Analyses of shocked quartz from the K-P boundary

The precise cause and timing of the Cretaceous-Paleocene (K-P) mass extinction 65 Ma ago remains a matter of debate. Many advocate that the extinction was caused by a meteorite impact at Chicxulub, Mexico, and a number of potential kill-mechanisms have been proposed for this. Although we now have good constraints on the size of this impact and chemistry of the target rocks, estimates of its environmental consequences are hindered by a lack of knowledge about the obliquity of this impact. An oblique impact is likely to have been far more catastrophic than a sub-vertical one, because greater volumes of volatiles would have been released into the atmosphere. The principal purpose of this study was to characterize shocked quartz within distal K-P ejecta, to investigate whether the quartz distribution carried a signature of the direction and angle of impact. Our analyses show that the total number, maximum and average size of shocked quartz grains all decrease gradually with paleodistance from Chicxulub. We do not find particularly high abundances in Pacific sites relative to Atlantic and European sites, as has been previously reported, and the size-distribution around Chicxulub is relatively symmetric. Ejecta samples at any one site display features that are indicative of a wide range of shock pressures, but the mean degree of shock increases with paleodistance. These shock- and size-distributions are both consistent with the K-P layer having been formed by a single impact at Chicxulub. One site in the South Atlantic contains quartz indicating an anomalously high average shock degree, that may be indicative of an oblique impact with an uprange direction to the southeast +/- 45°. The apparent continuous coverage of proximal ejecta in this quadrant of the crater, however, suggests a relatively high impact angle of >45°. We conclude that some of the more extreme predictions of the environmental consequences of a low-angle impact at Chicxulub are probably not applicable.

Symmetry considerations in the empirical k.p Hamiltonian for the study of intermediate band solar cells

With the purpose of assessing the absorption coefficients of quantum dot solar cells, symmetry considerations are introduced into a Hamiltonian whose eigenvalues are empirical. In this way, the proper transformation from the Hamiltonian's diagonalized form to the form that relates it with Γ-point exact solutions through k.p envelope functions is built accounting for symmetry. Forbidden transitions are thus determined reducing the calculation burden and permitting a thoughtful discussion of the possible options for this transformation. The agreement of this model with the measured external quantum efficiency of a prototype solar cell is found to be excellent.

Manual of the mosses of North America. By Léo Lesquereux and Thomas P. James. With six plates illustrating the genera.

copy 1

Tongsang ki chʻan : 5-kwŏn k��p kwŏnsu /

Korean translation of a novel in dramatic form, originally in Chinese.

Ueber das Eigenthümliche der deutschen Universitäten; ein Vortrag in der K.P. Academie gemeinnütziger Wissenschaften zu Erfurt am 10. September 1833.

Mode of access: Internet.

Pushkin : dokumenty Gosudarstvennago i S.-Peterburgskago glavnago arkhivov Ministerstva inostrannykh di͡e︡l, otnosi͡a︡shchīesi͡a︡ k sluzhbi͡e︡ ego 1831-1837 gg. S semʹi͡u︡ snimkami s avtografov Pushkina i odnim snimkom s podlinnago svidi͡e︡telʹstva ob okonchanīi im kursa v Imperatorskom t͡s︡arskoselʹskom lit͡s︡ei͡e︡ /

Includes bibliographical references.

James Brooker, UM track 1923

[Michiganensian caption: Brooker was forced into second place in the Conference pole vault, but Brownell of Illinois was forced to break the world's collegiate record to beat him.]

Speech of Mr. J.J. Hardin, of Illinois : reviewing the principles of James K. Polk & the leaders of modern democracy, delivered in the House of Representatives of the United States, June 3, 1844.

Mode of access: Internet.

James K. Polk, a political biography,

Mode of access: Internet.

The diary of James K. Polk during his presidency, 1845 to 1849, now first printed from the original manuscript in the collections of the Chicago Historical Society.

Reprint of the 1910 ed. published by A. C. McClurg, Chicago, which was issued as v. 6-9 of the Chicago Historical Society's collection.

Domestic exchange and rates of collection by Bank U.S.and its branches. Documents submitted by Mr.Polk,from the Committee of ways and means,January 10,1835.

At head of title:23d Congress,2d session. Doc.No.71. Ho.of Reps. Treas.Dept.

Search for gravitational wave ringdowns from perturbed intermediate mass black holes in LIGO-Virgo data from 2005-2010

We report results from a search for gravitational waves produced by perturbed intermediate mass black holes ( IMBH) in data collected by LIGO and Virgo between 2005 and 2010. The search was sensitive to astrophysical sources that produced damped sinusoid gravitational wave signals, also known as ringdowns, with frequency 50 <= f(0)/Hz <= 2000 and decay timescale 0.0001 less than or similar to tau/s less than or similar to 0.1 characteristic of those produced in mergers of IMBH pairs. No significant gravitational wave candidate was detected. We report upper limits on the astrophysical coalescence rates of IMBHs with total binary mass 50 <= M/ M circle dot <= 450 and component mass ratios of either 1: 1 or 4: 1. For systems with total mass 100 <= M/M circle dot <= 150, we report a 90% confidence upper limit on the rate of binary IMBH mergers with nonspinning and equal mass components of 6.9 x 10(-8) Mpc(-3) yr(-1). We also report a rate upper limit for ringdown waveforms from perturbed IMBHs, radiating 1% of their mass as gravitational waves in the fundamental, l = m = 2, oscillation mode, that is nearly three orders of magnitude more stringent than previous results.