Acceptance speech for the Barringer Award of the Meteoritical Society,July 30, 2013     

Walter Alvarez 《Meteoritics & planetary science》2013,48(9):1712-1714

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An excerpt of X‐shooter operations at Paranal     

C. Martayan  A. Alvarez  P. Bristow  R. Castillo  H. Dekker  S. D'Odorico  V. Mainieri  E. Mason  A. Modigliani  S. Moehler  P. Moller  F. Patat  E. Pena  C. Reinero  J. Vernet  J. Vinther  M. Vuckovic  all the engineers who work a lot on X‐shooter 《Astronomische Nachrichten》2011,332(3):222-223

We report on the current performances and measurements done with X‐shooter during its first year of operations at Paranal. We present the current instrumental problems, recent and future improvements, and give advice for the observations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Organic matter fractionation in aggregates typical Argiudolls southeastern Buenos Aires and its relation to different soil uses: a preliminary study     

Maria Fernanda Alvarez  Margarita Luisa Osterrieth  Julio Luis del Río 《Environmental Earth Sciences》2012,65(2):505-515

Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredón, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a) cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA), and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in SOC (7.2–8.6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates (5.6–10% and 6.9–13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3–0.5%). Fulvic acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for more than 50 years.  相似文献   

Degradation Efficiency of Textile and Wood Processing Industry Wastewater by Photocatalytic Process Using In Situ Ultrafiltration Membrane          下载免费PDF全文

Nurdan Doruk  Hüseyin Cengiz Yatmaz  Nadir Dizge 《洁净——土壤、空气、水》2016,44(3):224-231

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Mapping geology in Djelfa District (Saharan Atlas,Algeria), using Landsat 7 ETM+ data: an alternative method to discern lithology and structural elements     

Kamel Amri  Ghilles Rabai  Imene Meriem Benbakhti  Mohamed Nadir Khennouche 《Arabian Journal of Geosciences》2017,10(4):87

Djelfa area in the central Saharan Atlas is characterized by its high lithological diversity with different facies from the Triassic to the Tertiary. The lack of published geological maps of the region (Djelfa) prompted us to test specific processing of satellite images (ratio bands, principal component analysis) in order to establish a lithological discrimination of the region. Several treatments allowed us to map the lineaments highlighting the various tectonic structures of the region. The combination of field and remote sensing data pointed out the double influence of the E-W Eocene and N-S Miocene phases in the structuration of these regions. As a large part of the Djelfa area is inaccessible, the obtained results undeniably contribute to a better understanding of the local geology.  相似文献   

Effects of fish school structures on acoustic scattering     

Alvarez  A.; Ye  Z. 《ICES Journal of Marine Science》1999,56(3):361-369

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Deterministic Seismic Zoning of Eastern Cuba   总被引：1，自引：0，他引：1  

L. Alvarez  F. Vaccari  G. F. Panza 《Pure and Applied Geophysics》1999,156(3):469-486

—A deterministic seismic zoning of Cuba is performed by modelling, with modal summation, the complete P-SV and SH waves fields generated by point-source earthquakes buried in flat-layered anelastic media. The results of the computation, performed for periods greater than 1 second, are presented in two sets of maps of maximum displacement (d _max), maximum velocity (v _max) and design ground acceleration (DGA), obtained by using two different criteria in the definition of the input magnitude: (1) values reported in the earthquake catalogue (M _obs) and (2) values determined from seismotectonic considerations (M _max). A comparison with the results of a previous probabilistic seismic zoning is made to test the possibility of making intensity — ground motion conversion with the aid of log-linear regressions.  相似文献   

Drainage on evolving fold-thrust belts: a study of transverse canyons in the Apennines   总被引：1，自引：0，他引：1  

Alvarez 《Basin Research》1999,11(3):267-284

Anticlinal ridges of the actively deforming Umbria–Marche Apennines fold-thrust belt are transected by deep gorges, accommodating a drainage pattern which almost completely ignores the presence of pronounced anticlinal mountains. Because the region was below sea level until the folds began to form, simple antecedence cannot explain these transverse canyons. In addition, the fold belt is too young for there to have been a flat-lying cover from which the rivers could have been superposed.
In 1978, Mazzanti & Trevisan proposed an explanation for these gorges which deserves wider recognition. They suggested that the Apennine fold ridges emerged from the sea in sequence, with the erosional debris from each ridge piling up against the next incipient ridge to emerge, gradually extending the coastal plain seaward. The new coastal plain adjacent to each incipient anticline provided a flat surface on which a newly elongated river could cross the fold, positioning it to cut a gorge as the fold grew. Their mechanism is thus a combination of antecedence and superposition in which folds, overlying sedimentary cover and downstream elongations of the rivers all form at the same time.
A study of Apennine drainage, using the sequence of older-to-younger transected Apennine folds as a proxy for the historical evolution of drainage cutting through a single fold, shows that transverse drainage forms when sedimentation dominates at the advancing coastline. Longitudinal drainage forms when uplift dominates, the folds first emerge as offshore islands and the Mazzanti–Trevisan mechanism is suppressed.
Complicating factors include several departures from steady-state growth of the fold-thrust belt, a possible case of precursory submarine drainage, early emergence of anticlinal culminations and the location of several transverse canyons at the structurally highest point along anticlinal axes.  相似文献   

Experimental study of a 45-MHz array for radio astronomy     

H. Alvarez  J. Aparici  J. May  F. Olmos 《Experimental Astronomy》1994,5(3-4):315-328

The University of Chile transit radiotelescope is a 528-dipole array operating at 45 MHz. We present a comparison of an experimental study of the antenna radiation pattern with the basic theoretical pattern in three dimensions. We concentrate in the meridian plane diagram since this is particularly difficult to measure for an array like ours. The comparison shows excellent agreement. We have measured several important antenna parameters like the effective area as a function of zenith distance, the orientation of the plane of the array and the pointing accuracy. We include a detailed treatment of these subjects since not much information related to low frequency arrays for radio astronomy can be found in the literature. We discuss the importance of knowing these parameters in the preparation of the 45-MHz Sky Survey under way at the University of Chile Radio Observatory.  相似文献   

On the spectra of type-III solar radio bursts observed at low frequencies     

Héctor Alvarez 《Solar physics》1982,81(2):355-362

The spectra of strong bursts observed at low frequencies by OGO-5 during 1968–1970 are presented. They usually exhibit an intense main peak between 100 kHz and 1 MHz, and sometimes a less intense secondary peak between 1 and 3.5 MHz. Main peaks of 10^–12 Wm^–2 Hz^–1 or more were obtained in very strong events, but because of antenna calibration problems those could be one or two orders of magnitude too high. Recently published work supports the finding that type III bursts at low frequencies can be at least four orders of magnitude more intense than at ground-based frequencies of observation. It is found that the energy received at the Earth increases with decreasing frequency approximately as f ^–n, where 3 n 4.  相似文献