1,721,475 research outputs found
A theory-based dinamical model of exaptive innovation processes
No full textA major problem in research on innovations is the understanding of invention, that is, the origin of innovations. In this paper we propose that radical innovations are created by a process of 'exaptation', and we introduce a dynamical model which describes how it may happen. In particular, our model is focussed on the interplay between artifact innovation and attributions of functionality. We propose that the explicit representation of artifacts and categories eases the understanding of the exaptation phenomenon, seen in this context as a shift in terms of “leading attributions”, and allows the identification of the elements favouring the emergence of innovation
Prospective randomized, double-blind, controlled trial comparing Lichtenstein's repair of inguinal hernia with polypropylene mesh versus Surgisis gold soft tissue graft: preliminary results
No full textINTRODUCTION: Although polypropylene mesh are the preferred
prosthesis materials for the tension-free hernioplasties because
they handle well and become quickly integrated, having reduced
the recurrence rate below 1\%, some problems with their use are
still to be addressed (postoperative pain, long-term discomfort,
infections, intestinal obstruction and fistulization). In order
to answer to these disadvantages, a new degradable and
reabsorbable material, the porcine small intestinal submucosa
(SIS mesh gold, Surgisis), has recently been used in humans for
laparoscopic hernia repairs. Aim to our study is to evaluate the
safety and efficacy of the Lichtenstein's hernioplasty using the
Surgisis gold soft tissue graft, as a mesh, and to compare it
with the traditional Lichtenstein procedure performed with
polypropylene mesh. METHODS: A prospective, randomised,
double-blinded comparison of Lichtenstein's repair of inguinal
hernia with polypropylene mesh versus Surgisis ES soft tissue
graft was carried out at the Department of Emergency Surgery of
St Orsola-Malpighi University Hospital with the participation of
4 surgeons who accept to standardise the Lichtenstein's
procedures with the two different types of meshes. RESULTS: From
july 2002 up to now 20 patients submitted to Lichtenstein's
repair of inguinal hernia using Surgisis gold mesh with a 6 month
minimum follow-up were enrolled. 12 subjects were treated with
Surgisis ES mesh, while 8 were treated polypropylene mesh. There
were not intraoperative or postoperatively complications. No
recurrences and wound infections were observed. The
post-hernioplasty acute and chronic pain/discomfort (tested with
visual analogue scale and simple verbal scale) and
parenteral/oral analgesic consumption were lower in Surgisis ES
group. CONCLUSIONS: Lichtenstein's hernioplasty using the
Surgisis gold soft tissue graft has a promising safety and
efficacy
Surgery or antibiotics for acute appendicitis? Take care about study's design and methodology!
No full text
Dynamical critical systems for information processing: a preliminary study
No full textA general and inspiring hypothesis states that organizationsand systems subject to evolutionary pressure tend to reach a particularstate, often called critical: in particular, in presence of changing environ-ments the critical systems could have signicant advantages with respectto ordered or chaotic systems. From the previous consideration naturallyfollows the question if also articial systems could take advantage fromoperating in critical conditions, with respect to more ordered (and lessexible) structures. In order to study this topic some methodological is-sues have to be solved; this work shows the rst results of the proposedresearch approach
A theory based dynamical model of innovation processes
No full textWe present an agent-based model of innovation processes, based upon a theory of innovation by Lane and Maxfield. The theory inspires and constrains the features of the model, thus reducing the embarasse de richesse that is one of the major methodological problems of agent-based modeling. Artifacts are produced by agents using recipes; the basic dynamics, absent innovation, is one of production and sales, where the external world supplies “raw materials” and external demand. Depending upon the initial conditions, self-sustaining cycles of production and exchange can emerge among the agents. Innovation – that is, the generation of new recipes, in particular desired directions, called “goals” – results in substantial modification of the system dynamics. Two innovation regimes are introduced: a “lonely” mode, in which each agent tries to introduce new products by itself, and a “relational” mode, in which two agents can improve their reciprocal knowledge and can decide to try to jointly develop a new artifact
Distributed processes in an agent-based model of innovation
No full textIn this work we investigate the conditions inuencing the creation of noveltiesand their diusion through networks composed by agents interacting via theexchange of artifacts. By means of simulation we veried that the presence ofstereotyped routines deeply inuences (negatively) the robustness properties ofthe system, whereas the impact of strong spatial limitations or of a particularkind of direct information exchange (a request system) have more complexconsequences, not all aligned to the same direction. None of these results isobvious, nor can it be simply deduced from the qualitative theory. Therefore,the simulations could make possible comparisons between the model behaviorsand the theory claims, indicating new ways of improvement and developmen
Intraperitoneal chemotherapy for ovarian cancer with peritoneal metastases, systematic review of the literature and focused personal experience
Full text linkEpithelial ovarian cancer (EOC) causes 60% of ovarian cancer cases and is the fourth most common cause of death from cancer in women. The standard of care for EOC includes a combination of surgery followed by intravenous chemotherapy. Intraperitoneal (IP) chemotherapy (CT) has been introduced into the therapeutic algorithm of EOC with positive results. To explore existing results regarding intraperitoneal chemotherapy a systematic review of the literature and an analysis of our own institutional prospective database of patients treated with cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (HIPEC) for EOC at different stages were conducted. The focused report concerning our personal experience with advanced EOC treated with cytoreductive surgery and HIPEC produced the following results: In 57 patients cisplatin + paclitaxel as HIPEC was the only significant factor improving overall survival (OS) at multivariate analysis (OR 6.54, 95% CI: 1.24-34.47, P=0.027). Patients treated with HIPEC cisplatin + paclitaxel showed a median OS of 46 months (SD 6.4, 95% CI: 33.4-58.6), while patients treated with other HIPEC regimens showed a median OS of 12 months (SD 3.1, 95% CI: 6.0-18.0). The 2y-OS was 72% and 3y-OS was 68% for cisplatin + paclitaxel as HIPEC, while the 2y- and 3y-OS was 0% for other HIPEC regimens. Patients treated with HIPEC cisplatin + paclitaxel showed a median disease-free survival (DFS) of 13 months (SD 1.6, 95% CI: 9.9-16.1), while patients treated with other HIPEC regimens showed a median DFS of 8 months (SD 3.1, 95% CI: 1.9-14.1). In conclusion, HIPEC cisplatin + paclitaxel in ovarian cancer showed positive results that may be considered semi-definitive according to the level of evidence and should be considered a starting point for further investigations. At present HIPEC cisplatin + paclitaxel should be proposed to patients with advanced ovarian cancer as standard treatment at almost all stages of disease. Platinum + taxane-based intraperitoneal regimens demonstrated superior results compared to other regimens
Nanocellulose-based membranes for CO2 capture
No full textA new type of hydrophilic polymeric membrane based on microfibrillated cellulose (MFC) has been investigated to determine its potential in the field of gas separation, with special reference to carbon capture and natural gas sweetening. In particular, pure MFC films and MFC/Lupamin® (a commercial polyvinylamine produced by BASF) nanocomposite membrane have been synthesized and characterized. The effect of relative humidity on gas permeability was considered and independent water vapor sorption experiments were also carried out in order to correlate the permeation results to the actual water content in the materials. The experimental results showed that very good CO2/N2 and CO2/CH4 selectivity (in the order of 500 and 350 respectively) could be reached by using pure MFC films, which however showed limited CO2 permeability, never exceeding 25 Barrer, even at the highest relative humidity investigated. To increase the transmembrane flux, a hydrophilic polyvinylamine (Lupamin®) has been added to the pure MFC: the addition caused a marked increase in permeability of up to one order of magnitude but decreased the selectivity to about the same extent, thus decreasing the overall membrane performance. The reason of such behavior seems to be related to the amount of water absorbed by the membrane as the MFC/Lupamin nanocomposite resulted to be highly swollen by water vapor. Nonetheless, both the investigated materials showed separation performances that are above the 2008 Robeson's upper bound for CO2/N2 and CO2/CH4 systems, disclosing an attractive potential for the production of advanced gas separation membranes
Effect of relative humidity and temperature on gas transport in Matrimid®: Experimental study and modeling
No full textThe influence of water vapor on the gas permeability of a commercial polyimide, Matrimid® 5218, has
been extensively investigated at three different temperatures (25, 35 and 45 1C), and with four different
penetrant gases (CH 4 , N 2 , CO 2 and He), varying the relative humidity in the range 0–75%.
In all tests performed, the permeability coefficient decreases as the concentration of water vapor in
the membrane increases. In particular, the influence of the presence of water on gas permeability is very
similar for all penetrants, as the same permeability decrease is found, at a given relative humidity,
despite the different thermodynamic and kinetic characteristics of the probe gases considered.
As temperature is raised, the gas permeability is enhanced, as expected. On the other hand, its decrease
with respect to the dry polymer values, as relative humidity increases, is not affected by temperature, and it
remains substantially unaltered from 25 to 45 1C, suggesting that such phenomenon can be directly related
to the amount of water dissolved in the membrane, which is also unaffected by temperature.
Based on the experimental evidence, a simple model is proposed to describe the permeation process
under humid conditions, in the framework of the free volume theory. In particular, it has been considered
that absorbed water molecules influence gas permeability by occupying polymer free volume, reducing its
availability to other penetrants with lower condensability. The model describes accurately the experi-
mental data using only two adjustable parameters for the polymer-water-penetrant system, once the water
solubility is estimated from sorption measurements
- …
