Effects of a localized beam on the dynamics of excitable cavity solitons

We study the dynamical behavior of dissipative solitons in an optical cavity filled with a Kerr medium when a localized beam is applied on top of the homogeneous pumping. In particular, we report on the excitability regime that cavity solitons exhibits which is emergent property since the system is not locally excitable. The resulting scenario differs in an important way from the case of a purely homogeneous pump and now two different excitable regimes, both Class I, are shown. The whole scenario is presented and discussed, showing that it is organized by three codimension-2 points. Moreover, the localized beam can be used to control important features, such as the excitable threshold, improving the possibilities for the experimental observation of this phenomenon.Comment: 9 Pages, 12 figure

Penta-Hepta Defect Motion in Hexagonal Patterns

Structure and dynamics of penta-hepta defects in hexagonal patterns is studied in the framework of coupled amplitude equations for underlying plane waves. Analytical solution for phase field of moving PHD is found in the far field, which generalizes the static solution due to Pismen and Nepomnyashchy (1993). The mobility tensor of PHD is calculated using combined analytical and numerical approach. The results for the velocity of PHD climbing in slightly non-optimal hexagonal patterns are compared with numerical simulations of amplitude equations. Interaction of penta-hepta defects in optimal hexagonal patterns is also considered.Comment: 4 pages, Postscript (submitted to PRL

Exergames for falls prevention in sheltered homes:A feasibility study

Introduction:Falls prevention is a global priority given its substantial impact on older adults and cost to healthcare systems. Advances in telerehabilitation technology such as `exergaming’ show potential for delivering accessible, engaging exercise programs for older adults. This study aimed to establish the feasibility, acceptability and usability of exergaming in sheltered housing.Methods: A mixed-methods study with participants randomised in 2 sheltered housing facilities to intervention (n = 1 home, 12 participants) and control (n = 1 home 2, 12 participants) provided usual care for all, (physiotherapy prescribed strength and balance exercises and falls prevention advice) and a 6-week supervised exergaming programme (MIRA) offered 3 times per week to the intervention group only. At 6 weeks, feasibility, usability and acceptability outcomes were collected and analysed using descriptive statistics; qualitative focus groups with participants and interviews with staff were also completed and thematically analysed to elicit barriers and facilitators to usability and acceptability.Results: Mean exercise per week increased from 10.6 to 14.1 minutes in the control group and 9.6 to 36.8 minutes in the intervention group. All study processes and measures appeared feasible; 72% of those invited consented to taking part and 92% completed 6-week follow-up. Individual domains for the System Usability Scores (SUS) showed participants felt veryconfident’usingthesystemwith⊃port(70%),wod−’sinℎℎ⊃or(70%),̲like to use exergames frequently’ (50%) and found the system easy→use’(90%).However,theyalsofe&lt;they→’(90%).,ℎ&lt;ℎneeded to learn a lot at the beginning’ (40%) and would `need technical support’ (70%) for independent use of the exergames. Mean overall SUS was 63 reflecting moderate usability for independent use. Qualitative data indicated exergames were well received and highlighted motivational and social aspects; costs and set up. Staff also felt exergaming complemented traditional care.Discussion: Our study contributes to the evidence guiding the use of exergames to deliver suitable falls prevention interventions for older adults within sheltered housing in community settings.<br/

Exergames for falls prevention in sheltered homes:A feasibility study

Introduction:Falls prevention is a global priority given its substantial impact on older adults and cost to healthcare systems. Advances in telerehabilitation technology such as `exergaming’ show potential for delivering accessible, engaging exercise programs for older adults. This study aimed to establish the feasibility, acceptability and usability of exergaming in sheltered housing.Methods: A mixed-methods study with participants randomised in 2 sheltered housing facilities to intervention (n = 1 home, 12 participants) and control (n = 1 home 2, 12 participants) provided usual care for all, (physiotherapy prescribed strength and balance exercises and falls prevention advice) and a 6-week supervised exergaming programme (MIRA) offered 3 times per week to the intervention group only. At 6 weeks, feasibility, usability and acceptability outcomes were collected and analysed using descriptive statistics; qualitative focus groups with participants and interviews with staff were also completed and thematically analysed to elicit barriers and facilitators to usability and acceptability.Results: Mean exercise per week increased from 10.6 to 14.1 minutes in the control group and 9.6 to 36.8 minutes in the intervention group. All study processes and measures appeared feasible; 72% of those invited consented to taking part and 92% completed 6-week follow-up. Individual domains for the System Usability Scores (SUS) showed participants felt veryconfident’usingthesystemwith⊃port(70%),wod−’sinℎℎ⊃or(70%),̲like to use exergames frequently’ (50%) and found the system easy→use’(90%).However,theyalsofe&lt;they→’(90%).,ℎ&lt;ℎneeded to learn a lot at the beginning’ (40%) and would `need technical support’ (70%) for independent use of the exergames. Mean overall SUS was 63 reflecting moderate usability for independent use. Qualitative data indicated exergames were well received and highlighted motivational and social aspects; costs and set up. Staff also felt exergaming complemented traditional care.Discussion: Our study contributes to the evidence guiding the use of exergames to deliver suitable falls prevention interventions for older adults within sheltered housing in community settings.<br/

Late Quaternary evolution of a lowland anastomosing river system: Geological-topographic inheritance, non-uniformity and implications for biodiversity and management

Lowland multiple-channel rivers are characterised by floodplain-corridor heterogeneity, high ecological and heritage value, and can be in quasi-stable states. This holistic study of a surviving temperate zone example (Culm, UK) uses geomorphological mapping, 14C, direct sediment dating (OSL, fallout radionuclides), and palaeoecology. This reveals the evolution of a channel-floodplain system from an initial braided state in the Late Pleistocene to its late Holocene anastomosing state. After the Pleistocene Holocene transition the reduced channel system incised into its braid-plain, only able to rework gravels locally due to reduced competence in relation to inherited bounding sediment calibre. This resulted in the creation of terrace islands, palaeochannels, and a stable anastomosing pattern dominated by channel junctions, bifurcations and palaeochannel intersections. Survey, coring and excavation reveal a persistence of mid-channel bars and riffles at channel junctions, and where channels crossed palaeochannel fills. In common with most other European lowland rivers this system evolves in the later Holocene due to both climate and catchment changes with a major hydrological critical transition in the mid-Holocene (c. 5300 BP). However, in the case of the Culm, the increase in fine sediment supply often seen in lowland catchments in the Middle-Late Holocene, occurred later, and was insufficient to convert the system to a single medium-low sinuosity channel-floodplain. This allowed the persistence of high heterogeneity and biodiversity (including the persistence of riffle beetles) as part of multiple-scales of non-uniformity. Indeed the pool-riffle persistence is an example of this system’s non-uniformity, being due, at least in part, to the effects of previous channel history. This paper reveals why this river survived in a multichannel state, and by implication, why others did not. These results are being used in the bespoke eco-heritage management of the Culm, but could also inform the restoration of other former multi-channel lowland temperate river systems worldwide

Spatial correlations in hexagons generated via a Kerr nonlinearity

We consider the hexagonal pattern forming in the cross-section of an optical beam produced by a Kerr cavity, and we study the quantum correlations characterizing this structure. By using arguments related to the symmetry broken by the pattern formation, we identify a complete scenario of six-mode entanglement. Five independent phase quadratures combinations, connecting the hexagonal modes, are shown to exhibit sub-shot-noise fluctuations. By means of a non-linear quantum calculation technique, quantum correlations among the mode photon numbers are demonstrated and calculated.Comment: ReVTeX file, 20 pages, 7 eps figure

Frequency selection by soliton excitation in nondegenerate intracavity downconversion

We show that soliton excitation in intracavity downconversion naturally selects a strictly defined frequency difference between the signal and idler fields. In particular, this phenomenon implies that if the signal has smaller losses than the idler then its frequency is pulled away from the cavity resonance and the idler frequency is pulled towards the resonance and {\em vice versa}. The frequency selection is shown to be closely linked with the relative energy balance between the idler and signal fields.Comment: 5 pages, 3 figures. To appear in Phys Rev Let

Social phenotype-dependent selection of social environment in wild great and blue tits: an experimental study

There is growing evidence that individuals actively assess the match between their phenotype and their environment when making habitat choice decisions (so-called matching habitat choice). However, to our knowledge, no studies have considered how the social environment may interact with social phenotype in determining habitat choice, despite habitat choice being an inherently social process and growing evidence for individual variation in sociability. We conducted an experiment using wild great and blue tits to understand how birds integrate their social phenotype and social environment when choosing where and how to feed. We used programmable feeders to (i) record social interactions and estimate social phenotype, and (ii) experimentally manipulate the local density experienced by birds of differing social phenotype. By tracking feeder usage, we estimated how social environment and social phenotype predicted feeder choice and feeding behaviour. Both social environment and social phenotype predicted feeder usage, but a bird's decision to remain in a particular social environment did not depend on their social phenotype. By contrast, for feeding behaviour, responses to the social environment depended on social phenotype. Our results provide rare evidence of matching habitat choice and shed light on the dependence of habitat choice on between-individual differences in social phenotype

Searches for Ultra-Compact Dwarf Galaxies in Galaxy Groups

We present the results of a search for ultra-compact dwarf galaxies (UCDs) in six different galaxy groups: Dorado, NGC1400, NGC0681, NGC4038, NGC4697 and NGC5084. We searched in the apparent magnitude range 17.5 < b_j < 20.5 (except NGC5084: 19.2 < b_j < 21.0). We found 1 definite plus 2 possible UCD candidates in the Dorado group and 2 possible UCD candidates in the NGC1400 group. No UCDs were found in the other groups. We compared these results with predicted luminosities of UCDs in the groups according to the hypothesis that UCDs are globular clusters formed in galaxies. The theoretical predictions broadly agree with the observational results, but deeper surveys are needed to fully test the predictions.Comment: 8 pages, 2 figures, accepted for publication in MNRA