The GREGOR Fabry-P\'erot Interferometer

The GREGOR Fabry-P\'erot Interferometer (GFPI) is one of three first-light instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated mounting. Thanks to its large-format, high-cadence CCD detectors with sophisticated computer hard- and software it is capable of scanning spectral lines with a cadence that is sufficient to capture the dynamic evolution of the solar atmosphere. The field-of-view (FOV) of 50" x 38" is well suited for quiet Sun and sunspot observations. However, in the vector spectropolarimetric mode the FOV reduces to 25" x 38". The spectral coverage in the spectroscopic mode extends from 530-860 nm with a theoretical spectral resolution R of about 250,000, whereas in the vector spectropolarimetric mode the wavelength range is at present limited to 580-660 nm. The combination of fast narrow-band imaging and post-factum image restoration has the potential for discovery science concerning the dynamic Sun and its magnetic field at spatial scales down to about 50 km on the solar surface.Comment: 14 pages, 17 figures, 4 tables; pre-print of AN 333, p.880-893, 2012 (AN special issue to GREGOR

Impact of the earthworm Lumbricus terrestris (L.) on As, Cu, Pb and Zn mobility and speciation in contaminated soils

To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota

Theoretical study of incoherent phi photoproduction on a deuteron target

We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross section from bound protons to the free ones with the aim of comparing with recent results at LEPS. For this purpose we take into account Fermi motion in single scattering and rescattering of the phi to account for phi absorption on a second nucleon as well as the rescattering of the proton. We find that the contribution of the double scattering is much smaller than the typical cross section of gamma p to phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross section of gamma p to phi p in free space, and leads to a moderate reduction of the phi photoproduction cross section on a deuteron at forward angles if LEPS set up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase space in the free case. In particular, we find that for momentum transferred squared close to the maximum value, the Fermi motion changes drastically the shape of d sigma / dt, to the point that the ratio of this cross section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem the most indicated to find effects of a possible phi absorption in the deuteron. This reaction is studied theoretically as a function of t and the effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction.Comment: 17 pages, 16 figure

X-ray observations of highly obscured 9.7 micron sources: an efficient method for selecting Compton-thick AGN ?

Spitzer/IRS has revealed many sources with very deep Si features at 9.7micron (tau>1). We set out to investigate whether a strong Si absorption feature is a good indicator for the presence of a heavily obscured AGN. We compile X-ray spectroscopic observations available in the literature on the optically-thick,tau(9.7)>1 sources from the IRAS Seyfert sample. We find that the majority of the high-tau optically confirmed Seyferts (6/9) in this sample are probably CT. Thus we provide direct evidence for a connection between mid-IR optically-thick galaxies and CT AGN, with the success rate being close to 70% in the local Universe. This is at least comparable, if not better, than other rates obtained with photometric information in the mid to far-IR, or even mid-IR to Xray. However, this technique cannot provide complete CT AGN samples,ie there are many CT AGN which do not show significant Si absorption, with the most notable example being N1068. Having assessed the validity of the high 9.7micron technique locally, we attempt to construct a sample of candidate CT AGN at higher redshifts. We compile a sample of 7 high-tau sources in the GOODS and 5 in the Spitzer FLS. All these have been selected to have no PAH features EW(6.2)<0.3 in order to maximize the probability that they are AGN. 6 out of 7 sources in the GOODS have been detected in X-rays, while for the five FLS sources only X-ray flux upper limits are available. The high X-ray luminosities of the detected GOODS sources corroborates that these are AGN. For FLS, ancillary optical spectroscopy reveals hidden nuclei in two more sources. SED fitting can support the presence of an AGN in the vast majority of sources. We cannot derive useful X-ray spectroscopy constraints on whether these are CT. However, the low LX/L6 ratios, suggest that at least 4 out of the 6 detected sources in GOODS may be associated with CT AGN.Comment: 12 pages, to appear in A&A; version after language editin

The central energy source of 70micron-selected galaxies: Starburst or AGN?

We present the first AGN census in a sample of 61 galaxies selected at 70microns, a wavelength which should strongly favour the detection of star-forming systems. For the purpose of this study we take advantage of deep Chandra X-ray and Spitzer infrared (3.6-160micron) data, as well as optical spectroscopy and photometry from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey for the Extended Groth Strip (EGS) field. We investigate spectral line diagnostics ([OIII]/Hbeta and [NeIII]/[OII] ratios, Hdelta Balmer absorption line equivalent widths and the strength of the 4000Ang break), X-ray luminosities and spectral energy distributions (SEDs). We find that the 70micron sources are undergoing starburst episodes and are therefore characterised by a predominance of young stars. In addition, 13 per cent of the sources show AGN signatures and hence potentially host an AGN. When the sample is split into starbursts (SBs, 10^10<L_IR<10^11 L_solar), Luminous InfraRed Galaxies (LIRGs, 10^11<L_IR<10^12 L_solar) and UltraLuminous InfraRed Galaxies (ULIRGs,10^12<L_IR<10^13 L_solar), the AGN fraction becomes 0, 11 and 23 per cent respectively, showing an increase with total infrared luminosity. However, by examining the sources' panchromatic SEDs, we conclude that although the AGN is energetically important in 1 out of 61 objects, all 70micron-selected galaxies are primarily powered by star-formation.Comment: 20 pages, 14 figures, accepted for publication in MNRA

The star formation history of mass-selected galaxies in the COSMOS field

We explore the evolution of the specific star formation rate (SSFR) for 3.6um-selected galaxies of different M_* in the COSMOS field. The average SFR for sub-sets of these galaxies is estimated with stacked 1.4GHz radio continuum emission. We separately consider the total sample and a subset of galaxies (SF) that shows evidence for substantive recent star formation in the rest-frame optical SED. At 0.2<z<3 both populations show a strong and M_*-independent decrease in their SSFR towards z=0.2, best described by a power- law (1+z)^n, where n~4.3 for all galaxies and n~3.5 for SF sources. The decrease appears to have started at z>2, at least above 4x10^10M_Sun where our conclusions are most robust. We find a tight correlation with power-law dependence, SSFR (M_*)^beta, between SSFR and M_* at all z. It tends to flatten below ~10^10M_Sun if quiescent galaxies are included; if they are excluded a shallow index beta_SFG -0.4 fits the correlation. On average, higher M_* objects always have lower SSFRs, also among SF galaxies. At z>1.5 there is tentative evidence for an upper SSFR-limit that an average galaxy cannot exceed. It is suggested by a flattening of the SSFR-M_* relation (also for SF sources), but affects massive (>10^10M_Sun) galaxies only at the highest z. Below z=1.5 there thus is no direct evidence that galaxies of higher M_* experience a more rapid waning of their SSFR than lower M_* SF systems. In this sense, the data rule out any strong 'downsizing'. We combine our results with recent measurements of the galaxy (stellar) mass function in order to determine the characteristic mass of a SF galaxy (M_*=10^(10.6\pm0.4)M_Sun). In this sense, too, there is no 'downsizing'. Our analysis constitutes the most extensive SFR density determination with a single technique to z=3. Recent Herschel results are consistent with our results, but rely on far smaller samples.Comment: 37 pages, 14 figures, 7 tables; accepted for publication in the Astrophysical Journal; High resolution versions of all figures available at www.mpia-hd.mpg.de/homes/karim/research.htm

The porin and the permeating antibiotic: A selective diffusion barrier in gram-negative bacteria

Gram-negative bacteria are responsible for a large proportion of antibiotic resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds, including several classes of antibiotics. Bacterial adaptation to reduce influx through porins is an increasing problem worldwide that contributes, together with efflux systems, to the emergence and dissemination of antibiotic resistance. An exciting challenge is to decipher the genetic and molecular basis of membrane impermeability as a bacterial resistance mechanism. This Review outlines the bacterial response towards antibiotic stress on altered membrane permeability and discusses recent advances in molecular approaches that are improving our knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channel

Periglacial environments and frozen ground in the central Pyrenean high mountain area: Ground thermal regime and distribution of landforms and processes

Producción CientíficaThe periglacial belt is located in the highest parts of temperate mountains. The balance between mean air and ground temperatures and the presence of water determine the effectiveness of periglacial processes related to permafrost, the active layer or seasonally frozen ground (SFG). This study combines thermal and geomorphological data obtained in four Pyrenean massifs (Infierno‐Argualas, Posets, Maladeta and Monte Perdido) to improve knowledge on the occurrence and distribution of frozen ground. The methodology used is based on the study of landforms as frozen ground indicators, mapping processes, ground temperature analysis, basal temperature of snow, thermal mapping and geomatic surveys on rock glaciers and protalus lobes. In the Pyrenean high mountain areas the lower limit of frozen ground is at ~2,650m a.s.l., possible permafrost appears above 2,650m a.s.l. on north‐ and south‐facing slopes, and probable permafrost is dominant above 2,900m a.s.l. Unfrozen ground with cold‐associated geomorphological processes reach 2,900m a.s.l. and unfrozen and frozen ground distribution points to a patchy pattern throughout the periglacial belt. The most widespread frozen grounds are SFG. The thermal data, mean annual ground temperature, cold season temperatures, bottom temperature snow measurements, freeze/thaw cycles and distribution of landforms permit the establishment of a periglacial land system divided into three main belts: infraperiglacial, middle periglacial and supraperiglacial. The large number of processes and landforms that are involved and their altitudinal and spatial organization make up a complex environment that determines the geoecological dynamics of high mountain areas.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (projects CGL2015-68144-R / GL2017- 82216-R

Retrospective cohort study: Risk of gastrointestinal cancer in a symptomatic cohort after a complete colonoscopy: Role of faecal immunochemical test

BACKGROUND: Faecal immunochemical test (FIT) has been recommended to assess symptomatic patients for colorectal cancer (CRC) detection. Nevertheless, some conditions could theoretically favour blood originating in proximal areas of the gastrointestinal tract passing through the colon unmetabolized. A positive FIT result could be related to other gastrointestinal cancers (GIC). AIM: To assess the risk of GIC detection and related death in FIT-positive symptomatic patients (threshold 10 µg Hb/g faeces) without CRC. METHODS: Post hoc cohort analysis performed within two prospective diagnostic test studies evaluating the diagnostic accuracy of different FIT analytical systems for CRC and significant colonic lesion detection. Ambulatory patients with gastrointestinal symptoms referred consecutively for colonoscopy from primary and secondary healthcare, underwent a quantitative FIT before undergoing a complete colonoscopy. Patients without CRC were divided into two groups (positive and negative FIT) using the threshold of 10 µg Hb/g of faeces and data from follow-up were retrieved from electronic medical records of the public hospitals involved in the research. We determined the cumulative risk of GIC, CRC and upper GIC. Hazard rate (HR) was calculated adjusted by age, sex and presence of significant colonic lesion. RESULTS: We included 2709 patients without CRC and a complete baseline colonoscopy, 730 (26.9%) with FIT = 10 µgr Hb/gr. During a mean time of 45.5 ± 20.0 mo, a GIC was detected in 57 (2.1%) patients: An upper GIC in 35 (1.3%) and a CRC in 14 (0.5%). Thirty-six patients (1.3%) died due to GIC: 22 (0.8%) due to an upper GIC and 9 (0.3%) due to CRC. FIT-positive subjects showed a higher CRC risk (HR 3.8, 95%CI: 1.2-11.9) with no differences in GIC (HR 1.5, 95%CI: 0.8-2.7) or upper GIC risk (HR 1.0, 95%CI: 0.5-2.2). Patients with a positive FIT had only an increased risk of CRC-related death (HR 10.8, 95%CI: 2.1-57.1) and GIC-related death (HR 2.2, 95%CI: 1.1-4.3), with no differences in upper GIC-related death (HR 1.4, 95%CI: 0.6-3.3). An upper GIC was detected in 22 (0.8%) patients during the first year. Two variables were independently associated: anaemia (OR 5.6, 95%CI: 2.2-13.9) and age = 70 years (OR 2.7, 95%CI: 1.1-7.0). CONCLUSION: Symptomatic patients without CRC have a moderate risk increase in upper GIC, regardless of the FIT result. Patients with a positive FIT have an increased risk of post-colonoscopy CRC

Evidence for t\bar{t}\gamma Production and Measurement of \sigma_t\bar{t}\gamma / \sigma_t\bar{t}

Using data corresponding to 6.0/fb of ppbar collisions at sqrt(s) = 1.96 TeV collected by the CDF II detector, we present a cross section measurement of top-quark pair production with an additional radiated photon. The events are selected by looking for a lepton, a photon, significant transverse momentum imbalance, large total transverse energy, and three or more jets, with at least one identified as containing a b quark. The ttbar+photon sample requires the photon to have 10 GeV or more of transverse energy, and to be in the central region. Using an event selection optimized for the ttbar+photon candidate sample we measure the production cross section of, and the ratio of cross sections of the two samples. Control samples in the dilepton+photon and lepton+photon+\met, channels are constructed to aid in decay product identification and background measurements. We observe 30 ttbar+photon candidate events compared to the standard model expectation of 26.9 +/- 3.4 events. We measure the ttbar+photon cross section to be 0.18+0.08 pb, and the ratio of the cross section of ttbar+photon to ttbar to be 0.024 +/- 0.009. Assuming no ttbar+photon production, we observe a probability of 0.0015 of the background events alone producing 30 events or more, corresponding to 3.0 standard deviations.Comment: 9 pages, 3 figure