458 research outputs found
The effect of a nucleating agent on lamellar growth in melt-crystallizing polyethylene oxide
The effects of a (non co-crystallizing) nucleating agent on secondary
nucleation rate and final lamellar thickness in isothermally melt-crystallizing
polyethylene oxide are considered. SAXS reveals that lamellae formed in
nucleated samples are thinner than in the pure samples crystallized at the same
undercoolings. These results are in quantitative agreement with growth rate
data obtained by calorimetry, and are interpreted as the effect of a local
decrease of the basal surface tension, determined mainly by the nucleant
molecules diffused out of the regions being about to crystallize. Quantitative
agreement with a simple lattice model allows for some interpretation of the
mechanism.Comment: submitted to Journal of Applied Physics (first version on 22 Apr
2002
A real-time framework for fast data retrieval in an image database of volcano activity scenarios
Explosive Activity at Stromboli Volcano (Aeolian Islands) is continuously monitored by INGV-OE in order to
analyze its eruptive dynamics and specific scenarios. In particular, the images acquired from thermal cameras
represent a big collection of data. In order to extract useful information from thermal image sequences, we need
an efficient way to explore and retrieve information from a huge amount of data. In this work, a novel framework
capable of fast data retrieval, using the "metric space" concept, is shown. In the light of it, we implemented an
indexing algorithm related to similarity laws. The focal point is finding objects of a set that are âcloseâ in relation
to a given query, according to a similarity criterion. In order to perform this task, we performed morphological
image processing techniques to each video frame, in order to map the shape area of each explosion into a closed
curve, representing the explosion contour itself. In order to constitute a metric space, we chose a certain number of
features obtained from parameters related to this closed curve and used them as objects of this metric space where
similarity can be evaluated, using an appropriate âmetricâ function to calculate the distances. Unfortunately, this
approach has to deal with an intrinsic issue involving the complexity and the number of distance functions to be
calculated on a large amount of data. To overcome this drawback, we used a novel abstract data structure called
"K-Pole Tree", having the property of minimizing the number of distances to be calculated among objects. Our
method allows for fast retrieval of similar objects using an euclidean distance function among the features of the
metric space. Thus, we can cluster explosions related to different kinds of volcanic activity, using "pivot" items.
For example, given a known image sequence related to a particular type of explosion, it is possible to quickly and
easily find all the image sequences that contain only similar explosions. Our framework is able to both classify
each new explosion and dynamically insert the corresponding object into our tree data structure. This approach is
able to cluster the entire data space, ensuring that objects with similar features are grouped and classified together
Solid-Solid Interfaces in Protonic Ceramic Devices: A Critical Review
The literature concerning protonic ceramic devices is critically reviewed focusing the reader's attention on the structure, composition, and phenomena taking place at solid-solid interfaces. These interfaces play a crucial role in the overall device performance, and the relevance of understanding the phenomena taking place at the interfaces for the further improvement of electrochemical protonic ceramic devices is therefore stressed. The grain boundaries and heterostructures in electrolytic membranes, the electrode-electrolyte contacts, and the interfaces within composite anode and cathode materials are all considered, with specific concern to advanced techniques of characterization and to computational modeling by ab initio approaches. An outlook about future developments and improvements highlights the necessity of a deeper insight into the advanced analysis of what happens at the solid-solid interfaces and of in situ/operando investigations that are presently sporadic in the literature on protonic ceramic devices
A Dynamic Bayesian Network for Mt. Etna Volcano State Assessment
Nowadays, the real-time monitoring of Mt. Etna volcano is mostly delegated to one or more human experts in
volcanology, who interpret the data coming from different kind of monitoring networks. Among their duties, the
evaluation of the volcano state is one of the most critical task for civil protection purposes. Unfortunately, the
coupling of highly non-linear and complex volcanic dynamic processes leads to measurable effects that can show a
large variety of different behaviors. Moreover, due to intrinsic uncertainties and possible failures in some recorded
data the volcano state needs to be expressed in probabilistic terms, thus making the fast volcano state assessment
sometimes impracticable for the personnel on duty at the 24h control room. With the aim of aiding the personnel
on duty in volcano monitoring, here we present an expert system approach based on Bayesian networks to estimate
automatically the ongoing volcano state from all the available different kind of measurements. A Bayesian network
is a static probabilistic graphical model that represents a set of random variables and their conditional dependencies
via a directed acyclic graph. We consider model variables both the measurements and the possible states of the
volcano. In order to include the time in the model, we use a Dynamic Bayesian Network (DBN) which relates
variables to each other over adjacent time steps. The model output consists of an estimation of the probability
distribution of the feasible volcano states. We build the model by considering the long record of data from 2011 to
2014 and we cross-validate it by considering 3 years for parameter estimation and 1 year for testing in simulated real-time mode
Neutron Tomography at INES: First experimental results
A neutron tomography apparatus has been designed and installed at the Italian neutron experimental station (INES) at ISIS (UK). The instrument has a double aim: an additional opportunity for the INES users and a âbench testâ for an instrument component that will be proposed for installation on some of the new neutron scattering instruments of Target Station 2 (TS2) of ISIS. Here, we present the first experimental results achieved with this apparatus
Fusion rate enhancement due to energy spread of colliding nuclei
Experimental results for sub-barrier nuclear fusion reactions show cross
section enhancements with respect to bare nuclei which are generally larger
than those expected according to electron screening calculations. We point out
that energy spread of target or projectile nuclei is a mechanism which
generally provides fusion enhancement. We present a general formula for
calculating the enhancement factor and we provide quantitative estimate for
effects due to thermal motion, vibrations inside atomic, molecular or crystal
system, and due to finite beam energy width. All these effects are marginal at
the energies which are presently measurable, however they have to be considered
in future experiments at still lower energies. This study allows to exclude
several effects as possible explanation of the observed anomalous fusion
enhancements, which remain a mistery.Comment: 17 pages with 3 ps figure included. Revtex styl
PHOTOGRAMMETRIC TECHNIQUES FOR THE RECONSTRUCTION OF UNDERWATER 3D MODELS OF SEABED AND ARTIFACTS
The digital representation of hydraulic engineering works such as dykes or barriers is a sector that is becoming increasingly important. In general, however, the 3D relief of semi-submerged structures is still a problem. The Geomatics Laboratory in collaboration with CNR-IPCF of Messina as part of a broader project to analyze the variations of the coast lines and the seabed of the province of Reggio Calabria (southern Italy), has developed an experimental system of acquisition and processing of digital images acquired via UAV and (Remotely operated vehicle) ROV. The present note describes the design and construction characteristics of the ROV realized and used, the advantages and limitations of the use of a small and low-cost ROV, as well as the results obtained during the experimentation phase. The process of surveying of the sub-emerged structure inquired and the relative construction of a unique 3D model are also described. The two surveys were first elaborated separately and then united in a single reference system by means of the visible markers in the area straddling the sea surface. Finally, the bathymetry values obtained from the classic echo sounder system and those obtained from the model obtained were compared
Role of virtual break-up of projectile in astrophysical fusion reactions
We study the effect of virtual Coulomb break-up, commonly known as the dipole
polarizability, of the deuteron projectile on the astrophysical fusion reaction
3He(d,p)4He. We use the adiabatic approximation to estimate the potential shift
due to the E1 transition to the continuum states in the deuteron, and compute
the barrier penetrability in the WKB approximation. We find that the
enhancement of the penetrability due to the deuteron break-up is too small to
resolve the longstanding puzzle observed in laboratory measurements that the
electron screening effect is surprisingly larger than theoretical prediction
based on an atomic physics model. The effect of the 3He break-up in the
3He(d,p)4He reaction, as well as the 7Li break-up in the 7Li(p,alpha)4He
reaction is also discussed.Comment: 9 pages, 2 eps figure
Influence of tumor microenvironment and fibroblast population plasticity on melanoma growth, therapy resistance and immunoescape
Cutaneous melanoma (CM) tissue represents a network constituted by cancer cells and tumor microenvironment (TME). A key feature of CM is the high structural and cellular plasticity of TME, allowing its evolution with disease and adaptation to cancer cell and environmental alter-ations. In particular, during melanoma development and progression each component of TME by interacting with each other and with cancer cells is subjected to dramatic structural and cellular modifications. These alterations affect extracellular matrix (ECM) remodelling, phenotypic profile of stromal cells, cancer growth and therapeutic response. The stromal fibroblast populations of the TME include normal fibroblasts and melanomaâassociated fibroblasts (MAFs) that are highly abun-dant and flexible cell types interacting with melanoma and stromal cells and differently influencing CM outcomes. The shift from the normal microenvironment to TME and from normal fibroblasts to MAFs deeply sustains CM growth. Hence, in this article we review the features of the normal mi-croenvironment and TME and describe the phenotypic plasticity of normal dermal fibroblasts and MAFs, highlighting their roles in normal skin homeostasis and TME regulation. Moreover, we dis-cuss the influence of MAFs and their secretory profiles on TME remodelling, melanoma progres-sion, targeted therapy resistance and immunosurveillance, highlighting the cellular interactions, the signalling pathways and molecules involved in these processes
22Ne and 23Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for 22Ne(p,gamma)23Na
We investigate the impact of the new LUNA rate for the nuclear reaction NeNa on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally-pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre-main sequence up to the termination of the TP-AGB phase, of a set of stellar models with initial masses in the range , and metallicities , , and . We find that the new LUNA measures have much reduced the nuclear uncertainties of the Ne and Na AGB ejecta, which drop from factors of to only a factor of few for the lowest metallicity models. Relying on the most recent estimations for the destruction rate of Na, the uncertainties that still affect the Ne and Na AGB ejecta are mainly dominated by evolutionary aspects (efficiency of mass-loss, third dredge-up, convection). Finally, we discuss how the LUNA results impact on the hypothesis that invokes massive AGB stars as the main agents of the observed O-Na anti-correlation in Galactic globular clusters. We derive quantitative indications on the efficiencies of key physical processes (mass loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anti-correlation, and the observational constraints on the CNO abundance. Results for the corresponding chemical ejecta are made publicly available
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