5,162 research outputs found
Pre-relaxation in weakly interacting models
We consider time evolution in models close to integrable points with hidden
symmetries that generate infinitely many local conservation laws that do not
commute with one another. The system is expected to (locally) relax to a
thermal ensemble if integrability is broken, or to a so-called generalised
Gibbs ensemble if unbroken. In some circumstances expectation values exhibit
quasi-stationary behaviour long before their typical relaxation time. For
integrability-breaking perturbations, these are also called pre-thermalisation
plateaux, and emerge e.g. in the strong coupling limit of the Bose-Hubbard
model. As a result of the hidden symmetries, quasi-stationarity appears also in
integrable models, for example in the Ising limit of the XXZ model. We
investigate a weak coupling limit, identify a time window in which the effects
of the perturbations become significant and solve the time evolution through a
mean-field mapping. As an explicit example we study the XYZ spin-
chain with additional perturbations that break integrability. One of the most
intriguing results of the analysis is the appearance of persistent oscillatory
behaviour. To unravel its origin, we study in detail a toy model: the
transverse-field Ising chain with an additional nonlocal interaction
proportional to the square of the transverse spin per unit length [Phys. Rev.
Lett. 111, 197203 (2013)]. Despite being nonlocal, this belongs to a class of
models that emerge as intermediate steps of the mean-field mapping and shares
many dynamical properties with the weakly interacting models under
consideration.Comment: 69 pages, 17 figures, improved exposition, figures 1 and 13 added,
some typos correcte
A mentalist framework for linguistic and extralinguistic communication
We outline some components of a mentalist theory of human communicative competence. Communication in our species is an intentional and overt type of social interaction, based on each agent's capability of entertaining shared mental states and of acting so as to make certain mental states shared with the other. Communicative meaning is a matter of ascription: it is not an intrinsic property of a communicative act, but is instead created here and now as the shared construction of the interlocutors. We then discuss how communicative actions are superficially realized by our species, focusing in particular on the difference between linguistic and extralinguistic (that is, gestural) means of expression. Linguistic communication is the communicative use of a symbol system, whereas extralinguistic communication is the communicative use of a set of symbols. The difference turns out to be a matter of processing rather than of intrinsic structure
BanksÂ’ participation in the Eurosystem auctions and money market integration
Bidding Behaviour, auctions, open market operations, money market, liquidity management Abstract: We perform a panel analysis of bidding in the Eurosystem auctions, using individual data that include the bidder code, size, nationality and membership in a banking group. We find that an increase in interest rate volatility lowers the probability of bidding, but induces bidders to shade rates less. Large bidders participate more regularly, while group bidders demand larger amounts, showing an aptitude to act as liquidity brokers. Our findings support the transnational bank hypothesis (Freixas- Holthausen, 2005): banks with a multinational profile use their informational advantage to arbitrage out the differences in interest rates across countries, thus fostering money market integration.
Biological activity of Citrus spp. metabolites on Ceratitis capitata (Wiedemann).
The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is one of the most injurious pest at global level. During the last years, several electrophysiological and behavioural studies have been carried out in order to investigate plant volatile compound-insect interactions with the aim to use this knowledge in sustainable control techniques.
It has been observed that lemons are not attacked by medfly, probably because of the peel oil, that is toxic to other fruit flies. In the present paper electrophysiological recordings were conducted to evaluate the insect sensitivity to peel extract and peel oil of two Sicilian cultivars (Interdonato and Lunario) of Citrus x limon (L.) Burm.f. on C. capitata females. Behavioural bioassays were also performed to show their possible biological activity (repellent, antioviposition, insecticidal). C. limon peel extracts in different solvents (petroleum ether, dichloromethane and methanol) were investigated at various concentrations using a single cell recording technique (stimulation of tarsal taste chemosensilla). Different tarsal taste cell responses to the two cultivars were recorded. The higher sensitivity was evoked by C. limon Interdonato, particularly to the methanol extract, which elicited significant increases in the spike frequency at increasing concentrations. The peel oil of the same cultivars as well as that ones of other two C. limon varieties (Monachello and Femminello) have been tested by EAG techniques. The EAG data showed a high sensitivity (about -8.0/8.5mV) of the medfly antennae to the oils of Citrus spp. and a clear dose-response relationship. Responses of adult females (virgin and mated) to Citrus spp. peel extract were quantified in a double-choice test using yellow spheres (diameter 7.0cm) housed in field cages. Preliminary tests conducted on three extracts of C. limon Interdonato and Lunario have provided interesting results. It was recorded a general decrease of the oviposition on treated spheres compared to control and in the case of the cultivar Lunario, a mortality of insects
The role of posterior aortopexy in the treatment of left mainstem bronchus compression
OBJECTIVES: We reviewed the role of posterior aortopexy for left mainstem bronchus compression in infants and children.
METHODS: Eighteen children with respiratory symptoms were enrolled between 2005 and 2015 for surgical decompression of the left mainstem bronchus. The children were managed from diagnosis to follow-up by a dedicated tracheal team. Primary outcomes were the complete relief of symptoms or improvement with respect to preoperative clinical status.
RESULTS: The median age was 4 years (0.3-15.4) and the median weight was 13.2 kg (3, 1-40). Symptoms or indications for bronchoscopy included difficult weaning from mechanical ventilation (n = 3, 17%), difficult weaning from tracheotomy (n = 4, 22%), recurrent pneumonia (n = 4, 22%), wheezing (n = 3, 17%), atelectasis (n = 1, 5.5%), bitonal cough (n = 1, 5.5%) and stridor (n = 2, 11%). Associated malformations were present in 88.7%. The diagnosis was made by bronchoscopy and computed tomography. Indication for surgery was the presence of pulsations and reduction in the diameter of the left mainstem bronchus compression of more than 70%. Surgery was performed by left posterolateral thoracotomy. Aortopexy was done under bronchoscopic control. No early or late deaths were observed, nor were reoperations necessary. Residual malacia was observed in 8 children (44%). Median follow-up was 4.1 years (0.1-7.1). At last follow-up, 17/18 (94.4%) children showed adequate airway patency.
CONCLUSIONS: The intrathoracic location of the left mainstem bronchus predisposes it to compression. Vascular anomalies represent the most frequent causes. Aortopexy has been advocated as a safe and useful method to relieve the compression, and our results confirmed these findings. Management of these patients is challenging and requires a multidisciplinary team
Entanglement evolution and generalised hydrodynamics: interacting integrable systems
We investigate the dynamics of bipartite entanglement after the sudden
junction of two leads in interacting integrable models. By combining the
quasiparticle picture for the entanglement spreading with Generalised
Hydrodynamics we derive an analytical prediction for the dynamics of the
entanglement entropy between a finite subsystem and the rest. We find that the
entanglement rate between the two leads depends only on the physics at the
interface and differs from the rate of exchange of thermodynamic entropy. This
contrasts with the behaviour in free or homogeneous interacting integrable
systems, where the two rates coincide.Comment: 33 pages, 8 figures; v2 32 pages, 8 figures, improved presentation;
v3 32 pages, 8 figures, minor modification
Dune habitats vulnerability to the climate change
Italy sandy coasts are characterized by a great diversity of habitats and, at the same time, many of these coastal stretches are in erosive condition. The causes of erosion are represented by multiple factors essentially geomorphological but to which today others of a climatic change can be added. These are linked to the intensification of extreme climatic events and/or sea level rise. Therefore, it is important to understand, in areas where marine erosion is particularly strong, which are the most vulnerable and most threatened habitats. This paper sets out a summary of the results obtained up to now from the survey of dune habitats (sensu Directive 92/43/EEC) along the northern Tyrrhenian coast. This investigations, aim to point out the arrangement of these habitats in relation to extreme weather events and dune erosion and the different resilience in the face of important changes in the beach/dune system
Occurrence of acute oesophageal necrosis (black oesophagus) in a single tertiary centre
Acute oesophageal necrosis (AON) is a rare condition characterised by the endoscopic finding of diffuse, circumferential, black mucosal pigmentation of the oesophagus, which typically stops at the gastro-oesophageal junction. This observational study aimed to assess the occurrence, clinical characteristics and outcomes of AON in a consecutive endoscopic cohort in a single tertiary university centre. A retrospective analysis of endoscopic data of upper gastrointestinal endoscopy (UGE) was carried out from 2008 to 2018. Out of 25,970 UGE, 16 patients (0.06%) had AON; 75.0% were men with a median age of 75 years. Almost all patients underwent diagnosis during emergency UGE performed for gastrointestinal bleeding, but one patient was diagnosed during elective UGE for persistent vomiting and diarrhoea. All patients reported one or more pre-existing comorbidities and concomitant acute events. Two patients had AON as the first presentation of Zollinger-Ellison syndrome (ZES). One patient developed an oesophageal stenosis, and another patient presented a relapse of AON. Mortality was 50%, but no patient died as a direct consequence of AON. AON is a rare cause of gastrointestinal bleeding diagnosed mainly during emergency UGE. Our study showed that ZES might manifest with this critical presentation, and endoscopists must be aware of this evidence
Natural zeolites and white wines from Campania region (Southern Italy): a new contribution for solving some oenological problems
The purpose of this research is to provide a new mixture of Campanian zeolitized tuffs for solving two specific problems in the production of white wines: the protein and tartaric stability. In fact, a very frequent cause of turbidity and formation of organic deposits in white wines is the occurrence of thermolabile and thermostable proteins colloidal suspensions which precipitate in time, especially in summertime and during the storage and transport. Normally, to mitigate this risk wine producers use organic and inorganic stabilizers and clarifiers. The best known treatment, recognized also by the International Organisation of Vine and Wine (OIV) foresees the use of bentonite with a montmorillonite content not lower than 80%. The present paper aims at evaluating the use of two high zeolite grade Italian volcanoclastites such as the Neapolitan Yellow Tuff (NYT) and the Yellow Facies of the Campanian Ignimbrite (YFCI), in the treatment of three peculiar white wines of the Campanian region (Southern Italy): Falanghina, Fiano di Avellino and Greco di Tufo. Granulates were produced starting from tuff blocks as provided by quarries. Some grain size fractions have been prepared to investigate the zeolite content (phillipsite + chabazite + analcime) by X-ray diffraction (XRD). A 2-5 mm grain size fraction was chosen for NYT and a 5-10 mm for YFCI. Three Campanian monocultivar white wines were used for the test: the Falanghina 2006 vintage, the Fiano di Avellino DOCG 2007 vintage, and the Greco di Tufo DOCG 2008 vintage. 48 samples with mixture of the zeolitized tuffs, 1 sample with mixture of a synthetic zeolite A and 1 sample with mixture of a commercial sodium activated bentonite were prepared. ICP-OES analysis for the determination of ECEC, Ion Chromatography (IC) analyses for the determination of some major cations and Turbidimetric tests for the definition of the protein stabilization process before and after treatments were also carried out. It was evidenced that high zeolitized tuff/wine ratios enable the protein stabilization whereas a significant decrease of potassium ion after the treatment with a zeolite-rich powder improves the tartaric stability, a serious problem in all the wine productions. The results of these tests refer to a laboratory scale research. A transfer of the experiment to a pilot plant scale is in progress
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