256 research outputs found
Cosmological Parameter Estimation from SN Ia data: a Model-Independent Approach
We perform a model independent reconstruction of the cosmic expansion rate
based on type Ia supernova data. Using the Union 2.1 data set, we show that the
Hubble parameter behaviour allowed by the data without making any hypothesis
about cosmological model or underlying gravity theory is consistent with a flat
LCDM universe having H_0 = 70.43 +- 0.33 and Omega_m=0.297 +- 0.020, weakly
dependent on the choice of initial scatter matrix. This is in closer agreement
with the recently released Planck results (H_0 = 67.3 +- 1.2, Omega_m = 0.314
+- 0.020) than other standard analyses based on type Ia supernova data. We
argue this might be an indication that, in order to tackle subtle deviations
from the standard cosmological model present in type Ia supernova data, it is
mandatory to go beyond parametrized approaches
Current concepts in nanostructured contrast media development for In vivo photoacoustic imaging
Photoacoustic (PA) imaging is indeed one of the most promising bioimaging techniques for theranostics applications in humans, allowing for the visualization of blood vessels and melanomas with high spatial resolution. However, in order to overcome the endogenous contrast arising from interfering endogenous species such as haemoglobin and melanin, specific contrast agents need to be developed, allowing PAI to successfully identify targeted contrast in the range of wavelengths in which interference from the biomatrix is minimized. This has been first performed by small molecule dyes, which, however, suffer from some important limitations such as low hydrophilicity and short circulation times. For this reason, scientific research has recently directed its efforts towards the development of nanostructured contrast agents capable of providing efficient PA contrast at low concentrations with low toxicity and high biocompatibility. The principal nanostructures are based on (1) metal and semiconducting nanoparticles, amongst which variously shaped nano-gold plays the main role, (2) carbon nanomaterials, such as carbon nanotubes and graphene, and (3) conjugated polymer nanoparticles. In this review, the principal characteristics of this class of materials are reported and greater focus is directed towards in vivo studies. A detailed analysis is performed on various physical-chemical parameters that define the PA response of reported contrast agents, like absorption coefficients and photoacoustic efficiencies. By comparing the experimental data, this review provides a comprehensive tool for the evaluation of new nanostructured contrast agents for PA imaging
Searching for galaxy clusters in the Kilo-Degree Survey
In this paper, we present the tools used to search for galaxy clusters in the
Kilo Degree Survey (KiDS), and our first results. The cluster detection is
based on an implementation of the optimal filtering technique that enables us
to identify clusters as over-densities in the distribution of galaxies using
their positions on the sky, magnitudes, and photometric redshifts. The
contamination and completeness of the cluster catalog are derived using mock
catalogs based on the data themselves. The optimal signal to noise threshold
for the cluster detection is obtained by randomizing the galaxy positions and
selecting the value that produces a contamination of less than 20%. Starting
from a subset of clusters detected with high significance at low redshifts, we
shift them to higher redshifts to estimate the completeness as a function of
redshift: the average completeness is ~ 85%. An estimate of the mass of the
clusters is derived using the richness as a proxy. We obtained 1858 candidate
clusters with redshift 0 < z_c < 0.7 and mass 13.5 < log(M500/Msun) < 15 in an
area of 114 sq. degrees (KiDS ESO-DR2). A comparison with publicly available
Sloan Digital Sky Survey (SDSS)-based cluster catalogs shows that we match more
than 50% of the clusters (77% in the case of the redMaPPer catalog). We also
cross-matched our cluster catalog with the Abell clusters, and clusters found
by XMM and in the Planck-SZ survey; however, only a small number of them lie
inside the KiDS area currently available.Comment: 13 pages, 15 figures. Accepted for publication on Astronomy &
Astrophysic
Iridium-Functionalized Cellulose Microcrystals as a Novel Luminescent Biomaterial for Biocomposites
Microcrystalline cellulose (MCC) is an emerging material with outstanding properties in many scientific and industrial fields, in particular as an additive in composite materials. Its surface modification allows for the fine-tuning of its properties and the exploitation of these materials in a plethora of applications. In this paper, we present the covalent linkage of a luminescent Ir-complex onto the surface of MCC, representing the first incorporation of an organometallic luminescent probe in this biomaterial. This goal has been achieved with an easy and sustainable procedure, which employs a Bronsted-acid ionic liquid as a catalyst for the esterification reaction of -OH cellulose surface groups. The obtained luminescent cellulose microcrystals display high and stable emissions with the incorporation of only a small amount of iridium (III). Incorporation of MCC-Ir in dry and wet matrices, such as films and gels, has been also demonstrated, showing the maintenance of the luminescent properties even in possible final manufacturers
Synthesis and functionalization of casein nanoparticles with aptamers for triple-negative breast cancer targeting
This work shows the synthesis of a drug delivery system made of casein nanoparticles able to host hydrophobic molecules and be functionalized with aptamers targeting the epidermal growth factor receptor. In vitro cell viability and uptake analyses, performed on triple-negative breast cancer cells, confirmed the safety profile and the target selectivity
A novel theranostic gold nanorods- and adriamycin-loaded micelle for EpCA M targeting, laser ablation, and photoacoustic imaging of cancer stem cells in hepatocellular carcinoma
Introduction and purpose: Cancer stem cells (CSCs) present a higher capacity to evade being killed by cancer agents and developing chemoresistance, thus leading to failure of conventional anticancer therapeutics. Nanomaterials specifically designed for targeting and treating not only tumor cells, but also CSCs, may encompass therapeutic and diagnostic tools, thus successfully eradicating the tumor. Materials and methods: Polymeric micelles simultaneously loaded with gold nanorods (GNRs) and Adriamycin were prepared and used as a novel therapeutic and diagnostic weapon. Epithelial cell adhesion molecule (EpCAM) is an important CSC surface marker and has been exploited in this work as an active targeting agent. Photoacoustic imaging was applied for GNR individuation and tissue recognition. Results: The nanosystem was demonstrated to be able to elicit effective targeting of cancer cells and cause their killing, in particular under laser ablation. Moreover, ex vivo photoacoustic imaging is able to clearly identify tumor regions thanks to GNR\u2019s contrast. Conclusion: The nanosystem can be considered a powerful and promising theranostic weapon for hepatocellular carcinoma treatment
Optimized detection of shear peaks in weak lensing maps
We present a new method to extract cosmological constraints from weak lensing
(WL) peak counts, which we denote as `the hierarchical algorithm'. The idea of
this method is to combine information from WL maps sequentially smoothed with a
series of filters of different size, from the largest down to the smallest,
thus increasing the cosmological sensitivity of the resulting peak function. We
compare the cosmological constraints resulting from the peak abundance measured
in this way and the abundance obtained by using a filter of fixed size, which
is the standard practice in WL peak studies. For this purpose, we employ a
large set of WL maps generated by ray-tracing through N-body simulations, and
the Fisher matrix formalism. We find that if low-S/N peaks are included in the
analysis (S/N ~ 3), the hierarchical method yields constraints significantly
better than the single-sized filtering. For a large future survey such as
Euclid or LSST, combined with information from a CMB experiment like Planck,
the results for the hierarchical (single-sized) method are: \Delta n=0.0039
(0.004); \Delta \Omega m=0.002 (0.0045); \Delta \sigma 8=0.003 (0.006); \Delta
w=0.019 (0.0525). This forecast is conservative, as we assume no knowledge of
the redshifts of the lenses, and consider a single broad bin for the redshifts
of the sources. If only peaks with S/N >= 6 are considered, then there is
little difference between the results of the two methods. We also examine the
statistical properties of the hierarchical peak function: Its covariance matrix
has off-diagonal terms for bins with S/N <= 6 and aperture mass of M < 3 x
1e+14 Ms/h, the higher bins being largely uncorrelated and therefore well
described by a Poisson distribution.Comment: 17 pages, 13 figures, final version published in MNRA
Probabilistic physically-based cloud screening of satellite infra-red imagery for operational sea surface temperature retrieval
We propose and demonstrate a fully probabilistic (Bayesian) approach to the detection of cloudy pixels in thermal infrared (TIR) imagery observed from satellite over oceans. Using this approach, we show how to exploit the prior information and the fast forward modelling capability that are typically available in the operational context to obtain improved cloud detection. The probability of clear sky for each pixel is estimated by applying Bayes' theorem, and we describe how to apply Bayes' theorem to this problem in general terms. Joint probability density functions (PDFs) of the observations in the TIR channels are needed; the PDFs for clear conditions are calculable from forward modelling and those for cloudy conditions have been obtained empirically. Using analysis fields from numerical weather prediction as prior information, we apply the approach to imagery representative of imagers on polar-orbiting platforms. In comparison with the established cloud-screening scheme, the new technique decreases both the rate of failure to detect cloud contamination and the false-alarm rate by one quarter. The rate of occurrence of cloud-screening-related errors of >1 K in area-averaged SSTs is reduced by 83%. Copyright © 2005 Royal Meteorological Society
Snail regulates BMP and TGFβ pathways to control the differentiation status of glioma-initiating cells
Glioblastoma multiforme is a brain malignancy characterized by high heterogeneity, invasiveness, and resistance to current therapies, attributes related to the occurrence of glioma stem cells (GSCs). Transforming growth factor β (TGFβ) promotes self-renewal and bone morphogenetic protein (BMP) induces differentiation of GSCs. BMP7 induces the transcription factor Snail to promote astrocytic differentiation in GSCs and suppress tumor growth in vivo. We demonstrate that Snail represses stemness in GSCs. Snail interacts with SMAD signaling mediators, generates a positive feedback loop of BMP signaling and transcriptionally represses the TGFB1 gene, decreasing TGFβ1 signaling activity. Exogenous TGFβ1 counteracts Snail function in vitro, and in vivo promotes proliferation and re-expression of Nestin, confirming the importance of TGFB1 gene repression by Snail. In conclusion, novel insight highlights mechanisms whereby Snail differentially regulates the activity of the opposing BMP and TGFβ pathways, thus promoting an astrocytic fate switch and repressing stemness in GSCs
AMICO galaxy clusters in KiDS-DR3: cosmological constraints from counts and stacked weak-lensing
We present a cosmological analysis of abundances and stacked weak-lensing
profiles of galaxy clusters, exploiting the AMICO KiDS-DR3 catalogue. The
sample consists of 3652 galaxy clusters with intrinsic richness
, over an effective area of 377 deg, in the redshift range
. We quantified the purity and completeness of the sample
through simulations. The statistical analysis has been performed by
simultaneously modelling the comoving number density of galaxy clusters and the
scaling relation between the intrinsic richnesses and the cluster masses,
assessed through a stacked weak-lensing profile modelling. The fluctuations of
the matter background density, caused by super-survey modes, have been taken
into account in the likelihood. Assuming a flat CDM model, we
constrained , , , and the parameters of the mass-richness scaling relation. We
obtained ,
, . The constraint on
is consistent within 1 with the results from WMAP and Planck.
Furthermore, we got constraints on the cluster mass scaling relation in
agreement with those obtained from a previous weak-lensing only analysis.Comment: 12 pages, 7 figures, 2 tables. Accepted by A&
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