52 research outputs found
Preliminary analysis of the potential of LANDSAT imagery to study desertification
The use of LANDSAT imagery to define and delimit areas under process of desertification was investigated. Imagery for two different years (1973 and 1978) and two different seasons (dry and rainy seasons in 1976), were used to identify terrain morphology and vegetation cover. The analysis of LANDSAT interpretation, combined with geological and soil information obtained from published literature, allowed the identification of eleven ecological units which were classified corresponding to the degree of the Xique Xique region of Rio Sao Francisco
Development of heavily vegetated area in Brazil
There are no author-identified significant results in this report
Merging history as a function of halo environment
According to the hierarchical scenario, galaxies form via merging and
accretion of small objects. Using N-body simulations, we study the frequency of
merging events in the history of the halos. We find that at z<~2 the merging
rate of the overall halo population can be described by a simple power law
(1+z)^3. The main emphasis of the paper is on the effects of environment of
halos at the present epoch (z=0). We find that the halos located inside
clusters have formed earlier (dz \approx 1) than isolated halos of the same
mass. At low redshifts (z<1), the merger rate of cluster halos is 3 times lower
than that of isolated halos and 2 times lower than merger rate of halos that
end up in groups by z=0. At higher redshifts (z~1-4), progenitors of cluster
and group halos have 3--5 times higher merger rates than isolated halos. We
briefly discuss implications of our results for galaxy evolution in different
environments.Comment: submitted to the Astrophys. Journal; 11 pages, 9 figs., LaTeX (uses
emulateapj.sty
Automatic interpretation of LANDSAT data to characterize the dispersion of suspended sediments in Artificial Reservoirs
There are no author-identified significant results in this report
Integrated surveys of the natural resources in the Amazonia National Park (Topajos) based on LANDSAT images
There are no author-identified significant results in this report
Buffer gas cooling and trapping of atoms with small magnetic moments
Buffer gas cooling was extended to trap atoms with small magnetic moment
(mu). For mu greater than or equal to 3mu_B, 1e12 atoms were buffer gas cooled,
trapped, and thermally isolated in ultra high vacuum with roughly unit
efficiency. For mu < 3mu_B, the fraction of atoms remaining after full thermal
isolation was limited by two processes: wind from the rapid removal of the
buffer gas and desorbing helium films. In our current apparatus we trap atoms
with mu greater than or equal to 1.1mu_B, and thermally isolate atoms with mu
greater than or equal to 2mu_B. Extrapolation of our results combined with
simulations of the loss processes indicate that it is possible to trap and
evaporatively cool mu = 1mu_B atoms using buffer gas cooling.Comment: 17 pages, 4 figure
The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules
Beams of atoms and molecules are stalwart tools for spectroscopy and studies
of collisional processes. The supersonic expansion technique can create cold
beams of many species of atoms and molecules. However, the resulting beam is
typically moving at a speed of 300-600 m/s in the lab frame, and for a large
class of species has insufficient flux (i.e. brightness) for important
applications. In contrast, buffer gas beams can be a superior method in many
cases, producing cold and relatively slow molecules in the lab frame with high
brightness and great versatility. There are basic differences between
supersonic and buffer gas cooled beams regarding particular technological
advantages and constraints. At present, it is clear that not all of the
possible variations on the buffer gas method have been studied. In this review,
we will present a survey of the current state of the art in buffer gas beams,
and explore some of the possible future directions that these new methods might
take
Formation and dynamics of van der Waals molecules in buffer-gas traps
We show that weakly bound He-containing van der Waals molecules can be
produced and magnetically trapped in buffer-gas cooling experiments, and
provide a general model for the formation and dynamics of these molecules. Our
analysis shows that, at typical experimental parameters, thermodynamics favors
the formation of van der Waals complexes composed of a helium atom bound to
most open-shell atoms and molecules, and that complex formation occurs quickly
enough to ensure chemical equilibrium. For molecular pairs composed of a He
atom and an S-state atom, the molecular spin is stable during formation,
dissociation, and collisions, and thus these molecules can be magnetically
trapped. Collisional spin relaxations are too slow to affect trap lifetimes.
However, helium-3-containing complexes can change spin due to adiabatic
crossings between trapped and untrapped Zeeman states, mediated by the
anisotropic hyperfine interaction, causing trap loss. We provide a detailed
model for Ag3He molecules, using ab initio calculation of Ag-He interaction
potentials and spin interactions, quantum scattering theory, and direct Monte
Carlo simulations to describe formation and spin relaxation in this system. The
calculated rate of spin-change agrees quantitatively with experimental
observations, providing indirect evidence for molecular formation in
buffer-gas-cooled magnetic traps.Comment: 20 pages, 13 figure
Non-protein coding RNA biomarkers and differential expression in cancers: a review
<p>Abstract</p> <p>Background</p> <p>In these years a huge number of human transcripts has been found that do not code for proteins, named non-protein coding RNAs. In most cases, small (miRNAs, snoRNAs) and long RNAs (antisense RNA, dsRNA, and long RNA species) have many roles, functioning as regulators of other mRNAs, at transcriptional and post-transcriptional level, and controlling protein ubiquitination and degradation. Various species of npcRNAs have been found differentially expressed in different types of cancer. This review discusses the published data and new results on the expression of a subset of npcRNAs.</p> <p>Conclusion</p> <p>These results underscore the complexity of the RNA world and provide further evidence on the involvement of functional RNAs in cancer cell growth control.</p
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