3,468 research outputs found
Flexible Authentication in Vehicular Ad hoc Networks
A Vehicular Ad-Hoc Network (VANET) is a form of Mobile ad-hoc network, to
provide communications among nearby vehicles and between vehicles and nearby
fixed roadside equipment. The key operation in VANETs is the broadcast of
messages. Consequently, the vehicles need to make sure that the information has
been sent by an authentic node in the network. VANETs present unique challenges
such as high node mobility, real-time constraints, scalability, gradual
deployment and privacy. No existent technique addresses all these requirements.
In particular, both inter-vehicle and vehicle-to-roadside wireless
communications present different characteristics that should be taken into
account when defining node authentication services. That is exactly what is
done in this paper, where the features of inter-vehicle and vehicle-to-roadside
communications are analyzed to propose differentiated services for node
authentication, according to privacy and efficiency needs
El ácido úrico se asocia con características de un síndrome de resistencia insulínica en los niños obesos en etapas perdurables
Elevated plasma uric acid levels are associated with obesity
and could be an expression of insulin-resistant state.
The aim of the present study was to evaluate plasma uric
acid in obese and normal-weight children exclusively at prepubertal
stage and its relationship with anthropometric
measurements, intake, and features of the insulin resistance
syndrome. A study was performed in 34 obese and 20 normal-
weight prepubertal children. Nutrient intake was
determined using a 72 h recall questionnaire and a consumption
food frequency questionnaire. Anthropometric
parameters and fasting plasma lipids, glucose, insulin, leptin,
adiponectin, tumour necrosis factor (TNF-α) and uric
acid were measured. Multiple regression analysis was used
to identify association of anthropometric parameters, nutrient
intake and insulin resistance syndrome variables (arterial
blood pressure, plasma glucose, insulin, homeostasis
model assessment of insulin resistance index- HOMA- triacylglycerols
and, HDL-cholesterol) with uric acid. Plasma
uric concentration was significantly higher in the obese
group than in the control group and when adjusted by sex,
age and BMI was positively associated with tricipital skinfold
and insulin resistance, and negatively with adiponectin.
In multiple regression analysis, BMI, HDL-cholesterol and
adiponectin were independent predictors of plasma uric
acid. In conclusion, elevated levels of uric acid in obese children,
compared with lean subjects, at the prepubertal
period, seems to be an early metabolic alteration that is associated
with other features of insulin resistance syndrome.Los niveles elevados de ácido úrico plasmáticos se asocian
a la obesidad y pueden ser la expresión de un estado de
resistencia insulínica. El objetivo de este estudio ha sido
evaluar la concentración plasmática de ácido úrico en niños
obesos y normales, exclusivamente en edad prepuberal, y
determinar su relación con las medidas antropométricas, la
ingesta dietética y los parámetros asociados al síndrome de
resistencia insulínica. El estudio se llevó a cabo en 34 niños
obesos y 20 controles en edad prepuberal a los cuales se les
estimó su ingesta dietética mediante el registro de un cuestionario
de ingesta de alimentos de 72 h y un cuestionario de
frecuencia de consumo de alimentos y se determinaron,
además de los parámetros antropométricos, la glucosa, la
insulina, la leptina, la adiponectina y el factor de necrosis
tumoral alfa (TNF-α) plasmáticos. Se realizó un análisis de
regresión múltiple para identificar la asociación entre los
niveles de ácido úrico y los parámetros antropométricos, la
ingesta de nutrientes y las variables clásicas relacionadas
con el síndrome de resistencia insulínica (hipertensión, glucosa,
insulina, índice de resistencia insulínica HOMA, triglicéridos
y HDL-colesterol plasmáticos), así como con leptina,
adiponectina y TNF-α. La concentración plasmática
de ácido úrico fue significativamente más elevada en los
niños obesos que en los controles y, cuando se ajustó por
sexo, edad e índice de masa corporal, los niveles de ácido
úrico se asociaron con el pliegue tricipital y la resistencia
inulínica, y negativamente con la adiponectina. En el análisis
de regresión múltiple, el índice de masa corporal, el
HDL-colesterol y la adiponectina fueron predictores independientes
del ácido úrico plasmático. En conclusión, los
niveles elevados de ácido úrico en niños obesos en edad prepuberal,
comparado con los de los niños normales, representan
una alteración metabólica temprana asociada con la
resistencia insulínica.This work was supported by the Spanish Ministry of
Health and Consumer Affairs, the Spanish National Program
for Scientific Research, Development, and Technological
Innovation (I+D+I), and the Instituto de Salud
Carlos III (Spanish National Health Research Institute),
FEDER co-financed Project No. PI 051968. Mercedes
Gil-Campos was a research scientist appointed on a
training contract funded by the Carlos III Health
Research Institute
A systematic review of breast milk microbiota composition and the evidence for transfer to and colonisation of the infant gut
The intestinal microbiota plays a major role in infant health and development. However, the role of the breastmilk
microbiota in infant gut colonisation remains unclear. A systematic review was performed to evaluate the composition
of the breastmilk microbiota and evidence for transfer to/colonisation of the infant gut. Searches were performed
using PUBMED, OVID, LILACS and PROQUEST from inception until 18th March 2020 with a PUBMED update
to December 2021. 88 full texts were evaluated before final critique based on study power, sample contamination
avoidance, storage, purification process, DNA extraction/analysis, and consideration of maternal health and other
potential confounders. Risk of skin contamination was reduced mainly by breast cleaning and rejecting the first milk
drops. Sample storage, DNA extraction and bioinformatics varied. Several studies stored samples under conditions
that may selectively impact bacterial DNA preservation, others used preculture reducing reliability. Only 15 studies,
with acceptable sample size, handling, extraction, and bacterial analysis, considered transfer of bacteria to the
infant. Three reported bacterial transfer from infant to breastmilk. Despite consistent evidence for the breastmilk
microbiota, and recent studies using improved methods to investigate factors affecting its composition, few studies
adequately considered transfer to the infant gut providing very little evidence for effective impact on gut colonisation
Graph-Based Approach to the Edit Distance Cryptanalysis of Irregularly Clocked Linear Feedback Shift Registers
This paper proposes a speed-up of a known-plaintext attack on some stream ciphers
based on Linear Feedback Shift Registers (LFSRs). The algorithm consists of two basic steps:
first, to guess the initial seed value of one of the LFSRs, and then to use the resulting binary
sequence in order to deduce useful information about the cipher parameters. In particular, the
proposed divide-and-conquer attack is based on a combination of graph-based techniques with
edit distance concepts. While the original edit distance attack requires the exhaustive search over
the set of all possible initial states of the involved LFSR, this work presents a new heuristic optimization
that avoids the evaluation of an important number of initial states through the identification
of the most promising branches of the search graph. The strongest aspects of the proposal
are the facts that the obtained results from the attack are absolutely deterministic, and that many
inconsistent initial states of the target LFSRs are recognized and avoided during search.This work was supported by the Spanish Ministry of Science and Innovation and European
FEDER Fund under Project TIN2008-02236/TSI as well as by CDTI (Spain)and the companies INDRA, Unin Fenosa, Tecnobit, Visual Tool, Brainstorm, SAC and
Technosafe under Project Cenit-HESPERIA.Peer reviewe
Optimal selection and location of bess systems in medium-voltage rural distribution networks for minimizing greenhouse gas emissions
This paper explores a methodology to locate battery energy storage systems (BESS) in rural alternating current (AC) distribution networks fed by diesel generators to minimize total greenhouse gas emissions. A mixed-integer nonlinear programming (MINLP) model is formulated to represent the problem of greenhouse gas emissions minimization, considering power balance and devices capabilities as constraints. To model the BESS systems, a linear relationship is considered between the state of charge and the power injection/consumption using a charging/discharging coefficient. The solution of the MINLP model is reached through the general algebraic modeling system by employing the BONMIN solver. Numerical results in a medium-voltage AC distribution network composed of 33 nodes and 32 branches operated with 12.66 kV demonstrate the effectiveness of including BESS systems to minimize greenhouse gas emissions in diesel generators that feeds rural distribution networks
Secret Sharing Based on a Hard-on-Average Problem
The main goal of this work is to propose the design of secret sharing schemes
based on hard-on-average problems. It includes the description of a new
multiparty protocol whose main application is key management in networks. Its
unconditionally perfect security relies on a discrete mathematics problem
classiffied as DistNP-Complete under the average-case analysis, the so-called
Distributional Matrix Representability Problem. Thanks to the use of the search
version of the mentioned decision problem, the security of the proposed scheme
is guaranteed. Although several secret sharing schemes connected with
combinatorial structures may be found in the bibliography, the main
contribution of this work is the proposal of a new secret sharing scheme based
on a hard-on-average problem, which allows to enlarge the set of tools for
designing more secure cryptographic applications
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