1,128 research outputs found
Effect of Lowered Light Quality (R:FR Ratio) at Targeted Organs on Branching of Trifolium Repens
This report examined results from four similarly conducted experiments using Trifolium repens in which the R:FR ratio but not the photosynthetically active radiation (PAR) of incident light was altered at specific organ(s) of several successive phytomers or just at a single phytomer. Results indicate the local response to lowered R:FR light treatment was similar irrespective of the number of phytomers treated. This response pattern provides the means whereby plants can initiate strong localised responses to a heterogeneous light environment
Charge asymmetry in W + jets production at the LHC
The charge asymmetry in W + jets production at the LHC can serve to calibrate
the presence of New Physics contributions. We study the ratio {\sigma}(W^+ + n
jets)/{\sigma}(W^- + n jets) in the Standard Model for n <= 4, paying
particular attention to the uncertainty in the prediction from higher-order
perturbative corrections and uncertainties in parton distribution functions. We
show that these uncertainties are generally of order a few percent, making the
experimental measurement of the charge asymmetry ratio a particularly useful
diagnostic tool for New Physics contributions.Comment: 13 pages, 7 figures. Reference added. Slightly modified tex
Heat flow and calculus on metric measure spaces with Ricci curvature bounded below - the compact case
We provide a quick overview of various calculus tools and of the main results
concerning the heat flow on compact metric measure spaces, with applications to
spaces with lower Ricci curvature bounds.
Topics include the Hopf-Lax semigroup and the Hamilton-Jacobi equation in
metric spaces, a new approach to differentiation and to the theory of Sobolev
spaces over metric measure spaces, the equivalence of the L^2-gradient flow of
a suitably defined "Dirichlet energy" and the Wasserstein gradient flow of the
relative entropy functional, a metric version of Brenier's Theorem, and a new
(stronger) definition of Ricci curvature bound from below for metric measure
spaces. This new notion is stable w.r.t. measured Gromov-Hausdorff convergence
and it is strictly connected with the linearity of the heat flow.Comment: To the memory of Enrico Magenes, whose exemplar life, research and
teaching shaped generations of mathematician
Charge asymmetry ratio as a probe of quark flavour couplings of resonant particles at the LHC
We show how a precise knowledge of parton distribution functions, in
particular those of the u and d quarks, can be used to constrain a certain
class of New Physics models in which new heavy charged resonances couple to
quarks and leptons. We illustrate the method by considering a left-right
symmetric model with a W' from a SU(2)_R gauge sector produced in
quark-antiquark annihilation and decaying into a charged lepton and a heavy
Majorana neutrino. We discuss a number of quark and lepton mixing scenarios,
and simulate both signals and backgrounds in order to determine the size of the
expected charge asymmetry. We show that various quark-W' mixing scenarios can
indeed be constrained by charge asymmetry measurements at the LHC, particularly
at 14 TeV centre of mass energy.Comment: 14 pages, 3 figure
Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding
Within the broad class of multiferroics (compounds showing a coexistence of
magnetism and ferroelectricity), we focus on the subclass of "improper
electronic ferroelectrics", i.e. correlated materials where electronic degrees
of freedom (such as spin, charge or orbital) drive ferroelectricity. In
particular, in spin-induced ferroelectrics, there is not only a {\em
coexistence} of the two intriguing magnetic and dipolar orders; rather, there
is such an intimate link that one drives the other, suggesting a giant
magnetoelectric coupling. Via first-principles approaches based on density
functional theory, we review the microscopic mechanisms at the basis of
multiferroicity in several compounds, ranging from transition metal oxides to
organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic
frameworks, MOFs)Comment: 22 pages, 9 figure
Morphological stasis masks ecologically divergent coral species on tropical reefs
Coral reefs are the epitome of species diversity, yet the number of described scleractinian coral species, the framework-builders of coral reefs, remains moderate by comparison. DNA sequencing studies are rapidly challenging this notion by exposing a wealth of undescribed diversity, but the evolutionary and ecological significance of this diversity remains largely unclear. Here, we present an annotated genome for one of the most ubiquitous corals in the Indo-Pacific (Pachyseris speciosa) and uncover, through a comprehensive genomic and phenotypic assessment, that it comprises morphologically indistinguishable but ecologically divergent lineages. Demographic modeling based on whole-genome resequencing indicated that morphological crypsis (across micro- and macromorphological traits) was due to ancient morphological stasis rather than recent divergence. Although the lineages occur sympatrically across shallow and mesophotic habitats, extensive genotyping using a rapid molecular assay revealed differentiation of their ecological distributions. Leveraging "common garden'' conditions facilitated by the overlapping distributions, we assessed physiological and quantitative skeletal traits and demonstrated concurrent phenotypic differentiation. Lastly, spawning observations of genotyped colonies highlighted the potential role of temporal reproductive isolation in the limited admixture, with consistent genomic signatures in genes related to morphogenesis and reproduction. Overall, our findings demonstrate the presence of ecologically and phenotypically divergent coral species without substantial morphological differentiation and provide new leads into the potential mechanisms facilitating such divergence. More broadly, they indicate that our current taxonomic framework for reef-building corals may be scratching the surface of the ecologically relevant diversity on coral reefs, consequently limiting our ability to protect or restore this diversity effectively
Long term intrinsic cycling in human life course antibody responses to influenza A(H3N2): an observational and modeling study
Background: Over a life course, human adaptive immunity to antigenically mutable pathogens exhibits competitive and facilitative interactions. We hypothesize that such interactions may lead to cyclic dynamics in immune responses over a lifetime. Methods: To investigate the cyclic behavior, we analyzed hemagglutination inhibition titers against 21 historical influenza A(H3N2) strains spanning 47 years from a cohort in Guangzhou, China, and applied Fourier spectrum analysis. To investigate possible biological mechanisms, we simulated individual antibody profiles encompassing known feedbacks and interactions due to generally recognized immunological mechanisms. Results: We demonstrated a long-term periodicity (about 24 years) in individual antibody responses. The reported cycles were robust to analytic and sampling approaches. Simulations suggested that individual-level cross-reaction between antigenically similar strains likely explains the reported cycle. We showed that the reported cycles are predictable at both individual and birth cohort level and that cohorts show a diversity of phases of these cycles. Phase of cycle was associated with the risk of seroconversion to circulating strains, after accounting for age and pre-existing titers of the circulating strains. Conclusions: Our findings reveal the existence of long-term periodicities in individual antibody responses to A(H3N2). We hypothesize that these cycles are driven by preexisting antibody responses blunting responses to antigenically similar pathogens (by preventing infection and/or robust antibody responses upon infection), leading to reductions in antigen-specific responses over time until individual's increasing risk leads to an infection with an antigenically distant enough virus to generate a robust immune response. These findings could help disentangle cohort effects from individual-level exposure histories, improve our understanding of observed heterogeneous antibody responses to immunizations, and inform targeted vaccine strategy
Indigenous Research: Whose Priority? Journeys and Possibilities of Cross-Cultural Research in Geography
Allaeochelys libyca, a new carettochelyine turtle from the middle miocene (Langhian) of Libya
Fossil carettochelyine turtles are well known from the Paleogene of Europe (Allaeochelys), North America and Asia (Anosteira); however, the previously known Neogene fossil record is highly fragmentary and was therefore unsuitable for taxonomic analysis. In this work, we present a new carettochelyine taxon, Allaeochelys libyca, from the Middle Miocene (Langhian) of Gebel Zelten (Libya) based on an incomplete skull and disarticulated postcranial elements. The new taxon is diagnosed relative to the extant Carettochelys insculpta based on the placement of the foramen posterius canalis carotici interni close to the fenestra postotica, the horizontal orientation of the tubercula basioccipitalis, the substantial contribution of the opisthotic to the base of the tubercula basioccipitalis, the presence of a triangular pterygoid fossa, the arrangement of the mandibular condyles along a plane and the presence of an extremely well-developed fossa at the base of the processus mandibularis. A phylogenetic analysis of pancarettochelyids confirms the monophyly of Carettochelyidae and Carettochelyinae but resulted in a paraphyletic taxon, Allaeochelys. For the sake of nomenclatural stability, we provisionally retain the genus Allaeochelys as paraphyletic relative to the extant Carettochelys insculpta
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