Ridge event detection: T-phase signals from the Juan de Fuca spreading center

An analysis of T-phase source locations determined in the mid-1960s for an area of the northeast Pacific Ocean encompassing the Juan de Fuca spreading center reveals that most of the source locations are associated with regions where seamount chains intersect the spreading center and with edifices both along and near the spreading center. The T-phase source locations also tend to cluster on, or near, areas of the most concentrated and vigorous hydrothermal venting along the Juan de Fuca Ridge. Of the 58 T-phase source locations determined for a period from October 1964 through December 1966, only one was found to be associated with an earthquake detected by the National Geophysical Data Center/National Earthquake Information Service because of the characteristic small magnitude of spreading-center seismic events. Monitoring T-phase activity originating along the 80 000 km-long global seafloor spreading-center system offers a practical and unique opportunity to better understand the dynamics and oceanic effects of episodic spreading-center tectonic, volcanic, and hydrothermal processes.     

Ecosystem service values of sediment generation and entrapment by marginal coral reefs at Sodwana Bay,South Africa

Coral reefs provide a multitude of goods and services, some of which are difficult to value due to their intangible nature and the absence of markets to ascribe their relative worth. The coral reefs of Sodwana Bay on the northeast coast of South Africa provide several ecological goods and services, of which only two are considered here: namely, sediment generation and sediment entrapment. Both are deemed essential to the functioning of the Sodwana Bay economy. The replacement-cost method was used to estimate the annual financial cost of sediment provided to the study area if it were replaced by dredging. Sediment generation by the coral reefs was valued at R2.6–R4.8 million, and sediment entrapment valued at R71.8–R84.6 million, totalling between R74.4 million and R89.4 million (≈$5.6–$6.7 million, at R13.38/US$1) per year.     

Possible role of oceanic heat transport in early Eocene climate

Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an approximately 30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.     

Quenching of auroral hydrogen line emission by collisional ionization

With the aid of the classical impulse approximation a simple formula is derived for the cross section for electron loss from fast excited hydrogen atoms passing through a neutral gas. Detailed computations relevant to the quenching of hydrogen line emission in auroras are performed. It is found, incidentally, that the population distribution amongst the states of a level is unlikely to be brought into statistical equilibrium by the collisions suffered by the hydrogen atoms.     

Neoliberal development through technical assistance: Constructing communities of entrepreneurial subjects in Oaxaca, Mexico

Technical assistance (TA) has a long and varied history as a development practice. It initially emerged as a set of ‘hard’ programs, tools, and technologies delivered to developing countries by imported First World experts, typically in the agricultural and resource sectors. Later, in response to critical and antidevelopment theories, TA morphed into its ‘soft’ version, attempting to empower marginalized people in the Global South by delivering the know-how - often collaboratively generated - sufficient to produce forms of development ‘from below’. In spite of this shift in the politics and practices of TA, it remains susceptible to neoliberal styles of development that have proceeded apace with withdrawal of state institutions in the funding and operation of social and economic development programs, and with the concomitant rise of nongovernmental organizations (NGOs).In this paper, we follow the operation of one TA program operated by an intermediary NGO in Oaxaca, Mexico. We find that the program intersects with neoliberalization in two prominent ways, relying on a form of governmentality that codifies and prescribes: (a) the social spaces of action and need, and (b) learning subjects deficient in entrepreneurial initiative and know-how. We conclude by commenting on the political economic conditions that continue to underwrite TA as a development practice in spite of a decade or more of criticism directed at it and we consider the possibilities for its subversion.     

The angular momentum-vs-mass relation and the distribution of mass ratios for visual binary systems

The investigation of the angular momentum vs mass relation for binary stars is completed with a study of the 847 systems contained in theFourth Catalog of Orbits of Visual Binary Stars. Because bothJ andM of a visual binary depend steeply on the distance to the system (5th and 3rd powers, respectively), and many of the distances are not well known, the study makes use of an auxiliary parameterR which is independent of distance and proportional toJM ^–5/3.R appears to be uncorrelated withM for the 789 systems for which both can be determined. The non-correlation implies thatJ M ^5/3, expected from Kepler's third law, provides a better fit to the visual binaries than doesJ M ², predicted by some more complex considerations.The distribution functionf(q=M ₂/M₁) of mass ratios for the visual binaries results as a byproduct of the investigation. It peaks extremely sharply towardq=1.0 (much more so than for spectroscopic binaries). Because most visual binaries are wide enough to consist of stars that condensed independently (and so that can be thought of as chosen at random from an initial mass function), one expects the realf(q) to rise toward low ratios. Observational selection against the discovery and study of systems with large magnitude differences between the components must be very large indeed to account for the discrepancy between expectation and observation. The alternative is a mechanism for formation of wide binaries that favours equal components. The distribution of mass ratios for eclipsing binaries is given in an appendix. It peaks strongly atq=0.6–0.75 and largely reflects processes of angular momentum, mass, and energy exchange between the stars in contact systems.     

The eclipsing binary system W Cru

PhotoelectricUBV photometry of the long period southern eclipsing binary system W Cru gathered over an 18-mo period in 1984–1985 is presented and examined.The light curve is characterized by continuous Beta Lyrae-like variation: unexpected in such a long period (198.5 days) system; together with peculiar irregularities, of the order of 0.1 mag (or more inU) and time-scales of a few days.A high mass model (total mass 70M ) could be made to be roughly consistent with the data, though alternative models of much lower mass are also possible, and may turn out to be preferable, in terms of goodness-of-fit, as well as for theoretical reasons. The low mass models would require, though, the more massive component to be unseen (as now generally supposed for Lyrae itself).The photometry alone, or even combined with a known spectroscopic mass-function, seems unlikely to be able to furnish a single definitive solution, and more guidelines from reliable theoretical expectation may prove helpful in interpreting the data.     

Mangrove Range Expansion Rapidly Increases Coastal Wetland Carbon Storage

The climate change-induced expansion of mangroves into salt marshes could significantly alter the carbon (C) storage capacity of coastal wetlands, which have the highest average C storage per land area among unmanaged terrestrial ecosystems. Mangrove range expansion is occurring globally, but little is known about how these rapid climate-driven shifts may alter ecosystem C storage. Here, we quantify current C stocks in ecotonal wetlands across gradients of marsh- to mangrove-dominance, and use unique chronological maps of vegetation cover to estimate C stock changes from 2003 to 2010 in a 567-km² wildlife refuge in the mangrove-salt marsh ecotone. We report that over the 7-yr. period, total wetland C stocks increased 22 % due to mangrove encroachment into salt marshes. Newly established mangrove stands stored twice as much C on a per area basis as salt marsh primarily due to differences in aboveground biomass, and mangrove cover increased by 69 % during this short time interval. Wetland C storage within the wildlife refuge increased at a rate of 2.7 Mg C ha^?1 yr.^?1, more than doubling the naturally high coastal wetland C sequestration rates. Mangrove expansion could account for a globally significant increase of terrestrial C storage, which may exert a considerable negative feedback on warming.