Louisiana State University

About: Louisiana State University is a education organization based out in Baton Rouge, Louisiana, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 40206 authors who have published 76587 publications receiving 2566076 citations. The organization is also known as: LSU & Louisiana State University and Agricultural and Mechanical College.

Sedimentation rates determined by 137 Cs dating in a rapidly accreting salt marsh

Abstract: SEA-LEVEL records indicate that the coast of Louisiana and other parts of the Gulf Coast are rapidly subsiding1. Louisiana is now losing approximately 16 square miles of land per year, primarily to subsidence2; the rates of subsidence vary with location. Vertical marsh accretion is the process which counteracts subsidence and eustatic sea-level rise and prevents marsh deterioration, but, as in Louisiana's salt marshes, the pattern, rate and variability are sufficiently complicated to defy simple prediction. Conditions of marsh development vary throughout the coast, from the modern and Atchafalaya deltas through the abandoned deltas to the Chenier Plain3. In recent years, much of the coastal area such as Barataria Basin has been deprived of river-borne sediment through natural stream diversion and the construction of water-control embankments. In addition, dredging from petroleum operations has altered water flow and sedimentation patterns. The survival and productivity of Gulf Coast marshes depend on the influx and accumulation of sediment that offsets the effect of subsidence and maintains the marsh surface within the tidal range. To predict long-range trends in marsh stability, accurate measurements are needed of both subsidence and sedimentation rates. Information on subsidence is available from tide gauge measurements but no measurements have been made of sedimentation rates in marshland developed on Recent Mississippi alluvium. 137Cs, a fallout product of nuclear testing, has become a useful tool for dating recent sedimentary sequency in lakes4–8. We report here its use in the measurement of sedimentation rates in a Louisiana coastal marsh, the first report of such use in coastal marshes.

Reinforcement and other consequences of sympatry.

Abstract: The pattern of greater species mating discrimination between sympatric taxa than between allopatric taxa has been attributed to the strengthening of mate discrimination to avoid maladaptive hybridization. This process, termed reinforcement, has been highly contentious, particularly with regard to its role in speciation. Here, I review some recent studies of reinforcement, discuss alternative explanations for the pattern of greater species discrimination in sympatric taxa, and point to some new directions that may help to clarify the evolutionary forces involved. In particular, we need more ecological work on putative cases of reinforcement, more theoretical models that give diagnostic predictions of reinforcement relative to other modes of divergence, and empirical studies to evaluate these diagnostic predictions.

Herschel Detects a Massive Dust Reservoir in Supernova 1987A

Abstract: We report far-infrared and submillimeter observations of supernova 1987A, the star whose explosion was observed on 23 February 1987 in the Large Magellanic Cloud, a galaxy located 160,000 light years away. The observations reveal the presence of a population of cold dust grains radiating with a temperature of about 17 to 23 kelvin at a rate of about 220 times the luminosity of the Sun. The intensity and spectral energy distribution of the emission suggest a dust mass of about 0.4 to 0.7 times the mass of the Sun. The radiation must originate from the supernova ejecta and requires the efficient precipitation of all refractory material into dust. Our observations imply that supernovae can produce the large dust masses detected in young galaxies at very high redshifts.

States and Markets: The Advantage of an Early Start

Abstract: States and markets have sometimes been viewed as competitors, but in the last decade, there has been increasing agreement that a capable state can play an important facilitating role in the process of economic development. A number of studies have explored the empirical connection between measures of political stability and bureaucratic competence, on the one hand, and rates of economic growth, on the other. There is some evidence from these, and also arguments at the case study level, that a stable and competent state is indeed a contributing factor in economic growth. In this short paper, we investigate the possibility that differences not only in state capacity but more broadly, in the capacity to mount an effective drive toward economic development, derive in part from very long run historical processes giving rise to different potentials for growth. We test the idea that more longstanding experience with a national state in the past is associated, in recent times, with (a) greater political stability and better quality government, (b) higher incomes, and (c) faster rates of economic growth.