12,316 research outputs found
Growth Kinetics in the N-Component Model. Conserved Order Parameter
We extend the discussion of the growth kinetics of the large-N time-dependent
Ginzburg-Landau model with an order parameter described by a free
energy functional, to the conserved case. Quenches from a high temperature
initial state to a zero temperature state are studied for different selections
of parameters entering the effective potential. In all cases we obtain the
asymptotic form of the structure factor. As expected in analogy with the well
studied model, we find multiscaling behavior whenever stable
equilibrium is reached in the ordering region. On the other hand the present
model also displays a novel feature, namely the occurrence of metastable
relaxation.Comment: 20 pages,Plain Late
Strong Raman-induced non-instantaneous soliton interactions in gas-filled photonic crystal fibers
We have developed an analytical model based on the perturbation theory in
order to study the optical propagation of two successive intense solitons in
hollow-core photonic crystal fibers filled with Raman-active gases. Based on
the time delay between the two solitons, we have found that the trailing
soliton dynamics can experience unusual nonlinear phenomena such as spectral
and temporal soliton oscillations and transport towards the leading soliton.
The overall dynamics can lead to a spatiotemporal modulation of the refractive
index with a uniform temporal period and a uniform or chirped spatial period
Quasiparticle Electronic structure of Copper in the GW approximation
We show that the results of photoemission and inverse photoemission
experiments on bulk copper can be quantitatively described within
band-structure theory, with no evidence of effects beyond the
single-quasiparticle approximation. The well known discrepancies between the
experimental bandstructure and the Kohn-Sham eigenvalues of Density Functional
Theory are almost completely corrected by self-energy effects.
Exchange-correlation contributions to the self-energy arising from 3s and 3p
core levels are shown to be crucial.Comment: 4 pages, 2 figures embedded in the text. 3 footnotes modified and 1
reference added. Small modifications also in the text. Accepted for
publication in PR
A polymorphism at IGF1 locus is associated with anemia
In vitro and in vivo studies suggest that IGF-1 has a role in erythropoiesis. There is evidence that the rs35767 C/T polymorphism near IGF1 is associated with plasma IGF-1 levels. We investigated the effect of this polymorphism on hemoglobin (Hb) concentration and anemia. The study group comprised 3286 adult Whites. The rs35767 polymorphism was screened using a TaqMan allelic discrimination assay. The rs35767 polymorphism was not associated with age, gender, BMI, waist circumference, smoking, blood pressure, plasma glucose, HbA1c, type 2 diabetes, HOMA-IR, hsCRP, eGFR, and lipid profile. Erythrocyte sedimentation rate (ESR), fibrinogen, and fasting insulin levels were significantly lower in TT genotype carriers compared with C allele carriers. Hb concentration was significantly higher in carriers of the TT genotype compared with C allele carriers, and a lower proportion of TT carriers had anemia. As compared with TT genotype carriers, those bearing the CC genotype had a 2.4-fold higher risk of anemia (OR 2.40, 95%CI 1.19-4.82), and those with the CT genotype had a 2.0-fold higher risk of anemia (OR 2.06, 95%CI 1.04-4.11). The association remained significant when fasting insulin, eGFR, smoking, diabetes, ACE inhibitors, sartans or diuretics treatments, use of metformin and pioglitazone were added to the model, but its independence was not retained after inclusion of fibrinogen and ESR values into the model. In conclusion, rs35767 TT allele carriers exhibited significantly higher concentrations of Hb, and lower risk of anemia compared with C allele carriers supporting the idea that IGF-1 plays a role in erythropoiesis homeostasis
Lowest order Virtual Element approximation of magnetostatic problems
We give here a simplified presentation of the lowest order Serendipity
Virtual Element method, and show its use for the numerical solution of linear
magneto-static problems in three dimensions. The method can be applied to very
general decompositions of the computational domain (as is natural for Virtual
Element Methods) and uses as unknowns the (constant) tangential component of
the magnetic field on each edge, and the vertex values of the
Lagrange multiplier (used to enforce the solenoidality of the magnetic
induction ). In this respect the method can be seen
as the natural generalization of the lowest order Edge Finite Element Method
(the so-called "first kind N\'ed\'elec" elements) to polyhedra of almost
arbitrary shape, and as we show on some numerical examples it exhibits very
good accuracy (for being a lowest order element) and excellent robustness with
respect to distortions
Suitable classification of mortars from ancient roman and renaissance frescoes using thermal analysis and chemometrics
Background
Literature on mortars has mainly focused on the identification and characterization of their components in order to assign them to a specific historical period, after accurate classification. For this purpose, different analytical techniques have been proposed. Aim of the present study was to verify whether the combination of thermal analysis and chemometric methods could be used to obtain a fast but correct classification of ancient mortar samples of different ages (Roman era and Renaissance).
Results
Ancient Roman frescoes from Museo Nazionale Romano (Terme di Diocleziano, Rome, Italy) and Renaissance frescoes from Sistine Chapel and Old Vatican Rooms (Vatican City) were analyzed by thermogravimetry (TG) and differential thermal analysis (DTA). Principal Component analysis (PCA) on the main thermal data evidenced the presence of two clusters, ascribable to the two different ages. Inspection of the loadings allowed to interpret the observed differences in terms of the experimental variables.
Conclusions
PCA allowed differentiating the two kinds of mortars (Roman and Renaissance frescoes), and evidenced how the ancient Roman samples are richer in binder (calcium carbonate) and contain less filler (aggregate) than the Renaissance ones. It was also demonstrated how the coupling of thermoanalytical techniques and chemometric processing proves to be particularly advantageous when a rapid and correct differentiation and classification of cultural heritage samples of various kinds or ages has to be carried out
Mechanical behaviour with temperatures of aluminum matrix composites with CNTs
Aluminum is a very useful structural metal employed in different industrial sectors, in particular it is used in
large quantities in automotive, aeronautic and nautical industries. The main reasons of its wide use are: a very
good oxidation resistance, excellent ductility, low melting temperature (660 °C) and low density (2.71 g/cm3).
However, in order to reduce the emissions and fuel consumption is necessary to reduce the overall weight of
vehicles by increasing mechanical properties of the structural material. The improvement of mechanical
properties is normally achieved through use of reinforcement in materials, used like matrix, in order to improve
some specific characteristics.
In this work composites of carbon nanotubes (CNTs) dispersed in aluminum were made. The most difficulties
in the preparation of this type of composite are represented by the low wettability between metallic matrix and
fillers and the possibility of the oxidation of metal during melting with consequent decreasing of mechanical
proprieties. The composite was obtained by three consecutive step: the first one is the functionalization of
fillers surface to improve the fillers dispersion, the second one is the dispersion of fillers in the matrix by
powder mixing and the third one is the melting and casting of the mix prepared.
In particular, fillers used are multi walled carbon nanotubes (MWCNTs) with functionalized surface by
treatment with a solfonitric solution. Melting and casting are carried out with the aid of an induction furnace
with a controlled atmosphere system and centrifugal casting. Argon is the inert gas used to prevent the
oxidation of aluminium during fusion. Young’s modulus was evaluated at different temperature and correlated
with the different CNTs percentage. The dispersion rate of fillers and the microstructure of the sample were
evaluated by FESEM micrograph
Serendipity Face and Edge VEM Spaces
We extend the basic idea of Serendipity Virtual Elements from the previous
case (by the same authors) of nodal (-conforming) elements, to a more
general framework. Then we apply the general strategy to the case of
and conforming Virtual Element Methods, in two and three dimensions
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