999 research outputs found
Training Big Random Forests with Little Resources
Without access to large compute clusters, building random forests on large
datasets is still a challenging problem. This is, in particular, the case if
fully-grown trees are desired. We propose a simple yet effective framework that
allows to efficiently construct ensembles of huge trees for hundreds of
millions or even billions of training instances using a cheap desktop computer
with commodity hardware. The basic idea is to consider a multi-level
construction scheme, which builds top trees for small random subsets of the
available data and which subsequently distributes all training instances to the
top trees' leaves for further processing. While being conceptually simple, the
overall efficiency crucially depends on the particular implementation of the
different phases. The practical merits of our approach are demonstrated using
dense datasets with hundreds of millions of training instances.Comment: 9 pages, 9 Figure
The lactation cycle of the fur seal
The fur seal is a mammal with an unusual ability to turn its milk production on and off without significantly altering the gross morphology of the mammary gland. This atypical lactation cycle is due to the fact that maternal foraging and infant nursing are spatially and temporally separate (Bonner, 1984). Maternal care involves the suckling of offspring over a period of at least 4 months, but lactation can extend to more than 12 months. Following a perinatal fast of approximately 1 week, females depart the breeding colony to forage at sea and, for the remainder of lactation, alternate between short periods ashore suckling their young with longer periods of up to 4 weeks foraging at sea. Whilst foraging at sea, milk production in the fur seal mammary gland either ceases or is reduced (Arnould & Boyd, 1995b).<br /
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Research partnerships across international contexts : a practice of unity or plurality?
This work was supported by Engineering and Physical Sciences Research Council [grant number EP/T025034/1].Partnership is not a benign practice; it is culturally and ethically loaded. The way in which partnerships are construed in international research determines its design, ethics and impacts. Despite this, and the growing assumption of partnership practice in our field, the concept has become increasingly abstract and the practice under-analysed. This article provides critical perspectives of current understandings of partnership in international development research from three angles: the motivations behind partnership working; an epistemological perspective in relation to epistemic justice and the agency of language; and finally, the systems that mediate partnerships, and the range of resources that guide them. Publisher PDFPeer reviewe
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Host control and the evolution of cooperation in host microbiomes.
Humans, and many other species, are host to diverse symbionts. It is often suggested that the mutual benefits of host-microbe relationships can alone explain cooperative evolution. Here, we evaluate this hypothesis with evolutionary modelling. Our model predicts that mutual benefits are insufficient to drive cooperation in systems like the human microbiome, because of competition between symbionts. However, cooperation can emerge if hosts can exert control over symbionts, so long as there are constraints that limit symbiont counter evolution. We test our model with genomic data of two bacterial traits monitored by animal immune systems. In both cases, bacteria have evolved as predicted under host control, tending to lose flagella and maintain butyrate production when host-associated. Moreover, an analysis of bacteria that retain flagella supports the evolution of host control, via toll-like receptor 5, which limits symbiont counter evolution. Our work puts host control mechanisms, including the immune system, at the centre of microbiome evolution
The Dependence of Brown Dwarf Radii on Atmospheric Metallicity and Clouds: Theory and Comparison with Observations
Employing realistic and consistent atmosphere boundary conditions, we have
generated evolutionary models for brown dwarfs and very-low-mass stars (VLMs)
for different metallicities ([Fe/H]), with and without clouds. We find that the
spread in radius at a given mass and age can be as large as 10% to
25%, with higher-metallicity, higher-cloud-thickness atmospheres
resulting quite naturally in larger radii. For each 0.1 dex increase in [Fe/H],
radii increase by 1% to 2.5%, depending upon age and mass. We also
find that, while for smaller masses and older ages brown dwarf radii decrease
with increasing helium fraction () (as expected), for more massive brown
dwarfs and a wide range of ages they increase with helium fraction. The
increase in radius in going from to can be as large as
0.025 \rj\ (2.5%). Furthermore, we find that for VLMs an increase
in atmospheric metallicity from 0.0 to 0.5 dex, increases radii by 4%,
and from -0.5 to 0.5 dex by 10%. Therefore, we suggest that opacity due
to higher metallicity might naturally account for the apparent radius anomalies
in some eclipsing VLM systems. Ten to twenty-five percent variations in radius
exceed errors stemming from uncertainities in the equation of state alone. This
serves to emphasize that transit and eclipse measurements of brown dwarf radii
constrain numerous effects collectively, importantly including the atmosphere
and condensate cloud models, and not just the equation of state. At all times,
one is testing a multi-parameter theory, and not a universal radiusmass
relation.Comment: Accepted to the Astrophysical Journal, May 3, 201
Affinity Purification of Antibodies Specific for 1,4-Dihydropyridine Ca 2+ Channel Blockers
High-affinity antibodies specific for the 1,4-dihydropyridine Ca 2+ channel blockers have been produced in sheep and affinity purified using a dihydropyridine-Sepharose affinity column. Dihydropyridine-Sepharose affinity matrix was synthesized by reaction of aminohexyl-Sepharose with an affinity analogue of nifedipine, dimethyl l,4-dihydro-2,6-dimethyl-4-(2-isothiocyanatophenyl)-3,5-pyridinedicarboxylate. Residual amine groups were then blocked by carbodiimide-catalyzed acetylation. channels is important in mediation of contraction in cardiac and smooth muscle
Things can only get Stranger: theoretical and clinical reflections on Netflix’s Stranger Things
The popularity of Stranger Things lies in its ability to depict the unconscious aspects of personality and the psychological processes constellated during crucial years of development and maturation. First, Jung’s notions of the mother complex and dual mother archetype frame the metamorphoses experienced by Will Byers and El. Second, a psychoanalytic understanding of nostalgia, loss and mourning elucidates the associations audiences make between their own experiences and those of the show’s central characters. Ironically, it is through an exploration of the monstrous and the fantastic that the series draws us closer to what it means to be human; the stranger things get, the closer we come to reality and grasping the operations of the psyche
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