3,294 research outputs found
Ultrasonography of the reticulum in 30 healthy Saanen goats
Background: The reticulum plays a crucial role in the ruminant digestive tract because the primary cycle of rumen motility always starts with a reticular contraction. In contrast to cattle, there are only few results on the ultrasonographic examination of the reticulum in goats. Therefore, it was the goal of the present study, to describe the results of ultrasonography of the reticulum of 30 healthy Saanen goats. Methods: Ultrasonography was carried out on standing, non-sedated animals using a 5.0 MHz linear transducer. The shape, contour and motility of the reticulum were investigated. A nine-minute video recording of the reticulum was made for each goat and the frequency, duration and amplitude of reticular contractions were calculated as described for cattle. Results: The reticulum appeared as a crescent-shaped structure with a smooth contour located immediately adjacent to the diaphragm. 0.8 to 2.1 (1.41 ± 0.31) reticular contractions were seen per minute. In all goats, biphasic reticular contractions were observed. 90% of the goats also had monophasic reticular contractions, and two had triphasic contractions. During the nine-minute observation periods, there were 0 to 6 monophasic reticular contractions and 6 to 15 biphasic contractions per goat. The duration of the biphasic contractions was 6.56 ± 0.74 s, which was significantly longer than the monophasic contractions at 4.31 ± 0.81 s. The average interval between two reticular contractions was 45.06 ± 12.57 s. Conclusion: Ultrasonography of the reticulum in goats is a valuable tool to characterise the appearance and motility of this organ. In addition to the biphasic motility pattern seen in cattle the reticular motility of goats is characterized by monophasic reticular contractions. The results of the present study are an important contribution for better understanding of the reticular motility in goats
Charged pions from Ni on Ni collisions between 1 and 2 AGeV
Charged pions from Ni + Ni reactions at 1.05, 1.45 and 1.93 AGeV are measured
with the FOPI detector. The mean multiplicities per mean number of
participants increase with beam energy, in accordance with earlier studies of
the Ar + KCl and La + La systems. The pion kinetic energy spectra have concave
shape and are fitted by the superposition of two Boltzmann distributions with
different temperatures. These apparent temperatures depend only weakly on
bombarding energy. The pion angular distributions show a forward/backward
enhancement at all energies, but not the enhancement which was
observed in case of the Au + Au system. These features also determine the
rapidity distributions which are therefore in disagreement with the hypothesis
of one thermal source. The importance of the Coulomb interaction and of the
pion rescattering by spectator matter in producing these phenomena is
discussed.Comment: 22 pages, Latex using documentstyle[12pt,a4,epsfig], to appear in Z.
Phys.
Yukawa couplings and masses of non-chiral states for the Standard Model on D6-branes on T6/Z6'
The perturbative leading order open string three-point couplings for the
Standard Model with hidden USp(6) on fractional D6-branes on T6/Z6' from
arXiv:0806.3039 [hep-th], arXiv:0910.0843 [hep-th] are computed. Physical
Yukawa couplings consisting of holomorphic Wilsonian superpotential terms times
a non-holomorphic prefactor involving the corresponding classical open string
Kaehler metrics are given, and mass terms for all non-chiral matter states are
derived. The lepton Yukawa interactions are at leading order flavour diagonal,
while the quark sector displays a more intricate pattern of mixings. While N=2
supersymmetric sectors acquire masses via only two D6-brane displacements -
which also provide the hierarchies between up- and down-type Yukawas within one
quark or lepton generation -, the remaining vector-like states receive masses
via perturbative three-point couplings to some Standard Model singlet fields
with vevs along flat directions. Couplings to the hidden sector and messengers
for supersymmetry breaking are briefly discussed.Comment: 52 pages (including 8p. appendix); 5 figures; 14 tables; v2:
discussion in section 4.1.3 extended, footnote 5 added, typos corrected,
accepted by JHE
Attosecond physics at the nanoscale
Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this article we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as ATI and HHG. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nano physics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolution
Asymptotic Regge Trajectories of Non-strange Mesons
We analyze the asymptotic behavior of Regge trajectories of non-strange
mesons. In contrast to an existing belief, it is demonstrated that for the
asymptotically linear Regge trajectories the width of heavy hadrons cannot
linearly depend on their mass. Using the data on masses and widths of rho_J,
omega_J, a_J and f_J mesons for the spin values J \leq 6, we extract the
parameters of the asymptotically linear Regge trajectory predicted by the
finite width model of quark gluon bags. As it is shown the obtained parameters
for the data set B correspond to the cross-over temperature lying in the
interval 170.9-175.3 MeV which is consistent with the kinetic freeze-out
temperature of early hadronizing particles found in relativistic heavy ion
collisions at and above the highest SPS energy.Comment: 14 pages, 3 figure
The Herschel Exploitation of Local Galaxy Andromeda (HELGA) II: Dust and Gas in Andromeda
We present an analysis of the dust and gas in Andromeda, using Herschel
images sampling the entire far-infrared peak. We fit a modified-blackbody model
to ~4000 quasi-independent pixels with spatial resolution of ~140pc and find
that a variable dust-emissivity index (beta) is required to fit the data. We
find no significant long-wavelength excess above this model suggesting there is
no cold dust component. We show that the gas-to-dust ratio varies radially,
increasing from ~20 in the center to ~70 in the star-forming ring at 10kpc,
consistent with the metallicity gradient. In the 10kpc ring the average beta is
~1.9, in good agreement with values determined for the Milky Way (MW). However,
in contrast to the MW, we find significant radial variations in beta, which
increases from 1.9 at 10kpc to ~2.5 at a radius of 3.1kpc and then decreases to
1.7 in the center. The dust temperature is fairly constant in the 10kpc ring
(ranging from 17-20K), but increases strongly in the bulge to ~30K. Within
3.1kpc we find the dust temperature is highly correlated with the 3.6 micron
flux, suggesting the general stellar population in the bulge is the dominant
source of dust heating there. At larger radii, there is a weak correlation
between the star formation rate and dust temperature. We find no evidence for
'dark gas' in M31 in contrast to recent results for the MW. Finally, we
obtained an estimate of the CO X-factor by minimising the dispersion in the
gas-to-dust ratio, obtaining a value of (1.9+/-0.4)x10^20 cm^-2 [K kms^-1]^-1.Comment: 19 pages, 18 figures. Submitted to ApJ April 2012; Accepted July 201
Electric Field Control of Spin Transport
Spintronics is an approach to electronics in which the spin of the electrons
is exploited to control the electric resistance R of devices. One basic
building block is the spin-valve, which is formed if two ferromagnetic
electrodes are separated by a thin tunneling barrier. In such devices, R
depends on the orientation of the magnetisation of the electrodes. It is
usually larger in the antiparallel than in the parallel configuration. The
relative difference of R, the so-called magneto-resistance (MR), is then
positive. Common devices, such as the giant magneto-resistance sensor used in
reading heads of hard disks, are based on this phenomenon. The MR may become
anomalous (negative), if the transmission probability of electrons through the
device is spin or energy dependent. This offers a route to the realisation of
gate-tunable MR devices, because transmission probabilities can readily be
tuned in many devices with an electrical gate signal. Such devices have,
however, been elusive so far. We report here on a pronounced gate-field
controlled MR in devices made from carbon nanotubes with ferromagnetic
contacts. Both the amplitude and the sign of the MR are tunable with the gate
voltage in a predictable manner. We emphasise that this spin-field effect is
not restricted to carbon nanotubes but constitutes a generic effect which can
in principle be exploited in all resonant tunneling devices.Comment: 22 pages, 5 figure
J/psi production in a gluon plasma produced in Au-Au collisions at the Relativistic Heavy Ion Collider
Centrality dependence of J/psi production in Au-Au collisions at 200 GeV
nucleon-nucleon center of mass energy is studied using the Glauber model plus
the kinetic formation model. Initial J/psi production and destruction by
incoming nucleons are described by the Glauber model. J/psi-charm equilibration
in the gluon plasma is described by the kinetic formation model. We explore the
possibility of J/psi suppression suggested by the recent PHENIX data. We show
that the J/psi yield monotonically decreases with increasing centrality in the
kinetic formation model when the charm mass is smaller than a critical mass.
The final J/psi yield is between the value after the Glauber suppression and
the dynamical equilibrium value. This underscores the importance of both J/psi
production from d-Au collisions, which is essential in determining the Glauber
suppression, and high statistics Au-Au data, which can further constrain final
state J/psi-charm equilibration
Using the Technology Acceptance Model to conceptualise experiences of the usability and acceptability of a self-management app (COPD.Pal®) for Chronic Obstructive Pulmonary Disease
Chronic Obstructive Pulmonary Disease (COPD) is a long-term progressive inflammatory lung disease causing chronic breathlessness and many hospital admissions. It affects up to 1.2 million people in the UK. To help people with COPD self-manage their condition we developed, in partnership with healthcare users, a digital mobile phone app called COPD.Pal®. We report the first user feedback of COPD.Pal®, applying the Technology Acceptance Model (TAM) theoretical framework.
11 participants engaged with a click dummy version of COPD.Pal® before being asked questions relating to their experiences. A deductive, semantic, reflexive thematic analysis was conducted to analyse their individual and collective experiences. The study was registered at Clinical Trials.gov (NCT04142957).
Two overarching themes resulted: Ease of Use and Perceived Usefulness. Within the former, participants discussed how they wanted flexibility and choice in how they engaged with the app; including how often they used it. Additionally, they discussed how the app layout should make it straightforward to use, whilst unanimously agreeing that COPD.Pal® provided this. Within Perceived Usefulness, participants discussed how they wanted the information they entered into the app to be useful, in addition to the app providing resources regarding COPD. Lastly, there was disagreement regarding preferences for further app development.
We found that COPD.Pal® was usable and acceptable by people with COPD and TAM provided a useful theoretical framework for both structuring discussions with users and analysing their comments
Bayesian modeling of recombination events in bacterial populations
Background: We consider the discovery of recombinant segments jointly with their origins within multilocus DNA sequences from bacteria representing heterogeneous populations of fairly closely related species. The currently available methods for recombination detection capable of probabilistic characterization of uncertainty have a limited applicability in practice as the number of
strains in a data set increases.
Results: We introduce a Bayesian spatial structural model representing the continuum of origins over sites within the observed sequences, including a probabilistic characterization of uncertainty related to the origin of any particular site. To enable a statistically accurate and practically feasible approach to the analysis of large-scale data sets representing a single genus, we have developed a novel software tool (BRAT, Bayesian Recombination Tracker) implementing the model and the
corresponding learning algorithm, which is capable of identifying the posterior optimal structure and to estimate the marginal posterior probabilities of putative origins over the sites.
Conclusion: A multitude of challenging simulation scenarios and an analysis of real data from seven
housekeeping genes of 120 strains of genus Burkholderia are used to illustrate the possibilities
offered by our approach. The software is freely available for download at URL http://web.abo.fi/fak/
mnf//mate/jc/software/brat.html
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