ABSTRACT
Laser Guide Star Adaptive Optics (LGS-AO) is becoming routine in several astronomical observatories. The use of powerful lasers generates sensible Raman emissions on the uplink laser beam ...path, plus secondary Rayleigh scattering from atmospheric molecules and Mie scattering from aerosols. This paper reports the results of a campaign done with the 10.4m Gran Telescopio CANARIAS (GTC); this campaign was undertaken to assess the spectral and photometric contamination coming from a 589 nm laser uplink beam scattering and Raman emission induced on the GTC spectro-imager OSIRIS by laser launched ∼1 km off-axis. The photometric contamination is due to primary and secondary scattering of the uplink photons, as well by the Raman inelastic scattering. We have propagated the laser beam creating a mesospheric LGS, then pointed and focused the GTC telescope towards the uplink laser beam, at different heights and up to the LGS, taking into account the observing geometry. In our observations, the Raman emissions for O2 and N2 vibrational lines are visible at 20 km, weakening with altitude and becoming undetectable above 30 km. The scattering of the focused uplink beam is detectable at less than ±0.2 arcmin from the centre of the beam, while for the focused LGS the scattering is narrower, being detectable at less than ±0.1 arcmin around the plume. Recommendations for Laser Traffic Control Systems are given accordingly.
ABSTRACT
Spectral hole burning reduces sodium laser guide star efficiency. Due to photon recoil, atoms that are initially resonant with the single-frequency laser get Doppler shifted out of ...resonance, which reduces the return flux. Frequency-chirped (also known as frequency-swept) continuous-wave lasers have the potential to mitigate the effect of spectral hole burning and even increase the laser guide star efficiency beyond the theoretical limit of a single-frequency laser. We investigate the return flux of frequency-chirped laser guide stars and its dependence on environmental and chirping parameters. On-sky measurements of a frequency-chirped, single-frequency laser guide star are performed at the Roque de los Muchachos Observatory on La Palma. A fast photon-counting receiver system is employed to resolve the return-flux response during laser frequency sweeps gaining insights into the population dynamics of the sodium layer. At a launched laser power of 16.5 W, we find a maximum gain in return flux of 22 per cent compared to a fixed-frequency laser at a chirping amplitude of the order of 150 MHz and a chirping rate of 0.8 MHz µs−1. Time-resolved measurements during the chirping period confirm our understanding of the population dynamics in the sodium layer. These are the first measurements of return-flux enhancement for laser guide stars excited by a single-frequency-chirped continuous-wave laser. For higher laser powers, the effectiveness of chirping is expected to increase, which could be highly beneficial for telescopes equipped with high-power laser guide star adaptive optics systems.
Aims.We have analyzed the contrast of facular features identified in a large dataset of PSPT full-disk photometric images and SoHO/MDI magnetograms, obtained from 1998 to 2005. The aim of this work ...is to contribute to the improvement of semi-empirical atmospheric models and of irradiance studies and to understand the reasons for the controversial results of facular contrast already presented in the literature. Methods.We used different identification methods to analyze their effects upon the results obtained. We also analyzed the effects of the limited information content in the analyzed images. Results.We show that selection effects associated with the identification method may produce significant differences in the results. The facular contrast is not only a function of both selection methods and the heliocentric angle, but also of feature size, activity level, and content of the analyzed images. Comparisons of the results obtained with computations of the most recent semi-empirical atmospheric models of facular features show that these models reproduce limb-angle corrected contrast measurements with an offset up to ≈1% from the disk center to μ = 0.3.
Context. Mechanisms responsible for active-region formation, evolution, and decay have been investigated by many authors and several common features have been identified. In particular, a key element ...in the dispersal of the magnetic field seems to be the presence of magnetic elements, called moving magnetic features (MMFs). Aims. We analyze the short-lived sunspot group NOAA 10977, which appeared on the solar disk between 2 and 8 December 2007, to study the details of its emergence and decay phases. Methods. We performed a multi wavelength analysis of the region using images at visible (G band and Hα) and near-IR ($\ion{Ca}{ii}$) wavelengths acquired by both the IBIS instrument and SOT/HINODE, EUV images (17.1 nm) acquired by TRACE, and MDI and SOT magnetograms. Results. The observed region exhibits some peculiarities. During the emergence phase the formation of the f-pore was initially observed, while the p-polarity later formed a naked spot, i.e., a sunspot without a penumbra. We measured a moat flow around this spot, and observed some MMFs streaming out from it during the decay phase. The characteristics of these MMFs allowed us to classify them as type I (U-shaped) MMFs. They were also cospatial with sites of increased brightness both in the photosphere and the chromosphere. Conclusions. The presence of bipolar MMFs in a naked spot indicates that current interpretation of bipolar MMFs, as extensions of the penumbral filaments beyond the sunspot outer boundaries, should be revised, to take into account this observational evidence. We believe that our results provide new insights into improving models of sunspot evolution.
Objective
TROP‐2 (human trophoblast cell surface marker) is a gene‐related protein expressed in trophoblastic cells, which is also present in a variety of epithelial cancers and whose overexpression ...has been found to correlate with a poor prognosis. We analysed the possibility of using the expression of TROP‐2 to detect papillary thyroid carcinoma (PTC) on cytological and histological samples, and compared it with Hector Battifora mesothelial antigen‐1 (HBME‐1).
Methods
From 127 patients, 127 fine needle aspirates (FNAs), in which HBME‐1 was detected by immunocytochemistry (ICC), were re‐classified according to the Bethesda system for reporting thyroid cytopathology (TBSRTC): 20% were benign, 56% were atypical cells/follicular lesion of undetermined significance (AUS/FLUS), 4% were follicular neoplasm/suspicious for a follicular neoplasm, 5% were suspicious for malignancy and 16% were malignant. Sufficient material to test for TROP‐2 was available in 64 FNAs, 22 of which had a histological control. Including six additional cases in which the FNAs were not available, immunohistochemistry (IHC) was carried out with both markers on 94 cases.
Results
Among 88 FNAs with histological control, the sensitivity of HBME‐1 to predict PTC was 87.5% (28/32) and the specificity was 86% (48/56), whereas, in 22 FNAs, TROP‐2 sensitivity was 100% (13/13) and specificity was 89% (8/9). In 94 histological specimens in which IHC was carried out with both markers, the sensitivity and specificity were 82% and 86%, respectively, for HBME‐1 and 87% and 89%, respectively, for TROP‐2. The difference between the markers was not significant. Concordance between IHC and ICC was 76% for HBME‐1 and 91% for TROP‐2.
Conclusion
TROP‐2 can be used as well as HBME‐1 in thyroid cytology to detect PTC. Positivity for either or both markers could help to stratify the risk of malignancy in indeterminate FNAs. Larger studies are need to analyse its role in the behaviour of PTC and its variants.
Context. The increasing interest in the recovery of historic data and the availability of new hardware resources is leading to projects to digitize photographic archives of astronomical observations. ...In addition to preservation, solar archives are digitized because the observations stored in such archives have the potential of providing unique information about solar magnetism, which can improve knowledge about long-term solar changes. Aims. The solar tower of the Arcetri Astrophysical Observatory produced synoptic observations of the solar atmosphere from 1926 to 1974. The photographic archive contains about 13 000 plates of full-disk Ca II K and Hα spectroheliograms acquired during about 5000 observing days. The program for the digitization and distribution of the images of this archive was carried out at the Rome Astronomical Observatory and is now complete. Methods. Nearly 13 000 plates were scanned with a commercial device and stored on DVD, as well as in a database accessible online. Image processing was developed for the reduction of the data and their photographic calibration. Results. The obtained digital archive provides the astronomical community with the Arcetri historical solar observations and with measurements of solar features identified in such observations. As an example, we show some preliminary results concerning the temporal variability of facular regions identified in the time-series of Ca II K observations. Conclusions. Existing programs studying solar activity and variability, as well as new scientific projects, will benefit from the Arcetri digital archive, since it extends the temporal baseline of digital full-disk solar observations, and it provides data for the inter-calibration of results obtained from measurements performed in similar observations.
Administration of carbapenems to β-lactam-allergic patients has always been considered potentially harmful because of a 47.4% rate of cross-reactivity to imipenem reported in a single study. ...Nevertheless, recent studies have shown that the rate of cross-reactivity of imipenem and meropenem with penicillins is lower than 1%. The aim of this study was to evaluate the possibility of using ertapenem in patients with an established IgE-mediated β-lactam allergy.
We studied all participants who came to our allergy unit and had a clinical history of immediate hypersensitivity reactions to β-lactams. The inclusion criteria were a positive skin test result to at least 1 β-lactam molecule and/or positive specific IgE (when available). All participants underwent immediate-type skin tests with several β-lactam molecules including ertapenem. Challenges with intravenous ertapenem were performed on 2 different days in patients with negative skin test results.
We examined 49 patients with a clinical history of immediate reactions to β-lactams. All the patients had positive skin tests and/or positive specific IgE to at least 1 β-lactam reagent and negative carbapenem skin tests. Thirty-six patients agreed to undergo the challenges and 35 tolerated the full dose of ertapenem.
The practice of avoiding carbapenems in patients with β-lactam allergy should be abandoned considering the very low rate of cross-reactivity. β-Lactam-allergic patients who need ertapenem therapy should undergo skin tests and, if negative, a graded challenge to assess tolerability.
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