A Chronology of the Introduction of Domesticated Plants in Central Brazil

The paleoethnobotanical analysis of archaeological remains from two sites in central Brazil provides chronological data for the introduction of domesticated plants to the region. The sites of Lapa dos Bichos and Lapa Pintada, located in the northern portion of the state of Minas Gerais, are within rock shelters in limestone rock outcroppings. The dry conditions at the sites preserved both burnt and unburnt organic materials, including the seeds and fruits that were analyzed in this study. The chronological documentation for the introduction of domesticated plants is based on relative chronology from excavation stratigraphy and radiocarbon dating. The domesticated plants found include maize (Zea mays), manioc (cf. Manihot esculenta), cotton (cf. Gossypium barbadense), peanut (Arachis hypogaea), common bean (Phaseolus vulgaris), bottle gourd (Lagenaria siceraria), and squash (Cucurbita spp.). Central Brazil is not documented as the region of origin for these species and as such is a periphery where they were introduced. Maize and manioc are found in the strata dated between 750 and 2000 BP at Lapa dos Bichos and c. 1200 BP at Lapa Pintada; bottle gourd occurs in earlier strata (2000 to 4250 BP at Lapa dos Bichos). In addition to domesticated plants, numerous native plant foods were identified in the archaeological assemblage, such as palm nuts (Syagrus oleracea), passion fruit (Passiflora spp.), jatobá (Hymenaea spp.), umbu (Spondias tuberosa), and pequi (Caryocar brasiliensis). At the site of Lapa dos Bichos human habitation is known to span the entirety of the Holocene. Based on the archaeological macroscopic plant remains, the introduction of domesticated plants to central Brazil was a gradual process

Canonical Coordinates and Meson Spectra for Scalar Deformed N=4 SYM from the AdS/CFT Correspondence

Five supersymmetric scalar deformations of the AdS_5xS^5 geometry are investigated. By switching on condensates for the scalars in the N=4 multiplet with a form which preserves a subgroup of the original R-symmetry, disk and sphere configurations of D3-branes are formed in the dual supergravity background. The analytic, canonical metric for each geometry is formulated and the singularity structure is studied. Quarks are introduced into two of the corresponding field theories using D7-brane probes and the pseudoscalar meson spectrum is calculated. For one of the condensate configurations, a mass gap is found and shown analytically to be present in the massless limit. It is also found that there is a stepped spectrum with eigenstate degeneracy in the limit of small quark masses. In the case of a second, similar deformation, it is necessary to understand the full D3-D7 brane interaction to study the limit of small quark masses. It is seen that simple solutions to the equations of motion for the other three geometries are unlikely to exist.Comment: 16 pages, 7 figures, references added, typos correcte

Three Flavour QCD from the Holographic Principle

Building on recent research into five-dimensional holographic models of QCD, we extend this work by including the strange quark with an SU(3)_L\times SU(3)_R gauge symmetry in the five-dimensional theory. In addition we deform the naive $AdS$ metric with a single parameter, thereby breaking the conformal symmetry at low energies. The vector and axial vector sectors are studied in detail and both the masses and decay constants are calculated with the additional parameters. It is shown that with a single extra degree of freedom, exceptional agreement with experimental results can be obtained in the light quark sector while the kaon sector is found to give around 10% agreement with lattice results. We propose some simple extensions to this work to be taken up in future research.Comment: 9 pages, 1 figure, references adde

A note on conductivity and charge diffusion in holographic flavour systems

We analyze the charge diffusion and conductivity in a Dp/Dq holographic setup that is dual to a supersymmetric Yang-Mills theory in p+1 dimensions with N_f<< N_c flavour degrees of freedom at finite temperature and nonvanishing U(1) baryon number chemical potential. We provide a new derivation of the results that generalize the membrane paradigm to the present context. We perform a numerical analysis in the particular case of the D3/D7 flavor system. The results obtained support the validity of the Einstein relation at finite chemical potential.Comment: 15 pages, 3 figures, v2 with minor correction

A metastable equilibrium model for the relative abundances of microbial phyla in a hot spring

Many studies link the compositions of microbial communities to their environments, but the energetics of organism-specific biomass synthesis as a function of geochemical variables has rarely been assessed. We describe a thermodynamic model that integrates geochemical and metagenomic data for biofilms sampled at five sites along a thermal and chemical gradient in the outflow channel of the hot spring known as ‘‘Bison Pool’’ in Yellowstone National Park. The relative abundances of major phyla in individual communities sampled along the outflow channel are modeled by computing metastable equilibrium among model proteins with amino acid compositions derived from metagenomic sequences. Geochemical conditions are represented by temperature and activities of basis species, including pH and oxidation-reduction potential quantified as the activity of dissolved hydrogen. By adjusting the activity of hydrogen, the model can be tuned to closely approximate the relative abundances of the phyla observed in the community profiles generated from BLAST assignments. The findings reveal an inverse relationship between the energy demand to form the proteins at equal thermodynamic activities and the abundance of phyla in the community.Although the metabolisms used by many members of these communities are driven by chemical disequilibria, the results support the possibility that higher-level patterns of chemotrophic microbial ecosystems are shaped by metastable equilibrium states that depend on both the composition of biomass and the environmental conditions

Linear square-mass trajectories of radially and orbitally excited hadrons in holographic QCD

We consider a new approach towards constructing approximate holographic duals of QCD from experimental hadron properties. This framework allows us to derive a gravity dual which reproduces the empirically found linear square-mass trajectories of universal slope for radially and orbitally excited hadrons. Conformal symmetry breaking in the bulk is exclusively due to infrared deformations of the anti-de Sitter metric and governed by one free mass scale proportional to Lambda_QCD. The resulting background geometry exhibits dual signatures of confinement and provides the first examples of holographically generated linear trajectories in the baryon sector. The predictions for the light hadron spectrum include new relations between trajectory slopes and ground state masses and are in good overall agreement with experiment.Comment: 33 pages, 5 figures, updated to the extended version published in JHEP, vector meson bulk potential and metric corrected, comments and references added, phenomenology and conclusions unchange

Universal Holographic Chiral Dynamics in an External Magnetic Field

In this work we further extend the investigation of holographic gauge theories in external magnetic fields, continuing earlier work. We study the phenomenon of magnetic catalysis of mass generation in 1+3 and 1+2 dimensions, using D3/D7- and D3/D5-brane systems, respectively. We obtain the low energy effective actions of the corresponding pseudo Goldstone bosons and study their dispersion relations. The D3/D7 system exhibits the usual Gell-Mann--Oakes--Renner (GMOR) relation and a relativistic dispersion relation, while the D3/D5 system exhibits a quadratic non-relativistic dispersion relation and a modified linear GMOR relation. The low energy effective action of the D3/D5 system is related to that describing magnon excitations in a ferromagnet. We also study properties of general Dp/Dq systems in an external magnetic field and verify the universality of the magnetic catalysis of dynamical symmetry breaking.Comment: 41 pages, 11 figures, references adde

Embedding Flipped SU(5) into SO(10)

We embed the flipped SU(5) models into the SO(10) models. After the SO(10) gauge symmetry is broken down to the flipped SU(5) \times U(1)_X gauge symmetry, we can split the five/one-plets and ten-plets in the spinor \mathbf{16} and \mathbf{\bar{16}} Higgs fields via the stable sliding singlet mechanism. As in the flipped SU(5) models, these ten-plet Higgs fields can break the flipped SU(5) gauge symmetry down to the Standard Model gauge symmetry. The doublet-triplet splitting problem can be solved naturally by the missing partner mechanism, and the Higgsino-exchange mediated proton decay can be suppressed elegantly. Moreover, we show that there exists one pair of the light Higgs doublets for the electroweak gauge symmetry breaking. Because there exist two pairs of additional vector-like particles with similar intermediate-scale masses, the SU(5) and U(1)_X gauge couplings can be unified at the GUT scale which is reasonably (about one or two orders) higher than the SU(2)_L \times SU(3)_C unification scale. Furthermore, we briefly discuss the simplest SO(10) model with flipped SU(5) embedding, and point out that it can not work without fine-tuning.Comment: RevTex4, 28 pages, 3 figures, typos correcte

Challenges facing holographic models of QCD

This paper, written in memory of Manoj Banerjee, takes a critical look at holographic models of QCD focusing on ``practical'' models in which the five dimensional theory is treated classically. A number of theoretical and phenomenological challenges to the approach are discussed.Comment: This paper was written for an issue in memory of Manoj Banerjee in the Indian Journal of Physic

A correlation analysis of Light Microscopy and X-ray MicroCT imaging methods applied to archaeological plant remains’ morphological attributes visualization

In this work, several attributes of the internal morphology of drupaceous fruits found in the archaeological site Monte Castelo (Rondonia, Brazil) are analyzed by means of two different imaging methods. The aim is to explore similarities and differences in the visualization and analytical properties of the images obtained via High Resolution Light Microscopy and X-ray micro-computed tomography (X-ray MicroCT) methods. Both provide data about the three-layered pericarp (exo-, meso- and endocarp) of the studied exemplars, defined by cell differentiation, vascularisation, cellular contents, presence of sclerenchyma cells and secretory cavities. However, it is possible to identify a series of differences between the information that can be obtained through each of the methods. These variations are related to the definition of contours and fine details of some characteristics, their spatial distribution, size attributes, optical properties and material preservation. The results obtained from both imaging methods are complementary, contributing to a more exhaustive morphological study of the plant remains. X-ray MicroCT in phase-contrast mode represents a suitable non-destructive analytic technique when sample preservation is required