2,003 research outputs found
Opinion formation models based on game theory
A way to simulate the basic interactions between two individuals with
different opinions, in the context of strategic game theory, is proposed.
Various games are considered, which produce different kinds of opinion
formation dynamics. First, by assuming that all individuals (players) are
equals, we obtain the bounded confidence model of continuous opinion dynamics
proposed by Deffuant et al. In such a model a tolerance threshold is defined,
such that individuals with difference in opinion larger than the threshold can
not interact. Then, we consider that the individuals have different
inclinations to change opinion and different abilities in convincing the
others. In this way, we obtain the so-called ``Stubborn individuals and
Orators'' (SO) model, a generalization of the Deffuant et al. model, in which
the threshold tolerance is different for every couple of individuals. We
explore, by numerical simulations, the dynamics of the SO model, and we propose
further generalizations that can be implemented.Comment: 18 pages, 4 figure
Recanalization of the Native Artery in Patients with Bypass Failure
Our objective was to evaluate the possible role
of endovascular recanalization of occluded native artery
after a failed bypass graft in the case of either acute or
chronic limb-threatening ischemia otherwise leading to
amputation. In a single-center retrospective clinical analysis,
from January 2004 to March 2007 we collected 31
consecutive high-surgical-risk patients (32 limbs) with
critical limb ischemia following late ([30 days after surgery)
failure of open surgery bypass graft reconstruction.
All patients deemed unfit for surgery underwent tentative
endovascular recanalization of the native occluded arterial
tract. The mean follow-up period was 24 (range, 6–42)
months. Technical success was achieved in 30 (93.7%) of
32 limbs. The cumulative primary assisted patency calculated
by Kaplan–Meyer analysis was 92% and 88%,
respectively, at 12 and 24 months. The limb salvage rate
approached 90% at 30 months. In conclusion, our experience
shows the feasibility of occluded native artery endovascular
recanalization after a failed bypass graft, with
optimal results in terms of midterm arterial patency and
limb salvage. Our opinion is that successful recanalization
of the arterial tract previously considered unsuitable for
endovascular approach is allowed by improved competency
and experience of vascular specialists, as well as the
advances made in catheter and guidewire technology. This
group of patients would previously have been relegated to
repeat bypass grafts, with their inherently inferior patency
and recognized added technical demands. We recognize
previous surgical native artery disconnection and lack of
pedal runoff to be the main cause of technical failure.
Keywords Native artery Bypass failure
Endovascular recanalizatio
Comment on: ‘‘The dark nature of Somma-Vesuvius volcano:Evidence from the 3.5 ka BP Avellino eruption’’ by Milia A.Raspini A., Torrente M.M.,
We present here some criticism to the scientific content of the paper of Milia et al. [2007. The dark nature of Somma-Vesuvius volcano:
evidence from the 3.5 ka B.P. Avellino eruption. Quaternary International, 173–174, 57–66] published in Quaternary International.
Milia et al. (2007) interpreted seismic lines in the Gulf of Naples (southern Italy), and inferred the presence of deposits from a large debris
avalanche which occurred just before the Avellino eruption of Somma-Vesuvius volcano. The authors supported their seismic profile
interpretation with on-land stratigraphies and logs. However, we present here different on-land data that demonstrate the inconsistency
of the occurrence of any debris avalanche before or after the Avellino eruption, and we provide also an alternative interpretation for the
observed seismic facies offshore of Somma-Vesuvius
Successful Coronary Stent Retrieval From a Pedal Artery
The purpose of this article is to report complications
from a coronary drug-eluting stent lost in the
peripheral circulation. We report the case of successful
retrieval of a sirolimus coronary stent from a pedal artery in
a young patient who underwent coronary angiography for
previous anterior myocardial infarction. Recognition of
stent embolization requires adequate removal of the device
to avoid unwelcome clinical sequelae.
Keywords Coronary stent Microsnare technique
Peripheral embolization Stent retrieva
The Hemoglobins of the Antarctic Fishes Artedidraco orianae and Pogonophryne scotti AMINO ACID SEQUENCE, LACK OF COOPERATIVITY, AND LIGAND BINDING PROPERTIES
The oxygen-transport system of two species of Antarctic fishes belonging to the family Artedidraconidae,Artedidraco orianae and Pogonophryne scotti, was thoroughly investigated. The complete amino acid sequence of the α and β chains of the single hemoglobins of the two species was established. The oxygen-binding properties were also investigated, and were found not to differ significantly from those shown by blood, intact erythrocytes, and unstripped hemolysates. Both hemoglobins have unusually high oxygen affinity and display a relatively small Bohr effect; the Root effect is elicited only by organophosphates and is also reduced. Remarkably, the Hill coefficient is close to one in the whole pH range, indicating absence of cooperative oxygen binding which, in A. orianae hemoglobin, could be ascribed to the subunit heterogeneity shown upon oxygen dissociation. In comparison with the other families of the suborder Notothenioidei, the oxygen-transport system of these two species of Artedidraconidae has unique characteristics, which raise interesting questions on the mode of function of a multisubunit molecule and the relationship with cold adaptation
A GIS-Based Hydrogeological Approach to the Assessment of the Groundwater Circulation in the Ischia Volcanic Island (Italy)
Assessing the variations in space and time of groundwater circulation in volcanic islands is of paramount importance to the description of the hydro-geo-thermal system and implementation of hydrogeological, geochemical, and volcanic monitoring systems. In fact, the reliable reconstruction of the groundwater potentiometric surface in such composite volcanic aquifer systems can enable the identification of the most advantageous strategies for both the sustainable use of groundwater resources and the management of volcanic risk. Geographical Information System (GIS) platforms can support the integration and analysis of many spatial and temporal variables derived from monitoring of active volcanoes and the elaboration of spatially continuous data. However, open issues still affect the reliability and general applicability of common spatial interpolation methods in the case of groundwater potentiometric surfaces. This is related to the assessment of the main stratigraphic and volcano-tectonic features affecting the hydraulic head changes. With regard to the dynamically very active Ischia Island (Italy), this study illustrates a GIS-based hydrogeological approach to identify the most accurate interpolation method for mapping the potentiometric surface in complex hydrogeological terrains. The proposed approach has been applied to the existing dataset (1977–2003) stored by Istituto Nazionale di Geofisica e Vulcanologia. Based on a careful geological and hydrogeological survey, a total of 267 wells, from 5 to 250 m in depth, were processed. The data pre-processing involved four meteorological time-series data (1922–1997) and six long records of piezometric water levels (1930–1994). As a result, knowledge of the delineation of rather homogeneous stratigraphic and volcano-tectonic structures at the basin-scale has improved. Thus, new, more reliable potentiometric surfaces of the four main geothermal areas closest to the coast were produced during both dry and wet seasons. The reliability of the processed potentiometric surface was then validated by comparing the spatially continuous data with complementary field data. These findings point toward an optimal interpolation approach for representing the seasonal and areal distribution of main hydrogeological parameters in complex aquifer systems. Finally, insights into variations of hydrological behavior at an active volcanic area will foster an understanding of possible involvement of fresh and thermal waters in triggering phreatic explosions
B-type natriuretic peptide as a biochemical marker of left ventricular diastolic function: Assessment in asymptomatic patients 1 year after valve replacement for aortic stenosis.
Objectives: Left ventricular (LV) diastolic dysfunction after aortic valve replacement (AVR) carries a substantial risk of development of heart failure and reduced survival. In addition to echocardiography, B-type natriuretic peptide (BNP) provides a powerful incremental assessment of diastolic function. This study evaluates BNP as a marker of LV diastolic dysfunction in a cohort of patients with preserved LV ejection fraction who underwent AVR for pure aortic stenosis and the relationship between BNP values and the grade of LV diastolic dysfunction. Methods A total of 113 patients were included in the study. Echocardiographic evaluation was performed preoperatively, 5 days postoperatively and at 12-month follow-up, to assess LV dimensional and functional parameters. Diastolic function was labelled as normal, mild, moderate or severe dysfunction. Concomitantly, BNP levels were evaluated. Results Mild to severe diastolic dysfunction occurred preoperatively in all patients. At 12-month follow-up, 65 (62.5%) patients had mild and 25 (24.1%) moderate to severe diastolic dysfunction. BNP values, categorized for quartile distribution, correlated with diastolic dysfunction grade (P < 0.001 for each comparison). At receiver operating characteristic analysis, the BNP level of 120 pg/ml was 91% sensitive and 85% specific for diastolic disease, while 300 pg/ml was 80% sensitive and 91% specific for moderate or severe diastolic dysfunction. Twelve months after AVR, BNP values were strongly correlated with the significant echocardiographic parameters suggestive of diastolic dysfunction (P ≤ 0.006 in all cases). Conclusions The BNP level following AVR is related to diastolic disease severity and may complement echocardiographic evaluation when symptoms are unclear and LV function is difficult to interpret
Combined inguinal hernia in the elderly. Portraying the progression of hernia disease
Introduction: Identification of a combined hernia is a common occurrence in the course of inguinal hernia repair. This type of protrusion disease seems to affect the elderly, in particular. Very few investigations have been carried out to ascertain the structural changes that occur in the groin affected by this clinical condition. Method: Analysis of intraoperative findings of combined inguinal hernias evidenced in the elderly, from the most recent 100 groin hernia repair procedures carried out by a single operator, represents the basis of the article. Protrusions that presumably represent the forerunner of this type of hernia were also analyzed: double ipsilateral inguinal hernias composed of a direct and an indirect protrusion. The gross anatomical, as well as histological, modifications occurring during the development of combined protrusions were also evaluated. Results: Combined hernia was the most frequent protrusion in patients over 65 years, accounting for 36% of the total in this patient group. In the same patient cohort, double inguinal hernia further involves 22% of elderly subjects. Macroscopically, progressive disruption of the inguinal back wall and degenerative reabsorption of the inferior epigastric vessels were evidenced. Histologically, inflammatory infiltrate, significant nerve and vascular injuries, along with severe muscle degeneration were recognized. Conclusions: The results seem to confirm that inguinal hernia is an unremitting progressive disease caused by chronic compressive structural damage. Combined hernias represent a frequent clinical condition in the elderly consequent to long-term degenerative damage. Therapy of combined protrusions must consider the impact of visceral vector forces
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