1,907 research outputs found
Space–time clustering patterns in childhood leukaemia support a role for infection
Previous studies of space–time clustering in childhood leukaemia have produced equivocal and inconsistent results. To address this issue we have used Manchester Children's Tumour Registry leukaemia data in space–time clustering analyses. Knox tests for space–time interactions between cases were applied with fixed thresholds of close in space, < 5 km and close in time < 1 year apart. Addresses at birth as well as diagnosis were utilized. Tests were repeated replacing geographical distance with distance to the Nth nearest neighbour. N was chosen such that the mean distance was 5 km. Data were also examined by a second order procedure based on K-functions. All methods showed highly significant evidence of space–time clustering based on place of birth and time of diagnosis, particularly for all leukaemias aged 0–14 and 0–4 years, and acute lymphoblastic leukaemia (ALL) 0–4 years. Some results based on location at diagnosis were significant but mainly gave larger P -values. The results are consistent with an infectious hypothesis. Furthermore, we found an excess of male cases over females involved in space–time pairs. We suggest this may be related to genetic differences in susceptibility to infection between males and females. These findings provide the basis for future studies to identify possible infectious agents. © 2000 Cancer Research Campaig
Is optimal first-line chemotherapy deliverable in all newly diagnosed ovarian cancers? A population-based study
Phenotypic microarrays suggest Escherichia coli ST131 is not a metabolically distinct lineage of extra-intestinal pathogenic E. coli
Extraintestinal pathogenic E. coli (ExPEC) are the major aetiological agent of urinary tract infections (UTIs) in humans. The emergence of the CTX-M producing clone E. coli ST131 represents a major challenge to public health worldwide. A recent study on the metabolic potential of E. coli isolates demonstrated an association between the E. coli ST131 clone and enhanced utilisation of a panel of metabolic substrates. The studies presented here investigated the metabolic potential of ST131 and other major ExPEC ST isolates using 120 API test reagents and found that ST131 isolates demonstrated a lower metabolic activity for 5 of 120 biochemical tests in comparison to non-ST131 ExPEC isolates. Furthermore, comparative phenotypic microarray analysis showed a lack of specific metabolic profile for ST131 isolates countering the suggestion that these bacteria are metabolically fitter and therefore more successful human pathogens
What kind of memory has evolution wrought?: Introductory Article for the Special Issue of Memory: Adaptive memory: The emergence and nature of proximate mechanisms
It is without question that our memory system evolved through a process of natural selection. However, basic research into the evolutionary foundations of memory has begun in earnest only recently. This is quite peculiar as the majority, perhaps even all, of memory research relates to whether memory is adaptive or not. In this Special Issue of Memory we have assembled a variety of papers that represent the cutting edge in research on the evolution of memory. These papers are centred on issues about the ultimate and proximate explanations of memory, the development of the adaptive functions of memory, as well as the positive consequences that arise from the current evolutionary form that our memory has taken. In this introductory article we briefly outline these different areas and indicate why they are vital for a more complete theory of memory. Further we argue that, by adopting a more applied stance in the area of the evolution of memory, one of the many future directions in this field could be a new branch of psychology that addresses questions in evolutionary legal psychology
Strain-Engineering Mott-Insulating LaCuO
The transition temperature of unconventional superconductivity
is often tunable. For a monolayer of FeSe, for example, the sweet spot is
uniquely bound to titanium-oxide substrates. By contrast for
LaSrCuO thin films, such substrates are
sub-optimal and the highest is instead obtained using
LaSrAlO. An outstanding challenge is thus to understand the optimal
conditions for superconductivity in thin films: which microscopic parameters
drive the change in and how can we tune them? Here we
demonstrate, by a combination of x-ray absorption and resonant inelastic x-ray
scattering spectroscopy, how the Coulomb and magnetic-exchange interaction of
LaCuO thin films can be enhanced by compressive strain. Our experiments
and theoretical calculations establish that the substrate producing the largest
under doping also generates the largest nearest neighbour
hopping integral, Coulomb and magnetic-exchange interaction. We hence suggest
optimising the parent Mott state as a strategy for enhancing the
superconducting transition temperature in cuprates.Comment: 15 pages, 7 figures and 2 tables (including Supplementary
Information
Damped spin excitations in a doped cuprate superconductor with orbital hybridization
A resonant inelastic x-ray scattering study of overdamped spin excitations in slightly underdoped La2−x Srx CuO4 (LSCO) with x = 0.12 and 0.145 is presented. Three high-symmetry directions have been investigated: (1) the antinodal (0,0) → ( 1 ,0), (2) the nodal (0,0) → ( 1 , 1 ), and (3) the zone-boundary direction
2 4 4 ( 1 1 1 2 ,0) → ( 4 ,4 ) connecting these two. The overdamped excitations exhibit strong dispersions along (1) and (3), whereas a much more modest dispersion is found along (2). This is in strong contrast to the undoped compound
La2CuO4 (LCO) for which the strongest dispersions are found along (1) and (2). The t − t i − t ii − U Hubbard model used to explain the excitation spectrum of LCO predicts—for constant U/t —that the dispersion along (3) scales with (t i/t )2. However, the diagonal hopping t i extracted on LSCO using single-band models is low (t i/t ∼ −0.16) and decreasing with doping. We therefore invoked a two-orbital (dx2 −y2 and dz2 ) model which implies that t i is enhanced. This effect acts to enhance the zone-boundary dispersion within the Hubbard model. We thus conclude that hybridization of dx2 −y2 and dz2 states has a significant impact on the zone-boundary dispersion in LSCO
GLOBAL SIMULATIONS OF PROTOPLANETARY DISKS WITH OHMIC RESISTIVITY AND AMBIPOLAR DIFFUSION
Protoplanetary disks are believed to accrete onto their central T Tauri star
because of magnetic stresses. Recently published shearing box simulations
indicate that Ohmic resistivity, ambipolar diffusion and the Hall effect all
play important roles in disk evolution. In the presence of a vertical magnetic
field, the disk remains laminar between 1-5au, and a magnetocentrifugal disk
wind forms that provides an important mechanism for removing angular momentum.
Questions remain, however, about the establishment of a true physical wind
solution in the shearing box simulations because of the symmetries inherent in
the local approximation. We present global MHD simulations of protoplanetary
disks that include Ohmic resistivity and ambipolar diffusion, where the
time-dependent gas-phase electron and ion fractions are computed under FUV and
X-ray ionization with a simplified recombination chemistry. Our results show
that the disk remains laminar, and that a physical wind solution arises
naturally in global disk models. The wind is sufficiently efficient to explain
the observed accretion rates. Furthermore, the ionization fraction at
intermediate disk heights is large enough for magneto-rotational channel modes
to grow and subsequently develop into belts of horizontal field. Depending on
the ionization fraction, these can remain quasi-global, or break-up into
discrete islands of coherent field polarity. The disk models we present here
show a dramatic departure from our earlier models including Ohmic resistivity
only. It will be important to examine how the Hall effect modifies the
evolution, and to explore the influence this has on the observational
appearance of such systems, and on planet formation and migration.Comment: 18 pages, 12 figures, accepted for publication in Ap
Growth of CuCl thin films by magnetron sputtering for ultraviolet optoelectronic applications
Copper (I) chloride (CuCl) is a potential candidate for ultraviolet (UV) optoelectronics due to its close lattice match with Si (mismatch less than 0.4%) and a high UV excitonic emission at room temperature. CuCl thin films were deposited using radio frequency magnetron sputtering technique. The influence of target to substrate distance (dts) and sputtering pressure on the composition, microstructure, and UV emission properties of the films were analyzed. The films deposited with shorter target to substrate spacing (dts=3 cm) were found to be nonstoichiometric, and the film stoichiometry improves when the substrate is moved away from the target (dts=4.5 and 6 cm). A further increase in the spacing results in poor crystalline quality. The grain interface area increases when the sputtering pressure is increased from 1.1×10–³ to 1×10–² mbar at dts=6 cm. Room temperature cathodoluminescence spectrum shows an intense and sharp UV exciton (Z₃) emission at ~385 nm with a full width at half maximum of 16 nm for the films deposited at the optimum dts of 6 cm and a pressure of 1.1×10–³ mbar. A broad deep level emission in the green region (~515 nm) is also observed. The relative intensity of the UV to green emission peaks decreased when the sputtering pressure was increased, consistent with an increase in grain boundary area. The variation in the stoichiometry and the crystallinity are attributed to the change in the intensity and energy of the flux of materials from the target due to the interaction with the background gas molecules
Search for non-relativistic Magnetic Monopoles with IceCube
The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting
of Antarctic ice. The detector can be used to search for
signatures of particle physics beyond the Standard Model. Here, we describe the
search for non-relativistic, magnetic monopoles as remnants of the GUT (Grand
Unified Theory) era shortly after the Big Bang. These monopoles may catalyze
the decay of nucleons via the Rubakov-Callan effect with a cross section
suggested to be in the range of to
. In IceCube, the Cherenkov light from nucleon decays
along the monopole trajectory would produce a characteristic hit pattern. This
paper presents the results of an analysis of first data taken from May 2011
until May 2012 with a dedicated slow-particle trigger for DeepCore, a
subdetector of IceCube. A second analysis provides better sensitivity for the
brightest non-relativistic monopoles using data taken from May 2009 until May
2010. In both analyses no monopole signal was observed. For catalysis cross
sections of the flux of non-relativistic
GUT monopoles is constrained up to a level of at a 90% confidence level,
which is three orders of magnitude below the Parker bound. The limits assume a
dominant decay of the proton into a positron and a neutral pion. These results
improve the current best experimental limits by one to two orders of magnitude,
for a wide range of assumed speeds and catalysis cross sections.Comment: 20 pages, 20 figure
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