Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

On the regularity of binomial edge ideals

Abstract: We study the regularity of binomial edge ideals. For a closed graph G we show that the regularity of the binomial edge ideal JG coincides with the regularity of inlex(JG) and can be expressed in terms of the combinatorial data of G. In addition, we give positive answers to Matsuda-Murai conjecture (8) for some classes of graphs.

Berezin-Toeplitz quantization on Kaehler manifolds

Abstract: We study the Berezin-Toeplitz quantization on Kaehler manifolds. We explain first how to compute various associated asymptotic expansions, then we compute explicitly the first terms of the expansion of the kernel of the Berezin-Toeplitz operators, and of the composition of two Berezin-Toeplitz operators. As application we estimate the norm of Donaldson's Q-operator.

Protein tyrosine phosphatase structure-function relationships in regulation and pathogenesis.

Abstract: Protein phosphorylation on tyrosine residues is tightly controlled by protein tyrosine phosphatases (PTPs) at multiple levels: spatio-temporal expression, subcellular localization and post-translational modification. Structural and functional analysis of the PTP domains has provided insight into catalysis and regulatory mechanisms that control the enzymatic activity. Understanding the molecular basis of PTP regulation is of fundamental importance to dissect the pleiotropic effect of these enzymes in both health and disease. Here, we review recent insights into the regulation of receptor-like PTPs by extracellular ligands and into regulation by reversible oxidation that impairs catalysis directly. The physiological roles of PTPs are essential in homeostasis in eukaryotic cells and pertubation of their functional attributes causes different disease states. As an example, we discuss recent findings indicating how inappropriate oxidation of PTPs in cancer cells may contribute to cell transformation. On the other hand, PTPs from many pathogens are key virulence factors and manipulate signalling pathways in the host cells to promote invasion and survival of the microorganisms. This research area has received relatively little attention but has advanced remarkably. We review the structural features of pathogenic PTPs, their similarities and differences with eukaryotic PTPs, and the possible exploitation of this knowledge for therapeutic intervention.

Observational evidence of torus instability as trigger mechanism for coronal mass ejections: the 2011 august 4 filament eruption

Abstract: Solar filaments are magnetic structures often observed in the solar atmosphere and consist of plasma that is cooler and denser than their surroundings. They are visible for days—even weeks—which suggests that they are often in equilibrium with their environment before disappearing or erupting. Several eruption models have been proposed that aim to reveal what mechanism causes (or triggers) these solar eruptions. Validating these models through observations represents a fundamental step in our understanding of solar eruptions. We present an analysis of the observation of a filament eruption that agrees with the torus instability model. This model predicts that a magnetic flux rope embedded in an ambient field undergoes an eruption when the axis of the flux rope reaches a critical height that depends on the topology of the ambient field. We use the two vantage points of theSolar Dynamics Observatory (SDO) and the Solar TErrestrial RElations Observatory to reconstruct the three-dimensional shape of the filament, to follow its morphological evolution, and to determine its height just before eruption. The magnetograms acquired by SDO/Helioseismic and Magnetic Imager are used to infer the topology of the ambient field and to derive the critical height for the onset of the torus instability. Our analysis shows that the torus instability is the trigger of the eruption. We also find that some pre-eruptive processes, such as magnetic reconnection during the observed flares and flux cancellation at the neutral line, facilitated the eruption by bringing the filament to a region where the magnetic field was more vulnerable to the torus instability.

Bures distance as a measure of entanglement for two-mode squeezed thermal states

Abstract: We propose a reliable entanglement measure for a two-mode squeezed thermal state of the quantum electromagnetic field in terms of its Bures distance to the set of all separable states of the same kind. The requisite fidelity of a pair of two-mode squeezed thermal states is exactly evaluated. By applying the Peres-Simon criterion of separability, we find the closest separable state. This enables us to establish an insightful expression of the amount of entanglement. We also derive the relative entropy of a two-mode squeezed thermal state with respect to another one. This quantity is exploited in the pure-state case by undertaking a similar approximation for the entropic entanglement of a two-mode squeezed vacuum state. Comparison with previous work lends support to our approach that replaces the reference set of all separable Gaussian states by its subset consisting only of the squeezed thermal ones.