277 research outputs found
Surfactant-Mediated Epitaxial Growth of Single-Layer Graphene in an Unconventional Orientation on SiC
We report the use of a surfactant molecule during the epitaxy of graphene on
SiC(0001) that leads to the growth in an unconventional orientation, namely
rotation with respect to the SiC lattice. It yields a very
high-quality single-layer graphene with a uniform orientation with respect to
the substrate, on the wafer scale. We find an increased quality and homogeneity
compared to the approach based on the use of a pre-oriented template to induce
the unconventional orientation. Using spot profile analysis low energy electron
diffraction, angle-resolved photoelectron spectroscopy, and the normal
incidence x-ray standing wave technique, we assess the crystalline quality and
coverage of the graphene layer. Combined with the presence of a
covalently-bound graphene layer in the conventional orientation underneath, our
surfactant-mediated growth offers an ideal platform to prepare epitaxial
twisted bilayer graphene via intercalation.Comment: 7 pages, 3 figure
The Role of Corticothalamic Projections (Prelimbic Cortex to Nucleus Reuniens) in Working Memory
Working memory (WM) is the ability to store information for short periods of time and is used to execute tasks
WM has been understood to work via the medial prefrontal cortex (mPFC) and dorsal hippocampus (dHPC), but they do not directly project to each other
The nucleus reuniens of the thalamus (Re) is a “middle man” between the mPFC and dHPC
There are projections between the prelimbic cortex (PrL) and Re that may be used during WM
To test the connection of the PrL to Re, a delayed nonmatch to position (DNMTP) task was performe
Metal-insulator transition in the In/Si(111) surface
The metal-insulator transition observed in the In/Si(111)-4x1 reconstruction
is studied by means of ab initio calculations of a simplified model of the
surface. Different surface bands are identified and classified according to
their origin and their response to several structural distortions. We support
the, recently proposed [New J. of Phys. 7 (2005) 100], combination of a shear
and a Peierls distortions as the origin of the metal-insulator transition. Our
results also seem to favor an electronic driving force for the transition.Comment: Presented in the 23 European Conference in Surface Science, Berlin,
September 2005. Submitted to Surface Science (proceedings of the conference)
in August 200
Courtship of Ambystoma jeffersonianum
7 p. : ill. ; 24 cm.Includes bibliographical references (p. 6-7)
Structure analysis of the Ga-stabilized GaAs(001)-c(8x2) surface at high temperatures
Structure of the Ga-stabilized GaAs(001)-c(8x2) surface has been studied
using rocking-curve analysis of reflection high-energy electron diffraction
(RHEED). The c(8x2) structure emerges at temperatures higher than 600C, but is
unstable with respect to the change to the (2x6)/(3x6) structure at lower
temperatures. Our RHEED rocking-curve analysis at high temperatures revealed
that the c(8x2) surface has the structure which is basically the same as that
recently proposed by Kumpf et al. [Phys. Rev. Lett. 86, 3586 (2001)]. We found
that the surface atomic configurations are locally fluctuated at high
temperatures without disturbing the c(8x2) periodicity.Comment: 14 pages, 4 figures, 1 tabl
Ensemble modeling of very small ZnO nanoparticles
The detailed structural characterization of nanoparticles is a very important issue since it enables a precise understanding of their electronic, optical and magnetic properties. Here we introduce a new method for modeling the structure of very small particles by means of powder X-ray diffraction. Using thioglycerol-capped ZnO nanoparticles with a diameter of less than 3 nm as an example we demonstrate that our ensemble modeling method is superior to standard XRD methods like, e.g., Rietveld refinement. Besides fundamental properties (size, anisotropic shape and atomic structure) more sophisticated properties like imperfections in the lattice, a size distribution as well as strain and relaxation effects in the particles and-in particular-at their surface (surface relaxation effects) can be obtained. Ensemble properties, i.e., distributions of the particle size and other properties, can also be investigated which makes this method superior to imaging techniques like (high resolution) transmission electron microscopy or atomic force microscopy, in particular for very small nanoparticles. For the particles under study an excellent agreement of calculated and experimental X-ray diffraction patterns could be obtained with an ensemble of anisotropic polyhedral particles of three dominant sizes, wurtzite structure and a significant relaxation of Zn atoms close to the surface
Integrated watershed management in India: strategic policy and institutional options- New Priorities for Agricultural Research in Asia.Policy Brief No. AES-01
Community watersheds are growth engines for the
development of dryland areas. Since the beginning
of watershed programs, the approach is constantly
evolving in India. Today watershed projects do not focus
on water conservation solely; integrated watershed
management plays an important role in ensuring food
security, reducing poverty, protecting the environment
and addressing issues such as equity and improved
livelihoods
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