The neural origin for asymmetric coding of surface color in the primate visual cortex.

The coding privilege of end-spectral hues (red and blue) in the early visual cortex has been reported in primates. However, the origin of such bias remains unclear. Here, we provide a complete picture of the end-spectral bias in visual system by measuring fMRI signals and spiking activities in macaques. The correlated end-spectral biases between the LGN and V1 suggest a subcortical source for asymmetric coding. Along the ventral pathway from V1 to V4, red bias against green peaked in V1 and then declined, whereas blue bias against yellow showed an increasing trend. The feedforward and recurrent modifications of end-spectral bias were further revealed by dynamic causal modeling analysis. Moreover, we found that the strongest end-spectral bias in V1 was in layer 4C[Formula: see text]. Our results suggest that end-spectral bias already exists in the LGN and is transmitted to V1 mainly through the parvocellular pathway, then embellished by cortical processing.

Optimized Morphology Enables High-Efficiency Nonfullerene Ternary Organic Solar Cells.

Tuning the three-dimensional morphology in the active layer is an effective method to improve the performance of bulk heterojunction organic solar cells (OSCs). In this work, an acceptor-donor-acceptor structured small molecule ST10-CN-1 was synthesized and employed as the guest donor to fabricate ternary OSCs based on a PBDB-T:IT-M host binary system. The incorporation of ST10-CN-1 could broaden the active layer's absorption range of solar light thereby leading to a promotional short-circuit current. Moreover, adding an appropriate amount of ST10-CN-1 could effectively regulate the morphology of the active layer in both the lateral direction and vertical stratification. All of these morphological alterations helped to speed up the exciton dissociation, charge transit, and charge collecting processes, which in turn increased the power conversion efficiency. As a result, an excellent PCE of 11.5% for the ternary device based on PBDB-T:IT-M:ST10-CN-1 was obtained. The enhanced PCE was also linked to the formation of an alloylike state between PBDB-T and ST10-CN-1, as evidenced by the fact that the open circuit voltage of ternary OSCs lay between those for PBDB-T:IT-M (0.925 V) and ST10-CN-1:IT-M (1.064 V). This work illustrates that refining the morphology of the active layer by incorporating an appropriate third component is an effective way to further enhance the device's performance.

Linear and Nonlinear Two-Terminal Spin-Valve Effect from Chirality-Induced Spin Selectivity.

Various mechanisms of electrical generation of spin polarization in nonmagnetic materials have been a subject of broad interest for their underlying physics and device potential in spintronics. One such scheme is chirality-induced spin selectivity (CISS), with which structural chirality leads to different electric conductivities for electrons of opposite spins. The resulting effect of spin filtering has been reported for a number of chiral molecules assembled on different surfaces. However, the microscopic origin and transport mechanisms remain controversial. In particular, the fundamental Onsager relation was argued to preclude linear-response detection of CISS by a ferromagnet. Here, we report definitive observation of CISS-induced magnetoconductance in vertical heterojunctions of (Ga,Mn)As/AHPA-L molecules/Au, directly verifying spin filtering by the AHPA-L molecules via spin detection by the (Ga,Mn)As. The pronounced and robust magnetoconductance signals resulting from the use of a magnetic semiconductor enable a rigorous examination of its bias dependence, which shows both linear- and nonlinear-response components. The definitive identification of the linear-response CISS-induced two-terminal spin-valve effect places an important constraint for a viable theory of CISS and its device manifestations. The results present a promising route to spin injection and detection in semiconductors without using any magnetic material.

Bound fermion states in pinned vortices in the surface states of a superconducting topological insulator.

By analytically solving the Bogoliubov-de Gennes equations we study the fermion bound states at the center of the core of a vortex in a two-dimensional superconductor. The superconducting states are induced via proximity effect between ans-wave superconductor and the surface states of a strong topological insulator. The strong spin-orbit coupling locks the spin perpendicular to the momentum (Rashba interaction). A zero-energy Majorana state arises together with an equally spaced (Δ∞2/EF) sequence of fermion excitations. The spin-momentum locking is key to the formation of the Majorana state. We present analytical expressions for the energy spectrum and the wave functions of the bound states. The wave functions fall off exponentially with the distanceρfrom the core of the vortex asexp[-∫0ρdρ'Δ(ρ')/vF]. An analytic expression for the local density of states (LDOS) for the bound states is obtained. The particle-hole symmetry is broken in the LDOS as a consequence of the spin-orbit coupling. The spin-polarization of the bound states is discussed. We also obtain the energy shifts of the bound states in a small magnetic field. A unitary transformation relating the model with Rashba interaction to the Dirac Hamiltonian is presented.

Sonocrystallization of poly(3-hexylthiophene) in a marginal solvent.

The application of ultrasonication to P3HT in anisole can dramatically affect the crystallization of P3HT. The ultrasonication conditions were modulated by varying the ultrasonication time, ultrasonication power and ultrasonication temperature. Ultrasonicating at the dissolution temperature (85 °C) causes the concentration of the P3HT solution to fluctuate. When fixing the ultrasonication power at 100 W and ultrasonication time at 3 min, for P3HT crystallized in solution at 16 °C, the crystallization kinetics of ultrasonicated P3HT is slower than that of pristine P3HT. The nanofiber aggregation density and crystallinity of ultrasonicated P3HT are lower than those of pristine P3HT, and the nanofiber aggregation size is larger. For P3HT crystallized in solution at 20 °C, the crystallization kinetics, nanofiber morphology and crystallinity of ultrasonicated P3HT are similar to those of pristine P3HT. For P3HT crystallized in solution at 26 °C, the crystallization kinetics of ultrasonicated P3HT is faster than that of pristine P3HT, the nanofiber aggregation size is larger, and the crystallinity is higher. Fixing the crystallization temperature at 16 °C and varying the ultrasonication time and ultrasonication power can effectively modulate the crystallization kinetics of P3HT. When the P3HT solution is ultrasonicated at the crystallization temperature (16 °C), in addition to fluctuations in the concentration, ultrasonication promotes the disentanglement of P3HT chains. The combination of the two effects of ultrasonication is more beneficial for the crystallization of P3HT when solvophobic forces exist in a marginal solvent.