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Sample records for nuclear polarization applied

  1. Dynamic nuclear polarization in diamond

    NASA Astrophysics Data System (ADS)

    Nah, Seungjoo

    2016-07-01

    We study the dynamic nuclear polarization of nitrogen-vacancy (NV) centers in diamond through optical pumping. The polarization is enhanced due to the hyperfine interaction of nuclear spins as applied magnetic fields vary. This is a result of the averaging of excited states due to fast-phonon transitions in the excited states. The effect of dephasing, in the presence of a vibronic band, is shown to have little effect during the dynamic polarization.

  2. Optimizing dissolution dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows: Using broad line polarizing agents to efficiently polarize 1H spins. Increasing the magnetic field to 6.7 T and above. Applying microwave frequency modulation. Applying 1H-13C cross polarization. Transferring hyperpolarized solution through a magnetic tunnel.

  3. High frequency dynamic nuclear polarization.

    PubMed

    Ni, Qing Zhe; Daviso, Eugenio; Can, Thach V; Markhasin, Evgeny; Jawla, Sudheer K; Swager, Timothy M; Temkin, Richard J; Herzfeld, Judith; Griffin, Robert G

    2013-09-17

    During the three decades 1980-2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical, and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-γ nuclei such as the I = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime, roughly 150-660 GHz, and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades, scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low

  4. High Frequency Dynamic Nuclear Polarization

    PubMed Central

    Ni, Qing Zhe; Daviso, Eugenio; Can, Thach V.; Markhasin, Evgeny; Jawla, Sudheer K.; Swager, Timothy M.; Temkin, Richard J.; Herzfeld, Judith; Griffin, Robert G.

    2013-01-01

    Conspectus During the three decades 1980–2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-γ nuclei such as the I = ½ species 13C or 15N. The difficulty is still greater when quadrupolar nuclei, like 17O or 27Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime — roughly 150–660 GHz — and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low

  5. Cross-polarization for dissolution dynamic nuclear polarization.

    PubMed

    Batel, Michael; Däpp, Alexander; Hunkeler, Andreas; Meier, Beat H; Kozerke, Sebastian; Ernst, Matthias

    2014-10-21

    Dynamic nuclear polarization (DNP) in combination with subsequent dissolution of the sample allows the detection of low-γ nuclei in the solution state with a signal gain of up to tens of thousand times compared to experiments starting from Boltzmann conditions. The long polarization build-up times of typically more than one hour are a drawback of this technique. The combination of dissolution DNP with cross-polarization (CP) in the solid state was shown to have the potential to overcome this disadvantage. In this article we discuss the cross-polarization step under dissolution DNP conditions in more detail. We show that adiabatic half-passage pulses allow us to enhance the CP efficiency in power-limited DNP probes. As a low-power alternative to Hartmann-Hahn CP we also demonstrate the applicability of frequency-swept de- and re-magnetization pulses for polarization transfer via dipolar order. We investigate the implications and restrictions of the common solid-state DNP mechanisms to the DNP-CP technique and apply a spin-thermodynamic model based on the thermal-mixing mechanism. The model allows us to investigate the dynamics of the polarization levels in a system with two nuclear Zeeman reservoirs and explains the enhanced DNP efficiency upon solvent deuteration within a spin-thermodynamic picture. PMID:25182534

  6. Optimizing dissolution dynamic nuclear polarization.

    PubMed

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows. PMID:26920826

  7. Optimizing dissolution dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows:

  8. Polarized nuclear target based on parahydrogen induced polarization

    SciTech Connect

    D. Budker, M.P. Ledbetter, S. Appelt, L.S. Bouchard, B. Wojtsekhowski

    2012-12-01

    We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ({approx}100 HZ) polarization oscillation (akin to polarization reversal), and operation with large intensity of an electron beam.

  9. Polarized nuclear target based on parahydrogen induced polarization

    NASA Astrophysics Data System (ADS)

    Budker, D.; Ledbetter, M. P.; Appelt, S.; Bouchard, L. S.; Wojtsekhowski, B.

    2012-12-01

    We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast (˜100 Hz) polarization oscillation (akin to polarization reversal), and operation with large intensity of an electron beam.

  10. THz Dynamic Nuclear Polarization NMR

    PubMed Central

    Nanni, Emilio A.; Barnes, Alexander B.; Griffin, Robert G.; Temkin, Richard J.

    2013-01-01

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140–600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

  11. THz Dynamic Nuclear Polarization NMR.

    PubMed

    Nanni, Emilio A; Barnes, Alexander B; Griffin, Robert G; Temkin, Richard J

    2011-08-29

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140-600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

  12. Dynamic Nuclear Polarization of 17O: Direct Polarization

    PubMed Central

    Michaelis, Vladimir K.; Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

    2014-01-01

    Dynamic nuclear polarization of 17O was studied using four different polarizing agents – the biradical TOTAPOL, and the monoradicals trityl and SA-BDPA, as well as a mixture of the latter two. Field profiles, DNP mechanisms and enhancements were measured to better understand and optimize directly polarizing this low-gamma quadrupolar nucleus using both mono- and bi-radical polarizing agents. Enhancements were recorded < 88 K and were > 100 using the trityl (OX063) radical and < 10 with the other polarizing agents. The > 10,000 fold savings in acquisition time enabled a series of biologically relevant small molecules to be studied with small sample sizes and the measurement of various quadrupolar parameters. The results are discussed with comparison to room temperature studies and GIPAW quantum chemical calculations. These experimental results illustrate the strength of high field DNP and the importance of radical selection for studying low-gamma nuclei. PMID:24195759

  13. Polarization model applied to Uranian radio emission

    NASA Astrophysics Data System (ADS)

    Sawyer, C. B.; Neal, K. L.; Warwick, J. W.

    1991-04-01

    The total power and the degree of circular polarization as measured by the Planetary Radio Astronomy experiments on the Voyager spacecraft are modeled. For a source near the electron cyclotron frequency, the degree of circular polarization is determined by the angle between the wave vector and the field. It is shown that the observed strong circular polarization of Uranian smooth low-frequency (SLF) can be modeled as emission that is beamed along the direction of the magnetic field in a filled cone. The main observational constraints of SLF emission from Uranus are met by conjugate sources at about 21 deg from the magnetic equator.

  14. Development on dynamic nuclear polarized targets.

    SciTech Connect

    Penttila, S. I.

    2002-01-01

    Our interest in understanding the spin content of the nucleon has left its marks on the recent development, of the dynamic nuclear polarized (DNP) targets. This can be seen from the targets developed at CERN and SLAC for the measurement of the polarized spin structure functions in deep inelastic scattering. The results of the experiments indicated that less than 30% of the nucleon spin is carried by the quarks. This unpredicted small value initiated planning of new polarized target experiments to determine the gluon polarization on the nucleon using polarized real photons and polarized 'LiD targets. In several facilities very intense polarized photon beams are available at a wide energy range. During the next few years these photon beanis with DNP targets will be used to test the fundamental GDH sum rule. Other DNP target developments are also discussed.

  15. New versions of sources for nuclear polarized negative ion production

    SciTech Connect

    Dudnikov, V.G.; Shabalin, A.L. ); Wojtsekhowski, B.B. ); Belov, A.S.; Kuzik, V.E.; Plohinsky, Y.V.; Yakushev, V.P. )

    1992-10-05

    Several variants of sources for nuclear polarized negative ion production have been proposed and tested. The simple adaptation of a high intensity polarized proton source for nuclear polarized H[sup [minus

  16. In Situ Temperature Jump Dynamic Nuclear Polarization

    PubMed Central

    Joo, Chan-Gyu; Casey, Andrew; Turner, Christopher J.; Griffin, Robert G.

    2009-01-01

    Dynamic nuclear polarization is combined with temperature jump methods to develop a new 2D 13C- 13C NMR experiment that yields a factor or 100-170 increase insensitivity. The polaization step is performed at ∼100 K and the sample is subsequently melted with a 10.6 mm laser pulse to yield a sample with highly polarized 13C spins. 13C detected 2D 13C- 13C spectroscopy is performed in the usual manner. PMID:18942782

  17. Dynamic nuclear polarization polarizer for sterile use intent.

    PubMed

    Ardenkjaer-Larsen, Jan H; Leach, Andrew M; Clarke, Neil; Urbahn, John; Anderson, Denise; Skloss, Timothy W

    2011-10-01

    A novel polarizer based on the dissolution-dynamic nuclear polarization (DNP) method has been designed, built and tested. The polarizer differs from those previously described by being designed with sterile use intent and being compatible with clinical use. The main features are: (1) an integral, disposable fluid path containing all pharmaceuticals constituting a sterile barrier, (2) a closed-cycle cryogenic system designed to eliminate consumption of liquid cryogens and (3) multi-sample polarization to increase throughput. The fluid path consists of a vial with the agent to be polarized, a pair of concentric inlet and outlet tubes connected to a syringe with dissolution medium and a receiver, respectively. The fluid path can operate at up to 400 K and 2.0 MPa and generates volumes as high as 100 mL. An inline filter removes the amount of electron paramagnetic agent in the final product by more than 100-fold in the case of [1-(13)C]pyruvate. The system uses a sorption pump in conjunction with a conventional cryocooler. The system operates through cycles of pumping to low temperature and regeneration of the sorption pump. The magnet accommodates four samples at the same time. A temperature of less than 1 K was achieved for 68 h (no sample heat loads) with a liquid helium volume of 2.4 L. The regeneration of the liquid helium could be achieved in less than 10 h, and the transition to cold (< 1.2 K) was achieved in less than 90 min. A solid state polarization of 36 ± 4% for [1-(13)C]pyruvic acid was obtained with only 10 mW of microwave power. The loading of a sample adds less than 50 J of heat to the helium bath by introducing the sample over 15 min. The heat load imposed on the helium bath during dissolution was less than 70 J. The measured liquid state polarization was 18 ± 2%. PMID:21416540

  18. Voltage-induced conversion of helical to uniform nuclear spin polarization in a quantum wire

    NASA Astrophysics Data System (ADS)

    Kornich, Viktoriia; Stano, Peter; Zyuzin, Alexander A.; Loss, Daniel

    2015-05-01

    We study the effect of bias voltage on the nuclear spin polarization of a ballistic wire, which contains electrons and nuclei interacting via hyperfine interaction. In equilibrium, the localized nuclear spins are helically polarized due to the electron-mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Focusing here on nonequilibrium, we find that an applied bias voltage induces a uniform polarization, from both helically polarized and unpolarized spins available for spin flips. Once a macroscopic uniform polarization in the nuclei is established, the nuclear spin helix rotates with frequency proportional to the uniform polarization. The uniform nuclear spin polarization monotonically increases as a function of both voltage and temperature, reflecting a thermal activation behavior. Our predictions offer specific ways to test experimentally the presence of a nuclear spin helix polarization in semiconducting quantum wires.

  19. Demonstration of open-quantum-system optimal control in dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Sheldon, S.; Cory, D. G.

    2015-10-01

    Dynamic nuclear polarization (DNP) is used in nuclear magnetic resonance to transfer polarization from electron spins to nuclear spins. The resulting nuclear polarization enhancement can, in theory, be two or three orders of magnitude depending on the sample. In solid-state systems, however, there are competing mechanisms of DNP, which, when occurring simultaneously, reduce the net polarization enhancement of the nuclear spin. We present a simple quantum description of DNP and apply optimal control theory (OCT) with an open-quantum-system framework to design pulses that select one DNP process and suppress the others. We demonstrate experimentally an order of magnitude improvement in the DNP enhancement using OCT pulses.

  20. Nuclear Facilities and Applied Technologies at Sandia

    SciTech Connect

    Wheeler, Dave; Kaiser, Krista; Martin, Lonnie; Hanson, Don; Harms, Gary; Quirk, Tom

    2014-11-28

    The Nuclear Facilities and Applied Technologies organization at Sandia National Laboratories’ Technical Area Five (TA-V) is the leader in advancing nuclear technologies through applied radiation science and unique nuclear environments. This video describes the organization’s capabilities, facilities, and culture.

  1. Pulsed Dynamic Nuclear Polarization with Trityl Radicals.

    PubMed

    Mathies, Guinevere; Jain, Sheetal; Reese, Marcel; Griffin, Robert G

    2016-01-01

    Continuous-wave (CW) dynamic nuclear polarization (DNP) is now established as a method of choice to enhance the sensitivity in a variety of NMR experiments. Nevertheless, there remains a need for the development of more efficient methods to transfer polarization from electrons to nuclei. Of particular interest are pulsed DNP methods because they enable a rapid and efficient polarization transfer that, in contrast with CW DNP methods, is not attenuated at high magnetic fields. Here we report nuclear spin orientation via electron spin-locking (NOVEL) experiments using the polarizing agent trityl OX063 in glycerol/water at a temperature of 80 K and a magnetic field of 0.34 T. (1)H NMR signal enhancements up to 430 are observed, and the buildup of the local polarization occurs in a few hundred nanoseconds. Thus, NOVEL can efficiently dynamically polarize (1)H atoms in a system that is of general interest to the solid-state DNP NMR community. This is a first, important step toward the general application of pulsed DNP at higher fields. PMID:26651876

  2. Inhomogeneous dynamic nuclear polarization and suppression of electron polarization decay in a quantum dot

    NASA Astrophysics Data System (ADS)

    Wu, Na; Ding, Wenkui; Shi, Anqi; Zhang, Wenxian

    2016-08-01

    We investigate the dynamic nuclear polarization in a quantum dot. Due to the suppression of direct dipolar and indirect electron-mediated nuclear spin interactions by frequently injected electron spins, our analytical results under independent spin approximation agree well with quantum numerical simulations for a small number of nuclear spins. We find that the acquired nuclear polarization is highly inhomogeneous, proportional to the square of the local electron-nuclear hyperfine interaction constant. Starting from the inhomogeneously polarized nuclear spins, we further show that the electron polarization decay time can be extended 100 times even at a relatively low nuclear polarization.

  3. Medium polarization in asymmetric nuclear matter

    NASA Astrophysics Data System (ADS)

    Zhang, S. S.; Cao, L. G.; Lombardo, U.; Schuck, P.

    2016-04-01

    The influence of the medium polarization on the effective nuclear interaction of asymmetric nuclear matter is calculated in the framework of the induced interaction theory. The strong isospin dependence of the density and spin-density fluctuations is studied as it is driven by the interplay between the neutron and proton medium polarizations. Going from symmetric nuclear matter to pure neutron matter, the crossover of the induced interaction from attractive to repulsive in the spin-singlet state is determined as a function of the isospin imbalance. The density range in which the crossover occurs is also determined. For the spin-triplet state the induced interaction turns out to be always repulsive. The implications of the results for neutron star superfluid phases are briefly discussed.

  4. Microtesla MRI with dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Zotev, Vadim S.; Owens, Tuba; Matlashov, Andrei N.; Savukov, Igor M.; Gomez, John J.; Espy, Michelle A.

    2010-11-01

    Magnetic resonance imaging at microtesla fields is a promising imaging method that combines the pre-polarization technique and broadband signal reception by superconducting quantum interference device (SQUID) sensors to enable in vivo MRI at microtesla-range magnetic fields similar in strength to the Earth magnetic field. Despite significant advances in recent years, the potential of microtesla MRI for biomedical imaging is limited by its insufficient signal-to-noise ratio due to a relatively low sample polarization. Dynamic nuclear polarization (DNP) is a widely used approach that allows polarization enhancement by 2-4 orders of magnitude without an increase in the polarizing field strength. In this work, the first implementation of microtesla MRI with Overhauser DNP and SQUID signal detection is described. The first measurements of carbon-13 NMR spectra at microtesla fields are also reported. The experiments were performed at the measurement field of 96 μT, corresponding to Larmor frequency of 4 kHz for protons and 1 kHz for carbon-13. The Overhauser DNP was carried out at 3.5-5.7 mT fields using rf irradiation at 120 MHz. Objects for imaging included water phantoms and a cactus plant. Aqueous solutions of metabolically relevant sodium bicarbonate, pyruvate, alanine, and lactate, labeled with carbon-13, were used for NMR studies. All the samples were doped with TEMPO free radicals. The Overhauser DNP enabled nuclear polarization enhancement by factor as large as -95 for protons and as large as -200 for carbon-13, corresponding to thermal polarizations at 0.33 T and 1.1 T fields, respectively. These results demonstrate that SQUID-based microtesla MRI can be naturally combined with Overhauser DNP in one system, and that its signal-to-noise performance is greatly improved in this case. They also suggest that microtesla MRI can become an efficient tool for in vivo imaging of hyperpolarized carbon-13, produced by low-temperature dissolution DNP.

  5. Uncertainty minimization in NMR measurements of dynamic nuclear polarization of a proton target for nuclear physics experiments

    SciTech Connect

    Keller, Dustin M.

    2013-11-01

    A comprehensive investigation into the measurement uncertainty in polarization produced by Dynamic Nuclear Polarization is outlined. The polarization data taken during Jefferson Lab experiment E08-007 is used to obtain error estimates and to develop an algorithm to minimize uncertainty of the measurement of polarization in irradiated View the ^14NH_3 targets, which is readily applied to other materials. The target polarization and corresponding uncertainties for E08-007 are reported. The resulting relative uncertainty found in the target polarization is determined to be less than or equal to 3.9%.

  6. Rapid-melt Dynamic Nuclear Polarization

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Janssen, G.; Leggett, J.; Kentgens, A. P. M.; van Bentum, P. J. M.

    2015-09-01

    In recent years, Dynamic Nuclear Polarization (DNP) has re-emerged as a means to ameliorate the inherent problem of low sensitivity in nuclear magnetic resonance (NMR). Here, we present a novel approach to DNP enhanced liquid-state NMR based on rapid melting of a solid hyperpolarized sample followed by 'in situ' NMR detection. This method is applicable to small (10 nl to 1 μl) sized samples in a microfluidic setup. The method combines generic DNP enhancement in the solid state with the high sensitivity of stripline 1 H NMR detection in the liquid state. Fast cycling facilitates options for signal averaging or 2D structural analysis. Preliminary tests show solid-state 1 H enhancement factors of up to 500 for H2O/D2O/d6-glycerol samples doped with TEMPOL radicals. Fast paramagnetic relaxation with nitroxide radicals, In nonpolar solvents such as toluene, we find proton enhancement factors up to 400 with negligible relaxation losses in the liquid state, using commercially available BDPA radicals. A total recycling delay (including sample freezing, DNP polarization and melting) of about 5 s can be used. The present setup allows for a fast determination of the hyper-polarization as function of the microwave frequency and power. Even at the relatively low field of 3.4 T, the method of rapid melting DNP can facilitate the detection of small quantities of molecules in the picomole regime.

  7. Dynamic Nuclear Polarization as Kinetically Constrained Diffusion

    NASA Astrophysics Data System (ADS)

    Karabanov, A.; Wiśniewski, D.; Lesanovsky, I.; Köckenberger, W.

    2015-07-01

    Dynamic nuclear polarization (DNP) is a promising strategy for generating a significantly increased nonthermal spin polarization in nuclear magnetic resonance (NMR) and its applications that range from medicine diagnostics to material science. Being a genuine nonequilibrium effect, DNP circumvents the need for strong magnetic fields. However, despite intense research, a detailed theoretical understanding of the precise mechanism behind DNP is currently lacking. We address this issue by focusing on a simple instance of DNP—so-called solid effect DNP—which is formulated in terms of a quantum central spin model where a single electron is coupled to an ensemble of interacting nuclei. We show analytically that the nonequilibrium buildup of polarization heavily relies on a mechanism which can be interpreted as kinetically constrained diffusion. Beyond revealing this insight, our approach furthermore permits numerical studies of ensembles containing thousands of spins that are typically intractable when formulated in terms of a quantum master equation. We believe that this represents an important step forward in the quest of harnessing nonequilibrium many-body quantum physics for technological applications.

  8. Rapid-melt Dynamic Nuclear Polarization.

    PubMed

    Sharma, M; Janssen, G; Leggett, J; Kentgens, A P M; van Bentum, P J M

    2015-09-01

    In recent years, Dynamic Nuclear Polarization (DNP) has re-emerged as a means to ameliorate the inherent problem of low sensitivity in nuclear magnetic resonance (NMR). Here, we present a novel approach to DNP enhanced liquid-state NMR based on rapid melting of a solid hyperpolarized sample followed by 'in situ' NMR detection. This method is applicable to small (10nl to 1μl) sized samples in a microfluidic setup. The method combines generic DNP enhancement in the solid state with the high sensitivity of stripline (1)H NMR detection in the liquid state. Fast cycling facilitates options for signal averaging or 2D structural analysis. Preliminary tests show solid-state (1)H enhancement factors of up to 500 for H2O/D2O/d6-glycerol samples doped with TEMPOL radicals. Fast paramagnetic relaxation with nitroxide radicals, In nonpolar solvents such as toluene, we find proton enhancement factors up to 400 with negligible relaxation losses in the liquid state, using commercially available BDPA radicals. A total recycling delay (including sample freezing, DNP polarization and melting) of about 5s can be used. The present setup allows for a fast determination of the hyper-polarization as function of the microwave frequency and power. Even at the relatively low field of 3.4T, the method of rapid melting DNP can facilitate the detection of small quantities of molecules in the picomole regime. PMID:26225439

  9. Dynamic nuclear polarization in a magnetic resonance force microscope experiment.

    PubMed

    Issac, Corinne E; Gleave, Christine M; Nasr, Paméla T; Nguyen, Hoang L; Curley, Elizabeth A; Yoder, Jonilyn L; Moore, Eric W; Chen, Lei; Marohn, John A

    2016-04-01

    We report achieving enhanced nuclear magnetization in a magnetic resonance force microscope experiment at 0.6 tesla and 4.2 kelvin using the dynamic nuclear polarization (DNP) effect. In our experiments a microwire coplanar waveguide delivered radiowaves to excite nuclear spins and microwaves to excite electron spins in a 250 nm thick nitroxide-doped polystyrene sample. Both electron and proton spin resonance were observed as a change in the mechanical resonance frequency of a nearby cantilever having a micron-scale nickel tip. NMR signal, not observable from Curie-law magnetization at 0.6 T, became observable when microwave irradiation was applied to saturate the electron spins. The resulting NMR signal's size, buildup time, dependence on microwave power, and dependence on irradiation frequency was consistent with a transfer of magnetization from electron spins to nuclear spins. Due to the presence of an inhomogeneous magnetic field introduced by the cantilever's magnetic tip, the electron spins in the sample were saturated in a microwave-resonant slice 10's of nm thick. The spatial distribution of the nuclear polarization enhancement factor ε was mapped by varying the frequency of the applied radiowaves. The observed enhancement factor was zero for spins in the center of the resonant slice, was ε = +10 to +20 for spins proximal to the magnet, and was ε = -10 to -20 for spins distal to the magnet. We show that this bipolar nuclear magnetization profile is consistent with cross-effect DNP in a ∼10(5) T m(-1) magnetic field gradient. Potential challenges associated with generating and using DNP-enhanced nuclear magnetization in a nanometer-resolution magnetic resonance imaging experiment are elucidated and discussed. PMID:26964007

  10. Dynamic Nuclear Polarization of Sedimented Solutes

    PubMed Central

    Ravera, Enrico; Corzilius, Björn; Michaelis, Vladimir K.; Rosa, Camilla; Griffin, Robert G.; Luchinat, Claudio; Bertini, Ivano

    2013-01-01

    Using the 480 kDa iron-storage protein complex, apoferritin, as an example, we demonstrate that sizable dynamic nuclear polarization (DNP) enhancements can be obtained on sedimented protein samples. In sedimented solute DNP (SedDNP), the biradical polarizing agent is co-sedimented with the protein, but in the absence of a glass forming agent. We observe DNP enhancement factors ε>40 at a magnetic field of 5 T and temperatures below 90 K, indicating that the protein sediment state is “glassy” and suitable to disperse the biradical polarizing agent upon freezing. In contrast, frozen aqueous solutions of apoferritin yield ε ≈ 2. Results of SedDNP are compared to those obtained from samples prepared using the traditional glass forming agent glycerol. Collectively, these and results from previous investigations suggest that the sedimented state can be functionally described as a “microcrystalline glass” and in addition provides a new approach for preparation of samples for DNP experiments. PMID:23331059

  11. Dynamic nuclear polarization of spherical nanoparticles.

    PubMed

    Akbey, Ümit; Altin, Burcu; Linden, Arne; Özçelik, Serdar; Gradzielski, Michael; Oschkinat, Hartmut

    2013-12-21

    Spherical silica nanoparticles of various particle sizes (~10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e.g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size. We determined an approximate DNP penetration-depth (~4.2 or ~5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI). PMID:24192797

  12. Triton memory time in solid DT and its nuclear polarization

    SciTech Connect

    Souers, P. C.; Fearon, E. M.; Mapoles, E. R.; Sater, J. D.; Collins, G. W.; Gaines, J. R.; Sherman, R. H.; Bartlit, J. R.

    1988-01-01

    The expected value of nuclear spin polarization to inertial confinement fusion is recapitulated. A comparison of brute force versus dynamic nuclear polarization, as applied to solid deuterium-tritium, is given, and the need for a long triton polarization memory time (longitudinal nuclear relaxation time) is shown. The time constant for 25 mol%T/sub 2/-50 DT-25 D/sub 2/ is a short 0.3 s at 5/degree/K and waiting lowers it to 0.1 s. Use of 90 to 96 mol% molecular DT raises the time constant to 0.9 s and addition of about 20 mol% nH/sub 2/ increases it to 5 to 7 s. The theory shows that the species shortening the triton memory time is the J = 1 T/sub 2/, which can be reduced in our samples only by self-catalysis. The heating in order to mix in nH/sub 2/ increases the percent of J = 1 T/sub 2/ and mixing may not be perfect. The experiments have increased the triton memory time twenty-fold and shown that removal of the J = 1 T/sub 2/ is the key to improved results.

  13. Dynamic nuclear polarization at high magnetic fields

    PubMed Central

    Maly, Thorsten; Debelouchina, Galia T.; Bajaj, Vikram S.; Hu, Kan-Nian; Joo, Chan-Gyu; Mak–Jurkauskas, Melody L.; Sirigiri, Jagadishwar R.; van der Wel, Patrick C. A.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (μw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (γe/γl), being ∼660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (≥5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms—the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in μw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments. PMID:18266416

  14. Hyperpolarization of Frozen Hydrocarbon Gases by Dynamic Nuclear Polarization at 1.2 K.

    PubMed

    Vuichoud, Basile; Canet, Estel; Milani, Jonas; Bornet, Aurélien; Baudouin, David; Veyre, Laurent; Gajan, David; Emsley, Lyndon; Lesage, Anne; Copéret, Christophe; Thieuleux, Chloé; Bodenhausen, Geoffrey; Koptyug, Igor; Jannin, Sami

    2016-08-18

    We report a simple and general method for the hyperpolarization of condensed gases by dynamic nuclear polarization (DNP). The gases are adsorbed in the pores of structured mesoporous silica matrices known as HYPSOs (HYper Polarizing SOlids) that have paramagnetic polarizing agents covalently bound to the surface of the mesopores. DNP is performed at low temperatures and moderate magnetic fields (T = 1.2 K and B0 = 6.7 T). Frequency-modulated microwave irradiation is applied close to the electron spin resonance frequency (f = 188.3 GHz), and the electron spin polarization of the polarizing agents of HYPSO is transferred to the nuclear spins of the frozen gas. A proton polarization as high as P((1)H) = 70% can be obtained, which can be subsequently transferred to (13)C in natural abundance by cross-polarization, yielding up to P((13)C) = 27% for ethylene. PMID:27483034

  15. Polarization-sensitive optical coherence tomography applied to intervertebral disk

    NASA Astrophysics Data System (ADS)

    Matcher, Stephen J.; Winlove, Peter; Gangnus, Sergei V.

    2003-07-01

    Polarization-sensitive optical coherence tomography (PSOCT) is a powerful new optical imaging modality that is sensitive to the birefringence properties of tissues. It thus has potential applications in studying the large-scale ordering of collagen fibers within connective tisues and changes related to pathology. As a tissue for study by PSOCT, intervertebral disk respresents an interesting system as the collagen organization is believed to show pronounced variations with depth, on a spatial scale of about 100 μm. We have used a polarization-sensitive optical coherence tomography system to measure the birefringence properties of bovine caudal intervertebral disk and compared this with equine flexor tendon. The result for equine tendon, δ = (3.0 +/- 0.5)x10-3 at 1.3 μm, is in broad agreement with values reported for bovine tendon, while bovine intervertebral disk displays a birefringence of about half this, δ = 1.2 x 10-3 at 1.3 μm. While tendon appears to show a uniform fast-axis over 0.8 mm depth, intervertebral disk shows image contrast at all orientations relative to a linearly polarized input beam, suggesting a variation in fast-axis orientation with depth. These initial results suggest that PSOCT could be a useful tool to study collagen organization within this tissue and its variation with applied load and disease.

  16. Optical Polarization of Nuclear Spins in Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Falk, Abram L.; Klimov, Paul V.; Ivády, Viktor; Szász, Krisztián; Christle, David J.; Koehl, William F.; Gali, Ádám; Awschalom, David D.

    2015-06-01

    We demonstrate optically pumped dynamic nuclear polarization of 29Si nuclear spins that are strongly coupled to paramagnetic color centers in 4 H - and 6 H -SiC. The 9 9 % ±1 % degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 μ K . By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.

  17. Dynamic nuclear polarization and Hanle effect in (In,Ga)As/GaAs quantum dots. Role of nuclear spin fluctuations

    SciTech Connect

    Gerlovin, I. Ya.; Cherbunin, R. V.; Ignatiev, I. V.; Kuznetsova, M. S.; Verbin, S. Yu.; Flisinski, K.; Bayer, M.; Reuter, D.; Wieck, A. D.; Yakovlev, D. R.

    2013-12-04

    The degree of circular polarization of photoluminescence of (In,Ga)As quantum dots as a function of magnetic field applied perpendicular to the optical axis (Hanle effect) is experimentally studied. The measurements have been performed at various regimes of the optical excitation modulation. The analysis of experimental data has been performed in the framework of a vector model of regular nuclear spin polarization and its fluctuations. The analysis allowed us to evaluate the magnitude of nuclear polarization and its dynamics at the experimental conditions used.

  18. Nuclear polarization in heavy atoms and superheavy quasiatoms

    SciTech Connect

    Plunien, G. ); Mueller, B.; Greiner, W. ); Soff, G. )

    1991-06-01

    We consider the contribution of nuclear polarization to the Lamb shift of {ital K}- and {ital L}-shell electrons in heavy atoms and quasiatoms. Our formal approach is based on the concept of effective photon propagators with nuclear-polarization insertions treating effects of nuclear polarization on the same footing as usual QED radiative corrections. We explicitly derive the modification of the photon propagator for various collective nuclear excitations and calculate the corresponding effective self-energy shift perturbatively. The energy shift of the 1{ital s}{sub 1/2} state in {sub 92}{sup 238}U due to virtual excitation of nuclear rotational states is shown to be a considerable correction for atomic high-precision experiments. In contrast to this, nuclear-polarization effects are of minor importance for Lamb-shift studies in {sub 82}{sup 208}Pb.

  19. Local dynamic nuclear polarization using quantum point contacts

    SciTech Connect

    Wald, K.R.; Kouwenhoven, L.P.; McEuen, P.L. ); van der Vaart, N.C. ); Foxon, C.T. )

    1994-08-15

    We have used quantum point contacts (QPCs) to locally create and probe dynamic nuclear polarization (DNP) in GaAs heterostructures in the quantum Hall regime. DNP is created via scattering between spin-polarized Landau level electrons and the Ga and As nuclear spins, and it leads to hysteresis in the dc transport characteristics. The nuclear origin of this hysteresis is demonstrated by nuclear magnetic resonance (NMR). Our results show that QPCs can be used to create and probe local nuclear spin populations, opening up new possibilities for mesoscopic NMR experiments.

  20. Bulk nuclear polarization enhanced at room temperature by optical pumping.

    PubMed

    Fischer, Ran; Bretschneider, Christian O; London, Paz; Budker, Dmitry; Gershoni, David; Frydman, Lucio

    2013-08-01

    Bulk (13)C polarization can be strongly enhanced in diamond at room temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating single crystals at a ~50 mT field promoting anticrossings between electronic excited-state levels, followed by shuttling of the sample into an NMR setup and by subsequent (13)C detection. A nuclear polarization of ~0.5%--equivalent to the (13)C polarization achievable by thermal polarization at room temperature at fields of ~2000 T--was measured, and its bulk nature determined based on line shape and relaxation measurements. Positive and negative enhanced polarizations were obtained, with a generally complex but predictable dependence on the magnetic field during optical pumping. Owing to its simplicity, this (13)C room temperature polarizing strategy provides a promising new addition to existing nuclear hyperpolarization techniques. PMID:23952444

  1. Dynamic nuclear polarization in coal characterization: Final technical report

    SciTech Connect

    Maciel, G.E.

    1988-12-31

    The overall goal of this project was the development and application of new NMR techniques, based primarily on dynamic nuclear polarization (DNP), for elucidating organic structural details in coal samples. 1 fig.

  2. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1991-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  3. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1990-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neturons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  4. Optically enhanced nuclear cross polarization in acridine-doped fluorene

    SciTech Connect

    Oshiro, C.M.

    1982-06-01

    The objective of this work has been to create large polarizations of the dilute /sup 13/C nuclei in the solid state. The idea was to create /sup 1/H polarizations larger than Boltzmann and to use the proton enhanced nuclear induction spectroscopy cross polarization technique to then transfer this large polarization to the /sup 13/C spin system. Optical Nuclear Polarization (ONP) of acridine-doped fluorene single crystals was studied. In addition, ONP of powdered samples of the acridine-doped fluorene was studied. In general, many compounds do not crystallize easily or do not form large crystals suitable for NMR experiments. Powdered, amorphous and randomly dispersed samples are generally far more readily available than single crystals. One objective of this work has been to (first) create large /sup 1/H polarizations. Although large optical proton polarizations in single crystals have been reported previously, optically generated polarizations in powdered samples have not been reported. For these reasons, ONP studies of powdered samples of the acridine-doped fluorene were also undertaken. Using ONP in combination with the proton enhanced nuclear induction spectroscopy experiment, large /sup 13/C polarizations have been created in fluorene single crystals. These large /sup 13/C polarizations have permitted the determination of the seven incongruent chemical shielding tensors of the fluorene molecule. Part 2 of this thesis describes the proton enhanced nuclear induction spectroscopy experiment. Part 3 describes the ONP experiment. Part 4 is a description of the experimental set-up. Part 5 describes the data analysis for the determination of the chemical shielding tensors. Part 6 presents the results of the ONP experiments performed in this work and the chemical shielding tensors determined.

  5. Quantum limit for nuclear spin polarization in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Hildmann, Julia; Kavousanaki, Eleftheria; Burkard, Guido; Ribeiro, Hugo

    2014-05-01

    A recent experiment [E. A. Chekhovich et al., Phys. Rev. Lett. 104, 066804 (2010), 10.1103/PhysRevLett.104.066804] has demonstrated that high nuclear spin polarization can be achieved in self-assembled quantum dots by exploiting an optically forbidden transition between a heavy hole and a trion state. However, a fully polarized state is not achieved as expected from a classical rate equation. Here, we theoretically investigate this problem with the help of a quantum master equation and we demonstrate that a fully polarized state cannot be achieved due to formation of a nuclear dark state. Moreover, we show that the maximal degree of polarization depends on structural properties of the quantum dot.

  6. Applying Renormalization Group Techniques to Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Eldredge, Zachary; Bogner, Scott; Nunes, Filomena

    2013-10-01

    Nuclear reactions are commonly used to explore the physics of unstable nuclei. Therefore, it is important that accurate, computationally favorable methods exist to describe them. Reaction models often make use of effective nucleon-nucleus potentials (optical potentials) which fit low-energy scattering data and include an imaginary component to account for the removal of flux from the elastic channel. When describing reactions in momentum space, the coupling between low- and high-momentum states can pose a technical challenge. We would like potentials which allow us to compute low-momentum interactions without including highly virtual momentum states. A solution to this problem is to apply renormalization group (RG) techniques to produce a new effective potential in which high and low momentum degrees of freedom are decoupled, so that we need only consider momenta below some cutoff. This poster will present results relating to an implementation of RG techniques on optical potentials, including complex potentials and spin-orbit effects. We show that our evolved optical potentials reproduce bound states and scattering phase shifts without the inclusion of any momenta above a selected cutoff, and compare new potentials to old ones to examine the effect of transformation.

  7. Apparatus and method for polarizing polarizable nuclear species

    DOEpatents

    Hersman, F. William; Leuschner, Mark; Carberry, Jeannette

    2005-09-27

    The present invention is a polarizing process involving a number of steps. The first step requires moving a flowing mixture of gas, the gas at least containing a polarizable nuclear species and vapor of at least one alkali metal, with a transport velocity that is not negligible when compared with the natural velocity of diffusive transport. The second step is propagating laser light in a direction, preferably at least partially through a polarizing cell. The next step is directing the flowing gas along a direction generally opposite to the direction of laser light propagating. The next step is containing the flowing gas mixture in the polarizing cell. The final step is immersing the polarizing cell in a magnetic field. These steps can be initiated in any order, although the flowing gas, the propagating laser and the magnetic field immersion must be concurrently active for polarization to occur.

  8. Expeditious dissolution dynamic nuclear polarization without glassing agents.

    PubMed

    Lama, Bimala; Collins, James H P; Downes, Daniel; Smith, Adam N; Long, Joanna R

    2016-03-01

    The hyperpolarization of metabolic substrates at low temperature using dynamic nuclear polarization (DNP), followed by rapid dissolution and injection into an MRSI or NMR system, allows in vitro or in vivo observation and tracking of biochemical reactions and metabolites in real time. This article describes an elegant approach to sample preparation which is broadly applicable for the rapid polarization of aqueous small-molecule substrate solutions and obviates the need for glassing agents. We demonstrate its utility for solutions of sodium acetate, pyruvate and butyrate. The polarization behavior of substrates prepared using rapid freezing without glassing agents enabled a 1.5-3-fold time savings in polarization buildup, whilst removing the need for toxic glassing agents used as standard for dissolution DNP. The achievable polarization with fully aqueous substrate solutions was equal to that observed using standard approaches and glassing agents. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26915792

  9. Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR

    NASA Astrophysics Data System (ADS)

    Jannin, Sami; Bornet, Aurélien; Colombo, Sonia; Bodenhausen, Geoffrey

    2011-12-01

    Dynamic Nuclear Polarization (DNP) induced by saturation of ESR transitions of TEMPO at 1.2 K and 3.35 T is characterized by build-up rates that are typically 5 times faster for protons than for the carboxylic carbon-13 in acetate. We show that cross polarization from protons to carbon-13 allows one to achieve a polarization P( 13C) >20% in less than 10 min, twice as much as has been previously reported, in one-fifth of the time. This should open the way to an unprecedented improvement in the efficiency of dissolution DNP.

  10. Unconventional Coding Technique Applied to Multi-Level Polarization Modulation

    NASA Astrophysics Data System (ADS)

    Rutigliano, G. G.; Betti, S.; Perrone, P.

    2016-05-01

    A new technique is proposed to improve information confidentiality in optical-fiber communications without bandwidth consumption. A pseudorandom vectorial sequence was generated by a dynamic system algorithm and used to codify a multi-level polarization modulation based on the Stokes vector. Optical-fiber birefringence, usually considered as a disturbance, was exploited to obfuscate the signal transmission. At the receiver end, the same pseudorandom sequence was generated and used to decode the multi-level polarization modulated signal. The proposed scheme, working at the physical layer, provides strong information security without introducing complex processing and thus latency.

  11. Nuclear polarization contribution to the Lamb shift in heavy atoms

    SciTech Connect

    Plunien, G.; Mueller, B.; Greiner, W.; Soff, G.

    1989-05-15

    The energy shift of the 1s/sub 1/2/ state in /sub <2//sub 92//sup 38/U due to virtual excitation of nuclear rotational modes is shown to be a considerable correction for atomic high-precision experiments. In contrast to this, nuclear polarization effects are of minor importance for Lamb-shift studies in /sub <2//sub 82//sup 08/Pb.

  12. Investigation of ultrafast nuclear spin polarization induced by short laser pulses.

    PubMed

    Nakajima, Takashi

    2007-07-13

    We theoretically investigate the dynamics of nuclear spin induced by short laser pulses and show that ultrafast nuclear spin polarization can take place. Combined use of the hyperfine interaction together with the static electric field is the key for that. Specifically we apply the idea to unstable isotopes, (27)Mg and (37)Ca, with nuclear spin of 1/2 and 3/2, respectively, and show that 88% and 62% of nuclear spin polarization can be achieved within a few to tens of ns, which is 2-3 orders of magnitude shorter than the time needed for any known optical methods. Because of its ultrafast nature, our scheme would be very effective not only for stable nuclei but also unstable nuclei with a lifetime as short as mus. PMID:17678226

  13. Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization

    PubMed Central

    Gajan, David; Bornet, Aurélien; Vuichoud, Basile; Milani, Jonas; Melzi, Roberto; van Kalkeren, Henri A.; Veyre, Laurent; Thieuleux, Chloé; Conley, Matthew P.; Grüning, Wolfram R.; Schwarzwälder, Martin; Lesage, Anne; Copéret, Christophe; Bodenhausen, Geoffrey; Emsley, Lyndon; Jannin, Sami

    2014-01-01

    Hyperpolarization of substrates for magnetic resonance spectroscopy (MRS) and imaging (MRI) by dissolution dynamic nuclear polarization (D-DNP) usually involves saturating the ESR transitions of polarizing agents (PAs; e.g., persistent radicals embedded in frozen glassy matrices). This approach has shown enormous potential to achieve greatly enhanced nuclear spin polarization, but the presence of PAs and/or glassing agents in the sample after dissolution can raise concerns for in vivo MRI applications, such as perturbing molecular interactions, and may induce the erosion of hyperpolarization in spectroscopy and MRI. We show that D-DNP can be performed efficiently with hybrid polarizing solids (HYPSOs) with 2,2,6,6-tetramethyl-piperidine-1-oxyl radicals incorporated in a mesostructured silica material and homogeneously distributed along its pore channels. The powder is wetted with a solution containing molecules of interest (for example, metabolites for MRS or MRI) to fill the pore channels (incipient wetness impregnation), and DNP is performed at low temperatures in a very efficient manner. This approach allows high polarization without the need for glass-forming agents and is applicable to a broad range of substrates, including peptides and metabolites. During dissolution, HYPSO is physically retained by simple filtration in the cryostat of the DNP polarizer, and a pure hyperpolarized solution is collected within a few seconds. The resulting solution contains the pure substrate, is free from any paramagnetic or other pollutants, and is ready for in vivo infusion. PMID:25267650

  14. Mechanism of dynamic nuclear polarization in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Farrar, C. T.; Hall, D. A.; Gerfen, G. J.; Inati, S. J.; Griffin, R. G.

    2001-03-01

    Solid-state NMR signal enhancements of about two orders of magnitude (100-400) have been observed in dynamic nuclear polarization (DNP) experiments performed at high magnetic field (5 T) and low temperature (10 K) using the nitroxide radical 4-amino TEMPO as the source of electron polarization. Since the breadth of the 4-amino TEMPO EPR spectrum is large compared to the nuclear Larmor frequency, it has been assumed that thermal mixing (TM) is the dominate mechanism by which polarization is transferred from electron to nuclear spins. However, theoretical explanations of TM generally assume a homogeneously broadened EPR line and, since the 4-amino TEMPO line at 5 T is inhomogeneously broadened, they do not explain the observed DNP enhancements. Accordingly, we have developed a treatment of DNP that explicitly uses electron-electron cross-relaxation to mediate electron-nuclear polarization transfer. The process proceeds via spin flip-flops between pairs of electronic spin packets whose Zeeman temperatures differ from one another. To confirm the essential features of the model we have studied the field dependence of electron-electron double resonance (ELDOR) data and DNP enhancement data. Both are well simulated using a simple model of electron cross-relaxation in the inhomogeneously broadened 4-amino TEMPO EPR line.

  15. Dynamic Nuclear Polarization and the Paradox of Quantum Thermalization

    NASA Astrophysics Data System (ADS)

    De Luca, Andrea; Rosso, Alberto

    2015-08-01

    Dynamic nuclear polarization (DNP) is to date the most effective technique to increase the nuclear polarization opening disruptive perspectives for medical applications. In a DNP setting, the interacting spin system is quasi-isolated and brought out of equilibrium by microwave irradiation. Here we show that the resulting stationary state strongly depends on the ergodicity properties of the spin many-body eigenstates. In particular, the dipolar interactions compete with the disorder induced by local magnetic fields resulting in two distinct dynamical phases: while for weak interaction, only a small enhancement of polarization is observed, for strong interactions the spins collectively equilibrate to an extremely low effective temperature that boosts DNP efficiency. We argue that these two phases are intimately related to the problem of thermalization in closed quantum systems where a many-body localization transition can occur varying the strength of the interactions.

  16. The use of Dynamic Nuclear Polarization in coal research

    SciTech Connect

    Wind, R.A.

    1986-04-01

    In a variety of articles it has been shown that the presence of unpaired electrons in coal makes it possible to enhance the /sup 1/H and /sup 13/C NMR signals of this material by irradiating at or near the electron Larmor frequency: the Dynamic Nuclear Polarization (DNP) effect. It is found that in favourable cases the nuclear polarization can be enhanced by one to three orders of magnitude, which can e.g., be used as a fast method to characterize coal via /sup 13/C NMR. In this paper the DNP enhancement is investigated as a function of coal rank, and the observed behavior explained. Furthermore, special DNP experiments are given which provide information about the carbon percentage detected via /sup 1/H- /sup 13/C cross-polarization (CP).

  17. Water–Soluble Narrow Line Radicals for Dynamic Nuclear Polarization

    PubMed Central

    Haze, Olesya; Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.; Swager, Timothy M.

    2012-01-01

    The synthesis of air-stable highly water-soluble organic radicals containing a 1,3-bisdiphenylene-2-phenylallyl (BDPA) core is reported. A sulfonated derivative, SA-BDPA, retains the narrow EPR linewidth (<30 MHz at 5 T) of the parent BDPA in highly concentrated glycerol/water solutions (40 mM), which enables its use as polarizing agent for solid effect dynamic nuclear polarization (SE DNP). Sensitivity enhancement of 110 was obtained in high field magic-angle-spinning nuclear magnetic resonance (MAS NMR) experiments. The ease of synthesis and high maximum enhancements obtained with the BDPA-based radicals constitute a major advance over the trityl-type narrow line polarization agents. PMID:22917088

  18. Nuclear magnetic resonance imaging with hyper-polarized noble gases

    SciTech Connect

    Schmidt, D.M.; George, J.S.; Penttila, S.I.; Caprihan, A.

    1997-10-01

    This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The nuclei of noble gases can be hyper polarized through a laser-driven spin exchange to a degree many orders of magnitude larger than that attainable by thermal polarization without requiring a strong magnetic field. The increased polarization from the laser pumping enables a good nuclear magnetic resonance (NMR) signal from a gas. The main goal of this project was to demonstrate diffusion-weighted imaging of such hyper-polarized noble gas with magnetic resonance imaging (MRI). Possible applications include characterizing porosity of materials and dynamically imaging pressure distributions in biological or acoustical systems.

  19. Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes.

    PubMed

    Smith, Adam N; Twahir, Umar T; Dubroca, Thierry; Fanucci, Gail E; Long, Joanna R

    2016-08-18

    Dynamic nuclear polarization (DNP) enhanced solid-state NMR can provide orders of magnitude in signal enhancement. One of the most important aspects of obtaining efficient DNP enhancements is the optimization of the paramagnetic polarization agents used. To date, the most utilized polarization agents are nitroxide biradicals. However, the efficiency of these polarization agents is diminished when used with samples other than small molecule model compounds. We recently demonstrated the effectiveness of nitroxide labeled lipids as polarization agents for lipids and a membrane embedded peptide. Here, we systematically characterize, via electron paramagnetic (EPR), the dynamics of and the dipolar couplings between nitroxide labeled lipids under conditions relevant to DNP applications. Complemented by DNP enhanced solid-state NMR measurements at 600 MHz/395 GHz, a molecular rationale for the efficiency of nitroxide labeled lipids as DNP polarization agents is developed. Specifically, optimal DNP enhancements are obtained when the nitroxide moiety is attached to the lipid choline headgroup and local nitroxide concentrations yield an average e(-)-e(-) dipolar coupling of 47 MHz. On the basis of these measurements, we propose a framework for development of DNP polarization agents optimal for membrane protein structure determination. PMID:27434371

  20. Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids.

    PubMed

    Hu, Kan-Nian

    2011-09-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin-spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in high-field DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (<100 K). For example, large DNP enhancements (∼300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20K, nuclear polarization using lower microwave power (<100 mW) is possible by forcing a high proportion of biradicals to

  1. Polarizing Agents and Mechanisms for High-Field Dynamic Nuclear Polarization of Frozen Dielectric Solids

    PubMed Central

    Hu, Kan-Nian

    2011-01-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (< 100 K). For example, large DNP enhancements (~300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20 K, nuclear polarization using lower microwave power (< 100 mW) is possible by forcing a high proportion of biradicals to fulfill the

  2. Automated Microwave Frequency Control in Dynamic Nuclear Polarization Experiments

    NASA Astrophysics Data System (ADS)

    Scott, Ethan; Johnson, Ian; Keller, Dustin; Solid Polarized Target Group Team

    2016-03-01

    To achieve highest polarization levels in dynamic nuclear polarization (DNP) experiments, target materials must be subjected to microwave irradiation at a particular frequency determined by the difference in the nuclear Larmor and electron paramagnetic resonance (EPR) frequencies. However, this resonant frequency is variable; it drifts as a result of radiation damage. Manually adjusting the frequency to accommodate for this fluctuation can be difficult, and improper adjustments negatively impact the polarization. In response to this problem, a controller has been developed which automates the process of seeking and maintaining optimal frequency. The creation of such a controller has necessitated research into the correlation between microwave frequency and corresponding polarization growth or decay rates in DNP experiments. Knowledge gained from the research of this unique relationship has additionally lead to the development of a Monte-Carlo simulation which accurately models polarization as a function of frequency and a number of other parameters. The simulation and controller continue to be refined, however, recent DNP experimentation has confirmed the controller's effectiveness.

  3. Dynamic Nuclear Polarization with a Water-soluble Rigid Biradical

    PubMed Central

    Kiesewetter, Matthew K.; Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.; Swager, Timothy M.

    2012-01-01

    A new biradical polarizing agent, bTbtk-py, for dynamic nuclear polarization (DNP) experiments in aqueous media is reported. The synthesis is discussed in light of the requirements of the optimum, theoretical, biradical system. To date, the DNP NMR signal enhancement resulting from bTbtk-py is the largest of any biradical in the ideal glycerol/water solvent matrix, ε = 230. EPR and X-ray crystallography are used to characterize the molecule and suggest approaches for further optimizing the biradical distance and relative orientation. PMID:22372769

  4. Applied nuclear physics in support of SBSS

    SciTech Connect

    Strottman, D.

    1995-10-01

    Since the advent of the 800-MeV proton linear accelerator over 3 decades ago, the facilities on the Clinton P. Anderson Meson Physics Facility (LAMPF) mesa have pioneered many developments that provide unique capabilities within the Department of Energy (DOE) complex and in the world. New technologies based on the use of the world`s most intense, medium-energy linac, LAMPF, are being developed. They include destruction of long-lived components of nuclear waste, plutonium burning, energy production, production of tritium, and experiments for the science-based stockpile stewardship (SBSS) program. The design, assessment, and safety analysis of potential facilities involve the understanding of complex combinations of nuclear processes, which in turn establish new requirements on nuclear data that transcend the traditional needs of the fission and fusion reactor communities. Other areas of technology such as neutron and proton therapy applications are also placing new requirements on nuclear data. The proposed Los Alamos Neutron Science Center (LANSCE) now under discussion combined with the appropriate instrumentation will have unique features and capabilities of which there were previously only aspirations.

  5. Quantum theory of dynamic nuclear polarization in quantum dots

    NASA Astrophysics Data System (ADS)

    Economou, Sophia; Barnes, Edwin

    2013-03-01

    Nuclear spins play a major role in the dynamics of spin qubits in III-V semiconductor quantum dots. Although the hyperfine interaction between nuclear and electron (or hole) spins is typically viewed as the leading source of decoherence in these qubits, understanding how to experimentally control the nuclear spin polarization can not only ameliorate this problem, but in fact turn the nuclear spins into a valuable resource for quantum computing. Beyond extending decoherence times, control of this polarization can enable universal quantum computation as shown in singlet-triplet qubits and, in addition, offers the possibility of repurposing the nuclear spins into a robust quantum memory. In, we took a first step toward taking advantage of this resource by developing a general, fully quantum theory of non-unitary electron-nuclear spin dynamics with a periodic train of delta-function pulses as the external control driving the electron spin. Here, we extend this approach to other types of controls and further expand on the predictions and physical insights that emerge from the theory.

  6. Quantum mechanical theory of dynamic nuclear polarization in solid dielectrics

    PubMed Central

    Hu, Kan-Nian; Debelouchina, Galia T.; Smith, Albert A.; Griffin, Robert G.

    2011-01-01

    Microwave driven dynamic nuclear polarization (DNP) is a process in which the large polarization present in an electron spin reservoir is transferred to nuclei, thereby enhancing NMR signal intensities. In solid dielectrics there are three mechanisms that mediate this transfer—the solid effect (SE), the cross effect (CE), and thermal mixing (TM). Historically these mechanisms have been discussed theoretically using thermodynamic parameters and average spin interactions. However, the SE and the CE can also be modeled quantum mechanically with a system consisting of a small number of spins and the results provide a foundation for the calculations involving TM. In the case of the SE, a single electron–nuclear spin pair is sufficient to explain the polarization mechanism, while the CE requires participation of two electrons and a nuclear spin, and can be used to understand the improved DNP enhancements observed using biradical polarizing agents. Calculations establish the relations among the electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) frequencies and the microwave irradiation frequency that must be satisfied for polarization transfer via the SE or the CE. In particular, if δ, Δ < ω0I, where δ and Δ are the homogeneous linewidth and inhomogeneous breadth of the EPR spectrum, respectively, we verify that the SE occurs when ωM = ω0S ± ω0I, where ωM, ω0S and ω0I are, respectively, the microwave, and the EPR and NMR frequencies. Alternatively, when Δ > ω0I > δ, the CE dominates the polarization transfer. This two-electron process is optimized when ω0S1−ω0S2=ω0I and ωM∼ω0S1 orω0S2, where ω0S1 and ω0S2 are the EPR Larmor frequencies of the two electrons. Using these matching conditions, we calculate the evolution of the density operator from electron Zeeman order to nuclear Zeeman order for both the SE and the CE. The results provide insights into the influence of the microwave irradiation field, the

  7. Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis

    PubMed Central

    Elkouby, Yaniv M.; Jamieson-Lucy, Allison; Mullins, Mary C.

    2016-01-01

    The source of symmetry breaking in vertebrate oocytes is unknown. Animal—vegetal oocyte polarity is established by the Balbiani body (Bb), a conserved structure found in all animals examined that contains an aggregate of specific mRNAs, proteins, and organelles. The Bb specifies the oocyte vegetal pole, which is key to forming the embryonic body axes as well as the germline in most vertebrates. How Bb formation is regulated and how its asymmetric position is established are unknown. Using quantitative image analysis, we trace oocyte symmetry breaking in zebrafish to a nuclear asymmetry at the onset of meiosis called the chromosomal bouquet. The bouquet is a universal feature of meiosis where all telomeres cluster to one pole on the nuclear envelope, facilitating chromosomal pairing and meiotic recombination. We show that Bb precursor components first localize with the centrosome to the cytoplasm adjacent to the telomere cluster of the bouquet. They then aggregate around the centrosome in a specialized nuclear cleft that we identified, assembling the early Bb. We show that the bouquet nuclear events and the cytoplasmic Bb precursor localization are mechanistically coordinated by microtubules. Thus the animal—vegetal axis of the oocyte is aligned to the nuclear axis of the bouquet. We further show that the symmetry breaking events lay upstream to the only known regulator of Bb formation, the Bucky ball protein. Our findings link two universal features of oogenesis, the Bb and the chromosomal bouquet, to oocyte polarization. We propose that a meiotic—vegetal center couples meiosis and oocyte patterning. Our findings reveal a novel mode of cellular polarization in meiotic cells whereby cellular and nuclear polarity are aligned. We further reveal that in zygotene nests, intercellular cytoplasmic bridges remain between oocytes and that the position of the cytoplasmic bridge coincides with the location of the centrosome meiotic—vegetal organizing center. These

  8. Covariance Spectroscopy Applied to Nuclear Radiation Detection

    SciTech Connect

    Trainham, R., Tinsley, J., Keegan, R., Quam, W.

    2011-09-01

    Covariance spectroscopy is a method of processing second order moments of data to obtain information that is usually absent from average spectra. In nuclear radiation detection it represents a generalization of nuclear coincidence techniques. Correlations and fluctuations in data encode valuable information about radiation sources, transport media, and detection systems. Gaining access to the extra information can help to untangle complicated spectra, uncover overlapping peaks, accelerate source identification, and even sense directionality. Correlations existing at the source level are particularly valuable since many radioactive isotopes emit correlated gammas and neutrons. Correlations also arise from interactions within detector systems, and from scattering in the environment. In particular, correlations from Compton scattering and pair production within a detector array can be usefully exploited in scenarios where direct measurement of source correlations would be unfeasible. We present a covariance analysis of a few experimental data sets to illustrate the utility of the concept.

  9. PRESTO polarization transfer to quadrupolar nuclei: implications for dynamic nuclear polarization.

    PubMed

    Perras, Frédéric A; Kobayashi, Takeshi; Pruski, Marek

    2015-09-21

    We show both experimentally and numerically on a series of model systems that in experiments involving transfer of magnetization from (1)H to the quadrupolar nuclei under magic-angle-spinning (MAS), the PRESTO technique consistently outperforms traditionally used cross polarization (CP), affording more quantitative intensities, improved lineshapes, better overall sensitivity, and straightforward optimization. This advantage derives from the fact that PRESTO circumvents the convoluted and uncooperative spin dynamics during the CP transfer under MAS, by replacing the spin-locking of quadrupolar nuclei with a single central transition selective 90° pulse and using a symmetry-based recoupling sequence in the (1)H channel. This is of particular importance in the context of dynamic nuclear polarization (DNP) NMR of quadrupolar nuclei, where the efficient transfer of enhanced (1)H polarization is desired to obtain the highest sensitivity. PMID:26266874

  10. PRESTO polarization transfer to quadrupolar nuclei: Implications for dynamic nuclear polarization

    DOE PAGESBeta

    Perras, Frederic A.; Kobayashi, Takeshi; Pruski, Marek

    2015-08-04

    In this study, we show both experimentally and numerically on a series of model systems that in experiments involving transfer of magnetization from 1H to the quadrupolar nuclei under magic-angle-spinning (MAS), the PRESTO technique consistently outperforms traditionally used cross polarization (CP), affording more quantitative intensities, improved lineshapes, better overall sensitivity, and straightforward optimization. This advantage derives from the fact that PRESTO circumvents the convoluted and uncooperative spin dynamics during the CP transfer under MAS, by replacing the spin-locking of quadrupolar nuclei with a single central transition selective 90° pulse and using a symmetry-based recoupling sequence in the 1H channel. Thismore » is important in the context of dynamic nuclear polarization (DNP) NMR of quadrupolar nuclei, where the efficient transfer of enhanced 1H polarization is desired to obtain the highest sensitivity.« less

  11. PRESTO polarization transfer to quadrupolar nuclei: Implications for dynamic nuclear polarization

    SciTech Connect

    Perras, Frederic A.; Kobayashi, Takeshi; Pruski, Marek

    2015-08-04

    In this study, we show both experimentally and numerically on a series of model systems that in experiments involving transfer of magnetization from 1H to the quadrupolar nuclei under magic-angle-spinning (MAS), the PRESTO technique consistently outperforms traditionally used cross polarization (CP), affording more quantitative intensities, improved lineshapes, better overall sensitivity, and straightforward optimization. This advantage derives from the fact that PRESTO circumvents the convoluted and uncooperative spin dynamics during the CP transfer under MAS, by replacing the spin-locking of quadrupolar nuclei with a single central transition selective 90° pulse and using a symmetry-based recoupling sequence in the 1H channel. This is important in the context of dynamic nuclear polarization (DNP) NMR of quadrupolar nuclei, where the efficient transfer of enhanced 1H polarization is desired to obtain the highest sensitivity.

  12. Polarization Transfer from Ligands Hyperpolarized by Dissolution Dynamic Nuclear Polarization for Screening in Drug Discovery.

    PubMed

    Min, Hlaing; Sekar, Giridhar; Hilty, Christian

    2015-09-01

    Nuclear magnetic resonance (NMR) spectroscopy is a valuable technique for ligand screening, because it exhibits high specificity toward chemical structure and interactions. Dissolution dynamic nuclear polarization (DNP) is a recent advance in NMR methodology that enables the creation of non-equilibrium spin states, which can dramatically increase NMR sensitivity. Here, the transfer of such spin polarization from hyperpolarized ligand to protein is observed. Mixing hyperpolarized benzamidine with the serine protease trypsin, a "fingerprint" of enhanced protein signals is observed, which shows a different intensity profile than the equilibrium NMR spectrum of the protein, but coincides closely to the frequency profile of a saturation transfer difference (STD) NMR experiment. The DNP experiment benefits from hyperpolarization and enables observation of all frequencies in a single, rapid experiment. Based on these merits, it is an interesting alternative to the widely used STD experiment for identification of protein-ligand interactions. PMID:26315550

  13. Solid effect in magic angle spinning dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

    2012-08-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω _0 ^{ - 2} field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.

  14. Solid effect in magic angle spinning dynamic nuclear polarization

    PubMed Central

    Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

    2012-01-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\omega _0 ^{ - 2}\\end{equation*} \\end{document}ω0−2 field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements

  15. Solid effect in magic angle spinning dynamic nuclear polarization.

    PubMed

    Corzilius, Björn; Smith, Albert A; Griffin, Robert G

    2012-08-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω(0)(-2) field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ε = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of (1)H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear (1)H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect. PMID:22894339

  16. The spin-temperature theory of dynamic nuclear polarization and nuclear spin-lattice relaxation

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Wollan, D. S.

    1974-01-01

    A detailed derivation of the equations governing dynamic nuclear polarization (DNP) and nuclear spin lattice relaxation by use of the spin temperature theory has been carried to second order in a perturbation expansion of the density matrix. Nuclear spin diffusion in the rapid diffusion limit and the effects of the coupling of the electron dipole-dipole reservoir (EDDR) with the nuclear spins are incorporated. The complete expression for the dynamic nuclear polarization has been derived and then examined in detail for the limit of well resolved solid effect transitions. Exactly at the solid effect transition peaks, the conventional solid-effect DNP results are obtained, but with EDDR effects on the nuclear relaxation and DNP leakage factor included. Explicit EDDR contributions to DNP are discussed, and a new DNP effect is predicted.

  17. High-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame

    NASA Astrophysics Data System (ADS)

    Farrar, C. T.; Hall, D. A.; Gerfen, G. J.; Rosay, M.; Ardenkjær-Larsen, J.-H.; Griffin, R. G.

    2000-05-01

    A proton dynamic nuclear polarization (DNP) NMR signal enhancement (ɛ) close to thermal equilibrium, ɛ = 0.89, has been obtained at high field (B0 = 5 T, νepr = 139.5 GHz) using 15 mM trityl radical in a 40:60 water/glycerol frozen solution at 11 K. The electron-nuclear polarization transfer is performed in the nuclear rotating frame with microwave irradiation during a nuclear spin-lock pulse. The growth of the signal enhancement is governed by the rotating frame nuclear spin-lattice relaxation time (T1ρ), which is four orders of magnitude shorter than the nuclear spin-lattice relaxation time (T1n). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T1ρ and is not limited by the much slower lab frame nuclear spin-lattice relaxation rate (1/T1n). The increased repetition rate allowed in the nuclear rotating frame provides an effective enhancement per unit time1/2 of ɛt = 197. The nuclear rotating frame-DNP experiment does not require high microwave power; significant signal enhancements were obtained with a low-power (20 mW) Gunn diode microwave source and no microwave resonant structure. The symmetric trityl radical used as the polarization source is water-soluble and has a narrow EPR linewidth of 10 G at 139.5 GHz making it an ideal polarization source for high-field DNP/NMR studies of biological systems.

  18. Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Nichol, John M.; Harvey, Shannon P.; Shulman, Michael D.; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I.; Halperin, Bertrand I.; Yacoby, Amir

    2015-07-01

    The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.

  19. Quenching of dynamic nuclear polarization by spin–orbit coupling in GaAs quantum dots

    PubMed Central

    Nichol, John M.; Harvey, Shannon P.; Shulman, Michael D.; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I.; Halperin, Bertrand I.; Yacoby, Amir

    2015-01-01

    The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin–orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron–nuclear system, despite weak spin–orbit coupling in GaAs. Using Landau–Zener sweeps to measure static and dynamic properties of the electron spin–flip probability, we observe that the size of the spin–orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin–orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin–orbit coupling in central-spin systems. PMID:26184854

  20. Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots.

    PubMed

    Nichol, John M; Harvey, Shannon P; Shulman, Michael D; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I; Halperin, Bertrand I; Yacoby, Amir

    2015-01-01

    The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems. PMID:26184854

  1. Applying RFID technology in nuclear materials management.

    SciTech Connect

    Tsai, H.; Chen, K.; Liu, Y.; Norair, J. P.; Bellamy, S.; Shuler, J.; SRL; Savi Technology; DOE

    2008-01-01

    The Packaging Certification Program (PCP) of US Department of Energy (DOE) Environmental Management (EM), Office of Safety Management and Operations (EM-60), has developed a radio frequency identification (RFID) system for the management of nuclear materials. Argonne National Laboratory, a PCP supporting laboratory, and Savi Technology, a Lockheed Martin Company, are collaborating in the development of the RFID system, a process that involves hardware modification (form factor, seal sensor and batteries), software development and irradiation experiments. Savannah River National Laboratory and Argonne will soon field test the active RFID system on Model 9975 drums, which are used for storage and transportation of fissile and radioactive materials. Potential benefits of the RFID system are enhanced safety and security, reduced need for manned surveillance, real time access of status and history data, and overall cost effectiveness.

  2. Nuclear depolarization and absolute sensitivity in magic-angle spinning cross effect dynamic nuclear polarization.

    PubMed

    Mentink-Vigier, Frédéric; Paul, Subhradip; Lee, Daniel; Feintuch, Akiva; Hediger, Sabine; Vega, Shimon; De Paëpe, Gaël

    2015-09-14

    Over the last two decades solid state Nuclear Magnetic Resonance has witnessed a breakthrough in increasing the nuclear polarization, and thus experimental sensitivity, with the advent of Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP). To enhance the nuclear polarization of protons, exogenous nitroxide biradicals such as TOTAPOL or AMUPOL are routinely used. Their efficiency is usually assessed as the ratio between the NMR signal intensity in the presence and the absence of microwave irradiation εon/off. While TOTAPOL delivers an enhancement εon/off of about 60 on a model sample, the more recent AMUPOL is more efficient: >200 at 100 K. Such a comparison is valid as long as the signal measured in the absence of microwaves is merely the Boltzmann polarization and is not affected by the spinning of the sample. However, recent MAS-DNP studies at 25 K by Thurber and Tycko (2014) have demonstrated that the presence of nitroxide biradicals combined with sample spinning can lead to a depolarized nuclear state, below the Boltzmann polarization. In this work we demonstrate that TOTAPOL and AMUPOL both lead to observable depolarization at ≈110 K, and that the magnitude of this depolarization is radical dependent. Compared to the static sample, TOTAPOL and AMUPOL lead, respectively, to nuclear polarization losses of up to 20% and 60% at a 10 kHz MAS frequency, while Trityl OX63 does not depolarize at all. This experimental work is analyzed using a theoretical model that explains how the depolarization process works under MAS and gives new insights into the DNP mechanism and into the spin parameters, which are relevant for the efficiency of a biradical. In light of these results, the outstanding performance of AMUPOL must be revised and we propose a new method to assess the polarization gain for future radicals. PMID:26235749

  3. High Field Dynamic Nuclear Polarization NMR with Surfactant Sheltered Biradicals

    PubMed Central

    2015-01-01

    We illustrate the ability to place a water-insoluble biradical, bTbk, into a glycerol/water matrix with the assistance of a surfactant, sodium octyl sulfate (SOS). This surfactant approach enables a previously water insoluble biradical, bTbk, with favorable electron–electron dipolar coupling to be used for dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) experiments in frozen, glassy, aqueous media. Nuclear Overhauser enhancement (NOE) and paramagnetic relaxation enhancement (PRE) experiments are conducted to determine the distribution of urea and several biradicals within the SOS macromolecular assembly. We also demonstrate that SOS assemblies are an effective approach by which mixed biradicals are created through an assembly process. PMID:24506193

  4. Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

    2015-09-01

    Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160 K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea -eb - n } during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle

  5. Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization.

    PubMed

    Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

    2015-09-01

    Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea-eb-n} during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle. This

  6. Dynamic nuclear polarization of nucleic acid with endogenously bound manganese.

    PubMed

    Wenk, Patricia; Kaushik, Monu; Richter, Diane; Vogel, Marc; Suess, Beatrix; Corzilius, Björn

    2015-09-01

    We report the direct dynamic nuclear polarization (DNP) of (13)C nuclei of a uniformly [(13)C,(15)N]-labeled, paramagnetic full-length hammerhead ribozyme (HHRz) complex with Mn(2+) where the enhanced polarization is fully provided by the endogenously bound metal ion and no exogenous polarizing agent is added. A (13)C enhancement factor of ε = 8 was observed by intra-complex DNP at 9.4 T. In contrast, "conventional" indirect and direct DNP experiments were performed using AMUPol as polarizing agent where we obtained a (1)H enhancement factor of ε ≈ 250. Comparison with the diamagnetic (Mg(2+)) HHRz complex shows that the presence of Mn(2+) only marginally influences the (DNP-enhanced) NMR properties of the RNA. Furthermore two-dimensional correlation spectra ((15)N-(13)C and (13)C-(13)C) reveal structural inhomogeneity in the frozen, amorphous state indicating the coexistence of several conformational states. These demonstrations of intra-complex DNP using an endogenous metal ion as well as DNP-enhanced MAS NMR of RNA in general yield important information for the development of new methods in structural biology. PMID:26219517

  7. Enhancement of nuclear polarization with frequency modulated microwaves

    SciTech Connect

    Dulya, C.

    1995-04-01

    The authors report their discovery of a gain by a factor of two in the growth rate and of a gain by {approx} 1.7 in the maximum dynamic nuclear polarization (DNP) of deuteron in the large polarized targets of the Spin Muon Collaboration. These large gains resulted from a frequency modulation (FM) of the {approx} 69 GHz microwave field used for DNP; this FM had a 30 MHz amplitude and {approx} 1 KHz frequency. The target material is glassy deuterated 1-butanol doped with a paramagnetic Cr(V) complex. Measurements of the 430 MHz broad electron paramagnetic resonance (EPR) absorption spectrum in the 2.5 T field were performed by a novel differential bolometric technique. They show that FM gives rise to an additional microwave absorption which depends on the amplitude and frequency of FM and which is more pronounced in the edges of the EPR spectrum. For deuterons, polarizations of 0.46 and {minus}0.53 have been obtained. Similar although less dramatic effects were observed for protons where FM increased the polarization by less than 10% and the growth rate by {approx} 20%.

  8. NMR-based structural biology enhanced by dynamic nuclear polarization at high magnetic field.

    PubMed

    Koers, Eline J; van der Cruijsen, Elwin A W; Rosay, Melanie; Weingarth, Markus; Prokofyev, Alexander; Sauvée, Claire; Ouari, Olivier; van der Zwan, Johan; Pongs, Olaf; Tordo, Paul; Maas, Werner E; Baldus, Marc

    2014-11-01

    Dynamic nuclear polarization (DNP) has become a powerful method to enhance spectroscopic sensitivity in the context of magnetic resonance imaging and nuclear magnetic resonance spectroscopy. We show that, compared to DNP at lower field (400 MHz/263 GHz), high field DNP (800 MHz/527 GHz) can significantly enhance spectral resolution and allows exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes under magic angle spinning conditions. Applied to a membrane-embedded K(+) channel, this approach allowed us to refine the membrane-embedded channel structure and revealed conformational substates that are present during two different stages of the channel gating cycle. High-field DNP thus offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment. PMID:25284462

  9. Mechanisms of Dynamic Nuclear Polarization in Insulating Solids

    PubMed Central

    Can, T.V.; Ni, Q.Z.; Griffin, R.G.

    2015-01-01

    Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80–100 K. PMID:25797002

  10. Mechanisms of dynamic nuclear polarization in insulating solids

    NASA Astrophysics Data System (ADS)

    Can, T. V.; Ni, Q. Z.; Griffin, R. G.

    2015-04-01

    Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80-100 K.

  11. Fast passage dynamic nuclear polarization on rotating solids

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, Frederic; Akbey, Ümit; Hovav, Yonatan; Vega, Shimon; Oschkinat, Hartmut; Feintuch, Akiva

    2012-11-01

    Magic Angle Spinning (MAS) Dynamic Nuclear Polarization (DNP) has proven to be a very powerful way to improve the signal to noise ratio of NMR experiments on solids. The experiments have in general been interpreted considering the Solid-Effect (SE) and Cross-Effect (CE) DNP mechanisms while ignoring the influence of sample spinning. In this paper, we show experimental data of MAS-DNP enhancements of 1H and 13C in proline and SH3 protein in glass forming water/glycerol solvent containing TOTAPOL. We also introduce a theoretical model that aims at explaining how the nuclear polarization is built in MAS-DNP experiments. By using Liouville space based simulations to include relaxation on two simple spin models, {electron-nucleus} and {electron-electron-nucleus}, we explain how the basic MAS-SE-DNP and MAS-CE-DNP processes work. The importance of fast energy passages and short level anti-crossing is emphasized and the differences between static DNP and MAS-DNP is explained. During a single rotor cycle the enhancement in the {electron-electron-nucleus} system arises from MAS-CE-DNP involving at least three kinds of two-level fast passages: an electron-electron dipolar anti-crossing, a single quantum electron MW encounter and an anti-crossing at the CE condition inducing nuclear polarization in- or decrements. Numerical, powder-averaged, simulations were performed in order to check the influence of the experimental parameters on the enhancement efficiencies. In particular we show that the spinning frequency dependence of the theoretical MAS-CE-DNP enhancement compares favorably with the experimental 1H and 13C MAS-DNP enhancements of proline and SH3.

  12. Polarization of the nuclear surface in deformed nuclei

    NASA Astrophysics Data System (ADS)

    Scamps, Guillaume; Lacroix, Denis; Adamian, G. G.; Antonenko, N. V.

    2013-12-01

    The density profiles of around 750 nuclei are analyzed using the Skyrme energy density functional theory. Among them, more than 350 nuclei are found to be deformed. In addition to rather standard properties of the density, we report a nontrivial behavior of the nuclear diffuseness as the system becomes more and more deformed. Besides the geometric effects expected in a rigid body, the diffuseness acquires a rather complex behavior leading to a reduction of the diffuseness along the main axis of deformation simultaneously with an increase of the diffuseness along the other axis. The possible isospin dependence of this polarization is studied. This effect, which is systematically seen in medium and heavy nuclei, can affect the nuclear dynamical properties. A quantitative example is given with the fusion barrier in the 40Ca+238U reaction.

  13. Theoretical aspects of dynamic nuclear polarization in the solid state--spin temperature and thermal mixing.

    PubMed

    Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

    2013-01-01

    Dynamic nuclear polarization is a method which allows for a dramatic increase of the NMR signals due to polarization transfer between electrons and their neighboring nuclei, via microwave irradiation. These experiments have become popular in recent years due to the ability to create hyper-polarized chemically and biologically relevant molecules, in frozen glass forming mixtures containing free radicals. Three mechanisms have been proposed for the polarization transfer between electrons and their surrounding nuclei in such non-conducting samples: the solid effect and cross effect mechanisms, which are based on quantum mechanics and relaxation on small spin systems, and thermal mixing, which originates from the thermodynamic macroscopic notion of spin temperature. We have recently introduced a spin model, which is based on the density matrix formalism and includes relaxation, and applied it to study the solid effect and cross effect mechanisms on small spin systems. In this publication we use the same model to describe the thermal mixing mechanism, and the creation of spin temperature. This is obtained without relying on the spin temperature formalism. Simulations of small model systems are used on systems with homogeneously and inhomogeneously broadened EPR lines. For the case of a homogeneously broadened line we show that the nuclear enhancement results from the thermal mixing and solid effect mechanisms, and that spin temperatures are created in the system. In the inhomogeneous case the enhancements are attributed to the solid effect and cross effect mechanisms, but not thermal mixing. PMID:23160533

  14. Solvent-Free Dynamic Nuclear Polarization of Amorphous and Crystalline ortho-Terphenyl

    PubMed Central

    Ong, Ta-Chung; Mak-Jurkauskas, Melody L.; Walish, Joseph J.; Michaelis, Vladimir K.; Corzilius, Björn; Smith, Albert A.; Clausen, Andrew M.; Cheetham, Janet C.; Swager, Timothy M.; Griffin, Robert G.

    2014-01-01

    Dynamic nuclear polarization (DNP) of amorphous and crystalline ortho-terphenyl (OTP) in the absence of glass forming agents is presented in order to gauge the feasibility of applying DNP to pharmaceutical solid-state nuclear magnetic resonance experiments and to study the effect of intermolecular structure, or lack thereof, on the DNP enhancement. By way of 1H–13C cross-polarization, we obtained a DNP enhancement (ε) of 58 for 95% deuterated OTP in the amorphous state using the biradical bis-TEMPO terephthalate (bTtereph) and ε of 36 in the crystalline state. Measurements of the 1H T1 and electron paramagnetic resonance experiments showed the crystallization process led to phase separation of the polarization agent, creating an inhomogeneous distribution of radicals within the sample. Consequently, the effective radical concentration was decreased in the bulk OTP phase, and long-range 1H–1H spin diffusion was the main polarization propagation mechanism. Preliminary DNP experiments with the glass-forming anti-inflammation drug, indomethacin, showed promising results, and further studies are underway to prepare DNP samples using pharmaceutical techniques. PMID:23421391

  15. Investigation of a naphthalene pitch by high-resolution solid-state dynamic nuclear polarization.

    PubMed

    Zhou, J; Yang, B; Hu, J; Hu, H; Li, L; Qiu, J; Zeng, F; Ye, C

    1996-04-01

    The possibility of applying the dynamic nuclear polarization (DNP) technique to a study of char is explored with a naphthalene-derived pitch. It is shown that a 13C DNP enhancement factor of about 10(2) is obtained when the polarization is directly transferred from the unpaired electrons to the 13C nuclei. An undistorted spectrum with an enhancement factor of 8 is obtained by the DNP cross-polarization magic-angle spinning nuclear magnetic resonance (DNP-CP-MAS NMR) method. With such a high increase in S/N, it is possible to measure the 13C polarization time (Tp) and the spin-lattice relaxation time (T1) of the system in a reasonable experimental time. The resultant values are Tp = 19 s and T1 = 38 s, respectively. Based on the DNP enhancement as a function of the microwave frequency, it is found that the predominant DNP mechanism in the pitch is the solid-state effect. PMID:8784951

  16. Polarization enhanced Nuclear Quadrupole Resonance with an atomic magnetometer

    NASA Astrophysics Data System (ADS)

    Malone, Michael W.; Barrall, Geoffrey A.; Espy, Michelle A.; Monti, Mark C.; Alexson, Dimitri A.; Okamitsu, Jeffrey K.

    2016-05-01

    Nuclear Quadrupole Resonance (NQR) has been demonstrated for the detection of 14-N in explosive compounds. Application of a material specific radio-frequency (RF) pulse excites a response typically detected with a wire- wound antenna. NQR is non-contact and material specific, however fields produced by NQR are typically very weak, making demonstration of practical utility challenging. For certain materials, the NQR signal can be increased by transferring polarization from hydrogen nuclei to nitrogen nuclei using external magnetic fields. This polarization enhancement (PE) can enhance the NQR signal by an order of magnitude or more. Atomic magnetometers (AM) have been shown to improve detection sensitivity beyond a conventional antenna by a similar amount. AM sensors are immune to piezo-electric effects that hamper conventional NQR, and can be combined to form a gradiometer for effective RF noise cancellation. In principle, combining polarization enhancement with atomic magnetometer detection should yield improvement in signal-to-noise ratio that is the product of the two methods, 100-fold or more over conventional NQR. However both methods are even more exotic than traditional NQR, and have never been combined due to challenges in operating a large magnetic field and ultra-sensitive magnetic field sensor in proximity. Here we present NQR with and without PE with an atomic magnetometer, demonstrating signal enhancement greater than 20-fold for ammonium nitrate. We also demonstrate PE for PETN using a traditional coil for detection with an enhancement factor of 10. Experimental methods and future applications are discussed.

  17. Dynamic nuclear-polarization studies of paramagnetic species in solution

    SciTech Connect

    Glad, W.E.

    1982-07-01

    Dynamic Nuclear Polarization (DNP) was used to measure the electron spin lattice relaxation times, T/sub 1/, of transition metal ions in aqueous solution. Saturation which is induced in the electron spin system is transferred to the solvent proton spins by dipole-dipole interactions. The change in the polarization of the proton spins is much larger than it is in the electron spins. The change in proton polarization is easily measured by proton Nuclear Magnetic Resonance (NMR). In one experimental arrangement the sample solution was continuously flowed through a microwave cavity to the NMR coil. The NMR was observed with a continuous wave NMR spectrometer. In a second arrangement the whole sample tube was moved from within the microwave cavity to the NMR coil in less than 40 ms by a blast of compressed air. The NMR was then observed with a pulse-Fourier-transform spectrometer. With the second arrangement a mean-square microwave magnetic field at the sample of more than 10 G/sup 2/ is obtainable with 14 W of microwave power. Measurements of DNP at 9 GHz were made on aqueous solutions of VO/sup 2 +/, Mn/sup 2 +/, Cr(CN)/sub 6//sup 3 -/, Cu/sup 2 +/ and Cu(ethylenediamine)/sub 2/(H/sub 2/0)/sub 2//sup 2 +/ ions from 3 to 60/sup 0/C. It was also possible to observe DNP on resolved proton resonances from mixed water-acetonitrile solutions of VO/sup 2 +/ and Cr(CN)/sub 6//sup 3 -/ ions.

  18. A 3D-printed high power nuclear spin polarizer.

    PubMed

    Nikolaou, Panayiotis; Coffey, Aaron M; Walkup, Laura L; Gust, Brogan M; LaPierre, Cristen D; Koehnemann, Edward; Barlow, Michael J; Rosen, Matthew S; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-01-29

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of (129)Xe and (1)H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of "off-the-shelf" components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity (129)Xe polarization values in a 0.5 L optical pumping cell, including ∼74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the (129)Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10(-2) min(-1)] and in-cell (129)Xe spin-lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for (129)Xe and Rb (PRb ∼ 96%). Hyperpolarization-enhanced (129)Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  19. A 3D-Printed High Power Nuclear Spin Polarizer

    PubMed Central

    Nikolaou, Panayiotis; Coffey, Aaron M.; Walkup, Laura L.; Gust, Brogan M.; LaPierre, Cristen D.; Koehnemann, Edward; Barlow, Michael J.; Rosen, Matthew S.; Goodson, Boyd M.; Chekmenev, Eduard Y.

    2015-01-01

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of 129Xe and 1H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of “off-the-shelf” components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10−2 min−1] and in-cell 129Xe spin−lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  20. Image reconstruction techniques applied to nuclear mass models

    NASA Astrophysics Data System (ADS)

    Morales, Irving O.; Isacker, P. Van; Velazquez, V.; Barea, J.; Mendoza-Temis, J.; Vieyra, J. C. López; Hirsch, J. G.; Frank, A.

    2010-02-01

    A new procedure is presented that combines well-known nuclear models with image reconstruction techniques. A color-coded image is built by taking the differences between measured masses and the predictions given by the different theoretical models. This image is viewed as part of a larger array in the (N,Z) plane, where unknown nuclear masses are hidden, covered by a “mask.” We apply a suitably adapted deconvolution algorithm, used in astronomical observations, to “open the window” and see the rest of the pattern. We show that it is possible to improve significantly mass predictions in regions not too far from measured nuclear masses.

  1. Polarization of nuclear spins by a cold nanoscale resonator

    SciTech Connect

    Butler, Mark C.; Weitekamp, Daniel P.

    2011-12-15

    A cold nanoscale resonator coupled to a system of nuclear spins can induce spin relaxation. In the low-temperature limit where spin-lattice interactions are ''frozen out,'' spontaneous emission by nuclear spins into a resonant mechanical mode can become the dominant mechanism for cooling the spins to thermal equilibrium with their environment. We provide a theoretical framework for the study of resonator-induced cooling of nuclear spins in this low-temperature regime. Relaxation equations are derived from first principles, in the limit where energy donated by the spins to the resonator is quickly dissipated into the cold bath that damps it. A physical interpretation of the processes contributing to spin polarization is given. For a system of spins that have identical couplings to the resonator, the interaction Hamiltonian conserves spin angular momentum, and the resonator cannot relax the spins to thermal equilibrium unless this symmetry is broken by the spin Hamiltonian. The mechanism by which such a spin system becomes ''trapped'' away from thermal equilibrium can be visualized using a semiclassical model, which shows how an indirect spin-spin interaction arises from the coupling of multiple spins to one resonator. The internal spin Hamiltonian can affect the polarization process in two ways: (1) By modifying the structure of the spin-spin correlations in the energy eigenstates, and (2) by splitting the degeneracy within a manifold of energy eigenstates, so that zero-frequency off-diagonal terms in the density matrix are converted to oscillating coherences. Shifting the frequencies of these coherences sufficiently far from zero suppresses the development of resonator-induced correlations within the manifold during polarization from a totally disordered state. Modification of the spin-spin correlations by means of either mechanism affects the strength of the fluctuating spin dipole that drives the resonator. In the case where product states can be chosen as energy

  2. Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy, a new approach to study humic material?

    NASA Astrophysics Data System (ADS)

    Knicker, Heike; Lange, Sascha; van Rossum, Barth; Oschkinat, Hartmut

    2016-04-01

    Compared to solution NMR spectroscopy, solid-state NMR spectra suffer from broad resonance lines and low resolution. This could be overcome by the use of 2-dimenstional solid-state NMR pulse sequences. Until recently, this approach has been unfeasible as a routine tool in soil chemistry, mainly because of the low NMR sensitivity of the respective samples. A possibility to circumvent those sensitivity problems represents high-field Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy (Barnes et al., 2008), allowing considerable signal enhancements (Akbey et al., 2010). This is achieved by a microwave-driven transfer of polarization from a paramagnetic center to nuclear spins. Application of DNP to MAS spectra of biological systems (frozen solutions) showed enhancements of the factor 40 to 50 (Hall et al., 1997). Enhancements of this magnitude, thus may enable the use of at least some of the 2D solid-state NMR techniques that are presently already applied for pure proteins but are difficult to apply to soil peptides in their complex matrix. After adjusting the required acquisition parameters to the system "soil organic matter", lower but still promising enhancement factors were achieved. Additional optimization was performed and allowed the acquisition of 2D 13C and 15N solid-state NMR spectra of humified 13C and 15N enriched plant residues. Within the present contribution, the first solid-state DNP NMR spectra of humic material are presented. Those data demonstrate the great potential of this approach which certainly opens new doors for a better understanding of biochemical processes in soils, sediments and water. Akbey, Ü., Franks, W.T., Linden, A., Lange, S., Griffin, R.G., van Rossum, B.-J., Oschkinat, H., 2010. Dynamic nuclear polarization of deuterated proteins. Angewandte Chemie International Edition 49, 7803-7806. Barnes, A.B., De Paëpe, G., van der Wel, P.C.A., Hu, K.N., Joo, C.G., Bajaj, V.S., Mak-Jurkauskas, M.L., Sirigiri, J.R., Herzfeld, J

  3. Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K

    PubMed Central

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

    2012-01-01

    We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20–25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier (Thurber et al., J. Magn. Reson. 2008) [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids. PMID:23238592

  4. Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids.

  5. Chemistry and biochemistry of 13C hyperpolarized magnetic resonance using dynamic nuclear polarization

    PubMed Central

    Keshari, Kayvan R.; Wilson, David M.

    2014-01-01

    The study of transient chemical phenomena by conventional NMR has proved elusive, particularly for non-1H nuclei. For 13C, hyperpolarization using the dynamic nuclear polarization (DNP) technique has emerged as a powerful means to improve SNR. The recent development of rapid dissolution DNP methods has facilitated previously impossible in vitro and in vivo study of small molecules. This review presents the basics of the DNP technique, identification of appropriate DNP substrates, and approaches to increase hyperpolarized signal lifetimes. Also addressed are the biochemical events to which DNP-NMR has been applied, with descriptions of several probes that have met with in vivo success. PMID:24363044

  6. Chemistry and biochemistry of 13C hyperpolarized magnetic resonance using dynamic nuclear polarization.

    PubMed

    Keshari, Kayvan R; Wilson, David M

    2014-03-01

    The study of transient chemical phenomena by conventional NMR has proved elusive, particularly for non-(1)H nuclei. For (13)C, hyperpolarization using the dynamic nuclear polarization (DNP) technique has emerged as a powerful means to improve SNR. The recent development of rapid dissolution DNP methods has facilitated previously impossible in vitro and in vivo study of small molecules. This review presents the basics of the DNP technique, identification of appropriate DNP substrates, and approaches to increase hyperpolarized signal lifetimes. Also addressed are the biochemical events to which DNP-NMR has been applied, with descriptions of several probes that have met with in vivo success. PMID:24363044

  7. Multistability and spin diffusion enhanced lifetimes in dynamic nuclear polarization in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Forster, F.; Mühlbacher, M.; Schuh, D.; Wegscheider, W.; Giedke, G.; Ludwig, S.

    2015-12-01

    The control of nuclear spins in quantum dots is essential to explore their many-body dynamics and exploit their prospects for quantum information processing. We present a unique combination of dynamic nuclear spin polarization and electric-dipole-induced spin resonance in an electrostatically defined double quantum dot (DQD) exposed to the strongly inhomogeneous field of two on-chip nanomagnets. Our experiments provide direct and unrivaled access to the nuclear spin polarization distribution and allow us to establish and characterize multiple fixed points. Further, we demonstrate polarization of the DQD environment by nuclear spin diffusion which significantly stabilizes the nuclear spins inside the DQD.

  8. Dynamic nuclear polarization of nitrogen-15 in benzamide.

    PubMed

    Hu, J Z; Zhou, J; Yang, B; Li, L; Qiu, J; Ye, C; Solum, M S; Wind, R A; Pugmire, R J; Grant, D M

    1997-04-01

    A 15N dynamic nuclear polarization (DNP) experiment is reported in which a 15N DNP enhancement factor of approximately 2.6 x 10(2) is obtained on free radical doped samples of 99% 15N labeled benzamide. The free radicals BDPA (1:1 complex of alpha, gamma-bisdiphenylene-beta-phenylallyl with benzene) and DPPH (2,2-Di(4-tert-octylphenyl)-1-picrylhydrazyl) are used as dopants and the spin relaxation effects of adding these dopants are studied by means of changes in proton and nitrogen T1 values of the samples. The combination in solids of a very low natural abundance, 0.37%, a small gyromagnetic ratio, and a long spin-lattice relaxation time for 15N nuclei create severe sensitivity problems that, in large part, are ameliorated by the signal enhancement observed in the 15N DNP experiment on samples containing free electrons. PMID:9203286

  9. Overhauser dynamic nuclear polarization amplification of NMR flow imaging

    NASA Astrophysics Data System (ADS)

    Lingwood, Mark D.; Sederman, Andrew J.; Mantle, Mick D.; Gladden, Lynn F.; Han, Songi

    2012-03-01

    We describe the first study comparing the ability of phase shift velocity imaging and Overhauser dynamic nuclear polarization (DNP)-enhanced imaging to generate contrast for visualizing the flow of water. Prepolarization of water by the Overhauser DNP mechanism is performed in the 0.35 T fringe field of an unshielded 2.0 T non-clinical MRI magnet, followed by the rapid transfer of polarization-enhanced water to the 2.0 T imaging location. This technique, previously named remotely enhanced liquids for image contrast (RELIC), produces a continuous flow of hyperpolarized water and gives up to an -8.2-fold enhanced signal within the image with respect to thermally polarized signal at 2.0 T. Using flow through a cylindrical expansion phantom as a model system, spin-echo intensity images with DNP are compared to 3D phase shift velocity images to illustrate the complementary information available from the two techniques. The spin-echo intensity images enhanced with DNP show that the levels of enhancement provide an estimate of the transient propagation of flow, while the phase shift velocity images quantitatively measure the velocity of each imaging voxel. Phase shift velocity images acquired with and without DNP show that DNP weights velocity values towards those of the inflowing (DNP-enhanced) water, while velocity images without DNP more accurately reflect the average steady-state velocity of each voxel. We conclude that imaging with DNP prepolarized water better captures the transient path of water shortly after injection, while phase shift velocity imaging is best for quantifying the steady-state flow of water throughout the entire phantom.

  10. Highly Repeatable Dissolution Dynamic Nuclear Polarization for Heteronuclear NMR Metabolomics.

    PubMed

    Bornet, Aurélien; Maucourt, Mickaël; Deborde, Catherine; Jacob, Daniel; Milani, Jonas; Vuichoud, Basile; Ji, Xiao; Dumez, Jean-Nicolas; Moing, Annick; Bodenhausen, Geoffrey; Jannin, Sami; Giraudeau, Patrick

    2016-06-21

    At natural (13)C abundance, metabolomics based on heteronuclear NMR is limited by sensitivity. We have recently demonstrated how hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) assisted by cross-polarization (CP) provides a reliable way of enhancing the sensitivity of heteronuclear NMR in dilute mixtures of metabolites. In this Technical Note, we evaluate the precision of this experimental approach, a critical point for applications to metabolomics. The higher the repeatability, the greater the likelihood that one can detect small biologically relevant differences between samples. The average repeatability of our state-of-the-art D-DNP NMR equipment for samples of metabolomic relevance (20 mg dry weight tomato extracts) is 3.6% for signals above the limit of quantification (LOQ) and 6.4% when all the signals above the limit of detection (LOD) are taken into account. This first report on the repeatability of D-DNP highlights the compatibility of the technique with the requirements of metabolomics and confirms its potential as an analytical tool for such applications. PMID:27253320

  11. Accelerating Nuclear Magnetic Resonance (NMR) Analysis of Soil Organic Matter with Dynamic Nuclear Polarization (DNP) Enhancement

    NASA Astrophysics Data System (ADS)

    Normand, A. E.; Smith, A. N.; Long, J. R.; Reddy, K. R.

    2014-12-01

    13C magic angle spinning (MAS) solid state Nuclear Magnetic Resonance (ssNMR) has become an essential tool for discerning the chemical composition of soil organic matter (SOM). However, the technique is limited due to the inherent insensitivity of NMR resulting in long acquisition times, especially for low carbon (C) soil. The pursuits of higher magnetic fields or concentrating C with hydrofluoric acid are limited solutions for signal improvement. Recent advances in dynamic nuclear polarization (DNP) have addressed the insensitivity of NMR. DNP utilizes the greater polarization of an unpaired electron in a given magnetic field and transfers that polarization to an NMR active nucleus of interest via microwave irradiation. Signal enhancements of up to a few orders of magnitude have been achieved for various DNP experiments. In this novel study, we conduct DNP 13C cross-polarization (CP) MAS ssNMR experiments of SOM varying in soil C content and chemical composition. DNP signal enhancements reduce the experiment run time allowing samples with low C to be analyzed in hours rather than days. We compare 13C CP MAS ssNMR of SOM with multiple magnetic field strengths, hydrofluoric acid treatment, and novel DNP approaches. We also explore DNP surface enhanced NMR Spectroscopy (SENP) to determine the surface chemistry of SOM. The presented results and future DNP MAS ssNMR advances will lead to further understanding of the nature and processes of SOM.

  12. Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

    NASA Astrophysics Data System (ADS)

    Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.

    2014-07-01

    As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.

  13. Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

    SciTech Connect

    Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.

    2014-07-28

    As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF{sub 6} sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.

  14. Dynamic nuclear polarization in the hyperfine-field-dominant region

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-06-01

    Dynamic nuclear polarization (DNP) allows measuring enhanced nuclear magnetic resonance (NMR) signals. Though the efficiency of DNP has been known to increase at low fields, the usefulness of DNP has not been throughly investigated yet. Here, using a superconducting quantum interference device-based NMR system, we performed a series of DNP experiments with a nitroxide radical and measured DNP spectra at several magnetic fields down to sub-microtesla. In the DNP spectra, the large overlap of two peaks having opposite signs results in net enhancement factors, which are significantly lower than theoretical expectations [30] and nearly invariant with respect to magnetic fields below the Earth's field. The numerical analysis based on the radical's Hamiltonian provides qualitative explanations of such features. The net enhancement factor reached 325 at maximum experimentally, but our analysis reveals that the local enhancement factor at the center of the rf coil is 575, which is unaffected by detection schemes. We conclude that DNP in the hyperfine-field-dominant region yields sufficiently enhanced NMR signals at magnetic fields above 1 μ T.

  15. Solution NMR of polypeptides hyperpolarized by dynamic nuclear polarization.

    PubMed

    Ragavan, Mukundan; Chen, Hsueh-Ying; Sekar, Giridhar; Hilty, Christian

    2011-08-01

    Hyperpolarization of nuclear spins through techniques such as dynamic nuclear polarization (DNP) can greatly increase the signal-to-noise ratio in NMR measurements, thus eliminating the need for signal averaging. This enables the study of many dynamic processes which would otherwise not be amenable to study by NMR spectroscopy. A report of solid- to liquid-state DNP of a short peptide, bacitracin A, as well as of a full-length protein, L23, is presented here. The polypeptides are hyperpolarized at low temperature and dissolved for NMR signal acquisition in the liquid state in mixtures of organic solvent and water. Signal enhancements of 300-2000 are obtained in partially deuterated polypeptide when hyperpolarized on (13)C and of 30-180 when hyperpolarized on (1)H. A simulated spectrum is used to identify different resonances in the hyperpolarized (13)C spectra, and the relation between observed signal enhancement for various groups in the protein and relaxation parameters measured from the hyperpolarized samples is discussed. Thus far, solid- to liquid-state DNP has been used in conjunction with small molecules. The results presented here, however, demonstrate the feasibility of hyperpolarizing larger proteins, with potential applications toward the study of protein folding or macromolecular interactions. PMID:21651293

  16. Coherent transfer of nuclear spin polarization in field-cycling NMR experiments

    SciTech Connect

    Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L.; Vieth, Hans-Martin

    2013-12-28

    Coherent polarization transfer effects in a coupled spin network have been studied over a wide field range. The transfer mechanism is based on exciting zero-quantum coherences between the nuclear spin states by means of non-adiabatic field jump from high to low magnetic field. Subsequent evolution of these coherences enables conversion of spin order in the system, which is monitored after field jump back to high field. Such processes are most efficient when the spin system passes through an avoided level crossing during the field variation. The polarization transfer effects have been demonstrated for N-acetyl histidine, which has five scalar coupled protons; the initial spin order has been prepared by applying RF-pulses at high magnetic field. The observed oscillatory transfer kinetics is taken as a clear indication of a coherent mechanism; level crossing effects have also been demonstrated. The experimental data are in very good agreement with the theoretical model of coherent polarization transfer. The method suggested is also valid for other types of initial polarization in the spin system, most notably, for spin hyperpolarization.

  17. Dynamic nuclear polarization using frequency modulation at 3.34 T

    NASA Astrophysics Data System (ADS)

    Hovav, Y.; Feintuch, A.; Vega, S.; Goldfarb, D.

    2014-01-01

    During dynamic nuclear polarization (DNP) experiments polarization is transferred from unpaired electrons to their neighboring nuclear spins, resulting in dramatic enhancement of the NMR signals. While in most cases this is achieved by continuous wave (cw) irradiation applied to samples in fixed external magnetic fields, here we show that DNP enhancement of static samples can improve by modulating the microwave (MW) frequency at a constant field of 3.34 T. The efficiency of triangular shaped modulation is explored by monitoring the 1H signal enhancement in frozen solutions containing different TEMPOL radical concentrations at different temperatures. The optimal modulation parameters are examined experimentally and under the most favorable conditions a threefold enhancement is obtained with respect to constant frequency DNP in samples with low radical concentrations. The results are interpreted using numerical simulations on small spin systems. In particular, it is shown experimentally and explained theoretically that: (i) The optimal modulation frequency is higher than the electron spin-lattice relaxation rate. (ii) The optimal modulation amplitude must be smaller than the nuclear Larmor frequency and the EPR line-width, as expected. (iii) The MW frequencies corresponding to the enhancement maxima and minima are shifted away from one another when using frequency modulation, relative to the constant frequency experiments.

  18. Nuclear polarization study: new frontiers for tests of QED in heavy highly charged ions.

    PubMed

    Volotka, Andrey V; Plunien, Günter

    2014-07-11

    A systematic investigation of the nuclear polarization effects in one- and few-electron heavy ions is presented. The nuclear polarization corrections in the zeroth and first orders in 1/Z are evaluated to the binding energies, the hyperfine splitting, and the bound-electron g factor. It is shown that the nuclear polarization contributions can be substantially canceled simultaneously with the rigid nuclear corrections. This allows for new prospects for probing the QED effects in a strong electromagnetic field and the determination of fundamental constants. PMID:25062173

  19. A model for the polarization of neurons by extrinsically applied electric fields.

    PubMed Central

    Tranchina, D; Nicholson, C

    1986-01-01

    A model is presented for the subthreshold polarization of a neuron by an applied electric field. It gives insight into how morphological features of a neuron affect its polarizability. The neuronal model consists of one or more extensively branched dendritic trees, a lumped somatic impedance, and a myelinated axon with nodes of Ranvier. The dendritic trees branch according to the 3/2-power rule of Rall, so that each tree has an equivalent cylinder representation. Equations for the membrane potential at the soma and at the nodes of Ranvier, given an arbitrary specified external potential, are derived. The solutions determine the contributions made by the dendritic tree and the axon to the net polarization at the soma. In the case of a spatially constant electric field, both the magnitude and sign of the polarization depend on simple combinations of parameters describing the neuron. One important combination is given by the ratio of internal resistances for longitudinal current spread along the dendritic tree trunk and along the axon. A second is given by the ratio between the DC space constant for the dendritic tree trunk and the distance between nodes of Ranvier in the axon. A third is given by the product of the electric field and the space constant for the trunk of the dendritic tree. When a neuron with a straight axon is subjected to a constant field, the membrane potential decays exponentially with distance from the soma. Thus, the soma seems to be a likely site for action potential initiation when the field is strong enough to elicit suprathreshold polarization. In a simple example, the way in which orientation of the various parts of the neuron affects its polarization is examined. When an axon with a bend is subjected to a spatially constant field, polarization is focused at the bend, and this is another likely site for action potential initiation. PMID:3801574

  20. Nuclear spin polarized H and D by means of spin-exchange optical pumping

    NASA Astrophysics Data System (ADS)

    Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank

    1998-01-01

    Optically pumped spin-exchange sources for polarized hydrogen and deuterium atoms have been demonstrated to yield high atomic flow and high electron spin polarization. For maximum nuclear polarization the source has to be operated in spin temperature equilibrium, which has already been demonstrated for hydrogen. In spin temperature equilibrium the nuclear spin polarization PI equals the electron spin polarization PS for hydrogen and is even larger than PS for deuterium. We discuss the general properties of spin temperature equilibrium for a sample of deuterium atoms. One result are the equations PI=4PS/(3+PS2) and Pzz=PSṡPI, where Pzz is the nuclear tensor polarization. Furthermore we demonstrate that the deuterium atoms from our source are in spin temperature equilibrium within the experimental accuracy.

  1. Is solid-state NMR enhanced by dynamic nuclear polarization?

    PubMed

    Lee, Daniel; Hediger, Sabine; De Paëpe, Gaël

    2015-01-01

    The recent trend of high-field (~5-20 T), low-temperature (~100 K) ssNMR combined with dynamic nuclear polarization (DNP) under magic angle spinning (MAS) conditions is analyzed. A brief overview of the current theory of hyperpolarization for so-called MAS-DNP experiments is given, along with various reasons why the DNP-enhancement, the ratio of the NMR signal intensities obtained in the presence and absence of microwave irradiation suitable for hyperpolarization, should not be used alone to gauge the value of performing MAS-DNP experiments relative to conventional ssNMR. This is demonstrated through a dissection of the current conditions required for MAS-DNP with particular attention to resulting absolute sensitivities and spectral resolution. Consequently, sample preparation methods specifically avoiding the surplus of glass-forming solvents so as to improve the absolute sensitivity and resolution are discussed, as are samples that are intrinsically pertinent for MAS-DNP studies (high surface area, amorphous, and porous). Owing to their pertinence, examples of recent applications on these types of samples where chemically-relevant information has been obtained that would have been impossible without the sensitivity increases bestowed by MAS-DNP are also detailed. Additionally, a promising further implementation for MAS-DNP is exampled, whereby the sensitivity improvements shown for (correlation) spectroscopy of nuclei at low natural isotopic abundance, facilitate internuclear distance measurements, especially for long distances (absence of dipolar truncation). Finally, we give some speculative perspectives for MAS-DNP. PMID:25779337

  2. New Versions of Terahertz Radiation Sources for Dynamic Nuclear Polarization in Nuclear Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Kalynov, Yu. K.; Makhalov, P. B.; Fedotov, A. E.

    2014-01-01

    Dynamic nuclear polarization in strong-field nuclear magnetic resonance (NMR) spectroscopy requires terahertz radiation with moderate power levels. Nowadays, conventional gyrotrons are used almost exclusively to generate such radiation. In this review paper, we consider alternative variants of electronic microwave oscillators which require much weaker magnetic fields for their operation, namely, large-orbit gyrotrons operated at high cyclotron-frequency harmonics and Čerenkov-type devices, such as a backward-wave oscillator and a klystron frequency multiplier with tubular electron beams. Additionally, we consider the possibility to use the magnetic field created directly by the solenoid of an NMR spectrometer for operation of both the gyrotron and the backward-wave oscillator. Location of the oscillator in the spectrometer magnet makes it superfluous to use an additional superconducting magnet creating a strong field, significantly reduces the length of the radiation transmission line, and, in the case of Čerenkov-type devices, allows one to increase considerably the output-signal power. According to our calculations, all the electronic devices considered are capable of ensuring the power required for dynamic nuclear polarization (10 W or more) at a frequency of 260 GHz, whereas the gyrotrons, including their versions proposed in this paper, remain a single option at higher frequencies.

  3. Measurement of the nuclear polarization of hydrogen and deuterium molecules using a Lamb-shift polarimeter

    SciTech Connect

    Engels, Ralf Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Ströher, Hans; Weiss, Philipp; Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat; Schieck, Hans Paetz gen.

    2014-10-15

    Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H{sub 2}{sup +} (or D{sub 2}{sup +}) ions into the Lamb-shift polarimeter.

  4. Theoretical treatment of pulsed Overhauser dynamic nuclear polarization: Consideration of a general periodic pulse sequence

    NASA Astrophysics Data System (ADS)

    Nasibulov, E. A.; Kiryutin, A. S.; Yurkovskaya, A. V.; Vieth, H.-M.; Ivanov, K. L.

    2016-05-01

    A general theoretical approach to pulsed Overhauser-type dynamic nuclear polarization (DNP) is presented. Dynamic nuclear polarization is a powerful method to create non-thermal polarization of nuclear spins, thereby enhancing their nuclear magnetic resonance signals. The theory presented can treat pulsed microwave irradiation of electron paramagnetic resonance transitions for periodic pulse sequences of general composition. Dynamic nuclear polarization enhancement is analyzed in detail as a function of the microwave pulse length for rectangular pulses and pulses with finite rise time. Characteristic oscillations of the DNP enhancement are found when the pulse-length is stepwise increased, originating from coherent motion of the electron spins driven by the pulses. Experimental low-field DNP data are in very good agreement with this theoretical approach.

  5. Optically Induced Nuclear Spin Polarization in the Quantum Hall Regime: The Effect of Electron Spin Polarization through Exciton and Trion Excitations

    NASA Astrophysics Data System (ADS)

    Akiba, K.; Kanasugi, S.; Yuge, T.; Nagase, K.; Hirayama, Y.

    2015-07-01

    We study nuclear spin polarization in the quantum Hall regime through the optically pumped electron spin polarization in the lowest Landau level. The nuclear spin polarization is measured as a nuclear magnetic field BN by means of the sensitive resistive detection. We find the dependence of BN on the filling factor nonmonotonic. The comprehensive measurements of BN with the help of the circularly polarized photoluminescence measurements indicate the participation of the photoexcited complexes, i.e., the exciton and trion (charged exciton), in nuclear spin polarization. On the basis of a novel estimation method of the equilibrium electron spin polarization, we analyze the experimental data and conclude that the filling factor dependence of BN is understood by the effect of electron spin polarization through excitons and trions.

  6. Optically Induced Nuclear Spin Polarization in the Quantum Hall Regime: The Effect of Electron Spin Polarization through Exciton and Trion Excitations.

    PubMed

    Akiba, K; Kanasugi, S; Yuge, T; Nagase, K; Hirayama, Y

    2015-07-10

    We study nuclear spin polarization in the quantum Hall regime through the optically pumped electron spin polarization in the lowest Landau level. The nuclear spin polarization is measured as a nuclear magnetic field B(N) by means of the sensitive resistive detection. We find the dependence of B(N) on the filling factor nonmonotonic. The comprehensive measurements of B(N) with the help of the circularly polarized photoluminescence measurements indicate the participation of the photoexcited complexes, i.e., the exciton and trion (charged exciton), in nuclear spin polarization. On the basis of a novel estimation method of the equilibrium electron spin polarization, we analyze the experimental data and conclude that the filling factor dependence of B(N) is understood by the effect of electron spin polarization through excitons and trions. PMID:26207494

  7. Nuclear safety as applied to space power reactor systems

    SciTech Connect

    Cummings, G.E.

    1987-01-01

    To develop a strategy for incorporating and demonstrating safety, it is necessary to enumerate the unique aspects of space power reactor systems from a safety standpoint. These features must be differentiated from terrestrial nuclear power plants so that our experience can be applied properly. Some ideas can then be developed on how safe designs can be achieved so that they are safe and perceived to be safe by the public. These ideas include operating only after achieving a stable orbit, developing an inherently safe design, ''designing'' in safety from the start and managing the system development (design) so that it is perceived safe. These and other ideas are explored further in this paper.

  8. Dynamics of nuclear spin polarization induced and detected by coherently precessing electron spins in fluorine-doped ZnSe

    NASA Astrophysics Data System (ADS)

    Heisterkamp, F.; Kirstein, E.; Greilich, A.; Zhukov, E. A.; Kazimierczuk, T.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.

    2016-02-01

    We study the dynamics of optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer via time-resolved Kerr rotation. The nuclear polarization in the vicinity of a fluorine donor is induced by interaction with coherently precessing electron spins in a magnetic field applied in the Voigt geometry. It is detected by nuclei-induced changes in the electron spin coherence signal. This all-optical technique allows us to measure the longitudinal spin relaxation time T1 of the 77Se isotope in a magnetic field range from 10 to 130 mT under illumination. We combine the optical technique with radio frequency methods to address the coherent spin dynamics of the nuclei and measure Rabi oscillations, Ramsey fringes, and the nuclear spin echo. The inhomogeneous spin dephasing time T2* and the spin coherence time T2 of the 77Se isotope are measured. While the T1 time is on the order of several milliseconds, the T2 time is several hundred microseconds. The experimentally determined condition T1≫T2 verifies the validity of the classical model of nuclear spin cooling for describing the optically induced nuclear spin polarization.

  9. Self-Polarization and Dynamical Cooling of Nuclear Spins in Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Rudner, M. S.; Levitov, L. S.

    2007-07-01

    The spin-blockade regime of double quantum dots features coupled dynamics of electron and nuclear spins resulting from the hyperfine interaction. We explain observed nuclear self-polarization via a mechanism based on feedback of the Overhauser shift on electron energy levels, and propose to use the instability toward self-polarization as a vehicle for controlling the nuclear spin distribution. In the dynamics induced by a properly chosen time-dependent magnetic field, nuclear spin fluctuations can be suppressed significantly below the thermal level.

  10. : a highly water-soluble biradical for efficient dynamic nuclear polarization of biomolecules.

    PubMed

    Jagtap, Anil P; Geiger, Michel-Andreas; Stöppler, Daniel; Orwick-Rydmark, Marcella; Oschkinat, Hartmut; Sigurdsson, Snorri Th

    2016-05-19

    Dynamic nuclear polarization (DNP) is an efficient method to overcome the inherent low sensitivity of magic-angle spinning (MAS) solid-state NMR. We report a new polarizing agent (), designed for biological applications, that yielded an enhancement value of 244 in a microcrystalline SH3 domain sample at 110 K. PMID:27161650

  11. Effect of lanthanide ions on dynamic nuclear polarization enhancement and liquid-state T1 relaxation.

    PubMed

    Gordon, Jeremy W; Fain, Sean B; Rowland, Ian J

    2012-12-01

    In the dynamic nuclear polarization process, microwave irradiation facilitates exchange of polarization from a radical's unpaired electron to nuclear spins at cryogenic temperatures, increasing polarization by >10,000. Doping samples with Gd(3+) ions further increases the achievable solid-state polarization. However, on dissolution, paramagnetic lanthanide metals can be potent relaxation agents, decreasing liquid-state polarization. Here, the effects of lanthanide metals on the solid and liquid-state magnetic properties of [1-(13)C]pyruvate are studied. The results show that in addition to gadolinium, holmium increases not only the achievable polarization but also the rate of polarization. Liquid-state relaxation studies found that unlike gadolinium, holmium minimally affects T(1). Additionally, results reveal that linear contrast agents dissociate in pyruvic acid, greatly reducing liquid-state T(1). Although macrocyclic agents do not readily dissociate, they yield lower solid-state polarization. Results indicate that polarization with free lanthanides and subsequent chelation during dissolution produces the highest polarization enhancement while minimizing liquid-state relaxation. PMID:22367680

  12. Effect of Lanthanide Ions on Dynamic Nuclear Polarization Enhancement and Liquid State T1 Relaxation

    PubMed Central

    Gordon, Jeremy; Fain, Sean B.; Rowland, Ian J

    2012-01-01

    In the dynamic nuclear polarization process, microwave irradiation facilitates exchange of polarization from a radical’s unpaired electron to nuclear spins at cryogenic temperatures, increasing polarization by >10000. Doping samples with Gd3+ ions further increases the achievable solid-state polarization. However, upon dissolution, paramagnetic lanthanide metals can be potent relaxation agents, decreasing liquid-state polarization. Here, the effects of lanthanide metals on the solid and liquid-state magnetic properties of [1-13C]pyruvate are studied. The results show that in addition to gadolinium, holmium not only increases the achievable polarization but also the rate of polarization. Liquid-state relaxation studies found that unlike gadolinium, holmium minimally affects T1. Additionally, results reveal that linear contrast agents dissociate in pyruvic acid, greatly reducing liquid-state T1. While macrocyclic agents do not readily dissociate, they yield lower solid-state polarization. Results indicate that polarization with free lanthanides and subsequent chelation during dissolution produces the highest polarization enhancement while minimizing liquid-state relaxation. PMID:22367680

  13. Confinement and Diffusion Effects in Dynamical Nuclear Polarization in Low Dimensional Nanostructures

    NASA Astrophysics Data System (ADS)

    Henriksen, Dan; Tifrea, Ionel

    2012-02-01

    We investigate the dynamic nuclear polarization as it results from the hyperfine coupling between nonequilibrium electronic spins and nuclear spins in semiconductor nanostructures. The natural confinement provided by low dimensional nanostructures is responsible for an efficient nuclear spin - electron spin hyperfine coupling [1] and for a reduced value of the nuclear spin diffusion constant [2]. In the case of optical pumping, the induced nuclear spin polarization is position dependent even in the presence of nuclear spin diffusion. This effect should be measurable via optically induced nuclear magnetic resonance or time-resolved Faraday rotation experiments. We discuss the implications of our calculations for the case of GaAs quantum well structures.[4pt] [1] I. Tifrea and M. E. Flatt'e, Phys. Rev. B 84, 155319 (2011).[0pt] [2] A. Malinowski and R. T. Harley, Solid State Commun. 114, 419 (2000).

  14. Automated Variance Reduction Applied to Nuclear Well-Logging Problems

    SciTech Connect

    Wagner, John C; Peplow, Douglas E.; Evans, Thomas M

    2009-01-01

    typically performed for each desired detector response. This paper summarizes recent work to apply and evaluate the effectiveness of deterministic-adjoint-based variance reduction methods, including a recently developed method for simultaneous optimization of multiple detectors, for two simple nuclear well-logging tool problems that have been widely used in the variance reduction literature. The computational effectiveness of the method for simultaneous optimization is also compared to the use of multiple, individually optimized simulations for these simple well-logging problems.

  15. Automated Variance Reduction Applied to Nuclear Well-Logging Problems

    SciTech Connect

    Wagner, John C; Peplow, Douglas E.; Evans, Thomas M

    2008-01-01

    typically performed for each desired detector response. This paper summarizes recent work to apply and evaluate the effectiveness of deterministic-adjoint-based variance reduction methods, including a recently developed method for simultaneous optimization of multiple detectors, for two simple nuclear well-logging tool problems that have been widely used in the variance reduction literature. The computational effectiveness of the method for simultaneous optimization is also compared to the use of multiple, individually optimized simulations for these simple well-logging problems.

  16. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings.

    PubMed

    Thurber, Kent R; Tycko, Robert

    2012-08-28

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  17. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2012-01-01

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T1e is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  18. High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR

    PubMed Central

    Barnes, A.B.; Paëpe, G. De; van der Wel, P.C.A.; Hu, K.-N.; Joo, C.-G.; Bajaj, V.S.; Mak-Jurkauskas, M.L.; Sirigiri, J.R.; Herzfeld, J.; Temkin, R.J.; Griffin, R.G.

    2008-01-01

    Dynamic nuclear polarization (DNP) results in a substantial nuclear polarization enhancement through a transfer of the magnetization from electrons to nuclei. Recent years have seen considerable progress in the development of DNP experiments directed towards enhancing sensitivity in biological nuclear magnetic resonance (NMR). This review covers the applications, hardware, polarizing agents, and theoretical descriptions that were developed at the Francis Bitter Magnet Laboratory at Massachusetts Institute of Technology for high-field DNP experiments. In frozen dielectrics, the enhanced nuclear polarization developed in the vicinity of the polarizing agent can be efficiently dispersed to the bulk of the sample via 1H spin diffusion. This strategy has been proven effective in polarizing biologically interesting systems, such as nanocrystalline peptides and membrane proteins, without leading to paramagnetic broadening of the NMR signals. Gyrotrons have been used as a source of high-power (5–10 W) microwaves up to 460 GHz as required for the DNP experiments. Other hardware has also been developed allowing in situ microwave irradiation integrated with cryogenic magic-angle-spinning solid-state NMR. Advances in the quantum mechanical treatment are successful in describing the mechanism by which new biradical polarizing agents yield larger enhancements at higher magnetic fields. Finally, pulsed methods and solution experiments should play a prominent role in the future of DNP. PMID:19194532

  19. IBA-Europhysics Prize in Applied Nuclear Science and Nuclear Methods in Medicine

    NASA Astrophysics Data System (ADS)

    MacGregor, I. J. Douglas

    2014-03-01

    The Nuclear Physics Board of the European Physical Society is pleased to announce that the 2013 IBA-Europhysics Prize in Applied Nuclear Science and Nuclear Methods in Medicine is awarded to Prof. Marco Durante, Director of the Biophysics Department at GSI Helmholtz Center (Darmstadt, Germany); Professor at the Technical University of Darmstadt (Germany) and Adjunct Professor at the Temple University, Philadelphia, USA. The prize was presented in the closing Session of the INPC 2013 conference by Mr. Thomas Servais, R&D Manager for Accelerator Development at the IBA group, who sponsor the IBA Europhysics Prize. The Prize Diploma was presented by Dr. I J Douglas MacGregor, Chair-elect of the EPS Nuclear Physics Division and Chair of the IBA Prize committee.

  20. Hyperpolarization of Thin Films with Dynamic Nuclear Polarization Using Photoexcited Triplet Electrons

    NASA Astrophysics Data System (ADS)

    Tateishi, Kenichiro; Negoro, Makoto; Kagawa, Akinori; Uesaka, Tomohiro; Kitagawa, Masahiro

    2013-08-01

    With dynamic nuclear polarization using the photoexcited triplet electron spin (triplet-DNP) of pentacene, nuclear spins can be hyperpolarized even in a low magnetic field at room temperature. Several demonstrations have been performed using bulk crystals. Hyperpolarization in a thin film with triplet-DNP enables new applications, such as general NMR spectroscopy and the polarized target of unstable nuclei. In this work, we succeeded in polarizing 1H spins in a thin film fabricated by the cell method. We obtained a 1H spin polarization of 12.9% using a 7-μm-thick film of p-terphenyl doped with pentacene in 0.4 T at room temperature. We also obtained a 1H spin polarization of 3.9% in 0.4 T at 150 K using a 60-μm-thick film of trans-stilbene doped with pentacene, whose single crystal cannot be made easily by conventional methods.

  1. Applying fast calorimetry on a spent nuclear fuel calorimeter

    SciTech Connect

    Liljenfeldt, Henrik

    2015-04-15

    Recently at Los Alamos National Laboratory, sophisticated prediction algorithms have been considered for the use of calorimetry for treaty verification. These algorithms aim to predict the equilibrium temperature based on early data and therefore be able to shorten the measurement time while maintaining good accuracy. The algorithms have been implemented in MATLAB and applied on existing equilibrium measurements from a spent nuclear fuel calorimeter located at the Swedish nuclear fuel interim storage facility. The results show significant improvements in measurement time in the order of 15 to 50 compared to equilibrium measurements, but cannot predict the heat accurately in less time than the currently used temperature increase method can. This Is both due to uncertainties in the calibration of the method as well as identified design features of the calorimeter that limits the usefulness of equilibrium type measurements. The conclusions of these findings are discussed, and suggestions of both improvements of the current calorimeter as well as what to keep in mind in a new design are given.

  2. Comparative study of nuclear effects in polarized electron scattering from 3 He

    DOE PAGESBeta

    Ethier, J. J.; Melnitchouk, W.

    2013-11-01

    We present a detailed analysis of nuclear effects in inclusive electron scattering from polarized 3He nuclei for polarization asymmetries, structure functions and their moments, both in the nucleon resonance and deep-inelastic regions. We compare the results of calculations within the weak binding approximation at finite Q2 with the effective polarization ansatz often used in experimental data analyses, and explore the impact of Δ components in the nuclear wave function and nucleon off-shell corrections on extractions of the free neutron structure. Using the same framework we also make predictions for the Q2 dependence of quasielastic scattering from polarized 3He, data onmore » which can be used to constrain the spin-dependent nuclear smearing functions in 3He.« less

  3. Strongly polarizing weakly coupled 13C nuclear spins with optically pumped nitrogen-vacancy center

    PubMed Central

    Wang, Ping; Liu, Bao; Yang, Wen

    2015-01-01

    Enhancing the polarization of nuclear spins surrounding the nitrogen-vacancy (NV) center in diamond has recently attracted widespread attention due to its various applications. Here we present an analytical formula that not only provides a clear physical picture for the recently observed polarization reversal of strongly coupled13C nuclei over a narrow range of magnetic field [H. J. Wang et al., Nat. Commun. 4, 1940 (2013)], but also demonstrates the possibility to strongly polarize weakly coupled13C nuclei. This allows sensitive magnetic field control of the 13C nuclear spin polarization for NMR applications and significant suppression of the 13C nuclear spin noise to prolong the NV spin coherence time. PMID:26521962

  4. Comparative study of nuclear effects in polarized electron scattering from 3He

    DOE PAGESBeta

    Ethier, Jacob James; Melnitchouk, Wally

    2013-11-04

    We present a detailed analysis of nuclear effects in inclusive electron scattering from polarized 3He nuclei for polarization asymmetries, structure functions and their moments, both in the nucleon resonance and deep-inelastic regions. We compare the results of calculations within the weak binding approximation at finite Q2 with the effective polarization ansatz often used in experimental data analyses, and explore the impact of Δ components in the nuclear wave function and nucleon off-shell corrections on extractions of the free neutron structure. Using the same framework we also make predictions for the Q2 dependence of quasielastic scattering from polarized 3He, data onmore » which can be used to constrain the spin-dependent nuclear smearing functions in 3He.« less

  5. Nuclear-polarization correction to the bound-electron g factor in heavy hydrogenlike ions.

    PubMed

    Nefiodov, A V; Plunien, G; Soff, G

    2002-08-19

    The influence of nuclear polarization on the bound-electron g factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K- and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron g factor in highly charged ions. PMID:12190457

  6. A high-pressure polarized 3He gas target for nuclear-physics experiments using a polarized photon beam

    NASA Astrophysics Data System (ADS)

    Ye, Q.; Laskaris, G.; Chen, W.; Gao, H.; Zheng, W.; Zong, X.; Averett, T.; Cates, G. D.; Tobias, W. A.

    2010-04-01

    Following the first experiment on three-body photodisintegration of polarized 3He utilizing circularly polarized photons from High-Intensity Gamma Source (HI γ S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized 3He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce the photon beam-induced background. The target is based on the technique of spin exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is ˜ 62% determined from both NMR-AFP and EPR polarimetries. The phenomenological parameter that reflects the additional unknown spin relaxation processes, X , is estimated to be ˜ 0.10 and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 3He target cell used previously at HI γ S. This is the first time that the sol-gel coating technique has been used in a polarized 3He target for nuclear-physics experiments.

  7. Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37K

    NASA Astrophysics Data System (ADS)

    Fenker, B.; Behr, J. A.; Melconian, D.; Anderson, R. M. A.; Anholm, M.; Ashery, D.; Behling, R. S.; Cohen, I.; Craiciu, I.; Donohue, J. M.; Farfan, C.; Friesen, D.; Gorelov, A.; McNeil, J.; Mehlman, M.; Norton, H.; Olchanski, K.; Smale, S.; Thériault, O.; Vantyghem, A. N.; Warner, C. L.

    2016-07-01

    We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in the {β }+-decay of the same atoms. These results will be used to test the V ‑ A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of \\bar{P}=0.9913+/- 0.0009, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has 0.2 % statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to \\lt 0.1 % , allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.

  8. Efficient dynamic nuclear polarization of phosphorus in silicon in strong magnetic fields and at low temperatures

    NASA Astrophysics Data System (ADS)

    Järvinen, J.; Ahokas, J.; Sheludyakov, S.; Vainio, O.; Lehtonen, L.; Vasiliev, S.; Zvezdov, D.; Fujii, Y.; Mitsudo, S.; Mizusaki, T.; Gwak, M.; Lee, SangGap; Lee, Soonchil; Vlasenko, L.

    2014-12-01

    Efficient manipulation of nuclear spins is important for utilizing them as qubits for quantum computing. In this work we report record high polarizations of 31P and 29Si nuclear spins in P-doped silicon in a strong magnetic field (4.6 T) and at temperatures below 1 K. We reached 31P nuclear polarization values exceeding 98 % after 20 min of pumping the high-field electron spin resonance (ESR) line with a very small microwave power of 0.4 μ W . We evaluate that the ratio of the hyperfine-state populations increases by three orders of magnitude after 2 hours of pumping, and an extremely pure nuclear spin state can be created, with less than 0.01 ppb impurities. A negative dynamic nuclear polarization has been observed by pumping the low-field ESR line of 31P followed by the flip-flip cross relaxation, the transition which is fully forbidden for isolated donors. We estimate that while pumping the ESR transitions of 31P also the nuclei of 29Si get polarized, and polarization exceeding 60 % has been obtained. We performed measurements of relaxation rates of flip-flop and flip-flip transitions which turned out to be nearly temperature independent. Temperature dependence of the 31P nuclear relaxation was studied down to 0.75 K, below which the relaxation time became too long to be measured. We found that the polarization evolution under pumping and during relaxation deviates substantially from a simple exponential function of time. We suggest that the nonexponential polarization dynamics of 31P donors is mediated by the orientation of 29Si nuclei, which affect the transition probabilities of the forbidden cross-relaxation processes.

  9. Propagation of dynamic nuclear polarization across the xenon cluster boundaries: Elucidation of the spin-diffusion bottleneck

    NASA Astrophysics Data System (ADS)

    Pourfathi, M.; Kuzma, N. N.; Kara, H.; Ghosh, R. K.; Shaghaghi, H.; Kadlecek, S. J.; Rizi, R. R.

    2013-10-01

    Earlier Dynamic Nuclear Polarization (DNP) experiments with frozen xenon/1-propanol/trityl mixtures have demonstrated spontaneous formation of pure xenon clusters above 120 K, enabling spectrally-resolved real-time measurements of 129Xe nuclear magnetization in the clusters and in the surrounding radical-rich matrix. A spin-diffusion bottleneck was postulated to explain the peculiar time evolution of 129Xe signals in the clusters as well as the apparent discontinuity of 129Xe polarization across the cluster boundaries. A self-contained ab initio model of nuclear spin diffusion in heterogeneous systems is developed here, incorporating the intrinsic T1 relaxation towards the temperature-dependent equilibrium polarization and the spin-diffusion coefficients based on the measured NMR line widths and the known atomic densities in each compartment. This simple model provides the physical basis for the observed spin-diffusion bottleneck and is in a good quantitative agreement with the earlier measurements. A simultaneous fit of the model to the time-dependent NMR data at two different DNP frequencies provides excellent estimates of the cluster size, the intrinsic sample temperature, and 129Xe T1 constants. The model was also applied to the NMR data acquired during relaxation towards the thermal equilibrium after the microwaves were turned off, to estimate T1 relaxation time constants inside and outside the clusters. Fitting the model to the data during and after DNP provides consistent estimates of the cluster size.

  10. Application of blind source separation to real-time dissolution dynamic nuclear polarization.

    PubMed

    Hilty, Christian; Ragavan, Mukundan

    2015-01-20

    The use of a blind source separation (BSS) algorithm is demonstrated for the analysis of time series of nuclear magnetic resonance (NMR) spectra. This type of data is obtained commonly from experiments, where analytes are hyperpolarized using dissolution dynamic nuclear polarization (D-DNP), both in in vivo and in vitro contexts. High signal gains in D-DNP enable rapid measurement of data sets characterizing the time evolution of chemical or metabolic processes. BSS is based on an algorithm that can be applied to separate the different components contributing to the NMR signal and determine the time dependence of the signals from these components. This algorithm requires minimal prior knowledge of the data, notably, no reference spectra need to be provided, and can therefore be applied rapidly. In a time-resolved measurement of the enzymatic conversion of hyperpolarized oxaloacetate to malate, the two signal components are separated into computed source spectra that closely resemble the spectra of the individual compounds. An improvement in the signal-to-noise ratio of the computed source spectra is found compared to the original spectra, presumably resulting from the presence of each signal more than once in the time series. The reconstruction of the original spectra yields the time evolution of the contributions from the two sources, which also corresponds closely to the time evolution of integrated signal intensities from the original spectra. BSS may therefore be an approach for the efficient identification of components and estimation of kinetics in D-DNP experiments, which can be applied at a high level of automation. PMID:25506716

  11. Predicting the future distribution of Polar Bear Habitat in the polar basin from resource selection functions applied to 21st century general circulation model projections of sea ice

    USGS Publications Warehouse

    Durner, George M.; Douglas, David C.; Nielson, Ryan M.; Amstrup, Steven C.; McDonald, Trent L.

    2007-01-01

    Predictions of polar bear (Ursus maritimus) habitat distribution in the Arctic polar basin during the 21st century were developed to help understand the likely consequences of anticipated sea ice reductions on polar bear populations. We used location data from satellite-collared polar bears and environmental data (e.g., bathymetry, coastlines, and sea ice) collected between 1985–1995 to build habitat use models called Resource Selection Functions (RSF). The RSFs described habitats polar bears preferred in each of four seasons: summer (ice minimum), autumn (growth), winter (ice maximum) and spring (melt). When applied to the model source data and to independent data (1996–2006), the RSFs consistently identified habitats most frequently used by polar bears. We applied the RSFs to monthly maps of 21st century sea ice concentration predicted by 10 general circulation models (GCM) described in the International Panel of Climate Change Fourth Assessment Report. The 10 GCMs we used had high concordance between their simulations of 20th century summer sea ice extent and the actual ice extent derived from passive microwave satellite observations. Predictions of the amount and rate of change in polar bear habitat varied among GCMs, but all GCMs predicted net habitat losses in the polar basin during the 21st century. Projected losses in the highest-valued RSF habitat (optimal habitat) were greatest in the peripheral seas of the polar basin, especially the Chukchi Sea and Barents Sea. Losses were least in high-latitude regions where RSFs predicted an initial increase in optimal habitat followed by a modest decline. The largest seasonal reductions in habitat were predicted for spring and summer. Average area of optimal polar bear habitat during summer in the polar basin declined from an observed 1.0 million km2 in 1985–1995 (baseline) to a projected multi-model average of 0.58 million km2 in 2045–2054 (-42% change), 0.36 million km2 in 2070–2079 (-64% change), and 0

  12. Polarization and Color Filtering Applied to Enhance Photogrammetric Measurements of Reflective Surfaces

    NASA Technical Reports Server (NTRS)

    Wells, Jeffrey M.; Jones, Thomas W.; Danehy, Paul M.

    2005-01-01

    Techniques for enhancing photogrammetric measurement of reflective surfaces by reducing noise were developed utilizing principles of light polarization. Signal selectivity with polarized light was also compared to signal selectivity using chromatic filters. Combining principles of linear cross polarization and color selectivity enhanced signal-to-noise ratios by as much as 800 fold. More typical improvements with combining polarization and color selectivity were about 100 fold. We review polarization-based techniques and present experimental results comparing the performance of traditional retroreflective targeting materials, cornercube targets returning depolarized light, and color selectivity.

  13. Resonance-inclined optical nuclear spin polarization of liquids in diamond structures

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.

    2016-02-01

    Dynamic nuclear polarization (DNP) of molecules in a solution at room temperature has the potential to revolutionize nuclear magnetic resonance spectroscopy and imaging. The prevalent methods for achieving DNP in solutions are typically most effective in the regime of small interaction correlation times between the electron and nuclear spins, limiting the size of accessible molecules. To solve this limitation, we design a mechanism for DNP in the liquid phase that is applicable for large interaction correlation times. Importantly, while this mechanism makes use of a resonance condition similar to solid-state DNP, the polarization transfer is robust to a relatively large detuning from the resonance due to molecular motion. We combine this scheme with optically polarized nitrogen-vacancy (NV) center spins in nanodiamonds to design a setup that employs optical pumping and is therefore not limited by room temperature electron thermal polarization. We illustrate numerically the effectiveness of the model in a flow cell containing nanodiamonds immobilized in a hydrogel, polarizing flowing water molecules 4700-fold above thermal polarization in a magnetic field of 0.35 T, in volumes detectable by current NMR scanners.

  14. Polarized Nuclei: From Fundamental Nuclear Physics To Applications In Neutron Scattering and Magnetic Resonance Imaging

    SciTech Connect

    Brandt, B. van den; Hautle, P.; Konter, J. A.; Kurdzesau, F.; Piegsa, F. M.; Urrego-Blanco, J.-P.

    2008-02-06

    The methods of dynamically polarizing nuclei (DNP) have not only lead to the development of increasingly sophisticated polarized targets with which the role of spin in nuclear and particle interactions is investigated, but have also opened new possibilities in neutron science by exploiting the strong spin dependence of the neutron scattering. Very recently NMR and MRI have been a driving force behind a surge of interest in DNP methods, considering its tremendous potential for sensitivity enhancement. An overview of our current projects with dynamically polarized nuclei is given.

  15. Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields

    SciTech Connect

    Pagliero, Daniela; Laraoui, Abdelghani; Henshaw, Jacob D.; Meriles, Carlos A.

    2014-12-15

    We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave, and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.

  16. Solid-state nitrogen-14 nuclear magnetic resonance enhanced by dynamic nuclear polarization using a gyrotron.

    PubMed

    Vitzthum, Veronika; Caporini, Marc A; Bodenhausen, Geoffrey

    2010-07-01

    By combining indirect detection of 14N with dynamic nuclear polarization (DNP) using a gyrotron, the signal-to-noise ratio can be dramatically improved and the recovery delay between subsequent experiments can be shortened. Spectra of glassy samples of the amino acid proline doped with the stable bi-radical TOTAPOL rotating at 15.625 kHz at 110K were obtained in a 400 MHz solid-state NMR spectrometer equipped with a gyrotron for microwave irradiation at 263 GHz. DNP enhancement factors on the order of epsilon approximately 40 were achieved. The recovery delays can be reduced from 60 s without radicals at 300 K to 6 s with radicals at 110 K. In the absence of radicals at room temperature, the proton relaxation in proline is inefficient due to the absence of rotating methyl groups and other heat sinks, thus making long recovery delays mandatory. DNP allows one to reduce the acquisition times of 13C-detected 14N spectra from several days to a few hours. PMID:20488737

  17. Thermalization and many-body localization in systems under dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    De Luca, Andrea; Rodríguez-Arias, Inés; Müller, Markus; Rosso, Alberto

    2016-07-01

    We study the role of dipolar interactions in the standard protocol used to achieve dynamic nuclear polarization (DNP). We point out that a critical strength of interactions is required to obtain significant nuclear hyperpolarization. Otherwise, the electron spins do not thermalize among each other, due to the incipient many-body localization transition in the electron spin system. Only when the interactions are sufficiently strong, in the so-called spin-temperature regime, they establish an effective thermodynamic behavior in the out-of-equilibrium stationary state. The highest polarization is reached at a point where the spin temperature is just not able to establish itself anymore. We provide numerical predictions for the level of nuclear hyperpolarization and present an analytical technique to estimate the spin temperature as a function of interaction strength and quenched disorder. We show that, at sufficiently strong coupling, nuclear spins perfectly equilibrate to the spin temperature that establishes among the spins of radicals.

  18. Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials and organisms

    SciTech Connect

    Goodson, Boyd M.

    1999-12-01

    Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This dissertation is primarily concerned with the principles and practice of optically pumped nuclear magnetic resonance (OPNMR). The enormous sensitivity enhancement afforded by optical pumping noble gases can be exploited to permit a variety of novel NMR experiments across many disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, and zero-field NMR and MRI.

  19. Dynamic nuclear polarization solid-state NMR in heterogeneous catalysis research

    SciTech Connect

    Kobayashi, Takeshi; Perras, Frédéric A.; Slowing, Igor I.; Sadow, Aaron D.; Pruski, Marek

    2015-10-20

    In this study, a revolution in solid-state nuclear magnetic resonance (SSNMR) spectroscopy is taking place, attributable to the rapid development of high-field dynamic nuclear polarization (DNP), a technique yielding sensitivity improvements of 2–3 orders of magnitude. This higher sensitivity in SSNMR has already impacted materials research, and the implications of new methods on catalytic sciences are expected to be profound.

  20. Dynamic nuclear polarization solid-state NMR in heterogeneous catalysis research

    DOE PAGESBeta

    Kobayashi, Takeshi; Perras, Frédéric A.; Slowing, Igor I.; Sadow, Aaron D.; Pruski, Marek

    2015-10-20

    In this study, a revolution in solid-state nuclear magnetic resonance (SSNMR) spectroscopy is taking place, attributable to the rapid development of high-field dynamic nuclear polarization (DNP), a technique yielding sensitivity improvements of 2–3 orders of magnitude. This higher sensitivity in SSNMR has already impacted materials research, and the implications of new methods on catalytic sciences are expected to be profound.

  1. Spin polarized asymmetric nuclear matter and neutron star matter within the lowest order constrained variational method

    SciTech Connect

    Bordbar, G. H.; Bigdeli, M.

    2008-01-15

    In this paper, we calculate properties of the spin polarized asymmetrical nuclear matter and neutron star matter, using the lowest order constrained variational (LOCV) method with the AV{sub 18}, Reid93, UV{sub 14}, and AV{sub 14} potentials. According to our results, the spontaneous phase transition to a ferromagnetic state in the asymmetrical nuclear matter as well as neutron star matter do not occur.

  2. Implementation of polarization processes in a charge transport model applied on poly(ethylene naphthalate) films

    NASA Astrophysics Data System (ADS)

    Hoang, M.-Q.; Le Roy, S.; Boudou, L.; Teyssedre, G.

    2016-06-01

    One of the difficulties in unravelling transport processes in electrically insulating materials is the fact that the response, notably charging current transients, can have mixed contributions from orientation polarization and from space charge processes. This work aims at identifying and characterizing the polarization processes in a polar polymer in the time and frequency-domains and to implement the contribution of the polarization into a charge transport model. To do so, Alternate Polarization Current (APC) and Dielectric Spectroscopy measurements have been performed on poly(ethylene naphthalene 2,6-dicarboxylate) (PEN), an aromatic polar polymer, providing information on polarization mechanisms in the time- and frequency-domain, respectively. In the frequency-domain, PEN exhibits 3 relaxation processes termed β, β* (sub-glass transitions), and α relaxations (glass transition) in increasing order of temperature. Conduction was also detected at high temperatures. Dielectric responses were treated using a simplified version of the Havriliak-Negami model (Cole-Cole (CC) model), using 3 parameters per relaxation process, these parameters being temperature dependent. The time dependent polarization obtained from the CC model is then added to a charge transport model. Simulated currents issued from the transport model implemented with the polarization are compared with the measured APCs, showing a good consistency between experiments and simulations in a situation where the response comes essentially from dipolar processes.

  3. Dynamic nuclear polarization of carbonyl and methyl 13C spins in acetate using trityl OX063

    NASA Astrophysics Data System (ADS)

    Niedbalski, Peter; Parish, Christopher; Lumata, Lloyd

    2015-03-01

    Hyperpolarization via dissolution dynamic nuclear polarization (DNP) is a physics technique that amplifies the magnetic resonance signals by several thousand-fold for biomedical NMR spectroscopy and imaging (MRI). Herein we have investigated the effect of carbon-13 isotopic location on the DNP of acetate (one of the biomolecules commonly used for hyperpolarization) at 3.35 T and 1.4 K using a narrow ESR linewidth free radical trityl OX063. We have found that the carbonyl 13C spins yielded about twice the polarization produced in methyl 13C spins. Deuteration of the methyl group, beneficial in the liquid-state, did not produce an improvement in the polarization level at cryogenic conditions. Concurrently, the solid-state nuclear relaxation of these samples correlate with the polarization levels achieved. These results suggest that the location of the 13C isotopic labeling in acetate has a direct impact on the solid-state polarization achieved and is mainly governed by the nuclear relaxation leakage factor.

  4. Spin-labeled gel for the production of radical-free dynamic nuclear polarization enhanced molecules for NMR spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    McCarney, Evan R.; Han, Songi

    2008-02-01

    Dynamic nuclear polarization (DNP) has recently received much attention as a viable approach to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and the contrast of magnetic resonance imaging (MRI), where the significantly higher electron spin polarization of stable radicals is transferred to nuclear spins. In order to apply DNP-enhanced NMR and MRI signal to biological and in vivo systems, it is crucial to obtain highly polarized solution samples at ambient temperatures. As stable radicals are employed as the source for the DNP polarization transfer, it is also crucial that the highly polarized sample lacks residual radical concentration because the polarized molecules will be introduced to a biological system that will be sensitive to the presence of radicals. We developed an agarose-based porous media that is covalently spin-labeled with stable radicals. The loading of solvent accessible radical is sufficiently high and their mobility approximates that in solution, which ensures high efficiency for Overhauser mechanism induced DNP without physically releasing any measurable radical into the solution. Under ambient conditions at 0.35 T magnetic field, we measure the DNP enhancement efficiency of 1H signal of stagnant and continuously flowing water utilizing immobilized stable nitroxide radicals that contain two or three ESR hyperfine splitting lines and compare them to the performance of freely dissolved radicals.

  5. Topical Developments in High-Field Dynamic Nuclear Polarization

    PubMed Central

    Kiesewetter, Matthew K.; Frantz, Derik K.; Walish, Joseph J.; Ravera, Enrico; Luchinat, Claudio; Swager, Timothy M.; Griffin, Robert G.

    2015-01-01

    We report our recent efforts directed at improving high-field DNP experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ε = 25 to 82 that demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei including 13C, 2H, and 17O using trityl via the cross effect. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefit of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz / 460 GHz DNP system that improves microwave delivery and increases enhancements up to 50%. PMID:25977588

  6. Finite-temperature calculations for spin-polarized asymmetric nuclear matter with the lowest order constrained variational method

    SciTech Connect

    Bigdeli, M.; Bordbar, G. H.; Poostforush, A.

    2010-09-15

    The lowest order constrained variational technique has been used to investigate some of the thermodynamic properties of spin-polarized hot asymmetric nuclear matter, such as the free energy, symmetry energy, susceptibility, and equation of state. We have shown that the symmetry energy of the nuclear matter is substantially sensitive to the value of spin polarization. Our calculations show that the equation of state of the polarized hot asymmetric nuclear matter is stiffer for higher values of the polarization as well as the isospin asymmetry parameter. Our results for the free energy and susceptibility show that spontaneous ferromagnetic phase transition cannot occur for hot asymmetric matter.

  7. Equation of state of hot polarized nuclear matter and heavy-ion fusion reactions

    SciTech Connect

    Ghodsi, O. N.; Gharaei, R.

    2011-08-15

    We employ the equation of state of hot polarized nuclear matter to simulate the repulsive force caused by the incompressibility effects of nuclear matter in the fusion reactions of heavy colliding ions. The results of our studies reveal that temperature effects of compound nuclei have significant importance in simulating the repulsive force on the fusion reactions for which the temperature of the compound nucleus increases up to about 2 MeV. Since the equation of state of hot nuclear matter depends upon the density and temperature of the nuclear matter, it has been suggested that, by using this equation of state, one can simulate simultaneously both the effects of the precompound nucleons' emission and the incompressibility of nuclear matter to calculate the nuclear potential in fusion reactions within a static formalism such as the double-folding (DF) model.

  8. Dynamic nuclear polarization experiments at 14.1 T for solid-state NMR.

    PubMed

    Matsuki, Yoh; Takahashi, Hiroki; Ueda, Keisuke; Idehara, Toshitaka; Ogawa, Isamu; Toda, Mitsuru; Akutsu, Hideo; Fujiwara, Toshimichi

    2010-06-14

    Instrumentation for high-field dynamic nuclear polarization (DNP) at 14.1 T was developed to enhance the nuclear polarization for NMR of solids. The gyrotron generated 394.5 GHz submillimeter (sub-mm) wave with a power of 40 W in the second harmonic TE(0,6) mode. The sub-mm wave with a power of 0.5-3 W was transmitted to the sample in a low-temperature DNP-NMR probe with a smooth-wall circular waveguide system. The (1)H polarization enhancement factor of up to about 10 was observed for a (13)C-labeled compound with nitroxyl biradical TOTAPOL. The DNP enhancement was confirmed by the static magnetic field dependence of the NMR signal amplitude at 90 K. Improvements of the high-field DNP experiments are discussed. PMID:20518128

  9. Electron spin resonance and its implication on the maximum nuclear polarization of deuterated solid target materials

    SciTech Connect

    Heckmann, J.; Meyer, W.; Radtke, E.; Reicherz, G.; Goertz, S.

    2006-10-01

    ESR spectroscopy is an important tool in polarized solid target material research, since it allows us to study the paramagnetic centers, which are used for the dynamic nuclear polarization (DNP). The polarization behavior of the different target materials is strongly affected by the properties of these centers, which are added to the diamagnetic materials by chemical doping or irradiation. In particular, the ESR linewidth of the paramagnetic centers is a very important parameter, especially concerning the deuterated target materials. In this paper, the results of the first precise ESR measurements of the deuterated target materials at a DNP-relevant magnetic field of 2.5 T are presented. Moreover, these results allowed us to experimentally study the correlation between ESR linewidth and maximum deuteron polarization, as given by the spin-temperature theory.

  10. Formulation and utilization of choline based samples for dissolution dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Bowen, Sean; Ardenkjaer-Larsen, Jan Henrik

    2013-11-01

    Hyperpolarization by the dissolution dynamic nuclear polarization (DNP) technique permits the generation of high spin polarization of solution state. However, sample formulation for dissolution-DNP is often difficult, as concentration and viscosity must be optimized to yield a dissolved sample with sufficient concentration, while maintaining polarization during the dissolution process. The unique chemical properties of choline permit the generation of highly soluble salts as well as deep eutectic mixtures with carboxylic acids and urea. We describe the formulation of these samples and compare their performance to more traditional sample formulations. Choline yields stable samples with exceptional polarization performance while simultaneously offering the capability to easily remove the choline after dissolution, perform experiments with the hyperpolarized choline, or anything in between.

  11. Rigid Orthogonal bis-TEMPO Biradicals with Improved Solubility for Dynamic Nuclear Polarization

    PubMed Central

    Dane, Eric L.; Corzilius, Björn; Rizzato, Egon; Stocker, Pierre; Maly, Thorsten; Smith, Albert A.; Griffin, Robert G.; Ouari, Olivier; Tordo, Paul; Swager, Timothy M.

    2012-01-01

    The synthesis and characterization of oxidized bis-thioketal-trispiro dinitroxide biradicals that orient the nitroxides in a rigid, approximately orthogonal geometry is reported. The biradicals show better performance as polarizing agents in dynamic nuclear polarization (DNP) NMR experiments as compared to biradicals lacking the constrained geometry. In addition, the biradicals display improved solubility in aqueous media due to the presence of polar sulfoxides. The results suggest that the orientation of the radicals is not dramatically affected by the oxidation state of the sulfur atoms in the biradical, and we conclude that a biradical polarizing agent containing a mixture of oxidation states can be used for improved solubility without a loss in performance. PMID:22304384

  12. Reflectance spectroscopy with polarized light: is it sensitive to cellular and nuclear morphology

    NASA Astrophysics Data System (ADS)

    Sokolov, Konstantin; Drezek, Rebekah A.; Gossage, Kirk; Richards-Kortum, Rebecca R.

    1999-12-01

    We present a method for selective detection of size-dependent scattering characteristics of epithelial cells in vivo based on polarized illumination and polarization sensitive detection of scattered light. We illustrate the method using phantoms designed to simulate squamous epithelial tissue and progressing to epithelial tissue in vitro and in vivo. Elastic light scattering spectroscopy with polarized illumination/detection dramatically reduces background signals due to both diffuse stromal scattering and hemoglobin absorption. Resulting spectra can be described as a linear combination of forward and backscattering components determined from Mie theory. Nuclear sizes and refractive indices extracted by fitting experimental spectra to this model agree well with previous measurements. Reflectance spectroscopy with polarized light can provide quantitative morphological information which could potentially be used for non-invasive detection of neoplastic changes.

  13. Application of Dipole-dipole, Induced Polarization, and CSAMT Electrical Methods to Detect Evidence of an Underground Nuclear Explosion

    NASA Astrophysics Data System (ADS)

    Sweeney, J. J.; Felske, D.

    2013-12-01

    There is little experience with application of electrical methods that can be applied during the continuation period of an on-site inspection (OSI), one of the verification methods of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). In order add to such experience, we conducted controlled source audiomagnetotelluric (CSAMT), dipole-dipole resistivity, and induced polarization electrical measurements along three survey lines over and near to ground zero of an historic nuclear explosion. The presentation will provide details and results of the surveys, an assessment of application of the method toward the purposes of an OSI, and an assessment of the manpower and time requirements for data collection and processing that will impact OSI inspection team operations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. The nuclear frontier; Cornell's program of basic and applied research

    SciTech Connect

    Clark, D.D. . Dept. of Nuclear Science and Engineering)

    1992-01-01

    This paper discusses the Program in Nuclear Science and Engineering at Cornell, an interdisciplinary field that encompasses a wide range of research. Some faculty members and graduate students are working on the basic physics of nuclei, plasmas, and atoms, while other are investigating the interaction of radiation with matter and the basic mechanisms of radiation-induced failure in microelectronic devices. Some are developing new research techniques based on nuclear and atomic interactions, and others are adapting nuclear methods such as activation analysis to research in geology, biology, and archaeology. Some are investigating advanced types of ion and electron beams, while yet others are improving the generation of power from fission and seeking to generate it from fusion.

  15. Stabilizing nuclear spins around semiconductor electrons via the interplay of optical coherent population trapping and dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Onur, A. R.; de Jong, J. P.; O'Shea, D.; Reuter, D.; Wieck, A. D.; van der Wal, C. H.

    2016-04-01

    We experimentally demonstrate how coherent population trapping (CPT) for donor-bound electron spins in GaAs results in autonomous feedback that prepares stabilized states for the spin polarization of nuclei around the electrons. CPT was realized by excitation with two lasers to a bound-exciton state. Transmission studies of the spectral CPT feature on an ensemble of electrons directly reveal the statistical distribution of prepared nuclear-spin states. Tuning the laser driving from blue to red detuned drives a transition from one to two stable states. Our results have importance for ongoing research on schemes for dynamic nuclear-spin polarization, the central spin problem, and control of spin coherence.

  16. Solid-state dynamic nuclear polarization at 263 GHz: spectrometer design and experimental results†

    PubMed Central

    Rosay, Melanie; Tometich, Leo; Pawsey, Shane; Bader, Reto; Schauwecker, Robert; Blank, Monica; Borchard, Philipp M.; Cauffman, Stephen R.; Felch, Kevin L.; Weber, Ralph T.; Temkin, Richard J.; Griffin, Robert G.; Maas, Werner E.

    2015-01-01

    Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz 1H frequency is described. Microwaves are generated by a novel continuous-wave gyrotron, transmitted to the NMR probe via a transmission line, and irradiated on a 3.2 mm rotor for MAS DNP experiments. DNP signal enhancements of up to 80 have been measured at 95 K on urea and proline in water–glycerol with the biradical polarizing agent TOTAPOL. We characterize the experimental parameters affecting the DNP efficiency: the magnetic field dependence, temperature dependence and polarization build-up times, microwave power dependence, sample heating effects, and spinning frequency dependence of the DNP signal enhancement. Stable system operation, including DNP performance, is also demonstrated over a 36 h period. PMID:20449524

  17. Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate. Ph.D. Thesis - Va. Polytechnic Inst.

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.

    1971-01-01

    The dynamic nuclear polarization of hydrogen nuclei by the solid effect in single crystals of samarium doped lanthanum magnesium nitrate (Sm:LMN) was studied theoretically and experimentally. The equations of evolution governing the dynamic nuclear polarization by the solid effect were derived in detail using the spin temperature theory and the complete expression for the steady state enhancement of the nuclear polarization was calculated. Experimental enhancements of the proton polarization were obtained for eight crystals at 9.2 GHz and liquid helium temperatures. The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181 was measured for a 1.1 percent Sm:LMN crystal at 3.0 K. The maximum enhancements extrapolated with the theory using the experimental data for peak enhancement versus microwave power and correcting for leakage, agree with the ideal enhancement (240 in this experiment) within experimental error for three of the crystals.

  18. Solid-state dynamic nuclear polarization at 263 GHz: spectrometer design and experimental results.

    PubMed

    Rosay, Melanie; Tometich, Leo; Pawsey, Shane; Bader, Reto; Schauwecker, Robert; Blank, Monica; Borchard, Philipp M; Cauffman, Stephen R; Felch, Kevin L; Weber, Ralph T; Temkin, Richard J; Griffin, Robert G; Maas, Werner E

    2010-06-14

    Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz (1)H frequency is described. Microwaves are generated by a novel continuous-wave gyrotron, transmitted to the NMR probe via a transmission line, and irradiated on a 3.2 mm rotor for MAS DNP experiments. DNP signal enhancements of up to 80 have been measured at 95 K on urea and proline in water-glycerol with the biradical polarizing agent TOTAPOL. We characterize the experimental parameters affecting the DNP efficiency: the magnetic field dependence, temperature dependence and polarization build-up times, microwave power dependence, sample heating effects, and spinning frequency dependence of the DNP signal enhancement. Stable system operation, including DNP performance, is also demonstrated over a 36 h period. PMID:20449524

  19. Nuclear Spin Polarization of Phosphorus Donors in Silicon. Direct Evidence from 31P-Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Gumann, Patryk; Ramanathan, Chandrasekhar; Patange, Om; Moussa, Osama; Thewalt, Mike; Riemann, Helge; Abrosimov, Nikolay; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei; Cory, David G.

    2014-03-01

    We experimentally demonstrate the optical hyperpolarization and coherent control of 31P, nuclear spins in single crystal silicon via the inductive readout of the nuclear magnetic resonance (NMR) signal of 31P at a concentration of 1.5 x 1015 cc-1. The obtained polarization is sufficient the 31P spin polarization of 1.17 x 1015 in a 10 mm x 10 mm sample, observed in one FID with signal-to-noise ration of 113. The linewidth is 800 Hz. The Hahn echo pulse sequence reveals a 31P T2 time of 0.42 s at 1.6 K, which was extended by the Carr Purcell cycle to 1.2 s at the same temperature. The maximum build-up of the nuclear polarization was achieved within ~577 seconds, at 4.2 K, in 6.7 T, using optical excitations provided by an infra-red laser. This work has been supported by CERC Canada.

  20. Dynamic nuclear polarization of membrane proteins: covalently bound spin-labels at protein-protein interfaces.

    PubMed

    Wylie, Benjamin J; Dzikovski, Boris G; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H; McDermott, Ann E

    2015-04-01

    We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces. PMID:25828256

  1. Dynamic nuclear polarization with a cyclotron resonance maser at 5 T

    NASA Astrophysics Data System (ADS)

    Becerra, Lino R.; Gerfen, Gary J.; Temkin, Richard J.; Singel, David J.; Griffin, Robert G.

    1993-11-01

    DNP (dynamic nuclear polarization) experiments at 5 T are reported, in which a cycoltron resonance maser (gyrotron) is utilized as a 20 W, 140 GHz microwave source to perform the polarization. MAS (magic angle spinning) NMR spectroscopy with DNP has been performed on samples of polystyrene doped with the free radical BDPA (α,γ-bisdiphenylene-β-phenylallyl) at room temperature. Maximal DNP enhancements of ~10 for 1H and ~40 for 13C are observed and are considerably larger than expected. The DNP and spin relaxation mechanisms that lead to these enhancements at 5 T are discussed.

  2. Tailoring of Polarizing Agents in the bTurea Series for Cross-Effect Dynamic Nuclear Polarization in Aqueous Media.

    PubMed

    Sauvée, Claire; Casano, Gilles; Abel, Sébastien; Rockenbauer, Antal; Akhmetzyanov, Dimitry; Karoui, Hakim; Siri, Didier; Aussenac, Fabien; Maas, Werner; Weber, Ralph T; Prisner, Thomas; Rosay, Mélanie; Tordo, Paul; Ouari, Olivier

    2016-04-11

    A series of 18 nitroxide biradicals derived from bTurea has been prepared, and their enhancement factors ɛ ((1)H) in cross-effect dynamic nuclear polarization (CE DNP) NMR experiments at 9.4 and 14.1 T and 100 K in a DNP-optimized glycerol/water matrix ("DNP juice") have been studied. We observe that ɛ ((1)H) is strongly correlated with the substituents on the polarizing agents, and its trend is discussed in terms of different molecular parameters: solubility, average e-e distance, relative orientation of the nitroxide moieties, and electron spin relaxation times. We show that too short an e-e distance or too long a T1e can dramatically limit ɛ ((1)H). Our study also shows that the molecular structure of AMUPol is not optimal and its ɛ ((1)H) could be further improved through stronger interaction with the glassy matrix and a better orientation of the TEMPO moieties. A new AMUPol derivative introduced here provides a better ɛ ((1)H) than AMUPol itself (by a factor of ca. 1.2). PMID:26992052

  3. Dynamic nuclear polarization of {sup 29}Si nuclei in isotopically controlled phosphorus doped silicon

    SciTech Connect

    Hayashi, Hiroshi; Itahashi, Tatsumasa; Itoh, Kohei M.; Vlasenko, Leonid S.; Vlasenko, Marina P.

    2009-07-15

    Dynamic nuclear polarization (DNP) of {sup 29}Si nuclei in isotopically controlled silicon single crystals with the {sup 29}Si isotope abundance f{sub 29Si} varied from 1.2% to 99.2% is reported. It was found that both the DNP enhancement and {sup 29}Si nuclear spin-lattice relaxation time under saturation of the electron paramagnetic resonance transitions of phosphorus donors increase with the decrease in the {sup 29}Si abundance. A remarkably large steady-state DNP enhancement, E{sup ss}=2680 which is comparable to the theoretical upper limit of 3310, has been achieved through the ''resolved'' solid effect that has been identified clearly in the f{sub 29Si}=1.2% sample. The DNP enhancement depends not only on the {sup 29}Si abundance but also on the electron spin-lattice relaxation time that can be controlled by temperature and/or illumination. The linewidth of {sup 29}Si NMR spectra after DNP shows a linear dependence on f{sub 29Si} for f{sub 29Si}{<=}10% and changes to a square-root dependence for f{sub 29Si}{>=}50%. Comparison of experimentally determined nuclear polarization time with nuclear spin diffusion coefficients indicates that the rate of DNP is limited by the polarization transfer rather than by spin diffusion.

  4. Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange nuclear magnetic resonance

    NASA Technical Reports Server (NTRS)

    Butler, J. P.; Mair, R. W.; Hoffmann, D.; Hrovat, M. I.; Rogers, R. A.; Topulos, G. P.; Walsworth, R. L.; Patz, S.

    2002-01-01

    We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas in the pore space and 129Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.

  5. Polarization-maintaining, double-clad fiber amplifier employing externally applied stress-induced birefringence

    SciTech Connect

    Koplow, Jeffrey P.; Goldberg, Lew; Moeller, Robert P.; Kliner, Dahv A. V.

    2000-03-15

    We report a new approach to obtaining linear-polarization operation of a rare-earth-doped fiber amplifier in which the gain fiber is coiled under tension to induce birefringence. We demonstrated this method by constructing an Er/Yb-doped, double-clad, single-mode fiber amplifier with an output power of 530 mW and a polarization extinction ratio of >17 dB (when seeded with linearly polarized light) at a wavelength of {approx}1.5 {mu}m . The technique is achromatic, permits single- or multiple-pass operation of the amplifier, requires no additional components in the optical path, leaves the fiber ends unobstructed, and is inexpensive to implement. (c) 2000 Optical Society of America.

  6. Quantitative cw Overhauser Dynamic Nuclear Polarization for the Analysis of Local Water Dynamics

    PubMed Central

    Franck, John M.; Pavlova, Anna; Scott, John A.; Han, Songi

    2013-01-01

    Liquid state Overhauser Effect Dynamic Nuclear Polarization (ODNP) has experienced a recent resurgence of interest. The ODNP technique described here relies on the double resonance of electron spin resonance (ESR) at the most common, i.e. X-band (~ 10 GHz), frequency and 1H nuclear magnetic resonance (NMR) at ~ 15 MHz. It requires only a standard continuous wave (cw) ESR spectrometer with an NMR probe inserted or built into an X-band cavity. Our focus lies on reviewing a new and powerful manifestation of ODNP as a high frequency NMR relaxometry tool that probes dipolar cross relaxation between the electron spins and the 1H nuclear spins at X-band frequencies. This technique selectively measures the translational mobility of water within a volume extending 0.5–1.5 nm outward from a nitroxide radical spin probe that is attached to a targeted site of a macromolecule. This method has been applied to study the dynamics of water that hydrates or permeates the surface or interior of proteins, polymers, and lipid membrane vesicles. We begin by reviewing the recent advances that have helped develop ODNP into a tool for mapping the dynamic landscape of hydration water with sub-nanometer locality. In order to bind this work coherently together, and to place it in the context of the extensive body of research in the field of NMR relaxometry, we then rephrase the analytical model and extend the description of the ODNP-derived NMR signal enhancements. This extended model highlights several aspects of ODNP data analysis, including the importance of considering all possible effects of microwave sample heating, the need to consider the error associated with various relaxation rates, and the unique ability of ODNP to probe the electron–1H cross-relaxation process, which is uniquely sensitive to fast (tens of ps) dynamical processes. By implementing the relevant corrections in a stepwise fashion, this paper draws a consensus result from previous ODNP procedures, and then shows

  7. Nuclear safety as applied to space power reactor systems

    SciTech Connect

    Cummings, G.E.

    1987-01-01

    Current space nuclear power reactor safety issues are discussed with respect to the unique characteristics of these reactors. An approach to achieving adequate safety and a perception of safety is outlined. This approach calls for a carefully conceived safety program which makes uses of lessons learned from previous terrestrial power reactor development programs. This approach includes use of risk analyses, passive safety design features, and analyses/experiments to understand and control off-design conditions. The point is made that some recent accidents concerning terrestrial power reactors do not imply that space power reactors cannot be operated safety.

  8. Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260 GHz

    NASA Astrophysics Data System (ADS)

    Yoon, Dongyoung; Soundararajan, Murari; Cuanillon, Philippe; Braunmueller, Falk; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-01-01

    An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260 GHz at power levels less than 1 W. The sweep rate of frequency modulation can reach 14 kHz, and its amplitude is fixed at 50 MHz. In water/glycerol glassy ice doped with 40 mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15 K, thus giving a DNP enhancement of about 80. By employing λ / 4 and λ / 8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power.

  9. Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260GHz.

    PubMed

    Yoon, Dongyoung; Soundararajan, Murari; Cuanillon, Philippe; Braunmueller, Falk; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-01-01

    An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260GHz at power levels less than 1W. The sweep rate of frequency modulation can reach 14kHz, and its amplitude is fixed at 50MHz. In water/glycerol glassy ice doped with 40mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15K, thus giving a DNP enhancement of about 80. By employing λ/4 and λ/8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power. PMID:26759116

  10. Theoretical aspects of dynamic nuclear polarization in the solid state - The cross effect

    NASA Astrophysics Data System (ADS)

    Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

    2012-01-01

    In recent years Dynamic Nuclear Polarization (DNP) signal enhancement techniques have become an important and integral part of modern NMR and MRI spectroscopy. The DNP mechanisms transferring polarization from unpaired electrons to the nuclei in the sample is accomplished by microwave (MW) irradiation. For solid samples a distinction is made between three main enhancement processes: Solid Effect (SE), Cross Effect (CE) and Thermal Mixing (TM) DNP. In a recent study we revisited the solid state SE-DNP mechanism at high magnetic fields, using a spin density operator description involving spin relaxation, for the case of an isolated electron spin interacting with neighboring nuclei. In this publication we extend this study by considering the hyper-polarization of nuclei in systems containing two interacting electrons. In these spin systems both processes SE-DNP and CE-DNP are simultaneously active. As previously, a quantum description taking into account spin relaxation is used to calculate the dynamics of spin systems consisting of interacting electron pairs coupled to (core) nuclei. Numerical simulations are used to demonstrate the dependence of the SE- and CE-DNP enhancements on the MW irradiation power and frequency, on electron, nuclear and cross relaxation mechanisms and on the spin interactions. The influence of the presence of many nuclei on the hyper-polarization of an individual core nucleus is examined, showing the similarities between the two DNP processes. These studies also indicate the advantages of the CE- over the SE-DNP processes, both driving the polarization of the bulk nuclei, via the nuclear dipole-dipole interactions.

  11. Nuclear physics detector technology applied to plant biology research

    SciTech Connect

    Weisenberger, Andrew G.; Kross, Brian J.; Lee, Seung Joo; McKisson, John E.; Xi, Wenze; Zorn, Carl J.; Howell, Calvin; Crowell, A.S.; Reid, C.D.; Smith, Mark

    2013-08-01

    The ability to detect the emissions of radioactive isotopes through radioactive decay (e.g. beta particles, x-rays and gamma-rays) has been used for over 80 years as a tracer method for studying natural phenomena. More recently a positron emitting radioisotope of carbon: {sup 11}C has been utilized as a {sup 11}CO{sub 2} tracer for plant ecophysiology research. Because of its ease of incorporation into the plant via photosynthesis, the {sup 11}CO{sub 2} radiotracer is a powerful tool for use in plant biology research. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using {sup 11}CO{sub 2}. Presently there are several groups developing and using new PET instrumentation for plant based studies. Thomas Jefferson National Accelerator Facility (Jefferson Lab) in collaboration with the Duke University Phytotron and the Triangle Universities Nuclear Laboratory (TUNL) is involved in PET detector development for plant imaging utilizing technologies developed for nuclear physics research. The latest developments of the use of a LYSO scintillator based PET detector system for {sup 11}CO{sub 2} tracer studies in plants will be briefly outlined.

  12. Applying laser speckle images to skin science: skin lesion differentiation by polarization

    NASA Astrophysics Data System (ADS)

    Lee, Tim K.; Tchvialeva, Lioudmila; Dhadwal, Gurbir; Sotoodian, Bahman; Kalai, Sunil; Zeng, Haishan; Lui, Harvey; McLean, David I.

    2012-01-01

    Skin cancer is a worldwide health problem. It is the most common cancer in the countries with a large white population; furthermore, the incidence of malignant melanoma, the most dangerous form of skin cancer, has been increasing steadily over the last three decades. There is an urgent need to develop in-vivo, noninvasive diagnostic tools for the disease. This paper attempts to response to the challenge by introducing a simple and fast method based on polarization and laser speckle. The degree of maintaining polarization estimates the fraction of linearly maintaining polarization in the backscattered speckle field. Clinical experiments of 214 skin lesions including malignant melanomas, squamous cell carcinomas, basal cell carcinomas, nevi, and seborrheic keratoses demonstrated that such a parameter can potentially diagnose different skin lesion types. ROC analyses showed that malignant melanoma and seborrheic keratosis could be differentiated by both the blue and red lasers with the area under the curve (AUC) = 0.8 and 0.7, respectively. Also malignant melanoma and squamous cell carcinoma could be separated by the blue laser (AUC = 0.9), while nevus and seborrheic keratosis could be identified using the red laser (AUC = 0.7). These experiments demonstrated that polarization could be a potential in-vivo diagnostic indicator for skin diseases.

  13. Applying laser speckle images to skin science: skin lesion differentiation by polarization

    NASA Astrophysics Data System (ADS)

    Lee, Tim K.; Tchvialeva, Lioudmila; Dhadwal, Gurbir; Sotoodian, Bahman; Kalai, Sunil; Zeng, Haishan; Lui, Harvey; McLean, David I.

    2011-09-01

    Skin cancer is a worldwide health problem. It is the most common cancer in the countries with a large white population; furthermore, the incidence of malignant melanoma, the most dangerous form of skin cancer, has been increasing steadily over the last three decades. There is an urgent need to develop in-vivo, noninvasive diagnostic tools for the disease. This paper attempts to response to the challenge by introducing a simple and fast method based on polarization and laser speckle. The degree of maintaining polarization estimates the fraction of linearly maintaining polarization in the backscattered speckle field. Clinical experiments of 214 skin lesions including malignant melanomas, squamous cell carcinomas, basal cell carcinomas, nevi, and seborrheic keratoses demonstrated that such a parameter can potentially diagnose different skin lesion types. ROC analyses showed that malignant melanoma and seborrheic keratosis could be differentiated by both the blue and red lasers with the area under the curve (AUC) = 0.8 and 0.7, respectively. Also malignant melanoma and squamous cell carcinoma could be separated by the blue laser (AUC = 0.9), while nevus and seborrheic keratosis could be identified using the red laser (AUC = 0.7). These experiments demonstrated that polarization could be a potential in-vivo diagnostic indicator for skin diseases.

  14. Introducing Students to Plant Geography: Polar Ordination Applied to Hanging Gardens.

    ERIC Educational Resources Information Center

    Malanson, George P.; And Others

    1993-01-01

    Reports on a research study in which college students used a statistical ordination method to reveal relationships among plant community structures and physical, disturbance, and spatial variables. Concludes that polar ordination helps students understand the methodology of plant geography and encourages further student research. (CFR)

  15. Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures

    NASA Astrophysics Data System (ADS)

    Kuzma, N. N.; Pourfathi, M.; Kara, H.; Manasseh, P.; Ghosh, R. K.; Ardenkjaer-Larsen, J. H.; Kadlecek, S. J.; Rizi, R. R.

    2012-09-01

    During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, 129Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by 1H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of 129Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T1 relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of 129Xe polarization, from 5.3% to 21%.

  16. Polarization propagator approach to the dynamic nuclear electric shielding in LiH molecule

    NASA Astrophysics Data System (ADS)

    Lazzeretti, P.; Rossi, E.; Zanasi, R.

    1983-07-01

    The frequency dependence of the dipole electric polarizability and electric shielding tensors of hydrogen and lithium nuclei in the LiH molecule has been studied via some approximations to the polarization propagator method, i.e., STA, TDA, and RPA, allowing for dipole length, velocity, acceleration, and mixed formalisms. The RPA nuclear electric shieldings are in a fairly good agreement with the corresponding experimental data, a discrepancy being observed for the parallel component at the Li nucleus.

  17. Pair approximation for polarization interaction and adiabatic nuclear and electronic sampling method for fluids with dipole polarizability

    NASA Astrophysics Data System (ADS)

    Predota, Milan; Cummings, Peter T.; Chialvo, Ariel A.

    The adiabatic nuclear and electronic sampling method (ANES), originally formulated as an efficient Monte Carlo algorithm for systems with fluctuating charges, is applied to the simulation of a polarizable water model with induced dipole moments. Structural, thermodynamic and dipolar properties obtained by ANES and a newer algorithm, the pair approximation for polarization interaction (PAPI), are compared with full iteration. With the best parameters, the inaccuracy of both approximate methods was found to be comparable with the uncertainty of the full iteration. The PAPI method with iteration radius equal to the second minimum of the oxygen-oxygen correlation function is, depending on the convergence tolerance, 10-15 times faster than the full iteration for 256 molecules, and yields very accurate structure and thermodynamics with deviation about 0.3%. When the iteration radius is increased to the cutoff distance, exact results are recovered at the cost of decreased efficiency. The ANES method with small nuclear displacements proved to inefficiently sample the configurational space. Simulations at low electronic temperatures with large nuclear displacements are inaccurate for up to 100 electronic moves, and increasing this number would make the simulations as slow as the full iteration. The most accurate and efficient adiabatic ANES simulations are those with infinite electronic temperature, large nuclear displacements and 1-10 electronic moves. The extra freedom of induced dipoles in the ANES method at high electronic temperatures modifies the observed dipolar properties; however, the question of whether the dielectric constant is also modified needs further consideration.

  18. Applying twisted boundary conditions for few-body nuclear systems

    NASA Astrophysics Data System (ADS)

    Körber, Christopher; Luu, Thomas

    2016-05-01

    We describe and implement twisted boundary conditions for the deuteron and triton systems within finite volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twist angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length L ≈8 -14 fm. Of particular importance is our derivation and numerical verification of three-body analogs of "i-periodic" twist angles that eliminate the leading-order finite-volume effects to the three-body binding energy.

  19. Photothermal microscopy applied to the characterization of nuclear fuel pellets

    NASA Astrophysics Data System (ADS)

    Zaldivar Escola, F.; Martínez, O. E.; Mingolo, N.; Kempf, R.

    2013-04-01

    The photothermal photodeflection technique is shown to provide information on the homogeneity of fuel pellets, pore distribution, clustering detection of pure urania and gadolinea and to provide a two-dimensional mapping of the thermal diffusivity correlated to the composition of the interdiffused Gadolinium and Uranium oxide. Histograms of the thermal diffusivity distribution become a reliable quantitative way of quantifying the degree of homogeneity and the width of the histogram can be used as a direct measure of the homogeneity. These quantitative measures of the homogeneity of the samples at microscopic levels provides a protocol that can be used as a reliable specification and quality control method for nuclear fuels, substituting with a single test a battery of expensive, time consuming and operator dependent techniques.

  20. Optimization of 13C dynamic nuclear polarization: isotopic labeling of free radicals

    NASA Astrophysics Data System (ADS)

    Niedbalski, Peter; Parish, Christopher; Kiswandi, Andhika; Lumata, Lloyd

    Dynamic nuclear polarization (DNP) is a physics technique that amplifies the nuclear magnetic resonance (NMR) signals by transferring the high polarization of the electrons to the nuclear spins. Thus, the choice of free radical is crucial in DNP as it can directly affect the NMR signal enhancement levels, typically on the order of several thousand-fold in the liquid-state. In this study, we have investigated the efficiency of four variants of the well-known 4-oxo-TEMPO radical (normal 4-oxo-TEMPO plus its 15N-enriched and/or perdeuterated variants) for use in DNP of an important metabolic tracer [1-13C]acetate. Though the variants have significant differences in electron paramagnetic resonance (EPR) spectra, we have found that changing the composition of the TEMPO radical through deuteration or 15N doping yields no significant difference in 13C DNP efficiency at 3.35 T and 1.2 K. On the other hand, deuteration of the solvent causes a significant increase of 13C polarization that is consistent over all the 4-oxo-TEMPO variants. These findings are consistent with the thermal mixing model of DNP. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and the Robert A. Welch Foundation Grant No. AT-1877.

  1. A multi-sample 94 GHz dissolution dynamic-nuclear-polarization system.

    PubMed

    Batel, Michael; Krajewski, Marcin; Weiss, Kilian; With, Oliver; Däpp, Alexander; Hunkeler, Andreas; Gimersky, Martin; Pruessmann, Klaas P; Boesiger, Peter; Meier, Beat H; Kozerke, Sebastian; Ernst, Matthias

    2012-01-01

    We describe the design and initial performance results of a multi-sample dissolution dynamic-nuclear-polarization (DNP) polarizer based on a Helium-temperature NMR cryostat for use in a wide-bore NMR magnet with a room-temperature bore. The system is designed to accommodate up to six samples in a revolver-style sample changer that allows changing samples at liquid-Helium temperature and at pressures ranging from ambient pressure down to 1 mbar. The multi-sample setup is motivated by the desire to do repetitive in vivo measurements and to characterize the DNP process by investigating samples of different chemical composition. The system can be loaded with up to six samples simultaneously to reduce sample loading and unloading. Therefore, series of experiments can be carried out faster and more reliably. The DNP probe contains an oversized microwave cavity and includes EPR and NMR capabilities for monitoring the DNP process. In the solid state, DNP enhancements corresponding to ∼45% polarization for [1-(13)C]pyruvic acid with a trityl radical have been measured. In the initial liquid-state acquisition experiments described here, the polarization was found to be ∼13%, corresponding to an enhancement factor exceeding 16,000 relative to thermal polarization at 9.4 T and ambient temperature. PMID:22142831

  2. A multi-sample 94 GHz dissolution dynamic-nuclear-polarization system

    NASA Astrophysics Data System (ADS)

    Batel, Michael; Krajewski, Marcin; Weiss, Kilian; With, Oliver; Däpp, Alexander; Hunkeler, Andreas; Gimersky, Martin; Pruessmann, Klaas P.; Boesiger, Peter; Meier, Beat H.; Kozerke, Sebastian; Ernst, Matthias

    2012-01-01

    We describe the design and initial performance results of a multi-sample dissolution dynamic-nuclear-polarization (DNP) polarizer based on a Helium-temperature NMR cryostat for use in a wide-bore NMR magnet with a room-temperature bore. The system is designed to accommodate up to six samples in a revolver-style sample changer that allows changing samples at liquid-Helium temperature and at pressures ranging from ambient pressure down to 1 mbar. The multi-sample setup is motivated by the desire to do repetitive in vivo measurements and to characterize the DNP process by investigating samples of different chemical composition. The system can be loaded with up to six samples simultaneously to reduce sample loading and unloading. Therefore, series of experiments can be carried out faster and more reliably. The DNP probe contains an oversized microwave cavity and includes EPR and NMR capabilities for monitoring the DNP process. In the solid state, DNP enhancements corresponding to ˜45% polarization for [1- 13C]pyruvic acid with a trityl radical have been measured. In the initial liquid-state acquisition experiments described here, the polarization was found to be ˜13%, corresponding to an enhancement factor exceeding 16,000 relative to thermal polarization at 9.4 T and ambient temperature.

  3. Reverse micelles as a platform for dynamic nuclear polarization in solution NMR of proteins.

    PubMed

    Valentine, Kathleen G; Mathies, Guinevere; Bédard, Sabrina; Nucci, Nathaniel V; Dodevski, Igor; Stetz, Matthew A; Can, Thach V; Griffin, Robert G; Wand, A Joshua

    2014-02-19

    Despite tremendous advances in recent years, solution NMR remains fundamentally restricted due to its inherent insensitivity. Dynamic nuclear polarization (DNP) potentially offers significant improvements in this respect. The basic DNP strategy is to irradiate the EPR transitions of a stable radical and transfer this nonequilibrium polarization to the hydrogen spins of water, which will in turn transfer polarization to the hydrogens of the macromolecule. Unfortunately, these EPR transitions lie in the microwave range of the electromagnetic spectrum where bulk water absorbs strongly, often resulting in catastrophic heating. Furthermore, the residence times of water on the surface of the protein in bulk solution are generally too short for efficient transfer of polarization. Here we take advantage of the properties of solutions of encapsulated proteins dissolved in low viscosity solvents to implement DNP in liquids. Such samples are largely transparent to the microwave frequencies required and thereby avoid significant heating. Nitroxide radicals are introduced into the reverse micelle system in three ways: attached to the protein, embedded in the reverse micelle shell, and free in the aqueous core. Significant enhancements of the water resonance ranging up to ∼-93 at 0.35 T were observed. We also find that the hydration properties of encapsulated proteins allow for efficient polarization transfer from water to the protein. These and other observations suggest that merging reverse micelle encapsulation technology with DNP offers a route to a significant increase in the sensitivity of solution NMR spectroscopy of proteins and other biomolecules. PMID:24456213

  4. Cellular Solid-State NMR Investigation of a Membrane Protein Using Dynamic Nuclear Polarization

    PubMed Central

    Yamamoto, Kazutoshi; Caporini, Marc A.; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2014-01-01

    While an increasing number of structural biology studies successfully demonstrate the power of high-resolution structures and dynamics of membrane proteins in fully understanding their function, there is considerable interest in developing NMR approaches to obtain such information in a cellular setting. As long as the proteins inside the living cell tumble rapidly in the NMR timescale, recently developed in-cell solution NMR approaches can be applied towards the determination of 3D structural information. However, there are numerous challenges that need to be overcome to study membrane proteins inside a cell. Research in our laboratory is focused on developing a combination of solid-state NMR and biological approaches to overcome these challenges with a specific emphasis on obtaining high-resolution structural insights into electron transfer biological processes mediated by membrane-bound proteins like mammalian cytochrome b5, cytochrome P450 and cytochrome P450 reductase. In this study, we demonstrate the feasibility of using the signal-enhancement rendered by dynamic nuclear polarization (DNP) magic angle spinning (MAS) NMR spectroscopy for in-cell studies on a membrane-anchored protein. Our experimental results obtained from 13C-labeled membrane-anchored cytochrome b5 in native Escherichia coli cells show a ~16-fold DNP signal enhancement (ε). Further, results obtained from a 2D 13C/13C chemical shift correlation MAS experiment demonstrates that it is highly possible to suppress the background signals from other cellular contents for high-resolution structural studies on membrane proteins. We believe that this study would pave new avenues for high-resolution 3D structural studies on a variety of membrane-associated proteins and their complexes in the cellular context to fully understand their functional roles in physiological processes. PMID:25017802

  5. Applying activity-based costing to the nuclear medicine unit.

    PubMed

    Suthummanon, Sakesun; Omachonu, Vincent K; Akcin, Mehmet

    2005-08-01

    Previous studies have shown the feasibility of using activity-based costing (ABC) in hospital environments. However, many of these studies discuss the general applications of ABC in health-care organizations. This research explores the potential application of ABC to the nuclear medicine unit (NMU) at a teaching hospital. The finding indicates that the current cost averages 236.11 US dollars for all procedures, which is quite different from the costs computed by using ABC. The difference is most significant with positron emission tomography scan, 463 US dollars (an increase of 96%), as well as bone scan and thyroid scan, 114 US dollars (a decrease of 52%). The result of ABC analysis demonstrates that the operational time (machine time and direct labour time) and the cost of drugs have the most influence on cost per procedure. Clearly, to reduce the cost per procedure for the NMU, the reduction in operational time and cost of drugs should be analysed. The result also indicates that ABC can be used to improve resource allocation and management. It can be an important aid in making management decisions, particularly for improving pricing practices by making costing more accurate. It also facilitates the identification of underutilized resources and related costs, leading to cost reduction. The ABC system will also help hospitals control costs, improve the quality and efficiency of the care they provide, and manage their resources better. PMID:16102243

  6. Applying a microfacet model to polarized light scattering measurements of the Earth's surface

    NASA Astrophysics Data System (ADS)

    Kupinski, Meredith; Bradley, Christine; Diner, David; Xu, Feng; Chipman, Russell

    2015-09-01

    Representative examples from three-years of measurements from JPL's Ground-based Multiangle SpectroPolarimetric Imager (Ground-MSPI)[1] are compared to a model for the surface polarized bidirectional reflectance distribution matrix (BRDM). Ground-MSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire push-broom imagery of outdoor landscapes. The camera uses a photoelastic-modulator-based polarimetric imaging technique to measure linear Stokes parameters in three wavebands (470, 660, and 865 nm) with a +/-0.005 uncertainty in degree of linear polarization (DoLP). Comparisons between MSPI measurements, BRDM models, and common modifications to the model are made over a range of scattering angles determined from a fixed viewing geometry and varying sun positions over time. The BRDM model is comprised of a volumetric reflection term plus a specular reflection term of Fresnel-reflecting micro-facets. We consider modifications to this model using a shadowing function and two different micro-facet scattering density functions. We report the root-mean-square error (RMSE) between the Ground-MSPI measurements and BRDM model. The BRDM model predicts an angle of the linear polarization (AoLP) that is perpendicular to the scattering plane. This is usually, but not always, observed in Ground-MSPI measurements and in this work we offer explanations for some of the deviations from the model.

  7. New filter for iodine applied in nuclear medicine services.

    PubMed

    Ramos, V S; Crispim, V R; Brandão, L E B

    2013-12-01

    In Nuclear Medicine, radioiodine, in various chemical forms, is a key tracer used in diagnostic practices and/or therapy. Medical professionals may incorporate radioactive iodine during the preparation of the dose to be administered to the patient. In radioactive iodine therapy doses ranging from 3.7 to 7.4 GBq per patient are employed. Thus, aiming at reducing the risk of occupational contamination, we developed a low cost filter to be installed at the exit of the exhaust system (where doses of radioiodine are handled within fume hoods, and new filters will be installed at their exit), using domestic technology. The effectiveness of radioactive iodine retention by silver impregnated silica [10%] crystals and natural activated carbon was verified using radiotracer techniques. The results showed that natural activated carbon and silver impregnated silica are effective for I2 capture with large or small amounts of substrate but the use of activated carbon is restricted due to its low flash point (423 K). Besides, when poisoned by organic solvents, this flash point may become lower, causing explosions if absorbing large amounts of nitrates. To hold the CH3I gas, it was necessary to use natural activated carbon since it was not absorbed by SiO2+Ag crystals. We concluded that, for an exhaust flow range of (145 ± 2)m(3)/h, a double stage filter using SiO2+Ag in the first stage and natural activated carbon in the second stage is sufficient to meet radiological safety requirements. PMID:23974306

  8. p -shell carrier assisted dynamic nuclear spin polarization in single quantum dots at zero external magnetic field

    NASA Astrophysics Data System (ADS)

    Fong, C. F.; Ota, Y.; Harbord, E.; Iwamoto, S.; Arakawa, Y.

    2016-03-01

    Repeated injection of spin-polarized carriers in a quantum dot (QD) leads to the polarization of nuclear spins, a process known as dynamic nuclear spin polarization (DNP). Here, we report the observation of p-shell carrier assisted DNP in single QDs at zero external magnetic field. The nuclear field—measured by using the Overhauser shift of the singly charged exciton state of the QDs—continues to increase, even after the carrier population in the s-shell saturates. This is also accompanied by an abrupt increase in nuclear spin buildup time as p-shell emission overtakes that of the s shell. We attribute the observation to p-shell electrons strongly altering the nuclear spin dynamics in the QD, supported by numerical simulation results based on a rate equation model of coupling between electron and nuclear spin system. Dynamic nuclear spin polarization with p-shell carriers could open up avenues for further control to increase the degree of nuclear spin polarization in QDs.

  9. Achievement of high nuclear spin polarization using lanthanides as low-temperature NMR relaxation agents.

    PubMed

    Peat, David T; Horsewill, Anthony J; Köckenberger, Walter; Perez Linde, Angel J; Gadian, David G; Owers-Bradley, John R

    2013-05-28

    Many approaches are now available for achieving high levels of nuclear spin polarization. One of these methods is based on the notion that as the temperature is reduced, the equilibrium nuclear polarization will increase, according to the Boltzmann distribution. The main problem with this approach is the length of time it may take to approach thermal equilibrium at low temperatures, since nuclear relaxation times (characterized by the spin-lattice relaxation time T1) can become very long. Here, we show, by means of relaxation time measurements of frozen solutions, that selected lanthanide ions, in the form of their chelates with DTPA, can act as effective relaxation agents at low temperatures. Differential effects are seen with the different lanthanides that were tested, holmium and dysprosium showing highest relaxivity, while gadolinium is ineffective at temperatures of 20 K and below. These observations are consistent with the known electron-spin relaxation time characteristics of these lanthanides. The maximum relaxivity occurs at around 10 K for Ho-DTPA and 20 K for Dy-DTPA. Moreover, these two agents show only modest relaxivity at room temperature, and can thus be regarded as relaxation switches. We conclude that these agents can speed up solid state NMR experiments by reducing the T1 values of the relevant nuclei, and hence increasing the rate at which data can be acquired. They could also be of value in the context of a simple low-cost method of achieving several-hundred-fold improvements in polarization for experiments in which samples are pre-polarized at low temperatures, then rewarmed and dissolved immediately prior to analysis. PMID:23588269

  10. Low-Temperature Dynamic Nuclear Polarization at 9.4 Tesla With a 30 Milliwatt Microwave Source

    PubMed Central

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

    2010-01-01

    Dynamic nuclear polarization (DNP) can provide large signal enhancements in nuclear magnetic resonance (NMR) by transfer of polarization from electron spins to nuclear spins. We discuss several aspects of DNP experiments at 9.4 Tesla (400 MHz resonant frequency for 1H, 264 GHz for electron spins in organic radicals) in the 7–80 K temperature range, using a 30 mW, frequency-tunable microwave source and a quasi-optical microwave bridge for polarization control and low-loss microwave transmission. In experiments on frozen glycerol/water doped with nitroxide radicals, DNP signal enhancements up to a factor of 80 are observed (relative to 1H NMR signals with thermal equilibrium spin polarization). The largest sensitivity enhancements are observed with a new triradical dopant, DOTOPA-TEMPO. Field modulation with a 10 G root-mean-squared amplitude during DNP increases the nuclear spin polarizations by up to 135%. Dependencies of 1H NMR signal amplitudes, nuclear spin relaxation times, and DNP build-up times on the dopant and its concentration, temperature, microwave power, and modulation frequency are reported and discussed. The benefits of low-temperature DNP can be dramatic: the 1H spin polarization is increased approximately 1000-fold at 7 K with DNP, relative to thermal polarization at 80 K. PMID:20392658

  11. Low-temperature dynamic nuclear polarization at 9.4 T with a 30 mW microwave source

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    Dynamic nuclear polarization (DNP) can provide large signal enhancements in nuclear magnetic resonance (NMR) by transfer of polarization from electron spins to nuclear spins. We discuss several aspects of DNP experiments at 9.4 T (400 MHz resonant frequency for 1H, 264 GHz for electron spins in organic radicals) in the 7-80 K temperature range, using a 30 mW, frequency-tunable microwave source and a quasi-optical microwave bridge for polarization control and low-loss microwave transmission. In experiments on frozen glycerol/water doped with nitroxide radicals, DNP signal enhancements up to a factor of 80 are observed (relative to 1H NMR signals with thermal equilibrium spin polarization). The largest sensitivity enhancements are observed with a new triradical dopant, DOTOPA-TEMPO. Field modulation with a 10 G root-mean-squared amplitude during DNP increases the nuclear spin polarizations by up to 135%. Dependencies of 1H NMR signal amplitudes, nuclear spin relaxation times, and DNP build-up times on the dopant and its concentration, temperature, microwave power, and modulation frequency are reported and discussed. The benefits of low-temperature DNP can be dramatic: the 1H spin polarization is increased approximately 1000-fold at 7 K with DNP, relative to thermal polarization at 80 K.

  12. Nuclear spin polarization following intermediate-energy heavy-ion reactions

    SciTech Connect

    Groh, D. E.; Pinter, J. S.; Mantica, P. F.; Mertzimekis, T. J.; Stuchbery, A. E.; Khoa, D. T.

    2007-11-15

    Intermediate-energy heavy-ion collisions can produce a spin polarization of the projectile-like species. Spin polarization has been observed for both nucleon removal and nucleon pickup processes. Qualitative agreement with measured spin polarization as a function of the momentum of the projectile-like fragment is found in a kinematic model that considers conservation of linear and angular momentum and assumes peripheral interactions between the fast projectile and target. Better quantitative agreement was reached by including more realistic angular distributions and deorientation caused by {gamma}-ray emission and by correcting for the out-of-plane acceptance. The newly introduced corrections were found to apply to both nucleon removal and nucleon pickup processes.

  13. Applied Nuclear Science Research and Development progress report, June 1, 1984-May 31, 1985

    SciTech Connect

    Arthur, E.D.; Mutschlecner, A.D.

    1985-09-01

    This progress report describes the activities of the Los Alamos Applied Nuclear Science Group for June 1, 1984 through May 31, 1985. The topical content includes the theory and evaluation of nuclear cross sections; neutron cross section processing and testing; neutron activation, fission products and actinides; and core neutronics code development and application. 70 refs., 31 figs., 15 tabs. (WRF)

  14. {sup 1}H and {sup 15}N dynamic nuclear polarization studies of carbazole

    SciTech Connect

    Hu, J.Z.; Solum, M.S.; Wind, R.A.; Nilsson, B.L.; Peterson, M.A.; Pugmire, R.J.; Grant, D.M.

    2000-05-18

    {sup 15}N NMR experiments, combined with dynamic nuclear polarization (DNP), are reported on carbazole doped with the stable free radical 1,3-bisdiphenylene-2-phenylallyl (BDPA). Doping shortens the nuclear relaxation times and provides paramagnetic centers that can be used to enhance the nuclear signal by means of DNP so that {sup 15}N NMR experiments can be done in minutes. The factors were measured in a 1.4 T external field, using both unlabeled and 98% {sup 15}N labeled carbazole with doping levels varying between 0.65 and 5.0 wt {degree} BDPA. A doping level of approximately 1 wt {degree} produced optimal results. DNP enhancement factors of 35 and 930 were obtained for {sup 1}H and {sup 15}N, respectively, making it possible to perform {sup 15}N DNP NMR experiments at the natural abundance level.

  15. 1H and 15N Dynamic Nuclear Polarization Studies of Carbazole

    SciTech Connect

    Hu, Jian Zhi; Solum, Mark S.; Wind, Robert A.; Nilsson, Brad L.; Peterson, Matt A.; Pugmire, Ronald J.; Grant, David M.

    2000-01-01

    15N NMR experiments, combined with dynamic nuclear polarization (DNP), are reported on carbazole doped with the stable free radical 1,3 bisdiphenylene-2 phenylally1 (BDPA). Doping shortens the nuclear relaxation times and provides paramagnetic centers that can be used to enhance the nuclear signal by means of DNP so that 15 N NMR experiments can be done in minutes. The factors were measured in a 1.4 T external field, using both unlabeled and 98% 15N labeled carbazole with doping levels varying between 0.65 and 5.0 wt % BDPA. A doping level of approximately 1 wt % produced optimal results. DNP enhancement factors of 35 and 930 were obtained for 1H and 15N, respectively making it possible to perform 15N DNP NMR experiments at the natural abundance level.

  16. Correlation measurements in nuclear {beta}-decay using traps and polarized low energy beams

    SciTech Connect

    Naviliat-Cuncic, Oscar

    2013-05-06

    Precision measurements in nuclear {beta}-decay provide sensitive means to test discrete symmetries in the weak interaction and to determine some of the fundamental constants in semi-leptonic decays, like the coupling of the lightest quarks to charged weak bosons. The main motivation of such measurements is to find deviations from Standard Model predictions as possible indications of new physics. In this contribution I will focus on two topics related to precision measurements in nuclear {beta}-decay: i) the determination of the V{sub ud} element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix from nuclear mirror transitions and ii) the search for exotic scalar or tensor contributions from {beta}{nu} angular correlations. The purpose is to underline the role being played by experimental techniques based on the confinement of radioactive species with atom and ion traps as well as the plans to use low energy polarized beams.

  17. 250 GHz CW Gyrotron Oscillator for Dynamic Nuclear Polarization in Biological Solid State NMR

    PubMed Central

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13C,15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low

  18. 250 GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

    NASA Astrophysics Data System (ADS)

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2007-12-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U- 13C, 15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as

  19. 250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR.

    PubMed

    Bajaj, Vikram S; Hornstein, Melissa K; Kreischer, Kenneth E; Sirigiri, Jagadishwar R; Woskov, Paul P; Mak-Jurkauskas, Melody L; Herzfeld, Judith; Temkin, Richard J; Griffin, Robert G

    2007-12-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz (1)H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U-(13)C, (15)N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents

  20. Increasing oral absorption of polar neuraminidase inhibitors: a prodrug transporter approach applied to oseltamivir analogue.

    PubMed

    Gupta, Deepak; Varghese Gupta, Sheeba; Dahan, Arik; Tsume, Yasuhiro; Hilfinger, John; Lee, Kyung-Dall; Amidon, Gordon L

    2013-02-01

    Poor oral absorption is one of the limiting factors in utilizing the full potential of polar antiviral agents. The neuraminidase target site requires a polar chemical structure for high affinity binding, thus limiting oral efficacy of many high affinity ligands. The aim of this study was to overcome this poor oral absorption barrier, utilizing prodrug to target the apical brush border peptide transporter 1 (PEPT1). Guanidine oseltamivir carboxylate (GOCarb) is a highly active polar antiviral agent with insufficient oral bioavailability (4%) to be an effective therapeutic agent. In this report we utilize a carrier-mediated targeted prodrug approach to improve the oral absorption of GOCarb. Acyloxy(alkyl) ester based amino acid linked prodrugs were synthesized and evaluated as potential substrates of mucosal transporters, e.g., PEPT1. Prodrugs were also evaluated for their chemical and enzymatic stability. PEPT1 transport studies included [(3)H]Gly-Sar uptake inhibition in Caco-2 cells and cellular uptake experiments using HeLa cells overexpressing PEPT1. The intestinal membrane permeabilities of the selected prodrugs and the parent drug were then evaluated for epithelial cell transport across Caco-2 monolayers, and in the in situ rat intestinal jejunal perfusion model. Prodrugs exhibited a pH dependent stability with higher stability at acidic pHs. Significant inhibition of uptake (IC(50) <1 mM) was observed for l-valyl and l-isoleucyl amino acid prodrugs in competition experiments with [(3)H]Gly-Sar, indicating a 3-6 times higher affinity for PEPT1 compared to valacyclovir, a well-known PEPT1 substrate and >30-fold increase in affinity compared to GOCarb. The l-valyl prodrug exhibited significant enhancement of uptake in PEPT1/HeLa cells and compared favorably with the well-absorbed valacyclovir. Transepithelial permeability across Caco-2 monolayers showed that these amino acid prodrugs have a 2-5-fold increase in permeability as compared to the parent drug and

  1. A 129 GHz dynamic nuclear polarizer in a wide-bore superconducting magnet

    NASA Astrophysics Data System (ADS)

    Lumata, Lloyd; Martin, Richard; Jindal, Ashish; Malloy, Craig; Sherry, A. Dean; Conradi, Mark S.; Merritt, Matthew

    2011-03-01

    Dynamic nuclear polarization via fast dissolution method has allowed production of solutions containing highly-polarized nuclei (> 10 , 000 - foldenhancementoftheroom - temperatureliquid - stateNMRsignal) ofbio - moleculesfor invitro and invivo metabolicnuclearmagneticresonancespectroscopy (MRS) andimaging (MRI) . Herewepresenttheconstructionanduseofa 129 GHzdynamicnuclearpolarizerina 4.6 Twide - boresuperconductingmagnet . Therelativelylargebore (150 mm) ofthesuperconductingmagnetallowstheuseofacryostatseparatefromthemagnetandroutingofthemicrowavessuchthatthewaveguidedoesnothavetoberemovedbeforedissolution . A 100 mW microwave source operating at 129 GHz was used to irradiate the samples. The cryostat has a 10- liter liquid Helium capacity which lasts for 10-12 hrs of continuous operation. Base temperature of 1.15 K is achieved with a 450 m 3 / hr roots blower pump. Preliminary results will be discussed. This work is supported in part by the National Institutes of Health grant numbers 1R21EB009147-01 and RR02584.

  2. Efficient Dynamic Nuclear Polarization at 800 MHz/527 GHz with Trityl-Nitroxide Biradicals.

    PubMed

    Mathies, Guinevere; Caporini, Marc A; Michaelis, Vladimir K; Liu, Yangping; Hu, Kan-Nian; Mance, Deni; Zweier, Jay L; Rosay, Melanie; Baldus, Marc; Griffin, Robert G

    2015-09-28

    Cross-effect (CE) dynamic nuclear polarization (DNP) is a rapidly developing technique that enhances the signal intensities in magic-angle spinning (MAS) NMR spectra. We report CE DNP experiments at 211, 600, and 800 MHz using a new series of biradical polarizing agents referred to as TEMTriPols, in which a nitroxide (TEMPO) and a trityl radical are chemically tethered. The TEMTriPol molecule with the optimal performance yields a record (1) H NMR signal enhancement of 65 at 800 MHz at a concentration of 10 mM in a glycerol/water solvent matrix. The CE DNP enhancement for the TEMTriPol biradicals does not decrease as the magnetic field is increased in the manner usually observed for bis-nitroxides. Instead, the relatively strong exchange interaction between the trityl and nitroxide moieties determines the magnetic field at which the optimum enhancement is observed. PMID:26268156

  3. Dynamic Nuclear Polarization of membrane proteins: covalently bound spin-labels at protein-protein interfaces

    PubMed Central

    Wylie, Benjamin J; Dzikovski, Boris G.; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H.; McDermott, Ann E.

    2016-01-01

    We demonstrate that dynamic nuclear polarization (DNP) of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of 6-fold for the dimeric protein. The enhancement affect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces. PMID:25828256

  4. Focusing Sources on Induced Polarization and Electrical Resistivity Method Applied to Soil Pollution Problems

    NASA Astrophysics Data System (ADS)

    Tejero, A.; Lopez, A.; Induced Polarization Team

    2013-05-01

    In recent years the problems of soil contamination have been increasing and geophysical methods, particularly electrical resistivity tomography (ERT) have struggled to find and monitor cases of contamination. Moreover, Induced Polarization (IP) has shown promise in mapping contaminant plumes, although both techniques (ERT and IP) have problems like noise, inductive coupling, effects of electrodes, etc. limiting the precision and accuracy of the data. To overcome these problems, this paper introduces a novel technique of focusing sources. This technique reduces the effects of adjacent vertical formations and contacts due to the flowing of current in a vertical way at the zone where the electrode potentials have been deployed. This fact allows obtaining cleaner data of ERT and IP. In order to introduce the proposed technique a vertical contact synthetic model is studied and after to a cultivar area in Hidalgo State, México which presents different types of

  5. Applying polarity rapid assessment method and ultrafiltration to characterize NDMA precursors in wastewater effluents.

    PubMed

    Chen, Chao; Leavey, Shannon; Krasner, Stuart W; Mel Suffet, I H

    2014-06-15

    Certain nitrosamines in water are disinfection byproducts that are probable human carcinogens. Nitrosamines have diverse and complex precursors that include effluent organic matter, some anthropogenic chemicals, and natural (likely non-humic) substances. An easy and selective tool was first developed to characterize nitrosamine precursors in treated wastewaters, including different process effluents. This tool takes advantages of the polarity rapid assessment method (PRAM) and ultrafiltration (UF) (molecular weight distribution) to locate the fractions with the strongest contributions to the nitrosamine precursor pool in the effluent organic matter. Strong cation exchange (SCX) and C18 solid-phase extraction cartridges were used for their high selectivity for nitrosamine precursors. The details of PRAM operation, such as cartridge clean-up, capacity, pH influence, and quality control were included in this paper, as well as the main parameters of UF operation. Preliminary testing of the PRAM/UF method with effluents from one wastewater treatment plant gave very informative results. SCX retained 45-90% of the N-nitrosodimethylamine (NDMA) formation potential (FP)-a measure of the precursors-in secondary and tertiary wastewater effluents. These results are consistent with NDMA precursors likely having a positively charged amine group. C18 adsorbed 30-45% of the NDMAFP, which indicates that a substantial portion of these precursors were non-polar. The small molecular weight (MW) (<1 kDa) and large MW (>10 kDa) fractions obtained from UF were the primary contributors to NDMAFP. The combination of PRAM and UF brings important information on the characteristics of nitrosamine precursors in water with easy operation. PMID:24709532

  6. Control of transmission of right circularly polarized laser light in overdense plasma by applied magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Ma, Guangjin; Yu, Wei; Yu, M. Y.; Luan, Shixia; Wu, Dong

    2016-05-01

    The effect of a transient magnetic field on right-hand circularly polarized (RHCP) laser light propagation in overcritical-density plasma is investigated. When the electron gyrofrequency is larger than the wave frequency, RHCP light can propagate along the external magnetic field in an overcritical density plasma without resonance or cutoff. However, when the magnetic field falls to below the cyclotron resonance point, the propagating laser pulse will be truncated and the local plasma electrons resonantly heated. Particle-in-cell simulation shows that when applied to a thin slab, the process can produce intense two-cycle light pulses as well as long-lasting self-magnetic fields.

  7. Control of transmission of right circularly polarized laser light in overdense plasma by applied magnetic field pulses.

    PubMed

    Ma, Guangjin; Yu, Wei; Yu, M Y; Luan, Shixia; Wu, Dong

    2016-05-01

    The effect of a transient magnetic field on right-hand circularly polarized (RHCP) laser light propagation in overcritical-density plasma is investigated. When the electron gyrofrequency is larger than the wave frequency, RHCP light can propagate along the external magnetic field in an overcritical density plasma without resonance or cutoff. However, when the magnetic field falls to below the cyclotron resonance point, the propagating laser pulse will be truncated and the local plasma electrons resonantly heated. Particle-in-cell simulation shows that when applied to a thin slab, the process can produce intense two-cycle light pulses as well as long-lasting self-magnetic fields. PMID:27300997

  8. Microtubule Initiation from the Nuclear Surface Controls Cortical Microtubule Growth Polarity and Orientation in Arabidopsis thaliana

    PubMed Central

    Ambrose, Chris; Wasteneys, Geoffrey O.

    2014-01-01

    The nuclear envelope in plant cells has long been known to be a microtubule organizing center (MTOC), but its influence on microtubule organization in the cell cortex has been unclear. Here we show that nuclear MTOC activity favors the formation of longitudinal cortical microtubule (CMT) arrays. We used green fluorescent protein (GFP)-tagged gamma tubulin-complex protein 2 (GCP2) to identify nuclear MTOC activity and GFP-tagged End-Binding Protein 1b (EB1b) to track microtubule growth directions. We found that microtubules initiate from nuclei and enter the cortex in two directions along the long axis of the cell, creating bipolar longitudinal CMT arrays. Such arrays were observed in all cell types showing nuclear MTOC activity, including root hairs, recently divided cells in root tips, and the leaf epidermis. In order to confirm the causal nature of nuclei in bipolar array formation, we displaced nuclei by centrifugation, which generated a corresponding shift in the bipolarity split point. We also found that bipolar CMT arrays were associated with bidirectional trafficking of vesicular components to cell ends. Together, these findings reveal a conserved function of plant nuclear MTOCs and centrosomes/spindle pole bodies in animals and fungi, wherein all structures serve to establish polarities in microtubule growth. PMID:25008974

  9. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100 K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered.

  10. Interlayer transport of nuclear spin polarization in ν = 2/3 quantum Hall states

    NASA Astrophysics Data System (ADS)

    Tsuda, S.; Nguyen, M. H.; Terasawa, D.; Fukuda, A.; Zheng, Y. D.; Arai, T.; Sawada, A.

    2013-12-01

    We investigated the interlayer diffusion of nuclear spin polarization (NSP) by using the phase transition point of quantum Hall states at a Landau level filling factor of ν ν 2/3 in a double quantum well sample. When the NSP is current-pumped in one layer, the magnetoresistance in the other layer is enhanced after a delay of 150 s and the raising speed of this layer is lower than that of the pumped layer. The delay and lower value of the raising speed are explained by the diffusion of NSP.

  11. Interlayer transport of nuclear spin polarization in ν = 2/3 quantum Hall states

    SciTech Connect

    Tsuda, S.; Nguyen, M. H.; Terasawa, D.; Fukuda, A.; Zheng, Y. D.; Arai, T.; Sawada, A.

    2013-12-04

    We investigated the interlayer diffusion of nuclear spin polarization (NSP) by using the phase transition point of quantum Hall states at a Landau level filling factor of ν ν 2/3 in a double quantum well sample. When the NSP is current-pumped in one layer, the magnetoresistance in the other layer is enhanced after a delay of 150 s and the raising speed of this layer is lower than that of the pumped layer. The delay and lower value of the raising speed are explained by the diffusion of NSP.

  12. Dynamic nuclear polarization at 9T using a novel 250 Gyrotron microwave source

    NASA Astrophysics Data System (ADS)

    Griffin, Robert G.

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (˜5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz 1H frequencies.

  13. Dynamic nuclear polarization at 9T using a novel 250 gyrotron microwave source.

    PubMed

    Griffin, Robert G

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (∼5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz (1)H frequencies. PMID:22152359

  14. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR.

    PubMed

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered. PMID:26920834

  15. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    SciTech Connect

    Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.

    2015-06-21

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  16. Dynamic nuclear polarization in solid samples by electrical-discharge-induced radicals

    NASA Astrophysics Data System (ADS)

    Katz, Itai; Blank, Aharon

    2015-12-01

    Dynamic nuclear polarization (DNP) is a method for enhancing nuclear magnetic resonance (NMR) signals that has many potential applications in chemistry and medicine. Traditionally, DNP signal enhancement is achieved through the use of exogenous radicals mixed in a solution with the molecules of interest. Here we show that proton DNP signal enhancements can be obtained for solid samples without the use of solvent and exogenous radicals. Radicals are generated primarily on the surface of a solid sample using electrical discharges. These radicals are found suitable for DNP. They are stable under moderate vacuum conditions, yet readily annihilate upon compound dissolution or air exposure. This feature makes them attractive for use in medical applications, where the current variety of radicals used for DNP faces regulatory problems. In addition, this solvent-free method may be found useful for analytical NMR of solid samples which cannot tolerate solvents, such as certain pharmaceutical products.

  17. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Mance, Deni; Gast, Peter; Huber, Martina; Baldus, Marc; Ivanov, Konstantin L.

    2015-06-01

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between "bulk" and "core" nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  18. Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe

    SciTech Connect

    TonThat, D.M.; Augustine, M.P.; Pines, A.; Clarke, J. |

    1997-03-01

    We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 {Omega}. Low-field, {sup 1}H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies {lt}1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. {copyright} {ital 1997 American Institute of Physics.}

  19. Selective Protein Hyperpolarization in Cell Lysates Using Targeted Dynamic Nuclear Polarization.

    PubMed

    Viennet, Thibault; Viegas, Aldino; Kuepper, Arne; Arens, Sabine; Gelev, Vladimir; Petrov, Ognyan; Grossmann, Tom N; Heise, Henrike; Etzkorn, Manuel

    2016-08-26

    Nuclear magnetic resonance (NMR) spectroscopy has the intrinsic capabilities to investigate proteins in native environments. In general, however, NMR relies on non-natural protein purity and concentration to increase the desired signal over the background. We here report on the efficient and specific hyperpolarization of low amounts of a target protein in a large isotope-labeled background by combining dynamic nuclear polarization (DNP) and the selectivity of protein interactions. Using a biradical-labeled ligand, we were able to direct the hyperpolarization to the protein of interest, maintaining comparable signal enhancement with about 400-fold less radicals than conventionally used. We could selectively filter out our target protein directly from crude cell lysate obtained from only 8 mL of fully isotope-enriched cell culture. Our approach offers effective means to study proteins with atomic resolution in increasingly native concentrations and environments. PMID:27351143

  20. Dynamic Nuclear Polarization Methods in Solids and Solutions to Explore Membrane Proteins and Membrane Systems

    NASA Astrophysics Data System (ADS)

    Cheng, Chi-Yuan; Han, Songi

    2013-04-01

    Membrane proteins regulate vital cellular processes, including signaling, ion transport, and vesicular trafficking. Obtaining experimental access to their structures, conformational fluctuations, orientations, locations, and hydration in membrane environments, as well as the lipid membrane properties, is critical to understanding their functions. Dynamic nuclear polarization (DNP) of frozen solids can dramatically boost the sensitivity of current solid-state nuclear magnetic resonance tools to enhance access to membrane protein structures in native membrane environments. Overhauser DNP in the solution state can map out the local and site-specific hydration dynamics landscape of membrane proteins and lipid membranes, critically complementing the structural and dynamics information obtained by electron paramagnetic resonance spectroscopy. Here, we provide an overview of how DNP methods in solids and solutions can significantly increase our understanding of membrane protein structures, dynamics, functions, and hydration in complex biological membrane environments.

  1. Dynamic nuclear polarization methods in solids and solutions to explore membrane proteins and membrane systems.

    PubMed

    Cheng, Chi-Yuan; Han, Songi

    2013-01-01

    Membrane proteins regulate vital cellular processes, including signaling, ion transport, and vesicular trafficking. Obtaining experimental access to their structures, conformational fluctuations, orientations, locations, and hydration in membrane environments, as well as the lipid membrane properties, is critical to understanding their functions. Dynamic nuclear polarization (DNP) of frozen solids can dramatically boost the sensitivity of current solid-state nuclear magnetic resonance tools to enhance access to membrane protein structures in native membrane environments. Overhauser DNP in the solution state can map out the local and site-specific hydration dynamics landscape of membrane proteins and lipid membranes, critically complementing the structural and dynamics information obtained by electron paramagnetic resonance spectroscopy. Here, we provide an overview of how DNP methods in solids and solutions can significantly increase our understanding of membrane protein structures, dynamics, functions, and hydration in complex biological membrane environments. PMID:23331309

  2. Dynamic nuclear polarization in solid samples by electrical-discharge-induced radicals.

    PubMed

    Katz, Itai; Blank, Aharon

    2015-12-01

    Dynamic nuclear polarization (DNP) is a method for enhancing nuclear magnetic resonance (NMR) signals that has many potential applications in chemistry and medicine. Traditionally, DNP signal enhancement is achieved through the use of exogenous radicals mixed in a solution with the molecules of interest. Here we show that proton DNP signal enhancements can be obtained for solid samples without the use of solvent and exogenous radicals. Radicals are generated primarily on the surface of a solid sample using electrical discharges. These radicals are found suitable for DNP. They are stable under moderate vacuum conditions, yet readily annihilate upon compound dissolution or air exposure. This feature makes them attractive for use in medical applications, where the current variety of radicals used for DNP faces regulatory problems. In addition, this solvent-free method may be found useful for analytical NMR of solid samples which cannot tolerate solvents, such as certain pharmaceutical products. PMID:26547016

  3. THz-waves channeling in a monolithic saddle-coil for Dynamic Nuclear Polarization enhanced NMR

    NASA Astrophysics Data System (ADS)

    Macor, A.; de Rijk, E.; Annino, G.; Alberti, S.; Ansermet, J.-Ph.

    2011-10-01

    A saddle coil manufactured by electric discharge machining (EDM) from a solid piece of copper has recently been realized at EPFL for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance experiments (DNP-NMR) at 9.4 T. The corresponding electromagnetic behavior of radio-frequency (400 MHz) and THz (263 GHz) waves were studied by numerical simulation in various measurement configurations. Moreover, we present an experimental method by which the results of the THz-wave numerical modeling are validated. On the basis of the good agreement between numerical and experimental results, we conducted by numerical simulation a systematic analysis on the influence of the coil geometry and of the sample properties on the THz-wave field, which is crucial in view of the optimization of DNP-NMR in solids.

  4. THz-waves channeling in a monolithic saddle-coil for Dynamic Nuclear Polarization enhanced NMR.

    PubMed

    Macor, A; de Rijk, E; Annino, G; Alberti, S; Ansermet, J-Ph

    2011-10-01

    A saddle coil manufactured by electric discharge machining (EDM) from a solid piece of copper has recently been realized at EPFL for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance experiments (DNP-NMR) at 9.4 T. The corresponding electromagnetic behavior of radio-frequency (400 MHz) and THz (263 GHz) waves were studied by numerical simulation in various measurement configurations. Moreover, we present an experimental method by which the results of the THz-wave numerical modeling are validated. On the basis of the good agreement between numerical and experimental results, we conducted by numerical simulation a systematic analysis on the influence of the coil geometry and of the sample properties on the THz-wave field, which is crucial in view of the optimization of DNP-NMR in solids. PMID:21903436

  5. Dynamical magnetic and nuclear polarization in complex spin systems: semi-magnetic II-VI quantum dots

    NASA Astrophysics Data System (ADS)

    Abolfath, Ramin M.; Trojnar, Anna; Roostaei, Bahman; Brabec, Thomas; Hawrylak, Pawel

    2013-06-01

    Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems.

  6. Overhauser Geomagnetic Sensor Based on the Dynamic Nuclear Polarization Effect for Magnetic Prospecting.

    PubMed

    Ge, Jian; Dong, Haobin; Liu, Huan; Yuan, Zhiwen; Dong, He; Zhao, Zhizhuo; Liu, Yonghua; Zhu, Jun; Zhang, Haiyang

    2016-01-01

    Based on the dynamic nuclear polarization (DNP) effect, an alternative design of an Overhauser geomagnetic sensor is presented that enhances the proton polarization and increases the amplitude of the free induction decay (FID) signal. The short-pulse method is adopted to rotate the enhanced proton magnetization into the plane of precession to create an FID signal. To reduce the negative effect of the powerful electromagnetic interference, the design of the anti-interference of the pick-up coil is studied. Furthermore, the radio frequency polarization method based on the capacitive-loaded coaxial cavity is proposed to improve the quality factor of the resonant circuit. In addition, a special test instrument is designed that enables the simultaneous testing of the classical proton precession and the Overhauser sensor. Overall, comparison experiments with and without the free radical of the Overhauser sensors show that the DNP effect does effectively improve the amplitude and quality of the FID signal, and the magnetic sensitivity, resolution and range reach to 10 pT/Hz 1 / 2 @1 Hz, 0.0023 nT and 20-100 μ T, respectively. PMID:27258283

  7. Overhauser Geomagnetic Sensor Based on the Dynamic Nuclear Polarization Effect for Magnetic Prospecting

    PubMed Central

    Ge, Jian; Dong, Haobin; Liu, Huan; Yuan, Zhiwen; Dong, He; Zhao, Zhizhuo; Liu, Yonghua; Zhu, Jun; Zhang, Haiyang

    2016-01-01

    Based on the dynamic nuclear polarization (DNP) effect, an alternative design of an Overhauser geomagnetic sensor is presented that enhances the proton polarization and increases the amplitude of the free induction decay (FID) signal. The short-pulse method is adopted to rotate the enhanced proton magnetization into the plane of precession to create an FID signal. To reduce the negative effect of the powerful electromagnetic interference, the design of the anti-interference of the pick-up coil is studied. Furthermore, the radio frequency polarization method based on the capacitive-loaded coaxial cavity is proposed to improve the quality factor of the resonant circuit. In addition, a special test instrument is designed that enables the simultaneous testing of the classical proton precession and the Overhauser sensor. Overall, comparison experiments with and without the free radical of the Overhauser sensors show that the DNP effect does effectively improve the amplitude and quality of the FID signal, and the magnetic sensitivity, resolution and range reach to 10 pT/Hz1/2@1 Hz, 0.0023 nT and 20–100 μT, respectively. PMID:27258283

  8. Kinetic Parameters of Photo-Excited Triplet State of Pentacene Determined by Dynamic Nuclear Polarization

    NASA Astrophysics Data System (ADS)

    Kawahara, Tomomi; Sakaguchi, Satoshi; Tateishi, Kenichiro; Tang, Tsz Leung; Uesaka, Tomohiro

    2015-04-01

    The lifetimes and spin-lattice relaxation time of photo-excited triplet electron of pentacene doped in p-terphenyl at room temperature have been investigated. Values of spin-lattice relaxation time previously reported in ESR studies are inconsistent with each other. In this paper, we determined these time constants based on proton signals enhanced by dynamic nuclear polarization using the electrons (Triplet-DNP). The combined analysis of dependences of proton signal intensities on the delay time of polarization transfer and laser pulse structure allows us to disentangle contributions of the lifetimes and spin-lattice relaxation time. The lifetimes of triplet sublevels with ms = 0 and ±1 were determined to be 22.3 and 88 µs, respectively. The spin-lattice relaxation time was found to be longer than 300 µs, hence the time evolution of the electron population in the triplet state is governed by the lifetimes. It was also found that the proton signal enhancement is limited at a high repetition rate by the partial cancellation of the electron spin polarization by the remaining population produced by the preceding laser pulses.

  9. Thermosetting polymer for dynamic nuclear polarization: Solidification of an epoxy resin mixture including TEMPO

    NASA Astrophysics Data System (ADS)

    Noda, Yohei; Kumada, Takayuki; Yamaguchi, Daisuke; Shamoto, Shin-ichi

    2015-03-01

    We investigated the dynamic nuclear polarization (DNP) of typical thermosetting polymers (two-component type epoxy resins; Araldite® Standard or Araldite® Rapid) doped with a (2,2,6,6-tetramethylpiperidine-1-yl)oxy (TEMPO) radical. The doping process was developed by carefully considering the decomposition of TEMPO during the solidification of the epoxy resin. The TEMPO electron spin in each two-component paste decayed slowly, which was favorable for our study. Furthermore, despite the dissolved TEMPO, the mixture of the two-component paste successfully solidified. With the resulting TEMPO-doped epoxy-resin samples, DNP experiments at 1.2 K and 3.35 T indicated a magnitude of a proton-spin polarization up to 39%. This polarization is similar to that (35%) obtained for TEMPO-doped polystyrene (PS), which is often used as a standard sample for DNP. To combine this solidification of TEMPO-including mixture with a resin-casting technique enables a creation of polymeric target materials with a precise and complex structure.

  10. Large molecular weight nitroxide biradicals providing efficient dynamic nuclear polarization at temperatures up to 200 K.

    PubMed

    Zagdoun, Alexandre; Casano, Gilles; Ouari, Olivier; Schwarzwälder, Martin; Rossini, Aaron J; Aussenac, Fabien; Yulikov, Maxim; Jeschke, Gunnar; Copéret, Christophe; Lesage, Anne; Tordo, Paul; Emsley, Lyndon

    2013-08-28

    A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) are investigated as exogenous polarization sources for dynamic nuclear polarization (DNP) solid-state NMR at 9.4 T and with ca. 100 K sample temperatures. The impact of electron relaxation times on the DNP enhancement (ε) is examined, and we observe that longer inversion recovery and phase memory relaxation times provide larger ε. All radicals are tested in both bulk 1,1,2,2-tetrachloroethane solutions and in mesoporous materials, and the difference in ε between the two cases is discussed. The impact of the sample temperature and magic angle spinning frequency on ε is investigated for several radicals each characterized by a range of electron relaxation times. In particular, TEKPol, a bulky derivative of bTbK with a molecular weight of 905 g·mol(-1), is presented. Its high-saturation factor makes it a very efficient polarizing agent for DNP, yielding unprecedented proton enhancements of over 200 in both bulk and materials samples at 9.4 T and 100 K. TEKPol also yields encouraging enhancements of 33 at 180 K and 12 at 200 K, suggesting that with the continued improvement of radicals large ε may be obtained at higher temperatures. PMID:23961876