A caricature of a singular curvature flow in the plane

We study a singular parabolic equation of the total variation type in one dimension. The problem is a simplification of the singular curvature flow. We show existence and uniqueness of weak solutions. We also prove existence of weak solutions to the semi-discretization of the problem as well as convergence of the approximating sequences. The semi-discretization shows that facets must form. For a class of initial data we are able to study in details the facet formation and interactions and their asymptotic behavior. We notice that our qualitative results may be interpreted with the help of a special composition of multivalued operators

Effects of message appeal and service type in CSR communication strategies

Studies highlight the importance of corporate social responsibility (CSR) for companies' stakeholders. Consumers, however, are often unaware of such initiatives. Understanding how to effectively communicate socially responsible initiatives is an important challenge for both researchers and managers, who invest considerable resources in CSR initiatives. This study examines consumers' responses to two types of CSR initiatives (environment-related and employee-based) using two types of message appeals (emotional and rational) across two service types (hedonic and utilitarian). Responses provide data on consumers' awareness of CSR initiatives, attitudes toward the company, perceived company uniqueness, emotional response, and attributions of company motives to engage in CSR activities. Rational appeals more effectively communicate environment-related CSR initiatives, whereas emotional appeals more effectively communicate employee-based CSR initiatives. Effects on consumers' attributions of company motives to engage in CSR are significant in both service types. Finally, rational message appeals affect consumers' CSR awareness and emotional responses in utilitarian service

Structural Stability of the PsbQ Protein of Higher Plant Photosystem II

We have characterized the stability and folding behavior of the isolated extrinsic PsbQ protein of photosystem II (PSII) from a higher plant, Spinacia oleracea, using intrinsic protein fluorescence emission and near- and far-UV circular dichroism (CD) spectroscopy in combination with differential scanning calorimetry (DSC). Experimental results reveal that both chemical denaturation using guanidine hydrochloride (GdnHCl) and thermal unfolding of PsbQ proceed as a two-state reversible process. The denaturation free-energy changes (GD) at 20 C extrapolated from GdnHCl (4.0 ± 0.6 kcal mol-1) or thermal unfolding (4.4 ± 0.8 kcal mol-1) are very close. Moreover, the far-UV CD spectra of the denatured PsbQ registered at 90 C in the absence and presence of 6.0 M GdnHCl superimpose, leading us to conclude that both denatured states of PsbQ are structurally and energetically similar. The thermal unfolding of PsbQ has been also characterized by CD and DSC over a wide pH range. The stability of PsbQ is at its maximum at pH comprised between 5 and 8, being wider than the optimal pH for oxygen evolution in the lumen of thylakoid membranes. In addition, no significant structural changes were detected in PsbQ between 50 and 55 C in the pH range of 3-8, suggesting that PsbQ behaves as a soluble and stable particle in the lumen when it detaches from PSII under physiological stress conditions such as high temperature (45-50 C) or low pH (<5.0). Sedimentation experiments showed that, in solution at 20 C, the PsbQ protein is a monomer with an elongated shape.Spanish Minitry of Science and Technology (PB1998-0480 and AGL2004-00045)This work was funded by the Spanish Ministry of Science and Technology (project references PB1998-0480 and AGL2003-0045). M.B. holds a fellowship from the Spanish Ministry of Science and Technology.Peer reviewe

Gender recognition from a partial view of the face using local feature vectors

This paper proposes a gender recognition scheme focused on local appearance-based features to describe the top half of the face. Due to the fact that only the top half of the face is used, this is a feasible approach in those situations where the bottom half is hidden. In the experiments, several face detection methods with different precision levels are used in order to prove the robustness of the scheme with respect to variations in the accuracy level of the face detection proces

Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron

In this article we study the galactic evolution of the LiBeB elements within the framework of a detailed model of the chemical evolution of the Galaxy that includes galactic cosmic ray nucleosynthesis by particles accelerated in superbubbles. The chemical composition of the superbubble consists of varying proportions of ISM and freshly supernova synthesized material. The observational trends of 6 LiBeB evolution are nicely reproduced by models in which GCR come from a mixture of 25% of supernova material with 75% of ISM, except for 6 Li, for which maybe an extra source is required at low metallicities. To account for 7 Li evolution several additional sources have been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars). The model fulfills the energetic requirements for GCR acceleration.Comment: 25 pages, 9 figures. Accepted for publication in the Astrophysical Journa

Beyond a Fluorescent Probe: Inhibition of Cell Division Protein FtsZ by mant-GTP Elucidated by NMR and Biochemical Approaches

© 2015 American Chemical Society. FtsZ is the organizer of cell division in most bacteria and a target in the quest for new antibiotics. FtsZ is a tubulin-like GTPase, in which the active site is completed at the interface with the next subunit in an assembled FtsZ filament. Fluorescent mant-GTP has been extensively used for competitive binding studies of nucleotide analogs and synthetic GTP-replacing inhibitors possessing antibacterial activity. However, its mode of binding and whether the mant tag interferes with FtsZ assembly function were unknown. Mant-GTP exists in equilibrium as a mixture of C2′- and C3′-substituted isomers. We have unraveled the molecular recognition process of mant-GTP by FtsZ monomers. Both isomers bind in the anti glycosidic bond conformation: 2′-mant-GTP in two ribose puckering conformations and 3′-mant-GTP in the preferred C2′ endo conformation. In each case, the mant tag strongly interacts with FtsZ at an extension of the GTP binding site, which is also supported by molecular dynamics simulations. Importantly, mant-GTP binding induces archaeal FtsZ polymerization into inactive curved filaments that cannot hydrolyze the nucleotide, rather than straight GTP-hydrolyzing assemblies, and also inhibits normal assembly of FtsZ from the Gram-negative bacterium Escherichia coli but is hydrolyzed by FtsZ from Gram-positive Bacillus subtilis. Thus, the specific interactions provided by the fluorescent mant tag indicate a new way to search for synthetic FtsZ inhibitors that selectively suppress the cell division of bacterial pathogens.BFU2011-23416 and BFU2014-51823-R (J.M.A), CTQ2012-32065 (J.J.B.), CM 2010/BMD-2353 (J.J.B. and J.M.A.), FCT SFRH/BPD/65462/2009 and UID/Multi/04378/2013 (F.M.) and a FPI fellowship (L.B.R.A).Peer Reviewe

The stellar atmosphere simulation code Bifrost

Context: Numerical simulations of stellar convection and photospheres have been developed to the point where detailed shapes of observed spectral lines can be explained. Stellar atmospheres are very complex, and very different physical regimes are present in the convection zone, photosphere, chromosphere, transition region and corona. To understand the details of the atmosphere it is necessary to simulate the whole atmosphere since the different layers interact strongly. These physical regimes are very diverse and it takes a highly efficient massively parallel numerical code to solve the associated equations. Aims: The design, implementation and validation of the massively parallel numerical code Bifrost for simulating stellar atmospheres from the convection zone to the corona. Methods: The code is subjected to a number of validation tests, among them the Sod shock tube test, the Orzag-Tang colliding shock test, boundary condition tests and tests of how the code treats magnetic field advection, chromospheric radiation, radiative transfer in an isothermal scattering atmosphere, hydrogen ionization and thermal conduction. Results: Bifrost completes the tests with good results and shows near linear efficiency scaling to thousands of computing cores

Role of transport performance on neuron cell morphology

The compartmental model is a basic tool for studying signal propagation in neurons, and, if the model parameters are adequately defined, it can also be of help in the study of electrical or fluid transport. Here we show that the input resistance, in different networks which simulate the passive properties of neurons, is the result of an interplay between the relevant conductances, morphology and size. These results suggest that neurons must grow in such a way that facilitates the current flow. We propose that power consumption is an important factor by which neurons attain their final morphological appearance.Comment: 9 pages with 3 figures, submitted to Neuroscience Letter