150 research outputs found
Scheme for generating entangled states of two field modes in a cavity
This paper considers a two-level atom interacting with two cavity modes with
equal frequencies. Applying a unitary transformation, the system reduces to the
analytically solvable Jaynes-Cummings model. For some particular field states,
coherent and squeezed states, the transformation between the two bare basis's,
related by the unitary transformation, becomes particularly simple. It is shown
how to generate, the highly non-classical, entangled coherent states of the two
modes, both in the zero and large detuning cases. An advantage with the zero
detuning case is that the preparation is deterministic and no atomic
measurement is needed. For the large detuning situation a measurement is
required, leaving the field in either of two orthogonal entangled coherent
states.Comment: Accepted in J. Mod. Opt.; 12 pages; Replaced with revised version.
Extended discussion of experimental realizations, earlier studies in the
field and on the frequency dependence in the adiabatic eliminatio
The nested games of the UKâs EU referendum: ruptures, reconfigurations and lessons for Europe
The 2016 decision by the United Kingdom to withdraw from the European Union was a seminal one for both parties. In this special issue, we consider the extent to which the inter-penetration of the national and the European arenas produced significant opportunities for recasting political action. The nesting of these two levels matters firstly in allowing for the politicisation and mobilisation of domestic actors around European issues and secondly in explaining why seemingly sub-optimal or counter-productive actions are taken. The tensions this generated reached a critical juncture with the referendum, a rupture that highlights the extent to which a nominally second-order vote can have fundamental impacts on the first orderâs structure and preferences. Bringing together scholars from a wide range of approaches and covering various aspects of the Brexit process, this special issue offers a significant contribution to improving our understanding of an event that will shape British and European politics for a generation
Protracted timescales of lower crustal growth at the fast-spreading East Pacific Rise
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 5 (2012): 275-278, doi:10.1038/ngeo1378.Formation of the oceanic crust at mid-ocean ridges is a fundamental component of
plate tectonics. A majority of the crust at many ridges is composed of plutonic rocks
that form by crystallization of mantle-derived magmas within the crust. Recent
application of U/Pb dating to samples from in-situ oceanic crust has begun to
provide exciting new insight into the timing, duration and distribution of
magmatism during formation of the plutonic crust1-4. Previous studies have focused
on samples from slow-spreading ridges, however, the time scales and processes of
crustal growth are expected to vary with plate spreading rate. Here we present the
first high-precision dates from plutonic crust formed at the fast-spreading East
Pacific Rise (EPR). Individual zircon minerals yielded dates from 1.420â1.271
million years ago, with uncertainties of ± 0.006â0.081 million years. Within
individual samples, zircons record a range of dates of up to ~0.124 million years,
consistent with protracted crystallization or assimilation of older zircons from
adjacent rocks. The variability in dates is comparable to data from the Vema
lithospheric section on the Mid-Atlantic Ridge (MAR)3, suggesting that time scales
of magmatic processes in the lower crust may be similar at slow- and fast-spreading
ridges.This research was partially funded by NSF grant OCE-0727914 (SAB), a Cardiff
University International Collaboration Award (CJL) and NERC grant NE/C509023/1
(CJM).2012-07-2
Machina ex Deus? From Distributed to Orchestrated Agency
In this chapter, the author draws on a historical case study of the Australian wine industry to explore variations in collective agency. The inductively derived process model illustrates the emergence of a new profession of scientific win- emaking, which unfolds in three phases. Each phase is characterized by a dis- tinct form of agency: distributed agency during the earliest phase, coordinated agency during later phases, and orchestrated agency during consolidation. In addition to exploring the temporal shifts in agency, the study includes a detailed analysis of the early stages of distributed agency, examining how col- lective agency is achieved in the absence of shared intentions
Trees and shrubs as sources of fodder in Australia
Experience with browse plants in Australia is briefly reviewed in terms of their forage value to animals, their economic value to the landholder and their ecological contribution to landscape stability. Of the cultivated species only two have achieved any degree of commercial acceptance (Leucaena leucocephala and Chamaecytisus palmensis). Both of these are of sufficiently high forage value to be used as the sole source of feed during seasonal periods of nutritional shortage. Both are also leguminous shrubs that establish readily from seed. It is suggested that a limitation in their present use is the reliance on stands of single species which leaves these grazing systems vulnerable to disease and insects. Grazing systems so far developed for high production and persistence of cultivated species involve short periods of intense grazing followed by long periods of recovery. Similar management may be necessary in the arid and semi-arid rangelands where palatable browse species are in decline
Views and experiences of people with intellectual disabilities regarding intimate relationships: a qualitative metasynthesis
The aims of this review were to systematically identify, critically appraise and synthesize the results of existing qualitative literature exploring the views and experiences of intimate relationships amongst people with intellectual disabilities. Fourteen peer-reviewed articles were identified through a systematic search of eight databases, reference lists, citations, and relevant journals. The identified articles were appraised for quality, then synthesized using a metaethnography approach. No study met all quality criteria and references to ethical approval were often lacking. Interpretation of the findings suggested three key themes: the meaning of intimate relationships, external constraints and facilitators, and managing external constraints. Though many people with intellectual disabilities desire and benefit from intimate relationships, they experience restrictions that others do not, which can lead to isolation and loneliness. Intimate relationships are not always necessarily linked with sexual behavior; therefore, intimate relationships warrant their own focus in future research, as well as in education and training for people with intellectual disabilities and their caregivers. Within this, a commitment to transparency over research processes is needed, in particular with reference to how ethical approval was obtained, since this has been a shortcoming of research with this focus to date
Release of oxidizing fluids in subduction zones recorded by iron isotope zonation in garnet
Subduction zones are key regions of chemical and mass transfer between the Earthâs surface and mantle. During subduction, oxidized material is carried into the mantle and large amounts of water are released due to the breakdown of hydrous minerals such as lawsonite. Dehydration accompanied by the release of oxidizing species may play a key role in controlling redox changes in the subducting slab and overlying mantle wedge. Here we present measurements of oxygen fugacity, using garnetâepidote oxybarometry, together with analyses of the stable iron isotope composition of zoned garnets from Sifnos, Greece. We find that the garnet interiors grew under relatively oxidized conditions whereas garnet rims record more reduced conditions. Garnet ÎŽ56Fe increases from core to rim as the system becomes more reduced. Thermodynamic analysis shows that this change from relatively oxidized to more reduced conditions occurred during lawsonite dehydration. We conclude that the garnets maintain a record of progressive dehydration and that the residual mineral assemblages within the slab became more reduced during progressive subduction-zone dehydration. This is consistent with the hypothesis that lawsonite dehydration accompanied by the release of oxidizing species, such as sulfate, plays an important and measurable role in the global redox budget and contributes to sub-arc mantle oxidation in subduction zones
Nanotools for Neuroscience and Brain Activity Mapping
Neuroscience is at a crossroads. Great effort is being invested into deciphering specific neural interactions and circuits. At the same time, there exist few general theories or principles that explain brain function. We attribute this disparity, in part, to limitations in current methodologies. Traditional neurophysiological approaches record the activities of one neuron or a few neurons at a time. Neurochemical approaches focus on single neurotransmitters. Yet, there is an increasing realization that neural circuits operate at emergent levels, where the interactions between hundreds or thousands of neurons, utilizing multiple chemical transmitters, generate functional states. Brains function at the nanoscale, so tools to study brains must ultimately operate at this scale, as well. Nanoscience and nanotechnology are poised to provide a rich toolkit of novel methods to explore brain function by enabling simultaneous measurement and manipulation of activity of thousands or even millions of neurons. We and others refer to this goal as the Brain Activity Mapping Project. In this Nano Focus, we discuss how recent developments in nanoscale analysis tools and in the design and synthesis of nanomaterials have generated optical, electrical, and chemical methods that can readily be adapted for use in neuroscience. These approaches represent exciting areas of technical development and research. Moreover, unique opportunities exist for nanoscientists, nanotechnologists, and other physical scientists and engineers to contribute to tackling the challenging problems involved in understanding the fundamentals of brain function
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