2,246 research outputs found
Surgeon\u27s perspective on short bowel syndrome: Where are we?
Short bowel syndrome (SBS) is due to a massive loss of small bowel: the reduction of gut function is below the minimum necessary to maintain health (in adults) and growth (in children) so intravenous supplementation is required. Parenteral nutrition represents the milestone of treatment and surgical attempts should be limited only when the residual bowel is sufficient to increase absorption, reducing diarrhea and slowing the transit time of nutrients, water and electrolytes. The surgical techniques lengthen the bowel (tapering it) or reverse a segment of it: developed in children, nowadays are popular also among adults. The issue is mainly represented by the residual length of the small bowel where ileum has shown increased adaptive function than jejunum, but colon should be considered because of its importance in the digestive process. These concepts have been translated also in intestinal transplantation, where a colonic graft is nowadays widely used and the terminal ileum is the selected segment for a living-related donation. The whole replacement by a bowel or multivisceral transplant is still affected by poor long term outcome and must be reserved to a select population of SBS patients, affected by intestinal failure associated with irreversible complications of parenteral nutrition
Solution of Two-Body Bound State Problems with Confining Potentials
The homogeneous Lippmann-Schwinger integral equation is solved in momentum
space by using confining potentials. Since the confining potentials are
unbounded at large distances, they lead to a singularity at small momentum. In
order to remove the singularity of the kernel of the integral equation, a
regularized form of the potentials is used. As an application of the method,
the mass spectra of heavy quarkonia, mesons consisting from heavy quark and
antiquark , are calculated for linear and
quadratic confining potentials. The results are in good agreement with
configuration space and experimental results.Comment: 6 pages, 5 table
Characterizing dark interactions with the halo mass accretion history and structural properties
We study the halo mass accretion history (MAH) and its correlation with the
internal structural properties in coupled dark energy cosmologies (cDE). To
accurately predict all the non-linear effects caused by dark interactions, we
use the COupled Dark Energy Cosmological Simulations (CoDECS). We measure the
halo concentration at z=0 and the number of substructures above a mass
resolution threshold for each halo. Tracing the halo merging history trees back
in time, following the mass of the main halo, we develope a MAH model that
accurately reproduces the halo growth in term of M_{200} in the {\Lambda}CDM
Universe; we then compare the MAH in different cosmological scenarios. For cDE
models with a weak constant coupling, our MAH model can reproduce the
simulation results, within 10% of accuracy, by suitably rescaling the
normalization of the linear matter power spectrum at z=0, {\sigma}_8. However,
this is not the case for more complex scenarios, like the "bouncing" cDE model,
for which the numerical analysis shows a rapid growth of haloes at high
redshifts, that cannot be reproduced by simply rescaling the value of
{\sigma}_8. Moreover, at fixed value of {\sigma}_8, cold dark matter (CDM)
haloes in these cDE scenarios tend to be more concentrated and have a larger
amount of substructures with respect to {\Lambda}CDM predictions. Finally, we
present an accurate model that relates the halo concentration to the time at
which it assembles half or 4% of its mass. Combining this with our MAH model,
we show how halo concentrations change while varying only {\sigma}_8 in a
{\Lambda}CDM Universe, at fixed halo mass.Comment: 18 pages, 14 figures, accepted for publication in MNRA
Mass and Concentration estimates from Weak and Strong Gravitational Lensing: a Systematic Study
We study how well halo properties of galaxy clusters, like mass and
concentration, are recovered using lensing data. In order to generate a large
sample of systems at different redshifts we use the code MOKA. We measure halo
mass and concentration using weak lensing data alone (WL), fitting to an NFW
profile the reduced tangential shear profile, or by combining weak and strong
lensing data, by adding information about the size of the Einstein radius
(WL+SL). For different redshifts, we measure the mass and the concentration
biases and find that these are mainly caused by the random orientation of the
halo ellipsoid with respect to the line-of-sight. Since our simulations account
for the presence of a bright central galaxy, we perform mass and concentration
measurements using a generalized NFW profile which allows for a free inner
slope. This reduces both the mass and the concentration biases. We discuss how
the mass function and the concentration mass relation change when using WL and
WL+SL estimates. We investigate how selection effects impact the measured
concentration-mass relation showing that strong lens clusters may have a
concentration 20-30% higher than the average, at fixed mass, considering also
the particular case of strong lensing selected samples of relaxed clusters.
Finally, we notice that selecting a sample of relaxed galaxy clusters, as is
done in some cluster surveys, explain the concentration-mass relation biases.Comment: (1) DIFA-UniBO, (2) INAF-OABo, (3) INFN-BO, (4) JPL-Pasadena 18
pages, 19 figures - accepted for publication by MNRAS, two figures added for
comparison with SGAS-SDSS and LoCuSS cluster
Effective range from tetramer dissociation data for cesium atoms
The shifts in the four-body recombination peaks, due to an effective range
correction to the zero-range model close to the unitary limit, are obtained and
used to extract the corresponding effective range of a given atomic system. The
approach is applied to an ultracold gas of cesium atoms close to broad Feshbach
resonances, where deviations of experimental values from universal model
predictions are associated to effective range corrections. The effective range
correction is extracted, with a weighted average given by 3.9,
where is the van der Waals length scale; which is consistent with the
van der Waals potential tail for the system. The method can be generally
applied to other cold atom experimental setups to determine the contribution of
the effective range to the tetramer dissociation position.Comment: A section for two-, three- and four-boson bound state formalism is
added, accepted for publication in Phys. Rev.
Scaling functions of two-neutron separation energies of with finite range potentials
The behaviour of an Efimov excited state is studied within a three-body
Faddeev formalism for a general neutron-neutron-core system, where neutron-core
is bound and neutron-neutron is unbound, by considering zero-ranged as well as
finite-ranged two-body interactions. For the finite-ranged interactions we have
considered a one-term separable Yamaguchi potential. The main objective is to
study range corrections in a scaling approach, with focus in the exotic carbon
halo nucleus
Disentangling dark sector models using weak lensing statistics
We perform multi-plane ray-tracing using the GLAMER gravitational lensing
code within high-resolution light-cones extracted from the CoDECS simulations:
a suite of cosmological runs featuring a coupling between Dark Energy and Cold
Dark Matter. We show that the presence of the coupling is evident not only in
the redshift evolution of the normalisation of the convergence power spectrum,
but also in differences in non-linear structure formation with respect to
{\Lambda}CDM. Using a tomographic approach under the assumption of a
{\Lambda}CDM cosmology, we demonstrate that weak lensing measurements would
result in a {\sigma}8 value that changes with the source redshift if the true
underlying cosmology is a coupled Dark Energy one. This provides a generic null
test for these types of models. We also find that different models of coupled
Dark Energy can show either an enhanced or a suppressed correlation between
convergence maps with differing source redshifts as compared to {\Lambda}CDM.
This would provide a direct way to discriminate between different possible
realisations of the coupled Dark Energy scenario. Finally, we discuss the
impact of the coupling on several lensing observables for different source
redshifts and angular scales with realistic source redshift distributions for
current ground-based and future space-based lensing surveys.Comment: 17 pag. and 14 fig. replaced to match the accepted version (increased
the number of light-cone realisations
Update on chronic rejection after intestinal transplant. An overview from experimental settings to clinical outcomes
Chronic rejection affects the long-term survival of solid-organ transplants, accounting for an incidence of between 5% and 10% after intestinal/multivisceral transplant. Because of unclear symptoms and signs and endoscopic findings, the diagnosis is often delayed. Presently, allograft removal represents the only available therapy due to the absence of effective pharmacologic approaches. Extensive research, through animal models, has been performed over the past 20 years to clarify the complex immune- and nonimmune-mediated mechanisms behind the development of chronic allograft enteropathy, with the aim of elucidating how to avert chronic rejection. The role of donor-specific antibodies and the way to challenge them in the clinic have gained acceptance among transplant centers as one of the main steps to prevent chronic rejection, although no common protocol exists that can be applied in a systematic fashion. The adjunct of a liver graft when retrans planting is needed in a sensitized recipient due to its protective effect against humoral immunity. Multicenter studies and clinical trials are required to better understand the pathogenesis of chronic rejection and to find the therapeutic answer to this clinical query
Light storage protocols in Tm:YAG
We present two quantum memory protocols for solids: A stopped light approach
based on spectral hole burning and the storage in an atomic frequency comb.
These procedures are well adapted to the rare-earth ion doped crystals. We
carefully clarify the critical steps of both. On one side, we show that the
slowing-down due to hole-burning is sufficient to produce a complete mapping of
field into the atomic system. On the other side, we explain the storage and
retrieval mechanism of the Atomic Frequency Comb protocol. This two important
stages are implemented experimentally in Tm- doped
yttrium-aluminum-garnet crystal
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