448 research outputs found
Local pressure-induced metallization of a semiconducting carbon nanotube in a crossed junction
The electronic and vibrational density of states of a semiconducting carbon
nanotube in a crossed junction was investigated by elastic and inelastic
scanning tunneling spectroscopy. The strong radial compression of the nanotube
at the junction induces local metallization spatially confined to a few nm. The
local electronic modifications are correlated with the observed changes in the
radial breathing and G-band phonon modes, which react very sensitively to local
mechanical deformation. In addition, the experiments reveal the crucial
contribution of the image charges to the contact potential at nanotube-metal
interfaces
Uterine NK cells are critical in shaping DC immunogenic functions compatible with pregnancy progression.
Dendritic cell (DC) and natural killer (NK) cell interactions are important for the regulation of innate and adaptive immunity, but their relevance during early pregnancy remains elusive. Using two different strategies to manipulate the frequency of NK cells and DC during gestation, we investigated their relative impact on the decidualization process and on angiogenic responses that characterize murine implantation. Manipulation of the frequency of NK cells, DC or both lead to a defective decidual response characterized by decreased proliferation and differentiation of stromal cells. Whereas no detrimental effects were evident upon expansion of DC, NK cell ablation in such expanded DC mice severely compromised decidual development and led to early pregnancy loss. Pregnancy failure in these mice was associated with an unbalanced production of anti-angiogenic signals and most notably, with increased expression of genes related to inflammation and immunogenic activation of DC. Thus, NK cells appear to play an important role counteracting potential anomalies raised by DC expansion and overactivity in the decidua, becoming critical for normal pregnancy progression
Absolute frequency measurement of the magnesium intercombination transition
We report on a frequency measurement of the clock
transition of Mg on a thermal atomic beam. The intercombination
transition has been referenced to a portable primary Cs frequency standard with
the help of a femtosecond fiber laser frequency comb. The achieved uncertainty
is which corresponds to an increase in accuracy of six
orders of magnitude compared to previous results. The measured frequency value
permits the calculation of several other optical transitions from to
the -level system for Mg, Mg and Mg. We describe in
detail the components of our optical frequency standard like the stabilized
spectroscopy laser, the atomic beam apparatus used for Ramsey-Bord\'e
interferometry and the frequency comb generator and discuss the uncertainty
contributions to our measurement including the first and second order Doppler
effect. An upper limit of in one second for the short term
instability of our optical frequency standard was determined by comparison with
a GPS disciplined quartz oscillator.Comment: 8 pages, 8 figure
Tuning the electronic structures of armchair graphene nanoribbons through chemical edge modification: A theoretical study
We report combined first-principle and tight-binding (TB) calculations to
simulate the effects of chemical edge modifications on structural and
electronic properties. The C-C bond lengths and bond angles near the GNR edge
have considerable changes when edge carbon atoms are bounded to different
atoms. By introducing a phenomenological hopping parameter for
nearest-neighboring hopping to represent various chemical edge modifications,
we investigated the electronic structural changes of nanoribbons with different
widths based on the tight-binding scheme. Theoretical results show that addends
can change the band structures of armchair GNRs and even result in observable
metal-to-insulator transition.Comment: 4 pages and 4 figure
Fram Strait Studies (FRAMZY 2002 and ACSYS-ABSIS 2003) ice drifter data evaluation for sea ice kinematics and dynamics studies - technical report
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Johanna Ikävalko: Review of oil spill effects on Arctic marine ecosystem
Interface-Induced Room-Temperature Ferromagnetism in Hydrogenated Epitaxial Graphene
Quantum Matter and Optic
Interface-Induced Room-Temperature Ferromagnetism in Hydrogenated Epitaxial Graphene
Quantum Matter and Optic
Probing Quantum Confinement of Single-Walled Carbon Nanotubes by Resonant Soft-X-Ray Emission Spectroscopy
[[abstract]]We report the band-structure changes near Fermi level for single-walled carbon nanotubes (SWNTs) with diameters down to 1 nm from the study of soft-x-ray absorption and resonant emission spectroscopy. The observed quantum confinement of SWNTs affects both pi and sigma bands and bandgap through the rehybridization of pi and sigma orbitals. The significant changes of electronic structure are proved to be a measure for the mean diameter of the macroscopic amounts of SWNTs. (C) 2008 American Institute of Physics.[[notice]]補正完畢[[booktype]]紙
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