1,251 research outputs found
Classical Lie symmetries and reductions of a nonisospectral Lax pair
The classical Lie method is applied to a nonisospectral problem associated
with a system of partial differential equations in 2+1 dimensions (Maccari A,
J. Math. Phys. 39, (1998), 6547-6551). Identification of the classical Lie
symmetries provides a set of reductions that give rise to different nontrivial
spectral problems in 1+1 dimensions. The form in which the spectral parameter
of the 1+1 Lax pair is introduced is carefully described.Comment: 11 pages (v2: A typo corrected in the authors' names
Ácaros Fitoseidos de las islas Canarias (Acari, Phytoseiidae). II. Tenerife y La Gomera
Phytoseiid mites (Acari, Phytoseiidae) inhabiting plants in natural ecosystems from Tenerife and La Gomera islands (Canary Islands) have been studied. Surveys were conducted from 1997 to 2002. Eleven species were collected, one of them being reported for the first time from the Canary Islands and six of them reported for the first time from Tenerife and La Gomera islands. Euseius machadoi n. sp. collected from woody plants in the Canarian laurisilva is proposed as a new species.En muestreos realizados desde 1997 hasta 2002 se ha estudiado la fauna de ácaros fitoseidos (Acari, Phytoseiidae) asociada a plantas de ecosistemas naturales de las islas de Tenerife y La Gomera (Islas Canarias). Se han recolectado un total de 11 especies, siendo una de ellas citada por vez primera en las islas Canarias y seis de ellas citadas por primera vez en las islas de Tenerife y La Gomera. Euseius machadoi n. sp., recolectado en plantas leñosas de la laurisilva canaria, se propone como una nueva especie
Non-classical symmetries and the singular manifold method: A further two examples
This paper discusses two equations with the conditional Painleve property.
The usefulness of the singular manifold method as a tool for determining the
non-classical symmetries that reduce the equations to ordinary differential
equations with the Painleve property is confirmed once moreComment: 9 pages (latex), to appear in Journal of Physics
Proper motions in the VVV Survey: Results for more than 15 million stars across NGC 6544
Context: In the last six years, the VVV survey mapped 562 sq. deg. across the
bulge and southern disk of the Galaxy. However, a detailed study of these
regions, which includes globular clusters (GCs) and thousands of open
clusters is by no means an easy challenge. High differential reddening and
severe crowding along the line of sight makes highly hamper to reliably
distinguish stars belonging to different populations and/or systems. Aims: The
aim of this study is to separate stars that likely belong to the Galactic GC
NGC 6544 from its surrounding field by means of proper motion (PM) techniques.
Methods: This work was based upon a new astrometric reduction method optimized
for images of the VVV survey. Results: Photometry over the six years baseline
of the survey allowed us to obtain a mean precision of mas/yr, in
each PM coordinate, for stars with Ks < 15 mag. In the area studied here,
cluster stars separate very well from field stars, down to the main sequence
turnoff and below, allowing us to derive for the first time the absolute PM of
NGC 6544. Isochrone fitting on the clean and differential reddening corrected
cluster color magnitude diagram yields an age of 11-13 Gyr, and
metallicity [Fe/H] = -1.5 dex, in agreement with previous studies restricted to
the cluster core. We were able to derive the cluster orbit assuming an
axisymmetric model of the Galaxy and conclude that NGC 6544 is likely a halo
GC. We have not detected tidal tail signatures associated to the cluster, but a
remarkable elongation in the galactic center direction has been found. The
precision achieved in the PM determination also allows us to separate bulge
stars from foreground disk stars, enabling the kinematical selection of bona
fide bulge stars across the whole survey area. Our results show that VVV data
is perfectly suitable for this kind of analysis.Comment: 13 pages, 12 figures, accepted in A&
Digital imaging techniques for recording and analysing prehistoric rock art panels in Galicia (NW Iberia)
Several works have highlighted the relevance of 3D modelling techniques for the study of rock art, especially in case of deteriorated state of preservation. This paper presents a methodological approach to accurate document two Bronze Age rock art panels in Galicia (Spain), using photogrammetry SfM. The main aim is to show the application of digital enhancement techniques which have allowed the accurate depiction of the motifs and the correction of previous calques, focusing on the application of the exaggerated shading as a novel analytical method
Mappings preserving locations of movable poles: a new extension of the truncation method to ordinary differential equations
The truncation method is a collective name for techniques that arise from
truncating a Laurent series expansion (with leading term) of generic solutions
of nonlinear partial differential equations (PDEs). Despite its utility in
finding Backlund transformations and other remarkable properties of integrable
PDEs, it has not been generally extended to ordinary differential equations
(ODEs). Here we give a new general method that provides such an extension and
show how to apply it to the classical nonlinear ODEs called the Painleve
equations. Our main new idea is to consider mappings that preserve the
locations of a natural subset of the movable poles admitted by the equation. In
this way we are able to recover all known fundamental Backlund transformations
for the equations considered. We are also able to derive Backlund
transformations onto other ODEs in the Painleve classification.Comment: To appear in Nonlinearity (22 pages
SUCESIÓN ESTACIONAL DE LAS ALGAS EN EL RIO MANZANARES
The seasonal succession of algae attached to natural substrata in a section of the river Manzanares is given. Nutrients, light and current velocity were the factors that determined this succession: Diatoms - Green-algae - Diatoms + Bluegreen algae.Se estudia la sucesión estacional de las algas fijas a sustratos naturales en un tramo del río Manzanares. Dicha sucesión estuvo influida por el contenido de materia orgánica en el agua, luz y velocidad de la corriente, y es del tipo: Diatomeas -+ Clorofitas - Diatomeas + Cianofitas
Entropy and equilibrium state of free market models
Many recent models of trade dynamics use the simple idea of wealth exchanges
among economic agents in order to obtain a stable or equilibrium distribution
of wealth among the agents. In particular, a plain analogy compares the wealth
in a society with the energy in a physical system, and the trade between agents
to the energy exchange between molecules during collisions. In physical
systems, the energy exchange among molecules leads to a state of equipartition
of the energy and to an equilibrium situation where the entropy is a maximum.
On the other hand, in the majority of exchange models, the system converges to
a very unequal condensed state, where one or a few agents concentrate all the
wealth of the society while the wide majority of agents shares zero or almost
zero fraction of the wealth. So, in those economic systems a minimum entropy
state is attained. We propose here an analytical model where we investigate the
effects of a particular class of economic exchanges that minimize the entropy.
By solving the model we discuss the conditions that can drive the system to a
state of minimum entropy, as well as the mechanisms to recover a kind of
equipartition of wealth
Serum proteomics of active tuberculosis patients and contacts reveals unique processes activated during Mycobacterium tuberculosis infection.
Tuberculosis (TB) is the most lethal infection among infectious diseases. The specific aim of this study was to establish panels of serum protein biomarkers representative of active TB patients and their household contacts who were either infected (LTBI) or uninfected (EMI-TB Discovery Cohort, Pontevedra Region, Spain). A TMT (Tamdem mass tags) 10plex-based quantitative proteomics study was performed in quintuplicate containing a total of 15 individual serum samples per group. Peptides were analyzed in an LC-Orbitrap Elite platform, and raw data were processed using Proteome Discoverer 2.1. A total of 418 proteins were quantified. The specific protein signature of active TB patients was characterized by an accumulation of proteins related to complement activation, inflammation and modulation of immune response and also by a decrease of a small subset of proteins, including apolipoprotein A and serotransferrin, indicating the importance of lipid transport and iron assimilation in the progression of the disease. This signature was verified by the targeted measurement of selected candidates in a second cohort (EMI-TB Verification Cohort, Maputo Region, Mozambique) by ELISA and nephelometry techniques. These findings will aid our understanding of the complex metabolic processes associated with TB progression from LTBI to active disease
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