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31.
Sebastián E. Sabatini Iara Rocchetta Carlos M. Luquet Mariana I. Guido María del Carmen Ríos de Molina 《Limnologica》2011,41(4):356-362
The effect of chronic exposure to Escherichia coli on morphometrical parameters, different antioxidant defenses, lipid peroxidation and protein oxidation has been studied in digestive gland of the freshwater mussel Diplodon chilensis in the laboratory during 6 weeks. In, a parallel field study, we evaluated morphometrical and oxidative stress parameters in digestive glands of mussels collected from a sewage polluted area (SMA) and from a pristine area (control). Both sites were characterized by analyzing bacteriological and physic-chemical parameters. In the laboratory D. chilensis was able to filter bacteria at high concentrations with a clearing rate of 0.510 ± 0.036 L/h per gram of dry soft tissue mass. The digestive gland mass to shell length ratio (DGM/SL), reduced glutathione (GSH), lipid peroxidation, as concentration of thiobartituric acid reactive substances (TBARS), and glutathione-S-transferase (GST) activity of mussels fed with bacteria were significantly higher than those of control mussels after the fourth week. Fecal bacteria in lake water samples were undetectable in the control, and higher than 24,000 MPN (most probable number)/100 mL in SMA. DGM/SL was higher in SMA. No differences between sites were observed in total lipid and protein content, neither in superoxide dismutase activity. GSH content was higher in SMA, with no difference in the oxidized form. GST activity and MDA were significantly higher in SMA but protein oxidation was not affected. 相似文献
32.
A. Luque E. Ruiz-Agudo G. Cultrone E. Sebastián S. Siegesmund 《Environmental Earth Sciences》2011,62(7):1375-1386
One of the properties that makes marble such an excellent construction and ornamental material is its low porosity. It is
very difficult for water or decay agents to penetrate the internal structure of materials with no or few pores, so enhancing
the durability of these materials. However, environmental temperature fluctuations bring about significant physical changes
in marbles that result in an increase in porosity, due to the appearance of new microcracks and the expansion of existing
ones. These cracks offer new paths into the marble which make it easier for solutions containing pollutants to penetrate the
material. Thermal expansion tests were performed on three different types of marble known as White, Tranco, and Yellow Macael
(Almeria, Spain), after which an increase in porosity (from 17 to 73% depending on marble type) was observed, mainly due to
crack formation. The structural changes occurring during thermal expansion tests were more significant in the case of White
Macael samples, a fact that is not only related to its mineralogical composition but also to the morphology of the grains,
grain boundaries and crystal size. Our research suggests that thermally weathered White Macael marble could be more susceptible
to decay by other contaminant agents than Tranco or Yellow Macael. The use of hot-stage environmental scanning electron microscopy
is proposed as a valid tool for observing, both in situ and at high magnification, changes in the fracture system of building
stones induced by thermal stress. 相似文献
33.
José M. Ferrándiz Sebastián Ferrer María L. Sein-Echaluce 《Celestial Mechanics and Dynamical Astronomy》1987,40(3-4):315-328
A two-parameter time transformationdt=r 3/2(α0+α1 r)?1/2 dτ is proposed, where τ is the radial distance while α0 and α1 are, if not constants, at least conservative functions of positions and velocities. In Keplerian systems, the quadrature implied by the transformation may by carried out by elliptic functions. When α0=0, τ is the eccentric anomaly; if α1=0, then τ is the intermediate or elliptic anomaly. Considering several values of α0 and α1, numerical examples of the relation of thegeneralized elliptic anomaly τ with the classical and elliptic anomalies are given. Application of this transformation to some perturbed Kepler problems is briefly outlined. 相似文献
34.
Löbens Stefan Oriolo Sebastián Benowitz Jeff Wemmer Klaus Layer Paul Siegesmund Siegfried 《International Journal of Earth Sciences》2017,106(6):1991-2003
International Journal of Earth Sciences - Systematic 40Ar/39Ar feldspar data obtained from the Sierras Pampeanas are presented, filling the gap between available high-... 相似文献
35.
A coordinate system is defined on the phase space of a perturbed Keplerian system after the mean anomaly has been averaged out, for the purpose of explaining how eliminating the longitude of the ascending node reduces the orbital space to a two-dimensional sphere in case the system admits an axial symmetry. Concomitantly, on the submanifold of direct osculating ellipses, the CDM variables are replaced by functions which form the basis of a Poisson algebra isomorphic to the Lie algebra so(3) of the rotation group SO(3); furthermore, in these variables, the doubly reduced phase flow appears like a rotation of the reduced phase space. 相似文献
36.
In the main problem of artificial satellite theory, the difference between the Hamiltonian and Cid's radial intermediary is a function of the argument of latitude whose average over the mean anomaly is zero.Así debe ser—dijo cl Cura—; y en lo de casarsc vuestro amo, yo haré en ello todos mis poderíos. —MIGUEL de CERVANTES SAAVEDRA, El ingenioso hidalgo don Quijote de la Mancha. 相似文献
37.
Hydro‐morphodynamic evolution in a 90° movable bed discordant confluence with low discharge ratio 
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下载免费PDF全文 Sebastián Guillén‐Ludeña Mário J. Franca António H. Cardoso Anton J. Schleiss 《地球表面变化过程与地形》2015,40(14):1927-1938
Confluences with low discharge and momentum ratios, where narrow steep tributaries with high sediment load join a wide low‐gradient main channel that provides the main discharge, are often observed in high mountain regions such as in the upper‐Rhone river catchment in Switzerland. Few existing studies have examined the hydro‐morphodynamics of this type of river confluence while considering sediment discharge in both confluent channels. This paper presents the evolution of the bed morphology and hydrodynamics as observed in an experimental facility with a movable bed. For that purpose, one experiment was carried out in a laboratory confluence with low discharge and momentum ratios, where constant sediment rates were supplied to both flumes. During the experiment, bed topography and water surface elevations were systematically recorded. When the bed topography reached a steady state (so‐called equilibrium) and the outgoing sediment rate approximated the incoming rate, flow velocity was measured at 12 different points distributed throughout the confluence, and the grain size distribution of the bed surface was analyzed. Typical morphodynamic features of discordant confluences such as a bank‐attached bar and a flow deflection zone are identified in this study. Nevertheless, the presence of a marked scour hole in the discordant confluence and distinct flow regimes for the tributary and main channel, differ from results obtained in previous studies. Strong acceleration of the flow along the outer bank of the main channel is responsible for the scour hole. This erosion is facilitated by the sediment discharge into the confluence from the main channel which inhibits bed armoring in this region. The supercritical flow regime observed in the tributary is the hydrodynamic response to the imposed sediment rate in the tributary. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
38.
Seismic hazard in Buenos Aires,Argentina: A preliminary study on the effects of long‐distance earthquakes on tall buildings 下载免费PDF全文
下载免费PDF全文 The 2015 Illapel earthquake produced self‐evacuation of tall buildings in the city of Buenos Aires, Argentina, located 1280 km away from the epicenter. The ground motions in Buenos Aires due to the main event (Mw 8.3) and its aftershocks were registered by a new seismometer. The data collected allowed to estimate the maximum story drift ratios and top floor accelerations for tall buildings in Buenos Aires. The similarities between the response spectra and the Fourier amplitude spectra for the mainshock and its aftershocks show the influence that the dynamic properties of the 300‐m soil deposit have on the large acceleration amplification produced in these groups of buildings. 相似文献
39.
Sebastián M. Jovic Diego M. Guido Isidoro B. Schalamuk Francisco J. Ríos Colombo C. G. Tassinari Clemente Recio 《Mineralium Deposita》2011,46(3):257-271
The Pingüino deposit, located in the low sulfidation epithermal metallogenetical province of the Deseado Massif, Patagonia,
Argentina, represents a distinct deposit type in the region. It evolved through two different mineralization events: an early
In-bearing polymetallic event that introduced In, Zn, Pb, Ag, Cd, Au, As, Cu, Sn, W and Bi represented by complex sulfide
mineralogy, and a late Ag–Au quartz-rich vein type that crosscut and overprints the early polymetallic mineralization. The
indium-bearing polymetallic mineralization developed in three stages: an early Cu–Au–In–As–Sn–W–Bi stage (Ps1), a Zn–Pb–Ag–In–Cd–Sb stage (Ps2) and a late Zn–In–Cd (Ps3). Indium concentrations in the polymetallic veins show a wide range (3.4 to 1,184 ppm In). The highest indium values (up
to 1,184 ppm) relate to the Ps2 mineralization stage, and are associated with Fe-rich sphalerites, although significant In enrichment (up to 159 ppm) is
also present in the Ps1 paragenesis associated with Sn-minerals (ferrokesterite and cassiterite). The hydrothermal alteration associated with the
polymetallic mineralization is characterized by advanced argillic alteration within the immediate vein zone, and sericitic
alteration enveloping the vein zone. Fluid inclusion studies indicate homogenisation temperatures of 308.2–327°C for Ps1 and 255–312.4°C for Ps2, and low to moderate salinities (2 to 5 eq.wt.% NaCl and 4 to 9 eq.wt.% NaCl, respectively). δ34S values of sulfide minerals (+0.76‰ to +3.61‰) indicate a possible magmatic source for the sulfur in the polymetallic mineralization
while Pb isotope ratios for the sulfides and magmatic rocks (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 17.379 to 18.502; 15.588 to 15.730 and 38.234 to 38.756, respectively) are consistent with the possibility that
the Pb reservoirs for both had the same crustal source. Spatial relationships, hydrothermal alteration styles, S and Pb isotopic
data suggest a probable genetic relation between the polymetallic mineralization and dioritic intrusions that could have been
the source of metals and hydrothermal fluids. Mineralization paragenesis, alteration mineralogy, geochemical signatures, fluid
inclusion data and isotopic data, confirm that the In-bearing polymetallic mineralization from Pingüino deposit is a distinct
type, in comparison with the well-known epithermal low sulfidation mineralization from the Deseado Massif. 相似文献
40.
A common decay scenario in old and new buildings was simulated: the effects on masonry structures of salt efflorescence or subefflorescence produced by the rise of saline solution. Eight different types of masonry wall each made up of a combination of different construction materials (brick, calcarenite and four types of mortar were combined as follows: pure lime mortar, mortar + air entraining agent, mortar + pozzolana, mortar + air entraining agent + pozzolana) have been tested. These materials have different textures (strong anisotropy in brick, irregular-shaped pores in calcarenite, retraction fissures or rounded pores in mortars which also show a reduction of porosity along the contact area with the stone), different hydric behaviours (under total immersion brick + mortar specimens absorb water faster than calcarenite + mortar specimens) and different pore size distribution (brick shows unimodal pore distribution, whereas calcarenite and mortars are bimodal). In the salt weathering test, mortars interlayered with masonry blocks did not act as sacrificial layers. In fact, they allowed salts to rise through them and crystallize on the brick or calcarenite pieces causing the masonry structure to decay. Only the addition of an air-entraining agent partially hindered the capillary rise of the salt-laden solutions. 相似文献