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Electroluminescence (EL) efficiency is comparatively investigated in the c-plane blue and green multiplequantum-well (MQW) diodes over a wide temperature range (20-300 K) and as a function of injection current(0.01-10 mA). One striking result of the external quantum efficiency ex observed is that for the blue diodestrong EL quenching can occur at t emperatures below 100 K in agreement with the previous reports, while no significant EL collapse is seen below 100 K for the green MQW diode, especially at low injection currents. This means that the anomalous low temperature EL reduction observed for the blue (In,Ga)N MQW diode is not solely determined by temperature only but strongly modified bychanging the In content in the active layers, suggesting mechanisms ruled by forward-bias dependent weaker carrier capture for the shallow potential depth MQW rather than hole freeze-out at deep Mg acceptors.

Aims Tyrosine hydroxylase (TH) and GTP cyclohydrolase I (GCH) are the rate-limiting enzymes for the biosynthesis of catecholamines and tetrahydrobiopterin (BH4), respectively. Since catecholamines and BH4 are thought to be involved in the pathophysiology of CFS, we explored the genetic factors that influence CFS development and examined the possible association between the SNPs of the TH and GCH genes and the various characteristics of CFS patients. Main methods After drawing venous blood from CFS patients and controls, genomic DNA was then extracted from whole blood in accordance with standard procedures. Digestion patterns of the PCR products were used for genotyping the SNPs of GCH (rs841; C+243T) and TH (rs10770141; C−824T). We also performed questionnaires consisting of fatigue-scale and temperament and character inventory scale (TCI) to CFS patients. Key findings Our results demonstrated that the allele differences for the GCH and TH SNPs were not associated with CFS patients. We did find that the GCH gene with the C+243T polymorphism affected harm avoidance, while the TH gene with the C−824T polymorphism affected persistence in the CFS patients. The concept of persistence has been linked to specific personality, such as perfectionism, in CFS. Significance Our results suggest that the biosynthetic pathways of the monoamine neurotransmitters that are mediated by TH and GCH might be associated with the CFS clinical findings, because persistence is one of the typical personality traits observed in CFS and patients with major depressive disorder exhibit a higher harm avoidance score.

PURPOSE. The sense of vision in humans is robust, and visual flickering is rarely experienced. To investigate this mechanism, electrophysiological and molecular biological techniques were used on human cone and rod photoreceptors. METHODS. Voltage-gated currents were recorded using the patch-clamp technique on isolated human cones, and especially their voltage-gated Na + currents were analyzed in detail. Whether Na + channel transcripts could be detected .in single photoreceptors using RT-PCR was also examined, to test the expression of voltage-gated Na + channels in cones and/or rods. RESULTS. Under current-clamp conditions, blocking h currents (hyperpolarization-activated cationic currents) with Cs + , Tl + , or ZD7288 hyperpolarized the resting potentials of cones and rods by ∼10 to 15 mV, and surprisingly generated spontaneous action potentials. The spontaneous spikes were blocked by 1 μM tetrodotoxin, but not by 1 mM Co 2+ , suggesting that they were Na + spikes rather than Ca 2+ spikes. Under voltage-clamp conditions, application of Cs + and ZD7288 markedly decreased the steady inward current through the h channel. This is consistent with Cs + -induced hyperpolarization under a current-clamp condition. SCN2 Na + channel was observed in both cones and rods by single-cell RT-PCR analysis, suggesting that human photoreceptors express the SCN2 Na + channel. CONCLUSIONS. The data confirmed that voltage-gated Na + channels were expressed not only in human rods but also in cones by electrophysiological and molecular biological experiments. These results suggest that the h current may contribute to preventing visual flickering by inhibiting the generation of spontaneous Na + spikes in human photoreceptors.