Low energy excitations in crystalline perovskite oxides: Evidence from noise experiments

In this paper we report measurements of 1/f noise in a crystalline metallic oxide with perovskite structure down to 4.2K. The results show existence of localized excitations with average activation energy $\approx$ 70-80 meV which produce peak in the noise at T $\approx$ 35-40K. In addition, it shows clear evidence of tunnelling type two-level-systems (as in glasses) which show up in noise measurements below 30K.Comment: 11 pages, 4 figures, to appear in Phys Rev B, vol 58, 1st Dec issu

Effects of carbon, fertilizer, and drought on foliar chemistry of tree species in interior Alaska

Changes in foliarchemistryresultingfromchanges in forest-flooarnd min- eral-soilmoistureavailability,forest-floomricrobialenergysupply,andnitrogenavailability wereinvestigatedacross thesuccessional sequences in bothuplandand floodplainlandscape positions.Three amendments,sugar,sawdust,and nitrogenfertilizer(NH4NO3),were ap- plied to a series of threeupland and fourfloodplainsuccessional sites. The sugar and sawdusttreatmentwseredesignedtoincreasethecarbon:nitrogenratio(C/N)oftheforest floorto values typicalof black spruce sites (C/N = 50). The nitrogenfertilizertreatment was designed to equal estimatedyearlyN mineralizationin an attempto double available nitrogenin the forestfloor.A moistureexclusion treatmentwas designed to remove all summerrainfallfromthe treatmenptlots. Foliarphosphorusconcentrationwserehigherintheuplandsitesthanonthefloodplain. No consistentdifferenceswerereportedamongsuccessionalstageswithina landscapeunit. Theeffectofeithersugarorsawdusttreatmenwtastodecreasefoliarphosphorusconcen- trations.Sugar produced more significantdifferencesthan did sawdust. Sugar treatments decreased foliarnitrogenin all treespecies except forwhitespruce,while fertilizertended to increasefoliarnitrogenI.n thesecond yearfollowingtreatmentherewas notan increase in foliarnitrogenconcentrationresultingfromfertilizertreatment

Rest-Frame Mid-Infrared Detection of an Extremely Luminous Lyman Break Galaxy with the Spitzer Infrared Spectrograph (IRS)

We present the first rest-frame of approximately 4 microns detection of a Lyman break galaxy. The data were obtained using the 16 microns imaging capability of the Spitzer Infrared Spectrograph. The target object, J134026.44+634433.2, is an extremely luminous Lyman break galaxy at z=2.79, first identified in Sloan Digital Sky Survey (SDSS) spectra (as reported by Bentz et al.). The source is strongly detected with a flux of 0.94 +/- 0.02 mJy. Combining Spitzer and SDSS photometry with supporting ground-based J- and K-band data, we show that the spectral energy distribution is consistent with an actively star-forming galaxy. We also detect other objects in the Spitzer field of view, including a very red mid-infrared source. We find no evidence of a strong lens among the mid-infrared sources

Probing Optimal Reaction Energy for Synthesis of Element 119 from ⁵¹V+²⁴⁸Cm Reaction with Quasielastic Barrier Distribution Measurement

International audienceThe quasielastic barrier distribution of 51V+248Cm was extracted by measuring the excitation function of quasielastic backscattering using a gas-filled recoil ion separator, GARIS-III. The obtained barrier distribution is well explained by the coupled-channels calculation, indicating a significant effect of the rotational excitation of deformed 248Cm. From the measured average Coulomb barrier height and deformation parameters of 248Cm, the side-collision energy leading to a compact configuration of colliding nuclei was obtained. The relation between the side collision energy and the excitation function of the evaporation-residue cross sections in the 48Ca+248Cm system was evaluated as a reference for the 51V+248Cm case. The optimal reaction energy to synthesize a new element 119 at the 51V+248Cm fusion reaction (3n and 4n channels) was estimated with an aid of these experimental data