461 research outputs found
Atomic and Electronic Structures of Unreconstructed Polar MgO(111) Thin Film on Ag(111)
Atomic and electronic structures of a polar surface of MgO formed on Ag(111)
was investigated by using reflection high energy electron diffraction (RHEED),
Auger electron spectroscopy, electron energy loss spectroscopy (EELS), and
ultraviolet photoemission spectroscopy (UPS). A rather flat unreconstructed
polar MgO(111) 11 surface could be grown by alternate adsorption of Mg
and O on Ag(111). The stability of the MgO(111) surface was discussed in
terms of interaction between Ag and Mg atoms at the interface, and charge state
of the surface atoms. EELS of this surface did not show a band gap region, and
finite density of states appeared at the Fermi level in UPS. These results
suggest that a polar MgO(111) surface was not an insulating surface but a
semiconducting or metallic surface.Comment: 6 figures, to be published in Phys. Rev.
Effect of bonding of a CO molecule on the conductance of atomic metal wires
We have measured the effect of bonding of a CO molecule on the conductance of
Au, Cu, Pt, and Ni atomic contacts at 4.2 K. When CO gas is admitted to the
metal nano contacts, a conductance feature appears in the conductance histogram
near 0.5 of the quantum unit of conductance, for all metals. For Au, the
intensity of this fractional conductance feature can be tuned with the bias
voltage, and it disappears at high bias voltage (above 200 mV). The
bonding of CO to Au appears to be weakest, and associated with monotomic Au
wire formation.Comment: 6 figure
Evidence for a single hydrogen molecule connected by an atomic chain
Stable, single-molecule conducting-bridge configurations are typically
identified from peak structures in a conductance histogram. In previous work on
Pt with H at cryogenic temperatures it has been shown that a peak near 1
identifies a single molecule Pt-H-Pt bridge. The histogram shows
an additional structure with lower conductance that has not been identified.
Here, we show that it is likely due to a hydrogen decorated Pt chain in contact
with the H molecular bridge.Comment: 4 pages, 4 figure
Rocking motion induced charging of C60 on h-BN/Ni(111)
One monolayer of C60 on one monolayer of hexagonal boron nitride on nickel is
investigated by photoemission. Between 150 and 250 K the work function
decreases and the binding energy of the highest occupied molecular orbital
(HOMO) increases by approx. 100 meV. In parallel, the occupancy of the, in the
cold state almost empty, lowest unoccupied molecular orbital (LUMO) changes by
0.4 electrons. This charge redistribution is triggered by onset of molecular
rocking motion, i.e. by orientation dependent tunneling between the LUMO of C60
and the substrate. The magnitude of the charge transfer is large and cannot be
explained within a single particle picture. It is proposed to involve
electron-phonon coupling where C60- polaron formation leads to electron
self-trapping.Comment: 15 pages, 4 figure
Highly conductive molecular junctions based on direct binding of benzene to platinum electrodes
Highly conductive molecular junctions were formed by direct binding of
benzene molecules between two Pt electrodes. Measurements of conductance,
isotopic shift in inelastic spectroscopy and shot noise compared with
calculations provide indications for a stable molecular junction where the
benzene molecule is preserved intact and bonded to the Pt leads via carbon
atoms. The junction has a conductance comparable to that for metallic atomic
junctions (around 0.1-1 Go), where the conductance and the number of
transmission channels are controlled by the molecule's orientation at different
inter-electrode distances.Comment: 4 pages, 4 figure
Electric field induced charge injection or exhaustion in organic thin film transistor
The conductivity of organic semiconductors is measured {\it in-situ} and
continuously with a bottom contact configuration, as a function of film
thickness at various gate voltages. The depletion layer thickness can be
directly determined as a shift of the threshold thickness at which electric
current began to flow. The {\it in-situ} and continuous measurement can also
determine qualitatively the accumulation layer thickness together with the
distribution function of injected carriers. The accumulation layer thickness is
a few mono layers, and it does not depend on gate voltages, rather depends on
the chemical species.Comment: 4 figures, to be published in Phys. Rev.
Polar surface engineering in ultra-thin MgO(111)/Ag(111) -- possibility of metal-insulator transition and magnetism
A recent report [Kiguchi {\it et al.}, Phys. Rev. B {\bf 68}, 115402 (2003)]
that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes
metallic to reduce the electric dipole moment raises a question of what will
happen when we have fewer MgO layers. Here we have revealed, first
experimentally with electron energy-loss spectroscopy, that MgO(111) remains
metallic even when one-layer thick, and theoretically with the density
functional theory that the metallization should depend on the nature of the
substrate. We further show, with a spin-density functional calculation, that a
ferromagnetic instability may be expected for thicker films.Comment: 5 pages, 7 figure
Reexamination of the role of hematopoietic organs on the hematopoiesis in the silkworm, Bombyx mori
Larval hematopoietic organs (HPO) are thought as the only source of circulating hemocytes in most insects. In this paper, we re-checked the importance of hematopoietic organs to hematopoiesis in the silkworm through surgical operation to remove the organs from silkworm larvae at 12 h after 5 th ecdysis. We observed that there was no significant decrease of hemocyte density but higher ratio of cell division in the HPO-removed wandering larvae. We checked and compared the total hemocytes in circulation and in 4 hematopoietic organs of each larva and found that even we suppose all hemocytes could be released from 4 organs at one time, it could not meet the circulating hemocytes increase in vivo due to huge difference. In order to monitor hemocytes movement in the hematopoietic organs to get information on hemocytes releasing in vivo, we labeled the dividing hemocytes with 5-bromo-2’-deoxyuridine (BrdU) at 12 h after 5th ecdysis and observed BrdU-positive cells in the organs for several days. Our results show that the BrdU-labeled hemocytes were not released as quickly as we thought because there were still many BrdU-positive cells in the wandering organs and some cells even had almost no changed BrdU labeling. Therefore, the silkworm larvae have a novel hematopoiesis because circulating hemocyte division might contribute huge part to the hematopoiesis
BU10038 as a safe opioid analgesic with fewer side-effects after systemic and intrathecal administration in primates
© 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.Background: The marked increase in mis-use of prescription opioids has greatly affected our society. One potential solution is to develop improved analgesics which have agonist action at both mu opioid peptide (MOP) and nociceptin/orphanin FQ peptide (NOP) receptors. BU10038 is a recently identified bifunctional MOP/NOP partial agonist. The aim of this study was to determine the functional profile of systemic or spinal delivery of BU10038 in primates after acute and chronic administration. Methods: A series of behavioural and physiological assays have been established specifically to reflect the therapeutic (analgesia) and side-effects (abuse potential, respiratory depression, itch, physical dependence, and tolerance) of opioid analgesics in rhesus monkeys. Results: After systemic administration, BU10038 (0.001–0.01 mg kg −1 ) dose-dependently produced long-lasting antinociceptive and antihypersensitive effects. Unlike the MOP agonist oxycodone, BU10038 lacked reinforcing effects (i.e. little or no abuse liability), and BU10038 did not compromise the physiological functions of primates including respiration, cardiovascular activities, and body temperature at antinociceptive doses and a 10–30-fold higher dose (0.01–0.1 mg kg −1 ). After intrathecal administration, BU10038 (3 μg) exerted morphine-comparable antinociception and antihypersensitivity without itch scratching responses. Unlike morphine, BU10038 did not cause the development of physical dependence and tolerance after repeated and chronic administration. Conclusions: These in vivo findings demonstrate the translational potential of bifunctional MOP/NOP receptor agonists such as BU10038 as a safe, non-addictive analgesic with fewer side-effects in primates. This study strongly supports that bifunctional MOP/NOP agonists may provide improved analgesics and an alternative solution for the ongoing prescription opioid crisis.Peer reviewedFinal Published versio
Adsorbate and defect effects on electronic and transport properties of gold nanotubes
First-principles calculations have been performed to study the effects of
adsorbates (CO molecules and O atoms) and defects on electronic structures and
transport properties of Au nanotubes (Au(5, 3) and Au(5, 5)). For CO
adsorption, various adsorption sites of CO on the Au tubes were considered. The
vibrational frequency of the CO molecule was found to be very different for two
nearly degenerate stable adsorption configurations of Au(5, 3), implying the
possibility of distinguishing these two configurations via measuring the
vibrational frequency of CO in experiments. After CO adsorption, the
conductance of Au(5, 3) decreases by 0.9G0 and the conductance of Au(5, 5)
decreases by approximately 0.5G0. For O-adsorbed Au tubes, O atoms strongly
interact with Au tubes, leading to around 2G0 of drop in conductance for both
Au tubes. These results may have implications for Au-tube-based chemical
sensing. When a monovacancy defect is present, we found that, for both tubes,
the conductance decreases by around 1G0. Another type of defect arising from
the adhesion of one Au atom is also considered. For this case, it is found
that, for the Au(5, 3) tube, the defect decreases the conductance by nearly
1G0, whereas for Au(5, 5), the decrease in conductance is only 0.3G0.Comment: 7 pages, 8 figure
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