Graphene-based spintronic components

A major challenge of spintronics is in generating, controlling and detecting spin-polarized current. Manipulation of spin-polarized current, in particular, is difficult. We demonstrate here, based on calculated transport properties of graphene nanoribbons, that nearly +-100% spin-polarized current can be generated in zigzag graphene nanoribbons (ZGNRs) and tuned by a source-drain voltage in the bipolar spin diode, in addition to magnetic configurations of the electrodes. This unusual transport property is attributed to the intrinsic transmission selection rule of the spin subbands near the Fermi level in ZGNRs. The simultaneous control of spin current by the bias voltage and the magnetic configurations of the electrodes provides an opportunity to implement a whole range of spintronics devices. We propose theoretical designs for a complete set of basic spintronic devices, including bipolar spin diode, transistor and logic gates, based on ZGNRs.Comment: 14 pages, 4 figure

Coronal condensations caused by magnetic reconnection between solar coronal loops

Employing Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) multi-wavelength images, we report the coronal condensation during the magnetic reconnection (MR) between a system of open and closed coronal loops. Higher-lying magnetically open structures, observed in AIA 171 A images above the solar limb, move downward and interact with the lower-lying closed loops, resulting in the formation of dips in the former. An X-type structure forms at the interface. The interacting loops reconnect and disappear. Two sets of newly-reconnected loops then form and recede from the MR region. During the MR process, bright emission appears sequentially in the AIA 131 A and 304 A channels repeatedly in the dips of higher-lying open structures. This indicates the cooling and condensation process of hotter plasma from ~0.9 MK down to ~0.6 MK, and then to ~0.05 MK, also supported by the light curves of the AIA 171 A, 131 A, and 304 A channels. The part of higher-lying open structures supporting the condensations participate in the successive MR. The condensations without support by underlying loops then rain back to the solar surface along the newly-reconnected loops. Our results suggest that the MR between coronal loops leads to the condensation of hotter coronal plasma and its downflows. MR thus plays an active role in the mass cycle of coronal plasma because it can initiate the catastrophic cooling and condensation. This underlines that the magnetic and thermal evolution has to be treated together and cannot be separated, even in the case of catastrophic cooling.Comment: 10 pages, 6 figure

Properties and Keplerian Rotation of the Hot Core IRAS 20126+4104

We present Submillimeter Array observations of the massive star-forming region IRAS 20126+4104 in the millimeter continuum and in several molecular line transitions. With the SMA data, we have detected nine molecular transitions, including DCN, CH3OH, H2CO, and HC3N molecules, and imaged each molecular line. From the 1.3 mm continuum emission a compact millimeter source is revealed, which is also associated with H2O, OH, and CH3OH masers. Using a rotation temperature diagram (RTD), we derive that the rotational temperature and the column density of CH3OH are 200 K and 3.7\times 1017 cm-2, respectively. The calculated results and analysis further indicate that a hot core coincides with IRAS 20126+4104. The position-velocity diagrams of H2CO 3(0,3)-2(0,2) and HC3N 25-24 clearly present Keplerian rotation. Moreover, H2CO 3(0,3)-2(0,2) is found to trace the disk rotation for the first time.Comment: 17 pages, 5 figures, accepted by Ap

The p53 Pathway Controls SOX2-Mediated Reprogramming in the Adult Mouse Spinal Cord

Although the adult mammalian spinal cord lacks intrinsic neurogenic capacity, glial cells can be reprogrammed in vivo to generate neurons after spinal cord injury (SCI). How this reprogramming process is molecularly regulated, however, is not clear. Through a series of in vivo screens, we show here that the p53-dependent pathway constitutes a critical checkpoint for SOX2-mediated reprogramming of resident glial cells in the adult mouse spinal cord. While it has no effect on the reprogramming efficiency, the p53 pathway promotes cell-cycle exit of SOX2-induced adult neuroblasts (iANBs). As such, silencing of either p53 or p21 markedly boosts the overall production of iANBs. A neurotrophic milieu supported by BDNF and NOG can robustly enhance maturation of these iANBs into diverse but predominantly glutamatergic neurons. Together, these findings have uncovered critical molecular and cellular checkpoints that may be manipulated to boost neuron regeneration after SCI

Lanthanide chain assembled in metal-organic frameworks: slow relaxation of the magnetization in Dy (III) and Er (III) complexes

Three new LnIII-MOFs, {[Dy1.5(TAPB)1.5(DMF)]·9DMF}n (Ln = Dy (1), Er (2), Ho (3); TAPB = 4, 4′, 4″-(triazine‑2, 4, 6‑triyl‑tris‑(benzene‑4, 1-diyl)) tribenzoate), have been synthesized via a solvothermal method by using a trigonal N-containing tricarboxylate as the ligand. The coordination geometries around the central metal ions in the MOFs exhibit different deviations from ideal square antiprism (D4d symmetry) because of the coordinated solvent molecules. The ac magnetic susceptibility data is consistent with single chain magnet behavior for Dy(III) and Er(III) complexes, which have been studied by the noncritical scaling theory