1,365 research outputs found
Gaspare Polizzi, Leopardi e "le ragioni della verità"
No full textSi discute l'analisi che Polizzi propone sui rapporti leoapardiani con vari ambiti della letteratura scientifica e della filosofia della scienz
On surfaces with pg = q = 2, k2 = 5 and albanese map of degree 3
No full textWe construct a connected, irreducible component of the moduli space of minimal surfaces of general type with pg = q = 2 and K2 = 5, which contains both examples given by Chen-Hacon and the first author. This component is generically smooth of dimension 4, and all its points parametrize surfaces whose Albanese map is a generically finite triple cover
A new family of surfaces with pg=q=2 and K2=6 whose Albanese map has degree 4
No full textWe construct a new family of minimal surfaces of general type with pg = q = 2 and K2 = 6,
whose Albanese map is a quadruple cover of an abelian surface with polarization of type
(1, 3). We also show that this family provides an irreducible component of the moduli space
of surfaces with pg = q = 2 and K2 = 6. Finally, we prove that such a component is generically
smooth of dimension 4 and that it contains the two-dimensional family of product–quotient
examples previously constructed by the first author. The main tools we use are the Fourier–Mukai
transform and the Schr ̈odinger representation of the finite Heisenberg group H3
A new family of surfaces with pg = q = 2 and K2 = 6 whose Albanese map has degree 4
No full textWe construct a new family of minimal surfaces of general type with pg = q = 2 and K2 = 6, whose Albanese map is a quadruple cover of an abelian surface with polarization of type (1, 3). We also show that this family provides an irreducible component of the moduli space of surfaces with pg = q = 2 and K2 = 6. Finally, we prove that such a component is generically smooth of dimension 4 and that it contains the two-dimensional family of product-quotient examples previously constructed by the first author. The main tools we use are the Fourier-Mukai transform and the Schrödinger representation of the finite Heisenberg group H3
Surfaces with pg = q = 2, K2 = 6, and albanese map of degree 2
No full textWe classify minimal surfaces of general type with pg = q = 2 and K2 = 6 whose Albanese map is a generically finite double cover. We show that the corresponding moduli space is the disjoint union of three generically smooth irreducible components MIa, MIb, M II of dimension 4, 4, 3, respectively. © Canadian Mathematical Society 2012
Laser Ablation: An Easy Route To Obtain Gold And Silver Nanomaterials
No full textGold and silver nanoparticles (AuNP and AgNP) have a very important role in nanotechnolgy and nanoscience, due to their physical, chemical and biochemical properties. We produced colloidal solution of Au and Ag nanoparticles in a fast and inexpensive way by laser ablation of the bulk metals in a liquid buffer using the 1064 nm line of a Q -switched Nd – YAG laser. On one hand these solutions are stable without any external chemical reagent, so nanoparticles can be obtained free in solution. On the other hand we succesfully performed the laser ablation synthesis (LAS) in water and in organic solvents, so it is possible to functionalize these particles during as well as after the LAS, simply solubilizing the ligands in the appropriate solvent.[1,2] Furthermore we found that in toluene, LAS of AuNP produces a graphite – gold nanocomposite. The graphitic matrix determined the quenching of the characteristic surface plasmon absorption (SPA) of the AuNP, that can be restored by the matrix removal.[3]
The characterization of AuNP and AgNP solutions is easily achieved by UV – vis spectroscopy using the Mie Theory to fit the SPA. For free particles in solution we conveniently fitted the SPA with the Mie Model for compact spheres and the Gans model for spheroids. We verified that one can account for the isolated nanoparticles fraction using the Mie model for simple spheres and for the aggregated nanoparticles fraction using the Gans model for spheroids.[2] In the case of the graphite – AuNP composite we reproduced the SPA quenching using the Mie model extension for core@shell particles.[3] HRTEM images confirmed the results obtained with the UV-vis spectroscopy.
Finally we were able to obtain a certain control on the average size and aggregation of nanoparticles by laser treatment at 532 nm of AuNP solution.
[1] V. Amendola, G. Mattei, C. Cusan, M. Prato and M. Meneghetti; Synthetic Metals 2005; 155; 283–286
[2] Vincenzo Amendola, Stefano Polizzi and Moreno Meneghetti; J Phys Chem B 2006; 110; 7232-7237
[3] Vincenzo Amendola, Gian Andrea Rizzi, Stefano Polizzi and Moreno Meneghetti; J Phys Chem B 2005; 109; 23125-2312
Gaspare Polizzi, Giacomo Leopardi : la concezione dell'umano tra utopia e disincanto, Milano, Mimesis 2010
No full textRecensione al volume Gaspare Polizzi,Giacomo Leopardi: la concezione dell'umano tra utopia e disincanto, Mioano, Mimesis 201
Monodromy representations and surfaces with maximal Albanese dimension
No full textWe relate the existence of some surfaces of general type and maximal Albanese dimension to the existence of some monodromy representations of the braid group B2(C2) in the symmetric group Sn. Furthermore, we compute the number of such representations up to n= 9 , and we analyze the cases n∈{2,3,4}. For n=2,3 we recover some surfaces with pg= q= 2 recently studied (with different methods) by the author and his collaborators, whereas for n= 4 we obtain some conjecturally new examples
50 years of ice-front changes between the Adélie and Banzare Coasts, East Antarctica
No full textIce-front change may well be a sensitive indicator of regional climate change. We studied the coastal sector of Wilkes Land, East Antarctica, along the Adélie and Banzare Coasts, extending from Buchanan Bay (67°05′S, 144°30′ E) to Porpoise Bay (67°S, 128° E). The glaciers in this area drain the northern part of Dome C (area 270 000 km2). A comparison of maps, photographs and satellite images, dated several years apart, led to an estimation of the fluctuations of 18 ice fronts over the 50 years 1947-97. The area of the floating glaciers in 1963 was 3035 km2, and in 1989, 2785 km2. The main glaciers in the area are Zéléc, Astrolabe, du Français, Commandant Charcot and Pourquoi Pas for the Adélie Coast, and Dibble, May, Sandford and Frost Glaciers for the Clarie and Banzare Coasts. Most of the floating glaciers have shown cyclical behaviour without a marked trend, but a general reduction since 1947. The reduction in the area of floating glaciers since the 1950s may be linked to changes in ice-ocean interaction, as noted for the floating glaciers of the George V Coast and the Cape Adare area, and sea-ice extent. The calving behaviour of the main glacier tongues is characterized by an accumulation of icebergs projecting from the coast to form iceberg tongues, held in place by grounding and joined together by annual or perennial fast ice
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