Y. S. Yang

Bistable resistance memory switching effect in amorphous InGaZnO thin films

We report a bistable resistance switching effect in amorphous InGaZnO (a-IGZO) thin films deposited by a pulsed laser deposition method. The electrical properties of a-IGZO thin films were controlled by the oxygen partial pressure during deposition and this determined the resistance switching effect. We also observed the resistance switching effect with various electrodes such as Pt, Au, and Al. We suggest that the resistance switching effect is related to the formation of a conducting path by metal and/or oxygen vacancy defects in the a-IGZO matrix.We report a bistable resistance switching effect in amorphous InGaZnO (a-IGZO) thin films deposited by a pulsed laser deposition method. The electrical properties of a-IGZO thin films were controlled by the oxygen partial pressure during deposition and this determined the resistance switching effect. We also observed the resistance switching effect with various electrodes such as Pt, Au, and Al. We suggest that the resistance switching effect is related to the formation of a conducting path by metal and/or oxygen vacancy defects in the a-IGZO matrix.

Possible effect of norepinephrine transporter polymorphisms on methylphenidate-induced changes in neuropsychological function in attention-deficit hyperactivity disorder

BackgroundDysregulation of noradrenergic system may play important roles in pathophysiology of attention-deficit/hyperactivity disorder (ADHD). We examined the relationship between polymorphisms in the norepinephrine transporter SLC6A2 gene and attentional performance before and after medication in children with ADHD.MethodsFifty-three medication-naïve children with ADHD were genotyped and evaluated using the continuous performance test (CPT). After 8-weeks of methylphenidate treatment, these children were evaluated by CPT again. We compared the baseline CPT measures and the post-treatment changes in the CPT measures based on the G1287A and the A-3081T polymorphisms of SLC6A2.ResultsThere was no significant difference in the baseline CPT measures associated with the G1287A or A-3081T polymorphisms. After medication, however, ADHD subjects with the G/G genotype at the G1287A polymorphism showed a greater decrease in the mean omission error scores (p = 0.006) than subjects with the G/A or A/A genotypes, and subjects with the T allele at the A-3081T polymorphism (T/T or A/T) showed a greater decrease in the mean commission error scores (p = 0.003) than those with the A/A genotypes.ConclusionsOur results provide evidence for the possible role of the G1287A and A-3081T genotypes of SLC6A2 in methylphenidate-induced improvement in attentional performance and support the noradrenergic hypothesis for the pathophysiology of ADHD.

Regional brain perfusion before and after treatment with methylphenidate may be associated with the G1287A polymorphism of the norepinephrine transporter gene in children with attention-deficit/hyperactivity disorder.

The noradrenergic system modulates attention and arousal. Dysregulation of the noradrenergic system may be involved in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). This study intended to examine the differences in methylphenidate (MPH) treatment response and pre- and post-treatment cerebral perfusion associated with the G1287A and -3081(A/T) polymorphisms of the norepinephrine transporter (NET) gene in ADHD children. Thirty-seven drug-naïve ADHD children (8.9±1.8 years old, M=32, F=5) were genotyped. Next, baseline single-photon emission computed tomography (SPECT) and clinical assessments were carried out for ADHD subjects. After 8 weeks of MPH treatment, SPECT and clinical assessment were repeated. There were no differences in baseline clinical assessments or cerebral perfusion based on genotype. However, after treatment, ADHD children with the G/G genotype at the G1287A polymorphism showed more improvement in symptoms than children without the G/G genotype as evaluated by the Clinical Global Impressions-Improvement scale (p=0.022). Furthermore, ADHD children with the G/G genotype at the G1287A polymorphism showed hyperperfusion in the right inferior temporal gyrus (p<0.001, uncorrected) and middle temporal gyrus (p=0.001, uncorrected) compared to children without the G/G genotype. Although the results of this study should be interpreted cautiously, they suggest that polymorphisms of the NET gene may contribute to an intermediate phenotype. Further studies should clearly elucidate the relationship between treatment response and functional connectivity in the brain according to this genetic polymorphism.

White-Matter Connectivity and Methylphenidate-Induced Changes in Attentional Performance According to α2A-Adrenergic Receptor Gene Polymorphisms in Korean Children With Attention-Deficit Hyperactivity Disorder

The authors examined the association between the MspI C/G and DraI C/T genotypes of the α2A-adrenergic receptor gene and white-matter connectivity and attentional performance before and after medication in 53 children with attention-deficit hyperactivity disorder. Subjects who carried the T allele at the DraI polymorphism showed fewer changes in the mean commission error scores after 8 weeks of medication and decreased fractional anisotropy (FA) values in the right middle frontal cortex than subjects without the T allele. Subjects with the C allele at the MspI polymorphism showed decreased FA values in the right postcentral gyrus than subjects without.

Directional growth by low electric-field-controlled crystallization of bulk amorphous lithium tetraborate

Highly oriented rod-shaped crystals were grown during crystallization of bulk amorphous Li2B4O7 under a low ac electric field of ∼5V∕mm. The crystal c axis that is the long direction of rods and perpendicular to the flat surface of the sample is parallel to the applied electric-field direction. The oriented crystals, with an alignment within a declined angle of ∼15°, are so long along the c direction compared with those of other directions that the geometrical structure of each rod is quasi-one-dimensional. The measured electromechanical coupling coefficient of kt=0.47 is comparable to that of single-crystal Li2B4O7.

Thermal and mechanical properties of amorphous Zr65Al7.5Ni10Cu12.5Ag5 alloy containing nanocrystalline compound particles

The thermal and mechanical properties of an amorphous Zr 65 Al 7.5 Ni 10 Cu 12.5 Ag 5 alloy containing nanocrystalline compound phase were investigated. The Zr 3 Al 2 phase with a spherical shape has a fine size of about 20 nm and is dispersed homogeneously at an interparticle spacing of about 30 nm in an amorphous matrix. The crystallization onset temperature and supercooled liquid regions decrease significantly with an increasing precipitation amount of Zr 3 Al 2 phase, indicating an enhancement of thermal instability. This instability is presumably due to the change of the bonding nature among constituent atoms. The maximum tensile fracture strength (2070 MPa) of this mixed phase alloy is much higher than that (1200 MPa) for the amorphous single phase alloy with the same composition. Meanwhile, the good bending ductility of this alloy remains unchanged. Then, the fracture mode in the maximum tensile fracture strength was the shear type among the maximum shear plane. The significant increase of the tensile fracture strength is possibly due to the role of the nanoscale Zr 3 Al 2 particles as an effective barrier to suppress shear sliding of the amorphous matrix.