Iron and iron/manganese ratio in forage from Icelandic sheep farms: relation to scrapie

This study was undertaken in order to examine whether any connection existed between the amounts of iron in forage and the sporadic occurrence of scrapie observed in certain parts of Iceland. As iron and manganese are considered antagonistic in plants, calculation of the Fe/Mn ratios was also included by using results from Mn determination earlier performed in the same samples. Forage samples (n = 170) from the summer harvests of 2001–2003, were collected from 47 farms for iron and manganese analysis. The farms were divided into four categories: 1. Scrapie-free farms in scrapie-free areas (n = 9); 2. Scrapie-free farms in scrapie-afflicted areas (n = 17); 3. Scrapie-prone farms (earlier scrapie-afflicted, restocked farms) (n = 12); 4. Scrapie-afflicted farms (n = 9). Farms in categories 1 and 2 are collectively referred to as scrapie-free farms. The mean iron concentration in forage samples from scrapie-afflicted farms was significantly higher than in forage samples from farms in the other scrapie categories (P = 0.001). The mean Fe/Mn ratio in forage from scrapie-afflicted farms was significantly higher than in forage from scrapie-free and scrapie-prone farms (P < 0.001). The results indicated relative dominance of iron over manganese in forage from scrapie-afflicted farms as compared to farms in the other categories. Thus thorough knowledge of iron, along with manganese, in soil and vegetation on sheep farms could be a pivot in studies on sporadic scrapie

Energy Injection Episodes in Gamma Ray Bursts: The Light Curves and Polarization Properties of GRB 021004

Several GRB afterglow light curves deviate strongly from the power law decay observed in most bursts. We show that these variations can be accounted for by including refreshed shocks in the standard fireball model previously used to interpret the overall afterglow behavior. As an example we consider GRB 021004 that exhibited strong light curve variations and has a reasonably well time-resolved polarimetry. We show that the light curves in the R-band, X-rays and in the radio can be accounted for by four energy injection episodes in addition to the initial event. The polarization variations are shown to be a consequence of the injections.Comment: 4 pages, 2 figures. To appear in ApJ

“Securing the State”: James Madison, Federal Emergency Powers, and the Rise of the Liberal State in Postrevolutionary America

At a session of the Confederation Congress on February 19, 1787, James Madison rose to reflect on the federal government's failed attempts to mobilize an armed force to quell the Massachusetts Regulation, commonly known as Shays's Rebellion. The uprising, led by the Revolutionary War veteran Daniel Shays, had begun in August 1786 and was wreaking havoc throughout central and western Massachusetts and neighboring states. After a series of frustrated attempts to muster the militia to repress the “traitorous proceedings” in the fall of 1786, Secretary of War Henry Knox and the Massachusetts authorities, led by the old revolutionaries James Bowdoin and Samuel Adams, decided to invite the central government to claim new powers over domestic rebellion and forcibly put an end to the tumult. While the central government embraced the idea of new power, Congress was even more powerless to act than the state government and could only observe as the rebellion raged through Massachusetts during the winter of 1786–1787. In Madison's analysis, the problem of federal power boiled down to constitutional, institutional, and ideological factors. First, “it appeared rather difficult to reconcile an interference of Congress in the internal controversies of a State with the tenor of the Confederation which does not authorize it explicitly, and leaves to the States all powers not expressly delegated.” Second, Congress did not possess the fiscal or military capacity to act. It did not control a body of soldiers to deploy, and its attempts to request money from its constitutive states to raise a new army were met with indifference. Finally, federal imposition did not accord with republican ideology. Such action violated “the principles of Republican Gov.,” he noted, “which as they rest on the sense of the majority, necessarily suppose power and right always to be on the same side.

Max-and-Smooth: a two-step approach for approximate Bayesian inference in latent Gaussian models

This is the final version. Available on open access from International Society for Bayesian Analysis (ISBA) via the DOI in this record. With modern high-dimensional data, complex statistical models are necessary, requiring computationally feasible inference schemes. We introduce Max-and-Smooth, an approximate Bayesian inference scheme for a flexible class of latent Gaussian models (LGMs) where one or more of the likelihood parameters are modeled by latent additive Gaussian processes. Max-and-Smooth consists of two-steps. In the first step (Max), the likelihood function is approximated by a Gaussian density with mean and covariance equal to either (a) the maximum likelihood estimate and the inverse observed information, respectively, or (b) the mean and covariance of the normalized likelihood function. In the second step (Smooth), the latent parameters and hyperparameters are inferred and smoothed with the approximated likelihood function. The proposed method ensures that the uncertainty from the first step is correctly propagated to the second step. Since the approximated likelihood function is Gaussian, the approximate posterior density of the latent parameters of the LGM (conditional on the hyperparameters) is also Gaussian, thus facilitating efficient posterior inference in high dimensions. Furthermore, the approximate marginal posterior distribution of the hyperparameters is tractable, and as a result, the hyperparameters can be sampled independently of the latent parameters. In the case of a large number of independent data replicates, sparse precision matrices, and high-dimensional latent vectors, the speedup is substantial in comparison to an MCMC scheme that infers the posterior density from the exact likelihood function. The proposed inference scheme is demonstrated on one spatially referenced real dataset and on simulated data mimicking spatial, temporal, and spatio-temporal inference problems. Our results show that Max-and-Smooth is accurate and fast.NER

Multi-wavelength constraints on cosmic-ray leptons in the Galaxy

Cosmic rays (CRs) interact with the gas, the radiation field and the magnetic field in the Milky Way, producing diffuse emission from radio to gamma rays. Observations of this diffuse emission and comparison with detailed predictions are powerful tools to unveil the CR properties and to study CR propagation. We present various GALPROP CR propagation scenarios based on current CR measurements. The predicted synchrotron emission is compared to radio surveys, and synchrotron temperature maps from WMAP and Planck, while the predicted interstellar gamma-ray emission is compared to Fermi-LAT observations. We show how multi-wavelength observations of the Galactic diffuse emission can be used to help constrain the CR lepton spectrum and propagation. Finally we discuss how radio and microwave data could be used in understanding the diffuse Galactic gamma-ray emission observed with Fermi-LAT, especially at low energies.Comment: 8 pages, 5 figures; in Proceedings of the 34th International Cosmic Ray Conference (ICRC 2015), The Hague (The Netherlands); Oral contributio

Geology of Tindfjallajökull volcano, Iceland

The geology of Tindfjallajökull volcano, southern Iceland, is presented as a 1:50,000 scale map. Field mapping was carried out with a focus on indicators of past environments. A broad stratocone of interbedded fragmental rocks and lavas was constructed during Tindfjallajökull’s early development. This stratocone has been dissected by glacial erosion and overlain by a variety of mafic to silicic volcanic landforms. Eruption of silicic magma, which probably occurred subglacially, constructed a thick pile of breccia and lava lobes in the summit area. Mafic to intermediate flank eruptions continued through to the end of the last glacial period, producing lavas, hyaloclastite-dominated units and tuyas that preserve evidence of volcano-ice interactions. The Thórsmörk Ignimbrite, a regionally important chronostratigraphic marker, is present on the SE flank of the volcano. The geological mapping of Tindfjallajökull gives insights into the evolution of stratovolcanoes in glaciated regions and the influence of ice in their development