Microsoft C 与 MASM 混合编程的研究

讨论了Microsoft C语言中调用MASM 5．0汇编语言程序的方法，并针对一些易出现的问题，如程序接口部分的要求，C语言与汇编程序间参数的传递，寄存器的使用等，提出了解决办法．     

Negative intrinsic resistivity of an individual domain wall in epitaxial (Ga,Mn)As microdevices

Magnetic domains, and the boundaries that separate them (domain walls, DWs), play a central role in the science of magnetism. Understanding and controlling domains is important for many technological applications in spintronics, and may lead to new devices. Although theoretical efforts have elucidated several mechanisms underlying the resistance of a single DW, various experiments report conflicting results, even for the overall sign of the DW resistance. The question of whether an individual DW gives rise to an increase or decrease of the resistance therefore remains open. Here we report an approach to DW studies in a class of ferromagnetic semiconductors (as opposed to metals) that offer promise for spintronics. These experiments involve microdevices patterned from monocrystalline (Ga,Mn)As epitaxial layers. The giant planar Hall effect that we previously observed in this material enables direct, real-time observation of the propagation of an individual magnetic DW along multiprobe devices. We apply steady and pulsed magnetic fields, to trap and carefully position an individual DW within each separate device studied. This protocol reproducibly enables high-resolution magnetoresistance measurements across an individual wall. We consistently observe negative intrinsic DW resistance that scales with channel width. This appears to originate from sizeable quantum corrections to the magnetoresistance.     

Activation of specific interneurons improves V1 feature selectivity and visual perception

Inhibitory interneurons are essential components of the neural circuits underlying various brain functions. In the neocortex, a large diversity of GABA (γ-aminobutyric acid) interneurons has been identified on the basis of their morphology, molecular markers, biophysical properties and innervation pattern. However, how the activity of each subtype of interneurons contributes to sensory processing remains unclear. Here we show that optogenetic activation of parvalbumin-positive (PV+) interneurons in the mouse primary visual cortex (V1) sharpens neuronal feature selectivity and improves perceptual discrimination. Using multichannel recording with silicon probes and channelrhodopsin-2 (ChR2)-mediated optical activation, we found that increased spiking of PV+ interneurons markedly sharpened orientation tuning and enhanced direction selectivity of nearby neurons. These effects were caused by the activation of inhibitory neurons rather than a decreased spiking of excitatory neurons, as archaerhodopsin-3 (Arch)-mediated optical silencing of calcium/calmodulin-dependent protein kinase IIα (CAMKIIα)-positive excitatory neurons caused no significant change in V1 stimulus selectivity. Moreover, the improved selectivity specifically required PV+ neuron activation, as activating somatostatin or vasointestinal peptide interneurons had no significant effect. Notably, PV+ neuron activation in awake mice caused a significant improvement in their orientation discrimination, mirroring the sharpened V1 orientation tuning. Together, these results provide the first demonstration that visual coding and perception can be improved by increased spiking of a specific subtype of cortical inhibitory interneurons.