OS diversity for intrusion tolerance: Myth or reality?

One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper we present a study with operating systems (OS) vulnerability data from the NIST National Vulnerability Database. We have analyzed the vulnerabilities of 11 different OSes over a period of roughly 15 years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSes. Hence, our analysis provides a strong indication that building a system with diverse OSes may be a useful technique to improve its intrusion tolerance capabilities

Biological performance of natural-based polymers for tissue engineering scaffolding

[Excerpt] One of the open issues in the Tissue Engineering area is whether scaffolds are needed at all to regenerate many tissue defects. This is a fundamental question that may be answered by providing clear evidence of success by scaffold-less tissue regeneration strategies. In its absence, many groups within this research community are focused in the development of scaffold-dependent strategies. Natural-based biomaterials have been proposed and explored to meet the requirements of many applications in the Tissue Engineering and Regenerative Medicine. Among the important characteristics of those biomaterials it should be highlighted the easy biodegradation by normal metabolic pathways, the low cytotoxicity and low immunogenic reaction upon implantation and the myriad of properties obtained by combination of those materials with other biodegradable polymers. This later strategy has been pursued in our lab in the quest to obtain scaffolds that effectively help, assist and drive cells to regenerate connective tissues. [...]info:eu-repo/semantics/publishedVersio

Minimally Extended Left-Right Symmetric Model for Dark Matter with U(1) Portal

A minimal extension of the left-right symmetric model for neutrino masses that includes a vector-like singlet fermion dark matter (DM) is presented with the DM connected to the visible sector via a gauged U(1) portal. We discuss the symmetry breaking in this model and calculate the mass and mixings of the extra heavy neutral gauge boson at the TeV scale. The extra gauge boson can decay to both standard model particles as well to dark matter. We calculate the relic density of the singlet fermion dark matter and its direct detection cross section and use these constraints to obtain the allowed parameter range for the new gauge coupling and the dark matter mass.Comment: 19 pages, 8 figure

INJECTABLE HYBRID SYSTEM FOR STRONTIUM LOCAL DELIVERY TO PROMOTE BONE REGENERATION

In bone tissue regeneration strategies, injectable bone substitutes are very attractive since they can be applied with minimally invasive surgical procedures and can perfectly fill irregular defects created in cases of trauma, infection or tumor resection. These materials must combine adequate mechanical properties with the ability to induce new bone formation. Incorporating strontium (Sr) in bone substitute biomaterials may be a strategy to achieve high Sr concentrations, not in a systemic but in a local environment, taking advantage of the osteoanabolic and anti-osteoclastic activity of Sr, for the enhancement of new bone formation. In this context, the aim of the present work was to evaluate the response of a Sr-hybrid injectable system for bone regeneration, designed by our group, consisting of hydroxyapatite microspheres doped with Sr and an alginate vehicle crosslinked in situ with Sr, in an in vivo scenario. Two different animal models were used, rat (Wistar) and sheep (Merino Branco) critical sized bone defect. Non Sr-doped similar materials (Ca-hybrid) or empty defects were used as control. Sr-hybrid system led to an increased bone formation in both center and periphery of a rat critical sized defect compared to a non Sr–doped similar system, where new bone formation was restricted to the periphery. Moreover newly formed bone was identified as early as one week after its implantation in a sheep model. After eight weeks, the bone surrounded the microspheres, both in the periphery and in the center of the defect. Most importantly, the hybrid system provided a scaffold for cell migration and tissue ingrowth and offered structural support, as observed in both models. The effective improvement of local bone formation suggests that this might be a promising approach for bone regeneration, especially in osteoporotic conditions

The Branched Polymer Growth Model Revisited

The Branched Polymer Growth Model (BPGM) has been employed to study the kinetic growth of ramified polymers in the presence of impurities. In this article, the BPGM is revisited on the square lattice and a subtle modification in its dynamics is proposed in order to adapt it to a scenario closer to reality and experimentation. This new version of the model is denominated the Adapted Branched Polymer Growth Model (ABPGM). It is shown that the ABPGM preserves the functionalities of the monomers and so recovers the branching probability b as an input parameter which effectively controls the relative incidence of bifurcations. The critical locus separating infinite from finite growth regimes of the ABPGM is obtained in the (b,c) space (where c is the impurity concentration). Unlike the original model, the phase diagram of the ABPGM exhibits a peculiar reentrance.Comment: 8 pages, 10 figures. To be published in PHYSICA

Metallicity of M dwarfs III. Planet-metallicity and planet-stellar mass correlations of the HARPS GTO M dwarf sample

Aims. The aim of this work is the study of the planet-metallicity and the planet-stellar mass correlations for M dwarfs from the HARPS GTO M dwarf subsample Methods. We use a new method that takes advantage of the HARPS high-resolution spectra to increase the precision of metallicity, using previous photometric calibrations of [Fe/H] and effective temperature as starting values. Results. In this work we use our new calibration (rms = 0.08 dex) to study the planet-metallicity relation of our sample. The well-known correlation for Giant planet FGKM hosts with metallicity is present. Regarding Neptunians and smaller hosts no correlation is found but there is a hint that an anti-correlation with [Fe/H] may exist. We combined our sample with the California Planet Survey late-K and M-type dwarf sample to increase our statistics but found no new trends. We fitted a power law to the frequency histogram of the Jovian hosts for our sample and for the combined sample, f_p = C10^\alpha[Fe/H], using two different approaches: a direct bin fitting and a bayesian fitting procedure. We obtained a value for C between 0.02 and 0.04 and for \alpha between 1.26 and 2.94. Regarding stellar mass, an hypothetical correlation with planets was discovered, but was found to be the result of a detection bias.Comment: Accepted for publication in A&A. 18 pages, 11 Figures, 12 Table

German cultural standards from the Portuguese perspective

JEL Classification: F23 - Multinational Firms; International Business; M12 – Personnel Management.The purpose of this study is to identify the cultural standards of the Germans from the Portuguese perspective. The methodology used is the Cultural Standard Method, an innovative methodology that allows identifying with much more detail and rigor the cultural differences between two cultures. The instrument used is the narrative interview, a kind of open interviews in which interviewees, which are all Portuguese with an extensive working experience in Germany, present, by the order they consider more significant in terms of culture shock, the stories of incidents that occurred during their stay in Germany, which represent critical incidents that may be positive or negative. Critical incidents, analyzed with base on the process "Qualitative Content Analysis" allow to identify, at the end of the process, the relative cultural standards that result from the comparison between two cultures, in this case German and Portuguese culture. These results, only valid when comparing two cultures, do not allow generalizations or extrapolations in the comparison with other cultures. That is, they cannot be used to characterize a culture, as is the case of Germany, in general terms, as it is done in the dimension-based models. The results obtained, relative cultural standards, concerning German culture from the Portuguese perspective, are a contribution to those Portuguese who have to work with Germans and need to better understand the differences between the two cultures. Moreover, this work could be a reflection for all Germans who come to Portugal or that somehow have to deal with the Portuguese, allowing them to reflect on the issues that Portuguese regard as the most significant features of German culture, when compared with the Portuguese one.O objectivo deste estudo consiste em identificar os standards culturais dos alemães na perspectiva dos portugueses. A metodologia utilizada é o Método dos Standards Culturais, uma metodologia inovadora que permite identificar com muito mais detalhe e rigor as diferenças culturais entre duas culturas. O instrumento utilizado é a entrevista narrativa, um tipo de entrevista aberta em que os entrevistados, todos portugueses que tiveram larga experiência de trabalho na Alemanha, apresentam, pela ordem que os marcou mais em termos de choque cultural, as histórias de incidentes que aconteceram durante a sua estadia na Alemanha e que representam incidentes críticos, os quais podem ser positivos os negativos. Os incidentes críticos, analisados com base no processo “Qualitative Content Analysis” permitem identificar, no final do processo, os standards culturais relativos que resultam da comparação entre duas culturas, neste caso a cultura alemã e a Portuguesa. Estes resultados, válidos apenas quando comparamos duas culturas, não permitem generalizações ou extrapolações na comparação com outras culturas. Ou seja, não podem ser utilizados para caracterizar uma cultura, como é o caso da alemã, em termos gerais, tal como é feito nos modelos baseados nas dimensões. Os resultados obtidos, standards culturais relativos, referentes à cultura alemã na perspectiva dos portugueses, é um contributo para todos aqueles portugueses que tenham que trabalhar com alemães e necessitem de compreender melhor as diferenças entre as duas culturas. Por outro lado, este trabalho poderá constituir-se como uma reflexão para todos os alemães que venham a Portugal ou que de alguma forma tenham que lidar com portugueses, pois permite-lhes reflectir nos aspectos que os portugueses consideram como mais marcantes da cultura alemã, quando comparada com a portuguesa

Metallicity of M dwarfs IV. A high-precision [Fe/H] and Teff technique from high-resolution optical spectra for M dwarfs

Aims. In this work we develop a technique to obtain high precision determinations of both metallicity and effective temperature of M dwarfs in the optical. Methods. A new method is presented that makes use of the information of 4104 lines in the 530-690 nm spectral region. It consists in the measurement of pseudo equivalent widths and their correlation with established scales of [Fe/H] and $T_{eff}$. Results. Our technique achieves a $rms$ of 0.08$\pm$0.01 for [Fe/H], 91$\pm$13 K for $T_{eff}$, and is valid in the (-0.85, 0.26 dex), (2800, 4100 K), and (M0.0, M5.0) intervals for [Fe/H], $T_{eff}$ and spectral type respectively. We also calculated the RMSE$_{V}$ which estimates uncertainties of the order of 0.12 dex for the metallicity and of 293 K for the effective temperature. The technique has an activity limit and should only be used for stars with $\log{L_{H_{\alpha}}/L_{bol}} < -4.0$. Our method is available online at \url{http://www.astro.up.pt/resources/mcal}.Comment: Accepted in Astronomy and Astrophysics. Updated one important reference in the introduction. Some typos correcte