8,736 research outputs found
Time resolved pattern evolution in a large aperture laser
We have measured quasi-instantaneous transverse patterns in a broad aperture
laser. Non-ordered patterns yielding to boundary determined regular structures
in progressive time-integrated recording are observed. The linear analysis and
numerical integration of the full Maxwell-Bloch equations allow us to interpret
the features of the experiment. We show that this system being far from
threshold cannot be fully understood with a perturbative model.Comment: 7 pages, 5 GIF figures . To be published in Phys. Rev. Let
Protein adsorption onto Fe3O4 nanoparticles with opposite surface charge and its impact on cell uptake
Nanoparticles (NPs) engineered for biomedical applications are meant to be in
contact with protein-rich physiological fluids. These proteins are usually
adsorbed onto the NP surface, forming a swaddling layer called protein corona
that influences cell internalization. We present a study on protein adsorption
onto different magnetic NPs (MNPs) when immersed in cell culture medium, and
how these changes affect the cellular uptake. Two colloids with magnetite cores
of 25 nm, same hydrodynamic size and opposite surface charge were in situ
coated with (a) positive polyethyleneimine (PEI-MNPs) and (b) negative
poly(acrylic acid) (PAA-MNPs). After few minutes of incubation in cell culture
medium the wrapping of the MNPs by protein adsorption resulted in a 5-fold size
increase. After 24 h of incubation large MNP-protein aggregates with
hydrodynamic sizes 1500 to 3000 nm (PAA-MNPs and PEI-MNPs respectively) were
observed. Each cluster contained an estimated number of magnetic cores between
450 and 1000, indicating the formation of large aggregates with a "plum
pudding" structure of MNPs embedded into a protein network of negative surface
charge irrespective of the MNP_core charge. We demonstrated that PEI-MNPs are
incorporated in much larger amounts than the PAA-MNPs units. Quantitative
analysis showed that SH-SY5Y cells can incorporate 100 per cent of the added
PEI-MNPs up to about 100 pg per cell, whereas for PAA-MNPs the uptake was less
than 50 percent. The final cellular distribution showed also notable
differences regarding partial attachment to the cell membrane. These results
highlight the need to characterize the final properties of MNPs after protein
adsorption in biological media, and demonstrate the impact of these properties
on the internalization mechanisms in neural cells.Comment: 32 pages, 10 figure
Effective-Hamiltonian parameters for \emph{ab initio} energy-level calculations of SrCl:Yb and CsCaBr:Yb
Calculated energy levels from recent \emph{ab initio} studies of the
electronic structure of SrCl:Yb and CsCaBr:Yb are
fitted with a semi-empirical "crystal-field" Hamiltonian, which acts within the
model space . Parameters are obtained for the
minima of the potential-energy curves for each energy level and also for a
range of anion-cation separations. The parameters are compared with published
results parameters fitted to experimental data and to atomic calculations. The
states with significant character give a good approximation of the
impurity-trapped exciton states that appear in the \emph{ab initio}
calculations.Comment: Minor revisio
Polarization of the WMAP Point Sources
The detection of polarized sources in the WMAP 5-year data is a very
difficult task. The maps are dominated by instrumental noise and only a handful
of sources show up as clear peaks in the Q and U maps. Optimal linear filters
applied at the position of known bright sources detect with a high level of
significance a polarized flux P from many more sources, but estimates of P are
liable to biases. Using a new technique, named the "filtered fusion technique",
we have detected in polarization, with a significance level greater than 99.99%
in at least one WMAP channel, 22 objects, 5 of which, however, do not have a
plausible low radio frequency counterpart and are therefore doubtful. Estimated
polarized fluxes P < 400 mJy at 23 GHz were found to be severely affected by
the Eddington bias. The corresponding polarized flux limit for Planck/LFI at 30
GHz, obtained via realistic simulations, is 300 mJy. We have also obtained
statistical estimates of, or upper limits to the mean polarization degrees of
bright WMAP sources at 23, 33, 41, and 61 GHz, finding that they are of a few
percent.Comment: 10 pages, 6 figures. Accepted for publication in Ap
Analysis of CMB maps with 2D wavelets
We consider the 2D wavelet transform with two scales to study sky maps of
temperature anisotropies in the cosmic microwave background radiation (CMB). We
apply this technique to simulated maps of small sky patches of size 12.8 \times
12.8 square degrees and 1.5' \times 1.5' pixels. The relation to the standard
approach, based on the cl's is established through the introduction of the
scalogram. We consider temperature fluctuations derived from standard, open and
flat-Lambda CDM models. We analyze CMB anisotropies maps plus uncorrelated
Gaussian noise (uniform and non-uniform) at idfferent S/N levels. We explore in
detail the denoising of such maps and compare the results with other techniques
already proposed in the literature. Wavelet methods provide a good
reconstruction of the image and power spectrum. Moreover, they are faster than
previously proposed methods.Comment: latex file 7 pages + 5 postscript files + 1 gif file; accepted for
publication in A&A
Testosterone recovery after androgen deprivation therapy in prostate cancer: building a predictive model
Purpose: To analyze the variability, associated actors, and the design of nomograms for individualized testosterone recovery after cessation of androgen deprivation therapy (ADT). Materials and Methods: A longitudinal study was carried out with 208 patients in the period 2003 to 2019. Castrated and normogonadic testosterone levels were defined as 0.5 and 3.5 ng/mL, respectively. The cumulative incidence curve described the recovery of testosterone. Univariate and multivariate analyzes were performed to predict testosterone recovery with candidate prognostic factors prostate-specific antigen at diagnosis, clinical stage, Gleason score from biopsy, age at cessation of ADT, duration of ADT, primary therapy and use of LHRH (luteinizing hormone-releasing hormone) agonists. Results: The median follow-up duration in the study was 80 months (interquartile range, 49–99 mo). Twenty-five percent and 81% of patients did not recover the castrate and normogonadic levels, respectively. Duration of ADT and age at ADT cessation were significant predictors of testosterone recovery. We built two nomograms for testosterone recovery at 12, 24, 36, and 60 months. The castration recovery model had good calibration. The C-index was 0.677, with area under the receiver operating characteristic curve (AUC-ROC) of 0.736, 0.783, 0.782, and 0.780 at 12, 24, 36, and 60 months, respectively. The normogonadic recovery model overestimated the higher values of probability of recovery. The Cindex was 0.683, with AUC values of 0.812, 0.711, 0.708 and 0.693 at 12, 24, 36, and 60 months, respectively. Conclusions: Depending on the age of the patient and the length of treatment, clinicians may stop ADT and the castrated testosterone level will be maintained or, if the course of treatment has been short, we can estimate if it will return to normogonadic levels
Non-blind catalogue of extragalactic point sources from the Wilkinson Microwave Anisotropy Probe (WMAP) first 3--year survey data
We have used the MHW2 filter to obtain estimates of the flux densities at the
WMAP frequencies of a complete sample of 2491 sources, mostly brighter than 500
mJy at 5 GHz, distributed over the whole sky excluding a strip around the
Galactic equator (b < 5 degrees). After having detected 933 sources above the 3
sigma level in the MHW2 filtered maps - our New Extragalactic WMAP Point Source
(NEWPS_3sigma) Catalogue - we are left with 381 sources above 5 sigma in at
least one WMAP channel, 369 of which constitute our NEWPS_5sigma catalogue. It
is remarkable to note that 98 (i.e. 26%) sources detected above 5 sigma are
`new', they are not present in the WMAP catalogue. Source fluxes have been
corrected for the Eddington bias. Our flux density estimates before such
correction are generally in good agreement with the WMAP ones at 23 GHz. At
higher frequencies WMAP fluxes tend to be slightly higher than ours, probably
because WMAP estimates neglect the deviations of the point spread function from
a Gaussian shape. On the whole, above the estimated completeness limit of 1.1
Jy at 23 GHz we detected 43 sources missed by the blind method adopted by the
WMAP team. On the other hand, our low-frequency selection threshold left out 25
WMAP sources, only 12 of which, however, are 5 sigma detections and only 3 have
fluxes S at 23 GHz > 1.1 Jy. Thus, our approach proved to be competitive with,
and complementary to the WMAP one.Comment: 18 pages, 6 figures, 5 tables. Accepted for publication in ApJ
Eclipsed X-ray flares in binary stars: geometrical constraints on the flare's location and size
The observation of eclipses during X-rays flares taking place in active cool
stars binaries allows us to calculate the position and size of the flares. This
information cannot be derived by analyzing the decay of the flares, a
frequently used approach in the literature that requires the assumption of a
physical model. We make use of the eclipsing light curve to constrain the set
of possible solutions, from the geometrical point of view, in two flares of
Algol, and one flare in VW Cep. We make use of a technique developed with the
system SV Cam (i~90 deg) and generalize it to binary systems with arbitrary
inclination. The method simulates all possible geometrical situations that can
produce the times of the four contacts of the eclipse. As an approximation we
assume that the emitting region has a spherical shape that remains unchanged
during the eclipse. We however show that this is a good approximation for the
problem. The solutions observed indicate that in two of the three cases the
flare cannot be polar (lat<55 deg) and in a third one the flare can be placed
either near the pole or at other latitudes. The emitting regions must have a
small size (0.002-0.5 R_*), but if interpreted as the apex of coronal loops,
their length could actually be up to 3.1 R_* for one of the Algol flares. These
measurements imply a lower limit to the electron density in the emitting region
between log n_e(cm^-3) 10.4 and 14.0, and a magnetic field between 70 and 3500
G. Similar results are found if the emitting region is assumed to be
loop-shaped.Comment: 8 pages (17 in online version), 9 figures (18 in online version).
Figure 12 is a set of animated GIF, available also at
http://laeff.esa.es/users/jsanz/Papers/Eclipses/Videosweb . Accepted for
publication in A&
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