Commercial whaling,tourism, and boycotts: An economic perspective     

Guillermo E. Herrera  Porter Hoagland 《Marine Policy》2006

Commercial whaling is highly contentious, angering animal rights groups and conservation organizations, who threaten boycotts. Proponents of whaling argue that many whale stocks are plentiful enough to support sustainable harvests. In terms of economic efficiency, a nation's decision to engage in whaling depends on rents from the whaling industry, ecological and market linkages, and the potential for boycotts. We analyze the tradeoffs involved in a nation's decision to engage in whaling, whale-watching, and fishing. Scenarios exist in which whaling is economically rational. Indeed, sometimes it makes economic sense to subsidize whaling. In other circumstances, market pressures make commercial whaling inefficient.  相似文献   

Parent stars of extrasolar planets – VIII. Chemical abundances for 18 elements in 31 stars     

Guillermo Gonzalez  Chris Laws 《Monthly notices of the Royal Astronomical Society》2007,378(3):1141-1152

We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets (SWPs). The resulting abundances are combined with other similar studies of nearby SWPs and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of SWPs in the SPOCS data base. We encourage continued study of the abundance patterns of SWPs to resolve these discrepancies.  相似文献   

Spatio-temporal variability of benthic macroalgae in a coral reef system highly influenced by fluvial discharge: Veracruz,Gulf of Mexico     

Guillermo Horta-Puga  José Luis Tello-Musi  Alejandro Córdova  Adriana Gutiérrez-Carrillo  Jhoan Gutiérrez-Martínez  Aura Aletse Morales-Aranda 《Marine Ecology》2020,41(4):e12596

The Veracruz Reef System, in the southern Gulf of Mexico, is a suitable area for the study of the temporal and spatial variability of macroalgae abundance, at reef settings influenced by the fluvial discharge of the Jamapa River, and by human activities in the city and port of Veracruz. With this purpose, the bottom cover of each morpho-functional group of benthic macroalgae (frondoses, turf, and crustose corallines), and hermatypic corals, was determined at ten selected coral reefs, on a seasonal basis (rainy and dry seasons), for the 2009–2015 period. The average cover of benthic macroalgae was high (53.1%), with turf as the dominant morpho-functional group (31.9%), as in several reef ecosystems in the tropical Atlantic, followed by crustose corallines (15.2%), and frondoses (6.1%). Although turf macroalgae is dominant, due to their high temporal and spatial variability, the Veracruz Reef System could not be considered to be in a stable state, but just in an intermediate unstable equilibrium state, which is highly influenced by a high sediment load. As expected, nearshore reefs presented higher macroalgae covers, and unexpectedly, the outer-shelf reefs presented the highest cover of frondoses. Despite fluvial discharge influence, no differences in cover were found between the rainy and dry seasons. There was a negative and significantly correlation between the cover of frondoses and turf, which suggests that the driver/s of the abundance of these macroalgae, act in opposite ways for each group. Three clusters of reefs, defined by community structure and conservation degree, were determined: nearshore or degraded, offshore or moderately conserved, and conserved; and the entire Veracruz Reef System is considered to be in a moderately state of conservation.  相似文献   

Practicing community geography in times of crisis     

Shannon  Jerry  Torres  Hannah  Mariner  Kathryn A.  Hawthorne  Timothy L. 《GeoJournal》2021,87(2):151-157

Community geography emphasizes the centrality of community engagement to socially transformative research. This introduction to a special issue of GeoJournal on community geography outlines how this growing subfield provides a model for collaborative action with the crises of our time, from white supremacy through climate change. As the co-editors of this special issue, we summarize the contents of these 14 articles, grouping them by the shared themes of power, institutional partnerships, pedagogy, and methods.

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A Hubble Space Telescope/NICMOS view of the prototypical giant Hii region NGC604 in M33     

Rodolfo H. Barbá  Jesús Maíz Apellániz  Enrique Pérez  Mónica Rubio  Alberto Bolatto  Cecilia Fariña  Guillermo Bosch  Nolan R. Walborn 《Astrophysics and Space Science》2009,324(2-4):309-313

We present the first high-spatial-resolution near-infrared (NIR) imaging of NGC604, obtained with the NICMOS camera onboard the Hubble Space Telescope (HST). These NICMOS broad-band images reveal new NIR point sources, clusters, and diffuse structures. We find an excellent spatial correlation between the 8.4 GHz radio continuum and the 2.2 μm nebular emission. Moreover, massive young stellar object candidates appear aligned with these radio peaks, reinforcing the idea that those areas are star-forming regions. Three different scaled OB associations are recognized in the NICMOS images. The brightest NIR sources in our images have properties that suggest that they are red supergiant stars, of which one was previously known. This preliminary analysis of the NICMOS images shows the complexity of the stellar content of the NGC604 nebula.  相似文献   

Optical spectroscopy and Doppler tomography of Cygnus X-2     

P. Elebert  P. J. Callanan  M. A. P. Torres  M. R. Garcia 《Monthly notices of the Royal Astronomical Society》2009,395(4):2029-2038

We present phase resolved optical spectroscopy and Doppler tomography of V1341 Cygni, the optical counterpart to the neutron star low-mass X-ray binary (LMXB) Cygnus X-2 (Cyg X-2). We derive a radial velocity (RV) curve for the secondary star, finding a projected RV semi-amplitude of   K ₂= 79 ± 3 km s⁻¹  , leading to a mass function of  0.51 ± 0.06 M_⊙, ∼30  per cent lower than the previous estimate. We tentatively attribute the lower value of K ₂ (compared to that obtained by other authors) to variations in the X-ray irradiation of the secondary star at different epochs of observations. The limited phase coverage and/or longer timebase of previous observations may also contribute to the difference in K ₂. Our value for the mass function implies a primary mass of  1.5 ± 0.3 M_⊙  , somewhat lower than previous dynamical estimates, but consistent with the value found by analysis of type-I X-ray bursts from this system. Our Doppler tomography of the broad He  ii λ4686 line reveals that most of the emission from this line is produced on the irradiated face of the donor star, with little emission from the accretion disc. In contrast, the Doppler tomogram of the N  iii λ4640.64 Bowen blend line shows bright emission from near the gas stream/accretion disc impact region, with fainter emission from the gas stream and secondary star. This is the first LMXB for which the Bowen blend is dominated by emission from the gas stream/accretion disc impact region, without comparable emission from the secondary star. This has implications for the interpretation of Bowen blend Doppler tomograms of other LMXBs for which the ephemeris may not be accurately known.  相似文献   

Integrated spectroscopic study of 7 star clusters in the Small Magellanic Cloud     

M.L. Talavera  A.V. Ahumada  J.F.C. Santos  Jj. Clari  E. Bica  M.C. Parisi  M.C. Torres 《Astronomische Nachrichten》2010,331(3):323-329

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Self-Similar and Self-Affine Properties of Two-Dimensional Fracture Patterns in Rocks   总被引：1，自引：0，他引：1  

Alejandra Aguilar-Hernández  Guillermo Ramírez-Santiago 《Mathematical Geosciences》2010,42(8):925-954

In this paper, we investigate the fractal properties of binary maps of rock fractures at different scales and different geological types, as well as different families of fracture patterns obtained from a two-dimensional Laplacian growth model (LGM). From these analyses we figure out which families of the LGM patterns match the structural properties of the fracture binary maps. The LGM is defined in terms of a nonlinear map that depends on two parameters, λ and \mathfraka\mathfrak{a}, that respectively define the area and shape of the elements of the aggregate that conforms the patterns. The fractal dimension and roughness exponent of the LGM patterns are found to depend on \mathfraka\mathfrak{a}, with 0 < \mathfrak a < 10<\mathfrak {a}<1. From a detailed statistical analysis of these patterns we found that the fractal dimensions of capacity, correlation and information decrease monotonically as \mathfraka\mathfrak{a} increases. We also found that the values of these three fractal dimensions tend to collapse on top of each other as \mathfraka\lessapprox1\mathfrak{a}\lessapprox1. Remarkably, the fractal properties of rock fractures in the scales from millimeters up to a few meters appear to be well represented by the fractal structure of the LGM families of patterns with \mathfraka=0.15\mathfrak{a}=0.15 and 0.30, while the fractal properties of rock fractures in the scale of kilometers seems to be well represented by the LGM family with \mathfraka=0.90\mathfrak{a}=0.90. In addition, the three fractal dimension values of fracture binary maps in the scales from millimeters up to meters were found to be different between them. Nonetheless, for fractures in the scale of kilometers, the values of the three fractal dimensions are very close to each other as an indication of self-similar behavior. Analysis of the corrections to the scaling of the roughness exponent, ζ, suggests that they are negligible for the LGM family of fracture patterns with \mathfraka=0.9\mathfrak{a}=0.9. This finding points to a self-affine structure for this family of patterns. In fact, the calculated roughness exponent results are in the range of values characteristic of rock fractures.  相似文献   

Energy balance and turbulent flux partitioning in a corn–soybean rotation in the Midwestern US     

Guillermo Hernandez-Ramirez  Jerry L. Hatfield  John H. Prueger  Thomas J. Sauer 《Theoretical and Applied Climatology》2010,100(1-2):79-92

Quantifying the energy balance above plant canopies is critical for better understanding of water balance and changes in regional weather patterns. This study examined temporal variations of energy balance terms for contrasting canopies [corn (Zea mays L.) and soybean (Glycine max L. Merr.)]. We monitored energy balance for 4 years using eddy-covariance systems, net radiometers, and soil heat flux plates in adjacent production fields near Ames, Iowa. On an annual basis, soybean exhibited 20% and 30% lower sensible heat flux (H) and Bowen ratio than corn, respectively. As canopies developed, a gradual shift in turbulent fluxes occurred with decreasing H and increasing latent heat flux (LE), but with a more pronounced effect for corn. Conversely, during mid-growing season and as both canopies progressively senesced, H in general increased and LE decreased; however, soybean exhibited slightly greater LE and much lower H than corn. These temporal variations in magnitude and partitioning of turbulent fluxes translated into a pronounced energy imbalance for soybean (0.80) and an enhanced closure for corn (0.98) in August and September. These discrepancies could be directly associated with differences in momentum transport as shown by friction velocities of 0.34 and 0.28 m s^?1 for corn and soybean, respectively. These results support influential roles of plant canopy on intensity and mode of surface energy exchange processes.  相似文献   

Collective effects of stellar winds and unidentified gamma-ray sources     

Diego F. Torres  Eva Domingo-Santamaría 《Astrophysics and Space Science》2007,309(1-4):345-350

We study collective wind configurations produced by a number of massive stars, and obtain densities and expansion velocities of the stellar wind gas that is to be target, in this model, of hadronic interactions. We study the expected γ-ray emission from these regions, considering in an approximate way the effect of cosmic ray modulation. We compute secondary particle production (electrons from knock-on interactions and electrons and positrons from charged pion decay), and solve the loss equation with ionization, synchrotron, bremsstrahlung, inverse Compton, and expansion losses. We provide examples where configurations can produce sources for GLAST satellite, and the MAGIC, HESS, or VERITAS telescopes in non-uniform ways, i.e., with or without the corresponding counterparts. We show that in all cases we studied no EGRET source is expected.  相似文献