An intuition for two-photon excitation is gained by analogy to the coherent absorption of multiple photons requiring conservation of total energy and momentum. It is shown that two-photon excitation efficiency impro-ves when the two applied rf frequencies deviate from half-resonance. For two-photon NQR, it is shown that observable magnetization appears perpendicular to the excita-tion coil, requiring a second coil for detection, and that double quantum coherences are also generated. Several model systems and experimental geometries are used to demonstrate the peculiarities of two-photon excitation in NMR and NQR.

Eles, Philip Thomas

2005-07-01

118

Clinical decision support systems for brain tumor characterization using advanced magnetic resonance imaging techniques  

PubMed Central

In recent years, advanced magnetic resonance imaging (MRI) techniques, such as magnetic resonance spectroscopy, diffusion weighted imaging, diffusion tensor imaging and perfusion weighted imaging have been used in order to resolve demanding diagnostic problems such as brain tumor characterization and grading, as these techniques offer a more detailed and non-invasive evaluation of the area under study. In the last decade a great effort has been made to import and utilize intelligent systems in the so-called clinical decision support systems (CDSS) for automatic processing, classification, evaluation and representation of MRI data in order for advanced MRI techniques to become a part of the clinical routine, since the amount of data from the aforementioned techniques has gradually increased. Hence, the purpose of the current review article is two-fold. The first is to review and evaluate the progress that has been made towards the utilization of CDSS based on data from advanced MRI techniques. The second is to analyze and propose the future work that has to be done, based on the existing problems and challenges, especially taking into account the new imaging techniques and parameters that can be introduced into intelligent systems to significantly improve their diagnostic specificity and clinical application. PMID:24778769

Tsolaki, Evangelia; Kousi, Evanthia; Svolos, Patricia; Kapsalaki, Efthychia; Theodorou, Kyriaki; Kappas, Constastine; Tsougos, Ioannis

2014-01-01

119

The conformational changes induced by ubiquinone binding in the Na+-pumping NADH:ubiquinone oxidoreductase (Na+-NQR) are kinetically controlled by conserved glycines 140 and 141 of the NqrB subunit.  

PubMed

Na(+)-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is responsible for maintaining a sodium gradient across the inner bacterial membrane. This respiratory enzyme, which couples sodium pumping to the electron transfer between NADH and ubiquinone, is not present in eukaryotes and as such could be a target for antibiotics. In this paper it is shown that the site of ubiquinone reduction is conformationally coupled to the NqrB subunit, which also hosts the final cofactor in the electron transport chain, riboflavin. Previous work showed that mutations in conserved NqrB glycine residues 140 and 141 affect ubiquinone reduction and the proper functioning of the sodium pump. Surprisingly, these mutants did not affect the dissociation constant of ubiquinone or its analog HQNO (2-n-heptyl-4-hydroxyquinoline N-oxide) from Na(+)-NQR, which indicates that these residues do not participate directly in the ubiquinone binding site but probably control its accessibility. Indeed, redox-induced difference spectroscopy showed that these mutations prevented the conformational change involved in ubiquinone binding but did not modify the signals corresponding to bound ubiquinone. Moreover, data are presented that demonstrate the NqrA subunit is able to bind ubiquinone but with a low non-catalytically relevant affinity. It is also suggested that Na(+)-NQR contains a single catalytic ubiquinone binding site and a second site that can bind ubiquinone but is not active. PMID:25006248

Strickland, Madeleine; Juárez, Oscar; Neehaul, Yashvin; Cook, Darcie A; Barquera, Blanca; Hellwig, Petra

2014-08-22

120

Nanoscale imaging of plasmonic hot spots and dark modes with the photothermal-induced resonance technique.  

PubMed

The collective oscillation of conduction electrons, responsible for the localized surface plasmon resonances, enables engineering nanomaterials by tuning their optical response from the visible to terahertz as a function of nanostructure size, shape, and environment. While theoretical calculations helped tremendously in understanding plasmonic nanomaterials and optimizing their light matter interaction, only a few experimental techniques are available to study these materials with high spatial resolution. In this work, the photothermal-induced resonance (PTIR) technique is applied for the first time to image the dark plasmonic resonance of gold asymmetric split ring resonators (A-SRRs) in the mid-infrared (IR) spectral region with nanoscale resolution. Additionally, the chemically specific PTIR signal is used to map the local absorption enhancement of poly(methyl methacrylate) coated on A-SRRs, revealing hot spots with local enhancement factors up to ?30 at 100 nm lateral resolution. We argue that PTIR nanoscale characterization will facilitate the engineering and application of plasmonic nanomaterials for mid-IR applications. PMID:23777547

Lahiri, Basudev; Holland, Glenn; Aksyuk, Vladimir; Centrone, Andrea

2013-07-10

121

Resonance frequencies and Young's modulus determination of magnetorheological elastomers using the photoacoustic technique  

NASA Astrophysics Data System (ADS)

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.

Daniel Macias, J.; Ordonez-Miranda, J.; Alvarado-Gil, J. J.

2012-12-01

122

Extracting Information about the Rotator Cuff from Magnetic Resonance Images Using Deterministic and Random Techniques  

PubMed Central

We consider some methods to extract information about the rotator cuff based on magnetic resonance images; the study aims to define an alternative method of display that might facilitate the detection of partial tears in the supraspinatus tendon. Specifically, we are going to use families of ellipsoidal triangular patches to cover the humerus head near the affected area. These patches are going to be textured and displayed with the information of the magnetic resonance images using the trilinear interpolation technique. For the generation of points to texture each patch, we propose a new method that guarantees the uniform distribution of its points using a random statistical method. Its computational cost, defined as the average computing time to generate a fixed number of points, is significantly lower as compared with deterministic and other standard statistical techniques. PMID:25650281

De Los Ríos, F. A.; Paluszny, M.

2015-01-01

123

35 Cl, 79 Br, and 127 I NQR spectra and crystallographic parameters of some halomethylated phosphine oxides  

Microsoft Academic Search

1.The35Cl,79Br, and127I NQR spectra and the crystallographic parameters of a number of halomethylated phosphine oxides were measured.2.A structural nonequivalence of the bromine atoms was detected in (CH2Br)3PO.3.Phase transitions, with a change in the multipleticity of the NQR spectra, were recorded in (CH2Cl)3PO and (CH2I)3PO in the range 77–296°K.

V. V. Saatsazov; T. L. Khotsyanova; S. I. Kuznetsov

1975-01-01

124

A functional magnetic resonance imaging technique based on nulling extravascular gray matter signal  

Microsoft Academic Search

A new functional magnetic resonance imaging (fMRI) technique is proposed based on nulling the extravascular gray matter (GM) signal, using a spatially nonselective inversion pulse. The remaining MR signal provides cerebral blood volume (CBV) information from brain activation. A theoretical framework is provided to characterize the sources of GM-nulled (GMN) fMRI signal, effects of partial voluming of cerebrospinal fluid (CSF)

Yuji Shen; Risto A Kauppinen; Rishma Vidyasagar; Xavier Golay

2009-01-01

125

Comparative Study of Feeding Techniques for Three-Dimensional Cavity Resonators at 60 GHz  

Microsoft Academic Search

In this paper, various topologies of feeding structures are comparatively evaluated for 60-GHz three-dimensional integrated cavity resonators used in three-dimensional integrated RF modules. Three excitation techniques (slot excitation with a shorting via, slot excitation with a lambdag\\/4 open stub, probe excitation) have been evaluated using simulated and measured data. The probe excitation is demonstrated as an attractive option for wideband

Jong-Hoon Lee; Stéphane Pinel; John Papapolymerou; Joy Laskar; Manos M. Tentzeris

2007-01-01

126

High-efficiency fuel-cell power inverter with soft-switching resonant technique  

Microsoft Academic Search

In order to reduce the capital and overall operating cost of a fuel-cell system, a high-efficiency fuel-cell power inverter with a simple framework is required. The high-order two-inductance two-capacitance (LLCC) resonant technique is adopted in this study to implement a low-frequency 60-Hz sinewave voltage inverter utilized in the proton exchange membrane fuel-cell (PEMFC) system. The methodology for inverting dc voltage

Rong-Jong Wai; Rou-Yong Duan; Jeng-Dao Lee; Li-Wei Liu

2005-01-01

127

Magnetic resonance imaging segmentation techniques using batch-type learning vector quantization algorithms.  

PubMed

In this article, we propose batch-type learning vector quantization (LVQ) segmentation techniques for the magnetic resonance (MR) images. Magnetic resonance imaging (MRI) segmentation is an important technique to differentiate abnormal and normal tissues in MR image data. The proposed LVQ segmentation techniques are compared with the generalized Kohonen's competitive learning (GKCL) methods, which were proposed by Lin et al. [Magn Reson Imaging 21 (2003) 863-870]. Three MRI data sets of real cases are used in this article. The first case is from a 2-year-old girl who was diagnosed with retinoblastoma in her left eye. The second case is from a 55-year-old woman who developed complete left side oculomotor palsy immediately after a motor vehicle accident. The third case is from an 84-year-old man who was diagnosed with Alzheimer disease (AD). Our comparisons are based on sensitivity of algorithm parameters, the quality of MRI segmentation with the contrast-to-noise ratio and the accuracy of the region of interest tissue. Overall, the segmentation results from batch-type LVQ algorithms present good accuracy and quality of the segmentation images, and also flexibility of algorithm parameters in all the comparison consequences. The results support that the proposed batch-type LVQ algorithms are better than the previous GKCL algorithms. Specifically, the proposed fuzzy-soft LVQ algorithm works well in segmenting AD MRI data set to accurately measure the hippocampus volume in AD MR images. PMID:17275624

Yang, Miin-Shen; Lin, Karen Chia-Ren; Liu, Hsiu-Chih; Lirng, Jiing-Feng

2007-02-01

128

Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques  

SciTech Connect

We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

Häussler, Wolfgang [Heinz Maier-Leibnitz Zentrum, Technische Universität München, D-85748 Garching, Germany and Physik-Department E21, Technische Universität München, D-85748 Garching (Germany); Kredler, Lukas [Physik-Department E21, Technische Universität München, D-85748 Garching (Germany)

2014-05-15

129

Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques  

NASA Astrophysics Data System (ADS)

We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

Häussler, Wolfgang; Kredler, Lukas

2014-05-01

130

Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat  

NASA Technical Reports Server (NTRS)

La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for O = to or less than 0.3 and in the temperature range 1.6 + 450 K are analyzed in terms of Cu(++) magnetic correlations and dynamics. It is described how the magnetic correlations that would result from Cu-Cu exchange are reduced by mobile charge defects related to x-doping. A comprehensive picture is given which explains satisfactorily the x and T dependence of the correlation time, of the correlation length and of the Neel temperature T(sub n)(x) as well as being consistent with known electrical resistivity and magnetic susceptibility measurements. It is discussed how, in the superconducting samples, the mobile defects also cause the decrease, for T yields T(sub c)(+) of the hyperfine Cu electron-nucleus effective interaction, leading to the coexistence of quasi-localized, reduced magnetic moments from 3d Cu electrons and mobile oxygen p-hole carriers. The temperature dependence of the effective hyperfine field around the superconducting transition yields an activation energy which could be related to the pairing energy. New specific heat measurements are also presented and discussed in terms of the above picture.

Borsa, F.; Rigamonti, A.

1990-01-01

131

A biofilm microreactor system for simultaneous electrochemical and nuclear magnetic resonance techniques.  

PubMed

Nuclear magnetic resonance (NMR) techniques are ideally suited for the study of biofilms and for probing their microenvironments because these techniques allow for noninvasive interrogation and in situ monitoring with high resolution. By combining NMR with simultaneous electrochemical techniques, it is possible to sustain and study live biofilms respiring on electrodes. Here, we describe a biofilm microreactor system, including a reusable and a disposable reactor, that allows for simultaneous electrochemical and NMR techniques (EC-NMR) at the microscale. Microreactors were designed with custom radio frequency resonator coils, which allowed for NMR measurements of biofilms growing on polarized gold electrodes. For an example application of this system we grew Geobacter sulfurreducens biofilms on electrodes. EC-NMR was used to investigate growth medium flow velocities and depth-resolved acetate concentration inside the biofilm. As a novel contribution we used Monte Carlo error analysis to estimate the standard deviations of the acetate concentration measurements. Overall, we found that the disposable EC-NMR microreactor provided a 9.7 times better signal-to-noise ratio over the reusable reactor. The EC-NMR biofilm microreactor system can ultimately be used to correlate extracellular electron transfer rates with metabolic reactions and explore extracellular electron transfer mechanisms. PMID:24622544

Renslow, R S; Babauta, J T; Majors, P D; Mehta, H S; Ewing, R J; Ewing, T W; Mueller, K T; Beyenal, H

2014-01-01

132

Resonance  

NSDL National Science Digital Library

For advanced undergraduate students: Observe resonance in a collection of driven, damped harmonic oscillators. Vary the driving frequency and amplitude, the damping constant, and the mass and spring constant of each resonator. Notice the long-lived transients when damping is small, and observe the phase change for resonators above and below resonance.

Simulations, Phet I.; Dubson, Michael; Loeblein, Patricia; Olson, Jonathan; Perkins, Kathy; Gratny, Mindy

2011-07-20

133

Automatic detection of ionospheric Alfvén resonances using signal and image processing techniques  

NASA Astrophysics Data System (ADS)

Induction coils permit the measurement of small and very rapid changes of the magnetic field. A new set of induction coils in the UK (at L = 3.2) record magnetic field changes over an effective frequency range of 0.1-40 Hz, encompassing phenomena such as the Schumann resonances, magnetospheric pulsations and ionospheric Alfvén resonances (IARs). The IARs typically manifest themselves as a series of spectral resonance structures (SRSs) within the 1-10 Hz frequency range, usually appearing as fine bands or fringes in spectrogram plots and occurring almost daily during local night-time, disappearing during the daylight hours. The behaviour of the occurrence in frequency (f) and the difference in frequency between fringes (?f) varies throughout the year. In order to quantify the daily, seasonal and annual changes of the SRSs, we developed a new method based on signal and image processing techniques to identify the fringes and to quantify the values of f, ?f and other relevant parameters in the data set. The technique is relatively robust to noise though requires tuning of threshold parameters. We analyse 18 months of induction coil data to demonstrate the utility of the method.

Beggan, C. D.

2014-08-01

134

Vibrational techniques applied to photosynthesis: Resonance Raman and fluorescence line-narrowing.  

PubMed

Resonance Raman spectroscopy may yield precise information on the conformation of, and the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process. Selectivity is achieved via resonance with the absorption transition of the chromophore of interest. Fluorescence line-narrowing spectroscopy is a complementary technique, in that it provides the same level of information (structure, conformation, interactions), but in this case for the emitting pigment(s) only (whether isolated or in an ensemble of interacting chromophores). The selectivity provided by these vibrational techniques allows for the analysis of pigment molecules not only when they are isolated in solvents, but also when embedded in soluble or membrane proteins and even, as shown recently, in vivo. They can be used, for instance, to relate the electronic properties of these pigment molecules to their structure and/or the physical properties of their environment. These techniques are even able to follow subtle changes in chromophore conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman and fluorescence line-narrowing spectroscopies, the information content of the vibrational spectra of chlorophyll and carotenoid molecules is described in this article, together with the experiments which helped in determining which structural parameter(s) each vibrational band is sensitive to. A selection of applications is then presented, in order to illustrate how these techniques have been used in the field of photosynthesis, and what type of information has been obtained. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems. PMID:25268562

Gall, Andrew; Pascal, Andrew A; Robert, Bruno

2015-01-01

135

Direct imaging of neural currents using ultra-low field magnetic resonance techniques  

DOEpatents

Using resonant interactions to directly and tomographically image neural activity in the human brain using magnetic resonance imaging (MRI) techniques at ultra-low field (ULF), the present inventors have established an approach that is sensitive to magnetic field distributions local to the spin population in cortex at the Larmor frequency of the measurement field. Because the Larmor frequency can be readily manipulated (through varying B.sub.m), one can also envision using ULF-DNI to image the frequency distribution of the local fields in cortex. Such information, taken together with simultaneous acquisition of MEG and ULF-NMR signals, enables non-invasive exploration of the correlation between local fields induced by neural activity in cortex and more `distant` measures of brain activity such as MEG and EEG.

Volegov, Petr L. (Los Alamos, NM); Matlashov, Andrei N. (Los Alamos, NM); Mosher, John C. (Los Alamos, NM); Espy, Michelle A. (Los Alamos, NM); Kraus, Jr., Robert H. (Los Alamos, NM)

2009-08-11

136

Review of pyroelectric thermal energy harvesting and new MEMs based resonant energy conversion techniques  

SciTech Connect

Harvesting electrical energy from thermal energy sources using pyroelectric conversion techniques has been under investigation for over 50 years, but it has not received the attention that thermoelectric energy harvesting techniques have during this time period. This lack of interest stems from early studies which found that the energy conversion efficiencies achievable using pyroelectric materials were several times less than those potentially achievable with thermoelectrics. More recent modeling and experimental studies have shown that pyroelectric techniques can be cost competitive with thermoelectrics and, using new temperature cycling techniques, has the potential to be several times as efficient as thermoelectrics under comparable operating conditions. This paper will review the recent history in this field and describe the techniques that are being developed to increase the opportunities for pyroelectric energy harvesting. The development of a new thermal energy harvester concept, based on temperature cycled pyroelectric thermal-to-electrical energy conversion, are also outlined. The approach uses a resonantly driven, pyroelectric capacitive bimorph cantilever structure that can be used to rapidly cycle the temperature in the energy harvester. The device has been modeled using a finite element multi-physics based method, where the effect of the structure material properties and system parameters on the frequency and magnitude of temperature cycling, and the efficiency of energy recycling using the proposed structure, have been modeled. Results show that thermal contact conductance and heat source temperature differences play key roles in dominating the cantilever resonant frequency and efficiency of the energy conversion technique. This paper outlines the modeling, fabrication and testing of cantilever and pyroelectric structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermal-to-electrical energy conversion devices.

Hunter, Scott Robert [ORNL; Lavrik, Nickolay V [ORNL; Mostafa, Salwa [ORNL; Rajic, Slobodan [ORNL; Datskos, Panos G [ORNL

2012-01-01

137

A Second Look at Neutron Resonance Transmission Analysis as a Spent Fuel NDA Technique  

SciTech Connect

Many different nondestructive analysis techniques are currently being investigated as a part of the United States Department of Energy's Next Generation Safeguards Initiative (NGSI) seeking methods to quantify plutonium in spent fuel. Neutron Resonance Transmission Analysis (NRTA) is one of these techniques. Having first been explored in the mid-1970s for the analysis of individual spent-fuel pins a second look, using advanced simulation and modeling methods, is now underway to investigate the suitability of the NRTA technique for assaying complete spent nuclear fuel assemblies. The technique is similar to neutron time-of-flight methods used for cross-section determinations but operates over only the narrow 0.1-20 eV range where strong, distinguishable resonances exist for both the plutonium (239, 240, 241,242Pu) and uranium (235,236,238U) isotopes of interest in spent fuel. Additionally, in this energy range resonances exists for six important fission products (99Tc, 103Rh, 131Xe, 133Cs, 145Nd, and 152Sm) which provide additional information to support spent fuel plutonium assay determinations. Initial modeling shows excellent agreement with previously published experimental data for measurements of individual spent-fuel pins where plutonium assays were demonstrated to have a precision of 2-4%. Within the simulation and modeling analyses of this project scoping studies have explored fourteen different aspects of the technique including the neutron source, drift tube configurations, and gross neutron transmission as well as the impacts of fuel burn up, cooling time, and fission-product interferences. These results show that NRTA may be a very capable experimental technique for spent-fuel assay measurements. The results suggest sufficient transmission strength and signal differentiability is possible for assays through up to 8 pins. For an 8-pin assay (looking at an assembly diagonally), 64% of the pins in a typical 17 ? 17 array of a pressurized water reactor fuel assembly can be part of a complete transmission assay measurement with high precision. Analysis of rows with up to 12 pins may also be feasible but with diminished precision. Preliminary data analysis of an NRTA simulation has demonstrated the simplicity of the technique.

James W .Sterbentz; David L. Chichester

2011-07-01

138

Development of techniques in magnetic resonance and structural studies of the prion protein  

SciTech Connect

Magnetic resonance is the most powerful analytical tool used by chemists today. Its applications range from determining structures of large biomolecules to imaging of human brains. Nevertheless, magnetic resonance remains a relatively young field, in which many techniques are currently being developed that have broad applications. In this dissertation, two new techniques are presented, one that enables the determination of torsion angles in solid-state peptides and proteins, and another that involves imaging of heterogenous materials at ultra-low magnetic fields. In addition, structural studies of the prion protein via solid-state NMR are described. More specifically, work is presented in which the dependence of chemical shifts on local molecular structure is used to predict chemical shift tensors in solid-state peptides with theoretical ab initio surfaces. These predictions are then used to determine the backbone dihedral angles in peptides. This method utilizes the theoretical chemicalshift tensors and experimentally determined chemical-shift anisotropies (CSAs) to predict the backbone and side chain torsion angles in alanine, leucine, and valine residues. Additionally, structural studies of prion protein fragments are described in which conformationally-dependent chemical-shift measurements were made to gain insight into the structural differences between the various conformational states of the prion protein. These studies are of biological and pathological interest since conformational changes in the prion protein are believed to cause prion diseases. Finally, an ultra-low field magnetic resonance imaging technique is described that enables imaging and characterization of heterogeneous and porous media. The notion of imaging gases at ultra-low fields would appear to be very difficult due to the prohibitively low polarization and spin densities as well as the low sensitivities of conventional Faraday coil detectors. However, Chapter 5 describes how gas imaging at ultra-low fields is realized by incorporating the high sensitivities of a dc superconducting quantum interference device (SQUID) with the high polarizations attainable through optica11y pumping {sup 129}Xe gas.

Bitter, Hans-Marcus L.

2000-07-01

139

Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications  

PubMed Central

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging. PMID:21798021

2011-01-01

140

Ion cyclotron resonance spectroscopy. Cyclotron double resonance provides a new technique for the study of ion-molecule reaction mechanisms.  

PubMed

Ion cyclotron resonance spectroscopy yields information on many aspects of ion-molecule chemistry. The method is ideally suited for experiments involving ion energies below several electron volts, and hence provides a valuable complement to other techniques (27). eyclotron double resonance is uniquely suitable for establishing relationships between reactant ions and their product ions in complex ion-molecule reaction sequences. The double-resonance experiments with isotopic species yield information on reaction mechanisms and the nature of intermediate species. Ion-molecule reactions which occur at low energies are quite sensitive to the nature of functional groups and the details of molecular structure (28). Reactions of ions or neutral molecules with specific reagents in the cyclotron spectrometer can thus be used to characterize unknown species. Once the systematic ion-molecule chemistry of useful reagents has been worked out, it should be possible to proceed in a manner directly analogous to classical chemical methods. Suppose, for example, that reagents A(+), B(+), C(+), and D(+) each have characteristic reactions with different functional groups. Then these reagents can all be mixed with an unknown neutral species, X, and each of the reactions, X + A(+) --> ?, X + B(+) --> ?, . . . . can be examined. In contrast to solution chemistry, all the reagents can be added simultaneously to the unknown, since each of the specific reactions can be examined by cyclotron double resonance. The reactions which occur, the species synthesized , and the products of degradation then characterize X. The same methodology can be applied to characterize an unknown ionic epecies X(+), through use of neutral reagents A, B, C, and D. For example, proton transfer reactions to neuteal species have been applied in studying ions of mass 45 produced from various sources (29). The order of the proton affinities of the neutral reagent molecules are as follows: NH(3) isobutylene propene. Ions of mass 45 can be produced by the protonation of ethylene oxide (see structure III), the protonation of acetaldehyde (see structure IV), and the fragmentation of dimethyl ether (see structure V). Those ions might be expected to have, respectively, the three structures: Proton transfer from the mass-45 ions from sources III and IV to NH(3) and to isobutylene occurs readily, but not proton transfer to propene. For the ion from source V, proton transfer to NH3 occurs, but not proton transfer to isobutylene or propene. Thus the proton transfer reactions to various neutral reagents demonstrate that the mass-45 ions from the various sources are different. This example is only a rudimentary version of an approach to the characterization of unusual ionic species; niore sophisticated applications can follow when the systematic chemistry of more reagents is available. This approach should be ideal for comparing nonclassical carbonium ions produced by different routes. Some very interesting ionic species are produced by rearrangements in the fragmentation of molecules, following electron impact. Such molecular rearrangements frequently result in the fragmentation of an ion radical to another ion radical with the elimination of a small neutral species (30). It should be possible to run these reactions in reverse to check the postulated mechanisms. An interesting result of the systematic study of proton transfer to various functional groups is the finding that the proton affinity of various amines and pyridine is extremely high (31). Species such as VI and VII: might be expected to be very stable; they are in fact so stable that they are unreactive with respect to subsequent chemistry at the charge center. Thus, if there are other functional groups on the ion, the important reactions should occur at these functional groups. It should be possible to design species for which the presence of the charge has little influence on the reactivity of a neutral functional group. In this case the charge functions simply as an inert label which makes the study of neutral-neutral

Baldeschwieler, J D

1968-01-19

141

Magnetic resonance imaging of multiple sclerosis: a study of pulse-technique efficacy  

SciTech Connect

Forty-two patients with the clinical diagnosis of multiple sclerosis were examined by proton magnetic resonance imaging (MRI) at 0.5 T. An extensive protocol was used to facilitate a comparison of the efficacy of different pulse techniques. Results were also compared in 39 cases with high-resolution x-ray computed tomography (CT). MRI revealed characteristic abnormalities in each case, whereas CT was positive in only 15 of 33 patients. Cerebral abnormalities were best shown with the T2-weighted spin-echo sequence: brainstem lesions were best defined on the inversion-recovery sequence.

Runge, V.M.; Price, A.C.; Kirshner, H.S.; Allen, J.H.; Partain, C.L.; James, A.E. Jr.

1984-11-01

142

Magnetic resonance arthrography of the hip: technique and spectrum of findings in younger patients  

Microsoft Academic Search

Magnetic resonance(MR) imaging is the reference imaging technique in the evaluation of hip abnormalities. However, in some\\u000a pathological conditions—such as lesions of the labrum, cartilaginous lesions, femoroacetabular impingement, intra-articular\\u000a foreign bodies, or in the pre-operative work-up of developmental dysplasia of the hip—intra-articular injection of a contrast\\u000a medium is required to obtain a precise diagnosis. This article reviews the technical aspects,

Sébastien Aubry; Danny Bélanger; Caroline Giguère; Martin Lavigne

2010-01-01

143

Photooxidation of chlorins by quinones studied by nuclear magnetic resonance techniques  

PubMed Central

The reactions of photo-excited chlorophylls and pheophytins with quinones have been investigated by nuclear magnetic resonance techniques. In slightly alkaline solutions the quinone signals showed line broadening which is explained by degenerate electron transfer between semiquinone radical ions and their benzoquinone parents. In neutral solutions, chemically induced dynamic nuclear polarization was observed which is ascribed to the pair, chlorophyll cation-semiquinone anion. A kinetic analysis of the dependence of these effects upon the quinone concentration suggests that only the reactions of triplet-chlorophyll with the quinones give rise to chemically induced dynamic nuclear polarization effects. PMID:16592269

Lamola, Angelo A.; Manion, Marcia L.; Roth, Heinz D.; Tollin, Gordon

1975-01-01

144

Reduction of reset pulse in resonant frequency servo loop for resonant fiber-optic gyro by an auto-controlled reset technique.  

PubMed

Resonant fiber-optic gyro (RFOG) based on the Sagnac effect has the potential to achieve the inertial navigation system requirement with a short sensing coil. A high-accuracy resonant frequency servo loop is indispensable for a high-performance RFOG. A digital proportional-integral (PI) controller is always adopted in the resonant frequency servo loop. The resonant frequency of the optical fiber ring resonator drifts with environmental temperature changes. When the resonant frequency drift is beyond the tracking range of the resonant frequency servo loop, the digital PI controller overflows and outputs a reset signal. A large reset pulse, which is equivalent to a rotation rate error of 26°/h, has been observed at the output of the RFOG, while a long time is required for returning to the lock-in state simultaneously. To reduce the effect of the overflow resetting in the digital PI controller, an auto-controlled reset technique is proposed and experimentally demonstrated. As a result, the time for returning to the lock-in state is reduced to 5 ms from 8 s. With the integration time of 1 s, the equivalent accuracy of the resonant frequency servo loop is improved to 0.18°/h. PMID:24513942

Ma, Huilian; Lu, Xiao; Jin, Zhonghe

2013-12-20

145

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance  

E-print Network

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance S 20 November 2006 A radio-frequency tunable atomic magnetometer is developed for detection of nuclearHz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection

Romalis, Mike

146

Fast calculation of the Green's functions of a boxed resonator through Ewald's technique  

NASA Astrophysics Data System (ADS)

A novel technique for the fast calculation of the scalar and dyadic Green's functions of a rectangular cavity resonator is presented. The integral equations satisfied by the quasi-static Green's functions are efficiently solved by combining classical image theory and a decomposition strategy: the proposed technique expresses the electric and magnetic potential produced by the periodic set of images in terms of two rapidly convergent series. The key feature of the presented method lies in the introduction of an auxiliar distribution of Gaussian sources which makes the convergence of the periodic potential to be exponential, thus dramatically reducing the computation effort of the implemented tool. Consequently, the proposed approach becomes an essential algorithm to be readily used in computer-aided-design tools for the efficient electromagnetic characterization of passive microwave devices.

San Blas, A. A.; Coves, A.; Bressan, M.; Boria, Vincente E.; Gimeno, B.; Morro, J. V.

2004-04-01

147

Biochemical component identification by light scattering techniques in whispering gallery mode optical resonance based sensor  

NASA Astrophysics Data System (ADS)

Experimental data on detection and identification of variety of biochemical agents, such as proteins (albumin, interferon, C reactive protein), microelements (Na+, Ca+), antibiotic of different generations, in both single and multi component solutions under varied in wide range concentration are represented. Analysis has been performed on the light scattering parameters of whispering gallery mode (WGM) optical resonance based sensor with dielectric microspheres from glass and PMMA as sensitive elements fixed by spin - coating techniques in adhesive layer on the surface of substrate or directly on the coupling element. Sensitive layer was integrated into developed fluidic cell with a digital syringe. Light from tuneable laser strict focusing on and scattered by the single microsphere was detected by a CMOS camera. The image was filtered for noise reduction and integrated on two coordinates for evaluation of integrated energy of a measured signal. As the entrance data following signal parameters were used: relative (to a free spectral range) spectral shift of frequency of WGM optical resonance in microsphere and relative efficiency of WGM excitation obtained within a free spectral range which depended on both type and concentration of investigated agents. Multiplexing on parameters and components has been realized using spatial and spectral parameters of scattered by microsphere light with developed data processing. Biochemical component classification and identification of agents under investigation has been performed by network analysis techniques based on probabilistic network and multilayer perceptron. Developed approach is demonstrated to be applicable both for single agent and for multi component biochemical analysis.

Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Saetchnikov, Anton V.; Schweiger, Gustav; Ostendorf, Andreas

2014-03-01

148

Achievements in resonance Raman spectroscopy review of a technique with a distinct analytical chemistry potential.  

PubMed

In an extended introduction, key aspects of resonance Raman spectroscopy (RRS) such as enhanced sensitivity and selectivity are briefly discussed in comparison with normal RS. The analytical potential is outlined. Then achievements in different fields of research are highlighted in four sections, with emphasis on recent breakthroughs: (1) The use of visible RRS for analyzing carotenoids in biological matrices, for pigments and dyes as dealt with in art and forensics, and for characterizing carbon nanotubes. (2) The use of RRS in the deep UV (excitation below 260nm) in the bioanalytical and life sciences fields, including nucleic acids, proteins and protein-drug interactions. Metalloproteins can be studied by visible RRS in resonance with their chromophoric absorption. (3) Progress in theoretical calculations of RRS excitation profiles and enhancement factors, which ultimately might facilitate analytical RRS. (4) Instrumental and methodological achievements including fiber-optic UV-RRS, coupling of RRS to liquid chromatography and capillary electrophoresis. Sensitivities can approach the single-molecule level with surface-enhanced RRS or tip-enhanced RRS. Last but not least, promising fluorescence background rejection techniques based on time-gated detection will be presented. This review ends with a concluding section on future expectations for RRS, in particular its potential as an analytical technique. PMID:18082644

Efremov, Evtim V; Ariese, Freek; Gooijer, Cees

2008-01-14

149

Nuclear Quadrupole Resonance Studies of the Sorc Sequence and Nuclear Magnetic Resonance Studies of Polymers  

Microsoft Academic Search

The behavior of induction signals during steady -state pulse irradiation in ^{14} N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the

Jayakody R. Pemadasa Jayakody

1993-01-01

150

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging  

PubMed Central

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented. PMID:21160685

Maniam, Santhi; Szklaruk, Janio

2010-01-01

151

ABO Blood-Typing Using an Antibody Array Technique Based on Surface Plasmon Resonance Imaging  

PubMed Central

In this study, readily available antibodies that are used in standard agglutination tests were evaluated for their use in ABO blood typing by a surface plasmon resonance imaging (SPR imaging) technique. Five groups of antibodies, including mixed clones of anti-A, anti-B, and anti-AB, and single clones of anti-A and anti-B, were used to construct the five-line detection arrays using a multichannel flow cell in the SPR imager. The red blood cell (RBC) samples were applied to a multichannel flow cell that was orthogonal to the detection line arrays for blood group typing. We found that the blood samples were correctly grouped in less than 12 min by the SPR imaging technique, and the results were consistent with those of the standard agglutination technique for all 60 samples. We found that mixed clones of antibodies provided 33%–68% greater change in the SPR signal than the single-clone antibodies. Applying the SPR imaging technique using readily available antibodies may reduce the costs of the antibodies, shorten the measurement time, and increase the throughput. PMID:24021965

Houngkamhang, Nongluck; Vongsakulyanon, Apirom; Peungthum, Patjaree; Sudprasert, Krisda; Kitpoka, Pimpun; Kunakorn, Mongkol; Sutapun, Boonsong; Amarit, Ratthasart; Somboonkaew, Armote; Srikhirin, Toemsak

2013-01-01

152

A no-tune no-match wideband probe for nuclear quadrupole resonance spectroscopy in the VHF range  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) spectroscopy is a method for the characterization of chemical compounds containing so-called quadrupolar nuclei. Similar to nuclear magnetic resonance (NMR), the sample under investigation is irradiated with strong radiofrequency (RF) pulses, which stimulate the emission of weak RF signals from the quadrupolar nuclei. The signals are then amplified and Fourier transformed so as to obtain a spectrum. In principle, narrowband NQR spectra can be measured with NMR spectrometers. However, pure NQR signals require the absence of a static magnetic field and several special applications require the characterization of a substance over a large bandwidth, e.g. 50–100% of the central frequency, which is hardly possible with standard NMR equipment. Dedicated zero-field NQR equipment is not widespread and current concepts employ resonating probes which are tuned and matched over a wide range by using mechanical capacitors driven by stepper motors. While providing the highest signal to noise ratio (SNR) such probes are slow in operation and can only be operated from dedicated NMR consoles. We developed a low-cost NQR wideband probe without tuning and matching for applications in the very high frequency (VHF) range below 300?MHz. The probe coil was realized as part of a reactive network which approximates an exponential transmission line. The input reflection coefficient of the two developed prototype probe coils is ? 20?dB between 90–145?MHz and 74.5–99.5?MHz, respectively. Two wideband NQR spectra of published test substances were acquired with an SNR of better than 20?dB after sufficient averaging. The measured signals and the SNR correspond very well to the theoretically expected values and demonstrate the feasibility of the method. Because there is no need for tuning and matching, our probes can be operated easily from any available NMR console.

Scharfetter, Hermann; Petrovic, Andreas; Eggenhofer, Heidi; Stollberger, Rudolf

2014-12-01

153

Effect of the oxygen protonation on the electronic structure of urea in the solid state: A 14N NQR study  

NASA Astrophysics Data System (ADS)

The 14N NQR frequencies of urea complexes with H2O2 (1:1), NH4Cl (1:1), oxalic (2:1), phosphoric (1:1), and nitric acid (1:1) at 77 °K are reported. The analysis of the NQR data indicates that the population of the N nonbonding orbital decreases and that the population of the s N-H and N-C bonds increases as the degree of protonation of the O atom of urea increases. These changes are consistent with a larger weight of structures like C = N+H2 as the protonation increases. The NQR results are in agreement with those obtained from a CNDO/2 calculation for the uronioum ion [Yu. A. Panteleev and A. A. Lipovskii, Zhu. Struk. Khim. 17, 2 (1976)].

Murgich, Juan; Santana R., Magaly

1981-04-01

154

on Active Resonance and Flutter Suppression Techniques John B. Moore, PhD, FIEEE, FTS, Professor, Dept. of Systems Engineering, Australiwt-ffational University  

E-print Network

.- on Active Resonance and Flutter Suppression Techniques John B. Moore, PhD, FIEEE, FTS, Professor flutter suppression schemes. 2. Robust Resonance Suppression One potentiaf application of robust adaptive

Moore, John Barratt

155

Three-dimensional electron paramagnetic resonance imaging technique for mapping porosity in ceramics  

SciTech Connect

This paper reports on a three-dimensional (3D) electron paramagnetic resonance imaging (EPRI) method which was developed to probe the structure and size of pores in ceramic materials. The imaging device that was added to the EPR instrument consisted of a computer-controlled current source and magnetic field gradient. This add-on facility was tested using a well-defined diphenlpicrylhydrazzyl phantom sample. Pumice was then used to demonstrate the potential of the technique. This stone was immersed in a 0.5 mm {sup 15}N-substituted per-deutereted tempone water solution to fill the pores with spin labels. Images were reconstructed using a filtered back-projection technique. A two-dimensional (2D) imaging plane was constructed by collecting 33 projection planes over 180 {degrees}. A 3D image was derived from 22 planes each constructed by 22 projections. At present, the facility allows a resolution of 69 and 46 {mu}m for 2D and 3D imaging, respectively. Advancements of the imaging apparatus, software, and line width of the spin labels will be needed to enhance the resolution of this technique.

Kordas, G.; Kang, Y.H. (Science and Technology Center for Cement, Dept. of Materials Science and Engineering, Ceramics Div., Univ. of Illinois at Urbana-Champaign, Urbana, IL (US))

1991-04-01

156

Disbond Detection Technique for Liner/propellant Interface Using Ultrasonic Resonance and Lamb Waves  

NASA Astrophysics Data System (ADS)

Adhesive interface tests using ultrasonic waves are far superior to other nondestructive tests for detecting the disbond interface. However, a multilayered structure consisting of a steel case, rubber insulation, liner, and propellant poses many difficulties for analyzing ultrasonic waves because of the superposition of the reflected waves and the large differences in the acoustic impedances of the various materials. Therefore, ultrasonic tests for detecting the disbond interface of multilayered structures have been applied in very limited areas between the steel case and rubber insulation using an automatic system. The existing ultrasonic test cannot detect the disbond interface between the rubber and propellant of a multilayered structure because most of the ultrasonic waves are absorbed in the rubber material, which has low acoustic impedance. This problem could be overcome by amplifying the ultrasonic waves using the ultrasonic resonance method. The Lamb waves were used to evaluate the instability of the ultrasonic waves caused by the contact condition on the surface of the multilayered structure. In this paper, a new technique to detect the disbond interface between the liner and propellant using the property of ultrasonic resonance and Lamb waves is discussed in detail.

Kim, Dong-Ryun; Kim, Jae-Hoon

157

A study of the noncollinear ultrasonic-wave-mixing technique under imperfect resonance conditions.  

PubMed

Geometrical and material property changes cause deviations in the resonant conditions used for noncollinear wave mixing. These deviations are predicted and observed using the SV(?1)+L(?2)?L(?1+?2) interaction, where SV and L are the shear vertical and longitudinal waves, respectively, and ?1, ?2 are their frequencies. Numerical predictions, performed for the scattered secondary field in the far field zone, show three field features of imperfect resonance conditions: (1) rotation of a scattered beam, (2) decrease in the beam amplitude, and (3) beam splitting. The response of the nonlinear ultrasonic wave mixing technique is verified experimentally in two ways: (1) detection of a kissing bond between two polyvinyl chloride (PVC) plates, and (2) detection of subsurface micro-cracks in polymethyl methacrylate (PMMA). A predominant decrease in nonlinear wave energy is observed in both experiments. Beam rotation and splitting is observed in the kissing-bond experiment, while a minor increase in the nonlinear wave energy up to 100% is observed in the micro-cracked PMMA specimen. PMID:25497000

Dem?enko, A; Mainini, L; Korneev, V A

2015-03-01

158

Novel Technique for Cardiac Electromechanical Mapping with Magnetic Resonance Imaging Tagging and an Epicardial Electrode Sock  

PubMed Central

Near-simultaneous measurements of electrical and mechanical activation over the entire ventricular surface are now possible using magnetic resonance imaging tagging and a multielectrode epicardial sock. This new electromechanical mapping technique is demonstrated in the ventricularly paced canine heart. A 128-electrode epicardial sock and pacing electrodes were placed on the hearts of four anesthetized dogs. In the magnetic resonance scanner, tagged cine images (8–15 ms/frame) and sock electrode recordings (1000 Hz) were acquired under right-ventricular pacing and temporally referenced to the pacing stimulus. Electrical recordings were obtained during intermittent breaks in image acquisition, so that both data sets represented the same physiologic state. Since the electrodes were not visible in the images, electrode recordings and cine images were spatially registered with Gd-DTPA markers attached to the sock. Circumferential strain was calculated at locations corresponding to electrodes. For each electrode location, electrical and mechanical activation times were calculated and relationships between the two activation patterns were demonstrated. This method holds promise for improving understanding of the relationships between the patterns of electrical activation and contraction in the heart. PMID:12723684

Faris, Owen P.; Evans, Frank J.; Ennis, Daniel B.; Helm, Patrick A.; Taylor, Joni L.; Chesnick, A. Scott; Guttman, Michael A.; Ozturk, Cengizhan; Mcveigh, Elliot R.

2005-01-01

159

Development of a dispersive read-out technique for quantum measurements of nanomechanical resonators  

NASA Astrophysics Data System (ADS)

Over the last decade, there has been an active effort to prepare and measure mechanical structures in the quantum regime for the purpose of sensing weak forces and for studying fundamental topics in quantum mechanics such as quantum measurement, entanglement and decoherence in new macroscopic limits. One promsing tool for such studies is the qubit-coupled mechanical resonator. In this work we discuss some of our first results towards the development of a nanoelectromechanical system that integrates a charge-type superconducting qubit as a detector to probe the number-states of a nanomechanical mode. In our system the qubit-coupled nanoresonator is embedded in a superconducting microwave resonator (SMR); the SMR then serves to perform spectroscopic measurements of the qubit to infer the number-state statistics of the nanoresonator in a manner analogous to dispersive measurement techniques used in circuit and cavity QED to probe the number-states of electromagnetic cavities. We will discuss the design and measurement of our latest generation devices and the prospects for achieving single-phonon measurement resolution with this system.

Rouxinol, Francisco; Lahaye, Matthew; Hao, Hugo; Shim, Seung-Bo

2013-03-01

160

Resonance  

NSDL National Science Digital Library

All About Circuits is a website that â??provides a series of online textbooks covering electricity and electronics.â? Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This specific section, Resonance, is the sixth chapter in the Volume II textbook. Topics covered in this chapter include: electric pendulum, simple parallel resonance, simple series resonance, resonance in series-parallel circuits, and Q and bandwidth of a resonant circuit. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

Kuphaldt, Tony R.

161

DTA and NQR studies of polymorphism in p-chlorofluorobenzene  

Microsoft Academic Search

Differential thermal analysis, and the 35Cl Nuclear Quadrupole Resonance frequency (?Q) and spin-lattice relaxation time (T1) were measured as a function of temperature in p-chlorofluorobenzene. Three different phases were found according to the thermal history of the sample and only one was stable up to the melting point. In one of the phases, the presence of molecular reorientations can be

L. Cerioni; S. Perez; A. Wolfenson

2004-01-01

162

Further Evaluation of the Neutron Resonance Transmission Analysis (NRTA) Technique for Assaying Plutonium in Spent Fuel  

SciTech Connect

This is an end-of-year report (Fiscal Year (FY) 2011) for the second year of effort on a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The second-year goals for this project included: (1) assessing the neutron source strength needed for the NRTA technique, (2) estimating count times, (3) assessing the effect of temperature on the transmitted signal, (4) estimating plutonium content in a spent fuel assembly, (5) providing a preliminary assessment of the neutron detectors, and (6) documenting this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes work performed over a nine month period from January-September 2011 and is to be considered a follow-on or add-on report to our previous published summary report from December 2010 (INL/EXT-10-20620).

J. W. Sterbentz; D. L. Chichester

2011-09-01

163

Inhibition of the sodium-translocating NADH-ubiquinone oxidoreductase [Na+-NQR] decreases cholera toxin production in Vibrio cholerae O1 at the late exponential growth phase.  

PubMed

Two virulence factors produced by Vibrio cholerae, cholera toxin (CT) and toxin-corregulated pilus (TCP), are indispensable for cholera infection. ToxT is the central regulatory protein involved in activation of CT and TCP expression. We previously reported that lack of a respiration-linked sodium-translocating NADH-ubiquinone oxidoreductase (Na(+)-NQR) significantly increases toxT transcription. In this study, we further characterized this link and found that Na(+)-NQR affects toxT expression only at the early-log growth phase, whereas lack of Na(+)-NQR decreases CT production after the mid-log growth phase. Such decreased CT production was independent of toxT and ctxB transcription. Supplementing a respiratory substrate, l-lactate, into the growth media restored CT production in the nqrA-F mutant, suggesting that decreased CT production in the Na(+)-NQR mutant is dependent on electron transport chain (ETC) activity. This notion was supported by the observations that two chemical inhibitors, a Na(+)-NQR specific inhibitor 2-n-Heptyl-4-hydroxyquinoline N-oxide (HQNO) and a succinate dehydrogenase (SDH) inhibitor, thenoyltrifluoroacetone (TTFA), strongly inhibited CT production in both classical and El Tor biotype strains of V. cholerae. Accordingly, we propose the main respiratory enzyme of V. cholerae, as a potential drug target to treat cholera because human mitochondria do not contain Na(+)-NQR orthologs. PMID:24361395

Minato, Yusuke; Fassio, Sara R; Reddekopp, Rylan L; Häse, Claudia C

2014-01-01

164

Selective excitation of single and multiple quantum transitions for spin 7/2 in NQR  

NASA Astrophysics Data System (ADS)

The dynamics of spin 7/2 in pure NQR is considered. The orientation of the applied RF field is assumed arbitrary and ? ? 0. For this situation various selective pulses are considered and analytical results obtained. Shaped pulses are also treated. A key feature of this work is to construct the interaction representation from which an analytical calculation, using the computer program 'Maple', can be obtained in a tractable form. The results presented are general for all half integer spins of magnitude higher than 1/2.

Ageev, S. Z.; Sanctuary, B. C.

165

Roles of the Sodium-Translocating NADH:Quinone Oxidoreductase (Na+-NQR) on Vibrio cholerae Metabolism, Motility and Osmotic Stress Resistance  

PubMed Central

The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

Minato, Yusuke; Halang, Petra; Quinn, Matthew J.; Faulkner, Wyatt J.; Aagesen, Alisha M.; Steuber, Julia; Stevens, Jan F.; Häse, Claudia C.

2014-01-01

166

Roles of the sodium-translocating NADH:quinone oxidoreductase (Na+-NQR) on vibrio cholerae metabolism, motility and osmotic stress resistance.  

PubMed

The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

Minato, Yusuke; Fassio, Sara R; Kirkwood, Jay S; Halang, Petra; Quinn, Matthew J; Faulkner, Wyatt J; Aagesen, Alisha M; Steuber, Julia; Stevens, Jan F; Häse, Claudia C

2014-01-01

167

Optical properties of WO3 thin films using surface plasmon resonance technique  

NASA Astrophysics Data System (ADS)

Indigenously assembled surface plasmon resonance (SPR) technique has been exploited to study the thickness dependent dielectric properties of WO3 thin films. WO3 thin films (80 nm to 200 nm) have been deposited onto gold (Au) coated glass prism by sputtering technique. The structural, optical properties and surface morphology of the deposited WO3 thin films were studied using X-ray diffraction, UV-visible spectrophotometer, Raman spectroscopy, and Scanning electron microscopy (SEM). XRD analysis shows that all the deposited WO3 thin films are exhibiting preferred (020) orientation and Raman data indicates that the films possess single phase monoclinic structure. SEM images reveal the variation in grain size with increase in thickness. The SPR reflectance curves of the WO3/Au/prism structure were utilized to estimate the dielectric properties of WO3 thin films at optical frequency (? = 633 nm). As the thickness of WO3 thin film increases from 80 nm to 200 nm, the dielectric constant is seen to be decreasing from 5.76 to 3.42, while the dielectric loss reduces from 0.098 to 0.01. The estimated value of refractive index of WO3 film is in agreement to that obtained from UV-visible spectroscopy studies. The strong dispersion in refractive index is observed with wavelength of incident laser light.

Paliwal, Ayushi; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

2014-01-01

168

Optical properties of WO{sub 3} thin films using surface plasmon resonance technique  

SciTech Connect

Indigenously assembled surface plasmon resonance (SPR) technique has been exploited to study the thickness dependent dielectric properties of WO{sub 3} thin films. WO{sub 3} thin films (80?nm to 200?nm) have been deposited onto gold (Au) coated glass prism by sputtering technique. The structural, optical properties and surface morphology of the deposited WO{sub 3} thin films were studied using X-ray diffraction, UV-visible spectrophotometer, Raman spectroscopy, and Scanning electron microscopy (SEM). XRD analysis shows that all the deposited WO{sub 3} thin films are exhibiting preferred (020) orientation and Raman data indicates that the films possess single phase monoclinic structure. SEM images reveal the variation in grain size with increase in thickness. The SPR reflectance curves of the WO{sub 3}/Au/prism structure were utilized to estimate the dielectric properties of WO{sub 3} thin films at optical frequency (??=?633 nm). As the thickness of WO{sub 3} thin film increases from 80?nm to 200?nm, the dielectric constant is seen to be decreasing from 5.76 to 3.42, while the dielectric loss reduces from 0.098 to 0.01. The estimated value of refractive index of WO{sub 3} film is in agreement to that obtained from UV-visible spectroscopy studies. The strong dispersion in refractive index is observed with wavelength of incident laser light.

Paliwal, Ayushi; Sharma, Anjali; Gupta, Vinay, E-mail: drguptavinay@gmail.com, E-mail: vgupta@physics.du.ac.in [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Tomar, Monika [Department of Physics, Miranda House, University of Delhi, Delhi 110007 (India)

2014-01-28

169

Sedimentary rock porosity studied by electromagnetic techniques: nuclear magnetic resonance and dielectric permittivity  

NASA Astrophysics Data System (ADS)

The present work involves a comprehensive experimental study of porosity and pore size distribution of sedimentary rocks, from oil fields formations, by means of two electromagnetic techniques, namely proton (1H) nuclear magnetic resonance (NMR) and dielectric complex constant (DCC) as function of the frequency, both providing complementary results. The NMR yields an accurate determination of the relative pore size distribution and both movable and irreducible fluids. The DCC measurement provides the direct current electrical resistivity of the samples with different degrees of hydration. Thus, combining the results of both techniques allows the determination of the tortuosity index, by means of Archie's relation, and from it the average pore channel length. These measurements are performed on fully hydrated (saturated), centrifuged, dried, and cleaned rocks and also on samples with the irreducible fluids. Finally, the results are complemented with capillary pressure measurements to obtain the total volume associated with the pore channels related to the rock permeability. Additionally, the work presents a particular method to use a network analyzer to measure the DCC.

Ramia, M. E.; Martín, C. A.

2015-02-01

170

Biodegradation 9: 391, 1998. Nuclear Magnetic Resonance (NMR) Spectroscopy and Magnetic Resonance Imaging (MRI) are techniques of  

E-print Network

Biodegradation 9: 391, 1998. 391 Editorial Nuclear Magnetic Resonance (NMR) Spectroscopy applications. This special issue of Biodegradation is directed at presenting examples of applications of NMR with an introductionary paper about NMR and MRI in environmental science and engineering by Lens and Hemminga. With regard

Hemminga, Marcus A.

171

Effects of nonsinusoidal character of atomic modulation on NQR spin-lattice relaxation time of incommensurate phases  

Microsoft Academic Search

The present work is an extention of the theoretical calculation developed by Blinc to explain the temperature and frequency dependence of the spin-lattice relaxation time in incommensurate phases. We have evaluated the influence of the nonsinusoidal character of the atomic modulation, in the linear approximation, over the NQR spectra and over the spin-lattice relaxation due to direct and Raman processes.

Silvina C. Pérez; Clemar Schurrer; Alberto Wolfenson

2001-01-01

172

Dynamic modeling and predictive current control technique for new parallel resonant zero-voltage switching AC to DC converter  

Microsoft Academic Search

A new parallel resonant zero voltage switching (PRZVS) AC to DC power converter for power factor correction is proposed. The proposed single phase AC to DC converter enables zero voltage switching operation of all the power devices allowing the circuit to operate at high switching frequencies and high power levels. A dynamic model and a predictive current control technique for

Gun Woo Moon; Jae Won Ham; Jong Sun Ko; Myung Joong Youn

1993-01-01

173

Ru-NQR Study for Novel Phase Transition in CeRu2Al10  

NASA Astrophysics Data System (ADS)

We have performed Ru-NQR measurements on CeRu2Al10 exhibiting novel phase transition at an abnormally high temperature T0 = 27.3 K and on NdRu2Al10 with a magnetic transition temperature Tm = 2.4 K as a reference RKKY system. The splitting of the NQR line due to internal fields below T0 shows a mean-field-like monotonic increase, indicating no change in the magnetic structure below T0. The internal field strength is one order larger than those at Al sites in CeRu2Al10, and is comparable to that at the Ru site in NdRu2Al10 despite the sevenfold smaller magnitude of the 4f moment, being indicative of an enhanced conduction electron polarization at the Ru site. One of the causes of the high T0 might be the enhanced exchange coupling through the Ce–Ru–Ce path mediated by the enhanced conduction electron polarization. Being similar to that in the Al site, the nuclear spin–lattice relaxation rate 1/T1 shows a gap-like decrease below T0 without enhancement owing to a critical slowing down at T0, in contrast to the mean field 2nd-order transition.

Matsumura, Masahiro; Tomita, Naoya; Matsuoka, Junichirou; Kishimoto, Yasuki; Kato, Harukazu; Kitagawa, Kentaro; Nishioka, Takashi; Tanida, Hiroshi; Sera, Masafumi

2014-10-01

174

A Mutation in Na(+)-NQR Uncouples Electron Flow from Na(+) Translocation in the Presence of K(+).  

PubMed

The sodium-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is a bacterial respiratory enzyme that obtains energy from the redox reaction between NADH and ubiquinone and uses this energy to create an electrochemical Na(+) gradient across the cell membrane. A number of acidic residues in transmembrane helices have been shown to be important for Na(+) translocation. One of these, Asp-397 in the NqrB subunit, is a key residue for Na(+) uptake and binding. In this study, we show that when this residue is replaced with asparagine, the enzyme acquires a new sensitivity to K(+); in the mutant, K(+) both activates the redox reaction and uncouples it from the ion translocation reaction. In the wild-type enzyme, Na(+) (or Li(+)) accelerates turnover while K(+) alone does not activate. In the NqrB-D397N mutant, K(+) accelerates the same internal electron transfer step (2Fe-2S ? FMNC) that is accelerated by Na(+). This is the same step that is inhibited in mutants in which Na(+) uptake is blocked. NqrB-D397N is able to translocate Na(+) and Li(+), but when K(+) is introduced, no ion translocation is observed, regardless of whether Na(+) or Li(+) is present. Thus, this mutant, when it turns over in the presence of K(+), is the first, and currently the only, example of an uncoupled Na(+)-NQR. The fact the redox reaction and ion pumping become decoupled from each other only in the presence of K(+) provides a switch that promises to be a useful experimental tool. PMID:25486106

Shea, Michael E; Mezic, Katherine G; Juárez, Oscar; Barquera, Blanca

2015-01-20

175

Strong coupling between antiferromagnetic and superconducting order parameters of CeRhIn5 studied by I115n nuclear quadrupole resonance spectroscopy  

Microsoft Academic Search

We report on a pressure (P) -induced evolution of magnetism and superconductivity (SC) in a helical magnet CeRhIn5 with an incommensurate wave vector Qi=((1)\\/(2),(1)\\/(2),0.297) through the I115n nuclear quadrupole resonance (NQR) measurements under P . Systematic measurements of the I115n -NQR spectrum reveal that the commensurate antiferromagnetism (AFM) with Qc=((1)\\/(2),(1)\\/(2),(1)\\/(2)) is realized above Pm˜1.7GPa . An important finding is that

M. Yashima; H. Mukuda; Y. Kitaoka; H. Shishido; R. Settai; Y. Onuki

2009-01-01

176

Multiband Superconductivity in Filled-Skutterudite Compounds (Pr1-xLax)Os4Sb12: An Sb Nuclear-Quadrupole-Resonance Study  

Microsoft Academic Search

We report on the systematic evolution of normal-state properties and superconducting characteristics in filled-skutterudite compounds (Pr1-xLax)Os4Sb12 determined using Sb nuclear-quadrupole-resonance (NQR) experiments. The Sb-NQR spectra in these compounds have split into two sets, arising from different Sb12 cages containing either Pr or La, which enables us to measure two kinds of nuclear spin-lattice relaxation time T1Pr and T1La. In the

Mamoru Yogi; Takayuki Nagai; Yojyu Imamura; Hidekazu Mukuda; Yoshio Kitaoka; Daisuke Kikuchi; Hitoshi Sugawara; Yuji Aoki; Hideyuki Sato; Hisatomo Harima

2006-01-01

177

Assessment of magnetic resonance techniques to measure muscle damage 24?h after eccentric exercise.  

PubMed

The study examined which of a number of different magnetic resonance (MR) methods were sensitive to detecting muscle damage induced by eccentric exercise. Seventeen healthy, physically active participants, with muscle damage confirmed by non-MR methods were tested 24?h after performing eccentric exercise. Techniques investigated whether damage could be detected within the quadriceps muscle as a whole, and individually within the rectus femoris, vastus lateralis (VL), vastus medialis (VM), and vastus intermedius (VI). Relative to baseline values, significant changes were seen in leg and muscle cross-sectional areas and volumes and the resting inorganic phosphate concentration. Significant time effects over all muscles were also seen in the transverse relaxation time (T2) and apparent diffusion coefficient (ADC) values, with individually significant changes seen in the VL, VM, and VI for T2 and in the VI for ADC. A significant correlation was found between muscle volume and the average T2 change (r?=?0.59) but not between T2 and ADC or Pi alterations. There were no significant time effects over all muscles for magnetization transfer contrast images, for baseline pH, phosphocreatine (PCr), phosphodiester, or ATP metabolite concentrations or the time constant describing the rate of PCr recovery following exercise. PMID:24738493

Fulford, J; Eston, R G; Rowlands, A V; Davies, R C

2015-02-01

178

Determination of nucleic acids with a near infrared cyanine dye using resonance light scattering technique  

NASA Astrophysics Data System (ADS)

A new method for the determination of nucleic acids has been developed based on the enhancement effect of resonance light scattering (RLS) with a cationic near infrared (NIR) cyanine dye. Under the optimal conditions, the enhanced RLS intensity at 823 nm is proportional to the concentration of nucleic acids in the range of 0-400 ng mL -1 for both calf thymus DNA (CT DNA) and fish sperm DNA (FS DNA), 0-600 ng mL -1 for snake ovum RNA (SO RNA). The detection limits are 3.5 ng mL -1, 3.4 ng mL -1 and 2.9 ng mL -1 for CT DNA, FS DNA and SO RNA, respectively. Owing to performing in near infrared region, this method not only has high sensitivity endowed by RLS technique but also avoids possible spectral interference from background. It has been applied to the determination of nucleic acids in synthetic and real samples and satisfactory results were obtained.

Fang, Fang; Zheng, Hong; Li, Ling; Wu, Yuqin; Chen, Jinlong; Zhuo, Shujuan; Zhu, Changqing

2006-06-01

179

Variable-pitch rectangular cross-section radiofrequency coils for the nitrogen-14 nuclear quadrupole resonance investigation of sealed medicines packets.  

PubMed

The performance of rectangular radio frequency (RF) coils capable of being used to detect nuclear quadrupole resonance (NQR) signals from blister packs of medicines has been compared. The performance of a fixed-pitch RF coil was compared with that from two variable-pitch coils, one based on a design in the literature and the other optimized to obtain the most homogeneous RF field over the whole volume of the coil. It has been shown from (14)N NQR measurements with two medicines, the antibiotic ampicillin (as trihydrate) and the analgesic medicine Paracetamol, that the latter design gives NQR signal intensities almost independent of the distribution of the capsules or pills within the RF coil and is therefore more suitable for quantitative analysis. PMID:23057555

Barras, Jamie; Katsura, Shota; Sato-Akaba, Hideo; Itozaki, Hideo; Kyriakidou, Georgia; Rowe, Michael D; Althoefer, Kaspar A; Smith, John A S

2012-11-01

180

Isomorphism and disorder in o-chlorohalobenzenes studied by NQR.  

PubMed

In this work we present experimental results that allow to characterize different solid modifications found in o-chlorohalobenzenes. Three disordered phases have been found in o-chlorobromobenzene. The stable phase at high temperature (phase I) is also obtained by quenching the sample at 77 K. Slow cooling allow to obtain the low temperature phase III which, on heating, transforms to phase II at 183 K and this, in turns, transforms to phase I at T~210 K. The disorder evidenced through the Nuclear Quadrupole Resonance spectra, is attributed to a random occupation of chlorine and bromine sites. In all phases there is evidence of molecular reorientations out of the benzene ring plane around the pseudo-symmetry axis between the atoms of Cl and Br. In o-chlorofluorobenzene two phases have been found depending on the cooling rate. One phase is disordered due to the random exchange of the occupation of Cl and F sites. In this case, there is also evidence of molecular reorientations out of the benzene ring plane, but in this case the reorientation is around the pseudo-symmetry axis that pass through the C-Cl bonds. Comparisons with the behavior of o-dichlorobenzene are also made. PMID:24440588

Pérez, Silvina C; Wolfenson, Alberto; Zuriaga, Mariano

2014-01-01

181

Application of Resonant Frequency Eddy Current Technique on a Shot-Peened Nickel-Based Engine-Grade Material  

SciTech Connect

The shot peening conditions of a nickel-based engine-grade material were evaluated using a novel eddy current measurement technique. With this technique, the shift of a resonant frequency was found to be dependent on variables which also affect conventional eddy current testing. The cable effect is another important variable, which is often neglected in a routine eddy current testing, is also discussed. Experimental results showed that at high frequencies, the shot peening conditions were easily distinguishable using this frequency shift technique.

Ko, Ray T.; Sathish, Shamachary; Boehnlein, Thomas R. [Structural Integrity Division, University of Dayton Research Institute, 300 College Park Drive, Dayton, Ohio 45469-0120 (United States); Blodgett, Mark P. [Metals, Ceramics, and NDE Division, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)

2007-03-21

182

Determination of Soil Hydraulic Properties Using Magnetic Resonance Techniques and Classical Soil Physics Measurements  

NASA Astrophysics Data System (ADS)

Water and solute movement as any other transport processes through soil are influenced by the hydraulic properties of the soils. The heterogeneities of the soils imply heterogeneous spatial distribution of the hydraulic properties leading to heterogeneous distribution of soil water content. This may affects the water availability for plant growth, the groundwater contamination and nutrients losses within the root zone. The measurement techniques available today for the estimation of soil hydraulic parameters do not account for the heterogeneity of the sample and treat each measurement sample as a homogeneous representative volume. On the other side natural soils contain large heterogeneities mostly in terms of inclusions of different materials. Therefore the purpose of this study is to estimate soil hydraulic properties of a heterogeneous sample by combining classical multi-step-outflow (MSO) with magnetic resonance imaging (MRI) experiments. MSO experiments were performed on a sample filled with sand and sand-clay mixture in a coaxial structure. During each pressure application MRI images at 4.7 T (200 MHz) were recorded using a pure phase-encoding MRI sequence in order to provide information about the soil water content at specific locations within the coaxial sample. The recorded cumulative outflow and water content data were used as input data in the inversion of the MSO experiment. For the simulation and inversion of the MSO experiment we used the hydrological model HYDRUS-2D3D in which the initial hydraulic parameters of the two materials were estimated based on CPMG-T2 relaxation measurements on homogeneous sub-samples. The results show conclusively that the combination of the two MRI and MSO methods leads to a unique estimation of the hydraulic properties of two materials simultaneously.

Stingaciu, Laura R.; Weihermüller, Lutz; Pohlmeier, Andreas; Stapf, Siegfried; Vereecken, Harry

2011-03-01

183

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei.  

PubMed

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance. PMID:23231223

Prescott, D W; Malone, M W; Douglass, S P; Sauer, K L

2012-12-01

184

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei  

NASA Astrophysics Data System (ADS)

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance.

Prescott, D. W.; Malone, M. W.; Douglass, S. P.; Sauer, K. L.

2012-12-01

185

Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques.  

PubMed

F resonance energy transfer (FRET) occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (\\(\\uplambda_{\\textsc{ex}}\\sim\\) nm, \\(\\uplambda_{\\textsc{em}}\\sim\\) 350 nm), in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the proteinlocal environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic F resonance energy transfer (iFRET), a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins. PMID:25490136

Ghisaidoobe, Amar B T; Chung, Sang J

2014-01-01

186

Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques  

PubMed Central

Förster resonance energy transfer (FRET) occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (?EX ? 280 nm, ?EM ? 350 nm), in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the protein’s) local environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic Förster resonance energy transfer (iFRET), a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins. PMID:25490136

Ghisaidoobe, Amar B. T.; Chung, Sang J.

2014-01-01

187

Conformational isomerism of methyl dichloroacetate. An infrared, Raman and 35Cl NQR study  

NASA Astrophysics Data System (ADS)

The IR and Raman spectra of methyl dichloroacetate (M-DCA) have been recorded on the liquid, glassy and crystalline states. The vibrational assignment for M-DCA is proposed on the basis of the spectral comparisons between CCl nH 3? n COOCH 3 and CCl nH 5? n CONHCH 5 ( n = 0-3) in the solid state. The observed spectral data indicate that M-DCA exists as a conformational equilibrium in the liquid and in the glassy state and that the conformation in the crystalline state is entirely different from those in the liquid and glassy states. The 35Cl NQR spectrum suggests that the conformation of M-DCA in the crystalline state is the cis form in which one of the two chlorine atoms is located in the cis position with respect to the carbonyl group. Examination of vibrational spectra also leads to the same conclusion.

Mido, Yoshiyuki; Hashimoto, Masao

1985-10-01

188

Proposed Low-Power High-Speed Microring Resonator-Based Switching Technique for Dynamically Reconfigurable Optical Interconnects  

Microsoft Academic Search

The dynamic bandwidth re-allocation (DBR) technique balances traffic by re-allocating bandwidth from under-utilized links to over-utilized links in a network. In this letter, we propose a nonblocking, fast, low-power, and integratable optical switch that enables DBR. The basic building blocks of the proposed switch are silicon-on-insulator-based microring resonators. Analytical and numerical studies show that the active switch design gives similar

Chander Kochar; Avinash Kodi; Ahmed Louri

2007-01-01

189

A new magneto-elastic resonance based technique to determine magneto-mechanical parameters of amorphous ferromagnetic ribbons.  

PubMed

Measurement of the magneto-mechanical parameters characteristics of amorphous ribbons often requires complex or limited methods due to their very small thickness. In this paper, it is shown how one can establish and estimate the characteristics of a magnetostrictive resonator from the experimental frequency response free of any kind of mechanical measurement (stress or elongation). This technique which is completely developed with a ribbon exhibiting good resonator properties, is suitable to estimate the magneto-mechanical coupling coefficient k33 and the Young's modulus and also to establish the magnetostriction curves ?(H) of amorphous ribbons. Results obtained from resonators made of 2605SC and 2826 from Metglas(TM) ribbons confirmed the validity of the present technique. However, measurements performed on a thin foil of nickel demonstrate that the present method cannot be extended to semi-soft magnetic materials. The technique which is proposed, has serious advantages upon others as it is non-destructive, low cost and easy to develop compared to common ones. PMID:23635206

Le Bras, Y; Lasheras, A; Gutierrez, J; Mazaleyrat, F; Greneche, J M

2013-04-01

190

Weak Magnetic Order in Bilayered-Hydrate NaxCoO2\\cdotyH2O Structure Probed by Co Nuclear Quadrupole Resonance —Proposed Phase Diagram in Superconducting NaxCoO2\\cdotyH2O---  

NASA Astrophysics Data System (ADS)

A weak magnetic order was found in a nonsuperconducting bilayered-hydrate NaxCoO2\\cdotyH2O sample by Co nuclear quadrupole resonance (NQR) measurement. The nuclear spin-lattice relaxation rate divided by temperature 1/T_1T shows a prominent peak at 5.5 K, below which a Co NQR peak splits due to an internal field at the Co site. From the analyses of the Co NQR spectrum at 1.5 K, the internal field is evaluated to be ˜300 Oe and found to be in the ab-plane. The magnitude of the internal field suggests that the ordered moment is as small as ˜0.015 ?B using the hyperfine coupling constant reported previously. It is shown that the NQR frequency ?Q correlates with magnetic fluctuations from measurements of NQR spectra and 1/T_1T in various samples. The higher-?Q sample has stronger magnetic fluctuations. A possible phase diagram for NaxCoO2\\cdotyH2O is depicted using Tc and ?Q, in which the crystal distortion along the c-axis of the tilted CoO2 octahedron is considered to be a physical parameter. Superconductivity with the highest Tc is seemingly observed in the vicinity of a magnetic phase, suggesting strongly that magnetic fluctuations play an important role in the occurrence of superconductivity.

Ihara, Yoshihiko; Ishida, Kenji; Michioka, Chishiro; Kato, Masaki; Yoshimura, Kazuyoshi; Takada, Kazunori; Sasaki, Takayoshi; Sakurai, Hiroya; Takayama-Muromachi, Eiji

2005-03-01

191

Effects of nonsinusoidal character of atomic modulation on NQR spin-lattice relaxation time of incommensurate phases  

SciTech Connect

The present work is an extention of the theoretical calculation developed by Blinc to explain the temperature and frequency dependence of the spin-lattice relaxation time in incommensurate phases. We have evaluated the influence of the nonsinusoidal character of the atomic modulation, in the linear approximation, over the NQR spectra and over the spin-lattice relaxation due to direct and Raman processes. It is shown that the peak with lower intensity in the NQR spectra always has a larger T{sub 1} and viceversa. The results have been applied to bis(4-chlorophenyl)sulfone T{sub 1} and line-shape data. The temperature and frequency dependence of T{sub 1} are well reproduced if Raman processes are considered.

Perez, Silvina C.; Schurrer, Clemar; Wolfenson, Alberto

2001-06-01

192

Advanced numerical technique for analysis of surface and bulk acoustic waves in resonators using periodic metal gratings  

NASA Astrophysics Data System (ADS)

A numerical technique characterized by a unified approach for the analysis of different types of acoustic waves utilized in resonators in which a periodic metal grating is used for excitation and reflection of such waves is described. The combination of the Finite Element Method analysis of the electrode domain with the Spectral Domain Analysis (SDA) applied to the adjacent upper and lower semi-infinite regions, which may be multilayered and include air as a special case of a dielectric material, enables rigorous simulation of the admittance in resonators using surface acoustic waves, Love waves, plate modes including Lamb waves, Stonely waves, and other waves propagating along the interface between two media, and waves with transient structure between the mentioned types. The matrix formalism with improved convergence incorporated into SDA provides fast and robust simulation for multilayered structures with arbitrary thickness of each layer. The described technique is illustrated by a few examples of its application to various combinations of LiNbO3, isotropic silicon dioxide and silicon with a periodic array of Cu electrodes. The wave characteristics extracted from the admittance functions change continuously with the variation of the film and plate thicknesses over wide ranges, even when the wave nature changes. The transformation of the wave nature with the variation of the layer thicknesses is illustrated by diagrams and contour plots of the displacements calculated at resonant frequencies.

Naumenko, Natalya F.

2014-09-01

193

The Influence of the analysis technique on estimating liver iron overload using magnetic resonance imaging T2? quantification.  

PubMed

Iron toxicity is the major cause of tissue damage in patients with iron overload. Iron deposits mainly in the liver, where its concentration closely correlates with whole body iron overload. Different techniques have been proposed for estimating iron content, with liver biopsy being the gold standard despite its invasiveness and influence by sampling error. Recently, magnetic resonance imaging (MRI) has been established as an effective technique for evaluating iron overload by measuring T2(*) in the liver. However, various factors associated with the adopted analysis technique, mainly the exponential fitting model and signal averaging method, affect the resulting measurements. In this study, we evaluate the influences of these factors on T2(*) measurement in numerical phantom, calibrated phantoms, and nine patients with different degrees of iron overload. The results show different performances among the fitting models and signal averaging methods, which are affected by SNR, image quality and signal homogeneity inside the selected ROI for analysis. PMID:25571026

Ibrahim, El-Sayed H; Khalifa, Ayman M; Eldaly, Ahmed K

2014-08-01

194

Low-Cost and High-Q Millimeter-Wave Resonator Using Substrate Integrated Waveguide Technique  

Microsoft Academic Search

A substrate integrated waveguide (SIW) cavity directly coupled to a planar circuit, i.e. microstrip line or coplanar waveguide, is presented. Different coupling topologies and coupling probes are discussed. Empirical equations to predict the resonance frequencies of the cavity are provided. A temperature stability coupling topology were fabricated and measured. Finally, as an example of potential applications, a filter using two

Y. Cassivi; L. Perregrini; K. Wu; G. Conciauro

2002-01-01

195

Nuclear Quadrupole Resonance of Cu in High-Tc Bi-Pb-Sr-Ca-Cu-O  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) signals of Cu have been discovered in the high-Tc superconducting oxide Bi-Pb-Sr-Ca-Cu-O with Tc{=}109 K. It has been observed that there are two Cu sites with a different quadrupole coupling. The temperature dependence of the nuclear relaxation rate, 1\\/T1, was similar to that of the CuO2 plane in YBa2Cu3O7. It is found that the 1\\/T1 for

Kenji Fujiwara; Yoshio Kitaoka; Kunisuke Asayama; Hiroyuki Sasakura; Sinnosuke Minamigawa; Kiyotaka Nakahigashi; Shigemitsu Nakanishi; Mineo Kogachi; Nobuo Fukuoka; Akira Yanase

1989-01-01

196

Laser photolysis-resonance fluorescence technique (LP-RF) applied to the study of reactions of atmospheric interest  

NASA Astrophysics Data System (ADS)

Atomic chlorine is highly reactive with a variety of organic and inorganic compounds so that relatively small concentrations can compete with the tropospheric oxidants (OH, O3 and NO3) in determining the tropospheric fate of such compounds [1]. Besides, there is a lot of evidence that bromine compounds play significant role in the ozone chemistry both in the troposphere and in the stratosphere [2]. In this work we show the laser photolysis-resonance fluorescence technique (LP-RF) applied to the study of gas phase reactions of halogen atoms with volatile organic compounds (VOCs) of interest in atmospheric chemistry [3]. By means of this technique is possible to measure the rate constants of theses reactions, and subsequently obtain the Arrhenius parameters. Halogens atoms are produced in a excess of the VOC and He, by photolyzing Cl2 at 308 nm to obtain Cl atoms, or CF2Br2 at 248 nm for Br atoms, both cases using a pulsed excimer laser. The radiation (135 nm) from a microwave-driven lamp, through which He containing a low concentrations of Cl2 or Br2 was flowed, was used to excite the resonance fluorescence from the corresponding halogen atom in the jacketed Pyrex reaction cell. Signal were obtained using photon-counting techniques in conjunction with multichannel scaling. The fluorescence signal from the PMT was processed by a preamplifier and sent to an multichannel scaler to collect the time-resolved signal. The multichannel scaler was coupled to a microcomputer for further kinetics analysis.

Albaladejo, J.; Cuevas, C. A.; Notario, A.; Martínez, E.

197

NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts  

SciTech Connect

Copper and cobalt are the key elements in syngas conversion catalyst systems used for higher alcohol synthesis. Their proximity and synergy sensitively control the selectivity and efficiency of the process. It is believed that their outer electronic charge distribution which is responsible for their electrical and magnetic properties might be governing their catalytic properties also. To examine the correlation between catalytic and magnetic properties, a series of copper cobalt catalysts (Co/Cu ratio 5:1 to 5:5) with and without a support were prepared. The nuclear quadrupole resonance spectrum of copper and (zero-field) nuclear magnetic resonance spectrum of cobalt and magnetization and hysteresis character of the catalyst were analyzed. Similar to the catalytic results, the magnetic results also were found to be very sensitive to the preparation technique. The results indicate possible electron exchange between copper and cobalt, and cobalt and the support Titania.

Not Available

1991-01-14

198

31P magnetic resonance spectroscopy in the dorsolateral prefrontal cortex of schizophrenics with a volume selective technique--preliminary findings.  

PubMed

Pettegrew et al (Arch Gen Psychiatry 48:563-568, 1991) were the first to determine abnormalities concerning phospholipids and high energy metabolites in the dorsolateral prefrontal cortex of drug-naive schizophrenics with 31P magnetic resonance spectroscopy (MRS). Other investigations could not replicate these findings. We included in our study 13 schizophrenic inpatients and 14 age-matched controls. Whereas Pettegrew et al found increased levels of phosphodiesters and decreased levels of phosphomonoesters we measured decreased levels of phosphodiesters in the schizophrenics as compared to controls. One possible explanation for the contradictory findings of the both trials might be the different localization techniques used. PMID:9066987

Volz, H P; Rzanny, R; May, S; Hegewald, H; Preussler, B; Hajek, M; Kaiser, W A; Sauer, H

1997-03-15

199

Singular and Hypersingular Integral Equations Techniques for Gyrotron Coaxial Resonators with a Corrugated Insert  

Microsoft Academic Search

For the first time rigorous theory is developed for eigen traveling TM modes in the resonator of the coaxial cavity gyrotron\\u000a with a corrugated insert. This mathematical model can be applied for any corrugation parameters and wavelengths. Gyrotron\\u000a simulation software is developed and allows to calculate mode eigenvalues, electromagnetic field components and Ohmic losses\\u000a for eigen TE and TM modes.

Oleksiy S. Kononenko; Yuriy V. Gandel

2007-01-01

200

Neutron Resonance Transmission Analysis (NRTA): A Nondestructive Assay Technique for the Next Generation Safeguards Initiative’s Plutonium Assay Challenge  

SciTech Connect

This is an end-of-year report for a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The first-year goals for this project were modest and included: 1) developing a zero-order MCNP model for the NRTA technique, simulating data results presented in the literature, 2) completing a preliminary set of studies investigating important design and performance characteristics for the NRTA measurement technique, and 3) documentation of this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes a nine month period of work.

J. W. Sterbentz; D. L. Chichester

2010-12-01

201

The 14N NQR spectrum and the crystal structure of Ba[Fe(CN) 5NO] · 3H 2O at room temperature  

NASA Astrophysics Data System (ADS)

The previously reported 14N NQR spectrum of the CN groups of Ba [Fe (CN) 5NO] · 3H 2O (BNP) was shown to also contain lines of Na 2 [Fe (CN) 5NO] · 2H 2O used in the preparation of BNP. The number of NQR lines and their relative intensities in BNP confirmed that it has a Pbcm instead of a Pca2 1 space group at 293 K as previously assumed. The three CN sites found in BNP at room temperature are increased to five below 233 K and to eight below 131 K as a result of phase transitions. The effect on the NQR lines of the axial CN group of the disorder of some water molecules in BNP is also discussed.

Murgich, Juan; Bonalde, Ismardo

1990-07-01

202

Magnetic resonance as a technique to magnetic biosensors characterization in Neocapritermes opacus termites  

NASA Astrophysics Data System (ADS)

This experimental study quantitatively correlates the saturation magnetization obtained from hysteresis curves (SQUID measurements) to the second integral of the magnetic resonance (MR) spectra of Neocapritermes opacus termites. Termites were submitted to an iron private diet, feeding them with pure cellulose for up to four days. This diet cleans their guts of ingested detrital material, eliminating non-biogenic soil-derived magnetite from the ensuing analyses. A clear relation between total magnetic moment (emu) from SQUID measurements and the signal intensity (absorption area) from MR is given.

de Oliveira, J. F.; Wajnberg, E.; Esquivel, D. M. S.; Alves, O. C.

2005-07-01

203

Technique for magnetic susceptibility determination in the highly doped semiconductors by electron spin resonance  

NASA Astrophysics Data System (ADS)

A method for determining the magnetic susceptibility in the highly doped semiconductors is considered. It is suitable for the semiconductors near the metal - insulator transition when the conductivity changes very quickly with the temperature and the resonance line form distorts. A procedure that is based on double integration of the positive part of the derivative of the absorption line having a Dyson shape and takes into account the depth of the skin layer is described. Analysis is made for the example of arsenic-doped germanium samples at a rather high concentration corresponding to the insulator-metal phase transition.

Veinger, A. I.; Zabrodskii, A. G.; Tisnek, T. V.; Goloshchapov, S. I.; Semenikhin, P. V.

2014-08-01

204

Feasibility Study of Velocity and Temperature Measurements of an Arcjet Flow using Laser Resonance Doppler Velocimetric (LRDV) Technique  

NASA Technical Reports Server (NTRS)

Thermal Protection System (TPS) materials are used in space vehicles to shield from high heating environment encountered during their atmospheric reentry. Arcjet wind tunnels are used to simulate the flowfield encountered by the spacecrafts, and are used for testing TPS materials. How well these tests simulate the actual heating environment encountered by space vehicles depends on the characteristics of the simulated flow. The flow characterization requires the determination of temperature, concentration, and velocity of the various atomic and molecular species present in the flow. However, determining these parameters requires a complex set of both analytical and experimental procedures. The ability to properly simulate the flight environment is directly related to the accuracy with which these techniques can be used to define the arcjet Laser Resonance Doppler Velocimetric (LRDV) technique can be used to accurately determine the velocity and temperature of a gaseous species. In this technique, the medium is probed with a laser beam that is in resonance with an absorbing transition of the species. The absorption lineshape is Doppler-shifted due to the flow velocity of the species, and the frequency shift is detected as the variation in intensity of the fluorescence emitted by the species. Thus a measurement of the Doppler shift and the width of a spectral line can give both the temperature and the velocity of the flowfield. This summer, our project was to make a feasibility study to set up an experimental arrangement for the laser resonance Doppler velocimetric technique using a ring dye laser. Experiments required troubleshooting, cleaning, testing, and alignment of two lasers and several diagnostics instruments. All instruments and lasers necessary for the project worked well, but the output power of the broadband fundamental dye laser was limited to about 20 mW. This was quite low as compared to that necessary to obtain second harmonic oscillation at 327.49 nm for the LRDV studies. Further optimization of the dye laser optical elements is necessary before it can be used for the experiment, which requires narrowband (about 20 Mhz) laser operation.

Rob, Mohammad A.

1996-01-01

205

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

NASA Astrophysics Data System (ADS)

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.

Seliger, J.; Žagar, V.

2008-07-01

206

Resonance light scattering technique for the determination of protein with rutin and cetylpyridine bromide system  

NASA Astrophysics Data System (ADS)

A new resonance light scattering (RLS) assay of protein is presented. In Tris-NaOH (pH = 10.93) buffer, the RLS of rutin-cetylpyridine bromide (CPB) system can be greatly enhanced by protein, including bovine serum albumin (BSA) and human serum albumin (HSA). The enhanced RLS intensities are in proportion to the concentration of proteins in the range of 5 × 10 -9 to 2.5 × 10 -6 g ml -1 for BSA and 2.5 × 10 -8 to 3.5 × 10 -6 g ml -1 for HSA. The detection limits (S/N = 3) are 3.0 ng ml -1 for BSA and 10.0 ng ml -1 for HSA. Samples are determined satisfactorily.

Liu, Yang; Yang, Jinghe; Liu, Shufang; Wu, Xia; Su, Benyu; Wu, Tao

2005-02-01

207

Study on naringenin-CTMAB-DNA system by resonance light scattering technique and its analytical application  

NASA Astrophysics Data System (ADS)

A new high-sensitivity determination method of deoxyribonucleic acid (DNA) with detection limit at nanogram levels was proposed. Based on the measurement of resonance light scattering (RLS), it was found DNA could combine with naringenin and cetyltrimethylammonium bromide (CTMAB) in basic Tris-HCl buffer and produce enhanced RLS signal. The optimum conditions for this system were studied in detail. The enhanced intensity of RLS of naringenin-CTMAB at 353 nm was directly proportional to the concentration of DNA in the range of 0.017-1.7 ?g mL -1. The detection limit was 5.06 ng mL -1. Using the proposed method, the synthetic samples were analyzed with satisfactory results, the recovery was 99.3-105.0% and RSD was 0.7-3.7%.

Bi, Shuyun; Wang, Yu; Pang, Bo; Yan, Lili

2011-09-01

208

Determination of nucleic acids at nanogram level using resonance light scattering technique with Congo Red  

NASA Astrophysics Data System (ADS)

Based on the enhancement of the resonance light scattering (RLS) of Congo Red (CR) by nucleic acid, a new quantitative method for nucleic acid is developed. In the Tris-HCl buffer (pH 10.5), the weak light scattering of CR is greatly enhanced by addition of nucleic acid and CTMAB, the maximum peak is at 560 nm and the enhanced intensity of RLS is in proportion to the concentration of nucleic acid. The linear range is 1.0×10 -9 to 1.0×10 -6 g ml -1, 7.5×10 -8 to 1.0×10 -6 g ml -1 and 7.5×10 -8 to 2.5×10 -6 g ml -1 for herring sperm DNA, calf thymus DNA and yeast RNA, and the detection limits are 0.019, 0.89 and 1.2 ng ml -1 ( S/ N = 3), respectively. Actual biological samples were satisfactorily determined.

Wu, Xia; Wang, Yuebo; Wang, Minqin; Sun, Shuna; Yang, Jinghe; Luan, Yuxia

2005-01-01

209

Determination for micro amounts of nucleic acids by a resonance light scattering technique with dequalinium chloride.  

PubMed

Based on the strong enhancement effect of nucleic acids on resonance light scattering of dequalinium chloride, the determination method for micro amounts of nucleic acids has been developed. Under the experimental conditions (5.0x10(-5) mol l(-1) dequalinium, pH 7.0, at room temperature) the linear range of this assay is 0.04-10.0 mug ml(-1) for calf thymus DNA and fish sperm DNA, and 0.04-35.0 mug ml(-1) for yeast RNA. The detection limits (3sigma) are 6.2 ng ml(-1) for calf thymus DNA, 7.4 ng ml(-1) for fish sperm DNA, and 7.0 ng ml(-1) for yeast RNA, respectively. Almost no interference can be observed from ionic strength, proteins, nucleoside, and most of the metal ions. Six synthetic samples were determined satisfactorily. PMID:18968413

Li, Z P; Li, K A; Tong, S Y

2001-10-31

210

Determination of antibacterial quaternary ammonium compound in lozenges and human serum by resonance light scattering technique.  

PubMed

A method for the specific determination of an antibacterial quaternary ammonium compound Dequalinium chloride (DQC) was described in this paper. At pH 0.5, the resonance light scattering (RLS) intensity of sodium dodecyl benzene sulfonate (SDBS) remarkably was enhanced by adding DQC. A RLS peak at 392.0 nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DQC in the range of 0.096-2.88 microg/mL. The detection limit was 2.98 ng/mL and the correlation coefficient was r=0.9988 (n=9). The method was applied to the analysis of DQC in lozenges and human serum. The results indicated that the method was sensitive, simple, practical and useful in the clinical assay. PMID:18585882

Chen, Zhanguang; Peng, Yurui; Chen, Junhui; Zhu, Li

2008-11-01

211

Quantification of skeletal muscle mitochondrial function by (31) P magnetic resonance spectroscopy techniques: a quantitative review.  

PubMed

Magnetic resonance spectroscopy (MRS) can give information about cellular metabolism in vivo which is difficult to obtain in other ways. In skeletal muscle, non-invasive (31) P MRS measurements of the post-exercise recovery kinetics of pH, [PCr], [Pi] and [ADP] contain valuable information about muscle mitochondrial function and cellular pH homeostasis in vivo, but quantitative interpretation depends on understanding the underlying physiology. Here, by giving examples of the analysis of (31) P MRS recovery data, by some simple computational simulation, and by extensively comparing data from published studies using both (31) P MRS and invasive direct measurements of muscle O2 consumption in a common analytical framework, we consider what can be learnt quantitatively about mitochondrial metabolism in skeletal muscle using MRS-based methodology. We explore some technical and conceptual limitations of current methods, and point out some aspects of the physiology which are still incompletely understood. PMID:24773619

Kemp, G J; Ahmad, R E; Nicolay, K; Prompers, J J

2015-01-01

212

Early detection of periventricular leukomalacia by diffusion-weighted magnetic resonance imaging techniques  

Microsoft Academic Search

Periventricular leukomalacia (PVL), the principal form of brain injury in the premature infant, is characterized by overt focal necrotic lesions in periventricular white matter and less prominent, more diffuse cerebral white matter injury. The early detection of the latter, diffuse component of PVL is not consistently possible with conventional brain imaging techniques. We demonstrate the early detection of the diffuse

Terrie Inder; Petra S. Huppi; Gary P. Zientara; Stephan E. Maier; Ferenc A. Jolesz; Don di Salvo; Richard Robertson; Patrick D. Barnes; Joseph J. Volpe

1999-01-01

213

In-Situ Characterization of Tissue Blood Flow, Blood Content, and Water State Using New Techniques in Magnetic Resonance Imaging.  

NASA Astrophysics Data System (ADS)

Tissue blood flow, blood content, and water state have been characterized in-situ with new nuclear magnetic resonance imaging techniques. The sensitivities of standard techniques to the physiologic tissue parameters spin density (N_{rm r}) and relaxation times (T_1 and T_2 ) are mathematically defined. A new driven inversion method is developed so that tissue T_1 and T_2 changes produce cooperative intensity changes, yielding high contrast, high signal to noise, and sensitivity to a wider range of tissue parameters. The actual tissue parameters were imaged by automated collection of multiple-echo data having multiple T _1 dependence. Data are simultaneously fit by three-parameters to a closed-form expression, producing lower inter-parameter correlation and parameter noise than in separate T_1 or T_2 methods or pre-averaged methods. Accurate parameters are obtained at different field strengths. Parametric images of pathology demonstrate high sensitivity to tissue heterogeneity, and water content is determined in many tissues. Erythrocytes were paramagnetically labeled to study blood content and relaxation mechanisms. Liver and spleen relaxation were enhanced following 10% exchange of animal blood volumes. Rapid water exchange between intracellular and extracellular compartments was validated. Erythrocytes occupied 12.5% of renal cortex volume, and blood content was uniform in the liver, spleen and kidney. The magnitude and direction of flow velocity was then imaged. To eliminate directional artifacts, a bipolar gradient technique sensitized to flow in different directions was developed. Phase angle was reconstructed instead of intensity since the former has a 2pi -fold higher dynamic range. Images of flow through curves demonstrated secondary flow with a centrifugally-biased laminar profile and stationary velocity peaks along the curvature. Portal vein flow velocities were diminished or reversed in cirrhosis. Image artifacts have been characterized and removed. The foldover in magnified images was eliminated by exciting limited regions with orthogonal pi/2 and pi pulses. Off-midline regions were imaged by tandemly offsetting the phase-encoding and excitation. Artifacts due to non-steady-state conditions were demonstrated. The approach to steady state was defined by operators and vectors, and any repeated series of RF pulses was proven to produce a steady-state. The vector difference between the magnetization and its steady state value is relatively constant during the approach. The repetition time relative to T_1 is the main determinant of approach rate, and off-resonant RF pulses incoherent with the magnetization produce a more rapid approach than on-resonant pulses.

Conturo, Thomas Edward

214

Analysis of nuclear-quadrupole-resonance spectrum of incommensurate phases: The case of bis(4-chlorophenyl) sulfone  

Microsoft Academic Search

In this work, previous experimental studies of the 35Cl nuclear-quadrupole-resonance (NQR) line shape in the incommensurate phase of bis(4-chlorophenyl) sulfone were extended. The broad spectra in the incommensurate phase (IC) were measured using the Fourier transform of the nuclear signal to avoid systematic errors committed in some studies of this compound. The results were interpreted within the framework of the

J. Schneider; C. Schürrer; A. Wolfenson; A. Brunetti

1998-01-01

215

A study of the semiconductor compound ?uAlO2 by the method of nuclear quadrupole resonance of Cu  

NASA Astrophysics Data System (ADS)

The method of nuclear quadrupole resonance of Cu (NQR Cu) is used to study the samples of a semiconductor compound CuAlO2. The crystal structure of CuAlO2 belongs to the family of delafossite - the mineral of a basic CuFeO2 structure. Transparent semiconductor oxides, such as CuAlO2, have attracted recent attention as promising thermoelectric materials.

Matukhin, V. L.; Khabibulin, I. Kh.; Shul'gin, D. A.; Smidt, S. V.

2012-07-01

216

Non-cyclic geometric phase of nuclear quadrupole resonance signals of powdered samples.  

PubMed

The non-cyclic geometric phase of ¹?N and ³?Cl NQR signals induced by the character of trajectory of nuclear magnetization motion upon pulse r.f. excitation of powdered samples is studied. Analytical expressions for the geometric phases of NQR signals of the nuclei of spins I=1 and 3/2 upon nuclear magnetization rotation induced by means of r.f. pulses with frequency detuned from the resonance and for any impulse duration for a separate crystallite are obtained. It is shown that the geometric phase recorded for the signal from a powdered sample at ??=0 can be different from zero and can oscillate upon changes in duration of the r.f. excitation pulse. An alternative variant of the nutation experiment aimed at obtaining the asymmetry parameter ? from locations of frequency singularities in the nutation phase spectrum for nuclei of spin I=3/2 in powder substances is proposed. PMID:21463929

Glotova, O; Ponamareva, N; Sinyavsky, N; Nogaj, B

2011-01-01

217

Measurements of ocean surface spectrum from an aircraft using the two-frequency microwave resonance technique  

NASA Technical Reports Server (NTRS)

The present investigation is concerned with the results of a two-frequency (Delta k) microwave radar experiment conducted from an aircraft and aimed primarily at the development of remote sensing techniques to measure ocean surface wave spectral characteristics. The experiment was conducted as part of the Maritime Remote Sensing (MARSEN) project in the North Sea during the autumn of 1979. The objective was to demonstrate the feasibility of and study the performance of the Delta k technique from a higher altitude platform, at shallower incidence angles, and at higher Doppler velocities than earlier stationary platform experiments allowed. A quantitative engineering evaluation of the results of two comprehensive flights is provided, and the qualitative significance of the results is discussed from a geophysical point of view in terms of the existing theory.

Johnson, J. W.; Weissman, D. E.; Jones, W. L.

1982-01-01

218

Rapid and nondestructive determination of seed oil by pulsed nuclear magnetic resonance technique  

Microsoft Academic Search

The pulsed NMR technique for rapid and nondestructive determination of oil in oilseeds has been developed. The effects of\\u000a spin-lattice relaxation time, spin-spin relaxation time, seed moisture, angular position of the seeds, sample tube thickness,\\u000a and sample height upon the magnitude and reproducibility of the NMR signal were studied. Based upon these studies, various\\u000a parameters for seed oil analysis have

P. N. Tiwari; P. N. Gambhir; T. S. Rajan

1974-01-01

219

[Assessment with magnetic resonance of cartilage injuries of the knee with tridimensional techniques with fat suppression].  

PubMed

MR studies of chondral injuries of the knee are performed to obtain a high C/N ratio between the articular cartilage and such other structures as subchondral bone, intraarticular fat pad and synovial fluid. This goal has been achieved with the 3D SPGR fat-suppressed technique. This kind of sequence yields high spatial contrast resolution because of its contiguous thin (1.5 mm) slices and high contrast resolution between the hyaline cartilage, which is strongly hyperintense, and the surrounding structures (fat, synovial fluid, subchondral bone) which appear hypointense. From September, 1994, to February, 1995, we submitted to MRI 34 patients, adding the 3D fat-suppressed technique after the routine sequences. These volumetric sections were obtained to image the tibiofemoral joint cartilage in 15 patients and to study the patellofemoral compartment in 19 patients. Chondral injuries were graded according to Beguin and Locker classification and MR results were compared with arthroscopic findings. 3D SPGR fat-suppressed sequences permitted accurate chondral thickness evaluation and the depiction of cartilage injuries, especially in advanced injuries (stages 3 and 4). However, in earlier stages, this MR technique tends to overestimate globular hypointense areas in normal thickness cartilage. This MR pattern needs a close correlation with clinical findings and should be interpreted according to the presence/absence of other associated intraarticular injuries. PMID:9221410

Ginolfi, F; Cusati, B; Rotondo, A

1997-03-01

220

Perfusion Magnetic Resonance Imaging: A Comprehensive Update on Principles and Techniques  

PubMed Central

Perfusion is a fundamental biological function that refers to the delivery of oxygen and nutrients to tissue by means of blood flow. Perfusion MRI is sensitive to microvasculature and has been applied in a wide variety of clinical applications, including the classification of tumors, identification of stroke regions, and characterization of other diseases. Perfusion MRI techniques are classified with or without using an exogenous contrast agent. Bolus methods, with injections of a contrast agent, provide better sensitivity with higher spatial resolution, and are therefore more widely used in clinical applications. However, arterial spin-labeling methods provide a unique opportunity to measure cerebral blood flow without requiring an exogenous contrast agent and have better accuracy for quantification. Importantly, MRI-based perfusion measurements are minimally invasive overall, and do not use any radiation and radioisotopes. In this review, we describe the principles and techniques of perfusion MRI. This review summarizes comprehensive updated knowledge on the physical principles and techniques of perfusion MRI. PMID:25246817

Li, Ka-Loh; Ostergaard, Leif; Calamante, Fernando

2014-01-01

221

Perfusion magnetic resonance imaging: a comprehensive update on principles and techniques.  

PubMed

Perfusion is a fundamental biological function that refers to the delivery of oxygen and nutrients to tissue by means of blood flow. Perfusion MRI is sensitive to microvasculature and has been applied in a wide variety of clinical applications, including the classification of tumors, identification of stroke regions, and characterization of other diseases. Perfusion MRI techniques are classified with or without using an exogenous contrast agent. Bolus methods, with injections of a contrast agent, provide better sensitivity with higher spatial resolution, and are therefore more widely used in clinical applications. However, arterial spin-labeling methods provide a unique opportunity to measure cerebral blood flow without requiring an exogenous contrast agent and have better accuracy for quantification. Importantly, MRI-based perfusion measurements are minimally invasive overall, and do not use any radiation and radioisotopes. In this review, we describe the principles and techniques of perfusion MRI. This review summarizes comprehensive updated knowledge on the physical principles and techniques of perfusion MRI. PMID:25246817

Jahng, Geon-Ho; Li, Ka-Loh; Ostergaard, Leif; Calamante, Fernando

2014-01-01

222

Comprehensive Magnetic Resonance Enterography of Crohn?s Disease in the Pediatric Population: Technique, Interpretation, and Management.  

PubMed

Magnetic resonance enterography (MRE) plays a critical role in the management of Crohn?s disease in the pediatric population. The ability to provide dynamic assessment of disease burden, complications, and therapeutic response without ionizing radiation makes it an ideal tool for younger patients requiring frequent follow-up. With a growing array of available treatment options, a sound understanding of MRE is critical in directing management aimed at curbing the physical and emotional morbidity associated with the lifelong condition. The goal of this article is to provide a practical overview of MRE in the pediatric population. This includes a review of our technique, approach to interpretation, pictorial collection of findings, and discussion of the role MRE plays in management. PMID:25155516

Chehab, Monzer; Hlubocky, James; Olariu, Elena; Bloom, David; Nandalur, Kiran

2014-08-21

223

A Wafer-Level Sn-Rich Au—Sn Bonding Technique and Its Application in Surface Plasmon Resonance Sensors  

NASA Astrophysics Data System (ADS)

Sn-rich Au—Sn solder bonding is systematically investigated. High shear strength (64MPa) and good hermeticity (a leak rate lower than 1 × 10-7 torr·l/s) are obtained for Au—Sn solder with 54 wt% Sn bonded at 310°C. The AuSn2 phase with the highest Vickers-hardness among the four stable intermetallic compounds of the Au—Sn system makes a major contribution to the high bonding strength. This bonding technique has been successfully used to package the Surface Plasmon Resonance (SPR) sensors. The Sn-rich Au—Sn solder bonding provides a reliable, low-cost, low-temperature and wafer-level hermetic packaging solution for the micro-electromechanical system devices and has potential applications in high-end biomedical sensors.

Mao, Xu; Lv, Xing-Dong; Wei, Wei-Wei; Zhang, Zhe; Yang, Jin-Ling; Qi, Zhi-Mei; Yang, Fu-Hua

2014-05-01

224

A comparison of neural network and fuzzy clustering techniques in segmenting magnetic resonance images of the brain.  

PubMed

Magnetic resonance (MR) brain section images are segmented and then synthetically colored to give visual representations of the original data with three approaches: the literal and approximate fuzzy c-means unsupervised clustering algorithms, and a supervised computational neural network. Initial clinical results are presented on normal volunteers and selected patients with brain tumors surrounded by edema. Supervised and unsupervised segmentation techniques provide broadly similar results. Unsupervised fuzzy algorithms were visually observed to show better segmentation when compared with raw image data for volunteer studies. For a more complex segmentation problem with tumor/edema or cerebrospinal fluid boundary, where the tissues have similar MR relaxation behavior, inconsistency in rating among experts was observed, with fuzz-c-means approaches being slightly preferred over feedforward cascade correlation results. Various facets of both approaches, such as supervised versus unsupervised learning, time complexity, and utility for the diagnostic process, are compared. PMID:18276467

Hall, L O; Bensaid, A M; Clarke, L P; Velthuizen, R P; Silbiger, M S; Bezdek, J C

1992-01-01

225

A comparison of neural network and fuzzy clustering techniques in segmenting magnetic resonance images of the brain  

NASA Technical Reports Server (NTRS)

Magnetic resonance (MR) brain section images are segmented and then synthetically colored to give visual representations of the original data with three approaches: the literal and approximate fuzzy c-means unsupervised clustering algorithms and a supervised computational neural network, a dynamic multilayered perception trained with the cascade correlation learning algorithm. Initial clinical results are presented on both normal volunteers and selected patients with brain tumors surrounded by edema. Supervised and unsupervised segmentation techniques provide broadly similar results. Unsupervised fuzzy algorithms were visually observed to show better segmentation when compared with raw image data for volunteer studies. However, for a more complex segmentation problem with tumor/edema or cerebrospinal fluid boundary, where the tissues have similar MR relaxation behavior, inconsistency in rating among experts was observed.

Hall, Lawrence O.; Bensaid, Amine M.; Clarke, Laurence P.; Velthuizen, Robert P.; Silbiger, Martin S.; Bezdek, James C.

1992-01-01

226

Investigating the Impact of Biological Impurities on the Liquid Vein Network in Polycrystalline Ice Using Magnetic Resonance Techniques  

NASA Astrophysics Data System (ADS)

Recent work has demonstrated that microorganisms can occupy the liquid filled inter-crystalline vein network in ice and maintain their metabolic activity under these conditions. Additionally, certain cold tolerant microorganisms produce extra-cellular proteins (i.e., ice-binding proteins) that have the ability to bind to the prism face of an ice crystal and inhibit ice recrystallization. One such microorganism is Chryseobacterium sp. V3519-10, a bacterium isolated from a depth of 3519 m in the Vostok Ice Core, Antarctica. While such an adaptation can impact ice crystal structure, it is not known what effect these proteins may have on the liquid vein network and to what extent these organisms may control their habitat. This study uses magnetic resonance techniques to investigate the effects of chemical and biological impurities on the liquid vein structure in ice. Magnetic resonance techniques are powerful tools for probing pore structure and transport dynamics in porous media systems, however, their ability to characterize ice as a porous media has not yet been fully explored. Three experimental conditions were evaluated in this study. Ices were prepared from 7 g/L NaCl solutions with; 1) addition of a quantified amount of extra-cellular proteins (>30kDa) extracted from Chryseobacterium sp. V3519-10 2) addition of equivalent concentrations of the protein, Bovine Serum Albumin (BSA) and 3) no protein addition. Samples were frozen and analyzed at -15°C. The liquid vein structure, as a function of salt and protein concentrations, was characterized to obtain information on liquid water content, vein surface to volume ratios and tortuosity as a measure of vein network interconnectivity. These measurements were non-destructive and made at various time intervals after freezing to monitor the evolution of microstructure due to recrystallization and assess the effects of the added proteins.

Brox, T. I.; Vogt, S. J.; Brown, J. R.; Skidmore, M. L.; Codd, S. L.; Seymour, J. D.

2011-12-01

227

I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP\\/MAS of Organometallics  

Microsoft Academic Search

NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of ¹N via the quadrupolar interaction.

Ziegeweid

1995-01-01

228

Central role of the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) in sodium bioenergetics of Vibrio cholerae.  

PubMed

Abstract Vibrio cholerae is a Gram-negative bacterium that lives in brackish or sea water environments. Strains of V. cholerae carrying the pathogenicity islands infect the human gut and cause the fatal disease cholera. Vibrio cholerae maintains a Na+ gradient at its cytoplasmic membrane that drives substrate uptake, motility, and efflux of antibiotics. Here, we summarize the major Na+-dependent transport processes and describe the central role of the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR), a primary Na+ pump, in maintaining a Na+-motive force. The Na+-NQR is a membrane protein complex with a mass of about 220 kDa that couples the exergonic oxidation of NADH to the transport of Na+ across the cytoplasmic membrane. We describe the molecular architecture of this respiratory complex and summarize the findings how electron transport might be coupled to Na+-translocation. Moreover, recent advances in the determination of the three-dimensional structure of this complex are reported. PMID:25205724

Steuber, Julia; Halang, Petra; Vorburger, Thomas; Steffen, Wojtek; Vohl, Georg; Fritz, Günter

2014-12-01

229

[Transvaginal ultrasonography and nuclear magnetic resonance. Comparison of techniques in the evaluation of ovarian lesions].  

PubMed

A total of 53 patients were included in this study, aged between 21 and 72 years old and hospitalised with the diagnosis of ovarian tumour. All patients underwent a clinical examination, ultrasonography and NMR prior to surgery. The findings of ultrasonography and NMR were correlated with histological results in order to evaluate the value of these methods in the differential diagnosis of benign and malignant ovarian tumours. Histological tests revealed 46 benign tumours, 3 borderline cases and 4 malignant growths. Transvaginal ultrasonography revealed precisely 47 out of 53 ovarian tumours, and NMR 49 out of 53. The main limitation of both techniques was the tendency to overestimate ovarian lesions (specificity: ultrasonography 89%, NMR 93%). As far as concerns the identification of malignant lesions NMR does not appear to offer significant advantages in comparison to ultrasonography (sensitivity 85% ultrasonography = NMR). PMID:7854561

Mascaretti, G; Carta, G; Renzi, E; Peluzzi, C; Bonitatibus, A; Di Francesco, C L; Patacchiola, F; Moscarini, M

1994-11-01

230

Techniques for High-speed Cardiac Magnetic Resonance Imaging in Rats and Rabbits  

PubMed Central

Progress in research on hypertension, heart failure, aging, post-infarct remodeling, and the molecular basis of cardiovascular diseases in general has been greatly facilitated in recent years by the development of specialized small-mammal models by selective breeding and/or genetic alteration. Routine noninvasive evaluation of cardiac function and perfusion in these animals models, however, is difficult using existing methods. In principle, MRI can be used for this purpose, but in practice this is difficult because of problems related to RF coils, cardiac gating, and imaging pulse sequences. In this article, solutions to these problems are described that have allowed us to use MRI to routinely image the hearts of rats and rabbits. Specifically described are four RF coils, cardiac gating schemes, and an imaging pulse sequence specially designed for cardiac imaging in these animals on a 4.7 T Omega chemical-shift imaging (CSI) spectrometer. These techniques can be used to obtain, within 2 min, eight double-oblique short-axis images of the rat at different cardiac phases with 200 × 400 ?m in-plane resolution and a slice thickness of 2 mm. Moreover, myocardial tissue tagging can be performed with tag thicknesses and separations comparable to those used routinely in humans. The technical information is presented in sufficient detail to allow researchers at other sites to reproduce the results. This information should facilitate the use of MRI for the noninvasive examination of cardiac function and perfusion, which can be combined with other established techniques for the study of cardiovascular disease in specialized animal models. PMID:8978641

Rehwald, Wolfgang G.; Reeder, Scott B.; McVeigh, Elliot R.; Judd, Robert M.

2007-01-01

231

Time-domain simulations of nonlinear interaction in microring resonators using finite-difference and coupled mode techniques.  

PubMed

Nonlinear interactions within compact, on-chip microring resonant cavities is a topic of increasing interest in current silicon photonics research. Frequency combs, one of the emerging nonlinear applications in microring optics, offers great potential from both scientific and practical perspectives. However, the mechanisms of comb formation appear to differ from traditional frequency combs formed by pulsed femtosecond lasers, and thus require detailed elucidation through theory and simulation. Here we propose a technique to mimic the accuracy of finite-difference time domain (FDTD) full wave nonlinear optical simulations with only a small fraction of the computational resources. Our new hybrid approach combines a single linear FDTD simulation of the key interaction parameters, then directly inserts them into a coupled-mode theory simulation. Comparison of the hybrid approach and full FDTD shows a good match both in frequency domain and in time domain. Thus, it retains the advantage of FDTD in terms of direct connection with experimental designs, while finishing much faster and sidestepping stability issues associated with direct simulation of nonlinear phenomena. The hybrid technique produces several key results explored in this paper, including: demonstrating that comb formation can occur with both anomalous and normal dispersion; suggesting a new mechanism for incoherent (Type II) frequency comb formation; and illustrating a method for creating soliton-like pulses in on-chip microresonators. PMID:25321006

Shugayev, Roman; Bermel, Peter

2014-08-11

232

Experimental Models of Brain Ischemia: A Review of Techniques, Magnetic Resonance Imaging, and Investigational Cell-Based Therapies  

PubMed Central

Stroke continues to be a significant cause of death and disability worldwide. Although major advances have been made in the past decades in prevention, treatment, and rehabilitation, enormous challenges remain in the way of translating new therapeutic approaches from bench to bedside. Thrombolysis, while routinely used for ischemic stroke, is only a viable option within a narrow time window. Recently, progress in stem cell biology has opened up avenues to therapeutic strategies aimed at supporting and replacing neural cells in infarcted areas. Realistic experimental animal models are crucial to understand the mechanisms of neuronal survival following ischemic brain injury and to develop therapeutic interventions. Current studies on experimental stroke therapies evaluate the efficiency of neuroprotective agents and cell-based approaches using primarily rodent models of permanent or transient focal cerebral ischemia. In parallel, advancements in imaging techniques permit better mapping of the spatial-temporal evolution of the lesioned cortex and its functional responses. This review provides a condensed conceptual review of the state of the art of this field, from models and magnetic resonance imaging techniques through to stem cell therapies. PMID:24600434

Canazza, Alessandra; Minati, Ludovico; Boffano, Carlo; Parati, Eugenio; Binks, Sophie

2013-01-01

233

Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique  

NASA Astrophysics Data System (ADS)

The internal structures of thin films, particularly interfaces between different materials, are critical to system properties and performance across many disciplines, but characterization of buried interface topography is often unfeasible. In this work, we demonstrate that grazing resonant soft x-ray scattering (GRSoXS), a technique measuring diffusely scattered soft x rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces. By controlling and predicting the x-ray electric field intensity throughout the depth of the film and simultaneously the scattering contrast between materials, we are able to unambiguously identify the microstructure at different interfaces of a model polymer bilayer system. We additionally demonstrate the use of GRSoXS to selectively measure the topography of the surface and buried polymer-polymer interface in an organic thin-film transistor, revealing different microstructure and markedly differing evolution upon annealing. In such systems, where only indirect control of interface topography is possible, accurate measurement of the structure of interfaces for feedback is critically important. While we demonstrate the method here using organic materials, we also show that the technique is readily extendable to any thin-film system with elemental or chemical contrasts exploitable at absorption edges.

Gann, Eliot; Watson, Anne; Tumbleston, John R.; Cochran, Justin; Yan, Hongping; Wang, Cheng; Seok, Jaewook; Chabinyc, Michael; Ade, Harald

2014-12-01

234

A noncontact resonance frequency detection technique for the assessment of the interfacial bone defect around a dental implant.  

PubMed

This study employed a noncontact resonance frequency (RF) detection technique that was developed by our group to evaluate the interfacial bone in in vitro implant-bone models. Based on our method, the implant-bone structure was excited by the acoustic energy of a loudspeaker, and its vibration response was acquired with a capacitance sensor. The spectral analysis was used to characterize the first RF value. Two types of in vitro defect models, Buccal-Lingual (BL) and Mesial-Distal (MD), were constructed for the verification. The measurements of the RF for a defect model clamped at four different heights (9, 10, 11, and 12 mm) were performed in two sensing directions (BL and MD). Moreover, each model was also analyzed using an Osstell Mentor. The obtained two parameters, RF and ISQ (Implant Stability Quotient), were statistically analyzed through one-way analysis of variance (ANOVA) and linear regression analysis for comparisons. The RF and the ISQ values obtained for all of the defect models at the four clamp heights decreased significantly (p < 0.05) with an increase in the severity of the defect. The two parameters for each imperfection increase significantly (p < 0.05) with an increase in the clamp height. Additionally, the RFs of all of the defect models are linearly correlated with their corresponding ISQs for the four clamp heights and the two measuring orientations. Therefore, our developed technique is feasible for the assessment of the postoperative healing around a dental implant. PMID:23764430

Pan, Min-Chun; Zhuang, Han-Bo; Chen, Chin-Sung; Wu, Jer-Whey; Lee, Shyh-Yuan

2013-12-01

235

Improvement of the sensitivity of the surface plasmon resonance sensors based on multi-layer modulation techniques  

NASA Astrophysics Data System (ADS)

In this study, a multi-layer modulation technique was used in an SPR optical fiber sensor to enhance the sensitivity of the SPR optical fiber sensor by adjusting the SPR resonant wavelength. The sputtering process deposited 20 nm of TiO2, 11 nm of SiO2 and 30 nm of gold film on the material surface to change the refractive index. Regardless of the different refractive index solutions (1.32 and 1.36), the sensitivities in wavelength interrogation of the SPR optical fiber with the single gold thin film and multi-layers modulation were 1.08×10-5 RIUs and 1.74×10-6 RIUs, respectively. The results showed the significant differences between the different refractive index solutions of 1.32 and 1.36 using the 850 nm light source to analyze the SPR optical fiber sensor in real-time. The sensitivities in intensity interrogation of the SPR optical fiber with the single gold thin film and multi-layers modulation were 1.08×10-3 RIUs and 1.73×10-4 RIUs, respectively, which indicated that the multi-layer modulation techniques could enhance the sensitivity of the SPR optical fiber sensor. The compact size of the multi-layer SPR fiber sensor had a wider detecting range of the refractive index and higher sensitivity, which had the potential for other applications in biological analysis with suitable wavelength.

Zhao, Xihong; Chu-Su, Yu; Tsai, Woo-Hu; Wang, Ching-Ho; Chuang, Tsung-Liang; Lin, Chii-Wann; Tsao, Yu-Chia; Wu, Mu-Shiang

2015-01-01

236

Sensitive assay of protease activity on a micro/nanofluidics preconcentrator fused with the fluorescence resonance energy transfer detection technique.  

PubMed

A fast and sensitive assay of protease activity on a micro/nanofluidics preconcentrator combining with fluorescence resonance energy transfer (FRET) detection technique has been developed in a homogeneous real-time format. First, the functionalized nanoprobes are formed by loading dye labeled protein onto gold nanoparticles (AuNPs), in which, the photoluminescence of donor dye was strongly quenched by AuNPs due to FRET mechanisms. For protease activity assay, the nanoprobes are enriched by a micro/nanofluidics preconcentrator. When the target protease is transported to the enriched nanoprobes, cleavage of protein occurs as a consequence of molecular recognition of enzyme to substrate. The release of cleavage fragments from AuNPs nanoprobes leads to the enhancement of fluorescence and enables the protease activity assay on the micro/nanofluidics chip. As a demonstration, digestion of fluorescein isothiocyanate labeled dog serum albumin (FITC-DSA) by trypsin was used as a model reaction. Because of the highly efficient preconcentration and space confinement effect, significantly increased protein cleavage rate and protease assay sensitivity can be achieved with enhanced enzyme activity. The present micro/nanofluidics platform fused with the FRET detection technique is promising for fast and sensitive bioanalysis such as immunoassay, DNA hybridization, drug discovery, and clinical diagnosis. PMID:24568176

Wang, Chen; Ouyang, Jun; Wang, Yun-Yi; Ye, De-Kai; Xia, Xing-Hua

2014-03-18

237

Advanced Magnetic Resonance Imaging techniques to probe muscle structure and function  

NASA Astrophysics Data System (ADS)

Structural and functional Magnetic Resonance Imaging (MRI) studies of skeletal muscle allow the elucidation of muscle physiology under normal and pathological conditions. Continuing on the efforts of the Muscle Imaging and Modeling laboratory, the focus of the thesis is to (i) extend and refine two challenging imaging modalities: structural imaging using Diffusion Tensor Imaging (DTI) and functional imaging based on Velocity Encoded Phase Contrast Imaging (VE-PC) and (ii) apply these methods to explore age related structure and functional differences of the gastrocnemius muscle. Diffusion Tensor Imaging allows the study of tissue microstructure as well as muscle fiber architecture. The images, based on an ultrafast single shot Echo Planar Imaging (EPI) sequence, suffer from geometric distortions and low signal to noise ratio. A processing pipeline was developed to correct for distortions and to improve image Signal to Noise Ratio (SNR). DTI acquired on a senior and young cohort of subjects were processed through the pipeline and differences in DTI derived indices and fiber architecture between the two cohorts were explored. The DTI indices indicated that at the microstructural level, fiber atrophy was accompanied with a reduction in fiber volume fraction. At the fiber architecture level, fiber length and pennation angles decreased with age that potentially contribute to the loss of muscle force with age. Velocity Encoded Phase Contrast imaging provides tissue (e.g. muscle) velocity at each voxel which allows the study of strain and Strain Rate (SR) under dynamic conditions. The focus of the thesis was to extract 2D strain rate tensor maps from the velocity images and apply the method to study age related differences. The tensor mapping can potentially provide unique information on the extracellular matrix and lateral transmission the role of these two elements has recently emerged as important determinants of force loss with age. In the cross sectional study on aging, strain rate during isometric contraction was significantly reduced in the seniors; presumably from decrease in muscle slack and increase in stiffness with age. Other parameters of interest from this study that allow inferences on the ECM and lateral transmission are the asymmetry of deformation in the fiber cross section as well as the angle between the SR and muscle fiber. The last part of thesis, which is a 'work-in-progress', is the extension to 3D SR tensor mapping using a 3D spatial, 3D velocity encoded imaging sequence. This is combined with Diffusion Tensor Imaging to obtain the lead eigenvector (muscle fiber direction) at each voxel. The 3D SR is then rotated to the basis of the DTI to obtain a 'Fiber Aligned Strain rate: FASR'. The off diagonal elements of FASR are shear strain terms. Detailed analysis of the shear strain will provide a unique non-invasive method to probe lateral transmission.

Malis, Vadim

238

Water-soluble conjugated polymer as a platform for adenosine deaminase sensing based on fluorescence resonance energy transfer technique.  

PubMed

We report a new biosensor for adenosine deaminase (ADA) sensing based on water-soluble conjugated poly(9,9-bis(6'-N,N,N-trimethylammonium)hexyl)fluorine phenylene (PFP) and fluorescence resonance energy transfer technique. In this biosensor, PFP, DNAc-FI labeled with fluorescein (FAM), and ethidium bromide (EB) were used as the fluorescence energy donor, resonance gate, and the final fluorescence energy acceptor, respectively. In the absence of ADA, the adenosine aptamer forms a hairpin-like conformation with adenosine, which is far from its complementary single-stranded DNA (DNAc-FI). When PFP is excited at 380 nm, fluorescein emits strong green fluorescence via one-step FRET while EB has no fluorescence. After addition of ADA, adenosine is hydrolyzed to inosine and then double-stranded DNA (dsDNA) is formed between the aptamer and DNAc-FI, followed by EB intercalating into dsDNA. Once PFP is excited, EB will emit strong yellow fluorescence after two-step FRET from PFP to fluorescein and from fluorescein to EB. The sensitive ADA detection then is realized with a low detection limit of 0.5 U/L by measuring the FRET ratio of EB to fluorescein. Most importantly, the assay is accomplished homogeneously in 25 min without further treatments, which is much more simple and rapid than that reported in literature. Hence, this method demonstrates the sensitive, cost-effective, and rapid detection of ADA activity. It also opens an opportunity for designing promising sensors for other enzymes. PMID:24893272

Wang, Chun; Tang, Yanli; Liu, Yue; Guo, Yang

2014-07-01

239

An automatic method for detection and classification of Ionospheric Alfvén Resonances using signal and image processing techniques  

NASA Astrophysics Data System (ADS)

Induction coils permit us to measure the very rapid changes of the magnetic field. In June 2012, the British Geological Survey Geomagnetism team installed two high frequency (100 Hz) induction coil magnetometers at the Eskdalemuir Observatory (55.3° N, 3.2° W, L~3), in the Scottish Borders of the United Kingdom. The Eskdalemuir Observatory is one of the longest running geophysical sites in the UK (beginning operation in 1908) and is located in a rural valley with a quiet magnetic environment. The coils record magnetic field changes over an effective frequency range of about 0.1-40Hz, and encompass phenomena such as the Schumann resonances, magnetospheric pulsations and Ionospheric Alfvén Resonances (IAR). In this study we focus on the IAR, which are related to the vibration of magnetic field lines passing through the ionosphere, believed to be mainly excited by lower atmospheric electrical discharges. The IAR typically manifest as a series of spectral resonances structures (SRS) within the 1-6Hz frequency range, usually appearing a fine bands or fringes in spectrogram plots. The SRS tend to occur daily between 18.00-06.00UT at the Eskdalemuir site, disappearing during the daylight hours. They usually start as a single low frequency before bifurcating into 5-10 separate fringes, increasing in frequency until around midnight. The fringes also widen in frequency before fading around 06.00UT. Occasionally, the fringes decrease in frequency slightly around 03.00UT before fading. In order to quantify the daily, seasonal and annual changes of the SRS, we developed a new method to identify the fringes and to quantify their occurrence in frequency (f) and the change in frequency (?f). The method uses short time-series of 100 seconds to produce an FFT spectral plot from which the non-stationary peaks are identified using the residuals from a best-fit six order spline. This is repeated for an entire day of data. The peaks from each time-slice are placed into a matrix which is then treated as an image. In combination with the spectrogram image of that day, the SRS are identified using image processing techniques. The peaks can now be mapped as continuous lines throughout the spectrogram. Finally, we can investigate the f and ?f statistics over the entire length of the dataset. We intend to run the coils as a long term experiment. The data and code are available on request.

Beggan, Ciaran

2014-05-01

240

An ICR study of ion-molecule reactions of PH(n)+ ions. [of importance to interstellar chemistry, using ion cyclotron resonance techniques  

NASA Technical Reports Server (NTRS)

The reactions of PH(n)+ ions (n = 0-3) were examined with a number of neutrals using ion-cyclotron-resonance techniques. The reactions examined have significance for the distribution of phosphorus in interstellar molecules. The results indicate that interstellar molecules containing the P-O bond are likely to be more abundant than those containing the P-H bond.

Thorne, L. R.; Anicich, V. G.; Huntress, W. T.

1983-01-01

241

Magnetic Criticality and Unconventional Superconductivity in CeCoIn5: Study of 115In-Nuclear Quadrupole Resonance under Pressure  

Microsoft Academic Search

We report the systematic evolution of the superconducting (SC) characteristics of the heavy-fermion (HF) superconductor CeCoIn5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin-lattice relaxation rate 1\\/T1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs) specific to a quantum critical point (QCP). It is demonstrated that the marked suppression of AFM

M. Yashima; S. Kawasaki; Y. Kawasaki; G.-q. Zheng; Y. Kitaoka; H. Shishido; R. Settai; Y. Haga; Y. Onuki

2004-01-01

242

Microscopic properties of the heavy-fermion superconductor PuCoIn5 explored by nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

We report 115In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn5, in the temperature range 0.29K ? T ? 75K. The NQR parameters for the two crystallographically inequivalent In sites are determined, and their temperature dependence is investigated. A linear shift of the quadrupolar frequency with lowering temperature below the critical value Tc is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate T1-1(T) clearly signals a superconducting (SC) phase transition at Tc ? 2.3 K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to Tc. Analysis of the T1-1 data in the SC state suggests that PuCoIn5 is a strong-coupling d-wave superconductor.

Koutroulakis, G.; Yasuoka, H.; Chudo, H.; Tobash, P. H.; Mitchell, J. N.; Bauer, E. D.; Thompson, J. D.

2014-05-01

243

A comparative study of magnetic resonance venography techniques for the evaluation of the internal jugular veins in multiple sclerosis patients?  

PubMed Central

Background and Purpose The use of magnetic resonance imaging (MRI) to assess the vascular nature of diseases such as multiple sclerosis (MS) is a growing field of research. This work reports on the application of MR angiographic (MRA) and venographic (MRV) techniques in assessing the extracranial vasculature in MS patients. Materials and Methods A standardized MRI protocol containing 2D TOF-MRV and dynamic 3D contrast-enhanced (CE) MRAV was run for 170 MS patients and 40 healthy controls (HC). The cross-sectional area (CSA) of the internal jugular veins (IJVs) was measured at three neck levels in all subjects for both MRV techniques to determine the presence of venous stenoses. All data were analyzed retrospectively. Results For the values where both methods showed signal, the 3D method showed larger CSA measurement values compared to 2D methods in both IJVs, in both MS and HC subjects which was confirmed with student paired t-tests. Of the 170 MS patients, 93 (55%) in CE-MRAV and 103 (61%) in TOF-MRV showed stenosis in at least one IJV. The corresponding numbers for the 40 HC subjects were 2 (5%) and 4 (10%), respectively. Carotid ectasias with IJV stenosis were seen in 26 cases (15%) with 3D CE-MRAV and were not observable with 2D TOF-MRV. Carotid ectasias were not seen in the HC group. In the 2D TOF-MRV data, banding of the IJVs related to slow flow was seen in 58 (34%) MS cases and in no HC cases. MS patients showed lower average CSAs than the HC subjects. Conclusion The 3D CE MRAV depicted the vascular anatomy more completely than the 2D TOF-MRV. However, the 3D CE MRAV does not provide any information about the flow characteristics which are indirectly available in the 2D TOF-MRV in those cases where there is slow flow. PMID:23850076

Rahman, M. Tamizur; Sethi, Sean K.; Utriainen, David T.; Hewett, J. Joseph; Haacke, E. Mark

2014-01-01

244

Application of AI techniques to a voice-actuated computer system for reconstructing and displaying magnetic resonance imaging data  

NASA Astrophysics Data System (ADS)

To provide a means of rendering complex computer architectures languages and input/output modalities transparent to experienced and inexperienced users research is being conducted to develop a voice driven/voice response computer graphics imaging system. The system will be used for reconstructing and displaying computed tomography and magnetic resonance imaging scan data. In conjunction with this study an artificial intelligence (Al) control strategy was developed to interface the voice components and support software to the computer graphics functions implemented on the Sun Microsystems 4/280 color graphics workstation. Based on generated text and converted renditions of verbal utterances by the user the Al control strategy determines the user''s intent and develops and validates a plan. The program type and parameters within the plan are used as input to the graphics system for reconstructing and displaying medical image data corresponding to that perceived intent. If the plan is not valid the control strategy queries the user for additional information. The control strategy operates in a conversation mode and vocally provides system status reports. A detailed examination of the various AT techniques is presented with major emphasis being placed on their specific roles within the total control strategy structure. 1.

Sherley, Patrick L.; Pujol, Alfonso, Jr.; Meadow, John S.

1990-07-01

245

A Practical Approach for a Wide Range of Liver Iron Quantitation Using a Magnetic Resonance Imaging Technique  

PubMed Central

The goal of this study is to demonstrate a practical magnetic resonance imaging technique for quantifying a wide range of hepatic iron concentration (HIC) for hematologic oncology patients with transfusion iron overload in a routine clinical setting. To cover a wide range of T2* values from hematologic patients, we used a dual-acquisition method with two clinically available acquisition protocols on a 1.5T MRI scanner with different ?TEs to acquire data in two breath-holds. An in-house image postprocessing software tool was developed to generate T2*, iron maps, and water and fat images, when fat is presented in the liver. The resulting iron maps in DICOM format are transferred to the institutional electronic medical record system for review by radiologists. The measured liver T2* values for 28 patients ranged from 0.56 ± 0.13 to 25.0 ± 2.1 milliseconds. These T2* values corresponded to HIC values ranging from 1.2 ± 0.1?mg/g to 45.0 ± 10.0?mg/g (dry weight). A moderate correlation between overall serum ferritin levels and R2* was found with a correlation coefficient of 0.83. Repeated phantom scans confirmed that the precision of this method is better than 4% for T2* measurements. The dual- acquisition method also improved the ability to quantify HIC of the patients with hepatic steatosis. PMID:23365743

Hou, Ping; Popat, Uday R.; Lindsay, Richard J.; Jackson, Edward F.; Choi, Haesun

2012-01-01

246

Deuterium nuclear magnetic resonance of specifically labeled native collagen. Investigation of protein molecular dynamics using the quadrupolar echo technique.  

PubMed Central

Collagen was labeled with [3,3,3-d3]alanine and with [d10]leucine via tissue culture. 2H nuclear magnetic resonance (NMR) spectra were obtained of collagen in solution and as fibrils using the quadrupolar echo technique. The 2H NMR data for [3,3,3-d3]alanine-labeled collagen fibrils were analyzed in terms of a model for motion in which the molecule is considered to jump between two sites, separated azimuthally by an angle 2 delta, in a time which is rapid compared with the residence time in both sites. The data suggest that the molecule undergoes reorientation over an angle, 2 delta, of approximately 30 degrees in the fibrils, and that the average angle between the alanine C alpha--C beta bond axis and the long axis of the helix is approximately 75 degrees. Reorientation is possibly segmental. The T2 for [3,3,3-d3]alanine-labeled collagen fibrils was estimated to be 105 mus. The 2H NMR data for the methyl groups of [d10]leucine-labeled collagen were analyzed qualitatively. These data established that for collagen in solution and as fibrils, rotation occurs about the leucine side-chain bonds, in addition to threefold methyl rotation and reorientation of the peptide backbone. The T2 for the methyl groups of leucine-labeled collagen is estimated to be approximately 130 mus. Taken together, these data provide strong evidence that both polypeptide backbone reorientation and amino acid side-chain motion occur in collagen molecules in the fibrils. Stabilizing interactions that determine fibril structure must therefore depend upon at least two sets of contacts in any given local region. PMID:7248459

Jelinski, L W; Sullivan, C E; Batchelder, L S; Torchia, D A

1980-01-01

247

Evaluation of agglutination strength by a flow-induced cell movement assay based surface plasmon resonance (SPR) technique.  

PubMed

A flow-induced cell movement assay combined with a surface plasmon resonance (SPR) technique was developed to quantify the agglutination strength, derived from the standard tube-agglutination test. Red blood cells (RBCs), based on the ABO blood group system, were specifically captured by anti-A and/or anti-B antibodies immobilized on a sensor surface. The agglutination strength corresponds to the amount of antigen-antibody interactions or the strength of RBC adhesion. Under a shear flow, the adherent RBCs were forced to move out of the region of interest with different average cell velocities (vc) depending upon the adhesion strength and wall shear stress (WSS). That is, a higher adhesion strength (higher agglutination strength) or lower WSS represents a lower vc or vice versa. In this work, the agglutination strength was derived from the vc that was calculated from the time derivative of the relative SPR signal by using a simple model of cell movement response, whose validity was verified. The vc values of different samples were correlated with their agglutination strengths at a given WSS and antibody surface density. The vc decreased as the agglutination strength increased, which can be considered as a linear regression. The coefficient of variation of the calculated vc decreased to 0.1 as vc increased to 30 ?m min(-1). The sensitivity of this assay can be controlled by optimizing the antibody surface density or the WSS. This assay has the capability to resolve the antigen density of A1 and B RBCs from that of A1B RBCs. PMID:25474709

Sudprasert, Krisda; Peungthum, Patjaree; Vongsakulyanon, Apirom; Amarit, Ratthasart; Somboonkaew, Armote; Sutapun, Boonsong; Kitpoka, Pimpun; Kunakorn, Mongkol; Srikhirin, Toemsak

2014-12-01

248

Production of extracellular superoxide by human lymphoblast cell lines: comparison of electron spin resonance techniques and cytochrome C reduction assay.  

PubMed

Superoxide production by NADPH oxidases plays an important role in the development and progression of cardiovascular disease (CVD). However, measurement of superoxide (O(2)(-)), a marker of oxidative stress, remains a challenging task in clinical and translational studies. In this study we analyzed O(2)(-) production in cultured human lymphoblast cell lines by three different methods: (a) superoxide dismutase (SOD)-inhibitable cytochrome C reduction, (b) spin trapping of superoxide with 5-(ethoxycarbonyl)-5-methyl-1-pyrroline N-oxide (EMPO) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), and (c) using electron spin resonance (ESR) with the cell-permeable spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH). Lymphocytes were isolated and immortalized by an Epstein-Barr Virus (EBV)-transformation procedure. Superoxide was measured in cultured lymphoblast cell lines at baseline and upon stimulation with phorbol 12-myristate 13-acetate (PMA). Cytochrome C and the spin traps EMPO and DEPMPO detected two to five times less superoxide compared to CMH. Thus, CMH provided the most quantitative measurement of superoxide generation in human lymphoblast cell lines. Superoxide detection with CMH was linear dependent on cell concentration and was inhibited by SOD but not by catalase. Both cell-permeable polyethylene glycol (PEG)-SOD and extracellular Cu,Zn-SOD inhibited O(2)(-) detection by 90% in PMA-stimulated cells, suggesting a predominantly extracellular O(2)(-) generation in human lymphoblasts. Our study describes a new technique for O(2)(-) measurement in cultured human lymphoblasts using ESR and CMH. A highly sensitive in vitro measurement of O(2)(-) in human cell lines would allow investigators to study genotype/phenotype interactions in translational studies. PMID:17222393

Dikalov, Sergey I; Li, Wei; Mehranpour, Payam; Wang, Shaoshan S; Zafari, A Maziar

2007-04-01

249

Hydrogen transfer in hydrogen-bonded chloranilic acid studied by 35Cl NQR I - a 1:2 complex with 1,4-diazine  

NASA Astrophysics Data System (ADS)

35Cl NQR frequencies and spin-lattice relaxation time ( T1Q) and 1H NMR relaxation times ( T1H) in a H-bonded three molecular system, chloranilic acid-1,4-diazine (1:2) were measured to reveal H-motions in a symmetric two H-bonds in solid. A single 35Cl NQR frequency observed implies that the time-averaged structure of chloranilic acid is roughly monovalent in accordance with p Ka values in both acid and base. T1H temperature dependence was explained by a single relaxation mechanism due to the correlated H-transfer in two H-bonds, while that of T1Q yielded two relaxation processes. One of these undetected by 1H NMR was explained by the uncorrelated H-transfer.

Nihei, Taka-aki; Ishimaru, Shin'ichi; Ishida, Hiroyuki; Ishihara, Hideta; Ikeda, Ryuichi

2000-10-01

250

Invited article: Dielectric material characterization techniques and designs of high-Q resonators for applications from micro to millimeter-waves frequencies applicable at room and cryogenic temperatures.  

PubMed

Dielectric resonators are key elements in many applications in micro to millimeter wave circuits, including ultra-narrow band filters and frequency-determining components for precision frequency synthesis. Distributed-layered and bulk low-loss crystalline and polycrystalline dielectric structures have become very important for building these devices. Proper design requires careful electromagnetic characterization of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique for microwave applications, which has now become the standard for characterizing low-loss structures. This paper will give some of the most common characterization techniques used in the micro to millimeter wave regime at room and cryogenic temperatures for designing high-Q dielectric loaded cavities. PMID:24689557

Le Floch, Jean-Michel; Fan, Y; Humbert, Georges; Shan, Qingxiao; Férachou, Denis; Bara-Maillet, Romain; Aubourg, Michel; Hartnett, John G; Madrangeas, Valerie; Cros, Dominique; Blondy, Jean-Marc; Krupka, Jerzy; Tobar, Michael E

2014-03-01

251

Resonant behavior of dielectric objects (electrostatic resonances).  

PubMed

Resonant behavior of dielectric objects occurs at certain frequencies for which the object permittivity is negative and the free-space wavelength is large in comparison with the object dimensions. Unique physical features of these resonances are studied and a novel technique for the calculation of resonance values of permittivity, and hence resonance frequencies, is proposed. Scale invariance of resonance frequencies, unusually strong orthogonality properties of resonance modes, and a two-dimensional phenomenon of "twin" spectra are reported. The paper concludes with brief discussions of optical controllability of these resonances in semiconductor nanoparticles and a plausible, electrostatic resonance based, mechanism for nucleation and formation of ball lightning. PMID:14754117

Fredkin, D R; Mayergoyz, I D

2003-12-19

252

Strong coupling between antiferromagnetic and superconducting order parameters of CeRhIn5 studied by I115n nuclear quadrupole resonance spectroscopy  

NASA Astrophysics Data System (ADS)

We report on a pressure (P) -induced evolution of magnetism and superconductivity (SC) in a helical magnet CeRhIn5 with an incommensurate wave vector Qi=((1)/(2),(1)/(2),0.297) through the I115n nuclear quadrupole resonance (NQR) measurements under P . Systematic measurements of the I115n -NQR spectrum reveal that the commensurate antiferromagnetism (AFM) with Qc=((1)/(2),(1)/(2),(1)/(2)) is realized above Pm˜1.7GPa . An important finding is that the size of SC gap and Tc increase as the magnitude of the AFM moment decreases in the P region, where SC uniformly coexists with the commensurate AFM. This result provides evidence of strong coupling between the commensurate AFM order parameter (OP) and SC OP.

Yashima, M.; Mukuda, H.; Kitaoka, Y.; Shishido, H.; Settai, R.; ?nuki, Y.

2009-06-01

253

Infrared spectroscopic evidence of a redox-dependent conformational change involving ion binding residue NqrB-D397 in the Na(+)-pumping NADH:quinone oxidoreductase from Vibrio cholerae.  

PubMed

The Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR) is a unique respiratory enzyme that conserves energy by translocating Na(+) through the plasma membrane. Found only in prokaryotes, the enzyme serves as the point of entry of electrons into the respiratory chain in many pathogens, including Vibrio cholerae and Yersinia pestis. In this study, a combined electrochemical and Fourier transform infrared (FTIR) spectroscopic approach revealed that Na(+)-NQR undergoes significant conformational changes upon oxidoreduction, depending on the monovalent cation present (Na(+), Li(+), K(+), or Rb(+)). In the presence of the inhibitor Rb(+), additional conformational changes are evident, indicating a changed accessibility of the sodium binding sites. In electrochemically induced FTIR difference spectra, the involvement of deprotonated acid residues in the binding of cations, together with the spectral features, that point toward a monodentate binding mode for these acid residues in the oxidized form of the enzyme and bidentate binding in the reduced form could be identified. The measurements confirmed that NqrB-D397 is one of the acid residues involved in Na(+) and Li(+) binding. In the NqrB-D397E mutant, the spectral features characteristic of COO(-) groups are shifted, and a weakening of the hydrogen binding of the ion binding cluster is revealed. Finally, H-D exchange kinetics of amide protons confirmed that Na(+)-NQR adopts different conformations, with different accessibilities to the aqueous environment, depending on the cation present, which contributes to the selectivity mechanism of ion translocation. PMID:23566241

Neehaul, Yashvin; Juárez, Oscar; Barquera, Blanca; Hellwig, Petra

2013-05-01

254

Indicator dilution time-activity curves demonstrated by rapid magnetic resonance imaging techniques and paramagnetic contrast agent.  

PubMed

Indicator dilution time-activity curves are demonstrated using magnetic resonance imaging (MRI) as the detector and a paramagnetic contrast agent as the indicator. Manganese chloride was injected into a flow phantom. The nuclear magnetic resonance (MR) intensity was measured downstream. Several flow rates were used. The observed MR intensity decreased as the paramagnetic indicator passed through the imaging plane. The qualitative changes of the MR intensity decrease varied in accordance with indicator dilution theory. The equations for gradient refocused echoes, paramagnetic compound relaxation changes, and the indicator dilution analysis were combined and evaluated. Quantitative analysis demonstrates several problems in its implementation. PMID:2663765

Davis, P L; Wolf, G L; Gillen, J S

1989-05-01

255

Improved L-C resonant decay technique for Q measurement of quasilinear power inductors: New results for MPP and ferrite powdered cores  

NASA Technical Reports Server (NTRS)

The L-C resonant decay technique for measuring circuit Q or losses is improved by eliminating the switch from the inductor-capacitor loop. A MOSFET switch is used instead to momentarily connect the resonant circuit to an existing voltage source, which itself is gated off during the decay transient. Very reproducible, low duty cycle data could be taken this way over a dynamic voltage range of at least 10:1. Circuit Q is computed from a polynomial fit to the sequence of the decaying voltage maxima. This method was applied to measure the losses at 60 kHz in inductors having loose powder cores of moly permalloy and an Mn-Zn power ferrite. After the copper and capacitor losses are separated out, the resulting specific core loss is shown to be roughly as expected for the MPP powder, but anomalously high for the ferrite powder. Possible causes are mentioned.

Niedra, Janis M.; Gerber, Scott S.

1995-01-01

256

Quantitation of grey matter, white matter, and cerebrospinal fluid from spin-echo magnetic resonance images using an artificial neural network technique.  

PubMed

An operator independent technique has been developed to quantitate the volume of white matter (WM), grey matter (GM), and cerebrospinal fluid (CSF) using spin-echo magnetic resonance images. Using skull stripped spin-echo images, CSF was removed using an automated thresholding technique. The bimodal histogram of the remaining images was used to train a perceptron and a single hidden layer neural network to output the percentage of GM and WM in the image. The output values were compared with those of a semiautomated technique employing a least square fitting technique [graduated nonconvexity algorithm (GNC)] applied to the bimodal histogram. This semiautomated technique allowed for intervention by the radiologist. Fourteen normal volunteers with eight contiguous slices each were analyzed. The individual percentages of WM, GM, and CSF of 40 slices from five subjects not used in the training set as well as the total percentages of GM, WM, and CSF in each individual were predicted using the two artificial network architectures. GM, WM, and CSF percentages were predicted within 7% for individual slices while total percentages of WM, GM, and CSF were computed accurately with an absolute error of less than 5% when compared to the semiautomated technique involving a trained neuroradiologist. PMID:7700201

Raff, U; Scherzinger, A L; Vargas, P F; Simon, J H

1994-12-01

257

Oxygen isotope effect of the plane-copper NQR frequency in YBa2Cu4O8  

NASA Astrophysics Data System (ADS)

We report high-precision measurements of the temperature dependence of the plane-63Cu NQR line frequency ?Q(Cu2) and the linewidth in normal and superconducting 16O and 18O-exchanged YBa2Cu4O8. Whereas ?Q(Cu2) passes Tc very smoothly without a discontinuity either in value or slope, the linewidth increases in the normal conducting phase down to Tc and starts to decrease sharply in the superconducting phase to finally resume its high-temperature value of the normal phase. There is a well discernible oxygen isotope effect on the ?Q(Cu2) temperature dependencies. The temperature dependence of ?Q(Cu2) is described by an empirical expression consisting of two parts, one related to the thermal expansion of the lattice and the other due to charge redistribution during the formation of new electronic structures in the CuO2 planes. From the fit to the experimental data we determine for the conjectured formation of new electronic structures an energy scale ?(16O)=188.0(1.6) K and ?(18O)=180.0(1.6) K. This results in a partial oxygen isotope effect coefficient ??Q=0.42(11) which is larger than both the spin pseudogap coefficient ?PG=0.061(8) and the Tc coefficient ?Tc=0.056(12) [F. Raffa, T. Ohno, M. Mali, J. Roos, D. Brinkmann, K. Conder, and M. Eremin, Phys. Rev. Lett. 81, 5912 (1998)].

Mali, M.; Roos, J.; Keller, H.; Karpinski, J.; Conder, K.

2002-05-01

258

Field-tuned critical fluctuations in YFe2Al10: Evidence from magnetization, 27Al NMR, and NQR investigations  

NASA Astrophysics Data System (ADS)

We report magnetization, specific heat, and NMR investigations on YFe2Al10 over a wide range of temperature and magnetic field and zero field (NQR) measurements. Magnetic susceptibility, specific heat, and spin-lattice relaxation rate divided by T(1/T1T) follow a weak power law (˜T-0.4) temperature dependence, which is a signature of the critical fluctuations of Fe moments. The value of the Sommerfeld-Wilson ratio and the linear relation between 1/T1T and ? suggest the existence of ferromagnetic correlations in this system. No magnetic ordering down to 50 mK in Cp(T)/T and the unusual T and H scaling of the bulk and NMR data are associated with a magnetic instability which drives the system to quantum criticality. The magnetic properties of the system are tuned by field wherein ferromagnetic fluctuations are suppressed and a crossover from quantum critical to Fermi-liquid behavior is observed with increasing magnetic field.

Khuntia, P.; Strydom, A. M.; Wu, L. S.; Aronson, M. C.; Steglich, F.; Baenitz, M.

2012-12-01

259

Study of hydrogen in coals, polymers, oxides, and muscle water by nuclear magnetic resonance; extension of solid-state high-resolution techniques. [Hydrogen molybdenum bronze  

SciTech Connect

Nuclear magnetic resonance (NMR) spectroscopy has been an important analytical and physical research tool for several decades. One area of NMR which has undergone considerable development in recent years is high resolution NMR of solids. In particular, high resolution solid state /sup 13/C NMR spectra exhibiting features similar to those observed in liquids are currently achievable using sophisticated pulse techniques. The work described in this thesis develops analogous methods for high resolution /sup 1/H NMR of rigid solids. Applications include characterization of hydrogen aromaticities in fossil fuels, and studies of hydrogen in oxides and bound water in muscle.

Ryan, L.M.

1981-10-01

260

Pulsed Fourier-transform NQR of sup 14 N with a dc SQUID  

SciTech Connect

The zero-field free induction decay of solid ammonium perchlorate at 1.5 K has been directly detected with a dc superconducting quantum interference device. The Fourier-transform spectrum consists of three sharp lines at 17.4, 38.8, and 56.2 kHz arising from pure {sup 14}N nuclear quadrupole resonance transitions. The absence of splittings and resonance transitions from dipolar-coupled proton spins is attributed to reorientation of the ammonium groups by quantum tunneling in combination with motional averaging in the three proton levels characterized by the irreducible representation {ital T}. The measured {sup 14}N spin-spin relaxation time is 22{plus minus}2 ms and the spin-lattice relaxation time is 63{plus minus}6 ms.

Huerlimann, M.D.; Pennington, C.H.; Fan, N.Q.; Clarke, J.; Pines, A.; Hahn, E.L. (Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States) Department of Chemistry, University of California, Berkeley, Berkeley, California 94720 (United States) Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States))

1992-07-27

261

Optical investigation on plasmonic effect of the nanostructured surface plasmon resonance sensor chips fabricated by Langmuir-Blodgett technique  

NASA Astrophysics Data System (ADS)

We used the Langmuir-Blodgett (LB) method for preparation of defect-free and large-area silica-nanoparticlesmonolayer as a template for the fabrication of Au nanostructures on an Au-thinfilm for surface plasmon resonance (SPR). The dimensions of trigonal pyramid Au nanostructures were controlled by changing the particle size of the silica LB template. The nanostructured SPR chips provide the enhancement of sensitivity in SPR analysis compared to a conventional SPR chip when 20 % ethanol solution was used as an analyte. We took a theoretical approach by evaluating optical properties of the Au-nanostructures and nanostructured SPR chips in the view of plasmonic effect.

Yeon, Chanmi; Sung, So-Hee; Kim, Hyo-Sop; Kim, Jae-Ho

2011-10-01

262

Assessment of atrial septal defect morphology by transthoracic three dimensional echocardiography using standard grey scale and Doppler myocardial imaging techniques: comparison with magnetic resonance imaging and intraoperative findings  

PubMed Central

Objective—To determine whether transthoracic three dimensional echocardiography is an accurate non-invasive technique for defining the morphology of atrial septal defects (ASD).?Methods—In 34 patients with secundum ASD, mean (SD) age 20 (17) years (14 male, 20 female), the measurements obtained from three dimensional echocardiography were compared to those obtained from magnetic resonance imaging (MRI) or surgery. Three dimensional images were constructed to simulate the ASD view as seen by a surgeon. Measured variables were: maximum and minimum vertical and horizontal ASD dimension, and distances to inferior and superior vena cava, coronary sinus, and tricuspid valve. In each patient two ultrasound techniques were used to acquire three dimensional data: standard grey scale imaging (GSI) and Doppler myocardial imaging (DMI). ?Results—Good correlation was found in maximum ASD dimension (both horizontal and vertical) between three dimensional echocardiography and both MRI (GSI r = 0.96, SEE = 0.05 cm; DMI r = 0.97, SEE = 0.04 cm) and surgery (GSI r = 0.92, SEE = 0.06 cm; DMI r = 0.95, SEE = 0.06 cm). The systematic error was similar for both three dimensional techniques when compared to both MRI (GSI = 0.40 cm (27%); DMI = 0.38 cm (25%)) and surgery (GSI = 0.50 cm (29%); DMI = 0.37 cm (22%)). A significant difference was found in both horizontal and vertical ASD dimension changes during the cardiac cycle. This change was inversely correlated with age. These findings were consistent for both DMI and GSI technique. In children (age ? 17 years), the feasibility of detecting structures and undertaking measurements was similar for both echo techniques. However, in adult ASD patients (age ? 18 years) this feasibility was higher for DMI than for GSI.?Conclusions—Transthoracic three dimensional imaging using both GSI and DMI accurately displayed the varying morphology, dimensions, and spatial relations of ASD. However, DMI was a more effective technique than GSI in describing ASD morphology in adults.?? Keywords: atrial septal defect;  morphology;  three dimensional echocardiography;  magnetic resonance imaging PMID:9404256

Lange, A.; Walayat, M.; Turnbull, C.; Palka, P.; Mankad, P.; Sutherland, G.; Godman, M.

1997-01-01

263

Differences in graft orientation using the transtibial and anteromedial portal technique in anterior cruciate ligament reconstruction: a magnetic resonance imaging study.  

PubMed

The purpose of this study was to evaluate differences in graft orientation between transtibial (TT) and anteromedial (AM) portal technique using magnetic resonance imaging (MRI) in anterior cruciate ligament (ACL) reconstruction. Fifty-six patients who were undergoing ACL reconstruction underwent MRI of their healthy and reconstructed knee. Thirty patients had ACL reconstruction using the TT (group A), while in the remaining 26 the AM (group B) was used. In the femoral part graft orientation was evaluated in the coronal plane using the femoral graft angle (FGA). The FGA was defined as the angle between the axis of the femoral tunnel and the joint line. In the tibial part graft orientation was evaluated in the sagittal plane using the tibial graft angle (TGA). The TGA was defined as the angle between the axis of the tibial tunnel and a line perpendicular to the long axis of the tibia. The ACL angle of the normal knee in the sagittal view was also calculated. The mean FGA for group A was 72 degrees, while for the group B was 53 degrees and this was statistically significant (P < 0.001). The mean TGA for group A was 64 degrees, while for the group B was 63 degrees (P = 0.256). The mean intact ACL angle for group A was 52 degrees, while for the group B was 51 degrees. The difference between TGA and intact ACL angle was statistically significant (P < 0.001) for both groups. Using the AM portal technique, the ACL graft is placed in a more oblique direction in comparison with the TT technique in the femoral part. However, there are no differences between the two techniques in graft orientation in the tibial part. Normal sagittal obliquity is not restored with both techniques. PMID:19238359

Hantes, Michael Elias; Zachos, Vasilios C; Liantsis, Athanasios; Venouziou, Aaron; Karantanas, Apostolos H; Malizos, Konstantinos N

2009-08-01

264

Determination of dopamine at the nanogram level based on the formation of Prussian blue nanoparticles by resonance Rayleigh scattering technique  

NASA Astrophysics Data System (ADS)

In pH 2.6 HCl solution, dopamine (DA) could reduce Fe(III) to Fe(II), which further reacted with [Fe(CN) 6] 3- to form a Fe 3[Fe(CN) 6] 2 complex. By virtue of hydrophobic force and Van der Waals force, the complex aggregated to form Fe 3[Fe(CN) 6] 2 nanoparticles with the average diameter of about 20 nm. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS). The maximum wavelength of the ion-association complex was located at about 350 nm. The increment of scattering intensity (? IRRS) was directly proportional to the concentration of DA in the range of 0.06-1.0 ?g/mL. This method has high sensitivity and the detection limit (3 ?) for DA was 3.43 ng/mL. In this work, the characteristics of absorption and RRS spectra of this reaction have been studied. The optimum reaction condition and influencing factors have been investigated. The method was applied to the determination of DA in pharmaceutical samples with satisfactory results. Furthermore, the reaction mechanism and the reasons of RRS enhancement have been explored.

Dong, Jiang Xue; Wen, Wei; Li, Nian Bing; Luo, Hong Qun

2012-02-01

265

Video-rate resonant scanning multiphoton microscopy: An emerging technique for intravital imaging of the tumor microenvironment.  

PubMed

The abnormal tumor microenvironment fuels tumor progression, metastasis, immune suppression, and treatment resistance. Over last several decades, developments in and applications of intravital microscopy have provided unprecedented insights into the dynamics of the tumor microenvironment. In particular, intravital multiphoton microscopy has revealed the abnormal structure and function of tumor-associated blood and lymphatic vessels, the role of aberrant tumor matrix in drug delivery, invasion and metastasis of tumor cells, the dynamics of immune cell trafficking to and within tumors, and gene expression in tumors. However, traditional multiphoton microscopy suffers from inherently slow imaging rates-only a few frames per second, thus unable to capture more rapid events such as blood flow, lymphatic flow, and cell movement within vessels. Here, we report the development and implementation of a video-rate multiphoton microscope (VR-MPLSM) based on resonant galvanometer mirror scanning that is capable of recording at 30 frames per second and acquiring intravital multispectral images. We show that the design of the system can be readily implemented and is adaptable to various experimental models. As examples, we demonstrate the utility of the system to directly measure flow within tumors, capture metastatic cancer cells moving within the brain vasculature and cells in lymphatic vessels, and image acute responses to changes in a vascular network. VR-MPLSM thus has the potential to further advance intravital imaging and provide new insight into the biology of the tumor microenvironment. PMID:24353926

Kirkpatrick, Nathaniel D; Chung, Euiheon; Cook, Daniel C; Han, Xiaoxing; Gruionu, Gabriel; Liao, Shan; Munn, Lance L; Padera, Timothy P; Fukumura, Dai; Jain, Rakesh K

2012-01-01

266

Graphene quantum dots and the resonance light scattering technique for trace analysis of phenol in different water samples.  

PubMed

A novel, highly selective resonance light scattering (RLS) method was researched and developed for the analysis of phenol in different types of industrial water. An important aspect of the method involved the use of graphene quantum dots (GQDs), which were initially obtained from the pyrolysis of citric acid dissolved in aqueous solutions. The GQDs in the presence of horseradish peroxidase (HRP) and H2O2 were found to react quantitatively with phenol such that the RLS spectral band (310 nm) was quantitatively enhanced as a consequence of the interaction between the GQDs and the quinone formed in the above reaction. It was demonstrated that the novel analytical method had better selectivity and sensitivity for the determination of phenol in water as compared to other analytical methods found in the literature. Thus, trace amounts of phenol were detected over the linear ranges of 6.00×10(-8)-2.16×10(-6)M and 2.40×10(-6)-2.88×10(-5)M with a detection limit of 2.20×10(-8)M. In addition, three different spiked waste water samples and two untreated lake water samples were analysed for phenol. Satisfactory results were obtained with the use of the novel, sensitive and rapid RLS method. PMID:24840454

Sun, Ruiling; Wang, Yong; Ni, Yongnian; Kokot, Serge

2014-07-01

267

Application of Polypyrrole Multi-Walled Carbon Nanotube Composite Layer for Detection of Mercury, Lead and Iron Ions Using Surface Plasmon Resonance Technique  

PubMed Central

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

Sadrolhosseini, Amir Reza; Noor, A. S. M.; Bahrami, Afarin; Lim, H. N.; Talib, Zainal Abidin; Mahdi, Mohd. Adzir

2014-01-01

268

Application of polypyrrole multi-walled carbon nanotube composite layer for detection of mercury, lead and iron ions using surface plasmon resonance technique.  

PubMed

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

Sadrolhosseini, Amir Reza; Noor, A S M; Bahrami, Afarin; Lim, H N; Talib, Zainal Abidin; Mahdi, Mohd Adzir

2014-01-01

269

Treatment of subclinical hyperthyroidism: effect on left ventricular mass and function of the heart using magnetic resonance imaging technique  

PubMed Central

Purpose The aim of this study was to investigate structure and function of the heart in subclinical hyperthyroidism (SH) before and after obtaining euthyroidism by radioactive iodine treatment, using high precision and observer-independent magnetic resonance imaging (MRI) technology. Methods Cardiac MRI was performed before and after euthyroidism was obtained by radioactive iodine treatment in 12 otherwise healthy patients (11 women and one man, mean age 59 years, range 44–71 years) with a nodular goiter and SH, and compared with eight healthy controls investigated at baseline. Cardiac data were expressed as an index, as per body surface area, except for heart rate (HR) and ejection fraction. Results Post-treatment cardiac MRI was performed in median 139 days after a normalized serum TSH value had been recorded. During treatment, serum TSH increased from (median (range)) 0.01 (0.01–0.09) to 0.88 (0.27–3.99) mU/l. Patients with untreated SH had increased resting HR (P<0.01) as well as cardiac index (cardiac output as per body surface area) (P<0.01) compared with controls. Obtaining euthyroidism resulted in a significant decrease in left ventricular mass index (LVMI) of 2.7?g/m2 (P=0.034), in HR of 8?bpm (P=0.001), and in cardiac index of 0.24?l/min per m2 (P=0.017). Conclusions Normalization of thyroid function by radioactive iodine treatment of SH resulted in significant reductions in clinically important heart parameters such as LVMI, HR, and cardiac index. SH should be regarded as a condition in which aggressive treatment should be considered to protect cardiac function. PMID:25568332

Mark, Peter D; Andreassen, Mikkel; Petersen, Claus L; Kjaer, Andreas; Faber, Jens

2015-01-01

270

Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects  

SciTech Connect

Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantum-mechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies.The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics. The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nuclei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically.The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy. The fifth chapter continues to extend the principles of multiple quantum NMR spectroscopy of quadrupolar nuclei to make analogies between experiments in NMR/nuclear quadrupolar resonance (NQR) and experiments in atomic/molecular optics (AMO). These analogies are made through the Hamiltonian and density operator formalism of angular momentum dynamics in the presence of electric and magnetic fields.The sixth chapter investigates the use of the macroscopic nuclear dipolar field to encode the NMR spectrum of an analyte nucleus indirectly in the magnetization of a sensor nucleus. This technique could potentially serve as an encoding module for the recently developed NMR remote detection experiment. The feasibility of using hyperpolarized xenon-129 gas as a sensor is discussed. This work also reports the use of an optical atomic magnetometer to detect the nuclear magnetization of Xe-129 gas, which has potential applicability as a detection module for NMR remote detection experiments.

Urban, Jeffry Todd

2004-12-21

271

Isotope ratio of Cl NQR spin-lattice relaxation times in 1D hydrogen-bonding system of tetramethylpyrazine-chloranilic acid at high temperatures  

NASA Astrophysics Data System (ADS)

The temperature dependences of spin-lattice relaxation time T 1 of 35Cl and 37Cl NQR were studied for the co-crystal of tetramethylpyrazine (TMP) with chloranilic acid (H2ca), TMP-H2ca, in which one-dimensional hydrogen bonding is formed by alternate arrangement of TMP and H2ca. The isotope ratio 37Cl T 1 / 35Cl T 1 was determined to be 1.0 ± 0.1 above ca. 290 K where a steep decrease of spin-lattice relaxation time T 1 with increasing temperature was observed. In this temperature range it is suggested that the relaxation is originated from the slow fluctuation of electric field gradient (EFG). Beside EFG fluctuation due to the external-charge-density fluctuation, the small angle reorientation of the quantization axis triggered by a proton transfer motion between N...H-O and N-H...O hydrogen bonding states is proposed.

Asaji, Tetsuo

2013-05-01

272

Hydrogen bonding and proton transfer in cocrystals of 4,4'-bipyridyl and organic acids studied using nuclear quadrupole resonance.  

PubMed

Cocrystals of 4,4'-bipyridyl and several carboxylic acids were grown from the methanol solution of the cocrystal formers. Complete (14)N NQR spectra of these cocrystals have been measured using (1)H-(14)N nuclear quadrupole double resonance. The principal values of the quadrupole coupling tensor are calculated from the (14)N NQR frequencies. A large variation in the (14)N quadrupole coupling constant between 1.3 MHz and 4.7 MHz is observed. A very low (14)N quadrupole coupling constant, characteristic for proton transfer O-H···N ? O(-)···H-N(+), is observed in 4,4'-bipyridyl-oxalic acid (1?:?1). In 4,4'-bipyridyl-5-chlorosalycilic acid (1?:?1) the (14)N NQR data show the presence of a short, strong N···H···O hydrogen bond. A correlation of the principal values of the (14)N quadrupole coupling tensor is observed. The correlation is analyzed in the model, where the deformation of the lone pair electron orbital and the change of the population of the ?-electron orbital produce the variation of the (14)N quadrupole coupling tensor in the hydrogen bonded 4,4'-bipyridyl. The temperature variation of the (14)N quadrupole coupling tensor in 4,4'-bipyridyl-5-chlorosalycilic acid (1?:?1) is analyzed. Proton displacement within the N···H···O hydrogen bond and the change of the population of the ?-electron orbital at the two nitrogen positions in a 4,4'-bipyridyl molecule in the temperature interval between 157 K and 323 K are determined. PMID:25052623

Seliger, Janez; Žagar, Veselko

2014-09-14

273

Artificial neural network assisted kinetic spectrophotometric technique for simultaneous determination of paracetamol and p-aminophenol in pharmaceutical samples using localized surface plasmon resonance band of silver nanoparticles.  

PubMed

Spectrophotometric analysis method based on the combination of the principal component analysis (PCA) with the feed-forward neural network (FFNN) and the radial basis function network (RBFN) was proposed for the simultaneous determination of paracetamol (PAC) and p-aminophenol (PAP). This technique relies on the difference between the kinetic rates of the reactions between analytes and silver nitrate as the oxidizing agent in the presence of polyvinylpyrrolidone (PVP) which is the stabilizer. The reactions are monitored at the analytical wavelength of 420nm of the localized surface plasmon resonance (LSPR) band of the formed silver nanoparticles (Ag-NPs). Under the optimized conditions, the linear calibration graphs were obtained in the concentration range of 0.122-2.425?gmL(-1) for PAC and 0.021-5.245?gmL(-1) for PAP. The limit of detection in terms of standard approach (LODSA) and upper limit approach (LODULA) were calculated to be 0.027 and 0.032?gmL(-1) for PAC and 0.006 and 0.009?gmL(-1) for PAP. The important parameters were optimized for the artificial neural network (ANN) models. Statistical parameters indicated that the ability of the both methods is comparable. The proposed method was successfully applied to the simultaneous determination of PAC and PAP in pharmaceutical preparations. PMID:25528506

Khodaveisi, Javad; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad; Rohani Moghadam, Masoud; Hormozi-Nezhad, Mohammad Reza

2015-03-01

274

Comparison of the different responses of surface plasmon resonance and quartz crystal microbalance techniques at solid-liquid interfaces under various experimental conditions.  

PubMed

A molecular level understanding of the phenomena taking place at solid-liquid interfaces, ranging from changes in mass to conformation changes, is the key to developing and improving many chemical and biological systems and their scientific and medical applications. Surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) techniques are often coupled to achieve this understanding. We divided various experimentally relevant scenarios into the following six categories: boundary solutions; surface modifications; conformation; viscoelastic properties; molecular ruler; and mass sensitivity. For each case, based on theoretical analyses, we discuss the following four points with respect to discrete adsorbates at solid-liquid interfaces: (1) the different types of information that can be obtained, why it can be obtained and how to obtain it; (2) the origins of many current approaches and why they are imperfect; (3) guidelines for experimental design; and (4) possible studies, such as the effect of dimensional confinement and adsorption forces on the ability of conformational changes to occur on the receipt of external stimuli and the hysteresis in these changes. PMID:25575354

Fang, Jiajie; Ren, Chunlai; Zhu, Tao; Wang, Kaiyu; Jiang, Zhongying; Ma, Yuqiang

2015-02-01

275

A novel method for study of the aggregation of protein induced by metal ion aluminum(III) using resonance Rayleigh scattering technique  

NASA Astrophysics Data System (ADS)

We present a novel method for the study of the aggregation of protein induced by metal ion aluminum(III) using resonance Rayleigh scattering (RRS) technique. In neutral Tris-HCl medium, the effect of this aggregation of protein results in the enhancement of RRS intensity and the relationship between the enhancement of the RRS signal and the Al concentration is nonlinear. On this basis, we established a new method for the determination of the critical induced-aggregation concentrations ( CCIAC) of metal ion Al(III) inducing the protein aggregation. Our results show that many factors, such as, pH value, anions, salts, temperature and solvents have obvious effects. We also studied the extent of aggregation and structural changes using ultra-violet spectrometry, protein intrinsic fluorescence and circular dichroism to further understand the exact mechanisms of the aggregation characteristics of proteins induced by metal ion Al(III) at the molecular level, to help us to develop effective methods to investigate the toxicity of metal ion Al, and to provide theoretical and quantitative evidences for the development of appropriate treatments for neurodementia such as Parkinson's disease, Alzheimer's disease and dementia related to dialysis.

Long, Xiufen; Zhang, Caihua; Cheng, Jiongjia; Bi, Shuping

2008-01-01

276

C N.M.R. and N N.Q.R. in ferroelectric liquid crystals Polar versus quadrupolar ordering  

Microsoft Academic Search

C nuclear magnetic resonance and N nuclear quadrupole resonance spectra of ferroelectric smectic C*liquid crystals and their non-chiral analogues allow for a microscopic determination of the polar and quadrupolar (or bipolar) biasing of rotation around the long molecular axis as well as for a determination of the anisotropy in the fluctuations of this axis. The results show that the microscopic

R. Blinc; J. Dolinšek; M. Luzar; J. Seliger

1988-01-01

277

Nondestructive testing of adhesive bonds by nuclear quadrupole resonance method  

NASA Technical Reports Server (NTRS)

Inert, strain sensitive tracer, cuprous oxide, added to polymeric adhesive ensures sufficiently large signal to noise ratio in NQR system output. Method is successful, provided that RF-transparent structural materials are used between modified adhesive and probe of NQR spectrometer.

Hewitt, R. R.

1971-01-01

278

Resonances and resonance widths  

SciTech Connect

Two-dimensional betatron resonances are much more important than their simple one-dimensional counterparts and exhibit a strong dependence on the betatron phase advance per cell. A practical definition of ''width'' is expanded upon in order to display these relations in tables. A primarily pedagogical introduction is given to explain the tables, and also to encourage a wider capability for deriving resonance behavior and wider use of ''designer'' resonances.

Collins, T.

1986-05-01

279

Advanced MR imaging techniques in the evaluation of nonenhancing gliomas: perfusion-weighted imaging compared with proton magnetic resonance spectroscopy and tumor grade.  

PubMed

A significant number of nonenhancing (NE) gliomas are reported to be malignant. The purpose of this study was to compare the value of advanced MR imaging techniques, including T2*-dynamic susceptibility contrast PWI (DSC-PWI) and proton magnetic resonance spectroscopy ((1)HMRS) in the evaluation of NE gliomas. Twenty patients with NE gliomas underwent MRI including DSC-PWI and (1)HMRS. The relative CBV (rCBV) measurements were obtained from regions of maximum perfusion. The peak ratios of choline/creatine (Cho/Cr) and myo-inositol/creatine (mIns/Cr) were measured at a TE of 30 ms. Demographic features, tumor volumes, and PWI- and (1)HMRS-derived measures were compared between low-grade gliomas (LGGs) and high-grade gliomas (HGGs). In addition, the association of initial rCBV ratio with tumor progression was evaluated in LGGs. No significant difference was noted in age, sex or tumor size between LGGs and HGGs. Cho/Cr ratios were significantly higher in HGGs (1.7±0.63) than in LGGs (1.2±0.38). The receiver operating characteristic analysis demonstrated that a Cho/Cr ratio with a cutoff value of 1.3 could differentiate between LGG and HGG with a specificity of 100% and a sensitivity of 71.4%. There was no significant difference in the rCBV ratio and the mIns/Cr ratio between LGG and HGG. However, higher rCBV ratios were observed with more rapid progressions in LGGs. The results imply that Cho/Cr ratios are useful in distinguishing NE LGG from HGG and can be helpful in preoperative grading and biopsy guidance. On the other hand, rCBV ratios do not help in the distinction. PMID:24199813

Sahin, Neslin; Melhem, Elias R; Wang, Sumei; Krejza, Jaroslaw; Poptani, Harish; Chawla, Sanjeev; Verma, Gaurav

2013-10-01

280

Immediate effect of mind sound resonance technique on state anxiety and cognitive functions in patients suffering from generalized anxiety disorder: A self-controlled pilot study  

PubMed Central

Objectives: To compare the immediate effect of mind sound resonance technique (MSRT) with supine rest (SR) on state anxiety and psychomotor performance in 15 (eight male and seven female) right-handed generalized anxiety disorder patients (GAD) with an age range of 34.8 ± 12.8 years. Materials and Methods: Self as control design was followed. Diagnosis of GAD was made by a psychiatrist using sections of the Mini International Neuropsychiatric Interview (MINI). Participants practiced MSRT or SR (as control intervention) for 30 min at the same time for two consecutive days. The sequence of intervention was assigned randomly to the participants. State anxiety was assessed using state trait anxiety inventory (STAI; Form X1). Digit letter substitution task (DLST) was used to assess psychomotor performance, which involves visual scanning, mental flexibility, sustained attention, psychomotor speed and speed of information processing. Intervention was given in a quiet dark room on an empty stomach. Subjects received a training of MSRT and SR for 1 week before the data were taken. A pre-recorded audiotape was used to administer the technique of MSRT. Difference in scores after baseline and intervention was used to check normality, and was found to be normally distributed by the Kolmogrov–Smirnov test. The changes in STAI, DLST and difference in scores before and after two interventions (MSRT and SR) were compared using the paired samples t test. Results: As compared with baseline, STAI scores reduced and DLST scores increased significantly (STAI; P < 0.01; DLST; P < 0.01) after MSRT. After SR, there was a significant reduction in STAI scores from baseline (STAI; P < 0.05), but there was no significant change in the DLST scores (P = 0.26). Comparison of the difference in scores for DLST and STAI before and after the two interventions (MSRT and SR) showed a significantly higher score for DLST (P < 0.05) and a significantly lower score for STAI (P < 0.01) for MSRT as compared with SR. Conclusion: This pilot study suggests that MSRT may have a potential role in reducing state anxiety and enhancing psychomotor performance in patients suffering from GAD immediately after the practice. These findings need confirmation from studies with a larger sample size and randomized controlled design, which are implicated in the future. PMID:25558137

Dhansoia, Vipin; Bhargav, Hemant; Metri, Kashinath

2015-01-01

281

NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts. Quarterly technical progress report, September 14--December 15, 1990  

SciTech Connect

Copper and cobalt are the key elements in syngas conversion catalyst systems used for higher alcohol synthesis. Their proximity and synergy sensitively control the selectivity and efficiency of the process. It is believed that their outer electronic charge distribution which is responsible for their electrical and magnetic properties might be governing their catalytic properties also. To examine the correlation between catalytic and magnetic properties, a series of copper cobalt catalysts (Co/Cu ratio 5:1 to 5:5) with and without a support were prepared. The nuclear quadrupole resonance spectrum of copper and (zero-field) nuclear magnetic resonance spectrum of cobalt and magnetization and hysteresis character of the catalyst were analyzed. Similar to the catalytic results, the magnetic results also were found to be very sensitive to the preparation technique. The results indicate possible electron exchange between copper and cobalt, and cobalt and the support Titania.

Not Available

1991-01-14

282

Two-layered WGM resonator-based technique for microwave characterization of condensed matter with extremely high and extremely low losses  

Microsoft Academic Search

The main electrodynamic properties of two-layered quasi-optical sapphire resonator in a form of cylindrical ring, an inner hole in which was filled with liquid or (super)conductor were studied. The resonator war excited on whispering gallery modes in Ka-band and its microwave characteristics were investigated to obtain parameters of condensed matter under test. The calculation results are obtained using CST Microwave

Alexander A. Barannik; Nickolay T. Cherpak; Yuriy V. Prokopenko; Konstantin I. Torokhtiy; Elena N. Shaforost; Svetlana A. Vitusevich

2009-01-01

283

NMR and NQR studies of the heavy fermion superconductors CeTIn5 (T=Co and Ir)  

Microsoft Academic Search

We have carried out 115In and 59Co nuclear quadrupole resonance and nuclear magnetic resonance measurements on CeCoIn5 and CeIrIn5. The temperature T dependence of the nuclear spin-lattice relaxation rate 1\\/T1 of 115In in the normal state indicates that CeCoIn5 is located just at an antiferromagnetic instability, and CeIrIn5 is in the nearly antiferromagnetic region. In the superconducting state, 1\\/T1 has

Y. Kohori; Y. Yamato; Y. Iwamoto; T. Kohara; E. D. Bauer; M. B. Maple; J. L. Sarrao

2001-01-01

284

New aspects on URu2Si2 and CeT In5 (T=Rh, Ir, Co) observed by high pressure NMR and NQR  

NASA Astrophysics Data System (ADS)

NMR and NQR studies on two interesting systems (URu2Si2, CeTIn5) were performed under high pressure. (1) URu2Si2: In the pressure range 3.0 to 8.3 kbar, we have observed new 29Si NMR signals arising from the antiferromagnetic (AF) region besides the previously observed 29Si NMR signals which come from the paramagnetic (PM) region in the sample. This gives definite evidence for spatially-inhomogeneous development of AF ordering below T0 of 17.5 K. The volume fraction is enhanced by applied pressure, whereas the value of internal field (~ 91 mT) remains constant up to 8.3 kbar. In the AF region, the ordered moment is about one order of magnitude larger than 0.03 mB. (2) CeTIn5: The pressure and temperature (T) dependences of nuclear spin-lattice relaxation rate 1/T1 of 115In in CeTIn5 have shown that the superconductivity (SC) occurs close to an AF instability. From the T dependences of 1/T1and Knight shift below Tc, CeTIn5 has been found to exhibit non-s wave (probable d wave) SC with even parity and line nodes in the SC energy gap.

Kohara, T.

2002-05-01

285

Femtosecond-pulse two-photon resonant difference-frequency mixing in gases: A technique for tunable vacuum-ultraviolet femtosecond-pulse generation and a spectroscopic tool for studying atoms in strong laser fields  

NASA Astrophysics Data System (ADS)

Two-photon resonant and near-resonant four-wave difference-frequency mixing in gases in the interaction regime when laser pulse durations are comparable to or shorter than the medium polarization relaxation time T'2 is investigated. The results of experimental studies of the process in Ar and Kr using pump pulses from the ArF-excimer laser are presented demonstrating a generation of tunable short pulse radiation in the range 102-124 nm. The results are discussed in terms of a theoretical model based on a self-consistent solution of the Bloch equations for the atomic transitions and the Maxwell equations for the fields. This enables one to interpret specific nonstationary resonant and quasiresonant phenomena involved in the frequency conversion process. It is shown that the femtosecond-pulse four-wave frequency-mixing technique with probe pulses significantly shorter than the pump pulses makes it possible to study the coherent dynamics of an atomic transition exposed to an intense field. Using atomic Kr as the nonlinear medium, coherent Rabi oscillations and the subsequent phase relaxation of excitation were observed under the condition of two-photon interaction of Kr with femtosecond 193-nm laser pulses. The obtained information is important for controlling and optimizing processes of two-photon resonant frequency conversion and for time-resolved studies of Rydberg states in atoms and molecules.

Nazarkin, A.; Korn, G.; Kittelmann, O.; Ringling, J.; Hertel, I. V.

1997-07-01

286

Hybridization-driven gap in U3Bi4Ni3: a 209Bi NMR/NQR study  

SciTech Connect

We report {sup 209}Bi nuclear-magnetic-resonance and nuclear-quadrupole-resonance measurements on a single crystal of the Kondo insulator U{sub 3}Bi{sub 4}Ni{sub 3}. The {sup 209}Bi nuclear-spin-lattice relaxation rate (T{sub 1}{sup -1}) shows activated behavior and is well fit by a spin gap of 220 K. The {sup 209}Bi Knight shift (K) exhibits a strong temperature dependence arising from 5f electrons, in which K is negative at high temperatures and increases as the temperature is lowered. Below 50 K, K shows a broad maximum and decreases slightly upon further cooling. Our data provide insight into the evolution of the hyperfine fields in a fully gapped Kondo insulator based on 5f electron hybridization.

Baek, Seung H [Los Alamos National Laboratory

2009-01-01

287

Functional Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

Functional magnetic resonance imaging (fMRI), with its excellent spatial resolution and ability to visualize networks of neuroanatomical structures involved in complex information processing, has become the dominant technique for the study of brain function and its development. The accessibility of in-vivo pediatric brain-imaging techniques…

Voos, Avery; Pelphrey, Kevin

2013-01-01

288

Detection of graphene microelectromechanical system resonance  

NASA Astrophysics Data System (ADS)

We present an experimental setup for fast detection of resonances of graphene microelectromechanical structures of different quality. The relatively simple technique used to read-out of the resonance frequency is the main advantage of the proposed system. The resolution is good enough to detect vibrations of the graphene resonator with the quality factor of ˜24 and resonance frequency of 104 MHz.

Wiesner, M.; Lindvall, N.; Yurgens, A.

2014-12-01

289

DIVERSE RESONANCE TUNING STRATEGIES FOR WOMEN SINGERS  

E-print Network

that can increase loudness with little extra vocal effort [2,3,4]. Furthermore, it has been suggested resonances (R1 and R2) of the vocal tract. This allows diverse techniques of resonance tuning. Resonances by the first two acoustic resonances of the vocal tract, with frequencies R1 and R2. The resultant formants

Paris-Sud XI, Université de

290

Liquid chromatography/mass spectrometry and liquid chromatography/nuclear magnetic resonance as complementary analytical techniques for unambiguous identification of polymethoxylated flavones in residues from molecular distillation of orange peel oils (Citrus sinensis).  

PubMed

Liquid chromatography/mass spectrometry and liquid chromatography/nuclear magnetic resonance techniques with ultraviolet/diode array detection were used as complementary analytical tools for the reliable identification of polymethoxylated flavones in residues from molecular distillation of cold-pressed peel oils of Citrus sinensis. After development of a liquid chromatographic separation procedure, the presence of several polymethoxy flavones such as sinensetin, nobiletin, tangeretin, quercetogetin, heptamethoxyflavone, and other derivatives was unambiguously confirmed. In addition, proceranone, an acetylated tetranortriterpenoid with limonoid structure, was identified for the first time in citrus. PMID:16417279

Weber, Berthold; Hartmann, Beate; Stöckigt, Detlef; Schreiber, Klaus; Roloff, Michael; Bertram, Heinz-Jürgen; Schmidt, Claus O

2006-01-25

291

Investigation of 60Co ?-irradiated L-(-) malic acid, N-methyl- DL-valine and L-glutamic acid ?-ethyl ester by electron paramagnetic resonance technique  

NASA Astrophysics Data System (ADS)

The electron paramagnetic resonance spectra of ?-irradiated L-(-) malic acid, N-methyl- DL-valine and L-glutamic acid ?-ethyl ester powders have been investigation at room temperature. Radiation damage centres are attributed to HOOCCH 2?HCOOH, (CH 3) 2?CH(NHCH 3)COOH and C 2H 5OCOCH 2CH 2?(NH 2)COOH radicals, respectively. The spectra have been computer simulated. The EPR parameters of the observed radicals have been determined and discussed.

Ba?kan, M. Halim; Ayd?n, Murat; Osmano?lu, ?emsettin

292

Effect of a weak static magnetic field on nitrogen-14 quadrupole resonance in the case of an axially symmetric electric field gradient tensor.  

PubMed

The application of a weak static B0 magnetic field (less than 1 mT) may produce a well-defined splitting of the (14)N Quadrupole Resonance line when the electric field gradient tensor at the nitrogen nucleus level is of axial symmetry. It is theoretically shown and experimentally confirmed that the actual splitting (when it exists) as well as the line-shape and the signal intensity depends on three factors: (i) the amplitude of B0, (ii) the amplitude and pulse duration of the radio-frequency field, B1, used for detecting the NQR signal, and (iii) the relative orientation of B0 and B1. For instance, when B0 is parallel to B1 and regardless of the B0 value, the signal intensity is three times larger than when B0 is perpendicular to B1. This point is of some importance in practice since NQR measurements are almost always performed in the earth field. Moreover, in the course of this study, it has been recognized that important pieces of information regarding line-shape are contained in data points at the beginning of the free induction decay (fid) which, in practice, are eliminated for avoiding spurious signals due to probe ringing. It has been found that these data points can generally be retrieved by linear prediction (LP) procedures. As a further LP benefit, the signal intensity loss (by about a factor of three) is regained. PMID:24183810

Guendouz, Laouès; Aissani, Sarra; Marêché, Jean-François; Retournard, Alain; Marande, Pierre-Louis; Canet, Daniel

2013-01-01

293

Luminescence resonance energy transfer  

Microsoft Academic Search

Fluorescence resonance energy transfer (FRET), in which a fluorescent donor molecule transfers energy via a nonradiative dipole-dipole interaction to an acceptor molecule (which is usually a fluorescent molecule), is a standard spectroscopic technique for measuring distances in the 10-70 Angstrom range. We have used a luminescent europium chelate as donor and an organic dye, CY-5, as acceptor. This luminescence resonance

Paul R. Selvin; Tariq M. Rana; John E. Hearst

1994-01-01

294

Injection-controlled laser resonator  

DOEpatents

A new injection-controlled laser resonator incorporates self-filtering and self-imaging characteristics with an efficient injection scheme. A low-divergence laser signal is injected into the resonator, which enables the injection signal to be converted to the desired resonator modes before the main laser pulse starts. This injection technique and resonator design enable the laser cavity to improve the quality of the injection signal through self-filtering before the main laser pulse starts. The self-imaging property of the present resonator reduces the cavity induced diffraction effects and, in turn, improves the laser beam quality.

Chang, Jim J. (Dublin, CA)

1995-07-18

295

Comparison of semi-automated scar quantification techniques using high-resolution, 3-dimensional late-gadolinium-enhancement magnetic resonance imaging.  

PubMed

The quantification and modeling of myocardial scar is of expanding interest for image-guided therapy, particularly in the field of arrhythmia management. Migration towards high-resolution, three-dimensional (3D) MRI techniques for spatial mapping of myocardial scar provides superior spatial registration. However, to date no systematic comparison of available approaches to 3D scar quantification have been performed. In this study we compare the reproducibility of six 3D scar segmentation algorithms for determination of left ventricular scar volume. Additionally, comparison to two-dimensional (2D) scar quantification and 3D manual segmentation is performed. Thirty-five consecutive patients with ischemic cardiomyopathy were recruited and underwent conventional 2D late gadolinium enhancement (LGE) and 3D isotropic LGE imaging (voxel size 1.3 mm(3)) using a 3 T scanner. 3D LGE datasets were analyzed using six semi-automated segmentation techniques, including the signal threshold versus reference mean (STRM) technique at >2, >3, >5 and >6 standard deviations (SD) above reference myocardium, the full width at half maximum (FWHM) technique, and an optimization-based technique called hierarchical max flow (HMF). The mean ejection fraction was 32.1 ± 12.7 %. Reproducibility was greatest for HMF and FWHM techniques with intra-class correlation coefficient values ?0.95. 3D scar quantification and modeling is clinically feasible in patients with ischemic cardiomyopathy. While several approaches show acceptable reproducibility, HMF appears superior due to maintenance of accuracy towards manual segmentations. PMID:25307896

Rajchl, Martin; Stirrat, John; Goubran, Maged; Yu, Jeff; Scholl, David; Peters, Terry M; White, James A

2014-10-12

296

Binding investigation on the interaction between Methylene Blue (MB)/TiO2 nanocomposites and bovine serum albumin by resonance light-scattering (RLS) technique and fluorescence spectroscopy.  

PubMed

The interaction between Methylene Blue (MB)/TiO2 nanocomposites and bovine serum albumin (BSA) was investigated by resonance light scattering (RLS), fluorescence, three-dimension spectra and UV-vis absorbance spectroscopy. Several factors which may influence the RLS intensity were also investigated before characterizing MB/TiO2-BSA complex. It was proved that the mechanism of MB/TiO2 nanocomposites binding to BSA was mainly a result of the formation of MB/TiO2-BSA complex. The binding constant of MB/TiO2-BSA is 0.762 × 10(-5) L mol(-1) at 298K. By calculating the binding constant at different temperature, the thermodynamic parameters ?H, ?G, and ?S can be observed and deduced that the hydrophobic interactions played an important role to stabilize the complex. The distance r (3.73 nm) between donor (BSA) and acceptor (MB/TiO2) was obtained according to fluorescence resonance energy transfer (FRET). The binding site for MB/TiO2 on BSA was mainly located in sub-domain IIA. The UV-vis absorbance, circular dichroism and three dimension fluorescence have also been used to investigate the effect of MB/TiO2 on the conformation of BSA. PMID:23985421

Li, Yuesheng; Zhang, Yue; Sun, Shaofa; Zhang, Aiqing; Liu, Yi

2013-11-01

297

Nuclear quadrupole resonance studies of transparent conducting oxides.  

PubMed

We report (63,65)Cu spin-lattice relaxation rates measured by nuclear quadrupole resonance (NQR) in the delafossite compound CuYO(2) and CuYO(2):Ca over a temperature range from 200 to 450K. CuYO(2):Ca is a prototype transparent oxide exhibiting p-type electrical conductivity. Relaxation rates in CuYO(2):Ca are enhanced by one to two orders of magnitude relative to undoped material, exhibit much stronger temperature dependence, and contain contributions from magnetic and quadrupolar relaxation mechanisms with roughly equal strengths. Relaxation in undoped CuYO(2) is of purely quadrupolar origin and is attributed to interactions with lattice phonons. The main focus of this paper is the magnetic contribution to the relaxation rate in CuYO(2):Ca which is attributed to the hyperfine fields of carriers. It is argued that the dynamics of the hyperfine field are dominated by the hopping rate for carrier transfers between neighboring atoms in the copper planes of the delafossite structure. Comparison of the magnetic relaxation rates with the DC conductivity permits an estimate of the carrier concentration and mobility. PMID:15388186

Warren, W W; Rajabzadeh, A; Olheiser, T; Liu, J; Tate, J; Jayaraj, M K; Vanaja, K A

2004-01-01

298

SPECTRAL IMAGING TECHNIQUES FOR GRAIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Three spectral imaging techniques were employed for the purpose of assessing the quality of cereal grains. Each of these techniques provided unique, yet complementary, information. Nuclear magnetic resonance (NMR), also called magnetic resonance imaging (MRI), was used to detect mobile components ...

299

Clinical magnetic resonance imaging  

SciTech Connect

This book presents clinical applications of magnetic resonance imaging with a strong clinical orientation. Covers technique, instrumentation, and contrast agents. Describes MRI of the neck, brain, heart, spine, TMJ and orbit, chest abdomen, pelvis, and the joints. Also includes a high field atlas of the central nervous system.

Brady, T.J.; Edelman, R.R.

1988-01-01

300

Two-frequency heating technique at the 18 GHz electron cyclotron resonance ion source of the National Institute of Radiological Sciences  

SciTech Connect

The two-frequency heating technique was studied to increase the beam intensities of highly charged ions provided by the high-voltage extraction configuration (HEC) ion source at the National Institute of Radiological Sciences (NIRS). The observed dependences on microwave power and frequency suggested that this technique improved plasma stability but it required precise frequency tuning and more microwave power than was available before 2013. Recently, a new, high-power (1200 W) wide band-width (17.1–18.5 GHz) travelling-wave-tube amplifier (TWTA) was installed. After some single tests with klystron and TWT amplifiers the simultaneous injection of the two microwaves has been successfully realized. The dependence of highly charged ions (HCI) currents on the superposed microwave power was studied by changing only the output power of one of the two amplifiers, alternatively. While operating the klystron on its fixed 18.0 GHz, the frequency of the TWTA was swept within its full limits (17.1–18.5 GHz), and the effect of this frequency on the HCI-production rate was examined under several operation conditions. As an overall result, new beam records of highly charged argon, krypton, and xenon beams were obtained at the NIRS-HEC ion source by this high-power two-frequency operation mode.

Biri, S., E-mail: biri@atomki.hu [National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Institute for Nuclear Research (ATOMKI), H-4026 Debrecen, Bem tér 18/c (Hungary); Kitagawa, A.; Muramatsu, M.; Drentje, A. G. [National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan)] [National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Rácz, R. [Institute for Nuclear Research (ATOMKI), H-4026 Debrecen, Bem tér 18/c (Hungary)] [Institute for Nuclear Research (ATOMKI), H-4026 Debrecen, Bem tér 18/c (Hungary); Yano, K.; Kato, Y. [Graduated School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan)] [Graduated School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan); Sasaki, N.; Takasugi, W. [Accelerator Engineering Corporation (AEC), Inage, Chiba 263-0043 (Japan)] [Accelerator Engineering Corporation (AEC), Inage, Chiba 263-0043 (Japan)

2014-02-15

301

Radiation effects on poly(glycidyl methacrylate-co-ethyl methacrylate) copolymers and electron paramagnetic resonance characterization of vanadium hexacarbonyl using the technique of partial orientation. [Gamma radiation  

SciTech Connect

The effects of gamma radiation on a series of characterized copolymers, synthesized from different molar ratios of glycidyl methacrylate (GMA) and ethyl methacrylate (EMA), have been studied using a variety of techniques. Polymers were characterized using IR, NMR, GPC, and viscosity measurements. The analysis of radiation G values suggests that at glycidyl methacrylate concentrations below 10%, crosslinking does not predominate. However, at higher GMA concentrations, G values for crosslinking increase, and at GMA concentration over 60%, G values approach 10, a value only reached by chain reactions. Spectroscopic evidence is presented for the participation of the glycidyl group in radiation-induced reactions. FTIR studies on irradiated thin films of COP show decreases in the epoxide functional group regions, ca. 908 and 1250 cm/sup -1/. EPR results suggest that a paramagnetic species, possibly due to the epoxide group, is produced by irradiating the polymer. The EPR spectral parameters of V(CO)/sub 6/, a stable paramagnetic species have been resolved using the experimental technique of Partial Orientation. Slow-cooling an EPR sample of V(CO)/sub 6/ in cyclohexane produces crystallites containing the solute. When these crystallites are of sufficient size, resolution of the broadened EPR spectrum into the individual g tensors is observed. This induced resolution allows the precise assignment of the hyperfine coupling constants and g tensor values.

Payne, D.N. Jr.

1987-01-01

302

Optical resonator  

NASA Technical Reports Server (NTRS)

The invention discloses a semi-ring Fabry-Perot (SRFP) optical resonator structure comprising a medium including an edge forming a reflective facet and a waveguide within the medium, the waveguide having opposing ends formed by the reflective facet. The performance of the SRFP resonator can be further enhanced by including a Mach-Zehnder interferometer in the waveguide on one side of the gain medium. The optical resonator can be employed in a variety of optical devices. Laser structures using at least one SRFP resonator are disclosed where the resonators are disposed on opposite sides of a gain medium. Other laser structures employing one or more resonators on one side of a gain region are also disclosed.

Taghavi-Larigani, Shervin (Inventor); Vanzyl, Jakob J. (Inventor); Yariv, Amnon (Inventor)

2006-01-01

303

[Magnetic resonance tomography in questionable lesions of the ENT area. Examination technique and results of a prospective study of 1,493 patients].  

PubMed

1493 patients with various lesions in the head and neck region were prospectively evaluated with MR imaging (MRI) and other imaging modalities. The findings of MRI and conventional imaging techniques were correlated with histological findings. All MRI examinations were carried out on a 1.0 and 1.5 Tesla superconducting MR unit employing combined T1 and T2 weighed spin-echo sequences. Dynamic MRI with fast gradient-echo sequences and application of a paramagnetic contrast agent (Gd-DTPA) was additionally performed in 120 patients. 250 patients were examined with non-invasive MR angiography. Appropriate saturation enabled the visualization of either arterial or venous vascular structures. Analysis of metabolic parameters and tumor proliferation was possible through in-vivo spectroscopy in 60 patients. Highest values for specificity and sensitivity of MRI were achieved in the area of the skull base and petrous bone. In comparison to other imaging modalities, the exact differentiation of pathological alterations such as neurinoma, meningioma and glomus tumors succeeded with high accuracy. In the region of the naso- and oropharynx, plain MRI revealed in 77% of the cases adequate diagnostic information, which could be significantly increased with application of the paramagnetic contrast agent Gd-DTPA. Due to multiplanar slice orientation and improved soft tissue differentiation MRI proved to be superior to other imaging techniques in salivary glands and in the region of the neck. As a conclusion, the advantages of MRI are the depiction and visualization of small infiltrations as well as the high sensitivity and specificity of this imaging modality. PMID:1388473

Vogl, T J; Balzer, J; Grevers, G

1992-09-01

304

Magnetic Criticality and Unconventional Superconductivity in CeCoIn5: Study of 115In-Nuclear Quadrupole Resonance under Pressure  

NASA Astrophysics Data System (ADS)

We report the systematic evolution of the superconducting (SC) characteristics of the heavy-fermion (HF) superconductor CeCoIn5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin-lattice relaxation rate 1/T1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs) specific to a quantum critical point (QCP). It is demonstrated that the marked suppression of AFM SFs leads to a reduction in the SC energy gap or in the coupling strength of the Cooper pair. Tc, nevertheless, increases with increasing P due to the increase in HF bandwidth. This is expected to make the lifetime of quasi-particles sufficiently long.

Yashima, M.; Kawasaki, S.; Kawasaki, Y.; Zheng, G.-q.; Kitaoka, Y.; Shishido, H.; Settai, R.; Haga, Y.; ?nuki, Y.

2004-08-01

305

An Advanced Electron Spin Resonance (ESR) Spin-Trapping and LC/(ESR)/MS Technique for the Study of Lipid Peroxidation  

PubMed Central

There are two types of nutritionally important polyunsaturated fatty acids (PUFAs), namely ?-6s and ?-3s. PUFAs and their metabolites generated from lipid peroxidation via cyclooxygenase (COX) and lipoxygenase (LOX) are believed to be involved in a variety of physiological and pathological processes in the human body. Both COX- and LOX-catalyzed PUFA peroxidation are complex events that generate a series of radicals, which may then bind proteins, target DNA/RNA, and lead to a number of biological changes. However, due to the lack of an appropriate method, it was not possible until recently to identify the short-lived PUFA-derived radicals in COX-/LOX-catalyzed peroxidation. Failure to characterize free radicals during peroxidation has greatly restricted our knowledge about COX/LOX biology in human health. Here we review the development and refinement of combined ESR spin trapping and LC/ESR/MS to characterize PUFA-derived radicals formed from in vitro (cell-free) peroxidation. We also present the most recent approach for studying peroxidation in cells which allows us to directly assess the potential bioactivity of PUFA-derived free radicals. This advanced technique has resulted in a major breakthrough in radical structural characterization, as well as assessment of free radical-associated cell growth response, thereby greatly improving our knowledge of PUFAs, COX-/LOX-catalyzed lipid peroxidation, and their related biological consequences. PMID:23203086

Xu, Yi; Gu, Yan; Qian, Steven Y.

2012-01-01

306

Local magnetic and structural properties of the low-temperature orthorhombic to low-temperature tetragonal transition: A {sup 139}La NQR study in lightly hole-doped La{sub 1.8{minus}x}Eu{sub 0.2}Sr{sub x}CuO{sub 4}  

SciTech Connect

{sup 139}La nuclear quadrupole resistance (NQR) and relaxation measurements in lightly hole-doped La{sub 1.8{minus}x}Eu{sub 0.2}Sr{sub x}CuO{sub 4} have been used to investigate the microscopic properties of the low-temperature orthorhombic to low-temperature tetragonal transition. The transition is characterized by a sharp peak in {sup 139}La NQR relaxation rate, indicating phonon softening. We find that the structural phase transition is accompanied by a modification of the spin state. The data for the spin freezing and the recovery of sublattice magnetization at low T are presented and discussed in relation to the studies of La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and La{sub 2}Cu{sub 1{minus}x}Li{sub x}O{sub 4}. {copyright} {ital 1999} {ital The American Physical Society}

Suh, B.J.; Hammel, P.C. [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Huecker, M.; Buechner, B. [II. Physikalisches Institut, Universitaet zu Koeln, D-50937 Koeln (Germany)] [II. Physikalisches Institut, Universitaet zu Koeln, D-50937 Koeln (Germany)

1999-02-01

307

Local magnetic and structural properties of the low-temperature orthorhombic to low-temperature tetragonal transition: A 139La NQR study in lightly hole-doped La1.8-xEu0.2SrxCuO4  

NASA Astrophysics Data System (ADS)

139La nuclear quadrupole resistance (NQR) and relaxation measurements in lightly hole-doped La1.8-xEu0.2SrxCuO4 have been used to investigate the microscopic properties of the low-temperature orthorhombic to low-temperature tetragonal transition. The transition is characterized by a sharp peak in 139La NQR relaxation rate, indicating phonon softening. We find that the structural phase transition is accompanied by a modification of the spin state. The data for the spin freezing and the recovery of sublattice magnetization at low T are presented and discussed in relation to the studies of La2-xSrxCuO4 and La2Cu1-xLixO4.

Suh, B. J.; Hammel, P. C.; Hücker, M.; Büchner, B.

1999-02-01

308

Gaussian-Beam Laser-Resonator Program  

NASA Technical Reports Server (NTRS)

Gaussian Beam Laser Resonator Program models laser resonators by use of Gaussian-beam-propagation techniques. Used to determine radii of beams as functions of position in laser resonators. Algorithm used in program has three major components. First, ray-transfer matrix for laser resonator must be calculated. Next, initial parameters of beam calculated. Finally, propagation of beam through optical elements computed. Written in Microsoft FORTRAN (Version 4.01).

Cross, Patricia L.; Bair, Clayton H.; Barnes, Norman

1989-01-01

309

Probing spectroscopic like information using resonant scattering  

NASA Astrophysics Data System (ADS)

Resonant x-ray scattering can combine layer sensitivity of reflectivity technique with short-range structural sensitivity of absorption technique due to element specificity and contrast variation mechanism of resonant effect. We demonstrated the idea through depth profile study of chemical composition of multi-element thin film system at soft x-ray spectral range near boron K-absorption edge.

Nayak, M.; Lodha, G. S.

2012-06-01

310

Dynamic tuning of MEMS resonators via electromechanical feedback.  

PubMed

This paper introduces an active electrical technique for dynamic tuning of MEMS resonators. The proposed technique is based on using the resonator output current to generate displacement or acceleration signals by integration or differentiation operations, respectively. The resulting signal is then scaled to generate an appropriate tuning signal. When applied to the resonator through additional signal ports, the tuning signal electrically modifies the equivalent mechanical stiffness or mass of the resonator, thereby tuning the resonance frequency in a bidirectional fashion depending on the polarity of the scaling. This tuning scheme has been applied to a piezoelectric AlN-on-Si BAW square resonator to tune its 14.2 MHz resonance frequency by 22 kHz, equivalent to 1550 ppm. The proposed tuning technique can be applied to a wide range of MEMS resonators and resonant sensors, e.g., to compensate for temperature or process-induced variations in their resonance frequencies. PMID:25585397

Norouzpour-Shirazi, Arashk; Hodjat-Shamami, Mojtaba; Tabrizian, Roozbeh; Ayazi, Farrokh

2015-01-01

311

Tunable Resonant Scanners  

NASA Astrophysics Data System (ADS)

The most attractive features of resonant scanners are high reliability and eternal life as well as extremely low wobble and jitter. Power consumption is also low, electronic drive is simple, and the device is capable of handling large beams. All of these features are delivered at a low cost in a small package. The resonant scanner's use in numerous high precision applications, however, has been limited because of the difficulty in controlling its phase and resonant frequency. This paper introduces the concept of tunable/controllable resonant scanners, discusses their features, and offers a number of tuning techniques. It describes two angular scanner designs and presents data on tunable range and life tests. It also reviews applications for these new tunable resonant scanners that preserve the desirable features of earlier models while removing the old problems with synchronization or time base flexibility. The three major types of raster scanning applications where the tunable resonant scanner may be of benefit are: 1. In systems with multiple time bases such as multiple scanner networks or with scanners keyed to a common clock (the line frequency or data source) or a machine with multiple resonant scanners. A typical application is image and text transmission, also a printer with a large data base where a buffer is uneconomical. 2. In systems sharing data processing or laser equipment for reasons of cost or capacity, typically multiple work station manufacturing processes or graphic processes. 3. In systems with extremely precise time bases where the frequency stability of conventional scanners cannot be relied upon.

Montagu, Jean I.

1987-01-01

312

Mode Orientation Control For Sapphire Dielectric Ring Resonator  

NASA Technical Reports Server (NTRS)

Small sapphire tuning wedge used in technique for solving mode-purity problem associated with sapphire dielectric-ring resonator part of cryogenic microwave frequency discriminator. Breaks quasi-degeneracy of two modes and allows selective coupling to just one mode. Wedge mounted on axle entering resonator cavity and rotated while resonator cryogenically operating in vacuum. Furthermore, axle moved vertically to tune resonant frequency.

Santiago, David G.; Dick, G. John; Prata, Aluizio

1996-01-01

313

Zero field NMR and NQR  

Microsoft Academic Search

Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect

D. B. Zax; A. Bielecki; K. W. Zilm; A. Pines; D. P. Weitekamp

1985-01-01

314

MACHINERY RESONANCE AND DRILLING  

SciTech Connect

New developments in vibration analysis better explain machinery resonance, through an example of drill bit chattering during machining of rusted steel. The vibration of an operating drill motor was measured, the natural frequency of an attached spring was measured, and the two frequencies were compared to show that the system was resonant. For resonance to occur, one of the natural frequencies of a structural component must be excited by a cyclic force of the same frequency. In this case, the frequency of drill bit chattering due to motor rotation equaled the spring frequency (cycles per second), and the system was unstable. A soft rust coating on the steel to be drilled permitted chattering to start at the drill bit tip, and the bit oscillated on and off of the surface, which increased the wear rate of the drill bit. This resonant condition is typically referred to as a motor critical speed. The analysis presented here quantifies the vibration associated with this particular critical speed problem, using novel techniques to describe resonance.

Leishear, R.; Fowley, M.

2010-01-23

315

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy  

E-print Network

The signal intensity of electron spin resonance in magnetic resonance force microscopy MRFM experiments that magnetic resonance force microscopy MRFM is a new 3D imaging technique8,9 with the potential of achieving force microscopy Z. Zhanga) Condensed Matter and Thermal Physics Group, Materials Science and Technology

Hammel, P. Chris

316

Whole-body imaging of adoptively transferred T cells using magnetic resonance imaging, single photon emission computed tomography and positron emission tomography techniques, with a focus on regulatory T cells  

PubMed Central

Cell-based therapies using natural or genetically modified regulatory T cells (Tregs) have shown significant promise as immune-based therapies. One of the main difficulties facing the further advancement of these therapies is that the fate and localization of adoptively transferred Tregs is largely unknown. The ability to dissect the migratory pathway of these cells in a non-invasive manner is of vital importance for the further development of in-vivo cell-based immunotherapies, as this technology allows the fate of the therapeutically administered cell to be imaged in real time. In this review we will provide an overview of the current clinical imaging techniques used to track T cells and Tregs in vivo, including magnetic resonance imaging (MRI) and positron emission tomography (PET)/single photon emission computed tomography (SPECT). In addition, we will discuss how the finding of these studies can be used, in the context of transplantation, to define the most appropriate Treg subset required for cellular therapy. PMID:23574314

Leech, J M; Sharif-Paghaleh, E; Maher, J; Livieratos, L; Lechler, R I; Mullen, G E; Lombardi, G; Smyth, L A

2013-01-01

317

GAUSSIAN BEAM LASER RESONATOR PROGRAM  

NASA Technical Reports Server (NTRS)

In designing a laser cavity, the laser engineer is frequently concerned with more than the stability of the resonator. Other considerations include the size of the beam at various optical surfaces within the resonator or the performance of intracavity line-narrowing or other optical elements. Laser resonators obey the laws of Gaussian beam propagation, not geometric optics. The Gaussian Beam Laser Resonator Program models laser resonators using Gaussian ray trace techniques. It can be used to determine the propagation of radiation through laser resonators. The algorithm used in the Gaussian Beam Resonator program has three major components. First, the ray transfer matrix for the laser resonator must be calculated. Next calculations of the initial beam parameters, specifically, the beam stability, the beam waist size and location for the resonator input element, and the wavefront curvature and beam radius at the input surface to the first resonator element are performed. Finally the propagation of the beam through the optical elements is computed. The optical elements can be modeled as parallel plates, lenses, mirrors, dummy surfaces, or Gradient Index (GRIN) lenses. A Gradient Index lens is a good approximation of a laser rod operating under a thermal load. The optical system may contain up to 50 elements. In addition to the internal beam elements the optical system may contain elements external to the resonator. The Gaussian Beam Resonator program was written in Microsoft FORTRAN (Version 4.01). It was developed for the IBM PS/2 80-071 microcomputer and has been implemented on an IBM PC compatible under MS DOS 3.21. The program was developed in 1988 and requires approximately 95K bytes to operate.

Cross, P. L.

1994-01-01

318

Techniques for classifying acoustic resonant spectra  

SciTech Connect

A second-generation nondestructive evaluation (NDE) system that discriminates between different types of chemical munitions is under development. The NDE system extracts features from the acoustic spectra of known munitions, builds templates from these features, and performs classification by comparing features extracted from an unknown munition to a template library. Improvements over first-generation feature extraction template construction and classification algorithms are reported. Results are presented on the performance of the system and a large data set collected from surrogate-filled munitions.

Roberts, R.S.; Lewis, P.S.; Chen, J.T.; Vela, O.A.

1995-12-31

319

Resonant optothermoacoustic detection: technique for measuring weak  

E-print Network

is photoacoustic spec- troscopy (PAS), based on the detection of sound waves generated in a medium upon absorption detection (OTD) was first proposed and theoretically analyzed by Rosengren in 1972 [1]. The author suggested

320

Nuclear magnetic resonance contrast agents  

DOEpatents

A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC{sub 16}H{sub 14}N{sub 6}. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques. 10 figs.

Smith, P.H.; Brainard, J.R.; Jarvinen, G.D.; Ryan, R.R.

1997-12-30

321

Nuclear magnetic resonance contrast agents  

DOEpatents

A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC.sub.16 H.sub.14 N.sub.6. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques.

Smith, Paul H. (Los Alamos, NM); Brainard, James R. (Los Alamos, NM); Jarvinen, Gordon D. (Los Alamos, NM); Ryan, Robert R. (Los Alamos, NM)

1997-01-01

322

Improving the sensitivity of a high-Tc SQUID at MHz frequency using a normal metal transformer  

Microsoft Academic Search

Superconducting quantum interference devices (SQUIDs) can be used to detect the signals of nuclear quadrupole resonance (NQR). The NQR frequencies of some interesting materials are in the order of MHz. However, the sensitivity of a high-Tc SQUID is normally not enough to detect the weak NQR signals. To improve the sensitivity of a high-Tc SQUID at MHz frequency, we used

D. F. He; H. Itozaki; M. Tachiki

2006-01-01

323

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

324

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field\\u000a in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the\\u000a phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for\\u000a clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

325

Dark resonance  

SciTech Connect

We construct explicit models of particle dark matter where the attractive force in the dark matter sector creates a narrow near-threshold resonance that qualitatively changes the energy dependence of the annihilation cross section. In these models, the resonant enhancement of the dark matter annihilation can easily source the excess of energetic leptons observed by the PAMELA experiment. The distinct feature of these models is that by construction the enhancement of the annihilation cross section shuts off when the dark matter velocity falls below the typical Milky Way values, thus automatically satisfying constraints on dark matter annihilation imposed by the CMB anisotropies and gamma ray constraints from satellite galaxies. However, the resonant enhancement of annihilation can be probed through the most recent FERMI-LAT constraints on the diffuse galactic gamma ray emission.

An, Haipeng; Pospelov, Maxim, E-mail: han@perimeterinstitute.ca, E-mail: mpospelov@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, Waterloo, ON, N2J 2W9 (Canada)

2012-11-01

326

Design and testing of a low impedance transceiver circuit for nitrogen-14 nuclear quadrupole resonance.  

PubMed

A low impedance transceiver circuit consisting of a transmit-receive switch circuit, a class-D amplifier and a transimpedance amplifier (TIA) was newly designed and tested for a nitrogen-14 NQR. An NQR signal at 1.37MHz from imidazole was successfully observed with the dead time of ~85µs under the high Q transmission (Q~120) and reception (Q~140). The noise performance of the low impedance TIA with an NQR probe was comparable with a commercial low noise 50? amplifier (voltage input noise: 0.25 nV/Hz) which was also connected to the probe. The protection voltage for the pre-amplifier using the low impedance transceiver was ~10 times smaller than that for the pre-amplifier using a 50? conventional transceiver, which is suitable for NQR remote sensing applications. PMID:25293696

Sato-Akaba, Hideo

2014-01-01

327

A Comparison of FTNMR and FTIR Techniques.  

ERIC Educational Resources Information Center

Nuclear magnetic resonance and infrared are two spectroscopic methods that commonly use the Fourier transform technique. Discussed are the similarities and differences in the use of the Fourier transform in these two spectroscopic techniques. (CW)

Ahn, Myong-Ku

1989-01-01

328

87Rb and 85Rb NQR study of phase transitions in RbH3(SeO3)2 J. Seliger, V. 017Dagar, R. Blinc  

E-print Network

dependence of the quadrupole coupling constants and the asymmetry parameters on going into the ferroelectric SeO3. Nous avons confirmé l'existence d'une phase incommensurable intermédiaire entre Tc et Tc + 4 K. Abstract. 2014 The temperature dependence of the nuclear quadrupole resonance spectra of 85Rb and 87Rb

Paris-Sud XI, Université de

329

Electrostatic and Piezoelectric Testing Methods for RF MEMS Resonators  

Microsoft Academic Search

Two techniques to characterize diamond micromechanical resonator structures are described: (1) electrostatic testing, and (2) piezoelectric actuation with optical detection. It is found that, while the resonant frequency values obtained from the two techniques differ only by 3%, method (2) yield up to eight times larger estimates for the quality factor Q. After describing the techniques and discussing experimental results,

N. Sepulveda; M. Toledo-Quinones

2006-01-01

330

Evaluation of the Chromium Resonance Parameters Including Resonance Parameter Covariance  

SciTech Connect

The intent of this work is to report the results and describe the procedures utilized to evaluate the chromium isotopes' cross sections, i.e., (50)Cr, (52)Cr, (53)Cr, and (54)Cr, for criticality safety applications. The evaluations were done in the resolved resonance region using the reduced Reich-Moore R-matrix formalism. The novel aspect of this evaluation is the inclusion of new transmission and capture cross-section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) for energies below 100 keV and the extension of the (53)Cr energy region. The resonance analysis was performed with the multilevel R-matrix code, SAMMY, which utilizes the generalized least-squares technique based on the Bayes' theory. Complete sets of resonance parameters and resonance parameter covariance matrices (RPCMs) were obtained for each of the chromium isotopes from the SAMMY analysis of the experimental database.

Leal, Luiz C [ORNL; Derrien, Herve [ORNL; Guber, Klaus H [ORNL; Arbanas, Goran [ORNL; Wiarda, Dorothea [ORNL

2011-01-01

331

Optical Microspherical Resonators for Biomedical Sensing  

PubMed Central

Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, known as whispering gallery modes, can confer the resonator an exceptionally high quality factor Q, leading to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. These attractive characteristics make these miniaturized optical resonators especially suited as laser cavities and resonant filters, but also as very sensitive sensors. First, a brief analysis is presented of the characteristics of microspherical resonators, of their fabrication methods, and of the light coupling techniques. Then, we attempt to overview some of the recent advances in the development of microspherical biosensors, underlining a number of important applications in the biomedical field. PMID:22346603

Soria, Silvia; Berneschi, Simone; Brenci, Massimo; Cosi, Franco; Conti, Gualtiero Nunzi; Pelli, Stefano; Righini, Giancarlo C.

2011-01-01

332

Stochastic resonance in electrical circuits. I. Conventional stochastic resonance  

Microsoft Academic Search

Stochastic resonance (SR), a phenomenon in which a periodic signal in a nonlinear system can be amplified by added noise, is introduced and discussed. Techniques for investigating SR using electronic circuits are described in practical terms. The physical nature of SR, and the explanation of weak-noise SR as a linear response phenomenon, are considered. Conventional SR, for systems characterized by

Dmitrii G. Luchinsky; Riccardo Mannella; Peter V. E. McClintock; Nigel G. Stocks

1999-01-01

333

Methods for chemical exchange saturation transfer magnetic resonance imaging  

E-print Network

Chemical exchange saturation transfer (CEST) is a relatively new magnetic resonance imaging (MRI) acquisition technique that generates contrast dependent on tissue microenvironment, such as protein concentration and ...

Scheidegger, Rachel Nora

2013-01-01

334

Nuclear Resonance Fluorescence for Nuclear Materials Assay.  

E-print Network

??This dissertation examines the measurement of nuclear resonance fluorescence gamma-rays as a technique to non-destructively determine isotopic compositions of target materials that are of interest… (more)

Quiter, Brian Joseph

2010-01-01

335

All-Resonant Control of Superconducting Resonators  

E-print Network

An all-resonant method is proposed to control the quantum state of superconducting resonators. This approach uses a tunable artificial atom linearly coupled to resonators, and allows for efficient routes to Fock state synthesis, qudit logic operations, and synthesis of NOON states. This resonant approach is theoretically analyzed, and found to perform signficantly better than existing proposals using the same technology.

Frederick W. Strauch

2012-08-17

336

Nanotube resonator devices  

DOEpatents

A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

2014-05-06

337

Role of bromine in restoring superconductivity in YBa2Cu3Oy  

Microsoft Academic Search

63,65Cu nuclear quadrupole resonance (NQR), 63,65Cu and 79,81Br nuclear magnetic resonance (NMR), and Br K-edge x-ray-absorption fine-structure (XAFS) measurement techniques have been used to study the local structures of Cu and Br in well-characterized samples of deoxygenated and brominated YBa2Cu3Oy (YBCO). The combined results provide a detailed picture of the role of bromine in reoxygenating the YBCO structure and an

D. M. Potrepka; J. I. Budnick; D. B. Fenner; W. A. Hines; M. Balasubramanian; A. R. Moodenbaugh

1999-01-01

338

MRI temporal acceleration techniques.  

PubMed

In recent years, there has been an explosive growth of magnetic resonance imaging (MRI) techniques that allow faster scan speed by exploiting temporal or spatiotemporal redundancy of the images. These techniques improve the performance of dynamic imaging significantly across multiple clinical applications, including cardiac functional examinations, perfusion imaging, blood flow assessment, contrast-enhanced angiography, functional MRI, and interventional imaging, among others. The scan acceleration permits higher spatial resolution, increased temporal resolution, shorter scan duration, or a combination of these benefits. Along with the exciting developments is a dizzying proliferation of acronyms and variations of the techniques. The present review attempts to summarize this rapidly growing topic and presents conceptual frameworks to understand these techniques in terms of their underlying mechanics and connections. Techniques from view sharing, keyhole, k-t, to compressed sensing are covered. PMID:22903655

Tsao, Jeffrey; Kozerke, Sebastian

2012-09-01

339

Resonance Rings  

NSDL National Science Digital Library

This is an activity about resonance and where it is found in related to astronomy. Learners will construct two differently sized rings out of file folder paper and tape them to a piece of cardboard. Next, they will shake the cardboard from side to side, which shakes the rings, and observe what happens when the frequency of the shaking is gradually increased. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

340

Resonance IR: a coherent multidimensional analogue of resonance Raman.  

PubMed

This work demonstrates the use of triply resonant sum frequency (TRSF) spectroscopy as a "resonance IR" analogue to resonance Raman spectroscopy. TRSF is a four-wave-mixing process where three lasers with independent frequencies interact coherently with a sample to generate an output at their triple summation frequency. The first two lasers are in the infrared and result in two vibrational excitations, while the third laser is visible and induces a two-quantum anti-Stokes resonance Raman transition. The signal intensity grows when the laser frequencies are all in resonance with coupled vibrational and electronic states. The method therefore provides electronic enhancement of IR-active vibrational modes. These modes may be buried beneath solvent in the IR spectrum and also be Raman-inactive and therefore inaccessible by other techniques. The method is presented on the centrosymmetric complex copper phthalocyanine tetrasulfonate. In this study, the two vibrational frequencies were scanned across ring-breathing modes, while the visible frequency was left in resonance with the copper phthalocyanine tetrasulfonate Q band, resulting in a two-dimensional infrared plot that also reveals coupling between vibrational states. TRSF has the potential to be a very useful probe of structurally similar biological motifs such as hemes, as well as synthetic transition-metal complexes. PMID:24707979

Boyle, Erin S; Neff-Mallon, Nathan A; Handali, Jonathan D; Wright, John C

2014-05-01

341

Electrostatically driven micro resonator with a CMOS capacitive read out  

Microsoft Academic Search

An electrostatically driven micro resonator is fabricated from single-crystal silicon, using micromachining techniques. The displacement amplitude is measured through differential capacitance measurement, implemented on a CMOS interface circuit, which also provides the excitation clocks for the resonator. The unique feature of this micromechanical system is the integration method applied for attaching the resonator to the CMOS chip. The integration is

Yinon Satuby; Uri Ben-Yehuda; Claudio G. Jakobson; Jacob Shneider; D. Lavie; Y. Nemirovsky; S. Kaldor; M. Hershkovitz; E. Netzer

1995-01-01

342

Virtual magnetic resonance colonography  

PubMed Central

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques. PMID:12746264

Debatin, J; Lauenstein, T

2003-01-01

343

Sb-NQR probe for superconducting properties in the Pr-based filled-skutterudite compound PrRu4Sb12  

Microsoft Academic Search

We report the electronic and superconducting properties in the Pr-based filled-skutterudite superconductor PrRu4Sb12 with Tc=1.3 K via the measurements of nuclear-quadrupole-resonance frequency nuQ and nuclear-spin-lattice-relaxation time T1 of Sb nuclei. The temperature dependence of nuQ has revealed the energy scheme of Pr3+ crystal electric field that is consistent with an energy separation DeltaCEF˜70 K between the ground state and the

M. Yogi; H. Kotegawa; Y. Imamura; G.-Q. Zheng; Y. Kitaoka; H. Sugawara; H. Sato

2003-01-01

344

Resonant frequency of gold/polycarbonate hybrid nano resonators fabricated on plastics via nano-transfer printing  

PubMed Central

We report the fabrication of gold/polycarbonate (Au/PC) hybrid nano resonators on plastic substrates through a nano-transfer printing (nTP) technique, and the parametric studies of the resonant frequency of the resulting hybrid nano resonators. nTP is a nanofabrication technique that involves an assembly process by which a printable layer can be transferred from a transfer substrate to a device substrate. In this article, we applied nTP to fabricate Au/PC hybrid nano resonators on a PC substrate. When an AC voltage is applied, the nano resonator can be mechanically excited when the AC frequency reaches the resonant frequency of the nano resonator. We then performed systematic parametric studies to identify the parameters that govern the resonant frequency of the nano resonators, using finite element method. The quantitative results for a wide range of materials and geometries offer vital guidance to design hybrid nano resonators with a tunable resonant frequency in a range of more than three orders of magnitude (e.g., 10 KHz-100 MHz). Such nano resonators could find their potential applications in nano electromechanical devices. Fabricating hybrid nano resonators via nTP further demonstrates nTP as a potential fabrication technique to enable a low-cost and scalable roll-to-roll printing process of nanodevices. PMID:21711590

2011-01-01

345

System and method for regulating resonant inverters  

DOEpatents

A technique is provided for direct digital phase control of resonant inverters based on sensing of one or more parameters of the resonant inverter. The resonant inverter control system includes a switching circuit for applying power signals to the resonant inverter and a sensor for sensing one or more parameters of the resonant inverter. The one or more parameters are representative of a phase angle. The resonant inverter control system also includes a comparator for comparing the one or more parameters to a reference value and a digital controller for determining timing of the one or more parameters and for regulating operation of the switching circuit based upon the timing of the one or more parameters.

Stevanovic, Ljubisa Dragoljub (Clifton Park, NY); Zane, Regan Andrew (Superior, CO)

2007-08-28

346

Resonant Nucleation  

E-print Network

We investigate the role played by fast quenching on the decay of metastable (or false vacuum) states. Instead of the exponentially-slow decay rate per unit volume, $\\Gamma_{\\rm HN} \\sim \\exp[-E_b/k_BT]$ ($E_b$ is the free energy of the critical bubble), predicted by Homogeneous Nucleation theory, we show that under fast enough quenching the decay rate is a power law $\\Gamma_{\\rm RN} \\sim [E_b/k_BT]^{-B}$, where $B$ is weakly sensitive to the temperature. For a range of parameters, large-amplitude oscillations about the metastable state trigger the resonant emergence of coherent subcritical configurations. Decay mechanisms for different $E_b$ are proposed and illustrated in a (2+1)-dimensional scalar field model.

Marcelo Gleiser; Rafael Howell

2005-03-16

347

Investigation of the electronic effects in a series of halo derivatives of organosilicon compounds by the method of nuclear quadrupole resonance of 79 Br, 81 Br, and 127 I  

Microsoft Academic Search

1.The NQR spectra of certain bromo and iodo derivatives of organosilicon compounds were investigated.2.The correlation of the NQR frequencies and the quadrupole coupling constants with the induction and conjugation constants of the substituents at the silicon atom was constructed.

G. K. Semin; E. V. Bryukhova; M. A. Kadina; G. V. Frolova

1971-01-01

348

Experiments with Helmholtz Resonators.  

ERIC Educational Resources Information Center

Presents experiments that use Helmholtz resonators and have been designed for a sophomore-level course in oscillations and waves. Discusses the theory of the Helmholtz resonator and resonance curves. (JRH)

Greenslade, Thomas B., Jr.

1996-01-01

349

Nuclear quadrupole resonance of Cl 35 , Br 79 , Br 81 , and I 127 of halogen-containing organomercury compounds  

Microsoft Academic Search

1.The NQR spectra of halogens in a number of organomercury compounds of the RHgHal and p-ClC6 H4HgX types were investigated.2.In crystals of the compounds studied, coordination interactions arise between the mercury atoms and the halogens. However, when the type of coordination is preserved within a narrow series of compounds, the changes in the NQR frequencies may be determined by the

A. N. Nesmeyanov; O. Yu. Okhlobystin; E. V. Bryukhova; V. I. Bregadze; D. N. Kravtsov; B. A. Faingor; L. S. Golovchenko; G. K. Semin

1969-01-01

350

Regenerative feedback resonant circuit  

DOEpatents

A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

2014-09-02

351

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

352

Tunable resonator-based devices for producing variable delays and narrow spectral linewidths  

NASA Technical Reports Server (NTRS)

Devices with two or more coupled resonators to produce narrow spectral responses due to interference of signals that transmit through the resonators and techniques for operating such devices to achieve certain operating characteristics are described. The devices may be optical devices where optical resonators such as whispering gallery mode resonators may be used. In one implementation, at least one of the coupled optical resonators is a tunable resonator and is tuned to change its resonance frequency to tune the spectral response of the device. The described devices and techniques may be applied in optical filters, optical delays, optical waveform generators, and other applications.

Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor); Matsko, Andrey B. (Inventor); Ilchenko, Vladimir (Inventor)

2006-01-01

353

Three-Dimensional Imaging of Pulmonary Veins by a Novel Steady-State Free-Precession Magnetic Resonance Angiography Technique Without the Use of Intravenous Contrast Agent: Initial Experience  

Microsoft Academic Search

Purpose: To evaluate the feasibility of 3-dimensional (3D) steady-state free-precession (SSFP) magnetic resonance angiography (MRA) using non- selective radiofrequency excitation for imaging of pulmonary veins (PVs) without intravenous gadolinium chelate and to correlate the results with conventional contrast-enhanced MRA (CE-MRA). Material and Methods: Forty consecutive patients with history of atrial fibrillation underwent free-breathing respiratory navigator-gated electrocar- diogram-triggered SSFP MRA without

Mayil S. Krishnam; Anderanik Tomasian; Sachin Malik; Aparna Singhal; Alex Sassani; Gerhard Laub; J. Paul Finn; Stefan Ruehm

2009-01-01

354

"Resonances" in the dielectric absorption of DNA?  

PubMed Central

An attempt was made to confirm previous reports of resonant-like dielectric absorption of plasmid DNA in aqueous solutions at 1-10 GHz. The dielectric properties of the sample were measured using an automatic network analyzer with two different techniques. One technique used an open-ended coaxial probe immersed in the sample; the other employed a coaxial transmission line. No resonances were observed that could be attributed to the sample; however, resonance-type artifacts were prominent in the probe measurements. The coaxial line technique appears to be less susceptible to such artifacts. We note two important sources of error in the calibration of the automatic network analyzer using the probe technique. PMID:3307930

Foster, K R; Epstein, B R; Gealt, M A

1987-01-01

355

Stochastic resonance in electrical circuits. II. Nonconventional stochastic resonance  

Microsoft Academic Search

For pt.I see ibid., vol.46, no.9, pp.1205-14 (1999). Stochastic resonance (SR), in which a periodic signal in a nonlinear system can be amplified by added noise, is discussed. The application of circuit modeling techniques to the conventional form of SR, which occurs in static bistable potentials, was considered in a companion paper. Here, the investigation of nonconventional forms of SR

Dmitrii G. Luchinsky; Riccardo Mannella; Peter V. E. McClintock; Nigel G. Stocks

1999-01-01

356

LA-UR-97-40 Magnetic Resonance Force Microscopy With a  

E-print Network

LA-UR-97-40 Magnetic Resonance Force Microscopy With a Ferromagnetic Tip Mounted on the Force Resonance Force Microscope (MRFM) presents the oppor- tunity for a magnetic resonance imaging probe MRFM techniques. A crucial remaining challenge in the development of the magnetic resonance force

Hammel, P. Chris

357

Multifrequency spin resonance in diamond  

SciTech Connect

Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating-wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers.

Childress, Lilian; McIntyre, Jean [Department of Physics and Astronomy, Bates College, 44 Campus Ave, Lewiston, Maine 04240 (United States)

2010-09-15

358

Ion cyclotron resonance cell  

DOEpatents

An ion cyclotron resonance cell having two adjacent sections separated by a center trapping plate. The first section is defined by the center trapping plate, a first end trapping plate, and excitation and detector electrodes. The second section includes a second end trapping plate spaced apart from the center plate, a mirror, and an analyzer. The analyzer includes a wavelength-selective light detector, such as a detector incorporating an acousto-optical device (AOD) and a photodetector. One or more ion guides, grounded plates with holes for the ion beam, are positioned within the vacuum chamber of the mass spectrometer between the ion source and the cell. After ions are trapped and analyzed by ion cyclotron resonance techniques in the first section, the ions of interest are selected according to their mass and passed into the second section for optical spectroscopic studies. The trapped ions are excited by light from a laser and caused thereby to fluoresce. The fluorescent light emitted by the excited ions is reflected by the mirror and directed onto the detector. The AOD is scanned, and the photodetector output is recorded and analyzed. The ions remain in the second section for an extended period, enabling multiple studies to be carried out on the same ensemble of ions.

Weller, Robert R. (Aiken, SC)

1995-01-01

359

Luminescence resonance energy transfer  

SciTech Connect

Fluorescence resonance energy transfer (FRET), in which a fluorescent donor molecule transfers energy via a nonradiative dipole-dipole interaction to an acceptor molecule (which is usually a fluorescent molecule), is a standard spectroscopic technique for measuring distances in the 10-70 Angstrom range. We have used a luminescent europium chelate as donor and an organic dye, CY-5, as acceptor. This luminescence resonance energy transfer (LRET) has several advantages over the more conventional FRET. The distance at which 50% of the energy is transferred (R[sub 0]) is large, 70 [angstrom]; the donor lifetime is single exponential and long (0.63 ms in H[sub 2]O; 2.5 ms in D[sub 2]O), making lifetime measurements facile and highly accurate; the orientation dependence (k[sup 2]) of energy transfer is minimized by the donor's multiple electronic transitions and long lifetime, limiting uncertainty in the measured distance due to orientation effects to [+-]12% in the worst case; the sensitized emission of the acceptor can be measured with little or no interfering background, yielding a >50-fold improvement in signal to background over standard donor-acceptor pairs and enabling distances several times R[sub 0] to be measured. 13 refs., 4 figs.

Selvin, P.R.; Rana, T.M.; Hearst, J.E. (Univ. of California, Berkeley, CA (United States) Lawrence Berkeley Lab., CA (United States))

1994-06-29

360

Qualitative and Quantitative Evaluation of IGF-1R Kinase Activity Based on Surface Plasmon Resonance Biosensor  

E-print Network

Resonance Biosensor Xueling Li1 , Minghui-huang2 , Jian-Long Zhao1* , and MengSu Yang1,2** 1 Shanghai resonance biosensor technique was used to study IGF-1R kinase activity on a new peptide substrate derived. The study demonstrated that surface plasmon resonance biosensor as a sensitive real-time technique may

Hefei Institute of Intelligent Machines

361

Indirect (J) coupling of inequivalent ^75As nuclei in crystalline and glassy As_2Se3 and As_2S_3  

NASA Astrophysics Data System (ADS)

Indirect nuclear spin-spin couplings, or J couplings, were first observed in liquids using nuclear magnetic resonance (NMR) techniques [1]. Because of the nature of the quadrupole Hamiltonian in pure nuclear quadrupole resonance (NQR) experiments J couplings should be observable between inequivalent nuclei [2]. We present results of ^75As NQR measurements in crystalline and glassy As_2S3 and As_2Se_3. These ^75As NQR measurements were performed at various frequencies between about 55 and 75 MHz. The NQR frequency is determined by the electric field gradient (EFG) at the nucleus, and in these materials there are two non-equivalent sites in each of the two crystals. The J coupling can occur through several chemical bonds, and in our case this coupling must go through two As-S covalent bonds since the nearest neighbor As sites are separated by chalcogen atoms. Instead of the monotonic decay expected from relaxation spin-spin theory, the decays of the NQR Hahn echoes following a 90^0-180^0pulse sequence exhibit damped oscillations superimposed on an exponential decay. These damped oscillations can be explained by an indirect coupling (J coupling). Experimental values of the J couplings were obtained from the periods of the oscillations and calculations of the most probable transitions using 2^nd order perturbation theory. The value estimated by this method for the ^2J(^75As-S-^75As) in crystalline As_2S3 compares well with empirical estimates, which are obtained using an existing value of ^2J(^31P-S-^31P) and known scalings with atomic number from the literature. 1. E. L. Hahn and D. E Maxwell, Phys. Rev. 84, 1246 (1951). 2. T. P. Das and E. L. Hahn, Solid State Physics, supp 1, Nuclear Quadrupole Resonance Spectroscopy, p. 28, Academic Press 1958.

Whitaker, J.; Ahn, E.; Hart, P.; Williams, G. A.; Taylor, P. C.; Facelli, J. C.

2004-03-01

362

Sb-NQR probe for superconducting properties in the Pr-based filled-skutterudite compound PrRu4Sb12  

NASA Astrophysics Data System (ADS)

We report the electronic and superconducting properties in the Pr-based filled-skutterudite superconductor PrRu4Sb12 with Tc=1.3 K via the measurements of nuclear-quadrupole-resonance frequency ?Q and nuclear-spin-lattice-relaxation time T1 of Sb nuclei. The temperature dependence of ?Q has revealed the energy scheme of Pr3+ crystal electric field that is consistent with an energy separation ?CEF˜70 K between the ground state and the first-excited state. In the normal state, the Korringa relation of (1/T1T)Pr=const is valid, with [(1/T1T)Pr/(1/T1T)La]1/2˜1.44, where (1/T1T)La is for LaRu4Sb12. These results are understood in terms of a conventional Fermi-liquid picture in which the Pr-4f2 state derives neither magnetic nor quadrupolar degrees of freedom at low temperatures. In the superconducting state, 1/T1 shows a distinct coherence peak just below Tc, followed by an exponential decrease with a value of 2?/kBTc=3.1. These results demonstrate that PrRu4Sb12 is a typical weak-coupling s-wave superconductor, in strong contrast with the heavy-fermion superconductor PrOs4Sb12 that is in an unconventional strong coupling regime. The present study on PrRu4Sb12 highlights that the Pr-4f2-derived nonmagnetic doublet plays a key role in the unconventional electronic and superconducting properties in PrOs4Sb12.

Yogi, M.; Kotegawa, H.; Imamura, Y.; Zheng, G.-Q.; Kitaoka, Y.; Sugawara, H.; Sato, H.

2003-05-01

363

Tunable Variable Bandwidth\\/Frequency SAW Resonators  

Microsoft Academic Search

A SAW resonator device is demonstrated such that 3 dB fractional bandwidths of .l% to .05% can be achieved in the same device prior to implementation of input\\/output matching networks. Such matching networks have a deleterious effect on shape factor and out-ofband rejection. The technique used is one in which two or more resonant SAW cavities are acoustically coupled in-line

Jeff Stuart Schoenwald; Teledyne HEC

1977-01-01

364

Numerical Investigations of High Pressure Acoustic Waves in Resonators  

NASA Technical Reports Server (NTRS)

This presentation presents work on numerical investigations of nonlinear acoustic phenomena in resonators that can generate high-pressure waves using acoustic forcing of the flow. Time-accurate simulations of the flow in a closed cone resonator were performed at different oscillation frequencies and amplitudes, and the numerical results for the resonance frequency and fluid pressure increase match the GRC experimental data well. Work on cone resonator assembly simulations has started and will involve calculations of the flow through the resonator assembly with and without acoustic excitation. A new technique for direct calculation of resonance frequency of complex shaped resonators is also being investigated. Script-driven command procedures will also be developed for optimization of the resonator shape for maximum pressure increase.

Athavale, Mahesh; Pindera, Maciej; Daniels, Christopher C.; Steinetz, Bruce M.

2004-01-01

365

Opto-electronic oscillators having optical resonators  

NASA Technical Reports Server (NTRS)

Systems and techniques of incorporating an optical resonator in an optical part of a feedback loop in opto-electronic oscillators. This optical resonator provides a sufficiently long energy storage time and hence to produce an oscillation of a narrow linewidth and low phase noise. Certain mode matching conditions are required. For example, the mode spacing of the optical resonator is equal to one mode spacing, or a multiplicity of the mode spacing, of an opto-electronic feedback loop that receives a modulated optical signal and to produce an electrical oscillating signal.

Yao, Xiaotian Steve (Inventor); Maleki, Lutfollah (Inventor); Ilchenko, Vladimir (Inventor)

2003-01-01

366

Quasi-resonant converters - Topologies and characteristics  

NASA Astrophysics Data System (ADS)

In designing switching dc-dc converters, the effort to increase operating frequency to reduce weight, size, and cost of magnetic and filter elements is constantly hampered by higher switching stresses and switching losses. To overcome these obstacles, the concept of the 'resonant switch' is proposed. By incorporating additional inductor and capacitor elements to shape the semiconductor switch's current waveform, a 'zero-current switching' property can be realized. Based on the resonant switch technique, a new host of quasi-resonant converter circuits have been derived, which can be operated in the megahertz range.

Liu, Kwang-Hwa; Oruganti, Ramesh; Lee, Fred C. Y.

1987-01-01

367

Wheatstone bridge piezoresistive sensing for bulk-mode micromechanical resonator  

NASA Astrophysics Data System (ADS)

A balanced wheatstone bridge technique for piezoresistive detection in micromechanical resonators is demonstrated. Two identical beam resonators, which vibrate in the length extensional mode with 180° phase shift, are connected in serial to compose a wheatstone bridge. With the differential actuation configuration, this approach eliminates the capacitive feedthrough signal, which may heavily bury the piezoresistive signal of the resonator in traditional piezoresistive sensing approach. The proposed technique is experimentally validated. Experimental results show that the capacitive signal embedded in the piezoresistive sensing approach is nearly eliminated. This method provides an effective way for purely piezoresistive sensing of micromechanical resonators.

Wu, Guoqiang; Xu, Dehui; Xiong, Bin; Wang, Yuelin

2012-11-01

368

Niobium stripline resonators for microwave studies on superconductors  

NASA Astrophysics Data System (ADS)

Microwave spectroscopy is a powerful experimental tool to reveal information on the intrinsic properties of superconductors. Superconducting stripline resonators, where the material under study constitutes one of the ground planes, offer a high sensitivity to investigate superconducting bulk samples. In order to improve this measurement technique, we have studied stripline resonators made of niobium, and we compare the results to lead stripline resonators. With this technique we are able to determine the temperature dependence of the complex conductivity of niobium and the energy gap ?(0) = 2.1 meV. Finally we show measurements at the superconducting transition of a tantalum bulk sample using niobium stripline resonators.

Thiemann, Markus; Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold; Dressel, Martin; Scheffier, Marc

2014-12-01

369

Advances in resonance based NDT for ceramic components  

NASA Astrophysics Data System (ADS)

The application of resonance based non-destructive testing methods has been providing benefit to manufacturers of metal components in the automotive and aerospace industries for many years. Recent developments in resonance based technologies are now allowing the application of resonance NDT to ceramic components including turbine engine components, armor, and hybrid bearing rolling elements. Application of higher frequencies and advanced signal interpretation are now allowing Process Compensated Resonance Testing to detect both internal material defects and surface breaking cracks in a variety of ceramic components. Resonance techniques can also be applied to determine material properties of coupons and to evaluate process capability for new manufacturing methods.

Hunter, L. J.; Jauriqui, L. M.; Gatewood, G. D.; Sisneros, R.

2012-05-01

370

The effect of the potential on the surface plasmon resonance at a metal-liquid interface  

E-print Network

the observed physical effects as compared to measuring without surface plasmon resonance (SPR). In the traditional SPR sensing technique the variations of the refractive index of the sample medium induce changes in the angle of the resonance excitation, thus...

Lioubimov, Vladimir

2012-06-07

371

Temperature Sensors Based on WGM Optical Resonators  

NASA Technical Reports Server (NTRS)

A proposed technique for measuring temperature would exploit differences between the temperature dependences of the frequencies of two different electromagnetic modes of a whispering gallery-mode (WGM) optical resonator. An apparatus based on this technique was originally intended to be part of a control system for stabilizing a laser frequency in the face of temperature fluctuations. When suitably calibrated, apparatuses based on this technique could also serve as precise temperature sensors for purposes other than stabilization of lasers. A sensor according to the proposal would include (1) a transparent WGM dielectric resonator having at least two different sets of modes characterized by different thermo-optical constants and (2) optoelectronic instrumentation for measuring the difference between the temperature-dependent shifts of the resonance frequencies of the two sets of modes.

Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute; Itchenko, Vladimir; Matsko, Andrey; Strekalov, Dmitry

2008-01-01

372

Modulation techniques  

NASA Technical Reports Server (NTRS)

Bandwidth efficient digital modulation techniques, proposed for use on and/or applied to satellite channels, are reviewed. In a survey of recent works on digital modulation techniques, the performance of several schemes operating in various environments are compared. Topics covered include: (1) quadrature phase shift keying; (2) offset - QPSK and MSK; (3) combined modulation and coding; and (4) spectrally efficient modulation techniques.

Schilling, D. L.

1982-01-01

373

Multipass modes in an open resonator  

NASA Astrophysics Data System (ADS)

The papers dealing with multipass modes in open stable resonators are reviewed. A numerical model of an axially symmetric resonator is described that permits the properties of multipass modes to be studied in wave approximation. It is shown that for Fresnel numbers larger than unity, multiple reflections of radiation from the stable resonator mirrors lead to sustained quasi-stationary field oscillations in the resonator which are indicative of the essential contribution of multipass modes. The calculations in filling the resonator with the active medium have been performed for two types of lasers: with the on-axis and off-axis gain maxima. Resonator designs are suggested, trajectory selection techniques are considered to provide high-quality radiation at large Fresnel numbers. The confocal resonator properties are analyzed in the context of competition between single-pass and multipass modes. Relying on the results of calculations for multipass mode generation, a critical analysis of the experimental works is presented suggesting a logical explanation for the peculiarities which had not been physically interpreted in the original publications. An advanced understanding of the physics of multipass mode formations allowed us to put forward a special design of stable resonators for the generation of high quality radiation in high-power lasers.

Niziev, V. G.; Grishaev, R. V.; Panchenko, V. Ya

2015-02-01

374

Integral resonator gyroscope  

NASA Technical Reports Server (NTRS)

The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor); Yee, Karl Y. (Inventor)

2008-01-01

375

Transverse Relaxation of Cu Nuclear Spins in YBa2Cu3O6.98  

Microsoft Academic Search

We have measured the transverse relaxation of the planar Cu(2) nuclear spins in an oriented powder sample of YBa2Cu3O6.98 (Tc{=}92 K) by using the nuclear quadrupole resonance (NQR) technique. Above Tc, after subtraction of the Tl process, the spin echo envelope decay follows a Gaussian form, and its time constant is almost independent of temperature. In the vicinity of Tc,

Yutaka Itoh; Hiroshi Yasuoka; Yutaka Ueda

1990-01-01

376

Interventional magnetic resonance imaging.  

PubMed

The development of minimally invasive surgical and interventional techniques has created a need for more accurate and sensitive image guidance and monitoring. Magnetic resonance imaging, with its superior soft tissue discrimination and multiplanar facilities, seems the obvious choice for an ideal image-guidance tool. Until recently, the employment of MRI in this role has been prevented by the physical constraints of conventional, closed-configuration machines. The problem has now been overcome by the development of an open design allowing both horizontal and vertical access to the patient in the scanner so that procedures can be performed concurrent with image acquisition. This configuration, together with the use of fast gradient echo sequences which can scan at speeds close to real time, means that a wide range of interventional procedures can be performed with on-line image guidance and monitoring. In addition, the versatility of the open design means that patients can assume physiological positions to allow dynamic joint imaging to be performed. This opens up a whole new field in the understanding of joint pathophysiology. This review article discusses these recent technological developments and their clinical applications. In particular, the potential role in guidance of biopsies, monitoring of thermal ablation techniques and applications in endoscopic surgery is outlined. PMID:9534721

Lamb, G M; Gedroyc, W M

1997-11-01

377

Nuclear magnetic double resonance based on strong rf magnetic-field-induced coupling between spin systems  

Microsoft Academic Search

The origin of the rf magnetic-field-induced coupling between spin systems is discussed. A new nuclear-double-resonance technique employing this coupling is proposed, which has particular value in measuring pure nuclear-quadrupole-resonance spectra of integer-spin nuclei by nuclear double resonance. The sensitivity of the new technique is discussed for the case of 1H-14N double resonance in zero static magnetic field, as well as

J. Seliger; R. Blinc; M. Mali; R. Osredkar; A. Prelesnik

1975-01-01

378

Nanomechanical resonance detector  

DOEpatents

An embodiment of a nanomechanical frequency detector includes a support structure and a plurality of elongated nanostructures coupled to the support structure. Each of the elongated nanostructures has a particular resonant frequency. The plurality of elongated nanostructures has a range of resonant frequencies. An embodiment of a method of identifying an object includes introducing the object to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the object. An embodiment of a method of identifying a molecular species of the present invention includes introducing the molecular species to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the molecular species.

Grossman, Jeffrey C; Zettl, Alexander K

2013-10-29

379

Neutron resonance averaging  

SciTech Connect

The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

Chrien, R.E.

1986-10-01

380

Teaching Techniques  

E-print Network

the topic using other techniques. It is important that you know each member. Teaching Techniques Several teaching techniques are available: lecture, illus- trated talk, discussion, question and answer, demonstra- tion, work session or practical exercise... about the various shapes and distinguishing characteristics of insects, sketch them on a large sheet of paper or blackboard or show an actual specimen or picture. When the topic discussed is in the members? guide, you can have them follow along. 3...

Howard, Jeff W.

2005-05-10

381

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

TECHNOLOGICAL PROGRESS: Although cardiac magnetic resonance imaging (MRI) is now recognised as the imaging method of choice for the morphological study of the heart, recent technological progress have widened its indications to functional analysis of the heart rate, perfusion and contractility. FUNCTIONAL ASSESSMENT: The possibility of conducting pharmacological stress tests enhances the functional exploration of cardiac perfusion and contractility. The rapid sequences in apnea, tissue marking and injection of contrast products are all elements that help to refine the study of the locoregional consequences of an ischemia: does the myocardial tissue contract normally? Is it sufficiently perfused? Is it still viable? THE BENEFITS OF A NON-INVASIVE TECHNIQUE: The MRI offers clinicians a non-invasive and non-radiating imaging technique that is the perfect supplement to echocardiography. A reliable angio-coronary LRI technique would, for the first time, permit exploration of the coronary vascularisation, tissue perfusion and resulting contractility. PMID:15387389

Vignaux, Olivier

2004-07-31

382

Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Author's preface; 1. Introduction; 2. Basic theory; 3. Experimental methods; 4. Measurement of nuclear properties and general physical applications; 5. Nuclear magnetic resonance in liquids and gases; 6. Nuclear magnetic resonance in non-metallic solids; 7. Nuclear magnetic resonance in metals; 8. Quadrupole effects; Appendices 1-6; Glossary of symbols; Bibliography and author index; Subject index.

Andrew, E. R.

2009-06-01

383

Ovenized microelectromechanical system (MEMS) resonator  

DOEpatents

An ovenized micro-electro-mechanical system (MEMS) resonator including: a substantially thermally isolated mechanical resonator cavity; a mechanical oscillator coupled to the mechanical resonator cavity; and a heating element formed on the mechanical resonator cavity.

Olsson, Roy H; Wojciechowski, Kenneth; Kim, Bongsang

2014-03-11

384

Direct determination of state-to-state rotational energy transfer rate constants via a Raman-Raman double resonance technique: ortho-acetylene in v(2)=1 at 155 K.  

PubMed

A new technique for the direct determination of state-to-state rotational energy transfer rate constants in the gas phase is presented. It is based on two sequential stimulated Raman processes: the first one prepares the sample in a single rotational state of an excited vibrational level, and the second one, using the high resolution quasi-continuous stimulated Raman-loss technique, monitors the transfer of population to other rotational states of the same vibrational level as a function of the delay between the pump and the probe stages. The technique is applied to the odd-J rotational states of v(2)=1 acetylene at 155 K. The experimental layout, data acquisition, retrieval procedures, and numerical treatment are described. The quantity and quality of the data are high enough to allow a direct determination of the state-to-state rate constant matrix from a fit of the experimental data, with the only conditions of detailed balance and of a closed number of states. The matrix obtained from this direct fit is also compared with those obtained using some common fitting and scaling laws. PMID:20423177

Doménech, José L; Martínez, Raúl Z; Ramos, Angel; Bermejo, Dionisio

2010-04-21

385

Science Drivers and Technical Challenges for Advanced Magnetic Resonance  

SciTech Connect

This report recaps the "Science Drivers and Technical Challenges for Advanced Magnetic Resonance" workshop, held in late 2011. This exploratory workshop's goal was to discuss and address challenges for the next generation of magnetic resonance experimentation. During the workshop, participants from throughout the world outlined the science drivers and instrumentation demands for high-field dynamic nuclear polarization (DNP) and associated magnetic resonance techniques, discussed barriers to their advancement, and deliberated the path forward for significant and impactful advances in the field.

Mueller, Karl T.; Pruski, Marek; Washton, Nancy M.; Lipton, Andrew S.

2013-03-07

386

Secular resonances. [of asteroidal dynamics  

NASA Technical Reports Server (NTRS)

Theories and numerical experiments regarding secular resonances are reviewed. The basic dynamics and the positions of secular resonances are discussed, and secular perturbation theories for the nu16 resonance case, the nu6 resonance, and the nu5 resonance are addressed. What numerical experiments have revealed about asteroids located in secular resonances, the stability of secular resonances, variations of eccentricities and inclinations, and chaotic orbits is considered. Resonant transport of meteorites is discussed.

Scholl, H.; Froeschle, CH.; Kinoshita, H.; Yoshikawa, M.; Williams, J. G.

1989-01-01

387

The composite nature of the $?(1520)$ resonance  

E-print Network

Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the $\\Lambda(1520)$ resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-waves $\\pi\\Sigma^*$, $K\\Xi^*$ and the d-waves $\\bar{K}N$ and $\\pi\\Sigma$ channels applying the techniques of the chiral unitary approach. We obtain that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only $15 \\%$ weight of other kind of components into its wave function.

F. Aceti; E. Oset; L. Roca

2014-04-24

388

Composite nature of the ? (1520) resonance  

NASA Astrophysics Data System (ADS)

Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the ? (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave ??* and K? * and the d-wave K¯N and ?? channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of components in its wave function.

Aceti, F.; Oset, E.; Roca, L.

2014-08-01

389

Magnetic resonance on correlated semimetals: the case of U2Ru2Sn, CeRu4Sn6 and FeSb2  

NASA Astrophysics Data System (ADS)

A comparative magnetic resonance study on correlated semiconductors is presented. Nuclear spin-lattice relaxation measurements provide an excellent method to gain local information about the gap formation in this new class of materials. In contrast to U2Ru2Sn (?/kB approx 230 K) in CeRu4Sn6 the gap is slightly reduced (?/kB approx 200 K) and correlations form out of a residual density of states in the gap. For FeSb2 there is revived interest after classifying this system as the second Fe containing Kondo insulator beside FeSi. Surprisingly, FeSb2 shows a colossal Seebeck coefficient at low temperatures. Using 121,123Sb nuclei as a local probe, our NMR/NQR investigations strongly support the gap scenario. The spin-lattice relaxation rate 123(1/T1) in the entire investigated temperature range 2-200 K is perfectly fitted with rectangle DOS model with narrow impurity in-gap band. These in-gap states might originate the high thermopower observed. The obtained gap value is (?/kB approx 473 K).

Gippius, A. A.; Baenitz, M.; Rajarajan, A. K.; Bruening, E. M.; Okhotnikov, K.; Walstedt, R.; Strydom, A.; Mydosh, J.; Steglich, F.

2009-03-01

390

Efficient Techniques of ANN-Based Microwave  

E-print Network

.g., sintering) MW NDE/NDT Technique Where Used W F CW F CW F CW F C WorkshopWorkshopWorkshopWorkshop #12 in closed systems ­ an attractive technology of NDE/NDT capable of serving many practical needs. W F CW F CW of all the proposed techniques: NDE/NDT of objects in closed systems (resonators or waveguides

Yakovlev, Vadim

391

Continuous-wave 355-nm laser source based on doubly resonant sum-frequency mixing in an external resonator  

SciTech Connect

Using doubly resonant sum-frequency mixing between 1064 and 532 nm in an external resonator, we obtained 186 mW of continuous-wave ultraviolet output at {lambda}=355 nm with more than 20% conversion efficiency from the total incident power onto the mixing cavity. The resonator mirrors are shared by both the 1064a nd the 532-nm beams, yielding an optimum mode overlap between the two resonating modes. To maintain the simultaneous resonance, we locked the external resonator to the single-frequency green laser and locked the 1064-nm laser to the resonator. This technique can be applied to cw sum- or difference-frequency mixing of any two wavelengths. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

Kaneda, Y.; Kubota, S. [Kubota Opto-Electronics Laboratory, Sony Research Center, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141 (Japan)

1995-11-01

392

Split-resonator integrated-post MEMS gyroscope  

NASA Technical Reports Server (NTRS)

A split-resonator integrated-post vibratory microgyroscope may be fabricated using micro electrical mechanical systems (MEMS) fabrication techniques. The microgyroscope may include two gyroscope sections bonded together, each gyroscope section including resonator petals, electrodes, and an integrated half post. The half posts are aligned and bonded to act as a single post.

Bae, Youngsam (Inventor); Hayworth, Ken J. (Inventor); Shcheglov, Kirill V. (Inventor)

2004-01-01

393

Extremely Low Phase Noise SAW Resonator Oscillator Design and Performance  

Microsoft Academic Search

SAW resonator designs with overnioded cavities. very wide apertures. dual apertures, etc.. as well as modified fabrication techniques. have been used to realize an overall reduction in an oscillator's phase noise spectrum. i.e.. white +M. flicker FM. and random walk FM. The incident RF power handling capability of these SAW resonator designs is in excess of +20 dBm. a key

G. K. Montress; T. E. Parker; M. J. Loboda

1987-01-01

394

Determination of Membrane Protein Structure by Rotational Resonance NMR: Bacteriorhodopsin  

Microsoft Academic Search

Rotationally resonant magnetization exchange, a new nuclear magnetic resonance (NMR) technique for measuring internuclear distances between like spins in solids, was used to determine the distance between the C-8 and C-18 carbons of retinal in two model compounds and in the membrane protein bacteriorhodopsin. Magnetization transfer between inequivalent spins with an isotropic shift separation, delta, is driven by magic angle

F. Creuzet; A. McDermott; R. Gebhard; K. van der Hoef; M. B. Spijker-Assink; J. Herzfeld; J. Lugtenburg; M. H. Levitt; R. G. Griffin

1991-01-01

395

Performance of a wide FSR optical double ring resonator  

Microsoft Academic Search

This article presents a scheme of an optical ring resonator using digital signal processing technique. A very high free spectral range (FSR) is of paramount importance for commercial WDM system. Here the frequency response characteristics of a double ring resonator has been tailored up to an FSR of 200 GHz using delay line signal processing and Mason's rule.

Sabita Brata Dey; S. Mandal

2009-01-01

396

Distributed Active Filters for Harmonic Resonance Suppression in Industrial Facilities  

Microsoft Academic Search

Significant harmonics amplification in industry facilities has been reported. This phenomenon is identified as harmonic resonance between power factor correction capacitor banks and system inductors. Conventional active filter techniques aimed at harmonic current compensation are not effective under this resonance situation. This paper proposes a distributed active filter design for harmonics damping within industry facility. In this system, the active

Shen-Yuan Kuo; Tzung-Lin Lee; Chien-An Chen; Po-Tai Cheng; Ching-Tsai Pan

2007-01-01

397

Optical Helmholtz resonators  

NASA Astrophysics Data System (ADS)

Helmholtz resonators are widely used acoustic components able to select a single frequency. Here, based on an analogy between acoustics and electromagnetism wave equations, we present an electromagnetic 2D Helmholtz resonator made of a metallic slit-box structure. At the resonance, the light is funneled in the ?/800 apertures, and is subsequently absorbed in the cavity. As in acoustics, there is no higher order of resonance, which is an appealing feature for applications such as photodetection or thermal emission. Eventually, we demonstrate that the slit is of capacitive nature while the box behaves inductively. We derive an analytical formula for the resonance wavelength, which does not rely on wave propagation and therefore does not depend on the permittivity of the material filling the box. Besides, in contrast with half-wavelength resonators, the resonance wavelength can be engineered by both the slit aspect ratio and the box area.

Chevalier, Paul; Bouchon, Patrick; Haïdar, Riad; Pardo, Fabrice

2014-08-01

398

Local resonance bandgaps in periodic media: theory and experiment.  

PubMed

Periodic composites such as acoustic metamaterials use local resonance phenomenon in designing low frequency sub-Bragg bandgaps. These bandgaps emerge from a resonant scattering interaction between a propagating wave and periodically arranged resonators. This paper develops a receptance coupling technique to combine the dynamics of the resonator with the unit cell dynamics of the background medium to analyze flexural wave transmission in a periodic structure, involving a single degree of freedom coupling between the medium and the resonator. Receptance techniques allow for a straightforward extension to higher dimensional systems with multiple degrees of freedom coupling and for easier experimental measurements. Closed-form expressions for the location and width of sub-Bragg bandgaps are obtained. Rigid body modes of the unit cell of the background medium are shown to set the bounding frequencies for local resonance bandgaps. Results from the receptance analysis compare well with Bloch wave analysis and experiments performed on a finite structural beam with periodic masses and resonators. Stronger coupling and inertia of the resonator increase the local resonance bandgap width. Two-fold periodicity widens the Bragg bandgap, narrowed by local resonators, thus expanding the design space and highlighting the advantages of hierarchical periodicity. PMID:23967928

Raghavan, L; Phani, A Srikantha

2013-09-01

399

Some Applications of Neutron Resonance Capture Analysis  

SciTech Connect

The probability for nuclei to capture neutrons reveals sharp peaks, so-called 'resonances', which occur at neutron energies specific for each element. These resonances are very suitable for identifying and quantifying elements in objects and materials. They are the basis of an analytical method called 'Neutron-Resonance-Capture-Analysis' (NRCA). This is a fully non-destructive method applicable to almost all stable isotopes, which determines the bulk elemental composition, and does not require any sample preparation and results in negligible residual activity. Up to now NRCA has been mostly applied for archaeological applications. In this paper we review the technique and discuss the applicability of the technique in the biomedical field and in material science.

Postma, H.; Perego, R. C. [IRI, TU-Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Borella, A.; Siegler, P.; Wynants, R.; Schillebeeckx, P. [EC-JRC-IRMM, Retieseweg 111, B-2440 Gee (Belgium)l

2005-05-24

400

Magnetic resonance lymphography in gynaecological malignancies  

PubMed Central

Abstract Following the submission of this article to Cancer Imaging, unfortunately the European manufacturer of ferumoxtran-10 (Guerbet) has withdrawn the product pending further phase III studies. This is secondary to the view of the Committee for Medicinal Products for Human Use that the phase III data did not provide adequate statistical demonstration of the product's efficacy. Magnetic resonance lymphography holds much promise for the non-invasive evaluation of lymph nodes. The technique utilizes ultrasmall superparamagnetic particles of iron oxide and has been shown to be highly sensitive and specific in the diagnosis of malignant lymph nodes. This article reviews the technique and the performance of magnetic resonance lymphography in studies to date; alternative newer methods of nodal assessment such as fluorodeoxyglucose-positron emission tomography/computed tomography and diffusion-weighted magnetic resonance imaging are also discussed, with emphasis on gynaecological malignancies. PMID:20233680

Narayanan, Priya; Rockall, Andrea

2010-01-01

401

Acoustic ringing effects in pulsed nuclear magnetic resonance probes  

Microsoft Academic Search

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed.

M. L. Buess; G. L. Petersen

1978-01-01

402

Acoustic ringing effects in pulsed nuclear magnetic resonance probes.  

PubMed

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed. PMID:18699271

Buess, M L; Petersen, G L

1978-08-01

403

Magnetic Resonance Imaging Method For Estimating Cone Of Uncertainty  

Cancer.gov

The National Institute of Child Health and Human Development (NICHD), Section on Tissue Biophysics and Biomimetics, is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize magnetic resonance imaging techniques.

404

Ureteric access sheath aided insertion of resonance metal ureteric stent.  

PubMed

Ureteral obstruction caused by malignancy is a challenging and often complicated problem for urologists. We present a novel technique of ureteric access sheath aided insertion of a Resonance metal ureteric stent in the setting of a difficult obstruction. PMID:24879725

Winter, Matthew; Strahan, Stephen; Wines, Michael

2014-01-01

405

Electron Spin Resonance in Studies of Membranes and Proteins  

NSDL National Science Digital Library

We provide a review of current electron spin resonance (ESR) techniques for studying basic molecular mechanisms in membranes and proteins by using nitroxide spin labels. We illustrate these capabilities with recent examples.

P. P. Borbat (Cornell University;Baker Laboratory of Chemistry and Chemical Biology); A.J. Costa-Filho (Cornell University;Baker Laboratory of Chemistry and Chemical Biology); K.A. Earle (Cornell University;Baker Laboratory of Chemistry and Chemical Biology); J.K. Moscicki (Cornell University/Jagellonian University;Baker Laboratory of Chemistry and Chemical Biology/Smoluchowski Institute of Physics); J.H. Freed (Cornell University;Baker Laboratory of Chemistry and Chemical Biology)

2001-01-12

406

Model-based reconstruction of magnetic resonance spectroscopic imaging  

E-print Network

Magnetic resonance imaging (MRI) is a medical imaging technique that is used to obtain images of soft tissue throughout the body. Since its development in the 1970s, MRI has gained tremendous importance in clinical practice ...

Chatnuntawech, Itthi

2013-01-01

407

Explosives detection with quadrupole resonance analysis  

Microsoft Academic Search

The increase in international terrorist activity over the past decade has necessitated the exploration of new technologies for the detection of plastic explosives. Quadrupole resonance analysis (QRA) has proven effective as a technique for detecting the presence of plastic, sheet, and military explosive compounds in small quantities, and can also be used to identify narcotics such as heroin and cocaine

Timothy J. Rayner; Benjamin D. Thorson; Simon Beevor; Rebecca West; Ronald A. Krauss

1997-01-01

408

Myocardial tissue tagging with cardiovascular magnetic resonance  

Microsoft Academic Search

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional

Monda L Shehata; Susan Cheng; Nael F Osman; David A Bluemke; João AC Lima

2009-01-01

409

STROBOSCOPIC ARTICULOGRAPHY USING FAST MAGNETIC RESONANCE IMAGING  

Microsoft Academic Search

A method to display dynamic aspects of vocal tract configuration during speech production by means of fast magnetic resonance imaging (MRI) is presented. Data acquisition during repetitive movement relies on a stroboscopy-like procedure. The time res- olution achieved is 120 images per second in a selected plane. As compared to other techniques of kinematic measurements of speech motor processes, this

K. Mathiak; U. Klose; H. Ackermann; I. Hertrich; W.-E. Kincses; W. Grodd

410

Magnetic Resonance Imaging in Lewy Body Dementias  

Microsoft Academic Search

Dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) share common clinical, neuropsychological and pathological features. In clinical diagnosis, distinguishing between these conditions and other dementia subtypes such as Alzheimer’s disease (AD) can be difficult. Despite the development of consensus diagnostic criteria, sensitivity for diagnosis remains low, especially outside specialist centres. Neuroimaging techniques using magnetic resonance (MR) can assess

Rosie Watson; Andrew M. Blamire; John T. O’Brien

2009-01-01

411

Direct Phase Noise Measurements of SAW Resonators  

Microsoft Academic Search

The most significant contribution of SAW resonators is in the frequency control of low phase noise oscillators at UHF frequencies. Techniques for measuring the phase noise of oscillators are well known, but the contribution to that phase noise of the frequency determining element is usually estimated or found by indirect methods. We present a method for directly measuring the phase

Scott S. Elliott; Robert C. Bray

1984-01-01

412

Analytical Methods for Characterizing Magnetic Resonance Probes  

PubMed Central

SUMMARY The efficiency of Gd(III) contrast agents in magnetic resonance image enhancement is governed by a set of tunable structural parameters. Understanding and measuring these parameters requires specific analytical techniques. This Feature describes strategies to optimize each of the critical Gd(III) relaxation parameters for molecular imaging applications and the methods employed for their evaluation. PMID:22624599

Manus, Lisa M.; Strauch, Renee C.; Hung, Andy H.; Eckermann, Amanda L.; Meade, Thomas J.

2012-01-01

413

Magnetic Resonance Imaging in Endodontic Treatment Prediction  

Microsoft Academic Search

The necessary condition for successful endodontic treatment is the precise mapping of the shape of dental cavities. The aim of this work has been an elaboration and verification of the possibility of using three-dimensional (3D) spin echo magnetic resonance imaging (MRI) techniques in dentistry. Six extracted molar teeth were used for measurements without additional preparation and after endodontic preparation. MRI

Marta Tanasiewicz

2010-01-01

414

Imaging Intelligence with Proton Magnetic Resonance Spectroscopy  

ERIC Educational Resources Information Center

Proton magnetic resonance spectroscopy ([to the first power]H-MRS) is a technique for the assay of brain neurochemistry "in vivo." N-acetylaspartate (NAA), the most prominent metabolite visible within the [to the first power]H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA-cognition…

Jung, Rex E.; Gasparovic, Charles; Chavez, Robert S.; Caprihan, Arvind; Barrow, Ranee; Yeo, Ronald A.

2009-01-01

415

Resonances on hedgehog manifolds  

E-print Network

We discuss resonances for a nonrelativistic and spinless quantum particle confined to a two- or three-dimensional Riemannian manifold to which a finite number of semiinfinite leads is attached. Resolvent and scattering resonances are shown to coincide in this situation. Next we consider the resonances together with embedded eigenvalues and ask about the high-energy asymptotics of such a family. For the case when all the halflines are attached at a single point we prove that all resonances are in the momentum plane confined to a strip parallel to the real axis, in contrast to the analogous asymptotics in some metric quantum graphs; we illustrate it on several simple examples. On the other hand, the resonance behaviour can be influenced by a magnetic field. We provide an example of such a `hedgehog' manifold at which a suitable Aharonov-Bohm flux leads to absence of any true resonance, i.e. that corresponding to a pole outside the real axis.

Pavel Exner; Jiri Lipovsky

2013-02-21

416

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1  

E-print Network

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1 F inversion CAI technique in magnetic-resonance force microscopy MRFM . We study the problem: What component.67.Lx I. INTRODUCTION Magnetic-resonance force microscopy MRFM is striv- ing for its ultimate goal

Goan, Hsi-Sheng

417

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single-Spin Measurement  

E-print Network

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single using magnetic resonance force microscopy (MRFM) with a cyclic adiabatic inversion (CAI). This technique, 14].) One of them is based on a magnetic resonance force microscopy (MRFM). A MRFM was first proposed

Hammel, P. Chris

418

Magnetic resonance microscopy of embryos.  

PubMed

We demonstrate that magnetic resonance (MR) microscopy provides a mechanism to investigate normal and abnormal developmental anatomy in a non-destructive and distortion-free manner. Techniques for the fixation, embedding, perfusion and image acquisition of embryos between 3 and 30 mm crown rump length are described. We describe the perfusion of a contrast agent to enhance images of the developing embryonic vasculature. Data are acquired as three-dimensional isotropic arrays which permit images to be reformatted retrospectively in any plane. The data are available for archiving, distributing and for post-acquisition manipulations. MR microscopy is a fast technique for producing three-dimensional reconstructions and is free from registration and sectioning artifacts. PMID:9007215

Smith, B R; Linney, E; Huff, D S; Johnson, G A

1996-01-01

419

Advances in cardiac magnetic resonance imaging of congenital heart disease.  

PubMed

Due to advances in cardiac surgery, survival of patients with congenital heart disease has increased considerably during the past decades. Many of these patients require repeated cardiovascular magnetic resonance imaging to assess cardiac anatomy and function. In the past decade, technological advances have enabled faster and more robust cardiovascular magnetic resonance with improved image quality and spatial as well as temporal resolution. This review aims to provide an overview of advances in cardiovascular magnetic resonance hardware and acquisition techniques relevant to both pediatric and adult patients with congenital heart disease and discusses the techniques used to assess function, anatomy, flow and tissue characterization. PMID:25552386

Driessen, Mieke M P; Breur, Johannes M P J; Budde, Ricardo P J; van Oorschot, Joep W M; van Kimmenade, Roland R J; Sieswerda, Gertjan Tj; Meijboom, Folkert J; Leiner, Tim

2015-01-01

420

Application of Modal Sensitivity for Power System Harmonic Resonance Analysis  

SciTech Connect

Abstract—Harmonic resonance is closely related to the singularity of a network admittance matrix. The smallest eigenvalue of the matrix defines the mode of harmonic resonance. This paper applies this eigenvalue theory and proposes a method to determine which network components have significant contributions to a harmonic resonance phenomenon. The basic idea is to calculate the sensitivities of a resonance mode to the parameters of network components. The sensitivity results are then ranked to quantify the impact of each component. In this paper, the eigen-sensitivity theory as applied to harmonic resonance mode analysis is presented. Case studies are used to verify the theory. A practical example is given to illustrate the application of the proposed method. In addition, this paper further conducts extensive comparative analysis on three types of network oriented modal analysis techniques. The results have clarified the similarities and differences among the techniques.

Huang, Zhenyu; Cui, Yu; Xu, Wilsun

2007-02-15

421

Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators  

NASA Technical Reports Server (NTRS)

Techniques and devices using whispering gallery mode (WGM) optical resonators, where the optical materials of the WGM resonators exhibit an electro-optical effect to perform optical modulation. Examples of actively mode-locked lasers and other devices are described.

Matsko, Andrey B. (Inventor); Ilchenko, Vladimir (Inventor); Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor)

2006-01-01

422

Aseptic Technique  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET delves into aseptic technique and how to work under a laminar airflow hood. Using animations, quizzes, games, and a final evaluation, this interactive lesson will help students understand the lab and important techniques for biology technicians.

423

Miscellaneous Techniques  

NASA Astrophysics Data System (ADS)

Nondestructive way of determining the food quality is the need of the hour. Till now major methods such as colour measurements and their modeling; machine vision systems; X-ray, CT and MRI; NIR spectroscopy; electronic nose and tongue; and ultrasonic technology have been discussed in detail. These techniques, in general, are considered to be sophisticated and costly, and therefore probably are not being adopted as fast as it should be. I am however of the reverse opinion. While going through these techniques, it has been seen that majority of quality parameters have been measured and correlated with the signals obtained using different equipment.

Jha, Shyam N.

424

Acoustic resonance for nonmetallic mine detection  

SciTech Connect

The feasibility of acoustic resonance for detection of plastic mines was investigated by researchers at the Oak Ridge National Laboratory`s Instrumentation and Controls Division under an internally funded program. The data reported in this paper suggest that acoustic resonance is not a practical method for mine detection. Representative small plastic anti-personnel mines were tested, and were found to not exhibit detectable acoustic resonances. Also, non-metal objects known to have strong acoustic resonances were tested with a variety of excitation techniques, and no practical non-contact method of exciting a consistently detectable resonance in a buried object was discovered. Some of the experimental data developed in this work may be useful to other researchers seeking a method to detect buried plastic mines. A number of excitation methods and their pitfalls are discussed. Excitation methods that were investigated include swept acoustic, chopped acoustic, wavelet acoustic, and mechanical shaking. Under very contrived conditions, a weak response that could be attributed to acoustic resonance was observed, but it does not appear to be practical as a mine detection feature. Transfer properties of soil were investigated. Impulse responses of several representative plastic mines were investigated. Acoustic leakage coupling, and its implications as a disruptive mechanism were investigated.

Kercel, S.W.

1998-04-01

425

Mass spectrometry. [review of techniques  

NASA Technical Reports Server (NTRS)

Advances in mass spectrometry (MS) and its applications over the past decade are reviewed in depth, with annotated literature references. New instrumentation and techniques surveyed include: modulated-beam MS, chromatographic MS on-line computer techniques, digital computer-compatible quadrupole MS, selected ion monitoring (mass fragmentography), and computer-aided management of MS data and interpretation. Areas of application surveyed include: organic MS and electron impact MS, field ionization kinetics, appearance potentials, translational energy release, studies of metastable species, photoionization, calculations of molecular orbitals, chemical kinetics, field desorption MS, high pressure MS, ion cyclotron resonance, biochemistry, medical/clinical chemistry, pharmacology, and environmental chemistry and pollution studies.

Burlingame, A. L.; Kimble, B. J.; Derrick, P. J.

1976-01-01

426

MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW  

PubMed Central

Magnetic Resonance Elastography (MRE) is a rapidly developing technology for quantitatively assessing the mechanical properties of tissue. The technology can be considered to be an imaging-based counterpart to palpation, commonly used by physicians to diagnose and characterize diseases. The success of palpation as a diagnostic method is based on the fact that the mechanical properties of tissues are often dramatically affected by the presence of disease processes such as cancer, inflammation, and fibrosis. MRE obtains information about the stiffness of tissue by assessing the propagation of mechanical waves through the tissue with a special magnetic resonance imaging (MRI) technique. The technique essentially involves three steps: generating shear waves in the tissue,acquiring MR images depicting the propagation of the induced shear waves andprocessing the images of the shear waves to generate quantitative maps of tissue stiffness, called elastograms. MRE is already being used clinically for the assessment of patients with chronic liver diseases and is emerging as a safe, reliable and noninvasive alternative to liver biopsy for staging hepatic fibrosis. MRE is also being investigated for application to pathologies of other organs including the brain, breast, blood vessels, heart, kidneys, lungs and skeletal muscle. The purpose of this review article is to introduce this technology to clinical anatomists and to summarize some of the current clinical applications that are being pursued. PMID:20544947

Mariappan, Yogesh K; Glaser, Kevin J; Ehman, Richard L

2011-01-01

427

35Cl nuclear quadrupolar resonance study of 4,4'-dichlorobiphenyl sulphone  

Microsoft Academic Search

Pulsed NQR spectroscopy was used to search for a structural phase transition from a normal to an incommensurate phase and others in 4,4'-dichlorobiphenyl sulphone. The experimental results show the existence of a structural phase transition to an incommensurate phase at 150 K and another transition to a possible commensurate phase at 110 K.

J. M. Corberó; A. E. Wolfenson; D. J. Pusiol; A. H. Brunetti

1986-01-01

428

Hacking Techniques  

Microsoft Academic Search

With tales of hacked networks and websites being reported by the media daily, people assume that hacking must be easy. But, in truth, the tools and techniques employed by hackers are extremely complex, utilizing a broad range of technologies. The number of mechanisms for breaking into systems, whatever the objective, is on the increase with new tools emerging continuously. This

Richard Barber

2001-01-01

429

A Resonant Damping Study Using Piezoelectric Materials  

NASA Technical Reports Server (NTRS)

Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

2008-01-01

430

NMR techniques in the study of cardiovascular structure and functions  

SciTech Connect

The chapter titles of this book are: Introduction to NMR Techniques;Theory of NMR Probe Design;Overview of Magnetic Resonance Imaging to Study the Cardiovascular System;Vascular Anatomy and Physiology Studied with NMR Techniques;Assessment of Myocardial Ischemia and Infarction by Nuclear Magnetic Resonance Imaging;The Use of MRI in Congenital Heart Disease;Cardiomyopathies and Myocarditis Studied with NMR Techniques;Determination of Myocardial Mechanical Function with Magnetic Resonance Imaging Techniques;Determination of Flow Using NMR Techniques;The Use of Contrast Agents in Cardiac MRI;Can Cardiovascular Disease Be Effectively Evaluated with NMR Spectroscopy. NMR Studies of ATP Synthesis Reactions in the Isolated Heart;Studies of Intermediary Metabolism in the Heart by 13C NMR Spectroscopy;23Na and 39K NMR Spectroscopic Studies of the Intact Beating Heart;and Evaluation of Skeletal Muscle Metabolism in Patients with Congestive Heart Failure Using Phosphorus Nuclear Magnetic Resonance.

Osbakken, M.; Haselgrove, J.

1987-01-01

431

Resonant control of solitons  

NASA Astrophysics Data System (ADS)

It is shown that the effect of “scattering on resonance” can be used to control envelope solitons in the driven nonlinear Schrödinger equation. The control occurs by the frequency modulated driving with multiple crossing of the resonant frequency of the soliton.

Batalov, S. V.; Shagalov, A. G.

2013-05-01

432

Nanoengineering of optical resonances  

Microsoft Academic Search

Metal nanoshells, consisting of a dielectric core with a metallic shell of nanometer thickness, are a new, composite nanoparticle whose optical resonance can be “designed in” in a controlled manner. By varying the relative dimensions of the core and shell, the optical resonance of these nanoparticles can be varied over hundreds of nanometers in wavelength, across the visible and into

S. J. Oldenburg; R. D. Averitt; S. L. Westcott; N. J. Halas

1998-01-01

433

Nuclear Quadrupole Resonance  

Microsoft Academic Search

Nuclear quadrupole resonance is a recently developed branch of radio-frequency spectroscopy which is concerned with magnetic resonance absorption in crystals. This absorption is due to reorientation of the nonspherical atomic nuclei against crystalline electric fields. Related phenomena in isolated molecules are briefly mentioned in the Introduction A. This is followed in Sec. B by an elementary treatment of the electrostatic

H. G. Dehmelt

1954-01-01

434

Helioseismology The Resonant Sun  

E-print Network

Helioseismology The Resonant Sun Professor Bill Chaplin, School of Physics & Astronomy University Eddington #12;The Unseen Interior ''At first sight it would seem that the deep interior of the sun and stars;Overview What are resonant oscillations of the Sun? How do we observe the oscillations? What can we learn

435

The resonator handbook  

NASA Technical Reports Server (NTRS)

The purpose of this work is to extend resonator theory into the region in which the planar mirror is quite small. Results of the theoretical description are then extended to resonator design and experimental arrangements as discussed in further sections of this work. Finally, a discussion of dielectric measurements for small samples is included as a specific application of this work.

Cook, Jerry D.; Zhou, Shiliang

1993-01-01

436

MEMS resonator temperature compensation  

Microsoft Academic Search

This paper presents the study of an electromechanical resonator temperature compensation principle. It consists in the use of a coating material presenting opposite properties over temperature compared to the silicon resonator structural material. Simulated results, using the FEM Coventor® software, show the great potential of this CMOS compatible principle for industrial perspectives.

F. Casset; C. Durand; Y. Civet; E. Ollier; J. F. Carpentier; P. Ancey; P. Robert

2010-01-01

437

New microwave gas detector using dielectric resonator based on a whispering-gallery-mode  

Microsoft Academic Search

This work describes a novel concept of gas sensor based on RF-transduction technique. The sensor uses a millimeter-wave planar dielectric resonator operating with Whispering-Gallery-Modes. The dielectric resonator incorporates a sensitive material (TiO2 or SnO2) and two coplanar waveguides coupled to its input and output. In presence of gas, the dielectric permittivity of the resonator is modified and the resonant frequencies

Hamida Hallil; Philippe Ménini; Hervé Aubert

2009-01-01

438

Resonant snubber inverter  

DOEpatents

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 14 figs.

Lai, J.S.; Young, R.W. Sr.; Chen, D.; Scudiere, M.B.; Ott, G.W. Jr.; White, C.P.; McKeever, J.W.

1997-06-24

439

Polaritonic Feshbach resonance  

NASA Astrophysics Data System (ADS)

A Feshbach resonance occurs when the energy of two interacting free particles comes into resonance with a molecular bound state. When approaching this resonance, marked changes in the interaction strength between the particles can arise. Feshbach resonances provide a powerful tool for controlling the interactions in ultracold atomic gases, which can be switched from repulsive to attractive, and have allowed a range of many-body quantum physics effects to be explored. Here we demonstrate a Feshbach resonance based on the polariton spinor interactions in a semiconductor microcavity. By tuning the energy of two polaritons with anti-parallel spins across the biexciton bound state energy, we show an enhancement of attractive interactions and a prompt change to repulsive interactions. A mean-field two-channel model quantitatively reproduces the experimental results. This observation paves the way for a new tool for tuning polariton interactions and to move forward into quantum correlated polariton physics.

Takemura, N.; Trebaol, S.; Wouters, M.; Portella-Oberli, M. T.; Deveaud, B.

2014-07-01

440

Resonant snubber inverter  

DOEpatents

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Lai, Jih-Sheng (Knoxville, TN); Young, Sr., Robert W. (Oak Ridge, TN); Chen, Daoshen (Knoxville, TN); Scudiere, Matthew B. (Oak Ridge, TN); Ott, Jr., George W. (Knoxville, TN); White, Clifford P. (Knoxville, TN); McKeever, John W. (Oak Ridge, TN)

1997-01-01

441

Nanofabrication Techniques  

NSDL National Science Digital Library

This page from Foothill-De Anza Community College describes a course on nanoscience for those who need an introduction to the subject. This course is the fifth in a five course series that leads to a certificate in nanoscience, nanotechnology, and nanomaterials engineering. Students will obtain a survey of fabrication techniques as well as "hands-on experience creating thin film materials, and quality control 'shadowing' in a clean energy technology fabrication facility." The projects required by the class are also described.

2012-11-08

442

ON A NONLINEAR PARTIAL DIFFERENTIAL EQUATION ARISING IN MAGNETIC RESONANCE ELECTRICAL  

E-print Network

, which is electrical impedance tomography technique integrated with magnetic resonance imaging of a human body by means of the electrical impedance tomography(EIT) technique integrated with the magneticON A NONLINEAR PARTIAL DIFFERENTIAL EQUATION ARISING IN MAGNETIC RESONANCE ELECTRICAL IMPEDANCE

443

Evidence for Unconventional Strong-Coupling Superconductivity in PrOs4Sb12: An Sb Nuclear Quadrupole Resonance Study  

Microsoft Academic Search

We report Sb-NQR results which evidence a heavy-fermion (HF) behavior and an unconventional superconducting (SC) property in Pr(Os4Sb12 with Tc=1.85 K. The temperature (T) dependence of nuclear-spin-lattice-relaxation rate, 1\\/T1, and NQR frequency unravel a low-lying crystal-electric-field splitting below T0˜10 K, associated with Pr3+(4f2)-derived ground state. In the SC state, 1\\/T1 shows neither a coherence peak just below Tc K nor

H. Kotegawa; M. Yogi; Y. Imamura; Y. Kawasaki; G.-Q. Zheng; Y. Kitaoka; S. Ohsaki; H. Sugawara; Y. Aoki; H. Sato

2003-01-01

444

Mode Profiles in Waveguide-Coupled Resonators  

NASA Technical Reports Server (NTRS)

Surface acoustic wave (SAW) waveguide-coupled resonators are of considerable interest for narrow-band filter applications, though to date there has been very little published on the acoustic details of their operation. As in any resonator, one must fully understand its mode structure and herein we study the SAW mode profiles in these devices. Transverse mode profiles in the resonant cavity of the device were measured at various frequencies of interest using a knife-edge laser probe. In addition we predict the mode profiles for the device structure by two independent methods. One is a stack-matrix approach adapted from integrated optics and the other is a conventional analytical eigenmode analysis of the Helmholtz equation. Both modeling techniques are in good agreement with the measured results.

Hunt, William D.; Cameron, Tom; Saw, John C. B.; Kim, Yoonkee

1993-01-01

445

Normal state spin susceptibility in YBa 2Cu 3O 6.92 single crystal from 63Cu and 89Y nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We present an extensive nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) study of the normal state ( T> Tc) of an YBa 1.93Sr 0.07Cu 3O 6.92 single crystal ( Tc=90 K). The NMR data is interpreted using a model for the imaginary part of the dynamical electron spin susceptibility ??( q, ?) that is consistent with the inelastic neutron scattering (INS) experiments (carried out on the same sample investigated here): the q-dependence is assumed to be Gaussian (commensurate), with short and T independent coherence length ?. This model enabled us to perform a quantitative analysis of the planar copper spin-lattice and spin-spin relaxation rates which evidenced that a spin pseudogap starts to open at T*?130 K, confirming the INS results. Moreover, we show that the AF fluctuations contribution to yttrium relaxation is not negligible due to the dipolar coupling of the yttrium with the neighboring copper spins. The main signature of this feature is that a relation K??T1T=const does not hold for the yttrium site at higher temperatures. Our main conclusion is that, in order to explain the yttrium (and the planar oxygen) relaxation coherently with the INS results and the widely accepted one-band picture, the characteristic energy ?0 of the spin dynamics near q=0 must be strongly T dependent, otherwise the one-band description is not feasible. All the NMR results are interpreted within the ionic model of the hyperfine Hamiltonian taking into account the anisotropy of the g-factor and the static spin susceptibility ?s.

Auler, T.; Horvatic, M.; Gillet, J. A.; Berthier, C.; Berthier, Y.; Carretta, P.; Kitaoka, Y.; Ségransan, P.; Henry, J. Y.

1999-02-01

446

"Inventing new MRI techniques and applying them to important clinical  

E-print Network

"Inventing new MRI techniques and applying them to important clinical problems." Craig Meyer Engineering University of Virginia Charlottesville, VA 434.243.9495 MRI Research Group Our research focuses on inventing, developing and using new magnetic resonance imaging (MRI) techniques, especially techniques

Acton, Scott

447

LABCOM resonator Phase 3  

SciTech Connect

The purpose of this project was to develop quartz crystal resonator designs, production processes, and test capabilities for 5-MHz, 6.2-MHz, and 10-MHz resonators for Tactical Miniature Crystal Oscillator (TMXO) applications. GE Neutron Devices (GEND) established and demonstrated the capability to produce and test quartz crystal resonators for use in the TMXO developed by the US Army ERADCOM (now LABCOM). The goals in this project were based on the ERADCOM statement of work. The scope of work indicated that the resonator production facilities for this project would not be completely independent, but that they would be supported in part by equipment and processes in place at GEND used in US Department of Energy (DOE) work. In addition, provisions for production test equipment or or eventual technology transfer costs to a commercial supplier were clearly excluded from the scope of work. The demonstrated technical capability of the deep-etched blank design is feasible and practical. It can be manufactured in quantity with reasonable yield, and its performance is readily predictable. The ceramic flatpack is a very strong package with excellent hermeticity. The four-point mount supports the crystal to reasonable shock levels and does not perturb the resonator's natural frequency-temperature behavior. The package can be sealed with excellent yields. The high-temperature, high-vacuum processing developed for the TMXO resonator, including bonding the piezoid to its mount with conductive polyimide adhesive, is consistent with precision resonator fabrication. 1 fig., 6 tabs.

Keres, L.J.

1990-11-01

448

Surface plasmon resonance in protein–membrane interactions  

Microsoft Academic Search

Surface plasmon resonance (SPR) has become one of the most important techniques for studying macromolecular interactions. The most obvious advantages of SPR over other techniques are: direct and rapid determination of association and dissociation rates of binding process, no need for labelling of protein or lipids, and small amounts of sample used in the assay (often nM concentrations of proteins).

Mojca Beseni?ar; Peter Ma?ek; Jeremy H. Lakey; Gregor Anderluh

2006-01-01

449

Fabrication of cubic micron-scale 3D metamaterial resonators.  

SciTech Connect

We present a new fabrication technique called Membrane Projection Lithography for the production of three-dimensional metamaterials at infrared wavelengths. Using this technique, multilayer infrared metamaterials that include both in-plane and out-of-plane resonators can be fabricated.

Sinclair, Michael B.; Brener, Igal; Wendt, Joel Robert; Burckel, David Bruce; Ten Eyck, Gregory A.

2010-06-01

450

Applications of nuclear magnetic resonance imaging in process engineering  

Microsoft Academic Search

During the past decade, the application of nuclear magnetic resonance (NMR) imaging techniques to problems of relevance to the process industries has been identified. The particular strengths of NMR techniques are their ability to distinguish between different chemical species and to yield information simultaneously on the structure, concentration distribution and flow processes occurring within a given process unit. In this

Lynn F. Gladden; Paul Alexander

1996-01-01

451

Resonant optical antennas.  

PubMed

We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations that take into account the finite metallic conductivity at optical frequencies. Because optical antennas link propagating radiation and confined/enhanced optical fields, they should find applications in optical characterization, manipulation of nanostructures, and optical information processing. PMID:15947182

Mühlschlegel, P; Eisler, H-J; Martin, O J F; Hecht, B; Pohl, D W

2005-06-10

452

Tunable multiwalled nanotube resonator  

DOEpatents

A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

2013-11-05

453

Tunable multiwalled nanotube resonator  

DOEpatents

A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

Zettl, Alex K. (Kensington, CA); Jensen, Kenneth J. (Berkeley, CA); Girit, Caglar (Albany, CA); Mickelson, William E. (San Francisco, CA); Grossman, Jeffrey C. (Berkeley, CA)

2011-03-29

454

Explosives detection with quadrupole resonance analysis  

NASA Astrophysics Data System (ADS)

The increase in international terrorist activity over the past decade has necessitated the exploration of new technologies for the detection of plastic explosives. Quadrupole resonance analysis (QRA) has proven effective as a technique for detecting the presence of plastic, sheet, and military explosive compounds in small quantities, and can also be used to identify narcotics such as heroin and cocaine base. QRA is similar to the widely used magnetic resonance (MR) and magnetic resonance imaging (MRI) techniques, but has the considerable advantage that the item being inspected does not need to be immersed in a steady, homogeneous magnetic field. The target compounds are conclusively identified by their unique quadrupole resonance frequencies. Quantum magnetics has develop and introduced a product line of explosives and narcotics detection devices based upon QRA technology. The work presented here concerns a multi-compound QRA detection system designed to screen checked baggage, cargo, and sacks of mail at airports and other high-security facilities. The design philosophy and performance are discussed and supported by test results from field trials conducted in the United States and the United Kingdom. This detection system represents the current state of QRA technology for field use in both commercial and government sectors.

Rayner, Timothy J.; Thorson, Benjamin D.; Beevor, Simon; West, Rebecca; Krauss, Ronald A.

1997-02-01