Australian National University

About: Australian National University is a education organization based out in Canberra, Australian Capital Territory, Australia. It is known for research contribution in the topics: Population & Galaxy. The organization has 34419 authors who have published 109261 publications receiving 4315448 citations. The organization is also known as: The Australian National University & ANU.

Scaling Factors for Obtaining Fundamental Vibrational Frequencies and Zero-Point Energies from HF/6–31G* and MP2/6–31G* Harmonic Frequencies

Abstract: New scaling factors have been determined for obtaining fundamental vibrational frequencies and zero-point vibrational energies from harmonic frequencies calculated at the HF/6–31G* and MP2/6–31G* levels. The scaling factors for the fundamental frequencies have been derived from a comparison of a total of 1066 calculated frequencies for 122 molecules with corresponding experimental values, while the zero-point energy scaling factors were determined from a comparison of the computed values with the experimental zero-point energies for a set of 24 molecules. The scaling factors recommended are, respectively, 0.8929 and 0.9427 for HF/6–31G* and MP2/6–31G* fundamental frequencies, and 0.9135 and 0.9646 for HF/6–31G* and MP2/6–31G* zero-point energies. RMS errors were determined to be around 50 cm−1 for the HF and MP2 fundamental frequencies, and around 0.4 kJ mol−1 for the HF and MP2 zero-point energies.

An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30

Abstract: So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered(1-8) Each quasar contains a black hole with a mass of about one billion solar masses (10(9) M-circle dot)(2,6,7,9-13) The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies(14) Here we report the discovery of an ultraluminous quasar, SDSS J01001302+2802258, at redshift z = 630 It has an optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars On the basis of the deep absorption trough(15) on the blue side of the Lyman-alpha emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z > 61 quasars with lower luminosities(16) We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of similar to 12 x 10(10) M-circle dot, which is consistent with the 13 x 10(10) M-circle dot derived by assuming an Eddington-limited accretion rate

Contagion in financial networks

Abstract: This paper develops an analytical model of contagion in financial networks with arbitrary structure. We explore how the probability and potential impact of contagion is influenced by aggregate and ...

On the LASSO and its dual

Abstract: Proposed by Tibshirani, the least absolute shrinkage and selection operator (LASSO) estimates a vector of regression coefficients by minimizing the residual sum of squares subject to a constraint on the l 1-norm of the coefficient vector. The LASSO estimator typically has one or more zero elements and thus shares characteristics of both shrinkage estimation and variable selection. In this article we treat the LASSO as a convex programming problem and derive its dual. Consideration of the primal and dual problems together leads to important new insights into the characteristics of the LASSO estimator and to an improved method for estimating its covariance matrix. Using these results we also develop an efficient algorithm for computing LASSO estimates which is usable even in cases where the number of regressors exceeds the number of observations. An S-Plus library based on this algorithm is available from StatLib.

Zircon Thermometer Reveals Minimum Melting Conditions on Earliest Earth

Abstract: Ancient zircons from Western Australia9s Jack Hills preserve a record of conditions that prevailed on Earth not long after its formation. Widely considered to have been a uniquely violent period geodynamically, the Hadean Eon [4.5 to 4.0 billion years ago (Ga)] has recently been interpreted by some as far more benign—possibly even characterized by oceans like those of the present day. Knowledge of the crystallization temperatures of the Hadean zircons is key to this debate. A thermometer based on titanium content revealed that these zircons cluster strongly at ∼700°C, which is indistinguishable from temperatures of granitoid zircon growth today and strongly suggests a regulated mechanism producing zircon-bearing rocks during the Hadean. The temperatures substantiate the existence of wet, minimum-melting conditions within 200 million years of solar system formation. They further suggest that Earth had settled into a pattern of crust formation, erosion, and sediment recycling as early as 4.35 Ga.