1,657 research outputs found
Phylogenetic Analyses of Two Mitochondrial Metabolic Genes Sampled in Parallel from Angiosperms Find Fundamental Interlocus Incongruence
Plant molecular phylogeneticists have supported an analytical approach of combining loci from different genomes, but the
combination of mitochondrial sequences with chloroplast and nuclear sequences is potentially problematic. Low substitution rates
in mitochondrial genes should decrease saturation, which is especially useful for the study of deep divergences. However, individual
mitochondrial loci are insuffi ciently informative, so that combining congruent loci is necessary. For this study atp1 and
cox1 were selected, which are of similar lengths, encode components of the respiratory pathway, and generally lack introns. Thus,
these genes might be expected to have similar functional constraints, selection pressures, and evolutionary histories. Strictly parallel
sampling of 52 species was achieved as well as six additional composite terminals with representatives from the major angiosperm
clades. However, analyses of the separate loci produced strongly incongruent topologies. The source of the incongruence
was investigated by validating sequences with questionable affi nities, excluding RNA-edited nucleotides, deleting taxa with unexpected
phylogenetic associations, and comparing different phylogenetic methods. However, even after potential artifacts were
addressed and sites and taxa putatively associated with confl ict were excluded, the resulting gene trees for the two mitochondrial
loci were still substantially incongruent by all measures examined. Therefore, combining these loci in phylogenetic analysis may
be counterproductive to the goal of fully resolving the angiosperm phylogeny
CCR7 is required for the in vivo function of CD4+ CD25+ regulatory T cells
CCR7-mediated migration of naive T cells into the secondary lymphoid organs is a prerequisite for their encounter with mature dendritic cells, the productive presentation of cognate antigen, and consequent T cell proliferation and effector differentiation. Therefore, CCR7 was suggested to play an important role in the initiation of adaptive immune responses. In this study, we show that primary immunity can also develop in the absence of CCR7. Moreover, CCR7-deficient knockout (KO) mice display augmented immune responses. Our data cumulatively suggest that enhanced immunity in CCR7 KO mice is caused by the defective lymph node (LN) positioning of FoxP3(+) CD4(+) CD25(+) regulatory T cells (T reg cells) and the consequent impediment of their function. The FoxP3(+) T reg cells express CCR7 and, after their adoptive transfer, migrate into the LNs of wild-type mice. Here, they proliferate in situ upon antigen stimulation and inhibit the generation of antigen-specific T cells. Conversely, transferred CCR7-deficient T reg cells fail to migrate into the LNs and suppress antigen-induced T cell responses. The transfer of combinations of naive and T reg cells from wild-type and CCR7 KO mice into syngeneic severe combined immunodeficient mice directly demonstrates that CCR7-deficient T reg cells are less effective than their wild-type counterparts in preventing the development of inflammatory bowel diseas
2. Survey Of Urban Blood Donors And Rural Populations
A CAJM survey on the prevalence of Australia Antigen in the blood of Zimbabweans (formerly Rhodesians)Consequently a more comprehensive survey was undertaken to determine the general prevalence of the antigen in Rhodesia by testing African and European blood donors as examples of urban populations and, in contrast, certain African tribal groups as examples of rural populations. The results are presented here together with the findings in cases of hepatitis and leprosy which have come to hand subsequent to the pilot survey
Preventie van preferente stroming in de zandgrond van een golfbaan
Veel zandbovengronden met een grasvegetatie hebben waterafstotende eigenschappen. Deze hydrofobe eigenschappen komen naar voren als het vochtgehalte van de grond beneden een kritieke grens daalt. Na het bereiken van deze grens zal de infiltratiesnelheid van neerslag en beregeningswater sterk afnemen. De indringing van het water gaat dan ongelijkmatig en er ontstaan preferente stroombanen in de grond. Op golfbaan "De Pan" in Bosch en Duin onderzochten we de effecten van het toedienen van een surfactant op de bevochtiging en de variatie van het vochtgehalte van de toplaag in een fairwa
Superconductivity and non-metallicity induced by doping the topological insulators Bi2Se3 and Bi2Te3
We show that by Ca-doping the Bi2Se3 topological insulator, the Fermi level
can be fine tuned to fall inside the band gap and therefore suppress the bulk
conductivity. Non-metallic Bi2Se3 crystals are obtained. On the other hand, the
Bi2Se3 topological insulator can also be induced to become a bulk
superconductor, with Tc ~ 3.8 K, by copper intercalation in the van der Waals
gaps between the Bi2Se3 layers. Likewise, an as-grown crystal of metallic
Bi2Te3 can be turned into a non-metallic crystal by slight variation of the Te
content. The Bi2Te3 topological insulator shows small amounts of
superconductivity with Tc ~ 5.5 K when reacted with Pd to form materials of the
type PdxBi2Te3
A reflective conversation with Kobus Maree, Faculty of Education, University of Pretoria, South Africa
Always regarded as somewhat of an âoutsiderâ (the child of an Englishspeaking (Catholic)
mother and an Afrikaans (Protestant) father in an exclusively Afrikaans milieu) and growing
up extremely poor, seeing the hardship of others and realising howmuch talentwas going to
waste, Kobus Maree took a particular interest in gifted disadvantaged persons. A marginalised
loner, he almost inevitably developed creative abilities and took a keen interest in
creativity, giftedness and the education of gifted, disadvantaged learners. As an adult, his
research showed that many teachers in South Africa have to contend with the generally
poor socioeconomic background of learners. A dire need for appropriate teacher and
learner support materials, and school environments that are not conducive to achievement
(including inadequate facilities, overcrowded classrooms, lack of teacher and learner support
materials). SouthAfrica is at a critical stage in its education. It is therefore important for
educators to teach emotional intelligence in their classrooms. Our biggest challenge will be
tomaintain and enhance vitality in gifted education in a dynamic, ever-evolving environment.
A combination of scholarly leadership and strategic management to support gifted learners
is important. We should do all we can to promote societal transformation and diversity,
focussing anew on underrepresented groups (women and ethnic groups) who show
promise and support them. The widest array of partners possible including the big institutional
players, the entire teaching fraternity (including government departments), nongovernmental
organisations and miscellaneous interest groups together should develop
strategic, rolling five-year plans and make gifted education a priority.http://gei.sagepub.comam201
Spatial repellents: from discovery and development to evidence based validation
International public health workers are challenged by a burden of arthropod-borne disease that remains elevated despite best efforts in control programmes. With this challenge comes the opportunity to develop novel vector control paradigms to guide product development and programme implementation. The role of vector behaviour modification in disease control was first highlighted several decades ago but has received limited attention within the public health community. This paper presents current evidence highlighting the value of sub-lethal agents, specifically spatial repellents, and their use in global health, and identifies the primary challenges towards establishing a clearly defined and recommended role for spatial repellent products in disease control
Onset of entanglement
We have developed a theory of polymer entanglement using an extended
Cahn-Hilliard functional, with two extra terms. One is a nonlocal attractive
term, operating over mesoscales, which is interpreted as giving rise to
entanglement, and the other a local repulsive term indicative of excluded
volume interactions. We show how such a functional can be derived using notions
from gauge theory. We go beyond the Gaussian approximation, to the one-loop
level, to show that the system exhibits a crossover to a state of entanglement
as the average chain length between points of entanglement decreases. This
crossover is marked by critical slowing down, as the effective diffusion
constant goes to zero. We have also computed the tensile modulus of the system,
and we find a corresponding crossover to a regime of high modulus.Comment: 18 pages, with 4 figure
Effective Theoretical Approach to Back Reaction of the Dynamical Casimir Effect in 1+1 Dimensions
We present an approach to studying the Casimir effects by means of the
effective theory. An essential point of our approach is replacing the mirror
separation into the size of space S^1 in the adiabatic approximation. It is
natural to identify the size of space S^1 with the scale factor of the
Robertson-Walker-type metric. This replacement simplifies the construction of a
class of effective models to study the Casimir effects. To check the validity
of this replacement we construct a model for a scalar field coupling to the
two-dimensional gravity and calculate the Casimir effects by the effective
action for the variable scale factor. Our effective action consists of the
classical kinetic term of the mirror separation and the quantum correction
derived by the path-integral method. The quantum correction naturally contains
both the Casimir energy term and the back-reaction term of the dynamical
Casimir effect, the latter of which is expressed by the conformal anomaly. The
resultant effective action describes the dynamical vacuum pressure, i.e., the
dynamical Casimir force. We confirm that the force depends on the relative
velocity of the mirrors, and that it is always attractive and stronger than the
static Casimir force within the adiabatic approximation.Comment: Published Version, 16 pages, LaTeX2e with graphics package, 1 figur
Hull Consistency Under Monotonicity
International audienceWe prove that hull consistency for a system of equations or inequalities can be achieved in polynomial time providing that the underlying functions are monotone with respect to each variable. This result holds including when variables have multiple occurrences in the expressions of the functions, which is usually a pitfall for interval-based contractors. For a given constraint, an optimal contractor can thus be enforced quickly under monotonicity and the practical significance of this theoretical result is illustrated on a simple example
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