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Sample records for open gln spin

  1. Open Rotor Spin Test

    NASA Video Gallery

    An open rotor, also known as a high-speed propeller, is tested in a wind tunnel. The propeller moves much more quickly than a standard propeller, and the blades of the propeller are shaped differen...

  2. Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity1[OPEN

    PubMed Central

    Pedersen, Carsten

    2016-01-01

    Cytosolic GS1 (Gln synthetase) is central for ammonium assimilation in plants. High ammonium treatment enhanced the expression of the GS1 isogene Gln-1;2 encoding a low-affinity high-capacity GS1 protein in Arabidopsis (Arabidopsis thaliana) shoots. Under the same conditions, the expression of the high-affinity low-capacity isoform Gln-1;1 was reduced. The expression of Gln-1;3 did not respond to ammonium treatment while Gln-1;4 and Gln-1;5 isogenes in all cases were expressed at a very low level. Gln-2 was highly expressed in shoots but only at a very low level in roots. To investigate the specific functions of the two isogenes Gln-1;1 and Gln-1;2 in shoots for ammonium detoxification, single and double knock-out mutants were grown under standard N supply or with high ammonium provision. Phenotypes of the single mutant gln1;1 were similar to the wild type, while growth of the gln1;2 single mutant and the gln1;1:gln1;2 double mutant was significantly impaired irrespective of N regime. GS1 activity was significantly reduced in both gln1;2 and gln1;1:gln1;2. Along with this, the ammonium content increased while that of Gln decreased, showing that Gln-1;2 was essential for ammonium assimilation and amino acid synthesis. We conclude that Gln-1;2 is the main isozyme contributing to shoot GS1 activity in vegetative growth stages and can be up-regulated to relieve ammonium toxicity. This reveals, to our knowledge, a novel shoot function of Gln-1;2 in Arabidopsis shoots. PMID:27231101

  3. Bogomolny-Prasad-Sommerfeld monopoles and open spin chains

    NASA Astrophysics Data System (ADS)

    Doikou, Anastasia; Ioannidou, Theodora

    2011-09-01

    We construct SU(n + 1) Bogomolny-Prasad-Sommerfeld (BPS) spherically symmetric monopoles with minimal symmetry breaking by solving the full Weyl equation. In this context, we explore and discuss the existence of open spin chainlike part within the Weyl equation. For instance, in the SU(3) case the relevant spin chain is the 2-site spin 1/2 XXX chain with open boundary conditions. We exploit the existence of such a spin chain part in order to solve the full Weyl equation.

  4. The perils of spinning class: an open ankle fracture following a spinning exercise session.

    PubMed

    Butler, Daniel P; Henry, Francis P; Ghali, Shadi

    2013-12-01

    Spinning is an increasingly popular form of cycle-based exercise. The workouts are often of high-intensity and participants are intermittently encouraged to achieve a high crank-set-cadence rate. We report a unique case of an open ankle fracture requiring free flap coverage, which highlights the potential perils of spinning class. PMID:23773931

  5. Higher spins and open strings: Quartic interactions

    SciTech Connect

    Polyakov, Dimitri

    2011-02-15

    We analyze quartic gauge-invariant interactions of massless higher spin fields by using vertex operators constructed in our previous works and computing their 4-point amplitudes in superstring theory. The kinematic part of the quartic interactions of the higher spins is determined by the matter structure of their vertex operators; the nonlocality of the interactions is the consequence of the specific ghost structure of these operators. We compute explicitly the 4-point amplitude describing the complete gauge-invariant 1-1-3-3 quartic interaction (two massless spin 3 particles interacting with two photons) and comment on more general 1-1-s-s cases, particularly pointing out the structure of 1-1-5-5 coupling.

  6. Q-operators for the open Heisenberg spin chain

    NASA Astrophysics Data System (ADS)

    Frassek, Rouven; Szécsényi, István M.

    2015-12-01

    We construct Q-operators for the open spin-1/2 XXX Heisenberg spin chain with diagonal boundary matrices. The Q-operators are defined as traces over an infinite-dimensional auxiliary space involving novel types of reflection operators derived from the boundary Yang-Baxter equation. We argue that the Q-operators defined in this way are polynomials in the spectral parameter and show that they commute with transfer matrix. Finally, we prove that the Q-operators satisfy Baxter's TQ-equation and derive the explicit form of their eigenvalues in terms of the Bethe roots.

  7. PULSAR BINARY BIRTHRATES WITH SPIN-OPENING ANGLE CORRELATIONS

    SciTech Connect

    O'Shaughnessy, Richard; Kim, Chunglee E-mail: ckim@astro.lu.s

    2010-05-20

    One ingredient in an empirical birthrate estimate for pulsar binaries is the fraction of sky subtended by the pulsar beam: the pulsar beaming fraction. This fraction depends on both the pulsar's opening angle and the misalignment angle between its spin and magnetic axes. The current estimates for pulsar binary birthrates are based on an average value of beaming fractions for only two pulsars, i.e., PSRs B1913+16 and B1534+12. In this paper, we revisit the observed pulsar binaries to examine the sensitivity of birthrate predictions to different assumptions regarding opening angle and alignment. Based on empirical estimates for the relative likelihood of different beam half-opening angles and misalignment angles between the pulsar rotation and magnetic axes, we calculate an effective beaming correction factor, f{sub b,eff}, whose reciprocal is equivalent to the average fraction of all randomly selected pulsars that point toward us. For those pulsars without any direct beam geometry constraints, we find that f{sub b,eff} is likely to be smaller than 6, a canonically adopted value when calculating birthrates of Galactic pulsar binaries. We calculate f{sub b,eff} for PSRs J0737-3039A and J1141-6545, applying the currently available constraints for their beam geometry. As in previous estimates of the posterior probability density function P(R) for pulsar binary birthrates R, PSRs J0737-3039A and J1141-6545 still significantly contribute to, if not dominate, the Galactic birthrate of tight pulsar-neutron star (NS) and pulsar-white dwarf (WD) binaries, respectively. Our median posterior present-day birthrate predictions for tight PSR-NS binaries, wide PSR-NS binaries, and tight PSR-WD binaries given a preferred pulsar population model and beaming geometry are 89 Myr{sup -1}, 0.5 Myr{sup -1}, and 34 Myr{sup -1}, respectively. For long-lived PSR-NS binaries, these estimates include a weak (x1.6) correction for slowly decaying star formation in the galactic disk. For pulsars

  8. Spin polarized bound states in the continuum in open Aharonov-Bohm rings with the Rashba spin-orbit interaction.

    PubMed

    Bulgakov, Evgeny N; Sadreev, Almas F

    2016-07-01

    We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov-Bohm rings in the presence of the Rashba spin-orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase. PMID:27165662

  9. Spin density and orbital optimization in open shell systems: A rational and computationally efficient proposal

    NASA Astrophysics Data System (ADS)

    Giner, Emmanuel; Angeli, Celestino

    2016-03-01

    The present work describes a new method to compute accurate spin densities for open shell systems. The proposed approach follows two steps: first, it provides molecular orbitals which correctly take into account the spin delocalization; second, a proper CI treatment allows to account for the spin polarization effect while keeping a restricted formalism and avoiding spin contamination. The main idea of the optimization procedure is based on the orbital relaxation of the various charge transfer determinants responsible for the spin delocalization. The algorithm is tested and compared to other existing methods on a series of organic and inorganic open shell systems. The results reported here show that the new approach (almost black-box) provides accurate spin densities at a reasonable computational cost making it suitable for a systematic study of open shell systems.

  10. The GlnR Regulon in Streptococcus mutans Is Differentially Regulated by GlnR and PmrA.

    PubMed

    Chen, Yi-Ywan M; Chen, Yueh-Ying; Hung, Jui-Lung; Chen, Pei-Min; Chia, Jean-San

    2016-01-01

    GlnR-mediated repression of the GlnR regulon at acidic pH is required for optimal acid tolerance in Streptococcus mutans, the etiologic agent for dental caries. Unlike most streptococci, the GlnR regulon is also regulated by newly identified PmrA (SMUGS5_RS05810) at the transcriptional level in S. mutans GS5. Results from gel mobility shift assays confirmed that both GlnR and PmrA recognized the putative GlnR box in the promoter regions of the GlnR regulon genes. By using a chemostat culture system, we found that PmrA activated the expression of the GlnR regulon at pH 7, and that this activation was enhanced by excess glucose. Deletion of pmrA (strain ΔPmrA) reduced the survival rate of S. mutans GS5 at pH 3 moderately, whereas the GlnR mutant (strain ΔGlnR) exhibited an acid-sensitive phenotype in the acid killing experiments. Elevated biofilm formation in both ΔGlnR and ΔPmrA mutant strains is likely a result of indirect regulation of the GlnR regulon since GlnR and PmrA regulate the regulon differently. Taken together, it is suggested that activation of the GlnR regulon by PmrA at pH 7 ensures adequate biosynthesis of amino acid precursor, whereas repression by GlnR at acidic pH allows greater ATP generation for acid tolerance. The tight regulation of the GlnR regulon in response to pH provides an advantage for S. mutans to better survive in its primary niche, the oral cavity. PMID:27454482

  11. The GlnR Regulon in Streptococcus mutans Is Differentially Regulated by GlnR and PmrA

    PubMed Central

    Chen, Yi-Ywan M.; Chen, Yueh-Ying; Hung, Jui-Lung; Chen, Pei-Min; Chia, Jean-San

    2016-01-01

    GlnR-mediated repression of the GlnR regulon at acidic pH is required for optimal acid tolerance in Streptococcus mutans, the etiologic agent for dental caries. Unlike most streptococci, the GlnR regulon is also regulated by newly identified PmrA (SMUGS5_RS05810) at the transcriptional level in S. mutans GS5. Results from gel mobility shift assays confirmed that both GlnR and PmrA recognized the putative GlnR box in the promoter regions of the GlnR regulon genes. By using a chemostat culture system, we found that PmrA activated the expression of the GlnR regulon at pH 7, and that this activation was enhanced by excess glucose. Deletion of pmrA (strain ΔPmrA) reduced the survival rate of S. mutans GS5 at pH 3 moderately, whereas the GlnR mutant (strain ΔGlnR) exhibited an acid-sensitive phenotype in the acid killing experiments. Elevated biofilm formation in both ΔGlnR and ΔPmrA mutant strains is likely a result of indirect regulation of the GlnR regulon since GlnR and PmrA regulate the regulon differently. Taken together, it is suggested that activation of the GlnR regulon by PmrA at pH 7 ensures adequate biosynthesis of amino acid precursor, whereas repression by GlnR at acidic pH allows greater ATP generation for acid tolerance. The tight regulation of the GlnR regulon in response to pH provides an advantage for S. mutans to better survive in its primary niche, the oral cavity. PMID:27454482

  12. Open quantum billiard in a magnetic field: A perfect spin filter

    SciTech Connect

    Isupova, G. G. Malyshev, A. I.

    2015-10-15

    The transport properties of an open system, a circular billiard with attached channels, are studied in the presence of Rashba spin-orbit coupling. The inclusion of even a weak magnetic field in the structure plane is shown to cause the conductance to become dependent on the spin state of charge carriers. By choosing the system’s parameters, this property allows a spin filter based on it to be realized.

  13. Transcriptome Analysis of the Role of GlnD/GlnBK in Nitrogen Stress Adaptation by Sinorhizobium meliloti Rm1021

    PubMed Central

    Yurgel, Svetlana N.; Rice, Jennifer; Kahn, Michael L.

    2013-01-01

    Transcriptional changes in the nitrogen stress response (NSR) of wild type S. meliloti Rm1021, and isogenic strains missing both PII proteins, GlnB and GlnK, or carrying a ΔglnD-sm2 mutation were analyzed using whole-genome microarrays. This approach allowed us to identify a number of new genes involved in the NSR and showed that the response of these bacteria to nitrogen stress overlaps with other stress responses, including induction of the fixK2 transcriptional activator and genes that are part of the phosphate stress response. Our data also show that GlnD and GlnBK proteins may regulate many genes that are not part of the NSR. Analysis of transcriptome profiles of the Rm1021 ΔglnD-sm2 strain allowed us to identify several genes that appear to be regulated by GlnD without the participation of the PII proteins. PMID:23516427

  14. The open XXZ spin chain model and the topological basis realization

    NASA Astrophysics Data System (ADS)

    Wang, Qingyong; Du, Yangyang; Wu, Chunfeng; Wang, Gangcheng; Sun, Chunfang; Xue, Kang

    2016-07-01

    In this paper, it is shown that the Hamiltonian of the open spin-1 XXZ chain model can be constructed from the generators of the Birman-Murakami-Wenzl (B-M-W) algebra. Without the topological parameter d (describing the unknotted loop ◯ in topology) reducing to a fixed value, the topological basis states can be connected with the open XXZ spin chain. Then some particular properties of the topological basis states in this system have been investigated. We find that the topological basis states are the three eigenstates of a four-spin-1 XXZ chain model without boundary term. Specifically, all the spin single states of the system fall on the topological basis subspace. And the number of the spin single states of the system is equal to that of the topological basis states.

  15. Expression of glnB and a glnB-Like Gene (glnK) in a Ribulose Bisphosphate Carboxylase/Oxygenase-Deficient Mutant of Rhodobacter sphaeroides

    PubMed Central

    Qian, Yilei; Tabita, F. Robert

    1998-01-01

    In a ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO)-deficient mutant of Rhodobacter sphaeroides, strain 16PHC, nitrogenase activity was derepressed in the presence of ammonia under photoheterotrophic growth conditions. Previous studies also showed that reintroduction of a functional RubisCO and Calvin-Benson-Bassham (CBB) pathway suppressed the deregulation of nitrogenase synthesis in this strain. In this study, the derepression of nitrogenase synthesis in the presence of ammonia in strain 16PHC was further explored by using a glnB::lacZ fusion, since the product of the glnB gene is known to have a negative effect on ammonia-regulated nif control. It was found that glnB expression was repressed in strain 16PHC under photoheterotrophic growth conditions with either ammonia or glutamate as the nitrogen source; glutamine synthetase (GS) levels were also affected in this strain. However, when cells regained a functional CBB pathway by trans complementation of the deleted genes, wild-type levels of GS and glnB expression were restored. Furthermore, a glnB-like gene, glnK, was isolated from this organism, and its expression was found to be under tight nitrogen control in the wild type. Surprisingly, glnK expression was found to be derepressed in strain 16PHC under photoheterotrophic conditions in the presence of ammonia. PMID:9721307

  16. OpenACC programs of the Swendsen-Wang multi-cluster spin flip algorithm

    NASA Astrophysics Data System (ADS)

    Komura, Yukihiro

    2015-12-01

    We present sample OpenACC programs of the Swendsen-Wang multi-cluster spin flip algorithm. OpenACC is a directive-based programming model for accelerators without requiring modification to the underlying CPU code itself. In this paper, we deal with the classical spin models as with the sample CUDA programs (Komura and Okabe, 2014), that is, two-dimensional (2D) Ising model, three-dimensional (3D) Ising model, 2D Potts model, 3D Potts model, 2D XY model and 3D XY model. We explain the details of sample OpenACC programs and compare the performance of the present OpenACC implementations with that of the CUDA implementations for the 2D and 3D Ising models and the 2D and 3D XY models.

  17. Quasilocal conservation laws in XXZ spin-1/2 chains: Open, periodic and twisted boundary conditions

    NASA Astrophysics Data System (ADS)

    Prosen, Tomaž

    2014-09-01

    A continuous family of quasilocal exact conservation laws is constructed in the anisotropic Heisenberg (XXZ) spin-1/2 chain for periodic (or twisted) boundary conditions and for a set of commensurate anisotropies densely covering the entire easy plane interaction regime. All local conserved operators follow from the standard (Hermitian) transfer operator in fundamental representation (with auxiliary spin s=1/2), and are all even with respect to a spin flip operation. However, the quasilocal family is generated by differentiation of a non-Hermitian highest weight transfer operator with respect to a complex auxiliary spin representation parameter s and includes also operators of odd parity. For a finite chain with open boundaries the time derivatives of quasilocal operators are not strictly vanishing but result in operators localized near the boundaries of the chain. We show that a simple modification of the non-Hermitian transfer operator results in exactly conserved, but still quasilocal operators for periodic or generally twisted boundary conditions. As an application, we demonstrate that implementing the new exactly conserved operator family for estimating the high-temperature spin Drude weight results, in the thermodynamic limit, in exactly the same lower bound as for almost conserved family and open boundaries. Under the assumption that the bound is saturating (suggested by agreement with previous thermodynamic Bethe ansatz calculations) we propose a simple explicit construction of infinite time averages of local operators such as the spin current.

  18. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    PubMed Central

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  19. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-05-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins.

  20. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl.

    PubMed

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp(3)-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp(3)-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  1. Graphene-diamond interface: Gap opening and electronic spin injection

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Guo, Meng; Huang, Baibiao

    2012-06-01

    Creating a finite band gap, injecting electronic spin, and finding a suitable substrate are the three important challenges for building graphene-based devices. Here, first-principles calculations are performed to investigate the electronic and magnetic properties of graphene adsorbed on the (111) surface of diamond, which is synthesized experimentally [Nature10.1038/nature09979 472, 74 (2011); J. Appl. Phys.10.1063/1.3627370 110, 044324 (2011); Nano Lett.10.1021/nl204545q 12, 1603 (2012); ACS Nano10.1021/nn204362p 6, 1018 (2012)]. Our results reveal that the graphene adsorbed on the diamond surface is a semiconductor with a finite gap depending on the adsorption arrangements due to the variation of on-site energy induced by the diamond surface, with the extra advantage of maintaining main characters of the linear band dispersion of graphene. More interestingly, different from typical graphene/semiconductor hybrid systems, we find that electronic spin can arise ``intrinsically'' in graphene owing to the exchange proximity interaction between electrons in graphene and localized electrons in the diamond surface rather than the characteristic graphene states. These predications strongly revive this new synthesized system as a viable candidate to overcome all the aforementioned challenges, providing an ideal platform for future graphene-based electronics.

  2. Spin vectors of asteroids: Updated statistical properties and open problems

    NASA Astrophysics Data System (ADS)

    Paolicchi, Paolo; Kryszczyńska, Agnieszka

    2012-12-01

    Only in a limited number of cases the observations supply complete information on the spin vectors of asteroids. A complex analysis is required to compute the orientation (latitude and longitude) of poles, and often multiple solutions and strong discrepancies among the outcomes of different methods are present. The spin vector catalog, maintained at Poznan observatory, lists the available (presently less than 200, and not always unambiguous) pole data. The statistical analysis of the data, published in 2007, is now becoming obsolete, due to a significant growth of the database. In the present paper we update the analysis, confirming several features already highlighted by the previous paper, and finding some new results. In particular, the excess of prograde vs. retrograde Main Belt asteroids is now significant for all cataloged bodies smaller than 100 km. The rarity of poles close to the ecliptic plane, resulting from the previous analysis, but recently questioned, is confirmed, with a fundamental contribution of bodies smaller than 40 km. Only after a future - both qualitative and quantitative - improvement of the database, such as that expected to come out from forthcoming space missions, such as GAIA, we will be able to obtain a statistically robust scenario, hopefully free from possible relevant selection effects.

  3. Self-similar spectral structures and edge-locking hierarchy in open-boundary spin chains

    SciTech Connect

    Haque, Masudul

    2010-07-15

    For an anisotropic Heisenberg (XXZ) spin chain, we show that an open boundary induces a series of approximately self-similar features at different energy scales, high up in the eigenvalue spectrum. We present a nonequilibrium phenomenon related to this fractal structure, involving states in which a connected block near the edge is polarized oppositely to the rest of the chain. We show that such oppositely polarized blocks can be 'locked' to the edge of the spin chain and that there is a hierarchy of edge-locking effects at various orders of the anisotropy. The phenomenon enables dramatic control of quantum-state transmission and magnetization control.

  4. Spin-polarized electron current from carbon-doped open armchair boron nitride nanotubes: Implication for nano-spintronic devices

    NASA Astrophysics Data System (ADS)

    Zhou, Gang; Duan, Wenhui

    2007-03-01

    Spin-polarized density functional calculations show that the substitutional doping of carbon (C) atom at the mouth changes the atomic and spin configurations of open armchair boron nitride nanotubes (BNNTs). The occupied/unoccupied deep gap states are observed with the significant spin-splitting. The structures and spin-polarized properties are basically stable under the considerable electric field, which is important for practical applications. The magnetization mechanism is attributed to the interactions of s, p states between the C and its neighboring B or N atoms. Ultimately, advantageous geometrical and electronic effects mean that C-doped open armchair BNNTs would have promising applications in nano-spintronic devices.

  5. Generalized Coordinate Bethe Ansatz for open spin chains with non-diagonal boundaries

    NASA Astrophysics Data System (ADS)

    Ragoucy, E.

    2012-02-01

    We introduce a generalization of the original Coordinate Bethe Ansatz that allows to treat the case of open spin chains with non-diagonal boundary matrices. We illustrate it on two cases: the XXX and XXZ chains. Short review on a joint work with N. Crampe (L2C) and D. Simon (LPMA), see arXiv:1009.4119, arXiv:1105.4119 and arXiv:1106.3264.

  6. Recurrence relations of higher spin BPST vertex operators for open strings

    NASA Astrophysics Data System (ADS)

    Fu, Chih-Hao; Lee, Jen-Chi; Tan, Chung-I.; Yang, Yi

    2013-08-01

    We calculate higher-spin Brower-Polchinski-Strassler-Tan (BPST) vertex operators for an open bosonic string and express these operators in terms of a Kummer function of the second kind. We derive an infinite number of recurrence relations among BPST vertex operators of different string states. These recurrence relations among BPST vertex operators lead to the recurrence relations among Regge string scattering amplitudes discovered recently.

  7. Torque Enhancement, Spin Equilibrium, and Jet Power from Disk-Induced Opening of Pulsar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Parfrey, Kyle; Spitkovsky, Anatoly; Beloborodov, Andrei M.

    2016-05-01

    The interaction of a rotating star’s magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk–magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-detection of frequency increases during outbursts of SAX J1808.4-3658 and XTE J1814-338, and may be generally responsible for preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated by the surrounding environment, the resulting jet can satisfy the power requirements of the highly relativistic outflows from Cir X-1 and Sco X-1. In this framework, the jet power scales relatively weakly with accretion rate, {L}{{j}}\\propto {\\dot{M}}4/7, and would be suppressed at high accretion rates only if the stellar magnetic moment is sufficiently low.

  8. Structures of Arg- and Gln-type bacterial cysteine dioxygenase homologs: Arg- and Gln-type Bacterial CDO Homologs

    DOE PAGESBeta

    Driggers, Camden M.; Hartman, Steven J.; Karplus, P. Andrew

    2015-01-01

    In some bacteria, cysteine is converted to cysteine sulfinic acid by cysteine dioxygenases (CDO) that are only ~15–30% identical in sequence to mammalian CDOs. Among bacterial proteins having this range of sequence similarity to mammalian CDO are some that conserve an active site Arg residue (“Arg-type” enzymes) and some having a Gln substituted for this Arg (“Gln-type” enzymes). Here, we describe a structure from each of these enzyme types by analyzing structures originally solved by structural genomics groups but not published: a Bacillus subtilis “Arg-type” enzyme that has cysteine dioxygenase activity (BsCDO), and a Ralstonia eutropha “Gln-type” CDO homolog ofmore » uncharacterized activity (ReCDOhom). The BsCDO active site is well conserved with mammalian CDO, and a cysteine complex captured in the active site confirms that the cysteine binding mode is also similar. The ReCDOhom structure reveals a new active site Arg residue that is hydrogen bonding to an iron-bound diatomic molecule we have interpreted as dioxygen. Notably, the Arg position is not compatible with the mode of Cys binding seen in both rat CDO and BsCDO. As sequence alignments show that this newly discovered active site Arg is well conserved among “Gln-type” CDO enzymes, we conclude that the “Gln-type” CDO homologs are not authentic CDOs but will have substrate specificity more similar to 3-mercaptopropionate dioxygenases.« less

  9. Structures of Arg- and Gln-type bacterial cysteine dioxygenase homologs: Arg- and Gln-type Bacterial CDO Homologs

    SciTech Connect

    Driggers, Camden M.; Hartman, Steven J.; Karplus, P. Andrew

    2015-01-01

    In some bacteria, cysteine is converted to cysteine sulfinic acid by cysteine dioxygenases (CDO) that are only ~15–30% identical in sequence to mammalian CDOs. Among bacterial proteins having this range of sequence similarity to mammalian CDO are some that conserve an active site Arg residue (“Arg-type” enzymes) and some having a Gln substituted for this Arg (“Gln-type” enzymes). Here, we describe a structure from each of these enzyme types by analyzing structures originally solved by structural genomics groups but not published: a Bacillus subtilis “Arg-type” enzyme that has cysteine dioxygenase activity (BsCDO), and a Ralstonia eutropha “Gln-type” CDO homolog of uncharacterized activity (ReCDOhom). The BsCDO active site is well conserved with mammalian CDO, and a cysteine complex captured in the active site confirms that the cysteine binding mode is also similar. The ReCDOhom structure reveals a new active site Arg residue that is hydrogen bonding to an iron-bound diatomic molecule we have interpreted as dioxygen. Notably, the Arg position is not compatible with the mode of Cys binding seen in both rat CDO and BsCDO. As sequence alignments show that this newly discovered active site Arg is well conserved among “Gln-type” CDO enzymes, we conclude that the “Gln-type” CDO homologs are not authentic CDOs but will have substrate specificity more similar to 3-mercaptopropionate dioxygenases.

  10. Development of New Open-Shell Perturbation and Coupled-Cluster Theories Based on Symmetric Spin Orbitals

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Arnold, James O. (Technical Monitor)

    1994-01-01

    A new spin orbital basis is employed in the development of efficient open-shell coupled-cluster and perturbation theories that are based on a restricted Hartree-Fock (RHF) reference function. The spin orbital basis differs from the standard one in the spin functions that are associated with the singly occupied spatial orbital. The occupied orbital (in the spin orbital basis) is assigned the delta(+) = 1/square root of 2(alpha+Beta) spin function while the unoccupied orbital is assigned the delta(-) = 1/square root of 2(alpha-Beta) spin function. The doubly occupied and unoccupied orbitals (in the reference function) are assigned the standard alpha and Beta spin functions. The coupled-cluster and perturbation theory wave functions based on this set of "symmetric spin orbitals" exhibit much more symmetry than those based on the standard spin orbital basis. This, together with interacting space arguments, leads to a dramatic reduction in the computational cost for both coupled-cluster and perturbation theory. Additionally, perturbation theory based on "symmetric spin orbitals" obeys Brillouin's theorem provided that spin and spatial excitations are both considered. Other properties of the coupled-cluster and perturbation theory wave functions and models will be discussed.

  11. Mutational analysis of GlnB residues critical for NifA activation in Azospirillum brasilense.

    PubMed

    Inaba, Juliana; Thornton, Jeremy; Huergo, Luciano Fernandes; Monteiro, Rose Adele; Klassen, Giseli; Pedrosa, Fábio de Oliveira; Merrick, Mike; de Souza, Emanuel Maltempi

    2015-02-01

    PII proteins are signal transduction that sense cellular nitrogen status and relay this signals to other targets. Azospirillum brasilense is a nitrogen fixing bacterium, which associates with grasses and cereals promoting beneficial effects on plant growth and crop yields. A. brasilense contains two PII encoding genes, named glnB and glnZ. In this paper, glnB was mutagenised in order to identify amino acid residues involved in GlnB signaling. Two variants were obtained by random mutagenesis, GlnBL13P and GlnBV100A and a site directed mutant, GlnBY51F, was obtained. Their ability to complement nitrogenase activity of glnB mutant strains of A. brasilense were determined. The variant proteins were also overexpressed in Escherichia coli, purified and characterized biochemically. None of the GlnB variant forms was able to restore nitrogenase activity in glnB mutant strains of A. brasilense LFH3 and 7628. The purified GlnBY51F and GlnBL13P proteins could not be uridylylated by GlnD, whereas GlnBV100A was uridylylated but at only 20% of the rate for wild type GlnB. Biochemical and computational analyses suggest that residue Leu13, located in the α helix 1 of GlnB, is important to maintain GlnB trimeric structure and function. The substitution V100A led to a lower affinity for ATP binding. Together the results suggest that NifA activation requires uridylylated GlnB bound to ATP. PMID:25644954

  12. An open-shell restricted Hartree-Fock perturbation theory based on symmetric spin orbitals

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Jayatilaka, Dylan

    1993-01-01

    A new open-shell perturbation theory is formulated in terms of symmetric spin orbitals. Only one set of spatial orbitals is required, thereby reducing the number of independent coefficients in the perturbed wavefunctions. For second order, the computational cost is shown to be similar to a closed-shell calculation. This formalism is therefore more efficient than the recently developed RMP, ROMP or RMP-MBPT theories. The perturbation theory described herein was designed to have a close correspondence with our recently proposed coupled-cluster theory based on symmetric spin orbitals. The first-order wavefunction contains contributions from only doubly excited determinants. Equilibrium structures and vibrational frequencies determined from second-order perturbation theory are presented for OH, NH, CH, 02, NH2 and CH2.

  13. Trigluon correlations and single transverse spin asymmetry in open charm production

    SciTech Connect

    Kang Zhongbo; Qiu Jianwei

    2009-08-04

    We study the single transverse-spin asymmetry for open charm production in the semiinclusive lepton-hadron deep inelastic scattering (SIDIS) and pp collision. Within collinear factorization approach, we find that the asymmetry is sensitive to the twist-3 trigluon correlation functions in the proton. With a simple model for the trigluon correlation functions, we estimate the asymmetry in SIDIS for both COMPASS and eRHIC kinematics, as well as in pp collision at RHIC energy. We discuss the possibilities of extracting the trigluon correlation functions in these experiments.

  14. Characterization of Azorhizobium caulinodans glnB and glnA genes: involvement of the P(II) protein in symbiotic nitrogen fixation.

    PubMed Central

    Michel-Reydellet, N; Desnoues, N; Elmerich, C; Kaminski, P A

    1997-01-01

    The nucleotide sequence and transcriptional organization of Azorhizobium caulinodans ORS571 glnA, the structural gene for glutamine synthetase (GS), and glnB, the structural gene for the P(II) protein, have been determined. glnB and glnA are organized as a single operon transcribed from the same start site, under conditions of both nitrogen limitation and nitrogen excess. This start site may be used by two different promoters since the expression of a glnB-lacZ fusion was high in the presence of ammonia and enhanced under conditions of nitrogen limitation in the wild-type strain. The increase was not observed in rpoN or ntrC mutants. In addition, this fusion was overexpressed under both growth conditions, in the glnB mutant strain, suggesting that P(II) negatively regulates its own expression. A DNA motif, similar to a sigma54-dependent promoter consensus, was found in the 5' nontranscribed region. Thus, the glnBA operon seems to be transcribed from a sigma54-dependent promoter that operates under conditions of nitrogen limitation and from another uncharacterized promoter in the presence of ammonia. Both glnB and glnBA mutant strains derepress their nitrogenase in the free-living state, but only the glnBA mutant, auxotrophic for glutamine, does not utilize molecular nitrogen for growth. The level of GS adenylylation is not affected in the glnB mutant as compared to that in the wild type. Under symbiotic conditions, the glnB and glnBA mutant strains induced Fix- nodules on Sesbania rostrata roots. P(II) is the first example in A. caulinodans of a protein required for symbiotic nitrogen fixation but dispensable in bacteria growing in the free-living state. PMID:9171403

  15. Communication: Spin densities within a unitary group based spin-adapted open-shell coupled-cluster theory: Analytic evaluation of isotropic hyperfine-coupling constants for the combinatoric open-shell coupled-cluster scheme

    SciTech Connect

    Datta, Dipayan Gauss, Jürgen

    2015-07-07

    We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and M{sub S} = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH{sub 2}CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.

  16. Glutamine synthetase-constitutive mutation affecting the glnALG upstream promoter of Escherichia coli.

    PubMed Central

    León, P; Romero, D; Garciarrubio, A; Bastarrachea, F; Covarrubias, A A

    1985-01-01

    The spontaneous gln-76 mutation of Escherichia coli (Osorio et al., Mol. Gen. Genet. 194:114-123, 1984) was previously shown to be responsible for the cis-dominant constitutive expression of the glnA gene in the absence of a glnG-glnF activator system. Nucleotide sequence analysis has now revealed that gln-76 is a single transversion T.A to A.T, an up-promoter mutation affecting the -10 region of glnAp1, the upstream promoter of the glnALG control region. Both, wild-type and gln-76 DNA control regions were cloned into the promoter-probe plasmid pKO1. Galactokinase activity determinations of cells carrying the fused plasmids showed 10-fold more effective expression mediated by gln-76 than by the glnA wild-type control region. Primer extension experiments with RNA from strains carrying the gln-76 control region indicated that the transcription initiation sites were the same in both the gln-76 mutant and the wild type. Images PMID:2866175

  17. An inhomogeneous T-Q equation for the open XXX chain with general boundary terms: completeness and arbitrary spin

    NASA Astrophysics Data System (ADS)

    Nepomechie, Rafael I.

    2013-11-01

    An inhomogeneous T-Q equation has recently been proposed by Cao, Yang, Shi and Wang for the open spin-1/2 XXX chain with general (nondiagonal) boundary terms. We argue that a simplified version of this equation describes all the eigenvalues of the transfer matrix of this model. We also propose a generating function for the inhomogeneous T-Q equations of arbitrary spin.

  18. Spin-orbit-path hybrid Greenberger-Horne-Zeilinger entanglement and open-destination teleportation with multiple degrees of freedom

    SciTech Connect

    Chen Lixiang; She Weilong

    2011-03-15

    We propose a scheme to generate hybrid Greenberger-Horne-Zeilinger (GHZ) entanglement where multiple photons are entangled in different degrees of freedom of spin, orbital angular momentum (OAM), and path (linear momentum). The generation involves mapping the preliminary OAM entanglement of photon pairs onto their spin-orbit and spin-path degrees of freedom, respectively. Based on the hybrid GHZ entanglement, we demonstrate an open-destination teleportation with multiples degrees of freedom, via which a spin state of a single photon is teleported onto a superposition of multiple photons with the postselection technique and the original information could be read out at any photon in individual spin, OAM, or the linear-momentum state. Our scheme holds promise for asymmetric optical quantum network.

  19. Clostridium difficile toxin A induces intestinal epithelial cell apoptosis and damage: role of Gln and Ala-Gln in toxin A effects.

    PubMed

    Brito, Gerly A C; Carneiro-Filho, Benedito; Oriá, Reinaldo B; Destura, Raul V; Lima, Aldo A M; Guerrant, Richard L

    2005-07-01

    The aim of this study was to investigate the effect of Clostridium difficile toxin A (TxA) on intestinal epithelial cell migration, apoptosis, and transepithelial resistance and to evaluate the effect of glutamine (Gln) and its stable derivative, alanyl-glutamine (Ala-Gln), on TxA-induced damage. Migration was measured in rat intestinal epithelial cells (IEC-6) 6 and 24 hr after a razor scrape of the cell monolayer. Cell proliferation was indirectly measured utilizing the tetrazolium salt WST-1. The cells were incubated with TxA (1-100 ng/ml) in medium without Gln or medium containing Gln or Ala-Gln (1-30 mM). Apoptosis was quantified in IEC-6 cells using annexin V assay. Transepithelial resistance was measured using an epithelial voltohmmeter across T84 cells seeded on a transwell filter. TxA-induced a dose-dependent reduction of migration and also caused dose and time-dependent apoptosis in IEC-6 cells. Gln and Aln-Gln significantly enhanced IEC-6 cell migration and proliferation. Gln and Ala-Gln also prevented the inhibition of migration, apoptosis, and the initial drop in transepithelial resistance induced by TxA. In conclusion, both peptides reduced toxin-induced epithelial damage and thus might play an adjunctive role in C. difficile-induced colitis therapy. PMID:16047471

  20. A domain in the transcription activator Gln3 specifically required for rapamycin responsiveness.

    PubMed

    Rai, Rajendra; Tate, Jennifer J; Shanmuganatham, Karthik; Howe, Martha M; Cooper, Terrance G

    2014-07-01

    Nitrogen-responsive control of Gln3 localization is implemented through TorC1-dependent (rapamycin-responsive) and TorC1-independent (nitrogen catabolite repression-sensitive and methionine sulfoximine (Msx)-responsive) regulatory pathways. We previously demonstrated amino acid substitutions in a putative Gln3 α-helix(656-666), which are required for a two-hybrid Gln3-Tor1 interaction, also abolished rapamycin responsiveness of Gln3 localization and partially abrogated cytoplasmic Gln3 sequestration in cells cultured under nitrogen-repressive conditions. Here, we demonstrate these three characteristics are not inextricably linked together. A second distinct Gln3 region (Gln3(510-589)) is specifically required for rapamycin responsiveness of Gln3 localization, but not for cytoplasmic Gln3 sequestration under repressive growth conditions or relocation to the nucleus following Msx addition. Aspartate or alanine substitution mutations throughout this region uniformly abolish rapamycin responsiveness. Contained within this region is a sequence with a predicted propensity to form an α-helix(583-591), one side of which consists of three hydrophobic amino acids flanked by serine residues. Substitution of aspartate for even one of these serines abolishes rapamycin responsiveness and increases rapamycin resistance without affecting either of the other two Gln3 localization responses. In contrast, alanine substitutions decrease rapamycin resistance. Together, these data suggest that targets in the C-terminal portion of Gln3 required for the Gln3-Tor1 interaction, cytoplasmic Gln3 sequestration, and Gln3 responsiveness to Msx addition and growth in poor nitrogen sources are distinct from those needed for rapamycin responsiveness. PMID:24847055

  1. Role of open boundary conditions on the hysteretic behaviour of one-dimensional spin crossover nanoparticles

    SciTech Connect

    Chiruta, Daniel; Linares, Jorge E-mail: miya@spin.phys.s.u-tokyo.ac.jp; Boukheddaden, Kamel; Miyashita, Seiji E-mail: miya@spin.phys.s.u-tokyo.ac.jp

    2014-05-21

    In order to explain clearly the role of the open boundary conditions (OBCs) on phase transition in one dimensional system, we consider an Ising model with both short-range (J) and long-range (G) interactions, which has allowed us to study the cooperative nature of spin-crossover (SCO) materials at the nanometer scale. At this end, we developed a transfer-matrix method for one-dimensional (1D) SCO system with free boundary conditions, and we give numerical evidences for how the thermal spin transition curves vary as a function of the physical parameters (J, G) or an applied pressure. Moreover for OBCs case, we have derived the bulk, surface and finite-size contributions to the free energy and we have investigated the variation of these energies as function of J and system size. We have found that the surface free energy behaves like J〈σ〉{sup 2}, where 〈σ〉 is the average magnetization per site. Since the properties of the nanometric scale are dramatically influenced by the system's size (N), our analytical outcomes for the size dependence represent a step to achieve new characteristic of the future devices and also a way to find various novel properties which are absent in the bulk materials.

  2. Modeling structural transitions from the periplasmic-open state of lactose permease and interpretations of spin label experiments.

    PubMed

    Zhuang, Xiaohong; Klauda, Jeffery B

    2016-07-01

    Lactose permease of E. coli (LacY) is a secondary active transporter (SAT) that belongs to the major facilitator superfamily (MFS). Experimental structures of the cytoplasmic-open and more recently occluded-like structure have been determined, however, the crystal structure of LacY in the periplasmic-open state is still not available. The periplasmic-open LacY structure is important for understanding complete proton/sugar transport process of LacY as well as other similar SAT proteins. Previously, a structural model of periplasmic-open LacY has been obtained through a two-step hybrid implicit-explicit (IM-EX) simulation method (JMB404: 506). Molecular dynamics simulations are performed to further test the IM-EX model for the periplasmic-open LacY with ββ-(Galp)2 in a lipid membrane. The comparison of the calculated pore radii to the data of the crystal structure indicates that the IM-EX model of LacY remains periplasmic-open in E269-protonated states. The neighbor residue distance change based on Cα are very similar in simulation results, but they are significantly different in double electron-electron resonance (DEER) experimental data, which motivates us to perform the molecular dynamics dummy spin-label (MDDS) simulations to test the effect of spin labels (size and internal flexibility) on DEER spin label distance measurements. The MDDS simulation results show that the orientation and movement of the spin labels significantly affect the residue pair distance measurement. DEER data alone may not provide an accurate guide for predicting protein structures. MDDS simulations can be applied to analyze the distance distribution due to spin labels and also aid in proper interpretation of DEER experimental data. PMID:27107553

  3. Spin polarized bound states in the continuum in open Aharonov–Bohm rings with the Rashba spin–orbit interaction

    NASA Astrophysics Data System (ADS)

    Bulgakov, Evgeny N.; Sadreev, Almas F.

    2016-07-01

    We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov–Bohm rings in the presence of the Rashba spin–orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase.

  4. Probing the holographic principle using dynamical gauge effects from open spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Zhao, Jianshi; Price, Craig; Liu, Qi; Gemelke, Nathan

    2016-05-01

    Dynamical gauge fields result from locally defined symmetries and an effective over-labeling of quantum states. Coupling atoms weakly to a reservoir of laser modes can create an effective dynamical gauge field purely due to the disregard of information in the optical states. Here we report measurements revealing effects of open spin-orbit coupling in a system where an effective model can be formed from a non-abelian SU(2) × U(1) field theory following the Yang-Mills construct. Forming a close analogy to dynamical gauge effects in quantum chromodynamics, we extract a measure of atomic motion which reveals the analog of a closing mass gap for the relevant gauge boson, shedding insight on long standing open problems in gauge-fixing scale anomalies. Using arguments following the holographic principle, we measure scaling relations which can be understood by quantifying information present in the local potential. New prospects using these techniques for developing fractionalization of multi-particle and macroscopic systems using dissipative and non-abelian gauge fields will also be discussed. We acknowledge support from NSF Award No. 1068570, and the Charles E. Kaufman Foundation.

  5. Glutamine synthetase of Klebsiella aerogenes: properties of glnD mutants lacking uridylyltransferase.

    PubMed Central

    Foor, F; Cedergren, R J; Streicher, S L; Rhee, S G; Magasanik, B

    1978-01-01

    The glnD mutation of Klebsiella aerogenes is cotransducible by phage P1 with pan (requirement for pantothenate) and leads to a loss of uridylytransferase and uridylyl-removing enzyme, components of the glutamine synthetase adenylylation system. This defect results in an inability to deadenylylate glutamine synthetase rapidly and in a requirement for glutamine for normal growth. Suppression of the glnD mutation are located at the glutamine synthetase structural gene glnA. PMID:26659

  6. Three of Four GlnR Binding Sites Are Essential for GlnR-Mediated Activation of Transcription of the Amycolatopsis mediterranei nas Operon

    PubMed Central

    Wang, Ying; Wang, Jing-Zhi; Shao, Zhi-Hui; Yuan, Hua; Lu, Yin-Hua; Jiang, Wei-Hong

    2013-01-01

    In Amycolatopsis mediterranei U32, genes responsible for nitrate assimilation formed one operon, nasACKBDEF, whose transcription is induced by the addition of nitrate. Here, we characterized GlnR as a direct transcriptional activator for the nas operon. The GlnR-protected DNA sequences in the promoter region of the nas operon were characterized by DNase I footprinting assay, the previously deduced Streptomyces coelicolor double 22-bp GlnR binding consensus sequences comprising a1, b1, a2, and b2 sites were identified, and the sites were then mutated individually to test their roles in both the binding of GlnR in vitro and the GlnR-mediated transcriptional activation in vivo. The results clearly showed that only three GlnR binding sites (a1, b1, and b2 sites) were required by GlnR for its specific binding to the nas promoter region and efficient activation of the transcription of the nas operon in U32, while the a2 site seemed unnecessary. PMID:23543714

  7. XPC Lys939Gln polymorphism, smoking and risk of sporadic colorectal cancer among Malaysians

    PubMed Central

    Ahmad Aizat, Abdul Aziz; Siti Nurfatimah, Mohd Shahpudin; Aminudin, Mustapha Mohd; Ankathil, Ravindran

    2013-01-01

    AIM: To investigate the risk association of xeroderma pigmentosum group C (XPC) Lys939Gln polymorphism alone and in combination with cigarette smoking on colorectal cancer (CRC) predisposition. METHODS: Peripheral blood samples of 510 study subjects (255 CRC patients, 255 controls)were collected. DNA was extracted and genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism. The association between polymorphic genotype and CRC predisposition was determined using the OR and 95%CI. RESULTS: The frequency of the homozygous variant (Gln/Gln) genotype was significantly higher in cases compared with controls (16.0% vs 10.2%, P = 0.049). The Gln/Gln genotype of XPC showed a significantly higher association with the risk of CRC (OR = 1.884; 95%CI: 1.082-3.277; P = 0.025). In the case of allele frequencies, variant allele C was associated with a significantly increased risk of CRC (OR = 1.375; 95%CI: 1.050-1.802; P = 0.020). Moreover, the risk was markedly higher for those who were carriers of the Gln/Gln variant genotype and were also cigarette smokers (OR = 3.409; 95%CI: 1.061-10.949; P = 0.032). CONCLUSION: The XPC Gln/Gln genotype alone and in combination with smoking increases the risk of CRC among Malaysians. PMID:23801864

  8. Temperature- and nitrogen source-dependent regulation of GlnR target genes in Listeria monocytogenes.

    PubMed

    Kaspar, Daniela; Auer, Franziska; Schardt, Jakob; Schindele, Franziska; Ospina, Alberto; Held, Claudia; Ehrenreich, Armin; Scherer, Siegfried; Müller-Herbst, Stefanie

    2014-06-01

    The ubiquitous pathogen Listeria monocytogenes lives either saprophytically in the environment or within cells in a vertebrate host, thus adapting its lifestyle to its ecological niche. Growth experiments at 24 and 37 °C (environmental and host temperature) with ammonium or glutamine as nitrogen sources revealed that ammonium is the preferred nitrogen source of L. monocytogenes. Reduced growth on glutamine is more obvious at 24 °C. Global transcriptional microarray analyses showed that the most striking difference in temperature-dependent transcription was observed for central nitrogen metabolism genes, glnR (glutamine synthetase repressor GlnR), glnA (glutamine synthetase GlnA), amtB (ammonium transporter AmtB), glnK (PII regulatory protein GlnK), and gdh (glutamate dehydrogenase) when cells were grown on glutamine. When grown on ammonium, both at 24 and 37 °C, the transcriptional level of these genes resembles that of cells grown with glutamine at 37 °C. Electrophoretic mobility shift assay studies and qPCR analyses in the wild-type L. monocytogenes and the deletion mutant L. monocytogenes ∆glnR revealed that the transcriptional regulator GlnR is directly involved in temperature- and nitrogen source-dependent regulation of the respective genes. Glutamine, a metabolite known to influence GlnR activity, seems unlikely to be the (sole) intracellular signal mediating this temperature-and nitrogen source-dependent metabolic adaptation. PMID:24801548

  9. Local conservation laws in spin-\\frac{1}{2} XY chains with open boundary conditions

    NASA Astrophysics Data System (ADS)

    Fagotti, Maurizio

    2016-06-01

    We revisit the conserved quantities of the spin-\\frac{1}{2} XY model with open boundary conditions. In the absence of a transverse field, we find new families of local charges and show that half of the seeming conservation laws are conserved only if the number of sites is odd. In even chains the set of noninteracting charges is abelian, like in the periodic case when the number of sites is odd. In odd chains the set is doubled and becomes non-abelian, like in even periodic chains. The dependence of the charges on the parity of the chain’s size undermines the common belief that the thermodynamic limit of diagonal ensembles exists. We consider also the transverse-field Ising chain, where the situation is more ordinary. The generalization to the XY model in a transverse field is not straightforward and we propose a general framework to carry out similar calculations. We conjecture the form of the bulk part of the local charges and discuss the emergence of quasilocal conserved quantities. We provide evidence that in a region of the parameter space there is a reduction of the number of quasilocal conservation laws invariant under chain inversion. As a by-product, we study a class of block-Toeplitz-plus-Hankel operators and identify the conditions that their symbols satisfy in order to commute with a given block-Toeplitz.

  10. The wild-type gene for glutamine synthetase restores ammonia control of nitrogen fixation to Gln- (glnA) mutants of Rhodopseudomonas capsulata.

    PubMed Central

    Scolnik, P A; Virosco, J; Haselkorn, R

    1983-01-01

    The wild-type glnA gene, coding for glutamine synthetase, was cloned from the photosynthetic bacterium Rhodopseudomonas capsulata by using a cosmid library to complement the Gln- phenotype of an Escherichia coli glnA deletion strain. The original cosmid plasmid contained 37 kilobase pairs (kbp) of R. capsulata DNA, of which only 2 kbp was necessary for Gln complementation in E. coli. A plasmid containing this 2-kbp insert was mobilized into G29, a Gln- mutant of R. capsulata which is also unable to repress nitrogenase in ammonia-containing media (Nifc phenotype). The 2-kbp fragment restored glutamine-independent growth and ammonia repression of nitrogenase, indicating that in R. capsulata, production of the signal for nitrogen repression of nif depends on the activity of the glnA gene. Repression of nitrogenase was shown, by hybridization of RNA to cloned nif DNA, to occur at the level of transcription in the wild-type and the complemented G29 strains. Images PMID:6134715

  11. Radiation of spin waves from the open end of a microscopic magnetic-film waveguide

    NASA Astrophysics Data System (ADS)

    Demidov, Vladislav E.; Demokritov, Sergej O.; Birt, Daniel; O'Gorman, Brian; Tsoi, Maxim; Li, Xiaoqin

    2009-07-01

    We have studied experimentally the radiation of spin waves from a permalloy-film microwaveguide into a continuous permalloy film. We show that due to a strong mismatch of the spin-wave spectrum caused by a variation in the demagnetizing field at the interface between the waveguide and the film, a frequency interval exists, where spin waves experience total reflection from the junction penetrating into the permalloy film in a tunnelinglike manner. At frequencies above this interval, complex frequency-dependent radiation patterns were observed characterized by a preferential radiation direction appearing due to the intrinsic anisotropy of the spin-wave dispersion characteristics in the film.

  12. Radiation of spin waves from the open end of a microscopic magnetic-film waveguide

    NASA Astrophysics Data System (ADS)

    Birt, Daniel; Demidov, Vladislav; Demokritov, Sergej; O'Gorman, Brian; Tsoi, Maxim; Li, Xiaoqin

    2010-03-01

    We have studied experimentally the radiation of spin waves from a permalloy-film microwaveguide into a continuous permalloy film. We show that due to a strong mismatch of the spin-wave spectrum caused by a variation in the demagnetizing field at the interface between the waveguide and the film, a frequency interval exists, where spin waves experience total reflection from the junction penetrating into the permalloy film in a tunnelinglike manner. At frequencies above this interval, complex frequency-dependent radiation patterns were observed characterized by a preferential radiation direction appearing due to the intrinsic anisotropy of the spin-wave dispersion characteristics in the film.

  13. Open spin chains with generic integrable boundaries: Baxter equation and Bethe ansatz completeness from separation of variables

    NASA Astrophysics Data System (ADS)

    Kitanine, N.; Maillet, J. M.; Niccoli, G.

    2014-05-01

    We solve the longstanding problem of defining a functional characterization of the spectrum of the transfer matrix associated with the most general spin-1/2 representations of the six-vertex reflection algebra for general inhomogeneous chains. The corresponding homogeneous limit reproduces the spectrum of the Hamiltonian of the spin-1/2 open XXZ and XXX quantum chains with the most general integrable boundaries. The spectrum is characterized by a second order finite difference functional equation of Baxter type with an inhomogeneous term which vanishes only for some special but yet interesting non-diagonal boundary conditions. This functional equation is shown to be equivalent to the known separation of variables (SOV) representation, hence proving that it defines a complete characterization of the transfer matrix spectrum. The polynomial form of the Q-function allows us to show that a finite system of generalized Bethe equations can also be used to describe the complete transfer matrix spectrum.

  14. Can density functional methods be used for open-shell actinide molecules? Comparison with multiconfigurational spin-orbit studies

    NASA Astrophysics Data System (ADS)

    Clavaguéra-Sarrio, Carine; Vallet, Valérie; Maynau, Daniel; Marsden, Colin J.

    2004-09-01

    The geometries, electronic structures, and vibrational frequencies of two isoelectronic compounds PuO22+ and PuN2 have been studied in detail at the density functional theory (DFT) and multiconfigurational ab initio levels of theory. Dynamic correlation was taken into account using second-order perturbation theory (CASPT2) and the variational difference-dedicated configuration interaction method for comparison with the results of the DFT study. Spin-orbit effects were included within the framework of an effective uncontracted spin-orbit configuration-interaction method which considers electron correlation effects and spin-orbit coupling on equal footing. The twelve lowest f-f electronic transitions are reported. The electronic ground state of both systems is found to be the Ω=4 component of 3Hg. We thus disagree with an earlier assignment of the ground state of PuN2 [E. F. Archibong and A. K. Ray, J. Mol. Struct: THEOCHEM 530, 165 (2000)]. Spin-orbit effects are small on both the geometry and vibrational frequencies of the ground states of PuO22+ and PuN2, but they completely change the distribution of electronically excited states. A comparison of results obtained with the two classes of methods allows us to demonstrate that an unambiguous assignment of the electronic ground state and electronic spectra requires the use of multireference methods including spin-orbit coupling. Single-reference methods such as DFT provide a reasonable description of the electronic properties of ground states of these open-shell systems, and therefore also of their structural and vibrational properties. The experimental antisymmetric stretching frequency of matrix-isolated PuN2 is reproduced well by both CASPT2 and DFT calculations; generalized gradient approximation formulations of DFT are more successful than hybrid versions in this respect. Ground-state properties of UO22+, UN2, UO2, PuO22+, and PuN2 are compared and discussed.

  15. XPC Lys939Gln polymorphism contributes to colorectal cancer susceptibility: evidence from a meta-analysis

    PubMed Central

    2014-01-01

    Abstract Background Published studies investigating the association between XPC Lys939Gln polymorphism and colorectal cancer (CRC) risk reported inconclusive results. We performed a meta-analysis to derive a precise estimation of the relationship. Methods A comprehensive literature search was done in databases PubMed, EMBASE, and Cochrane library up to December 2013. The association between XPC Lys939Gln polymorphism and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs). Results Eight studies with 3,301 cases and 4,177 controls were included in the meta-analysis. We observed that the XPC Lys939Gln polymorphism was correlated with an increased CRC risk when all studies were pooled into the meta-analysis (Gln/lys vs. Lys/Lys: OR = 1.293, 95% CI 1.169–1.430, P = 0.000; Gln/Gln + Gln/lys vs. Lys/Lys: OR = 1.260, 95% CI 1.145–1.388, P = 0.000). In stratified analyses by ethnicity, smoking, and study quality, significant increased CRC risk was found in Asians (Gln/lys vs. Lys/Lys: OR = 1.345, 95% CI 1.187–1.523, P = 0.000; Gln/Gln + Gln/lys vs. Lys/Lys: OR = 1.317, 95% CI 1.170–1.484, P = 0.000), nonsmokers (Gln/Gln + Gln/lys vs. Lys/Lys: OR = 1.286, 95% CI 1.020–1.622, P = 0.033), and high quality studies. In subgroup analysis by source of control, significant increased CRC risk was found in both hospital-based studies and population-based studies. However, in subgroup analysis according to cancer location, no any significant association was detected. Conclusions This meta-analysis suggests that the XPC is a candidate gene for CRC susceptibility. The XPC Lys939Gln polymorphism may play an important role in CRC development among Asians and nonsmokers. Further large and well-designed studies are needed to confirm this association. Virtual Slides The virtual slide(s) for this article can be found here: http

  16. Haloferax mediterranei GlnK proteins are post-translationally modified by uridylylation.

    PubMed

    Pedro-Roig, Laia; Camacho, Mónica; Bonete, María José

    2013-04-01

    In this work we report for the first time a post-translational modification of PII homologues from the Archaea Domain. Haloferax mediterranei is the first haloarchaea whose PII proteins have been studied, it possesses two of them (GlnK1 and GlnK2 ), both encoded adjacent to a gene for the ammonia transporter Amt. An approach based on 2DE, anti-GlnK immunoblot and peptide mass fingerprint (MALDI-TOF-MS) of the reactive spots showed that GlnK proteins in H. mediterranei are post-translationally uridylylated. A third spot with lower pI suggests the existence of a non-descript post-translational modification in this protein family. PMID:23420616

  17. Multiple Targets on the Gln3 Transcription Activator Are Cumulatively Required for Control of Its Cytoplasmic Sequestration.

    PubMed

    Rai, Rajendra; Tate, Jennifer J; Cooper, Terrance G

    2016-01-01

    A remarkable characteristic of nutritional homeostatic mechanisms is the breadth of metabolite concentrations to which they respond, and the resolution of those responses; adequate but rarely excessive. Two general ways of achieving such exquisite control are known: stoichiometric mechanisms where increasing metabolite concentrations elicit proportionally increasing responses, and the actions of multiple independent metabolic signals that cumulatively generate appropriately measured responses. Intracellular localization of the nitrogen-responsive transcription activator, Gln3, responds to four distinct nitrogen environments: nitrogen limitation or short-term starvation, i.e., nitrogen catabolite repression (NCR), long-term starvation, glutamine starvation, and rapamycin inhibition of mTorC1. We have previously identified unique sites in Gln3 required for rapamycin-responsiveness, and Gln3-mTor1 interaction. Alteration of the latter results in loss of about 50% of cytoplasmic Gln3 sequestration. However, except for the Ure2-binding domain, no evidence exists for a Gln3 site responsible for the remaining cytoplasmic Gln3-Myc(13) sequestration in nitrogen excess. Here, we identify a serine/threonine-rich (Gln3477-493) region required for effective cytoplasmic Gln3-Myc(13) sequestration in excess nitrogen. Substitutions of alanine but not aspartate for serines in this peptide partially abolish cytoplasmic Gln3 sequestration. Importantly, these alterations have no effect on the responses of Gln3-Myc(13) to rapamycin, methionine sulfoximine, or limiting nitrogen. However, cytoplasmic Gln3-Myc(13) sequestration is additively, and almost completely, abolished when mutations in the Gln3-Tor1 interaction site are combined with those in Gln3477-493 cytoplasmic sequestration site. These findings clearly demonstrate that multiple individual regulatory pathways cumulatively control cytoplasmic Gln3 sequestration. PMID:26976442

  18. Multiple Targets on the Gln3 Transcription Activator Are Cumulatively Required for Control of Its Cytoplasmic Sequestration

    PubMed Central

    Rai, Rajendra; Tate, Jennifer J.; Cooper, Terrance G.

    2016-01-01

    A remarkable characteristic of nutritional homeostatic mechanisms is the breadth of metabolite concentrations to which they respond, and the resolution of those responses; adequate but rarely excessive. Two general ways of achieving such exquisite control are known: stoichiometric mechanisms where increasing metabolite concentrations elicit proportionally increasing responses, and the actions of multiple independent metabolic signals that cumulatively generate appropriately measured responses. Intracellular localization of the nitrogen-responsive transcription activator, Gln3, responds to four distinct nitrogen environments: nitrogen limitation or short-term starvation, i.e., nitrogen catabolite repression (NCR), long-term starvation, glutamine starvation, and rapamycin inhibition of mTorC1. We have previously identified unique sites in Gln3 required for rapamycin-responsiveness, and Gln3-mTor1 interaction. Alteration of the latter results in loss of about 50% of cytoplasmic Gln3 sequestration. However, except for the Ure2-binding domain, no evidence exists for a Gln3 site responsible for the remaining cytoplasmic Gln3-Myc13 sequestration in nitrogen excess. Here, we identify a serine/threonine-rich (Gln3477–493) region required for effective cytoplasmic Gln3-Myc13 sequestration in excess nitrogen. Substitutions of alanine but not aspartate for serines in this peptide partially abolish cytoplasmic Gln3 sequestration. Importantly, these alterations have no effect on the responses of Gln3-Myc13 to rapamycin, methionine sulfoximine, or limiting nitrogen. However, cytoplasmic Gln3-Myc13 sequestration is additively, and almost completely, abolished when mutations in the Gln3-Tor1 interaction site are combined with those in Gln3477–493 cytoplasmic sequestration site. These findings clearly demonstrate that multiple individual regulatory pathways cumulatively control cytoplasmic Gln3 sequestration. PMID:26976442

  19. A new class of realizations of the lie algebra gl(n + 1, ℓ)

    NASA Astrophysics Data System (ADS)

    Burdík, Č.

    1986-11-01

    In this paper, we apply the previously published method (J. Phys. A 18(1985) 3101) to the construction of boson realizations for Lie algebras gl(n + 1, ℓ). These realizations are expressed by means of certain recurrent formulae in terms of r(n + 1 - r) canonical pairs and generators of the subalgebra gl(r, ℓ) + gl(n + 1 - r, ℓ), where r = 1,2,..., n. They are skew-Hermitean and Schurean.

  20. Characterization of the glnK-amtB operon of Azotobacter vinelandii.

    PubMed

    Meletzus, D; Rudnick, P; Doetsch, N; Green, A; Kennedy, C

    1998-06-01

    To determine whether in Azotobacter vinelandii the PII protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding PII was isolated and characterized. Its deduced translation product was highly similar to PII proteins from other organisms, with the greatest degree of relatedness being exhibited to the Escherichia coli glnK gene product. A gene designated amtB was found downstream of and was contranscribed with glnK as in E. coli. The AmtB protein is similar to functionally characterized ammonium transport proteins from a few other eukaryotes and one other prokaryote. glnK and amtB comprise an operon. Attempts to isolate a stable glnK mutant strain were unsuccessful, suggesting that glnK, like glnA, is an essential gene in A. vinelandii. amtB mutants were isolated, and although growth on limiting amounts of ammonium was similar in the mutant and wild-type strains, the mutants were unable to transport [14C]methylammonium. PMID:9620984

  1. Characterization of the glnK-amtB Operon of Azotobacter vinelandii

    PubMed Central

    Meletzus, Dietmar; Rudnick, Paul; Doetsch, Natalie; Green, Andrew; Kennedy, Christina

    1998-01-01

    To determine whether in Azotobacter vinelandii the PII protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding PII was isolated and characterized. Its deduced translation product was highly similar to PII proteins from other organisms, with the greatest degree of relatedness being exhibited to the Escherichia coli glnK gene product. A gene designated amtB was found downstream of and was cotranscribed with glnK as in E. coli. The AmtB protein is similar to functionally characterized ammonium transport proteins from a few other eukaryotes and one other prokaryote. glnK and amtB comprise an operon. Attempts to isolate a stable glnK mutant strain were unsuccessful, suggesting that glnK, like glnA, is an essential gene in A. vinelandii. amtB mutants were isolated, and although growth on limiting amounts of ammonium was similar in the mutant and wild-type strains, the mutants were unable to transport [14C]methylammonium. PMID:9620984

  2. Dynamics of open quantum spin systems: An assessment of the quantum master equation approach.

    PubMed

    Zhao, P; De Raedt, H; Miyashita, S; Jin, F; Michielsen, K

    2016-08-01

    Data of the numerical solution of the time-dependent Schrödinger equation of a system containing one spin-1/2 particle interacting with a bath of up to 32 spin-1/2 particles is used to construct a Markovian quantum master equation describing the dynamics of the system spin. The procedure of obtaining this quantum master equation, which takes the form of a Bloch equation with time-independent coefficients, accounts for all non-Markovian effects inasmuch the general structure of the quantum master equation allows. Our simulation results show that, with a few rather exotic exceptions, the Bloch-type equation with time-independent coefficients provides a simple and accurate description of the dynamics of a spin-1/2 particle in contact with a thermal bath. A calculation of the coefficients that appear in the Redfield master equation in the Markovian limit shows that this perturbatively derived equation quantitatively differs from the numerically estimated Markovian master equation, the results of which agree very well with the solution of the time-dependent Schrödinger equation. PMID:27627265

  3. Characterization of a gene, glnL, the product of which is involved in the regulation of nitrogen utilization in Escherichia coli.

    PubMed Central

    Chen, Y M; Backman, K; Magasanik, B

    1982-01-01

    DNA was prepared from a strain of Escherichia coli bearing a mutation which confers the GlnC phenotype (inability to reduce the expression of glnA and other nitrogen-regulated operons in response to ammonia in the growth medium). A fragment of this DNA carrying glnA, the structural gene for glutamine synthetase, was cloned on plasmid pBR322. By using recombination in vitro, we mapped the GlnC mutation to a region between glnA and glnG. This region defines a gene, glnL, which codes for a trans-acting product; the GlnC mutant produces an altered product. The glnL product plays a key role in the communication of information concerning the quality and abundance of the nitrogen source in the growth medium to a destination responsible for the regulation of glnA and other genes for enzymes responsible for nitrogen utilization. PMID:6120930

  4. Quantizing Open Spin Chains with Variable Length and Giant Gravitons in the Anti-de Sitter-Space/Conformal Field-Theory Correspondence

    SciTech Connect

    Berenstein, David; Correa, Diego H.; Vazquez, Samuel E.

    2005-11-04

    We study an XXX open spin chain with variable number of sites, where the variability is introduced only at the boundaries. This model arises naturally in the study of giant gravitons in the anti-de Sitter-space/conformal field-theory correspondence. We show how to quantize the spin chain by mapping its states to a bosonic lattice of finite length with sources and sinks of particles at the boundaries. Using coherent states, we show how the Hamiltonian for the bosonic lattice gives the correct description of semiclassical open strings ending on giant gravitons.

  5. Lethality of glnD null mutations in Azotobacter vinelandii is suppressible by prevention of glutamine synthetase adenylylation.

    PubMed

    Colnaghi, R; Rudnick, P; He, L; Green, A; Yan, D; Larson, E; Kennedy, C

    2001-05-01

    GlnD is a pivotal protein in sensing intracellular levels of fixed nitrogen and has been best studied in enteric bacteria, where it reversibly uridylylates two related proteins, PII and GlnK. The uridylylation state of these proteins determines the activities of glutamine synthetase (GS) and NtrC. Results presented here demonstrate that glnD is an essential gene in Azotobacter vinelandii. Null glnD mutations were introduced into the A. vinelandii genome, but none could be stably maintained unless a second mutation was present that resulted in unregulated activity of GS. One mutation, gln-71, occurred spontaneously to give strain MV71, which failed to uridylylate the GlnK protein. The second, created by design, was glnAY407F (MV75), altering the adenylylation site of GS. The gln-71 mutation is probably located in glnE, encoding adenylyltransferase, because introducing the Escherichia coli glnE gene into MV72, a glnD(+) derivative of MV71, restored the regulation of GS activity. GlnK-UMP is therefore apparently required for GS to be sufficiently deadenylylated in A. vinelandii for growth to occur. The DeltaglnD GS(c) isolates were Nif(-), which could be corrected by introducing a nifL mutation, confirming a role for GlnD in mediating nif gene regulation via some aspect of the NifL/NifA interaction. MV71 was unexpectedly NtrC(+), suggesting that A. vinelandii NtrC activity might be regulated differently than in enteric organisms. PMID:11320130

  6. GlnR-Mediated Regulation of ectABCD Transcription Expands the Role of the GlnR Regulon to Osmotic Stress Management

    PubMed Central

    Shao, ZhiHui; Deng, WanXin; Li, ShiYuan; He, JuanMei; Ren, ShuangXi; Huang, WeiRen; Lu, YinHua; Zhao, GuoPing

    2015-01-01

    ABSTRACT Ectoine and hydroxyectoine are excellent compatible solutes for bacteria to deal with environmental osmotic stress and temperature damages. The biosynthesis cluster of ectoine and hydroxyectoine is widespread among microorganisms, and its expression is activated by high salinity and temperature changes. So far, little is known about the mechanism of the regulation of the transcription of ect genes and only two MarR family regulators (EctR1 in methylobacteria and the EctR1-related regulator CosR in Vibrio cholerae) have been found to negatively regulate the expression of ect genes. Here, we characterize GlnR, the global regulator for nitrogen metabolism in actinomycetes, as a negative regulator for the transcription of ectoine/hydroxyectoine biosynthetic genes (ect operon) in Streptomyces coelicolor. The physiological role of this transcriptional repression by GlnR is proposed to protect the intracellular glutamate pool, which acts as a key nitrogen donor for both the nitrogen metabolism and the ectoine/hydroxyectoine biosynthesis. IMPORTANCE High salinity is deleterious, and cells must evolve sophisticated mechanisms to cope with this osmotic stress. Although production of ectoine and hydroxyectoine is one of the most frequently adopted strategies, the in-depth mechanism of regulation of their biosynthesis is less understood. So far, only two MarR family negative regulators, EctR1 and CosR, have been identified in methylobacteria and Vibrio, respectively. Here, our work demonstrates that GlnR, the global regulator for nitrogen metabolism, is a negative transcriptional regulator for ect genes in Streptomyces coelicolor. Moreover, a close relationship is found between nitrogen metabolism and osmotic resistance, and GlnR-mediated regulation of ect transcription is proposed to protect the intracellular glutamate pool. Meanwhile, the work reveals the multiple roles of GlnR in bacterial physiology. PMID:26170409

  7. Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity.

    PubMed

    Guan, Miao; de Bang, Thomas C; Pedersen, Carsten; Schjoerring, Jan K

    2016-07-01

    Cytosolic GS1 (Gln synthetase) is central for ammonium assimilation in plants. High ammonium treatment enhanced the expression of the GS1 isogene Gln-1;2 encoding a low-affinity high-capacity GS1 protein in Arabidopsis (Arabidopsis thaliana) shoots. Under the same conditions, the expression of the high-affinity low-capacity isoform Gln-1;1 was reduced. The expression of Gln-1;3 did not respond to ammonium treatment while Gln-1;4 and Gln-1;5 isogenes in all cases were expressed at a very low level. Gln-2 was highly expressed in shoots but only at a very low level in roots. To investigate the specific functions of the two isogenes Gln-1;1 and Gln-1;2 in shoots for ammonium detoxification, single and double knock-out mutants were grown under standard N supply or with high ammonium provision. Phenotypes of the single mutant gln1;1 were similar to the wild type, while growth of the gln1;2 single mutant and the gln1;1:gln1;2 double mutant was significantly impaired irrespective of N regime. GS1 activity was significantly reduced in both gln1;2 and gln1;1:gln1;2 Along with this, the ammonium content increased while that of Gln decreased, showing that Gln-1;2 was essential for ammonium assimilation and amino acid synthesis. We conclude that Gln-1;2 is the main isozyme contributing to shoot GS1 activity in vegetative growth stages and can be up-regulated to relieve ammonium toxicity. This reveals, to our knowledge, a novel shoot function of Gln-1;2 in Arabidopsis shoots. PMID:27231101

  8. Non-markovian mesoscopic dissipative dynamics of open quantum spin chains

    NASA Astrophysics Data System (ADS)

    Benatti, F.; Carollo, F.; Floreanini, R.; Narnhofer, H.

    2016-01-01

    We study the dissipative dynamics of N quantum spins with Lindblad generator consisting of operators scaling as fluctuations, namely with the inverse square-root of N. In the large N limit, the microscopic dissipative time-evolution converges to a non-Markovian unitary dynamics on strictly local operators, while at the mesoscopic level of fluctuations it gives rise to a dissipative non-Markovian dynamics. The mesoscopic time-evolution is Gaussian and exhibits either a stable or an unstable asymptotic character; furthermore, the mesoscopic dynamics builds correlations among fluctuations that survive in time even when the original microscopic dynamics is unable to correlate local observables.

  9. The crystal structure of human GlnRS provides basis for the development of neurological disorders

    PubMed Central

    Ognjenović, Jana; Wu, Jiang; Matthies, Doreen; Baxa, Ulrich; Subramaniam, Sriram; Ling, Jiqiang; Simonović, Miljan

    2016-01-01

    Cytosolic glutaminyl-tRNA synthetase (GlnRS) is the singular enzyme responsible for translation of glutamine codons. Compound heterozygous mutations in GlnRS cause severe brain disorders by a poorly understood mechanism. Herein, we present crystal structures of the wild type and two pathological mutants of human GlnRS, which reveal, for the first time, the domain organization of the intact enzyme and the structure of the functionally important N-terminal domain (NTD). Pathological mutations mapping in the NTD alter the domain structure, and decrease catalytic activity and stability of GlnRS, whereas missense mutations in the catalytic domain induce misfolding of the enzyme. Our results suggest that the reduced catalytic efficiency and a propensity of GlnRS mutants to misfold trigger the disease development. This report broadens the spectrum of brain pathologies elicited by protein misfolding and provides a paradigm for understanding the role of mutations in aminoacyl-tRNA synthetases in neurological diseases. PMID:26869582

  10. Structures of Arg- and Gln-type bacterial cysteine dioxygenase homologs

    PubMed Central

    Driggers, Camden M; Hartman, Steven J; Karplus, P Andrew

    2015-01-01

    In some bacteria, cysteine is converted to cysteine sulfinic acid by cysteine dioxygenases (CDO) that are only ∼15–30% identical in sequence to mammalian CDOs. Among bacterial proteins having this range of sequence similarity to mammalian CDO are some that conserve an active site Arg residue (“Arg-type” enzymes) and some having a Gln substituted for this Arg (“Gln-type” enzymes). Here, we describe a structure from each of these enzyme types by analyzing structures originally solved by structural genomics groups but not published: a Bacillus subtilis “Arg-type” enzyme that has cysteine dioxygenase activity (BsCDO), and a Ralstonia eutropha “Gln-type” CDO homolog of uncharacterized activity (ReCDOhom). The BsCDO active site is well conserved with mammalian CDO, and a cysteine complex captured in the active site confirms that the cysteine binding mode is also similar. The ReCDOhom structure reveals a new active site Arg residue that is hydrogen bonding to an iron-bound diatomic molecule we have interpreted as dioxygen. Notably, the Arg position is not compatible with the mode of Cys binding seen in both rat CDO and BsCDO. As sequence alignments show that this newly discovered active site Arg is well conserved among “Gln-type” CDO enzymes, we conclude that the “Gln-type” CDO homologs are not authentic CDOs but will have substrate specificity more similar to 3-mercaptopropionate dioxygenases. PMID:25307852

  11. The crystal structure of human GlnRS provides basis for the development of neurological disorders

    DOE PAGESBeta

    Ognjenovic, Jana; Wu, Jiang; Matthies, Doreen; Baxa, Ulrich; Subramaniam, Sriram; Ling, Jiqiang; Simonovic, Miljan

    2016-02-10

    Cytosolic glutaminyl-tRNA synthetase (GlnRS) is the singular enzyme responsible for translation of glutamine codons. Compound heterozygous mutations in GlnRS cause severe brain disorders by a poorly understood mechanism. Herein, we present crystal structures of the wild type and two pathological mutants of human GlnRS, which reveal, for the first time, the domain organization of the intact enzyme and the structure of the functionally important N-terminal domain (NTD). Pathological mutations mapping in the NTD alter the domain structure, and decrease catalytic activity and stability of GlnRS, whereas missense mutations in the catalytic domain induce misfolding of the enzyme. Our results suggestmore » that the reduced catalytic efficiency and a propensity of GlnRS mutants to misfold trigger the disease development. As a result, this report broadens the spectrum of brain pathologies elicited by protein misfolding and provides a paradigm for understanding the role of mutations in aminoacyl-tRNA synthetases in neurological diseases. Keywords« less

  12. Role of GlnK in NifL-mediated regulation of NifA activity in Azotobacter vinelandii.

    PubMed

    Rudnick, Paul; Kunz, Christopher; Gunatilaka, Malkanthi K; Hines, Eric R; Kennedy, Christina

    2002-02-01

    In several diazotrophic species of Proteobacteria, P(II) signal transduction proteins have been implicated in the regulation of nitrogen fixation in response to NH(4)(+) by several mechanisms. In Azotobacter vinelandii, expression of nifA, encoding the nif-specific activator, is constitutive, and thus, regulation of NifA activity by the flavoprotein NifL appears to be the primary level of nitrogen control. In vitro and genetic evidence suggests that the nitrogen response involves the P(II)-like GlnK protein and GlnD (uridylyltransferase/uridylyl-removing enzyme), which reversibly uridylylates GlnK in response to nitrogen limitation. Here, the roles of GlnK and GlnK-UMP in A. vinelandii were studied to determine whether the Nif (-) phenotype of glnD strains was due to an inability to modify GlnK, an effort previously hampered because glnK is an essential gene in this organism. A glnKY51F mutation, encoding an unuridylylatable form of the protein, was stable only in a strain in which glutamine synthetase activity is not inhibited by NH(4)(+), suggesting that GlnK-UMP is required to signal adenylyltransferase/adenylyl-removing enzyme-mediated deadenylylation. glnKY51F strains were significantly impaired for diazotrophic growth and expression of a nifH-lacZ fusion. NifL interacted with GlnK and GlnKY51F in a yeast two-hybrid system. Together, these data are consistent with those obtained from in vitro experiments (Little et al., EMBO J., 19:6041-6050, 2000) and support a model for regulation of NifA activity in which unmodified GlnK stimulates NifL inhibition and uridylylation of GlnK in response to nitrogen limitation prevents this function. This model is distinct from one proposed for the related bacterium Klebsiella pneumoniae, in which unmodified GlnK relieves NifL inhibition instead of stimulating it. PMID:11790752

  13. A meta-analysis of xeroderma pigmentosum gene D Ls751Gln polymorphism and susceptibility to hepatocellular carcinoma.

    PubMed

    Wang, Yu; Zhao, Yingren; Zhang, Aiyun; Ma, Juan; Wang, Zhenzhen; Zhang, Xu

    2015-01-01

    Hepatocellular carcinoma (HCC) is one of most common malignant tumors worldwide, but with unclear mechanisms. Xeroderma pigmentosum gene D (XPD) is one important DNA damage repair gene and can be involved in protein mutation. Currently little has been known about XPD polymorphism and HCC susceptibility in Chinese people. This study used a meta-analysis approach to comprehensively investigate the correlation between XPD polymorphism and HCC susceptibility in Chinese population, based on previously published literatures. A computer retrieval system was used to collect all case-control studies about XPD Lys751Gln polymorphism and HCC susceptibility. Data in literatures were extracted for meta-analysis. After the primary screening, four independent studies, which were published in 3 English articles and one Chinese article, were recruited in this study. There were 1,717 samples included in all studies. Using Gln/Gln + Lys/Gln, Lys/Lys + Lys/Gln and Lys allels as the reference, HCC disease alleles including Lys/Lys, Gln/Gln and Gln had OR values (95% CI, I(2)) of 1.007 (0.657~4.672, 91%), 3.516 (0.220~20.661, 48%) and 3.225 (0.278~12.326, 84%), respectively. The polymorphism of XPD751 loci is closely correlated with primary HCC. Lys751Gln polymorphism of XPD gene can be used as one susceptibility factor for HCC. PMID:26722489

  14. A Glutamine/Asparagine-Rich Fragment of Gln3, but not the Full-Length Protein, Aggregates in Saccharomyces cerevisiae.

    PubMed

    Antonets, K S; Sargsyan, H M; Nizhnikov, A A

    2016-04-01

    The amino acid sequence of protein Gln3 in yeast Saccharomyces cerevisiae has a region enriched with Gln (Q) and Asn (N) residues. In this study, we analyzed the effects of overexpression of Gln3 and its Q/N-rich fragment fused with yellow fluorescent protein (YFP). Being overexpressed, full-length Gln3-YFP does not form aggregates, inhibits vegetative growth, and demonstrates nuclear localization, while the Q/N-rich fragment (Gln3QN) fused with YFP forms aggregates that do not colocalize with the nucleus and do not affect growth of the cells. Although detergent-resistant aggregates of Gln3QN are formed in the absence of yeast prions, the aggregation of Gln3QN significantly increases in the presence of [PIN(+)] prion, while in the presence of two prions, [PSI(+)] and [PIN(+)], the percentage of cells with Gln3QN aggregates is significantly lower than in the strain bearing only [PIN(+)]. Data on colocalization demonstrate that this effect is mediated by interaction between Gln3QN aggregates and [PSI(+)] and [PIN(+)] prions. PMID:27293098

  15. The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters.

    PubMed Central

    Foster-Hartnett, D; Kranz, R G

    1994-01-01

    The protein encoded by glnB of Rhodobacter capsulatus is part of a nitrogen-sensing cascade which regulates the expression of nitrogen fixation genes (nif). The expression of glnB was studied by using lacZ fusions, primer extension analysis, and in vitro DNase I footprinting. Our results suggest that glnB is transcribed from two promoters, one of which requires the R. capsulatus ntrC gene but is rpoN independent. Another promoter upstream of glnB is repressed by NtrC; purified R. capsulatus NtrC binds to sites that overlap this distal promoter region. Images PMID:8051036

  16. Quantum transport, anomalous dephasing, and spin-orbit coupling in an open ballistic bismuth nanocavity

    NASA Astrophysics Data System (ADS)

    Hackens, B.; Minet, J. P.; Faniel, S.; Farhi, G.; Gustin, C.; Issi, J. P.; Heremans, J. P.; Bayot, V.

    2003-03-01

    The phase coherence time τφ and spin-orbit coupling time τso are measured in a bismuth quasiballistic nanocavity and in bismuth thin films using weak antilocalization and universal conductance fluctuations. The cavity is found to be zero dimensional for phase-coherent processes at low temperature. Weak antilocalization seems weakly affected by this drastic reduction of dimensionality. The temperature dependence of τφ is similar in both types of samples, qualitatively consistent with low-energy transfer two-dimensional electron-electron interaction effects as the dominant dephasing mechanism. Strikingly, τφ in the dot is found to be an order-of-magnitude smaller than in the film, and orders-of-magnitude smaller than the theoretical prediction.

  17. The "Gln-Type" Thiol Dioxygenase from Azotobacter vinelandii is a 3-Mercaptopropionic Acid Dioxygenase.

    PubMed

    Pierce, Brad S; Subedi, Bishnu P; Sardar, Sinjinee; Crowell, Joshua K

    2015-12-29

    Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the O2-dependent oxidation of l-cysteine to produce cysteinesulfinic acid. Bacterial CDOs have been subdivided as either "Arg-type" or "Gln-type" on the basis of the identity of conserved active site residues. To date, "Gln-type" enzymes remain largely uncharacterized. It was recently noted that the "Gln-type" enzymes are more homologous with another thiol dioxygenase [3-mercaptopropionate dioxygenase (MDO)] identified in Variovorax paradoxus, suggesting that enzymes of the "Gln-type" subclass are in fact MDOs. In this work, a putative "Gln-type" thiol dioxygenase from Azotobacter vinelandii (Av) was purified to homogeneity and characterized. Steady-state assays were performed using three substrates [3-mercaptopropionic acid (3mpa), l-cysteine (cys), and cysteamine (ca)]. Despite comparable maximal velocities, the "Gln-type" Av enzyme exhibited a specificity for 3mpa (kcat/KM = 72000 M(-1) s(-1)) nearly 2 orders of magnitude greater than those for cys (110 M(-1) s(-1)) and ca (11 M(-1) s(-1)). Supporting X-band electron paramagnetic resonance (EPR) studies were performed using nitric oxide (NO) as a surrogate for O2 binding to confirm obligate-ordered addition of substrate prior to NO. Stoichimetric addition of NO to solutions of 3mpa-bound enzyme quantitatively yields an iron-nitrosyl species (Av ES-NO) with EPR features consistent with a mononuclear (S = (3)/2) {FeNO}(7) site. Conversely, two distinct substrate-bound conformations were observed in Av ES-NO samples prepared with cys and ca, suggesting heterogeneous binding within the enzymatic active site. Analytical EPR simulations are provided to establish the relative binding affinity for each substrate (3map > cys > ca). Both kinetic and spectroscopic results presented here are consistent with 3mpa being the preferred substrate for this enzyme. PMID:26624219

  18. An Association between Single Nucleotide Polymorphisms of Lys751Gln ERCC2 Gene and Ovarian Cancer in Polish Women

    PubMed Central

    Michalska, Magdalena M.; Samulak, Dariusz; Romanowicz, Hanna; Sobkowski, Maciej; Smolarz, Beata

    2015-01-01

    Aim. The aim of this study was to evaluate the role of the Lys751Gln (rs13181) ERCC2 gene polymorphism in clinical parameters and the risk for development of ovarian cancer. Material and Methods. The study consisted of 430 patients with ovarian cancer (mean age: 53.2 ± 10.11) and 430 healthy subjects (mean age: 50.31 ± 18.21). Analysis of the gene polymorphisms was performed using the PCR-based restriction fragment length polymorphism (PCR-RFLP). The odds ratios (ORs) and 95% confidence intervals (CIs) for each genotype and allele were calculated. Results. The results obtained indicate that the genotype Gln/Gln is associated with an increased risk of ovarian cancer (OR 5.01; 95% CI 3.37–7.43; p < 0.0001). Association of Lys751Gln polymorphism with histological grading showed increased ERCC2 Gln/Gln (OR = 6.96; 95% CI 3.41–14.21; p < 0.0001) genotype in grading 1 as well as Gln allele overrepresentation (OR = 4.98; 95% CI 3.37–7.40; p < 0.0001) in G1 ovarian patients. Finally, with clinical FIGO staging under evaluation, an increase in ERCC2 Gln/Gln homozygote frequencies in staging I and Gln allele frequencies in SI were observed. Conclusion. On the basis of these results, we conclude that ERCC2 gene polymorphism Lys751Gln may be associated with an increased risk of ovarian carcinoma. PMID:26526682

  19. Nuclear Gln3 Import Is Regulated by Nitrogen Catabolite Repression Whereas Export Is Specifically Regulated by Glutamine.

    PubMed

    Rai, Rajendra; Tate, Jennifer J; Shanmuganatham, Karthik; Howe, Martha M; Nelson, David; Cooper, Terrance G

    2015-11-01

    Gln3, a transcription activator mediating nitrogen-responsive gene expression in Saccharomyces cerevisiae, is sequestered in the cytoplasm, thereby minimizing nitrogen catabolite repression (NCR)-sensitive transcription when cells are grown in nitrogen-rich environments. In the face of adverse nitrogen supplies, Gln3 relocates to the nucleus and activates transcription of the NCR-sensitive regulon whose products transport and degrade a variety of poorly used nitrogen sources, thus expanding the cell's nitrogen-acquisition capability. Rapamycin also elicits nuclear Gln3 localization, implicating Target-of-rapamycin Complex 1 (TorC1) in nitrogen-responsive Gln3 regulation. However, we long ago established that TorC1 was not the sole regulatory system through which nitrogen-responsive regulation is achieved. Here we demonstrate two different ways in which intracellular Gln3 localization is regulated. Nuclear Gln3 entry is regulated by the cell's overall nitrogen supply, i.e., by NCR, as long accepted. However, once within the nucleus, Gln3 can follow one of two courses depending on the glutamine levels themselves or a metabolite directly related to glutamine. When glutamine levels are high, e.g., glutamine or ammonia as the sole nitrogen source or addition of glutamine analogues, Gln3 can exit from the nucleus without binding to DNA. In contrast, when glutamine levels are lowered, e.g., adding additional nitrogen sources to glutamine-grown cells or providing repressive nonglutamine nitrogen sources, Gln3 export does not occur in the absence of DNA binding. We also demonstrate that Gln3 residues 64-73 are required for nuclear Gln3 export. PMID:26333687

  20. Schelling segregation in an open city: A kinetically constrained Blume-Emery-Griffiths spin-1 system

    NASA Astrophysics Data System (ADS)

    Gauvin, Laetitia; Nadal, Jean-Pierre; Vannimenus, Jean

    2010-06-01

    In the 70s Schelling introduced a multiagent model to describe the segregation dynamics that may occur with individuals having only weak preferences for “similar” neighbors. Recently variants of this model have been discussed, in particular, with emphasis on the links with statistical physics models. Whereas these models consider a fixed number of agents moving on a lattice, here, we present a version allowing for exchanges with an external reservoir of agents. The density of agents is controlled by a parameter which can be viewed as measuring the attractiveness of the city lattice. This model is directly related to the zero-temperature dynamics of the Blume-Emery-Griffiths spin-1 model, with kinetic constraints. With a varying vacancy density, the dynamics with agents making deterministic decisions leads to a variety of “phases” whose main features are the characteristics of the interfaces between clusters of agents of different types. The domains of existence of each type of interface are obtained analytically as well as numerically. These interfaces may completely isolate the agents leading to another type of segregation as compared to what is observed in the original Schelling model, and we discuss its possible socioeconomic correlates.

  1. Tomograms for open quantum systems: In(finite) dimensional optical and spin systems

    NASA Astrophysics Data System (ADS)

    Thapliyal, Kishore; Banerjee, Subhashish; Pathak, Anirban

    2016-03-01

    Tomograms are obtained as probability distributions and are used to reconstruct a quantum state from experimentally measured values. We study the evolution of tomograms for different quantum systems, both finite and infinite dimensional. In realistic experimental conditions, quantum states are exposed to the ambient environment and hence subject to effects like decoherence and dissipation, which are dealt with here, consistently, using the formalism of open quantum systems. This is extremely relevant from the perspective of experimental implementation and issues related to state reconstruction in quantum computation and communication. These considerations are also expected to affect the quasiprobability distribution obtained from experimentally generated tomograms and nonclassicality observed from them.

  2. Association of leptin receptor gene Gln223Arg polymorphism with susceptibility to colorectal cancer

    PubMed Central

    Arkani, Maral; Safaei, Akram; Pourhoseingholi, Mohamad Amin; Mohebbi, Seyed Reza; Fatemi, Seyed Reza; Vafaei, Mohammad

    2011-01-01

    Aim Leptin is a 16 kDa polypeptide hormone which secreted by adipose tissue and has an important role in energy balance, insulin pathway and inflammation, because of that it may play an important role in colorectal cancer (CRC). Leptin exerts its effect through the leptin receptor (LEPR) a member of the class I cytokine receptor family. Background We have investigated whether glutamine to arginine substitution (Gln223Arg) in exon 6 of the leptin receptor gene, has implications for susceptibility to CRC. Patients and methods Polymerase chain reaction (PCR) and restriction enzyme digestion (RFLP) was performed to evaluate the association between the Gln223Arg polymorphism of the LEPR and CRC risk in a case-control study in 346 subjects involving 173 cases with CRC and 173 controls. Results There was no statistically evidence of significant difference in genotype and allele frequencies between the cases with CRC and controls for the Gln223Arg polymorphism of LEPR, before or after adjusting for confounders (age, BMI, sex, and smoking status). Furthermore, no significant difference was observed between the CRC cases and controls by BMI, sex and smoking status. Conclusion Our findings suggest that the LEPR Gln223Arg polymorphism is not associated with the risk of CRC in Iranian population. PMID:24834182

  3. Leptin receptor expression and Gln223Arg polymorphism as prognostic markers in oral and oropharyngeal cancer.

    PubMed

    Rodrigues, P R S; Maia, L L; Santos, M; Peterle, G T; Alves, L U; Takamori, J T; Souza, R P; Barbosa, W M; Mercante, A M C; Nunes, F D; Carvalho, M B; Tajara, E H; Louro, I D; Silva-Conforti, A M A

    2015-01-01

    The leptin gene product is released into the blood stream, passes through the blood-brain barrier, and finds the leptin receptor (LEPR) in the central nervous system. This hormone regulates food intake, hematopoiesis, inflammation, immunity, differentiation, and cell proliferation. The LEPR Gln223Arg polymorphism has been reported to alter receptor function and expression, both of which have been related with prognostics in several tumor types. Furthermore, several studies have shown a relationship between the Gln223Arg polymorphism and tumor development, and its role in oral and oropharyngeal squamous cell carcinoma is now well understood. In this study, 315 DNA samples were used for LEPR Gln223Arg genotyping and 87 primary oral and oropharyngeal squamous cell carcinomas were used for immunohistochemical expression analysis, such that a relationship between these and tumor development and prognosis could be established. Homozygous LEPR Arg223 was found to be associated with a 2-fold reduction in oral and oropharyngeal cancer risk. In contrast, the presence of the Arg223 allele in tumors was associated with worse disease-free and disease-specific survival. Low LEPR expression was found to be an independent risk factor, increasing the risk for lymph node metastasis 4-fold. In conclusion, the Gln223Arg polymorphism and LEPR expression might be valuable markers for oral and oropharyngeal cancer, suggesting that LEPR might serve as a potential target for future therapies. PMID:26634459

  4. Giant magnetoelastic effect at the opening of a spin-gap in Ba3BiIr2O9.

    PubMed

    Miiller, Wojciech; Avdeev, Maxim; Zhou, Qingdi; Kennedy, Brendan J; Sharma, Neeraj; Kutteh, Ramzi; Kearley, Gordon J; Schmid, Siegber; Knight, Kevin S; Blanchard, Peter E R; Ling, Chris D

    2012-02-15

    As compared to 3d (first-row) transition metals, the 4d and 5d transition metals have much more diffuse valence orbitals. Quantum cooperative phenomena that arise due to changes in the way these orbitals overlap and interact, such as magnetoelasticity, are correspondingly rare in 4d and 5d compounds. Here, we show that the 6H-perovskite Ba(3)BiIr(2)O(9), which contains 5d Ir(4+) (S = 1/2) dimerized into isolated face-sharing Ir(2)O(9) bioctahedra, exhibits a giant magnetoelastic effect, the largest of any known 5d compound, associated with the opening of a spin-gap at T* = 74 K. The resulting first-order transition is characterized by a remarkable 4% increase in Ir-Ir distance and 1% negative thermal volume expansion. The transition is driven by a dramatic change in the interactions among Ir 5d orbitals, and represents a crossover between two very different, competing, ground states: one that optimizes direct Ir-Ir bonding (at high temperature), and one that optimizes Ir-O-Ir magnetic superexchange (at low temperature). PMID:22296219

  5. Mechanism of Disruption of the Amt-GlnK Complex by PII-Mediated Sensing of 2-Oxoglutarate

    PubMed Central

    Maier, Sarah; Schleberger, Paula; Lü, Wei; Wacker, Tobias; Pflüger, Tobias; Litz, Claudia; Andrade, Susana L. A.

    2011-01-01

    GlnK proteins regulate the active uptake of ammonium by Amt transport proteins by inserting their regulatory T-loops into the transport channels of the Amt trimer and physically blocking substrate passage. They sense the cellular nitrogen status through 2-oxoglutarate, and the energy level of the cell by binding both ATP and ADP with different affinities. The hyperthermophilic euryarchaeon Archaeoglobus fulgidus possesses three Amt proteins, each encoded in an operon with a GlnK ortholog. One of these proteins, GlnK2 was recently found to be incapable of binding 2-OG, and in order to understand the implications of this finding we conducted a detailed structural and functional analysis of a second GlnK protein from A. fulgidus, GlnK3. Contrary to Af-GlnK2 this protein was able to bind both ATP/2-OG and ADP to yield inactive and functional states, respectively. Due to the thermostable nature of the protein we could observe the exact positioning of the notoriously flexible T-loops and explain the binding behavior of GlnK proteins to their interaction partner, the Amt proteins. A thermodynamic analysis of these binding events using microcalorimetry evaluated by microstate modeling revealed significant differences in binding cooperativity compared to other characterized PII proteins, underlining the diversity and adaptability of this class of regulatory signaling proteins. PMID:22039461

  6. Point mutation Gln121-Arg increased temperature optima of Bacillus lipase (1.4 subfamily) by fifteen degrees.

    PubMed

    Goomber, Shelly; Kumar, Rakesh; Singh, Ranvir; Mishra, Neelima; Kaur, Jagdeep

    2016-07-01

    Small molecular weight Bacillus lipases are industrially attractive because of its alkaline optimum pH, broad substrate specificity and production in high yield by overexpression both in Escherichia coli and Bacillus subtilis. Its major limitation of being mesophilic in nature is constantly targeted by laboratory evolution studies. Herein metagenomically isolated Bacillus LipJ was randomly evolved by error prone PCR and library of variants were screened for enhanced thermostability. Point mutant Gln121Arg was extensively characterized and it showed dramatic shift of Temp. opt to 50°C compared to 37°C for parent enzyme. Thermostability studies at 45°C and 50°C determined six fold increase in half life for point variant Gln121Arg compared to LipJ. Circular dichroism (CD) and tryptophan fluorescence study established enhanced thermostability of Gln121Arg. Specific activity of point variant Gln121Arg was comparable to wild type with increased substrate affinity (Km reduced). Reduced kcat for variant Gln121Arg infer that kinetic and catalytic efficiency of mutant was compromised. Structural implications by homolog modelling predicted Gln121 to be placed within longest loop of the structure at surface. Localization of loop due to additional polar interactions by Arg121 to protein core defines molecular basis of enhanced thermostability of random point variant Gln121Arg. PMID:27083848

  7. Comparative genome analysis of central nitrogen metabolism and its control by GlnR in the class Bacilli

    PubMed Central

    2012-01-01

    Background The assimilation of nitrogen in bacteria is achieved through only a few metabolic conversions between alpha-ketoglutarate, glutamate and glutamine. The enzymes that catalyze these conversions are glutamine synthetase, glutaminase, glutamate dehydrogenase and glutamine alpha-ketoglutarate aminotransferase. In low-GC Gram-positive bacteria the transcriptional control over the levels of the related enzymes is mediated by four regulators: GlnR, TnrA, GltC and CodY. We have analyzed the genomes of all species belonging to the taxonomic families Bacillaceae, Listeriaceae, Staphylococcaceae, Lactobacillaceae, Leuconostocaceae and Streptococcaceae to determine the diversity in central nitrogen metabolism and reconstructed the regulation by GlnR. Results Although we observed a substantial difference in the extent of central nitrogen metabolism in the various species, the basic GlnR regulon was remarkably constant and appeared not affected by the presence or absence of the other three main regulators. We found a conserved regulatory association of GlnR with glutamine synthetase (glnRA operon), and the transport of ammonium (amtB-glnK) and glutamine/glutamate (i.e. via glnQHMP, glnPHQ, gltT, alsT). In addition less-conserved associations were found with, for instance, glutamate dehydrogenase in Streptococcaceae, purine catabolism and the reduction of nitrite in Bacillaceae, and aspartate/asparagine deamination in Lactobacillaceae. Conclusions Our analyses imply GlnR-mediated regulation in constraining the import of ammonia/amino-containing compounds and the production of intracellular ammonia under conditions of high nitrogen availability. Such a role fits with the intrinsic need for tight control of ammonia levels to limit futile cycling. PMID:22607086

  8. The Synechococcus Strain PCC 7942 glnN Product (Glutamine Synthetase III) Helps Recovery from Prolonged Nitrogen Chlorosis

    PubMed Central

    Sauer, Jörg; Dirmeier, Ulrike; Forchhammer, Karl

    2000-01-01

    We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacterium Synechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression of glnN is impaired in NtcA- and PII-deficient mutants. The only parameter which was negatively affected in the glnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen. PMID:10986271

  9. The Synechococcus strain PCC 7942 glnN product (glutamine synthetase III) helps recovery from prolonged nitrogen chlorosis.

    PubMed

    Sauer, J; Dirmeier, U; Forchhammer, K

    2000-10-01

    We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacterium Synechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression of glnN is impaired in NtcA- and P(II)-deficient mutants. The only parameter which was negatively affected in the glnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen. PMID:10986271

  10. Arabidopsis thaliana GLN2-Encoded Glutamine Synthetase Is Dual Targeted to Leaf Mitochondria and Chloroplasts

    PubMed Central

    Taira, Masakazu; Valtersson, Ulrika; Burkhardt, Brad; Ludwig, Robert A.

    2004-01-01

    In higher plants, photorespiratory Gly oxidation in leaf mitochondria yields ammonium in large amounts. Mitochondrial ammonium must somehow be recovered as glutamate in chloroplasts. As the first step in that recovery, we report glutamine synthetase (GS) activity in highly purified Arabidopsis thaliana mitochondria isolated from light-adapted leaf tissue. Leaf mitochondrial GS activity is further induced in response to either physiological CO2 limitation or transient darkness. Historically, whether mitochondria are fully competent for oxidative phosphorylation in actively photorespiring leaves has remained uncertain. Here, we report that light-adapted, intact, leaf mitochondria supplied with Gly as sole energy source are fully competent for oxidative phosphorylation. Purified intact mitochondria efficiently use Gly oxidation (as sole energy, NH3, and CO2 source) to drive conversion of l-Orn to l-citrulline, an ATP-dependent process. An A. thaliana genome-wide search for nuclear gene(s) encoding mitochondrial GS activity yielded a single candidate, GLN2. Stably transgenic A. thaliana ecotype Columbia plants expressing a p35S∷GLN2∷green fluorescent protein (GFP) chimeric reporter were constructed. When observed by laser scanning confocal microscopy, leaf mesophyll and epidermal tissue of transgenic plants showed punctate GFP fluorescence that colocalized with mitochondria. In immunoblot experiments, a 41-kD chimeric GLN2∷GFP protein was present in both leaf mitochondria and chloroplasts of these stably transgenic plants. Therefore, the GLN2 gene product, heretofore labeled plastidic GS-2, functions in both leaf mitochondria and chloroplasts to faciliate ammonium recovery during photorespiration. PMID:15273293

  11. The quantum Casimir operators of {U}_q{(\\mathfrak {gl}_{n})} and their eigenvalues

    NASA Astrophysics Data System (ADS)

    Li, Junbo

    2010-08-01

    We show that the quantum Casimir operators of the quantum linear group constructed in early work of Bracken, Gould and Zhang together with one obvious central element generate the entire center of {U}_q{(\\mathfrak {gl}_{n})}. As a byproduct of the proof, we obtain intriguing new formulae for eigenvalues of these quantum Casimir operators, which are expressed in terms of the characters of a class of finite-dimensional irreducible representations of the classical general linear algebra.

  12. Analytic first derivatives for a spin-adapted open-shell coupled cluster theory: Evaluation of first-order electrical properties

    SciTech Connect

    Datta, Dipayan Gauss, Jürgen

    2014-09-14

    An analytic scheme is presented for the evaluation of first derivatives of the energy for a unitary group based spin-adapted coupled cluster (CC) theory, namely, the combinatoric open-shell CC (COSCC) approach within the singles and doubles approximation. The widely used Lagrange multiplier approach is employed for the derivation of an analytical expression for the first derivative of the energy, which in combination with the well-established density-matrix formulation, is used for the computation of first-order electrical properties. Derivations of the spin-adapted lambda equations for determining the Lagrange multipliers and the expressions for the spin-free effective density matrices for the COSCC approach are presented. Orbital-relaxation effects due to the electric-field perturbation are treated via the Z-vector technique. We present calculations of the dipole moments for a number of doublet radicals in their ground states using restricted open-shell Hartree-Fock (ROHF) and quasi-restricted HF (QRHF) orbitals in order to demonstrate the applicability of our analytic scheme for computing energy derivatives. We also report calculations of the chlorine electric-field gradients and nuclear quadrupole-coupling constants for the CCl, CH{sub 2}Cl, ClO{sub 2}, and SiCl radicals.

  13. Orbital-optimized opposite-spin scaled second order correlation: An economical method to improve the description of open-shell molecules

    SciTech Connect

    Lochan, Rohini C.; Head-Gordon, Martin

    2007-01-01

    Coupled cluster methods based on Brueckner orbitals are well-known to resolve the problems of symmetry-breaking and spin-contamination that are often associated with Hartree-Fock orbitals. However their computational cost is large enough to prevent application to large molecules. Here they present a simple approximation where the orbitals are optimized with the mean-field energy plus a correlation energy taken as the opposite-spin component of the second order many-body correlation energy, scaled by an empirically chosen parameter (recommended as 1.2 for general applications). This optimized 2nd order opposite spin (abbreviated as O2) method requires fourth order computation on each orbital iteration. O2 is shown to yield predictions of structure and frequencies for closed shell molecules that are very similar to scaled second order Moller-Plesset methods. However it yields substantial improvements for open shell molecules, where problems with spin-contamination and symmetry breaking are shown to be greatly reduced.

  14. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: application to transition metal L-edge X-ray absorption spectroscopy.

    PubMed

    Roemelt, Michael; Maganas, Dimitrios; DeBeer, Serena; Neese, Frank

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S' = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS = S,..., -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory∕ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  15. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Roemelt, Michael; Maganas, Dimitrios; DeBeer, Serena; Neese, Frank

    2013-05-01

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S' = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS = S, …, -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  16. Characterization of a Glutamate Transporter Operon, glnQHMP, in Streptococcus mutans and Its Role in Acid Tolerance▿ †

    PubMed Central

    Krastel, Kirsten; Senadheera, Dilani B.; Mair, Richard; Downey, Jennifer S.; Goodman, Steven D.; Cvitkovitch, Dennis G.

    2010-01-01

    Glutamate contributes to the acid tolerance response (ATR) of many Gram-negative and Gram-positive bacteria, but its role in the ATR of the oral bacterium Streptococcus mutans is unknown. This study describes the discovery and characterization of a glutamate transporter operon designated glnQHMP (Smu.1519 to Smu.1522) and investigates its potential role in acid tolerance. Deletion of glnQHMP resulted in a 95% reduction in transport of radiolabeled glutamate compared to the wild-type UA159 strain. The addition of glutamate to metabolizing UA159 cells resulted in an increased production of acidic end products, whereas the glnQHMP mutant produced less lactic acid than UA159, suggesting a link between glutamate metabolism and acid production and possible acid tolerance. To investigate this possibility, we conducted a microarray analysis with glutamate and under pH 5.5 and pH 7.5 conditions which showed that expression of the glnQHMP operon was downregulated by both glutamate and mild acid. We also measured the growth kinetics of UA159 and its glnQHMP-negative derivative at pH 5.5 and found that the mutant doubled at a much slower rate than the parent strain but survived at pH 3.5 significantly better than the wild type. Taken together, these findings support the involvement of the glutamate transporter operon glnQHMP in the acid tolerance response in S. mutans. PMID:20023025

  17. XRCC1 Arg194Trp and Arg399Gln polymorphisms and arsenic methylation capacity are associated with urothelial carcinoma

    SciTech Connect

    Chiang, Chien-I; Huang, Ya-Li; Chen, Wei-Jen; Shiue, Horng-Sheng; Huang, Chao-Yuan; Pu, Yeong-Shiau; Lin, Ying-Chin; Hsueh, Yu-Mei

    2014-09-15

    The association between DNA repair gene polymorphisms and bladder cancer has been widely studied. However, few studies have examined the correlation between urothelial carcinoma (UC) and arsenic or its metabolites. The aim of this study was to examine the association between polymorphisms of the DNA repair genes, XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln, with urinary arsenic profiles and UC. To this end, we conducted a hospital-based case–control study with 324 UC patients and 647 age- and gender-matched non-cancer controls. Genomic DNA was used to examine the genotype of XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln by PCR-restriction fragment length polymorphism analysis (PCR-RFLP). Urinary arsenic profiles were measured by high performance liquid chromatography (HPLC) linked with hydride generator and atomic absorption spectrometry. The XRCC1 399 Gln/Gln and 194 Arg/Trp and Trp/Trp genotypes were significantly related to UC, and the odds ratio (OR) and 95% confidence interval (95%CI) were 1.68 (1.03–2.75) and 0.66 (0.48–0.90), respectively. Participants with higher total urinary arsenic levels, a higher percentage of inorganic arsenic (InAs%) and a lower percentage of dimethylarsinic acid (DMA%) had a higher OR of UC. Participants carrying XRCC1 risk diplotypes G-C/G-C, A-C/A-C, and A-T/G-T, and who had higher total arsenic levels, higher InAs%, or lower DMA% compared to those with other XRCC1 diplotypes had a higher OR of UC. Our results suggest that the XRCC1 399 Gln/Gln and 194 Arg/Arg DNA repair genes play an important role in poor arsenic methylation capacity, thereby increasing the risk of UC in non-obvious arsenic exposure areas. - Highlights: • The XRCC1 399Gln/Gln genotype was significantly associated with increased OR of UC. • The XRCC1 194 Arg/Trp and Trp/Trp genotype had a significantly decreased OR of UC. • Combined effect of the XRCC1 genotypes and poor arsenic methylation capacity on

  18. Generalized mean-field approach to simulate the dynamics of large open spin ensembles with long range interactions

    NASA Astrophysics Data System (ADS)

    Krämer, Sebastian; Ritsch, Helmut

    2015-12-01

    We numerically study the collective coherent and dissipative dynamics in spin lattices with long range interactions in one, two and three dimensions. For generic geometric configurations with a small spin number, which are fully solvable numerically, we show that a dynamical mean-field approach based upon a spatial factorization of the density operator often gives a surprisingly accurate representation of the collective dynamics. Including all pair correlations at any distance in the spirit of a second order cumulant expansion improves the numerical accuracy by at least one order of magnitude. We then apply this truncated expansion method to simulate large numbers of spins from about ten in the case of the full quantum model, a few thousand, if all pair correlations are included, up to several ten-thousands in the mean-field approximation. We find collective modifications of the spin dynamics in surprisingly large system sizes. In 3D, the mutual interaction strength does not converge to a desired accuracy within the maximum system sizes we can currently implement. Extensive numerical tests help in identifying interaction strengths and geometric configurations where our approximations perform well and allow us to state fairly simple error estimates. By simulating systems of increasing size we show that in one and two dimensions we can include as many spins as needed to capture the properties of infinite size systems with high accuracy. As a practical application our approach is well suited to provide error estimates for atomic clock setups or super radiant lasers using magic wavelength optical lattices.

  19. Relative Rates of Amino Acid Import via the ABC Transporter GlnPQ Determine the Growth Performance of Lactococcus lactis

    PubMed Central

    Fulyani, Faizah; Schuurman-Wolters, Gea K.; Slotboom, Dirk-Jan

    2015-01-01

    ABSTRACT The GlnPQ transporter from Lactococcus lactis has the remarkable feature of having two substrate-binding domains (SBDs) fused to the N terminus of the transmembrane domain (TMD), and thus four SBDs are present in the homodimeric complex. Although X-ray structures and ligand binding data are available for both SBDs, little is known of how different amino acids compete with each other for transport via GlnPQ. Here we show GlnPQ has a broader substrate specificity than previously thought, with the ability to take up asparagine, glutamine, and glutamic acid, albeit via different routes and with different affinities. Asparagine and glutamine compete with each other at the level of binding to SBD1 and SBD2 (with differences in dissociation constant), but at the same time SBD1 and SBD2 compete with each other at the level of interaction with the translocator domain (with differences in affinity constant and rate of transport). Although glutamine transport via SBD1 is outcompeted by physiological concentrations of asparagine, SBD2 ensures high rates of import of the essential amino acid glutamine. Taken together, this study demonstrates that even in the presence of competing asparagine concentrations, GlnPQ has a high capacity to transport glutamine, which matches the high needs of the cell for glutamine and glutamate. IMPORTANCE GlnPQ is an ATP-binding cassette (ABC) transporter for glutamine, glutamic acid, and asparagine. The system is essential in various Gram-positive bacteria, including L. lactis and several pathogens. Here we show how the amino acids compete with each other for binding to the multiple SBDs of GlnPQ and how these SBDs compete with each other for substrate delivery to the transporter. Overall, our results show that GlnPQ has evolved to transport diverse substrates via different paths and to optimally acquire the abundant and essential amino acid glutamine. PMID:26553850

  20. Spectroscopic Identification of Cyclic Imide b2-Ions from Peptides Containing Gln and Asn Residues

    NASA Astrophysics Data System (ADS)

    Grzetic, Josipa; Oomens, Jos

    2013-08-01

    In mass-spectrometry based peptide sequencing, formation of b- and y-type fragments by cleavage of the amide C-N bond constitutes the main dissociation pathway of protonated peptides under low-energy collision induced dissociation (CID). The structure of the b 2 fragment ion from peptides containing glutamine (Gln) and asparagine (Asn) residues is investigated here by infrared ion spectroscopy using the free electron laser FELIX. The spectra are compared with theoretical spectra calculated using density functional theory for different possible isomeric structures as well as to experimental spectra of synthesized model systems. The spectra unambiguously show that the b2-ions do not possess the common oxazolone structure, nor do they possess the alternative diketopiperazine structure. Instead, cyclic imide structures are formed through nucleophilic attack by the amide nitrogen atom of the Gln and Asn side chains. The alternative pathway involving nucleophilic attack from the side-chain amide oxygen atom leading to cyclic isoimide structures, which had been suggested by several authors, can clearly be excluded based on the present IR spectra. This mechanism is perhaps surprising as the amide oxygen atom is considered to be the better nucleophile; however, computations show that the products formed via attack by the amide nitrogen are considerably lower in energy. Hence, b2-ions with Asn or Gln in the second position form structures with a five-membered succinimide or a six-membered glutarimide ring, respectively. b2-Ions formed from peptides with Asn in the first position are spectroscopically shown to possess the classical oxazolone structure.

  1. TLR7 Gln11Leu single nucleotide polymorphism and susceptibility to cutaneous melanoma

    PubMed Central

    ELEFANTI, LISA; SACCO, GIORGIA; STAGNI, CAMILLA; RASTRELLI, MARCO; MENIN, CHIARA; RUSSO, IRENE; ALAIBAC, MAURO

    2016-01-01

    Cutaneous melanoma is a life-threatening skin cancer. Its incidence is rapidly increasing, and early diagnosis is the main factor able to improve its poor prognosis. Toll-like receptors (TLRs) are transmembrane glycoproteins that recognize pathogen- and damage-associated molecular patterns, against which TLRs activate the innate immune response and initiate the adaptive immune response. Genetic variations of these receptors may alter the immune system, and are involved in evolution and susceptibility to various diseases, including cancer. The aim of the present study was to evaluate whether the presence of TLR7 glutamine (Gln) 11 leucine (Leu) polymorphism confers an increased susceptibility to cutaneous melanoma. For that purpose, a case-control study was performed with 182 melanoma cases and 89 controls. To highlight the possible association between the aforementioned polymorphism and the susceptibility to melanoma, 93 cases of single melanoma and 89 cases of multiple primary melanoma (MPM) were compared in the present study. Since the TLR7 gene is localized on the chromosome X, the allelic frequency of the Gln11Leu polymorphism was analyzed separately in males and females. The distribution of allele frequencies between melanoma cases and controls (P=0.245) and between single melanoma and MPM cases (P=0.482) was not significant. Therefore, the present results do not suggest an association between TLR7 Gln11Leu polymorphism and susceptibility to cutaneous melanoma. Further studies are required to analyze the influence of other TLR polymorphisms on the susceptibility to malignant melanoma and the involvement of innate immunity in this malignancy. PMID:27347137

  2. Structural analysis of APOB variants, p.(Arg3527Gln), p.(Arg1164Thr) and p.(Gln4494del), causing Familial Hypercholesterolaemia provides novel insights into variant pathogenicity

    PubMed Central

    Fernández-Higuero, J. A.; Etxebarria, A.; Benito-Vicente, A.; Alves, A. C.; Arrondo, J. L. R.; Ostolaza, H.; Bourbon, M.; Martin, C.

    2015-01-01

    Familial hypercholesterolaemia (FH) is an inherited autosomal dominant disorder resulting from defects in the low-density lipoprotein receptor (LDLR), in the apolipoprotein B (APOB) or in the proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. In the majority of the cases FH is caused by mutations occurring within LDLR, while only few mutations in APOB and PCSK9 have been proved to cause disease. p.(Arg3527Gln) was the first mutation in APOB being identified and characterized. Recently two novel pathogenic APOB variants have been described: p.(Arg1164Thr) and p.(Gln4494del) showing impaired LDLR binding capacity, and diminished LDL uptake. The objective of this work was to analyse the structure of p.(Arg1164Thr) and p.(Gln4494del) variants to gain insight into their pathogenicity. Secondary structure of the human ApoB100 has been investigated by infrared spectroscopy (IR) and LDL particle size both by dynamic light scattering (DLS) and electron microscopy. The results show differences in secondary structure and/or in particle size of p.(Arg1164Thr) and p.(Gln4494del) variants compared with wild type. We conclude that these changes underlie the defective binding and uptake of p.(Arg1164Thr) and p.(Gln4494del) variants. Our study reveals that structural studies on pathogenic variants of APOB may provide very useful information to understand their role in FH disease. PMID:26643808

  3. Asthma: Gln27Glu and Arg16Gly polymorphisms of the beta2-adrenergic receptor gene as risk factors

    PubMed Central

    2014-01-01

    Background Asthma is caused by both environmental and genetic factors. The ADRB2 gene, which encodes the beta 2-adrenergic receptor, is one of the most extensively studied genes with respect to asthma prevalence and severity. The Arg16Gly (+46A > G) and Gln27Glu (+79C > G) polymorphisms in the ADRB2 gene cause changes in the amino acids flanking the receptor ligand site, altering the response to bronchodilators and the risk of asthma through complex pathways. The ADRB2 polymorphisms affect beta-adrenergic bronchodilator action and are a tool to identify at-risk populations. Objective To determine the frequency of these two polymorphisms in allergic asthma patients and healthy subjects and to correlate these data with the occurrence and severity of asthma. Methods Eighty-eight allergic asthma patients and 141 healthy subjects were included in this study. The ADRB2 polymorphisms were analyzed using the amplification-refractory mutation system – polymerase chain reaction (ARMS-PCR) technique. The statistical analysis was performed with the SPSS 21.0 software using the Fisher’s Exact and χ2 tests. Results The ADRB2 polymorphisms were associated with asthma occurrence. The Arg16Arg, Gln27Gln and Gln27Glu genotypes were risk factors; the odds ratios were 6.782 (CI = 3.07 to 16.03), 2.120 (CI = 1.22 to 3.71) and 8.096 (CI = 3.90 to 17.77), respectively. For the Gly16Gly and Glu27Glu genotypes, the odds ratios were 0.312 (CI = 0.17 to 0.56) and 0.084 (CI = 0.04 to 0.17), respectively. The haplotype analysis showed that there were associations between the following groups: Arg16Arg-Gln27Gln (OR = 5.108, CI = 1.82 to 16.37), Gly16Gly-Glu27Glu (OR = 2.816, CI = 1.25 to 6.54), Arg16Gly-Gln27Glu (OR = 0.048, CI = 0.01 to 0.14) and Gly16Gly-Gln27Glu (OR = 0.1036, CI = 0.02 to 0.39). The polymorphism Gln27Glu was associated with asthma severity, as the Gln27Gln genotype was a risk factor for severe asthma (OR

  4. Effects of Ala-Gln feeding strategies on growth, metabolism, and crowding stress resistance of juvenile Cyprinus carpio var. Jian.

    PubMed

    Chen, Xiu-Mei; Guo, Gui-Liang; Sun, Li; Yang, Qiu-Shi; Wang, Gui-Qin; Qin, Gui-Xin; Zhang, Dong-Ming

    2016-04-01

    The present study was conducted to evaluate the effects of different L-alanyl-l-glutamine (Ala-Gln) feeding strategies on the growth performance, metabolism and crowding stress resistance related parameters in juvenile Jian carp (Cyprinus carpio var. Jian) under crowded condition (80 g/L). Juvenile Jian carp (initial weight 26.1 ± 0.6 g) were distributed into five groups which fed with graded concentrations (0% or 1.0%) of Ala-Gln for eight weeks. Control group (I, 0/0) fed with control diet (0% Ala-Gln) throughout the feeding trial. The other four groups employed different control and experimental diet feeding strategies ranging from two weeks control diet fed and two weeks experimental diet (1% Ala-Gln) fed (II, 0/2) to eight weeks experimental diet fed (V, 4/4). Results revealed that Mean weight gain (MEG) under all different feeding strategies of Ala-Gln were significantly higher than that of the control group (p < 0.05), and MEG of group II (201.90%) was even higher than that of group IV (184.70%). Liver glycogen and blood total protein of groups II, III and V were significantly higher than that in groups I and IV (p < 0.05). The highest level of serum thyroxine (10.07 ng/ml), insulin-like growth factor-I (52.40 ng/ml) and insulin (9.73 μ IU/mL) were observed in group V. However, diet supplemented with Ala-Gln did not affect the levels of serum glucose, cortisol and catecholamine in fish. The mRNA expression of GR1a, GR1b and GR2 were also significantly changed in Ala-Gln supplementation groups compared with control group (p < 0.05). After fish intraperitoneally injected with virulent Aeromonas hydrophila, the fish survival rates were significantly increased in all Ala-Gln supplementation groups compared with control group (p < 0.05). Results from the present experiment showed the importance of dietary supplementation of Ala-Gln in benefaction of the growth performance, metabolism and crowding stress resistance in Jian carp breeding. The

  5. The effect of Gly-Gln [ß-endorphin30-31] on morphine-evoked serotonin and GABA efflux in the nucleus accumbens of conscious rats.

    PubMed

    Basaran, Nesrin F; Buyukuysal, R Levent; Sertac Yilmaz, M; Aydin, Sami; Cavun, Sinan; Millington, William R

    2016-08-01

    Glycyl-L-glutamine (Gly-Gln; β-endorphin30-31) is an endogenous dipeptide synthesized through the post-translational processing of β-endorphin1-31. Central Gly-Gln administration inhibits the rewarding properties of morphine and attenuates morphine tolerance, dependence and withdrawal although it does not interfere with morphine analgesia. In an earlier study, we found that Gly-Gln inhibits morphine-induced dopamine efflux in the nucleus accumbens (NAc), consistent with its ability to inhibit morphine reward. To further investigate the mechanism responsible for its central effects we tested whether i.c.v. Gly-Gln administration influences the rise in extracellular serotonin and GABA concentrations evoked by morphine in the NAc. Conscious rats were treated with Gly-Gln (100nmol/5μl) or saline i.c.v. followed, 2min later, by morphine (2.5mg/kg) or saline i.p. and extracellular serotonin and GABA concentrations were analyzed by microdialysis and HPLC. Morphine administration increased extracellular serotonin and GABA concentrations significantly within 20min, as shown previously. Unexpectedly, Gly-Gln also increased extracellular serotonin concentrations significantly in control animals. Combined treatment with Gly-Gln+morphine also elevated extracellular serotonin concentrations although the magnitude of the response did not differ significantly from the effect of Gly-Gln or morphine, given alone suggesting that Gly-Gln suppressed morphine induced serotonin efflux. Gly-Gln abolished the morphine-induced rise in extracellular GABA concentrations but had no effect on extracellular GABA when given alone to otherwise untreated animals. These data show that Gly-Gln stimulates NAc serotonin efflux and, together with earlier studies, support the hypothesis that Gly-Gln inhibits the rewarding effects of morphine by modulating morphine induced dopamine, GABA and serotonin efflux in the NAc. PMID:26861257

  6. Co-Expression of Wild-Type P2X7R with Gln460Arg Variant Alters Receptor Function

    PubMed Central

    Aprile-Garcia, Fernando; Metzger, Michael W.; Paez-Pereda, Marcelo; Stadler, Herbert; Acuña, Matías; Liberman, Ana C.; Senin, Sergio A.; Gerez, Juan; Hoijman, Esteban; Refojo, Damian; Mitkovski, Mišo; Panhuysen, Markus; Stühmer, Walter; Holsboer, Florian; Deussing, Jan M.; Arzt, Eduardo

    2016-01-01

    The P2X7 receptor is a member of the P2X family of ligand-gated ion channels. A single-nucleotide polymorphism leading to a glutamine (Gln) by arginine (Arg) substitution at codon 460 of the purinergic P2X7 receptor (P2X7R) has been associated with mood disorders. No change in function (loss or gain) has been described for this SNP so far. Here we show that although the P2X7R-Gln460Arg variant per se is not compromised in its function, co-expression of wild-type P2X7R with P2X7R-Gln460Arg impairs receptor function with respect to calcium influx, channel currents and intracellular signaling in vitro. Moreover, co-immunoprecipitation and FRET studies show that the P2X7R-Gln460Arg variant physically interacts with P2X7R-WT. Specific silencing of either the normal or polymorphic variant rescues the heterozygous loss of function phenotype and restores normal function. The described loss of function due to co-expression, unique for mutations in the P2RX7 gene so far, explains the mechanism by which the P2X7R-Gln460Arg variant affects the normal function of the channel and may represent a mechanism of action for other mutations. PMID:26986975

  7. Nitrogen regulator GlnR controls uptake and utilization of non-phosphotransferase-system carbon sources in actinomycetes.

    PubMed

    Liao, Cheng-Heng; Yao, Lili; Xu, Ya; Liu, Wei-Bing; Zhou, Ying; Ye, Bang-Ce

    2015-12-22

    The regulatory mechanisms underlying the uptake and utilization of multiple types of carbohydrates in actinomycetes remain poorly understood. In this study, we show that GlnR (central regulator of nitrogen metabolism) serves as a universal regulator of nitrogen metabolism and plays an important, previously unknown role in controlling the transport of non-phosphotransferase-system (PTS) carbon sources in actinomycetes. It was observed that GlnR can directly interact with the promoters of most (13 of 20) carbohydrate ATP-binding cassette (ABC) transporter loci and can activate the transcription of these genes in response to nitrogen availability in industrial, erythromycin-producing Saccharopolyspora erythraea. Deletion of the glnR gene resulted in severe growth retardation under the culture conditions used, with select ABC-transported carbohydrates (maltose, sorbitol, mannitol, cellobiose, trehalose, or mannose) used as the sole carbon source. Furthermore, we found that GlnR-mediated regulation of carbohydrate transport was highly conserved in actinomycetes. These results demonstrate that GlnR serves a role beyond nitrogen metabolism, mediating critical functions in carbon metabolism and crosstalk of nitrogen- and carbon-metabolism pathways in response to the nutritional states of cells. These findings provide insights into the molecular regulation of transport and metabolism of non-PTS carbohydrates and reveal potential applications for the cofermentation of biomass-derived sugars in the production of biofuels and bio-based chemicals. PMID:26644570

  8. Arg287Gln VARIANT OF EPHX2 AND EPOXYEICOSATRIENOIC ACIDS ARE ASSOCIATED WITH INSULIN SENSITIVITY IN HUMANS

    PubMed Central

    Ramirez, Claudia E.; Shuey, Megan M.; Milne, Ginger L.; Gilbert, Kimberly; Hui, Nian; Yu, Chang; Luther, James M.; Brown, Nancy J.

    2014-01-01

    Epoxyeicosatrienoic acids (EETs) protect against the development of insulin resistance in rodents. EETs are hydrolyzed to less biologically active diols by soluble epoxide hydrolase (encoded for by EPHX2). Functional variants of EPHX2 encode for enzymes with increased (Lys55Arg) or decreased (Arg287Gln) hydrolase activity. This study tested the hypothesis that variants of EPHX2 are associated with insulin sensitivity or secretion in humans. Subjects participating in metabolic phenotyping studies were genotyped. Eighty-five subjects underwent hyperglycemic clamps. There was no relationship between the Lys55Arg genotype and insulin sensitivity or secretion. In contrast, the EPHX2 287Gln variant was associated with higher insulin sensitivity index (p=0.019 controlling for body mass index and metabolic syndrome). Also, there was an interactive effect of EPHX2 Arg287Gln genotype and body mass index on insulin sensitivity index (p=0.029). There was no relationship between EPHX2 Arg287Gln genotype and acute or late-phase glucose-stimulated insulin secretion, but disposition index was higher in 287Gln carriers compared with Arg/Arg (p=0.022). Plasma EETs correlated with insulin sensitivity index (r=0.64, p=0.015 for total EETs) and were decreased in the metabolic syndrome. A genetic variant that results in decreased soluble epoxide hydrolase activity is associated with increased insulin sensitivity, as are higher EETs. PMID:25173047

  9. Gln40 deamidation blocks structural reconfiguration and activation of SCF ubiquitin ligase complex by Nedd8

    PubMed Central

    Yu, Clinton; Mao, Haibin; Novitsky, Eric J.; Tang, Xiaobo; Rychnovsky, Scott D.; Zheng, Ning; Huang, Lan

    2015-01-01

    The full enzymatic activity of the cullin-RING ubiquitin ligases (CRLs) requires a ubiquitin-like protein (that is, Nedd8) modification. By deamidating Gln40 of Nedd8 to glutamate (Q40E), the bacterial cycle-inhibiting factor (Cif) family is able to inhibit CRL E3 activities, thereby interfering with cellular functions. Despite extensive structural studies on CRLs, the molecular mechanism by which Nedd8 Gln40 deamidation affects CRL functions remains unclear. We apply a new quantitative cross-linking mass spectrometry approach to characterize three different types of full-length human Cul1–Rbx1 complexes and uncover major Nedd8-induced structural rearrangements of the CRL1 catalytic core. More importantly, we find that those changes are not induced by Nedd8(Q40E) conjugation, indicating that the subtle change of a single Nedd8 amino acid is sufficient to revert the structure of the CRL catalytic core back to its unmodified form. Our results provide new insights into how neddylation regulates the conformation and activity of CRLs. PMID:26632597

  10. No association of LEPR Gln223Arg polymorphism with leptin, obesity or metabolic disturbances in children

    PubMed Central

    2009-01-01

    Objective The aim of the study was to investigate whether the Gln223Arg in the leptin receptor may influence body weight, leptin concentration, and metabolic parameters in children. Materials and methods The examined group included 101 obese children (58 girls and 43 boys) with BMI 31.41 ± 5.03 kg/m2 (BMI ≥ 2 SDS) and the control group consisted of 41 children with BMI 20.0 ± 0.80 kg/m2 (BMI < 1.0 SDS). Polymorphism identification was performed in total genomic DNA using PCRRFLP method. Results The distribution of genotypes LEPR was the following: in the obese group: AA - 20.8%, AG-55.4%, GG-23.8%; in the control group AA-31.7%, AG-53.65%, GG-14.65%. Comparative analyses between AA homozygous children and carriers of G alleles did not confirm any relation between the analyzed polymorphism and BMI, leptin concentrations, and metabolic disturbances in children with obesity. Conclusion In children with obesity we did not observe association of the LEPR Gln223Arg gene polymorphism with obesity, leptin, insulin resistance, and metabolic abnormalities. PMID:20156757

  11. Post-translational Serine/Threonine Phosphorylation and Lysine Acetylation: A Novel Regulatory Aspect of the Global Nitrogen Response Regulator GlnR in S. coelicolor M145

    PubMed Central

    Amin, Rafat; Franz-Wachtel, Mirita; Tiffert, Yvonne; Heberer, Martin; Meky, Mohamed; Ahmed, Yousra; Matthews, Arne; Krysenko, Sergii; Jakobi, Marco; Hinder, Markus; Moore, Jane; Okoniewski, Nicole; Maček, Boris; Wohlleben, Wolfgang; Bera, Agnieszka

    2016-01-01

    Soil-dwelling Streptomyces bacteria such as S.coelicolor have to constantly adapt to the nitrogen (N) availability in their habitat. Thus, strict transcriptional and post-translational control of the N-assimilation is fundamental for survival of this species. GlnR is a global response regulator that controls transcription of the genes related to the N-assimilation in S. coelicolor and other members of the Actinomycetales. GlnR represents an atypical orphan response regulator that is not activated by the phosphorylation of the conserved aspartate residue (Asp 50). We have applied transcriptional analysis, LC-MS/MS analysis and electrophoretic mobility shift assays (EMSAs) to understand the regulation of GlnR in S. coelicolor M145. The expression of glnR and GlnR-target genes was revisited under four different N-defined conditions and a complex N-rich condition. Although, the expression of selected GlnR-target genes was strongly responsive to changing N-concentrations, the glnR expression itself was independent of the N-availability. Using LC-MS/MSanalysis we demonstrated that GlnR was post-translationally modified. The post-translational modifications of GlnR comprise phosphorylation of the serine/threonine residues and acetylation of lysine residues. In the complex N-rich medium GlnR was phosphorylated on six serine/threonine residues and acetylated on one lysine residue. Under defined N-excess conditions only two phosphorylated residues were detected whereas under defined N-limiting conditions no phosphorylation was observed. GlnR phosphorylation is thus clearly correlated with N-rich conditions. Furthermore, GlnR was acetylated on four lysine residues independently of the N-concentration in the defined media and on only one lysine residue in the complex N-rich medium. Using EMSAs we demonstrated that phosphorylation inhibited the binding of GlnR to its targets genes, whereas acetylation had little influence on the formation of GlnR-DNA complex. This study clearly

  12. Post-translational Serine/Threonine Phosphorylation and Lysine Acetylation: A Novel Regulatory Aspect of the Global Nitrogen Response Regulator GlnR in S. coelicolor M145.

    PubMed

    Amin, Rafat; Franz-Wachtel, Mirita; Tiffert, Yvonne; Heberer, Martin; Meky, Mohamed; Ahmed, Yousra; Matthews, Arne; Krysenko, Sergii; Jakobi, Marco; Hinder, Markus; Moore, Jane; Okoniewski, Nicole; Maček, Boris; Wohlleben, Wolfgang; Bera, Agnieszka

    2016-01-01

    Soil-dwelling Streptomyces bacteria such as S.coelicolor have to constantly adapt to the nitrogen (N) availability in their habitat. Thus, strict transcriptional and post-translational control of the N-assimilation is fundamental for survival of this species. GlnR is a global response regulator that controls transcription of the genes related to the N-assimilation in S. coelicolor and other members of the Actinomycetales. GlnR represents an atypical orphan response regulator that is not activated by the phosphorylation of the conserved aspartate residue (Asp 50). We have applied transcriptional analysis, LC-MS/MS analysis and electrophoretic mobility shift assays (EMSAs) to understand the regulation of GlnR in S. coelicolor M145. The expression of glnR and GlnR-target genes was revisited under four different N-defined conditions and a complex N-rich condition. Although, the expression of selected GlnR-target genes was strongly responsive to changing N-concentrations, the glnR expression itself was independent of the N-availability. Using LC-MS/MSanalysis we demonstrated that GlnR was post-translationally modified. The post-translational modifications of GlnR comprise phosphorylation of the serine/threonine residues and acetylation of lysine residues. In the complex N-rich medium GlnR was phosphorylated on six serine/threonine residues and acetylated on one lysine residue. Under defined N-excess conditions only two phosphorylated residues were detected whereas under defined N-limiting conditions no phosphorylation was observed. GlnR phosphorylation is thus clearly correlated with N-rich conditions. Furthermore, GlnR was acetylated on four lysine residues independently of the N-concentration in the defined media and on only one lysine residue in the complex N-rich medium. Using EMSAs we demonstrated that phosphorylation inhibited the binding of GlnR to its targets genes, whereas acetylation had little influence on the formation of GlnR-DNA complex. This study clearly

  13. The Role of Gln61 in HRas GTP Hydrolysis: A Quantum Mechanics/Molecular Mechanics Study

    PubMed Central

    Martín-García, Fernando; Mendieta-Moreno, Jesús Ignacio; López-Viñas, Eduardo; Gómez-Puertas, Paulino; Mendieta, Jesús

    2012-01-01

    Activation of the water molecule involved in GTP hydrolysis within the HRas⋅RasGAP system is analyzed using a tailored approach based on hybrid quantum mechanics/molecular mechanics (QM/MM) simulation. A new path emerges: transfer of a proton from the attacking water molecule to a second water molecule, then a different proton is transferred from this second water molecule to the GTP. Gln61 will stabilize the transient OH− and H3O+ molecules thus generated. This newly proposed mechanism was generated by using, for the first time to our knowledge, the entire HRas-RasGAP protein complex in a QM/MM simulation context. It also offers a rational explanation for previous experimental results regarding the decrease of GTPase rate found in the HRas Q61A mutant and the increase exhibited by the HRas Q61E mutant. PMID:22225809

  14. Association of a functional polymorphism (Gln261Arg) in 12-lipoxygenase with breast cancer

    PubMed Central

    PRASAD, VIDUDALA V.T.S.; KOLLI, PADMA; MOGANTI, DIVYA

    2011-01-01

    The overexpression of arachidonyl lipoxygenase-12 (ALOX12) in breast cancer has been reported. Hence, we examined whether a non-synonymous polymorphism of ALOX12 (mRNA, A835G; Gln261Arg) is associated with breast cancer in females. The polymorphism was detected in genomic DNA by PCR-RFLP. The association between the A835G polymorphism and breast cancer risk was measured by odds ratio (OR) with 95% confidence intervals (CIs) using Fisher's exact test, and differences were considered significant at p<0.05. The frequencies of AA (wild-type), GG (homozygous variant) and AG (heterozygous variant) were 59.5, 0.9 and 39.6% in the controls, and 39.3, 2.5 and 58.2% in the breast cancer cases, respectively. The frequency of the AG genotype was higher in the patients compared to the controls (p<0.0014). The frequency of the GG variant was 2.5 and 0.9% in the cancer subjects and controls, respectively. The relative risk of breast cancer was 2 times greater (OR=2.227) at 95% CI when compared to the relative risk of the heterozygous variant. For the GG genotype, the risk was 4 times greater (OR=4.125) at 95% CI than that of the controls, suggesting a positive association of the AG genotype with the occurrence of breast cancer. The frequencies of the polymorphism were different in different populations. The Arg/Gln and Arg/Arg variants were associated with an increased risk of breast cancer, and the frequencies of the variants differed considerably among various populations. The identification of a gene with links to breast cancer may impact screening, diagnosis and drug development. PMID:22977504

  15. Association of xeroderma pigmentosum group D (Asp312Asn, Lys751Gln) and cytidine deaminase (Lys27Gln, Ala70Thr) polymorphisms with outcome in Chinese non-small cell lung cancer patients treated with cisplatin-gemcitabine.

    PubMed

    Zhou, M; Ding, Y J; Feng, Y; Zhang, Q R; Xiang, Y; Wan, H Y

    2014-01-01

    Xeroderma pigmentosum group D (XPD) plays a key role in the repair of DNA and platinum resistance lesions. Cytidine deaminase (CDA) genes determine the velocity of gemcitabine catalysis. This study aimed to investigate the relationship between XPD and CDA genotypes and outcome in non-small lung cancer (NSCLC) patients. We used polymerase chain reaction-restriction fragment length polymorphism to evaluate genetic polymorphisms of XPD (Asp312Asn and Lys751Gln) and CDA (Lys27Gln and Ala70Thr) in 93 NSCLC patients treated with a cisplatin-gemcitabine regimen. There were no significant correlations between the XPD polymorphisms Asp312Asn and Lys751Gln with clinical benefits (P>0.05). Time to progression (TTP) did not differ between patients with wild type genotypes and those heterozygous for the single nucleotide polymorphism loci of XPD. However, a significant difference was observed in overall survival (OS) between XPD Asp312Asp and XPD Asp312Asn individuals (20.0 vs 12.4 months, P=0.04). Furthermore, the OS of patients with wild type genotypes was longer (20.5 months) than that of patients carrying the XPD 751Lys/Gln polymorphism (11.5 months). No significant differences in TTP or OS were observed in patients carrying different genotypes of CDA Lys27Gln, and no mutations were observed at the CDA Ala70Thr site. These results provide suggestive evidence of a favorable effect for the XPD 312Asp/Asp and XPD 751Lys/Lys genotypes with respect to overall survival rates in platinum-treated NSCLC patients. However, the CDA 27 polymorphism does not appear to affect the efficacy of gemcitabine. PMID:24841663

  16. Structure and thermodynamics of effector molecule binding to the nitrogen signal transduction PII protein GlnZ from Azospirillum brasilense.

    PubMed

    Truan, Daphné; Bjelić, Saša; Li, Xiao-Dan; Winkler, Fritz K

    2014-07-29

    The trimeric PII signal transduction proteins regulate the function of a variety of target proteins predominantly involved in nitrogen metabolism. ATP, ADP and 2-oxoglutarate (2-OG) are key effector molecules influencing PII binding to targets. Studies of PII proteins have established that the 20-residue T-loop plays a central role in effector sensing and target binding. However, the specific effects of effector binding on T-loop conformation have remained poorly documented. We present eight crystal structures of the Azospirillum brasilense PII protein GlnZ, six of which are cocrystallized and liganded with ADP or ATP. We find that interaction with the diphosphate moiety of bound ADP constrains the N-terminal part of the T-loop in a characteristic way that is maintained in ADP-promoted complexes with target proteins. In contrast, the interactions with the triphosphate moiety in ATP complexes are much more variable and no single predominant interaction mode is apparent except for the ternary MgATP/2-OG complex. These conclusions can be extended to most investigated PII proteins of the GlnB/GlnK subfamily. Unlike reported for other PII proteins, microcalorimetry reveals no cooperativity between the three binding sites of GlnZ trimers for any of the three effectors under carefully controlled experimental conditions. PMID:24846646

  17. Leptin receptor polymorphism Gln223Arg (rs1137101) in oral squamous cell carcinoma and potentially malignant oral lesions.

    PubMed

    Domingos, Patrícia Luciana Batista; Farias, Lucyana Conceição; Pereira, Camila Santos; das Graças Pena, Geórgia; Reis, Tatiana Carvalho; Silva, Rosângela Ramos Veloso; Fraga, Carlos Alberto de Carvalho; de Souza, Marcela Gonçalves; Soares, Mariana Batista; Jones, Kimberly Marie; Menezes, Elytania Veiga; Nobre, Sérgio Avelino Mota; Rodrigues Neto, João Felício; de Paula, Alfredo Maurício Batista; Velásquez-Meléndez, Jorge Gustavo; Sena Guimarães, André Luiz

    2014-01-01

    The purpose of this study was to assess the LEPR gene Gln223Arg polymorphism (rs1137101) in oral squamous cell carcinoma (OSCC) and in potentially malignant oral lesions (PMOL) in comparison to normal oral mucosa in a Brazilian population. Smokers (n = 89) were selected from a representative sample of 471 individuals from the general population of Montes Claros, Brazil. Participants were age and gender matched to patients with OSCC (n = 25) and oral epithelial dysplasia (n = 25). We investigated the LEPR Gln223Arg polymorphism (A>G; rs1137101) in these groups. Genotype variants were assessed by RFLP-PCR, using MspI (HPAII) restriction endonuclease. The institutional review board of the Universidade Estadual de Montes Claros approved the study (process number 2667/2011). Written informed consent for this study was obtained from all participants. The GG genotype (Arg223Arg) appears to be the more relevant polymorphic variant in OSCC. It occurred, approximately, twice as frequently in OSCC patients than in the general population. In contrast, the A allele in its homozygosis form (Gln223Gln) is significantly associated with the development of PMOL; 80% of the samples from the PMOL group exhibit AA genotype. Our findings suggest new insights regarding LEPR gene variations in the development of OSCC and PMOL. PMID:26034683

  18. Spin-Orbit Caloritronics

    NASA Astrophysics Data System (ADS)

    Manchon, Aurelien; Ndiaye, Papa Birame; Moon, Jung-Hwan; Lee, Hyun-Woo; Lee, Kyung-Jin

    2014-03-01

    Utilizing spin-orbit coupling to enable the electrical manipulation of ferromagnets has recently attracted a considerable amount of interest. This spin-orbit torque appears in magnetic systems displaying inversion symmetry breaking. Another adjacent emerging topic, spin caloritronics, aims at exploiting magnonic spin currents driven by temperature gradients, allowing for the transmission of information and the control of magnetic domain walls. In this work, we demonstrate that a magnon flow generates torques on the local magnetization when subjected to Dzyaloshinskii-Moriya interaction (DMI) just as an electron flow generates torques when submitted to Rashba interaction. A direct consequence is the capability to control the magnetization direction of a homogeneous ferromagnet by applying a temperature gradient or local RF excitations. Merging the spin-orbit torques with spin caloritronics is rendered possible by the emergence of DMI in magnetic materials and opens promising avenues in the development of chargeless information technology.

  19. Spin guides and spin splitters: waveguide analogies in one-dimensional spin chains.

    PubMed

    Makin, Melissa I; Cole, Jared H; Hill, Charles D; Greentree, Andrew D

    2012-01-01

    Here we show a mapping between waveguide theory and spin-chain transport, opening an alternative approach to solid-state quantum information transport. By applying temporally varying control profiles to a spin chain, we design a virtual waveguide or "spin guide" to conduct spin excitations along defined space-time trajectories of the chain. We show that the concepts of confinement, adiabatic bend loss, and beam splitting can be mapped from optical waveguide theory to spin guides, and hence to "spin splitters." Importantly, the spatial scale of applied control pulses is required to be large compared to the interspin spacing, thereby allowing the design of scalable control architectures. PMID:22304287

  20. Atypical OmpR/PhoB Subfamily Response Regulator GlnR of Actinomycetes Functions as a Homodimer, Stabilized by the Unphosphorylated Conserved Asp-focused Charge Interactions*

    PubMed Central

    Lin, Wei; Wang, Ying; Han, Xiaobiao; Zhang, Zilong; Wang, Chengyuan; Wang, Jin; Yang, Huaiyu; Lu, Yinhua; Jiang, Weihong; Zhao, Guo-Ping; Zhang, Peng

    2014-01-01

    The OmpR/PhoB subfamily protein GlnR of actinomycetes is an orphan response regulator that globally coordinates the expression of genes related to nitrogen metabolism. Biochemical and genetic analyses reveal that the functional GlnR from Amycolatopsis mediterranei is unphosphorylated at the potential phosphorylation Asp50 residue in the N-terminal receiver domain. The crystal structure of this receiver domain demonstrates that it forms a homodimer through the α4-β5-α5 dimer interface highly similar to the phosphorylated typical response regulator, whereas the so-called “phosphorylation pocket” is not conserved, with its space being occupied by an Arg52 from the β3-α3 loop. Both in vitro and in vivo experiments confirm that GlnR forms a functional homodimer via its receiver domain and suggest that the charge interactions of Asp50 with the highly conserved Arg52 and Thr9 in the receiver domain may be crucial in maintaining the proper conformation for homodimerization, as also supported by molecular dynamics simulations of the wild type GlnR versus the deficient mutant GlnR(D50A). This model is backed by the distinct phenotypes of the total deficient GlnR(R52A/T9A) double mutant versus the single mutants of GlnR (i.e. D50N, D50E, R52A and T9A), which have only minor effects upon both dimerization and physiological function of GlnR in vivo, albeit their DNA binding ability is weakened compared with that of the wild type. By integrating the supportive data of GlnRs from the model Streptomyces coelicolor and the pathogenic Mycobacterium tuberculosis, we conclude that the actinomycete GlnR is atypical with respect to its unphosphorylated conserved Asp residue being involved in the critical Arg/Asp/Thr charge interactions, which is essential for maintaining the biologically active homodimer conformation. PMID:24733389

  1. XRCC1 Arg399Gln was associated with repair capacity for DNA damage induced by occupational chromium exposure

    PubMed Central

    2012-01-01

    Background Occupational chromium exposure may induce DNA damage and lead to lung cancer and other work-related diseases. DNA repair gene polymorphisms, which may alter the efficiency of DNA repair, thus may contribute to genetic susceptibility of DNA damage. The aim of this study was to test the hypothesis that the genetic variations of 9 major DNA repair genes could modulate the hexavalent chromium (Cr (VI))-induced DNA damage. Findings The median (P25-P75) of Olive tail moment was 0.93 (0.58–1.79) for individuals carrying GG genotype of XRCC1 Arg399Gln (G/A), 0.73 (0.46–1.35) for GA heterozygote and 0.50 (0.43–0.93) for AA genotype. Significant difference was found among the subjects with three different genotypes (P = 0.048) after adjusting the confounding factors. The median of Olive tail moment of the subjects carrying A allele (the genotypes of AA and GA) was 0.66 (0.44–1.31), which was significantly lower than that of subjects with GG genotype (P = 0.043). The A allele conferred a significantly reduced risk of DNA damage with the OR of 0.39 (95% CI: 0.15–0.99, P = 0.048). No significant association was found between the XRCC1Arg194Trp, ERCC1 C8092A, ERCC5 His1104Asp, ERCC6 Gly399Asp, GSTP1 Ile105Val, OGG1 Ser326Cys, XPC Lys939Gln, XPD Lys751Gln and DNA damage. Conclusion The polymorphism of Arg399Gln in XRCC1 was associated with the Cr (VI)- induced DNA damage. XRCC1 Arg399Gln may serve as a genetic biomarker of susceptibility for Cr (VI)- induced DNA damage. PMID:22642904

  2. Crystal structure of the GlnZ-DraG complex reveals a different form of PII-target interaction

    PubMed Central

    Rajendran, Chitra; Gerhardt, Edileusa C. M.; Bjelic, Sasa; Gasperina, Antonietta; Scarduelli, Marcelo; Pedrosa, Fábio O.; Chubatsu, Leda S.; Merrick, Mike; Souza, Emanuel M.; Winkler, Fritz K.; Huergo, Luciano F.; Li, Xiao-Dan

    2011-01-01

    Nitrogen metabolism in bacteria and archaea is regulated by a ubiquitous class of proteins belonging to the PIIfamily. PII proteins act as sensors of cellular nitrogen, carbon, and energy levels, and they control the activities of a wide range of target proteins by protein-protein interaction. The sensing mechanism relies on conformational changes induced by the binding of small molecules to PII and also by PII posttranslational modifications. In the diazotrophic bacterium Azospirillum brasilense, high levels of extracellular ammonium inactivate the nitrogenase regulatory enzyme DraG by relocalizing it from the cytoplasm to the cell membrane. Membrane localization of DraG occurs through the formation of a ternary complex in which the PII protein GlnZ interacts simultaneously with DraG and the ammonia channel AmtB. Here we describe the crystal structure of the GlnZ-DraG complex at 2.1 Å resolution, and confirm the physiological relevance of the structural data by site-directed mutagenesis. In contrast to other known PII complexes, the majority of contacts with the target protein do not involve the T-loop region of PII. Hence this structure identifies a different mode of PII interaction with a target protein and demonstrates the potential for PII proteins to interact simultaneously with two different targets. A structural model of the AmtB-GlnZ-DraG ternary complex is presented. The results explain how the intracellular levels of ATP, ADP, and 2-oxoglutarate regulate the interaction between these three proteins and how DraG discriminates GlnZ from its close paralogue GlnB. PMID:22074780

  3. Enhanced spin polarization in graphene with spin energy gap induced by spin-orbit coupling and strain

    SciTech Connect

    Liu, Zheng-Fang; Wu, Qing-Ping E-mail: aixichen@ecjtu.jx.cn; Chen, Ai-Xi E-mail: aixichen@ecjtu.jx.cn; Xiao, Xian-Bo; Liu, Nian-Hua

    2014-05-28

    We investigate the possibility of spin polarization in graphene. The result shows that a spin energy gap can be opened in the presence of both spin-orbit coupling and strain. We find that high spin polarization with large spin-polarized current is achieved in the spin energy gap. However, only one of the two modulations is present, no spin polarization can be generated. So the combination of the two modulations provides a way to design tunable spin polarization without need for a magnetic element or an external magnetic field.

  4. A review on the derivation of the spin-Restricted Hartree—Fock (RHF) Self-Consistent Field (SCF) equations for open-shell systems. Description of different methods to handle the off-diagonal Lagrangian multipliers coupling closed and open shells

    NASA Astrophysics Data System (ADS)

    Krebs, Stefan

    1999-02-01

    A detailed review is presented on the spin-Restricted Hartree—Fock (RHF) Self-Consistent Field (SCF) method (i) for high-spin ( M s = S) open-shell systems and (ii) for singlet systems with two occupied open-shell orbitals, either of two different irreducible representations (Irreps) or of the same Irrep. Basic knowledge, such as the Born—Oppenheimer separation and approximation, the model of independent particles, Slater determinants and important rules of Group Theory, is shortly summarized. The RHF equations are derived by a minimization of the energy expectation value for the lowest state of a given Irrep and spin multiplicity, described by a spin-adapted wavefunction composed of a single Slater determinant in the high-spin case and a linear combination of two determinants in the open-shell singlet case. Molecular symmetry is considered throughout the paper. The Roothaan method as well as two other widely used methods to handle the orthogonality constraints for the spin orbitals of the respective Slater determinant(s) are described. Detailed algorithms for performing an RHF—SCF procedure with each of these methods are presented.

  5. Openings

    PubMed Central

    Selwyn, Peter A.

    2015-01-01

    Reviewing his clinic patient schedule for the day, a physician reflects on the history of a young woman he has been caring for over the past 9 years. What starts out as a routine visit then turns into a unique opening for communication and connection. A chance glimpse out the window of the exam room leads to a deeper meditation on parenthood, survival, and healing, not only for the patient but also for the physician. How many missed opportunities have we all had, without even realizing it, to allow this kind of fleeting but profound opening? PMID:26195687

  6. Openings.

    PubMed

    Selwyn, Peter A

    2015-01-01

    Reviewing his clinic patient schedule for the day, a physician reflects on the history of a young woman he has been caring for over the past 9 years. What starts out as a routine visit then turns into a unique opening for communication and connection. A chance glimpse out the window of the exam room leads to a deeper meditation on parenthood, survival, and healing, not only for the patient but also for the physician. How many missed opportunities have we all had, without even realizing it, to allow this kind of fleeting but profound opening? PMID:26195687

  7. CheMPS2: A free open-source spin-adapted implementation of the density matrix renormalization group for ab initio quantum chemistry

    NASA Astrophysics Data System (ADS)

    Wouters, Sebastian; Poelmans, Ward; Ayers, Paul W.; Van Neck, Dimitri

    2014-06-01

    The density matrix renormalization group (DMRG) has become an indispensable numerical tool to find exact eigenstates of finite-size quantum systems with strong correlation. In the fields of condensed matter, nuclear structure and molecular electronic structure, it has significantly extended the system sizes that can be handled compared to full configuration interaction, without losing numerical accuracy. For quantum chemistry (QC), the most efficient implementations of DMRG require the incorporation of particle number, spin and point group symmetries in the underlying matrix product state (MPS) ansatz, as well as the use of so-called complementary operators. The symmetries introduce a sparse block structure in the MPS ansatz and in the intermediary contracted tensors. If a symmetry is non-abelian, the Wigner-Eckart theorem allows to factorize a tensor into a Clebsch-Gordan coefficient and a reduced tensor. In addition, the fermion signs have to be carefully tracked. Because of these challenges, implementing DMRG efficiently for QC is not straightforward. Efficient and freely available implementations are therefore highly desired. In this work we present CheMPS2, our free open-source spin-adapted implementation of DMRG for ab initio QC. Around CheMPS2, we have implemented the augmented Hessian Newton-Raphson complete active space self-consistent field method, with exact Hessian. The bond dissociation curves of the 12 lowest states of the carbon dimer were obtained at the DMRG(28 orbitals, 12 electrons, DSU(2) = 2500)/cc-pVDZ level of theory. The contribution of 1 s core correlation to the X1Σg+ bond dissociation curve of the carbon dimer was estimated by comparing energies at the DMRG(36o, 12e, DSU(2) = 2500)/cc-pCVDZ and DMRG-SCF(34o, 8e, DSU(2) = 2500)/cc-pCVDZ levels of theory.

  8. Theory of open quantum systems with bath of electrons and phonons and spins: Many-dissipaton density matrixes approach

    SciTech Connect

    Yan, YiJing

    2014-02-07

    This work establishes a strongly correlated system-and-bath dynamics theory, the many-dissipaton density operators formalism. It puts forward a quasi-particle picture for environmental influences. This picture unifies the physical descriptions and algebraic treatments on three distinct classes of quantum environments, electron bath, phonon bath, and two-level spin or exciton bath, as their participating in quantum dissipation processes. Dynamical variables for theoretical description are no longer just the reduced density matrix for system, but remarkably also those for quasi-particles of bath. The present theoretical formalism offers efficient and accurate means for the study of steady-state (nonequilibrium and equilibrium) and real-time dynamical properties of both systems and hybridizing environments. It further provides universal evaluations, exact in principle, on various correlation functions, including even those of environmental degrees of freedom in coupling with systems. Induced environmental dynamics could be reflected directly in experimentally measurable quantities, such as Fano resonances and quantum transport current shot noise statistics.

  9. Association between the XRCC1 Arg399Gln Polymorphism and Risk of Cancer: Evidence from 297 Case–Control Studies

    PubMed Central

    Yi, Liu; Xiao-feng, He; Yun-tao, Lu; Hao, Long; Ye, Song; Song-tao, Qi

    2013-01-01

    Background The Arg399Gln polymorphism in the X-ray cross-complementing group 1 (XRCC1) had been implicated in cancer susceptibility. The previous published data on the association between XRCC1 Arg399Gln polymorphism and cancer risk remained controversial. Methodology/Principal Findings To derive a more precise estimation of the association between the XRCC1 Arg399Gln polymorphism and overall cancer risk, we performed a meta-analysis of 297 case-control studies, in which a total of 93,941 cases and 121,480 controls were included. Overall, significantly increased cancer risk was observed in any genetic model (dominant model: odds ration [OR] = 1.04, 95% confidence interval [CI] = 1.01–1.07; recessive model: OR = 1.08, 95% CI = 1.03–1.13; additive model: OR = 1.09, 95% CI = 1.04–1.14) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, significantly elevated hepatocellular and breast cancers risk were observed in Asians (dominant model: OR = 1.39, 95% CI = 1.06–1.84) and in Indians (dominant model: OR = 1.64, 95% CI = 1.31–2.04; recessive model: OR = 1.94, 95% CI = 1.09–3.47; additive model: OR = 2.06, 95% CI = 1.50–2.84), respectively. Conclusions/Significance This meta-analysis suggests the participation of XRCC1 Arg399Gln is a genetic susceptibility for hepatocellular cancer in Asians and breast cancer in Indians. Moreover, our work also points out the importance of new studies for Arg399Gln association in some cancer types, such as glioma, gastric cancer, and oral cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC1 Arg399Gln polymorphism in cancer development. PMID:24205095

  10. The Arg399Gln polymorphism in the XRCC1 gene is associated with increased risk of hematological malignancies.

    PubMed

    Du, Liang; Liu, Yuqi; Xue, Pei; Song, Chenxi; Shen, Jiani; He, Qing; Peng, Yuanling; Tong, Xiang; Tang, Lizhi; Zhang, Yonggang

    2015-06-01

    The associations between the Arg399Gln polymorphism in X-ray repair cross-complementing gene 1 (XRCC1) gene and the risk of hematological malignancies have been extensively investigated. However, the results were inconsistent. The objective of the current study is to investigate the association by meta-analysis. We searched PubMed database, Embase database, CNKI database, Wanfang database, and Weipu database, covering all studies until August 7, 2013. Statistical analysis was performed by using the Revman4.2 software and the Stata10.0 software. A total of 27 case-control studies concerning the Arg399Gln polymorphism were included from 26 articles. The results suggested that the Arg399Gln polymorphism was not associated with an increased/decreased risk of hematological malignancies in total analysis (OR = 1.15, 95 % confidence interval (CI) = 0.97-1.35, P = 0.10 for Arg/Gln + Gln/Gln vs. Arg/Arg). In the subgroup analysis by ethnicity and cancer types, significant association was found in Asians (OR = 1.35, 95 % CI = 1.04-1.75, P = 0.03) but not in Europeans (OR = 1.07, 95 % CI = 0.86-1.33, P = 0.56), and in leukemia (OR = 1.25, 95 % CI = 1.02-1.54, P = 0.03) but not in lymphoma (OR = 0.98, 95 % CI = 0.80-1.20, P = 0.84) or myeloma (OR = 1.13, 95 % CI = 0.23-5.69, P = 0.88). The current meta-analysis indicated that the Arg399Gln polymorphism in the XRCC1 gene might be a risk factor for hematological malignancies in Asians or for leukemia. In future, more large-scale case-control studies are needed to validate these results. PMID:25619474

  11. Role of GlnR in Acid-Mediated Repression of Genes Encoding Proteins Involved in Glutamine and Glutamate Metabolism in Streptococcus mutans▿ †

    PubMed Central

    Chen , Pei-Min; Chen, Yi-Ywan M.; Yu, Sung-Liang; Sher, Singh; Lai, Chern-Hsiung; Chia, Jean-San

    2010-01-01

    The acid tolerance response (ATR) is one of the major virulence traits of Streptococcus mutans. In this study, the role of GlnR in acid-mediated gene repression that affects the adaptive ATR in S. mutans was investigated. Using a whole-genome microarray and in silico analyses, we demonstrated that GlnR and the GlnR box (ATGTNAN7TNACAT) were involved in the transcriptional repression of clusters of genes encoding proteins involved in glutamine and glutamate metabolism under acidic challenge. Reverse transcription-PCR (RT-PCR) analysis revealed that the coordinated regulation of the GlnR regulon occurred 5 min after acid treatment and that prolonged acid exposure (30 min) resulted in further reduction in expression. A lower level but consistent reduction in response to acidic pH was also observed in chemostat-grown cells, confirming the negative regulation of GlnR. The repression by GlnR through the GlnR box in response to acidic pH was further confirmed in the citBZC operon, containing genes encoding the first three enzymes in the glutamine/glutamate biosynthesis pathway. The survival rate of the GlnR-deficient mutant at pH 2.8 was more than 10-fold lower than that in the wild-type strain 45 min after acid treatment, suggesting that the GlnR regulon participates in S. mutans ATR. It is hypothesized that downregulation of the synthesis of the amino acid precursors in response to acid challenge would promote citrate metabolism to pyruvate, with the consumption of H+ and potential ATP synthesis. Such regulation will ensure an optimal acid adaption in S. mutans. PMID:20173059

  12. Spin-Wave Diode

    NASA Astrophysics Data System (ADS)

    Lan, Jin; Yu, Weichao; Wu, Ruqian; Xiao, Jiang

    2015-10-01

    A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.

  13. New homozygous SPINK5 mutation, p.Gln333X, in a Turkish pedigree with Netherton syndrome.

    PubMed

    Fong, K; Akdeniz, S; Isi, H; Taskesen, M; McGrath, J A; Lai-Cheong, J E

    2011-06-01

    Netherton syndrome (NS) is a rare autosomal recessive genodermatosis caused by loss-of-function mutations in the SPINK5 gene. The clinical features include congenital ichthyosis, trichorrhexis invaginata and atopy. In this study, we report a new homozygous SPINK5 mutation, p.Gln333X, responsible for NS in affected members of two closely related Turkish families, and provide an overview of the genotype-phenotype correlation in this condition. PMID:21564178

  14. Identification of BC005512 as a DNA Damage Responsive Murine Endogenous Retrovirus of GLN Family Involved in Cell Growth Regulation

    PubMed Central

    Wu, Yuanfeng; Qi, Xinming; Gong, Likun; Xing, Guozhen; Chen, Min; Miao, Lingling; Yao, Jun; Suzuki, Takayoshi; Furihata, Chie; Luan, Yang; Ren, Jin

    2012-01-01

    Genotoxicity assessment is of great significance in drug safety evaluation, and microarray is a useful tool widely used to identify genotoxic stress responsive genes. In the present work, by using oligonucleotide microarray in an in vivo model, we identified an unknown gene BC005512 (abbreviated as BC, official full name: cDNA sequence BC005512), whose expression in mouse liver was specifically induced by seven well-known genotoxins (GTXs), but not by non-genotoxins (NGTXs). Bioinformatics revealed that BC was a member of the GLN family of murine endogenous retrovirus (ERV). However, the relationship to genotoxicity and the cellular function of GLN are largely unknown. Using NIH/3T3 cells as an in vitro model system and quantitative real-time PCR, BC expression was specifically induced by another seven GTXs, covering diverse genotoxicity mechanisms. Additionally, dose-response and linear regression analysis showed that expression level of BC in NIH/3T3 cells strongly correlated with DNA damage, measured using the alkaline comet assay,. While in p53 deficient L5178Y cells, GTXs could not induce BC expression. Further functional studies using RNA interference revealed that down-regulation of BC expression induced G1/S phase arrest, inhibited cell proliferation and thus suppressed cell growth in NIH/3T3 cells. Together, our results provide the first evidence that BC005512, a member from GLN family of murine ERV, was responsive to DNA damage and involved in cell growth regulation. These findings could be of great value in genotoxicity predictions and contribute to a deeper understanding of GLN biological functions. PMID:22514700

  15. Leading and next-to-leading order gluon polarization in the nucleon and longitudinal double spin asymmetries from open charm muoproduction

    NASA Astrophysics Data System (ADS)

    Adolph, C.; Alekseev, M. G.; Alexakhin, V. Yu.; Alexandrov, Yu.; Alexeev, G. D.; Amoroso, A.; Antonov, A. A.; Austregesilo, A.; Badełek, B.; Balestra, F.; Barth, J.; Baum, G.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bertini, R.; Bettinelli, M.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bordalo, P.; Bradamante, F.; Braun, C.; Bravar, A.; Bressan, A.; Büchele, M.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S. U.; Cicuttin, A.; Crespo, M. L.; Dalla Torre, S.; Das, S.; Dasgupta, S. S.; Dasgupta, S.; Denisov, O. Yu.; Dhara, L.; Donskov, S. V.; Doshita, N.; Duic, V.; Dünnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P. D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; Finger, M., Jr.; Fischer, H.; Franco, C.; du Fresne von Hohenesche, N.; Friedrich, J. M.; Frolov, V.; Garfagnini, R.; Gautheron, F.; Gavrichtchouk, O. P.; Gerassimov, S.; Geyer, R.; Giorgi, M.; Gnesi, I.; Gobbo, B.; Goertz, S.; Grabmüller, S.; Grasso, A.; Grube, B.; Gushterski, R.; Guskov, A.; Guthörl, T.; Haas, F.; von Harrach, D.; Heinsius, F. H.; Herrmann, F.; Heß, C.; Hinterberger, F.; Horikawa, N.; Höppner, Ch.; d'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, O.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Joosten, R.; Kabuß, E.; Kang, D.; Ketzer, B.; Khaustov, G. V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koblitz, S.; Koivuniemi, J. H.; Kolosov, V. N.; Kondo, K.; Königsmann, K.; Konorov, I.; Konstantinov, V. F.; Korzenev, A.; Kotzinian, A. M.; Kouznetsov, O.; Krämer, M.; Kroumchtein, Z. V.; Kunne, F.; Kurek, K.; Lauser, L.; Lednev, A. A.; Lehmann, A.; Levorato, S.; Lichtenstadt, J.; Liska, T.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G. K.; Mann, A.; Marchand, C.; Martin, A.; Marzec, J.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Morreale, A.; Mutter, A.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V. I.; Nowak, W.-D.; Nunes, A. S.; Olshevsky, A. G.; Ostrick, M.; Padee, A.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Perevalova, E.; Pesaro, G.; Peshekhonov, D. V.; Piragino, G.; Platchkov, S.; Pochodzalla, J.; Polak, J.; Polyakov, V. A.; Pretz, J.; Quaresma, M.; Quintans, C.; Rajotte, J.-F.; Ramos, S.; Rapatsky, V.; Reicherz, G.; Rocco, E.; Rondio, E.; Rossiyskaya, N. S.; Ryabchikov, D. I.; Samoylenko, V. D.; Sandacz, A.; Sapozhnikov, M. G.; Sarkar, S.; Savin, I. A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schlüter, T.; Schmidt, A.; Schmidt, K.; Schmitt, L.; Schmïden, H.; Schönning, K.; Schopferer, S.; Schott, M.; Shevchenko, O. Yu.; Silva, L.; Sinha, L.; Sissakian, A. N.; Slunecka, M.; Smirnov, G. I.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Sznajder, P.; Takekawa, S.; Ter Wolbeek, J.; Tessaro, S.; Tessarotto, F.; Tkatchev, L. G.; Uhl, S.; Uman, I.; Vandenbroucke, M.; Virius, M.; Vlassov, N. V.; Wang, L.; Weisrock, T.; Wilfert, M.; Windmolders, R.; Wiślicki, W.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zhuravlev, N.; Zvyagin, A.

    2013-03-01

    The gluon polarization in the nucleon was measured using open charm production by scattering 160GeV/c polarized muons off longitudinally polarized protons or deuterons. The data were taken by the COMPASS Collaboration between 2002 and 2007. A detailed account is given of the analysis method that includes the application of neural networks. Several decay channels of D0 mesons are investigated. Longitudinal spin asymmetries of the D meson production cross sections are extracted in bins of D0 transverse momentum and energy. At leading order QCD accuracy, the average gluon polarization is determined as ⟨Δg/g⟩LO=-0.06±0.21(stat.)±0.08(syst.) at the scale ⟨μ2⟩≈13(GeV/c)2 and an average gluon momentum fraction ⟨x⟩≈0.11. The average gluon polarization is also obtained at next-to-leading order QCD accuracy as ⟨Δg/g⟩ NLO=-0.13±0.15(stat.)±0.15(syst.) at the scale ⟨μ2⟩≈13(GeV/c)2 and ⟨x⟩≈0.20.

  16. Photosynthetic electron transport controls nitrogen assimilation in cyanobacteria by means of posttranslational modification of the glnB gene product.

    PubMed Central

    Tsinoremas, N F; Castets, A M; Harrison, M A; Allen, J F; Tandeau de Marsac, N

    1991-01-01

    A glnB gene is identified in the cyanobacterium Synechococcus sp. PCC 7942, and its gene product is found to be covalently modified as a result of imbalance in electron transfer in photosynthesis, where photosystem II is favored over photosystem I. The gene was cloned and sequenced and found to encode a polypeptide of 112 amino acid residues, whose sequence shows a high degree of similarity to the Escherichia coli regulatory protein, PII. In E. coli, PII is involved in signal transduction in transcriptional and post-translational regulation of nitrogen assimilation. Increase in ammonium ion concentration is shown to decrease covalent modification of the Synechococcus PII protein, as in enteric bacteria. We therefore propose that the photosynthetic electron transport chain may regulate the pathway of nitrogen assimilation in cyanobacteria by means of posttranslational, covalent modification of the glnB gene product. The existence of the glnB gene in different strains of cyanobacteria is demonstrated and its implications are discussed. Images PMID:1905010

  17. Analysis of Gln223Agr polymorphism of Leptin Receptor Gene in type II diabetic mellitus subjects among Malaysians.

    PubMed

    Etemad, Ali; Ramachandran, Vasudevan; Pishva, Seyyed Reza; Heidari, Farzad; Aziz, Ahmad Fazli Abdul; Yusof, Ahmad Khairuddin Mohamed; Pei, Chong Pei; Ismail, Patimah

    2013-01-01

    Leptin is known as the adipose peptide hormone. It plays an important role in the regulation of body fat and inhibits food intake by its action. Moreover, it is believed that leptin level deductions might be the cause of obesity and may play an important role in the development of Type 2 Diabetes Mellitus (T2DM), as well as in cardiovascular diseases (CVD). The Leptin Receptor (LEPR) gene and its polymorphisms have not been extensively studied in relation to the T2DM and its complications in various populations. In this study, we have determined the association of Gln223Agr loci of LEPR gene in three ethnic groups of Malaysia, namely: Malays, Chinese and Indians. A total of 284 T2DM subjects and 281 healthy individuals were recruited based on International Diabetes Federation (IDF) criteria. Genomic DNA was extracted from the buccal specimens of the subjects. The commercial polymerase chain reaction (PCR) method was carried out by proper restriction enzyme MSP I to both amplify and digest the Gln223Agr polymorphism. The p-value among the three studied races was 0.057, 0.011 and 0.095, respectively. The values such as age, WHR, FPG, HbA1C, LDL, HDL, Chol and Family History were significantly different among the subjects with Gln223Agr polymorphism of LEPR (p < 0.05). PMID:24051404

  18. A common IL-13 Arg130Gln single nucleotide polymorphism among Chinese atopy patients with allergic rhinitis.

    PubMed

    Wang, Min; Xing, Zhi-Min; Lu, Chao; Ma, You-Xiang; Yu, De-Lin; Yan, Zheng; Wang, Shen-Wu; Yu, Li-Sheng

    2003-10-01

    Allergic rhinitis is a major public health problem and has seen its prevalence increase during the past few decades. Interleukin 13 (IL-13) has been implicated in the pathogenesis and in the regulation of immunoglobulin E (IgE) production. Single nucleotide polymorphisms (SNPs) have been found in both the coding sequence and the promoter region of IL-13, and such SNPs have been associated with allergic asthma. We have investigated whether IL-13 SNPs are associated with allergic rhinitis. Among 188 Chinese adult patients with allergic rhinitis and 87 normal controls, no significant difference was found in either allele or haplotype frequency of the SNPs between the two groups. Within patients, there was a significant association of the IL-13 Arg130Gln SNP, but not of the IL-13 promoter -1112(C/T) SNP, with serum total IgE levels. Patients with a Gln/Gln genotype showed much higher serum total IgE than those with an Arg/Arg genotype. When tested for serum-specific IgE, patients allergic to Derp 1, but not those allergic to Artemisia pollen, showed a significant association with the IL-13 promoter SNP. Thus, our results suggest a possible involvement of IL-13 SNPs in the regulation of IgE production in response to allergens in this Chinese population. PMID:12928861

  19. Analysis of Gln223Agr Polymorphism of Leptin Receptor Gene in Type II Diabetic Mellitus Subjects among Malaysians

    PubMed Central

    Etemad, Ali; Ramachandran, Vasudevan; Pishva, Seyyed Reza; Heidari, Farzad; Aziz, Ahmad Fazli Abdul; Yusof, Ahmad Khairuddin Mohamed; Pei, Chong Pei; Ismail, Patimah

    2013-01-01

    Leptin is known as the adipose peptide hormone. It plays an important role in the regulation of body fat and inhibits food intake by its action. Moreover, it is believed that leptin level deductions might be the cause of obesity and may play an important role in the development of Type 2 Diabetes Mellitus (T2DM), as well as in cardiovascular diseases (CVD). The Leptin Receptor (LEPR) gene and its polymorphisms have not been extensively studied in relation to the T2DM and its complications in various populations. In this study, we have determined the association of Gln223Agr loci of LEPR gene in three ethnic groups of Malaysia, namely: Malays, Chinese and Indians. A total of 284 T2DM subjects and 281 healthy individuals were recruited based on International Diabetes Federation (IDF) criteria. Genomic DNA was extracted from the buccal specimens of the subjects. The commercial polymerase chain reaction (PCR) method was carried out by proper restriction enzyme MSP I to both amplify and digest the Gln223Agr polymorphism. The p-value among the three studied races was 0.057, 0.011 and 0.095, respectively. The values such as age, WHR, FPG, HbA1C, LDL, HDL, Chol and Family History were significantly different among the subjects with Gln223Agr polymorphism of LEPR (p < 0.05). PMID:24051404

  20. PREFACE: Spin Electronics

    NASA Astrophysics Data System (ADS)

    Dieny, B.; Sousa, R.; Prejbeanu, L.

    2007-04-01

    tunnel junctions were introduced as memory elements in new types of non-volatile magnetic memories (MRAM). A first 4Mbit product was launched by Freescale in July 2006. Future generations of memories are being developed by academic groups or companies. the combination of magnetic elements with CMOS components opens a whole new paradigm in hybrid electronic components which can change the common conception of the architecture of complex electronic components with a much tighter integration of logic and memory. the steady magnetic excitations stimulated by spin-transfer might be used in a variety of microwave components provided the output power can be increased. Intense research and development efforts are being aimed at increasing this power by the synchronization of oscillators. The articles compiled in this special issue of Journal of Physics: Condensed Matter, devoted to spin electronics, review these recent developments. All the contributors are greatly acknowledged.

  1. Co-Inactivation of GlnR and CodY Regulators Impacts Pneumococcal Cell Wall Physiology

    PubMed Central

    Johnston, Calum; Bootsma, Hester J.; Aldridge, Christine; Manuse, Sylvie; Gisch, Nicolas; Schwudke, Dominik; Hermans, Peter W. M.; Grangeasse, Christophe; Polard, Patrice; Vollmer, Waldemar; Claverys, Jean-Pierre

    2015-01-01

    CodY, a nutritional regulator highly conserved in low G+C Gram-positive bacteria, is essential in Streptococcus pneumoniae (the pneumococcus). A published codY mutant possessed suppressing mutations inactivating the fatC and amiC genes, respectively belonging to iron (Fat/Fec) and oligopeptide (Ami) ABC permease operons, which are directly repressed by CodY. Here we analyzed two additional published codY mutants to further explore the essentiality of CodY. We show that one, in which the regulator of glutamine/glutamate metabolism glnR had been inactivated by design, had only a suppressor in fecE (a gene in the fat/fec operon), while the other possessed both fecE and amiC mutations. Independent isolation of three different fat/fec suppressors thus establishes that reduction of iron import is crucial for survival without CodY. We refer to these as primary suppressors, while inactivation of ami, which is not essential for survival of codY mutants and acquired after initial fat/fec inactivation, can be regarded as a secondary suppressor. The availability of codY- ami+ cells allowed us to establish that CodY activates competence for genetic transformation indirectly, presumably by repressing ami which is known to antagonize competence. The glnR codY fecE mutant was then found to be only partially viable on solid medium and hypersensitive to peptidoglycan (PG) targeting agents such as the antibiotic cefotaxime and the muramidase lysozyme. While analysis of PG and teichoic acid composition uncovered no alteration in the glnR codY fecE mutant compared to wildtype, electron microscopy revealed altered ultrastructure of the cell wall in the mutant, establishing that co-inactivation of GlnR and CodY regulators impacts pneumococcal cell wall physiology. In light of rising levels of resistance to PG-targeting antibiotics of natural pneumococcal isolates, GlnR and CodY constitute potential alternative therapeutic targets to combat this debilitating pathogen, as co

  2. Tensor spin observables and spin stucture at low Q2

    SciTech Connect

    Slifer, Karl J.

    2015-04-01

    We discuss recent spin structure results from Jefferson Lab, and outline an emerging program to study tensor spin observables using solid deuteron targets. These new experiments open the potential to study hidden color, the tensor nature of short range correlations, and to probe for exotic gluonic states.

  3. Hydrodynamics of spin-polarized transport and spin pendulum

    SciTech Connect

    Gurzhi, R. N. Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V.

    2007-07-15

    The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.

  4. Lactosylated Gramicidin-based lipid nanoparticles (Lac-GLN) for targeted delivery of anti-miR-155 to hepatocellular carcinoma

    PubMed Central

    Zhang, Mengzi; Zhou, Xiaoju; Wang, Bo; Yung, Bryant C.; Lee, Ly J.; Ghoshal, Kalpana; Lee, Robert J.

    2013-01-01

    Lactosylated gramicidin-containing lipid nanoparticles (Lac-GLN) were developed for delivery of anti-microRNA-155 (anti-miR-155) to hepatocellular carcinoma (HCC) cells. MiR-155 is an oncomiR frequently elevated in HCC. The Lac-GLN formulation contained N-lactobionyl-dioleoyl phosphatidylethanolamine (Lac-DOPE), a ligand for the asialoglycoprotein receptor (ASGR), and an antibiotic peptide gramicidin A. The nanoparticles exhibited a mean particle diameter of 73 nm, zeta potential of +3.5 mV, anti-miR encapsulation efficiency of 88%, and excellent colloidal stability at 4°C. Lac-GLN effectively delivered anti-miR-155 to HCC cells with a 16.1- and 4.1-fold up-regulation of miR-155 targets C/EBPβ and FOXP3 genes, respectively, and exhibited significant greater efficiency over Lipofectamine 2000. In mice, intravenous injection of Lac-GLN containing Cy3-anti-miR-155 led to preferential accumulation of the anti-miR-155 in hepatocytes. Intravenous administration of 1.5 mg/kg anti-miR-155 loaded Lac-GLN resulted in up-regulation of C/EBPβ and FOXP3 by 6.9- and 2.2- fold, respectively. These results suggest potential application of Lac-GLN as a liver-specific delivery vehicle for anti-miR therapy. PMID:23567045

  5. Suppression of the impurity-induced local magnetism by the opening of a spin pseudogap in Ni-doped Sr2CuO3

    NASA Astrophysics Data System (ADS)

    Utz, Yannic; Hammerath, Franziska; Nishimoto, Satoshi; Hess, Christian; Beesetty, Neela Sekhar; Saint-Martin, Romuald; Revcolevschi, Alexandre; Büchner, Bernd; Grafe, Hans-Joachim

    2015-08-01

    The S =1 /2 antiferromagnetic Heisenberg spin chain compound Sr2CuO3 doped with 1 % and 2 % of Ni impurities has been studied by means of 63Cu nuclear magnetic resonance. A strong decrease of the spin-lattice relaxation rate T1-1 at low temperatures points toward a spin gap, while a stretching exponent λ <1 and a frequency dependence of T1-1 indicate that this spin gap varies spatially and should rather be characterized as a spin pseudogap. The magnitude of the spin pseudogap scales with doping level. Our results therefore evidence the finite-size character of this phenomenon. Moreover, an unusual narrowing of the low-temperature NMR lines reveals the suppression of the impurity-induced staggered paramagnetic response with increasing doping level.

  6. Geometrical spin symmetry and spin

    SciTech Connect

    Pestov, I. B.

    2011-07-15

    Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.

  7. Lack of association between XPG Asp1104His and XPF Arg415Gln polymorphism and breast cancer risk: a meta-analysis of case-control studies.

    PubMed

    Ding, Da-Peng; He, Xiao-Feng; Zhang, Ying

    2011-08-01

    The xeroderma pigmentosum group G (XPG or ERCC5) and group F (XPF or ERCC4) play an important role in DNA repair, and produce dual incision 3' and 5' to the damaged nucleotide fragment. Several polymorphisms in the XPF and XPG gene have been described, including the commonly occurring Asp1104His in XPG and Arg415Gln in XPF. The published data on the association between these polymorphisms and breast cancer remained controversial. This meta-analysis of literatures was performed to derive a more precise estimation of the relationship. A total of 17 studies were identified to the meta-analysis, including 5,235 cases and 5,685 controls for XPG Asp1104His (from ten studies) and 3,910 cases and 3,985 controls for XPF Arg415Gln (from seven studies). Overall, no significantly elevated breast cancer risk was found in all genetic models when all studies were pooled into the meta-analysis (for XPG Asp1104His Asp/His vs. Asp/Asp: OR 1.02, 95% CI 0.94-1.11; His/His vs. Asp/Asp: OR 0.96, 95% CI 0.83-1.11; dominant model: OR 1.01, 95% CI 0.94-1.09; and for XPF Arg415Gln Arg/Gln vs. Arg/Arg: OR 1.00, 95% CI 0.89-1.12; Gln/Gln vs. Arg/Arg: OR 2.40, 95% CI 0.62-9.22; dominant model: OR 1.03, 95% CI 0.90-1.18). In stratified analyses, we observed an overall OR of 5.20 (95% CI 2.08-12.95) for breast cancer developing risk in the Caucasian ethnicity, comparing Gln/Gln type to wild-type Arg/Arg for Arg415Gln polymorphism. In conclusion, this meta-analysis suggests that XPG Asp1104His polymorphism is not associated with increased breast cancer risk, and XPF Arg415Gln may be a low-penetrant risk factor in the Caucasian ethnicity for developing breast cancer. PMID:21424776

  8. Ehrlichia chaffeensis Proliferation Begins with NtrY/NtrX and PutA/GlnA Upregulation and CtrA Degradation Induced by Proline and Glutamine Uptake

    PubMed Central

    Cheng, Zhihui; Lin, Mingqun

    2014-01-01

    ABSTRACT How the obligatory intracellular bacterium Ehrlichia chaffeensis begins to replicate upon entry into human monocytes is poorly understood. Here, we examined the potential role of amino acids in initiating intracellular replication. PutA converts proline to glutamate, and GlnA converts glutamate to glutamine. E. chaffeensis PutA and GlnA complemented Escherichia coli putA and glnA mutants. Methionine sulfoximine, a glutamine synthetase inhibitor, inhibited E. chaffeensis GlnA activity and E. chaffeensis infection of human cells. Incubation of E. chaffeensis with human cells rapidly induced putA and glnA expression that peaked at 24 h postincubation. E. chaffeensis took up proline and glutamine but not glutamate. Pretreatment of E. chaffeensis with a proline transporter inhibitor (protamine), a glutamine transporter inhibitor (histidine), or proline analogs inhibited E. chaffeensis infection, whereas pretreatment with proline or glutamine enhanced infection and upregulated putA and glnA faster than no treatment or glutamate pretreatment. The temporal response of putA and glnA expression was similar to that of NtrY and NtrX, a two-component system, and electrophoretic mobility shift assays showed specific binding of recombinant E. chaffeensis NtrX (rNtrX) to the promoter regions of E. chaffeensis putA and glnA. Furthermore, rNtrX transactivated E. chaffeensis putA and glnA promoter-lacZ fusions in E. coli. Growth-promoting activities of proline and glutamine were also accompanied by rapid degradation of the DNA-binding protein CtrA. Our results suggest that proline and glutamine uptake regulates putA and glnA expression through NtrY/NtrX and facilitates degradation of CtrA to initiate a new cycle of E. chaffeensis growth. PMID:25425236

  9. A method for distance determination in proteins using a designed metal ion binding site and site-directed spin labeling: evaluation with T4 lysozyme.

    PubMed Central

    Voss, J; Salwiński, L; Kaback, H R; Hubbell, W L

    1995-01-01

    The use of molecular genetics to introduce both a metal ion binding site and a nitroxide spin label into the same protein opens the use of paramagnetic metalnitroxyl interactions to estimate intramolecular distances in a wide variety of proteins. In this report, a His-Xaa3-His metal ion binding motif was introduced at the N terminus of the long interdomain helix of T4 lysozyme (Lys-65 --> His/Gln-69 --> His) of three mutants, each containing a single nitroxide-labeled cysteine residue at position 71, 76, or 80. The results show that Cu(II)-induced relaxation effects on the nitroxide can be quantitatively analyzed in terms of interspin distance in the range of 10-25 A using Redfield theory, as first suggested by Leigh [Leigh, J.S. (1970) J. Chem. Phys. 52, 2608-2612]. Of particular interest is the observation that distances can be determined both under rigid lattice conditions in frozen solution and in the presence of motion of the spins at room temperature under physiological conditions. The method should be particularly attractive for investigating structure in membrane proteins that are difficult to crystallize. In the accompanying paper, the technique is applied to a polytopic membrane protein, lactose permease. Images Fig. 1 PMID:8618888

  10. Frequencies of the Arg16Gly, Gln27Glu and Thr164Ile Adrenoceptor β2 Polymorphisms among Omanis

    PubMed Central

    Al-Balushi, Khalid; Zadjali, Fahad; Al-Sinani, Sawsan; Al-Zadjali, Al-Muatasim; Bayoumi, Riad

    2015-01-01

    Objectives: This study aimed to assess the distribution of missense mutations in the adrenoceptor β2 (ADRB2) gene in an Omani cohort. Methods: This study was carried out between May 2014 and March 2015 at the Sultan Qaboos University, Muscat, Oman. Blood samples were taken from 316 unrelated Omani subjects. Genotyping for rs1042713 (c.46A>G, p.Arg16Gly), rs1042714 (c.79C>G, p.Gln27Glu) and rs1800888 (c.491C>T, p.Thr164Ile) polymorphisms was performed by real-time polymerase chain reaction using single nucleotide polymorphism (SNP) genotyping assays. The allelic frequencies of these polymorphisms were estimated on the basis of the observed numbers of specific alleles from the genotype data for male and female subjects. The genotype frequencies for each polymorphism were tested for deviation from the Hardy-Weinberg equilibrium. Results: Gly16 and Glu27 were the most frequent variants found among the cohort (63% and 75%, respectively). The Ile164 variant was not detected in the study population. There was a significant linkage disequilibrium between the rs1042713 and rs1042714 SNPs (r2 = 0.209; P ≤0.001). The most observed haplotypes were Gly16-Gln27 and Arg16-Gln27 (0.37 and 0.38, respectively). The frequency of Gly16-Glu27 was 0.25, comprising all Glu27 carriers. Conclusion: The allelic distribution of variants in this Omani cohort was similar to distributions reported among Caucasian populations. PMID:26629374

  11. Myosin-induced changes in F-actin: fluorescence probing of subdomain 2 by dansyl ethylenediamine attached to Gln-41.

    PubMed Central

    Kim, E; Miller, C J; Motoki, M; Seguro, K; Muhlrad, A; Reisler, E

    1996-01-01

    Actin labeled at Gln-41 with dansyl ethylenediamine (DED) via transglutaminase reaction was used for monitoring the interaction of myosin subfragment 1 (S1) with the His-40-Gly-42 site in the 38-52 loop on F-actin. Proteolytic digestions of F-actin with subtilisin and trypsin, and acto-S1 ATPase measurements on heat-treated F-actin revealed that the labeling of Gln-41 had a stabilizing effect on subdomain 2 and the actin filaments. DED on Gln-41 had no effect on the values of K(m) and Vmax of the acto-S1 ATPase and the sliding velocities of actin filaments in the in vitro motility assays. This suggests either that S1 does not bind to the 40-42 site on actin or that such binding is not functionally important. The binding of monoclonal antidansyl IgG to DED-F-actin did not affect acto-S1 binding in the absence of nucleotides, indicating that the 40-42 site does not contribute much to rigor acto-S1 binding. Myosin-induced changes in subdomain 2 on actin were manifested through an increase in the fluorescence of DED-F-actin, a decrease in the accessibility of the probe to collisional quenchers, and a partial displacement of antidansyl IgG from actin by S1. It is proposed that these changes in the 38-52 loop on actin originate from S1 binding to other myosin recognition sites on actin. Images FIGURE 7 FIGURE 8 PMID:8785300

  12. Raman Spectroscopy Reveals Direct Chromophore Interactions in the Leu/Gln105 Spectral Tuning Switch of Proteorhodopsins

    PubMed Central

    Kralj, Joel M.; Spudich, Elena N.; Spudich, John L.; Rothschild, Kenneth J.

    2013-01-01

    Proteorhodopsins are an extensive family of photoactive membrane proteins found in proteobacteria distributed throughout the world’s oceans which are often classified as green- or blue-absorbing (GPR and BPR, respectively) on the basis of their visible absorption maxima. GPR and BPR have significantly different properties including photocycle lifetimes and wavelength dependence on pH. Previous studies revealed that these different properties are correlated with a single residue, Leu105 in GPR and Gln105 in BPR, although the molecular basis for the different properties of GPR and BPR has not yet been elucidated. We have studied the unexcited states of GPR and BPR using resonance Raman spectroscopy which enhances almost exclusively chromophore vibrations. We find that both spectra are remarkably similar, indicating that the retinylidene structure of GPR and BPR are almost identical. However, the frequency of a band assigned to the retinal C13-methyl-rock vibration is shifted from 1006 cm−1 in GPR to 1012 cm−1 in BPR. A similar shift is observed in the GPR mutant L105Q indicating Leu and Gln residues interact differently with the retinal C13-methyl group. The environment of the Schiff base of GPR and BPR differ as indicated by differences in the H/D induced down-shift of the Schiff base vibration. Residues located in transmembrane helices (D–G) do not contribute to the observed differences in the protein–chromophore interaction between BPR and GPR based on the Raman spectra of chimeras. These results support a model whereby the substitution of the hydrophilic Gln105 in BPR with the smaller hydrophobic Leu105 in GPR directly alters the environment of both the retinal C13 group and the Schiff base. PMID:18717545

  13. Spin manipulation in nanoscale superconductors

    NASA Astrophysics Data System (ADS)

    Beckmann, D.

    2016-04-01

    The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined.

  14. Spin manipulation in nanoscale superconductors.

    PubMed

    Beckmann, D

    2016-04-27

    The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined. PMID:27001949

  15. A novel mutation (Arg169Gln) of the cardiac ryanodine receptor gene causing exercise-induced bidirectional ventricular tachycardia.

    PubMed

    Hsueh, Chia-Hsiang; Weng, Yi-Chun; Chen, Chao-Yu; Lin, Tin-Kwang; Lin, Yen-Hung; Lai, Ling-Ping; Lin, Jiunn-Lee

    2006-04-01

    An 18-year-old woman presented with exercise induced sudden collapse. Series of cardiac work up revealed no structural cardiac abnormalities. Bidirectional ventricular tachycardia occurred during a treadmill exercise test. Under the impression of catecholaminergic polymorphic ventricular tachycardia, we screened the cardiac ryanodine receptor gene for mutation. We identified a novel heterozygous mutation at the 169th amino acid (Arg169Gln). This amino acid is highly conserved among many species and this mutation was not present in 50 normal control subjects. This patient was treated with a beta-block with good response. PMID:16517285

  16. hPEPT1 affinity and translocation of selected Gln-Sar and Glu-Sar dipeptide derivatives.

    PubMed

    Eriksson, André Huss; Elm, Peter L; Begtrup, Mikael; Nielsen, Robert; Steffansen, Bente; Brodin, Birger

    2005-01-01

    The intestinal di- and tripeptide transporter hPEPT1 is considered responsible for the absorption of di- and tripeptides arising from digestion, along with several drugs and prodrugs. In order to gather information on the binding site of the protein, several structure-affinity relationships have been suggested. However, these are not necessarily predictive of compounds that are actually translocated by hPEPT1. More information on affinity to and translocation via hPEPT1 of side-chain-modified dipeptides may be gained by conducting a study of selected dipeptide derivatives with variety in size, hydrophobicity, and bond type. The aim of the present study was to synthesize new esters and amides based on L-Glu-Sar and investigate the effects that bond type and size of modification of the N-terminal side chain of sarcosine-containing dipeptides have on the affinity to and translocation via hPEPT1. The esters L-Glu(O-i-Bu)-Sar and L-Glu(OCH(2)Ada)-Sar and the amides L-Gln(N,N-dimethyl)-Sar and L-Gln(N-piperidinyl)-Sar were synthesized, and affinity to and translocation via hPEPT1 were investigated in mature Caco-2 cell monolayers, grown on permeable supports. Affinity was estimated in a competition assay using (14)C-labeled Gly-Sar. Translocation was measured as fluorescence ratios induced by the substrates using the fluorescent probe BCECF and an epifluorescence microscope setup. All compounds showed high affinity to hPEPT1, but only the amides L-Gln(N,N-dimethyl)-Sar and L-Gln(N-piperidinyl)-Sar were translocated by hPEPT1. hPEPT1 is very susceptible to modifications of the N-terminal amino acid side chain of dipeptidomimetic substrates, in terms of achieving compounds with high affinity for the transporter. However, as affinity is not predictive of translocation, derivatization in this position must be performed with great caution since some of the compounds investigated turn out not to be translocated by the transporter. PMID:15934785

  17. Meta-analysis of two ERCC2 (XPD) polymorphisms, Asp312Asn and Lys751Gln, in breast cancer.

    PubMed

    Pabalan, Noel; Francisco-Pabalan, Ofelia; Sung, Lillian; Jarjanazi, Hamdi; Ozcelik, Hilmi

    2010-11-01

    The excision repair cross-complementing group 2 gene (ERCC2) plays a key role in DNA repair. Several polymorphisms in the ERCC2 gene have been described, including the commonly occurring Lys751Gln and Asp312Asn polymorphisms. Studies investigating the association of these polymorphisms with breast cancer risk produced controversial results. To evaluate these associations presented in diverse populations, we have conducted a meta-analysis based on 40 studies from 33 publications in PubMed which included analyses of Lys751Gln (14,545 cases, 15,352 controls) and Asp312Asn polymorphisms (16,254 cases, 14,006 controls). Overall findings of both polymorphisms have implicated null effects (OR = 1.01-1.03) when the analyses were limited to the statistically powerful (≥80%) studies. Although modestly increased statistically significant breast cancer risk was detected in the underpowered studies (≤80%), removal of outliers resulted in null associations. Ethnic stratification showed non-significant and relatively null associations for both polymorphisms with breast cancer risk for the overall Caucasians as well as North American and the European sub-populations. Although statistically increased and decreased risks were observed for the homogenous populations of African-Americans (Lys751Gln, OR 1.25, 95% CI 1.03-1.53, P = 0.03) and Asians (Asp312Asn, ORs: 0.53-0.55, P values: 0.02-0.03), respectively, this may be the result of small sample size. Analyses of the homogeneous adduct studies, with relatively large sample size, exhibited increased risk for Lys751Gln (OR 1.20, 95% CI (1.02-1.41), P = 0.03) and Asp312Asn (OR 1.17 95% CI 1.02-1.34, P = 0.03) under the dominant genetic model. In conclusion, our results suggest null associations of both polymorphisms in the overall and the Caucasian subgroups, although some effects can be suggested for relatively smaller minority studies. Increased risk effect was more visible when the adduct studies are considered, suggesting the

  18. Transposon mutations in the 5' end of glnD, the gene for a nitrogen regulatory sensor, that suppress the osmosensitive phenotype caused by otsBA lesions in Escherichia coli.

    PubMed

    Tøndervik, Anne; Torgersen, Haakon R; Botnmark, Hans K; Strøm, Arne R

    2006-06-01

    GlnD of Escherichia coli is a bifunctional signal-transducing enzyme (102.4 kDa) which uridylylates the allosteric regulatory protein PII and deuridylylates PII-UMP in response to growth with nitrogen excess or limitation, respectively. GlnD catalyzes these reactions in response to high or low levels of cytoplasmic glutamine, respectively, and indirectly directs the expression of nitrogen-regulated genes, e.g., the glnK-amtB operon. We report that chromosomal mini-Tn10 insertions situated after nucleotide number 997 or 1075 of glnD partially suppressed the osmosensitive phenotype of DeltaotsBA or otsA::Tn10 mutations (defective osmoregulatory trehalose synthesis). Strains carrying these glnD::mini-Tn10 mutations either completely repressed the expression of trp::(glnKp-lacZ) or induced this reporter system to nearly 60% of the wild-type glnD level in response to nitrogen availability, an essentially normal response. This was in contrast to the much-studied glnD99::Tn10 mutation, which carries its insertion in the 3' end of the gene, causes a complete repression of glnKp-lacZ expression under all growth conditions, and also confers leaky glutamine auxotrophy. When expressed from the Pm promoter in plasmid constructs, the present glnD mutations produced proteins with an apparent mass of 39 or 42 kDa. These proteins were deduced to comprise 344 or 370 N-terminal residues, respectively, harboring the known nucleotidyltransferase domain of GlnD, plus a common C-terminal addition of 12 residues encoded by IS10. They lacked three other domains of GlnD. Apparently, the transferase domain by itself enabled the cells to catalyze the uridylylation reaction and direct nitrogen-regulated gene expression. Our data indicate that there exists a link between osmotic stress and the nitrogen response. PMID:16740928

  19. Transposon Mutations in the 5′ End of glnD, the Gene for a Nitrogen Regulatory Sensor, That Suppress the Osmosensitive Phenotype Caused by otsBA Lesions in Escherichia coli

    PubMed Central

    Tøndervik, Anne; Torgersen, Haakon R.; Botnmark, Hans K.; Strøm, Arne R.

    2006-01-01

    GlnD of Escherichia coli is a bifunctional signal-transducing enzyme (102.4 kDa) which uridylylates the allosteric regulatory protein PII and deuridylylates PII-UMP in response to growth with nitrogen excess or limitation, respectively. GlnD catalyzes these reactions in response to high or low levels of cytoplasmic glutamine, respectively, and indirectly directs the expression of nitrogen-regulated genes, e.g., the glnK-amtB operon. We report that chromosomal mini-Tn10 insertions situated after nucleotide number 997 or 1075 of glnD partially suppressed the osmosensitive phenotype of ΔotsBA or otsA::Tn10 mutations (defective osmoregulatory trehalose synthesis). Strains carrying these glnD::mini-Tn10 mutations either completely repressed the expression of trp::(glnKp-lacZ) or induced this reporter system to nearly 60% of the wild-type glnD level in response to nitrogen availability, an essentially normal response. This was in contrast to the much-studied glnD99::Tn10 mutation, which carries its insertion in the 3′ end of the gene, causes a complete repression of glnKp-lacZ expression under all growth conditions, and also confers leaky glutamine auxotrophy. When expressed from the Pm promoter in plasmid constructs, the present glnD mutations produced proteins with an apparent mass of 39 or 42 kDa. These proteins were deduced to comprise 344 or 370 N-terminal residues, respectively, harboring the known nucleotidyltransferase domain of GlnD, plus a common C-terminal addition of 12 residues encoded by IS10. They lacked three other domains of GlnD. Apparently, the transferase domain by itself enabled the cells to catalyze the uridylylation reaction and direct nitrogen-regulated gene expression. Our data indicate that there exists a link between osmotic stress and the nitrogen response. PMID:16740928

  20. DNA Repair Gene (XRCC1) Polymorphism (Arg399Gln) Associated with Schizophrenia in South Indian Population: A Genotypic and Molecular Dynamics Study

    PubMed Central

    Sujitha, S. P.; Kumar, D. Thirumal; Doss, C. George Priya; Aavula, K.; Ramesh, R.; Lakshmanan, S.; Gunasekaran, S.; Anilkumar, G.

    2016-01-01

    This paper depicts the first report from an Indian population on the association between the variant Arg399Gln of XRCC1 locus in the DNA repair system and schizophrenia, the debilitating disease that affects 1% of the world population. Genotypic analysis of a total of 523 subjects (260 patients and 263 controls) revealed an overwhelming presence of Gln399Gln in the case subjects against the controls (P < 0.0068), indicating significant level of association of this nsSNP with schizophrenia; the Gln399 allele frequency was also perceptibly more in cases than in controls (p < 0.003; OR = 1.448). The results of the genotypic studies were further validated using pathogenicity and stability prediction analysis employing computational tools [I-Mutant Suite, iStable, PolyPhen2, SNAP, and PROVEAN], with a view toassess the magnitude of deleteriousness of the mutation. The pathogenicity analysis reveals that the nsSNP could be deleterious inasmuch as it could affect the functionality of the gene, and interfere with protein function. Molecular dynamics simulation of 60ns was performed using GROMACS to analyse structural change due to a mutation (Arg399Gln) that was never examined before. RMSD, RMSF, hydrogen bonds, radius of gyration and SASA analysis showedthe existence of asignificant difference between the native and the mutant protein. The present study gives astrong indication that the XRCC1 locus deserves serious attention, as it could be a potential candidatecontributing to the etio-pathogenesis of the disease. PMID:26824244

  1. Analysis of the IDS Gene in 38 Patients with Hunter Syndrome: The c.879G>A (p.Gln293Gln) Synonymous Variation in a Female Create Exonic Splicing

    PubMed Central

    Zhang, Huiwen; Li, Jing; Zhang, Xinshun; Wang, Yu; Qiu, Wenjuan; Ye, Jun; Han, Lianshu; Gao, Xiaolan; Gu, Xuefan

    2011-01-01

    Background Hunter syndrome (mucopolysaccharidosis type II, MPS II) is a rare disease inherited in an X-linked autosomal recessive pattern. It is the prevailing form of the mucopolysaccharidoses in China. Here we investigated mutations of IDS (iduronate 2-sulfatase) gene in 38 unrelated Chinese patients, one of which is a female. Methods Peripheral leucocytes were collected from the patients and the IDS gene was amplified to looking for the variations. For a female patient, the X chromosome status was analyzed by androgen receptor X-inactivation assay and the mutation impact on RNA level was further performed by reverse transcription polymerase chain reaction. Results We discovered that point mutations constituted the major form while mutations in codon p.R468 defined the largest number of patients in our cohort. Consistent with data from other ethnic groups, exons 9 and 3 had comparatively more mutations, while exon 2 had quite a few mutations unique to Chinese patients. Of the 30 different mutations identified, only 9 were novel: one was a premature termination mutation, i.e., c.196C>T (p.Gln66X); three were missense mutations, i.e., c.200T>C (p.Leu67Pro), c.215T>C (p.Leu72Pro), c.389C>T (p.Thr130Ile); one was a small deletion, i.e., c.1104_1122del19 (p.Ser369ArgfsX16); and one was a deletion that spanned both exons 8 and 9 deletion leading to gross structural changes in the IDS gene. In addition, a synonymous mutation c.879G>A (p.Gln293Gln) was identified in a female Hunter disease patient, which resulted in loss of the original splicing site, activated a cryptic splicing site upstream, leading to a 28 bp deletion and a premature termination at p. Tyr285GlufsX47. Together with concurrent skewed X-inactivation this was believed to facilitate the development of Hunter disease in this girl. Conclusions In conclusion, the molecular analysis of IDS gene in Chinese patients confirmed the Hunter disease diagnosis and expanded the mutation and clinical spectrum of this

  2. Structural and Functional Study of the GlnB22-Insulin Mutant Responsible for Maturity-Onset Diabetes of the Young

    PubMed Central

    Křížková, Květoslava; Veverka, Václav; Maletínská, Lenka; Hexnerová, Rozálie; Brzozowski, Andrzej M.; Jiráček, Jiří; Žáková, Lenka

    2014-01-01

    The insulin gene mutation c.137G>A (R46Q), which changes an arginine at the B22 position of the mature hormone to glutamine, causes the monogenic diabetes variant maturity-onset diabetes of the young (MODY). In MODY patients, this mutation is heterozygous, and both mutant and wild-type (WT) human insulin are produced simultaneously. However, the patients often depend on administration of exogenous insulin. In this study, we chemically synthesized the MODY mutant [GlnB22]-insulin and characterized its biological and structural properties. The chemical synthesis of this insulin analogue revealed that its folding ability is severely impaired. In vitro and in vivo tests showed that its binding affinity and biological activity are reduced (both approximately 20% that of human insulin). Comparison of the solution structure of [GlnB22]-insulin with the solution structure of native human insulin revealed that the most significant structural effect of the mutation is distortion of the B20-B23 β-turn, leading to liberation of the B chain C-terminus from the protein core. The distortion of the B20-B23 β-turn is caused by the extended conformational freedom of the GlnB22 side chain, which is no longer anchored in a hydrogen bonding network like the native ArgB22. The partially disordered [GlnB22]-insulin structure appears to be one reason for the reduced binding potency of this mutant and may also be responsible for its low folding efficiency in vivo. The altered orientation and flexibility of the B20-B23 β-turn may interfere with the formation of disulfide bonds in proinsulin bearing the R46Q (GlnB22) mutation. This may also have a negative effect on the WT proinsulin simultaneously biosynthesized in β-cells and therefore play a major role in the development of MODY in patients producing [GlnB22]-insulin. PMID:25423173

  3. Quantitative assessment of the association between XRCC1 Arg399Gln and Arg194Trp polymorphisms and risk of cutaneous melanoma.

    PubMed

    Jiang, Huayong; Xu, Weidong; Zhang, Fuli; Wei, Li; Wang, Yajie; Wang, Yadi; Liu, Chuan

    2016-06-01

    Accumulating evidence has suggested that the XRCC1 Arg399Gln and Arg194Trp polymorphisms might be related to cutaneous melanoma susceptibility. However, epidemiologic findings have been inconsistent. We have assessed reported studies by meta-analysis to perform a more precise estimation of the association between the XRCC1 two polymorphisms (Arg399Gln, Arg194Trp) and risk of cutaneous melanoma. A total of seven eligible articles were selected for this meta-analysis, including 3454 cases and 3811 controls for the XRCC1 Arg399Gln polymorphism and 1256 cases and 1575 controls for the XRCC1 Arg194Trp polymorphism. Overall, no significant associations were found in all genetic models when the studies were pooled into the meta-analysis for the Arg399Gln and Arg194Trp polymorphisms. When stratified by source of control, significant associations were found for the Arg399Gln polymorphism in the population-based subgroup under AA versus GG [odds ratio (OR)=1.43, 95% confidence interval (CI)=1.08-1.88]; the dominant model AA/GA versus GG (OR=1.25, 95% CI=1.04-1.51); and the recessive model AA versus GA/GG (OR=1.31, 95% CI=1.01-1.68). No significant associations were found for the Arg194Trp polymorphism in the subgroup analysis. This meta-analysis suggested that the XRCC1 Arg399Gln polymorphism was a risk factor for cutaneous melanoma in population-based subgroup. PMID:26967970

  4. Association of XPD (Lys751Gln) and XRCC1 (Arg280His) gene polymorphisms in myelodysplastic syndrome.

    PubMed

    Joshi, Dolly; Korgaonkar, Seema; Shanmukhaiah, Chandrakala; Vundinti, Babu Rao

    2016-01-01

    Myelodysplastic syndromes (MDSs) are heterogeneous hematopoietic disease characterized by ineffective haematopoiesis that frequently transforms into acute leukaemia. Alterations in many individual biologic pathways have been reported in MDS pathophysiology. Disease progression along the MDS, acute myeloid leukemia (AML) continuum is believed to be a consequence of stepwise accumulation of DNA mutations which infers a defect in DNA repair. The present study investigated the association between DNA repair genes (XRCC1, XRCC3, OGG1, XPD and RAD51) and the risk of developing MDS. The study was carried out in 92 primary MDS patients. The genotyping study was carried out by PCR-RFLP technique. We have studied seven single-nucleotide polymorphisms (SNPs) of five DNA repair genes (XRCC1 (Arg194Trp, Arg280His, Arg399Gln), XRCC3, XPD, RAD51 and OGG1). Significantly, a high frequency of DNA repair gene XRCC1 (Arg280His) (p=0.05) and XPD (Lys751Gln) (p=0.01) polymorphism was observed in MDS patients compared to controls. The distribution of polymorphisms in MDS subgroups showed a significant association of XRCC1 with RAEB I compared to other subgroup. Though a high frequency of XRCC1 gene polymorphism was observed in farmers and tobacco chewers, it was not statistically significant. Our study suggests that XRCC1 (Arg280His) and XPD polymorphisms are associated with risk of MDS and XRCC1 polymorphism strongly associated with advanced MDS subgroup. Hence, these polymorphisms can be used as a prognostic marker in MDS. PMID:26482462

  5. Spin hydrodynamic generation

    NASA Astrophysics Data System (ADS)

    Takahashi, R.; Matsuo, M.; Ono, M.; Harii, K.; Chudo, H.; Okayasu, S.; Ieda, J.; Takahashi, S.; Maekawa, S.; Saitoh, E.

    2016-01-01

    Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.

  6. Geometric spin echo under zero field

    PubMed Central

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-01-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936

  7. Geometric spin echo under zero field.

    PubMed

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-01-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936

  8. Geometric spin echo under zero field

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-05-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors.

  9. Identification and functional characterization of NifA variants that are independent of GlnB activation in the photosynthetic bacterium Rhodospirillum rubrum.

    PubMed

    Zou, Xiaoxiao; Zhu, Yu; Pohlmann, Edward L; Li, Jilun; Zhang, Yaoping; Roberts, Gary P

    2008-09-01

    The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tightly regulated in response to ammonium and oxygen. However, the mechanisms for the regulation of NifA activity are quite different among various nitrogen-fixing bacteria. Unlike the well-studied NifL-NifA regulatory systems in Klebsiella pneumoniae and Azotobacter vinelandii, in Rhodospirillum rubrum NifA is activated by a direct protein-protein interaction with the uridylylated form of GlnB, which in turn causes a conformational change in NifA. We report the identification of several substitutions in the N-terminal GAF domain of R. rubrum NifA that allow NifA to be activated in the absence of GlnB. Presumably these substitutions cause conformational changes in NifA necessary for activation, without interaction with GlnB. We also found that wild-type NifA can be activated in a GlnB-independent manner under certain growth conditions, suggesting that some other effector(s) can also activate NifA. An attempt to use Tn5 mutagenesis to obtain mutants that altered the pool of these presumptive effector(s) failed, though much rarer spontaneous mutations in nifA were detected. This suggests that the necessary alteration of the pool of effector(s) for NifA activation cannot be obtained by knockout mutations. PMID:18757802

  10. XRCC1 Arg399Gln Polymorphism Confers Risk of Breast Cancer in American Population: A Meta-Analysis of 10846 Cases and 11723 Controls

    PubMed Central

    Sun, Yong; Zhao, Li; Peng, Yang; Zhou, Shudong; Li, Lixia; Chen, Sidong; Gao, Yanhui

    2014-01-01

    Background In the X-ray repair cross-complementing group 1 (XRCC1) gene, a polymorphism, Arg399Gln (rs25487), has been shown to change neoconservative amino acid and thus result in alternation of DNA repair capacity. Numerous studies have investigated the association between Arg399Gln and breast cancer risk in the American population, but yielding inconsistent results. This study aimed to clarify the role of this polymorphism in susceptibility to breast cancer. Methods Literatures were searched in multiple databases including PubMed, Springer Link, Ovid, EBSCO and ScienceDirect databases up to April 2013. A comprehensive meta-analysis was conducted to estimate the overall odds ratio (OR), by integrating data from 18 case control studies of 10846 cases and 11723 controls in the American population. Results Overall, significant association was observed between the Arg399Gln polymorphism and breast cancer risk under the random-effects model (OR for dominant model = 1.12, 95% CI: 1.02–1.24, Pheterogeneity = 0.003; OR for additive model = 1.07, 95% CI: 1.01–1.14, Pheterogeneity = 0.017). Further sensitivity analysis supported the robust stability of this current result by showing similar ORs before and after removal of a single study. Conclusions This meta-analysis suggests that the XRCC1 Arg399Gln polymorphism may significantly contribute to susceptibility of breast cancer in the American population. PMID:24489692

  11. Spin-orbit coupling in actinide cations

    NASA Astrophysics Data System (ADS)

    Bagus, Paul S.; Ilton, Eugene S.; Martin, Richard L.; Jensen, Hans Jørgen Aa.; Knecht, Stefan

    2012-09-01

    The limiting case of Russell-Saunders coupling, which leads to a maximum spin alignment for the open shell electrons, usually explains the properties of high spin ionic crystals with transition metals. For actinide compounds, the spin-orbit splitting is large enough to cause a significantly reduced spin alignment. Novel concepts are used to explain the dependence of the spin alignment on the 5f shell occupation. We present evidence that the XPS of ionic actinide materials may provide direct information about the angular momentum coupling within the 5f shell.

  12. Spin-polarized quasiparticle transport in exchange-split superconducting aluminum on europium sulfide

    NASA Astrophysics Data System (ADS)

    Wolf, M. J.; Sürgers, C.; Fischer, G.; Beckmann, D.

    2014-10-01

    We report on nonlocal spin transport in mesoscopic superconducting aluminum wires in contact with the ferromagnetic insulator europium sulfide. We find spin injection and long-range spin transport in the regime of the exchange splitting induced by europium sulfide. Our results demonstrate that spin transport in superconductors can be manipulated by ferromagnetic insulators, and opens a path to control spin currents in superconductors.

  13. Crystal Structure of a Thermostable Alanine Racemase from Thermoanaerobacter tengcongensis MB4 Reveals the Role of Gln360 in Substrate Selection

    PubMed Central

    Wang, Xiaoyan; Xu, Shujing; Ju, Jiansong; Xu, Xiaoling

    2015-01-01

    Pyridoxal 5’-phosphate (PLP) dependent alanine racemase catalyzes racemization of L-Ala to D-Ala, a key component of the peptidoglycan network in bacterial cell wall. It has been extensively studied as an important antimicrobial drug target due to its restriction in eukaryotes. However, many marketed alanine racemase inhibitors also act on eukaryotic PLP-dependent enzymes and cause side effects. A thermostable alanine racemase (AlrTt) from Thermoanaerobacter tengcongensis MB4 contains an evolutionarily non-conserved residue Gln360 in inner layer of the substrate entryway, which is supposed to be a key determinant in substrate specificity. Here we determined the crystal structure of AlrTt in complex with L-Ala at 2.7 Å resolution, and investigated the role of Gln360 by saturation mutagenesis and kinetic analysis. Compared to typical bacterial alanine racemase, presence of Gln360 and conformational changes of active site residues disrupted the hydrogen bonding interactions necessary for proper PLP immobilization, and decreased both the substrate affinity and turnover number of AlrTt. However, it could be complemented by introduction of hydrophobic amino acids at Gln360, through steric blocking and interactions with a hydrophobic patch near active site pocket. These observations explained the low racemase activity of AlrTt, revealed the essential role of Gln360 in substrate selection, and its preference for hydrophobic amino acids especially Tyr in bacterial alanine racemization. Our work will contribute new insights into the alanine racemization mechanism for antimicrobial drug development. PMID:26218070

  14. The ERCC2/XPD Lys751Gln polymorphism affects DNA repair of benzo[a]pyrene induced damage, tested in an in vitro model.

    PubMed

    Xiao, Sha; Cui, Su; Lu, Xiaobo; Guan, Yangyang; Li, Dandan; Liu, Qiufang; Cai, Yuan; Jin, Cuihong; Yang, Jinghua; Wu, Shengwen; van der Straaten, Tahar

    2016-08-01

    Nucleotide excision repair (NER) is an important defense mechanism of the body to exogenous carcinogens and mutagens, such as benzo[a]pyrene (B[a]P). Genetic polymorphisms in ERCC2/XPD, a critical element in NER, are thought to be associated with individual's cancer susceptibility. Although ERCC2/XPD Lys751Gln (rs13181) is the most studied polymorphism, the impact of this polymorphism on DNA repair capacity to carcinogen remains unclear. In the present study, cDNA clones carrying different genotypes of ERCC2/XPD (Lys751Gln) were introduced into an ERCC2/XPD deficient cell line (UV5) in a well-controlled biological system. After B[a]P treatment, cell growth inhibition rates and DNA damage levels in all cells were detected respectively. As expected, we found that the DNA repair capacity in UV5 cells was restored to levels similar to wildtype parent AA8 cells upon introduction of the cDNA clone of ERCC2/XPD (Lys751). Interestingly, after B[a]P treatment, transfected cells expressing variant ERCC2/XPD (751Gln) showed an enhanced cellular sensitivity and a diminished DNA repair capacity. The wildtype genotype AA (Lys) was found to be associated with a higher DNA repair capacity as compared to its polymorphic genotype CC (Gln). These data indicate that ERCC2/XPD Lys751Gln polymorphism affects DNA repair capacity after exposure to environmental carcinogens such as B[a]P in this well-controlled in vitro system and could act as a biomarker to increase the predictive value to develop cancer. PMID:27139774

  15. Arg16Gly and Gln27Glu β2 adrenergic polymorphisms influence cardiac autonomic modulation and baroreflex sensitivity in healthy young Brazilians.

    PubMed

    Atala, Magda M; Goulart, Alessandra; Guerra, Grazia M; Mostarda, Cristiano; Rodrigues, Bruno; Mello, Priscila R; Casarine, Dulce E; Irigoyen, Maria-Claudia; Pereira, Alexandre C; Consolim-Colombo, Fernanda M

    2015-01-01

    The association between functional β2 adrenergic receptor (β2-AR) polymorphisms and cardiac autonomic modulation is still unclear. Thus, two common polymorphisms in the β2-AR gene (Gln27Glu β2 and Arg16Gly β2) were studied to determine whether they might affect tonic and reflex cardiac sympathetic activity in healthy young subjects. A total of 213 healthy young white subjects of both genders (53% female), aged 18-30 years (23.5±3.4 y), had their continuous blood pressure curves noninvasively recorded by Finometer at baseline, and other hemodynamic parameters, as cardiac autonomic modulation, baroreflex sensitivity, and allele, genotype, and diplotype frequencies calculated. Associations were made between Arg16Gly β2 and Gln27Glu β2 polymorphisms and between β2-AR diplotypes and all variables. The heart rate was significantly lower (P<0.001) in the presence of homozygous Arg/Arg alleles (60.9±1.5 bpm) than in that of Arg/Gly heterozygotes (65.9±1.0 bpm) or Gly/Gly homozygotes (66.3±1.2 bpm). Homozygous carriers of Arg16 allele had an alpha index (19.2±1.3) significantly higher (P<0.001) than that of the subjects with the Gly allele Gly/Gly (14.5±0.7) or Arg/Gly (14.6±0.7). Furthermore, the recessive Glu27Glu and the heterozygous Gln27Glu genotypes had a higher percentage of low-frequency components (LF%) than the homozygous Gln27Gln (15.1% vs. 16.0% vs. 8.2%, P=0.03, respectively). In healthy young subjects, the presence of β2-AR Arg16 allele in a recessive model was associated with higher baroreflex sensitivity, and increased parasympathetic modulation in studied individuals. PMID:25755837

  16. Arg16Gly and Gln27Glu β2 adrenergic polymorphisms influence cardiac autonomic modulation and baroreflex sensitivity in healthy young Brazilians

    PubMed Central

    Atala, Magda M; Goulart, Alessandra; Guerra, Grazia M; Mostarda, Cristiano; Rodrigues, Bruno; Mello, Priscila R; Casarine, Dulce E; Irigoyen, Maria-Claudia; Pereira, Alexandre C; Consolim-Colombo, Fernanda M

    2015-01-01

    The association between functional β2 adrenergic receptor (β2-AR) polymorphisms and cardiac autonomic modulation is still unclear. Thus, two common polymorphisms in the β2-AR gene (Gln27Glu β2 and Arg16Gly β2) were studied to determine whether they might affect tonic and reflex cardiac sympathetic activity in healthy young subjects. A total of 213 healthy young white subjects of both genders (53% female), aged 18-30 years (23.5±3.4 y), had their continuous blood pressure curves noninvasively recorded by Finometer at baseline, and other hemodynamic parameters, as cardiac autonomic modulation, baroreflex sensitivity, and allele, genotype, and diplotype frequencies calculated. Associations were made between Arg16Gly β2 and Gln27Glu β2 polymorphisms and between β2-AR diplotypes and all variables. The heart rate was significantly lower (P<0.001) in the presence of homozygous Arg/Arg alleles (60.9±1.5 bpm) than in that of Arg/Gly heterozygotes (65.9±1.0 bpm) or Gly/Gly homozygotes (66.3±1.2 bpm). Homozygous carriers of Arg16 allele had an alpha index (19.2±1.3) significantly higher (P<0.001) than that of the subjects with the Gly allele Gly/Gly (14.5±0.7) or Arg/Gly (14.6±0.7). Furthermore, the recessive Glu27Glu and the heterozygous Gln27Glu genotypes had a higher percentage of low-frequency components (LF%) than the homozygous Gln27Gln (15.1% vs. 16.0% vs. 8.2%, P=0.03, respectively). In healthy young subjects, the presence of β2-AR Arg16 allele in a recessive model was associated with higher baroreflex sensitivity, and increased parasympathetic modulation in studied individuals. PMID:25755837

  17. Spin filter for arbitrary spins by substrate engineering.

    PubMed

    Pal, Biplab; Römer, Rudolf A; Chakrabarti, Arunava

    2016-08-24

    We design spin filters for particles with potentially arbitrary spin [Formula: see text] using a one-dimensional periodic chain of magnetic atoms as a quantum device. Describing the system within a tight-binding formalism we present an analytical method to unravel the analogy between a one-dimensional magnetic chain and a multi-strand ladder network. This analogy is crucial, and is subsequently exploited to engineer gaps in the energy spectrum by an appropriate choice of the magnetic substrate. We obtain an exact correlation between the magnitude of the spin of the incoming beam of particles and the magnetic moment of the substrate atoms in the chain desired for opening up of a spectral gap. Results of spin polarized transport, calculated within a transfer matrix formalism, are presented for particles having half-integer as well as higher spin states. We find that the chain can be made to act as a quantum device which opens a transmission window only for selected spin components over certain ranges of the Fermi energy, blocking them in the remaining part of the spectrum. The results appear to be robust even when the choice of the substrate atoms deviates substantially from the ideal situation, as verified by extending the ideas to the case of a 'spin spiral'. Interestingly, the spin spiral geometry, apart from exhibiting the filtering effect, is also seen to act as a device flipping spins-an effect that can be monitored by an interplay of the system size and the period of the spiral. Our scheme is applicable to ultracold quantum gases, and might inspire future experiments in this direction. PMID:27352129

  18. Realization of a micrometre-scale spin-wave interferometer

    NASA Astrophysics Data System (ADS)

    Rousseau, O.; Rana, B.; Anami, R.; Yamada, M.; Miura, K.; Ogawa, S.; Otani, Y.

    2015-05-01

    The recent development of spin dynamics opens perspectives for various applications based on spin waves, including logic devices. The first important step in the realization of spin-wave-based logics is the manipulation of spin-wave interference. Here, we present the experimental realization of a micrometre-scale spin-wave interferometer consisting of two parallel spin-wave waveguides. The spin waves propagate through the waveguides and the superposition or interference of the electrical signals corresponding to the spin waves is measured. A direct current flowing through a metal wire underneath one of the spin-wave waveguides affects the propagation properties of the corresponding spin wave. The signal of constructive or destructive interference depends on the magnitude and direction of the applied direct current. Thus, the present work demonstrates a unique manipulation of spin-wave interference.

  19. Realization of a micrometre-scale spin-wave interferometer

    PubMed Central

    Rousseau, O.; Rana, B.; Anami, R.; Yamada, M.; Miura, K.; Ogawa, S.; Otani, Y.

    2015-01-01

    The recent development of spin dynamics opens perspectives for various applications based on spin waves, including logic devices. The first important step in the realization of spin-wave-based logics is the manipulation of spin-wave interference. Here, we present the experimental realization of a micrometre-scale spin-wave interferometer consisting of two parallel spin-wave waveguides. The spin waves propagate through the waveguides and the superposition or interference of the electrical signals corresponding to the spin waves is measured. A direct current flowing through a metal wire underneath one of the spin-wave waveguides affects the propagation properties of the corresponding spin wave. The signal of constructive or destructive interference depends on the magnitude and direction of the applied direct current. Thus, the present work demonstrates a unique manipulation of spin-wave interference. PMID:25975283

  20. Role of VicRKX and GlnR in pH-Dependent Regulation of the Streptococcus salivarius 57.I Urease Operon.

    PubMed

    Huang, Szu-Chuan; Chen, Yi-Ywan M

    2016-01-01

    Ureolysis by Streptococcus salivarius is critical for pH homeostasis of dental plaque and prevention of dental caries. The expression of S. salivarius urease is induced by acidic pH and carbohydrate excess. The differential expression is mainly controlled at the transcriptional level from the promoter 5' to ureI (p ureI ). Our previous study demonstrates that CodY represses p ureI by binding to a CodY box 5' to p ureI , and the repression is more pronounced in cells grown at pH 7 than in cells grown at pH 5.5. Recent sequence analysis revealed a putative VicR consensus and two GlnR boxes 5' to the CodY box. The results of DNA affinity precipitation assay, electrophoretic mobility shift assay, and chromatin immunoprecipitation-PCR analysis confirmed that both GlnR and VicR interact with the predicted binding sites in p ureI . Isogenic mutant strains (vicRKX null and glnR null) and their derivatives (harboring S. salivarius vicRKX and glnR, respectively) were generated in a recombinant Streptococcus gordonii strain harboring a p ureI-chloramphenicol acetyltransferase gene fusion on gtfG to investigate the regulation of VicR and GlnR. The results indicated that GlnR activates, whereas VicR represses, p ureI expression. The repression by VicR is more pronounced at pH 7, whereas GlnR is more active at pH 5.5. Furthermore, the VicR box acts as an upstream element to enhance p ureI expression in the absence of the cognate regulator. The overall regulation by CodY, VicR, and GlnR in response to pH ensures an optimal expression of urease in S. salivarius when the enzyme is most needed. IMPORTANCE Dental plaque rich in alkali-producing bacteria is less cariogenic, and thus, urease-producing Streptococcus salivarius has been considered as a therapeutic agent for dental caries control. Being one of the few ureolytic microbes in the oral cavity, S. salivarius strain 57.I promotes its competitiveness by mass-producing urease only at acidic growth pH. Here, we

  1. Role of VicRKX and GlnR in pH-Dependent Regulation of the Streptococcus salivarius 57.I Urease Operon

    PubMed Central

    Huang, Szu-Chuan

    2016-01-01

    ABSTRACT Ureolysis by Streptococcus salivarius is critical for pH homeostasis of dental plaque and prevention of dental caries. The expression of S. salivarius urease is induced by acidic pH and carbohydrate excess. The differential expression is mainly controlled at the transcriptional level from the promoter 5′ to ureI (pureI). Our previous study demonstrates that CodY represses pureI by binding to a CodY box 5′ to pureI, and the repression is more pronounced in cells grown at pH 7 than in cells grown at pH 5.5. Recent sequence analysis revealed a putative VicR consensus and two GlnR boxes 5′ to the CodY box. The results of DNA affinity precipitation assay, electrophoretic mobility shift assay, and chromatin immunoprecipitation-PCR analysis confirmed that both GlnR and VicR interact with the predicted binding sites in pureI. Isogenic mutant strains (vicRKX null and glnR null) and their derivatives (harboring S. salivarius vicRKX and glnR, respectively) were generated in a recombinant Streptococcus gordonii strain harboring a pureI-chloramphenicol acetyltransferase gene fusion on gtfG to investigate the regulation of VicR and GlnR. The results indicated that GlnR activates, whereas VicR represses, pureI expression. The repression by VicR is more pronounced at pH 7, whereas GlnR is more active at pH 5.5. Furthermore, the VicR box acts as an upstream element to enhance pureI expression in the absence of the cognate regulator. The overall regulation by CodY, VicR, and GlnR in response to pH ensures an optimal expression of urease in S. salivarius when the enzyme is most needed. IMPORTANCE Dental plaque rich in alkali-producing bacteria is less cariogenic, and thus, urease-producing Streptococcus salivarius has been considered as a therapeutic agent for dental caries control. Being one of the few ureolytic microbes in the oral cavity, S. salivarius strain 57.I promotes its competitiveness by mass-producing urease only at acidic growth pH. Here, we

  2. Charge and spin transport in mesoscopic superconductors

    PubMed Central

    Wolf, M J; Hübler, F; Kolenda, S

    2014-01-01

    Summary Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin. Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models. Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures. PMID:24605283

  3. The Impact of LEP G-2548A and LEPR Gln223Arg Polymorphisms on Adiposity, Leptin, and Leptin-Receptor Serum Levels in a Mexican Mestizo Population

    PubMed Central

    Chavarria-Avila, Efraín; Gomez-Bañuelos, Eduardo; Ruiz-Quezada, Sandra-Luz; Castro-Albarran, Jorge; Sánchez-López, Lizeth; Martín-Marquez, Beatriz Teresita; Navarro-Hernández, Rosa-Elena

    2015-01-01

    The polymorphisms in leptin (LEP G-2548A) and leptin-receptor (LEPR Gln223Arg) seem to influence obesity and lipid metabolism among others. The aim of this study was to investigate the effect of these polymorphisms on adiposity, leptin (sLeptin), and leptin-receptor (sLeptin-receptor) serum concentrations as well as inflammation markers. We included 382 adults originally from Western Mexico. They were genotyped by PCR-RFLP. Obese individuals showed higher sLeptin (58.2 ± 31.35 ng/mL) but lower sLeptin-receptor (12.6 ± 3.74 ng/mL) levels than normal weight ones (17.6 ± 14.62 ng/mL, 17.4 ± 4.62 ng/mL, resp.), P < 0.001. Obese subjects carriers of Arg/Arg genotype had more (P = 0.016) sLeptin-receptor (14.7 ± 4.96 ng/mL) and less (P = 0.004) sLeptin (44.0 ± 28.12 ng/mL) levels than Gln/Gln genotype (11.0 ± 2.92 ng/mL, 80.3 ± 33.24 ng/mL, resp.). Body fat mass was lower (P from 0.003 to 0.045) for A/A (36.5% ± 6.80) or Arg/Arg (36.8% ± 6.82) genotypes with respect to G/G (41.3% ± 5.52) and G/A (41.6% ± 5.61) or Gln/Gln (43.7% ± 4.74) and Gln/Arg (41.0% ± 5.52) genotypes carriers. Our results suggest that LEP -2548A and LEPR 223Arg could be genetic markers of less body fat mass accumulation in obese subjects from Western Mexico. PMID:26064921

  4. Spin filter for arbitrary spins by substrate engineering

    NASA Astrophysics Data System (ADS)

    Pal, Biplab; Römer, Rudolf A.; Chakrabarti, Arunava

    2016-08-01

    We design spin filters for particles with potentially arbitrary spin S≤ft(=1/2,1,3/2,\\ldots \\right) using a one-dimensional periodic chain of magnetic atoms as a quantum device. Describing the system within a tight-binding formalism we present an analytical method to unravel the analogy between a one-dimensional magnetic chain and a multi-strand ladder network. This analogy is crucial, and is subsequently exploited to engineer gaps in the energy spectrum by an appropriate choice of the magnetic substrate. We obtain an exact correlation between the magnitude of the spin of the incoming beam of particles and the magnetic moment of the substrate atoms in the chain desired for opening up of a spectral gap. Results of spin polarized transport, calculated within a transfer matrix formalism, are presented for particles having half-integer as well as higher spin states. We find that the chain can be made to act as a quantum device which opens a transmission window only for selected spin components over certain ranges of the Fermi energy, blocking them in the remaining part of the spectrum. The results appear to be robust even when the choice of the substrate atoms deviates substantially from the ideal situation, as verified by extending the ideas to the case of a ‘spin spiral’. Interestingly, the spin spiral geometry, apart from exhibiting the filtering effect, is also seen to act as a device flipping spins—an effect that can be monitored by an interplay of the system size and the period of the spiral. Our scheme is applicable to ultracold quantum gases, and might inspire future experiments in this direction.

  5. Multi centric origin of Hb D-Punjab [beta121(GH4)Glu-->Gln, GAA>CAA].

    PubMed

    Yavarian, Majid; Karimi, Mehran; Paran, Farideh; Neven, Catherine; Harteveld, Cornelis L; Giordano, Piero C

    2009-01-01

    Hb D-Punjab [beta121(GH4)Glu-->Gln, GAA>CAA], common in the northern Indian province, is often unexpectedly found in other populations. To study the multi centric origin of this variant which is causing sickle cell disease in association with Hb S [beta6(A3)Glu-->Val, GAG>GTG], we have examined the haplotype of the Hb D allele in different populations. We studied 43 alleles from south Iran (Hormozgan and Fars provinces) and 14 from Holland and Belgium using high performance liquid chromatography (HPLC), capillary electrophoresis, direct sequencing and/or restriction enzyme analysis. In Iranians, four haplotypes were observed at different frequencies: haplotype I [+ - - - -,+ +] at 67.5%, subhaplotype I' [+ - - - -,- +] at 17.5%, haplotype V [- + - - +,+ +] at 10.0% and haplotype III [- + - + +,+ +] at 5.0%. All European cases were on haplotype I. The occurrence of high Hb D frequencies on a single haplotype in specific regions can be expected if we consider founder effect and genetic drift mechanisms. However, considering that haplotype I is the most common haplotype worldwide, that Hb D-Punjab is reported in different populations on different haplotypes, and that codon beta121 is a site on which six different mutations are reported, we may expect to observe Hb D-Punjab in different populations, possibly because of a relatively higher occurrence of de novo mutations, generating unexpected risk from mixtures of allochtonous Hb S and indigenous Hb D-Punjab or vice versa. PMID:19958184

  6. Magnetoelectric control of spin currents

    NASA Astrophysics Data System (ADS)

    Gómez, J. E.; Vargas, J. M.; Avilés-Félix, L.; Butera, A.

    2016-06-01

    The ability to control the spin current injection has been explored on a hybrid magnetoelectric system consisting of a (011)-cut ferroelectric lead magnesium niobate-lead titanate (PMNT) single crystal, a ferromagnetic FePt alloy, and a metallic Pt. With this PMNT/FePt/Pt structure we have been able to control the magnetic field position or the microwave excitation frequency at which the spin pumping phenomenon between FePt and Pt occurs. We demonstrate that the magnetoelectric heterostructure operating in the L-T (longitudinal magnetized-transverse polarized) mode couples the PMNT crystal to the magnetostrictive FePt/Pt bilayer, displaying a strong magnetoelectric coefficient of ˜140 Oe cm kV-1. Our results show that this mechanism can be effectively exploited as a tunable spin current intensity emitter and open the possibility to create an oscillating or a bistable switch to effectively manipulate spin currents.

  7. Spin transport in epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Tbd, -

    2014-03-01

    Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non volatile devices such as the new STT-MRAM. Beyond its widely distributed application in data storage it aims at providing more complex architectures and a powerful beyond CMOS solution for information processing. The recent discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. We will present experimental results allowing us to assess the potential of graphene for spintronics. We will show that unprecedented highly efficient spin information transport can occur in epitaxial graphene leading to large spin signals and macroscopic spin diffusion lengths (~ 100 microns), a key enabler for the advent of envisioned beyond-CMOS spin-based logic architectures. We will also show that how the device behavior is well explained within the framework of the Valet-Fert drift-diffusion equations. Furthermore, we will show that a thin graphene passivation layer can prevent the oxidation of a ferromagnet, enabling its use in novel humide/ambient low-cost processes for spintronics devices, while keeping its highly surface sensitive spin current polarizer/analyzer behavior and adding new enhanced spin filtering property. These different experiments unveil promising uses of graphene for spintronics.

  8. Spin ejector

    DOEpatents

    Andersen, John A.; Flanigan, John J.; Kindley, Robert J.

    1978-01-01

    The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.

  9. Measurement of the levels of leptin, BDNF associated with polymorphisms LEP G2548A, LEPR Gln223Arg and BDNF Val66Met in Thai with metabolic syndrome

    PubMed Central

    2014-01-01

    Background Metabolic syndrome is a cluster of metabolic risk factors including dyslipidemia, impaired glucose tolerance, hypertension and central obesity. BDNF (Brain-derived neurotrophic factor) and leptin have been implied in the energy homeostasis. The purposes of this study were to examine concentrations of leptin, BDNF and biochemical parameters in metabolic-syndrome subjects and healthy controls, and also to search for associations of leptin gene (LEP) G2548A, leptin receptor gene (LEPR) Gln223Arg, and BDNF gene (BDNF) Val66Met polymorphisms with leptin levels, BDNF levels and metabolic syndrome among Thais. Methods The case-controlled design was performed using 322 Thai volunteers (160 metabolic-syndrome subjects; 162 controls) during the health screening program. Metabolic syndrome was assessed by using the modified National Cholesterol Education Program, Adult Treatment Panel III criteria. The levels of leptin, BDNF, insulin, glucose and lipids were measured in samples. Genotyping of LEP G2548A, LEPR Gln223Arg and BDNF Val66Met was carried out using polymerase chain reaction-restriction fragment length polymorphism technique. Results Serum leptin levels were significantly higher in the metabolic-syndrome group than the control group (p < 0.01), but the BDNF difference between them was not significant. Significant associations of LEPR Gln223Arg polymorphism were found with leptin and glucose levels (p < 0.05), after adjusting for potential covariates. This LEPR polymorphism in the metabolic-syndrome group was also significantly more frequent than in the control group (p < 0.05). However, other gene polymorphisms, LEP G2548A and BDNF Val66Met, showed no significant relationship with leptin levels, BDNF levels or metabolic syndrome. Conclusion These findings suggest leptin levels are linked with metabolic syndrome. LEPR Gln223Arg polymorphism impacted leptin concentrations, and this gene polymorphism may influence susceptibility to metabolic syndrome among

  10. Generation of full polarization in ferromagnetic graphene with spin energy gap

    SciTech Connect

    Wu, Qing-Ping; Liu, Zheng-Fang E-mail: aixichen@ecjtu.edu.cn; Liu, Zhi-Min; Chen, Ai-Xi E-mail: aixichen@ecjtu.edu.cn; Xiao, Xian-Bo

    2014-12-22

    We propose a workable scheme for the generation of full spin polarization in ferromagnetic graphene system with strain or Rashba spin-orbit interaction. A spin energy gap can be opened in ferromagnetic graphene system in the presence of strain or Rashba spin-orbit interaction, leading to the full polarization in the spin energy gap. In addition, under the combined modulation of strain and Rashba spin-orbit interaction, the ferromagnetic graphene system can generate significantly large spin-polarized current with a full polarization in the spin energy gap. It is anticipated to apply such a phenomenon to design the electron spin devices based on the graphene.

  11. Roles of PucR, GlnR, and TnrA in Regulating Expression of the Bacillus subtilis ure P3 Promoter

    PubMed Central

    Brandenburg, Jaclyn L.; Wray, Jr., Lewis V.; Beier, Lars; Jarmer, Hanne; Saxild, Hans H.; Fisher, Susan H.

    2002-01-01

    Expression of the P3 promoter of the Bacillus subtilis ureABC operon is activated during nitrogen-limited growth by PucR, the transcriptional regulator of the purine-degradative genes. Addition of allantoic acid, a purine-degradative intermediate, to nitrogen-limited cells stimulated transcription of ure P3 twofold. Since urea is produced during purine degradation in B. subtilis, regulation of ureABC expression by PucR allows purines to be completely degraded to ammonia. The nitrogen transcription factor TnrA was found to indirectly regulate ure P3 expression by activating pucR expression. The two consensus GlnR/TnrA binding sites located in the ure P3 promoter region were shown to be required for negative regulation by GlnR. Mutational analysis indicates that a cooperative interaction occurs between GlnR dimers bound at these two sites. B. subtilis is the first example where urease expression is both nitrogen regulated and coordinately regulated with the enzymes involved in purine transport and degradation. PMID:12374841

  12. Roles of Residues Arg-61 and Gln-38 of Human DNA Polymerase η in Bypass of Deoxyguanosine and 7,8-Dihydro-8-oxo-2'-deoxyguanosine.

    PubMed

    Su, Yan; Patra, Amritraj; Harp, Joel M; Egli, Martin; Guengerich, F Peter

    2015-06-26

    Like the other Y-family DNA polymerases, human DNA polymerase η (hpol η) has relatively low fidelity and is able to tolerate damage during DNA synthesis, including 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxoG), one of the most abundant DNA lesions in the genome. Crystal structures show that Arg-61 and Gln-38 are located near the active site and may play important roles in the fidelity and efficiency of hpol η. Site-directed mutagenesis was used to replace these side chains either alone or together, and the wild type or mutant proteins were purified and tested by replicating DNA past deoxyguanosine (G) or 8-oxoG. The catalytic activity of hpol η was dramatically disrupted by the R61M and Q38A/R61A mutations, as opposed to the R61A and Q38A single mutants. Crystal structures of hpol η mutant ternary complexes reveal that polarized water molecules can mimic and partially compensate for the missing side chains of Arg-61 and Gln-38 in the Q38A/R61A mutant. The combined data indicate that the positioning and positive charge of Arg-61 synergistically contribute to the nucleotidyl transfer reaction, with additional influence exerted by Gln-38. In addition, gel filtration chromatography separated multimeric and monomeric forms of wild type and mutant hpol η, indicating the possibility that hpol η forms multimers in vivo. PMID:25947374

  13. Mutagenic analysis of the a subunit of the F1F0 ATP synthase in Escherichia coli: Gln-252 through Tyr-263.

    PubMed

    Hartzog, P E; Cain, B D

    1993-03-01

    The a subunit of F1F0 ATP synthase contains a highly conserved region near its carboxyl terminus which is thought to be important in proton translocation. Cassette site-directed mutagenesis was used to study the roles of four conserved amino acids Gln-252, Phe-256, Leu-259, and Tyr-263. Substitution of basic amino acids at each of these four sites resulted in marked decreases in enzyme function. Cells carrying a subunit mutations Gln-252-->Lys, Phe-256-->Arg, Leu-259-->Arg, and Tyr-263-->Arg all displayed growth characteristics suggesting substantial loss of ATP synthase function. Studies of both ATP-driven proton pumping and proton permeability of stripped membranes indicated that proton translocation through F0 was affected by the mutations. Other mutations, such as the Phe-256-->Asp mutation, also resulted in reduced enzyme activity. However, more conservative amino acid substitutions generated at these same four positions produced minimal losses of F1F0 ATP synthase. The effects of mutations and, hence, the relative importance of the amino acids for enzyme function appeared to decrease with proximity to the carboxyl terminus of the a subunit. The data are most consistent with the hypothesis that the region between Gln-252 and Tyr-263 of the a subunit has an important structural role in F1F0 ATP synthase. PMID:8383111

  14. Nitrogen Starvation and TorC1 Inhibition Differentially Affect Nuclear Localization of the Gln3 and Gat1 Transcription Factors Through the Rare Glutamine tRNACUG in Saccharomyces cerevisiae

    PubMed Central

    Tate, Jennifer J.; Rai, Rajendra; Cooper, Terrance G.

    2015-01-01

    A leucine, leucyl-tRNA synthetase–dependent pathway activates TorC1 kinase and its downstream stimulation of protein synthesis, a major nitrogen consumer. We previously demonstrated, however, that control of Gln3, a transcription activator of catabolic genes whose products generate the nitrogenous precursors for protein synthesis, is not subject to leucine-dependent TorC1 activation. This led us to conclude that excess nitrogen-dependent down-regulation of Gln3 occurs via a second mechanism that is independent of leucine-dependent TorC1 activation. A major site of Gln3 and Gat1 (another GATA-binding transcription activator) control occurs at their access to the nucleus. In excess nitrogen, Gln3 and Gat1 are sequestered in the cytoplasm in a Ure2-dependent manner. They become nuclear and activate transcription when nitrogen becomes limiting. Long-term nitrogen starvation and treatment of cells with the glutamine synthetase inhibitor methionine sulfoximine (Msx) also elicit nuclear Gln3 localization. The sensitivity of Gln3 localization to glutamine and inhibition of glutamine synthesis prompted us to investigate the effects of a glutamine tRNA mutation (sup70-65) on nitrogen-responsive control of Gln3 and Gat1. We found that nuclear Gln3 localization elicited by short- and long-term nitrogen starvation; growth in a poor, derepressive medium; Msx or rapamycin treatment; or ure2Δ mutation is abolished in a sup70-65 mutant. However, nuclear Gat1 localization, which also exhibits a glutamine tRNACUG requirement for its response to short-term nitrogen starvation or growth in proline medium or a ure2Δ mutation, does not require tRNACUG for its response to rapamycin. Also, in contrast with Gln3, Gat1 localization does not respond to long-term nitrogen starvation. These observations demonstrate the existence of a specific nitrogen-responsive component participating in the control of Gln3 and Gat1 localization and their downstream production of nitrogenous precursors

  15. Nitrogen starvation and TorC1 inhibition differentially affect nuclear localization of the Gln3 and Gat1 transcription factors through the rare glutamine tRNACUG in Saccharomyces cerevisiae.

    PubMed

    Tate, Jennifer J; Rai, Rajendra; Cooper, Terrance G

    2015-02-01

    A leucine, leucyl-tRNA synthetase-dependent pathway activates TorC1 kinase and its downstream stimulation of protein synthesis, a major nitrogen consumer. We previously demonstrated, however, that control of Gln3, a transcription activator of catabolic genes whose products generate the nitrogenous precursors for protein synthesis, is not subject to leucine-dependent TorC1 activation. This led us to conclude that excess nitrogen-dependent down-regulation of Gln3 occurs via a second mechanism that is independent of leucine-dependent TorC1 activation. A major site of Gln3 and Gat1 (another GATA-binding transcription activator) control occurs at their access to the nucleus. In excess nitrogen, Gln3 and Gat1 are sequestered in the cytoplasm in a Ure2-dependent manner. They become nuclear and activate transcription when nitrogen becomes limiting. Long-term nitrogen starvation and treatment of cells with the glutamine synthetase inhibitor methionine sulfoximine (Msx) also elicit nuclear Gln3 localization. The sensitivity of Gln3 localization to glutamine and inhibition of glutamine synthesis prompted us to investigate the effects of a glutamine tRNA mutation (sup70-65) on nitrogen-responsive control of Gln3 and Gat1. We found that nuclear Gln3 localization elicited by short- and long-term nitrogen starvation; growth in a poor, derepressive medium; Msx or rapamycin treatment; or ure2Δ mutation is abolished in a sup70-65 mutant. However, nuclear Gat1 localization, which also exhibits a glutamine tRNACUG requirement for its response to short-term nitrogen starvation or growth in proline medium or a ure2Δ mutation, does not require tRNACUG for its response to rapamycin. Also, in contrast with Gln3, Gat1 localization does not respond to long-term nitrogen starvation. These observations demonstrate the existence of a specific nitrogen-responsive component participating in the control of Gln3 and Gat1 localization and their downstream production of nitrogenous precursors. This

  16. GlnD is essential for NifA activation, NtrB/NtrC-regulated gene expression, and posttranslational regulation of nitrogenase activity in the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum.

    PubMed

    Zhang, Yaoping; Pohlmann, Edward L; Roberts, Gary P

    2005-02-01

    GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of P(II) proteins, which in turn regulate a variety of other proteins. We report here the characterization of glnD mutants from the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike glnD mutations in Azotobacter vinelandii and some other bacteria, glnD deletion mutations are not lethal in R. rubrum. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N(2). The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a DeltaglnD strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in nif gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms. PMID:15687189

  17. Superfluid spin transport through easy-plane ferromagnetic insulators.

    PubMed

    Takei, So; Tserkovnyak, Yaroslav

    2014-06-01

    Superfluid spin transport-dissipationless transport of spin-is theoretically studied in a ferromagnetic insulator with easy-plane anisotropy. We consider an open geometry where the spin current is injected into the ferromagnet from one side by a metallic reservoir with a nonequilibrium spin accumulation and ejected into another metallic reservoir located downstream. Spin transport is studied using a combination of magnetoelectric circuit theory, Landau-Lifshitz-Gilbert phenomenology, and microscopic linear-response theory. We discuss how spin superfluidity can be probed in a magnetically mediated negative electron-drag experiment. PMID:24949786

  18. Association between Toll-like receptor 7 Gln11Leu single-nucleotide polymorphism and basal cell carcinoma

    PubMed Central

    RUSSO, IRENE; CONA, CAMILLA; SAPONERI, ANDREA; BASSETTO, FRANCO; BALDO, VINCENZO; ALAIBAC, MAURO

    2016-01-01

    Non-melanoma skin cancers (NMSC) are the most common form of human skin cancer. The majority of NMSC are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) with a BCC:SCC incidence ratio of 4:1 in immunocompetent patients. Toll-like receptors (TLRs) are transmembrane glycoproteins that recognize pathogen-associated molecular patterns and damage-associated molecular patterns, against which they activate the innate immune response and initiate the adaptive immune response. Genetic variations of these receptors can alter the immune system and are involved in evolution and susceptibility of various diseases, including cancer. Imiquimod, an agonist of TLR7, is applied topically in the treatment of premalignant and malignant skin disorders, in particular BCC. The high efficacy of this TLR7 agonist toward BCC supports a possible role of this receptor in the induction of BCC and, consequently, polymorphisms of this receptor could be responsible for a greater or lesser susceptibility to BCC. The aim of the present study was to evaluate whether the presence of the functional TLR7 rs179008/Gln11Leu promoter polymorphism conferred an increased susceptibility to BCC. A case-control study with 177 BCC cases and 158 controls was performed to highlight the possible association between this polymorphism and the susceptibility to BCC. As the TLR7 gene is localized on chromosome X, the allelic frequency of this polymorphism was analyzed separately in males and females. The analysis of the distribution of frequencies of wild-type TLR7 and variant TLR7 carrying the single-nucleotide polymorphism (SNP) rs179008 in patients with BCC and healthy subjects did not reveal any statistically significant difference between cases and controls. This study does not suggest the involvement of the SNP rs179008 of TLR7 in the susceptibility to BCC, but cannot exclude a role for TLR7 in BCC carcinogenesis considering the high efficacy of the TLR7 agonist, imiquimod, in the treatment of this

  19. Spin pumping and spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Saitoh, Eiji

    2012-02-01

    Utilization of a spin current, a flow of electrons' spins in a solid, is the key technology in spintronics that will allow the achievement of efficient magnetic memories and computing devices. In this technology, generation and detection of spin currents are necessary. Here, we review inverse spin-Hall effect and spin-current-generation phenomena recently discovered both in metals and insulators: inverse spin-Hall effect, spin pumping, and spin Seebeck effect. (1)Spin pumping and spin torque in a Mott insulator system We found that spin pumping and spin torque effects appear also at an interface between Pt and an insulator YIG.. This means that we can connect a spin current carried by conduction electrons and a spin-wave spin current flowing in insulators. We demonstrate electric signal transmission by using these effects and interconversion of the spin currents [1]. (2) Spin Seebeck effect We have observed, by using the inverse spin-Hall effect [2], spin voltage generation from a heat current in a NiFe, named the spin-Seebeck effect [3]. Surprisingly, spin-Seebeck effect was found to appear even in insulators [4], a situation completely different from conventional charge Seebeck effect. The result implies an important role of elementary excitation in solids beside charge in the spin Seebeck effect. In the talk, we review the recent progress of the research on this effect. This research is collaboration with K. Ando, K. Uchida, Y. Kajiwara, S. Maekawa, G. E. W. Bauer, S. Takahashi, and J. Ieda. [4pt] [1] Y. Kajiwara and E. Saitoh et al. Nature 464 (2010) 262. [0pt] [2] E. Saitoh et al., Appl. Phys. Lett. 88 (2006) 182509. [0pt] [3] K. Uchida and E. Saitoh et al., Nature 455 (2008)778. [0pt] [4] K. Uchida and E. Saitoh et al.,Nature materials 9 (2010) 894 - 897.

  20. Realization of a spin-wave multiplexer.

    PubMed

    Vogt, K; Fradin, F Y; Pearson, J E; Sebastian, T; Bader, S D; Hillebrands, B; Hoffmann, A; Schultheiss, H

    2014-01-01

    Recent developments in the field of spin dynamics--like the interaction of charge and heat currents with magnons, the quasi-particles of spin waves--opens the perspective for novel information processing concepts and potential applications purely based on magnons without the need of charge transport. The challenges related to the realization of advanced concepts are the spin-wave transport in two-dimensional structures and the transfer of existing demonstrators to the micro- or even nanoscale. Here we present the experimental realization of a microstructured spin-wave multiplexer as a fundamental building block of a magnon-based logic. Our concept relies on the generation of local Oersted fields to control the magnetization configuration as well as the spin-wave dispersion relation to steer the spin-wave propagation in a Y-shaped structure. Thus, the present work illustrates unique features of magnonic transport as well as their possible utilization for potential technical applications. PMID:24759754

  1. Tensor spin observables and spin stucture at low Q{sup 2}

    SciTech Connect

    Slifer, K.

    2015-04-10

    We discuss recent spin structure results from Jefferson Lab, and outline an emerging program to study tensor spin observables using solid deuteron targets. These new experiments open the potential to study hidden color, the tensor nature of short range correlations, and to probe for exotic gluonic states.

  2. Spin valve effect of the interfacial spin accumulation in yttrium iron garnet/platinum bilayers

    SciTech Connect

    Jin, Lichuan; Zhang, Dainan; Zhang, Huaiwu Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong; Fan, Xin; Xiao, John Q.

    2014-09-29

    We report the spin valve effect in yttrium iron garnet/platinum (YIG/Pt) bilayers. The spin Hall effect (SHE) generates spin accumulation at the YIG/Pt interface and can be opened/closed by magnetization switching in the electrical insulator YIG. The interfacial spin accumulation was measured in both YIG/Pt and YIG/Cu/Pt structures using a planar Hall configuration. The spin valve effect remained, even after a 2 nm thick Cu layer was inserted between the YIG and Pt layers, which aimed to exclude the induced magnetization at the YIG/Pt interface. The transverse Hall voltage and switching field were dependent on the applied charge current density. The origin of this behavior can be explained by the SHE induced torque exerted on the domain wall, caused by the transfer of the spin angular momentum from the spin-polarized current to the YIG magnetic moment.

  3. Spin valve effect of the interfacial spin accumulation in yttrium iron garnet/platinum bilayers

    NASA Astrophysics Data System (ADS)

    Jin, Lichuan; Zhang, Dainan; Zhang, Huaiwu; Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong; Fan, Xin; Xiao, John Q.

    2014-09-01

    We report the spin valve effect in yttrium iron garnet/platinum (YIG/Pt) bilayers. The spin Hall effect (SHE) generates spin accumulation at the YIG/Pt interface and can be opened/closed by magnetization switching in the electrical insulator YIG. The interfacial spin accumulation was measured in both YIG/Pt and YIG/Cu/Pt structures using a planar Hall configuration. The spin valve effect remained, even after a 2 nm thick Cu layer was inserted between the YIG and Pt layers, which aimed to exclude the induced magnetization at the YIG/Pt interface. The transverse Hall voltage and switching field were dependent on the applied charge current density. The origin of this behavior can be explained by the SHE induced torque exerted on the domain wall, caused by the transfer of the spin angular momentum from the spin-polarized current to the YIG magnetic moment.

  4. Emergent spin

    SciTech Connect

    Creutz, Michael

    2014-03-15

    Quantum mechanics and relativity in the continuum imply the well known spin–statistics connection. However for particles hopping on a lattice, there is no such constraint. If a lattice model yields a relativistic field theory in a continuum limit, this constraint must “emerge” for physical excitations. We discuss a few models where a spin-less fermion hopping on a lattice gives excitations which satisfy the continuum Dirac equation. This includes such well known systems such as graphene and staggered fermions. -- Highlights: •The spin–statistics theorem is not required for particles on a lattice. •Spin emerges dynamically when spinless fermions have a relativistic continuum limit. •Graphene and staggered fermions are examples of this phenomenon. •The phenomenon is intimately tied to chiral symmetry and fermion doubling. •Anomaly cancellation is a crucial feature of any valid lattice fermion action.

  5. High spin isomer beam line at RIKEN

    SciTech Connect

    Kishida, T.; Ideguchi, E.; Wu, H.Y.

    1996-12-31

    Nuclear high spin states have been the subject of extensive experimental and theoretical studies. For the production of high spin states, fusion reactions are usually used. The orbital angular momentum brought in the reaction is changed into the nuclear spin of the compound nucleus. However, the maximum induced angular momentum is limited in this mechanism by the maximum impact parameter of the fusion reaction and by the competition with fission reactions. It is, therefore, difficult to populate very high spin states, and as a result, large {gamma}-detector arrays have been developed in order to detect subtle signals from such very high spin states. The use of high spin isomers in the fusion reactions can break this limitation because the high spin isomers have their intrinsic angular momentum, which can bring the additional angular momentum without increasing the excitation energy. There are two methods to use the high spin isomers for secondary reactions: the use of the high spin isomers as a target and that as a beam. A high spin isomer target has already been developed and used for several experiments. But this method has an inevitable shortcoming that only {open_quotes}long-lived{close_quotes} isomers can be used for a target: {sup 178}Hf{sup m2} (16{sup +}) with a half-life of 31 years in the present case. By developing a high spin isomer beam, the authors can utilize various short-lived isomers with a short half-life around 1 {mu}s. The high spin isomer beam line of RIKEN Accelerator Facility is a unique apparatus in the world which provides a high spin isomer as a secondary beam. The combination of fusion-evaporation reaction and inverse kinematics are used to produce high spin isomer beams; in particular, the adoption of `inverse kinematics` is essential to use short-lived isomers as a beam.

  6. Positivity of spin foam amplitudes

    NASA Astrophysics Data System (ADS)

    Baez, John C.; Christensen, J. Daniel

    2002-04-01

    The amplitude for a spin foam in the Barrett-Crane model of Riemannian quantum gravity is given as a product over its vertices, edges and faces, with one factor of the Riemannian 10j symbols appearing for each vertex, and simpler factors for the edges and faces. We prove that these amplitudes are always nonnegative for closed spin foams. As a corollary, all open spin foams going between a fixed pair of spin networks have real amplitudes of the same sign. This means one can use the Metropolis algorithm to compute expectation values of observables in the Riemannian Barrett-Crane model, as in statistical mechanics, even though this theory is based on a real-time (eiS) rather than imaginary-time e-S path integral. Our proof uses the fact that when the Riemannian 10j symbols are nonzero, their sign is positive or negative depending on whether the sum of the ten spins is an integer or half-integer. For the product of 10j symbols appearing in the amplitude for a closed spin foam, these signs cancel. We conclude with some numerical evidence suggesting that the Lorentzian 10j symbols are always nonnegative, which would imply similar results for the Lorentzian Barrett-Crane model.

  7. Snell's Law for Spin Waves

    NASA Astrophysics Data System (ADS)

    Stigloher, J.; Decker, M.; Körner, H. S.; Tanabe, K.; Moriyama, T.; Taniguchi, T.; Hata, H.; Madami, M.; Gubbiotti, G.; Kobayashi, K.; Ono, T.; Back, C. H.

    2016-07-01

    We report the experimental observation of Snell's law for magnetostatic spin waves in thin ferromagnetic Permalloy films by imaging incident, refracted, and reflected waves. We use a thickness step as the interface between two media with different dispersion relations. Since the dispersion relation for magnetostatic waves in thin ferromagnetic films is anisotropic, deviations from the isotropic Snell's law known in optics are observed for incidence angles larger than 25 ° with respect to the interface normal between the two magnetic media. Furthermore, we can show that the thickness step modifies the wavelength and the amplitude of the incident waves. Our findings open up a new way of spin wave steering for magnonic applications.

  8. Water proton spin saturation affects measured protein backbone 15 N spin relaxation rates

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Tjandra, Nico

    2011-12-01

    Protein backbone 15N NMR spin relaxation rates are useful in characterizing the protein dynamics and structures. To observe the protein nuclear-spin resonances a pulse sequence has to include a water suppression scheme. There are two commonly employed methods, saturating or dephasing the water spins with pulse field gradients and keeping them unperturbed with flip-back pulses. Here different water suppression methods were incorporated into pulse sequences to measure 15N longitudinal T1 and transversal rotating-frame T1ρ spin relaxation. Unexpectedly the 15N T1 relaxation time constants varied significantly with the choice of water suppression method. For a 25-kDa Escherichiacoli. glutamine binding protein (GlnBP) the T1 values acquired with the pulse sequence containing a water dephasing gradient are on average 20% longer than the ones obtained using a pulse sequence containing the water flip-back pulse. In contrast the two T1ρ data sets are correlated without an apparent offset. The average T1 difference was reduced to 12% when the experimental recycle delay was doubled, while the average T1 values from the flip-back measurements were nearly unchanged. Analysis of spectral signal to noise ratios ( s/ n) showed the apparent slower 15N relaxation obtained with the water dephasing experiment originated from the differences in 1H N recovery for each relaxation time point. This in turn offset signal reduction from 15N relaxation decay. The artifact becomes noticeable when the measured 15N relaxation time constant is comparable to recycle delay, e.g., the 15N T1 of medium to large proteins. The 15N relaxation rates measured with either water suppression schemes yield reasonable fits to the structure. However, data from the saturated scheme results in significantly lower Model-Free order parameters (< S2> = 0.81) than the non-saturated ones (< S2> = 0.88), indicating such order parameters may be previously underestimated.

  9. 40 CFR Table 3 to Subpart Wwww of... - Organic HAP Emissions Limits for Existing Open Molding Sources, New Open Molding Sources Emitting...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... mold is vented during spinning and cureb. resin application with the mold closed, and the mold is not vented during spinning and cure c. resin application with the mold open, and the mold is vented during spinning and cure d. resin application with the mold open, and the mold is not vented during spinning...

  10. 40 CFR Table 3 to Subpart Wwww of... - Organic HAP Emissions Limits for Existing Open Molding Sources, New Open Molding Sources Emitting...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... mold is vented during spinning and cureb. resin application with the mold closed, and the mold is not vented during spinning and cure c. resin application with the mold open, and the mold is vented during spinning and cure d. resin application with the mold open, and the mold is not vented during spinning...

  11. Paramagnetic and Antiferromagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Wu, Stephen

    We report on the observation of the longitudinal spin Seebeck effect in both antiferromagnetic and paramagnetic insulators. By using a microscale on-chip local heater, it is possible to generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. This technique allows us to easily access low temperatures (200 mK) and high magnetic fields (14 T) through conventional dilution refrigeration and superconducting magnet setups. By exploring this regime, we detect the spin Seebeck effect through the spin-flop transition in antiferromagnetic MnF2 when a large magnetic field (>9 T) is applied along the easy axis direction. Using the same technique, we are also able to resolve a spin Seebeck effect from the paramagnetic phase of geometrically frustrated antiferromagnet Gd3Ga5O12 (gadolinium gallium garnet) and antiferromagnetic DyScO3 (DSO). Since these measurements occur above the ordering temperatures of these two materials, short-range magnetic order is implicated as the cause of the spin Seebeck effect in these systems. The discovery of the spin Seebeck effect in these two materials classes suggest that both antiferromagnetic spin waves and spin excitations from short range magnetic order may be used to generate spin current from insulators and that the spin wave spectra of individual materials are highly important to the specifics of the longitudinal spin Seebeck effect. Since insulating antiferromagnets and paramagnets are far more common than the typical insulating ferrimagnetic materials used in spin Seebeck experiments, this discovery opens up a large new class of materials for use in spin caloritronic devices. All authors acknowledge support of the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. The use of facilities at the Center for Nanoscale Materials, was supported by the U.S. DOE, BES under Contract No. DE-AC02-06CH11357.

  12. Spin injection into semiconductors

    NASA Astrophysics Data System (ADS)

    Oestreich, M.; Hübner, J.; Hägele, D.; Klar, P. J.; Heimbrodt, W.; Rühle, W. W.; Ashenford, D. E.; Lunn, B.

    1999-03-01

    The injection of spin-polarized electrons is presently one of the major challenges in semiconductor spin electronics. We propose and demonstrate a most efficient spin injection using diluted magnetic semiconductors as spin aligners. Time-resolved photoluminescence with a Cd0.98Mn0.02Te/CdTe structure proves the feasibility of the spin-alignment mechanism.

  13. Gln-tRNAGln synthesis in a dynamic transamidosome from Helicobacter pylori, where GluRS2 hydrolyzes excess Glu-tRNAGln

    PubMed Central

    Huot, Jonathan L.; Fischer, Frédéric; Corbeil, Jacques; Madore, Éric; Lorber, Bernard; Diss, Guillaume; Hendrickson, Tamara L.; Kern, Daniel; Lapointe, Jacques

    2011-01-01

    In many bacteria and archaea, an ancestral pathway is used where asparagine and glutamine are formed from their acidic precursors while covalently linked to tRNAAsn and tRNAGln, respectively. Stable complexes formed by the enzymes of these indirect tRNA aminoacylation pathways are found in several thermophilic organisms, and are called transamidosomes. We describe here a transamidosome forming Gln-tRNAGln in Helicobacter pylori, an ε-proteobacterium pathogenic for humans; this transamidosome displays novel properties that may be characteristic of mesophilic organisms. This ternary complex containing the non-canonical GluRS2 specific for Glu-tRNAGln formation, the tRNA-dependent amidotransferase GatCAB and tRNAGln was characterized by dynamic light scattering. Moreover, we observed by interferometry a weak interaction between GluRS2 and GatCAB (KD = 40 ± 5 µM). The kinetics of Glu-tRNAGln and Gln-tRNAGln formation indicate that conformational shifts inside the transamidosome allow the tRNAGln acceptor stem to interact alternately with GluRS2 and GatCAB despite their common identity elements. The integrity of this dynamic transamidosome depends on a critical concentration of tRNAGln, above which it dissociates into separate GatCAB/tRNAGln and GluRS2/tRNAGln complexes. Ester bond protection assays show that both enzymes display a good affinity for tRNAGln regardless of its aminoacylation state, and support a mechanism where GluRS2 can hydrolyze excess Glu-tRNAGln, ensuring faithful decoding of Gln codons. PMID:21813455

  14. GSTP1 Ile105Val and XRCC1 Arg399Gln gene polymorphisms contribute to the clinical outcome of patients with advanced non-small cell lung cancer.

    PubMed

    Bu, L; Zhang, L B; Mao, X; Wang, P

    2016-01-01

    Glutathione S-transferase P1 (GSTP1) and X-ray repair cross-complementing group 1 (XRCC1) genetic variations may in-fluence the efficacy of chemotherapy in various cancers. We investi-gated the possible roles of GSTP1 Ile105Val and XRCC1 Arg194Trp, and Arg399Gln gene polymorphisms in the prognosis of advanced non-small cell lung carcinoma (NSCLC) patients with cisplatin-based chemotherapy. Between January 2010 and December 2012, this study consecutively recruited 141 patients with advanced NSCLC from the First People's Hospital of Yunnan Province. Logistic regression analy-sis showed that individuals carrying the GG genotype were associated with a better response to chemotherapy than those with the wide-type genotype, with an adjusted odds ratio (95% confidence interval, CI) of 4.07 (1.06-25.06). Moreover, we observed that the AA genotype of XRCC1 Arg399Gln was correlated with a greater complete response + partial response to chemotherapy than that with the GG genotype (odds ratio = 2.71, 95%CI = 1.13-10.08). Based on the Cox hazard proportional model, the GG genotype of GSTP1 Ile105Val was found to be associated with a lower risk of death from all causes as compared to that with the AA genotype (hazard ratio = 0.07, 95%CI = 0.01-0.34). In summary, we suggest that GSTP1 Ile105Val and XRCC1 Arg399Gln polymorphisms could influence the response to chemotherapy and sur-vival of advanced NSCLC. PMID:27323109

  15. Spin noise in mixed Spin Systems

    NASA Astrophysics Data System (ADS)

    Bauch, Erik; Junghyun, Paul; Singh, Swati; Devakul, Trithep; Feguin, Adrian; Hart, Connor; Walsworth, Ronald

    2016-05-01

    The spin noise due to interaction of multiple spin species in mixed spin systems provides a fundamental limit to ultra-sensitive ensemble sensing and quantum information applications. In our work, we investigate the interaction of dense nuclear 13C spins with electronic nitrogen spins using Nitrogen-Vacancy centers in diamond. Our work shows experimentally and theoretically, that under certain conditions, spin noise is greatly suppressed and the coherence time of NV centers improved by order of magnitudes, providing a pathway to engineering high density ensemble samples with long coherence times at room temperature.

  16. The effect of nitrate addition on abundance of nirK, nirS and gln genes in acidified Norway spruce forest soil

    NASA Astrophysics Data System (ADS)

    Bárta, Jiří; Tahovská, Karolina; Kaåa, Jiří; Antrå¯Čková, Hana Å.

    2010-05-01

    The denitrification is the main biotic process leading to loses of fixed nitrogen as well as removal of excess of nitrate (NO3-) from the soil environment. The reduction of NO2- to nitric oxide (NO) distinguishes the 'true' denitrifiers from other nitrate-respiring bacteria. This reaction is catalyzed by two different types of nitrite reductases, either a cytochrome cd1 encoded by nirS gene (nirS denitrifiers) or a Cu-containing enzyme encoded by nirK gene (nirK denitrifiers). The nirS denitrifiers are located mostly in rhizosphere, while the nirK denitrifiers are more abundant in bulk soil. These two groups can be also classified as markers of denitrification. Glutamine synthetase is one of the main bacterial NH4+ assimilating enzymes; it is coded by glnI gene. Glutamine synthetase is mostly active when N is the limiting factor for bacterial growth. There is recent evidence that the activity may be affected by the presence of alternative N source (i.e. NO3-). However, in anaerobic condition NO3- can be used also by the denitrifying bacteria so there may be strong competition for this nutrient. The laboratory experiment was performed to evaluate the effect of nitrates (NO3-) on abundance of nirK, nirS and gln gene copy numbers. The amount of NO3- corresponded to the actual atmospheric depositions on experimental sites in the Bohemian Forest. Litter organic layer (0-5cm of soil) was used for laboratory incubation experiment. Four replicates of control (no addition of NO3-), and NO3-addition were incubated anaerobically for one month. After the incubation DNA was extracted and the number of nirK, nirS and gln gene copies was determined using qPCR (SYBRGreen methodology). Results showed that the addition of NO3- significantly increased the number of nirK and nirS denitrifiers from 5.9x106 to 1.1x107 and from not detectable amount to 1.4x106, respectively. The gln gene copy number was also higher after NO3-addition. However, the difference was not statistically

  17. Integrable deformations of the XXZ spin chain

    NASA Astrophysics Data System (ADS)

    Beisert, Niklas; Fiévet, Lucas; de Leeuw, Marius; Loebbert, Florian

    2013-09-01

    We consider integrable deformations of the XXZ spin chain for periodic and open boundary conditions. In particular, we classify all long-range deformations and study their impact on the spectrum. As compared to the XXX case, we have the z-spin at our disposal, which induces two additional deformations: the short-range magnetic twist and a new long-range momentum-dependent twist.

  18. Ultrafast and Gigantic Spin Injection in Semiconductors

    NASA Astrophysics Data System (ADS)

    Battiato, M.; Held, K.

    2016-05-01

    The injection of spin currents in semiconductors is one of the big challenges of spintronics. Motivated by the ultrafast demagnetization and spin injection into metals, we propose an alternative femtosecond route based on the laser excitation of superdiffusive spin currents in a ferromagnet such as Ni. Our calculations show that even though only a fraction of the current crosses the Ni-Si interface, the laser-induced creation of strong transient electrical fields at a ferromagnet-semiconductor interface allows for the injection of chargeless spin currents with record spin polarizations of 80%. Beyond that they are pulsed on the time scale of 100 fs which opens the door for new experiments and ultrafast spintronics.

  19. Ultrafast and Gigantic Spin Injection in Semiconductors.

    PubMed

    Battiato, M; Held, K

    2016-05-13

    The injection of spin currents in semiconductors is one of the big challenges of spintronics. Motivated by the ultrafast demagnetization and spin injection into metals, we propose an alternative femtosecond route based on the laser excitation of superdiffusive spin currents in a ferromagnet such as Ni. Our calculations show that even though only a fraction of the current crosses the Ni-Si interface, the laser-induced creation of strong transient electrical fields at a ferromagnet-semiconductor interface allows for the injection of chargeless spin currents with record spin polarizations of 80%. Beyond that they are pulsed on the time scale of 100 fs which opens the door for new experiments and ultrafast spintronics. PMID:27232029

  20. The bacterial signal transduction protein GlnB regulates the committed step in fatty acid biosynthesis by acting as a dissociable regulatory subunit of acetyl-CoA carboxylase.

    PubMed

    Gerhardt, Edileusa C M; Rodrigues, Thiago E; Müller-Santos, Marcelo; Pedrosa, Fabio O; Souza, Emanuel M; Forchhammer, Karl; Huergo, Luciano F

    2015-03-01

    Biosynthesis of fatty acids is one of the most fundamental biochemical pathways in nature. In bacteria and plant chloroplasts, the committed and rate-limiting step in fatty acid biosynthesis is catalyzed by a multi-subunit form of the acetyl-CoA carboxylase enzyme (ACC). This enzyme carboxylates acetyl-CoA to produce malonyl-CoA, which in turn acts as the building block for fatty acid elongation. In Escherichia coli, ACC is comprised of three functional modules: the biotin carboxylase (BC), the biotin carboxyl carrier protein (BCCP) and the carboxyl transferase (CT). Previous data showed that both bacterial and plant BCCP interact with signal transduction proteins belonging to the PII family. Here we show that the GlnB paralogues of the PII proteins from E. coli and Azospirillum brasiliense, but not the GlnK paralogues, can specifically form a ternary complex with the BC-BCCP components of ACC. This interaction results in ACC inhibition by decreasing the enzyme turnover number. Both the BC-BCCP-GlnB interaction and ACC inhibition were relieved by 2-oxoglutarate and by GlnB uridylylation. We propose that the GlnB protein acts as a 2-oxoglutarate-sensitive dissociable regulatory subunit of ACC in Bacteria. PMID:25557370

  1. The complete mitochondrial genome sequence of Cynoglossus abbreviatus (Pleuronectiformes: Cynoglossidae) with control region translocation and tRNA-Gln gene inversion.

    PubMed

    Shi, Wei; Gong, Li; Kong, Xiao-Yu

    2016-05-01

    Cynoglossus abbreviatus (Cynoglossidae, Soleoidei) is characterized by a bilaterally asymmetrical with both eyes on the left side. In this study, the complete mitogenome of this tongue sole has been reported for the first time. The gene order in C. abbreviatus mitogenome possesses a novel rearrangement like other tonguefish. The tRNA-Gln gene moves from the light strand to the heavy strand, accompanied by tRNA-Ile gene shuffling, leaving a large non-coding region (88 bp) between these two tRNAs. Additionally, the control region translocates to the place between ND1 and tRNA-Gln genes. The total length is 16,417 bp, with 30.9%, 29.5%, 24.9% and 14.7% for A, T, C and G, respectively (60.4% for AT content). These molecular data will provide useful information about the mechanism of gene reorganization in Cynoglossidae mitogenome and further phylogenetic study on Pleuronectiformes. PMID:25427811

  2. Lack of association between XPC Lys939Gln polymorphism and prostate cancer risk: an updated meta-analysis based on 3039 cases and 3253 controls

    PubMed Central

    Wu, Haoran; Lv, Zhong; Wang, Xugang; Zhang, Liang; Mo, Naixin

    2015-01-01

    Several studies have evaluated the relationship between xeroderma pigmentosum complementation group C (XPC) variants and prostate cancer (PCa) risk. However, the results remain inconclusive. The objective of this study was to identify the role of XPC Lys939Gln variant on PCa occurrence. Relevant case-control studies published between 2000 and 2014 were retrieved in electronic databases. The pooled odds ratio (ORs) and 95% confidence interval (CI) were employed to calculate the strength of association. Finally, a total of eight articles including 3039 PCa patients and 3203 healthy controls were screened out. Our results found that the frequency of C allele was a little higher in PCa cases than that in control, but it was not associated with the increased risk of PCa (C vs. A: OR=1.05, 95% CI=0.98-1.13, P=0.19). This insignificant association was also observed in other genetic models (P>0.05). In subgroup analysis by ethnicity, no significant relationship was found in any study-population (Asian, Caucasian and African) as well. In conclusions, our results indicated that XPC Lys939Gln polymorphism was not associated with PCa susceptibility. Further large well-designed epidemiologic studies with gene-gene and gene-environment interaction should be included and considered. PMID:26770390

  3. Relationships between plasma leptin levels, leptin G2548A, leptin receptor Gln223Arg polymorphisms and gestational diabetes mellitus in Chinese population

    PubMed Central

    Yang, Mei; Peng, Songxu; Li, Wei; Wan, Zhihua; Fan, Linlin; Du, Yukai

    2016-01-01

    The purposes of this study were to examine concentrations of leptin and biochemical parameters in gestational diabetes mellitus (GDM) patients and normal glucose tolerance (NGT) individuals, and also to explore the links of leptin (LEP) G2548A and leptin receptor (LEPR) Gln223Arg polymorphisms with leptin levels and GDM risk among Chinese. Our study included 357 GDM and 355 NGT individuals who were at 24~30 gestational weeks. Plasma leptin and insulin levels were analyzed by ELISA. Gene polymorphisms were genotyped using TaqMan real-time polymerase chain reaction assay. The results showed that plasma leptin levels were significantly higher in the impaired fasting glucose (IFG) group than NGT group (34.35 (26.54, 56.48) ng/mL vs 26.31 (17.99, 37.87) ng/mL, P < 0.05). Plasma leptin levels correlated with plasma fasting insulin levels, pre-pregnant body mass index, homeostasis model assessment-insulin resistance and quantitative insulin sensitivity check index both in GDM and NGT group (P < 0.05). However, neither LEP G2548A nor LEPR Gln223Arg polymorphisms were significantly associated with GDM risk and plasma leptin levels (P > 0.05). Our findings showed that high leptin level was associated with GDM. And larger and more rigorous researches were needed to further explore the association of LEP and LEPR gene polymorphisms and GDM among Chinese population. PMID:27034205

  4. Leptin Receptor Gene Gln223Arg Polymorphism Is Not Associated with Hypertension: A Preliminary Population-Based Cross-Sectional Study

    PubMed Central

    Pena, Geórgia das Graças; Guimarães, Andre L. S.; Veloso, Rosângela R.; Reis, Tatiana C.; Gomes, Crizian S.; Neto, João F. R.; Velasquez-Melendez, Gustavo

    2014-01-01

    Hypertension is responsible for high morbidity and mortality as one of the most important cardiometabolic risk factors. The aim of the study was to investigate whether the Gln223Arg in the leptin receptor (LEPR) influences the prevalence of hypertension. A cross-sectional study was carried out in individuals aged ≥ 18 years. Polymorphism identification was performed using PCR-RFLP analysis. Participants with blood pressure ≥ 140/90 mmHg or medication use were considered hypertensive. Frequencies, means, cross-tabulations, and multivariate models were produced to study differences in hypertension prevalence by genotypes. The study includes 470 participants. The frequency of GG polymorphism variant was 10.43%, 46.81% AG, and 42.77% AA. The distribution of hypertension frequency by LEPR genotypes was the following: AA 43.8%, AG 40.4%, and GG 40.8%; there were no significant differences between groups. Comparative analysis which used multivariate Poisson regression adjusted by many potential confounders (age, sex, schooling, smoking, alcohol intake, obesity, and family history of parental obesity) did not modify this result. In this large sample of population-based study, the association of the LEPR Gln223Arg gene polymorphism with hypertension was not observed. PMID:24772364

  5. Cellular model of TAR DNA-binding protein 43 (TDP-43) aggregation based on its C-terminal Gln/Asn-rich region.

    PubMed

    Budini, Mauricio; Buratti, Emanuele; Stuani, Cristiana; Guarnaccia, Corrado; Romano, Valentina; De Conti, Laura; Baralle, Francisco E

    2012-03-01

    TDP-43 is one of the major components of the neuronal and glial inclusions observed in several neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration. These characteristic aggregates are a "landmark" of the disease, but their role in the pathogenesis is still obscure. In previous works, we have shown that the C-terminal Gln/Asn-rich region (residues 321-366) of TDP-43 is involved in the interaction of this protein with other members of the heterogeneous nuclear ribonucleoprotein protein family. Furthermore, we have shown that the interaction through this region is important for TDP-43 splicing inhibition of cystic fibrosis transmembrane regulator exon 9, and there were indications that it was involved in the aggregation process. Our experiments show that in cell lines and primary rat neuronal cultures, the introduction of tandem repeats carrying the 331-369-residue Gln/Asn region from TDP-43 can trigger the formation of phosphorylated and ubiquitinated aggregates that recapitulate many but not all the characteristics observed in patients. These results establish a much needed cell-based TDP-43 aggregation model useful to investigate the mechanisms involved in the formation of inclusions and the gain- and loss-of-function consequences of TDP-43 aggregation within cells. In addition, it will be a powerful tool to test novel therapeutic strategies/effectors aimed at preventing/reducing this phenomenon. PMID:22235134

  6. Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata1[w

    PubMed Central

    Berry, Alison M.; Murphy, Terence M.; Okubara, Patricia A.; Jacobsen, Karin R.; Swensen, Susan M.; Pawlowski, Katharina

    2004-01-01

    Gln synthetase (GS) is the key enzyme of primary ammonia assimilation in nitrogen-fixing root nodules of legumes and actinorhizal (Frankia-nodulated) plants. In root nodules of Datisca glomerata (Datiscaceae), transcripts hybridizing to a conserved coding region of the abundant nodule isoform, DgGS1-1, are abundant in uninfected nodule cortical tissue, but expression was not detectable in the infected zone or in the nodule meristem. Similarly, the GS holoprotein is immunolocalized exclusively to the uninfected nodule tissue. Phylogenetic analysis of the full-length cDNA of DgGS1-1 indicates affinities with cytosolic GS genes from legumes, the actinorhizal species Alnus glutinosa, and nonnodulating species, Vitis vinifera and Hevea brasilensis. The D. glomerata nodule GS expression pattern is a new variant among reported root nodule symbioses and may reflect an unusual nitrogen transfer pathway from the Frankia nodule microsymbiont to the plant infected tissue, coupled to a distinctive nitrogen cycle in the uninfected cortical tissue. Arg, Gln, and Glu are the major amino acids present in D. glomerata nodules, but Arg was not detected at high levels in leaves or roots. Arg as a major nodule nitrogen storage form is not found in other root nodule types except in the phylogenetically related Coriaria. Catabolism of Arg through the urea cycle could generate free ammonium in the uninfected tissue where GS is expressed. PMID:15247391

  7. The Master T-Operator for Inhomogeneous XXX Spin Chain and mKP Hierarchy

    NASA Astrophysics Data System (ADS)

    Zabrodin, Anton

    2014-01-01

    Following the approach of [Alexandrov A., Kazakov V., Leurent S., Tsuboi Z., Zabrodin A., J. High Energy Phys. 2013 (2013), no. 9, 064, 65 pages, arXiv:1112.3310], we show how to construct the master T-operator for the quantum inhomogeneous GL(N) XXX spin chain with twisted boundary conditions. It satisfies the bilinear identity and Hirota equations for the classical mKP hierarchy. We also characterize the class of solutions to the mKP hierarchy that correspond to eigenvalues of the master T-operator and study dynamics of their zeros as functions of the spectral parameter. This implies a remarkable connection between the quantum spin chain and the classical Ruijsenaars-Schneider system of particles.

  8. Effects of Inorganic Carbon Limitation on the Metabolome of the Synechocystis sp. PCC 6803 Mutant Defective in glnB Encoding the Central Regulator PII of Cyanobacterial C/N Acclimation

    PubMed Central

    Schwarz, Doreen; Orf, Isabel; Kopka, Joachim; Hagemann, Martin

    2014-01-01

    Cyanobacteria are the only prokaryotes performing oxygenic photosynthesis. Non-diazotrophic strains such as the model Synechocystis sp. PCC 6803 depend on a balanced uptake and assimilation of inorganic carbon and nitrogen sources. The internal C/N ratio is sensed via the PII protein (GlnB). We analyzed metabolic changes of the ΔglnB mutant of Synechocystis sp. PCC 6803 under different CO2 availability. The identified metabolites provided a snapshot of the central C/N metabolism. Cells of the ΔglnB mutant shifted to carbon-limiting conditions, i.e. a decreased C/N ratio, showed changes in intermediates of the sugar storage and particularly of the tricarboxylic acid cycle, arginine, and glutamate metabolism. The changes of the metabolome support the notion that the PII protein is primarily regulating the N-metabolism whereas the changes in C-metabolism are probably secondary effects of the PII deletion. PMID:24957024

  9. Spin-Spin Coupling in Asteroidal Binaries

    NASA Astrophysics Data System (ADS)

    Batygin, Konstantin; Morbidelli, Alessandro

    2015-11-01

    Gravitationally bound binaries constitute a substantial fraction of the small body population of the solar system, and characterization of their rotational states is instrumental to understanding their formation and dynamical evolution. Unlike planets, numerous small bodies can maintain a perpetual aspheroidal shape, giving rise to a richer array of non-trivial gravitational dynamics. In this work, we explore the rotational evolution of triaxial satellites that orbit permanently deformed central objects, with specific emphasis on quadrupole-quadrupole interactions. Our analysis shows that in addition to conventional spin-orbit resonances, both prograde and retrograde spin-spin resonances naturally arise for closely orbiting, highly deformed bodies. Application of our results to the illustrative examples of (87) Sylvia and (216) Kleopatra multi-asteroid systems implies capture probabilities slightly below ~10% for leading-order spin-spin resonances. Cumulatively, our results suggest that spin-spin coupling may be consequential for highly elongated, tightly orbiting binary objects.

  10. Spin-liquid condensate of spinful bosons.

    PubMed

    Lian, Biao; Zhang, Shoucheng

    2014-08-22

    We introduce the concept of a bosonic spin liquid condensate (SLC), where spinful bosons in a lattice form a zero-temperature spin disordered charge condensate that preserves the spin rotation symmetry, but breaks the U(1) symmetry due to a spinless order parameter with charge one. It has an energy gap to all the spin excitations. We show that such SLC states can be realized in a system of spin S ≥ 2 bosons. In particular, we analyze the SLC phase diagram in the spin 2 case using a mean-field variational wave function method. We show there is a direct analogy between the SLC and the resonating-valence-bond state. PMID:25192078

  11. RHIC SPIN FLIPPER

    SciTech Connect

    BAI,M.; ROSER, T.

    2007-06-25

    This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.

  12. Robust micromagnet design for fast electrical manipulations of single spins in quantum dots

    NASA Astrophysics Data System (ADS)

    Yoneda, Jun; Otsuka, Tomohiro; Takakura, Tatsuki; Pioro-Ladrière, Michel; Brunner, Roland; Lu, Hong; Nakajima, Takashi; Obata, Toshiaki; Noiri, Akito; Palmstrøm, Christopher J.; Gossard, Arthur C.; Tarucha, Seigo

    2015-08-01

    Tailoring spin coupling to electric fields is central to spintronics and spin-based quantum information processing. We present an optimal micromagnet design that produces appropriate stray magnetic fields to mediate fast electrical spin manipulations in nanodevices. We quantify the practical requirements for spatial field inhomogeneity and tolerance for misalignment with spins, and propose a design scheme to improve the spin-rotation frequency (to exceed 50 MHz in GaAs nanostructures). We then validate our design by experiments in separate devices. Our results will open a route to rapidly control solid-state electron spins with limited lifetimes and to study coherent spin dynamics in solids.

  13. Spin projection chromatography

    NASA Astrophysics Data System (ADS)

    Danieli, E. P.; Pastawski, H. M.; Levstein, P. R.

    2004-01-01

    We formulate the many-body spin dynamics at high temperature within the non-equilibrium Keldysh formalism. For the simplest XY interaction, analytical expressions in terms of the one particle solutions are obtained for linear and ring configurations. For small rings of even spin number, the group velocities of excitations depend on the parity of the total spin projection. This should enable a dynamical filtering of spin projections with a given parity i.e., a spin projection chromatography.

  14. Magnons, Spin Current and Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Maekawa, Sadamichi

    2012-02-01

    When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

  15. Spin-filtering at COSY

    NASA Astrophysics Data System (ADS)

    Weidemann, Christian; PAX Collaboration

    2011-05-01

    The Spin Filtering experiments at COSY and AD at CERN within the framework of the Polarized Antiproton EXperiments (PAX) are proposed to determine the spin-dependent cross sections in bar pp scattering by observation of the buildup of polarization of an initially unpolarized stored antiproton beam after multiple passage through an internal polarized gas target. In order to commission the experimental setup for the AD and to understand the relevant machine parameters spin-filtering will first be done with protons at COSY. A first major step toward this goal has been achieved with the installation of the required mini-β section in summer 2009 and it's commissioning in January 2010. The target chamber together with the atomic beam source and the so-called Breit-Rabi polarimeter have been installed and commissioned in summer 2010. In addition an openable storage cell has been used. It provides a target thickness of 5·1013 atoms/cm2. We report on the status of spin-filtering experiments at COSY and the outcome of a recent beam time including studies on beam lifetime limitations like intra-beam scattering and the electron-cooling performance as well as machine acceptance studies.

  16. Hierarchical spin-orbital polarization of a giant Rashba system

    PubMed Central

    Bawden, Lewis; Riley, Jonathan M.; Kim, Choong H.; Sankar, Raman; Monkman, Eric J.; Shai, Daniel E.; Wei, Haofei I.; Lochocki, Edward B.; Wells, Justin W.; Meevasana, Worawat; Kim, Timur K.; Hoesch, Moritz; Ohtsubo, Yoshiyuki; Le Fèvre, Patrick; Fennie, Craig J.; Shen, Kyle M.; Chou, Fangcheng; King, Phil D. C.

    2015-01-01

    The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics. It is typically assumed to manifest as a momentum-dependent splitting of a single initially spin-degenerate band into two branches with opposite spin polarization. Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two “spin-split” branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration. This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector. PMID:26601268

  17. Modulation of pure spin currents with a ferromagnetic insulator

    NASA Astrophysics Data System (ADS)

    Villamor, Estitxu; Isasa, Miren; Vélez, Saül; Bedoya-Pinto, Amilcar; Vavassori, Paolo; Hueso, Luis E.; Bergeret, F. Sebastián; Casanova, Fèlix

    2015-01-01

    We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y3F e5O12 (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the nonlocal resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a path towards the development of spin logics.

  18. Noncommutativity due to spin

    NASA Astrophysics Data System (ADS)

    Gomes, M.; Kupriyanov, V. G.; da Silva, A. J.

    2010-04-01

    Using the Berezin-Marinov pseudoclassical formulation of the spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spatial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external electromagnetic field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, ΔxΔy≥θ2/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.

  19. Spin Rotation of Formalism for Spin Tracking

    SciTech Connect

    Luccio,A.

    2008-02-01

    The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.

  20. The mitochondrial tRNA(Gln) T4353C mutation may not be associated with essential hypertension in Han Chinese population.

    PubMed

    Meng, Xing; Pei, Hui; Lan, Chao

    2016-09-01

    We reported here the possible role of a mitochondrial tRNA mutation: T4353C in clinical expression of essential hypertension in Chinese population. The human mammalian mitochondrial tRNA database was used to analyze the conservation index of this mutation between different species. Moreover, phylogenetic analysis showed that the T4353C mutation belonged to human mitochondrial haplogroup HV, a West Eurasian haplogroup found throughout Western Asia and Eastern European but was infrequent in China. In addition, structural prediction of the T4353C mutation indicated that this transition did not alter the secondary structure of tRNA(Gln). Together, our data indicated that the T4353C mutation occurred infrequent and may not be associated with essential hypertension in Han Chinese population. PMID:25693701

  1. Spin Circuit Representation for Spin Pumping Phenomena

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal; Datta, Supriyo

    2015-03-01

    There has been enormous progress in the field of spintronics and nanomagnetics in recent years with the discovery of many new materials and phenomena and it remains a formidable challenge to integrate these phenomena into functional devices and evaluate their potential. To facilitate this process a modular approach has been proposed whereby different phenomena are represented by spin circuit components. Unlike ordinary circuit components, these spin circuit components are characterized by 4-component voltages and currents (one for charge and three for spin). In this talk we will (1) present a spin circuit representation for spin pumping phenomena, (2) combine it with a spin circuit representation for the spin Hall effect to show that it reproduces established results obtained earlier by other means, and finally (3) use it to propose a possible method for enhancing the spin pumping efficiency by an order of magnitude through the addition of a spin sink layer. This work was supported by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  2. Influence of ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms on body weight and body composition changes after a controlled weight-loss intervention.

    PubMed

    Szendrei, Barbara; González-Lamuño, Domingo; Amigo, Teresa; Wang, Guan; Pitsiladis, Yannis; Benito, Pedro J; Gomez-Candela, Carmen; Calderón, Francisco J; Cupeiro, Rocío

    2016-03-01

    The β-2 and β-3 adrenergic receptors (ADRB2 and ADRB3) are thought to play a role in energy expenditure and lipolysis. However, the effects of the ADRB2 glutamine (Gln) 27 glutamic acid (glutamate) (Glu) and ADRB3 tryptophan (Trp) 64 arginine (Arg) polymorphisms on weight loss remain controversial. The aim of this study was to investigate the effect of these polymorphisms on changes in weight and body composition during a controlled weight-loss program. One hundred seventy-three healthy overweight and obese participants (91 women, 82 men) aged 18-50 years participated in a 22-week-long intervention based on a hypocaloric diet and exercise. They were randomly assigned to 1 of 4 groups: strength, endurance, strength and endurance combined, and physical activity recommendations only. Body weight, body mass index (BMI), and body composition variables were assessed before and after the intervention. Genetic analysis was carried out according to standard protocols. No effect of the ADRB2 gene was shown on final weight, BMI, or body composition, although in the supervised male group, Glu27 carriers tended to have greater weight (p = 0.019, 2.5 kg) and BMI (p = 0.019, 0.88 kg/m(2)) reductions than did noncarriers. There seems to be an individual effect of the ADRB3 polymorphism on fat mass (p = 0.004) and fat percentage (p = 0.036), in addition to an interaction with exercise for fat mass (p = 0.038). After the intervention, carriers of the Arg64 allele had a greater fat mass and fat percentage than did noncarriers (p = 0.004, 2.8 kg). In conclusion, the ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms may influence weight loss and body composition, although the current evidence is weak; however, further studies are necessary to clarify their roles. PMID:26888112

  3. Spin Seebeck power generators

    SciTech Connect

    Cahaya, Adam B.; Tretiakov, O. A.; Bauer, Gerrit E. W.

    2014-01-27

    We derive expressions for the efficiency and figure of merit of two spin caloritronic devices based on the spin Seebeck effect (SSE), i.e., the generation of spin currents by a temperature gradient. The inverse spin Hall effect is conventionally used to detect the SSE and offers advantages for large area applications. We also propose a device that converts spin current into electric one by means of a spin-valve detector, which scales favorably to small sizes and approaches a figure of merit of 0.5 at room temperature.

  4. Snell's Law for Spin Waves.

    PubMed

    Stigloher, J; Decker, M; Körner, H S; Tanabe, K; Moriyama, T; Taniguchi, T; Hata, H; Madami, M; Gubbiotti, G; Kobayashi, K; Ono, T; Back, C H

    2016-07-15

    We report the experimental observation of Snell's law for magnetostatic spin waves in thin ferromagnetic Permalloy films by imaging incident, refracted, and reflected waves. We use a thickness step as the interface between two media with different dispersion relations. Since the dispersion relation for magnetostatic waves in thin ferromagnetic films is anisotropic, deviations from the isotropic Snell's law known in optics are observed for incidence angles larger than 25° with respect to the interface normal between the two magnetic media. Furthermore, we can show that the thickness step modifies the wavelength and the amplitude of the incident waves. Our findings open up a new way of spin wave steering for magnonic applications. PMID:27472134

  5. Magnetization dynamics of topological defects and the spin solid in a kagome artificial spin ice

    NASA Astrophysics Data System (ADS)

    Bhat, V. S.; Heimbach, F.; Stasinopoulos, I.; Grundler, D.

    2016-04-01

    We report broadband spin-wave spectroscopy on kagome artificial spin ice (ASI) made of large arrays of interconnected Ni80Fe20 nanobars. Spectra taken in saturated and disordered states exhibit a series of resonances with characteristic magnetic field dependencies. Making use of micromagnetic simulations, we identify resonances that reflect the spin-solid-state and monopole-antimonopole pairs on Dirac strings. The latter resonances allow for the generation of highly charged vertices in ASIs via microwave-assisted switching. Our findings open further perspectives for fundamental studies on ASIs and their usage in reprogrammable magnonics.

  6. Spin transistor action from hidden Onsager reciprocity.

    PubMed

    Adagideli, İ; Lutsker, V; Scheid, M; Jacquod, Ph; Richter, K

    2012-06-01

    We investigate generic Hamiltonians for confined electrons with weak inhomogeneous spin-orbit coupling. Using a local gauge transformation we show how the SU(2) Hamiltonian structure reduces to a U(1)×U(1) structure for spinless fermions in a fictitious orbital magnetic field, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals, thus allowing one to switch the generated spin current on or off. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings. PMID:23003980

  7. 3He Spin Filter for Neutrons

    PubMed Central

    Batz, M.; Baeßler, S.; Heil, W.; Otten, E. W.; Rudersdorf, D.; Schmiedeskamp, J.; Sobolev, Y.; Wolf, M.

    2005-01-01

    The strongly spin-dependent absorption of neutrons in nuclear spin-polarized 3He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable 3He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts. PMID:27308139

  8. Integral dependent spin couplings in CI calculations

    NASA Astrophysics Data System (ADS)

    Iberle, K.; Davidson, E. R.

    1982-06-01

    Although the number of ways to combine Slater determinants to form spin eigenfunctions increases rapidly with the number of open shells, most of these spin couplings will make only a small contribution to a given state, provided the spin coupling is chosen judiciously. The technique of limiting calculations to the interacting subspace pioneered by Bunge (1970) was employed by Munch and Davidson (1975) to the vanadium atom. The use of an interacting space looses its advantage in more complex cases. However, the problem can always be reduced to only one interacting spin coupling by making the coefficients integral dependent. The present investigation is concerned with the performance of integral dependent interacting couplings, taking into account the results of three test calculations.

  9. Antiferromagnetic Spin Wave Field-Effect Transistor.

    PubMed

    Cheng, Ran; Daniels, Matthew W; Zhu, Jian-Gang; Xiao, Di

    2016-01-01

    In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field-effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. Our findings open up the exciting possibility of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale. PMID:27048928

  10. Antiferromagnetic Spin Wave Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Cheng, Ran; Daniels, Matthew W.; Zhu, Jian-Gang; Xiao, Di

    2016-04-01

    In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field-effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. Our findings open up the exciting possibility of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale.

  11. Antiferromagnetic Spin Wave Field-Effect Transistor

    PubMed Central

    Cheng, Ran; Daniels, Matthew W.; Zhu, Jian-Gang; Xiao, Di

    2016-01-01

    In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field-effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. Our findings open up the exciting possibility of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale. PMID:27048928

  12. Antiferromagnetic Spin Wave Field-Effect Transistor

    DOE PAGESBeta

    Cheng, Ran; Daniels, Matthew W.; Zhu, Jian-Gang; Xiao, Di

    2016-04-06

    In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. In conclusion, our findings open up the exciting possibilitymore » of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale.« less

  13. Thermally driven magnetic precession in spin valves

    NASA Astrophysics Data System (ADS)

    Luc, David; Waintal, Xavier

    2014-10-01

    We investigate the angular dependence of the spin torque generated when applying a temperature difference across a spin valve. Our study shows the presence of a nontrivial fixed point in this angular dependence. This fixed point opens the possibility for a temperature gradient to stabilize radio frequency oscillations without the need for an external magnetic field. This so-called "wavy" behavior can already be found upon applying a voltage difference across a spin valve but we find that this effect is much more pronounced with a temperature difference. We find that a spin asymmetry of the Seebeck coefficient of the order of 20 μ VK -1 should be large enough for a temperature gradient of a few degrees to trigger the radio-frequency oscillations. Our semiclassical theory is fully parametrized with experimentally measured(able) parameters and allows one to quantitatively predict the amplitude of the torque.

  14. Integral dependent spin couplings in CI calculations

    NASA Technical Reports Server (NTRS)

    Iberle, K.; Davidson, E. R.

    1982-01-01

    Although the number of ways to combine Slater determinants to form spin eigenfunctions increases rapidly with the number of open shells, most of these spin couplings will make only a small contribution to a given state, provided the spin coupling is chosen judiciously. The technique of limiting calculations to the interacting subspace pioneered by Bunge (1970) was employed by Munch and Davidson (1975) to the vanadium atom. The use of an interacting space looses its advantage in more complex cases. However, the problem can always be reduced to only one interacting spin coupling by making the coefficients integral dependent. The present investigation is concerned with the performance of integral dependent interacting couplings, taking into account the results of three test calculations.

  15. Nitrogen-source regulation of yeast gamma-glutamyl transpeptidase synthesis involves the regulatory network including the GATA zinc-finger factors Gln3, Nil1/Gat1 and Gzf3.

    PubMed Central

    Springael, Jean-Yves; Penninckx, Michel J

    2003-01-01

    In Saccharomyces cerevisiae, the CIS2 gene encodes gamma-glutamyl transpeptidase (gamma-GT; EC 2.3.2.2), the main GSH-degrading enzyme. The promoter region of CIS2 contains one stress-response element (CCCCT) and eight GAT(T/A)A core sequences, probably involved in nitrogen-regulated transcription. We show in the present study that expression of CIS2 is indeed regulated according to the nature of the nitrogen source. Expression is highest in cells growing on a poor nitrogen source such as urea. Under these conditions, the GATA zinc-finger transcription factors Nil1 and Gln3 are both required for CIS2 expression, Nil1 appearing as the more important factor. We further show that Gzf3, another GATA zinc-finger protein, acts as a negative regulator in nitrogen-source control of CIS2 expression. During growth on a preferred nitrogen source like NH(4)(+), CIS2 expression is repressed through a mechanism involving (at least) the Gln3-binding protein Ure2/GdhCR. Induction of CIS2 expression during nitrogen starvation is dependent on Gln3 and Nil1. Furthermore, rapamycin causes similar CIS2 activation, indicating that the target of rapamycin signalling pathway controls CIS2 expression via Gln3 and Nil1 in nitrogen-starved cells. Finally, our results show that CIS2 expression is induced mainly by nitrogen starvation but apparently not by other types of stress. PMID:12529169

  16. PREFACE: SPIN2010 - Preface for Conference Proceedings

    NASA Astrophysics Data System (ADS)

    Ströher, Hans; Rathmann, Frank

    2011-03-01

    SPIN2010, the 19th International Spin Physics Symposium, took place between 27 September and 2 October, 2010 on the campus of Forschungszentrum Jülich GmbH (FZJ) in Jülich, Germany. The scientific program of this Symposium included many topics related to spin phenomena in particle and nuclear physics as well as those in related fields. The International Spin Physics Symposium series has combined the High Energy Spin Symposia and the Nuclear Polarization Conferences since 2000. The most recent two Symposia were held in Virginia, USA (October 2008) and in Kyoto, Japan (October 2006). The meeting was opened by the chairman of the Board of Management of Jülich Forschungszentrum, Professor Achim Bachem, who cordially welcomed the participants from all over the world and gave a brief introduction to the Center and the research conducted there. The scientific program consisted of plenary sessions and parallel sessions and included the following topics: Fundamental symmetries and spin Spin structure of hadrons Spin physics beyond the Standard Model Spin in hadronic reactions Spin physics with photons and leptons Spin physics in nuclear reactions and nuclei Acceleration, storage, and polarimetry of polarized beams Polarized ion and lepton sources and targets Future facilities and experiments Medical and technological applications of spin physics The 6-day symposium had about 300 participants. In total 35 plenary talks (including 3 summaries of other spin physics meetings) and 163 contributed talks were given. The contents of many of these can be found in the present contributions, arranged according to the above topics and the time sequence. In addition, a public lecture on "Drall in der Quantenwelt", presented by H O Meyer (Bloomington) was received very well. Participants had the option to visit the Cooler synchrotron COSY at the Nuclear Physics Institute (IKP) and the 9.4 T MRT-PET hybrid scanner at the Institute of Neuroscience and Medicine (INM), two unique

  17. Cooperative spin decoherence in finite spin chains

    NASA Astrophysics Data System (ADS)

    Delgado, Fernando; Fernandez-Rossier, Joaquin

    2014-03-01

    Overcoming the problem of relaxation and decoherence of magnetic nanostructures is one of the mayor goals in magnetic data storage. Although spin chains with as few as 12 magnetic atoms have revealed stability in cryogenic conditions, understanding the mechanism leading to these effects is essential for the engineered of stable structures. Here we consider the problem of spin decoherence and relaxation of finite size quantum spin chains due to elastic and spin conserving interactions with an electron gas. Specifically, we consider how the decoherence (T2) and relaxation (T1) times between the two degenerate ground states of a chain of N coupled spins compares with the one of an isolated spin in the same environment. We find that the spin decoherence time of Ising chains can be either enhanced or suppressed depending on the matching between the Fermi wavelength 2 π /kF and the inter-spin distance a. In particular, we find that depending on the values of kF a , it can show, for certain values that depends on the dimensionality of the electron gas, a cooperative enhancement proportional to N2 of the decoherence, analogous to super radiance decay of atom ensembles, or a suppression.

  18. Spin structure functions

    SciTech Connect

    Jian-ping Chen, Alexandre Deur, Sebastian Kuhn, Zein-eddine Meziani

    2011-06-01

    Spin-dependent observables have been a powerful tool to probe the internal structure of the nucleon and to understand the dynamics of the strong interaction. Experiments involving spin degrees of freedom have often brought out surprises and puzzles. The so-called "spin crisis" in the 1980s revealed the limitation of naive quark-parton models and led to intensive worldwide efforts, both experimental and theoretical, to understand the nucleon spin structure. With high intensity and high polarization of both the electron beam and targets, Jefferson Lab has the world's highest polarized luminosity and the best figure-of-merit for precision spin structure measurements. It has made a strong impact in this subfield of research. This chapter will highlight Jefferson Lab's unique contributions in the measurements of valence quark spin distributions, in the moments of spin structure functions at low to intermediate Q2, and in the transverse spin structure.

  19. Intrastrand cross-linked actin between Gln-41 and Cys-374. I. Mapping of sites cross-linked in F-actin by N-(4-azido-2-nitrophenyl) putrescine.

    PubMed

    Hegyi, G; Mák, M; Kim, E; Elzinga, M; Muhlrad, A; Reisler, E

    1998-12-22

    A new heterobifunctional photo-cross-linking reagent, N-(4-azido-2-nitrophenyl)-putrescine (ANP), was synthesized and covalently bound to Gln-41 of rabbit skeletal muscle actin by a bacterial transglutaminase-mediated reaction. Up to 1.0 mol of the reagent was incorporated per mole of G-actin; at least 90% of it was bound to Gln-41 while a minor fraction (about 8%) was attached to Gln-59. The labeled G-actin was polymerized, and the resulting F-actin was intermolecularly cross-linked by irradiation with UV light. The labeled and cross-linked peptides were isolated from either a complete or limited tryptic digest of cross-linked actin. In the limited digest the tryptic cleavage was restricted to arginine by succinylation of the lysyl residues. N-terminal sequencing and mass spectrometry indicated that the cross-linked peptides contained residues 40-50 (or 40-62 in the arginine limited digest) and residues 373-375, and that the actual cross-linking took place between Gln-41 and Cys-374. This latter finding was also supported by the inhibition of Cys-374 labeling with a fluorescent probe in the cross-linked actin. The dynamic length of ANP, between 11.1 and 12.5 A, constrains to that range the distance between the gamma-carboxyl group of Gln-41 in one monomer and the sulfur atom of Cys-374 in an adjacent monomer. This is consistent with the distances between these two residues on adjacent monomers of the same strand in the long-pitch helix in the structural models of F-actin [Holmes, K. C., Popp, D., Gebhard, W., and Kabsch, W. (1990) Nature 347, 44-49 and Lorenz, M., Popp, D., and Holmes, K. C. (1993) J. Mol. Biol. 234, 826-836]. The effect of cross-linking on the function of actin is described in the companion papers. PMID:9922144

  20. Spinning eggs and ballerinas

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2013-01-01

    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction between the egg and the surface on which it spins.

  1. Indirect control of antiferromagnetic domain walls with spin current.

    PubMed

    Wieser, R; Vedmedenko, E Y; Wiesendanger, R

    2011-02-11

    The indirect controlled displacement of an antiferromagnetic domain wall by a spin current is studied by Landau-Lifshitz-Gilbert spin dynamics. The antiferromagnetic domain wall can be shifted both by a spin-polarized tunnel current of a scanning tunneling microscope or by a current driven ferromagnetic domain wall in an exchange coupled antiferromagnetic-ferromagnetic layer system. The indirect control of antiferromagnetic domain walls opens up a new and promising direction for future spin device applications based on antiferromagnetic materials. PMID:21405493

  2. 40 CFR Table 3 to Subpart Wwww of... - Organic HAP Emissions Limits for Existing Open Molding Sources, New Open Molding Sources Emitting...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... closed, and the mold is vented during spinning and cureb. resin application with the mold closed, and the mold is not vented during spinning and cure c. resin application with the mold open, and the mold is vented during spinning and cure d. resin application with the mold open, and the mold is not...

  3. 40 CFR Table 3 to Subpart Wwww of... - Organic HAP Emissions Limits for Existing Open Molding Sources, New Open Molding Sources Emitting...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... closed, and the mold is vented during spinning and cureb. resin application with the mold closed, and the mold is not vented during spinning and cure c. resin application with the mold open, and the mold is vented during spinning and cure d. resin application with the mold open, and the mold is not...

  4. The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains.

    PubMed

    Fertitta, Edoardo; El Khatib, Muammar; Bendazzoli, Gian Luigi; Paulus, Beate; Evangelisti, Stefano; Leininger, Thierry

    2015-12-28

    The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection Sz has been derived. PMID:26723672

  5. The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains

    SciTech Connect

    Fertitta, Edoardo; Paulus, Beate; El Khatib, Muammar; Evangelisti, Stefano; Leininger, Thierry

    2015-12-28

    The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection S{sub z} has been derived.

  6. Spinning Eggs and Ballerinas

    ERIC Educational Resources Information Center

    Cross, Rod

    2013-01-01

    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…

  7. Spin transport measurements in gallium arsenide quantum dots

    NASA Astrophysics Data System (ADS)

    Folk, Joshua Alexander

    This thesis presents a series of measurements investigating the spin physics of lateral quantum dots, defined electrostatically in the 2-D electron gas at the interface of a GaAs/AlGaAs heterostructure. The experiments span a range from open dots, where the leads of the dot carry at least one fully transmitting mode, to closed dots, where the leads are set to be tunnel barriers. For open dots, spin physics is inferred from measurements of conductance fluctuations; the effects of spin degeneracy in the orbital levels as well as a spin-orbit interaction are observed. In the closed dot measurements, ground state spin transitions as electrons are added to the dot may be determined from the motion of Coulomb blockade peaks in an in-plane magnetic field. In addition, this thesis demonstrates for the first time a direct measurement of the spin polarization of current emitted from a quantum dot, or a quantum point contact, during transport. These experiments make use of a spin-sensitive focusing geometry in which a quantum point contact serves as a spin analyzer for the mesoscopic device under test. Measurements are presented both in the open dot regime, where good agreement with theory is found, as well as the closed dot regime, where the data defies a simple theoretical explanation.

  8. Macroscopic rotation of photon polarization induced by a single spin.

    PubMed

    Arnold, Christophe; Demory, Justin; Loo, Vivien; Lemaître, Aristide; Sagnes, Isabelle; Glazov, Mikhaïl; Krebs, Olivier; Voisin, Paul; Senellart, Pascale; Lanco, Loïc

    2015-01-01

    Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling. Here we report the enhancement by three orders of magnitude of the spin-photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ± 6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network. PMID:25687134

  9. The Steady Spin

    NASA Technical Reports Server (NTRS)

    Fuchs, Richard; Schmidt, Wilhelm

    1931-01-01

    With the object of further clarifying the problem of spinning, the equilibrium of the forces and moments acting on an airplane is discussed in light of the most recent test data. Convinced that in a spin the flight attitude by only small angles of yaw is more or less completely steady, the study is primarily devoted to an investigation of steady spin with no side slip. At small angles, wholly arbitrary and perfectly steady spins may be forced, depending on the type of control displacements. But at large angles only very steep and only "approaching steady" spins are possible, no matter what the control displacements.

  10. Generalized Momentum Control of the Spin-Stabilized Magnetospheric Multiscale (MMS) Formation

    NASA Technical Reports Server (NTRS)

    Benegalrao, Suyog; Queen, Steven; Shah, Neerav; Blackman, Kathleen

    2015-01-01

    Angular momentum control maneuvers required to keep spin-axis in science box. Traditional approach uses de-coupled modes for pointing, spin, nutation Impractical for MMS Frequency and Number of maneuvers (Orbit Control, Pointing, Nutation, Spin, four observatories, every 2-4 weeks). Difficult to implement de-coupled open-loop control with flexible wire booms. Desire a unified angular momentum controller. Comprehensively control pointing, spin, and nutation.

  11. Inverse spin Hall effect by spin injection

    NASA Astrophysics Data System (ADS)

    Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

    2007-09-01

    Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

  12. Spin Transport in Silicon

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian

    2008-03-01

    Silicon has been broadly viewed as the ideal material for spintronics due to its low atomic weight, lattice inversion symmetry, and near lack of nuclear spin, resulting in exceptionally long spin lifetime. Despite this appeal, however, the experimental difficulties of achieving coherent spin transport in silicon were overcome for the first time only recently, by using unique spin-polarized hot-electron injection and detection techniques. [1] Our subsequent observations of very long spin lifetimes and transit lengths [2] have impact on prospects for Silicon spintronics as the basis for a new paradigm of information processing. [1] Ian Appelbaum, Biqin Huang, and Douwe J. Monsma, ``Electronic measurement and control of spin transport in silicon,'' Nature 447, 295 (2007). [2] Biqin Huang, Douwe J. Monsma, and Ian Appelbaum, ``Coherent spin transport through a 350-micron-thick silicon wafer,'' Phys. Rev. Lett. 99, 177209 (2007).

  13. Electron spin from self interaction

    SciTech Connect

    Spavieri, G. |

    1992-06-01

    The author explores the possibility that the electron self-interaction is the origin of the spin and of the radiative effects of QED. The electron is conceived as a charged, massless, point particle with a quantum or stochastic, internal motion about its center of mass and bound by a self-interaction potential. The hydrodynamic equations of motion describing the electron in its center of mass frame are related to non-Markovian stochastic equations recently used to derive the Schroedinger equation. By averaging over this stochastic internal motion and identifying the energy with the rest mass energy, the angular momentum exhibits properties characteristic of spin. The electromagnetic self-interactions added to the Hamiltonian of the particle correct the g factor to yield the anomalous value (g{minus}2)/2 {approx} 1159.7(2.3) X 10{sup {minus}6} in agreement with experiment. Calculations of other {open_quotes}radiative{close_quotes} effects including the Lamb shift are presented. The results obtained are finite and suggest that the QED corrections attributed to radiative effects could be obtained classically, i.e., without second quantization and renormalization, by complementing the Dirac theory with this self-interaction mechanism. The g factor dependence on the external magnetic field of this and other spin models is compared with that of QED, showing that these theories can be tested by the present precision measurements of the g factor. 33 refs., 2 tabs.

  14. Inactivation of the regulatory protein B of soluble methane monooxygenase from Methylococcus capsulatus (Bath) by proteolysis can be overcome by a Gly to Gln modification.

    PubMed

    Lloyd, J S; Bhambra, A; Murrell, J C; Dalton, H

    1997-08-15

    The regulatory protein B of soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), exists as a mixture of the full-length active form and truncated forms, B' and B". Electrospray ionisation mass spectrometry (ESI-MS) was used to identify a cleavage site between Met12 and Gly13, such that 12 amino acids were lost from the N-terminus of protein B. This truncate was designated B' and molecular masses were assigned to proteins B and B' of 15,852.6+/-0.4 Da and 14,629.5+/-0.3 Da, respectively. A cleavage site between Gln29 and Val30 was also identified such that 29 amino acids were lost from the N-terminus of protein B. This truncate was designated B" and had a molecular mass of 12,709.93+/-0.02 Da. Proteins B' and B" were found to be inactive in the sMMO system. Addition of protease inhibitors or the heterologous expression of protein B in various strains of lon-deficient or ompT-deficient Escherichia coli, did not inhibit B' formation. Expression of protein B as a glutathione S-transferase fusion protein and subsequent purification of protein B from E. coli using affinity chromatography resulted in preparations of protein B with higher enzyme activities than that of wild-type protein B. However, ESI-MS confirmed that protein B' was still present. Alteration of the Met12-Gly13 cleavage site to Met12-Gln13 revealed that the stability of G13Q at 20 degrees C and 37 degrees C was higher than that of wild-type preparations. ESI-MS indicated that protein B' was absent and could only be identified after prolonged incubation at room temperature. The amount of active protein B present in the cell may be controlled by protein B cleavage, thereby regulating electron transfer. Alternatively, it may allow protein B to maintain a certain conformation necessary for enzyme activity and this may control the activity of sMMO in response to the supply of methane to the cell. PMID:9310362

  15. Site-directed mutagenesis of Gln103 reveals the influence of this residue on the redox properties and stability of MauG.

    PubMed

    Shin, Sooim; Yukl, Erik T; Sehanobish, Esha; Wilmot, Carrie M; Davidson, Victor L

    2014-03-01

    The diheme enzyme MauG catalyzes a six-electron oxidation that is required for the posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived cofactor, tryptophan tryptophylquinone (TTQ). Crystallographic and computational studies have implicated Gln103 in stabilizing the Fe(IV)═O moiety of the bis-Fe(IV) state by hydrogen bonding. The role of Gln103 was probed by site-directed mutagenesis. Q103L and Q103E mutations resulted in no expression and very little expression of the protein, respectively. Q103A MauG exhibited oxidative damage when isolated. Q103N MauG was isolated at levels comparable to that of wild-type MauG and exhibited normal activity in catalyzing the biosynthesis of TTQ from preMADH. The crystal structure of the Q103N MauG-preMADH complex suggests that a water may mediate hydrogen bonding between the shorter Asn103 side chain and the Fe(IV)═O moiety. The Q103N mutation caused the two redox potentials associated with the diferric/diferrous redox couple to become less negative, although the redox cooperativity of the hemes of MauG was retained. Upon addition of H2O2, Q103N MauG exhibits changes in the absorbance spectrum in the Soret and near-IR regions consistent with formation of the bis-Fe(IV) redox state. However, the rate of spontaneous return of the spectrum in the Soret region was 4.5-fold greater for Q103N MauG than for wild-type MauG. In contrast, the rate of spontaneous decay of the absorbance at 950 nm, which is associated with charge-resonance stabilization of the high-valence state, was similar for wild-type MauG and Q103N MauG. This suggests that as a consequence of the mutation a different distribution of resonance structures stabilizes the bis-Fe(IV) state. These results demonstrate that subtle changes in the structure of the side chain of residue 103 can significantly affect the overall protein stability of MauG and alter the redox properties of the

  16. Information storage capacity of discrete spin systems

    SciTech Connect

    Yoshida, Beni

    2013-11-15

    Understanding the limits imposed on information storage capacity of physical systems is a problem of fundamental and practical importance which bridges physics and information science. There is a well-known upper bound on the amount of information that can be stored reliably in a given volume of discrete spin systems which are supported by gapped local Hamiltonians. However, all the previously known systems were far below this theoretical bound, and it remained open whether there exists a gapped spin system that saturates this bound. Here, we present a construction of spin systems which saturate this theoretical limit asymptotically by borrowing an idea from fractal properties arising in the Sierpinski triangle. Our construction provides not only the best classical error-correcting code which is physically realizable as the energy ground space of gapped frustration-free Hamiltonians, but also a new research avenue for correlated spin phases with fractal spin configurations. -- Highlights: •We propose a spin model with fractal ground states and study its coding properties. •We show that the model asymptotically saturates a theoretical limit on information storage capacity. •We discuss its relations to various theoretical physics problems.

  17. Cavity-Assisted Spin Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Zhu, Chuanzhou; Dong, Lin; Pu, Han

    We consider a single ultracold atom trapped inside a single-mode optical cavity, where a two-photon Raman process induces an effective coupling between atom's pseudo-spin and external center-of-mass (COM) motion. Without the COM motion, this system is described by the Jaynes-Cummings (JC) model. We show how the atomic COM motion dramatically modifies the predictions based on the JC model. We also investigated the situation when cavity pumping and decay are taken into account. We take a quantum Master equation approach to study this open system and again show how the cavity-induced spin-orbit coupling affects the properties of the system.

  18. Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach

    SciTech Connect

    Eslami, Leila Esmaeilzadeh, Mahdi

    2014-02-28

    Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.

  19. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves

    NASA Astrophysics Data System (ADS)

    Wong, P. K. Johnny; Zhang, Wen; Wu, Jing; Will, Iain G.; Xu, Yongbing; Xia, Ke; Holmes, Stuart N.; Farrer, Ian; Beere, Harvey E.; Ritchie, Dave A.

    2016-07-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET.

  20. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves

    PubMed Central

    Wong, P. K. Johnny; Zhang, Wen; Wu, Jing; Will, Iain G.; Xu, Yongbing; Xia, Ke; Holmes, Stuart N.; Farrer, Ian; Beere, Harvey E.; Ritchie, Dave A.

    2016-01-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET. PMID:27432047

  1. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves.

    PubMed

    Wong, P K Johnny; Zhang, Wen; Wu, Jing; Will, Iain G; Xu, Yongbing; Xia, Ke; Holmes, Stuart N; Farrer, Ian; Beere, Harvey E; Ritchie, Dave A

    2016-01-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET. PMID:27432047

  2. Spin-flip configuration interaction singles with exact spin-projection: Theory and applications to strongly correlated systems

    NASA Astrophysics Data System (ADS)

    Tsuchimochi, Takashi

    2015-10-01

    Spin-flip approaches capture static correlation with the same computational scaling as the ordinary single reference methods. Here, we extend spin-flip configuration interaction singles (SFCIS) by projecting out intrinsic spin-contamination to make it spin-complete, rather than by explicitly complementing it with spin-coupled configurations. We give a general formalism of spin-projection for SFCIS, applicable to any spin states. The proposed method is viewed as a natural unification of SFCIS and spin-projected CIS to achieve a better qualitative accuracy at a low computational cost. While our wave function ansatz is more compact than previously proposed spin-complete SF approaches, it successfully offers more general static correlation beyond biradicals without sacrificing good quantum numbers. It is also shown that our method is invariant with respect to open-shell orbital rotations, due to the uniqueness of spin-projection. We will report benchmark calculations to demonstrate its qualitative performance on strongly correlated systems, including conical intersections that appear both in ground-excited and excited-excited degeneracies.

  3. Pulsed electron-electron double resonance spectroscopy between a high-spin Mn(2+) ion and a nitroxide spin label.

    PubMed

    Akhmetzyanov, D; Plackmeyer, J; Endeward, B; Denysenkov, V; Prisner, T F

    2015-03-14

    Pulsed Electron-Electron Double Resonance (PELDOR) has attracted considerable attention for biomolecular applications, as it affords precise measurements of distances between pairs of spin labels in the range of 1.5-8 nm. Usually nitroxide moieties incorporated by site-directed spin labelling with cysteine residues are used as spin probes in protein systems. Recently, naturally occurring cofactors and metal ions have also been explored as paramagnetic spin species for such measurements. In this work we investigate the performance of PELDOR between a nitroxide spin label and a high-spin Mn(2+) ion in a synthetic model compound at Q-band (34 GHz) and G-band (180 GHz). We demonstrate that the distances obtained with high-frequency PELDOR are in good agreement with structural predictions. At Q-band frequencies experiments have been performed by probing either the high-spin Mn(2+) ion or the nitroxide spin label. At G-band frequencies we have been able to detect changes in the dipolar oscillation frequency, depending on the pump-probe positions across the g-tensor resolved nitroxide EPR spectrum. These changes result from the restricted mobility of the nitroxide spin label in the model compound. Our results demonstrate that the high-spin Mn(2+) ion can be used for precise distance measurements and open the doors for many biological applications, as naturally occurring Mg(2+) sites can be readily exchanged for Mn(2+). PMID:25669744

  4. Stripe phase and double-roton excitations in interacting spin-orbit-coupled spin-1 Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Sun, Kuei; Qu, Chunlei; Xu, Yong; Zhang, Yongping; Zhang, Chuanwei

    Spin-orbit (SO) coupling plays a major role in many important phenomena in condensed matter physics. However, the SO coupling physics in high-spin systems, especially with superfluids, has not been well explored because of the spin half of electrons in solids. In this context, the recent experimental realization of spin-orbit coupling in spin-1 Bose-Einstein condensates (BECs) has opened a completely new avenue for exploring SO-coupled high-spin superfluids. Nevertheless, the experiment has only revealed the single-particle physics of the system. Here, we study the effects of interactions between atoms on the ground states and collective excitations of SO-coupled spin-1 BECs in the presence of a spin-tensor potential. We find that ferromagnetic interaction between atoms can induce a stripe phase exhibiting two modulating patterns. We characterize the phase transitions between different phases using the spin-tensor density as well as the collective dipole motion of the BEC. We show that there exists a new type of double maxon-roton structure in the Bogoliubov-excitation spectrum, attributing to the three band minima of the SO-coupled spin-1 BEC. Our work could motivate further theoretical and experimental study along this direction.

  5. Spin-flip configuration interaction singles with exact spin-projection: Theory and applications to strongly correlated systems

    SciTech Connect

    Tsuchimochi, Takashi

    2015-10-14

    Spin-flip approaches capture static correlation with the same computational scaling as the ordinary single reference methods. Here, we extend spin-flip configuration interaction singles (SFCIS) by projecting out intrinsic spin-contamination to make it spin-complete, rather than by explicitly complementing it with spin-coupled configurations. We give a general formalism of spin-projection for SFCIS, applicable to any spin states. The proposed method is viewed as a natural unification of SFCIS and spin-projected CIS to achieve a better qualitative accuracy at a low computational cost. While our wave function ansatz is more compact than previously proposed spin-complete SF approaches, it successfully offers more general static correlation beyond biradicals without sacrificing good quantum numbers. It is also shown that our method is invariant with respect to open-shell orbital rotations, due to the uniqueness of spin-projection. We will report benchmark calculations to demonstrate its qualitative performance on strongly correlated systems, including conical intersections that appear both in ground-excited and excited-excited degeneracies.

  6. Associations between Dietary Patterns, ADRβ2 Gln27Glu and ADRβ3 Trp64Arg with Regard to Serum Triglyceride Levels: J-MICC Study.

    PubMed

    Nanri, Hinako; Nishida, Yuichiro; Nakamura, Kazuyo; Tanaka, Keitaro; Naito, Mariko; Yin, Guang; Hamajima, Nobuyuki; Takashima, Naoyuki; Suzuki, Sadao; Nindita, Yora; Kohno, Michiko; Uemura, Hirokazu; Koyama, Teruhide; Hosono, Satoyo; Mikami, Haruo; Kubo, Michiaki; Tanaka, Hideo

    2016-01-01

    Interactions between dietary patterns and 2 β-adrenergic receptor (ADRβ) gene polymorphisms (ADRβ2 Gln27Glu and ADRβ3 Trp64Arg) were examined with regard to the effects on serum triglyceride levels. The cross-sectional study comprised 1720 men and women (aged 35-69 years) enrolled in the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study. Genotyping was conducted using a multiplex polymerase chain reaction-based invader assay. We used 46 items from a validated short food frequency questionnaire and examined major dietary patterns by factor analysis. We identified four dietary patterns: healthy, Western, seafood and bread patterns. There was no significant association between any dietary pattern and serum triglyceride levels. After a separate genotype-based analysis, significant interactions between ADRβ3 Trp64Arg genotype and the bread pattern (p for interaction = 0.01) were associated with serum triglyceride levels; specifically, after adjusting for confounding factors, Arg allele carriers with the bread pattern had lower serum triglycerides (p for trend = 0.01). However, the Trp/Trp homozygous subjects with the bread pattern showed no association with serum triglycerides (p for trend = 0.55). Interactions between other dietary patterns and ADRβ polymorphisms were not significant for serum triglyceride levels. Our findings suggest that ADRβ3 polymorphism modifies the effects of the bread pattern on triglyceride levels. PMID:27608039

  7. Progressive Lower Extremity Weakness and Axonal Sensorimotor Polyneuropathy from a Mutation in KIF5A (c.611G>A;p.Arg204Gln)

    PubMed Central

    Jerath, Nivedita U.; Grider, Tiffany; Shy, Michael E.

    2015-01-01

    Introduction. Hereditary Spastic Paraplegia (HSP) is a rare hereditary disorder that primarily involves progressive spasticity of the legs (hamstrings, quadriceps, and calves). Methods. A 27-year-old gentleman was a fast runner and able to play soccer until age 9 when he developed slowly progressive weakness. He was wheelchair-bound by age 25. He was evaluated by laboratory testing, imaging, electrodiagnostics, and molecular genetics. Results. Electrodiagnostic testing revealed an axonal sensorimotor polyneuropathy. Genetic testing for HSP in 2003 was negative; repeat testing in 2013 revealed a mutation in KIF5A (c.611G>A;p.Arg204Gln). Conclusions. A recent advance in neurogenetics has allowed for more genes and mutations to be identified; over 76 different genetic loci for HSP and 59 gene products are currently known. Even though our patient had a sensorimotor polyneuropathy on electrodiagnostic testing and a 2003 HSP genetic panel that was negative, a repeat HSP genetic panel was performed in 2013 due to the advancement in neurogenetics. This revealed a mutation in KIF5A. PMID:26543653

  8. Subtle structural changes in the Asp251Gly/Gln307His P450 BM3 mutant responsible for new activity toward diclofenac, tolbutamide and ibuprofen.

    PubMed

    Di Nardo, Giovanna; Dell'Angelo, Valentina; Catucci, Gianluca; Sadeghi, Sheila J; Gilardi, Gianfranco

    2016-07-15

    This paper reports the structure of the double mutant Asp251Gly/Gln307His (named A2) generated by random mutagenesis, able to produce 4'-hydroxydiclofenac, 2-hydroxyibuprofen and 4-hydroxytolbutamide from diclofenac, ibuprofen and tolbutamide, respectively. The 3D structure of the substrate-free mutant shows a conformation similar to the closed one found in the substrate-bound wild type enzyme, but with a higher degree of disorder in the region of the G-helix and F-G loop. This is due to the mutation Asp251Gly that breaks the salt bridge between Aps251 on I-helix and Lys224 on G-helix, allowing the G-helix to move away from I-helix and conferring a higher degree of flexibility to this element. This subtle structural change is accompanied by long-range structural rearrangements of the active site with the rotation of Phe87 and a reorganization of catalytically important water molecules. The impact of these structural features on thermal stability, reduction potential and electron transfer is investigated. The data demonstrate that a single mutation far from the active site triggers an increase in protein flexibility in a key region, shifting the conformational equilibrium toward the closed form that is ready to accept electrons and enter the P450 catalytic cycle as soon as a substrate is accepted. PMID:26718083

  9. Spin Hall effects

    NASA Astrophysics Data System (ADS)

    Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

    2015-10-01

    Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

  10. Electric field effects on spin accumulation in Nb-doped SrTiO{sub 3} using tunable spin injection contacts at room temperature

    SciTech Connect

    Kamerbeek, A. M.; Vries, E. K. de; Wees, B. J. van; Banerjee, T.; Dankert, A.; Dash, S. P.

    2014-05-26

    We report on features in charge transport and spin injection in an oxide semiconductor, Nb-doped SrTiO{sub 3}. This is demonstrated using electrically tunable spin injection contacts which exploit the large electric field at the interface and its interplay with the relative permittivity of the semiconductor. We realize spin accumulation in Nb-doped SrTiO{sub 3} which displays a unique dependence of the spin lifetime with bias polarity. These findings suggest a strong influence of the interface electric field on the charge transport as well as on spin accumulation unlike in conventional semiconductors and opens up promising avenues in oxide spintronics.

  11. Spin caloritronics in graphene

    SciTech Connect

    Ghosh, Angsula; Frota, H. O.

    2015-06-14

    Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.

  12. Picosecond Spin Caloritronics

    NASA Astrophysics Data System (ADS)

    Cahill, David G.

    The coupling of spin and heat, i.e., spin caloritronics, gives rise to new physical phenomena in nanoscale spin devices and new ways to manipulate local magnetization. Our work in this field takes advantage of recent advances in the measurement and understanding of heat transport at the nanoscale using ultrafast lasers. We use a picosecond duration pump laser pulses as a source of heat and picosecond duration probe laser pulses to detect changes in temperature, spin accumulation, and spin transfer torque using a combination of time-domain thermoreflectance and time-resolved magneto-optic Kerr effect Our pump-probe optical methods enable us to change the temperature of ferromagnetic layers on a picosecond time-scale and generate enormous heat fluxes on the order of 100 GW m-2 that persist for ~ 30 ps. Thermally-driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The spin-dependent Seebeck effect of a perpendicular ferromagnetic layer converts a heat current into spin current, which in turn can be used to exert a spin transfer torque (STT) on a second ferromagnetic layer with in-plane magnetization. Using a [Co,Ni] multilayer as the source of spin, an energy fluence of ~ 4 J m-2 creates thermal STT sufficient to induce ~ 1 % tilting of the magnetization of a 2 nm-thick CoFeB layer.

  13. Spin coating apparatus

    DOEpatents

    Torczynski, John R.

    2000-01-01

    A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.

  14. Graphene-based half-metal and spin-semiconductor for spintronic applications

    NASA Astrophysics Data System (ADS)

    Qi, Jingshan; Chen, Xiaofang; Hu, Kaige; Feng, Ji

    2016-03-01

    In this letter we propose a strategy to make graphene become a half-metal or spin-semiconductor by combining the magnetic proximity effects and sublattice symmetry breaking in graphone/graphene and graphone/graphene/BN heterostructures. Exchange interactions lift the spin degeneracy and sublattice symmetry breaking opens a band gap in graphene. More interestingly, the gap opening depends on the spin direction and the competition between the sublattice asymmetry and exchange field determines the system is a half-metal or a spin-semiconductor. By first-principles calculations and a low-energy effective model analysis, we elucidate the underlying physical mechanism of spin-dependent gap opening and spin degeneracy splitting. This offers an alternative practical platform for graphene-based spintronics.

  15. Graphene-based half-metal and spin-semiconductor for spintronic applications.

    PubMed

    Qi, Jingshan; Chen, Xiaofang; Hu, Kaige; Feng, Ji

    2016-03-31

    In this letter we propose a strategy to make graphene become a half-metal or spin-semiconductor by combining the magnetic proximity effects and sublattice symmetry breaking in graphone/graphene and graphone/graphene/BN heterostructures. Exchange interactions lift the spin degeneracy and sublattice symmetry breaking opens a band gap in graphene. More interestingly, the gap opening depends on the spin direction and the competition between the sublattice asymmetry and exchange field determines the system is a half-metal or a spin-semiconductor. By first-principles calculations and a low-energy effective model analysis, we elucidate the underlying physical mechanism of spin-dependent gap opening and spin degeneracy splitting. This offers an alternative practical platform for graphene-based spintronics. PMID:26933773

  16. Rockets for spin recovery

    NASA Technical Reports Server (NTRS)

    Whipple, R. D.

    1980-01-01

    The potential effectiveness of rockets as an auxiliary means for an aircraft to effect recovery from spins was investigated. The advances in rocket technology produced by the space effort suggested that currently available systems might obviate many of the problems encountered in earlier rocket systems. A modern fighter configuration known to exhibit a flat spin mode was selected. An analytical study was made of the thrust requirements for a rocket spin recovery system for the subject configuration. These results were then applied to a preliminary systems study of rocket components appropriate to the problem. Subsequent spin tunnel tests were run to evaluate the analytical results.

  17. Polariton spin whirls

    NASA Astrophysics Data System (ADS)

    Cilibrizzi, P.; Sigurdsson, H.; Liew, T. C. H.; Ohadi, H.; Wilkinson, S.; Askitopoulos, A.; Shelykh, I. A.; Lagoudakis, P. G.

    2015-10-01

    We report on the observation of spin whirls in a radially expanding polariton condensate formed under nonresonant optical excitation. Real space imaging of polarization- and time-resolved photoluminescence reveals a spiralling polarization pattern in the plane of the microcavity. Simulations of the spatiotemporal dynamics of a spinor condensate reveal the crucial role of polariton interactions with a spinor exciton reservoir. Harnessing spin-dependent interactions between the exciton reservoir and polariton condensates allows for the manipulation of spin currents and the realization of dynamic collective spin effects in solid-state systems.

  18. Paramagnetic spin pumping.

    PubMed

    Shiomi, Y; Saitoh, E

    2014-12-31

    We have demonstrated spin pumping from a paramagnetic state of an insulator La2NiMnO6 into a Pt film. Single-crystalline films of La2NiMnO6 which exhibit a ferromagnetic order at TC≈270  K were grown by pulsed laser deposition. The inverse spin Hall voltage induced by spin-current injection has been observed in the Pt layer not only in the ferromagnetic phase of La2NiMnO6, but also in a wide temperature range above TC. The efficient spin pumping in the paramagnetic phase is ascribable to ferromagnetic correlation, not to ferromagnetic order. PMID:25615367

  19. Spin-mediated Hybrid Quantum Optomechanics

    NASA Astrophysics Data System (ADS)

    Shaffer, Airlia; Chang, Laura; Patil, Yogesh Sharad; Bariani, Francesco; Singh, Swati; Date, Aditya; Chakram, Srivatsan; Schwab, Keith; Meystre, Pierre; Vengalattore, Mukund

    2015-05-01

    We describe our realization of a hybrid quantum system where a macroscopic mechanical resonator is coupled to the collective spin of an ultracold gas through a remote optical interface. Through this interface, the spin ensemble is capable of sympathetic cooling, sub-SQL detection and quantum control of the mechanical resonator. As such, this hybrid quantum system presents a powerful scheme to combine the robustness of the mesoscopic resonator with the sensitivity and coherence of the spin ensemble. Our ongoing studies of this system include various aspects of quantum metrology and the out-of-equilibrium dynamics of open quantum systems. This work is supported by the ARO MURI on non-equilibrium dynamics, the DARPA QuASAR program through a grant from the ARO and an NSF INSPIRE award.

  20. Terahertz Antiferromagnetic Spin Hall Nano-Oscillator

    NASA Astrophysics Data System (ADS)

    Cheng, Ran; Xiao, Di; Brataas, Arne

    2016-05-01

    We consider the current-induced dynamics of insulating antiferromagnets in a spin Hall geometry. Sufficiently large in-plane currents perpendicular to the Néel order trigger spontaneous oscillations at frequencies between the acoustic and the optical eigenmodes. The direction of the driving current determines the chirality of the excitation. When the current exceeds a threshold, the combined effect of spin pumping and current-induced torques introduces a dynamic feedback that sustains steady-state oscillations with amplitudes controllable via the applied current. The ac voltage output is calculated numerically as a function of the dc current input for different feedback strengths. Our findings open a route towards terahertz antiferromagnetic spin-torque oscillators.

  1. Terahertz Antiferromagnetic Spin Hall Nano-Oscillator.

    PubMed

    Cheng, Ran; Xiao, Di; Brataas, Arne

    2016-05-20

    We consider the current-induced dynamics of insulating antiferromagnets in a spin Hall geometry. Sufficiently large in-plane currents perpendicular to the Néel order trigger spontaneous oscillations at frequencies between the acoustic and the optical eigenmodes. The direction of the driving current determines the chirality of the excitation. When the current exceeds a threshold, the combined effect of spin pumping and current-induced torques introduces a dynamic feedback that sustains steady-state oscillations with amplitudes controllable via the applied current. The ac voltage output is calculated numerically as a function of the dc current input for different feedback strengths. Our findings open a route towards terahertz antiferromagnetic spin-torque oscillators. PMID:27258884

  2. Spin-spin and spin-orbit interaction effects of two-electron quantum dots

    NASA Astrophysics Data System (ADS)

    Vaseghi, B.; Rezaei, G.; Taghizadeh, S. F.; Shahedi, Z.

    2014-09-01

    Simultaneous effects of spin-spin and spin-orbit interactions on the energy spectrum of a two-electron spherical quantum dot with parabolic confinement and under the influence of external electric and magnetic fields are investigated. We have calculated energy eigenvalues and eigenvectors of the system for different spin states. Results show that effects of spin-spin interactions are negligible in comparison with those of the spin-orbit interactions. Spin-orbit interaction splits energy levels and removes degeneracy of different spin states. Moreover it is seen that energy eigenvalues and levels splitting strongly depend on the external magnetic field and the dot dimensions.

  3. Effect of spin rotation coupling on spin transport

    SciTech Connect

    Chowdhury, Debashree Basu, B.

    2013-12-15

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup →}⋅p{sup →} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup →}⋅p{sup →} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.

  4. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    SciTech Connect

    Wójcik, P. Adamowski, J. Wołoszyn, M.; Spisak, B. J.

    2015-07-07

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics.

  5. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    NASA Astrophysics Data System (ADS)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-07-01

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics.

  6. Coherent transport and manipulation of spins in indirect-exciton nanostructures

    NASA Astrophysics Data System (ADS)

    Violante, A.; Hey, R.; Santos, P. V.

    2015-03-01

    We report on the coherent control and transport of indirect-exciton (IX) spins in GaAs double quantum well (DQW) nanostructures. The spin dynamics was investigated by optically generating spins using a focused, circularly polarized light spot and by probing their spatial distribution using spatially and polarization resolved photoluminescence spectroscopy. Optically injected IX spins precess while moving over distances exceeding 20 μ m from the excitation spot with a precession length that depends on the spin transport direction as well as on the bias applied across the DQW structure. This behavior is attributed to the spin precession in the effective magnetic field induced by the spin-orbit interaction. From the dependence of the spin dynamics on the transport direction, bias, and external magnetic fields we directly determined the Dresselhaus and Rashba electron spin splitting coefficients for the DQW structure. The precession dynamics is essentially independent of the IX density, thus indicating that the long spin lifetimes are not associated with IX collective effects. The long IX lifetimes, together with the negligible contribution of holes to the spin dynamics, are rather attributed to spatial separation of the electron and hole wave functions by the electric field, which reduces the electron-hole exchange interaction. If extended to the single-exciton regime, the present results on coherent spin precession over long transport distances as well as the control of the spin vector using electric and magnetic fields open the way for the application of IX spins in quantum information processing.

  7. Spin Waves in Quasiequilibrium Spin Systems

    SciTech Connect

    Bedell, Kevin S.; Dahal, Hari P.

    2006-07-28

    Using the Landau Fermi liquid theory we discovered a new propagating transverse spin wave in a paramagnetic system which is driven slightly out of equilibrium without applying an external magnetic field. We find a gapless mode which describes the uniform precession of the magnetization in the absence of a magnetic field. We also find a gapped mode associated with the precession of the spin current around the internal field. The gapless mode has a quadratic dispersion leading to a T{sup 3/2} contribution to the specific heat. These modes significantly contribute to the dynamic structure function.

  8. Sparkling and Spinning Words.

    ERIC Educational Resources Information Center

    Carlson, Ruth Kearney

    1964-01-01

    Teachers should foster in children's writing the use of words with "sparkle" and "spin"--"sparkle" implying brightness and vitality, "spin" connoting industry, patience, and painstaking work. By providing creative listening experiences with good children's or adult literature, the teacher can encourage students to broaden their imaginations and…

  9. Single-spin CCD.

    PubMed

    Baart, T A; Shafiei, M; Fujita, T; Reichl, C; Wegscheider, W; Vandersypen, L M K

    2016-04-01

    Spin-based electronics or spintronics relies on the ability to store, transport and manipulate electron spin polarization with great precision. In its ultimate limit, information is stored in the spin state of a single electron, at which point quantum information processing also becomes a possibility. Here, we demonstrate the manipulation, transport and readout of individual electron spins in a linear array of three semiconductor quantum dots. First, we demonstrate single-shot readout of three spins with fidelities of 97% on average, using an approach analogous to the operation of a charge-coupled device (CCD). Next, we perform site-selective control of the three spins, thereby writing the content of each pixel of this 'single-spin charge-coupled device'. Finally, we show that shuttling an electron back and forth in the array hundreds of times, covering a cumulative distance of 80 μm, has negligible influence on its spin projection. Extrapolating these results to the case of much larger arrays points at a diverse range of potential applications, from quantum information to imaging and sensing. PMID:26727201

  10. Centralizers of spin subalgebras

    NASA Astrophysics Data System (ADS)

    Arizmendi, Gerardo; Herrera, Rafael

    2015-11-01

    We determine the centralizers of certain isomorphic copies of spin subalgebras spin(r) in so(dr m), where dr is the dimension of a real irreducible representation of Clr0, the even Clifford algebra determined by the positive definite inner product on Rr, where r, m ∈ N.

  11. Coherent spin-networks

    SciTech Connect

    Bianchi, Eugenio; Magliaro, Elena; Perini, Claudio

    2010-07-15

    In this paper we discuss a proposal of coherent states for loop quantum gravity. These states are labeled by a point in the phase space of general relativity as captured by a spin-network graph. They are defined as the gauge-invariant projection of a product over links of Hall's heat kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the spin-foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). These states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli.

  12. Spin coating of electrolytes

    DOEpatents

    Stetter, Joseph R.; Maclay, G. Jordan

    1989-01-01

    Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

  13. Antiferromagnetic Spin Seebeck Effect.

    PubMed

    Wu, Stephen M; Zhang, Wei; Kc, Amit; Borisov, Pavel; Pearson, John E; Jiang, J Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-01

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF_{2}. A device scale on-chip heater is deposited on a bilayer of MnF_{2} (110) (30  nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF_{2} (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF_{2} through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9  T) are applied parallel to the easy axis of the MnF_{2} thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected. PMID:26991198

  14. Hadron Spin Dynamics

    SciTech Connect

    Brodsky, Stanley J.

    2002-01-09

    Spin effects in exclusive and inclusive reactions provide an essential new dimension for testing QCD and unraveling hadron structure. Remarkable new experiments from SLAC, HERMES (DESY), and Jefferson Lab present many challenges to theory, including measurements at HERMES and SMC of the single spin asymmetries in ep {yields} e{prime}{pi}X where the proton is polarized normal to the scattering plane. This type of single spin asymmetry may be due to the effects of rescattering of the outgoing quark on the spectators of the target proton, an effect usually neglected in conventional QCD analyses. Many aspects of spin, such as single-spin asymmetries and baryon magnetic moments are sensitive to the dynamics of hadrons at the amplitude level, rather than probability distributions. I will illustrate the novel features of spin dynamics for relativistic systems by examining the explicit form of the light-front wavefunctions for the two-particle Fock state of the electron in QED, thus connecting the Schwinger anomalous magnetic moment to the spin and orbital momentum carried by its Fock state constituents and providing a transparent basis for understanding the structure of relativistic composite systems and their matrix elements in hadronic physics. I also present a survey of outstanding spin puzzles in QCD, particularly A{sub NN} in elastic pp scattering, the J/{psi} {yields} {rho}{pi} puzzle, and J/{psi} polarization at the Tevatron.

  15. Single spin magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  16. Single spin magnetic resonance.

    PubMed

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution. PMID:27378060

  17. Single-spin CCD

    NASA Astrophysics Data System (ADS)

    Baart, T. A.; Shafiei, M.; Fujita, T.; Reichl, C.; Wegscheider, W.; Vandersypen, L. M. K.

    2016-04-01

    Spin-based electronics or spintronics relies on the ability to store, transport and manipulate electron spin polarization with great precision. In its ultimate limit, information is stored in the spin state of a single electron, at which point quantum information processing also becomes a possibility. Here, we demonstrate the manipulation, transport and readout of individual electron spins in a linear array of three semiconductor quantum dots. First, we demonstrate single-shot readout of three spins with fidelities of 97% on average, using an approach analogous to the operation of a charge-coupled device (CCD). Next, we perform site-selective control of the three spins, thereby writing the content of each pixel of this ‘single-spin charge-coupled device’. Finally, we show that shuttling an electron back and forth in the array hundreds of times, covering a cumulative distance of 80 μm, has negligible influence on its spin projection. Extrapolating these results to the case of much larger arrays points at a diverse range of potential applications, from quantum information to imaging and sensing.

  18. Crystal Structure of the Mobile Metallo-β-Lactamase AIM-1 from Pseudomonas aeruginosa: Insights into Antibiotic Binding and the Role of Gln157

    PubMed Central

    Borra, Pardha S.; Brandsdal, Bjørn Olav; Edvardsen, Kine Susann Waade; Spencer, James; Walsh, Timothy R.; Samuelsen, Ørjan

    2012-01-01

    Metallo-β-lactamase (MBL) genes confer resistance to virtually all β-lactam antibiotics and are rapidly disseminated by mobile genetic elements in Gram-negative bacteria. MBLs belong to three different subgroups, B1, B2, and B3, with the mobile MBLs largely confined to subgroup B1. The B3 MBLs are a divergent subgroup of predominantly chromosomally encoded enzymes. AIM-1 (Adelaide IMipenmase 1) from Pseudomonas aeruginosa was the first B3 MBL to be identified on a readily mobile genetic element. Here we present the crystal structure of AIM-1 and use in silico docking and quantum mechanics and molecular mechanics (QM/MM) calculations, together with site-directed mutagenesis, to investigate its interaction with β-lactams. AIM-1 adopts the characteristic αβ/βα sandwich fold of MBLs but differs from other B3 enzymes in the conformation of an active site loop (residues 156 to 162) which is involved both in disulfide bond formation and, we suggest, interaction with substrates. The structure, together with docking and QM/MM calculations, indicates that the AIM-1 substrate binding site is narrower and more restricted than those of other B3 MBLs, possibly explaining its higher catalytic efficiency. The location of Gln157 adjacent to the AIM-1 zinc center suggests a role in drug binding that is supported by our in silico studies. However, replacement of this residue by either Asn or Ala resulted in only modest reductions in AIM-1 activity against the majority of β-lactam substrates, indicating that this function is nonessential. Our study reveals AIM-1 to be a subclass B3 MBL with novel structural and mechanistic features. PMID:22664968

  19. The cytocompatability of polyhydroxyalkanoates coated with a fusion protein of PHA repressor protein (PhaR) and Lys-Gln-Ala-Gly-Asp-Val (KQAGDV) polypeptide.

    PubMed

    Dong, Cui-Ling; Li, Shi-Yan; Wang, Yang; Dong, Ying; Tang, James Zhenggui; Chen, Jin-Chun; Chen, Guo-Qiang

    2012-03-01

    Microbial polyhydroxyalkanoates (PHAs) are a family of polyesters with biodegradability, biocompatibility and adjustable mechanical properties that are under intensive development for bioimplant applications. In this research, a fusion protein of PHA repressor protein (PhaR) and Lys-Gln-Ala-Gly-Asp-Val (KQAGDV) oligopeptide (PhaR-KQAGDV) was utilized to enhance the PHA cytocompatability via a mechanism of PhaR hydrophobically binding to PHA coupled with KQAGDV oligopeptide, a specific ligand to the integrins on the cell surface, for promotion of cell adhesion. The PhaR-KQAGDV fusion protein successfully produced and purified from recombinant E. coli was used to coat the surfaces of several PHA including poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), respectively. The PhaR was observed to bind efficiently on all PHA surfaces measured by the fluorescence intensity of PhaR-EGFP as compared to the uncoated (PhaR negative) PHA films. The PHA surface hydrophilicity measured by water contact angles was significantly improved after PhaR-KQAGDV coating. Observations under confocal microscope and scanning electron microscopy, together with CCK-8 assays clearly demonstrated that adhesion and proliferation of human vascular smooth muscle cells (HvSMCs) inoculated on PHA films were much better on PhaR-KQAGDV coated surfaces than the non-coated control ones. The convenient physical coating approach for enhanced PHA cytocompatibility provides an advantage for PHA based tissue engineering. PMID:22206593

  20. Thermal Spin Transfer Torques

    NASA Astrophysics Data System (ADS)

    Bauer, Gerrit

    2009-03-01

    The coupling between spin and charge in electronic transport is studied in the field of spintronics. Heat currents are coupled to both charge and spin currents as well [1]. This extension of spintronics to what may be called ``spin caloritronics'' recently enjoys renewed attention [2]. The spin-transfer torque associated with electric currents can excite magnetizations in nanostructures, switching magnetic configuration in spin valves and move domain walls in magnetic wires when exceeding critical values of the order of 10^7Acm-2 [3]. Also heat currents transfer spin angular momentum [4], either intrinsically or via the thermoelectric generation of particle spin currents. We predict that temperature differences of the order of 100 K over typical metallic nanostructures cause effects equivalent to the critical charge current densities. In this talk I will give a brief review of various aspects of spin caloritronics with emphasis on thermal spin transfer torques. This work has been carried out in collaboration with Moosa Hatami, Qinfang Zhang, Paul Kelly, Hans Joakim Skadsem, Arne Brataas and Sadamichi Maekawa. [4pt] [1] M. Johnson and R.H. Silsbee, Phys. Rev. B 35, 4959 (1987).[0pt] [2] International Workshop on Spin Caloritronics, Lorentz Center of Leiden University, 9-13 February 2009, http://www.lorentzcenter.nl/lc/web/2009/323/info.php3?wsid=323[0pt] [3] D. C. Ralph and M. D. Stiles, J. Magn. Magn. Mater. 320, 1190 (2008).[0pt] [4] M. Hatami, G.E.W. Bauer, Q. Zhang, and P.J. Kelly, Phys. Rev. Lett. 99, 066603 (2007).

  1. Thermal spin fluctuations in spinor Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Melé-Messeguer, M.; Juliá-Díaz, B.; Polls, A.; Santos, L.

    2013-03-01

    We study the thermal activation of spin fluctuations in dynamically stable spinor Bose-Einstein condensates. We analyze the specific cases of a nondipolar spin-1 condensate in the state m=0, where thermal activation results from spin-changing collisions, and of a chromium condensate in the maximally stretched state m=-3, where thermal spin fluctuations are due to dipole-induced spin relaxation. In both cases, we show that the low energy associated to the spinor physics may be employed for thermometry purposes down to extremely low temperatures, typically impossible to measure in Bose-Einstein condensates with the usual thermometric techniques. Moreover, the peculiar dependence of the system's entropy with the applied Zeeman energy opens a possible route for adiabatic cooling.

  2. Aspects of metric-like higher-spin geometry

    SciTech Connect

    Francia, D.

    2012-09-24

    We consider the higher-derivative equations obtained setting to zero the divergence of the higher-spin curvatures in metric-like form, showing their equivalence to the second-order equations emerging from the tensionless limit of open string field theory, propagating reducible spectra of particles with different spins. This result can be viewed as complementary to the possibility of setting to zero a single trace of the higher-spin field strengths, yielding an equation known to imply Fronsdal's equation in the compensator form. We review the general context and results obtained in the investigation of metric-like higher-spin geometry, the structure of the corresponding non-local actions, together with their links to more conventional, local forms including a recently proposed one for higher-spin theories with transverse gauge invariance.

  3. Foucault's pendulum, a classical analog for the electron spin state

    NASA Astrophysics Data System (ADS)

    Linck, Rebecca A.

    Spin has long been regarded as a fundamentally quantum phenomena that is incapable of being described classically. To bridge the gap and show that aspects of spin's quantum nature can be described classically, this work uses a classical Lagrangian based on the coupled oscillations of Foucault's pendulum as an analog for the electron spin state in an external magnetic field. With this analog it is possible to demonstrate that Foucault's pendulum not only serves as a basis for explaining geometric phase, but is also a basis for reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured electron spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

  4. All electrical propagating spin wave spectroscopy with broadband wavevector capability

    NASA Astrophysics Data System (ADS)

    Ciubotaru, F.; Devolder, T.; Manfrini, M.; Adelmann, C.; Radu, I. P.

    2016-07-01

    We developed an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down to 125 nm wide inductive antennas, which award ultra broadband wavevector capability. The wavevector selection can be done by applying an excitation frequency above the ferromagnetic resonance. Wavevector demultiplexing is done at the spin wave detector thanks to the rotation of the spin wave phase upon propagation. A simple model accounts for the main features of the apparatus transfer functions. Our approach opens an avenue for the all electrical study of wavevector-dependent spin wave properties including dispersion spectra or non-reciprocal propagation.

  5. The physics of spin rectification and its application

    NASA Astrophysics Data System (ADS)

    Gui, YongSheng; Bai, LiHui; Hu, CanMing

    2013-01-01

    A coherent nonlinear coupling between the charge and spin dynamics of electrons results in the rectification of microwaves, which is enhanced through resonant magnetization dynamics such as ferromagnetic resonance. This property, known as the spin rectification effect, enables the spin dynamics within a material to be electrically detected with a high sensitivity. Techniques utilizing this property have been widely used to study the magnetization dynamics of various ferromagnetic materials and structures in the past decade. Additionally, the coherent nature of spin rectification opens the door for spintronic devices to be used in phase-resolved microwave sensing techniques. In this work we review the physics of spin rectification and its applications in several interesting topics of magnetism and spintronics.

  6. Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling

    PubMed Central

    Hou, Yan-Hua; Yu, Zhenhua

    2015-01-01

    Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations. PMID:26483090

  7. Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects

    SciTech Connect

    Elyasi, Mehrdad; Bhatia, Charanjit S.; Yang, Hyunsoo

    2015-02-14

    We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets.

  8. Electrical creation of spin polarization in silicon at room temperature

    NASA Astrophysics Data System (ADS)

    Jansen, Ron

    2010-03-01

    The integration of magnetism and mainstream semiconductor electronics could impact information technology in ways beyond imagination. A pivotal step is the implementation of spin-based electronic functionality in silicon devices. Much of the interest in silicon derives from its prevalence in semiconductor technology and from the robustness and longevity of spin as it is only weakly coupled to other degrees of freedom in the material. Recently it has become possible to induce and detect spin polarization in otherwise non-magnetic semiconductors (GaAs and Si) using all-electrical structures, but so far at temperatures below 150 K and only in n-type material. The main challenges are: (i) to design fully electrical silicon-based spintronic devices with large spin signals, (ii) to demonstrate device operation at room temperature, (iii) to do so for n-type and p-type material, and (iv) to find ways to manipulate spins and spin flow with a gate electric field. After a brief overview of the state of affairs, our recent advances in these areas are described. In particular, we demonstrate room-temperature electrical injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect, and the electrical detection of the induced spin accumulation. It is shown that a spin splitting as large as 2.9 meV can be created in Si at room temperature, corresponding to an electron spin polarization of 4.6%. The results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature, and to the exploration of their prospects as well as the fundamental rules that govern their behavior. [4pt] [1] S.P. Dash, S. Sharma, R.S. Patel, M.P. de Jong and R. Jansen, Nature 462, 491 (2009).

  9. Real-time observation of Snell’s law for spin waves in thin ferromagnetic films

    NASA Astrophysics Data System (ADS)

    Tanabe, Kenji; Matsumoto, Ryo; Ohe, Jun-ichiro; Murakami, Shuichi; Moriyama, Takahiro; Chiba, Daichi; Kobayashi, Kensuke; Ono, Teruo

    2014-05-01

    We report the real-time observation of spin-wave propagation across a step inserted between two ferromagnetic films with different thicknesses. Because the dispersion relation of the spin wave depends on the thickness of the film, the step works as a junction to affect the spin wave propagation. When the spin wave transmits through the junction, the wavenumber undergoes modulation as per Snell’s law, which states that the refraction index is proportional to the wavenumber. From the viewpoint of magnonics, the present achievement opens up new possibilities of controlling the wavenumber of spin waves.

  10. Control of the spin to charge conversion using the inverse Rashba-Edelstein effect

    SciTech Connect

    Sangiao, S.; De Teresa, J. M.; Morellon, L.; Martinez-Velarte, M. C.; Lucas, I.; Viret, M.

    2015-04-27

    We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of the spin to charge conversion in a spin pumping experiment. Using the intrinsic symmetry of the “Inverse Rashba Edelstein Effect” (IREE) in a Bi/Ag interface, the charge current changes sign when reversing the order of the Ag and Bi stacking. This confirms the IREE nature of the conversion of spin into charge in these interfaces and opens the way to tailoring the spin sensing voltage by an appropriate trilayer sequence.

  11. Gluon Spin Contribution to The Nucleon Spin

    NASA Astrophysics Data System (ADS)

    Arash, Firooz; Shahveh, Abolfazl; Taghavi-Shahri, Fateme

    2010-10-01

    We have calculated δg/ g in the nucleon at all measured kinematics. The smallness of δg/ g in the measured kinematics should not be interpreted as the the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, Δ g( Q2) can be sizable.

  12. Inverse spin Hall effect in a closed loop circuit

    SciTech Connect

    Omori, Y.; Auvray, F.; Wakamura, T.; Niimi, Y.; Fert, A.

    2014-06-16

    We present measurements of inverse spin Hall effects (ISHEs), in which the conversion of a spin current into a charge current via the ISHE is detected not as a voltage in a standard open circuit but directly as the charge current generated in a closed loop. The method is applied to the ISHEs of Bi-doped Cu and Pt. The derived expression of ISHE for the loop structure can relate the charge current flowing into the loop to the spin Hall angle of the SHE material and the resistance of the loop.

  13. Foucault's Pendulum, Analog for an Electron Spin State

    NASA Astrophysics Data System (ADS)

    Linck, Rebecca

    2012-11-01

    The classical Lagrangian that describes the coupled oscillations of Foucault's pendulum presents an interesting analog to an electron's spin state in an external magnetic field. With a simple modification, this classical Lagrangian yields equations of motion that directly map onto the Schrodinger-Pauli Equation. This analog goes well beyond the geometric phase, reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

  14. Rotational bands terminating at maximal spin in the valence space

    SciTech Connect

    Ragnarsson, I.; Afanasjev, A.V.

    1996-12-31

    For nuclei with mass A {le} 120, the spin available in {open_quotes}normal deformation configurations{close_quotes} is experimentally accessible with present detector systems. Of special interest are the nuclei which show collective features at low or medium-high spin and where the corresponding rotational bands with increasing spin can be followed in a continuous way to or close to a non-collective terminating state. Some specific features in this context are discussed for nuclei in the A = 80 region and for {sup 117,118}Xe.

  15. Realizing dipolar spin models with arrays of superconducting qubits

    NASA Astrophysics Data System (ADS)

    Dalmonte, M.; Mirzaei, S. I.; Muppalla, P. R.; Marcos, D.; Zoller, P.; Kirchmair, G.

    2015-11-01

    We propose a platform for quantum many body simulations of dipolar spin models using current circuit QED technology. Our basic building blocks are 3D transmon qubits where we use the naturally occurring dipolar interactions to realize interacting spin systems. This opens the way toward the realization of a broad class of tunable spin models in both two- and one-dimensional geometries. We illustrate the potential offered by these systems in the context of dimerized Majumdar-Ghosh-type phases, archetypical examples of quantum magnetism, showing how such phases are robust against disorder and decoherence and could be observed within state-of-the-art experiments.

  16. Interfacial spin-filter assisted spin transfer torque effect in Co/BeO/Co magnetic tunnel junction

    SciTech Connect

    Tang, Y.-H. Chu, F.-C.

    2015-03-07

    The first-principles calculation is employed to demonstrate the spin-selective transport properties and the non-collinear spin-transfer torque (STT) effect in the newly proposed Co/BeO/Co magnetic tunnel junction. The subtle spin-polarized charge transfer solely at O/Co interface gives rise to the interfacial spin-filter (ISF) effect, which can be simulated within the tight binding model to verify the general expression of STT. This allows us to predict the asymmetric bias behavior of non-collinear STT directly via the interplay between the first-principles calculated spin current densities in collinear magnetic configurations. We believe that the ISF effect, introduced by the combination between wurtzite-BeO barrier and the fcc-Co electrode, may open a new and promising route in semiconductor-based spintronics applications.

  17. Macroscopic rotation of photon polarization induced by a single spin

    PubMed Central

    Arnold, Christophe; Demory, Justin; Loo, Vivien; Lemaître, Aristide; Sagnes, Isabelle; Glazov, Mikhaïl; Krebs, Olivier; Voisin, Paul; Senellart, Pascale; Lanco, Loïc

    2015-01-01

    Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10−3 degrees due to poor spin–photon coupling. Here we report the enhancement by three orders of magnitude of the spin–photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ±6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network. PMID:25687134

  18. Spin-orbit coupling and quantum spin Hall effect for neutral atoms without spin flips.

    PubMed

    Kennedy, Colin J; Siviloglou, Georgios A; Miyake, Hirokazu; Burton, William Cody; Ketterle, Wolfgang

    2013-11-27

    We propose a scheme which realizes spin-orbit coupling and the quantum spin Hall effect for neutral atoms in optical lattices without relying on near resonant laser light to couple different spin states. The spin-orbit coupling is created by modifying the motion of atoms in a spin-dependent way by laser recoil. The spin selectivity is provided by Zeeman shifts created with a magnetic field gradient. Alternatively, a quantum spin Hall Hamiltonian can be created by all-optical means using a period-tripling, spin-dependent superlattice. PMID:24329453

  19. Resonant Tunneling Spin Pump

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  20. Towards a Compositional SPIN

    NASA Technical Reports Server (NTRS)

    Pasareanu, Corina S.; Giannakopoulou, Dimitra

    2006-01-01

    This paper discusses our initial experience with introducing automated assume-guarantee verification based on learning in the SPIN tool. We believe that compositional verification techniques such as assume-guarantee reasoning could complement the state-reduction techniques that SPIN already supports, thus increasing the size of systems that SPIN can handle. We present a "light-weight" approach to evaluating the benefits of learning-based assume-guarantee reasoning in the context of SPIN: we turn our previous implementation of learning for the LTSA tool into a main program that externally invokes SPIN to provide the model checking-related answers. Despite its performance overheads (which mandate a future implementation within SPIN itself), this approach provides accurate information about the savings in memory. We have experimented with several versions of learning-based assume guarantee reasoning, including a novel heuristic introduced here for generating component assumptions when their environment is unavailable. We illustrate the benefits of learning-based assume-guarantee reasoning in SPIN through the example of a resource arbiter for a spacecraft. Keywords: assume-guarantee reasoning, model checking, learning.

  1. Spin forming development

    SciTech Connect

    Gates, W.G.

    1982-05-01

    Bendix product applications require the capability of fabricating heavy gage, high strength materials. Five commercial sources have been identified that have the capability of spin forming metal thicknesses greater than 9.5 mm and four equiment manufacturers produce machines with this capability. Twelve assemblies selected as candidates for spin forming applications require spin forming of titanium, 250 maraging steel, 17-4 pH stainless steel, Nitronic 40 steel, 304 L stainless steel, and 6061 aluminum. Twelve parts have been cold spin formed from a 250 maraging steel 8.1 mm wall thickness machine preform, and six have been hot spin formed directly from 31.8-mm-thick flat plate. Thirty-three Ti-6Al-4V titanium alloy parts and 26 17-4 pH stainless steel parts have been hot spin formed directly from 31.8-mm-thick plate. Hot spin forming directly from plate has demonstrated the feasibility and favorable economics of this fabrication technique for Bendix applications.

  2. Spin models and boson sampling

    NASA Astrophysics Data System (ADS)

    Garcia Ripoll, Juan Jose; Peropadre, Borja; Aspuru-Guzik, Alan

    Aaronson & Arkhipov showed that predicting the measurement statistics of random linear optics circuits (i.e. boson sampling) is a classically hard problem for highly non-classical input states. A typical boson-sampling circuit requires N single photon emitters and M photodetectors, and it is a natural idea to rely on few-level systems for both tasks. Indeed, we show that 2M two-level emitters at the input and output ports of a general M-port interferometer interact via an XY-model with collective dissipation and a large number of dark states that could be used for quantum information storage. More important is the fact that, when we neglect dissipation, the resulting long-range XY spin-spin interaction is equivalent to boson sampling under the same conditions that make boson sampling efficient. This allows efficient implementations of boson sampling using quantum simulators & quantum computers. We acknowledge support from Spanish Mineco Project FIS2012-33022, CAM Research Network QUITEMAD+ and EU FP7 FET-Open Project PROMISCE.

  3. Electron spin decoherence in nuclear spin baths and dynamical decoupling

    SciTech Connect

    Zhao, N.; Yang, W.; Ho, S. W.; Hu, J. L.; Wan, J. T. K.; Liu, R. B.

    2011-12-23

    We introduce the quantum theory of the electron spin decoherence in a nuclear spin bath and the dynamical decoupling approach for protecting the electron spin coherence. These theories are applied to various solid-state systems, such as radical spins in molecular crystals and NV centers in diamond.

  4. Quantum Spin Hall Effect

    SciTech Connect

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  5. Contrasting spin dynamics

    SciTech Connect

    Ning, F. L.; Ahilan, K.; Imai, T.; Sefat, A. S.; McGuire, Michael A; Sales, Brian C; Mandrus, David; Cheng, P.; Shen, B.; Wen, H.-H.

    2010-01-01

    We report the first NMR investigation of spin dynamics in the overdoped nonsuperconducting regime of Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} up to x=0.26. We demonstrate that the absence of interband transitions with large momentum transfer Q{sub AF}-({pi}/a,0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x {ge} 0.15. Our experimental results provide direct evidence for a correlation between T{sub c} and the strength of Q{sub AF} antiferromagnetic spin fluctuations.

  6. Spin of the proton

    SciTech Connect

    Nathan Isgur

    1996-12-01

    The author argues that their response to the spin crisis should not be to abandon the naive quark model baby, but rather to allow it to mature. In particular, he advocates dressing the baby in qq pairs, first showing that this can be done without compromising the naive quark model's success with either spectroscopy or the OZI rule. Finally, he shows that despite their near invisibility elsewhere, pairs do play an important role in the proton's spin structure by creating an antipolarized qq sea. In the context of an explicit calculation he demonstrates that it is plausible that the entire ''spin crisis'' arises from this effect.

  7. Higher spin cosmology

    NASA Astrophysics Data System (ADS)

    Krishnan, Chethan; Raju, Avinash; Roy, Shubho; Thakur, Somyadip

    2014-02-01

    We construct cosmological solutions of higher spin gravity in 2+1 dimensional de Sitter space. We show that a consistent thermodynamics can be obtained for their horizons by demanding appropriate holonomy conditions. This is equivalent to demanding the integrability of the Euclidean boundary conformal field theory partition function, and it reduces to Gibbons-Hawking thermodynamics in the spin-2 case. By using the prescription of Maldacena, we relate the thermodynamics of these solutions to those of higher spin black holes in AdS3.

  8. Spin gap in the single spin-1/2 chain cuprate Sr1.9Ca0.1CuO3

    NASA Astrophysics Data System (ADS)

    Hammerath, F.; Brüning, E. M.; Sanna, S.; Utz, Y.; Beesetty, N. S.; Saint-Martin, R.; Revcolevschi, A.; Hess, C.; Büchner, B.; Grafe, H.-J.

    2014-05-01

    We report Cu63 nuclear magnetic resonance and muon spin rotation measurements on the S =1/2 antiferromagnetic Heisenberg spin chain compound Sr1.9Ca0.1CuO3. An exponentially decreasing spin-lattice relaxation rate T1-1 indicates the opening of a spin gap. This behavior is very similar to what has been observed for the cognate zigzag spin chain compound Sr0.9Ca0.1CuO2, and it confirms that the occurrence of a spin gap upon Ca doping is independent of the interchain exchange coupling J'. Our results therefore suggest that the appearance of a spin gap in an antiferromagnetic Heisenberg spin chain is induced by a local bond disorder of the intrachain exchange coupling J. A low-temperature upturn of T1-1 evidences growing magnetic correlations. However, zero-field muon spin rotation measurements down to 1.5 K confirm the absence of magnetic order in this compound, which is most likely suppressed by the opening of the spin gap.

  9. Realization of an all-electric spin transistor using quantum point contacts

    NASA Astrophysics Data System (ADS)

    Chen, Tse-Ming; Chuang, Pojen; Ho, Sheng-Chin; Smith, Luke; Sfigakis, Francois; Pepper, Michael; Chen, Chin-Hung; Fan, Ju-Chun; Griffiths, Jonathan; Farrer, Ian; Beere, Harvey; Jones, Geb; Ritchie, Dave

    The spin field effect transistor envisioned by Datta and Das opens a gateway to spin information processing. Although the coherent manipulation of electron spins in semiconductors is now possible, the realization of a functional spin field effect transistor for information processing has yet to be achieved, owing to several fundamental challenges such as the low spin-injection efficiency due to resistance mismatch, spin relaxation, and the spread of spin precession angles. Alternative spin transistor designs have therefore been proposed, but these differ from the field effect transistor concept and require the use of optical or magnetic elements, which pose difficulties for the incorporation into integrated circuits. Here, we present an all-electric all-semiconductor spin field effect transistor, in which these obstacles are overcome by employing two quantum point contacts as spin injectors and detectors. Distinct engineering architectures of spin-orbit coupling are exploited for the quantum point contacts and the central semiconductor channel to achieve complete control of the electron spins--spin injection, manipulation, and detection--in a purely electrical manner. Such a device is compatible with large-scale integration and hold promise for future spintronic devices for information processing. Ref: P. Chuang et al., Nat. Nanotechnol. 10, 35 (2015).

  10. All-electric all-semiconductor spin field-effect transistors

    NASA Astrophysics Data System (ADS)

    Chuang, Pojen; Ho, Sheng-Chin; Smith, L. W.; Sfigakis, F.; Pepper, M.; Chen, Chin-Hung; Fan, Ju-Chun; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, Tse-Ming

    2015-01-01

    The spin field-effect transistor envisioned by Datta and Das opens a gateway to spin information processing. Although the coherent manipulation of electron spins in semiconductors is now possible, the realization of a functional spin field-effect transistor for information processing has yet to be achieved, owing to several fundamental challenges such as the low spin-injection efficiency due to resistance mismatch, spin relaxation and the spread of spin precession angles. Alternative spin transistor designs have therefore been proposed, but these differ from the field-effect transistor concept and require the use of optical or magnetic elements, which pose difficulties for incorporation into integrated circuits. Here, we present an all-electric and all-semiconductor spin field-effect transistor in which these obstacles are overcome by using two quantum point contacts as spin injectors and detectors. Distinct engineering architectures of spin-orbit coupling are exploited for the quantum point contacts and the central semiconductor channel to achieve complete control of the electron spins (spin injection, manipulation and detection) in a purely electrical manner. Such a device is compatible with large-scale integration and holds promise for future spintronic devices for information processing.

  11. Spin pumping and inverse spin Hall effects—Insights for future spin-orbitronics (invited)

    SciTech Connect

    Zhang, Wei Jungfleisch, Matthias B.; Jiang, Wanjun; Fradin, Frank Y.; Pearson, John E.; Hoffmann, Axel; Sklenar, Joseph; Ketterson, John B.

    2015-05-07

    Quantification of spin-charge interconversion has become increasingly important in the fast-developing field of spin-orbitronics. Pure spin current generated by spin pumping acts as a sensitive probe for many bulk and interface spin-orbit effects, which has been indispensable for the discovery of many promising new spin-orbit materials. We apply spin pumping and inverse spin Hall effect experiments, as a useful metrology, and study spin-orbit effects in a variety of metals and metal interfaces. We quantify the spin Hall effects in Ir and W using the conventional bilayer structures and discuss the self-induced voltage in a single layer of ferromagnetic permalloy. Finally, we extend our discussions to multilayer structures and quantitatively reveal the spin current flow in two consecutive normal metal layers.

  12. Electron spin decoherence in silicon carbide nuclear spin bath

    NASA Astrophysics Data System (ADS)

    Yang, Li-Ping

    In this paper, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of 29Si (4.7 counter-intuitive result, is the suppression of heteronuclear-spin flip-flop process in finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.

  13. Spin waves in a persistent spin-current Fermi liquid

    SciTech Connect

    Feldmann, J. D.; Bedell, K. S.

    2010-06-15

    We report two theoretical results for transverse spin waves, which arise in a system with a persistent spin current. Using Fermi liquid theory, we introduce a spin current in the ground state of a polarized or unpolarized Fermi liquid, and we derive the resultant spin waves using the Landau kinetic equation. The resulting spin waves have a q{sup 1} and q{sup 1/2} dispersion to leading order for the polarized and unpolarized systems, respectively.

  14. Spin Foam and Regge Calculus

    NASA Astrophysics Data System (ADS)

    Gionti, S. J. Gabriele

    2013-01-01

    Recent results in Local Regge Calculus are confronted with Spin Foam Formalism. Introducing Barrett-Crane Quantization in Local Regge Calculus makes it possible to associate a unique Spin jh with an hinge h, fulfilling one of the requirements of Spin Foam definition. It is shown that inter-twiner terms of Spin Foam can follow from the closure constraint in Local Regge Calculus.

  15. Quantum entanglement between diamond spin qubits separated by 3 meters

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald

    2013-03-01

    Entanglement of spatially separated objects is one of the most intriguing phenomena that can occur in physics. This can lead ``spooky action at a distance'' where measurement of one object instantaneously affects the state of the other object. Besides being of fundamental interest, entanglement is also a valuable resource in quantum information technology enabling secure quantum communication networks and distributed quantum computing. Here we present our most recent results towards the realization of scalable quantum networks with solid-state qubits. We have entangled two spin qubits in diamond, each associated with a nitrogen vacancy center in diamond. The two diamonds reside in separate setups three meters apart from each other. With no direct interaction between the two spins to mediate the entanglement, we make use of a scheme based on quantum measurements: we perform a joint measurement on photons emitted by the NV centers that are entangled with the electron spins. The detection of the photons projects the spins into an entangled state. We verify the generated entanglement by single-shot readout of the spin qubits in different bases and correlating the results. These results open the door to a range of exciting opportunities. For instance, the remote entanglement can be extended to nuclear spins near the NV center. Our recent experiments demonstrate robust methods for initializing, controlling and entangling nuclear spins by using the electron spin as an ancilla. Entanglement of remote quantum registers will enable deterministic quantum teleportation, distributed quantum computing tasks and the implementation of an elementary quantum repeater.

  16. Spin-Torque Ferromagnetic Resonance Spectroscopy of Permalloy Nanowires

    NASA Astrophysics Data System (ADS)

    Boone, Carl; Katine, Jordan; Childress, Jeff; Zhu, Jian; Cheng, Xiao; Krivorotov, Ilya

    2009-03-01

    We develop a technique for studies of spectral properties of spin waves excited by spin transfer torque in metallic ferromagnetic nanowires, and apply this technique to measure frequencies and damping constants of several low-energy quantized spin wave modes in permalloy nanowires of rectangular cross section. Our measurements demonstrate that the spin wave spectrum of nanowires as narrow as 100 nm is well described by an analytic theory of dipole-exchange spin waves in thin ferromagnetic strips. Geometric quantization of the spin wave spectrum in nanowires significantly reduces the phase space for magnon-magnon scattering leading to opening and closing of discrete scattering channels as a function of magnetic field. These scattering channels manifest themselves as peaks in plots of spin wave damping versus magnetic field. In particular, we observe damping enhancement of the lowest energy spin wave mode at the values of magnetic field corresponding to three-magnon confluence processes in which two lowest energy magnons merge into a single higher-energy mode magnon.

  17. Strong mechanical driving of a single electron spin

    NASA Astrophysics Data System (ADS)

    Barfuss, A.; Teissier, J.; Neu, E.; Nunnenkamp, A.; Maletinsky, P.

    2015-10-01

    Quantum devices for sensing and computing applications require coherent quantum systems, which can be manipulated in fast and robust ways. Such quantum control is typically achieved using external electromagnetic fields, which drive the system’s orbital, charge or spin degrees of freedom. However, most existing approaches require complex and unwieldy gate structures, and with few exceptions are limited to the regime of weak coherent driving. Here, we present a novel approach to coherently drive a single electronic spin using internal strain fields in an integrated quantum device. Specifically, we employ time-varying strain in a diamond cantilever to induce long-lasting, coherent oscillations of an embedded nitrogen-vacancy (NV) centre spin. We perform direct spectroscopy of the phonon-dressed states emerging from this drive and observe hallmarks of the sought-after strong-driving regime, where the spin rotation frequency exceeds the spin splitting. Furthermore, we employ our continuous strain driving to significantly enhance the NV’s spin coherence time. Our room-temperature experiments thereby constitute an important step towards strain-driven, integrated quantum devices and open new perspectives to investigate unexplored regimes of strongly driven multilevel systems and exotic spin dynamics in hybrid spin-oscillator devices.

  18. MMS Spin Test

    NASA Video Gallery

    The four Magnetospheric Multiscale observatories all undergo what's called a spin test, to learn how well the spacecraft are balanced. It also provides information on how well the mass properties o...

  19. Pluto's Spinning Moons

    NASA Video Gallery

    Most inner moons in the solar system keep one face pointed toward their central planet; this animation shows that certainly isn’t the case with the small moons of Pluto, which behave like spinning ...

  20. ^3He Spin Pump

    NASA Astrophysics Data System (ADS)

    Yamaguchi, A.; Ishimoto, H.; Kojima, H.

    2009-03-01

    The superfluid component of ^3He A1 phase is spin-polarized. The process of forcing the superfluid component through a spin filtering structure, in a manner of mechano-magnetic effect, can be used to increase the spin polarization beyond the equilibrium under a given applied magnetic field. We have constructed a test cell in which a glass capillary array acts as the spin (and entropy) filter and an electrostatically actuated diaphragm forces the superfluid flow through it. Preliminary results show that a maximum relative increase of polarization by 50 % could be achieved. The maximum increase in polarization appears to be limited by the critical superfluid flow through the channels in the glass capillary array. The dependence of the observed effects on temperature, pressure and magnetic field will be presented.

  1. The spin deep within

    SciTech Connect

    Stackhouse, S.

    2008-10-08

    The electronic configuration of iron impurities in lower-mantle minerals influences their physical properties, but it is not well constrained. New studies suggest that ferrous iron in silicate phases exists mainly in an intermediate spin state.

  2. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    SciTech Connect

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-05-07

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  3. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    NASA Astrophysics Data System (ADS)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-05-01

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  4. Energy efficient hybrid computing systems using spin devices

    NASA Astrophysics Data System (ADS)

    Sharad, Mrigank

    Emerging spin-devices like magnetic tunnel junctions (MTJ's), spin-valves and domain wall magnets (DWM) have opened new avenues for spin-based logic design. This work explored potential computing applications which can exploit such devices for higher energy-efficiency and performance. The proposed applications involve hybrid design schemes, where charge-based devices supplement the spin-devices, to gain large benefits at the system level. As an example, lateral spin valves (LSV) involve switching of nanomagnets using spin-polarized current injection through a metallic channel such as Cu. Such spin-torque based devices possess several interesting properties that can be exploited for ultra-low power computation. Analog characteristic of spin current facilitate non-Boolean computation like majority evaluation that can be used to model a neuron. The magneto-metallic neurons can operate at ultra-low terminal voltage of ˜20mV, thereby resulting in small computation power. Moreover, since nano-magnets inherently act as memory elements, these devices can facilitate integration of logic and memory in interesting ways. The spin based neurons can be integrated with CMOS and other emerging devices leading to different classes of neuromorphic/non-Von-Neumann architectures. The spin-based designs involve `mixed-mode' processing and hence can provide very compact and ultra-low energy solutions for complex computation blocks, both digital as well as analog. Such low-power, hybrid designs can be suitable for various data processing applications like cognitive computing, associative memory, and currentmode on-chip global interconnects. Simulation results for these applications based on device-circuit co-simulation framework predict more than ˜100x improvement in computation energy as compared to state of the art CMOS design, for optimal spin-device parameters.

  5. Interaction between spin-wave excitations and pure spin currents in magnetic structures

    NASA Astrophysics Data System (ADS)

    Azevedo, Antonio

    2012-02-01

    The generation of pure spin current (PSC) in magnetic structures has attracted much attention not only for its fundamental importance in spintronics, but also because it opens up potential applications. One of the most exciting aspects of this area is the interplay between spin-waves (SW) and PSC. Here we report experimental results in which the PSC, generated by both spin pumping (SPE) [1] and spin Seebeck (SSE) [2] effects, can exert a spin-transfer torque sufficient to compensate the SW relaxation in yttrium iron garnet (YIG)/non-magnetic structures. By measuring the propagation of SW packets in single-crystal YIG films we were able to observe the amplification of volume and magnetostatic modes (MSW) by both SSE and SHE [3,4]. The excitation and detection of the SW packets is carried out by using a MSW delay line device. In both cases the amplification is attributed to the spin-transfer torque due to PSC generated by SSE as well as SHE. It will also be presented new results in which PSC are simultaneously excited by SSE and SPE effects in YIG films. While the spin current generated by SPE is obtained by exciting the ferromagnetic resonance (FMR) of the YIG film, the spin current due to SSE is created by applying a temperature gradient along the film plane. The effect of the superposition of both spin currents is characterized by measuring the spin Hall voltage (VH) along thin strips of Pt deposited on top of the YIG films. Whereas VH corresponding to the uniform FMR is amplified due the SSE the voltages corresponding to the other magnetostatic spin-wave modes are attenuated [5]. [4pt] [1] Y. Tserkovnyak, et al., Rev. Mod. Phys. 77, 1375 (2005).[0pt] [2] K. Uchida, et al., Nature 455, 778 (2008).[0pt] [3] E. Padr'on-Hern'andez, A. Azevedo, and S. M. Rezende, Phys. Rev. Letts., 107, 197203 (2011).[0pt] [4] E. Padr'on-Hern'andez, A. Azevedo, and S. M. Rezende, Appl. Phys. Letts., 99 (2011) in press.[0pt] [5] G.L. da Silva, L.H. Vilela-Leão, S. M. Rezende and A

  6. Spin in Hadron Reactions

    SciTech Connect

    Aidala, Christine A.

    2009-08-04

    The Relativistic Heavy Ion Collider (RHIC) has brought the study of spin effects in hadronic collisions to a new energy regime. In conjunction with other experiments at facilities around the world, much can be learned from the high-energy polarized proton collisions RHIC provides, allowing the collider to serve as a powerful tool to continue to understand the rich subtleties and surprises of spin effects in QCD, some of which were originally discovered more than three decades ago.

  7. Litter-Spinning Retarders

    NASA Technical Reports Server (NTRS)

    Wilson, John C.

    1995-01-01

    Aerodynamic plates stop litter from spinning during hoisting by helicopter. Features of proposed litter-spinning retarders include convenience of deployment and independence from ground restraint. Retarder plate(s) folded flat against bottom of litter during storage or while litter is loaded. Plate(s) held in storage position by latch that releases manually or automatically as litter is hoisted. Upon release, springs move plates into deployed position.

  8. Test of Einstein equivalence principle for 0-spin and half-integer-spin atoms: search for spin-gravity coupling effects.

    PubMed

    Tarallo, M G; Mazzoni, T; Poli, N; Sutyrin, D V; Zhang, X; Tino, G M

    2014-07-11

    We report on a conceptually new test of the equivalence principle performed by measuring the acceleration in Earth's gravity field of two isotopes of strontium atoms, namely, the bosonic (88)Sr isotope which has no spin versus the fermionic (87)Sr isotope which has a half-integer spin. The effect of gravity on the two atomic species has been probed by means of a precision differential measurement of the Bloch frequency for the two atomic matter waves in a vertical optical lattice. We obtain the values η=(0.2±1.6)×10(-7) for the Eötvös parameter and k=(0.5±1.1)×10(-7) for the coupling between nuclear spin and gravity. This is the first reported experimental test of the equivalence principle for bosonic and fermionic particles and opens a new way to the search for the predicted spin-gravity coupling effects. PMID:25062176

  9. Higher-spin theory and holography

    NASA Astrophysics Data System (ADS)

    Gaberdiel, Matthias; Vasiliev, Mikhail

    2013-05-01

    , this has triggered a significant amount of activity in this general area. Among other things, the constraints that are implied by the higher-spin symmetries were analysed (see the paper by Maldacena and Zhiboedov in this issue [9]), and a fairly concrete proposal for how higher-spin theories are related to string theory was made (see the paper by Chang, Minwalla, Sharma and Yin in this issue [10]). Furthermore, a lower dimensional version of the conjecture was put forward by Gaberdiel and Gopakumar [11] that was subsequently also checked in some detail. These dualities hold the promise of offering insights into the inner workings of the AdS/CFT correspondence since they are complex enough to capture the essence of the duality, while at the same time being sufficiently simple in order to allow for a detailed analysis. Moreover, the methods specifically developed in higher-spin theory may be useful for understanding a general mechanism underlying holography, both in higher-spin models and beyond (see the paper by Vasiliev in this issue [12]). Another fascinating aspect of these higher-spin theories lies in the fact that the higher-spin symmetries mix generically fields of different spin, and in particular, the spin-2 metric and higher-spin excitations are related to one another by gauge transformations. As a result, higher-spin theories require a modification of the standard framework of Riemannian geometry since the usual diffeomorphism-invariant tensors are not gauge invariant any longer. In particular, higher-spin theories may therefore open the way towards understanding fundamental concepts of space-time geometry; for example, they may well have key lessons in store for how string theory resolves space-time singularities. In this issue we have collected together a number of review papers, summarizing the aforementioned recent developments, as well as research papers indicating current directions of interest in the study of higher-spin gauge theories. We hope that it

  10. The spin Hall effect and spin-orbit torques in SH-metal/normal metal/ferromagnetic trilayers

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh-Hai; Pai, Chi-Feng; Ralph, Daniel C.; Buhrman, Robert A.

    2014-03-01

    The spin Hall effect (SHE) in ferromagnet/transition metal bilayer structures has been demonstrated to be a powerful means for producing pure spin currents and for exerting spin-orbit damping-like and field-like torques on the ferromagnetic layer. Large spin Hall angles have been reported for Pt, β-Ta and β-W films and have been utilized to achieve magnetic switching of in-plane and out-of-plane magnetized nanomagnets, spin torque auto-oscillators, and the control of high velocity domain wall motion. In general the spin orbit torques and the effective damping are predicted to depend directly on the spin-mixing conductance of the SHE/ferromagnet interface. This opens up the possibility of tuning these properties with the insertion of a very thin layer of another metal between the SH metal and the ferromagnet. Here we will report on experiments with such trilayer structures where we have studied the variation of the effective spin Hall angle and the effective damping constant with the choice and thickness of the insertion layer. Our results indicate that there is considerable opportunity to optimize the effectiveness and energy efficiency of the damping-like torque through engineering of such trilayer structures.

  11. Spin Transfer from an Optically Pumped Alkali Vapor to a Solid

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2007-05-01

    We report enhancement of the spin polarization of Cs133 nuclei in CsH salt by spin transfer from an optically pumped cesium vapor. The nuclear polarization was 4.0 times the equilibrium polarization at 9.4 T and 137°C, with larger enhancements at lower fields. This work is the first demonstration of spin transfer from a polarized alkali vapor to the nuclei of a solid, opening up new possibilities for research in hyperpolarized materials.

  12. Spin Transfer from an Optically Pumped Alkali Vapor to a Solid

    SciTech Connect

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2007-05-04

    We report enhancement of the spin polarization of {sup 133}Cs nuclei in CsH salt by spin transfer from an optically pumped cesium vapor. The nuclear polarization was 4.0 times the equilibrium polarization at 9.4 T and 137 deg. C, with larger enhancements at lower fields. This work is the first demonstration of spin transfer from a polarized alkali vapor to the nuclei of a solid, opening up new possibilities for research in hyperpolarized materials.

  13. Designing electron spin textures and spin interferometers by shape deformations

    NASA Astrophysics Data System (ADS)

    Ying, Zu-Jian; Gentile, Paola; Ortix, Carmine; Cuoco, Mario

    2016-08-01

    We demonstrate that the spin orientation of an electron propagating in a one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be manipulated on demand by changing the geometry of the nanosystem. Shape deformations that result in a nonuniform curvature give rise to complex three-dimensional spin textures in space. We employ the paradigmatic example of an elliptically deformed quantum ring to unveil the way to get an all-geometrical and all-electrical control of the spin orientation. The resulting spin textures exhibit a tunable topological character with windings around the radial and the out-of-plane directions. We show that these topologically nontrivial spin patterns affect the spin interference effect in the deformed ring, thereby resulting in different geometry-driven ballistic electronic transport behaviors. Our results establish a deep connection between electronic spin textures, spin transport, and the nanoscale shape of the system.

  14. Spin-current emission governed by nonlinear spin dynamics

    PubMed Central

    Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

    2015-01-01

    Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators. PMID:26472712

  15. Spin-current emission governed by nonlinear spin dynamics.

    PubMed

    Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

    2015-01-01

    Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators. PMID:26472712

  16. Association of Toll-like receptor 2 Arg753Gln and Toll-like receptor 1 Ile602Ser single-nucleotide polymorphisms with leptospirosis in an Argentine population.

    PubMed

    Cédola, Maia; Chiani, Yosena; Pretre, Gabriela; Alberdi, Lucrecia; Vanasco, Bibiana; Gómez, Ricardo M

    2015-06-01

    Toll-like receptor 2 (TLR2), a member of the Toll-like receptor family, plays an important role in the recognition of and subsequent immune response activation against leptospirosis in humans. The genetic polymorphism in TLR2 of an arginine to glutamine substitution at residue 753 (Arg753Gln) has been associated with a negative influence on TLR2 function, which may, in turn, determine the innate host response to Leptospira spp. This bacterium signals through TLR2/TLR1 heterodimers in human cells. The aim of the present study was to investigate the Arg753Gln single-nucleotide polymorphism (SNP) of the TLR2 gene, and the isoleucine to serine transversion at position 602 (Ile602Ser) of the TLR1 gene (previously associated with Lyme disease), in leptospirosis patients compared to healthy controls, carrying out a retrospective case/control study. The TLR2 polymorphism adenine (A) allele was observed in 7.3% of leptospirosis patients but was not found in the control group, whereas the guanine (G) allele of the TLR1 polymorphism was found in 63.6% of patients and 41.6% of controls. Susceptibility to leptospirosis disease was increased 10.57-fold for carriers of the TLR2 G/A genotype (P=0.0493) and 3.85-fold for carriers of the TLR1 G/G genotype (P=0.0428). Furthermore, the risk of developing hepatic insufficiency and jaundice was increased 18.86- and 27.60-fold for TLR2 G/A carriers, respectively. Similarly, the risk of developing jaundice was increased 12.67-fold for TLR1 G allele carriers (G/G and T/G genotypes). In conclusion, the present data suggest that the TLR2 Arg753Gln and TLR1 Ile602Ser SNPs influence the risk of developing leptospirosis and its severity. PMID:25784560

  17. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling

    PubMed Central

    Caetano, R. A.

    2016-01-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices. PMID:27009836

  18. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Caetano, R. A.

    2016-03-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices.

  19. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling.

    PubMed

    Caetano, R A

    2016-01-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices. PMID:27009836

  20. Development of a spinning wave heat engine

    NASA Technical Reports Server (NTRS)

    Zinn, B. T.; Powell, E. A.; Hubbartt, J. E.

    1982-01-01

    A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.

  1. The determination of the in situ structure by nuclear spin contrast variation

    SciTech Connect

    Stuhrmann, H.B.; Nierhaus, K.H.

    1994-12-31

    Polarized neutron scattering from polarized nuclear spins in hydrogenous substances opens a new way of contrast variation. The enhanced contrast due to proton spin polarization was used for the in situ structure determination of tRNA of the functional complex of the E.coli ribosome.

  2. Cavity QED Based on Collective Magnetic Dipole Coupling: Spin Ensembles as Hybrid Two-Level Systems

    NASA Astrophysics Data System (ADS)

    Imamoǧlu, Atac

    2009-02-01

    We analyze the magnetic dipole coupling of an ensemble of spins to a superconducting microwave stripline structure, incorporating a Josephson junction based transmon qubit. We show that this system is described by an embedded Jaynes-Cummings model: in the strong coupling regime, collective spin-wave excitations of the ensemble of spins pick up the nonlinearity of the cavity mode, such that the two lowest eigenstates of the coupled spin wave-microwave cavity-Josephson junction system define a hybrid two-level system. The proposal described here enables new avenues for nonlinear optics using optical photons coupled to spin ensembles via Raman transitions. The possibility of strong coupling cavity QED with magnetic dipole transitions also opens up the possibility of extending quantum information processing protocols to spins in silicon or graphene, without the need for single-spin confinement.

  3. Quantum spin dynamics with pairwise-tunable, long-range interactions.

    PubMed

    Hung, C-L; González-Tudela, Alejandro; Cirac, J Ignacio; Kimble, H J

    2016-08-23

    We present a platform for the simulation of quantum magnetism with full control of interactions between pairs of spins at arbitrary distances in 1D and 2D lattices. In our scheme, two internal atomic states represent a pseudospin for atoms trapped within a photonic crystal waveguide (PCW). With the atomic transition frequency aligned inside a band gap of the PCW, virtual photons mediate coherent spin-spin interactions between lattice sites. To obtain full control of interaction coefficients at arbitrary atom-atom separations, ground-state energy shifts are introduced as a function of distance across the PCW. In conjunction with auxiliary pump fields, spin-exchange versus atom-atom separation can be engineered with arbitrary magnitude and phase, and arranged to introduce nontrivial Berry phases in the spin lattice, thus opening new avenues for realizing topological spin models. We illustrate the broad applicability of our scheme by explicit construction for several well-known spin models. PMID:27496329

  4. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon

    PubMed Central

    Averyanov, Dmitry V.; Karateeva, Christina G.; Karateev, Igor A.; Tokmachev, Andrey M.; Vasiliev, Alexander L.; Zolotarev, Sergey I.; Likhachev, Igor A.; Storchak, Vyacheslav G.

    2016-01-01

    Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics. PMID:26957146

  5. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon

    NASA Astrophysics Data System (ADS)

    Averyanov, Dmitry V.; Karateeva, Christina G.; Karateev, Igor A.; Tokmachev, Andrey M.; Vasiliev, Alexander L.; Zolotarev, Sergey I.; Likhachev, Igor A.; Storchak, Vyacheslav G.

    2016-03-01

    Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics.

  6. Direct observation of finite size effects in chains of antiferromagnetically coupled spins.

    PubMed

    Guidi, T; Gillon, B; Mason, S A; Garlatti, E; Carretta, S; Santini, P; Stunault, A; Caciuffo, R; van Slageren, J; Klemke, B; Cousson, A; Timco, G A; Winpenny, R E P

    2015-01-01

    Finite spin chains made of few magnetic ions are the ultimate-size structures that can be engineered to perform spin manipulations for quantum information devices. Their spin structure is expected to show finite size effects and its knowledge is of great importance both for fundamental physics and applications. Until now a direct and quantitative measurement of the spatial distribution of the magnetization of such small structures has not been achieved even with the most advanced microscopic techniques. Here we present measurements of the spin density distribution of a finite chain of eight spin-3/2 ions using polarized neutron diffraction. The data reveal edge effects that are a consequence of the finite size and of the parity of the chain and indicate a noncollinear spin arrangement. This is in contrast with the uniform spin distribution observed in the parent closed chain and the collinear arrangement in odd-open chains. PMID:25952539

  7. Ultrafast spin-polarization control of Dirac fermions in topological insulators

    NASA Astrophysics Data System (ADS)

    Sánchez-Barriga, J.; Golias, E.; Varykhalov, A.; Braun, J.; Yashina, L. V.; Schumann, R.; Minár, J.; Ebert, H.; Kornilov, O.; Rader, O.

    2016-04-01

    Three-dimensional topological insulators (TIs) are characterized by spin-polarized Dirac-cone surface states that are protected from backscattering by time-reversal symmetry. Control of the spin polarization of topological surface states (TSSs) using femtosecond light pulses opens novel perspectives for the generation and manipulation of dissipationless surface spin currents on ultrafast time scales. Using time-, spin-, and angle-resolved spectroscopy, we directly monitor the ultrafast response of the spin polarization of photoexcited TSSs to circularly polarized femtosecond pulses of infrared light. We achieve all-optical switching of the transient out-of-plane spin polarization, which relaxes in about 1.2 ps. Our observations establish the feasibility of ultrafast optical control of spin-polarized Dirac fermions in TIs and pave the way for optospintronic applications at ultimate speeds.

  8. Exchange and electric fields enhanced spin thermoelectric performance of germanene nano-ribbon.

    PubMed

    Zheng, Jun; Chi, Feng; Guo, Yong

    2015-07-29

    The spin thermoelectric performance in a germanene nano-ribbon is studied by using the nonequilibrium Green's function method. We demonstrate theoretically that the temperature bias [Formula: see text] can generate spin thermopower when an exchange field breaks the edge states of germanene leads. However, the spin thermoelectric efficiency is quite low with its maximum [Formula: see text]. When applying strong electric field in the central region, a relatively large spin-dependent band gap can be opened, and hence the spin figure of merit is predicted to be more than 100 times larger than the case without external field. The remarkably enhancement of [Formula: see text] (larger than one) comes from the suppression of the thermal conductance and the improvement of the spin Seebeck effect. These striking properties make ferromagnetic leads germanene nano-ribbon a promising pure spin thermoelectric nanogenerator. PMID:26139695

  9. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon.

    PubMed

    Averyanov, Dmitry V; Karateeva, Christina G; Karateev, Igor A; Tokmachev, Andrey M; Vasiliev, Alexander L; Zolotarev, Sergey I; Likhachev, Igor A; Storchak, Vyacheslav G

    2016-01-01

    Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics. PMID:26957146

  10. 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.

  11. Amplification of Spin Waves by Thermal Spin-Transfer Torque

    NASA Astrophysics Data System (ADS)

    Padrón-Hernández, E.; Azevedo, A.; Rezende, S. M.

    2011-11-01

    We observe amplification of spin-wave packets propagating along a film of single-crystal yttrium iron garnet subject to a transverse temperature gradient. The spin waves are excited and detected with standard techniques used in magnetostatic microwave delay lines in the 1-2 GHz frequency range. The amplification is attributed to the action of a thermal spin-transfer torque acting on the magnetization that opposes the relaxation and which is created by spin currents generated through the spin-Seebeck effect. The experimental data are interpreted with a spin-wave model that gives an amplification gain in very good agreement with the data.

  12. Spin correlation and Majorana spectrum in chiral spin liquids in a decorated-honeycomb Kitaev model

    NASA Astrophysics Data System (ADS)

    Nasu, Joji; Motome, Yukitoshi

    2016-02-01

    Temperature evolution of the spin correlation and excitation spectrum is investigated for the Kitaev model defined on a decorated honeycomb lattice by using the quantum Monte Carlo simulation in the Majorana fermion representation. The ground state of this quantum spin model is given by two kinds of chiral spin liquids: one is topologically trivial with Abelian anyon excitations, and the other is topologically nontrivial with non-Abelian anyon excitations. While lowering temperature, the model exhibits several crossovers in the paramagnetic state, which originate from the fractionalization of quantum spins into Majorana fermions, in addition to a phase transition associated with time reversal symmetry breaking. We show that the spin correlation develops around the crossover temperatures, whereas it shows a slight change at the critical temperature, as in other Kitaev-type models. We also calculate the excitation spectrum in terms of Majorana fermions, and find that the excitation gap in the non-Abelian phase is fragile against thermal fluctuations of the Z2 fluxes, while that in the Abelian phase remains open.

  13. Spin pumping by magnetopolaritons

    NASA Astrophysics Data System (ADS)

    Cao, Yunshan; Yan, Peng; Huebl, Hans; Goennenwein, Sebastian; Bauer, Gerrit

    2015-03-01

    Recent experiments report the strong coupling of microwaves to the magnetic insulator yttrium iron garnet with weakly damped magnetization dynamics. We developed a scattering approach to study the coupled magnetization and microwave cavities beyond the paramagnetic/macrospin and rotating wave approximations that are implicit in the Tavis-Cummings model. To this end we solve the coupled Landau-Lifshitz-Gilbert and Maxwell's equations for a thin film magnet in a microwave cavity, leading to rich ferromagnetic spin wave resonance spectra of the transmitted or absorbed microwaves. Our method is valid for the full parameter range spanning the weak to strong coupling limits. We demonstrate strong coupling achievement not only for the FMR mode but also for standing spin waves, although the lowest excitation has a decisive leading role for coupling strength. Spin pumping in FI|N bilayers as detected by inverse spin Hall voltages provides additional access to study strong coupling electrically. Funding from the European Union Seventh Framework Programme [FP7-People-2012-ITN] under Grant Agreement 316657 (SpinIcur).

  14. Overview of spin physics

    SciTech Connect

    Yokosawa, A.

    1992-12-23

    Spin physics activities at medium and high energies became significantly active when polarized targets and polarized beams became accessible for hadron-hadron scattering experiments. My overview of spin physics will be inclined to the study of strong interaction using facilities at Argonne ZGS, Brookhaven AGS (including RHIC), CERN, Fermilab, LAMPF, an SATURNE. In 1960 accelerator physicists had already been convinced that the ZGS could be unique in accelerating a polarized beam; polarized beams were being accelerated through linear accelerators elsewhere at that time. However, there was much concern about going ahead with the construction of a polarized beam because (i) the source intensity was not high enough to accelerate in the accelerator, (ii) the use of the accelerator would be limited to only polarized-beam physics, that is, proton-proton interaction, and (iii) p-p elastic scattering was not the most popular topic in high-energy physics. In fact, within spin physics, [pi]-nucleon physics looked attractive, since the determination of spin and parity of possible [pi]p resonances attracted much attention. To proceed we needed more data beside total cross sections and elastic differential cross sections; measurements of polarization and other parameters were urgently needed. Polarization measurements had traditionally been performed by analyzing the spin of recoil protons. The drawbacks of this technique are: (i) it involves double scattering, resulting in poor accuracy of the data, and (ii) a carbon analyzer can only be used for a limited region of energy.

  15. Harnessing spin precession with dissipation

    NASA Astrophysics Data System (ADS)

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors.

  16. Harnessing spin precession with dissipation

    PubMed Central

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors. PMID:26816050

  17. Second derivatives for approximate spin projection methods

    SciTech Connect

    Thompson, Lee M.; Hratchian, Hrant P.

    2015-02-07

    The use of broken-symmetry electronic structure methods is required in order to obtain correct behavior of electronically strained open-shell systems, such as transition states, biradicals, and transition metals. This approach often has issues with spin contamination, which can lead to significant errors in predicted energies, geometries, and properties. Approximate projection schemes are able to correct for spin contamination and can often yield improved results. To fully make use of these methods and to carry out exploration of the potential energy surface, it is desirable to develop an efficient second energy derivative theory. In this paper, we formulate the analytical second derivatives for the Yamaguchi approximate projection scheme, building on recent work that has yielded an efficient implementation of the analytical first derivatives.

  18. Quasiequilibria in open quantum systems

    SciTech Connect

    Walls, Jamie D.

    2010-03-15

    In this work, the steady-state or quasiequilibrium resulting from periodically modulating the Liouvillian of an open quantum system, L-circumflex-circumflex(t), is investigated. It is shown that differences between the quasiequilibrium and the instantaneous equilibrium occur due to nonadiabatic contributions from the gauge field connecting the instantaneous eigenstates of L-circumflex-circumflex(t) to a fixed basis. These nonadiabatic contributions are shown to result in an additional rotation and/or depolarization for a single spin-1/2 in a time-dependent magnetic field and to affect the thermal mixing of two coupled spins interacting with a time-dependent magnetic field.

  19. Spin-transfer torque on a single magnetic adatom

    NASA Astrophysics Data System (ADS)

    Delgado, Fernando; José Palacios, Juan; Fernández-Rossier, Joaquín

    2010-03-01

    We theoretically show how the spin orientation of a single magnetic adatom can be controlled by spin polarized electrons in a scanning tunnelling microscope configuration. The underlying physical mechanism is spin assisted inelastic tunnelling. Experiments with Mn adatoms deposited on a Cu2N surface have been reported for non-polarized currents [1-2]. We show that by changing the direction of the applied current, the orientation of the magnetic adatom can be completely reversed on a time scale that ranges from a few nanoseconds to microseconds, depending on bias and temperature. The changes in the adatom magnetization direction are, in turn, reflected in the tunnelling conductance. Therefore, this effect opens the possibility of writing/reading a single spin without the need of a local magnetic field.[4pt] [1] C.F. Hirjibehedin, C. P. Lutz, A. J. Heinrich, Science 312, 1021 (2006).[0pt] [2] C. Hirjibehedin et al., Science 317, 1199 (2007).

  20. Atom-diatom scattering dynamics of spinning molecules

    SciTech Connect

    Eyles, C. J.; Floß, J.; Averbukh, I. Sh.; Leibscher, M.

    2015-01-14

    We present full quantum mechanical scattering calculations using spinning molecules as target states for nuclear spin selective atom-diatom scattering of reactive D+H{sub 2} and F+H{sub 2} collisions. Molecules can be forced to rotate uni-directionally by chiral trains of short, non-resonant laser pulses, with different nuclear spin isomers rotating in opposite directions. The calculations we present are based on rotational wavepackets that can be created in this manner. As our simulations show, target molecules with opposite sense of rotation are predominantly scattered in opposite directions, opening routes for spatially and quantum state selective scattering of close chemical species. Moreover, two-dimensional state resolved differential cross sections reveal detailed information about the scattering mechanisms, which can be explained to a large degree by a classical vector model for scattering with spinning molecules.

  1. Robust spin squeezing preservation in photonic crystal cavities

    NASA Astrophysics Data System (ADS)

    Zhong, Wo-Jun; Li, Yan-Ling; Xiao, Xing; Xie, Ying-Mao

    2016-08-01

    We show that the robust spin squeezing preservation can be achieved by utilizing detuning modification for an ensemble of N separate two-level atoms embedded in photonic crystal cavities (PCC). In particular, we explore the different dynamical behaviors of spin squeezing between isotropic and anisotropic PCC cases when the atomic frequency is inside the band gap. In both cases, it is shown that the robust preservation of spin squeezing is completely determined by the formation of bound states. Intriguingly, we find that unlike the isotropic case where steady-state spin squeezing varies smoothly when the atomic frequency moves from the inside to the outside band edge, a sudden transition occurs for the anisotropic case. The present results may be of direct importance for, e.g. quantum metrology in open quantum systems.

  2. Atom-diatom scattering dynamics of spinning molecules.

    PubMed

    Eyles, C J; Floss, J; Averbukh, I Sh; Leibscher, M

    2015-01-14

    We present full quantum mechanical scattering calculations using spinning molecules as target states for nuclear spin selective atom-diatom scattering of reactive D+H2 and F+H2 collisions. Molecules can be forced to rotate uni-directionally by chiral trains of short, non-resonant laser pulses, with different nuclear spin isomers rotating in opposite directions. The calculations we present are based on rotational wavepackets that can be created in this manner. As our simulations show, target molecules with opposite sense of rotation are predominantly scattered in opposite directions, opening routes for spatially and quantum state selective scattering of close chemical species. Moreover, two-dimensional state resolved differential cross sections reveal detailed information about the scattering mechanisms, which can be explained to a large degree by a classical vector model for scattering with spinning molecules. PMID:25591357

  3. Spin-valve phototransistor

    NASA Astrophysics Data System (ADS)

    Huang, Biqin; Altfeder, Igor; Appelbaum, Ian

    2007-01-01

    The spin-valve phototransistor is a semiconductor-ferromagnetic metal multilayer-semiconductor transistor operated by photoexciting hot electrons in the emitter semiconductor into a Schottky collector. This device uses an ultra-high vacuum-bonded float zone Si/multilayer/n-InP structure. To distinguish the emitter interband-excited component of collector current from base/collector internal photoemission, a lock-in spectroscopy sensitive only to the magnetocurrent is used. The experimental results indicate a pathway to improve the magnetocurrent of a related device, the spin-valve photodiode, by increasing the fraction of hot electron current that travels through both layers of the ferromagnetic spin valve and demonstrate that hot electrons photogenerated in one semiconductor can be collected by another through a thin ferromagnetic multilayer.

  4. Doped Artificial Spin Ice

    NASA Astrophysics Data System (ADS)

    Olson Reichhardt, Cynthia; Libal, Andras; Reichhardt, Charles

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal and vortex artificial spin ice realizations allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloids is suppressed near the doping sites. These results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.

  5. Mechanical spin bearings

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1998-01-01

    A spin bearing assembly including, a pair of mutually opposing complementary bearing support members having mutually spaced apart bearing support surfaces which may be, for example, bearing races and a set of spin bearings located therebetween. Each spin bearing includes a pair of end faces, a central rotational axis passing through the end faces, a waist region substantially mid-way between the end faces and having a first thickness dimension, and discrete side surface regions located between the waist region and the end faces and having a second thickness dimension different from the first thickness dimension of the waist region and wherein the side surface regions further have respective curvilinear contact surfaces adapted to provide a plurality of bearing contact points on the bearing support members.

  6. Spinning fluids reactor

    DOEpatents

    Miller, Jan D; Hupka, Jan; Aranowski, Robert

    2012-11-20

    A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.

  7. Fermi spin current contribution in spin wave spectrum of spin-1/2 fermions

    NASA Astrophysics Data System (ADS)

    Andreev, Pavel; Kuzmenkov, Leonid

    2016-05-01

    General theory predicts the presence of the thermal part of the spin current in the spin evolution equation for bosons and fermions. For bosons in Bose-Einstein condensate state, it is equal to zero. However, for degenerate fermions it is non zero and it can give a considerable contribution since it describes the Pauli blocking. In this work, we consider spin-1/2 partially polarized fermions. We derive an equation of state for the thermal part of the spin current of degenerate fermions and call it Fermi spin current. We present the spin evolution equation with the Fermi spin current as a part of applied hydrodynamic model. We consider spectrum of collective excitation and describe contribution of the Fermi spin current in the spin wave spectrum. The work of P.A. was supported by the Russian Foundation for Basic Research (Grant No. 16-32-00886) and the Dynasty foundation.

  8. Spin filter and spin valve in ferromagnetic graphene

    SciTech Connect

    Song, Yu Dai, Gang

    2015-06-01

    We propose and demonstrate that a EuO-induced and top-gated graphene ferromagnetic junction can be simultaneously operated as a spin filter and a spin valve. We attribute such a remarkable result to a coexistence of a half-metal band and a common energy gap for opposite spins in ferromagnetic graphene. We show that both the spin filter and the spin valve can be effectively controlled by a back gate voltage, and they survive for practical metal contacts and finite temperature. Specifically, larger single spin currents and on-state currents can be reached with contacts with work functions similar to graphene, and the spin filter can operate at higher temperature than the spin valve.

  9. Spin-orbit coupling and spin relaxation in phosphorene

    NASA Astrophysics Data System (ADS)

    Kurpas, Marcin; Gmitra, Martin; Fabian, Jaroslav

    We employ first principles density functional theory calculations to study intrinsic and extrinsic spin-orbit coupling in monolayer phosphorene. We also extract the spin-mixing amplitudes of the Bloch wave functions to give realistic estimates of the Elliott-Yafet spin relaxation rate. The most remarkable result is the striking anisotropy in both spin-orbit coupling and spin relaxation rates, which could be tested experimentally in spin injection experiments. We also identify spin hot spots in the electronic structure of phosphorene at accidental bands anticrossings. We compare the Elliott-Yafet with Dyakonov-Perel spin relaxation times, obtained from extrinsic couplings in an applied electric field. We also compare the results in phosphorene with those of black phosphorous. This work is supported by the DFG SPP 1538, SFB 689, and by the EU Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship.

  10. Generation of spin currents by surface plasmon resonance

    PubMed Central

    Uchida, K.; Adachi, H.; Kikuchi, D.; Ito, S.; Qiu, Z.; Maekawa, S.; Saitoh, E.

    2015-01-01

    Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light–electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY2Fe5O12 bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY2Fe5O12 interface. This spin-current generation cannot be explained by conventional heating effects, requiring us to introduce nonequilibrium magnons excited by surface-plasmon-induced evanescent electromagnetic fields in BiY2Fe5O12. This plasmonic spin pumping integrates surface plasmons with spin-current physics, opening the door to plasmonic spintronics. PMID:25569821

  11. Long distance spin communication in chemical vapour deposited graphene

    PubMed Central

    Kamalakar, M. Venkata; Groenveld, Christiaan; Dankert, André; Dash, Saroj P.

    2015-01-01

    Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ∼6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications. PMID:25857650

  12. Continuum model for chiral induced spin selectivity in helical molecules

    SciTech Connect

    Medina, Ernesto; González-Arraga, Luis A.; Finkelstein-Shapiro, Daniel; Mujica, Vladimiro; Berche, Bertrand

    2015-05-21

    A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p{sub z} type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective π{sub z} − π{sub z} coupling via interbase p{sub x,y} − p{sub z} hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.

  13. Long distance spin communication in chemical vapour deposited graphene

    NASA Astrophysics Data System (ADS)

    Kamalakar, M. Venkata; Groenveld, Christiaan; Dankert, André; Dash, Saroj P.

    2015-04-01

    Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ~6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications.

  14. Spin fluctations and heavy fermions in the Kondo lattice

    SciTech Connect

    Khaliullin, G.G.

    1994-09-01

    This paper studies the spectrum of the spin and electronic excitations of the Kondo lattice at low temperatures. To avoid unphysical states, the Mattis {open_quotes}drone{close_quotes}-fermion representation for localized spins is employed. First, the known Fermi liquid properties of a single impurity are examined. The behavior of the correlator between a localized spin and the electron spin density at large distances shows that the effective interaction between electrons on the Fermi level and low-energy localized spin fluctuations scales as {rho}{sup {minus}1}, where {rho} is the band-state density. This fact is developed into a renormalization of the band spectrum in a periodic lattice. If the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between localized spins is much smaller than the Kondo fluctuation frequency {omega}{sub k}, the temperature of the crossover to the single-parameter Fermi liquid mode is determined by {omega}{sub k}. When the RKKY interaction becomes of order {omega}{sub k}, there is a new scale {omega}{sub sf}, the energy of the (antiferromagnetic) paramagnon mode, with {omega}{sub sf}{much_lt}{omega}{sub k}. Here the coherent Fermi liquid regime is realized only below a temperature T{sub coh} of order {omega}{sub sf}, while above T{sub coh} quasiparticle damping exhibits a linear temperature dependence. Finally, the nuclear-spin relaxation rate is calculated. 42 refs.

  15. Optical spin excitations in quantum spin ladders

    NASA Astrophysics Data System (ADS)

    Simutis, Gediminas; Gvasaliya, Severian; Xiao, Fan; Landee, Christopher; Zheludev, Andrey

    We present a Raman spectroscopy study of magnetic excitations in quantum spin ladders. We start with a strong-rung ladder Cu(Qnx)(Cl1-xBrx)2. It has recently attracted attention due to proposal that the ratio of leg to rung exchange can be varied continuously by substituting Br for Cl. We have measured the Raman spectra for the hole doping series and report on the scattering from two magnons. We extract the onset and cutoff of the scattering for the whole series and compare it to the estimates from previous bulk measurements as well as numerical calculations. We find that the magnetic spectrum indeed varies continuously as the halogen ions are exchanged. The general behavior is found to be consistent with expectations, however small systematic deviations persist. The difference can potentially be explained by the existence of three-dimensional coupling, however more systematic computational studies are needed to ascertain the origin of the inconsistencies. Having established the analysis using the strong rung case, we then turn our attention to other ladder systems. Unusual magnetic signal is found in a strong leg spin ladder, which is discussed in terms of selection rules and an unexpected energy scale.

  16. Spin Charge Separation in the Quantum Spin Hall State

    SciTech Connect

    Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum spin Hall state is a topologically non-trivial insulator state protected by the time reversal symmetry. We show that such a state always leads to spin-charge separation in the presence of a {pi} flux. Our result is generally valid for any interacting system. We present a proposal to experimentally observe the phenomenon of spin-charge separation in the recently discovered quantum spin Hall system.

  17. Squeezed spin states: Squeezing the spin uncertainty relations

    NASA Technical Reports Server (NTRS)

    Kitagawa, Masahiro; Ueda, Masahito

    1993-01-01

    The notion of squeezing in spin systems is clarified, and the principle for spin squeezing is shown. Two twisting schemes are proposed as building blocks for spin squeezing and are shown to reduce the standard quantum noise, s/2, of the coherent S-spin state down to the order of S(sup 1/3) and 1/2. Applications to partition noise suppression are briefly discussed.

  18. Inhomogeneously broadened spin masers

    NASA Astrophysics Data System (ADS)

    Romalis, M. V.; Happer, W.

    1999-08-01

    Hyperpolarized 3He gas, where the nuclear spin polarization has been increased to several tens of percent by optical pumping, can couple such a large negative resistance into an external circuit that masing can ensue. The masing threshold can be suppressed by application of a magnetic field gradient. However, edge enhancement, that is, the less effective diffusional damping of the precessing magnetization at the container walls, can lower the masing threshold. The edge enhancement of the masing is greatly modified by magnetic self-interactions of the spins.

  19. Measuring Black Hole Spin

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    1999-09-01

    WE PROPOSE TO CARRY OUT A SYSTEMATIC STUDY OF EMISSION AND ABSORPTION SPECTRAL FEATURES THAT ARE OFTEN SEEN IN X-RAY SPECTRA OF BLACK HOLE BINARIES. THE EXCELLENT SENSITIVITY AND ENERGY RESOLUTION OF THE ACIS/HETG COMBINATION WILL NOT ONLY HELP RESOLVE AMBIGUITIES IN INTERPRETING THESE FEATURES, BUT MAY ALLOW MODELLING OF THE EMISSION LINE PROFILES IN DETAIL. THE PROFILES MAY CONTAIN INFORMATION ON SUCH FUNDAMENTAL PROPERTIES AS THE SPIN OF BLACK HOLES. THEREFORE, THIS STUDY COULD LEAD TO A MEASUREMENT OF BLACK HOLE SPIN FOR SELECTED SOURCES. THE RESULT CAN THEN BE DIRECTLY COMPARED WITH THOSE FROM PREVIOUS STUDIES BASED ON INDEPENDENT METHODS.

  20. Spin Currents in Silicon

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian

    2011-03-01

    I will discuss the results of our recent spin injection experiments using long-distance non-degenerate undoped (and n-type doped) Si devices. We have a unique capability to recover the details of electron transport on a sub-ns timescale through a ``Larmor clock'' transformation of spin precession data, despite using only quasistatic current measurements. I suggest that this is potentially a new tool for probing non-equilibrium phenomena in semiconductors, revealing both intrinsic and extrinsic materials properties through sensitivity to subtleties of the bandstructure and impurity spectrum. Supported by ONR and NSF.

  1. Spin labeling EPR.

    PubMed

    Klare, Johann P; Steinhoff, Heinz-Jürgen

    2009-01-01

    Site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy has emerged as an efficient tool to elucidate the structure and conformational dynamics of biomolecules under native-like conditions. This article summarizes the basics as well as recent progress of site-directed spin labeling. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the sensory rhodopsin-transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis and the photosynthetic reaction center from Rhodobacter sphaeroides R26. PMID:19728138

  2. Spin, Gravity, and Inertia

    NASA Astrophysics Data System (ADS)

    Obukhov, Yuri N.

    2001-01-01

    The gravitational effects in the relativistic quantum mechanics are investigated. The exact Foldy-Wouthuysen transformation is constructed for the Dirac particle coupled to the static spacetime metric. As a direct application, we analyze the nonrelativistic limit of the theory. The new term describing the specific spin (gravitational moment) interaction effect is recovered in the Hamiltonian. The comparison of the true gravitational coupling with the purely inertial case demonstrates that the spin relativistic effects do not violate the equivalence principle for the Dirac fermions.

  3. 15-Foot Spin Tunnel

    NASA Technical Reports Server (NTRS)

    1934-01-01

    Constructing the forms for the foundation of the 15-Foot Spin Tunnel. Charles Zimmerman was given the assignment to design and build a larger spin tunnel that would supplant the 5-foot Vertical Wind Tunnel. Authorization to build the tunnel using funds from the Federal Public Works Administration (PWA) came in June 1933. Construction started in late winter 1934 and the tunnel was operational in April 1935. The initial construction costs were $64,000. The first step was to pour the foundation for the tunnel and the housing which would encase the wind tunnel.

  4. Higher Spin Holography

    NASA Astrophysics Data System (ADS)

    Chang, Chi-Ming

    This dissertation splits into two distinct halves. The first half is devoted to the study of the holography of higher spin gauge theory in AdS 3. We present a conjecture that the holographic dual of W N minimal model in a 't Hooft-like large N limit is an unusual "semi-local" higher spin gauge theory on AdS3 x 1. At each point on the S1 lives a copy of three-dimensional Vasiliev theory, that contains an infinite tower of higher spin gauge fields coupled to a single massive complex scalar propagating in AdS3. The Vasiliev theories at different points on the S1 are correlated only through the AdS3 boundary conditions on the massive scalars. All but one single tower of higher spin symmetries are broken by the boundary conditions. This conjecture is checked by comparing tree-level two- and three-point functions, and also one-loop partition functions on both side of the duality. The second half focuses on the holography of higher spin gauge theory in AdS 4. We demonstrate that a supersymmetric and parity violating version of Vasiliev's higher spin gauge theory in AdS4 admits boundary conditions that preserve N = 0,1,2,3,4 or 6 supersymmetries. In particular, we argue that the Vasiliev theory with U( M) Chan-Paton and N = 6 boundary condition is holographically dual to the 2+1 dimensional U(N) k x U(M) -k ABJ theory in the limit of large N, k and finite M. In this system all bulk higher spin fields transform in the adjoint of the U(M) gauge group, whose bulk t'Hooft coupling is M/N. Our picture suggests that the supersymmetric Vasiliev theory can be obtained as a limit of type IIA string theory in AdS4 x CP3, and that the non-Abelian Vasiliev theory at strong bulk 't Hooft coupling smoothly turn into a string field theory. The fundamental string is a singlet bound state of Vasiliev's higher spin particles held together by U(M) gauge interactions.

  5. Spin Wave Genie

    Energy Science and Technology Software Center (ESTSC)

    2015-02-16

    The four-dimensional scattering function S(Q,w) obtained by inelastic neutron scattering measurements provides unique "dynamical fingerprints" of the spin state and interactions present in complex magnetic materials. Extracting this information however is currently a slow and complex process that may take an expert -depending on the complexity of the system- up to several weeks of painstaking work to complete. Spin Wave Genie was created to abstract and automate this process. It strives to both reduce themore » time to complete this analysis and make these calculations more accessible to a broader group of scientists and engineers.« less

  6. Spin Wave Genie

    SciTech Connect

    2015-02-16

    The four-dimensional scattering function S(Q,w) obtained by inelastic neutron scattering measurements provides unique "dynamical fingerprints" of the spin state and interactions present in complex magnetic materials. Extracting this information however is currently a slow and complex process that may take an expert -depending on the complexity of the system- up to several weeks of painstaking work to complete. Spin Wave Genie was created to abstract and automate this process. It strives to both reduce the time to complete this analysis and make these calculations more accessible to a broader group of scientists and engineers.

  7. The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.

    PubMed Central

    Contreras, A; Drummond, M; Bali, A; Blanco, G; Garcia, E; Bush, G; Kennedy, C; Merrick, M

    1991-01-01

    We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product. PMID:1683868

  8. The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.

    PubMed

    Contreras, A; Drummond, M; Bali, A; Blanco, G; Garcia, E; Bush, G; Kennedy, C; Merrick, M

    1991-12-01

    We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product. PMID:1683868

  9. Spin Hall and spin Nernst effects: temperature dependence

    NASA Astrophysics Data System (ADS)

    Dyrdal, Anna; Barnas, Jozef; Dugaev, Vitalii

    We have considered temperature dependence of spin Hall and spin Nernst effect in two-dimensional electron gas with spin-orbit interaction of Rashba type [arXiv:1510.03080]. In our considerations we have employed the approach based on the Matsubara Green functions. The formalism used in the case of electric field as a driving force was subsequently adopted to the situation of a spin current driven by a temperature gradient. To achieve this, we have used the concept of an auxiliary vector field. Such a description gives the possibility to consider all mechanisms leading to the spin Hall and spin Nernst effect on equal footing and also their behavior at finite temperatures. Both spin Hall and spin Nernst conductivities were calculated in the approximation including the vertex correction. The total spin Hall conductivity, including vertex correction, has been shown to vanish exactly in the whole temperature range. Thus, our results extend the earlier ones to an arbitrary temperatures. In turn, the total spin Nernst conductivity remains finite when the vertex corrections are included. Using the Ioffe-Regel localization criterion, we have also estimated the range of parameters where the calculated results for the spin Hall and spin Nernst conductivities are applicable.

  10. Spin current swapping and spin hall effect in disordered metals

    NASA Astrophysics Data System (ADS)

    Saidaoui, Hamed; Pauyac, Christian; Manchon, Aurelien

    2015-03-01

    The conversion of charge currents into spin currents via the spin Hall effect has attracted intense experimental and theoretical efforts lately, providing an efficient means to generate electric signals and manipulate the magnetization of single layers. More recently, it was proposed that spin-dependent scattering induced by spin-orbit coupled impurities also produces a so-called spin swapping, i.e. an exchange between the spin angular momentum and linear momentum of itinerant electrons. In this work, we investigate the nature of spin swapping and its interplay with extrinsic spin Hall effect and spin relaxation in finite size normal metals. We use two complementary methods based on non-equilibrium Green's function technique. The first method consists in rigorously deriving the drift-diffusion equation of the spin accumulation in the presence of spin-orbit coupled impurities from quantum kinetics using Wigner expansion. The second method is the real-space tight binding modeling of a finite system in the presence of spin-orbit coupled disorder.

  11. Attitude stability of spinning satellites

    NASA Technical Reports Server (NTRS)

    Caughey, T. K.

    1980-01-01

    Some problems of attitude stability of spinning satellites are treated in a rigorous manner. With certain restrictions, linearized stability analysis correctly predicts the attitude stability of spinning satellites, even in the critical cases of the Liapunov-Poincare stability theory.

  12. Suppression of Walker breakdown in magnetic domain wall propagation through structural control of spin wave emission

    NASA Astrophysics Data System (ADS)

    Burn, David M.; Atkinson, Del

    2013-06-01

    The control of individual magnetic domain walls has potential for future spintronic memory and data processing applications. The speed and reliability of such devices are determined by the dynamic properties of the domain walls. Typically, spin precession limitations lead to Walker breakdown, limiting wall velocity resulting in low mobility. Here, we show the suppression of Walker breakdown by the careful design of small amplitude periodic nanowire structuring to match the periodicity of domain wall spin structure transformations. This opens up a channel for energy dissipation via spin wave emission, allowing a domain wall to maintain its spin structure during propagation.

  13. Spin-orbit interactions in electronic structure quantum Monte Carlo methods

    NASA Astrophysics Data System (ADS)

    Melton, Cody A.; Zhu, Minyi; Guo, Shi; Ambrosetti, Alberto; Pederiva, Francesco; Mitas, Lubos

    2016-04-01

    We develop generalization of the fixed-phase diffusion Monte Carlo method for Hamiltonians which explicitly depends on particle spins such as for spin-orbit interactions. The method is formulated in a zero-variance manner and is similar to the treatment of nonlocal operators in commonly used static-spin calculations. Tests on atomic and molecular systems show that it is very accurate, on par with the fixed-node method. This opens electronic structure quantum Monte Carlo methods to a vast research area of quantum phenomena in which spin-related interactions play an important role.

  14. Full control of the spin-wave damping in a magnetic insulator using spin orbit torque

    NASA Astrophysics Data System (ADS)

    Klein, Olivier

    2015-03-01

    The spin-orbit interaction (SOI) has been an interesting and useful addition in the field of spintronics by opening it to non-metallic magnet. It capitalizes on adjoining a strong SOI normal metal next to a thin magnetic layer. The SOI converts a charge current, Jc, into a spin current, Js, with an efficiency parametrized by ΘSH, the spin Hall angle. An important benefit of the SOI is that Jc and Js are linked through a cross-product, allowing a charge current flowing in-plane to produce a spin current flowing out-of-plane. Hence it enables the transfer of spin angular momentum to non-metallic materials and in particular to insulating oxides, which offer improved performance compared to their metallic counterparts. Among all oxides, Yttrium Iron Garnet (YIG) holds a special place for having the lowest known spin-wave (SW) damping factor. Until recently the transmission of spin current through the YIG|Pt interface has been subject to debate. While numerous experiments have reported that Js produced by the excitation of ferromagnetic resonance (FMR) in YIG can cross efficiently the YIG|Pt interface and be converted into Jc in Pt through the inverse spin Hall effect (ISHE), most attempts to observe the reciprocal effect, where Js produced in Pt by the direct spin Hall effect (SHE) is transferred to YIG, resulting in damping compensation, have failed. This has been raising fundamental questions about the reciprocity of the spin transparency of the interface between a metal and a magnetic insulator. In this talk it will be demonstrated that the threshold current for damping compensation can be reached in a 5 μm diameter YIG(20nm)|Pt(7nm) disk. Reduction of both the thickness and lateral size of a YIG-structure were key to reach the microwave generation threshold current, Jc*. The experimental evidence rests upon the measurement of the ferromagnetic resonance linewidth as a function of Idc using a magnetic resonance force microscope (MRFM). It is shwon that the

  15. A quantum phase switch between a single solid-state spin and a photon.

    PubMed

    Sun, Shuo; Kim, Hyochul; Solomon, Glenn S; Waks, Edo

    2016-06-01

    Interactions between single spins and photons are essential for quantum networks and distributed quantum computation. Achieving spin-photon interactions in a solid-state device could enable compact chip-integrated quantum circuits operating at gigahertz bandwidths. Many theoretical works have suggested using spins embedded in nanophotonic structures to attain this high-speed interface. These proposals implement a quantum switch where the spin flips the state of the photon and a photon flips the spin state. However, such a switch has not yet been realized using a solid-state spin system. Here, we report an experimental realization of a spin-photon quantum switch using a single solid-state spin embedded in a nanophotonic cavity. We show that the spin state strongly modulates the polarization of a reflected photon, and a single reflected photon coherently rotates the spin state. These strong spin-photon interactions open up a promising direction for solid-state implementations of high-speed quantum networks and on-chip quantum information processors using nanophotonic devices. PMID:26854569

  16. Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

    NASA Astrophysics Data System (ADS)

    Munsch, Mathieu; Wüst, Gunter; Kuhlmann, Andreas V.; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Poggio, Martino; Warburton, Richard J.

    2014-09-01

    The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.

  17. Optimizing Spin Generation in 2D Materials: Topological Insulators and Graphene

    NASA Astrophysics Data System (ADS)

    Chen, Ching-Tzu

    Novel two-dimensional electronic systems with Dirac-like dispersion present unique opportunities for spintronic applications. In this seminar I will discuss two specific examples. First we examine the potential of topological insulators as spin-source materials. Using a new spin-polarized tunneling method, giant charge-spin conversion efficiency in topological insulators is revealed, well exceeding that in conventional magnetic tunnel junctions. Through a comparative study between Bi2Se3 and (Bi,Sb)2Te3, we verify the topological-surface-state origin of the observed giant spin signals and further extract the energy dependence of the effective spin polarization in Bi2Se3. Next we explore the potential of interfacial exchange interaction in 2D materials for spin control and spin generation. Using graphene as a prototype, we demonstrate that its coupling to a model magnetic insulator (EuS) produces a substantial magnetic exchange field (>14 T), which yields orders-of-magnitude enhancement in the spin signal originated from the Zeeman spin-Hall effect. Furthermore, the strong exchange field lifts the spin degeneracy of graphene in the quantum Hall regime, which may lead to interesting spin-polarized edge transport and thus open up new application space for classical and quantum information processing.

  18. All Spin Digital Circuits

    NASA Astrophysics Data System (ADS)

    Behin-Aein, Behtash; Datta, Deepanjan; Salahuddin, Sayeef; Datta, Supriyo

    2009-03-01

    Switching of a magnetic free layer using spin polarized current has been demonstrated in Magnetic Tunnel Junction (MTJ) devices. Currently MTJ's are being studied for memory and microwave oscillator applications. The purpose of this talk is to explore a modified MTJ where a clock pulse via the fixed layer facilities the switching of the free layer in accordance with a weak bias provided by an input magnet in the form of a spin current. Based on the Landau-Lifshitz-Gilbert equation (LLG) augmented with spin torque functions, we show the switching energy and the switching time of the free layer which indicates the possibility of very low power digital logic applications. Ordinary digital circuits store information in the form of capacitor charges that communicate through electrical interconnects. The purpose of this paper is to show that modified MTJ's can be the basis for all spin digital circuits. Our primary objective is to stimulate proof of concept experiments that could usher in a whole new set of devices suitable for spintronic circuits.

  19. 20-Foot Spin Tunnel

    NASA Technical Reports Server (NTRS)

    1947-01-01

    Construction of a typical model used in the 20-Foot Spin Tunnel. >From 'Characteristics of Nine Research Wind Tunnels of the Langley Aeronautical Laboratory': 'Dynamic models are used for free-spinning tunnel tests. A dynamic model is one for which geometric similarity between model and airplane is extended to obtain geometric similarity of the paths of motion of corresponding points by maintaining constant, in addition to the scale ratio of linear dimensions, three other ratios, that of force, mass, and time. In model testing, however, complete similarity can generally not be duplicated and some compromise is necessary. For free-spinning-model tests in the NACA 20-foot tunnel, the ratio of inertia to frictional or viscous forces (Reynolds number) is not maintained constant, but the ratio of inertia to gravity forces (Froude number) is maintained constant.' 'Models used in the spin tunnel until recently [this report was written in 1957] were made primarily of balsa and reinforced with hardwood. Now, plastic models are being used almost entirely, because they are more durable and when properly constructed are no heavier than balsa models. The models are constructed accurately to scale by pressing plastic material and class cloth into a previously constructed mold. A typical mod is shown in [this picture]. The model is swung as a torsional pendulum and is ballasted to obtain dynamic similarity by placing lead weights in suitable locations within the model wings and fuselage. Corrections are made for the effect of ambient and entrapped air.'

  20. Artificial frustrated spin systems

    NASA Astrophysics Data System (ADS)

    Perrin, Y.; Chioar, I. A.; Nguyen, V. D.; Lacour, D.; Hehn, M.; Montaigne, F.; Canals, B.; Rougemaille, N.

    2015-09-01

    Complex architectures of nanostructures are routinely elaborated using bottom-up or nanofabrication processes. This technological capability allows scientists to engineer materials with properties that do not exist in nature, but also to manufacture model systems to explore fundamental issues in condensed matter physics. Two-dimensional frustrated arrays of magnetic nanostructures are one class of systems for which theoretical predictions can be tested experimentally. These systems have been the subject of intense research in the last few years and allowed the investigation of a rich physics and fascinating phenomena, such as the exploration of the extensively degenerate ground-state manifolds of spin ice systems, the evidence of new magnetic phases in purely two-dimensional lattices, and the observation of pseudoexcitations involving classical analogues of magnetic monopoles. We show here, experimentally and theoretically, that simple magnetic geometries can lead to unconventional, non-collinear spin textures. For example, kagome arrays of inplane magnetized nano-islands do not show magnetic order. Instead, these systems are characterized by spin textures with intriguing properties, such as chirality, coexistence of magnetic order and disorder, and charge crystallization. Magnetic frustration effects in lithographically patterned kagome arrays of nanomagnets with out-of-plane magnetization also lead to an unusal, and still unknown, magnetic ground state manifold. Besides the influence of the lattice geometry, the micromagnetic nature of the elements constituting the arrays introduce the concept of chiral magnetic monopoles, bringing additional complexity into the physics of artificial frustrated spin systems.

  1. Does the Moon Spin?

    ERIC Educational Resources Information Center

    Collins, Robert; Simpson, Frances

    2007-01-01

    In this article, the authors explore the question, "Does the Moon spin?", and show how the question is investigated. They emphasise the importance of the process by which people work out what they know, by "learning from the inside out." They stress that those involved in science education have to challenge current conceptions and ideas, making…

  2. TRANSVERSITY SINGLE SPIN ASYMMETRIES.

    SciTech Connect

    BOER,D.

    2001-04-27

    The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.

  3. Spin Physics at HERMES

    SciTech Connect

    Hasch, D.

    2007-06-13

    The HERMES experiment at DESY is a second generation experiment to study the spin structure of the nucleon by measuring not only inclusive but also semi-inclusive and exclusive processes in deep-inelastic lepton scattering. An overview of most recent results is given.

  4. Spin Physics with CLAS

    SciTech Connect

    Yelena Prok

    2010-05-01

    Inelastic scattering using polarized nucleon targets and polarized charged lepton beams allows the extraction of double and single spin asymmetries that provide information about the helicity structure of the nucleon. A program designed to study such processes at low and intermediate $Q^2$ for the proton and deuteron has been pursued by the CLAS Collaboration at Jefferson Lab since 1998. Our inclusive data with high statistical precision and extensive kinematic coverage allow us to better constrain the polarized parton distributions and to accurately determine various moments of spin structure function $g_1$ as a function of $Q^2$. The latest results will be shown, illustrating our contribution to the world data, with comparisons of the data with NLO global fits, phenomenological models, chiral perturbation theory and the GDH and Bjorken sum rules. The semi-inclusive measurements of single and double spin asymmetries for charged and neutral pions are also show, indicating the importance of the orbital motion of quarks in understanding the spin structure of the nucleon.

  5. Transverse Spin at RHIC

    NASA Astrophysics Data System (ADS)

    Wang, Xiaorong

    2016-03-01

    In recent years, there has been exciting development in both experimental and theoretical studies of transverse spin asymmetries in polarized p+p and and DIS collisions. As a unique polarized proton-proton collider, Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) provides a unique opportunity to investigate the novel physics mechanisms that cause the large single spin asymmetry at the forward rapidity. Both PHENIX and STAR experiments have been studying the transverse spin asymmetries with a variety of final state particles in different kinematic regimes since 2006. Especially, recent theoretical development on scattering a polarized probe on the saturated nuclear may provide a unique way to probe the gluon and quark TMDs. RHIC successfully ran polarized p+Au collisions in 2015. We will expect to have new results from polarized d+Au to compare with existing results from p+p collision to extend our understanding of QCD. Further more, In 2015, PHENIX installed MPC-ex calorimeter at very forward region to measure direct photon AN and STAR installed Roman Pots to study the diffractive events in polarized p+p and p+Au collisions. The recent results on transverse polarized p+p and p+Au collisions from both PHENIX and STAR experiments will be presented in this talk. I will also briefly discuss the possibility for the transverse Spin program at future experiments sPHENIX and forward sPHENIX at RHIC. Supported by US Department of Energy and RIKEN Brookhaven Research Center.

  6. Layered kagome spin ice

    NASA Astrophysics Data System (ADS)

    Hamp, James; Dutton, Sian; Mourigal, Martin; Mukherjee, Paromita; Paddison, Joseph; Ong, Harapan; Castelnovo, Claudio

    Spin ice materials provide a rare instance of emergent gauge symmetry and fractionalisation in three dimensions: the effective degrees of freedom of the system are emergent magnetic monopoles, and the extensively many `ice rule' ground states are those devoid of monopole excitations. Two-dimensional (kagome) analogues of spin ice have also been shown to display a similarly rich behaviour. In kagome ice however the ground-state `ice rule' condition implies the presence everywhere of magnetic charges. As temperature is lowered, an Ising transition occurs to a charge-ordered state, which can be mapped to a dimer covering of the dual honeycomb lattice. A second transition, of Kosterlitz-Thouless or three-state Potts type, occurs to a spin-ordered state at yet lower temperatures, due to small residual energy differences between charge-ordered states. Inspired by recent experimental capabilities in growing spin ice samples with selective (layered) substitution of non-magnetic ions, in this work we investigate the fate of the two ordering transitions when individual kagome layers are brought together to form a three-dimensional pyrochlore structure coupled by long range dipolar interactions. We also consider the response to substitutional disorder and applied magnetic fields.

  7. Stabilizing a spinning Skylab.

    NASA Technical Reports Server (NTRS)

    Seltzer, S. M.; Justice, D. W.; Schweitzer, G.; Patel, J. S.

    1972-01-01

    This paper presents the results of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

  8. Stabilizing a spinning Skylab

    NASA Technical Reports Server (NTRS)

    Seltzer, S. M.; Patel, J. S.; Justice, D. W.; Schweitzer, G. E.

    1972-01-01

    The results are presented of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

  9. Nucleon spin structure

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Ruan, Jianhong

    2015-10-01

    This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear quantum chromodynamics (QCD) evolution equation — the Dokshitzer-Gribov-Lipatov-Altarelli-Paris (DGLAP) equation with the parton recombination corrections, where the nucleon is almost consisted only of valence quarks. We find that the contribution of the gluon polarization to the nucleon spin structure is much larger than the predictions of most other theories. This result suggests that a significant orbital angular momentum of the gluons is required to balance the gluon spin momentum. (ii) The spin structure function g1p of the proton is studied, where the perturbative evolution of parton distributions and nonperturbative vector meson dominance (VMD) model are used. We predict g1p asymptotic behavior at small x from lower Q2 to higher Q2. The results are compatible with the data including the early HERA estimations and COMPASS new results. (iii) The generalized Gerasimov-Drell-Hearn (GDH) sum rule is understood based on the polarized parton distributions of the proton with the higher twist contributions. A simple parameterized formula is proposed to clearly present the contributions of different components in the proton to Γ 1p(Q2). The results suggest a possible extended objects with size 0.2-0.3 fm inside the proton.

  10. Circuit-quantum electrodynamics with direct magnetic coupling to single-atom spin qubits in isotopically enriched {sup 28}Si

    SciTech Connect

    Tosi, Guilherme Mohiyaddin, Fahd A.; Morello, Andrea; Huebl, Hans

    2014-08-15

    Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified {sup 28}Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.

  11. Spin Transport in Semiconductor heterostructures

    SciTech Connect

    Domnita Catalina Marinescu

    2011-02-22

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  12. An overview of spin physics

    SciTech Connect

    Prescott, C.Y.

    1991-07-01

    Spin physics is playing an increasingly important role in high energy experiments and theory. This review looks at selected topics in high energy spin physics that were discussed at the 9th International Symposium on High Energy Spin Physics at Bonn in September 1990.

  13. Continuous quantum measurement in spin environments

    NASA Astrophysics Data System (ADS)

    Xie, Dong; Wang, An Min

    2015-08-01

    We derive a stochastic master equation (SME) which describes the decoherence dynamics of a system in spin environments conditioned on the measurement record. Markovian and non-Markovian nature of environment can be revealed by a spectroscopy method based on weak continuous quantum measurement. On account of that correlated environments can lead to a non-local open system which exhibits strong non-Markovian effects although the local dynamics are Markovian, the spectroscopy method can be used to demonstrate that there is correlation between two environments.

  14. Gluonic Spin Contribution to Proton Spin at NLO

    SciTech Connect

    Casey, Andrew

    2011-05-24

    In 1988, when the EMC results showed that the quarks had a much smaller contribution to the spin of the proton than previously thought, the 'Proton Spin Crisis' began. Since then, considerable effort has been directed into discovering the main contributors to proton spin and how much each contributes. One such contributor is the gluonic spin component. QCD NLO evolution equations are combined with boundary conditions obtained from heavy quark decoupling expressions to evolve the equations from infinity to the mass of the charm quark in order to determine the gluonic spin contribution.

  15. Hole localization and spin coupling in [pi]-mono- and [pi]-dications of [mu]-oxoporphyrin dimers, relevance to structure of oxidized [open quotes]special pair[close quotes] in photosynthetic reaction centers

    SciTech Connect

    Binstead, R.A.; Hush, N.S. )

    1993-12-16

    The antiferromagnetically coupled cofacial [mu]-oxoiron(III) dimers of octaethylporphyrin (OEP) and [alpha],[beta],[gamma],[Delta]-tetraphenylporphyrin (TPP) can be oxidized in two one-electron steps to yield [pi]-monocations and [pi]-dications. Hitherto unreported absorption bands are observed in the mid-infrared region in the spectra of the monocations. These are identified as intervalence transitions of dynamically trapped holes. The electron-phonon coupling energies (CH[sub 2]Cl[sub 2] solution, 295 K) are 0.31 [+-] 0.04 eV, and the inter-ring, predominantly through-space, electronic coupling constants J are 0.07 and 0.03 eV, respectively. The small values of J are a consequence of the large mean plane separation of the porphyrin rings (4.53 A). Since it is impossible that the electron-phonon coupling energies will vary greatly between cofacial porphyrin dimers, it is suggested that absorption hands around 1 eV in the [pi]-monocations of [open quotes]sandwich[close quotes] compounds such as M[sup III]P[sub 2] or M[sup IV]P[sub 2][sup +], where P is a porphyrin and M are lanthanide, actinide, or transition metals (3-12) observed under similar conditions will have electronic ground states that are delocalized on at least the vibrational time scale, with frequency maxima equal to 2J in the tight-binding approximation. The thermal inter-ring hole-transfer times in the [mu]-oxo dimer monocations are estimated to be approximately 1 ps. The relevance of these results to the problem of the structure of the oxidized [open quotes]special pair[close quotes] in the photosynthetic reaction center is briefly discussed. 52 refs., 4 figs., 5 tabs.

  16. Spin Circuit Representation of Spin Pumping in Topological Insulators

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    Earlier we developed spin circuit representation of spin pumping and combined it with the spin circuit representation for the inverse spin Hall effect to show that it reproduces the established results in literature. Here we construct the spin circuit representation of spin pumping in topological insulators. The discovery of spin-polarized surface states in three-dimensional (3D) topological insulators (TIs) with strong spin-orbit coupling is promising for the development of spintronics. There is considerable bulk conduction too in 3D TIs (e.g., Bi2Se3) apart from possessing the surface states. We utilize the spin circuit model for spin orbit torques in topological insulator surface states to develop the equivalent circuit model of spin pumping in topological insulators. Such equivalent circuit model developed here can be utilized to analyze available experimental results and evaluate more complex structures. This work was supported by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  17. Excitation of coherent propagating spin waves by pure spin currents

    NASA Astrophysics Data System (ADS)

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics.

  18. Excitation of coherent propagating spin waves by pure spin currents.

    PubMed

    Demidov, Vladislav E; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  19. State diagram of an orthogonal spin transfer spin valve device

    SciTech Connect

    Ye, Li; Wolf, Georg; Pinna, Daniele; Chaves-O'Flynn, Gabriel D.; Kent, Andrew D.

    2015-05-21

    We present the switching characteristics of a spin-transfer device that incorporates a perpendicularly magnetized spin-polarizing layer with an in-plane magnetized free and fixed magnetic layer, known as an orthogonal spin transfer spin valve device. This device shows clear switching between parallel (P) and antiparallel (AP) resistance states and the reverse transition (AP → P) for both current polarities. Further, hysteretic transitions are shown to occur into a state with a resistance intermediate between that of the P and AP states, again for both current polarities. These unusual spin-transfer switching characteristics can be explained within a simple macrospin model that incorporates thermal fluctuations and considers a spin-polarized current that is tilted with respect to the free layer's plane, due to the presence of the spin-transfer torque from the polarizing layer.

  20. Modeling spin transport with current-sensing spin detectors

    NASA Astrophysics Data System (ADS)

    Li, Jing; Appelbaum, Ian

    2010-03-01

    The impulse response (or ``Green's function'') of a current-sensing spin detector is derived analytically by incorporating the proper boundary conditions. This result is also compared to a Monte Carlo simulation (which automatically takes the proper boundary conditions into account) and an empirical spin transit time distribution obtained from experimental spin precession measurements. In the strong drift-dominated transport regime, this spin current impulse response can be approximated by multiplying the spin density impulse response by the average drift velocity. However, in weak drift fields, large modeling errors up to a factor of 3 in most-probable spin transit time can be incurred unless the full spin current Green's function is used.

  1. Modeling spin transport with current-sensing spin detectors

    NASA Astrophysics Data System (ADS)

    Li, Jing; Appelbaum, Ian

    2009-10-01

    By incorporating the proper boundary conditions, we analytically derive the impulse response (or "Green's function") of a current-sensing spin detector. We also compare this result to a Monte Carlo simulation (which automatically takes the proper boundary condition into account) and an empirical spin transit time distribution obtained from experimental spin precession measurements. In the strong drift-dominated transport regime, this spin current impulse response can be approximated by multiplying the spin density impulse response by the average drift velocity. However, in weak drift fields, large modeling errors up to a factor of 3 in most-probable spin transit time can be incurred unless the full spin current Green's function is used.

  2. Spin wave excitation patterns generated by spin torque oscillators

    NASA Astrophysics Data System (ADS)

    Macià, F.; Hoppensteadt, F. C.; Kent, A. D.

    2014-01-01

    Spin torque nano-oscillators (STNO) are nanoscale devices that can convert a direct current into short wavelength spin wave excitations in a ferromagnetic layer. We show that arrays of STNO can be used to create directional spin wave radiation similarly to electromagnetic antennas. Combining STNO excitations with planar spin waves also creates interference patterns. We show that these interference patterns are static and have information on the wavelength and phase of the spin waves emitted from the STNO. We describe a means of actively controlling spin wave radiation patterns with the direct current flowing through STNO, which is useful in on-chip communication and information processing and could be a promising technique for studying short wavelength spin waves in different materials.

  3. Spin quantum Hall effects in featureless nonfractionalized spin-1 magnets

    NASA Astrophysics Data System (ADS)

    Lu, Yuan-Ming; Lee, Dung-Hai

    2014-05-01

    The Affleck-Kennedy-Lieb-Tasaki state (or Haldane phase) in a spin-1 chain represents a large class of gapped topological paramagnets that host symmetry-protected gapless excitations on the boundary. In this work, we show how to realize this type of featureless spin-1 state on a generic two-dimensional lattice. These states have a gapped spectrum in the bulk, but they support gapless edge states protected by spin rotational symmetry along a certain direction, and they exhibit the spin quantum Hall effect. Using a fermion representation of integer spins, we show a concrete example of such spin-1 topological paramagnets on a kagome lattice, and we suggest a microscopic spin-1 Hamiltonian that may realize it.

  4. Excitation of coherent propagating spin waves by pure spin currents

    PubMed Central

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  5. Pseudospin, real spin, and spin polarization of photoemitted electrons

    NASA Astrophysics Data System (ADS)

    Yu, Rui; Weng, Hongming; Fang, Zhong; Dai, Xi

    2016-08-01

    In this paper, we discuss the connections between pseudospin, real spin of electrons in a material, and spin polarization of photoemitted electrons out of a material. By investigating these three spin textures for Bi2Se3 and SmB6 compounds, we find that the spin orientation of photoelectrons for SmB6 has a different correspondence to pseudospin and real spin compared to Bi2Se3 , due to the different symmetry properties of the photoemission matrix between the initial and final states. We calculate the spin polarization and circular dichroism spectra of photoemitted electrons for both compounds, which can be detected by spin-resolved and circular dichroism angle-resolved photoemission spectroscopy experiments.

  6. Electrical spin injection and detection of spin precession in room temperature bulk GaN lateral spin valves

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Aniruddha; Baten, Md Zunaid; Bhattacharya, Pallab

    2016-01-01

    We report the measurement of diffusive electronic spin transport characteristics in an epitaxial wurtzite GaN lateral spin valve at room temperature. Hanle spin precession and non-local spin accumulation measurements have been performed with the spin valves fabricated with FeCo/MgO spin contacts. Electron spin relaxation length and spin-flip lifetime of 176 nm and 37 ps, respectively, are derived from analysis of results obtained from four-terminal Hanle spin precession measurements at 300 K. The role of dislocations and defects in bulk GaN has also been examined in the context of electronic spin relaxation dynamics.

  7. Spin Hall controlled magnonic microwaveguides

    SciTech Connect

    Demidov, V. E.; Urazhdin, S.; Rinkevich, A. B.; Reiss, G.; Demokritov, S. O.

    2014-04-14

    We use space-resolved magneto-optical spectroscopy to study the influence of spin Hall effect on the excitation and propagation of spin waves in microscopic magnonic waveguides. We find that the spin Hall effect not only increases the spin-wave propagation length, but also results in an increased excitation efficiency due to the increase of the dynamic susceptibility in the vicinity of the inductive antenna. We show that the efficiency of the propagation length enhancement is strongly dependant on the type of the excited spin-wave mode and its wavelength.

  8. RHIC spin flipper commissioning results

    SciTech Connect

    Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.

    2012-05-20

    The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.

  9. Single-shot readout of multiple nuclear spin qubits in diamond under ambient conditions.

    PubMed

    Dréau, A; Spinicelli, P; Maze, J R; Roch, J-F; Jacques, V

    2013-02-01

    We use the electronic spin of a single nitrogen-vacancy defect in diamond to observe the real-time evolution of neighboring single nuclear spins under ambient conditions. Using a diamond sample with a natural abundance of (13)C isotopes, we first demonstrate high fidelity initialization and single-shot readout of an individual (13)C nuclear spin. By including the intrinsic (14)N nuclear spin of the nitrogen-vacancy defect in the quantum register, we then report the simultaneous observation of quantum jumps linked to both nuclear spin species, providing an efficient initialization of the two qubits. These results open up new avenues for diamond-based quantum information processing including active feedback in quantum error correction protocols and tests of quantum correlations with solid-state single spins at room temperature. PMID:23432227

  10. Electron spin polarization in strong-field ionization of xenon atoms

    NASA Astrophysics Data System (ADS)

    Hartung, Alexander; Morales, Felipe; Kunitski, Maksim; Henrichs, Kevin; Laucke, Alina; Richter, Martin; Jahnke, Till; Kalinin, Anton; Schöffler, Markus; Schmidt, Lothar Ph. H.; Ivanov, Misha; Smirnova, Olga; Dörner, Reinhard

    2016-08-01

    As a fundamental property of the electron, the spin plays a decisive role in the electronic structure of matter, from solids to molecules and atoms, for example, by causing magnetism. Yet, despite its importance, the spin dynamics of the electrons released during the interaction of atoms with strong ultrashort laser pulses has remained experimentally unexplored. Here, we report the experimental detection of electron spin polarization by the strong-field ionization of xenon atoms and support our results with theoretical analysis. We found up to 30% spin polarization changing its sign with electron energy. This work opens the new dimension of spin to strong-field physics. It paves the way to the production of sub-femtosecond spin-polarized electron pulses with applications ranging from probing the magnetic properties of matter at ultrafast timescales to testing chiral molecular systems with sub-femtosecond temporal and sub-ångström spatial resolutions.

  11. Quantum spin dynamics with pairwise-tunable, long-range interactions

    PubMed Central

    Hung, C.-L.; González-Tudela, Alejandro; Cirac, J. Ignacio; Kimble, H. J.

    2016-01-01

    We present a platform for the simulation of quantum magnetism with full control of interactions between pairs of spins at arbitrary distances in 1D and 2D lattices. In our scheme, two internal atomic states represent a pseudospin for atoms trapped within a photonic crystal waveguide (PCW). With the atomic transition frequency aligned inside a band gap of the PCW, virtual photons mediate coherent spin–spin interactions between lattice sites. To obtain full control of interaction coefficients at arbitrary atom–atom separations, ground-state energy shifts are introduced as a function of distance across the PCW. In conjunction with auxiliary pump fields, spin-exchange versus atom–atom separation can be engineered with arbitrary magnitude and phase, and arranged to introduce nontrivial Berry phases in the spin lattice, thus opening new avenues for realizing topological spin models. We illustrate the broad applicability of our scheme by explicit construction for several well-known spin models. PMID:27496329

  12. Spin thermoelectric efficiency across a normal-metal/ferromagnetic-insulator interface

    NASA Astrophysics Data System (ADS)

    Yan, Yonghong; Wu, Haifei; Jiang, Feng

    2016-08-01

    We investigate the spin and heat transport across a normal-metal/ferromagnetic-insulator (NM/FI) interface based on the s-d exchange model. Under a certain temperature gradient, the heat current carried by magnons partly flows into the metal, and is partly converted to spin power corresponding to spin current. We find that when the magnon dispersion of the FI (such as yttrium iron garnet) is quadratic, the conversion efficiency of heat current to spin power is about ηs ∼ 0.2ηC with ηC being the Carnot efficiency. The corresponding spin thermopower is roughly Ss ∼ 110 μ V / K . The efficiency and the spin thermopower can be enhanced by opening a gap via, for example, introducing a magnetic field. Effects of temperature in the presence of a gap and dimensionality are also discussed briefly.

  13. Atomic-like spin noise in solid-state demonstrated with manganese in cadmium telluride.

    PubMed

    Cronenberger, S; Scalbert, D; Ferrand, D; Boukari, H; Cibert, J

    2015-01-01

    Spin noise spectroscopy is an optical technique which can probe spin resonances non-perturbatively. First applied to atomic vapours, it revealed detailed information about nuclear magnetism and the hyperfine interaction. In solids, this approach has been limited to carriers in semiconductor heterostructures. Here we show that atomic-like spin fluctuations of Mn ions diluted in CdTe (bulk and quantum wells) can be detected through the Kerr rotation associated to excitonic transitions. Zeeman transitions within and between hyperfine multiplets are clearly observed in zero and small magnetic fields and reveal the local symmetry because of crystal field and strain. The linewidths of these resonances are close to the dipolar limit. The sensitivity is high enough to open the way towards the detection of a few spins in systems where the decoherence due to nuclear spins can be suppressed by isotopic enrichment, and towards spin resonance microscopy with important applications in biology and materials science. PMID:26382137

  14. Atomic-like spin noise in solid-state demonstrated with manganese in cadmium telluride

    NASA Astrophysics Data System (ADS)

    Cronenberger, S.; Scalbert, D.; Ferrand, D.; Boukari, H.; Cibert, J.

    2015-09-01

    Spin noise spectroscopy is an optical technique which can probe spin resonances non-perturbatively. First applied to atomic vapours, it revealed detailed information about nuclear magnetism and the hyperfine interaction. In solids, this approach has been limited to carriers in semiconductor heterostructures. Here we show that atomic-like spin fluctuations of Mn ions diluted in CdTe (bulk and quantum wells) can be detected through the Kerr rotation associated to excitonic transitions. Zeeman transitions within and between hyperfine multiplets are clearly observed in zero and small magnetic fields and reveal the local symmetry because of crystal field and strain. The linewidths of these resonances are close to the dipolar limit. The sensitivity is high enough to open the way towards the detection of a few spins in systems where the decoherence due to nuclear spins can be suppressed by isotopic enrichment, and towards spin resonance microscopy with important applications in biology and materials science.

  15. Voltage-driven spin-transfer torque in a magnetic particle

    SciTech Connect

    Gartland, P. Davidović, D.

    2015-10-26

    We discuss a spin-transfer torque device, where the role of the soft ferromagnetic layer is played by a magnetic particle or a magnetic molecule, in weak tunnel contact with two spin polarized leads. We investigate if the magnetization of the particle can be manipulated electronically, in the regime where the critical current for magnetization switching is negligibly weak, which could be due to the reduced particle dimensions. Using master equation simulations to evaluate the effects of spin-orbit anisotropy energy fluctuations on spin-transfer, we obtain reliable reading and writing of the magnetization state of such magnetic particle, and find that the device relies on a critical voltage rather than a critical current. The critical voltage is governed by the spin-orbit energy shifts of discrete levels in the particle. This finding opens a possibility to significantly reduce the power dissipation involved in spin-transfer torque switching, by using very small magnetic particles or molecules.

  16. Versatile microwave-driven trapped ion spin system for quantum information processing

    PubMed Central

    Piltz, Christian; Sriarunothai, Theeraphot; Ivanov, Svetoslav S.; Wölk, Sabine; Wunderlich, Christof

    2016-01-01

    Using trapped atomic ions, we demonstrate a tailored and versatile effective spin system suitable for quantum simulations and universal quantum computation. By simply applying microwave pulses, selected spins can be decoupled from the remaining system and, thus, can serve as a quantum memory, while simultaneously, other coupled spins perform conditional quantum dynamics. Also, microwave pulses can change the sign of spin-spin couplings, as well as their effective strength, even during the course of a quantum algorithm. Taking advantage of the simultaneous long-range coupling between three spins, a coherent quantum Fourier transform—an essential building block for many quantum algorithms—is efficiently realized. This approach, which is based on microwave-driven trapped ions and is complementary to laser-based methods, opens a new route to overcoming technical and physical challenges in the quest for a quantum simulator and a quantum computer. PMID:27419233

  17. Atomic-like spin noise in solid-state demonstrated with manganese in cadmium telluride

    PubMed Central

    Cronenberger, S.; Scalbert, D.; Ferrand, D.; Boukari, H.; Cibert, J.

    2015-01-01

    Spin noise spectroscopy is an optical technique which can probe spin resonances non-perturbatively. First applied to atomic vapours, it revealed detailed information about nuclear magnetism and the hyperfine interaction. In solids, this approach has been limited to carriers in semiconductor heterostructures. Here we show that atomic-like spin fluctuations of Mn ions diluted in CdTe (bulk and quantum wells) can be detected through the Kerr rotation associated to excitonic transitions. Zeeman transitions within and between hyperfine multiplets are clearly observed in zero and small magnetic fields and reveal the local symmetry because of crystal field and strain. The linewidths of these resonances are close to the dipolar limit. The sensitivity is high enough to open the way towards the detection of a few spins in systems where the decoherence due to nuclear spins can be suppressed by isotopic enrichment, and towards spin resonance microscopy with important applications in biology and materials science. PMID:26382137

  18. Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation.

    PubMed

    Schellekens, A J; Kuiper, K C; de Wit, R R J C; Koopmans, B

    2014-01-01

    Spin currents have an important role in many proposed spintronic devices, as they govern the switching process of magnetic bits in random access memories or drive domain wall motion in magnetic shift registers. The generation of these spin currents has to be fast and energy efficient for realization of these envisioned devices. Recently it has been shown that femtosecond pulsed-laser excitation of thin magnetic films creates intense and ultrafast spin currents. Here we utilize this method to change the orientation of the magnetization in a magnetic bilayer by spin-transfer torque on sub-picosecond timescales. By analysing the dynamics of the magnetic bilayer after laser excitation, the rich physics governing ultrafast spin-transfer torque are elucidated opening up new pathways to ultrafast magnetization reversal, but also providing a new method to quantify optically induced spin currents generated on femtosecond timescales. PMID:25007881

  19. Controllable magnetic correlation between two impurities by spin-orbit coupling in graphene

    PubMed Central

    Hu, F. M.; Kou, Liangzhi; Frauenheim, Thomas

    2015-01-01

    Two magnetic impurities on the edge of a zigzag graphene nanoribbon strongly interact with each other via indirect coupling, which can be mediated by conducting carriers. By means of Quantum Monte Carlo (QMC) simulations, we find that the spin-orbit coupling λ and the chemical potential μ in system can be used to drive the transition of local-spin exchange from ferromagnetism to anti-ferromagnetism. Since the tunable ranges for λ and μ in graphene are experimentally reachable, we thus open the possibilities for its device application. The symmetry in spatial distribution is broken by the vertical and the transversal spin-spin correlations due to the effect of spin-orbit coupling, leading to the spatial anisotropy of spin exchange, which distinguish our findings from the case in normal Fermi liquid. PMID:25754911

  20. Versatile microwave-driven trapped ion spin system for quantum information processing.

    PubMed

    Piltz, Christian; Sriarunothai, Theeraphot; Ivanov, Svetoslav S; Wölk, Sabine; Wunderlich, Christof

    2016-07-01

    Using trapped atomic ions, we demonstrate a tailored and versatile effective spin system suitable for quantum simulations and universal quantum computation. By simply applying microwave pulses, selected spins can be decoupled from the remaining system and, thus, can serve as a quantum memory, while simultaneously, other coupled spins perform conditional quantum dynamics. Also, microwave pulses can change the sign of spin-spin couplings, as well as their effective strength, even during the course of a quantum algorithm. Taking advantage of the simultaneous long-range coupling between three spins, a coherent quantum Fourier transform-an essential building block for many quantum algorithms-is efficiently realized. This approach, which is based on microwave-driven trapped ions and is complementary to laser-based methods, opens a new route to overcoming technical and physical challenges in the quest for a quantum simulator and a quantum computer. PMID:27419233

  1. Control of spin dynamics in a two-dimensional electron gas by electromagnetic dressing

    NASA Astrophysics Data System (ADS)

    Pervishko, A. A.; Kibis, O. V.; Morina, S.; Shelykh, I. A.

    2015-11-01

    We solved the Schrödinger problem for a two-dimensional electron gas (2DEG) with the Rashba spin-orbit interaction in the presence of a strong high-frequency electromagnetic field (dressing field). The found eigenfunctions and eigenenergies of the problem are used to describe the spin dynamics of the dressed 2DEG within the formalism of the density matrix response function. Solving the equations of spin dynamics, we show that the dressing field can switch the spin relaxation in the 2DEG between the cases corresponding to the known Elliott-Yafet and D'yakonov-Perel' regimes. As a result, the spin properties of the 2DEG can be tuned by a high-frequency electromagnetic field. The present effect opens an unexplored way for controlling the spin with light and, therefore, forms the physical prerequisites for creating light-tuned spintronics devices.

  2. Electrical control of spin in topological insulators

    NASA Astrophysics Data System (ADS)

    Chang, Kai

    2012-02-01

    by changing the gate voltage. It provides us a new way to control surface magnetism electrically. The gap opened by doped magnetic ions can lead to a short-range Bloembergen-Rowland interaction. The competition among the Heisenberg, Ising, and DM terms leads to rich spin configurations and an anomalous Hall effect on different lattices [4]. There are many proposals for quantum computation scheme are based on the spin in semiconductor quantum dots. Topological insulator quantum dots display a very different behavior with that of conventional semiconductor quantum dots [5]. In sharp contrast to conventional semiconductor quantum dots, the quantum states in the gap of the HgTe QD are fully spin-polarized and show ring-like density distributions near the boundary of the QD and optically dark. The persistent charge currents and magnetic moments, i.e., the Aharonov-Bohm effect, can be observed in such a QD structure. This feature offers us a practical way to detect these exotic ring-like edge states by using the SQUID technique. [0pt]Refs: [1] W. Yang, Kai Chang, and S. C. Zhang, Phys. Rev. Lett. 100, 056602 (2008); J. Li and Kai Chang, Appl. Phys. Lett. 95, 222110 (2009). [2] L. B. Zhang, Kai Chang, X. C. Xie, H. Buhmann and L. W. Molenkamp, New J. Phys. 12, 083058 (2010). [3] L. B. Zhang, F. Cheng, F. Zhai and Kai Chang, Phys. Rev. B 83 081402(R) (2011); Z. H. Wu, F. Zhai, F. M. Peeters, H. Q. Xu and Kai Chang, Phys, Rev. Lett. 106, 176802 (2011). [4] J. J. Zhu, D. X. Yao, S. C. Zhang, and Kai Chang, Phys. Rev. Lett. 106, 097201 (2011). [5] Kai Chang, and Wen-Kai Lou, Phys. Rev. Lett. 106, 206802 (2011).

  3. Spin Funneling for Enhanced Spin Injection into Ferromagnets.

    PubMed

    Sayed, Shehrin; Diep, Vinh Q; Camsari, Kerem Yunus; Datta, Supriyo

    2016-01-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

  4. Spin Funneling for Enhanced Spin Injection into Ferromagnets

    NASA Astrophysics Data System (ADS)

    Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

    2016-07-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

  5. Electron-spin dynamics induced by photon spins

    NASA Astrophysics Data System (ADS)

    Bauke, Heiko; Ahrens, Sven; Keitel, Christoph H.; Grobe, Rainer

    2014-10-01

    Strong rotating magnetic fields may cause a precession of the electron's spin around the rotation axis of the magnetic field. The superposition of two counterpropagating laser beams with circular polarization and opposite helicity features such a rotating magnetic field component but also carries spin. The laser's spin density, which can be expressed in terms of the laser's electromagnetic fields and potentials, couples to the electron's spin via a relativistic correction to the Pauli equation. We show that the quantum mechanical interaction of the electron's spin with the laser's rotating magnetic field and with the laser's spin density counteract each other in such a way that a net spin rotation remains with a precession frequency that is much smaller than the frequency one would expect from the rotating magnetic field alone. In particular, the frequency scales differently with the laser's electric field strength depending on whether relativistic corrections are taken into account or not. Thus, the relativistic coupling of the electron's spin to the laser's spin density changes the dynamics not only quantitatively but also qualitatively as compared to the nonrelativistic theory. The electron's spin dynamics are a genuine quantum mechanical relativistic effect.

  6. All-electric spin transistor using perpendicular spins

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hoon; Bae, Joohyung; Min, Byoung-Chul; Kim, Hyung-jun; Chang, Joonyeon; Koo, Hyun Cheol

    2016-04-01

    All-electric spin transistor is demonstrated using perpendicular spins in an InAs quantum well channel. For the injection and detection of perpendicular spins in the quantum well channel, we use Tb20Fe62Co18/Co40Fe40B20 electrodes, where the Tb20Fe62Co18 layer produces the perpendicular magnetization and the Co40Fe40B20 layer enhances the spin polarization. In this spin transistor device, a gate-controlled spin signal as large as 80 mΩ is observed at 10 K without an external magnetic field. In order to confirm the spin injection and relaxation independently, we measure the three-terminal Hanle effect with an in-plane magnetic field, and obtain a spin signal of 1.7 mΩ at 10 K. These results clearly present that the electric field is an efficient way to modulate spin orientation in a strong spin-orbit interaction system.

  7. Spin Funneling for Enhanced Spin Injection into Ferromagnets

    PubMed Central

    Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

    2016-01-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

  8. Muon spin rotation studies

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The bulk of the muon spin rotation research work centered around the development of the muon spin rotation facility at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL). The collimation system was both designed and fabricated at Virginia State University. This improved collimation system, plus improvements in detectors and electronics enabled the acquisition of spectra free of background out to 15 microseconds. There were two runs at Brookhaven in 1984, one run was devoted primarily to beam development and the other run allowed several successful experiments to be performed. The effect of uniaxial strain on an Fe(Si) crystal at elevated temperature (360K) was measured and the results are incorporated herein. A complete analysis of Fe pulling data taken earlier is included.

  9. Spin effects and compactification

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.; Teryaev, Oleg V.

    2014-02-01

    We consider the dynamics of Dirac particles moving in the curved spaces with one coordinate subjected to compactification and thus interpolating smoothly between three- and two-dimensional spaces. We use the model of compactification, which allows us to perform the exact Foldy-Wouthuysen transformation of the Dirac equation and then to obtain the exact solutions of the equations of motion for momentum and spin in the classical limit. The spin precesses with the variable angular velocity, and a "flick" may appear in the remnant two-dimensional space once or twice during the period. We note an irreversibility in the particle dynamics because the particle can always penetrate from the lower-dimensional region to the higher-dimensional region, but not inversely.

  10. Art of spin decomposition

    SciTech Connect

    Chen Xiangsong; Sun Weimin; Wang Fan; Goldman, T.

    2011-04-01

    We analyze the problem of spin decomposition for an interacting system from a natural perspective of constructing angular-momentum eigenstates. We split, from the total angular-momentum operator, a proper part which can be separately conserved for a stationary state. This part commutes with the total Hamiltonian and thus specifies the quantum angular momentum. We first show how this can be done in a gauge-dependent way, by seeking a specific gauge in which part of the total angular-momentum operator vanishes identically. We then construct a gauge-invariant operator with the desired property. Our analysis clarifies what is the most pertinent choice among the various proposals for decomposing the nucleon spin. A similar analysis is performed for extracting a proper part from the total Hamiltonian to construct energy eigenstates.

  11. Neutron phase spin echo

    NASA Astrophysics Data System (ADS)

    Piegsa, Florian M.; Hautle, Patrick; Schanzer, Christian

    2016-04-01

    A novel neutron spin resonance technique is presented based on the well-known neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of 4 ×10-7 can be resolved, corresponding to an energy resolution of better than 3 neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing energy resolutions in the 10 peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  12. Ground State Spin Logic

    NASA Astrophysics Data System (ADS)

    Whitfield, James; Faccin, Mauro; Biamonte, Jacob

    2013-03-01

    Designing and optimizing cost functions and energy landscapes is a problem encountered in many fields of science and engineering. These landscapes and cost functions can be embedded and annealed in experimentally controllable spin Hamiltonians. Using an approach based on group theory and symmetries, we examine the embedding of Boolean logic gates into the ground-state subspace of such spin systems. We describe parameterized families of diagonal Hamiltonians and symmetry operations which preserve the ground-state subspace encoding the truth tables of Boolean formulas. The ground-state embeddings of adder circuits are used to illustrate how gates are combined and simplified using symmetry. Our work is relevant for experimental demonstrations of ground-state embeddings found in both classical optimization as well as adiabatic quantum optimization.

  13. Magnetic nano-oscillator driven by pure spin current

    NASA Astrophysics Data System (ADS)

    Demidov, Vladislav E.; Urazhdin, Sergei; Ulrichs, Henning; Tiberkevich, Vasyl; Slavin, Andrei; Baither, Dietmar; Schmitz, Guido; Demokritov, Sergej O.

    2012-12-01

    With the advent of pure-spin-current sources, spin-based electronic (spintronic) devices no longer require electrical charge transfer, opening new possibilities for both conducting and insulating spintronic systems. Pure spin currents have been used to suppress noise caused by thermal fluctuations in magnetic nanodevices, amplify propagating magnetization waves, and to reduce the dynamic damping in magnetic films. However, generation of coherent auto-oscillations by pure spin currents has not been achieved so far. Here we demonstrate the generation of single-mode coherent auto-oscillations in a device that combines local injection of a pure spin current with enhanced spin-wave radiation losses. Counterintuitively, radiation losses enable excitation of auto-oscillation, suppressing the nonlinear processes that prevent auto-oscillation by redistributing the energy between different modes. Our devices exhibit auto-oscillations at moderate current densities, at a microwave frequency tunable over a wide range. These findings suggest a new route for the implementation of nanoscale microwave sources for next-generation integrated electronics.

  14. Duality Between Spin Networks and the 2D Ising Model

    NASA Astrophysics Data System (ADS)

    Bonzom, Valentin; Costantino, Francesco; Livine, Etera R.

    2016-06-01

    The goal of this paper is to exhibit a deep relation between the partition function of the Ising model on a planar trivalent graph and the generating series of the spin network evaluations on the same graph. We provide respectively a fermionic and a bosonic Gaussian integral formulation for each of these functions and we show that they are the inverse of each other (up to some explicit constants) by exhibiting a supersymmetry relating the two formulations. We investigate three aspects and applications of this duality. First, we propose higher order supersymmetric theories that couple the geometry of the spin networks to the Ising model and for which supersymmetric localization still holds. Secondly, after interpreting the generating function of spin network evaluations as the projection of a coherent state of loop quantum gravity onto the flat connection state, we find the probability distribution induced by that coherent state on the edge spins and study its stationary phase approximation. It is found that the stationary points correspond to the critical values of the couplings of the 2D Ising model, at least for isoradial graphs. Third, we analyze the mapping of the correlations of the Ising model to spin network observables, and describe the phase transition on those observables on the hexagonal lattice. This opens the door to many new possibilities, especially for the study of the coarse-graining and continuum limit of spin networks in the context of quantum gravity.

  15. Dusty spin plasmas

    SciTech Connect

    Brodin, G.; Marklund, M.; Zamanian, J.

    2008-09-07

    A fluid model is derived, taking into account the effect of spin magnetization of electrons as well as of magnetized dust grains. The model is analyzed, and it is found that both the acoustic velocity and the Alfven velocity is decreased due to the magnetization effects. Furthermore, for low-temperature high density plasmas, it is found that the linear wave modes can be unstable, due to the magnetic attraction of individual fluid elements. The significance of our results are discussed.

  16. Spin Physics at HERMES

    SciTech Connect

    Contalbrigo, M.

    2007-11-19

    The HERMES experiment at DESY is a second generation experiment to study the spin structure of the nucleon by measuring not only inclusive but also semi-inclusive and exclusive processes in deep-inelastic lepton scattering where both beam and target can be polarised. An overview of finalized measurements and an outlook to upcoming new results is given for data taken with hydrogen and deuterium targets with longitudinal and transverse nucleon polarisation.

  17. Spin and gravitation

    NASA Technical Reports Server (NTRS)

    Ray, J. R.

    1982-01-01

    The fundamental variational principle for a perfect fluid in general relativity is extended so that it applies to the metric-torsion Einstein-Cartan theory. Field equations for a perfect fluid in the Einstein-Cartan theory are deduced. In addition, the equations of motion for a fluid with intrinsic spin in general relativity are deduced from a special relativistic variational principle. The theory is a direct extension of the theory of nonspinning fluids in special relativity.

  18. Recovery of spinning satellites

    NASA Technical Reports Server (NTRS)

    Coppey, J. M.; Mahaffey, W. R.

    1977-01-01

    The behavior of a space tug and a spinning satellite in a coupled configuration was simulated and analyzed. A docking concept was developed to investigate the requirements pertaining to the design of a docking interface. Sensing techniques and control requirements for the chase vehicle were studied to assess the feasibility of an automatic docking. The effects of nutation dampers and liquid propellant slosh motion upon the docking transient were investigated.

  19. Spinning out a star.

    PubMed

    Lord, Michael D; Mandel, Stanley W; Wager, Jeffrey D

    2002-06-01

    Spinouts rarely take off; most, in fact, fall into one or more of four traps that doom them from the start. Some companies spin out ventures that are too close to the core of their businesses, in effect selling off their crown jewels. Sometimes, a parent company uses the spinout primarily to pawn off debt or expenses or to quickly raise external capital for itself. Other times, a company may try to spin out an area of its business that lacks one or more of the critical legs of a successful company--a coherent business model, say, or a solid financial base. And in many cases, parent companies can't bring themselves to sever their ownership ties and give up control of their spinouts. R.J. Reynolds, the tobacco giant, managed to avoid these traps when it successfully spun out a most unlikely venture, the pharmaceutical company Targacept. As the story illustrates, the problem with spinouts is similar to the problem of rich children. Their parents have the wherewithal to spoil them or shelter them or cling to them, but what they need is tough love and discipline--much the same discipline that characterizes successful start-ups. R.J. Reynolds recognized that it didn't know that much about the pharmaceutical business and couldn't merely try to spin out a small clone of itself. It had to treat the venture as if it were essentially starting from scratch, with a passionate entrepreneurial leader, a solid business plan, help from outside partners in the industry, and ultimately substantial venture backing. That these lessons are less obvious to executives contemplating spinning out ventures closer to their core businesses may be why so many spinouts fail. PMID:12048993

  20. Spin-driven inflation

    NASA Astrophysics Data System (ADS)

    Obukhov, Yuri N.

    1993-11-01

    Following recent studies of Ford, we suggest - in the framework of general relativity - an inflationary cosmological model with self-interacting spinning matter. A generalization of the standard fluid model is discussed and estimates of the physical parameters of the evolution are given. I would like to thank Professor Friedrich W. Hehl for the careful reading of the manuscript and useful advice. This research was supported by the Alexander von Humboldt Foundation (Bonn).