Stark tuning of the charge states of a two-donor molecule in silicon.

A singly ionized two-donor molecule in silicon is an interesting test-bed system for implementing a quantum bit using charge degrees of freedom at the atomic limit of device fabrication. The operating principles of such a device are based on wavefunction symmetries defined by charge localizations and energy gaps in the spectrum. The Stark-shifted electronic structure of a two-donor phosphorus molecule is investigated using a multi-million-atom tight-binding framework. The effects of surface (S) and barrier (B) gates are analyzed for various voltage regimes. It is found that gate control is smooth for any donor separation, although at certain donor orientations the S and B gates may alter in functionality. Effects such as interface ionization, saturation of the lowest energy gap, and sensitivity to donor and gate placements are also investigated. Excited molecular states of P(2) + are found to impose limits on the allowed donor separations and operating gate voltages for coherent operation. This work therefore outlines and analyzes the various issues that are of importance in the design and control of such donor molecular systems.

Mapping donor electron wave function deformations at a sub-Bohr orbit resolution.

Quantum wave function engineering of dopant-based Si nanostructures reveals new physics in the solid state, and is expected to play a vital role in future nanoelectronics. Central to any fundamental understanding or application is the ability to accurately characterize the deformation of the electron wave functions in these atom-based structures through electric and magnetic field control. We present a method for mapping the subtle changes that occur in the electron wave function through the measurement of the hyperfine tensor probed by (29)Si impurities. We calculate Stark parameters for six shells around the donor. Our results show that detecting the donor electron wave function deformation is possible with resolution at the sub-Bohr radius level.

The vasodilatory effect of ketamine is independent of the N-methyl-D-aspartate receptor: lack of functional N-methyl-D-aspartate receptors in rat mesenteric artery smooth muscle.

BACKGROUND AND OBJECTIVE: Ketamine, which is a general anaesthetic that induces a dissociative anaesthesia, acts by blocking the N-methyl-D-aspartate receptor (NMDAr) in the brain. Although ketamine elevates blood pressure under the clinical setting, the in-vitro effect of ketamine is vasodilatory. However, it is not clear yet whether the vasodilation by ketamine involves functions of the NMDAr. Therefore, we examined whether the NMDAr is functional in vascular smooth muscle and whether the vasodilatory effect of ketamine is associated with the NMDAr. METHODS: We measured isometric tension of endothelium-denuded arterial rings from rat mesentery. The relaxing effects of ketamine, after rings were precontracted with noradrenaline (10 mumol l) or high KCl (70 mmol l), were examined. The effects of DL-2-amino-5-phosphonopentanoic acid (AP-5), a competitive NMDAr blocker that is structurally distinct from ketamine, were also examined. The relaxing effects of ketamine in the presence of AP-5 were compared with those in the absence of AP-5. The effects of NMDAr agonists N-methyl-D-aspartate and glutamate were analysed in order to examine the existence of a functional NMDAr. RESULTS: Both S(+)-ketamine and racemic(+/-)-ketamine, with similar potencies and efficacies and in a concentration-dependent manner, relaxed the precontracted arterial rings. However, AP-5 neither relaxed the arteries nor affected the vasodilatory actions of ketamine. N-methyl-D-aspartate and glutamate (0.01-1 mmol l) had negligible effects on isometric tension under the resting or precontracted condition. CONCLUSION: These results suggest that the NMDAr is not functional in vascular smooth muscle, and the vasodilatory action of ketamine is independent of the NMDAr in the rat mesenteric artery.

Collateral projection from the locus coeruleus to whisker-related sensory and motor brain regions of the rat.

The primary goal of this study was to examine whether the locus coeruleus (LC) provides collateral projections to whisker-related, sensorimotor brain regions. After injections of retrograde tracers into the primary sensory (S1) barrel field/primary whisker motor (M1) cortices, ventroposteromedial (VPM)/ventrolateral (VL) thalamic nuclei, or principal sensory trigeminal (Pr5)/facial motor (Mo7) nuclei, the distribution of double-labeled neurons within the LC was examined. Our observations indicated that a large number of individual LC cells provided axon collaterals to S1-M1 or VPM-VL regions, whereas only a few projected to Pr5-Mo7 nuclei. The laterality and the distribution of dual-projecting LC neurons were as follows. 1) The neurons projecting to the S1-M1 cortices were predominantly ipsilateral (96% +/- 0.7%). Labeled neurons were located ventrally at the rostral pole but were evenly distributed along the dorsoventral aspect of the principal LC. 2) The cells projecting to the VPM-VL nuclei were bilateral, with ipsilateral (68% +/- 2.3%) dominance. Neurons were observed at the rostrocaudal extent of the LC, where the labeling was most pronounced at the ventral, principal LC. 3) The neurons projecting to the Pr5-Mo7 regions exhibited slightly contralateral (56% +/- 2.9%) dominance, where labeled cells were confined within the ventral margin of the principal subdivision. Taken together, the present observations demonstrate that each subdivision of the LC possesses a differential functional organization with respect to its collateral projection to whisker-related sensorimotor targets, suggesting that the nucleus might play a modulatory role in vibrissal sensorimotor integration that allows the guidance of behavioral action essential for the survival of the animal.

Prevalence and risk factors of non-alcoholic fatty liver disease among Korean adults.

BACKGROUND AND AIM: Differences in the prevalence of non-alcoholic fatty liver disease (NAFLD) between Eastern and Western populations are primarily attributable to differences in definitions and biased population selection. Thus, the aim of the present study was to accurately determine the actual prevalence of NAFLD by sonography and to characterize the risk factors for NAFLD. METHODS: The present cross-sectional study was performed with data obtained from 6,648 subjects, all of whom were older than 20 years of age (3,530 men and 3,118 women). The term 'non-drinker' was applied to men who consumed less than 30 g alcohol/day and to women who consumed less than 20 g alcohol/day. Non-alcoholic fatty liver disease was defined as a sonographically detected fatty liver in the absence of viral hepatitis in a non-drinker. RESULTS: Of the 1,613 subjects who were diagnosed with sonographic fatty liver, 1,240 were non-drinkers and had no viral hepatitis. Overall, the unadjusted and age-adjusted prevalences of NAFLD were 18.7% (23% in men, 13.7% in women) and 16.1% (21.6% in men, 11.2% in women), respectively. Multivariate analysis revealed that several risk factors were profoundly associated with the prevalence of NAFLD, including obesity, insulin resistance, hyperlipidemia and hyperglycemia in both genders, as well as age, menopausal status and estrogen medication in women only. CONCLUSIONS: These results demonstrate that the prevalence of NAFLD in Korean adults, according to sonographic surveys, is comparable to that seen in more developed countries. From the perspective of increasing obesity, the high prevalence rates noted in the study may herald an increased burden of chronic liver disease in the Korean population.

Retrograde study of hypocretin-1 (orexin-A) projections to subdivisions of the dorsal raphe nucleus in the rat.

A retrograde tracer, WGA-apo-HRP-gold (WG), was injected into each subdivision of the dorsal raphe (DR) nucleus, and subsequent orexin-A immunostaining was performed for the tuberal region of the hypothalamus in order to investigate orexin projections to the DR. Similar to previous studies, the majority of orexin-single-labeled neurons were observed at the dorsal half of the lateral hypothalamus (LH), the circle around the fornix, i.e., perifornical nucleus (PeF), and the area dorsal to the fornix. The present study reports that hypothalamic neurons exhibited differential projections to each subdivision of the DR. Following WG injections into rostral DR, WG-single-labeled cells were observed at the dorsal half of the LH as well as dorsomedial hypothalamic nucleus. The major input to the intermediate DR originates from the ventromedial portion of the LH, PeF, and the area dorsal to the PeF, whereas one to lateral wing DR derived from PeF as well as the ventrolateral portion of the LH. Following WG injections into caudal DR, WG-single-labeled cells were located at ventromedial LH and the ventrolateral portion of the posterior hypothalamus. Following WG injections into each DR subdivision, WG/orexin-double-labeled neurons were observed at LH, PeF, and the area dorsal to the PeF. Only a few double-labeled cells were observed in dorsomedial and posterior hypothalamic nuclei. Our observations suggest that various hypothalamic neurons differentially project to each subdivision of the DR, a portion of which is orexin-immunoreactive. These orexin-immunoreactive DR-projecting hypothalamic neurons might have wake-related influences over a variety of brain functions subject to DR efferent regulation, including affective behavior, autonomic control, nociception, cognition, and sensorimotor integration.