Dietary variations in three co-occurring rockfish species off the Pacific Northwest during anomalous oceanographic events in 1998 and 1999

Stomach samples from three rockfish species, yellowtail (Sebastes f lavidus), widow (S. entomelas), and canary (S. pinniger) rockfish, seasonally collected off the Pacific Northwest in 1998 and 1999, provided quantitative information on the food habits of these species during and after the 1997–98 El Niño event. Although euphausiids were the most common major prey of all three predators, gelatinous zooplankton and fishes were the most commonly consumed prey items during some seasonal quarters. The influence of the El Niño event was evident in the diets. Anomalous prey items, including the southern euphausiid species Nyctiphanes simplex and juveniles of Pacific whiting (Merluccius productus) frequently appeared in the diets in the spring and summer of 1998. The results of stomach contents analyses, based on 905 stomach samples from 49 trawl hauls during seven commercial fishing trips and from 56 stations during research surveys, were consistent with the timing of occurrence and the magnitude of change in biomass of some zooplankton species reported from zooplankton studies in the northern California Current during the 1997–98 El Niño. Our findings indicate that the observed variations of prey groups in some rockfish diets may be a function of prey variability related to climate and environment changes

Supermassive black holes as the regulators of star formation in central galaxies

We present a relationship between the black hole mass, stellar mass, and star formation rate of a diverse group of 91 galaxies with dynamically-measured black hole masses. For our sample of galaxies with a variety of morphologies and other galactic properties, we find that the specific star formation rate is a smoothly decreasing function of the ratio between black hole mass and stellar mass, or what we call the specific black hole mass. In order to explain this relation, we propose a physical framework where the gradual suppression of a galaxy's star formation activity results from the adjustment to an increase in specific black hole mass and, accordingly, an increase in the amount of heating. From this framework, it follows that at least some galaxies with intermediate specific black hole masses are in a steady state of partial quiescence with intermediate specific star formation rates, implying that both transitioning and steady-state galaxies live within this region known as the "green valley." With respect to galaxy formation models, our results present an important diagnostic with which to test various prescriptions of black hole feedback and its effects on star formation activity.Comment: 15 pages, 4 figures, 2 tables. Accepted for publication in The Astrophysical Journa

Electron and phonon band-structure calculations for the antipolar SrPt3_{3}P antiperovskite superconductor: Evidence of low-energy two-dimensional phonons

SrPt3P has recently been reported to exhibit superconductivity with Tc = 8.4 K. To explore its superconducting mechanism, we have performed electron and phonon band calculations based on the density functional theory, and found that the superconductivity in SrPt3P is well described by the strong coupling phonon-mediated mechanism. We have demonstrated that superconducting charge carriers come from pd\pi-hybridized bands between Pt and P ions, which couple to low energy (~ 5 meV) phonon modes confined on the ab in-plane. These in-plane phonon modes, which do not break antipolar nature of SrPt3P, enhance both the electron-phonon coupling constant \lambda and the critical temperature Tc. There is no hint of a specific phonon softening feature in the phonon dispersion, and the effect of the spin-orbit coupling on the superconductivity is found to be negligible.Comment: 5 pages, 5 figures, 1 tabl

Curie temperature and critical thickness of ferroelectric thin films

Author name used in this publication: C. H. Woo2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Magnetoelectric effects due to elastic coupling in ferroelectric/ferromagnetic multilayers

Author name used in this publication: C. H. Woo2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Characterization of a Reductively-Activated Elimination Pathway Relevant to the Biological Chemistry of the Kinamycins and Lomaiviticins

The lomaiviticins (1 and 2) and kinamycins (3–5) are bacterial metabolites with potent antimicrobial and antiproliferative activities. Herein we establish that 1–5 are capable of generating electrophilic acylfulvene intermediates (6) under mildly reducing conditions. These acylfulvenes 6 are formed by a multistep process comprising two-electron reduction and loss of dinitrogen to form an ortho-quinone methide, followed by elimination. Based on these studies, the structure of the product formed from 1 in DNA-cleavage assays is proposed (26). We also show that the bis(hydroxynaphthoquinone) substructures of the lomaiviticins activate the metabolites toward reduction. Finally, based on COMPARE and time-dependent cell response profiling analyses, we show that kinamycin C (4) and the monomeric lomaiviticin aglycon (24) operate by a mechanism of action that is distinct from simple diazofluorenes, such as 23

Effect of ferromagnetic contacts on spin accumulation in an all-metallic lateral spin-valve system: Semiclassical spin drift-diffusion equations

We study the effect of the ferromagnetic (FM) contacts on the spin accumulation in the lateral spin valve system for the collinear magnetization configurations. When an additional FM electrode is introduced in the all-metallic lateral spin-valve system, we find that the transresistance can be fractionally suppressed or very weakly influenced depending on the position of the additional FM electrode, and relative magnitudes of contact resistance and the bulk resistance defined over the spin diffusion length. Nonlocal spin signals such as nonlocal voltage drop and leakage spin currents are independent of the magnetization orientation of the additional FM electrode. Even when the additional contact is nonmagnetic, nonlocal spin signals can be changed by the spin current leaking into the nonmagnetic electrode.Comment: 13 pages, 1 figure, revised versio