195,715 research outputs found
Recommended from our members
Photo of Mr. Noe P. Jimenez (Photograph)
No full textMr. Noe P. Jimenez poses for the camera
Recommended from our members
A letter from Sarita Jimenez to Dr. Hector P. Garcia, asking for his support in her nomination for a delegation. Included is her Vitae.
No full textA letter from Sarita Jimenez to Dr. Hector P. Garcia, asking for his support in her nomination for a delegation. Included is her Vitae
Recommended from our members
A letter from Javier Jimenez-Ugarte to Dr. Hector P. Garcia, informing him that he won't be able to attend the Founder's Freedom Banquet.
No full textA letter from Javier Jimenez-Ugarte, Ambassador at the Houston Consulate of Spain, to Dr. Hector P. Garcia, informing him that he won't be able to attend the Founder's Freedom Banquet
Geochemical and petrographic characterization of the Bella Rica hydrothermal gold mineralization (Ponce Enriquez, Ecuador)
No full textBella Rica is sited in the Ponce Enriquez mining district (south of Ecuador), one of the most important gold mining areas in Ecuador, active since 1980’s. Gold mesothermal mineralization is hosted within Cretaceous mafic volcanic rocks of Pallatanga Units (Pratt et al., 2005).
The high level of heavy metal(loid)s concentration (As, Cu, Cd, Zn, and Pb) in stream sediments and other matrixes (surface water, soil, and biological) has been discussed in several studies (e.g., Williams et al., 2000; Jiménez-Oyola et al., 2021). The presence of heavy metal(loid)s in the mining district has been considered as due to the superposition of geogenic sources and mining activity. Gold is recovered by leaching with cyanide and flotation in artisanal activity and by a combination of amalgamation with mercury in the illegal mining activity. Despite aforementioned environmental investigations, the studies on the characterization and origin of the Au mineralization are still limited.
With the aim of contributing to the regional geological background, in this study, we present new data on the geochemical and petrographic features of the hydrothermal gold mineralization in the Ponce Enriquez area. Detailed maps of the distribution of selected heavy metal(loid)s are provided. Furthermore, petrologic investigations are carried out with the aim to characterize temperatures and composition of hydrothermal fluids involved in the genesis of Ponce Enriquez ore deposit. These data can help to increase the regional geological knowledge and the promotion of the sustainable development of Ecuador metalliferous mineral sector.
Jimenez-Oyola S., Garcia-Martinez M.-J., Ortega M.F., Chavez E., Garcia-Garizabal I. & Bolonio D. (2021) - Ecological and probabilistic human health risk assessment of heavy metal(loid)s in river sediments affected by mining activities in Ecuador. Environ. Geochem. Health, 43, 4459-4474.
Pratt W.T., Duque P. & Ponce M. (2005) - An autochthonous geological model for the eastern Andes of Ecuador. Tectonophysics, 399, 251-278.
Williams T.M., Dunkley P.N., Cruz E., Actimbay V., Gaibor A., Lopez E., Baez N. & Aspden J.A. (2000) - Regional geochemical reconnaissance of the Cordillera Occidental of Ecuador: economic and environmental applications. Appl. Geochem., 15, 531-550
Designation of European Working Group on Legionella Infection (EWGLI) amplified fragment polymorphism types of Legionella pneumophila serogroup 1 and results of intercentre proficiency testing using a standard protocol.
No full text
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Application of an all-solid-state diode-laser-based sensor for carbon monoxide detection by optical absorption in the 4.4 4.8 ��m spectral region
No full textAn all-solid-state continuous-wave (cw) laser system for mid-infrared absorption measurements
of the carbon monoxide (CO) molecule has been developed and demonstrated. The single-mode, tunable
output of an external-cavity diode laser (ECDL) is difference-frequency mixed (DFM) with the output of a
550-mW diode-pumped cw Nd:YAG laser in a periodically-poled lithium niobate (PPLN) crystal to
produce tunable cw radiation in the mid-infrared. The wavelength of the 860-nm ECDL can be coarse
tuned between 860.78 to 872.82 nm allowing the sensor to be operated in the 4.4 4.8 ��m region. Results
from single-pass mid-IR direct absorption experiments for CO concentration measurements are discussed.
CO measurements were performed in CO/CO2/N2 mixtures in a room temperature gas cell that allowed the
evaluation of the sensor operation and data reduction procedures. Field testing was performed at two
locations: in the exhaust of a well-stirred reactor (WSR) at Wright-Patterson Air Force Base and the
exhaust of a gas turbine at Honeywell Engines and Systems. Field tests demonstrated the feasibility of the
sensor for operation in harsh combustion environments but much improvement in the sensor design and
operation was required. Experiments in near-adiabatic hydrogen/air CO2-doped flames were performed
featuring two-line thermometry in the 4.8 ��m spectral region. The sensor concentration measurement
uncertainty was estimated at 2% for gas cell testing. CO concentration measurements agreed within 15%
of conventional extractive sampling at WSR, and for the flame experiments the repeatability of the peak
absorption gives a system uncertainty of 10%. The noise equivalent CO detection limit for these
experiments was estimated at 2 ppm per meter, for combustion gas at 1000 K assuming a SNR ratio of 1
Quantum motion of a squeezed mechanical oscillator attained via an optomechanical experiment
No full textWe experimentally investigate a mechanical squeezed state realized in a parametrically modulated membrane resonator embedded in an optical cavity. We demonstrate that a quantum characteristic of the squeezed dynamics can be revealed and quantified even in a moderately warm oscillator, through the analysis of motional sidebands. We provide a theoretical framework for quantitatively interpreting the observations and present an extended comparison with the experiment. A notable result is that the spectral shape of each motional sideband provides a clear signature of a quantum mechanical squeezed state without the necessity of absolute calibrations, in particular in the regime where residual fluctuations in the squeezed quadrature are reduced below the zero-point level. </p
Maximum Search Using P Systems
No full textSeveral algorithms of maximum search are investigated and eval-
uated in different types of P systems, namely using priorities, multiple nested
membranes and linked transport. The proposed solutions are expected to find
application in a wide range of problems. In particular, the authors are currently working on modeling an algorithm for DNA sequence alignment using
P systems
- …
