1,681 research outputs found
Optimal linear filter design for systems with correlation in the measurement matrices and noises: recursive algorithm and applications
This paper addresses the optimal least-squares linear estimation problem for a class of discrete-time stochastic systems with random parameter matrices and correlated additive noises. The system presents the following main features: (1) one-step correlated and cross-correlated random parameter matrices in the observation equation are assumed; (2) the process and measurement noises are one-step autocorrelated and two-step cross-correlated. Using an innovation approach and these correlation assumptions, a recursive algorithm with a simple computational procedure is derived for the optimal linear filter. As a significant application of the proposed results, the optimal recursive filtering problem in multi-sensor systems with missing measurements and random delays can be addressed. Numerical simulation examples are used to demonstrate the feasibility of the proposed filtering algorithm, which is also compared with other filters that have been proposed.Ministerio de Ciencia e Innovación [FPU programme] [grant number MTM2011-24718
Quadratic estimation problem in discrete-time stochastic systems with random parameter matrices
This paper addresses the least-squares quadratic filtering problem in
discrete-time stochastic systems with random parameter matrices in both
the state and measurement equations. Defining a suitable augmented system, this problem is reduced to the least-squares linear filtering problem
of the augmented state based on the augmented observations. Under the
assumption that the moments, up to the fourth-order one, of the original
state and measurement vectors are known, a recursive algorithm for the optimal linear filter of the augmented state is designed, from which the optimal
quadratic filter of the original state is obtained. As a particular case, the
proposed results are applied to multi-sensor systems with state-dependent
multiplicative noise and fading measurements and, finally, a numerical simulation example illustrates the performance of the proposed quadratic filter
in comparison with the linear one and also with other filters in the existing
literature.Ministerio de Economía y Competitividad (Grant No. MTM2014-52291-P and FPU programme
A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis
We present a comprehensive asteroseismic study of the double-mode
high-amplitude delta Scuti star HD 187642 (RV Arietis). The modelling includes
some of the most recent techniques: 1) effects of rotation on both equilibrium
models and adiabatic oscillation spectrum, 2) non-adiabatic study of radial and
non-radial modes, 3) relationship between the fundamental radial mode and the
first overtone in the framework of Petersen diagrams. The analysis reveals that
two of the observed frequencies are very probably identified as the fundamental
and first overtone radial modes. Analysis of the colour index variations,
together with theoretical non-adiabatic calculations, points to models in the
range of [7065,7245] K in effective temperature and of [1190, 1270] Myr in
stellar age. These values were found to be compatible with those obtained using
the three other asteroseismic techniques.Comment: accepted for publication in A&
Quantum Conductance Steps in Solutions of Multiwalled Carbon Nanotubes
We have prepared solutions of multiwalled carbon nanotubes in Aroclor 1254, a
mixture of polychlorinated biphenyls. The solutions are stable at room
temperature. Transport measurements were performed using a scanning--tunneling
probe on a sample prepared by spin--coating of the solution on gold substrates.
Conductance steps were clearly seen. An histogram of a high number of traces
shows maximum peaks at integer values of the conductance quantum , demonstrating ballistic transport at room temperature along the carbon
nanotube over distances longer than .Comment: 4 pages and 2 figure
Topological structural alerts modulations of mammalian cell mutagenicity for halogenated derivatives
Genotoxicity is a key toxicity endpoint for current regulatory requirements regarding new
and existing chemicals. However, genotoxicity testing is time-consuming and costly, and
involves the use of laboratory animals. This has motivated the development of computational
approaches, designed to predict genotoxicity without the need to conduct laboratory
tests. Currently, many existing computational methods, like quantitative structure–activity
relationship (QSAR) models, provide limited information about the possible mechanisms
involved in mutagenicity or predictions based on structural alerts (SAs) do not take
statistical models into account. This paper describes an attempt to address this problem by
using the TOPological Substructural MOlecular Design (TOPS-MODE) approach to
develop and validate improved QSAR models for predicting the mutagenicity of a range of
halogenated derivatives. Our most predictive model has an accuracy of 94.12%, exhibits
excellent cross-validation and external set statistics. A reasonable interpretation of the
model in term of SAs was achieved by means of bond contributions to activity. The results
obtained led to the following conclusions: primary halogenated derivatives are more mutagenic
than secondary ones; and substitution of chlorine by bromine increases mutagenicity
while polyhalogenation decreases activity. The paper demonstrates the potential of the
TOPS-MODE approach in developing QSAR models for identifying structural alerts for
mutagenicity, combining high predictivity with relevant mechanistic interpretation.Ciencias AmbientalesCiencias de la AlimentaciónFarmaciaIngeniería, Industria y ConstrucciónMedicin
Short Communication: The potential of portable near infrared spectroscopy for assuring quality and authenticity in the food chain, using Iberian hams as an example
This communication assesses the use of a portable near infrared (NIR) instrument to measure quantitative (fatty acid profile) properties and qualitative (‘Premium’ and ‘Non-premium’) categories of individual Iberian pork carcasses at the slaughterhouse. Acorn-fed Iberian pigs have more unsaturated fats than pigs fed conventional compound feed. Recent advances in miniaturisation have led to a number of handheld NIR devices being developed, allowing processing decisions to be made earlier, significantly reducing time and costs. The most common methods used for assessing quality and authenticity of Iberian hams are analysis of the fatty acid composition of subcutaneous fat using gas chromatography and DNA analysis. In this study, NIR calibrations for fatty acids and classification as premium or non-premium ham, based on carcass fat measured in situ, were developed using a portable NIR spectrometer. The accuracy of the quantitative equations was evaluated through the standard error of cross validation or standard error of prediction of 0.84 for palmitic acid (C16:0), 0.94 for stearic acid (C18:0), 1.47 for oleic acid (C18:1) and 0.58 for linoleic acid (C18:2). Qualitative calibrations provided acceptable results, with up to 98% of samples (n = 234) correctly classified with probabilities ⩾0.9. Results indicated a portable NIR instrument has the potential to be used to measure quality and authenticity of Iberian pork carcasses
Dielectric susceptibility of the Coulomb-glass
We derive a microscopic expression for the dielectric susceptibility
of a Coulomb glass, which corresponds to the definition used in classical
electrodynamics, the derivative of the polarization with respect to the
electric field. The fluctuation-dissipation theorem tells us that is a
function of the thermal fluctuations of the dipole moment of the system. We
calculate numerically for three-dimensional Coulomb glasses as a
function of temperature and frequency
High spatial resolution optical imaging of the multiple T Tauri system LkH{\alpha} 262/LkH{\alpha} 263
We report high spatial resolution i' band imaging of the multiple T Tauri
system LkH 262/LkH 263 obtained during the first commissioning
period of the Adaptive Optics Lucky Imager (AOLI) at the 4.2 m William Herschel
Telescope, using its Lucky Imaging mode. AOLI images have provided photometry
for each of the two components LkH 263 A and B (0.41 arcsec separation)
and marginal evidence for an unresolved binary or a disc in LkH 262.
The AOLI data combined with previously available and newly obtained optical and
infrared imaging show that the three components of LkH 263 are
co-moving, that there is orbital motion in the AB pair, and, remarkably, that
LkH 262-263 is a common proper motion system with less than 1 mas/yr
relative motion. We argue that this is a likely five-component gravitationally
bounded system. According to BT-settl models the mass of each of the five
components is close to 0.4 M and the age is in the range 1-2 Myr. The
presence of discs in some of the components offers an interesting opportunity
to investigate the formation and evolution of discs in the early stages of
multiple very low-mass systems. In particular, we provide tentative evidence
that the disc in 263C could be coplanar with the orbit of 263AB.Comment: 11 pages, 7 figures, Accepted 2016 May
Risk factors for premature aging of placenta: comparative study of perinatal outcomes between grannum grade III placentas and grannum grade I-II placentas
Introduction: The placenta aging has been related with intrauterine fetal growth, low maternal age, Caucasian, multiparity, hypertensive states and smoking habit. Grannum P. classification is the most used for its assessment. The association between grade III placenta (G3P) and ex-smoking or smokeexposed pregnants has not been studied
Main outcome: To asses if smoking, being an ex-smoker or a passive-smoker is a risk factor for developing grade III placenta, as well as if there is a smoking-free period of time to avoid the effect of smoking over placenta
Material and methods: A retrospective case-control study of single pregnancies followed-up at the Obstetric Ultrasound Unit between January 2013 and January 2014. Placental grading according to Grannum classification was stablished through abdominal approach between 34-36 weeks of gestation and two groups were established: grade III placenta and grade I-II placenta (G1-2P)
Maternal and paternal characteristics, type of delivery and perinatal outcomes were collected
Results: Baseline characteristics were similar between the two groups. In G3P the incidence of hypertensive disease of pregnancy was higher(p=0,0107). The percentage was similar for premature birth, 1st and 5th minute Apgar, type of delivery and cesarean due to risk of loss of fetal wellbeing. A lower neonatal weight was found in G3P, at the same median days at delivery, with a mean difference of 148,156(p=0,008313. Regarding weight percentile, it was found a p35 in G3P and a p47,5 in G1- 2P(p=0,08235)
15% of the total pregnant were smokers. In G3P group it was found a higher frequency of smokers and ex-smokers since 1st trimester of pregnancy (p=0.0001), as well as pregnant non-smokers with an smoking partner(p=0,0001). There was an strong evidence for association between pregnant smokers and smoking partners(p=0,0001). No difference was found regarding to neonatal weight comparing smokers, ex-smokers and ex-smokers since 1st trimester of pregnancy. The length of pregnancy was lower between G3P pregnant smokers compared to G1-2P pregnant smokers, with a mean difference of 8 days (p=0,00091)
Conclusions: There is a strong evidence for association between smoking during pregnancy, quitting smoking at the beginning of the pregnancy or being a passive smoker with development of G3P
Some pregnant smokers don`t develop premature aging of placenta, it could be due to either other parameters or a later aging (data were collected between 34-36 weeks). The association between quitting smoking at the beginning of the pregnancy and not having a smoking partner reduces the risk of developing G3
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