533 research outputs found
Critical exponents from parallel plate geometries subject to periodic and antiperiodic boundary conditions
We introduce a renormalized 1PI vertex part scalar field theory setting in
momentum space to computing the critical exponents and , at least
at two-loop order, for a layered parallel plate geometry separated by a
distance L, with periodic as well as antiperiodic boundary conditions on the
plates. We utilize massive and massless fields in order to extract the
exponents in independent ultraviolet and infrared scaling analysis,
respectively, which are required in a complete description of the scaling
regions for finite size systems. We prove that fixed points and other critical
amounts either in the ultraviolet or in the infrared regime dependent on the
plates boundary condition are a general feature of normalization conditions. We
introduce a new description of typical crossover regimes occurring in finite
size systems. Avoiding these crossovers, the three regions of finite size
scaling present for each of these boundary conditions are shown to be
indistinguishable in the results of the exponents in periodic and antiperiodic
conditions, which coincide with those from the (bulk) infinite system.Comment: Modified introduction and some references; new crossover regimes
discussion improved; Appendixes expanded. 48 pages, no figure
Human-Data Interaction Syllabus for Undergraduate and Graduate Courses
The phenomenon of the data deluge is a reality and the volume of data produced by people and companies is much greater than what can be handled and analyzed. Data play a crucial role in guiding the efficient utilization of technological resources for companies, aiding them in product and service management. Moreover, individuals who have become adept data producers and consumers are increasingly orienting their lives toward data. To address this evolving trend, there is a growing imperative to educate Computing professionals. These professionals are required to design technology solutions that facilitate the synergy between individuals and data, a phenomenon known as Human-Data Interaction (HDI). This paper introduces a suggested minimum syllabus for HDI courses, with the aim of addressing the key themes associated with the interaction between individuals and data. The complexity and depth of HDI topics justify a dedicated course, preventing the risk of essential content being fragmented or inadequately covered if dispersed across different courses
Quantum scattering in one dimension
A self-contained discussion of nonrelativistic quantum scattering is
presented in the case of central potentials in one space dimension, which will
facilitate the understanding of the more complex scattering theory in two and
three dimensions. The present discussion illustrates in a simple way the
concept of partial-wave decomposition, phase shift, optical theorem and
effective-range expansion.Comment: 8 page
Hydromorphological implications of local tributary widening for river rehabilitation
The hydromorphological implications of the local widening of a tributary where it enters a confluence were investigated in a laboratory setting that is representative of the 20 major confluences on the channelized Upper Rhone River. Although local tributary widening reduces the confluence angle, it amplifies the hydromorphosedimentary processes in the confluence hydrodynamic zone (CHZ), because local widening reduces the effective flow area, causing increased tributary velocities and momentum flux. The reduction in effective flow area is caused by an increase in bed elevation and by lateral constriction of the flow induced by flow stagnation at the upstream corner of the confluence. The increased tributary velocities amplify the two-layer flow structure in the CHZ. Flow originating from the tributary is confined to the upper part of the water column and is more markedly directed outward than flow in the lower part of the water column originating from the main channel. A shear layer characterized by increased turbulence activity develops at the interface between the two flow layers. The increased tributary velocities enhance bed discordance, the penetration of the tributary into the CHZ and the channel bed gradients in the postconfluence channel. The results indicate that local tributary widening can enhance heterogeneity in sediment substrate, flow velocities and flow depths. Widening may therefore enhance local habitat and improve the connectivity of the tributary to the main river network. This may, in turn, provide favorable conditions for the improvement and reestablishment of ecological river functions, without having adverse impact on flood safety
Flow and sediment dynamics in channel confluences
Confluences with relatively low discharge and momentum flux ratios where a small steep tributary with a high supply of poorly sorted sediment joins a large, low-gradient main channel commonly occur in nature, but they have not yet been investigated. Measurements of the three-dimensional velocity field, turbulence, sediment transport, bed material grain size and morphology are reported in a laboratory setting that is representative of confluences on the Upper Rhone River, Switzerland. The difference between the low-flow depth in the steep tributary and the higher flow depth in the main channel creates a marked bed discordance in the tributary zone. Due to this bed discordance, the tributary flow penetrates into the main channel mainly in the upper part of the water column, whereas the main-channel flow is hardly hindered by the tributary in the lower part of the water column, giving rise to a two-layer flow structure in the confluence zone. In confluences with high supply of coarse sediment from the tributary, the development of a deposition bar downstream from the confluence reduces the flow area and causes flow acceleration that contributes to an increase in sediment transport capacity. The sediment supplied by the tributary is mainly sorted and transported on the face of the bar by the near-bed flow originating from the main channel. The sediment transport capacity is further increased by the three-dimensionality of the flow, which is characterized by maximum velocities occurring near the bed, and by a considerable increase in turbulent kinetic energy generated in the shear layer at the interface of the flows originating from the main channel and the tributary. A conceptual model is proposed for the hydro-morpho-sedimentary processes, and compared to existing conceptual models for confluences with different characteristics
Critical behavior of generic competing systems
Generic higher character Lifshitz critical behaviors are described using
field theory and -expansion renormalization group methods. These
critical behaviors describe systems with arbitrary competing interactions. We
derive the scaling relations and the critical exponents at the two-loop level
for anisotropic and isotropic points of arbitrary higher character. The
framework is illustrated for the -vector model describing a
-dimensional system. The anisotropic behaviors are derived in terms of many
independent renormalization group transformations, each one characterized by
independent correlation lengths. The isotropic behaviors can be understood
using only one renormalization group transformation. Feynman diagrams are
solved for the anisotropic behaviors using a new dimensional regularization
associated to a generalized orthogonal approximation. The isotropic diagrams
are treated using this approximation as well as with a new exact technique to
compute the integrals. The entire procedure leads to the analytical solution of
generic loop order integrals with arbitrary external momenta. The property of
universality class reduction is also satisfied when the competing interactions
are turned off. We show how the results presented here reduce to the usual
-fold Lifshitz critical behaviors for both isotropic and anisotropic
criticalities.Comment: RevTex, 54 pages, 3 figures; version accepted for publication in
Physical Review
A new picture of the Lifshitz critical behavior
New field theoretic renormalization group methods are developed to describe
in a unified fashion the critical exponents of an m-fold Lifshitz point at the
two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close
to 8) situations. The general theory is illustrated for the N-vector phi^4
model describing a d-dimensional system. A new regularization and
renormalization procedure is presented for both types of Lifshitz behavior. The
anisotropic cases are formulated with two independent renormalization group
transformations. The description of the isotropic behavior requires only one
type of renormalization group transformation. We point out the conceptual
advantages implicit in this picture and show how this framework is related to
other previous renormalization group treatments for the Lifshitz problem. The
Feynman diagrams of arbitrary loop-order can be performed analytically provided
these integrals are considered to be homogeneous functions of the external
momenta scales. The anisotropic universality class (N,d,m) reduces easily to
the Ising-like (N,d) when m=0. We show that the isotropic universality class
(N,m) when m is close to 8 cannot be obtained from the anisotropic one in the
limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in
good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe
Description of the nest of two Thamnophilidae species in Brazilian Amazon
Many Thamnophilidae species have poorly known breeding. Here we describe the nests and eggs of two species, Epinecrophylla ornata from a terra firme forest, and Myrmotherula assimilis from a flooded forest in Brazil. Knowledge on the natural history of these species is important for future conservation strategies. © 2016, Sociedade Brasileira de Ornitologia. All rights reserved
The Forage Selection Program at the Cerrados Research Center--33 Years of Contributions for the Tropics
Immunization With The Maebl M2 Domain Protects Against Lethal Plasmodium Yoelii Infection.
Malaria remains a world-threatening disease largely because of the lack of a long-lasting and fully effective vaccine. MAEBL is a type 1 transmembrane molecule with a chimeric cysteine-rich ectodomain homologous to regions of the Duffy binding-like erythrocyte binding protein and apical membrane antigen 1 (AMA1) antigens. Although MAEBL does not appear to be essential for the survival of blood-stage forms, ectodomains M1 and M2, homologous to AMA1, seem to be involved in parasite attachment to erythrocytes, especially M2. MAEBL is necessary for sporozoite infection of mosquito salivary glands and is expressed in liver stages. Here, the Plasmodium yoelii MAEBL-M2 domain was expressed in a prokaryotic vector. C57BL/6J mice were immunized with doses of P. yoelii recombinant protein rPyM2-MAEBL. High levels of antibodies, with balanced IgG1 and IgG2c subclasses, were achieved. rPyM2-MAEBL antisera were capable of recognizing the native antigen. Anti-MAEBL antibodies recognized different MAEBL fragments expressed in CHO cells, showing stronger IgM and IgG responses to the M2 domain and repeat region, respectively. After a challenge with P. yoelii YM (lethal strain)-infected erythrocytes (IE), up to 90% of the immunized animals survived and a reduction of parasitemia was observed. Moreover, splenocytes harvested from immunized animals proliferated in a dose-dependent manner in the presence of rPyM2-MAEBL. Protection was highly dependent on CD4(+), but not CD8(+), T cells toward Th1. rPyM2-MAEBL antisera were also able to significantly inhibit parasite development, as observed in ex vivo P. yoelii erythrocyte invasion assays. Collectively, these findings support the use of MAEBL as a vaccine candidate and open perspectives to understand the mechanisms involved in protection.833781-379
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