3,341 research outputs found
Native Plants to Arid Areas: A Genetic Reservoir for Drought-Tolerant Crops
Droughts are common in arid areas. These cause important losses in crop production, while the increasing population demands more food and goods. Cultivars able to produce under drought conditions are required to avoid or reduce production losses. Plants have evolved different mechanisms to face drought, and many genes have been already discovered in model and cultivated plants that are involved in this trait. Some of these genes have been successfully transformed into cultivated plants for drought tolerance. Plants native to arid lands may possess variants of drought tolerance mechanisms as compared to mesophytic or model plants. Also, different drought-related genes can be revealed. Studies using high-throughput and bioinformatic tools may allow to discover new genes and give new insights on the mechanisms involved in drought tolerance. However, still scarce studies in plants native to arid lands show that there are many drought-related genes that have not been already characterized and potentially they may be novel genes. These novel genes may be used to improve crops for drought tolerance. Therefore, more physiological, transcriptomic, proteomic, and metabolomic studies are needed on plants native to the deserts
Disponibilidad biológica de lisina de cuatro harinas de pescado anchoveta (engraulis mordax)
Se determinó la disponibilidad biológica de lisina de cuatro lotes de harina de anchoveta (Engraulis mordax) a través de dos metodologías con el propósito de compararlas y de ajustarlas para disminuir las diferencias entre ellas
A Finite Quantum Gravity Field Theory Model
We discuss the quantization of Delta gravity, a two symmetric tensors model
of gravity. This model, in Cosmology, shows accelerated expansion without a
cosmological constant. We present the transformation which
defines the geometry of the model. Then we show that all delta type models live
at one loop only. We apply this to General Relativity and we calculate the one
loop divergent part of the Effective Action showing its null contribution in
vacuum, implying a finite model. Then we proceed to study the existence of
ghosts in the model. Finally, we study the form of the finite quantum
corrections to the classical action of the model.Comment: Latex, 33 page
Short bowel syndrome presenting with re-feeding syndrome in a Han Chinese patient: a case report
Very high energy particle acceleration powered by the jets of the microquasar SS 433
SS 433 is a binary system containing a supergiant star that is overflowing
its Roche lobe with matter accreting onto a compact object (either a black hole
or neutron star). Two jets of ionized matter with a bulk velocity of
extend from the binary, perpendicular to the line of sight, and
terminate inside W50, a supernova remnant that is being distorted by the jets.
SS 433 differs from other microquasars in that the accretion is believed to be
super-Eddington, and the luminosity of the system is erg
s. The lobes of W50 in which the jets terminate, about 40 pc from the
central source, are expected to accelerate charged particles, and indeed radio
and X-ray emission consistent with electron synchrotron emission in a magnetic
field have been observed. At higher energies (>100 GeV), the particle fluxes of
rays from X-ray hotspots around SS 433 have been reported as flux
upper limits. In this energy regime, it has been unclear whether the emission
is dominated by electrons that are interacting with photons from the cosmic
microwave background through inverse-Compton scattering or by protons
interacting with the ambient gas. Here we report TeV -ray observations
of the SS 433/W50 system where the lobes are spatially resolved. The TeV
emission is localized to structures in the lobes, far from the center of the
system where the jets are formed. We have measured photon energies of at least
25 TeV, and these are certainly not Doppler boosted, because of the viewing
geometry. We conclude that the emission from radio to TeV energies is
consistent with a single population of electrons with energies extending to at
least hundreds of TeV in a magnetic field of ~micro-Gauss.Comment: Preprint version of Nature paper. Contacts: S. BenZvi, B. Dingus, K.
Fang, C.D. Rho , H. Zhang, H. Zho
ESPRESSO: The next European exoplanet hunter
The acronym ESPRESSO stems for Echelle SPectrograph for Rocky Exoplanets and
Stable Spectroscopic Observations; this instrument will be the next VLT high
resolution spectrograph. The spectrograph will be installed at the
Combined-Coud\'e Laboratory of the VLT and linked to the four 8.2 m Unit
Telescopes (UT) through four optical Coud\'e trains. ESPRESSO will combine
efficiency and extreme spectroscopic precision. ESPRESSO is foreseen to achieve
a gain of two magnitudes with respect to its predecessor HARPS, and to improve
the instrumental radial-velocity precision to reach the 10 cm/s level. It can
be operated either with a single UT or with up to four UTs, enabling an
additional gain in the latter mode. The incoherent combination of four
telescopes and the extreme precision requirements called for many innovative
design solutions while ensuring the technical heritage of the successful HARPS
experience. ESPRESSO will allow to explore new frontiers in most domains of
astrophysics that require precision and sensitivity. The main scientific
drivers are the search and characterization of rocky exoplanets in the
habitable zone of quiet, nearby G to M-dwarfs and the analysis of the
variability of fundamental physical constants. The project passed the final
design review in May 2013 and entered the manufacturing phase. ESPRESSO will be
installed at the Paranal Observatory in 2016 and its operation is planned to
start by the end of the same year.Comment: 12 pages, figures included, accepted for publication in Astron. Nach
Constraining the Ratio in TeV Cosmic Rays with Observations of the Moon Shadow by HAWC
An indirect measurement of the antiproton flux in cosmic rays is possible as
the particles undergo deflection by the geomagnetic field. This effect can be
measured by studying the deficit in the flux, or shadow, created by the Moon as
it absorbs cosmic rays that are headed towards the Earth. The shadow is
displaced from the actual position of the Moon due to geomagnetic deflection,
which is a function of the energy and charge of the cosmic rays. The
displacement provides a natural tool for momentum/charge discrimination that
can be used to study the composition of cosmic rays. Using 33 months of data
comprising more than 80 billion cosmic rays measured by the High Altitude Water
Cherenkov (HAWC) observatory, we have analyzed the Moon shadow to search for
TeV antiprotons in cosmic rays. We present our first upper limits on the
fraction, which in the absence of any direct measurements, provide
the tightest available constraints of on the antiproton fraction for
energies between 1 and 10 TeV.Comment: 10 pages, 5 figures. Accepted by Physical Review
- …