Finite rigid sets and homologically non-trivial spheres in the curve complex of a surface

Aramayona and Leininger have provided a "finite rigid subset" $\mathfrak{X}(\Sigma)$ of the curve complex $\mathscr{C}(\Sigma)$ of a surface $\Sigma = \Sigma^n_g$, characterized by the fact that any simplicial injection $\mathfrak{X}(\Sigma) \to \mathscr{C}(\Sigma)$ is induced by a unique element of the mapping class group $\mathrm{Mod}(\Sigma)$. In this paper we prove that, in the case of the sphere with $n\geq 5$ marked points, the reduced homology class of the finite rigid set of Aramayona and Leininger is a $\mathrm{Mod}(\Sigma)$-module generator for the reduced homology of the curve complex $\mathscr{C}(\Sigma)$, answering in the affirmative a question posed by Aramayona and Leininger. For the surface $\Sigma = \Sigma_g^n$ with $g\geq 3$ and $n\in \{0,1\}$ we find that the finite rigid set $\mathfrak{X}(\Sigma)$ of Aramayona and Leininger contains a proper subcomplex $X(\Sigma)$ whose reduced homology class is a $\mathrm{Mod}(\Sigma)$-module generator for the reduced homology of $\mathscr{C}(\Sigma)$ but which is not itself rigid.Comment: 21 pages, 7 figures; Section 4 revised along with minor corrections throughou

National Security Risks? Uncertainty, Austerity and Other Logics of Risk in the UK government’s National Security Strategy

Risk scholars within Security studies have argued that the concept of security has gone through a fundamental transformation away from a threat-based conceptualisation of defence, urgency and exceptionality to one of preparedness, precautions and prevention of future risks, some of which are calculable, others of which are not. This article explores whether and how the concept of security is changing due to this ‘rise of risk’, through a hermeneutically grounded conceptual and discourse analysis of the United Kingdom government’s national security strategy (NSS) from 1998 to 2011. We ask how risk-security language is employed in the NSS; what factors motivate such discursive shifts; and what, if any, consequences of these shifts can be discerned in UK national security practices. Our aim is twofold: to better understand shifts in the security understandings and policies of UK authorities; and to contribute to the conceptual debate on the significance of the rise of risk as a component of the concept of security

Impurity transport in Alcator C-Mod in the presence of poloidal density variation induced by ion cyclotron resonance heating

Impurity particle transport in an ion cyclotron resonance heated Alcator C-Mod discharge is studied with local gyrokinetic simulations and a theoretical model including the effect of poloidal asymmetries and elongation. In spite of the strong minority temperature anisotropy in the deep core region, the poloidal asymmetries are found to have a negligible effect on the turbulent impurity transport due to low magnetic shear in this region, in agreement with the experimental observations. According to the theoretical model, in outer core regions poloidal asymmetries may contribute to the reduction of the impurity peaking, but uncertainties in atomic physics processes prevent quantitative comparison with experiments.Comment: 32 pages, 12 figure

Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod

© 2020 Author(s). Analysis and modeling of rotation reversal hysteresis experiments show that a single turbulent bifurcation is responsible for the Linear to Saturated Ohmic Confinement (LOC/SOC) transition and concomitant intrinsic rotation reversal on Alcator C-Mod. Plasmas on either side of the reversal exhibit different toroidal rotation profiles and therefore different turbulence characteristics despite the profiles of density and temperature, which are indistinguishable within measurement uncertainty. Elements of this bifurcation are also shown to persist for auxiliary heated L-modes. The deactivation of subdominant (in the linear growth rate and contribution to heat transport) ion temperature gradient and trapped electron mode instabilities is identified as the only possible change in turbulence within a reduced quasilinear transport model across the reversal, which is consistent with the measured profiles and inferred heat and particle fluxes. Experimental constraints on a possible change from strong to weak turbulence, outside the description of the quasilinear model, are also discussed. These results indicate an explanation for the LOC/SOC transition that provides a mechanism for the hysteresis through the dynamics of subdominant modes and changes in their relative populations and does not involve a change in the most linearly unstable ion-scale drift-wave instability

Scale morphologies of freshwater fishes at Tembat Forest Reserve, Terengganu, Malaysia

Scales are calcium carbonate and collagen-contained structures embedded within the fish epidermis and useful for species identification. This study aimed to describe morphological characteristics of scales and use the differences to prepare keys to species. Fishes were sampled from selected rivers of Tembat Forest Reserve, Hulu Terengganu. Specimens caught were from 3 families (Cyprinidae, Channidae, Nandidae) and 17 species. Each species was represented by ten individuals (size ranges 2.5 - 50 cm TL). The scales were removed, soaked in H2O2 (0.5%), NH3 (0.3%), DH2O and mounted between a pair of glass slides for digital photographing. The morphological descriptions were based on types of scales, distinctiveness of radii arrangement at the anterior field, radii cover, radii distribution, overall shape, focus position and focus pattern. Keys to species were constructed based on these scale morphological characters described. Measurements of scale total length (L), total width (W), rostral field length (L1) and caudal field length (L2) of the scales were taken using Image J software. The inter-specific variation among scales was indicated by L1/L, L2/L, L1/L2 and W/L indices through multiple comparison tests (ANOVA). It was found that all 17 species showed significant differences with at least one other species in all four indices. Pristolepis grootii (Bleeker 1852) was the only one that significantly different (p<0.05) from other 16 species in the first three indices. Species that showed the least significant differences among species was Probarbus jullieni (Sauvage 1880). The differences among the scales were primarily due to the different types of scale that was either ctenoid or cycloid

Capability in the digital: institutional media management and its dis/contents

This paper explores how social media spaces are occupied, utilized and negotiated by the British Military in relation to the Ministry of Defence’s concerns and conceptualizations of risk. It draws on data from the DUN Project to investigate the content and form of social media about defence through the lens of ‘capability’, a term that captures and describes the meaning behind multiple representations of the military institution. But ‘capability’ is also a term that we hijack and extend here, not only in relation to the dominant presence of ‘capability’ as a representational trope and the extent to which it is revealing of a particular management of social media spaces, but also in relation to what our research reveals for the wider digital media landscape and ‘capable’ digital methods. What emerges from our analysis is the existence of powerful, successful and critically long-standing media and reputation management strategies occurring within the techno-economic online structures where the exercising of ‘control’ over the individual – as opposed to the technology – is highly effective. These findings raise critical questions regarding the extent to which ‘control’ and management of social media – both within and beyond the defence sector – may be determined as much by cultural, social, institutional and political influence and infrastructure as the technological economies. At a key moment in social media analysis, then, when attention is turning to the affordances, criticisms and possibilities of data, our research is a pertinent reminder that we should not forget the active management of content that is being similarly, if not equally, effective

Green practices in hotel industry: factors influencing the implementation / Fauziah Deraman…[et al.]

There has been a tremendous effort in creating awareness and to increase the number of establishments with green practices in hotel industry. This is due to undeniable negative environmental impacts derived from hotel activities. Therefore, hotels are grabbing this opportunity to preserve the environment and at the same time, they are reaping benefits from the green practices. However, despite the promising benefits they may gain, the hotels’ participation in green practices are still low due to several factors that influenced the hotels whether to implement the green practices or remain with the current operational practices. Thus, the aim of this study is to determine the influencing factors toward the implementation of green practices in hotels and to identify the most influencing among all factors. Three factors were identified, which were cost, consumers’ support, and employees’ support. Details regarding these three factors had been discussed by previous researchers. As a result, consumers’ support had been identified as the most influencing factor towards the implementation of green practices in hotel

Heterotic M(atrix) Strings and Their Interactions

Following recent proposal of Dijkgraaf, Verlinde and Verlinde, we show that the M(atrix) theory compactified on $S_1/Z_2$ provides with a non-perturbative description of second-quantized light-cone heterotic string. This so-called heterotic M(atrix) string theory is defined by two-dimensional (8,0) supersymmetric chiral gauge theory with gauge group SO(2N) in the large N limit. We argue that at strong coupling fixed point the chiral gauge theory flows to a (8,0) superconformal field theory defined via $S_N$ symmetric product space orbifold. We show that the leading order correction to the strong coupling expansion corresponds to a unique irrelevant operator of scaling dimension three and describes joining and splitting cubic interactions of light-cone heterotic string. We also speculate on M(atrix) description of bosonic strings via dimensional reduction of d=26 Yang-Mills theory.Comment: 20 pages, section 3.1 expanded, more references adde