735 research outputs found
Palaeogenomics of the Hydrocarbon Producing Microalga Botryococcus braunii
This is the final version. Available from the publisher via the DOI in this record.Botryococcus braunii is a colonial microalga that appears early in the fossil record and is a sensitive proxy
of environmental and hydroclimatic conditions. Palaeozoic Botryococcus fossils which contribute up
to 90% of oil shales and approximately 1% of crude oil, co-localise with diagnostic geolipids from the
degradation of source-signature hydrocarbons. However more recent Holocene sediments demonstrate
no such association. Consequently, Botryococcus are identifed in younger sediments by morphology
alone, where potential misclassifcations could lead to inaccurate paleoenvironmental reconstructions.
Here we show that a combination of fow cytometry and ancient DNA (aDNA) sequencing can
unambiguously identify Botryococcus microfossils in Holocene sediments with hitherto unparalleled
accuracy and rapidity. The application of aDNA sequencing to microfossils ofers a far-reaching
opportunity for understanding environmental change in the recent geological record. When allied
with other high-resolution palaeoenvironmental information such as aDNA sequencing of humans
and megafauna, aDNA from microfossils may allow a deeper and more precise understanding of past
environments, ecologies and migrations.Medical Research Council (MRC)Wellcome TrustBiotechnology and Biological Science Research Council (BBSRC
Tropical and mid-latitude forcing of continental Antarctic temperatures
Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipitation, ocean circulation and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually resolved record of δD – a proxy for temperature – from the geographic South Pole where we find a significant influence from extratropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a significant influence on mid- to high-latitude SH climate, modulated by the tropical Pacific Ocean. This work adds to a growing body of literature confirming the important roles of tropical and mid-latitude atmospheric circulation variability on Antarctic temperatures. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.C.S.M. Turney, C.J. Fogwill, A.R. Klekociuk, T.D. van Ommen, M.A.J. Curran, A.D. Moy, and J.G. Palme
Inducing safer oblique trees without costs
Decision tree induction has been widely studied and applied. In safety applications, such as determining whether a chemical process is safe or whether a person has a medical condition, the cost of misclassification in one of the classes is significantly higher than in the other class. Several authors have tackled this problem by developing cost-sensitive decision tree learning algorithms or have suggested ways of changing the
distribution of training examples to bias the decision tree learning process so as to take account of costs. A prerequisite for applying such algorithms is the availability of costs of misclassification.
Although this may be possible for some applications, obtaining reasonable estimates of costs of misclassification is not easy in the area of safety.
This paper presents a new algorithm for applications where the cost of misclassifications cannot be quantified, although the cost of misclassification in one class is known to be significantly higher than in another class. The algorithm utilizes linear discriminant analysis to identify oblique relationships between continuous attributes and then carries out an appropriate modification to ensure that the resulting tree errs on the side of safety. The algorithm is evaluated with respect to one of the best known cost-sensitive algorithms (ICET), a well-known oblique decision tree algorithm (OC1) and an algorithm that utilizes robust linear programming
Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene
The Amundsen Sea Low (ASL) plays a major role in the climate and environment
of Antarctica and the Southern Ocean, including surface air temperature and
sea ice concentration changes. Unfortunately, a relative dearth of
observational data across the Amundsen and Bellingshausen seas prior to the
satellite era (post-1979) limits our understanding of the past behaviour and
impact of the ASL. The limited proxy evidence for changes in the ASL are
primarily restricted to the Antarctic where ice core evidence suggests a
deepening of the atmospheric pressure system during the late Holocene.
However, no data have previously been reported from the northern side of the
ASL. Here we report a high-resolution, multi-proxy study of a 5000-year-long
peat record from the Falkland Islands, a location sensitive to contemporary
ASL dynamics which modulates northerly and westerly airflow across the
southwestern South Atlantic sector of the Southern Ocean. In combination with
climate reanalysis, we find a marked period of wetter, colder conditions most
likely the result of enhanced southerly airflow between 5000 and 2500 years
ago, suggesting limited ASL influence over the region. After 2500 years ago,
drier and warmer conditions were established, implying more westerly airflow
and the increased projection of the ASL onto the South Atlantic. The possible
role of the equatorial Pacific via atmospheric teleconnections in driving
this change is discussed. Our results are in agreement with Antarctic ice
core records and fjord sediments from the southern South American coast, and
suggest that the Falkland Islands provide a valuable location for reconstructing
high southern latitude atmospheric circulation changes on multi-decadal to
millennial timescales.</p
Ecological risk assessment of nano-enabled pesticides: a perspective on problem formulation
Plant protection products containing nanomaterials that alter the functionality or risk profile of active ingredients (nano-enabled pesticides) promise many benefits over conventional pesticide products. These benefits may include improved formulation characteristics, easier application, better targeting of pest species, increased efficacy, lower application rates, and enhanced environmental safety. After many years of research and development, nano-enabled pesticides are starting to make their way into the market. The introduction of this technology raises a number of issues for regulators, including how does the ecological risk assessment of nano-enabled pesticide products differ from that of conventional plant protection products? In this paper, a group drawn from regulatory agencies, academia, research, and the agrochemicals industry offers a perspective on relevant considerations pertaining to the problem formulation phase of the ecological risk assessment of nano-enabled pesticides.Glen W. Walker, Rai S. Kookana, Natalie E. Smith, Melanie Kah, Casey L. Doolette, Philip T. Reeves, Wess Lovell, Darren J. Anderson, Terence W. Turney, and Divina A. Navarr
Blended Learning in Health Education: Three Case Studies
Blended learning in which online education is combined with face-to-face education is especially useful for (future) health care professionals who need to keep up-to-date. Blended learning can make learning more efficient, for instance by removing barriers of time and distance. In the past distance-based learning activities have often been associated with traditional delivery-based methods, individual learning and limited contact. The central question in this paper is: can blended learning be active and collaborative? Three cases of blended, active and collaborative learning are presented. In case 1 a virtual classroom is used to realize online problem-based learning (PBL). In case 2 PBL cases are presented in Second Life, a 3D immersive virtual world. In case 3 discussion forums, blogs and wikis were used. In all cases face-to-face meetings were also organized. Evaluation results of the three cases clearly show that active, collaborative learning at a distance is possible. Blended learning enables the use of novel instructional methods and student-centred education. The three cases employ different educational methods, thus illustrating diverse possibilities and a variety of learning activities in blended learning. Interaction and communication rules, the role of the teacher, careful selection of collaboration tools and technical preparation should be considered when designing and implementing blended learning
New Multithreaded Hybrid CPU/GPU Approach to Hartree−Fock
In this article, a new multithreaded Hartree–Fock CPU/GPU method is presented which utilizes automatically generated code and modern C++ techniques to achieve a significant improvement in memory usage and computer time. In particular, the newly implemented Rys Quadrature and Fock Matrix algorithms, implemented as a stand-alone C++ library, with C and Fortran bindings, provides up to 40% improvement over the traditional Fortran Rys Quadrature. The C++ GPU HF code provides approximately a factor of 17.5 improvement over the corresponding C++ CPU code
Searches at HERA for Squarks in R-Parity Violating Supersymmetry
A search for squarks in R-parity violating supersymmetry is performed in e^+p
collisions at HERA at a centre of mass energy of 300 GeV, using H1 data
corresponding to an integrated luminosity of 37 pb^(-1). The direct production
of single squarks of any generation in positron-quark fusion via a Yukawa
coupling lambda' is considered, taking into account R-parity violating and
conserving decays of the squarks. No significant deviation from the Standard
Model expectation is found. The results are interpreted in terms of constraints
within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM
and the minimal Supergravity model, and their sensitivity to the model
parameters is studied in detail. For a Yukawa coupling of electromagnetic
strength, squark masses below 260 GeV are excluded at 95% confidence level in a
large part of the parameter space. For a 100 times smaller coupling strength
masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table
Global Peak in Atmospheric Radiocarbon Provides a Potential Definition for the Onset of the Anthropocene Epoch in 1965
Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the ‘Anthropocene’. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precisely-dated tree-ring records from Campbell Island (Southern Ocean) that capture peak atmospheric radiocarbon (14C) resulting from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. The only alien tree on the island, a Sitka spruce (Picea sitchensis), allows us to seasonally-resolve Southern Hemisphere atmospheric 14C, demonstrating the ‘bomb peak’ in this remote and pristine location occurred in the last-quarter of 1965 (October-December), coincident with the broader changes associated with the post-World War II ‘Great Acceleration’ in industrial capacity and consumption. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or ‘golden spike’, marking the onset of the Anthropocene Epoch
Judging parental competence: A cross‐country analysis of judicial decision makers' written assessment of mothers' parenting capacities in newborn removal cases
This paper examines the discretionary reasoning of the judiciary in three jurisdictions, England, Germany and Norway, in cases deciding whether a newborn child is safe with her parents or intervention is necessary. Our analysis focuses on one specific dimension of decision makers' exercise of discretion, namely, if and how the strengths and weaknesses of the mother are considered. The data material consists of all decisions concerning care orders of newborns from one large city in Germany from 2015 to 2017 (n = 27) and 2016 in Norway (n = 76) and all publicly available newborn removal decisions in England for 2015–2017 (n = 14). The findings reveal a high number of risk factors in the cases and less focus on risk‐reducing factors. The situation of the newborn is considered to be harmful, as most cases result in a care order. Judicial discretion differs by how much information, and what types of factors, are included in the justification for the decision. A learning point for decision makers and policymakers would be to actively undertake a balancing act between risk‐increasing and risk‐reducing factors.publishedVersio
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