Star formation rates and chemical abundances of emission line galaxies in intermediate-redshift clusters

We examine the evolutionary status of luminous, star-forming galaxies in intermediate-redshift clusters by considering their star formation rates and the chemical and ionsiation properties of their interstellar emitting gas. Our sample consists of 17 massive, star-forming, mostly disk galaxies with M_{B}<-20, in clusters with redshifts in the range 0.31< z <0.59, with a median of =0.42. We compare these galaxies with the identically selected and analysed intermediate-redshift field sample of Mouhcine et al. (2006), and with local galaxies from the Nearby Field Galaxy Survey of Jansen et al. (2000). From our optical spectra we measure the equivalent widths of OII, Hbeta and OIII emission lines to determine diagnostic line ratios, oxygen abundances, and extinction-corrected star formation rates. The star-forming galaxies in intermediate-redshift clusters display emission line equivalent widths which are, on average, significantly smaller than measured for field galaxies at comparable redshifts. However, a contrasting fraction of our cluster galaxies have equivalent widths similar to the highest observed in the field. This tentatively suggests a bimodality in the star-formation rates per unit luminosity for galaxies in distant clusters. We find no evidence for further bimodalities, or differences between our cluster and field samples, when examining additional diagnostics and the oxygen abundances of our galaxies. This maybe because no such differences exist, perhaps because the cluster galaxies which still display signs of star-formation have recently arrived from the field. In order to examine this topic with more certainty, and to further investigate the way in which any disparity varies as a function of cluster properties, larger spectroscopic samples are needed.Comment: 10 pages, 6 figures, MNRAS in pres

Ammonia emissions from deciduous forest after leaf fall

The understanding of biochemical feedback mechanisms in the climate system is lacking knowledge in relation to bi-directional ammonia (NH3) exchange between natural ecosystems and the atmosphere. We therefore study the atmospheric NH3 fluxes during a 25-day period during autumn 2010 (21 October to 15 November) for the Danish beech forest Lille Bøgeskov to address the hypothesis that NH3 emissions occur from deciduous forests in relation to leaf fall. This is accomplished by using observations of vegetation status, NH3 fluxes and model calculations. Vegetation status was observed using plant area index (PAI) and leaf area index (LAI). NH3 fluxes were measured using the relaxed eddy accumulation (REA) method. The REA-based NH3 concentrations were compared to NH3 denuder measurements. Model calculations of the atmospheric NH3 concentration were obtained with the Danish Ammonia MOdelling System (DAMOS). The relative contribution from the forest components to the atmospheric NH3 flux was assessed using a simple two-layer bi-directional canopy compensation point model. A total of 57.7% of the fluxes measured showed emission and 19.5% showed deposition. A clear tendency of the flux going from deposition of −0.25 ± 0.30 μg NH3-N m−2 s−1 to emission of up to 0.67 ± 0.28 μg NH3-N m−2 s−1 throughout the measurement period was found. In the leaf fall period (23 October to 8 November), an increase in the atmospheric NH3 concentrations was related to the increasing forest NH3 flux. Following leaf fall, the magnitude and temporal structure of the measured NH3 emission fluxes could be adequately reproduced with the bi-directional resistance model; it suggested the forest ground layer (soil and litter) to be the main contributing component to the NH3 emissions. The modelled concentration from DAMOS fits well the measured concentrations before leaf fall, but during and after leaf fall, the modelled concentrations are too low. The results indicate that the missing contribution to atmospheric NH3 concentration from vegetative surfaces related to leaf fall are of a relatively large magnitude. We therefore conclude that emissions from deciduous forests are important to include in model calculations of atmospheric NH3 for forest ecosystems. Finally, diurnal variations in the measured NH3 concentrations were related to meteorological conditions, forest phenology and the spatial distribution of local anthropogenic NH3 sources. This suggests that an accurate description of ammonia fluxes over forest ecosystems requires a dynamic description of atmospheric and vegetation processes

Top-down controlled alpha band activity in somatosensory areas determines behavioral performance in a discrimination task

The brain receives a rich flow of information which must be processed according to behavioral relevance. How is the state of the sensory system adjusted to up- or downregulate processing according to anticipation? We used magnetoencephalography to investigate whether prestimulus alpha band activity (8 - 14 Hz) reflects allocation of attentional resources in the human somatosensory system. Subjects performed a tactile discrimination task where a visual cue directed attention to their right or left hand. The strength of attentional modulation was controlled by varying the reliability of the cue in three experimental blocks (100%, 75%, or 50% valid cueing). While somatosensory prestimulus alpha power lateralized strongly with a fully predictive cue (100%), lateralization was decreased with lower cue reliability (75%) and virtually absent if the cue had no predictive value at all (50%). Importantly, alpha lateralization influenced the subjects' behavioral performance positively: both accuracy and speed of response improved with the degree of alpha lateralization. This study demonstrates that prestimulus alpha lateralization in the somatosensory system behaves similarly to posterior alpha activity observed in visual attention tasks. Our findings extend the notion that alpha band activity is involved in shaping the functional architecture of the working brain by determining both the engagement and disengagement of specific regions: the degree of anticipation modulates the alpha activity in sensory regions in a graded manner. Thus, the alpha activity is under top-down control and seems to play an important role for setting the state of sensory regions to optimize processing

Self-organized Criticality and Absorbing States: Lessons from the Ising Model

We investigate a suggested path to self-organized criticality. Originally, this path was devised to "generate criticality" in systems displaying an absorbing-state phase transition, but closer examination of the mechanism reveals that it can be used for any continuous phase transition. We used the Ising model as well as the Manna model to demonstrate how the finite-size scaling exponents depend on the tuning of driving and dissipation rates with system size.Our findings limit the explanatory power of the mechanism to non-universal critical behavior.Comment: 5 pages, 2 figures, REVTeX

The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy

We have carried out spectroscopic observations in 4 cluster fields using Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk field and cluster galaxies at $0.06 \le z \le 1.20$. Seventy-seven of these show emission lines, and 33 provide reasonably-secure determinations of the galaxies' rotation velocity. The rotation velocities, luminosities, colours and emission-line properties of these galaxies are used to study the possible effects of the cluster environment on the star-formation history of the galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at similar reshifts we find no measurable difference in rest-frame $B$-band luminosity at a given rotation velocity (the formal difference is $0.18\pm0.33$mag). The colours of the cluster emission line galaxies are only marginally redder in rest-frame $B-V$ (by $0.06\pm0.04$mag) than the field galaxies in our sample. Taken at face value, these results seem to indicate that bright star-forming cluster spirals are similar to their field counterparts in their star-formation properties. However, we find that the fraction of disk galaxies with absorption-line spectra (i.e., with no current star formation) is larger in clusters than in the field by a factor of $\sim3$--5. This suggests that the cluster environment has the overall effect of switching off star formation in (at least) some spiral galaxies. To interpret these observational results, we carry out simulations of the possible effects of the cluster environment on the star-formation history of disk galaxies and thus their photometric and spectroscopic properties. Finally, we evaluate the evolution of the rest-frame absolute $B$-band magnitude per unit redshift at fixed rotation velocity.Comment: 21 pages, 13 figures, accepted for publication in MNRA

Factors affecting degradation of barley straw in sacco and microbial activity in the rumen of cows fed fibre-rich diets. JI: The level of supplemental fishmeal

A diet composed of 76.2% untreated barley straw + 23.8% rye grass hay was given to three nonlactating cows at 90% of ad libitum intake. The cows were supplemented via cannulae with three differents levels of fishmeal in arder to make the ration up to 8%, 10% and 14% crude protein on a dry-matter basis. Treatments were arranged in a Latin Square design. Nylon bags containing untreated barley straw were incubated in the rumen 01 the cows for up to 72 h. Degradability of dry matter, total organic matter and the individual components of the cell wall of barley straw were affected by the protein level of the dlel. The Inclusion of fishmeal to a Ievel of 14% dietary protein produced the highest degradability of all parameters measured. The protein level also affected ammonia and total VFA concentrations; both fermentation products were highest in the treatment with the high fishmeal level. Rumen pH and rumen outflow rate of Iiquid and particulate phases were not affected by protein level. The ATP concentration found in the solid residue, remaining after removal of the liquid phase from the rumen content, Increases with increasing fishmeal level., while ATP in the Iiquid phase remained unchanged. This indicates that, under the conditions of this study, fishmeal exerts its effects on the microbes intimately associated lo the fibre, and not upon the whole microbial population. The microbial DNA concentration of digesta nylon bags increased during the first 24 h of incubation and then decreased until the end of incubation, indicating a process of colonization and depletion of degradable substrates.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la UNLPam.), Publicado en Animal Feed Science Technology, 70: 11-22, 1998

Spitzer bright, UltraVISTA faint sources in COSMOS: the contribution to the overall population of massive galaxies at z=3-7

We have analysed a sample of 574 Spitzer 4.5 micron-selected galaxies with [4.5]24 (AB) over the UltraVISTA ultra-deep COSMOS field. Our aim is to investigate whether these mid-IR bright, near-IR faint sources contribute significantly to the overall population of massive galaxies at redshifts z>=3. By performing a spectral energy distribution (SED) analysis using up to 30 photometric bands, we have determined that the redshift distribution of our sample peaks at redshifts z~2.5-3.0, and ~32% of the galaxies lie at z>=3. We have studied the contribution of these sources to the galaxy stellar mass function (GSMF) at high redshifts. We found that the [4.5]24 galaxies produce a negligible change to the GSMF previously determined for Ks_auto<24 sources at 3=<z<4, but their contribution is more important at 4=~50% of the galaxies with stellar masses Mst>~6 x 10^10 Msun. We also constrained the GSMF at the highest-mass end (Mst>~2 x 10^11 Msun) at z>=5. From their presence at 5=<z<6, and virtual absence at higher redshifts, we can pinpoint quite precisely the moment of appearance of the first most massive galaxies as taking place in the ~0.2 Gyr of elapsed time between z~6 and z~5. Alternatively, if very massive galaxies existed earlier in cosmic time, they should have been significantly dust-obscured to lie beyond the detection limits of current, large-area, deep near-IR surveys.Comment: 18 pages, 15 figures, 4 tables. Updated to match version in press at the Ap

Fish schooling as a basis for vertical axis wind turbine farm design

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighbouring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely-spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbours, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially-isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16x16 wind turbines. Results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs.Comment: Submitted for publication in BioInspiration and Biomimetics. Note: The technology described in this paper is protected under both US and international pending patents filed by the California Institute of Technolog

Simulation of GNSS reflected signals and estimation of position accuracy in GNSS-challenged environment

Abstract The paper describes the development and testing of a simulation tool, called QualiSIM. The tool estimates GNSS-based position accuracy based on a simulation of the environment surrounding the GNSS antenna, with a special focus on city-scape environments with large amounts of signal reflections from non-line-of-sight satellites. The signal reflections are implemented using the extended geometric path length of the signal path caused by reflections from the surrounding buildings. Based on real GPS satellite positions, simulated Galileo satellite positions, models of atmospheric effect on the satellite signals, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the environment we are able to estimate the position accuracy given several prerequisites as described in the paper. The result is a modelling of the signal path from satellite to receiver, the satellite availability, the extended pseudoranges caused by signal reflection, and an estimate of the position accuracy based on a least squares adjustment of the extended pseudoranges. The paper describes the models and algorithms used and a verification test where the results of QualiSIM are compared with results from collection of real GPS data in an environment with much signal reflection.</jats:p

Finite driving rates in interface models of Barkhausen noise

We consider a single-interface model for the description of Barkhausen noise in soft ferromagnetic materials. Previously, the model had been used only in the adiabatic regime of infinitely slow field ramping. We introduce finite driving rates and analyze the scaling of event sizes and durations for different regimes of the driving rate. Coexistence of intermittency, with non-trivial scaling laws, and finite-velocity interface motion is observed for high enough driving rates. Power spectra show a decay $\sim \omega^{-t}$, with $t<2$ for finite driving rates, revealing the influence of the internal structure of avalanches.Comment: 7 pages, 6 figures, RevTeX, final version to be published in Phys. Rev.