33,968 research outputs found

    On the unlikelihood of specific long range forces in immunologic and enzymatic reactions

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    In the past few years, a great many experiments have been performed by Rothen (24, 25) which he has interpreted as suggesting that antigen and antibody, and enzyme and substrate proteins, can react specifically, although separated by distances of hundreds of angstroms. This hypothesis seems to conflict with evidence accumulated from many other investigations indicating that short range interactions, involving distances usually associated with electrostatic and van der Waals’ forces, and hydrogen bonds, of the order of 5 A, operate in these reactions. We have therefore engaged in a critical analysis of the experimental techniques used by Rothen to determine whether some interpretation other than that invoking the existence of specific long range forces could be found to explain his experimental results

    Representing Childhood and Forced Migration: Narratives of Borders and Belonging in European Screen Content for Children

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    This article explores representations of childhood and forced migration within a selection of European screen content for and about children. Based on the findings of a research project that examined the intersections of children’s media, diversity, and forced migration in Europe (www.euroarabchildrensmedia.org), funded by the UK’s Arts and Humanities Research Council, the article highlights different ways in which ideas of borders and belonging are constructed and deconstructed in a selection of films and television programmes that feature children with an immigration background. Drawing on ideas around the “politics of pity” (Arendt), the analysis explores conditions under which narratives of otherness arise when it comes to representing forcibly displaced children within European-produced children’s screen media. It also examines screen media that destabilize borders of “us” and “the other” by emphasizing the agency of children from migration backgrounds, and revealing both the similarities and the differences between European children with immigration backgrounds and White European-born children. It is argued here that, operating according to the notions of living “together-in-difference” (Ang), “narratability” (Chouliaraki and Stolic), and “the struggle for belonging” (Kebede), these representations destabilize narratives of borders and otherness, suggesting that children with a family history of immigration “belong” to European societies in the same ways as White European-born children

    Measurements of Partial Reflections at 3.18 Mhz Using the CW Radar Technique

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    An equipment for measuring partial reflections using the FM-CW-radar principle at 3.18 MHz, installed at the Ionospheric Observatory Juliusruh of the CISTP (HHI), is described. The linear FM-chirp of 325 kHz bandwidth is Gaussian-weighted in amplitude and gives a height resolution of 1.5 km (chirp length is 0.6 sec). Preliminary results are presented for the first observation period in winter 1982/83

    Magnetic Field Induced Phase Transitions in YBa2Cu4O8

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    The cc-axis resistivity measurements in YBa_2Cu_4O_8 from Hussey et al. for magnetic field orientations along the c-axis as well as within the ab-plane are analyzed and interpreted using the scaling theory for static and dynamic classical critical phenomena. We identify a superconductor to normal conductor transition for both field orientations as well as a normal conductor to insulator transition at a critical field H_c||a with dynamical critical exponent z=1, leading to a multicritical point where superconducting, normal conducting and insulating phases coexist

    Fundamental constraints for the mechanism of superconductivity in cuprates

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    Considerable progress has been made over the last decade in understanding the phenomenological properties of the cuprate high-Tc_{c} superconductors and in producing well characterized high quality materials. Nevertheless, the pairing mechanism itself remains controversial. We establish a criterion to test theories for layered superconductors relying on a substantial interlayer contribution. The criterion is based on the ratio of the interlayer contribution to the total superfluid density, which is traced back to the inverse squared effective mass anisotropy. The anisotropy can be measured rather accurately by various experimental techniques. It turns out that models relying on interlayer pairing cannot be considered as serious candidates for the mechanism of superconductivity in cuprate superconductors

    Radiation Damping Effects in Two Level Maser Oscillators

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    Several experiments [1,2] have noted recently that when an inverted two-level spin system was permitted to radiate spontaneously, the resulting oscillation was characterized by an appreciable amplitude modulation. The phenomenon was first believed to be the result of interference of different spin packets in an inhomogeneously broadened spectrum [1]. A theoretical analysis (which will be reported separately) shows that this is not the case. The spins are not independent but are coupled together by means of their radiation field. This explanation has since been by its original authors