8,562 research outputs found
Isospin breaking in the nucleon mass and the sensitivity of β decays to new physics
We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in β decay if nonstandard interactions are present. In particular, the isovector (pseudo)scalar charge gS(P) of the nucleon can be related to the difference (sum) of the nucleon masses in the absence of electromagnetic effects. Using recent determinations of these quantities from phenomenological and lattice QCD studies we obtain the accurate values gS=1.02(11) and gP=349(9) in the modified minimal subtraction scheme at μ=2 GeV. The consequences for searches of nonstandard scalar interactions in nuclear β decays are studied, finding for the corresponding Wilson coefficient εS=0.0012(24) at 90% C.L., which is significantly more stringent than current LHC bounds and previous low-energy bounds using less precise gS values. We argue that our results could be rapidly improved with updated computations and the direct calculation of certain ratios in lattice QCD. Finally, we discuss the pion-pole enhancement of gP, which makes β decays much more sensitive to nonstandard pseudoscalar interactions than previously thought
A Nexafs Study of Nitric Oxide Layers Adsorbed from a nitrite Solution onto a Pt(111) Surface
NO molecules adsorbed on a Pt(111) surface from dipping in an acidic nitrite
solution are studied by near edge X-ray absorption fine structure spectroscopy
(NEXAFS), X-ray photoelectron spectroscopy (XPS), low energy electron
diffraction (LEED) and scanning tunnelling microscopy (STM) techniques. LEED
patterns and STM images show that no long range ordered structures are formed
after NO adsorption on a Pt(111) surface. Although the total NO coverage is
very low, spectroscopic features in N K-edge and O K-edge absorption spectra
have been singled out and related to the different species induced by this
preparation method. From these measurements it is concluded that the NO
molecule is adsorbed trough the N atom in an upright conformation. The maximum
saturation coverage is about 0.3 monolayers, and although nitric oxide is the
major component, nitrite and nitrogen species are slightly co-adsorbed on the
surface. The results obtained from this study are compared with those
previously reported in the literature for NO adsorbed on Pt(111) under UHV
conditions
Relación entre la composición química corporal, la fertilidad y la prolificidad en conejas primíparas.
En este trabajo se ha estudiado el efecto de la composición química corporal, estimada mediante el método de impedancia bioeléctrica (BIA) en la primera y segunda inseminación artificial (IA), sobre la fertilidad y la prolificidad de conejas primíparas. Se utilizaron los datos de 137 conejas procedentes de dos granjas que utilizaban dos genéticas distintas (UPV e Hyplus) y tres ritmos reproductivos (R4: inseminación a los 4 días tras el parto y destete a los 28 días, R11: inseminación a los 11 días postparto y destete a 35 días y R14: inseminación a los 14 días tras el parto y destete a los 42 días). La fertilidad media observada en el segundo parto fue de un 56,2% y el porcentaje de nacidos vivos, sobre los nacidos totales, fue de un 87,5%, no encontrándose diferencias entre los ritmos utilizados. El aumento de la proporción de proteína corporal, grasa y energía en la primera IA tuvieron un efecto positivo (P=0,007; P=0,03 y P<0,001, respectivamente) sobre la fertilidad del segundo parto. Igualmente, un mayor contenido en grasa (P<0,001) y energía (P<0,001) en la segunda IA también incrementaron la fertilidad del segundo parto. El incremento del ratio proteína/energía corporal de las conejas, determinado en las dos IA, tuvo un efecto negativo sobre la fertilidad en el segundo parto (P<0,001), observándose mejores resultados en conejas con 12 g proteína/MJ respecto a otras con valores superiores. El porcentaje de nacidos vivos (P<0,001), sobre los nacidos totales, aumentó con la proporción de proteína de las conejas en el momento de la segunda IA, pero esta última no tuvo efecto sobre la fertilidad.
This study evaluated the effect of chemical body composition at first and second artificial inseminations (AI), determined by bioelectric impedance technique (BIA), on fertility and prolificacy of primiparous rabbit does. Data of 137 does from two farms using two different genetics (UPV and Hyplus) and three breeding systems were analyzed. Fertility was 56.2 % and the percentage of kits born alive over total born was 87.5 %. Breeding system had no effect on fertility or the percentage of kits born alive. Higher body protein, fat and energy of the rabbit doe at first artificial insemination (AI) increased the fertility in the second parity (P=0.007, P=0.03 and P<0.001 respectively). Fat and energy content of the doe at the second AI affected positively fertility in the second parity (P<0.001 and P<0.001 respectively), while protein influenced positively only prolificacy (P<0.001). The increase of the ratio protein/energy in both AI moments had a negative influence on fertility in the second parity (P<0.001), rabbit does with 12 g protein/MJ showed a higher fertility than those with higher value
On the algorithmic construction of classifying spaces and the isomorphism problem for biautomatic groups
We show that the isomorphism problem is solvable in the class of central
extensions of word-hyperbolic groups, and that the isomorphism problem for
biautomatic groups reduces to that for biautomatic groups with finite centre.
We describe an algorithm that, given an arbitrary finite presentation of an
automatic group , will construct explicit finite models for the skeleta
of and hence compute the integral homology and cohomology of
.Comment: 21 pages, 4 figure
Interpreting the kinematics of the extended gas in distant radiogalaxies from 8-10m telescope spectra
The nature of the extreme kinematics in the extended gas of distant radio
galaxies (z>0.7) is still an open question. With the advent of the 8-10 m
telescope generation and the development of NIR arrays we are in the position
for the first time to develop a more detailed study by using lines other than
Lya and [OII]3727 depending on redshift. In this paper we review the main
sources of uncertainty in the interpretation of the emission line kinematics:
the presence of several kinematic components, Lya absorption by neutral
gas/dust and the contribution of scattered light to some of the lines. As an
example, several kinematic components can produce apparent, false rotation
curves. We propose methods to solve these uncertainties. We propose to extend
the methods applied to low redshift radio galaxies to investigate the nature of
the kinematics in distant radio galaxies: by means of the spectral
decomposition of the strong optical emission lines (redshifted into the NIR) we
can isolate the different kinematic components and study the emission line
ratios for the individual components. If shocks are responsible for the extreme
kinematics, we should be able to isolate a kinematic component (the shocked
gas) with large FWHM (>900 km/s), low ionization level [OIII]5007/Hb~2-4 and
weak HeII4686/Hb<0.07, together with a narrow component (~few hundred km/s)
with higher ionization level and strong HeII emission (HeII/Hb~0.5)Comment: 11 pages, 6 Figures, to be published in A&A Supplement Serie
Disorder induced phase segregation in La2/3Ca1/3MnO3 manganites
Neutron powder diffraction experiments on La2/3Ca1/3MnO3 over a broad
temperature range above and below the metal-insulator transition have been
analyzed beyond the Rietveld average approach by use of Reverse Monte Carlo
modelling. This approach allows the calculation of atomic pair distribution
functions and spin correlation functions constrained to describe the observed
Bragg and diffuse nuclear and magnetic scattering. The results evidence phase
separation within a paramagnetic matrix into ferro and antiferromagnetic
domains correlated to anistropic lattice distortions in the vicinity of the
metal-insulator transition.Comment: 3 pages, 4 figures. Submitted to Phys. Rev. Lett. Figure 1 replace
Mid-infrared imaging- and spectro-polarimetric subarcsecond observations of NGC 1068
We present sub-arcsecond 7.513 m imaging- and spectro-polarimetric
observations of NGC 1068 using CanariCam on the 10.4-m Gran Telescopio
CANARIAS. At all wavelengths, we find:
(1) A 90 60 pc extended polarized feature in the northern ionization
cone, with a uniform 44 polarization angle. Its polarization
arises from dust and gas emission in the ionization cone, heated by the active
nucleus and jet, and further extinguished by aligned dust grains in the host
galaxy. The polarization spectrum of the jet-molecular cloud interaction at
24 pc from the core is highly polarized, and does not show a silicate
feature, suggesting that the dust grains are different from those in the
interstellar medium.
(2) A southern polarized feature at 9.6 pc from the core. Its
polarization arises from a dust emission component extinguished by a large
concentration of dust in the galaxy disc. We cannot distinguish between dust
emission from magnetically aligned dust grains directly heated by the jet close
to the core, and aligned dust grains in the dusty obscuring material
surrounding the central engine. Silicate-like grains reproduce the polarized
dust emission in this feature, suggesting different dust compositions in both
ionization cones.
(3) An upper limit of polarization degree of 0.3 per cent in the core. Based
on our polarization model, the expected polarization of the obscuring dusty
material is 0.1 per cent in the 813 m wavelength range. This
low polarization may be arising from the passage of radiation through aligned
dust grains in the shielded edges of the clumps.Comment: 17 pages, 10 figures, accepted for publication at MNRA
Dynamical fermion mass generation at a tricritical point in strongly coupled U(1) lattice gauge theory
Fermion mass generation in the strongly coupled U(1) lattice gauge theory
with fermion and scalar fields of equal charge is investigated by means of
numerical simulation with dynamical fermions. Chiral symmetry of this model is
broken by the gauge interaction and restored by the light scalar. We present
evidence for the existence of a particular, tricritical point of the
corresponding phase boundary where the continuum limit might possibly be
constructed. It is of interest as a model for dynamical symmetry breaking and
mass generation due to a strong gauge interaction. In addition to the massive
and unconfined fermion F and Goldstone boson , a gauge ball of mass and some other states are found. Tricritical exponents appear
to be non-classical.Comment: 21 page
GJ 900: A new hierarchical system with low-mass components
Speckle interferometric observations made with the 6 m telescope of the
Special Astrophysical Observatory of the Russian Academy of Sciences in 2000
revealed the triple nature of the nearby ( mas)
low-mass young ( Myr) star GJ 900. The configuration of the triple
system allowed it to be dynamically unstable. Differential photometry performed
from 2000 through 2004 yielded - and -band absolute magnitudes and
spectral types for the components to be =6.660.08,
=9.150.11, =10.080.26, =4.840.08,
=6.760.20, =7.390.31, K5--K7,
M3--M4, M5--M6. The ``mass--luminosity''
relation is used to estimate the individual masses of the components:
,
,
. From the observations of the
components relative motion in the period 2000--2006, we conclude that GJ 900 is
a hierarchical triple star with the possible orbital periods
P80 yrs and P20 yrs. An analysis of the 2MASS
images of the region around GJ 900 leads us to suggest that the system can
include other very-low-mass components.Comment: 7 pages, 5 figure
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