1,884 research outputs found

    Language-universal constraints on the segmentation of English

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    Two word-spotting experiments are reported that examine whether the Possible-Word Constraint (PWC) [1] is a language-specific or language-universal strategy for the segmentation of continuous speech. The PWC disfavours parses which leave an impossible residue between the end of a candidate word and a known boundary. The experiments examined cases where the residue was either a CV syllable with a lax vowel, or a CVC syllable with a schwa. Although neither syllable context is a possible word in English, word-spotting in both contexts was easier than with a context consisting of a single consonant. The PWC appears to be language-universal rather than language-specific

    Iron Displacements and Magnetoelastic Coupling in the Spin-Ladder Compound BaFe2Se3

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    We report long-range ordered antiferromagnetism concomitant with local iron displacements in the spin-ladder compound BaFe2_2Se3_3. Short-range magnetic correlations, present at room temperature, develop into long-range antiferromagnetic order below TN_N = 256 K, with no superconductivity down to 1.8 K. Built of ferromagnetic Fe4_4 plaquettes, the magnetic ground state correlates with local displacements of the Fe atoms. These iron displacements imply significant magnetoelastic coupling in FeX4_4-based materials, an ingredient hypothesized to be important in the emergence of superconductivity. This result also suggests that knowledge of these local displacements is essential for properly understanding the electronic structure of these systems. As with the copper oxide superconductors two decades ago, our results highlight the importance of reduced dimensionality spin ladder compounds in the study of the coupling of spin, charge, and atom positions in superconducting materials

    Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure

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    The temperature and pressure dependence of the partial density of phonon states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear inelastic scattering (NIS). The high energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features towards higher energies by ~4% with decreasing temperature from 296 K to 10 K was found. However, no detectable change at the tetragonal - orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase of the superconducting temperature from 8 K to 34 K, results in an increase of the optical phonon mode energies at 296 K by ~12%, and an even more pronounced increase for the lowest-lying transversal acoustic mode. Despite these strong pressure-induced modifications of the phonon-DOS we conclude that the pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the framework of classical electron-phonon coupling. This result suggests the importance of spin fluctuations to the observed superconductivity

    Orbital Selective Magnetism in the Spin-Ladder Iron Selenides Ba1x_{1-x}Kx_{x}Fe2_2Se3_3

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    Here we show that the 2.80(8) {\mu}B/Fe block antiferromagnetic order of BaFe2Se3 transforms into stripe antiferromagnetic order in KFe2Se3 with a decrease in moment to 2.1(1) {\mu}B/Fe. This reduction is larger than expected from the change in electron count from Ba2+^{2+} to K+^{+}, and occurs with the loss of the displacements of Fe atoms from ideal positions in the ladders, as found by neutron pair distribution function analysis. Intermediate compositions remain insulating, and magnetic susceptibility measurements show a suppression of magnetic order and probable formation of a spin-glass. Together, these results imply an orbital-dependent selection of magnetic versus bonded behavior, driven by relative bandwidths and fillings.Comment: Final versio

    Cost-effectiveness of continuous glucose monitoring and intensive insulin therapy for type 1 diabetes

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    <p>Abstract</p> <p>Background</p> <p>Our objective was to determine the cost-effectiveness of Continuous Glucose Monitoring (CGM) technology with intensive insulin therapy compared to self-monitoring of blood glucose (SMBG) in adults with type 1 diabetes in the United States.</p> <p>Methods</p> <p>A Markov cohort analysis was used to model the long-term disease progression of 12 different diabetes disease states, using a cycle length of 1 year with a 33-year time horizon. The analysis uses a societal perspective to model a population with a 20-year history of diabetes with mean age of 40. Costs are expressed in US2007,effectivenessinqualityadjustedlifeyears(QALYs).Parameterestimatesandtheirrangeswerederivedfromtheliterature.UtilityestimatesweredrawnfromtheEQ5Dcatalogue.ProbabilitieswerederivedfromtheDiabetesControlandComplicationsTrial(DCCT),theUnitedKingdomProspectiveDiabetesStudy(UKPDS),andtheWisconsinEpidemiologicStudyofDiabeticRetinopathy.CostsandQALYswerediscountedat3US 2007, effectiveness in quality-adjusted life years (QALYs). Parameter estimates and their ranges were derived from the literature. Utility estimates were drawn from the EQ-5D catalogue. Probabilities were derived from the Diabetes Control and Complications Trial (DCCT), the United Kingdom Prospective Diabetes Study (UKPDS), and the Wisconsin Epidemiologic Study of Diabetic Retinopathy. Costs and QALYs were discounted at 3% per year. Univariate and Multivariate probabilistic sensitivity analyses were conducted using 10,000 Monte Carlo simulations.</p> <p>Results</p> <p>Compared to SMBG, use of CGM with intensive insulin treatment resulted in an expected improvement in effectiveness of 0.52 QALYs, and an expected increase in cost of 23,552, resulting in an ICER of approximately 45,033/QALY.Forawillingnesstopay(WTP)of45,033/QALY. For a willingness-to-pay (WTP) of 100,000/QALY, CGM with intensive insulin therapy was cost-effective in 70% of the Monte Carlo simulations.</p> <p>Conclusions</p> <p>CGM with intensive insulin therapy appears to be cost-effective relative to SMBG and other societal health interventions.</p

    Magnetism and structure of LixCoO2 and comparison to NaxCoO2

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    The magnetic properties and structure of LixCoO2 for x between 0.5 and 1.0 are reported. Co4+ is found to be high-spin in LixCoO2 for x between 0.94 and 1.0 and low-spin for x between 0.50 and 0.78. Weak antiferromagnetic coupling is observed, increasing in strength as more Co4+ is introduced. At an x value of about 0.65, the temperature-independent contribution to the magnetic susceptibility and the electronic contribution to the specific heat are largest. Neutron diffraction analysis reveals that the lithium oxide layer expands perpendicular to the basal plane and the Li ions displace from their ideal octahedral sites with decreasing x. A comparison of the structures of the NaxCoO2 and LixCoO2 systems reveals that the CoO2 layer changes substantially with alkali content in the former but is relatively rigid in the latter. Further, the CoO6 octahedra in LixCoO2 are less distorted than those in NaxCoO2. We postulate that these structural differences strongly influence the physical properties in the two systems
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