1,363 research outputs found
Book Reviews: Poetic Artifice, Levity of Design and On Violence in the Work of J.H. Prynne
Book reviews of the following academic titles: Poetic Artifice: A Theory of Twentieth-Century Poetry by Veronica Forrest-Thomson and Gareth Farmer (ed.), Bristol: Shearsman, 240 pp., 2016. Review by Calum Gardner. Levity of Design: Man and Modernity in the Poetry of J. H. Prynne by Wit Píetrzak, Newcastle upon Tyne: Cambridge Scholars Publishing, 162 pp., 2012. Review by Lisa Jeschke. On Violence in the Work of J. H. Prynne by Matthew Hall, Newcastle upon Tyne: Cambridge Scholars Publishing, 226 pp., 2015. Review by Lisa Jeschke
Cu-based metalorganic systems: an ab initio study of the electronic structure
Within a first principles framework, we study the electronic structure of the
recently synthesized polymeric coordination compound
Cu(II)-2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene (CuCCP), which has been
suggested to be a good realization of a Heisenberg spin-1/2 chain with
antiferromagnetic coupling. By using a combination of classical with ab initio
quantum mechanical methods, we design on the computer reliable modified
structures of CuCCP aimed at studying effects of Cu-Cu coupling strength
variations on this spin-1/2 system. For this purpose, we performed two types of
modifications on CuCCP. In one case, we replaced H in the linker by i) an
electron donating group (NH2) and ii) an electron withdrawing group (CN), while
the other modification consisted in adding H2O and NH3 molecules in the
structure which change the local coordination of the Cu(II) ions. With the
NMTO-downfolding method we provide a quantitative analysis of the modified
electronic structure and the nature of the Cu-Cu interaction paths in these new
structures and discuss its implications for the underlying microscopic model.Comment: 18 pages, 11 figures, final versio
Framework and guidelines for implementing the proposed IUCN Environmental Impact Classification for Alien Taxa (EICAT)
Recently, Blackburn et al. (2014) developed a simple, objective and transparent method for classifying alien taxa in terms of the magnitude of their detrimental environmental impacts in recipient areas. Here, we present a comprehensive framework and guidelines for implementing this method, which we term the Environmental Impact Classification for Alien Taxa, or EICAT. We detail criteria for applying the EICAT scheme in a consistent and comparable fashion, prescribe the supporting information that should be supplied along with classifications, and describe the process for implementing the method. This comment aims to draw the attention of interested parties to the framework and guidelines, and to present them in their entirety in a location where they are freely accessible to any potential users
Boom‐bust dynamics in biological invasions: towards an improved application of the concept
Boom‐bust dynamics – the rise of a population to outbreak levels, followed by a dramatic decline – have been associated with biological invasions and offered as a reason not to manage troublesome invaders. However, boom‐bust dynamics rarely have been critically defined, analyzed, or interpreted. Here, we define boom‐bust dynamics and provide specific suggestions for improving the application of the boom‐bust concept. Boom‐bust dynamics can arise from many causes, some closely associated with invasions, but others occurring across a wide range of ecological settings, especially when environmental conditions are changing rapidly. As a result, it is difficult to infer cause or predict future trajectories merely by observing the dynamic. We use tests with simulated data to show that a common metric for detecting and describing boom‐bust dynamics, decline from an observed peak to a subsequent trough, tends to severely overestimate the frequency and severity of busts, and should be used cautiously if at all. We review and test other metrics that are better suited to describe boom‐bust dynamics. Understanding the frequency and importance of boom‐bust dynamics requires empirical studies of large, representative, long‐term data sets that use clear definitions of boom‐bust, appropriate analytical methods, and careful interpretations
Human amniotic fluid glycoproteins expressing sialyl Lewis carbohydrate antigens stimulate progesterone production in human trophoblasts in vitro
Background: Progesterone is thought to mediate immune modulator effects by regulating uterine responsiveness. The aim of the study was to clarify the effect of transferrin and glycodelin A (former name PP14) as sialyl Lewis X-expressing glycoproteins on the release of progesterone by trophoblast cells in vitro. Methods: Cytotrophoblast cells were prepared from human term placentas by standard dispersion of villous tissue followed by a Percoll gradient centrifugation step. Trophoblasts were incubated with varying concentrations (50-300 mug/ml) of human amniotic fluid- and serum-transferrin as well as with glycodelin A. Culture supernatants were assayed for progesterone, human chorionic gonadotropin (hCG) and cortisol by enzyme immunometric methods. Results: The release of progesterone is increased in amniotic fluid transferrin- and glycodelin A-treated trophoblast cell cultures compared to untreated trophoblast cells. There is no relation between transferrin and the hCG or cortisol production of trophoblast cells. Conclusion: The results suggest that sialyl Lewis carbohydrate antigen-expressing amniotic fluid glycoproteins modulate the endocrine function of trophoblasts in culture by upregulating progesterone production. Copyright (C) 2004 S. Karger AG, Basel
Towards a common description of liquid-state and solid-state cases
Chemically Induced Dynamic Nuclear Polarization (CIDNP) is an efficient method
of creating non-equilibrium polarization of nuclear spins by using chemical
reactions, which have radical pairs as intermediates. The CIDNP effect
originates from (i) electron spin-selective recombination of radical pairs and
(ii) the dependence of the inter-system crossing rate in radical pairs on the
state of magnetic nuclei. The CIDNP effect can be investigated by using
Nuclear Magnetic Resonance(NMR) methods. The gain from CIDNP is then two-fold:
it allows one to obtain considerable amplification of NMR signals; in
addition, it provides a very useful tool for investigating elusive radicals
and radical pairs. While the mechanisms of the CIDNP effect in liquids are
well established and understood, detailed analysis of solid-state CIDNP
mechanisms still remains challenging; likewise a common theoretical frame for
the description of CIDNP in both solids and liquids is missing. Difficulties
in understanding the spin dynamics that lead to the CIDNP effect in the solid-
state case are caused by the anisotropy of spin interactions, which increase
the complexity of spin evolution. In this work, we propose to analyze CIDNP in
terms of level crossing phenomena, namely, to attribute features in the CIDNP
magnetic field dependence to Level Crossings (LCs) and Level Anti-Crossings
(LACs) in a radical pair. This approach allows one to describe liquid-state
CIDNP; the same holds for the solid-state case where anisotropic interactions
play a significant role in CIDNP formation. In solids, features arise
predominantly from LACs, since in most cases anisotropic couplings result in
perturbations, which turn LCs into LACs. We have interpreted the CIDNP
mechanisms in terms of the LC/LAC concept. This consideration allows one to
find analytical expressions for a wide magnetic field range, where several
different mechanisms are operative; furthermore, the LAC description gives a
way to determine CIDNP sign rules. Thus, LCs/LACs provide a consistent
description of CIDNP in both liquids and solids with the prospect of
exploiting it for the analysis of short-lived radicals and for optimizing the
polarization level
Field-induced nematic-like magnetic transition in an iron pnictide superconductor, Ca(PtAs)((FePt)As)
We report a high magnetic field study up to 55 T of the nearly optimally
doped iron-pnictide superconductor Ca(PtAs)
((FePt)As) (x=0.078(6)) with a Tc 10 K using
magnetic torque, tunnel diode oscillator technique and transport measurements.
We determine the superconducting phase diagram, revealing an anisotropy of the
irreversibility field up to a factor of 10 near Tc and signatures of multiband
superconductivity. Unexpectedly, we find a spin-flop like anomaly in magnetic
torque at 22 T, when the magnetic field is applied perpendicular to the ab
planes, which becomes significantly more pronounced as the temperature is
lowered to 0.33 K. As our superconducting sample lies well outside the
antiferromagnetic region of the phase diagram, the observed field-induced
transition in torque indicates a spin-flop transition not of long-range ordered
moments, but of nematic-like antiferromagnetic fluctuations.Comment: Latex, 4 figure
Theory for the Ultrafast Structural Response of optically excited small clusters: Time-dependence of the Ionization Potential
Combining an electronic theory with molecular dynamics simulations we present
results for the ultrafast structural changes in small clusters. We determine
the time scale for the change from the linear to a triangular structure after
the photodetachment process Ag. We show that the
time-dependent change of the ionization potential reflects in detail the
internal degrees of freedom, in particular coherent and incoherent motion, and
that it is sensitive to the initial temperature. We compare with experiment and
point out the general significance of our results.Comment: 10 pages, Revtex, 3 postscript figure
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