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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, M. L.; Yesinowski, J. P.; Miller, J. 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.

2006-06-01

3

Optimised NQR pulse technique for the effective detection of Heroin Base.  

PubMed

The nuclear quadrupole resonance (NQR) method has been applied to Heroin Base (HB) to find an optimised multi-pulse technique for effective detection of HB. Experimental results of applying the proposed spin-locking multi-pulse (SLMP) technique to nitrogen-14 NQR in this sample are presented and convincingly demonstrate as a path towards efficient detection. A detection using a sequence of this character could be achieved over real-world scan volumes for screening of goods. All experiments were carried out at room temperature. PMID:18342493

Rudakov, T N; Hayes, P A; Flexman, J H

2008-03-01

4

New technologies: nuclear quadrupole resonance as an explosive and narcotic detection technique  

Microsoft Academic Search

Possibilities of detecting nuclear quadrupole resonance (NQR) signals in explosives and drugs are considered. Direct and indirect NQR techniques for searching substances are described and the potentialities of various experimental methods are compared.

Vadim S Grechishkin; Nikolai Ya Sinyavskii

1997-01-01

5

INSTRUMENTS AND METHODS OF INVESTIGATION: New technologies: nuclear quadrupole resonance as an explosive and narcotic detection technique  

NASA Astrophysics Data System (ADS)

Possibilities of detecting nuclear quadrupole resonance (NQR) signals in explosives and drugs are considered. Direct and indirect NQR techniques for searching substances are described and the potentialities of various experimental methods are compared.

Grechishkin, Vadim S.; Sinyavskii, Nikolai Ya

1997-04-01

6

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

7

Multi-Frequency Resonances in Pure Multiple-Pulse NQR  

NASA Astrophysics Data System (ADS)

We have observed multi-frequency resonances in a system with a spin 3/2 irradiated simultaneously by a multiple-pulse radiofrequency sequence and a low frequency field swept in the range 0 ÷ 80 kHz. The theoretical description of the effect is presented using both the rotating frame approximation and the Floquet theory. Both approaches give indentical results at the calculation of the resonance frequencies, transition probabilities and shifts of resonance frequency. The calculated magnetization vs. the frequency of the low-frequency field agrees with the obtained experimental data.

Furman, G. B.; Kibrik, G. E.; Polyakov, A. Yu.

2004-12-01

8

Nuclear quadrupole resonance detection of explosives: an overview  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a spectroscopic technique closely related to Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI). These techniques, and NQR in particular, induce signals from the material being interrogated that are very specific to the chemical and physical structure of the material, but are relatively insensitive to the physical form of the material. NQR explosives detection exploits this specificity to detect explosive materials, in contrast to other well known techniques that are designed to detect explosive devices. The past two decades have seen a large research and development effort in NQR explosives detection in the United States aimed at transportation security and military applications. Here, I will briefly describe the physical basis for NQR before discussing NQR developments over the past decade, with particular emphasis on landmine detection and the use of NQR in combating IED's. Potential future directions for NQR research and development are discussed.

Miller, Joel B.

2011-05-01

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

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

11

Pulsed Spin Locking in Spin-1 NQR: Broadening Mechanisms  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a branch of magnetic resonance physics that allows for the detection of spin I > 1/2 nuclei in crystalline and semi-crystalline materials. Through the application of a resonant radio frequency (rf) pulse, the nuclei's response is to create an oscillating magnetic moment at a frequency unique to the target substance. This creates the NQR signal, which is typically weak and rapidly decaying. The decay is due to the various line broadening mechanisms, the relative strengths of which are functions of the specific material, in addition to thermal relaxation processes. Through the application of a series of rf pulses the broadening mechanisms can be refocused, narrowing the linewidth and extending the signal in time. Three line broadening mechanisms are investigated to explain the NQR signal's linewidth and behavior. The first, electric field gradient (EFG) inhomogeneity, is due to variations in the local electric environment among the target nuclei, for instance from crystal imperfections. While EFG inhomogeneity can vary between samples of the same chemical composition and structure, the other broadening mechanisms of homonuclear and heteronuclear dipolar coupling are specific to this composition and structure. Simple analytical models are developed that explain the NQR signal response to pulse sequences by accounting for the behavior of each broadening mechanism. After a general theoretical introduction, a model of pairs of spin-1 nuclei is investigated, and the refocusing behaviors of EFG and homonuclear dipolar coupling are analyzed. This reveals the conditions where EFG is refocused but homonuclear dipolar coupling is not. In this case the resulting signal shows a rapid decay, the rate of which becomes a measure of interatomic distances. This occurs even in the more complex case of a powder sample with its many randomly oriented crystallites, under particular pulsing conditions. Many target NQR compounds are rich in hydrogen, and therefore might have a significant heteronuclear dipolar coupling component. To incorporate this, a second model is developed composed of two different nuclear species, one spin 1 the other spin 1/2, although the work can be extended to additional spin species. This model reveals that heteronuclear dipolar coupling for this system behaves just like EFG broadening under spin locking, and that the strong homonuclear response is still observable. The experimental results closely match theoretical predictions, and the conclusions greatly expand the number of target substances that are suitable for this measurement technique of homonuclear dipolar coupling. The combined results explain why certain pulse sequences perform better than others for substance detection: it is because of the relative strengths of the line broadening mechanisms. Therefore the ability to measure homonuclear dipolar coupling's contribution to the linewidth is useful not only for material characterization, but also for substance detection. By explaining the conditions that reveal homonuclear coupling, we make it possible to measure the relative broadening strengths, increasing the efficiency of NQR in these roles.

Malone, Michael W.

12

Application of the spherical tensor method for Two-Frequency pure NQR of spin I =1 nuclei  

Microsoft Academic Search

The results of a theoretical investigation of two-frequency excitation in pure nuclear quadrupole resonance (NQR) for a spinI=1 nucleus with a nonaxial elecric field gradient are presented. The multipole tensor operator technique is used for the treatment\\u000a of the one- and two-frequency pulse excitations. The results are applied to the characterization of the two-frequency signal\\u000a of nitrogen14N nuclei. The experiments

G. V. Mozjoukhine

2002-01-01

13

Numerical simulation of NQR/NMR: Applications in quantum computing.  

PubMed

A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php. PMID:21324720

Possa, Denimar; Gaudio, Anderson C; Freitas, Jair C C

2011-04-01

14

Stark effect of 14N NQR in single crystals of ferroelectric NaNO2  

Microsoft Academic Search

The effects of the external electric field on 14N nuclear quadrupole resonance (NQR) have been investigated in the ferroelectric phase of sodium nitrite (NaNO2) single crystals with either the single domain or the multidomain structure. NQR measurements of two resonance lines of n and n were made at 77 K under the external electric field up to 25 kV\\/cm. The

S. H. Choh; Y. J. Park; H. K. Kim; Y. M. Chang

1989-01-01

15

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

16

Optimal filtering in multipulse sequences for nuclear quadrupole resonance detection  

NASA Astrophysics Data System (ADS)

The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of explosive and narcotic substances has been studied. Various approaches to increase the signal to noise ratio (SNR) of signal detection are considered. We discussed two modifications of the phase-alternated multiple-pulse sequence (PAMS): the 180° pulse sequence with a preparatory pulse and the 90° pulse sequence. The advantages of optimal filtering to detect NQR in the case of the coherent steady-state precession have been analyzed. It has been shown that this technique is effective in filtering high-frequency and low-frequency noise and increasing the reliability of NQR detection. Our analysis also shows the PAMS with 180° pulses is more effective than PSL sequence from point of view of the application of optimal filtering procedure to the steady-state NQR signal.

Osokin, D. Ya.; Khusnutdinov, R. R.; Mozzhukhin, G. V.; Rameev, B. Z.

2014-05-01

17

Radio-frequency tunable atomic magnetometer for detection of solid-state NQR  

NASA Astrophysics Data System (ADS)

We constructed a potassium atomic magnetometer which resonantly detects rf magnetic fields with subfemtotesla sensitivity. The resonance frequency is set by the Zeeman resonance of the potassium atoms in a static magnetic field applied to the magnetometer cell. Strong optical pumping of the potassium atoms into a stretched state reduces spin-exchange broadening of the Zeeman resonance, resulting in relatively small linewidth of about 200 Hz (half-width at half-maximum). The magnetometer was used to detect ^14N NQR signal from powdered ammonium nitrate at 423 kHz, with sensitivity an order of magnitude higher than with a conventional room temperature pickup coil with comparable geometry. The demonstrated sensitivity of 0.24 fT/Hz^1/2 can be improved by several means, including use of higher power lasers for pumping and probing. Our technique can potentially be used to develop a mobile, open-access NQR spectrometer for detection of nitrogen-containing solids of interest in security applications.

Lee, S.-K.; Sauer, K. L.; Seltzer, S. J.; Alem, O.; Romalis, M. V.

2007-06-01

18

Investigation of Structural Information for Boron - Solids and Aluminates via NMR and Nqr Studies.  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) has been prevailed in investigating local structures for a variety of materials: various oxide glasses, zeolites, superconductors, etc. Since glasses have short range ordered structures instead of long range ordered ones in crystals, NMR is usually more useful in determining the local structures for many glasses than any other detection methods do. Along with NMR, Nuclear Quadrupole Resonance (NQR) has become important recently for obtaining structural information from such glasses. The NQR studies prove in this thesis that they provide more accurate structural information than the NMR studies have done. This study presents boron and aluminum NMR, and NQR studies for some borate glasses and compounds, icosahedral boron-rich solids, some crystalline aluminosilicates. Various borates were employed to acquire structural information as well as to determine the quadrupole parameters (the quadrupole coupling constant Q_{cc } and the asymmetry parameter eta ) using NQR under a guidance of NMR or vice versa. By NQR a previously unknown boron site was observed for vitreous Li_2OcdotB _2O_3. The boron site had an intermediate Q_{cc } value in-between the reported value ranges of Q_{cc} for BO _3 and BO_4 sites, and was concluded to be a previously unknown BO _4 site. The NMR and NQR studies were performed on some icosachedral boron-rich solids: alpha -rhombohedral boron (B_{12}), beta-boron (B_{105 }) and boron carbide (B_{12 }C_3). Strong NQR responses were obtained from boron atoms in the C-B-C chains along with several other NQR responses from boron atoms in the icosahedral. These NQR results were consistent with the NMR studies by Silver and Bray, and those by Hynes and Alexander. Also, for the icosahedral boron-rich solids, the ^{11}B NMR studies revealed the possibility of chemical shifts due to two distinct boron sites in the icosahedra. A very interesting phenomenon was found from an isotopic change of boron nuclei (substitution of ^{10}B for ^{11}B) in boron carbide: in ^{11}B high field (7.05 Tesla) NMR spectra, two distinct peaks separated by some chemical shifts for unenriched boron carbide (B _{12}C_3) became a single peak for ^{10} B enriched boron carbide (90.61 at.% of ^{10}B). Three different forms of crystalline aluminosilicate (Al_2SiO_5) were studied by NQR. The NQR study yielded more accurate values of the quadrupole parameters for ^ {27}Al than the previous NMR single crystal study did.

Lee, Donghoon

19

Low-frequency nuclear quadrupole resonance with a dc SQUID  

SciTech Connect

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

Chang, J.W.

1991-07-01

20

Cooperative Phenomenon of Ferromagnetism and Unconventional Superconductivity in UGe2: A 73Ge-NQR Study under Pressure  

Microsoft Academic Search

We report on a cooperative phenomenon of ferromagnetism and unconventional superconductivity (SC) in UGe2 through the measurements of 73Ge nuclear-quadrupole-resonance (NQR) under pressure (P). The NQR spectra evidenced phase separation into ferromagnetic and paramagnetic phases in the vicinity of Pc˜ 1.5 GPa, pointing to a first-order transition. The measurements of nuclear-spin-lattice-relaxation-rate 1\\/T1 revealed that SC emerges under the background of

Atsushi Harada; Shinji Kawasaki; Hisashi Kotegawa; Yoshio Kitaoka; Yoshinori Haga; Etsuji Yamamoto; Yoshichika Onuki; K. M. Itoh; Eugene Haller; Hisatomo Harima

2005-01-01

21

Cooperative Phenomenon of Ferromagnetism and Unconventional Superconductivity in UGe2: A 73Ge-NQR Study under Pressure  

NASA Astrophysics Data System (ADS)

We report on a cooperative phenomenon of ferromagnetism and unconventional superconductivity (SC) in UGe2 through the measurements of 73Ge nuclear-quadrupole-resonance (NQR) under pressure (P). The NQR spectra evidenced phase separation into ferromagnetic and paramagnetic phases in the vicinity of Pc˜ 1.5 GPa, pointing to a first-order transition. The measurements of nuclear-spin-lattice-relaxation-rate 1/T1 revealed that SC emerges under the background of ferromagnetism, but not of the paramagnetic phase.

Harada, A.; Kawasaki, S.; Kotegawa, H.; Kitaoka, Y.; Haga, Y.; Yamamoto, E.; ?nuki, Y.; Itoh, K. M.; Haller, E. E.; Harima, H.

2005-10-01

22

FPGA based pulsed NQR spectrometer  

NASA Astrophysics Data System (ADS)

An NQR spectrometer for the frequency range of 1 MHz to 5 MHZ has been designed constructed and tested using an FPGA module. Consisting of four modules viz. Transmitter, Probe, Receiver and computer controlled (FPGA & Software) module containing frequency synthesizer, pulse programmer, mixer, detection and display, the instrument is capable of exciting nuclei with a power of 200W and can detect signal of a few microvolts in strength. 14N signal from NaNO2 has been observed with the expected signal strength.

Hemnani, Preeti; Rajarajan, A. K.; Joshi, Gopal; Motiwala, Paresh D.; Ravindranath, S. V. G.

2014-04-01

23

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

24

14N NQR in the tetrazole family  

NASA Astrophysics Data System (ADS)

14N NQR frequencies and spin-lattice relaxation times were measured in technologically important 5-aminotetrazole and 5-aminotetrazole monohydrate at different temperatures between 77 K and 300 K. Five NQR triplets ?+, ?- and ?0 were found for the five inequivalent nitrogen atoms in each compound between 0.7 MHz and 4 MHz. Carr-Purcell based multipulse sequences were used to accumulate quadrupole echo signals before the FFT analysis. Assignment of the frequencies to atomic positions was made and the results are analysed in relation to the molecular chemical bonds and possible H-bonds in the crystal structures. The new NQR frequencies are reasonably related to the previously published NQR spectrum of the third family member, 1H-tetrazole.

Pirnat, Janez; Lužnik, Janko; Jazbinšek, Vojko; Žagar, Veselko; Seliger, Janez; Klapötke, Thomas M.; Trontelj, Zvonko

2009-10-01

25

Low-temperature nuclear quadrupole resonance studies of antimony and application to thermometry  

Microsoft Academic Search

The spin-lattice retaxation time, Tsb1, of finely divided powdered metallic antinomy immersed in liquid sp3He was measured using pulsed Nuclear Quadrupole Resonance (NQR) techniques. In this technique, the nuclear quadrupole resonant antinomy nuclei were saturated using an RF pulse. The recovery back to equilibrium was monitored using short inspection pulses and the magnetization recovery follows a recovery curve characterized by

Edgar Baylon Genio

1997-01-01

26

Resonant Wave-Particle Manipulation Techniques  

NASA Astrophysics Data System (ADS)

Charged particle dynamics can be altered considerably even by weak electromagnetic waves if some of the particles are in resonance. Depending on the wave parameters, the resonances in the phase space can either be well separated, in which case the particle dynamics is regular almost everywhere, or they can overlap leading to stochastic particle motion in a large volume of the phase space. Although different, both of these regimes allow one to manipulate particle ensembles by arranging resonant interactions with appropriate waves. This thesis is devoted to studying two wave-particle manipulation techniques having potential applications in fusion and laser-plasma interaction research. Specifically, we study the alpha-channeling effect (which relies on stochastic diffusion of resonant particles) and the so-called negative-mass effect (NME) (which involves the conservation of the adiabatic invariant). The alpha-channeling effect entails the use of radio-frequency waves to expel and cool high-energetic alpha particles born in a fusion reactor; the device reactivity can then be increased even further by redirecting the extracted energy to fuel ions. Recently, the alpha-channeling technique, originally proposed for tokamaks, was shown to be suitable for application in mirror machines as well. In the first part of this thesis, we deepen the understanding of issues and possibilities of the alpha-channeling implementation in open-ended reactors. We verify the feasibility of this technique and identify specific waves and supplementary techniques, which can potentially be used for implementing the alpha-channeling in realistic mirror devices. We also propose a new technique for using the alpha-channeling wave energy to catalyze fusion reaction by employing minority ions as a mediator species. In the second part of this thesis, the NME manifesting itself as an unusual response of a resonant particle to external adiabatic perturbations mimicking the behavior of a particle with a negative mass, is discussed. Using the Hamiltonian perturbation theory, the calculation of the effective parallel mass is extended to the non-vacuum waves and the NME is shown to be robust. Also, the consequences of radiation friction and collisions with the background particles on the NME are studied and new collective phenomena emerging in plasmas with negative-mass particles are considered.

Zhmoginov, Andrey I.

27

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.

Fagan, Andrew J.

2012-01-01

28

A general numerical analysis of time-domain NQR experiments.  

PubMed

We introduce a general numerical approach for solving the Liouville equation of an isolated quadrupolar nuclide that can be used to analyze the unitary dynamics of time-domain NQR experiments. A numerical treatment is necessitated by the dimensionality of the Liouville space, which precludes analytical, closed form solutions for I > 3/2. Accurate simulations of experimental nutation curves, forbidden transition intensities, powder and single crystal spectra, and off-resonance irradiation dynamics can be computed with this method. We also examine the validity of perturbative approximations where the signal intensity of a transition is proportional to the transition moment between the eigenstates of the system, thus providing a simple basis for determining selection rules. Our method allows us to calculate spectra for all values of the asymmetry parameter, eta, and sample orientations relative to the coil axis. We conclude by demonstrating the methodology for calculating the response of the quadrupole system to amplitude- and frequency-modulated pulses. PMID:16996760

Harel, Elad; Cho, Herman

2006-12-01

29

State equations based resonant converters modeling technique  

Microsoft Academic Search

State equations for resonant converters are developed by using orthogonal circuit synthesis. Low frequency state variables are selected for the resonant circuit, such as envelopes of resonant inductor current and resonant capacitor voltage, phase angle between inverter output voltage and output current. For a given resonant tank, its orthogonal counterpart is constructed. These two orthogonal tanks are combined into a

Yingqi Zhang; P. C. Sen

2010-01-01

30

Pressure and temperature dependence of the chlorine NQR in caesium and sodium chlorates.  

PubMed

The (35)Cl nuclear quadrupole resonance (NQR) frequencies (nu(Q)) in caesium and sodium chlorates were measured as a function of temperature, from 77 to 300 K at different pressures up to 5.1 kbar, and the data were analysed to estimate the volume dependence of the electric field gradient (EFG), torsional frequency and also the contributions to the NQR frequency from static and dynamic effects. The variation of spin-lattice relaxation time with pressure at different temperatures was studied in the case of sodium chlorate and at room temperature in case of caesium chlorate. The pressure dependence of the spin-lattice relaxation time (T(1)) suggests that the relaxation is mainly due to the torsional motions. PMID:18324738

Ramesh, K P; Suresh, K S; Raghavendra Rao, C; Ramakrishna, J

2008-06-01

31

Magnetic penetration depth measurements with the microstrip resonator technique  

Microsoft Academic Search

The microstrip resonator technique is a convenient way to sensitively measure the temperature dependence of the magnetic penetration depth ?(T) in superconducting thin films. Because the method relies on measuring the resonant frequency of a high-Q transmission line resonator at microwave frequencies, one can very precisely measure small changes in ?(T). This technique is applied to studying the low-temperature dependence

S. M. Anlage; B. W. Langley; H. J. Snortland; C. B. Eom; T. H. Geballe; M. R. Beasley

1990-01-01

32

Ru NQR Probe of Superconducting Property in Impurity-Doped CeRu 2  

Microsoft Academic Search

Superconducting characteristics of CeRu2 have been investigated by systematic measurements of the nuclear-spin lattice relaxation rate, 1\\/T1 of 101Ru on pure and impurity-substituted CeRu2, employing an NQR technique in zero magnetic field. (1\\/T1) for CeRu2 shows a broad coherence plateau just below T c followed by an exponential decrease well below T c. By contrast, a distinct coherence peak of

Hidekazu Mukuda; Kenji Ishida; Yoshio Kitaoka; Kunisuke Asayama

1998-01-01

33

NQR Line Broadening Due to Crystal Lattice Imperfections and Its Relationship to Shock Sensitivity  

NASA Astrophysics Data System (ADS)

The hydrodynamic hot spot model is used to explain the difference between shock sensitive and shock insensitive explosives. Among the major factors that influence the shock sensitivity of energetic compounds are the quality and particle size of the energetic crystals used to formulate the cast plastic bonded explosive. As do all energetic compounds, RDX and HMX exhibit internal crystal defects the magnitude and type of which depend on the manufacturing process used to synthesize and re-crystallize the energetic compound. Nuclear Quadrupole Resonance (NQR) spectroscopy was used to determine the crystal quality of RDX, HMX and CL-20 obtained from various manufacturers. The NQR experimental results are discussed. Cast plastic bonded explosives were made using the RDX and HMX obtained from the various manufacturers and subsequently subjected to the NOL large-scale gap test (LSGT). The results of the LSGT are discussed and correlated with the NQR results. A relationship between the crystal defect density and shock initiation pressure of the plastic bonded explosive is developed and discussed.

Caulder, S. M.; Buess, M. L.; Garroway, A. N.; Miller, P. J.

2004-07-01

34

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 C2221 and P21 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

35

35Cl-NQR and DFT study of electronic structure of amlodipine and felodipine vascular-selective drugs from the dihydropyridine Ca ++ antagonists group  

NASA Astrophysics Data System (ADS)

Amlodipine (AM) and felodipine (FL) have been studied in solid state by the nuclear quadrupole resonance (NQR) and density functional theory (DFT). The results have shown that NQR data do not permit a differentiation between R and S enantiomers, which is a consequence of the symmetry of the 4-aryl ring, whereas they permit a differentiation between free bases and salts. The HOMO-LUMO gap is smaller for AM than for FL, which suggests smaller energy of excitation for AM. The absolute hardness, chemical potential and electrophilicity of both AM enantiomers are lower than the corresponding values for FL enantiomers, suggesting that AM should be more reactive than FL in unimolecular reactions.

Latosi?ska, J. N.; Latosi?ska, M.; Kasprzak, J.

2008-09-01

36

Multiple-pulse NQR dynamics of spin systems with strong heteronuclear coupling  

NASA Astrophysics Data System (ADS)

The results are presented of a theoretical consideration of the nuclear quadrupole resonance (NQR) and spin—spin relaxation for a paramagnetic body containing nuclei of two different sorts coupled by the strong homonuclear and heteronuclear dipole—dipole interactions and influenced by an external multiple-pulse radiofrequency magnetic field acting only on nuclei of one sort. Kinetic equations were obtained giving the possibility of finding the time dependence of the magnetization of the body and the kinetic coefficients calculated as a function of the multiple-pulse field parameters. The possibilities of using the results in question for molecular structure and molecular dynamics investigations are briefly surveyed.

Furman, G. B.; Shaposhnikov, I. G.

1994-05-01

37

Non-contrast-enhanced magnetic resonance angiography: techniques and applications.  

PubMed

Non-contrast-enhanced magnetic resonance angiography has gained renewed interest since the discovery of the association between gadolinium-based contrast agents and nephrogenic systemic fibrosis. The following article is an overview of the different magnetic resonance angiography sequences, the technical possibilities and new developments. Clinical options and recent advancements will be highlighted, and recommendations for non-contrast-enhanced magnetic resonance angiography techniques in different anatomical regions will be given. Furthermore, the authors seek to predict the future of non-contrast-enhanced magnetic resonance angiography, with special focus on patients at risk. PMID:22149527

Blankholm, Anne Dorte; Ringgaard, Steffen

2012-01-01

38

Correlation of far-infrared and nuclear quadrupole resonance studies in 1,3,5-tribromobenzene  

NASA Astrophysics Data System (ADS)

The torsional modes that contribute to the change in nuclear quadrupole resonance (NQR) frequencies with temperatures in 1,3,5-tribromobenzene are indentified by correlating the observed variation of 79Br NQR frequencies with temperature with the theoretical expectations using the low frequency vibrational modes obtained from the far-infrared (FIR) spectrum.

Venkatacharyulu, P.; Krishnamurthy, V.

1991-02-01

39

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

40

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, M. L.; Yesinowski, J. P.; Miller, J. B.

1994-03-01

41

Magnetic resonance imaging of neuroblastoma using current techniques  

Microsoft Academic Search

We evaluated the ability of current magnetic resonance (MR) scanning techniques to detect and stage neuroblastoma in children, using surgical and histopathologic correlation. We prospectively and retrospectively reviewed 16 MR examinations from 14 patients with neuroblastoma (13 patients) or ganglioneuroblastoma (1 patient) and compared these to computed tomography (CT) (5 patients) and pathology (all patients). Sequences included: precontrast T1-weighted and

Carolyn M Sofka; Richard C Semelka; Nikolaos L Kelekis; Suvipapun Worawattanakul; Charles J Chung; Stuart Gold; Lynn A Fordham

1999-01-01

42

Study of Superconducting Hg by Nuclear Magnetic Resonance Techniques  

Microsoft Academic Search

Since nuclear magnetic resonance techniques can provide rather microscopic information about conduction electrons in metals, their application to the study of superconducting metals is of considerable interest. The difficulties associated with the failure of magnetic fields to penetrate inside superconductors can be overcome by the use of dense colloids consisting of particles mostly less than 500 A in diameter. The

F. Reif

1957-01-01

43

Measuring Cerebral Blood Flow Using Magnetic Resonance Imaging Techniques  

Microsoft Academic Search

Magnetic resonance imaging techniques measuring CBF have developed rapidly in the last decade, resulting in a wide range of available methods. The most successful approaches are based either on dynamic tracking of a bolus of a paramagnetic contrast agent (dynamic susceptibility contrast) or on arterial spin labeling. This review discusses their principles, possible pitfalls, and potential for absolute quantification and

Fernando Calamante; David L. Thomas; Gaby S. Pell; Jonna Wiersma; Robert Turner

1999-01-01

44

A Novel Active Vibration Absorption Technique: Delayed Resonator  

Microsoft Academic Search

A new concept of active vibration absorption for dynamic structures is presented. This new methodology, delayed resonator, originates from a proportional position feedback excitation utilized on an otherwise conventional mass-spring-damper absorber. The critical feature of the technique is utilization of a controlled time delay in the feedback loop, which is traditionally looked upon as an undesirable element in dynamic controls.

N. Olgac; B. T. Holm-Hansen

1994-01-01

45

Stability and molecular dynamics of chloroxylenol (API of antiseptics and drugs) in solid state studied by 35Cl-NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

Thermal stability of 4-chloro-3,5-dimethyl-phenol (chloroxylenol) in solid state has been studied by 35Cl-NQR spectroscopy. Two NQR resonance lines at the frequencies 34.348 and 34.415 MHz at 77 K have been assigned to chlorine atoms from two crystallographically inequivalent molecules on the basis of the B3LYP/6-311++G ?? results. The temperature dependence of the resonance frequency and full width at half maximum suggest the occurrence of small-angle torsional oscillations of the mean activation energy of 3.83 kJ/mol and rotation of both methyl groups around their symmetry axis C3 with the activation energies 12.49 and 11.27 kJ/mol for CH 3 in molecule A and B, respectively. B3LYP/6-311++G ?? method reproduced very well the activation energies of both motions.

Latosi?ska, J. N.; Tomczak, M. A.; Kasprzak, J.

2009-02-01

46

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 2400 to 3000ppm. 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

47

NQR spin-echo methods at very low temperatures  

Microsoft Academic Search

Pulsed methods may be successfully used in very low temperature NMR or NQR experiments provided good thermal anchoring of the sample is achieved. In order to reduce heating effects, it is advantageous to use rf pulses that are shorter than the standard magnetization tipping pulses used at higher temperatures. The present work describes the use of short nonstandard rf pulses

I. P. Goudemond; J. M. Keartland; M. J. R. Hoch

1991-01-01

48

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

49

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

50

Nuclear quadrupole resonance of boron in borate glasses  

NASA Astrophysics Data System (ADS)

A continuous wave nuclear quadrupole resonance spectrometer that has a high sensitivity even at low frequencies has been built. Boron and aluminum NQR has been detected in the region 200 kHz to 1.4 MHz. For the first time, boron NQR has been detected in a glass. The NQR spectrum of pure B 20 3 glass is consistent with 85 ± 2% of the boron atoms belonging to boroxol rings. In sodium borate glasses, the number of borons in boroxol rings decreases with increasing sodium content, until when sodium oxide comprises 20 mol% of the glass less than 2% of the borons are in boroxol rings.

Gravina, Samuel J.; Bray, Phillip J.

51

27Al-NQR\\/NMR Study of Kondo Semiconductor CeFe2Al10  

Microsoft Academic Search

27Al-NQR\\/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1\\/T1 above about 20

Yukihiro Kawamura; Shingo Edamoto; Tomoaki Takesaka; Takashi Nishioka; Harukazu Kato; Masahiro Matsumura; Yo Tokunaga; Shinsaku Kambe; Hiroshi Yasuoka

2010-01-01

52

The single NqrB and NqrC subunits in the Na(+)-translocating NADH: quinone oxidoreductase (Na(+)-NQR) from Vibrio cholerae each carry one covalently attached FMN.  

PubMed

The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is the prototype of a novel class of flavoproteins carrying a riboflavin phosphate bound to serine or threonine by a phosphodiester bond to the ribityl side chain. This membrane-bound, respiratory complex also contains one non-covalently bound FAD, one non-covalently bound riboflavin, ubiquinone-8 and a [2Fe-2S] cluster. Here, we report the quantitative analysis of the full set of flavin cofactors in the Na(+)-NQR and characterize the mode of linkage of the riboflavin phosphate to the membrane-bound NqrB and NqrC subunits. Release of the flavin by ?-elimination and analysis of the cofactor demonstrates that the phosphate group is attached at the 5'-position of the ribityl as in authentic FMN and that the Na(+)-NQR contains approximately 1.7mol covalently bound FMN per mol non-covalently bound FAD. Therefore, each of the single NqrB and NqrC subunits in the Na(+)-NQR carries a single FMN. Elimination of the phosphodiester bond yields a dehydro-2-aminobutyrate residue, which is modified with ?-mercaptoethanol by Michael addition. Proteolytic digestion followed by mass determination of peptide fragments reveals exclusive modification of threonine residues, which carry FMN in the native enzyme. The described reactions allow quantification and localization of the covalently attached FMNs in the Na(+)-NQR and in related proteins belonging to the Rhodobacter nitrogen fixation (RNF) family of enzymes. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). PMID:22366169

Casutt, Marco S; Schlosser, Andreas; Buckel, Wolfgang; Steuber, Julia

2012-10-01

53

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

54

Experimental study of the structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se by means of NQR and EPR spectroscopy  

NASA Astrophysics Data System (ADS)

The structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se has been studied by means of both NQR (nuclear quadrupole resonance) and EPR (electron paramagnetic resonance) spectroscopy. It is investigated that in the glasses of both systems the value of the electric field gradient at the resonating nuclei grows with increasing concentration of the clusters As2Se3 and Sb2Se3, thereby increasing the NQR resonance frequencies. It appears that for the Ge-As-Se system the structural transition from a two-dimensional to three-dimensional structure occurs at average coordination number = 2.45. The EPR spectral parameters of glasses depend on the composition, the average coordination number and the temperature, and these are discussed. The effect of "ageing" for CGS (chalcogenide glassy semiconductors) of As-Sb-Se system due to partial crystallization of the sample is observed from the EPR spectra.

Bolebrukh, Olga N.; Sinyavsky, Nikolay Ya.; Korneva, Irina P.; Dobosz, Bernadeta; Ostafin, Michal; Nogaj, Boleslaw; Krzyminiewski, Ryszard

2013-12-01

55

Advanced techniques in pediatric abdominopelvic oncologic magnetic resonance imaging.  

PubMed

Advances in the treatment of pediatric abdominopelvic malignancies have increased survival drastically. Imaging is critical in initial tumor characterization/staging, assessment of treatment response, and surveillance following therapy. Magnetic resonance imaging (MRI) is playing an increasing role in the care of these patients due to its lack of ionizing radiation, superior contrast resolution and the ability to characterize tumors based on tissue characteristics (e.g., T1 and T2 relaxation times). Modern MR techniques also allow for assessment of tumors based on functional characteristics. This article is focused on emerging MRI technologies and potential applications in the imaging of pediatric abdominopelvic malignancies. PMID:24183528

Smith, Ethan A

2013-11-01

56

Functional magnetic resonance imaging: imaging techniques and contrast mechanisms.  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a widely used technique for generating images or maps of human brain activity. The applications of the technique are widespread in cognitive neuroscience and it is hoped they will eventually extend into clinical practice. The activation signal measured with fMRI is predicated on indirectly measuring changes in the concentration of deoxyhaemoglobin which arise from an increase in blood oxygenation in the vicinity of neuronal firing. The exact mechanisms of this blood oxygenation level dependent (BOLD) contrast are highly complex. The signal measured is dependent on both the underlying physiological events and the imaging physics. BOLD contrast, although sensitive, is not a quantifiable measure of neuronal activity. A number of different imaging techniques and parameters can be used for fMRI, the choice of which depends on the particular requirements of each functional imaging experiment. The high-speed MRI technique, echo-planar imaging provides the basis for most fMRI experiments. The problems inherent to this method and the ways in which these may be overcome are particularly important in the move towards performing functional studies on higher field MRI systems. Future developments in techniques and hardware are also likely to enhance the measurement of brain activity using MRI.

Howseman, A M; Bowtell, R W

1999-01-01

57

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

58

An ultra-broadband low-frequency magnetic resonance system  

NASA Astrophysics Data System (ADS)

MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3 MHz frequency range without using conventional resonant circuits for either transmission or reception. This “non-resonant” approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range.

Mandal, S.; Utsuzawa, S.; Cory, D. G.; Hürlimann, M.; Poitzsch, M.; Song, Y.-Q.

2014-05-01

59

Possible stripe fluctuations in La2 - x - yNdySrxCuO4 at room temperature observed by 63Cu NQR spectroscopy  

NASA Astrophysics Data System (ADS)

63Cu nuclear quadrupole resonance (NQR) studies at room temperature were reported on six Nd-doped La2 - xSrxCuO4 samples. The NQR spectrum for La1.48Nd0.4Sr0.12CuO4 has a different line shape compared with those from the other samples, which is similar to the case of the insulating La2CuO4. This may suggest that the stripe fluctuations at such a special Nd and Sr doping fall into the frequency window of 63Cu NQR. The spectra of the other five samples were analysed by pairs of 63Cu and 65Cu Gaussians at A and B sites. The full width of half-maxim (FWHM) for 63Cu at B sites is anomalously large for La1.45Nd0.4Sr0.15CuO4, which was considered to be related to the stripe fluctuations.

Zhang, Q.-M.; Ying, X. N.; Gu, M.; Wang, Y. N.

2005-04-01

60

NMR and NQR parameters of the SiC-doped on the (4,4) armchair single-walled BPNT: a computational study.  

PubMed

The structural properties, NMR and NQR parameters in the pristine and silicon carbide (SiC) doped boron phosphide nanotubes (BPNTs) were calculated using DFT methods (BLYP, B3LYP/6-31G) in order to evaluate the influence of SiC-doped on the (4,4) armchair BPNTs. Nuclear magnetic resonance (NMR) parameters including isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (13)C, (29)Si, (11)B, and (31)P atoms and quadrupole coupling constant (C ( Q )), and asymmetry parameter (? ( Q )) at the sites of various (11)B nuclei were calculated in pristine and SiC- doped (4,4) armchair boron phosphide nanotubes models. The calculations indicated that doping of (11)B and (31)P atoms by C and Si atoms had a more significant influence on the calculated NMR and NQR parameters than did doping of the B and P atoms by Si and C atoms. In comparison with the pristine model, the SiC- doping in Si(P)C(B) model of the (4,4) armchair BPNTs reduces the energy gaps of the nanotubes and increases their electrical conductance. The NMR results showed that the B and P atoms which are directly bonded to the C atoms in the SiC-doped BPNTs have significant changes in the NMR parameters with respect to the B and P atoms which are directly bonded to the Si atoms in the SiC-doped BPNTs. The NQR results showed that in BPNTs, the B atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BPNTs. Also, the NMR and NQR results detect that the Fig. 1b (Si(P)C(B)) model is a more reactive material than the pristine and the Fig. 1a (Si(B)C(p)) models of the (4,4) armchair BPNTs. PMID:21625895

Baei, Mohammad T; Sayyad-Alangi, S Zahra; Moradi, Ali Varasteh; Torabi, Parviz

2012-03-01

61

Resonant frequency calculations using a hybrid perturbation-Galerkin technique  

NASA Technical Reports Server (NTRS)

A two-step hybrid perturbation Galerkin technique is applied to the problem of determining the resonant frequencies of one or several degree of freedom nonlinear systems involving a parameter. In one step, the Lindstedt-Poincare method is used to determine perturbation solutions which are formally valid about one or more special values of the parameter (e.g., for large or small values of the parameter). In step two, a subset of the perturbation coordinate functions determined in step one is used in Galerkin type approximation. The technique is illustrated for several one degree of freedom systems, including the Duffing and van der Pol oscillators, as well as for the compound pendulum. For all of the examples considered, it is shown that the frequencies obtained by the hybrid technique using only a few terms from the perturbation solutions are significantly more accurate than the perturbation results on which they are based, and they compare very well with frequencies obtained by purely numerical methods.

Geer, James F.; Andersen, Carl M.

1991-01-01

62

The two-frequency nuclear quadrupole resonance for explosives detection  

Microsoft Academic Search

The two-frequency nuclear quadrupole resonance (NQR) of14N nuclei is described for purposes of explosives detection. Two applications are known: two-frequency NQR for increasing the\\u000a signal intensity, two-frequency NQR for improved reliability of explosives detection. The two-frequency experiments were carried\\u000a out in hexahydro-1,3,5-trinitro-s-triazine C3H6N6O6 and sodium nitrite NaNO2 as a substitute for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocycine C4H8N8O8. The two-frequency sequences for NQR are proposed

G. V. Mozjoukhine

2000-01-01

63

^63Cu NQR relaxation in the p-type transparent conductor CuScO_2:Mg  

NASA Astrophysics Data System (ADS)

Transparent conducting oxides with p-type conductivity are of interest as electronic complements to the more familiar n-type transparent conductors. This paper reports the first results of a study of carrier spin dynamics in p-type CuScO_2:Mg using ^63Cu nuclear spin-lattice relaxation measurements. Relaxation rates 1/T1 have been measured by nuclear quadrupole resonance (NQR) over the range 280 K to 400 K. The ^63Cu NQR frequency is found to be 28,135 ± 5 kHz at 300 K and to decrease linearly with temperature over the experimental range. The value of 1/T1 at 300 K is 130 ± 10 s-1. The rate is weakly dependent on temperature and increases by only about 15 % up to 400 K. This behavior contrasts sharply with results obtained previously(1. A. Rajabzadeh, J. Tate and W. Warren, Bull. Am. Phys. Soc. 48, 1009 (2003).) for the related material CuYO_2:Ca. In that material, relaxation rates for ^63Cu and ^65Cu were strongly temperature dependent, being approximately thermally-activated with activation energy 152 ± 10 meV. The nuclear relaxation properties of CuScO_2:Mg are suggestive of more conventional metallic transport in CuScO_2:Mg compared with CuYO_2:Ca.

Rossi, Vincent; Tate, Janet; Warren, William; Li, Jun; Sleight, Arthur

2003-05-01

64

Nuclear quadrupole resonance lineshape analysis for different motional models: stochastic Liouville approach.  

PubMed

A general theory of lineshapes in nuclear quadrupole resonance (NQR), based on the stochastic Liouville equation, is presented. The description is valid for arbitrary motional conditions (particularly beyond the valid range of perturbation approaches) and interaction strengths. It can be applied to the computation of NQR spectra for any spin quantum number and for any applied magnetic field. The treatment presented here is an adaptation of the "Swedish slow motion theory," [T. Nilsson and J. Kowalewski, J. Magn. Reson. 146, 345 (2000)] originally formulated for paramagnetic systems, to NQR spectral analysis. The description is formulated for simple (Brownian) diffusion, free diffusion, and jump diffusion models. The two latter models account for molecular cooperativity effects in dense systems (such as liquids of high viscosity or molecular glasses). The sensitivity of NQR slow motion spectra to the mechanism of the motional processes modulating the nuclear quadrupole interaction is discussed. PMID:22168707

Kruk, D; Earle, K A; Mielczarek, A; Kubica, A; Milewska, A; Moscicki, J

2011-12-14

65

Unconventional Pairing States in Heavy-Fermion Superconductors Studied by the NQR/NMR Experiments  

NASA Astrophysics Data System (ADS)

We review the studies on the unconventional superconducting pairing states and their relevance with magnetism in the f-electron derived heavy-fermion (HF) systems by means of nuclear-magnetic-resonance (NMR) and nuclear-quadrupole-resonance (NQR). These studies have unraveled a rich variety of the phenomena in the ground state of HF systems. In this article, we address an intimate relationship between the onset of strong-coupling superconductivity (SC) and critical magnetic fluctuations emerging in the vicinity of quantum critical point (QCP). Furthermore, we focus on the novel phase diagram of the HF antiferromagnet CeRhIn5 under pressure which is characterized by the tetracritical point separating the pure antiferromagnetism (AFM) phase, the AFM+SC uniformly coexisting phase, and the paramagnetic SC phase. A comparison is also presented on the AFM+SC uniformly coexisting phase in high-temperature superconductors as the function of carrier doping. As a consequence, we raise a question; Do we need a bosonic glue to pair electrons in these superconductors? Finally, we address a possible origin of the novel SC in the itinerant ferromagnet UGe2, which is mediated by ferromagnetic spin-density fluctuations relevant with the first-order transition inside the ferromagnetic states.

Kitaoka, Yoshio; Mukuda, Hidekazu; Yashima, Mitsuharu; Harada, Atsushi

2007-05-01

66

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

67

Resonant frequencies and quality factors for optical equilateral triangle resonators calculated by FDTD technique and the Pade approximation  

Microsoft Academic Search

The mode wavelength and quality factor (Q-factor) for resonant modes in optical equilateral triangle resonators (ETR's) are calculated by the finite-difference time-domain (FDTD) technique and the Pade approximation. For an ETR with the side length of 3 ?m and the refractive index of 3.2, we get the mode wavelength interval of about 70 nm and the Q-factor of the fundamental

Wei-Hua Guo; Yong-Zhen Huang; Qi-Ming Wang

2000-01-01

68

Phonon detection technique for the study of the temperature coefficient of resonance frequency in clamped-clamped beam resonators  

NASA Astrophysics Data System (ADS)

In this paper, we utilize a phonon detection technique to determine the temperature coefficient of resonant frequency TCf of MEMS resonators. The technique adopted is highly sensitive to device motions and allows for TCf measurement with less than 5 ppm °C-1 error. In addition, it can also characterize multiple resonators fabricated on the same die or wafer using a single piezoelectric element. Although the multiple devices have to be measured sequentially, the data acquisition time per resonator is short, making the technique an ideal wafer level characterization tool for high volume device testing. The devices used in our TCf experiments are comb-actuated clamped-clamped beam resonators fabricated using the SOIMUMPs process from MEMSCAP. The clamped-clamped architecture of these devices makes them especially prone to thermal-induced strain. A theoretical framework for analyzing the TCf of these resonators was also derived. Experiments on 16 sample devices show that altering the length L and width w of the clamped-clamped beam improves the TCf of the devices by up to 22%. From our TCf measurements, it was also deduced that a mismatch in the thermal expansion coefficients of the SOI structural and substrate layers caused the thermal-induced strain on our samples. The mismatch was determined to be 3.8 × 10-8 °C-1 for one particular sample die.

Wong, C.-L.; Palaniapan, M.

2009-06-01

69

Copper Nqr and NMR Study of Metal-Substituted Yttrium BARIUM(2) COPPER(3) OXYGEN(7) and Yttrium BARIUM(2) COPPER(4) OXYGEN(8)  

NASA Astrophysics Data System (ADS)

Pulsed nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) have been used to investigate the effect of metal-substitution for copper in YBa_2Cu_3O_7 (YBCO123) and YBa_2Cu_4O_8 (YBCO124). Among many metal substitutions, Zn has an especially dramatic effect in suppressing the superconducting temperature T_{c}, and hence superconductivity. More interesting is that Zn and Fe have the same T_{c} suppression effect in YBCO124. This study focuses on the Zn substitutions in YBCO123 and Zn, Fe, and Co substitutions in YBCO124. In Zn doped YBCO123, Cu(2), plane site, NQR spectra and the frequency dependence of the spin-lattice relaxation rates have been measured over a temperature range from 77 K to 300 K to study the correlation of the suppression of the relaxation rate with the distance between the probe Cu nuclei and the impurity. It is found that the relaxation rate is insensitive to the variation of the NQR resonance frequency. However, by comparing the results of the Zn doped YBCO124 with those of YBCO123, it can be concluded that the suppression of the relaxation rate for both YBCO compounds in the normal state is caused by destruction of short-range antiferromagnetic correlation with substitution of nonmagnetic ion Zn on the Cu(2) sites. NQR and NMR measurements were carried out on both Cu(2), plane, and Cu(1), chain sites, for various concentrations of Zn, Fe, and Co dopants in YBCO124 over a temperature range from 77 K to 300 K. A strong correlation of the enhancement of Cu(2) spin lattice relaxation rate and suppression of superconductivity by impurities was found. The temperature dependence of the Cu(2) NMR linewidth exhibits a strong RKKY type exchange interaction below 225 K for Zn and Fe doped samples, which indicates the formation of the local magnetic moment. The enhancement of the relaxation rate is caused by the local magnetic moment Fe^ {+3} ion and the moments on Cu(2) neighbors when Zn^{+2} is substituted on Cu(2). This study gives us a clear picture of the spin pseudogap behavior in the high temperature superconductor cuprates. It also suggests that the magnetic moment on the CuO_2 plane may relate to the suppression of T_{c} in metal-substituted YBCO124.

Cheng, Show-Jye

70

A Narrowband Impedance Measurement Technique forThickness Shear Mode Resonator Sensors  

SciTech Connect

This paper discusses a new technique for measuring the impedance response of thickness shear mode (TSM) resonators used as fluid monitors and chemical sensors. The technique simulates the swept frequency measurements performed by an automatic network analyzer (ANA), determining the complex reflection scattering parameter, S1l, from single port devices. Unlike oscillator circuits most often used with TSM resonators, narrowband spectral measurements are not limited by cable capacitance between resonator and oscillator allowing placement of the sensor in severe environments. Only noise produced by long cable lengths limits performance and sensor sensitivity. This new technique utilizes a simple swept frequency source operating near the crystal resonance, a unique directional coupler to provide the reference and reflected RF signals, an I & Q demodulation circuit that returns two dc voltages, and computational algorithms for determining sensor response parameters. Performance, has been evaluated by comparing TSM resonator responses using this new technique to those from a commercial ANA.

Cernosek, R.W.; Pohl, R.; Rumpf, A.N.; Sanchez, G.J.; Wojahn, C.K.

1999-06-02

71

A new characterization technique for lossy piezoceramic resonators  

Microsoft Academic Search

Piezoelectricity was discovered by the brothers Curie in 1880. They found that, in certain materials such as zincblende, tourmaline, can sugar, topaz and quartz, mechanical stresses were accompanied by the production of electric surface charges. The piezoelectric effect remained a curiosity until the early 1920s when it was utilized to realize crystal resonators for the stabilization of oscillators, thereby launching

Robert Allan Pastore Jr.

2000-01-01

72

Polymeric microring resonator using nanoimprint technique based on a stamp incorporating a smoothing buffer Layer  

Microsoft Academic Search

A polymeric microring resonator has been proposed and fabricated using the nanoimprint technique based on a stamp incorporating a smoothing buffer layer. It played a pivotal role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing its scattering loss. Eventually, the quality factor of the resonator could be enhanced. It also helped narrow

Do-Hwan Kim; Jung-Gyu Im; Sang-Shin Lee; Seh-Won Ahn; Ki-Dong Lee

2005-01-01

73

Ferromagnetic Quantum Critical Fluctuations and Anomalous Coexistence of Ferromagnetism and Superconductivity in UCoGe Revealed by Co-NMR and NQR Studies  

NASA Astrophysics Data System (ADS)

Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies were carried out for the recently discovered UCoGe, in which the ferromagnetic and superconducting (SC) transitions are reported to occur at TCurie˜ 3 K and TS˜ 0.8 K [Huy et al.: Phys. Rev. Lett. 99 (2007) 067006], in order to investigate the coexistence of ferromagnetism and superconductivity as well as the normal-state and SC properties from a microscopic point of view. From the nuclear spin-lattice relaxation rate 1/T1 and Knight-shift measurements, we confirm that ferromagnetic fluctuations that possess a quantum critical character are present above TCurie and also the occurrence of a ferromagnetic transition at 2.5 K in our polycrystalline sample. The magnetic fluctuations in the normal state show that UCoGe is an itinerant ferromagnet similar to ZrZn2 and YCo2. The onset SC transition is identified at TS˜ 0.7 K, below which 1/T1 arising from 30% of the volume fraction starts to decrease due to the opening of the SC gap. This component of 1/T1, which follows a T3 dependence in the temperature range 0.3-0.1 K, coexists with the magnetic components of 1/T1 showing a \\sqrt{T} dependence below TS. From the NQR measurements in the SC state, we suggest that the self-induced vortex state is realized in UCoGe.

Ohta, Tetsuya; Nakai, Yusuke; Ihara, Yoshihiko; Ishida, Kenji; Deguchi, Kazuhiko; Sato, Noriaki K.; Satoh, Isamu

2008-02-01

74

The magnetic resonance sounding technique and its use for groundwater investigations  

Microsoft Academic Search

A commercial version of the magnetic resonance sounding (MRS) technique became available in 1996. At that time, ITC research team started to investigate the MRS technique with respect to its appropriateness to groundwater investigations. MRS is the only non-invasive surface geophysical technique with an inherent selectivity to free hydrogen and, therefore, to groundwater. The signal amplitude inversion allows quantifying free

J. Roy; M. Lubczynski

2003-01-01

75

Magnetic resonance elastography technique for breast tissue in-vitro elasticity measurement  

Microsoft Academic Search

A soft tissue elasticity measurement technique based on Magnetic Resonance Elastography (MRE) is presented. In this technique, a tissue specimen is encased in a gelatine-agar block with known elasticity modulus. This block is slowly compressed using a MRI compatible device and displacements are measured using a phase contrast MRI technique. These displacements are processed using an iterative MRE model and

Abbas Samani; Chris Luginbuhl; Donald B. Plewes

2002-01-01

76

Application of Resonance Fluorescence Technique for Helium-Like Carbon Diagnostics on the T-10 Tokamak.  

National Technical Information Service (NTIS)

Application of laser resonance fluorescence (LRF) technique for investigation of light element multicharged ion behaviour has been analysed. Description of radiation source using dye laser frequency doubling by means of potassium pentaborate crystal is pr...

I. V. Moskalenko D. A. Shcheglov

1985-01-01

77

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

78

Nuclear quadrupole spin dynamics: How weak RF pulses and double resonance cross-relaxation contribute to explosives detection  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) is a type of radio-frequency (rf) spectroscopy which can detect quadrupolar nuclei (I > 1/2), such as nitrogen, in crystalline solids. NQR spectroscopy is useful for the detection of the many types of explosives containing 14N, however it suffers from a low signal to noise ratio (SNR) particularly in samples with long spin-lattice relaxation times. To improve the SNR the nuclear quadrupole spin dynamics are exploited in two limiting cases: systems with long spin relaxation times and systems where the excitation power is limited. The former is addressed through double resonance effects and the latter through spin echoes created by weak rf pulses. The double resonance effect occurs in samples that also contain a second faster relaxing nuclear species, such as 1H in ammonium nitrate. In this sample an 1H-14N double resonance can be created between the species that improves the SNR. While the focus is on the common case of solids containing both nitrogen and hydrogen, the theory is generally applicable to solids containing spin-1 and spin-1/2 nuclei. A model of this system is developed that treats the motionally averaged secular dipolar Hamiltonian as a perturbation of the combined quadrupole and Zeeman Hamiltonians. This model reveals three types of double resonance conditions, involving static and rf fields, and predicts expressions for the cross-relaxation rate (Wd) between the two species. Using this cross-relaxation rate, in addition to the hydrogen and nitrogen autorelaxation rates, expressions governing the relaxation back to equilibrium in a spin-1/2 and spin-1 system are determined. The three different types of double resonance conditions are created experimentally; one of them for the first time in any system and another for the first time in a solid. Under these double resonance conditions, the increase in Wd and improvements in SNR are explored both theoretically and experimentally using ammonium nitrate. The second effect investigated is the NQR spin echo that forms after excitation of a powder sample by a single weak resonant radio-frequency pulse. This single-pulse echo is identified for the first time, and when applications are limited by a weak rf field, can be used effectively to increase the SNR over conventional detection techniques.

Prescott, David

79

Structural characterization of Agarose Using an Acoustic Resonance Technique  

NASA Astrophysics Data System (ADS)

Electric fields play an important role in gel electrophoresis, the process by which macromolecules travel, under the influence of an electric field, through a gel matrix and separate according to size. Agarose is commonly used for DNA electrophoresis; it is technologically important to understand the effect of electric fields upon agarose gels to develop methods for separation of longer DNA. This investigation centers on using fourier frequency analysis of light scattered from agarose gels to probe how the acoustic properties (a function of the structural properties) are affected by the application of electric fields. The experimental approach and preliminary findings which correlate acoustic resonance results with various regions of the agarose phase diagram will be presented. Acknowledgement is made to the Donors of The Petroleum Research Fund, administered by the American Chemical Society, for support of this research.

White, James D.; Ploplis Andrews, Anna

1996-11-01

80

Methods for magnetic resonance analysis using magic angle technique  

DOEpatents

Methods of performing a magnetic resonance analysis of a biological object are disclosed that include placing the object in a main magnetic field (that has a static field direction) and in a radio frequency field; rotating the object at a frequency of less than about 100 Hz around an axis positioned at an angle of about 54.degree.44' relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a phase-corrected magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. In particular embodiments the method includes pulsing the radio frequency to provide at least two of a spatially selective read pulse, a spatially selective phase pulse, and a spatially selective storage pulse. Further disclosed methods provide pulse sequences that provide extended imaging capabilities, such as chemical shift imaging or multiple-voxel data acquisition.

Hu, Jian Zhi (Richland, WA); Wind, Robert A. (Kennewick, WA); Minard, Kevin R. (Kennewick, WA); Majors, Paul D. (Kennewick, WA)

2011-11-22

81

27Al-NQR Study on Novel Phase Transition in CeOs2Al10  

NASA Astrophysics Data System (ADS)

We have performed 27Al-NQR measurements in CeOs2Al10 which exhibits a novel phase transition at T0=29 K The NQR parameters determined for all the Al sites in ambient pressure were compared with those in CeRu2Al10 with T0=27 K and CeFe2Al10 with no phase transition. The distinct NQR splitting just below T0=32.5 K under pressure 0.66 GPa ensures an enhancement of T0 and a homogeneous transition. Despite the increase of T0, the nuclear spin-lattice relaxation rate 1/Tl is suppressed over whole range of temperature than in ambient pressure. The characteristic features of no critical slowing down at T0 and of the remarkable decrease of 1/T1T starting at T > T0 become prominent under pressure, suggesting an approach to Kondo semiconductor in a valence fluctuation regime.

Matsumura, M.; Inagaki, T.; Kato, H.; Nishioka, T.; Tanida, H.; Sera, M.

2012-12-01

82

NQR1 controls lifespan by regulating the promotion of respiratory metabolism in yeast  

PubMed Central

Summary The activity and expression of plasma membrane NADH coenzyme Q reductase is increased by calorie restriction (CR) in rodents. Although this effect is well established and is necessary for CR's ability to delay aging, the mechanism is unknown. Here we show that the Saccharomyces cerevisiae homolog, NQR1, resides at the plasma membrane and when overexpressed extends both replicative and chronological lifespan. We show that NQR1 extends replicative lifespan in a SIR2-dependent manner by shifting cells towards respiratory metabolism. Chronological lifespan extension, in contrast, occurs via a SIR2-independent decrease in ethanol production. We conclude that NQR1 is a key mediator of lifespan extension by CR through its effects on yeast metabolism and discuss how these findings could suggest a function for this protein in lifespan extension in mammals.

Jimenez-Hidalgo, Maria; Santos-Ocana, Carlos; Padilla, Sergio; Villalba, Jose M.; Lopez-Lluch, Guillermo; Martin-Montalvo, Alejandro; Minor, Robin K.; Sinclair, David A.; de Cabo, Rafael; Navas, Placido

2009-01-01

83

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.

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

2012-01-01

84

Magnetostriction measurements on thin films by a slot-line ferromagnetic resonance technique (abstract)  

Microsoft Academic Search

We report on a new technique for the determination of the linear magnetostriction constant of thin films. The technique uses the shift in ferromagnetic resonance (FMR) of a magnetostrictive sample upon application of an external stress. A circular thin film is deposited onto a fused quartz plate by ion beam sputter deposition. The plate is mounted in a cantilever configuration,

S. A. Oliver; V. G. Harris; C. Vittoria

1990-01-01

85

A technique for accurate magnetic resonance imaging in the presence of field inhomogeneities  

Microsoft Academic Search

A technique for producing geometrically accurate magnetic resonance images (MRIs) with undistorted intensity in the face of high levels of static field inhomogeneity arising from either source is presented. The technique requires the acquisition of two images of the same object with altered gradients. On the basis of a knowledge of these gradients it employs an automatic postprocessing step that

Hsuan Chang; J. M. Fitzpatrick

1992-01-01

86

Recent Developments of the Resonance Light Scattering Technique: Technical Evolution, New Probes and Applications  

Microsoft Academic Search

The resonance light scattering (RLS) technique, scanning simultaneously the excitation and emission monochromators of a common spectrofluorometer to detect enhanced RLS signals, has been used for designating bio?assemblies, aggregation species, and analytical purposes. Herein, we review the reports since our last mini?review in 2003 concerning the new derived RLS techniques, RLS probes, and their applications.

Jian Ling; Cheng Zhi Huang; Yuan Fang Li; Yun Fei Long; Qie Gen Liao

2007-01-01

87

Magnetic resonance imaging of coronary arteries: technique and preliminary results  

Microsoft Academic Search

BACKGROUND--Coronary artery imaging is an important investigation for the management of coronary artery disease. The only reliable technique presently available, x ray contrast angiography, is invasive and is associated with a small morbidity and mortality. Alternative non-invasive imaging would be useful, but the small calibre and tortuosity of the coronary vessels, and cardiac and respiratory motion create formidable imaging problems.

D J Pennell; J Keegan; D N Firmin; P D Gatehouse; S R Underwood; D B Longmore

1993-01-01

88

Density functional calculations of 14N and 11B NQR parameters in the H-capped (6,0) and (4,4) single-walled BN nanotubes  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were performed to calculate nitrogen-14 and boron-11 nuclear quadrupole resonance (NQR) spectroscopy parameters in the representative considered models of zigzag and armchair boron nitride nanotubes (BNNTs) for the first time. The considered models consisting of 1 nm length of H-capped (6,0) and (4,4) single-walled BNNT were first allowed to fully relax and then the NQR calculations were performed on the geometrically optimized models. The evaluated nuclear quadrupole coupling constants and asymmetry parameters for the mentioned nuclei reveal that the considered models can be divided into four layers of nuclei with an equivalent electrostatic environment where those nuclei at the ends of tubes have a very strong electrostatic environment compared to the other nuclei along the length of tubes. Those nuclei at the center of the tube length also have an equivalent electrostatic environment. The calculations were performed based on the B3LYP DFT method and 6-311G** and 6-311++G** standard basis sets using the Gaussian 98 package of program.

Mirzaei, Mahmoud; Hadipour, Nasser L.

2008-02-01

89

Cu-NQR of CeCu2Si2 under high pressure  

NASA Astrophysics Data System (ADS)

We have measured 63Cu-NQR spectral lines and nuclear spin-lattice relaxation time T1 under pressure up to 5.4 GPa. Daphne oil 7474 is used as the pressure-transmitting medium to obtain good hydrostaticity. NQR frequency 63?q above 4 GPa suddenly decreases from the linear pressure dependence in the low pressure range (P <= 3.5 GPa). The observed sudden downward deviation of 63?q is associated with an increase of Ce valence. Above 4.5 GPa, the linear pressure dependence of 63?q is observed again, most likely related to the sharp crossover to the high valence state.

Fujiwara, K.; Iwata, M.; Okazaki, Y.; Ikeda, Y.; Araki, S.; Kobayashi, T. C.; Murata, K.; Geibel, C.; Steglich, F.

2012-12-01

90

Superconductivity and magnetic fluctuations in Cd(2))Re(2)O(7) via Cd nuclear magnetic resonance and re nuclear quadrupole resonance.  

PubMed

We report Cd nuclear magnetic resonance (NMR) and Re nuclear quadrupole resonance (NQR) studies on Cd(2)Re(2)O(7), the first superconductor among pyrochlore oxides (T(c) approximately 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 T(c) 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. PMID:12097064

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

2002-07-01

91

Advances in magnetic resonance neuroimaging techniques in the evaluation of neonatal encephalopathy.  

PubMed

Magnetic resonance (MR) imaging has become an essential tool in the evaluation of neonatal encephalopathy. Magnetic resonance-compatible neonatal incubators allow sick neonates to be transported to the MR scanner, and neonatal head coils can improve signal-to-noise ratio, critical for advanced MR imaging techniques. Refinement of conventional imaging techniques include the use of PROPELLER techniques for motion correction. Magnetic resonance spectroscopic imaging and diffusion tensor imaging provide quantitative assessment of both brain development and brain injury in the newborn with respect to metabolite abnormalities and hypoxic-ischemic injury. Knowledge of normal developmental changes in MR spectroscopy metabolite concentration and diffusion tensor metrics is essential to interpret pathological cases. Perfusion MR and functional MR can provide additional physiological information. Both MR spectroscopy and diffusion tensor imaging can provide additional information in the differential of neonatal encephalopathy, including perinatal white matter injury, hypoxic-ischemic brain injury, metabolic disease, infection, and birth injury. PMID:17607141

Panigrahy, Ashok; Blüml, Stefan

2007-02-01

92

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

93

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

94

Wavelet-based enhancements to nuclear quadrupole resonance explosives detectors  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is effective for the detecting 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 proved. 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 mine detection. For this application, NQR processing time must be reduced to less than one second. False alarm response due to acoustic and piezoelectric ringing must be suppressed. Also, as TNT is the most prevalent explosive found in land mines NWR detection of TNT must be made practical despite unfavorable relaxation times. 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 response and various false alarm signatures in the absence of explosive compounds.

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

1998-03-01

95

Apodization of coupled resonator optical waveguide devices through a longitudinal offset technique  

NASA Astrophysics Data System (ADS)

In this paper, a novel technique to set the coupling constant between cells of a coupled resonator optical waveguide (CROW) device, in order to tailor the filter response, is presented. It is known that using the same K value for all the couplers produces filtering responses with significant side-lobes for the side-coupled integrated spaced sequence of resonators (SCISSOR) or significant ripples in the pass-band for the direct coupled microrings (CROW). It is also known that the side-lobes/ripples can be reduced, and the pass/reject bands can be made wider, by apodizing the K value of each individual coupler in the structure, starting from a nominal K value (either increasing or decreasing it). This technique consists on changing the effective length of the coupling section by applying a longitudinal offset between the resonators. On the contrary, the conventional techniques are based in the transversal change of the distance between the ring resonators, in steps that are commonly below the current fabrication resolution step (nm scale), leading to strong restrictions in the designs. The technique has been experimentally demonstrated employing a racetrack ring resonator geometry. The proposed longitudinal offset technique allows a more precise control of the coupling and presents an increased robustness against the fabrication limitations, since the needed resolution step is two orders of magnitude higher. Both techniques are compared in terms of the transmission response of CROW devices, under finite fabrication resolution steps. The offset technique presented is sufficient by itself for apodization, and optimized CROW's can be produced with a fixed distance between the rings, solely by changing the offsets.

Doménech, J. D.; Muñoz, P.; Capmany, J.

2010-04-01

96

Sensing of chemical substances using SQUID-based nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Using a high- Tc radio frequency superconducting quantum interference device (rf SQUID) with a normal metal transformer, we successfully detected the nuclear quadrupole resonance (NQR) at about 888 kHz of 14N in p-nitrotoluene (PNT) at room temperature. Only one coil was used as the resonator coil for the transmission and the pickup coil of the transformer. To reduce the influence of the strong excitation field, cross diodes and switches were inserted in the transformer. The signal-to-noise ratio of the NQR spectrum using high- Tc rf SQUID system was comparable to that of using a low noise preamplifier.

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

2007-10-01

97

Measurement of the spin-lattice relaxation time in the NQR of light nuclei  

SciTech Connect

This work proposed a method for increasing the signal/noise ratio in NQR by preliminary magnetization of the sample in a constant magnetic field B/sub 0/ and it subsequent adiabatic demagnetization. The proposed method for the measurement of spin-lattice relaxation times is verified experimentally with a number of compounds. The results agree well with published data.

Anferov, V.P.; Anferova, S.V.; Grechishkin, V.S.; Sinyavskii, N.Ya.

1988-01-01

98

Resonantly enhanced strip-line technique to measure microwave permeability of thin films  

NASA Astrophysics Data System (ADS)

The sensitivity of a reflective single-port strip-line technique is increased by 10-20 times by amplification of a measured reflectivity response at a set of resonance frequencies. The resonant behavior is organized by connecting the strip cell to a network analyzer through a capacitor with a long coaxial cable. The capacitance defines the amplification; the cable length defines the resonance frequencies. S-parameters of the coaxial-to-strip junction and the field inhomogeneity inside the cell are accounted for by a reference measurement of sample with known constitutive parameters. Two methods for permeability calculation are suggested. The fist method is based on the comparison of Lorentzian parameters of resonance reflectivity curves. The second method is based on numerical solution of Fresnel's equation. The enhancement is essential at low-frequency part of the band, where the cell reflectivity is close to unity and the sensitivity of non-resonant technique is poor. The technique sensitivity is estimated by permeability measurements of Al stripes with different cross-section.

Starostenko, S. N.; Rozanov, K. N.

2009-10-01

99

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

100

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

101

Surface plasmon resonance reflectance imaging technique for near-field (~100 nm) fluidic characterization  

Microsoft Academic Search

Surface plasmon resonance (SPR) reflectance imaging technique is devised as a label-free visualization tools to characterize\\u000a near-field (100 nm) fluidic transport properties. The key idea is that the SPR reflectance intensity varies with the near-field\\u000a refractive index (RI) of the test fluid, which in turn depends on the micro\\/nano-fluidic scalar properties, such as concentrations,\\u000a temperatures, and phases. The SPR sensor techniques

Kenneth D. Kihm

2010-01-01

102

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

103

Microwave resonance lamp absorption technique for measuring temperature and OH number density in combustion environments  

NASA Technical Reports Server (NTRS)

A simple technique for simultaneous determination of temperature and OH number density is described, along with characteristic results obtained from measurements using a premixed, hydrogen air flat flame burner. The instrumentation is based upon absorption of resonant radiation from a flowing microwave discharge lamp, and is rugged, relatively inexpensive, and very simple to operate.

Lempert, Walter R.

1988-01-01

104

Magnetic resonance techniques in the evaluation of the perinatal brain: recent advances and future directions  

Microsoft Academic Search

Magnetic resonance (MR) techniques are attractive for use in the developing brain because of their resolving power and their relative noninvasiveness. Their ability to provide detailed structural as well as metabolic and functional information without the use of ionizing radiation is unique. Conventional MR Imaging has widely proven its potential for identifying normal and pathologic brain morphology. Functional MR imaging

Petra S. Huppi; Terrie E. Inder

2001-01-01

105

Computation of resonant frequencies and quality factors of cavities by FDTD technique and Pade approximation  

Microsoft Academic Search

The finite-difference time domain (FDTD) technique and the Pade approximation with Baker's algorithm are used to calculate the mode frequencies and quality factors of cavities. Comparing with the fast Fourier transformation\\/Pade method, we find that the Pade approximation and the Baker's algorithm can obtain exact resonant frequencies and quality factors based on a much shorter time record of the FDTD

Wei-Hua Guo; Wei-Jun Li; Yong-Zhen Huang

2001-01-01

106

The GT resonance revealed in {beta}{sup +}-decay using new experimental techniques  

SciTech Connect

The GT beta decay of {sup 150}Ho has been studied with a Total Absorption Spectrometer (TAS), with an array of 6 Euroball CLUSTER Ge detectors (the CLUSTER CUBE), and with an alpha detector. The three techniques complement each other. The results provide the first observation of an extremely sharp resonance in GT beta decay.

Agramunt, J.; Algora, A.; Cano-Ott, D.; Gadea, A.; Martinez, T.; Ribio, B.; Tain, J. L. [Instituto de Fisica Corpuscular, Dr. Moliner 50, E-46100 Burjassot-Valencia (Spain); Batist, L.; Moroz, F.; Wittmann, V. [St. Petersburg Nuclear Physics Institute, 188-350 Gatchina (Russian Federation); Borcea, R.; Collatz, R.; Gerl, J.; Gorska, M.; Guilbaud, O.; Grawe, H.; Hellstroem, M.; Hu, Z.; Kirchner, R.; Liu, W. [Gesellschaft fuer Schwerionenforschung, D-64220 Darmstadt (Germany)] (and others)

1998-12-21

107

An accurate frequency measuring technique using paramagnetic resonance phenomena in the X-band region  

Microsoft Academic Search

This paper presents a method of measuring frequency in the microwave region by comparing it to a very stable low frequency standard. The technique described here was used to calibrate a cavity wavemeter for an experiment in microwave spectroscopy. The calibration procedure is based on the use of electron and nuclear resonances as they are observed in the presence of

P. Crandell

1958-01-01

108

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

109

Novel phase diagram of superconductivity and ferromagnetism in UGe2: a 73Ge-NQR study under high pressure  

Microsoft Academic Search

We report on the pressure-induced novel phases of ferromagnetism (FM) and superconductivity (SC) in the itinerant ferromagnet UGe2 through 73Ge-NQR measurements under pressure (P). The P dependence of the NQR spectrum points to a first-order transition from strongly to weakly polarized ferromagnetic phases (SP and WP) around a critical pressure of P_{\\\\mathrm {c}}^*\\\\sim 1.2 GPa. Furthermore, it shows the phase

Y. Kitaoka; H. Kotegawa; A. Harada; S. Kawasaki; Y. Kawasaki; Y. Haga; E. Yamamoto; Y. Onuki; K. M. Itoh; E. E. Haller; H. Harima

2005-01-01

110

Evidence for the microscopic coexistence of superconductivity and ferromagnetism in UGe2:Ge-NMR\\/NQR study  

Microsoft Academic Search

We report on the pressure-induced novel phases of ferromagnetism and superconductivity (SC) in the itinerant ferromagnet UGe2 via the 73Ge-NQR measurements under pressure (P). The NQR spectrum has revealed that the ferromagnetic phases are separated into weakly and strongly polarized phases around a critical value of Pc*˜1.2GPa, pointing to a first-order transition around Pc*. Here we present further evidence for

A. Harada; H. Kotegawa; Y. Kawasaki; G.-Q. Zheng; Y. Kitaoka; E. Yamamoto; Y. Haga; Y. Onuki; K. Itoh; E. E. Haller

2005-01-01

111

Evidence for Uniform Coexistence of Ferromagnetism and Unconventional Superconductivity in UGe2: A 73Ge-NQR Study under Pressure  

Microsoft Academic Search

We report on the itinerant ferromagnetic superconductor UGe2 through 73Ge-NQR measurements under pressure (P). The P dependence of the NQR spectrum signals a first-order transition from the low-temperature (T) and low-P ferromagnetic phase (FM2) to high-T and high-P one (FM1) around a critical pressure of Px ˜ 1.2 GPa. The superconductivity exhibiting a maximum value of Tsc=0.7 K at Px

H. Kotegawa; A. Harada; S. Kawasaki; Y. Kawasaki; Y. Kitaoka; Y. Haga; E. Yamamoto; Y. Onuki; K. M. Itoh; E. E. Haller; H. Harima

2005-01-01

112

Stereoelectronic structure and 35Cl NQR parameters of 4-(trichlorgermyl)butan-2-one using ab initio calculations  

NASA Astrophysics Data System (ADS)

The results of ab initio calculations at the RHF/6-31G(d) and MP2/6-31G(d) levels of two stable structures of the 4-(trichlorgermyl)butan-2-one molecule with total optimization of their geometry have been represented. The structure with pentacoordinated Ge atom is energetically more advantageous as compared with that with tetracoordinated one. Using these results, the 35Cl nuclear quadrupole resonance (NQR) frequencies and asymmetry parameters of the electric field gradient (EFG) at the 35Cl nuclei in molecule with pentacoordinated Ge atom have been assessed, the frequencies satisfactorily agreeing with experimental data. Calculations at the RHF/6-31G(d) level have been performed also at various Ge⋯O distances. It has been demonstrated that convergence of the Ge and O coordination centers leads to the increase of positive charge at the Ge coordination center and of negative charge at the O coordination center, at that, electron density from the Ge atom shifts mainly to the axial Cl atom and from the C atom of carbonyl group - to its O atom. The electron density transfer from the O to Ge atom does not occur.

Feshin, V. P.; Feshina, E. V.

2012-03-01

113

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

NASA Astrophysics Data System (ADS)

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.

1990-04-01

114

NOTES ON EXPERIMENTAL TECHNIQUE AND APPARATUS: A method for continuous observation of frequency-capacitance change around resonance and anti-resonance for piezoelectric material  

Microsoft Academic Search

A method of displaying the dielectric behaviour of piezoelectric materials near resonance is described. It is pointed out that the technique offers certain advantages when rapid changes in behaviour are expected.

J. Storry; J. R. Kirkman

1966-01-01

115

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.

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

2014-01-01

116

High efficiency resonance ionization mass spectrometric analysis by external laser cavity enhancement techniques  

SciTech Connect

The demand to measure high dynamic range isotope ratios on small samples with resonance ionization mass spectrometry (RIMS) continues to increase. This paper discusses high ionization efficiency methods which can be applied to continuous wave (cw) RIMS to potentially achieve several tens of percent ionization efficiencies for certain elements. The primary technique under development to achieve this is an external laser cavity which can generate very high circulating laser powers. 12 refs., 3 figs.

Johnson, S.G.; Rios, E.L.; Miller, C.M.; Fearey, B.L.

1991-01-01

117

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

118

Advantages and disadvantages of nuclear magnetic resonance spectroscopy as a hyphenated technique  

Microsoft Academic Search

A general overview of the advancements and applications of nuclear magnetic resonance (NMR) hyphenated with other analytical techniques is given from a practical point of view. Details on the advantages and disadvantages of the hyphenation of NMR with liquid chromatography as LC–NMR and also with mass spectrometry as LC–MS–NMR are demonstrated with two examples. Current developments of NMR with other

Maria Victoria Silva Elipe

2003-01-01

119

Nuclear quadrupole resonance and nuclear magnetic resonance of copper in the high-T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/  

SciTech Connect

The /sup 65/Cu and /sup 63/Cu zero-field nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) at 4.7 and 8.5 T and the spin-lattice relaxation time T/sub 1/ at 8.5 T are measured in the superconducting oxide YBa/sub 2/Cu/sub 3/O/sub 7-//sub 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 assign the /sup 63/Cu NQR line at 22 MHz to the Cu site with oxygen coordination 5. T/sub 1/ is dominated by the quadrupolar relaxation due to spin-phonon coupling.

Furo, I.; Janossy, A.; Mihaly, L.; Banki, P.; Pocsik, I.; Bakonyi, I.; Heinmaa, I.; Joon, E.; Lippmaa, E.

1987-10-01

120

Neutral-Ionic Phase Transition in DMTTF-QCl4 Investigated by 35Cl NQR  

NASA Astrophysics Data System (ADS)

We report a 35Cl NQR investigation into the neutral-ionic (NI) phase transition in DMTTF-QCl4 (4,4'-dimethyltetrathiafulvalene- p-chloranil), the end material of the family containing an NI quantum transition system. Four distinct lines with comparable intensities were observed well below Tc=65 K; this observation is consistent with the antiferroelectric nature of the ionic phase. The temperature dependences of the spectral shift and splitting below Tc are moderate in contrast with the case of TTF-QCl4. Low-energy charge-lattice fluctuations are observed around Tc as a drastic increase of 1/T1, allowing the observation of the quantum fluctuations in a chemically substituted complex. An analysis of the NQR spectra yields detailed temperature variations in the charge transfer and the concomitant lattice distortion around the NI transition.

Iwase, Fumitatsu; Miyagawa, Kazuya; Fujiyama, Shigeki; Kanoda, Kazushi; Horiuchi, Sachio; Tokura, Yoshinori

2007-07-01

121

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

122

Conformations and intermolecular interactions pattern in solid chloroxylenol and triclosan (API of anti-infective agents and drugs). A (35) Cl NQR, (1) H-(14) ?N NQDR, X-ray and DFT/QTAIM study.  

PubMed

Two antibacterial and antifungal agents, chloroxylenol (4-chloro-3,5-dimethyl-phenol) and triclosan (5-chloro-2-(2',4'-dichlorophenoxy)-phenol), were studied experimentally in solid state with an X-ray, (35) Cl-nuclear quadrupole resonance (NQR) and (17) O-nuclear quadrupole double resonance (NQDR) spectroscopies and, theoretically, with the density functional theory/quantum theory of atoms in molecules (DFT/QTAIM). The crystallographic structure of triclosan, which crystallises in space group P3(1) with one molecule in the asymmetric unit [a?=?12.64100(10), b?=?12.64100(10), c = 6.71630(10) Å], was solved with an X-ray and refined to a final R-factor of 2.81% at room temperature. The NQR frequencies of (35) Cl and (17) O were detected with the help of the density functional theory (DFT) assigned to particular chlorine and oxygen sites in the molecules of both compounds. The NQR frequencies at (35) Cl sites in chloroxylenol and triclosan were found to be more differentiated than frequencies at the (17) O site. The former better describes the substituent withdrawing effects connected to ?-electron delocalization within the benzene rings and the influence of temperature; whereas, those at the (17) O site provide more information on O-H bond and intermolecular interactions pattern. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but the opposite to those adopted when it was bound to different inhibitors. According to an X-ray study, temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90?K and at room temperature (RT). The scattering of NQR frequencies reproduced by the DFT under assumption of the X-ray data at 90?K and RT is found to be a good indicator of the quality of resolution of the crystallographic structure. Copyright © 2012 John Wiley & Sons, Ltd. PMID:22354770

Latosi?ska, J N; Latosi?ska, M; Tomczak, M A; Seliger, J; Zagar, V; Maurin, J K

2012-02-21

123

Addition compounds of antimony trichloride and tribromide. Crystal structure and charge transfer from NQR data  

NASA Astrophysics Data System (ADS)

The correlation analysis of the quadrupcle coupling constants(QCC) for the antimony nuclei in the intermolecular compounds of SbCl 3 and SbBr 3 with aromatic hydrocarbons is carried out. The results confirm a supposition about the general similarity of the crystal structures of these complexes. The correlative dependence between the antimony QCC values and also the results of the chlorine and bromine NQR spectra Investigation permit the evaluation of the relative acceptor strength of the antimony trihalide molecules.

Kjuntsel, I. A.; Gordeev, A. D.

124

Unconventional superconductivity in ferromagnetic UGe2: a 73Ge nuclear magnetic resonance\\/nuclear quadrupole resonance study  

Microsoft Academic Search

We report 73Ge nuclear magnetic resonance\\/nuclear quadrupole resonance (NMR\\/NQR) measurements on the itinerant ferromagnetic superconductor UGe2 at ambient pressure (P = 0) and P = 1.3 GPa. Measurements of the nuclear spin-lattice relaxation rate 1\\/T1 of the 73Ge NMR at P = 0 have revealed a T1T = constant behaviour well below TCurie = 52 K, evidencing the presence of

H. Kotegawa; S. Kawasaki; A. Harada; Y. Kawasaki; K. Okamoto; G.-q. Zheng; Y. Kitaoka; E. Yamamoto; Y. Haga; Y. Onuki; K. M. Itoh; E. E. Haller

2003-01-01

125

14N nuclear quadrupole resonance of p-nitrotoluene using a high-Tc rf SQUID  

NASA Astrophysics Data System (ADS)

Using a high-Tc radio-frequency superconducting quantum interference device (rf SQUID), we successfully detected nuclear quadrupole resonance (NQR) at about 887 kHz for 14N in p-nitrotoluene (PNT). A normal metal transformer made of copper wire was used to improve the sensitivity of the high-Tc rf SQUID and pulse-controlled rf switches and cross diodes were inserted in the transformer to reduce the influence of the strong excitation field. The preliminary results for NQR detection using the high-Tc SQUID had a similar signal-to-noise ratio to that of using a low noise preamplifier.

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

2007-03-01

126

27Al-NQR/NMR Study of Kondo Semiconductor CeFe2Al10  

NASA Astrophysics Data System (ADS)

27Al-NQR/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1/T1 above about 20 K, following the Korringa law (T1T = const.) below 20 K, indicates a pseudogap opening near the Fermi level. The gap magnitude of 70 K with a mid-gap state of 42% is estimated based on a rectangular density of states. The gap magnitude is much larger than the gap of 15 K evaluated previously from the electrical resistivity, which suggests CeFe2Al10 to be a Kondo semiconductor with a Kondo temperature much higher than 300 K.

Kawamura, Yukihiro; Edamoto, Shingo; Takesaka, Tomoaki; Nishioka, Takashi; Kato, Harukazu; Matsumura, Masahiro; Tokunaga, Yo; Kambe, Shinsaku; Yasuoka, Hiroshi

2010-10-01

127

Isotope effect on the temperature dependence of the 35Cl NQR frequency in (NH4)2RuCl6  

NASA Astrophysics Data System (ADS)

The 35Cl nuclear quadrupole resonance frequencies and spin-lattice relaxation times for (NH4)2RuCl6, (ND4)2RuCl6, (NH4)2SnCl6, and (ND4)2SnCl6 were measured in the temperature range 4.2-300 K. In these four compounds, it was confirmed that no phase transition occurs in the observed temperature range. At 4.2 K, discrepancies of the NQR frequency between non-deuterated and deuterated compounds, which are attributed to the difference in the spatial distributions of hydrogen (deuterium) atoms in the ground states of the rotational motion of ammonium ion, reached to 24 kHz and 23 kHz for the ruthenate compounds and the stannate compounds, respectively. The separation between the ground and the first excited states of the rotational motion of the ammonium ion was estimated to be 466 J mol-1 and 840 J mol-1 for (ND4)2RuCl6 and (NH4)2RuCl6, respectively, by least-square fitting calculations of temperature dependence of the NQR frequency. For (ND4)2SnCl6 and (NH4)2SnCl6, these quantities were estimated to be 501 J mol-1 and 1544 J mol-1, respectively. It was clarified that the T1 minimum, which has been observed for the stannate compounds at around 60 K as a feature of the temperature dependence, was dependent on a method of sample preparation. It is concluded that the minimum is not an essential character of the ammonium hexachlorostannate(IV) since the crystals prepared in strong acid condition to prevent a partial substitution of chlorine atoms by hydroxyl groups, did not show such T1 minimum.

Kume, Yoshio; Amino, Daiki; Asaji, Tetsuo

2013-07-01

128

Frequency-Temperature Compensation Techniques for High-Q Microwave Resonators  

NASA Astrophysics Data System (ADS)

Low-noise high-stability resonator oscillators based on high-Q monolithic sapphire ``Whispering Gallery'' (WG)-mode resonators have become important devices for telecommunication, radar and metrological applications. The extremely high quality factor of sapphire, of 2 x10^5 at room temperature, 5 x10^7 at liquid nitrogen temperature and 5 x10^9 at liquid helium temperature has enabled the lowest phase noise and highly frequency-stable oscillators in the microwave regime to be constructed. To create an oscillator with exceptional frequency stability, the resonator must have its frequency-temperature dependence annulled at some temperature, as well as a high quality factor. The Temperature Coefficient of Permittivity (TCP) for sapphire is quite large, at 10-100parts per million/K above 77K. This mechanism allows temperature fluctuations to transform to resonator frequency fluctuations.A number of research groups worldwide have investigated various methods of compensating the TCP of a sapphire dielectric resonator at different temperatures. The usual electromagnetic technique of annulment involves the use of paramagnetic impurities contributing an opposite temperature coefficient of the magnetic susceptibility to the TCP. This technique has only been realized successfully in liquid helium environments. Near 4K the thermal expansion and permittivity effects are small and only small quantities of the paramagnetic ions are necessary to compensate the mode frequency. Compensation is due to impurity ions that were incidentally left over from the manufacturing process.Recently, there has been an effort to dispense with the need for liquid helium and make a compact flywheel oscillator for the new generation of primary frequency standards such as the cesium fountain at the Laboratoire Primaire du Temps et des Fréquences (LPTF), France. To achieve the stability limit imposed by quantum projection noise requires that the local oscillator stability is of the order of 10^-14. Currently work is under way to achieve this goal in space-borne and mobile liquid-nitrogen-cooled systems. The work appears promising and, as at early 2000, the realization of this goal should not be far off.In this contribution we review techniques that cancel the TCP of sapphire and other dielectric resonators. Details of the temperature control system required to achieve current and target frequency stabilities are discussed.

Hartnett, John G.; Tobar, Michael E.

129

Antitank and Antipersonnel Mine Detection Test Results for a Nuclear Quadrupole Resonance Detection System.  

National Technical Information Service (NTIS)

This report summarizes the results of an interim test of a system that uses the nuclear quadrupole resonance (NQR) signature of explosives for the detection of antipersonnel (AP) and antitank (AT) land mines. The system, designed and built by Quantum Magn...

F. S. Rotondo E. Ayers

2000-01-01

130

Resonant-type MEMS transducers excited by two acoustic emission simulation techniques  

NASA Astrophysics Data System (ADS)

Acoustic emission testing is a passive nondestructive testing technique used to identify the onset and characteristics of damage through the detection and analysis of transient stress waves. Successful detection and implementation of acoustic emission requires good coupling, high transducer sensitivity and ability to discriminate noise from real signals. We report here detection of simulated acoustic emission signals using a MEMS chip fabricated in the multi-user polysilicon surface micromachining (MUMPs) process. The chip includes 18 different transducers with 10 different resonant frequencies in the range of 100 kHz to 1 MHz. It was excited by two different source simulation techniques; pencil lead break and impact loading. The former simulation was accomplished by breaking 0.5 mm lead on the ceramic package. Four transducer outputs were collected simultaneously using a multi-channel oscilloscope. The impact loading was repeated for five different diameter ball bearings. Traditional acoustic emission waveform analysis methods were applied to both data sets to illustrate the identification of different source mechanisms. In addition, a sliding window Fourier transform was performed to differentiate frequencies in time-frequency-amplitude domain. The arrival and energy contents of each resonant frequency were investigated in time-magnitude plots. The advantages of the simultaneous excitation of resonant transducers on one chip are discussed and compared with broadband acoustic emission transducers.

Ozevin, Didem; Greve, David W.; Oppenheim, Irving J.; Pessiki, Stephen

2004-07-01

131

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

132

Oxidative Stress Imaging in Live Animals with Techniques Based on Electron Paramagnetic Resonance  

PubMed Central

Oxidative stress has been the object of considerable biological and biochemical investigation. Quantification has been difficult although the quantitative level of products of biological oxidations in tissues and tissue products has emerged as a widely used technique. The relationship between these products and the amount of oxidative stress is less clear. Imaging oxidative stress with electron paramagnetic resonance related magnetic resonance imaging, while not addressing the specific issue of quantification of initiating events, focuses on the anatomic specific location of the oxidative stress. Moreover, the relative quantification of oxidative stress of one location against another is possible, sharpening our understanding of oxidative stress. This promises to improve our understanding of oxidative stress and its deleterious consequences and enhance our understanding of the effectiveness of interventions to modulate oxidative stress and its consequences.

Elas, Martyna; Ichikawa, Kazuhiro; Halpern, Howard J.

2013-01-01

133

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

134

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

135

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

136

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

137

Thickness-induced resonance-based complex permittivity measurement technique for barium strontium titanate ceramics at microwave frequency.  

PubMed

Thickness-induced resonance would be the major factor of uncertainty for complex permittivity measurement by using transmission/reflection method when the thickness of sample is several integer multiples of the half wavelength. A new technique for complex permittivity measurement was presented in this paper using the thickness-induced resonance for barium strontium titanate (BST) ceramics at microwave frequency. Simulated and experimental results show that there are some resonance peaks on the transmittance versus frequency curve and the complex permittivity can be calculated from the resonance. PMID:19947747

Xia, Song; Xu, Zhuo; Wei, Xiaoyong

2009-11-01

138

Motion estimation of tagged cardiac magnetic resonance images using variational techniques.  

PubMed

This work presents a new method for motion estimation of tagged cardiac magnetic resonance sequences based on variational techniques. The variational method has been improved by adding a new term in the optical flow equation that incorporates tracking points with high stability of phase. Results were obtained through simulated and real data, and were validated by manual tracking and with respect to a reference state-of-the-art method: harmonic phase imaging (HARP). The error, measured in pixels per frame, obtained with the proposed variational method is one order of magnitude smaller than the one achieved by the reference method, and it requires a lower computational cost. PMID:20413267

Carranza-Herrezuelo, N; Bajo, A; Sroubek, F; Santamarta, C; Cristobal, G; Santos, A; Ledesma-Carbayo, M J

2010-09-01

139

New developments in magnetic resonance imaging techniques for shoulder instability in athletes  

PubMed Central

Magnetic resonance (MR) imaging can be a very useful tool in the evaluation of instability in the athlete’s shoulder. Technical options of MR imaging, such as arthrography, higher power magnets, and shoulder positioning, have enhanced MR evaluation of the shoulder. This update discusses the application of new MR techniques to a variety of shoulder instability patterns, including anterior instability, posterior instability, and atraumatic multidirectional instability. Specific applications of MR imaging in the postoperative patient is discussed. Finally, we describe the future directions of MR imaging in the setting of shoulder instability.

McAdams, Timothy R; Fredericson, Michael; Vogelsong, Melissa; Gold, Garry

2010-01-01

140

Myocardial tagging by cardiovascular magnetic resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications.  

PubMed

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

Ibrahim, El-Sayed H

2011-01-01

141

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.

2011-01-01

142

Structural study of selected polyhalogenated benzimidazoles (protein kinase CK2 inhibitors) by nuclear quadrupole double resonance, X-ray, and density functional theory.  

PubMed

Protein kinase CK2 inhibitors, polyhalogenated benzimidazoles, have been studied experimentally in solid state by NMR-NQR double resonance and X-ray and theoretically by the density functional theory (DFT). Six resonance frequencies on (14)N have been detected and assigned to particular nitrogen sites in each polyhalogenated benzimidazole molecule. The effects of prototropic annular tautomerism and polymorphism related to stable cluster formation due to intermolecular hydrogen bonding interactions on the (14)N NQR parameters have been analyzed within the DFT and AIM (atoms in molecules) formalism. The studies suggest that all polyhalogenobenzimidazoles are isostructural and can exhibit polymorphism and that (14)N NQR is very sensitive to hydrogen bondings but less sensitive to the specific arrangement of the hydrogen bonded molecules. NQDR and DFT results suggest the presence of the prototropic annular tautomerism 50:50, which is in a good agreement with the X-ray and (1)H NMR data. PMID:20055520

Latosi?ska, J N; Latosi?ska, M; Seliger, J; Zagar, V; Maurin, J K; Orzeszko, A; Kazimierczuk, Z

2010-01-14

143

Dimensional characterization of a quasispherical resonator by microwave and coordinate measurement techniques  

NASA Astrophysics Data System (ADS)

We describe the dimensional characterization of copper quasisphere NPL-Cranfield 2. The quasisphere is assembled from two hemispheres such that the internal shape is a triaxial ellipsoid, the major axes of which have nominal radii 62.000 mm, 62.031 mm and 62.062 mm. The artefact has been manufactured using diamond-turning technology and shows a deviation from design form of less than ±1 µm over most of its surface. Our characterization involves both coordinate measuring machine (CMM) experiments and microwave resonance spectroscopy. We have sought to reduce the dimensional uncertainty below the maximum permissible error of the CMM by comparative measurements with silicon and Zerodur spheres of known volume. Using this technique we determined the equivalent radius with an uncertainty of u(k = 1) = 114 nm, a fractional uncertainty of 1.8 parts in 106. Due to anisotropy of the probe response, we could only determine the eccentricities of the quasihemispheres with a fractional uncertainty of approximately 2%. Our microwave characterization uses the TM11 to TM18 resonances. We find the equivalent radius inferred from analysis of these modes to be consistent within ±4 nm with an overall uncertainty u(k = 1) = 11 nm. We discuss corrections for surface conductivity, waveguide perturbations and dielectric surface layers. We find that the CMM radius estimates derived from each hemisphere cannot be used to accurately predict the equivalent radius of the assembled resonator for two reasons. Firstly, the equatorial flanges are flat only to within ±1 µm, leading to an equatorial 'gap' whose dimension cannot be reliably estimated. Secondly, the resonator undergoes significant elastic distortion when the bolts connecting the hemispheres are tightened. We provide CMM and microwave measurements to support these conclusions in addition to finite-element modelling. Finally, we consider the implications of this work on a forthcoming experiment to determine the Boltzmann constant with a relative uncertainty below 1 part in 106.

Underwood, R.; Flack, D.; Morantz, P.; Sutton, G.; Shore, P.; de Podesta, M.

2011-02-01

144

High-Frequency Mode Conversion Technique for Stiff Lesion Detection with Magnetic Resonance Elastography  

PubMed Central

A novel imaging technique is described in which the mode conversion of longitudinal waves is used for the qualitative detection of stiff lesions within soft tissue using Magnetic Resonance Elastography (MRE) methods. Due to the viscoelastic nature of tissue, high-frequency shear waves attenuate rapidly in soft tissues but much less in stiff tissues. By introducing minimally attenuating longitudinal waves at a significantly high frequency into tissue, shear waves produced at interfaces by mode conversion will be detectable in stiff regions, but will be significantly attenuated and thus not detectable in the surrounding soft tissue. This contrast can be used to detect the presence of stiff tissue. The proposed technique is shown to readily depict hard regions (mimicking tumors) present in tissue-simulating phantoms and ex vivo breast tissue. In vivo feasibility is demonstrated on a patient with liver metastases where the tumors are readily distinguished. Preliminary evidence also suggests that quantitative stiffness measurements of stiff regions obtained with this technique are more accurate than those from conventional MRE because of the short shear wavelengths. This rapid, qualitative technique may lend itself to applications in which the localization of stiff, suspicious neoplasms is coupled with more sensitive techniques for thorough characterization.

Mariappan, Yogesh K; Glaser, Kevin J; Manduca, Armando; Romano, Anthony J; Venkatesh, Sudhakar K; Yin, Meng; Ehman, Richard L

2011-01-01

145

Phase-stepping technique for highly sensitive microscopic surface plasmon resonance biosensor.  

PubMed

In this paper, the phase-stepping technique is applied to improve a phase-sensitive surface plasmon resonance biosensor based on differential interferometry between focused radially polarized and azimuthally polarized cylindrical vector beams. Detailed analysis is presented for the phase-stepping method, and the least squares unwrapping algorithm is employed to detect the phase distribution in correspondence to the refractive index of sample. Benefiting from the phase-stepping technique, both the measurement speed and sensitivity are improved significantly. The proposed sensor maintains high sensitivity of 9.4×10-7??RIU/1° and a wide dynamic range of 0.35 RIU simultaneously. Furthermore, the real-time binding reaction process of bovine serum albumin with antibody is monitored to verify the system for potential biological applications. PMID:24663261

Zhang, Chonglei; Wang, Rong; Wang, Yijia; Zhu, Siwei; Min, Changjun; Yuan, X-C

2014-02-10

146

A new pulse width reduction technique for pulsed electron paramagnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

We present a new technique for a microwave pulse modulator that generates a short microwave pulse of approximately 1 ns for use in an electron paramagnetic resonance (EPR) spectrometer. A quadruple-frequency multiplier that generates a signal of 16-20 GHz from an input of 4-5 GHz was employed to reduce the rise and fall times of the pulse prepared by a PIN diode switch. We examined the transient response characteristics of a commercial frequency multiplier and found that the device can function as a multiplier for pulsed signal even though it was designed for continuous wave operation. We applied the technique to a Ku band pulsed EPR spectrometer and successfully observed a spin echo signal with a broad excitation bandwidth of approximately 1.6 mT using 80° pulses of 1.5 ns.

Ohba, Yasunori; Nakazawa, Shigeaki; Kazama, Shunji; Mizuta, Yukio

2008-03-01

147

A technique for reconstruction of global lightning distance profile from background Schumann resonance signal  

NASA Astrophysics Data System (ADS)

An inverse problem solution is considered for revealing the total worldwide lightning intensity and its distance distribution based on the decomposition of the average background Schumann resonance (SR) spectra. The one-site technique developed can be applied without invoking any preliminary suppositions about the spatial structure of the world thunderstorm activity. The technique enables to reduce the influence of additive noises occurring in experimental measurements. Linear combinations of the average power spectra of the electric and magnetic field are employed for the inverse problem solution emphasizing in this way distance dependence or basic SR peaks. Ratios between the average electric and magnetic spectra and between their linear combinations, which enable to eliminate the source spectrum influence, have been considered for the solution of the inverse problem. Influence of errors in the source model and propagation parameters has numerically been studied on the recovered field spectra values of the total lightning intensity and its distance profile.

Shvets, A. V.

2001-07-01

148

Resonance  

NSDL National Science Digital Library

All About Circuits is a website that âÂÂprovides 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.

2008-07-07

149

Structure and phase transition in bis(pyrrolidinium) hexachlorometallates, (C 4H 8NH 2) 2MCl 6 (M=Sn, Te and Pt), studied by X-ray diffraction, 35Cl NQR and DSC  

NASA Astrophysics Data System (ADS)

Single crystal X-ray diffraction, 35Cl nuclear quadrupole resonance (NQR) and differential scanning calorimetry (DSC) measurements were taken for bis(pyrrolidinium) hexachlorometallates, (C 4H 8NH 2) 2MCl 6 (M=Sn, Te and Pt). A solid-solid phase transition was observed at 150(1), 159(1) and 134(1) K for stannate, tellurate and platinate, respectively. 35Cl NQR signals were observed in stannate and platinate, both of which showed a two-line spectrum in the high-temperature phase and a three-line spectrum in the low-temperature phase. The high-temperature phases of the three complexes were found to be isostructural with each other belonging to the space group C2/ m (#12). The C 4H 8NH 2+ and MCl 62- ions are connected by N-H⋯Cl hydrogen bonds forming parallel sheets in the crystals. Disorder of the cation ring appears in these high-temperature phases. Semi-empirical MO calculations were performed to estimate the stable structure of the pyrrolidinium ion.

Ishida, H.; Furukawa, Y.; Sato, S.; Kashino, S.

2000-06-01

150

Frequencies of nuclear resonances for copper and electronic wave function of antiferromagnetic La2CuO4  

Microsoft Academic Search

Calculated values of the frequencies of nuclear magnetic and quadrupole resonances (for65Cuv(NMR) = 107 MHz, v(NQR) = 32 MHz) are close to the experimental values (100 MHz and 29.5 MHz). This coincidence is a reliable test of the obtained electronic wave function.

V. V. Flambaum; O. P. Sushkov

1990-01-01

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.

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

2013-01-01

152

Assessment of Valvular Regurgitation Using Cine Magnetic Resonance Imaging Coupled with Phase Compensation Technique: Comparison with Doppler Color Flow Mapping  

Microsoft Academic Search

To elucidate whether or not a newly developed technique in cinematic-displayed (cine) magnetic resonance imaging (MRI) can improve the semiquantitative evaluation of valvular regurgitant flow, 20 patients with valvular lesions were studied. Three pulse sequences of cine MRI, ie, standard, short echo time (TE), and rephasing scans, were compared with reference obtained by Doppler color flow mapping. Short TE technique

Shusaku Ohnishi; Sugao Fukui; Hideo Kusuoka; Akira Kitabatake; Michitoshi Inoue; Takenobu Kamada

1992-01-01

153

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

154

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.

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

2014-01-01

155

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

156

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.

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

157

Novel Design of Sagnac Interferometry Assisted with Surface Plasmon Resonance Based Sensor Technique  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate a novel design to investigate interfacial reaction of optical activity materials, utilizing a Sagnac interferometer assisted with surface plasmon resonance based sensor technique. Upon application to interrogate optical activity, the type-2 optical configuration of close loop in this work can entirely encircle the interaction zone of surface plasmon resonance reacting with optical activity medium, while the type-1 optical configuration of close loop does partially. The greater the geometrical phase owing to the encircled interaction zone between optical activity medium and polarized light, the larger the phase shift of interference pattern modulated by the concentration of optical activity medium. The slope of phase shift in interference phase pattern of p-wave vs. concentration of dextrose solution determined with this method is greatly improved, 3000 times better than that with Lee's method, 18,600 times with Lin's method, and 222,000 times with Chou's method. Besides, the pinch point of phase shift vs. concentration indicates the ending of interference pattern phase shift as the concentration of each tested optical activity medium keeps climbing up, and can reflect the strong dependence of molecular shape during interfacial adsorption.

Li, Yu-Chu M.; Huang, Chao-Ming; Chang, Wei-Chin; Lin, Kai-Jan; Chang, Sheng-Chih; Yao, Sheng-Cheng

2011-06-01

158

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

159

A novel 5 displacement spin-labeling technique for electron paramagnetic resonance spectroscopy of RNA.  

PubMed Central

An RNA spin-labeling technique was developed using the well-characterized interaction between the HIV Rev peptide and the Rev response element (RRE) RNA as a model system. Spin-labeled RNA molecules were prepared by incorporating guanosine monophosphorothioate (GMPS) at the 5' end using T7 RNA polymerase and then covalently attaching a thiol-specific nitroxide spin label. Three different constructs of the RRE RNA were made by strategically displacing the 5' end within the native three-dimensional structure. Nitroxide-to-nitroxide distance measurements were made between the specifically bound RNA and peptide using electron paramagnetic resonance (EPR) spectroscopy. The dipolar EPR method can reliably measure distances up to 25 A, the calculation of which is derived from the 1/r3 dependence of the broadening of EPR lines in motionally frozen samples. This RNA-labeling technique, dubbed 5' displacement spin labeling, extends the usefulness of the dipolar EPR method developed for analysis of protein structure. The advantage of this technique is that it is applicable to large RNA systems such as the ribosome, which are difficult to study by other structural methods.

Macosko, J C; Pio, M S; Tinoco, I; Shin, Y K

1999-01-01

160

Implant stability evaluation by resonance frequency analysis in the fit lock technique. A clinical study  

PubMed Central

Summary Surgical procedures for the application of implants in the lateral-superior sectors are affected by the availability of the residual bone. When this condition is lower than 5 mm it is recommended that techniques involving two therapeutic phases, a reconstructive and an applicative one, as reported in the international literature, are adopted. The authors propose here a new method with the potential to apply implants simultaneously with the reconstructive phase. The aim of this longitudinal retrospective study was to evaluate the stability of implants applied with the fit lock technique in the upper maxillarys in us with bone availability lower than 4 mm by measuring resonance frequency at different follow-up periods The seme as urements, carried out on 30 implants, were analysed with specific statistical procedures. The results indicate that the stability of the implants inserted with the fit lock method increases progressively over time in a statistically significant manner. The stability recorded after one year from the insertion (ISQ T2) is significantly higher than that recorded after six months (ISQ T1), and this is significantly higher than that recorded at the time of implant placement (ISQ T0). The implants inserted in the maxillary zones with scarce bone availability and applied with this technique showed a similar stability as reported with other techniques. In light of the results, the authors confirm that the primary stability represents the basic requirement to guarantee a correct healing of the implant and demonstrate that the fit lock technique also all ows reaching this condition when bone availability is minimal.

Falisi, Giovanni; Galli, Massimo; Velasquez, Pedro Vittorini; Rivera, Juan Carlos Gallegos; Di Paolo, Carlo

2013-01-01

161

Surface plasmon resonance reflectance imaging technique for near-field (~100 nm) fluidic characterization  

NASA Astrophysics Data System (ADS)

Surface plasmon resonance (SPR) reflectance imaging technique is devised as a label-free visualization tools to characterize near-field (100 nm) fluidic transport properties. The key idea is that the SPR reflectance intensity varies with the near-field refractive index (RI) of the test fluid, which in turn depends on the micro/nano-fluidic scalar properties, such as concentrations, temperatures, and phases. The SPR sensor techniques have been widely used in many different areas, particularly in the biomedical and biophysical societies. While flow visualization techniques based on RI detection have been extensively well documented (Merzkirch 1987), the use of SPR imaging for fluidic applications has been introduced only recently since the author’s group presented a series of related studies in the past few years. The primary goal of this review article is two-fold: (1) Introduction of the working principles of the SPR imaging as a fluidic sensor, and (2) Presentation of example measurement applications for various fluidic scalar properties using the SPR imaging sensor technique. Section 1 summarizes the history and the basic principle of SPR by focusing on the Kretschmann’s theory and Sect. 2 describes the laboratory SPR imaging system specifically designed for fluidic applications. Section 3 presents the optical and material properties that affect the SPR measurement capabilities and sensitivity. Section 4 presents example applications of the implemented SPR for different near-field characterization problems, including (1) micromixing concentration field, (2) convective/diffusion of salinity distributions, (3) full-field thermometry, and (4) fingerprinting of crystallized nanofluidic self assembly. Sections 5 and 6 discuss the spatial measurement resolutions of the SPR imaging technique and the overall measurement sensitivities, respectively. Section 7 presents a few suggestions to further enhance the SPR measurement accuracy particularly for near-field fluidic characterization.

Kihm, Kenneth D.

2009-07-01

162

Complimentary effect of yogic sound resonance relaxation technique in patients with common neck pain  

PubMed Central

Background: Studies have shown that conventional treatment methods with drugs, physiotherapy and exercises for common neck pain (CNP) may be inadequate. Yoga techniques have been found to be effective complimentary therapies in chronic low back pain and also for stress reduction in other diseases. Objective: The aim of the study was to examine the complimentary role of a yogic relaxation called mind sound resonance technique (MSRT) in non-surgical management of CNP. Materials and Methods: In this randomized controlled study, 60 patients with CNP were assigned to two groups (yoga, n=30) and (control, n=30). The yoga group received yogic MSRT for 20 minutes in supine position after the conventional physiotherapy program for 30 minutes using pre-recorded audio CD and the control group had non-guided supine rest for 20 minutes (after physiotherapy), for 10 days. MSRT provides deep relaxation for both mind and body by introspective experience of the sound resonance in the whole body while repeating the syllables A, U, M and Om and a long chant (Mahamrityunjaya mantra) several times in a meaningful sequence. Both the groups had pre and post assessments using visual pain analog scale, tenderness scoring key, neck disability score (NDS) questionnaire, goniometric measurement of cervical spinal flexibility, and state and trait anxiety inventory-Y1 (STAI-Y1). Results: Mann-Whitney U test showed significant difference between groups in pain (P<0.01), tenderness (P<0.01), neck movements (P<0.01). NDS (P<0.01) and state anxiety (STAI-Y1) showed higher reduction in yoga (P<0.01) than that in the control group. Wilcoxon’s test showed a significant improvement in both groups on all variables (P<0.01). Conclusions: Yoga relaxation through MSRT adds significant complimentary benefits to conventional physiotherapy for CNP by reducing pain, tenderness, disability and state anxiety and providing improved flexibility.

Yogitha, Bali; Nagarathna, R; John, Ebnezar; Nagendra, HR

2010-01-01

163

Nuclear quadrupole resonance of explosives: Simultaneous detection of RDX and PETN in semtex  

Microsoft Academic Search

We have used nuclear quadrupole resonance (NQR) for the detection of14N in explosives and introduce a new method for the simultaneous detection of the explosives cyclotrimethylene trinitramine\\u000a (RDX) and pentaerythritol tetranitrate (PETN). We have developed an interleaved pulse sequence, which provides efficient excitation\\u000a of both RDX and PETN, to drive a solenoid coil that is doubly resonant at 3.41 and

R. I. Jenkinson; J. M. Bradley; G. N. Shilstone

2004-01-01

164

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

165

Heteronuclear X-Y double-resonance solid-state NMR: Techniques for structural characterization of inorganic materials  

NASA Astrophysics Data System (ADS)

Since the introduction of the Magic Angle Spinning (MAS) technique, solid state NMR has become an increasingly important tool in the characterization of inorganic materials. Solid state NMR experiments, however, can be very time consuming due to the low sensitivities and/or low natural abundances for many of the NMR active nuclei. Furthermore, under MAS conditions, interactions arising from the dipolar coupling are averaged to zero and any dipolar information lost. The goal of this research is to develop and apply double resonance NMR techniques which (1) may increase the sensitivity of many NMR active nuclei and (2) may preserve the resolution achieved by MAS while re-introducing the dipolar coupling information. Because of the dependence on the internuclear distance, r, the heteronuclear dipole coupling can be exploited to obtain information on local environments, internuclear distances, and to aid in spectral editing and phase identification. This study focuses on the double resonance techniques: Cross Polarization with Magic Angle Spinning (CPMAS), Heteronuclear Double Quantum Filtering (HDQF), Spin Echo Double Resonance (SEDOR), and Rotational Echo DOuble Resonance (REDOR). These techniques may be used to examine a wide variety of systems. The application of these techniques to the following systems will be demonstrated: (1) Semiconductor alloys in the CdSiAssb{2-x}Psb{x} system; (2) Crystalline and amorphous ternary Al-P-Se system; (3) Crystalline and amorphous borosilicates; (4) Zirconium phosphate substituted with vanadium.

Hudalla, Christopher John

166

Study of a defect detection accuracy of a granite nondestructive resonance technique based on a laser interferometer  

NASA Astrophysics Data System (ADS)

A nondestructive testing technique based on a resonance approach and a laser interferometer device is introduced in the presented paper. It utilizes a not synchronized with an acquisition device and low power excitation source. Induced vibrations are acquired using high resolution laser interferometer in a configuration of a vibrometer. As a result, the test equipment is significantly simplified and tailored to the industry requirements. Sample evaluation process is based on a processing that fits lowest order resonance frequencies to p-wave and s-wave frequencies. Obtained velocities are used to fit higher order resonance frequencies present in the response with positions and lengths of resonators formed by cracks or flaws. Presented research focuses on an assessment of accuracy and sensitivity of the introduced method. Performed measurements revealed that it is possible to obtain decent parameters for industry applications.

Pod?orny, Tomasz; Budzy?, Grzegorz; Rzepka, Janusz; Tkaczyk, Jakub

2014-05-01

167

Sodium and potassium salts of dichloroisocyanuric acid and their hydrates as antimicrobials agents studied by 35Cl-NQR spectroscopy and DFT calculations  

Microsoft Academic Search

The electronic structure of dichloroisocyanuric acid derivatives was analysed by 35Cl-NQR spectroscopy and DFT calculations. Here we concentrate our attention on three different factors: type of metallic substituent (sodium and potassium), temperature of the sample (liquid nitrogen and room) and degree of hydration (an amount of water molecules attached to analysed compounds). In particular, all the variations in 35Cl-NQR frequencies

A. Walczak; B. Brycki; M. Kaczmarek; O. Kh. Poleshchuk; M. Ostafin; B. Nogaj

2006-01-01

168

Parametric resonance for vibration energy harvesting with design techniques to passively reduce the initiation threshold amplitude  

NASA Astrophysics Data System (ADS)

A vibration energy harvester designed to access parametric resonance can potentially outperform the conventional direct resonant approach in terms of power output achievable given the same drive acceleration. Although linear damping does not limit the resonant growth of parametric resonance, a damping dependent initiation threshold amplitude exists and limits its onset. Design approaches have been explored in this paper to passively overcome this limitation in order to practically realize and exploit the potential advantages. Two distinct design routes have been explored, namely an intrinsically lower threshold through a pendulum-lever configuration and amplification of base excitation fed into the parametric resonator through a cantilever-initial-spring configuration. Experimental results of the parametric resonant harvesters with these additional enabling designs demonstrated an initiation threshold up to an order of magnitude lower than otherwise, while attaining a much higher power peak than direct resonance.

Jia, Yu; Yan, Jize; Soga, Kenichi; Seshia, Ashwin A.

2014-06-01

169

A study of the nonorthogonal FDTD method versus the conventional FDTD technique for computing resonant frequencies of cylindrical cavities  

Microsoft Academic Search

The nonorthogonal finite-difference-time-domain (FDTD) technique is used to compute the resonant frequencies of dielectric-filled cylindrical cavities. Because the method is based on the nonorthogonal coordinate system, it is not restricted to specific geometries, e.g. rectangular or axially symmetric geometries, and is suitable for analyzing cavities of arbitrary shape. The advantages of this technique over the conventional FDTD algorithm with a

Paul H. Harms; Jin-Fa Lee; Raj Mittra

1992-01-01

170

Circular Dichroism and Photoelectron Angular Distributions of Excited States of Cesium and Rubidium Using Resonantly Enhanced Multiphoton Ionization Techniques  

Microsoft Academic Search

Resonantly enhanced multiphoton ionization (REMPI) techniques are used to study spin-orbit effects in the photoelectron angular distributions (PEAD) of excited ns (n = 8-13) states of cesium. The asymmetry parameters are shown to exhibit an energy dependence in the region of the Cooper minimum of the photoionization cross section, supporting predictions made by inclusion of relativistic coupling in the continuum.

Luis Edgardo Cuellar

1993-01-01

171

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

Microsoft Academic Search

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

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

1992-01-01

172

The use of electron spin resonance techniques to determine gamma ray exposure of $\\\\alpha$-keratin in human hair  

Microsoft Academic Search

The objective of this research was to determine the potential for using electron spin resonance (ESR) techniques with human $\\\\alpha$-keratin (hair) as a measure of gamma ray exposure. Samples of black, brown, and blond hair from six healthy white human volunteers ages 19 to 47 were examined. Samples from each person were throughly mixed and split into 8 parts of

Thomas Edward Johnson

1997-01-01

173

Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3 : An In115 -NQR study under pressure  

NASA Astrophysics Data System (ADS)

We report on pressure-induced unconventional superconductivity (SC) in the heavy-fermion (HF) antiferromagnet CeIn3 by means of nuclear-quadrupole-resonance (NQR) studies conducted under a high pressure. The temperature (T) and pressure (P) dependences of the In-NQR spectra have revealed a first-order quantum-phase transition (QPT) from antiferromagnetism (AFM) to paramagnetism (PM) at a critical pressure Pc=2.46GPa at which AFM disappears with a minimum value of TN(Pc)=1.2K . High-energy x-ray scattering measurements under P show a progressive decrease in the lattice density without any change in the crystal structure, whereas an increase in the NQR frequency (?Q) indicates an increase in the hybridization between 4f electrons and conduction electrons, which stabilizes the HF-PM state. This competition between the AFM phase where TN is reduced and the formation of the HF-PM phase triggers the first-order QPT at Pc=2.46GPa . Despite the lack of an AFM quantum critical point in the P-T phase diagram, we highlight the fact that unconventional SC occurs in both phases of AFM and PM. The measurements of the nuclear spin-lattice relaxation rate 1/T1 in the AFM phase have provided evidence for the uniformly coexisting AFM+SC phase. Remarkably, the significant increase in 1/T1 upon cooling in the AFM phase has revealed the development of low-lying magnetic excitations down to Tc in the AFM phase; it is indeed relevant to the onset of the uniformly coexisting AFM+SC phase. In the HF-PM phase where AFM fluctuations are not developed, 1/T1 decreases without the coherence peak just below Tc , followed by a power-law-like T dependence that indicates an unconventional SC with a line-node gap. Remarkably, Tc has a peak around Pc in the HF-PM phase as well as in the AFM phase. In other words, an SC dome exists with a maximum value of Tc=230mK around Pc , indicating that the origin of the pressure-induced HF SC in CeIn3 is not relevant to AFM spin fluctuations but to the emergence of the first-order QPT in CeIn3 . These phenomena observed in CeIn3 should be understood in terms of the first-order QPT because these new phases of matter are induced by applying P . When the AFM critical temperature is suppressed at the termination point of the first-order QPT, Pc=2.46GPa , the diverging AFM spin-density fluctuations emerge at the critical point from AFM to PM. The results with CeIn3 leading to a new type of quantum criticality deserve further theoretical investigations.

Kawasaki, S.; Yashima, M.; Kitaoka, Y.; Takeda, K.; Shimizu, K.; Oishi, Y.; Takata, M.; Kobayashi, T. C.; Harima, H.; Araki, S.; Shishido, H.; Settai, R.; ?nuki, Y.

2008-02-01

174

Oxygen limited thermal tolerance in fish?--Answers obtained by nuclear magnetic resonance techniques.  

PubMed

In various phyla of marine invertebrates limited capacities of both ventilatory and circulatory performance were found to set the borders of the thermal tolerance window with limitations in aerobic scope and onset of hypoxia as a first line of sensitivity to both cold and warm temperature extremes. The hypothesis of oxygen limited thermal tolerance has recently been investigated in fish using a combination of non-invasive nuclear magnetic resonance (NMR) methodology with invasive techniques. In contrast to observations in marine invertebrates arterial oxygen tensions in fish were independent of temperature, while venous oxygen tensions displayed a thermal optimum. As the fish heart relies on venous oxygen supply, limited cardio-circulatory capacity is concluded to set the first level of thermal intolerance in fish. Nonetheless, maximized ventilatory capacity is seen to support circulation in maintaining the width of thermal tolerance windows. The interdependent setting of low and high tolerance limits is interpreted to result from trade-offs between optimized tissue functional capacity and baseline oxygen demand and energy turnover co-determined by the adjustment of mitochondrial densities and functional properties to a species-specific temperature range. At temperature extremes, systemic hypoxia will elicit metabolic depression, thereby widening the thermal window transiently sustained especially in those species preadapted to hypoxic environments. PMID:15288597

Pörtner, H O; Mark, F C; Bock, C

2004-08-12

175

In vivo biodistribution and biological impact of injected carbon nanotubes using magnetic resonance techniques  

PubMed Central

Background: Single-walled carbon nanotubes (SWCNT) hold promise for applications as contrast agents and target delivery carriers in the field of nanomedicine. When administered in vivo, their biodistribution and pharmacological profile needs to be fully characterized. The tissue distribution of carbon nanotubes and their potential impact on metabolism depend on their shape, coating, and metallic impurities. Because standard radiolabeled or fluorescently-labeled pharmaceuticals are not well suited for long-term in vivo follow-up of carbon nanotubes, alternative methods are required. Methods: In this study, noninvasive in vivo magnetic resonance imaging (MRI) investigations combined with high-resolution magic angle spinning (HR-MAS), Raman spectroscopy, iron assays, and histological analysis ex vivo were proposed and applied to assess the biodistribution and biological impact of intravenously injected pristine (raw and purified) and functionalized SWCNT in a 2-week longitudinal study. Iron impurities allowed raw detection of SWCNT in vivo by susceptibility-weighted MRI. Results: A transitional accumulation in the spleen and liver was observed by MRI. Raman spectroscopy, iron assays, and histological findings confirmed the MRI readouts. Moreover, no acute toxicological effect on the liver metabolic profile was observed using the HR-MAS technique, as confirmed by quantitative real-time polymerase chain reaction analysis. Conclusion: This study illustrates the potential of noninvasive MRI protocols for longitudinal assessment of the biodistribution of SWCNT with associated intrinsic metal impurities. The same approach can be used for any other magnetically-labeled nanoparticles.

Al Faraj, Achraf; Fauvelle, Florence; Luciani, Nathalie; Lacroix, Ghislaine; Levy, Michael; Cremillieux, Yannick; Canet-Soulas, Emmanuelle

2011-01-01

176

Heteroepitaxy of 3C SiC by electron cyclotron resonance-CVD technique  

NASA Astrophysics Data System (ADS)

In this work we mainly report on the analysis of polycrystalline 3C-SiC films grown by electron cyclotron resonance-chemical vapor deposition (ECR-CVD) on 4 in. (1 0 0) and (1 1 1) c-Si wafers, using a H 2+SiH 4+CH 4 gas mixture at substrate temperatures in the range 930-1050 °C. Structural properties of the films were analyzed by X-ray diffractometry, micro-Raman spectroscopy and transmission electron microscopy, while the elemental composition was determined by Rutherford backscattering (RBS) technique. Micro-Raman measurements performed on the SiC layers show a peak around 796 cm -1 due to transversal optical phonons of the crystalline SiC matrix, while neither carbon clusterization in graphitic phase nor Si clusterization in amorphous phase was observed. TEM analyses show a polycrystalline columnar structure with lateral crystal dimensions ranging from 300 up to 1400 Å. The crystals orientation is very close to that of (1 0 0) and (1 1 1) Si substrates, as revealed by X-ray and electron diffraction.

Mandracci, P.; Chiodoni, A.; Cicero, G.; Ferrero, S.; Giorgis, F.; Pirri, C. F.; Barucca, G.; Musumeci, P.; Reitano, R.

2001-12-01

177

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

178

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

179

Local indentation modulus characterization of diamondlike carbon films by atomic force acoustic microscopy two contact resonance frequencies imaging technique  

SciTech Connect

Two contact resonance frequencies atomic force acoustic microscopy imaging technique has been used to evaluate local indentation modulus of a diamondlike carbon film deposited on a molybdenum foil by laser ablation from glassy carbon target. Acoustic images were obtained by measuring both first and second contact resonance frequency at each point of the scanned area, and then numerically evaluating local contact stiffness and reconstructing an indentation modulus bidimensional pattern. The wide difference of the indentation modulus values allows to detect the presence of residual glassy carbon agglomerates in the diamondlike carbon film.

Passeri, D.; Bettucci, A.; Germano, M.; Rossi, M.; Alippi, A.; Sessa, V.; Fiori, A.; Tamburri, E.; Terranova, M.L. [Dipartimento di Energetica, Universita di Roma 'La Sapienza', Via A. Scarpa 16, 00161 Rome (Italy); Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma 'Tor Vergata' and Micro and Nano-structured Systems Laboratory (MINASlab), Via della Ricerca Scientifica, 00133 Rome (Italy)

2006-03-20

180

First-principles study of (75)As NQR in arsenic-chalcogenide compounds.  

PubMed

We present a theoretical study of the nuclear quadrupole interaction, ?(Q), of (75)As in crystalline and amorphous materials containing sulfur and selenium, and compare them with experiment. We studied a combination of hydrogen-terminated molecular clusters and periodic cells at various levels of quantum chemical theory. The results show clearly that the standard density functional theory (DFT) approximations, LDA and GGA, underestimate the nuclear quadrupole (NQR) interaction systematically, while Hartree-Fock theory overestimates it to an even greater degree. However, various levels of configuration interaction and the B3LYP hybrid exchange-correlation functional, which includes some exact exchange, give very good quantitative agreement for As bonded only to the chalcogen species. As-As bonds require highly converged basis sets. We have performed a systematic study of the effect of local distortions around an arsenic atom on ?(Q) and ?. Using a simple, semiclassical model, we have combined our total energy results with our NQR calculations to predict ?(Q) lineshapes for bond angle and bond length distortions. Our predictions for lineshape, including first and second moments, are in excellent agreement with the results of Su et al for a-As(2)S(3), a-As(2)Se(3) and a-AsSe. We offer new insight into the distortions that led to this inhomogeneous broadening. Our results show clearly that, for trivalent arsenic atoms with zero or one arsenic nearest neighbor, symmetric bond stretching is the predominant contributor to the ?(Q) linewidth. However, in the presence of two arsenic nearest neighbors, distortions of the As-As-As apex angle dominates and, in fact, leads to a much larger second moment, in agreement with experiment. PMID:21406910

Edwards, Arthur H; Taylor, P C; Campbell, Kristy A; Pineda, Andrew C

2011-02-01

181

First-principles study of 75As NQR in arsenic-chalcogenide compounds  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the nuclear quadrupole interaction, ?Q, of 75As in crystalline and amorphous materials containing sulfur and selenium, and compare them with experiment. We studied a combination of hydrogen-terminated molecular clusters and periodic cells at various levels of quantum chemical theory. The results show clearly that the standard density functional theory (DFT) approximations, LDA and GGA, underestimate the nuclear quadrupole (NQR) interaction systematically, while Hartree-Fock theory overestimates it to an even greater degree. However, various levels of configuration interaction and the B3LYP hybrid exchange-correlation functional, which includes some exact exchange, give very good quantitative agreement for As bonded only to the chalcogen species. As-As bonds require highly converged basis sets. We have performed a systematic study of the effect of local distortions around an arsenic atom on ?Q and ?. Using a simple, semiclassical model, we have combined our total energy results with our NQR calculations to predict ?Q lineshapes for bond angle and bond length distortions. Our predictions for lineshape, including first and second moments, are in excellent agreement with the results of Su et al for a-As2S3, a-As2Se3 and a-AsSe. We offer new insight into the distortions that led to this inhomogeneous broadening. Our results show clearly that, for trivalent arsenic atoms with zero or one arsenic nearest neighbor, symmetric bond stretching is the predominant contributor to the ?Q linewidth. However, in the presence of two arsenic nearest neighbors, distortions of the As-As-As apex angle dominates and, in fact, leads to a much larger second moment, in agreement with experiment.

Edwards, Arthur H.; Taylor, P. C.; Campbell, Kristy A.; Pineda, Andrew C.

2011-02-01

182

Freqauen,Modulated Technique for the Study of the Tonks-Dattner Resonances.  

National Technical Information Service (NTIS)

A new method of observing the resonance spectrum of a plasma column irradiated by microwave energy is described. Using a frequency-swept backward-wave oscillator, the resonances are observed as a function of frequency under constant plasma conditions. (Au...

A. A. Cremin M. C. Sexton

1965-01-01

183

Microwave resonator technique for moisture content and mass determination in single soybean seeds  

Microsoft Academic Search

Principles are presented relating to the use of a microwave resonant cavity for determining simultaneously the mass and moisture content of individual soybean seeds. Measurement of the resonant frequency shift and change in the transmission characteristics of the cavity when the soybean seed is inserted provides the necessary information for calculating the mass of water in the seed and the

A. W. Kraszewski; S. O. Nelson

1994-01-01

184

Time domain theory of open waveguide resonators: Canonical problems and a generalized matrix technique  

Microsoft Academic Search

In this paper, we consider new solutions and algorithms for initial boundary-value problems in the electromagnetic theory of open waveguide resonators. The approaches are based on a description of the scattering properties of such resonators in terms of the transform operators for an evolutionary basis of the non-stationary signal, that have the same significance in the course of analyses in

Yuriy K. Sirenko; Nataliya P. Yashina

2003-01-01

185

Evidence for the microscopic coexistence of superconductivity and ferromagnetism in UGe2:73Ge-NMR/NQR study  

NASA Astrophysics Data System (ADS)

We report on the pressure-induced novel phases of ferromagnetism and superconductivity (SC) in the itinerant ferromagnet UGe2 via the 73Ge-NQR measurements under pressure ( P). The NQR spectrum has revealed that the ferromagnetic phases are separated into weakly and strongly polarized phases around a critical value of Pc*?1.2 GPa, pointing to a first-order transition around Pc*. Here we present further evidence for the phase separation into ferromagnetic and paramagnetic phases around a critical pressure Pc?1.6 GPa. The measurements of nuclear spin-lattice relaxation rate 1/T1 have probed that SC sets only in the ferromagnetic phase at Tsc?0.2 K, but it does not in the paramagnetic phase.

Harada, A.; Kotegawa, H.; Kawasaki, Y.; Zheng, G.-q.; Kitaoka, Y.; Yamamoto, E.; Haga, Y.; ?nuki, Y.; Itoh, K.; Haller, E. E.

2005-04-01

186

Isotopomer measurement techniques in metabolic flux analysis I: nuclear magnetic resonance.  

PubMed

Two-dimensional [(1)H, (13)C] heteronuclear single quantum correlation (HSQC) spectroscopy nuclear magnetic resonance (NMR) is a comprehensive tool in metabolic flux analysis using (13)C-labeling experiments. NMR is particularly relevant when extensive isotopomer measurements are required, such as for plant cells and tissues, which contain multiple cellular compartments. Several isotope isomers (isotopomers) can be detected and their distribution extracted quantitatively from a single 2-D HSQC NMR spectrum. For example, 2-D HSQC detects the labeling patterns of adjacent carbon atoms and provides the enrichment of individual carbon atoms of the amino acids and glucosyl and mannosyl units present in hydrolysates of glycosylated protein. The HSQC analysis can quantitatively distinguish differences between the glucosyl units in the starch hydrolysate and a protein hydrolysate of plant biomass: this specifies crucial information about compartmentalization in the plant system. The peak structures obtained from the HSQC experiment show multiplet patterns that are directly related to the isotopomer abundances. These abundances have a nonlinear relationship to the fluxes via isotopomer balancing. Fluxes are obtained from the numerical solution of these balances and a stoichiometric model that includes biomass composition data as well as consumption rates of carbohydrate and nitrogen sources. Herein, we describe the methods for the experimental measurements for flux analysis, i.e., determination of the biomass composition (lipid, protein, soluble sugar, and starch) as well as detailed procedures of acid hydrolysis of protein and starch samples and NMR sample preparation, using soybean embryo culture as the model plant system. Techniques to obtain the relative intensity of 16 amino acids and glucosyl units for protein hydrolysate and the glucosyl units of starch hydrolysate of soybean embryos in 2-D HSQC NMR spectra also are provided. PMID:24218211

Truong, Quyen X; Yoon, Jong Moon; Shanks, Jacqueline V

2014-01-01

187

Measuring aortic pulse wave velocity using high-field cardiovascular magnetic resonance: comparison of techniques  

PubMed Central

Background The assessment of arterial stiffness is increasingly used for evaluating patients with different cardiovascular diseases as the mechanical properties of major arteries are often altered. Aortic stiffness can be noninvasively estimated by measuring pulse wave velocity (PWV). Several methods have been proposed for measuring PWV using velocity-encoded cardiovascular magnetic resonance (CMR), including transit-time (TT), flow-area (QA), and cross-correlation (XC) methods. However, assessment and comparison of these techniques at high field strength has not yet been performed. In this work, the TT, QA, and XC techniques were clinically tested at 3 Tesla and compared to each other. Methods Fifty cardiovascular patients and six volunteers were scanned to acquire the necessary images. The six volunteer scans were performed twice to test inter-scan reproducibility. Patient images were analyzed using the TT, XC, and QA methods to determine PWV. Two observers analyzed the images to determine inter-observer and intra-observer variabilities. The PWV measurements by the three methods were compared to each other to test inter-method variability. To illustrate the importance of PWV using CMR, the degree of aortic stiffness was assessed using PWV and related to LV dysfunction in five patients with diastolic heart failure patients and five matched volunteers. Results The inter-observer and intra-observer variability results showed no bias between the different techniques. The TT and XC results were more reproducible than the QA; the mean (SD) inter-observer/intra-observer PWV differences were -0.12(1.3)/-0.04(0.4) for TT, 0.2(1.3)/0.09(0.9) for XC, and 0.6(1.6)/0.2(1.4) m/s for QA methods, respectively. The correlation coefficients (r) for the inter-observer/intra-observer comparisons were 0.94/0.99, 0.88/0.94, and 0.83/0.92 for the TT, XC, and QA methods, respectively. The inter-scan reproducibility results showed low variability between the repeated scans (mean (SD) PWV difference = -0.02(0.4) m/s and r = 0.96). The inter-method variability results showed strong correlation between the TT and XC measurements, but less correlation with QA: r = 0.95, 0.87, and 0.89, and mean (SD) PWV differences = -0.12(1.0), 0.8(1.7), and 0.65(1.6) m/s for TT-XC, TT-QA, and XC-QA, respectively. Finally, in the group of diastolic heart failure patient, PWV was significantly higher (6.3 ± 1.9 m/s) than in volunteers (3.5 ± 1.4 m/s), and the degree of LV diastolic dysfunction showed good correlation with aortic PWV. Conclusions In conclusion, while each of the studied methods has its own advantages and disadvantages, at high field strength, the TT and XC methods result in closer and more reproducible aortic PWV measurements, and the associated image processing requires less user interaction, than in the QA method. The choice of the analysis technique depends on the vessel segment geometry and available image quality.

2010-01-01

188

Accuracy of single-cut adjustment technique for double resonant Brillouin fiber lasers  

NASA Astrophysics Data System (ADS)

We present a detailed error analysis of the algorithm for adjustment of double resonance in short-length Brillouin ring fiber laser. Adjusted laser cavity is simultaneously resonant for the pump and Stokes radiations. We demonstrate that this algorithm provides an accuracy of 1–7 MHz for the resonance peak location under conditions of regular uncertainties in measurement and cutting. Demonstrated approach is equally useful for the design of singlemode fiber lasers with ultra-narrow optical spectra, Q-switched Brillouin fiber lasers as well as for applications employing high power fiber cavities free from stimulated Brillouin scattering.

López-Mercado, Cesar A.; Spirin, Vasily V.; Kablukov, Sergey I.; Zlobina, Ekaterina A.; Zolotovskiy, Igor O.; Mégret, Patrice; Fotiadi, Andrei A.

2014-06-01

189

Mass perturbation techniques for tuning and decoupling of a Disk Resonator Gyroscope  

NASA Astrophysics Data System (ADS)

Axisymmetric microelectromechanical (MEM) vibratory rate gyroscopes are designed so that the two Coriolis-coupled modes exploited for rate sensing possess equal modal frequencies and so that the central post which attaches the resonator to the sensor case is a nodal point of the these two modes. The former quality maximizes the signal-to-noise ratio of the sensor, while the latter quality eliminates any coupling of linear acceleration to the modes of interest, which, if present, creates spurious rate signals in response to linear vibration of the sensor case. When the gyro resonators are fabricated, however, small mass and stiffness asymmetries cause the frequencies of the two modes to deviate from each other and couple these modes to linear acceleration. In a resonator post-fabrication step, these effects can be reduced by altering the mass distribution of the resonator. In this dissertation, a scale model of the axisymmetric resonator of the Disk Resonator Gyroscope (DRG) is used to develop and test methods that successfully reduce frequency detuning (Part I) and linear acceleration coupling (Part II) through guided mass perturbations.

Schwartz, David

190

Study on cellulose acetate membranes for reverse osmosis and polyethersulfone membranes for ultrafiltration by electron spin resonance technique  

Microsoft Academic Search

Electron spin resonance (ESR) technique was used to study cellulose acetate (CA) membranes for reverse osmosis (RO) and polyethersulfone (PES) membranes for ultrafiltration. TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy — free radical) was used as a spin probe that was brought into the membranes by immersing the membranes into solutions involving TEMPO, or by blending TEMPO into membrane casting solutions. It was found that

K. C. Khulbe; T. Matsuura; C. Y. Feng

2002-01-01

191

Fast resonance-detection technique for single-frequency operation of injection-seeded Nd:YAG lasers  

Microsoft Academic Search

A new technique for maintaining single-frequency output from injection-seeded Nd:YAG lasers is described. It involves quickly sweeping the slave-cavity longitudinal-mode spectrum when the flash lamps have created a maximum population inversion. An interference signal is detected by fast electronics, and the Q switch is opened when the slave cavity is resonant with the injected field.

S. W. Henderson; E. H. Yuen; E. S. Fry

1986-01-01

192

IMPLANTABLE RESONATORS - A TECHNIQUE FOR REPEATED MEASUREMENT OF OXYGEN AT MULTIPLE DEEP SITES WITH IN VIVO EPR  

PubMed Central

EPR oximetry using implantable resonators allow measurements at much deeper sites than are possible with surface resonators (> 80 mm vs. 10 mm) and have greater sensitivity at any depth. We report here the development of an improvement of the technique that now enables us to obtain the information from multiple sites and at a variety of depths. The measurements from the various sites are resolved using a simple magnetic field gradient. In the rat brain multi-probe implanted resonators measured pO2 at several sites simultaneously for over 6 months to record under normoxic, hypoxic and hyperoxic conditions. This technique also facilitates measurements in moving parts of the animal such as the heart, because the orientation of the paramagnetic material relative to the sensitive small loop is not altered by the motion. The measured response is very fast, enabling measurements in real time of physiological and pathological changes such as experimental cardiac ischemia in the mouse heart. The technique also is quite useful for following changes in tumor pO2, including applications with simultaneous measurements in tumors and adjacent normal tissues.

Li, Hongbin; Hou, Huagang; Sucheta, Artur; Williams, Benjamin B.; Lariviere, Jean P.; Khan, Nadeem; Lesniewski, Piotr N.; Swartz, Harold M.

2013-01-01

193

Detection of plastic explosives in luggage with 14 N nuclear quadrupole resonance spectroscopy  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) of14N nuclei has many advantages as a method for detecting nitrogen-containing explosives, the most important are very high chemical\\u000a specificity, true noninvasive operation and detection of bulk explosive in situ only (no vapor or particular capture needed).\\u000a One of the most high explosives is hexogen (RDX) often used by terrorists in plasticized forms. The ring nitrogen

M. Ostafin; B. Nogaj

2000-01-01

194

Time domain theory of open waveguide resonators: Canonical problems and a generalized matrix technique  

NASA Astrophysics Data System (ADS)

In this paper, we consider new solutions and algorithms for initial boundary-value problems in the electromagnetic theory of open waveguide resonators. The approaches are based on a description of the scattering properties of such resonators in terms of the transform operators for an evolutionary basis of the non-stationary signal, that have the same significance in the course of analyses in time domain as generalized scattering matrixes in frequency domain. All suggested approaches imply using mathematically correct computational procedures at the key stages of forming the solution, in particular, the analytical regularization method—the semi-inversion method.

Sirenko, Yuriy K.; Yashina, Nataliya P.

2003-04-01

195

Techniques for Multidimensional Measurements and Analysis of Yield of Nuclear Products Fission by Resonance Neutrons.  

National Technical Information Service (NTIS)

Using IBR-30 neutron pulse source ensuring on 57 m flight path 70 ns/m time resolution the gamma-ray spectroscopy along with the spectroscopy of neutrons following fission by resonance neutrons is carried out. An ionization chamber containing 10 g of uran...

S. A. Antonov A. A. Bogdzel' N. A. Gundorin

1985-01-01

196

Circuit techniques for enhancing the clock data compensation effect under resonant supply noise  

Microsoft Academic Search

Recent publications have shown that clock jitter can improve timing margin through the compensation effect between the clock cycle and the datapath delay under the influence of resonant supply noise. In this paper, novel phase-shifted clock buffer designs are proposed to enhance this ldquobeneficial jitter effectrdquo. Compared with existing designs, our design saves 85% of the clock buffer area while

Dong Jiao; Jie Gu; Chris H. Kim

2009-01-01

197

A Technique for Regional Analysis of Femorotibial Cartilage Thickness Based on Quantitative Magnetic Resonance Imaging  

Microsoft Academic Search

The objective of this work was to develop a methodology for measuring cartilage thickness in anatomically based subregions in the tibial and in the central weight-bearing femoral cartilage from magnetic resonance (MR) images. The tibial plateau was divided into a central area of the total subchondral bone area (tAB), and anterior, posterior, internal, and external subregions surrounding it. In the

Wolfgang Wirth; Felix Eckstein

2008-01-01

198

Development of a Magnetic Resonance Imaging Technique for Measuring Emulsion Coalescence  

NASA Astrophysics Data System (ADS)

The kinetics of emulsion coalescence determine emulsion stability and rheology. In an opaque, concentrated emulsion, conventional optical methods for monitoring the droplet size distribution are often impractical, and cannot distinguish between flocculation and coalescence. Nuclear magnetic resonance (NMR) is uniquely suited to measuring droplet size distributions by observing restricted diffusion, which is unaffected by flocculation. We aim to quantify the effect of shear flow on coalescence of a concentrated emulsion. We have constructed a combined annular Couette flow cell and magnetic resonance imaging probe. We have extracted the droplet size distribution in a quiescent emulsion from restricted diffusion curves and shown that the NMR method produces nearly quantitative agreement with light scattering measurements. Data from monitoring the droplet size distribution, droplet concentration and velocity profiles over time in the flowing emulsion system will be presented.

Powell, Robert; D"Avila, Marcos; Shapley, Nina; Walton, Jeffrey; Phillips, Ronald; Dungan, Stephanie

2000-11-01

199

An improved Lorentzian technique for evaluating resonance characteristics of the Earth-ionosphere cavity  

NASA Astrophysics Data System (ADS)

The effectiveness of various formulations of the Lorentzian procedure for estimating Schumann resonance (SR) characteristics of the Earth-ionosphere waveguide from transient electromagnetic signals is tested in the limits of a simplified, spherically uniform model of the resonator. It is shown that the major improvement, in comparison with the "classic" Lorentzian formulation, is achieved by consideration of the intra-modal phase interference. The effect of the "limited frequency dispersion" inherent in the "classic" Lorentzian approach - that is of substantial importance at the lowest SR modes - can be effectively neutralized by interpolating the values for the propagation parameter between the adjacent modal frequencies. Several practical aspects of applying the Lorentzian procedure to transient signals are also discussed.

Mushtak, Vadim C.; Williams, Earle R.

2009-02-01

200

A new resonant active clamping technique for bi-directional converters in HEVs  

Microsoft Academic Search

In this paper a resonant active clamp circuit is presented, addressing the efficient optimization of a bidirectional DCDC converter for hybrid electric vehicles applications. The converter structure is based on a combination of two dc\\/dc topologies connected through a high frequency transformer, a full-bridge stage modulated in phase shift for step-down operations and a current-source push-pull stage used as step-up.

Mario Cacciato; A. Consoli; V. Crisafulli; G. Vitale; N. Abbate

2010-01-01

201

Predicting caking behaviors in powdered foods using a low-field nuclear magnetic resonance (NMR) technique  

Microsoft Academic Search

This study is concerned with caking of powder mixes. Our previous study tied the caking process to the nuclear magnetic resonance (NMR) spin–spin (T2) relaxation characteristics exhibited by powder ingredients subjected to temperature scan from –20°C to 110°C (Journal of Food Science 65 (1) (2000) 134). Four temperature–T2 curve patterns were identified, each of which represents a group of powder

Myong-Soo Chung; Roger Ruan; Paul Chen; Jin-Ho Kim; Tae-Hoi Ahn; Chang-Kyu Baik

2003-01-01

202

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

Microsoft Academic Search

This paper reports on the results of a two-frequency (??) microwave radar experiment for measuring the spectral characteristics of the large-scale ocean surface gravity waves from an aircraft. The experiment was conducted as part of the 1979 Maritime Remote Sensing (MARSEN) project. A coherent Ku-band radar was used to study the Bragg type resonance matching of the electromagnetic wavelength at

J. W. JOHNSON; D. E. WEISSMAN; W. L. JONES

1982-01-01

203

Sodium and potassium salts of dichloroisocyanuric acid and their hydrates as antimicrobials agents studied by 35Cl-NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

The electronic structure of dichloroisocyanuric acid derivatives was analysed by 35Cl-NQR spectroscopy and DFT calculations. Here we concentrate our attention on three different factors: type of metallic substituent (sodium and potassium), temperature of the sample (liquid nitrogen and room) and degree of hydration (an amount of water molecules attached to analysed compounds). In particular, all the variations in 35Cl-NQR frequencies upon hydration of salts containing sodium and potassium ions are explained as a consequence of H-bonds formation and accompanied effects of charge redistribution. Our studies can be useful in searching for the derivatives of dichloroisocyanuric acid revealing higher antimicrobial activity.

Walczak, A.; Brycki, B.; Kaczmarek, M.; Poleshchuk, O. Kh.; Ostafin, M.; Nogaj, B.

2006-06-01

204

Fundamentals of Pulsed Nitrogen-14 Quadrupole Resonance  

NASA Astrophysics Data System (ADS)

The essential features of nitrogen-14 Nuclear Quadrupole Resonance, a new tool based on density matrix calculations is proposed. After a brief review of the density matrix theory, it is demonstrated that, for each of the three NQR transitions, the (3,3) density matrix can be reduced to a (2,2) matrix, evidently easier to handle. (2,2) rotation matrices are defined for predicting, in a straightforward manner, the system evolution under a rf pulse. The first example treated by this methodology concerns nutation experiments (evolution of the signal amplitude as a function of the pulse length) and it is shown that the NMR (Nuclear Magnetic Resonance) flip angle, in the case of powder samples, should be substituted by a pseudo flip angle which is no longer proportional to the pulse length. Still for powder samples, it is demonstrated that, in NQR, data averaging continuously improves when shortening the repetition time. Finally it has been possible to define proper phase cycles in view of measuring relaxation times (T1 and T2) by a two-pulse sequence. In all cases, experimental verifications were performed in order to assess this methodology.

Canet, Daniel; Ferrari, Maude

205

Age dependent variation of cerebral perfusion assessed by magnetic resonance continuous arterial spin labeling technique  

Microsoft Academic Search

Arterial spin labeling is a MR technique for the measurement of perfusion that exploits as diffusible tracer the arterial blood water spins. Since ASL technique provides a completely non-invasive way to measure quantitatively cerebral perfusion, it may be especially suitable for pediatric studies, related to perfusion alterations. The aim of this work is to study the behavior of cerebral perfusion

L. Biagi; M. Tosetti; A. Abbruzzese; M. C. Bianchi; D. Alsop; A. D. Guerra

2004-01-01

206

Study of dielectric films in superconducting resonators using pulse echo techniques  

NASA Astrophysics Data System (ADS)

Energy absorption by two-level systems (TLS) in amorphous dielectric films is a source of decoherence in superconducting qubits, but their microscopic nature is unknown in specific films. To reveal their nature it is helpful to study their dynamics, which we do by embedding them in the parallel-plate capacitor of a linear resonator that is coupled to probing fields through a coplanar waveguide. Measurements are performed at 4-8 GHz and 25-200 mK on amorphous silicon nitride films. We will report on progress to extract the coherence times, field coupling, and the corresponding distributions of these tunneling states.

Ramanayaka, A. N.; Sarabi, B.; Stoutimore, M. J. A.; Osborn, K. D.

2013-03-01

207

Determination of dysprosium by resonance light scattering technique in the presence of BPMPHD  

NASA Astrophysics Data System (ADS)

Dysprosium has been determined by resonance light scattering (RLS) method in the presence of 1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexanedione (BPMPHD) at pH 5.5. The Dy-BPMPHD system has three characteristic peaks at 358, 399 and 450 nm, especially the peak at 358 nm, which is proportional to the concentration of Dy 3+ in the range of 1.0×10 -10-1.0×10 -5 mol l -1. The detection limit (S/N=2) is 5.6×10 -12 mol l -1. Synthetic samples are determined satisfactorily. A new sensitive method for detection of dysprosium has been proposed.

Sun, Shuna; Wu, Xia; Yang, Jinghe; Li, Lei; Wang, Yuebo

2004-01-01

208

Contrast-enhanced magnetic resonance angiography.Theory, technique and practical application  

Microsoft Academic Search

Summary  \\u000a Contrast enhanced (CE) magnetic resonance angiography affords angiographic depiction of extended vascular territories with\\u000a high quality and diagnostic value. A prerequisite is the fast acquisition of a three-dimensional gradient-echo data set during\\u000a the injection of a bolus of a T1-shortening contrast agent. We describe the dependence of the quality of CE-MRA on technical\\u000a parameters of different MR-scanners and consider

M. K. Stehling; M. Niedermeyer; G. Laub

1997-01-01

209

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

210

High resolution image acquisition from magnetic resonance and computed tomography scans using the curvelet fusion algorithm with inverse interpolation techniques.  

PubMed

We present a new approach, based on the curvelet transform, for the fusion of magnetic resonance and computed tomography images. The objective of this fusion process is to obtain images, with as much detail as possible, for medical diagnosis. This approach is based on the application of the additive wavelet transform on both images and the segmentation of their detail planes into small overlapping tiles. The ridgelet transform is then applied on each of these tiles, and the fusion process is performed on the ridgelet transforms of the tiles. To maximize the benefit of the fused images, inverse interpolation techniques are used to obtain high resolution images from the low resolution fused images. Three inverse interpolation techniques are presented and compared. Simulation results show the superiority of the proposed curvelet fusion approach to the traditional discrete wavelet transform fusion technique. Results also reveal that inverse interpolation techniques have succeeded in obtaining high resolution images from the fused images with better quality than that of the traditional cubic spline interpolation technique. PMID:20062497

Ali, Fatma E; El-Dokany, Ibrahim M; Saad, Abdelfattah A; Al-Nuaimy, Waleed; Abd El-Samie, Fathi E

2010-01-01

211

Sensitive Determination of Proteins with Naphthol Green B by Resonance Light Scattering Technique  

NASA Astrophysics Data System (ADS)

A new quantitative determination method for trace proteins using naphthol green B (NGB) by resonance light scattering (RLS) spectroscopy has been developed. The method is based on the interaction of protein and NGB at pH 3.00, which causes a substantial enhancement of the resonance scattering signal of NGB in the wavelength range 300-550 nm with the maximum RLS at 392.0 nm. Under optimum conditions, the linear range is 0.010-28.2 ?g/ml for bovine serum albumin (BSA) and 0.010-31.3 ?g/ml for human serum albumin (HSA). The detection limits (S/N=3) are 8.2 ng/ml for BSA and 7.9 ng/ml for HSA, respectively. There is little or no interference from amino acids, most of the metal ions, or other coexisting substances. The easy-to-use method, with high sensitivity and good reproducibility, was satisfactorily applied to the determination of total protein in human serum samples. The determination results for human serum samples are identical to those provided by clinical physicians.

Gu, B.; Zhong, H.; Li, X.-M.; Wang, Y.-Z.; Ding, B.-C.; Cheng, Z.-P.; Zhang, L.-L.; Li, S.-P.; Yao, C.

2013-09-01

212

Study of the pygmy dipole resonance in 94Mo using the (?,???) coincidence technique  

NASA Astrophysics Data System (ADS)

The (?,?'?) reaction at E?=136 MeV was used to study the electric dipole response in the open-shell vibrational nucleus 94Mo below the neutron-separation threshold. The coincidence experiment has been performed at the Kernfysisch Versneller Instituut in Groningen, The Netherlands, exploiting the Big-Bite Spectrometer and an array of large volume High-Purity Germanium (HPGe) detectors. Due to the excellent energy resolution and high selectivity to transitions stemming from the pygmy dipole resonance, singles ?-scattering cross sections could be determined for individual electric dipole excitations between 4 and 8 MeV. For three of the excited low-lying J?=1- states in 94Mo a ?-decay branch into the J?=21+ state could be observed. The experiment extends the systematic studies of the pygmy dipole resonance by real-photon scattering (?,?') experiments and (?,?'?) experiments. Recently, a (?,?') experiment on 94Mo was performed at the Darmstadt High-Intensity Photon Setup at the S-DALINAC in Darmstadt, Germany, permitting the comparison of B(E1)? strength distribution and ?-scattering cross sections.

Derya, V.; Endres, J.; Elvers, M.; Harakeh, M. N.; Pietralla, N.; Romig, C.; Savran, D.; Scheck, M.; Siebenhühner, F.; Stoica, V. I.; Wörtche, H. J.; Zilges, A.

2013-05-01

213

Hyperpolarized Magnetic Resonance: A Novel Technique for the In Vivo Assessment of Cardiovascular Disease  

PubMed Central

Non-invasive imaging plays a central role in cardiovascular disease for determining diagnosis, prognosis, and optimizing patient management. Recent experimental studies have demonstrated that monitoring hyperpolarized 13C-labelled tracers with magnetic resonance imaging and spectroscopy (MRI and MRS) offers a new way to investigate the normal and diseased heart, and that the technology may be useful in patients with heart disease. In this review, we show how hyperpolarized 13C-labelled tracers are generated and have been applied experimentally, and outline the methodological advances currently underway to enable translation of hyperpolarized 13C MRI and MRS into the clinic. Using hyperpolarized 13C-labelled metabolites and metabolic MRI and MRS could help assessment of many human cardiovascular diseases, including coronary artery disease, heart failure and metabolic cardiomyopathies. We discuss the clinical areas in which the technology may, in the future, aid in the diagnosis and management of patients with cardiovascular diseases, including dynamic investigations of in vivo metabolism, coronary angiography and quantitative perfusion imaging. It is possible that, in the future, hyperpolarized magnetic resonance will play a major role in clinical cardiology.

Schroeder, Marie A.; Clarke, Kieran; Neubauer, Stefan; Tyler, Damian J.

2011-01-01

214

Thermal-wave interferometry of gas-liquid applied to a thermal-wave resonator cavity technique  

NASA Astrophysics Data System (ADS)

We propose the potential use of thermal-wave interferometry in measuring thermal diffusivities of two media with a thermal-wave resonator cavity technique. In the derived expression for a two-layer configuration, during cavity length probing of the upper medium, the physical and thermal properties of the lower medium were reasonably assumed to be independent of cavity length; hence each of the two slopes of signal versus cavity length actually determines the thermal diffusivity of the corresponding medium. In order to check the validity of the proposed model, we measure the thermal diffusivity of air and glycerol. A good linear relation of the amplitude and the phase with respect to cavity length in the thermally thick region of both media was observed, and the thermal diffusivities of air and glycerol obtained were close to the literature values. We suggest the potential application of thermal-wave resonator cavity technique to measure the thermal properties of a single-layer fluid in a general thermal condition where the advantage is that the signal-to-noise ratio is normally high compared to the thermally thick case. This can be achieved possibly by coating the pyroelectric transducer with a thermally thick solid material prior to any measurements.

Azmi, B. Z.; Liaw, H. S.; Abbas, Z.

2005-07-01

215

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

216

Determination of dysprosium by resonance light scattering technique in the presence of BPMPHD.  

PubMed

Dysprosium has been determined by resonance light scattering (RLS) method in the presence of 1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexanedione (BPMPHD) at pH 5.5. The Dy-BPMPHD system has three characteristic peaks at 358, 399 and 450 nm, especially the peak at 358 nm, which is proportional to the concentration of Dy(3+) in the range of 1.0 x 10(-10)-1.0 x 10(-5) mol l(-1). The detection limit (S/N=2) is 5.6 x 10(-12) mol l(-1). Synthetic samples are determined satisfactorily. A new sensitive method for detection of dysprosium has been proposed. PMID:14670486

Sun, Shuna; Wu, Xia; Yang, Jinghe; Li, Lei; Wang, Yuebo

2004-01-01

217

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

218

Studies in Low Dimensional Spin Dynamics via the Electron Spin Resonance Technique  

NASA Astrophysics Data System (ADS)

We have performed studies at room temperature as well as at low temperatures on the electron paramagnetic resonance profile of nearly one dimensional magnetic systems, TMMC:Cu and TMMC:Cd. This studies have focussed on the variation of the line width, the line shift and the line shape as a function of impurities and temperature. We have specifically directed our attention towards dimensionality effects i.e. studies of these crucial magnetic parameters as a function of the polar angles (THETA) and (phi) which the one dimensional axis of these systems makes with the external magnetic field H(,o). We have found the EPR line shape of TMMC is asymmetric (distorted) at X-Band frequencies. These results are presented and discussed in relationship to previously published work on these and related systems and to appropriate theoretical models.

Khattak, Nazir Shah

219

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

220

Numerical and measurement based study of the resonance frequency technique to detect anti-personnel mines  

Microsoft Academic Search

The simulations show that it is useful to explore this technique further towards a practical design. Currently some first experiments seem to support some of the findings from FDTD simulations. We have identified a number of practical problems with the laboratory measurements that need to be tackled. We need to find an optimum polarization state that enhances the presence of

F. Olyslager; J. Fortuny; A. Franchois; G. Nesti; A. J. Sieber

1998-01-01

221

Biochemical sensors using high-Q polymer microring resonators fabricated by an imprinting technique  

Microsoft Academic Search

High Q-factor polymer microrings, fabricated using imprinting technique, were demonstrated as biochemical sensors. They could provide label-free detection and capability of detecting small and large biomolecules with a detection limit as small as 250 pg\\/mm2.

C.-Y. Cbao; W. Fung; L. J. Guo

2005-01-01

222

Evidence for Uniform Coexistence of Ferromagnetism and Unconventional Superconductivity in UGe2: A 73Ge-NQR Study under Pressure  

NASA Astrophysics Data System (ADS)

We report on the itinerant ferromagnetic superconductor UGe2 through 73Ge-NQR measurements under pressure (P). The P dependence of the NQR spectrum signals a first-order transition from the low-temperature (T) and low-P ferromagnetic phase (FM2) to high-T and high-P one (FM1) around a critical pressure of Px ˜ 1.2 GPa. The superconductivity exhibiting a maximum value of Tsc=0.7 K at Px ˜ 1.2 GPa, was found to take place in connection with the P-induced first-order transition. The nuclear spin-lattice relaxation rate 1/T1 has probed the ferromagnetic transition, exhibiting a peak at the Curie temperature as well as a decrease without the coherence peak below~Tsc. These results reveal the uniformly coexistent phase of ferromagnetism and unconventional superconductivity with a line--node gap. We remark on an intimate interplay between the onset of superconductivity and the underlying electronic state for the ferromagnetic phases.

Kotegawa, H.; Harada, A.; Kawasaki, S.; Kawasaki, Y.; Kitaoka, Y.; Haga, Y.; Yamamoto, E.; ?nuki, Y.; Itoh, K. M.; Haller, E. E.; Harima, H.

2005-02-01

223

N.Q.R measurements of low energy Chiral structures in powdered glassy As2Se3  

NASA Astrophysics Data System (ADS)

Experimental and theoretical work on the As-chalcogen glasses have shown that in the glassy state the local cylindrical symmetry associated with the elemental pyramidal unit is preserved. Here we introduce a local paracrystalline model of glassy As2Se3. This model is based on a tight binding calculation of the electric field gradient (EFG) at the core of an As atom located at the apex of the pyramidal structure. This EFG is shown to be hyper sensitive to the bond angles and bond lengths the As atom forms with the chalcogen nearest neighbors, as well as the hybrid angle formed with second neighbor As atoms. A continuous variation of the bonding parameters produces a unique set of these pyramidal units which are shown to fit the NQR data for powdered glassy samples. The best fit to the NQR data indicates that the pyramidal units organize themselves into Chiral structures in the glass. A plot of the electronic energy per molecular site shows that the chiral structures have on average a lower electronic energy than a random configuration.

Nelson, Chris

2012-02-01

224

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

225

Elucidation of fundamental properties of helium in metals by nuclear magnetic resonance techniques  

SciTech Connect

The nuclear magnetic resonance (NMR) properties of very high density {sup 3}He in metals are discussed in the context of the corresponding properties in relatively high density bulk {sup 3}He. In particular, the effects of the {sup 3}He diffusion on the contribution of the {sup 3}He-{sup 3}He dipolar interaction to the lineshape and to the spin-lattice relaxation parameter (T{sub 1}) are described. It is shown that the temperature dependence of the lineshape and of T{sub 1} are independent sources of information about helium density and also about helium diffusivity. Moreover, T{sub 1} is shown to be a sensitive indicator of melting transitions in bulk {sup 3}He. Palladium tritide is presented as a model system for NMR studies of {sup 3}He in metals. Experimental NMR studies of this system reveal behavior analogous to what has been observed for bulk helium. Evidence for a {sup 3}He phase transition near 250 K is provided by the temperature dependence of T{sub 1}. Assuming this to be a melting transition, a density is obtained from the bulk helium EOS that is in good agreement with theory and with swelling measurements on related metal tritides. {sup 3}He NMR measurements have also provided information about the density distribution, helium diffusivity, and mean bubble size in palladium tritide. 22 refs., 8 figs.

Abell, G.C.

1990-01-01

226

A sensitive resveratrol assay with a simple probe methylene blue by resonance light scattering technique  

NASA Astrophysics Data System (ADS)

A novel resonance light scattering (RLS) method was developed for the determination of resveratrol based on the interaction between resveratrol and methylene blue (MB). It was found that at pH 8.69, the weak RLS intensity of MB was remarkably enhanced by the addition of trace amount of resveratrol with the maximum peak located at 385.0 nm. Under the optimum conditions, a good linear relationship between the enhanced RLS intensities and the concentrations of resveratrol was obtained over the range of 2.0-14.0 ?g ml -1 with the detection limit (3 ?) of 0.63 ?g ml -1. The results of the analysis of resveratrol in synthetic samples and human urine are satisfactory, which showed it may provide a more sensitive, convenient, rapid and reproducible method for the detection of resveratrol, especially in biological and pharmaceutical field. In this work, the characteristics of RLS, absorption and fluorescence spectra of the resveratrol-MB system, the influencing factors and the optimum conditions of the reaction were investigated.

Xiang, Haiyan; Dai, Kaijin; Luo, Qizhi; Duan, Wenjun; Xie, Yang

2011-01-01

227

Examination of molecular interaction sites of acetanilides with organic matter surrogates using nuclear magnetic resonance techniques.  

PubMed

The dynamics of acetanilide pesticide interactions with organic matter (OM) surrogates were examined using nuclear magnetic resonance (NMR) spectroscopy. Differences in the relative changes in (13)C and (1)H spin-lattice relaxation times (T(1)) were measured at multiple molecular sites of metolachlor and the probe compound acetanilide to identify interaction sites and/or surfaces between the molecules and dissolved and colloidal OM surrogates. The decrease in T(1) at specific sites of acetanilide molecules was a function of the OM used and its concentration. High-affinity interactions at nonaromatic sites of metolachlor and acetanilide were observed with cellulose, chitin, and collagen, but interactions with lignin occurred with less site specificity and involved both aromatic and nonaromatic sites of the molecules. Changes in relaxation were compared to calculated and experimentally determined binding coefficients (K(oc)). The T(1) relaxation of the aromatic sites of acetanilides showed better relations with K(oc) than the nonaromatic sites. This study shows that NMR relaxation measurements can identify the high-affinity molecular interaction sites of acetanilides to OM surrogates. PMID:12797751

Jayasundera, Shalini; Schmidt, Walter F; Hapeman, Cathleen J; Torrents, Alba

2003-06-18

228

Determination of proteins with tetracarboxy manganese(II) phthalocyanine by resonance light scattering technique.  

PubMed

A novel method for the determination of proteins by using tetracarboxy manganese(II) phthalocyanine (MnC4Pc) as a resonance light scattering (RLS) probe has been developed. At pH 3.0 Britton-Robinson (B-R) buffer solution, the RLS intensity of MnC4Pc at 385 nm is greatly enhanced in the presence of proteins. The effects of pH, reaction time, concentration of MnC4Pc and interfering substances on the enhanced RLS intensity are investigated, respectively. Under optimal conditions, the linear ranges of the calibration curves are 0-2.00 microg mL(-1) for bovine serum albumin (BSA) and human serum albumin (HSA), 0.0-1.75 microg mL(-1) for human-IgG and ovalbumin, with a detection limit of 16.37 ng mL(-1) BSA, 17.62 ng mL(-1) HSA, 19.41 ng mL(-1) human-IgG and 20.72 ng mL(-1) ovalbumin. The method has been applied to the determination of total proteins in human serum samples collected from a hospital and the results are in good agreement with those reported by the hospital. PMID:18450504

Tang, Ning-Li; Peng, Jin-Yun

2008-12-15

229

Determination of proteins with tetracarboxy manganese(II) phthalocyanine by resonance light scattering technique  

NASA Astrophysics Data System (ADS)

A novel method for the determination of proteins by using tetracarboxy manganese(II) phthalocyanine (MnC 4Pc) as a resonance light scattering (RLS) probe has been developed. At pH 3.0 Britton-Robinson (B-R) buffer solution, the RLS intensity of MnC 4Pc at 385 nm is greatly enhanced in the presence of proteins. The effects of pH, reaction time, concentration of MnC 4Pc and interfering substances on the enhanced RLS intensity are investigated, respectively. Under optimal conditions, the linear ranges of the calibration curves are 0-2.00 ?g mL -1 for bovine serum albumin (BSA) and human serum albumin (HSA), 0.0-1.75 ?g mL -1 for human-IgG and ovalbumin, with a detection limit of 16.37 ng mL -1 BSA, 17.62 ng mL -1 HSA, 19.41 ng mL -1 human-IgG and 20.72 ng mL -1 ovalbumin. The method has been applied to the determination of total proteins in human serum samples collected from a hospital and the results are in good agreement with those reported by the hospital.

Tang, Ning-Li; Peng, Jin-Yun

2008-12-01

230

Novel electro-optical coupling technique for magnetic resonance-compatible positron emission tomography detectors.  

PubMed

A new magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL) diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs. PMID:19397853

Olcott, Peter D; Peng, Hao; Levin, Craig S

2009-01-01

231

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

232

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

233

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

234

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

235

Quantitative Evaluation of Left Ventricular Wall Motion in Patient with Coronary Artery Bypass Grafting Using Magnetic Resonance Tagging Technique  

NASA Astrophysics Data System (ADS)

Left ventricular wall motions during systole were investigated from a mechanical perspective by using a magnetic resonance tagging technique. Subjects were 7 patients with coronary artery bypass grafting (CABG). First, by analyzing strain in the left ventricular wall, cardiac contractility was evaluated in the patients with CABG. Next, by calculating displacement in the myocardial wall, paradoxical movements following CABG were quantitatively evaluated. Strain analysis showed local decreases in circumferential strain in 4 of 7 subjects. The results of displacement analysis clarified that following CABG, the degree of radial displacement was small in the septal wall and large in the lateral wall, and circumferential displacement towards the septal wall occurred in the anterior and posterior walls. Since this behavior was seen in both reduced and normal cardiac contractility groups, paradoxical movements in the present patients were not caused by reduced cardiac contractility, but rather by rigid-body motion of the entire heart.

Inaba, Tadashi; Nakano, Takahiro; Tsutsumi, Masakazu; Kawasaki, Shingo; Kinosada, Yasutomi; Tokuda, Masataka

236

Resonance light scattering technique as a new tool to determine the binding mode of anticancer drug oridonin to DNA.  

PubMed

In this study, a sensitive and reliable assay has been developed to determine the binding mode of oridonin to DNA in vitro using resonance light scattering (RLS) technique. The binding mode of ORI with DNA has been confirmed by measuring the changes of RLS intensity under different pH and ionic strength. It is the ORI that is intercalated into the double helix DNA to destroy its template function and inhibit the synthesis of DNA. Moreover, the RLS assay result was validated by seasoned vitro methods. The proposed RLS assay is not only an unprecedented one for primarily determine the binding mode of oridonin to DNA, but also a simple, sensitive, objective and straightforward method for the detection of ORI. PMID:23827178

Chen, Zhanguang; Wang, Zhen; Chen, Junhui; Chen, Xi; Wu, Jiahui; Wu, Yanyu; Liang, Jieyao

2013-08-01

237

Structural and biophysical characterisation of G protein-coupled receptor ligand binding using resonance energy transfer and fluorescent labelling techniques.  

PubMed

The interaction between ligands and the G protein-coupled receptors (GPCRs) to which they bind has long been the focus of intensive investigation. The signalling cascades triggered by receptor activation, due in most cases to ligand binding, are of great physiological and medical importance; indeed, GPCRs are targeted by in excess of 30% of small molecule therapeutic medicines. Attempts to identify further pharmacologically useful GPCR ligands, for receptors with known and unknown endogenous ligands, continue apace. In earlier days direct assessment of such interactions was restricted largely to the use of ligands incorporating radioactive isotope labels as this allowed detection of the ligand and monitoring its interaction with the GPCR. This use of such markers has continued with the development of ligands labelled with fluorophores and their application to the study of receptor-ligand interactions using both light microscopy and resonance energy transfer techniques, including homogenous time-resolved fluorescence resonance energy transfer. Details of ligand-receptor interactions via X-ray crystallography are advancing rapidly as methods suitable for routine production of substantial amounts and stabilised forms of GPCRs have been developed and there is hope that this may become as routine as the co-crystallisation of serine/threonine kinases with ligands, an approach that has facilitated widespread use of rapid structure-based ligand design. Conformational changes involved in the activation of GPCRs, widely predicted by biochemical and biophysical means, have inspired the development of intramolecular FRET-based sensor forms of GPCRs designed to investigate the events following ligand binding and resulting in a signal propagation across the cell membrane. Finally, a number of techniques are emerging in which ligand-GPCR binding can be studied in ways that, whilst indirect, are able to monitor its results in an unbiased and integrated manner. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding. PMID:23590995

Ward, Richard J; Milligan, Graeme

2014-01-01

238

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

239

[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

240

Pulse echo and combined resonance techniques: a full set of LGT acoustic wave constants and temperature coefficients.  

PubMed

This work reports on the determination of langatate elastic and piezoelectric constants and their associated temperature coefficients employing 2 independent methods, the pulse echo overlap (PEO) and a combined resonance technique (CRT) to measure bulk acoustic wave (BAW) phase velocities. Details on the measurement techniques are provided and discussed, including the analysis of the couplant material in the PEO technique used to couple signal to the sample, which showed to be an order of magnitude more relevant than the experimental errors involved in the data extraction. At room temperature, elastic and piezoelectric constants were extracted by the PEO and the CRT methods and showed results consistent to within a few percent for the elastic constants. Both raw acquired data and optimized constants, based on minimization routines applied to all the modes involved in the measurements, are provided and discussed. Comparison between the elastic constants and their temperature behavior with the literature reveals the recent efforts toward the consistent growth and characterization of LGT, in spite of significant variations (between 1 and 30%) among the constants extracted by different groups at room temperature. The density, dielectric permittivity constants, and respective temperature coefficients used in this work have also been independently determined based on samples from the same crystal boule. The temperature behavior of the BAW modes was extracted using the CRT technique, which has the advantage of not relying on temperature dependent acoustic couplants. Finally, the extracted temperature coefficients for the elastic and piezoelectric constants between room temperature and 120 degrees C are reported and discussed in this work. PMID:19406707

Sturtevant, Blake T; Davulis, Peter M; da Cunha, Mauricio Pereira

2009-04-01

241

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

242

Experimental models of brain ischemia: a review of techniques, magnetic resonance imaging, and investigational cell-based therapies.  

PubMed

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

2014-01-01

243

Evaluation of MafG interaction with Maf recognition element arrays by surface plasmon resonance imaging technique.  

PubMed

Specific interactions between transcription factors and cis-acting DNA sequence motifs are primary events for the transcriptional regulation. Many regulatory elements appear to diverge from the most optimal recognition sequences. To evaluate affinities of a transcription factor to various suboptimal sequences, we have developed a new detection method based on the surface plasmon resonance (SPR) imaging technique. Transcription factor MafG and its recognition sequence MARE (Maf recognition elements) were adopted to evaluate the new method. We modified DNA immobilization procedure on to the gold chip, so that a double-stranded DNA array was successfully fabricated. We further found that a hydrophilic flexible spacer composed of the poly (ethylene glycol) moiety between DNA and alkanethiol self-assembled monolayers on the surface is effective for preventing nonspecific adsorption and facilitating specific binding of MafG. Multiple interaction profiles between MafG and six of MARE-related sequences were observed by the SPR imaging technique. The kinetic values obtained by SPR imaging showed very good correlation with those obtained from electrophoretic gel mobility shift assays, although absolute values were deviated from each other. These results demonstrate that the double-stranded DNA array fabricated with the modified multistep procedure can be applied for the comprehensive analysis of the transcription factor-DNA interaction. PMID:15009092

Kyo, Motoki; Yamamoto, Tae; Motohashi, Hozumi; Kamiya, Terue; Kuroita, Toshihiro; Tanaka, Toshiyuki; Engel, James Douglas; Kawakami, Bunsei; Yamamoto, Masayuki

2004-02-01

244

Comparison of the results of computerized tomographic and diffusion-weighted magnetic resonance imaging techniques in inflammatory bowel diseases  

PubMed Central

Aim To compare the findings obtained by computerised tomography (CT) enterography, which uses oral neutral contrast material and non-contrasted diffusion-weighted magnetic resonance imaging (DW-MRI) technique and reveal the diagnostic value of DW-MRI in patients with inflammatory bowel diseases. Methods Patients with established or clinically suspect diagnosis of inflammatory bowel disease were included in the study. CT enterography and DW-MRI obtained from the patients were evaluated by a radiologist blinded to the endoscopic and/or histopathological results. Duodenum, jejunum, ileal loops, ascending, transverse, descending colon, sigmoid colon and rectum were evaluated in that order as for general imaging quality, luminal distension and adequate visualization of the intestinal wall. Image qualities of neutral contrast CT-enterography and DW-MRI were compared. Results The study included 31 patients. Based on statistical analyses, the best correlation between the results of CT-enterography and diffusion-weighted imaging (DWI) were observed in the evaluation of transverse colon, ileum and duodenum in order of decreasing frequency and with an almost perfect compatibility. Radiological findings of sigmoid colon, jejunum and descending colon were completely compatible. However, a moderate degree of compatibility was estimated between radiological findings of rectum and cecum. Conclusions Though conventional enteroclysis is the gold standard method among radiological imaging techniques used for the evaluation of inflammatory small intestinal abnormalities, CT enterography and DW-MRI are alternative methods that can be used effectively to obtain useful information.

Erturk, Sukru Mehmet; Cakmakci, Selma; Bayram, Aysel; Tokgoz, Safiye; Caliskan, Kosti Can; Celebi, Irfan

2013-01-01

245

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.

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

2013-01-01

246

[Lymph nodes of the neck. Diagnosis using magnetic resonance with gradient-echo technique].  

PubMed

As for the pathologic conditions of neck lymph nodes, the clinician needs to know if the involved node is reactive, phlogistic, or neoplastic in nature. If accurate tumor staging is required, imaging techniques play a fundamental role. Our study was aimed at assessing the actual role of MR imaging in the evaluation of neck lymph node involvement. The study was performed using an MR Max Plus by General Electrics operating with an 0.5 T superconductive magnet. We employed gradient-echo (GE) pulse sequences with TR 500, TE 15 ms and 90 degrees flip angle for T1-weighted images, and with TR 500, TE 30 ms and 25-30 degrees flip angles for T2-weighted images; for Pd-T2-weighted images, TR was 520, TE 30 ms, and flip angles were 40-45 degrees. The results were correlated with histopathologic findings obtained at biopsy. The advantages of GE sequences were: 1) whole neck imaging--thus saving time, and reducing radiation dose and contrast media; 2) optimal anatomical and topographic evaluation of the lesion; 3) imaging of the longitudinal diameter of the node; 4) higher sensitivity for lymph node tissue modifications; 5) imaging of necrosis, hemorrhage, and/or fibrosis. GE sequences were especially useful for accurate tumor staging, in the follow-up, and to verify response to therapy. However, even though MR imaging has proven to have high sensitivity, its specificity was similar to that of contrast-enhanced CT. Further studies with the use of paramagnetic contrast media are needed to solve these problems. PMID:2028032

Andreula, C F; Farchi, G; Pavone, V; Racanelli, A; Carella, A

1991-04-01

247

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

248

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

249

High precision micro-impulse measurements for micro-thrusters based on torsional pendulum and sympathetic resonance techniques.  

PubMed

A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a ?N s-class ablative pulsed plasma thruster. According to theoretical analysis on the dynamical behaviors of a torsional pendulum, the resonance amplification effect of micro-signals is presented. In addition, a new micro-impulse measurement method based on sympathetic resonance theory is proposed as an improvement of the original single pulse measurement method. In contrast with the single pulse measurement method, the advantages of sympathetic resonance method are significant. First, because of the magnification of vibration signals due to resonance processes, measurement precision for the sympathetic resonance method becomes higher especially in reducing reading error. With an increase in peak number, the relative errors induced by readout of voltage signals decrease to approximately ±1.9% for the sympathetic resonance mode, whereas the relative error in single pulse mode is estimated as ±13.4%. Besides, by using the resonance amplification effect the sympathetic resonance method makes it possible to measure an extremely low-impulse beyond the resolution of a thrust stand without redesigning or purchasing a new one. Moreover, because of the simple operational principle and structure the sympathetic resonance method is much more convenient and inexpensive to be implemented than other high-precision methods. Finally, the sympathetic resonance measurement method can also be applied in other thrust stands to improve further the ability to measure the low-impulse bits. PMID:24387474

Zhang, Daixian; Wu, Jianjun; Zhang, Rui; Zhang, Hua; He, Zhen

2013-12-01

250

Phase stability in fMRI time series: effect of noise regression, off-resonance correction and spatial filtering techniques.  

PubMed

Although the majority of fMRI studies exploit magnitude changes only, there is an increasing interest regarding the potential additive information conveyed by the phase signal. This integrated part of the complex number furnished by the MR scanners can also be used for exploring direct detection of neuronal activity and for thermography. Few studies have explicitly addressed the issue of the available signal stability in the context of phase time-series, and therefore we explored the spatial pattern of frequency specific phase fluctuations, and evaluated the effect of physiological noise components (heart beat and respiration) on the phase signal. Three categories of retrospective noise reduction techniques were explored and the temporal signal stability was evaluated in terms of a physiologic noise model, for seven fMRI measurement protocols in eight healthy subjects at 3T, for segmented CSF, gray and white matter voxels. We confirmed that for most processing methods, an efficient use of the phase information is hampered by the fact that noise from physiological and instrumental sources contributes significantly more to the phase than to the magnitude instability. Noise regression based on the phase evolution of the central k-space point, RETROICOR, or an orthonormalized combination of these were able to reduce their impact, but without bringing phase stability down to levels expected from the magnitude signal. Similar results were obtained after targeted removal of scan-to-scan variations in the bulk magnetic field by the dynamic off-resonance in k-space (DORK) method and by the temporal off-resonance alignment of single-echo time series technique (TOAST). We found that spatial high-pass filtering was necessary, and in vivo a Gaussian filter width of 20mm was sufficient to suppress physiological noise and bring the phase fluctuations to magnitude levels. Stronger filters brought the fluctuations down to levels dictated by thermal noise contributions, and for 62.5mm(3) voxels the phase stability was as low as 5 mrad (0.27°). In conditions of low SNR(o) and high temporal sampling rate (short TR); we achieved an upper bound for the phase instabilities at 0.0017 ppm, which is close to the dHb contribution to the GM/WM phase contrast. PMID:22079450

Hagberg, Gisela E; Bianciardi, Marta; Brainovich, Valentina; Cassara, Antonino Mario; Maraviglia, Bruno

2012-02-15

251

Distortion and Orientation for Triplet Coronene in Different n-Heptane Shpol'skii Sites Using Phosphorescence-Polarized Microwave Double Resonance Techniques.  

National Technical Information Service (NTIS)

Using phosphorescence microwave double resonance techniques, the type of distortion and the orientation of the magnetic axes are determined for triplet coronene molecules in different Shpol'skii sites in n-heptane single crystals at 1.6 K. Coronene triple...

A. M. Merle W. M. Pitts M. A. El-Sayed

1977-01-01

252

Evaluation of Elevated Mean Pulmonary Arterial Pressure Based on Magnetic Resonance 4D Velocity Mapping: Comparison of Visualization Techniques  

PubMed Central

Purpose Three-dimensional (3D) magnetic resonance phase contrast imaging (PC-MRI) allows non-invasive diagnosis of pulmonary hypertension (PH) and estimation of elevated mean pulmonary arterial pressure (mPAP) based on vortical motion of blood in the main pulmonary artery. The purpose of the present study was to compare the presence and duration of PH-associated vortices derived from different flow visualization techniques with special respect to their performance for non-invasive assessment of elevated mPAP and diagnosis of PH. Methods Fifty patients with suspected PH (23 patients with and 27 without PH) were investigated by right heart catheterization and time-resolved PC-MRI of the main pulmonary artery. PC-MRI data were visualized with dedicated prototype software, providing 3D vector, multi-planar reformatted (MPR) 2D vector, streamline, and particle trace representation of flow patterns. Persistence of PH-associated vortical blood flow (tvortex) was evaluated with all visualization techniques. Dependencies of tvortex on visualization techniques were analyzed by means of correlation and receiver operating characteristic (ROC) curve analysis. Results tvortex values from 3D vector visualization correlated strongly with those from other visualization techniques (r?=?0.98, 0.98 and 0.97 for MPR, streamline and particle trace visualization, respectively). Areas under ROC curves for diagnosis of PH based on tvortex did not differ significantly and were 0.998 for 3D vector, MPR vector and particle trace visualization and 0.999 for streamline visualization. Correlations between elevated mPAP and tvortex in patients with PH were r?=?0.96, 0.93, 0.95 and 0.92 for 3D vector, MPR vector, streamline and particle trace visualization, respectively. Corresponding standard deviations from the linear regression lines ranged between 3 and 4 mmHg. Conclusion 3D vector, MPR vector, streamline as well as particle trace visualization of time-resolved 3D PC-MRI data of the main pulmonary artery can be employed for accurate vortex-based diagnosis of PH and estimation of elevated mPAP.

Kovacs, Gabor; Stalder, Aurelien F.; Gulsun, Mehmet A.; Greiser, Andreas; Olschewski, Horst; Fuchsjager, Michael

2013-01-01

253

Irreversible change in the T1 temperature dependence with thermal dose using the proton resonance frequency-T1 technique.  

PubMed

Denaturation of macromolecules within the tissues is believed to be the major factor contributing to the damage of tissues upon hyperthermia. As a result, the value of the spin-lattice relaxation time T1 of the tissue water, which is related to the translational and rotational rates of water, represents an intrinsic probe for investigating structural changes in tissues at high temperature. Therefore, the goal of this work is to investigate whether the simultaneous measurement of temperature and T1 using a hybrid proton resonance frequency (PRF)-T1 measurement technique can be used to detect irreversible changes in T1 that might be indicative of tissue damage. A new hybrid PRF-T1 sequence was implemented based on the variable flip angle driven-equilibrium single-pulse observation (DESPOT)1 method from a standard three dimensional segmented echo-planar imaging sequence by alternating two flip angles from measurement to measurement. The structural changes of the heated tissue volumes were analyzed based on the derived T1 values and the corresponding PRF temperatures. Using the hybrid PRF-T1 technique, we demonstrate that the change of spin lattice relaxation time T1 is reversible with temperature for low thermal dose (thermal dose ? 240 cumulative equivalent minutes [CEM] 43°C) and irreversible with temperature after significant accumulation of thermal dose in ex vivo chicken breast tissue. These results suggest that the hybrid PRF-T1 method may be a potentially powerful tool to investigate the extent and mechanism of heat damage of biological tissues. PMID:22576265

Diakite, Mahamadou; Payne, Allison; Todd, Nick; Parker, Dennis L

2013-04-01

254

A novel curcumin assay with the metal ion Cu (II) as a simple probe by resonance light scattering technique  

NASA Astrophysics Data System (ADS)

A fantastic resonance light scattering (RLS) enhancement phenomenon was found when the interaction between the metal ion Cu (II) and a natural antioxidant curcumin (C 21H 20O 6) occurred in certain conditions. Based on this phenomenon, a novel and convenient assay of curcumin was developed and successfully applied on the determination of curcumin in human urine samples. This assay applied the RLS technique with a common metal ion Cu (II) as the spectral probe. In the pH range of 6.5-7.5, the interaction between Cu (II) and curcumin occurred and the weak RLS intensity of Cu (II) was greatly enhanced by curcumin. The maximum peak was located at 538.5 nm. Under the optimum conditions, the enhanced RLS intensity was proportional to the concentration of curcumin ranging from 0.4 to 60 ?g ml -1 with the detection limit of 0.07 ?g ml -1. The synthetic and human urine samples were determined satisfactorily. Good recoveries (98.8-102.5%) were obtained in the determination of urine samples, which proved that the assay proposed was reliable and applicable in the determination of curcumin in body fluid. In this work, the RLS and fluorescence spectral characteristics of the chemicals, the optimum conditions of the reaction and the influencing factors were investigated.

Chen, Zhanguang; Zhu, Li; Song, Tianhe; Chen, Junhui; Guo, Zhiming

2009-04-01

255

Circular dichroism and photoelectron angular distributions of excited states of cesium and rubidium using resonantly enhanced multiphoton ionization techniques  

SciTech Connect

Resonantly enhanced multiphoton ionization (REMPI) techniques are used to study spin-orbit effects in the photoelectron angular distributions (PEAD) of excited ns (n = 8-13) states of cesium. The asymmetry parameters are shown to exhibit an energy dependence in the region of the Cooper minimum of the photoionization cross section, supporting predictions made by inclusion of relativistic coupling in the continuum. REMPI is also used to study the photoelectron angular distribution of excited n[sup 2]P[sub 3/2] and n[sup 2]P[sub 1/2] state of cesium and rubidium. The measured asymmetry parameters for the PEADs of n[sup 2]P[sub 3/2] states are found to deviate signi ficantly from theoretical predictions. The difference is attributed to depolarization of the angular momentum polarization due to hyperfine coupling. Circular dichroism effects in the photoelectron angular distributions (CDAD) are used to measure alignment of the excited n[sup 2]P[sub 3/2] states of cesium and rubidium. Angular distributions of the n[sup 2]P[sub 1/2] states are used to show that isotropic states do not exhibit CDAD.

Cuellar, L.E.

1993-01-01

256

Dynamics of paramagnetic agents by off-resonance rotating frame technique in the presence of magnetization transfer effect  

NASA Astrophysics Data System (ADS)

The simple method for measuring the rotational correlation time of paramagnetic ion chelates via off-resonance rotating frame technique is challenged in vivo by the magnetization transfer effect. A theoretical model for the spin relaxation of water protons in the presence of paramagnetic ion chelates and magnetization transfer effect is described. This model considers the competitive relaxations of water protons by the paramagnetic relaxation pathway and the magnetization transfer pathway. The influence of magnetization transfer on the total residual z-magnetization has been quantitatively evaluated in the context of the magnetization map and various difference magnetization profiles for the macromolecule conjugated Gd-DTPA in cross-linked protein gels. The numerical simulations and experimental validations confirm that the rotational correlation time for the paramagnetic ion chelates can be measured even in the presence of strong magnetization transfer. This spin relaxation model also provides novel approaches to enhance the detection sensitivity for paramagnetic labeling by suppressing the spin relaxations caused by the magnetization transfer. The inclusion of the magnetization transfer effect allows us to use the magnetization map as a simulation tool to design efficient paramagnetic labeling targeting at specific tissues, to design experiments running at low RF power depositions, and to optimize the sensitivity for detecting paramagnetic labeling. Thus, the presented method will be a very useful tool for the in vivo applications such as molecular imaging via paramagnetic labeling.

Zhang, Huiming; Xie, Yang

2007-02-01

257

Calculation of quantum-limit cyclotron-resonance linewidths in Ge and Si by the isolation-projection technique  

NASA Astrophysics Data System (ADS)

On the basis of the line-shape theory introduced by the isolation-projection technique, we calculate the cyclotron-resonance half-linewidths for intravalley-deformation-potential scattering in the quantum limit. For comparison of the theoretical values with the experimental data, the effective deformation-potential constant (E1) is chosen as the fitting parameter, as in the works of Bagguley, Flaxen, and Stradling [Phys. Lett. 1, 111 (1962)], Stradling and Zhukov [Proc. Phys. Soc. 87, 263 (1966)], Ito, Kawamura, and Fukai [Phys. Lett. 13, 26 (1964)], and Murase, Enjouji, and Otsuka [J. Phys. Soc. Jpn. 29, 1248 (1970)]. In the best fitting, we obtain E1=12.7 eV for Ge and E1=7.90 eV for Si, which are similar to the values obtained by the other authors. In the quantum limit, the half-linewidths in Ge and Si are in good agreement with the experimental data of Kobori, Ohyama, and Otsuka [J. Phys. Soc. Jpn. 59, 2141 (1990)], except for the extremely low-temperature region.

Cho, Yong Jai; Choi, Sang Don

1994-05-01

258

INDO Investigation of the halogen N.Q.R. frequencies and 14 N nuclear quadrupole coupling constants of halothiophenes and halopyridines  

Microsoft Academic Search

The 35Cl, 79Br, and 127I N.Q.R. frequencies of a number of halothiophenes and halopyridines and the 14N nuclear quadrupole coupling constants of halopyridines have been determined in terms of the Kaplansky-Whitehead theory with the INDO MO approximations using a consistent set of atomic parameters derived from SCF Hartree-Fock calculations. The theoretical spectral properties are in satisfactory overall agreement with experiment.

V. Galasso

1974-01-01

259

A spectroscopic study of the D(0u+) ion-pair state of Br2 by the optical-optical double-resonance technique  

Microsoft Academic Search

An optical-optical double-resonance technique has been applied to study the D(0u+) ion-pair state of Br2 in a one-photon resonant three-photon absorption. The OODR transition proceeds through the high vibrational level of the B3Pi(0u+) state, which compromises a large Franck-Condon shift required for the excitation of Br2 from the X1Sigmag+ state to the D(0u+) state. Dunham parameters of the D(0u+) state,

Takashi Ishiwata; Atsuto Tokunaga; Tsutomu Shinzawa; Ikuzo Tanaka

1984-01-01

260

Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe3 under Pressure: A 73Ge-Nuclear-Quadrupole-Resonance Study  

NASA Astrophysics Data System (ADS)

We report a 73Ge nuclear-quadrupole-resonance (NQR) study on novel evolution of unconventional superconductivity in antiferromagnetic (AFM) CeNiGe3. The measurements of the 73Ge-NQR spectrum and the nuclear spin-lattice relaxation rate (1/T1) have revealed that the unconventional superconductivity evolves inside a commensurate AFM phase around the pressure (P) where Néel temperature TN exhibits its maximum at 8.5 K. The superconducting transition temperature TSC has been found to be enhanced with increasing TN, before reaching the quantum critical point at which the AFM order collapses. Above TSC, the AFM structure transits from an incommensurate spin-density-wave order to a commensurate AFM order at T˜ 2 K, accompanied by a longitudinal spin-density fluctuation. With regard to heavy-fermion compounds, these novel phenomena have hitherto never been reported in the P-T phase diagram.

Harada, Atsushi; Mukuda, Hidekazu; Kitaoka, Yoshio; Thamizhavel, Arumugam; Okuda, Yusuke; Settai, Rikio; ?nuki, Yoshichika; Itoh, Kouhei M.; Haller, Eugene E.; Harima, Hisatomo

2008-10-01

261

Evidence for Ca substituting Ba in YBa 2- xCa xCu 4O 8± y: a nuclear quadrupole resonance investigation  

NASA Astrophysics Data System (ADS)

For the understanding of the Tc enhancement in Ca doped YBa 2Cu 4O 8± y it is crucial to know which crystallographic site the Ca +2 ion is occupying. We investigated this problem by measuring the Cu nuclear quadrupole resonance (NQR) spectrum at 100 K in YBa 2Cu 4O 8± y doped with 10% Ca ( Tc = 91 K). The NQR lines of the plane and chain Cu sites appear at the same frequencies vq as in the pure compound, however, both lines are broadend by static defects. Within the linewidths no temperature dependence of vq was observed and no indication for magnetic ordering at the Cu sites was found. At 20 600 Mhz, near to the Cu(1) line, a resonance line has been detected which is absent in the pure YBa 2- xCa xCu 4O 8± y spectrum. Based on NQR arguments we assign this new line to Cu(1) nuclei whose electric field gradients are disturbed by Ca +2 ions occupying Ba +2 sites. We concluded that a major fraction of Ca ions occupy Ba sites, therefore the increase of Tc by Ca doping cannot be explained by an increase of the hole concentration.

Mangelschots, I.; Mali, M.; Roos, J.; Zimmermann, H.; Brinkmann, D.; Rusiecki, S.; Karpinski, J.; Kaldis, E.; Jilek, E.

1990-12-01

262

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

263

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.

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

1980-01-01

264

Low-temperature nuclear quadrupole resonance studies of antimony and application to thermometry  

NASA Astrophysics Data System (ADS)

The spin-lattice retaxation time, Tsb1, of finely divided powdered metallic antinomy immersed in liquid sp3He was measured using pulsed Nuclear Quadrupole Resonance (NQR) techniques. In this technique, the nuclear quadrupole resonant antinomy nuclei were saturated using an RF pulse. The recovery back to equilibrium was monitored using short inspection pulses and the magnetization recovery follows a recovery curve characterized by the relaxation time Tsb1. Tsb1 measurements were performed at temperatures ranging from 150 mK to 1.25 mK. Temperatures down to 11 mK were achieved by using a dilution refrigerator. Lower temperatures were achieved using adiabatic nuclear demagnetization of a copper bundle starting at 8.5 Tesla (7.5 Tesla average field over the copper bundle). The sample was cooled by immersion in liquid sp3He which is in thermal contact with silver sinter packed in the bottom of a silver cell. This cell was bolted onto a cold plate attached to the copper bundle. It was found that a low temperatures starting near 75 mK, the measured total relaxation was significantly enhanced with respect to the Korringa relaxation, the dominant relaxation mechanism expected for a metal at these temperatures. This enhancement is attributed to a surface relaxation mechanism mediated by the surface sp3He atoms. In systems immersed in liquid sp3He, a surface relaxation mechanism is present due to a modulation of the interaction between the solid-like sp3He atoms on the surface and the surface spins. This modulation is due to the quantum zero-point motion of the sp3He atoms on the surface. This phenomenon has been well studied in insulating systems using Nuclear Magnetic Resonance. The measurements undertaken in this study demonstrate that this phenomenon is present in a metallic and quadrupolar system. This surface relaxation mechanism becomes the dominant relaxation mechanism at low temperatures. Considering the surface and bulk spins as belonging to different phases, a two phase relaxation analysis was used to extract the surface relaxation parameters. This work helps explain previous relaxation measurements by other groups, on powdered metals (with spin I? 0) immersed in liquid sp3He. In these studies, anomalies were reported whose features are consisted with the surface relaxation mechanism discussed in this work. Using magnetic field perturbed NQR, the intensity ratio of two transitions was studied from 1.4 mK to 0.25 mK. The intensity ratio was observed to change as a function of temperature. A comparison is made with the expected Boltzmann distribution. This intensity ratio can be used as a self-calibrating, absolute thermometer for the ultra-low temperature region.

Genio, Edgar Baylon

1997-11-01

265

Ultra-Sensitive Biological Detection via Nanoparticle-Based Magnetically Amplified Surface Plasmon Resonance (Mag-SPR) Techniques.  

National Technical Information Service (NTIS)

The report contains final reports from four separate projects co- funded by AFOSR/AOARD and Korean MEST. The four projects were (1) Ultra- Sensitive Biological Detection via Nanoparticle-Based Magnetically Amplified Surface Plasmon Resonance (Mag-SPR) Tec...

A. P. Alivisatos D. Choi J. Cheon J. Kim K. Lee

2008-01-01

266

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

267

Precision fabrication techniques and analysis on high-Q evanescent-mode resonators and filters of different geometries  

Microsoft Academic Search

High-Q evanescent-mode resonators and filters are realized by both silicon micromachining and layer-by-layer polymer processing. Capacitively loaded cavities can be reduced to a size much smaller than a wavelength, but still have a much higher unloaded Q than lumped elements. The loaded resonators are utilized for reduced-size filters with a low insertion loss enabled by the relatively high-Q factor. The

Xun Gong; Alexandros Margomenos; Bosui Liu; Shloke Hajela; Linda P. B. Katehi; William J. Chappell

2004-01-01

268

Resonant Third-Order Optical Nonlinearities of Silicon 2,3-Naphthalocyanine Dioctyloxide Measured by Femtosecond Degenerate Four-Wave Mixing Technique  

Microsoft Academic Search

The third-order optical nonlinearities of silicon 2,3-naphthalocyanine dioctyloxide (SiNc) were measured by a femtosecond degenerate four-wave mixing technique under resonant conditions. The electronic second molecular hyperpolarizability gammae of SiNc was determined to be as high as 9× 10-29 esu. The electronic third-order susceptibility of polystyrene films doped with SiNc was measured to be on the order of 10-9 esu. The

Gang Fu; Osamu Asada; Kazuo Kasatani; Hiroaki Okamoto; Shunsuke Takenaka

2005-01-01

269

Quasi-Resonant DC Link Control of 3Dimensional Hysteresis Current PWM Technique in 3Phase 4Wired Power Quality Compensator  

Microsoft Academic Search

In this paper, quasi-resonant DC link (QRDCL) softswitching 3-dimensional hysteresis current control for power quality compensator is investigated. Power quality compensator here is the shunt active power filter in the 3-phase 4-wire system to compensate the imbalance, reactive power, harmonics and neutral current. The 3-dimensional hysteresis current PWM technique changes the system frame from a-b-c coordinate to alpha-beta-O coordinate for

Ming-hui Zhan; Man-chung Wong; Ying-duo Han

2005-01-01

270

Electron paramagnetic resonance measurements of free radicals in the intact beating heart: a technique for detection and characterization of free radicals in whole biological tissues.  

PubMed Central

Free radicals have been hypothesized to be important mediators of disease in a variety of organs and tissues. Electron paramagnetic resonance (EPR) spectroscopy can be applied to directly measure free radicals; however, it has not been possible to measure important biological radicals in situ because conventional spectrometer designs are not suitable for the performance of measurements on whole organs or tissues. We report the development of an EPR spectrometer designed for optimum performance in measuring free radicals in intact biological organs or tissues. This spectrometer consists of a 1- to 2-GHz microwave bridge with the source locked to the resonant frequency of a recessed gap loop-gap resonator. With this spectrometer, radical concentrations as low as 0.4 microM can be measured. Isolated beating hearts were studied in which simultaneous real time measurements of free radicals and cardiac contractile function were performed. This in vivo EPR technique was applied to study the kinetics of free radical uptake and metabolism in normally perfused and globally ischemic hearts. In addition, we show that this technique can be used to noninvasively measure tissue oxygen consumption. Thus, it is demonstrated that EPR spectroscopy can be applied to directly measure in vivo free radical metabolism and tissue oxygen consumption. This technique offers great promise in the study of in vivo free radical generation and the effects of this radical generation on whole biological tissues.

Zweier, J L; Kuppusamy, P

1988-01-01

271

Breast magnetic resonance imaging technique at 1.5 T and 3 T: requirements for quality imaging and American College of Radiology accreditation.  

PubMed

Although there are multiple variations in acquisition protocols for breast magnetic resonance (MR) imaging, there is agreement that components of high-quality technique include a bilateral acquisition obtained with a dedicated breast coil. Further, key pulse sequences should be included and spatial and temporal resolution should be sufficiently high to assess lesion morphology and kinetics. Artifacts must be recognized and avoided. The American College of Radiology Breast MRI Accreditation Program requirements provide minimum standards to guide facilities in technique. MR imaging at 3 T is increasingly available and offers signal-to-noise ratio advantages over 1.5 T but also some technical challenges. PMID:23928238

DeMartini, Wendy B; Rahbar, Habib

2013-08-01

272

Note: Matching index technique for avoiding higher order mode resonance in accelerators: INDUS-2 accelerator as a case study  

SciTech Connect

Resonance between circulating beam frequencies and RF cavity Higher Order Modes (HOMs) of accelerators can lead to coupled-bunch instabilities. Shifting these HOMs to avoid the resonance is a topic of active interest. A study has been carried out for the accelerating cavities of the INDUS-2. For quantitative measure of deciding which modes have to be moved and by how much, we introduce a new index called the matching index (I{sub M}), as a measure of how close a HOM is to the nearest beam mode. Depending on the value of I{sub M}, the operating scenarios are classified as safe and unsafe.

Jain, V.; Joshi, S. C. [Raja Ramanna Centre for Advanced Technology, RRCAT, Indore 452013 (India)] [Raja Ramanna Centre for Advanced Technology, RRCAT, Indore 452013 (India); Bhandarkar, U. V. [Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai 400076, Mumbai (India)] [Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai 400076, Mumbai (India); Krishnagopal, S. [Bhabha Atomic Research Centre, Mumbai 400085 (India) [Bhabha Atomic Research Centre, Mumbai 400085 (India); Centre for Excellence in Basic Sciences, Mumbai 400098 (India)

2013-08-15

273

Measurement of the 183 keV Resonance in 17O(p,alpha)14N using a Novel Technique  

SciTech Connect

We have developed a novel technique for measurements of low energy (p,alpha) reactions using heavy ion beams and a differentially-pumped windowless gas target. We applied this new approach to study the 183 keV resonance in the 17O(p,alpha)14}N reaction. We report a resonance energy (center-of-mass) of 183.5{+0.1}{-0.4} keV, a resonance strength of 1.70 +/- 0.15 meV, and set an upper limit (95\\% confidence) on the total width of the state of < 0.1 keV. This resonance is important for the 17O(p,alpha)14}N reaction rate, and we find that 18F production is significantly decreased in low mass ONeMg novae but less affected in more energetic novae. We also report the first determination of the stopping power for oxygen ions in hydrogen gas near the peak of the Bragg curve (E=193 keV/u) to be (63+/-1)e-15 eV-cm2.

Moazen, Brian H [ORNL; Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Chae, Kyung Yuk [ORNL; Chipps, Kelly A [ORNL; Domizioli, Carlo P [ORNL; Fitzgerald, Ryan [ORNL; Greife, Uwe [ORNL; Hix, William Raphael [ORNL; Grzywacz-Jones, Kate L [ORNL; KOZUB, RAYMOND L [ORNL; Lingerfelt, Eric J [ORNL; Livesay, Jake [ORNL; Nesaraja, Caroline D [ORNL; Pain, Steven D [ORNL; Roberts, Luke F [ORNL; Shriner, Jr., John F [ORNL; Smith, Michael Scott [ORNL; Thomas, Jeffrey S [ORNL

2007-01-01

274

Point mutation detection with the sandwich method employing hydrogel nanospheres by the surface plasmon resonance imaging technique  

Microsoft Academic Search

We propose a surface modification procedure to construct DNA arrays for use in surface plasmon resonance (SPR) imaging studies for the highly sensitive detection of a K-ras point mutation, enhanced with hydrogel nanospheres. A homobifunctional alkane dithiol was adsorbed on Au film to obtain the thiol surface, and ethyleneglycol diglycidylether (EGDE) was reacted to insert the ethyleneglycol moiety, which can

Aya Okumura; Yasunobu Sato; Motoki Kyo; Haruma Kawaguchi

2005-01-01

275

s-wave superconductivity in superconducting BaTi2Sb2O revealed by 121/123Sb-NMR/nuclear quadrupole resonance measurements  

NASA Astrophysics Data System (ADS)

We report the 121/123Sb-NMR/nuclear quadrupole resonance (NQR) measurements on the superconductor BaTi2Sb2O with a two-dimensional Ti2O square-net layer formed with Ti3+ (3d1). NQR measurements revealed that the in-plane four-fold symmetry is broken at the Sb site below TA˜40 K, without an internal field appearing at the Sb site. These exclude a spin-density wave (SDW)/ charge density wave (CDW) ordering with incommensurate correlations, but can be understood with the commensurate CDW ordering at TA. The spin-lattice relaxation rate 1/T1, measured at the four-fold symmetry breaking site, decreases below superconducting (SC) transition temperature Tc, indicative of the microscopic coexistence of superconductivity and the CDW/SDW phase below TA. Furthermore, 1/T1 of 121Sb-NQR shows a coherence peak just below Tc and decreases exponentially at low temperatures. These results are in sharp contrast with those in cuprate and iron-based superconductors, and strongly suggest that its SC symmetry is classified to an ordinary s-wave state.

Kitagawa, S.; Ishida, K.; Nakano, K.; Yajima, T.; Kageyama, H.

2013-02-01

276

NMR and NQR study of the electronic and structural properties of Al-Cu-Fe and Al-Cu-Ru quasicrystals  

SciTech Connect

[sup 27]Al and [sup 63,65]Cu NMR is reported for powdered stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and crystalline approximants, and for an Al-Pd-Mn single-grain quasicrystal. [sup 27]Al NQR spectra at 4.2 K were observed in Al-Cu-Fe and Al-Cu-Ru samples. From quadrupole-perturbed NMR spectra at different magnetic fields, and from zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant successfully explained the observed NQR spectra. The average local gradient is largely determined by the [ital p]-electron wave function at the Al site, while the width of the distribution is due to EFG lattice contribution. Comparison of [sup 63]Cu and [sup 27]Al NMR shows the EFG distribution at the two sites is similar, but the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more [ital s]-type wave function of the conduction electrons. Overall spread of EFG values is well reproduced by calculation based on the approximant. However, the experimental spectra indicate a much larger number of nonequivalent sites when compared with the simulated NQR spectra based on the 1/1 approximant. The short-range, local chemical order is well represented by the approximant, but differences in coordination must be included at intermediate range in the quasicrystal. Measured [sup 27]Al Knight shift, magnetic susceptibility, and nuclear spin-lattice relaxation time as a function of temperature indicate reduced density of states at the Fermi level by a factor of 7 or 8 from the value in Al metal, consistent with the notion of a pseudogap for these quasicrystals. No differences in measured parameters were detected as a function of composition of the quasicrystalline alloys.

Shastri, A.; Borsa, F.; Torgeson, D.R.; Shield, J.E.; Goldman, A.I. (Ames Laboratory, U.S. Department of Energy and Department of Physics Astronomy, Iowa State University, Ames, Iowa 50011 (United States))

1994-12-01

277

Direct quantification of ?-globulin in human blood serum by resonance light scattering techniques without separation of human serum albumin  

Microsoft Academic Search

We describe the preparation and characterization of functionalized nano-PbS. The functionalized nanoparticles are water-soluble. Reaction of mercaptoacetic acid functionalized nano-PbS with ?-globulin (?-IgG) results in an enhanced resonance light scattering (RLS) at 385nm. Based on this, a new direct quantitative method for ?-globulin in blood serum samples without separation of human serum albumin is established. Under optimal conditions, the enhanced

Leyu Wang; Lun Wang; Hongqi Chen; Ling Li; Ling Dong; Tingting Xia; Fuzhong Dong; Zhiqing Xu

2003-01-01

278

Deposition of ultra-thin diamond-like carbon protective coating on magnetic disks by electron cyclotron resonance plasma technique  

Microsoft Academic Search

Diamond-like carbon (DLC) films were prepared on Si and magnetic disks using an electron cyclotron resonance assisted microwave plasma chemical vapour deposition system with variable radio-frequency (rf) substrate bias. Surface morphology of disks deposited with 10 nm DLC was observed under atomic force microscopy (AFM), which revealed surfaces smoother than the uncoated disk. The root-mean-square roughness decreased with increasing substrate

M. K. Fung; W. C. Chan; K. H. Lai; I. Bello; C. S. Lee; N. B. Wong; S. T. Lee

1999-01-01

279

Using a pole-placement switching technique to avoid resonance in systems forced by a swept sinewave disturbance  

NASA Astrophysics Data System (ADS)

Many forced systems are prone to undesirable levels of oscillation if lightly damped modes are present with their frequency range of operation. Rotary systems, for example, can experience these problems during the speed up or speed down stage of operation. Resonant motion can damage or effect the accuracy of operation of such systems and is, therefore, highly undesirable. Many closed-loop controllers avoid this by suppressing the mode itself such that at resonance the modal vibration amplitude is small (i.e. highly damped). The current work presents an alternative novel switching controller, which suppresses the system not by applying a high amount of damping but rather by moving the resonant mode such that it is never excited. From the basis of an accurate plant model, two pole-placement controllers are designed and implemented both in simulation and experiment on a cantilever smart structure. These controllers are shown to successfully change the natural frequency value, while retaining the same damping ratio value. A novel switching system is employed that calculates the optimal switching position by running a simulation of the desired systems in parallel to the controlled open-loop system. Moreover, the system minimises transients occurred by switching back and forth between controllers, thus increasing the efficiency of the system. By comparing the experimental results to a conventional high damping pole-placement controller that applies a similar amount of control effort, a lower overall level of amplitude suppression can be seen.

Scott, Robin G.; Weightman, Andrew P. H.; Levesley, Martin C.

2004-07-01

280

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

281

Conceptual Study on New Isotope Analysis Technique with Resonance Ionization Mass Spectrometry Using Inductively Coupled Plasma as an Atomic Source (ICP-RIMS)  

NASA Astrophysics Data System (ADS)

We have proposed the novel isotope analysis technique with Resonance Ionization Mass Spectrometry using Inductively Coupled Plasma as an atomic source (ICP-RIMS). Each component of ICP-RIMS is conceptually designed. We conclude that the orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS) driven by a high-repetition-rate pulsed laser would be suitable system for ICP-RIMS. We, additionally, suggest that the first vacuum stage of the vacuum interface, which is between the sampling and skimmer cones, is desired to maintain as low pressure as possible in order to suppress the Doppler broadening and to skim the supersonic jet effectively.

Watanabe, K.; Higuchi, Y.; Tomita, H.; Kawarabayashi, J.; Uritani, A.; Iguchi, T.

2009-03-01

282

Conceptual Study on New Isotope Analysis Technique with Resonance Ionization Mass Spectrometry Using Inductively Coupled Plasma as an Atomic Source (ICP-RIMS)  

SciTech Connect

We have proposed the novel isotope analysis technique with Resonance Ionization Mass Spectrometry using Inductively Coupled Plasma as an atomic source (ICP-RIMS). Each component of ICP-RIMS is conceptually designed. We conclude that the orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS) driven by a high-repetition-rate pulsed laser would be suitable system for ICP-RIMS. We, additionally, suggest that the first vacuum stage of the vacuum interface, which is between the sampling and skimmer cones, is desired to maintain as low pressure as possible in order to suppress the Doppler broadening and to skim the supersonic jet effectively.

Watanabe, K.; Uritani, A. [Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan); Higuchi, Y.; Tomita, H.; Kawarabayashi, J.; Iguchi, T. [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

2009-03-17

283

Resonant Third-Order Optical Nonlinearities of Silicon 2,3-Naphthalocyanine Dioctyloxide Measured by Femtosecond Degenerate Four-Wave Mixing Technique  

NASA Astrophysics Data System (ADS)

The third-order optical nonlinearities of silicon 2,3-naphthalocyanine dioctyloxide (SiNc) were measured by a femtosecond degenerate four-wave mixing technique under resonant conditions. The electronic second molecular hyperpolarizability ?e of SiNc was determined to be as high as 9× 10-29 esu. The electronic third-order susceptibility of polystyrene films doped with SiNc was measured to be on the order of 10-9 esu. The nonlinear response of the doped films was found to be very fast and almost instantaneous in the perpendicular configuration.

Fu, Gang; Asada, Osamu; Kasatani, Kazuo; Okamoto, Hiroaki; Takenaka, Shunsuke

2005-06-01

284

Multipulse sequences for explosives detection by NQR under conditions of magnetoacoustic and piezoelectric ringing  

Microsoft Academic Search

A number of methods for cancelling magnetoacoustic and piezoelectric ringing signals in the spectroscopy of the nuclear quadrupole\\u000a resonance are presented. The suggested methods include using the sequence (?0)?-(?-?x-2?-?\\u000a y\\u000a -2?-??x\\u000a -2?-??y\\u000a -?)\\u000a n\\u000a and a multipulse analog of the two-pulse Hahn sequence with the first pulse replaced by a short steady-state sequence. Another\\u000a method presented is the method of

V. T. Mikhaltsevitch; T. N. Rudakov; J. H. Flexman; P. A. Hayes; W. P. Chisholm

2004-01-01

285

Improved Non Linear Time Series Forecasting Using Non Linear Analysis Techniques and RBF Neural Networks for MRS Signals and Chaotic Diode Resonator Circuits  

NASA Astrophysics Data System (ADS)

A novel non linear signal prediction method is presented using non linear signal analysis and deterministic chaos techniques in combination with Radial Basis Functions (RBF) Neural Networks for diode resonator chaotic circuits, used in industrial processes, as well as for Magnetic Resonance Spectroscopy (MRS) processes. The Time series analysis is performed by the method proposed by Grasberger and Procaccia, involving estimation of the correlation and minimum embedding dimension as well as of the corresponding Kolmogorov entropy. These parameters are used to construct the first stage of a one step / multistep predictor while an RBF Artificial Neural Network (ANN) is involved in the second stage to enhance prediction results. The novelty of the proposed two stage predictor lies on that the RBF ANN is employed as a second order predictor, that is, as an error predictor of the non-linear signal analysis stage application. This novel two stage predictor is evaluated through an extensive experimental study for both resonator circuits for industrial processes as well as for MRS signals in a preliminary stage of analysis. Different types of Neural Networks are compared as well.

Karras, D. A.; Hanias, M. P.

286

Evaluation of [sup 31]P magnetic resonance spectroscopy localization techniques in human myocardium and soft-tissue sarcomas  

SciTech Connect

The overall goals of this thesis are to establish and evaluate [sup 31]P MR spectroscopy localization techniques for their application to the study of human myocardium and sarcomas. Several localization techniques which include 1D-CSI, ISIS, ISIS/CSI, and 2D-CSI were evaluated in the myocardial muscle of normal subjects and patients receiving 5-fluorouracil (5-FU) chemotherapy. Among these localization techniques, 2D-CSI is recommended since it shows good selectivity, good flexibility and a good compromise between sensitivity patient toleration limits. These localization techniques were also evaluated in patients with osteosarcoma and soft-tissue sarcomas. Among these localization techniques, 1D-CSI is recommended for big and superficial tumors. Further definition of the voxel is provided by using 2D-CSI or 3D-CSI in the case of small or deep seated tumors. Several techniques that should improve the [sup 31]P MR spectroscopic study of patients in the future are evaluated on the phantom. These include the presaturation of the chest wall muscle for improved myocardial spectral using the CSI sequence, implementation of the BIR-4 pulse for variable angle adjustable pulse, and the proton decoupling technique for improved resolution and sensitivity. The good performance of the phantoms studies show that these techniques can be further extended to the normal subject and patient studies.

Li, Chun-Wei.

1993-01-01

287

Differentiation of normal and neoplastic bone tissue in dynamic gadolinium-enhanced magnetic resonance imaging: validation of a semiautomated technique  

Microsoft Academic Search

Purpose  This study was undertaken to clinically validate the accuracy of a semiautomated software tool for analysing the enhancement\\u000a curve in focal malignant bone lesions.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  Twenty-three patients affected by cancer with malignant focal bone lesions underwent dynamic gadolinium-enhanced magnetic\\u000a resonance (MR) imaging using the following protocol: T1-weighted turbo spin-echo sequences (time to repeat [TR] 600 ms, time\\u000a to echo

F. D’Agostino; P. Dell’Aia; C. C. Quattrocchi; R. Del Vescovo; R. Setola; R. F. Grasso; B. Beomonte Zobel

2010-01-01

288

Novel Phase Transition in CeRu2Al10 Probed by 27Al-NQR/NMR —No Evidence of Magnetic Ordering—  

NASA Astrophysics Data System (ADS)

The 27Al-NQR/NMR measurements of CeRu2Al10 were carried out to clarify the unusual phase transition at T0=27 K. Distinct NQR peaks associated with five nonequivalent Al sites have been observed at T > T0, and each peak is successfully assigned to their respective Al sites. Below the transition temperature T < T0, each peak simply splits into two peaks except for one site. This indicates that the phase transition is not accompanied by magnetic order, but is presumably associated with the onset of structural transition with lowering symmetry. The nuclear spin-lattice relaxation rate 1/T1 suggests a local moment picture above T*˜ 60 K, and the development of Kondo coherence toward T0. Below T0, 1/T1 shows a gaplike decrease with a gap magnitude of 106 K, being consistent with the macroscopic measurements. The Korringa term below 10 K after the gaplike decrease suggests a gap opening over a portion of the Fermi surface.

Matsumura, Masahiro; Kawamura, Yukihiro; Edamoto, Shingo; Takesaka, Tomoaki; Kato, Harukazu; Nishioka, Takashi; Tokunaga, Yo; Kambe, Shinsaku; Yasuoka, Hiroshi

2009-12-01

289

NQR investigation of pressure-induced charge transfer in oxygen-deficient YBa sub 2 Cu sub 3 O sub 7-. delta. (. delta. = 0. 38)  

SciTech Connect

Measurements of the pressure dependence of {sup 63}Cu nuclear quadrupole frequency in YBa{sub 2}Cu{sub 3}O{sub 6.62} from ambient pressure up to 1.5 GPa at 4k have been performed. {Tc} was found to increase with pressure: d{Tc}/dp {approximately} 5 K/GPa. All observed NQR lines are linear in pressure: dln{nu}{sub Q}/dp=z. We found positive z for the empty chain sites, consistent with ionic (Cu{sup 1+}) configuration in which the atom simply feels a squeezing lattice. Planar coppers close to the empty chains have positive z, while those that are close to full chains have z {approximately} 0. We present an analysis of the NQR result on the basis of the charge transfer model in which the mobile charges migrate from the chain to the plane sites. We deduced that a transfer of 0.021 holes to the O(2,3) sites would explain the result in YBa{sub 2}Cu{sub 3}O{sub 6.62}, whereas only 0.007 holes transfer in fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7}.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H. (Los Alamos National Lab., NM (United States)); Takigawa, M. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center)

1992-01-01

290

NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P-semiconductors.  

PubMed

Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model. PMID:22588584

Baei, Mohammad T; Peyghan, Ali Ahmadi; Tavakoli, Khadijeh; Babaheydari, Ali Kazemi; Moghimi, Masoumeh

2012-09-01

291

High precision measurement of the 11Li and 9Li quadrupole moment ratio using zero-field ?-NQR  

NASA Astrophysics Data System (ADS)

The ratio of electric quadrupole moments of 11Li and 9Li was measured using the zero-field ?-detected nuclear quadrupole resonance technique at Triumf-Isac. The precision on the ratio Q11/Q9 = 1.0775(12) was improved by more than one order of magnitude and an absolute value for the quadrupole moment of 11Li was inferred. Systematic effects, as argued here, are not expected to contribute to the ratio on this scale. The zero-field spin-lattice relaxation time for 8Li implanted within SrTiO3 at 295?K in zero-field was found to be T1 = 1.73(2)?s. A comparison of the quadrupole moments of 9, 11Li and their ratio is made with the latest models, however, no conclusion may yet be drawn owing to the size of the theoretical uncertainties.

Voss, A.; Pearson, M. R.; Buchinger, F.; Crawford, J. E.; Kiefl, R. F.; Levy, C. D. P.; MacFarlane, W. A.; Mané, E.; Morris, G. D.; Shelbaya, O. T. J.; Song, Q.; Wang, D.

2014-01-01

292

Surface plasmon resonance technique for directly probing the interaction of DNA and graphene oxide and ultra-sensitive biosensing.  

PubMed

The binding of DNA with graphene oxide (GO) is important for applications in disease diagnosis, genetic screening, and drug discovery. The standard assay methods are mainly limited to indirect observation via fluorescence labeling. Here we report the use of surface plasmon resonance for direct sensing of DNA/GO binding. We show that this can be used for ultra-sensitive detection of single-stranded DNA (ssDNA). Furthermore, the results provide a more direct probe of DNA/GO binding abilities and confirm that hydrogen bonding plays a key role in the interaction between GO and ssDNA. This enables to a novel biosensor for highly sensitive and selective detection of ssDNA based on indirect competitive inhibition assay (ICIA). We report development of such a sensor with a linear dynamic range of 10(-14)-10(-6)M, a detection limit of 10fM and a high level of stability during repeated regeneration. PMID:24686149

Xue, Tianyu; Cui, Xiaoqiang; Guan, Weiming; Wang, Qiyu; Liu, Chang; Wang, Haitao; Qi, Kun; Singh, D J; Zheng, Weitao

2014-08-15

293

A sensitive and simple method for the determination of chondroitin sulfate a with crystal violet by resonance rayleigh scattering technique.  

PubMed

Resonance Rayleigh scattering (RRS) spectra resulting from interaction between chondroitin sulfate A (CSA) and crystal violet (CV) have been investigated and applied to the determination of CSA. Though the intensity of RRS has proved very weak for CSA and CV, respectively, it can be greatly enhanced when both interact and form a supramolecular complex. A new RRS spectrum appears with a maximum scattering peak at 328 nm. In this paper, the optimum conditions of the interaction, influencing factors, and the relationship between the relative intensity of RRS (DeltaI) and the concentration of CSA have been thoroughly investigated. A new method of determination for the trace amount of CSA has been developed, which combines a simple procedure, high sensitivity, and a low detection limit of 4.8 ng/mL. It has been applied with satisfactory results to the determination of CSA in CSA injection samples and synthetic samples. PMID:16143959

Li, Taishan; Liu, Shaopu; Liu, Zhongfang; Hu, Xiaoli

2005-09-01

294

Magnetic Resonance Studies of Coal. Volume III.  

National Technical Information Service (NTIS)

Electron spin resonance (ESR) and Electron-Nuclear Double Resonance (ENDOR) techniques have been used to study natural radical centers in Alabama coals. Also Nuclear Magnetic Resonance (NMR) techniques have been used for a preliminary study of the hydroge...

I. Miyagawa C. Alexander

1981-01-01

295

Biosensing Based on Surface Plasmon Resonance of Gold Nanohole and Nanoring Arrays Fabricated by a Novel Nanosphere Lithography Technique  

Microsoft Academic Search

An optical biosensor based on gold nanohole arrays was developed using a new nanosphere lithography technique. A vertical deposition method was used to deposit multilayers of a polystyrene (PS) - gold composite on a silanized glass substrate. The SEM images have shown that the gold nanohole and nanoring arrays are distributed uniformly on the substrate. The sensitivity of the gold

Farah Fida; Ramin Banan-sadeghian; Ahmad-reza Hajiaboli; Yahia Djaoued; Simona Badilescu; Subramanian Balaji; M. Kahrizi; Vo-van Truong

2008-01-01

296

Nuclear magnetic resonance experiments with dc SQUID amplifiers  

SciTech Connect

The development and fabrication of dc SQUIDs (Superconducting QUantum Interference Devices) with Nb/Al{sub 2}O{sub 3}/Nb Josephson junctions is described. A theory of the dc SQUID as a radio-frequency amplifier is presented, with an optimization strategy that accounts for the loading and noise contributions of the postamplifier and maximizes the signal-to-noise ratio of the total system. The high sensitivity of the dc SQUID is extended to high field NMR. A dc SQUID is used as a tuned radio-frequency amplifier to detect pulsed nuclear magnetic resonance at 32 MHz from a metal film in a 3.5 Tesla static field. A total system noise temperature of 11 K has been achieved, at a bath temperature of 4.2 K. The minimum number of nuclear Bohr magnetons observable from a free precession signal after a single pulse is about 2 {times} 10{sup 17} in a bandwidth of 25 kHz. In a separate experiment, a dc SQUID is used as a rf amplifier in a NQR experiment to observe a new resonance response mechanism. The net electric polarization of a NaClO{sub 3} crystal due to the precessing electric quadrupole moments of the Cl nuclei is detected at 30 MHz. The sensitivity of NMR and NQR spectrometers using dc SQUID amplifiers is compared to the sensitivity of spectrometers using conventional rf amplifiers. A SQUID-based spectrometer has a voltage sensitivity which is comparable to the best achieved by a FET-based spectrometer, at these temperatures and operating frequencies.

Heaney, M.B. (California Univ., Berkeley, CA (USA). Dept. of Physics Lawrence Berkeley Lab., CA (USA))

1990-11-01

297

Nucleic acids determination using the complex of eriochrome black T and silver nanoparticles in a resonance light scattering technique  

NASA Astrophysics Data System (ADS)

A novel method for the determination of nucleic acids by using silver nanoparticle (AgNPs)-eriochrome black T (EBT) as a resonance light scattering (RLS) probe has been developed. Under optimum conditions, there are linear relationships between the quenching extent of RLS intensity and the concentration of nucleic acids in the range of 4.0 × 10 -9-4.0 × 10 -7, 4.0 × 10 -7-1.6 × 10 -6 g mL -1 for fish sperm DNA (fsDNA) and 4.0 × 10 -8-2.0 × 10 -6 g mL -1 for yeast RNA (yRNA). Their detection limits (S/N = 3) are 2.0 ng mL -1 and 21 ng mL -1, respectively. The results indicate that AgNPs can form wirelike aggregates and nanoslices in the presence of the EBT. Whereas, when nucleic acids are added into the AgNPs-EBT system, the dynamic balance of AgNPs-EBT system is destroyed and the nanoparticles undergo dispersion again, leading to the RLS intensity of AgNPs-EBT system quenching. Meanwhile, the conformation of fsDNA is changed by the synergistic effect of AgNPs and EBT.

Zhou, Haiping; Wu, Xia; Meng, Fanhui; Yang, Jinghe; Wang, Minqin

2011-02-01

298

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

299

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

PubMed

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 (?I(RRS)) 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. PMID:22137013

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

2012-02-01

300

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 (310nm) 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

301

A novel technique for the three-dimensional visualization of radio-frequency ablation lesions using delayed enhancement magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The detection of radio-frequency ablation lesions has been shown to be feasible using delayed enhancement magnetic resonance imaging (MRI). However, it is the determination of the lesion patterns that is of import for correlation with clinical outcome and location of gaps. Visualisation of ablation patterns on two-dimensional (2D) MR images is not intuitive. We present a technique for the three-dimensional (3D) visualisation of ablation patterns by creating a surface from a segmentation of the cardiac chamber of interest, fusing with the delayed enhancement MRI and integrating the MR signal along vectors normal to the cardiac surface. Areas of delayed enhancement will have a larger integral value than healthy myocardium. Maximum intensity projection (MIP) values were used to colour code the cardiac surface for 3D visualisation of the areas of delayed enhancement. The technique was applied to three patients with a cardiac arrhythmia, with successful visualisation of the ablation pattern. Patterns of delayed enhancement were correlated with ablation points derived from electro-anatomical mapping systems (EAMS) and were found to have similar patterns. This visualisation technique allows for the intuitive visualisation of ablation lesions and has many applications for use in electrophysiology.

Knowles, Benjamin R.; Caulfield, Dennis; Ginks, Matthew; Cooklin, Michael; Bostock, Julian; Rinaldi, Aldo; Gill, Jaswinder; Razavi, Reza; Schaeffter, Tobias; Rhode, Kawal S.

2009-02-01

302

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

303

The analytical application and spectral investigation of DNA-CPB-emodin and sensitive determination of DNA by resonance Rayleigh light scattering technique.  

PubMed

A new sensitive DNA probe containing cetylpyridinium bromide (CPB) and emodin (an effective component of Chinese herbal medicine) was developed using the resonance Rayleigh light scattering (RLS) technique. A novel assay was first developed to detect DNA at nanogram level based on the ternary system of DNA-CPB-emodin. The RLS signal of DNA was enhanced remarkably in the presence of emodin-CPB, and the enhanced RLS intensity at 340.0 nm was in direct proportion to DNA concentration in the range of 0.01-2.72 ?g mL(-1) with a good linear relationship. The detection limit was 1.5 ng mL(-1). Three synthetic DNA samples were measured obtaining satisfactory results, the recovery was 97.6-107.3%. PMID:23103464

Bi, Shuyun; Wang, Yu; Wang, Tianjiao; Pang, Bo; Zhao, Tingting

2013-01-15

304

The analytical application and spectral investigation of DNA-CPB-emodin and sensitive determination of DNA by resonance Rayleigh light scattering technique  

NASA Astrophysics Data System (ADS)

A new sensitive DNA probe containing cetylpyridinium bromide (CPB) and emodin (an effective component of Chinese herbal medicine) was developed using the resonance Rayleigh light scattering (RLS) technique. A novel assay was first developed to detect DNA at nanogram level based on the ternary system of DNA-CPB-emodin. The RLS signal of DNA was enhanced remarkably in the presence of emodin-CPB, and the enhanced RLS intensity at 340.0 nm was in direct proportion to DNA concentration in the range of 0.01-2.72 ?g mL-1 with a good linear relationship. The detection limit was 1.5 ng mL-1. Three synthetic DNA samples were measured obtaining satisfactory results, the recovery was 97.6-107.3%.

Bi, Shuyun; Wang, Yu; Wang, Tianjiao; Pang, Bo; Zhao, Tingting

2013-01-01

305

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°.

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

2014-01-01

306

Third-order optical nonlinearities of sol-gel silica coating films containing metal porphyrin derivatives measured by resonant femtosecond degenerate four-wave mixing technique  

NASA Astrophysics Data System (ADS)

Third-order optical nonlinearities of sol-gel silica coating films containing metal porphyrin derivatives were measured under resonant conditions by the femtosecond degenerate four-wave mixing (DFWM) technique. Temporal profiles of the DFWM signal were measured with a time resolution of 0.3 ps, and were found to consist of two components, the coherent instantaneous nonlinear response and the delayed response with a decay time constant of several to several hundred ps. The latter can be attributed to population grating of an excited state, and contribution of slow component was very little for a zinc porphyrin derivative. The values of electronic component of the optical nonlinear susceptibility, ?(3) xxxx, for these films were ca. 2 x 10-10 esu.

Kasatani, Kazuo; Okamoto, Hiroaki; Takenaka, Shunsuke

2003-11-01

307

Detection and identification of underwater targets by resonance or resonant scattering  

Microsoft Academic Search

This paper presents the resonance or resonant scattering technique for detection and identification of underwater targets. Based on the resonance theory and the resonant scattering theory (RST), all underwater objects resonate at their natural frequencies when impinged by acoustic energy. These resonating natural frequencies appear as modulations on the frequency domain of the target echoes. Since these natural resonances are

Gee-In Goo

1997-01-01

308

A novel intubation technique for minimally invasive longitudinal studies of rat lungs using hyperpolarized 3He magnetic resonance imaging.  

PubMed

Hyperpolarized noble gas (HNG) magnetic resonance imaging (MRI) has been shown to be useful for studying rodent models of lung disease. Image quality can be substantially degraded by signal loss from molecular oxygen entering the airway, requiring invasive surgery to ensure a good seal between the endotracheal (ET) tube and trachea. A modified Foley catheter having an inflatable cuff near the tip provides a novel approach for ensuring image quality for HNG MRI, thereby enabling longitudinal studies and reducing animal numbers. A Foley catheter was modified for rodent intubation and to minimize dead space. Three pairs of age-matched male Sprague Dawley rats 400 (30) g were used. Two pairs were intubated using the Foley and the third with an intravenous catheter. Leak rates were measured from pressure versus time curves within each animal. The pairs were euthanized immediately or six days postrecovery to assess the effects of the procedure on animal health, as reflected by histological examination. The Foley catheter resulted in minimal leak rates (-0.20 (0.03) versus -0.16 (0.05) cmH(2)O/s), and were shown to be well below upper-limit leak rates of -0.5 and -0.7 cmH(2)O/s. Tracheal samples from rats in a separate Foley group (not mechanically ventilated) showed superficial damage six days postextubation (grade = 0). (3)He imaging performed using the Foley showed good image quality. Though some technical issues remain to be solved, a modified Foley catheter used as an ET tube offers the potential to enable longitudinal studies in rodents and reduce animal numbers. PMID:23097565

Fox, M S; Welch, I; Hobson, D; Santyr, G E

2012-10-01

309

Surface-enhanced resonance Raman scattering (SERRS) spectroscopy: a powerful technique for the forensic analysis of colorants?  

NASA Astrophysics Data System (ADS)

During the past five years work in our laboratory has been concentrated on developing SERRS spectroscopy and making it a simple and robust technique for the analyses of colorants. It has proved to be highly discriminative, extremely sensitive and possible to identify dyes in mixtures without their prior separation. Additionally, by using concentrated silver colloid solutions, in-situ analyses have now been accomplished with minimal or in some cases no visual destruction of the item being examined and with virtually no background interference from the surfaces on which the stains or smears have been deposited. To illustrate the methodology and the potential of SERRS various applications including the in-situ analyses of the dyes on cotton fibers and stains from cosmetics, shoe polishes, inks and drinks on various surfaces are presented.

White, Peter C.; Rodger, Caroline; Rutherford, Vicky; Finnon, Yvonne; Smith, W. Ewen; Fitzgerald, Mary P.

1999-02-01

310

Panoramic radiograph, computed tomography or magnetic resonance imaging. Which imaging technique should be preferred in bisphosphonate-associated osteonecrosis of the jaw? A prospective clinical study.  

PubMed

It was the aim of the present study to find out which radiological imaging techniques allow assessing the extent of bisphosphonate-associated osteonecrosis of the jaw (BONJ) in an adequate way. Twenty-four patients suffering from BONJ were included in the study. Before surgery, each patient was examined with panoramic radiograph, contrast-enhanced magnetic resonance imaging (MRI) and non-enhanced computed tomography. The detectability of BONJ was assessed for the three imaging techniques. The extent of the jaw region affected by BONJ was determined in MRI and CT scans and compared to the intra-operative situation. The detectability of BONJ lesions was 54% for panoramic radiographs, 92% for MRI scans and 96% for computed tomography (CT) scans. The intra-operatively assessed extent of BONJ correlated significantly with the measurements on CT scans (p = 0.0004) but did not correlate significantly with the measurements in MRI scans (p = 0.241). The intra-operatively measured extent of BONJ differed significantly from the CT measurements (p = 0.00003) but not from the MRI data (p = 0.137). Although MRI as well as CT have a high detectability for BONJ lesions that exceeds that of panoramic radiographs by far, both techniques show problems with the exact assessment of the extent of BONJ lesions in the individual patients. Therefore, the relevance of MRI and CT for the preoperative assessment of the extent of BONJ lesions is limited. Future research should focus on the identification of imaging techniques that allow assessing the extent of BONJ lesions with a higher accuracy. PMID:19513765

Stockmann, Philipp; Hinkmann, Fabian M; Lell, Michael M; Fenner, Matthias; Vairaktaris, Eleftherios; Neukam, Friedrich-Wilhelm; Nkenke, Emeka

2010-06-01

311

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

312

14N nuclear quadrupole resonance of picolinic, nicotinic, isonicotinic and dinicotinic acids  

NASA Astrophysics Data System (ADS)

The 14N nuclear quadrupole resonance (NQR) quadrupole coupling tensors of picolinic, nicotinic, isonicotinic and dinicotinic acids have been determined. Two different 14N quadrupole coupling constants 1007 kHz and 4159 kHz have been observed for picolinic acid demonstrating the presence of both protonated and non-protonated nitrogen atoms in this system in the solid. Only one set of non-protonated 14N NQR lines has been observed in other pyridinecarboxylic acids demonstrating the absence of the protonated zwitter ion forms observed in picolinic acid. The non-protonated 14N quadrupole coupling constant is the highest for the non-protonated nitrogen in picolinic acid and decreases to 3774 kHz in nicotinic acid and 3570 kHz in isonicotinic acid. It is the lowest in dinicotinic acid where the corresponding 14N quadrupole coupling constant is 2794 kHz. The observed anomalous decrease in the 14N quadrupole coupling constant of dinicotinic acid with decreasing temperature is tentatively explained as reflecting the increase in the residence time of the N-H⋯O bonded proton in the potential well close to the nitrogen.

Seliger, J.; Žagar, V.; Zidanšek, A.; Blinc, R.

2006-12-01

313

Development of a label-free immunosensor based on surface plasmon resonance technique for the detection of anti-Leishmania infantum antibodies in canine serum.  

PubMed

In this work, a surface plasmon resonance (SPR) immunosensor was developed using an 11-mercaptoundecanoic acid (11-MUA) modified gold SPR sensor chip for the detection of anti-Leishmania infantum antibodies. The soluble antigens of L. infantum were securely immobilized on an SPR gold disk by an 11-MUA self-assembled monolayer. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques were employed in the characterization of the antigen immobilization. After the immunosensor construction, canine serum positive for visceral leishmaniasis was added to its surface and showed significant variation in the SPR angle, indicating excellent sensitivity of the technique for antigen-antibody interaction detection. Moreover, the addition of negative serum was accompanied by a smaller response, demonstrating that the immunosensor shows good specificity against anti-L. infantum antibodies. Therefore, this work demonstrates the successful development of an SPR sensor for anti-L. infantum antibodies detection in short time, showing a great perspective as a sensing system of visceral leishmaniasis in endemic regions. PMID:23500472

Souto, Dênio E P; Silva, Jussara V; Martins, Helen R; Reis, Alexandre B; Luz, Rita C S; Kubota, Lauro T; Damos, Flávio S

2013-08-15

314

A selective and sensitive assay of berberine using total internal reflected resonance light scattering technique with fluorescein at the water/1,2-dichloroethane interface.  

PubMed

An assay of berberine (BE) was developed with good selectivity and sensitivity based on the total internal reflected resonance light scattering (TIR-RLS) signals from water/1,2-dichloroethane (H(2)O/DCE) interface. Under optimal conditions, amphiphilic complex formed by BE and fluorescein (Flu) was adsorbed to H(2)O/DCE interface, resulting in good separation of BE from the coexisting foreign substances in aqueous phase and significant enrichment of BE at the interface. This enriched species at the interface was found corresponding to enhanced TIR-RLS signals located at 370.0 nm. Proportional relationships were established between the enhanced TIR-RLS intensity and the BE in the range of 3.2 x 10(-9) to 3.2 x 10(-6) mol l(-1) with the limit of detections (3sigma) being 1.3 ng ml(-1). Favorable sensitivity of TIR-RLS technique was demonstrated superior to that of high-performance liquid-chromatography (HPLC) method. The feasibility of the proposed technique was validated by the satisfactory performance of intra-assay and inter-assay BE in tablets. PMID:15030893

Pang, Xiao Bing; Huang, Cheng Zhi

2004-04-01

315

Adaptive optics sensing and control technique to optimize the resonance of the Laguerre-Gauss 33 mode in Fabry-Perot cavities  

NASA Astrophysics Data System (ADS)

Second and third generation gravitational wave interferometric detectors will be limited in their sensitivity by thermal noise of the core optics. One way to reduce this contribution is to use an input laser beam with a more uniform distribution of the power: for this reason the use of the Laguerre-Gauss LG3,3 mode as interferometer input has been suggested. The main issue with this approach is the fact that in resonant cavities with spherical mirrors the input mode will be degenerate with nine other modes. This implies very stringent requirements on the mirror surface quality, beyond the present polishing technology capabilities: it is not possible to obtain mirrors with low enough surface roughness to meet the requirements for the operation of a gravitational wave detector. In a previous paper an approach to apply in situ thermal corrections to the main surface of the mirrors was proposed. In this paper we develop further the technique, showing that it is possible to compute the optimal correction using only the information that can be extracted from the intensity images in reflection of the resonant cavity, without any a priori knowledge of the mirror surface maps. We test our proposal using optical simulations and we are able to considerably improve the quality of the beam reflected from a cavity with realistic mirror surface maps: without any correction the purity of the reflected beam was degraded to below 90%; with the proposed adaptive optics system we could recover a purity of 99.96%. The implementation of the proposed system would allow the use of a LG3,3 input mode with the mirror qualities available today. In addition we show that it is possible to correct the aberrations introduced by both mirrors acting only on one of the two. In this way it is possible to avoid introducing unwanted thermal lensing in the input mirrors.

Vajente, G.; Day, R. A.

2013-06-01

316

Aqueous phase behavior of tetraethylene glycol decanoyl ester (C9COE4) and Ether (C10E4) investigated by nuclear magnetic resonance spectroscopic techniques.  

PubMed

The binary phase diagram of tetraethylene glycol decanoyl ester (C9COE4) was investigated in the micellar region by PGSE-NMR (pulse field gradient spin echo nuclear magnetic resonance) and in the lamellar liquid crystalline state by 2H NMR. Its behavior was compared to the ether counterpart, tetraethylene glycol decanoyl ether (C10E4), whose phase diagram is well-described. The determination of the self-diffusion coefficient as a function of concentration permitted not only a determination of the critical micellar concentration (cmc) values but also the determination of the size and shape of micelles formed by both compounds. The evolution of the self-diffusion coefficients in the vicinity of the cloud point was also studied, showing no micellar growth with increasing temperature. 2H NMR analyses at the border of and within the liquid crystalline region gave an insight into the lamellar phase structure. We investigated in detail the lamellar phase of both compounds by comparing the values of quadrupolar splittings (Deltanu) measured under the same conditions. Lower Deltanu values were found for the ester compared to the ether: since the ester probably binds more water than the ether, these lower Deltanu values would indicate a lower order parameter in the liquid crystal phase. NMR techniques, either PGSE-NMR or 2H NMR, were confirmed as useful tools to characterize aqueous phase behavior of surfactants, providing supplementary information to the classical techniques such as visual observations, polarized optical microscopy (POM), and surface tension measurements. They also provide a unique insight into the molecular organization in the different phases formed. PMID:17929840

Fournial, Anne-Gaëlle; Zhu, Ying; Molinier, Valérie; Vermeersch, Gaston; Aubry, Jean-Marie; Azaroual, Nathalie

2007-11-01

317

An investigation on the interaction of DNA with hesperetin/apigenin in the presence of CTAB by resonance Rayleigh light scattering technique and its analytical application.  

PubMed

Two new systems for measuring DNA at nanogram levels by a resonance Rayleigh light scattering (RLS) technique with a common spectrofluorometer were proposed. In the presence of cetyltrimethylammonium bromide (CTAB), the interaction of DNA with hesperetin and apigenin (two effective components of Chinese herbal medicine) could enhance RLS signals with the maximum peak at 363 and 433 nm respectively. The enhanced intensity of RLS was directly proportional to the concentration of DNA in the range of 0.022-4.4 ?g mL(-1) for DNA-CTAB-hesperetin system and 0.013-4.4 ?g mL(-1) for DNA-CTAB-apigenin system. The detection limit was 2.34 ng mL(-1) and 2.97 ng mL(-1) respectively. Synthetic samples were measured satisfactorily. The recovery of DNA-CTAB-hesperetin system was 97.3-101.9% and that of DNA-CTAB-apigenin system was 101.2-109.5%. PMID:22336048

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

2012-05-01

318

An investigation on the interaction of DNA with hesperetin/apigenin in the presence of CTAB by resonance Rayleigh light scattering technique and its analytical application  

NASA Astrophysics Data System (ADS)

Two new systems for measuring DNA at nanogram levels by a resonance Rayleigh light scattering (RLS) technique with a common spectrofluorometer were proposed. In the presence of cetyltrimethylammonium bromide (CTAB), the interaction of DNA with hesperetin and apigenin (two effective components of Chinese herbal medicine) could enhance RLS signals with the maximum peak at 363 and 433 nm respectively. The enhanced intensity of RLS was directly proportional to the concentration of DNA in the range of 0.022-4.4 ?g mL-1 for DNA-CTAB-hesperetin system and 0.013-4.4 ?g mL-1 for DNA-CTAB-apigenin system. The detection limit was 2.34 ng mL-1 and 2.97 ng mL-1 respectively. Synthetic samples were measured satisfactorily. The recovery of DNA-CTAB-hesperetin system was 97.3-101.9% and that of DNA-CTAB-apigenin system was 101.2-109.5%.

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

2012-05-01

319

System and Method for Regulating Resonant Inverters.  

National Technical Information Service (NTIS)

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 resonan...

L. D. Stevanovic R. A. Zane

2004-01-01

320

Cavity Resonators.  

National Technical Information Service (NTIS)

The microwave cavity resonator may be used in the field of electron spin resonance spectroscopy for studying samples of paramagnetic materials which are supported within the resonator. The resonator passes a maximum amount of light through the walls to th...

E. L. Cochran

1965-01-01

321

Stochastic Resonance  

NASA Astrophysics Data System (ADS)

Preface; 1. Introduction and motivation; 2. Stochastic resonance: its definitions, history and debates; 3. Stochastic quantization; 4. Suprathreshold stochastic resonance: encoding; 5. Suprathreshold stochastic resonance: large N encoding; 6. Suprathreshold stochastic resonance: decoding; 7. Suprathreshold stochastic resonance: large N decoding; 8. Optimal stochastic quantization; 9. SSR, neural coding, and performance tradeoffs; 10. Stochastic resonance in the auditory system; 11. The future of stochastic resonance and suprathreshold stochastic resonance; Appendices; References; Index.

McDonnell, Mark D.; Stocks, Nigel G.; Pearce, Charles E. M.; Abbott, Derek

2012-10-01

322

Kinetics of electrochemically controlled surface reactions on bulk and thin film metals studied with Fourier transform impedance spectroscopy and surface plasmon resonance techniques  

NASA Astrophysics Data System (ADS)

In the work presented in this thesis, the surface sensitive electrochemical techniques of cyclic voltametry (CV), potential step (PS) and Fourier transform impedance spectroscopy (FT-EIS), as well as the optical technique of surface plasmon resonance (SPR), were used to probe a wide variety of surface processes at various metal/liquid interface. Three polycrystalline metals (Au, Ta and Cu) and a Cr-coated gold film were used for these studies in different aqueous environments. A combination of CV with FT-EIS and PS was used to investigate electronic and structural proprieties of a modified bulk electrode of Au. This experimental system involved under potential deposition (UPD) of Bi3+ on Au in a supporting aqueous electrolyte containing ClO-4 . UPD range of Bi3+ was determined, and adsorption kinetics of Bi3+ in the presence of coadsorbing anion, ClO-4 were quantified. Potentiodynamic growth of oxide films of Ta in the following electrolytes NaNO3, NaNO3 + 5wt% H2O2, NaOH and NaOH + 5wt% H2O2 had been investigated. The oxide films were grown in the range -0.1 ? +0.4V (high electric field) at a scan rate of 10 mV/s. Time resolved A.C. impedance spectroscopy measurements in the frequency range (0.1--20 KHz) were performed to characterize the surface reactions of oxide formation. The results are interpreted in terms of charge conductivity O2- through the oxide film, and disintegration of H2O2 into OH-. In a high pH medium (pH 12), dissociation of H2O2 was catalytically enhanced. This led to destabilization of the electrogenerated tantalum oxide surface film in the form of a soluble hexatantalate species. In contrast with the electrolytes, NaNO3, NaNO3 + 5wt% H2O2, NaOH, where only the oxide growth was observed, the A.C. impedance spectroscopy measurements in NaOH + 5wt% H 2O2 showed competition between oxide formation and its removal. These results are relevant for chemical slurry design in chemical mechanical polishing (CMP) of Ta. Further investigations were performed by studying potential galvanic corrosion effects that are susceptible to occur during planarization process in CMP technology. A combination of FT-EIS with potentiodynamic polarization and galvanic current measurements showed evidence of these effects when Cu (interconnected material in integrated circuits) and Ta (barrier material) were brought into electrical contact via abrasive-free polishing solutions. Quantitative analyses of kinetics of these effects were performed. Catalytic activity of a thin film Au (˜40 nm) toward methanol oxidation in alkaline medium for direct methanol fuel cell (DMFC) was carried out in this part of the work. A relatively unique combined technique of FT-EIS and SPR was used to perform this study. The FT-EIS data provided detailed kinetic parameters that characterize electro-oxidation of methanol. This led to a quantitative understanding of the mechanism of the probed surface reactions. At the same time, the SPR data provided with high accuracy the optical parameters and electronic characteristics of the thin film Au. The combined technique provided a complete understanding of the observed surface reactions, and showed consistency in data.

Assiongbon, Kankoe A.

323

Novel antagonists acting at the P2Y(1) purinergic receptor: synthesis and conformational analysis using potentiometric and nuclear magnetic resonance titration techniques.  

PubMed

The human P2Y(1) receptor is widely distributed in many tissues and has a classical structure of a G protein-coupled receptor. Activated by adenosine-5'-diphosphate (ADP), this receptor is essential for platelet aggregation. In the present paper, we describe the synthesis of novel P2Y(1) antagonists that could be of interest at least as tools to define the physiological roles of the P2Y(1) receptor, at best as new antithrombotic agents. Thus, we prepared the 2,N(6)-dimethyl-2'-deoxyadenosine-3',5'-bisphosphate derivative, 1e. The biological activity was demonstrated by the ability of compound 1e to inhibit ADP-induced platelet aggregation, shape change, and intracellular calcium rise. This compound was a full antagonist at the P2Y(1) receptor with a pA(2) value of 7.11 +/- 0.11 and was found to be 4-fold more potent than the reference N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate (1a, pA(2) = 6.55 +/- 0.05), revealing the potency-enhancing effects of the 2-methyl group. The better activity of 1e as compared to 1a was analyzed using both potentiometric and nuclear magnetic resonance titration techniques, which highlighted specific conformational features of this compound. These results clearly indicate the preference for both compounds for an anti conformation at the N-glycosyl linkage. Furthermore, the percentage of S conformer of 1e is close to that of 1a, which is nearly 70% at pH = 2.8 and increases dramatically when pH increases. From the macroprotonation constants, it can be noted that compound 1e is significantly more basic than 1a. This is indeed expected for the N1 adenine nitrogen due to the electron-donating character of the methyl moiety. By considering the microconstants of the phosphate groups, the higher basicity of P3 and P5 for 1e may be due to the decrease in the local dielectric constant induced by the substitution of the hydrogen atom by a more lipophilic methyl group. Thus, it may be suggested that the gain in activity of 1e when compared to the reference compound 1a would result from its gain in basicity rather than steric and conformational modifications. The synthesis of the first selective radioligand acting at the P2Y(1) receptor ([(33)P]-N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate, 17) is also reported and will be used in the future for efficient screening needed for drug optimization. PMID:11831909

Raboisson, Pierre; Baurand, Anthony; Cazenave, Jean-Pierre; Gachet, Christian; Retat, Myriam; Spiess, Bernard; Bourguignon, Jean-Jacques

2002-02-14

324

Novel multisample dielectric resonators for electron paramagnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

We have developed and tested two types of novel dielectric resonators for simultaneous recording of electron paramagnetic resonance (EPR) spectra from two to four samples. The resonator of the first type contains two holes, and the other resonator contains four holes for introduction of the samples. Also, the resonator structure includes a pair of gradient coils. Dielectric resonators made of materials with high dielectric constant with low losses can be inserted into the standard EPR cavity or waveguide in the maximum microwave magnetic field. Gradient coils are located outside the cavity (or waveguide) so that their axes are parallel to the static magnetic field. Computer simulations were made to obtain microwave characteristics of the resonators such as resonant frequency, sizes, and distribution of the fields. Spacing of the point samples and optimum value of the magnetic-field gradient have been chosen correctly. The designed resonators can be applied in express analysis using EPR technique, for instance.

Golovina, Iryna S.; Kolesnik, Sergiy P.; Geifman, Ilia N.; Belous, Anatoliy G.

2010-04-01

325

Bonding and molecular motions in the 1:1 molecular complexes of 1,4-diazabicyclo[2.2.2]octane with tetrahalomethane as studied by means of NQR  

NASA Astrophysics Data System (ADS)

NQR spectra were observed in the complexes of 1,4-diazabicyclo[2.2.2]octane (DABCO) with tetrachloromethane and tetrabromomethane at various temperatures. A phase transition was found at 319 K for DABCO·CBr 4. From spin-lattice relaxation times of nitrogen-14 in DABCO·CBr 4, the activation energy of the reorientation of DABCO about the N?N axis was calculated to be 18.3 kJ/mol which agrees with the value obtained from the second moment of proton NMR spectra. The bond nature is discussed using the Townes-Dailey treatment.

Okuda, T.; Suzuki, T.; Negita, H.

1983-12-01

326

Resonance Ionization, Mass Spectrometry.  

ERIC Educational Resources Information Center

Discussed is an analytical technique that uses photons from lasers to resonantly excite an electron from some initial state of a gaseous atom through various excited states of the atom or molecule. Described are the apparatus, some analytical applications, and the precision and accuracy of the technique. Lists 26 references. (CW)

Young, J. P.; And Others

1989-01-01

327

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

328

NQR investigation of pressure-induced charge transfer in oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} ({delta} = 0.38)  

SciTech Connect

Measurements of the pressure dependence of {sup 63}Cu nuclear quadrupole frequency in YBa{sub 2}Cu{sub 3}O{sub 6.62} from ambient pressure up to 1.5 GPa at 4k have been performed. {Tc} was found to increase with pressure: d{Tc}/dp {approximately} 5 K/GPa. All observed NQR lines are linear in pressure: dln{nu}{sub Q}/dp=z. We found positive z for the empty chain sites, consistent with ionic (Cu{sup 1+}) configuration in which the atom simply feels a squeezing lattice. Planar coppers close to the empty chains have positive z, while those that are close to full chains have z {approximately} 0. We present an analysis of the NQR result on the basis of the charge transfer model in which the mobile charges migrate from the chain to the plane sites. We deduced that a transfer of 0.021 holes to the O(2,3) sites would explain the result in YBa{sub 2}Cu{sub 3}O{sub 6.62}, whereas only 0.007 holes transfer in fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7}.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H. [Los Alamos National Lab., NM (United States); Takigawa, M. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center

1992-03-01

329

Relaxation Anomalies of 69/71Ga NQR in the Paramagnetic State of the Itinerant Antiferromagnet UGa3: Possible Evidence for a Crossover to Localized Spin Fluctuations and Development of Orbital Fluctuations of 5f-electrons at High Temperatures  

NASA Astrophysics Data System (ADS)

The microscopic magnetic properties of the itinerant 5f-electron antiferromagnet UGa3 (TN=67 K) have been investigated in the paramagnetic state by means of Ga NQR studies of the two naturally abundant isotopes 69Ga and 71Ga. A striking and unusual increase of the nuclear longitudinal relaxation rate 1/T1 has been observed above 230 K, which includes a strong component of nuclear quadrupolar relaxation. Both the magnetic and quadrupolar relaxation rates have been found to increase simultaneously above 230 K. Correspondingly, the NQR frequencies also show a clear deviation from lower-T T3/2-dependence above 230 K. These results are discussed in terms of a crossover from lower-T itinerant to higher-T more localized spin fluctuations and associated orbital fluctuations on the part of the U 5f electrons. A mechanism of transferred quadrupole interaction is presented, through which the fluctuations among the U 5f orbitals involve those among the counter-anion Ga 4p orbitals and thereby cause quadrupolar relaxation of the Ga nuclear spins.

Takagi, Shigeru; Muraoka, Hideaki; Matsuda, Tatsuma D.; Haga, Yoshinori; Kambe, Shinsaku; Walstedt, Russell E.; Yamamoto, Etsuji; ?nuki, Yoshichika

2004-02-01

330

Supramolecular synthon pattern in solid clioquinol and cloxiquine (APIs of antibacterial, antifungal, antiaging and antituberculosis drugs) studied by ³?Cl NQR, ¹H-¹?O and ¹H-¹?N NQDR and DFT/QTAIM.  

PubMed

The quinolinol derivatives clioquinol (5-chloro-7-iodo-8-quinolinol, Quinoform) and cloxiquine (5-chloro-8-quinolinol) were studied experimentally in the solid state via ³?Cl NQR, ¹H-¹?O and ¹H-¹?N NQDR spectroscopies, and theoretically by density functional theory (DFT). The supramolecular synthon pattern of O-H···N hydrogen bonds linking dimers and ?-? stacking interactions were described within the QTAIM (quantum theory of atoms in molecules) /DFT (density functional theory) formalism. Both proton donor and acceptor sites in O-H···N bonds were characterized using ¹H-¹?O and ¹H-¹?N NQDR spectroscopies and QTAIM. The possibility of the existence of O-H···H-O dihydrogen bonds was excluded. The weak intermolecular interactions in the crystals of clioquinol and cloxiquine were detected and examined. The results obtained in this work suggest that considerable differences in the NQR parameters for the planar and twisted supramolecular synthons permit differentiation between specific polymorphic forms, and indicate that the more planar supramolecular synthons are accompanied by a greater number of weaker hydrogen bonds linking them and stronger ?···? stacking interactions. PMID:21080020

Latosi?ska, Jolanta Natalia; Latosi?ska, Magdalena; Tomczak, Marzena Agnieszka; Seliger, Janez; Zagar, Veselko

2011-07-01

331

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

332

Simple and sensitive assay for nucleic acids by use of the resonance light-scattering technique with the anionic dye methyl blue in the presence of cetyltrimethylammonium bromide  

Microsoft Academic Search

.  This is the first report on the determination of nucleic acids based on the enhancement of resonance light scattering (RLS)\\u000a of the anionic dye methyl blue (MB) in the presence of cetyltrimethylammonium bromide (CTMAB). In tris(hydroxymethyl) aminomethane\\u000a buffer of pH 9.0, MB and nucleic acids react with CTMAB to form large particles of complex, which results in strong enhanced\\u000a RLS

Changqun Cai; Hang Gong; Xiaoming Chen

2007-01-01

333

Microstrip resonators for electron paramagnetic resonance experiments  

NASA Astrophysics Data System (ADS)

In this article we evaluate the performance of an electron paramagnetic resonance (EPR) setup using a microstrip resonator (MR). The design and characterization of the resonator are described and parameters of importance to EPR and spin manipulation are examined, including cavity quality factor, filling factor, and microwave magnetic field in the sample region. Simulated microwave electric and magnetic field distributions in the resonator are also presented and compared with qualitative measurements of the field distribution obtained by a perturbation technique. Based on EPR experiments carried out with a standard marker at room temperature and a MR resonating at 8.17 GHz, the minimum detectable number of spins was found to be 5×1010 spins/GHz1/2 despite the low MR unloaded quality factor Q0=60. The functionality of the EPR setup was further evaluated at low temperature, where the spin resonance of Cr dopants present in a GaAs wafer was detected at 2.3 K. The design and characterization of a more versatile MR targeting an improved EPR sensitivity and featuring an integrated biasing circuit for the study of samples that require an electrical contact are also discussed.

Torrezan, A. C.; Mayer Alegre, T. P.; Medeiros-Ribeiro, G.

2009-07-01

334

An Analysis of Perturbed Confocal Resonators.  

National Technical Information Service (NTIS)

An analytical technique is developed for computing mode functions and associated diffraction losses of perturbed multimode optical resonators. It is based upon a consistent field formulation of resonance in an open two-mirror system. To illustrate the met...

J. F. Asmus

1964-01-01

335

Electromagnetic coupling effects in pairs of split-ring resonators  

Microsoft Academic Search

We measure the absolute extinction cross-section spectrum of isolated pairs of split-ring resonators by a modulation technique. The spectral position of the magnetic resonance depends on the separation of the split-ring resonators.

N. Feth; S. Linden; M. Husnik; M. Wegener; M. Konig; K. Stannigel; J. Niegemann; K. Busch

2009-01-01

336

Quantitative determination of proteins at nanogram levels by the resonance light-scattering technique with composite nanoparticles of CdS/PAA  

NASA Astrophysics Data System (ADS)

This paper describes the development of composite nanoparticles. A novel composite nanoparticle has been prepared by an in situ polymerization method. The nano-CdS has been prepared, then the polymerization of acrylic acid (AA) was carried out by initiator potassium persulfate (KPS) under ultrasonic irradiation. The surface of the composite nanoparticles was covered with abundant carboxylic groups (-COOH). The nanoparticles are water-soluble, stable and biocompatible. Reaction of the composite nanoparticles with proteins results in an enhanced resonance light scattering (RLS) at 380 nm. Based on this, a new resonance light-scattering (RLS) method was developed for the determination of proteins including BSA, HSA and human ?-IgG. Under the optimum conditions, the enhanced RLS intensity is linearly proportional to the concentration of proteins. The liner range is 0.1-15 ?g mL -1 for HSA, 0.2-20 ?g mL -1 for BSA and 0.1-50.0 ?g mL -1 for human ?-IgG, respectively. The method has been applied to the determination of the total protein in human serum samples collected from the hospital and the results are in good agreement with those reported by the hospital. This method proved to be very sensitive, rapid, simple and tolerant of most interfering substances.

Chen, Hongqi; Xu, Fagong; Hong, Shi; Wang, Lun

2006-10-01

337

Transverse-Mode Spurious Suppression Technique for Surface Acoustic Wave Resonator with Zero Temperature Coefficient of Frequency on a SiO2/Al/LiNbO3 Structure  

NASA Astrophysics Data System (ADS)

In this paper, we describe a suppression technique of transverse-mode spurious responses for a surface acoustic wave (SAW) resonator with a near zero temperature coefficient of frequency (TCF) on a SiO2/Al/LiNbO3 structure. We investigated the thinning of SiO2 on the dummy electrode region and studied how the transverse-mode responses change with remaining SiO2 thickness h on the dummy electrode region. As the results, we clarified that the remaining SiO2 thickness h on the dummy electrode region has an optimum value and could suppress the transverse-mode spurious responses completely when H and h are set at 0.35 ? and 0.20 ?, respectively. It was demonstrated that the selective SiO2 removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO2/Al/LiNbO3 structure for a wide range of SiO2 thicknesses, provided that the SiO2 thickness at the dummy electrode region is adjusted properly.

Nakanishi, Hidekazu; Nakamura, Hiroyuki; Tsurunari, Tetsuya; Fujiwara, Joji; Hamaoka, Yosuke; Hashimoto, Ken-ya

2012-07-01

338

Damping of cavity-mode resonances in PCB power-bus structures using lossy slot resonators  

Microsoft Academic Search

In this paper, a novel technique suppressing cavity- mode resonances in PCB power-bus structures by using lossy slot resonators is presented. Guidelines for an optimized damping of the modal resonances are specified, which are based on rules derived recently for an appropriate selection and placement of damping capacitors. The effectiveness of the presented damping technique is shown by simulations as

Matthias Hampe; Stefan Dickmann

2006-01-01

339

A Study of the Nucleation Process in Liquid Bi and Bi-TE Alloys Using the Nuclear Magnetic Resonance (NMR) Technique.  

National Technical Information Service (NTIS)

The NMR technique has been utilized, for the first time, to study the liquid to solid transformation in metallic systems; i.e., in bismuth and bismuth-tellurium alloys. The freezing process of Bi or the Bi alloys was followed by monitoring the intensity o...

T. Takahashi W. A. Tiller

1968-01-01

340

Classification of magnetic resonance images  

Microsoft Academic Search

The aim of the paper is to compare classification error of the classifiers applied to magnetic resonance images for each descriptor used for feature extraction. We compared several Support Vector Machine (SVM) techniques, neural networks and k nearest neighbor classifier for classification of Magnetic Resonance Images (MRIs). Different descriptors are applied to provide feature extraction from the images. The dataset

Katarina Trojacanec; Gjorgji Madzarov; Dejan Gjorgjevikj; Suzana Loskovska

2010-01-01

341

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

342

A gas-jet transport and catcher technique for on-line production of radioactive ion beams using an electron cyclotron resonance ion-source  

SciTech Connect

Radioactive ion beams (RIB) have been produced on-line, using a gas-jet recoil transport coupled Electron Cyclotron Resonance (ECR) ion-source at the VECC-RIB facility. Radioactive atoms/molecules carried through the gas-jet were stopped in a catcher placed inside the ECR plasma chamber. A skimmer has been used to remove bulk of the carrier gas at the ECR entrance. The diffusion of atoms/molecules through the catcher has been verified off-line using stable isotopes and on-line through transmission of radioactive reaction products. Beams of {sup 14}O (71 s), {sup 42}K (12.4 h), {sup 43}K (22.2 h), and {sup 41}Ar (1.8 h) have been produced by bombarding nitrogen and argon gas targets with proton and alpha particle beams from the K130 cyclotron at VECC. Typical measured intensity of RIB at the separator focal plane is found to be a few times 10{sup 3} particles per second (pps). About 3.2 Multiplication-Sign 10{sup 3} pps of 1.4 MeV {sup 14}O RIB has been measured after acceleration through a radiofrequency quadrupole linac. The details of the gas-jet coupled ECR ion-source and RIB production experiments are presented along with the plans for the future.

Naik, V.; Chakrabarti, A.; Bhattacharjee, M.; Karmakar, P.; Bandyopadhyay, A.; Dechoudhury, S.; Mondal, M.; Pandey, H. K.; Lavanyakumar, D.; Mandi, T. K.; Dutta, D. P.; Kundu Roy, T.; Bhowmick, D.; Sanyal, D.; Srivastava, S. C. L.; Ray, A.; Ali, Md. S. [Variable Energy Cyclotron Centre (VECC), Sector-1, Block-AF, Bidhan Nagar, Kolkata 700064 (India); Bhattacharjee, S. [UGC-DAE CSR, Kolkata Centre, III/LB-8, Bidhan Nagar, Kolkata 700098 (India)

2013-03-15

343

Maximum toe flexor muscle strength and quantitative analysis of human plantar intrinsic and extrinsic muscles by a magnetic resonance imaging technique  

PubMed Central

Background The aims of this study were to investigate the relationships between the maximum isometric toe flexor muscle strength (TFS) and cross-sectional area (CSA) of the plantar intrinsic and extrinsic muscles and to identify the major determinant of maximum TFS among CSA of the plantar intrinsic and extrinsic muscles. Methods Twenty six young healthy participants (14 men, 12 women; age, 20.4?±?1.6 years) volunteered for the study. TFS was measured by a specific designed dynamometer, and CSA of plantar intrinsic and extrinsic muscles were measured using magnetic resonance imaging (MRI). To measure TFS, seated participants optimally gripped the bar with their toes and exerted maximum force on the dynamometer. For each participant, the highest force produced among three trials was used for further analysis. To measure CSA, serial T1-weighted images were acquired. Results TFS was significantly correlated with CSA of the plantar intrinsic and extrinsic muscles. Stepwise multiple linear regression analyses identified that the major determinant of TFS was CSA of medial parts of plantar intrinsic muscles (flexor hallucis brevis, flexor digitorum brevis, quadratus plantae, lumbricals and abductor hallucis). There was no significant difference between men and women in TFS/CSA. Conclusions CSA of the plantar intrinsic and extrinsic muscles is one of important factors for determining the maximum TFS in humans.

2014-01-01

344

A gas-jet transport and catcher technique for on-line production of radioactive ion beams using an electron cyclotron resonance ion-source  

NASA Astrophysics Data System (ADS)

Radioactive ion beams (RIB) have been produced on-line, using a gas-jet recoil transport coupled Electron Cyclotron Resonance (ECR) ion-source at the VECC-RIB facility. Radioactive atoms/molecules carried through the gas-jet were stopped in a catcher placed inside the ECR plasma chamber. A skimmer has been used to remove bulk of the carrier gas at the ECR entrance. The diffusion of atoms/molecules through the catcher has been verified off-line using stable isotopes and on-line through transmission of radioactive reaction products. Beams of 14O (71 s), 42K (12.4 h), 43K (22.2 h), and 41Ar (1.8 h) have been produced by bombarding nitrogen and argon gas targets with proton and alpha particle beams from the K130 cyclotron at VECC. Typical measured intensity of RIB at the separator focal plane is found to be a few times 103 particles per second (pps). About 3.2 × 103 pps of 1.4 MeV 14O RIB has been measured after acceleration through a radiofrequency quadrupole linac. The details of the gas-jet coupled ECR ion-source and RIB production experiments are presented along with the plans for the future.

Naik, V.; Chakrabarti, A.; Bhattacharjee, M.; Karmakar, P.; Bandyopadhyay, A.; Bhattacharjee, S.; Dechoudhury, S.; Mondal, M.; Pandey, H. K.; Lavanyakumar, D.; Mandi, T. K.; Dutta, D. P.; Kundu Roy, T.; Bhowmick, D.; Sanyal, D.; Srivastava, S. C. L.; Ray, A.; Ali, Md. S.

2013-03-01

345

Systematic evaluation of magnetic resonance imaging and spectroscopy techniques for imaging a transgenic model of Alzheimer's disease (A?PP/PS1).  

PubMed

Murine models of Alzheimer's disease (AD) provide means to detect and follow biomarker changes similar to those observed in humans. Non-invasive biomarkers, such as those provided by magnetic resonance imaging (MRI) and spectroscopy (MRS) methods are highly desirable, however, systematic studies of in vivo MRI/MRS methods to characterize the cerebral morphology and metabolic pattern of these mice remain scarce. We investigated sixteen consecutive slices from the brain of wild-type and A?PP/PS1 mice, obtaining a collection of T2 weighted, diffusion weighted and magnetization transfer weighted images as well as 1H PRESS spectra from the cortical and subcortical areas. Compared to controls, A?PP/PS1 mice show significant regional hyperintensities in T2 weighted images of the cerebral cortex, significant ventricular enlargement, and decreased hippocampal area and fractional magnetization transfer. MRS demonstrated an increase in the ratio of choline (Cho) to creatine (Cr) in the cortical and subcortical areas of the transgenic animals. A logistic regression classifier was implemented considering all parameters investigated, and revealed the most characteristic changes and allowed for the correct classification of control and A?PP/PS1 mice. In summary, the present results provide a useful frame to evaluate optimal MRI/MRS biomarkers for the characterization of AD models, potentially applicable in drug discovery processes, because of their non-invasive and repeatable nature in longitudinal studies. PMID:22406445

Esteras, Noemí; Alquézar, Carolina; Bartolomé, Fernando; Antequera, Desiree; Barrios, Laura; Carro, Eva; Cerdán, Sebastián; Martín-Requero, Angeles

2012-01-01

346

Visualization of the Foramen Intervertebral Nerve Root of Cervical Spine with 3.0 Tesla Magnetic Resonance Imaging: A Comparison of Three-dimensional Acquisition Techniques.  

PubMed

Identification of the compression factor in cervical disc herniation and cervical spondylotic radioculopathy is often problematic when using two-dimensional magnetic resonance imaging (MRI). This prompted us to compare and examined three-dimensional sequences, coherent oscillatory state acquisition for the manipulation of image contrast (COSMIC), fast imaging employing steady state acquisition (FIESTA) and T2 star weighted MR angiography (SWAN) with 3.0-Tesla (T) MRI to visualize the foramen intervertebral nerve root for the cervical spine. Fat-suppressed COSMIC (FS-COSMIC) sequence gave the highest signal intensity ratio (1.85±0.06) of the nerve root and vertebral arch. A significant difference in signal intensity ratio of the nerve root was found between FS-COSMIC and FIESTA sequences. No significant difference was found between the FS-COSMIC and FIESTA sequences in the cerebrospinal fluid and the spinal cord. The FS-COSMIC sequence proved to be the most suitable sequence for intra and extra dura matter. PMID:25055947

Shishido, Hiroki; Takashima, Hiroyuki; Takebayashi, Tsuneo; Akatsuka, Yoshihiro; Imamura, Rui; Nagahama, Hiroshi; Shirase, Ryuzi

2014-07-01

347

Possible Multiple Gap Superconductivity with Line Nodes in Heavily Hole-Doped Superconductor KFe2As2 Studied by 75As Nuclear Quadrupole Resonance and Specific Heat  

NASA Astrophysics Data System (ADS)

We report the 75As nuclear quadrupole resonance (NQR) and specific heat measurements of the heavily hole-doped superconductor KFe2As2 (superconducting transition temperature Tc? 3.5 K). The spin-lattice relaxation rate 1/T1 in the superconducting state exhibits a gradual temperature dependence with no coherence peak below Tc. The quasiparticle specific heat CQP/T shows a small jump, which is about 30% of the electronic specific heat coefficient just below Tc. The CQP/T suggests the existence of low-energy quasiparticle excitation at the lowest measurement temperature T=0.4 K? Tc/10. The T dependences of 1/T1 and CQP/T can be explained by a multiple nodal superconducting gap scenario rather than by a multiple fully gapped s±-wave scenario determined using simple gap analysis.

Fukazawa, Hideto; Yamada, Yuji; Kondo, Kenji; Saito, Taku; Kohori, Yoh; Kuga, Kentarou; Matsumoto, Yosuke; Nakatsuji, Satoru; Kito, Hijiri; Shirage, Parasharam M.; Kihou, Kunihiro; Takeshita, Nao; Lee, Chul-Ho; Iyo, Akira; Eisaki, Hiroshi

2009-08-01

348

Morphological resonances for multicomponent immunoassays  

NASA Astrophysics Data System (ADS)

An immunoassay technique capable of detecting and identifying a number of species of microorganisms in a single analysis is described. The method uses optical-resonance size discrimination of microspheres to identify antibodies to which stained microorganisms are bound.

Whitten, W. B.; Shapiro, M. J.; Ramsey, J. M.; Bronk, B. V.

1995-06-01

349

Chemically Polished High Frequency Resonators.  

National Technical Information Service (NTIS)

The upper frequency limit of quartz resonators is determined by the physical properties of quartz and restrictions imposed by processing techniques. More often than not, the processing limitations are reached long before the physical limitations. Mechanic...

W. P. Hanson

1983-01-01

350

Efficient computation of resonant frequencies and quality factors of cavities via a combination of the finite-difference time-domain technique and the Pade approximation  

Microsoft Academic Search

An efficient method for analyzing cavity structures by using the fast Fourier transform (FFT)\\/Pade technique, in combination with the finite-difference time-domain (FDTD) method, is presented. Without sacrificing the accuracy of the results, this new method significantly reduces the computational time compared to that needed where the conventional FFT algorithm is used. The usefulness of this approach is demonstrated by modeling

Supriyo Dey; Raj Mittra

1998-01-01

351

The synthesis and application of 1-( o-nitrophenyl)-3-(2-thiazolyl)triazene for the determination of palladium(II) by the resonance enhanced Rayleigh light-scattering technique  

NASA Astrophysics Data System (ADS)

The resonance Rayleigh light-scattering (RRLS) signal of a new triazene reagent; 1-( o-nitrophenyl)-3-(2-thiazolyl)triazene ( o-NPTT), was firstly synthesized and characterized in this paper at 500-600 nm wavelength range and can be enhanced remarkably by Pd 2+. According to this phenomenon, a new method was developed for the determination of Pd 2+ by the RRLS technique in the presence of Tween-80. The calibration graph showed good linearity over a concentration range of 5.0-700 ?g l -1 with a detection limit of 1.0 ?g l -1. There are almost no foreign ions interfered in the determination at a more than fivefold concentration of Pd 2+. The method is relatively sensitive, of good selectivity and has been successfully used for the determination of trace palladium in the slag of fertilizer factories and catalyst samples.

Cao, Qiu-E.; Zhao, Yunkun; Yao, Xiaojun; Hu, Zhide; Xu, Qiheng

2000-06-01

352

Acoustic detection of microbubble resonance  

NASA Astrophysics Data System (ADS)

Large numbers of acoustic signals from single lipid-shelled Definity® microbubbles have been measured using a calibrated microacoustic system and a two population response observed. Theoretical results based on the Mooney-Rivlin strain softening shell model have been used to identify these populations as primary resonant and off-primary resonant scatter. An experimentally measured size distribution was used to provide the initial resting radius for the simulations, and the responses agree well with the experimental data. In this way, the primary resonant or off-primary resonant behavior of a microbubble can be studied, with potential benefits to both signal processing techniques and microbubble manufacture.

Thomas, D. H.; Looney, P.; Steel, R.; Pelekasis, N.; McDicken, W. N.; Anderson, T.; Sboros, V.

2009-06-01

353

Mechanical characterization of articular cartilage by combining magnetic resonance imaging and finite-element analysis—a potential functional imaging technique  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) provides a method for non-invasive characterization of cartilage composition and structure. We aimed to see whether T1 and T2 relaxation times are related to proteoglycan (PG) and collagen-specific mechanical properties of articular cartilage. Specifically, we analyzed whether variations in the depthwise collagen orientation, as assessed by the laminae obtained from T2 profiles, affect the mechanical characteristics of cartilage. After MRI and unconfined compression tests of human and bovine patellar cartilage samples, fibril-reinforced poroviscoelastic finite-element models (FEM), with depthwise collagen orientations implemented from quantitative T2 maps (3 laminae for human, 3-7 laminae for bovine), were constructed to analyze the non-fibrillar matrix modulus (PG specific), fibril modulus (collagen specific) and permeability of the samples. In bovine cartilage, the non-fibrillar matrix modulus (R = -0.64, p < 0.05) as well as the initial permeability (R = 0.70, p < 0.05) correlated with T1. In bovine cartilage, T2 correlated positively with the initial fibril modulus (R = 0.62, p = 0.05). In human cartilage, the initial fibril modulus correlated negatively (R = -0.61, p < 0.05) with T2. Based on the simulations, cartilage with a complex collagen architecture (5 or 7 laminae), leading to high bulk T2 due to magic angle effects, provided higher compressive stiffness than tissue with a simple collagen architecture (3 laminae). Our results suggest that T1 reflects PG-specific mechanical properties of cartilage. High T2 is characteristic to soft cartilage with a classical collagen architecture. Contradictorily, high bulk T2 can also be found in stiff cartilage with a multilaminar collagen fibril network. By emerging MRI and FEM, the present study establishes a step toward functional imaging of articular cartilage.

Julkunen, P.; Korhonen, R. K.; Nissi, M. J.; Jurvelin, J. S.

2008-05-01

354

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

PubMed

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. PMID:24593510

Biri, S; Kitagawa, A; Muramatsu, M; Drentje, A G; Rácz, R; Yano, K; Kato, Y; Sasaki, N; Takasugi, W

2014-02-01

355

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

NASA Astrophysics Data System (ADS)

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.; Kitagawa, A.; Muramatsu, M.; Drentje, A. G.; Rácz, R.; Yano, K.; Kato, Y.; Sasaki, N.; Takasugi, W.

2014-02-01

356

Ferromagnetic resonance properties of LPE YIG films  

Microsoft Academic Search

This is the first report of the ferromagnetic resonance properties of thin single-crystal YIG films grown by liquid phase epitaxy techniques (LPE). The resonance linewidths of photoetched disks are close to that of bulk YIG for both parallel and perpendicular resonance without any annealing of the films. A new type of surface spin wave, localized at the air-film interface, is

RODNEY D. HENRY; PAUL J. BESSER; D. M. HEINZ; J. E. MEE

1973-01-01

357

Magnetic resonance image segmentation using semi-automated software for quantification of knee articular cartilage--initial evaluation of a technique for paired scans  

PubMed Central

Purpose Software-based image analysis is important for studies of cartilage changes in knee osteoarthritis (OA). This study describes an evaluation of a semi-automated cartilage segmentation software tool capable of quantifying paired images for potential use in longitudinal studies of knee OA. We describe the methodology behind the analysis and demonstrate its use by determination of test–retest analysis precision of duplicate knee magnetic resonance imaging (MRI) data sets. Methods Test–retest knee MR images of 12 subjects with a range of knee health were evaluated from the Osteoarthritis Initiative (OAI) pilot MR study. Each subject was removed from the magnet between the two scans. The 3D DESS (sagittal, 0.456 mm×0.365 mm, 0.7 mm slice thickness, TR 16.5 ms, TE 4.7 ms) images were obtained on a 3-T Siemens Trio MR system with a USA Instruments quadrature transmit–receive extremity coil. Segmentation of one 3D-image series was first performed and then the corresponding retest series was segmented by viewing both image series concurrently in two adjacent windows. After manual registration of the series, the first segmentation cartilage outline served as an initial estimate for the second segmentation. We evaluated morphometric measures of the bone and cartilage surface area (tAB and AC), cartilage volume (VC), and mean thickness (ThC.me) for medial/lateral tibia (MT/LT), total femur (F) and patella (P). Test–retest reproducibility was assessed using the root-mean square coefficient of variation (RMS CV%). Results For the paired analyses, RMS CV % ranged from 0.9% to 1.2% for VC, from 0.3% to 0.7% for AC, from 0.6% to 2.7% for tAB and 0.8% to 1.5% for ThC.me. Conclusion Paired image analysis improved the measurement precision of cartilage segmentation. Our results are in agreement with other publications supporting the use of paired analysis for longitudinal studies of knee OA.

Brem, M. H.; Lang, P. K.; Neumann, G.; Schlechtweg, P. M.; Schneider, E.; Jackson, R.; Yu, J.; Eaton, C. B.; Hennig, F. F.; Yoshioka, H.; Pappas, G.; Duryea, J.

2010-01-01

358

Determination of protein in milk powder using 2-sulfophenylazo-rhodanine as a probe by the enhanced resonance Rayleigh light-scattering technique.  

PubMed

In this paper, the interaction between 2-sulfophenylazo-rhodanine and protein was investigated by Rayleigh light-scattering technique. Based on this, a novel method for the determination of protein was developed. The effects of different conditions, such as acidity and media, were investigated thoroughly, and the optimum conditions were confirmed. Bis(2-ethylhexyl)sulfosuccinate (AOT) microemulsion, which is introduced into the protein determination, markedly increased the sensitivity of the system by changing the microenvironment. In pH 2.80 Britton-Robinson buffer solution in the presence of AOT microemulsion, the detection limits of bovine serum albumin, human serum albumin, ovalbumin, and gamma-globulin are 5.4, 4.5, 9.8, and 10.1 ng/mL, respectively. The method developed in this paper has been applied to the determination of protein in milk powder with satisfactory results. PMID:17042187

Wei, Qin; Li, Yan; Dong, Wenying; Du, Bin

2006-01-01

359

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

360

Frequency Trimming for MEMS Resonator Oscillators  

Microsoft Academic Search

This paper presents various frequency trimming methodologies with the focus on silicon based micromechanical resonators. The techniques include mechanical trimming and pure electronic trimming. The experimental results showed the frequency accuracy have reached 2.6 ppm for mechanical trimming and lppm for electronic trimming. Furthermore, the technique of digital electronic trimming resolved the temperature compensation issues for MEMS resonators at the

Wan-Thai Hsu; A. R. Brown

2007-01-01

361

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

362

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

363

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

364

Laser Resonator  

NASA Technical Reports Server (NTRS)

An optical resonator cavity configuration has a unitary mirror with oppositely directed convex and concave reflective surfaces disposed into one fold and concertedly reversing both ends of a beam propagating from a laser rod disposed between two total internal reflection prisms. The optical components are rigidly positioned with perpendicularly crossed virtual rooflines by a compact optical bed. The rooflines of the internal reflection prisms, are arranged perpendicularly to the axis of the laser beam and to the optical axes of the optical resonator components.

Harper, L. L. (inventor)

1983-01-01

365

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

Cell-based therapies using natural or genetically modified regulatory T cells (T(regs)) 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 T(regs) 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 T(regs) 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 T(reg) 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

2013-05-01

366

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.

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

2013-01-01

367

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

368

Biological magnetic resonance: vol. 5  

SciTech Connect

This book discusses magnetic resonance techniques (NMR and ESR) as applied to biochemical research. Topics considered include the applications of carbon-13 NMR spectroscopy in investigations of metabolic pathways in vivo, the use of nitrogen-15 NMR in studies of systems of biological interest, phosphorus-31 NMR investigations of enzyme systems, the principles and state-of-the-art advances in the use of oxygen isotopes in phosphorus-31 and oxygen-17 NMR studies of biophosphates, and electron spin resonance and nuclear magnetic resonance studies of lipid-protein interactions in membranes.

Berliner, L.J.; Reuben, J.

1983-01-01

369

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

370

Spurious Resonances and Modelling of Composite Resonators.  

National Technical Information Service (NTIS)

Several three-dimensional models have been developed for explaining the characteristics of composite resonators. The agreement between the resonance spectra predicted by the models and the experimental data is excellent, including spurious resonance frequ...

K. B. Yoo H. Ueberall D. Ashrafi S. Ashrafi

1983-01-01

371

Magnetic Resonance Fingerprinting  

PubMed Central

Summary Magnetic Resonance (MR) is an exceptionally powerful and versatile measurement technique. The basic structure of an MR experiment has remained nearly constant for almost 50 years. Here we introduce a novel paradigm, Magnetic Resonance Fingerprinting (MRF) that permits the non-invasive quantification of multiple important properties of a material or tissue simultaneously through a new approach to data acquisition, post-processing and visualization. MRF provides a new mechanism to quantitatively detect and analyze complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to specifically identify the presence of a target material or tissue, which will increase the sensitivity, specificity, and speed of an MR study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern recognition algorithm, MRF inherently suppresses measurement errors and thus can improve accuracy compared to previous approaches.

Ma, Dan; Gulani, Vikas; Seiberlich, Nicole; Liu, Kecheng; Sunshine, Jeffrey L.; Duerk, Jeffrey L.; Griswold, Mark A.

2013-01-01

372

Study of lignification by noninvasive techniques in growing maize internodes. An investigation by Fourier transform infrared cross-polarization-magic angle spinning 13C-nuclear magnetic resonance spectroscopy and immunocytochemical transmission electron microscopy.  

PubMed Central

Noninvasive techniques were used for the study in situ of lignification in the maturing cell walls of the maize (Zea mays L.) stem. Within the longitudinal axis of a developing internode all of the stages of lignification can be found. The synthesis of the three types of lignins, p-hydroxyphenylpropane (H), guaiacyl (G), and syringyl (S), was investigated in situ by cross-polarization-magic angle spinning 13C-solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and immunocytochemical electron microscopy. The first lignin appearing in the parenchyma is of the G-type preceeding the incorporation of S nuclei in the later stages. However, in vascular bundles, typical absorption bands of S nuclei are visible in the Fourier transform infrared spectra at the earliest stage of lignification. Immunocytochemical determination of the three types of lignin in transmission electron microscopy was possible thanks to the use of antisera prepared against synthetic H, G, and the mixed GS dehydrogenative polymers (K. Ruel, O. Faix, J.P. Joseleau [1994] J Trace Microprobe Tech 12: 247-265). The specificity of the immunological probes demonstrated that there are differences in the relative temporal synthesis of the H, G, and GS lignins in the different tissues undergoing lignification. Considering the intermonomeric linkages predominating in the antigens used for the preparation of the immunological probes, the relative intensities of the labeling obtained provided, for the first time to our knowledge, information about the macromolecular nature of lignins (condensed versus noncondensed) in relation to their ultrastructural localization and development stage.

Joseleau, J P; Ruel, K

1997-01-01

373

Magnetic resonance imaging of acquired cardiac disease.  

PubMed Central

Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease. Images

Carrol, C L; Higgins, C B; Caputo, G R

1996-01-01

374

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.

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

2011-01-01

375

Sealed-cavity resonant microbeam accelerometer  

Microsoft Academic Search

Resonant microbeam strain-sensing elements have been combined with a highly symmetric multiwafer silicon microstructure to form the first micromachined accelerometer with a polysilicon resonant microbeam pickoff. The MARIMBA (micromachined resonant integrated microbeam accelerometer) uniquely combines bulk-micromachining with advanced surface-micromachining techniques and a multiple-wafer structure to produce an all-silicon acceleration sensor capsule with a direct acceleration-to-digital frequency output. The microbeams are

D. W. Burns; R. D. Horning; W. R. Herb; J. D. Zook; H. Guckel

1996-01-01

376

Acoustic resonance spectroscopy in nuclear safeguards  

SciTech Connect

Objects resonate at specific frequencies when mechanically excited. The specific resonance frequencies are a function of shape, size, material of construction, and contents of the object. This paper discusses the use of acoustic resonance spectroscopy (ARS) to monitor containers and detect tampering. Evaluation of this technique is based on simulated storage simulations. Although these simulations show promise for this application of ARS, final evaluation will require actual field testing.

Olinger, C.T.; Lyon, M.J.; Stanbro, W.D.; Mullen, M.F.; Sinha, D.N.

1993-08-01

377

Subharmonic growth by parametric resonance  

NASA Astrophysics Data System (ADS)

An experimental investigation is conducted in order to quantify the nonlinear and parametric resonance mechanisms that are associated with the subharmonic growth in the transition to turbulence in plane mixing layers. Higher-order digital statistical analysis techniques are used to investigate the nonlinear and parametric mechanisms responsible for the energy transfer to the subharmonic. The results show that the dominant interaction is a parametric resonance mechanism between the fundamental and the subharmonic modes which leads to a pronounced growth of the subharmonic. Measurements also indicate that the fundamental, besides interacting with the subharmonic, is also engaged in redistributing its energy to the other Fourier components of the flow via nonlinear three-wave interactions. Local wavenumber measurements verify that frequency-wavenumber resonance matching conditions exist between the fundamental and subharmonic in the region where the subharmonic gains its energy by parametric resonance. The results are in general agreement with theoretical models by Kelly (1967), and Monkewitz (1988) on subharmonic growth.

Hajj, M. R.; Miksad, R. W.; Powers, E. J.

1992-03-01

378

All-resonant control of superconducting resonators.  

PubMed

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 significantly better than existing proposals using the same technology. PMID:23215585

Strauch, Frederick W

2012-11-21

379

Split ring resonator sensors for infrared detection of single molecular monolayers  

Microsoft Academic Search

We report a surface enhanced molecular detection technique with zeptomole sensitivity that relies on resonant coupling of plasmonic modes of split ring resonators and infrared vibrational modes of a self-assembled monolayer of octadecanthiol molecules. Large near-field enhancements at the gap of split ring resonators allow for this resonant coupling when the molecular absorption peaks overlap spectrally with the plasmonic resonance.

Ertugrul Cubukcu; Shuang Zhang; Yong-Shik Park; Guy Bartal; Xiang Zhang

2009-01-01

380

Nonlinear resonant ultrasound spectroscopy (NRUS) applied to damage assessment in bone  

Microsoft Academic Search

Nonlinear resonant ultrasound spectroscopy (NRUS) is a resonance-based technique exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency(ies) of an object is studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity is manifest by a shift in the resonance frequency. This study shows the feasibility of this technique for

Marie Muller; Alexander Sutin; Robert Guyer; Maryline Talmant; Pascal Laugier; Paul A. Johnson

2005-01-01

381

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

382

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.

383

Microwave and millimeter-wave high-Q micromachined resonators  

Microsoft Academic Search

Alternative techniques for integrating high quality factor res- onators using micromachining techniques have been investigated. Two methods are presented which include suspending microstrip lines thin di- electric membranes resulting in an effective dielectric constant of near unity, and integrating three-dimensional micromachined waveguide cavity resonators with planar feedlines. These resonators show large improve- ments in quality factor over conventional techniques, and

Andrew R. Brown; Pierre Blondy; Gabriel M. Rebeiz

1999-01-01

384

Regulation of flexible structures via internal resonance  

Microsoft Academic Search

A technique based on internal resonance is proposed to control the vibrations of a cantilevered, flexible beam. The controller is based on a dc motor with a rigid beam\\/tip mass configuration attached to the motor shaft. A 2:1 internal resonance condition is established for this system by specifying the topology in such a fashion that the first two natural frequencies

K. L. Tuer; A. P. Duquette; M. F. Golnaraghi

1992-01-01

385

Raman heterodyne detection of electron paramagnetic resonance.  

PubMed

We report the detection of an electron paramagnetic resonance signal using Raman heterodyne spectroscopy, a rf -optical double-resonance technique. The signals are associated with the nitrogen-vacancy center in diamond, which has a spin-triplet ground state. A three-line spectrum associated with the nitrogen hyperfine structure is observed for various magnetic field strengths and crystal orientations. PMID:19770973

Holliday, K; He, X F; Fisk, P T; Manson, N B

1990-09-01

386

Resonance absolute quantum reflection at selected energies.  

PubMed

We present one-dimensional local potentials with an absolute reflection at a given energy value which can be above barriers. The corresponding energy dependence of a reflection coefficient exhibits resonance behavior. The inversion technique provides the potentials with specified widths of reflection resonances, their number and positions. The multichannel systems (exact models) with a complete reflection are also given. PMID:11690195

Chabanov, V M; Zakhariev, B N

2001-10-15

387

Resonance Characteristics of Micro Cantilever in Liquid  

Microsoft Academic Search

The resonance characteristics of a micro cantilever are experimentally and theoretically studied. The micro cantilever is vibrated by thermal excitation using laser exposure and the frequency responses of the micro cantilever in air, acetone and water are experimentally evaluated based on an optical measurement technique. It is demonstrated that the resonance frequencies in water decrease to about one-tenth of the

Yoshihiko Hirai; Ryosuke Mori; Hisao Kikuta; Nobuhiro Kato; Koji Inoue; Yoshio Tanaka

1998-01-01

388

Techniques for imaging neuroscience  

Microsoft Academic Search

In the last 20 years, a number of non-invasive spatial mapping techniques have been demonstrated to provide powerful insights into the operation of the brain during task performance. These are, in order of their emergence as robust technologies: positron emission tomography, source localization with EEG and MEG, and functional magnetic resonance imaging. The imaging neuroscience study areas represented in this

Robert Turner; Terry Jones

2003-01-01

389

Double resonant quadrature birdcage.  

PubMed

The combined acquisition of proton images and localized spectra is considered essential to the application of NMR techniques to human and animal research. The ideal imaging/spectroscopy coil for our purposes would be one that provides the highest possible signal-to-noise, high homogeneity, and operation on two or more frequencies without retuning requirements or cable changes. To address these needs we have developed a quadrature double-tuned birdcage. We have incorporated our earlier work on the transformer coupled double-tuned surface coil into the birdcage structure by placing two birdcages in a coaxial configuration. This structure resonates at 34.6 MHz (phosphorus resonance at 2.0 T) and 85.5 MHz (proton resonance at 2.0 T). The quadrature performance of this coil for phosphorus was excellent, with a signal-to-noise that was 133% of our linear reference. The proton performance was less efficient, with a signal to noise that was 67% of our linear reference, but still quite sufficient for imaging. A phosphorus spectra and proton image of a rat abdomen are shown. PMID:8396709

Fitzsimmons, J R; Beck, B L; Brooker, H R

1993-07-01

390

Study of Resonant Loss for Helix TWTs.  

National Technical Information Service (NTIS)

One of the most effective techniques for eliminating backward wave oscillations (BWOs) in helix type traveling wave tubes (TWTs) is resonant loss. The fundamental purpose of this program was to perform experimental work which would give a more complete un...

C. E. Hobrecht

1979-01-01

391

International Society for Magnetic Resonance in Medicine  

MedlinePLUS

... Links Workshop & Educational Course Series ISMRM Workshop on Functional MRI: Emerging Techniques & New Interpretations 22-25 June ... Are The International Society for Magnetic Resonance in Medicine is a nonprofit professional association dedicated to promoting ...

392

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

393

Microwave and millimeter-wave resonant tunneling diodes  

NASA Technical Reports Server (NTRS)

Several demonstrated resonant tunneling devices including oscillators, mixers, multiplexers, and a variable negative resistance are discussed. Techniques of the millimeter/submillimeter regime are also discussed.

Sollner, T. C. L. Gerhard; Brown, Elliott R.; Goodhue, W. D.

1987-01-01

394

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

395

Orbital electronegativities and the determination of s and d hybridization in various halides from nuclear quadrupole resonance frequencies  

Microsoft Academic Search

The use of Orbital Electronegativities in the interpretation of NQR results for various halides is discussed, and an attempt to determine the amount of d hybridization in s and p bonding is made. The ionic characters are assessed.

M. A. Whitehead; H. H. Jaffé

1963-01-01

396

Resonator modeling by field tracing: a flexible approach for fully vectorial laser resonator modeling  

NASA Astrophysics Data System (ADS)

Nowadays lasers cover a broad spectrum of applications, like laser material processing, metrology and communications. Therefore a broad variety of different lasers, containing various active media and resonator setups, are used to provide high design flexibility. The optimization of such multi-parameter laser setups requires powerful simulation techniques. In literature mainly three practical resonator modeling techniques can be found: Rigorous techniques, e.g. the finite element method (FEM), approximated solutions based on paraxial Gaussian beam tracing by ABCD matrices and the Fox and Li algorithm are used to analyze transversal resonator modes. All of these existing approaches have in common, that only a single simulation technique is used for the whole resonator. In contrast we reformulate the scalar Fox and Li integral equation for resonator eigenmode calculation into a fully vectorial field tracing operator equation. This allows the flexible combination of different modeling techniques in different subdomains of the resonator. The work introduces the basic concepts of field tracing in resonators to calculate vectorial, transversal eigenmodes of stable and unstable resonators.

Asoubar, Daniel; Wyrowski, Frank; Schweitzer, Hagen; Hellmann, Christian; Kuhn, Michael

2014-05-01

397

Magnetic resonance imaging of acetabular labral tears.  

PubMed

The acetabular labrum plays an important role in hip biomechanical function and stability. Labral tears can result in appreciable clinical symptoms and joint dysfunction and may predispose the hip to chondral damage and osteoarthritis. Magnetic resonance imaging is an effective tool for detecting and characterizing labral tears. Direct magnetic resonance arthrography is the most commonly used and validated technique for evaluating the labrum. However, indirect magnetic resonance arthrography and non-arthrographic magnetic resonance imaging are two less invasive and less resource-intensive techniques that should also be considered. Orthopaedic surgeons and radiologists should strive to develop and implement minimally and noninvasive diagnostic magnetic resonance imaging protocols for the investigation of labral pathology. PMID:21543685

Rakhra, Kawan S

2011-05-01

398

Compensation of thermal nonlinearity effect in optical resonators.  

PubMed

Thermal nonlinearity is known to cause bistability in Whispering Gallery Mode (WGM) resonators and to destabilize the red slope of the Lorentzian resonant curve. We demonstrate an optical technique that allows compensation of the thermal effect and forces the resonances to appear linear with both red and blue slopes stable. PMID:21503047

Grudinin, Ivan; Lee, Hansuek; Chen, Tong; Vahala, Kerry

2011-04-11

399

Asymptotic analysis of unstable laser resonators with circular mirrors  

Microsoft Academic Search

The asymptotic methods developed by Horwitz for the analysis of strip unstable laser resonators are extended to resonators with circular mirrors. The theory is developed and shown to give results in good agreement with results obtained using more conventional techniques, with substantial savings in computer time. The interleaving of the resonator eigenvalue graphs is seen to persist, even at very

R. R. Butts; P. V. Avizonis; Frank S. Tomkins

1978-01-01

400

Photonic coherence phenomena in coupled optical resonators  

NASA Astrophysics Data System (ADS)

A structure consisting of N coupled optical resonators exhibits resonances that split into N higher-Q modes due to coherent coupling between resonators. This has a direct analogy with other types of oscillators. In particular, for two (or any even number of) coupled optical resonators, this mode splitting leads to a cancellation of absorption on resonance as a result of classical destructive interference of the symmetric and antisymmetric modes of the system. An analogy between this effect and electromagnetically-induced transparency in an atomic system is explored. Furthermore, a variety of photonic coherence phenomena in passive and active coupled optical resonators is investigated. Specifically, the effective dispersive and absorptive steady-state response of coupled resonators is derived and used to determine the conditions for coupled-resonator-induced transparency and absorption, lasing without gain, and cooperative cavity emission. These effects rely on coherent photon trapping, in direct analogy with coherent population trapping phenomena in atomic systems. It is also demonstrated that the coupled-mode equations are formally identical to the two-level atom Schrodinger equation in the rotating-wave approximation. The impulse response of coupled resonators is also derived. It is found that the coupled-resonator photon dynamics display damped Rabi oscillations, which facilitates adiabatic coherent photon transfer techniques such as stimulated Raman adiabatic passage. These effects are predicted directly from coupled-mode theory, and thus are not unique to atoms, but rather are fundamental to systems of coherently coupled resonators. It is also theoretically predicted that in coupled optical resonators slow and fast light can propagate without attenuation. In systems of coupled resonators, slow light can propagate without attenuation by a cancellation of absorption as a result of mode splitting and destructive interference, whereas transparent fast light propagation can be achieved with the assistance of gain and splitting of the intracavity resonances, which consequently switches the dispersion from normal to anomalous.

Chang, Hongrok

401

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

402

Coexistence of Antiferromagnetism with Superconductivity in CePt2In7: Microscopic Phase Diagram Determined by In115 NMR and NQR  

NASA Astrophysics Data System (ADS)

Single crystals of the heavy-fermion antiferromagnet CePt2In7 with a Néel temperature (TN) of 5.2 K at ambient pressure have been investigated by zero-field In115-nuclear magnetic and quadrupole resonance measurements as a function of applied pressure. Within the antiferromagnetic state, the character of Ce's 4f electron appears to change from localized to itinerantlike at P*˜2.4 GPa, approximately the pressure where superconductivity first emerges. With increased pressure, the superconducting transition Tc reaches a maximum just at or slightly before antiferromagnetic order disappears, and not at the pressure Pc˜3.4 GPa, where the steeply decreasing Néel boundary extrapolates to zero temperature. For P >Pc, the spin relaxation rate drops sharply by more than 2 orders of magnitude at Tc, suggestive of a first-order transition.

Sakai, H.; Tokunaga, Y.; Kambe, S.; Ronning, F.; Bauer, E. D.; Thompson, J. D.

2014-05-01

403

Resonant frequency of gold/polycarbonate hybrid nano resonators fabricated on plastics via nano-transfer printing  

NASA Astrophysics Data System (ADS)

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.

Dechaumphai, Edward; Zhang, Zhao; Siwak, Nathan P.; Ghodssi, Reza; Li, Teng

2011-12-01

404

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.

2011-01-01

405

Magnetic resonance in the differential diagnosis of dementia  

Microsoft Academic Search

Summary.   Magnetic resonance became an important tool for the differential diagnosis of dementia. Magnetic resonance imaging is the\\u000a preferred method to exclude treatable entities accompagnied by dementing symptoms. New techniques including diffusion and\\u000a perfusion magnetic resonance imaging are helpful for the differentiation between vascular dementia and degenerative disorders.\\u000a Magnetic Resonance spectroscopy evolves as a tool for the diagnosis of different

S. R. Felber

2002-01-01

406

Paramagnetic resonance in GaN-based single quantum wells  

Microsoft Academic Search

We report electrically-detected magnetic resonance (EDMR) and electroluminescence-detected magnetic resonance (ELDMR) results on InGaN\\/AlGaN single-quantum-well light emitting diodes. The dominant feature detected by either technique is a broad resonance (?B≈13 mT) at g≈2.01 due to a deep defect. Depending on bias, this defect results in either an increase or a decrease in electroluminescence at resonance while the EDMR gives a

W. E. Carlos; Shuji Nakamura

1997-01-01

407

Magnetic resonance imaging and magnetic resonance spectroscopic imaging of prostate cancer  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) are evolving techniques that offer noninvasive evaluation of anatomic and metabolic features of prostate cancer. The ability of MRI to determine the location and extent of the tumor and to identify metastatic spread is useful in the pretreatment setting, enabling treatment decision-making that is evidence-based. MRSI of the prostate gland

Renata Huzjan; Evis Sala; Hedvig Hricak

2005-01-01

408

Mechanical resonance of individual nanostructures  

NASA Astrophysics Data System (ADS)

In this thesis the non-contact mode atomic force microscopy (NCM AFM) was used to measure very high frequency (VHF) mechanical resonance (MR) of individual nanostructures. The effect of coupling between the probe and sample on the measured resonant frequency, for both contact mode AFM (CM AFM) and NCM AFM, was analytically evaluated and showed the NCM AFM as superior due to the gentle interaction. The NCM AFM was experimentally validated by first demonstrating a high frequency resonant measurement of a piezo. An electrically driven piezo (with a 1 cm2 Si piece glued on top) was found to have a clear MR of ˜11.8 MHz using the NCM AFM resonant technique. We also showed that the NCM AFM technique was able to detect a 41 MHz vibration. Comparing the optically measured MR of a series of cantilevers with NCM AFM measured MR showed virtually no shift of the resonant frequency of the sample cantilevers. In addition, the sample cantilever was driven at its first harmonic frequency while the vertical displacement along its length was measured and its length dependence matched the expected 1st order mode shape. After having had experimentally validated the NCM AFM technique we went on to measure the VHF (>30 MHz) MR of individual rods and springs. These nanostructures were grown using a newly built oblique angle ebeam deposition (OAED) system. The MR of individual rods showed resonant peaks ranging from ˜30 MHz to ˜160 MHz. The MR of the rods were further confirmed by observing scanning electron microscopy (SEM) image blurring (rod vibration). Nanometer scale spring samples were grown in the OAED system. The MR of the spring samples was measured and found to lie between ˜30 and ˜300 MHz. The measured MR of both rod and spring samples were compared with theoretical values. The comparison took into account variations in sample geometry and had good agreement. This thesis work demonstrates for the first time the validity of the using the NCM AFM technique to measure the mechanical resonance frequency of individual nanostructures.

Parker, Thomas C.

409

Effective resonance levels  

Microsoft Academic Search

A method based on the use of effective resonance integrals or group cross sections with resonance self-shielding factors has come into extensive use in calculations of resonance absorption in homogeneous systems. An attempt is made to extend the subgroup treatment, which was initially formulated for the region of forbidden resonances, to the allowed region as applicable to heterogeneous media. A

B. P. Kochurov

1986-01-01

410

Extended fundamental frequency analysis of the LCC resonant converter  

Microsoft Academic Search

Fundamental frequency techniques are used to analyze the series-parallel resonant converter under heavy load conditions, both with a continuous, but distorted parallel capacitor voltage waveform, and with a discontinuous capacitor voltage waveform. The analysis is validated with results from an experimental prototype. The application of the technique to the parallel-loaded L-C resonant converter is also considered.

Andrew J. Forsyth; Gillian A. Ward; Stefan V. Mollov

2003-01-01

411

Abdominal magnetic resonance elastography.  

PubMed

Magnetic resonance elastography (MRE) is a magnetic resonance imaging-based technique for quantitatively assessing the mechanical properties of tissues based on the propagation of shear waves. Multiple studies have described many potential applications of MRE, from characterizing tumors to detecting diffuse disease processes. Studies have shown that MRE can be successfully implemented to assess abdominal organs. The first clinical application of MRE to be well documented is the detection and characterization of hepatic fibrosis, which systematically increases the stiffness of liver tissue. In this diagnostic role, it offers a safer, less expensive, and potentially more accurate alternative to invasive liver biopsy. Emerging results suggest that measurements of liver and spleen stiffness may provide an indirect way to assess portal hypertension. Preliminary studies have demonstrated that it is possible to use MRE to evaluate the mechanical properties of other abdominal structures, such as the pancreas and kidneys. Steady technical progress in developing practical protocols for applying MRE in the abdomen and the pelvis provides opportunities to explore many other potential applications of this emerging technology. PMID:20010062

Yin, Meng; Chen, Jun; Glaser, Kevin J; Talwalkar, Jayant A; Ehman, Richard L

2009-04-01

412

Nuclear Resonance Fluorescence of 237 Np  

SciTech Connect

Identification and characterization of fissile material is of international concern because of the possibility of proliferation. For safeguards applications, techniques providing isotopic information are necessary [1]. However, few techniques can distinguish between fissile isotopes. Nuclear resonance fluorescence is one technique that can be used in applications to identify and quantify isotopic content. NRF has also been proposed in several detector systems as a viable way to identify fissile material in cargo containers [2, 3]. It is necessary to measure the characteristic resonances of each isotope that is to be distinguished in identification and assay applications.

Angell, Chris T.; Yee, R.; Joshi, T.; Swanberg, E.; Norman, E. B.; Hicks, C. L.; Klimenko, A.; Korbly, Steve; Wilson, C.; Kulp, W. D.; Warren, Glen A.; Bray, T. H.; Copping, R.; Glans, P.A.; Tyliszczak, T.; Shuh, David K.

2010-11-15

413

"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.

Foster, K R; Epstein, B R; Gealt, M A

1987-01-01

414

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

415

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

416

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

417

Folded dipole plasmonic resonators.  

PubMed

A class of folded ordered plasmonic dipole nanoresonators based on insulator-metal-insulator (IMI) slab waveguides is proposed and studied. This work is motivated by the development of a novel fabrication process that avoids the need for direct write nanolithography and instead relies on accessible UV lithography and other top-down parallel fabrication techniques that result in metallic dolmen structures with nanometre sized gaps. In this context, the dolmen geometry consists of two vertical segments supporting a flat horizontal slab. It is shown using frequency domain finite element analysis that such structures, which are essentially folded dipole antennas, resonate in a similar manner to their linear unfolded counterparts. The effect of the likely fabrication features is also studied. PMID:24216810

Choonee, K; Syms, R R A

2013-11-01

418

Doubly rotated contoured quartz resonators  

Microsoft Academic Search

Doubly rotated contoured quartz resonators are used in the design of temperature-compensated stable clocks and dual-mode sensors for simultaneous measurements of pressure and temperature. The design of these devices is facilitated by models that can predict frequency spectra associated with the three thickness modes and temperature and stress-induced frequency changes as a function of crystalline orientation. The Stevens-Tiersten technique for

Bikash K. Sinha

2001-01-01

419

Magnetic resonance neurography: technical considerations.  

PubMed

Proper performance of magnetic resonance neurography (MRN) is essential not only to make the examination easier to interpret but also for its accurate evaluation. This article outlines the technical considerations of MRN, various imaging pulse sequences available on current scanners, as well as their relative advantages and disadvantages. In addition, a guide to the optimal use of high-resolution and high-contrast MRN technique is provided, which will aid clinicians in attaining a good-quality examination. PMID:24210313

Chhabra, Avneesh; Flammang, Aaron; Padua, Abraham; Carrino, John A; Andreisek, Gustav

2014-02-01

420

Triply resonant sum frequency spectroscopy: combining advantages of resonance Raman and 2D-IR.  

PubMed

This article describes the new multidimensional spectroscopy technique triply resonant sum frequency spectroscopy, a four-wave mixing technique sharing advantages of both 2D-IR and resonance Raman experiments. In this technique, lasers with three independent frequencies interact coherently within a sample and generate an output frequency at their triple summation. The output intensity depends on coupled electronic and vibrational resonances in the sample. We use an organic dye as a model system to demonstrate fully resonant, fully coherent multidimensional spectroscopy using two independently tunable mid-infrared vibrational interactions and one visible electronic interaction. When the pulses are time ordered, the method has a single coherence pathway, eliminating interference between pathways. Fundamental vibrational transitions appear on one axis and overtones and combinations bands on the other, allowing anharmonicities of the modes to be determined easily and conveying molecular coupling information. The experiments demonstrate coupling between seven vibrational ring modes and an electronic state, the resolution of a Fermi resonance, detection of low concentrations, elimination of excitation pulse scattering and fluorescence, background suppression of solvent and co-solutes, and observation of coherence dephasing dynamics. The electronic resonance enhancements used in this methodology are similar to the enhancements responsible for resonance Raman spectroscopy and can be considered resonance 2D-IR spectroscopy. PMID:24160771

Boyle, Erin S; Neff-Mallon, Nathan A; Wright, John C

2013-11-27

421

Gallium nitride nanowire electromechanical resonators  

NASA Astrophysics Data System (ADS)

Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of