Evolutionary neural networks : models and applications

The scaling problems which afflict attempts to optimise neural networks (NNs) with genetic algorithms (GAs) are disclosed. A novel GA-NN hybrid is introduced, based on the bumptree, a little-used connectionist model. As well as being computationally efficient, the bumptree is shown to be more amenable to genetic coding lthan other NN models. A hierarchical genetic coding scheme is developed for the bumptree and shown to have low redundancy, as well as being complete and closed with respect to the search space. When applied to optimising bumptree architectures for classification problems the GA discovers bumptrees which significantly out-perform those constructed using a standard algorithm. The fields of artificial life, control and robotics are identified as likely application areas for the evolutionary optimisation of NNs. An artificial life case-study is presented and discussed. Experiments are reported which show that the GA-bumptree is able to learn simulated pole balancing and car parking tasks using only limited environmental feedback. A simple modification of the fitness function allows the GA-bumptree to learn mappings which are multi-modal, such as robot arm inverse kinematics. The dynamics of the 'geographic speciation' selection model used by the GA-bumptree are investigated empirically and the convergence profile is introduced as an analytical tool. The relationships between the rate of genetic convergence and the phenomena of speciation, genetic drift and punctuated equilibrium arc discussed. The importance of genetic linkage to GA design is discussed and two new recombination operators arc introduced. The first, linkage mapped crossover (LMX) is shown to be a generalisation of existing crossover operators. LMX provides a new framework for incorporating prior knowledge into GAs.Its adaptive form, ALMX, is shown to be able to infer linkage relationships automatically during genetic search

Suicide Information Database-Cymru: a protocol for a population-based, routinely collected data linkage study to explore risks and patterns of healthcare contact prior to suicide to identify opportunities for intervention

Introduction Prevention of suicide is a global public health challenge extending beyond mental health services. Linking routinely collected health and social care system data records for the same individual across different services and over time has enormous potential in suicide research. Most previous research linking suicide mortality data with routinely collected electronic health records involves only one or two domains of healthcare provision such as psychiatric inpatient care. This protocol paper describes the development of a population-based, routinely collected data linkage study: the Suicide Information Database Cymru (SID-Cymru). SID-Cymru aims to contribute to the information available on people who complete suicide. Methods and analysis SID-Cymru will facilitate a series of electronic case–control studies based in the Secure Anonymised Information Linkage (SAIL) Databank. We have identified 2664 cases of suicide in Wales between 2003 and 2011 from routinely collected mortality data using International Classification of Diseases, Tenth Revision, codes X60–X84 (intentional self-harm) and Y10–Y34 (undetermined intent). Each case will be matched by age and sex to at least five controls. Records will be collated and linked from routinely collected health and social data in Wales for each individual. Conditional logistic regression will be applied to produce crude and confounder (including general practice, socioeconomic status) adjusted ORs. Ethics and dissemination The SAIL Databank has the required ethical permissions in place to analyse anonymised data. Ethical approval has been granted by the Information Governance Review Panel (IGRP). Findings will be disseminated through peer-reviewed publications, consultations with stakeholders and national/international conference presentations. The improved understanding of the prior health, nature of previous contacts with services and wider social circumstances of those who complete suicide will assist in prevention policy, service organisation and delivery. SID-Cymru is funded through the National Institute for Social Care and Health Research, Welsh Government (RFS-12-25)

Conformational properties of biocompatible poly(2-ethyl-2-oxazoline)s in phosphate buffered saline

Inspired by the increasing popularity of poly(2-ethyl-2-oxazoline) (PEtOx) for biomedical applications, this study reports the complete and thorough solution analysis of the homologous series of biocompatible PEtOx samples in a very broad range of molecular weights ranging from 11.2 x 10(3) g mol(-1) up to 260 x 10(3) g mol(-1). The main focus of the research was on the determination of the conformational properties of PEtOx macromolecules at a temperature of 37 degrees C in phosphate buffered saline (PBS) simulating the parameters of physiological media. The polymers were studied in PBS solutions by analytical ultracentrifugation, dynamic light scattering (DLS), translational diffusion, and intrinsic viscosity measurements in a temperature range from 15 degrees C up to 72 degrees C. The complete set of Kuhn-Mark-Houwink-Sakurada scaling relationships revealed linear trends over the whole range of the studied molar masses, while the determined scaling indices at 37 degrees C correspond to the coil conformation in a thermodynamically good solvent ([eta] = 0.045 x M-0.62, s(0) = 0.010 x M-0.46 and D-0 = 1750 x M-0.54). Based on the intrinsic viscosity values (most sensitive characteristic to the size variations of polymer coils, [eta] similar to r(3)), it was demonstrated that PEtOx macromolecules in PBS solutions undergo a transition from swollen polymer coils with gradual deterioration of thermodynamic quality of solutions within the temperature range of 15-45 degrees C, reaching theta-conditions at 55 degrees C with further precipitation at 62-72 degrees C. Also, to the best of our knowledge, the conformational parameters (equilibrium rigidity/the Kuhn segment length and the diameter of the polymer chain) of PEtOx macromolecules were evaluated under physiological conditions for the first time and constitute A = 1.8 +/- 0.3 nm and d = 0.7 +/- 0.4 nm. These equilibrium rigidity values classify PEtOx as a flexible macromolecule with rigidity similar to that of poly(ethylene glycol). For the first time, we were able to demonstrate a direct influence of thermosensitivity on the rigidity of the biocompatible polymer: PEtOx. The Kuhn segment length is undoubtedly decreasing when approaching the LCST

Review article: The hydrology of debris-covered glaciers – state of the science and future research directions

authorsversionNon peer reviewe

Continuous borehole optical televiewing reveals variable englacial debris concentrations at Khumbu Glacier, Nepal

Surface melting of High Mountain Asian debris-covered glaciers shapes the seasonal water supply to millions of people. This melt is strongly influenced by the spatially variable thickness of the supraglacial debris layer, which is itself partially controlled by englacial debris concentration and melt-out. Here, we present measurements of deep englacial debris concentrations from debris-covered Khumbu Glacier, Nepal, based on four borehole optical televiewer logs, each up to 150 m long. The mean borehole englacial debris content is ≤ 0.7% by volume in the glacier’s mid-to-upper ablation area, and increases to 6.4% by volume near the terminus. These concentrations are higher than those reported for other valley glaciers, although those measurements relate to discrete samples while our approach yields a continuous depth profile. The vertical distribution of englacial debris increases with depth, but is also highly variable, which will complicate predictions of future rates of surface melt and debris exhumation at such glaciers

Hydrology of debris-covered glaciers in High Mountain Asia

The hydrological characteristics of debris-covered glaciers are known to be fundamentally different from those of clean-ice glaciers, even within the same climatological, geological, and geomorphological setting. Understanding how these characteristics influence the timing and magnitude of meltwater discharge is particularly important for regions where downstream communities rely on this resource for sanitation, irrigation, and hydropower, such as High Mountain Asia. The hydrology of debris-covered glaciers is complex: rugged surface topographies typically route meltwater through compound supraglacial-englacial systems involving both channels and ponds, as well as pathways that remain unknown. Low-gradient tongues that extend several kilometres retard water conveyance and promote englacial storage. Englacial conduits are frequently abandoned and reactivated as water supply changes, new lines of permeability are exploited, and drainage is captured due to high rates of surface and subsurface change. Seasonal influences, such as the monsoon, are superimposed on these distinctive characteristics, reorganising surface and subsurface drainage rapidly from one season to the next. Recent advances in understanding have mostly come from studies aimed at quantifying and describing supraglacial processes; little is known about the subsurface hydrology, particularly the nature (or even existence) of subglacial drainage. In this review, we consider in turn the supraglacial, englacial, subglacial, and proglacial hydrological domains of debris-covered glaciers in High Mountain Asia. We summarise different lines of evidence to establish the current state of knowledge and, in doing so, identify major knowledge gaps. Finally, we use this information to suggest six themes for future hydrological research at High Mountain Asian debris-covered glaciers in order to make timely long-term predictions of changes in the water they supply

Clinical and morphological characteristic of the case of secondary enucleation of the eye with retinoblastoma

Purpose: To analyze case of secondary enucleation of a child’s eye with recurrent retinoblastoma (RB) developing due to parents’ failure to take the child to surveillance appointments after salvage eye therapy. Material and Methods: Observation and treatment of a 10-month child diagnosed with bilateral RB. The right eye was diagnosed with RB at stage T1N0M0, and the left eye, with RB at stage T3cN0M0 complicated by secondary glaucoma. Results: Salvage eye therapy was performed which included six cycles of combined multiagent chemotherapy (with systemic intravitreal chemoreduction melphalan injection), followed by three courses of laser coagulation of tumor focus in the right eye and additional seventh local chemotherapy in the left eye. As a result, type 4 RB regression pattern in the right eye, and was developed incomplete type 2 RB regression pattern (“fish-flesh” appearance) in the left eye. However, after the child did not visit the medical care facility for surveillance and treatment during seven months, tumor regrowth developed. Secondary enucleation of the left eye was performed due to big tumor size, anterior chamber involvement blindness, and the absence of visual functions without prospects for their improvement. Histopathology found undifferentiated retinoblastoma with invasion into the episclera, the child was administered two cycles of chemoreduction as well as external beam radiotherapy of the left orbit using a medical linear accelerator system. Conclusion: Should tumor recurrence occur or if there is no tumor control, urgent secondary enucleation with eye ball histopathology and, if indicated, further adjuvant therapy are recommended to prevent metastasis and save child’s life

The Role of Differential Ablation and Dynamic Detachment in Driving Accelerating Mass Loss From a Debris-Covered Himalayan Glacier

Sustained mass loss from Himalayan glaciers is causing supraglacial debris to expand and thicken, with the expectation that thicker debris will suppress ablation and extend glacier longevity. However, debris-covered glaciers are losing mass at similar rates to clean-ice glaciers in High Mountain Asia. This rapid mass loss is attributed to the combined effects of; (a) low or reversed mass balance gradients across debris-covered glacier tongues, (b) differential ablation processes that locally enhance ablation within the debris-covered section of the glacier, for example, at ice cliffs and supraglacial ponds, and (c) a decrease in ice flux from the accumulation area in response to climatic warming. Adding meter-scale spatial variations in supraglacial debris thickness to an ice-flow model of Khumbu Glacier, Nepal, increased mass loss by 47% relative to simulations assuming a continuous debris layer over a 31-year period (1984–2015 CE) but overestimated the reduction in ice flux. Therefore, we investigated if simulating the effects of dynamic detachment of the upper active glacier from the debris-covered tongue would give a better representation of glacier behavior, as suggested by observations of change in glacier dynamics and structure indicating that this process occurred during the last 100 years. Observed glacier change was reproduced more reliably in simulations of the active, rather than entire, glacier extent, indicating that Khumbu Glacier has passed a dynamic tipping point by dynamically detaching from the heavily debris-covered tongue that contains 20% of the former ice volume

Be‐10 dating of ice‐marginal moraines in the Khumbu Valley, Nepal, Central Himalaya, reveals the response of monsoon‐influenced glaciers to Holocene climate change

The dynamic response of large mountain glaciers to climatic forcing operates over timescales of several centuries and therefore understanding how these glaciers change requires observations of their behavior through the Holocene. We used Be-10 exposure-age dating and geomorphological mapping to constrain the evolution of glaciers in the Khumbu Valley in the Everest region of Nepal. Khumbu and Lobuche Glaciers are surrounded by high-relief lateral and terminal moraines from which seven glacial stages were identified and dated to 7.4 ± 0.2, 5.0 ± 0.3, 3.9 ± 0.1, 2.8 ± 0.2, 1.3 ± 0.1, 0.9 ± 0.02, and 0.6 ± 0.16 ka. These stages correlate to each of the seven latest Holocene regional glacial stages identified across the monsoon-influenced Himalaya, demonstrating that a coherent record of high elevation terrestrial palaeoclimate change can be extracted from dynamic mountain landscapes. The time-constrained moraine complex represents a catchment-wide denudation rate of 0.8–1.4 mm a−1 over the last 8 kyr. The geometry of the ablation area of Khumbu Glacier changed around 4 ka from a broad, shallow ice tongue to become narrower and thicker as restricted by the topographic barrier of the terminal moraine complex