563 research outputs found
Organismos tipo micoplasma associados ao superbrotamento do picão.
Plantas de picão (Bidens pilosa L.) mostrando anomalias do tipo superbrotamento pro- cedentes do Estado do Paraná, foram estudadas por microscopia eletrônica. Foi constatada a presença de corpúsculos tipo micoplasma nos tubos crivados do floema. São observadas duas formas destes microorganismos, uma globular, grande, com diâmetro entre 350 e 900 nm e outra forma pequena, pleomorfica, com diâmetro de 1·50-250nm. A ultraestrutura destes organismos é discutida em relação a outros agentes fitopatogênicos que podem ser encontra- dos no floema
Genetic mechanisms underlying spermatic and testicular traits within and among cattle breeds: systematic review and prioritization of GWAS results1
[EN] Reduced bull fertility imposes economic losses in bovine herds. Specifically, testicular and spermatic traits are important indicators of reproductive efficiency. Several genome-wide association studies (GWAS) have identified genomic regions associated with these fertility traits. The aims of this study were as follows: 1) to perform a systematic review of GWAS results for spermatic and testicular traits in cattle and 2) to identify key functional candidate genes for these traits. The identification of functional candidate genes was performed using a systems biology approach, where genes shared between traits and studies were evaluated by a guilt by association gene prioritization (GUILDify and ToppGene software) in order to identify the best functional candidates. These candidate genes were integrated and analyzed breeds. Results showed that GWAS for testicular-related traits have been developed for beef breeds only, whereas the majority of GWAS for spermatic-related traits were conducted using dairy breeds. comparing traits measured within the same study, the highest number of genes shared between different traits was observed, indicating a high impact of the population genetic structure and environmental effects. Several chromosomal regions were enriched for functional candidate genes associated with fertility traits. Moreover, multiple functional candidate genes were enriched for markers in a species-specific basis, taurine (Bos taurus) or indicine (Bos indicus). For the different candidate regions identified in the GWAS in the literature, functional candidate genes were detected as follows: B. Taurus chromosome X (BTX) (TEX11, IRAK, CDK16, ATP7A, ATRX, HDAC6, FMR1, L1CAM, MECP2, etc.), BTA17 (TRPV4 and DYNLL1), and BTA14 (MOS, FABP5, ZFPM2). These genes are responsible for regulating metabolic pathways or biological processes associated with fertility, such as progression of spermatogenesis, control of ciliary activity, development of Sertoli cells, DNA integrity in spermatozoa, and homeostasis of testicular cells. This study represents the first systematic review on male fertility traits in cattle using a system biology approach to identify key candidate genes for these traits.S
Vacuum decay in quantum field theory
We study the contribution to vacuum decay in field theory due to the
interaction between the long and short-wavelength modes of the field. The field
model considered consists of a scalar field of mass with a cubic term in
the potential. The dynamics of the long-wavelength modes becomes diffusive in
this interaction. The diffusive behaviour is described by the reduced Wigner
function that characterizes the state of the long-wavelength modes. This
function is obtained from the whole Wigner function by integration of the
degrees of freedom of the short-wavelength modes. The dynamical equation for
the reduced Wigner function becomes a kind of Fokker-Planck equation which is
solved with suitable boundary conditions enforcing an initial metastable vacuum
state trapped in the potential well. As a result a finite activation rate is
found, even at zero temperature, for the formation of true vacuum bubbles of
size . This effect makes a substantial contribution to the total decay
rate.Comment: 27 pages, RevTeX, 1 figure (uses epsf.sty
Vacuum decay in quantum field theory
We study the contribution to vacuum decay in field theory due to the
interaction between the long and short-wavelength modes of the field. The field
model considered consists of a scalar field of mass with a cubic term in
the potential. The dynamics of the long-wavelength modes becomes diffusive in
this interaction. The diffusive behaviour is described by the reduced Wigner
function that characterizes the state of the long-wavelength modes. This
function is obtained from the whole Wigner function by integration of the
degrees of freedom of the short-wavelength modes. The dynamical equation for
the reduced Wigner function becomes a kind of Fokker-Planck equation which is
solved with suitable boundary conditions enforcing an initial metastable vacuum
state trapped in the potential well. As a result a finite activation rate is
found, even at zero temperature, for the formation of true vacuum bubbles of
size . This effect makes a substantial contribution to the total decay
rate.Comment: 27 pages, RevTeX, 1 figure (uses epsf.sty
Vacuum Instabilities with a Wrong-Sign Higgs-Gluon-Gluon Amplitude
The recently discovered 125 GeV boson appears very similar to a Standard
Model Higgs, but with data favoring an enhanced h to gamma gamma rate. A number
of groups have found that fits would allow (or, less so after the latest
updates, prefer) that the h-t-tbar coupling have the opposite sign. This can be
given meaning in the context of an electroweak chiral Lagrangian, but it might
also be interpreted to mean that a new colored and charged particle runs in
loops and produces the opposite-sign hGG amplitude to that generated by
integrating out the top, as well as a contribution reinforcing the W-loop
contribution to hFF. In order to not suppress the rate of h to WW and h to ZZ,
which appear to be approximately Standard Model-like, one would need the loop
to "overshoot," not only canceling the top contribution but producing an
opposite-sign hGG vertex of about the same magnitude as that in the SM. We
argue that most such explanations have severe problems with fine-tuning and,
more importantly, vacuum stability. In particular, the case of stop loops
producing an opposite-sign hGG vertex of the same size as the Standard Model
one is ruled out by a combination of vacuum decay bounds and LEP constraints.
We also show that scenarios with a sign flip from loops of color octet charged
scalars or new fermionic states are highly constrained.Comment: 20 pages, 8 figures; v2: references adde
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
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