High-Resolution Magnetic Force Microscopy Using Carbon Nanotube Probes Fabricated Directly by Microwave Plasma-Enhanced Chemical Vapor Deposition

Carbon nanotubes (CNTs) have been successfully grown on the tip apex of an atomic force microscopy (AFM) cantilever by microwave plasma-enhanced chemical vapor deposition (MPECVD). Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal that the diameter of the CNTs is ∼30 nm and the magnetic particles with diameter of ∼20 nm, which was used as catalyst for the CNT growth, exist on the top. This CNT probe has been applied to magnetic force microscopy (MFM) on the ultrahigh-density magnetic recording media with 1200 kilo flux change per inch (kfci)

Evaluation of Cardiovascular Stress Reaction Using HPCD Method on a Beat-by-beat Basis

In order to establish a bionic model/system in cardiovascular fields, comprehension of hemodynamics is important. In this study, a novel beat-by-beat hemodynamic system evaluation method named “beat-by-beat HPCD method” is proposed and evaluated.　Gregg’s theoretically driven model of hemodynamics which was called “HPCD method” is improved by using non-invasive and beat-by-beat cardiovascular measurement of mean blood pressure and cardiac output. Continuous beat-by-beat measurements of MBP and CO were done on three healthy male subjects during three hours. In the measurement, a five minutes cold pressor test was executed in each subject and also each subject did exercise using a bicycle ergometer in five minutes and walked during 15 minutes. Measured beat-by-beat MBP and CO can derive beat-by-beat HP (hemodynamic profile) and CO (compensation deficit). Then, beat-by-beat changes clearly observed from plots on HP axis and CD axis plane. More vascular response can be observed on cold pressor and more myocardial response can be observed on ergometer exercise. During walking period, the response is intermediate between cold pressor and ergometer exercise. Finally, the proposed method can be considered as applicable to evaluate cardiovascular bionic system especially on evaluation of a person being subjected to stress. Keywords: hemodynamics; stress; cardiovascular system; hemodynamic profile and compensation deficit mode

The cost of obtaining rewards enhances the reward prediction error signal of midbrain dopamine neurons

Midbrain dopamine neurons are known to encode reward prediction errors (RPE) used to update value predictions. Here, we examine whether RPE signals coded by midbrain dopamine neurons are modulated by the cost paid to obtain rewards, by recording from dopamine neurons in awake behaving monkeys during performance of an effortful saccade task. Dopamine neuron responses to cues predicting reward and to the delivery of rewards were increased after the performance of a costly action compared to a less costly action, suggesting that RPEs are enhanced following the performance of a costly action. At the behavioral level, stimulus-reward associations are learned faster after performing a costly action compared to a less costly action. Thus, information about action cost is processed in the dopamine reward system in a manner that amplifies the following dopamine RPE signal, which in turn promotes more rapid learning under situations of high cost

Indirectly Pumped 3.7 THz InGaAs/InAlAs Quantum-Cascade Lasers Grown by Metal-Organic Vapor-Phase Epitaxy

Device-performances of 3.7 THz indirect-pumping quantum- cascade lasers are demonstrated in an InGaAs/InAlAs material system grown by metal-organic vapor-phase epitaxy. The lasers show a low threshold-current-density of ~420 A/cm2 and a peak output power of ~8 mW at 7 K, no sign of parasitic currents with recourse to well-designed coupled-well injectors in the indirect pump scheme, and a maximum operating temperature of Tmax~100 K. The observed roll-over of output intensities in current ranges below maximum currents and limitation of Tmax are discussed with a model for electron-gas heating in injectors. Possible ways toward elevation of Tmax are suggested