On recent SFR calibrations and the constant SFR approximation

Star Formation Rate (SFR) inferences are based in the so-called constant SFR approximation, where synthesis models are require to provide a calibration; we aims to study the key points of such approximation to produce accurate SFR inferences. We use the intrinsic algebra used in synthesis models, and we explore how SFR can be inferred from the integrated light without any assumption about the underling Star Formation history (SFH). We show that the constant SFR approximation is actually a simplified expression of more deeper characteristics of synthesis models: It is a characterization of the evolution of single stellar populations (SSPs), acting the SSPs as sensitivity curve over different measures of the SFH can be obtained. As results, we find that (1) the best age to calibrate SFR indices is the age of the observed system (i.e. about 13Gyr for z=0 systems); (2) constant SFR and steady-state luminosities are not requirements to calibrate the SFR; (3) it is not possible to define a SFR single time scale over which the recent SFH is averaged, and we suggest to use typical SFR indices (ionizing flux, UV fluxes) together with no typical ones (optical/IR fluxes) to correct the SFR from the contribution of the old component of the SFH, we show how to use galaxy colors to quote age ranges where the recent component of the SFH is stronger/softer than the older component. Particular values of SFR calibrations are (almost) not affect by this work, but the meaning of what is obtained by SFR inferences does. In our framework, results as the correlation of SFR time scales with galaxy colors, or the sensitivity of different SFR indices to sort and long scale variations in the SFH, fit naturally. In addition, the present framework provides a theoretical guide-line to optimize the available information from data/numerical experiments to improve the accuracy of SFR inferences.Comment: A&A accepted, 13 pages, 4 Figure

Performance Comparison in the "Follicular Neoplasm" Category Between the American, British, Italian, and Japanese Systems for Reporting Thyroid Cytopathology

It is now almost ten years that the United Stated of America, England, Italy and Japan had their own reporting system to classify thyroid lesions. Important confusion and uncertainties dominated the "follicular-patterned lesions", a category also known as the "gray zone". Every cytopathologist was using a personal terminology to describe and call lesions made up of a variable admixture of macro- and microfollicular structures. These personal views varied considerably between cytopathologists and generated a great deal of confusion among patients (the cytological report being almost incomprehensible to them), clinicians and even within the same cytopathology community. With the advent of national reporting systems, things changed in a better way and standardized reporting systems became the standard of practice in thyroid cytology. The outcome of the widespread use of standardized diagnostic categories was the reduction of descriptive diagnoses and the improved communication between pathologists, clinicians and patients. In this article we review the major reporting systems, analyze their similarities and differences in the "indeterminate" or "follicular-patterned" diagnostic categories, and when possible, try to assess their performance

Density waves and star formation in grand design spirals

HII regions in the arms of spiral galaxies are indicators of recent star-forming processes. They may have been caused by the passage of the density wave or simply created by other means near the arms. The study of these regions may give us clues to clarifying the controversy over the existence of a triggering scenario, as proposed in the density wave theory. Using H$\alpha$ direct imaging, we characterize the HII regions from a sample of three grand design galaxies: NGC5457, NGC628 and NGC6946. Broad band images in R and I were used to determine the position of the arms. The HII regions found to be associated with arms were selected for the study. The age and the star formation rate of these HII regions was obtained using measures on the H$\alpha$ line. The distance between the current position of the selected HII regions and the position they would have if they had been created in the centre of the arm is calculated. A parameter, T, which measures whether a region was created in the arm or in the disc, is defined. With the help of the T parameter we determine that the majority of regions were formed some time after the passage of the density wave, with the regions located `behind the arm' (in the direction of the rotation of the galaxy) the zone they should have occupied had they been formed in the centre of the arm. The presence of the large number of regions created after the passage of the arm may be explained by the effect of the density wave, which helps to create the star-forming regions after its passage. There is clear evidence of triggering for NGC5457 and a co-rotation radius is proposed. A more modest triggering seems to exist for NGC628 and non significant evidence of triggering are found for NGC6946.Comment: 10 pages, 20 figures, accepted for publication in A&

Study of star-forming galaxies in SDSS up to redshift 0.4: I. Metallicity evolution

The chemical composition of the gas in galaxies versus cosmic time provides a very important tool for understanding galaxy evolution. Although there are many studies at high redshift, they are rather scarce at lower redshifts. However, low redshift studies can provide important clues about the evolution of galaxies, furnishing the required link between local and high redshift universe. In this work we focus on the metallicity of the gas of star-forming galaxies at low redshift, looking for signs of chemical evolution. To analyze the metallicity contents star-forming galaxies of similar luminosities and masses at different redshifts. With this purpose, we present a study of the metallicity of relatively massive (log(M_star/M_sun)>10.5) star forming galaxies from SDSS--DR5 (Sloan Digital Sky Survey--Data Release 5), using different redshift intervals from 0.04 to 0.4. We used data processed with the STARLIGHT spectral synthesis code, correcting the fluxes for dust extinction, estimating metallicities using the R_23 method, and segregating the samples with respect to the value of the [NII]6583/[OII]3727 line ratio in order to break the R_23 degeneracy selecting the upper branch. We analyze the luminosity and mass-metallicity relations, and the effect of the Sloan fiber diameter looking for possible biases. By dividing our redshift samples in intervals of similar magnitude and comparing them, significant signs of metallicity evolution are found. Metallicity correlates inversely with redshift: from redshift 0 to 0.4 a decrement of ~0.1 dex in 12+log(O/H) is found.Comment: 11 pages, 9 figures, Accepted for publication in A&

Hazardous cross-reaction in a thyroid fine needle aspiration.

Thyroid fine-needle aspiration cytology (FNAC) is one of the most performed medical procedures worldwide. <sup>1</sup> It is used as a diagnostic test to separate benign thyroid nodules (colloidal and hyperplastic nodules) from thyroid malignancies, either primary (papillary thyroid carcinoma (PTC), medullary thyroid carcinoma (MTC), poorly differentiated thyroid carcinoma (PDTC), anaplastic thyroid carcinoma (ATC)) or less often metastatic. <sup>2</sup> The negative and positive predictive values (NPV and PPV) of this procedure in The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) are respectively 97% and 98% for the benign and malignant categories. This article is protected by copyright. All rights reserved

Induction of heat shock protein expression in cervical epithelial cells by human semen.

OBJECTIVE: The 70kD heat shock protein (Hsp70), induced when cells are subjected to environmental stress, prevents the denaturation and incorrect folding of polypeptides and may expedite replication and transmission of DNA and RNA viruses. We analyzed whether messenger RNA (mRNA) for Hsp70 was expressed following exposure of a cultured human cervical cell line (HeLa cells) to human semen or in cervical cells from sexually active women. STUDY DESIGN: HeLa cells were co-cultured with a 1:50 dilution of semen from four men or with purified spermatozoa or cell-free seminal fluid. Endocervical swabs were acquired at mid-cycle from 53 women. Heat shock protein 70 mRNA was detected by a reverse transcriptase-polymerase chain reaction utilizing specific primer pairs and analysis on agarose gels. In cervical cells Hsp70 mRNA was measured identically followed by hybridization with an Hsp70-specific internal probe and detection by enzyme-linked immunosorbent assay (ELISA). Cervical immunoglobulin A (IgA) antibodies to the human Hsp70 were determined by ELISA. RESULTS: HeLa cell-semen co-culture resulted in the induction of Hsp70 mRNA. In addition, cell-free seminal plasma and motile sperm incubated individually with HeLa cells also induced this mRNA. Heat shock protein 70 mRNA was detected in 28 (52.8%) of 53 endocervical samples obtained from women at various time points following intercourse. The percentage of samples expressing this mRNA was 37.5% at less than 10 hours, 64.3% at 10 hours, 70% at 11 hours, and between 36% and 50% at later times after semen exposure. The detection of cervical IgA antibodies to the Hsp70 was highly associated with Hsp70 gene transcription. CONCLUSION: Human semen induces transcription of Hsp70 in cervical epithelial cells

OTELO survey: optimal emission-line flux determination with OSIRIS/GTC

Emission-line galaxies are important targets for understanding the chemical evolution of galaxies in the universe. Deep, narrow-band imaging surveys allow to detect and study the flux and the equivalent widths (EW) of the emission line studied. The present work has been developed within the context of the OTELO project, an emission line survey using the Tunable Filters (TF) of OSIRIS, the first generation instrument on the GTC 10.4m telescope located in La Palma, Spain, that will observe through selected atmospheric windows relatively free of sky emission lines. With a total survey area of 0.1 square degrees distributed in different fields, reaching a 5 \sigma depth of 10^-18 erg/cm^2/s and detecting objects of EW < 0.3 A, OTELO will be the deepest emission line survey to date. As part of the OTELO preparatory activities, the objective of this study is to determine the best combination of sampling and full width at half maximum (FWHM) for the OSIRIS tunable filters for deblending H\alpha from [NII] lines by analyzing the flux errors obtained. We simulated the OTELO data by convolving a complete set of synthetic HII galaxies in EW with different widths of the OSIRIS TFs. We estimated relative flux errors of the recovered H\alpha and [NII]6583 lines. We found that, for the red TF, a FWHM of 12 A and a sampling of 5 A is an optimal combination that allow deblending H\alpha from the [NII]6583 line with a flux error lower than 20%. This combination will allow estimating SFRs and metallicities using the H\alpha flux and the N2 method, respectively.Comment: 16 pages, 9 figures. Some authors added. Accepted for publication in PAS