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

Service-Dominant Logic and Value in Tourism Management: A Qualitative Study within Spanish Hotels Managers

With the award-winning article of Vargo and Lusch (2004), a new concept was introduced, called Service-Dominant logic (S-D logic). This paper aims to apply S-D logic to the tourism sector by determining if this new approach, by means of the importance of value co-creation, can affect the perceptions of value in the mind of the consumer and, thus, be used as a source of competitive advantage if adopted by tourism service providers. In this paper a conceptual framework is established through a literature review on both S-D logic and value in tourism. After a review of both topics, links between them are conceptually explored. With empirical research methods this study analyzed the applicability of the ten foundational premises of S-D logic in the tourist experience. Through exploratory research, we conducted in-depth interviews with hotel directors in the tourism sector in order to generate qualitative data and provide valuable knowledge to make conclusions on the managerial implications that the practical use of this new mindset would entail. Tourism managers should consider these new ideas in practice as a way to enhance value co-creation and differentiate themselves from the competition

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

Towards three-dimensional non-invasive recording of incised rock art

Ancient art cut into rock is difficult to research and manage off-site without precise three-dimensional records. Experiments with photographic modelling by the authors led to a relatively accessible and economical way of making them

Asymmetric wormholes in Palatini f(R)f(\mathcal{R}) gravity: Energy conditions, absorption and quasibound states

We investigate the absorption properties of reflection-asymmetric wormholes constructed via the thin-shell formalism in Palatini $f({\cal R})$ gravity. Such wormholes come from the matching of two Reissner-Nordstr\"om spacetimes at a time-like hypersurface (shell), which, according to the junction conditions in Palatini $f({\cal R})$ gravity, can have positive or negative energy density. Using numerical methods we investigate several configurations that satisfy the junction conditions, and analyze how the parameters of the system affect the absorption spectra. We confirm that the absorption cross section of wormholes at low frequencies significantly departs from that of black holes, and observe that in configurations made out of two naked singularities, the absorption spectra exhibit new features due to the effective light ring associated to the wormhole throat. The possibility of observing the presence of resonances at high frequencies is also discussed.Comment: 18 pages, 13 figures, revtex4-2 styl

Cork harvest planning and climate: High air humidity favors availability of airborne inoculum of Diplodia corticola

Producción CientíficaThe canker disease caused by Diplodia corticola is one of the most important emerging pathologies of cork oak (Quercus suber) in western Europe. The fungus is dispersed by borer insects, although it is also thought that the spores can be dispersed by wind and rain. The aim of this study was to evaluate the presence of airborne inoculum of D. corticola in managed cork oak stands during cork harvesting season. Semi-passive spore traps were set in eight sampling plots in Catalonia (north-eastern Spain) in summer of 2020. Traps were replaced every week and the number of D. corticolas spores per sampling event was estimated based on a specific nested-qPCR protocol. Spatial-temporal distribution of airborne inoculum accumulation along sampling areas was analyzed using generalized additive models (GAMs). The availability of airborne inoculum resulted rather low with noticeable accumulation peaks in some of the sampled areas. The fitted GAM revealed a positive effect of high air humidity during the sampling period on the availability of spores. This study represents the first attempt to model the spore release of this emerging pathogen, and it provides insights for developing D. corticola canker control strategies based on the precise timing of cork harvesting operations.Centro de Ciencias Forestales de Cataluña (CTFC) (E-25-2020-0115755

Twisted One-Dimensional Charge Transfer and Related Y-Shaped Chromophores with a 4 H-Pyranylidene Donor: Synthesis and Optical Properties

Three series of push-pull derivatives bearing 4H-pyranylidene as electron donor group and a variety of acceptors were designed. On one hand, one-dimensional chromophores with a thiophene ring (series 1H) or 5-dimethylaminothiophene moiety (series 1N) as an auxiliary donor, non-coplanar with the p-conjugated system, were synthesized. On the other hand, related two-dimensional (2D) Y-shaped chromophores (series 2) were also prepared to compare how the diverse architectures affect the electrochemical, linear, and second-order nonlinear optical (NLO) properties. The presence of the 5-dimethylaminothiophene moiety in the exocyclic C= C bond of the pyranylidene unit gives rise to oxidation potentials rarely low, and the protonation (with an excess of trifluoroacetic acid) of its derivatives results in the apparition of a new blue-shifted band in the UV-visible spectra. The analysis of the properties of derivatives with and without the additional thiophene ring shows that this auxiliary donor leads to a higher NLO response, accompanied by an enhanced transparency. Y-shaped chromophores of series 2 present a blue-shifted absorption, higher molar extinction coefficients, and higher Eox values compared to their linear twisted counterparts. As concerns NLO properties, 2D Y-shaped architecture gives rise to somewhat lower µß values (except for thiobarbiturate derivatives)

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

Imidazole and imidazolium antibacterial drugs derived from amino acids

The antibacterial activity of imidazole and imidazolium salts is highly dependent upon their lipophilicity, which can be tuned through the introduction of different hydrophobic substituents on the nitrogen atoms of the imidazole or imidazolium ring of the molecule. Taking this into consideration, we have synthesized and characterized a series of imidazole and imidazolium salts derived from L-valine and L-phenylalanine containing different hydrophobic groups and tested their antibacterial activity against two model bacterial strains, Gram-negative E. coli and Gram-positive B. subtilis. Importantly, the results demonstrate that the minimum bactericidal concentration (MBC) of these derivatives can be tuned to fall close to the cytotoxicity values in eukaryotic cell lines. The MBC value of one of these compounds toward B. subtilis was found to be lower than the IC50 cytotoxicity value for the control cell line, HEK-293. Furthermore, the aggregation behavior of these compounds has been studied in pure water, in cell culture media, and in mixtures thereof, in order to determine if the compounds formed self-assembled aggregates at their bioactive concentrations with the aim of determining whether the monomeric species were in fact responsible for the observed antibacterial activity. Overall, these results indicate that imidazole and imidazolium compounds derived from L-valine and L-phenylalanine—with different alkyl lengths in the amide substitution—can serve as potent antibacterial agents with low cytotoxicity to human cell lines