386 research outputs found
Self-energies in itinerant magnets: A focus on Fe and Ni
We present a detailed study of local and non-local correlations in the
electronic structure of elemental transition metals carried out by means of the
Quasiparticle Self-consistent GW (QSGW ) and Dynamical Mean Field Theory
(DMFT). Recent high resolution ARPES and Haas-van Alphen data of two typical
transition metal systems (Fe and Ni) are used as case study. (i) We find that
the properties of Fe are very well described by QSGW. Agreement with cyclotron
and very clean ARPES measurements is excellent, provided that final-state
scattering is taken into account. This establishes the exceptional reliability
of QSGW also in metallic systems. (ii) Nonetheless QSGW alone is not able to
provide an adequate description of the Ni ARPES data due to strong local spin
fluctuations. We surmount this deficiency by combining nonlocal charge
fluctuations in QSGW with local spin fluctuations in DMFT (QSGW + 'Magnetic
DMFT'). (iii) Finally we show that the dynamics of the local fluctuations are
actually not crucial. The addition of an external static field can lead to
similarly good results if non-local correlations are included through QSGW
Determination of n-3 index and arachidonic acid/eicosapentaenoic acid ratio in dried blood spot by gas chromatography
Background: Clinical and epidemiological studies suggest that analysis of the polyunsaturated fatty acids (PUFAs) is essential to evaluate nutritional requirements and disease risk. We describe a simple, sensitive and non-invasive method for estimating the n-3 index and arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio in dried blood spots (DBSs). Experimental: After obtaining DBSs on a spot card, PUFAs were transesterified (direct, acidic transesterification) and subsequently extracted with n-hexane. Gas chromatography with flame ionization detection (GC-FID) was used to analyze the extracted PUFAs, and then n-3 index and AA/EPA ratio were calculated. Method validation showed satisfactory precision and linearity. Conclusion: This analysis is simple and reliable to estimate PUFA status, and it was successfully applied to samples from 20 subjects, demonstrating its applicability
Riptide: a proton-recoil track imaging detector for fast neutrons
Riptide is a detector concept aiming to track fast neutrons. It is based on
neutron--proton elastic collisions inside a plastic scintillator, where the
neutron momentum can be measured by imaging the scintillation light. More
specifically, by stereoscopically imaging the recoil proton tracks, the
proposed apparatus provides neutron spectrometry capability and enable the
online analysis of the specific energy loss along the track. In principle, the
spatial and topological event reconstruction enables particle discrimination,
which is a crucial property for neutron detectors. In this contribution, we
report the advances on the Riptide detector concept. In particular, we have
developed a Geant4 optical simulation to demonstrate the possibility of
reconstructing with sufficient precision the tracks and the vertices of neutron
interactions inside a plastic scintillator. To realistically model the optics
of the scintillation detector, mono-energetic protons were generated inside a
cm cubic BC-408 scintillator, and the produced optical
photons were propagated and then recorded on a scoring plane corresponding to
the surfaces of the cube. The photons were then transported through an optical
system to a cm photo sensitive area with 1 Megapixel. Moreover,
we have developed two different analysis procedures to reconstruct 3D tracks:
one based on data fitting and one on Principal Component Analysis. The main
results of this study will be presented with a particular focus on the role of
the optical system and the attainable spatial and energy resolution.Comment: Prepared for submission to JINS
The challenging Silent sinus syndrome
The Silent sinus syndrome (SSS), first described in 1964 by Montgomery, is considered a relatively
rare pathological entity, but it is presumably underdiagnosed and underreported. Terms such as imploding
antrum and chronic maxillary atelectasis (CMA) have interchangeably been used to describe this syndrome,
even though CMA has been postulated to represent either a different entity or a stage of evolution of the same
disease. Bilateral involvement has been documented in a limited number of cases. Silent ethmoid sinus and
silent frontal sinus syndromes have been described. The prevalent initial presentation is facial asymmetry with
progressive “silent” painless unilateral enophthalmos and hypoglobus, and rarely diplopia. Isolated maxillary
sinus hypoplasia must be differentiated. The etiopathogenesis is poorly understood and still under debate.
According to the diagnostic criteria, SSS should spontaneously develops in absence of previous trauma or
surgery. Secondary SSS to trauma or surgery, or to other causes like inflammation or tumor, has been
documented in literature. The diagnosis relies on the CT, which typically shows unilateral hypoplastic and
opacified maxillary sinus with inward bowing and remodeling of the sinus walls and inferior displacement of
the orbital floor, an enlarged retroantral fat pad, a lateralized uncinate process, and a blocked ostiomeatal
complex. The treatment of SSS aims at restoring the eye position and orbital floor height, to prevent
progression of enophthalmos, to restore ventilation and drainage of the sinus. These objectives are achieved in
single or two-stage surgery. The timing for management of the orbital floor is still under debate.The universally
accepted treatment is surgical and usually accomplished by endoscopic sinus surgery. Associated middle
turbinate hypertrophy and septal deviation must be previously addressed. Precise and gentle endoscopic
removal of the obstruction of the ethmoid infundibulum, simply performing an inferior posteroanterior
uncinectomy, since the uncinate process has constantly been found atelectatic and adherent to the lateral nasal
wall, can reestablish the patency of the natural maxillary ostium. In our experience, following middle meatal
antrostomy, long-term observation with staged orbital surgery, if required, is recommended. In this study, we
present our cases with a focus on surgical stratagems developed in order to reduce the risk of injuring the orbit
and to achieve long-lasting results
Nasal tip sutures: how to control shape and orientation in rhinoplasty
Nasal tip surgery is universally recognized as the most challenging part of the rhinoplasty procedure.
"The tip makes the nose”. Narrowing the anatomically complex alar cartilages can lead to functional and
aesthetic unfavourable outcomes. A thorough understanding of the ideal surface aesthetics and contours and
spatial relationships of the structures of the nose tip is mandatory. In primary rhinoplasty, a very large
percentage of visible tip deformities involve two major areas: the domes and the lateral crura. Suture techniques
have the potential to modify the position, shape and definition of the tip. However, even sutures may result in
changes beyond the main goals for which they are placed. The final suture effects are influenced by factors
such as forces intrinsic to the cartilages, the degree of suture tightening, and limitations posed by the soft-tissue
attachments. The closed delivery approach is our favourite. In a step-by-step fashion, first the medial pillar of
the tripod should be addressed, establishing stable and strong tip support and basic dome projection symmetry.
Subsequently and in our experience, in a standard procedure shaping lateral crura and domes, using reversible
techniques that preserve structural integrity of the rimstrip, would be advisable. One of the main goals is not
only to narrow the tip but to change the angle of rotation of the lateral crus surface in relation to the sagittal
upper septal margin. Once marked the new dome defining point, with a variable combination of the lateral
crural steal technique, sutures such as cranial tip sutures (CTS) and hemitransdomal sutures (HTS) might
produce the needed outcome of everting and rotating the caudal margin of the lateral crura above the cranial
edge. These sutures can gradually increase domal convexity and reduce lateral crura convexity. Additional
dome equalization suture can guarantee more symmetry and then one or more lateral crural spanning sutures
help in achieving supplementary eversion of the lateral crus. After establishing adequate projection, the tip
rotation or position sutures are placed between the cranial edge of intermediate crura and the dorsal septum.
The personal association of suture techniques is presented in this study and the long-term subjective and
objective results are discussed along with the pros and cons
Nasal tip sutures: how to control shape and orientation in rhinoplasty
Nasal tip surgery is universally recognized as the most challenging part of the rhinoplasty procedure.
"The tip makes the nose”. Narrowing the anatomically complex alar cartilages can lead to functional and
aesthetic unfavourable outcomes. A thorough understanding of the ideal surface aesthetics and contours and
spatial relationships of the structures of the nose tip is mandatory. In primary rhinoplasty, a very large
percentage of visible tip deformities involve two major areas: the domes and the lateral crura. Suture techniques
have the potential to modify the position, shape and definition of the tip. However, even sutures may result in
changes beyond the main goals for which they are placed. The final suture effects are influenced by factors
such as forces intrinsic to the cartilages, the degree of suture tightening, and limitations posed by the soft-tissue
attachments. The closed delivery approach is our favourite. In a step-by-step fashion, first the medial pillar of
the tripod should be addressed, establishing stable and strong tip support and basic dome projection symmetry.
Subsequently and in our experience, in a standard procedure shaping lateral crura and domes, using reversible
techniques that preserve structural integrity of the rimstrip, would be advisable. One of the main goals is not
only to narrow the tip but to change the angle of rotation of the lateral crus surface in relation to the sagittal
upper septal margin. Once marked the new dome defining point, with a variable combination of the lateral
crural steal technique, sutures such as cranial tip sutures (CTS) and hemitransdomal sutures (HTS) might
produce the needed outcome of everting and rotating the caudal margin of the lateral crura above the cranial
edge. These sutures can gradually increase domal convexity and reduce lateral crura convexity. Additional
dome equalization suture can guarantee more symmetry and then one or more lateral crural spanning sutures
help in achieving supplementary eversion of the lateral crus. After establishing adequate projection, the tip
rotation or position sutures are placed between the cranial edge of intermediate crura and the dorsal septum.
The personal association of suture techniques is presented in this study and the long-term subjective and
objective results are discussed along with the pros and cons
The challenging Silent sinus syndrome
The Silent sinus syndrome (SSS), first described in 1964 by Montgomery, is considered a relatively
rare pathological entity, but it is presumably underdiagnosed and underreported. Terms such as imploding
antrum and chronic maxillary atelectasis (CMA) have interchangeably been used to describe this syndrome,
even though CMA has been postulated to represent either a different entity or a stage of evolution of the same
disease. Bilateral involvement has been documented in a limited number of cases. Silent ethmoid sinus and
silent frontal sinus syndromes have been described. The prevalent initial presentation is facial asymmetry with
progressive “silent” painless unilateral enophthalmos and hypoglobus, and rarely diplopia. Isolated maxillary
sinus hypoplasia must be differentiated. The etiopathogenesis is poorly understood and still under debate.
According to the diagnostic criteria, SSS should spontaneously develops in absence of previous trauma or
surgery. Secondary SSS to trauma or surgery, or to other causes like inflammation or tumor, has been
documented in literature. The diagnosis relies on the CT, which typically shows unilateral hypoplastic and
opacified maxillary sinus with inward bowing and remodeling of the sinus walls and inferior displacement of
the orbital floor, an enlarged retroantral fat pad, a lateralized uncinate process, and a blocked ostiomeatal
complex. The treatment of SSS aims at restoring the eye position and orbital floor height, to prevent
progression of enophthalmos, to restore ventilation and drainage of the sinus. These objectives are achieved in
single or two-stage surgery. The timing for management of the orbital floor is still under debate.The universally
accepted treatment is surgical and usually accomplished by endoscopic sinus surgery. Associated middle
turbinate hypertrophy and septal deviation must be previously addressed. Precise and gentle endoscopic
removal of the obstruction of the ethmoid infundibulum, simply performing an inferior posteroanterior
uncinectomy, since the uncinate process has constantly been found atelectatic and adherent to the lateral nasal
wall, can reestablish the patency of the natural maxillary ostium. In our experience, following middle meatal
antrostomy, long-term observation with staged orbital surgery, if required, is recommended. In this study, we
present our cases with a focus on surgical stratagems developed in order to reduce the risk of injuring the orbit
and to achieve long-lasting results
A proton-recoil track imaging system for fast neutrons: the RIPTIDE detector
Fast neutron detection is often based on the neutron-proton elastic
scattering reaction: the ionization caused by recoil protons in a hydrogenous
material constitutes the basic information for the design and development of a
class of neutron detectors. Although experimental techniques have continuously
improved, proton-recoil track imaging remains still at the frontier of
n-detection systems, due to the high photon sensitivity required. Several
state-of-the-art approaches for neutron tracking by using n-p single and double
scattering - referred to as Recoil Proton Track Imaging (RPTI) - can be found
in the literature. So far, they have showed limits in terms of detection
efficiency, complexity, cost, and implementation. In order to address some of
these deficiencies, we have proposed RIPTIDE a novel recoil-proton track
imaging detector in which the light output produced by a fast scintillator is
used to perform a complete reconstruction in space and time of the interaction
events. The proposed idea is viable thanks to the dramatic advances in low
noise and single photon counting achieved in the last decade by new scientific
CMOS cameras as well as pixel sensors, like Timepix or MIMOSIS. In this
contribution, we report the advances on the RIPTIDE concept: Geant4 Monte Carlo
simulations, light collection tests as well as state-of-the-art approach to
image readout, processing and fast analysis.Comment: proceeding of the 23rd International Workshop on Radiation Imaging
Detectors, IWoRID 2022, 26-30 June 2022, Riva del Garda (TN), Ital
Neutrino masses and mixings in a seesaw framework
Assuming the seesaw mechanism for hierarchical neutrino masses, we calculate
the heavy neutrino masses under the hypotheses that the mixing in the Dirac
leptonic sector is similar to the quark mixing () and that
or , where is the Dirac mass matrix of
neutrinos. As a result we find that for the vacuum
oscillation solution of the solar neutrino problem leads to a scale for the
heavy neutrino mass well above the unification scale, while for the MSW
solutions there is agreement with this scale. For the vacuum
solution is consistent with the unification scale, and the MSW solutions with
an intermediate scale. The mass of the lightest heavy neutrino can be as small
as GeV.Comment: 13 pages RevTex, no figures. Revised versio
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