711 research outputs found
Six-dimensional D_N theory and four-dimensional SO-USp quivers
We realize four-dimensional N=2 superconformal quiver gauge theories with
alternating SO and USp gauge groups as compactifications of the six-dimensional
D_N theory with defects. The construction can be used to analyze infinitely
strongly-coupled limits and S-dualities of such gauge theories, resulting in a
new class of isolated four-dimensional N=2 superconformal field theories with
SO(2N)^3 flavor symmetry.Comment: 30 pages, 12 figures; v2: published versio
Generalized plane-fronted gravitational waves in any dimension
We study the gravitational waves in spacetimes of arbitrary dimension. They
generalize the pp-waves and the Kundt waves, obtained earlier in four
dimensions. Explicit solutions of the Einstein and Einstein-Maxwell equations
are derived for an arbitrary cosmological constant.Comment: Revtex, 18 pages, no figure
Nested shallow geothermal systems
The long-term sustainability of shallow geothermal systems in dense urbanized areas can be potentially compromised by the existence of thermal interfaces. Thermal interferences between systems have to be avoided to prevent the loss of system performance. Nevertheless, in this work we provide evidence of a positive feedback from thermal interferences in certain controlled situations. Two real groundwater heat pump systems were investigated using real exploitation data sets to estimate the thermal energy demand bias and, by extrapolation, to assess the nature of thermal interferences between the systems. To do that, thermal interferences were modelled by means of a calibrated and validated 3D city-scale numerical model reproducing groundwater flow and heat transport. Results obtained showed a 39% (522 MWh·yr-1) energy imbalance towards cooling for one of the systems, which generated a hot thermal plume towards the downgradient and second system investigated. The nested system in the hot thermal plume only used groundwater for heating, thus establishing a positive symbiotic relationship between them. Considering the energy balance of both systems together, a reduced 9% imbalance was found, hence ensuring the long-term sustainability and renewability of the shallow geothermal resource exploited. The nested geothermal systems described illustrate the possibilities of a new management strategy in shallow geothermal energy governance
Methods for Compression of Feedback in Adaptive Multicarrier 4G Schemes
In this paper, several algorithms for compressing the feedback of channel quality
information are presented and analyzed. These algorithms are developed for a proposed
adaptive modulation scheme for future multi-carrier 4G mobile systems. These strategies
compress the feedback data and, used together with opportunistic scheduling, drastically
reduce the feedback data rate. Thus the adaptive modulation schemes become more suitable
and efficient to be implemented in future mobile systems, increasing data throughput and
overall system performance.This work has been partly funded by the Spanish government with projects MACAWI
(TEC 2005-07477-c02-02), MAMBO2 (CCG06-UC3M-TIC-0698), and European COST Action 289 and is
a result of work done within this European actio
The causal boundary of wave-type spacetimes
A complete and systematic approach to compute the causal boundary of
wave-type spacetimes is carried out. The case of a 1-dimensional boundary is
specially analyzed and its critical appearance in pp-wave type spacetimes is
emphasized. In particular, the corresponding results obtained in the framework
of the AdS/CFT correspondence for holography on the boundary, are reinterpreted
and very widely generalized. Technically, a recent new definition of causal
boundary is used and stressed. Moreover, a set of mathematical tools is
introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type
arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small
modifications. To appear in JHE
New solutions in 3D gravity
We study gravitational theory in 1+2 spacetime dimensions which is determined
by the Lagrangian constructed as a sum of the Einstein-Hilbert term plus the
two (translational and rotational) gravitational Chern-Simons terms. When the
corresponding coupling constants vanish, we are left with the purely Einstein
theory of gravity. We obtain new exact solutions for the gravitational field
equations with the nontrivial material sources. Special attention is paid to
plane-fronted gravitational waves (in case of the Maxwell field source) and to
the circularly symmetric as well as the anisotropic cosmological solutions
which arise for the ideal fluid matter source.Comment: Revtex, 21 pages, no figure
Flower induction and development in saffron: Timing and hormone signalling pathways
[EN] The demand for saffron is expected to rise in the coming years due to its nutraceutical and medicinal properties. To cope with this, it will be necessary to develop a mechanised production of saffron. Upgrading the production methods requires accurate control of the flowering time in this species. Nevertheless, little is known about the control of flowering time in Crocus sativus L. The aim of this study is to gain insight into the floral induction regulatory networks operating in this species. A transcriptomic analysis was performed from saffron main buds in different stages of development. The identification of putative integrators of flowering time signals, like FT, as well as meristem identity genes, such as LFY and TFL1, permitted the definition of the time of flowering induction of the buds, being able to use them as molecular markers. The identification of the transcripts encoded by a DROOPING LEAF-like (DL) gene is of particular relevance because this gene might be a novel factor for carpel specification in saffron.
To elucidate the hormonal signalling networks working during flower induction, transcriptomic data were used, and the content of IAA, ABA and gibberellins was determined in competent and non-competent buds to flower, during the saffron life cycle. Our results suggested that ABA might be negatively regulating corm dormancy release, but its involvement in flower induction cannot be ruled out. ABI5 and the mediator of ABA regulated dormancy gene MARD1, could be key players of this pathway. In addition, a drop in GA4 levels may also be a necessary, but insufficient, condition for floral induction and development. DELLA, TFL1 and PIF3 genes might be involved in the gibberellin pathway. Notably, IAA seems to be a positive regulator of the process, involving MP/ARF5 and ANT genes in the pathway. Taken together, these results pave the way to the unveiling of the regulatory networks controlling the vegetative-to-reproductive phase change in saffron.The activities of this study have been supported by a project funded by the "Ministerio de Ciencia, Innovacion y Universidades de Espana" [AGL2016-77078-R].Renau-Morata, B.; Nebauer, SG.; GarcĂa-Carpintero, V.; Cañizares Sales, J.; Minguet, E.; De Los Mozos, M.; Molina Romero, RV. (2021). Flower induction and development in saffron: Timing and hormone signalling pathways. Industrial Crops and Products. 164:1-19. https://doi.org/10.1016/j.indcrop.2021.113370S11916
CD24-targeted intraoperative fluorescence image-guided surgery leads to improved cytoreduction of ovarian cancer in a preclinical orthotopic surgical model
Background: The completeness of resection is a key prognostic indicator in patients with ovarian cancer, and the application of tumour-targeted fluorescence image-guided surgery (FIGS) has led to improved detection of peritoneal metastases during cytoreductive surgery. CD24 is highly expressed in ovarian cancer and has been shown to be a suit
Riemannian Sparse Coding for Positive Definite Matrices
International audienceInspired by the great success of sparse coding for vector valued data, our goal is to represent symmetric positive definite (SPD) data matrices as sparse linear combinations of atoms from a dictionary, where each atom itself is an SPD matrix. Since SPD matrices follow a non-Euclidean (in fact a Riemannian) geometry, existing sparse coding techniques for Euclidean data cannot be directly extended. Prior works have approached this problem by defining a sparse coding loss function using either extrinsic similarity measures (such as the log-Euclidean distance) or kernelized variants of statistical measures (such as the Stein divergence, Jeffrey's divergence, etc.). In contrast, we propose to use the intrinsic Riemannian distance on the manifold of SPD matrices. Our main contribution is a novel mathematical model for sparse coding of SPD matrices; we also present a computationally simple algorithm for optimizing our model. Experiments on several computer vision datasets showcase superior classification and retrieval performance compared with state-of-the-art approaches
Nuclear parton distributions at next to leading order
We perform a next to leading order QCD global analysis of nuclear deep
inelastic scattering and Drell-Yan data using the convolution approach to
parameterize nuclear parton densities. We find both a significant improvement
in the agreement with data compared to previous extractions, and substantial
differences in the scale dependence of nuclear effects compared to leading
order analyses.Comment: 9 pages, 10 figure
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