4,287 research outputs found
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
Hamiltonian symplectic embedding of the massive noncommutative U(1) Theory
We show that the massive noncommutative U(1) theory is embedded in a gauge
theory using an alternative systematic way, which is based on the symplectic
framework. The embedded Hamiltonian density is obtained after a finite number
of steps in the iterative symplectic process, oppositely to the result proposed
using the BFFT formalism. This alternative formalism of embedding shows how to
get a set of dynamically equivalent embedded Hamiltonian densities.Comment: 16 pages, no figures, revtex4, corrected version, references
additione
Feeding behaviour of broiler chickens: a review on the biomechanical characteristics
Feed related costs are the main drivers of profitability of commercial poultry farms, and good nutrition is mainly responsible for the exceptional growth rate responses of current poultry species. So far, most research on the poultry feeding behaviour addresses the productivity indices and birds' physiological responses, but few studies have considered the biomechanical characteristics involved in this process. This paper aims to review biomechanical issues related to feed behaviour of domestic chickens to address some issues related to the feed used in commercial broiler chicken production, considering feed particle size, physical form and the impact of feeders during feeding. It is believed that the biomechanical evaluation might suggest a new way for feed processing to meet the natural feeding behaviour of the birds
Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light
Gaseous and liquid xenon particle detectors are being used in a number of
applications including dark matter search and neutrino-less double beta decay
experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors
both as electrical insulator and as a light reflector to improve the efficiency
of detection of scintillation photons. However, xenon emits in the vacuum
ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE
are not sufficiently known.
In this work we report on measurements of PTFE reflectance, including its
angular distribution, for the xenon scintillation light. Various samples of
PTFE, manufactured by different processes (extruded, expanded, skived and
pressed) have been studied. The data were interpreted with a physical model
comprising both specular and diffuse reflections. The reflectance obtained for
these samples ranges from about 47% to 66% for VUV light. Fluoropolymers,
namely ETFE, FEP and PFA were also measured
Haemophilus Influenzae Serotype A Septic Arthritis – A Rare Aetiology
Descreve-se um caso raro de artrite séptca por Haemophilus Influenzae (Hi) serotipo a (Hia)numa criança com o programa nacional de vacinação atualizado e antecendentes pessoais e familiares irrelevantes. A doente não apresentava fatores de risco e o estudo imunológico realizado não revelou alterações. Existem poucos casos relatados a nÃvel mundial de infecção Hia e, de acordo com a revisão bibliográfica realizada. este é o primeiro caso de infecção osteoarticular por Hia descrito na Europa. No contexto deste caso, salienta-se a importância da determinação da estirpe na era pós-vacinal, bem como a exclusão de fatores predisponentes de doença invasiva por Hi não-b em idade pediátrica
Design of nano- and microfiber combined scaffolds by electrospinning of collagen onto starch-based fiber meshes : a man-made equivalent of natural extracellular matrix
Mimicking the structural organization and biologic function of natural extracellular matrix has been one of the
main goals of tissue engineering. Nevertheless, the majority of scaffolding materials for bone regeneration
highlights biochemical functionality in detriment of mechanical properties. In this work we present a rather
innovative construct that combines in the same structure electrospun type I collagen nanofibers with starchbased
microfibers. These combined structures were obtained by a two-step methodology and structurally consist
in a type I collagen nano-network incorporated on a macro starch-based support. The morphology of the
developed structures was assessed by several microscopy techniques and the collagenous nature of the nanonetwork
was confirmed by immunohistochemistry. In addition, and especially regarding the requirements of
large bone defects, we also successfully introduced the concept of layer by layer, as a way to produce thicker
structures. In an attempt to recreate bone microenvironment, the design and biochemical composition of the
combined structures also envisioned bone-forming cells and endothelial cells (ECs). The inclusion of a type I
collagen nano-network induced a stretched morphology and improved the metabolic activity of osteoblasts.
Regarding ECs, the presence of type I collagen on the combined structures provided adhesive support and
obviated the need of precoating with fibronectin. It was also importantly observed that ECs on the nano-network
organized into circular structures, a three-dimensional arrangement distinct from that observed for osteoblasts
and resembling the microcappillary-like organizations formed during angiogenesis. By providing simultaneously
physical and chemical cues for cells, the herein-proposed combined structures hold a great potential in
bone regeneration as a man-made equivalent of extracellular matrixK. Tuzlakoglu and M. I. Santos thank the Portuguese Foundation for Science and Technology for their Ph.D. scholarship (SFRH/BD/8502/2002 and SFRH/BD/13428/2003). This work was partially supported by FCT Foundation for Science and Technology, through funds from the POCTI and/or FEDER programs and by the European Union funded STREP Project HIPPOCRATES (NMP3-CT-2003-505758). This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283). Work developed under the cooperation agreement between UM-3B's research group and the Hospital de S. Marcos, Braga. The authors thank to L. Goreti Pinto for her help on confocal microscopy studies
Noncommutative Metafluid Dynamics
In this paper we define a noncommutative (NC) Metafluid Dynamics
\cite{Marmanis}. We applied the Dirac's quantization to the Metafluid Dynamics
on NC spaces. First class constraints were found which are the same obtained in
\cite{BJP}. The gauge covariant quantization of the non-linear equations of
fields on noncommutative spaces were studied. We have found the extended
Hamiltonian which leads to equations of motion in the gauge covariant form. In
addition, we show that a particular transformation \cite{Djemai} on the usual
classical phase space (CPS) leads to the same results as of the
-deformation with . Besides, we will shown that an additional
term is introduced into the dissipative force due the NC geometry. This is an
interesting feature due to the NC nature induced into model.Comment: 11 page
Assessment of cognitive functions in patients with multiple sclerosis applying the normative values of the Rao’s brief repeatable battery in the Portuguese population
Background: The Brief Repeatable Battery of Neuropsychological Tests (BRBN-T) is one of the most sensitive and
used measures for detecting cognitive impairment in Multiple Sclerosis (MS).
Objective: The aim of this study was to adapt and validate this battery to the Portuguese population of MS
patients.
Methods: The Portuguese version of the BRBN-T was applied to a stratified control national sample of 326
individuals considering sex, age, educational level and geographic location and also a clinical sample of 115 MS
patients from several national hospitals. Through the exploration of its psychometrics properties, the Portuguese
BRBN-T norms were produced.
Results: The normative data is presented as a regression-based formula to adjust test scores for gender, education
and age, and the results reveal the BRBN-T has the ability to differentiate between MS patients and healthy
participant’s cognitive performance.
Conclusion: This study demonstrated in our clinical population a good ability to detect cognitive impairment. Its
clearly contributed to reinforcing the neuropsychological assessment in Portugal in patients with MS, by providing
a new set of instruments, which can be used in the clinical practice, and in future studies. Moreover, it will allow a
rigorous and precise support in relation to neuropsychological assessment for future longitudinal studies and
clinical trials.info:eu-repo/semantics/publishedVersio
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