Geometrical Phase Transition on WO3_3 Surface

A topographical study on an ensemble of height profiles obtained from atomic force microscopy techniques on various independently grown samples of tungsten oxide WO$_3$ is presented by using ideas from percolation theory. We find that a continuous 'geometrical' phase transition occurs at a certain critical level-height $\delta_c$ below which an infinite island appears. By using the finite-size scaling analysis of three independent percolation observables i.e., percolation probability, percolation strength and the mean island-size, we compute some critical exponents which characterize the transition. Our results are compatible with those of long-range correlated percolation. This method can be generalized to a topographical classification of rough surface models.Comment: 3 pages, 4 figures, to appear in Applied Physics Letters (2010

Sociological Knowledge and Transformation at ‘Diversity University’, UK

This chapter is based on a case study of one UK university sociology department and shows how sociology knowledge can transform the lives of ‘non-traditional’ students. The research from which the case is drawn focused on four departments teaching sociology-related subjects in universities positioned differently in UK league tables. It explored the question of the relationship between university reputation, pedagogic quality and curriculum knowledge, challenging taken-for-granted judgements about ‘quality’ and in conceptualising ‘just’ university pedagogy by taking Basil Bernstein’s ideas about how ‘powerful’ knowledge is distributed in society to illuminate pedagogy and curriculum. The project took the view that ‘power’ lies in the acquisition of specific (inter)disciplinary knowledges which allows the formation of disciplinary identities by way of developing the means to think about and act in the world in specific ways. We chose to focus on sociology because (1) university sociology is taken up by all socio-economic classes in the UK and is increasingly taught in courses in which the discipline is applied to practice; (2) it is a discipline that historically pursues social and moral ambition which assists exploration of the contribution of pedagogic quality to individuals and society beyond economic goals; (3) the researchers teach and research sociology or sociology of education - an understanding of the subjects under discussion is essential to make judgements about quality. ‘Diversity’ was one of four case study universities. It ranks low in university league tables; is located in a large, multi-cultural English inner city; and, its students are likely to come from lower socio-economic and/or ethnic minority groups, as well as being the first in their families to attend university. To make a case for transformative teaching at Diversity, the chapter draws on longitudinal interviews with students, interviews with tutors, curriculum documents, recordings of teaching, examples of student work, and a survey. It establishes what we can learn from the case of sociology at Diversity, arguing that equality, quality and transformation for individuals and society are served by a university curriculum which is research led and challenging combined with pedagogical practices which give access to difficult-to-acquire and powerful knowledge

Noise Generation in Hot Jets

A prediction method based on the generalized acoustic analogy is presented, and used to evaluate aerodynamic noise radiated from high speed hot jets. The set of Euler equations are split into their respective non-radiating and residual components. Under certain conditions, the residual equations are rearranged to form a wave equation. This equation consists of a third-order wave operator, plus a number of nonlinear terms that are identified with the equivalent sources of sound and their statistical characteristics are modeled. A specialized RANS solver provides the base flow as well as turbulence quantities and temperature fluctuations that determine the source strength. The main objective here is to evaluate the relative contribution from various source elements to the far-field spectra and to show the significance of temperature fluctuations as a source of aerodynamic noise in hot jets

Constraining Form Factors with the Method of Unitarity Bounds

The availability of a reliable bound on an integral involving the square of the modulus of a form factor on the unitarity cut allows one to constrain the form factor at points inside the analyticity domain and its shape parameters, and also to isolate domains on the real axis and in the complex energy plane where zeros are excluded. In this lecture note, we review the mathematical techniques of this formalism in its standard form, known as the method of unitarity bounds, and recent developments which allow us to include information on the phase and modulus along a part of the unitarity cut. We also provide a brief summary of some results that we have obtained in the recent past, which demonstrate the usefulness of the method for precision predictions on the form factors.Comment: 12 pages, 2 figures; Lecture given at the DAE-BRNS Workshop on Hadron Physics, Bhabha Atomic Research Centre, Mumbai, India, October 31-November 4, 2011, submitted to Proceeding

MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters -- III. Cataclysmic variables -- Implications of model assumptions

In this third of a series of papers related to cataclysmic variables (CVs) and related objects, we analyse the population of CVs in a set of 12 globular cluster models evolved with the MOCCA Monte Carlo code, for two initial binary populations (IBPs), two choices of common-envelope phase (CEP) parameters, and three different models for the evolution of CVs and the treatment of angular momentum loss. When more realistic models and parameters are considered, we find that present-day cluster CV duty cycles are extremely-low ($\lesssim 0.1$ per cent) which makes their detection during outbursts rather difficult. Additionally, the IBP plays a significant role in shaping the CV population properties, and models that follow the Kroupa IBP are less affected by enhanced angular momentum loss. We also predict from our simulations that CVs formed dynamically in the past few Gyr (massive CVs) correspond to bright CVs (as expected), and that faint CVs formed several Gyr ago (dynamically or not) represent the overwhelming majority. Regarding the CV formation rate, we rule out the notion that it is similar irrespective of the cluster properties. Finally, we discuss the differences in the present-day CV properties related to the IBPs, the initial cluster conditions, the CEP parameters, formation channels, the CV evolution models, and the angular momentum loss treatments.Comment: 18 pages, 7 figures, 2 tables; accepted for publication in MNRA

Phantom Accretion by Five Dimensional Charged Black Hole

This paper deals with the dynamical behavior of phantom field near five dimensional charged black hole. We formulate equations of motion for steady-state spherically symmetric flow of phantom fluids. It is found that phantom energy accretes onto black holes for $u<0$. Further, the location of critical point of accretion are evaluated that leads to mass to charge ratio for 5D charged black hole. This ratio implies that accretion cannot transform a black hole into a naked singularity. We would like to mention here that this work is an irreducible extension of 4D charged black hole.Comment: 8 pages, accepted for publication in Mod. Phys. Lett.

Progress Toward Improving Jet Noise Predictions in Hot Jets

An acoustic analogy methodology for improving noise predictions in hot round jets is presented. Past approaches have often neglected the impact of temperature fluctuations on the predicted sound spectral density, which could be significant for heated jets, and this has yielded noticeable acoustic under-predictions in such cases. The governing acoustic equations adopted here are a set of linearized, inhomogeneous Euler equations. These equations are combined into a single third order linear wave operator when the base flow is considered as a locally parallel mean flow. The remaining second-order fluctuations are regarded as the equivalent sources of sound and are modeled. It is shown that the hot jet effect may be introduced primarily through a fluctuating velocity/enthalpy term. Modeling this additional source requires specialized inputs from a RANS-based flowfield simulation. The information is supplied using an extension to a baseline two equation turbulence model that predicts total enthalpy variance in addition to the standard parameters. Preliminary application of this model to a series of unheated and heated subsonic jets shows significant improvement in the acoustic predictions at the 90 degree observer angle