Feigenbaum graphs: a complex network perspective of chaos

The recently formulated theory of horizontal visibility graphs transforms time series into graphs and allows the possibility of studying dynamical systems through the characterization of their associated networks. This method leads to a natural graph-theoretical description of nonlinear systems with qualities in the spirit of symbolic dynamics. We support our claim via the case study of the period-doubling and band-splitting attractor cascades that characterize unimodal maps. We provide a universal analytical description of this classic scenario in terms of the horizontal visibility graphs associated with the dynamics within the attractors, that we call Feigenbaum graphs, independent of map nonlinearity or other particulars. We derive exact results for their degree distribution and related quantities, recast them in the context of the renormalization group and find that its fixed points coincide with those of network entropy optimization. Furthermore, we show that the network entropy mimics the Lyapunov exponent of the map independently of its sign, hinting at a Pesin-like relation equally valid out of chaos.Comment: Published in PLoS ONE (Sep 2011

Sarah's birth. How the medicalisation of childbirth may be shaped in different settings: vignette from a study of routine intervention in Jeddah, Saudi Arabia

Background The expansion of the medicalisation of childbirth has been described in the literature as being a global phenomenon. The vignette described in this paper, selected from an ethnographic study of routine intervention in Saudi Arabian hospitals illustrates how the worldwide spread of the bio-medical model does not take place within a cultural vacuum. Aim To illuminate the ways in which the medicalisation of birth may be understood and practised in different cultural settings, through a vignette of a specific birth, drawn as a typical case from an ethnographic study that investigated clinical decision-making in the second stage of labour in Saudi Arabia. Methods Ethnographic data collection methods, including participant observation and interviews. The data presented in this paper are drawn from ethnographic field notes collected during field work in Saudi Arabia, and informed by analysis of a wider set of field notes and interviews with professionals working in this context. Findings While the medicalisation of care is a universal phenomenon, the ways in which the care of women is managed using routine medical intervention are framed by the local cultural context in which these practices take place. Discussion The ethnographic data presented in this paper shows the medicalisation of birth thesis to be incomplete. The evidence presented in this paper illustrates how local belief systems are not so much subsumed by the expansion of the bio-medical model of childbirth, rather they may actively facilitate a process of localised reinterpretation of such universalised and standardised practices. In this case, aspects of the social and cultural context of Jeddah operates to intensify the biomedical model at the expense of respectful maternity care. Conclusion In this article, field note data on the birth of one Saudi Arabian woman is used as an illustration of how the medicalisation of childbirth has been appropriated and reinterpreted in Jeddah, Saudi Arabia

Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis

The morphology of roots and root systems influences the efficiency by which plants acquire nutrients and water, anchor themselves and provide stability to the surrounding soil. Plant genotype and the biotic and abiotic environment significantly influence root morphology, growth and ultimately crop yield. The challenge for researchers interested in phenotyping root systems is, therefore, not just to measure roots and link their phenotype to the plant genotype, but also to understand how the growth of roots is influenced by their environment. This review discusses progress in quantifying root system parameters (e.g. in terms of size, shape and dynamics) using imaging and image analysis technologies and also discusses their potential for providing a better understanding of root:soil interactions. Significant progress has been made in image acquisition techniques, however trade-offs exist between sample throughput, sample size, image resolution and information gained. All of these factors impact on downstream image analysis processes. While there have been significant advances in computation power, limitations still exist in statistical processes involved in image analysis. Utilizing and combining different imaging systems, integrating measurements and image analysis where possible, and amalgamating data will allow researchers to gain a better understanding of root:soil interactions

Stronger Neural Modulation by Visual Motion Intensity in Autism Spectrum Disorders

Theories of autism spectrum disorders (ASD) have focused on altered perceptual integration of sensory features as a possible core deficit. Yet, there is little understanding of the neuronal processing of elementary sensory features in ASD. For typically developed individuals, we previously established a direct link between frequency-specific neural activity and the intensity of a specific sensory feature: Gamma-band activity in the visual cortex increased approximately linearly with the strength of visual motion. Using magnetoencephalography (MEG), we investigated whether in individuals with ASD neural activity reflect the coherence, and thus intensity, of visual motion in a similar fashion. Thirteen adult participants with ASD and 14 control participants performed a motion direction discrimination task with increasing levels of motion coherence. A polynomial regression analysis revealed that gamma-band power increased significantly stronger with motion coherence in ASD compared to controls, suggesting excessive visual activation with increasing stimulus intensity originating from motion-responsive visual areas V3, V6 and hMT/V5. Enhanced neural responses with increasing stimulus intensity suggest an enhanced response gain in ASD. Response gain is controlled by excitatory-inhibitory interactions, which also drive high-frequency oscillations in the gamma-band. Thus, our data suggest that a disturbed excitatoryinhibitory balance underlies enhanced neural responses to coherent motion in ASD

Collaborative care for depression and anxiety problems

This review is published as a Cochrane Review in the Cochrane Database of Systematic Reviews 2012, Issue 10. Cochrane Reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and the Cochrane Database of Systematic Reviews should be consulted for the most recent version of the Review.Common mental health problems, such as depression and anxiety, are estimated to affect up to 15% of the UK population at any one time, and health care systems worldwide need to implement interventions to reduce the impact and burden of these conditions. Collaborative care is a complex intervention based on chronic disease management models that may be effective in the management of these common mental health problems

The Bodyguard of the Caliphs During the Umayyad and the Early Abbasid Periods

During early Islam, the <em>ḥaras</em> was a government unit that was responsible for the personal security of the caliph. Since the reign of the first Umayyad Caliph, Mu‘āwiya b. Abī Sufyān, the <em>ḥaras</em>, headed by a <em>ḥaras</em> chief, protected all caliphs. This paper will attempt to describe the functions of the <em>ḥaras</em> during the Umayyad and the early Abbasid caliphates by delineating the characteristics of the <em>ḥaras</em> chiefs under the different caliphs. As with other institutions during early Islam, accounts that refer to the <em>ḥaras</em> offer information about the men who headed it rather than about the institution itself, making it necessary to employ the method of prosopography in order to arrive at an adequate description of the institution. The majority of the <em>ḥaras</em> chiefs appear to have been <em>mawālī</em>, often entrusted with administrative offices in addition to heading the <em>ḥaras</em>. It seems that the <em>ḥaras</em> chiefs were responsible not only for protecting the caliphs, but also for carrying out executions. The establishment of the <em>ḥaras</em>, the qualifications of the <em>ḥaras</em> chiefs and the weapons used by members of this body are also discussed. This significant institution has not yet received due attention in the literature. I hope to provide a useful outline and to open up a space for further research.<br><br>Durante los principios del Islam el <em>ḥaras</em> fue una unidad del gobierno, responsable de la seguridad personal de los califas. Desde el reinado del primer califa omeya Mu‘āwiya b. Abī Sufyān, el <em>ḥaras</em> que estaba bajo las ordenes de su jefe, custodió a todos los califas. El propósito de este artículo es describir el papel del <em>ḥaras</em> durante el periodo del Califato Omeya y el principio del Califato Abbasí y describir las características de los jefes del <em>ḥaras</em> bajo los diferentes califas. Al igual que con otras instituciones durante el comienzo del Islam, la información relacionada con el <em>ḥaras</em> se basa en la vida y obra de los hombres que los encabezaban y no tanto en los datos específicos de la institución. Esto hace necesario el uso del método prosopográfico para conseguir una descripción adecuada de la institución. La mayoría de los dirigentes del <em>ḥaras</em> fueron <em>mawālī</em> y muchas veces eran responsables de las funciones administrativas, además de comandar el <em>ḥaras</em>. Sus dirigentes no solo eran responsables de la protección de los califas, sino tambien de ejecutar sus órdenes. Este artículo explica también la creación del <em>ḥaras</em>, las cualidades de sus líderes y las armas que utilizaban. Este grupo tan importante ha recibido poca atención por parte de la investigación actual

Strategic plan for integrated care of patients with kidney failure

There is a huge gap between the number of patients worldwide requiring versus those actually receiving safe, sustainable, and equitable care for kidney failure. To address this, the International Society of Nephrology coordinated the development of a Strategic Plan for Integrated Care of Patients with Kidney Failure. Implementation of the plan will require engagement of the whole kidney community over the next 5-10 years