1,684 research outputs found
PCA detection and denoising of Zeeman signatures in stellar polarised spectra
Our main objective is to develop a denoising strategy to increase the signal
to noise ratio of individual spectral lines of stellar spectropolarimetric
observations.
We use a multivariate statistics technique called Principal Component
Analysis. The cross-product matrix of the observations is diagonalized to
obtain the eigenvectors in which the original observations can be developed.
This basis is such that the first eigenvectors contain the greatest variance.
Assuming that the noise is uncorrelated a denoising is possible by
reconstructing the data with a truncated basis. We propose a method to identify
the number of eigenvectors for an efficient noise filtering.
Numerical simulations are used to demonstrate that an important increase of
the signal to noise ratio per spectral line is possible using PCA denoising
techniques. It can be also applied for detection of magnetic fields in stellar
atmospheres. We analyze the relation between PCA and commonly used well-known
techniques like line addition and least-squares deconvolution. Moreover, PCA is
very robust and easy to compute.Comment: accepted to be published in A&
A Mathematical Assessment of the Isolation Tree Method for Outliers Detection in Big Data
In this paper, the mathematical analysis of the Isolation Random Forest
Method (IRF Method) for anomaly detection is presented. We show that the IRF
space can be endowed with a probability induced by the Isolation Tree algorithm
(iTree). In this setting, the convergence of the IRF method is proved using the
Law of Large Numbers. A couple of counterexamples are presented to show that
the original method is inconclusive and no quality certificate can be given,
when using it as a means to detect anomalies. Hence, an alternative version of
IRF is proposed, whose mathematical foundation, as well as its limitations, are
fully justified. Finally, numerical experiments are presented to compare the
performance of the classic IRF with the proposed one.Comment: 21 pages, 14 figures, 3 table
Primer registro de Achimenes admirabilis (Gesneriaceae) para la flora de Tabasco, México
ResumenSe da a conocer un nuevo registro de Achimenes admirabilis para México. Esta especie solo se había registrado en los estados de Oaxaca y Veracruz. Colectas recientes en el área municipal de Tenosique, extienden el intervalo de distribución de la especie al estado de Tabasco.AbstractA new record of Achimenes admirabilis is reported for Mexico. This species had only been reported in the states of Oaxaca and Veracruz. Recent collections in the municipality of Tenosique, extend its range to the state of Tabasco
Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection, photometric and spectroscopic observations
We present the study of nineteen low X-ray luminosity galaxy clusters (L 0.5--45 erg s), selected from the ROSAT
Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin
et al. 1998) and the revised version of Mullis et al. (2003) in the redshift
range of 0.16 to 0.7. This is the introductory paper of a series presenting the
sample selection, photometric and spectroscopic observations and data
reduction. Photometric data in different passbands were taken for eight galaxy
clusters at Las Campanas Observatory; three clusters at Cerro Tololo
Interamerican Observatory; and eight clusters at the Gemini Observatory.
Spectroscopic data were collected for only four galaxy clusters using Gemini
telescopes. With the photometry, the galaxies were defined based on the
star-galaxy separation taking into account photometric parameters. For each
galaxy cluster, the catalogues contain the PSF and aperture magnitudes of
galaxies within the 90\% completeness limit. They are used together with
structural parameters to study the galaxy morphology and to estimate
photometric redshifts. With the spectroscopy, the derived galaxy velocity
dispersion of our clusters ranged from 507 km~s for [VMF98]022 to 775
km~s for [VMF98]097 with signs of substructure. Cluster membership has
been extensively discussed taking into account spectroscopic and photometric
redshift estimates. In this sense, members are the galaxies within a projected
radius of 0.75 Mpc from the X-ray mission peak and with cluster centric
velocities smaller than the cluster velocity dispersion or 6000 km~s,
respectively. These results will be used in forthcoming papers to study, among
the main topics, the red cluster sequence, blue cloud and green populations;
the galaxy luminosity function and cluster dynamics.Comment: 13 pages, 6 tables, 9 figures. Uses emulateapj. Accepted for
publication in The Astronomical Journal. Some formatting errors fixe
Differences reported in the lifespan and aging of male Wistar rats maintained on diets containing fat with different fatty acid profiles (virgin olive, sunflower or fish oils) are not reflected by histopathological lesions found at death in central nervous and endocrine systems
The present study was designed to examine if dietary fat sources that have shown differences in lifespan and if
some aging-related aspects can modulate the range of histopathologic changes in central nervous and endocrine
systems that occur during the lifespan of Wistar rats. Moreover, it was attempted to gain insight into the relationship
between longevity and the development of the different pathological changes, as well as possible
interaction with diet. In order to achieve this, male Wistar rats were randomly assigned to three experimental
groups fed semisynthetic and isoenergetic diets from weaning until death with different dietary fat sources,
namely virgin olive, sunflower, or fish oil. An individual follow-up until death of each animal was performed.
Incidence, severity, and burden of specific or group (i.e., neoplastic or non-neoplastic proliferative and nonproliferative)
of lesions was calculated along with individual’s disease and individual organ lesion burden.
Most of the histopathological lesions found have been described in previous studies. Neoplasms, and in particular
pituitary adenomas followed by brain tumors, were the most prevalent lesions found in the rats and the main
cause of death involving both systems. Incidence of brain lesions was associated with age-at-death. Assayed
dietary fats did not present differential effects on pathological changes occurring in endocrine and central
nervous systems throughout rat lifespan.Spanish Government AGL2008-01057Government of Andalusia AGR83
3-Phase Rectifier System with very demanding dynamic load
This paper present a distributed power architecture for aerospace application with very restrictive specifications. Additionally, the rectifier switching frequency has to be synchronized with an external frequency clock to minimize the interference of the converter harmonics with the load. In order to protect the 3 phase generator against high load steps, an intermediate bus (based in a high capacitance) to provide energy to the loads during the high load steps is included. Prototypes of the rectifier and EMI filter are built and the energy control is validated
Modulation of oxidative stress and TNFα secretion by peritoneal macrophages of arthritic rats fed with a flavonoid-enriched diet
Does native Trypanosoma cruzi calreticulin mediate growth inhibition of a mammary tumor during infection?
Indexación: Web of Science.Background: For several decades now an antagonism between Trypanosoma cruzi infection and tumor development has been detected. The molecular basis of this phenomenon remained basically unknown until our proposal that T. cruzi Calreticulin (TcCRT), an endoplasmic reticulum-resident chaperone, translocated-externalized by the parasite, may mediate at least an important part of this effect. Thus, recombinant TcCRT (rTcCRT) has important in vivo antiangiogenic and antitumor activities. However, the relevant question whether the in vivo antitumor effect of T. cruzi infection is indeed mediated by the native chaperone (nTcCRT), remains open. Herein, by using specific modified anti-rTcCRT antibodies (Abs), we have neutralized the antitumor activity of T. cruzi infection and extracts thereof, thus identifying nTcCRT as a valid mediator of this effect.
Methods: Polyclonal anti-rTcCRT F(ab')(2) Ab fragments were used to reverse the capacity of rTcCRT to inhibit EAhy926 endothelial cell (EC) proliferation, as detected by BrdU uptake. Using these F(ab')(2) fragments, we also challenged the capacity of nTcCRT, during T. cruzi infection, to inhibit the growth of an aggressive mammary adenocarcinoma cell line (TA3-MTXR) in mice. Moreover, we determined the capacity of anti-rTcCRT Abs to reverse the antitumor effect of an epimastigote extract (EE). Finally, the effects of these treatments on tumor histology were evaluated.
Results: The rTcCRT capacity to inhibit ECs proliferation was reversed by anti-rTcCRT F(ab')(2) Ab fragments, thus defining them as valid probes to interfere in vivo with this important TcCRT function. Consequently, during infection, these Ab fragments also reversed the in vivo experimental mammary tumor growth. Moreover, anti-rTcCRT Abs also neutralized the antitumor effect of an EE, again identifying the chaperone protein as an important mediator of this anti mammary tumor effect. Finally, as determined by conventional histological parameters, in infected animals and in those treated with EE, less invasive tumors were observed while, as expected, treatment with F(ab')(2) Ab fragments increased malignancy.
Conclusion: We have identified translocated/externalized nTcCRT as responsible for at least an important part of the anti mammary tumor effect of the chaperone observed during experimental infections with T. cruzi.http://bmccancer.biomedcentral.com/articles/10.1186/s12885-016-2764-
Effects of a cocoa diet on an intestinal inflammation model in rats
Cocoa is a rich source of fiber and flavonoids with recognized antioxidant and anti-inflammatory potential. The aim of this study was to evaluate the effects of a cocoa-enriched diet on rats with dextran sulphate sodium (DSS)-induced colitis. Wistar rats were fed with either a 5% cocoa diet or standard diet. Colon inflammation was induced by DSS in the drinking water: 5% for 6 days and 2% over the following 9 days. Colitis was assessed by body weight loss, stool consistency and blood presence in stools. A group of animals fed standard diet was treated with quercitrin (1 mg/kg) after colitis establishment. After 2 weeks of DSS treatment, the colon oxidative and inflammatory status and lymphocyte composition from blood and mesenteric lymph nodes (MLN) were assessed. The cocoa-fed group did not exhibit amelioration of clinical colitis but displayed higher antioxidant activity than the colitic reference group by the restoration of colon glutathione content and prevention of lipid peroxidation. The cocoa diet showed anti-inflammatory potential because it down-regulated serum TNF-alpha, colon iNOS activity and decreased colon cell infiltration. Lymphocyte composition in MLN was not modified by drinking DSS, but there was an increase in the proportion of NK and regulatory T cells in the blood. These changes were not modified by cocoa. In conclusion, cocoa intake may help to inhibit the negative oxidative effects consequent to colitis, although this action is not enough to abrogate the intestinal inflammation significantly
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