Lobe interactions within the thallus margin and the maintenance of symmetry in the lichen Parmelia conspersa (Ehrh. ex Ach.)Ach.

This study determined whether the radial growth of lobes of the foliose lichen Parmelia conspersa (Ehrh. ex Ach.)Ach. was influenced by the radial growth and morphology of their closest neighbours and whether such interactions influence thallus symmetry. The radial growth and morphology of a sample of adjacent lobes from six thalli was measured. Positive correlations were observed between radial growth and lobe width in three thalli and with the degree of bifurcation of the lobe in two thalli. Negative correlations between the radial growth of adjacent lobes were observed in four thalli suggesting that faster growing lobes may inhibit the growth of their neighbours.Lobes glued next to individual lobes had no signifiacnt effect on the radial growth of wide or narrow lobes. Lobes glued 1-2 mm in front of their neighbours exhibited an intital phase of increased radial growth and then a phase of slower growth. Radial growth decreased when the lobes were glued 2 mm behind their neighbours and these lobes were essentially eliminated by the growth of the adjacent lobes. The data suggest that lobe interactions may incresae lobe growth variation within a thallus. However, the decrease in radial growth of lobes which protrude from the margin and the elimination of slower growing lobes may help to maintain thallus symmetry.

Lobe growth variation and the maintenance of symmetry in foliose lichen thalli

The aim of this study was to determine how thallus symmetry could be maintained in foliose lichens when variation in the growth of individual lobes may be high. Hence, the radial growth of a sample of lobes was studied monthly, over 22 months, in 7 thalli of Parmelia conspersa (Ehrh. Ex Ach.) Ach. And 5 thalli of P. glabratula ssp fuliginosa (fr. ex Duby) Laund. The degree of variation in the total radial growth of different lobes within a thallus over 22 months varied between thalli. Individual lobes showed a fluctuating pattern of radial growth from month to month with alternating periods of fast and slow growth. Monthly variations in radial growth of different lobes were synchronized in some but not in all thalli. Few significant correlations were found between the radial growth of individual lobes and total monthly rainfall or shortwave radiation. The levels of ribitol, arabitol and mannitol were measured in individual lobes. All three polyols varied significantly between lobes within a thallus suggesting that variations in algal phostosynthesis and in the partitioning of fungal polyols may contribute to lobe growth variation. The effect on thallus symmetry of lobes which grew radially either consistently faster or slower than average was studied. Slow growing lobes were overgrown, and gaps in the perimeter were eliminated by the growth of neighbouring lobes, in approximately 7 to 9 months. However, a rapidly growing lobe, with its neighbours removed on either side, continued to grow radially at the same rate as rapidly growing control lobes. The results suggested that lobe growth variation results from a combination of factors which may include the origin of the lobes, lobe morphology and the patterns of algal cell division and hyphal elongation in different lobes. No convincing evidence was found to suggest that exchange of carbohydrate occurred between lobes which would tend to equalize their radial growth. Hence, the fluctuating pattern of lobe growth observed may be sufficient to maintain a degree of symmetry in most thalli. In addition, slow growing lobes would tend to be overgrown by faster growing neighbours thus preventing the formation of indentations in the thallus perimeter.

Symmetry of coherent vortices in plane couette flow

A numerical continuation method is carried out in a homotopy space connecting two different flows, the Plane Couette Flow (PCF) and the Laterally Heated Flow in a vertical slot (LHF). This numerical continuation method enables us to obtain an exact steady solution in PCF. The new solution has the shape of hairpin vortices (HVS: hairpin vortex solution), which is observed ubiquitously in turbulent shear flows.

Strong localization of whispering gallery modes in an optical fiber via asymmetric perturbation of the translation symmetry

Recently introduced Surface Nanoscale Axial Photonics (SNAP) is based on whispering gallery modes circulating around the optical FIber surface and undergoing slow axial propagation. In this paper we develop the theory of propagation of whispering gallery modes in a SNAP microresonator, which is formed by nanoscale asymmetric perturbation of the FIber translation symmetry and called here a nanobump microresonator. The considered modes are localized near a closed stable geodesic situated at the FIber surface. A simple condition for the stability of this geodesic corresponding to the appearance of a high Q-factor nanobump microresonator is found. The results obtained are important for engineering of SNAP devices and structures.

Breaking down barriers:teenage girls’ perceptions of engineering as a study and career choice

Background: Stereotypically perceived to be an ‘all male’ occupation, engineering has for many years failed to attract high numbers of young women [1,2]. The reasons for this are varied, but tend to focus on misconceptions of the profession as being more suitable for men. In seeking to investigate this issue a participatory research approach was adopted [3] in which two 17 year-old female high school students interviewed twenty high school girls. Questions focused on the girls’ perceptions of engineering as a study and career choice. The findings were recorded and analysed using qualitative techniques. The study identified three distinctive ‘influences’ as being pivotal to girls’ perceptions of engineering; pedagogical; social; and, familial. Pedagogical Influences: Pedagogical influences tended to focus on science and maths. In discussing science, the majority of the girls identified biology and chemistry as more ‘realistic’ whilst physics was perceived to more suitable for boys. The personality of the teacher, and how a particular subject is taught, proved to be important influences shaping opinions. Social Influences: Societal influences were reflected in the girls’ career choice with the majority considering medical or social science related careers. Although all of the girls believed engineering to be ‘male dominated’, none believed that a woman should not be engineer. Familial Influences: Parental influence was identified as key to career and study choice; only two of the girls had discussed engineering with their parents of which only one was being actively encouraged to pursue a career in engineering. Discussion: The study found that one of the most significant barriers to engineering is a lack of awareness. Engineering did not register in the girls’ lives, it was not taught in school, and only one had met a female engineer. Building on the study findings, the discussion considers how engineering could be made more attractive to young women. Whilst misconceptions about what an engineer is need to be addressed, other more fundamental pedagogical barriers, such as the need to make physics more attractive to girls and the need to develop the curriculum so as to meet the learning needs of 21st Century students are discussed. By drawing attention to the issues around gender and the barriers to engineering, this paper contributes to current debates in this area – in doing so it provides food for thought about policy and practice in engineering and engineering education.

Breaking down the non-normality of daily stock returns

This paper investigates whether the non-normality typically observed in daily stock-market returns could arise because of the joint existence of breaks and GARCH effects. It proposes a data-driven procedure to credibly identify the number and timing of breaks and applies it on the benchmark stock-market indices of 27 OECD countries. The findings suggest that a substantial element of the observed deviations from normality might indeed be due to the co-existence of breaks and GARCH effects. However, the presence of structural changes is found to be the primary reason for the non-normality and not the GARCH effects. Also, there is still some remaining excess kurtosis that is unlikely to be linked to the specification of the conditional volatility or the presence of breaks. Finally, an interesting sideline result implies that GARCH models have limited capacity in forecasting stock-market volatility.

Self-sustained clusters and ergodicity breaking in spin models

Self-sustained spin clusters are analytically linked to ergodicity breaking in fully connected Ising and Sherrington-Kirkpatick (SK) models, relating the less understood spin space to the well understood state space. This correspondence is established through the absence of clusters in the paramagnetic phase, the presence of one dominant cluster in the Ising ferromagnet, and the formation of nontrivial clusters in SK spin glass. Yet unobserved phenomena are also revealed such as a first order phase transition in cluster sizes in the SK ferromagnet. The method could be adapted to investigate other spin models. © 2013 American Physical Society.

Bandpass switching based on a nonlinear optical loop mirror and an in-fibre grating reflector

Nonlinear optical loop mirror (NOLM) requires breaking the loop symmetry to enable the counter propagating pulses to acquire a differential π phase shift. This is achieved with either an asymmetric fused fibre coupler at the input or by the inclusion of an asymmetrically located gain or loss element within the loop. By introducing a frequency selective loss element, nonlinear switching may be confined to a narrow band of wavelengths or multiple wavelengths. This configuration may have applications in time-wavelength demultiplexing. We demonstrate this technique of bandpass switching in the soliton regime using a fibre-Bragg grating reflector as the wavelength dependent loss.

Pair breaking and bound states in disordered superconductors

We study the effects of inhomogeneous pairing interactions and impurities in short-coherence-length superconductors. Within the Born approximation, the effects of pairing disorder and magnetic impurities are identical. The T-matrices for pairing disorder sites with and without an impurity give rise to bound states within the BCS (Bardeen-Cooper-Schrieffer) gap, consistent with scanning tunnelling microscopy results on Bi2Sr2CaCu2O8+δ with Zn or Ni impurities.

Isomerism as Manifestation of Intrinsic Symmetry of Molecules: Lunn–Senior’s Theory

This article presents the principal results of the doctoral thesis “Isomerism as internal symmetry of molecules” by Valentin Vankov Iliev (Institute of Mathematics and Informatics), successfully defended before the Specialised Academic Council for Informatics and Mathematical Modelling on 15 December, 2008.

Breaking out of the silo mentality

The return to methods focusing on language and experience following the dominance of experimental methods has in the last few decades led to debate, dialogue, and disagreement regarding the status of qualitative and quantitative methods. However, a recent focus on impact has brought an air of pragmatism to the research arena. In what ways, then, is psychology moving from entrenched mono methods approaches that have epitomised its development until recently, to describing and discussing ways in which mixed and pluralistic research can advance and contribute to further, deeper psychological understanding?.

The Kim Dynasty and North-East Asian security:breaking the cycle of crises?

Purpose—This article considers North Korea and the notion of crisis, by linking historical development over the Korean peninsula to the conflict resolution literature, and investigates why despite a large number of destabilizing events, a war involving Pyongyang has yet to erupt. Design/methodology—This article uses historical data and a framework developed by Aggarwal et al., in order to highlight patterns of interaction between states such as the United States, North Korea and South Korea, organizations such as the United Nations, as well as processes such as the Six- Party Talks and the Agreed Framework. The article then develops a crisis framework based on conflict resolution and negotiation literature, and applies it to three North Korean administrations. Findings—Findings suggest that an open- ended understanding of time (for all parties involved on the peninsula) leads to an impossibility to reach a threshold where full- scale war would be triggered, thus leaving parties in a stable state of crisis for which escalating moves and de- escalating techniques might become irrelevant. Practical implications—It is hoped that this article will help further endeavors linking conflict resolution theoretical frameworks to the Korean peninsula security situation. In the case of the Korean peninsula, time has been understood as open-ended, leading parties to a lingering state of heightened hostilities that oscillates toward war, but that is controlled enough not to reach it. In-depth analysis of particular security sectors such as nuclear energy, food security, or missile testing would prove particularly useful in understanding the complexity of the Korean peninsula situation to a greater extent. It is hoped that this paper will help further endeavours linking conflict resolution theoretical frameworks to the Korean peninsula security situation. Originality/value—This research suggests that regarding the Korean peninsula, time has been understood as open- ended, leading parties to a lingering state of heightened.

The Kim Dynasty and North-East Asian security:breaking the cycle of crises

This article considers North Korea and the notion of crisis, by linking historical development over the Korean peninsula to the conflict resolution literature, and investigates why despite a large number of destabilising events, a war involving Pyongyang has yet to erupt. The paper considers historical data and uses a framework developed by Aggarwal et al. in order to highlight patterns of interaction between states such as the United States, North Korea and South Korea, organisations such as the United Nations, as well as processes such as the Six-Party Talk and the Agreed Framework. The paper then develops a crisis framework based on conflict resolution and negotiation literature, and applies it to three North Korean administrations. Findings suggests that an elastic understanding of time (for all parties involved on the peninsula) leads to an impossibility to reach a threshold where full-scale war would be triggered, thus leaving parties in a stable state of crisis for which escalating moves and de-escalating techniques might become irrelevant.

Activated escape from polarization pulling in fibre Raman amplifiers

Fluctuation-induced escape (FIE) from a metastable state with probability controlled by external force is a process inherent in many physical phenomena such as diffusion in crystals, protein folding, activated chemical reactions etc. [1-3]. In this work we present a novel example of FIE problem, considering a very practical nonlinear system recently emerged in the area of fibre telecommunications. Unlike the standard FIE problems where noise is time-dependent, in fibre Raman amplifier (FRA) the role of noise is played by frozen fluctuations of parameters (random birefringence) along the fibre span which result from the breaking of cylindrical symmetry during the fibre drawing [4-6]. The role of periodic forcing in this problem is played by the periodic fibre spinning, leading to key model that is formally similar to the time-domain equations for periodically forced escape [1-3]. © 2011 IEEE.