144 research outputs found
Unexpected Presentation of Tracheoesophageal Fistula During Intubation in a Pediatric Patient
Tracheoesophageal fistula (TEF) is an abnormal connection between the trachea and esophagus. This report presents a rare case of a pediatric patient who developed a TEF due to battery ingestion, which was diagnosed during intubation and resulted in cardiac arrest. A 4-year-old child with a two-year history of battery ingestion presented with severe dehydration, weight loss, and recurrent respiratory tract infections. Chest X-ray revealed a radiopaque foreign body in the esophagus. During general anesthesia for central venous line insertion and after endotracheal intubation, some difficulties in ventilation occurred, characterized by the inability to reach tidal volume, absence of capnography, and stomach distention which led to hypoxia and ultimately to cardiac arrest. Prompt resuscitation (CPR) was initiated, and selective right bronchial intubation during CPR improved the patient's condition. Subsequent bronchofibroscopy performed in the ICU confirmed the TEF, which was surgically corrected during the hospital stay. TEF poses challenges in anesthesia and airway management, particularly when positive pressure ventilation is used. In this case, the TEF was diagnosed during intubation, highlighting the critical role of clinical expertise and prompt intervention in managing this unexpected pediatric critical event.info:eu-repo/semantics/publishedVersio
Pathways to folding, nucleation events and native geometry
We perform extensive Monte Carlo simulations of a lattice model and the Go
potential to investigate the existence of folding pathways at the level of
contact cluster formation for two native structures with markedly different
geometries. Our analysis of folding pathways revealed a common underlying
folding mechanism, based on nucleation phenomena, for both protein models.
However, folding to the more complex geometry (i.e. that with more non-local
contacts) is driven by a folding nucleus whose geometric traits more closely
resemble those of the native fold. For this geometry folding is clearly a more
cooperative process.Comment: Accepted in J. Chem. Phy
Stochastic theory of non-equilibrium wetting
We study a Langevin equation describing non-equilibrium depinning and wetting
transitions. Attention is focused on short-ranged attractive
substrate-interface potentials. We confirm the existence of first order
depinning transitions, in the temperature-chemical potential diagram, and a
tricritical point beyond which the transition becomes a non-equilibrium
complete wetting transition. The coexistence of pinned and depinned interfaces
occurs over a finite area, in line with other non-equilibrium systems that
exhibit first order transitions. In addition, we find two types of phase
coexistence, one of which is characterized by spatio-temporal intermittency
(STI). A finite size analysis of the depinning time is used to characterize the
different coexisting regimes. Finally, a stationary distribution of
characteristic triangles or facets was shown to be responsible for the
structure of the STI phase.Comment: To appear in Europhys. Lett. // 3 figure
Newspaper covers as display windows in a pandemic season: analysis of three Portuguese daily newspapers
Neste artigo, que Ă© uma sĂntese de um estudo realizado no MediaLab CIES-Iscte , parte-se da ideia de pandemia enquanto evento mediático e da mediatização como aspeto estruturante da narrativa jornalĂstica, para propor trĂŞs modelos de montras jornalĂsticas – de saldos, de produto e de diversidade em que se considera as caracterĂsticas e critĂ©rios de noticiabilidade adotados por cada um dos veĂculos analisados. A análise englobou trĂŞs dimensões: a distribuição do conteĂşdo no espaço fĂsico e hierárquico do jornal (manchete, centro e periferia); as marcas, que podem ser palavras destacadas nos tĂtulos e chamadas; e os recursos imagĂ©ticos utilizados.
A pesquisa teve em conta 90 capas dos jornais Correio da ManhĂŁ, Jornal de NotĂcias e PĂşblico publicadas durante os primeiros 30 dias de cobertura da pandemia em Portugal, divididos em trĂŞs ciclos: o primeiro, entre a divulgação dos primeiros casos identificados de COVID-19 em Portugal (3 de março de 2020) e a declaração do estado de alerta em Portugal (12 de março); o segundo, desde o encerramento das escolas (13 de março) Ă vĂ©spera da notĂcia do decreto presidencial que autoriza ao governo decretar estado de emergĂŞncia (18 de março); o terceiro, da repercussĂŁo do decreto presidencial (19 de março) atĂ© Ă vĂ©spera da aprovação do decreto de emergĂŞncia na Assembleia da RepĂşblica (1 de abril).
O estudo conclui que as narrativas nas capas dos jornais sĂŁo diferentes entre si e afetadas pelos modelos de montras, os quais refletem a dicotomia entre os interesses jornalĂsticos e os interesses comerciais, questionando se o pĂşblico-modelo que norteia a construção das diferentes montras Ă© apenas um, entre vários possĂveis, “retrato-robô”, para fazer «vender» jornais, ou um claro identificador sociocultural dos pĂşblicos da imprensa escrita portuguesa?info:eu-repo/semantics/publishedVersio
Interfacial motion in flexo- and order-electric switching between nematic filled states
We consider a nematic liquid crystal, in coexistence with its isotropic
phase, in contact with a substrate patterned with rectangular grooves. In such
a system, the nematic phase may fill the grooves without the occurrence of
complete wetting. There may exist multiple (meta)stable filled states, each
characterised by the type of distortion (bend or splay) in each corner of the
groove and by the shape of the nematic-isotropic interface, and additionally
the plateaux that separate the grooves may be either dry or wet with a thin
layer of nematic. Using numerical simulations, we analyse the dynamical
response of the system to an externally- applied electric field, with the aim
of identifying switching transitions between these filled states. We find that
order-electric coupling between the fluid and the field provides a means of
switching between states where the plateaux between grooves are dry and states
where they are wet by a nematic layer, without affecting the configuration of
the nematic within the groove. We find that flexoelectric coupling may change
the nematic texture in the groove, provided that the flexoelectric coupling
differentiates between the types of distortion at the corners of the substrate.
We identify intermediate stages of the transitions, and the role played by the
motion of the nematic-isotropic interface. We determine quantitatively the
field magnitudes and orientations required to effect each type of transition.Comment: 14 pages, 12 fig
[68Ga]Ga-DOTANOC Uptake at Pancreatic Head/Uncinate Process: Is It a Persistent Diagnostic Pitfall Over Time?
Simple Summary The purpose of the present study is to describe the frequency of non-malignant [68Ga]Ga-DOTANOC uncinate process (UP) uptake and to evaluate its variations over time. Among the first 6 months of enrolment of a monocentric prospective observational electronic archive, analyses of a large number of PET/CT scans (n = 268) of NEN pts (n = 172) demonstrated that: UP uptake is a frequent finding (observed in almost half of the cases, slightly higher than previously reported), mostly presenting with a diffuse pattern and, interestingly, characterized by variations over time in almost one third of the cases. The consciousness of this diagnostic pitfall is of utmost importance for accurate [68Ga]Ga-DOTANOC PET/CT reporting, since the pancreas represents one of the most frequent sites of NEN. Purpose: [68Ga]Ga-DOTA-peptide uptake in the pancreatic head/uncinate process (UP) is a frequent PET/CT finding. Although mostly physiologic, it can represent a pitfall in PET/CT reading, especially when focal. An increased frequency of UP uptake has been reported in patients (pts) affected by diabetes mellitus (DM). The aim of the study is to describe the frequency of [68Ga]Ga-DOTANOC UP uptake to evaluate its variations over time and its possible correlation with DM. Methods: In September 2017, a monocentric prospective observational electronic archive was initiated at our center to collect clinical and imaging data of pts undergoing [68Ga]Ga-DOTANOC PET/CT. Among the pts enrolled in the first 6 months (Sept 2017 to Feb 2018), those presenting [68Ga]Ga-DOTANOC PET/CT uptake at UP level were included. Pts with UP lesions already documented on CT/MRI or those that underwent surgical excision of UP before PET/CT were excluded from the analysis. [68Ga]Ga-DOTANOC UP uptake was classified as diffuse or focal and compared with the pattern observed in previous PET/CT scans performed at our center. An increased frequency of UP uptake was also correlated with the presence of DM. Results: In the first 6 months, 253 pts were enrolled in the archive and 172 out of them were included in the analysis. UP increased uptake was frequently observed (77/172, 44.8%) and was mostly diffuse (62/77). In 75/172 pts (43.6%), previous [68Ga]Ga-DOTANOC PET/CT scans were available (overall 268 scans; number of previous PET per pt range: 1-20) and were retrospectively reviewed. Despite the fact that, in most pts, the uptake pattern was stable over time (54/75 pts, 72%), it changed in approximately one third of cases (21/75, 28%). Among DM pts (29/172), only 10/29 (34.4%) presented increased UP uptake. Conclusions: UP [68Ga]Ga-DOTANOC uptake is a frequent non-malignant finding (slightly higher than previously reported), mostly presenting with a diffuse pattern. However, contrary to previous reports, our data show that the pattern of uptake may vary over time in approximately one third of the cases and it is not more frequently observed in pts with DM
Nonequilibrium wetting transitions with short range forces
We analyze within mean-field theory as well as numerically a KPZ equation
that describes nonequilibrium wetting. Both complete and critical wettitng
transitions were found and characterized in detail. For one-dimensional
substrates the critical wetting temperature is depressed by fluctuations. In
addition, we have investigated a region in the space of parameters (temperature
and chemical potential) where the wet and nonwet phases coexist. Finite-size
scaling analysis of the interfacial detaching times indicates that the finite
coexistence region survives in the thermodynamic limit. Within this region we
have observed (stable or very long-lived) structures related to spatio-temporal
intermittency in other systems. In the interfacial representation these
structures exhibit perfect triangular (pyramidal) patterns in one (two
dimensions), that are characterized by their slope and size distribution.Comment: 11 pages, 5 figures. To appear in Physical Review
Orientational transitions in a nematic confined by competing surfaces
The effect of confinement on the orientational structure of a nematic liquid
crystal model has been investigated by using a version of density-functional
theory (DFT). We have focused on the case of a nematic confined by opposing
flat surfaces, in slab geometry (slit pore), which favor planar molecular
alignment (parallel to the surface) and homeotropic alignment (perpendicular to
the surface), respectively. The spatial dependence of the tilt angle of the
director with respect to the surface normal has been studied, as well as the
tensorial order parameter describing the molecular order around the director.
For a pore of given width, we find that, for weak surface fields, the alignment
of the nematic director is perpendicular to the surface in a region next to the
surface favoring homeotropic alignment, and parallel along the rest of the
pore, with a interface separating these regions (S phase). For strong surface
fields, the director is distorted uniformly, the tilt angle exhibiting a linear
dependence with the distance normal to the surface (L phase). Our calculations
reveal the existence of a first-order transition between the two director
configurations, which is driven by changes in the surface field strength, and
also by changes in the pore width. In the latter case the transition occurs,
for a given surface field, between the S phase for narrow pores and the L phase
for wider pores. A link between the L-S transition and the anchoring transition
observed for the semi-infinite case is proposed. We also provide calculations
with a phenomenological approach that yields the same main result that DFT in
the scale length where this is valid.Comment: submitted to PR
Equilibrium self-assembly of colloids with distinct interaction sites: Thermodynamics, percolation, and cluster distribution functions
We calculate the equilibrium thermodynamic properties, percolation threshold, and cluster distribution functions for a model of associating colloids, which consists of hard spherical particles having on their surfaces three short-ranged attractive sites (sticky spots) of two different types, A and B. The thermodynamic properties are calculated using Wertheim's perturbation theory of associating fluids. This also allows us to find the onset of self-assembly, which can be quantified by the maxima of the specific heat at constant volume. The percolation threshold is derived, under the no-loop assumption, for the correlated bond model: In all cases it is two percolated phases that become identical at a critical point, when one exists. Finally, the cluster size distributions are calculated by mapping the model onto an effective model, characterized by a-state-dependent-functionality (f) over bar and unique bonding probability (p) over bar. The mapping is based on the asymptotic limit of the cluster distributions functions of the generic model and the effective parameters are defined through the requirement that the equilibrium cluster distributions of the true and effective models have the same number-averaged and weight-averaged sizes at all densities and temperatures. We also study the model numerically in the case where BB interactions are missing. In this limit, AB bonds either provide branching between A-chains (Y-junctions) if epsilon(AB)/epsilon(AA) is small, or drive the formation of a hyperbranched polymer if epsilon(AB)/epsilon(AA) is large. We find that the theoretical predictions describe quite accurately the numerical data, especially in the region where Y-junctions are present. There is fairly good agreement between theoretical and numerical results both for the thermodynamic (number of bonds and phase coexistence) and the connectivity properties of the model (cluster size distributions and percolation locus)
- …