Characterizing rainfall erosivity by kinetic power-Median volume diameter relationship

Kinetic power, i.e. kinetic energy per unit time and area, is the variable widely used to represent the rainfall erosivity which affects soil loss and sediment yield. This paper shows the results of an experimental investigation using the raindrop size distributions (DSDs) measured by an optical disdrometer installed at the Department of Agricultural, Food and Forestry Sciences of University of Palermo in Italy (June 2006-March 2014) and at the El Teularet experimental station in Spain (July 2015-May 2016). At first an analysis of the DSDs aggregated into intensity classes is carried out, then the measured kinetic power values are determined. The aggregated DSDs allowed to establish that the median volume diameter of the distribution is affected by raindrops characterized by the greatest values of the diameters that composes precipitation. The measured kinetic power values allowed to verify the reliability of kinetic power-rainfall intensity relationships proposed by Wischmeier and Smith and Kinnell. Finally, using all the available measurements of kinetic power, rainfall intensity and median volume diameter obtained in different climatic contexts and by different measurement techniques, this paper demonstrates that the ratio between kinetic power and rainfall intensity depends strictly only on median volume diameter of the distribution according to a single site-independent relationship. Therefore the estimate of the kinetic energy per unit volume of rainfall does not require the knowledge of the whole drop size distribution. The reliability of a theoretical relationship relating the kinetic power per unit volume of rainfall to median volume diameter is also positively verified using all available measurements

Flow resistance law in channels with fully submerged and rigid vegetation

The estimate of flow resistance in vegetated channels is a challenging topic for programming riparian vegetation management, controlling channel conveyance and flooding propensity, for designing soil bioengineering practices. In this paper, measurements collected by Gualtieri et al. (2018), in a flume where rigid cylinders were set in two arrangements (staggered, aligned) at high submergence ratios (ratio between the water depth and the vegetation height greater than 5), were used to study the effect of rigid submerged vegetation on estimating flow resistance. The theoretical flow resistance equation, obtained by integrating the power flow velocity distribution, was first summarized. Then, this flow resistance equation was calibrated and tested by measurements of Gualtieri et al. (2018). In particular, a relationship between the Γ function of the power velocity distribution, the channel slope, the flow Froude number, and the submergence ratio was established by using the available measurements carried out for the two arrangements with different stem concentrations. The calibration of this relationship was carried out by (i) distinguishing measurements corresponding to different vegetation arrangements (staggered, aligned), (ii) joining all available data, and (iii) using only a scale factor representing the effect of vegetation arrangements. For the cases (ii) and (iii), the analysis demonstrated that the theoretical flow resistance equation allows an accurate estimate of the Darcy–Weisbach friction factor, which is characterized by errors that are always less than 5% and less than or equal to 2.5% for 88% of the investigated cases

Measuring supermassive black holes with gas kinematics - II. The LINERs IC 989, NGC 5077, and NGC 6500

We present results from a kinematical study of the gas in the nucleus of a sample of three LINER galaxies, obtained from archival HST/STIS long-slit spectra. We found that, while for the elliptical galaxy NGC 5077, the observed velocity curves are consistent with gas in regular rotation around the galaxy's center, this is not the case for the two remaining objects. By modeling the surface brightness distribution and rotation curve from the emission lines in NGC 5077, we found that the observed kinematics of the circumnuclear gas can be accurately reproduced by adding to the stellar mass component a black hole mass of M_bh = 6.8 (-2.8,+4.3) 10**8 M_sun (uncertainties at a 1 sigma level); the radius of its sphere of influence (R_sph ~ 0".34) is well-resolved at the HST resolution. The BH mass estimate in NGC 5077 is in fairly good agreement with both the M_bh-M_bul (with an upward scatter of ~ 0.4 dex) and M_bh-sigma correlations (with an upward scatter of 0.5 dex in the Tremaine et al. form and essentially no scatter using the Ferrarese et al. form) and provides further support for the presence of a connection between the ``residuals'' from the M_bh-sigma correlation and the bulge effective radius. This indicates the presence of a black hole's ``fundamental plane'' in the sense that a combination of at least sigma and R_e drives the correlations between M_bh and host bulge properties.Comment: Accepted for publication in A&

The Chandra COSMOS Survey, I: Overview and Point Source Catalog

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra} program that has imaged the central 0.5 sq.deg of the COSMOS field (centered at 10h, +02deg) with an effective exposure of ~160ksec, and an outer 0.4sq.deg. area with an effective exposure of ~80ksec. The limiting source detection depths are 1.9e-16 erg cm(-2) s(-1) in the Soft (0.5-2 keV) band, 7.3e(-16) erg cm^-2 s^-1 in the Hard (2-10 keV) band, and 5.7e(-16) erg cm(-2) s(-1) in the Full (0.5-10 keV) band. Here we describe the strategy, design and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of <2e(-5) (1655 in the Full, 1340 in the Soft, and 1017 in the Hard bands). By using a grid of 36 heavily (~50%) overlapping pointing positions with the ACIS-I imager, a remarkably uniform (to 12%) exposure across the inner 0.5 sq.deg field was obtained, leading to a sharply defined lower flux limit. The widely different PSFs obtained in each exposure at each point in the field required a novel source detection method, because of the overlapping tiling strategy, which is described in a companion paper. (Puccetti et al. Paper II). This method produced reliable sources down to a 7-12 counts, as verified by the resulting logN-logS curve, with sub-arcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper (Civano et al. Paper III). The full catalog is described here in detail, and is available on-line.Comment: Revised to omit egregious bold facing and fix missing ',' in author lis

Galaxy bulges and their massive black holes: a review

With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590 references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer Publishin

Predicting rainfall erosivity by momentum and kinetic energy in Mediterranean environment

Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion and it is used around the world for assessing and predicting soil loss on agricultural lands. Erosivity can be represented in terms of both rainfall momentum and kinetic energy, both calculated per unit time and area. Contrasting results on the representativeness of these two variables are available: some authors stated that momentum and kinetic energy are practically interchangeable in soil loss estimation while other found that kinetic energy is the most suitable expression of rainfall erosivity. The direct and continuous measurements of momentum and kinetic energy by a disdrometer allow also to establish a relationship with rainfall intensity at the study site. At first in this paper a comparison between the momentum-rainfall intensity relationships measured at Palermo and El Teularet by an optical disdrometer is presented. For a fixed rainfall intensity the measurements showed that the rainfall momentum values measured at the two experimental sites are not coincident. However both datasets presented a threshold value of rainfall intensity over which the rainfall momentum assumes a quasi-constant value. Then the reliability of a theoretically deduced relationship, linking momentum, rainfall intensity and median volume diameter, is positively verified using measured raindrop size distributions. An analysis to assess which variable, momentum or kinetic energy per unit area and time, is the best predictor of erosivity in Italy and Spain was also carried out. This investigation highlighted that the rainfall kinetic energy per unit area and time can be substituted by rainfall momentum as index for estimating the rainfall erosivity, and this result does not depend on the site where precipitation occurs. Finally, rainfall intensity measurements and soil loss data collected from the bare plots equipped at Sparacia experimental area were used to verify the reliability of some rainfall erosivity indices and their ability to distinguish the type of involved soil erosion processes

Un nuovo campionatore per la misura della perdita di suolo in parcelle attrezzate

Le misure di perdita di suolo in parcelle attrezzate necessitano la conoscenza del peso del materiale eroso intercettato nella sezione terminale delle parcelle. Nell’area sperimentale di Sparacia attrezzata per la misura della perdita di suolo i deflussi torbidi prodotti in seguito ad un evento erosivo vengono convogliati mediante una grondaia posta a valle di ciascuna parcella all’interno di vasche di accumulo. Per misurare la frazione di materiale solido presente nel volume della sospensione raccolto in dette vasche, si propone l’utilizzo di un nuovo campionatore appositamente predisposto. Esso consiste in un cilindro di ottone, di noto diametro, dotato nella sezione terminale di una valvola di chiusura. Lo strumento infisso nel volume raccolto, una volta chiusa la sezione terminale, consente di estrarre una colonna rappresentativa della miscela torbida presente in vasca. Per la validazione del campionatore sono state condotte prove su cilindri di diametro 20 cm e su una vasca avente in pianta forma pressoché quadrata e dimensioni di 1 m2. Le misure hanno dimostrato una buona affidabilità dello strumento nel riprodurre la concentrazione effettiva presente nel miscuglio fangoso. Soltanto per basse concentrazioni è necessaria l’applicazione di un fattore correttivo, peraltro di modesta entità, per tenere conto di un lieve difetto nella modalità di chiusura della valvola.Plot soil loss measurements need the knowledge of the weight of the soil material delivered at the plot lower end. The Sparacia experimental area is equipped for measuring plot soil loss. The runoff and associated sediments are intercepted by a gutter placed along the lower end of the plot and collected into a storage system consisting of tanks. Use of a new sampler for measuring the sediment collected into the tanks is proposed. The sampler is a brass cylinder of known diameter with a gate valve located at its end section. Infixing sampler and closing the valve allow to extract a column representative of the turbid suspension collected into the tank. To validate the sampler, experiments were carried out using both cylinders with a diameter equal to 20 cm and a tank having a quasi-square horizontal crosssection with an area equal to 1 m2. The measurements demonstrated a good reliability of the sampler to reproduce the actual concentration of the suspension. Only for lowest concentration values a small corrective factor needs for taking into account an imperfection of the valve closure system

Microscopic biasing of discrete-time quantum trajectories

We develop a microscopic theory for biasing the quantum trajectories of an open quantum system, which permits to render rare trajectories typical. To this end we consider a discrete-time quantum dynamics, where the open system collides sequentially with qubit probes which are then measured. A theoretical framework is built in terms of thermodynamic functionals in order to characterize its quantum trajectories (each embodied by a sequence of measurement outcomes). We show that the desired biasing is achieved by suitably modifying the Kraus operators describing the discrete open system dynamics. From a microscopical viewpoint and for short collision times, this corresponds to adding extra collisions which enforce the system to follow a desired rare trajectory. The above extends the theory of biased quantum trajectories from Lindblad-like dynamics to sequences of arbitrary dynamical maps, providing at once a transparent physical interpretation

Polyester microplastic fibers affect soil physical properties and erosion as a function of soil type

Microplastics are recognized as a factor of global change contaminating many environmental compartments. Agricultural soils are very likely to receive microplastic contamination and are of particular concern due to their role in food production. Microplastic fibers have already been shown to be able to affect soil properties, but their effect on different soil types is poorly understood. Moreover, limited information is available on how the presence of this pollutant can affect soil water erosion processes, which are extremely important issues in many environments. In the light of this, we performed two experiments (carried out on a microscale) to investigate how the presence of polyester microplastic fibers affects soil physical and hydrological parameters and processes such as aggregate formation and soil erosion in three different agricultural soil types (a Vertisol, an Entisol, and an Alfisol). Our data show that the effects of polyester microplastic fibers on soil physical parameters and erosion are strongly dependent on soil type. We found that microplastic fiber contamination can affect soil bulk density, capacitive indicators of soil physical quality, and decrease the formation of new aggregates (labile in the incubation period applied in our experiments) but did not affect their stability in water. However, we found that polyester microplastic fibers reduced soil loss and sediment concentration, especially in the most erodible soils. In this paper, we provide some hypotheses, but certainly future data are still needed to confirm or disprove our hypotheses. Overall, our results highlight the importance of broadly exploring soil properties, such as texture, mineralogy, organic carbon content, etc., to better understand how the various soil types respond to microplastic fiber contamination