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Sample records for nuclear dynamics iii

  1. Dynamic Nuclear Polarization of 1H, 13C, and 59Co in a Tris(ethylenediamine)cobalt(III) Crystalline Lattice Doped with Cr(III)

    PubMed Central

    2015-01-01

    The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that 1H, 13C, and 59Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins. PMID:25069794

  2. Dynamic nuclear polarization of (1)H, (13)C, and (59)Co in a tris(ethylenediamine)cobalt(III) crystalline lattice doped with Cr(III).

    PubMed

    Corzilius, Björn; Michaelis, Vladimir K; Penzel, Susanne A; Ravera, Enrico; Smith, Albert A; Luchinat, Claudio; Griffin, Robert G

    2014-08-20

    The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that (1)H, (13)C, and (59)Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins.

  3. Friction in nuclear dynamics

    SciTech Connect

    Swiatecki, W.J.

    1985-03-01

    The problem of dissipation in nuclear dynamics is related to the breaking down of nuclear symmetries and the transition from ordered to chaotic nucleonic motions. In the two extreme idealizations of the perfectly Ordered Regime and the fully Chaotic Regime, the nucleus should behave as an elastic solid or an overdamped fluid, respectively. In the intermediate regime a complicated visco-elastic behaviour is expected. The discussion is illustrated by a simple estimate of the frequency of the giant quadrupole resonance in the Ordered Regime and by applications of the wall and window dissipation formulae in the Chaotic Regime. 51 refs.

  4. Extended Deterrence, Nuclear Proliferation, and START III

    SciTech Connect

    Speed, R.D.

    2000-06-20

    Early in the Cold War, the United States adopted a policy of ''extended nuclear deterrence'' to protect its allies by threatening a nuclear strike against any state that attacks these allies. This threat can (in principle) be used to try to deter an enemy attack using conventional weapons or one using nuclear, chemical, or biological weapons. The credibility of a nuclear threat has long been subject to debate and is dependent on many complex geopolitical factors, not the least of which is the military capabilities of the opposing sides. The ending of the Cold War has led to a significant decrease in the number of strategic nuclear weapons deployed by the United States and Russia. START II, which was recently ratified by the Russian Duma, will (if implemented) reduce the number deployed strategic nuclear weapons on each side to 3500, compared to a level of over 11,000 at the end of the Cold War in 1991. The tentative limit established by Presidents Clinton and Yeltsin for START III would reduce the strategic force level to 2000-2500. However, the Russians (along with a number of arms control advocates) now argue that the level should be reduced even further--to 1500 warheads or less. The conventional view is that ''deep cuts'' in nuclear weapons are necessary to discourage nuclear proliferation. Thus, as part of the bargain to get the non-nuclear states to agree to the renewal of the Nuclear Non-Proliferation Treaty, the United States pledged to work towards greater reductions in strategic forces. Without movement in the direction of deep cuts, it is thought by many analysts that some countries may decide to build their own nuclear weapons. Indeed, this was part of the rationale India used to justify its own nuclear weapons program. However, there is also some concern that deep cuts (to 1500 or lower) in the U.S. strategic nuclear arsenal could have the opposite effect. The fear is that such cuts might undermine extended deterrence and cause a crisis in confidence

  5. PREFACE: Nuclear Physics in Astrophysics III

    NASA Astrophysics Data System (ADS)

    Bemmerer, D.; Grosse, E.; Junghans, A. R.; Schwengner, R.; Wagner, A.

    2008-01-01

    The Europhysics Conference `Nuclear Physics in Astrophysics III' (NPA3) took place from 26 31 March 2007 in Dresden, Germany, hosted by Forschungszentrum Dresden-Rossendorf. The present special issue of Journal of Physics G: Nuclear and Particle Physics contains all peer-reviewed contributions to the proceedings of this conference. NPA3 is the third conference in the Nuclear Physics in Astrophysics series of conferences devoted to the interplay between nuclear physics and astrophysics. The first and second editions of the series were held in 2002 and 2005 in Debrecen, Hungary. NPA3 has been organized under the auspices of the Nuclear Physics Board of the European Physical Society as its XXI Divisional Conference. The conference marks the 50th anniversary of the landmark paper B2FH published in 1957 by E M Burbidge, G R Burbidge, W A Fowler and F Hoyle. A public lecture by Claus Rolfs (Ruhr-Universität Bochum, Germany) commemorated the progress achieved since 1957. NPA3 aimed to bring together experimental and theoretical nuclear physicists, astrophysicists and astronomers to address the important part played by nuclear physics in current astrophysical problems. A total of 130 participants from 71 institutions in 26 countries attended the conference, presenting 33 invited and 38 contributed talks and 25 posters on six subject areas. The astrophysical motivation and the nuclear tools employed to address it are highlighted by the titles of the subject areas: Big Bang Nucleosynthesis Stellar Nucleosynthesis and Low Cross Section Measurement Explosive Nucleosynthesis and Nuclear Astrophysics with Photons Nuclei far from Stability and Radioactive Ion Beams Dense Matter in Neutron Stars and Relativistic Nuclear Collisions Neutrinos in Nuclear Astrophysics The presentations and discussions proved that Nuclear Astrophysics is a truly interdisciplinary subject. The remarkable progress in astronomical observations achieved in recent years is matched by advances in

  6. Gd(iii) and Mn(ii) complexes for dynamic nuclear polarization: small molecular chelate polarizing agents and applications with site-directed spin labeling of proteins.

    PubMed

    Kaushik, Monu; Bahrenberg, Thorsten; Can, Thach V; Caporini, Marc A; Silvers, Robert; Heiliger, Jörg; Smith, Albert A; Schwalbe, Harald; Griffin, Robert G; Corzilius, Björn

    2016-10-21

    We investigate complexes of two paramagnetic metal ions Gd(3+) and Mn(2+) to serve as polarizing agents for solid-state dynamic nuclear polarization (DNP) of (1)H, (13)C, and (15)N at magnetic fields of 5, 9.4, and 14.1 T. Both ions are half-integer high-spin systems with a zero-field splitting and therefore exhibit a broadening of the mS = -1/2 ↔ +1/2 central transition which scales inversely with the external field strength. We investigate experimentally the influence of the chelator molecule, strong hyperfine coupling to the metal nucleus, and deuteration of the bulk matrix on DNP properties. At small Gd-DOTA concentrations the narrow central transition allows us to polarize nuclei with small gyromagnetic ratio such as (13)C and even (15)N via the solid effect. We demonstrate that enhancements observed are limited by the available microwave power and that large enhancement factors of >100 (for (1)H) and on the order of 1000 (for (13)C) can be achieved in the saturation limit even at 80 K. At larger Gd(iii) concentrations (≥10 mM) where dipolar couplings between two neighboring Gd(3+) complexes become substantial a transition towards cross effect as dominating DNP mechanism is observed. Furthermore, the slow spin-diffusion between (13)C and (15)N, respectively, allows for temporally resolved observation of enhanced polarization spreading from nuclei close to the paramagnetic ion towards nuclei further removed. Subsequently, we present preliminary DNP experiments on ubiquitin by site-directed spin-labeling with Gd(3+) chelator tags. The results hold promise towards applications of such paramagnetically labeled proteins for DNP applications in biophysical chemistry and/or structural biology.

  7. 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.

  8. Nuclear pulse. III - Playing a wild card

    NASA Astrophysics Data System (ADS)

    Broad, W. J.

    1981-06-01

    Implications of the phenomenon of electromagnetic pulse (EMP), a high-voltage by-product of nuclear explosions in space which could render useless unprotected communications equipment and power grids over a wide area, for the feasibility of conducting a limited nuclear war by the United States are discussed. Arguments on the one hand that the effects of EMP demand direct investigation and should be protected against by the hardening of U.S. military communications are summarized and contrasted with those on the other hand which assert that the presence of EMP, as well as other exotic nuclear effects, would, despite any attempts at hardening, make it impossible to maintain the precision of command and control necessary for a limited nuclear action against Soviet military targets. Uncertainties about Soviet intentions in regard to the use of EMP as a weapon are also pointed out.

  9. Nuclear fission with diffusive dynamics

    NASA Astrophysics Data System (ADS)

    Cha, D.; Bertsch, G. F.

    1992-07-01

    We investigate the dynamics of nuclear fission, assuming purely diffusive motion up to the saddle point. The resulting Smoluchowski equation is solved for conditions appropriate to the 16O+142Nd-->158Er reaction at 207 MeV. The solution is characterized by an equilibration time τ0 for the system to reach steady state, and the fission decay rate in steady state, Λ. We find that the equilibration time τ0 plays a very small role in determining the number of prescission neutrons. The diffusion coefficient extracted from the experimental data is larger than the theoretical in the work of Bush, Bertsch, and Brown by a factor of 5-11.

  10. Semiclassical approaches to nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Magner, A. G.; Gorpinchenko, D. V.; Bartel, J.

    2017-01-01

    The extended Gutzwiller trajectory approach is presented for the semiclassical description of nuclear collective dynamics, in line with the main topics of the fruitful activity of V.G. Solovjov. Within the Fermi-liquid droplet model, the leptodermous effective surface approximation was applied to calculations of energies, sum rules, and transition densities for the neutron-proton asymmetry of the isovector giant-dipole resonance and found to be in good agreement with the experimental data. By using the Strutinsky shell correctionmethod, the semiclassical collective transport coefficients, such as nuclear inertia, friction, stiffness, and moments of inertia, can be derived beyond the quantum perturbation approximation of the response function theory and the cranking model. The averaged particle-number dependences of the low-lying collective vibrational states are described in good agreement with the basic experimental data, mainly due to the enhancement of the collective inertia as compared to its irrotational flow value. Shell components of the moment of inertia are derived in terms of the periodic-orbit free-energy shell corrections. A good agreement between the semiclassical extended Thomas-Fermi moments of inertia with shell corrections and the quantum results is obtained for different nuclear deformations and particle numbers. Shell effects are shown to be exponentially dampted out with increasing temperature in all the transport coefficients.

  11. 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

  12. 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.

  13. Assembly dynamics of PML nuclear bodies in living cells.

    PubMed

    Brand, Peter; Lenser, Thorsten; Hemmerich, Peter

    2010-03-05

    The mammalian cell nucleus contains a variety of organelles or nuclear bodies which contribute to key nuclear functions. Promyelocytic leukemia nuclear bodies (PML NBs) are involved in the regulation of apoptosis, antiviral responses, the DNA damage response and chromatin structure, but their precise biochemical function in these nuclear pathways is unknown. One strategy to tackle this problem is to assess the biophysical properties of the component parts of these macromolecular assemblies in living cells. In this study we determined PML NB assembly dynamics by live cell imaging, combined with mathematical modeling. For the first time, dynamics of PML body formation were measured in cells lacking endogenous PML. We show that all six human nuclear PML isoforms are able to form nuclear bodies in PML negative cells. All isoforms exhibit individual exchange rates at NBs in PML positive cells but PML I, II, III and IV are static at nuclear bodies in PML negative cells, suggesting that these isoforms require additional protein partners for efficient exchange. PML V turns over at PML Nbs very slowly supporting the idea of a structural function for this isoform. We also demonstrate that SUMOylation of PML at Lysine positions K160 and/or K490 are required for nuclear body formation in vivo.We propose a model in which the isoform specific residence times of PML provide both, structural stability to function as a scaffold and flexibility to attract specific nuclear proteins for efficient biochemical reactions at the surface of nuclear bodies.MCS code: 92C37.

  14. Pion scattering and nuclear dynamics

    SciTech Connect

    Johnson, M.B.

    1988-01-01

    A phenomenological optical-model analysis of pion elastic scattering and single- and double-charge-exchange scattering to isobaric-analog states is reviewed. Interpretation of the optical-model parameters is briefly discussed, and several applications and extensions are considered. The applications include the study of various nuclear properties, including neutron deformation and surface-fluctuation contributions to the density. One promising extension for the near future would be to develop a microscopic approach based on powerful momentum-space methods brought to existence over the last decade. In this, the lowest-order optical potential as well as specific higher-order pieces would be worked out in terms of microscopic pion-nucleon and delta-nucleon interactions that can be determined within modern meson-theoretical frameworks. A second extension, of a more phenomenological nature, would use coupled-channel methods and shell-model wave functions to study dynamical nuclear correlations in pion double charge exchange. 35 refs., 11 figs., 1 tab.

  15. Fermionic Molecular Dynamics for Nuclear Dynamics and Thermodynamics

    NASA Astrophysics Data System (ADS)

    Hasnaoui, K. H. O.; Chomaz, Ph; Gulminelli, F.

    A new Fermionic Molecular Dynamics (FMD) model based on a Skyrme functional is proposed in this paper. After introducing the basic formalism, some first applications to nuclear structure and nuclear thermodynamics are presented.

  16. Nuclear EGFRvIII resists hypoxic microenvironment induced apoptosis via recruiting ERK1/2 nuclear translocation

    SciTech Connect

    Xie, Hui; Yang, Jinfeng; Xing, Wenjing; Dong, Yucui; Ren, Huan

    2016-02-05

    Glioblastoma (GBM) is the most aggressive type of primary brain tumor. Its interaction with the tumor microenvironment promotes tumor progression. Furthermore, GBM bearing expression of EGFRvIII displays more adaptation to tumor microenvironment related stress. But the mechanisms were poorly understood. Here, we presented evidence that in the human U87MG glioblastoma tumor model, EGFRvIII overexpression led aberrant kinase activation and nuclear translocation of EGFRvIII/ERK1/2 under hypoxia, which induced growth advantage by resisting apoptosis. Additionally, EGFRvIII defective in nuclear entry impaired this capacity in hypoxia adaptation, and partially interrupted ERK1/2 nuclear translocation. Pharmacology or genetic interference ERK1/2 decreased hypoxia resistance triggered by EGFRvIII expression, but not EGFRvIII nuclear translocation. In summary, this study identified a novel role for EGFRvIII in hypoxia tolerance, supporting an important link between hypoxia and subcellular localization alterations of the receptor. - Highlights: • Nuclear translocation of EGFRvIII contributes to GBM cell apoptotic resistance by hypoxia. • Nuclear ERK1/2 facilitates EGFRvIII in hypoxia resistance. • EGFRvIII nuclear translocation is not dependent on ERK1/2.

  17. Dynamical Aspects of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Kliman, J.; Itkis, M. G.; Gmuca, Š.

    2008-11-01

    Fission dynamics. Dependence of scission-neutron yield on light-fragment mass for [symbol]=1/2 [et al.]. Dynamics of capture quasifission and fusion-fission competition / L. Stuttgé ... [et al.] -- Fission-fission. The processes of fusion-fission and quasi-fission of superheavy nuclei / M. G. Itkis ... [et al.]. Fission and quasifission in the reactions [symbol]Ca+[symbol]Pb and [symbol]Ni+[symbol]W / G. N. Knyazheva ... [et al.]. Mass-energy characteristics of reactions [symbol]Fe+[symbol][symbol][symbol]266Hs and [symbol]Mg+[symbol]Cm[symbol][symbol]Hs at Coulomb barrier / L. Krupa ... [et al.]. Fusion of heavy ions at extreme sub-barrier energies / Ş. Mişicu and H. Esbensen. Fusion and fission dynamics of heavy nuclear system / V. Zagrebaev and W. Greiner. Time-dependent potential energy for fusion and fission processes / A. V. Karpov ... [et al.] -- Superheavy elements. Advances in the understanding of structure and production mechanisms for superheavy elements / W. Greiner and V. Zagrebaev. Fission barriers of heaviest nuclei / A. Sobiczewski ... [et al.]. Possibility of synthesizing doubly magic superheavy nuclei / Y Aritomo ... [et al.]. Synthesis of superheavy nuclei in [symbol]Ca-induced reactions / V. K. Utyonkov ... [et al.] -- Fragmentation. Production of neutron-rich nuclei in the nucleus-nucleus collisions around the Fermi energy / M. Veselský. Signals of enlarged core in [symbol]Al / Y. G. Ma ... [et al.] -- Exotic modes. New insight into the fission process from experiments with relativistic heavy-ion beams / K.-H. Schmidt ... [et al.]. New results for the intensity of bimodal fission in binary and ternary spontaneous fission of [symbol]Cf / C. Goodin ... [et al.]. Rare fission modes: study of multi-cluster decays of actinide nuclei / D. V. Kamanin ... [et al.]. Energy distribution of ternary [symbol]-particles in [symbol]Cf(sf) / M. Mutterer ... [et al.]. Preliminary results of experiment aimed at searching for collinear cluster tripartition of

  18. Order, chaos and nuclear dynamics: An introduction

    SciTech Connect

    Swiatecki, W.J.

    1990-08-01

    This is an introductory lecture illustrating by simple examples the anticipated effect on collective nuclear dynamics of a transition from order to chaos in the motions of nucleons inside an idealized nucleus. The destruction of order is paralleled by a transition from a rubber-like to a honey-like behaviour of the independent-particle nuclear model. 10 refs., 6 figs.

  19. 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

  20. Carrier dynamics in III-nitride semiconductors

    NASA Astrophysics Data System (ADS)

    Liu, Kai

    In the past decade, III-nitride semiconductors had a considerable impact in solid state lighting and high speed high power electronics. As technology develops, high Al content III-nitride semiconductors lead the edge of research. It opens the door to many applications especially portable ones: from homeland security, bio-analytical, medical diagnostic, air and water disinfection, sterilization, chemical sensing systems, non-line-of-sight (NLOS) communications, to high-density optical data storage. In this thesis, we first study GaN epilayers, as well as more complicate high Al content AlGaN/AlGaN MQW structures used as active media for deep UV LEDs. We theoretically study the photoluminescence (PL) dynamics in high quality GaN epilayers by establishing a new decay model. In our model, surface recombination, diffusion, and re-absorption are taken into account. Our model is in excellent agreement with experimental data obtained by time-resolved PL. Our results show that the carrier diffusion and surface recombination play key roles in the PL decay. For high Al content AlGaN/AlGaN MQW structures, we first present the investigation of built-in electric fields in AlxGa1-xN/Al yGa1-yN MQWs embedded into p-i-n structure by using photoluminescence experiments. By comparison of the Stark shifts induced by the p-i-n structure and by photo-excited free carrier screening, we evaluate the intrinsic electric field induced by piezoelectric and spontaneous polarizations. Furthermore we investigate carrier dynamics in sets of identically grown Al0.35Ga0.65N/Al 0.49Ga0.51N MQW structures with well widths varying from 1.65 to 5.0 nm by TR-PL and LITG techniques. We observed screening of the built-in electric field by free non-equilibrium carriers and localization governed PL kinetics at different decay stages. A decrease of carrier lifetime with increasing well width is observed and attributed to the carrier localization occurring due to well width fluctuations of the quantum well

  1. Spastin and ESCRT-III coordinate mitotic spindle disassembly and nuclear envelope sealing.

    PubMed

    Vietri, Marina; Schink, Kay O; Campsteijn, Coen; Wegner, Catherine Sem; Schultz, Sebastian W; Christ, Liliane; Thoresen, Sigrid B; Brech, Andreas; Raiborg, Camilla; Stenmark, Harald

    2015-06-11

    At the onset of metazoan cell division the nuclear envelope breaks down to enable capture of chromosomes by the microtubule-containing spindle apparatus. During anaphase, when chromosomes have separated, the nuclear envelope is reassembled around the forming daughter nuclei. How the nuclear envelope is sealed, and how this is coordinated with spindle disassembly, is largely unknown. Here we show that endosomal sorting complex required for transport (ESCRT)-III, previously found to promote membrane constriction and sealing during receptor sorting, virus budding, cytokinesis and plasma membrane repair, is transiently recruited to the reassembling nuclear envelope during late anaphase. ESCRT-III and its regulatory AAA (ATPase associated with diverse cellular activities) ATPase VPS4 are specifically recruited by the ESCRT-III-like protein CHMP7 to sites where the reforming nuclear envelope engulfs spindle microtubules. Subsequent association of another ESCRT-III-like protein, IST1, directly recruits the AAA ATPase spastin to sever microtubules. Disrupting spastin function impairs spindle disassembly and results in extended localization of ESCRT-III at the nuclear envelope. Interference with ESCRT-III functions in anaphase is accompanied by delayed microtubule disassembly, compromised nuclear integrity and the appearance of DNA damage foci in subsequent interphase. We propose that ESCRT-III, VPS4 and spastin cooperate to coordinate nuclear envelope sealing and spindle disassembly at nuclear envelope-microtubule intersection sites during mitotic exit to ensure nuclear integrity and genome safeguarding, with a striking mechanistic parallel to cytokinetic abscission.

  2. Protein-water dynamics in antifreeze protein III activity

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Bäumer, Alexander; Meister, Konrad; Bischak, Connor G.; DeVries, Arthur L.; Leitner, David M.; Havenith, Martina

    2016-03-01

    We combine Terahertz absorption spectroscopy (THz) and molecular dynamics (MD) simulations to investigate the underlying molecular mechanism for the antifreeze activity of one class of antifreeze protein, antifreeze protein type III (AFP-III) with a focus on the collective water hydrogen bond dynamics near the protein. After summarizing our previous work on AFPs, we present a new investigation of the effects of cosolutes on protein antifreeze activity by adding sodium citrate to the protein solution of AFP-III. Our results reveal that for AFP-III, unlike some other AFPs, the addition of the osmolyte sodium citrate does not affect the hydrogen bond dynamics at the protein surface significantly, as indicated by concentration dependent THz measurements. The present data, in combination with our previous THz measurements and molecular simulations, confirm that while long-range solvent perturbation is a necessary condition for the antifreeze activity of AFP-III, the local binding affinity determines the size of the hysteresis.

  3. Dynamics of a nuclear invasion

    NASA Astrophysics Data System (ADS)

    Roper, Marcus; Simonin, Anna; Glass, N. Louise

    2009-11-01

    Filamentous fungi grow as a network of continuous interconnected tubes, containing nuclei that move freely through a shared cytoplasm. Wild fungi are frequently chimerical: two nuclei from the same physiological individual may be genetically different. Such internal diversity can arise either from spontaneous mutations during nuclear division, or by nuclear exchange when two individuals fuse, sharing their resources and organelles to become a single individual. This diversity is thought to be essential to adaptation in plant pathogens, allowing, for instance, an invading fungus to present many different genetic identities against its host's immune response. However, it is clear that the presence of multiple genetic lineages within the same physiological individual can also pose challenges - lineages that are present in growing hyphal tips will multiply preferentially. Nuclei must therefore be kept well mixed across a growing front. By applying models developed to describe mixing of fluids in microfluidic reactors to experimental observations of lineage mixing in a growing Neurospora crassa colony, we show how this mixing is achieved. In particular we analyze the individual contributions from interdigitation of hyphae and from nuclear transport.

  4. The dynamic nature of the nuclear envelope

    PubMed Central

    Arnone, James T; Walters, Alison D; Cohen-Fix, Orna

    2013-01-01

    In eukaryotes, chromosomes are encased by a dynamic nuclear envelope. In contrast to metazoans, where the nuclear envelope disassembles during mitosis, many fungi including budding yeast undergo “closed mitosis,” where the nuclear envelope remains intact throughout the cell cycle. Consequently, during closed mitosis the nuclear envelope must expand to accommodate chromosome segregation to the two daughter cells. A recent study by Witkin et al. in budding yeast showed that if progression through mitosis is delayed, for example due to checkpoint activation, the nuclear envelope continues to expand despite the block to chromosome segregation. Moreover, this expansion occurs at a specific region of the nuclear envelope- adjacent to the nucleolus- forming an extension referred to as a “flare.” These observations raise questions regarding the regulation of nuclear envelope expansion both in budding yeast and in higher eukaryotes, the mechanisms confining mitotic nuclear envelope expansion to a particular region and the possible consequences of failing to regulate nuclear envelope expansion during the cell cycle. PMID:23873576

  5. Nuclear dynamics of K¯ bound states

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Friedman, E.; Gal, A.

    2006-07-01

    nuclear bound states were generated dynamically within a relativistic mean field (RMF) model. Substantial polarization of the core nucleus was found for light nuclei. The behavior of the dynamically calculated width ΓK¯ as function of the K¯ binding energy was studied. A lower limit of ΓK¯ ˜ 35 - 45 MeV for 1s K¯ nuclear states in light nuclei such as 12C was placed on the width expected for deep binding in the range B K¯ ˜ 100 - 200 MeV.

  6. Nuclear quantum dynamics in dense hydrogen

    PubMed Central

    Kang, Dongdong; Sun, Huayang; Dai, Jiayu; Chen, Wenbo; Zhao, Zengxiu; Hou, Yong; Zeng, Jiaolong; Yuan, Jianmin

    2014-01-01

    Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scattering or many-body collisions between particles, is crucial for the dynamics of planet's evolution and hydrodynamical processes in inertial confinement confusion. Here, using improved ab initio path-integral molecular dynamics simulations, we investigated the nuclear quantum dynamics regarding transport behaviors of dense hydrogen up to the temperatures of 1 eV. With the inclusion of nuclear quantum effects (NQEs), the ionic diffusions are largely higher than the classical treatment by the magnitude from 20% to 146% as the temperature is decreased from 1 eV to 0.3 eV at 10 g/cm3, meanwhile, electrical and thermal conductivities are significantly lowered. In particular, the ionic diffusion is found much larger than that without NQEs even when both the ionic distributions are the same at 1 eV. The significant quantum delocalization of ions introduces remarkably different scattering cross section between protons compared with classical particle treatments, which explains the large difference of transport properties induced by NQEs. The Stokes-Einstein relation, Wiedemann-Franz law, and isotope effects are re-examined, showing different behaviors in nuclear quantum dynamics. PMID:24968754

  7. Nuclear Dynamics of Heterochromatin Repair.

    PubMed

    Amaral, Nuno; Ryu, Taehyun; Li, Xiao; Chiolo, Irene

    2017-02-01

    Repairing double-strand breaks (DSBs) is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination and chromosome rearrangements. Recent studies in Drosophila cells revealed that faithful homologous recombination (HR) repair of heterochromatic DSBs relies on the relocalization of DSBs to the nuclear periphery before Rad51 recruitment. We summarize here the exciting progress in understanding this pathway, including conserved responses in mammalian cells and surprising similarities with mechanisms in yeast that deal with DSBs in distinct sites that are difficult to repair, including other repeated sequences. We will also point out some of the most important open questions in the field and emerging evidence suggesting that deregulating these pathways might have dramatic consequences for human health.

  8. 10 CFR 76.117 - Special nuclear material of low strategic significance-Category III.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 2 2010-01-01 2010-01-01 false Special nuclear material of low strategic significance-Category III. 76.117 Section 76.117 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safeguards and Security § 76.117 Special nuclear material of low...

  9. 10 CFR 76.117 - Special nuclear material of low strategic significance-Category III.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Special nuclear material of low strategic significance-Category III. 76.117 Section 76.117 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safeguards and Security § 76.117 Special nuclear material of low strategic...

  10. 10 CFR 76.117 - Special nuclear material of low strategic significance-Category III.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 2 2011-01-01 2011-01-01 false Special nuclear material of low strategic significance-Category III. 76.117 Section 76.117 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safeguards and Security § 76.117 Special nuclear material of low strategic...

  11. 10 CFR 76.117 - Special nuclear material of low strategic significance-Category III.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 2 2014-01-01 2014-01-01 false Special nuclear material of low strategic significance-Category III. 76.117 Section 76.117 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safeguards and Security § 76.117 Special nuclear material of low strategic...

  12. 10 CFR 76.117 - Special nuclear material of low strategic significance-Category III.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 2 2013-01-01 2013-01-01 false Special nuclear material of low strategic significance-Category III. 76.117 Section 76.117 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safeguards and Security § 76.117 Special nuclear material of low strategic...

  13. The sapphire backscattering monochromator at the Dynamics beamline P01 of PETRA III

    DOE PAGES

    Alexeev, P.; Asadchikov, V.; Bessas, D.; ...

    2016-02-23

    Here, we report on a high resolution sapphire backscattering monochromator installed at the Dynamics beamline P01 of PETRA III. The device enables nuclear resonance scattering experiments on M ossbauer isotopes with transition energies between 20 and 60 keV with sub-meV to meV resolution. In a first performance test with 119Sn nuclear resonance at a X-ray energy of 23.88 keV an energy resolution of 1.34 meV was achieved. Moreover, the device extends the field of nuclear resonance scattering at the PETRA III synchrotron light source to many further isotopes like 151Eu, 149Sm, 161Dy, 125Te and 121Sb.

  14. The sapphire backscattering monochromator at the Dynamics beamline P01 of PETRA III

    SciTech Connect

    Alexeev, P.; Asadchikov, V.; Bessas, D.; Butashin, A.; Deryabin, A.; Dill, F. -U.; Ehnes, A.; Herlitschke, M.; Hermann, R. P.; Jafari, A.; Prokhorov, I.; Roshchin, B.; Röhlsberger, R.; Schlage, K.; Sergueev, I.; Siemens, A.; Wille, H. -C.

    2016-02-23

    Here, we report on a high resolution sapphire backscattering monochromator installed at the Dynamics beamline P01 of PETRA III. The device enables nuclear resonance scattering experiments on M ossbauer isotopes with transition energies between 20 and 60 keV with sub-meV to meV resolution. In a first performance test with 119Sn nuclear resonance at a X-ray energy of 23.88 keV an energy resolution of 1.34 meV was achieved. Moreover, the device extends the field of nuclear resonance scattering at the PETRA III synchrotron light source to many further isotopes like 151Eu, 149Sm, 161Dy, 125Te and 121Sb.

  15. The sapphire backscattering monochromator at the Dynamics beamline P01 of PETRA III

    NASA Astrophysics Data System (ADS)

    Alexeev, P.; Asadchikov, V.; Bessas, D.; Butashin, A.; Deryabin, A.; Dill, F.-U.; Ehnes, A.; Herlitschke, M.; Hermann, R. P.; Jafari, A.; Prokhorov, I.; Roshchin, B.; Röhlsberger, R.; Schlage, K.; Sergueev, I.; Siemens, A.; Wille, H.-C.

    2016-12-01

    We report on a high resolution sapphire backscattering monochromator installed at the Dynamics beamline P01 of PETRA III. The device enables nuclear resonance scattering experiments on Mössbauer isotopes with transition energies between 20 and 60 keV with sub-meV to meV resolution. In a first performance test with 119Sn nuclear resonance at a X-ray energy of 23.88 keV an energy resolution of 1.34 meV was achieved. The device extends the field of nuclear resonance scattering at the PETRA III synchrotron light source to many further isotopes like 151Eu, 149Sm, 161Dy, 125Te and 121Sb.

  16. The nuclear magnetic resonance spectra of bisphthalocyaninatolanthanide (III). Interim report

    SciTech Connect

    Tsutsui, M.; Kasuga, K.

    1980-06-01

    The NMR spectra of bisphthalocyaninatolanthanide (III) complexes (La, Nd, Sm, and Eu) have been examined. An effect of a macrocyclic-ring current and induced shift caused by lanthanide (III) ions were discussed.

  17. Fluid dynamical description of relativistic nuclear collisions

    NASA Technical Reports Server (NTRS)

    Nix, J. R.; Strottman, D.

    1982-01-01

    On the basis of both a conventional relativistic nuclear fluid dynamic model and a two fluid generalization that takes into account the interpenetration of the target and projectile upon contact, collisions between heavy nuclei moving at relativistic speeds are calculated. This is done by solving the relevant equations of motion numerically in three spatial dimensions by use of particle in cell finite difference computing techniques. The effect of incorporating a density isomer, or quasistable state, in the nuclear equation of state at three times normal nuclear density, and the effect of doubling the nuclear compressibility coefficient are studied. For the reaction 20Ne + 238U at a laboratory bombarding energy per nucleon of 393 MeV, the calculated distributions in energy and angle of outgoing charged particles are compared with recent experimental data both integrated over all impact parameters and for nearly central collisions.

  18. Alpha Radiolysis of Nuclear Solvent Extraction Ligands Used for An(III) and Ln(III) Separations

    SciTech Connect

    Mezyk, Stephen P.; Mincher, Bruce J.; Nilsson, Mikael

    2016-08-01

    This document is the final report for the Nuclear Energy Universities Program (NEUP) grant 10-910 (DE-AC07-05ID14517) “Alpha Radiolysis of Nuclear Solvent Extraction Ligands used for An(III) and Ln(III) Separations”. The goal of this work was to obtain a quantitative understanding of the impacts of both low Linear Energy Transfer (LET, gamma-rays) and high LET (alpha particles) radiation chemistry occurring in future large-scale separations processes. This quantitative understanding of the major radiation effects on diluents and ligands is essential for optimal process implementation, and could result in significant cost savings in the future.

  19. The Nuclear Magnetic Resonance Spectra of Bisphthalocyaninatolanthanide (III).

    DTIC Science & Technology

    1980-06-01

    examined. An effect of a macrocyclic -ring current and an induced shift caused by lanthanide (III) ions were discussed. INTRODUCTION NMR studies of...reported some NMR results of lithium, zinc, 2 and uranyl phthalocyanines. Lanthanide complexes such as acethylacetonato- lanthanide (III) and its...University, College Station, TX 77843 (Received , 1980) The NHR spectra of bisphthalocyaninatolanthanide(III) complexes (La, Nd, Sm, and Eu) have been

  20. Cluster dynamics transcending chemical dynamics toward nuclear fusion.

    PubMed

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-07-11

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 10(15)-10(20) W.cm(-2)). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C(4+)(D(+))(4))(n) and (D(+)I(22+))(n) at I(M) = 10(18) W.cm(-2), that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D(2))(n), (HT)(n), (CD(4))(n), (DI)(n), (CD(3)I)(n), and (CH(3)I)(n) clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D(2))(n) clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions, e.g., (12)C(P,gamma)(13)N driven by CE of (CH(3)I)(n) clusters, were explored.

  1. Cluster dynamics transcending chemical dynamics toward nuclear fusion

    PubMed Central

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-01-01

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 1015–1020 W·cm−2). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C4+(D+)4)n and (D+I22+)n at IM = 1018 W·cm−2, that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D2)n, (HT)n, (CD4)n, (DI)n, (CD3I)n, and (CH3I)n clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D2)n clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions, e.g., 12C(P,γ)13N driven by CE of (CH3I)n clusters, were explored. PMID:16740666

  2. 78 FR 77508 - Duke Energy Carolinas, LLC; William States Lee III Nuclear Station, Units 1 and 2; Combined...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-23

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION Duke Energy Carolinas, LLC; William States Lee III Nuclear Station, Units 1 and 2; Combined Licenses Application Review AGENCY: Nuclear Regulatory Commission. ACTION: Final environmental impact...

  3. Nuclear quests for supernova dynamics and nucleosynthesis

    SciTech Connect

    Langanke, K.; Martinez-Pinedo, G.

    2011-10-28

    Nuclear physics plays a crucial role in various aspects of core collapse supernovae. The collapse dynamics is strongly influenced by electron captures. Using modern many-body theory improved capture rates have been derived recently with the important result that the process is dominated by capture on nuclei until neutrino trapping is achieved. Following the core bounce the ejected matter is the site of interesting nucleosynthesis. The early ejecta are proton-rich and give rise to the recently discovered {nu}p-process. Later ejecta might be neutron-rich and can be one site of the r-process. The manuscript discusses recent progress in describing nuclear input relevant for the supernova dynamics and nucleosynthesis.

  4. Nuclear dynamical diffraction using synchrotron radiation

    SciTech Connect

    Brown, Dennis Eugene

    1993-05-01

    The scattering of synchrotron radiation by nuclei is extensively explored in this thesis. From the multipole electric field expansion resulting from time-dependent nonrelativistic perturbation theory, a dynamical scattering theory is constructed. This theory is shown, in the many particle limit, to be equivalent to the semi-classical approach where a quantum mechanical scattering amplitude is used in the Maxwell inhomogeneous wave equation. The Moessbauer specimen whose low-lying energy levels were probed is a ferromagnetic lattice of 57Fe embedded in a yttrium iron garnet (YIG) crystal matrix. The hyperfine fields in YIG thin films were studied at low and room temperature using time-resolved quantum beat spectroscopy. Nuclear hyperfine structure quantum beats were measured using a fast plastic scintillator coincidence photodetector and associated electronics having a time resolution of 2.5 nsec. The variation of the quantum beat patterns near the Bragg [0 0 2] diffraction peak gave a Lamb-Moessbauer factor of 8.2±0.4. Exploring characteristic dynamical features in the higher order YIG [0 0 10] reflection revealed that one of the YIG crystals had bifurcated into two different layers. The dynamics of nuclear superradiance was explored. This phenomenon includes the radiative speedup exhibited by a collective state of particles, and, in striking concurrence, resonance frequency shifts. A speedup of a factor of 4 in the total decay rate and a beat frequency shift of 11/2 natural resonance linewidths were observed. Nuclear resonance scattering was also found to be a useful way of performing angular interferometry experiments, and it was used to observe the phase shift of a rotated quantum state. On the whole, nuclear dynamical diffraction theory has superbly explained many of the fascinating features of resonant magnetic dipole radiation scattered by a lattice of nuclei.

  5. Ultrafast electronic dynamics driven by nuclear motion

    NASA Astrophysics Data System (ADS)

    Vendrell, Oriol

    2016-05-01

    The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

  6. L-band Overhauser dynamic nuclear polarization.

    PubMed

    Garcia, Sandra; Walton, Jeffrey H; Armstrong, Brandon; Han, Songi; McCarthy, Michael J

    2010-03-01

    We present the development of an Overhauser dynamic nuclear polarization (DNP) instrument at 0.04 T using 1.1 GHz (L-band) electron spin resonance frequencies (ESR) and 1.7 MHz (1)H nuclear magnetic resonance frequencies. Using this home-built DNP system, the electron-nucleus coupling factor of 4-oxo-TEMPO dissolved in water was determined as 0.39+/-0.06 at 0.04 T. The higher coupling factor obtained at this field compared to higher magnetic fields, such as 0.35 T, directly translates to higher enhancement of the NMR signal and opens up a wider time scale window for observing water dynamics interacting with macromolecular systems, including proteins, polymers or lipid vesicles. The higher enhancements obtained will facilitate the observation of water dynamics at correlation times up to 10 ns, that corresponds to more than one order of magnitude slower dynamics than accessible at 0.35 T using X-band ESR frequencies. Copyright (c) 2009 Elsevier Inc. All rights reserved.

  7. Classical Molecular Dynamics Simulation of Nuclear Fuel

    SciTech Connect

    Devanathan, Ram; Krack, Matthias; Bertolus, Marjorie

    2015-10-10

    Molecular dynamics simulation is well suited to study primary damage production by irradiation, defect interactions with fission gas atoms, gas bubble nucleation, grain boundary effects on defect and gas bubble evolution in nuclear fuel, and the resulting changes in thermo-mechanical properties. In these simulations, the forces on the ions are dictated by interaction potentials generated by fitting properties of interest to experimental data. The results obtained from the present generation of potentials are qualitatively similar, but quantitatively different. There is a need to refine existing potentials to provide a better representation of the performance of polycrystalline fuel under a variety of operating conditions, and to develop models that are equipped to handle deviations from stoichiometry. In addition to providing insights into fundamental mechanisms governing the behaviour of nuclear fuel, MD simulations can also provide parameters that can be used as inputs for mesoscale models.

  8. Dynamic critical temperature in MnIIFeIII bimetallic oxalates

    NASA Astrophysics Data System (ADS)

    Huang, Jinhua; Shi, Xiaoling; Song, Zhaoyuan; Shi, Yingguo

    2017-08-01

    MnIIFeIII bimetallic oxalates are described by a spin-5/2 Blume-Capel (BC) model on a layered honeycomb structure. The effects of the interlayer coupling, the single-ion anisotropy and the oscillating magnetic field on the dynamic critical temperature of the compounds are studied by a effective-field method based on Glauber-type stochastic dynamic. Dynamic phase diagrams are presented in the DA /|J1 |- T /|J1 | and T /|J1 |-h0 /|J1 | planes, and the first-order phase transition lines and the critical end point are found. Compensated magnetization regions have also been plotted and the compounds exhibit an uncompensated magnetization in the antiferromagnetic phase. In particular, a two-compensation-temperature phenomenon has also been observed in MnIIFeIII bimetallic oxalates.

  9. Threedimensional dynamics of nuclear decay modes

    NASA Astrophysics Data System (ADS)

    Mirea, M.; Poenaru, D. N.; Greiner, W.

    1994-03-01

    We study nondissipative fission dynamics in a wide range of mass asymmetry, covering three groups of nuclear decay modes: cluster radioactivities; alpha-decay and cold fission. The WKB action integral is calculated by using the Werner-Wheeler inertia tensor and the deformation energy within Yukawa-plus-exponential model extended to binary systems with different charge densities. The optimum dynamical trajectory in a threedimensional deformation space (elongation, necking-in and mass-asymmetry) is determined by solving a nonlinear system of differential equations. This new method is illustrated for three decay modes of234U: α-decay, Mg-radioactivity and cold fission with100Zr as a light fragment.

  10. Co-transcriptional nuclear actin dynamics

    PubMed Central

    Percipalle, Piergiorgio

    2013-01-01

    Actin is a key player for nuclear structure and function regulating both chromosome organization and gene activity. In the cell nucleus actin interacts with many different proteins. Among these proteins several studies have identified classical nuclear factors involved in chromatin structure and function, transcription and RNA processing as well as proteins that are normally involved in controlling the actin cytoskeleton. These discoveries have raised the possibility that nuclear actin performs its multi task activities through tight interactions with different sets of proteins. This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states. Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity. By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified. PMID:23138849

  11. Pulsed Dynamic Nuclear Polarization with Trityl Radicals.

    PubMed

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

    2016-01-07

    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.

  12. Overhauser Dynamic Nuclear Polarization Studies on Local Water Dynamics.

    PubMed

    Kaminker, Ilia; Barnes, Ryan; Han, Songi

    2015-01-01

    Overhauser dynamic nuclear polarization (ODNP) is an emerging technique for quantifying translational water dynamics in the vicinity (<1 nm) of stable radicals that can be chemically attached to macromolecules of interest. This has led to many in-depth and enlightening studies of hydration water of biomolecules, revolving around the role of solvent dynamics in the structure and function of proteins, nucleic acids, and lipid bilayer membranes. Still to date, a complete and fully automated ODNP instrument is not commercialized. The purpose of this chapter is to share the technical know-how of the hardware, theory, measurement, and data analysis method needed to successfully utilize and disseminate the ODNP technique. © 2015 Elsevier Inc. All rights reserved.

  13. Dynamic Nuclear Spin Resonance in n-GaAs

    NASA Astrophysics Data System (ADS)

    Chen, Y. S.; Reuter, D.; Wieck, A. D.; Bacher, G.

    2011-10-01

    The dynamics of optically detected nuclear magnetic resonance is studied in n-GaAs via time-resolved Kerr rotation using an on-chip microcoil for rf field generation. Both optically allowed and optically forbidden NMR are observed with a dynamics controlled by the interplay between dynamic nuclear polarization via hyperfine interaction with optically generated spin-polarized electrons and nuclear spin depolarization due to magnetic resonance absorption. Comparing the characteristic nuclear spin relaxation rate obtained in experiment with master equation simulations, the underlying nuclear spin depolarization mechanism for each resonance is extracted.

  14. Dynamics of Nuclear Regions of Galaxies

    NASA Technical Reports Server (NTRS)

    Miller, Richard H.

    1996-01-01

    Current research carried out with the help of the ASEE-NASA Summer Faculty Program, at NASA-Ames, is concentrated on the dynamics of nuclear regions of galaxies. From a dynamical point of view a galaxy is a collection of around 10(sup 11) stars like our Sun, each of which moves in the summed gravitational field of all the remaining stars. Thus galaxy dynamics becomes a self-consistent n-body problem with forces given by Newtonian gravitation. Strong nonlinearity in the gravitational force and the inherent nonlinearity of self-consistent problems both argue for a numerical approach. The technique of numerical experiments consis of constructing an environment in the computer that is as close as possible to the physical conditions in a real galaxy and then carrying out experiments much like laboratory experiments in physics or engineering, in this environment. Computationally, an experiment is an initial value problem, and a good deal of thought and effort goes into the design of the starting conditions that serve as initial values. Experiments are run at Ames because all the 'equipment' is in place-the programs, the necessary computational power, and good facilities for post-run analysis. Our goal for this research program is to study the nuclear regions in detail and this means replacing most of the galaxy by a suitable boundary condition to allow the full capability of numerical experiments to be brought to bear on a small region perhaps 1/1000 of the linear dimensions of an entire galaxy. This is an extremely delicate numerical problem, one in which some small feature overlook, can easily lead to a collapse or blow-up of the entire system. All particles attract each other in gravitational problems, and the 1/r(sup 2) force is: (1) nonlinear; (2) strong at short range; (3) long-range, and (4) unscreened at any distance.

  15. Human DNA ligase III recognizes DNA ends by dynamic switching between two DNA-bound states.

    PubMed

    Cotner-Gohara, Elizabeth; Kim, In-Kwon; Hammel, Michal; Tainer, John A; Tomkinson, Alan E; Ellenberger, Tom

    2010-07-27

    Human DNA ligase III has essential functions in nuclear and mitochondrial DNA replication and repair and contains a PARP-like zinc finger (ZnF) that increases the extent of DNA nick joining and intermolecular DNA ligation, yet the bases for ligase III specificity and structural variation among human ligases are not understood. Here combined crystal structure and small-angle X-ray scattering results reveal dynamic switching between two nick-binding components of ligase III: the ZnF-DNA binding domain (DBD) forms a crescent-shaped surface used for DNA end recognition which switches to a ring formed by the nucleotidyl transferase (NTase) and OB-fold (OBD) domains for catalysis. Structural and mutational analyses indicate that high flexibility and distinct DNA binding domain features in ligase III assist both nick sensing and the transition from nick sensing by the ZnF to nick joining by the catalytic core. The collective results support a "jackknife model" in which the ZnF loads ligase III onto nicked DNA and conformational changes deliver DNA into the active site. This work has implications for the biological specificity of DNA ligases and functions of PARP-like zinc fingers.

  16. Human DNA Ligase III Recognizes DNA Ends by Dynamic Switching between Two DNA-Bound States

    SciTech Connect

    Cotner-Gohara, Elizabeth; Kim, In-Kwon; Hammel, Michal; Tainer, John A.; Tomkinson, Alan E.; Ellenberger, Tom

    2010-09-13

    Human DNA ligase III has essential functions in nuclear and mitochondrial DNA replication and repair and contains a PARP-like zinc finger (ZnF) that increases the extent of DNA nick joining and intermolecular DNA ligation, yet the bases for ligase III specificity and structural variation among human ligases are not understood. Here combined crystal structure and small-angle X-ray scattering results reveal dynamic switching between two nick-binding components of ligase III: the ZnF-DNA binding domain (DBD) forms a crescent-shaped surface used for DNA end recognition which switches to a ring formed by the nucleotidyl transferase (NTase) and OB-fold (OBD) domains for catalysis. Structural and mutational analyses indicate that high flexibility and distinct DNA binding domain features in ligase III assist both nick sensing and the transition from nick sensing by the ZnF to nick joining by the catalytic core. The collective results support a 'jackknife model' in which the ZnF loads ligase III onto nicked DNA and conformational changes deliver DNA into the active site. This work has implications for the biological specificity of DNA ligases and functions of PARP-like zinc fingers.

  17. Protein kinase A regulates RNA polymerase III transcription through the nuclear localization of Maf1

    PubMed Central

    Moir, Robyn D.; Lee, JaeHoon; Haeusler, Rebecca A.; Desai, Neelam; Engelke, David R.; Willis, Ian M.

    2006-01-01

    Maf1 is an essential and specific mediator of transcriptional repression in the RNA polymerase (pol) III system. Maf1-dependent repression occurs in response to a wide range of conditions, suggesting that the protein itself is targeted by the major nutritional and stress-signaling pathways. We show that Maf1 is a substrate for cAMP-dependent PKA in vitro and is differentially phosphorylated on PKA sites in vivo under normal versus repressing conditions. PKA activity negatively regulates Maf1 function because strains with unregulated high PKA activity block repression of pol III transcription in vivo, and strains lacking all PKA activity are hyperrepressible. Nuclear accumulation of Maf1 is required for transcriptional repression and is regulated by two nuclear localization sequences in the protein. An analysis of PKA phosphosite mutants shows that the localization of Maf1 is affected via the N-terminal nuclear localization sequence. In particular, mutations that prevent phosphorylation at PKA consensus sites promote nuclear accumulation of Maf1 without inducing repression. These results indicate that negative regulation of Maf1 by PKA is achieved by inhibiting its nuclear import and suggest that a PKA-independent activation step is required for nuclear Maf1 to function in the repression of pol III transcription. Finally, we report a previously undescribed phenotype for Maf1 in tRNA gene-mediated silencing of nearby RNA pol II transcription. PMID:17005718

  18. 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.

  19. Membrane Binding by CHMP7 Coordinates ESCRT-III-Dependent Nuclear Envelope Reformation.

    PubMed

    Olmos, Yolanda; Perdrix-Rosell, Anna; Carlton, Jeremy G

    2016-10-10

    In addition to its role in membrane abscission during cytokinesis, viral budding, endosomal sorting, and plasma membrane repair [1], the endosomal sorting complex required for transport-III (ESCRT-III) machinery has recently been shown to seal holes in the reforming nuclear envelope (NE) during mitotic exit [2, 3]. ESCRT-III also acts during interphase to repair the NE upon migration-induced rupture [4, 5], highlighting its key role as an orchestrator of membrane integrity at this organelle. While NE localization of ESCRT-III is dependent upon the ESCRT-III component CHMP7 [3], it is unclear how this complex is able to engage nuclear membranes. Here we show that the N terminus of CHMP7 acts as a novel membrane-binding module. This membrane-binding ability allows CHMP7 to bind to the ER, an organelle continuous with the NE, and it provides a platform to direct NE recruitment of ESCRT-III during mitotic exit. CHMP7's N terminus comprises tandem Winged-Helix domains [6], and, by using homology modeling and structure-function analysis, we identify point mutations that disrupt membrane binding and prevent both ER localization of CHMP7 and its subsequent enrichment at the reforming NE. These mutations also prevent assembly of downstream ESCRT-III components at the reforming NE and proper establishment of post-mitotic nucleo-cytoplasmic compartmentalization. These data identify a novel membrane-binding activity within an ESCRT-III subunit that is essential for post-mitotic nuclear regeneration.

  20. [Fundamental bases of digital information processing in nuclear cardiology (III)].

    PubMed

    Cuarón, A; González, C; García Moreira, C

    1984-01-01

    This article describes the transformation of the gamma-camera images into digital form. The incidence of a gamma photon on the detector, produces two voltage pulses, which are proportional to the coordinates of the incidence points, and a digital pulse, indicative of the occurrence of the event. The coordinate pulses passes through a analog-digital converter, that is activated by the pulse. The result is the appearance of a digital number at the out-put of the converter, which is proportional to the voltage at its in-put. This number, is stored on the accumulation memory of the system, either on a list mode or on a matrix mode. Static images can be stored on a single matrix. Dynamic data can be stored on a series of matrixes, each representing a different period of acquisition. It is also possible to capture information on a series of matrixes syncronized with the electrocardiogram of the patient. In this instance, each matrix represents a distinct period of the cardiac cycle. Data stored on the memory, can be used to process and display images and quantitative histograms on a video screen. In order to do that, it is necessary to translate the digital data on the memory to voltage levels, and to transform these on light levels on the screen. This, is achieved through a digital analog converter. The reading of the digital memory must be syncronic with the electronic scanning of the video screen.

  1. Subfemtosecond quantum nuclear dynamics in water isotopomers.

    PubMed

    Rao, B Jayachander; Varandas, A J C

    2015-05-21

    Subfemtosecond quantum dynamics studies of all water isotopomers in the X̃ (2)B1 and à (2)A1 electronic states of the cation formed by Franck-Condon ionization of the neutral ground electronic state are reported. Using the ratio of the autocorrelation functions for the isotopomers as obtained from the solution of the time-dependent Schrödinger equation in a grid representation, high-order harmonic generation signals are calculated as a function of time. The results are found to be in agreement with the available experimental findings and with our earlier study for D2O(+)/H2O(+). Maxima are predicted in the autocorrelation function ratio at various times. Their origin and occurrence is explained by calculating expectation values of the bond lengths and bond angle of the water isotopomers as a function of time. The values so calculated for the (2)B1 and (2)A1 electronic states of the cation show quasiperiodic oscillations that can be associated with the time at which the nuclear wave packet reaches the minima of the potential energy surface, there being responsible for the peaks in the HHG signals.

  2. Microtesla MRI with dynamic nuclear polarization

    PubMed Central

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

    2010-01-01

    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 two-four 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 microtesla, 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 field 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 high as −95 for protons and as high 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 the low-temperature dissolution DNP

  3. Structure, dynamics and function of nuclear pore complexes

    PubMed Central

    D’Angelo, M. A.; Hetzer, M. W.

    2009-01-01

    Nuclear pore complexes are large aqueous channels that penetrate the nuclear envelope, connecting the nuclear interior with the cytoplasm. Until recently, these macromolecular complexes were viewed as static structures whose only function was to control the molecular trafficking between the two compartments. It has now become evident that this simplistic scenario is inaccurate and that nuclear pore complexes are highly dynamic multiprotein assemblies involved in diverse cellular processes ranging from the organization of the cytoskeleton to gene expression. In this review, we will discuss the most recent developments in the nuclear pore complex field, focusing in the assembly, disassembly, maintenance and function of this macromolecular structure. PMID:18786826

  4. Influence of electronic—nuclear coupling on dynamics

    NASA Astrophysics Data System (ADS)

    Longo, Ricardo; Diz, Agustín; Deumens, Erik; Öhrn, Yngve

    1994-04-01

    Electronic nuclear dynamics (END), a recently developed explicitly time-dependent theory treats fully the electronic—nuclear coupling. The END theory at the level of a model that employs a single complex spin-unrestricted determinantal wavefunction for the electrons and classical nuclei has been implemented in the computer code ENDyne. It permits comparisons of the full dynamics at this level of treatment with one where the electronic—nuclear coupling is neglected. The neglect of coupling terms is shown to have quite drastic influence on the detailed dynamics of ion—atom and ion—molecule collisions.

  5. 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

  6. Self-sustaining dynamical nuclear polarization oscillations in quantum dots.

    PubMed

    Rudner, M S; Levitov, L S

    2013-02-22

    Early experiments on spin-blockaded double quantum dots revealed robust, large-amplitude current oscillations in the presence of a static (dc) source-drain bias. Despite experimental evidence implicating dynamical nuclear polarization, the mechanism has remained a mystery. Here we introduce a minimal albeit realistic model of coupled electron and nuclear spin dynamics which supports self-sustained oscillations. Our mechanism relies on a nuclear spin analog of the tunneling magnetoresistance phenomenon (spin-dependent tunneling rates in the presence of an inhomogeneous Overhauser field) and nuclear spin diffusion, which governs dynamics of the spatial profile of nuclear polarization. The proposed framework naturally explains the differences in phenomenology between vertical and lateral quantum dot structures as well as the extremely long oscillation periods.

  7. Nuclear fuel: a new market dynamic

    SciTech Connect

    Kee, Edward D.

    2007-12-15

    After almost 20 years of low nuclear fuel prices, buyers have come to expect that these low and stable nuclear fuel prices will continue. This conventional wisdom may not reflect the significant changes and higher prices that growing demand, and the end of secondary sources of uranium and enrichment, will bring. (author)

  8. 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.

  9. RAVEN: Dynamic Event Tree Approach Level III Milestone

    SciTech Connect

    Andrea Alfonsi; Cristian Rabiti; Diego Mandelli; Joshua Cogliati; Robert Kinoshita

    2013-07-01

    Conventional Event-Tree (ET) based methodologies are extensively used as tools to perform reliability and safety assessment of complex and critical engineering systems. One of the disadvantages of these methods is that timing/sequencing of events and system dynamics are not explicitly accounted for in the analysis. In order to overcome these limitations several techniques, also know as Dynamic Probabilistic Risk Assessment (DPRA), have been developed. Monte-Carlo (MC) and Dynamic Event Tree (DET) are two of the most widely used D-PRA methodologies to perform safety assessment of Nuclear Power Plants (NPP). In the past two years, the Idaho National Laboratory (INL) has developed its own tool to perform Dynamic PRA: RAVEN (Reactor Analysis and Virtual control ENvironment). RAVEN has been designed to perform two main tasks: 1) control logic driver for the new Thermo-Hydraulic code RELAP-7 and 2) post-processing tool. In the first task, RAVEN acts as a deterministic controller in which the set of control logic laws (user defined) monitors the RELAP-7 simulation and controls the activation of specific systems. Moreover, the control logic infrastructure is used to model stochastic events, such as components failures, and perform uncertainty propagation. Such stochastic modeling is deployed using both MC and DET algorithms. In the second task, RAVEN processes the large amount of data generated by RELAP-7 using data-mining based algorithms. This report focuses on the analysis of dynamic stochastic systems using the newly developed RAVEN DET capability. As an example, a DPRA analysis, using DET, of a simplified pressurized water reactor for a Station Black-Out (SBO) scenario is presented.

  10. RAVEN. Dynamic Event Tree Approach Level III Milestone

    SciTech Connect

    Alfonsi, Andrea; Rabiti, Cristian; Mandelli, Diego; Cogliati, Joshua; Kinoshita, Robert

    2014-07-01

    Conventional Event-Tree (ET) based methodologies are extensively used as tools to perform reliability and safety assessment of complex and critical engineering systems. One of the disadvantages of these methods is that timing/sequencing of events and system dynamics are not explicitly accounted for in the analysis. In order to overcome these limitations several techniques, also know as Dynamic Probabilistic Risk Assessment (DPRA), have been developed. Monte-Carlo (MC) and Dynamic Event Tree (DET) are two of the most widely used D-PRA methodologies to perform safety assessment of Nuclear Power Plants (NPP). In the past two years, the Idaho National Laboratory (INL) has developed its own tool to perform Dynamic PRA: RAVEN (Reactor Analysis and Virtual control ENvironment). RAVEN has been designed to perform two main tasks: 1) control logic driver for the new Thermo-Hydraulic code RELAP-7 and 2) post-processing tool. In the first task, RAVEN acts as a deterministic controller in which the set of control logic laws (user defined) monitors the RELAP-7 simulation and controls the activation of specific systems. Moreover, the control logic infrastructure is used to model stochastic events, such as components failures, and perform uncertainty propagation. Such stochastic modeling is deployed using both MC and DET algorithms. In the second task, RAVEN processes the large amount of data generated by RELAP-7 using data-mining based algorithms. This report focuses on the analysis of dynamic stochastic systems using the newly developed RAVEN DET capability. As an example, a DPRA analysis, using DET, of a simplified pressurized water reactor for a Station Black-Out (SBO) scenario is presented.

  11. Measurements of nuclear spin dynamics by spin-noise spectroscopy

    SciTech Connect

    Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S.; Kavokin, K. V.; Glazov, M. M.; Vladimirova, M.; Scalbert, D.; Cronenberger, S.; Lemaître, A.; Bloch, J.

    2015-06-15

    We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.

  12. Measurements of nuclear spin dynamics by spin-noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Ryzhov, I. I.; Poltavtsev, S. V.; Kavokin, K. V.; Glazov, M. M.; Kozlov, G. G.; Vladimirova, M.; Scalbert, D.; Cronenberger, S.; Kavokin, A. V.; Lemaître, A.; Bloch, J.; Zapasskii, V. S.

    2015-06-01

    We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.

  13. Dynamics and regulation of nuclear import and nuclear movements of HIV-1 complexes

    PubMed Central

    Burdick, Ryan C.; Chen, Jianbo; Sastri, Jaya; Hu, Wei-Shau

    2017-01-01

    The dynamics and regulation of HIV-1 nuclear import and its intranuclear movements after import have not been studied. To elucidate these essential HIV-1 post-entry events, we labeled viral complexes with two fluorescently tagged virion-incorporated proteins (APOBEC3F or integrase), and analyzed the HIV-1 dynamics of nuclear envelope (NE) docking, nuclear import, and intranuclear movements in living cells. We observed that HIV-1 complexes exhibit unusually long NE residence times (1.5±1.6 hrs) compared to most cellular cargos, which are imported into the nuclei within milliseconds. Furthermore, nuclear import requires HIV-1 capsid (CA) and nuclear pore protein Nup358, and results in significant loss of CA, indicating that one of the viral core uncoating steps occurs during nuclear import. Our results showed that the CA-Cyclophilin A interaction regulates the dynamics of nuclear import by delaying the time of NE docking as well as transport through the nuclear pore, but blocking reverse transcription has no effect on the kinetics of nuclear import. We also visualized the translocation of viral complexes docked at the NE into the nucleus and analyzed their nuclear movements and determined that viral complexes exhibited a brief fast phase (<9 min), followed by a long slow phase lasting several hours. A comparison of the movement of viral complexes to those of proviral transcription sites supports the hypothesis that HIV-1 complexes quickly tether to chromatin at or near their sites of integration in both wild-type cells and cells in which LEDGF/p75 was deleted using CRISPR/cas9, indicating that the tethering interactions do not require LEDGF/p75. These studies provide novel insights into the dynamics of viral complex-NE association, regulation of nuclear import, viral core uncoating, and intranuclear movements that precede integration site selection. PMID:28827840

  14. Nuclear chiral dynamics and phases of QCD

    NASA Astrophysics Data System (ADS)

    Weise, W.

    2012-04-01

    This presentation starts with a brief review of our current picture of QCD phases, derived from lattice QCD thermodynamics and from models based on the symmetries and symmetry breaking patterns of QCD. Typical approaches widely used in this context are the PNJL and chiral quark-meson models. It is pointed out, however, that the modeling of the phase diagram in terms of quarks as quasiparticles misses important and well known nuclear physics constraints. In the hadronic phase of QCD governed by confinement and spontaneously broken chiral symmetry, in-medium chiral effective field theory is the appropriate framework, with pions and nucleons as active degrees of freedom. Nuclear chiral thermodynamics is outlined and the liquid-gas phase transition is described. The density and temperature dependence of the chiral condensate is deduced. As a consequence of two- and three-body correlations in the nuclear medium, no tendency towards a first-order chiral phase transition is found at least up to twice the baryon density of normal nuclear matter and up to temperatures of about 100 MeV. Isospin-asymmetric nuclear matter and neutron matter are also discussed. An outlook is given on new tightened constraints for the equation-of-state of cold and highly compressed matter as implied by a recently observed two-solar-mass neutron star.

  15. Theory of dynamic nuclear polarization and feedback in quantum dots

    NASA Astrophysics Data System (ADS)

    Economou, Sophia E.; Barnes, Edwin

    2014-04-01

    An electron confined in a quantum dot interacts with its local nuclear spin environment through the hyperfine contact interaction. This interaction combined with external control and relaxation or measurement of the electron spin allows for the generation of dynamic nuclear polarization. The quantum nature of the nuclear bath, along with the interplay of coherent external fields and incoherent dynamics in these systems renders a wealth of intriguing phenomena seen in recent experiments such as electron Zeeman frequency focusing, hysteresis, and line dragging. We develop in detail a fully quantum, self-consistent theory that can be applied to such experiments and that moreover has predictive power. Our theory uses the operator sum representation formalism in order to incorporate the incoherent dynamics caused by the additional, Markovian bath, which in self-assembled dots is the vacuum field responsible for electron-hole optical recombination. The beauty of this formalism is that it reduces the complexity of the problem by encoding the joint dynamics of the external coherent and incoherent driving in an effective dynamical map that only acts on the electron spin subspace. This, together with the separation of time scales in the problem, allows for a tractable and analytically solvable formalism. The key role of entanglement between the electron spin and the nuclear spins in the formation of dynamic nuclear polarization naturally follows from our solution. We demonstrate the theory in detail for an optical pulsed experiment and present an in-depth discussion and physical explanation of our results.

  16. Altered nuclear dynamics in MDX myofibers.

    PubMed

    Iyer, Shama R; Shah, Sameer B; Valencia, Ana P; Schneider, Martin F; Hernández-Ochoa, Erick O; Stains, Joseph P; Blemker, Silvia S; Lovering, Richard M

    2017-03-01

    Duchenne muscular dystrophy (DMD) is a genetic disorder in which the absence of dystrophin leads to progressive muscle degeneration and weakness. Although the genetic basis is known, the pathophysiology of dystrophic skeletal muscle remains unclear. We examined nuclear movement in wild-type (WT) and muscular dystrophy mouse model for DMD (MDX) (dystrophin-null) mouse myofibers. We also examined expression of proteins in the linkers of nucleoskeleton and cytoskeleton (LINC) complex, as well as nuclear transcriptional activity via histone H3 acetylation and polyadenylate-binding nuclear protein-1. Because movement of nuclei is not only LINC dependent but also microtubule dependent, we analyzed microtubule density and organization in WT and MDX myofibers, including the application of a unique 3D tool to assess microtubule core structure. Nuclei in MDX myofibers were more mobile than in WT myofibers for both distance traveled and velocity. MDX muscle shows reduced expression and labeling intensity of nesprin-1, a LINC protein that attaches the nucleus to the microtubule and actin cytoskeleton. MDX nuclei also showed altered transcriptional activity. Previous studies established that microtubule structure at the cortex is disrupted in MDX myofibers; our analyses extend these findings by showing that microtubule structure in the core is also disrupted. In addition, we studied malformed MDX myofibers to better understand the role of altered myofiber morphology vs. microtubule architecture in the underlying susceptibility to injury seen in dystrophic muscles. We incorporated morphological and microtubule architectural concepts into a simplified finite element mathematical model of myofiber mechanics, which suggests a greater contribution of myofiber morphology than microtubule structure to muscle biomechanical performance.NEW & NOTEWORTHY Microtubules provide the means for nuclear movement but show altered organization in the muscular dystrophy mouse model (MDX

  17. BOLD VENTURE COMPUTATION SYSTEM for nuclear reactor core analysis, Version III

    SciTech Connect

    Vondy, D.R.; Fowler, T.B.; Cunningham, G.W. III.

    1981-06-01

    This report is a condensed documentation for VERSION III of the BOLD VENTURE COMPUTATION SYSTEM for nuclear reactor core analysis. An experienced analyst should be able to use this system routinely for solving problems by referring to this document. Individual reports must be referenced for details. This report covers basic input instructions and describes recent extensions to the modules as well as to the interface data file specifications. Some application considerations are discussed and an elaborate sample problem is used as an instruction aid. Instructions for creating the system on IBM computers are also given.

  18. Towards a self-consistent dynamical nuclear model

    NASA Astrophysics Data System (ADS)

    Roca-Maza, X.; Niu, Y. F.; Colò, G.; Bortignon, P. F.

    2017-04-01

    Density functional theory (DFT) is a powerful and accurate tool, exploited in nuclear physics to investigate the ground-state and some of the collective properties of nuclei along the whole nuclear chart. Models based on DFT are not, however, suitable for the description of single-particle dynamics in nuclei. Following the field theoretical approach by A Bohr and B R Mottelson to describe nuclear interactions between single-particle and vibrational degrees of freedom, we have taken important steps towards the building of a microscopic dynamic nuclear model. In connection with this, one important issue that needs to be better understood is the renormalization of the effective interaction in the particle-vibration approach. One possible way to renormalize the interaction is by the so-called subtraction method. In this contribution, we will implement the subtraction method in our model for the first time and study its consequences.

  19. Dynamic Nuclear Polarization of β-Cyclodextrin Macromolecules.

    PubMed

    Caracciolo, Filippo; Carretta, Pietro; Filibian, Marta; Melone, Lucio

    2017-03-30

    (1)H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of β-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/TPOL) and of the nuclear spin-lattice relaxation rate (1/T1n) consistent with a thermal mixing regime. The temperature dependence of 1/T1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics. The high-temperature relaxation is driven by molecular motions, and 1/T1n was studied at room temperature in liquid solutions for dilution levels close to the ones typically used for in vivo studies.

  20. Nonadiabatic evolution of electronic states by electron nuclear dynamics theory

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    The problem of how to determine the nonadiabatic content of any given dynamic process involving molecular motion is addressed in the context of Electron Nuclear Dynamics (END) theory. Specifically, it is proposed to cast the dynamic END wave function into the language of static electronic configurations with time dependent complex-valued amplitudes. This is achieved by adiabatic transport of an electronic basis along the classical nuclear trajectories of the studied molecular system, as yielded by END simulation. Projecting the dynamic wave function on this basis yields a natural distinction between adiabatic and nonadiabatic components of the motion considered. Tracing the evolution of the leading configurations is shown to be a helpful device for clarifying the physical nature of electronic excitation processes. For illustration of these concepts, dynamic configuration analysis is applied to the scattering of a proton by a lithium atom.

  1. Dynamical cooling of nuclear spins in double quantum dots.

    PubMed

    Rudner, M S; Levitov, L S

    2010-07-09

    Electrons trapped in quantum dots can exhibit quantum-coherent spin dynamics over long timescales. These timescales are limited by the coupling of electron spins to the disordered nuclear spin background, which is a major source of noise and dephasing in such systems. We propose a scheme for controlling and suppressing fluctuations of nuclear spin polarization in double quantum dots, which uses nuclear spin pumping in the spin-blockade regime. We show that nuclear spin polarization fluctuations can be suppressed when electronic levels in the two dots are properly positioned near resonance. The proposed mechanism is analogous to that of optical Doppler cooling. The Overhauser shift due to fluctuations of nuclear polarization brings electron levels in and out of resonance, creating internal feedback to suppress fluctuations. Estimates indicate that a better than 10-fold reduction of fluctuations is possible.

  2. Dynamic Systems Analysis Report for Nuclear Fuel Recycle

    SciTech Connect

    Brent Dixon; Sonny Kim; David Shropshire; Steven Piet; Gretchen Matthern; Bill Halsey

    2008-12-01

    This report examines the time-dependent dynamics of transitioning from the current United States (U.S.) nuclear fuel cycle where used nuclear fuel is disposed in a repository to a closed fuel cycle where the used fuel is recycled and only fission products and waste are disposed. The report is intended to help inform policy developers, decision makers, and program managers of system-level options and constraints as they guide the formulation and implementation of advanced fuel cycle development and demonstration efforts and move toward deployment of nuclear fuel recycling infrastructure.

  3. Dynamics of nuclear receptor gene expression during Pacific oyster development.

    PubMed

    Vogeler, Susanne; Bean, Tim P; Lyons, Brett P; Galloway, Tamara S

    2016-09-29

    Nuclear receptors are a highly conserved set of ligand binding transcription factors, with essential roles regulating aspects of vertebrate and invertebrate biology alike. Current understanding of nuclear receptor regulated gene expression in invertebrates remains sparse, limiting our ability to elucidate gene function and the conservation of developmental processes across phyla. Here, we studied nuclear receptor expression in the early life stages of the Pacific oyster, Crassostrea gigas, to identify at which specific key stages nuclear receptors are expressed RESULTS: We used quantitative RT-PCR to determine the expression profiles of 34 nuclear receptors, revealing three developmental key stages, during which nuclear receptor expression is dynamically regulated: embryogenesis, mid development from gastrulation to trochophore larva, and late larval development prior to metamorphosis. Clustering of nuclear receptor expression patterns demonstrated that transcriptional regulation was not directly related to gene phylogeny, suggesting closely related genes may have distinct functions. Expression of gene homologs of vertebrate retinoid receptors suggests participation in organogenesis and shell-formation, as they are highly expressed at the gastrulation and trochophore larval initial shell formation stages. The ecdysone receptor homolog showed high expression just before larval settlement, suggesting a potential role in metamorphosis. Throughout early oyster development nuclear receptors exhibited highly dynamic expression profiles, which were not confined by gene phylogeny. These results provide fundamental information on the presence of nuclear receptors during key developmental stages, which aids elucidation of their function in the developmental process. This understanding is essential as ligand sensing nuclear receptors can be disrupted by xenobiotics, a mode of action through which anthropogenic environmental pollutants have been found to mediate effects.

  4. Fluctuations and symmetry energy in nuclear fragmentation dynamics.

    PubMed

    Colonna, M

    2013-01-25

    Within a dynamical description of nuclear fragmentation, based on the liquid-gas phase transition scenario, we explore the relation between neutron-proton density fluctuations and nuclear symmetry energy. We show that, along the fragmentation path, isovector fluctuations follow the evolution of the local density and approach an equilibrium value connected to the local symmetry energy. Higher-density regions are characterized by smaller average asymmetry and narrower isotopic distributions. This dynamical analysis points out that fragment final state isospin fluctuations can probe the symmetry energy of the density domains from which fragments originate.

  5. Magnetic-field cycling instrumentation for dynamic nuclear polarization-nuclear magnetic resonance using photoexcited triplets.

    PubMed

    Kagawa, Akinori; Negoro, Makoto; Takeda, Kazuyuki; Kitagawa, Masahiro

    2009-04-01

    To advance static solid-state NMR with hyperpolarized nuclear spins, a system has been developed enabling dynamic nuclear polarization (DNP) using electron spins in the photoexcited triplet state with X-band microwave apparatus, followed by static solid-state nuclear magnetic resonance (NMR) experiments using the polarized nuclear-spin system with a goniometer. In order to perform the DNP and NMR procedures in different magnetic fields, the DNP system and the NMR system are spatially separated, between which the sample can be shuttled while its orientation is controlled in a reproducible fashion. We demonstrate that the system developed in this work is operational for solid-state NMR with hyperpolarized nuclear-spin systems in static organic materials, and also discuss the application of our system.

  6. Nuclear dynamical deformation induced hetero- and euchromatin positioning

    NASA Astrophysics Data System (ADS)

    Awazu, Akinori

    2015-09-01

    We studied the role of active deformation dynamics in cell nuclei in chromatin positioning. Model chains containing two types of regions, with high (euchromatic) or low (heterochromatic) mobility, were confined in a pulsating container simulating a nucleus showing dynamic deformations. Brownian dynamic simulations show that the positioning of low mobility regions changes from sites near the periphery to the center if the affinity between these regions and the container periphery disappears. The former and latter positionings are similar to the "conventional" and "inverted" chromatin positionings in nuclei of normal differentiated cells and cells lacking Lamin-related proteins. Additionally, nuclear dynamical deformation played essential roles in "inverted" chromatin positioning.

  7. Nuclear Reactions and Stellar Evolution: Unified Dynamics

    SciTech Connect

    Bauer, W.; Strother, T.

    2007-10-26

    Motivated by the success of kinetic theory in the description of observables in intermediate and high energy heavy ion collisions, we use kinetic theory to model the dynamics of collapsing iron cores in type II supernova explosions. The algorithms employed to model the collapse, some preliminary results and predictions, and the future of the code are discussed.

  8. Electron-Nuclear Dynamics of Molecular Systems

    DTIC Science & Technology

    1994-04-18

    approach with a completely general form of trial function yields the time - dependent Schr ~ dinger equation . Restricting the...dynamical equations approximating the time - dependent SchrOdinger equation . These equations govern the time evolution of the relevant state vector parameters... equations that apprximate the Apuit 18, 1994 time - dependent Schradinger equation and govern the time evolution of

  9. Neutron detection of the Triga Mark III reactor, using nuclear track methodology

    SciTech Connect

    Espinosa, G. Golzarri, J. I.; Raya-Arredondo, R.; Cruz-Galindo, S.; Sajo-Bohus, L.

    2015-07-23

    Nuclear Track Methodology (NTM), based on the neutron-proton interaction is one often employed alternative for neutron detection. In this paper we apply NTM to determine the Triga Mark III reactor operating power and neutron flux. The facility nuclear core, loaded with 85 Highly Enriched Uranium as fuel with control rods in a demineralized water pool, provide a neutron flux around 2 × 10{sup 12} n cm{sup −2} s{sup −1}, at the irradiation channel TO-2. The neutron field is measured at this channel, using Landauer{sup ®} PADC as neutron detection material, covered by 3 mm Plexiglas{sup ®} as converter. After exposure, plastic detectors were chemically etched to make observable the formed latent tracks induced by proton recoils. The track density was determined by a custom made Digital Image Analysis System. The resulting average nuclear track density shows a direct proportionality response for reactor power in the range 0.1-7 kW. We indicate several advantages of the technique including the possibility to calibrate the neutron flux density measured at low reactor power.

  10. Developing polarizable potential for molecular dynamics of Cm(III)-carbonate complexes in liquid water.

    PubMed

    Spezia, Riccardo; Jeanvoine, Yannick; Vuilleumier, Rodolphe

    2014-08-01

    In this work we have developed a polarizable potential to study Cm(III) forming complexes with carbonate anions in liquid water. The potential was developed by employing an extension of the procedure that we used to study the hydration of lanthanoids(III) and actinoids(III). Force field performances were benchmarked against DFT results obtained by both geometry optimization and Car-Parrinello molecular dynamics. With this polarizable potential, we run extended molecular dynamics simulations in liquid water from which we were able to identify structural and dynamical properties of such systems. In particular, water exchange dynamics were analyzed in detail. We obtained an average of three water molecules in the first shell of Cm(III) that show a relatively fast exchange dynamic (faster than for bare ions). Summarizing these results, we were able to draw an analogy to the results from the lanthanoid(III) series. In particular, it seems that Cm(III) behaves more like Nd(III) than Gd(III), as one would expect based on the recent hydration results and on f orbital occupancy.

  11. The intricacy of nuclear membrane dynamics during nucleophagy

    PubMed Central

    Mijaljica, Dalibor; Prescott, Mark

    2010-01-01

    The cell nucleus is an organelle bounded by a double-membrane which undergoes drastic reorganization during major cellular events such as cell division and apoptosis. Maintenance of proper nuclear structure, function and dynamics is central to organelle vitality. Over recent years growing evidence has shown that parts of the nucleus can be specifically degraded by an autophagic process termed nucleophagy. The process is best described in the yeast, Saccharomyces cerevisiae, where piecemeal microautophagy of the nucleus or nucleophagy (micronucleophagy) requires direct interaction of the nuclear membrane with that of the vacuole (the yeast lytic compartment). Here, we review the process of nucleophagy in the context of nuclear membrane dynamics, and examine the evidence for autophagic degradation of the nucleus in mammalian cells. Finally, we discuss the importance of nucleophagy as a ‘housecleaning’ mechanism for the nucleus under both normal and disease conditions. PMID:21327066

  12. Dynamic Simulation and Optimization of Nuclear Hydrogen Production Systems

    SciTech Connect

    Paul I. Barton; Mujid S. Kaximi; Georgios Bollas; Patricio Ramirez Munoz

    2009-07-31

    This project is part of a research effort to design a hydrogen plant and its interface with a nuclear reactor. This project developed a dynamic modeling, simulation and optimization environment for nuclear hydrogen production systems. A hybrid discrete/continuous model captures both the continuous dynamics of the nuclear plant, the hydrogen plant, and their interface, along with discrete events such as major upsets. This hybrid model makes us of accurate thermodynamic sub-models for the description of phase and reaction equilibria in the thermochemical reactor. Use of the detailed thermodynamic models will allow researchers to examine the process in detail and have confidence in the accurary of the property package they use.

  13. Molecular interferometer to decode attosecond electron–nuclear dynamics

    PubMed Central

    Palacios, Alicia; González-Castrillo, Alberto; Martín, Fernando

    2014-01-01

    Understanding the coupled electronic and nuclear dynamics in molecules by using pump–probe schemes requires not only the use of short enough laser pulses but also wavelengths and intensities that do not modify the intrinsic behavior of the system. In this respect, extreme UV pulses of few-femtosecond and attosecond durations have been recognized as the ideal tool because their short wavelengths ensure a negligible distortion of the molecular potential. In this work, we propose the use of two twin extreme UV pulses to create a molecular interferometer from direct and sequential two-photon ionization processes that leave the molecule in the same final state. We theoretically demonstrate that such a scheme allows for a complete identification of both electronic and nuclear phases in the wave packet generated by the pump pulse. We also show that although total ionization yields reveal entangled electronic and nuclear dynamics in the bound states, doubly differential yields (differential in both electronic and nuclear energies) exhibit in addition the dynamics of autoionization, i.e., of electron correlation in the ionization continuum. Visualization of such dynamics is possible by varying the time delay between the pump and the probe pulses. PMID:24591647

  14. Molecular interferometer to decode attosecond electron-nuclear dynamics.

    PubMed

    Palacios, Alicia; González-Castrillo, Alberto; Martín, Fernando

    2014-03-18

    Understanding the coupled electronic and nuclear dynamics in molecules by using pump-probe schemes requires not only the use of short enough laser pulses but also wavelengths and intensities that do not modify the intrinsic behavior of the system. In this respect, extreme UV pulses of few-femtosecond and attosecond durations have been recognized as the ideal tool because their short wavelengths ensure a negligible distortion of the molecular potential. In this work, we propose the use of two twin extreme UV pulses to create a molecular interferometer from direct and sequential two-photon ionization processes that leave the molecule in the same final state. We theoretically demonstrate that such a scheme allows for a complete identification of both electronic and nuclear phases in the wave packet generated by the pump pulse. We also show that although total ionization yields reveal entangled electronic and nuclear dynamics in the bound states, doubly differential yields (differential in both electronic and nuclear energies) exhibit in addition the dynamics of autoionization, i.e., of electron correlation in the ionization continuum. Visualization of such dynamics is possible by varying the time delay between the pump and the probe pulses.

  15. System dynamics: An introduction & applications to the nuclear industry

    SciTech Connect

    Hansen, K.F.; Golay, M.W.

    1997-03-01

    The field of nuclear technology has been developing for over 50 years and has moved from the laboratory into a very large commercial industry. The growth in the underlying science and engineering has been remarkable both in its breadth and depth. The ability to design, analyze, and understand the behavior of nuclear plants is firmly established. There remain many challenging technical problems, but success of the industry is not contingent upon solving those technical problems. Rather, the success of the industry will be determined by a wider array of concerns than pure technology. For instance, nuclear plants in the future will have to compete economically against efficient, versatile, and reliable fossil technologies. In addition, potential users must be assured that the indirect costs, such as those of environmental effects and waste disposal, are acceptable. Finally, public perceptions about risks must somehow be allayed, if not resolved. The objective of this paper is to provide an introduction to a tool that may be useful to the industry in addressing the types of issues suggested above. The tool discussed is system dynamics. It has been used with considerable success in many other fields in ways that are similar to the needs of the nuclear field. In the second section of the paper the authors provide some background on the system dynamics method and illustrate how system dynamics models are constructed. In section 3 they discuss two applications in the nuclear field, the first relating to construction of nuclear plants and the second in the operation of a nuclear utility in the social/political environment of today in the United States. They conclude with some summary comments.

  16. Optically induced dynamic nuclear spin polarisation in diamond

    NASA Astrophysics Data System (ADS)

    Scheuer, Jochen; Schwartz, Ilai; Chen, Qiong; Schulze-Sünninghausen, David; Carl, Patrick; Höfer, Peter; Retzker, Alexander; Sumiya, Hitoshi; Isoya, Junichi; Luy, Burkhard; Plenio, Martin B.; Naydenov, Boris; Jelezko, Fedor

    2016-01-01

    The sensitivity of magnetic resonance imaging (MRI) depends strongly on nuclear spin polarisation and, motivated by this observation, dynamical nuclear spin polarisation has recently been applied to enhance MRI protocols (Kurhanewicz et al 2011 Neoplasia 13 81). Nuclear spins associated with the 13C carbon isotope (nuclear spin I = 1/2) in diamond possess uniquely long spin lattice relaxation times (Reynhardt and High 2011 Prog. Nucl. Magn. Reson. Spectrosc. 38 37). If they are present in diamond nanocrystals, especially when strongly polarised, they form a promising contrast agent for MRI. Current schemes for achieving nuclear polarisation, however, require cryogenic temperatures. Here we demonstrate an efficient scheme that realises optically induced 13C nuclear spin hyperpolarisation in diamond at room temperature and low ambient magnetic field. Optical pumping of a nitrogen-vacancy centre creates a continuously renewable electron spin polarisation which can be transferred to surrounding 13C nuclear spins. Importantly for future applications we also realise polarisation protocols that are robust against an unknown misalignment between magnetic field and crystal axis.

  17. Conformational Dynamics of DNA Repair by Escherichia coli Endonuclease III*

    PubMed Central

    Kuznetsov, Nikita A.; Kladova, Olga A.; Kuznetsova, Alexandra A.; Ishchenko, Alexander A.; Saparbaev, Murat K.; Zharkov, Dmitry O.; Fedorova, Olga S.

    2015-01-01

    Escherichia coli endonuclease III (Endo III or Nth) is a DNA glycosylase with a broad substrate specificity for oxidized or reduced pyrimidine bases. Endo III possesses two types of activities: N-glycosylase (hydrolysis of the N-glycosidic bond) and AP lyase (elimination of the 3′-phosphate of the AP-site). We report a pre-steady-state kinetic analysis of structural rearrangements of the DNA substrates and uncleavable ligands during their interaction with Endo III. Oligonucleotide duplexes containing 5,6-dihydrouracil, a natural abasic site, its tetrahydrofuran analog, and undamaged duplexes carried fluorescent DNA base analogs 2-aminopurine and 1,3-diaza-2-oxophenoxazine as environment-sensitive reporter groups. The results suggest that Endo III induces several fast sequential conformational changes in DNA during binding, lesion recognition, and adjustment to a catalytically competent conformation. A comparison of two fluorophores allowed us to distinguish between the events occurring in the damaged and undamaged DNA strand. Combining our data with the available structures of Endo III, we conclude that this glycosylase uses a multistep mechanism of damage recognition, which likely involves Gln41 and Leu81 as DNA lesion sensors. PMID:25869130

  18. Role of class III phosphatidylinositol 3-kinase during programmed nuclear death of Tetrahymena thermophila.

    PubMed

    Akematsu, Takahiko; Fukuda, Yasuhiro; Attiq, Rizwan; Pearlman, Ronald E

    2014-02-01

    Programmed nuclear death (PND) in the ciliate protozoan Tetrahymena thermophila is a novel type of autophagy that occurs during conjugation, in which only the parental somatic macronucleus is destined to die and is then eliminated from the progeny cytoplasm. Other coexisting nuclei, however, such as new micro- and macronuclei are unaffected. PND starts with condensation in the nucleus followed by apoptotic DNA fragmentation, lysosomal acidification, and final resorption. Because of the peculiarity in the process and the absence of some ATG genes in this organism, the mechanism of PND has remained unclear. In this study, we focus on the role of class III phosphatidylinositol 3-kinase (PtdIns3K, corresponding to yeast Vps34) in order to identify central regulators of PND. We identified the sole Tetrahymena thermophila ortholog (TtVPS34) to yeast Vps34 and human PIK3C3 (the catalytic subunit of PtdIns3K), through phylogenetic analysis, and generated the gene knockdown mutant for functional analysis. Loss of TtVPS34 activity prevents autophagosome formation on the parental macronucleus, and this nucleus escapes from the lysosomal pathway. In turn, DNA fragmentation and final resorption of the nucleus are drastically impaired. These phenotypes are similar to the situation in the ATG8Δ mutants of Tetrahymena, implying an inextricable link between TtVPS34 and TtATG8s in controlling PND as well as general macroautophagy. On the other hand, TtVPS34 does not appear responsible for the nuclear condensation and does not affect the progeny nuclear development. These results demonstrate that TtVPS34 is critically involved in the nuclear degradation events of PND in autophagosome formation rather than with an involvement in commitment to the death program.

  19. Role of class III phosphatidylinositol 3-kinase during programmed nuclear death of Tetrahymena thermophila

    PubMed Central

    Akematsu, Takahiko; Fukuda, Yasuhiro; Attiq, Rizwan; Pearlman, Ronald E

    2014-01-01

    Programmed nuclear death (PND) in the ciliate protozoan Tetrahymena thermophila is a novel type of autophagy that occurs during conjugation, in which only the parental somatic macronucleus is destined to die and is then eliminated from the progeny cytoplasm. Other coexisting nuclei, however, such as new micro- and macronuclei are unaffected. PND starts with condensation in the nucleus followed by apoptotic DNA fragmentation, lysosomal acidification, and final resorption. Because of the peculiarity in the process and the absence of some ATG genes in this organism, the mechanism of PND has remained unclear. In this study, we focus on the role of class III phosphatidylinositol 3-kinase (PtdIns3K, corresponding to yeast Vps34) in order to identify central regulators of PND. We identified the sole Tetrahymena thermophila ortholog (TtVPS34) to yeast Vps34 and human PIK3C3 (the catalytic subunit of PtdIns3K), through phylogenetic analysis, and generated the gene knockdown mutant for functional analysis. Loss of TtVPS34 activity prevents autophagosome formation on the parental macronucleus, and this nucleus escapes from the lysosomal pathway. In turn, DNA fragmentation and final resorption of the nucleus are drastically impaired. These phenotypes are similar to the situation in the ATG8Δ mutants of Tetrahymena, implying an inextricable link between TtVPS34 and TtATG8s in controlling PND as well as general macroautophagy. On the other hand, TtVPS34 does not appear responsible for the nuclear condensation and does not affect the progeny nuclear development. These results demonstrate that TtVPS34 is critically involved in the nuclear degradation events of PND in autophagosome formation rather than with an involvement in commitment to the death program. PMID:24280724

  20. High-frequency dynamic nuclear polarization in the nuclear rotating frame.

    PubMed

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

    2000-05-01

    A proton dynamic nuclear polarization (DNP) NMR signal enhancement (epsilon) close to thermal equilibrium, epsilon = 0.89, has been obtained at high field (B(0) = 5 T, nu(epr) = 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 (T(1rho)), which is four orders of magnitude shorter than the nuclear spin-lattice relaxation time (T(1n)). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T(1rho) and is not limited by the much slower lab frame nuclear spin-lattice relaxation rate (1/T(1n)). The increased repetition rate allowed in the nuclear rotating frame provides an effective enhancement per unit time(1/2) of epsilon(t) = 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. Copyright 2000 Academic Press.

  1. Neutron-Proton equilibration in dynamically deformed nuclear systems.

    NASA Astrophysics Data System (ADS)

    Rodriguez Manso, Alis; McIntosh, A. B.; Jedele, A.; Yennello, S. J.

    2017-01-01

    Understanding the nuclear Equation of State (nEoS) is fundamental for describing nuclear reaction dynamics, understanding the origin of the elements and characterizing the structure of neutron stars. The density dependence of the asymmetry energy still represents the largest uncertainty in the nEoS. We demonstrate a new time-sensitive method for studying reaction dynamics that may allow new types of constraints on the asymmetry energy. We study neutron-proton equilibration in dynamically deformed nuclear systems by investigating the correlations between the largest fragments produced in collisions of 70Zn +70Zn, 64Zn +64Zn, 64Ni +64Ni and 70Zn +64Zn at 35 MeV per nucleon measured at the Cyclotron Institute at Texas A&M University. The extent of equilibration is investigated using the rotation angle as a clock. The equilibration follows an exponential trend with consistent rate constants across a wide variety of reaction partners and systems, indicating the equilibration follows first order kinetics. The statistical and dynamical components are separated on average; the equilibration curve for the purely dynamical is consistent with the overall equilibration curve, indicating the robustness of the method to statistical contamination.

  2. Electro-Nuclear clock transitions in a Ho(III) moleular nanomagnet

    NASA Astrophysics Data System (ADS)

    Komijani, Dorsa; Shiddiq, M.; Duan, Y.; Gaita-Arino, A.; Coronado, E.; Hill, S.

    One of the challenges in the field of quantum information processing involves protecting qubits against decoherence. The primary source of decoherence in spin qubits at low temperatures is the dipolar interaction, which can be minimized using so-called clock transitions. Here, we report pulsed EPR studies of the Holmium Polyoxometalate, [Na]9 [ HoxY1 - x(W5O18)2 ] , where we observe electro-nuclear clock transitions that involve coupled dynamics of the electron and nuclear spins (ΔmJ = +/- 8 and ΔmI = +/- 1). These transitions are formally forbidden in EPR. However, the symmetry of this molecule generates admixtures of the ground doublet (mJ = +/- 4) through second order perturbation, and application of a transverse magnetic field mixes mI and mI +/- 1 states, allowing such transitions to occur in the vicinity of avoided level crossings. Pulsed EPR measurements on an x = 0.1 sample, were carried out at a temperature of 5 K at X-band. These experiments suggest an enhancement in the coherence time at these electro-nuclear clock transitions which is significant for applications in hybrid magnetic qubits, where manipulation of the nuclear spin is controlled by EPR pulses. This work was supported by the NSF (DMR-1309463) and AFOSR.

  3. Molecular Mechanism of Overhauser Dynamic Nuclear Polarization in Insulating Solids.

    PubMed

    Pylaeva, Svetlana; Ivanov, Konstantin L; Baldus, Marc; Sebastiani, Daniel; Elgabarty, Hossam

    2017-05-18

    Dynamic nuclear polarization (DNP), a technique that significantly enhances NMR signals, is experiencing a renaissance owing to enormous methodological developments. In the heart of DNP is a polarization transfer mechanism that endows nuclei with much larger electronic spin polarization. Polarization transfer via the Overhauser effect (OE) is traditionally known to be operative only in liquids and conducting solids. Very recently, surprisingly strong OE-DNP in insulating solids has been reported, with a DNP efficiency that increases with the magnetic field strength. Here we offer an explanation for these perplexing observations using a combination of molecular dynamics and spin dynamics simulations. Our approach elucidates the underlying molecular stochastic motion, provides cross-relaxation rates, explains the observed sign of the NMR enhancement, and estimates the role of nuclear spin diffusion. The presented theoretical description opens the door for rational design of novel polarizing agents for OE-DNP in insulating solids.

  4. Nuclear dynamics at the balance energy

    NASA Astrophysics Data System (ADS)

    Sood, Aman D.; Puri, Rajeev K.

    2004-09-01

    We study the mass dependence of various quantities (like the average and maximum density, collision rate, participant-spectator matter, and temperature, as well as time zones for higher density) by simulating different reactions at the energy of vanishing flow. This study is carried out within the framework of the quantum molecular dynamics model. Our findings clearly indicate the existence of a power law in all the above quantities calculated at the balance energy. A significant mass dependence exists for the temperature reached in the central sphere. All other quantities at the balance energy are either rather insensitive or depend weakly on the system size. The time zone for the higher density as well as the time of maximal density and collision rate follow a power law inverse to the energy of vanishing flow. The participant matter at the balance energy shows a remarkable lack of mass dependence that makes it a good candidate for studying the balance energy.

  5. Analytic representation of the target acquisition process in NUFAM (Nuclear Fire Planning and Assessment Model) III. Final report, November 1988-March 1989

    SciTech Connect

    Youngren, M.A.

    1989-03-01

    This paper describes a method for determining the probability that a combat unit is acquired, available for fire by a nuclear weapon, is fired on, and is hit by a nuclear weapon. This method was incorporated as part of the Nuclear Fire Planning and Assessment Model III (NUFAM III) used at the Concept Analysis Agency (CAA). The target acquisition data required are the Probability of Operational Target Acquisition (POTA) values generated by the CAA Target Acquisition Study III (TAS III). The basic approach used alternating renewal processes to represent the acquisition status and movement state of each unit in NUFAM III.

  6. Time-dependent density-functional description of nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Nakatsukasa, Takashi; Matsuyanagi, Kenichi; Matsuo, Masayuki; Yabana, Kazuhiro

    2016-10-01

    The basic concepts and recent developments in the time-dependent density-functional theory (TDDFT) for describing nuclear dynamics at low energy are presented. The symmetry breaking is inherent in nuclear energy density functionals, which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in the description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, the quantum fluctuations associated with slow collective motions are explicitly treated assuming that time evolution of densities is determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field.

  7. Molecular chaperone-mediated nuclear protein dynamics.

    PubMed

    Echtenkamp, Frank J; Freeman, Brian C

    2014-05-01

    Homeostasis requires effective action of numerous biological pathways including those working along a genome. The variety of processes functioning in the nucleus is considerable, yet the number of employed factors eclipses this total. Ideally, individual components assemble into distinct complexes and serially operate along a pathway to perform work. Adding to the complexity is a multitude of fluctuating internal and external signals that must be monitored to initiate, continue or halt individual activities. While cooperative interactions between proteins of the same process provide a mechanism for rapid and precise assembly, the inherent stability of such organized structures interferes with the proper timing of biological events. Further prolonging the longevity of biological complexes are crowding effects resulting from the high concentration of intracellular macromolecules. Hence, accessory proteins are required to destabilize the various assemblies to efficiently transition between structures, avoid off-pathway competitive interactions, and to terminate pathway activity. We suggest that molecular chaperones have evolved, in part, to manage these challenges by fostering a general and continuous dynamic protein environment within the nucleus.

  8. Nuclear structure and dynamics with density functional theory

    NASA Astrophysics Data System (ADS)

    Stetcu, Ionel

    2015-10-01

    Even in the absence of ab initio methods capable of tackling heavy nuclei without restrictions, one can obtain an ab initio description of ground-state properties by means of the density functional theory (DFT), and its extension to superfluid systems in its local variant, the superfluid local density approximation (SLDA). Information about the properties of excited states can be obtained in the same framework by using an extension to the time-dependent (TD) phenomena. Unlike other approaches in which the nuclear structure information is used as a separate input into reaction models, the TD approach treats on the same footing the nuclear structure and dynamics, and is well suited to provide more reliable description for a large number of processes involving heavy nuclei, from the nuclear response to electroweak probes, to nuclear reactions, such as neutron-induced reactions, or nuclear fusion and fission. Such processes, sometimes part of integrated nuclear systems, have important applications in astrophysics, energy production, global security, etc. In this talk, I will present the simulation of a simple reaction, that is the Coulomb excitation of a 238U nucleus, and discuss the application of the TD-DFT formalism to the description of induced fission. I gratefully acknowledge partial support of the U.S. Department of Energy through an Early Career Award of the LANL/LDRD Program.

  9. Dynamic nuclear polarisation via the integrated solid effect I: theory

    NASA Astrophysics Data System (ADS)

    Henstra, A.; Wenckebach, W. Th.

    2014-07-01

    In the hyperpolarisation method known as dynamic nuclear polarisation (DNP), a small amount of unpaired electron spins is added to the sample containing the nuclear spins and the polarisation of these unpaired electron spins is transferred to the nuclear spins by means of a microwave field. Traditional DNP uses weak continuous wave (CW) microwave fields, so perturbation methods can be used to calculate the polarisation transfer. A much faster transfer of the electron spin polarisation is obtained with the integrated solid effect (ISE) which uses strong pulsed microwave fields. As in nuclear orientation via electron spin locking, the polarisation transfer is coherent, similar to the coherence transfer between nuclear spins. This paper presents a theoretical approach to calculate this polarisation transfer. ISE is successfully used for a fast polarisation transfer from short-lived photo-excited triplet states to the surrounding nuclear spins in molecular crystals. These triplet states are strongly aligned in the photo-excitation process and do not require the low temperatures and strong magnetic fields needed to polarise the electron spins in traditional DNP. In the following paper, the theory is applied to the system naphthalene-h8 doped with pentacene-d14 which provides the photo-excited triplet states, and compared with experimental results.

  10. Parvovirus Induced Alterations in Nuclear Architecture and Dynamics

    PubMed Central

    Ihalainen, Teemu O.; Niskanen, Einari A.; Jylhävä, Juulia; Paloheimo, Outi; Dross, Nicolas; Smolander, Hanna; Langowski, Jörg; Timonen, Jussi; Vihinen-Ranta, Maija

    2009-01-01

    The nucleus of interphase eukaryotic cell is a highly compartmentalized structure containing the three-dimensional network of chromatin and numerous proteinaceous subcompartments. DNA viruses induce profound changes in the intranuclear structures of their host cells. We are applying a combination of confocal imaging including photobleaching microscopy and computational methods to analyze the modifications of nuclear architecture and dynamics in parvovirus infected cells. Upon canine parvovirus infection, expansion of the viral replication compartment is accompanied by chromatin marginalization to the vicinity of the nuclear membrane. Dextran microinjection and fluorescence recovery after photobleaching (FRAP) studies revealed the homogeneity of this compartment. Markedly, in spite of increase in viral DNA content of the nucleus, a significant increase in the protein mobility was observed in infected compared to non-infected cells. Moreover, analyzis of the dynamics of photoactivable capsid protein demonstrated rapid intranuclear dynamics of viral capsids. Finally, quantitative FRAP and cellular modelling were used to determine the duration of viral genome replication. Altogether, our findings indicate that parvoviruses modify the nuclear structure and dynamics extensively. Intranuclear crowding of viral components leads to enlargement of the interchromosomal domain and to chromatin marginalization via depletion attraction. In conclusion, parvoviruses provide a useful model system for understanding the mechanisms of virus-induced intranuclear modifications. PMID:19536327

  11. Sharp transitions in nuclear dynamics: Limits to collectivity and stability

    NASA Astrophysics Data System (ADS)

    Colonna, M.; Di Toro, M.; Latora, V.; Smerzi, A.

    Two limiting cases of nuclear dynamics are analysed in details: the disappearing of giant collective motions in hot nuclei and the nuclear disassembly in violent heavy ion collisions. It is shown that sharp transitions occur in the dynamical behaviour of finite nuclei. For collective vibration built on excited states we get a dramatic increase of the widths due to the enhancement of two body collisions with increasing temperature. The case of hot Giant Dipole Resonances (GDR) is discussed. As a consequence of the competition with neutron evaporation we get a sharp quenching of giant photon emission. Pre-equilibrium effects on the GDR formation are also accounted for. Limiting temperatures for the observation of GDR γ-decays are deduced for various nuclei, ranging from 6.0 to 3.5 MeV with increasing mass number. A detailed study of the onset of a new multifragmentation mechanism in violent heavy ion collisions around 50 MeV/u beam energy for symmetric partners is performed. It is shown that the nuclear system enters a dynamical instability region and fragments are directly produced from the growing of fluctuations. An hybrid model is developped just coupling average informations on the system entering the critical region to a statistical multifragmentration decay picture. Some hints towards a fully dynamical description of fragment production are finally discussed.

  12. Parvovirus induced alterations in nuclear architecture and dynamics.

    PubMed

    Ihalainen, Teemu O; Niskanen, Einari A; Jylhävä, Juulia; Paloheimo, Outi; Dross, Nicolas; Smolander, Hanna; Langowski, Jörg; Timonen, Jussi; Vihinen-Ranta, Maija

    2009-06-17

    The nucleus of interphase eukaryotic cell is a highly compartmentalized structure containing the three-dimensional network of chromatin and numerous proteinaceous subcompartments. DNA viruses induce profound changes in the intranuclear structures of their host cells. We are applying a combination of confocal imaging including photobleaching microscopy and computational methods to analyze the modifications of nuclear architecture and dynamics in parvovirus infected cells. Upon canine parvovirus infection, expansion of the viral replication compartment is accompanied by chromatin marginalization to the vicinity of the nuclear membrane. Dextran microinjection and fluorescence recovery after photobleaching (FRAP) studies revealed the homogeneity of this compartment. Markedly, in spite of increase in viral DNA content of the nucleus, a significant increase in the protein mobility was observed in infected compared to non-infected cells. Moreover, analysis of the dynamics of photoactivable capsid protein demonstrated rapid intranuclear dynamics of viral capsids. Finally, quantitative FRAP and cellular modelling were used to determine the duration of viral genome replication. Altogether, our findings indicate that parvoviruses modify the nuclear structure and dynamics extensively. Intranuclear crowding of viral components leads to enlargement of the interchromosomal domain and to chromatin marginalization via depletion attraction. In conclusion, parvoviruses provide a useful model system for understanding the mechanisms of virus-induced intranuclear modifications.

  13. Nuclear proton dynamics and interactions with calcium signaling.

    PubMed

    Hulikova, Alzbeta; Swietach, Pawel

    2016-07-01

    Biochemical signals acting on the nucleus can regulate gene expression. Despite the inherent affinity of nucleic acids and nuclear proteins (e.g. transcription factors) for protons, little is known about the mechanisms that regulate nuclear pH (pHnuc), and how these could be exploited to control gene expression. Here, we show that pHnuc dynamics can be imaged using the DNA-binding dye Hoechst 33342. Nuclear pores allow the passage of medium-sized molecules (calcein), but protons must first bind to mobile buffers in order to gain access to the nucleoplasm. Fixed buffering residing in the nucleus of permeabilized cells was estimated to be very weak on the basis of the large amplitude of pHnuc transients evoked by photolytic H(+)-uncaging or exposure to weak acids/bases. Consequently, the majority of nuclear pH buffering is sourced from the cytoplasm in the form of mobile buffers. Effective proton diffusion was faster in nucleoplasm than in cytoplasm, in agreement with the higher mobile-to-fixed buffering ratio in the nucleus. Cardiac myocyte pHnuc changed in response to maneuvers that alter nuclear Ca(2+) signals. Blocking Ca(2+) release from inositol-1,4,5-trisphosphate receptors stably alkalinized the nucleus. This Ca(2+)-pH interaction may arise from competitive binding to common chemical moieties. Competitive binding to mobile buffers may couple the efflux of Ca(2+)via nuclear pores with a counterflux of protons. This would generate a stable pH gradient between cytoplasm and nucleus that is sensitive to the state of nuclear Ca(2+) signaling. The unusual behavior of protons in the nucleus provides new mechanisms for regulating cardiac nuclear biology. Copyright © 2015. Published by Elsevier Ltd.

  14. Decoherence and fluctuation dynamics of the quantum dot nuclear spin bath probed by nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Chekhovich, Evgeny A.

    2017-06-01

    Dynamics of nuclear spin decoherence and nuclear spin flip-flops in self-assembled InGaAs/GaAs quantum dots are studied experimentally using optically detected nuclear magnetic resonance (NMR). Nuclear spin-echo decay times are found to be in the range 1-4 ms. This is a factor of ~3 longer than in strain-free GaAs/AlGaAs structures and is shown to result from strain-induced quadrupolar effects that suppress nuclear spin flip-flops. The correlation times of the flip-flops are examined using a novel frequency-comb NMR technique and are found to exceed 1 s, a factor of ~1000 longer than in strain-free structures. These findings complement recent studies of electron spin coherence and reveal the paradoxical dual role of the quadrupolar effects in self-assembled quantum dots: large increase of the nuclear spin bath coherence and at the same time significant reduction of the electron spin-qubit coherence. Approaches to increasing electron spin coherence are discussed. In particular the nanohole filled GaAs/AlGaAs quantum dots are an attractive option: while their optical quality matches the self-assembled dots the quadrupolar effects measured in NMR spectra are a factor of 1000 smaller.

  15. Controlling the Excited-State Dynamics of Nuclear Spin Isomers Using the Dynamic Stark Effect.

    PubMed

    Waldl, Maria; Oppel, Markus; González, Leticia

    2016-07-14

    Stark control of chemical reactions uses intense laser pulses to distort the potential energy surfaces of a molecule, thus opening new chemical pathways. We use the concept of Stark shifts to convert a local minimum into a local maximum of the potential energy surface, triggering constructive and destructive wave-packet interferences, which then induce different dynamics on nuclear spin isomers in the electronically excited state of a quinodimethane derivative. Model quantum-dynamical simulations on reduced dimensionality using optimized ultrashort laser pulses demonstrate a difference of the excited-state dynamics of two sets of nuclear spin isomers, which ultimately can be used to discriminate between these isomers.

  16. Molecular Dynamics of Nuclear Pasta in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Briggs, Christian; da Silva Schneider, Andre

    2014-09-01

    During a core collapse supernova, a massive star undergoes rapid contraction followed by a massive explosion on the order of a hundred trillion trillion nuclear bombs in less than a second. While most matter is expelled at high speeds, what remains can form a neutron star. The bulk of a neutron star does not contain separate nuclei but is itself a single nucleus of radius ~10 km. In the crust of a neutron star, density is low enough that some matter exists as distinct nuclei arranged into crystalline lattice dominated by electromagnetic forces. Between the crust and core lies an interesting interface where matter is neither a single nucleus nor separate nuclei. It exists in a frustrated phase; competition between electromagnetic and strong nuclear forces causes exotic shapes to emerge, referred to as nuclear pasta. We use Molecular Dynamics (MD) to simulate nuclear pasta, with densities between nuclear saturation density and approximately one-tenth saturation density. Using MD particle trajectories, we compute the static structure factor S(q) and dynamical response function to describe both electron-pasta and neutrino-pasta scattering. We relate the structure and properties of nuclear pasta phases to features in S(q). Finally, one can integrate over S(q) to determine transport properties such as the electrical and thermal conductivity. This may help provide a better understanding of X-ray observations of neutron stars. During a core collapse supernova, a massive star undergoes rapid contraction followed by a massive explosion on the order of a hundred trillion trillion nuclear bombs in less than a second. While most matter is expelled at high speeds, what remains can form a neutron star. The bulk of a neutron star does not contain separate nuclei but is itself a single nucleus of radius ~10 km. In the crust of a neutron star, density is low enough that some matter exists as distinct nuclei arranged into crystalline lattice dominated by electromagnetic forces

  17. Pasta Elasticity: Molecular dynamics simulations of nuclear pasta deformations

    NASA Astrophysics Data System (ADS)

    Caplan, M. E.; Horowitz, C. J.; Berry, D. K.

    2015-04-01

    Nuclear pasta is expected in the inner crust of neutron stars at densities near the nuclear saturation density. In this work, the elastic properties of pasta are calculated from large scale molecular dynamics simulations by deforming the simulation volume. Our model uses a semi-classical two-nucleon potential that reproduces nuclear saturation. We report the shear modulus and breaking strain of a variety of pasta phases for different temperatures, densities, and proton fractions. The presence of pasta in neutron stars could have significant effects on crustal oscillations and could be inferred from observations of soft-gamma repeaters. Additionally, these elastic parameters will enable us to improve estimates of the maximum size and lifetime of ``mountains'' on the crust, which could efficiently radiate gravitational waves.

  18. 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

  19. A dynamical systems model for nuclear power plant risk

    NASA Astrophysics Data System (ADS)

    Hess, Stephen Michael

    The recent transition to an open access generation marketplace has forced nuclear plant operators to become much more cost conscious and focused on plant performance. Coincidentally, the regulatory perspective also is in a state of transition from a command and control framework to one that is risk-informed and performance-based. Due to these structural changes in the economics and regulatory system associated with commercial nuclear power plant operation, there is an increased need for plant management to explicitly manage nuclear safety risk. Application of probabilistic risk assessment techniques to model plant hardware has provided a significant contribution to understanding the potential initiating events and equipment failures that can lead to core damage accidents. Application of the lessons learned from these analyses has supported improved plant operation and safety over the previous decade. However, this analytical approach has not been nearly as successful in addressing the impact of plant processes and management effectiveness on the risks of plant operation. Thus, the research described in this dissertation presents a different approach to address this issue. Here we propose a dynamical model that describes the interaction of important plant processes among themselves and their overall impact on nuclear safety risk. We first provide a review of the techniques that are applied in a conventional probabilistic risk assessment of commercially operating nuclear power plants and summarize the typical results obtained. The limitations of the conventional approach and the status of research previously performed to address these limitations also are presented. Next, we present the case for the application of an alternative approach using dynamical systems theory. This includes a discussion of previous applications of dynamical models to study other important socio-economic issues. Next, we review the analytical techniques that are applicable to analysis of

  20. Dynamic model for simulating the acceptance problem of nuclear energy

    SciTech Connect

    Seifritz, W.; Mennig, J.

    1987-01-01

    Nonlinear dynamics are attaining greater interest in different fields of application. Since the early 1980s, these methods have been applied intensively to a variety of very different general problems, such as the description of political and economic processes as well as the symbiotic behavior in the flora and fauna. The authors have tried to apply these mathematical methods to the dynamic behavior inherent in the problem of the acceptance of nuclear energy. The model, which simplifies the real situation, is two-dimensional and describes the symbiosis of two individuals: the capacity of nuclear power plants P and their acceptance A by the public. It is clear that in reality the acceptance problem depends on a series of other variables as well. However, it is believed that our investigations reveal some universal properties inherent to our socioeconomic system: nonlinearity and dissipative processes.

  1. Quantum nuclear dynamics in the photophysics of diamondoids

    NASA Astrophysics Data System (ADS)

    Patrick, Christopher E.; Giustino, Feliciano

    2013-06-01

    The unusual electronic properties of diamondoids, the nanoscale relatives of diamond, make them attractive for applications ranging from drug delivery to field emission displays. Identifying the fundamental origin of these properties has proven highly challenging, with even the most advanced quantum many-body calculations unable to reproduce measurements of a quantity as ubiquitous as the optical gap. Here, by combining first-principles calculations and Importance Sampling Monte Carlo methods, we show that the quantum dynamics of carbon nuclei is key to understanding the electronic and optical properties of diamondoids. Quantum nuclear effects dramatically modify the absorption lineshapes and renormalize the optical gaps. These findings allow us to formulate a complete theory of optical absorption in diamondoids, and establish the universal role of quantum nuclear dynamics in nanodiamond across the length scales.

  2. Dynamic Nuclear Polarization and the Paradox of Quantum Thermalization.

    PubMed

    De Luca, Andrea; Rosso, Alberto

    2015-08-21

    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.

  3. PREFACE: 30th Winter Workshop on Nuclear Dynamics (WWND2014)

    NASA Astrophysics Data System (ADS)

    Bellwied, Rene; Geurts, Frank; Timmins, Anthony

    2014-09-01

    These are the proceedings of the 30th Winter Workshop on Nuclear Dynamics, which was held in Galveston, Texas, in April 2014. As in previous years, the unique character of this conference series has allowed us to bring together nuclear scientists with very different interests to discuss recent progress and scientific achievements. Out of the 67 contributions at WWND 2014 we have selected these 34 manuscripts. The topics capture the range of theoretical and experimental advances in our field. On the experimental side we saw very exciting results from the RHIC beam energy scan program and the p-p, p-Pb and Pb-Pb runs at the highest collision energies at the LHC. On the theory side the system size dependence of the experimental measurements led to a detailed evaluation of the initial conditions and plasma propagation using a wide variety of phenomenological approaches. These results were complemented by the most recent continuum extrapolated data from lattice in order to model the complete evolution of the relativistic heavy ion system. These proceedings of the 30th Winter Workshop on Nuclear Dynamics again provide a snapshot of the status of the field. The articles, many of which were written by some of the most promising young scientists in the field, are documenting the excitement and achievements that are characteristic for modern day nuclear science. Rene Bellwied (University of Houston) Frank Geurts (Rice University) Anthony Timmins (University of Houston)

  4. Nuclear dynamics during the resonant Auger decay of water molecules.

    PubMed

    Eroms, Matthis; Vendrell, Oriol; Jungen, Martin; Meyer, Hans-Dieter; Cederbaum, Lorenz S

    2009-04-21

    The resonant Auger decay of water molecules is investigated. Here, the excitation process, the motion of the nuclei, and the decay of the resonantly excited state take place on the same (femtosecond) time scale. Therefore, a multistep picture is not suitable. Instead, the nuclear wave packet at each instant of time is a result of several competing and interfering contributions. The resonant Auger decay of water is simulated and its dynamics is studied in detail. An analysis of the final vibrational distribution is given. The multiconfiguration time-dependent Hartree method is used to study the intricate multidimensional dynamics. The potential energy surfaces have been calculated using a multireference configuration interaction method.

  5. A model for electron nuclear dynamics of a monatomic chain

    NASA Astrophysics Data System (ADS)

    Calais, Jean-Louis; Deumens, Erik; Ohrn, Yngve

    1994-05-01

    The Electron Nuclear Dynamics (END) approach is developed for a linear chain in a parametrized model inspired by the PPP (Pariser-Parr-Pople) model. Particular attention is given to the model parameters, and the choice of basis functions in this time-dependent theory. The resulting equations of motion include electronic-vibrational couplings. Explicit analysis of the simplest model leads to coupling between the highest frequency longitudinal vibrational mode and the electrons.

  6. A model for electron nuclear dynamics of a monatomic chain

    NASA Astrophysics Data System (ADS)

    Calais, Jean-Louis; Deumens, Erik; Öhrn, Yngve

    1994-09-01

    The electron nuclear dynamics (END) approach is developed for a linear chain in a parametrized model inspired by the PPP (Pariser-Parr-Pople) model. Particular attention is given to the model parameters, and the choice of basis functions in this time-dependent theory. The resulting equations of motion include electronic-vibrational couplings. Explicit analysis of the simplest model leads to coupling between the highest frequency longitudinal vibrational mode and the electrons.

  7. Stochastic Mean-Field Dynamics For Nuclear Collisions

    SciTech Connect

    Ayik, Sakir

    2008-11-11

    We discuss a stochastic approach to improve description of nuclear dynamics beyond the mean-field approximation at low energies. For small amplitude fluctuations, this approach gives a result for the dispersion of a one-body observable that is identical to the result obtained previously through a variational approach. Furthermore, it incorporates one-body dissipation and fluctuation mechanisms in accordance with quantal fluctuation-dissipation relation.

  8. Static and dynamic high power, space nuclear electric generating systems

    NASA Technical Reports Server (NTRS)

    Wetch, J. R.; Begg, L. L.; Koester, J. K.

    1985-01-01

    Space nuclear electric generating systems concepts have been assessed for their potential in satisfying future spacecraft high power (several megawatt) requirements. Conceptual designs have been prepared for reactor power systems using the most promising static (thermionic) and the most promising dynamic conversion processes. Component and system layouts, along with system mass and envelope requirements have been made. Key development problems have been identified and the impact of the conversion process selection upon thermal management and upon system and vehicle configuration is addressed.

  9. Dynamic Oligomerization of Integrase Orchestrates HIV Nuclear Entry

    PubMed Central

    Borrenberghs, Doortje; Dirix, Lieve; De Wit, Flore; Rocha, Susana; Blokken, Jolien; De Houwer, Stéphanie; Gijsbers, Rik; Christ, Frauke; Hofkens, Johan; Hendrix, Jelle; Debyser, Zeger

    2016-01-01

    Nuclear entry is a selective, dynamic process granting the HIV-1 pre-integration complex (PIC) access to the chromatin. Classical analysis of nuclear entry of heterogeneous viral particles only yields averaged information. We now have employed single-virus fluorescence methods to follow the fate of single viral pre-integration complexes (PICs) during infection by visualizing HIV-1 integrase (IN). Nuclear entry is associated with a reduction in the number of IN molecules in the complexes while the interaction with LEDGF/p75 enhances IN oligomerization in the nucleus. Addition of LEDGINs, small molecule inhibitors of the IN-LEDGF/p75 interaction, during virus production, prematurely stabilizes a higher-order IN multimeric state, resulting in stable IN multimers resistant to a reduction in IN content and defective for nuclear entry. This suggests that a stringent size restriction determines nuclear pore entry. Taken together, this work demonstrates the power of single-virus imaging providing crucial insights in HIV replication and enabling mechanism-of-action studies. PMID:27830755

  10. Ultrafast photochemical dynamics of the hexaaquairon(III) ion

    NASA Astrophysics Data System (ADS)

    Danforth, Rebecca A.; Kohler, Bern

    2017-09-01

    UV excitation of [Fe(H2O)6]3+ generates hydroxyl radicals in low quantum yield, but the events that compete with this photochemistry are obscure. To elucidate the primary events, acidic, aqueous iron(III) perchlorate solutions were studied by femtosecond pump-probe spectroscopy. We report a new decay channel in which ligand-to-metal charge transfer (LMCT) excitation of [Fe(H2O)6]3+ hydrolyzes a coordinated water molecule, releasing a proton and forming the iron(III) monohydroxy ion in less than 1 ps. This efficient channel, which is observed here for the first time, competes with hydroxyl radical generation and represents a novel observation of photoacidity in a metal coordination complex.

  11. 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

    2016-04-07

    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.

  12. Dynamic regulation of Drosophila nuclear receptor activity in vivo

    PubMed Central

    Palanker, Laura; Necakov, Aleksandar S.; Sampson, Heidi M.; Ni, Ruoyu; Hu, Chun; Thummel, Carl S.; Krause, Henry M.

    2007-01-01

    Nuclear receptors are a large family of transcription factors that play major roles in development, metamorphosis, metabolism and disease. To determine how, where and when nuclear receptors are regulated by small chemical ligands and/or protein partners, we have used a ‘ligand sensor’ system to visualize spatial activity patterns for each of the 18 Drosophila nuclear receptors in live developing animals. Transgenic lines were established that express the ligand binding domain of each nuclear receptor fused to the DNA-binding domain of yeast GAL4. When combined with a GAL4-responsive reporter gene, the fusion proteins show tissue- and stage-specific patterns of activation. We show that these responses accurately reflect the presence of endogenous and exogenously added hormone, and that they can be modulated by nuclear receptor partner proteins. The amnioserosa, yolk, midgut and fat body, which play major roles in lipid storage, metabolism and developmental timing, were identified as frequent sites of nuclear receptor activity. We also see dynamic changes in activation that are indicative of sweeping changes in ligand and/or co-factor production. The screening of a small compound library using this system identified the angular psoralen angelicin and the insect growth regulator fenoxycarb as activators of the Ultraspiracle (USP) ligand-binding domain. These results demonstrate the utility of this system for the functional dissection of nuclear receptor pathways and for the development of new receptor agonists and antagonists that can be used to modulate metabolism and disease and to develop more effective means of insect control. PMID:16914501

  13. nuclear bound states in a dynamical model

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Friedman, E.; Gal, A.

    2006-05-01

    A comprehensive data base of K-atom level shifts and widths is re-analyzed in order to study the density dependence of the K¯-nuclear optical potential. Significant departure from a tρ form is found only for ρ(r)/ρ ≲ 0.2 and extrapolation to nuclear-matter density ρ yields an attractive potential, about 170 MeV deep. Partial restoration of chiral symmetry compatible with pionic atoms and low-energy pion-nuclear data plays no role at the relevant low-density regime, but this effect is not ruled out at densities of order ρ and beyond. K¯-nuclear bound states are generated across the periodic table self consistently, using a relativistic mean-field model Lagrangian which couples the K¯ to the scalar and vector meson fields mediating the nuclear interactions. The reduced phase space available for K¯ absorption from these bound states is taken into account by adding an energy-dependent imaginary term which underlies the corresponding K¯-nuclear level widths, with a strength required by fits to the atomic data. Substantial polarization of the core nucleus is found for light nuclei, and the binding energies and widths calculated in this dynamical model differ appreciably from those calculated for a static nucleus. A wide range of binding energies is spanned by varying the K¯ couplings to the meson fields. Our calculations provide a lower limit of Γ=50±10 MeV on the width of nuclear bound states for K¯-binding energy in the range B˜100-200 MeV. Comments are made on the interpretation of the FINUDA experiment at DAΦNE which claimed evidence for deeply bound Kpp states in light nuclei.

  14. Insights into nuclear dynamics using live-cell imaging approaches.

    PubMed

    Bigley, Rachel B; Payumo, Alexander Y; Alexander, Jeffrey M; Huang, Guo N

    2017-03-01

    The nucleus contains the genetic blueprint of the cell and myriad interactions within this subcellular structure are required for gene regulation. In the current scientific era, characterization of these gene regulatory networks through biochemical techniques coupled with systems-wide 'omic' approaches has become commonplace. However, these strategies are limited because they represent a mere snapshot of the cellular state. To obtain a holistic understanding of nuclear dynamics, relevant molecules must be studied in their native contexts in living systems. Live-cell imaging approaches are capable of providing quantitative assessment of the dynamics of gene regulatory interactions within the nucleus. We survey recent insights into what live-cell imaging approaches have provided the field of nuclear dynamics. In this review, we focus on interactions of DNA with other DNA loci, proteins, RNA, and the nuclear envelope. WIREs Syst Biol Med 2017, 9:e1372. doi: 10.1002/wsbm.1372 For further resources related to this article, please visit the WIREs website.

  15. Dynamical Green's function and an exact optical potential for electron-molecule scattering including nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Brand, Joachim; Cederbaum, Lorenz S.; Meyer, Hans-Dieter

    1999-10-01

    We derive a rigorous optical potential for electron-molecule scattering including the effects of nuclear dynamics by extending the common many-body Green's function approach to optical potentials beyond the fixed-nuclei limit for molecular targets. Our formalism treats the projectile electron and the nuclear motion of the target molecule on the same footing whereby the dynamical optical potential rigorously accounts for the complex many-body nature of the scattering target. One central result of the present work is that the common fixed-nuclei optical potential is a valid adiabatic approximation to the dynamical optical potential even when projectile and nuclear motion are (nonadiabatically) coupled as long as the scattering energy is well below the electronic excitation thresholds of the target. For extremely low projectile velocities, however, when the cross sections are most sensitive to the scattering potential, we expect the influences of the nuclear dynamics on the optical potential to become relevant. For these cases, a systematic way to improve the adiabatic approximation to the dynamical optical potential is presented that yields nonlocal operators with respect to the nuclear coordinates.

  16. Dynamic nuclear polarization studies on deuterated nitroxyl spin probes.

    PubMed

    David Jebaraj, D; Utsumi, Hideo; Milton Franklin Benial, A

    2017-10-01

    Detailed dynamic nuclear polarization and electron spin resonance studies were carried out for 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl,3-methoxycarbonyl-2,2,5,5-tetramethy pyrolidine-1-oxyl nitroxyl radicals and their corresponding deuterated nitroxyl radicals, used in Overhauser-enhanced magnetic resonance imaging for the first time. The dynamic nuclear polarization parameters such as dynamic nuclear polarization (DNP) factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for deuterated nitroxyl radicals. DNP enhancement increases with agent concentration up to 3 mm and decreases above 3 mm. The proton spin-lattice relaxation time and the longitudinal relaxivity parameters were estimated. The leakage factor increases with increasing agent concentration up to 3 mm and reaches plateau in the region 3-5 mm. The coupling parameter shows the interaction between the electron and nuclear spins to be mainly dipolar in origin. DNP spectrum exhibits that the full width at half maximum values are higher for undeuterated nitroxyl radicals compared with deuterated nitroxyl radicals, which leads to the increase in DNP enhancement. The ESR parameters such as, the line width, line shape, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were calculated. The narrow line width was observed for deuterated nitroxyl radicals compared with undeuterated nitroxyl radicals, which leads to the higher saturation parameter value and DNP enhancement. The novelty of the work permits clear understanding of the DNP parameters determining the higher DNP enhancement compared with the undeuterated nitroxyl radicals. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  17. Dynamics of hot and dense nuclear and partonic matter

    SciTech Connect

    Bratkovskaya, E. L.; Cassing, W.; Linnyk, O.; Konchakovski, V. P.; Voronyuk, V.; Ozvenchuk, V.

    2012-06-15

    The dynamics of hot and dense nuclear matter is discussed from the microscopic transport point of view. The basic concepts of the Hadron-String-Dynamical transport model (HSD)-derived from Kadanoff-Baym equations in phase phase-are presented as well as 'highlights' of HSD results for different observables in heavy-ion collisions from 100 A MeV (SIS) to 21 A TeV(RHIC) energies. Furthermore, a novel extension of the HSD model for the description of the partonic phase-the Parton-Hadron-String-Dynamics (PHSD) approach-is introduced. PHSD includes a nontrivial partonic equation of state-in line with lattice QCD-as well as covariant transition rates from partonic to hadronic degrees of freedom. The sensitivity of hadronic observables to the partonic phase is demonstrated for relativistic heavy-ion collisions from the FAIR/NICA up to the RHIC energy regime.

  18. 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.

  19. Survey of Dynamic Simulation Programs for Nuclear Fuel Reprocessing

    SciTech Connect

    Troy J. Tranter; Daryl R. Haefner

    2008-06-01

    The absence of any industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other industries. Modeling programs to simulate the dynamic behavior of nuclear fuel separations and processing were originally developed to support the US government’s mission of weapons production and defense fuel recovery. Consequently there has been little effort is the US devoted towards improving this specific process simulation capability during the last two or three decades. More recent work has been focused on elucidating chemical thermodynamics and developing better models of predicting equilibrium in actinide solvent extraction systems. These equilibrium models have been used to augment flowsheet development and testing primarily at laboratory scales. The development of more robust and complete process models has not kept pace with the vast improvements in computational power and user interface and is significantly behind simulation capability in other chemical processing and separation fields.

  20. Nuclear magnetic resonance probes of membrane biophysics: Structure and dynamics

    NASA Astrophysics Data System (ADS)

    Leftin, Avigdor

    The phospholipid membrane is a self-assembled, dynamic molecular system that may exist alone in association with only water, or in complex systems comprised of multiple lipid types and proteins. In this dissertation the intra- and inter-molecular forces responsible for the atomistic, molecular and collective equilibrium structure and dynamics are studied by nuclear magnetic resonance spectroscopy (NMR). The multinuclear NMR measurements and various experimental techniques are able to provide data that enable the characterization of the hierarchical spatio-temporal organization of the phospholipid membrane. The experimental and theoretical studies conducted target membrane interactions ranging from model systems composed of only water and lipids, to multiple component domain forming membranes that are in association with peripheral and trans-membrane proteins. These measurements consisit of frequency spectrum lineshapes and nuclear-spin relaxation rates obtained using 2H NMR, 13C NMR, 31P NMR and 1H NMR. The changes of these experimental observables are interpreted within a statistical thermodynamic framework that allows the membrane structure, activation energies, and correlation times of motion to be determined. The cases presented demonstrate how fundamental principles of NMR spectroscopy may be applied to a host of membranes, leading to the biophysical characterization of membrane structure and dynamics.

  1. 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.

  2. Neural dynamic optimization for control systems.III. Applications.

    PubMed

    Seong, C Y; Widrow, B

    2001-01-01

    For pt.II. see ibid., p. 490-501. The paper presents neural dynamic optimization (NDO) as a method of optimal feedback control for nonlinear multi-input-multi-output (MIMO) systems. The main feature of NDO is that it enables neural networks to approximate the optimal feedback solution whose existence dynamic programming (DP) justifies, thereby reducing the complexities of computation and storage problems of the classical methods such as DP. This paper demonstrates NDO with several applications including control of autonomous vehicles and of a robot-arm, while the two other companion papers of this topic describes the background for the development of NDO and present the theory of the method, respectively.

  3. Hydrophilic 2,9-bis-triazolyl-1,10-phenanthroline ligands enable selective Am(iii) separation: a step further towards sustainable nuclear energy.

    PubMed

    Edwards, Alyn C; Mocilac, Pavle; Geist, Andreas; Harwood, Laurence M; Sharrad, Clint A; Burton, Neil A; Whitehead, Roger C; Denecke, Melissa A

    2017-05-02

    The first hydrophilic, 1,10-phenanthroline derived ligands consisting of only C, H, O and N atoms for the selective extraction of Am(iii) from spent nuclear fuel are reported herein. One of these 2,9-bis-triazolyl-1,10-phenanthroline (BTrzPhen) ligands combined with a non-selective extracting agent, was found to exhibit process-suitable selectivity for Am(iii) over Eu(iii) and Cm(iii), providing a clear step forward.

  4. Computational fluid dynamics studies of nuclear rocket performance

    NASA Technical Reports Server (NTRS)

    Stubbs, Robert M.; Benson, Thomas J.; Kim, Suk C.

    1991-01-01

    A CFD analysis of a low pressure nuclear rocket concept is presented with the use of an advanced chemical kinetics, Navier-Stokes code. The computations describe the flow field in detail,including gas dynamic, thermodynamic and chemical properties, as well as global performance quantities such as specific impulse. Computational studies of several rocket nozzle shapes are conducted in an attempt to maximize hydrogen recombination. These Navier-Stokes calculations, which include real gas and viscous effects, predict lower performance values than have been reported heretofore.

  5. Computational fluid dynamics studies of nuclear rocket performance

    NASA Technical Reports Server (NTRS)

    Stubbs, Robert M.; Kim, Suk C.; Benson, Thomas J.

    1994-01-01

    A CFD analysis of a low pressure nuclear rocket concept is presented with the use of an advanced chemical kinetics, Navier-Stokes code. The computations describe the flow field in detail, including gas dynamic, thermodynamic and chemical properties, as well as global performance quantities such as specific impulse. Computational studies of several rocket nozzle shapes are conducted in an attempt to maximize hydrogen recombination. These Navier-Stokes calculations, which include real gas and viscous effects, predict lower performance values than have been reported heretofore.

  6. Electron nuclear dynamics of H + + H 2O collisions

    NASA Astrophysics Data System (ADS)

    Hedström, M.; Morales, J. A.; Deumens, E.; Öhrn, Y.

    1997-11-01

    Proton water collisions at 46 eV in the center of mass frame are studied within the electron nuclear dynamics theory (END). The electronic degrees of freedom are described with a coherent state formulation of determinantal wavefunctions. The nuclei are treated as classical particles but full nonadiabatic couplings are retained. The equations of motion are formulated in a generalized phase space and bypass the use of preconstructed potential energy surfaces. Differential cross sections for inelastic and electron transfer reactions as well as energy transfer are compared with experiment.

  7. Dynamic nuclear polarization with a water-soluble rigid biradical.

    PubMed

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

    2012-03-14

    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.

  8. Frozen Acrylamide Gels as Dynamic Nuclear Polarization Matrices.

    PubMed

    Viger-Gravel, Jasmine; Berruyer, Pierrick; Gajan, David; Basset, Jean-Marie; Lesage, Anne; Tordo, Paul; Ouari, Olivier; Emsley, Lyndon

    2017-07-17

    Aqueous acrylamide gels can be used to provide dynamic nuclear polarization (DNP) NMR signal enhancements of around 200 at 9.4 T and 100 K. The enhancements are shown to increase with crosslinker concentration and low concentrations of the AMUPol biradical. This DNP matrix can be used in situations where conventional incipient wetness methods fail, such as to obtain DNP surface enhanced NMR spectra from inorganic nanoparticles. In particular, we obtain (113) Cd spectra from CdTe-COOH NPs in minutes. The spectra clearly indicate a highly disordered cadmium-rich surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Nuclear dynamics during ascospore germination in Sordaria macrospora.

    PubMed

    Teichert, Ines

    2017-01-01

    The ascomycete Sordaria macrospora has a long history as a model organism for studying fungal sexual development. Starting from an ascospore, sexual fruiting bodies (perithecia) develop within seven days and discharge new ascospores. Sexual development has been studied in detail, revealing genes required for perithecium formation and ascospore germination. However, the germination process per se has not yet been examined. Here I analyze nuclear dynamics during ascospore germination using a fluorescently labeled histone. Live-cell imaging revealed that nuclei are transported into germination vesicles that form on one side of the spore. Polar growth is established from these vesicles. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Nuclear Hybrid Energy System Modeling: RELAP5 Dynamic Coupling Capabilities

    SciTech Connect

    Piyush Sabharwall; Nolan Anderson; Haihua Zhao; Shannon Bragg-Sitton; George Mesina

    2012-09-01

    The nuclear hybrid energy systems (NHES) research team is currently developing a dynamic simulation of an integrated hybrid energy system. A detailed simulation of proposed NHES architectures will allow initial computational demonstration of a tightly coupled NHES to identify key reactor subsystem requirements, identify candidate reactor technologies for a hybrid system, and identify key challenges to operation of the coupled system. This work will provide a baseline for later coupling of design-specific reactor models through industry collaboration. The modeling capability addressed in this report focuses on the reactor subsystem simulation.

  11. Nuclear spin dynamics in double quantum dots: Multistability, dynamical polarization, criticality, and entanglement

    NASA Astrophysics Data System (ADS)

    Schuetz, M. J. A.; Kessler, E. M.; Vandersypen, L. M. K.; Cirac, J. I.; Giedke, G.

    2014-05-01

    We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically defined double quantum dot in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections.

  12. Quantitative Analysis of Lens Nuclear Density Using Optical Coherence Tomography (OCT) with a Liquid Optics Interface: Correlation between OCT Images and LOCS III Grading

    PubMed Central

    Park, Jin Hyoung

    2016-01-01

    Purpose. To quantify whole lens and nuclear lens densities using anterior-segment optical coherence tomography (OCT) with a liquid optics interface and evaluate their correlation with Lens Opacities Classification System III (LOCS III) lens grading and corrected distance visual acuity (BCVA). Methods. OCT images of the whole lens and lens nucleus of eyes with age-related nuclear cataract were analyzed using ImageJ software. The lens grade and nuclear density were represented in pixel intensity units (PIU) and correlations between PIU, BCVA, and LOCS III were assessed. Results. Forty-seven eyes were analyzed. The mean whole lens and lens nuclear densities were 26.99 ± 5.23 and 19.43 ± 6.15 PIU, respectively. A positive linear correlation was observed between lens opacities (R2 = 0.187, p < 0.01) and nuclear density (R2 = 0.316, p < 0.01) obtained from OCT images and LOCS III. Preoperative BCVA and LOCS III were also positively correlated (R2 = 0.454, p < 0.01). Conclusions. Whole lens and lens nuclear densities obtained from OCT correlated with LOCS III. Nuclear density showed a higher positive correlation with LOCS III than whole lens density. OCT with a liquid optics interface is a potential quantitative method for lens grading and can aid in monitoring and managing age-related cataracts. PMID:27651952

  13. Design (and) principles of nuclear dynamics in Stockholm

    PubMed Central

    Shav-Tal, Yaron; Lammerding, Jan

    2015-01-01

    The structural organization of the nucleus and its content has drawn increasing interest in recent years, as it is has become evident that the spatial and temporal arrangement of the genome and associated structures plays a crucial role in transcriptional regulation and numerous other functions. Shining light on the dynamic nature of this organization, along with the processes controlling it, were the topics of the Wenner-Gren Foundations international symposium "Nuclear Dynamics: Design (and) Principles." The meeting, organized by Piorgiogio Percipalle, Maria Vartiainen, Neus Visa, and Ann-Kristin Östlund-Farrants, brought over 60 participants, including 20 international speakers, to Stockholm, Sweden from August 19–22, 2015 to share the latest developments in the field. Given the unpublished nature of many of the talks, we have focused on covering the discussed topics and highlighting the latest trends in this exciting and rapidly evolving field. PMID:26730816

  14. Analysis of nuclear thermal propulsion systems using computational fluid dynamics

    SciTech Connect

    Stubbs, R.M. ); Kim, S.C. ); Papp, J.L. )

    1993-01-20

    Computational fluid dynamics (CFD) analyses of nuclear rockets with relatively low chamber pressures were carried out to assess the merits of using such low pressures to take advantage of hydrogen dissociation and recombination. The computations, using a Navier-Stokes code with chemical kinetics, describe the flow field in detail, including gas dynamics, thermodynamic and chemical properties, and provide global performance quantities such as specific impulse and thrust. Parametric studies were performed varying chamber temperature, chamber pressure and nozzle size. Chamber temperature was varied between 2700 K and 3600 K, and chamber pressure between 0.1 atm. and 10 atm. Performance advantages associated with lower chamber pressures are shown to occur at the higher chamber temperatures. Viscous losses are greater at lower chamber pressures and can be decreased in larger nozzles where the boundary layer is a smaller fraction of the flow field.

  15. Analysis of nuclear thermal propulsion systems using computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Stubbs, Robert M.; Kim, Suk C.; Papp, John L.

    1993-01-01

    Computational fluid dynamics (CFD) analyses of nuclear rockets with relatively low chamber pressures were carried out to assess the merits of using such low pressures to take advantage of hydrogen dissociation and recombination. The computations, using a Navier-Stokes code with chemical kinetics, describe the flow field in detail, including gas dynamics, thermodynamic and chemical properties, and provide global performance quantities such as specific impulse and thrust. Parametric studies were performed varying chamber temperature, chamber pressure and nozzle size. Chamber temperature was varied between 2700 K and 3600 K, and chamber pressure between 0.1 atm. and 10 atm. Performance advantages associated with lower chamber pressures are shown to occur at the higher chamber temperatures. Viscous losses are greater at lower chamber pressures and can be decreased in larger nozzles where the boundary layer is a smaller fraction of the flow field.

  16. Hydroxyapatites: Key Structural Questions and Answers from Dynamic Nuclear Polarization.

    PubMed

    Leroy, César; Aussenac, Fabien; Bonhomme-Coury, Laure; Osaka, Akiyoshi; Hayakawa, Satoshi; Babonneau, Florence; Coelho-Diogo, Cristina; Bonhomme, Christian

    2017-10-03

    We demonstrate that NMR/DNP (Dynamic Nuclear Polarization) allows an unprecedented description of carbonate substituted hydroxyapatite (CHAp). Key structural questions related to order/disorder and clustering of carbonates are tackled using distance sensitive DNP experiments using (13)C-(13)C recoupling. Such experiments are easily implemented due to unprecedented DNP gain (orders of magnitude). DNP is efficiently mediated by quasi one-dimensional spin diffusion through the hydroxyl columns present in the CHAp structure (thought of as "highways" for spin diffusion). For spherical nanoparticles and ϕ < 100 nm, it is numerically shown that spin diffusion allows their study as a whole. Most importantly, we demonstrate also that the DNP study at 100 K leads to data which are comparable to data obtained at room temperature (in terms of spin dynamics and line shape resolution). Finally, all 2D DNP experiments can be interpreted in terms of domains exhibiting well identified types of substitution: local order and carbonate clustering are clearly favored.

  17. Hanford spent nuclear fuel project recommended path forward, volume III: Alternatives and path forward evaluation supporting documentation

    SciTech Connect

    Fulton, J.C.

    1994-10-01

    Volume I of the Hanford Spent Nuclear Fuel Project - Recommended Path Forward constitutes an aggressive series of projects to construct and operate systems and facilities to safely retrieve, package, transport, process, and store K Basins fuel and sludge. Volume II provided a comparative evaluation of four Alternatives for the Path Forward and an evaluation for the Recommended Path Forward. Although Volume II contained extensive appendices, six supporting documents have been compiled in Volume III to provide additional background for Volume II.

  18. Structure and dynamics of the fibronectin-III domains of Aplysia californica cell adhesion molecules.

    PubMed

    Kelly, Catherine M; Muzard, Julien; Brooks, Bernard R; Lee, Gil U; Buchete, Nicolae-Viorel

    2015-04-21

    Due to their homophilic and heterophilic binding properties, cell adhesion molecules (CAMs) such as integrin, cadherin and the immunoglobulin superfamily CAMs are of primary importance in cell-cell and cell-substrate interactions, signalling pathways and other crucial biological processes. We study the molecular structures and conformational dynamics of the two fibronectin type III (Fn-III) extracellular domains of the Aplysia californica CAM (apCAM) protein, by constructing and probing an atomically-detailed structural model based on apCAM's homology with other CAMs. The stability and dynamic properties of the Fn-III domains, individually and in tandem, are probed and analysed using all-atom explicit-solvent molecular dynamics (MD) simulations and normal mode analysis of their corresponding elastic network models. The refined structural model of the Fn-III tandem of apCAM reveals a specific pattern of amino acid interactions that controls the stability of the β-sheet rich structure and could affect apCAM's response to physical or chemical changes of its environment. It also exposes the important role of several specific charged residues in modulating the structural properties of the linker segment connecting the two Fn-III domains, as well as of the inter-domain interface.

  19. 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.

  20. Correlated electron-nuclear dissociation dynamics: classical versus quantum motion

    NASA Astrophysics Data System (ADS)

    Schaupp, Thomas; Albert, Julian; Engel, Volker

    2017-01-01

    We investigate the coupled electron-nuclear dynamics in a model system which undergoes dissociation. In choosing different initial conditions, the cases of adiabatic and non-adiabatic dissociation are realized. We treat the coupled electronic and nuclear motion in the complete configuration space so that classically, no surface hopping procedures have to be incorporated in the case that more than a single adiabatic electronic state is populated during the fragmentation. Due to the anharmonic interaction potential, it is expected that classical mechanics substantially deviate from quantum mechanics. However, we provide examples where the densities and fragmentation yields obtained from the two treatments are in astonishingly strong agreement in the case that one starts in the electronic ground state initially. As expected, larger deviations are found if one starts in electronically excited states where trajectories are sampled from the more spatially extended electronic wave function. In that case, higher initial energies are accessed, and the motion proceeds in regions with increasing degree of anharmonicity. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

  1. Nuclear factor E2-related factor 2 dependent overexpression of sulfiredoxin and peroxiredoxin III in human lung cancer.

    PubMed

    Kim, Young Sun; Lee, Hye Lim; Lee, Ki Bum; Park, Joo Hun; Chung, Wou Young; Lee, Keu Sung; Sheen, Seung Soo; Park, Kwang Joo; Hwang, Sung Chul

    2011-09-01

    Oxidative stress results in protein oxidation and is implicated in carcinogenesis. Sulfiredoxin (Srx) is responsible for the enzymatic reversal of inactivated peroxiredoxin (Prx). Nuclear factor E2-related factor 2 (Nrf2) binds to antioxidant responsive elements and upregulates the expression of Srx and Prx during oxidative stress. We aimed to elucidate the biological functions and potential roles of Srx in lung cancer. To study the roles of Srx and Prx III in lung cancer, we compared the protein levels of Nrf2, Prxs, thioredoxin, and Srx in 40 surgically resected human lung cancer tissues using immunoblot and immunohistochemical analyses. Transforming growth factor-β(1), tumor necrosis factor-α, and camptothecin treatment were used to examine Prx III inactivation in Mv1Lu mink lung epithelial cells and A549 lung cancer cells. Prx I and Prx III proteins were markedly overexpressed in lung cancer tissues. A significant increase in the oxidized form of a cysteine sulfhydryl at the catalytic site of Prxs was found in carcinogenic lung tissue compared to normal lung tissue. Densitometric analyses of immunoblot data revealed significant Srx expression, which was higher in squamous cell carcinoma tissue (60%, 12/20) than in adenocarcinoma (20%, 4/20). Also, Nrf2 was present in the nuclear compartment of cancer cells. Srx and Prx III proteins were markedly overexpressed in human squamous cell carcinoma, suggesting that these proteins may play a protective role against oxidative injury and compensate for the high rate of mitochondrial metabolism in lung cancer.

  2. ESCRT-III and Vps4: a dynamic multipurpose tool for membrane budding and scission.

    PubMed

    Alonso Y Adell, Manuel; Migliano, Simona M; Teis, David

    2016-09-01

    Complex molecular machineries bud, scission and repair cellular membranes. Components of the multi-subunit endosomal sorting complex required for transport (ESCRT) machinery are enlisted when multivesicular bodies are generated, extracellular vesicles are formed, the plasma membrane needs to be repaired, enveloped viruses bud out of host cells, defective nuclear pores have to be cleared, the nuclear envelope must be resealed after mitosis and for final midbody abscission during cytokinesis. While some ESCRT components are only required for specific processes, the assembly of ESCRT-III polymers on target membranes and the action of the AAA-ATPase Vps4 are mandatory for every process. In this review, we summarize the current knowledge of structural and functional features of ESCRT-III/Vps4 assemblies in the growing pantheon of ESCRT-dependent pathways. We describe specific recruitment processes for ESCRT-III to different membranes, which could be useful to selectively inhibit ESCRT function during specific processes, while not affecting other ESCRT-dependent processes. Finally, we speculate how ESCRT-III and Vps4 might function together and highlight how the characterization of their precise spatiotemporal organization will improve our understanding of ESCRT-mediated membrane budding and scission in vivo.

  3. Calculation of Cross Sections in Electron-Nuclear Dynamics

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, R.; Sabin, John R.; Deumens, E.; Öhrn, Y.

    In this work, we present an overview of the study of total and differential cross section calculations within the electron-nuclear dynamics (END). END is a method to solve the time-dependent Schrödinger equation in a non-adiabatic approach to direct dynamics. The method takes advantage of a coherent state representation of the molecular wave function. A quantum-mechanical Lagrangian formulation is employed to approximate the Schrödinger equation, via the time-dependent variational principle, to a set of coupled first-order differential equations in time for the END. We obtain the final wave function for the system allowing the determination of collisional properties of interest, as for example, deflection functions, charge exchange probabilities and amplitudes, and differential cross sections. We discuss the use and selection of basis sets for both the electronic description of the colliding systems as well as for their importance in the description of electron capture. As quantum effects are important in many cases and lacking for classical nuclei, we discuss the Schiff methodology and its advantages over other traditional methods for including semiclassical corrections. Time-lapse rendering of the dynamics of the participating electrons and atomic nuclei provides for a detailed view of dynamical and reactive processes. Comparison to experimental and other theoretical results is provided where appropriate data are available.

  4. 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

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

    PubMed

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

    2011-03-28

    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 < ω(0I), where δ and Δ are the homogeneous linewidth and inhomogeneous breadth of the EPR spectrum, respectively, we verify that the SE occurs when ω(M) = ω(0S) ± ω(0I), where ω(M), ω(0S) and ω(0I) are, respectively, the microwave, and the EPR and NMR frequencies. Alternatively, when Δ > ω(0I) > δ, the CE dominates the polarization transfer. This two-electron process is optimized when ω(0S(1))-ω(0S(2)) = ω(0I) and ω(M)~ω(0S(1)) or ω(0S(2)), where ω(0S(1)) and ω(0S(2)) 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

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

    PubMed

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

    2012-08-07

    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.

  7. 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

  8. Nonadiabatic quantum molecular dynamics with hopping. III. Photoinduced excitation and relaxation of organic molecules

    NASA Astrophysics Data System (ADS)

    Fischer, M.; Handt, J.; Schmidt, R.

    2014-07-01

    Photoinduced excitation and relaxation of organic molecules (C2H4 and CH2NH2+) are investigated by means of nonadiabatic quantum molecular dynamics with hopping (NA-QMD-H), developed recently [Fischer, Handt, and Schmidt, paper I of this series, Phys. Rev. A 90, 012525 (2014), 10.1103/PhysRevA.90.012525]. This method is first applied to molecules assumed to be initially ad hoc excited to an electronic surface. Special attention is drawn to elaborate the role of electron-nuclear correlations, i.e., of quantum effects in the nuclear dynamics. It is found that they are essential for a realistic description of the long-time behavior of the electronic relaxation process, but only of minor importance to portray the short-time scenario of the nuclear dynamics. Migration of a hydrogen atom, however, is identified as a quantum effect in the nuclear motion. Results obtained with explicit inclusion of an fs-laser field are presented as well. It is shown that the laser-induced excitation process generally leads to qualitatively different gross features of the relaxation dynamics, as compared to the field-free case. Nevertheless, the nuclear wave packet contains all subtleties of the cis-trans isomerization mechanism as observed without a laser field.

  9. Solvation of Co(III)-cysteinato complexes in water: a DFT-based molecular dynamics study.

    PubMed

    Spezia, Riccardo; Bresson, Carole; Den Auwer, Christophe; Gaigeot, Marie-Pierre

    2008-05-22

    Structural, dynamical, and vibrational properties of complexes made of metal cobalt(III) coordinated to different amounts of cysteine molecules were investigated with DFT-based Car-Parrinello molecular dynamics (CPMD) simulations in liquid water solution. The systems are composed of Co(III):3Cys and Co(III):2Cys immersed in liquid water which are modeled by about 110 explicit water molecules, thus one of the biggest molecular systems studied with ab initio molecular simulations so far. In such a way, we were able to investigate structural and dynamical properties of a model of a typical metal binding site used by several proteins. Cobalt, mainly a toxicological agent, can replace the natural binding metal and thus modify the biochemical activity. The structure of the surrounding solvent around the metal-ligands complexes is reported in detail, as well as the metal-ligands coordination bonds, using radial distribution functions and electronic analyses with Mayer bond orders. Structures of the Cocysteine complexes are found in very good agreement with EXAFS experimental data, stressing the importance of considering the surrounding solvent in the modeling. A vibrational analysis is also conducted and compared to experiment, which strengthens the reliability of the solvent interactions with the Cocysteine complexes from our molecular dynamics simulations, as well as the dynamics of the systems. From this preliminary analysis, we could suggest a vibrational fingerprint able to distinguish Co(III):2Cys from Co(III):3Cys. Our simulations also show the importance of considering a quantum explicit solvent, as solute-to-solvent proton transfer events have been observed.

  10. Homometallic Dy(III) Complexes of Varying Nuclearity from 2 to 21: Synthesis, Structure, and Magnetism.

    PubMed

    Biswas, Sourav; Das, Sourav; Acharya, Joydev; Kumar, Vierandra; van Leusen, Jan; Kögerler, Paul; Herrera, Juan Manuel; Colacio, Enrique; Chandrasekhar, Vadapalli

    2017-04-11

    The synthesis, structure, and magnetic properties of four Dy(III) coordination compounds isolated as [Dy2 (LH2 )2 (μ2 -η(1) :η(1) -Piv)]Cl⋅2 MeOH⋅H2 O (1), [Dy4 (LH)2 (μ3 -OH)2 (Piv)4 (MeOH)2 ]⋅4 MeOH⋅2 H2 O (2), [Dy6 (LH2 )3 (tfa)3 (O3 PtBu)(Cl)3 ]Cl4 ⋅15.5 H2 O⋅4 MeOH⋅5 CHCl3 (3) and [Dy21 (L)7 (LH)7 (tfa)7 ]Cl7 ⋅15 H2 O⋅7 MeOH⋅12 CHCl3 (4) are reported (Piv=pivalate, tfa=1,1,1-trifluoroacetylacetone, O3 PtBu=tert-butylphosphonate). Among these, 3 displays an equilateral triangle topology with a side length of 9.541 Å and a rare pentagonal-bipyramidal Dy(3+) environment, whereas complex 4 exhibits a single-stranded nanowheel structure with the highest nuclearity known for a homometallic lanthanide cluster structure. A tentative model of the dc magnetic susceptibility and the low-temperature magnetization of compounds 1 and 2 indicates that the former exhibits weak ferromagnetic intramolecular exchange interaction between the Dy(3+) ions, whereas in the latter both intramolecular ferromagnetic and antiferromagnetic magnetic exchange interactions are present. Compounds 1, 3, and 4 exhibit frequency-dependent ac signals below 15 K at zero bias field, but without exhibiting any maximum above 2 K at frequencies up to 1400 Hz. The observed slow relaxation of the magnetization suggests that these compounds could exhibit single molecule magnet (SMM) behavior with either a thermal energy barrier for the reversal of the magnetization that is not high enough to block the magnetization above 2 K, or there exists quantum tunneling of the magnetization (QTM).

  11. Distinct molecular structures of nuclear class I, II, and III DNA-dependent RNA polymerases.

    PubMed

    Sklar, V E; Schwartz, L B; Roeder, R G

    1975-01-01

    Class III RNA polymerases purified from the murine plasmacytoma MOPC 315 and from Xenopus laevis ovaries were compared. The subunit structures of the chromatographically distinct murine enzymes IIIA and IIIB were indistinguishable and were remarkably similar to that of the amphibian enzyme III. The plasmacytoma class III RNA polymerases were also compared with purified plasmacytoma RNA polymerases I and II. Sedimentation studies indicated that RNA polymerase III si significantly larger than RNA polymerase II, which is slightly larger than RNA polymerase I. Structural analyses showed that the molecular weights of the large subunits present in the class III enzymes (138,000 and 155,000) differ from those of the class II enzymes (140,000 and either 170,000, 205,000, or 240,000) and from those of the class I enzymes (117,000 and 195,000). Some low-molecular-weight subunits are also unique to each enzyme class. These results clearly distinguish the class I, II, and III enzymes on a structural basis. In addition, polypeptides of molecular weight 29,000 and 19,000 were found in all enzyme classes, a polypeptide of molecular weight 52,000 was found only in class I and III enzymes, and a polypeptide of molecular weight 41,000 was found only in class II and III enzymes. These findings are discussed in terms of the function and regulation of the RNA polymerases.

  12. 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.

  13. 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.

  14. Computational fluid dynamics (CFD) and its potential for nuclear applications

    SciTech Connect

    Weber, D.P.; Wei, T.Y.C.; Rock, D.T.; Rizwan-Uddin; Brewster, R.A.; Jonnavithula, S.

    1999-11-01

    The purpose of this paper is to examine the use of these advanced models, methods and computing environments for nuclear applications to determine if the industry can expect to derive the same benefit as other industries, such as the automotive and the aerospace industries. As an example, the authors will examine the use of modern computational fluid dynamics (CFD) capability for subchannel analysis, which is an important part of the analysis technology used by utilities to ensure safe and economical design and operation of reactors. In the current deregulated environment, it is possible that by use of these enhanced techniques, the thermal and electrical output of current reactors may be increased without any increase in cost and at no compromise in safety.

  15. 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

  16. Mechanisms of dynamic nuclear polarization in insulating solids.

    PubMed

    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. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Overhauser Dynamic Nuclear Polarization-Enhanced NMR Relaxometry.

    PubMed

    Franck, John M; Kausik, Ravinath; Han, Songi

    2013-09-15

    We present a new methodological basis for selectively illuminating a dilute population of fluid within a porous medium. Specifically, transport in porous materials can be analyzed by now-standard nuclear magnetic resonance (NMR) relaxometry and NMR pulsed field gradient (PFG) diffusometry methods in combination with with the prominent NMR signal amplification tool, dynamic nuclear polarization (DNP). The key components of the approach introduced here are (1) to selectively place intrinsic or extrinsic paramagnetic probes at the site or local volume of interest within the sample, (2) to amplify the signal from the local solvent around the paramagnetic probes with Overhauser DNP, which is performed in situ and under ambient conditions, and (3) to observe the ODNP-enhanced solvent signal with 1D or 2D NMR relaxometry methods, thus selectively amplifying only the relaxation dynamics of the fluid that resides in or percolates through the local porous volume that contains the paramagnetic probe. Here, we demonstrate the proof of principle of this approach by selectively amplifying the NMR signal of only one solvent population, which is in contact with a paramagnetic probe and occluded from a second solvent population. An apparent one-component T2 relaxation decay is shown to actually contain two distinct solvent populations. The approach outlined here should be universally applicable to a wide range of other 1D and 2D relaxometry and PFG diffusometry measurements, including T1-T2 or T1-D correlation maps, where the occluded population containing the paramagnetic probes can be selectively amplified for its enhanced characterization.

  18. Overhauser Dynamic Nuclear Polarization-Enhanced NMR Relaxometry

    PubMed Central

    Franck, John M.; Kausik, Ravinath; Han, Songi

    2013-01-01

    We present a new methodological basis for selectively illuminating a dilute population of fluid within a porous medium. Specifically, transport in porous materials can be analyzed by now-standard nuclear magnetic resonance (NMR) relaxometry and NMR pulsed field gradient (PFG) diffusometry methods in combination with with the prominent NMR signal amplification tool, dynamic nuclear polarization (DNP). The key components of the approach introduced here are (1) to selectively place intrinsic or extrinsic paramagnetic probes at the site or local volume of interest within the sample, (2) to amplify the signal from the local solvent around the paramagnetic probes with Overhauser DNP, which is performed in situ and under ambient conditions, and (3) to observe the ODNP-enhanced solvent signal with 1D or 2D NMR relaxometry methods, thus selectively amplifying only the relaxation dynamics of the fluid that resides in or percolates through the local porous volume that contains the paramagnetic probe. Here, we demonstrate the proof of principle of this approach by selectively amplifying the NMR signal of only one solvent population, which is in contact with a paramagnetic probe and occluded from a second solvent population. An apparent one-component T2 relaxation decay is shown to actually contain two distinct solvent populations. The approach outlined here should be universally applicable to a wide range of other 1D and 2D relaxometry and PFG diffusometry measurements, including T1–T2 or T1-D correlation maps, where the occluded population containing the paramagnetic probes can be selectively amplified for its enhanced characterization. PMID:23837010

  19. Correlation of lens density measured using the Pentacam Scheimpflug system with the Lens Opacities Classification System III grading score and visual acuity in age-related nuclear cataract.

    PubMed

    Pei, X; Bao, Y; Chen, Y; Li, X

    2008-11-01

    To investigate the relationship between lens density measured with the Pentacam Scheimpflug System and grading score using the Lens Opacities Classification System (LOCS) III as well as that between lens density and visual acuity in age-related nuclear cataract patients. Lens density and grading score were evaluated in 138 cases (180 eyes) with age-related nuclear cataract. LogMAR visual acuity was tested with the Early Treatment Diabetic Retinopathy Study chart. The correlations between lens density value and LOCS III nuclear opacity (NO) and nuclear colour (NC) grading score and that between lens density value and logMAR visual acuity were analysed. There was a linear increasing relationship between lens density value and LOCS III grading score in nuclear cataract patients. Lens density value had a stronger significant correlation with LOCS III NO score than that with NC score. The correlation between the nuclear lens density value and logMAR visual acuity was stronger than that between NO score and logMAR visual acuity or between NC score and logMAR visual acuity. Lens density as a quantitative and objective parameter can present the degree of NO and associated visual impairment due to nuclear cataract. The LOCS III criterion as an economic cataract grading system provides data that are in satisfactory concordance with the results obtained using the Pentacam Scheimpflug system.

  20. 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

  1. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex

    NASA Astrophysics Data System (ADS)

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-01

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

  2. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

    PubMed

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-28

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

  3. Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy.

    PubMed

    Zhou, J; Li, L; Hu, H; Yang, B; Dan, Z; Qiu, J; Guo, J; Chen, F; Ye, C

    1994-11-01

    The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

  4. 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.

  5. Electrochemical Gold(III) Sensor with High Sensitivity and Tunable Dynamic Range.

    PubMed

    Wu, Yao; Lai, Rebecca Y

    2016-02-16

    We report the design and fabrication of a sensitive, specific, and selective electrochemical ion (E-ION) sensor for detection of Au(III). The signaling mechanism is based on the interactions between Au(III) and adenine; formation of these complexes rigidifies the methylene blue (MB)-modified oligoadenine probes, resulting in a concentration-dependent reduction in the MB signal. The dynamic range of the sensor can be tuned by simply changing the length of the DNA probe (six (A6) or 12 (A12) adenines). Independent of the probe length, both sensors have demonstrated to be sensitive, with a limits of detection of 50 and 20 nM for the A6 and A12 sensors, respectively. With further optimization, this sensing strategy may offer a promising approach for analyzing Au(III).

  6. Coupled electron-nuclear wavepacket dynamics in potassium dimers

    NASA Astrophysics Data System (ADS)

    Braun, Hendrike; Bayer, Tim; Sarpe, Cristian; Siemering, Robert; de Vivie-Riedle, Regina; Baumert, Thomas; Wollenhaupt, Matthias

    2014-06-01

    Recently we have demonstrated control of valence-bond excitation of a molecule due to the interplay of the induced charge oscillation with the precisely tailored phase of the driving laser field (Bayer et al 2013 Phys. Rev. Lett. 110 123003). In this contribution we describe in more detail the two-colour experiment—a control pulse sequence followed by an ionizing probe pulse of a different wavelength. We provide details on the quantum dynamics simulations carried out to reproduce and to analyse the experimental results. The procedure for averaging over the focal intensity distribution in the interaction region and the method for orientation averaging, which are both crucial for the reproduction of our strong-field measurements, are also described in detail. The analysis of the temporal evolution of the expectation values of the wavepackets on the relevant potentials, the induced energetic shifts in the molecule and the modulation in the charge oscillation provides further insights into the interplay of the coupled nuclear-electron dynamics. Because the measured photoelectron spectra reveal the population of the target states we describe the quantum mechanical approach to calculate the photoelectron spectra and rationalize the results using Mulliken's difference potential method.

  7. A new sample environment for cryogenic nuclear resonance scattering experiments on single crystals and microsamples at P01, PETRA III

    NASA Astrophysics Data System (ADS)

    Rackwitz, Sergej; Faus, Isabelle; Schmitz, Markus; Kelm, Harald; Krüger, Hans-Jörg; Andersson, K. Kristoffer; Hersleth, Hans-Petter; Achterhold, Klaus; Schlage, Kai; Wille, Hans-Christian; Schünemann, Volker; Wolny, Juliusz A.

    2014-04-01

    In order to carry out orientation dependent nuclear resonance scattering (NRS) experiments on small single crystals of e.g. iron proteins and/or chemical complexes but also on surfaces and other micrometer-sized samples a 2-circle goniometer including sample positioning optics has been installed at beamline P01, PETRA III, DESY, Hamburg. This sample environment is now available for all users of this beamline. Sample cooling is performed with a cryogenic gas stream which allows NRS measurements in the temperature range from 80 up to 400 K. In a first test this new sample environment has been used in order to investigate the orientation dependence of the nuclear inelastic scattering (NIS) signature of (i) a dinuclear iron(II) spin crossover (SCO) system and (ii) a hydrogen peroxide treated metmyoglobin single crystal.

  8. Maritime Dynamic Traffic Generator. Volume III: Density Data on World Maps

    DTIC Science & Technology

    1975-06-01

    AD-A012 498 MARITIME DYNAMIC TR/\\FFIC GENERATOR. VOLUME III: DENSITY DATA ON WORLD MAPS Franklin D. MacKenzie Transportation Systems Center Cambridqe... Transportation Systems Center i]. ContractorGrant No. Kendall Square (Camhridge MA 02142 13. Type of Report and Period Covered 12. Sponsorini"Agency Name and... Transportation • Systems Center to define and analyze requirements for navigation and communica .. ..... .. tion services throtgh a satellite for commercial

  9. 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.

  10. NMR and molecular dynamics studies of the conformational epitope of the type III group B Streptococcus capsular polysaccharide and derivatives.

    PubMed

    Brisson, J R; Uhrinova, S; Woods, R J; van der Zwan, M; Jarrell, H C; Paoletti, L C; Kasper, D L; Jennings, H J

    1997-03-18

    The conformational epitope of the type III group B Streptococcus capsular polysaccharide (GBSP III) exhibits unique properties which can be ascribed to the presence of sialic acid in its structure and the requirement for an extended binding site. By means of NMR and molecular dynamics studies on GBSP III and its fragments, the extended epitope of GBSP III was further defined. The influence of sialic acid on the conformational properties of GBSP III was examined by performing conformational analysis on desialylated GBSP III, which is identical to the polysaccharide of Streptococcus pneumoniae type 14, and also on oxidized and reduced GBSP III. Conformational changes were gauged by 1H and 13C chemical shift analysis, NOE, 1D selective TOCSY-NOESY experiments, J(HH) and J(CH) variations, and NOE of OH resonances. Changes in mobility were examined by 13C T1 and T2 measurements. Unrestrained molecular dynamics simulations with explicit water using the AMBER force field and the GLYCAM parameter set were used to assess static and dynamic conformational models, simulate the observable NMR parameters and calculate helical parameters. GBSP III was found to be capable of forming extended helices. Hence, the length dependence of the conformational epitope could be explained by its location on extended helices within the random coil structure of GBSP III. The interaction of sialic acid with the backbone of the PS was also found to be important in defining the conformational epitope of GBSP III.

  11. The dynamic nature of the nuclear envelope: lessons from closed mitosis.

    PubMed

    Arnone, James T; Walters, Alison D; Cohen-Fix, Orna

    2013-01-01

    In eukaryotes, chromosomes are encased by a dynamic nuclear envelope. In contrast to metazoans, where the nuclear envelope disassembles during mitosis, many fungi including budding yeast undergo "closed mitosis," where the nuclear envelope remains intact throughout the cell cycle. Consequently, during closed mitosis the nuclear envelope must expand to accommodate chromosome segregation to the two daughter cells. A recent study by Witkin et al. in budding yeast showed that if progression through mitosis is delayed, for example due to checkpoint activation, the nuclear envelope continues to expand despite the block to chromosome segregation. Moreover, this expansion occurs at a specific region of the nuclear envelope- adjacent to the nucleolus- forming an extension referred to as a "flare." These observations raise questions regarding the regulation of nuclear envelope expansion both in budding yeast and in higher eukaryotes, the mechanisms confining mitotic nuclear envelope expansion to a particular region and the possible consequences of failing to regulate nuclear envelope expansion during the cell cycle.

  12. Quantitative cw Overhauser effect dynamic nuclear polarization for the analysis of local water dynamics.

    PubMed

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

    2013-10-01

    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 (∼10GHz), 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. We focus 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. It allows one 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 how such data can be

  13. 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

  14. Nuclear magnetic resonance studies of macroscopic morphology and dynamics

    SciTech Connect

    Barrall, Geoffrey Alden

    1995-09-01

    Nuclear magnetic resonance techniques are traditionally used to study molecular level structure and dynamics with a noted exception in medically applied NMR imaging (MRI). In this work, new experimental methods and theory are presented relevant to the study of macroscopic morphology and dynamics using NMR field gradient techniques and solid state two-dimensional exchange NMR. The goal in this work is not to take some particular system and study it in great detail, rather it is to show the utility of a number of new and novel techniques using ideal systems primarily as a proof of principle. By taking advantage of the analogy between NMR imaging and diffraction, one may simplify the experiments necessary for characterizing the statistical properties of the sample morphology. For a sample composed of many small features, e.g. a porous medium, the NMR diffraction techniques take advantage of both the narrow spatial range and spatial isotropy of the sample`s density autocorrelation function to obtain high resolution structural information in considerably less time than that required by conventional NMR imaging approaches. The time savings of the technique indicates that NMR diffraction is capable of finer spatial resolution than conventional NMR imaging techniques. Radio frequency NMR imaging with a coaxial resonator represents the first use of cylindrically symmetric field gradients in imaging. The apparatus as built has achieved resolution at the micron level for water samples, and has the potential to be very useful in the imaging of circularly symmetric systems. The study of displacement probability densities in flow through a random porous medium has revealed the presence of features related to the interconnectedness of the void volumes. The pulsed gradient techniques used have proven successful at measuring flow properties for time and length scales considerably shorter than those studied by more conventional techniques.

  15. Dynamic nuclear polarization NMR spectroscopy of microcrystalline solids.

    PubMed

    Rossini, Aaron J; Zagdoun, Alexandre; Hegner, Franziska; Schwarzwälder, Martin; Gajan, David; Copéret, Christophe; Lesage, Anne; Emsley, Lyndon

    2012-10-10

    Dynamic nuclear polarization (DNP) solid-state NMR has been applied to powdered microcrystalline solids to obtain sensitivity enhancements on the order of 100. Glucose, sulfathiazole, and paracetamol were impregnated with bis-nitroxide biradical (bis-cyclohexyl-TEMPO-bisketal, bCTbK) solutions of organic solvents. The organic solvents were carefully chosen to be nonsolvents for the compounds, so that DNP-enhanced solid-state NMR spectra of the unaltered solids could be acquired. A theoretical model is presented that illustrates that for externally doped organic solids characterized by long spin-lattice relaxation times (T(1)((1)H) > 200 s), (1)H-(1)H spin diffusion can relay enhanced polarization over micrometer length scales yielding substantial DNP enhancements (ε). ε on the order of 60 are obtained for microcrystalline glucose and sulfathiazole at 9.4 T and with temperatures of ca. 105 K. The large gain in sensitivity enables the rapid acquisition of (13)C-(13)C correlation spectra at natural isotopic abundance. It is anticipated that this will be a general method for enhancing the sensitivity of solid-state NMR experiments of organic solids.

  16. Dissolution Dynamic Nuclear Polarization capability study with fluid path.

    PubMed

    Malinowski, Ronja M; Lipsø, Kasper W; Lerche, Mathilde H; Ardenkjær-Larsen, Jan H

    2016-11-01

    Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. VISION -- A Dynamic Model of the Nuclear Fuel Cycle

    SciTech Connect

    J. J. Jacobson; A. M. Yacout; S. J. Piet; D. E. Shropshire; G. E. Matthern

    2006-02-01

    The Advanced Fuel Cycle Initiative’s (AFCI) fundamental objective is to provide technology options that – if implemented – would enable long-term growth of nuclear power while improving sustainability and energy security. The AFCI organization structure consists of four areas; Systems Analysis, Fuels, Separations and Transmutations. The Systems Analysis Working Group is tasked with bridging the program technical areas and providing the models, tools, and analyses required to assess the feasibility of design and deploy¬ment options and inform key decision makers. An integral part of the Systems Analysis tool set is the development of a system level model that can be used to examine the implications of the different mixes of reactors, implications of fuel reprocessing, impact of deployment technologies, as well as potential “exit” or “off ramp” approaches to phase out technologies, waste management issues and long-term repository needs. The Verifiable Fuel Cycle Simulation Model (VISION) is a computer-based simulation model that allows performing dynamic simulations of fuel cycles to quantify infrastructure requirements and identify key trade-offs between alternatives. VISION is intended to serve as a broad systems analysis and study tool applicable to work conducted as part of the AFCI (including costs estimates) and Generation IV reactor development studies.

  18. 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.

  19. Dissolution Dynamic Nuclear Polarization capability study with fluid path

    NASA Astrophysics Data System (ADS)

    Malinowski, Ronja M.; Lipsø, Kasper W.; Lerche, Mathilde H.; Ardenkjær-Larsen, Jan H.

    2016-11-01

    Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies.

  20. Spontaneous Tl(I)-to-Tl(III) oxidation in dynamic heterobimetallic Hg(II)/Tl(I) porphyrin complexes.

    PubMed

    Ndoyom, Victoria; Fusaro, Luca; Roisnel, Thierry; Le Gac, Stéphane; Boitrel, Bernard

    2016-01-11

    Strapped heterobimetallic Hg(II)/Tl(I) porphyrin complexes, with both metal ions bridged by the N-core in a dynamic way, undergo spontaneous Tl(I)-to-Tl(III) oxidation leading to a mono-Tl(III) complex and a mixed valence Tl(I)/Tl(III) bimetallic complex. It provides a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

  1. Nuclear Magnetic Resonance Studies of II-Vi and Iii-V Semiconductor Alloys

    NASA Astrophysics Data System (ADS)

    Shi, Jian-Hui

    In this thesis, I show how the basic solid-state NMR techniques can be used to study the local electronic structures of II-VI and III-V semiconductor alloys on an atomic scale. We have focused our studies on a few high quality samples, mainly Hg_{rm 1-x}Cd_{rm x} Te in the II-VI group, In-based binary III-V bulk semiconductors InP, InAs and InSb, and the III-V alloys Ga_{rm 1-x}In _{rm x}As. For solid-state-recrystallized device-quality bulk Hg_{rm 1-x}Cd _{rm x}Te samples, with x equal to 0.2, 0.22 and 0.28, corresponding to the narrow-gap semiconducting side of the band-inversion configurations, we have obtained detailed band-edge symmetry information, and site-selective quantitative charge carrier orbital characteristics on an atomic scale. Our study also indicated that a random cation distribution model well described the materials. We have investigated ^{115 }In magnetic resonance frequency shifts and the temperature dependence of these shifts in In-based III-V binary semiconductors. We have extracted the chemical shifts from the total shifts for these III-V semiconductors at 303K and 77K. Our NMR study of these binary semiconductors not only enhanced the understanding of electronic properties of these compounds, but also served as a reference for our NMR studies of III-V alloys. We performed ^{115}In NMR studies for dilute III-V semiconductor alloy Ga _{rm 1-x}In_ {rm x}As with x equal to 0.72%. Spectra clearly indicating the local electronic configurations were obtained. We carried out a series of field orientation studies, and determined the field gradient which is due to In-In pairs. This study provided evidence of local clustering of In atoms.

  2. Information flow and protein dynamics: the interplay between nuclear magnetic resonance spectroscopy and molecular dynamics simulations.

    PubMed

    Pastor, Nina; Amero, Carlos

    2015-01-01

    Proteins participate in information pathways in cells, both as links in the chain of signals, and as the ultimate effectors. Upon ligand binding, proteins undergo conformation and motion changes, which can be sensed by the following link in the chain of information. Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations represent powerful tools for examining the time-dependent function of biological molecules. The recent advances in NMR and the availability of faster computers have opened the door to more detailed analyses of structure, dynamics, and interactions. Here we briefly describe the recent applications that allow NMR spectroscopy and MD simulations to offer unique insight into the basic motions that underlie information transfer within and between cells.

  3. Information flow and protein dynamics: the interplay between nuclear magnetic resonance spectroscopy and molecular dynamics simulations

    PubMed Central

    Pastor, Nina; Amero, Carlos

    2015-01-01

    Proteins participate in information pathways in cells, both as links in the chain of signals, and as the ultimate effectors. Upon ligand binding, proteins undergo conformation and motion changes, which can be sensed by the following link in the chain of information. Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations represent powerful tools for examining the time-dependent function of biological molecules. The recent advances in NMR and the availability of faster computers have opened the door to more detailed analyses of structure, dynamics, and interactions. Here we briefly describe the recent applications that allow NMR spectroscopy and MD simulations to offer unique insight into the basic motions that underlie information transfer within and between cells. PMID:25999971

  4. Mitochondrial Dynamics Tracking with Two-Photon Phosphorescent Terpyridyl Iridium(III) Complexes

    NASA Astrophysics Data System (ADS)

    Huang, Huaiyi; Zhang, Pingyu; Qiu, Kangqiang; Huang, Juanjuan; Chen, Yu; Ji, Liangnian; Chao, Hui

    2016-02-01

    Mitochondrial dynamics, including fission and fusion, control the morphology and function of mitochondria, and disruption of mitochondrial dynamics leads to Parkinson’s disease, Alzheimer’s disease, metabolic diseases, and cancers. Currently, many types of commercial mitochondria probes are available, but high excitation energy and low photo-stability render them unsuitable for tracking mitochondrial dynamics in living cells. Therefore, mitochondrial targeting agents that exhibit superior anti-photo-bleaching ability, deep tissue penetration and intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds that use low-energy near-infrared excitation lasers have emerged as non-invasive tools for cell imaging. In this work, terpyridyl cyclometalated Ir(III) complexes (Ir1-Ir3) are demonstrated as one- and two-photon phosphorescent probes for real-time imaging and tracking of mitochondrial morphology changes in living cells.

  5. Solvent-dependent absorption and electronic relaxation dynamics of iron (III) tetra-4-N-methylpyridylporphine

    NASA Astrophysics Data System (ADS)

    Williams, Lenzi J.; Knappenberger, Kenneth L.

    2017-03-01

    Solvent-dependent excited-state relaxation dynamics of iron (III) tetra-4-N-methylpyridylporphine (FeTMPyP) were investigated using steady-state and femtosecond spectroscopies. Soret absorption for water-dispersed FeTMPyP consisted of two spectrally broad components centered at 3.12 eV and 2.92 eV, corresponding to π → π∗ and charge-transfer (C-T) transitions. The C-T transition exhibited inverse-dielectric-dependent energy shifts. Following 400-nm excitation, dynamics proceeded by femtosecond internal conversion from the initially prepared π∗ state to the C-T state, followed by solvent-dependent C-T relaxation. The C-T energy shifts and relaxation rates exhibited correlated dielectric dependences. C-T absorption energy and relaxation dynamics of FeTMPyP are sensitive indicators of surrounding dielectric environments.

  6. Mitochondrial Dynamics Tracking with Two-Photon Phosphorescent Terpyridyl Iridium(III) Complexes.

    PubMed

    Huang, Huaiyi; Zhang, Pingyu; Qiu, Kangqiang; Huang, Juanjuan; Chen, Yu; Ji, Liangnian; Chao, Hui

    2016-02-11

    Mitochondrial dynamics, including fission and fusion, control the morphology and function of mitochondria, and disruption of mitochondrial dynamics leads to Parkinson's disease, Alzheimer's disease, metabolic diseases, and cancers. Currently, many types of commercial mitochondria probes are available, but high excitation energy and low photo-stability render them unsuitable for tracking mitochondrial dynamics in living cells. Therefore, mitochondrial targeting agents that exhibit superior anti-photo-bleaching ability, deep tissue penetration and intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds that use low-energy near-infrared excitation lasers have emerged as non-invasive tools for cell imaging. In this work, terpyridyl cyclometalated Ir(III) complexes (Ir1-Ir3) are demonstrated as one- and two-photon phosphorescent probes for real-time imaging and tracking of mitochondrial morphology changes in living cells.

  7. Mitochondrial Dynamics Tracking with Two-Photon Phosphorescent Terpyridyl Iridium(III) Complexes

    PubMed Central

    Huang, Huaiyi; Zhang, Pingyu; Qiu, Kangqiang; Huang, Juanjuan; Chen, Yu; Ji, Liangnian; Chao, Hui

    2016-01-01

    Mitochondrial dynamics, including fission and fusion, control the morphology and function of mitochondria, and disruption of mitochondrial dynamics leads to Parkinson’s disease, Alzheimer’s disease, metabolic diseases, and cancers. Currently, many types of commercial mitochondria probes are available, but high excitation energy and low photo-stability render them unsuitable for tracking mitochondrial dynamics in living cells. Therefore, mitochondrial targeting agents that exhibit superior anti-photo-bleaching ability, deep tissue penetration and intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds that use low-energy near-infrared excitation lasers have emerged as non-invasive tools for cell imaging. In this work, terpyridyl cyclometalated Ir(III) complexes (Ir1-Ir3) are demonstrated as one- and two-photon phosphorescent probes for real-time imaging and tracking of mitochondrial morphology changes in living cells. PMID:26864567

  8. 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. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  9. Linking Microbial Dynamics and Physicochemical Processes in High-temperature Acidic Fe(III)- Mineralizing Systems

    NASA Astrophysics Data System (ADS)

    Inskeep, W.

    2014-12-01

    Microbial activity is responsible for the mineralization of Fe(III)-oxides in high-temperature chemotrophic communities that flourish within oxygenated zones of low pH (2.5 - 4) geothermal outflow channels (Yellowstone National Park, WY). High-temperature Fe(II)-oxidizing communities contain several lineages of Archaea, and are excellent model systems for studying microbial interactions and spatiotemporal dynamics across geochemical gradients. We hypothesize that acidic Fe(III)-oxide mats form as a result of constant interaction among primary colonizers including Hydrogenobaculum spp. (Aquificales) and Metallosphaera spp. (Sulfolobales), and subsequent colonization by archaeal heterotrophs, which vary in abundance as a function of oxygen, pH and temperature. We are integrating a complementary suite of geochemical, stable isotope, genomic, proteomic and modeling analyses to study the role of microorganisms in Fe(III)-oxide mat development, and to elucidate the primary microbial interactions that are coupled with key abiotic events. Curated de novo assemblies of major phylotypes are being used to analyze additional -omics datasets from these microbial mats. Hydrogenobaculum spp. (Aquificales) are the dominant bacterial population(s) present, and predominate during early mat development (< 30 d). Other Sulfolobales populations known to oxidize Fe(II) and fix carbon dioxide (e.g., Metallosphaera spp.) represent a secondary stage of mat development (e.g., 14 - 30 d). Hydrogenobaculum filaments appear to promote the nucleation and subsequent mineralization of Fe(III)-oxides, which likely affect the growth and turnover rates of these organisms. Other heterotrophs colonize Fe(III)-oxide mats during succession (> 30 d), including novel lineages of Archaea and representatives within the Crenarchaeota, Euryarchaeota, Thaumarchaeota and Nanoarchaeota. In situ oxygen consumption rates show that steep gradients occur within the top 1 mm of mat surface, and which correlate with

  10. Overhauser dynamic nuclear polarization amplification of NMR flow imaging.

    PubMed

    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 0.35T fringe field of an unshielded 2.0T non-clinical MRI magnet, followed by the rapid transfer of polarization-enhanced water to the 2.0T 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 2.0T. 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. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. 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%.

  12. 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.

  13. Final report. Conceptual studies nuclear energy center Lake Hartwell, S. C. , Phase III

    SciTech Connect

    Not Available

    1981-01-01

    This document summarizes a conceptual study on the feasibility and practicality of developing a nuclear energy center (NEC) at a specific site in the SSEB region. The site selected for this conceptual study is at Lake Hartwell, South Carolina. The conceptual NEC at Lake Hartwell consists of twelve nuclear electric generating units, arranged on the site in four clusters of three units each, known as triads. The nominal distance between triads was selected as 2-1/2 miles. Each unit was assumed to be a 1250 MW(e). The total electric output of 15,000 MWe would be transmitted to five major utilities in South Carolina, North Carolina, and Georgia. The basic finding was that the concept of a NEC on the Lake Hartwell site is feasible, but further analysis of institutional issues and possible legislation would be required.

  14. Quantum wavepacket ab initio molecular dynamics: an approach for computing dynamically averaged vibrational spectra including critical nuclear quantum effects.

    PubMed

    Sumner, Isaiah; Iyengar, Srinivasan S

    2007-10-18

    We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.

  15. Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations.

    PubMed

    Karabanov, Alexander; Kwiatkowski, Grzegorz; Perotto, Carlo U; Wiśniewski, Daniel; McMaster, Jonathan; Lesanovsky, Igor; Köckenberger, Walter

    2016-11-02

    A theory of dynamic nuclear polarisation (DNP) by thermal mixing is suggested based on purely quantum considerations. A minimal 6-level microscopic model is developed to test the theory and link it to the well-known thermodynamic model. Optimal conditions for the nuclear polarization enhancement and effects of inhomogeneous broadening of the electron resonance are discussed. Macroscopic simulations of nuclear polarization spectra displaying good agreement with experiments, involving BDPA and trityl free radicals, are presented.

  16. Electron-Nuclear Spin Dynamics in a Mesoscopic Solid-State Quantum Computer

    SciTech Connect

    Berman, G.P.; Campbell, D.K.; Doolen, G.D.; Nagaev, K.E.

    1998-12-07

    We numerically simulate the process of nuclear spin measurement in Kane's quantum computer. For this purpose, we model the quantum dynamics of two coupled nuclear spins located on {sup 31}P donors implanted in Si. We estimate the minimum time of measurement necessary for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic one and the probability of error for typical values of external noise.

  17. Global magnetospheric dynamics - Reporter reviews and global magnetospheric dynamics; 1989 IAGA Division III, Symposia Papers

    NASA Astrophysics Data System (ADS)

    Siscoe, George L.

    1990-12-01

    Topics presented include 1987-1989 magnetosheath, magnetopause and low latitude boundary layer research; the morphology of magnetic merging at the magnetopause; the global dynamics of the magnetosphere for northward IMF conditions; and some recent advances in magnetospheric substorm research. Consideration is also given to the energetic particles in the environment of the earth's magnetosphere, ULF waves on the ground and in space, the magnetic field of the magnetospheric ring current and its dynamics during magnetic storms, and a review of extraterrestrial magnetosphere research during 1987-1989.

  18. Silica materials with wall-embedded nitroxides provide efficient polarization matrices for dynamic nuclear polarization NMR.

    PubMed

    Besson, Eric; Ziarelli, Fabio; Bloch, Emily; Gerbaud, Guillaume; Queyroy, Séverine; Viel, Stéphane; Gastaldi, Stéphane

    2016-04-25

    Hybrid mesoporous silica materials with wall-embedded nitroxides are shown to efficiently polarize impregnated substrates in high-field dynamic nuclear polarization magic-angle spinning solid-state NMR experiments.

  19. [Mn(III)Mn(IV)2Mo14O56](17-): A Mixed-Valence Meso-Polyoxometalate Anion Encapsulated by a 64-Nuclearity Silver Cluster.

    PubMed

    Wang, Jian-Yu; Liu, Kuan-Guan; Guan, Zong-Jie; Nan, Zi-Ang; Lin, Yu-Mei; Wang, Quan-Ming

    2016-07-18

    A 64-nuclearity silver cluster encapsulating a unique POM anion [Mn(III)Mn(IV)2Mo14O56](17-) has been synthesized. The formation of the templating core performs a reassembly process for increasing nuclearities from {MnMo9} to {Mn3Mo14}. It represents a rare inorganic meso anion containing mixed-valent Mn that is built up by d-{Mn(IV)Mo7} and l-{Mn(IV)Mo7} units connecting together through a {Mn(III)} fragment.

  20. Spectroscopic studies on two mono nuclear iron (III) complexes derived from a schiff base and an azodye

    SciTech Connect

    Mini, S. Sadasivan, V.; Meena, S. S. Bhatt, Pramod

    2014-10-15

    Two new mono nuclear Fe(III) complexes of an azodye (ANSN) and a Schiff base (FAHP) are reported. The azodye is prepared by coupling diazotized 1-amino-2-naphthol-4-sulphonicacid with 2-naphthol and the Schiff base is prepared by condensing 2-amino-3-hydroxy pyridine with furfural. The complexes were synthesized by the reaction of FeCl{sub 3}Ðœ‡2H{sub 2}O with respective ligands. They were characterized on the basis of elemental analysis and spectral studies like IR, NMR, Electronic and M.ssbauer. Magnetic susceptibility and Molar conductance of complexes at room temperature were studied. Based on the spectroscopic evidences and other analytical data the complexes are formulated as[Fe(ANSN)Cl(H{sub 2}O){sub 2}] and [Fe(FAHP)Cl{sub 2}(H{sub 2}O){sub 2}].

  1. Spectroscopic studies on two mono nuclear iron (III) complexes derived from a schiff base and an azodye

    NASA Astrophysics Data System (ADS)

    Mini, S.; Sadasivan, V.; Meena, S. S.; Bhatt, Pramod

    2014-10-01

    Two new mono nuclear Fe(III) complexes of an azodye (ANSN) and a Schiff base (FAHP) are reported. The azodye is prepared by coupling diazotized 1-amino-2-naphthol-4-sulphonicacid with 2-naphthol and the Schiff base is prepared by condensing 2-amino-3-hydroxy pyridine with furfural. The complexes were synthesized by the reaction of FeCl3˙2H2O with respective ligands. They were characterized on the basis of elemental analysis and spectral studies like IR, NMR, Electronic and M.ssbauer. Magnetic susceptibility and Molar conductance of complexes at room temperature were studied. Based on the spectroscopic evidences and other analytical data the complexes are formulated as[Fe(ANSN)Cl(H2O)2] and [Fe(FAHP)Cl2(H2O)2].

  2. Electron nuclear dynamics of proton collisions with methane at 30 eV

    NASA Astrophysics Data System (ADS)

    Jacquemin, D.; Morales, J. A.; Deumens, E.; Öhrn, Y.

    1997-10-01

    The reactive collisions of protons with methane molecules at 30 eV in the laboratory frame are studied with the electron nuclear dynamics (END). The results from this theoretical approach, which does not invoke the Born-Oppenheimer approximation and does not impose any constraints on the nuclear dynamics, are compared to the results from time-of-flight measurements. Total differential cross sections and integral cross sections as well as fragmentation ratios and energy loss spectra are discussed.

  3. 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).

  4. Nuclear dynamics consequence analysis of SNF disposed in volcanic tuff

    SciTech Connect

    Sanchez, L.C.; Cochrane, K.; Rath, J.S.; Taylor, L.L.

    1998-05-01

    This paper describes criticality analyses for spent nuclear fuels in a geologic repository. The analyses investigated criticality potential, criticality excursion consequences, and the probability frequency for nuclear criticality. Key findings include: expected number of fissions per excursion range from 10{sup 17} to 10{sup 20}, repeated rate of criticalities range from 3 to 30 per year, and the probability frequency for criticality initiators (based on rough-order-of-magnitude calculations) is 7{times}10{sup {minus}7}. Overall results indicate that criticality consequences are a minor contribution to the biological hazards caused by the disposal of spent nuclear material.

  5. 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.

  6. Real-time tracking mitochondrial dynamic remodeling with two-photon phosphorescent iridium (III) complexes.

    PubMed

    Huang, Huaiyi; Yang, Liang; Zhang, Pingyu; Qiu, Kangqiang; Huang, Juanjuan; Chen, Yu; Diao, JiaJie; Liu, Jiankang; Ji, Liangnian; Long, Jiangang; Chao, Hui

    2016-03-01

    Mitochondrial fission and fusion control the shape, size, number, and function of mitochondria in the cells of organisms from yeast to mammals. The disruption of mitochondrial fission and fusion is involved in severe human diseases such as Parkinson's disease, Alzheimer's disease, metabolic diseases, and cancers. Agents that can real-time track the mitochondrial dynamics are of great importance. However, the short excitation wavelengths and rapidly photo-bleaching properties of commercial mitochondrial dyes render them unsuitable for tracking mitochondrial dynamics. Thus, mitochondrial targeting agents that exhibit superior photo-stability under continual light irradiation, deep tissue penetration and at intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds employ low-energy near-infrared light and have emerged as a non-invasive tool for real-time cell imaging. Here, cyclometalated Ir(III) complexes (Ir1-Ir5) are demonstrated as one- and two-photon phosphorescent probes for the real-time imaging and tracking of mitochondrial fission and fusion. The results indicate that Ir2 is well suited for two-photon phosphorescent tracking of mitochondrial fission and fusion in living cells and in Caenorhabditis elegans (C. elegans). This study provides a practical use for mitochondrial targeting two-photon phosphorescent Ir(III) complexes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Probing nuclear dynamics of oriented HeH+ with odd-even high-order harmonics

    NASA Astrophysics Data System (ADS)

    Li, W. Y.; Yu, S. J.; Wang, S.; Chen, Y. J.

    2016-11-01

    We study the electron-nuclear coupled dynamics for oriented HeH+ molecules in strong laser fields numerically and analytically. At small orientation angles, the asymmetric molecule tends to stretch to distances larger than the equilibrium separation and strong even harmonics are emitted. We show that the permanent dipole of the system plays an important role in the vibrational dynamics of the nuclear wave packet. The nuclear motion and the molecular structure can be read from the spectra and ellipticity of odd-even high harmonics. Our results also have implications for strong-field ionization of the asymmetric system.

  8. DNA Ligase III is critical for mtDNA integrity but not Xrcc1-mediated nuclear DNA repair

    PubMed Central

    Gao, Yankun; Katyal, Sachin; Lee, Youngsoo; Zhao, Jingfeng; Rehg, Jerold E.; Russell, Helen R.; McKinnon, Peter J.

    2011-01-01

    DNA replication and repair in mammalian cells involves three distinct DNA ligases; ligase I (Lig1), ligase III (Lig3) and ligase IV (Lig4)1. Lig3 is considered a key ligase during base excision repair because its stability depends upon its nuclear binding partner Xrcc1, a critical factor for this DNA repair pathway2,3. Lig3 is also present in the mitochondria where its role in mitochondrial DNA (mtDNA) maintenance is independent of Xrcc14. However, the biological role of Lig3 is unclear as inactivation of murine Lig3 results in early embryonic lethality5. Here we report that Lig3 is essential for mtDNA integrity but dispensable for nuclear DNA repair. Inactivation of Lig3 in the mouse nervous system resulted in mtDNA loss leading to profound mitochondrial dysfunction, disruption of cellular homeostasis and incapacitating ataxia. Similarly, inactivation of Lig3 in cardiac muscle resulted in mitochondrial dysfunction and defective heart pump function leading to heart failure. However, Lig3 inactivation did not result in nuclear DNA repair deficiency, indicating essential DNA repair functions of Xrcc1 can occur in the absence of Lig3. Instead, we found that Lig1 was critical for DNA repair, but in a cooperative manner with Lig3. Additionally, Lig3 deficiency did not recapitulate the hallmark features of neural Xrcc1 inactivation such as DNA damage-induced cerebellar interneuron loss6, further underscoring functional separation of these DNA repair factors. Therefore, our data reveal that the critical biological role of Lig3 is to maintain mtDNA integrity and not Xrcc1-dependent DNA repair. PMID:21390131

  9. Dynamics of quantum dot nuclear spin polarization controlled by a single electron.

    PubMed

    Maletinsky, P; Badolato, A; Imamoglu, A

    2007-08-03

    We present measurements of the buildup and decay of nuclear spin polarization in a single semiconductor quantum dot. Our experiment shows that we polarize the nuclei in a few milliseconds, while their decay dynamics depends drastically on external parameters. We show that a single electron can very efficiently depolarize nuclear spins in milliseconds whereas in the absence of the electron the nuclear spin lifetime is on the scale of seconds. This lifetime is further enhanced by 1-2 orders of magnitude by quenching the nonsecular nuclear dipole-dipole interactions with a magnetic field of 1 mT.

  10. Energetic considerations of the vibrational potential function in the effective nuclear charge model. III

    NASA Astrophysics Data System (ADS)

    Ohwada, Ken

    1984-02-01

    The Parr-Gadre homogeneity condition for the molecular electronic energy with respect to the atomic number is examined in detail with the use of the model potential in the effective nuclear charge model previously proposed. The energy deviation from such a condition is closely related to that of the total molecular SCF energy from the eigenvalue sum, and it is shown that the R-dependent (R; internuclear distance) terms in the model potential contribute significantly to that deviation. The approximate analytic formulas for the chemical potentials of molecules are derived from both the model potential and the results of a low-order gradient expansion in the electron density. It is especially emphasized that the chemical potential change depends mainly upon the correction terms, in the model potential, describing the behavior of delocalized electrons in the molecule.

  11. Executive summary. Conceptual studies nuclear energy center Lake Hartwell, S. C. , Phase III

    SciTech Connect

    Not Available

    1981-01-01

    This document summarizes a conceptual study on the feasibility and practicality of developing a nuclear energy center (NEC) at a specific site in the SSEB region. The site selected for this conceptual study is at Lake Hartwell, South Carolina. The conceptual NEC at Lake Hartwell consists of twelve 1250-MW(e) LWRs arranged on the site in four cluster of three units each, know as triads. The nominal distance between triads was selected as 2-1/2 miles. The total electric output of 15,000 MWe to be generated by the NEC would be transmitted to five major utilities in South Carolina, North Carolina, and Georgia. Objective of the study was to assess the technical, socioeconomic, environmental, and institutional issues relating to the NEC at the conceptual study site. The basic finding was that the concept of a NEC on the Lake Hartwell site is feasible, but further analysis of institutional issues and possible legislation would be required.

  12. Microtubules as key coordinators of nuclear envelope and endoplasmic reticulum dynamics during mitosis.

    PubMed

    Schlaitz, Anne-Lore

    2014-07-01

    During mitosis, cells comprehensively restructure their interior to promote the faithful inheritance of DNA and cytoplasmic contents. In metazoans, this restructuring entails disassembly of the nuclear envelope, redistribution of its components into the endoplasmic reticulum (ER) and eventually nuclear envelope reassembly around the segregated chromosomes. The microtubule cytoskeleton has recently emerged as a critical regulator of mitotic nuclear envelope and ER dynamics. Microtubules and associated molecular motors tear open the nuclear envelope in prophase and remove nuclear envelope remnants from chromatin. Additionally, two distinct mechanisms of microtubule-based regulation of ER dynamics operate later in mitosis. First, association of the ER with microtubules is reduced, preventing invasion of ER into the spindle area, and second, organelle membrane is actively cleared from metaphase chromosomes. However, we are only beginning to understand the role of microtubules in shaping and distributing ER and other organelles during mitosis.

  13. Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS

    SciTech Connect

    Beifiori, Alessandra; Saglia, Roberto P.; Bender, Ralf; Senger, Robert; Thomas, Daniel; Maraston, Claudia; Steele, Oliver; Masters, Karen L.; Pforr, Janine; Tojeiro, Rita; Johansson, Jonas; Nichol, Robert C.; Chen, Yan-Mei; Wake, David; Bolton, Adam; Brownstein, Joel R.; Leauthaud, Alexie; Schneider, Donald P.; Skibba, Ramin; Pan, Kaike; and others

    2014-07-10

    We study the redshift evolution of the dynamical properties of ∼180, 000 massive galaxies from SDSS-III/BOSS combined with a local early-type galaxy sample from SDSS-II in the redshift range 0.1 ≤ z ≤ 0.6. The typical stellar mass of this sample is M{sub *} ∼2 × 10{sup 11} M{sub ☉}. We analyze the evolution of the galaxy parameters effective radius, stellar velocity dispersion, and the dynamical to stellar mass ratio with redshift. As the effective radii of BOSS galaxies at these redshifts are not well resolved in the Sloan Digital Sky Survey (SDSS) imaging we calibrate the SDSS size measurements with Hubble Space Telescope/COSMOS photometry for a sub-sample of galaxies. We further apply a correction for progenitor bias to build a sample which consists of a coeval, passively evolving population. Systematic errors due to size correction and the calculation of dynamical mass are assessed through Monte Carlo simulations. At fixed stellar or dynamical mass, we find moderate evolution in galaxy size and stellar velocity dispersion, in agreement with previous studies. We show that this results in a decrease of the dynamical to stellar mass ratio with redshift at >2σ significance. By combining our sample with high-redshift literature data, we find that this evolution of the dynamical to stellar mass ratio continues beyond z ∼ 0.7 up to z > 2 as M{sub dyn}/M{sub *} ∼(1 + z){sup –0.30±0.12}, further strengthening the evidence for an increase of M{sub dyn}/M{sub *} with cosmic time. This result is in line with recent predictions from galaxy formation simulations based on minor merger driven mass growth, in which the dark matter fraction within the half-light radius increases with cosmic time.

  14. Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance.

    PubMed

    Siaw, Ting Ann; Fehr, Matthias; Lund, Alicia; Latimer, Allegra; Walker, Shamon A; Edwards, Devin T; Han, Song-I

    2014-09-21

    For the broadest dissemination of solid-state dynamic nuclear polarization (ssDNP) enhanced NMR as a material characterization tool, the ability to employ generic mono-nitroxide radicals as spin probes is critical. A better understanding of the factors contributing to ssDNP efficiency is needed to rationally optimize the experimental condition for the practically accessible spin probes at hand. This study seeks to advance the mechanistic understanding of ssDNP by examining the effect of electron spin dynamics on ssDNP performance at liquid helium temperatures (4-40 K). The key observation is that bi-radicals and mono-radicals can generate comparable nuclear spin polarization at 4 K and 7 T, which is in contrast to the observation for ssDNP at liquid nitrogen temperatures (80-150 K) that finds bi-radicals to clearly outperform mono-radicals. To rationalize this observation, we analyze the change in the DNP-induced nuclear spin polarization (Pn) and the characteristic ssDNP signal buildup time as a function of electron spin relaxation rates that are modulated by the mono- and bi-radical spin concentration. Changes in Pn are consistent with a systematic variation in the product of the electron spin-lattice relaxation time and the electron spin flip-flop rate that constitutes an integral saturation factor of an inhomogeneously broadened EPR spectrum. We show that the comparable Pn achieved with both radical species can be reconciled with a comparable integral EPR saturation factor. Surprisingly, the largest Pn is observed at an intermediate spin concentration for both mono- and bi-radicals. At the highest radical concentration, the stronger inter-electron spin dipolar coupling favors ssDNP, while oversaturation diminishes Pn, as experimentally verified by the observation of a maximum Pn at an intermediate, not the maximum, microwave (μw) power. At the maximum μw power, oversaturation reduces the electron spin population differential that must be upheld between

  15. Deuterium-substitution effects on relaxation times and interligand nuclear Overhauser effects for assignment of ligand resonances and isomer identification in cobalt(III) complexes

    SciTech Connect

    Storm, C.B.; Turner, A.H.; Rowan, N.S.

    1985-04-10

    Relaxation time, T/sub 1/, and nuclear Overhauser effects are reported for nine imidazole complexes and one histidine complex of Co(III). From these values unequivocal resonance and isomer assignments can be made. The deuterium substitution effect of T/sub 1/'s has been used to determine intranuclear distances and molecular configurations.

  16. Dynamical model of antishadowing of the nuclear gluon distribution

    NASA Astrophysics Data System (ADS)

    Frankfurt, L.; Guzey, V.; Strikman, M.

    2017-05-01

    We explore the theoretical observation that within the leading twist approximation, the nuclear effects of shadowing and antishadowing in nonperturbative nuclear parton distribution functions (nPDFs) at the input QCD evolution scale involve diffraction on nucleons of a nuclear target and originate from merging of two parton ladders belonging to two different nucleons, which are close in the rapidity space. It allows us to propose that for a given momentum fraction xI P carried by the diffractive exchange, nuclear shadowing and antishadowing should compensate each other in the momentum sum rule for nPDFs locally on the interval ln(x /xI P)≤1 . We realize this by constructing an explicit model of nuclear gluon antishadowing, which has a wide support in x ,10-4

  17. Slow Molecular Motions in Ionic Liquids Probed by Cross-Relaxation of Nuclear Spins During Overhauser Dynamic Nuclear Polarization.

    PubMed

    Banerjee, Abhishek; Dey, Arnab; Chandrakumar, Narayanan

    2016-11-14

    Solution-state Overhauser dynamic nuclear polarization (ODNP) at moderate fields, performed by saturating the electron spin resonance (ESR) of a free radical added to the sample of interest, is well known to lead to significant NMR signal enhancements in the steady state, owing to electron-nuclear cross-relaxation. Here it is shown that under conditions which limit radical access to the molecules of interest, the time course of establishment of ODNP can provide a unique window into internuclear cross-relaxation, and reflects relatively slow molecular motions. This behavior, modeled mathematically by a three-spin version of the Solomon equations (one unpaired electron and two nuclear spins), is demonstrated experimentally on the (19) F/(1) H system in ionic liquids. Bulky radicals in these viscous environments turn out to be just the right setting to exploit these effects. Compared to standard nuclear Overhauser effect (NOE) work, the present experiment offers significant improvement in dynamic range and sensitivity, retains usable chemical shift information, and reports on molecular motions in the sub-megahertz (MHz) to tens of MHz range-motions which are not accessed at high fields. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Nuclear Dynamics Consequence Analysis (NDCA) for the Disposal of Spent Nuclear Fuel in an Underground Geologic Repository - Volume 3: Appendices

    SciTech Connect

    Taylor, L.L.; Wilson, J.R.; Sanchez, L.C.; Aguilar, R.; Trellue, H.R.; Cochrane, K.; Rath, J.S.

    1998-10-01

    The United States Department of Energy Office of Environmental Management's (DOE/EM's) National Spent Nuclear Fuel Program (NSNFP), through a collaboration between Sandia National Laboratories (SNL) and Idaho National Engineering and Environmental Laboratory (INEEL), is conducting a systematic Nuclear Dynamics Consequence Analysis (NDCA) of the disposal of SNFs in an underground geologic repository sited in unsaturated tuff. This analysis is intended to provide interim guidance to the DOE for the management of the SNF while they prepare for final compliance evaluation. This report presents results from a Nuclear Dynamics Consequence Analysis (NDCA) that examined the potential consequences and risks of criticality during the long-term disposal of spent nuclear fuel owned by DOE-EM. This analysis investigated the potential of post-closure criticality, the consequences of a criticality excursion, and the probability frequency for post-closure criticality. The results of the NDCA are intended to provide the DOE-EM with a technical basis for measuring risk which can be used for screening arguments to eliminate post-closure criticality FEPs (features, events and processes) from consideration in the compliance assessment because of either low probability or low consequences. This report is composed of an executive summary (Volume 1), the methodology and results of the NDCA (Volume 2), and the applicable appendices (Volume 3).

  19. Measurement of the excited-state transverse hyperfine coupling in NV centers via dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Poggiali, F.; Cappellaro, P.; Fabbri, N.

    2017-05-01

    Precise knowledge of a quantum system's Hamiltonian is a critical pre-requisite for its use in many quantum information technologies. Here, we report a method for the precise characterization of the nonsecular part of the excited-state Hamiltonian of an electronic-nuclear spin system in diamond. The method relies on the investigation of the dynamic nuclear polarization mediated by the electronic spin, which is currently exploited as a primary tool for initializing nuclear qubits and performing enhanced nuclear magnetic resonance. By measuring the temporal evolution of the population of the ground-state hyperfine levels of a nitrogen-vacancy center, we obtain the first direct estimation of the excited-state transverse hyperfine coupling between its electronic and nitrogen nuclear spin. Our method could also be applied to other electron-nuclear spin systems, such as those related to defects in silicon carbide.

  20. Local Water Dynamics in Coacervated Polyelectrolytes Monitored Through Dynamic Nuclear Polarization-Enhanced 1H NMR

    PubMed Central

    Kausik, Ravinath; Srivastava, Aasheesh; Korevaar, Peter A.; Stucky, Galen; Waite, J. Herbert

    2009-01-01

    We present the first study of quantifying the diffusion coefficient of interfacial water on polyelectrolyte surfaces of systems fully dispersed in bulk water under ambient conditions. Such measurements were made possible through the implementation of a recently introduced Dynamic Nuclear Polarization (DNP) technique to selectively amplify the nuclear magnetic resonance (NMR) signal of hydration water that is interacting with specifically located spin labels on polyelectrolyte surfaces. The merit of this novel capability is demonstrated in this report through the measurement of solvent microvisosity on the surface of two types of oppositely charged polyelectrolytes, when freely dissolved versus when complexed to form a liquid-liquid colloidal phase called complex coacervates. These complex coacervates were formed through electrostatic complexation between the imidazole-based cationic homopolymer poly(N-vinylimidazole) (PVIm), and anionic polypeptide polyaspartate (PAsp) in the pH range of 4.5 – 6.0, under which conditions the coacervate droplets are highly fluidic yet densely packed with polyelectrolytes. We also investigated the rotational diffusion coefficients of the spin labels covalently bound to the polyelectrolyte chains for both PVIm and PAsp, showing a 5 fold change in the rotational correlation time as well as anisotropy parameter upon coacervation, which represents a surprisingly small decrease given the high polymer concentration inside the dense microdroplets. For both DNP and ESR experiments, the polymers were covalently tagged with stable nitroxide radical spin labels (∼1 wt %) to probe the local solvent and polymer segment dynamics. We found that the surface water diffusion coefficients near uncomplexed PVIm and PAsp at pH 8 differ, and are around D∼1.3×10−9 m2 / s. In contrast, inside the complex coacervate phase, the water diffusion coefficient in the immediate vicinity of either polyelectrolyte was D∼ 0.25×10−9 m2 / s, which is about

  1. The multi-configuration electron-nuclear dynamics method applied to LiH.

    PubMed

    Ulusoy, Inga S; Nest, Mathias

    2012-02-07

    The multi-configuration electron-nuclear dynamics (MCEND) method is a nonadiabatic quantum dynamics approach to the description of molecular processes. MCEND is a combination of the multi-configuration time-dependent Hartree (MCTDH) method for atoms and its antisymmetrized equivalent MCTDHF for electrons. The purpose of this method is to simultaneously describe nuclear and electronic wave packets in a quantum dynamical way, without the need to calculate potential energy surfaces and diabatic coupling functions. In this paper we present first exemplary calculations of MCEND applied to the LiH molecule, and discuss computational and numerical details of our implementation.

  2. Role of electron-nuclear coupled dynamics on charge migration induced by attosecond pulses in glycine

    NASA Astrophysics Data System (ADS)

    Lara-Astiaso, Manuel; Palacios, Alicia; Decleva, Piero; Tavernelli, Ivano; Martín, Fernando

    2017-09-01

    We present a theoretical study of charge dynamics initiated by an attosecond XUV pulse in the glycine molecule, which consists in delocalized charge fluctuations all over the molecular skeleton. For this, we have explicitly used the actual electron wave packet created by such a broadband pulse. We show that, for the chosen pulse, charge dynamics in glycine is barely affected by nuclear motion or non adiabatic effects during the first 8 fs, and that the initial electronic coherences do not dissipate during the first 20 fs. In contrast, small variations in the initial nuclear positions, compatible with the geometries expected in the Franck-Condon region, lead to noticeable changes in this dynamics.

  3. Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence

    NASA Astrophysics Data System (ADS)

    Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.; Malhado, João Pedro

    2017-02-01

    Knowledge about the electronic motion in molecules is essential for our understanding of chemical reactions and biological processes. The advent of attosecond techniques opens up the possibility to induce electronic motion, observe it in real time, and potentially steer it. A fundamental question remains the factors influencing electronic decoherence and the role played by nuclear motion in this process. Here, we simulate the dynamics upon ionization of the polyatomic molecules paraxylene and modified bismethylene-adamantane, with a quantum mechanical treatment of both electron and nuclear dynamics using the direct dynamics variational multiconfigurational Gaussian method. Our simulations give new important physical insights about the expected decoherence process. We have shown that the decoherence of electron dynamics happens on the time scale of a few femtoseconds, with the interplay of different mechanisms: the dephasing is responsible for the fast decoherence while the nuclear overlap decay may actually help maintain it and is responsible for small revivals.

  4. Electron nuclear dynamics of LiH and HF in an intense laser field

    NASA Astrophysics Data System (ADS)

    Broeckhove, J.; Coutinho-Neto, M. D.; Deumens, E.; Öhrn, Y.

    1997-12-01

    The electron nuclear dynamics theory (END) extended to include a time-dependent external field is briefly described. The dynamical equations, in addition to the full electron nuclear coupling terms, now also contain the interactions of both the nuclei and the electrons with the external field. This extended END theory is applied to the study of vibrational excitations of the simple diatomics HF and LiH. The END results using an intense infrared laser field are compared with those of molecular dynamics as well as those from quantum wave-packet calculations. While the effect of the nonadiabatic electron-nuclear coupling terms on the vibrational dynamics is negligible for the chosen application, the electron-field coupling has a significant impact.

  5. Loss of lamin A function increases chromatin dynamics in the nuclear interior

    NASA Astrophysics Data System (ADS)

    Bronshtein, I.; Kepten, E.; Kanter, I.; Berezin, S.; Lindner, M.; Redwood, Abena B.; Mai, S.; Gonzalo, S.; Foisner, R.; Shav-Tal, Y.; Garini, Y.

    2015-08-01

    Chromatin is organized in a highly ordered yet dynamic manner in the cell nucleus, but the principles governing this organization remain unclear. Similarly, it is unknown whether, and how, various proteins regulate chromatin motion and as a result influence nuclear organization. Here by studying the dynamics of different genomic regions in the nucleus of live cells, we show that the genome has highly constrained dynamics. Interestingly, depletion of lamin A strikingly alters genome dynamics, inducing a dramatic transition from slow anomalous diffusion to fast and normal diffusion. In contrast, depletion of LAP2α, a protein that interacts with lamin A and chromatin, has no such effect on genome dynamics. We speculate that chromosomal inter-chain interactions formed by lamin A throughout the nucleus contribute to chromatin dynamics, and suggest that the molecular regulation of chromatin diffusion by lamin A in the nuclear interior is critical for the maintenance of genome organization.

  6. Coal-fired propulsion system dynamics. Volume III. Dynamic analysis of the cv-3600. Final report

    SciTech Connect

    Greenlee, T.L.; Pearsons, J.L.

    1982-12-01

    This volume summarizes the results of a thorough analysis of the CV-3600 dynamic model that was discussed in Volume II. The purpose of this effort was to determine general engineering details and specifications for coal-fired propulsion systems based on a detailed analysis of a specific propulsion system design. The basis for these specifications included the sensitivity of ship propulsion system response to component parameter and control variations such as grate travel speed and controls, spreader and distributor feed and controls, fan speed and damper controls, steam dump (sizing, control valve characteristics and controls), feedwater pump controls (drum level controls), throttle control, and desuperheater steam attemperation controls. To develop greater insight into the effects of these variations, both open-loop (without control) and closed-loop (with control) versions of the propulsion system were studied. The open and closed-loop responses were further analyzed through the use of linear models and eigenvalue analyses. Specific conclusions regarding desirable trends in component specification are provided as part of the conclusions in this volume.

  7. Dynamics of Synoptic Eddy and Low-Frequency Flow Interaction. Part III: Baroclinic Model Results.

    NASA Astrophysics Data System (ADS)

    Pan, L.-L.; Jin, F.-F.; Watanabe, M.

    2006-07-01

    In this three-part study, a linear closure has been developed for the synoptic eddy and low-frequency flow (SELF) interaction and demonstrated that internal dynamics plays an important role in generating the leading low-frequency modes in the extratropical circulation anomalies during cold seasons.In Part III, a new linearized primitive equation system is first derived for time-mean flow anomalies. The dynamical operator of the system includes a traditional part depending on the observed climatological mean state and an additional part from the SELF feedback closure utilizing the observed climatological properties of synoptic eddy activity. The latter part relates nonlocally all the anomalous eddy-forcing terms in equations of momentum, temperature, and surface pressure to the time-mean flow anomalies. Using the observational data, the closure was validated with reasonable success, and it was found that terms of the SELF feedback in the momentum and pressure equations tend to reinforce the low-frequency modes, whereas those in the thermodynamic equation tends to damp the temperature anomalies to make the leading modes equivalent barotropic. Through singular vector analysis of the linear dynamical operator, it is highlighted that the leading modes of the system resemble the observed patterns of the Arctic Oscillation, Antarctic Oscillation, and Pacific North American pattern, in which the SELF feedback plays an essential role, consistent with the finding of the barotropic model study in Part II.


  8. Dynamical structure of solar radio burst type III as evidence of energy of solar flares

    NASA Astrophysics Data System (ADS)

    Hamidi, Zety Sharizat Binti

    2013-11-01

    Observations of low frequency solar type III radio bursts associated with the ejection of plasma oscillations localized disturbance is due to excitation atoms in the plasma frequency incoherent radiations play a dominant role at the meter and decimeter wavelengths. Here, we report the results of the dynamical structure of solar flare type III that occurred on 9th March 2012 at National Space Centre, Sg Lang, Selangor, Malaysia by using the CALLISTO system. These bursts are associated with solar flare type M6 which suddenly ejected in the active region AR 1429 starting at 03:32 UT and ending at 05:00 UT with the peak at 04:12 UT. The observation showed an initial strong burst occurred due to strong signal at the beginning of the phase. We also found that both solar burst and flares tend to be a numerous on the same day and probability of chance coincidence is high. It is clearly seen that an impulsive lace burst was detected at 4:24 UT and it is more plausible that the energies are confined to the top of the loop when we compared with X-ray results. Associated with this event was type II with velocities 1285 km/s and type IV radio sweeps along with a full halo Coronal Mass Ejections (CMEs) first seen in SOHO/LASCO C2 imagery at 09/0426 Z. We concluded that the significance of study solar burst type III lies in the fact that the emission at decimetric wavelength comes from the role of magnetic field in active region that may provide the key to the energy release mechanism in a flare.

  9. Dynamic changes in morphometric analysis in patients following Class III bimaxillary surgery.

    PubMed

    Downarowicz, Patrycja; Matthews-Brzozowska, Teresa; Kawala, Beata; Drohomyretska, Myroslava

    2012-01-01

    Prognathism of the mandible is a skeletal Class III abnormality, caused either by excessive forward growth of the mandible or maxillary underdevelopment. The aim of the study was to assess dynamic changes in morphometric analysis on subjects presenting with Class III malocclusions before orthodontic treatment, before bimaxillary surgery and after surgery. The sample consisted of 30 non-growing patients, at the age of 18 to 30, treated with mandibular set-back sagittal split osteotomy and maxillary Le Fort I advancement. Cephalometric analysis by Segner and Hasund was performed. Lateral cephalograms were taken at the beginning of orthodontic treatment (T0), immediately before surgery (T1) and at least 3-6 months after surgery (T2). The results showed that there was normalization of the cephalometric variables after surgery. In the sagittal plane the following skeletal changes were observed: preoperative anterior mandibular growth confirmed by SNB increased angle was significantly reduced after surgery; preoperative decreased SNA angle largely increased after surgery. Statistically significant GntgoAr mandible angle decreased after surgery in relation to the beginning state. Also, the H angle was increased as a result of orthodontic-surgical treatment which influenced positively on face esthetics. The results of our study indicate that there was a significant improvement in the correlation between soft and hard tissue change in the facial profiles of the Class III bimaxillary surgery patients, which was improved by the H angle. The face's photographs and cephalometric analysis indicate, after the operation there is a decrease of total face length, but the lower part still remains longer than a middle part of the face.

  10. Dynamical effects in the Coulomb expansion following nuclear fragmentation

    SciTech Connect

    Chung, K.C.; Donangelo, R.; Schechter, H.

    1987-09-01

    The effects of the Coulomb expansion on the fragment kinetic energy spectrum for a fragmentating hot nuclear system is investigated. In particular, /sup 12/C-fragment spectra are calculated and compared with those predicted by the uniform expansion approximation. The results indicate that the energy spectra of fragments are quite sensitive to the details of the Coulomb expansion treatment.

  11. Dynamic evaluation of a nuclear main steam isolation valve actuator

    SciTech Connect

    Patten, A.J.

    1981-09-01

    Architect and Engineering Specifications for ASME Section III, Class I values include seismic requirements of natural frequency determination of the valve and valve actuator. Detailed tests of the springs were conducted to evaluate the effect of these component resonators on the actuator assembly. The importance of using clear, concise definitions within contract documents is discussed as related to the interpretation of experimental results. 16 refs.

  12. Dynamic observation of phase transformation behaviors in indium(III) selenide nanowire based phase change memory.

    PubMed

    Huang, Yu-Ting; Huang, Chun-Wei; Chen, Jui-Yuan; Ting, Yi-Hsin; Lu, Kuo-Chang; Chueh, Yu-Lun; Wu, Wen-Wei

    2014-09-23

    Phase change random access memory (PCRAM) has been extensively investigated for its potential applications in next-generation nonvolatile memory. In this study, indium(III) selenide (In2Se3) was selected due to its high resistivity ratio and lower programming current. Au/In2Se3-nanowire/Au phase change memory devices were fabricated and measured systematically in an in situ transmission electron microscope to perform a RESET/SET process under pulsed and dc voltage swept mode, respectively. During the switching, we observed the dynamic evolution of the phase transformation process. The switching behavior resulted from crystalline/amorphous change and revealed that a long pulse width would induce the amorphous or polycrystalline state by different pulse amplitudes, supporting the improvement of the writing speed, retention, and endurance of PCRAM.

  13. Revival of the Intermolecular Nuclear Overhauser Effect for Mapping Local Protein Hydration Dynamics.

    PubMed

    Braun, Daniel; Schmollngruber, Michael; Steinhauser, Othmar

    2017-07-20

    The highly heterogeneous hydration dynamics of protein-water interfaces is considered important for protein stability and dynamics, protein folding, enzymatic activity, and even drug design. The nuclear Overhauser effect (NOE) between protein and water protons is the only experimental observable which, in principle, can provide a map of locally resolved hydration dynamics. However, its utility was questioned in various theoretical studies that emphasized the contributions of long-range NOE interactions. We show by a detailed analysis based on molecular dynamics simulations that, contrary to recent claims, the protein-water NOE is an excellent observable to map local hydration dynamics at the protein surface.

  14. Electron dynamics following photoionization: Decoherence due to the nuclear-wave-packet width

    NASA Astrophysics Data System (ADS)

    Vacher, Morgane; Steinberg, Lee; Jenkins, Andrew J.; Bearpark, Michael J.; Robb, Michael A.

    2015-10-01

    The advent of attosecond techniques opens up the possibility to observe experimentally electron dynamics following ionization of molecules. Theoretical studies of pure electron dynamics at single fixed nuclear geometries in molecules have demonstrated oscillatory charge migration at a well-defined frequency but often neglecting the natural width of the nuclear wave packet. The effect on electron dynamics of the spatial delocalization of the nuclei is an outstanding question. Here, we show how the inherent distribution of nuclear geometries leads to dephasing. Using a simple analytical model, we demonstrate that the conditions for a long-lived electronic coherence are a narrow nuclear wave packet and almost parallel potential-energy surfaces of the states involved. We demonstrate with numerical simulations the decoherence of electron dynamics for two real molecular systems (paraxylene and polycyclic norbornadiene), which exhibit different decoherence time scales. To represent the quantum distribution of geometries of the nuclear wave packet, the Wigner distribution function is used. The electron dynamics decoherence result has significant implications for the interpretation of attosecond spectroscopy experiments since one no longer expects long-lived oscillations.

  15. Dynamic Covalent Chemistry of Aldehyde Enamines: Bi(III) - and Sc(III) -Catalysis of Amine-Enamine Exchange.

    PubMed

    Zhang, Yang; Xie, Sheng; Yan, Mingdi; Ramström, Olof

    2017-09-04

    The dynamic exchange of enamines from secondary amines and enolizable aldehydes has been demonstrated in organic solvents. The enamine exchange with amines was efficiently catalyzed by Bi(OTf)3 and Sc(OTf)3 (2 mol %) and the equilibria (60 mm) could be attained within hours at room temperature. The formed dynamic covalent systems displayed high stabilities in basic environment with <2 % by-product formation within one week after complete equilibration. This study expands the scope of dynamic C-N bonds from imine chemistry to enamines, enabling further dynamic methodologies in exploration of this important class of structures in systems chemistry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Compartmental analysis of dynamic nuclear medicine data: models and identifiability

    NASA Astrophysics Data System (ADS)

    Delbary, Fabrice; Garbarino, Sara; Vivaldi, Valentina

    2016-12-01

    Compartmental models based on tracer mass balance are extensively used in clinical and pre-clinical nuclear medicine in order to obtain quantitative information on tracer metabolism in the biological tissue. This paper is the first of a series of two that deal with the problem of tracer coefficient estimation via compartmental modelling in an inverse problem framework. Specifically, here we discuss the identifiability problem for a general n-dimension compartmental system and provide uniqueness results in the case of two-compartment and three-compartment compartmental models. The second paper will utilize this framework in order to show how nonlinear regularization schemes can be applied to obtain numerical estimates of the tracer coefficients in the case of nuclear medicine data corresponding to brain, liver and kidney physiology.

  17. Dynamical in situ nuclear-magnetic-resonance tensile apparatus

    NASA Astrophysics Data System (ADS)

    Hackelöer, H. J.; Kanert, O.; Tamler, H.; De Hosson, J. Th. M.

    1983-03-01

    A combination of a servohydraulic tensile machine and NMR pulse spectrometer is described enabling nuclear-spin relaxation rates to be recorded simultaneously with stress-strain data incorporating tension as well as compression of nonmetallic as well as of metallic samples. The data of the mechanical system are as follows: Maximum load: 5000 N; minimum deformation speed: 10 μm s-1, maximum deformation speed: 3×105 μm s-1; deformation stroke: digitally controlled between 1 and 8×103 μm; bandwidth: dc to 1 kHz; resolution: 2-4 μm; temperature conditions of the sample: from 80 to 570 K. The operation and performance of the system is described by means of experiments observing nuclear-spin relaxation rates which are induced by the movement of dislocations due to the finite deformation rate of the sample.

  18. JINA Workshop Nuclear Physics in Hot Dense Dynamic Plasmas

    SciTech Connect

    Kritcher, A L; Cerjan, C; Landen, O; Libby, S; Chen, M; Wilson, B; Knauer, J; Mcnabb, D; Caggiano, J; Bleauel, D; Weideking, M; Kozhuharov, C; Brandau, C; Stoehlker, T; Meot, V; Gosselin, G; Morel, P; Schneider, D; Bernstein, L A

    2011-03-07

    Measuring NEET and NEEC is relevant for probing stellar cross-sections and testing atomic models in hot plasmas. Using NEEC and NEET we can excite nuclear levels in laboratory plasmas: (1) NIF: Measure effect of excited nuclear levels on (n,{gamma}) cross-sections, 60% and never been measured; (2) Omega, Test cross-sections for creating these excited levels via NEEC and NEET. Will allow us to test models that estimate resonance overlap of atomic states with the nucleus: (1) Average Atom model (AA) (CEA&LLNL), single average wave-function potential; (2) Super Transition Array (STA) model (LLNL), More realistic individual configuration potentials NEET experimental data is scarce and not in a plasma environment, NEEC has not yet been observed.

  19. Dynamic Computer Model of a Stirling Space Nuclear Power System

    DTIC Science & Technology

    2006-05-04

    I would like to thank all Naval Academy faculty involved with the Trident Scholar program . The committee readers (Professors Cerza, Nakos, and...obstacles in structural integrity , stowing for launch, deployment in orbit, and sun pointing that are far from being solved with current technology. 6...the Systems for Nuclear Auxiliary Power (SNAP) program . This program resulted in the only reactor flown in space by the United States. Also, Russia

  20. Automatic Nuclear Segmentation Using Multiscale Radial Line Scanning With Dynamic Programming.

    PubMed

    Xu, Hongming; Lu, Cheng; Berendt, Richard; Jha, Naresh; Mandal, Mrinal

    2017-10-01

    In the diagnosis of various cancers by analyzing histological images, automatic nuclear segmentation is an important step. However, nuclear segmentation is a difficult problem because of overlapping nuclei, inhomogeneous staining, and presence of noisy pixels and other tissue components. In this paper, we present an automatic technique for nuclear segmentation in skin histological images. The proposed technique first applies a bank of generalized Laplacian of Gaussian kernels to detect nuclear seeds. Based on the detected nuclear seeds, a multiscale radial line scanning method combined with dynamic programming is applied to extract a set of candidate nuclear boundaries. The gradient, intensity, and shape information are then integrated to determine the optimal boundary for each nucleus in the image. Nuclear overlap limitation is finally imposed based on a Dice coefficient measure such that the obtained nuclear contours do not severely intersect with each other. Experiments have been thoroughly performed on two datasets with H&E and Ki-67 stained images, which show that the proposed technique is superior to conventional schemes of nuclear segmentation.

  1. 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.

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

    DOE PAGES

    Kobayashi, Takeshi; Perras, Frédéric A.; Slowing, Igor I.; ...

    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.

  3. Electron-Nuclear Dynamics of collision processes: Charge exchange and energy loss

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, Remigio; Sabin, John R.; Öhrn, Yngve; Deumens, Erik

    2004-03-01

    We present the Electron-Nuclear Dynamics (END) method for the study of time-dependent scattering processes. The END is a general approach for treating time-dependent problems which includes the dynamics of electrons and nuclei simultaneously by considering the full electron-nuclear coupling in the system and thus eliminates the necessity of constructing potential-energy surfaces. The theory approximates the time dependent Schrödinger equation starting from the time dependent variational principle by deriving a Hamiltonian dynamical system for time dependent nuclear and electronic wave function parameters. The wave function is described in a coherent state manifold, which leads to a system of Hamilton's equations of motion. Emphasis is put on electron exchange, differential cross section and energy loss (stopping cross section) of collision of ions, atoms and molecules involving H, He, C, N, O, and Ne atoms. We compare our results to available experimental data.

  4. Efficient and dynamic nuclear localization of green fluorescent protein via RNA binding

    SciTech Connect

    Kitamura, Akira; Nakayama, Yusaku; Kinjo, Masataka

    2015-07-31

    Classical nuclear localization signal (NLS) sequences have been used for artificial localization of green fluorescent protein (GFP) in the nucleus as a positioning marker or for measurement of the nuclear-cytoplasmic shuttling rate in living cells. However, the detailed mechanism of nuclear retention of GFP-NLS remains unclear. Here, we show that a candidate mechanism for the strong nuclear retention of GFP-NLS is via the RNA-binding ability of the NLS sequence. GFP tagged with a classical NLS derived from Simian virus 40 (GFP-NLS{sup SV40}) localized not only in the nucleoplasm, but also to the nucleolus, the nuclear subdomain in which ribosome biogenesis takes place. GFP-NLS{sup SV40} in the nucleolus was mobile, and intriguingly, the diffusion coefficient, which indicates the speed of diffusing molecules, was 1.5-fold slower than in the nucleoplasm. Fluorescence correlation spectroscopy (FCS) analysis showed that GFP-NLS{sup SV40} formed oligomers via RNA binding, the estimated molecular weight of which was larger than the limit for passive nuclear export into the cytoplasm. These findings suggest that the nuclear localization of GFP-NLS{sup SV40} likely results from oligomerization mediated via RNA binding. The analytical technique used here can be applied for elucidating the details of other nuclear localization mechanisms, including those of several types of nuclear proteins. In addition, GFP-NLS{sup SV40} can be used as an excellent marker for studying both the nucleoplasm and nucleolus in living cells. - Highlights: • Nuclear localization signal-tagged GFP (GFP-NLS) showed clear nuclear localization. • The GFP-NLS dynamically localized not only in the nucleoplasm, but also to the nucleolus. • The nuclear localization of GFP-NLS results from transient oligomerization mediated via RNA binding. • Our NLS-tagging procedure is ideal for use in artificial sequestration of proteins in the nucleus.

  5. System analysis shows distinct mechanisms and common principles of nuclear envelope protein dynamics

    PubMed Central

    Zuleger, Nikolaj; Kelly, David A.; Richardson, A. Christine; Kerr, Alastair R. W.; Goldberg, Martin W.; Goryachev, Andrew B.

    2011-01-01

    The nuclear envelope contains >100 transmembrane proteins that continuously exchange with the endoplasmic reticulum and move within the nuclear membranes. To better understand the organization and dynamics of this system, we compared the trafficking of 15 integral nuclear envelope proteins using FRAP. A surprising 30-fold range of mobilities was observed. The dynamic behavior of several of these proteins was also analyzed after depletion of ATP and/or Ran, two functions implicated in endoplasmic reticulum–inner nuclear membrane translocation. This revealed that ATP- and Ran-dependent translocation mechanisms are distinct and not used by all inner nuclear membrane proteins. The Ran-dependent mechanism requires the phenylalanine-glycine (FG)-nucleoporin Nup35, which is consistent with use of the nuclear pore complex peripheral channels. Intriguingly, the addition of FGs to membrane proteins reduces FRAP recovery times, and this also depends on Nup35. Modeling of three proteins that were unaffected by either ATP or Ran depletion indicates that the wide range in mobilities could be explained by differences in binding affinities in the inner nuclear membrane. PMID:21444689

  6. A time-correlation function approach to nuclear dynamical effects in X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Karsten, Sven; Bokarev, Sergey I.; Aziz, Saadullah G.; Ivanov, Sergei D.; Kühn, Oliver

    2017-06-01

    Modern X-ray spectroscopy has proven itself as a robust tool for probing the electronic structure of atoms in complex environments. Despite working on energy scales that are much larger than those corresponding to nuclear motions, taking nuclear dynamics and the associated nuclear correlations into account may be of importance for X-ray spectroscopy. Recently, we have developed an efficient protocol to account for nuclear dynamics in X-ray absorption and resonant inelastic X-ray scattering spectra [Karsten et al., J. Phys. Chem. Lett. 8, 992 (2017)], based on ground state molecular dynamics accompanied with state-of-the-art calculations of electronic excitation energies and transition dipoles. Here, we present an alternative derivation of the formalism and elaborate on the developed simulation protocol using gas phase and bulk water as examples. The specific spectroscopic features stemming from the nuclear motions are analyzed and traced down to the dynamics of electronic energy gaps and transition dipole correlation functions. The observed tendencies are explained on the basis of a simple harmonic model, and the involved approximations are discussed. The method represents a step forward over the conventional approaches that treat the system in full complexity and provides a reasonable starting point for further improvements.

  7. 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

    2015-07-17

    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.

  8. 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

  9. Quantum Trajectory-Electronic Structure Approach for Exploring Nuclear Effects in the Dynamics of Nanomaterials.

    PubMed

    Garashchuk, Sophya; Jakowski, Jacek; Wang, Lei; Sumpter, Bobby G

    2013-12-10

    A massively parallel, direct quantum molecular dynamics method is described. The method combines a quantum trajectory (QT) representation of the nuclear wave function discretized into an ensemble of trajectories with an electronic structure (ES) description of electrons, namely using the density functional tight binding (DFTB) theory. Quantum nuclear effects are included into the dynamics of the nuclei via quantum corrections to the classical forces. To reduce computational cost and increase numerical accuracy, the quantum corrections to dynamics resulting from localization of the nuclear wave function are computed approximately and included into selected degrees of freedom representing light particles where the quantum effects are expected to be the most pronounced. A massively parallel implementation, based on the message passing interface allows for efficient simulations of ensembles of thousands of trajectories at once. The QTES-DFTB dynamics approach is employed to study the role of quantum nuclear effects on the interaction of hydrogen with a model graphene sheet, revealing that neglect of nuclear effects can lead to an overestimation of adsorption.

  10. 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.

  11. A Model for Electron Nuclear Dynamics of a Monatomic Chain

    DTIC Science & Technology

    1994-05-16

    density in cell m) and that on atom n. Due to the choice of basis functions these parameters depend on the di tane In3 - fI -- R but not on the...p2Msaers and t&e choice of basis functions in this time-dependent *hWry. The res Iul ing equations of moioon include eACcvOnic-vibrational couplings...of basis functions in molecular or crystal orbitals, or of "nuclear" type, i.e. characterizn the state vectors for the nuclei. The method has the

  12. Impact of pion dynamics on nuclear shell structure

    NASA Astrophysics Data System (ADS)

    Litvinova, Elena

    2015-10-01

    Spin-isospin response in exotic nuclear systems is investigated. It is found that in some nuclei excitations with pionic quantum numbers (0-, 1+, 2-, …) appear at very low energies with large transition probabilities, which is an indication of the vicinity of the onset of pion condensation. As an example, 2- components of the spin-dipole resonance in 78Ni and 132Sn are considered. The existence of such modes points out to the necessity of taking into account their coupling to other elementary modes of excitation, e.g. single-quasiparticle ones. This coupling is introduced in the theory for the first time. Thereby, both rho-meson and pion-exchange contributions to the nucleon-nucleon interaction are included in the relativistic framework beyond the Hartree-Fock approximation. Namely, classes of Feynman diagrams are selected according to their significance for nuclear spectroscopic characteristics, such as single-particle energies and strength functions, and included into the nucleonic self-energy in all orders of meson-exchange. As an illustration, the impact of these new contributions on the single-particle energies of 100Sn is discussed.

  13. Impact of pion dynamics on nuclear shell structure

    SciTech Connect

    Litvinova, Elena

    2015-10-15

    Spin-isospin response in exotic nuclear systems is investigated. It is found that in some nuclei excitations with pionic quantum numbers (0{sup −}, 1{sup +}, 2{sup −}, …) appear at very low energies with large transition probabilities, which is an indication of the vicinity of the onset of pion condensation. As an example, 2{sup −} components of the spin-dipole resonance in {sup 78}Ni and {sup 132}Sn are considered. The existence of such modes points out to the necessity of taking into account their coupling to other elementary modes of excitation, e.g. single-quasiparticle ones. This coupling is introduced in the theory for the first time. Thereby, both rho-meson and pion-exchange contributions to the nucleon-nucleon interaction are included in the relativistic framework beyond the Hartree-Fock approximation. Namely, classes of Feynman diagrams are selected according to their significance for nuclear spectroscopic characteristics, such as single-particle energies and strength functions, and included into the nucleonic self-energy in all orders of meson-exchange. As an illustration, the impact of these new contributions on the single-particle energies of {sup 100}Sn is discussed.

  14. Molecular dynamics-based selectivity for Fast-Field-Cycling relaxometry by Overhauser and solid effect dynamic nuclear polarization.

    PubMed

    Neudert, Oliver; Mattea, Carlos; Stapf, Siegfried

    2017-03-01

    In the last decade nuclear spin hyperpolarization methods, especially Dynamic Nuclear Polarization (DNP), have provided unprecedented possibilities for various NMR techniques by increasing the sensitivity by several orders of magnitude. Recently, in-situ DNP-enhanced Fast Field Cycling (FFC) relaxometry was shown to provide appreciable NMR signal enhancements in liquids and viscous systems. In this work, a measurement protocol for DNP-enhanced NMR studies is introduced which enables the selective detection of nuclear spin hyperpolarized by either Overhauser effect or solid effect DNP. Based on field-cycled DNP and relaxation studies it is shown that these methods allow for the independent measurement of polymer and solvent nuclear spins in a concentrated solution of high molecular weight polybutadiene in benzene doped with α,γ-bisdiphenylene-β-phenylallyl radical. Appreciable NMR signal enhancements of about 10-fold were obtained for both constituents. Moreover, qualitative information about the dynamics of the radical and solvent was obtained. Selective DNP-enhanced FFC relaxometry is applied for the measurement of the (1)H nuclear magnetic relaxation dispersion of both constituents with improved precision. The introduced method is expected to greatly facilitate NMR studies of complex systems with multiple overlapping signal contributions that cannot be distinguished by standard methods. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Molecular dynamics-based selectivity for Fast-Field-Cycling relaxometry by Overhauser and solid effect dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Neudert, Oliver; Mattea, Carlos; Stapf, Siegfried

    2017-03-01

    In the last decade nuclear spin hyperpolarization methods, especially Dynamic Nuclear Polarization (DNP), have provided unprecedented possibilities for various NMR techniques by increasing the sensitivity by several orders of magnitude. Recently, in-situ DNP-enhanced Fast Field Cycling (FFC) relaxometry was shown to provide appreciable NMR signal enhancements in liquids and viscous systems. In this work, a measurement protocol for DNP-enhanced NMR studies is introduced which enables the selective detection of nuclear spin hyperpolarized by either Overhauser effect or solid effect DNP. Based on field-cycled DNP and relaxation studies it is shown that these methods allow for the independent measurement of polymer and solvent nuclear spins in a concentrated solution of high molecular weight polybutadiene in benzene doped with α,γ-bisdiphenylene-β-phenylallyl radical. Appreciable NMR signal enhancements of about 10-fold were obtained for both constituents. Moreover, qualitative information about the dynamics of the radical and solvent was obtained. Selective DNP-enhanced FFC relaxometry is applied for the measurement of the 1H nuclear magnetic relaxation dispersion of both constituents with improved precision. The introduced method is expected to greatly facilitate NMR studies of complex systems with multiple overlapping signal contributions that cannot be distinguished by standard methods.

  16. Studies in protein dynamics using heteronuclear nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vugmeyster, Liliya

    Dynamic processes in proteins are important for their biological function. Several issues in protein dynamics are addressed by applying existing NMR methodologies to investigate dynamics of several small proteins. Amide H/D exchange rates have been measured for the N-terminal domain of the ribosomal protein L9, residues 1--56. The results suggest that the structure of the domain is preserved in isolation and that the stability of the isolated domain is comparable to the stability of this domain in intact L9. Single domain proteins can fold in vitro at rates in excess of 1 x 104 s-1. Measurement of folding rates of this magnitude poses a considerable technical challenge. Off-resonance 15N R1rho measurements are shown to be capable of measuring such fast protein folding rates. The measurements were performed on a sample of the peripheral subunit-binding domain from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus 15N labeled at Ala 11. Fast intramolecular motions (on ps-ns time scale) can be studied by heteronuclear laboratory frame NMR relaxation. The temperature dependence of the backbone dynamics of the 36-resiude subdomain of the F-actin bundling protein villin has been investigated by studying the temperature dependence of order parameters obtained from 15N relaxation measurements. The results support the hypothesis that one of the possible mechanisms of thermostability is to lower the heat capacity difference between the folded and unfolded states by lowering the contribution from the backbone dynamics. A commonly used model-free approach for the interpretation of the relaxation data for macromolecules in solution is modified to correct for the decoupling approximation between the overall and internal motions.

  17. Characterization of structure and dynamics of an aqueous scandium(III) ion by an extended ab initio QM/MM molecular dynamics simulation.

    PubMed

    Vchirawongkwin, Viwat; Kritayakornupong, Chinapong; Tongraar, Anan; Rode, Bernd M

    2012-10-14

    Hydration structure and dynamics of an aqueous Sc(III) solution were characterized by means of an extended ab initio quantum mechanical/molecular dynamical (QM/MM) molecular dynamics simulation at Hartree-Fock level. A monocapped trigonal prismatic structure composed of seven water molecules surrounding scandium(III) ion was proposed by the QM/MM simulation including the quantum mechanical effects for the first and second hydration shells. The mean Sc(III)-O bond length of 2.14 Å was identified for six prism water molecules with one capping water located at around 2.26 Å, reproducing well the X-ray diffraction data. The Sc(III)-O stretching frequency of 432 cm(-1) corresponding to a force constant of 130 N m(-1), evaluated from the enlarged QM/MM simulation, is in good agreement with the experimentally determined value of 430 cm(-1) (128 N m(-1)). Various water exchange processes in the second hydration shell of the hydrated Sc(III) ion predict a mean ligand residence time of 7.3 ps.

  18. Correlated electron-nuclear dynamics with conditional wave functions.

    PubMed

    Albareda, Guillermo; Appel, Heiko; Franco, Ignacio; Abedi, Ali; Rubio, Angel

    2014-08-22

    The molecular Schrödinger equation is rewritten in terms of nonunitary equations of motion for the nuclei (or electrons) that depend parametrically on the configuration of an ensemble of generally defined electronic (or nuclear) trajectories. This scheme is exact and does not rely on the tracing out of degrees of freedom. Hence, the use of trajectory-based statistical techniques can be exploited to circumvent the calculation of the computationally demanding Born-Oppenheimer potential-energy surfaces and nonadiabatic coupling elements. The concept of the potential-energy surface is restored by establishing a formal connection with the exact factorization of the full wave function. This connection is used to gain insight from a simplified form of the exact propagation scheme.

  19. The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass

    NASA Astrophysics Data System (ADS)

    Chatzopoulos, S.; Fritz, T. K.; Gerhard, O.; Gillessen, S.; Wegg, C.; Genzel, R.; Pfuhl, O.

    2015-02-01

    We derive new constraints on the mass, rotation, orbit structure, and statistical parallax of the Galactic old nuclear star cluster and the mass of the supermassive black hole. We combine star counts and kinematic data from Fritz et al., including 2500 line-of-sight velocities and 10 000 proper motions obtained with VLT instruments. We show that the difference between the proper motion dispersions σl and σb cannot be explained by rotation, but is a consequence of the flattening of the nuclear cluster. We fit the surface density distribution of stars in the central 1000 arcsec by a superposition of a spheroidal cluster with scale ˜100 arcsec and a much larger nuclear disc component. We compute the self-consistent two-integral distribution function f(E, Lz) for this density model, and add rotation self-consistently. We find that (i) the orbit structure of the f(E, Lz) gives an excellent match to the observed velocity dispersion profiles as well as the proper motion and line-of-sight velocity histograms, including the double-peak in the vl-histograms. (ii) This requires an axial ratio near q1 = 0.7 consistent with our determination from star counts, q1 = 0.73 ± 0.04 for r < 70 arcsec. (iii) The nuclear star cluster is approximately described by an isotropic rotator model. (iv) Using the corresponding Jeans equations to fit the proper motion and line-of-sight velocity dispersions, we obtain best estimates for the nuclear star cluster mass, black hole mass, and distance M*(r < 100 arcsec) = (8.94 ± 0.31|stat ± 0.9|syst) × 106 M⊙, M• = (3.86 ± 0.14|stat ± 0.4|syst) × 106 M⊙, and R0 = 8.27 ± 0.09|stat ± 0.1|syst kpc, where the estimated systematic errors account for additional uncertainties in the dynamical modelling. (v) The combination of the cluster dynamics with the S-star orbits around Sgr A* strongly reduces the degeneracy between black hole mass and Galactic Centre distance present in previous S-star studies. A joint statistical analysis with the

  20. Quantum dynamics of nuclear spins and spin relaxation in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Mkhitaryan, V. V.; Dobrovitski, V. V.

    2017-06-01

    We investigate the role of the nuclear-spin quantum dynamics in hyperfine-induced spin relaxation of hopping carriers in organic semiconductors. The fast-hopping regime, when the carrier spin does not rotate much between subsequent hops, is typical for organic semiconductors possessing long spin coherence times. We consider this regime and focus on a carrier random-walk diffusion in one dimension, where the effect of the nuclear-spin dynamics is expected to be the strongest. Exact numerical simulations of spin systems with up to 25 nuclear spins are performed using the Suzuki-Trotter decomposition of the evolution operator. Larger nuclear-spin systems are modeled utilizing the spin-coherent state P -representation approach developed earlier. We find that the nuclear-spin dynamics strongly influences the carrier spin relaxation at long times. If the random walk is restricted to a small area, it leads to the quenching of carrier spin polarization at a nonzero value at long times. If the random walk is unrestricted, the carrier spin polarization acquires a long-time tail, decaying as 1 /√{t } . Based on the numerical results, we devise a simple formula describing the effect quantitatively.

  1. Dynamic Behavior of Microtubules during Dynein-dependent Nuclear Migrations of Meiotic Prophase in Fission Yeast

    PubMed Central

    Yamamoto, Ayumu; Tsutsumi, Chihiro; Kojima, Hiroaki; Oiwa, Kazuhiro; Hiraoka, Yasushi

    2001-01-01

    During meiotic prophase in fission yeast, the nucleus migrates back and forth between the two ends of the cell, led by the spindle pole body (SPB). This nuclear oscillation is dependent on astral microtubules radiating from the SPB and a microtubule motor, cytoplasmic dynein. Here we have examined the dynamic behavior of astral microtubules labeled with the green fluorescent protein during meiotic prophase with the use of optical sectioning microscopy. During nuclear migrations, the SPB mostly follows the microtubules that extend toward the cell cortex. SPB migrations start when these microtubules interact with the cortex and stop when they disappear, suggesting that these microtubules drive nuclear migrations. The microtubules that are followed by the SPB often slide along the cortex and are shortened by disassembly at their ends proximal to the cortex. In dynein-mutant cells, where nuclear oscillations are absent, the SPB never migrates by following microtubules, and microtubule assembly/disassembly dynamics is significantly altered. Based on these observations, together with the frequent accumulation of dynein at a cortical site where the directing microtubules interact, we propose a model in which dynein drives nuclear oscillation by mediating cortical microtubule interactions and regulating the dynamics of microtubule disassembly at the cortex. PMID:11739791

  2. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule

    PubMed Central

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-01-01

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules. PMID:28218294

  3. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule.

    PubMed

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-02-20

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH(2+) by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH(2+) reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.

  4. Cell cycle-dependent alteration in NAC1 nuclear body dynamics and morphology

    NASA Astrophysics Data System (ADS)

    Wu, Pei-Hsun; Hung, Shen-Hsiu; Ren, Tina; Shih, Ie-Ming; Tseng, Yiider

    2011-02-01

    NAC1, a BTB/POZ family member, has been suggested to participate in maintaining the stemness of embryonic stem cells and has been implicated in the pathogenesis of human cancer. In ovarian cancer, NAC1 upregulation is associated with disease aggressiveness and with the development of chemoresistance. Like other BTB/POZ proteins, NAC1 forms discrete nuclear bodies in non-dividing cells. To investigate the biological role of NAC1 nuclear bodies, we characterized the expression dynamics of NAC1 nuclear bodies during different phases of the cell cycle. Fluorescence recovery after photobleaching assays revealed that NAC1 was rapidly exchanged between the nucleoplasm and NAC1 nuclear bodies in interphase cells. The number of NAC1 bodies significantly increased and their size decreased in the S phase as compared to the G0/G1 and G2 phases. NAC1 nuclear bodies disappeared and NAC1 became diffuse during mitosis. NAC1 nuclear bodies reappeared immediately after completion of mitosis. These results indicate that a cell cycle-dependent regulatory mechanism controls NAC1 body formation in the nucleus and suggest that NAC1 body dynamics are associated with mitosis or cytokinesis.

  5. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-02-01

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.

  6. Nuclear structure of 124Xe in dynamic PPQ model

    NASA Astrophysics Data System (ADS)

    Gupta, J. B.

    2014-07-01

    The Xe isotopes in the A = 130 region, with low quadrupole deformation β, are good examples of the γ-soft nuclei. Recent data of 124Xe exhibit well developed K-bands of ground, Kπ = 21+, 02+, 03+ and 41+. Its spectrum is studied in relation to the underlying dynamic symmetries. The absolute intra- and inter-band B (E2) values and the B (E2) ratios are compared with the theoretical predictions of the dynamic pairing plus quadrupole model in the microscopic approach, and the interacting boson model IBM-1. The potential energy surface illustrates the γ-soft character. The variation of inertia tensor over the (β , γ) space is studied, and the spread of the wave functions of three Iπ =0+ and two 2+ states over the (β , γ) space illustrate their varied character. Comparison is done with the dynamic symmetries of IBM for different bands. The O(6) symmetry breaking and preservation of the O(5) and O(6) symmetry are reviewed.

  7. Electron nuclear dynamics for a zig-zag chain of nitrogen atoms

    NASA Astrophysics Data System (ADS)

    Pohl, Anna; Calais, Jean-Louis

    1995-02-01

    We study the nitrogen zig-zag chain with two atoms per unit cell within the electron nuclear dynamics (END) formalism. This amounts to an approximate solution of the time-dependent Schrödinger equation for all the particles in the system. In the present approximation the nuclei are treated classically. The time dependence of the electronic motion is brought in through time-dependent linear combinations of fixed Bloch sums. This implies that the immediate mutual interaction between electronic and nuclear motion is taken into account. We investigate in particular the long-range terms of the interaction so as to arrive at convergent lattice sums. Before going to the general case when electronic and nuclear motion is coupled, we investigate the special cases of END traditional lattice dynamics and the random phase approximation (RPA) for the electrons.

  8. Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution

    NASA Astrophysics Data System (ADS)

    Gross, Simon; Barmet, Christoph; Dietrich, Benjamin E.; Brunner, David O.; Schmid, Thomas; Pruessmann, Klaas P.

    2016-12-01

    High-field magnets of up to tens of teslas in strength advance applications in physics, chemistry and the life sciences. However, progress in generating such high fields has not been matched by corresponding advances in magnetic field measurement. Based mostly on nuclear magnetic resonance, dynamic high-field magnetometry is currently limited to resolutions in the nanotesla range. Here we report a concerted approach involving tailored materials, magnetostatics and detection electronics to enhance the resolution of nuclear magnetic resonance sensing by three orders of magnitude. The relative sensitivity thus achieved amounts to 1 part per trillion (10-12). To exemplify this capability we demonstrate the direct detection and relaxometry of nuclear polarization and real-time recording of dynamic susceptibility effects related to human heart function. Enhanced high-field magnetometry will generally permit a fresh look at magnetic phenomena that scale with field strength. It also promises to facilitate the development and operation of high-field magnets.

  9. Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution.

    PubMed

    Gross, Simon; Barmet, Christoph; Dietrich, Benjamin E; Brunner, David O; Schmid, Thomas; Pruessmann, Klaas P

    2016-12-02

    High-field magnets of up to tens of teslas in strength advance applications in physics, chemistry and the life sciences. However, progress in generating such high fields has not been matched by corresponding advances in magnetic field measurement. Based mostly on nuclear magnetic resonance, dynamic high-field magnetometry is currently limited to resolutions in the nanotesla range. Here we report a concerted approach involving tailored materials, magnetostatics and detection electronics to enhance the resolution of nuclear magnetic resonance sensing by three orders of magnitude. The relative sensitivity thus achieved amounts to 1 part per trillion (10(-12)). To exemplify this capability we demonstrate the direct detection and relaxometry of nuclear polarization and real-time recording of dynamic susceptibility effects related to human heart function. Enhanced high-field magnetometry will generally permit a fresh look at magnetic phenomena that scale with field strength. It also promises to facilitate the development and operation of high-field magnets.

  10. Nuclear Dynamical Correlation Effects in X-ray Spectroscopy from a Theoretical Time-Domain Perspective.

    PubMed

    Karsten, Sven; Ivanov, Sergei D; Aziz, Saadullah G; Bokarev, Sergey I; Kühn, Oliver

    2017-03-02

    To date X-ray spectroscopy has become a routine tool that can reveal highly local and element-specific information on the electronic structure of atoms in complex environments. Here, we focus on nuclear dynamical correlation effects in X-ray spectra and develop a rigorous time-correlation function method employing ground state classical molecular dynamics simulations. The importance of nuclear correlation phenomena is demonstrated by comparison against the results from the conventional sampling approach performed on the same data set for gas phase water. In contrast to the first-order absorption, second-order resonant inelastic scattering spectra exhibit pronounced fingerprints of nuclear motions. The developed methodology is not biased to a particular electronic structure method and, owing to its generality, can be applied to, e.g., X-ray photoelectron and Auger spectroscopies.

  11. Quantum dynamical simulations for nuclear spin selective laser control of ortho- and para-fulvene.

    PubMed

    Belz, S; Grohmann, T; Leibscher, M

    2009-07-21

    In the present paper we explore the prospects for laser control of the photoinduced nonadiabatic dynamics of para- and ortho-fulvene with the help of quantum dynamical simulations. Previous investigations [Bearpark et al., J. Am. Chem. Soc. 118, 5253 (1996); Alfalah et al., J. Chem. Phys. 130, 124318 (2009)] show that photoisomerization of fulvene is hindered by ultrafast radiationless decay through a conical intersection at planar configuration. Here, we demonstrate that photoisomerization can nevertheless be initiated by damping unfavorable nuclear vibrations with properly designed laser pulses. Moreover, we show that the resulting intramolecular torsion is nuclear spin selective. The selectivity of the photoexcitation with respect to the nuclear spin isomers can be further enhanced by applying an optimized sequence of two laser pulses.

  12. Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution

    PubMed Central

    Gross, Simon; Barmet, Christoph; Dietrich, Benjamin E.; Brunner, David O.; Schmid, Thomas; Pruessmann, Klaas P.

    2016-01-01

    High-field magnets of up to tens of teslas in strength advance applications in physics, chemistry and the life sciences. However, progress in generating such high fields has not been matched by corresponding advances in magnetic field measurement. Based mostly on nuclear magnetic resonance, dynamic high-field magnetometry is currently limited to resolutions in the nanotesla range. Here we report a concerted approach involving tailored materials, magnetostatics and detection electronics to enhance the resolution of nuclear magnetic resonance sensing by three orders of magnitude. The relative sensitivity thus achieved amounts to 1 part per trillion (10−12). To exemplify this capability we demonstrate the direct detection and relaxometry of nuclear polarization and real-time recording of dynamic susceptibility effects related to human heart function. Enhanced high-field magnetometry will generally permit a fresh look at magnetic phenomena that scale with field strength. It also promises to facilitate the development and operation of high-field magnets. PMID:27910860

  13. Communication: Adiabatic and non-adiabatic electron-nuclear motion: Quantum and classical dynamics.

    PubMed

    Albert, Julian; Kaiser, Dustin; Engel, Volker

    2016-05-07

    Using a model for coupled electronic-nuclear motion we investigate the range from negligible to strong non-adiabatic coupling. In the adiabatic case, the quantum dynamics proceeds in a single electronic state, whereas for strong coupling a complete transition between two adiabatic electronic states takes place. It is shown that in all coupling regimes the short-time wave-packet dynamics can be described using ensembles of classical trajectories in the phase space spanned by electronic and nuclear degrees of freedom. We thus provide an example which documents that the quantum concept of non-adiabatic transitions is not necessarily needed if electronic and nuclear motion is treated on the same footing.

  14. Widths of K¯-nuclear deeply bound states in a dynamical model

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Friedman, E.; Gal, A.

    2005-01-01

    The relativistic mean field (RMF) model is applied to a system of nucleons and a Kbar meson, interacting via scalar and vector boson fields. The model incorporates the standard RMF phenomenology for bound nucleons and, for the Kbar meson, it relates to low-energy Kbar N and K- atom phenomenology. Deeply bound Kbar nuclear states are generated dynamically across the periodic table and are exhibited for 12C and 16O over a wide range of binding energies. Substantial polarization of the core nucleus is found for these light nuclei. Absorption modes are also included dynamically, considering explicitly both the resulting compressed nuclear density and the reduced phase space for Kbar absorption from deeply bound states. The behavior of the calculated width as function of the Kbar binding energy is studied in order to explore limits on the possible existence of narrow Kbar nuclear states.

  15. Manipulation of dynamic nuclear spin polarization in single quantum dots by photonic environment engineering

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

    Optically induced dynamic nuclear spin polarization (DNP) in a semiconductor quantum dot (QD) requires many cycles of excitation of spin polarized carriers and carrier recombination. As such, the radiative lifetime of the exciton containing the electron becomes one of the limiting factors of DNP. In principle, changing the radiative lifetime of the exciton will affect DNP and thus the nuclear spin polarization. Here, we demonstrate the manipulation of DNP in single QDs through the engineering of the photonic environment using two-dimensional photonic crystals. We find that the achievable degree of nuclear spin polarization can be controlled through the modification of exciton radiative lifetime. Our results show the promise of achieving a higher degree of nuclear spin polarization via photonic environment engineering, with implications on spin-based quantum information processing.

  16. MarsSedEx III: linking Computational Fluid Dynamics (CFD) and reduced gravity experiments

    NASA Astrophysics Data System (ADS)

    Kuhn, N. J.; Kuhn, B.; Gartmann, A.

    2015-12-01

    Nikolaus J. Kuhn (1), Brigitte Kuhn (1), and Andres Gartmann (2) (1) University of Basel, Physical Geography, Environmental Sciences, Basel, Switzerland (nikolaus.kuhn@unibas.ch), (2) Meteorology, Climatology, Remote Sensing, Environmental Sciences, University of Basel, Switzerland Experiments conducted during the MarsSedEx I and II reduced gravity experiments showed that using empirical models for sediment transport on Mars developed for Earth violates fluid dynamics. The error is caused by the interaction between runing water and sediment particles, which affect each other in a positive feedback loop. As a consequence, the actual flow conditions around a particle cannot be represented by drag coefficients derived on Earth. This study exmines the implications of such gravity effects on sediment movement on Mars, with special emphasis on the limits of sandstones and conglomerates formed on Earth as analogues for sedimentation on Mars. Furthermore, options for correctiong the errors using a combination of CFD and recent experiments conducted during the MarsSedEx III campaign are presented.

  17. The Meiotic Nuclear Lamina Regulates Chromosome Dynamics and Promotes Efficient Homologous Recombination in the Mouse

    PubMed Central

    Schmitt, Johannes; Göb, Eva; Baar, Johannes; Ortega, Sagrario; Benavente, Ricardo; Alsheimer, Manfred

    2013-01-01

    The nuclear lamina is the structural scaffold of the nuclear envelope and is well known for its central role in nuclear organization and maintaining nuclear stability and shape. In the past, a number of severe human disorders have been identified to be associated with mutations in lamins. Extensive research on this topic has provided novel important clues about nuclear lamina function. These studies have contributed to the knowledge that the lamina constitutes a complex multifunctional platform combining both structural and regulatory functions. Here, we report that, in addition to the previously demonstrated significance for somatic cell differentiation and maintenance, the nuclear lamina is also an essential determinant for germ cell development. Both male and female mice lacking the short meiosis-specific A-type lamin C2 have a severely defective meiosis, which at least in the male results in infertility. Detailed analysis revealed that lamin C2 is required for telomere-driven dynamic repositioning of meiotic chromosomes. Loss of lamin C2 affects precise synapsis of the homologs and interferes with meiotic double-strand break repair. Taken together, our data explain how the nuclear lamina contributes to meiotic chromosome behaviour and accurate genome haploidization on a mechanistic level. PMID:23382700

  18. Dynamic Operations Wayfinding System (DOWS) for Nuclear Power Plants

    SciTech Connect

    Boring, Ronald Laurids; Ulrich, Thomas Anthony; Lew, Roger Thomas

    2015-08-01

    A novel software tool is proposed to aid reactor operators in respond- ing to upset plant conditions. The purpose of the Dynamic Operations Wayfind- ing System (DOWS) is to diagnose faults, prioritize those faults, identify paths to resolve those faults, and deconflict the optimal path for the operator to fol- low. The objective of DOWS is to take the guesswork out of the best way to combine procedures to resolve compound faults, mitigate low threshold events, or respond to severe accidents. DOWS represents a uniquely flexible and dy- namic computer-based procedure system for operators.

  19. Dynamics of Nuclear DNA Quantities during Zygote Development in Barley.

    PubMed Central

    Mogensen, H. L.; Holm, P. B.

    1995-01-01

    Quantities of DNA were estimated in the nuclei of mechanically isolated egg and zygote protoplasts in two cultivars of barley using 4[prime],6-diamidino-2-phenylindole staining and microfluorometry. Unlike many previous studies on DNA amounts within the sex cells of flowering plants, we obtained consistent and unambiguous results indicating that the egg and sperm nuclei are at the 1C DNA level (basic haploid amount) at the time of karyogamy. Karyogamy was initiated within 60 min postpollination, and the male chromatin became completely integrated into the egg nucleus within 6 to 7 hr postpollination (hpp). Zygotic nuclear DNA levels began to increase at ~9 to 12 hpp in cultivar Alexis and at 12 to 15 hpp in cultivar Igri. The 4C DNA complement was reached in most zygotes by 22 to 26 hpp in cultivar Alexis and by 23 to 29 hpp in cultivar Igri. These data are fundamental to a better understanding of fertilization and zygote maturation in flowering plants. They are also relevant to studies in which the timing of zygotic DNA replication is of interest, such as ongoing investigations on genetic transformations in barley using the microinjection technique. PMID:12242375

  20. Inferring Diffusion Dynamics from FCS in Heterogeneous Nuclear Environments

    PubMed Central

    Tsekouras, Konstantinos; Siegel, Amanda P.; Day, Richard N.; Pressé, Steve

    2015-01-01

    Fluorescence correlation spectroscopy (FCS) is a noninvasive technique that probes the diffusion dynamics of proteins down to single-molecule sensitivity in living cells. Critical mechanistic insight is often drawn from FCS experiments by fitting the resulting time-intensity correlation function, G(t), to known diffusion models. When simple models fail, the complex diffusion dynamics of proteins within heterogeneous cellular environments can be fit to anomalous diffusion models with adjustable anomalous exponents. Here, we take a different approach. We use the maximum entropy method to show—first using synthetic data—that a model for proteins diffusing while stochastically binding/unbinding to various affinity sites in living cells gives rise to a G(t) that could otherwise be equally well fit using anomalous diffusion models. We explain the mechanistic insight derived from our method. In particular, using real FCS data, we describe how the effects of cell crowding and binding to affinity sites manifest themselves in the behavior of G(t). Our focus is on the diffusive behavior of an engineered protein in 1) the heterochromatin region of the cell’s nucleus as well as 2) in the cell’s cytoplasm and 3) in solution. The protein consists of the basic region-leucine zipper (BZip) domain of the CCAAT/enhancer-binding protein (C/EBP) fused to fluorescent proteins. PMID:26153697

  1. Some coherent-states aspects of the electron nuclear dynamics theory: past and present

    NASA Astrophysics Data System (ADS)

    Morales, Jorge A.

    2010-11-01

    Past and present coherent-states (CS) efforts with the electron nuclear dynamics (END) theory at its simplest level (SL-END) are reviewed. END is a time-dependent, variational, non-adiabatic, direct-dynamics method that describes simultaneously the nuclei and electrons of a molecular system. Within that characterization, SL-END adopts a classical-mechanics description for the nuclei and a quantum single-determinantal representation for the electrons. From its very inception, SL-END has been associated with the CS theory. CS sets are continuous and over-complete sets that satisfy the resolution of identity with a positive measure. Different CS sets can play an astonishing number of roles within SL-END that have several practical consequences. Originally, SL-END utilized the canonical and Thouless CS sets to correctly represent the nuclear and electronic parts of the SL-END wavefunction, respectively, thus defining a proper phase space for the SL-END dynamical equations. Later, canonical and rotational CS sets were used for reconstructing quantum vibrational and quantum rotational descriptions from the SL-END classical nuclear dynamics. That development proved essential to calculate state-resolved properties in ion-molecule and atom-molecule collisions with SL-END. Present CS efforts include a time-dependent Kohn-Sham density-functional-theory direct-dynamic method in the END framework and a CS approach to the charge-equilibration model inter alia.

  2. Restrained torsional dynamics of nuclear DNA in living proliferative mammalian cells.

    PubMed Central

    Tramier, M; Kemnitz, K; Durieux, C; Coppey, J; Denjean, P; Pansu, R B; Coppey-Moisan, M

    2000-01-01

    Physical parameters, describing the state of chromatinized DNA in living mammalian cells, were revealed by in situ fluorescence dynamic properties of ethidium in its free and intercalated states. The lifetimes and anisotropy decays of this cationic chromophore were measured within the nuclear domain, by using the ultra-sensitive time-correlated single-photon counting technique, confocal microscopy, and ultra-low probe concentrations. We found that, in living cells: 1) free ethidium molecules equilibrate between extracellular milieu and nucleus, demonstrating that the cation is naturally transported into the nucleus; 2) the intercalation of ethidium into chromatinized DNA is strongly inhibited, with relaxation of the inhibition after mild (digitonin) cell treatment; 3) intercalation sites are likely to be located in chromatin DNA; and 4) the fluorescence anisotropy relaxation of intercalated molecules is very slow. The combination of fluorescence kinetic and fluorescence anisotropy dynamics indicates that the torsional dynamics of nuclear DNA is highly restrained in living cells. PMID:10777758

  3. Nuclear dynamics of radiation-induced foci in euchromatin and heterochromatin

    SciTech Connect

    Chiolo, Irene; Tang, Jonathan; Georgescu, Walter; Costes, Sylvain V.

    2013-10-01

    Repair of double strand breaks (DSBs) is essential for cell survival and genome integrity. While much is known about the molecular mechanisms involved in DSB repair and checkpoint activation, the roles of nuclear dynamics of radiation-induced foci (RIF) in DNA repair are just beginning to emerge. Here, we summarize results from recent studies that point to distinct features of these dynamics in two different chromatin environments: heterochromatin and euchromatin. We also discuss how nuclear architecture and chromatin components might control these dynamics, and the need of novel quantification methods for a better description and interpretation of these phenomena. These studies are expected to provide new biomarkers for radiation risk and new strategies for cancer detection and treatment.

  4. Nuclear dynamics of radiation-induced foci in euchromatin and heterochromatin.

    PubMed

    Chiolo, Irene; Tang, Jonathan; Georgescu, Walter; Costes, Sylvain V

    2013-10-01

    Repair of double strand breaks (DSBs) is essential for cell survival and genome integrity. While much is known about the molecular mechanisms involved in DSB repair and checkpoint activation, the roles of nuclear dynamics of radiation-induced foci (RIF) in DNA repair are just beginning to emerge. Here, we summarize results from recent studies that point to distinct features of these dynamics in two different chromatin environments: heterochromatin and euchromatin. We also discuss how nuclear architecture and chromatin components might control these dynamics, and the need of novel quantification methods for a better description and interpretation of these phenomena. These studies are expected to provide new biomarkers for radiation risk and new strategies for cancer detection and treatment.

  5. Nuclear dynamics and phase polymorphism in solid formic acid.

    PubMed

    Krzystyniak, Maciej; Drużbicki, Kacper; Romanelli, Giovanni; Gutmann, Matthias J; Rudić, Svemir; Imberti, Silvia; Fernandez-Alonso, Felix

    2017-03-29

    We apply a unique sequence of structural and dynamical neutron-scattering techniques, augmented with density-functional electronic-structure calculations, to establish the degree of polymorphism in an archetypal hydrogen-bonded system - crystalline formic acid. Using this combination of experimental and theoretical techniques, the hypothesis by Zelsmann on the coexistence of the β1 and β2 phases above 220 K is tested. Contrary to the postulated scenario of proton-transfer-driven phase coexistence, the emerging picture is one of a quantitatively different structural change over this temperature range, whereby the loosening of crystal packing promotes temperature-induced shearing of the hydrogen-bonded chains. The presented work, therefore, solves a fifty-year-old puzzle and provides a suitable framework for the use neutron-Compton-scattering techniques in the exploration of phase polymorphism in condensed matter.

  6. Electron-nuclear wave-packet dynamics through a conical intersection

    NASA Astrophysics Data System (ADS)

    Hader, Kilian; Albert, Julian; Gross, E. K. U.; Engel, Volker

    2017-02-01

    We investigate the coupled electron-nuclear dynamics in a model system showing a conical intersection (CoIn) between two excited state potential energy surfaces. Within the model, a single electron and nucleus move in two dimensions in an external static field. It is demonstrated that the nuclear density conserves its initial Gaussian shape when directly passing the CoIn, whereas the electronic density remains approximately constant. This is in sharp contrast to the picture which evolves from an analysis within the basis of adiabatic electronic states. There, dramatic changes are seen in the dynamics of the different nuclear components of the total wave function. It is thus documented that, in the case of a highly efficient population transfer between the respective adiabatic states, neither the nuclear nor the electronic density is influenced by the existence of a CoIn. This is the case because the nuclear-electronic wave packet moves on the complete potential energy surface which changes its topology smoothly as a function of all particle coordinates.

  7. Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Sharma, Girish; Economou, Sophia E.; Barnes, Edwin

    2017-09-01

    The interplay of Ising spin-orbit coupling and nontrivial band topology in transition metal dichalcogenides (TMDs) produces anomalous transport and optical properties that are very different from a regular two-dimensional (2D) electron gas. The spin-momentum locking of optically excited carriers near a valley point can give rise to an anomalous spin-valley Hall current under the application of an in-plane electric field. TMDs also exhibit strong electron-nuclear hyperfine interactions, but their effect on spin-valley-locked currents remains unknown. Here, we show that hyperfine interactions can create a feedback mechanism in which spin-valley currents generate significant dynamical nuclear polarization which in turn Zeeman shifts excitonic transitions out of resonance with an optical driving field, saturating the production of spin-valley polarization. We propose an experimental signature of dynamic nuclear polarization which can be detected via measurements of the anomalous Hall current. Our results help to elucidate the interplay of valley polarization and nuclear-spin dynamics in TMDs.

  8. Coupled electron-nuclear quantum dynamics through and around a conical intersection

    NASA Astrophysics Data System (ADS)

    Albert, Julian; Hader, Kilian; Engel, Volker

    2017-08-01

    In solving the time-dependent Schrödinger equation for a coupled electron-nuclear system, we study the motion of wave packets in a model which exhibits a conical intersection (CoIn) of adiabatic potential energy surfaces. Three different situations are studied. In the first case, an efficient non-adiabatic transition takes place while the wave packet passes the region of the CoIn. It is demonstrated that during these times, the nuclear probability density retains its Gaussian shape and the electronic density remains approximately constant. Second, dynamics are regarded where non-adiabatic transitions do not take place, and the nuclear dynamics follows a circle around the location of the CoIn. During this motion, the electronic density is shown to rotate. The comparison with the Born-Oppenheimer nuclear dynamics reveals the geometrical phase being associated with the circular motion. This phase is clearly revealed by an analysis of time-dependent autocorrelation functions and spectra obtained from the numerically exact and the Born-Oppenheimer calculation. The intermediate situation with a small non-adiabatic transition probability is characterized by wave-packet splitting into several fractions.

  9. Nuclear magnetic resonance of external protons using continuous dynamical decoupling with shallow NV centers

    NASA Astrophysics Data System (ADS)

    de Las Casas, Charles; Ohno, Kenichi; Awschalom, David D.

    2015-03-01

    The nitrogen vacancy (NV) center in diamond is a paramagnetic defect with excellent spin properties that can reside within a few nanometers of the diamond surface, enabling atomic-scale magnetic resonance sensing of external nuclear spins. Here we use rotating frame longitudinal spin relaxation (T1ρ) based sensing schemes, known as Continuous Dynamical Decoupling (CDD), to detect external nuclear spins with shallow NV centers (<5 nm from the surface). Distinguishing neighboring nuclear spins from each other requires the NV center be near enough to create differences in the hyperfine shifts and coupling strengths of the nuclei. However, spin coherence time and consequently the sensitivity of dynamical decoupling techniques degrade sharply as NVs become shallower. We use strong continuous driving to overcome this fast decoherence and detect an ensemble of external nuclear spins using a single shallow NV center with a short T2 (<2 μs) at magnetic fields as high as 0.5 Tesla. The increased sensitivity of this method relative to pulsed dynamical decoupling techniques demonstrates the benefits of CDD for sensing with very shallow NV centers. This work was supported by DARPA, AFOSR, and the DIAMANT program.

  10. Nuclear structure and reactions in the fermionic molecular dynamics approach

    NASA Astrophysics Data System (ADS)

    Neff, T.; Feldmeier, H.

    2008-05-01

    The Fermionic Molecular Dynamics (FMD) model uses Gaussian wave packets as single-particle states. Intrinsic many-body basis states are constructed as Slater determinants which have to be projected on parity, angular momentum and total linear momentum to restore the symmetries of the Hamiltonian. The flexibility of the Gaussian basis allows to economically describe states with shell structures as well as states featuring clustering or halos. We use an effective interaction that is derived from the realistic Argonne V18 interaction by means of the Unitary Correlation Operator Method (UCOM). A phenomenological momentum-dependent two-body correction simulates contributions from missing three-body forces and three-body correlations. We discuss 12C with a special emphasis on the structure of the excited 0+ and 2+ states. We analyze the degree of α-clustering and confirm, taking inelastic electron scattering data into account, the conjecture that the Hoyle state has to be understood as a loosely bound system of alpha particles. We will also present first results on the application of FMD for the calculation of scattering phase shifts in 3He — 4He.

  11. Chaotic features of nuclear structure and dynamics: selected topics

    NASA Astrophysics Data System (ADS)

    Zelevinsky, Vladimir; Volya, Alexander

    2016-03-01

    Quantum chaos has become an important element of our knowledge about physics of complex systems. In typical mesoscopic systems of interacting particles the dynamics invariably become chaotic when the level density, growing by combinatorial reasons, leads to the increasing probability of mixing simple mean-field (particle-hole) configurations. The resulting stationary states have exceedingly complicated structures that are comparable to those in random matrix theory. We discuss the main properties of mesoscopic quantum chaos and show that it can serve as a justification for application of statistical mechanics to mesoscopic systems. We show that quantum chaos becomes a powerful instrument for experimental, theoretical and computational work. The generalization to open systems and effects in the continuum are discussed with the help of the effective non-Hermitian Hamiltonian; it is shown how to formulate this approach for numerous problems of quantum signal transmission. The artificially introduced randomness can also be helpful for a deeper understanding of physics. We indicate the problems that require more investigation so as to be understood further.

  12. Key Role of Polyphosphoinositides in Dynamics of Fusogenic Nuclear Membrane Vesicles

    PubMed Central

    Zhendre, Vanessa; Grélard, Axelle; Garnier-LHomme, Marie; Buchoux, Sébastien; Larijani, Banafshé; Dufourc, Erick J.

    2011-01-01

    The role of phosphoinositides has been thoroughly described in many signalling and membrane trafficking events but their function as modulators of membrane structure and dynamics in membrane fusion has not been investigated. We have reconstructed models that mimic the composition of nuclear envelope precursor membranes with naturally elevated amounts of phosphoinositides. These fusogenic membranes (membrane vesicle 1(MV1) and nuclear envelope remnants (NER) are critical for the assembly of the nuclear envelope. Phospholipids, cholesterol, and polyphosphoinositides, with polyunsaturated fatty acid chains that were identified in the natural nuclear membranes by lipid mass spectrometry, have been used to reconstruct complex model membranes mimicking nuclear envelope precursor membranes. Structural and dynamic events occurring in the membrane core and at the membrane surface were monitored by solid-state deuterium and phosphorus NMR. “MV1-like” (PC∶PI∶PIP∶PIP2, 30∶20∶18∶12, mol%) membranes that exhibited high levels of PtdIns, PtdInsP and PtdInsP2 had an unusually fluid membrane core (up to 20% increase, compared to membranes with low amounts of phosphoinositides to mimic the endoplasmic reticulum). “NER-like” (PC∶CH∶PI∶PIP∶PIP2, 28∶42∶16∶7∶7, mol%) membranes containing high amounts of both cholesterol and phosphoinositides exhibited liquid-ordered phase properties, but with markedly lower rigidity (10–15% decrease). Phosphoinositides are the first lipids reported to counterbalance the ordering effect of cholesterol. At the membrane surface, phosphoinositides control the orientation dynamics of other lipids in the model membranes, while remaining unchanged themselves. This is an important finding as it provides unprecedented mechanistic insight into the role of phosphoinositides in membrane dynamics. Biological implications of our findings and a model describing the roles of fusogenic membrane vesicles are proposed. PMID:21931619

  13. Electron nuclear dynamics of H + +H2 collisions at Elab=30 eV

    NASA Astrophysics Data System (ADS)

    Morales, Jorge; Diz, Agustin; Deumens, E.; Öhrn, Yngve

    1995-12-01

    Proton collisions with hydrogen molecules at 30 eV in the laboratory frame is a simple ion-molecule system exhibiting a number of distinct processes such as inelastic scattering, charge transfer, rearrangement, and dissociation. The electron nuclear dynamics (END) theory which allows full electron nuclear coupling and which does not restrict the system from reaching any of the possible product channels, is applied to this sytem to produce transition probabilities, differential, and integral (vibrationally resolved) cross sections. Comparisons with experiment demonstrate that END, even in its simplest implementation, with a single determinantal state for the electrons and with classical nuclei, yields results that are competitive with other theoretical approaches.

  14. Dynamic considerations in the development of centrifugal separators used for reprocessing nuclear fuel

    SciTech Connect

    Strunk, W.D.; Singh, S.P.; Tuft, R.M.

    1988-01-01

    The development of centrifugal separators has been a key ingredient in improving the process used for reprocessing of spent nuclear fuel. The separators are used to segregate uranium and plutonium from the fission products produced by a controlled nuclear reaction. The separators are small variable speed centrifuges, designed to operate in a harsh environment. Dynamic problems were detected by vibration analysis and resolved using modal analysis and trending. Problems with critical speeds, resonances in the base, balancing, weak components, precision manufacturing, and short life have been solved.

  15. Solid effect in the electron spin dressed state: A new approach for dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Weis, V.; Bennati, M.; Rosay, M.; Griffin, R. G.

    2000-10-01

    We describe a new type of solid effect for dynamic nuclear polarization (DNP) that is based on simultaneous, near resonant microwave (mw) and radio frequency (rf) irradiation of a coupled electron nuclear spin system. The interaction of the electron spin with the mw field is treated as an electron spin dressed state. In contrast to the customary laboratory frame solid effect, it is possible to obtain nuclear polarization with the dressed state solid effect (DSSE) even in the absence of nonsecular hyperfine coupling. Efficient, selective excitation of dressed state transitions generates nuclear polarization in the nuclear laboratory frame on a time scale of tens of μs, depending on the strength of the electron-nuclear coupling, the mw and rf offset and field strength. The experiment employs both pulsed mw and rf irradiation at a repetition rate comparable to T1e-1, where T1e is the electronic spin lattice relaxation time. The DSSE is demonstrated on a perdeuterated BDPA radical in a protonated matrix of polystyrene.

  16. Nuclear classical dynamics of H2 in an intense laser field

    NASA Astrophysics Data System (ADS)

    Sami, Firoozeh; Vafaee, Mohsen; Shokri, Babak

    2011-08-01

    In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization, respectively. In the second part of the paper, the time-dependent Schrödinger and Newton equations are solved simultaneously for the electrons and the nuclei of H2, respectively. The electron and nuclei dynamics are separated on the basis of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390, 532 and 780 nm) and intensities (5 × 1014 and 5 × 1015 W cm-2) of the ultrashort intense laser pulses with a sinus second-order envelope function are used. The behaviour of the time-dependent classical nuclear dynamics in the absence and presence of the laser field is investigated and compared. In the absence of the laser field, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.

  17. The dynamics of nuclear receptors and nuclear receptor coregulators in the pathogenesis of endometriosis

    PubMed Central

    Han, Sang Jun; O'Malley, Bert W.

    2014-01-01

    BACKGROUND Endometriosis is defined as the colonization and growth of endometrial tissue at anatomic sites outside the uterine cavity. Up to 15% of reproductive-aged women in the USA suffer from painful symptoms of endometriosis, such as infertility, pelvic pain, menstrual cycle abnormalities and increased risk of certain cancers. However, many of the current clinical treatments for endometriosis are not sufficiently effective and yield unacceptable side effects. There is clearly an urgent need to identify new molecular mechanisms that critically underpin the initiation and progression of endometriosis in order to develop more specific and effective therapeutics which lack the side effects of current therapies. The aim of this review is to discuss how nuclear receptors (NRs) and their coregulators promote the progression of endometriosis. Understanding the pathogenic molecular mechanisms for the genesis and maintenance of endometriosis as modulated by NRs and coregulators can reveal new therapeutic targets for alternative endometriosis treatments. METHODS This review was prepared using published gene expression microarray data sets obtained from patients with endometriosis and published literature on NRs and their coregulators that deal with endometriosis progression. Using the above observations, our current understanding of how NRs and NR coregulators are involved in the progression of endometriosis is summarized. RESULTS Aberrant levels of NRs and NR coregulators in ectopic endometriosis lesions are associated with the progression of endometriosis. As an example, endometriotic cell-specific alterations in gene expression are correlated with a differential methylation status of the genome compared with the normal endometrium. These differential epigenetic regulations can generate favorable cell-specific NR and coregulator milieus for endometriosis progression. Genetic alterations, such as single nucleotide polymorphisms and insertion/deletion polymorphisms of NR

  18. Automated motion correction based on target tracking for dynamic nuclear medicine studies

    NASA Astrophysics Data System (ADS)

    Cao, Xinhua; Tetrault, Tracy; Fahey, Fred; Treves, Ted

    2008-03-01

    Nuclear medicine dynamic studies of kidneys, bladder and stomach are important diagnostic tools. Accurate generation of time-activity curves from regions of interest (ROIs) requires that the patient remains motionless for the duration of the study. This is not always possible since some dynamic studies may last from several minutes to one hour. Several motion correction solutions have been explored. Motion correction using external point sources is inconvenient and not accurate especially when motion results from breathing, organ motion or feeding rather than from body motion alone. Centroid-based motion correction assumes that activity distribution is only inside the single organ (without background) and uniform, but this approach is impractical in most clinical studies. In this paper, we present a novel technique of motion correction that first tracks the organ of interest in a dynamic series then aligns the organ. The implementation algorithm for target tracking-based motion correction consists of image preprocessing, target detection, target positioning, motion estimation and prediction, tracking (new search region generation) and target alignment. The targeted organ is tracked from the first frame to the last one in the dynamic series to generate a moving trajectory of the organ. Motion correction is implemented by aligning the organ ROIs in the image series to the location of the organ in the first image. The proposed method of motion correction has been applied to several dynamic nuclear medicine studies including radionuclide cystography, dynamic renal scintigraphy, diuretic renography and gastric emptying scintigraphy.

  19. The influence of nuclear compartmentalisation on stochastic dynamics of self-repressing gene expression.

    PubMed

    Sturrock, Marc; Li, Shiyu; Shahrezaei, Vahid

    2017-07-07

    Gene expression is an inherently noisy process. This noise is generally thought to be deleterious as precise internal regulation of biochemical reactions is essential for cell growth and survival. Self-repression of gene expression, which is the simplest form of a negative feedback loop, is commonly believed to be employed by cellular systems to decrease the stochastic fluctuations in gene expression. When there is some delay in autoregulation, it is also believed that this system can generate oscillations. In eukaryotic cells, mRNAs that are synthesised in the nucleus must be exported to the cytoplasm to function in protein synthesis, whereas proteins must be transported into the nucleus from the cytoplasm to regulate the expression levels of genes. Nuclear transport thus plays a critical role in eukaryotic gene expression and regulation. Some recent studies have suggested that nuclear retention of mRNAs can control noise in mRNA expression. However, the effect of nuclear transport on protein noise and its interplay with negative feedback regulation is not completely understood. In this paper, we systematically compare four different simple models of gene expression. By using simulations and applying the linear noise approximation to the corresponding chemical master equations, we investigate the influence of nuclear import and export on noise in gene expression in a negative autoregulatory feedback loop. We first present results consistent with the literature, i.e., that negative feedback can effectively buffer the variability in protein levels, and nuclear retention can decrease mRNA noise levels. Interestingly we find that when negative feedback is combined with nuclear retention, an amplification in gene expression noise can be observed and is dependant on nuclear translocation rates. Finally, we investigate the effect of nuclear compartmentalisation on the ability of self-repressing genes to exhibit stochastic oscillatory dynamics. Copyright © 2017 Elsevier

  20. Inhibition of Nuclear Transport of NF-ĸB p65 by the Salmonella Type III Secretion System Effector SpvD

    PubMed Central

    Rolhion, Nathalie; Furniss, R. Christopher D.; Grabe, Grzegorz; Ryan, Aindrias; Liu, Mei; Matthews, Sophie A.; Holden, David W.

    2016-01-01

    Salmonella enterica replicates in macrophages through the action of effector proteins translocated across the vacuolar membrane by a type III secretion system (T3SS). Here we show that the SPI-2 T3SS effector SpvD suppresses proinflammatory immune responses. SpvD prevented activation of an NF-ĸB-dependent promoter and caused nuclear accumulation of importin-α, which is required for nuclear import of p65. SpvD interacted specifically with the exportin Xpo2, which mediates nuclear-cytoplasmic recycling of importins. We propose that interaction between SpvD and Xpo2 disrupts the normal recycling of importin-α from the nucleus, leading to a defect in nuclear translocation of p65 and inhibition of activation of NF-ĸB regulated promoters. SpvD down-regulated pro-inflammatory responses and contributed to systemic growth of bacteria in mice. This work shows that a bacterial pathogen can manipulate host cell immune responses by interfering with the nuclear transport machinery. PMID:27232334

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

    PubMed

    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, 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 (13)C 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 (13)C MAS NMR spectra of frozen solutions of uniformly (13)C-labeled l-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly (13)C-labeled amino acids. Published by Elsevier Inc.

  2. 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

  3. Prospects for sub-micron solid state nuclear magnetic resonance imaging with low-temperature dynamic nuclear polarization.

    PubMed

    Thurber, Kent R; Tycko, Robert

    2010-06-14

    We evaluate the feasibility of (1)H nuclear magnetic resonance (NMR) imaging with sub-micron voxel dimensions using a combination of low temperatures and dynamic nuclear polarization (DNP). Experiments are performed on nitroxide-doped glycerol-water at 9.4 T and temperatures below 40 K, using a 30 mW tunable microwave source for DNP. With DNP at 7 K, a 0.5 microL sample yields a (1)H NMR signal-to-noise ratio of 770 in two scans with pulsed spin-lock detection and after 80 db signal attenuation. With reasonable extrapolations, we infer that (1)H NMR signals from 1 microm(3) voxel volumes should be readily detectable, and voxels as small as 0.03 microm(3) may eventually be detectable. Through homonuclear decoupling with a frequency-switched Lee-Goldburg spin echo technique, we obtain 830 Hz (1)H NMR linewidths at low temperatures, implying that pulsed field gradients equal to 0.4 G/d or less would be required during spatial encoding dimensions of an imaging sequence, where d is the resolution in each dimension.

  4. Nuclear proliferation and civilian nuclear power. Report of the Nonproliferation Alternative Systems Assessment Program. Volume III. Resources and fuel cycle facilities

    SciTech Connect

    Not Available

    1980-06-01

    The ability of uranium supply and the rest of the nuclear fuel cycle to meet the demand for nuclear power is an important consideration in future domestic and international planning. Accordingly, the purpose of this assessment is to evaluate the adequacy of potential supply for various nuclear resources and fuel cycle facilities in the United States and in the world outside centrally planned economy areas (WOCA). Although major emphasis was placed on uranium supply and demand, material resources (thorium and heavy water) and facility resources (separative work, spent fuel storage, and reprocessing) were also considered.

  5. Narrowing of the Overhauser field distribution by feedback-enhanced dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Tenberg, S.; McNeil, R. P. G.; Rubbert, S.; Bluhm, H.

    2015-11-01

    In many electron spin qubit systems coherent control is impaired by the fluctuating nuclear spin bath of the host material. Previous experiments have shown dynamic nuclear polarization with feedback to significantly prolong the inhomogeneous dephasing time T2* by narrowing the distribution of nuclear Overhauser field fluctuations. We present a model relating the achievable narrowing of the Overhauser field to both the pump rate and the noise magnitude and find reasonable agreement with experimental data. It shows that former experiments on gated GaAs quantum dots were limited by the pump rate of the pumping mechanism used. Here we propose an alternative feedback scheme using electron dipole spin resonance. Sequentially applying two ac electric fields with frequencies slightly detuned from the desired Larmor frequency results in a pump curve with a stable fixed point. Our model predicts that T2* values on the order of microseconds can be achieved.

  6. Electron paramagnetic resonance study of the nuclear spin dynamics in an AlAs quantum well

    NASA Astrophysics Data System (ADS)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2016-12-01

    The nuclear spin dynamics in an asymmetrically doped 16-nm AlAs quantum well grown along the [001] direction has been studied experimentally using the time decay of the Overhauser shift of paramagnetic resonance of conduction electrons. The nonzero spin polarization of nuclei causing the initial observed Overhauser shift is due the relaxation of the nonequilibrium spin polarization of electrons into the nuclear subsystem near electron paramagnetic resonance owing to the hyperfine interaction. The measured relaxation time of nuclear spins near the unity filling factor is (530 ± 30) min at the temperature T = 0.5 K. This value exceeds the characteristic spin relaxation times of nuclei in GaAs/AlGaAs heterostructures by more than an order of magnitude. This fact indicates the decrease in the strength of the hyperfine interaction in the AlAs quantum well in comparison with GaAs/AlGaAs heterostructures.

  7. 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.

  8. 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.

  9. {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.

  10. Automated nuclear material recovery and decontamination of large steel dynamic experiment containers

    SciTech Connect

    Dennison, D.K.; Gallant, D.A.; Nelson, D.C.; Stovall, L.A.; Wedman, D.E.

    1999-03-01

    A key mission of the Los Alamos National Laboratory (LANL) is to reduce the global nuclear danger through stockpile stewardship efforts that ensure the safety and reliability of nuclear weapons. In support of this mission LANL performs dynamic experiments on special nuclear materials (SNM) within large steel containers. Once these experiments are complete, these containers must be processed to recover residual SNM and to decontaminate the containers to below low level waste (LLW) disposal limits which are much less restrictive for disposal purposes than transuranic (TRU) waste limits. The purpose of this paper is to describe automation efforts being developed by LANL for improving the efficiency, increasing worker safety, and reducing worker exposure during the material cleanout and recovery activities performed on these containers.

  11. Mapping the Dynamics of the Glucocorticoid Receptor within the Nuclear Landscape.

    PubMed

    Stortz, Martin; Presman, Diego M; Bruno, Luciana; Annibale, Paolo; Dansey, Maria V; Burton, Gerardo; Gratton, Enrico; Pecci, Adali; Levi, Valeria

    2017-07-24

    The distribution of the transcription machinery among different sub-nuclear domains raises the question on how the architecture of the nucleus modulates the transcriptional response. Here, we used fluorescence fluctuation analyses to quantitatively explore the organization of the glucocorticoid receptor (GR) in the interphase nucleus of living cells. We found that this ligand-activated transcription factor diffuses within the nucleus and dynamically interacts with bodies enriched in the coregulator NCoA-2, DNA-dependent foci and chromatin targets. The distribution of the receptor among the nuclear compartments depends on NCoA-2 and the conformation of the receptor as assessed with synthetic ligands and GR mutants with impaired transcriptional abilities. Our results suggest that the partition of the receptor in different nuclear reservoirs ultimately regulates the concentration of receptor available for the interaction with specific targets, and thus has an impact on transcription regulation.

  12. Measuring Process Dynamics and Nuclear Migration for Clones of Neural Progenitor Cells

    PubMed Central

    De La Hoz, Edgar Cardenas; Winter, Mark R.; Apostolopoulou, Maria; Temple, Sally

    2016-01-01

    Neural stem and progenitor cells (NPCs) generate processes that extend from the cell body in a dynamic manner. The NPC nucleus migrates along these processes with patterns believed to be tightly coupled to mechanisms of cell cycle regulation and cell fate determination. Here, we describe a new segmentation and tracking approach that allows NPC processes and nuclei to be reliably tracked across multiple rounds of cell division in phase-contrast microscopy images. Results are presented for mouse adult and embryonic NPCs from hundreds of clones, or lineage trees, containing tens of thousands of cells and millions of segmentations. New visualization approaches allow the NPC nuclear and process features to be effectively visualized for an entire clone. Significant differences in process and nuclear dynamics were found among type A and type C adult NPCs, and also between embryonic NPCs cultured from the anterior and posterior cerebral cortex. PMID:27878138

  13. Measuring Process Dynamics and Nuclear Migration for Clones of Neural Progenitor Cells.

    PubMed

    De La Hoz, Edgar Cardenas; Winter, Mark R; Apostolopoulou, Maria; Temple, Sally; Cohen, Andrew R

    2016-10-01

    Neural stem and progenitor cells (NPCs) generate processes that extend from the cell body in a dynamic manner. The NPC nucleus migrates along these processes with patterns believed to be tightly coupled to mechanisms of cell cycle regulation and cell fate determination. Here, we describe a new segmentation and tracking approach that allows NPC processes and nuclei to be reliably tracked across multiple rounds of cell division in phase-contrast microscopy images. Results are presented for mouse adult and embryonic NPCs from hundreds of clones, or lineage trees, containing tens of thousands of cells and millions of segmentations. New visualization approaches allow the NPC nuclear and process features to be effectively visualized for an entire clone. Significant differences in process and nuclear dynamics were found among type A and type C adult NPCs, and also between embryonic NPCs cultured from the anterior and posterior cerebral cortex.

  14. Pumping of Dynamic Nuclear Polarization in GaAs Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Pal, Arijeet; Nichol, John; Shulman, Michael; Harvey, Shannon; Rashba, Emmanuel; Yacoby, Amir; Halperin, Bertrand

    2015-03-01

    Control of nuclear spins in semiconductors is essential for spin qubits realized using gate-defined quantum dots (QDs) for quantum computing. One qubit realization uses the singlet (S) and triplet Sz = 0 (T0) states of two electrons in a double QD. The difference in the Overhauser fields on the two dots provides an axis of rotation on the Bloch sphere orthogonal to the one produced by the exchange interaction. These fields, in turn, may be modified by a dynamic nuclear polarization protocol, in which the electronic system is swept repeatedly through the level crossing between the S and T+ states. In any given sweep, the hyperfine interaction may cause a transition from S to T+, thereby transferring electronic spin polarization to the nuclear spins. We find the dependence of the polarization process on the asymmetry of the electron wave function, which is induced by the Zeeman field even in geometrically symmetric dots and which leads to pumping of the difference in Overhauser fields. We further report on correlations between S -T+ transitions, which capture the macroscopic nuclear spin dynamics and the various relaxation mechanisms in this system. A semi-classical theoretical model is formulated which is in good agreement with the experimental observations.

  15. Varicella-zoster virus induces the formation of dynamic nuclear capsid aggregates

    SciTech Connect

    Lebrun, Marielle; Thelen, Nicolas; Thiry, Marc; Riva, Laura; Ote, Isabelle; Condé, Claude; Vandevenne, Patricia; Di Valentin, Emmanuel; Bontems, Sébastien; Sadzot-Delvaux, Catherine

    2014-04-15

    The first step of herpesviruses virion assembly occurs in the nucleus. However, the exact site where nucleocapsids are assembled, where the genome and the inner tegument are acquired, remains controversial. We created a recombinant VZV expressing ORF23 (homologous to HSV-1 VP26) fused to the eGFP and dually fluorescent viruses with a tegument protein additionally fused to a red tag (ORF9, ORF21 and ORF22 corresponding to HSV-1 UL49, UL37 and UL36). We identified nuclear dense structures containing the major capsid protein, the scaffold protein and maturing protease, as well as ORF21 and ORF22. Correlative microscopy demonstrated that the structures correspond to capsid aggregates and time-lapse video imaging showed that they appear prior to the accumulation of cytoplasmic capsids, presumably undergoing the secondary egress, and are highly dynamic. Our observations suggest that these structures might represent a nuclear area important for capsid assembly and/or maturation before the budding at the inner nuclear membrane. - Highlights: • We created a recombinant VZV expressing the small capsid protein fused to the eGFP. • We identified nuclear dense structures containing capsid and procapsid proteins. • Correlative microscopy showed that the structures correspond to capsid aggregates. • Procapsids and partial capsids are found within the aggregates of WT and eGFP-23 VZV. • FRAP and FLIP experiments demonstrated that they are dynamic structures.

  16. Site-Specific Hydration Dynamics in the Nonpolar Core of a Molten Globule by Dynamic Nuclear Polarization of Water

    PubMed Central

    Armstrong, Brandon D.; Choi, Jennifer; López, Carlos; Wesener, Darryl A.; Hubbell, Wayne; Cavagnero, Silvia; Han, Songi

    2011-01-01

    Water-protein interactions play a direct role in protein folding. The chain collapse that accompanies protein folding involves extrusion of water from the nonpolar core. For many proteins, including apomyoglobin (apoMb), hydrophobic interactions drive an initial collapse to an intermediate state before folding to the final structure. However, the debate continues as to whether the core of the collapsed intermediate state is hydrated and, if so, what the dynamic nature of this water is. A key challenge is that protein hydration dynamics is significantly heterogeneous, yet suitable experimental techniques for measuring hydration dynamics with site-specificity are lacking. Here, we introduce Overhauser dynamic nuclear polarization at 0.35 T via site-specific nitroxide spin labels as a unique tool to probe internal and surface protein hydration dynamics with site-specific resolution in the molten globular, native, and unfolded protein states. The 1H NMR signal enhancement of water carries information about the local dynamics of the solvent within ~10 Å of a spin label. EPR is used synergistically to gain insights on local polarity and mobility of the spin-labeled protein. Several buried and solvent-exposed sites of apoMb are examined, each bearing a covalently bound nitroxide spin label. We find that the hydrophobic core of the apoMb molten globule is hydrated with water bearing significant translational dynamics, only 4–6-fold slower than that of bulk water. The hydration dynamics of the native state is heterogeneous, while the acid-unfolded state bears fast-diffusing hydration water. This study provides a high-resolution glimpse at the folding-dependent nature of protein hydration dynamics. PMID:21443207

  17. Site-specific hydration dynamics in the nonpolar core of a molten globule by dynamic nuclear polarization of water.

    PubMed

    Armstrong, Brandon D; Choi, Jennifer; López, Carlos; Wesener, Darryl A; Hubbell, Wayne; Cavagnero, Silvia; Han, Songi

    2011-04-20

    Water-protein interactions play a direct role in protein folding. The chain collapse that accompanies protein folding involves extrusion of water from the nonpolar core. For many proteins, including apomyoglobin (apoMb), hydrophobic interactions drive an initial collapse to an intermediate state before folding to the final structure. However, the debate continues as to whether the core of the collapsed intermediate state is hydrated and, if so, what the dynamic nature of this water is. A key challenge is that protein hydration dynamics is significantly heterogeneous, yet suitable experimental techniques for measuring hydration dynamics with site-specificity are lacking. Here, we introduce Overhauser dynamic nuclear polarization at 0.35 T via site-specific nitroxide spin labels as a unique tool to probe internal and surface protein hydration dynamics with site-specific resolution in the molten globular, native, and unfolded protein states. The (1)H NMR signal enhancement of water carries information about the local dynamics of the solvent within ∼10 Å of a spin label. EPR is used synergistically to gain insights on local polarity and mobility of the spin-labeled protein. Several buried and solvent-exposed sites of apoMb are examined, each bearing a covalently bound nitroxide spin label. We find that the nonpoloar core of the apoMb molten globule is hydrated with water bearing significant translational dynamics, only 4-6-fold slower than that of bulk water. The hydration dynamics of the native state is heterogeneous, while the acid-unfolded state bears fast-diffusing hydration water. This study provides a high-resolution glimpse at the folding-dependent nature of protein hydration dynamics.

  18. Spin dynamics of a confined electron interacting with magnetic or nuclear spins: A semiclassical approach

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    2015-03-01

    A physically transparent and mathematically simple semiclassical model is employed to examine dynamics in the central-spin problem. The results reproduce previous findings obtained by various quantum approaches and, at the same time, provide information on the electron spin dynamics and Berry's phase effects over a wider range of experimentally relevant parameters than available previously. This development is relevant to dynamics of bound magnetic polarons and spin dephasing of an electron trapped by an impurity or a quantum dot, and coupled by a contact interaction to neighboring localized magnetic impurities or nuclear spins. Furthermore, it substantiates the applicability of semiclassical models to simulate dynamic properties of spintronic nanostructures with a mesoscopic number of spins.

  19. Real-time electron dynamics simulation of two-electron transfer reactions induced by nuclear motion

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasumitsu; Yamashita, Koichi

    2012-04-01

    Real-time electron dynamics of two-electron transfer reactions induced by nuclear motion is calculated by three methods: the numerically exact propagation method, the time-dependent Hartree (TDH) method and the Ehrenfest method. We find that, as long as the nuclei move as localized wave packets, the TDH and Ehrenfest methods can reproduce the exact electron dynamics of a simple charge transfer reaction model containing two electrons qualitatively well, even when nonadiabatic transitions between adiabatic states occur. In particular, both methods can reproduce the cases where a complete two-electron transfer reaction occurs and those where it does not occur.

  20. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    NASA Astrophysics Data System (ADS)

    Kowalewski, Markus; Bennett, Kochise; Rouxel, Jérémy R.; Mukamel, Shaul

    2016-07-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences. We demonstrate how streaked photoelectrons offer a novel tool for monitoring nonadiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can provide high time resolution direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  1. Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T.

    PubMed

    Brownbill, Nick J; Gajan, David; Lesage, Anne; Emsley, Lyndon; Blanc, Frédéric

    2017-02-23

    We report (17)O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

  2. Discrimination of nuclear spin isomers exploiting the excited state dynamics of a quinodimethane derivative

    SciTech Connect

    Obaid, Rana; Kinzel, Daniel; Oppel, Markus González, Leticia

    2014-10-28

    Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.

  3. Light-induced nuclear export reveals rapid dynamics of epigenetic modifications

    PubMed Central

    Yumerefendi, Hayretin; Lerner, Andrew Michael; Zimmerman, Seth Parker; Hahn, Klaus; Bear, James E; Strahl, Brian D.; Kuhlman, Brian

    2016-01-01

    We engineered a photoactivatable system for rapidly and reversibly exporting proteins from the nucleus by embedding a nuclear export signal in the LOV2 domain from phototropin 1. Fusing the chromatin modifier Bre1 to the photoswitch, we achieved light-dependent control of histone H2B monoubiquitylation in yeast, revealing fast turnover of the ubiquitin mark. Moreover, this inducible system allowed us to dynamically monitor the status of epigenetic modifications dependent on H2B ubiquitylation. PMID:27089030

  4. Acetylation dynamics of human nuclear proteins during the ionizing radiation-induced DNA damage response.

    PubMed

    Bennetzen, Martin V; Larsen, Dorthe Helena; Dinant, Christoffel; Watanabe, Sugiko; Bartek, Jiri; Lukas, Jiri; Andersen, Jens S

    2013-06-01

    Genotoxic insults, such as ionizing radiation (IR), cause DNA damage that evokes a multifaceted cellular DNA damage response (DDR). DNA damage signaling events that control protein activity, subcellular localization, DNA binding, protein-protein interactions, etc. rely heavily on time-dependent posttranslational modifications (PTMs). To complement our previous analysis of IR-induced temporal dynamics of nuclear phosphoproteome, we now identify a range of human nuclear proteins that are dynamically regulated by acetylation, and predominantly deacetylation, during IR-induced DDR by using mass spectrometry-based proteomic approaches. Apart from cataloging acetylation sites through SILAC proteomic analyses before IR and at 5 and 60 min after IR exposure of U2OS cells, we report that: (1) key components of the transcriptional machinery, such as EP300 and CREBBP, are dynamically acetylated; (2) that nuclear acetyltransferases themselves are regulated, not on the protein abundance level, but by (de)acetylation; and (3) that the recently reported p53 co-activator and methyltransferase MLL3 is acetylated on five lysines during the DDR. For selected examples, protein immunoprecipitation and immunoblotting were used to assess lysine acetylation status and thereby validate the mass spectrometry data. We thus present evidence that nuclear proteins, including those known to regulate cellular functions via epigenetic modifications of histones, are regulated by (de)acetylation in a timely manner upon cell's exposure to genotoxic insults. Overall, these results present a resource of temporal profiles of a spectrum of protein acetylation sites during DDR and provide further insights into the highly dynamic nature of regulatory PTMs that help orchestrate the maintenance of genome integrity.

  5. Discrimination of nuclear spin isomers exploiting the excited state dynamics of a quinodimethane derivative.

    PubMed

    Obaid, Rana; Kinzel, Daniel; Oppel, Markus; González, Leticia

    2014-10-28

    Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.

  6. Influence of deuteration in the glassing matrix on 13C dynamic nuclear polarization†

    PubMed Central

    Lumata, Lloyd; Merritt, Matthew E.

    2013-01-01

    Replacement of protons by deuterons in the glassing solvents led to 2–3-fold improvement of the 13C dynamic nuclear polarization (DNP) solid-state NMR signal for samples doped with large electron spin resonance (ESR) linewidth free radicals galvinoxyl, DPPH, and 4-oxo-TEMPO. Meanwhile, the reverse effect is observed for 13C DNP using small ESR linewidth free radicals BDPA and trityl OX063. PMID:23552448

  7. Electron dynamics upon ionization: Control of the timescale through chemical substitution and effect of nuclear motion

    SciTech Connect

    Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.; Mendive-Tapia, David

    2015-03-07

    Photoionization can generate a non-stationary electronic state, which leads to coupled electron-nuclear dynamics in molecules. In this article, we choose benzene cation as a prototype because vertical ionization of the neutral species leads to a Jahn-Teller degeneracy between ground and first excited states of the cation. Starting with equal populations of ground and first excited states, there is no electron dynamics in this case. However, if we add methyl substituents that break symmetry but do not radically alter the electronic structure, we see charge migration: oscillations in the spin density that we can correlate with particular localized electronic structures, with a period depending on the gap between the states initially populated. We have also investigated the effect of nuclear motion on electron dynamics using a complete active space self-consistent field (CASSCF) implementation of the Ehrenfest method, most previous theoretical studies of electron dynamics having been carried out with fixed nuclei. In toluene cation for instance, simulations where the nuclei are allowed to move show significant differences in the electron dynamics after 3 fs, compared to simulations with fixed nuclei.

  8. Protection of centre spin coherence by dynamic nuclear spin polarization in diamond.

    PubMed

    Liu, Gang-Qin; Jiang, Qian-Qing; Chang, Yan-Chun; Liu, Dong-Qi; Li, Wu-Xia; Gu, Chang-Zhi; Po, Hoi Chun; Zhang, Wen-Xian; Zhao, Nan; Pan, Xin-Yu

    2014-09-07

    We experimentally investigate the protection of electron spin coherence of a nitrogen-vacancy (NV) centre in diamond by dynamic nuclear spin polarization (DNP). The electron spin decoherence of an NV centre is caused by the magnetic field fluctuation of the (13)C nuclear spin bath, which contributes large thermal fluctuation to the centre electron spin when it is in an equilibrium state at room temperature. To address this issue, we continuously transfer the angular momentum from electron spin to nuclear spins, and pump the nuclear spin bath to a polarized state under the Hartmann-Hahn condition. The bath polarization effect is verified by the observation of prolongation of the electron spin coherence time (T). Optimal conditions for the DNP process, including the pumping pulse duration and repeat numbers, are proposed by numerical simulation and confirmed by experiment. We also studied the depolarization effect of laser pulses. Our results provide a new route for quantum information processing and quantum simulation using the polarized nuclear spin bath.

  9. Probing nuclear dynamics in jet production with a global event shape

    NASA Astrophysics Data System (ADS)

    Kang, Zhong-Bo; Liu, Xiaohui; Mantry, Sonny; Qiu, Jian-Wei

    2013-10-01

    We study single jet production in electron-nucleus collisions e-+NA→J+X, using the 1-jettiness (τ1) global event shape. It inclusively quantifies the pattern of radiation in the final state, gives enhanced sensitivity to soft radiation at wide angles from the nuclear beam and final-state jet, and facilitates the resummation of large Sudakov logarithms associated with the veto on additional jets. Through their effect on the observed pattern of radiation, 1-jettiness can be a useful probe of nuclear parton distribution functions and power corrections from dynamical effects in the nuclear medium. This formalism allows for the standard jet shape analysis while simultaneously providing sensitivity to soft radiation at wide angles from the jet. We use a factorization framework for cross-sections differential in τ1 and the transverse momentum (PJT) and rapidity (y) of the jet, in the region τ1≪PJT. The restriction τ1≪PJT allows only soft radiation between the nuclear beam and jet directions, thereby acting as a veto on additional jets. This region is also insensitive to the details of the jet algorithm, allowing for better theoretical control over resummation, while providing enhanced sensitivity to nuclear medium effects. We give numerical results at leading twist, with resummation at the next-to-next-to-leading logarithmic level of accuracy, for a variety of nuclear targets. Such studies would be ideal for the electron-ion collider and the LHeC proposals for a future electron-ion collider, where a range of nuclear targets are planned.

  10. Electron-Nuclear Dynamics of atomic and molecular collisions: Charge exchange and energy loss

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, Remigio; Sabin, John R.; Ohrn, Yngve; Deumens, Erik

    2004-05-01

    Processes like electron exchange (capture and loss), bond breaking, and chemical reactions are difficult to visualize and treat in a time-independent approach. In this work, we present the Electron-Nuclear Dynamics (END) method for the study of time-dependent scattering processes. The END is a general approach for treating time-dependent problems which includes the dynamics of electrons and nuclei simultaneously by considering the full electron-nuclear coupling in the system and thus eliminates the necessity of constructing potential-energy surfaces. The theory approximates the time dependent Schrödinger equation starting from the time dependent variational principle (TDVP) by deriving a Hamiltonian dynamical system for time dependent nuclear and electronic wave function parameters. The wave function is described in a coherent state manifold, which leads to a system of Hamilton's equations of motion. The resulting system of coupled, first order, ordinary differential equations approximates the Schrödinger equation. A detailed analysis of the END equations is given for the case of a single-determinantal state for the electrons and a classical treatment of the nuclei. Emphasis is put on electron exchange, differential cross section and energy loss (stopping cross section) of collision of ions, atoms and molecules involving H, He, C, N, O, and Ne atoms. We compare our results to available experimental data.

  11. Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

    NASA Astrophysics Data System (ADS)

    Lípari, S.; Díaz, R.; Taniguchi, Y.; Terlevich, R.; Dottori, H.; Carranza, G.

    2000-08-01

    ouflow axis (at P.A.~160deg). We analyze in detail the physical conditions in the giant H II regions located in the asymmetric spiral arms, the two main optical nuclei, and the outflow component (using long-slit spectroscopy, plus standard models of photoionization, shocks, and starbursts). We present four detailed emission-line ratios (N II/Hα, S II/Hα, S II/S II), and FWHM (Hα) maps for the central region (30''×30'' rmax~22''~4 kpc), with a spatial resolution of 1". In the central region (r~5-6 kpc) we detected that the nuclear starburst and the extended giant H II regions (in the spiral arms) have very similar properties, i.e., high metallicity and low-ionization spectra, with Teff=35,000 K, solar abundance, a range of Te~6000-7000 K, and Ne~100-1000 cm-3. The nuclear and extended outflow shows properties typical of galactic wind/shocks, associated with the nuclear starburst. We suggest that the interaction between dynamical effects, the galactic wind (outflow), low-energy cosmic rays, and the molecular+ionized gas (probably in the inflow phase) could be the possible mechanism that generate the ``similar extended properties in the massive star formation, at a scale of 5-6 kpc!'' We have also studied the presence of the close merger/interacting systems NGC 3256C (at ~150 kpc, ΔV=-100 km s-1) and the possible association between the NGC 3256 and 3263 groups of galaxies. In conclusion, these results suggest that NGC 3256 is the product of a multiple merger, which generated an extended massive star formation process with an associated galactic wind plus a nuclear inflow. Therefore, NGC 3256 is another example in which the relation between mergers and extreme starburst (and the powerful galactic wind, ``multiple'' Type II supernova explosions) play an important role in the evolution of galaxies (the hypothesis of Rieke et al., Joseph et al., Terlevich et al., Heckman et al., and Lípari et al.). Based on observations obtained at the Hubble Space Telescope (HST; Wide

  12. Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.

    PubMed

    Högele, A; Kroner, M; Latta, C; Claassen, M; Carusotto, I; Bulutay, C; Imamoglu, A

    2012-05-11

    Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system.

  13. Summary of findings: Calvert Cliffs Nuclear Power Plant aquatic monitoring program. Volume III, appendices d-h

    SciTech Connect

    Not Available

    1980-08-01

    The report includes baseline studies for environmental impacts of Clavert Cliffs Nuclear Power Plant construction which is located on the Chesapeake Bay. The appendix summarizes monitoring studies on: benthic invertebrates (including clams, crabs, and oysters); finfish; and ecosystem.

  14. Analysis of sensitivity enhancement by dynamic nuclear polarization in solid-state NMR: a case study of functionalized mesoporous materials.

    PubMed

    Kobayashi, Takeshi; Lafon, Olivier; Thankamony, Aany S Lilly; Slowing, Igor I; Kandel, Kapil; Carnevale, Diego; Vitzthum, Veronika; Vezin, Hervé; Amoureux, Jean-Paul; Bodenhausen, Geoffrey; Pruski, Marek

    2013-04-21

    We systematically studied the enhancement factor (per scan) and the sensitivity enhancement (per unit time) in (13)C and (29)Si cross-polarization magic angle spinning (CP-MAS) NMR boosted by dynamic nuclear polarization (DNP) of functionalized mesoporous silica nanoparticles (MSNs). Specifically, we separated contributions due to: (i) microwave irradiation, (ii) quenching by paramagnetic effects, (iii) the presence of frozen solvent, (iv) the temperature, as well as changes in (v) relaxation and (vi) cross-polarization behaviour. No line-broadening effects were observed for MSNs when lowering the temperature from 300 to 100 K. Notwithstanding a significant signal reduction due to quenching by TOTAPOL radicals, DNP-CP-MAS at 100 K provided global sensitivity enhancements of 23 and 45 for (13)C and (29)Si, respectively, relative to standard CP-MAS measurements at room temperature. The effects of DNP were also ascertained by comparing with state-of-the-art two-dimensional heteronuclear (1)H{(13)C} and (29)Si{(1)H} correlation spectra, using, respectively, indirect detection or Carr-Purcell-Meiboom-Gill (CPMG) refocusing to boost signal acquisition. This study highlights opportunities for further improvements through the development of high-field DNP, better polarizing agents, and improved capabilities for low-temperature MAS.

  15. Nonadiabatic nuclear dynamics of the ammonia cation studied by surface hopping classical trajectory calculations

    SciTech Connect

    Belyaev, Andrey K.; Domcke, Wolfgang; Lasser, Caroline Trigila, Giulio

    2015-03-14

    The Landau–Zener (LZ) type classical-trajectory surface-hopping algorithm is applied to the nonadiabatic nuclear dynamics of the ammonia cation after photoionization of the ground-state neutral molecule to the excited states of the cation. The algorithm employs a recently proposed formula for nonadiabatic LZ transition probabilities derived from the adiabatic potential energy surfaces. The evolution of the populations of the ground state and the two lowest excited adiabatic states is calculated up to 200 fs. The results agree well with quantum simulations available for the first 100 fs based on the same potential energy surfaces. Three different time scales are detected for the nuclear dynamics: Ultrafast Jahn–Teller dynamics between the excited states on a 5 fs time scale; fast transitions between the excited state and the ground state within a time scale of 20 fs; and relatively slow partial conversion of a first-excited-state population to the ground state within a time scale of 100 fs. Beyond 100 fs, the adiabatic electronic populations are nearly constant due to a dynamic equilibrium between the three states. The ultrafast nonradiative decay of the excited-state populations provides a qualitative explanation of the experimental evidence that the ammonia cation is nonfluorescent.

  16. What Can Be Learned from Nuclear Resonance Vibrational Spectroscopy: Vibrational Dynamics and Hemes.

    PubMed

    Scheidt, W Robert; Li, Jianfeng; Sage, J Timothy

    2017-09-18

    Nuclear resonance vibrational spectroscopy (NRVS; also known as nuclear inelastic scattering, NIS) is a synchrotron-based method that reveals the full spectrum of vibrational dynamics for Mössbauer nuclei. Another major advantage, in addition to its completeness (no arbitrary optical selection rules), is the unique selectivity of NRVS. The basics of this recently developed technique are first introduced with descriptions of the experimental requirements and data analysis including the details of mode assignments. We discuss the use of NRVS to probe (57)Fe at the center of heme and heme protein derivatives yielding the vibrational density of states for the iron. The application to derivatives with diatomic ligands (O2, NO, CO, CN(-)) shows the strong capabilities of identifying mode character. The availability of the complete vibrational spectrum of iron allows the identification of modes not available by other techniques. This permits the correlation of frequency with other physical properties. A significant example is the correlation we find between the Fe-Im stretch in six-coordinate Fe(XO) hemes and the trans Fe-N(Im) bond distance, not possible previously. NRVS also provides uniquely quantitative insight into the dynamics of the iron. For example, it provides a model-independent means of characterizing the strength of iron coordination. Prediction of the temperature-dependent mean-squared displacement from NRVS measurements yields a vibrational "baseline" for Fe dynamics that can be compared with results from techniques that probe longer time scales to yield quantitative insights into additional dynamical processes.

  17. Nuclear Y-Box-binding Protein-1 Expression Predicts Poor Clinical Outcome in Stage III Colorectal Cancer.

    PubMed

    Shiraiwa, Sachiko; Kinugasa, Tetsushi; Kawahara, Akihiko; Mizobe, Tomoaki; Ohchi, Takafumi; Yuge, Kotaro; Fujino, Shinya; Katagiri, Mitsuhiro; Shimomura, Susumu; Tajiri, Kensuke; Sudo, Tomoya; Kage, Masayoshi; Kuwano, Michihiko; Akagi, Yoshito

    2016-07-01

    Y-Box-binding protein-1 (YB-1), a DNA/RNA-binding protein, is an important oncogenic transcription and translation factor. We aimed to evaluate the relationships between nuclear YB-1 expression, epidermal growth factor receptor (EGFR) status, and poor clinical outcomes in patients with colorectal cancer (CRC). Nuclear YB-1 expression was immunohistochemically analyzed in CRC tissues obtained from 124 patients who underwent curative resection between 2005 and 2008. Correlations between nuclear YB-1 expression, various clinicopathological characteristics, EGFR status, and prognostic factors were evaluated. High-grade nuclear YB-1 expression was detected in 62.9% of cases and was found to be an independent predictor of poorer overall survival (p<0.001) and relapse-free survival (p<0.001). A trend was also observed towards a positive correlation between nuclear YB-1 expression and EGFR status (p=0.051). Nuclear YB-1 expression is a useful prognostic biomarker that correlates with EGFR status in patients with CRC. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  18. Glycan flexibility: insights into nanosecond dynamics from a microsecond molecular dynamics simulation explaining an unusual nuclear Overhauser effect.

    PubMed

    Landström, Jens; Widmalm, Göran

    2010-01-26

    An atomistic all-atom molecular dynamics simulation of the trisaccharide beta-D-ManpNAc-(1-->4)[alpha-D-Glcp-(1-->3)]-alpha-L-Rhap-OMe with explicit solvent molecules has been carried out. The trisaccharide represents a model for the branching region of the O-chain polysaccharide of a strain from Aeromonas salmonicida. The extensive MD simulations having a 1-micros duration revealed a conformational dynamics process on the nanosecond time scale, that is, a 'time window' not extensively investigated for carbohydrates to date. The results obtained from the MD simulation underscore the predictive power of molecular simulations in studies of biomolecular systems and also explain an unusual nuclear Overhauser effect originating from conformational exchange. 2009 Elsevier Ltd. All rights reserved.

  19. Dynamic Nuclear Polarization and Relaxation of H and D Atoms in Solid Mixtures of Hydrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Sheludiakov, S.; Ahokas, J.; Järvinen, J.; Vainio, O.; Lehtonen, L.; Vasiliev, S.; Lee, D. M.; Khmelenko, V. V.

    2017-04-01

    We report on a study of dynamic nuclear polarization and electron and nuclear spin relaxation of atomic hydrogen and deuterium in solid molecular matrices of H2, D2, and HD mixtures. The electron and nuclear spin relaxation times (T_{1e} and T_{1N}) were measured within the temperature range 0.15-2.5 K in a magnetic field of 4.6 T, conditions which ensure a high polarization of electron spins. We found that T_{1e} is nearly temperature independent in this temperature range, while T_{1N} decreased by two orders of magnitude upon raising temperature. Such strong temperature dependence is typical for the nuclear Orbach mechanism of relaxation via the electron spins. We found that the nuclear spins of H atoms in solid D2 and D2{:}HD can be efficiently polarized by the Overhauser effect. Pumping the forbidden transitions of H atoms also leads to DNP, with the efficiency strongly dependent on the concentration of D atoms. This behavior indicates the cross effect mechanism of the DNP and nuclear relaxation, which turns out to be well resolved in the conditions of our experiments. Efficient DNP of H atoms was also observed when pumping the middle D line located in the center of the ESR spectrum. This phenomenon can be explained in terms of clusters or pairs of H atoms with a strong exchange interaction. These clusters have partially allowed transitions in the center of the ESR spectrum, and DNP may be created via the resolved cross effect.

  20. Electrostatic Potential Determined Magnetic Dynamics Observed in Two Mononuclear β-Diketone Dysprosium(III) Single-Molecule Magnets.

    PubMed

    Cen, Pei-Pei; Zhang, Sheng; Liu, Xiang-Yu; Song, Wei-Ming; Zhang, Yi-Quan; Xie, Gang; Chen, San-Ping

    2017-03-20

    Two β-diketone mononuclear Dy(III) compounds, formulated as Dy(BTFA)3(H2O)2 (1) and Dy(BTFA)3(bpy) (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone, bpy = 2,2'-bipyridine), were prepared. Compound 1 can be identified to transform to 2 in the attendance of bpy coligand, when the local geometry symmetry of eight-coordinated Dy(III) ion changes from a dodecahedron (D2d) in 1 to a square antiprism (D4d) in 2. Fine-tuning structure aroused by auxiliary ligand has dramatical impact on magnetic properties of compounds 1 and 2. Magnetic investigations demonstrate that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnets (SMMs) behavior with different effective barriers (ΔE/kB) of 93.09 K for 1 under zero direct-current (DC) field as well as 296.50 K for 1 and 151.01 K for 2 under 1200 Oe DC field, respectively. As noticed, compound 1 possesses higher effective barrier than 2, despite 1 exhibiting a lower geometrical symmetry of the Dy(III) ion. Ab initio studies reveal that the Kramers doublet ground state is predominantly axial with the gz tensors of two compounds matching the Ising-limit factor of 20 anticipated for the pure MJ = ±15/2 state. Electrostatic analysis confirms the uniaxial anisotropy directions, highlighting that the proper electrostatic distribution of the coordination sphere around Ln(III) center is the critical factor to improve the magnetic anisotropy and determine the dynamic behaviors of SMMs.

  1. Spent nuclear fuel system dynamic stability under normal conditions of transportation

    DOE PAGES

    Jiang, Hao; Wang, Jy-An John

    2016-10-14

    In a horizontal layout of a spent nuclear fuel (SNF) assembly under normal conditions of transportation (NCT), the fuel assembly’s skeleton formed by guide tubes and spacer grids is the primary load bearing structure for carrying and transferring the vibration loads within an SNF assembly. Therefore, the integrity of guide tubes and spacer grids will dictate the vibration amplitude/intensity of the fuel assembly during transport, and must be considered when designing multipurpose purpose canister (MPC) for safe SNF transport. This paper investigates the SNF assembly deformation dynamics during normal vibration mode, as well as the transient shock mode inside themore » cask during NCT. In conclusion, dynamic analyses were performed in the frequency domain to study frequency characteristic of the fuel assembly system and in the time domain to simulate the transient dynamic response of the fuel assembly.« less

  2. Spent nuclear fuel system dynamic stability under normal conditions of transportation

    SciTech Connect

    Jiang, Hao; Wang, Jy-An John

    2016-10-14

    In a horizontal layout of a spent nuclear fuel (SNF) assembly under normal conditions of transportation (NCT), the fuel assembly’s skeleton formed by guide tubes and spacer grids is the primary load bearing structure for carrying and transferring the vibration loads within an SNF assembly. Therefore, the integrity of guide tubes and spacer grids will dictate the vibration amplitude/intensity of the fuel assembly during transport, and must be considered when designing multipurpose purpose canister (MPC) for safe SNF transport. This paper investigates the SNF assembly deformation dynamics during normal vibration mode, as well as the transient shock mode inside the cask during NCT. In conclusion, dynamic analyses were performed in the frequency domain to study frequency characteristic of the fuel assembly system and in the time domain to simulate the transient dynamic response of the fuel assembly.

  3. Lattice dynamics in spin-crossover nanoparticles through nuclear inelastic scattering

    NASA Astrophysics Data System (ADS)

    Félix, Gautier; Mikolasek, Mirko; Peng, Haonan; Nicolazzi, William; Molnár, Gábor; Chumakov, Aleksandr I.; Salmon, Lionel; Bousseksou, Azzedine

    2015-01-01

    We used nuclear inelastic scattering (NIS) to investigate the lattice dynamics in [Fe(pyrazine)(Ni(CN)4)] spin crossover nanoparticles. The vibrational density of states of iron was extracted from the NIS data, which allowed to determine characteristic thermodynamical and lattice dynamical parameters as well as their spin-state dependence. The optical part of the NIS spectra compares well with the Raman scattering data reflecting the expansion/contraction of the coordination octahedron during the spin transition. From the acoustic part, we extracted the sound velocity in the low-spin (vLS=2073 ±31 m s-1) and high-spin (vHS=1942 ±23 m s-1) states of the particles. The spin-state dependence of this parameter is of primary interest to rationalize the spin-transition behavior in solids as well as its dynamics and finite size effects.

  4. Evolution of Dengue Virus Type 3 Genotype III in Venezuela: Diversification, Rates and Population Dynamics

    PubMed Central

    2010-01-01

    Background Dengue virus (DENV) is a member of the genus Flavivirus of the family Flaviviridae. DENV are comprised of four distinct serotypes (DENV-1 through DENV-4) and each serotype can be divided in different genotypes. Currently, there is a dramatic emergence of DENV-3 genotype III in Latin America. Nevertheless, we still have an incomplete understanding of the evolutionary forces underlying the evolution of this genotype in this region of the world. In order to gain insight into the degree of genetic variability, rates and patterns of evolution of this genotype in Venezuela and the South American region, phylogenetic analysis, based on a large number (n = 119) of envelope gene sequences from DENV-3 genotype III strains isolated in Venezuela from 2001 to 2008, were performed. Results Phylogenetic analysis revealed an in situ evolution of DENV-3 genotype III following its introduction in the Latin American region, where three different genetic clusters (A to C) can be observed among the DENV-3 genotype III strains circulating in this region. Bayesian coalescent inference analyses revealed an evolutionary rate of 8.48 × 10-4 substitutions/site/year (s/s/y) for strains of cluster A, composed entirely of strains isolated in Venezuela. Amino acid substitution at position 329 of domain III of the E protein (A→V) was found in almost all E proteins from Cluster A strains. Conclusions A significant evolutionary change between DENV-3 genotype III strains that circulated in the initial years of the introduction in the continent and strains isolated in the Latin American region in recent years was observed. The presence of DENV-3 genotype III strains belonging to different clusters was observed in Venezuela, revealing several introduction events into this country. The evolutionary rate found for Cluster A strains circulating in Venezuela is similar to the others previously established for this genotype in other regions of the world. This suggests a lack of correlation

  5. Evolution of dengue virus type 3 genotype III in Venezuela: diversification, rates and population dynamics.

    PubMed

    Ramírez, Alvaro; Fajardo, Alvaro; Moros, Zoila; Gerder, Marlene; Caraballo, Gerson; Camacho, Daria; Comach, Guillermo; Alarcón, Victor; Zambrano, Julio; Hernández, Rosa; Moratorio, Gonzalo; Cristina, Juan; Liprandi, Ferdinando

    2010-11-18

    Dengue virus (DENV) is a member of the genus Flavivirus of the family Flaviviridae. DENV are comprised of four distinct serotypes (DENV-1 through DENV-4) and each serotype can be divided in different genotypes. Currently, there is a dramatic emergence of DENV-3 genotype III in Latin America. Nevertheless, we still have an incomplete understanding of the evolutionary forces underlying the evolution of this genotype in this region of the world. In order to gain insight into the degree of genetic variability, rates and patterns of evolution of this genotype in Venezuela and the South American region, phylogenetic analysis, based on a large number (n = 119) of envelope gene sequences from DENV-3 genotype III strains isolated in Venezuela from 2001 to 2008, were performed. Phylogenetic analysis revealed an in situ evolution of DENV-3 genotype III following its introduction in the Latin American region, where three different genetic clusters (A to C) can be observed among the DENV-3 genotype III strains circulating in this region. Bayesian coalescent inference analyses revealed an evolutionary rate of 8.48 x 10⁻⁴ substitutions/site/year (s/s/y) for strains of cluster A, composed entirely of strains isolated in Venezuela. Amino acid substitution at position 329 of domain III of the E protein (A→V) was found in almost all E proteins from Cluster A strains. A significant evolutionary change between DENV-3 genotype III strains that circulated in the initial years of the introduction in the continent and strains isolated in the Latin American region in recent years was observed. The presence of DENV-3 genotype III strains belonging to different clusters was observed in Venezuela, revealing several introduction events into this country. The evolutionary rate found for Cluster A strains circulating in Venezuela is similar to the others previously established for this genotype in other regions of the world. This suggests a lack of correlation among DENV genotype III

  6. Dynamic Complexity Study of Nuclear Reactor and Process Heat Application Integration

    SciTech Connect

    J'Tia Patrice Taylor; David E. Shropshire

    2009-09-01

    Abstract This paper describes the key obstacles and challenges facing the integration of nuclear reactors with process heat applications as they relate to dynamic issues. The paper also presents capabilities of current modeling and analysis tools available to investigate these issues. A pragmatic approach to an analysis is developed with the ultimate objective of improving the viability of nuclear energy as a heat source for process industries. The extension of nuclear energy to process heat industries would improve energy security and aid in reduction of carbon emissions by reducing demands for foreign derived fossil fuels. The paper begins with an overview of nuclear reactors and process application for potential use in an integrated system. Reactors are evaluated against specific characteristics that determine their compatibility with process applications such as heat outlet temperature. The reactor system categories include light water, heavy water, small to medium, near term high-temperature, and far term high temperature reactors. Low temperature process systems include desalination, district heating, and tar sands and shale oil recovery. High temperature processes that support hydrogen production include steam reforming, steam cracking, hydrogen production by electrolysis, and far-term applications such as the sulfur iodine chemical process and high-temperature electrolysis. A simple static matching between complementary systems is performed; however, to gain a true appreciation for system integration complexity, time dependent dynamic analysis is required. The paper identifies critical issues arising from dynamic complexity associated with integration of systems. Operational issues include scheduling conflicts and resource allocation for heat and electricity. Additionally, economic and safety considerations that could impact the successful integration of these systems are considered. Economic issues include the cost differential arising due to an integrated

  7. 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.

  8. Nuclear dynamics during germination, conidiation, and hyphal fusion of Fusarium oxysporum.

    PubMed

    Ruiz-Roldán, M Carmen; Köhli, Michael; Roncero, M Isabel G; Philippsen, Peter; Di Pietro, Antonio; Espeso, Eduardo A

    2010-08-01

    In many fungal pathogens, infection is initiated by conidial germination. Subsequent stages involve germ tube elongation, conidiation, and vegetative hyphal fusion (anastomosis). Here, we used live-cell fluorescence to study the dynamics of green fluorescent protein (GFP)- and cherry fluorescent protein (ChFP)-labeled nuclei in the plant pathogen Fusarium oxysporum. Hyphae of F. oxysporum have uninucleated cells and exhibit an acropetal nuclear pedigree, where only the nucleus in the apical compartment is mitotically active. In contrast, conidiation follows a basopetal pattern, whereby mononucleated microconidia are generated by repeated mitotic cycles of the subapical nucleus in the phialide, followed by septation and cell abscission. Vegetative hyphal fusion is preceded by directed growth of the fusion hypha toward the receptor hypha and followed by a series of postfusion nuclear events, including mitosis of the apical nucleus of the fusion hypha, migration of a daughter nucleus into the receptor hypha, and degradation of the resident nucleus. These previously unreported patterns of nuclear dynamics in F. oxysporum could be intimately related to its pathogenic lifestyle.

  9. Electronic decoherence following photoionization: Full quantum-dynamical treatment of the influence of nuclear motion

    NASA Astrophysics Data System (ADS)

    Arnold, Caroline; Vendrell, Oriol; Santra, Robin

    2017-03-01

    Photoionization using attosecond pulses can lead to the formation of coherent superpositions of the electronic states of the parent ion. However, ultrafast electron ejection triggers not only electronic but also nuclear dynamics—leading to electronic decoherence, which is typically neglected on time scales up to tens of femtoseconds. We propose a full quantum-dynamical treatment of nuclear motion in an adiabatic framework, where nuclear wave packets move on adiabatic potential energy surfaces expanded up to second order at the Franck-Condon point. We show that electronic decoherence is caused by the interplay of a large number of nuclear degrees of freedom and by the relative topology of the potential energy surfaces. Application to H2O , paraxylene, and phenylalanine shows that an initially coherent state evolves to an electronically mixed state within just a few femtoseconds. In these examples the fast vibrations involving hydrogen atoms do not affect electronic coherence at short times. Conversely, vibrational modes involving the whole molecular skeleton, which are slow in the ground electronic state, quickly destroy it upon photoionization.

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

    PubMed

    Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

    2010-12-01

    Dynamic nuclear polarization has gained high popularity in recent years, due to advances in the experimental aspects of this methodology for increasing the NMR and MRI signals of relevant chemical and biological compounds. The DNP mechanism relies on the microwave (MW) irradiation induced polarization transfer from unpaired electrons to the nuclei in a sample. In this publication we present nuclear polarization enhancements of model systems in the solid state at high magnetic fields. These results were obtained by numerical calculations based on the spin density operator formalism. Here we restrict ourselves to samples with low electron concentrations, where the dipolar electron-electron interactions can be ignored. Thus the DNP enhancement of the polarizations of the nuclei close to the electrons is described by the Solid Effect mechanism. Our numerical results demonstrate the dependence of the polarization enhancement on the MW irradiation power and frequency, the hyperfine and nuclear dipole-dipole spin interactions, and the relaxation parameters of the system. The largest spin system considered in this study contains one electron and eight nuclei. In particular, we discuss the influence of the nuclear concentration and relaxation on the polarization of the core nuclei, which are coupled to an electron, and are responsible for the transfer of polarization to the bulk nuclei in the sample via spin diffusion. Copyright © 2010 Elsevier Inc. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

    2010-12-01

    Dynamic nuclear polarization has gained high popularity in recent years, due to advances in the experimental aspects of this methodology for increasing the NMR and MRI signals of relevant chemical and biological compounds. The DNP mechanism relies on the microwave (MW) irradiation induced polarization transfer from unpaired electrons to the nuclei in a sample. In this publication we present nuclear polarization enhancements of model systems in the solid state at high magnetic fields. These results were obtained by numerical calculations based on the spin density operator formalism. Here we restrict ourselves to samples with low electron concentrations, where the dipolar electron-electron interactions can be ignored. Thus the DNP enhancement of the polarizations of the nuclei close to the electrons is described by the Solid Effect mechanism. Our numerical results demonstrate the dependence of the polarization enhancement on the MW irradiation power and frequency, the hyperfine and nuclear dipole-dipole spin interactions, and the relaxation parameters of the system. The largest spin system considered in this study contains one electron and eight nuclei. In particular, we discuss the influence of the nuclear concentration and relaxation on the polarization of the core nuclei, which are coupled to an electron, and are responsible for the transfer of polarization to the bulk nuclei in the sample via spin diffusion.

  12. Quantitative rate determination by dynamic nuclear polarization enhanced NMR of a Diels-Alder reaction.

    PubMed

    Zeng, Haifeng; Lee, Youngbok; Hilty, Christian

    2010-11-01

    Emerging techniques for hyperpolarization of nuclear spins, foremost dynamic nuclear polarization (DNP), lend unprecedented sensitivity to nuclear magnetic resonance spectroscopy. Sufficient signal can be obtained from a single scan, and reactions even far from equilibrium can be studied in real-time. When following the progress of a reaction by nuclear magnetic resonance, however, spin relaxation occurs concomitantly with the reaction to alter resonance line intensities. Here, we present a model for accounting for spin-relaxation in such reactions studied by hyperpolarized NMR. The model takes into account auto- and cross-relaxation in dipole-dipole coupled spin systems and is therefore applicable to NMR of hyperpolarized protons, the most abundant NMR-active nuclei. Applied to the Diels-Alder reaction of 1,4-dipheneylbutadiene (DPBD) with 4-phenyl-1,2,4-triazole-3,5-dione (PTD), reaction rates could be obtained accurately and reproducibly. Additional parameters available from the same experiment include relaxation rates of the reaction product, which may yield further information about the molecular properties of the product. The method presented is also compatible with an experiment where a single spin in the reactant is labeled in its spin-state by a selective radio frequency pulse for subsequent tracking through the reaction, allowing the unambiguous identification of its position in the product molecule. In this case, the chemical shift specificity of high-resolution NMR can allow for the simultaneous determination of reaction rates and mechanistic information in one experiment.

  13. Dynamic nuclear polarization via thermal mixing: Beyond the high temperature approximation

    NASA Astrophysics Data System (ADS)

    Wenckebach, W. Th.

    2017-04-01

    Dynamic Nuclear Polarization (DNP) via the mechanism of thermal mixing has proven itself most powerful for the orientation of nuclear spins in polarized targets and hyperpolarization for magnetic resonance imaging (MRI). Unfortunately, theoretical descriptions of this mechanism have been limited to using-at least partially-the high temperature approximation, in which Boltzmann factors are expanded linearly. However, the high nuclear spin polarization required and obtained for these applications does not justify such approximations. This article extends the description of thermal mixing beyond the high temperature approximation, so Boltzmann factors are not expanded. It applies for DNP in samples doped with paramagnetic centres, for which the electron spin resonance spectrum is mainly inhomogeneously broadened by g-value anisotropy. It verifies Provotorov's hypothesis that fast spectral diffusion leads to a density matrix containing two inverse spin temperatures: the inverse electron Zeeman temperature and the inverse electron non-Zeeman temperature, while thermal mixing equalizes the nuclear Zeeman temperature and the electron non-Zeeman temperature. Equations are derived for the evolution of these temperatures and the energy flows between the spins and the lattice. Solutions are given for DNP of proton spins in samples doped with the radical TEMPO.

  14. Cytoplasmic dynamics of the general nuclear import machinery in apically growing syncytial cells.

    PubMed

    Etxebeste, Oier; Villarino, María; Markina-Iñarrairaegui, Ane; Araújo-Bazán, Lidia; Espeso, Eduardo A

    2013-01-01

    Karyopherins are transporters involved in the bidirectional, selective and active transport of macromolecules through nuclear pores. Importin-β1 is the paradigm of karyopherins and, together with its cargo-adapter importin-α, mediates the general nuclear import pathway. Here we show the existence of different cellular pools of both importin-α and -β1 homologues, KapA and KapB, in the coenocytic ascomycete Aspergillus nidulans. Fluorescence analysis of haploid and diploid strains expressing KapB::GFP and/or KapA::mRFP showed patches of both karyopherins concurrently translocating long distances in apically-growing cells. Anterograde and retrograde movements allowed those patches to reach cell tips and distal regions with an average speed in the range of μm/s. This bidirectional traffic required microtubules as well as kinesin and dynein motors, since it is blocked by benomyl and also by the inactivation of the dynein/dynactin complex through nudA1 or nudK317 mutations. Deletion of Kinesin-3 motor UncA, required for the transport through detyrosinated microtubules, strongly inhibited KapA and KapB movement along hyphae. Overall, this is the first report describing the bidirectional dynamics of the main nuclear import system in coenocytic fungi. A functional link is proposed between two key cellular machines of the filamentous fungal cell: nuclear transport and the tip-growth apparatus.

  15. Chromatin Dynamics in Interphase Nuclei and Its Implications for Nuclear Structure

    PubMed Central

    Abney, James R.; Cutler, Bryan; Fillbach, Misty L.; Axelrod, Daniel; Scalettar, Bethe A.

    1997-01-01

    Translational dynamics of chromatin in interphase nuclei of living Swiss 3T3 and HeLa cells was studied using fluorescence microscopy and fluorescence recovery after photobleaching. Chromatin was fluorescently labeled using dihydroethidium, a membrane-permeant derivative of ethidium bromide. After labeling, a laser was used to bleach small (∼0.4 μm radius) spots in the heterochromatin and euchromatin of cells of both types. These spots were observed to persist for >1 h, implying that interphase chromatin is immobile over distance scales ⩾0.4 μm. Over very short times (<1 s), a partial fluorescence recovery within the spots was observed. This partial recovery is attributed to independent dye motion, based on comparison with results obtained using ethidium homodimer-1, which binds essentially irreversibly to nucleic acids. The immobility observed here is consistent with chromosome confinement to domains in interphase nuclei. This immobility may reflect motion-impeding steric interactions that arise in the highly concentrated nuclear milieu or outright attachment of the chromatin to underlying nuclear substructures, such as nucleoli, the nuclear lamina, or the nuclear matrix. PMID:9199163

  16. 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

  17. 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.

  18. Dynamic nuclear polarization via thermal mixing: Beyond the high temperature approximation.

    PubMed

    Wenckebach, W Th

    2017-04-01

    Dynamic Nuclear Polarization (DNP) via the mechanism of thermal mixing has proven itself most powerful for the orientation of nuclear spins in polarized targets and hyperpolarization for magnetic resonance imaging (MRI). Unfortunately, theoretical descriptions of this mechanism have been limited to using-at least partially-the high temperature approximation, in which Boltzmann factors are expanded linearly. However, the high nuclear spin polarization required and obtained for these applications does not justify such approximations. This article extends the description of thermal mixing beyond the high temperature approximation, so Boltzmann factors are not expanded. It applies for DNP in samples doped with paramagnetic centres, for which the electron spin resonance spectrum is mainly inhomogeneously broadened by g-value anisotropy. It verifies Provotorov's hypothesis that fast spectral diffusion leads to a density matrix containing two inverse spin temperatures: the inverse electron Zeeman temperature and the inverse electron non-Zeeman temperature, while thermal mixing equalizes the nuclear Zeeman temperature and the electron non-Zeeman temperature. Equations are derived for the evolution of these temperatures and the energy flows between the spins and the lattice. Solutions are given for DNP of proton spins in samples doped with the radical TEMPO.

  19. Dynamic nuclear spin polarization of liquids and gases in contact with nanostructured diamond.

    PubMed

    Abrams, Daniel; Trusheim, Matthew E; Englund, Dirk R; Shattuck, Mark D; Meriles, Carlos A

    2014-05-14

    Optical pumping of spin polarization can produce almost complete spin order but its application is restricted to select atomic gases and condensed matter systems. Here, we theoretically investigate a novel route to nuclear spin hyperpolarization in arbitrary fluids in which target molecules are exposed to polarized paramagnetic centers located near the surface of a host material. We find that adsorbed nuclear spins relax to positive or negative polarization depending on the average paramagnetic center depth and nanoscale surface topology. For the particular case of optically pumped nitrogen-vacancy centers in diamond, we calculate strong nuclear spin polarization at moderate magnetic fields provided the crystal surface is engineered with surface roughness in the few-nanometer range. The equilibrium nuclear spin temperature depends only weakly on the correlation time describing the molecular adsorption dynamics and is robust in the presence of other, unpolarized paramagnetic centers. These features could be exploited to polarize flowing liquids or gases, as we illustrate numerically for the model case of a fluid brought in contact with an optically pumped diamond nanostructure.

  20. Relevance of electron spin dissipative processes to dynamic nuclear polarization via thermal mixing.

    PubMed

    Serra, Sonia Colombo; Filibian, Marta; Carretta, Pietro; Rosso, Alberto; Tedoldi, Fabio

    2014-01-14

    The available theoretical approaches aiming at describing Dynamic Nuclear spin Polarization (DNP) in solutions containing molecules of biomedical interest and paramagnetic centers are not able to model the behaviour observed upon varying the concentration of trityl radicals or the polarization enhancement caused by moderate addition of gadolinium complexes. In this manuscript, we first show experimentally that the nuclear steady state polarization reached in solutions of pyruvic acid with 15 mM trityl radicals is substantially independent on the average internuclear distance. This evidences a leading role of electron (over nuclear) spin relaxation processes in determining the ultimate performances of DNP. Accordingly, we have devised a variant of the Thermal Mixing model for inhomogenously broadened electron resonance lines which includes a relaxation term describing the exchange of magnetic anisotropy energy of the electron spin system with the lattice. Thanks to this additional term, the dependence of the nuclear polarization on the electron concentration can be properly accounted for. Moreover, the model predicts a strong increase of the final polarization upon shortening the electron spin-lattice relaxation time, providing a possible explanation for the effect of gadolinium doping.

  1. The Planetary Nebula System and Dynamics of NGC 5128. III. Kinematics and Halo Mass Distributions

    NASA Astrophysics Data System (ADS)

    Hui, Xiaohui; Ford, Holland C.; Freeman, Kenneth C.; Dopita, Michael A.

    1995-08-01

    We present a study of the halo dynamics and mass distributions of the nearby giant elliptical galaxy NGC 5128 using planetary nebulae (PNs) as test particles. Radial velocities of 433 PNs were obtained with multifiber spectrographs on both the Anglo-Australian Telescope (AAT) and the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope. The velocities were measured from the [O III] λ5007 emission line with a typical 1 σ error of ±4 km s-1 and ±30 km s-1 for the AAT and the CTIO data, respectively. These PNs cover the entire galaxy to a radius of 10 kpc and extend along the photometric major axis out to 20 kpc. The PN velocity field shows the distinctive characteristics of a triaxial potential: the galaxy's rotation axis is offset from its photometric minor axis by 39°±10°. the rotation axis and the line of maximum rotation are likely not orthogonal. We also find that the ordered motions of the stars become more important with increasing radius compared to their random motions. The rotation reaches approximately 100 km s-1 and 50 km s-1 along the photometric major and minor axes, giving a local V/σ ratio of about 1.0 and 0.5, respectively. The aximuthal variation of the velocity dispersion appears to be modulated by rotation, i.e., it reaches a maximum where the largest rotation is observed and drops to a minimum at zero rotation. The amplitude of this modulation is about 20km s-1, compared to a mean dispersion velocity of 110 km s-1. The kinematics of the globular clusters depend on the metallicity Taking [Fe/H] = -1.0 as the dividing point, the metal-poor clusters do not show any significant rotation. However, the metal-rich clusters show both major and minor axis rotation, and the amplitudes of the rotation are similar to that of the PNs. The stellar velocity dispersion measured from absorption-line spectra together with an Hα rotation curve of the dust lane suggest that the stellar orbits are isotropic and the mass-to-light ratio (M/LB) is 3

  2. Peopling The American Colonies, Episode III. Resource Material Development: Population Dynamics in Eighth Grade American History.

    ERIC Educational Resources Information Center

    Massialas, Byron G.; And Others

    This is the third unit in a series that introduces population concepts into the eighth grade American history curriculum. (See SO 013 782 for an overview to the guide.) In Episode III, the history topic is the late colonial periods. Unit objectives are to (1) examine the effects of different lifestyles on population changes in America and England;…

  3. A new nuclear magnetic resonance algorithm to determine equilibrium constants of the species in the B(III)-H2O system.

    PubMed

    Botello, J C; Morales-Domínguez, E; Domínguez, J M; Gutiérrez, A; Rojas-Hernández, A; Ramírez, M T

    2003-05-01

    Several efforts have been attempted to study species formation by Nuclear Magnetic Resonance (NMR) in systems with several chemical equilibria present. The majority of these are qualitative and only a few have tried to relate component fractions of a distribution diagram with experimental area fractions determined from NMR spectra to obtain equilibrium constants values. In this work we present a new focus that attempts to relate the species concentration fractions in the system with area fractions beneath NMR peaks to achieve this task. 11B-NMR data of B(III)-H2O systems have been processed with the aid of formation constant values (-log *beta) obtained by potentiometry which are 9.17+/-0.01 for B(OH)3, 9.79+/-0.08 for B2O(OH)5-, 19.90+/-0.09 for B3O3(OH)4- and 38.50+/-0.04 for B5O6(OH)4-, form B(III)-H2O systems with 0.075 M< or = [B(III)]total< or = 0.700 M, in agreement with previous reports and NMR behavior. The treatment of NMR data developed in this work gives a new methodology to obtain formation constants and suggests the possibility to establish a generalization of Beer's law to NMR spectroscopy.

  4. Principles of chromatin organization in yeast: relevance of polymer models to describe nuclear organization and dynamics.

    PubMed

    Wang, Renjie; Mozziconacci, Julien; Bancaud, Aurélien; Gadal, Olivier

    2015-06-01

    Nuclear organization can impact on all aspects of the genome life cycle. This organization is thoroughly investigated by advanced imaging and chromosome conformation capture techniques, providing considerable amount of datasets describing the spatial organization of chromosomes. In this review, we will focus on polymer models to describe chromosome statics and dynamics in the yeast Saccharomyces cerevisiae. We suggest that the equilibrium configuration of a polymer chain tethered at both ends and placed in a confined volume is consistent with the current literature, implying that local chromatin interactions play a secondary role in yeast nuclear organization. Future challenges are to reach an integrated multi-scale description of yeast chromosome organization, which is crucially needed to improve our understanding of the regulation of genomic transaction.

  5. Control Systems for a Dynamic Multi-Physics Model of a Nuclear Hybrid Energy System

    SciTech Connect

    Greenwood, Michael Scott; Fugate, David W; Cetiner, Sacit M

    2017-01-01

    A Nuclear Hybrid Energy System (NHES) uses a nuclear reactor as the basic power generation unit, and the power generated is used by multiple customers as either thermal power, electrical power, or both. The definition and architecture of a particular NHES can be adapted based on the needs and opportunities of different local markets. For example, locations in need of potable water may be best served by coupling a desalination plant to the NHES. Similarly, a location near oil refineries may have a need for emission-free hydrogen production. Using the flexible, multi-domain capabilities of Modelica, Argonne National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory are investigating the dynamics (e.g., thermal hydraulics and electrical generation/consumption) and cost of a hybrid system. This paper examines the NHES work underway, emphasizing the control system developed for individual subsystems and the overall supervisory control system.

  6. Minireview: Steroid/Nuclear Receptor-Regulated Dynamics of Occluding and Anchoring Junctions

    PubMed Central

    Kapadia, Bhumika J.

    2014-01-01

    A diverse set of physiological signals control intercellular interactions by regulating the structure and function of occluding junctions (tight junctions) and anchoring junctions (adherens junctions and desmosomes). These plasma membrane junctions are comprised of multiprotein complexes of transmembrane and cytoplasmic peripheral plasma membrane proteins. Evidence from many hormone-responsive tissues has shown that expression, modification, molecular interactions, stability, and localization of junctional complex-associated proteins can be targeted by nuclear hormone receptors and their ligands through transcriptional and nontranscriptional mechanisms. The focus of this minireview is to discuss molecular, cellular, and physiological studies that directly link nuclear receptor- and ligand-triggered signaling pathways to the regulation of occluding and anchoring junction dynamics. PMID:25203673

  7. Dynamic properties of nuclear pore complex proteins in gp210 deficient cells.

    PubMed

    Eriksson, Charlotta; Rustum, Cecilia; Hallberg, Einar

    2004-08-13

    Gp210, an integral membrane protein of the nuclear pore complex (NPC), is believed to be involved in NPC biogenesis. To test this hypothesis, we have investigated dynamic properties of the NPC and distribution of NPC proteins in NIH/3T3 cells lacking gp210. POM121 (the other integral NPC protein) and NUP107 (of the NUP107/160 complex) were correctly distributed at the nuclear pores in the absence of gp210. Furthermore, fluorescence recovery after photobleaching experiments showed that POM121 and NUP107 remained stably associated at the NPCs. We conclude that gp210 cannot be required for incorporation of POM121 or NUP107 or be required for maintaining NPC stability.

  8. 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.

  9. 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.

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

    PubMed

    Mance, Deni; Gast, Peter; Huber, Martina; Baldus, Marc; 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.

  11. 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. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. 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.}

  13. 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.

  14. 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.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    TonThat, Dinh M.; Augustine, Matthew P.; Pines, Alexander; Clarke, John

    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 Ω. Low-field, 1H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies <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.

  18. Alignment dependent ultrafast electron-nuclear dynamics in molecular high-order harmonic generation

    NASA Astrophysics Data System (ADS)

    Li, Mu-Zi; Jia, Guang-Rui; Bian, Xue-Bin

    2017-02-01

    We investigated the high-order harmonic generation (HHG) process of diatomic molecular ion H2+ in non-Born-Oppenheimer approximations (NBOA). The corresponding three-dimensional time-dependent Schrödinger equation is solved with arbitrary alignment angles. It is found that the nuclear motion can lead to spectral modulation of HHG in both the tunneling and multiphoton ionization regimes. The universal redshifts of the whole spectrum are unique in molecular HHG. The spectral width of HHG increases in NBOA. We calculated possible influences on redshifts of HHG in real experimental conditions and found that redshifts decrease with the increase of alignment angles of the molecules and are sensitive to the initial vibrational states. It can be used to extract the ultrafast electron-nuclear dynamics and image molecular structure. It will be instructive to related experiments.

  19. 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.

  20. 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.

  1. Theoretical methods for attosecond electron and nuclear dynamics: applications to the H2 molecule

    NASA Astrophysics Data System (ADS)

    Palacios, Alicia; Sanz-Vicario, José Luis; Martín, Fernando

    2015-12-01

    Attosecond science, born at the beginning of this century with the generation of the first bursts of light with durations shorter than a femtosecond, has opened the way to look at electron dynamics in atoms and molecules at its natural timescale. Thus controlling chemical reactions at the electronic level or obtaining time-resolved images of the electronic motion has become a goal for many physics and chemistry laboratories all over the world. The new experimental capabilities have spurred the development of sophisticated theoretical methods that can accurately predict phenomena occurring in the sub-fs timescale. This review provides an overview of the capabilities of existing theoretical tools to describe electron and nuclear dynamics resulting from the interaction of femto- and attosecond UV/XUV radiation with simple molecular targets. We describe one of these methods in more detail, the time-dependent Feshbach close-coupling (TDFCC) formalism, which has been used successfully over the years to investigate various attosecond phenomena in the hydrogen molecule and can easily be extended to other diatomics. In addition to describing the details of the method and discussing its advantages and limitations, we also provide examples of the new physics that one can learn by applying it to different problems: from the study of the autoionization decay that follows attosecond UV excitation to the imaging of the coupled electron and nuclear dynamics in H2 using different UV-pump/IR-probe and UV-pump/UV-probe schemes.

  2. FOREWORD: International Summer School for Advanced Studies 'Dynamics of open nuclear systems' (PREDEAL12)

    NASA Astrophysics Data System (ADS)

    Delion, D. S.; Zamfir, N. V.; Raduta, A. R.; Gulminelli, F.

    2013-02-01

    This proceedings volume contains the invited lectures and contributions presented at the International Summer School on Nuclear Physics held at Trei Brazi, a summer resort of the Bioterra University, near the city of Predeal, Romania, on 9-20 July 2012. The long tradition of International Summer Schools on Nuclear Physics in Romania dates as far back as 1964, with the event being scheduled every two years. During this period of almost 50 years, many outstanding nuclear scientists have lectured on various topics related to nuclear physics and particle physics. This year we celebrate the 80th birthday of Aureliu Sandulescu, one of the founders of the Romanian school of theoretical nuclear physics. He was Serban Titeica's PhD student, one of Werner Heisenberg's PhD students, and he organized the first edition of this event. Aureliu Sandulescu's major contributions to the field of theoretical nuclear physics are related in particular to the prediction of cluster radioactivity, the physics of open quantum systems and the innovative technique of detecting superheavy nuclei using the double magic projectile 48Ca (Calcium), nowadays a widely used method at the JINR—Dubna and GSI—Darmstadt laboratories. The title of the event, 'Dynamics of Open Nuclear Systems', is in recognition of Aureliu Sandulescu's great personality. The lectures were attended by Romanian and foreign Master and PhD students and young researchers in nuclear physics. About 25 reputable professors and researchers in nuclear physics delivered lectures during this period. According to a well-established tradition, an interval of two hours was allotted for each lecture (including discussions). Therefore we kept a balance between the school and conference format. Two lectures were held during the morning and afternoon sessions. After lecture sessions, three or four oral contributions were given by young scientists. This was a good opportunity for them to present the results of their research in front of

  3. Autophagy contributes to regulation of nuclear dynamics during vegetative growth and hyphal fusion in Fusarium oxysporum.

    PubMed

    Corral-Ramos, Cristina; Roca, M Gabriela; Di Pietro, Antonio; Roncero, M Isabel G; Ruiz-Roldán, Carmen

    2015-01-01

    In the fungal pathogen Fusarium oxysporum, vegetative hyphal fusion triggers nuclear mitotic division in the invading hypha followed by migration of a nucleus into the receptor hypha and degradation of the resident nucleus. Here we examined the role of autophagy in fusion-induced nuclear degradation. A search of the F. oxysporum genome database for autophagy pathway components identified putative orthologs of 16 core autophagy-related (ATG) genes in yeast, including the ubiquitin-like protein Atg8, which is required for the formation of autophagosomal membranes. F. oxysporum Foatg8Δ mutants were generated in a strain harboring H1-cherry fluorescent protein (ChFP)-labeled nuclei to facilitate analysis of nuclear dynamics. The Foatg8Δ mutants did not show MDC-positive staining in contrast to the wild type and the FoATG8-complemented (cFoATG8) strain, suggesting that FoAtg8 is required for autophagy in F. oxysporum. The Foatg8Δ strains displayed reduced rates of hyphal growth, conidiation, and fusion, and were significantly attenuated in virulence on tomato plants and in the nonvertebrate animal host Galleria mellonella. In contrast to wild-type hyphae, which are almost exclusively composed of uninucleated hyphal compartments, the hyphae of the Foatg8Δ mutants contained a significant fraction of hyphal compartments with 2 or more nuclei. The increase in the number of nuclei per hyphal compartment was particularly evident after hyphal fusion events. Time-lapse microscopy analyses revealed abnormal mitotic patterns during vegetative growth in the Foatg8Δ mutants. Our results suggest that autophagy mediates nuclear degradation after hyphal fusion and has a general function in the control of nuclear distribution in F. oxysporum.

  4. Taxonomical and functional microbial community dynamics in an Anammox-ASBR system under different Fe (III) supplementation.

    PubMed

    Wang, Xiao; Shu, Duntao; Yue, Hong

    2016-12-01

    In the present study, we explored the metabolic versatility of anaerobic ammonium oxidation (anammox) bacteria in a variety of Fe (III) concentrations. Specifically, we investigated the impacts of Fe (III) on anammox growth rates, on nitrogen removal performance, and on microbial community dynamics. The results from our short-term experiments revealed that Fe (III) concentrations (0.04-0.10 mM) significantly promote the specific anammox growth rate from 0.1343 to 0.1709 d(-1). In the long-term experiments, the Anammox-anaerobic sequencing batch reactor (ASBR) was operated over 120 days and achieved maximum NH4(+)-N, NO2(-)-N, and TN efficiencies of 90.98 ± 0.35, 93.78 ± 0.29, and 83.66 ± 0.46 %, respectively. Pearson's correlation coefficients between anammox-(narG + napA), anammox-nrfA, and anammox-FeRB all exceeded r = 0.820 (p < 0.05), confirming an interaction and ecological association among the nitrogen and iron-cycling-related microbial communities. Illumina MiSeq sequencing indicated that Chloroflexi (34.39-39.31 %) was the most abundant phylum in an Anammox-ASBR system, followed by Planctomycetes (30.73-35.31 %), Proteobacteria (15.40-18.61 %), and Chlorobi (4.78-6.58 %). Furthermore, we found that higher Fe (III) supplementation (>0.06 mM) could result in the community succession of anammox species, in which Candidatus Brocadia and Candidatus Kuenenia were the dominant anammox bacteria species. Combined analyses indicated that the coupling of anammox, dissimilatory nitrogen reduction to ammonium, and iron reduction accounted for nitrogen loss in the Anammox-ASBR system. Overall, the knowledge gained in this study provides novel insights into the microbial community dynamics and metabolic potential of anammox bacteria under Fe (III) supplementation.

  5. Dynamic nuclear polarization NMR spectroscopy allows high-throughput characterization of microporous organic polymers.

    PubMed

    Blanc, Frédéric; Chong, Samantha Y; McDonald, Tom O; Adams, Dave J; Pawsey, Shane; Caporini, Marc A; Cooper, Andrew I

    2013-10-16

    Dynamic nuclear polarization (DNP) solid-state NMR was used to obtain natural abundance (13)C and (15)N CP MAS NMR spectra of microporous organic polymers with excellent signal-to-noise ratio, allowing for unprecedented details in the molecular structure to be determined for these complex polymer networks. Sensitivity enhancements larger than 10 were obtained with bis-nitroxide radical at 14.1 T and low temperature (∼105 K). This DNP MAS NMR approach allows efficient, high-throughput characterization of libraries of porous polymers prepared by combinatorial chemistry methods.

  6. Dynamical behavior of nuclear reaction systems disturbed by fluid motion in the solar sore

    NASA Astrophysics Data System (ADS)

    Jiulin, Du

    1993-11-01

    Using Euler's equation of motion, the equation for disturbed fluid motion against a hydrostatic equilibrium has been derived, and the nonequilibrium dynamical equation of a P-PI nuclear reaction system driven by He-3 has been analyzed using developed nonequilibrium theory. We find that the system in the solar core is unstable in the layer extending from about 0.2 solar radius to 0.4 solar radius if the core is disturbed by fluid motion; this instability may be related to thermal diffusion.

  7. Rigid orthogonal bis-TEMPO biradicals with improved solubility for dynamic nuclear polarization.

    PubMed

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

    2012-02-17

    The synthesis and characterization of oxidized bis-thioketal-trispiro dinitroxide biradicals that orient the nitroxides in a rigid, approximately orthogonal geometry are 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.

  8. Ettingshausen Effect around a Landau Level Filling Factor ν=3 Studied by Dynamic Nuclear Polarization

    NASA Astrophysics Data System (ADS)

    Komori, Yosuke; Sakuma, Satoru; Okamoto, Tohru

    2007-10-01

    A spin current perpendicular to the electric current is investigated around a Landau level filling factor ν=3 in a GaAs/AlGaAs two-dimensional electron system. Measurements of dynamic nuclear polarization in the vicinity of the edge of a specially designed Hall bar sample indicate that the direction of the spin current with respect to the Hall electric field reverses its polarity at ν=3, where the dissipative current carried by holes in the spin up Landau level is replaced with that by electrons in the spin down Landau level.

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

    PubMed

    Keshari, Kayvan R; Wilson, David M

    2014-03-07

    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.

  10. 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

  11. 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.

  12. 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.

  13. Systematics of precise nuclear fusion cross sections: the need for a new dynamical treatment of fusion?

    NASA Astrophysics Data System (ADS)

    Newton, J. O.; Butt, R. D.; Dasgupta, M.; Hinde, D. J.; Gontchar, I. I.; Morton, C. R.; Hagino, K.

    2004-04-01

    A large number of precision fusion excitation functions, at energies above the average fusion barriers, have been fitted using the Woods-Saxon form for the nuclear potential. Values of the empirical diffuseness parameter greatly exceed those which generally reproduce elastic scattering data and tend to increase strongly with the reaction charge product Z1Z2. Possible reasons for this may lie in the Woods-Saxon form being inappropriate, or in the reduction of fusion cross sections by processes such as deep-inelastic collisions. These results point to a need for renewed efforts in dynamical calculations of fusion.

  14. Synthesis, crystal structures, photoluminescent, magnetic and chiroptical properties of two homochiral ErIII complexes with different nuclearity

    NASA Astrophysics Data System (ADS)

    Li, Xi-Li; Liu, Ying-Fan; Zhang, Xue-Li; Cheng, Conghui; Zheng, Xianjun; Zhu, Cancan; Zhou, Liming

    2017-06-01

    Employing chiral bis-bidentate N-donor ligand, (+)-2,5-bis(4,5-pinene-2-pyridyl) pyrazine (L), as a bridging ligand for Er(dbm)3H2O, and depending on the ratio control of reactants, two mono- and dinuclear homochiral ErIII complexes with the formulae Er(dbm)3L·2H2O (1) (dbm- = dibenzoylmethanate) and Er2(dbm)6L·6H2O (2) have been synthesized and structurally characterized. Circular dichroic (CD) spectra verify their chiroptical activities. Investigations on the luminescent properties of complexes 1 and 2 demonstrate that they exhibit characteristic near-infrared (NIR) luminescence of the ErIII ion at around 1533 nm and the emission intensity of the mononuclear complex 1 is much larger than that of dinuclear species 2, the reason of which is elucidated in this work. In addition, the measurements of magnetic properties indicate that the direct-current (dc) magnetic behaviors of complexes 1 and 2 mainly result from the thermal depopulation of the excited MJ sublevels of the ErIII ions. Notablely, complex 2 is the first example of chiral polynuclear lanthanide complexes with NIR-luminescence property.

  15. Optical Properties of Iridium(III) Cyclometalates: Excited State Interaction with Small Molecules and Dynamics of Light-Harvesting Materials

    NASA Astrophysics Data System (ADS)

    Schwartz, Kyle Robert

    The research presented in this thesis concerns the use and understanding of luminescent Ir(III) cyclometalates. Areas of research involve the design, synthesis, and characterization of novel luminescent Ir(III) cyclometalates, including photophysical investigation of their phosphorescent excited states using steady-state and time resolved absorption/luminescence spectroscopies. This broad research description may be further separated into two subareas: study of excited state interaction with small molecules and excited-state dynamics of metal-organic light harvesting dyads. Interaction of Ir(III) cyclometalates with the small molecule carbon dioxide (CO2) is the subject of Chapter One. Most optical detection schemes previously developed for CO2 use indirect detection methods, which rely upon measuring changes in pH brought about by hydrolysis of CO 2 on of CO2 were accomplished through development of a system where hydrazine, a simple amino ligand, when coupled into the coordination sphere of an Ir(III) cyclometalate reacts with CO2. The result of this reaction provides a shift in the luminescence wavelength, a previously unobserved optical response for CO2 detection. Chapter Two investigates phosphorescent excited states and their ability to function as triplet sensitizers for the generation of singlet oxygen ( 1O2) and luminescent probes for molecular oxygen (O 2) concentration. Interaction of phosphorescent excited states with O2 results in energy transfer from the luminescent probe to O 2, quenching the phosphorescent excited state. Energy transfer also generates the reactive oxygen species (ROS) 1O2. We have used this duality to develop an analytical methodology to follow the serendipitously discovered photoreactivity of 1O2 with common organic solvent dimethyl sulfoxide (DMSO) using the luminescence profile of Ir(III) and Ru(II) phosphors. In Chapter Three a detailed study involving the design, synthesis, and characterization of the electrochemical and

  16. Effect of tacticity on the segmental dynamics of polypropylene melts investigated by 13C nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Lippow, S. M.; Qiu, XiaoHua; Ediger, M. D.

    2001-09-01

    13C nuclear magnetic resonance (NMR) T1 and nuclear Overhauser effect measurements are reported for syndiotactic and isotactic polypropylene from their melting points to 525 K. These results indicate that the segmental dynamics of syndiotactic polypropylene are 1.7 times slower than for isotactic polypropylene at 500 K. Recent molecular dynamics computer simulations [Antoniadis, Samara, and Theodorou, Macromolecules 32, 8635 (1999)] predict this trend qualitatively but predict too large a dependence of dynamics upon tacticity. The contribution of normal mode relaxation to the decay of the C-H vector autocorrelation function is significantly larger for syndiotactic polypropylene than for either isotactic or atactic polypropylene.

  17. Fibronectin module FN(III)9 adsorption at contrasting solid model surfaces studied by atomistic molecular dynamics.

    PubMed

    Kubiak-Ossowska, Karina; Mulheran, Paul A; Nowak, Wieslaw

    2014-08-21

    The mechanism of human fibronectin adhesion synergy region (known as integrin binding region) in repeat 9 (FN(III)9) domain adsorption at pH 7 onto various and contrasting model surfaces has been studied using atomistic molecular dynamics simulations. We use an ionic model to mimic mica surface charge density but without a long-range electric field above the surface, a silica model with a long-range electric field similar to that found experimentally, and an Au {111} model with no partial charges or electric field. A detailed description of the adsorption processes and the contrasts between the various model surfaces is provided. In the case of our model silica surface with a long-range electrostatic field, the adsorption is rapid and primarily driven by electrostatics. Because it is negatively charged (-1e), FN(III)9 readily adsorbs to a positively charged surface. However, due to its partial charge distribution, FN(III)9 can also adsorb to the negatively charged mica model because of the absence of a long-range repulsive electric field. The protein dipole moment dictates its contrasting orientation at these surfaces, and the anchoring residues have opposite charges to the surface. Adsorption on the model Au {111} surface is possible, but less specific, and various protein regions might be involved in the interactions with the surface. Despite strongly influencing the protein mobility, adsorption at these model surfaces does not require wholesale FN(III)9 conformational changes, which suggests that the biological activity of the adsorbed protein might be preserved.

  18. Dynamics of water-alcohol mixtures: Insights from nuclear magnetic resonance, broadband dielectric spectroscopy, and triplet solvation dynamics

    SciTech Connect

    Sauer, D.; Schuster, B.; Rosenstihl, M.; Schneider, S.; Blochowicz, T.; Stühn, B.; Vogel, M.; Talluto, V.; Walther, T.

    2014-03-21

    We combine {sup 2}H nuclear magnetic resonance (NMR), broadband dielectric spectroscopy (BDS), and triplet solvation dynamics (TSD) to investigate molecular dynamics in glass-forming mixtures of water and propylene glycol in very broad time and temperature ranges. All methods yield consistent results for the α process of the studied mixtures, which hardly depends on the composition and shows Vogel-Fulcher temperature dependence as well as Cole-Davidson spectral shape. The good agreement between BDS and TDS data reveals that preferential solvation of dye molecules in microheterogeneous mixtures does not play an important role. Below the glass transition temperature T{sub g}, NMR and BDS studies reveal that the β process of the mixtures shows correlation times, which depend on the water concentration, but exhibit a common temperature dependence, obeying an Arrhenius law with an activation energy of E{sub a} = 0.54  eV, as previously reported for mixtures of water with various molecular species. Detailed comparison of NMR and BDS correlation functions for the β process unravels that the former decay faster and more stretched than the latter. Moreover, the present NMR data imply that propylene glycol participates in the β process and, hence, it is not a pure water process, and that the mechanism for molecular dynamics underlying the β process differs in mixtures of water with small and large molecules.

  19. Dynamics of water-alcohol mixtures: Insights from nuclear magnetic resonance, broadband dielectric spectroscopy, and triplet solvation dynamics

    NASA Astrophysics Data System (ADS)

    Sauer, D.; Schuster, B.; Rosenstihl, M.; Schneider, S.; Talluto, V.; Walther, T.; Blochowicz, T.; Stühn, B.; Vogel, M.

    2014-03-01

    We combine 2H nuclear magnetic resonance (NMR), broadband dielectric spectroscopy (BDS), and triplet solvation dynamics (TSD) to investigate molecular dynamics in glass-forming mixtures of water and propylene glycol in very broad time and temperature ranges. All methods yield consistent results for the α process of the studied mixtures, which hardly depends on the composition and shows Vogel-Fulcher temperature dependence as well as Cole-Davidson spectral shape. The good agreement between BDS and TDS data reveals that preferential solvation of dye molecules in microheterogeneous mixtures does not play an important role. Below the glass transition temperature Tg, NMR and BDS studies reveal that the β process of the mixtures shows correlation times, which depend on the water concentration, but exhibit a common temperature dependence, obeying an Arrhenius law with an activation energy of Ea = 0.54 eV, as previously reported for mixtures of water with various molecular species. Detailed comparison of NMR and BDS correlation functions for the β process unravels that the former decay faster and more stretched than the latter. Moreover, the present NMR data imply that propylene glycol participates in the β process and, hence, it is not a pure water process, and that the mechanism for molecular dynamics underlying the β process differs in mixtures of water with small and large molecules.

  20. The impact of interface bonding efficiency on high-burnup spent nuclear fuel dynamic performance

    SciTech Connect

    Jiang, Hao; Wang, Jy-An John; Wang, Hong

    2016-09-26

    Finite element analysis (FEA) was used to investigate the impact of interfacial bonding efficiency at pellet-pellet and pellet-clad interfaces of high-burnup (HBU) spent nuclear fuel (SNF) on system dynamic performance. Bending moments M were applied to FEA model to evaluate the system responses. From bending curvature, κ, flexural rigidity EI can be estimated as EI = M/κ. The FEA simulation results were benchmarked with experimental results from cyclic integrated reversal bending fatigue test (CIRFT) of HBR fuel rods. The consequence of interface debonding between fuel pellets and cladding is a redistribution of the loads carried by the fuel pellets to the clad, which results in a reduction in composite rod system flexural rigidity. Furthermore, the interface bonding efficiency at the pellet-pellet and pellet-clad interfaces can significantly dictate the SNF system dynamic performance. With the consideration of interface bonding efficiency, the HBU SNF fuel property was estimated with CIRFT test data.

  1. The impact of interface bonding efficiency on high-burnup spent nuclear fuel dynamic performance

    SciTech Connect

    Jiang, Hao; Wang, Jy-An John; Wang, Hong

    2016-09-26

    Finite element analysis (FEA) was used to investigate the impact of interfacial bonding efficiency at pellet-pellet and pellet-clad interfaces of high-burnup (HBU) spent nuclear fuel (SNF) on system dynamic performance. Bending moments M were applied to FEA model to evaluate the system responses. From bending curvature, κ, flexural rigidity EI can be estimated as EI = M/κ. The FEA simulation results were benchmarked with experimental results from cyclic integrated reversal bending fatigue test (CIRFT) of HBR fuel rods. The consequence of interface debonding between fuel pellets and cladding is a redistribution of the loads carried by the fuel pellets to the clad, which results in a reduction in composite rod system flexural rigidity. Furthermore, the interface bonding efficiency at the pellet-pellet and pellet-clad interfaces can significantly dictate the SNF system dynamic performance. With the consideration of interface bonding efficiency, the HBU SNF fuel property was estimated with CIRFT test data.

  2. The fragile-to-strong dynamic crossover transition in confined water: nuclear magnetic resonance results

    NASA Astrophysics Data System (ADS)

    Mallamace, F.; Broccio, M.; Corsaro, C.; Faraone, A.; Wanderlingh, U.; Liu, L.; Mou, C.-Y.; Chen, S. H.

    2006-04-01

    By means of a nuclear magnetic resonance experiment, we give evidence of the existence of a fragile-to-strong dynamic crossover transition (FST) in confined water at a temperature TL=223±2K. We have studied the dynamics of water contained in 1D cylindrical nanoporous matrices (MCM-41-S) in the temperature range 190-280K, where experiments on bulk water were so far hampered by crystallization. The FST is clearly inferred from the T dependence of the inverse of the self-diffusion coefficient of water (1/D) as a crossover point from a non-Arrhenius to an Arrhenius behavior. The combination of the measured self-diffusion coefficient D and the average translational relaxation time ⟨τT⟩, as measured by neutron scattering, shows the predicted breakdown of Stokes-Einstein relation in deeply supercooled water.

  3. The fragile-to-strong dynamic crossover transition in confined water: nuclear magnetic resonance results.

    PubMed

    Mallamace, F; Broccio, M; Corsaro, C; Faraone, A; Wanderlingh, U; Liu, L; Mou, C-Y; Chen, S H

    2006-04-28

    By means of a nuclear magnetic resonance experiment, we give evidence of the existence of a fragile-to-strong dynamic crossover transition (FST) in confined water at a temperature T(L)=223+/-2 K. We have studied the dynamics of water contained in 1D cylindrical nanoporous matrices (MCM-41-S) in the temperature range 190-280 K, where experiments on bulk water were so far hampered by crystallization. The FST is clearly inferred from the T dependence of the inverse of the self-diffusion coefficient of water (1D) as a crossover point from a non-Arrhenius to an Arrhenius behavior. The combination of the measured self-diffusion coefficient D and the average translational relaxation time tau(T), as measured by neutron scattering, shows the predicted breakdown of Stokes-Einstein relation in deeply supercooled water.

  4. Attosecond Probing of Nuclear Dynamics with Trajectory-Resolved High-Harmonic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lan, Pengfei; Ruhmann, Marc; He, Lixin; Zhai, Chunyang; Wang, Feng; Zhu, Xiaosong; Zhang, Qingbin; Zhou, Yueming; Li, Min; Lein, Manfred; Lu, Peixiang

    2017-07-01

    We report attosecond-scale probing of the laser-induced dynamics in molecules. We apply the method of high-harmonic spectroscopy, where laser-driven recolliding electrons on various trajectories record the motion of their parent ion. Based on the transient phase-matching mechanism of high-order harmonic generation, short and long trajectories contributing to the same harmonic order are distinguishable in both the spatial and frequency domains, giving rise to a one-to-one map between time and photon energy for each trajectory. The short and long trajectories in H2 and D2 are used simultaneously to retrieve the nuclear dynamics on the attosecond and ångström scale. Compared to using only short trajectories, this extends the temporal range of the measurement to one optical cycle. The experiment is also applied to methane and ammonia molecules.

  5. Time-dependent density-functional theory method in the electron nuclear dynamics framework

    NASA Astrophysics Data System (ADS)

    Ajith Perera, S.; McLaurin, Patrick M.; Grimes, Thomas V.; Morales, Jorge A.

    2010-08-01

    A time-dependent density-functional theory (DFT) dynamics method in the electron nuclear dynamics (END) framework is presented. This time-dependent variational method treats simultaneously the nuclei and electrons of a system without utilizing predetermined potential energy surfaces. Like the simplest-level END, this method adopts a classical-mechanics description for the nuclei and a Thouless single-determinantal representation for the electrons. However, the electronic description is now expressed in a Kohn-Sham DFT form that provides electron correlation effects absent in the simplest-level END. Current implementation of this method employs the adiabatic approximation in the exchange-correlation action and potential. Simulations of molecular vibrations and proton-molecule reactions attest to the accuracy of the present method.

  6. Communication: Heterogeneous water dynamics on a clathrate hydrate lattice detected by multidimensional oxygen nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Adjei-Acheamfour, Mischa; Storek, Michael; Böhmer, Roland

    2017-05-01

    Previous deuteron nuclear magnetic resonance studies revealed conflicting evidence regarding the possible motional heterogeneity of the water dynamics on the hydrate lattice of an ice-like crystal. Using oxygen-17 nuclei as a sensitive quadrupolar probe, the reorientational two-time correlation function displays a clear nonexponentiality. To check whether this dispersive behavior is a consequence of dynamic heterogeneity or rather of an intrinsic nonexponentiality, a multidimensional, four-time magnetic resonance experiment was devised that is generally applicable to strongly quadrupolarly perturbed half-integer nuclei such as oxygen-17. Measurements of an appropriate four-time function demonstrate that it is possible to select a subensemble of slow water molecules. Its mean time scale is compared to theoretical predictions and evidence for significant motional heterogeneity is found.

  7. Nuclear dynamics of influenza A virus ribonucleoproteins revealed by live-cell imaging studies

    SciTech Connect

    Loucaides, Eva M.; Kirchbach, Johann C. von; Foeglein, Agnes; Sharps, Jane; Fodor, Ervin; Digard, Paul

    2009-11-10

    The negative sense RNA genome of influenza A virus is transcribed and replicated in the nuclei of infected cells by the viral RNA polymerase. Only four viral polypeptides are required but multiple cellular components are potentially involved. We used fluorescence recovery after photobleaching (FRAP) to characterise the dynamics of GFP-tagged viral ribonucleoprotein (RNP) components in living cells. The nucleoprotein (NP) displayed very slow mobility that significantly increased on formation of transcriptionally active RNPs. Conversely, single or dimeric polymerase subunits showed fast nuclear dynamics that decreased upon formation of heterotrimers, suggesting increased interaction of the full polymerase complex with a relatively immobile cellular component(s). Treatment with inhibitors of cellular transcription indicated that in part, this reflected an interaction with cellular RNA polymerase II. Analysis of mutated influenza virus polymerase complexes further suggested that this was through an interaction between PB2 and RNA Pol II separate from PB2 cap-binding activity.

  8. 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.

  9. Time-Domain Nuclear Magnetic Resonance Investigation of Water Dynamics in Different Ginger Cultivars.

    PubMed

    Huang, Chongyang; Zhou, Qi; Gao, Shan; Bao, Qingjia; Chen, Fang; Liu, Chaoyang

    2016-01-20

    Different ginger cultivars may contain different nutritional and medicinal values. In this study, a time-domain nuclear magnetic resonance method was employed to study water dynamics in different ginger cultivars. Significant differences in transverse relaxation time T2 values assigned to the distribution of water in different parts of the plant were observed between Henan ginger and four other ginger cultivars. Ion concentration and metabolic analysis showed similar differences in Mn ion concentrations and organic solutes among the different ginger cultivars, respectively. On the basis of Pearson's correlation analysis, many organic solutes and 6-gingerol, the main active substance of ginger, exhibited significant correlations with water distribution as determined by NMR T2 relaxation, suggesting that the organic solute differences may impact water distribution. Our work demonstrates that low-field NMR relaxometry provides useful information about water dynamics in different ginger cultivars as affected by the presence of different organic solutes.

  10. 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.

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

    DOE PAGES

    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

  12. Constrained molecular dynamics II: An N-body approach to nuclear systems

    SciTech Connect

    Papa, M. . E-mail: massimo.papa@ct.infn.it; Giuliani, G.; Bonasera, A.

    2005-09-20

    In this work, we illustrate the basic development of the constrained molecular dynamics applied to the N-body problem in nuclear physics. The heavy computational tasks related to quantum effects, to the Fermionic nature of the system have been resolved out by defining a set of transformations based on the concept of impulsive forces. In particular, in the implemented version II of the constrained molecular dynamics model the problem related to the non-conservation of the total angular momentum has been solved. This problem affects other semi-classical microscopic approaches due to the 'hard core' repulsive interaction and, more generally, to the usage of random forces. The effect of the restored conservation law on the fusion cross-section for the {sup 40}Ca + {sup 40}Ca system is also briefly discussed.

  13. Dynamic use of geoscience information to develop scientific understanding for a nuclear waste repository

    SciTech Connect

    Cook, N.G.W.; Tsang, C.F.

    1990-01-01

    The development and safety evaluation of a nuclear waste geologic repository require a proper scientific understanding of the site response. Such scientific understanding depends on information from a number of geoscience disciplines, including geology, geophysics, geochemistry, geomechanics and hydrogeology. The information comes in four stages: (1) general regional survey data base, (2) surface-based testing, (3) exploratory shaft testing, and (4) repository construction and evaluation. A discussion is given on the dynamic use of the information through the different stages. We point out the need for abstracting, deriving and updating a quantitative spatial and process model (QSPM) to develop a scientific understanding of site responses as a crucial element in the dynamic procedure. 2 figs.

  14. Predicted spatio-temporal dynamics of radiocesium deposited onto forests following the Fukushima nuclear accident

    PubMed Central

    Hashimoto, Shoji; Matsuura, Toshiya; Nanko, Kazuki; Linkov, Igor; Shaw, George; Kaneko, Shinji

    2013-01-01

    The majority of the area contaminated by the Fukushima Dai-ichi nuclear power plant accident is covered by forest. To facilitate effective countermeasure strategies to mitigate forest contamination, we simulated the spatio-temporal dynamics of radiocesium deposited into Japanese forest ecosystems in 2011 using a model that was developed after the Chernobyl accident in 1986. The simulation revealed that the radiocesium inventories in tree and soil surface organic layer components drop rapidly during the first two years after the fallout. Over a period of one to two years, the radiocesium is predicted to move from the tree and surface organic soil to the mineral soil, which eventually becomes the largest radiocesium reservoir within forest ecosystems. Although the uncertainty of our simulations should be considered, the results provide a basis for understanding and anticipating the future dynamics of radiocesium in Japanese forests following the Fukushima accident. PMID:23995073

  15. FINESSE: study of the issues, experiments and facilities for fusion nuclear technology research and development. Interim report. Volume III

    SciTech Connect

    Abdou, M.

    1984-10-01

    This chapter deals with the analysis and engineering scaling of solid breeded blankets. The limits under which full component behavior can be achieved under changed test conditions are explored. The characterization of these test requirements for integrated testing contributes to the overall test matrix and test plan for the understanding and development of fusion nuclear technology. The second chapter covers the analysis and engineering scaling of liquid metal blankets. The testing goals for a complete blanket program are described. (MOW)

  16. Facioscapulohumeral muscular dystrophy (FSHD) region gene 1 (FRG1) is a dynamic nuclear and sarcomeric protein.

    PubMed

    Hanel, Meredith L; Sun, Chia-Yun Jessica; Jones, Takako I; Long, Steven W; Zanotti, Simona; Milner, Derek; Jones, Peter L

    2011-02-01

    Facioscapulohumeral muscular dystrophy (FSHD) region gene 1 (FRG1) is a candidate gene for mediating FSHD pathophysiology, however, very little is known about the endogenous FRG1 protein. This study uses immunocytochemistry (ICC) and histology to provide insight into FRG1's role in vertebrate muscle development and address its potential involvement in FSHD pathophysiology. In cell culture, primary myoblast/myotube cultures, and mouse and human muscle sections, FRG1 showed distinct nuclear and cytoplasmic localizations and nuclear shuttling assays indicated the subcellular pools of FRG1 are linked. During myoblast differentiation, FRG1's subcellular distribution changed dramatically with FRG1 eventually associating with the matured Z-discs. This Z-disc localization was confirmed using isolated mouse myofibers and found to be maintained in adult human skeletal muscle biopsies. Thus, FRG1 is not likely involved in the initial assembly and alignment of the Z-disc but may be involved in sarcomere maintenance or signaling. Further analysis of human tissue showed FRG1 is strongly expressed in arteries, veins, and capillaries, the other prominently affected tissue in FSHD. Overall, we show that in mammalian cells, FRG1 is a dynamic nuclear and cytoplasmic protein, however in muscle, FRG1 is also a developmentally regulated sarcomeric protein suggesting FRG1 may perform a muscle-specific function. Thus, FRG1 is the only FSHD candidate protein linked to the muscle contractile machinery and may address why the musculature and vasculature are specifically susceptible in FSHD.

  17. Analysis of the H(2)(+) with H(2) reaction using electron nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Oreiro, Juan J. G.

    The END formalism addresses the solution of the time- dependent Schrodinger equation, treating both electrons and nuclei simultaneously. It differs from the other traditional fully quantum mechanical time-dependent methods in that it does not require a potential energy surface (PES) to carry the nuclear motion. The interaction between electronic and nuclear motion is, therefore, obtained in a transparent way, not relying on PES gradients to obtain the coupling between electrons and nuclei. We analyze the H2+ + H2 reaction at energies below 4 eV using different approximations and basis sets. Other than the choice of initial conditions, form of wave function, and basis set, no constraints are imposed on the system evolution. The nuclei are treated in the classical limit, and the electronic part is described by a single determinantal, unrestricted wave function. We obtain properties, such as Mulliken populations, transition probabilities, and cross-sections, from the resulting trajectories. These results are compared with other current theoretical approaches, and with experimental values. The relevance of the electron- nuclear coupling is estimated by comparing the END trajectories with molecular dynamics calculations for selected initial conditions in different basis sets.

  18. Classical nuclear dynamics on a single time-dependent potential in electronic non-adiabatic processes

    NASA Astrophysics Data System (ADS)

    Agostini, Federica; Abedi, Ali; Suzuki, Yasumitsu; Min, Seung Kyu; Maitra, Neepa T.; Gross, E. K. U.

    2015-03-01

    The Born-Oppenheimer (BO) approximation allows to visualize the coupled electron-nuclear dynamics in molecular systems as a set of nuclei moving on a single potential energy surface representing the effect of the electrons in a given eigenstate. Many interesting phenomena, however, such as vision or charge separation in organic photovoltaic materials, take place in conditions beyond its range of validity. Nevertheless, the basic construct of the adiabatic treatment, the BO potential energy surfaces, is employed to describe non-adiabatic processes and the full problem is represented in terms of adiabatic states and transitions among them in regions of strong non-adiabatic coupling. But the concept of single potential energy is lost. The alternative point of view arising in the framework of the exact factorization of the electron-nuclear wave function will be presented. A single, time-dependent, potential energy provides the force driving the nuclear motion and is adopted as starting point for the development of quantum-classical approximations to the full quantum mechanical problem.

  19. Logical operations with single x-ray photons via dynamically-controlled nuclear resonances

    PubMed Central

    Gunst, Jonas; Keitel, Christoph H.; Pálffy, Adriana

    2016-01-01

    Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented. PMID:27118340

  20. Visualization of the dynamic multimerization of human Cytomegalovirus pp65 in punctuate nuclear foci

    SciTech Connect

    Cui Zongqiang; Zhang Ke; Zhang Zhiping; Liu Yalan; Zhou Yafeng; Wei Hongping; Zhang Xian-En

    2009-09-30

    The phosphorylated protein pp65 of human Cytomegalovirus (HCMV) is the predominant virion protein and the major tegument constituent. It plays important roles in HCMV infection and virion assembly. Live cell imaging and fluorescence recovery after photobleaching (FRAP) analysis showed that HCMV pp65 accumulated dynamically in punctuate nuclear foci when transiently expressed in mammalian cells. Fluorescence resonance energy transfer (FRET) imaging disclosed that pp65 can self-interact in its localization foci. Yeast two-hybrid assay verified that pp65 is a self-associating protein, and the N-terminal amino acids 14-22 were determined to be essential for pp65 self-association. However, these amino acids were not related to pp65 localization in the specific nuclear foci. The interaction of pp65 and ppUL97 was also studied by FRET microscopy, and the result suggested that there is another signal sequence in pp65, being the ppUL97 phosphorylation site, that is responsible for localization of pp65 in nuclear foci. These results help to understand the function of pp65 in HCMV infection and virion morphogenesis.

  1. 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

  2. Magic angle spinning NMR of proteins: high-frequency dynamic nuclear polarization and (1)H detection.

    PubMed

    Su, Yongchao; Andreas, Loren; Griffin, Robert G

    2015-01-01

    Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on (13)C- and (15)N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and (1)H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 10(2) to 10(3), thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, (1)H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively (2)H-labeled proteins.

  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. Logical operations with single x-ray photons via dynamically-controlled nuclear resonances

    NASA Astrophysics Data System (ADS)

    Gunst, Jonas; Keitel, Christoph H.; Pálffy, Adriana

    2016-04-01

    Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented.

  5. 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.

  6. Dynamic Nuclear Polarization Fast Field Cycling Method for the Selective Study of Molecular Dynamics in Block Copolymers.

    PubMed

    Gizatullin, Bulat; Neudert, Oliver; Stapf, Siegfried; Mattea, Carlos

    2017-09-06

    Dynamic nuclear polarization (DNP) is one of the most useful methods to increase sensitivity in NMR spectroscopy. It is based on the transfer of magnetization from an electron to the nuclear spin system. Based on previous work that demonstrated the feasibility of integrating DNP with fast field cycling (FFC) relaxometry and the possibility to distinguish between different mechanisms, such as the Overhauser effect (OE) and the solid effect (SE), the first FFC study of the differential relaxation properties of a copolymer is presented. For this purpose, concentrated solutions of the polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymer and the corresponding homopolymers were investigated. T1 -T2 relaxation data are discussed in terms of molecular mobility and the presence of radicals. The DNP selective data indicate a dominant SE contribution to the enhancement of the NMR signal for both blocks of the triblock copolymer and for the homopolymer solutions. The enhancement factors are different for both polymer types and in the copolymer, which is explained by the individual (1) H T1 relaxation times and different electron-nucleus coupling strength. The T1 relaxation dispersion measurements of the SE enhanced signal were performed, which led to improved signal-to-noise ratios that allowed the site-specific separation of relaxation times and their dependence on the Larmor frequency with a higher accuracy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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

  8. Carrier dynamics and Coulomb-enhanced capture in III-nitride quantum heterostructures

    SciTech Connect

    David, Aurelien Hurni, Christophe A.; Young, Nathan G.; Craven, Michael D.

    2016-07-18

    A detailed study of the small-signal response of III-Nitride quantum well (QW) light-emitting diodes is presented, in which the electrical and optical responses are simultaneously measured. A complete transport-recombination model is introduced to account for measurements. This allows for a proper evaluation of the recombination lifetime and for the accurate quantification of thermionic carrier escape from the QW. Further, a yet-unreported carrier capture mechanism is identified and quantified; it increases with the carrier density in the QW and bears the signature of a Coulomb in-scattering process.

  9. Carrier dynamics and Coulomb-enhanced capture in III-nitride quantum heterostructures

    NASA Astrophysics Data System (ADS)

    David, Aurelien; Hurni, Christophe A.; Young, Nathan G.; Craven, Michael D.

    2016-07-01

    A detailed study of the small-signal response of III-Nitride quantum well (QW) light-emitting diodes is presented, in which the electrical and optical responses are simultaneously measured. A complete transport-recombination model is introduced to account for measurements. This allows for a proper evaluation of the recombination lifetime and for the accurate quantification of thermionic carrier escape from the QW. Further, a yet-unreported carrier capture mechanism is identified and quantified; it increases with the carrier density in the QW and bears the signature of a Coulomb in-scattering process.

  10. High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

    SciTech Connect

    Adelnia, Fatemeh; Lascialfari, Alessandro; Mariani, Manuel; Ammannato, Luca; Caneschi, Andrea; Rovai, Donella; Winpenny, Richard; Timco, Grigore; Corti, Maurizio Borsa, Ferdinando

    2015-05-07

    We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.

  11. Fermi resonance in CO2: Mode assignment and quantum nuclear effects from first principles molecular dynamics

    NASA Astrophysics Data System (ADS)

    Basire, Marie; Mouhat, Félix; Fraux, Guillaume; Bordage, Amélie; Hazemann, Jean-Louis; Louvel, Marion; Spezia, Riccardo; Bonella, Sara; Vuilleumier, Rodolphe

    2017-04-01

    Vibrational spectroscopy is a fundamental tool to investigate local atomic arrangements and the effect of the environment, provided that the spectral features can be correctly assigned. This can be challenging in experiments and simulations when double peaks are present because they can have different origins. Fermi dyads are a common class of such doublets, stemming from the resonance of the fundamental excitation of a mode with the overtone of another. We present a new, efficient approach to unambiguously characterize Fermi resonances in density functional theory (DFT) based simulations of condensed phase systems. With it, the spectral features can be assigned and the two resonating modes identified. We also show how data from DFT simulations employing classical nuclear dynamics can be post-processed and combined with a perturbative quantum treatment at a finite temperature to include analytically thermal quantum nuclear effects. The inclusion of these effects is crucial to correct some of the qualitative failures of the Newtonian dynamics simulations at a low temperature such as, in particular, the behavior of the frequency splitting of the Fermi dyad. We show, by comparing with experimental data for the paradigmatic case of supercritical CO2, that these thermal quantum effects can be substantial even at ambient conditions and that our scheme provides an accurate and computationally convenient approach to account for them.

  12. Fermi resonance in CO2: Mode assignment and quantum nuclear effects from first principles molecular dynamics.

    PubMed

    Basire, Marie; Mouhat, Félix; Fraux, Guillaume; Bordage, Amélie; Hazemann, Jean-Louis; Louvel, Marion; Spezia, Riccardo; Bonella, Sara; Vuilleumier, Rodolphe

    2017-04-07

    Vibrational spectroscopy is a fundamental tool to investigate local atomic arrangements and the effect of the environment, provided that the spectral features can be correctly assigned. This can be challenging in experiments and simulations when double peaks are present because they can have different origins. Fermi dyads are a common class of such doublets, stemming from the resonance of the fundamental excitation of a mode with the overtone of another. We present a new, efficient approach to unambiguously characterize Fermi resonances in density functional theory (DFT) based simulations of condensed phase systems. With it, the spectral features can be assigned and the two resonating modes identified. We also show how data from DFT simulations employing classical nuclear dynamics can be post-processed and combined with a perturbative quantum treatment at a finite temperature to include analytically thermal quantum nuclear effects. The inclusion of these effects is crucial to correct some of the qualitative failures of the Newtonian dynamics simulations at a low temperature such as, in particular, the behavior of the frequency splitting of the Fermi dyad. We show, by comparing with experimental data for the paradigmatic case of supercritical CO2, that these thermal quantum effects can be substantial even at ambient conditions and that our scheme provides an accurate and computationally convenient approach to account for them.

  13. Advances and applications of dynamic-angle spinning nuclear magnetic resonance

    SciTech Connect

    Baltisberger, Jay Harvey

    1993-06-01

    This dissertation describes nuclear magnetic resonance experiments and theory which have been developed to study quadrupolar nuclei (those nuclei with spin greater than one-half) in the solid state. Primarily, the technique of dynamic-angle spinning (DAS) is extensively reviewed and expanded upon in this thesis. Specifically, the improvement in both the resolution (two-dimensional pure-absorptive phase methods and DAS angle choice) and sensitivity (pulse-sequence development), along with effective spinning speed enhancement (again through choice of DAS conditions or alternative multiple pulse schemes) of dynamic-angle spinning experiment was realized with both theory and experimental examples. The application of DAS to new types of nuclei (specifically the {sup 87}Rb and {sup 85}Rb nuclear spins) and materials (specifically amorphous solids) has also greatly expanded the possibilities of the use of DAS to study a larger range of materials. This dissertation is meant to demonstrate both recent advances and applications of the DAS technique, and by no means represents a comprehensive study of any particular chemical problem.

  14. Dynamic sorting of nuclear components into distinct nucleolar caps during transcriptional inhibition.

    PubMed

    Shav-Tal, Yaron; Blechman, Janna; Darzacq, Xavier; Montagna, Cristina; Dye, Billy T; Patton, James G; Singer, Robert H; Zipori, Dov

    2005-05-01

    Nucleolar segregation is observed under some physiological conditions of transcriptional arrest. This process can be mimicked by transcriptional arrest after actinomycin D treatment leading to the segregation of nucleolar components and the formation of unique structures termed nucleolar caps surrounding a central body. These nucleolar caps have been proposed to arise from the segregation of nucleolar components. We show that contrary to prevailing notion, a group of nucleoplasmic proteins, mostly RNA binding proteins, relocalized from the nucleoplasm to a specific nucleolar cap during transcriptional inhibition. For instance, an exclusively nucleoplasmic protein, the splicing factor PSF, localized to nucleolar caps under these conditions. This structure also contained pre-rRNA transcripts, but other caps contained either nucleolar proteins, PML, or Cajal body proteins and in addition nucleolar or Cajal body RNAs. In contrast to the capping of the nucleoplasmic components, nucleolar granular component proteins dispersed into the nucleoplasm, although at least two (p14/ARF and MRP RNA) were retained in the central body. The nucleolar caps are dynamic structures as determined using photobleaching and require energy for their formation. These findings demonstrate that the process of nucleolar segregation and capping involves energy-dependent repositioning of nuclear proteins and RNAs and emphasize the dynamic characteristics of nuclear domain formation in response to cellular stress.

  15. Genomic DNA hypomethylation by histone deacetylase inhibition implicates DNMT1 nuclear dynamics.

    PubMed

    Arzenani, Mohsen Karimi; Zade, Atosa Esteki; Ming, Yu; Vijverberg, Susanne J H; Zhang, Zhe; Khan, Zahidul; Sadique, Syed; Kallenbach, Lorenz; Hu, LiFu; Vukojević, Vladana; Ekström, Tomas J

    2011-10-01

    Histone deacetylase inhibitors (HDACi) are promising antitumor drugs acting through reactivation of silenced tumor suppressor genes. Several HDACi are currently in clinical trials both for hematological and solid tissue malignancies. Cooperative action of HDACi and DNA methylation inhibitors (DNMTi) has been reported, making combined treatment an attractive choice for cancer therapy. There is some evidence that synergistic effects of HDACi and DNMTi are achieved by their action on common targets, including DNA methyltransferase 1 (DNMT1). To further analyze this interaction, we investigated the effect of the HDACi trichostatin A on global and gene-specific DNA methylation and applied methods with single molecule sensitivity, confocal laser scanning microscopy with avalanche photodiode detectors (APD imaging) and fluorescence correlation spectroscopy (FCS), to study its effect on the nuclear dynamics of DNMT1 in live cells. Our data show that trichostatin A treatment reduces global DNA methylation and the DNMT1 protein level and alters DNMT1 nuclear dynamics and interactions with chromatin. The mechanisms underlying these effects are apparently distinct from the mechanisms of action of the DNMT inhibitor 5-azacytidine. Our study sheds light on the molecular mechanisms underlying the synergistic action of HDACi and DNMTi and may also help to define improved policies for cancer treatment.

  16. Dynamics of asymmetric binary glass formers. II. Results from nuclear magnetic resonance spectroscopy

    SciTech Connect

    Bock, D.; Kahlau, R.; Pötzschner, B.; Körber, T.; Wagner, E.; Rössler, E. A.

    2014-03-07

    Various {sup 2}H and {sup 31}P nuclear magnetic resonance (NMR) spectroscopy techniques are applied to probe the component dynamics of the binary glass former tripropyl phosphate (TPP)/polystyrene-d{sub 3} (PS) over the full concentration range. The results are quantitatively compared to those of a dielectric spectroscopy (DS) study on the same system previously published [R. Kahlau, D. Bock, B. Schmidtke, and E. A. Rössler, J. Chem. Phys. 140, 044509 (2014)]. While the PS dynamics does not significantly change in the mixtures compared to that of neat PS, two fractions of TPP molecules are identified, one joining the glass transition of PS in the mixture (α{sub 1}-process), the second reorienting isotropically (α{sub 2}-process) even in the rigid matrix of PS, although at low concentration resembling a secondary process regarding its manifestation in the DS spectra. Pronounced dynamical heterogeneities are found for the TPP α{sub 2}-process, showing up in extremely stretched, quasi-logarithmic stimulated echo decays. While the time window of NMR is insufficient for recording the full correlation functions, DS results, covering a larger dynamical range, provide a satisfactory interpolation of the NMR data. Two-dimensional {sup 31}P NMR spectra prove exchange within the broadly distributed α{sub 2}-process. As demonstrated by {sup 2}H NMR, the PS matrix reflects the faster α{sub 2}-process of TPP by performing a spatially highly hindered motion on the same timescale.

  17. High-field Overhauser dynamic nuclear polarization in silicon below the metal-insulator transition.

    PubMed

    Dementyev, Anatoly E; Cory, David G; Ramanathan, Chandrasekhar

    2011-04-21

    Single crystal silicon is an excellent system to explore dynamic nuclear polarization (DNP), as it exhibits a continuum of properties from metallic to insulating as a function of doping concentration and temperature. At low doping concentrations DNP has been observed to occur via the solid effect, while at very high-doping concentrations an Overhauser mechanism is responsible. Here we report the hyperpolarization of (29)Si in n-doped silicon crystals, with doping concentrations in the range of (1-3) × 10(17) cm(-3). In this regime exchange interactions between donors become extremely important. The sign of the enhancement in our experiments and its frequency dependence suggest that the (29)Si spins are directly polarized by donor electrons via an Overhauser mechanism within exchange-coupled donor clusters. The exchange interaction between donors only needs to be larger than the silicon hyperfine interaction (typically much smaller than the donor hyperfine coupling) to enable this Overhauser mechanism. Nuclear polarization enhancement is observed for a range of donor clusters in which the exchange energy is comparable to the donor hyperfine interaction. The DNP dynamics are characterized by a single exponential time constant that depends on the microwave power, indicating that the Overhauser mechanism is a rate-limiting step. Since only about 2% of the silicon nuclei are located within 1 Bohr radius of the donor electron, nuclear spin diffusion is important in transferring the polarization to all the spins. However, the spin-diffusion time is much shorter than the Overhauser time due to the relatively weak silicon hyperfine coupling strength. In a 2.35 T magnetic field at 1.1 K, we observed a DNP enhancement of 244 ± 84 resulting in a silicon polarization of 10.4 ± 3.4% following 2 h of microwave irradiation.

  18. Theoretical aspects of Dynamic Nuclear Polarization in the solid state - the cross effect.

    PubMed

    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. Copyright © 2011 Elsevier Inc. All rights reserved.

  19. Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 From The Nuclear Stellar Dynamics

    NASA Technical Reports Server (NTRS)

    Bower, G. A.; Green, R. F.; Bender, R.; Gebhardt, K.; Lauer, T. R.; Magorrian, J.; Richstone, D. O.; Danks, A.; Gull, T.; Hutchings, J.

    2000-01-01

    We analyze the nuclear stellar dynamics of the SBO galaxy NGC 1023, utilizing observational data both from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope and from the ground. The stellar kinematics measured from these long-slit spectra show rapid rotation (V equals approx. 70 km/s at a distance of O.1 deg = 4.9 pc from the nucleus) and increasing velocity dispersion toward the nucleus (where sigma = 295 +/- 30 km/s). We model the observed stellar kinematics assuming an axisymmetric mass distribution with both two and three integrals of motion. Both modeling techniques point to the presence of a central dark compact mass (which presumably is a supermassive black hole) with confidence > 99%. The isotropic two-integral models yield a best-fitting black hole mass of (6.0 +/- 0.4) x 10(exp 7) solar masses and mass-to-light ratio (M/L(sub v)) of 5.38 +/- 0.08, and the goodness-of-fit (CHI(exp 2)) is insensitive to reasonable values for the galaxy's inclination. The three-integral models, which non-parametrically fit the observed line-of-sight velocity distribution as a function of position in the galaxy, suggest a black hole mass of (3.9 +/- 0.4) x 10(exp 7) solar masses and M/L(sub v) of 5.56 +/- 0.02 (internal errors), and the edge-on models are vastly superior fits over models at other inclinations. The internal dynamics in NGC 1023 as suggested by our best-fit three-integral model shows that the velocity distribution function at the nucleus is tangentially anisotropic, suggesting the presence of a nuclear stellar disk. The nuclear line of sight velocity distribution has enhanced wings at velocities >= 600 km/s from systemic, suggesting that perhaps we have detected a group of stars very close to the central dark mass.

  20. Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

    SciTech Connect

    Mendive-Tapia, David; Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.

    2013-07-28

    Coupled electron-nuclear dynamics, implemented using the Ehrenfest method, has been used to study charge migration with fixed nuclei, together with charge transfer when nuclei are allowed to move. Simulations were initiated at reference geometries of neutral benzene and 2-phenylethylamine (PEA), and at geometries close to potential energy surface crossings in the cations. Cationic eigenstates, and the so-called sudden approximation, involving removal of an electron from a correlated ground-state wavefunction for the neutral species, were used as initial conditions. Charge migration without coupled nuclear motion could be observed if the Ehrenfest simulation, using the sudden approximation, was started near a conical intersection where the states were both strongly coupled and quasi-degenerate. Further, the main features associated with charge migration were still recognizable when the nuclear motion was allowed to couple. In the benzene radical cation, starting from the reference neutral geometry with the sudden approximation, one could observe sub-femtosecond charge migration with a small amplitude, which results from weak interaction with higher electronic states. However, we were able to engineer large amplitude charge migration, with a period between 10 and 100 fs, corresponding to oscillation of the electronic structure between the quinoid and anti-quinoid cationic electronic configurations, by distorting the geometry along the derivative coupling vector from the D{sub 6h} Jahn-Teller crossing to lower symmetry where the states are not degenerate. When the nuclear motion becomes coupled, the period changes only slightly. In PEA, in an Ehrenfest trajectory starting from the D{sub 2} eigenstate and reference geometry, a partial charge transfer occurs after about 12 fs near the first crossing between D{sub 1}, D{sub 2} (N{sup +}-Phenyl, N-Phenyl{sup +}). If the Ehrenfest propagation is started near this point, using the sudden approximation without coupled

  1. Sensing actin dynamics: Structural basis for G-actin-sensitive nuclear import of MAL

    SciTech Connect

    Hirano, Hidemi; Matsuura, Yoshiyuki

    2011-10-22

    Highlights: {yields} MAL has a bipartite NLS that binds to Imp{alpha} in an extended conformation. {yields} Mutational analyses verified the functional significance of MAL-Imp{alpha} interactions. {yields} Induced folding and NLS-masking by G-actins inhibit nuclear import of MAL. -- Abstract: The coordination of cytoskeletal actin dynamics with gene expression reprogramming is emerging as a crucial mechanism to control diverse cellular processes, including cell migration, differentiation and neuronal circuit assembly. The actin-binding transcriptional coactivator MAL (also known as MRTF-A/MKL1/BSAC) senses G-actin concentration and transduces Rho GTPase signals to serum response factor (SRF). MAL rapidly shuttles between the cytoplasm and the nucleus in unstimulated cells but Rho-induced depletion of G-actin leads to MAL nuclear accumulation and activation of transcription of SRF:MAL-target genes. Although the molecular and structural basis of actin-regulated nucleocytoplasmic shuttling of MAL is not understood fully, it is proposed that nuclear import of MAL is mediated by importin {alpha}/{beta} heterodimer, and that G-actin competes with importin {alpha}/{beta} for the binding to MAL. Here we present structural, biochemical and cell biological evidence that MAL has a classical bipartite nuclear localization signal (NLS) in the N-terminal 'RPEL' domain containing Arg-Pro-X-X-X-Glu-Leu (RPEL) motifs. The NLS residues of MAL adopt an extended conformation and bind along the surface groove of importin-{alpha}, interacting with the major- and minor-NLS binding sites. We also present a crystal structure of wild-type MAL RPEL domain in complex with five G-actins. Comparison of the importin-{alpha}- and actin-complexes revealed that the binding of G-actins to MAL is associated with folding of NLS residues into a helical conformation that is inappropriate for importin-{alpha} recognition.

  2. Magnetization Dynamics Changes of Dysprosium(III) Single-Ion Magnets Associated with Guest Molecules.

    PubMed

    Zhang, Sheng; Ke, Hongshan; Sun, Lin; Li, Xin; Shi, Quan; Xie, Gang; Wei, Qing; Yang, Desuo; Wang, Wenyuan; Chen, Sanping

    2016-04-18

    Two Dy(III) single-ion magnets with a trigonal dodecahedron (D2d) for 1 and an approximately square-antiprismatic (SAP, D4d) N2O6 coordination environment for 2, formulated as [Dy(Phen)(tfmb)3] (1) and [Dy(Phen)(tfmb)3]·0.5(1,4-dioxane) (2) (tfmb = 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione, Phen = 1,10-phenanthroline), were obtained. Therein, complex 1 was transformed to 2 in 1,4-dioxane solution. Structural analysis shows that complexes 1 and 2 have differing local symmetry of Dy(III) ions. Magnetic studies indicate that the barrier heights (ΔE/kB) of 1 and 2 are 63.56 and 102.82 K under zero dc field as well as 118.50 and 164.55 K under 1200 Oe dc field, respectively. Based on the frequency dependencies of the ac susceptibilities, the effective barriers (ΔE/kB) and the pre-exponential factors (τ0) are 67.05 K and 4.57 × 10(-6) s for 1 and 95.88 K and 2.39 × 10(-7) s for 2 under zero dc field. The present work illustrates that guest-determined notable structure change results in different barrier heights.

  3. Characterization of nuclear localization signals in the type III effectors HsvG and HsvB of the gall-forming bacterium Pantoea agglomerans.

    PubMed

    Weinthal, Dan M; Barash, Isaac; Tzfira, Tzvi; Gaba, Victor; Teper, Doron; Sessa, Guido; Manulis-Sasson, Shulamit

    2011-05-01

    HsvG and HsvB, two paralogous type III effectors of the gall-forming bacteria Pantoea agglomerans pv. gypsophilae and P. agglomerans pv. betae, determine host specificity on gypsophila and beet, respectively. They were previously shown to be DNA-binding proteins imported into host and non-host nuclei and might act as transcriptional activators. Sequence analysis of these effectors did not detect canonical nuclear localization signals (NLSs), but two basic amino acid clusters designated putative NLS1 and NLS2 were detected in their N-terminal and C-terminal regions, respectively. pNIA assay for nuclear import in yeast and bombardment of melon leaves with each of the NLSs fused to a 2xYFP reporter indicated that putative NLS1 and NLS2 were functional in transport of HsvG into the nucleus. A yeast two-hybrid assay showed that HsvB, HsvG, putative NLS1, putative NLS2, HsvG converted into HsvB, or HsvB converted into HsvG by exchanging the repeat domain, all interacted with AtKAP-α and importin-α3 of Arabidopsis thaliana. Deletion analysis of the NLS domains in HsvG suggested that putative NLS1 or NLS2 were required for pathogenicity on gypsophila cuttings and presumably for import of HsvG into the nucleus. This study demonstrates the presence of two functional NLSs in the type III effectors HsvG and HsvB.

  4. Dynamic parameters test of Haiyang Nuclear Power Engineering in reactor areas, China

    NASA Astrophysics Data System (ADS)

    Zhou, N.; Zhao, S.; Sun, L.

    2012-12-01

    Haiyang Nuclear Power Project is located in Haiyang city, China. It consists of 6×1000MW AP1000 Nuclear Power generator sets. The dynamic parameters of the rockmass are essential for the design of the nuclear power plant. No.1 and No.2 reactor area are taken as research target in this paper. Sonic logging, single hole and cross-hole wave velocity are carried out respectively on the site. There are four types of rock lithology within the measured depth. They are siltstone, fine sandstone, shale and allgovite. The total depth of sonic logging is 409.8m and 2049 test points. The sound wave velocity of the rocks are respectively 5521 m/s, 5576m/s, 5318 m/s and 5576 m/s. Accroding to the statistic data, among medium weathered fine sandstone, fairly broken is majority, broken and relatively integrity are second, part of integrity. Medium weathered siltstone, relatively integrity is mojority, fairly broken is second. Medium weathered shale, fairly broken is majority, broken and relatively integrity for the next and part of integrity. Slight weathered fine sandstone, siltstone, shale and allgovite, integrity is the mojority, relatively integrity for the next, part of fairly broken.The single hole wave velocity tests are set in two boreholesin No.1 reactor area and No.2 reactor area respectively. The test depths of two holes are 2-24m, and the others are 2-40m. The wave velocity data are calculated at different depth in each holes and dynamic parameters. According to the test statistic data, the wave velocity and the dynamic parameter values of rockmass are distinctly influenced by the weathering degree. The test results are list in table 1. 3 groups of cross hole wave velocity tests are set for No.1 and 2 reactor area, No.1 reactor area: B16, B16-1, B20(Direction:175°, depth: 100m); B10, B10-1, B11(269°, 40m); B21, B21-1, B17(154°, 40m); with HB16, HB10, HB21 as trigger holes; No.2 reactor area: B47, B47-1, HB51(176°, 100m); B40, B40-1, B41(272°, 40m); B42, B42-1, B

  5. Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics simulations of hydrogen transfer reactions in enzymes

    NASA Astrophysics Data System (ADS)

    Billeter, Salomon R.; Webb, Simon P.; Iordanov, Tzvetelin; Agarwal, Pratul K.; Hammes-Schiffer, Sharon

    2001-04-01

    A hybrid approach for simulating proton and hydride transfer reactions in enzymes is presented. The electronic quantum effects are incorporated with an empirical valence bond approach. The nuclear quantum effects of the transferring hydrogen are included with a mixed quantum/classical molecular dynamics method in which the hydrogen nucleus is described as a multidimensional vibrational wave function. The free energy profiles are obtained as functions of a collective reaction coordinate. A perturbation formula is derived to incorporate the vibrationally adiabatic nuclear quantum effects into the free energy profiles. The dynamical effects are studied with the molecular dynamics with quantum transitions (MDQT) surface hopping method, which incorporates nonadiabatic transitions among the adiabatic hydrogen vibrational states. The MDQT method is combined with a reactive flux approach to calculate the transmission coefficient and to investigate the real-time dynamics of reactive trajectories. This hybrid approach includes nuclear quantum effects such as zero point energy, hydrogen tunneling, and excited vibrational states, as well as the dynamics of the complete enzyme and solvent. The nuclear quantum effects are incorporated during the generation of the free energy profiles and dynamical trajectories rather than subsequently added as corrections. Moreover, this methodology provides detailed mechanistic information at the molecular level and allows the calculation of rates and kinetic isotope effects. An initial application of this approach to the enzyme liver alcohol dehydrogenase is also presented.

  6. Dynamics of Langmuir and ion-sound waves in type III solar radio sources

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Willes, A. J.; Cairns, I. H.

    1993-01-01

    The study traces the evolution of Langmuir and ion-sound waves in type III sources, incorporating linear growth, linear damping, and nonlinear electrostatic decay. Improved estimates are obtained for the wavenumber range of growing waves and the nonlinear coupling coefficient for the decay process. It is shown that the conditions in the solar wind do not allow a steady state to be attained; instead, bursty linear and nonlinear interactions take place, consistent with the highly inhomogeneous and impulsive waves actually observed. Nonlinear growth is found to be rapid enough to saturate the growth of the parent Langmuir waves in the available interaction time. The competing processes of nonlinear wave collapse and quasi-linear relaxation are discussed, and it is concluded that neither is responsible for the saturation of Langmuir growth.

  7. Dynamics of Wet Oxidation of High-AL-Content III-V Materials

    SciTech Connect

    Ashby, C.I.H.

    1999-01-27

    Oxidation of layers of high-Al-content III-V materials by water vapor has become the enabling process for high-efficiency vertical cavity surface emitting lasers (VCSELS) and has potential applications for reducing substrate current leakage in GaAs-on-insulator (GOI) MESFETS. Because of the established importance of wet oxidation in optoelectronic devices and its potential applications in electronic devices, it has become increasingly important to understand the mechanism of wet oxidation and how it might be expected to affect both the fabrication and subsequent operation of devices that have been made using this technique. The mechanism of wet oxidation and the consequence of this mechanism for heterostructure design and ultimate device operation are discussed here.

  8. Generation of a transgenic medaka (Oryzias latipes) strain for visualization of nuclear dynamics in early developmental stages.

    PubMed

    Inoue, Takanobu; Iida, Atsuo; Maegawa, Shingo; Sehara-Fujisawa, Atsuko; Kinoshita, Masato

    2016-12-01

    In this study, we verified nuclear transport activity of an artificial nuclear localization signal (aNLS) in medaka fish (Oryzias latipes). We generated a transgenic medaka strain expresses the aNLS tagged enhanced green fluorescent protein (EGFP) driven by a medaka beta-actin promoter. The aNLS-EGFP was accumulated in the nuclei of somatic tissues and yolk nuclei of oocytes, but undetectable in the spermatozoa. The fluorescent signal was observed from immediately after fertilization by a maternal contribution. Furthermore, male and female pronuclei were visualized in fertilized eggs, and nuclear dynamics of pronuclear fusion and subsequent cleavage were captured by time-lapse imaging. In contrast, SV40NLS exhibited no activity of nuclear transport in early embryos. In conclusion, the aNLS possesses a strong nuclear localization activity and is a useful probe for fluorescent observation of the pronuclei and nuclei in early developmental stage of medaka.

  9. Dynamic characteristics of peripheral jet ACV. III - Coupling motion of heaving and pitching

    NASA Astrophysics Data System (ADS)

    Mori, T.; Maeda, H.

    The paper presents the dynamic characteristics of peripheral jet ACV (Air Cushion Vehicle) which has two degrees of freedom, i.e., heaving and pitching motion. The experiments are carried out for an ACV model, noting that the experimental results agree considerably with the analytical values. Furthermore, the response characteristics of ACV induced by the ground board oscillations of various modes are also investigated.

  10. Prediction of ground motion and dynamic stress change in Baekdusan (Changbaishan) volcano caused by a North Korean nuclear explosion

    PubMed Central

    Hong, Tae-Kyung; Choi, Eunseo; Park, Seongjun; Shin, Jin Soo

    2016-01-01

    Strong ground motions induce large dynamic stress changes that may disturb the magma chamber of a volcano, thus accelerating the volcanic activity. An underground nuclear explosion test near an active volcano constitutes a direct treat to the volcano. This study examined the dynamic stress changes of the magma chamber of Baekdusan (Changbaishan) that can be induced by hypothetical North Korean nuclear explosions. Seismic waveforms for hypothetical underground nuclear explosions at North Korean test site were calculated by using an empirical Green’s function approach based on a source-spectral model of a nuclear explosion; such a technique is efficient for regions containing poorly constrained velocity structures. The peak ground motions around the volcano were estimated from empirical strong-motion attenuation curves. A hypothetical M7.0 North Korean underground nuclear explosion may produce peak ground accelerations of 0.1684 m/s2 in the horizontal direction and 0.0917 m/s2 in the vertical direction around the volcano, inducing peak dynamic stress change of 67 kPa on the volcano surface and ~120 kPa in the spherical magma chamber. North Korean underground nuclear explosions with magnitudes of 5.0–7.6 may induce overpressure in the magma chamber of several tens to hundreds of kilopascals. PMID:26884136

  11. Prediction of ground motion and dynamic stress change in Baekdusan (Changbaishan) volcano caused by a North Korean nuclear explosion.

    PubMed

    Hong, Tae-Kyung; Choi, Eunseo; Park, Seongjun; Shin, Jin Soo

    2016-02-17

    Strong ground motions induce large dynamic stress changes that may disturb the magma chamber of a volcano, thus accelerating the volcanic activity. An underground nuclear explosion test near an active volcano constitutes a direct treat to the volcano. This study examined the dynamic stress changes of the magma chamber of Baekdusan (Changbaishan) that can be induced by hypothetical North Korean nuclear explosions. Seismic waveforms for hypothetical underground nuclear explosions at North Korean test site were calculated by using an empirical Green's function approach based on a source-spectral model of a nuclear explosion; such a technique is efficient for regions containing poorly constrained velocity structures. The peak ground motions around the volcano were estimated from empirical strong-motion attenuation curves. A hypothetical M7.0 North Korean underground nuclear explosion may produce peak ground accelerations of 0.1684 m/s(2) in the horizontal direction and 0.0917 m/s(2) in the vertical direction around the volcano, inducing peak dynamic stress change of 67 kPa on the volcano surface and ~120 kPa in the spherical magma chamber. North Korean underground nuclear explosions with magnitudes of 5.0-7.6 may induce overpressure in the magma chamber of several tens to hundreds of kilopascals.

  12. Gating current harmonics. III. Dynamic transients and steady states with intact sodium inactivation gating.

    PubMed Central

    Fohlmeister, J F; Adelman, W J

    1986-01-01

    Internally perfused squid giant axons with intact sodium inactivation gating were prepared for gating current experiments. Gating current records were obtained in sinusoidally driven dynamic steady states and as dynamic transients as functions of the mean membrane potential and the frequency of the command sinusoid. Controls were obtained after internal protease treatment of the axons that fully removed inactivation. The nonlinear analysis consisted of determining and interpreting the harmonic content in the current records. The results indicate the presence of three kinetic processes, two of which are associated with activation gating (the so-called primary and secondary processes), and the third with inactivation gating. The dynamic steady state data show that inactivation gating does not contribute a component to the gating current, and has no direct voltage-dependence of its own. Rather, the inactivation kinetics appear to be coupled to the primary activation kinetics, and the coupling mechanism appears to be one of reciprocal steric hindrance between two molecular components. The mechanism allows the channel to become inactivated without first entering the conducting state, and will do so in about 40 percent of depolarizing voltage-clamp steps to 0 mV. The derived model kinetics further indicate that the conducting state may flicker between open and closed with the lifetime of either state being 10 microseconds. Dynamic transients generated by the model kinetics (i.e., the behavior of the harmonic components as a function of time after an instantaneous change in the mean membrane potential from a holding potential of -80 mV) match the experimental dynamic transients in all details. These transients have a duration of 7-10 ms (depending on the level of depolarization), and are the result of the developing inactivation following the discontinuous voltage change. A detailed hypothetical molecular model of the channel and gating machinery is presented. PMID

  13. Probing the Dynamics of a Nuclear Spin Bath in Diamond through Time-Resolved Central Spin Magnetometry

    NASA Astrophysics Data System (ADS)

    Dréau, A.; Jamonneau, P.; Gazzano, O.; Kosen, S.; Roch, J.-F.; Maze, J. R.; Jacques, V.

    2014-09-01

    Using fast electron spin resonance spectroscopy of a single nitrogen-vacancy defect in diamond, we demonstrate real-time readout of the Overhauser field produced by its nuclear spin environment under ambient conditions. These measurements enable narrowing the Overhauser field distribution by postselection, corresponding to a conditional preparation of the nuclear spin bath. Correlations of the Overhauser field fluctuations are quantitatively inferred by analyzing the Allan deviation over consecutive measurements. This method allows us to extract the dynamics of weakly coupled nuclear spins of the reservoir.

  14. Observation of hysteretic transport due to dynamic nuclear spin polarization in a GaAs lateral double quantum dot.

    PubMed

    Kobayashi, Takashi; Hitachi, Kenichi; Sasaki, Satoshi; Muraki, Koji

    2011-11-18

    We report a new transport feature in a GaAs lateral double quantum dot that emerges for magnetic-field sweeps and shows hysteresis due to dynamic nuclear spin polarization (DNP). This DNP signal appears in the Coulomb blockade regime by virtue of the finite interdot tunnel coupling and originates from the crossing between ground levels of the spin triplet and singlet extensively used for nuclear spin manipulations in pulsed-gate experiments. The magnetic-field dependence of the current level is suggestive of unbalanced DNP between the two dots, which opens up the possibility of controlling electron and nuclear spin states via dc transport.

  15. Hairpin structures in DNA containing arabinofuranosylcytosine. A combination of nuclear magnetic resonance and molecular dynamics

    SciTech Connect

    Pieters, J.M.L.; de Vroom, E.; van der Marel, G.A.; van Boom, J.H.; Altona, C. ); Koning, T.H.G.; Kaptein, R. )

    1990-01-23

    Nuclear magnetic resonance (NMR) and model-building studies were carried out on the hairpin form of the octamer d(CG{sup a}CTAGCG) ({sup a}C = arabinofuranosylcytosine), referred to as the TA compound. The nonexchangeable protons of the TA compound were assigned by means of nuclear Overhauser effect spectroscopy (NOESY) and correlated spectroscopy (COSY). Form a detailed analysis of the coupling data and of the NOESY spectra the following conclusions are reached: (i) the hairpin consists of a stem of three Watson-Crick type base pairs, and the two remaining residues, T(4) and dA(5), participate in a loop. (ii) All sugar rings show conformational flexibility although a strong preference for the S-type (C2{prime}-endo) conformer is observed. (iii) The thymine does not stack upon the 3{prime} side of the stem as expected, but swings into the minor groove. (iv) At the 5{prime}-3{prime} loop-stem junction a stacking discontinuity occurs as a consequence of a sharp turn in that part of the backbone, caused by the unusual {beta}{sup +} and {gamma}{sup t} torsion angles in residue dG(6). (v) The A base slides over the 5{prime} side of the stem to stack upon the {sup a}C(3) residue at the 3{prime} side of the stem in an antiparallel fashion. On the basis of J couplings and a set approximate proton-proton distances from NOE cross peaks, a model for the hairpin was constructed.

  16. P-body components, Dhh1 and Pat1, are involved in tRNA nuclear-cytoplasmic dynamics

    PubMed Central

    Hurto, Rebecca L.; Hopper, Anita K.

    2011-01-01

    The nuclear-cytoplasmic distribution of tRNA depends on the balance between tRNA nuclear export/re-export and retrograde tRNA nuclear import in Saccharomyces cerevisiae. The distribution of tRNA is sensitive to nutrient availability as cells deprived of various nutrients exhibit tRNA nuclear accumulation. Starvation induces numerous events that result in translational repression and P-body formation. This study investigated the possible coordination of these responses with tRNA nuclear-cytoplasmic distribution. Dhh1 and Pat1 function in parallel to promote translation repression and P-body formation in response to starvation. Loss of both, Dhh1 and Pat1, results in a failure to repress translation and to induce P-body formation in response to glucose starvation. This study reports that nutrient deprived dhh1 pat1 cells also fail to accumulate tRNA within nuclei. Conversely, inhibition of translation initiation and induction of P-body formation by overproduction of Dhh1 or Pat1 cause tRNA nuclear accumulation in nutrient-replete conditions. Also, loss of the mRNA decapping activator, Lsm1, causes tRNA nuclear accumulation. However, the coordination between P-body formation, translation repression, and tRNA distribution is limited to the early part of the P-body formation/translation repression pathway as loss of mRNA decapping or 5′ to 3′ degradation does not influence tRNA nuclear-cytoplasmic dynamics. The data provide the first link between P-body formation/translation initiation and tRNA nuclear-cytoplasmic dynamics. The current model is that Dhh1 and Pat1 function in parallel to promote starvation-induced tRNA nuclear accumulation. PMID:21398402

  17. Hydration structures of U(III) and U(IV) ions from ab initio molecular dynamics simulations

    SciTech Connect

    Leung, Kevin; Nenoff, Tina M.

    2012-08-21

    We apply DFT+U-based ab initio molecular dynamics simulations to study the hydration structures of U(III) and U(IV) ions, pertinent to redox reactions associated with uranium salts in aqueous media. U(III) is predicted to be coordinated to 8 water molecules, while U(IV) has a hydration number between 7 and 8. At least one of the innershell water molecules of the hydrated U(IV) complex becomes spontaneously deprotonated. As a result, the U(IV)-O pair correlation function exhibits a satellite peak at 2.15 A associated with the shorter U(IV)-(OH{sup -}) bond. This feature is not accounted for in analysis of extended x-ray absorption fine structure and x-ray adsorption near edge structure measurements, which yield higher estimates of U(IV) hydration numbers. This suggests that it may be useful to include the effect of possible hydrolysis in future interpretation of experiments, especially when the experimental pH is close to the reported hydrolysis equilibrium constant value.

  18. 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

  19. Dynamic nuclear polarization assisted spin diffusion for the solid effect case.

    PubMed

    Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

    2011-02-21

    The dynamic nuclear polarization (DNP) process in solids depends on the magnitudes of hyperfine interactions between unpaired electrons and their neighboring (core) nuclei, and on the dipole-dipole interactions between all nuclei in the sample. The polarization enhancement of the bulk nuclei has been typically described in terms of a hyperfine-assisted polarization of a core nucleus by microwave irradiation followed by a dipolar-assisted spin diffusion process in the core-bulk nuclear system. This work presents a theoretical approach for the study of this combined process using a density matrix formalism. In particular, solid effect DNP on a single electron coupled to a nuclear spin system is considered, taking into account the interactions between the spins as well as the main relaxation mechanisms introduced via the electron, nuclear, and cross-relaxation rates. The basic principles of the DNP-assisted spin diffusion mechanism, polarizing the bulk nuclei, are presented, and it is shown that the polarization of the core nuclei and the spin diffusion process should not be treated separately. To emphasize this observation the coherent mechanism driving the pure spin diffusion process is also discussed. In order to demonstrate the effects of the interactions and relaxation mechanisms on the enhancement of the nuclear polarization, model systems of up to ten spins are considered and polarization buildup curves are simulated. A linear chain of spins consisting of a single electron coupled to a core nucleus, which in turn is dipolar coupled to a chain of bulk nuclei, is considered. The interaction and relaxation parameters of this model system were chosen in a way to enable a critical analysis of the polarization enhancement of all nuclei, and are not far from the values of (13)C nuclei in frozen (glassy) organic solutions containing radicals, typically used in DNP at high fields. Results from the simulations are shown, demonstrating the complex dependences of the DNP

  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. Development and application of the dynamic system doctor to nuclear reactor probabilistic risk assessments.

    SciTech Connect

    Kunsman, David Marvin; Aldemir, Tunc; Rutt, Benjamin; Metzroth, Kyle; Catalyurek, Umit; Denning, Richard; Hakobyan, Aram; Dunagan, Sean C.

    2008-05-01

    This LDRD project has produced a tool that makes probabilistic risk assessments (PRAs) of nuclear reactors - analyses which are very resource intensive - more efficient. PRAs of nuclear reactors are being increasingly relied on by the United States Nuclear Regulatory Commission (U.S.N.R.C.) for licensing decisions for current and advanced reactors. Yet, PRAs are produced much as they were 20 years ago. The work here applied a modern systems analysis technique to the accident progression analysis portion of the PRA; the technique was a system-independent multi-task computer driver routine. Initially, the objective of the work was to fuse the accident progression event tree (APET) portion of a PRA to the dynamic system doctor (DSD) created by Ohio State University. Instead, during the initial efforts, it was found that the DSD could be linked directly to a detailed accident progression phenomenological simulation code - the type on which APET construction and analysis relies, albeit indirectly - and thereby directly create and analyze the APET. The expanded DSD computational architecture and infrastructure that was created during this effort is called ADAPT (Analysis of Dynamic Accident Progression Trees). ADAPT is a system software infrastructure that supports execution and analysis of multiple dynamic event-tree simulations on distributed environments. A simulator abstraction layer was developed, and a generic driver was implemented for executing simulators on a distributed environment. As a demonstration of the use of the methodological tool, ADAPT was applied to quantify the likelihood of competing accident progression pathways occurring for a particular accident scenario in a particular reactor type using MELCOR, an integrated severe accident analysis code developed at Sandia. (ADAPT was intentionally created with flexibility, however, and is not limited to interacting with only one code. With minor coding changes to input files, ADAPT can be linked to other

  2. Effects of proton irradiation on luminescence and carrier dynamics of self-assembled III-V quatum dots

    NASA Technical Reports Server (NTRS)

    Leon, R.; Marcinkevicius, S.; Siegert, J.; Magness, B.; Taylor, W.; Lobo, C.

    2002-01-01

    The effects of proton irradiation (1.5 MeV) on photoluminescence intensities and carrier dynamics were compared between III-V quantum dots and similar quantum well structures. A significant enhancement in radiation tolerance is seen with three-dimensional quantum confinement. Measurements were carried out in different quantum dot (QD) structures, varying in material (InGaAs/GaAs and InAlAs/AlGaAs), QD surface density (4x10^8 to 3x10'^10 cm^-2), and substrate orientation [(100) and (311) B]. Similar trends were observed for all QD samples. A slight increase in PL emission after low to intermediate proton doses, are also observed in InGaAs/GaAs (100) QD structures. The latter is explained in terms of more efficient carrier transfer from the wetting layer via radiation-induced defects.

  3. The hydration properties of Eu(II) and Eu(III): An ab initio quantum mechanical molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Canaval, Lorenz R.; Rode, Bernd M.

    2015-01-01

    A comparison of the hydration characteristics of di- and trivalent europium ions in aqueous solution is presented. The established quantum mechanical charge-field molecular dynamics (QMCF-MD) approach yielded two 30 ps simulations. Significant differences among the two species were found in the Eu-O radial distribution functions, both in good agreement with experiments. The first shell coordination numbers of 8.1 and 8.9 were observed for Eu(II) and Eu(III), respectively. The mean residence time of first shell ligands differ by more than one order of magnitude, the divalent ion's hydration shell being more flexible, which is underlined by a weak ion-water bond strength.

  4. Nuclear Dynamics Consequence Analysis (NDCA) for the Disposal of Spent Nuclear Fuel in an Underground Geologic Repository--Volume 1: Executive Summary

    SciTech Connect

    Taylor, L.L.; Wilson, J.R.; Sanchez, L.Z.; Aguilar, R.; Trellue, H.R.; Cochrane, K.; Rath, J.S.

    1998-10-01

    The US Department of Energy Office of Environmental Management's (DOE/EM's) National Spent Nuclear Fuel Program (NSNFP), through a collaboration between Sandia National Laboratories (SNL) and Idaho National Engineering and Environmental Laboratory (INEEL), is conducting a systematic Nuclear Dynamics Consequence Analysis (NDCA) of the disposal of SNFs in an underground geologic repository sited in unsaturated tuff. This analysis is intended to provide interim guidance to the DOE for the management of the SNF while they prepare for final compliance evaluation. This report presents results from a Nuclear Dynamics Consequence Analysis (NDCA) that examined the potential consequences and risks of criticality during the long-term disposal of spent nuclear fuel owned by DOE-EM. This analysis investigated the potential of post-closure criticality, the consequences of a criticality excursion, and the probability frequency for post-closure criticality. The results of the NDCA are intended to provide the DOE-EM with a technical basis for measuring risk which can be used for screening arguments to eliminate post-closure criticality FEPs (features, events and processes) from consideration in the compliance assessment because of either low probability or low consequences. This report is composed of an executive summary (Volume 1), the methodology and results of the NDCA (Volume 2), and the applicable appendices (Volume 3).

  5. Nuclear Dynamics Consequence Analysis (NDCA) for the Disposal of Spent Nuclear Fuel in an Underground Geologic Repository--Volume 2: Methodology and Results

    SciTech Connect

    Taylor, L.L.; Wilson, J.R.; Sanchez, L.C.; Aguilar, R.; Trellue, H.R.; Cochrane, K.; Rath, J.S.

    1998-10-01

    The US Department of Energy Office of Environmental Management's (DOE/EM's) National Spent Nuclear Fuel Program (NSNFP), through a collaboration between Sandia National Laboratories (SNL) and Idaho National Engineering and Environmental Laboratory (INEEL), is conducting a systematic Nuclear Dynamics Consequence Analysis (NDCA) of the disposal of SNFs in an underground geologic repository sited in unsaturated tuff. This analysis is intended to provide interim guidance to the DOE for the management of the SNF while they prepare for final compliance evaluation. This report presents results from a Nuclear Dynamics Consequence Analysis (NDCA) that examined the potential consequences and risks of criticality during the long-term disposal of spent nuclear fuel owned by DOE-EM. This analysis investigated the potential of post-closure criticality, the consequences of a criticality excursion, and the probability frequency for post-closure criticality. The results of the NDCA are intended to provide the DOE-EM with a technical basis for measuring risk which can be used for screening arguments to eliminate post-closure criticality FEPs (features, events and processes) from consideration in the compliance assessment because of either low probability or low consequences. This report is composed of an executive summary (Volume 1), the methodology and results of the NDCA (Volume 2), and the applicable appendices (Volume 3).

  6. Characterization and comparison of 128x128 element nuclear optical dynamic display system resistive arrays

    NASA Astrophysics Data System (ADS)

    Hayes, Alexander G.; Caraco, Fino J.; Harrison, David C.; Sorvari, John M.

    2006-05-01

    Dynamic infrared scene projection is a common technology used to provide end to end testing and characterization of infrared sensor systems. Scene projection technology will play an increasing role in infrared system evaluation and development as the cost and risk of flight testing increases and new display technologies begin to emerge. This paper describes a series of tests performed in the Seeker Experimental System (SES) at MIT Lincoln Laboratory (MIT LL). A small collection of 128×128 element Nuclear Optical Dynamic Display System (NODDS) resistive arrays were tested and compared using FIESTA drive electronics developed by ATK Mission Research. The residual spatial nonuniformity of the NODDS arrays were calculated after applying a sparse grid based nonuniformity correction algorithm developed at MIT LL. The nonuniformity correction algorithm is a slightly modified version of the industry standard sparse grid technique and is outlined in this paper. Additional metrics used to compare the arrays include emitter temporal response, raw nonuniformity, transfer function smoothness, dynamic range, and bad display pixel characteristics.

  7. Dynamic modeling efforts for system interface studies for nuclear hydrogen production.

    SciTech Connect

    Vilim, R. B.; Nuclear Engineering Division

    2007-08-15

    System interface studies require not only identifying economically optimal equipment configurations, which involves studying mainly full power steady-state operation, but also assessing the operability of a design during load change and startup and assessing safety-related behavior during upset conditions. This latter task is performed with a dynamic simulation code. This report reviews the requirements of such a code. It considers the types of transients that will need to be simulated, the phenomena that will be present, the models best suited for representing the phenomena, and the type of numerical solution scheme for solving the models to obtain the dynamic response of the combined nuclear-hydrogen plant. Useful insight into plant transient behavior prior to running a dynamics code is obtained by some simple methods that take into account component time constants and energy capacitances. Methods for determining reactor stability, plant startup time, and temperature response during load change, and tripping of the reactor are described. Some preliminary results are presented.

  8. Photophysics, photoelectrical properties and photoconductivity relaxation dynamics of quantum-sized bismuth(III) sulfide thin films

    SciTech Connect

    Pejova, Biljana . E-mail: biljana@iunona.pmf.ukim.edu.mk; Tanusevski, Atanas; Grozdanov, Ivan

    2005-06-15

    Electrical and photoelectrical properties (including both the stationary photoresponse and the photocarriers' relaxation dynamics) of nanocrystalline semiconducting bismuth(III) sulfide thin films were investigated. The experimental design of photoelectrical properties was achieved by controlling the chemistry of the deposition process (varying the reagent concentration in the reaction system) and also by physical means (controlling the crystal dimensions by post-deposition annealing). The band gap energy of thin films characterized by most pronounced photoelectrical properties was calculated, on the basis of measured photoconductivity spectral response curves, by several approaches. All of the obtained values are in very good agreement with the corresponding ones obtained from optical spectroscopy data within the framework of parabolic approximation for dispersion relation. On the basis of measured temperature dependence of dark electrical resistivity of nanocrystalline bismuth(III) sulfide films, the thermal band gap energy and the ionization energy of the impurity level (of donor type) were calculated. The corresponding values are 1.50 and 0.42eV. Dynamics of non-equilibrium charge carriers' relaxation processes was studied with the oscilloscopic method. By analysis of the photoconductivity decay kinetics data it is found that recombination of non-equilibrium charge carriers is carried out according to the linear mechanism. The calculated relaxation time of photoexcited charge carriers is 1.58ms, the relaxation processes occurring via local trapping centers. Recombination processes occurring via a single-type trapping center can be described within the framework of the Schockley-Read model. The practically linear regime detected in the measured lux-ampere characteristics of the studied films ({delta}{sigma}{approx}{phi}{sup 0.98}) indicate as well a linear recombination mechanism of the photoexcited charge carriers.

  9. Dynamic two-center interference in high-order harmonic generation from molecules with attosecond nuclear motion.

    PubMed

    Baker, S; Robinson, J S; Lein, M; Chirilă, C C; Torres, R; Bandulet, H C; Comtois, D; Kieffer, J C; Villeneuve, D M; Tisch, J W G; Marangos, J P

    2008-08-01

    We report a new dynamic two-center interference effect in high-harmonic generation from H2, in which the attosecond nuclear motion of H2+ initiated at ionization causes interference to be observed at lower harmonic orders than would be the case for static nuclei. To enable this measurement we utilize a recently developed technique for probing the attosecond nuclear dynamics of small molecules. The experimental results are reproduced by a theoretical analysis based upon the strong-field approximation which incorporates the temporally dependent two-center interference term.

  10. Nuclear quantum effect on intramolecular hydrogen bond of hydrogen maleate anion: An ab initio path integral molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Kawashima, Yukio; Tachikawa, Masanori

    2013-05-01

    Ab initio path integral molecular dynamics simulation was performed to understand the nuclear quantum effect on the hydrogen bond of hydrogen malonate anion. Static calculation predicted the proton transfer barrier as 0.12 kcal/mol. Conventional ab initio molecular dynamics simulation at 300 K found proton distribution with a double peak on the proton transfer coordinate. Inclusion of thermal effect alone elongates the hydrogen bond length, which increases the barrier height. Inclusion of nuclear quantum effect washes out this barrier, and distributes a single broad peak in the center. H/D isotope effect on the proton transfer is also discussed.

  11. Transformations of galaxies - III. Encounter dynamics and tidal response as functions of galaxy structure

    NASA Astrophysics Data System (ADS)

    Barnes, Joshua E.

    2016-01-01

    Tidal interactions between disc galaxies depend on galaxy structure, but the details of this relationship are incompletely understood. I have constructed a three-parameter grid of bulge/disc/halo models broadly consistent with Λ cold dark matter, and simulated an extensive series of encounters using these models. Halo mass and extent strongly influence the dynamics of orbit evolution. In close encounters, the transfer of angular momentum mediated by the dynamical response of massive, extended haloes can reverse the direction of orbital motion of the central galaxies after their first passage. Tidal response is strongly correlated with the ratio ve/vc of escape to circular velocity within the participating discs. Moreover, the same ratio also correlates with the rate at which tidal tails are reaccreted by their galaxies of origin; consequently, merger remnants with `twin tails', such as NGC 7252, may prove hard to reproduce unless (ve/vc)2 ≲ 5.5. The tidal morphology of an interacting system can provide useful constraints on progenitor structure. In particular, encounters in which halo dynamics reverses orbital motion exhibit a distinctive morphology which may be recognized observationally. Detailed models attempting to reproduce observations of interacting galaxies should explore the likely range of progenitor structures along with other encounter parameters.

  12. Optimal control design of NMR and dynamic nuclear polarization experiments using monotonically convergent algorithms.

    PubMed

    Maximov, Ivan I; Tosner, Zdenĕk; Nielsen, Niels Chr

    2008-05-14

    Optimal control theory has recently been introduced to nuclear magnetic resonance (NMR) spectroscopy as a means to systematically design and optimize pulse sequences for liquid- and solid-state applications. This has so far primarily involved numerical optimization using gradient-based methods, which allow for the optimization of a large number of pulse sequence parameters in a concerted way to maximize the efficiency of transfer between given spin states or shape the nuclear spin Hamiltonian to a particular form, both within a given period of time. Using such tools, a variety of new pulse sequences with improved performance have been developed, and the NMR spin engineers have been challenged to consider alternative routes for analytical experiment design to meet similar performance. In addition, it has lead to increasing demands to the numerical procedures used in the optimization process in terms of computational speed and fast convergence. With the latter aspect in mind, here we introduce an alternative approach to numerical experiment design based on the Krotov formulation of optimal control theory. For practical reasons, the overall radio frequency power delivered to the sample should be minimized to facilitate experimental implementation and avoid excessive sample heating. The presented algorithm makes explicit use of this requirement and iteratively solves the stationary conditions making sure that the maximum of the objective is reached. It is shown that this method is faster per iteration and takes different paths within a control space than gradient-based methods. In the present work, the Krotov approach is demonstrated by the optimization of NMR and dynamic nuclear polarization experiments for various spin systems and using different constraints with respect to radio frequency and microwave power consumption.

  13. Neurochemical dynamics of acute orofacial pain in the human trigeminal brainstem nuclear complex.

    PubMed

    de Matos, Nuno M P; Hock, Andreas; Wyss, Michael; Ettlin, Dominik A; Brügger, Mike

    2017-09-04

    The trigeminal brainstem sensory nuclear complex is the first central relay structure mediating orofacial somatosensory and nociceptive perception. Animal studies suggest a substantial involvement of neurochemical alterations at such basal CNS levels in acute and chronic pain processing. Translating this animal based knowledge to humans is challenging. Human related examining of brainstem functions are challenged by MR related peculiarities as well as applicability aspects of experimentally standardized paradigms. Based on our experience with an MR compatible human orofacial pain model, the aims of the present study were twofold: 1) from a technical perspective, the evaluation of proton magnetic resonance spectroscopy at 3 T regarding measurement accuracy of neurochemical profiles in this small brainstem nuclear complex and 2) the examination of possible neurochemical alterations induced by an experimental orofacial pain model. Data from 13 healthy volunteers aged 19-46 years were analyzed and revealed high quality spectra with significant reductions in total N-acetylaspartate (N-acetylaspartate + N-acetylaspartylglutamate) (-3.7%, p = 0.009) and GABA (-10.88%, p = 0.041) during the pain condition. These results might reflect contributions of N-acetylaspartate and N-acetylaspartylglutamate in neuronal activity-dependent physiologic processes and/or excitatory neurotransmission, whereas changes in GABA might indicate towards a reduction in tonic GABAergic functioning during nociceptive signaling. Summarized, the present study indicates the applicability of (1)H-MRS to obtain neurochemical dynamics within the human trigeminal brainstem sensory nuclear complex. Further developments are needed to pave the way towards bridging important animal based knowledge with human research to understand the neurochemistry of orofacial nociception and pain. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Arabidopsis HFR1 is a potential nuclear substrate regulated by the Xanthomonas type III effector XopD(Xcc8004).

    PubMed

    Tan, Choon Meng; Li, Meng-Ying; Yang, Pei-Yun; Chang, Shu Heng; Ho, Yi-Ping; Lin, Hong; Deng, Wen-Ling; Yang, Jun-Yi

    2015-01-01

    XopDXcc8004, a type III effector of Xanthomonas campestris pv. campestris (Xcc) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopDXcc8004, in planta, a transgenic approach combined with inducible promoter to analyze the effects of XopDXcc8004 in Arabidopsis was done. Here, the expression of XopDXcc8004, in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopDXcc8004 transgenic plants. Moreover, XopDXcc8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopDXcc8004.

  15. Arabidopsis HFR1 Is a Potential Nuclear Substrate Regulated by the Xanthomonas Type III Effector XopDXcc8004

    PubMed Central

    Tan, Choon Meng; Li, Meng-Ying; Yang, Pei-Yun; Chang, Shu Heng; Ho, Yi-Ping; Lin, Hong; Deng, Wen-Ling; Yang, Jun-Yi

    2015-01-01

    XopDXcc8004, a type III effector of Xanthomonas campestris pv. campestris (Xcc) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopDXcc8004, in planta, a transgenic approach combined with inducible promoter to analyze the effects of XopDXcc8004 in Arabidopsis was done. Here, the expression of XopDXcc8004, in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopDXcc8004 transgenic plants. Moreover, XopDXcc8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopDXcc8004. PMID:25647296

  16. Fragmentation dynamics of meso-tetraphenyl iron (III) porphyrin chloride dication under energy control.

    PubMed

    Li, B; Allouche, A R; Bernard, J; Brédy, R; Qian, D B; Ma, X; Martin, S; Chen, L

    2017-03-28

    Meso-tetraphenyl iron (III) porphyrin chloride dications (FeTPPCl(2+))(*) were prepared in collisions with F(+) and H(+) at 3 keV. The dominant fragmentation channels were observed to involve the loss of the Cl atom and the successive loss of neutral phenyl groups for both collisional systems. The mass spectra in correlation with the deposited excitation energy distributions of the parent ions for the main fragmentation channels were measured by using the collision induced dissociation under energy control method. The global excitation energy distribution was found to be shifted to lower energies in collisions with H(+) compared to collisions with F(+) showing a noteworthy change of the excitation energy window using different projectile ions. Partial excitation energy distributions of the parent ions FeTPPCl(2+) were obtained for each fragmentation group. In a theoretical work, we have calculated the dissociation energies for the loss of one and two phenyl groups, including phenyl and (phenyl ± H). The energy barrier for the hydrogen atom transfer during the loss of (phenyl-H) has been also calculated. The measured energy difference for the successive loss of two phenyl groups was compared with the theoretical values.

  17. Fragmentation dynamics of meso-tetraphenyl iron (III) porphyrin chloride dication under energy control

    NASA Astrophysics Data System (ADS)

    Li, B.; Allouche, A. R.; Bernard, J.; Brédy, R.; Qian, D. B.; Ma, X.; Martin, S.; Chen, L.

    2017-03-01

    Meso-tetraphenyl iron (III) porphyrin chloride dications (FeTPPCl2+)* were prepared in collisions with F+ and H+ at 3 keV. The dominant fragmentation channels were observed to involve the loss of the Cl atom and the successive loss of neutral phenyl groups for both collisional systems. The mass spectra in correlation with the deposited excitation energy distributions of the parent ions for the main fragmentation channels were measured by using the collision induced dissociation under energy control method. The global excitation energy distribution was found to be shifted to lower energies in collisions with H+ compared to collisions with F+ showing a noteworthy change of the excitation energy window using different projectile ions. Partial excitation energy distributions of the parent ions FeTPPCl2+ were obtained for each fragmentation group. In a theoretical work, we have calculated the dissociation energies for the loss of one and two phenyl groups, including phenyl and (phenyl ± H). The energy barrier for the hydrogen atom transfer during the loss of (phenyl-H) has been also calculated. The measured energy difference for the successive loss of two phenyl groups was compared with the theoretical values.

  18. Ultrafast excited-state dynamics in vitamin B12 and related cob(III)alamins.

    PubMed

    Shiang, Joseph J; Cole, Allwyn G; Sension, Roseanne J; Hang, Kun; Weng, Yuxiang; Trommel, Jenna S; Marzilli, Luigi G; Lian, Tianquan

    2006-01-25

    Femtosecond transient IR and visible absorption spectroscopies have been employed to investigate the excited-state photophysics of vitamin B12 (cyanocobalamin, CNCbl) and the related cob(III)alamins, azidocobalamin (N3Cbl), and aquocobalamin (H2OCbl). Excitation of CNCbl, H2OCbl, or N3Cbl results in rapid formation of a short-lived excited state followed by ground-state recovery on time scales ranging from a few picoseconds to a few tens of picoseconds. The lifetime of the intermediate state is influenced by the sigma-donating ability of the axial ligand, decreasing in the order CNCbl > N3Cbl > H2OCbl, and by the polarity of the solvent, decreasing with increasing solvent polarity. The peak of the excited-state visible absorption spectrum is shifted to ca. 490 nm, and the shape of the spectrum is characteristic of weak axial ligands, similar to those observed for cob(II)alamin, base-off cobalamins, or cobinamides. Transient IR spectra of the upper CN and N3 ligands are red-shifted 20-30 cm(-1) from the ground-state frequencies, consistent with a weakened Co-upper ligand bond. These results suggest that the transient intermediate state can be attributed to a corrin ring pi to Co 3d(z2) ligand to metal charge transfer (LMCT) state. In this state bonds between the cobalt and the axial ligands are weakened and lengthened with respect to the corresponding ground states.

  19. H-1 Dynamic Nuclear Polarization in Supercritical Ethylene at 1.4 T

    SciTech Connect

    Wind, Robert A. ); Shi, Bai; Hu, Jian Zhi ); Solum, Mark S.; Ellis, Paul D. ); Grant, David M.; Pugmire, Ronald J.; Taylor, Craig M.; Yonker, Clement R. )

    2000-03-01

    H1 dynamic nuclear polarization (DNP) has been measured in supercritical ethylene in the pressure range 60-300 bar and in an external field of 1.4 T. A single-cell sapphire tube was used as a high pressure cell and powdered 1,3-bisdiphenylene-2-phenyl allyl(BDPA) free radicals were added and distributed at the wall of the cell. At all pressures the dominant DNP effect was a positive Overhauser enhancement, caused by proton-electron contact interactions at the fluid/solid radical interface. The observed enhancements varied from 12 at 67 bar to 17 at 300 bar. Besides the Overhauser enhancement, also a small solid state and thermal mixing enhancement were observed, indicating that part of the ethylene is absorbed at the radical surface for a prolonged time. These data indicate that DNP-enhanced NMR has the potential of extending the impact of NMR in research areas involving supercritical fluids.

  20. 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. Copyright © 2016 Elsevier Inc. All rights reserved.