2,791 research outputs found

    Nutation versus angular dependent NQR spectroscopy and the impact of underdoping on charge inhomogeneities in YBa2_2Cu3_3Oy_y

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    We describe two different nuclear quadrupole resonance (NQR) based techniques, designed to measure the local asymmetry of the internal electric field gradient, and the tilt angle of the main NQR principal axis z from the crystallographic axis c. These techniques use the dependence of the NQR signal on the duration of the radio frequency (rf) pulse and on the direction of the rf field H1 with respect to the crystal axis. The techniques are applied to oriented powder of YBa2_{2}Cu%_{3}Oy_{y} fully enriched with 63Cu. Measurements were performed at different frequencies, corresponding to different in-plane copper sites with respect to the dopant. Combining the results from both techniques, we conclude that oxygen deficiency in the chain layer lead to a rotation of the NQR main principal axis at the nearby Cu on the CuO2 planes by 20+-degrees. This occurs with no change to the asymmetry. The axis rotation associated with oxygen deficiency means that there must be electric field inhomogeneities in the CuO2 planes only in the vicinity of the missing oxygen.Comment: 9 pages, 10 figure

    The Herbertsmithite Hamiltonian: μ\muSR measurements on single crystals

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    We present transverse field muon spin rotation/relaxation measurements on single crystals of the spin-1/2 kagome antiferromagnet Herbertsmithite. We find that the spins are more easily polarized when the field is perpendicular to the kagome plane. We demonstrate that the difference in magnetization between the different directions cannot be accounted for by Dzyaloshinksii-Moriya type interactions alone, and that anisotropic axial interaction is present.Comment: 8 pages, 3 figures, accepted to JPCM special issue on geometrically frustrated magnetis

    Spin Echo Decay in a Stochastic Field Environment

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    We derive a general formalism with which it is possible to obtain the time dependence of the echo size for a spin in a stochastic field environment. Our model is based on ``strong collisions''. We examine in detail three cases where: (I) the local field is Ising-like, (II) the field distribution is continuous and has a finite second moment, and (III) the distribution is Lorentzian. The first two cases show a T2 minimum effect and are exponential in time cubed for short times. The last case can be approximated by a phenomenological stretched exponential.Comment: 11 pages + 3 postscript figure

    Common Loons Respond Adaptively to a Black Fly that Reduces Nesting Success

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    Nesting birds must often cope with harassment from biting insects, but it is difficult to ascertain what effect such pests might have on breeding success and population dynamics. We tested the hypothesis that a black fly (Simulium annulus) that feeds on the blood of nesting Common Loons (Gavia immer) causes nest abandonment in this charismatic diving bird. In addition, we measured effects of fly-induced abandonment on a loon population, and examined potential predictors of fly abundance and nest abandonment. We also tested a second hypothesis, which holds that loon pairs that abandon a nest owing to flies should often remain at the site for their subsequent nesting attempt, since fly outbreaks last only 1–2 weeks. All predictions of the fly-induced abandonment hypothesis were supported, including strong correlations between fly counts and rate of abandonment, reduced incubation during severe fly years, and increased abandonment during cool springs, which promote longevity of the flies. The correlation between nest abandonment and population breeding success suggests that S. annulus reduced the chick fledging rate by as much as 23% in a year of severe infestation. Fly numbers on loons and their nests were highest when temperatures were high and winds were light. Surprisingly, however, exposure to the prevailing wind increased, not decreased, nest abandonment, perhaps because of wave action. Lake size was inversely and female age directly correlated with abandonment rate, possibly due to food limitation in small lakes and senescence of females, respectively. Finally, pairs that abandoned a first nest renested at the same site with much greater frequency than did pairs that lost eggs to a predator, indicating that loons are capable of responding adaptively to a cause of nest failure that is time- but not space-dependent

    Analisis Perkembangan Kemampuan Keuangan Daerah pada Pemerintah Provinsi Sulawesi Utara Tahun Anggaran 2014-2018

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    This study aims to determine how the development of regional financial capability in the North Sulawesi provincial government from its level of independence, level of dependency, decentralization ratio, and financial growth. The main characteristic of the region's ability to organize its government is the ability in its finances to finance the administration of the regional government. This type of research is qualitative research. Descriptive method is an analytical method used in this thesis research, that is every data - data obtained, analyzed based on theories relevant to the problem to be discussed to obtain the results of the analysis which is then concluded and provides advice. The results of descriptive analysis of the North Cellebes Province LRA APBD data show that from 2014 to 2018, the Regional Original Revenue development is still lacking, has not experienced a significant increase because Transfer Funds still dominate the Regional Revenue of North Cellebes Province. The conclusion is that there has been an improvement even though it is lacking, but based on the calculation of the financial ratios the Financial Ability is still in the near-able valuation

    Sustained expansion of NKT cells and antigen-specific T cells after injection of α-galactosyl-ceramide loaded mature dendritic cells in cancer patients

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    Natural killer T (NKT) cells are distinct glycolipid reactive innate lymphocytes that are implicated in the resistance to pathogens and tumors. Earlier attempts to mobilize NKT cells, specifically, in vivo in humans met with limited success. Here, we evaluated intravenous injection of monocyte-derived mature DCs that were loaded with a synthetic NKT cell ligand, α-galactosyl-ceramide (α-GalCer; KRN-7000) in five patients who had advanced cancer. Injection of α-GalCer-pulsed, but not unpulsed, dendritic cells (DCs) led to \u3e100-fold expansion of several subsets of NKT cells in all patients; these could be detected for up to 6 mo after vaccination. NKT activation was associated with an increase in serum levels of interleukin-12 p40 and IFN-γ inducible protein-10. In addition, there was an increase in memory CD8+ T cells specific for cytomegalovirus in vivo in response to α-GalCer-loaded DCs, but not unpulsed DCs. These data demonstrate the feasibility of sustained expansion of NKT cells in vivo in humans, including patients who have advanced cancer, and suggest that NKT activation might help to boost adaptive T cell immunity in vivo

    Ga NMR study of the local susceptibility in SrCr8Ga4O19: pseudogap and paramagnetic defects

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    We present the first Ga(4f) NMR study of the Cr susceptibility in the archetype of Kagome based frustrated antiferromagnets, SrCr8_{8}Ga4_{4}O19_{19}. Our major finding is that the susceptibility of the frustrated lattice goes through a maximum around 50 K. Our data also supports the existence of paramagnetic ``clusters'' of spins, responsible for the Curie behavior observed in the macroscopic susceptibility at low T. These results set novel features for the constantly debated physics of geometrically frustrated magnets.Comment: 4 pages, 5 figures Submitted to Phys. Rev. Let

    Model-independent analysis for determining mass splittings of heavy baryons

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    We study the hyperfine mass differences of heavy hadrons in the heavy quark effect theory (HQET). The effects of one-gluon exchange interaction are considered for the heavy mesons and baryons. Base on the known experimental data, we predict the masses of some heavy baryons in a model-independent way.Comment: 14 pages, 1 figur

    Evolution from a nodeless gap to d(x2-y2) form in underdoped La(2-x)SrxCuO4

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    Using angle-resolved photoemission (ARPES), it is revealed that the low-energy electronic excitation spectra of highly underdoped superconducting and non-superconducting La(2-x)SrxCuO4 cuprates are gapped along the entire underlying Fermi surface at low temperatures. We show how the gap function evolves to a d(x2-y2) form as increasing temperature or doping, consistent with the vast majority of ARPES studies of cuprates. Our results provide essential information for uncovering the symmetry of the order parameter(s) in strongly underdoped cuprates, which is a prerequisite for understanding the pairing mechanism and how superconductivity emerges from a Mott insulator.Comment: 5 pages, 4 figure
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