Optical photometry of the UCM Lists I and II

We present Johnson B CCD photometry for the whole sample of galaxies of the Universidad Complutense de Madrid (UCM) Survey Lists I and II. They constitute a well-defined and complete sample of galaxies in the Local Universe with active star formation. The data refer to 191 S0 to Irr galaxies at an averaged redshift of 0.027, and complement the already published Gunn r, J and K photometries. In this paper the observational and reduction features are discussed in detail, and the new colour information is combined to search for clues on the properties of the galaxies, mainly by comparing our sample with other surveys.Comment: 14 pages, 7 PostScript figures, accepted for publication in A&AS, also available vi ftp at ftp://cutrex.fis.ucm.es/pub/OUT/pag/PAPERS

Conversion of methanogenic substrates in anaerobic reactors : metals, mass transport, and toxicity

The EGSB systems represents an attractive option to extend further the use of anaerobic technology for wastewater treatment, particularly with respect to waste streams originating from chemical industries. Frequently chemical waste streams are unbalanced with respect to nutrients and/or micronutrients and furthermore these streams may contain toxic-biodegradable compounds. To reduce toxicity high recycle ratios may be applied as in the case of EGSB reactors however, this at the same time may adversely affect the substrate conversion rates due to mass transport limitations. These aspects were considered in this research. The main objectives of the work described in the thesis were to assess the kinetic impact of (i) nickel and cobalt limitations on the methanogenic degradation of methanol, (ii) the relative importance of mass transport phenomena in methanogenic granular sludge, and (iii) to characterize the toxicity and biodegradation of formaldehyde in the anaerobic conversion of methanogenic substrates. Particularly in the case of anaerobic systems, the ubiquitous presence of sulfides resulting from sulfate reduction and organic matter mineralization will lead to strong metal precipitation as metal sulfides. These precipitated metals are not directly available for the biomass. It is shown here that precipitation-dissolution kinetics of metal sulfides may play a key role in the bioavailability of essential metals.We furthermore showed that nutrient limitations can be overcome if the essential metals are added continuously at a proper rate so that their availability in solution can fulfill the requirement for biomass activity and growth. The metal dosing rates utilized range from 0.05 to 0.2μmol/h corresponding to metal to methanol ratios of 0.1-0.4 (μmol/g methanol-COD) and these values agree well with the calculated metal requirements based on the biomass yield and Ni and Co content of methylotrophic methanogens ( Methanosarcina sp.) grown on methanol. With respect to mass transport phenomena, it was found that at liquid upflow velocities exceeding 1 m/h liquid-film (external) mass transfer limitations normally can be neglected for acetate degrading methanogenic granular sludge. On the contrary, a clear increase in apparent K S -value was found at increasing mean granule diameters. Herewith we have clearly shown that anaerobic biofilms can be internally transport limited. In addition we also demonstrated that substrate transport in the biofilm can be described by diffusion, and that there was no evidence of convective flow due to biogas production in the anaerobic granules. Regarding formaldehyde conversion and toxicity, we demonstrated that methanogenesis from formaldehyde mainly occurred after intermediate formation of methanol and formate.Furthermore it was shown that the characteristics of formaldehyde toxicity were independent of the methanotrophic substrate used (methanol or acetate). Formaldehyde toxicity was in part reversible since once the formaldehyde concentration was extremely low or virtually removed from the system, the methane production rate was partially recovered. Since the degree of this recovery was not complete, we conclude that formaldehyde toxicity was also irreversible. The irreversible toxicity likely can be attributed to biomass formaldehyde-related decay. Independent of the mode of formaldehyde addition (slug or continuous), a certain amount of formaldehyde irrevocably reduced the methane production rate to a certain extent, hence the irreversible toxicity was dependent on the total amount of formaldehyde added to the system. This finding suggest that in order to treat formaldehyde containing waste streams a balance between formaldehyde-related decay and biomass growth should be attained. We furthermore showed that the biomass diversity may play a key role in the outcome of toxicity tests. Therefore we recommend that metabolic characterization of methanogenic sludge should be an integral component of toxicity studies and we describe a newly developed methodology that can be used for that purpose.</p

Evaluation of Sedentary Behavior and Physical Activity Levels Using Different Accelerometry Protocols in Children from the GENOBOX Study

Background Physical activity (PA) has acquired a significant relevance due to the health benefits associated with its practice. Accelerometers are an effective tool to assess PA; however, the diversity of cut-off points used to define different PA intensities through accelerometry could interfere in the interpretation of the findings among studies. Objectives The present study aimed to examine the sedentary behavior (SB) and physical activity (PA) levels in children using six selected accelerometry protocols based on diverse cut-off points. Methods Clinical examination, anthropometric measurements, and PA evaluation by accelerometry were assessed in 543 selected children (10 +/- 2.4 years old) from the Spanish GENOBOX study. The ActiLife data scoring program was used to determine daily min spent in SB, and light, moderate, vigorous and moderate-vigorous PA using six validated accelerometry protocols differing in their cut-off points. Results Very different estimations for SB and PA intensity levels were found in children, independently of the non-wear-time algorithm selected, and considering puberty stages, age and body mass index. The time spent in daily SB varied from 471 to 663.7 min, PA ranged from 141 to 301.6 min, and the moderate-vigorous PA was reported between 20.7 and 180.2 min. Conclusion The choice of a particular accelerometry protocol considering these factors is important to evaluate SB or PA intensities to suit the characteristics of the sample researched. It seems necessary to establish future lines of research that include different analytical approaches to measure SB and PA by accelerometry based on standardized and validated methodology

Stellar populations in local star-forming galaxies. I.-Data and modelling procedure

We present an analysis of the integrated properties of the stellar populations in the Universidad Complutense de Madrid Survey of Halpha-selected galaxies. In this paper, the first of a series, we describe in detail the techniques developed to model star-forming galaxies using a mixture of stellar populations, and taking into account the observational uncertainties. We assume a recent burst of star formation superimposed on a more evolved population. The effects of the nebular continuum, line emission and dust attenuation are taken into account. We also test different model assumptions including the choice of specific evolutionary synthesis model, initial mass function, star formation scenario and the treatment of dust extinction. Quantitative tests are applied to determine how well these models fit our multi-wavelength observations for the UCM sample. Our observations span the optical and near infrared, including both photometric and spectroscopic data. Our results indicate that extinction plays a key role in this kind of studies, revealing that low- and high-extinction objects may require very different extinction laws and must be treated differently. We also demonstrate that the UCM Survey galaxies are best described by a short burst of star formation occurring within a quiescent galaxy, rather than by continuous star formation. A detailed discussion on the inferred parameters, such as the age, burst strength, metallicity, star formation rate, extinction and total stellar mass for individual objects, is presented in paper II of this series.Comment: 18 pages, 8 PostScript figures, minor changes to match the published versio

Can we favour growth of multi-centennial beech trees by reducing competition of their offspring?

Evaluación del efecto de reducir la competencia entre hayas en el crecimiento de hayas centenarias y de porvenir

Luminosity and Stellar Mass Functions of Local Star-Forming Galaxies

We present the optical and near-infrared luminosity and mass functions of the local star-forming galaxies in the Universidad Complutense de Madrid Survey. A bivariate method which explicitly deals with the Halpha selection of the survey is used when estimating these functions. Total stellar masses have been calculated on a galaxy-by-galaxy basis taking into account differences in star formation histories. The main difference between the luminosity distributions of the UCM sample and the luminosity functions of the local galaxy population is a lower normalization (phi^*), indicating a lower global volume density of UCM galaxies. The typical near-infrared luminosity (L^*) of local star-forming galaxies is fainter than that of normal galaxies. This is a direct consequence of the lower stellar masses of our objects. However, at optical wavelengths (B and r) the luminosity enhancement arising from the young stars leads to M^* values that are similar to those of normal galaxies. The fraction of the total optical and near infrared luminosity density in the local Universe associated with star-forming galaxies is 10-20%. Fitting the total stellar mass function using a Schechter parametrization we obtain alpha=-1.15+/-0.15, log({M}^*)=10.82+/-0.17 Msun and log(phi^*)=-3.04+/-0.20 Mpc^{-3}. This gives an integrated total stellar mass density of 10^{7.83+/-0.07} Msun Mpc^{-3} in local star-forming galaxies (H_0=70 km s^{-1} Mpc^{-1}, Omega_M=0.3, Lambda=0.7). The volume-averaged burst strength of the UCM galaxies is b=0.04+/-0.01, defined as the ratio of the mass density of stars formed in recent bursts (age<10 Myr) to the total stellar mass density in UCM galaxies. Finally, we derive that, in the local Universe, (13+/-3)% of the total baryon mass density in the form of stars is associated with star-forming galaxies.Comment: 12 pages, 2 PostScript figures, published in ApJL. Minor changes to match the published versio

SWI/SNF regulates a transcriptional programme that induces senescence to prevent liver cancer

Oncogene-induced senescence (OIS) is a potent tumour suppressor mechanism. To identify senescence regulators relevant to cancer, we screened an shRNA library targeting genes deleted in hepatocellular carcinoma (HCC). Here, we describe how knockdown of the SWI/SNF component ARID1B prevents OIS and cooperates with RAS to induce liver tumours. ARID1B controls p16INK4a and p21CIP1a transcription but also regulates DNA damage, oxidative stress and p53 induction, suggesting that SWI/SNF uses additional mechanisms to regulate senescence. To systematically identify SWI/SNF targets regulating senescence, we carried out a focused shRNA screen. We discovered several new senescence regulators including ENTPD7, an enzyme that hydrolyses nucleotides. ENTPD7 affects oxidative stress, DNA damage and senescence. Importantly, expression of ENTPD7 or inhibition of nucleotide synthesis in ARID1B-depleted cells results in re-establishment of senescence. Our results identify novel mechanisms by which epigenetic regulators can affect tumor progression and suggest that pro-senescence therapies could be employed against SWI/SNF-mutated cancers

Beryllium abundances in stars hosting giant planets

We have derived beryllium abundances in a wide sample of stars hosting planets, with spectral types in the range F7V-K0V, aimed at studying in detail the effects of the presence of planets on the structure and evolution of the associated stars. Predictions from current models are compared with the derived abundances and suggestions are provided to explain the observed inconsistencies. We show that while still not clear, the results suggest that theoretical models may have to be revised for stars with Teff<5500K. On the other hand, a comparison between planet host and non-planet host stars shows no clear difference between both populations. Although preliminary, this result favors a ``primordial'' origin for the metallicity ``excess'' observed for the planetary host stars. Under this assumption, i.e. that there would be no differences between stars with and without giant planets, the light element depletion pattern of our sample of stars may also be used to further investigate and constraint Li and Be depletion mechanisms.Comment: A&A in press -- accepted on the 22/02/2002 (11 pages, 6 figures included