Nonlocal transistor based on pure crossed Andreev reflection in a EuO-graphene/superconductor hybrid structure

We study the interband transport in a superconducting device composed of graphene with EuO-induced exchange interaction. We show that pure crossed Andreev reflection can be generated exclusively without the parasitic local Andreev reflection and elastic cotunnelling over a wide range of bias and Fermi levels in an EuO-graphene/superconductor/EuO-graphene device. The pure non-local conductance exhibits rapid on/off switching and oscillatory behavior when the Fermi levels in the normal and the superconducting leads are varied. The oscillation reflects the quasiparticle propagation in the superconducting lead and can be used as a tool to probe the subgap quasiparticle mode in superconducting graphene, which is inaccessible from the current-voltage characteristics. Our results suggest that the device can be used as a highly tunable transistor that operates purely in the non-local and spin-polarized transport regime.Comment: 5 pages, 4 figures; To appear in Phys. Rev.

Revisiting the interacting model of new agegraphic dark energy

In this paper, a new version of the interacting model of new agegraphic dark energy (INADE) is proposed and analyzed in detail. The interaction between dark energy and dark matter is reconsidered. The interaction term $Q=bH_0\rho_{\rm de}^\alpha\rho_{\rm dm}^{1-\alpha}$ is adopted, which abandons the Hubble expansion rate $H$ and involves both $\rho_{\rm de}$ and $\rho_{\rm dm}$. Moreover, the new initial condition for the agegraphic dark energy is used, which solves the problem of accommodating baryon matter and radiation in the model. The solution of the model can be given using an iterative algorithm. A concrete example for the calculation of the model is given. Furthermore, the model is constrained by using the combined Planck data (Planck+BAO+SNIa+$H_0$) and the combined WMAP-9 data (WMAP+BAO+SNIa+$H_0$). Three typical cases are considered: (A) $Q=bH_0\rho_{\rm de}$, (B) $Q=bH_0\sqrt{\rho_{\rm de}\rho_{\rm dm}}$, and (C) $Q=bH_0\rho_{\rm dm}$, which correspond to $\alpha=1$, 1/2, and 0, respectively. The departures of the models from the $\Lambda$CDM model are measured by the $\Delta$BIC and $\Delta$AIC values. It is shown that the INADE model is better than the NADE model in the fit, and the INADE(A) model is the best in fitting data among the three cases.Comment: 6 pages, 2 figure

Klein tunneling and cone transport in AA-stacked bilayer graphene

We investigate the quantum tunneling of electrons in an AA-stacked bilayer graphene (BLG) $n$-$p$ junction and $n$-$p$-$n$ junction. We show that Klein tunneling of an electron can occur in this system. The quasiparticles are not only chiral but are additionally described by a `cone index'. Due to the orthogonality of states with different cone indexes, electron transport across a potential barrier must strictly conserve the cone index and this leads to the protected cone transport which is unique in AA-stacked BLG. Together with the negative refraction of electrons, electrons residing in different cones can be spatially separated according to their cone index when transmitted across an $n$-$p$ junction. This suggests the possibility of `cone-tronic' devices based on AA-stacked BLG. Finally, we calculate the junction conductance of the system.Comment: 11 pages, 7 figures; corrected typo, final submitted versio

The Cross-Section of Volatility and Expected Returns

We examine the pricing of aggregate volatility risk in the cross-section of stock returns. Consistent with theory, we find that stocks with high sensitivities to innovations in aggregate volatility have low average returns. In addition, we find that stocks with high idiosyncratic volatility relative to the Fama and French (1993) model have abysmally low average returns. This phenomenon cannot be explained by exposure to aggregate volatility risk. Size, book-to-market, momentum, and liquidity effects cannot account for either the low average returns earned by stocks with high exposure to systematic volatility risk or for the low average returns of stocks with high idiosyncratic volatility.

Trajectories of Union Transition in Emerging Adulthood: Socioeconomic Status and Race/Ethnicity Differences in the National Longitudinal Survey of Youth 1997 Cohort

ObjectiveThe objective of this study was to describe the patterns of union transition in emerging adulthood for the 1980 to 1984 cohort and examine its associations with socioeconomic status and race/ethnicity.BackgroundResearch on diverging destinies of cohabitation and marriage tends to focus on singular transitions rather than entire individual trajectories composed of dimensions such as timing, order, duration, and number of transitions.MethodDrawing on monthly prospective data from the National Longitudinal Survey of Youth 1997, social sequence analysis was used to classify union transition trajectories from ages 16 to 30. Multinomial logistic regression was used to assess the probability of membership in each cluster.ResultsThe findings showed the following six key clusters of trajectories: mostly single (37.6%), some cohabiting (13.8%), serial cohabiting (10.6%), early 20s marriage (11.4%), late 20s marriage (22.5%), and turbulent (4.1%). We found that young adults were most likely to be in the “mostly single” cluster, regardless of socioeconomic status and race/ethnicity. Individuals with college degrees tended to marry in their late 20s, whereas individuals without college degrees were more likely to be in “serial cohabiting” and “turbulent” clusters. Individuals who lived with neither of their biological parents were more likely to belong to “early 20s marriage” and “turbulent” clusters when compared with those who lived with at least one of their biological parents. Blacks were more likely to remain single, whereas non‐Hispanic Whites were more likely to marry sometime in their 20s.ConclusionEvidence for diverging trajectories exists in this recent cohort, but we also find that most young adults in fact stay single. We also highlight the benefits of considering multiple aspects of trajectories concurrently, especially as relationship instability and complexity increase.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154487/1/jomf12662.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154487/2/jomf12662_am.pd

Stress Resistance Screen in a Human Primary Cell Line Identifies Small Molecules That Affect Aging Pathways and Extend Caenorhabditis elegans' Lifespan.

Increased resistance to environmental stress at the cellular level is correlated with the longevity of long-lived mutants and wild-animal species. Moreover, in experimental organisms, screens for increased stress resistance have yielded mutants that are long-lived. To find entry points for small molecules that might extend healthy longevity in humans, we screened ∼100,000 small molecules in a human primary-fibroblast cell line and identified a set that increased oxidative-stress resistance. Some of the hits fell into structurally related chemical groups, suggesting that they may act on common targets. Two small molecules increased C. elegans' stress resistance, and at least 9 extended their lifespan by ∼10-50%. We further evaluated a chalcone that produced relatively large effects on lifespan and were able to implicate the activity of two, stress-response regulators, NRF2/skn-1 and SESN/sesn-1, in its mechanism of action. Our findings suggest that screening for increased stress resistance in human cells can enrich for compounds with promising pro-longevity effects. Further characterization of these compounds may reveal new ways to extend healthy human lifespan