Some results of 22-year monitoring (1982–2003) of Sagittarius B2 in the 1.35-cm line     

E. E. Lekht  O. Ramírez Hernández  A. M. Tolmachev 《Astronomy Reports》2004,48(12):965-978

A catalog of λ=1.35 cm water-vapor maser spectra in Sgr B2 obtained in 1992–2003 is presented; this supplements our results for earlier observations in 1982–1992. Sgr B2 was monitored using the 22 m radio telescope of the Pushchino Radio Astronomy Observatory. The whole monitoring dataset for 1982–2003 has been analyzed. The emission received is a superposition of radiation from various parts of the entire Sgr B2 region, but the main contribution is made by two sources: Sgr B2(M) and Sgr B2(N). The monitoring did not reveal any long-term component of the integrated maser flux variations with a period shorter than 20 years. The flare component of the flux variability and a short-period component with a mean period of two years have been found. The latter are correlated with variations of the velocity centroid, supporting the reality of the short-period variations. It is likely that all the various types of variations are inherent to both Sgr B2(M) and Sgr B2(N), and represent a superposition of the variations occurring in each of these sources. There is an alternation of maxima of the emission from Sgr B2(M) and Sgr B2(N).  相似文献   

Measuring geocentric radial coordinates with a non-fiducial GPS network     

A. Rius  J. M. Juan  M. Hernández-Pajares  A. M. Madrigal 《Journal of Geodesy》1995,69(4):320-328

In this paper we address the problem of estimating the short term precision of the geocentric radial coordinate of a GPS receiver placed on the Earth crust using a non-fiducial approach. The network used in our analysis contains 35 receivers distributed globally. We have analyzed the data with two different strategies: global and regional. In the global strategy the results obtained, which are compatible with those of Heflin et al. (1992) and Blewitt et al. (1992), provide a weighted root mean square of the residuals (wrms) one order of magnitude larger than the formal errors of the individual estimates. Our regional strategy is based on the assumption that errors in the orbit determination induce errors in the receiver positions, correlated up to large scales. This approach allows us to obtain a significant agreement between the wrms and the formal errors.  相似文献   

Crater Lake Temperature Changes of the 2005 Eruption of Santa Ana Volcano,El Salvador,Central America     

P. A. Hernández  N. M. Pérez  J. C. Varekamp  B. Henriquez  A. Hernández  J. Barrancos  E. Padrón  D. Calvo  G. Melián 《Pure and Applied Geophysics》2007,164(12):2507-2522

A sudden eruption at Santa Ana occurred on 1 October 2005, producing an ash-and-gas plume to a height in excess of 10 km above the volcano. Several days before, thermal infrared images of the crater provided precursory signals of the eruption. A significant increase in the extent and intensity of the fumarolic field inside the crater rim and of the surface temperature of the crater’s lake was observed. Changes in energy input was also estimated to explain the increase in lake temperature based on energy/mass balance calculations.  相似文献   

Precursory Subsurface 222Rn and 220Rn Degassing Signatures of the 2004 Seismic Crisis at Tenerife, Canary Islands     

Nemesio M. Pérez  Pedro A. Hernández  Eleazar Padrón  Gladys Melián  Rayco Marrero  Germán Padilla  José Barrancos  Dácil Nolasco 《Pure and Applied Geophysics》2007,164(12):2431-2448

Precursory geochemical signatures of radon degassing in the subsurface of the Tenerife Island were observed several months prior to the recent 2004 seismic-volcanic crisis. These premonitory signatures were detected by means of a continuous monitoring of ²²²Rn and ²²⁰Rn activity from a bubbling CO₂-rich gas spot located at 2.850 m depth inside a horizontal gallery for groundwater exploitation at Tenerife. Multivariate Regression Analysis (MRA) on time series of the radon activity was applied to eliminate the radon activity fluctuation due to external variables such as barometric pressure, temperature and relative humidity as well as power supply. Material Failure Forecast Method (FFM) was successfully applied to forecast the anomalous seismicity registered in Tenerife Island in 2004. The changes in the ²²²Rn/²²⁰Rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and/or changes in the vertical permeability induced by seismic activity.  相似文献   

Laboratory tests of steel simple torsionally unbalanced models     

Jaime De‐la‐Colina  Qutberto Acuña  Alejandro Hernández  Jesús Valdés 《地震工程与结构动力学》2007,36(7):887-907

The objective of this work is to obtain estimations of the amplification factors α and δ used for torsion design of buildings, from experiments. For this study, simple one‐storey torsionally unbalanced (TU) steel models were considered. Models consisted of a deck supported on four columns with a selected arrangement of hinges at column ends. Two theoretical structural eccentricities (e = 0.05 and 0.15) were considered. Models were excited with a simple long‐period pendulum consisting of a hanging platform with a forced‐vibration generator on it. Eight models were tested at several excitation levels (frequencies and force magnitudes) in both ranges of behaviour: elastic and inelastic. Experiments were conducted at three frequency ratios of excitation. Registered accelerations of the pendulum platform indicate that the experimental set‐up leads to excitations that resemble narrow‐band seismic ground motions. Frame shear force estimations, based on accelerations recorded at both deck sides, indicate that torsion design factors (α and δ) depend on eccentricity. Estimations of frame shears based on measurements indicate that for normalized eccentricities e ? 0.025, the amplification α can be between 2 and 3; while δ factor resulted between 0.0 and 1.6. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Quaternary sedimentation and active faulting along the Ecuadorian shelf: preliminary results of the ATACAMES Cruise (2012)     

F. Michaud  J. N. Proust  J. Y. Collot  J. F. Lebrun  C. Witt  G. Ratzov  H. Pouderoux  C. Martillo  M. J. Hernández  G. Loayza  L. Penafiel  L. Schenini  A. Dano  M. Gonzalez  D. Barba  L. De Min  G. Ponce  A. Urresta  M. Calderon 《Marine Geophysical Researches》2015,36(1):81-98

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Nesting ecology of East Pacific green turtles at Playa Cabuyal,Gulf of Papagayo,Costa Rica          下载免费PDF全文

Pilar Santidrián Tomillo  Spencer A. Roberts  Ricardo Hernández  James R. Spotila  Frank V. Paladino 《Marine Ecology》2015,36(3):506-516

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Monitoring the Solar Radius from the Royal Observatory of the Spanish Navy since 1773     

J. M. Vaquero  M. C. Gallego  J. J. Ruiz-Lorenzo  T. López-Moratalla  V. M. S. Carrasco  A. J. P. Aparicio  F. J. González-González  E. Hernández-García 《Solar physics》2016,291(6):1599-1612

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Detection of spatial fluctuations of non-point source fecal pollution in coral reef surrounding waters in southwestern Puerto Rico using PCR-based assays     

Bonkosky M  Hernández-Delgado EA  Sandoz B  Robledo IE  Norat-Ramírez J  Mattei H 《Marine pollution bulletin》2009,58(1):45-54

Human fecal contamination of coral reefs is a major cause of concern. Conventional methods used to monitor microbial water quality cannot be used to discriminate between different fecal pollution sources. Fecal coliforms, enterococci, and human-specific Bacteroides (HF183, HF134), general Bacteroides-Prevotella (GB32), and Clostridium coccoides group (CP) 16S rDNA PCR assays were used to test for the presence of non-point source fecal contamination across the southwestern Puerto Rico shelf. Inshore waters were highly turbid, consistently receiving fecal pollution from variable sources, and showing the highest frequency of positive molecular marker signals. Signals were also detected at offshore waters in compliance with existing microbiological quality regulations. Phylogenetic analysis showed that most isolates were of human fecal origin. The geographic extent of non-point source fecal pollution was large and impacted extensive coral reef systems. This could have deleterious long-term impacts on public health, local fisheries and in tourism potential if not adequately addressed.  相似文献   

SO2 Emission from Active Volcanoes Measured Simultaneously by COSPEC and mini-DOAS   总被引：1，自引：0，他引：1  

José Barrancos  José I. Roselló  David Calvo  Eleazar Padrón  Gladys Melián  Pedro A. Hernández  Nemesio M. Pérez  Millán M. Millán  Bo Galle 《Pure and Applied Geophysics》2008,165(1):115-133

We measured SO₂ emission rate from six volcanoes in Latin America (Santa Ana, El Salvador; San Cristóbal and Masaya, Nicaragua; Arenal and Poás, Costa Rica; Tungurahua and Sierra Negra, Ecuador) and from Mt. Etna, Italy, using two different remote sensing techniques: COSPEC (COrrelation SPECtrometer) and miniDOAS (miniaturized Differential Optical Absorption Spectroscopy). One of the goals of this study was to evaluate the differences in SO₂ emission rates obtained by these two methods. The observed average SO₂ emission rates measured during this study were 2688 t·d⁻¹ from Tungurahua in July 2006, 2375 t·d⁻¹ in September 2005 and 480 t·d⁻¹ in February 2006 from Santa Ana, 1200 t·d⁻¹ in May 2005 from Etna, 955 t·d⁻¹ in March 2006 and 1165 t·d⁻¹ in December 2006 from Masaya, 5400 t·d⁻¹ of March 7, 2006 and 265 t·d⁻¹ in March 2006 from San Cristobal, 113 t·d⁻¹ in April 2006 from Arenal, 104 t·d⁻¹ in April 2006 from Poás and 11 t·d⁻¹ in July 2006 from Sierra Negra volcano. Most of the observed relative differences of SO₂ emission measurements from COSPEC and miniDOAS were lower than 10%.  相似文献