395 research outputs found

    Understanding Anthropological Understanding: for a merological anthropology

    Get PDF
    In this paper I argue for a merological anthropology in which ideas of ‘partiality’ and ‘practical adequacy’ provide a way out of the impasse of relativism which is implied by post-modernism and the related abandonment of a concern with ‘truth’. Ideas such as ‘aptness’ and ‘faithfulness’ enable us to re-establish empirical foundations without having to espouse a simple realism which has been rightly criticised. Ideas taken from ethnomethodology, particularly the way we bootstrap from ‘practical adequacy’ to ‘warrants for confidence’ point to a merological anthropology in which we recognize that we do not and cannot know everything, but that we can have reasons for being confident in the little we know

    Magneto-Transport Properties of Doped RuSr2_2GdCu2_2O8_8

    Get PDF
    RuSr2_2GdCu2_2O8_8, in which magnetic order and superconductivity coexist with TMagneticT_{Magnetic}≫\ggTcT_c, is a complex material which poses new and important questions to our understanding of the interplay between magnetic and superconducting (SC) order. Resistivity, Hall effect and thermopower measurements on sintered ceramic RuSr2_2GdCu2_2O8_8 are presented, together with results on a broad range of substituted analogues. The Hall effect and thermopower both show anomalous decreases below TMagneticT_{Magnetic} which may be explained within a simple two-band model by a transition from localized to more itinerant behavior in the RuO2_2 layer at TMagneticT_{Magnetic}.Comment: 10 pages, 7 figures, submitted to Phys. Rev. B., correspondence to [email protected]

    Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity

    Full text link
    The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx} orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized description of the in-plane electron correlations the superconducting order parameter is found to be a orbital-singlet spin-triplet with two spatial components. The spatial anisotropy is 7%. The different components of the order parameter give rise to two-dimensional gapless fluctuations. The phase transition is of third order. The temperature dependence of the pair density, specific heat, NQR, Knight shift, and susceptibility are in agreement with experimental results.Comment: 20 pages REVTEX, 3 figure

    Crystal structure, electronic, and magnetic properties of the bilayered rhodium oxide Sr3Rh2O7

    Get PDF
    The bilayered rhodium oxide Sr3Rh2O7 was synthesized by high-pressure and high-temperature heating techniques. The single-phase polycrystalline sample of Sr3Rh2O7 was characterized by measurements of magnetic susceptibility, electrical resistivity, specific heat, and thermopower. The structural characteristics were investigated by powder neutron diffraction study. The rhodium oxide Sr3Rh2O7 [Bbcb, a = 5.4744(8) A, b = 5.4716(9) A, c = 20.875(2) A] is isostructural to the metamagnetic metal Sr3Ru2O7, with five 4d electrons per Rh, which is electronically equivalent to the hypothetic bilayered ruthenium oxide, where one electron per Ru is doped into the Ru-327 unit. The present data show the rhodium oxide Sr3Rh2O7 to be metallic with enhanced paramagnetism, similar to Sr3Ru2O7. However, neither manifest contributions from spin fluctuations nor any traces of a metamagnetic transition were found within the studied range from 2 K to 390 K below 70 kOe.Comment: To be published in PR

    Entrapment of a Network of Domain Walls

    Full text link
    We explore the idea of a network of defects to live inside a domain wall in models of three real scalar fields, engendering the Z_2 x Z_3 symmetry. The field that governs the Z_2 symmetry generates a domain wall, and entraps the hexagonal network formed by the three-junctions of the model of two scalar fields that describes the remaining Z_3 symmetry. If the host domain wall bends to the spherical form, in the thin wall approximation there may appear non-topological structures hosting networks that accept diverse patterns. If Z_3 is also broken, the model may generate a buckyball containing sixty junctions, a fullerene-like structure. Applications to cosmology are outlined.Comment: Revtex, 4 pages, 2 ps figures; version to appear in Phys. Rev. D, Rapid Communicatio

    Domain wall generation by fermion self-interaction and light particles

    Get PDF
    A possible explanation for the appearance of light fermions and Higgs bosons on the four-dimensional domain wall is proposed. The mechanism of light particle trapping is accounted for by a strong self-interaction of five-dimensional pre-quarks. We obtain the low-energy effective action which exhibits the invariance under the so called \tau-symmetry. Then we find a set of vacuum solutions which break that symmetry and the five-dimensional translational invariance. One type of those vacuum solutions gives rise to the domain wall formation with consequent trapping of light massive fermions and Higgs-like bosons as well as massless sterile scalars, the so-called branons. The induced relations between low-energy couplings for Yukawa and scalar field interactions allow to make certain predictions for light particle masses and couplings themselves, which might provide a signature of the higher dimensional origin of particle physics at future experiments. The manifest translational symmetry breaking, eventually due to some gravitational and/or matter fields in five dimensions, is effectively realized with the help of background scalar defects. As a result the branons acquire masses, whereas the ratio of Higgs and fermion (presumably top-quark) masses can be reduced towards the values compatible with the present-day phenomenology. Since the branons do not couple to fermions and the Higgs bosons do not decay into branons, the latter ones are essentially sterile and stable, what makes them the natural candidates for the dark matter in the Universe.Comment: 34 pages, 2 figures, JHEP style,few important refs. adde

    B->eta(') Form Factors in QCD

    Full text link
    We calculate the semileptonic form factors f+B→η(q2)f_+^{B\to \eta}(q^2) and f+B→η′(q2)f_+^{B\to \eta'}(q^2) from QCD sum rules on the light-cone (LCSRs), to NLO in QCD, and for small to moderate q^2, 0≤q2≤16GeV20\leq q^2\leq 16 {\rm GeV}^2. We include in particular the so-called singlet contribution, i.e.\ weak annihilation of the B meson with the emission of two gluons which, thanks to the U(1)A_{\rm A} anomaly, couple directly to \etap. This effect is included to leading-twist accuracy. This contribution has been neglected in previous calculations of the form factors from LCSRs. We find that the singlet contribution to f+B→η′f_+^{B\to \eta'} can be up to 20%, while that to f+B→ηf_+^{B\to \eta} is, as expected, much smaller and below 3%. We also suggest to measure the ratio B(B→η′eν)/B(B→ηeν){\cal B}(B\to\eta' e \nu)/{\cal B}(B\to \eta e \nu) to better constrain the size of the singlet contribution.Comment: 21 pages; version to appear in JHE

    Assessing the activity of faults in continental interiors: Palaeoseismic insights from SE Kazakhstan

    Get PDF
    The presence of fault scarps is a first-order criterion for identifying active faults. Yet the preservation of these features depends on the recurrence interval between surface rupturing events, combined with the rates of erosional and depositional processes that act on the landscape. Within arid continental interiors single earthquake scarps can be preserved for thousands of years, and yet the interval between surface ruptures on faults in these regions may be much longer, such that the lack of evidence for surface faulting in the morphology may not preclude activity on those faults. In this study we investigate the 50 km-long ‘Toraigyr’ thrust fault in the northern Tien Shan. From palaeoseismological trenching we show that two surface rupturing earthquakes occurred in the last 39.9±2.7 ka\textbf{39.9±2.7 ka} BP, but only the most recent event (3.15–3.6 ka BP) has a clear morphological expression. We conclude that a landscape reset took place in between the two events, likely as a consequence of the climatic change at the end of the last glacial maximum. These findings illustrate that in the Tien Shan evidence for the most recent active faulting can be easily obliterated by climatic processes due to the long earthquake recurrence intervals. Our results illustrate the problems related to the assessment of active tectonic deformation and seismic hazard assessments in continental interior settings.This study was financed by NERC and ESRC (Earthquakes without Frontiers project, Grant code: EwF_NE/J02001X/1_1), and the Centre for Observation and Modelling of Earthquakes and Tectonics (COMET). KOMPSAT-2 imagery was obtained through a category-1 award to RTW. EJC thanks St. Edmund Hall for travel support. RTW was supported during this research by a University Research Fellowship from the Royal Society of London

    IFCC Working Group Recommendations for Assessing Commutability Part 3 : Using the Calibration Effectiveness of a Reference Material

    Get PDF
    A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator based on its ability to fulfill its intended use in a calibration traceability scheme to produce equivalent clinical sample (CS) results among different measurement procedures (MPs) for the same measurand. Three sources of systematic error are elucidated in the context of creating the calibration model for translating MP signals to measurand amounts: calibration fit, calibrator level trueness, and commutability. An example set of 40 CS results from 7 MPs is used to illustrate estimation of bias and variability for each MP. The candidate RM is then used to recalibrate each MP, and its effectiveness in reducing the systematic error among the MPs within an acceptable level of equivalence based on medical requirements confirms its commutability for those MPs. The RM is declared noncommutable for MPs for which, after recalibration, the CS results do not agree with those from other MPs. When a lack of agreement is found, other potential causes, including lack of calibration fit, should be investigated before concluding the RM is noncommutable. The RM is considered fit for purpose for those MPs where commutability is demonstrate

    IFCC Working Group Recommendations for Assessing Commutability Part 2 : Using the Difference in Bias between a Reference Material and Clinical Samples

    Get PDF
    A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator, trueness control, or external quality assessment sample based on the difference in bias between an RM and clinical samples (CSs) measured using 2 different measurement procedures (MPs). This difference in bias is compared with a criterion based on a medically relevant difference between an RM and CS results to make a conclusion regarding commutability. When more than 2 MPs are included, the commutability is assessed pairwise for all combinations of 2 MPs. This approach allows the same criterion to be used for all combinations of MPs included in the assessment. The assessment is based on an error model that allows estimation of various random and systematic sources of error, including those from sample-specific effects of interfering substances. An advantage of this approach is that the difference in bias between an RM and the average bias of CSs at the concentration (i.e., amount of substance present or quantity value) of the RM is determined and its uncertainty estimated. An RM is considered fit for purpose for those MPs for which commutability is demonstrated
    • …
    corecore