Delay Equations and Radiation Damping

Starting from delay equations that model field retardation effects, we study the origin of runaway modes that appear in the solutions of the classical equations of motion involving the radiation reaction force. When retardation effects are small, we argue that the physically significant solutions belong to the so-called slow manifold of the system and we identify this invariant manifold with the attractor in the state space of the delay equation. We demonstrate via an example that when retardation effects are no longer small, the motion could exhibit bifurcation phenomena that are not contained in the local equations of motion.Comment: 15 pages, 1 figure, a paragraph added on page 5; 3 references adde

New summing algorithm using ensemble computing

We propose an ensemble algorithm, which provides a new approach for evaluating and summing up a set of function samples. The proposed algorithm is not a quantum algorithm, insofar it does not involve quantum entanglement. The query complexity of the algorithm depends only on the scaling of the measurement sensitivity with the number of distinct spin sub-ensembles. From a practical point of view, the proposed algorithm may result in an exponential speedup, compared to known quantum and classical summing algorithms. However in general, this advantage exists only if the total number of function samples is below a threshold value which depends on the measurement sensitivity.Comment: 13 pages, 0 figures, VIth International Conference on Quantum Communication, Measurement and Computing (Boston, 2002

Comparison of methods for determining unsaturated hydraulic conductivity in the wet range to evaluate the sensitivity of detectors

The design of passive lysimeters or wetting front detectors determines the tensions at which they collect a water sample from an unsaturated soil. When deployed in the field to help manage irrigation, it is necessary to know the minimum flux of water that can be sampled by a passive lysimeter and how this relates to the drainage flux at field capacity. This requires a good estimate of the unsaturated hydraulic conductivity characteristic, K(h), in the wet range (< 10 kPa). We compared various field, laboratory and theoretical approaches for obtaining the K(h) function and compared these to a reference K(h) function derived by applying inverse modelling approaches to field drainage experimental data. The Van Genuchten model and three of the pedotransfer models produced K(h) functions with a root mean square error of less than 5% compared to the reference, and appear to be simple methods of obtaining a reasonable estimate of unsaturated hydraulic conductivity. However, despite the goodness of fit, there can be a 10-fold difference in conductivity at a given tension < 10 kPa estimated from the different methods. Moreover, water content at field capacity depends entirely on whether field capacity is defined as time elapsed after saturation, a set tension or a minimum flux.Funding for this research was provided by the Water Research Commission (WRC), South Africa, as part of the WRC research project entitled ‘Adapting the wetting front detector to the needs of small-scale furrow irrigators and providing a basis for the interpretation of salt and nutrient measurements from the water sample’.http://www.wrc.org.zanf201

The Gelfand widths of ℓp\ell_p-balls for 0<p≤10<p\leq 1

We provide sharp lower and upper bounds for the Gelfand widths of $\ell_p$-balls in the $N$-dimensional $\ell_q^N$-space for $0<p\leq 1$ and $p<q \leq 2$. Such estimates are highly relevant to the novel theory of compressive sensing, and our proofs rely on methods from this area.Comment: 15 page

Groundwater–surface water interactions in an ephemeral savanna catchment, Kruger National Park

The semi-arid conditions in savanna landscapes ensure that ephemeral drainage dominates the hydrological network in these dryland systems. Quantification of their hydrological processes is important to inform ecosystem understanding and future conservation efforts under a changing climate, and to provide guidance for restoration. By combining in situ hydrometric observations, hydrochemistry, remote sensing and a soil water balance model, we characterise the groundwater–surface water interactions in ephemeral low-order catchments of the granitoid regions of the southern Kruger National Park (KNP). Streams at the lowest orders are augmented by lateral interflows from the catena, although the second-and third-order stream reaches are conduits for groundwater recharge to the fractured rock aquifer; the soils of the crests and foot-slopes also show preferential flow, and are truly recharge soils, whilst the duplex soils of the midslopes clearly show their responsive nature to a low soil moisture deficit in the shallow horizons. Actual evaporation (aET) differed between catena elements with surprisingly little variation at third-order hillslopes, with the greatest overall aET at the first order. Meanwhile, soil water balances demonstrated a significant variation in storage of the riparian zones as a result of interflow from upslope and aET losses. Furthermore, data support broader-scale observations that groundwater recharge through the vadose zone to the fractured rock aquifer is dependent upon threshold antecedent precipitation conditions. Moderate precipitation events (5 mm/day – 35 mm/day) over a 2–3 week period initiate groundwater responses with a 2–3 month lag, whilst intense precipitation events (>100 mm/day) are expressed within 2–3 weeks

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.Comment: 5 chapters, 160 pages, 107 figure

Setting research priorities to improve global newborn health and prevent stillbirths by 2025

Acknowledgements: The authors thank the expert group for their time and effort in this priority–setting exercise, and the contribution of anonymous reviewers to the final version of this report. We acknowledge inputs from Dr Diane Morof from Centers for Disease Control and Prevention, USA. Funding: This work was supported by Save the Children.Peer reviewedPublisher PD

Esophagectomy without mortality: What can surgeons do?

Introduction: Surgical resection remains the mainstay treatment for patients with localized esophageal cancer. It is, however, a complex procedure. Mortality rate used to be high, but in recent years, death rate has been reduced to below 5% in specialized centers. Methods: Outcome of esophagectomy can be improved by paying attention to (1) appropriate patient section, (2) choice of surgical techniques and their execution, and (3) optimizing perioperative care. A volume-outcome relationship is also evident. Surgeons can perform esophagectomy without mortality, but a multi-disciplinary team management is essential to achieve this goal. © 2009 The Society for Surgery of the Alimentary Tract.postprin

Mapping of HNF4α target genes in intestinal epithelial cells

© 2009 Boyd et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Setting research priorities to improve global newborn health and prevent stillbirths by 2025.

BACKGROUND: In 2013, an estimated 2.8 million newborns died and 2.7 million were stillborn. A much greater number suffer from long term impairment associated with preterm birth, intrauterine growth restriction, congenital anomalies, and perinatal or infectious causes. With the approaching deadline for the achievement of the Millennium Development Goals (MDGs) in 2015, there was a need to set the new research priorities on newborns and stillbirth with a focus not only on survival but also on health, growth and development. We therefore carried out a systematic exercise to set newborn health research priorities for 2013-2025. METHODS: We used adapted Child Health and Nutrition Research Initiative (CHNRI) methods for this prioritization exercise. We identified and approached the 200 most productive researchers and 400 program experts, and 132 of them submitted research questions online. These were collated into a set of 205 research questions, sent for scoring to the 600 identified experts, and were assessed and scored by 91 experts. RESULTS: Nine out of top ten identified priorities were in the domain of research on improving delivery of known interventions, with simplified neonatal resuscitation program and clinical algorithms and improved skills of community health workers leading the list. The top 10 priorities in the domain of development were led by ideas on improved Kangaroo Mother Care at community level, how to improve the accuracy of diagnosis by community health workers, and perinatal audits. The 10 leading priorities for discovery research focused on stable surfactant with novel modes of administration for preterm babies, ability to diagnose fetal distress and novel tocolytic agents to delay or stop preterm labour. CONCLUSION: These findings will assist both donors and researchers in supporting and conducting research to close the knowledge gaps for reducing neonatal mortality, morbidity and long term impairment. WHO, SNL and other partners will work to generate interest among key national stakeholders, governments, NGOs, and research institutes in these priorities, while encouraging research funders to support them. We will track research funding, relevant requests for proposals and trial registers to monitor if the priorities identified by this exercise are being addressed