Phase separation in asymmetrical fermion superfluids

Motivated by recent developments on cold atom traps and high density QCD we consider fermionic systems composed of two particle species with different densities. We argue that a mixed phase composed of normal and superfluid components is the energetically favored ground state. We suggest how this phase separation can be used as a probe of fermion superfluidity in atomic traps.Comment: 9 pages, LaTeX2e, version to appear in Phys.Rev.Let

Voicing Rivers through ontopoetics:A co-operative inquiry

A co-operative inquiry was established to explore the experience of a panpsychic world of sentient beings rather than inert objects, a world in which mind—sentience, subjectivity, and the will of self-realization—is a fundamental aspect of matter, just as matter is a fundamental aspect of mind. The nature of worldviews, the fundamental basis of our perceiving, thinking, valuing, and acting, is addressed and a brief outline of living cosmos panpsychism offered. The inquiry asks, could we humans, through intentional engagement, relate to the rivers as beings, subjects, or other-than-human persons in their own right? How might we engage with the rivers through personal relationship, ceremony, and invocation? What are the possibilities for reciprocal communication? In short, how might rivers speak?.</p

Joint modelling compared with two stage methods for analysing longitudinal data and prospective outcomes: A simulation study of childhood growth and BP

© The Author(s) 2014. There is a growing debate with regards to the appropriate methods of analysis of growth trajectories and their association with prospective dependent outcomes. Using the example of childhood growth and adult BP, we conducted an extensive simulation study to explore four two-stage and two joint modelling methods, and compared their bias and coverage in estimation of the (unconditional) association between birth length and later BP, and the association between growth rate and later BP (conditional on birth length). We show that the two-stage method of using multilevel models to estimate growth parameters and relating these to outcome gives unbiased estimates of the conditional associations between growth and outcome. Using simulations, we demonstrate that the simple methods resulted in bias in the presence of measurement error, as did the two-stage multilevel method when looking at the total (unconditional) association of birth length with outcome. The two joint modelling methods gave unbiased results, but using the re-inflated residuals led to undercoverage of the confidence intervals. We conclude that either joint modelling or the simpler two-stage multilevel approach can be used to estimate conditional associations between growth and later outcomes, but that only joint modelling is unbiased with nominal coverage for unconditional associations

Measurement of 222Rn dissolved in water at the Sudbury Neutrino Observatory

The technique used at the Sudbury Neutrino Observatory (SNO) to measure the concentration of 222Rn in water is described. Water from the SNO detector is passed through a vacuum degasser (in the light water system) or a membrane contact degasser (in the heavy water system) where dissolved gases, including radon, are liberated. The degasser is connected to a vacuum system which collects the radon on a cold trap and removes most other gases, such as water vapor and nitrogen. After roughly 0.5 tonnes of H2O or 6 tonnes of D2O have been sampled, the accumulated radon is transferred to a Lucas cell. The cell is mounted on a photomultiplier tube which detects the alpha particles from the decay of 222Rn and its daughters. The overall degassing and concentration efficiency is about 38% and the single-alpha counting efficiency is approximately 75%. The sensitivity of the radon assay system for D2O is equivalent to ~3 E(-15) g U/g water. The radon concentration in both the H2O and D2O is sufficiently low that the rate of background events from U-chain elements is a small fraction of the interaction rate of solar neutrinos by the neutral current reaction.Comment: 14 pages, 6 figures; v2 has very minor change

A radium assay technique using hydrous titanium oxide adsorbent for the Sudbury Neutrino Observatory

As photodisintegration of deuterons mimics the disintegration of deuterons by neutrinos, the accurate measurement of the radioactivity from thorium and uranium decay chains in the heavy water in the Sudbury Neutrino Observatory (SNO) is essential for the determination of the total solar neutrino flux. A radium assay technique of the required sensitivity is described that uses hydrous titanium oxide adsorbent on a filtration membrane together with a beta-alpha delayed coincidence counting system. For a 200 tonne assay the detection limit for 232Th is a concentration of 3 x 10^(-16) g Th/g water and for 238U of 3 x 10^(-16) g U/g water. Results of assays of both the heavy and light water carried out during the first two years of data collection of SNO are presented.Comment: 12 pages, 4 figure

Using resource graphs to represent conceptual change

We introduce resource graphs, a representation of linked ideas used when reasoning about specific contexts in physics. Our model is consistent with previous descriptions of resources and coordination classes. It can represent mesoscopic scales that are neither knowledge-in-pieces or large-scale concepts. We use resource graphs to describe several forms of conceptual change: incremental, cascade, wholesale, and dual construction. For each, we give evidence from the physics education research literature to show examples of each form of conceptual change. Where possible, we compare our representation to models used by other researchers. Building on our representation, we introduce a new form of conceptual change, differentiation, and suggest several experimental studies that would help understand the differences between reform-based curricula.Comment: 27 pages, 14 figures, no tables. Submitted for publication to the Physical Review Special Topics Physics Education Research on March 8, 200

Conceptualising sustainability in UK urban Regeneration: a discursive Formation

Despite the wide usage and popular appeal of the concept of sustainability in UK policy, it does not appear to have challenged the status quo in urban regeneration because policy is not leading in its conceptualisation and therefore implementation. This paper investigates how sustainability has been conceptualised in a case-based research study of the regeneration of Eastside in Birmingham, UK, through policy and other documents, and finds that conceptualisations of sustainability are fundamentally limited. The conceptualisation of sustainability operating within urban regeneration schemes should powerfully shape how they make manifest (or do not) the principles of sustainable development. Documents guide, but people implement regeneration—and the disparate conceptualisations of stakeholders demonstrate even less coherence than policy. The actions towards achieving sustainability have become a policy ‘fix’ in Eastside: a necessary feature of urban policy discourse that is limited to solutions within market-based constraints

Recent advances in classical electromagnetic theory

The early Sections of the present Thesis utilise a metric-free and connection-free approach so as derive the foundations of classical electrodynamics. More specifically, following a tradition established by Kottler [65], Cartan [14] and van Dantzig [137], Maxwell's theory is introduced without making reference to a notion of distance or parallel transport. With very few exceptions, the relevant concepts are derived from first principles. Indeed, Maxwell's theory is constructed starting from three experimentally justified axioms: (i) electric charge is conserved, (ii) the force acting on a test charge due to the electromagnetic field is the standard Lorentz one, (iii) magnetic flux is conserved. To be precise, a strictly deductive approach requires that three further postulates are introduced, as explained in the manual [41] by Hehl and Obukhov. Nevertheless, a shortened formalism is observed to be adequate for the purpose of this work. In nearly all cases, the electromagnetic medium is demanded to be local and linear. Moreover, the propagation of light is studied in the approximate geometrical optics regime. Lindell's astute derivation of the dispersion equation [80] is reformulated in the widespread mathematical language of tensor indices. The method devised in Ref. [80] is integrated with the analysis due to Dahl [16] of the space encompassing the physically viable polarisations. As a result, the geometry associated with the dispersion equation is investigated with considerable rigour. From the literature it is known that, to a great extent, the notion of distance can be viewed as a by-product of Maxwell's theory. In fact, imposing that the constitutive law is electric-magnetic reciprocal and skewon-free determines, albeit non-uniquely, a Lorentzian metric. A novel proof of this statement is examined. In addition, the unimodular forerunner of electric-magnetic reciprocity, defined in earlier works by Lindell [79] and Perlick [112], is shown to preserve the energy-momentum tensor.Open Acces