Climate,environment, and humans in North America’s Great Basin during the Younger Dryas, 12,900–11,600 calendar years ago

Global climate change associated with the onset of the Younger Dryas chronozone affected different regions of the northern hemisphere in different ways. In the Great Basin of western North America, the effect was positive for human populations. Relatively cool temperatures causing effectively wetter conditions filled some pluvial basins with shallow but permanent lakes and other basins with well-watered marshes or meadows. Vegetation communities dominated by sagebrush and grasses promoted healthy and diverse animal populations. Ten archaeological sites from the region have been dated to the Younger Dryas chronozone. Evidence from these sites indicates that Paleoindians with skull shapes and mitochondrial DNA similar to modern western North American Indians occupied the region. These early humans produced a material culture characterized predominantly by large stemmed bifacial points, although one site contained a small fluted point. Curated tool forms and technological activities represented in analyzed lithic assemblages suggest a highly mobile settlement strategy, and redundant short-term occupations of sites indicate frequent and long-distance residential moves across territories spanning distances of up to 400 km. Paleoindian subsistence pursuits focused on artiodactyls (primarily mule deer, bighorn sheep, and pronghorn antelope), leporids (chiefly jackrabbits), birds (sage grouse and waterfowl), insects (grasshoppers), and possibly fish. Easy-to-process plants like cactus pads were also eaten, but small seeds do not seem to have been an important part of Great Basin human diets until long after the Younger Dryas, closer to 9500 cal BP. The Great Basin record contains no evidence for natural catastrophe at the onset of the chronozone. Instead, the Younger Dryas appears to have been among the best of times for human foragers in this region of North America.     

Economic benefit of the protection program for the Steller sea lion

This paper examines willingness to pay (WTP) for an endangered species across geographically nested samples using the Contingent Valuation Method (CVM). The three samples range from (1) the boroughs that contain critical habitat for the Steller sea lion to (2) the state that contains these boroughs to and (3) the entire United States. Depending on the assumptions of the model, WTP varies tremendously from sample to sample. WTP for the United States is the highest and it is the lowest for the boroughs. The null hypotheses that mean WTP estimates are greater then zero were rejected for the boroughs and the state but were not rejected for the United States based on the 95% confidence intervals.     

In situ tensile fracture toughness of surficial cohesive marine sediments

This study reports the first in situ measurements of tensile fracture toughness, K _IC, of soft, surficial, cohesive marine sediments. A newly developed probe continuously measures the stress required to cause tensile failure in sediments to depths of up to 1 m. Probe measurements are in agreement with standard laboratory methods of K _IC measurements in both potter’s clay and natural sediments. The data comprise in situ depth profiles from three field sites in Nova Scotia, Canada. Measured K _IC at two muddy sites (median grain size of 23–50 μm) range from near zero at the sediment surface to >1,800 Pa m^1/2 at 0.2 m depth. These profiles also appear to identify the bioturbated/mixed depth. K _IC for a sandy site (>90% sand) is an order of magnitude lower than for the muddy sediments, and reflects the lack of cohesion/adhesion. A comparison of K _IC, median grain size, and porosity in muddy sediments indicates that consolidation increases fracture strength, whereas inclusion of sand causes weakening; thus, sand-bearing layers can be easily identified in K _IC profiles. K _IC and vane-measured shear strength correlate strongly, which suggests that the vane measurements should perhaps be interpreted as shear fracture toughness, rather than shear strength. Comparison of in situ probe-measured values with K _IC of soils and gelatin shows that sediments have a K _IC range intermediate between denser compacted soils and softer, elastic gelatin.     

The C/CO ratio in B335 and the decaying dark matter neutrino hypothesis

C¹⁸O J  = 2–1, C¹⁷O J  = 2–1 and [C  I ] ³P₁–³P₀ emission from the dense cold cloud B335 has been observed and modelled in order to determine the C/CO ratio. The observed ratio is compared with a prediction by Tarafdar who assumes a mechanism in which the CO dissociation is caused by photons of energy ∼ 13.8 eV. These were postulated by Sciama to result from the decay of dark matter neutrinos. Our value for the C/CO ratio sets an upper limit to the strength of the neutrino decay dissociation process, thus providing a significant datum for interstellar chemistry theory.     

Two-body motion in the post-Newtonian approximation

The motion of two massive particles is considered within the framework of the first post-Newtonian approximation. The system Hamiltonian is constructed and normalized through first order using a canonical transformation method of implicit variables. Closed-form solutions for the Delaunay elements in the phase space are obtained. The bridge between the phase space and the state space of the Lagrangian of the motion is provided by a velocity-dependent Legendre transformation. By explicit inversion of this transformation, expressions for the Keplerian elements in the state space are obtained from the Delaunay element solutions.     

The High-Resolution Coronal Imager (Hi-C)

The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈?0.3?–?0.4′′), high-cadence (≈?5 seconds) images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe xii 19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1′′?pixel^?1. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions.     

H2 in molecular shocks: observations from 2 to 12 microns

We present spectroscopy of the molecular shock in the supernova remnant IC 443. The H₂ level populations in IC 443 are nearly identical to Orion Peak 1 (Brand et al. 1988; Parmar et al. 1994) and are consistent with a partially dissociative J-shock. The similarity with Orion suggests the shock processes which dominate the emission in both regions are essentially identical.     

A note on first-order normalizations of perturbed Keplerian systems

Techniques are developed to facilitate the transformation of a perturbed Keplerian system into Deláunay normal form at first order. The implicit dependence of the Hamiltonian on 1, the mean anomaly, through the explicit variable f, the true anomaly, or E, the eccentric anomaly, is removed through first order for terms of the form:

Numerical simulations of hot halo gas in galaxy mergers

Galaxy merger simulations have explored the behaviour of gas within the galactic disc, yet the dynamics of hot gas within the galaxy halo have been neglected. We report on the results of high-resolution hydrodynamic simulations of colliding galaxies with metal-free hot halo gas. To isolate the effect of the halo gas, we simulate only the dark matter halo and the hot halo gas over a range of mass ratios, gas fractions and orbital configurations to constrain the shocks and gas dynamics within the progenitor haloes. We find that (i) a strong shock is produced in the galaxy haloes before the first passage, increasing the temperature of the gas by almost an order of magnitude to   T ∼ 10^6.3 K  . (ii) The X-ray luminosity of the shock is strongly dependent on the gas fraction; it is  ≳10³⁹ erg s⁻¹  for halo gas fractions larger than 10 per cent. (iii) The hot diffuse gas in the simulation produces X-ray luminosities as large as  10⁴² erg s⁻¹  . This contributes to the total X-ray background in the Universe. (iv) We find an analytic fit to the maximum X-ray luminosity of the shock as a function of merger parameters. This fit can be used in semi-analytic recipes of galaxy formation to estimate the total X-ray emission from shocks in merging galaxies. (v) ∼10–20 per cent of the initial gas mass is unbound from the galaxies for equal-mass mergers, while 3–5 per cent of the gas mass is released for the 3:1 and 10:1 mergers. This unbound gas ends up far from the galaxy and can be a feasible mechanism to enrich the intergalactic medium with metals.