Collective Diffusion and a Random Energy Landscape

Starting from a master equation in a quantum Hamiltonian form and a coupling to a heat bath we derive an evolution equation for a collective hopping process under the influence of a stochastic energy landscape. There results different equations in case of an arbitrary occupation number per lattice site or in a system under exclusion. Based on scaling arguments it will be demonstrated that both systems belong below the critical dimension $d_c$ to the same universality class leading to anomalous diffusion in the long time limit. The dynamical exponent $z$ can be calculated by an $\epsilon = d_c-d$ expansion. Above the critical dimension we discuss the differences in the diffusion constant for sufficient high temperatures. For a random potential we find a higher mobility for systems with exclusion.Comment: 15 pages, no figure

Electron spin relaxation in organic semiconductors probed through muSR

Muon spin spectroscopy and in particular the avoided level crossing technique is introduced, with the aim of showing it as a very sensitive local probe for electron spin relaxation in organic semiconductors. Avoided level crossing data on TMS-pentacene at different temperatures are presented, and they are analysed to extract the electron spin relaxation rate, that is shown to increase on increasing the temperature from 0.02 MHz to 0.33 MHz at 3 K and 300 K respectively.Comment: International Conference TSN2010 "Trends in spintronics and nanomagnetism

Differential effects of age on involuntary and voluntary autobiographical memory

"This article may not exactly replicate the final version published in the APA journal. It is not the copy of record." Original article can be found at: http://psycnet.apa.org/journals/pag/24/2/397/ Copyright American Psychological Association. DOI: 10.1037/a0015785Research on aging and autobiographical memory has focused almost exclusively on voluntary autobiographical memory. However, in everyday life, autobiographical memories often come to mind spontaneously without deliberate attempt to retrieve anything. In the present study, diary and word-cue methods were used to compare the involuntary and voluntary memories of 44 young and 38 older adults. The results showed that older adults reported fewer involuntary and voluntary memories than did younger adults. Additionally, the life span distribution of involuntary and voluntary memories did not differ in young adults (a clear recency effect) or in older adults (a recency effect and a reminiscence bump). Despite these similarities between involuntary and voluntary memories, there were also important differences in terms of the effects of age on some memory characteristics. Thus, older adults’ voluntary memories were less specific and were recalled more slowly than those of young adults, but there were no reliable age differences in the specificity of involuntary memories. Moreover, older adults rated their involuntary memories as more positive than did young adults, but this positivity effect was not found for voluntary memories. Theoretical implications of these findings for research on autobiographical memory and cognitive aging are discussedPeer reviewe

Detection of C-type natriuretic peptide (CNP) transcript in the rat heart and immune organs

Previous studies suggested the expression of mRNA, coding for CNP, exclusively in the central nervous system. In the present study, using the polymerase chain reaction (PCR) technique instead of the less sensitive Northern blot hybridization, CNP-specific sequences have also been detected in rat atria and ventricles of the heart as well as in organs of the immune system (thymus, spleen and lymph nodes). Parallel PCR-assays documented ANP-mRNA in these tissues. To verify specificity of the PCR-products, Southern blots have been hybridized with a third internal oligonucleotide and amplification products have been sequenced. The relative level of CNP-mRNA in these tissues was estimated to be in the range of 1-9% of total brain CNP transcripts. The results suggest that the peptide may have a peripheral as well as a central site of action. In light of its pronounced effect on cell proliferation, particular interest should focus on a possible role of CNP in the immune system

Spectral Properties near the Mott Transition in the One-Dimensional Hubbard Model

Single-particle spectral properties near the Mott transition in the one-dimensional Hubbard model are investigated by using the dynamical density-matrix renormalization group method and the Bethe ansatz. The pseudogap, hole-pocket behavior, spectral-weight transfer, and upper Hubbard band are explained in terms of spinons, holons, antiholons, and doublons. The Mott transition is characterized by the emergence of a gapless mode whose dispersion relation extends up to the order of hopping t (spin exchange J) in the weak (strong) interaction regime caused by infinitesimal doping.Comment: 4 pages, 2 figure

Radial distribution of gas and dust in spiral galaxies: The case of M 99 (NGC 4254) and M 100 (NGC 4321)

By combining Herschel-SPIRE data with archival Spitzer, H i , and CO maps, we investigate the spatial distribution of gas and dust in the two famous grand-design spirals M 99 and M 100 in the Virgo cluster. Thanks to the unique resolution and sensitivity of the Herschel-SPIRE photometer, we are for the first time able to measure the distribution and extent of cool, submillimetre (submm)-emitting dust inside and beyond the optical radius. We compare this with the radial variation in both the gas mass and the metallicity. Although we adopt a model-independent, phenomenological approach, our analysis provides important insights. We find the dust extending to at least the optical radius of the galaxy and showing breaks in its radial profiles at similar positions as the stellar distribution. The colour indices f350/f500 and f250/f350 decrease radially consistent with the temperature decreasing with radius. We also find evidence of an increasing gas to dust ratio with radius in the outer regions of both galaxies

The dust morphology of the elliptical Galaxy M86 with SPIRE

We present Herschel-SPIRE observations at 250–500 μm of the giant elliptical galaxy M 86 and examine the distribution of the resolved cold dust emission and its relation with other galactic tracers. The SPIRE images reveal three dust components: emission from the central region; a dust lane extending north-south; and a bright emission feature 10 kpc to the south-east. We estimate that ~10^6 M_☉ of dust is spatially coincident with atomic and ionized hydrogen, originating from stripped material from the nearby spiral NGC 4438 due to recent tidal interactions with M 86. The gas-to-dust ratio of the cold gas component ranges from ~20–80. We discuss the different heating mechanisms for the dust features

On the metal-insulator transition in the two-chain model of correlated fermions

The doping-induced metal-insulator transition in two-chain systems of correlated fermions is studied using a solvable limit of the t-J model and the fact that various strong- and weak-coupling limits of the two-chain model are in the same phase, i.e. have the same low-energy properties. It is shown that the Luttinger-liquid parameter K_\rho takes the universal value unity as the insulating state (half-filling) is approached, implying dominant d-type superconducting fluctuations, independently of the interaction strength. The crossover to insulating behavior of correlations as the transition is approached is discussed.Comment: 7 pages, 1 figur

The central region of spiral galaxies as seen by Herschel: M 81, M 99, and M 100

With appropriate spatial resolution, images of spiral galaxies in thermal infrared (~10 μm and beyond) often reveal a bright central component, distinct from the stellar bulge, superimposed on a disk with prominent spiral arms. ISO and Spitzer studies have shown that much of the scatter in the mid-infrared colors of spiral galaxies is related to changes in the relative importance of these two components, rather than to other modifications, such as the morphological type or star formation rate, that affect the properties of the galaxy as a whole. With the Herschel imaging capability from 70 to 500 μm, we revisit this two-component approach at longer wavelengths, to see if it still provides a working description of the brightness distribution of galaxies, and to determine its implications on the interpretation of global far-infrared properties of galaxies. We quantify the luminosity of the central component by both a decomposition of the radial surface brightness profile and a direct extraction in 2D. We find the central component contribution is variable within the three galaxies in our sample, possibly connected more directly to the presence of a bar than to the morphological type. The central component’s relative contribution is at its maximum in the mid-infrared range and drops around 160 μm to reach a constant value beyond 200 μm. The central component contains a greater fraction of hot dust than the disk component, and while the colors of the central components are scattered, colors of the disk components are more homogenous from one galaxy to the next