730 research outputs found
The Little Book of Viruses
Michael Emerman reviews science writer Carl Zimmer's latest book
Field evaluation of rigid and flexible scarifier shanks
Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale
Field evaluation of rigid and flexible scarifier shanks
Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale
Mimivirus Gene Promoters Exhibit an Unprecedented Conservation among all Eukaryotes
The initial analysis of the recently sequenced genome of Acanthamoeba
polyphaga Mimivirus, the largest known double-stranded DNA virus, predicted a
proteome of size and complexity more akin to small parasitic bacteria than to
other nucleo-cytoplasmic large DNA viruses, and identified numerous functions
never before described in a virus. It has been proposed that the Mimivirus
lineage could have emerged before the individualization of cellular organisms
from the 3 domains of life. An exhaustive in silico analysis of the non-coding
moiety of all known viral genomes, now uncovers the unprecedented perfect
conservation of a AAAATTGA motif in close to 50% of the Mimivirus genes. This
motif preferentially occurs in genes transcribed from the predicted leading
strand and is associated with functions required early in the viral infectious
cycle, such as transcription and protein translation. A comparison with the
known promoter of unicellular eukaryotes, in particular amoebal protists,
strongly suggests that the AAAATTGA motif is the structural equivalent of the
TATA box core promoter element. This element is specific to the Mimivirus
lineage, and may correspond to an ancestral promoter structure predating the
radiation of the eukaryotic kingdoms. This unprecedented conservation of core
promoter regions is another exceptional features of Mimivirus, that again
raises the question of its evolutionary origin
Charge Transfer from Regularized Symmetry-Adapted Perturbation Theory
16 pages, 16 figure
Low energy measurement of the 7Be(p,gamma)8B cross section
We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm =
185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi).
Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^*
decay, respectively, were measured using a large acceptance spectrometer. The
zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a
weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is
deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let
The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters
The role of the bridging ligand on the effective Heisenberg coupling
parameters is analyzed in detail. This analysis strongly suggests that the
ligand-to-metal charge transfer excitations are responsible for a large part of
the final value of the magnetic coupling constant. This permits to suggest a
new variant of the Difference Dedicated Configuration Interaction (DDCI)
method, presently one of the most accurate and reliable for the evaluation of
magnetic effective interactions. This new method treats the bridging ligand
orbitals mediating the interaction at the same level than the magnetic orbitals
and preserves the high quality of the DDCI results while being much less
computationally demanding. The numerical accuracy of the new approach is
illustrated on various systems with one or two magnetic electrons per magnetic
center. The fact that accurate results can be obtained using a rather reduced
configuration interaction space opens the possibility to study more complex
systems with many magnetic centers and/or many electrons per center.Comment: 7 pages, 4 figure
Three-Dimensional Reconstruction of the Giant Mimivirus Particle with an X-Ray Free-Electron Laser
Citation: Ekeberg, T., Svenda, M., Abergel, C., Maia, F., Seltzer, V., Claverie, J. M., . . . Hajdu, J. (2015). Three-Dimensional Reconstruction of the Giant Mimivirus Particle with an X-Ray Free-Electron Laser. Physical Review Letters, 114(9), 6. doi:10.1103/PhysRevLett.114.098102We present a proof-of-concept three-dimensional reconstruction of the giant mimivirus particle from experimentally measured diffraction patterns from an x-ray free-electron laser. Three-dimensional imaging requires the assembly of many two-dimensional patterns into an internally consistent Fourier volume. Since each particle is randomly oriented when exposed to the x-ray pulse, relative orientations have to be retrieved from the diffraction data alone. We achieve this with a modified version of the expand, maximize and compress algorithm and validate our result using new methods.Additional Authors: Andersson, I.;Loh, N. D.;Martin, A. V.;Chapman, H.;Bostedt, C.;Bozek, J. D.;Ferguson, K. R.;Krzywinski, J.;Epp, S. W.;Rolles, D.;Rudenko, A.;Hartmann, R.;Kimmel, N.;Hajdu, J
- …